Merge 69e0affa (automated)

102 files changed, 1691 insertions, 3716 deletions

diff --git a/pkg/sentry/control/proc.go b/pkg/sentry/control/proc.go
index 66a506584..6ae60c5cb 100644
--- a/pkg/sentry/control/proc.go
+++ b/pkg/sentry/control/proc.go
@@ -28,7 +28,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs/host"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/limits"
 	"gvisor.dev/gvisor/pkg/sentry/usage"
@@ -123,9 +122,8 @@ func ExecAsync(proc *Proc, args *ExecArgs) (*kernel.ThreadGroup, kernel.ThreadID
 // TTYFileOperations that wraps the TTY is also returned.
 func (proc *Proc) execAsync(args *ExecArgs) (*kernel.ThreadGroup, kernel.ThreadID, *host.TTYFileOperations, error) {
 	// Import file descriptors.
-	l := limits.NewLimitSet()
-	fdm := proc.Kernel.NewFDMap()
-	defer fdm.DecRef()
+	fdTable := proc.Kernel.NewFDTable()
+	defer fdTable.DecRef()
 
 	// No matter what happens, we should close all files in the FilePayload
 	// before returning. Any files that are imported will be duped.
@@ -149,9 +147,9 @@ func (proc *Proc) execAsync(args *ExecArgs) (*kernel.ThreadGroup, kernel.ThreadI
 		WorkingDirectory:        args.WorkingDirectory,
 		Root:                    args.Root,
 		Credentials:             creds,
-		FDMap:                   fdm,
+		FDTable:                 fdTable,
 		Umask:                   0022,
-		Limits:                  l,
+		Limits:                  limits.NewLimitSet(),
 		MaxSymlinkTraversals:    linux.MaxSymlinkTraversals,
 		UTSNamespace:            proc.Kernel.RootUTSNamespace(),
 		IPCNamespace:            proc.Kernel.RootIPCNamespace(),
@@ -212,7 +210,7 @@ func (proc *Proc) execAsync(args *ExecArgs) (*kernel.ThreadGroup, kernel.ThreadI
 		}
 
 		// Add the file to the FD map.
-		if err := fdm.NewFDAt(kdefs.FD(appFD), appFile, kernel.FDFlags{}, l); err != nil {
+		if err := fdTable.NewFDAt(ctx, int32(appFD), appFile, kernel.FDFlags{}); err != nil {
 			return nil, 0, nil, err
 		}
 	}
diff --git a/pkg/sentry/fs/ashmem/area.go b/pkg/sentry/fs/ashmem/area.go
deleted file mode 100644
index 3b8d6ca89..000000000
--- a/pkg/sentry/fs/ashmem/area.go
+++ /dev/null
@@ -1,308 +0,0 @@
-// Copyright 2018 The gVisor Authors.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package ashmem
-
-import (
-	"sync"
-
-	"gvisor.dev/gvisor/pkg/abi/linux"
-	"gvisor.dev/gvisor/pkg/sentry/arch"
-	"gvisor.dev/gvisor/pkg/sentry/context"
-	"gvisor.dev/gvisor/pkg/sentry/fs"
-	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
-	"gvisor.dev/gvisor/pkg/sentry/fs/tmpfs"
-	"gvisor.dev/gvisor/pkg/sentry/memmap"
-	"gvisor.dev/gvisor/pkg/sentry/usage"
-	"gvisor.dev/gvisor/pkg/sentry/usermem"
-	"gvisor.dev/gvisor/pkg/syserror"
-	"gvisor.dev/gvisor/pkg/waiter"
-)
-
-const (
-	// namePrefix is the name prefix assumed and forced by the Linux implementation.
-	namePrefix = "dev/ashmem"
-
-	// nameLen is the maximum name length.
-	nameLen = 256
-)
-
-// Area implements fs.FileOperations.
-//
-// +stateify savable
-type Area struct {
-	fsutil.FileNoFsync              `state:"nosave"`
-	fsutil.FileNoSplice             `state:"nosave"`
-	fsutil.FileNoopFlush            `state:"nosave"`
-	fsutil.FileNotDirReaddir        `state:"nosave"`
-	fsutil.FileUseInodeUnstableAttr `state:"nosave"`
-	waiter.AlwaysReady              `state:"nosave"`
-
-	ad *Device
-
-	// mu protects fields below.
-	mu        sync.Mutex `state:"nosave"`
-	tmpfsFile *fs.File
-	name      string
-	size      uint64
-	perms     usermem.AccessType
-	pb        *PinBoard
-}
-
-// Release implements fs.FileOperations.Release.
-func (a *Area) Release() {
-	a.mu.Lock()
-	defer a.mu.Unlock()
-	if a.tmpfsFile != nil {
-		a.tmpfsFile.DecRef()
-		a.tmpfsFile = nil
-	}
-}
-
-// Seek implements fs.FileOperations.Seek.
-func (a *Area) Seek(ctx context.Context, file *fs.File, whence fs.SeekWhence, offset int64) (int64, error) {
-	a.mu.Lock()
-	defer a.mu.Unlock()
-	if a.size == 0 {
-		return 0, syserror.EINVAL
-	}
-	if a.tmpfsFile == nil {
-		return 0, syserror.EBADF
-	}
-	return a.tmpfsFile.FileOperations.Seek(ctx, file, whence, offset)
-}
-
-// Read implements fs.FileOperations.Read.
-func (a *Area) Read(ctx context.Context, file *fs.File, dst usermem.IOSequence, offset int64) (int64, error) {
-	a.mu.Lock()
-	defer a.mu.Unlock()
-	if a.size == 0 {
-		return 0, nil
-	}
-	if a.tmpfsFile == nil {
-		return 0, syserror.EBADF
-	}
-	return a.tmpfsFile.FileOperations.Read(ctx, file, dst, offset)
-}
-
-// Write implements fs.FileOperations.Write.
-func (a *Area) Write(ctx context.Context, file *fs.File, src usermem.IOSequence, offset int64) (int64, error) {
-	return 0, syserror.ENOSYS
-}
-
-// ConfigureMMap implements fs.FileOperations.ConfigureMMap.
-func (a *Area) ConfigureMMap(ctx context.Context, file *fs.File, opts *memmap.MMapOpts) error {
-	a.mu.Lock()
-	defer a.mu.Unlock()
-	if a.size == 0 {
-		return syserror.EINVAL
-	}
-
-	if !a.perms.SupersetOf(opts.Perms) {
-		return syserror.EPERM
-	}
-	opts.MaxPerms = opts.MaxPerms.Intersect(a.perms)
-
-	if a.tmpfsFile == nil {
-		tmpfsInodeOps := tmpfs.NewInMemoryFile(ctx, usage.Tmpfs, fs.UnstableAttr{})
-		tmpfsInode := fs.NewInode(ctx, tmpfsInodeOps, fs.NewPseudoMountSource(ctx), fs.StableAttr{})
-		dirent := fs.NewDirent(ctx, tmpfsInode, namePrefix+"/"+a.name)
-		tmpfsFile, err := tmpfsInode.GetFile(ctx, dirent, fs.FileFlags{Read: true, Write: true})
-		// Drop the extra reference on the Dirent.
-		dirent.DecRef()
-
-		if err != nil {
-			return err
-		}
-
-		// Truncate to the size set by ASHMEM_SET_SIZE ioctl.
-		err = tmpfsInodeOps.Truncate(ctx, tmpfsInode, int64(a.size))
-		if err != nil {
-			return err
-		}
-		a.tmpfsFile = tmpfsFile
-		a.pb = NewPinBoard()
-	}
-
-	return a.tmpfsFile.ConfigureMMap(ctx, opts)
-}
-
-// Ioctl implements fs.FileOperations.Ioctl.
-func (a *Area) Ioctl(ctx context.Context, _ *fs.File, io usermem.IO, args arch.SyscallArguments) (uintptr, error) {
-	// Switch on ioctl request.
-	switch args[1].Uint() {
-	case linux.AshmemSetNameIoctl:
-		name, err := usermem.CopyStringIn(ctx, io, args[2].Pointer(), nameLen-1, usermem.IOOpts{
-			AddressSpaceActive: true,
-		})
-		if err != nil {
-			return 0, err
-		}
-
-		a.mu.Lock()
-		defer a.mu.Unlock()
-
-		// Cannot set name for already mapped ashmem.
-		if a.tmpfsFile != nil {
-			return 0, syserror.EINVAL
-		}
-		a.name = name
-		return 0, nil
-
-	case linux.AshmemGetNameIoctl:
-		a.mu.Lock()
-		var local []byte
-		if a.name != "" {
-			nameLen := len([]byte(a.name))
-			local = make([]byte, nameLen, nameLen+1)
-			copy(local, []byte(a.name))
-			local = append(local, 0)
-		} else {
-			nameLen := len([]byte(namePrefix))
-			local = make([]byte, nameLen, nameLen+1)
-			copy(local, []byte(namePrefix))
-			local = append(local, 0)
-		}
-		a.mu.Unlock()
-
-		if _, err := io.CopyOut(ctx, args[2].Pointer(), local, usermem.IOOpts{
-			AddressSpaceActive: true,
-		}); err != nil {
-			return 0, syserror.EFAULT
-		}
-		return 0, nil
-
-	case linux.AshmemSetSizeIoctl:
-		a.mu.Lock()
-		defer a.mu.Unlock()
-
-		// Cannot set size for already mapped ashmem.
-		if a.tmpfsFile != nil {
-			return 0, syserror.EINVAL
-		}
-		a.size = uint64(args[2].SizeT())
-		return 0, nil
-
-	case linux.AshmemGetSizeIoctl:
-		return uintptr(a.size), nil
-
-	case linux.AshmemPinIoctl, linux.AshmemUnpinIoctl, linux.AshmemGetPinStatusIoctl:
-		// Locking and unlocking is ok since once tmpfsFile is set, it won't be nil again
-		// even after unmapping! Unlocking is needed in order to avoid a deadlock on
-		// usermem.CopyObjectIn.
-
-		// Cannot execute pin-related ioctls before mapping.
-		a.mu.Lock()
-		if a.tmpfsFile == nil {
-			a.mu.Unlock()
-			return 0, syserror.EINVAL
-		}
-		a.mu.Unlock()
-
-		var pin linux.AshmemPin
-		_, err := usermem.CopyObjectIn(ctx, io, args[2].Pointer(), &pin, usermem.IOOpts{
-			AddressSpaceActive: true,
-		})
-		if err != nil {
-			return 0, syserror.EFAULT
-		}
-
-		a.mu.Lock()
-		defer a.mu.Unlock()
-		return a.pinOperation(pin, args[1].Uint())
-
-	case linux.AshmemPurgeAllCachesIoctl:
-		return 0, nil
-
-	case linux.AshmemSetProtMaskIoctl:
-		prot := uint64(args[2].ModeT())
-		perms := usermem.AccessType{
-			Read:    prot&linux.PROT_READ != 0,
-			Write:   prot&linux.PROT_WRITE != 0,
-			Execute: prot&linux.PROT_EXEC != 0,
-		}
-
-		a.mu.Lock()
-		defer a.mu.Unlock()
-
-		// Can only narrow prot mask.
-		if !a.perms.SupersetOf(perms) {
-			return 0, syserror.EINVAL
-		}
-
-		// TODO(b/30946773,gvisor.dev/issue/153): If personality flag
-		// READ_IMPLIES_EXEC is set, set PROT_EXEC if PORT_READ is set.
-
-		a.perms = perms
-		return 0, nil
-
-	case linux.AshmemGetProtMaskIoctl:
-		return uintptr(a.perms.Prot()), nil
-	default:
-		// Ioctls irrelevant to Ashmem.
-		return 0, syserror.EINVAL
-	}
-}
-
-// pinOperation should only be called while holding a.mu.
-func (a *Area) pinOperation(pin linux.AshmemPin, op uint32) (uintptr, error) {
-	// Page-align a.size for checks.
-	pageAlignedSize, ok := usermem.Addr(a.size).RoundUp()
-	if !ok {
-		return 0, syserror.EINVAL
-	}
-	// Len 0 means everything onward.
-	if pin.Len == 0 {
-		pin.Len = uint32(pageAlignedSize) - pin.Offset
-	}
-	// Both Offset and Len have to be page-aligned.
-	if pin.Offset%uint32(usermem.PageSize) != 0 {
-		return 0, syserror.EINVAL
-	}
-	if pin.Len%uint32(usermem.PageSize) != 0 {
-		return 0, syserror.EINVAL
-	}
-	// Adding Offset and Len must not cause an uint32 overflow.
-	if end := pin.Offset + pin.Len; end < pin.Offset {
-		return 0, syserror.EINVAL
-	}
-	// Pin range must not exceed a's size.
-	if uint32(pageAlignedSize) < pin.Offset+pin.Len {
-		return 0, syserror.EINVAL
-	}
-	// Handle each operation.
-	r := RangeFromAshmemPin(pin)
-	switch op {
-	case linux.AshmemPinIoctl:
-		if a.pb.PinRange(r) {
-			return linux.AshmemWasPurged, nil
-		}
-		return linux.AshmemNotPurged, nil
-
-	case linux.AshmemUnpinIoctl:
-		// TODO(b/30946773): Implement purge on unpin.
-		a.pb.UnpinRange(r)
-		return 0, nil
-
-	case linux.AshmemGetPinStatusIoctl:
-		if a.pb.RangePinnedStatus(r) {
-			return linux.AshmemIsPinned, nil
-		}
-		return linux.AshmemIsUnpinned, nil
-
-	default:
-		panic("unreachable")
-	}
-
-}
diff --git a/pkg/sentry/fs/ashmem/ashmem_state_autogen.go b/pkg/sentry/fs/ashmem/ashmem_state_autogen.go
deleted file mode 100755
index 13defb033..000000000
--- a/pkg/sentry/fs/ashmem/ashmem_state_autogen.go
+++ /dev/null
@@ -1,123 +0,0 @@
-// automatically generated by stateify.
-
-package ashmem
-
-import (
-	"gvisor.dev/gvisor/pkg/state"
-)
-
-func (x *Area) beforeSave() {}
-func (x *Area) save(m state.Map) {
-	x.beforeSave()
-	m.Save("ad", &x.ad)
-	m.Save("tmpfsFile", &x.tmpfsFile)
-	m.Save("name", &x.name)
-	m.Save("size", &x.size)
-	m.Save("perms", &x.perms)
-	m.Save("pb", &x.pb)
-}
-
-func (x *Area) afterLoad() {}
-func (x *Area) load(m state.Map) {
-	m.Load("ad", &x.ad)
-	m.Load("tmpfsFile", &x.tmpfsFile)
-	m.Load("name", &x.name)
-	m.Load("size", &x.size)
-	m.Load("perms", &x.perms)
-	m.Load("pb", &x.pb)
-}
-
-func (x *Device) beforeSave() {}
-func (x *Device) save(m state.Map) {
-	x.beforeSave()
-	m.Save("InodeSimpleAttributes", &x.InodeSimpleAttributes)
-}
-
-func (x *Device) afterLoad() {}
-func (x *Device) load(m state.Map) {
-	m.Load("InodeSimpleAttributes", &x.InodeSimpleAttributes)
-}
-
-func (x *PinBoard) beforeSave() {}
-func (x *PinBoard) save(m state.Map) {
-	x.beforeSave()
-	m.Save("Set", &x.Set)
-}
-
-func (x *PinBoard) afterLoad() {}
-func (x *PinBoard) load(m state.Map) {
-	m.Load("Set", &x.Set)
-}
-
-func (x *Range) beforeSave() {}
-func (x *Range) save(m state.Map) {
-	x.beforeSave()
-	m.Save("Start", &x.Start)
-	m.Save("End", &x.End)
-}
-
-func (x *Range) afterLoad() {}
-func (x *Range) load(m state.Map) {
-	m.Load("Start", &x.Start)
-	m.Load("End", &x.End)
-}
-
-func (x *Set) beforeSave() {}
-func (x *Set) save(m state.Map) {
-	x.beforeSave()
-	var root *SegmentDataSlices = x.saveRoot()
-	m.SaveValue("root", root)
-}
-
-func (x *Set) afterLoad() {}
-func (x *Set) load(m state.Map) {
-	m.LoadValue("root", new(*SegmentDataSlices), func(y interface{}) { x.loadRoot(y.(*SegmentDataSlices)) })
-}
-
-func (x *node) beforeSave() {}
-func (x *node) save(m state.Map) {
-	x.beforeSave()
-	m.Save("nrSegments", &x.nrSegments)
-	m.Save("parent", &x.parent)
-	m.Save("parentIndex", &x.parentIndex)
-	m.Save("hasChildren", &x.hasChildren)
-	m.Save("keys", &x.keys)
-	m.Save("values", &x.values)
-	m.Save("children", &x.children)
-}
-
-func (x *node) afterLoad() {}
-func (x *node) load(m state.Map) {
-	m.Load("nrSegments", &x.nrSegments)
-	m.Load("parent", &x.parent)
-	m.Load("parentIndex", &x.parentIndex)
-	m.Load("hasChildren", &x.hasChildren)
-	m.Load("keys", &x.keys)
-	m.Load("values", &x.values)
-	m.Load("children", &x.children)
-}
-
-func (x *SegmentDataSlices) beforeSave() {}
-func (x *SegmentDataSlices) save(m state.Map) {
-	x.beforeSave()
-	m.Save("Start", &x.Start)
-	m.Save("End", &x.End)
-	m.Save("Values", &x.Values)
-}
-
-func (x *SegmentDataSlices) afterLoad() {}
-func (x *SegmentDataSlices) load(m state.Map) {
-	m.Load("Start", &x.Start)
-	m.Load("End", &x.End)
-	m.Load("Values", &x.Values)
-}
-
-func init() {
-	state.Register("ashmem.Area", (*Area)(nil), state.Fns{Save: (*Area).save, Load: (*Area).load})
-	state.Register("ashmem.Device", (*Device)(nil), state.Fns{Save: (*Device).save, Load: (*Device).load})
-	state.Register("ashmem.PinBoard", (*PinBoard)(nil), state.Fns{Save: (*PinBoard).save, Load: (*PinBoard).load})
-	state.Register("ashmem.Range", (*Range)(nil), state.Fns{Save: (*Range).save, Load: (*Range).load})
-	state.Register("ashmem.Set", (*Set)(nil), state.Fns{Save: (*Set).save, Load: (*Set).load})
-	state.Register("ashmem.node", (*node)(nil), state.Fns{Save: (*node).save, Load: (*node).load})
-	state.Register("ashmem.SegmentDataSlices", (*SegmentDataSlices)(nil), state.Fns{Save: (*SegmentDataSlices).save, Load: (*SegmentDataSlices).load})
-}
diff --git a/pkg/sentry/fs/ashmem/device.go b/pkg/sentry/fs/ashmem/device.go
deleted file mode 100644
index 776f54abe..000000000
--- a/pkg/sentry/fs/ashmem/device.go
+++ /dev/null
@@ -1,61 +0,0 @@
-// Copyright 2018 The gVisor Authors.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-// Package ashmem implements Android ashmem module (Anonymus Shared Memory).
-package ashmem
-
-import (
-	"gvisor.dev/gvisor/pkg/abi/linux"
-	"gvisor.dev/gvisor/pkg/sentry/context"
-	"gvisor.dev/gvisor/pkg/sentry/fs"
-	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
-	"gvisor.dev/gvisor/pkg/sentry/usermem"
-)
-
-// Device implements fs.InodeOperations.
-//
-// +stateify savable
-type Device struct {
-	fsutil.InodeGenericChecker       `state:"nosave"`
-	fsutil.InodeNoExtendedAttributes `state:"nosave"`
-	fsutil.InodeNoopAllocate         `state:"nosave"`
-	fsutil.InodeNoopRelease          `state:"nosave"`
-	fsutil.InodeNoopTruncate         `state:"nosave"`
-	fsutil.InodeNoopWriteOut         `state:"nosave"`
-	fsutil.InodeNotDirectory         `state:"nosave"`
-	fsutil.InodeNotMappable          `state:"nosave"`
-	fsutil.InodeNotSocket            `state:"nosave"`
-	fsutil.InodeNotSymlink           `state:"nosave"`
-	fsutil.InodeVirtual              `state:"nosave"`
-
-	fsutil.InodeSimpleAttributes
-}
-
-var _ fs.InodeOperations = (*Device)(nil)
-
-// NewDevice creates and initializes a Device structure.
-func NewDevice(ctx context.Context, owner fs.FileOwner, fp fs.FilePermissions) *Device {
-	return &Device{
-		InodeSimpleAttributes: fsutil.NewInodeSimpleAttributes(ctx, owner, fp, linux.ANON_INODE_FS_MAGIC),
-	}
-}
-
-// GetFile implements fs.InodeOperations.GetFile.
-func (ad *Device) GetFile(ctx context.Context, d *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
-	return fs.NewFile(ctx, d, flags, &Area{
-		ad:        ad,
-		tmpfsFile: nil,
-		perms:     usermem.AnyAccess,
-	}), nil
-}
diff --git a/pkg/sentry/fs/ashmem/pin_board.go b/pkg/sentry/fs/ashmem/pin_board.go
deleted file mode 100644
index c5400dd94..000000000
--- a/pkg/sentry/fs/ashmem/pin_board.go
+++ /dev/null
@@ -1,127 +0,0 @@
-// Copyright 2018 The gVisor Authors.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package ashmem
-
-import "gvisor.dev/gvisor/pkg/abi/linux"
-
-const maxUint64 = ^uint64(0)
-
-// setFunctions implements segment.Functions generated from segment.Functions for
-// uint64 Key and noValue Value. For more information, see the build file and
-// segment set implementation at pkg/segment/set.go.
-type setFunctions struct{}
-
-// noValue is a type of range attached value, which is irrelevant here.
-type noValue struct{}
-
-// MinKey implements segment.Functions.MinKey.
-func (setFunctions) MinKey() uint64 {
-	return 0
-}
-
-// MaxKey implements segment.Functions.MaxKey.
-func (setFunctions) MaxKey() uint64 {
-	return maxUint64
-}
-
-// ClearValue implements segment.Functions.ClearValue.
-func (setFunctions) ClearValue(*noValue) {
-	return
-}
-
-// Merge implements segment.Functions.Merge.
-func (setFunctions) Merge(Range, noValue, Range, noValue) (noValue, bool) {
-	return noValue{}, true
-}
-
-// Split implements segment.Functions.Split.
-func (setFunctions) Split(Range, noValue, uint64) (noValue, noValue) {
-	return noValue{}, noValue{}
-}
-
-// PinBoard represents a set of pinned ranges in ashmem.
-//
-// segment.Set is used for implementation where segments represent
-// ranges of pinned bytes, while gaps represent ranges of unpinned
-// bytes. All ranges are page-aligned.
-//
-// +stateify savable
-type PinBoard struct {
-	Set
-}
-
-// NewPinBoard creates a new pin board with all pages pinned.
-func NewPinBoard() *PinBoard {
-	var pb PinBoard
-	pb.PinRange(Range{0, maxUint64})
-	return &pb
-}
-
-// PinRange pins all pages in the specified range and returns true
-// if there are any newly pinned pages.
-func (pb *PinBoard) PinRange(r Range) bool {
-	pinnedPages := false
-	for gap := pb.LowerBoundGap(r.Start); gap.Ok() && gap.Start() < r.End; {
-		common := gap.Range().Intersect(r)
-		if common.Length() == 0 {
-			gap = gap.NextGap()
-			continue
-		}
-		pinnedPages = true
-		gap = pb.Insert(gap, common, noValue{}).NextGap()
-	}
-	return pinnedPages
-}
-
-// UnpinRange unpins all pages in the specified range.
-func (pb *PinBoard) UnpinRange(r Range) {
-	for seg := pb.LowerBoundSegment(r.Start); seg.Ok() && seg.Start() < r.End; {
-		common := seg.Range().Intersect(r)
-		if common.Length() == 0 {
-			seg = seg.NextSegment()
-			continue
-		}
-		seg = pb.RemoveRange(common).NextSegment()
-	}
-}
-
-// RangePinnedStatus returns false if there's at least one unpinned page in the
-// specified range.
-func (pb *PinBoard) RangePinnedStatus(r Range) bool {
-	for gap := pb.LowerBoundGap(r.Start); gap.Ok() && gap.Start() < r.End; {
-		common := gap.Range().Intersect(r)
-		if common.Length() == 0 {
-			gap = gap.NextGap()
-			continue
-		}
-		return false
-	}
-	return true
-}
-
-// RangeFromAshmemPin converts ashmem's original pin structure
-// to Range.
-func RangeFromAshmemPin(ap linux.AshmemPin) Range {
-	if ap.Len == 0 {
-		return Range{
-			uint64(ap.Offset),
-			maxUint64,
-		}
-	}
-	return Range{
-		uint64(ap.Offset),
-		uint64(ap.Offset) + uint64(ap.Len),
-	}
-}
diff --git a/pkg/sentry/fs/ashmem/uint64_range.go b/pkg/sentry/fs/ashmem/uint64_range.go
deleted file mode 100755
index d71a10b16..000000000
--- a/pkg/sentry/fs/ashmem/uint64_range.go
+++ /dev/null
@@ -1,62 +0,0 @@
-package ashmem
-
-// A Range represents a contiguous range of T.
-//
-// +stateify savable
-type Range struct {
-	// Start is the inclusive start of the range.
-	Start uint64
-
-	// End is the exclusive end of the range.
-	End uint64
-}
-
-// WellFormed returns true if r.Start <= r.End. All other methods on a Range
-// require that the Range is well-formed.
-func (r Range) WellFormed() bool {
-	return r.Start <= r.End
-}
-
-// Length returns the length of the range.
-func (r Range) Length() uint64 {
-	return r.End - r.Start
-}
-
-// Contains returns true if r contains x.
-func (r Range) Contains(x uint64) bool {
-	return r.Start <= x && x < r.End
-}
-
-// Overlaps returns true if r and r2 overlap.
-func (r Range) Overlaps(r2 Range) bool {
-	return r.Start < r2.End && r2.Start < r.End
-}
-
-// IsSupersetOf returns true if r is a superset of r2; that is, the range r2 is
-// contained within r.
-func (r Range) IsSupersetOf(r2 Range) bool {
-	return r.Start <= r2.Start && r.End >= r2.End
-}
-
-// Intersect returns a range consisting of the intersection between r and r2.
-// If r and r2 do not overlap, Intersect returns a range with unspecified
-// bounds, but for which Length() == 0.
-func (r Range) Intersect(r2 Range) Range {
-	if r.Start < r2.Start {
-		r.Start = r2.Start
-	}
-	if r.End > r2.End {
-		r.End = r2.End
-	}
-	if r.End < r.Start {
-		r.End = r.Start
-	}
-	return r
-}
-
-// CanSplitAt returns true if it is legal to split a segment spanning the range
-// r at x; that is, splitting at x would produce two ranges, both of which have
-// non-zero length.
-func (r Range) CanSplitAt(x uint64) bool {
-	return r.Contains(x) && r.Start < x
-}
diff --git a/pkg/sentry/fs/ashmem/uint64_set.go b/pkg/sentry/fs/ashmem/uint64_set.go
deleted file mode 100755
index a4860175a..000000000
--- a/pkg/sentry/fs/ashmem/uint64_set.go
+++ /dev/null
@@ -1,1270 +0,0 @@
-package ashmem
-
-import (
-	"bytes"
-	"fmt"
-)
-
-const (
-	// minDegree is the minimum degree of an internal node in a Set B-tree.
-	//
-	// - Any non-root node has at least minDegree-1 segments.
-	//
-	// - Any non-root internal (non-leaf) node has at least minDegree children.
-	//
-	// - The root node may have fewer than minDegree-1 segments, but it may
-	// only have 0 segments if the tree is empty.
-	//
-	// Our implementation requires minDegree >= 3. Higher values of minDegree
-	// usually improve performance, but increase memory usage for small sets.
-	minDegree = 3
-
-	maxDegree = 2 * minDegree
-)
-
-// A Set is a mapping of segments with non-overlapping Range keys. The zero
-// value for a Set is an empty set. Set values are not safely movable nor
-// copyable. Set is thread-compatible.
-//
-// +stateify savable
-type Set struct {
-	root node `state:".(*SegmentDataSlices)"`
-}
-
-// IsEmpty returns true if the set contains no segments.
-func (s *Set) IsEmpty() bool {
-	return s.root.nrSegments == 0
-}
-
-// IsEmptyRange returns true iff no segments in the set overlap the given
-// range. This is semantically equivalent to s.SpanRange(r) == 0, but may be
-// more efficient.
-func (s *Set) IsEmptyRange(r Range) bool {
-	switch {
-	case r.Length() < 0:
-		panic(fmt.Sprintf("invalid range %v", r))
-	case r.Length() == 0:
-		return true
-	}
-	_, gap := s.Find(r.Start)
-	if !gap.Ok() {
-		return false
-	}
-	return r.End <= gap.End()
-}
-
-// Span returns the total size of all segments in the set.
-func (s *Set) Span() uint64 {
-	var sz uint64
-	for seg := s.FirstSegment(); seg.Ok(); seg = seg.NextSegment() {
-		sz += seg.Range().Length()
-	}
-	return sz
-}
-
-// SpanRange returns the total size of the intersection of segments in the set
-// with the given range.
-func (s *Set) SpanRange(r Range) uint64 {
-	switch {
-	case r.Length() < 0:
-		panic(fmt.Sprintf("invalid range %v", r))
-	case r.Length() == 0:
-		return 0
-	}
-	var sz uint64
-	for seg := s.LowerBoundSegment(r.Start); seg.Ok() && seg.Start() < r.End; seg = seg.NextSegment() {
-		sz += seg.Range().Intersect(r).Length()
-	}
-	return sz
-}
-
-// FirstSegment returns the first segment in the set. If the set is empty,
-// FirstSegment returns a terminal iterator.
-func (s *Set) FirstSegment() Iterator {
-	if s.root.nrSegments == 0 {
-		return Iterator{}
-	}
-	return s.root.firstSegment()
-}
-
-// LastSegment returns the last segment in the set. If the set is empty,
-// LastSegment returns a terminal iterator.
-func (s *Set) LastSegment() Iterator {
-	if s.root.nrSegments == 0 {
-		return Iterator{}
-	}
-	return s.root.lastSegment()
-}
-
-// FirstGap returns the first gap in the set.
-func (s *Set) FirstGap() GapIterator {
-	n := &s.root
-	for n.hasChildren {
-		n = n.children[0]
-	}
-	return GapIterator{n, 0}
-}
-
-// LastGap returns the last gap in the set.
-func (s *Set) LastGap() GapIterator {
-	n := &s.root
-	for n.hasChildren {
-		n = n.children[n.nrSegments]
-	}
-	return GapIterator{n, n.nrSegments}
-}
-
-// Find returns the segment or gap whose range contains the given key. If a
-// segment is found, the returned Iterator is non-terminal and the
-// returned GapIterator is terminal. Otherwise, the returned Iterator is
-// terminal and the returned GapIterator is non-terminal.
-func (s *Set) Find(key uint64) (Iterator, GapIterator) {
-	n := &s.root
-	for {
-
-		lower := 0
-		upper := n.nrSegments
-		for lower < upper {
-			i := lower + (upper-lower)/2
-			if r := n.keys[i]; key < r.End {
-				if key >= r.Start {
-					return Iterator{n, i}, GapIterator{}
-				}
-				upper = i
-			} else {
-				lower = i + 1
-			}
-		}
-		i := lower
-		if !n.hasChildren {
-			return Iterator{}, GapIterator{n, i}
-		}
-		n = n.children[i]
-	}
-}
-
-// FindSegment returns the segment whose range contains the given key. If no
-// such segment exists, FindSegment returns a terminal iterator.
-func (s *Set) FindSegment(key uint64) Iterator {
-	seg, _ := s.Find(key)
-	return seg
-}
-
-// LowerBoundSegment returns the segment with the lowest range that contains a
-// key greater than or equal to min. If no such segment exists,
-// LowerBoundSegment returns a terminal iterator.
-func (s *Set) LowerBoundSegment(min uint64) Iterator {
-	seg, gap := s.Find(min)
-	if seg.Ok() {
-		return seg
-	}
-	return gap.NextSegment()
-}
-
-// UpperBoundSegment returns the segment with the highest range that contains a
-// key less than or equal to max. If no such segment exists, UpperBoundSegment
-// returns a terminal iterator.
-func (s *Set) UpperBoundSegment(max uint64) Iterator {
-	seg, gap := s.Find(max)
-	if seg.Ok() {
-		return seg
-	}
-	return gap.PrevSegment()
-}
-
-// FindGap returns the gap containing the given key. If no such gap exists
-// (i.e. the set contains a segment containing that key), FindGap returns a
-// terminal iterator.
-func (s *Set) FindGap(key uint64) GapIterator {
-	_, gap := s.Find(key)
-	return gap
-}
-
-// LowerBoundGap returns the gap with the lowest range that is greater than or
-// equal to min.
-func (s *Set) LowerBoundGap(min uint64) GapIterator {
-	seg, gap := s.Find(min)
-	if gap.Ok() {
-		return gap
-	}
-	return seg.NextGap()
-}
-
-// UpperBoundGap returns the gap with the highest range that is less than or
-// equal to max.
-func (s *Set) UpperBoundGap(max uint64) GapIterator {
-	seg, gap := s.Find(max)
-	if gap.Ok() {
-		return gap
-	}
-	return seg.PrevGap()
-}
-
-// Add inserts the given segment into the set and returns true. If the new
-// segment can be merged with adjacent segments, Add will do so. If the new
-// segment would overlap an existing segment, Add returns false. If Add
-// succeeds, all existing iterators are invalidated.
-func (s *Set) Add(r Range, val noValue) bool {
-	if r.Length() <= 0 {
-		panic(fmt.Sprintf("invalid segment range %v", r))
-	}
-	gap := s.FindGap(r.Start)
-	if !gap.Ok() {
-		return false
-	}
-	if r.End > gap.End() {
-		return false
-	}
-	s.Insert(gap, r, val)
-	return true
-}
-
-// AddWithoutMerging inserts the given segment into the set and returns true.
-// If it would overlap an existing segment, AddWithoutMerging does nothing and
-// returns false. If AddWithoutMerging succeeds, all existing iterators are
-// invalidated.
-func (s *Set) AddWithoutMerging(r Range, val noValue) bool {
-	if r.Length() <= 0 {
-		panic(fmt.Sprintf("invalid segment range %v", r))
-	}
-	gap := s.FindGap(r.Start)
-	if !gap.Ok() {
-		return false
-	}
-	if r.End > gap.End() {
-		return false
-	}
-	s.InsertWithoutMergingUnchecked(gap, r, val)
-	return true
-}
-
-// Insert inserts the given segment into the given gap. If the new segment can
-// be merged with adjacent segments, Insert will do so. Insert returns an
-// iterator to the segment containing the inserted value (which may have been
-// merged with other values). All existing iterators (including gap, but not
-// including the returned iterator) are invalidated.
-//
-// If the gap cannot accommodate the segment, or if r is invalid, Insert panics.
-//
-// Insert is semantically equivalent to a InsertWithoutMerging followed by a
-// Merge, but may be more efficient. Note that there is no unchecked variant of
-// Insert since Insert must retrieve and inspect gap's predecessor and
-// successor segments regardless.
-func (s *Set) Insert(gap GapIterator, r Range, val noValue) Iterator {
-	if r.Length() <= 0 {
-		panic(fmt.Sprintf("invalid segment range %v", r))
-	}
-	prev, next := gap.PrevSegment(), gap.NextSegment()
-	if prev.Ok() && prev.End() > r.Start {
-		panic(fmt.Sprintf("new segment %v overlaps predecessor %v", r, prev.Range()))
-	}
-	if next.Ok() && next.Start() < r.End {
-		panic(fmt.Sprintf("new segment %v overlaps successor %v", r, next.Range()))
-	}
-	if prev.Ok() && prev.End() == r.Start {
-		if mval, ok := (setFunctions{}).Merge(prev.Range(), prev.Value(), r, val); ok {
-			prev.SetEndUnchecked(r.End)
-			prev.SetValue(mval)
-			if next.Ok() && next.Start() == r.End {
-				val = mval
-				if mval, ok := (setFunctions{}).Merge(prev.Range(), val, next.Range(), next.Value()); ok {
-					prev.SetEndUnchecked(next.End())
-					prev.SetValue(mval)
-					return s.Remove(next).PrevSegment()
-				}
-			}
-			return prev
-		}
-	}
-	if next.Ok() && next.Start() == r.End {
-		if mval, ok := (setFunctions{}).Merge(r, val, next.Range(), next.Value()); ok {
-			next.SetStartUnchecked(r.Start)
-			next.SetValue(mval)
-			return next
-		}
-	}
-	return s.InsertWithoutMergingUnchecked(gap, r, val)
-}
-
-// InsertWithoutMerging inserts the given segment into the given gap and
-// returns an iterator to the inserted segment. All existing iterators
-// (including gap, but not including the returned iterator) are invalidated.
-//
-// If the gap cannot accommodate the segment, or if r is invalid,
-// InsertWithoutMerging panics.
-func (s *Set) InsertWithoutMerging(gap GapIterator, r Range, val noValue) Iterator {
-	if r.Length() <= 0 {
-		panic(fmt.Sprintf("invalid segment range %v", r))
-	}
-	if gr := gap.Range(); !gr.IsSupersetOf(r) {
-		panic(fmt.Sprintf("cannot insert segment range %v into gap range %v", r, gr))
-	}
-	return s.InsertWithoutMergingUnchecked(gap, r, val)
-}
-
-// InsertWithoutMergingUnchecked inserts the given segment into the given gap
-// and returns an iterator to the inserted segment. All existing iterators
-// (including gap, but not including the returned iterator) are invalidated.
-//
-// Preconditions: r.Start >= gap.Start(); r.End <= gap.End().
-func (s *Set) InsertWithoutMergingUnchecked(gap GapIterator, r Range, val noValue) Iterator {
-	gap = gap.node.rebalanceBeforeInsert(gap)
-	copy(gap.node.keys[gap.index+1:], gap.node.keys[gap.index:gap.node.nrSegments])
-	copy(gap.node.values[gap.index+1:], gap.node.values[gap.index:gap.node.nrSegments])
-	gap.node.keys[gap.index] = r
-	gap.node.values[gap.index] = val
-	gap.node.nrSegments++
-	return Iterator{gap.node, gap.index}
-}
-
-// Remove removes the given segment and returns an iterator to the vacated gap.
-// All existing iterators (including seg, but not including the returned
-// iterator) are invalidated.
-func (s *Set) Remove(seg Iterator) GapIterator {
-
-	if seg.node.hasChildren {
-
-		victim := seg.PrevSegment()
-
-		seg.SetRangeUnchecked(victim.Range())
-		seg.SetValue(victim.Value())
-		return s.Remove(victim).NextGap()
-	}
-	copy(seg.node.keys[seg.index:], seg.node.keys[seg.index+1:seg.node.nrSegments])
-	copy(seg.node.values[seg.index:], seg.node.values[seg.index+1:seg.node.nrSegments])
-	setFunctions{}.ClearValue(&seg.node.values[seg.node.nrSegments-1])
-	seg.node.nrSegments--
-	return seg.node.rebalanceAfterRemove(GapIterator{seg.node, seg.index})
-}
-
-// RemoveAll removes all segments from the set. All existing iterators are
-// invalidated.
-func (s *Set) RemoveAll() {
-	s.root = node{}
-}
-
-// RemoveRange removes all segments in the given range. An iterator to the
-// newly formed gap is returned, and all existing iterators are invalidated.
-func (s *Set) RemoveRange(r Range) GapIterator {
-	seg, gap := s.Find(r.Start)
-	if seg.Ok() {
-		seg = s.Isolate(seg, r)
-		gap = s.Remove(seg)
-	}
-	for seg = gap.NextSegment(); seg.Ok() && seg.Start() < r.End; seg = gap.NextSegment() {
-		seg = s.Isolate(seg, r)
-		gap = s.Remove(seg)
-	}
-	return gap
-}
-
-// Merge attempts to merge two neighboring segments. If successful, Merge
-// returns an iterator to the merged segment, and all existing iterators are
-// invalidated. Otherwise, Merge returns a terminal iterator.
-//
-// If first is not the predecessor of second, Merge panics.
-func (s *Set) Merge(first, second Iterator) Iterator {
-	if first.NextSegment() != second {
-		panic(fmt.Sprintf("attempt to merge non-neighboring segments %v, %v", first.Range(), second.Range()))
-	}
-	return s.MergeUnchecked(first, second)
-}
-
-// MergeUnchecked attempts to merge two neighboring segments. If successful,
-// MergeUnchecked returns an iterator to the merged segment, and all existing
-// iterators are invalidated. Otherwise, MergeUnchecked returns a terminal
-// iterator.
-//
-// Precondition: first is the predecessor of second: first.NextSegment() ==
-// second, first == second.PrevSegment().
-func (s *Set) MergeUnchecked(first, second Iterator) Iterator {
-	if first.End() == second.Start() {
-		if mval, ok := (setFunctions{}).Merge(first.Range(), first.Value(), second.Range(), second.Value()); ok {
-
-			first.SetEndUnchecked(second.End())
-			first.SetValue(mval)
-			return s.Remove(second).PrevSegment()
-		}
-	}
-	return Iterator{}
-}
-
-// MergeAll attempts to merge all adjacent segments in the set. All existing
-// iterators are invalidated.
-func (s *Set) MergeAll() {
-	seg := s.FirstSegment()
-	if !seg.Ok() {
-		return
-	}
-	next := seg.NextSegment()
-	for next.Ok() {
-		if mseg := s.MergeUnchecked(seg, next); mseg.Ok() {
-			seg, next = mseg, mseg.NextSegment()
-		} else {
-			seg, next = next, next.NextSegment()
-		}
-	}
-}
-
-// MergeRange attempts to merge all adjacent segments that contain a key in the
-// specific range. All existing iterators are invalidated.
-func (s *Set) MergeRange(r Range) {
-	seg := s.LowerBoundSegment(r.Start)
-	if !seg.Ok() {
-		return
-	}
-	next := seg.NextSegment()
-	for next.Ok() && next.Range().Start < r.End {
-		if mseg := s.MergeUnchecked(seg, next); mseg.Ok() {
-			seg, next = mseg, mseg.NextSegment()
-		} else {
-			seg, next = next, next.NextSegment()
-		}
-	}
-}
-
-// MergeAdjacent attempts to merge the segment containing r.Start with its
-// predecessor, and the segment containing r.End-1 with its successor.
-func (s *Set) MergeAdjacent(r Range) {
-	first := s.FindSegment(r.Start)
-	if first.Ok() {
-		if prev := first.PrevSegment(); prev.Ok() {
-			s.Merge(prev, first)
-		}
-	}
-	last := s.FindSegment(r.End - 1)
-	if last.Ok() {
-		if next := last.NextSegment(); next.Ok() {
-			s.Merge(last, next)
-		}
-	}
-}
-
-// Split splits the given segment at the given key and returns iterators to the
-// two resulting segments. All existing iterators (including seg, but not
-// including the returned iterators) are invalidated.
-//
-// If the segment cannot be split at split (because split is at the start or
-// end of the segment's range, so splitting would produce a segment with zero
-// length, or because split falls outside the segment's range altogether),
-// Split panics.
-func (s *Set) Split(seg Iterator, split uint64) (Iterator, Iterator) {
-	if !seg.Range().CanSplitAt(split) {
-		panic(fmt.Sprintf("can't split %v at %v", seg.Range(), split))
-	}
-	return s.SplitUnchecked(seg, split)
-}
-
-// SplitUnchecked splits the given segment at the given key and returns
-// iterators to the two resulting segments. All existing iterators (including
-// seg, but not including the returned iterators) are invalidated.
-//
-// Preconditions: seg.Start() < key < seg.End().
-func (s *Set) SplitUnchecked(seg Iterator, split uint64) (Iterator, Iterator) {
-	val1, val2 := (setFunctions{}).Split(seg.Range(), seg.Value(), split)
-	end2 := seg.End()
-	seg.SetEndUnchecked(split)
-	seg.SetValue(val1)
-	seg2 := s.InsertWithoutMergingUnchecked(seg.NextGap(), Range{split, end2}, val2)
-
-	return seg2.PrevSegment(), seg2
-}
-
-// SplitAt splits the segment straddling split, if one exists. SplitAt returns
-// true if a segment was split and false otherwise. If SplitAt splits a
-// segment, all existing iterators are invalidated.
-func (s *Set) SplitAt(split uint64) bool {
-	if seg := s.FindSegment(split); seg.Ok() && seg.Range().CanSplitAt(split) {
-		s.SplitUnchecked(seg, split)
-		return true
-	}
-	return false
-}
-
-// Isolate ensures that the given segment's range does not escape r by
-// splitting at r.Start and r.End if necessary, and returns an updated iterator
-// to the bounded segment. All existing iterators (including seg, but not
-// including the returned iterators) are invalidated.
-func (s *Set) Isolate(seg Iterator, r Range) Iterator {
-	if seg.Range().CanSplitAt(r.Start) {
-		_, seg = s.SplitUnchecked(seg, r.Start)
-	}
-	if seg.Range().CanSplitAt(r.End) {
-		seg, _ = s.SplitUnchecked(seg, r.End)
-	}
-	return seg
-}
-
-// ApplyContiguous applies a function to a contiguous range of segments,
-// splitting if necessary. The function is applied until the first gap is
-// encountered, at which point the gap is returned. If the function is applied
-// across the entire range, a terminal gap is returned. All existing iterators
-// are invalidated.
-//
-// N.B. The Iterator must not be invalidated by the function.
-func (s *Set) ApplyContiguous(r Range, fn func(seg Iterator)) GapIterator {
-	seg, gap := s.Find(r.Start)
-	if !seg.Ok() {
-		return gap
-	}
-	for {
-		seg = s.Isolate(seg, r)
-		fn(seg)
-		if seg.End() >= r.End {
-			return GapIterator{}
-		}
-		gap = seg.NextGap()
-		if !gap.IsEmpty() {
-			return gap
-		}
-		seg = gap.NextSegment()
-		if !seg.Ok() {
-
-			return GapIterator{}
-		}
-	}
-}
-
-// +stateify savable
-type node struct {
-	// An internal binary tree node looks like:
-	//
-	//   K
-	//  / \
-	// Cl Cr
-	//
-	// where all keys in the subtree rooted by Cl (the left subtree) are less
-	// than K (the key of the parent node), and all keys in the subtree rooted
-	// by Cr (the right subtree) are greater than K.
-	//
-	// An internal B-tree node's indexes work out to look like:
-	//
-	//   K0 K1 K2  ...   Kn-1
-	//  / \/ \/ \  ...  /  \
-	// C0 C1 C2 C3 ... Cn-1 Cn
-	//
-	// where n is nrSegments.
-	nrSegments int
-
-	// parent is a pointer to this node's parent. If this node is root, parent
-	// is nil.
-	parent *node
-
-	// parentIndex is the index of this node in parent.children.
-	parentIndex int
-
-	// Flag for internal nodes that is technically redundant with "children[0]
-	// != nil", but is stored in the first cache line. "hasChildren" rather
-	// than "isLeaf" because false must be the correct value for an empty root.
-	hasChildren bool
-
-	// Nodes store keys and values in separate arrays to maximize locality in
-	// the common case (scanning keys for lookup).
-	keys     [maxDegree - 1]Range
-	values   [maxDegree - 1]noValue
-	children [maxDegree]*node
-}
-
-// firstSegment returns the first segment in the subtree rooted by n.
-//
-// Preconditions: n.nrSegments != 0.
-func (n *node) firstSegment() Iterator {
-	for n.hasChildren {
-		n = n.children[0]
-	}
-	return Iterator{n, 0}
-}
-
-// lastSegment returns the last segment in the subtree rooted by n.
-//
-// Preconditions: n.nrSegments != 0.
-func (n *node) lastSegment() Iterator {
-	for n.hasChildren {
-		n = n.children[n.nrSegments]
-	}
-	return Iterator{n, n.nrSegments - 1}
-}
-
-func (n *node) prevSibling() *node {
-	if n.parent == nil || n.parentIndex == 0 {
-		return nil
-	}
-	return n.parent.children[n.parentIndex-1]
-}
-
-func (n *node) nextSibling() *node {
-	if n.parent == nil || n.parentIndex == n.parent.nrSegments {
-		return nil
-	}
-	return n.parent.children[n.parentIndex+1]
-}
-
-// rebalanceBeforeInsert splits n and its ancestors if they are full, as
-// required for insertion, and returns an updated iterator to the position
-// represented by gap.
-func (n *node) rebalanceBeforeInsert(gap GapIterator) GapIterator {
-	if n.parent != nil {
-		gap = n.parent.rebalanceBeforeInsert(gap)
-	}
-	if n.nrSegments < maxDegree-1 {
-		return gap
-	}
-	if n.parent == nil {
-
-		left := &node{
-			nrSegments:  minDegree - 1,
-			parent:      n,
-			parentIndex: 0,
-			hasChildren: n.hasChildren,
-		}
-		right := &node{
-			nrSegments:  minDegree - 1,
-			parent:      n,
-			parentIndex: 1,
-			hasChildren: n.hasChildren,
-		}
-		copy(left.keys[:minDegree-1], n.keys[:minDegree-1])
-		copy(left.values[:minDegree-1], n.values[:minDegree-1])
-		copy(right.keys[:minDegree-1], n.keys[minDegree:])
-		copy(right.values[:minDegree-1], n.values[minDegree:])
-		n.keys[0], n.values[0] = n.keys[minDegree-1], n.values[minDegree-1]
-		zeroValueSlice(n.values[1:])
-		if n.hasChildren {
-			copy(left.children[:minDegree], n.children[:minDegree])
-			copy(right.children[:minDegree], n.children[minDegree:])
-			zeroNodeSlice(n.children[2:])
-			for i := 0; i < minDegree; i++ {
-				left.children[i].parent = left
-				left.children[i].parentIndex = i
-				right.children[i].parent = right
-				right.children[i].parentIndex = i
-			}
-		}
-		n.nrSegments = 1
-		n.hasChildren = true
-		n.children[0] = left
-		n.children[1] = right
-		if gap.node != n {
-			return gap
-		}
-		if gap.index < minDegree {
-			return GapIterator{left, gap.index}
-		}
-		return GapIterator{right, gap.index - minDegree}
-	}
-
-	copy(n.parent.keys[n.parentIndex+1:], n.parent.keys[n.parentIndex:n.parent.nrSegments])
-	copy(n.parent.values[n.parentIndex+1:], n.parent.values[n.parentIndex:n.parent.nrSegments])
-	n.parent.keys[n.parentIndex], n.parent.values[n.parentIndex] = n.keys[minDegree-1], n.values[minDegree-1]
-	copy(n.parent.children[n.parentIndex+2:], n.parent.children[n.parentIndex+1:n.parent.nrSegments+1])
-	for i := n.parentIndex + 2; i < n.parent.nrSegments+2; i++ {
-		n.parent.children[i].parentIndex = i
-	}
-	sibling := &node{
-		nrSegments:  minDegree - 1,
-		parent:      n.parent,
-		parentIndex: n.parentIndex + 1,
-		hasChildren: n.hasChildren,
-	}
-	n.parent.children[n.parentIndex+1] = sibling
-	n.parent.nrSegments++
-	copy(sibling.keys[:minDegree-1], n.keys[minDegree:])
-	copy(sibling.values[:minDegree-1], n.values[minDegree:])
-	zeroValueSlice(n.values[minDegree-1:])
-	if n.hasChildren {
-		copy(sibling.children[:minDegree], n.children[minDegree:])
-		zeroNodeSlice(n.children[minDegree:])
-		for i := 0; i < minDegree; i++ {
-			sibling.children[i].parent = sibling
-			sibling.children[i].parentIndex = i
-		}
-	}
-	n.nrSegments = minDegree - 1
-
-	if gap.node != n {
-		return gap
-	}
-	if gap.index < minDegree {
-		return gap
-	}
-	return GapIterator{sibling, gap.index - minDegree}
-}
-
-// rebalanceAfterRemove "unsplits" n and its ancestors if they are deficient
-// (contain fewer segments than required by B-tree invariants), as required for
-// removal, and returns an updated iterator to the position represented by gap.
-//
-// Precondition: n is the only node in the tree that may currently violate a
-// B-tree invariant.
-func (n *node) rebalanceAfterRemove(gap GapIterator) GapIterator {
-	for {
-		if n.nrSegments >= minDegree-1 {
-			return gap
-		}
-		if n.parent == nil {
-
-			return gap
-		}
-
-		if sibling := n.prevSibling(); sibling != nil && sibling.nrSegments >= minDegree {
-			copy(n.keys[1:], n.keys[:n.nrSegments])
-			copy(n.values[1:], n.values[:n.nrSegments])
-			n.keys[0] = n.parent.keys[n.parentIndex-1]
-			n.values[0] = n.parent.values[n.parentIndex-1]
-			n.parent.keys[n.parentIndex-1] = sibling.keys[sibling.nrSegments-1]
-			n.parent.values[n.parentIndex-1] = sibling.values[sibling.nrSegments-1]
-			setFunctions{}.ClearValue(&sibling.values[sibling.nrSegments-1])
-			if n.hasChildren {
-				copy(n.children[1:], n.children[:n.nrSegments+1])
-				n.children[0] = sibling.children[sibling.nrSegments]
-				sibling.children[sibling.nrSegments] = nil
-				n.children[0].parent = n
-				n.children[0].parentIndex = 0
-				for i := 1; i < n.nrSegments+2; i++ {
-					n.children[i].parentIndex = i
-				}
-			}
-			n.nrSegments++
-			sibling.nrSegments--
-			if gap.node == sibling && gap.index == sibling.nrSegments {
-				return GapIterator{n, 0}
-			}
-			if gap.node == n {
-				return GapIterator{n, gap.index + 1}
-			}
-			return gap
-		}
-		if sibling := n.nextSibling(); sibling != nil && sibling.nrSegments >= minDegree {
-			n.keys[n.nrSegments] = n.parent.keys[n.parentIndex]
-			n.values[n.nrSegments] = n.parent.values[n.parentIndex]
-			n.parent.keys[n.parentIndex] = sibling.keys[0]
-			n.parent.values[n.parentIndex] = sibling.values[0]
-			copy(sibling.keys[:sibling.nrSegments-1], sibling.keys[1:])
-			copy(sibling.values[:sibling.nrSegments-1], sibling.values[1:])
-			setFunctions{}.ClearValue(&sibling.values[sibling.nrSegments-1])
-			if n.hasChildren {
-				n.children[n.nrSegments+1] = sibling.children[0]
-				copy(sibling.children[:sibling.nrSegments], sibling.children[1:])
-				sibling.children[sibling.nrSegments] = nil
-				n.children[n.nrSegments+1].parent = n
-				n.children[n.nrSegments+1].parentIndex = n.nrSegments + 1
-				for i := 0; i < sibling.nrSegments; i++ {
-					sibling.children[i].parentIndex = i
-				}
-			}
-			n.nrSegments++
-			sibling.nrSegments--
-			if gap.node == sibling {
-				if gap.index == 0 {
-					return GapIterator{n, n.nrSegments}
-				}
-				return GapIterator{sibling, gap.index - 1}
-			}
-			return gap
-		}
-
-		p := n.parent
-		if p.nrSegments == 1 {
-
-			left, right := p.children[0], p.children[1]
-			p.nrSegments = left.nrSegments + right.nrSegments + 1
-			p.hasChildren = left.hasChildren
-			p.keys[left.nrSegments] = p.keys[0]
-			p.values[left.nrSegments] = p.values[0]
-			copy(p.keys[:left.nrSegments], left.keys[:left.nrSegments])
-			copy(p.values[:left.nrSegments], left.values[:left.nrSegments])
-			copy(p.keys[left.nrSegments+1:], right.keys[:right.nrSegments])
-			copy(p.values[left.nrSegments+1:], right.values[:right.nrSegments])
-			if left.hasChildren {
-				copy(p.children[:left.nrSegments+1], left.children[:left.nrSegments+1])
-				copy(p.children[left.nrSegments+1:], right.children[:right.nrSegments+1])
-				for i := 0; i < p.nrSegments+1; i++ {
-					p.children[i].parent = p
-					p.children[i].parentIndex = i
-				}
-			} else {
-				p.children[0] = nil
-				p.children[1] = nil
-			}
-			if gap.node == left {
-				return GapIterator{p, gap.index}
-			}
-			if gap.node == right {
-				return GapIterator{p, gap.index + left.nrSegments + 1}
-			}
-			return gap
-		}
-		// Merge n and either sibling, along with the segment separating the
-		// two, into whichever of the two nodes comes first. This is the
-		// reverse of the non-root splitting case in
-		// node.rebalanceBeforeInsert.
-		var left, right *node
-		if n.parentIndex > 0 {
-			left = n.prevSibling()
-			right = n
-		} else {
-			left = n
-			right = n.nextSibling()
-		}
-
-		if gap.node == right {
-			gap = GapIterator{left, gap.index + left.nrSegments + 1}
-		}
-		left.keys[left.nrSegments] = p.keys[left.parentIndex]
-		left.values[left.nrSegments] = p.values[left.parentIndex]
-		copy(left.keys[left.nrSegments+1:], right.keys[:right.nrSegments])
-		copy(left.values[left.nrSegments+1:], right.values[:right.nrSegments])
-		if left.hasChildren {
-			copy(left.children[left.nrSegments+1:], right.children[:right.nrSegments+1])
-			for i := left.nrSegments + 1; i < left.nrSegments+right.nrSegments+2; i++ {
-				left.children[i].parent = left
-				left.children[i].parentIndex = i
-			}
-		}
-		left.nrSegments += right.nrSegments + 1
-		copy(p.keys[left.parentIndex:], p.keys[left.parentIndex+1:p.nrSegments])
-		copy(p.values[left.parentIndex:], p.values[left.parentIndex+1:p.nrSegments])
-		setFunctions{}.ClearValue(&p.values[p.nrSegments-1])
-		copy(p.children[left.parentIndex+1:], p.children[left.parentIndex+2:p.nrSegments+1])
-		for i := 0; i < p.nrSegments; i++ {
-			p.children[i].parentIndex = i
-		}
-		p.children[p.nrSegments] = nil
-		p.nrSegments--
-
-		n = p
-	}
-}
-
-// A Iterator is conceptually one of:
-//
-// - A pointer to a segment in a set; or
-//
-// - A terminal iterator, which is a sentinel indicating that the end of
-// iteration has been reached.
-//
-// Iterators are copyable values and are meaningfully equality-comparable. The
-// zero value of Iterator is a terminal iterator.
-//
-// Unless otherwise specified, any mutation of a set invalidates all existing
-// iterators into the set.
-type Iterator struct {
-	// node is the node containing the iterated segment. If the iterator is
-	// terminal, node is nil.
-	node *node
-
-	// index is the index of the segment in node.keys/values.
-	index int
-}
-
-// Ok returns true if the iterator is not terminal. All other methods are only
-// valid for non-terminal iterators.
-func (seg Iterator) Ok() bool {
-	return seg.node != nil
-}
-
-// Range returns the iterated segment's range key.
-func (seg Iterator) Range() Range {
-	return seg.node.keys[seg.index]
-}
-
-// Start is equivalent to Range().Start, but should be preferred if only the
-// start of the range is needed.
-func (seg Iterator) Start() uint64 {
-	return seg.node.keys[seg.index].Start
-}
-
-// End is equivalent to Range().End, but should be preferred if only the end of
-// the range is needed.
-func (seg Iterator) End() uint64 {
-	return seg.node.keys[seg.index].End
-}
-
-// SetRangeUnchecked mutates the iterated segment's range key. This operation
-// does not invalidate any iterators.
-//
-// Preconditions:
-//
-// - r.Length() > 0.
-//
-// - The new range must not overlap an existing one: If seg.NextSegment().Ok(),
-// then r.end <= seg.NextSegment().Start(); if seg.PrevSegment().Ok(), then
-// r.start >= seg.PrevSegment().End().
-func (seg Iterator) SetRangeUnchecked(r Range) {
-	seg.node.keys[seg.index] = r
-}
-
-// SetRange mutates the iterated segment's range key. If the new range would
-// cause the iterated segment to overlap another segment, or if the new range
-// is invalid, SetRange panics. This operation does not invalidate any
-// iterators.
-func (seg Iterator) SetRange(r Range) {
-	if r.Length() <= 0 {
-		panic(fmt.Sprintf("invalid segment range %v", r))
-	}
-	if prev := seg.PrevSegment(); prev.Ok() && r.Start < prev.End() {
-		panic(fmt.Sprintf("new segment range %v overlaps segment range %v", r, prev.Range()))
-	}
-	if next := seg.NextSegment(); next.Ok() && r.End > next.Start() {
-		panic(fmt.Sprintf("new segment range %v overlaps segment range %v", r, next.Range()))
-	}
-	seg.SetRangeUnchecked(r)
-}
-
-// SetStartUnchecked mutates the iterated segment's start. This operation does
-// not invalidate any iterators.
-//
-// Preconditions: The new start must be valid: start < seg.End(); if
-// seg.PrevSegment().Ok(), then start >= seg.PrevSegment().End().
-func (seg Iterator) SetStartUnchecked(start uint64) {
-	seg.node.keys[seg.index].Start = start
-}
-
-// SetStart mutates the iterated segment's start. If the new start value would
-// cause the iterated segment to overlap another segment, or would result in an
-// invalid range, SetStart panics. This operation does not invalidate any
-// iterators.
-func (seg Iterator) SetStart(start uint64) {
-	if start >= seg.End() {
-		panic(fmt.Sprintf("new start %v would invalidate segment range %v", start, seg.Range()))
-	}
-	if prev := seg.PrevSegment(); prev.Ok() && start < prev.End() {
-		panic(fmt.Sprintf("new start %v would cause segment range %v to overlap segment range %v", start, seg.Range(), prev.Range()))
-	}
-	seg.SetStartUnchecked(start)
-}
-
-// SetEndUnchecked mutates the iterated segment's end. This operation does not
-// invalidate any iterators.
-//
-// Preconditions: The new end must be valid: end > seg.Start(); if
-// seg.NextSegment().Ok(), then end <= seg.NextSegment().Start().
-func (seg Iterator) SetEndUnchecked(end uint64) {
-	seg.node.keys[seg.index].End = end
-}
-
-// SetEnd mutates the iterated segment's end. If the new end value would cause
-// the iterated segment to overlap another segment, or would result in an
-// invalid range, SetEnd panics. This operation does not invalidate any
-// iterators.
-func (seg Iterator) SetEnd(end uint64) {
-	if end <= seg.Start() {
-		panic(fmt.Sprintf("new end %v would invalidate segment range %v", end, seg.Range()))
-	}
-	if next := seg.NextSegment(); next.Ok() && end > next.Start() {
-		panic(fmt.Sprintf("new end %v would cause segment range %v to overlap segment range %v", end, seg.Range(), next.Range()))
-	}
-	seg.SetEndUnchecked(end)
-}
-
-// Value returns a copy of the iterated segment's value.
-func (seg Iterator) Value() noValue {
-	return seg.node.values[seg.index]
-}
-
-// ValuePtr returns a pointer to the iterated segment's value. The pointer is
-// invalidated if the iterator is invalidated. This operation does not
-// invalidate any iterators.
-func (seg Iterator) ValuePtr() *noValue {
-	return &seg.node.values[seg.index]
-}
-
-// SetValue mutates the iterated segment's value. This operation does not
-// invalidate any iterators.
-func (seg Iterator) SetValue(val noValue) {
-	seg.node.values[seg.index] = val
-}
-
-// PrevSegment returns the iterated segment's predecessor. If there is no
-// preceding segment, PrevSegment returns a terminal iterator.
-func (seg Iterator) PrevSegment() Iterator {
-	if seg.node.hasChildren {
-		return seg.node.children[seg.index].lastSegment()
-	}
-	if seg.index > 0 {
-		return Iterator{seg.node, seg.index - 1}
-	}
-	if seg.node.parent == nil {
-		return Iterator{}
-	}
-	return segmentBeforePosition(seg.node.parent, seg.node.parentIndex)
-}
-
-// NextSegment returns the iterated segment's successor. If there is no
-// succeeding segment, NextSegment returns a terminal iterator.
-func (seg Iterator) NextSegment() Iterator {
-	if seg.node.hasChildren {
-		return seg.node.children[seg.index+1].firstSegment()
-	}
-	if seg.index < seg.node.nrSegments-1 {
-		return Iterator{seg.node, seg.index + 1}
-	}
-	if seg.node.parent == nil {
-		return Iterator{}
-	}
-	return segmentAfterPosition(seg.node.parent, seg.node.parentIndex)
-}
-
-// PrevGap returns the gap immediately before the iterated segment.
-func (seg Iterator) PrevGap() GapIterator {
-	if seg.node.hasChildren {
-
-		return seg.node.children[seg.index].lastSegment().NextGap()
-	}
-	return GapIterator{seg.node, seg.index}
-}
-
-// NextGap returns the gap immediately after the iterated segment.
-func (seg Iterator) NextGap() GapIterator {
-	if seg.node.hasChildren {
-		return seg.node.children[seg.index+1].firstSegment().PrevGap()
-	}
-	return GapIterator{seg.node, seg.index + 1}
-}
-
-// PrevNonEmpty returns the iterated segment's predecessor if it is adjacent,
-// or the gap before the iterated segment otherwise. If seg.Start() ==
-// Functions.MinKey(), PrevNonEmpty will return two terminal iterators.
-// Otherwise, exactly one of the iterators returned by PrevNonEmpty will be
-// non-terminal.
-func (seg Iterator) PrevNonEmpty() (Iterator, GapIterator) {
-	gap := seg.PrevGap()
-	if gap.Range().Length() != 0 {
-		return Iterator{}, gap
-	}
-	return gap.PrevSegment(), GapIterator{}
-}
-
-// NextNonEmpty returns the iterated segment's successor if it is adjacent, or
-// the gap after the iterated segment otherwise. If seg.End() ==
-// Functions.MaxKey(), NextNonEmpty will return two terminal iterators.
-// Otherwise, exactly one of the iterators returned by NextNonEmpty will be
-// non-terminal.
-func (seg Iterator) NextNonEmpty() (Iterator, GapIterator) {
-	gap := seg.NextGap()
-	if gap.Range().Length() != 0 {
-		return Iterator{}, gap
-	}
-	return gap.NextSegment(), GapIterator{}
-}
-
-// A GapIterator is conceptually one of:
-//
-// - A pointer to a position between two segments, before the first segment, or
-// after the last segment in a set, called a *gap*; or
-//
-// - A terminal iterator, which is a sentinel indicating that the end of
-// iteration has been reached.
-//
-// Note that the gap between two adjacent segments exists (iterators to it are
-// non-terminal), but has a length of zero. GapIterator.IsEmpty returns true
-// for such gaps. An empty set contains a single gap, spanning the entire range
-// of the set's keys.
-//
-// GapIterators are copyable values and are meaningfully equality-comparable.
-// The zero value of GapIterator is a terminal iterator.
-//
-// Unless otherwise specified, any mutation of a set invalidates all existing
-// iterators into the set.
-type GapIterator struct {
-	// The representation of a GapIterator is identical to that of an Iterator,
-	// except that index corresponds to positions between segments in the same
-	// way as for node.children (see comment for node.nrSegments).
-	node  *node
-	index int
-}
-
-// Ok returns true if the iterator is not terminal. All other methods are only
-// valid for non-terminal iterators.
-func (gap GapIterator) Ok() bool {
-	return gap.node != nil
-}
-
-// Range returns the range spanned by the iterated gap.
-func (gap GapIterator) Range() Range {
-	return Range{gap.Start(), gap.End()}
-}
-
-// Start is equivalent to Range().Start, but should be preferred if only the
-// start of the range is needed.
-func (gap GapIterator) Start() uint64 {
-	if ps := gap.PrevSegment(); ps.Ok() {
-		return ps.End()
-	}
-	return setFunctions{}.MinKey()
-}
-
-// End is equivalent to Range().End, but should be preferred if only the end of
-// the range is needed.
-func (gap GapIterator) End() uint64 {
-	if ns := gap.NextSegment(); ns.Ok() {
-		return ns.Start()
-	}
-	return setFunctions{}.MaxKey()
-}
-
-// IsEmpty returns true if the iterated gap is empty (that is, the "gap" is
-// between two adjacent segments.)
-func (gap GapIterator) IsEmpty() bool {
-	return gap.Range().Length() == 0
-}
-
-// PrevSegment returns the segment immediately before the iterated gap. If no
-// such segment exists, PrevSegment returns a terminal iterator.
-func (gap GapIterator) PrevSegment() Iterator {
-	return segmentBeforePosition(gap.node, gap.index)
-}
-
-// NextSegment returns the segment immediately after the iterated gap. If no
-// such segment exists, NextSegment returns a terminal iterator.
-func (gap GapIterator) NextSegment() Iterator {
-	return segmentAfterPosition(gap.node, gap.index)
-}
-
-// PrevGap returns the iterated gap's predecessor. If no such gap exists,
-// PrevGap returns a terminal iterator.
-func (gap GapIterator) PrevGap() GapIterator {
-	seg := gap.PrevSegment()
-	if !seg.Ok() {
-		return GapIterator{}
-	}
-	return seg.PrevGap()
-}
-
-// NextGap returns the iterated gap's successor. If no such gap exists, NextGap
-// returns a terminal iterator.
-func (gap GapIterator) NextGap() GapIterator {
-	seg := gap.NextSegment()
-	if !seg.Ok() {
-		return GapIterator{}
-	}
-	return seg.NextGap()
-}
-
-// segmentBeforePosition returns the predecessor segment of the position given
-// by n.children[i], which may or may not contain a child. If no such segment
-// exists, segmentBeforePosition returns a terminal iterator.
-func segmentBeforePosition(n *node, i int) Iterator {
-	for i == 0 {
-		if n.parent == nil {
-			return Iterator{}
-		}
-		n, i = n.parent, n.parentIndex
-	}
-	return Iterator{n, i - 1}
-}
-
-// segmentAfterPosition returns the successor segment of the position given by
-// n.children[i], which may or may not contain a child. If no such segment
-// exists, segmentAfterPosition returns a terminal iterator.
-func segmentAfterPosition(n *node, i int) Iterator {
-	for i == n.nrSegments {
-		if n.parent == nil {
-			return Iterator{}
-		}
-		n, i = n.parent, n.parentIndex
-	}
-	return Iterator{n, i}
-}
-
-func zeroValueSlice(slice []noValue) {
-
-	for i := range slice {
-		setFunctions{}.ClearValue(&slice[i])
-	}
-}
-
-func zeroNodeSlice(slice []*node) {
-	for i := range slice {
-		slice[i] = nil
-	}
-}
-
-// String stringifies a Set for debugging.
-func (s *Set) String() string {
-	return s.root.String()
-}
-
-// String stringifies a node (and all of its children) for debugging.
-func (n *node) String() string {
-	var buf bytes.Buffer
-	n.writeDebugString(&buf, "")
-	return buf.String()
-}
-
-func (n *node) writeDebugString(buf *bytes.Buffer, prefix string) {
-	if n.hasChildren != (n.nrSegments > 0 && n.children[0] != nil) {
-		buf.WriteString(prefix)
-		buf.WriteString(fmt.Sprintf("WARNING: inconsistent value of hasChildren: got %v, want %v\n", n.hasChildren, !n.hasChildren))
-	}
-	for i := 0; i < n.nrSegments; i++ {
-		if child := n.children[i]; child != nil {
-			cprefix := fmt.Sprintf("%s- % 3d ", prefix, i)
-			if child.parent != n || child.parentIndex != i {
-				buf.WriteString(cprefix)
-				buf.WriteString(fmt.Sprintf("WARNING: inconsistent linkage to parent: got (%p, %d), want (%p, %d)\n", child.parent, child.parentIndex, n, i))
-			}
-			child.writeDebugString(buf, fmt.Sprintf("%s- % 3d ", prefix, i))
-		}
-		buf.WriteString(prefix)
-		buf.WriteString(fmt.Sprintf("- % 3d: %v => %v\n", i, n.keys[i], n.values[i]))
-	}
-	if child := n.children[n.nrSegments]; child != nil {
-		child.writeDebugString(buf, fmt.Sprintf("%s- % 3d ", prefix, n.nrSegments))
-	}
-}
-
-// SegmentDataSlices represents segments from a set as slices of start, end, and
-// values. SegmentDataSlices is primarily used as an intermediate representation
-// for save/restore and the layout here is optimized for that.
-//
-// +stateify savable
-type SegmentDataSlices struct {
-	Start  []uint64
-	End    []uint64
-	Values []noValue
-}
-
-// ExportSortedSlice returns a copy of all segments in the given set, in ascending
-// key order.
-func (s *Set) ExportSortedSlices() *SegmentDataSlices {
-	var sds SegmentDataSlices
-	for seg := s.FirstSegment(); seg.Ok(); seg = seg.NextSegment() {
-		sds.Start = append(sds.Start, seg.Start())
-		sds.End = append(sds.End, seg.End())
-		sds.Values = append(sds.Values, seg.Value())
-	}
-	sds.Start = sds.Start[:len(sds.Start):len(sds.Start)]
-	sds.End = sds.End[:len(sds.End):len(sds.End)]
-	sds.Values = sds.Values[:len(sds.Values):len(sds.Values)]
-	return &sds
-}
-
-// ImportSortedSlice initializes the given set from the given slice.
-//
-// Preconditions: s must be empty. sds must represent a valid set (the segments
-// in sds must have valid lengths that do not overlap). The segments in sds
-// must be sorted in ascending key order.
-func (s *Set) ImportSortedSlices(sds *SegmentDataSlices) error {
-	if !s.IsEmpty() {
-		return fmt.Errorf("cannot import into non-empty set %v", s)
-	}
-	gap := s.FirstGap()
-	for i := range sds.Start {
-		r := Range{sds.Start[i], sds.End[i]}
-		if !gap.Range().IsSupersetOf(r) {
-			return fmt.Errorf("segment overlaps a preceding segment or is incorrectly sorted: [%d, %d) => %v", sds.Start[i], sds.End[i], sds.Values[i])
-		}
-		gap = s.InsertWithoutMerging(gap, r, sds.Values[i]).NextGap()
-	}
-	return nil
-}
-func (s *Set) saveRoot() *SegmentDataSlices {
-	return s.ExportSortedSlices()
-}
-
-func (s *Set) loadRoot(sds *SegmentDataSlices) {
-	if err := s.ImportSortedSlices(sds); err != nil {
-		panic(err)
-	}
-}
diff --git a/pkg/sentry/fs/binder/binder.go b/pkg/sentry/fs/binder/binder.go
deleted file mode 100644
index eef54d787..000000000
--- a/pkg/sentry/fs/binder/binder.go
+++ /dev/null
@@ -1,260 +0,0 @@
-// Copyright 2018 The gVisor Authors.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-// Package binder implements Android Binder IPC module.
-package binder
-
-import (
-	"sync"
-
-	"gvisor.dev/gvisor/pkg/abi/linux"
-	"gvisor.dev/gvisor/pkg/sentry/arch"
-	"gvisor.dev/gvisor/pkg/sentry/context"
-	"gvisor.dev/gvisor/pkg/sentry/fs"
-	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
-	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/memmap"
-	"gvisor.dev/gvisor/pkg/sentry/pgalloc"
-	"gvisor.dev/gvisor/pkg/sentry/platform"
-	"gvisor.dev/gvisor/pkg/sentry/usage"
-	"gvisor.dev/gvisor/pkg/sentry/usermem"
-	"gvisor.dev/gvisor/pkg/syserror"
-	"gvisor.dev/gvisor/pkg/waiter"
-)
-
-const (
-	currentProtocolVersion = 8
-
-	// mmapSizeLimit is the upper limit for mapped memory size in Binder.
-	mmapSizeLimit = 4 * 1024 * 1024 // 4MB
-)
-
-// Device implements fs.InodeOperations.
-//
-// +stateify savable
-type Device struct {
-	fsutil.InodeGenericChecker       `state:"nosave"`
-	fsutil.InodeNoExtendedAttributes `state:"nosave"`
-	fsutil.InodeNoopAllocate         `state:"nosave"`
-	fsutil.InodeNoopRelease          `state:"nosave"`
-	fsutil.InodeNoopTruncate         `state:"nosave"`
-	fsutil.InodeNoopWriteOut         `state:"nosave"`
-	fsutil.InodeNotDirectory         `state:"nosave"`
-	fsutil.InodeNotMappable          `state:"nosave"`
-	fsutil.InodeNotSocket            `state:"nosave"`
-	fsutil.InodeNotSymlink           `state:"nosave"`
-	fsutil.InodeVirtual              `state:"nosave"`
-
-	fsutil.InodeSimpleAttributes
-}
-
-var _ fs.InodeOperations = (*Device)(nil)
-
-// NewDevice creates and initializes a Device structure.
-func NewDevice(ctx context.Context, owner fs.FileOwner, fp fs.FilePermissions) *Device {
-	return &Device{
-		InodeSimpleAttributes: fsutil.NewInodeSimpleAttributes(ctx, owner, fp, 0),
-	}
-}
-
-// GetFile implements fs.InodeOperations.GetFile.
-//
-// TODO(b/30946773): Add functionality to GetFile: Additional fields will be
-// needed in the Device structure, initialize them here. Also, Device will need
-// to keep track of the created Procs in order to implement BINDER_READ_WRITE
-// ioctl.
-func (bd *Device) GetFile(ctx context.Context, d *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
-	return fs.NewFile(ctx, d, flags, &Proc{
-		bd:   bd,
-		task: kernel.TaskFromContext(ctx),
-		mfp:  pgalloc.MemoryFileProviderFromContext(ctx),
-	}), nil
-}
-
-// Proc implements fs.FileOperations and fs.IoctlGetter.
-//
-// +stateify savable
-type Proc struct {
-	fsutil.FileNoFsync              `state:"nosave"`
-	fsutil.FileNoSplice             `state:"nosave"`
-	fsutil.FileNotDirReaddir        `state:"nosave"`
-	fsutil.FileUseInodeUnstableAttr `state:"nosave"`
-	waiter.AlwaysReady              `state:"nosave"`
-
-	bd   *Device
-	task *kernel.Task
-	mfp  pgalloc.MemoryFileProvider
-
-	// mu protects fr.
-	mu sync.Mutex `state:"nosave"`
-
-	// mapped is memory allocated from mfp.MemoryFile() by AddMapping.
-	mapped platform.FileRange
-}
-
-// Release implements fs.FileOperations.Release.
-func (bp *Proc) Release() {
-	bp.mu.Lock()
-	defer bp.mu.Unlock()
-	if bp.mapped.Length() != 0 {
-		bp.mfp.MemoryFile().DecRef(bp.mapped)
-	}
-}
-
-// Seek implements fs.FileOperations.Seek.
-//
-// Binder doesn't support seek operation (unless in debug mode).
-func (bp *Proc) Seek(ctx context.Context, file *fs.File, whence fs.SeekWhence, offset int64) (int64, error) {
-	return offset, syserror.EOPNOTSUPP
-}
-
-// Read implements fs.FileOperations.Read.
-//
-// Binder doesn't support read operation (unless in debug mode).
-func (bp *Proc) Read(ctx context.Context, file *fs.File, dst usermem.IOSequence, offset int64) (int64, error) {
-	return 0, syserror.EOPNOTSUPP
-}
-
-// Write implements fs.FileOperations.Write.
-//
-// Binder doesn't support write operation.
-func (bp *Proc) Write(ctx context.Context, file *fs.File, src usermem.IOSequence, offset int64) (int64, error) {
-	return 0, syserror.EOPNOTSUPP
-}
-
-// Flush implements fs.FileOperations.Flush.
-//
-// TODO(b/30946773): Implement.
-func (bp *Proc) Flush(ctx context.Context, file *fs.File) error {
-	return nil
-}
-
-// ConfigureMMap implements fs.FileOperations.ConfigureMMap.
-func (bp *Proc) ConfigureMMap(ctx context.Context, file *fs.File, opts *memmap.MMapOpts) error {
-	// Compare drivers/android/binder.c:binder_mmap().
-	if caller := kernel.TaskFromContext(ctx); caller != bp.task {
-		return syserror.EINVAL
-	}
-	if opts.Length > mmapSizeLimit {
-		opts.Length = mmapSizeLimit
-	}
-	opts.MaxPerms.Write = false
-
-	// TODO(b/30946773): Binder sets VM_DONTCOPY, preventing the created vma
-	// from being copied across fork(), but we don't support this yet. As
-	// a result, MMs containing a Binder mapping cannot be forked (MM.Fork will
-	// fail when AddMapping returns EBUSY).
-
-	return fsutil.GenericConfigureMMap(file, bp, opts)
-}
-
-// Ioctl implements fs.FileOperations.Ioctl.
-//
-// TODO(b/30946773): Implement.
-func (bp *Proc) Ioctl(ctx context.Context, _ *fs.File, io usermem.IO, args arch.SyscallArguments) (uintptr, error) {
-	// Switch on ioctl request.
-	switch uint32(args[1].Int()) {
-	case linux.BinderVersionIoctl:
-		ver := &linux.BinderVersion{
-			ProtocolVersion: currentProtocolVersion,
-		}
-		// Copy result to user-space.
-		_, err := usermem.CopyObjectOut(ctx, io, args[2].Pointer(), ver, usermem.IOOpts{
-			AddressSpaceActive: true,
-		})
-		return 0, err
-	case linux.BinderWriteReadIoctl:
-		// TODO(b/30946773): Implement.
-		fallthrough
-	case linux.BinderSetIdleTimeoutIoctl:
-		// TODO(b/30946773): Implement.
-		fallthrough
-	case linux.BinderSetMaxThreadsIoctl:
-		// TODO(b/30946773): Implement.
-		fallthrough
-	case linux.BinderSetIdlePriorityIoctl:
-		// TODO(b/30946773): Implement.
-		fallthrough
-	case linux.BinderSetContextMgrIoctl:
-		// TODO(b/30946773): Implement.
-		fallthrough
-	case linux.BinderThreadExitIoctl:
-		// TODO(b/30946773): Implement.
-		return 0, syserror.ENOSYS
-	default:
-		// Ioctls irrelevant to Binder.
-		return 0, syserror.EINVAL
-	}
-}
-
-// AddMapping implements memmap.Mappable.AddMapping.
-func (bp *Proc) AddMapping(ctx context.Context, ms memmap.MappingSpace, ar usermem.AddrRange, offset uint64, _ bool) error {
-	bp.mu.Lock()
-	defer bp.mu.Unlock()
-	if bp.mapped.Length() != 0 {
-		// mmap has been called before, which binder_mmap() doesn't like.
-		return syserror.EBUSY
-	}
-	// Binder only allocates and maps a single page up-front
-	// (drivers/android/binder.c:binder_mmap() => binder_update_page_range()).
-	fr, err := bp.mfp.MemoryFile().Allocate(usermem.PageSize, usage.Anonymous)
-	if err != nil {
-		return err
-	}
-	bp.mapped = fr
-	return nil
-}
-
-// RemoveMapping implements memmap.Mappable.RemoveMapping.
-func (*Proc) RemoveMapping(context.Context, memmap.MappingSpace, usermem.AddrRange, uint64, bool) {
-	// Nothing to do. Notably, we don't free bp.mapped to allow another mmap.
-}
-
-// CopyMapping implements memmap.Mappable.CopyMapping.
-func (bp *Proc) CopyMapping(ctx context.Context, ms memmap.MappingSpace, srcAR, dstAR usermem.AddrRange, offset uint64, _ bool) error {
-	// Nothing to do. Notably, this is one case where CopyMapping isn't
-	// equivalent to AddMapping, as AddMapping would return EBUSY.
-	return nil
-}
-
-// Translate implements memmap.Mappable.Translate.
-func (bp *Proc) Translate(ctx context.Context, required, optional memmap.MappableRange, at usermem.AccessType) ([]memmap.Translation, error) {
-	// TODO(b/30946773): In addition to the page initially allocated and mapped
-	// in AddMapping (Linux: binder_mmap), Binder allocates and maps pages for
-	// each transaction (Linux: binder_ioctl => binder_ioctl_write_read =>
-	// binder_thread_write => binder_transaction => binder_alloc_buf =>
-	// binder_update_page_range). Since we don't actually implement
-	// BinderWriteReadIoctl (Linux: BINDER_WRITE_READ), we only ever have the
-	// first page.
-	var err error
-	if required.End > usermem.PageSize {
-		err = &memmap.BusError{syserror.EFAULT}
-	}
-	if required.Start == 0 {
-		return []memmap.Translation{
-			{
-				Source: memmap.MappableRange{0, usermem.PageSize},
-				File:   bp.mfp.MemoryFile(),
-				Offset: bp.mapped.Start,
-				Perms:  usermem.AnyAccess,
-			},
-		}, err
-	}
-	return nil, err
-}
-
-// InvalidateUnsavable implements memmap.Mappable.InvalidateUnsavable.
-func (bp *Proc) InvalidateUnsavable(ctx context.Context) error {
-	return nil
-}
diff --git a/pkg/sentry/fs/binder/binder_state_autogen.go b/pkg/sentry/fs/binder/binder_state_autogen.go
deleted file mode 100755
index 1f321e3b6..000000000
--- a/pkg/sentry/fs/binder/binder_state_autogen.go
+++ /dev/null
@@ -1,40 +0,0 @@
-// automatically generated by stateify.
-
-package binder
-
-import (
-	"gvisor.dev/gvisor/pkg/state"
-)
-
-func (x *Device) beforeSave() {}
-func (x *Device) save(m state.Map) {
-	x.beforeSave()
-	m.Save("InodeSimpleAttributes", &x.InodeSimpleAttributes)
-}
-
-func (x *Device) afterLoad() {}
-func (x *Device) load(m state.Map) {
-	m.Load("InodeSimpleAttributes", &x.InodeSimpleAttributes)
-}
-
-func (x *Proc) beforeSave() {}
-func (x *Proc) save(m state.Map) {
-	x.beforeSave()
-	m.Save("bd", &x.bd)
-	m.Save("task", &x.task)
-	m.Save("mfp", &x.mfp)
-	m.Save("mapped", &x.mapped)
-}
-
-func (x *Proc) afterLoad() {}
-func (x *Proc) load(m state.Map) {
-	m.Load("bd", &x.bd)
-	m.Load("task", &x.task)
-	m.Load("mfp", &x.mfp)
-	m.Load("mapped", &x.mapped)
-}
-
-func init() {
-	state.Register("binder.Device", (*Device)(nil), state.Fns{Save: (*Device).save, Load: (*Device).load})
-	state.Register("binder.Proc", (*Proc)(nil), state.Fns{Save: (*Proc).save, Load: (*Proc).load})
-}
diff --git a/pkg/sentry/fs/dev/dev.go b/pkg/sentry/fs/dev/dev.go
index fb6c30ff0..d4bbd9807 100644
--- a/pkg/sentry/fs/dev/dev.go
+++ b/pkg/sentry/fs/dev/dev.go
@@ -20,8 +20,6 @@ import (
 
