2 files changed, 340 insertions, 0 deletions
diff --git a/pkg/sentry/fs/proc/seqfile/seqfile.go b/pkg/sentry/fs/proc/seqfile/seqfile.go
new file mode 100644
index 000000000..8364d86ed
--- /dev/null
+++ b/pkg/sentry/fs/proc/seqfile/seqfile.go
@@ -0,0 +1,282 @@
+// Copyright 2018 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package seqfile
+
+import (
+	"io"
+	"sync"
+
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/fsutil"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/proc/device"
+	ktime "gvisor.googlesource.com/gvisor/pkg/sentry/kernel/time"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+	"gvisor.googlesource.com/gvisor/pkg/syserror"
+	"gvisor.googlesource.com/gvisor/pkg/waiter"
+)
+
+// SeqHandle is a helper handle to seek in the file.
+type SeqHandle interface{}
+
+// SeqData holds the data for one unit in the file.
+//
+// +stateify savable
+type SeqData struct {
+	// The data to be returned to the user.
+	Buf []byte
+
+	// A seek handle used to find the next valid unit in ReadSeqFiledata.
+	Handle SeqHandle
+}
+
+// SeqSource is a data source for a SeqFile file.
+type SeqSource interface {
+	// NeedsUpdate returns true if the consumer of SeqData should call
+	// ReadSeqFileData again. Generation is the generation returned by
+	// ReadSeqFile or 0.
+	NeedsUpdate(generation int64) bool
+
+	// Returns a slice of SeqData ordered by unit and the current
+	// generation. The first entry in the slice is greater than the handle.
+	// If handle is nil then all known records are returned. Generation
+	// must always be greater than 0.
+	ReadSeqFileData(ctx context.Context, handle SeqHandle) ([]SeqData, int64)
+}
+
+// SeqGenerationCounter is a counter to keep track if the SeqSource should be
+// updated. SeqGenerationCounter is not thread-safe and should be protected
+// with a mutex.
+type SeqGenerationCounter struct {
+	// The generation that the SeqData is at.
+	generation int64
+}
+
+// SetGeneration sets the generation to the new value, be careful to not set it
+// to a value less than current.
+func (s *SeqGenerationCounter) SetGeneration(generation int64) {
+	s.generation = generation
+}
+
+// Update increments the current generation.
+func (s *SeqGenerationCounter) Update() {
+	s.generation++
+}
+
+// Generation returns the current generation counter.
+func (s *SeqGenerationCounter) Generation() int64 {
+	return s.generation
+}
+
+// IsCurrent returns whether the given generation is current or not.
+func (s *SeqGenerationCounter) IsCurrent(generation int64) bool {
+	return s.Generation() == generation
+}
+
+// SeqFile is used to provide dynamic files that can be ordered by record.
+//
+// +stateify savable
+type SeqFile struct {
+	fsutil.InodeGenericChecker `state:"nosave"`
+	fsutil.InodeNoopRelease    `state:"nosave"`
+	fsutil.InodeNoopWriteOut   `state:"nosave"`
+	fsutil.InodeNotAllocatable `state:"nosave"`
+	fsutil.InodeNotDirectory   `state:"nosave"`
+	fsutil.InodeNotMappable    `state:"nosave"`
+	fsutil.InodeNotSocket      `state:"nosave"`
+	fsutil.InodeNotSymlink     `state:"nosave"`
+	fsutil.InodeNotTruncatable `state:"nosave"`
+	fsutil.InodeVirtual        `state:"nosave"`
+
+	fsutil.InodeSimpleExtendedAttributes
+	fsutil.InodeSimpleAttributes
+
+	// mu protects the fields below.
+	mu sync.Mutex `state:"nosave"`
+
+	SeqSource
+
+	source     []SeqData
+	generation int64
+	lastRead   int64
+}
+
+var _ fs.InodeOperations = (*SeqFile)(nil)
+
+// NewSeqFile returns a seqfile suitable for use by external consumers.
+func NewSeqFile(ctx context.Context, source SeqSource) *SeqFile {
+	return &SeqFile{
+		InodeSimpleAttributes: fsutil.NewInodeSimpleAttributes(ctx, fs.RootOwner, fs.FilePermsFromMode(0444), linux.PROC_SUPER_MAGIC),
+		SeqSource:             source,
+	}
+}
+
+// NewSeqFileInode returns an Inode with SeqFile InodeOperations.
