Merge branch 'master' into iptables-write-filter-proto

28 files changed, 2452 insertions, 914 deletions

diff --git a/pkg/sentry/fsimpl/kernfs/filesystem.go b/pkg/sentry/fsimpl/kernfs/filesystem.go
index 79759e0fc..a4600ad47 100644
--- a/pkg/sentry/fsimpl/kernfs/filesystem.go
+++ b/pkg/sentry/fsimpl/kernfs/filesystem.go
@@ -22,7 +22,6 @@ import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/fspath"
 	"gvisor.dev/gvisor/pkg/sentry/context"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
@@ -40,7 +39,7 @@ func (fs *Filesystem) stepExistingLocked(ctx context.Context, rp *vfs.ResolvingP
 		return nil, syserror.ENOTDIR
 	}
 	// Directory searchable?
-	if err := d.inode.CheckPermissions(rp.Credentials(), vfs.MayExec); err != nil {
+	if err := d.inode.CheckPermissions(ctx, rp.Credentials(), vfs.MayExec); err != nil {
 		return nil, err
 	}
 afterSymlink:
@@ -182,8 +181,8 @@ func (fs *Filesystem) walkParentDirLocked(ctx context.Context, rp *vfs.Resolving
 //
 // Preconditions: Filesystem.mu must be locked for at least reading. parentInode
 // == parentVFSD.Impl().(*Dentry).Inode. isDir(parentInode) == true.
-func checkCreateLocked(rp *vfs.ResolvingPath, parentVFSD *vfs.Dentry, parentInode Inode) (string, error) {
-	if err := parentInode.CheckPermissions(rp.Credentials(), vfs.MayWrite|vfs.MayExec); err != nil {
+func checkCreateLocked(ctx context.Context, rp *vfs.ResolvingPath, parentVFSD *vfs.Dentry, parentInode Inode) (string, error) {
+	if err := parentInode.CheckPermissions(ctx, rp.Credentials(), vfs.MayWrite|vfs.MayExec); err != nil {
 		return "", err
 	}
 	pc := rp.Component()
@@ -206,7 +205,7 @@ func checkCreateLocked(rp *vfs.ResolvingPath, parentVFSD *vfs.Dentry, parentInod
 // checkDeleteLocked checks that the file represented by vfsd may be deleted.
 //
 // Preconditions: Filesystem.mu must be locked for at least reading.
-func checkDeleteLocked(rp *vfs.ResolvingPath, vfsd *vfs.Dentry) error {
+func checkDeleteLocked(ctx context.Context, rp *vfs.ResolvingPath, vfsd *vfs.Dentry) error {
 	parentVFSD := vfsd.Parent()
 	if parentVFSD == nil {
 		return syserror.EBUSY
@@ -214,36 +213,12 @@ func checkDeleteLocked(rp *vfs.ResolvingPath, vfsd *vfs.Dentry) error {
 	if parentVFSD.IsDisowned() {
 		return syserror.ENOENT
 	}
-	if err := parentVFSD.Impl().(*Dentry).inode.CheckPermissions(rp.Credentials(), vfs.MayWrite|vfs.MayExec); err != nil {
+	if err := parentVFSD.Impl().(*Dentry).inode.CheckPermissions(ctx, rp.Credentials(), vfs.MayWrite|vfs.MayExec); err != nil {
 		return err
 	}
 	return nil
 }
 
-// checkRenameLocked checks that a rename operation may be performed on the
-// target dentry across the given set of parent directories. The target dentry
-// may be nil.
-//
-// Precondition: isDir(dstInode) == true.
-func checkRenameLocked(creds *auth.Credentials, src, dstDir *vfs.Dentry, dstInode Inode) error {
-	srcDir := src.Parent()
-	if srcDir == nil {
-		return syserror.EBUSY
-	}
-	if srcDir.IsDisowned() {
-		return syserror.ENOENT
-	}
-	if dstDir.IsDisowned() {
-		return syserror.ENOENT
-	}
-	// Check for creation permissions on dst dir.
-	if err := dstInode.CheckPermissions(creds, vfs.MayWrite|vfs.MayExec); err != nil {
-		return err
-	}
-
-	return nil
-}
-
 // Release implements vfs.FilesystemImpl.Release.
 func (fs *Filesystem) Release() {
 }
@@ -269,7 +244,7 @@ func (fs *Filesystem) GetDentryAt(ctx context.Context, rp *vfs.ResolvingPath, op
 		if !d.isDir() {
 			return nil, syserror.ENOTDIR
 		}
-		if err := inode.CheckPermissions(rp.Credentials(), vfs.MayExec); err != nil {
+		if err := inode.CheckPermissions(ctx, rp.Credentials(), vfs.MayExec); err != nil {
 			return nil, err
 		}
 	}
@@ -302,7 +277,7 @@ func (fs *Filesystem) LinkAt(ctx context.Context, rp *vfs.ResolvingPath, vd vfs.
 	if err != nil {
 		return err
 	}
-	pc, err := checkCreateLocked(rp, parentVFSD, parentInode)
+	pc, err := checkCreateLocked(ctx, rp, parentVFSD, parentInode)
 	if err != nil {
 		return err
 	}
@@ -339,7 +314,7 @@ func (fs *Filesystem) MkdirAt(ctx context.Context, rp *vfs.ResolvingPath, opts v
 	if err != nil {
 		return err
 	}
-	pc, err := checkCreateLocked(rp, parentVFSD, parentInode)
+	pc, err := checkCreateLocked(ctx, rp, parentVFSD, parentInode)
 	if err != nil {
 		return err
 	}
@@ -367,7 +342,7 @@ func (fs *Filesystem) MknodAt(ctx context.Context, rp *vfs.ResolvingPath, opts v
 	if err != nil {
 		return err
 	}
-	pc, err := checkCreateLocked(rp, parentVFSD, parentInode)
+	pc, err := checkCreateLocked(ctx, rp, parentVFSD, parentInode)
 	if err != nil {
 		return err
 	}
@@ -401,7 +376,7 @@ func (fs *Filesystem) OpenAt(ctx context.Context, rp *vfs.ResolvingPath, opts vf
 		if err != nil {
 			return nil, err
 		}
-		if err := inode.CheckPermissions(rp.Credentials(), ats); err != nil {
+		if err := inode.CheckPermissions(ctx, rp.Credentials(), ats); err != nil {
 			return nil, err
 		}
 		return inode.Open(rp, vfsd, opts.Flags)
@@ -420,7 +395,7 @@ func (fs *Filesystem) OpenAt(ctx context.Context, rp *vfs.ResolvingPath, opts vf
 		if mustCreate {
 			return nil, syserror.EEXIST
 		}
-		if err := inode.CheckPermissions(rp.Credentials(), ats); err != nil {
+		if err := inode.CheckPermissions(ctx, rp.Credentials(), ats); err != nil {
 			return nil, err
 		}
 		return inode.Open(rp, vfsd, opts.Flags)
@@ -432,7 +407,7 @@ afterTrailingSymlink:
 		return nil, err
 	}
 	// Check for search permission in the parent directory.
-	if err := parentInode.CheckPermissions(rp.Credentials(), vfs.MayExec); err != nil {
+	if err := parentInode.CheckPermissions(ctx, rp.Credentials(), vfs.MayExec); err != nil {
 		return nil, err
 	}
 	// Reject attempts to open directories with O_CREAT.
@@ -450,7 +425,7 @@ afterTrailingSymlink:
 	}
 	if childVFSD == nil {
 		// Already checked for searchability above; now check for writability.
-		if err := parentInode.CheckPermissions(rp.Credentials(), vfs.MayWrite); err != nil {
+		if err := parentInode.CheckPermissions(ctx, rp.Credentials(), vfs.MayWrite); err != nil {
 			return nil, err
 		}
 		if err := rp.Mount().CheckBeginWrite(); err != nil {
@@ -485,7 +460,7 @@ afterTrailingSymlink:
 			goto afterTrailingSymlink
 		}
 	}
-	if err := childInode.CheckPermissions(rp.Credentials(), ats); err != nil {
+	if err := childInode.CheckPermissions(ctx, rp.Credentials(), ats); err != nil {
 		return nil, err
 	}
 	return childInode.Open(rp, childVFSD, opts.Flags)
@@ -545,13 +520,13 @@ func (fs *Filesystem) RenameAt(ctx context.Context, rp *vfs.ResolvingPath, oldPa
 	srcVFSD := &src.vfsd
 
 	// Can we remove the src dentry?
-	if err := checkDeleteLocked(rp, srcVFSD); err != nil {
+	if err := checkDeleteLocked(ctx, rp, srcVFSD); err != nil {
 		return err
 	}
 
 	// Can we create the dst dentry?
 	var dstVFSD *vfs.Dentry
-	pc, err := checkCreateLocked(rp, dstDirVFSD, dstDirInode)
+	pc, err := checkCreateLocked(ctx, rp, dstDirVFSD, dstDirInode)
 	switch err {
 	case nil:
 		// Ok, continue with rename as replacement.
@@ -607,7 +582,7 @@ func (fs *Filesystem) RmdirAt(ctx context.Context, rp *vfs.ResolvingPath) error
 		return err
 	}
 	defer rp.Mount().EndWrite()
-	if err := checkDeleteLocked(rp, vfsd); err != nil {
+	if err := checkDeleteLocked(ctx, rp, vfsd); err != nil {
 		return err
 	}
 	if !vfsd.Impl().(*Dentry).isDir() {
@@ -683,7 +658,7 @@ func (fs *Filesystem) SymlinkAt(ctx context.Context, rp *vfs.ResolvingPath, targ
 	if err != nil {
 		return err
 	}
-	pc, err := checkCreateLocked(rp, parentVFSD, parentInode)
+	pc, err := checkCreateLocked(ctx, rp, parentVFSD, parentInode)
 	if err != nil {
 		return err
 	}
@@ -712,7 +687,7 @@ func (fs *Filesystem) UnlinkAt(ctx context.Context, rp *vfs.ResolvingPath) error
 		return err
 	}
 	defer rp.Mount().EndWrite()
-	if err := checkDeleteLocked(rp, vfsd); err != nil {
+	if err := checkDeleteLocked(ctx, rp, vfsd); err != nil {
 		return err
 	}
 	if vfsd.Impl().(*Dentry).isDir() {
diff --git a/pkg/sentry/fsimpl/kernfs/inode_impl_util.go b/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
index 1d469a0db..1700fffd9 100644
--- a/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
+++ b/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
@@ -262,7 +262,7 @@ func (a *InodeAttrs) SetStat(_ *vfs.Filesystem, opts vfs.SetStatOptions) error {
 }
 
 // CheckPermissions implements Inode.CheckPermissions.
-func (a *InodeAttrs) CheckPermissions(creds *auth.Credentials, ats vfs.AccessTypes) error {
+func (a *InodeAttrs) CheckPermissions(_ context.Context, creds *auth.Credentials, ats vfs.AccessTypes) error {
 	mode := a.Mode()
 	return vfs.GenericCheckPermissions(
 		creds,
@@ -510,3 +510,47 @@ type InodeSymlink struct {
 func (InodeSymlink) Open(rp *vfs.ResolvingPath, vfsd *vfs.Dentry, flags uint32) (*vfs.FileDescription, error) {
 	return nil, syserror.ELOOP
 }
+
+// StaticDirectory is a standard implementation of a directory with static
+// contents.
+//
+// +stateify savable
+type StaticDirectory struct {
+	InodeNotSymlink
+	InodeDirectoryNoNewChildren
+	InodeAttrs
+	InodeNoDynamicLookup
+	OrderedChildren
+}
+
+var _ Inode = (*StaticDirectory)(nil)
+
+// NewStaticDir creates a new static directory and returns its dentry.
+func NewStaticDir(creds *auth.Credentials, ino uint64, perm linux.FileMode, children map[string]*Dentry) *Dentry {
+	inode := &StaticDirectory{}
+	inode.Init(creds, ino, perm)
+
+	dentry := &Dentry{}
+	dentry.Init(inode)
+
+	inode.OrderedChildren.Init(OrderedChildrenOptions{})
+	links := inode.OrderedChildren.Populate(dentry, children)
+	inode.IncLinks(links)
+
+	return dentry
+}
+
+// Init initializes StaticDirectory.
+func (s *StaticDirectory) Init(creds *auth.Credentials, ino uint64, perm linux.FileMode) {
+	if perm&^linux.PermissionsMask != 0 {
+		panic(fmt.Sprintf("Only permission mask must be set: %x", perm&linux.PermissionsMask))
+	}
+	s.InodeAttrs.Init(creds, ino, linux.ModeDirectory|perm)
+}
+
+// Open implements kernfs.Inode.
+func (s *StaticDirectory) Open(rp *vfs.ResolvingPath, vfsd *vfs.Dentry, flags uint32) (*vfs.FileDescription, error) {
+	fd := &GenericDirectoryFD{}
+	fd.Init(rp.Mount(), vfsd, &s.OrderedChildren, flags)
+	return fd.VFSFileDescription(), nil
+}
diff --git a/pkg/sentry/fsimpl/kernfs/kernfs.go b/pkg/sentry/fsimpl/kernfs/kernfs.go
index bb12f39a2..85bcdcc57 100644
--- a/pkg/sentry/fsimpl/kernfs/kernfs.go
+++ b/pkg/sentry/fsimpl/kernfs/kernfs.go
@@ -320,7 +320,7 @@ type inodeMetadata interface {
 	// CheckPermissions checks that creds may access this inode for the
 	// requested access type, per the the rules of
 	// fs/namei.c:generic_permission().
-	CheckPermissions(creds *auth.Credentials, atx vfs.AccessTypes) error
+	CheckPermissions(ctx context.Context, creds *auth.Credentials, atx vfs.AccessTypes) error
 
 	// Mode returns the (struct stat)::st_mode value for this inode. This is
 	// separated from Stat for performance.
diff --git a/pkg/sentry/fsimpl/kernfs/symlink.go b/pkg/sentry/fsimpl/kernfs/symlink.go
index 068063f4e..f19f12854 100644
--- a/pkg/sentry/fsimpl/kernfs/symlink.go
+++ b/pkg/sentry/fsimpl/kernfs/symlink.go
@@ -20,7 +20,9 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 )
 
-type staticSymlink struct {
+// StaticSymlink provides an Inode implementation for symlinks that point to
+// a immutable target.
+type StaticSymlink struct {
 	InodeAttrs
 	InodeNoopRefCount
 	InodeSymlink
@@ -28,18 +30,25 @@ type staticSymlink struct {
 	target string
 }
 
-var _ Inode = (*staticSymlink)(nil)
+var _ Inode = (*StaticSymlink)(nil)
 
 // NewStaticSymlink creates a new symlink file pointing to 'target'.
-func NewStaticSymlink(creds *auth.Credentials, ino uint64, perm linux.FileMode, target string) *Dentry {
-	inode := &staticSymlink{target: target}
-	inode.Init(creds, ino, linux.ModeSymlink|perm)
+func NewStaticSymlink(creds *auth.Credentials, ino uint64, target string) *Dentry {
+	inode := &StaticSymlink{}
+	inode.Init(creds, ino, target)
 
 	d := &Dentry{}
 	d.Init(inode)
 	return d
 }
 
-func (s *staticSymlink) Readlink(_ context.Context) (string, error) {
+// Init initializes the instance.
+func (s *StaticSymlink) Init(creds *auth.Credentials, ino uint64, target string) {
+	s.target = target
+	s.InodeAttrs.Init(creds, ino, linux.ModeSymlink|0777)
+}
+
+// Readlink implements Inode.
+func (s *StaticSymlink) Readlink(_ context.Context) (string, error) {
 	return s.target, nil
 }
diff --git a/pkg/sentry/fsimpl/proc/BUILD b/pkg/sentry/fsimpl/proc/BUILD
index 1f44b3217..f69aa19c4 100644
--- a/pkg/sentry/fsimpl/proc/BUILD
+++ b/pkg/sentry/fsimpl/proc/BUILD
@@ -7,22 +7,17 @@ go_library(
     name = "proc",
     srcs = [
         "filesystem.go",
-        "loadavg.go",
-        "meminfo.go",
-        "mounts.go",
-        "net.go",
-        "stat.go",
-        "sys.go",
+        "subtasks.go",
         "task.go",
         "task_files.go",
         "tasks.go",
         "tasks_files.go",
-        "version.go",
+        "tasks_net.go",
+        "tasks_sys.go",
     ],
     importpath = "gvisor.dev/gvisor/pkg/sentry/fsimpl/proc",
     deps = [
         "//pkg/abi/linux",
-        "//pkg/binary",
         "//pkg/log",
         "//pkg/sentry/context",
         "//pkg/sentry/fs",
@@ -30,8 +25,10 @@ go_library(
         "//pkg/sentry/inet",
         "//pkg/sentry/kernel",
         "//pkg/sentry/kernel/auth",
+        "//pkg/sentry/kernel/time",
         "//pkg/sentry/limits",
         "//pkg/sentry/mm",
+        "//pkg/sentry/safemem",
         "//pkg/sentry/socket",
         "//pkg/sentry/socket/unix",
         "//pkg/sentry/socket/unix/transport",
@@ -39,6 +36,7 @@ go_library(
         "//pkg/sentry/usermem",
         "//pkg/sentry/vfs",
         "//pkg/syserror",
+        "//pkg/tcpip/header",
     ],
 )
 
@@ -47,7 +45,7 @@ go_test(
     size = "small",
     srcs = [
         "boot_test.go",
-        "net_test.go",
+        "tasks_sys_test.go",
         "tasks_test.go",
     ],
     embed = [":proc"],
diff --git a/pkg/sentry/fsimpl/proc/filesystem.go b/pkg/sentry/fsimpl/proc/filesystem.go
index d09182c77..f49819187 100644
--- a/pkg/sentry/fsimpl/proc/filesystem.go
+++ b/pkg/sentry/fsimpl/proc/filesystem.go
@@ -47,7 +47,12 @@ func (ft *procFSType) GetFilesystem(ctx context.Context, vfsObj *vfs.VirtualFile
 	procfs := &kernfs.Filesystem{}
 	procfs.VFSFilesystem().Init(vfsObj, procfs)
 
-	_, dentry := newTasksInode(procfs, k, pidns)
+	var data *InternalData
+	if opts.InternalData != nil {
+		data = opts.InternalData.(*InternalData)
+	}
+
+	_, dentry := newTasksInode(procfs, k, pidns, data.Cgroups)
 	return procfs.VFSFilesystem(), dentry.VFSDentry(), nil
 }
 