 	"gvisor.dev/gvisor/pkg/sentry/context"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
-	"gvisor.dev/gvisor/pkg/sentry/fs/ashmem"
-	"gvisor.dev/gvisor/pkg/sentry/fs/binder"
 	"gvisor.dev/gvisor/pkg/sentry/fs/ramfs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/tmpfs"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
@@ -81,7 +79,7 @@ func newSymlink(ctx context.Context, target string, msrc *fs.MountSource) *fs.In
 }
 
 // New returns the root node of a device filesystem.
-func New(ctx context.Context, msrc *fs.MountSource, binderEnabled bool, ashmemEnabled bool) *fs.Inode {
+func New(ctx context.Context, msrc *fs.MountSource) *fs.Inode {
 	contents := map[string]*fs.Inode{
 		"fd":     newSymlink(ctx, "/proc/self/fd", msrc),
 		"stdin":  newSymlink(ctx, "/proc/self/fd/0", msrc),
@@ -118,16 +116,6 @@ func New(ctx context.Context, msrc *fs.MountSource, binderEnabled bool, ashmemEn
 		"ptmx": newSymlink(ctx, "pts/ptmx", msrc),
 	}
 
-	if binderEnabled {
-		binder := binder.NewDevice(ctx, fs.RootOwner, fs.FilePermsFromMode(0666))
-		contents["binder"] = newCharacterDevice(ctx, binder, msrc)
-	}
-
-	if ashmemEnabled {
-		ashmem := ashmem.NewDevice(ctx, fs.RootOwner, fs.FilePermsFromMode(0666))
-		contents["ashmem"] = newCharacterDevice(ctx, ashmem, msrc)
-	}
-
 	iops := ramfs.NewDir(ctx, contents, fs.RootOwner, fs.FilePermsFromMode(0555))
 	return fs.NewInode(ctx, iops, msrc, fs.StableAttr{
 		DeviceID:  devDevice.DeviceID(),
diff --git a/pkg/sentry/fs/dev/fs.go b/pkg/sentry/fs/dev/fs.go
index cbc2c2f9b..55f8af704 100644
--- a/pkg/sentry/fs/dev/fs.go
+++ b/pkg/sentry/fs/dev/fs.go
@@ -15,19 +15,10 @@
 package dev
 
 import (
-	"strconv"
-
 	"gvisor.dev/gvisor/pkg/sentry/context"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
-	"gvisor.dev/gvisor/pkg/syserror"
 )
 
-// Optional key containing boolean flag which specifies if Android Binder IPC should be enabled.
-const binderEnabledKey = "binder_enabled"
-
-// Optional key containing boolean flag which specifies if Android ashmem should be enabled.
-const ashmemEnabledKey = "ashmem_enabled"
-
 // filesystem is a devtmpfs.
 //
 // +stateify savable
@@ -67,33 +58,7 @@ func (*filesystem) Flags() fs.FilesystemFlags {
 
 // Mount returns a devtmpfs root that can be positioned in the vfs.
 func (f *filesystem) Mount(ctx context.Context, device string, flags fs.MountSourceFlags, data string, _ interface{}) (*fs.Inode, error) {
-	// device is always ignored.
 	// devtmpfs backed by ramfs ignores bad options. See fs/ramfs/inode.c:ramfs_parse_options.
 	//  -> we should consider parsing the mode and backing devtmpfs by this.
-
-	// Parse generic comma-separated key=value options.
-	options := fs.GenericMountSourceOptions(data)
-
-	// binerEnabledKey is optional and binder is disabled by default.
-	binderEnabled := false
-	if beStr, exists := options[binderEnabledKey]; exists {
-		var err error
-		binderEnabled, err = strconv.ParseBool(beStr)
-		if err != nil {
-			return nil, syserror.EINVAL
-		}
-	}
-
-	// ashmemEnabledKey is optional and ashmem is disabled by default.
-	ashmemEnabled := false
-	if aeStr, exists := options[ashmemEnabledKey]; exists {
-		var err error
-		ashmemEnabled, err = strconv.ParseBool(aeStr)
-		if err != nil {
-			return nil, syserror.EINVAL
-		}
-	}
-
-	// Construct the devtmpfs root.
-	return New(ctx, fs.NewNonCachingMountSource(ctx, f, flags), binderEnabled, ashmemEnabled), nil
+	return New(ctx, fs.NewNonCachingMountSource(ctx, f, flags)), nil
 }
diff --git a/pkg/sentry/fs/dirent.go b/pkg/sentry/fs/dirent.go
index 28651e58b..fbca06761 100644
--- a/pkg/sentry/fs/dirent.go
+++ b/pkg/sentry/fs/dirent.go
@@ -229,11 +229,13 @@ func newDirent(inode *Inode, name string) *Dirent {
 	if inode != nil {
 		inode.MountSource.IncDirentRefs()
 	}
-	return &Dirent{
+	d := Dirent{
 		Inode:    inode,
 		name:     name,
 		children: make(map[string]*refs.WeakRef),
 	}
+	d.EnableLeakCheck("fs.Dirent")
+	return &d
 }
 
 // NewNegativeDirent returns a new root negative Dirent. Otherwise same as NewDirent.
diff --git a/pkg/sentry/fs/file.go b/pkg/sentry/fs/file.go
index 8e1f5674d..bb8117f89 100644
--- a/pkg/sentry/fs/file.go
+++ b/pkg/sentry/fs/file.go
@@ -130,14 +130,15 @@ type File struct {
 // to false respectively.
 func NewFile(ctx context.Context, dirent *Dirent, flags FileFlags, fops FileOperations) *File {
 	dirent.IncRef()
-	f := &File{
+	f := File{
 		UniqueID:       uniqueid.GlobalFromContext(ctx),
 		Dirent:         dirent,
 		FileOperations: fops,
 		flags:          flags,
 	}
 	f.mu.Init()
-	return f
+	f.EnableLeakCheck("fs.File")
+	return &f
 }
 
 // DecRef destroys the File when it is no longer referenced.
diff --git a/pkg/sentry/fs/file_overlay.go b/pkg/sentry/fs/file_overlay.go
index c6cbd5631..9820f0b13 100644
--- a/pkg/sentry/fs/file_overlay.go
+++ b/pkg/sentry/fs/file_overlay.go
@@ -347,13 +347,14 @@ func (*overlayFileOperations) ConfigureMMap(ctx context.Context, file *File, opt
 		// preventing us from saving a proper inode mapping for the
 		// file.
 		file.IncRef()
-		id := &overlayMappingIdentity{
+		id := overlayMappingIdentity{
 			id:          opts.MappingIdentity,
 			overlayFile: file,
 		}
+		id.EnableLeakCheck("fs.overlayMappingIdentity")
 
 		// Swap out the old MappingIdentity for the wrapped one.
-		opts.MappingIdentity = id
+		opts.MappingIdentity = &id
 		return nil
 	}
 
diff --git a/pkg/sentry/fs/gofer/handles.go b/pkg/sentry/fs/gofer/handles.go
index b87c4f150..27eeae3d9 100644
--- a/pkg/sentry/fs/gofer/handles.go
+++ b/pkg/sentry/fs/gofer/handles.go
@@ -79,11 +79,12 @@ func newHandles(ctx context.Context, file contextFile, flags fs.FileFlags) (*han
 		newFile.close(ctx)
 		return nil, err
 	}
-	h := &handles{
+	h := handles{
 		File: newFile,
 		Host: hostFile,
 	}
-	return h, nil
+	h.EnableLeakCheck("gofer.handles")
+	return &h, nil
 }
 
 type handleReadWriter struct {
diff --git a/pkg/sentry/fs/gofer/path.go b/pkg/sentry/fs/gofer/path.go
index b91386909..8c17603f8 100644
--- a/pkg/sentry/fs/gofer/path.go
+++ b/pkg/sentry/fs/gofer/path.go
@@ -145,16 +145,17 @@ func (i *inodeOperations) Create(ctx context.Context, dir *fs.Inode, name string
 	defer d.DecRef()
 
