Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

1 files changed, 167 insertions, 0 deletions

diff --git a/pkg/sentry/fs/fdpipe/pipe.go b/pkg/sentry/fs/fdpipe/pipe.go
new file mode 100644
index 000000000..f7bbd4aff
--- /dev/null
+++ b/pkg/sentry/fs/fdpipe/pipe.go
@@ -0,0 +1,167 @@
+// Copyright 2018 Google Inc.
+//
+// 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 fdpipe implements common namedpipe opening and accessing logic.
+package fdpipe
+
+import (
+	"os"
+	"sync"
+	"syscall"
+
+	"gvisor.googlesource.com/gvisor/pkg/fd"
+	"gvisor.googlesource.com/gvisor/pkg/log"
+	"gvisor.googlesource.com/gvisor/pkg/secio"
+	"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/safemem"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+	"gvisor.googlesource.com/gvisor/pkg/syserror"
+	"gvisor.googlesource.com/gvisor/pkg/waiter"
+	"gvisor.googlesource.com/gvisor/pkg/waiter/fdnotifier"
+)
+
+// pipeOperations are the fs.FileOperations of a host pipe.
+type pipeOperations struct {
+	fsutil.PipeSeek      `state:"nosave"`
+	fsutil.NotDirReaddir `state:"nosave"`
+	fsutil.NoFsync       `state:"nosave"`
+	fsutil.NoopFlush     `state:"nosave"`
+	fsutil.NoMMap        `state:"nosave"`
+	fsutil.NoIoctl       `state:"nosave"`
+	waiter.Queue         `state:"nosave"`
+
+	// flags are the flags used to open the pipe.
+	flags fs.FileFlags `state:".(fs.FileFlags)"`
+
+	// opener is how the pipe was opened.
+	opener NonBlockingOpener `state:"wait"`
+
+	// file represents the host pipe.
+	file *fd.FD `state:"nosave"`
+
+	// mu protects readAheadBuffer access below.
+	mu sync.Mutex `state:"nosave"`
+
+	// readAheadBuffer contains read bytes that have not yet been read
+	// by the application but need to be buffered for save-restore for correct
+	// opening semantics.  The readAheadBuffer will only be non-empty when the
+	// is first opened and will be drained by subsequent reads on the pipe.
+	readAheadBuffer []byte
+}
+
+// newPipeOperations returns an implementation of fs.FileOperations for a pipe.
+func newPipeOperations(ctx context.Context, opener NonBlockingOpener, flags fs.FileFlags, file *fd.FD, readAheadBuffer []byte) (*pipeOperations, error) {
+	pipeOps := &pipeOperations{
+		flags:           flags,
+		opener:          opener,
+		file:            file,
+		readAheadBuffer: readAheadBuffer,
+	}
+	if err := pipeOps.init(); err != nil {
+		return nil, err
+	}
+	return pipeOps, nil
+}
+
+// init initializes p.file.
+func (p *pipeOperations) init() error {
+	var s syscall.Stat_t
+	if err := syscall.Fstat(p.file.FD(), &s); err != nil {
+		log.Warningf("pipe: cannot stat fd %d: %v", p.file.FD(), err)
+		return syscall.EINVAL
+	}
+	if s.Mode&syscall.S_IFIFO != syscall.S_IFIFO {
+		log.Warningf("pipe: cannot load fd %d as pipe, file type: %o", p.file.FD(), s.Mode)
+		return syscall.EINVAL
+	}
+	if err := syscall.SetNonblock(p.file.FD(), true); err != nil {
+		return err
+	}
+	if err := fdnotifier.AddFD(int32(p.file.FD()), &p.Queue); err != nil {
+		return err
+	}
+	return nil
+}
+
+// EventRegister implements waiter.Waitable.EventRegister.
+func (p *pipeOperations) EventRegister(e *waiter.Entry, mask waiter.EventMask) {
+	p.Queue.EventRegister(e, mask)
+	fdnotifier.UpdateFD(int32(p.file.FD()))
+}
+
+// EventUnregister implements waiter.Waitable.EventUnregister.
+func (p *pipeOperations) EventUnregister(e *waiter.Entry) {
+	p.Queue.EventUnregister(e)
+	fdnotifier.UpdateFD(int32(p.file.FD()))
+}
+
+// Readiness returns a mask of ready events for stream.
+func (p *pipeOperations) Readiness(mask waiter.EventMask) (eventMask waiter.EventMask) {
+	return fdnotifier.NonBlockingPoll(int32(p.file.FD()), mask)
+}
+
+// Release implements fs.FileOperations.Release.
+func (p *pipeOperations) Release() {
+	fdnotifier.RemoveFD(int32(p.file.FD()))
+	p.file.Close()
+	p.file = nil
+}
+
+// Read implements fs.FileOperations.Read.
+func (p *pipeOperations) Read(ctx context.Context, file *fs.File, dst usermem.IOSequence, offset int64) (int64, error) {
+	// Drain the read ahead buffer, if it contains anything first.
+	var bufN int
+	var bufErr error
+	p.mu.Lock()
+	if len(p.readAheadBuffer) > 0 {
+		bufN, bufErr = dst.CopyOut(ctx, p.readAheadBuffer)
+		p.readAheadBuffer = p.readAheadBuffer[bufN:]
+		dst = dst.DropFirst(bufN)
+	}
+	p.mu.Unlock()
+	if dst.NumBytes() == 0 || bufErr != nil {
+		return int64(bufN), bufErr
+	}
+
+	// Pipes expect full reads.
+	n, err := dst.CopyOutFrom(ctx, safemem.FromIOReader{secio.FullReader{p.file}})
+	total := int64(bufN) + n
+	if err != nil && isBlockError(err) {
+		return total, syserror.ErrWouldBlock
+	}
+	return total, err
+}
+
+// Write implements fs.FileOperations.Write.
+func (p *pipeOperations) Write(ctx context.Context, file *fs.File, src usermem.IOSequence, offset int64) (int64, error) {
+	n, err := src.CopyInTo(ctx, safemem.FromIOWriter{p.file})
+	if err != nil && isBlockError(err) {
+		return n, syserror.ErrWouldBlock
+	}
+	return n, err
+}
+
+// isBlockError unwraps os errors and checks if they are caused by EAGAIN or
+// EWOULDBLOCK. This is so they can be transformed into syserror.ErrWouldBlock.
+func isBlockError(err error) bool {
+	if err == syserror.EAGAIN || err == syserror.EWOULDBLOCK {
+		return true
+	}
+	if pe, ok := err.(*os.PathError); ok {
+		return isBlockError(pe.Err)
+	}
+	return false
+}