@@ -67,3 +72,20 @@ func newDentry(creds *auth.Credentials, ino uint64, perm linux.FileMode, inode d
 	d.Init(inode)
 	return d
 }
+
+type staticFile struct {
+	kernfs.DynamicBytesFile
+	vfs.StaticData
+}
+
+var _ dynamicInode = (*staticFile)(nil)
+
+func newStaticFile(data string) *staticFile {
+	return &staticFile{StaticData: vfs.StaticData{Data: data}}
+}
+
+// InternalData contains internal data passed in to the procfs mount via
+// vfs.GetFilesystemOptions.InternalData.
+type InternalData struct {
+	Cgroups map[string]string
+}
diff --git a/pkg/sentry/fsimpl/proc/loadavg.go b/pkg/sentry/fsimpl/proc/loadavg.go
deleted file mode 100644
index 5351d86e8..000000000
--- a/pkg/sentry/fsimpl/proc/loadavg.go
+++ /dev/null
@@ -1,42 +0,0 @@
-// 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 proc
-
-import (
-	"bytes"
-	"fmt"
-
-	"gvisor.dev/gvisor/pkg/sentry/context"
-	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
-)
-
-// loadavgData backs /proc/loadavg.
-//
-// +stateify savable
-type loadavgData struct {
-	kernfs.DynamicBytesFile
-}
-
-var _ dynamicInode = (*loadavgData)(nil)
-
-// Generate implements vfs.DynamicBytesSource.Generate.
-func (d *loadavgData) Generate(ctx context.Context, buf *bytes.Buffer) error {
-	// TODO(b/62345059): Include real data in fields.
-	// Column 1-3: CPU and IO utilization of the last 1, 5, and 10 minute periods.
-	// Column 4-5: currently running processes and the total number of processes.
-	// Column 6: the last process ID used.
-	fmt.Fprintf(buf, "%.2f %.2f %.2f %d/%d %d\n", 0.00, 0.00, 0.00, 0, 0, 0)
-	return nil
-}
diff --git a/pkg/sentry/fsimpl/proc/meminfo.go b/pkg/sentry/fsimpl/proc/meminfo.go
deleted file mode 100644
index cbdd4f3fc..000000000
--- a/pkg/sentry/fsimpl/proc/meminfo.go
+++ /dev/null
@@ -1,79 +0,0 @@
-// 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 proc
-
-import (
-	"bytes"
-	"fmt"
-
-	"gvisor.dev/gvisor/pkg/sentry/context"
-	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
-	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/usage"
-	"gvisor.dev/gvisor/pkg/sentry/usermem"
-)
-
-// meminfoData implements vfs.DynamicBytesSource for /proc/meminfo.
-//
-// +stateify savable
-type meminfoData struct {
-	kernfs.DynamicBytesFile
-
-	// k is the owning Kernel.
-	k *kernel.Kernel
-}
-
-var _ dynamicInode = (*meminfoData)(nil)
-
-// Generate implements vfs.DynamicBytesSource.Generate.
-func (d *meminfoData) Generate(ctx context.Context, buf *bytes.Buffer) error {
-	mf := d.k.MemoryFile()
-	mf.UpdateUsage()
-	snapshot, totalUsage := usage.MemoryAccounting.Copy()
-	totalSize := usage.TotalMemory(mf.TotalSize(), totalUsage)
-	anon := snapshot.Anonymous + snapshot.Tmpfs
-	file := snapshot.PageCache + snapshot.Mapped
-	// We don't actually have active/inactive LRUs, so just make up numbers.
-	activeFile := (file / 2) &^ (usermem.PageSize - 1)
-	inactiveFile := file - activeFile
-
-	fmt.Fprintf(buf, "MemTotal:       %8d kB\n", totalSize/1024)
-	memFree := (totalSize - totalUsage) / 1024
-	// We use MemFree as MemAvailable because we don't swap.
-	// TODO(rahat): When reclaim is implemented the value of MemAvailable
-	// should change.
-	fmt.Fprintf(buf, "MemFree:        %8d kB\n", memFree)
-	fmt.Fprintf(buf, "MemAvailable:   %8d kB\n", memFree)
-	fmt.Fprintf(buf, "Buffers:               0 kB\n") // memory usage by block devices
-	fmt.Fprintf(buf, "Cached:         %8d kB\n", (file+snapshot.Tmpfs)/1024)
-	// Emulate a system with no swap, which disables inactivation of anon pages.
-	fmt.Fprintf(buf, "SwapCache:             0 kB\n")
-	fmt.Fprintf(buf, "Active:         %8d kB\n", (anon+activeFile)/1024)
-	fmt.Fprintf(buf, "Inactive:       %8d kB\n", inactiveFile/1024)
-	fmt.Fprintf(buf, "Active(anon):   %8d kB\n", anon/1024)
-	fmt.Fprintf(buf, "Inactive(anon):        0 kB\n")
-	fmt.Fprintf(buf, "Active(file):   %8d kB\n", activeFile/1024)
-	fmt.Fprintf(buf, "Inactive(file): %8d kB\n", inactiveFile/1024)
-	fmt.Fprintf(buf, "Unevictable:           0 kB\n") // TODO(b/31823263)
-	fmt.Fprintf(buf, "Mlocked:               0 kB\n") // TODO(b/31823263)
-	fmt.Fprintf(buf, "SwapTotal:             0 kB\n")
-	fmt.Fprintf(buf, "SwapFree:              0 kB\n")
-	fmt.Fprintf(buf, "Dirty:                 0 kB\n")
-	fmt.Fprintf(buf, "Writeback:             0 kB\n")
-	fmt.Fprintf(buf, "AnonPages:      %8d kB\n", anon/1024)
-	fmt.Fprintf(buf, "Mapped:         %8d kB\n", file/1024) // doesn't count mapped tmpfs, which we don't know
-	fmt.Fprintf(buf, "Shmem:          %8d kB\n", snapshot.Tmpfs/1024)
-	return nil
-}
diff --git a/pkg/sentry/fsimpl/proc/mounts.go b/pkg/sentry/fsimpl/proc/mounts.go
deleted file mode 100644
index 8683cf677..000000000
--- a/pkg/sentry/fsimpl/proc/mounts.go
+++ /dev/null
@@ -1,33 +0,0 @@
-// 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 proc
-
-import "gvisor.dev/gvisor/pkg/sentry/kernel"
-
-// TODO(gvisor.dev/issue/1195): Implement mountInfoFile and mountsFile.
-
-// mountInfoFile implements vfs.DynamicBytesSource for /proc/[pid]/mountinfo.
-//
-// +stateify savable
-type mountInfoFile struct {
-	t *kernel.Task
-}
-
-// mountsFile implements vfs.DynamicBytesSource for /proc/[pid]/mounts.
-//
-// +stateify savable
-type mountsFile struct {
-	t *kernel.Task
-}
diff --git a/pkg/sentry/fsimpl/proc/net.go b/pkg/sentry/fsimpl/proc/net.go
deleted file mode 100644
index fd46eebf8..000000000
--- a/pkg/sentry/fsimpl/proc/net.go
+++ /dev/null
@@ -1,338 +0,0 @@
-// 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 proc
-
-import (
-	"bytes"
-	"fmt"
-
-	"gvisor.dev/gvisor/pkg/abi/linux"
-	"gvisor.dev/gvisor/pkg/binary"
-	"gvisor.dev/gvisor/pkg/log"
-	"gvisor.dev/gvisor/pkg/sentry/context"
-	"gvisor.dev/gvisor/pkg/sentry/fs"
-	"gvisor.dev/gvisor/pkg/sentry/inet"
-	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/socket"
-	"gvisor.dev/gvisor/pkg/sentry/socket/unix"
-	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
-	"gvisor.dev/gvisor/pkg/sentry/vfs"
-)
-
-// ifinet6 implements vfs.DynamicBytesSource for /proc/net/if_inet6.
-//
-// +stateify savable
-type ifinet6 struct {
-	s inet.Stack
-}
-
-var _ vfs.DynamicBytesSource = (*ifinet6)(nil)
-
-func (n *ifinet6) contents() []string {
-	var lines []string
-	nics := n.s.Interfaces()
-	for id, naddrs := range n.s.InterfaceAddrs() {
-		nic, ok := nics[id]
-		if !ok {
-			// NIC was added after NICNames was called. We'll just
-			// ignore it.
-			continue
-		}
-
-		for _, a := range naddrs {
-			// IPv6 only.
-			if a.Family != linux.AF_INET6 {
-				continue
-			}
-
-			// Fields:
-			// IPv6 address displayed in 32 hexadecimal chars without colons
-			// Netlink device number (interface index) in hexadecimal (use nic id)
-			// Prefix length in hexadecimal
-			// Scope value (use 0)
-			// Interface flags
-			// Device name
-			lines = append(lines, fmt.Sprintf("%032x %02x %02x %02x %02x %8s\n", a.Addr, id, a.PrefixLen, 0, a.Flags, nic.Name))
-		}
-	}
-	return lines
-}
-
-// Generate implements vfs.DynamicBytesSource.Generate.
-func (n *ifinet6) Generate(ctx context.Context, buf *bytes.Buffer) error {
-	for _, l := range n.contents() {
-		buf.WriteString(l)
-	}
-	return nil
-}
-
-// netDev implements vfs.DynamicBytesSource for /proc/net/dev.
-//
-// +stateify savable
-type netDev struct {
-	s inet.Stack
-}
-
-var _ vfs.DynamicBytesSource = (*netDev)(nil)
-
-// Generate implements vfs.DynamicBytesSource.Generate.
-func (n *netDev) Generate(ctx context.Context, buf *bytes.Buffer) error {
-	interfaces := n.s.Interfaces()
-	buf.WriteString("Inter-|   Receive                                                |  Transmit\n")
-	buf.WriteString(" face |bytes    packets errs drop fifo frame compressed multicast|bytes    packets errs drop fifo colls carrier compressed\n")
-
-	for _, i := range interfaces {
-		// Implements the same format as
-		// net/core/net-procfs.c:dev_seq_printf_stats.
-		var stats inet.StatDev
-		if err := n.s.Statistics(&stats, i.Name); err != nil {
-			log.Warningf("Failed to retrieve interface statistics for %v: %v", i.Name, err)
-			continue
-		}
-		fmt.Fprintf(
-			buf,
-			"%6s: %7d %7d %4d %4d %4d %5d %10d %9d %8d %7d %4d %4d %4d %5d %7d %10d\n",
-			i.Name,
-			// Received
-			stats[0], // bytes
-			stats[1], // packets
-			stats[2], // errors
-			stats[3], // dropped
-			stats[4], // fifo
-			stats[5], // frame
-			stats[6], // compressed
-			stats[7], // multicast
-			// Transmitted
-			stats[8],  // bytes
-			stats[9],  // packets
-			stats[10], // errors
-			stats[11], // dropped
-			stats[12], // fifo
-			stats[13], // frame
-			stats[14], // compressed
-			stats[15], // multicast
-		)
-	}
-
-	return nil
-}
-
-// netUnix implements vfs.DynamicBytesSource for /proc/net/unix.
-//
-// +stateify savable
-type netUnix struct {
-	k *kernel.Kernel
-}
-
-var _ vfs.DynamicBytesSource = (*netUnix)(nil)
-
-// Generate implements vfs.DynamicBytesSource.Generate.
-func (n *netUnix) Generate(ctx context.Context, buf *bytes.Buffer) error {
-	buf.WriteString("Num       RefCount Protocol Flags    Type St Inode Path\n")
-	for _, se := range n.k.ListSockets() {
-		s := se.Sock.Get()
-		if s == nil {
-			log.Debugf("Couldn't resolve weakref %v in socket table, racing with destruction?", se.Sock)
-			continue
-		}
-		sfile := s.(*fs.File)
-		if family, _, _ := sfile.FileOperations.(socket.Socket).Type(); family != linux.AF_UNIX {
-			s.DecRef()
-			// Not a unix socket.
-			continue
-		}
-		sops := sfile.FileOperations.(*unix.SocketOperations)
-
-		addr, err := sops.Endpoint().GetLocalAddress()
-		if err != nil {
-			log.Warningf("Failed to retrieve socket name from %+v: %v", sfile, err)
-			addr.Addr = "<unknown>"
-		}
-
-		sockFlags := 0
-		if ce, ok := sops.Endpoint().(transport.ConnectingEndpoint); ok {
-			if ce.Listening() {
-				// For unix domain sockets, linux reports a single flag
-				// value if the socket is listening, of __SO_ACCEPTCON.
-				sockFlags = linux.SO_ACCEPTCON
-			}
-		}
-
-		// In the socket entry below, the value for the 'Num' field requires
-		// some consideration. Linux prints the address to the struct
-		// unix_sock representing a socket in the kernel, but may redact the
-		// value for unprivileged users depending on the kptr_restrict
-		// sysctl.
-		//
-		// One use for this field is to allow a privileged user to
-		// introspect into the kernel memory to determine information about
-		// a socket not available through procfs, such as the socket's peer.
-		//
-		// In gvisor, returning a pointer to our internal structures would
-		// be pointless, as it wouldn't match the memory layout for struct
-		// unix_sock, making introspection difficult. We could populate a
-		// struct unix_sock with the appropriate data, but even that
-		// requires consideration for which kernel version to emulate, as
-		// the definition of this struct changes over time.
-		//
-		// For now, we always redact this pointer.
-		fmt.Fprintf(buf, "%#016p: %08X %08X %08X %04X %02X %5d",
-			(*unix.SocketOperations)(nil), // Num, pointer to kernel socket struct.
-			sfile.ReadRefs()-1,            // RefCount, don't count our own ref.
-			0,                             // Protocol, always 0 for UDS.
-			sockFlags,                     // Flags.
-			sops.Endpoint().Type(),        // Type.
-			sops.State(),                  // State.
-			sfile.InodeID(),               // Inode.
-		)
-
-		// Path
-		if len(addr.Addr) != 0 {
-			if addr.Addr[0] == 0 {
-				// Abstract path.
-				fmt.Fprintf(buf, " @%s", string(addr.Addr[1:]))
-			} else {
-				fmt.Fprintf(buf, " %s", string(addr.Addr))
-			}
-		}
-		fmt.Fprintf(buf, "\n")
-
-		s.DecRef()
-	}
-	return nil
-}
-
-// netTCP implements vfs.DynamicBytesSource for /proc/net/tcp.
-//
-// +stateify savable
-type netTCP struct {
-	k *kernel.Kernel
-}
-
-var _ vfs.DynamicBytesSource = (*netTCP)(nil)
-
-func (n *netTCP) Generate(ctx context.Context, buf *bytes.Buffer) error {
-	t := kernel.TaskFromContext(ctx)
-	buf.WriteString("  sl  local_address rem_address   st tx_queue rx_queue tr tm->when retrnsmt   uid  timeout inode                                                     \n")
-	for _, se := range n.k.ListSockets() {
-		s := se.Sock.Get()
-		if s == nil {
-			log.Debugf("Couldn't resolve weakref %+v in socket table, racing with destruction?", se.Sock)
-			continue
-		}
-		sfile := s.(*fs.File)
-		sops, ok := sfile.FileOperations.(socket.Socket)
-		if !ok {
-			panic(fmt.Sprintf("Found non-socket file in socket table: %+v", sfile))
-		}
-		if family, stype, _ := sops.Type(); !(family == linux.AF_INET && stype == linux.SOCK_STREAM) {
-			s.DecRef()
-			// Not tcp4 sockets.
-			continue
-		}
-
-		// Linux's documentation for the fields below can be found at
-		// https://www.kernel.org/doc/Documentation/networking/proc_net_tcp.txt.
-		// For Linux's implementation, see net/ipv4/tcp_ipv4.c:get_tcp4_sock().
-		// Note that the header doesn't contain labels for all the fields.
-
-		// Field: sl; entry number.
-		fmt.Fprintf(buf, "%4d: ", se.ID)
-
-		portBuf := make([]byte, 2)
-
-		// Field: local_adddress.
-		var localAddr linux.SockAddrInet
-		if local, _, err := sops.GetSockName(t); err == nil {
-			localAddr = *local.(*linux.SockAddrInet)
-		}
-		binary.LittleEndian.PutUint16(portBuf, localAddr.Port)
-		fmt.Fprintf(buf, "%08X:%04X ",
-			binary.LittleEndian.Uint32(localAddr.Addr[:]),
-			portBuf)
-
-		// Field: rem_address.
-		var remoteAddr linux.SockAddrInet
-		if remote, _, err := sops.GetPeerName(t); err == nil {
-			remoteAddr = *remote.(*linux.SockAddrInet)
-		}
-		binary.LittleEndian.PutUint16(portBuf, remoteAddr.Port)
-		fmt.Fprintf(buf, "%08X:%04X ",
-			binary.LittleEndian.Uint32(remoteAddr.Addr[:]),
-			portBuf)
-
-		// Field: state; socket state.
-		fmt.Fprintf(buf, "%02X ", sops.State())
-
-		// Field: tx_queue, rx_queue; number of packets in the transmit and
-		// receive queue. Unimplemented.
-		fmt.Fprintf(buf, "%08X:%08X ", 0, 0)
-
-		// Field: tr, tm->when; timer active state and number of jiffies
-		// until timer expires. Unimplemented.
-		fmt.Fprintf(buf, "%02X:%08X ", 0, 0)
-
-		// Field: retrnsmt; number of unrecovered RTO timeouts.
-		// Unimplemented.
-		fmt.Fprintf(buf, "%08X ", 0)
-
-		// Field: uid.
-		uattr, err := sfile.Dirent.Inode.UnstableAttr(ctx)
-		if err != nil {
-			log.Warningf("Failed to retrieve unstable attr for socket file: %v", err)
-			fmt.Fprintf(buf, "%5d ", 0)
-		} else {
-			fmt.Fprintf(buf, "%5d ", uint32(uattr.Owner.UID.In(t.UserNamespace()).OrOverflow()))
-		}
-
-		// Field: timeout; number of unanswered 0-window probes.
-		// Unimplemented.
-		fmt.Fprintf(buf, "%8d ", 0)
-
-		// Field: inode.
-		fmt.Fprintf(buf, "%8d ", sfile.InodeID())
-
-		// Field: refcount. Don't count the ref we obtain while deferencing
-		// the weakref to this socket.
-		fmt.Fprintf(buf, "%d ", sfile.ReadRefs()-1)
-
-		// Field: Socket struct address. Redacted due to the same reason as
-		// the 'Num' field in /proc/net/unix, see netUnix.ReadSeqFileData.
-		fmt.Fprintf(buf, "%#016p ", (*socket.Socket)(nil))
-
-		// Field: retransmit timeout. Unimplemented.
-		fmt.Fprintf(buf, "%d ", 0)
-
-		// Field: predicted tick of soft clock (delayed ACK control data).
-		// Unimplemented.
-		fmt.Fprintf(buf, "%d ", 0)
-
-		// Field: (ack.quick<<1)|ack.pingpong, Unimplemented.
-		fmt.Fprintf(buf, "%d ", 0)
-
-		// Field: sending congestion window, Unimplemented.
-		fmt.Fprintf(buf, "%d ", 0)
-
-		// Field: Slow start size threshold, -1 if threshold >= 0xFFFF.
-		// Unimplemented, report as large threshold.
-		fmt.Fprintf(buf, "%d", -1)
-
-		fmt.Fprintf(buf, "\n")
-
-		s.DecRef()
-	}
-
-	return nil
-}
diff --git a/pkg/sentry/fsimpl/proc/stat.go b/pkg/sentry/fsimpl/proc/stat.go
deleted file mode 100644
index 50894a534..000000000
--- a/pkg/sentry/fsimpl/proc/stat.go
+++ /dev/null
@@ -1,129 +0,0 @@
-// 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 proc
-
-import (
-	"bytes"
-	"fmt"
-
-	"gvisor.dev/gvisor/pkg/abi/linux"
-	"gvisor.dev/gvisor/pkg/sentry/context"
-	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
-	"gvisor.dev/gvisor/pkg/sentry/kernel"
-)
-
-// cpuStats contains the breakdown of CPU time for /proc/stat.
-type cpuStats struct {
-	// user is time spent in userspace tasks with non-positive niceness.
-	user uint64
-
-	// nice is time spent in userspace tasks with positive niceness.
-	nice uint64
-
-	// system is time spent in non-interrupt kernel context.
-	system uint64
-
-	// idle is time spent idle.
-	idle uint64
-
-	// ioWait is time spent waiting for IO.
-	ioWait uint64
-
-	// irq is time spent in interrupt context.
-	irq uint64
-
-	// softirq is time spent in software interrupt context.
-	softirq uint64
-
-	// steal is involuntary wait time.
-	steal uint64
-
-	// guest is time spent in guests with non-positive niceness.
-	guest uint64
-
-	// guestNice is time spent in guests with positive niceness.
-	guestNice uint64
-}
-
-// String implements fmt.Stringer.
-func (c cpuStats) String() string {
-	return fmt.Sprintf("%d %d %d %d %d %d %d %d %d %d", c.user, c.nice, c.system, c.idle, c.ioWait, c.irq, c.softirq, c.steal, c.guest, c.guestNice)
-}
-
-// statData implements vfs.DynamicBytesSource for /proc/stat.
-//
-// +stateify savable
-type statData struct {
-	kernfs.DynamicBytesFile
-
-	// k is the owning Kernel.
-	k *kernel.Kernel
-}
-
-var _ dynamicInode = (*statData)(nil)
-
-// Generate implements vfs.DynamicBytesSource.Generate.
-func (s *statData) Generate(ctx context.Context, buf *bytes.Buffer) error {
-	// TODO(b/37226836): We currently export only zero CPU stats. We could
-	// at least provide some aggregate stats.
-	var cpu cpuStats
-	fmt.Fprintf(buf, "cpu  %s\n", cpu)
-
-	for c, max := uint(0), s.k.ApplicationCores(); c < max; c++ {
-		fmt.Fprintf(buf, "cpu%d %s\n", c, cpu)
-	}
-
-	// The total number of interrupts is dependent on the CPUs and PCI
-	// devices on the system. See arch_probe_nr_irqs.
-	//
-	// Since we don't report real interrupt stats, just choose an arbitrary
-	// value from a representative VM.
-	const numInterrupts = 256
-
-	// The Kernel doesn't handle real interrupts, so report all zeroes.
-	// TODO(b/37226836): We could count page faults as #PF.
-	fmt.Fprintf(buf, "intr 0") // total
-	for i := 0; i < numInterrupts; i++ {
-		fmt.Fprintf(buf, " 0")
-	}
-	fmt.Fprintf(buf, "\n")
-
-	// Total number of context switches.
-	// TODO(b/37226836): Count this.
-	fmt.Fprintf(buf, "ctxt 0\n")
-
-	// CLOCK_REALTIME timestamp from boot, in seconds.
-	fmt.Fprintf(buf, "btime %d\n", s.k.Timekeeper().BootTime().Seconds())
-
-	// Total number of clones.
-	// TODO(b/37226836): Count this.
-	fmt.Fprintf(buf, "processes 0\n")
-
-	// Number of runnable tasks.
-	// TODO(b/37226836): Count this.
-	fmt.Fprintf(buf, "procs_running 0\n")
-
-	// Number of tasks waiting on IO.
-	// TODO(b/37226836): Count this.
-	fmt.Fprintf(buf, "procs_blocked 0\n")
-
-	// Number of each softirq handled.
-	fmt.Fprintf(buf, "softirq 0") // total
-	for i := 0; i < linux.NumSoftIRQ; i++ {
-		fmt.Fprintf(buf, " 0")
-	}
-	fmt.Fprintf(buf, "\n")
-	return nil
-}
diff --git a/pkg/sentry/fsimpl/proc/subtasks.go b/pkg/sentry/fsimpl/proc/subtasks.go
new file mode 100644
index 000000000..91eded415
--- /dev/null
+++ b/pkg/sentry/fsimpl/proc/subtasks.go
@@ -0,0 +1,128 @@
+// 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 proc
+
+import (
+	"sort"
+	"strconv"
+
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sentry/context"
+	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/syserror"
+)
+
+// subtasksInode represents the inode for /proc/[pid]/task/ directory.
+//
+// +stateify savable
+type subtasksInode struct {
+	kernfs.InodeNotSymlink
+	kernfs.InodeDirectoryNoNewChildren
+	kernfs.InodeAttrs
+	kernfs.OrderedChildren
+
+	task              *kernel.Task
+	pidns             *kernel.PIDNamespace
+	inoGen            InoGenerator
+	cgroupControllers map[string]string
+}
+
+var _ kernfs.Inode = (*subtasksInode)(nil)
+
+func newSubtasks(task *kernel.Task, pidns *kernel.PIDNamespace, inoGen InoGenerator, cgroupControllers map[string]string) *kernfs.Dentry {
+	subInode := &subtasksInode{
+		task:              task,
+		pidns:             pidns,
+		inoGen:            inoGen,
+		cgroupControllers: cgroupControllers,
+	}
+	// Note: credentials are overridden by taskOwnedInode.
+	subInode.InodeAttrs.Init(task.Credentials(), inoGen.NextIno(), linux.ModeDirectory|0555)
+	subInode.OrderedChildren.Init(kernfs.OrderedChildrenOptions{})
+
+	inode := &taskOwnedInode{Inode: subInode, owner: task}
+	dentry := &kernfs.Dentry{}
+	dentry.Init(inode)
+
+	return dentry
+}
+
+// Valid implements kernfs.inodeDynamicLookup.
+func (i *subtasksInode) Valid(ctx context.Context) bool {
+	return true
+}
+
+// Lookup implements kernfs.inodeDynamicLookup.
+func (i *subtasksInode) Lookup(ctx context.Context, name string) (*vfs.Dentry, error) {
+	tid, err := strconv.ParseUint(name, 10, 32)
+	if err != nil {
+		return nil, syserror.ENOENT
+	}
+
+	subTask := i.pidns.TaskWithID(kernel.ThreadID(tid))
+	if subTask == nil {
+		return nil, syserror.ENOENT
+	}
+	if subTask.ThreadGroup() != i.task.ThreadGroup() {
+		return nil, syserror.ENOENT
+	}
+
+	subTaskDentry := newTaskInode(i.inoGen, subTask, i.pidns, false, i.cgroupControllers)
+	return subTaskDentry.VFSDentry(), nil
+}
+
+// IterDirents implements kernfs.inodeDynamicLookup.
+func (i *subtasksInode) IterDirents(ctx context.Context, cb vfs.IterDirentsCallback, offset, relOffset int64) (int64, error) {
+	tasks := i.task.ThreadGroup().MemberIDs(i.pidns)
+	if len(tasks) == 0 {
+		return offset, syserror.ENOENT
+	}
+
+	tids := make([]int, 0, len(tasks))
+	for _, tid := range tasks {
+		tids = append(tids, int(tid))
+	}
+
+	sort.Ints(tids)
+	for _, tid := range tids[relOffset:] {
+		dirent := vfs.Dirent{
+			Name:    strconv.FormatUint(uint64(tid), 10),
+			Type:    linux.DT_DIR,
+			Ino:     i.inoGen.NextIno(),
+			NextOff: offset + 1,
+		}
+		if !cb.Handle(dirent) {
+			return offset, nil
+		}
+		offset++
+	}
+	return offset, nil
+}
+
+// Open implements kernfs.Inode.
+func (i *subtasksInode) Open(rp *vfs.ResolvingPath, vfsd *vfs.Dentry, flags uint32) (*vfs.FileDescription, error) {
+	fd := &kernfs.GenericDirectoryFD{}
+	fd.Init(rp.Mount(), vfsd, &i.OrderedChildren, flags)
+	return fd.VFSFileDescription(), nil
+}
+
+// Stat implements kernfs.Inode.
+func (i *subtasksInode) Stat(vsfs *vfs.Filesystem) linux.Statx {
+	stat := i.InodeAttrs.Stat(vsfs)
+	stat.Nlink += uint32(i.task.ThreadGroup().Count())
+	return stat
+}
diff --git a/pkg/sentry/fsimpl/proc/sys.go b/pkg/sentry/fsimpl/proc/sys.go
deleted file mode 100644
index b88256e12..000000000
--- a/pkg/sentry/fsimpl/proc/sys.go
+++ /dev/null
@@ -1,51 +0,0 @@
-// 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 proc
-
-import (
-	"bytes"
-	"fmt"
-
-	"gvisor.dev/gvisor/pkg/sentry/context"
-	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/vfs"
-)
-
-// mmapMinAddrData implements vfs.DynamicBytesSource for
-// /proc/sys/vm/mmap_min_addr.
-//
-// +stateify savable
-type mmapMinAddrData struct {
-	k *kernel.Kernel
-}
-
-var _ vfs.DynamicBytesSource = (*mmapMinAddrData)(nil)
-
-// Generate implements vfs.DynamicBytesSource.Generate.
-func (d *mmapMinAddrData) Generate(ctx context.Context, buf *bytes.Buffer) error {
-	fmt.Fprintf(buf, "%d\n", d.k.Platform.MinUserAddress())
-	return nil
-}
-
-// +stateify savable
-type overcommitMemory struct{}
-
-var _ vfs.DynamicBytesSource = (*overcommitMemory)(nil)
-
-// Generate implements vfs.DynamicBytesSource.Generate.
-func (d *overcommitMemory) Generate(ctx context.Context, buf *bytes.Buffer) error {
-	fmt.Fprintf(buf, "0\n")
-	return nil
-}
diff --git a/pkg/sentry/fsimpl/proc/task.go b/pkg/sentry/fsimpl/proc/task.go
index 11a64c777..a0580f20d 100644
--- a/pkg/sentry/fsimpl/proc/task.go
+++ b/pkg/sentry/fsimpl/proc/task.go
@@ -15,6 +15,9 @@
 package proc
 