 	// Construct the new file, caching the handles if allowed.
-	h := &handles{
+	h := handles{
 		File: newFile,
 		Host: hostFile,
 	}
+	h.EnableLeakCheck("gofer.handles")
 	if iops.fileState.canShareHandles() {
 		iops.fileState.handlesMu.Lock()
-		iops.fileState.setSharedHandlesLocked(flags, h)
+		iops.fileState.setSharedHandlesLocked(flags, &h)
 		iops.fileState.handlesMu.Unlock()
 	}
-	return NewFile(ctx, d, name, flags, iops, h), nil
+	return NewFile(ctx, d, name, flags, iops, &h), nil
 }
 
 // CreateLink uses Create to create a symlink between oldname and newname.
diff --git a/pkg/sentry/fs/gofer/session.go b/pkg/sentry/fs/gofer/session.go
index 9f7660ed1..69d08a627 100644
--- a/pkg/sentry/fs/gofer/session.go
+++ b/pkg/sentry/fs/gofer/session.go
@@ -241,7 +241,7 @@ func Root(ctx context.Context, dev string, filesystem fs.Filesystem, superBlockF
 	}
 
 	// Construct the session.
-	s := &session{
+	s := session{
 		connID:          dev,
 		msize:           o.msize,
 		version:         o.version,
@@ -250,13 +250,14 @@ func Root(ctx context.Context, dev string, filesystem fs.Filesystem, superBlockF
 		superBlockFlags: superBlockFlags,
 		mounter:         mounter,
 	}
+	s.EnableLeakCheck("gofer.session")
 
 	if o.privateunixsocket {
 		s.endpoints = newEndpointMaps()
 	}
 
 	// Construct the MountSource with the session and superBlockFlags.
-	m := fs.NewMountSource(ctx, s, filesystem, superBlockFlags)
+	m := fs.NewMountSource(ctx, &s, filesystem, superBlockFlags)
 
 	// Given that gofer files can consume host FDs, restrict the number
 	// of files that can be held by the cache.
@@ -290,7 +291,7 @@ func Root(ctx context.Context, dev string, filesystem fs.Filesystem, superBlockF
 		return nil, err
 	}
 
-	sattr, iops := newInodeOperations(ctx, s, s.attach, qid, valid, attr, false)
+	sattr, iops := newInodeOperations(ctx, &s, s.attach, qid, valid, attr, false)
 	return fs.NewInode(ctx, iops, m, sattr), nil
 }
 
diff --git a/pkg/sentry/fs/gofer/session_state.go b/pkg/sentry/fs/gofer/session_state.go
index 29a79441e..d045e04ff 100644
--- a/pkg/sentry/fs/gofer/session_state.go
+++ b/pkg/sentry/fs/gofer/session_state.go
@@ -111,5 +111,4 @@ func (s *session) afterLoad() {
 			panic("failed to restore endpoint maps: " + err.Error())
 		}
 	}
-
 }
diff --git a/pkg/sentry/fs/host/host_state_autogen.go b/pkg/sentry/fs/host/host_state_autogen.go
index 9611da42a..f0e1c4b88 100755
--- a/pkg/sentry/fs/host/host_state_autogen.go
+++ b/pkg/sentry/fs/host/host_state_autogen.go
@@ -95,17 +95,17 @@ func (x *inodeFileState) load(m state.Map) {
 
 func (x *ConnectedEndpoint) save(m state.Map) {
 	x.beforeSave()
+	m.Save("ref", &x.ref)
 	m.Save("queue", &x.queue)
 	m.Save("path", &x.path)
-	m.Save("ref", &x.ref)
 	m.Save("srfd", &x.srfd)
 	m.Save("stype", &x.stype)
 }
 
 func (x *ConnectedEndpoint) load(m state.Map) {
+	m.Load("ref", &x.ref)
 	m.Load("queue", &x.queue)
 	m.Load("path", &x.path)
-	m.Load("ref", &x.ref)
 	m.LoadWait("srfd", &x.srfd)
 	m.Load("stype", &x.stype)
 	m.AfterLoad(x.afterLoad)
diff --git a/pkg/sentry/fs/host/socket.go b/pkg/sentry/fs/host/socket.go
index 7fedc88bc..44c4ee5f2 100644
--- a/pkg/sentry/fs/host/socket.go
+++ b/pkg/sentry/fs/host/socket.go
@@ -47,12 +47,12 @@ const maxSendBufferSize = 8 << 20
 //
 // +stateify savable
 type ConnectedEndpoint struct {
-	queue *waiter.Queue
-	path  string
-
 	// ref keeps track of references to a connectedEndpoint.
 	ref refs.AtomicRefCount
 
+	queue *waiter.Queue
+	path  string
+
 	// If srfd >= 0, it is the host FD that file was imported from.
 	srfd int `state:"wait"`
 
@@ -133,6 +133,8 @@ func NewConnectedEndpoint(ctx context.Context, file *fd.FD, queue *waiter.Queue,
 	// AtomicRefCounters start off with a single reference. We need two.
 	e.ref.IncRef()
 
+	e.ref.EnableLeakCheck("host.ConnectedEndpoint")
+
 	return &e, nil
 }
 
diff --git a/pkg/sentry/fs/inode.go b/pkg/sentry/fs/inode.go
index e4aae1135..f4ddfa406 100644
--- a/pkg/sentry/fs/inode.go
+++ b/pkg/sentry/fs/inode.go
@@ -86,12 +86,14 @@ type LockCtx struct {
 // NewInode takes a reference on msrc.
 func NewInode(ctx context.Context, iops InodeOperations, msrc *MountSource, sattr StableAttr) *Inode {
 	msrc.IncRef()
-	return &Inode{
+	i := Inode{
 		InodeOperations: iops,
 		StableAttr:      sattr,
 		Watches:         newWatches(),
 		MountSource:     msrc,
 	}
+	i.EnableLeakCheck("fs.Inode")
+	return &i
 }
 
 // DecRef drops a reference on the Inode.
diff --git a/pkg/sentry/fs/inode_overlay.go b/pkg/sentry/fs/inode_overlay.go
index b247fa514..24b769cfc 100644
--- a/pkg/sentry/fs/inode_overlay.go
+++ b/pkg/sentry/fs/inode_overlay.go
@@ -567,6 +567,12 @@ func overlayCheck(ctx context.Context, o *overlayEntry, p PermMask) error {
 	if o.upper != nil {
 		err = o.upper.check(ctx, p)
 	} else {
+		if p.Write {
+			// Since writes will be redirected to the upper filesystem, the lower
+			// filesystem need not be writable, but must be readable for copy-up.
+			p.Write = false
+			p.Read = true
+		}
 		err = o.lower.check(ctx, p)
 	}
 	o.copyMu.RUnlock()
diff --git a/pkg/sentry/fs/mount.go b/pkg/sentry/fs/mount.go
index 912495528..7a9692800 100644
--- a/pkg/sentry/fs/mount.go
+++ b/pkg/sentry/fs/mount.go
@@ -138,12 +138,14 @@ func NewMountSource(ctx context.Context, mops MountSourceOperations, filesystem
 	if filesystem != nil {
 		fsType = filesystem.Name()
 	}
-	return &MountSource{
+	msrc := MountSource{
 		MountSourceOperations: mops,
 		Flags:                 flags,
 		FilesystemType:        fsType,
 		fscache:               NewDirentCache(DefaultDirentCacheSize),
 	}
+	msrc.EnableLeakCheck("fs.MountSource")
+	return &msrc
 }
 
 // DirentRefs returns the current mount direntRefs.
diff --git a/pkg/sentry/fs/mounts.go b/pkg/sentry/fs/mounts.go
index 281364dfc..693ffc760 100644
--- a/pkg/sentry/fs/mounts.go
+++ b/pkg/sentry/fs/mounts.go
@@ -181,12 +181,14 @@ func NewMountNamespace(ctx context.Context, root *Inode) (*MountNamespace, error
 		d: newRootMount(1, d),
 	}
 
-	return &MountNamespace{
+	mns := MountNamespace{
 		userns:  creds.UserNamespace,
 		root:    d,
 		mounts:  mnts,
 		mountID: 2,
-	}, nil
+	}
+	mns.EnableLeakCheck("fs.MountNamespace")
+	return &mns, nil
 }
 
 // UserNamespace returns the user namespace associated with this mount manager.
@@ -661,6 +663,11 @@ func (mns *MountNamespace) ResolveExecutablePath(ctx context.Context, wd, name s
 		}
 		defer d.DecRef()
 
+		// Check that it is a regular file.
+		if !IsRegular(d.Inode.StableAttr) {
+			continue
+		}
+
 		// Check whether we can read and execute the found file.
 		if err := d.Inode.CheckPermission(ctx, PermMask{Read: true, Execute: true}); err != nil {
 			log.Infof("Found executable at %q, but user cannot execute it: %v", binPath, err)
diff --git a/pkg/sentry/fs/proc/fds.go b/pkg/sentry/fs/proc/fds.go
index ea7aded9a..bee421d76 100644
--- a/pkg/sentry/fs/proc/fds.go
+++ b/pkg/sentry/fs/proc/fds.go
@@ -25,7 +25,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs/proc/device"
 	"gvisor.dev/gvisor/pkg/sentry/fs/ramfs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
@@ -42,8 +41,8 @@ func walkDescriptors(t *kernel.Task, p string, toInode func(*fs.File, kernel.FDF
 	var file *fs.File
 	var fdFlags kernel.FDFlags
 	t.WithMuLocked(func(t *kernel.Task) {
-		if fdm := t.FDMap(); fdm != nil {
-			file, fdFlags = fdm.GetDescriptor(kdefs.FD(n))
+		if fdTable := t.FDTable(); fdTable != nil {
+			file, fdFlags = fdTable.Get(int32(n))
 		}
 	})
 	if file == nil {
@@ -56,36 +55,31 @@ func walkDescriptors(t *kernel.Task, p string, toInode func(*fs.File, kernel.FDF
 // toDentAttr callback for each to get a DentAttr, which it then emits. This is
 // a helper for implementing fs.InodeOperations.Readdir.
 func readDescriptors(t *kernel.Task, c *fs.DirCtx, offset int64, toDentAttr func(int) fs.DentAttr) (int64, error) {
-	var fds kernel.FDs
+	var fds []int32
 	t.WithMuLocked(func(t *kernel.Task) {
-		if fdm := t.FDMap(); fdm != nil {
-			fds = fdm.GetFDs()
+		if fdTable := t.FDTable(); fdTable != nil {
+			fds = fdTable.GetFDs()
 		}
 	})
 
-	fdInts := make([]int, 0, len(fds))
-	for _, fd := range fds {
-		fdInts = append(fdInts, int(fd))
-	}
-
-	// Find the fd to start at.
-	idx := sort.SearchInts(fdInts, int(offset))
-	if idx == len(fdInts) {
+	// Find the appropriate starting point.
+	idx := sort.Search(len(fds), func(i int) bool { return fds[i] >= int32(offset) })
+	if idx == len(fds) {
 		return offset, nil
 	}
-	fdInts = fdInts[idx:]
+	fds = fds[idx:]
 
-	var fd int
-	for _, fd = range fdInts {
+	// Serialize all FDs.
+	for _, fd := range fds {
 		name := strconv.FormatUint(uint64(fd), 10)
-		if err := c.DirEmit(name, toDentAttr(fd)); err != nil {
+		if err := c.DirEmit(name, toDentAttr(int(fd))); err != nil {
 			// Returned offset is the next fd to serialize.
 			return int64(fd), err
 		}
 	}
 	// We serialized them all.  Next offset should be higher than last
 	// serialized fd.
-	return int64(fd + 1), nil
+	return int64(fds[len(fds)-1] + 1), nil
 }
 
 // fd implements fs.InodeOperations for a file in /proc/TID/fd/.
@@ -154,9 +148,9 @@ func (f *fd) Close() error {
 type fdDir struct {
 	ramfs.Dir
 
-	// We hold a reference on the task's fdmap but only keep an indirect
-	// task pointer to avoid Dirent loading circularity caused by fdmap's
-	// potential back pointers into the dirent tree.
+	// We hold a reference on the task's FDTable but only keep an indirect
+	// task pointer to avoid Dirent loading circularity caused by the
+	// table's back pointers into the dirent tree.
 	t *kernel.Task
 }
 
diff --git a/pkg/sentry/fs/proc/task.go b/pkg/sentry/fs/proc/task.go
index b2e36aeee..ef0ca3301 100644
--- a/pkg/sentry/fs/proc/task.go
+++ b/pkg/sentry/fs/proc/task.go
@@ -580,8 +580,8 @@ func (s *statusData) ReadSeqFileData(ctx context.Context, h seqfile.SeqHandle) (
 	var fds int
 	var vss, rss, data uint64
 	s.t.WithMuLocked(func(t *kernel.Task) {
-		if fdm := t.FDMap(); fdm != nil {
-			fds = fdm.Size()
+		if fdTable := t.FDTable(); fdTable != nil {
+			fds = fdTable.Size()
 		}
 		if mm := t.MemoryManager(); mm != nil {
 			vss = mm.VirtualMemorySize()
diff --git a/pkg/sentry/fs/tty/terminal.go b/pkg/sentry/fs/tty/terminal.go
index 8290f2530..b7cecb2ed 100644
--- a/pkg/sentry/fs/tty/terminal.go
+++ b/pkg/sentry/fs/tty/terminal.go
@@ -38,9 +38,11 @@ type Terminal struct {
 
 func newTerminal(ctx context.Context, d *dirInodeOperations, n uint32) *Terminal {
 	termios := linux.DefaultSlaveTermios
-	return &Terminal{
+	t := Terminal{
 		d:  d,
 		n:  n,
 		ld: newLineDiscipline(termios),
 	}
+	t.EnableLeakCheck("tty.Terminal")
+	return &t
 }
diff --git a/pkg/sentry/kernel/auth/atomicptr_credentials.go b/pkg/sentry/kernel/auth/atomicptr_credentials_unsafe.go
index 4535c958f..4535c958f 100755
--- a/pkg/sentry/kernel/auth/atomicptr_credentials.go
+++ b/pkg/sentry/kernel/auth/atomicptr_credentials_unsafe.go
diff --git a/pkg/sentry/kernel/epoll/epoll.go b/pkg/sentry/kernel/epoll/epoll.go
index 33c7dccae..9c0a4e1b4 100644
--- a/pkg/sentry/kernel/epoll/epoll.go
+++ b/pkg/sentry/kernel/epoll/epoll.go
@@ -26,7 +26,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/anon"
 	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
@@ -61,7 +60,7 @@ const (
 // +stateify savable
 type FileIdentifier struct {
 	File *fs.File `state:"wait"`
-	Fd   kdefs.FD
+	Fd   int32
 }
 
 // pollEntry holds all the state associated with an event poll entry, that is,
diff --git a/pkg/sentry/kernel/fd_map.go b/pkg/sentry/kernel/fd_map.go
deleted file mode 100644
index 786936a7d..000000000
--- a/pkg/sentry/kernel/fd_map.go
+++ /dev/null
@@ -1,364 +0,0 @@
-// Copyright 2018 The gVisor Authors.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package kernel
-
-import (
-	"bytes"
-	"fmt"
-	"sort"
-	"sync"
-	"sync/atomic"
-	"syscall"
-
-	"gvisor.dev/gvisor/pkg/abi/linux"
-	"gvisor.dev/gvisor/pkg/refs"
-	"gvisor.dev/gvisor/pkg/sentry/fs"
-	"gvisor.dev/gvisor/pkg/sentry/fs/lock"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
-	"gvisor.dev/gvisor/pkg/sentry/limits"
-)
-
-// FDs is an ordering of FD's that can be made stable.
-type FDs []kdefs.FD
-
-func (f FDs) Len() int {
-	return len(f)
-}
-
-func (f FDs) Swap(i, j int) {
-	f[i], f[j] = f[j], f[i]
-}
-
-func (f FDs) Less(i, j int) bool {
-	return f[i] < f[j]
-}
-
-// FDFlags define flags for an individual descriptor.
-//
-// +stateify savable
-type FDFlags struct {
-	// CloseOnExec indicates the descriptor should be closed on exec.
-	CloseOnExec bool
-}
-
-// ToLinuxFileFlags converts a kernel.FDFlags object to a Linux file flags
-// representation.
-func (f FDFlags) ToLinuxFileFlags() (mask uint) {
-	if f.CloseOnExec {
-		mask |= linux.O_CLOEXEC
-	}
-	return
-}
-
-// ToLinuxFDFlags converts a kernel.FDFlags object to a Linux descriptor flags
-// representation.
-func (f FDFlags) ToLinuxFDFlags() (mask uint) {
-	if f.CloseOnExec {
-		mask |= linux.FD_CLOEXEC
-	}
-	return
-}
-
-// descriptor holds the details about a file descriptor, namely a pointer the
-// file itself and the descriptor flags.
-//
-// +stateify savable
-type descriptor struct {
-	file  *fs.File
-	flags FDFlags
-}
-
-// FDMap is used to manage File references and flags.
-//
-// +stateify savable
-type FDMap struct {
-	refs.AtomicRefCount
-	k     *Kernel
-	files map[kdefs.FD]descriptor
-	mu    sync.RWMutex `state:"nosave"`
-	uid   uint64
-}
-
-// ID returns a unique identifier for this FDMap.
-func (f *FDMap) ID() uint64 {
-	return f.uid
-}
-
-// NewFDMap allocates a new FDMap that may be used by tasks in k.
-func (k *Kernel) NewFDMap() *FDMap {
-	return &FDMap{
-		k:     k,
-		files: make(map[kdefs.FD]descriptor),
-		uid:   atomic.AddUint64(&k.fdMapUids, 1),
-	}
-}
-
-// destroy removes all of the file descriptors from the map.
-func (f *FDMap) destroy() {
-	f.RemoveIf(func(*fs.File, FDFlags) bool {
-		return true
-	})
-}
-
-// DecRef implements RefCounter.DecRef with destructor f.destroy.
-func (f *FDMap) DecRef() {
-	f.DecRefWithDestructor(f.destroy)
-}
-
-// Size returns the number of file descriptor slots currently allocated.
-func (f *FDMap) Size() int {
-	f.mu.RLock()
-	defer f.mu.RUnlock()
-
-	return len(f.files)
-}
-
-// String is a stringer for FDMap.
-func (f *FDMap) String() string {
-	f.mu.RLock()
-	defer f.mu.RUnlock()
-
-	var b bytes.Buffer
-	for k, v := range f.files {
-		n, _ := v.file.Dirent.FullName(nil /* root */)
-		b.WriteString(fmt.Sprintf("\tfd:%d => name %s\n", k, n))
-	}
-	return b.String()
-}
-
-// NewFDFrom allocates a new FD guaranteed to be the lowest number available
-// greater than or equal to from. This property is important as Unix programs
-// tend to count on this allocation order.
-func (f *FDMap) NewFDFrom(fd kdefs.FD, file *fs.File, flags FDFlags, limitSet *limits.LimitSet) (kdefs.FD, error) {
-	if fd < 0 {
-		// Don't accept negative FDs.
-		return 0, syscall.EINVAL
-	}
-
-	f.mu.Lock()
-	defer f.mu.Unlock()
-
-	// Finds the lowest fd not in the handles map.
-	lim := limitSet.Get(limits.NumberOfFiles)
-	for i := fd; lim.Cur == limits.Infinity || i < kdefs.FD(lim.Cur); i++ {
-		if _, ok := f.files[i]; !ok {
-			file.IncRef()
-			f.files[i] = descriptor{file, flags}
-			return i, nil
-		}
-	}
-
-	return -1, syscall.EMFILE
-}
-
-// NewFDAt sets the file reference for the given FD. If there is an
-// active reference for that FD, the ref count for that existing reference
-// is decremented.
-func (f *FDMap) NewFDAt(fd kdefs.FD, file *fs.File, flags FDFlags, limitSet *limits.LimitSet) error {
-	if fd < 0 {
-		// Don't accept negative FDs.
-		return syscall.EBADF
-	}
-
-	// In this one case we do not do a defer of the Unlock.  The
-	// reason is that we must have done all the work needed for
-	// discarding any old open file before we return to the
-	// caller. In other words, the DecRef(), below, must have
-	// completed by the time we return to the caller to ensure
-	// side effects are, in fact, effected. A classic example is
-	// dup2(fd1, fd2); if fd2 was already open, it must be closed,
-	// and we don't want to resume the caller until it is; we have
-	// to block on the DecRef(). Hence we can not just do a 'go
-	// oldfile.DecRef()', since there would be no guarantee that
-	// it would be done before we the caller resumed. Since we
-	// must wait for the DecRef() to finish, and that could take
-	// time, it's best to first call f.muUnlock beore so we are
-	// not blocking other uses of this FDMap on the DecRef() call.
-	f.mu.Lock()
-	oldDesc, oldExists := f.files[fd]
-	lim := limitSet.Get(limits.NumberOfFiles).Cur
-	// if we're closing one then the effective limit is one
-	// more than the actual limit.
-	if oldExists && lim != limits.Infinity {
-		lim++
-	}
-	if lim != limits.Infinity && fd >= kdefs.FD(lim) {
-		f.mu.Unlock()
-		return syscall.EMFILE
-	}
-
-	file.IncRef()
-	f.files[fd] = descriptor{file, flags}
-	f.mu.Unlock()
-
-	if oldExists {
-		oldDesc.file.DecRef()
-	}
-	return nil
-}
-
-// SetFlags sets the flags for the given file descriptor, if it is valid.
-func (f *FDMap) SetFlags(fd kdefs.FD, flags FDFlags) {
-	f.mu.Lock()
-	defer f.mu.Unlock()
-
-	desc, ok := f.files[fd]
-	if !ok {
-		return
-	}
-
-	f.files[fd] = descriptor{desc.file, flags}
-}
-
-// GetDescriptor returns a reference to the file and the flags for the FD. It
-// bumps its reference count as well. It returns nil if there is no File
-// for the FD, i.e. if the FD is invalid. The caller must use DecRef
-// when they are done.
-func (f *FDMap) GetDescriptor(fd kdefs.FD) (*fs.File, FDFlags) {
-	f.mu.RLock()
-	defer f.mu.RUnlock()
-
-	if desc, ok := f.files[fd]; ok {
-		desc.file.IncRef()
-		return desc.file, desc.flags
-	}
-	return nil, FDFlags{}
-}
-
-// GetFile returns a reference to the File for the FD and bumps
-// its reference count as well. It returns nil if there is no File
-// for the FD, i.e. if the FD is invalid. The caller must use DecRef
-// when they are done.
-func (f *FDMap) GetFile(fd kdefs.FD) *fs.File {
-	f.mu.RLock()
-	if desc, ok := f.files[fd]; ok {
-		desc.file.IncRef()
-		f.mu.RUnlock()
-		return desc.file
-	}
-	f.mu.RUnlock()
-	return nil
-}
-
-// fds returns an ordering of FDs.
-func (f *FDMap) fds() FDs {
-	fds := make(FDs, 0, len(f.files))
-	for fd := range f.files {
-		fds = append(fds, fd)
-	}
-	sort.Sort(fds)
-	return fds
-}
-
-// GetFDs returns a list of valid fds.
-func (f *FDMap) GetFDs() FDs {
-	f.mu.RLock()
-	defer f.mu.RUnlock()
-	return f.fds()
-}
-
-// GetRefs returns a stable slice of references to all files and bumps the
-// reference count on each.  The caller must use DecRef on each reference when
-// they're done using the slice.
-func (f *FDMap) GetRefs() []*fs.File {
-	f.mu.RLock()
-	defer f.mu.RUnlock()
-
-	fds := f.fds()
-	fs := make([]*fs.File, 0, len(fds))
-	for _, fd := range fds {
-		desc := f.files[fd]
-		desc.file.IncRef()
-		fs = append(fs, desc.file)
-	}
-	return fs
-}
-
-// Fork returns an independent FDMap pointing to the same descriptors.
-func (f *FDMap) Fork() *FDMap {
-	f.mu.RLock()
-	defer f.mu.RUnlock()
-
-	clone := f.k.NewFDMap()
-
-	// Grab a extra reference for every file.
-	for fd, desc := range f.files {
-		desc.file.IncRef()
-		clone.files[fd] = desc
-	}
-
-	// That's it!
-	return clone
-}
-
-// unlock releases all file locks held by this FDMap's uid.  Must only be
-// called on a non-nil *fs.File.
-func (f *FDMap) unlock(file *fs.File) {
-	id := lock.UniqueID(f.ID())
-	file.Dirent.Inode.LockCtx.Posix.UnlockRegion(id, lock.LockRange{0, lock.LockEOF})
-}
-
-// inotifyFileClose generates the appropriate inotify events for f being closed.
-func inotifyFileClose(f *fs.File) {
-	var ev uint32
-	d := f.Dirent
-
-	if fs.IsDir(d.Inode.StableAttr) {
-		ev |= linux.IN_ISDIR
-	}
-
-	if f.Flags().Write {
-		ev |= linux.IN_CLOSE_WRITE
-	} else {
-		ev |= linux.IN_CLOSE_NOWRITE
-	}
-
-	d.InotifyEvent(ev, 0)
-}
-
-// Remove removes an FD from the FDMap, and returns (File, true) if a File
-// one was found. Callers are expected to decrement the reference count on
-// the File. Otherwise returns (nil, false).
-func (f *FDMap) Remove(fd kdefs.FD) (*fs.File, bool) {
-	f.mu.Lock()
-	desc := f.files[fd]
-	delete(f.files, fd)
-	f.mu.Unlock()
-	if desc.file != nil {
-		f.unlock(desc.file)
-		inotifyFileClose(desc.file)
-		return desc.file, true
-	}
-	return nil, false
-}
-
-// RemoveIf removes all FDs where cond is true.
-func (f *FDMap) RemoveIf(cond func(*fs.File, FDFlags) bool) {
-	var removed []*fs.File
-	f.mu.Lock()
-	for fd, desc := range f.files {
-		if desc.file != nil && cond(desc.file, desc.flags) {
-			delete(f.files, fd)
-			removed = append(removed, desc.file)
-		}
-	}
-	f.mu.Unlock()
-
-	for _, file := range removed {
-		f.unlock(file)
-		inotifyFileClose(file)
-		file.DecRef()
-	}
-}
diff --git a/pkg/sentry/kernel/fd_table.go b/pkg/sentry/kernel/fd_table.go
new file mode 100644
index 000000000..1f3a57dc1
--- /dev/null
+++ b/pkg/sentry/kernel/fd_table.go
@@ -0,0 +1,380 @@
+// Copyright 2018 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package kernel
+
+import (
+	"bytes"
+	"fmt"
+	"math"
+	"sync"
+	"sync/atomic"
+	"syscall"
+
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/refs"
+	"gvisor.dev/gvisor/pkg/sentry/context"
+	"gvisor.dev/gvisor/pkg/sentry/fs"
+	"gvisor.dev/gvisor/pkg/sentry/fs/lock"
+	"gvisor.dev/gvisor/pkg/sentry/limits"
+)
+
+// FDFlags define flags for an individual descriptor.
+//
+// +stateify savable
+type FDFlags struct {
+	// CloseOnExec indicates the descriptor should be closed on exec.
+	CloseOnExec bool
+}
+
+// ToLinuxFileFlags converts a kernel.FDFlags object to a Linux file flags
+// representation.
+func (f FDFlags) ToLinuxFileFlags() (mask uint) {
+	if f.CloseOnExec {
+		mask |= linux.O_CLOEXEC
+	}
+	return
+}
+
+// ToLinuxFDFlags converts a kernel.FDFlags object to a Linux descriptor flags
+// representation.
+func (f FDFlags) ToLinuxFDFlags() (mask uint) {
+	if f.CloseOnExec {
+		mask |= linux.FD_CLOEXEC
+	}
+	return
+}
+
+// descriptor holds the details about a file descriptor, namely a pointer to
+// the file itself and the descriptor flags.
+//
+// Note that this is immutable and can only be changed via operations on the
+// descriptorTable.
+//
+// +stateify savable
+type descriptor struct {
+	file  *fs.File
+	flags FDFlags
+}
+
+// FDTable is used to manage File references and flags.
+//
+// +stateify savable
+type FDTable struct {
+	refs.AtomicRefCount
+	k *Kernel
+
+	// uid is a unique identifier.
+	uid uint64
+
+	// mu protects below.
+	mu sync.Mutex `state:"nosave"`
+
+	// used contains the number of non-nil entries.
+	used int32
+
+	// descriptorTable holds descriptors.
+	descriptorTable `state:".(map[int32]descriptor)"`
+}
+
+func (f *FDTable) saveDescriptorTable() map[int32]descriptor {
+	m := make(map[int32]descriptor)
+	f.forEach(func(fd int32, file *fs.File, flags FDFlags) {
+		m[fd] = descriptor{
+			file:  file,
+			flags: flags,
+		}
+	})
+	return m
+}
+
+func (f *FDTable) loadDescriptorTable(m map[int32]descriptor) {
+	f.init() // Initialize table.
+	for fd, d := range m {
+		f.set(fd, d.file, d.flags)
+
+		// Note that we do _not_ need to acquire a extra table
+		// reference here. The table reference will already be
+		// accounted for in the file, so we drop the reference taken by
+		// set above.
+		d.file.DecRef()
+	}
+}
+
+// drop drops the table reference.
+func (f *FDTable) drop(file *fs.File) {
+	// Release locks.
+	file.Dirent.Inode.LockCtx.Posix.UnlockRegion(lock.UniqueID(f.uid), lock.LockRange{0, lock.LockEOF})
+
+	// Send inotify events.
+	d := file.Dirent
+	var ev uint32
+	if fs.IsDir(d.Inode.StableAttr) {
+		ev |= linux.IN_ISDIR
+	}
+	if file.Flags().Write {
+		ev |= linux.IN_CLOSE_WRITE
+	} else {
+		ev |= linux.IN_CLOSE_NOWRITE
+	}
+	d.InotifyEvent(ev, 0)
+
+	// Drop the table reference.
+	file.DecRef()
+}
+
+// ID returns a unique identifier for this FDTable.
+func (f *FDTable) ID() uint64 {
+	return f.uid
+}
+
+// NewFDTable allocates a new FDTable that may be used by tasks in k.
+func (k *Kernel) NewFDTable() *FDTable {
+	f := &FDTable{
+		k:   k,
+		uid: atomic.AddUint64(&k.fdMapUids, 1),
+	}
+	f.init()
+	return f
+}
+
+// destroy removes all of the file descriptors from the map.
+func (f *FDTable) destroy() {
+	f.RemoveIf(func(*fs.File, FDFlags) bool {
+		return true
+	})
+}
+
+// DecRef implements RefCounter.DecRef with destructor f.destroy.
+func (f *FDTable) DecRef() {
+	f.DecRefWithDestructor(f.destroy)
+}
+
+// Size returns the number of file descriptor slots currently allocated.
+func (f *FDTable) Size() int {
+	size := atomic.LoadInt32(&f.used)
+	return int(size)
+}
+
+// forEach iterates over all non-nil files.
+//
+// It is the caller's responsibility to acquire an appropriate lock.
+func (f *FDTable) forEach(fn func(fd int32, file *fs.File, flags FDFlags)) {
+	fd := int32(0)
+	for {
+		file, flags, ok := f.get(fd)
+		if !ok {
+			break
+		}
+		if file != nil {
+			if !file.TryIncRef() {
+				continue // Race caught.
+			}
+			fn(int32(fd), file, flags)
+			file.DecRef()
+		}
+		fd++
+	}
+}
+
+// String is a stringer for FDTable.
+func (f *FDTable) String() string {
+	var b bytes.Buffer
+	f.forEach(func(fd int32, file *fs.File, flags FDFlags) {
+		n, _ := file.Dirent.FullName(nil /* root */)
+		b.WriteString(fmt.Sprintf("\tfd:%d => name %s\n", fd, n))
+	})
+	return b.String()
+}
+
+// NewFDs allocates new FDs guaranteed to be the lowest number available
+// greater than or equal to the fd parameter. All files will share the set
+// flags. Success is guaranteed to be all or none.
+func (f *FDTable) NewFDs(ctx context.Context, fd int32, files []*fs.File, flags FDFlags) (fds []int32, err error) {
+	if fd < 0 {
+		// Don't accept negative FDs.
+		return nil, syscall.EINVAL
+	}
+
+	// Default limit.
+	end := int32(math.MaxInt32)
+
+	// Ensure we don't get past the provided limit.
+	if limitSet := limits.FromContext(ctx); limitSet != nil {
+		lim := limitSet.Get(limits.NumberOfFiles)
+		if lim.Cur != limits.Infinity {
+			end = int32(lim.Cur)
+		}
+		if fd >= end {
+			return nil, syscall.EMFILE
+		}
+	}
+
+	f.mu.Lock()
+	defer f.mu.Unlock()
+
+	// Install all entries.
+	for i := fd; i < end && len(fds) < len(files); i++ {
+		if d, _, _ := f.get(i); d == nil {
+			f.set(i, files[len(fds)], flags) // Set the descriptor.
+			fds = append(fds, i)             // Record the file descriptor.
+		}
+	}
+
+	// Failure? Unwind existing FDs.
+	if len(fds) < len(files) {
+		for _, i := range fds {
+			f.set(i, nil, FDFlags{}) // Zap entry.
+		}
+		return nil, syscall.EMFILE
+	}
+
+	return fds, nil
+}
+
+// NewFDAt sets the file reference for the given FD. If there is an active
+// reference for that FD, the ref count for that existing reference is
+// decremented.
+func (f *FDTable) NewFDAt(ctx context.Context, fd int32, file *fs.File, flags FDFlags) error {
+	if fd < 0 {
+		// Don't accept negative FDs.
+		return syscall.EBADF
+	}
+
+	f.mu.Lock()
+	defer f.mu.Unlock()
+
+	// Check the limit for the provided file.
+	if limitSet := limits.FromContext(ctx); limitSet != nil {
+		if lim := limitSet.Get(limits.NumberOfFiles); lim.Cur != limits.Infinity && uint64(fd) >= lim.Cur {
+			return syscall.EMFILE
+		}
+	}
+
+	// Install the entry.
+	f.set(fd, file, flags)
+	return nil
+}
+
+// SetFlags sets the flags for the given file descriptor.
+//
+// True is returned iff flags were changed.
+func (f *FDTable) SetFlags(fd int32, flags FDFlags) error {
+	if fd < 0 {
+		// Don't accept negative FDs.
+		return syscall.EBADF
+	}
+
+	f.mu.Lock()
+	defer f.mu.Unlock()
+
+	file, _, _ := f.get(fd)
+	if file == nil {
+		// No file found.
+		return syscall.EBADF
+	}
+
+	// Update the flags.
+	f.set(fd, file, flags)
+	return nil
+}
+
+// Get returns a reference to the file and the flags for the FD or nil if no
+// file is defined for the given fd.
+//
+// N.B. Callers are required to use DecRef when they are done.
+//
+//go:nosplit
+func (f *FDTable) Get(fd int32) (*fs.File, FDFlags) {
+	if fd < 0 {
+		return nil, FDFlags{}
+	}
+
+	for {
+		file, flags, _ := f.get(fd)
+		if file != nil {
+			if !file.TryIncRef() {
+				continue // Race caught.
+			}
+			// Reference acquired.
+			return file, flags
+		}
+		// No file available.
+		return nil, FDFlags{}
+	}
+}
+
+// GetFDs returns a list of valid fds.
+func (f *FDTable) GetFDs() []int32 {
+	fds := make([]int32, 0, f.used)
+	f.forEach(func(fd int32, file *fs.File, flags FDFlags) {
+		fds = append(fds, fd)
+	})
+	return fds
+}
+
+// GetRefs returns a stable slice of references to all files and bumps the
+// reference count on each. The caller must use DecRef on each reference when
+// they're done using the slice.
+func (f *FDTable) GetRefs() []*fs.File {
+	files := make([]*fs.File, 0, f.Size())
+	f.forEach(func(_ int32, file *fs.File, flags FDFlags) {
+		file.IncRef() // Acquire a reference for caller.
+		files = append(files, file)
+	})
+	return files
+}
+
+// Fork returns an independent FDTable.
+func (f *FDTable) Fork() *FDTable {
+	clone := f.k.NewFDTable()
+
+	f.forEach(func(fd int32, file *fs.File, flags FDFlags) {
+		// The set function here will acquire an appropriate table
+		// reference for the clone. We don't need anything else.
+		clone.set(fd, file, flags)
+	})
+	return clone
+}
+
+// Remove removes an FD from and returns a non-file iff successful.
+//
+// N.B. Callers are required to use DecRef when they are done.
+func (f *FDTable) Remove(fd int32) *fs.File {
+	if fd < 0 {
+		return nil
+	}
+
+	f.mu.Lock()
+	defer f.mu.Unlock()
+
+	orig, _, _ := f.get(fd)
+	if orig != nil {
+		orig.IncRef()             // Reference for caller.
+		f.set(fd, nil, FDFlags{}) // Zap entry.
+	}
+	return orig
+}
+
+// RemoveIf removes all FDs where cond is true.
+func (f *FDTable) RemoveIf(cond func(*fs.File, FDFlags) bool) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+
+	f.forEach(func(fd int32, file *fs.File, flags FDFlags) {
+		if cond(file, flags) {
+			f.set(fd, nil, FDFlags{}) // Clear from table.
+		}
+	})
+}
diff --git a/pkg/sentry/kernel/fd_table_unsafe.go b/pkg/sentry/kernel/fd_table_unsafe.go
new file mode 100644
index 000000000..e009df974
--- /dev/null
+++ b/pkg/sentry/kernel/fd_table_unsafe.go
@@ -0,0 +1,103 @@
+// Copyright 2018 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package kernel
+
+import (
+	"sync/atomic"
+	"unsafe"
+
+	"gvisor.dev/gvisor/pkg/sentry/fs"
+)
+
+type descriptorTable struct {
+	// slice is a *[]unsafe.Pointer, where each element is actually
+	// *descriptor object, updated atomically.
+	//
+	// Changes to the slice itself requiring holding FDTable.mu.
+	slice unsafe.Pointer `state:".(map[int32]*descriptor)"`
+}
+
+// init initializes the table.
+func (f *FDTable) init() {
+	var slice []unsafe.Pointer // Empty slice.
+	atomic.StorePointer(&f.slice, unsafe.Pointer(&slice))
+}
+
+// get gets a file entry.
+//
+// The boolean indicates whether this was in range.
+//
+//go:nosplit
+func (f *FDTable) get(fd int32) (*fs.File, FDFlags, bool) {
+	slice := *(*[]unsafe.Pointer)(atomic.LoadPointer(&f.slice))
+	if fd >= int32(len(slice)) {
+		return nil, FDFlags{}, false
+	}
+	d := (*descriptor)(atomic.LoadPointer(&slice[fd]))
+	if d == nil {
+		return nil, FDFlags{}, true
+	}
+	return d.file, d.flags, true
+}
+
+// set sets an entry.
+//
+// This handles accounting changes, as well as acquiring and releasing the
+// reference needed by the table iff the file is different.
+//
+// Precondition: mu must be held.
+func (f *FDTable) set(fd int32, file *fs.File, flags FDFlags) {
+	slice := *(*[]unsafe.Pointer)(atomic.LoadPointer(&f.slice))
+
+	// Grow the table as required.
+	if last := int32(len(slice)); fd >= last {
+		end := fd + 1
+		if end < 2*last {
+			end = 2 * last
+		}
+		slice = append(slice, make([]unsafe.Pointer, end-last)...)
+		atomic.StorePointer(&f.slice, unsafe.Pointer(&slice))
+	}
+
+	// Create the new element.
+	var d *descriptor
+	if file != nil {
+		d = &descriptor{
+			file:  file,
+			flags: flags,
+		}
+	}
+
+	// Update the single element.
+	orig := (*descriptor)(atomic.SwapPointer(&slice[fd], unsafe.Pointer(d)))
+
+	// Acquire a table reference.
+	if file != nil && (orig == nil || file != orig.file) {
+		file.IncRef()
+	}
+
+	// Drop the table reference.
+	if orig != nil && file != orig.file {
+		f.drop(orig.file)
+	}
+
+	// Adjust used.
+	switch {
+	case orig == nil && file != nil:
+		atomic.AddInt32(&f.used, 1)
+	case orig != nil && file == nil:
+		atomic.AddInt32(&f.used, -1)
+	}
+}
diff --git a/pkg/sentry/kernel/fs_context.go b/pkg/sentry/kernel/fs_context.go
index 938239aeb..ded27d668 100644
--- a/pkg/sentry/kernel/fs_context.go
+++ b/pkg/sentry/kernel/fs_context.go
@@ -51,11 +51,13 @@ type FSContext struct {
 func newFSContext(root, cwd *fs.Dirent, umask uint) *FSContext {
 	root.IncRef()
 	cwd.IncRef()
-	return &FSContext{
+	f := FSContext{
 		root:  root,
 		cwd:   cwd,
 		umask: umask,
 	}
+	f.EnableLeakCheck("kernel.FSContext")
+	return &f
 }
 
 // destroy is the destructor for an FSContext.
diff --git a/pkg/sentry/kernel/futex/atomicptr_bucket.go b/pkg/sentry/kernel/futex/atomicptr_bucket_unsafe.go
index d3fdf09b0..d3fdf09b0 100755
--- a/pkg/sentry/kernel/futex/atomicptr_bucket.go
+++ b/pkg/sentry/kernel/futex/atomicptr_bucket_unsafe.go
diff --git a/pkg/sentry/kernel/futex/futex.go b/pkg/sentry/kernel/futex/futex.go
index 3bd5c04af..278cc8143 100644
--- a/pkg/sentry/kernel/futex/futex.go
+++ b/pkg/sentry/kernel/futex/futex.go
@@ -729,14 +729,14 @@ func (m *Manager) UnlockPI(t Target, addr usermem.Addr, tid uint32, private bool
 	}
 	b := m.lockBucket(&k)
 
-	err = m.unlockPILocked(t, addr, tid, b)
+	err = m.unlockPILocked(t, addr, tid, b, &k)
 
 	k.release()
 	b.mu.Unlock()
 	return err
 }
 
-func (m *Manager) unlockPILocked(t Target, addr usermem.Addr, tid uint32, b *bucket) error {
+func (m *Manager) unlockPILocked(t Target, addr usermem.Addr, tid uint32, b *bucket, key *Key) error {
 	cur, err := t.LoadUint32(addr)
 	if err != nil {
 		return err
@@ -746,7 +746,22 @@ func (m *Manager) unlockPILocked(t Target, addr usermem.Addr, tid uint32, b *buc
 		return syserror.EPERM
 	}
 
-	if b.waiters.Empty() {
+	var next *Waiter  // Who's the next owner?
+	var next2 *Waiter // Who's the one after that?
+	for w := b.waiters.Front(); w != nil; w = w.Next() {
+		if !w.key.matches(key) {
+			continue
+		}
+
+		if next == nil {
+			next = w
+		} else {
+			next2 = w
+			break
+		}
+	}
+
+	if next == nil {
 		// It's safe to set 0 because there are no waiters, no new owner, and the
 		// executing task is the current owner (no owner died bit).
 		prev, err := t.CompareAndSwapUint32(addr, cur, 0)
@@ -761,12 +776,10 @@ func (m *Manager) unlockPILocked(t Target, addr usermem.Addr, tid uint32, b *buc
 		return nil
 	}
 
-	next := b.waiters.Front()
-
 	// Set next owner's TID, waiters if there are any. Resets owner died bit, if
 	// set, because the executing task takes over as the owner.
 	val := next.tid
-	if next.Next() != nil {
+	if next2 != nil {
 		val |= linux.FUTEX_WAITERS
 	}
 
diff --git a/pkg/sentry/kernel/kdefs/kdefs_state_autogen.go b/pkg/sentry/kernel/kdefs/kdefs_state_autogen.go
deleted file mode 100755
index cef77125b..000000000
--- a/pkg/sentry/kernel/kdefs/kdefs_state_autogen.go
+++ /dev/null
@@ -1,4 +0,0 @@
-// automatically generated by stateify.
-
-package kdefs
-
diff --git a/pkg/sentry/kernel/kernel.go b/pkg/sentry/kernel/kernel.go
index 47dadc43a..38b49cba2 100644
--- a/pkg/sentry/kernel/kernel.go
+++ b/pkg/sentry/kernel/kernel.go
@@ -155,7 +155,7 @@ type Kernel struct {
 	// cpuClockTicker increments cpuClock.
 	cpuClockTicker *ktime.Timer `state:"nosave"`
 
-	// fdMapUids is an ever-increasing counter for generating FDMap uids.
+	// fdMapUids is an ever-increasing counter for generating FDTable uids.
 	//
 	// fdMapUids is mutable, and is accessed using atomic memory operations.
 	fdMapUids uint64
@@ -400,8 +400,8 @@ func (k *Kernel) flushMountSourceRefs() error {
 
 	// There may be some open FDs whose filesystems have been unmounted. We
 	// must flush those as well.
-	return k.tasks.forEachFDPaused(func(desc descriptor) error {
-		desc.file.Dirent.Inode.MountSource.FlushDirentRefs()
+	return k.tasks.forEachFDPaused(func(file *fs.File) error {
+		file.Dirent.Inode.MountSource.FlushDirentRefs()
 		return nil
 	})
 }
@@ -410,35 +410,35 @@ func (k *Kernel) flushMountSourceRefs() error {
 // task.
 //
 // Precondition: Must be called with the kernel paused.
-func (ts *TaskSet) forEachFDPaused(f func(descriptor) error) error {
+func (ts *TaskSet) forEachFDPaused(f func(*fs.File) error) (err error) {
 	ts.mu.RLock()
 	defer ts.mu.RUnlock()
 	for t := range ts.Root.tids {
 		// We can skip locking Task.mu here since the kernel is paused.
-		if t.fds == nil {
+		if t.fdTable == nil {
 			continue
 		}
-		for _, desc := range t.fds.files {
-			if err := f(desc); err != nil {
-				return err
+		t.fdTable.forEach(func(_ int32, file *fs.File, _ FDFlags) {
+			if lastErr := f(file); lastErr != nil && err == nil {
+				err = lastErr
 			}
-		}
+		})
 	}
-	return nil
+	return err
 }
 
 func (ts *TaskSet) flushWritesToFiles(ctx context.Context) error {
-	return ts.forEachFDPaused(func(desc descriptor) error {
-		if flags := desc.file.Flags(); !flags.Write {
+	return ts.forEachFDPaused(func(file *fs.File) error {
+		if flags := file.Flags(); !flags.Write {
 			return nil
 		}
-		if sattr := desc.file.Dirent.Inode.StableAttr; !fs.IsFile(sattr) && !fs.IsDir(sattr) {
+		if sattr := file.Dirent.Inode.StableAttr; !fs.IsFile(sattr) && !fs.IsDir(sattr) {
 			return nil
 		}
 		// Here we need all metadata synced.
-		syncErr := desc.file.Fsync(ctx, 0, fs.FileMaxOffset, fs.SyncAll)
+		syncErr := file.Fsync(ctx, 0, fs.FileMaxOffset, fs.SyncAll)
 		if err := fs.SaveFileFsyncError(syncErr); err != nil {
-			name, _ := desc.file.Dirent.FullName(nil /* root */)
+			name, _ := file.Dirent.FullName(nil /* root */)
 			// Wrap this error in ErrSaveRejection
 			// so that it will trigger a save
 			// error, rather than a panic. This
@@ -483,14 +483,12 @@ func (ts *TaskSet) unregisterEpollWaiters() {
 	defer ts.mu.RUnlock()
 	for t := range ts.Root.tids {
 		// We can skip locking Task.mu here since the kernel is paused.
-		if fdmap := t.fds; fdmap != nil {
-			for _, desc := range fdmap.files {
-				if desc.file != nil {
-					if e, ok := desc.file.FileOperations.(*epoll.EventPoll); ok {
-						e.UnregisterEpollWaiters()
-					}
+		if t.fdTable != nil {
+			t.fdTable.forEach(func(_ int32, file *fs.File, _ FDFlags) {
+				if e, ok := file.FileOperations.(*epoll.EventPoll); ok {
+					e.UnregisterEpollWaiters()
 				}
-			}
+			})
 		}
 	}
 }
@@ -538,6 +536,8 @@ func (k *Kernel) LoadFrom(r io.Reader, net inet.Stack) error {
 	}
 	log.Infof("Memory load took [%s].", time.Since(memoryStart))
 