+func NewSeqFileInode(ctx context.Context, source SeqSource, msrc *fs.MountSource) *fs.Inode {
+	iops := NewSeqFile(ctx, source)
+	sattr := fs.StableAttr{
+		DeviceID:  device.ProcDevice.DeviceID(),
+		InodeID:   device.ProcDevice.NextIno(),
+		BlockSize: usermem.PageSize,
+		Type:      fs.SpecialFile,
+	}
+	return fs.NewInode(iops, msrc, sattr)
+}
+
+// UnstableAttr returns unstable attributes of the SeqFile.
+func (s *SeqFile) UnstableAttr(ctx context.Context, inode *fs.Inode) (fs.UnstableAttr, error) {
+	uattr, err := s.InodeSimpleAttributes.UnstableAttr(ctx, inode)
+	if err != nil {
+		return fs.UnstableAttr{}, err
+	}
+	uattr.ModificationTime = ktime.NowFromContext(ctx)
+	return uattr, nil
+}
+
+// GetFile implements fs.InodeOperations.GetFile.
+func (s *SeqFile) GetFile(ctx context.Context, dirent *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
+	return fs.NewFile(ctx, dirent, flags, &seqFileOperations{seqFile: s}), nil
+}
+
+// findIndexAndOffset finds the unit that corresponds to a certain offset.
+// Returns the unit and the offset within the unit. If there are not enough
+// units len(data) and leftover offset is returned.
+func findIndexAndOffset(data []SeqData, offset int64) (int, int64) {
+	for i, buf := range data {
+		l := int64(len(buf.Buf))
+		if offset < l {
+			return i, offset
+		}
+		offset -= l
+	}
+	return len(data), offset
+}
+
+// updateSourceLocked requires that s.mu is held.
+func (s *SeqFile) updateSourceLocked(ctx context.Context, record int) {
+	var h SeqHandle
+	if record == 0 {
+		h = nil
+	} else {
+		h = s.source[record-1].Handle
+	}
+	// Save what we have previously read.
+	s.source = s.source[:record]
+	var newSource []SeqData
+	newSource, s.generation = s.SeqSource.ReadSeqFileData(ctx, h)
+	s.source = append(s.source, newSource...)
+}
+
+// seqFileOperations implements fs.FileOperations.
+//
+// +stateify savable
+type seqFileOperations struct {
+	fsutil.FileGenericSeek          `state:"nosave"`
+	fsutil.FileNoIoctl              `state:"nosave"`
+	fsutil.FileNoMMap               `state:"nosave"`
+	fsutil.FileNoSplice             `state:"nosave"`
+	fsutil.FileNoopFlush            `state:"nosave"`
+	fsutil.FileNoopFsync            `state:"nosave"`
+	fsutil.FileNoopRelease          `state:"nosave"`
+	fsutil.FileNotDirReaddir        `state:"nosave"`
+	fsutil.FileUseInodeUnstableAttr `state:"nosave"`
+	waiter.AlwaysReady              `state:"nosave"`
+
+	seqFile *SeqFile
+}
+
+var _ fs.FileOperations = (*seqFileOperations)(nil)
+
+// Write implements fs.FileOperations.Write.
+func (*seqFileOperations) Write(context.Context, *fs.File, usermem.IOSequence, int64) (int64, error) {
+	return 0, syserror.EACCES
+}
+
+// Read implements fs.FileOperations.Read.
+func (sfo *seqFileOperations) Read(ctx context.Context, file *fs.File, dst usermem.IOSequence, offset int64) (int64, error) {
+	sfo.seqFile.mu.Lock()
+	defer sfo.seqFile.mu.Unlock()
+
+	sfo.seqFile.NotifyAccess(ctx)
+	defer func() { sfo.seqFile.lastRead = offset }()
+
+	updated := false
+
+	// Try to find where we should start reading this file.
+	i, recordOffset := findIndexAndOffset(sfo.seqFile.source, offset)
+	if i == len(sfo.seqFile.source) {
+		// Ok, we're at EOF. Let's first check to see if there might be
+		// more data available to us. If there is more data, add it to
+		// the end and try reading again.
+		if !sfo.seqFile.SeqSource.NeedsUpdate(sfo.seqFile.generation) {
+			return 0, io.EOF
+		}
+		oldLen := len(sfo.seqFile.source)
+		sfo.seqFile.updateSourceLocked(ctx, len(sfo.seqFile.source))
+		updated = true
+		// We know that we had consumed everything up until this point
+		// so we search in the new slice instead of starting over.
+		i, recordOffset = findIndexAndOffset(sfo.seqFile.source[oldLen:], recordOffset)
+		i += oldLen
+		// i is at most the length of the slice which is
+		// len(sfo.seqFile.source) - oldLen. So at most i will be equal to
+		// len(sfo.seqFile.source).