 import (
+	"bytes"
+	"fmt"
+
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/context"
 	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
@@ -40,33 +43,37 @@ type taskInode struct {
 
 var _ kernfs.Inode = (*taskInode)(nil)
 
-func newTaskInode(inoGen InoGenerator, task *kernel.Task, pidns *kernel.PIDNamespace, isThreadGroup bool) *kernfs.Dentry {
+func newTaskInode(inoGen InoGenerator, task *kernel.Task, pidns *kernel.PIDNamespace, isThreadGroup bool, cgroupControllers map[string]string) *kernfs.Dentry {
 	contents := map[string]*kernfs.Dentry{
-		//"auxv":      newAuxvec(t, msrc),
-		//"cmdline":   newExecArgInode(t, msrc, cmdlineExecArg),
-		//"comm":      newComm(t, msrc),
-		//"environ":   newExecArgInode(t, msrc, environExecArg),
+		"auxv":    newTaskOwnedFile(task, inoGen.NextIno(), 0444, &auxvData{task: task}),
+		"cmdline": newTaskOwnedFile(task, inoGen.NextIno(), 0444, &cmdlineData{task: task, arg: cmdlineDataArg}),
+		"comm":    newComm(task, inoGen.NextIno(), 0444),
+		"environ": newTaskOwnedFile(task, inoGen.NextIno(), 0444, &cmdlineData{task: task, arg: environDataArg}),
 		//"exe":       newExe(t, msrc),
 		//"fd":        newFdDir(t, msrc),
 		//"fdinfo":    newFdInfoDir(t, msrc),
-		//"gid_map":   newGIDMap(t, msrc),
-		"io":   newTaskOwnedFile(task, inoGen.NextIno(), defaultPermission, newIO(task, isThreadGroup)),
-		"maps": newTaskOwnedFile(task, inoGen.NextIno(), defaultPermission, &mapsData{task: task}),
+		"gid_map": newTaskOwnedFile(task, inoGen.NextIno(), 0644, &idMapData{task: task, gids: true}),
+		"io":      newTaskOwnedFile(task, inoGen.NextIno(), 0400, newIO(task, isThreadGroup)),
+		"maps":    newTaskOwnedFile(task, inoGen.NextIno(), 0444, &mapsData{task: task}),
 		//"mountinfo": seqfile.NewSeqFileInode(t, &mountInfoFile{t: t}, msrc),
 		//"mounts":    seqfile.NewSeqFileInode(t, &mountsFile{t: t}, msrc),
-		//"ns":        newNamespaceDir(t, msrc),
-		"smaps":  newTaskOwnedFile(task, inoGen.NextIno(), defaultPermission, &smapsData{task: task}),
-		"stat":   newTaskOwnedFile(task, inoGen.NextIno(), defaultPermission, &taskStatData{t: task, pidns: pidns, tgstats: isThreadGroup}),
-		"statm":  newTaskOwnedFile(task, inoGen.NextIno(), defaultPermission, &statmData{t: task}),
-		"status": newTaskOwnedFile(task, inoGen.NextIno(), defaultPermission, &statusData{t: task, pidns: pidns}),
-		//"uid_map":   newUIDMap(t, msrc),
+		"ns": newTaskOwnedDir(task, inoGen.NextIno(), 0511, map[string]*kernfs.Dentry{
+			"net":  newNamespaceSymlink(task, inoGen.NextIno(), "net"),
+			"pid":  newNamespaceSymlink(task, inoGen.NextIno(), "pid"),
+			"user": newNamespaceSymlink(task, inoGen.NextIno(), "user"),
+		}),
+		"smaps":   newTaskOwnedFile(task, inoGen.NextIno(), 0444, &smapsData{task: task}),
+		"stat":    newTaskOwnedFile(task, inoGen.NextIno(), 0444, &taskStatData{task: task, pidns: pidns, tgstats: isThreadGroup}),
+		"statm":   newTaskOwnedFile(task, inoGen.NextIno(), 0444, &statmData{task: task}),
+		"status":  newTaskOwnedFile(task, inoGen.NextIno(), 0444, &statusData{task: task, pidns: pidns}),
+		"uid_map": newTaskOwnedFile(task, inoGen.NextIno(), 0644, &idMapData{task: task, gids: false}),
 	}
 	if isThreadGroup {
-		//contents["task"] = p.newSubtasks(t, msrc)
+		contents["task"] = newSubtasks(task, pidns, inoGen, cgroupControllers)
+	}
+	if len(cgroupControllers) > 0 {
+		contents["cgroup"] = newTaskOwnedFile(task, inoGen.NextIno(), 0444, newCgroupData(cgroupControllers))
 	}
-	//if len(p.cgroupControllers) > 0 {
-	//	contents["cgroup"] = newCGroupInode(t, msrc, p.cgroupControllers)
-	//}
 
 	taskInode := &taskInode{task: task}
 	// Note: credentials are overridden by taskOwnedInode.
@@ -127,6 +134,23 @@ func newTaskOwnedFile(task *kernel.Task, ino uint64, perm linux.FileMode, inode
 	return d
 }
 
+func newTaskOwnedDir(task *kernel.Task, ino uint64, perm linux.FileMode, children map[string]*kernfs.Dentry) *kernfs.Dentry {
+	dir := &kernfs.StaticDirectory{}
+
+	// Note: credentials are overridden by taskOwnedInode.
+	dir.Init(task.Credentials(), ino, perm)
+
+	inode := &taskOwnedInode{Inode: dir, owner: task}
+	d := &kernfs.Dentry{}
+	d.Init(inode)
+
+	dir.OrderedChildren.Init(kernfs.OrderedChildrenOptions{})
+	links := dir.OrderedChildren.Populate(d, children)
+	dir.IncLinks(links)
+
+	return d
+}
+
 // Stat implements kernfs.Inode.
 func (i *taskOwnedInode) Stat(fs *vfs.Filesystem) linux.Statx {
 	stat := i.Inode.Stat(fs)
@@ -137,7 +161,7 @@ func (i *taskOwnedInode) Stat(fs *vfs.Filesystem) linux.Statx {
 }
 
 // CheckPermissions implements kernfs.Inode.
-func (i *taskOwnedInode) CheckPermissions(creds *auth.Credentials, ats vfs.AccessTypes) error {
+func (i *taskOwnedInode) CheckPermissions(_ context.Context, creds *auth.Credentials, ats vfs.AccessTypes) error {
 	mode := i.Mode()
 	uid, gid := i.getOwner(mode)
 	return vfs.GenericCheckPermissions(
@@ -188,3 +212,38 @@ func newIO(t *kernel.Task, isThreadGroup bool) *ioData {
 	}
 	return &ioData{ioUsage: t}
 }
+
+func newNamespaceSymlink(task *kernel.Task, ino uint64, ns string) *kernfs.Dentry {
+	// Namespace symlinks should contain the namespace name and the inode number
+	// for the namespace instance, so for example user:[123456]. We currently fake
+	// the inode number by sticking the symlink inode in its place.
+	target := fmt.Sprintf("%s:[%d]", ns, ino)
+
+	inode := &kernfs.StaticSymlink{}
+	// Note: credentials are overridden by taskOwnedInode.
+	inode.Init(task.Credentials(), ino, target)
+
+	taskInode := &taskOwnedInode{Inode: inode, owner: task}
+	d := &kernfs.Dentry{}
+	d.Init(taskInode)
+	return d
+}
+
+// newCgroupData creates inode that shows cgroup information.
+// From man 7 cgroups: "For each cgroup hierarchy of which the process is a
+// member, there is one entry containing three colon-separated fields:
+//   hierarchy-ID:controller-list:cgroup-path"
+func newCgroupData(controllers map[string]string) dynamicInode {
+	buf := bytes.Buffer{}
+
+	// The hierarchy ids must be positive integers (for cgroup v1), but the
+	// exact number does not matter, so long as they are unique. We can
+	// just use a counter, but since linux sorts this file in descending
+	// order, we must count down to preserve this behavior.
+	i := len(controllers)
+	for name, dir := range controllers {
+		fmt.Fprintf(&buf, "%d:%s:%s\n", i, name, dir)
+		i--
+	}
+	return newStaticFile(buf.String())
+}
diff --git a/pkg/sentry/fsimpl/proc/task_files.go b/pkg/sentry/fsimpl/proc/task_files.go
index 93f0e1aa8..7bc352ae9 100644
--- a/pkg/sentry/fsimpl/proc/task_files.go
+++ b/pkg/sentry/fsimpl/proc/task_files.go
@@ -17,15 +17,20 @@ package proc
 import (
 	"bytes"
 	"fmt"
+	"io"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/context"
 	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/limits"
 	"gvisor.dev/gvisor/pkg/sentry/mm"
+	"gvisor.dev/gvisor/pkg/sentry/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/usage"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/syserror"
 )
 
 // mm gets the kernel task's MemoryManager. No additional reference is taken on
@@ -41,6 +46,256 @@ func getMM(task *kernel.Task) *mm.MemoryManager {
 	return tmm
 }
 
+// getMMIncRef returns t's MemoryManager. If getMMIncRef succeeds, the
+// MemoryManager's users count is incremented, and must be decremented by the
+// caller when it is no longer in use.
+func getMMIncRef(task *kernel.Task) (*mm.MemoryManager, error) {
+	if task.ExitState() == kernel.TaskExitDead {
+		return nil, syserror.ESRCH
+	}
+	var m *mm.MemoryManager
+	task.WithMuLocked(func(t *kernel.Task) {
+		m = t.MemoryManager()
+	})
+	if m == nil || !m.IncUsers() {
+		return nil, io.EOF
+	}
+	return m, nil
+}
+
+type bufferWriter struct {
+	buf *bytes.Buffer
+}
+
+// WriteFromBlocks writes up to srcs.NumBytes() bytes from srcs and returns
+// the number of bytes written. It may return a partial write without an
+// error (i.e. (n, nil) where 0 < n < srcs.NumBytes()). It should not
+// return a full write with an error (i.e. srcs.NumBytes(), err) where err
+// != nil).
+func (w *bufferWriter) WriteFromBlocks(srcs safemem.BlockSeq) (uint64, error) {
+	written := srcs.NumBytes()
+	for !srcs.IsEmpty() {
+		w.buf.Write(srcs.Head().ToSlice())
+		srcs = srcs.Tail()
+	}
+	return written, nil
+}
+
+// auxvData implements vfs.DynamicBytesSource for /proc/[pid]/auxv.
+//
+// +stateify savable
+type auxvData struct {
+	kernfs.DynamicBytesFile
+
+	task *kernel.Task
+}
+
+var _ dynamicInode = (*auxvData)(nil)
+
+// Generate implements vfs.DynamicBytesSource.Generate.
+func (d *auxvData) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	m, err := getMMIncRef(d.task)
+	if err != nil {
+		return err
+	}
+	defer m.DecUsers(ctx)
+
+	// Space for buffer with AT_NULL (0) terminator at the end.
+	auxv := m.Auxv()
+	buf.Grow((len(auxv) + 1) * 16)
+	for _, e := range auxv {
+		var tmp [8]byte
+		usermem.ByteOrder.PutUint64(tmp[:], e.Key)
+		buf.Write(tmp[:])
+
+		usermem.ByteOrder.PutUint64(tmp[:], uint64(e.Value))
+		buf.Write(tmp[:])
+	}
+	return nil
+}
+
+// execArgType enumerates the types of exec arguments that are exposed through
+// proc.
+type execArgType int
+
+const (
+	cmdlineDataArg execArgType = iota
+	environDataArg
+)
+
+// cmdlineData implements vfs.DynamicBytesSource for /proc/[pid]/cmdline.
+//
+// +stateify savable
+type cmdlineData struct {
+	kernfs.DynamicBytesFile
+
+	task *kernel.Task
+
+	// arg is the type of exec argument this file contains.
+	arg execArgType
+}
+
+var _ dynamicInode = (*cmdlineData)(nil)
+
+// Generate implements vfs.DynamicBytesSource.Generate.
+func (d *cmdlineData) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	m, err := getMMIncRef(d.task)
+	if err != nil {
+		return err
+	}
+	defer m.DecUsers(ctx)
+
+	// Figure out the bounds of the exec arg we are trying to read.
+	var ar usermem.AddrRange
+	switch d.arg {
+	case cmdlineDataArg:
+		ar = usermem.AddrRange{
+			Start: m.ArgvStart(),
+			End:   m.ArgvEnd(),
+		}
+	case environDataArg:
+		ar = usermem.AddrRange{
+			Start: m.EnvvStart(),
+			End:   m.EnvvEnd(),
+		}
+	default:
+		panic(fmt.Sprintf("unknown exec arg type %v", d.arg))
+	}
+	if ar.Start == 0 || ar.End == 0 {
+		// Don't attempt to read before the start/end are set up.
+		return io.EOF
+	}
+
+	// N.B. Technically this should be usermem.IOOpts.IgnorePermissions = true
+	// until Linux 4.9 (272ddc8b3735 "proc: don't use FOLL_FORCE for reading
+	// cmdline and environment").
+	writer := &bufferWriter{buf: buf}
+	if n, err := m.CopyInTo(ctx, usermem.AddrRangeSeqOf(ar), writer, usermem.IOOpts{}); n == 0 || err != nil {
+		// Nothing to copy or something went wrong.
+		return err
+	}
+
+	// On Linux, if the NULL byte at the end of the argument vector has been
+	// overwritten, it continues reading the environment vector as part of
+	// the argument vector.
+	if d.arg == cmdlineDataArg && buf.Bytes()[buf.Len()-1] != 0 {
+		if end := bytes.IndexByte(buf.Bytes(), 0); end != -1 {
+			// If we found a NULL character somewhere else in argv, truncate the
+			// return up to the NULL terminator (including it).
+			buf.Truncate(end)
+			return nil
+		}
+
+		// There is no NULL terminator in the string, return into envp.
+		arEnvv := usermem.AddrRange{
+			Start: m.EnvvStart(),
+			End:   m.EnvvEnd(),
+		}
+
+		// Upstream limits the returned amount to one page of slop.
+		// https://elixir.bootlin.com/linux/v4.20/source/fs/proc/base.c#L208
+		// we'll return one page total between argv and envp because of the
+		// above page restrictions.
+		if buf.Len() >= usermem.PageSize {
+			// Returned at least one page already, nothing else to add.
+			return nil
+		}
+		remaining := usermem.PageSize - buf.Len()
+		if int(arEnvv.Length()) > remaining {
+			end, ok := arEnvv.Start.AddLength(uint64(remaining))
+			if !ok {
+				return syserror.EFAULT
+			}
+			arEnvv.End = end
+		}
+		if _, err := m.CopyInTo(ctx, usermem.AddrRangeSeqOf(arEnvv), writer, usermem.IOOpts{}); err != nil {
+			return err
+		}
+
+		// Linux will return envp up to and including the first NULL character,
+		// so find it.
+		if end := bytes.IndexByte(buf.Bytes()[ar.Length():], 0); end != -1 {
+			buf.Truncate(end)
+		}
+	}
+
+	return nil
+}
+
+// +stateify savable
+type commInode struct {
+	kernfs.DynamicBytesFile
+
+	task *kernel.Task
+}
+
+func newComm(task *kernel.Task, ino uint64, perm linux.FileMode) *kernfs.Dentry {
+	inode := &commInode{task: task}
+	inode.DynamicBytesFile.Init(task.Credentials(), ino, &commData{task: task}, perm)
+
+	d := &kernfs.Dentry{}
+	d.Init(inode)
+	return d
+}
+
+func (i *commInode) CheckPermissions(ctx context.Context, creds *auth.Credentials, ats vfs.AccessTypes) error {
+	// This file can always be read or written by members of the same thread
+	// group. See fs/proc/base.c:proc_tid_comm_permission.
+	//
+	// N.B. This check is currently a no-op as we don't yet support writing and
+	// this file is world-readable anyways.
+	t := kernel.TaskFromContext(ctx)
+	if t != nil && t.ThreadGroup() == i.task.ThreadGroup() && !ats.MayExec() {
+		return nil
+	}
+
+	return i.DynamicBytesFile.CheckPermissions(ctx, creds, ats)
+}
+
+// commData implements vfs.DynamicBytesSource for /proc/[pid]/comm.
+//
+// +stateify savable
+type commData struct {
+	kernfs.DynamicBytesFile
+
+	task *kernel.Task
+}
+
+var _ dynamicInode = (*commData)(nil)
+
+// Generate implements vfs.DynamicBytesSource.Generate.
+func (d *commData) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	buf.WriteString(d.task.Name())
+	buf.WriteString("\n")
+	return nil
+}
+
+// idMapData implements vfs.DynamicBytesSource for /proc/[pid]/{gid_map|uid_map}.
+//
+// +stateify savable
+type idMapData struct {
+	kernfs.DynamicBytesFile
+
+	task *kernel.Task
+	gids bool
+}
+
+var _ dynamicInode = (*idMapData)(nil)
+
+// Generate implements vfs.DynamicBytesSource.Generate.
+func (d *idMapData) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	var entries []auth.IDMapEntry
+	if d.gids {
+		entries = d.task.UserNamespace().GIDMap()
+	} else {
+		entries = d.task.UserNamespace().UIDMap()
+	}
+	for _, e := range entries {
+		fmt.Fprintf(buf, "%10d %10d %10d\n", e.FirstID, e.FirstParentID, e.Length)
+	}
+	return nil
+}
+
 // mapsData implements vfs.DynamicBytesSource for /proc/[pid]/maps.
 //
 // +stateify savable
@@ -83,7 +338,7 @@ func (d *smapsData) Generate(ctx context.Context, buf *bytes.Buffer) error {
 type taskStatData struct {
 	kernfs.DynamicBytesFile
 
