summaryrefslogtreecommitdiffhomepage
path: root/pkg/sentry/syscalls/linux/vfs2/splice.go
diff options
context:
space:
mode:
Diffstat (limited to 'pkg/sentry/syscalls/linux/vfs2/splice.go')
-rw-r--r--pkg/sentry/syscalls/linux/vfs2/splice.go490
1 files changed, 490 insertions, 0 deletions
diff --git a/pkg/sentry/syscalls/linux/vfs2/splice.go b/pkg/sentry/syscalls/linux/vfs2/splice.go
new file mode 100644
index 000000000..75bfa2c79
--- /dev/null
+++ b/pkg/sentry/syscalls/linux/vfs2/splice.go
@@ -0,0 +1,490 @@
+// 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 vfs2
+
+import (
+ "io"
+
+ "gvisor.dev/gvisor/pkg/abi/linux"
+ "gvisor.dev/gvisor/pkg/sentry/arch"
+ "gvisor.dev/gvisor/pkg/sentry/kernel"
+ "gvisor.dev/gvisor/pkg/sentry/kernel/pipe"
+ "gvisor.dev/gvisor/pkg/sentry/vfs"
+ "gvisor.dev/gvisor/pkg/syserror"
+ "gvisor.dev/gvisor/pkg/usermem"
+ "gvisor.dev/gvisor/pkg/waiter"
+)
+
+// Splice implements Linux syscall splice(2).
+func Splice(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+ inFD := args[0].Int()
+ inOffsetPtr := args[1].Pointer()
+ outFD := args[2].Int()
+ outOffsetPtr := args[3].Pointer()
+ count := int64(args[4].SizeT())
+ flags := args[5].Int()
+
+ if count == 0 {
+ return 0, nil, nil
+ }
+ if count > int64(kernel.MAX_RW_COUNT) {
+ count = int64(kernel.MAX_RW_COUNT)
+ }
+
+ // Check for invalid flags.
+ if flags&^(linux.SPLICE_F_MOVE|linux.SPLICE_F_NONBLOCK|linux.SPLICE_F_MORE|linux.SPLICE_F_GIFT) != 0 {
+ return 0, nil, syserror.EINVAL
+ }
+
+ // Get file descriptions.
+ inFile := t.GetFileVFS2(inFD)
+ if inFile == nil {
+ return 0, nil, syserror.EBADF
+ }
+ defer inFile.DecRef(t)
+ outFile := t.GetFileVFS2(outFD)
+ if outFile == nil {
+ return 0, nil, syserror.EBADF
+ }
+ defer outFile.DecRef(t)
+
+ // Check that both files support the required directionality.
+ if !inFile.IsReadable() || !outFile.IsWritable() {
+ return 0, nil, syserror.EBADF
+ }
+
+ // The operation is non-blocking if anything is non-blocking.
+ //
+ // N.B. This is a rather simplistic heuristic that avoids some
+ // poor edge case behavior since the exact semantics here are
+ // underspecified and vary between versions of Linux itself.
+ nonBlock := ((inFile.StatusFlags()|outFile.StatusFlags())&linux.O_NONBLOCK != 0) || (flags&linux.SPLICE_F_NONBLOCK != 0)
+
+ // At least one file description must represent a pipe.
+ inPipeFD, inIsPipe := inFile.Impl().(*pipe.VFSPipeFD)
+ outPipeFD, outIsPipe := outFile.Impl().(*pipe.VFSPipeFD)
+ if !inIsPipe && !outIsPipe {
+ return 0, nil, syserror.EINVAL
+ }
+
+ // Copy in offsets.
+ inOffset := int64(-1)
+ if inOffsetPtr != 0 {
+ if inIsPipe {
+ return 0, nil, syserror.ESPIPE
+ }
+ if inFile.Options().DenyPRead {
+ return 0, nil, syserror.EINVAL
+ }
+ if _, err := t.CopyIn(inOffsetPtr, &inOffset); err != nil {
+ return 0, nil, err
+ }
+ if inOffset < 0 {
+ return 0, nil, syserror.EINVAL
+ }
+ }
+ outOffset := int64(-1)
+ if outOffsetPtr != 0 {
+ if outIsPipe {
+ return 0, nil, syserror.ESPIPE
+ }
+ if outFile.Options().DenyPWrite {
+ return 0, nil, syserror.EINVAL
+ }
+ if _, err := t.CopyIn(outOffsetPtr, &outOffset); err != nil {
+ return 0, nil, err
+ }
+ if outOffset < 0 {
+ return 0, nil, syserror.EINVAL
+ }
+ }
+
+ // Move data.
+ var (
+ n int64
+ err error
+ )
+ dw := dualWaiter{
+ inFile: inFile,
+ outFile: outFile,
+ }
+ defer dw.destroy()
+ for {
+ // If both input and output are pipes, delegate to the pipe
+ // implementation. Otherwise, exactly one end is a pipe, which
+ // we ensure is consistently ordered after the non-pipe FD's
+ // locks by passing the pipe FD as usermem.IO to the non-pipe
+ // end.
+ switch {
+ case inIsPipe && outIsPipe:
+ n, err = pipe.Splice(t, outPipeFD, inPipeFD, count)
+ case inIsPipe:
+ if outOffset != -1 {
+ n, err = outFile.PWrite(t, inPipeFD.IOSequence(count), outOffset, vfs.WriteOptions{})
+ outOffset += n
+ } else {
+ n, err = outFile.Write(t, inPipeFD.IOSequence(count), vfs.WriteOptions{})
+ }
+ case outIsPipe:
+ if inOffset != -1 {
+ n, err = inFile.PRead(t, outPipeFD.IOSequence(count), inOffset, vfs.ReadOptions{})
+ inOffset += n
+ } else {
+ n, err = inFile.Read(t, outPipeFD.IOSequence(count), vfs.ReadOptions{})
+ }
+ default:
+ panic("not possible")
+ }
+
+ if n != 0 || err != syserror.ErrWouldBlock || nonBlock {
+ break
+ }
+ if err = dw.waitForBoth(t); err != nil {
+ break
+ }
+ }
+
+ // Copy updated offsets out.