+	log.Infof("Overall load took [%s]", time.Since(loadStart))
+
 	// Ensure that all pending asynchronous work is complete:
 	//   - namedpipe opening
 	//   - inode file opening
@@ -602,9 +602,9 @@ type CreateProcessArgs struct {
 	// Credentials is the initial credentials.
 	Credentials *auth.Credentials
 
-	// FDMap is the initial set of file descriptors. If CreateProcess succeeds,
-	// it takes a reference on FDMap.
-	FDMap *FDMap
+	// FDTable is the initial set of file descriptors. If CreateProcess succeeds,
+	// it takes a reference on FDTable.
+	FDTable *FDTable
 
 	// Umask is the initial umask.
 	Umask uint
@@ -789,9 +789,9 @@ func (k *Kernel) CreateProcess(args CreateProcessArgs) (*ThreadGroup, ThreadID,
 		return nil, 0, errors.New(se.String())
 	}
 
-	// Take a reference on the FDMap, which will be transferred to
+	// Take a reference on the FDTable, which will be transferred to
 	// TaskSet.NewTask().
-	args.FDMap.IncRef()
+	args.FDTable.IncRef()
 
 	// Create the task.
 	config := &TaskConfig{
@@ -799,7 +799,7 @@ func (k *Kernel) CreateProcess(args CreateProcessArgs) (*ThreadGroup, ThreadID,
 		ThreadGroup:             tg,
 		TaskContext:             tc,
 		FSContext:               newFSContext(root, wd, args.Umask),
-		FDMap:                   args.FDMap,
+		FDTable:                 args.FDTable,
 		Credentials:             args.Credentials,
 		AllowedCPUMask:          sched.NewFullCPUSet(k.applicationCores),
 		UTSNamespace:            args.UTSNamespace,
@@ -871,7 +871,7 @@ func (k *Kernel) pauseTimeLocked() {
 	}
 
 	// By precondition, nothing else can be interacting with PIDNamespace.tids
-	// or FDMap.files, so we can iterate them without synchronization. (We
+	// or FDTable.files, so we can iterate them without synchronization. (We
 	// can't hold the TaskSet mutex when pausing thread group timers because
 	// thread group timers call ThreadGroup.SendSignal, which takes the TaskSet
 	// mutex, while holding the Timer mutex.)
@@ -882,14 +882,14 @@ func (k *Kernel) pauseTimeLocked() {
 				it.PauseTimer()
 			}
 		}
-		// This means we'll iterate FDMaps shared by multiple tasks repeatedly,
+		// This means we'll iterate FDTables shared by multiple tasks repeatedly,
 		// but ktime.Timer.Pause is idempotent so this is harmless.
-		if fdm := t.fds; fdm != nil {
-			for _, desc := range fdm.files {
-				if tfd, ok := desc.file.FileOperations.(*timerfd.TimerOperations); ok {
+		if t.fdTable != nil {
+			t.fdTable.forEach(func(_ int32, file *fs.File, _ FDFlags) {
+				if tfd, ok := file.FileOperations.(*timerfd.TimerOperations); ok {
 					tfd.PauseTimer()
 				}
-			}
+			})
 		}
 	}
 	k.timekeeper.PauseUpdates()
@@ -914,12 +914,12 @@ func (k *Kernel) resumeTimeLocked() {
 				it.ResumeTimer()
 			}
 		}
-		if fdm := t.fds; fdm != nil {
-			for _, desc := range fdm.files {
-				if tfd, ok := desc.file.FileOperations.(*timerfd.TimerOperations); ok {
+		if t.fdTable != nil {
+			t.fdTable.forEach(func(_ int32, file *fs.File, _ FDFlags) {
+				if tfd, ok := file.FileOperations.(*timerfd.TimerOperations); ok {
 					tfd.ResumeTimer()
 				}
-			}
+			})
 		}
 	}
 }
diff --git a/pkg/sentry/kernel/kernel_state_autogen.go b/pkg/sentry/kernel/kernel_state_autogen.go
index 56c59e76c..b24036d33 100755
--- a/pkg/sentry/kernel/kernel_state_autogen.go
+++ b/pkg/sentry/kernel/kernel_state_autogen.go
@@ -61,21 +61,24 @@ func (x *descriptor) load(m state.Map) {
 	m.Load("flags", &x.flags)
 }
 
-func (x *FDMap) beforeSave() {}
-func (x *FDMap) save(m state.Map) {
+func (x *FDTable) beforeSave() {}
+func (x *FDTable) save(m state.Map) {
 	x.beforeSave()
+	var descriptorTable map[int32]descriptor = x.saveDescriptorTable()
+	m.SaveValue("descriptorTable", descriptorTable)
 	m.Save("AtomicRefCount", &x.AtomicRefCount)
 	m.Save("k", &x.k)
-	m.Save("files", &x.files)
 	m.Save("uid", &x.uid)
+	m.Save("used", &x.used)
 }
 
-func (x *FDMap) afterLoad() {}
-func (x *FDMap) load(m state.Map) {
+func (x *FDTable) afterLoad() {}
+func (x *FDTable) load(m state.Map) {
 	m.Load("AtomicRefCount", &x.AtomicRefCount)
 	m.Load("k", &x.k)
-	m.Load("files", &x.files)
 	m.Load("uid", &x.uid)
+	m.Load("used", &x.used)
+	m.LoadValue("descriptorTable", new(map[int32]descriptor), func(y interface{}) { x.loadDescriptorTable(y.(map[int32]descriptor)) })
 }
 
 func (x *FSContext) beforeSave() {}
@@ -536,8 +539,8 @@ func (x *Task) save(m state.Map) {
 	m.Save("k", &x.k)
 	m.Save("containerID", &x.containerID)
 	m.Save("tc", &x.tc)
-	m.Save("fsc", &x.fsc)
-	m.Save("fds", &x.fds)
+	m.Save("fsContext", &x.fsContext)
+	m.Save("fdTable", &x.fdTable)
 	m.Save("vforkParent", &x.vforkParent)
 	m.Save("exitState", &x.exitState)
 	m.Save("exitTracerNotified", &x.exitTracerNotified)
@@ -592,8 +595,8 @@ func (x *Task) load(m state.Map) {
 	m.Load("k", &x.k)
 	m.Load("containerID", &x.containerID)
 	m.Load("tc", &x.tc)
-	m.Load("fsc", &x.fsc)
-	m.Load("fds", &x.fds)
+	m.Load("fsContext", &x.fsContext)
+	m.Load("fdTable", &x.fdTable)
 	m.Load("vforkParent", &x.vforkParent)
 	m.Load("exitState", &x.exitState)
 	m.Load("exitTracerNotified", &x.exitTracerNotified)
@@ -1118,7 +1121,7 @@ func init() {
 	state.Register("kernel.AbstractSocketNamespace", (*AbstractSocketNamespace)(nil), state.Fns{Save: (*AbstractSocketNamespace).save, Load: (*AbstractSocketNamespace).load})
 	state.Register("kernel.FDFlags", (*FDFlags)(nil), state.Fns{Save: (*FDFlags).save, Load: (*FDFlags).load})
 	state.Register("kernel.descriptor", (*descriptor)(nil), state.Fns{Save: (*descriptor).save, Load: (*descriptor).load})
-	state.Register("kernel.FDMap", (*FDMap)(nil), state.Fns{Save: (*FDMap).save, Load: (*FDMap).load})
+	state.Register("kernel.FDTable", (*FDTable)(nil), state.Fns{Save: (*FDTable).save, Load: (*FDTable).load})
 	state.Register("kernel.FSContext", (*FSContext)(nil), state.Fns{Save: (*FSContext).save, Load: (*FSContext).load})
 	state.Register("kernel.IPCNamespace", (*IPCNamespace)(nil), state.Fns{Save: (*IPCNamespace).save, Load: (*IPCNamespace).load})
 	state.Register("kernel.Kernel", (*Kernel)(nil), state.Fns{Save: (*Kernel).save, Load: (*Kernel).load})
diff --git a/pkg/sentry/kernel/seqatomic_taskgoroutineschedinfo.go b/pkg/sentry/kernel/seqatomic_taskgoroutineschedinfo_unsafe.go
index be6b07629..895abb129 100755
--- a/pkg/sentry/kernel/seqatomic_taskgoroutineschedinfo.go
+++ b/pkg/sentry/kernel/seqatomic_taskgoroutineschedinfo_unsafe.go
@@ -1,11 +1,12 @@
 package kernel
 
 import (
+	"unsafe"
+
 	"fmt"
 	"gvisor.dev/gvisor/third_party/gvsync"
 	"reflect"
 	"strings"
-	"unsafe"
 )
 
 // SeqAtomicLoad returns a copy of *ptr, ensuring that the read does not race
diff --git a/pkg/sentry/kernel/sessions.go b/pkg/sentry/kernel/sessions.go
index 355984140..81fcd8258 100644
--- a/pkg/sentry/kernel/sessions.go
+++ b/pkg/sentry/kernel/sessions.go
@@ -294,6 +294,7 @@ func (tg *ThreadGroup) createSession() error {
 		id:     SessionID(id),
 		leader: tg,
 	}
+	s.refs.EnableLeakCheck("kernel.Session")
 
 	// Create a new ProcessGroup, belonging to that Session.
 	// This also has a single reference (assigned below).
@@ -307,6 +308,7 @@ func (tg *ThreadGroup) createSession() error {
 		session:    s,
 		ancestors:  0,
 	}
+	pg.refs.EnableLeakCheck("kernel.ProcessGroup")
 
 	// Tie them and return the result.
 	s.processGroups.PushBack(pg)
@@ -378,11 +380,13 @@ func (tg *ThreadGroup) CreateProcessGroup() error {
 	// We manually adjust the ancestors if the parent is in the same
 	// session.
 	tg.processGroup.session.incRef()
-	pg := &ProcessGroup{
+	pg := ProcessGroup{
 		id:         ProcessGroupID(id),
 		originator: tg,
 		session:    tg.processGroup.session,
 	}
+	pg.refs.EnableLeakCheck("kernel.ProcessGroup")
+
 	if tg.leader.parent != nil && tg.leader.parent.tg.processGroup.session == pg.session {
 		pg.ancestors++
 	}
@@ -390,20 +394,20 @@ func (tg *ThreadGroup) CreateProcessGroup() error {
 	// Assign the new process group; adjust children.
 	oldParentPG := tg.parentPG()
 	tg.forEachChildThreadGroupLocked(func(childTG *ThreadGroup) {
-		childTG.processGroup.incRefWithParent(pg)
+		childTG.processGroup.incRefWithParent(&pg)
 		childTG.processGroup.decRefWithParent(oldParentPG)
 	})
 	tg.processGroup.decRefWithParent(oldParentPG)
-	tg.processGroup = pg
+	tg.processGroup = &pg
 
 	// Add the new process group to the session.
-	pg.session.processGroups.PushBack(pg)
+	pg.session.processGroups.PushBack(&pg)
 
 	// Ensure this translation is added to all namespaces.
 	for ns := tg.pidns; ns != nil; ns = ns.parent {
 		local := ns.tgids[tg]
-		ns.pgids[pg] = ProcessGroupID(local)
-		ns.processGroups[ProcessGroupID(local)] = pg
+		ns.pgids[&pg] = ProcessGroupID(local)
+		ns.processGroups[ProcessGroupID(local)] = &pg
 	}
 
 	return nil
diff --git a/pkg/sentry/kernel/shm/shm.go b/pkg/sentry/kernel/shm/shm.go
index 3e9fe70e2..5bd610f68 100644
--- a/pkg/sentry/kernel/shm/shm.go
+++ b/pkg/sentry/kernel/shm/shm.go
@@ -224,6 +224,7 @@ func (r *Registry) newShm(ctx context.Context, pid int32, key Key, creator fs.Fi
 		creatorPID:    pid,
 		changeTime:    ktime.NowFromContext(ctx),
 	}
+	shm.EnableLeakCheck("kernel.Shm")
 
 	// Find the next available ID.
 	for id := r.lastIDUsed + 1; id != r.lastIDUsed; id++ {
diff --git a/pkg/sentry/kernel/syslog.go b/pkg/sentry/kernel/syslog.go
index 175d1b247..8227ecf1d 100644
--- a/pkg/sentry/kernel/syslog.go
+++ b/pkg/sentry/kernel/syslog.go
@@ -67,6 +67,7 @@ func (s *syslog) Log() []byte {
 		"Creating process schedule...",
 		"Generating random numbers by fair dice roll...",
 		"Rewriting operating system in Javascript...",
+		"Reticulating splines...",
 		"Consulting tar man page...",
 		"Forking spaghetti code...",
 		"Checking naughty and nice process list...",
diff --git a/pkg/sentry/kernel/task.go b/pkg/sentry/kernel/task.go
index 2e3a39d3b..e91f82bb3 100644
--- a/pkg/sentry/kernel/task.go
+++ b/pkg/sentry/kernel/task.go
@@ -236,15 +236,15 @@ type Task struct {
 	// tc is protected by mu, and is owned by the task goroutine.
 	tc TaskContext
 
-	// fsc is the task's filesystem context.
+	// fsContext is the task's filesystem context.
 	//
-	// fsc is protected by mu, and is owned by the task goroutine.
-	fsc *FSContext
+	// fsContext is protected by mu, and is owned by the task goroutine.
+	fsContext *FSContext
 
-	// fds is the task's file descriptor table.
+	// fdTable is the task's file descriptor table.
 	//
-	// fds is protected by mu, and is owned by the task goroutine.
-	fds *FDMap
+	// fdTable is protected by mu, and is owned by the task goroutine.
+	fdTable *FDTable
 
 	// If vforkParent is not nil, it is the task that created this task with
 	// vfork() or clone(CLONE_VFORK), and should have its vforkStop ended when
@@ -602,7 +602,7 @@ func (t *Task) Value(key interface{}) interface{} {
 	case context.CtxThreadGroupID:
 		return int32(t.ThreadGroup().ID())
 	case fs.CtxRoot:
-		return t.fsc.RootDirectory()
+		return t.fsContext.RootDirectory()
 	case fs.CtxDirentCacheLimiter:
 		return t.k.DirentCacheLimiter
 	case inet.CtxStack:
@@ -668,7 +668,7 @@ func (t *Task) SyscallRestartBlock() SyscallRestartBlock {
 func (t *Task) IsChrooted() bool {
 	realRoot := t.tg.mounts.Root()
 	defer realRoot.DecRef()
-	root := t.fsc.RootDirectory()
+	root := t.fsContext.RootDirectory()
 	if root != nil {
 		defer root.DecRef()
 	}
@@ -689,16 +689,55 @@ func (t *Task) TaskContext() *TaskContext {
 // Precondition: The caller must be running on the task goroutine, or t.mu must
 // be locked.
 func (t *Task) FSContext() *FSContext {
-	return t.fsc
+	return t.fsContext
 }
 
-// FDMap returns t's FDMap. FDMap does not take an additional reference on the
-// returned FDMap.
+// FDTable returns t's FDTable. FDMTable does not take an additional reference
+// on the returned FDMap.
 //
 // Precondition: The caller must be running on the task goroutine, or t.mu must
 // be locked.
-func (t *Task) FDMap() *FDMap {
-	return t.fds
+func (t *Task) FDTable() *FDTable {
+	return t.fdTable
+}
+
+// GetFile is a convenience wrapper t.FDTable().GetFile.
+//
+// Precondition: same as FDTable.
+func (t *Task) GetFile(fd int32) *fs.File {
+	f, _ := t.fdTable.Get(fd)
+	return f
+}
+
+// NewFDs is a convenience wrapper for t.FDTable().NewFDs.
+//
+// This automatically passes the task as the context.
+//
+// Precondition: same as FDTable.
+func (t *Task) NewFDs(fd int32, files []*fs.File, flags FDFlags) ([]int32, error) {
+	return t.fdTable.NewFDs(t, fd, files, flags)
+}
+
+// NewFDFrom is a convenience wrapper for t.FDTable().NewFDs with a single file.
+//
+// This automatically passes the task as the context.
+//
+// Precondition: same as FDTable.
+func (t *Task) NewFDFrom(fd int32, file *fs.File, flags FDFlags) (int32, error) {
+	fds, err := t.fdTable.NewFDs(t, fd, []*fs.File{file}, flags)
+	if err != nil {
+		return 0, err
+	}
+	return fds[0], nil
+}
+
+// NewFDAt is a convenience wrapper for t.FDTable().NewFDAt.
+//
+// This automatically passes the task as the context.
+//
+// Precondition: same as FDTable.
+func (t *Task) NewFDAt(fd int32, file *fs.File, flags FDFlags) error {
+	return t.fdTable.NewFDAt(t, fd, file, flags)
 }
 
 // WithMuLocked executes f with t.mu locked.
diff --git a/pkg/sentry/kernel/task_clone.go b/pkg/sentry/kernel/task_clone.go
index b5cc3860d..0916fd658 100644
--- a/pkg/sentry/kernel/task_clone.go
+++ b/pkg/sentry/kernel/task_clone.go
@@ -214,20 +214,20 @@ func (t *Task) Clone(opts *CloneOptions) (ThreadID, *SyscallControl, error) {
 		}
 	}
 
-	var fsc *FSContext
+	var fsContext *FSContext
 	if opts.NewFSContext {
-		fsc = t.fsc.Fork()
+		fsContext = t.fsContext.Fork()
 	} else {
-		fsc = t.fsc
-		fsc.IncRef()
+		fsContext = t.fsContext
+		fsContext.IncRef()
 	}
 
-	var fds *FDMap
+	var fdTable *FDTable
 	if opts.NewFiles {
-		fds = t.fds.Fork()
+		fdTable = t.fdTable.Fork()
 	} else {
-		fds = t.fds
-		fds.IncRef()
+		fdTable = t.fdTable
+		fdTable.IncRef()
 	}
 
 	pidns := t.tg.pidns
@@ -251,8 +251,8 @@ func (t *Task) Clone(opts *CloneOptions) (ThreadID, *SyscallControl, error) {
 		ThreadGroup:             tg,
 		SignalMask:              t.SignalMask(),
 		TaskContext:             tc,
-		FSContext:               fsc,
-		FDMap:                   fds,
+		FSContext:               fsContext,
+		FDTable:                 fdTable,
 		Credentials:             creds,
 		Niceness:                t.Niceness(),
 		NetworkNamespaced:       t.netns,
@@ -485,22 +485,22 @@ func (t *Task) Unshare(opts *SharingOptions) error {
 		// namespace"
 		t.ipcns = NewIPCNamespace(creds.UserNamespace)
 	}
-	var oldfds *FDMap
+	var oldFDTable *FDTable
 	if opts.NewFiles {
-		oldfds = t.fds
-		t.fds = oldfds.Fork()
+		oldFDTable = t.fdTable
+		t.fdTable = oldFDTable.Fork()
 	}
-	var oldfsc *FSContext
+	var oldFSContext *FSContext
 	if opts.NewFSContext {
-		oldfsc = t.fsc
-		t.fsc = oldfsc.Fork()
+		oldFSContext = t.fsContext
+		t.fsContext = oldFSContext.Fork()
 	}
 	t.mu.Unlock()
-	if oldfds != nil {
-		oldfds.DecRef()
+	if oldFDTable != nil {
+		oldFDTable.DecRef()
 	}
-	if oldfsc != nil {
-		oldfsc.DecRef()
+	if oldFSContext != nil {
+		oldFSContext.DecRef()
 	}
 	return nil
 }
diff --git a/pkg/sentry/kernel/task_exec.go b/pkg/sentry/kernel/task_exec.go
index cd85acaef..17a089b90 100644
--- a/pkg/sentry/kernel/task_exec.go
+++ b/pkg/sentry/kernel/task_exec.go
@@ -195,7 +195,7 @@ func (r *runSyscallAfterExecStop) execute(t *Task) taskRunState {
 	t.tg.pidns.owner.mu.Unlock()
 
 	// Remove FDs with the CloseOnExec flag set.
-	t.fds.RemoveIf(func(file *fs.File, flags FDFlags) bool {
+	t.fdTable.RemoveIf(func(file *fs.File, flags FDFlags) bool {
 		return flags.CloseOnExec
 	})
 
diff --git a/pkg/sentry/kernel/task_exit.go b/pkg/sentry/kernel/task_exit.go
index b97d65185..535f03e50 100644
--- a/pkg/sentry/kernel/task_exit.go
+++ b/pkg/sentry/kernel/task_exit.go
@@ -265,8 +265,8 @@ func (*runExitMain) execute(t *Task) taskRunState {
 	// Releasing the MM unblocks a blocked CLONE_VFORK parent.
 	t.unstopVforkParent()
 
-	t.fsc.DecRef()
-	t.fds.DecRef()
+	t.fsContext.DecRef()
+	t.fdTable.DecRef()
 
 	// If this is the last task to exit from the thread group, release the
 	// thread group's resources.
diff --git a/pkg/sentry/kernel/task_log.go b/pkg/sentry/kernel/task_log.go
index cf48663b6..a29e9b9eb 100644
--- a/pkg/sentry/kernel/task_log.go
+++ b/pkg/sentry/kernel/task_log.go
@@ -63,7 +63,7 @@ func (t *Task) DebugDumpState() {
 	if mm := t.MemoryManager(); mm != nil {
 		t.Debugf("Mappings:\n%s", mm)
 	}
-	t.Debugf("FDMap:\n%s", t.fds)
+	t.Debugf("FDTable:\n%s", t.fdTable)
 }
 
 // debugDumpRegisters logs register state at log level debug.
diff --git a/pkg/sentry/kernel/task_start.go b/pkg/sentry/kernel/task_start.go
index 72caae537..a88bf3951 100644
--- a/pkg/sentry/kernel/task_start.go
+++ b/pkg/sentry/kernel/task_start.go
@@ -52,9 +52,10 @@ type TaskConfig struct {
 	// succeeds.
 	FSContext *FSContext
 
-	// FDMap is the FDMap of the new task. A reference must be held on FDMap,
-	// which is transferred to TaskSet.NewTask whether or not it succeeds.
-	FDMap *FDMap
+	// FDTable is the FDTableof the new task. A reference must be held on
+	// FDMap, which is transferred to TaskSet.NewTask whether or not it
+	// succeeds.
+	FDTable *FDTable
 
 	// Credentials is the Credentials of the new task.
 	Credentials *auth.Credentials
@@ -90,7 +91,7 @@ func (ts *TaskSet) NewTask(cfg *TaskConfig) (*Task, error) {
 	if err != nil {
 		cfg.TaskContext.release()
 		cfg.FSContext.DecRef()
-		cfg.FDMap.DecRef()
+		cfg.FDTable.DecRef()
 		return nil, err
 	}
 	return t, nil
@@ -112,8 +113,8 @@ func (ts *TaskSet) newTask(cfg *TaskConfig) (*Task, error) {
 		signalMask:      cfg.SignalMask,
 		signalStack:     arch.SignalStack{Flags: arch.SignalStackFlagDisable},
 		tc:              *tc,
-		fsc:             cfg.FSContext,
-		fds:             cfg.FDMap,
+		fsContext:       cfg.FSContext,
+		fdTable:         cfg.FDTable,
 		p:               cfg.Kernel.Platform.NewContext(),
 		k:               cfg.Kernel,
 		ptraceTracees:   make(map[*Task]struct{}),
diff --git a/pkg/sentry/loader/loader.go b/pkg/sentry/loader/loader.go
index edfdac2a7..baa12d9a0 100644
--- a/pkg/sentry/loader/loader.go
+++ b/pkg/sentry/loader/loader.go
@@ -54,7 +54,7 @@ func readFull(ctx context.Context, f *fs.File, dst usermem.IOSequence, offset in
 // openPath opens name for loading.
 //
 // openPath returns the fs.Dirent and an *fs.File for name, which is not
-// installed in the Task FDMap. The caller takes ownership of both.
+// installed in the Task FDTable. The caller takes ownership of both.
 //
 // name must be a readable, executable, regular file.
 func openPath(ctx context.Context, mm *fs.MountNamespace, root, wd *fs.Dirent, maxTraversals *uint, name string) (*fs.Dirent, *fs.File, error) {
diff --git a/pkg/sentry/mm/aio_context.go b/pkg/sentry/mm/aio_context.go
index c9a942023..1b746d030 100644
--- a/pkg/sentry/mm/aio_context.go
+++ b/pkg/sentry/mm/aio_context.go
@@ -213,7 +213,9 @@ func newAIOMappable(mfp pgalloc.MemoryFileProvider) (*aioMappable, error) {
 	if err != nil {
 		return nil, err
 	}
-	return &aioMappable{mfp: mfp, fr: fr}, nil
+	m := aioMappable{mfp: mfp, fr: fr}
+	m.EnableLeakCheck("mm.aioMappable")
+	return &m, nil
 }
 
 // DecRef implements refs.RefCounter.DecRef.
diff --git a/pkg/sentry/mm/special_mappable.go b/pkg/sentry/mm/special_mappable.go
index 2f8651a0a..ea2d7af74 100644
--- a/pkg/sentry/mm/special_mappable.go
+++ b/pkg/sentry/mm/special_mappable.go
@@ -45,7 +45,9 @@ type SpecialMappable struct {
 //
 // Preconditions: fr.Length() != 0.
 func NewSpecialMappable(name string, mfp pgalloc.MemoryFileProvider, fr platform.FileRange) *SpecialMappable {
-	return &SpecialMappable{mfp: mfp, fr: fr, name: name}
+	m := SpecialMappable{mfp: mfp, fr: fr, name: name}
+	m.EnableLeakCheck("mm.SpecialMappable")
+	return &m
 }
 
 // DecRef implements refs.RefCounter.DecRef.
diff --git a/pkg/sentry/platform/kvm/filters.go b/pkg/sentry/platform/kvm/filters.go
new file mode 100644
index 000000000..7d949f1dd
--- /dev/null
+++ b/pkg/sentry/platform/kvm/filters.go
@@ -0,0 +1,33 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package kvm
+
+import (
+	"syscall"
+
+	"gvisor.dev/gvisor/pkg/seccomp"
+)
+
+// SyscallFilters returns syscalls made exclusively by the KVM platform.
+func (*KVM) SyscallFilters() seccomp.SyscallRules {
+	return seccomp.SyscallRules{
+		syscall.SYS_ARCH_PRCTL:      {},
+		syscall.SYS_IOCTL:           {},
+		syscall.SYS_MMAP:            {},
+		syscall.SYS_RT_SIGSUSPEND:   {},
+		syscall.SYS_RT_SIGTIMEDWAIT: {},
+		0xffffffffffffffff:          {}, // KVM uses syscall -1 to transition to host.
+	}
+}
diff --git a/pkg/sentry/platform/kvm/kvm.go b/pkg/sentry/platform/kvm/kvm.go
index b49d7f3c4..ee4cd2f4d 100644
--- a/pkg/sentry/platform/kvm/kvm.go
+++ b/pkg/sentry/platform/kvm/kvm.go
@@ -141,3 +141,17 @@ func (k *KVM) NewContext() platform.Context {
 		machine: k.machine,
 	}
 }
+
+type constructor struct{}
+
+func (*constructor) New(f *os.File) (platform.Platform, error) {
+	return New(f)
+}
+
+func (*constructor) OpenDevice() (*os.File, error) {
+	return OpenDevice()
+}
+
+func init() {
+	platform.Register("kvm", &constructor{})
+}
diff --git a/pkg/sentry/platform/kvm/machine.go b/pkg/sentry/platform/kvm/machine.go
index 7d92e16cc..679087e25 100644
--- a/pkg/sentry/platform/kvm/machine.go
+++ b/pkg/sentry/platform/kvm/machine.go
@@ -426,7 +426,12 @@ func (c *vCPU) unlock() {
 		// Normal state.
 	case vCPUUser | vCPUGuest | vCPUWaiter:
 		// Force a transition: this must trigger a notification when we
-		// return from guest mode.
+		// return from guest mode. We must clear vCPUWaiter here
+		// anyways, because BounceToKernel will force a transition only
+		// from ring3 to ring0, which will not clear this bit. Halt may
+		// workaround the issue, but if there is no exception or
+		// syscall in this period, BounceToKernel will hang.
+		atomicbitops.AndUint32(&c.state, ^vCPUWaiter)
 		c.notify()
 	case vCPUUser | vCPUWaiter:
 		// Waiting for the lock to be released; the responsibility is
diff --git a/pkg/sentry/platform/platform.go b/pkg/sentry/platform/platform.go
index eccbe2336..ec22dbf87 100644
--- a/pkg/sentry/platform/platform.go
+++ b/pkg/sentry/platform/platform.go
@@ -19,8 +19,10 @@ package platform
 
 import (
 	"fmt"
+	"os"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/seccomp"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
@@ -93,6 +95,9 @@ type Platform interface {
 	// Platforms for which this does not hold may panic if PreemptAllCPUs is
 	// called.
 	PreemptAllCPUs() error
+
+	// SyscallFilters returns syscalls made exclusively by this platform.
+	SyscallFilters() seccomp.SyscallRules
 }
 
 // NoCPUPreemptionDetection implements Platform.DetectsCPUPreemption and
@@ -347,3 +352,26 @@ type File interface {
 func (fr FileRange) String() string {
 	return fmt.Sprintf("[%#x, %#x)", fr.Start, fr.End)
 }
+
+// Constructor represents a platform type.
+type Constructor interface {
+	New(deviceFile *os.File) (Platform, error)
+	OpenDevice() (*os.File, error)
+}
+
+// platforms contains all available platform types.
+var platforms = map[string]Constructor{}
+
+// Register registers a new platform type.
+func Register(name string, platform Constructor) {
+	platforms[name] = platform
+}
+
+// Lookup looks up the platform constructor by name.
+func Lookup(name string) (Constructor, error) {
+	p, ok := platforms[name]
+	if !ok {
+		return nil, fmt.Errorf("unknown platform: %v", name)
+	}
+	return p, nil
+}
diff --git a/pkg/sentry/kernel/kdefs/kdefs.go b/pkg/sentry/platform/ptrace/filters.go
index 304da2032..1e07cfd0d 100644
--- a/pkg/sentry/kernel/kdefs/kdefs.go
+++ b/pkg/sentry/platform/ptrace/filters.go
@@ -1,4 +1,4 @@
-// Copyright 2018 The gVisor Authors.
+// Copyright 2019 The gVisor Authors.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -12,9 +12,22 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// Package kdefs defines common kernel definitions.
-//
-package kdefs
+package ptrace
+
+import (
+	"syscall"
+
+	"golang.org/x/sys/unix"
+	"gvisor.dev/gvisor/pkg/seccomp"
+)
 
-// FD is a File Descriptor.
-type FD int32
+// SyscallFilters returns syscalls made exclusively by the ptrace platform.
+func (*PTrace) SyscallFilters() seccomp.SyscallRules {
+	return seccomp.SyscallRules{
+		unix.SYS_GETCPU:            {},
+		unix.SYS_SCHED_SETAFFINITY: {},
+		syscall.SYS_PTRACE:         {},
+		syscall.SYS_TGKILL:         {},
+		syscall.SYS_WAIT4:          {},
+	}
+}
diff --git a/pkg/sentry/platform/ptrace/ptrace.go b/pkg/sentry/platform/ptrace/ptrace.go
index ee7e0640c..6fd30ed25 100644
--- a/pkg/sentry/platform/ptrace/ptrace.go
+++ b/pkg/sentry/platform/ptrace/ptrace.go
@@ -45,6 +45,7 @@
 package ptrace
 
 import (
+	"os"
 	"sync"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
@@ -236,3 +237,17 @@ func (p *PTrace) NewAddressSpace(_ interface{}) (platform.AddressSpace, <-chan s
 func (*PTrace) NewContext() platform.Context {
 	return &context{}
 }
+
+type constructor struct{}
+
+func (*constructor) New(*os.File) (platform.Platform, error) {
+	return New()
+}
+
+func (*constructor) OpenDevice() (*os.File, error) {
+	return nil, nil
+}
+
+func init() {
+	platform.Register("ptrace", &constructor{})
+}
diff --git a/pkg/sentry/platform/ptrace/subprocess_linux.go b/pkg/sentry/platform/ptrace/subprocess_linux.go
index dc3475494..87ded0bbd 100644
--- a/pkg/sentry/platform/ptrace/subprocess_linux.go
+++ b/pkg/sentry/platform/ptrace/subprocess_linux.go
@@ -306,7 +306,7 @@ func (s *subprocess) createStub() (*thread, error) {
 		arch.SyscallArgument{Value: 0},
 		arch.SyscallArgument{Value: 0})
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("creating stub process: %v", err)
 	}
 
 	// Wait for child to enter group-stop, so we don't stop its
@@ -325,7 +325,7 @@ func (s *subprocess) createStub() (*thread, error) {
 		arch.SyscallArgument{Value: 0},
 		arch.SyscallArgument{Value: 0})
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("waiting on stub process: %v", err)
 	}
 
 	childT := &thread{
diff --git a/pkg/sentry/platform/ring0/defs_impl.go b/pkg/sentry/platform/ring0/defs_impl.go
index 8efc3825f..d4bfc5a4a 100755
--- a/pkg/sentry/platform/ring0/defs_impl.go
+++ b/pkg/sentry/platform/ring0/defs_impl.go
@@ -1,14 +1,14 @@
 package ring0
 
 import (
+	"syscall"
+
 	"fmt"
 	"gvisor.dev/gvisor/pkg/cpuid"
 	"gvisor.dev/gvisor/pkg/sentry/platform/ring0/pagetables"
+	"gvisor.dev/gvisor/pkg/sentry/usermem"
 	"io"
 	"reflect"
-	"syscall"
-
-	"gvisor.dev/gvisor/pkg/sentry/usermem"
 )
 
 var (
diff --git a/pkg/sentry/platform/ring0/kernel_amd64.go b/pkg/sentry/platform/ring0/kernel_amd64.go
index 3577b5127..0feff8778 100644
--- a/pkg/sentry/platform/ring0/kernel_amd64.go
+++ b/pkg/sentry/platform/ring0/kernel_amd64.go
@@ -70,6 +70,14 @@ func (c *CPU) init() {
 	c.tss.ist1Lo = uint32(stackAddr)
 	c.tss.ist1Hi = uint32(stackAddr >> 32)
 
+	// Set the I/O bitmap base address beyond the last byte in the TSS
+	// to block access to the entire I/O address range.
+	//
+	// From section 18.5.2 "I/O Permission Bit Map" from Intel SDM vol1:
+	// I/O addresses not spanned by the map are treated as if they had set
+	// bits in the map.
+	c.tss.ioPerm = tssLimit + 1
+
 	// Permanently set the kernel segments.
 	c.registers.Cs = uint64(Kcode)
 	c.registers.Ds = uint64(Kdata)
diff --git a/pkg/sentry/socket/control/control.go b/pkg/sentry/socket/control/control.go
index b646dc258..4f4a20dfe 100644
--- a/pkg/sentry/socket/control/control.go
+++ b/pkg/sentry/socket/control/control.go
@@ -23,7 +23,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
 	"gvisor.dev/gvisor/pkg/syserror"
@@ -63,7 +62,7 @@ type RightsFiles []*fs.File
 func NewSCMRights(t *kernel.Task, fds []int32) (SCMRights, error) {
 	files := make(RightsFiles, 0, len(fds))
 	for _, fd := range fds {
-		file, _ := t.FDMap().GetDescriptor(kdefs.FD(fd))
+		file := t.GetFile(fd)
 		if file == nil {
 			files.Release()
 			return nil, syserror.EBADF
@@ -109,7 +108,9 @@ func rightsFDs(t *kernel.Task, rights SCMRights, cloexec bool, max int) ([]int32
 	files, trunc := rights.Files(t, max)
 	fds := make([]int32, 0, len(files))
 	for i := 0; i < max && len(files) > 0; i++ {
-		fd, err := t.FDMap().NewFDFrom(0, files[0], kernel.FDFlags{cloexec}, t.ThreadGroup().Limits())
+		fd, err := t.NewFDFrom(0, files[0], kernel.FDFlags{
+			CloseOnExec: cloexec,
+		})
 		files[0].DecRef()
 		files = files[1:]
 		if err != nil {
@@ -315,8 +316,7 @@ func PackTimestamp(t *kernel.Task, timestamp int64, buf []byte) []byte {
 // Parse parses a raw socket control message into portable objects.
 func Parse(t *kernel.Task, socketOrEndpoint interface{}, buf []byte) (transport.ControlMessages, error) {
 	var (
-		fds linux.ControlMessageRights
-
+		fds       linux.ControlMessageRights
 		haveCreds bool
 		creds     linux.ControlMessageCredentials
 	)
diff --git a/pkg/sentry/socket/epsocket/epsocket.go b/pkg/sentry/socket/epsocket/epsocket.go
index 2a38e370a..9d1bcfd41 100644
--- a/pkg/sentry/socket/epsocket/epsocket.go
+++ b/pkg/sentry/socket/epsocket/epsocket.go
@@ -40,7 +40,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
 	"gvisor.dev/gvisor/pkg/sentry/inet"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/socket"
@@ -286,14 +285,14 @@ func bytesToIPAddress(addr []byte) tcpip.Address {
 // GetAddress reads an sockaddr struct from the given address and converts it
 // to the FullAddress format. It supports AF_UNIX, AF_INET and AF_INET6
 // addresses.
-func GetAddress(sfamily int, addr []byte) (tcpip.FullAddress, *syserr.Error) {
+func GetAddress(sfamily int, addr []byte, strict bool) (tcpip.FullAddress, *syserr.Error) {
 	// Make sure we have at least 2 bytes for the address family.
 	if len(addr) < 2 {
 		return tcpip.FullAddress{}, syserr.ErrInvalidArgument
 	}
 
 	family := usermem.ByteOrder.Uint16(addr)
-	if family != uint16(sfamily) {
+	if family != uint16(sfamily) && (!strict && family != linux.AF_UNSPEC) {
 		return tcpip.FullAddress{}, syserr.ErrAddressFamilyNotSupported
 	}
 
@@ -318,7 +317,7 @@ func GetAddress(sfamily int, addr []byte) (tcpip.FullAddress, *syserr.Error) {
 	case linux.AF_INET:
 		var a linux.SockAddrInet
 		if len(addr) < sockAddrInetSize {
-			return tcpip.FullAddress{}, syserr.ErrBadAddress
+			return tcpip.FullAddress{}, syserr.ErrInvalidArgument
 		}
 		binary.Unmarshal(addr[:sockAddrInetSize], usermem.ByteOrder, &a)
 
@@ -331,7 +330,7 @@ func GetAddress(sfamily int, addr []byte) (tcpip.FullAddress, *syserr.Error) {
 	case linux.AF_INET6:
 		var a linux.SockAddrInet6
 		if len(addr) < sockAddrInet6Size {
-			return tcpip.FullAddress{}, syserr.ErrBadAddress
+			return tcpip.FullAddress{}, syserr.ErrInvalidArgument
 		}
 		binary.Unmarshal(addr[:sockAddrInet6Size], usermem.ByteOrder, &a)
 
@@ -344,6 +343,9 @@ func GetAddress(sfamily int, addr []byte) (tcpip.FullAddress, *syserr.Error) {
 		}
 		return out, nil
 
+	case linux.AF_UNSPEC:
+		return tcpip.FullAddress{}, nil
+
 	default:
 		return tcpip.FullAddress{}, syserr.ErrAddressFamilyNotSupported
 	}
@@ -466,7 +468,7 @@ func (s *SocketOperations) Readiness(mask waiter.EventMask) waiter.EventMask {
 // Connect implements the linux syscall connect(2) for sockets backed by
 // tpcip.Endpoint.
 func (s *SocketOperations) Connect(t *kernel.Task, sockaddr []byte, blocking bool) *syserr.Error {
-	addr, err := GetAddress(s.family, sockaddr)
+	addr, err := GetAddress(s.family, sockaddr, false /* strict */)
 	if err != nil {
 		return err
 	}
@@ -499,7 +501,7 @@ func (s *SocketOperations) Connect(t *kernel.Task, sockaddr []byte, blocking boo
 // Bind implements the linux syscall bind(2) for sockets backed by
 // tcpip.Endpoint.
 func (s *SocketOperations) Bind(t *kernel.Task, sockaddr []byte) *syserr.Error {
-	addr, err := GetAddress(s.family, sockaddr)
+	addr, err := GetAddress(s.family, sockaddr, true /* strict */)
 	if err != nil {
 		return err
 	}
@@ -537,7 +539,7 @@ func (s *SocketOperations) blockingAccept(t *kernel.Task) (tcpip.Endpoint, *wait
 
 // Accept implements the linux syscall accept(2) for sockets backed by
 // tcpip.Endpoint.
-func (s *SocketOperations) Accept(t *kernel.Task, peerRequested bool, flags int, blocking bool) (kdefs.FD, interface{}, uint32, *syserr.Error) {
+func (s *SocketOperations) Accept(t *kernel.Task, peerRequested bool, flags int, blocking bool) (int32, interface{}, uint32, *syserr.Error) {
 	// Issue the accept request to get the new endpoint.
 	ep, wq, terr := s.Endpoint.Accept()
 	if terr != nil {
@@ -575,10 +577,9 @@ func (s *SocketOperations) Accept(t *kernel.Task, peerRequested bool, flags int,
 		}
 	}
 
-	fdFlags := kernel.FDFlags{
+	fd, e := t.NewFDFrom(0, ns, kernel.FDFlags{
 		CloseOnExec: flags&linux.SOCK_CLOEXEC != 0,
-	}
-	fd, e := t.FDMap().NewFDFrom(0, ns, fdFlags, t.ThreadGroup().Limits())
+	})
 
 	t.Kernel().RecordSocket(ns)
 
@@ -1924,7 +1925,7 @@ func (s *SocketOperations) SendMsg(t *kernel.Task, src usermem.IOSequence, to []
 
 	var addr *tcpip.FullAddress
 	if len(to) > 0 {
-		addrBuf, err := GetAddress(s.family, to)
+		addrBuf, err := GetAddress(s.family, to, true /* strict */)
 		if err != nil {
 			return 0, err
 		}
diff --git a/pkg/sentry/socket/hostinet/socket.go b/pkg/sentry/socket/hostinet/socket.go
index c63f3aacf..7f69406b7 100644
--- a/pkg/sentry/socket/hostinet/socket.go
+++ b/pkg/sentry/socket/hostinet/socket.go
@@ -26,7 +26,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/socket"
@@ -190,7 +189,7 @@ func (s *socketOperations) Connect(t *kernel.Task, sockaddr []byte, blocking boo
 }
 
 // Accept implements socket.Socket.Accept.
-func (s *socketOperations) Accept(t *kernel.Task, peerRequested bool, flags int, blocking bool) (kdefs.FD, interface{}, uint32, *syserr.Error) {
+func (s *socketOperations) Accept(t *kernel.Task, peerRequested bool, flags int, blocking bool) (int32, interface{}, uint32, *syserr.Error) {
 	var peerAddr []byte
 	var peerAddrlen uint32
 	var peerAddrPtr *byte
@@ -236,11 +235,11 @@ func (s *socketOperations) Accept(t *kernel.Task, peerRequested bool, flags int,
 	}
 	defer f.DecRef()
 
-	fdFlags := kernel.FDFlags{
+	kfd, kerr := t.NewFDFrom(0, f, kernel.FDFlags{
 		CloseOnExec: flags&syscall.SOCK_CLOEXEC != 0,
-	}
-	kfd, kerr := t.FDMap().NewFDFrom(0, f, fdFlags, t.ThreadGroup().Limits())
+	})
 	t.Kernel().RecordSocket(f)
+
 	return kfd, peerAddr, peerAddrlen, syserr.FromError(kerr)
 }
 
diff --git a/pkg/sentry/socket/netlink/socket.go b/pkg/sentry/socket/netlink/socket.go
index ecc1e2d53..f3d6c1e9b 100644
--- a/pkg/sentry/socket/netlink/socket.go
+++ b/pkg/sentry/socket/netlink/socket.go
@@ -27,7 +27,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/socket"
 	"gvisor.dev/gvisor/pkg/sentry/socket/netlink/port"
@@ -272,7 +271,7 @@ func (s *Socket) Connect(t *kernel.Task, sockaddr []byte, blocking bool) *syserr
 }
 
 // Accept implements socket.Socket.Accept.
-func (s *Socket) Accept(t *kernel.Task, peerRequested bool, flags int, blocking bool) (kdefs.FD, interface{}, uint32, *syserr.Error) {
+func (s *Socket) Accept(t *kernel.Task, peerRequested bool, flags int, blocking bool) (int32, interface{}, uint32, *syserr.Error) {
 	// Netlink sockets never support accept.
 	return 0, nil, 0, syserr.ErrNotSupported
 }
diff --git a/pkg/sentry/socket/rpcinet/socket.go b/pkg/sentry/socket/rpcinet/socket.go
index cc7b964ea..ccaaddbfc 100644
--- a/pkg/sentry/socket/rpcinet/socket.go
+++ b/pkg/sentry/socket/rpcinet/socket.go
@@ -26,7 +26,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/socket"
 	"gvisor.dev/gvisor/pkg/sentry/socket/rpcinet/conn"
@@ -286,7 +285,7 @@ func rpcAccept(t *kernel.Task, fd uint32, peer bool) (*pb.AcceptResponse_ResultP
 }
 
 // Accept implements socket.Socket.Accept.
-func (s *socketOperations) Accept(t *kernel.Task, peerRequested bool, flags int, blocking bool) (kdefs.FD, interface{}, uint32, *syserr.Error) {
+func (s *socketOperations) Accept(t *kernel.Task, peerRequested bool, flags int, blocking bool) (int32, interface{}, uint32, *syserr.Error) {
 	payload, se := rpcAccept(t, s.fd, peerRequested)
 
 	// Check if we need to block.
@@ -336,10 +335,9 @@ func (s *socketOperations) Accept(t *kernel.Task, peerRequested bool, flags int,
 	})
 	defer file.DecRef()
 