-	t *kernel.Task
+	task *kernel.Task
 
 	// If tgstats is true, accumulate fault stats (not implemented) and CPU
 	// time across all tasks in t's thread group.
@@ -98,40 +353,40 @@ var _ dynamicInode = (*taskStatData)(nil)
 
 // Generate implements vfs.DynamicBytesSource.Generate.
 func (s *taskStatData) Generate(ctx context.Context, buf *bytes.Buffer) error {
-	fmt.Fprintf(buf, "%d ", s.pidns.IDOfTask(s.t))
-	fmt.Fprintf(buf, "(%s) ", s.t.Name())
-	fmt.Fprintf(buf, "%c ", s.t.StateStatus()[0])
+	fmt.Fprintf(buf, "%d ", s.pidns.IDOfTask(s.task))
+	fmt.Fprintf(buf, "(%s) ", s.task.Name())
+	fmt.Fprintf(buf, "%c ", s.task.StateStatus()[0])
 	ppid := kernel.ThreadID(0)
-	if parent := s.t.Parent(); parent != nil {
+	if parent := s.task.Parent(); parent != nil {
 		ppid = s.pidns.IDOfThreadGroup(parent.ThreadGroup())
 	}
 	fmt.Fprintf(buf, "%d ", ppid)
-	fmt.Fprintf(buf, "%d ", s.pidns.IDOfProcessGroup(s.t.ThreadGroup().ProcessGroup()))
-	fmt.Fprintf(buf, "%d ", s.pidns.IDOfSession(s.t.ThreadGroup().Session()))
+	fmt.Fprintf(buf, "%d ", s.pidns.IDOfProcessGroup(s.task.ThreadGroup().ProcessGroup()))
+	fmt.Fprintf(buf, "%d ", s.pidns.IDOfSession(s.task.ThreadGroup().Session()))
 	fmt.Fprintf(buf, "0 0 " /* tty_nr tpgid */)
 	fmt.Fprintf(buf, "0 " /* flags */)
 	fmt.Fprintf(buf, "0 0 0 0 " /* minflt cminflt majflt cmajflt */)
 	var cputime usage.CPUStats
 	if s.tgstats {
-		cputime = s.t.ThreadGroup().CPUStats()
+		cputime = s.task.ThreadGroup().CPUStats()
 	} else {
-		cputime = s.t.CPUStats()
+		cputime = s.task.CPUStats()
 	}
 	fmt.Fprintf(buf, "%d %d ", linux.ClockTFromDuration(cputime.UserTime), linux.ClockTFromDuration(cputime.SysTime))
-	cputime = s.t.ThreadGroup().JoinedChildCPUStats()
+	cputime = s.task.ThreadGroup().JoinedChildCPUStats()
 	fmt.Fprintf(buf, "%d %d ", linux.ClockTFromDuration(cputime.UserTime), linux.ClockTFromDuration(cputime.SysTime))
-	fmt.Fprintf(buf, "%d %d ", s.t.Priority(), s.t.Niceness())
-	fmt.Fprintf(buf, "%d ", s.t.ThreadGroup().Count())
+	fmt.Fprintf(buf, "%d %d ", s.task.Priority(), s.task.Niceness())
+	fmt.Fprintf(buf, "%d ", s.task.ThreadGroup().Count())
 
 	// itrealvalue. Since kernel 2.6.17, this field is no longer
 	// maintained, and is hard coded as 0.
 	fmt.Fprintf(buf, "0 ")
 
 	// Start time is relative to boot time, expressed in clock ticks.
-	fmt.Fprintf(buf, "%d ", linux.ClockTFromDuration(s.t.StartTime().Sub(s.t.Kernel().Timekeeper().BootTime())))
+	fmt.Fprintf(buf, "%d ", linux.ClockTFromDuration(s.task.StartTime().Sub(s.task.Kernel().Timekeeper().BootTime())))
 
 	var vss, rss uint64
-	s.t.WithMuLocked(func(t *kernel.Task) {
+	s.task.WithMuLocked(func(t *kernel.Task) {
 		if mm := t.MemoryManager(); mm != nil {
 			vss = mm.VirtualMemorySize()
 			rss = mm.ResidentSetSize()
@@ -140,14 +395,14 @@ func (s *taskStatData) Generate(ctx context.Context, buf *bytes.Buffer) error {
 	fmt.Fprintf(buf, "%d %d ", vss, rss/usermem.PageSize)
 
 	// rsslim.
-	fmt.Fprintf(buf, "%d ", s.t.ThreadGroup().Limits().Get(limits.Rss).Cur)
+	fmt.Fprintf(buf, "%d ", s.task.ThreadGroup().Limits().Get(limits.Rss).Cur)
 
 	fmt.Fprintf(buf, "0 0 0 0 0 " /* startcode endcode startstack kstkesp kstkeip */)
 	fmt.Fprintf(buf, "0 0 0 0 0 " /* signal blocked sigignore sigcatch wchan */)
 	fmt.Fprintf(buf, "0 0 " /* nswap cnswap */)
 	terminationSignal := linux.Signal(0)
-	if s.t == s.t.ThreadGroup().Leader() {
-		terminationSignal = s.t.ThreadGroup().TerminationSignal()
+	if s.task == s.task.ThreadGroup().Leader() {
+		terminationSignal = s.task.ThreadGroup().TerminationSignal()
 	}
 	fmt.Fprintf(buf, "%d ", terminationSignal)
 	fmt.Fprintf(buf, "0 0 0 " /* processor rt_priority policy */)
@@ -164,7 +419,7 @@ func (s *taskStatData) Generate(ctx context.Context, buf *bytes.Buffer) error {
 type statmData struct {
 	kernfs.DynamicBytesFile
 
-	t *kernel.Task
+	task *kernel.Task
 }
 
 var _ dynamicInode = (*statmData)(nil)
@@ -172,7 +427,7 @@ var _ dynamicInode = (*statmData)(nil)
 // Generate implements vfs.DynamicBytesSource.Generate.
 func (s *statmData) Generate(ctx context.Context, buf *bytes.Buffer) error {
 	var vss, rss uint64
-	s.t.WithMuLocked(func(t *kernel.Task) {
+	s.task.WithMuLocked(func(t *kernel.Task) {
 		if mm := t.MemoryManager(); mm != nil {
 			vss = mm.VirtualMemorySize()
 			rss = mm.ResidentSetSize()
@@ -189,7 +444,7 @@ func (s *statmData) Generate(ctx context.Context, buf *bytes.Buffer) error {
 type statusData struct {
 	kernfs.DynamicBytesFile
 
-	t     *kernel.Task
+	task  *kernel.Task
 	pidns *kernel.PIDNamespace
 }
 
@@ -197,23 +452,23 @@ var _ dynamicInode = (*statusData)(nil)
 
 // Generate implements vfs.DynamicBytesSource.Generate.
 func (s *statusData) Generate(ctx context.Context, buf *bytes.Buffer) error {
-	fmt.Fprintf(buf, "Name:\t%s\n", s.t.Name())
-	fmt.Fprintf(buf, "State:\t%s\n", s.t.StateStatus())
-	fmt.Fprintf(buf, "Tgid:\t%d\n", s.pidns.IDOfThreadGroup(s.t.ThreadGroup()))
-	fmt.Fprintf(buf, "Pid:\t%d\n", s.pidns.IDOfTask(s.t))
+	fmt.Fprintf(buf, "Name:\t%s\n", s.task.Name())
+	fmt.Fprintf(buf, "State:\t%s\n", s.task.StateStatus())
+	fmt.Fprintf(buf, "Tgid:\t%d\n", s.pidns.IDOfThreadGroup(s.task.ThreadGroup()))
+	fmt.Fprintf(buf, "Pid:\t%d\n", s.pidns.IDOfTask(s.task))
 	ppid := kernel.ThreadID(0)
-	if parent := s.t.Parent(); parent != nil {
+	if parent := s.task.Parent(); parent != nil {
 		ppid = s.pidns.IDOfThreadGroup(parent.ThreadGroup())
 	}
 	fmt.Fprintf(buf, "PPid:\t%d\n", ppid)
 	tpid := kernel.ThreadID(0)
-	if tracer := s.t.Tracer(); tracer != nil {
+	if tracer := s.task.Tracer(); tracer != nil {
 		tpid = s.pidns.IDOfTask(tracer)
 	}
 	fmt.Fprintf(buf, "TracerPid:\t%d\n", tpid)
 	var fds int
 	var vss, rss, data uint64
-	s.t.WithMuLocked(func(t *kernel.Task) {
+	s.task.WithMuLocked(func(t *kernel.Task) {
 		if fdTable := t.FDTable(); fdTable != nil {
 			fds = fdTable.Size()
 		}
@@ -227,13 +482,13 @@ func (s *statusData) Generate(ctx context.Context, buf *bytes.Buffer) error {
 	fmt.Fprintf(buf, "VmSize:\t%d kB\n", vss>>10)
 	fmt.Fprintf(buf, "VmRSS:\t%d kB\n", rss>>10)
 	fmt.Fprintf(buf, "VmData:\t%d kB\n", data>>10)
-	fmt.Fprintf(buf, "Threads:\t%d\n", s.t.ThreadGroup().Count())
-	creds := s.t.Credentials()
+	fmt.Fprintf(buf, "Threads:\t%d\n", s.task.ThreadGroup().Count())
+	creds := s.task.Credentials()
 	fmt.Fprintf(buf, "CapInh:\t%016x\n", creds.InheritableCaps)
 	fmt.Fprintf(buf, "CapPrm:\t%016x\n", creds.PermittedCaps)
 	fmt.Fprintf(buf, "CapEff:\t%016x\n", creds.EffectiveCaps)
 	fmt.Fprintf(buf, "CapBnd:\t%016x\n", creds.BoundingCaps)
-	fmt.Fprintf(buf, "Seccomp:\t%d\n", s.t.SeccompMode())
+	fmt.Fprintf(buf, "Seccomp:\t%d\n", s.task.SeccompMode())
 	// We unconditionally report a single NUMA node. See
 	// pkg/sentry/syscalls/linux/sys_mempolicy.go.
 	fmt.Fprintf(buf, "Mems_allowed:\t1\n")
diff --git a/pkg/sentry/fsimpl/proc/tasks.go b/pkg/sentry/fsimpl/proc/tasks.go
index d8f92d52f..51f634716 100644
--- a/pkg/sentry/fsimpl/proc/tasks.go
+++ b/pkg/sentry/fsimpl/proc/tasks.go
@@ -15,6 +15,7 @@
 package proc
 
 import (
+	"bytes"
 	"sort"
 	"strconv"
 
@@ -28,9 +29,8 @@ import (
 )
 
 const (
-	defaultPermission = 0444
-	selfName          = "self"
-	threadSelfName    = "thread-self"
+	selfName       = "self"
+	threadSelfName = "thread-self"
 )
 
 // InoGenerator generates unique inode numbers for a given filesystem.
@@ -54,22 +54,28 @@ type tasksInode struct {
 	// Linux. So handle them outside of OrderedChildren.
 	selfSymlink       *vfs.Dentry
 	threadSelfSymlink *vfs.Dentry
+
+	// cgroupControllers is a map of controller name to directory in the
+	// cgroup hierarchy. These controllers are immutable and will be listed
+	// in /proc/pid/cgroup if not nil.
+	cgroupControllers map[string]string
 }
 
 var _ kernfs.Inode = (*tasksInode)(nil)
 
-func newTasksInode(inoGen InoGenerator, k *kernel.Kernel, pidns *kernel.PIDNamespace) (*tasksInode, *kernfs.Dentry) {
+func newTasksInode(inoGen InoGenerator, k *kernel.Kernel, pidns *kernel.PIDNamespace, cgroupControllers map[string]string) (*tasksInode, *kernfs.Dentry) {
 	root := auth.NewRootCredentials(pidns.UserNamespace())
 	contents := map[string]*kernfs.Dentry{
-		//"cpuinfo":     newCPUInfo(ctx, msrc),
-		//"filesystems": seqfile.NewSeqFileInode(ctx, &filesystemsData{}, msrc),
-		"loadavg": newDentry(root, inoGen.NextIno(), defaultPermission, &loadavgData{}),
-		"meminfo": newDentry(root, inoGen.NextIno(), defaultPermission, &meminfoData{k: k}),
-		"mounts":  kernfs.NewStaticSymlink(root, inoGen.NextIno(), defaultPermission, "self/mounts"),
-		"stat":    newDentry(root, inoGen.NextIno(), defaultPermission, &statData{k: k}),
-		//"uptime":      newUptime(ctx, msrc),
-		//"version": newVersionData(root, inoGen.NextIno(), k),
-		"version": newDentry(root, inoGen.NextIno(), defaultPermission, &versionData{k: k}),
+		"cpuinfo": newDentry(root, inoGen.NextIno(), 0444, newStaticFile(cpuInfoData(k))),
+		//"filesystems": newDentry(root, inoGen.NextIno(), 0444, &filesystemsData{}),
+		"loadavg": newDentry(root, inoGen.NextIno(), 0444, &loadavgData{}),
+		"sys":     newSysDir(root, inoGen),
+		"meminfo": newDentry(root, inoGen.NextIno(), 0444, &meminfoData{}),
+		"mounts":  kernfs.NewStaticSymlink(root, inoGen.NextIno(), "self/mounts"),
+		"net":     newNetDir(root, inoGen, k),
+		"stat":    newDentry(root, inoGen.NextIno(), 0444, &statData{}),
+		"uptime":  newDentry(root, inoGen.NextIno(), 0444, &uptimeData{}),
+		"version": newDentry(root, inoGen.NextIno(), 0444, &versionData{}),
 	}
 
 	inode := &tasksInode{
@@ -77,6 +83,7 @@ func newTasksInode(inoGen InoGenerator, k *kernel.Kernel, pidns *kernel.PIDNames
 		inoGen:            inoGen,
 		selfSymlink:       newSelfSymlink(root, inoGen.NextIno(), 0444, pidns).VFSDentry(),
 		threadSelfSymlink: newThreadSelfSymlink(root, inoGen.NextIno(), 0444, pidns).VFSDentry(),
+		cgroupControllers: cgroupControllers,
 	}
 	inode.InodeAttrs.Init(root, inoGen.NextIno(), linux.ModeDirectory|0555)
 
@@ -110,7 +117,7 @@ func (i *tasksInode) Lookup(ctx context.Context, name string) (*vfs.Dentry, erro
 		return nil, syserror.ENOENT
 	}
 
-	taskDentry := newTaskInode(i.inoGen, task, i.pidns, true)
+	taskDentry := newTaskInode(i.inoGen, task, i.pidns, true, i.cgroupControllers)
 	return taskDentry.VFSDentry(), nil
 }
 
@@ -216,3 +223,20 @@ func (i *tasksInode) Stat(vsfs *vfs.Filesystem) linux.Statx {
 
 	return stat
 }
+
+func cpuInfoData(k *kernel.Kernel) string {
+	features := k.FeatureSet()
+	if features == nil {
+		// Kernel is always initialized with a FeatureSet.
+		panic("cpuinfo read with nil FeatureSet")
+	}
+	var buf bytes.Buffer
+	for i, max := uint(0), k.ApplicationCores(); i < max; i++ {
+		features.WriteCPUInfoTo(i, &buf)
+	}
+	return buf.String()
+}
+
+func shmData(v uint64) dynamicInode {
+	return newStaticFile(strconv.FormatUint(v, 10))
+}
diff --git a/pkg/sentry/fsimpl/proc/tasks_files.go b/pkg/sentry/fsimpl/proc/tasks_files.go
index 91f30a798..ad3760e39 100644
--- a/pkg/sentry/fsimpl/proc/tasks_files.go
+++ b/pkg/sentry/fsimpl/proc/tasks_files.go
@@ -15,6 +15,7 @@
 package proc
 
 import (
+	"bytes"
 	"fmt"
 	"strconv"
 