+		if i == len(sfo.seqFile.source) {
+			return 0, io.EOF
+		}
+	}
+
+	var done int64
+	// We're reading parts of a record, finish reading the current object
+	// before continuing on to the next. We don't refresh our data source
+	// before this record is completed.
+	if recordOffset != 0 {
+		n, err := dst.CopyOut(ctx, sfo.seqFile.source[i].Buf[recordOffset:])
+		done += int64(n)
+		dst = dst.DropFirst(n)
+		if dst.NumBytes() == 0 || err != nil {
+			return done, err
+		}
+		i++
+	}
+
+	// Next/New unit, update the source file if necessary. Make an extra
+	// check to see if we've seeked backwards and if so always update our
+	// data source.
+	if !updated && (sfo.seqFile.SeqSource.NeedsUpdate(sfo.seqFile.generation) || sfo.seqFile.lastRead > offset) {
+		sfo.seqFile.updateSourceLocked(ctx, i)
+		// recordOffset is 0 here and we won't update records behind the
+		// current one so recordOffset is still 0 even though source
+		// just got updated. Just read the next record.
+	}
+
+	// Finish by reading all the available data.
+	for _, buf := range sfo.seqFile.source[i:] {
+		n, err := dst.CopyOut(ctx, buf.Buf)
+		done += int64(n)
+		dst = dst.DropFirst(n)
+		if dst.NumBytes() == 0 || err != nil {
+			return done, err
+		}
+	}
+
+	// If the file shrank (entries not yet read were removed above)
+	// while we tried to read we can end up with nothing read.
+	if done == 0 && dst.NumBytes() != 0 {
+		return 0, io.EOF
+	}
+	return done, nil
+}
diff --git a/pkg/sentry/fs/proc/seqfile/seqfile_state_autogen.go b/pkg/sentry/fs/proc/seqfile/seqfile_state_autogen.go
new file mode 100755
index 000000000..c3b15d513
--- /dev/null
+++ b/pkg/sentry/fs/proc/seqfile/seqfile_state_autogen.go
@@ -0,0 +1,58 @@
+// automatically generated by stateify.
+
+package seqfile
+
+import (
+	"gvisor.googlesource.com/gvisor/pkg/state"
+)
+
+func (x *SeqData) beforeSave() {}
+func (x *SeqData) save(m state.Map) {
+	x.beforeSave()
+	m.Save("Buf", &x.Buf)
+	m.Save("Handle", &x.Handle)
+}
+
+func (x *SeqData) afterLoad() {}
+func (x *SeqData) load(m state.Map) {
+	m.Load("Buf", &x.Buf)
+	m.Load("Handle", &x.Handle)
+}
+
+func (x *SeqFile) beforeSave() {}
+func (x *SeqFile) save(m state.Map) {
+	x.beforeSave()
+	m.Save("InodeSimpleExtendedAttributes", &x.InodeSimpleExtendedAttributes)
+	m.Save("InodeSimpleAttributes", &x.InodeSimpleAttributes)
+	m.Save("SeqSource", &x.SeqSource)
+	m.Save("source", &x.source)
+	m.Save("generation", &x.generation)
+	m.Save("lastRead", &x.lastRead)
+}
+
+func (x *SeqFile) afterLoad() {}
+func (x *SeqFile) load(m state.Map) {
+	m.Load("InodeSimpleExtendedAttributes", &x.InodeSimpleExtendedAttributes)
+	m.Load("InodeSimpleAttributes", &x.InodeSimpleAttributes)
+	m.Load("SeqSource", &x.SeqSource)
+	m.Load("source", &x.source)
+	m.Load("generation", &x.generation)
+	m.Load("lastRead", &x.lastRead)
+}
+
+func (x *seqFileOperations) beforeSave() {}
+func (x *seqFileOperations) save(m state.Map) {
+	x.beforeSave()
+	m.Save("seqFile", &x.seqFile)
+}
+
+func (x *seqFileOperations) afterLoad() {}
+func (x *seqFileOperations) load(m state.Map) {
+	m.Load("seqFile", &x.seqFile)
+}
+
+func init() {
+	state.Register("seqfile.SeqData", (*SeqData)(nil), state.Fns{Save: (*SeqData).save, Load: (*SeqData).load})
+	state.Register("seqfile.SeqFile", (*SeqFile)(nil), state.Fns{Save: (*SeqFile).save, Load: (*SeqFile).load})
+	state.Register("seqfile.seqFileOperations", (*seqFileOperations)(nil), state.Fns{Save: (*seqFileOperations).save, Load: (*seqFileOperations).load})
+}