-	fdFlags := kernel.FDFlags{
+	fd, err := t.NewFDFrom(0, file, kernel.FDFlags{
 		CloseOnExec: flags&linux.SOCK_CLOEXEC != 0,
-	}
-	fd, err := t.FDMap().NewFDFrom(0, file, fdFlags, t.ThreadGroup().Limits())
+	})
 	if err != nil {
 		return 0, nil, 0, syserr.FromError(err)
 	}
diff --git a/pkg/sentry/socket/socket.go b/pkg/sentry/socket/socket.go
index 933120f34..0efa58a58 100644
--- a/pkg/sentry/socket/socket.go
+++ b/pkg/sentry/socket/socket.go
@@ -27,7 +27,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
@@ -53,7 +52,7 @@ type Socket interface {
 	// Accept implements the accept4(2) linux syscall.
 	// Returns fd, real peer address length and error. Real peer address
 	// length is only set if len(peer) > 0.
-	Accept(t *kernel.Task, peerRequested bool, flags int, blocking bool) (kdefs.FD, interface{}, uint32, *syserr.Error)
+	Accept(t *kernel.Task, peerRequested bool, flags int, blocking bool) (int32, interface{}, uint32, *syserr.Error)
 
 	// Bind implements the bind(2) linux syscall.
 	Bind(t *kernel.Task, sockaddr []byte) *syserr.Error
diff --git a/pkg/sentry/socket/unix/transport/connectioned.go b/pkg/sentry/socket/unix/transport/connectioned.go
index e4c416233..73d2df15d 100644
--- a/pkg/sentry/socket/unix/transport/connectioned.go
+++ b/pkg/sentry/socket/unix/transport/connectioned.go
@@ -143,7 +143,9 @@ func NewPair(ctx context.Context, stype linux.SockType, uid UniqueIDProvider) (E
 	}
 
 	q1 := &queue{ReaderQueue: a.Queue, WriterQueue: b.Queue, limit: initialLimit}
+	q1.EnableLeakCheck("transport.queue")
 	q2 := &queue{ReaderQueue: b.Queue, WriterQueue: a.Queue, limit: initialLimit}
+	q2.EnableLeakCheck("transport.queue")
 
 	if stype == linux.SOCK_STREAM {
 		a.receiver = &streamQueueReceiver{queueReceiver: queueReceiver{q1}}
@@ -294,12 +296,14 @@ func (e *connectionedEndpoint) BidirectionalConnect(ctx context.Context, ce Conn
 	}
 
 	readQueue := &queue{ReaderQueue: ce.WaiterQueue(), WriterQueue: ne.Queue, limit: initialLimit}
+	readQueue.EnableLeakCheck("transport.queue")
 	ne.connected = &connectedEndpoint{
 		endpoint:   ce,
 		writeQueue: readQueue,
 	}
 
 	writeQueue := &queue{ReaderQueue: ne.Queue, WriterQueue: ce.WaiterQueue(), limit: initialLimit}
+	writeQueue.EnableLeakCheck("transport.queue")
 	if e.stype == linux.SOCK_STREAM {
 		ne.receiver = &streamQueueReceiver{queueReceiver: queueReceiver{readQueue: writeQueue}}
 	} else {
diff --git a/pkg/sentry/socket/unix/transport/connectionless.go b/pkg/sentry/socket/unix/transport/connectionless.go
index e987519f0..c7f7c5b16 100644
--- a/pkg/sentry/socket/unix/transport/connectionless.go
+++ b/pkg/sentry/socket/unix/transport/connectionless.go
@@ -41,7 +41,9 @@ var (
 // NewConnectionless creates a new unbound dgram endpoint.
 func NewConnectionless(ctx context.Context) Endpoint {
 	ep := &connectionlessEndpoint{baseEndpoint{Queue: &waiter.Queue{}}}
-	ep.receiver = &queueReceiver{readQueue: &queue{ReaderQueue: ep.Queue, WriterQueue: &waiter.Queue{}, limit: initialLimit}}
+	q := queue{ReaderQueue: ep.Queue, WriterQueue: &waiter.Queue{}, limit: initialLimit}
+	q.EnableLeakCheck("transport.queue")
+	ep.receiver = &queueReceiver{readQueue: &q}
 	return ep
 }
 
@@ -52,29 +54,24 @@ func (e *connectionlessEndpoint) isBound() bool {
 
 // Close puts the endpoint in a closed state and frees all resources associated
 // with it.
-//
-// The socket will be a fresh state after a call to close and may be reused.
-// That is, close may be used to "unbind" or "disconnect" the socket in error
-// paths.
 func (e *connectionlessEndpoint) Close() {
 	e.Lock()
-	var r Receiver
-	if e.Connected() {
-		e.receiver.CloseRecv()
-		r = e.receiver
-		e.receiver = nil
-
+	if e.connected != nil {
 		e.connected.Release()
 		e.connected = nil
 	}
+
 	if e.isBound() {
 		e.path = ""
 	}
+
+	e.receiver.CloseRecv()
+	r := e.receiver
+	e.receiver = nil
 	e.Unlock()
-	if r != nil {
-		r.CloseNotify()
-		r.Release()
-	}
+
+	r.CloseNotify()
+	r.Release()
 }
 
 // BidirectionalConnect implements BoundEndpoint.BidirectionalConnect.
@@ -137,6 +134,9 @@ func (e *connectionlessEndpoint) Connect(ctx context.Context, server BoundEndpoi
 	}
 
 	e.Lock()
+	if e.connected != nil {
+		e.connected.Release()
+	}
 	e.connected = connected
 	e.Unlock()
 
diff --git a/pkg/sentry/socket/unix/unix.go b/pkg/sentry/socket/unix/unix.go
index 6190de0c5..637168714 100644
--- a/pkg/sentry/socket/unix/unix.go
+++ b/pkg/sentry/socket/unix/unix.go
@@ -28,7 +28,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/socket"
 	"gvisor.dev/gvisor/pkg/sentry/socket/control"
@@ -69,10 +68,13 @@ func New(ctx context.Context, endpoint transport.Endpoint, stype linux.SockType)
 
 // NewWithDirent creates a new unix socket using an existing dirent.
 func NewWithDirent(ctx context.Context, d *fs.Dirent, ep transport.Endpoint, stype linux.SockType, flags fs.FileFlags) *fs.File {
-	return fs.NewFile(ctx, d, flags, &SocketOperations{
+	s := SocketOperations{
 		ep:    ep,
 		stype: stype,
-	})
+	}
+	s.EnableLeakCheck("unix.SocketOperations")
+
+	return fs.NewFile(ctx, d, flags, &s)
 }
 
 // DecRef implements RefCounter.DecRef.
@@ -108,7 +110,7 @@ func (s *SocketOperations) Endpoint() transport.Endpoint {
 
 // extractPath extracts and validates the address.
 func extractPath(sockaddr []byte) (string, *syserr.Error) {
-	addr, err := epsocket.GetAddress(linux.AF_UNIX, sockaddr)
+	addr, err := epsocket.GetAddress(linux.AF_UNIX, sockaddr, true /* strict */)
 	if err != nil {
 		return "", err
 	}
@@ -191,7 +193,7 @@ func (s *SocketOperations) blockingAccept(t *kernel.Task) (transport.Endpoint, *
 
 // Accept implements the linux syscall accept(2) for sockets backed by
 // a transport.Endpoint.
-func (s *SocketOperations) Accept(t *kernel.Task, peerRequested bool, flags int, blocking bool) (kdefs.FD, interface{}, uint32, *syserr.Error) {
+func (s *SocketOperations) Accept(t *kernel.Task, peerRequested bool, flags int, blocking bool) (int32, interface{}, uint32, *syserr.Error) {
 	// Issue the accept request to get the new endpoint.
 	ep, err := s.ep.Accept()
 	if err != nil {
@@ -226,10 +228,9 @@ func (s *SocketOperations) Accept(t *kernel.Task, peerRequested bool, flags int,
 		}
 	}
 
-	fdFlags := kernel.FDFlags{
+	fd, e := t.NewFDFrom(0, ns, kernel.FDFlags{
 		CloseOnExec: flags&linux.SOCK_CLOEXEC != 0,
-	}
-	fd, e := t.FDMap().NewFDFrom(0, ns, fdFlags, t.ThreadGroup().Limits())
+	})
 	if e != nil {
 		return 0, nil, 0, syserr.FromError(e)
 	}
diff --git a/pkg/sentry/strace/poll.go b/pkg/sentry/strace/poll.go
index 57cf6b139..5187594a7 100644
--- a/pkg/sentry/strace/poll.go
+++ b/pkg/sentry/strace/poll.go
@@ -21,7 +21,6 @@ import (
 	"gvisor.dev/gvisor/pkg/abi"
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	slinux "gvisor.dev/gvisor/pkg/sentry/syscalls/linux"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
 )
@@ -50,7 +49,7 @@ func pollFD(t *kernel.Task, pfd *linux.PollFD, post bool) string {
 	if post {
 		revents = PollEventSet.Parse(uint64(pfd.REvents))
 	}
-	return fmt.Sprintf("{FD: %s, Events: %s, REvents: %s}", fd(t, kdefs.FD(pfd.FD)), PollEventSet.Parse(uint64(pfd.Events)), revents)
+	return fmt.Sprintf("{FD: %s, Events: %s, REvents: %s}", fd(t, pfd.FD), PollEventSet.Parse(uint64(pfd.Events)), revents)
 }
 
 func pollFDs(t *kernel.Task, addr usermem.Addr, nfds uint, post bool) string {
diff --git a/pkg/sentry/strace/socket.go b/pkg/sentry/strace/socket.go
index f9cf2eb21..386b40af7 100644
--- a/pkg/sentry/strace/socket.go
+++ b/pkg/sentry/strace/socket.go
@@ -332,7 +332,7 @@ func sockAddr(t *kernel.Task, addr usermem.Addr, length uint32) string {
 
 	switch family {
 	case linux.AF_INET, linux.AF_INET6, linux.AF_UNIX:
-		fa, err := epsocket.GetAddress(int(family), b)
+		fa, err := epsocket.GetAddress(int(family), b, true /* strict */)
 		if err != nil {
 			return fmt.Sprintf("%#x {Family: %s, error extracting address: %v}", addr, familyStr, err)
 		}
diff --git a/pkg/sentry/strace/strace.go b/pkg/sentry/strace/strace.go
index 86e9c5690..311389547 100644
--- a/pkg/sentry/strace/strace.go
+++ b/pkg/sentry/strace/strace.go
@@ -31,7 +31,6 @@ import (
 	"gvisor.dev/gvisor/pkg/seccomp"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	pb "gvisor.dev/gvisor/pkg/sentry/strace/strace_go_proto"
 	slinux "gvisor.dev/gvisor/pkg/sentry/syscalls/linux"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
@@ -133,7 +132,7 @@ func path(t *kernel.Task, addr usermem.Addr) string {
 	return fmt.Sprintf("%#x %s", addr, path)
 }
 
-func fd(t *kernel.Task, fd kdefs.FD) string {
+func fd(t *kernel.Task, fd int32) string {
 	root := t.FSContext().RootDirectory()
 	if root != nil {
 		defer root.DecRef()
@@ -151,7 +150,7 @@ func fd(t *kernel.Task, fd kdefs.FD) string {
 		return fmt.Sprintf("AT_FDCWD %s", name)
 	}
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		// Cast FD to uint64 to avoid printing negative hex.
 		return fmt.Sprintf("%#x (bad FD)", uint64(fd))
@@ -375,7 +374,7 @@ func (i *SyscallInfo) pre(t *kernel.Task, args arch.SyscallArguments, maximumBlo
 		}
 		switch i.format[arg] {
 		case FD:
-			output = append(output, fd(t, kdefs.FD(args[arg].Int())))
+			output = append(output, fd(t, args[arg].Int()))
 		case WriteBuffer:
 			output = append(output, dump(t, args[arg].Pointer(), args[arg+1].SizeT(), maximumBlobSize))
 		case WriteIOVec:
diff --git a/pkg/sentry/syscalls/epoll.go b/pkg/sentry/syscalls/epoll.go
index c710ec9e3..87dcad18b 100644
--- a/pkg/sentry/syscalls/epoll.go
+++ b/pkg/sentry/syscalls/epoll.go
@@ -15,25 +15,23 @@
 package syscalls
 
 import (
-	"syscall"
 	"time"
 
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/epoll"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
+	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
 
 // CreateEpoll implements the epoll_create(2) linux syscall.
-func CreateEpoll(t *kernel.Task, closeOnExec bool) (kdefs.FD, error) {
+func CreateEpoll(t *kernel.Task, closeOnExec bool) (int32, error) {
 	file := epoll.NewEventPoll(t)
 	defer file.DecRef()
 
-	flags := kernel.FDFlags{
+	fd, err := t.NewFDFrom(0, file, kernel.FDFlags{
 		CloseOnExec: closeOnExec,
-	}
-	fd, err := t.FDMap().NewFDFrom(0, file, flags, t.ThreadGroup().Limits())
+	})
 	if err != nil {
 		return 0, err
 	}
@@ -42,25 +40,25 @@ func CreateEpoll(t *kernel.Task, closeOnExec bool) (kdefs.FD, error) {
 }
 
 // AddEpoll implements the epoll_ctl(2) linux syscall when op is EPOLL_CTL_ADD.
-func AddEpoll(t *kernel.Task, epfd kdefs.FD, fd kdefs.FD, flags epoll.EntryFlags, mask waiter.EventMask, userData [2]int32) error {
+func AddEpoll(t *kernel.Task, epfd int32, fd int32, flags epoll.EntryFlags, mask waiter.EventMask, userData [2]int32) error {
 	// Get epoll from the file descriptor.
-	epollfile := t.FDMap().GetFile(epfd)
+	epollfile := t.GetFile(epfd)
 	if epollfile == nil {
-		return syscall.EBADF
+		return syserror.EBADF
 	}
 	defer epollfile.DecRef()
 
 	// Get the target file id.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
-		return syscall.EBADF
+		return syserror.EBADF
 	}
 	defer file.DecRef()
 
 	// Extract the epollPoll operations.
 	e, ok := epollfile.FileOperations.(*epoll.EventPoll)
 	if !ok {
-		return syscall.EBADF
+		return syserror.EBADF
 	}
 
 	// Try to add the entry.
@@ -68,25 +66,25 @@ func AddEpoll(t *kernel.Task, epfd kdefs.FD, fd kdefs.FD, flags epoll.EntryFlags
 }
 
 // UpdateEpoll implements the epoll_ctl(2) linux syscall when op is EPOLL_CTL_MOD.
-func UpdateEpoll(t *kernel.Task, epfd kdefs.FD, fd kdefs.FD, flags epoll.EntryFlags, mask waiter.EventMask, userData [2]int32) error {
+func UpdateEpoll(t *kernel.Task, epfd int32, fd int32, flags epoll.EntryFlags, mask waiter.EventMask, userData [2]int32) error {
 	// Get epoll from the file descriptor.
-	epollfile := t.FDMap().GetFile(epfd)
+	epollfile := t.GetFile(epfd)
 	if epollfile == nil {
-		return syscall.EBADF
+		return syserror.EBADF
 	}
 	defer epollfile.DecRef()
 
 	// Get the target file id.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
-		return syscall.EBADF
+		return syserror.EBADF
 	}
 	defer file.DecRef()
 
 	// Extract the epollPoll operations.
 	e, ok := epollfile.FileOperations.(*epoll.EventPoll)
 	if !ok {
-		return syscall.EBADF
+		return syserror.EBADF
 	}
 
 	// Try to update the entry.
@@ -94,25 +92,25 @@ func UpdateEpoll(t *kernel.Task, epfd kdefs.FD, fd kdefs.FD, flags epoll.EntryFl
 }
 
 // RemoveEpoll implements the epoll_ctl(2) linux syscall when op is EPOLL_CTL_DEL.
-func RemoveEpoll(t *kernel.Task, epfd kdefs.FD, fd kdefs.FD) error {
+func RemoveEpoll(t *kernel.Task, epfd int32, fd int32) error {
 	// Get epoll from the file descriptor.
-	epollfile := t.FDMap().GetFile(epfd)
+	epollfile := t.GetFile(epfd)
 	if epollfile == nil {
-		return syscall.EBADF
+		return syserror.EBADF
 	}
 	defer epollfile.DecRef()
 
 	// Get the target file id.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
-		return syscall.EBADF
+		return syserror.EBADF
 	}
 	defer file.DecRef()
 
 	// Extract the epollPoll operations.
 	e, ok := epollfile.FileOperations.(*epoll.EventPoll)
 	if !ok {
-		return syscall.EBADF
+		return syserror.EBADF
 	}
 
 	// Try to remove the entry.
@@ -120,18 +118,18 @@ func RemoveEpoll(t *kernel.Task, epfd kdefs.FD, fd kdefs.FD) error {
 }
 
 // WaitEpoll implements the epoll_wait(2) linux syscall.
-func WaitEpoll(t *kernel.Task, fd kdefs.FD, max int, timeout int) ([]epoll.Event, error) {
+func WaitEpoll(t *kernel.Task, fd int32, max int, timeout int) ([]epoll.Event, error) {
 	// Get epoll from the file descriptor.
-	epollfile := t.FDMap().GetFile(fd)
+	epollfile := t.GetFile(fd)
 	if epollfile == nil {
-		return nil, syscall.EBADF
+		return nil, syserror.EBADF
 	}
 	defer epollfile.DecRef()
 
 	// Extract the epollPoll operations.
 	e, ok := epollfile.FileOperations.(*epoll.EventPoll)
 	if !ok {
-		return nil, syscall.EBADF
+		return nil, syserror.EBADF
 	}
 
 	// Try to read events and return right away if we got them or if the
@@ -164,7 +162,7 @@ func WaitEpoll(t *kernel.Task, fd kdefs.FD, max int, timeout int) ([]epoll.Event
 		}
 
 		if err := t.BlockWithDeadline(ch, haveDeadline, deadline); err != nil {
-			if err == syscall.ETIMEDOUT {
+			if err == syserror.ETIMEDOUT {
 				return nil, nil
 			}
 
diff --git a/pkg/sentry/syscalls/linux/error.go b/pkg/sentry/syscalls/linux/error.go
index ac3905c5c..264301bfa 100644
--- a/pkg/sentry/syscalls/linux/error.go
+++ b/pkg/sentry/syscalls/linux/error.go
@@ -17,7 +17,6 @@ package linux
 import (
 	"io"
 	"sync"
-	"syscall"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/log"
@@ -54,7 +53,7 @@ func handleIOError(t *kernel.Task, partialResult bool, err, intr error, op strin
 		// Do not consume the error and return it as EFBIG.
 		// Simultaneously send a SIGXFSZ per setrlimit(2).
 		t.SendSignal(kernel.SignalInfoNoInfo(linux.SIGXFSZ, t, t))
-		return syscall.EFBIG
+		return syserror.EFBIG
 	case syserror.ErrInterrupted:
 		// The syscall was interrupted. Return nil if it completed
 		// partially, otherwise return the error code that the syscall
diff --git a/pkg/sentry/syscalls/linux/linux64.go b/pkg/sentry/syscalls/linux/linux64.go
index 7f18b1ac8..51db2d8f7 100644
--- a/pkg/sentry/syscalls/linux/linux64.go
+++ b/pkg/sentry/syscalls/linux/linux64.go
@@ -16,8 +16,6 @@
 package linux
 
 import (
-	"syscall"
-
 	"gvisor.dev/gvisor/pkg/abi"
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
@@ -50,335 +48,335 @@ var AMD64 = &kernel.SyscallTable{
 	Table: map[uintptr]kernel.Syscall{
 		0:   syscalls.Supported("read", Read),
 		1:   syscalls.Supported("write", Write),
-		2:   syscalls.Supported("open", Open),
+		2:   syscalls.PartiallySupported("open", Open, "Options O_DIRECT, O_NOATIME, O_PATH, O_TMPFILE, O_SYNC are not supported.", nil),
 		3:   syscalls.Supported("close", Close),
-		4:   syscalls.Undocumented("stat", Stat),
-		5:   syscalls.Undocumented("fstat", Fstat),
-		6:   syscalls.Undocumented("lstat", Lstat),
-		7:   syscalls.Undocumented("poll", Poll),
-		8:   syscalls.Undocumented("lseek", Lseek),
-		9:   syscalls.Undocumented("mmap", Mmap),
-		10:  syscalls.Undocumented("mprotect", Mprotect),
-		11:  syscalls.Undocumented("munmap", Munmap),
-		12:  syscalls.Undocumented("brk", Brk),
-		13:  syscalls.Undocumented("rt_sigaction", RtSigaction),
-		14:  syscalls.Undocumented("rt_sigprocmask", RtSigprocmask),
-		15:  syscalls.Undocumented("rt_sigreturn", RtSigreturn),
-		16:  syscalls.Undocumented("ioctl", Ioctl),
-		17:  syscalls.Undocumented("pread64", Pread64),
-		18:  syscalls.Undocumented("pwrite64", Pwrite64),
-		19:  syscalls.Undocumented("readv", Readv),
-		20:  syscalls.Undocumented("writev", Writev),
-		21:  syscalls.Undocumented("access", Access),
-		22:  syscalls.Undocumented("pipe", Pipe),
-		23:  syscalls.Undocumented("select", Select),
-		24:  syscalls.Undocumented("sched_yield", SchedYield),
-		25:  syscalls.Undocumented("mremap", Mremap),
-		26:  syscalls.Undocumented("msync", Msync),
-		27:  syscalls.Undocumented("mincore", Mincore),
-		28:  syscalls.Undocumented("madvise", Madvise),
-		29:  syscalls.Undocumented("shmget", Shmget),
-		30:  syscalls.Undocumented("shmat", Shmat),
-		31:  syscalls.Undocumented("shmctl", Shmctl),
-		32:  syscalls.Undocumented("dup", Dup),
-		33:  syscalls.Undocumented("dup2", Dup2),
-		34:  syscalls.Undocumented("pause", Pause),
-		35:  syscalls.Undocumented("nanosleep", Nanosleep),
-		36:  syscalls.Undocumented("getitimer", Getitimer),
-		37:  syscalls.Undocumented("alarm", Alarm),
-		38:  syscalls.Undocumented("setitimer", Setitimer),
-		39:  syscalls.Undocumented("getpid", Getpid),
-		40:  syscalls.Undocumented("sendfile", Sendfile),
-		41:  syscalls.Undocumented("socket", Socket),
-		42:  syscalls.Undocumented("connect", Connect),
-		43:  syscalls.Undocumented("accept", Accept),
-		44:  syscalls.Undocumented("sendto", SendTo),
-		45:  syscalls.Undocumented("recvfrom", RecvFrom),
-		46:  syscalls.Undocumented("sendmsg", SendMsg),
-		47:  syscalls.Undocumented("recvmsg", RecvMsg),
-		48:  syscalls.Undocumented("shutdown", Shutdown),
-		49:  syscalls.Undocumented("bind", Bind),
-		50:  syscalls.Undocumented("listen", Listen),
-		51:  syscalls.Undocumented("getsockname", GetSockName),
-		52:  syscalls.Undocumented("getpeername", GetPeerName),
-		53:  syscalls.Undocumented("socketpair", SocketPair),
-		54:  syscalls.Undocumented("setsockopt", SetSockOpt),
-		55:  syscalls.Undocumented("getsockopt", GetSockOpt),
-		56:  syscalls.Undocumented("clone", Clone),
-		57:  syscalls.Undocumented("fork", Fork),
-		58:  syscalls.Undocumented("vfork", Vfork),
-		59:  syscalls.Undocumented("execve", Execve),
-		60:  syscalls.Undocumented("exit", Exit),
-		61:  syscalls.Undocumented("wait4", Wait4),
-		62:  syscalls.Undocumented("kill", Kill),
-		63:  syscalls.Undocumented("uname", Uname),
-		64:  syscalls.Undocumented("semget", Semget),
-		65:  syscalls.Undocumented("semop", Semop),
-		66:  syscalls.Undocumented("semctl", Semctl),
-		67:  syscalls.Undocumented("shmdt", Shmdt),
-		68:  syscalls.ErrorWithEvent("msgget", syscall.ENOSYS, "", []string{"gvisor.dev/issue/135"}), // TODO(b/29354921)
-		69:  syscalls.ErrorWithEvent("msgsnd", syscall.ENOSYS, "", []string{"gvisor.dev/issue/135"}), // TODO(b/29354921)
-		70:  syscalls.ErrorWithEvent("msgrcv", syscall.ENOSYS, "", []string{"gvisor.dev/issue/135"}), // TODO(b/29354921)
-		71:  syscalls.ErrorWithEvent("msgctl", syscall.ENOSYS, "", []string{"gvisor.dev/issue/135"}), // TODO(b/29354921)
-		72:  syscalls.Undocumented("fcntl", Fcntl),
-		73:  syscalls.Undocumented("flock", Flock),
-		74:  syscalls.Undocumented("fsync", Fsync),
-		75:  syscalls.Undocumented("fdatasync", Fdatasync),
-		76:  syscalls.Undocumented("truncate", Truncate),
-		77:  syscalls.Undocumented("ftruncate", Ftruncate),
-		78:  syscalls.Undocumented("getdents", Getdents),
-		79:  syscalls.Undocumented("getcwd", Getcwd),
-		80:  syscalls.Undocumented("chdir", Chdir),
-		81:  syscalls.Undocumented("fchdir", Fchdir),
-		82:  syscalls.Undocumented("rename", Rename),
-		83:  syscalls.Undocumented("mkdir", Mkdir),
-		84:  syscalls.Undocumented("rmdir", Rmdir),
-		85:  syscalls.Undocumented("creat", Creat),
-		86:  syscalls.Undocumented("link", Link),
-		87:  syscalls.Undocumented("link", Unlink),
-		88:  syscalls.Undocumented("symlink", Symlink),
-		89:  syscalls.Undocumented("readlink", Readlink),
-		90:  syscalls.Undocumented("chmod", Chmod),
-		91:  syscalls.Undocumented("fchmod", Fchmod),
-		92:  syscalls.Undocumented("chown", Chown),
-		93:  syscalls.Undocumented("fchown", Fchown),
-		94:  syscalls.Undocumented("lchown", Lchown),
-		95:  syscalls.Undocumented("umask", Umask),
-		96:  syscalls.Undocumented("gettimeofday", Gettimeofday),
-		97:  syscalls.Undocumented("getrlimit", Getrlimit),
-		98:  syscalls.Undocumented("getrusage", Getrusage),
-		99:  syscalls.Undocumented("sysinfo", Sysinfo),
-		100: syscalls.Undocumented("times", Times),
-		101: syscalls.Undocumented("ptrace", Ptrace),
-		102: syscalls.Undocumented("getuid", Getuid),
-		103: syscalls.Undocumented("syslog", Syslog),
-		104: syscalls.Undocumented("getgid", Getgid),
-		105: syscalls.Undocumented("setuid", Setuid),
-		106: syscalls.Undocumented("setgid", Setgid),
-		107: syscalls.Undocumented("geteuid", Geteuid),
-		108: syscalls.Undocumented("getegid", Getegid),
-		109: syscalls.Undocumented("setpgid", Setpgid),
-		110: syscalls.Undocumented("getppid", Getppid),
-		111: syscalls.Undocumented("getpgrp", Getpgrp),
-		112: syscalls.Undocumented("setsid", Setsid),
-		113: syscalls.Undocumented("setreuid", Setreuid),
-		114: syscalls.Undocumented("setregid", Setregid),
-		115: syscalls.Undocumented("getgroups", Getgroups),
-		116: syscalls.Undocumented("setgroups", Setgroups),
-		117: syscalls.Undocumented("setresuid", Setresuid),
-		118: syscalls.Undocumented("getresuid", Getresuid),
-		119: syscalls.Undocumented("setresgid", Setresgid),
-		120: syscalls.Undocumented("setresgid", Getresgid),
-		121: syscalls.Undocumented("getpgid", Getpgid),
-		122: syscalls.ErrorWithEvent("setfsuid", syscall.ENOSYS, "", []string{"gvisor.dev/issue/260"}), // TODO(b/112851702)
-		123: syscalls.ErrorWithEvent("setfsgid", syscall.ENOSYS, "", []string{"gvisor.dev/issue/260"}), // TODO(b/112851702)
-		124: syscalls.Undocumented("getsid", Getsid),
-		125: syscalls.Undocumented("capget", Capget),
-		126: syscalls.Undocumented("capset", Capset),
-		127: syscalls.Undocumented("rt_sigpending", RtSigpending),
-		128: syscalls.Undocumented("rt_sigtimedwait", RtSigtimedwait),
-		129: syscalls.Undocumented("rt_sigqueueinfo", RtSigqueueinfo),
-		130: syscalls.Undocumented("rt_sigsuspend", RtSigsuspend),
-		131: syscalls.Undocumented("sigaltstack", Sigaltstack),
-		132: syscalls.Undocumented("utime", Utime),
-		133: syscalls.Undocumented("mknod", Mknod),
-		134: syscalls.Error("uselib", syscall.ENOSYS, "Obsolete", nil),
-		135: syscalls.ErrorWithEvent("personality", syscall.EINVAL, "Unable to change personality.", nil),
-		136: syscalls.ErrorWithEvent("ustat", syscall.ENOSYS, "Needs filesystem support.", nil),
-		137: syscalls.Undocumented("statfs", Statfs),
-		138: syscalls.Undocumented("fstatfs", Fstatfs),
-		139: syscalls.ErrorWithEvent("sysfs", syscall.ENOSYS, "", []string{"gvisor.dev/issue/165"}),
-		140: syscalls.Undocumented("getpriority", Getpriority),
-		141: syscalls.Undocumented("setpriority", Setpriority),
+		4:   syscalls.Supported("stat", Stat),
+		5:   syscalls.Supported("fstat", Fstat),
+		6:   syscalls.Supported("lstat", Lstat),
+		7:   syscalls.Supported("poll", Poll),
+		8:   syscalls.Supported("lseek", Lseek),
+		9:   syscalls.PartiallySupported("mmap", Mmap, "Generally supported with exceptions. Options MAP_FIXED_NOREPLACE, MAP_SHARED_VALIDATE, MAP_SYNC MAP_GROWSDOWN, MAP_HUGETLB are not supported.", nil),
+		10:  syscalls.Supported("mprotect", Mprotect),
+		11:  syscalls.Supported("munmap", Munmap),
+		12:  syscalls.Supported("brk", Brk),
+		13:  syscalls.Supported("rt_sigaction", RtSigaction),
+		14:  syscalls.Supported("rt_sigprocmask", RtSigprocmask),
+		15:  syscalls.Supported("rt_sigreturn", RtSigreturn),
+		16:  syscalls.PartiallySupported("ioctl", Ioctl, "Only a few ioctls are implemented for backing devices and file systems.", nil),
+		17:  syscalls.Supported("pread64", Pread64),
+		18:  syscalls.Supported("pwrite64", Pwrite64),
+		19:  syscalls.Supported("readv", Readv),
+		20:  syscalls.Supported("writev", Writev),
+		21:  syscalls.Supported("access", Access),
+		22:  syscalls.Supported("pipe", Pipe),
+		23:  syscalls.Supported("select", Select),
+		24:  syscalls.Supported("sched_yield", SchedYield),
+		25:  syscalls.Supported("mremap", Mremap),
+		26:  syscalls.PartiallySupported("msync", Msync, "Full data flush is not guaranteed at this time.", nil),
+		27:  syscalls.PartiallySupported("mincore", Mincore, "Stub implementation. The sandbox does not have access to this information. Reports all mapped pages are resident.", nil),
+		28:  syscalls.PartiallySupported("madvise", Madvise, "Options MADV_DONTNEED, MADV_DONTFORK are supported. Other advice is ignored.", nil),
+		29:  syscalls.PartiallySupported("shmget", Shmget, "Option SHM_HUGETLB is not supported.", nil),
+		30:  syscalls.PartiallySupported("shmat", Shmat, "Option SHM_RND is not supported.", nil),
+		31:  syscalls.PartiallySupported("shmctl", Shmctl, "Options SHM_LOCK, SHM_UNLOCK are not supported.", nil),
+		32:  syscalls.Supported("dup", Dup),
+		33:  syscalls.Supported("dup2", Dup2),
+		34:  syscalls.Supported("pause", Pause),
+		35:  syscalls.Supported("nanosleep", Nanosleep),
+		36:  syscalls.Supported("getitimer", Getitimer),
+		37:  syscalls.Supported("alarm", Alarm),
+		38:  syscalls.Supported("setitimer", Setitimer),
+		39:  syscalls.Supported("getpid", Getpid),
+		40:  syscalls.Supported("sendfile", Sendfile),
+		41:  syscalls.PartiallySupported("socket", Socket, "Limited support for AF_NETLINK, NETLINK_ROUTE sockets. Limited support for SOCK_RAW.", nil),
+		42:  syscalls.Supported("connect", Connect),
+		43:  syscalls.Supported("accept", Accept),
+		44:  syscalls.Supported("sendto", SendTo),
+		45:  syscalls.Supported("recvfrom", RecvFrom),
+		46:  syscalls.Supported("sendmsg", SendMsg),
+		47:  syscalls.PartiallySupported("recvmsg", RecvMsg, "Not all flags and control messages are supported.", nil),
+		48:  syscalls.PartiallySupported("shutdown", Shutdown, "Not all flags and control messages are supported.", nil),
+		49:  syscalls.PartiallySupported("bind", Bind, "Autobind for abstract Unix sockets is not supported.", nil),
+		50:  syscalls.Supported("listen", Listen),
+		51:  syscalls.Supported("getsockname", GetSockName),
+		52:  syscalls.Supported("getpeername", GetPeerName),
+		53:  syscalls.Supported("socketpair", SocketPair),
+		54:  syscalls.PartiallySupported("setsockopt", SetSockOpt, "Not all socket options are supported.", nil),
+		55:  syscalls.PartiallySupported("getsockopt", GetSockOpt, "Not all socket options are supported.", nil),
+		56:  syscalls.PartiallySupported("clone", Clone, "Mount namespace (CLONE_NEWNS) not supported. Options CLONE_PARENT, CLONE_SYSVSEM not supported.", nil),
+		57:  syscalls.Supported("fork", Fork),
+		58:  syscalls.Supported("vfork", Vfork),
+		59:  syscalls.Supported("execve", Execve),
+		60:  syscalls.Supported("exit", Exit),
+		61:  syscalls.Supported("wait4", Wait4),
+		62:  syscalls.Supported("kill", Kill),
+		63:  syscalls.Supported("uname", Uname),
+		64:  syscalls.Supported("semget", Semget),
+		65:  syscalls.PartiallySupported("semop", Semop, "Option SEM_UNDO not supported.", nil),
+		66:  syscalls.PartiallySupported("semctl", Semctl, "Options IPC_INFO, SEM_INFO, IPC_STAT, SEM_STAT, SEM_STAT_ANY, GETNCNT, GETZCNT not supported.", nil),
+		67:  syscalls.Supported("shmdt", Shmdt),
+		68:  syscalls.ErrorWithEvent("msgget", syserror.ENOSYS, "", []string{"gvisor.dev/issue/135"}), // TODO(b/29354921)
+		69:  syscalls.ErrorWithEvent("msgsnd", syserror.ENOSYS, "", []string{"gvisor.dev/issue/135"}), // TODO(b/29354921)
+		70:  syscalls.ErrorWithEvent("msgrcv", syserror.ENOSYS, "", []string{"gvisor.dev/issue/135"}), // TODO(b/29354921)
+		71:  syscalls.ErrorWithEvent("msgctl", syserror.ENOSYS, "", []string{"gvisor.dev/issue/135"}), // TODO(b/29354921)
+		72:  syscalls.PartiallySupported("fcntl", Fcntl, "Not all options are supported.", nil),
+		73:  syscalls.PartiallySupported("flock", Flock, "Locks are held within the sandbox only.", nil),
+		74:  syscalls.PartiallySupported("fsync", Fsync, "Full data flush is not guaranteed at this time.", nil),
+		75:  syscalls.PartiallySupported("fdatasync", Fdatasync, "Full data flush is not guaranteed at this time.", nil),
+		76:  syscalls.Supported("truncate", Truncate),
+		77:  syscalls.Supported("ftruncate", Ftruncate),
+		78:  syscalls.Supported("getdents", Getdents),
+		79:  syscalls.Supported("getcwd", Getcwd),
+		80:  syscalls.Supported("chdir", Chdir),
+		81:  syscalls.Supported("fchdir", Fchdir),
+		82:  syscalls.Supported("rename", Rename),
+		83:  syscalls.Supported("mkdir", Mkdir),
+		84:  syscalls.Supported("rmdir", Rmdir),
+		85:  syscalls.Supported("creat", Creat),
+		86:  syscalls.Supported("link", Link),
+		87:  syscalls.Supported("unlink", Unlink),
+		88:  syscalls.Supported("symlink", Symlink),
+		89:  syscalls.Supported("readlink", Readlink),
+		90:  syscalls.Supported("chmod", Chmod),
+		91:  syscalls.PartiallySupported("fchmod", Fchmod, "Options S_ISUID and S_ISGID not supported.", nil),
+		92:  syscalls.Supported("chown", Chown),
+		93:  syscalls.Supported("fchown", Fchown),
+		94:  syscalls.Supported("lchown", Lchown),
+		95:  syscalls.Supported("umask", Umask),
+		96:  syscalls.Supported("gettimeofday", Gettimeofday),
+		97:  syscalls.Supported("getrlimit", Getrlimit),
+		98:  syscalls.PartiallySupported("getrusage", Getrusage, "Fields ru_maxrss, ru_minflt, ru_majflt, ru_inblock, ru_oublock are not supported. Fields ru_utime and ru_stime have low precision.", nil),
+		99:  syscalls.PartiallySupported("sysinfo", Sysinfo, "Fields loads, sharedram, bufferram, totalswap, freeswap, totalhigh, freehigh not supported.", nil),
+		100: syscalls.Supported("times", Times),
+		101: syscalls.PartiallySupported("ptrace", Ptrace, "Options PTRACE_PEEKSIGINFO, PTRACE_SECCOMP_GET_FILTER not supported.", nil),
+		102: syscalls.Supported("getuid", Getuid),
+		103: syscalls.PartiallySupported("syslog", Syslog, "Outputs a dummy message for security reasons.", nil),
+		104: syscalls.Supported("getgid", Getgid),
+		105: syscalls.Supported("setuid", Setuid),
+		106: syscalls.Supported("setgid", Setgid),
+		107: syscalls.Supported("geteuid", Geteuid),
+		108: syscalls.Supported("getegid", Getegid),
+		109: syscalls.Supported("setpgid", Setpgid),
+		110: syscalls.Supported("getppid", Getppid),
+		111: syscalls.Supported("getpgrp", Getpgrp),
+		112: syscalls.Supported("setsid", Setsid),
+		113: syscalls.Supported("setreuid", Setreuid),
+		114: syscalls.Supported("setregid", Setregid),
+		115: syscalls.Supported("getgroups", Getgroups),
+		116: syscalls.Supported("setgroups", Setgroups),
+		117: syscalls.Supported("setresuid", Setresuid),
+		118: syscalls.Supported("getresuid", Getresuid),
+		119: syscalls.Supported("setresgid", Setresgid),
+		120: syscalls.Supported("getresgid", Getresgid),
+		121: syscalls.Supported("getpgid", Getpgid),
+		122: syscalls.ErrorWithEvent("setfsuid", syserror.ENOSYS, "", []string{"gvisor.dev/issue/260"}), // TODO(b/112851702)
+		123: syscalls.ErrorWithEvent("setfsgid", syserror.ENOSYS, "", []string{"gvisor.dev/issue/260"}), // TODO(b/112851702)
+		124: syscalls.Supported("getsid", Getsid),
+		125: syscalls.Supported("capget", Capget),
+		126: syscalls.Supported("capset", Capset),
+		127: syscalls.Supported("rt_sigpending", RtSigpending),
+		128: syscalls.Supported("rt_sigtimedwait", RtSigtimedwait),
+		129: syscalls.Supported("rt_sigqueueinfo", RtSigqueueinfo),
+		130: syscalls.Supported("rt_sigsuspend", RtSigsuspend),
+		131: syscalls.Supported("sigaltstack", Sigaltstack),
+		132: syscalls.Supported("utime", Utime),
+		133: syscalls.PartiallySupported("mknod", Mknod, "Device creation is not generally supported. Only regular file and FIFO creation are supported.", nil),
+		134: syscalls.Error("uselib", syserror.ENOSYS, "Obsolete", nil),
+		135: syscalls.ErrorWithEvent("personality", syserror.EINVAL, "Unable to change personality.", nil),
+		136: syscalls.ErrorWithEvent("ustat", syserror.ENOSYS, "Needs filesystem support.", nil),
+		137: syscalls.PartiallySupported("statfs", Statfs, "Depends on the backing file system implementation.", nil),
+		138: syscalls.PartiallySupported("fstatfs", Fstatfs, "Depends on the backing file system implementation.", nil),
+		139: syscalls.ErrorWithEvent("sysfs", syserror.ENOSYS, "", []string{"gvisor.dev/issue/165"}),
+		140: syscalls.PartiallySupported("getpriority", Getpriority, "Stub implementation.", nil),
+		141: syscalls.PartiallySupported("setpriority", Setpriority, "Stub implementation.", nil),
 		142: syscalls.CapError("sched_setparam", linux.CAP_SYS_NICE, "", nil),
-		143: syscalls.Undocumented("sched_getparam", SchedGetparam),
-		144: syscalls.Undocumented("sched_setscheduler", SchedSetscheduler),
-		145: syscalls.Undocumented("sched_getscheduler", SchedGetscheduler),
-		146: syscalls.Undocumented("sched_get_priority_max", SchedGetPriorityMax),
-		147: syscalls.Undocumented("sched_get_priority_min", SchedGetPriorityMin),
-		148: syscalls.ErrorWithEvent("sched_rr_get_interval", syscall.EPERM, "", nil),
-		149: syscalls.Undocumented("mlock", Mlock),
-		150: syscalls.Undocumented("munlock", Munlock),
-		151: syscalls.Undocumented("mlockall", Mlockall),
-		152: syscalls.Undocumented("munlockall", Munlockall),
+		143: syscalls.PartiallySupported("sched_getparam", SchedGetparam, "Stub implementation.", nil),
+		144: syscalls.PartiallySupported("sched_setscheduler", SchedSetscheduler, "Stub implementation.", nil),
+		145: syscalls.PartiallySupported("sched_getscheduler", SchedGetscheduler, "Stub implementation.", nil),
+		146: syscalls.PartiallySupported("sched_get_priority_max", SchedGetPriorityMax, "Stub implementation.", nil),
+		147: syscalls.PartiallySupported("sched_get_priority_min", SchedGetPriorityMin, "Stub implementation.", nil),
+		148: syscalls.ErrorWithEvent("sched_rr_get_interval", syserror.EPERM, "", nil),
+		149: syscalls.PartiallySupported("mlock", Mlock, "Stub implementation. The sandbox lacks appropriate permissions.", nil),
+		150: syscalls.PartiallySupported("munlock", Munlock, "Stub implementation. The sandbox lacks appropriate permissions.", nil),
+		151: syscalls.PartiallySupported("mlockall", Mlockall, "Stub implementation. The sandbox lacks appropriate permissions.", nil),
+		152: syscalls.PartiallySupported("munlockall", Munlockall, "Stub implementation. The sandbox lacks appropriate permissions.", nil),
 		153: syscalls.CapError("vhangup", linux.CAP_SYS_TTY_CONFIG, "", nil),
-		154: syscalls.Error("modify_ldt", syscall.EPERM, "", nil),
-		155: syscalls.Error("pivot_root", syscall.EPERM, "", nil),
-		156: syscalls.Error("sysctl", syscall.EPERM, `syscall is "worthless"`, nil),
-		157: syscalls.Undocumented("prctl", Prctl),
-		158: syscalls.Undocumented("arch_prctl", ArchPrctl),
+		154: syscalls.Error("modify_ldt", syserror.EPERM, "", nil),
+		155: syscalls.Error("pivot_root", syserror.EPERM, "", nil),
+		156: syscalls.Error("sysctl", syserror.EPERM, "Deprecated. Use /proc/sys instead.", nil),
+		157: syscalls.PartiallySupported("prctl", Prctl, "Not all options are supported.", nil),
+		158: syscalls.PartiallySupported("arch_prctl", ArchPrctl, "Options ARCH_GET_GS, ARCH_SET_GS not supported.", nil),
 		159: syscalls.CapError("adjtimex", linux.CAP_SYS_TIME, "", nil),
-		160: syscalls.Undocumented("setrlimit", Setrlimit),
-		161: syscalls.Undocumented("chroot", Chroot),
-		162: syscalls.Undocumented("sync", Sync),
+		160: syscalls.PartiallySupported("setrlimit", Setrlimit, "Not all rlimits are enforced.", nil),
+		161: syscalls.Supported("chroot", Chroot),
+		162: syscalls.PartiallySupported("sync", Sync, "Full data flush is not guaranteed at this time.", nil),
 		163: syscalls.CapError("acct", linux.CAP_SYS_PACCT, "", nil),
 		164: syscalls.CapError("settimeofday", linux.CAP_SYS_TIME, "", nil),
-		165: syscalls.Undocumented("mount", Mount),
-		166: syscalls.Undocumented("umount2", Umount2),
+		165: syscalls.PartiallySupported("mount", Mount, "Not all options or file systems are supported.", nil),
+		166: syscalls.PartiallySupported("umount2", Umount2, "Not all options or file systems are supported.", nil),
 		167: syscalls.CapError("swapon", linux.CAP_SYS_ADMIN, "", nil),
 		168: syscalls.CapError("swapoff", linux.CAP_SYS_ADMIN, "", nil),
 		169: syscalls.CapError("reboot", linux.CAP_SYS_BOOT, "", nil),
-		170: syscalls.Undocumented("sethostname", Sethostname),
-		171: syscalls.Undocumented("setdomainname", Setdomainname),
+		170: syscalls.Supported("sethostname", Sethostname),
+		171: syscalls.Supported("setdomainname", Setdomainname),
 		172: syscalls.CapError("iopl", linux.CAP_SYS_RAWIO, "", nil),
 		173: syscalls.CapError("ioperm", linux.CAP_SYS_RAWIO, "", nil),
 		174: syscalls.CapError("create_module", linux.CAP_SYS_MODULE, "", nil),
 		175: syscalls.CapError("init_module", linux.CAP_SYS_MODULE, "", nil),
 		176: syscalls.CapError("delete_module", linux.CAP_SYS_MODULE, "", nil),
-		177: syscalls.Error("get_kernel_syms", syscall.ENOSYS, "Not supported in > 2.6", nil),
-		178: syscalls.Error("query_module", syscall.ENOSYS, "Not supported in > 2.6", nil),
+		177: syscalls.Error("get_kernel_syms", syserror.ENOSYS, "Not supported in Linux > 2.6.", nil),
+		178: syscalls.Error("query_module", syserror.ENOSYS, "Not supported in Linux > 2.6.", nil),
 		179: syscalls.CapError("quotactl", linux.CAP_SYS_ADMIN, "", nil), // requires cap_sys_admin for most operations
-		180: syscalls.Error("nfsservctl", syscall.ENOSYS, "Does not exist > 3.1", nil),
-		181: syscalls.Error("getpmsg", syscall.ENOSYS, "Not implemented in Linux", nil),
-		182: syscalls.Error("putpmsg", syscall.ENOSYS, "Not implemented in Linux", nil),
-		183: syscalls.Error("afs_syscall", syscall.ENOSYS, "Not implemented in Linux", nil),
-		184: syscalls.Error("tuxcall", syscall.ENOSYS, "Not implemented in Linux", nil),
-		185: syscalls.Error("security", syscall.ENOSYS, "Not implemented in Linux", nil),
-		186: syscalls.Undocumented("gettid", Gettid),
-		187: syscalls.ErrorWithEvent("readahead", syscall.ENOSYS, "", []string{"gvisor.dev/issue/261"}), // TODO(b/29351341)
-		188: syscalls.ErrorWithEvent("setxattr", syscall.ENOTSUP, "Requires filesystem support", nil),
-		189: syscalls.ErrorWithEvent("lsetxattr", syscall.ENOTSUP, "Requires filesystem support", nil),
-		190: syscalls.ErrorWithEvent("fsetxattr", syscall.ENOTSUP, "Requires filesystem support", nil),
-		191: syscalls.ErrorWithEvent("getxattr", syscall.ENOTSUP, "Requires filesystem support", nil),
-		192: syscalls.ErrorWithEvent("lgetxattr", syscall.ENOTSUP, "Requires filesystem support", nil),
-		193: syscalls.ErrorWithEvent("fgetxattr", syscall.ENOTSUP, "Requires filesystem support", nil),
-		194: syscalls.ErrorWithEvent("listxattr", syscall.ENOTSUP, "Requires filesystem support", nil),
-		195: syscalls.ErrorWithEvent("llistxattr", syscall.ENOTSUP, "Requires filesystem support", nil),
-		196: syscalls.ErrorWithEvent("flistxattr", syscall.ENOTSUP, "Requires filesystem support", nil),
-		197: syscalls.ErrorWithEvent("removexattr", syscall.ENOTSUP, "Requires filesystem support", nil),
-		198: syscalls.ErrorWithEvent("lremovexattr", syscall.ENOTSUP, "Requires filesystem support", nil),
-		199: syscalls.ErrorWithEvent("fremovexattr", syscall.ENOTSUP, "Requires filesystem support", nil),
-		200: syscalls.Undocumented("tkill", Tkill),
-		201: syscalls.Undocumented("time", Time),
-		202: syscalls.Undocumented("futex", Futex),
-		203: syscalls.Undocumented("sched_setaffinity", SchedSetaffinity),
-		204: syscalls.Undocumented("sched_getaffinity", SchedGetaffinity),
-		205: syscalls.Error("set_thread_area", syscall.ENOSYS, "Expected to return ENOSYS on 64-bit", nil),
-		206: syscalls.Undocumented("io_setup", IoSetup),
-		207: syscalls.Undocumented("io_destroy", IoDestroy),
-		208: syscalls.Undocumented("io_getevents", IoGetevents),
-		209: syscalls.Undocumented("io_submit", IoSubmit),
-		210: syscalls.Undocumented("io_cancel", IoCancel),
-		211: syscalls.Error("get_thread_area", syscall.ENOSYS, "Expected to return ENOSYS on 64-bit", nil),
+		180: syscalls.Error("nfsservctl", syserror.ENOSYS, "Removed after Linux 3.1.", nil),
+		181: syscalls.Error("getpmsg", syserror.ENOSYS, "Not implemented in Linux.", nil),
+		182: syscalls.Error("putpmsg", syserror.ENOSYS, "Not implemented in Linux.", nil),
+		183: syscalls.Error("afs_syscall", syserror.ENOSYS, "Not implemented in Linux.", nil),
+		184: syscalls.Error("tuxcall", syserror.ENOSYS, "Not implemented in Linux.", nil),
+		185: syscalls.Error("security", syserror.ENOSYS, "Not implemented in Linux.", nil),
+		186: syscalls.Supported("gettid", Gettid),
+		187: syscalls.ErrorWithEvent("readahead", syserror.ENOSYS, "", []string{"gvisor.dev/issue/261"}), // TODO(b/29351341)
+		188: syscalls.Error("setxattr", syserror.ENOTSUP, "Requires filesystem support.", nil),
+		189: syscalls.Error("lsetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil),
+		190: syscalls.Error("fsetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil),
+		191: syscalls.ErrorWithEvent("getxattr", syserror.ENOTSUP, "Requires filesystem support.", nil),
+		192: syscalls.ErrorWithEvent("lgetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil),
+		193: syscalls.ErrorWithEvent("fgetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil),
+		194: syscalls.ErrorWithEvent("listxattr", syserror.ENOTSUP, "Requires filesystem support.", nil),
+		195: syscalls.ErrorWithEvent("llistxattr", syserror.ENOTSUP, "Requires filesystem support.", nil),
+		196: syscalls.ErrorWithEvent("flistxattr", syserror.ENOTSUP, "Requires filesystem support.", nil),
+		197: syscalls.ErrorWithEvent("removexattr", syserror.ENOTSUP, "Requires filesystem support.", nil),
+		198: syscalls.ErrorWithEvent("lremovexattr", syserror.ENOTSUP, "Requires filesystem support.", nil),
+		199: syscalls.ErrorWithEvent("fremovexattr", syserror.ENOTSUP, "Requires filesystem support.", nil),
+		200: syscalls.Supported("tkill", Tkill),
+		201: syscalls.Supported("time", Time),
+		202: syscalls.PartiallySupported("futex", Futex, "Robust futexes not supported.", nil),
+		203: syscalls.PartiallySupported("sched_setaffinity", SchedSetaffinity, "Stub implementation.", nil),
+		204: syscalls.PartiallySupported("sched_getaffinity", SchedGetaffinity, "Stub implementation.", nil),
+		205: syscalls.Error("set_thread_area", syserror.ENOSYS, "Expected to return ENOSYS on 64-bit", nil),
+		206: syscalls.PartiallySupported("io_setup", IoSetup, "Generally supported with exceptions. User ring optimizations are not implemented.", []string{"gvisor.dev/issue/204"}),
+		207: syscalls.PartiallySupported("io_destroy", IoDestroy, "Generally supported with exceptions. User ring optimizations are not implemented.", []string{"gvisor.dev/issue/204"}),
+		208: syscalls.PartiallySupported("io_getevents", IoGetevents, "Generally supported with exceptions. User ring optimizations are not implemented.", []string{"gvisor.dev/issue/204"}),
+		209: syscalls.PartiallySupported("io_submit", IoSubmit, "Generally supported with exceptions. User ring optimizations are not implemented.", []string{"gvisor.dev/issue/204"}),
+		210: syscalls.PartiallySupported("io_cancel", IoCancel, "Generally supported with exceptions. User ring optimizations are not implemented.", []string{"gvisor.dev/issue/204"}),
+		211: syscalls.Error("get_thread_area", syserror.ENOSYS, "Expected to return ENOSYS on 64-bit", nil),
 		212: syscalls.CapError("lookup_dcookie", linux.CAP_SYS_ADMIN, "", nil),
-		213: syscalls.Undocumented("epoll_create", EpollCreate),
-		214: syscalls.ErrorWithEvent("epoll_ctl_old", syscall.ENOSYS, "Deprecated", nil),
-		215: syscalls.ErrorWithEvent("epoll_wait_old", syscall.ENOSYS, "Deprecated", nil),
-		216: syscalls.ErrorWithEvent("remap_file_pages", syscall.ENOSYS, "Deprecated since 3.16", nil),
-		217: syscalls.Undocumented("getdents64", Getdents64),
-		218: syscalls.Undocumented("set_tid_address", SetTidAddress),
-		219: syscalls.Undocumented("restart_syscall", RestartSyscall),
-		220: syscalls.ErrorWithEvent("semtimedop", syscall.ENOSYS, "", []string{"gvisor.dev/issue/137"}), // TODO(b/29354920)
-		221: syscalls.Undocumented("fadvise64", Fadvise64),
-		222: syscalls.Undocumented("timer_create", TimerCreate),
-		223: syscalls.Undocumented("timer_settime", TimerSettime),
-		224: syscalls.Undocumented("timer_gettime", TimerGettime),
-		225: syscalls.Undocumented("timer_getoverrun", TimerGetoverrun),
-		226: syscalls.Undocumented("timer_delete", TimerDelete),
-		227: syscalls.Undocumented("clock_settime", ClockSettime),
-		228: syscalls.Undocumented("clock_gettime", ClockGettime),
-		229: syscalls.Undocumented("clock_getres", ClockGetres),
-		230: syscalls.Undocumented("clock_nanosleep", ClockNanosleep),
-		231: syscalls.Undocumented("exit_group", ExitGroup),
-		232: syscalls.Undocumented("epoll_wait", EpollWait),
-		233: syscalls.Undocumented("epoll_ctl", EpollCtl),
-		234: syscalls.Undocumented("tgkill", Tgkill),
-		235: syscalls.Undocumented("utimes", Utimes),
-		236: syscalls.Error("vserver", syscall.ENOSYS, "Not implemented by Linux", nil),
+		213: syscalls.Supported("epoll_create", EpollCreate),
+		214: syscalls.ErrorWithEvent("epoll_ctl_old", syserror.ENOSYS, "Deprecated.", nil),
+		215: syscalls.ErrorWithEvent("epoll_wait_old", syserror.ENOSYS, "Deprecated.", nil),
+		216: syscalls.ErrorWithEvent("remap_file_pages", syserror.ENOSYS, "Deprecated since Linux 3.16.", nil),
+		217: syscalls.Supported("getdents64", Getdents64),
+		218: syscalls.Supported("set_tid_address", SetTidAddress),
+		219: syscalls.Supported("restart_syscall", RestartSyscall),
+		220: syscalls.ErrorWithEvent("semtimedop", syserror.ENOSYS, "", []string{"gvisor.dev/issue/137"}), // TODO(b/29354920)
+		221: syscalls.PartiallySupported("fadvise64", Fadvise64, "Not all options are supported.", nil),
+		222: syscalls.Supported("timer_create", TimerCreate),
+		223: syscalls.Supported("timer_settime", TimerSettime),
+		224: syscalls.Supported("timer_gettime", TimerGettime),
+		225: syscalls.Supported("timer_getoverrun", TimerGetoverrun),
+		226: syscalls.Supported("timer_delete", TimerDelete),
+		227: syscalls.Supported("clock_settime", ClockSettime),
+		228: syscalls.Supported("clock_gettime", ClockGettime),
+		229: syscalls.Supported("clock_getres", ClockGetres),
+		230: syscalls.Supported("clock_nanosleep", ClockNanosleep),
+		231: syscalls.Supported("exit_group", ExitGroup),
+		232: syscalls.Supported("epoll_wait", EpollWait),
+		233: syscalls.Supported("epoll_ctl", EpollCtl),
+		234: syscalls.Supported("tgkill", Tgkill),
+		235: syscalls.Supported("utimes", Utimes),
+		236: syscalls.Error("vserver", syserror.ENOSYS, "Not implemented by Linux", nil),
 		237: syscalls.PartiallySupported("mbind", Mbind, "Stub implementation. Only a single NUMA node is advertised, and mempolicy is ignored accordingly, but mbind() will succeed and has effects reflected by get_mempolicy.", []string{"gvisor.dev/issue/262"}),
-		238: syscalls.Undocumented("set_mempolicy", SetMempolicy),
-		239: syscalls.Undocumented("get_mempolicy", GetMempolicy),
-		240: syscalls.ErrorWithEvent("mq_open", syscall.ENOSYS, "", []string{"gvisor.dev/issue/136"}),         // TODO(b/29354921)
-		241: syscalls.ErrorWithEvent("mq_unlink", syscall.ENOSYS, "", []string{"gvisor.dev/issue/136"}),       // TODO(b/29354921)
-		242: syscalls.ErrorWithEvent("mq_timedsend", syscall.ENOSYS, "", []string{"gvisor.dev/issue/136"}),    // TODO(b/29354921)
-		243: syscalls.ErrorWithEvent("mq_timedreceive", syscall.ENOSYS, "", []string{"gvisor.dev/issue/136"}), // TODO(b/29354921)
-		244: syscalls.ErrorWithEvent("mq_notify", syscall.ENOSYS, "", []string{"gvisor.dev/issue/136"}),       // TODO(b/29354921)
-		245: syscalls.ErrorWithEvent("mq_getsetattr", syscall.ENOSYS, "", []string{"gvisor.dev/issue/136"}),   // TODO(b/29354921)
+		238: syscalls.PartiallySupported("set_mempolicy", SetMempolicy, "Stub implementation.", nil),
+		239: syscalls.PartiallySupported("get_mempolicy", GetMempolicy, "Stub implementation.", nil),
+		240: syscalls.ErrorWithEvent("mq_open", syserror.ENOSYS, "", []string{"gvisor.dev/issue/136"}),         // TODO(b/29354921)
+		241: syscalls.ErrorWithEvent("mq_unlink", syserror.ENOSYS, "", []string{"gvisor.dev/issue/136"}),       // TODO(b/29354921)
+		242: syscalls.ErrorWithEvent("mq_timedsend", syserror.ENOSYS, "", []string{"gvisor.dev/issue/136"}),    // TODO(b/29354921)
+		243: syscalls.ErrorWithEvent("mq_timedreceive", syserror.ENOSYS, "", []string{"gvisor.dev/issue/136"}), // TODO(b/29354921)
+		244: syscalls.ErrorWithEvent("mq_notify", syserror.ENOSYS, "", []string{"gvisor.dev/issue/136"}),       // TODO(b/29354921)
+		245: syscalls.ErrorWithEvent("mq_getsetattr", syserror.ENOSYS, "", []string{"gvisor.dev/issue/136"}),   // TODO(b/29354921)
 		246: syscalls.CapError("kexec_load", linux.CAP_SYS_BOOT, "", nil),
-		247: syscalls.Undocumented("waitid", Waitid),
-		248: syscalls.Error("add_key", syscall.EACCES, "Not available to user", nil),
-		249: syscalls.Error("request_key", syscall.EACCES, "Not available to user", nil),
-		250: syscalls.Error("keyctl", syscall.EACCES, "Not available to user", nil),
+		247: syscalls.Supported("waitid", Waitid),
+		248: syscalls.Error("add_key", syserror.EACCES, "Not available to user.", nil),
+		249: syscalls.Error("request_key", syserror.EACCES, "Not available to user.", nil),
+		250: syscalls.Error("keyctl", syserror.EACCES, "Not available to user.", nil),
 		251: syscalls.CapError("ioprio_set", linux.CAP_SYS_ADMIN, "", nil), // requires cap_sys_nice or cap_sys_admin (depending)
 		252: syscalls.CapError("ioprio_get", linux.CAP_SYS_ADMIN, "", nil), // requires cap_sys_nice or cap_sys_admin (depending)
-		253: syscalls.Undocumented("inotify_init", InotifyInit),
-		254: syscalls.Undocumented("inotify_add_watch", InotifyAddWatch),
-		255: syscalls.Undocumented("inotify_rm_watch", InotifyRmWatch),
+		253: syscalls.PartiallySupported("inotify_init", InotifyInit, "inotify events are only available inside the sandbox.", nil),
+		254: syscalls.PartiallySupported("inotify_add_watch", InotifyAddWatch, "inotify events are only available inside the sandbox.", nil),
+		255: syscalls.PartiallySupported("inotify_rm_watch", InotifyRmWatch, "inotify events are only available inside the sandbox.", nil),
 		256: syscalls.CapError("migrate_pages", linux.CAP_SYS_NICE, "", nil),
-		257: syscalls.Undocumented("openat", Openat),
-		258: syscalls.Undocumented("mkdirat", Mkdirat),
-		259: syscalls.Undocumented("mknodat", Mknodat),
-		260: syscalls.Undocumented("fchownat", Fchownat),
-		261: syscalls.Undocumented("futimesat", Futimesat),
-		262: syscalls.Undocumented("fstatat", Fstatat),
-		263: syscalls.Undocumented("unlinkat", Unlinkat),
-		264: syscalls.Undocumented("renameat", Renameat),
-		265: syscalls.Undocumented("linkat", Linkat),
-		266: syscalls.Undocumented("symlinkat", Symlinkat),
-		267: syscalls.Undocumented("readlinkat", Readlinkat),
-		268: syscalls.Undocumented("fchmodat", Fchmodat),
-		269: syscalls.Undocumented("faccessat", Faccessat),
-		270: syscalls.Undocumented("pselect", Pselect),
-		271: syscalls.Undocumented("ppoll", Ppoll),
-		272: syscalls.Undocumented("unshare", Unshare),
-		273: syscalls.Error("set_robust_list", syscall.ENOSYS, "Obsolete", nil),
-		274: syscalls.Error("get_robust_list", syscall.ENOSYS, "Obsolete", nil),
-		275: syscalls.PartiallySupported("splice", Splice, "Stub implementation", []string{"gvisor.dev/issue/138"}), // TODO(b/29354098)
-		276: syscalls.ErrorWithEvent("tee", syscall.ENOSYS, "", []string{"gvisor.dev/issue/138"}),                   // TODO(b/29354098)
-		277: syscalls.Undocumented("sync_file_range", SyncFileRange),
-		278: syscalls.ErrorWithEvent("vmsplice", syscall.ENOSYS, "", []string{"gvisor.dev/issue/138"}), // TODO(b/29354098)
-		279: syscalls.CapError("move_pages", linux.CAP_SYS_NICE, "", nil),                              // requires cap_sys_nice (mostly)
-		280: syscalls.Undocumented("utimensat", Utimensat),
-		281: syscalls.Undocumented("epoll_pwait", EpollPwait),
-		282: syscalls.ErrorWithEvent("signalfd", syscall.ENOSYS, "", []string{"gvisor.dev/issue/139"}), // TODO(b/19846426)
-		283: syscalls.Undocumented("timerfd_create", TimerfdCreate),
-		284: syscalls.Undocumented("eventfd", Eventfd),
-		285: syscalls.Undocumented("fallocate", Fallocate),
-		286: syscalls.Undocumented("timerfd_settime", TimerfdSettime),
-		287: syscalls.Undocumented("timerfd_gettime", TimerfdGettime),
-		288: syscalls.Undocumented("accept4", Accept4),
-		289: syscalls.ErrorWithEvent("signalfd4", syscall.ENOSYS, "", []string{"gvisor.dev/issue/139"}), // TODO(b/19846426)
-		290: syscalls.Undocumented("eventfd2", Eventfd2),
-		291: syscalls.Undocumented("epoll_create1", EpollCreate1),
-		292: syscalls.Undocumented("dup3", Dup3),
-		293: syscalls.Undocumented("pipe2", Pipe2),
-		294: syscalls.Undocumented("inotify_init1", InotifyInit1),
-		295: syscalls.Undocumented("preadv", Preadv),
-		296: syscalls.Undocumented("pwritev", Pwritev),
-		297: syscalls.Undocumented("rt_tgsigqueueinfo", RtTgsigqueueinfo),
-		298: syscalls.ErrorWithEvent("perf_event_open", syscall.ENODEV, "No support for perf counters", nil),
-		299: syscalls.Undocumented("recvmmsg", RecvMMsg),
-		300: syscalls.ErrorWithEvent("fanotify_init", syscall.ENOSYS, "Needs CONFIG_FANOTIFY", nil),
-		301: syscalls.ErrorWithEvent("fanotify_mark", syscall.ENOSYS, "Needs CONFIG_FANOTIFY", nil),
-		302: syscalls.Undocumented("prlimit64", Prlimit64),
-		303: syscalls.ErrorWithEvent("name_to_handle_at", syscall.EOPNOTSUPP, "Needs filesystem support", nil),
-		304: syscalls.ErrorWithEvent("open_by_handle_at", syscall.EOPNOTSUPP, "Needs filesystem support", nil),
+		257: syscalls.Supported("openat", Openat),
+		258: syscalls.Supported("mkdirat", Mkdirat),
+		259: syscalls.Supported("mknodat", Mknodat),
+		260: syscalls.Supported("fchownat", Fchownat),
+		261: syscalls.Supported("futimesat", Futimesat),
+		262: syscalls.Supported("fstatat", Fstatat),
+		263: syscalls.Supported("unlinkat", Unlinkat),
+		264: syscalls.Supported("renameat", Renameat),
+		265: syscalls.Supported("linkat", Linkat),
+		266: syscalls.Supported("symlinkat", Symlinkat),
+		267: syscalls.Supported("readlinkat", Readlinkat),
+		268: syscalls.Supported("fchmodat", Fchmodat),
+		269: syscalls.Supported("faccessat", Faccessat),
+		270: syscalls.Supported("pselect", Pselect),
+		271: syscalls.Supported("ppoll", Ppoll),
+		272: syscalls.PartiallySupported("unshare", Unshare, "Mount, cgroup namespaces not supported. Network namespaces supported but must be empty.", nil),
+		273: syscalls.Error("set_robust_list", syserror.ENOSYS, "Obsolete.", nil),
+		274: syscalls.Error("get_robust_list", syserror.ENOSYS, "Obsolete.", nil),
+		275: syscalls.PartiallySupported("splice", Splice, "Stub implementation.", []string{"gvisor.dev/issue/138"}), // TODO(b/29354098)
+		276: syscalls.ErrorWithEvent("tee", syserror.ENOSYS, "", []string{"gvisor.dev/issue/138"}),                   // TODO(b/29354098)
+		277: syscalls.PartiallySupported("sync_file_range", SyncFileRange, "Full data flush is not guaranteed at this time.", nil),
+		278: syscalls.ErrorWithEvent("vmsplice", syserror.ENOSYS, "", []string{"gvisor.dev/issue/138"}), // TODO(b/29354098)
+		279: syscalls.CapError("move_pages", linux.CAP_SYS_NICE, "", nil),                               // requires cap_sys_nice (mostly)
+		280: syscalls.Supported("utimensat", Utimensat),
+		281: syscalls.Supported("epoll_pwait", EpollPwait),
+		282: syscalls.ErrorWithEvent("signalfd", syserror.ENOSYS, "", []string{"gvisor.dev/issue/139"}), // TODO(b/19846426)
+		283: syscalls.Supported("timerfd_create", TimerfdCreate),
+		284: syscalls.Supported("eventfd", Eventfd),
+		285: syscalls.PartiallySupported("fallocate", Fallocate, "Not all options are supported.", nil),
+		286: syscalls.Supported("timerfd_settime", TimerfdSettime),
+		287: syscalls.Supported("timerfd_gettime", TimerfdGettime),
+		288: syscalls.Supported("accept4", Accept4),
+		289: syscalls.ErrorWithEvent("signalfd4", syserror.ENOSYS, "", []string{"gvisor.dev/issue/139"}), // TODO(b/19846426)
+		290: syscalls.Supported("eventfd2", Eventfd2),
+		291: syscalls.Supported("epoll_create1", EpollCreate1),
+		292: syscalls.Supported("dup3", Dup3),
+		293: syscalls.Supported("pipe2", Pipe2),
+		294: syscalls.Supported("inotify_init1", InotifyInit1),
+		295: syscalls.Supported("preadv", Preadv),
+		296: syscalls.Supported("pwritev", Pwritev),
+		297: syscalls.Supported("rt_tgsigqueueinfo", RtTgsigqueueinfo),
+		298: syscalls.ErrorWithEvent("perf_event_open", syserror.ENODEV, "No support for perf counters", nil),
+		299: syscalls.PartiallySupported("recvmmsg", RecvMMsg, "Not all flags and control messages are supported.", nil),
+		300: syscalls.ErrorWithEvent("fanotify_init", syserror.ENOSYS, "Needs CONFIG_FANOTIFY", nil),
+		301: syscalls.ErrorWithEvent("fanotify_mark", syserror.ENOSYS, "Needs CONFIG_FANOTIFY", nil),
+		302: syscalls.Supported("prlimit64", Prlimit64),
+		303: syscalls.Error("name_to_handle_at", syserror.EOPNOTSUPP, "Not supported by gVisor filesystems", nil),
+		304: syscalls.Error("open_by_handle_at", syserror.EOPNOTSUPP, "Not supported by gVisor filesystems", nil),
 		305: syscalls.CapError("clock_adjtime", linux.CAP_SYS_TIME, "", nil),
-		306: syscalls.Undocumented("syncfs", Syncfs),
-		307: syscalls.Undocumented("sendmmsg", SendMMsg),
-		308: syscalls.ErrorWithEvent("setns", syscall.EOPNOTSUPP, "Needs filesystem support", []string{"gvisor.dev/issue/140"}), // TODO(b/29354995)
-		309: syscalls.Undocumented("getcpu", Getcpu),
-		310: syscalls.ErrorWithEvent("process_vm_readv", syscall.ENOSYS, "", []string{"gvisor.dev/issue/158"}),
-		311: syscalls.ErrorWithEvent("process_vm_writev", syscall.ENOSYS, "", []string{"gvisor.dev/issue/158"}),
+		306: syscalls.PartiallySupported("syncfs", Syncfs, "Depends on backing file system.", nil),
+		307: syscalls.PartiallySupported("sendmmsg", SendMMsg, "Not all flags and control messages are supported.", nil),
+		308: syscalls.ErrorWithEvent("setns", syserror.EOPNOTSUPP, "Needs filesystem support", []string{"gvisor.dev/issue/140"}), // TODO(b/29354995)
+		309: syscalls.Supported("getcpu", Getcpu),
+		310: syscalls.ErrorWithEvent("process_vm_readv", syserror.ENOSYS, "", []string{"gvisor.dev/issue/158"}),
+		311: syscalls.ErrorWithEvent("process_vm_writev", syserror.ENOSYS, "", []string{"gvisor.dev/issue/158"}),
 		312: syscalls.CapError("kcmp", linux.CAP_SYS_PTRACE, "", nil),
 		313: syscalls.CapError("finit_module", linux.CAP_SYS_MODULE, "", nil),
-		314: syscalls.ErrorWithEvent("sched_setattr", syscall.ENOSYS, "gVisor does not implement a scheduler.", []string{"gvisor.dev/issue/264"}), // TODO(b/118902272)
-		315: syscalls.ErrorWithEvent("sched_getattr", syscall.ENOSYS, "gVisor does not implement a scheduler.", []string{"gvisor.dev/issue/264"}), // TODO(b/118902272)
-		316: syscalls.ErrorWithEvent("renameat2", syscall.ENOSYS, "", []string{"gvisor.dev/issue/263"}),                                           // TODO(b/118902772)
-		317: syscalls.Undocumented("seccomp", Seccomp),
-		318: syscalls.Undocumented("getrandom", GetRandom),
-		319: syscalls.Undocumented("memfd_create", MemfdCreate),
+		314: syscalls.ErrorWithEvent("sched_setattr", syserror.ENOSYS, "gVisor does not implement a scheduler.", []string{"gvisor.dev/issue/264"}), // TODO(b/118902272)
+		315: syscalls.ErrorWithEvent("sched_getattr", syserror.ENOSYS, "gVisor does not implement a scheduler.", []string{"gvisor.dev/issue/264"}), // TODO(b/118902272)
+		316: syscalls.ErrorWithEvent("renameat2", syserror.ENOSYS, "", []string{"gvisor.dev/issue/263"}),                                           // TODO(b/118902772)
+		317: syscalls.Supported("seccomp", Seccomp),
+		318: syscalls.Supported("getrandom", GetRandom),
+		319: syscalls.Supported("memfd_create", MemfdCreate),
 		320: syscalls.CapError("kexec_file_load", linux.CAP_SYS_BOOT, "", nil),
 		321: syscalls.CapError("bpf", linux.CAP_SYS_ADMIN, "", nil),
-		322: syscalls.ErrorWithEvent("execveat", syscall.ENOSYS, "", []string{"gvisor.dev/issue/265"}),    // TODO(b/118901836)
-		323: syscalls.ErrorWithEvent("userfaultfd", syscall.ENOSYS, "", []string{"gvisor.dev/issue/266"}), // TODO(b/118906345)
-		324: syscalls.ErrorWithEvent("membarrier", syscall.ENOSYS, "", []string{"gvisor.dev/issue/267"}),  // TODO(b/118904897)
-		325: syscalls.Undocumented("mlock2", Mlock2),
+		322: syscalls.ErrorWithEvent("execveat", syserror.ENOSYS, "", []string{"gvisor.dev/issue/265"}),    // TODO(b/118901836)
+		323: syscalls.ErrorWithEvent("userfaultfd", syserror.ENOSYS, "", []string{"gvisor.dev/issue/266"}), // TODO(b/118906345)
+		324: syscalls.ErrorWithEvent("membarrier", syserror.ENOSYS, "", []string{"gvisor.dev/issue/267"}),  // TODO(b/118904897)
+		325: syscalls.PartiallySupported("mlock2", Mlock2, "Stub implementation. The sandbox lacks appropriate permissions.", nil),
 