@@ -23,6 +24,9 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/time"
+	"gvisor.dev/gvisor/pkg/sentry/usage"
+	"gvisor.dev/gvisor/pkg/sentry/usermem"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
@@ -90,3 +94,244 @@ func (s *threadSelfSymlink) Readlink(ctx context.Context) (string, error) {
 	}
 	return fmt.Sprintf("%d/task/%d", tgid, tid), nil
 }
+
+// cpuStats contains the breakdown of CPU time for /proc/stat.
+type cpuStats struct {
+	// user is time spent in userspace tasks with non-positive niceness.
+	user uint64
+
+	// nice is time spent in userspace tasks with positive niceness.
+	nice uint64
+
+	// system is time spent in non-interrupt kernel context.
+	system uint64
+
+	// idle is time spent idle.
+	idle uint64
+
+	// ioWait is time spent waiting for IO.
+	ioWait uint64
+
+	// irq is time spent in interrupt context.
+	irq uint64
+
+	// softirq is time spent in software interrupt context.
+	softirq uint64
+
+	// steal is involuntary wait time.
+	steal uint64
+
+	// guest is time spent in guests with non-positive niceness.
+	guest uint64
+
+	// guestNice is time spent in guests with positive niceness.
+	guestNice uint64
+}
+
+// String implements fmt.Stringer.
+func (c cpuStats) String() string {
+	return fmt.Sprintf("%d %d %d %d %d %d %d %d %d %d", c.user, c.nice, c.system, c.idle, c.ioWait, c.irq, c.softirq, c.steal, c.guest, c.guestNice)
+}
+
+// statData implements vfs.DynamicBytesSource for /proc/stat.
+//
+// +stateify savable
+type statData struct {
+	kernfs.DynamicBytesFile
+
+	// k is the owning Kernel.
+	k *kernel.Kernel
+}
+
+var _ dynamicInode = (*statData)(nil)
+
+// Generate implements vfs.DynamicBytesSource.Generate.
+func (s *statData) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	// TODO(b/37226836): We currently export only zero CPU stats. We could
+	// at least provide some aggregate stats.
+	var cpu cpuStats
+	fmt.Fprintf(buf, "cpu  %s\n", cpu)
+
+	for c, max := uint(0), s.k.ApplicationCores(); c < max; c++ {
+		fmt.Fprintf(buf, "cpu%d %s\n", c, cpu)
+	}
+
+	// The total number of interrupts is dependent on the CPUs and PCI
+	// devices on the system. See arch_probe_nr_irqs.
+	//
+	// Since we don't report real interrupt stats, just choose an arbitrary
+	// value from a representative VM.
+	const numInterrupts = 256
+
+	// The Kernel doesn't handle real interrupts, so report all zeroes.
+	// TODO(b/37226836): We could count page faults as #PF.
+	fmt.Fprintf(buf, "intr 0") // total
+	for i := 0; i < numInterrupts; i++ {
+		fmt.Fprintf(buf, " 0")
+	}
+	fmt.Fprintf(buf, "\n")
+
+	// Total number of context switches.
+	// TODO(b/37226836): Count this.
+	fmt.Fprintf(buf, "ctxt 0\n")
+
+	// CLOCK_REALTIME timestamp from boot, in seconds.
+	fmt.Fprintf(buf, "btime %d\n", s.k.Timekeeper().BootTime().Seconds())
+
+	// Total number of clones.
+	// TODO(b/37226836): Count this.
+	fmt.Fprintf(buf, "processes 0\n")
+
+	// Number of runnable tasks.
+	// TODO(b/37226836): Count this.
+	fmt.Fprintf(buf, "procs_running 0\n")
+
+	// Number of tasks waiting on IO.
+	// TODO(b/37226836): Count this.
+	fmt.Fprintf(buf, "procs_blocked 0\n")
+
+	// Number of each softirq handled.
+	fmt.Fprintf(buf, "softirq 0") // total
+	for i := 0; i < linux.NumSoftIRQ; i++ {
+		fmt.Fprintf(buf, " 0")
+	}
+	fmt.Fprintf(buf, "\n")
+	return nil
+}
+
+// loadavgData backs /proc/loadavg.
+//
+// +stateify savable
+type loadavgData struct {
+	kernfs.DynamicBytesFile
+}
+
+var _ dynamicInode = (*loadavgData)(nil)
+
+// Generate implements vfs.DynamicBytesSource.Generate.
+func (d *loadavgData) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	// TODO(b/62345059): Include real data in fields.
+	// Column 1-3: CPU and IO utilization of the last 1, 5, and 10 minute periods.
+	// Column 4-5: currently running processes and the total number of processes.
+	// Column 6: the last process ID used.
+	fmt.Fprintf(buf, "%.2f %.2f %.2f %d/%d %d\n", 0.00, 0.00, 0.00, 0, 0, 0)
+	return nil
+}
+
+// meminfoData implements vfs.DynamicBytesSource for /proc/meminfo.
+//
+// +stateify savable
+type meminfoData struct {
+	kernfs.DynamicBytesFile
+
+	// k is the owning Kernel.
+	k *kernel.Kernel
+}
+
+var _ dynamicInode = (*meminfoData)(nil)
+
+// Generate implements vfs.DynamicBytesSource.Generate.
+func (d *meminfoData) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	mf := d.k.MemoryFile()
+	mf.UpdateUsage()
+	snapshot, totalUsage := usage.MemoryAccounting.Copy()
+	totalSize := usage.TotalMemory(mf.TotalSize(), totalUsage)
+	anon := snapshot.Anonymous + snapshot.Tmpfs
+	file := snapshot.PageCache + snapshot.Mapped
+	// We don't actually have active/inactive LRUs, so just make up numbers.
+	activeFile := (file / 2) &^ (usermem.PageSize - 1)
+	inactiveFile := file - activeFile
+
+	fmt.Fprintf(buf, "MemTotal:       %8d kB\n", totalSize/1024)
+	memFree := (totalSize - totalUsage) / 1024
+	// We use MemFree as MemAvailable because we don't swap.
+	// TODO(rahat): When reclaim is implemented the value of MemAvailable
+	// should change.
+	fmt.Fprintf(buf, "MemFree:        %8d kB\n", memFree)
+	fmt.Fprintf(buf, "MemAvailable:   %8d kB\n", memFree)
+	fmt.Fprintf(buf, "Buffers:               0 kB\n") // memory usage by block devices
+	fmt.Fprintf(buf, "Cached:         %8d kB\n", (file+snapshot.Tmpfs)/1024)
+	// Emulate a system with no swap, which disables inactivation of anon pages.
+	fmt.Fprintf(buf, "SwapCache:             0 kB\n")
+	fmt.Fprintf(buf, "Active:         %8d kB\n", (anon+activeFile)/1024)
+	fmt.Fprintf(buf, "Inactive:       %8d kB\n", inactiveFile/1024)
+	fmt.Fprintf(buf, "Active(anon):   %8d kB\n", anon/1024)
+	fmt.Fprintf(buf, "Inactive(anon):        0 kB\n")
+	fmt.Fprintf(buf, "Active(file):   %8d kB\n", activeFile/1024)
+	fmt.Fprintf(buf, "Inactive(file): %8d kB\n", inactiveFile/1024)
+	fmt.Fprintf(buf, "Unevictable:           0 kB\n") // TODO(b/31823263)
+	fmt.Fprintf(buf, "Mlocked:               0 kB\n") // TODO(b/31823263)
+	fmt.Fprintf(buf, "SwapTotal:             0 kB\n")
+	fmt.Fprintf(buf, "SwapFree:              0 kB\n")
+	fmt.Fprintf(buf, "Dirty:                 0 kB\n")
+	fmt.Fprintf(buf, "Writeback:             0 kB\n")
+	fmt.Fprintf(buf, "AnonPages:      %8d kB\n", anon/1024)
+	fmt.Fprintf(buf, "Mapped:         %8d kB\n", file/1024) // doesn't count mapped tmpfs, which we don't know
+	fmt.Fprintf(buf, "Shmem:          %8d kB\n", snapshot.Tmpfs/1024)
+	return nil
+}
+
+// uptimeData implements vfs.DynamicBytesSource for /proc/uptime.
+//
+// +stateify savable
+type uptimeData struct {
+	kernfs.DynamicBytesFile
+}
+
+var _ dynamicInode = (*uptimeData)(nil)
+
+// Generate implements vfs.DynamicBytesSource.Generate.
+func (*uptimeData) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	k := kernel.KernelFromContext(ctx)
+	now := time.NowFromContext(ctx)
+
+	// Pretend that we've spent zero time sleeping (second number).
+	fmt.Fprintf(buf, "%.2f 0.00\n", now.Sub(k.Timekeeper().BootTime()).Seconds())
+	return nil
+}
+
+// versionData implements vfs.DynamicBytesSource for /proc/version.
+//
+// +stateify savable
+type versionData struct {
+	kernfs.DynamicBytesFile
+
+	// k is the owning Kernel.
+	k *kernel.Kernel
+}
+
+var _ dynamicInode = (*versionData)(nil)
+
+// Generate implements vfs.DynamicBytesSource.Generate.
+func (v *versionData) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	init := v.k.GlobalInit()
+	if init == nil {
+		// Attempted to read before the init Task is created. This can
+		// only occur during startup, which should never need to read
+		// this file.
+		panic("Attempted to read version before initial Task is available")
+	}
+
+	// /proc/version takes the form:
+	//
+	// "SYSNAME version RELEASE (COMPILE_USER@COMPILE_HOST)
+	// (COMPILER_VERSION) VERSION"
+	//
+	// where:
+	// - SYSNAME, RELEASE, and VERSION are the same as returned by
+	// sys_utsname
+	// - COMPILE_USER is the user that build the kernel
+	// - COMPILE_HOST is the hostname of the machine on which the kernel
+	// was built
+	// - COMPILER_VERSION is the version reported by the building compiler
+	//
+	// Since we don't really want to expose build information to
+	// applications, those fields are omitted.
+	//
+	// FIXME(mpratt): Using Version from the init task SyscallTable
+	// disregards the different version a task may have (e.g., in a uts
+	// namespace).
+	ver := init.Leader().SyscallTable().Version
+	fmt.Fprintf(buf, "%s version %s %s\n", ver.Sysname, ver.Release, ver.Version)
+	return nil
+}
diff --git a/pkg/sentry/fsimpl/proc/tasks_net.go b/pkg/sentry/fsimpl/proc/tasks_net.go
new file mode 100644
index 000000000..3dbf3ba41
--- /dev/null
+++ b/pkg/sentry/fsimpl/proc/tasks_net.go
@@ -0,0 +1,784 @@
+// 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 proc
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"reflect"
+	"time"
+
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/log"
+	"gvisor.dev/gvisor/pkg/sentry/context"
+	"gvisor.dev/gvisor/pkg/sentry/fs"
+	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
+	"gvisor.dev/gvisor/pkg/sentry/inet"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/socket"
+	"gvisor.dev/gvisor/pkg/sentry/socket/unix"
+	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
+	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/syserror"
+	"gvisor.dev/gvisor/pkg/tcpip/header"
+)
+
+func newNetDir(root *auth.Credentials, inoGen InoGenerator, k *kernel.Kernel) *kernfs.Dentry {
+	var contents map[string]*kernfs.Dentry
+	if stack := k.NetworkStack(); stack != nil {
+		const (
+			arp       = "IP address       HW type     Flags       HW address            Mask     Device"
+			netlink   = "sk       Eth Pid    Groups   Rmem     Wmem     Dump     Locks     Drops     Inode"
+			packet    = "sk       RefCnt Type Proto  Iface R Rmem   User   Inode"
+			protocols = "protocol  size sockets  memory press maxhdr  slab module     cl co di ac io in de sh ss gs se re sp bi br ha uh gp em"
+			ptype     = "Type Device      Function"
+			upd6      = "  sl  local_address                         remote_address                        st tx_queue rx_queue tr tm->when retrnsmt   uid  timeout inode"
+		)
+		psched := fmt.Sprintf("%08x %08x %08x %08x\n", uint64(time.Microsecond/time.Nanosecond), 64, 1000000, uint64(time.Second/time.Nanosecond))
+
+		contents = map[string]*kernfs.Dentry{
+			"dev":  newDentry(root, inoGen.NextIno(), 0444, &netDevData{stack: stack}),
+			"snmp": newDentry(root, inoGen.NextIno(), 0444, &netSnmpData{stack: stack}),
+
+			// The following files are simple stubs until they are implemented in
+			// netstack, if the file contains a header the stub is just the header
+			// otherwise it is an empty file.
+			"arp":       newDentry(root, inoGen.NextIno(), 0444, newStaticFile(arp)),
+			"netlink":   newDentry(root, inoGen.NextIno(), 0444, newStaticFile(netlink)),
+			"netstat":   newDentry(root, inoGen.NextIno(), 0444, &netStatData{}),
+			"packet":    newDentry(root, inoGen.NextIno(), 0444, newStaticFile(packet)),
+			"protocols": newDentry(root, inoGen.NextIno(), 0444, newStaticFile(protocols)),
+
+			// Linux sets psched values to: nsec per usec, psched tick in ns, 1000000,
+			// high res timer ticks per sec (ClockGetres returns 1ns resolution).
+			"psched": newDentry(root, inoGen.NextIno(), 0444, newStaticFile(psched)),
+			"ptype":  newDentry(root, inoGen.NextIno(), 0444, newStaticFile(ptype)),
+			"route":  newDentry(root, inoGen.NextIno(), 0444, &netRouteData{stack: stack}),
+			"tcp":    newDentry(root, inoGen.NextIno(), 0444, &netTCPData{kernel: k}),
+			"udp":    newDentry(root, inoGen.NextIno(), 0444, &netUDPData{kernel: k}),
+			"unix":   newDentry(root, inoGen.NextIno(), 0444, &netUnixData{kernel: k}),
+		}
+
+		if stack.SupportsIPv6() {
+			contents["if_inet6"] = newDentry(root, inoGen.NextIno(), 0444, &ifinet6{stack: stack})
+			contents["ipv6_route"] = newDentry(root, inoGen.NextIno(), 0444, newStaticFile(""))
+			contents["tcp6"] = newDentry(root, inoGen.NextIno(), 0444, &netTCP6Data{kernel: k})
+			contents["udp6"] = newDentry(root, inoGen.NextIno(), 0444, newStaticFile(upd6))
+		}
+	}
+
+	return kernfs.NewStaticDir(root, inoGen.NextIno(), 0555, contents)
+}
+
+// ifinet6 implements vfs.DynamicBytesSource for /proc/net/if_inet6.
+//
+// +stateify savable
+type ifinet6 struct {
+	kernfs.DynamicBytesFile
+
+	stack inet.Stack
+}
+
+var _ dynamicInode = (*ifinet6)(nil)
+
+func (n *ifinet6) contents() []string {
+	var lines []string
+	nics := n.stack.Interfaces()
+	for id, naddrs := range n.stack.InterfaceAddrs() {
+		nic, ok := nics[id]
+		if !ok {
+			// NIC was added after NICNames was called. We'll just ignore it.
+			continue
+		}
+
+		for _, a := range naddrs {
+			// IPv6 only.
+			if a.Family != linux.AF_INET6 {
+				continue
+			}
+
+			// Fields:
+			// IPv6 address displayed in 32 hexadecimal chars without colons
+			// Netlink device number (interface index) in hexadecimal (use nic id)
+			// Prefix length in hexadecimal
+			// Scope value (use 0)
+			// Interface flags
+			// Device name
+			lines = append(lines, fmt.Sprintf("%032x %02x %02x %02x %02x %8s\n", a.Addr, id, a.PrefixLen, 0, a.Flags, nic.Name))
+		}
+	}
+	return lines
+}
+
+// Generate implements vfs.DynamicBytesSource.Generate.
+func (n *ifinet6) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	for _, l := range n.contents() {
+		buf.WriteString(l)
+	}
+	return nil
+}
+
+// netDevData implements vfs.DynamicBytesSource for /proc/net/dev.
+//
+// +stateify savable
+type netDevData struct {
+	kernfs.DynamicBytesFile
+
+	stack inet.Stack
+}
+
+var _ dynamicInode = (*netDevData)(nil)
+
+// Generate implements vfs.DynamicBytesSource.Generate.
+func (n *netDevData) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	interfaces := n.stack.Interfaces()
+	buf.WriteString("Inter-|   Receive                                                |  Transmit\n")
+	buf.WriteString(" face |bytes    packets errs drop fifo frame compressed multicast|bytes    packets errs drop fifo colls carrier compressed\n")
+
+	for _, i := range interfaces {
+		// Implements the same format as
+		// net/core/net-procfs.c:dev_seq_printf_stats.
+		var stats inet.StatDev
+		if err := n.stack.Statistics(&stats, i.Name); err != nil {
+			log.Warningf("Failed to retrieve interface statistics for %v: %v", i.Name, err)
+			continue
+		}
+		fmt.Fprintf(
+			buf,
+			"%6s: %7d %7d %4d %4d %4d %5d %10d %9d %8d %7d %4d %4d %4d %5d %7d %10d\n",
+			i.Name,
+			// Received
+			stats[0], // bytes
+			stats[1], // packets
+			stats[2], // errors
+			stats[3], // dropped
+			stats[4], // fifo
+			stats[5], // frame
+			stats[6], // compressed
+			stats[7], // multicast
+			// Transmitted
+			stats[8],  // bytes
+			stats[9],  // packets
+			stats[10], // errors
+			stats[11], // dropped
+			stats[12], // fifo
+			stats[13], // frame
+			stats[14], // compressed
+			stats[15], // multicast
+		)
+	}
+
+	return nil
+}
+
+// netUnixData implements vfs.DynamicBytesSource for /proc/net/unix.
+//
+// +stateify savable
+type netUnixData struct {
+	kernfs.DynamicBytesFile
+
+	kernel *kernel.Kernel
+}
+
+var _ dynamicInode = (*netUnixData)(nil)
+
+// Generate implements vfs.DynamicBytesSource.Generate.
+func (n *netUnixData) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	buf.WriteString("Num       RefCount Protocol Flags    Type St Inode Path\n")
+	for _, se := range n.kernel.ListSockets() {
+		s := se.Sock.Get()
+		if s == nil {
+			log.Debugf("Couldn't resolve weakref %v in socket table, racing with destruction?", se.Sock)
+			continue
+		}
+		sfile := s.(*fs.File)
+		if family, _, _ := sfile.FileOperations.(socket.Socket).Type(); family != linux.AF_UNIX {
+			s.DecRef()
+			// Not a unix socket.
+			continue
+		}
+		sops := sfile.FileOperations.(*unix.SocketOperations)
+
+		addr, err := sops.Endpoint().GetLocalAddress()
+		if err != nil {
+			log.Warningf("Failed to retrieve socket name from %+v: %v", sfile, err)
+			addr.Addr = "<unknown>"
+		}
+
+		sockFlags := 0
+		if ce, ok := sops.Endpoint().(transport.ConnectingEndpoint); ok {
+			if ce.Listening() {
+				// For unix domain sockets, linux reports a single flag
+				// value if the socket is listening, of __SO_ACCEPTCON.
+				sockFlags = linux.SO_ACCEPTCON
+			}
+		}
+
+		// In the socket entry below, the value for the 'Num' field requires
+		// some consideration. Linux prints the address to the struct
+		// unix_sock representing a socket in the kernel, but may redact the
+		// value for unprivileged users depending on the kptr_restrict
+		// sysctl.
+		//
+		// One use for this field is to allow a privileged user to
+		// introspect into the kernel memory to determine information about
+		// a socket not available through procfs, such as the socket's peer.
+		//
+		// In gvisor, returning a pointer to our internal structures would
+		// be pointless, as it wouldn't match the memory layout for struct
+		// unix_sock, making introspection difficult. We could populate a
+		// struct unix_sock with the appropriate data, but even that
+		// requires consideration for which kernel version to emulate, as
+		// the definition of this struct changes over time.
+		//
+		// For now, we always redact this pointer.
+		fmt.Fprintf(buf, "%#016p: %08X %08X %08X %04X %02X %5d",
+			(*unix.SocketOperations)(nil), // Num, pointer to kernel socket struct.
+			sfile.ReadRefs()-1,            // RefCount, don't count our own ref.
+			0,                             // Protocol, always 0 for UDS.
+			sockFlags,                     // Flags.
+			sops.Endpoint().Type(),        // Type.
+			sops.State(),                  // State.
+			sfile.InodeID(),               // Inode.
+		)
+
+		// Path
+		if len(addr.Addr) != 0 {
+			if addr.Addr[0] == 0 {
+				// Abstract path.
+				fmt.Fprintf(buf, " @%s", string(addr.Addr[1:]))
+			} else {
+				fmt.Fprintf(buf, " %s", string(addr.Addr))
+			}
+		}
+		fmt.Fprintf(buf, "\n")
+
+		s.DecRef()
+	}
+	return nil
+}
+
+func networkToHost16(n uint16) uint16 {
+	// n is in network byte order, so is big-endian. The most-significant byte
+	// should be stored in the lower address.
+	//
+	// We manually inline binary.BigEndian.Uint16() because Go does not support
+	// non-primitive consts, so binary.BigEndian is a (mutable) var, so calls to
+	// binary.BigEndian.Uint16() require a read of binary.BigEndian and an
+	// interface method call, defeating inlining.
+	buf := [2]byte{byte(n >> 8 & 0xff), byte(n & 0xff)}
+	return usermem.ByteOrder.Uint16(buf[:])
+}
+
+func writeInetAddr(w io.Writer, family int, i linux.SockAddr) {
+	switch family {
+	case linux.AF_INET:
+		var a linux.SockAddrInet
+		if i != nil {
+			a = *i.(*linux.SockAddrInet)
+		}
+
+		// linux.SockAddrInet.Port is stored in the network byte order and is
+		// printed like a number in host byte order. Note that all numbers in host
+		// byte order are printed with the most-significant byte first when
+		// formatted with %X. See get_tcp4_sock() and udp4_format_sock() in Linux.
+		port := networkToHost16(a.Port)
+
+		// linux.SockAddrInet.Addr is stored as a byte slice in big-endian order
+		// (i.e. most-significant byte in index 0). Linux represents this as a
+		// __be32 which is a typedef for an unsigned int, and is printed with
+		// %X. This means that for a little-endian machine, Linux prints the
+		// least-significant byte of the address first. To emulate this, we first
+		// invert the byte order for the address using usermem.ByteOrder.Uint32,
+		// which makes it have the equivalent encoding to a __be32 on a little
+		// endian machine. Note that this operation is a no-op on a big endian
+		// machine. Then similar to Linux, we format it with %X, which will print
+		// the most-significant byte of the __be32 address first, which is now
+		// actually the least-significant byte of the original address in
+		// linux.SockAddrInet.Addr on little endian machines, due to the conversion.
+		addr := usermem.ByteOrder.Uint32(a.Addr[:])
+
+		fmt.Fprintf(w, "%08X:%04X ", addr, port)
+	case linux.AF_INET6:
+		var a linux.SockAddrInet6
+		if i != nil {
+			a = *i.(*linux.SockAddrInet6)
+		}
+
+		port := networkToHost16(a.Port)
+		addr0 := usermem.ByteOrder.Uint32(a.Addr[0:4])
+		addr1 := usermem.ByteOrder.Uint32(a.Addr[4:8])
+		addr2 := usermem.ByteOrder.Uint32(a.Addr[8:12])
+		addr3 := usermem.ByteOrder.Uint32(a.Addr[12:16])
+		fmt.Fprintf(w, "%08X%08X%08X%08X:%04X ", addr0, addr1, addr2, addr3, port)
+	}
+}
+
+func commonGenerateTCP(ctx context.Context, buf *bytes.Buffer, k *kernel.Kernel, family int) error {
+	// t may be nil here if our caller is not part of a task goroutine. This can
+	// happen for example if we're here for "sentryctl cat". When t is nil,
+	// degrade gracefully and retrieve what we can.
+	t := kernel.TaskFromContext(ctx)
+
+	for _, se := range k.ListSockets() {
+		s := se.Sock.Get()
+		if s == nil {
+			log.Debugf("Couldn't resolve weakref with ID %v in socket table, racing with destruction?", se.ID)
+			continue
+		}
+		sfile := s.(*fs.File)
+		sops, ok := sfile.FileOperations.(socket.Socket)
+		if !ok {
+			panic(fmt.Sprintf("Found non-socket file in socket table: %+v", sfile))
+		}
+		if fa, stype, _ := sops.Type(); !(family == fa && stype == linux.SOCK_STREAM) {
+			s.DecRef()
+			// Not tcp4 sockets.
+			continue
+		}
+
+		// Linux's documentation for the fields below can be found at
+		// https://www.kernel.org/doc/Documentation/networking/proc_net_tcp.txt.