 		// Syscalls after 325 are "backports" from versions of Linux after 4.4.
-		326: syscalls.ErrorWithEvent("copy_file_range", syscall.ENOSYS, "", nil),
-		327: syscalls.Undocumented("preadv2", Preadv2),
-		328: syscalls.Undocumented("pwritev2", Pwritev2),
+		326: syscalls.ErrorWithEvent("copy_file_range", syserror.ENOSYS, "", nil),
+		327: syscalls.Supported("preadv2", Preadv2),
+		328: syscalls.PartiallySupported("pwritev2", Pwritev2, "Flag RWF_HIPRI is not supported.", nil),
 		332: syscalls.Supported("statx", Statx),
 	},
 
diff --git a/pkg/sentry/syscalls/linux/sigset.go b/pkg/sentry/syscalls/linux/sigset.go
index 00b7e7cf2..333013d8c 100644
--- a/pkg/sentry/syscalls/linux/sigset.go
+++ b/pkg/sentry/syscalls/linux/sigset.go
@@ -15,8 +15,6 @@
 package linux
 
 import (
-	"syscall"
-
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
@@ -27,7 +25,7 @@ import (
 // STOP are clear.
 func copyInSigSet(t *kernel.Task, sigSetAddr usermem.Addr, size uint) (linux.SignalSet, error) {
 	if size != linux.SignalSetSize {
-		return 0, syscall.EINVAL
+		return 0, syserror.EINVAL
 	}
 	b := t.CopyScratchBuffer(8)
 	if _, err := t.CopyInBytes(sigSetAddr, b); err != nil {
diff --git a/pkg/sentry/syscalls/linux/sys_aio.go b/pkg/sentry/syscalls/linux/sys_aio.go
index 7081d1a45..f56411bfe 100644
--- a/pkg/sentry/syscalls/linux/sys_aio.go
+++ b/pkg/sentry/syscalls/linux/sys_aio.go
@@ -21,7 +21,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/eventfd"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/mm"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
@@ -55,7 +54,7 @@ type ioCallback struct {
 
 	OpCode  uint16
 	ReqPrio int16
-	FD      uint32
+	FD      int32
 
 	Buf    uint64
 	Bytes  uint64
@@ -65,7 +64,7 @@ type ioCallback struct {
 	Flags     uint32
 
 	// eventfd to signal if IOCB_FLAG_RESFD is set in flags.
-	ResFD uint32
+	ResFD int32
 }
 
 // ioEvent describes an I/O result.
@@ -292,7 +291,7 @@ func performCallback(t *kernel.Task, file *fs.File, cbAddr usermem.Addr, cb *ioC
 
 // submitCallback processes a single callback.
 func submitCallback(t *kernel.Task, id uint64, cb *ioCallback, cbAddr usermem.Addr) error {
-	file := t.FDMap().GetFile(kdefs.FD(cb.FD))
+	file := t.GetFile(cb.FD)
 	if file == nil {
 		// File not found.
 		return syserror.EBADF
@@ -302,7 +301,7 @@ func submitCallback(t *kernel.Task, id uint64, cb *ioCallback, cbAddr usermem.Ad
 	// Was there an eventFD? Extract it.
 	var eventFile *fs.File
 	if cb.Flags&_IOCB_FLAG_RESFD != 0 {
-		eventFile = t.FDMap().GetFile(kdefs.FD(cb.ResFD))
+		eventFile = t.GetFile(cb.ResFD)
 		if eventFile == nil {
 			// Bad FD.
 			return syserror.EBADF
diff --git a/pkg/sentry/syscalls/linux/sys_epoll.go b/pkg/sentry/syscalls/linux/sys_epoll.go
index 14a61cfa5..4a2b9f061 100644
--- a/pkg/sentry/syscalls/linux/sys_epoll.go
+++ b/pkg/sentry/syscalls/linux/sys_epoll.go
@@ -15,12 +15,10 @@
 package linux
 
 import (
-	"syscall"
-
+	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/epoll"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	"gvisor.dev/gvisor/pkg/sentry/syscalls"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
 	"gvisor.dev/gvisor/pkg/syserror"
@@ -30,11 +28,11 @@ import (
 // EpollCreate1 implements the epoll_create1(2) linux syscall.
 func EpollCreate1(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
 	flags := args[0].Int()
-	if flags & ^syscall.EPOLL_CLOEXEC != 0 {
+	if flags & ^linux.EPOLL_CLOEXEC != 0 {
 		return 0, nil, syserror.EINVAL
 	}
 
-	closeOnExec := flags&syscall.EPOLL_CLOEXEC != 0
+	closeOnExec := flags&linux.EPOLL_CLOEXEC != 0
 	fd, err := syscalls.CreateEpoll(t, closeOnExec)
 	if err != nil {
 		return 0, nil, err
@@ -61,46 +59,43 @@ func EpollCreate(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.S
 
 // EpollCtl implements the epoll_ctl(2) linux syscall.
 func EpollCtl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	epfd := kdefs.FD(args[0].Int())
+	epfd := args[0].Int()
 	op := args[1].Int()
-	fd := kdefs.FD(args[2].Int())
+	fd := args[2].Int()
 	eventAddr := args[3].Pointer()
 
 	// Capture the event state if needed.
 	flags := epoll.EntryFlags(0)
 	mask := waiter.EventMask(0)
 	var data [2]int32
-	if op != syscall.EPOLL_CTL_DEL {
-		var e syscall.EpollEvent
+	if op != linux.EPOLL_CTL_DEL {
+		var e linux.EpollEvent
 		if _, err := t.CopyIn(eventAddr, &e); err != nil {
 			return 0, nil, err
 		}
 
-		if e.Events&syscall.EPOLLONESHOT != 0 {
+		if e.Events&linux.EPOLLONESHOT != 0 {
 			flags |= epoll.OneShot
 		}
 
-		// syscall.EPOLLET is incorrectly generated as a negative number
-		// in Go, see https://github.com/golang/go/issues/5328 for
-		// details.
-		if e.Events&-syscall.EPOLLET != 0 {
+		if e.Events&linux.EPOLLET != 0 {
 			flags |= epoll.EdgeTriggered
 		}
 
 		mask = waiter.EventMaskFromLinux(e.Events)
 		data[0] = e.Fd
-		data[1] = e.Pad
+		data[1] = e.Data
 	}
 
 	// Perform the requested operations.
 	switch op {
-	case syscall.EPOLL_CTL_ADD:
+	case linux.EPOLL_CTL_ADD:
 		// See fs/eventpoll.c.
 		mask |= waiter.EventHUp | waiter.EventErr
 		return 0, nil, syscalls.AddEpoll(t, epfd, fd, flags, mask, data)
-	case syscall.EPOLL_CTL_DEL:
+	case linux.EPOLL_CTL_DEL:
 		return 0, nil, syscalls.RemoveEpoll(t, epfd, fd)
-	case syscall.EPOLL_CTL_MOD:
+	case linux.EPOLL_CTL_MOD:
 		// Same as EPOLL_CTL_ADD.
 		mask |= waiter.EventHUp | waiter.EventErr
 		return 0, nil, syscalls.UpdateEpoll(t, epfd, fd, flags, mask, data)
@@ -132,7 +127,7 @@ func copyOutEvents(t *kernel.Task, addr usermem.Addr, e []epoll.Event) error {
 
 // EpollWait implements the epoll_wait(2) linux syscall.
 func EpollWait(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	epfd := kdefs.FD(args[0].Int())
+	epfd := args[0].Int()
 	eventsAddr := args[1].Pointer()
 	maxEvents := int(args[2].Int())
 	timeout := int(args[3].Int())
diff --git a/pkg/sentry/syscalls/linux/sys_eventfd.go b/pkg/sentry/syscalls/linux/sys_eventfd.go
index 7dbe84884..8a34c4e99 100644
--- a/pkg/sentry/syscalls/linux/sys_eventfd.go
+++ b/pkg/sentry/syscalls/linux/sys_eventfd.go
@@ -15,12 +15,11 @@
 package linux
 
 import (
-	"syscall"
-
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/eventfd"
+	"gvisor.dev/gvisor/pkg/syserror"
 )
 
 const (
@@ -38,7 +37,7 @@ func Eventfd2(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 	allOps := uint(EFD_SEMAPHORE | EFD_NONBLOCK | EFD_CLOEXEC)
 
 	if flags & ^allOps != 0 {
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 
 	event := eventfd.New(t, uint64(initVal), flags&EFD_SEMAPHORE != 0)
@@ -47,10 +46,9 @@ func Eventfd2(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 	})
 	defer event.DecRef()
 
-	fd, err := t.FDMap().NewFDFrom(0, event, kernel.FDFlags{
+	fd, err := t.NewFDFrom(0, event, kernel.FDFlags{
 		CloseOnExec: flags&EFD_CLOEXEC != 0,
-	},
-		t.ThreadGroup().Limits())
+	})
 	if err != nil {
 		return 0, nil, err
 	}
diff --git a/pkg/sentry/syscalls/linux/sys_file.go b/pkg/sentry/syscalls/linux/sys_file.go
index 3ef7441c2..2e00a91ce 100644
--- a/pkg/sentry/syscalls/linux/sys_file.go
+++ b/pkg/sentry/syscalls/linux/sys_file.go
@@ -26,7 +26,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/fasync"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/limits"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
@@ -34,7 +33,7 @@ import (
 )
 
 // fileOpAt performs an operation on the second last component in the path.
-func fileOpAt(t *kernel.Task, dirFD kdefs.FD, path string, fn func(root *fs.Dirent, d *fs.Dirent, name string, remainingTraversals uint) error) error {
+func fileOpAt(t *kernel.Task, dirFD int32, path string, fn func(root *fs.Dirent, d *fs.Dirent, name string, remainingTraversals uint) error) error {
 	// Extract the last component.
 	dir, name := fs.SplitLast(path)
 	if dir == "/" {
@@ -60,7 +59,7 @@ func fileOpAt(t *kernel.Task, dirFD kdefs.FD, path string, fn func(root *fs.Dire
 }
 
 // fileOpOn performs an operation on the last entry of the path.
-func fileOpOn(t *kernel.Task, dirFD kdefs.FD, path string, resolve bool, fn func(root *fs.Dirent, d *fs.Dirent, remainingTraversals uint) error) error {
+func fileOpOn(t *kernel.Task, dirFD int32, path string, resolve bool, fn func(root *fs.Dirent, d *fs.Dirent, remainingTraversals uint) error) error {
 	var (
 		d   *fs.Dirent // The file.
 		wd  *fs.Dirent // The working directory (if required.)
@@ -78,7 +77,7 @@ func fileOpOn(t *kernel.Task, dirFD kdefs.FD, path string, resolve bool, fn func
 		rel = wd
 	} else {
 		// Need to extract the given FD.
-		f = t.FDMap().GetFile(dirFD)
+		f = t.GetFile(dirFD)
 		if f == nil {
 			return syserror.EBADF
 		}
@@ -131,7 +130,7 @@ func copyInPath(t *kernel.Task, addr usermem.Addr, allowEmpty bool) (path string
 	return path, dirPath, nil
 }
 
-func openAt(t *kernel.Task, dirFD kdefs.FD, addr usermem.Addr, flags uint) (fd uintptr, err error) {
+func openAt(t *kernel.Task, dirFD int32, addr usermem.Addr, flags uint) (fd uintptr, err error) {
 	path, dirPath, err := copyInPath(t, addr, false /* allowEmpty */)
 	if err != nil {
 		return 0, err
@@ -184,8 +183,9 @@ func openAt(t *kernel.Task, dirFD kdefs.FD, addr usermem.Addr, flags uint) (fd u
 		defer file.DecRef()
 
 		// Success.
-		fdFlags := kernel.FDFlags{CloseOnExec: flags&linux.O_CLOEXEC != 0}
-		newFD, err := t.FDMap().NewFDFrom(0, file, fdFlags, t.ThreadGroup().Limits())
+		newFD, err := t.NewFDFrom(0, file, kernel.FDFlags{
+			CloseOnExec: flags&linux.O_CLOEXEC != 0,
+		})
 		if err != nil {
 			return err
 		}
@@ -201,7 +201,7 @@ func openAt(t *kernel.Task, dirFD kdefs.FD, addr usermem.Addr, flags uint) (fd u
 	return fd, err // Use result in frame.
 }
 
-func mknodAt(t *kernel.Task, dirFD kdefs.FD, addr usermem.Addr, mode linux.FileMode) error {
+func mknodAt(t *kernel.Task, dirFD int32, addr usermem.Addr, mode linux.FileMode) error {
 	path, dirPath, err := copyInPath(t, addr, false /* allowEmpty */)
 	if err != nil {
 		return err
@@ -285,7 +285,7 @@ func Mknod(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 
 // Mknodat implements the linux syscall mknodat(2).
 func Mknodat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	dirFD := kdefs.FD(args[0].Int())
+	dirFD := args[0].Int()
 	path := args[1].Pointer()
 	mode := linux.FileMode(args[2].ModeT())
 	// We don't need this argument until we support creation of device nodes.
@@ -294,7 +294,7 @@ func Mknodat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysca
 	return 0, nil, mknodAt(t, dirFD, path, mode)
 }
 
-func createAt(t *kernel.Task, dirFD kdefs.FD, addr usermem.Addr, flags uint, mode linux.FileMode) (fd uintptr, err error) {
+func createAt(t *kernel.Task, dirFD int32, addr usermem.Addr, flags uint, mode linux.FileMode) (fd uintptr, err error) {
 	path, dirPath, err := copyInPath(t, addr, false /* allowEmpty */)
 	if err != nil {
 		return 0, err
@@ -326,6 +326,7 @@ func createAt(t *kernel.Task, dirFD kdefs.FD, addr usermem.Addr, flags uint, mod
 			if err != nil {
 				break
 			}
+			defer found.DecRef()
 
 			// We found something (possibly a symlink). If the
 			// O_EXCL flag was passed, then we can immediately
@@ -346,31 +347,41 @@ func createAt(t *kernel.Task, dirFD kdefs.FD, addr usermem.Addr, flags uint, mod
 			}
 
 			// Try to resolve the symlink directly to a Dirent.
-			resolved, err := found.Inode.Getlink(t)
-			if err == nil || err != fs.ErrResolveViaReadlink {
+			var resolved *fs.Dirent
+			resolved, err = found.Inode.Getlink(t)
+			if err == nil {
 				// No more resolution necessary.
-				found.DecRef()
-				found = resolved
+				defer resolved.DecRef()
 				break
 			}
+			if err != fs.ErrResolveViaReadlink {
+				return err
+			}
+
+			// Are we able to resolve further?
+			if remainingTraversals == 0 {
+				return syscall.ELOOP
+			}
 
 			// Resolve the symlink to a path via Readlink.
-			path, err := found.Inode.Readlink(t)
+			var path string
+			path, err = found.Inode.Readlink(t)
 			if err != nil {
 				break
 			}
 			remainingTraversals--
 
 			// Get the new parent from the target path.
+			var newParent *fs.Dirent
 			newParentPath, newName := fs.SplitLast(path)
-			newParent, err := t.MountNamespace().FindInode(t, root, parent, newParentPath, &remainingTraversals)
+			newParent, err = t.MountNamespace().FindInode(t, root, parent, newParentPath, &remainingTraversals)
 			if err != nil {
 				break
 			}
+			defer newParent.DecRef()
 
 			// Repeat the process with the parent and name of the
 			// symlink target.
-			parent.DecRef()
 			parent = newParent
 			name = newName
 		}
@@ -378,9 +389,6 @@ func createAt(t *kernel.Task, dirFD kdefs.FD, addr usermem.Addr, flags uint, mod
 		var newFile *fs.File
 		switch err {
 		case nil:
-			// The file existed.
-			defer found.DecRef()
-
 			// Like sys_open, check for a few things about the
 			// filesystem before trying to get a reference to the
 			// fs.File. The same constraints on Check apply.
@@ -423,8 +431,9 @@ func createAt(t *kernel.Task, dirFD kdefs.FD, addr usermem.Addr, flags uint, mod
 		}
 
 		// Success.
-		fdFlags := kernel.FDFlags{CloseOnExec: flags&linux.O_CLOEXEC != 0}
-		newFD, err := t.FDMap().NewFDFrom(0, newFile, fdFlags, t.ThreadGroup().Limits())
+		newFD, err := t.NewFDFrom(0, newFile, kernel.FDFlags{
+			CloseOnExec: flags&linux.O_CLOEXEC != 0,
+		})
 		if err != nil {
 			return err
 		}
@@ -458,7 +467,7 @@ func Open(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallC
 
 // Openat implements linux syscall openat(2).
 func Openat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	dirFD := kdefs.FD(args[0].Int())
+	dirFD := args[0].Int()
 	addr := args[1].Pointer()
 	flags := uint(args[2].Uint())
 	if flags&linux.O_CREAT != 0 {
@@ -497,7 +506,7 @@ func (ac accessContext) Value(key interface{}) interface{} {
 	}
 }
 
-func accessAt(t *kernel.Task, dirFD kdefs.FD, addr usermem.Addr, resolve bool, mode uint) error {
+func accessAt(t *kernel.Task, dirFD int32, addr usermem.Addr, resolve bool, mode uint) error {
 	const rOK = 4
 	const wOK = 2
 	const xOK = 1
@@ -552,7 +561,7 @@ func Access(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 
 // Faccessat implements linux syscall faccessat(2).
 func Faccessat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	dirFD := kdefs.FD(args[0].Int())
+	dirFD := args[0].Int()
 	addr := args[1].Pointer()
 	mode := args[2].ModeT()
 	flags := args[3].Int()
@@ -562,10 +571,10 @@ func Faccessat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sys
 
 // Ioctl implements linux syscall ioctl(2).
 func Ioctl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	request := int(args[1].Int())
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -574,12 +583,12 @@ func Ioctl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 	// Shared flags between file and socket.
 	switch request {
 	case linux.FIONCLEX:
-		t.FDMap().SetFlags(fd, kernel.FDFlags{
+		t.FDTable().SetFlags(fd, kernel.FDFlags{
 			CloseOnExec: false,
 		})
 		return 0, nil, nil
 	case linux.FIOCLEX:
-		t.FDMap().SetFlags(fd, kernel.FDFlags{
+		t.FDTable().SetFlags(fd, kernel.FDFlags{
 			CloseOnExec: true,
 		})
 		return 0, nil, nil
@@ -723,9 +732,9 @@ func Chdir(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 
 // Fchdir implements the linux syscall fchdir(2).
 func Fchdir(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -747,44 +756,47 @@ func Fchdir(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 
 // Close implements linux syscall close(2).
 func Close(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 
-	file, ok := t.FDMap().Remove(fd)
-	if !ok {
+	// Note that Remove provides a reference on the file that we may use to
+	// flush. It is still active until we drop the final reference below
+	// (and other reference-holding operations complete).
+	file := t.FDTable().Remove(fd)
+	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
 	defer file.DecRef()
 
 	err := file.Flush(t)
-	return 0, nil, handleIOError(t, false /* partial */, err, syscall.EINTR, "close", file)
+	return 0, nil, handleIOError(t, false /* partial */, err, syserror.EINTR, "close", file)
 }
 
 // Dup implements linux syscall dup(2).
 func Dup(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
 	defer file.DecRef()
 
-	newfd, err := t.FDMap().NewFDFrom(0, file, kernel.FDFlags{}, t.ThreadGroup().Limits())
+	newFD, err := t.NewFDFrom(0, file, kernel.FDFlags{})
 	if err != nil {
 		return 0, nil, syserror.EMFILE
 	}
-	return uintptr(newfd), nil, nil
+	return uintptr(newFD), nil, nil
 }
 