+		// For Linux's implementation, see net/ipv4/tcp_ipv4.c:get_tcp4_sock().
+		// Note that the header doesn't contain labels for all the fields.
+
+		// Field: sl; entry number.
+		fmt.Fprintf(buf, "%4d: ", se.ID)
+
+		// Field: local_adddress.
+		var localAddr linux.SockAddr
+		if t != nil {
+			if local, _, err := sops.GetSockName(t); err == nil {
+				localAddr = local
+			}
+		}
+		writeInetAddr(buf, family, localAddr)
+
+		// Field: rem_address.
+		var remoteAddr linux.SockAddr
+		if t != nil {
+			if remote, _, err := sops.GetPeerName(t); err == nil {
+				remoteAddr = remote
+			}
+		}
+		writeInetAddr(buf, family, remoteAddr)
+
+		// Field: state; socket state.
+		fmt.Fprintf(buf, "%02X ", sops.State())
+
+		// Field: tx_queue, rx_queue; number of packets in the transmit and
+		// receive queue. Unimplemented.
+		fmt.Fprintf(buf, "%08X:%08X ", 0, 0)
+
+		// Field: tr, tm->when; timer active state and number of jiffies
+		// until timer expires. Unimplemented.
+		fmt.Fprintf(buf, "%02X:%08X ", 0, 0)
+
+		// Field: retrnsmt; number of unrecovered RTO timeouts.
+		// Unimplemented.
+		fmt.Fprintf(buf, "%08X ", 0)
+
+		// Field: uid.
+		uattr, err := sfile.Dirent.Inode.UnstableAttr(ctx)
+		if err != nil {
+			log.Warningf("Failed to retrieve unstable attr for socket file: %v", err)
+			fmt.Fprintf(buf, "%5d ", 0)
+		} else {
+			creds := auth.CredentialsFromContext(ctx)
+			fmt.Fprintf(buf, "%5d ", uint32(uattr.Owner.UID.In(creds.UserNamespace).OrOverflow()))
+		}
+
+		// Field: timeout; number of unanswered 0-window probes.
+		// Unimplemented.
+		fmt.Fprintf(buf, "%8d ", 0)
+
+		// Field: inode.
+		fmt.Fprintf(buf, "%8d ", sfile.InodeID())
+
+		// Field: refcount. Don't count the ref we obtain while deferencing
+		// the weakref to this socket.
+		fmt.Fprintf(buf, "%d ", sfile.ReadRefs()-1)
+
+		// Field: Socket struct address. Redacted due to the same reason as
+		// the 'Num' field in /proc/net/unix, see netUnix.ReadSeqFileData.
+		fmt.Fprintf(buf, "%#016p ", (*socket.Socket)(nil))
+
+		// Field: retransmit timeout. Unimplemented.
+		fmt.Fprintf(buf, "%d ", 0)
+
+		// Field: predicted tick of soft clock (delayed ACK control data).
+		// Unimplemented.
+		fmt.Fprintf(buf, "%d ", 0)
+
+		// Field: (ack.quick<<1)|ack.pingpong, Unimplemented.
+		fmt.Fprintf(buf, "%d ", 0)
+
+		// Field: sending congestion window, Unimplemented.
+		fmt.Fprintf(buf, "%d ", 0)
+
+		// Field: Slow start size threshold, -1 if threshold >= 0xFFFF.
+		// Unimplemented, report as large threshold.
+		fmt.Fprintf(buf, "%d", -1)
+
+		fmt.Fprintf(buf, "\n")
+
+		s.DecRef()
+	}
+
+	return nil
+}
+
+// netTCPData implements vfs.DynamicBytesSource for /proc/net/tcp.
+//
+// +stateify savable
+type netTCPData struct {
+	kernfs.DynamicBytesFile
+
+	kernel *kernel.Kernel
+}
+
+var _ dynamicInode = (*netTCPData)(nil)
+
+func (d *netTCPData) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	buf.WriteString("  sl  local_address rem_address   st tx_queue rx_queue tr tm->when retrnsmt   uid  timeout inode                                                     \n")
+	return commonGenerateTCP(ctx, buf, d.kernel, linux.AF_INET)
+}
+
+// netTCP6Data implements vfs.DynamicBytesSource for /proc/net/tcp6.
+//
+// +stateify savable
+type netTCP6Data struct {
+	kernfs.DynamicBytesFile
+
+	kernel *kernel.Kernel
+}
+
+var _ dynamicInode = (*netTCP6Data)(nil)
+
+func (d *netTCP6Data) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	buf.WriteString("  sl  local_address                         remote_address                        st tx_queue rx_queue tr tm->when retrnsmt   uid  timeout inode\n")
+	return commonGenerateTCP(ctx, buf, d.kernel, linux.AF_INET6)
+}
+
+// netUDPData implements vfs.DynamicBytesSource for /proc/net/udp.
+//
+// +stateify savable
+type netUDPData struct {
+	kernfs.DynamicBytesFile
+
+	kernel *kernel.Kernel
+}
+
+var _ dynamicInode = (*netUDPData)(nil)
+
+// Generate implements vfs.DynamicBytesSource.Generate.
+func (d *netUDPData) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	// t may be nil here if our caller is not part of a task goroutine. This can
+	// happen for example if we're here for "sentryctl cat". When t is nil,
+	// degrade gracefully and retrieve what we can.
+	t := kernel.TaskFromContext(ctx)
+
+	for _, se := range d.kernel.ListSockets() {
+		s := se.Sock.Get()
+		if s == nil {
+			log.Debugf("Couldn't resolve weakref with ID %v in socket table, racing with destruction?", se.ID)
+			continue
+		}
+		sfile := s.(*fs.File)
+		sops, ok := sfile.FileOperations.(socket.Socket)
+		if !ok {
+			panic(fmt.Sprintf("Found non-socket file in socket table: %+v", sfile))
+		}
+		if family, stype, _ := sops.Type(); family != linux.AF_INET || stype != linux.SOCK_DGRAM {
+			s.DecRef()
+			// Not udp4 socket.
+			continue
+		}
+
+		// For Linux's implementation, see net/ipv4/udp.c:udp4_format_sock().
+
+		// Field: sl; entry number.
+		fmt.Fprintf(buf, "%5d: ", se.ID)
+
+		// Field: local_adddress.
+		var localAddr linux.SockAddrInet
+		if t != nil {
+			if local, _, err := sops.GetSockName(t); err == nil {
+				localAddr = *local.(*linux.SockAddrInet)
+			}
+		}
+		writeInetAddr(buf, linux.AF_INET, &localAddr)
+
+		// Field: rem_address.
+		var remoteAddr linux.SockAddrInet
+		if t != nil {
+			if remote, _, err := sops.GetPeerName(t); err == nil {
+				remoteAddr = *remote.(*linux.SockAddrInet)
+			}
+		}
+		writeInetAddr(buf, linux.AF_INET, &remoteAddr)
+
+		// Field: state; socket state.
+		fmt.Fprintf(buf, "%02X ", sops.State())
+
+		// Field: tx_queue, rx_queue; number of packets in the transmit and
+		// receive queue. Unimplemented.
+		fmt.Fprintf(buf, "%08X:%08X ", 0, 0)
+
+		// Field: tr, tm->when. Always 0 for UDP.
+		fmt.Fprintf(buf, "%02X:%08X ", 0, 0)
+
+		// Field: retrnsmt. Always 0 for UDP.
+		fmt.Fprintf(buf, "%08X ", 0)
+
+		// Field: uid.
+		uattr, err := sfile.Dirent.Inode.UnstableAttr(ctx)
+		if err != nil {
+			log.Warningf("Failed to retrieve unstable attr for socket file: %v", err)
+			fmt.Fprintf(buf, "%5d ", 0)
+		} else {
+			creds := auth.CredentialsFromContext(ctx)
+			fmt.Fprintf(buf, "%5d ", uint32(uattr.Owner.UID.In(creds.UserNamespace).OrOverflow()))
+		}
+
+		// Field: timeout. Always 0 for UDP.
+		fmt.Fprintf(buf, "%8d ", 0)
+
+		// Field: inode.
+		fmt.Fprintf(buf, "%8d ", sfile.InodeID())
+
+		// Field: ref; reference count on the socket inode. Don't count the ref
+		// we obtain while deferencing the weakref to this socket.
+		fmt.Fprintf(buf, "%d ", sfile.ReadRefs()-1)
+
+		// Field: Socket struct address. Redacted due to the same reason as
+		// the 'Num' field in /proc/net/unix, see netUnix.ReadSeqFileData.
+		fmt.Fprintf(buf, "%#016p ", (*socket.Socket)(nil))
+
+		// Field: drops; number of dropped packets. Unimplemented.
+		fmt.Fprintf(buf, "%d", 0)
+
+		fmt.Fprintf(buf, "\n")
+
+		s.DecRef()
+	}
+	return nil
+}
+
+// netSnmpData implements vfs.DynamicBytesSource for /proc/net/snmp.
+//
+// +stateify savable
+type netSnmpData struct {
+	kernfs.DynamicBytesFile
+
+	stack inet.Stack
+}
+
+var _ dynamicInode = (*netSnmpData)(nil)
+
+type snmpLine struct {
+	prefix string
+	header string
+}
+
+var snmp = []snmpLine{
+	{
+		prefix: "Ip",
+		header: "Forwarding DefaultTTL InReceives InHdrErrors InAddrErrors ForwDatagrams InUnknownProtos InDiscards InDelivers OutRequests OutDiscards OutNoRoutes ReasmTimeout ReasmReqds ReasmOKs ReasmFails FragOKs FragFails FragCreates",
+	},
+	{
+		prefix: "Icmp",
+		header: "InMsgs InErrors InCsumErrors InDestUnreachs InTimeExcds InParmProbs InSrcQuenchs InRedirects InEchos InEchoReps InTimestamps InTimestampReps InAddrMasks InAddrMaskReps OutMsgs OutErrors OutDestUnreachs OutTimeExcds OutParmProbs OutSrcQuenchs OutRedirects OutEchos OutEchoReps OutTimestamps OutTimestampReps OutAddrMasks OutAddrMaskReps",
+	},
+	{
+		prefix: "IcmpMsg",
+	},
+	{
+		prefix: "Tcp",
+		header: "RtoAlgorithm RtoMin RtoMax MaxConn ActiveOpens PassiveOpens AttemptFails EstabResets CurrEstab InSegs OutSegs RetransSegs InErrs OutRsts InCsumErrors",
+	},
+	{
+		prefix: "Udp",
+		header: "InDatagrams NoPorts InErrors OutDatagrams RcvbufErrors SndbufErrors InCsumErrors IgnoredMulti",
+	},
+	{
+		prefix: "UdpLite",
+		header: "InDatagrams NoPorts InErrors OutDatagrams RcvbufErrors SndbufErrors InCsumErrors IgnoredMulti",
+	},
+}
+
+func toSlice(a interface{}) []uint64 {
+	v := reflect.Indirect(reflect.ValueOf(a))
+	return v.Slice(0, v.Len()).Interface().([]uint64)
+}
+
+func sprintSlice(s []uint64) string {
+	if len(s) == 0 {
+		return ""
+	}
+	r := fmt.Sprint(s)
+	return r[1 : len(r)-1] // Remove "[]" introduced by fmt of slice.
+}
+
+// Generate implements vfs.DynamicBytesSource.
+func (d *netSnmpData) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	types := []interface{}{
+		&inet.StatSNMPIP{},
+		&inet.StatSNMPICMP{},
+		nil, // TODO(gvisor.dev/issue/628): Support IcmpMsg stats.
+		&inet.StatSNMPTCP{},
+		&inet.StatSNMPUDP{},
+		&inet.StatSNMPUDPLite{},
+	}
+	for i, stat := range types {
+		line := snmp[i]
+		if stat == nil {
+			fmt.Fprintf(buf, "%s:\n", line.prefix)
+			fmt.Fprintf(buf, "%s:\n", line.prefix)
+			continue
+		}
+		if err := d.stack.Statistics(stat, line.prefix); err != nil {
+			if err == syserror.EOPNOTSUPP {
+				log.Infof("Failed to retrieve %s of /proc/net/snmp: %v", line.prefix, err)
+			} else {
+				log.Warningf("Failed to retrieve %s of /proc/net/snmp: %v", line.prefix, err)
+			}
+		}
+
+		fmt.Fprintf(buf, "%s: %s\n", line.prefix, line.header)
+
+		if line.prefix == "Tcp" {
+			tcp := stat.(*inet.StatSNMPTCP)
+			// "Tcp" needs special processing because MaxConn is signed. RFC 2012.
+			fmt.Sprintf("%s: %s %d %s\n", line.prefix, sprintSlice(tcp[:3]), int64(tcp[3]), sprintSlice(tcp[4:]))
+		} else {
+			fmt.Sprintf("%s: %s\n", line.prefix, sprintSlice(toSlice(stat)))
+		}
+	}
+	return nil
+}
+
+// netRouteData implements vfs.DynamicBytesSource for /proc/net/route.
+//
+// +stateify savable
+type netRouteData struct {
+	kernfs.DynamicBytesFile
+
+	stack inet.Stack
+}
+
+var _ dynamicInode = (*netRouteData)(nil)
+
+// Generate implements vfs.DynamicBytesSource.
+// See Linux's net/ipv4/fib_trie.c:fib_route_seq_show.
+func (d *netRouteData) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	fmt.Fprintf(buf, "%-127s\n", "Iface\tDestination\tGateway\tFlags\tRefCnt\tUse\tMetric\tMask\tMTU\tWindow\tIRTT")
+
+	interfaces := d.stack.Interfaces()
+	for _, rt := range d.stack.RouteTable() {
+		// /proc/net/route only includes ipv4 routes.
+		if rt.Family != linux.AF_INET {
+			continue
+		}
+
+		// /proc/net/route does not include broadcast or multicast routes.
+		if rt.Type == linux.RTN_BROADCAST || rt.Type == linux.RTN_MULTICAST {
+			continue
+		}
+
+		iface, ok := interfaces[rt.OutputInterface]
+		if !ok || iface.Name == "lo" {
+			continue
+		}
+
+		var (
+			gw     uint32
+			prefix uint32
+			flags  = linux.RTF_UP
+		)
+		if len(rt.GatewayAddr) == header.IPv4AddressSize {
+			flags |= linux.RTF_GATEWAY
+			gw = usermem.ByteOrder.Uint32(rt.GatewayAddr)
+		}
+		if len(rt.DstAddr) == header.IPv4AddressSize {
+			prefix = usermem.ByteOrder.Uint32(rt.DstAddr)
+		}
+		l := fmt.Sprintf(
+			"%s\t%08X\t%08X\t%04X\t%d\t%d\t%d\t%08X\t%d\t%d\t%d",
+			iface.Name,
+			prefix,
+			gw,
+			flags,
+			0, // RefCnt.
+			0, // Use.
+			0, // Metric.
+			(uint32(1)<<rt.DstLen)-1,
+			0, // MTU.
+			0, // Window.
+			0, // RTT.
+		)
+		fmt.Fprintf(buf, "%-127s\n", l)
+	}
+	return nil
+}
+
+// netStatData implements vfs.DynamicBytesSource for /proc/net/netstat.
+//
+// +stateify savable
+type netStatData struct {
+	kernfs.DynamicBytesFile
+
+	stack inet.Stack
+}
+
+var _ dynamicInode = (*netStatData)(nil)
+
+// Generate implements vfs.DynamicBytesSource.
+// See Linux's net/ipv4/fib_trie.c:fib_route_seq_show.
+func (d *netStatData) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	buf.WriteString("TcpExt: SyncookiesSent SyncookiesRecv SyncookiesFailed " +
+		"EmbryonicRsts PruneCalled RcvPruned OfoPruned OutOfWindowIcmps " +
+		"LockDroppedIcmps ArpFilter TW TWRecycled TWKilled PAWSPassive " +
+		"PAWSActive PAWSEstab DelayedACKs DelayedACKLocked DelayedACKLost " +
+		"ListenOverflows ListenDrops TCPPrequeued TCPDirectCopyFromBacklog " +
+		"TCPDirectCopyFromPrequeue TCPPrequeueDropped TCPHPHits TCPHPHitsToUser " +
+		"TCPPureAcks TCPHPAcks TCPRenoRecovery TCPSackRecovery TCPSACKReneging " +
+		"TCPFACKReorder TCPSACKReorder TCPRenoReorder TCPTSReorder TCPFullUndo " +
+		"TCPPartialUndo TCPDSACKUndo TCPLossUndo TCPLostRetransmit " +
+		"TCPRenoFailures TCPSackFailures TCPLossFailures TCPFastRetrans " +
+		"TCPForwardRetrans TCPSlowStartRetrans TCPTimeouts TCPLossProbes " +
+		"TCPLossProbeRecovery TCPRenoRecoveryFail TCPSackRecoveryFail " +
+		"TCPSchedulerFailed TCPRcvCollapsed TCPDSACKOldSent TCPDSACKOfoSent " +
+		"TCPDSACKRecv TCPDSACKOfoRecv TCPAbortOnData TCPAbortOnClose " +
+		"TCPAbortOnMemory TCPAbortOnTimeout TCPAbortOnLinger TCPAbortFailed " +
+		"TCPMemoryPressures TCPSACKDiscard TCPDSACKIgnoredOld " +
+		"TCPDSACKIgnoredNoUndo TCPSpuriousRTOs TCPMD5NotFound TCPMD5Unexpected " +
+		"TCPMD5Failure TCPSackShifted TCPSackMerged TCPSackShiftFallback " +
+		"TCPBacklogDrop TCPMinTTLDrop TCPDeferAcceptDrop IPReversePathFilter " +
+		"TCPTimeWaitOverflow TCPReqQFullDoCookies TCPReqQFullDrop TCPRetransFail " +
+		"TCPRcvCoalesce TCPOFOQueue TCPOFODrop TCPOFOMerge TCPChallengeACK " +
+		"TCPSYNChallenge TCPFastOpenActive TCPFastOpenActiveFail " +
+		"TCPFastOpenPassive TCPFastOpenPassiveFail TCPFastOpenListenOverflow " +
+		"TCPFastOpenCookieReqd TCPSpuriousRtxHostQueues BusyPollRxPackets " +
+		"TCPAutoCorking TCPFromZeroWindowAdv TCPToZeroWindowAdv " +
+		"TCPWantZeroWindowAdv TCPSynRetrans TCPOrigDataSent TCPHystartTrainDetect " +
+		"TCPHystartTrainCwnd TCPHystartDelayDetect TCPHystartDelayCwnd " +
+		"TCPACKSkippedSynRecv TCPACKSkippedPAWS TCPACKSkippedSeq " +
+		"TCPACKSkippedFinWait2 TCPACKSkippedTimeWait TCPACKSkippedChallenge " +
+		"TCPWinProbe TCPKeepAlive TCPMTUPFail TCPMTUPSuccess")
+	return nil
+}
diff --git a/pkg/sentry/fsimpl/proc/tasks_sys.go b/pkg/sentry/fsimpl/proc/tasks_sys.go
new file mode 100644
index 000000000..aabf2bf0c
--- /dev/null
+++ b/pkg/sentry/fsimpl/proc/tasks_sys.go
@@ -0,0 +1,143 @@
+// 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 proc
+
+import (
+	"bytes"
+	"fmt"
+
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sentry/context"
+	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+)
+
+// newSysDir returns the dentry corresponding to /proc/sys directory.
+func newSysDir(root *auth.Credentials, inoGen InoGenerator) *kernfs.Dentry {
+	return kernfs.NewStaticDir(root, inoGen.NextIno(), 0555, map[string]*kernfs.Dentry{
+		"kernel": kernfs.NewStaticDir(root, inoGen.NextIno(), 0555, map[string]*kernfs.Dentry{
+			"hostname": newDentry(root, inoGen.NextIno(), 0444, &hostnameData{}),
+			"shmall":   newDentry(root, inoGen.NextIno(), 0444, shmData(linux.SHMALL)),
+			"shmmax":   newDentry(root, inoGen.NextIno(), 0444, shmData(linux.SHMMAX)),
+			"shmmni":   newDentry(root, inoGen.NextIno(), 0444, shmData(linux.SHMMNI)),
+		}),
+		"vm": kernfs.NewStaticDir(root, inoGen.NextIno(), 0555, map[string]*kernfs.Dentry{
+			"mmap_min_addr":     newDentry(root, inoGen.NextIno(), 0444, &mmapMinAddrData{}),
+			"overcommit_memory": newDentry(root, inoGen.NextIno(), 0444, newStaticFile("0\n")),
+		}),
+		"net": newSysNetDir(root, inoGen),
+	})
+}
+
+// newSysNetDir returns the dentry corresponding to /proc/sys/net directory.
+func newSysNetDir(root *auth.Credentials, inoGen InoGenerator) *kernfs.Dentry {
+	return kernfs.NewStaticDir(root, inoGen.NextIno(), 0555, map[string]*kernfs.Dentry{
+		"net": kernfs.NewStaticDir(root, inoGen.NextIno(), 0555, map[string]*kernfs.Dentry{
+			"ipv4": kernfs.NewStaticDir(root, inoGen.NextIno(), 0555, map[string]*kernfs.Dentry{
+				// Add tcp_sack.
+				// TODO(gvisor.dev/issue/1195): tcp_sack allows write(2)
+				// "tcp_sack": newTCPSackInode(ctx, msrc, s),
+
+				// The following files are simple stubs until they are implemented in
+				// netstack, most of these files are configuration related. We use the
+				// value closest to the actual netstack behavior or any empty file, all
+				// of these files will have mode 0444 (read-only for all users).
+				"ip_local_port_range":     newDentry(root, inoGen.NextIno(), 0444, newStaticFile("16000   65535")),
+				"ip_local_reserved_ports": newDentry(root, inoGen.NextIno(), 0444, newStaticFile("")),
+				"ipfrag_time":             newDentry(root, inoGen.NextIno(), 0444, newStaticFile("30")),
+				"ip_nonlocal_bind":        newDentry(root, inoGen.NextIno(), 0444, newStaticFile("0")),
+				"ip_no_pmtu_disc":         newDentry(root, inoGen.NextIno(), 0444, newStaticFile("1")),
+
+				// tcp_allowed_congestion_control tell the user what they are able to
+				// do as an unprivledged process so we leave it empty.
+				"tcp_allowed_congestion_control":   newDentry(root, inoGen.NextIno(), 0444, newStaticFile("")),
+				"tcp_available_congestion_control": newDentry(root, inoGen.NextIno(), 0444, newStaticFile("reno")),
+				"tcp_congestion_control":           newDentry(root, inoGen.NextIno(), 0444, newStaticFile("reno")),
+
+				// Many of the following stub files are features netstack doesn't
+				// support. The unsupported features return "0" to indicate they are
+				// disabled.
+				"tcp_base_mss":              newDentry(root, inoGen.NextIno(), 0444, newStaticFile("1280")),
+				"tcp_dsack":                 newDentry(root, inoGen.NextIno(), 0444, newStaticFile("0")),
+				"tcp_early_retrans":         newDentry(root, inoGen.NextIno(), 0444, newStaticFile("0")),
+				"tcp_fack":                  newDentry(root, inoGen.NextIno(), 0444, newStaticFile("0")),
+				"tcp_fastopen":              newDentry(root, inoGen.NextIno(), 0444, newStaticFile("0")),
+				"tcp_fastopen_key":          newDentry(root, inoGen.NextIno(), 0444, newStaticFile("")),
+				"tcp_invalid_ratelimit":     newDentry(root, inoGen.NextIno(), 0444, newStaticFile("0")),
+				"tcp_keepalive_intvl":       newDentry(root, inoGen.NextIno(), 0444, newStaticFile("0")),
+				"tcp_keepalive_probes":      newDentry(root, inoGen.NextIno(), 0444, newStaticFile("0")),
+				"tcp_keepalive_time":        newDentry(root, inoGen.NextIno(), 0444, newStaticFile("7200")),
+				"tcp_mtu_probing":           newDentry(root, inoGen.NextIno(), 0444, newStaticFile("0")),
+				"tcp_no_metrics_save":       newDentry(root, inoGen.NextIno(), 0444, newStaticFile("1")),
+				"tcp_probe_interval":        newDentry(root, inoGen.NextIno(), 0444, newStaticFile("0")),
+				"tcp_probe_threshold":       newDentry(root, inoGen.NextIno(), 0444, newStaticFile("0")),
+				"tcp_retries1":              newDentry(root, inoGen.NextIno(), 0444, newStaticFile("3")),
+				"tcp_retries2":              newDentry(root, inoGen.NextIno(), 0444, newStaticFile("15")),
+				"tcp_rfc1337":               newDentry(root, inoGen.NextIno(), 0444, newStaticFile("1")),
+				"tcp_slow_start_after_idle": newDentry(root, inoGen.NextIno(), 0444, newStaticFile("1")),
+				"tcp_synack_retries":        newDentry(root, inoGen.NextIno(), 0444, newStaticFile("5")),
+				"tcp_syn_retries":           newDentry(root, inoGen.NextIno(), 0444, newStaticFile("3")),
+				"tcp_timestamps":            newDentry(root, inoGen.NextIno(), 0444, newStaticFile("1")),
+			}),
+			"core": kernfs.NewStaticDir(root, inoGen.NextIno(), 0555, map[string]*kernfs.Dentry{
+				"default_qdisc": newDentry(root, inoGen.NextIno(), 0444, newStaticFile("pfifo_fast")),
+				"message_burst": newDentry(root, inoGen.NextIno(), 0444, newStaticFile("10")),
+				"message_cost":  newDentry(root, inoGen.NextIno(), 0444, newStaticFile("5")),
+				"optmem_max":    newDentry(root, inoGen.NextIno(), 0444, newStaticFile("0")),
+				"rmem_default":  newDentry(root, inoGen.NextIno(), 0444, newStaticFile("212992")),
+				"rmem_max":      newDentry(root, inoGen.NextIno(), 0444, newStaticFile("212992")),
+				"somaxconn":     newDentry(root, inoGen.NextIno(), 0444, newStaticFile("128")),
+				"wmem_default":  newDentry(root, inoGen.NextIno(), 0444, newStaticFile("212992")),
+				"wmem_max":      newDentry(root, inoGen.NextIno(), 0444, newStaticFile("212992")),
+			}),
+		}),
+	})
+}
+
+// mmapMinAddrData implements vfs.DynamicBytesSource for
+// /proc/sys/vm/mmap_min_addr.
+//
+// +stateify savable
+type mmapMinAddrData struct {
+	kernfs.DynamicBytesFile
+
+	k *kernel.Kernel
+}
+
+var _ dynamicInode = (*mmapMinAddrData)(nil)
+
+// Generate implements vfs.DynamicBytesSource.Generate.
+func (d *mmapMinAddrData) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	fmt.Fprintf(buf, "%d\n", d.k.Platform.MinUserAddress())
+	return nil
+}
+
+// hostnameData implements vfs.DynamicBytesSource for /proc/sys/kernel/hostname.
+//
+// +stateify savable
+type hostnameData struct {
+	kernfs.DynamicBytesFile
+}
+
+var _ dynamicInode = (*hostnameData)(nil)
+
+// Generate implements vfs.DynamicBytesSource.Generate.
+func (*hostnameData) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	utsns := kernel.UTSNamespaceFromContext(ctx)
+	buf.WriteString(utsns.HostName())
+	buf.WriteString("\n")
+	return nil
+}
diff --git a/pkg/sentry/fsimpl/proc/net_test.go b/pkg/sentry/fsimpl/proc/tasks_sys_test.go
index 20a77a8ca..0a1d3f34b 100644
--- a/pkg/sentry/fsimpl/proc/net_test.go
+++ b/pkg/sentry/fsimpl/proc/tasks_sys_test.go
@@ -31,7 +31,7 @@ func newIPv6TestStack() *inet.TestStack {
 }
 
 func TestIfinet6NoAddresses(t *testing.T) {
-	n := &ifinet6{s: newIPv6TestStack()}
+	n := &ifinet6{stack: newIPv6TestStack()}
 	var buf bytes.Buffer
 	n.Generate(contexttest.Context(t), &buf)
 	if buf.Len() > 0 {
@@ -62,7 +62,7 @@ func TestIfinet6(t *testing.T) {
 		"101112131415161718191a1b1c1d1e1f 02 80 00 00     eth1\n": {},
 	}
 
-	n := &ifinet6{s: s}
+	n := &ifinet6{stack: s}
 	contents := n.contents()
 	if len(contents) != len(want) {
 		t.Errorf("Got len(n.contents()) = %d, want = %d", len(contents), len(want))
diff --git a/pkg/sentry/fsimpl/proc/tasks_test.go b/pkg/sentry/fsimpl/proc/tasks_test.go
index ca8c87ec2..002d2f73b 100644
--- a/pkg/sentry/fsimpl/proc/tasks_test.go
+++ b/pkg/sentry/fsimpl/proc/tasks_test.go
@@ -69,12 +69,16 @@ func checkDots(dirs []vfs.Dirent) ([]vfs.Dirent, error) {
 
 func checkTasksStaticFiles(gots []vfs.Dirent) ([]vfs.Dirent, error) {
 	wants := map[string]vfs.Dirent{
+		"cpuinfo":     {Type: linux.DT_REG},
 		"loadavg":     {Type: linux.DT_REG},
 		"meminfo":     {Type: linux.DT_REG},
 		"mounts":      {Type: linux.DT_LNK},
+		"net":         {Type: linux.DT_DIR},
 		"self":        selfLink,
 		"stat":        {Type: linux.DT_REG},
+		"sys":         {Type: linux.DT_DIR},
 		"thread-self": threadSelfLink,
+		"uptime":      {Type: linux.DT_REG},
 		"version":     {Type: linux.DT_REG},
 	}
 	return checkFiles(gots, wants)
@@ -82,12 +86,21 @@ func checkTasksStaticFiles(gots []vfs.Dirent) ([]vfs.Dirent, error) {
 
 func checkTaskStaticFiles(gots []vfs.Dirent) ([]vfs.Dirent, error) {
 	wants := map[string]vfs.Dirent{
-		"io":     {Type: linux.DT_REG},
-		"maps":   {Type: linux.DT_REG},
-		"smaps":  {Type: linux.DT_REG},
-		"stat":   {Type: linux.DT_REG},
-		"statm":  {Type: linux.DT_REG},
-		"status": {Type: linux.DT_REG},
+		"auxv":    {Type: linux.DT_REG},
+		"cgroup":  {Type: linux.DT_REG},
+		"cmdline": {Type: linux.DT_REG},
+		"comm":    {Type: linux.DT_REG},
+		"environ": {Type: linux.DT_REG},
+		"gid_map": {Type: linux.DT_REG},
+		"io":      {Type: linux.DT_REG},
+		"maps":    {Type: linux.DT_REG},
+		"ns":      {Type: linux.DT_DIR},
+		"smaps":   {Type: linux.DT_REG},
+		"stat":    {Type: linux.DT_REG},
+		"statm":   {Type: linux.DT_REG},
+		"status":  {Type: linux.DT_REG},
+		"task":    {Type: linux.DT_DIR},
+		"uid_map": {Type: linux.DT_REG},
 	}
 	return checkFiles(gots, wants)
 }
@@ -133,7 +146,15 @@ func setup() (context.Context, *vfs.VirtualFilesystem, vfs.VirtualDentry, error)
 	vfsObj.MustRegisterFilesystemType("procfs", &procFSType{}, &vfs.RegisterFilesystemTypeOptions{
 		AllowUserMount: true,
 	})
-	mntns, err := vfsObj.NewMountNamespace(ctx, creds, "", "procfs", &vfs.GetFilesystemOptions{})
+	fsOpts := vfs.GetFilesystemOptions{
+		InternalData: &InternalData{
+			Cgroups: map[string]string{
+				"cpuset": "/foo/cpuset",
+				"memory": "/foo/memory",
+			},
+		},
+	}
+	mntns, err := vfsObj.NewMountNamespace(ctx, creds, "", "procfs", &fsOpts)
 	if err != nil {
 		return nil, nil, vfs.VirtualDentry{}, fmt.Errorf("NewMountNamespace(): %v", err)
 	}
diff --git a/pkg/sentry/fsimpl/proc/version.go b/pkg/sentry/fsimpl/proc/version.go
deleted file mode 100644
index 367f2396b..000000000
--- a/pkg/sentry/fsimpl/proc/version.go
+++ /dev/null
@@ -1,70 +0,0 @@
-// 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 proc
-
-import (
-	"bytes"
-	"fmt"
-
-	"gvisor.dev/gvisor/pkg/sentry/context"
-	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
-	"gvisor.dev/gvisor/pkg/sentry/kernel"
-)
-
-// versionData implements vfs.DynamicBytesSource for /proc/version.
-//
-// +stateify savable
-type versionData struct {
-	kernfs.DynamicBytesFile
-
-	// k is the owning Kernel.
-	k *kernel.Kernel
-}
-
-var _ dynamicInode = (*versionData)(nil)
-
-// Generate implements vfs.DynamicBytesSource.Generate.
-func (v *versionData) Generate(ctx context.Context, buf *bytes.Buffer) error {
-	init := v.k.GlobalInit()
-	if init == nil {
-		// Attempted to read before the init Task is created. This can
-		// only occur during startup, which should never need to read
-		// this file.
-		panic("Attempted to read version before initial Task is available")
-	}
-
-	// /proc/version takes the form:
-	//
-	// "SYSNAME version RELEASE (COMPILE_USER@COMPILE_HOST)
-	// (COMPILER_VERSION) VERSION"
-	//
-	// where:
-	// - SYSNAME, RELEASE, and VERSION are the same as returned by
-	// sys_utsname
-	// - COMPILE_USER is the user that build the kernel
-	// - COMPILE_HOST is the hostname of the machine on which the kernel
-	// was built
-	// - COMPILER_VERSION is the version reported by the building compiler
-	//
-	// Since we don't really want to expose build information to
-	// applications, those fields are omitted.
-	//
-	// FIXME(mpratt): Using Version from the init task SyscallTable
-	// disregards the different version a task may have (e.g., in a uts
-	// namespace).
-	ver := init.Leader().SyscallTable().Version
-	fmt.Fprintf(buf, "%s version %s %s\n", ver.Sysname, ver.Release, ver.Version)
-	return nil
-}
diff --git a/pkg/sentry/fsimpl/tmpfs/BUILD b/pkg/sentry/fsimpl/tmpfs/BUILD
index 82f5c2f41..7601c7c04 100644
--- a/pkg/sentry/fsimpl/tmpfs/BUILD
+++ b/pkg/sentry/fsimpl/tmpfs/BUILD
@@ -40,6 +40,7 @@ go_library(
         "//pkg/sentry/kernel",
         "//pkg/sentry/kernel/auth",
         "//pkg/sentry/kernel/pipe",
+        "//pkg/sentry/kernel/time",
         "//pkg/sentry/memmap",
         "//pkg/sentry/pgalloc",
         "//pkg/sentry/platform",
@@ -77,6 +78,7 @@ go_test(
     srcs = [
         "pipe_test.go",
         "regular_file_test.go",
+        "stat_test.go",
     ],
     embed = [":tmpfs"],
     deps = [
diff --git a/pkg/sentry/fsimpl/tmpfs/filesystem.go b/pkg/sentry/fsimpl/tmpfs/filesystem.go
index 26979729e..4cd7e9aea 100644
--- a/pkg/sentry/fsimpl/tmpfs/filesystem.go
+++ b/pkg/sentry/fsimpl/tmpfs/filesystem.go
@@ -56,7 +56,8 @@ afterSymlink:
 	}
 	next := nextVFSD.Impl().(*dentry)
 	if symlink, ok := next.inode.impl.(*symlink); ok && rp.ShouldFollowSymlink() {
-		// TODO: symlink traversals update access time
+		// TODO(gvisor.dev/issues/1197): Symlink traversals updates
+		// access time.
 		if err := rp.HandleSymlink(symlink.target); err != nil {
 			return nil, err
 		}
@@ -501,7 +502,8 @@ func (fs *filesystem) RenameAt(ctx context.Context, rp *vfs.ResolvingPath, oldPa
 		oldParent.inode.decLinksLocked()
 		newParent.inode.incLinksLocked()
 	}
-	// TODO: update timestamps and parent directory sizes
+	// TODO(gvisor.dev/issues/1197): Update timestamps and parent directory
+	// sizes.
 	vfsObj.CommitRenameReplaceDentry(renamedVFSD, &newParent.vfsd, newName, replacedVFSD)
 	return nil
 }
@@ -555,15 +557,11 @@ func (fs *filesystem) RmdirAt(ctx context.Context, rp *vfs.ResolvingPath) error
 func (fs *filesystem) SetStatAt(ctx context.Context, rp *vfs.ResolvingPath, opts vfs.SetStatOptions) error {
 	fs.mu.RLock()
 	defer fs.mu.RUnlock()
-	_, err := resolveLocked(rp)
+	d, err := resolveLocked(rp)
 	if err != nil {
 		return err
 	}
-	if opts.Stat.Mask == 0 {
-		return nil
-	}
-	// TODO: implement inode.setStat
-	return syserror.EPERM
+	return d.inode.setStat(opts.Stat)
 }
 
 // StatAt implements vfs.FilesystemImpl.StatAt.
@@ -587,7 +585,7 @@ func (fs *filesystem) StatFSAt(ctx context.Context, rp *vfs.ResolvingPath) (linu
 	if err != nil {
 		return linux.Statfs{}, err
 	}
-	// TODO: actually implement statfs
+	// TODO(gvisor.dev/issues/1197): Actually implement statfs.
 	return linux.Statfs{}, syserror.ENOSYS
 }
 
diff --git a/pkg/sentry/fsimpl/tmpfs/regular_file.go b/pkg/sentry/fsimpl/tmpfs/regular_file.go
index f200e767d..5fa70cc6d 100644
--- a/pkg/sentry/fsimpl/tmpfs/regular_file.go
+++ b/pkg/sentry/fsimpl/tmpfs/regular_file.go
@@ -63,6 +63,41 @@ func (fs *filesystem) newRegularFile(creds *auth.Credentials, mode linux.FileMod
 	return &file.inode
 }
 
+// truncate grows or shrinks the file to the given size. It returns true if the
+// file size was updated.
+func (rf *regularFile) truncate(size uint64) (bool, error) {
+	rf.mu.Lock()
+	defer rf.mu.Unlock()
+
+	if size == rf.size {
+		// Nothing to do.
+		return false, nil
+	}
+
+	if size > rf.size {
+		// Growing the file.
+		if rf.seals&linux.F_SEAL_GROW != 0 {
+			// Seal does not allow growth.
+			return false, syserror.EPERM
+		}
+		rf.size = size
+		return true, nil
+	}
+
+	// Shrinking the file
+	if rf.seals&linux.F_SEAL_SHRINK != 0 {
+		// Seal does not allow shrink.
+		return false, syserror.EPERM
+	}
+
+	// TODO(gvisor.dev/issues/1197): Invalidate mappings once we have
+	// mappings.
+
+	rf.data.Truncate(size, rf.memFile)
+	rf.size = size
+	return true, nil
+}
+
 type regularFileFD struct {
 	fileDescription
 
diff --git a/pkg/sentry/fsimpl/tmpfs/regular_file_test.go b/pkg/sentry/fsimpl/tmpfs/regular_file_test.go
index 3731c5b6f..034a29fdb 100644
--- a/pkg/sentry/fsimpl/tmpfs/regular_file_test.go
+++ b/pkg/sentry/fsimpl/tmpfs/regular_file_test.go
@@ -18,6 +18,7 @@ import (
 	"bytes"
 	"fmt"
 	"io"
+	"sync/atomic"
 	"testing"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
@@ -29,10 +30,12 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 )
 
-// newFileFD creates a new file in a new tmpfs mount, and returns the FD. If
-// the returned err is not nil, then cleanup should be called when the FD is no
-// longer needed.
-func newFileFD(ctx context.Context, filename string) (*vfs.FileDescription, func(), error) {
+// nextFileID is used to generate unique file names.
+var nextFileID int64
+
+// newTmpfsRoot creates a new tmpfs mount, and returns the root. If the error
+// is not nil, then cleanup should be called when the root is no longer needed.
+func newTmpfsRoot(ctx context.Context) (*vfs.VirtualFilesystem, vfs.VirtualDentry, func(), error) {
 	creds := auth.CredentialsFromContext(ctx)
 
 	vfsObj := vfs.New()
@@ -41,36 +44,124 @@ func newFileFD(ctx context.Context, filename string) (*vfs.FileDescription, func
 	})
 	mntns, err := vfsObj.NewMountNamespace(ctx, creds, "", "tmpfs", &vfs.GetFilesystemOptions{})
 	if err != nil {
-		return nil, nil, fmt.Errorf("failed to create tmpfs root mount: %v", err)
+		return nil, vfs.VirtualDentry{}, nil, fmt.Errorf("failed to create tmpfs root mount: %v", err)
 	}
 	root := mntns.Root()
+	return vfsObj, root, func() {
+		root.DecRef()
+		mntns.DecRef(vfsObj)
+	}, nil
+}
+
+// newFileFD creates a new file in a new tmpfs mount, and returns the FD. If
+// the returned err is not nil, then cleanup should be called when the FD is no
+// longer needed.
+func newFileFD(ctx context.Context, mode linux.FileMode) (*vfs.FileDescription, func(), error) {
+	creds := auth.CredentialsFromContext(ctx)
+	vfsObj, root, cleanup, err := newTmpfsRoot(ctx)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	filename := fmt.Sprintf("tmpfs-test-file-%d", atomic.AddInt64(&nextFileID, 1))
 
 	// Create the file that will be write/read.
 	fd, err := vfsObj.OpenAt(ctx, creds, &vfs.PathOperation{
-		Root:               root,
-		Start:              root,
-		Path:               fspath.Parse(filename),
-		FollowFinalSymlink: true,
+		Root:  root,
+		Start: root,
+		Path:  fspath.Parse(filename),
 	}, &vfs.OpenOptions{
 		Flags: linux.O_RDWR | linux.O_CREAT | linux.O_EXCL,
-		Mode:  0644,
+		Mode:  linux.ModeRegular | mode,
 	})
 	if err != nil {
-		root.DecRef()
-		mntns.DecRef(vfsObj)
+		cleanup()
 		return nil, nil, fmt.Errorf("failed to create file %q: %v", filename, err)
 	}
 
-	return fd, func() {
-		root.DecRef()
-		mntns.DecRef(vfsObj)
-	}, nil
+	return fd, cleanup, nil
+}
+
+// newDirFD is like newFileFD, but for directories.
+func newDirFD(ctx context.Context, mode linux.FileMode) (*vfs.FileDescription, func(), error) {
+	creds := auth.CredentialsFromContext(ctx)
+	vfsObj, root, cleanup, err := newTmpfsRoot(ctx)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	dirname := fmt.Sprintf("tmpfs-test-dir-%d", atomic.AddInt64(&nextFileID, 1))
+
+	// Create the dir.
+	if err := vfsObj.MkdirAt(ctx, creds, &vfs.PathOperation{
+		Root:  root,
+		Start: root,
+		Path:  fspath.Parse(dirname),
+	}, &vfs.MkdirOptions{
+		Mode: linux.ModeDirectory | mode,
+	}); err != nil {
+		cleanup()
+		return nil, nil, fmt.Errorf("failed to create directory %q: %v", dirname, err)
+	}
+
+	// Open the dir and return it.
+	fd, err := vfsObj.OpenAt(ctx, creds, &vfs.PathOperation{
+		Root:  root,
+		Start: root,
+		Path:  fspath.Parse(dirname),
+	}, &vfs.OpenOptions{
+		Flags: linux.O_RDONLY | linux.O_DIRECTORY,
+	})
+	if err != nil {
+		cleanup()
+		return nil, nil, fmt.Errorf("failed to open directory %q: %v", dirname, err)
+	}
+
+	return fd, cleanup, nil
+}
+
+// newPipeFD is like newFileFD, but for pipes.
+func newPipeFD(ctx context.Context, mode linux.FileMode) (*vfs.FileDescription, func(), error) {
+	creds := auth.CredentialsFromContext(ctx)
+	vfsObj, root, cleanup, err := newTmpfsRoot(ctx)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	pipename := fmt.Sprintf("tmpfs-test-pipe-%d", atomic.AddInt64(&nextFileID, 1))
+
+	// Create the pipe.
+	if err := vfsObj.MknodAt(ctx, creds, &vfs.PathOperation{
+		Root:  root,
+		Start: root,
+		Path:  fspath.Parse(pipename),
+	}, &vfs.MknodOptions{
+		Mode: linux.ModeNamedPipe | mode,
+	}); err != nil {
+		cleanup()
+		return nil, nil, fmt.Errorf("failed to create pipe %q: %v", pipename, err)
+	}
+
+	// Open the pipe and return it.
+	fd, err := vfsObj.OpenAt(ctx, creds, &vfs.PathOperation{
+		Root:  root,
+		Start: root,
+		Path:  fspath.Parse(pipename),
+	}, &vfs.OpenOptions{
+		Flags: linux.O_RDWR,
+	})
+	if err != nil {
+		cleanup()
+		return nil, nil, fmt.Errorf("failed to open pipe %q: %v", pipename, err)
+	}
+
+	return fd, cleanup, nil
 }
 