 // Dup2 implements linux syscall dup2(2).
 func Dup2(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	oldfd := kdefs.FD(args[0].Int())
-	newfd := kdefs.FD(args[1].Int())
+	oldfd := args[0].Int()
+	newfd := args[1].Int()
 
 	// If oldfd is a valid file descriptor, and newfd has the same value as oldfd,
 	// then dup2() does nothing, and returns newfd.
 	if oldfd == newfd {
-		oldFile := t.FDMap().GetFile(oldfd)
+		oldFile := t.GetFile(oldfd)
 		if oldFile == nil {
 			return 0, nil, syserror.EBADF
 		}
@@ -800,21 +812,21 @@ func Dup2(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallC
 
 // Dup3 implements linux syscall dup3(2).
 func Dup3(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	oldfd := kdefs.FD(args[0].Int())
-	newfd := kdefs.FD(args[1].Int())
+	oldfd := args[0].Int()
+	newfd := args[1].Int()
 	flags := args[2].Uint()
 
 	if oldfd == newfd {
 		return 0, nil, syserror.EINVAL
 	}
 
-	oldFile := t.FDMap().GetFile(oldfd)
+	oldFile := t.GetFile(oldfd)
 	if oldFile == nil {
 		return 0, nil, syserror.EBADF
 	}
 	defer oldFile.DecRef()
 
-	err := t.FDMap().NewFDAt(newfd, oldFile, kernel.FDFlags{CloseOnExec: flags&linux.O_CLOEXEC != 0}, t.ThreadGroup().Limits())
+	err := t.NewFDAt(newfd, oldFile, kernel.FDFlags{CloseOnExec: flags&linux.O_CLOEXEC != 0})
 	if err != nil {
 		return 0, nil, err
 	}
@@ -857,10 +869,10 @@ func fSetOwn(t *kernel.Task, file *fs.File, who int32) {
 
 // Fcntl implements linux syscall fcntl(2).
 func Fcntl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	cmd := args[1].Int()
 
-	file, flags := t.FDMap().GetDescriptor(fd)
+	file, flags := t.FDTable().Get(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -868,9 +880,10 @@ func Fcntl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 
 	switch cmd {
 	case linux.F_DUPFD, linux.F_DUPFD_CLOEXEC:
-		from := kdefs.FD(args[2].Int())
-		fdFlags := kernel.FDFlags{CloseOnExec: cmd == linux.F_DUPFD_CLOEXEC}
-		fd, err := t.FDMap().NewFDFrom(from, file, fdFlags, t.ThreadGroup().Limits())
+		from := args[2].Int()
+		fd, err := t.NewFDFrom(from, file, kernel.FDFlags{
+			CloseOnExec: cmd == linux.F_DUPFD_CLOEXEC,
+		})
 		if err != nil {
 			return 0, nil, err
 		}
@@ -879,7 +892,7 @@ func Fcntl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 		return uintptr(flags.ToLinuxFDFlags()), nil, nil
 	case linux.F_SETFD:
 		flags := args[2].Uint()
-		t.FDMap().SetFlags(fd, kernel.FDFlags{
+		t.FDTable().SetFlags(fd, kernel.FDFlags{
 			CloseOnExec: flags&linux.FD_CLOEXEC != 0,
 		})
 	case linux.F_GETFL:
@@ -897,7 +910,7 @@ func Fcntl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 
 		// Copy in the lock request.
 		flockAddr := args[2].Pointer()
-		var flock syscall.Flock_t
+		var flock linux.Flock
 		if _, err := t.CopyIn(flockAddr, &flock); err != nil {
 			return 0, nil, err
 		}
@@ -940,17 +953,17 @@ func Fcntl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 			return 0, nil, err
 		}
 
-		// The lock uid is that of the Task's FDMap.
-		lockUniqueID := lock.UniqueID(t.FDMap().ID())
+		// The lock uid is that of the Task's FDTable.
+		lockUniqueID := lock.UniqueID(t.FDTable().ID())
 
 		// These locks don't block; execute the non-blocking operation using the inode's lock
 		// context directly.
 		switch flock.Type {
-		case syscall.F_RDLCK:
+		case linux.F_RDLCK:
 			if !file.Flags().Read {
 				return 0, nil, syserror.EBADF
 			}
-			if cmd == syscall.F_SETLK {
+			if cmd == linux.F_SETLK {
 				// Non-blocking lock, provide a nil lock.Blocker.
 				if !file.Dirent.Inode.LockCtx.Posix.LockRegion(lockUniqueID, lock.ReadLock, rng, nil) {
 					return 0, nil, syserror.EAGAIN
@@ -962,11 +975,11 @@ func Fcntl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 				}
 			}
 			return 0, nil, nil
-		case syscall.F_WRLCK:
+		case linux.F_WRLCK:
 			if !file.Flags().Write {
 				return 0, nil, syserror.EBADF
 			}
-			if cmd == syscall.F_SETLK {
+			if cmd == linux.F_SETLK {
 				// Non-blocking lock, provide a nil lock.Blocker.
 				if !file.Dirent.Inode.LockCtx.Posix.LockRegion(lockUniqueID, lock.WriteLock, rng, nil) {
 					return 0, nil, syserror.EAGAIN
@@ -978,7 +991,7 @@ func Fcntl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 				}
 			}
 			return 0, nil, nil
-		case syscall.F_UNLCK:
+		case linux.F_UNLCK:
 			file.Dirent.Inode.LockCtx.Posix.UnlockRegion(lockUniqueID, rng)
 			return 0, nil, nil
 		default:
@@ -1031,7 +1044,7 @@ const (
 // Fadvise64 implements linux syscall fadvise64(2).
 // This implementation currently ignores the provided advice.
 func Fadvise64(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	length := args[2].Int64()
 	advice := args[3].Int()
 
@@ -1040,7 +1053,7 @@ func Fadvise64(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sys
 		return 0, nil, syserror.EINVAL
 	}
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -1066,7 +1079,7 @@ func Fadvise64(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sys
 	return 0, nil, nil
 }
 
-func mkdirAt(t *kernel.Task, dirFD kdefs.FD, addr usermem.Addr, mode linux.FileMode) error {
+func mkdirAt(t *kernel.Task, dirFD int32, addr usermem.Addr, mode linux.FileMode) error {
 	path, _, err := copyInPath(t, addr, false /* allowEmpty */)
 	if err != nil {
 		return err
@@ -1111,14 +1124,14 @@ func Mkdir(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 
 // Mkdirat implements linux syscall mkdirat(2).
 func Mkdirat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	dirFD := kdefs.FD(args[0].Int())
+	dirFD := args[0].Int()
 	addr := args[1].Pointer()
 	mode := linux.FileMode(args[2].ModeT())
 
 	return 0, nil, mkdirAt(t, dirFD, addr, mode)
 }
 
-func rmdirAt(t *kernel.Task, dirFD kdefs.FD, addr usermem.Addr) error {
+func rmdirAt(t *kernel.Task, dirFD int32, addr usermem.Addr) error {
 	path, _, err := copyInPath(t, addr, false /* allowEmpty */)
 	if err != nil {
 		return err
@@ -1158,7 +1171,7 @@ func Rmdir(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 	return 0, nil, rmdirAt(t, linux.AT_FDCWD, addr)
 }
 
-func symlinkAt(t *kernel.Task, dirFD kdefs.FD, newAddr usermem.Addr, oldAddr usermem.Addr) error {
+func symlinkAt(t *kernel.Task, dirFD int32, newAddr usermem.Addr, oldAddr usermem.Addr) error {
 	newPath, dirPath, err := copyInPath(t, newAddr, false /* allowEmpty */)
 	if err != nil {
 		return err
@@ -1201,7 +1214,7 @@ func Symlink(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysca
 // Symlinkat implements linux syscall symlinkat(2).
 func Symlinkat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
 	oldAddr := args[0].Pointer()
-	dirFD := kdefs.FD(args[1].Int())
+	dirFD := args[1].Int()
 	newAddr := args[2].Pointer()
 
 	return 0, nil, symlinkAt(t, dirFD, newAddr, oldAddr)
@@ -1243,7 +1256,7 @@ func mayLinkAt(t *kernel.Task, target *fs.Inode) error {
 // linkAt creates a hard link to the target specified by oldDirFD and oldAddr,
 // specified by newDirFD and newAddr.  If resolve is true, then the symlinks
 // will be followed when evaluating the target.
-func linkAt(t *kernel.Task, oldDirFD kdefs.FD, oldAddr usermem.Addr, newDirFD kdefs.FD, newAddr usermem.Addr, resolve, allowEmpty bool) error {
+func linkAt(t *kernel.Task, oldDirFD int32, oldAddr usermem.Addr, newDirFD int32, newAddr usermem.Addr, resolve, allowEmpty bool) error {
 	oldPath, _, err := copyInPath(t, oldAddr, allowEmpty)
 	if err != nil {
 		return err
@@ -1257,7 +1270,7 @@ func linkAt(t *kernel.Task, oldDirFD kdefs.FD, oldAddr usermem.Addr, newDirFD kd
 	}
 
 	if allowEmpty && oldPath == "" {
-		target := t.FDMap().GetFile(oldDirFD)
+		target := t.GetFile(oldDirFD)
 		if target == nil {
 			return syserror.EBADF
 		}
@@ -1319,9 +1332,9 @@ func Link(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallC
 
 // Linkat implements linux syscall linkat(2).
 func Linkat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	oldDirFD := kdefs.FD(args[0].Int())
+	oldDirFD := args[0].Int()
 	oldAddr := args[1].Pointer()
-	newDirFD := kdefs.FD(args[2].Int())
+	newDirFD := args[2].Int()
 	newAddr := args[3].Pointer()
 
 	// man linkat(2):
@@ -1346,7 +1359,7 @@ func Linkat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 	return 0, nil, linkAt(t, oldDirFD, oldAddr, newDirFD, newAddr, resolve, allowEmpty)
 }
 
-func readlinkAt(t *kernel.Task, dirFD kdefs.FD, addr usermem.Addr, bufAddr usermem.Addr, size uint) (copied uintptr, err error) {
+func readlinkAt(t *kernel.Task, dirFD int32, addr usermem.Addr, bufAddr usermem.Addr, size uint) (copied uintptr, err error) {
 	path, dirPath, err := copyInPath(t, addr, false /* allowEmpty */)
 	if err != nil {
 		return 0, err
@@ -1396,7 +1409,7 @@ func Readlink(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 
 // Readlinkat implements linux syscall readlinkat(2).
 func Readlinkat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	dirFD := kdefs.FD(args[0].Int())
+	dirFD := args[0].Int()
 	addr := args[1].Pointer()
 	bufAddr := args[2].Pointer()
 	size := args[3].SizeT()
@@ -1405,7 +1418,7 @@ func Readlinkat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sy
 	return n, nil, err
 }
 
-func unlinkAt(t *kernel.Task, dirFD kdefs.FD, addr usermem.Addr) error {
+func unlinkAt(t *kernel.Task, dirFD int32, addr usermem.Addr) error {
 	path, dirPath, err := copyInPath(t, addr, false /* allowEmpty */)
 	if err != nil {
 		return err
@@ -1435,7 +1448,7 @@ func Unlink(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 
 // Unlinkat implements linux syscall unlinkat(2).
 func Unlinkat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	dirFD := kdefs.FD(args[0].Int())
+	dirFD := args[0].Int()
 	addr := args[1].Pointer()
 	flags := args[2].Uint()
 	if flags&linux.AT_REMOVEDIR != 0 {
@@ -1463,7 +1476,7 @@ func Truncate(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 
 	if uint64(length) >= t.ThreadGroup().Limits().Get(limits.FileSize).Cur {
 		t.SendSignal(&arch.SignalInfo{
-			Signo: int32(syscall.SIGXFSZ),
+			Signo: int32(linux.SIGXFSZ),
 			Code:  arch.SignalInfoUser,
 		})
 		return 0, nil, syserror.EFBIG
@@ -1496,10 +1509,10 @@ func Truncate(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 
 // Ftruncate implements linux syscall ftruncate(2).
 func Ftruncate(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	length := args[1].Int64()
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -1523,7 +1536,7 @@ func Ftruncate(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sys
 
 	if uint64(length) >= t.ThreadGroup().Limits().Get(limits.FileSize).Cur {
 		t.SendSignal(&arch.SignalInfo{
-			Signo: int32(syscall.SIGXFSZ),
+			Signo: int32(linux.SIGXFSZ),
 			Code:  arch.SignalInfoUser,
 		})
 		return 0, nil, syserror.EFBIG
@@ -1614,7 +1627,7 @@ func chown(t *kernel.Task, d *fs.Dirent, uid auth.UID, gid auth.GID) error {
 	return nil
 }
 
-func chownAt(t *kernel.Task, fd kdefs.FD, addr usermem.Addr, resolve, allowEmpty bool, uid auth.UID, gid auth.GID) error {
+func chownAt(t *kernel.Task, fd int32, addr usermem.Addr, resolve, allowEmpty bool, uid auth.UID, gid auth.GID) error {
 	path, _, err := copyInPath(t, addr, allowEmpty)
 	if err != nil {
 		return err
@@ -1622,7 +1635,7 @@ func chownAt(t *kernel.Task, fd kdefs.FD, addr usermem.Addr, resolve, allowEmpty
 
 	if path == "" {
 		// Annoying. What's wrong with fchown?
-		file := t.FDMap().GetFile(fd)
+		file := t.GetFile(fd)
 		if file == nil {
 			return syserror.EBADF
 		}
@@ -1656,11 +1669,11 @@ func Lchown(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 
 // Fchown implements linux syscall fchown(2).
 func Fchown(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	uid := auth.UID(args[1].Uint())
 	gid := auth.GID(args[2].Uint())
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -1671,7 +1684,7 @@ func Fchown(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 
 // Fchownat implements Linux syscall fchownat(2).
 func Fchownat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	dirFD := kdefs.FD(args[0].Int())
+	dirFD := args[0].Int()
 	addr := args[1].Pointer()
 	uid := auth.UID(args[2].Uint())
 	gid := auth.GID(args[3].Uint())
@@ -1701,7 +1714,7 @@ func chmod(t *kernel.Task, d *fs.Dirent, mode linux.FileMode) error {
 	return nil
 }
 
-func chmodAt(t *kernel.Task, fd kdefs.FD, addr usermem.Addr, mode linux.FileMode) error {
+func chmodAt(t *kernel.Task, fd int32, addr usermem.Addr, mode linux.FileMode) error {
 	path, _, err := copyInPath(t, addr, false /* allowEmpty */)
 	if err != nil {
 		return err
@@ -1722,10 +1735,10 @@ func Chmod(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 
 // Fchmod implements linux syscall fchmod(2).
 func Fchmod(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	mode := linux.FileMode(args[1].ModeT())
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -1736,7 +1749,7 @@ func Fchmod(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 
 // Fchmodat implements linux syscall fchmodat(2).
 func Fchmodat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	mode := linux.FileMode(args[2].ModeT())
 
@@ -1752,7 +1765,7 @@ func defaultSetToSystemTimeSpec() fs.TimeSpec {
 	}
 }
 
-func utimes(t *kernel.Task, dirFD kdefs.FD, addr usermem.Addr, ts fs.TimeSpec, resolve bool) error {
+func utimes(t *kernel.Task, dirFD int32, addr usermem.Addr, ts fs.TimeSpec, resolve bool) error {
 	setTimestamp := func(root *fs.Dirent, d *fs.Dirent, _ uint) error {
 		// Does the task own the file?
 		if !d.Inode.CheckOwnership(t) {
@@ -1785,7 +1798,7 @@ func utimes(t *kernel.Task, dirFD kdefs.FD, addr usermem.Addr, ts fs.TimeSpec, r
 			// Linux returns EINVAL in this case. See utimes.c.
 			return syserror.EINVAL
 		}
-		f := t.FDMap().GetFile(dirFD)
+		f := t.GetFile(dirFD)
 		if f == nil {
 			return syserror.EBADF
 		}
@@ -1813,7 +1826,7 @@ func Utime(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 	// No timesAddr argument will be interpreted as current system time.
 	ts := defaultSetToSystemTimeSpec()
 	if timesAddr != 0 {
-		var times syscall.Utimbuf
+		var times linux.Utime
 		if _, err := t.CopyIn(timesAddr, &times); err != nil {
 			return 0, nil, err
 		}
@@ -1853,7 +1866,7 @@ func timespecIsValid(ts linux.Timespec) bool {
 
 // Utimensat implements linux syscall utimensat(2).
 func Utimensat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	dirFD := kdefs.FD(args[0].Int())
+	dirFD := args[0].Int()
 	pathnameAddr := args[1].Pointer()
 	timesAddr := args[2].Pointer()
 	flags := args[3].Int()
@@ -1888,7 +1901,7 @@ func Utimensat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sys
 
 // Futimesat implements linux syscall futimesat(2).
 func Futimesat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	dirFD := kdefs.FD(args[0].Int())
+	dirFD := args[0].Int()
 	pathnameAddr := args[1].Pointer()
 	timesAddr := args[2].Pointer()
 
@@ -1912,7 +1925,7 @@ func Futimesat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sys
 	return 0, nil, utimes(t, dirFD, pathnameAddr, ts, true)
 }
 
-func renameAt(t *kernel.Task, oldDirFD kdefs.FD, oldAddr usermem.Addr, newDirFD kdefs.FD, newAddr usermem.Addr) error {
+func renameAt(t *kernel.Task, oldDirFD int32, oldAddr usermem.Addr, newDirFD int32, newAddr usermem.Addr) error {
 	newPath, _, err := copyInPath(t, newAddr, false /* allowEmpty */)
 	if err != nil {
 		return err
@@ -1960,21 +1973,21 @@ func Rename(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 
 // Renameat implements linux syscall renameat(2).
 func Renameat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	oldDirFD := kdefs.FD(args[0].Int())
+	oldDirFD := args[0].Int()
 	oldPathAddr := args[1].Pointer()
-	newDirFD := kdefs.FD(args[2].Int())
+	newDirFD := args[2].Int()
 	newPathAddr := args[3].Pointer()
 	return 0, nil, renameAt(t, oldDirFD, oldPathAddr, newDirFD, newPathAddr)
 }
 
 // Fallocate implements linux system call fallocate(2).
 func Fallocate(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	mode := args[1].Int64()
 	offset := args[2].Int64()
 	length := args[3].Int64()
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -2005,7 +2018,7 @@ func Fallocate(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sys
 	}
 	if uint64(size) >= t.ThreadGroup().Limits().Get(limits.FileSize).Cur {
 		t.SendSignal(&arch.SignalInfo{
-			Signo: int32(syscall.SIGXFSZ),
+			Signo: int32(linux.SIGXFSZ),
 			Code:  arch.SignalInfoUser,
 		})
 		return 0, nil, syserror.EFBIG
@@ -2023,10 +2036,10 @@ func Fallocate(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sys
 
 // Flock implements linux syscall flock(2).
 func Flock(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	operation := args[1].Int()
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		// flock(2): EBADF fd is not an open file descriptor.
 		return 0, nil, syserror.EBADF
@@ -2133,8 +2146,9 @@ func MemfdCreate(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.S
 	defer dirent.DecRef()
 	defer file.DecRef()
 
-	fdFlags := kernel.FDFlags{CloseOnExec: cloExec}
-	newFD, err := t.FDMap().NewFDFrom(0, file, fdFlags, t.ThreadGroup().Limits())
+	newFD, err := t.NewFDFrom(0, file, kernel.FDFlags{
+		CloseOnExec: cloExec,
+	})
 	if err != nil {
 		return 0, nil, err
 	}
diff --git a/pkg/sentry/syscalls/linux/sys_getdents.go b/pkg/sentry/syscalls/linux/sys_getdents.go
index dea872672..63e2c5a5d 100644
--- a/pkg/sentry/syscalls/linux/sys_getdents.go
+++ b/pkg/sentry/syscalls/linux/sys_getdents.go
@@ -17,20 +17,19 @@ package linux
 import (
 	"bytes"
 	"io"
-	"syscall"
 
+	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/binary"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
 // Getdents implements linux syscall getdents(2) for 64bit systems.
 func Getdents(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	size := int(args[2].Uint())
 
@@ -46,7 +45,7 @@ func Getdents(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 
 // Getdents64 implements linux syscall getdents64(2).
 func Getdents64(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	size := int(args[2].Uint())
 
@@ -62,8 +61,8 @@ func Getdents64(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sy
 
 // getdents implements the core of getdents(2)/getdents64(2).
 // f is the syscall implementation dirent serialization function.
-func getdents(t *kernel.Task, fd kdefs.FD, addr usermem.Addr, size int, f func(*dirent, io.Writer) (int, error)) (uintptr, error) {
-	dir := t.FDMap().GetFile(fd)
+func getdents(t *kernel.Task, fd int32, addr usermem.Addr, size int, f func(*dirent, io.Writer) (int, error)) (uintptr, error) {
+	dir := t.GetFile(fd)
 	if dir == nil {
 		return 0, syserror.EBADF
 	}
@@ -83,7 +82,7 @@ func getdents(t *kernel.Task, fd kdefs.FD, addr usermem.Addr, size int, f func(*
 
 	switch err := handleIOError(t, ds.Written() > 0, rerr, kernel.ERESTARTSYS, "getdents", dir); err {
 	case nil:
-		dir.Dirent.InotifyEvent(syscall.IN_ACCESS, 0)
+		dir.Dirent.InotifyEvent(linux.IN_ACCESS, 0)
 		return uintptr(ds.Written()), nil
 	case io.EOF:
 		return 0, nil
@@ -147,21 +146,21 @@ func smallestDirent64(a arch.Context) uint {
 func toType(nodeType fs.InodeType) uint8 {
 	switch nodeType {
 	case fs.RegularFile, fs.SpecialFile:
-		return syscall.DT_REG
+		return linux.DT_REG
 	case fs.Symlink:
-		return syscall.DT_LNK
+		return linux.DT_LNK
 	case fs.Directory, fs.SpecialDirectory:
-		return syscall.DT_DIR
+		return linux.DT_DIR
 	case fs.Pipe:
-		return syscall.DT_FIFO
+		return linux.DT_FIFO
 	case fs.CharacterDevice:
-		return syscall.DT_CHR
+		return linux.DT_CHR
 	case fs.BlockDevice:
-		return syscall.DT_BLK
+		return linux.DT_BLK
 	case fs.Socket:
-		return syscall.DT_SOCK
+		return linux.DT_SOCK
 	default:
-		return syscall.DT_UNKNOWN
+		return linux.DT_UNKNOWN
 	}
 }
 
diff --git a/pkg/sentry/syscalls/linux/sys_inotify.go b/pkg/sentry/syscalls/linux/sys_inotify.go
index 9cfa660fa..b2c7b3444 100644
--- a/pkg/sentry/syscalls/linux/sys_inotify.go
+++ b/pkg/sentry/syscalls/linux/sys_inotify.go
@@ -15,14 +15,12 @@
 package linux
 
 import (
-	"syscall"
-
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/anon"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
+	"gvisor.dev/gvisor/pkg/syserror"
 )
 
 const allFlags = int(linux.IN_NONBLOCK | linux.IN_CLOEXEC)
@@ -32,7 +30,7 @@ func InotifyInit1(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.
 	flags := int(args[0].Int())
 
 	if flags&^allFlags != 0 {
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 
 	dirent := fs.NewDirent(t, anon.NewInode(t), "inotify")
@@ -44,9 +42,9 @@ func InotifyInit1(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.
 	n := fs.NewFile(t, dirent, fileFlags, fs.NewInotify(t))
 	defer n.DecRef()
 
-	fd, err := t.FDMap().NewFDFrom(0, n, kernel.FDFlags{
+	fd, err := t.NewFDFrom(0, n, kernel.FDFlags{
 		CloseOnExec: flags&linux.IN_CLOEXEC != 0,
-	}, t.ThreadGroup().Limits())
+	})
 
 	if err != nil {
 		return 0, nil, err
@@ -63,18 +61,18 @@ func InotifyInit(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.S
 
 // fdToInotify resolves an fd to an inotify object. If successful, the file will
 // have an extra ref and the caller is responsible for releasing the ref.
-func fdToInotify(t *kernel.Task, fd kdefs.FD) (*fs.Inotify, *fs.File, error) {
-	file := t.FDMap().GetFile(fd)
+func fdToInotify(t *kernel.Task, fd int32) (*fs.Inotify, *fs.File, error) {
+	file := t.GetFile(fd)
 	if file == nil {
 		// Invalid fd.
-		return nil, nil, syscall.EBADF
+		return nil, nil, syserror.EBADF
 	}
 
 	ino, ok := file.FileOperations.(*fs.Inotify)
 	if !ok {
 		// Not an inotify fd.
 		file.DecRef()
-		return nil, nil, syscall.EINVAL
+		return nil, nil, syserror.EINVAL
 	}
 
 	return ino, file, nil
@@ -82,7 +80,7 @@ func fdToInotify(t *kernel.Task, fd kdefs.FD) (*fs.Inotify, *fs.File, error) {
 
 // InotifyAddWatch implements the inotify_add_watch() syscall.
 func InotifyAddWatch(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	mask := args[2].Uint()
 
@@ -93,7 +91,7 @@ func InotifyAddWatch(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kern
 	// "EINVAL: The given event mask contains no valid events."
 	// -- inotify_add_watch(2)
 	if validBits := mask & linux.ALL_INOTIFY_BITS; validBits == 0 {
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 
 	ino, file, err := fdToInotify(t, fd)
@@ -110,11 +108,11 @@ func InotifyAddWatch(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kern
 	err = fileOpOn(t, linux.AT_FDCWD, path, resolve, func(root *fs.Dirent, dirent *fs.Dirent, _ uint) error {
 		// "IN_ONLYDIR: Only watch pathname if it is a directory." -- inotify(7)
 		if onlyDir := mask&linux.IN_ONLYDIR != 0; onlyDir && !fs.IsDir(dirent.Inode.StableAttr) {
-			return syscall.ENOTDIR
+			return syserror.ENOTDIR
 		}
 
 		// Copy out to the return frame.
-		fd = kdefs.FD(ino.AddWatch(dirent, mask))
+		fd = ino.AddWatch(dirent, mask)
 
 		return nil
 	})
@@ -123,7 +121,7 @@ func InotifyAddWatch(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kern
 
 // InotifyRmWatch implements the inotify_rm_watch() syscall.
 func InotifyRmWatch(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	wd := args[1].Int()
 
 	ino, file, err := fdToInotify(t, fd)
diff --git a/pkg/sentry/syscalls/linux/sys_lseek.go b/pkg/sentry/syscalls/linux/sys_lseek.go
index a3813b818..297e920c4 100644
--- a/pkg/sentry/syscalls/linux/sys_lseek.go
+++ b/pkg/sentry/syscalls/linux/sys_lseek.go
@@ -18,17 +18,16 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
 // Lseek implements linux syscall lseek(2).
 func Lseek(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	offset := args[1].Int64()
 	whence := args[2].Int()
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
diff --git a/pkg/sentry/syscalls/linux/sys_mmap.go b/pkg/sentry/syscalls/linux/sys_mmap.go
index d831833bc..58a05b5bb 100644
--- a/pkg/sentry/syscalls/linux/sys_mmap.go
+++ b/pkg/sentry/syscalls/linux/sys_mmap.go
@@ -20,7 +20,6 @@ import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/mm"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
@@ -40,7 +39,7 @@ func Brk(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallCo
 func Mmap(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
 	prot := args[2].Int()
 	flags := args[3].Int()
-	fd := kdefs.FD(args[4].Int())
+	fd := args[4].Int()
 	fixed := flags&linux.MAP_FIXED != 0
 	private := flags&linux.MAP_PRIVATE != 0
 	shared := flags&linux.MAP_SHARED != 0
@@ -80,7 +79,7 @@ func Mmap(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallC
 
 	if !anon {
 		// Convert the passed FD to a file reference.
-		file := t.FDMap().GetFile(fd)
+		file := t.GetFile(fd)
 		if file == nil {
 			return 0, nil, syserror.EBADF
 		}
diff --git a/pkg/sentry/syscalls/linux/sys_pipe.go b/pkg/sentry/syscalls/linux/sys_pipe.go
index 7c1bea43d..418d7fa5f 100644
--- a/pkg/sentry/syscalls/linux/sys_pipe.go
+++ b/pkg/sentry/syscalls/linux/sys_pipe.go
@@ -15,20 +15,19 @@
 package linux
 
 import (
-	"syscall"
-
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
+	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/pipe"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/syserror"
 )
 
 // pipe2 implements the actual system call with flags.
 func pipe2(t *kernel.Task, addr usermem.Addr, flags uint) (uintptr, error) {
 	if flags&^(linux.O_NONBLOCK|linux.O_CLOEXEC) != 0 {
-		return 0, syscall.EINVAL
+		return 0, syserror.EINVAL
 	}
 	r, w := pipe.NewConnectedPipe(t, pipe.DefaultPipeSize, usermem.PageSize)
 
@@ -38,25 +37,18 @@ func pipe2(t *kernel.Task, addr usermem.Addr, flags uint) (uintptr, error) {
 	w.SetFlags(linuxToFlags(flags).Settable())
 	defer w.DecRef()
 
-	rfd, err := t.FDMap().NewFDFrom(0, r, kernel.FDFlags{
-		CloseOnExec: flags&linux.O_CLOEXEC != 0},
-		t.ThreadGroup().Limits())
-	if err != nil {
-		return 0, err
-	}
-
-	wfd, err := t.FDMap().NewFDFrom(0, w, kernel.FDFlags{
-		CloseOnExec: flags&linux.O_CLOEXEC != 0},
-		t.ThreadGroup().Limits())
+	fds, err := t.NewFDs(0, []*fs.File{r, w}, kernel.FDFlags{
+		CloseOnExec: flags&linux.O_CLOEXEC != 0,
+	})
 	if err != nil {
-		t.FDMap().Remove(rfd)
 		return 0, err
 	}
 
-	if _, err := t.CopyOut(addr, []kdefs.FD{rfd, wfd}); err != nil {
-		t.FDMap().Remove(rfd)
-		t.FDMap().Remove(wfd)
-		return 0, syscall.EFAULT
+	if _, err := t.CopyOut(addr, fds); err != nil {
+		// The files are not closed in this case, the exact semantics
+		// of this error case are not well defined, but they could have
+		// already been observed by user space.
+		return 0, syserror.EFAULT
 	}
 	return 0, nil
 }
diff --git a/pkg/sentry/syscalls/linux/sys_poll.go b/pkg/sentry/syscalls/linux/sys_poll.go
index ef6211218..7a13beac2 100644
--- a/pkg/sentry/syscalls/linux/sys_poll.go
+++ b/pkg/sentry/syscalls/linux/sys_poll.go
@@ -21,7 +21,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/limits"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
@@ -64,7 +63,7 @@ func initReadiness(t *kernel.Task, pfd *linux.PollFD, state *pollState, ch chan
 		return
 	}
 
-	file := t.FDMap().GetFile(kdefs.FD(pfd.FD))
+	file := t.GetFile(pfd.FD)
 	if file == nil {
 		pfd.REvents = linux.POLLNVAL
 		return
@@ -265,7 +264,7 @@ func doSelect(t *kernel.Task, nfds int, readFDs, writeFDs, exceptFDs usermem.Add
 				// immediately to ensure we don't leak. Note, another thread
 				// might be about to close fd. This is racy, but that's
 				// OK. Linux is racy in the same way.
-				file := t.FDMap().GetFile(kdefs.FD(fd))
+				file := t.GetFile(fd)
 				if file == nil {
 					return 0, syserror.EBADF
 				}
diff --git a/pkg/sentry/syscalls/linux/sys_prctl.go b/pkg/sentry/syscalls/linux/sys_prctl.go
index 9d70881fd..98db32d77 100644
--- a/pkg/sentry/syscalls/linux/sys_prctl.go
+++ b/pkg/sentry/syscalls/linux/sys_prctl.go
@@ -16,15 +16,14 @@ package linux
 
 import (
 	"fmt"
-	"syscall"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	"gvisor.dev/gvisor/pkg/sentry/mm"
+	"gvisor.dev/gvisor/pkg/syserror"
 )
 
 // Prctl implements linux syscall prctl(2).
@@ -37,7 +36,7 @@ func Prctl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 	case linux.PR_SET_PDEATHSIG:
 		sig := linux.Signal(args[1].Int())
 		if sig != 0 && !sig.IsValid() {
-			return 0, nil, syscall.EINVAL
+			return 0, nil, syserror.EINVAL
 		}
 		t.SetParentDeathSignal(sig)
 		return 0, nil, nil
@@ -68,7 +67,7 @@ func Prctl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 			d = mm.UserDumpable
 		default:
 			// N.B. Userspace may not pass SUID_DUMP_ROOT.
-			return 0, nil, syscall.EINVAL
+			return 0, nil, syserror.EINVAL
 		}
 		t.MemoryManager().SetDumpability(d)
 		return 0, nil, nil
@@ -89,7 +88,7 @@ func Prctl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 		} else if val == 1 {
 			t.SetKeepCaps(true)
 		} else {
-			return 0, nil, syscall.EINVAL
+			return 0, nil, syserror.EINVAL
 		}
 
 		return 0, nil, nil
@@ -97,7 +96,7 @@ func Prctl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 	case linux.PR_SET_NAME:
 		addr := args[1].Pointer()
 		name, err := t.CopyInString(addr, linux.TASK_COMM_LEN-1)
-		if err != nil && err != syscall.ENAMETOOLONG {
+		if err != nil && err != syserror.ENAMETOOLONG {
 			return 0, nil, err
 		}
 		t.SetName(name)
@@ -117,22 +116,22 @@ func Prctl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 
 	case linux.PR_SET_MM:
 		if !t.HasCapability(linux.CAP_SYS_RESOURCE) {
-			return 0, nil, syscall.EPERM
+			return 0, nil, syserror.EPERM
 		}
 
 		switch args[1].Int() {
 		case linux.PR_SET_MM_EXE_FILE:
-			fd := kdefs.FD(args[2].Int())
+			fd := args[2].Int()
 
-			file := t.FDMap().GetFile(fd)
+			file := t.GetFile(fd)
 			if file == nil {
-				return 0, nil, syscall.EBADF
+				return 0, nil, syserror.EBADF
 			}
 			defer file.DecRef()
 
 			// They trying to set exe to a non-file?
 			if !fs.IsFile(file.Dirent.Inode.StableAttr) {
-				return 0, nil, syscall.EBADF
+				return 0, nil, syserror.EBADF
 			}
 
 			// Set the underlying executable.
@@ -154,12 +153,12 @@ func Prctl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 			t.Kernel().EmitUnimplementedEvent(t)
 			fallthrough
 		default:
-			return 0, nil, syscall.EINVAL
+			return 0, nil, syserror.EINVAL
 		}
 
 	case linux.PR_SET_NO_NEW_PRIVS:
 		if args[1].Int() != 1 || args[2].Int() != 0 || args[3].Int() != 0 || args[4].Int() != 0 {
-			return 0, nil, syscall.EINVAL
+			return 0, nil, syserror.EINVAL
 		}
 		// no_new_privs is assumed to always be set. See
 		// kernel.Task.updateCredsForExec.
@@ -167,14 +166,14 @@ func Prctl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 
 	case linux.PR_GET_NO_NEW_PRIVS:
 		if args[1].Int() != 0 || args[2].Int() != 0 || args[3].Int() != 0 || args[4].Int() != 0 {
-			return 0, nil, syscall.EINVAL
+			return 0, nil, syserror.EINVAL
 		}
 		return 1, nil, nil
 
 	case linux.PR_SET_SECCOMP:
 		if args[1].Int() != linux.SECCOMP_MODE_FILTER {
 			// Unsupported mode.
-			return 0, nil, syscall.EINVAL
+			return 0, nil, syserror.EINVAL
 		}
 
 		return 0, nil, seccomp(t, linux.SECCOMP_SET_MODE_FILTER, 0, args[2].Pointer())
@@ -185,7 +184,7 @@ func Prctl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 	case linux.PR_CAPBSET_READ:
 		cp := linux.Capability(args[1].Uint64())
 		if !cp.Ok() {
-			return 0, nil, syscall.EINVAL
+			return 0, nil, syserror.EINVAL
 		}
 		var rv uintptr
 		if auth.CapabilitySetOf(cp)&t.Credentials().BoundingCaps != 0 {
@@ -196,7 +195,7 @@ func Prctl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 	case linux.PR_CAPBSET_DROP:
 		cp := linux.Capability(args[1].Uint64())
 		if !cp.Ok() {
-			return 0, nil, syscall.EINVAL
+			return 0, nil, syserror.EINVAL
 		}
 		return 0, nil, t.DropBoundingCapability(cp)
 
@@ -221,7 +220,7 @@ func Prctl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 		t.Kernel().EmitUnimplementedEvent(t)
 		fallthrough
 	default:
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 
 	return 0, nil, nil
diff --git a/pkg/sentry/syscalls/linux/sys_read.go b/pkg/sentry/syscalls/linux/sys_read.go
index a1965f490..b2474e60d 100644
--- a/pkg/sentry/syscalls/linux/sys_read.go
+++ b/pkg/sentry/syscalls/linux/sys_read.go
@@ -21,7 +21,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/socket"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
@@ -39,11 +38,11 @@ const (
 // they can do large reads all at once.  Bug for bug.  Same for other read
 // calls below.
 func Read(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	size := args[2].SizeT()
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -75,12 +74,12 @@ func Read(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallC
 
 // Pread64 implements linux syscall pread64(2).
 func Pread64(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	size := args[2].SizeT()
 	offset := args[3].Int64()
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -122,11 +121,11 @@ func Pread64(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysca
 
 // Readv implements linux syscall readv(2).
 func Readv(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	iovcnt := int(args[2].Int())
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -152,12 +151,12 @@ func Readv(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 
 // Preadv implements linux syscall preadv(2).
 func Preadv(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	iovcnt := int(args[2].Int())
 	offset := args[3].Int64()
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -201,13 +200,13 @@ func Preadv2(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysca
 	// splits the offset argument into a high/low value for compatibility with
 	// 32-bit architectures. The flags argument is the 5th argument.
 
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	iovcnt := int(args[2].Int())
 	offset := args[3].Int64()
 	flags := int(args[5].Int())
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
diff --git a/pkg/sentry/syscalls/linux/sys_sched.go b/pkg/sentry/syscalls/linux/sys_sched.go
index 434bbb322..99f6993f5 100644
--- a/pkg/sentry/syscalls/linux/sys_sched.go
+++ b/pkg/sentry/syscalls/linux/sys_sched.go
@@ -15,11 +15,10 @@
 package linux
 
 import (
-	"syscall"
-
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/syserror"
 )
 
 const (
@@ -37,13 +36,13 @@ func SchedGetparam(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel
 	pid := args[0].Int()
 	param := args[1].Pointer()
 	if param == 0 {
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 	if pid < 0 {
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 	if pid != 0 && t.PIDNamespace().TaskWithID(kernel.ThreadID(pid)) == nil {
-		return 0, nil, syscall.ESRCH
+		return 0, nil, syserror.ESRCH
 	}
 	r := SchedParam{schedPriority: onlyPriority}
 	if _, err := t.CopyOut(param, r); err != nil {
@@ -57,10 +56,10 @@ func SchedGetparam(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel
 func SchedGetscheduler(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
 	pid := args[0].Int()
 	if pid < 0 {
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 	if pid != 0 && t.PIDNamespace().TaskWithID(kernel.ThreadID(pid)) == nil {
-		return 0, nil, syscall.ESRCH
+		return 0, nil, syserror.ESRCH
 	}
 	return onlyScheduler, nil, nil
 }
@@ -71,20 +70,20 @@ func SchedSetscheduler(t *kernel.Task, args arch.SyscallArguments) (uintptr, *ke
 	policy := args[1].Int()
 	param := args[2].Pointer()
 	if pid < 0 {
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 	if policy != onlyScheduler {
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 	if pid != 0 && t.PIDNamespace().TaskWithID(kernel.ThreadID(pid)) == nil {
-		return 0, nil, syscall.ESRCH
+		return 0, nil, syserror.ESRCH
 	}
 	var r SchedParam
 	if _, err := t.CopyIn(param, &r); err != nil {
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 	if r.schedPriority != onlyPriority {
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 	return 0, nil, nil
 }
diff --git a/pkg/sentry/syscalls/linux/sys_seccomp.go b/pkg/sentry/syscalls/linux/sys_seccomp.go
index 4885b5e40..18510ead8 100644
--- a/pkg/sentry/syscalls/linux/sys_seccomp.go
+++ b/pkg/sentry/syscalls/linux/sys_seccomp.go
@@ -15,13 +15,12 @@
 package linux
 
 import (
-	"syscall"
-
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/bpf"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/syserror"
 )
 
 // userSockFprog is equivalent to Linux's struct sock_fprog on amd64.
@@ -43,7 +42,7 @@ func seccomp(t *kernel.Task, mode, flags uint64, addr usermem.Addr) error {
 	// We only support SECCOMP_SET_MODE_FILTER at the moment.
 	if mode != linux.SECCOMP_SET_MODE_FILTER {
 		// Unsupported mode.
-		return syscall.EINVAL
+		return syserror.EINVAL
 	}
 
 	tsync := flags&linux.SECCOMP_FILTER_FLAG_TSYNC != 0
@@ -51,7 +50,7 @@ func seccomp(t *kernel.Task, mode, flags uint64, addr usermem.Addr) error {
 	// The only flag we support now is SECCOMP_FILTER_FLAG_TSYNC.
 	if flags&^linux.SECCOMP_FILTER_FLAG_TSYNC != 0 {
 		// Unsupported flag.
-		return syscall.EINVAL
+		return syserror.EINVAL
 	}
 
 	var fprog userSockFprog
@@ -65,7 +64,7 @@ func seccomp(t *kernel.Task, mode, flags uint64, addr usermem.Addr) error {
 	compiledFilter, err := bpf.Compile(filter)
 	if err != nil {
 		t.Debugf("Invalid seccomp-bpf filter: %v", err)
-		return syscall.EINVAL
+		return syserror.EINVAL
 	}
 
 	return t.AppendSyscallFilter(compiledFilter, tsync)
diff --git a/pkg/sentry/syscalls/linux/sys_socket.go b/pkg/sentry/syscalls/linux/sys_socket.go
index ccdb079bb..195734257 100644
--- a/pkg/sentry/syscalls/linux/sys_socket.go
+++ b/pkg/sentry/syscalls/linux/sys_socket.go
@@ -15,7 +15,6 @@
 package linux
 
 import (
-	"syscall"
 	"time"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
@@ -23,7 +22,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/socket"
 	"gvisor.dev/gvisor/pkg/sentry/socket/control"
@@ -132,7 +130,7 @@ func CopyInMessageHeader64(t *kernel.Task, addr usermem.Addr, msg *MessageHeader
 // from the untrusted address space range.
 func CaptureAddress(t *kernel.Task, addr usermem.Addr, addrlen uint32) ([]byte, error) {
 	if addrlen > maxAddrLen {
-		return nil, syscall.EINVAL
+		return nil, syserror.EINVAL
 	}
 
 	addrBuf := make([]byte, addrlen)
@@ -154,7 +152,7 @@ func writeAddress(t *kernel.Task, addr interface{}, addrLen uint32, addrPtr user
 	}
 
 	if int32(bufLen) < 0 {
-		return syscall.EINVAL
+		return syserror.EINVAL
 	}
 
 	// Write the length unconditionally.
@@ -187,7 +185,7 @@ func Socket(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 
 	// Check and initialize the flags.
 	if stype & ^(0xf|linux.SOCK_NONBLOCK|linux.SOCK_CLOEXEC) != 0 {
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 
 	// Create the new socket.
@@ -200,9 +198,9 @@ func Socket(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 	})
 	defer s.DecRef()
 
-	fd, err := t.FDMap().NewFDFrom(0, s, kernel.FDFlags{
+	fd, err := t.NewFDFrom(0, s, kernel.FDFlags{
 		CloseOnExec: stype&linux.SOCK_CLOEXEC != 0,
-	}, t.ThreadGroup().Limits())
+	})
 	if err != nil {
 		return 0, nil, err
 	}
@@ -219,15 +217,12 @@ func SocketPair(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sy
 
 	// Check and initialize the flags.
 	if stype & ^(0xf|linux.SOCK_NONBLOCK|linux.SOCK_CLOEXEC) != 0 {
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 
 	fileFlags := fs.SettableFileFlags{
 		NonBlocking: stype&linux.SOCK_NONBLOCK != 0,
 	}
-	fdFlags := kernel.FDFlags{
-		CloseOnExec: stype&linux.SOCK_CLOEXEC != 0,
-	}
 
 	// Create the socket pair.
 	s1, s2, e := socket.Pair(t, domain, linux.SockType(stype&0xf), protocol)
@@ -240,20 +235,16 @@ func SocketPair(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sy
 	defer s2.DecRef()
 
 	// Create the FDs for the sockets.
-	fd1, err := t.FDMap().NewFDFrom(0, s1, fdFlags, t.ThreadGroup().Limits())
-	if err != nil {
-		return 0, nil, err
-	}
-	fd2, err := t.FDMap().NewFDFrom(0, s2, fdFlags, t.ThreadGroup().Limits())
+	fds, err := t.NewFDs(0, []*fs.File{s1, s2}, kernel.FDFlags{
+		CloseOnExec: stype&linux.SOCK_CLOEXEC != 0,
+	})
 	if err != nil {
-		t.FDMap().Remove(fd1)
 		return 0, nil, err
 	}
 
 	// Copy the file descriptors out.
-	if _, err := t.CopyOut(socks, []int32{int32(fd1), int32(fd2)}); err != nil {
-		t.FDMap().Remove(fd1)
-		t.FDMap().Remove(fd2)
+	if _, err := t.CopyOut(socks, fds); err != nil {
+		// Note that we don't close files here; see pipe(2) also.
 		return 0, nil, err
 	}
 
@@ -262,21 +253,21 @@ func SocketPair(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sy
 
 // Connect implements the linux syscall connect(2).
 func Connect(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	addrlen := args[2].Uint()
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
-		return 0, nil, syscall.EBADF
+		return 0, nil, syserror.EBADF
 	}
 	defer file.DecRef()
 
 	// Extract the socket.
 	s, ok := file.FileOperations.(socket.Socket)
 	if !ok {
-		return 0, nil, syscall.ENOTSOCK
+		return 0, nil, syserror.ENOTSOCK
 	}
 
 	// Capture address and call syscall implementation.
@@ -291,23 +282,23 @@ func Connect(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysca
 
 // accept is the implementation of the accept syscall. It is called by accept
 // and accept4 syscall handlers.
-func accept(t *kernel.Task, fd kdefs.FD, addr usermem.Addr, addrLen usermem.Addr, flags int) (uintptr, error) {
+func accept(t *kernel.Task, fd int32, addr usermem.Addr, addrLen usermem.Addr, flags int) (uintptr, error) {
 	// Check that no unsupported flags are passed in.
 	if flags & ^(linux.SOCK_NONBLOCK|linux.SOCK_CLOEXEC) != 0 {
-		return 0, syscall.EINVAL
+		return 0, syserror.EINVAL
 	}
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
-		return 0, syscall.EBADF
+		return 0, syserror.EBADF
 	}
 	defer file.DecRef()
 