 // Test that we can write some data to a file and read it back.`
 func TestSimpleWriteRead(t *testing.T) {
 	ctx := contexttest.Context(t)
-	fd, cleanup, err := newFileFD(ctx, "simpleReadWrite")
+	fd, cleanup, err := newFileFD(ctx, 0644)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -116,7 +207,7 @@ func TestSimpleWriteRead(t *testing.T) {
 
 func TestPWrite(t *testing.T) {
 	ctx := contexttest.Context(t)
-	fd, cleanup, err := newFileFD(ctx, "PRead")
+	fd, cleanup, err := newFileFD(ctx, 0644)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -171,7 +262,7 @@ func TestPWrite(t *testing.T) {
 
 func TestPRead(t *testing.T) {
 	ctx := contexttest.Context(t)
-	fd, cleanup, err := newFileFD(ctx, "PRead")
+	fd, cleanup, err := newFileFD(ctx, 0644)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -222,3 +313,124 @@ func TestPRead(t *testing.T) {
 		}
 	}
 }
+
+func TestTruncate(t *testing.T) {
+	ctx := contexttest.Context(t)
+	fd, cleanup, err := newFileFD(ctx, 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer cleanup()
+
+	// Fill the file with some data.
+	data := bytes.Repeat([]byte("gVisor is awsome"), 100)
+	written, err := fd.Write(ctx, usermem.BytesIOSequence(data), vfs.WriteOptions{})
+	if err != nil {
+		t.Fatalf("fd.Write failed: %v", err)
+	}
+
+	// Size should be same as written.
+	sizeStatOpts := vfs.StatOptions{Mask: linux.STATX_SIZE}
+	stat, err := fd.Stat(ctx, sizeStatOpts)
+	if err != nil {
+		t.Fatalf("fd.Stat failed: %v", err)
+	}
+	if got, want := int64(stat.Size), written; got != want {
+		t.Errorf("fd.Stat got size %d, want %d", got, want)
+	}
+
+	// Truncate down.
+	newSize := uint64(10)
+	if err := fd.SetStat(ctx, vfs.SetStatOptions{
+		Stat: linux.Statx{
+			Mask: linux.STATX_SIZE,
+			Size: newSize,
+		},
+	}); err != nil {
+		t.Errorf("fd.Truncate failed: %v", err)
+	}
+	// Size should be updated.
+	statAfterTruncateDown, err := fd.Stat(ctx, sizeStatOpts)
+	if err != nil {
+		t.Fatalf("fd.Stat failed: %v", err)
+	}
+	if got, want := statAfterTruncateDown.Size, newSize; got != want {
+		t.Errorf("fd.Stat got size %d, want %d", got, want)
+	}
+	// We should only read newSize worth of data.
+	buf := make([]byte, 1000)
+	if n, err := fd.PRead(ctx, usermem.BytesIOSequence(buf), 0, vfs.ReadOptions{}); err != nil && err != io.EOF {
+		t.Fatalf("fd.PRead failed: %v", err)
+	} else if uint64(n) != newSize {
+		t.Errorf("fd.PRead got size %d, want %d", n, newSize)
+	}
+	// Mtime and Ctime should be bumped.
+	if got := statAfterTruncateDown.Mtime.ToNsec(); got <= stat.Mtime.ToNsec() {
+		t.Errorf("fd.Stat got Mtime %v, want > %v", got, stat.Mtime)
+	}
+	if got := statAfterTruncateDown.Ctime.ToNsec(); got <= stat.Ctime.ToNsec() {
+		t.Errorf("fd.Stat got Ctime %v, want > %v", got, stat.Ctime)
+	}
+
+	// Truncate up.
+	newSize = 100
+	if err := fd.SetStat(ctx, vfs.SetStatOptions{
+		Stat: linux.Statx{
+			Mask: linux.STATX_SIZE,
+			Size: newSize,
+		},
+	}); err != nil {
+		t.Errorf("fd.Truncate failed: %v", err)
+	}
+	// Size should be updated.
+	statAfterTruncateUp, err := fd.Stat(ctx, sizeStatOpts)
+	if err != nil {
+		t.Fatalf("fd.Stat failed: %v", err)
+	}
+	if got, want := statAfterTruncateUp.Size, newSize; got != want {
+		t.Errorf("fd.Stat got size %d, want %d", got, want)
+	}
+	// We should read newSize worth of data.
+	buf = make([]byte, 1000)
+	if n, err := fd.PRead(ctx, usermem.BytesIOSequence(buf), 0, vfs.ReadOptions{}); err != nil && err != io.EOF {
+		t.Fatalf("fd.PRead failed: %v", err)
+	} else if uint64(n) != newSize {
+		t.Errorf("fd.PRead got size %d, want %d", n, newSize)
+	}
+	// Bytes should be null after 10, since we previously truncated to 10.
+	for i := uint64(10); i < newSize; i++ {
+		if buf[i] != 0 {
+			t.Errorf("fd.PRead got byte %d=%x, want 0", i, buf[i])
+			break
+		}
+	}
+	// Mtime and Ctime should be bumped.
+	if got := statAfterTruncateUp.Mtime.ToNsec(); got <= statAfterTruncateDown.Mtime.ToNsec() {
+		t.Errorf("fd.Stat got Mtime %v, want > %v", got, statAfterTruncateDown.Mtime)
+	}
+	if got := statAfterTruncateUp.Ctime.ToNsec(); got <= statAfterTruncateDown.Ctime.ToNsec() {
+		t.Errorf("fd.Stat got Ctime %v, want > %v", got, stat.Ctime)
+	}
+
+	// Truncate to the current size.
+	newSize = statAfterTruncateUp.Size
+	if err := fd.SetStat(ctx, vfs.SetStatOptions{
+		Stat: linux.Statx{
+			Mask: linux.STATX_SIZE,
+			Size: newSize,
+		},
+	}); err != nil {
+		t.Errorf("fd.Truncate failed: %v", err)
+	}
+	statAfterTruncateNoop, err := fd.Stat(ctx, sizeStatOpts)
+	if err != nil {
+		t.Fatalf("fd.Stat failed: %v", err)
+	}
+	// Mtime and Ctime should not be bumped, since operation is a noop.
+	if got := statAfterTruncateNoop.Mtime.ToNsec(); got != statAfterTruncateUp.Mtime.ToNsec() {
+		t.Errorf("fd.Stat got Mtime %v, want %v", got, statAfterTruncateUp.Mtime)
+	}
+	if got := statAfterTruncateNoop.Ctime.ToNsec(); got != statAfterTruncateUp.Ctime.ToNsec() {
+		t.Errorf("fd.Stat got Ctime %v, want %v", got, statAfterTruncateUp.Ctime)
+	}
+}
diff --git a/pkg/sentry/fsimpl/tmpfs/stat_test.go b/pkg/sentry/fsimpl/tmpfs/stat_test.go
new file mode 100644
index 000000000..ebe035dee
--- /dev/null
+++ b/pkg/sentry/fsimpl/tmpfs/stat_test.go
@@ -0,0 +1,232 @@
+// Copyright 2020 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 tmpfs
+
+import (
+	"fmt"
+	"testing"
+
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/contexttest"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+)
+
+func TestStatAfterCreate(t *testing.T) {
+	ctx := contexttest.Context(t)
+	mode := linux.FileMode(0644)
+
+	// Run with different file types.
+	// TODO(gvisor.dev/issues/1197): Also test symlinks and sockets.
+	for _, typ := range []string{"file", "dir", "pipe"} {
+		t.Run(fmt.Sprintf("type=%q", typ), func(t *testing.T) {
+			var (
+				fd      *vfs.FileDescription
+				cleanup func()
+				err     error
+			)
+			switch typ {
+			case "file":
+				fd, cleanup, err = newFileFD(ctx, mode)
+			case "dir":
+				fd, cleanup, err = newDirFD(ctx, mode)
+			case "pipe":
+				fd, cleanup, err = newPipeFD(ctx, mode)
+			default:
+				panic(fmt.Sprintf("unknown typ %q", typ))
+			}
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer cleanup()
+
+			got, err := fd.Stat(ctx, vfs.StatOptions{})
+			if err != nil {
+				t.Fatalf("Stat failed: %v", err)
+			}
+
+			// Atime, Ctime, Mtime should all be current time (non-zero).
+			atime, ctime, mtime := got.Atime.ToNsec(), got.Ctime.ToNsec(), got.Mtime.ToNsec()
+			if atime != ctime || ctime != mtime {
+				t.Errorf("got atime=%d ctime=%d mtime=%d, wanted equal values", atime, ctime, mtime)
+			}
+			if atime == 0 {
+				t.Errorf("got atime=%d, want non-zero", atime)
+			}
+
+			// Btime should be 0, as it is not set by tmpfs.
+			if btime := got.Btime.ToNsec(); btime != 0 {
+				t.Errorf("got btime %d, want 0", got.Btime.ToNsec())
+			}
+
+			// Size should be 0.
+			if got.Size != 0 {
+				t.Errorf("got size %d, want 0", got.Size)
+			}
+
+			// Nlink should be 1 for files, 2 for dirs.
+			wantNlink := uint32(1)
+			if typ == "dir" {
+				wantNlink = 2
+			}
+			if got.Nlink != wantNlink {
+				t.Errorf("got nlink %d, want %d", got.Nlink, wantNlink)
+			}
+
+			// UID and GID are set from context creds.
+			creds := auth.CredentialsFromContext(ctx)
+			if got.UID != uint32(creds.EffectiveKUID) {
+				t.Errorf("got uid %d, want %d", got.UID, uint32(creds.EffectiveKUID))
+			}
+			if got.GID != uint32(creds.EffectiveKGID) {
+				t.Errorf("got gid %d, want %d", got.GID, uint32(creds.EffectiveKGID))
+			}
+
+			// Mode.
+			wantMode := uint16(mode)
+			switch typ {
+			case "file":
+				wantMode |= linux.S_IFREG
+			case "dir":
+				wantMode |= linux.S_IFDIR
+			case "pipe":
+				wantMode |= linux.S_IFIFO
+			default:
+				panic(fmt.Sprintf("unknown typ %q", typ))
+			}
+
+			if got.Mode != wantMode {
+				t.Errorf("got mode %x, want %x", got.Mode, wantMode)
+			}
+
+			// Ino.
+			if got.Ino == 0 {
+				t.Errorf("got ino %d, want not 0", got.Ino)
+			}
+		})
+	}
+}
+
+func TestSetStatAtime(t *testing.T) {
+	ctx := contexttest.Context(t)
+	fd, cleanup, err := newFileFD(ctx, 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer cleanup()
+
+	allStatOptions := vfs.StatOptions{Mask: linux.STATX_ALL}
+
+	// Get initial stat.
+	initialStat, err := fd.Stat(ctx, allStatOptions)
+	if err != nil {
+		t.Fatalf("Stat failed: %v", err)
+	}
+
+	// Set atime, but without the mask.
+	if err := fd.SetStat(ctx, vfs.SetStatOptions{Stat: linux.Statx{
+		Mask:  0,
+		Atime: linux.NsecToStatxTimestamp(100),
+	}}); err != nil {
+		t.Errorf("SetStat atime without mask failed: %v")
+	}
+	// Atime should be unchanged.
+	if gotStat, err := fd.Stat(ctx, allStatOptions); err != nil {
+		t.Errorf("Stat got error: %v", err)
+	} else if gotStat.Atime != initialStat.Atime {
+		t.Errorf("Stat got atime %d, want %d", gotStat.Atime, initialStat.Atime)
+	}
+
+	// Set atime, this time included in the mask.
+	setStat := linux.Statx{
+		Mask:  linux.STATX_ATIME,
+		Atime: linux.NsecToStatxTimestamp(100),
+	}
+	if err := fd.SetStat(ctx, vfs.SetStatOptions{Stat: setStat}); err != nil {
+		t.Errorf("SetStat atime with mask failed: %v")
+	}
+	if gotStat, err := fd.Stat(ctx, allStatOptions); err != nil {
+		t.Errorf("Stat got error: %v", err)
+	} else if gotStat.Atime != setStat.Atime {
+		t.Errorf("Stat got atime %d, want %d", gotStat.Atime, setStat.Atime)
+	}
+}
+
+func TestSetStat(t *testing.T) {
+	ctx := contexttest.Context(t)
+	mode := linux.FileMode(0644)
+
+	// Run with different file types.
+	// TODO(gvisor.dev/issues/1197): Also test symlinks and sockets.
+	for _, typ := range []string{"file", "dir", "pipe"} {
+		t.Run(fmt.Sprintf("type=%q", typ), func(t *testing.T) {
+			var (
+				fd      *vfs.FileDescription
+				cleanup func()
+				err     error
+			)
+			switch typ {
+			case "file":
+				fd, cleanup, err = newFileFD(ctx, mode)
+			case "dir":
+				fd, cleanup, err = newDirFD(ctx, mode)
+			case "pipe":
+				fd, cleanup, err = newPipeFD(ctx, mode)
+			default:
+				panic(fmt.Sprintf("unknown typ %q", typ))
+			}
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer cleanup()
+
+			allStatOptions := vfs.StatOptions{Mask: linux.STATX_ALL}
+
+			// Get initial stat.
+			initialStat, err := fd.Stat(ctx, allStatOptions)
+			if err != nil {
+				t.Fatalf("Stat failed: %v", err)
+			}
+
+			// Set atime, but without the mask.
+			if err := fd.SetStat(ctx, vfs.SetStatOptions{Stat: linux.Statx{
+				Mask:  0,
+				Atime: linux.NsecToStatxTimestamp(100),
+			}}); err != nil {
+				t.Errorf("SetStat atime without mask failed: %v")
+			}
+			// Atime should be unchanged.
+			if gotStat, err := fd.Stat(ctx, allStatOptions); err != nil {
+				t.Errorf("Stat got error: %v", err)
+			} else if gotStat.Atime != initialStat.Atime {
+				t.Errorf("Stat got atime %d, want %d", gotStat.Atime, initialStat.Atime)
+			}
+
+			// Set atime, this time included in the mask.
+			setStat := linux.Statx{
+				Mask:  linux.STATX_ATIME,
+				Atime: linux.NsecToStatxTimestamp(100),
+			}
+			if err := fd.SetStat(ctx, vfs.SetStatOptions{Stat: setStat}); err != nil {
+				t.Errorf("SetStat atime with mask failed: %v")
+			}
+			if gotStat, err := fd.Stat(ctx, allStatOptions); err != nil {
+				t.Errorf("Stat got error: %v", err)
+			} else if gotStat.Atime != setStat.Atime {
+				t.Errorf("Stat got atime %d, want %d", gotStat.Atime, setStat.Atime)
+			}
+		})
+	}
+}
diff --git a/pkg/sentry/fsimpl/tmpfs/tmpfs.go b/pkg/sentry/fsimpl/tmpfs/tmpfs.go
index 701826f90..1d4889c89 100644
--- a/pkg/sentry/fsimpl/tmpfs/tmpfs.go
+++ b/pkg/sentry/fsimpl/tmpfs/tmpfs.go
@@ -31,6 +31,7 @@ import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/context"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/pgalloc"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/sync"
@@ -47,6 +48,9 @@ type filesystem struct {
 	// memFile is used to allocate pages to for regular files.
 	memFile *pgalloc.MemoryFile
 
+	// clock is a realtime clock used to set timestamps in file operations.
+	clock time.Clock
+
 	// mu serializes changes to the Dentry tree.
 	mu sync.RWMutex
 
@@ -59,8 +63,10 @@ func (fstype FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.Virt
 	if memFileProvider == nil {
 		panic("MemoryFileProviderFromContext returned nil")
 	}
+	clock := time.RealtimeClockFromContext(ctx)
 	fs := filesystem{
 		memFile: memFileProvider.MemoryFile(),
+		clock:   clock,
 	}
 	fs.vfsfs.Init(vfsObj, &fs)
 	root := fs.newDentry(fs.newDirectory(creds, 01777))
@@ -116,6 +122,9 @@ func (d *dentry) DecRef() {
 
 // inode represents a filesystem object.
 type inode struct {
+	// clock is a realtime clock used to set timestamps in file operations.
+	clock time.Clock
+
 	// refs is a reference count. refs is accessed using atomic memory
 	// operations.
 	//
@@ -126,26 +135,37 @@ type inode struct {
 	// filesystem.RmdirAt() drops the reference.
 	refs int64
 
-	// Inode metadata; protected by mu and accessed using atomic memory
-	// operations unless otherwise specified.
-	mu    sync.RWMutex
+	// Inode metadata. Writing multiple fields atomically requires holding
+	// mu, othewise atomic operations can be used.
+	mu    sync.Mutex
 	mode  uint32 // excluding file type bits, which are based on impl
 	nlink uint32 // protected by filesystem.mu instead of inode.mu
 	uid   uint32 // auth.KUID, but stored as raw uint32 for sync/atomic
 	gid   uint32 // auth.KGID, but ...
 	ino   uint64 // immutable
 
+	// Linux's tmpfs has no concept of btime.
+	atime int64 // nanoseconds
+	ctime int64 // nanoseconds
+	mtime int64 // nanoseconds
+
 	impl interface{} // immutable
 }
 
 const maxLinks = math.MaxUint32
 
 func (i *inode) init(impl interface{}, fs *filesystem, creds *auth.Credentials, mode linux.FileMode) {
+	i.clock = fs.clock
 	i.refs = 1
 	i.mode = uint32(mode)
 	i.uid = uint32(creds.EffectiveKUID)
 	i.gid = uint32(creds.EffectiveKGID)
 	i.ino = atomic.AddUint64(&fs.nextInoMinusOne, 1)
+	// Tmpfs creation sets atime, ctime, and mtime to current time.
+	now := i.clock.Now().Nanoseconds()
+	i.atime = now
+	i.ctime = now
+	i.mtime = now
 	// i.nlink initialized by caller
 	i.impl = impl
 }
@@ -213,15 +233,24 @@ func (i *inode) checkPermissions(creds *auth.Credentials, ats vfs.AccessTypes, i
 // Go won't inline this function, and returning linux.Statx (which is quite
 // big) means spending a lot of time in runtime.duffcopy(), so instead it's an
 // output parameter.
+//
+// Note that Linux does not guarantee to return consistent data (in the case of
+// a concurrent modification), so we do not require holding inode.mu.
 func (i *inode) statTo(stat *linux.Statx) {
-	stat.Mask = linux.STATX_TYPE | linux.STATX_MODE | linux.STATX_NLINK | linux.STATX_UID | linux.STATX_GID | linux.STATX_INO
+	stat.Mask = linux.STATX_TYPE | linux.STATX_MODE | linux.STATX_NLINK |
+		linux.STATX_UID | linux.STATX_GID | linux.STATX_INO | linux.STATX_ATIME |
+		linux.STATX_BTIME | linux.STATX_CTIME | linux.STATX_MTIME
 	stat.Blksize = 1 // usermem.PageSize in tmpfs
 	stat.Nlink = atomic.LoadUint32(&i.nlink)
 	stat.UID = atomic.LoadUint32(&i.uid)
 	stat.GID = atomic.LoadUint32(&i.gid)
 	stat.Mode = uint16(atomic.LoadUint32(&i.mode))
 	stat.Ino = i.ino
-	// TODO: device number
+	// Linux's tmpfs has no concept of btime, so zero-value is returned.
+	stat.Atime = linux.NsecToStatxTimestamp(i.atime)
+	stat.Ctime = linux.NsecToStatxTimestamp(i.ctime)
+	stat.Mtime = linux.NsecToStatxTimestamp(i.mtime)
+	// TODO(gvisor.dev/issues/1197): Device number.
 	switch impl := i.impl.(type) {
 	case *regularFile:
 		stat.Mode |= linux.S_IFREG
@@ -245,6 +274,75 @@ func (i *inode) statTo(stat *linux.Statx) {
 	}
 }
 
+func (i *inode) setStat(stat linux.Statx) error {
+	if stat.Mask == 0 {
+		return nil
+	}
+	i.mu.Lock()
+	var (
+		needsMtimeBump bool
+		needsCtimeBump bool
+	)
+	mask := stat.Mask
+	if mask&linux.STATX_MODE != 0 {
+		atomic.StoreUint32(&i.mode, uint32(stat.Mode))
+		needsCtimeBump = true
+	}
+	if mask&linux.STATX_UID != 0 {
+		atomic.StoreUint32(&i.uid, stat.UID)
+		needsCtimeBump = true
+	}
+	if mask&linux.STATX_GID != 0 {
+		atomic.StoreUint32(&i.gid, stat.GID)
+		needsCtimeBump = true
+	}
+	if mask&linux.STATX_SIZE != 0 {
+		switch impl := i.impl.(type) {
+		case *regularFile:
+			updated, err := impl.truncate(stat.Size)
+			if err != nil {
+				return err
+			}
+			if updated {
+				needsMtimeBump = true
+				needsCtimeBump = true
+			}
+		case *directory:
+			return syserror.EISDIR
+		case *symlink:
+			return syserror.EINVAL
+		case *namedPipe:
+			// Nothing.
+		default:
+			panic(fmt.Sprintf("unknown inode type: %T", i.impl))
+		}
+	}
+	if mask&linux.STATX_ATIME != 0 {
+		atomic.StoreInt64(&i.atime, stat.Atime.ToNsecCapped())
+		needsCtimeBump = true
+	}
+	if mask&linux.STATX_MTIME != 0 {
+		atomic.StoreInt64(&i.mtime, stat.Mtime.ToNsecCapped())
+		needsCtimeBump = true
+		// Ignore the mtime bump, since we just set it ourselves.
+		needsMtimeBump = false
+	}
+	if mask&linux.STATX_CTIME != 0 {
+		atomic.StoreInt64(&i.ctime, stat.Ctime.ToNsecCapped())
+		// Ignore the ctime bump, since we just set it ourselves.
+		needsCtimeBump = false
+	}
+	now := i.clock.Now().Nanoseconds()
+	if needsMtimeBump {
+		atomic.StoreInt64(&i.mtime, now)
+	}
+	if needsCtimeBump {
+		atomic.StoreInt64(&i.ctime, now)
+	}
+	i.mu.Unlock()
+	return nil
+}
+
 // allocatedBlocksForSize returns the number of 512B blocks needed to
 // accommodate the given size in bytes, as appropriate for struct
 // stat::st_blocks and struct statx::stx_blocks. (Note that this 512B block
@@ -291,9 +389,5 @@ func (fd *fileDescription) Stat(ctx context.Context, opts vfs.StatOptions) (linu
 
 // SetStat implements vfs.FileDescriptionImpl.SetStat.
 func (fd *fileDescription) SetStat(ctx context.Context, opts vfs.SetStatOptions) error {
-	if opts.Stat.Mask == 0 {
-		return nil
-	}
-	// TODO: implement inode.setStat
-	return syserror.EPERM
+	return fd.inode().setStat(opts.Stat)
 }