 	// Extract the socket.
 	s, ok := file.FileOperations.(socket.Socket)
 	if !ok {
-		return 0, syscall.ENOTSOCK
+		return 0, syserror.ENOTSOCK
 	}
 
 	// Call the syscall implementation for this socket, then copy the
@@ -322,7 +313,7 @@ func accept(t *kernel.Task, fd kdefs.FD, addr usermem.Addr, addrLen usermem.Addr
 	if peerRequested {
 		// NOTE(magi): Linux does not give you an error if it can't
 		// write the data back out so neither do we.
-		if err := writeAddress(t, peer, peerLen, addr, addrLen); err == syscall.EINVAL {
+		if err := writeAddress(t, peer, peerLen, addr, addrLen); err == syserror.EINVAL {
 			return 0, err
 		}
 	}
@@ -331,7 +322,7 @@ func accept(t *kernel.Task, fd kdefs.FD, addr usermem.Addr, addrLen usermem.Addr
 
 // Accept4 implements the linux syscall accept4(2).
 func Accept4(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	addrlen := args[2].Pointer()
 	flags := int(args[3].Int())
@@ -342,7 +333,7 @@ func Accept4(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysca
 
 // Accept implements the linux syscall accept(2).
 func Accept(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	addrlen := args[2].Pointer()
 
@@ -352,21 +343,21 @@ func Accept(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 
 // Bind implements the linux syscall bind(2).
 func Bind(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	addrlen := args[2].Uint()
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
-		return 0, nil, syscall.EBADF
+		return 0, nil, syserror.EBADF
 	}
 	defer file.DecRef()
 
 	// Extract the socket.
 	s, ok := file.FileOperations.(socket.Socket)
 	if !ok {
-		return 0, nil, syscall.ENOTSOCK
+		return 0, nil, syserror.ENOTSOCK
 	}
 
 	// Capture address and call syscall implementation.
@@ -380,20 +371,20 @@ func Bind(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallC
 
 // Listen implements the linux syscall listen(2).
 func Listen(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	backlog := args[1].Int()
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
-		return 0, nil, syscall.EBADF
+		return 0, nil, syserror.EBADF
 	}
 	defer file.DecRef()
 
 	// Extract the socket.
 	s, ok := file.FileOperations.(socket.Socket)
 	if !ok {
-		return 0, nil, syscall.ENOTSOCK
+		return 0, nil, syserror.ENOTSOCK
 	}
 
 	// Per Linux, the backlog is silently capped to reasonable values.
@@ -409,27 +400,27 @@ func Listen(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 
 // Shutdown implements the linux syscall shutdown(2).
 func Shutdown(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	how := args[1].Int()
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
-		return 0, nil, syscall.EBADF
+		return 0, nil, syserror.EBADF
 	}
 	defer file.DecRef()
 
 	// Extract the socket.
 	s, ok := file.FileOperations.(socket.Socket)
 	if !ok {
-		return 0, nil, syscall.ENOTSOCK
+		return 0, nil, syserror.ENOTSOCK
 	}
 
 	// Validate how, then call syscall implementation.
 	switch how {
 	case linux.SHUT_RD, linux.SHUT_WR, linux.SHUT_RDWR:
 	default:
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 
 	return 0, nil, s.Shutdown(t, int(how)).ToError()
@@ -437,23 +428,23 @@ func Shutdown(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 
 // GetSockOpt implements the linux syscall getsockopt(2).
 func GetSockOpt(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	level := args[1].Int()
 	name := args[2].Int()
 	optValAddr := args[3].Pointer()
 	optLenAddr := args[4].Pointer()
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
-		return 0, nil, syscall.EBADF
+		return 0, nil, syserror.EBADF
 	}
 	defer file.DecRef()
 
 	// Extract the socket.
 	s, ok := file.FileOperations.(socket.Socket)
 	if !ok {
-		return 0, nil, syscall.ENOTSOCK
+		return 0, nil, syserror.ENOTSOCK
 	}
 
 	// Read the length if present. Reject negative values.
@@ -464,7 +455,7 @@ func GetSockOpt(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sy
 		}
 
 		if optLen < 0 {
-			return 0, nil, syscall.EINVAL
+			return 0, nil, syserror.EINVAL
 		}
 	}
 
@@ -521,30 +512,30 @@ func getSockOpt(t *kernel.Task, s socket.Socket, level, name, len int) (interfac
 //
 // Note that unlike Linux, enabling SO_PASSCRED does not autobind the socket.
 func SetSockOpt(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	level := args[1].Int()
 	name := args[2].Int()
 	optValAddr := args[3].Pointer()
 	optLen := args[4].Int()
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
-		return 0, nil, syscall.EBADF
+		return 0, nil, syserror.EBADF
 	}
 	defer file.DecRef()
 
 	// Extract the socket.
 	s, ok := file.FileOperations.(socket.Socket)
 	if !ok {
-		return 0, nil, syscall.ENOTSOCK
+		return 0, nil, syserror.ENOTSOCK
 	}
 
 	if optLen <= 0 {
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 	if optLen > maxOptLen {
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 	buf := t.CopyScratchBuffer(int(optLen))
 	if _, err := t.CopyIn(optValAddr, &buf); err != nil {
@@ -561,21 +552,21 @@ func SetSockOpt(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sy
 
 // GetSockName implements the linux syscall getsockname(2).
 func GetSockName(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	addrlen := args[2].Pointer()
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
-		return 0, nil, syscall.EBADF
+		return 0, nil, syserror.EBADF
 	}
 	defer file.DecRef()
 
 	// Extract the socket.
 	s, ok := file.FileOperations.(socket.Socket)
 	if !ok {
-		return 0, nil, syscall.ENOTSOCK
+		return 0, nil, syserror.ENOTSOCK
 	}
 
 	// Get the socket name and copy it to the caller.
@@ -589,21 +580,21 @@ func GetSockName(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.S
 
 // GetPeerName implements the linux syscall getpeername(2).
 func GetPeerName(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	addrlen := args[2].Pointer()
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
-		return 0, nil, syscall.EBADF
+		return 0, nil, syserror.EBADF
 	}
 	defer file.DecRef()
 
 	// Extract the socket.
 	s, ok := file.FileOperations.(socket.Socket)
 	if !ok {
-		return 0, nil, syscall.ENOTSOCK
+		return 0, nil, syserror.ENOTSOCK
 	}
 
 	// Get the socket peer name and copy it to the caller.
@@ -617,31 +608,31 @@ func GetPeerName(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.S
 
 // RecvMsg implements the linux syscall recvmsg(2).
 func RecvMsg(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	msgPtr := args[1].Pointer()
 	flags := args[2].Int()
 
 	if t.Arch().Width() != 8 {
 		// We only handle 64-bit for now.
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
-		return 0, nil, syscall.EBADF
+		return 0, nil, syserror.EBADF
 	}
 	defer file.DecRef()
 
 	// Extract the socket.
 	s, ok := file.FileOperations.(socket.Socket)
 	if !ok {
-		return 0, nil, syscall.ENOTSOCK
+		return 0, nil, syserror.ENOTSOCK
 	}
 
 	// Reject flags that we don't handle yet.
 	if flags & ^(baseRecvFlags|linux.MSG_PEEK|linux.MSG_CMSG_CLOEXEC|linux.MSG_ERRQUEUE) != 0 {
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 
 	if file.Flags().NonBlocking {
@@ -663,7 +654,7 @@ func RecvMsg(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysca
 
 // RecvMMsg implements the linux syscall recvmmsg(2).
 func RecvMMsg(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	msgPtr := args[1].Pointer()
 	vlen := args[2].Uint()
 	flags := args[3].Int()
@@ -671,25 +662,25 @@ func RecvMMsg(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 
 	if t.Arch().Width() != 8 {
 		// We only handle 64-bit for now.
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 
 	// Reject flags that we don't handle yet.
 	if flags & ^(baseRecvFlags|linux.MSG_CMSG_CLOEXEC|linux.MSG_ERRQUEUE) != 0 {
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
-		return 0, nil, syscall.EBADF
+		return 0, nil, syserror.EBADF
 	}
 	defer file.DecRef()
 
 	// Extract the socket.
 	s, ok := file.FileOperations.(socket.Socket)
 	if !ok {
-		return 0, nil, syscall.ENOTSOCK
+		return 0, nil, syserror.ENOTSOCK
 	}
 
 	if file.Flags().NonBlocking {
@@ -704,7 +695,7 @@ func RecvMMsg(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 			return 0, nil, err
 		}
 		if !ts.Valid() {
-			return 0, nil, syscall.EINVAL
+			return 0, nil, syserror.EINVAL
 		}
 		deadline = t.Kernel().MonotonicClock().Now().Add(ts.ToDuration())
 		haveDeadline = true
@@ -724,7 +715,7 @@ func RecvMMsg(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 	for i := uint64(0); i < uint64(vlen); i++ {
 		mp, ok := msgPtr.AddLength(i * multipleMessageHeader64Len)
 		if !ok {
-			return 0, nil, syscall.EFAULT
+			return 0, nil, syserror.EFAULT
 		}
 		var n uintptr
 		if n, err = recvSingleMsg(t, s, mp, flags, haveDeadline, deadline); err != nil {
@@ -734,7 +725,7 @@ func RecvMMsg(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 		// Copy the received length to the caller.
 		lp, ok := mp.AddLength(messageHeader64Len)
 		if !ok {
-			return 0, nil, syscall.EFAULT
+			return 0, nil, syserror.EFAULT
 		}
 		if _, err = t.CopyOut(lp, uint32(n)); err != nil {
 			break
@@ -756,7 +747,7 @@ func recvSingleMsg(t *kernel.Task, s socket.Socket, msgPtr usermem.Addr, flags i
 	}
 
 	if msg.IovLen > linux.UIO_MAXIOV {
-		return 0, syscall.EMSGSIZE
+		return 0, syserror.EMSGSIZE
 	}
 	dst, err := t.IovecsIOSequence(usermem.Addr(msg.Iov), int(msg.IovLen), usermem.IOOpts{
 		AddressSpaceActive: true,
@@ -767,7 +758,7 @@ func recvSingleMsg(t *kernel.Task, s socket.Socket, msgPtr usermem.Addr, flags i
 
 	// FIXME(b/63594852): Pretend we have an empty error queue.
 	if flags&linux.MSG_ERRQUEUE != 0 {
-		return 0, syscall.EAGAIN
+		return 0, syserror.EAGAIN
 	}
 
 	// Fast path when no control message nor name buffers are provided.
@@ -792,7 +783,7 @@ func recvSingleMsg(t *kernel.Task, s socket.Socket, msgPtr usermem.Addr, flags i
 	}
 
 	if msg.ControlLen > maxControlLen {
-		return 0, syscall.ENOBUFS
+		return 0, syserror.ENOBUFS
 	}
 	n, mflags, sender, senderLen, cms, e := s.RecvMsg(t, dst, int(flags), haveDeadline, deadline, msg.NameLen != 0, msg.ControlLen)
 	if e != nil {
@@ -842,27 +833,27 @@ func recvSingleMsg(t *kernel.Task, s socket.Socket, msgPtr usermem.Addr, flags i
 
 // recvFrom is the implementation of the recvfrom syscall. It is called by
 // recvfrom and recv syscall handlers.
-func recvFrom(t *kernel.Task, fd kdefs.FD, bufPtr usermem.Addr, bufLen uint64, flags int32, namePtr usermem.Addr, nameLenPtr usermem.Addr) (uintptr, error) {
+func recvFrom(t *kernel.Task, fd int32, bufPtr usermem.Addr, bufLen uint64, flags int32, namePtr usermem.Addr, nameLenPtr usermem.Addr) (uintptr, error) {
 	if int(bufLen) < 0 {
-		return 0, syscall.EINVAL
+		return 0, syserror.EINVAL
 	}
 
 	// Reject flags that we don't handle yet.
 	if flags & ^(baseRecvFlags|linux.MSG_PEEK|linux.MSG_CONFIRM) != 0 {
-		return 0, syscall.EINVAL
+		return 0, syserror.EINVAL
 	}
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
-		return 0, syscall.EBADF
+		return 0, syserror.EBADF
 	}
 	defer file.DecRef()
 
 	// Extract the socket.
 	s, ok := file.FileOperations.(socket.Socket)
 	if !ok {
-		return 0, syscall.ENOTSOCK
+		return 0, syserror.ENOTSOCK
 	}
 
 	if file.Flags().NonBlocking {
@@ -903,7 +894,7 @@ func recvFrom(t *kernel.Task, fd kdefs.FD, bufPtr usermem.Addr, bufLen uint64, f
 
 // RecvFrom implements the linux syscall recvfrom(2).
 func RecvFrom(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	bufPtr := args[1].Pointer()
 	bufLen := args[2].Uint64()
 	flags := args[3].Int()
@@ -916,31 +907,31 @@ func RecvFrom(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 
 // SendMsg implements the linux syscall sendmsg(2).
 func SendMsg(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	msgPtr := args[1].Pointer()
 	flags := args[2].Int()
 
 	if t.Arch().Width() != 8 {
 		// We only handle 64-bit for now.
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
-		return 0, nil, syscall.EBADF
+		return 0, nil, syserror.EBADF
 	}
 	defer file.DecRef()
 
 	// Extract the socket.
 	s, ok := file.FileOperations.(socket.Socket)
 	if !ok {
-		return 0, nil, syscall.ENOTSOCK
+		return 0, nil, syserror.ENOTSOCK
 	}
 
 	// Reject flags that we don't handle yet.
 	if flags & ^(linux.MSG_DONTWAIT|linux.MSG_EOR|linux.MSG_MORE|linux.MSG_NOSIGNAL) != 0 {
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 
 	if file.Flags().NonBlocking {
@@ -953,32 +944,32 @@ func SendMsg(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysca
 
 // SendMMsg implements the linux syscall sendmmsg(2).
 func SendMMsg(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	msgPtr := args[1].Pointer()
 	vlen := args[2].Uint()
 	flags := args[3].Int()
 
 	if t.Arch().Width() != 8 {
 		// We only handle 64-bit for now.
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
-		return 0, nil, syscall.EBADF
+		return 0, nil, syserror.EBADF
 	}
 	defer file.DecRef()
 
 	// Extract the socket.
 	s, ok := file.FileOperations.(socket.Socket)
 	if !ok {
-		return 0, nil, syscall.ENOTSOCK
+		return 0, nil, syserror.ENOTSOCK
 	}
 
 	// Reject flags that we don't handle yet.
 	if flags & ^(linux.MSG_DONTWAIT|linux.MSG_EOR|linux.MSG_MORE|linux.MSG_NOSIGNAL) != 0 {
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 
 	if file.Flags().NonBlocking {
@@ -990,7 +981,7 @@ func SendMMsg(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 	for i := uint64(0); i < uint64(vlen); i++ {
 		mp, ok := msgPtr.AddLength(i * multipleMessageHeader64Len)
 		if !ok {
-			return 0, nil, syscall.EFAULT
+			return 0, nil, syserror.EFAULT
 		}
 		var n uintptr
 		if n, err = sendSingleMsg(t, s, file, mp, flags); err != nil {
@@ -1000,7 +991,7 @@ func SendMMsg(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 		// Copy the received length to the caller.
 		lp, ok := mp.AddLength(messageHeader64Len)
 		if !ok {
-			return 0, nil, syscall.EFAULT
+			return 0, nil, syserror.EFAULT
 		}
 		if _, err = t.CopyOut(lp, uint32(n)); err != nil {
 			break
@@ -1025,7 +1016,7 @@ func sendSingleMsg(t *kernel.Task, s socket.Socket, file *fs.File, msgPtr userme
 	if msg.ControlLen > 0 {
 		// Put an upper bound to prevent large allocations.
 		if msg.ControlLen > maxControlLen {
-			return 0, syscall.ENOBUFS
+			return 0, syserror.ENOBUFS
 		}
 		controlData = make([]byte, msg.ControlLen)
 		if _, err := t.CopyIn(usermem.Addr(msg.Control), &controlData); err != nil {
@@ -1045,7 +1036,7 @@ func sendSingleMsg(t *kernel.Task, s socket.Socket, file *fs.File, msgPtr userme
 
 	// Read data then call the sendmsg implementation.
 	if msg.IovLen > linux.UIO_MAXIOV {
-		return 0, syscall.EMSGSIZE
+		return 0, syserror.EMSGSIZE
 	}
 	src, err := t.IovecsIOSequence(usermem.Addr(msg.Iov), int(msg.IovLen), usermem.IOOpts{
 		AddressSpaceActive: true,
@@ -1079,23 +1070,23 @@ func sendSingleMsg(t *kernel.Task, s socket.Socket, file *fs.File, msgPtr userme
 
 // sendTo is the implementation of the sendto syscall. It is called by sendto
 // and send syscall handlers.
-func sendTo(t *kernel.Task, fd kdefs.FD, bufPtr usermem.Addr, bufLen uint64, flags int32, namePtr usermem.Addr, nameLen uint32) (uintptr, error) {
+func sendTo(t *kernel.Task, fd int32, bufPtr usermem.Addr, bufLen uint64, flags int32, namePtr usermem.Addr, nameLen uint32) (uintptr, error) {
 	bl := int(bufLen)
 	if bl < 0 {
-		return 0, syscall.EINVAL
+		return 0, syserror.EINVAL
 	}
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
-		return 0, syscall.EBADF
+		return 0, syserror.EBADF
 	}
 	defer file.DecRef()
 
 	// Extract the socket.
 	s, ok := file.FileOperations.(socket.Socket)
 	if !ok {
-		return 0, syscall.ENOTSOCK
+		return 0, syserror.ENOTSOCK
 	}
 
 	if file.Flags().NonBlocking {
@@ -1135,7 +1126,7 @@ func sendTo(t *kernel.Task, fd kdefs.FD, bufPtr usermem.Addr, bufLen uint64, fla
 
 // SendTo implements the linux syscall sendto(2).
 func SendTo(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	bufPtr := args[1].Pointer()
 	bufLen := args[2].Uint64()
 	flags := args[3].Int()
diff --git a/pkg/sentry/syscalls/linux/sys_splice.go b/pkg/sentry/syscalls/linux/sys_splice.go
index b6517313f..a7c98efcb 100644
--- a/pkg/sentry/syscalls/linux/sys_splice.go
+++ b/pkg/sentry/syscalls/linux/sys_splice.go
@@ -19,7 +19,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
@@ -81,8 +80,8 @@ func doSplice(t *kernel.Task, outFile, inFile *fs.File, opts fs.SpliceOpts, nonB
 
 // Sendfile implements linux system call sendfile(2).
 func Sendfile(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	outFD := kdefs.FD(args[0].Int())
-	inFD := kdefs.FD(args[1].Int())
+	outFD := args[0].Int()
+	inFD := args[1].Int()
 	offsetAddr := args[2].Pointer()
 	count := int64(args[3].SizeT())
 
@@ -92,13 +91,13 @@ func Sendfile(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 	}
 
 	// Get files.
-	outFile := t.FDMap().GetFile(outFD)
+	outFile := t.GetFile(outFD)
 	if outFile == nil {
 		return 0, nil, syserror.EBADF
 	}
 	defer outFile.DecRef()
 
-	inFile := t.FDMap().GetFile(inFD)
+	inFile := t.GetFile(inFD)
 	if inFile == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -163,9 +162,9 @@ func Sendfile(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 
 // Splice implements splice(2).
 func Splice(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	inFD := kdefs.FD(args[0].Int())
+	inFD := args[0].Int()
 	inOffset := args[1].Pointer()
-	outFD := kdefs.FD(args[2].Int())
+	outFD := args[2].Int()
 	outOffset := args[3].Pointer()
 	count := int64(args[4].SizeT())
 	flags := args[5].Int()
@@ -182,13 +181,13 @@ func Splice(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 	nonBlocking := (flags & linux.SPLICE_F_NONBLOCK) != 0
 
 	// Get files.
-	outFile := t.FDMap().GetFile(outFD)
+	outFile := t.GetFile(outFD)
 	if outFile == nil {
 		return 0, nil, syserror.EBADF
 	}
 	defer outFile.DecRef()
 
-	inFile := t.FDMap().GetFile(inFD)
+	inFile := t.GetFile(inFD)
 	if inFile == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -251,8 +250,8 @@ func Splice(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 
 // Tee imlements tee(2).
 func Tee(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	inFD := kdefs.FD(args[0].Int())
-	outFD := kdefs.FD(args[1].Int())
+	inFD := args[0].Int()
+	outFD := args[1].Int()
 	count := int64(args[2].SizeT())
 	flags := args[3].Int()
 
@@ -265,13 +264,13 @@ func Tee(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallCo
 	nonBlocking := (flags & linux.SPLICE_F_NONBLOCK) != 0
 
 	// Get files.
-	outFile := t.FDMap().GetFile(outFD)
+	outFile := t.GetFile(outFD)
 	if outFile == nil {
 		return 0, nil, syserror.EBADF
 	}
 	defer outFile.DecRef()
 
-	inFile := t.FDMap().GetFile(inFD)
+	inFile := t.GetFile(inFD)
 	if inFile == nil {
 		return 0, nil, syserror.EBADF
 	}
diff --git a/pkg/sentry/syscalls/linux/sys_stat.go b/pkg/sentry/syscalls/linux/sys_stat.go
index 9a5657254..5556bc276 100644
--- a/pkg/sentry/syscalls/linux/sys_stat.go
+++ b/pkg/sentry/syscalls/linux/sys_stat.go
@@ -20,7 +20,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
@@ -42,7 +41,7 @@ func Stat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallC
 
 // Fstatat implements linux syscall newfstatat, i.e. fstatat(2).
 func Fstatat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	statAddr := args[2].Pointer()
 	flags := args[3].Int()
@@ -54,7 +53,7 @@ func Fstatat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysca
 
 	if path == "" {
 		// Annoying. What's wrong with fstat?
-		file := t.FDMap().GetFile(fd)
+		file := t.GetFile(fd)
 		if file == nil {
 			return 0, nil, syserror.EBADF
 		}
@@ -93,10 +92,10 @@ func Lstat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 
 // Fstat implements linux syscall fstat(2).
 func Fstat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	statAddr := args[1].Pointer()
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -178,7 +177,7 @@ func copyOutStat(t *kernel.Task, dst usermem.Addr, sattr fs.StableAttr, uattr fs
 
 // Statx implements linux syscall statx(2).
 func Statx(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	pathAddr := args[1].Pointer()
 	flags := args[2].Int()
 	mask := args[3].Uint()
@@ -197,7 +196,7 @@ func Statx(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 	}
 
 	if path == "" {
-		file := t.FDMap().GetFile(fd)
+		file := t.GetFile(fd)
 		if file == nil {
 			return 0, nil, syserror.EBADF
 		}
@@ -285,10 +284,10 @@ func Statfs(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 
 // Fstatfs implements linux syscall fstatfs(2).
 func Fstatfs(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	statfsAddr := args[1].Pointer()
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
diff --git a/pkg/sentry/syscalls/linux/sys_sync.go b/pkg/sentry/syscalls/linux/sys_sync.go
index 37225735f..3e55235bd 100644
--- a/pkg/sentry/syscalls/linux/sys_sync.go
+++ b/pkg/sentry/syscalls/linux/sys_sync.go
@@ -19,7 +19,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
@@ -32,9 +31,9 @@ func Sync(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallC
 
 // Syncfs implements linux system call syncfs(2).
 func Syncfs(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -47,9 +46,9 @@ func Syncfs(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 
 // Fsync implements linux syscall fsync(2).
 func Fsync(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -63,9 +62,9 @@ func Fsync(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 //
 // At the moment, it just calls Fsync, which is a big hammer, but correct.
 func Fdatasync(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -79,6 +78,7 @@ func Fdatasync(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sys
 func SyncFileRange(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
 	var err error
 
+	fd := args[0].Int()
 	offset := args[1].Int64()
 	nbytes := args[2].Int64()
 	uflags := args[3].Uint()
@@ -97,8 +97,7 @@ func SyncFileRange(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel
 		nbytes = fs.FileMaxOffset
 	}
 
-	fd := kdefs.FD(args[0].Int())
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
diff --git a/pkg/sentry/syscalls/linux/sys_thread.go b/pkg/sentry/syscalls/linux/sys_thread.go
index 9e037bd7b..595eb9155 100644
--- a/pkg/sentry/syscalls/linux/sys_thread.go
+++ b/pkg/sentry/syscalls/linux/sys_thread.go
@@ -123,29 +123,29 @@ func ExitGroup(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sys
 func clone(t *kernel.Task, flags int, stack usermem.Addr, parentTID usermem.Addr, childTID usermem.Addr, tls usermem.Addr) (uintptr, *kernel.SyscallControl, error) {
 	opts := kernel.CloneOptions{
 		SharingOptions: kernel.SharingOptions{
-			NewAddressSpace:     flags&syscall.CLONE_VM == 0,
-			NewSignalHandlers:   flags&syscall.CLONE_SIGHAND == 0,
-			NewThreadGroup:      flags&syscall.CLONE_THREAD == 0,
+			NewAddressSpace:     flags&linux.CLONE_VM == 0,
+			NewSignalHandlers:   flags&linux.CLONE_SIGHAND == 0,
+			NewThreadGroup:      flags&linux.CLONE_THREAD == 0,
 			TerminationSignal:   linux.Signal(flags & exitSignalMask),
-			NewPIDNamespace:     flags&syscall.CLONE_NEWPID == syscall.CLONE_NEWPID,
-			NewUserNamespace:    flags&syscall.CLONE_NEWUSER == syscall.CLONE_NEWUSER,
-			NewNetworkNamespace: flags&syscall.CLONE_NEWNET == syscall.CLONE_NEWNET,
-			NewFiles:            flags&syscall.CLONE_FILES == 0,
-			NewFSContext:        flags&syscall.CLONE_FS == 0,
-			NewUTSNamespace:     flags&syscall.CLONE_NEWUTS == syscall.CLONE_NEWUTS,
-			NewIPCNamespace:     flags&syscall.CLONE_NEWIPC == syscall.CLONE_NEWIPC,
+			NewPIDNamespace:     flags&linux.CLONE_NEWPID == linux.CLONE_NEWPID,
+			NewUserNamespace:    flags&linux.CLONE_NEWUSER == linux.CLONE_NEWUSER,
+			NewNetworkNamespace: flags&linux.CLONE_NEWNET == linux.CLONE_NEWNET,
+			NewFiles:            flags&linux.CLONE_FILES == 0,
+			NewFSContext:        flags&linux.CLONE_FS == 0,
+			NewUTSNamespace:     flags&linux.CLONE_NEWUTS == linux.CLONE_NEWUTS,
+			NewIPCNamespace:     flags&linux.CLONE_NEWIPC == linux.CLONE_NEWIPC,
 		},
 		Stack:         stack,
-		SetTLS:        flags&syscall.CLONE_SETTLS == syscall.CLONE_SETTLS,
+		SetTLS:        flags&linux.CLONE_SETTLS == linux.CLONE_SETTLS,
 		TLS:           tls,
-		ChildClearTID: flags&syscall.CLONE_CHILD_CLEARTID == syscall.CLONE_CHILD_CLEARTID,
-		ChildSetTID:   flags&syscall.CLONE_CHILD_SETTID == syscall.CLONE_CHILD_SETTID,
+		ChildClearTID: flags&linux.CLONE_CHILD_CLEARTID == linux.CLONE_CHILD_CLEARTID,
+		ChildSetTID:   flags&linux.CLONE_CHILD_SETTID == linux.CLONE_CHILD_SETTID,
 		ChildTID:      childTID,
-		ParentSetTID:  flags&syscall.CLONE_PARENT_SETTID == syscall.CLONE_PARENT_SETTID,
+		ParentSetTID:  flags&linux.CLONE_PARENT_SETTID == linux.CLONE_PARENT_SETTID,
 		ParentTID:     parentTID,
-		Vfork:         flags&syscall.CLONE_VFORK == syscall.CLONE_VFORK,
-		Untraced:      flags&syscall.CLONE_UNTRACED == syscall.CLONE_UNTRACED,
-		InheritTracer: flags&syscall.CLONE_PTRACE == syscall.CLONE_PTRACE,
+		Vfork:         flags&linux.CLONE_VFORK == linux.CLONE_VFORK,
+		Untraced:      flags&linux.CLONE_UNTRACED == linux.CLONE_UNTRACED,
+		InheritTracer: flags&linux.CLONE_PTRACE == linux.CLONE_PTRACE,
 	}
 	ntid, ctrl, err := t.Clone(&opts)
 	return uintptr(ntid), ctrl, err
@@ -168,7 +168,7 @@ func Clone(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 func Fork(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
 	// "A call to fork() is equivalent to a call to clone(2) specifying flags
 	// as just SIGCHLD." - fork(2)
-	return clone(t, int(syscall.SIGCHLD), 0, 0, 0, 0)
+	return clone(t, int(linux.SIGCHLD), 0, 0, 0, 0)
 }
 
 // Vfork implements Linux syscall vfork(2).
@@ -178,7 +178,7 @@ func Vfork(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 	//
 	//     CLONE_VM | CLONE_VFORK | SIGCHLD
 	// """ - vfork(2)
-	return clone(t, syscall.CLONE_VM|syscall.CLONE_VFORK|int(syscall.SIGCHLD), 0, 0, 0, 0)
+	return clone(t, linux.CLONE_VM|linux.CLONE_VFORK|int(linux.SIGCHLD), 0, 0, 0, 0)
 }
 
 // parseCommonWaitOptions applies the options common to wait4 and waitid to
@@ -193,7 +193,7 @@ func parseCommonWaitOptions(wopts *kernel.WaitOptions, options int) error {
 		wopts.NonCloneTasks = true
 		wopts.CloneTasks = true
 	default:
-		return syscall.EINVAL
+		return syserror.EINVAL
 	}
 	if options&linux.WCONTINUED != 0 {
 		wopts.Events |= kernel.EventGroupContinue
@@ -210,7 +210,7 @@ func parseCommonWaitOptions(wopts *kernel.WaitOptions, options int) error {
 // wait4 waits for the given child process to exit.
 func wait4(t *kernel.Task, pid int, statusAddr usermem.Addr, options int, rusageAddr usermem.Addr) (uintptr, error) {
 	if options&^(linux.WNOHANG|linux.WUNTRACED|linux.WCONTINUED|linux.WNOTHREAD|linux.WALL|linux.WCLONE) != 0 {
-		return 0, syscall.EINVAL
+		return 0, syserror.EINVAL
 	}
 	wopts := kernel.WaitOptions{
 		Events:       kernel.EventExit | kernel.EventTraceeStop,
@@ -291,10 +291,10 @@ func Waitid(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 	rusageAddr := args[4].Pointer()
 
 	if options&^(linux.WNOHANG|linux.WEXITED|linux.WSTOPPED|linux.WCONTINUED|linux.WNOWAIT|linux.WNOTHREAD|linux.WALL|linux.WCLONE) != 0 {
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 	if options&(linux.WEXITED|linux.WSTOPPED|linux.WCONTINUED) == 0 {
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 	wopts := kernel.WaitOptions{
 		Events:       kernel.EventTraceeStop,
@@ -307,7 +307,7 @@ func Waitid(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 	case linux.P_PGID:
 		wopts.SpecificPGID = kernel.ProcessGroupID(id)
 	default:
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 
 	if err := parseCommonWaitOptions(&wopts, options); err != nil {
@@ -347,12 +347,12 @@ func Waitid(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 		return 0, nil, nil
 	}
 	si := arch.SignalInfo{
-		Signo: int32(syscall.SIGCHLD),
+		Signo: int32(linux.SIGCHLD),
 	}
 	si.SetPid(int32(wr.TID))
 	si.SetUid(int32(wr.UID))
 	// TODO(b/73541790): convert kernel.ExitStatus to functions and make
-	// WaitResult.Status a linux.WaitStatus
+	// WaitResult.Status a linux.WaitStatus.
 	s := syscall.WaitStatus(wr.Status)
 	switch {
 	case s.Exited():
@@ -374,7 +374,7 @@ func Waitid(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 		}
 	case s.Continued():
 		si.Code = arch.CLD_CONTINUED
-		si.SetStatus(int32(syscall.SIGCONT))
+		si.SetStatus(int32(linux.SIGCONT))
 	default:
 		t.Warningf("waitid got incomprehensible wait status %d", s)
 	}
@@ -395,16 +395,16 @@ func SetTidAddress(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel
 func Unshare(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
 	flags := args[0].Int()
 	opts := kernel.SharingOptions{
-		NewAddressSpace:     flags&syscall.CLONE_VM == syscall.CLONE_VM,
-		NewSignalHandlers:   flags&syscall.CLONE_SIGHAND == syscall.CLONE_SIGHAND,
-		NewThreadGroup:      flags&syscall.CLONE_THREAD == syscall.CLONE_THREAD,
-		NewPIDNamespace:     flags&syscall.CLONE_NEWPID == syscall.CLONE_NEWPID,
-		NewUserNamespace:    flags&syscall.CLONE_NEWUSER == syscall.CLONE_NEWUSER,
-		NewNetworkNamespace: flags&syscall.CLONE_NEWNET == syscall.CLONE_NEWNET,
-		NewFiles:            flags&syscall.CLONE_FILES == syscall.CLONE_FILES,
-		NewFSContext:        flags&syscall.CLONE_FS == syscall.CLONE_FS,
-		NewUTSNamespace:     flags&syscall.CLONE_NEWUTS == syscall.CLONE_NEWUTS,
-		NewIPCNamespace:     flags&syscall.CLONE_NEWIPC == syscall.CLONE_NEWIPC,
+		NewAddressSpace:     flags&linux.CLONE_VM == linux.CLONE_VM,
+		NewSignalHandlers:   flags&linux.CLONE_SIGHAND == linux.CLONE_SIGHAND,
+		NewThreadGroup:      flags&linux.CLONE_THREAD == linux.CLONE_THREAD,
+		NewPIDNamespace:     flags&linux.CLONE_NEWPID == linux.CLONE_NEWPID,
+		NewUserNamespace:    flags&linux.CLONE_NEWUSER == linux.CLONE_NEWUSER,
+		NewNetworkNamespace: flags&linux.CLONE_NEWNET == linux.CLONE_NEWNET,
+		NewFiles:            flags&linux.CLONE_FILES == linux.CLONE_FILES,
+		NewFSContext:        flags&linux.CLONE_FS == linux.CLONE_FS,
+		NewUTSNamespace:     flags&linux.CLONE_NEWUTS == linux.CLONE_NEWUTS,
+		NewIPCNamespace:     flags&linux.CLONE_NEWIPC == linux.CLONE_NEWIPC,
 	}
 	// "CLONE_NEWPID automatically implies CLONE_THREAD as well." - unshare(2)
 	if opts.NewPIDNamespace {
@@ -623,7 +623,7 @@ func Getpriority(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.S
 	who := kernel.ThreadID(args[1].Int())
 
 	switch which {
-	case syscall.PRIO_PROCESS:
+	case linux.PRIO_PROCESS:
 		// Look for who, return ESRCH if not found.
 		var task *kernel.Task
 		if who == 0 {
@@ -633,7 +633,7 @@ func Getpriority(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.S
 		}
 
 		if task == nil {
-			return 0, nil, syscall.ESRCH
+			return 0, nil, syserror.ESRCH
 		}
 
 		// From kernel/sys.c:getpriority:
@@ -641,13 +641,13 @@ func Getpriority(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.S
 		// will not return the normal nice-value, but a negated
 		// value that has been offset by 20"
 		return uintptr(20 - task.Niceness()), nil, nil
-	case syscall.PRIO_USER:
+	case linux.PRIO_USER:
 		fallthrough
-	case syscall.PRIO_PGRP:
+	case linux.PRIO_PGRP:
 		// PRIO_USER and PRIO_PGRP have no further implementation yet.
 		return 0, nil, nil
 	default:
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 }
 
@@ -669,7 +669,7 @@ func Setpriority(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.S
 	}
 
 	switch which {
-	case syscall.PRIO_PROCESS:
+	case linux.PRIO_PROCESS:
 		// Look for who, return ESRCH if not found.
 		var task *kernel.Task
 		if who == 0 {
@@ -679,17 +679,17 @@ func Setpriority(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.S
 		}
 
 		if task == nil {
-			return 0, nil, syscall.ESRCH
+			return 0, nil, syserror.ESRCH
 		}
 
 		task.SetNiceness(niceval)
-	case syscall.PRIO_USER:
+	case linux.PRIO_USER:
 		fallthrough
-	case syscall.PRIO_PGRP:
+	case linux.PRIO_PGRP:
 		// PRIO_USER and PRIO_PGRP have no further implementation yet.
 		return 0, nil, nil
 	default:
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 
 	return 0, nil, nil
diff --git a/pkg/sentry/syscalls/linux/sys_timer.go b/pkg/sentry/syscalls/linux/sys_timer.go
index ca5ccb7c3..d4134207b 100644
--- a/pkg/sentry/syscalls/linux/sys_timer.go
+++ b/pkg/sentry/syscalls/linux/sys_timer.go
@@ -15,13 +15,13 @@
 package linux
 
 import (
-	"syscall"
 	"time"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/syserror"
 )
 
 const nsecPerSec = int64(time.Second)
@@ -47,7 +47,7 @@ func copyItimerValIn(t *kernel.Task, addr usermem.Addr) (linux.ItimerVal, error)
 
 		return itv, nil
 	default:
-		return linux.ItimerVal{}, syscall.ENOSYS
+		return linux.ItimerVal{}, syserror.ENOSYS
 	}
 }
 
@@ -65,7 +65,7 @@ func copyItimerValOut(t *kernel.Task, addr usermem.Addr, itv *linux.ItimerVal) e
 		_, err := t.CopyOut(addr, itv)
 		return err
 	default:
-		return syscall.ENOSYS
+		return syserror.ENOSYS
 	}
 }
 
diff --git a/pkg/sentry/syscalls/linux/sys_timerfd.go b/pkg/sentry/syscalls/linux/sys_timerfd.go
index ea6d44315..1ce5ce4c3 100644
--- a/pkg/sentry/syscalls/linux/sys_timerfd.go
+++ b/pkg/sentry/syscalls/linux/sys_timerfd.go
@@ -20,7 +20,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/timerfd"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
@@ -49,9 +48,9 @@ func TimerfdCreate(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel
 		NonBlocking: flags&linux.TFD_NONBLOCK != 0,
 	})
 
-	fd, err := t.FDMap().NewFDFrom(0, f, kernel.FDFlags{
+	fd, err := t.NewFDFrom(0, f, kernel.FDFlags{
 		CloseOnExec: flags&linux.TFD_CLOEXEC != 0,
-	}, t.ThreadGroup().Limits())
+	})
 	if err != nil {
 		return 0, nil, err
 	}
@@ -61,7 +60,7 @@ func TimerfdCreate(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel
 
 // TimerfdSettime implements Linux syscall timerfd_settime(2).
 func TimerfdSettime(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	flags := args[1].Int()
 	newValAddr := args[2].Pointer()
 	oldValAddr := args[3].Pointer()
@@ -70,7 +69,7 @@ func TimerfdSettime(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kerne
 		return 0, nil, syserror.EINVAL
 	}
 
-	f := t.FDMap().GetFile(fd)
+	f := t.GetFile(fd)
 	if f == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -101,10 +100,10 @@ func TimerfdSettime(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kerne
 
 // TimerfdGettime implements Linux syscall timerfd_gettime(2).
 func TimerfdGettime(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	curValAddr := args[1].Pointer()
 
-	f := t.FDMap().GetFile(fd)
+	f := t.GetFile(fd)
 	if f == nil {
 		return 0, nil, syserror.EBADF
 	}
diff --git a/pkg/sentry/syscalls/linux/sys_tls.go b/pkg/sentry/syscalls/linux/sys_tls.go
index e3d1c6201..b3eb96a1c 100644
--- a/pkg/sentry/syscalls/linux/sys_tls.go
+++ b/pkg/sentry/syscalls/linux/sys_tls.go
@@ -17,11 +17,10 @@
 package linux
 
 import (
-	"syscall"
-
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/syserror"
 )
 
 // ArchPrctl implements linux syscall arch_prctl(2).
@@ -39,14 +38,14 @@ func ArchPrctl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sys
 	case linux.ARCH_SET_FS:
 		fsbase := args[1].Uint64()
 		if !t.Arch().SetTLS(uintptr(fsbase)) {
-			return 0, nil, syscall.EPERM
+			return 0, nil, syserror.EPERM
 		}
 
 	case linux.ARCH_GET_GS, linux.ARCH_SET_GS:
 		t.Kernel().EmitUnimplementedEvent(t)
 		fallthrough
 	default:
-		return 0, nil, syscall.EINVAL
+		return 0, nil, syserror.EINVAL
 	}
 
 	return 0, nil, nil
diff --git a/pkg/sentry/syscalls/linux/sys_write.go b/pkg/sentry/syscalls/linux/sys_write.go
index 3a5bf9ac4..5278c96a6 100644
--- a/pkg/sentry/syscalls/linux/sys_write.go
+++ b/pkg/sentry/syscalls/linux/sys_write.go
@@ -21,7 +21,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/socket"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
@@ -39,11 +38,11 @@ const (
 
 // Write implements linux syscall write(2).
 func Write(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	size := args[2].SizeT()
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -75,12 +74,12 @@ func Write(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 
 // Pwrite64 implements linux syscall pwrite64(2).
 func Pwrite64(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	size := args[2].SizeT()
 	offset := args[3].Int64()
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -122,11 +121,11 @@ func Pwrite64(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 
 // Writev implements linux syscall writev(2).
 func Writev(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	iovcnt := int(args[2].Int())
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -152,12 +151,12 @@ func Writev(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 
 // Pwritev implements linux syscall pwritev(2).
 func Pwritev(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	iovcnt := int(args[2].Int())
 	offset := args[3].Int64()
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -202,7 +201,7 @@ func Pwritev2(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 	// splits the offset argument into a high/low value for compatibility with
 	// 32-bit architectures. The flags argument is the 5th argument.
 
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	iovcnt := int(args[2].Int())
 	offset := args[3].Int64()
@@ -212,7 +211,7 @@ func Pwritev2(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 		return 0, nil, syserror.EACCES
 	}
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
diff --git a/pkg/sentry/syscalls/linux/timespec.go b/pkg/sentry/syscalls/linux/timespec.go
index 9ba0eba7a..4ff8f9234 100644
--- a/pkg/sentry/syscalls/linux/timespec.go
+++ b/pkg/sentry/syscalls/linux/timespec.go
@@ -15,7 +15,6 @@
 package linux
 
 import (
-	"syscall"
 	"time"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
@@ -70,7 +69,7 @@ func copyTimevalIn(t *kernel.Task, addr usermem.Addr) (linux.Timeval, error) {
 		tv.Usec = int64(usermem.ByteOrder.Uint64(in[8:]))
 		return tv, nil
 	default:
-		return linux.Timeval{}, syscall.ENOSYS
+		return linux.Timeval{}, syserror.ENOSYS
 	}
 }
 
@@ -84,7 +83,7 @@ func copyTimevalOut(t *kernel.Task, addr usermem.Addr, tv *linux.Timeval) error
 		_, err := t.CopyOutBytes(addr, out)
 		return err
 	default:
-		return syscall.ENOSYS
+		return syserror.ENOSYS
 	}
 }
 
@@ -104,7 +103,7 @@ func copyTimespecInToDuration(t *kernel.Task, timespecAddr usermem.Addr) (time.D
 			return 0, err
 		}
 		if !timespec.Valid() {
-			return 0, syscall.EINVAL
+			return 0, syserror.EINVAL
 		}
 		timeout = time.Duration(timespec.ToNsecCapped())
 	}
diff --git a/pkg/sentry/syscalls/syscalls.go b/pkg/sentry/syscalls/syscalls.go
index a5f3d8407..f88055676 100644
--- a/pkg/sentry/syscalls/syscalls.go
+++ b/pkg/sentry/syscalls/syscalls.go
@@ -26,7 +26,6 @@ package syscalls
 
 import (
 	"fmt"
-	"syscall"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
@@ -40,16 +39,7 @@ func Supported(name string, fn kernel.SyscallFn) kernel.Syscall {
 		Name:         name,
 		Fn:           fn,
 		SupportLevel: kernel.SupportFull,
-		Note:         "Full Support",
-	}
-}
-
-// Undocumented returns a syscall that is undocumented.
-func Undocumented(name string, fn kernel.SyscallFn) kernel.Syscall {
-	return kernel.Syscall{
-		Name:         name,
-		Fn:           fn,
-		SupportLevel: kernel.SupportUndocumented,
+		Note:         "Fully Supported.",
 	}
 }
 
@@ -65,7 +55,7 @@ func PartiallySupported(name string, fn kernel.SyscallFn, note string, urls []st
 }
 
 // Error returns a syscall handler that will always give the passed error.
-func Error(name string, err syscall.Errno, note string, urls []string) kernel.Syscall {
+func Error(name string, err error, note string, urls []string) kernel.Syscall {
 	if note != "" {
 		note = note + "; "
 	}
@@ -75,14 +65,14 @@ func Error(name string, err syscall.Errno, note string, urls []string) kernel.Sy
 			return 0, nil, err
 		},
 		SupportLevel: kernel.SupportUnimplemented,
-		Note:         fmt.Sprintf("%sReturns %q", note, err.Error()),
+		Note:         fmt.Sprintf("%sReturns %q.", note, err.Error()),
 		URLs:         urls,
 	}
 }
 
 // ErrorWithEvent gives a syscall function that sends an unimplemented
 // syscall event via the event channel and returns the passed error.
-func ErrorWithEvent(name string, err syscall.Errno, note string, urls []string) kernel.Syscall {
+func ErrorWithEvent(name string, err error, note string, urls []string) kernel.Syscall {
 	if note != "" {
 		note = note + "; "
 	}
@@ -93,7 +83,7 @@ func ErrorWithEvent(name string, err syscall.Errno, note string, urls []string)
 			return 0, nil, err
 		},
 		SupportLevel: kernel.SupportUnimplemented,
-		Note:         fmt.Sprintf("%sReturns %q", note, err.Error()),
+		Note:         fmt.Sprintf("%sReturns %q.", note, err.Error()),
 		URLs:         urls,
 	}
 }
@@ -115,7 +105,7 @@ func CapError(name string, c linux.Capability, note string, urls []string) kerne
 			return 0, nil, syserror.ENOSYS
 		},
 		SupportLevel: kernel.SupportUnimplemented,
-		Note:         fmt.Sprintf("%sReturns %q if the process does not have %s; %q otherwise", note, syserror.EPERM, c.String(), syserror.ENOSYS),
+		Note:         fmt.Sprintf("%sReturns %q if the process does not have %s; %q otherwise.", note, syserror.EPERM, c.String(), syserror.ENOSYS),
 		URLs:         urls,
 	}
 }
diff --git a/pkg/sentry/time/seqatomic_parameters.go b/pkg/sentry/time/seqatomic_parameters_unsafe.go
index b4fb0a7f0..f6560d0bb 100755
--- a/pkg/sentry/time/seqatomic_parameters.go
+++ b/pkg/sentry/time/seqatomic_parameters_unsafe.go
@@ -1,11 +1,12 @@
 package time
 
 import (
+	"unsafe"
+
 	"fmt"
 	"gvisor.dev/gvisor/third_party/gvsync"
 	"reflect"
 	"strings"
-	"unsafe"
 )
 
 // SeqAtomicLoad returns a copy of *ptr, ensuring that the read does not race