+ if inOffsetPtr != 0 {
+ if _, err := t.CopyOut(inOffsetPtr, &inOffset); err != nil {
+ return 0, nil, err
+ }
+ }
+ if outOffsetPtr != 0 {
+ if _, err := t.CopyOut(outOffsetPtr, &outOffset); err != nil {
+ return 0, nil, err
+ }
+ }
+
+ if n == 0 {
+ return 0, nil, err
+ }
+
+ // On Linux, inotify behavior is not very consistent with splice(2). We try
+ // our best to emulate Linux for very basic calls to splice, where for some
+ // reason, events are generated for output files, but not input files.
+ outFile.Dentry().InotifyWithParent(t, linux.IN_MODIFY, 0, vfs.PathEvent)
+ return uintptr(n), nil, nil
+}
+
+// Tee implements Linux syscall tee(2).
+func Tee(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+ inFD := args[0].Int()
+ outFD := args[1].Int()
+ count := int64(args[2].SizeT())
+ flags := args[3].Int()
+
+ if count == 0 {
+ return 0, nil, nil
+ }
+ if count > int64(kernel.MAX_RW_COUNT) {
+ count = int64(kernel.MAX_RW_COUNT)
+ }
+
+ // Check for invalid flags.
+ if flags&^(linux.SPLICE_F_MOVE|linux.SPLICE_F_NONBLOCK|linux.SPLICE_F_MORE|linux.SPLICE_F_GIFT) != 0 {
+ return 0, nil, syserror.EINVAL
+ }
+
+ // Get file descriptions.
+ inFile := t.GetFileVFS2(inFD)
+ if inFile == nil {
+ return 0, nil, syserror.EBADF
+ }
+ defer inFile.DecRef(t)
+ outFile := t.GetFileVFS2(outFD)
+ if outFile == nil {
+ return 0, nil, syserror.EBADF
+ }
+ defer outFile.DecRef(t)
+
+ // Check that both files support the required directionality.
+ if !inFile.IsReadable() || !outFile.IsWritable() {
+ return 0, nil, syserror.EBADF
+ }
+
+ // The operation is non-blocking if anything is non-blocking.
+ //
+ // N.B. This is a rather simplistic heuristic that avoids some
+ // poor edge case behavior since the exact semantics here are
+ // underspecified and vary between versions of Linux itself.
+ nonBlock := ((inFile.StatusFlags()|outFile.StatusFlags())&linux.O_NONBLOCK != 0) || (flags&linux.SPLICE_F_NONBLOCK != 0)
+
+ // Both file descriptions must represent pipes.
+ inPipeFD, inIsPipe := inFile.Impl().(*pipe.VFSPipeFD)
+ outPipeFD, outIsPipe := outFile.Impl().(*pipe.VFSPipeFD)
+ if !inIsPipe || !outIsPipe {
+ return 0, nil, syserror.EINVAL
+ }
+
+ // Copy data.
+ var (
+ n int64
+ err error
+ )
+ dw := dualWaiter{
+ inFile: inFile,
+ outFile: outFile,
+ }
+ defer dw.destroy()
+ for {
+ n, err = pipe.Tee(t, outPipeFD, inPipeFD, count)
+ if n != 0 || err != syserror.ErrWouldBlock || nonBlock {
+ break
+ }
+ if err = dw.waitForBoth(t); err != nil {
+ break
+ }
+ }
+ if n == 0 {
+ return 0, nil, err
+ }
+ outFile.Dentry().InotifyWithParent(t, linux.IN_MODIFY, 0, vfs.PathEvent)
+ return uintptr(n), nil, nil
+}
+
+// Sendfile implements linux system call sendfile(2).
+func Sendfile(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+ outFD := args[0].Int()
+ inFD := args[1].Int()
+ offsetAddr := args[2].Pointer()
+ count := int64(args[3].SizeT())
+
+ inFile := t.GetFileVFS2(inFD)
+ if inFile == nil {
+ return 0, nil, syserror.EBADF
+ }
+ defer inFile.DecRef(t)
+ if !inFile.IsReadable() {
+ return 0, nil, syserror.EBADF
+ }
+
+ outFile := t.GetFileVFS2(outFD)
+ if outFile == nil {
+ return 0, nil, syserror.EBADF
+ }
+ defer outFile.DecRef(t)
+ if !outFile.IsWritable() {
+ return 0, nil, syserror.EBADF
+ }
+
+ // Verify that the outFile Append flag is not set.
+ if outFile.StatusFlags()&linux.O_APPEND != 0 {
+ return 0, nil, syserror.EINVAL
+ }
+
+ // Verify that inFile is a regular file or block device. This is a
+ // requirement; the same check appears in Linux
+ // (fs/splice.c:splice_direct_to_actor).
+ if stat, err := inFile.Stat(t, vfs.StatOptions{Mask: linux.STATX_TYPE}); err != nil {
+ return 0, nil, err
+ } else if stat.Mask&linux.STATX_TYPE == 0 ||
+ (stat.Mode&linux.S_IFMT != linux.S_IFREG && stat.Mode&linux.S_IFMT != linux.S_IFBLK) {
+ return 0, nil, syserror.EINVAL
+ }
+
+ // Copy offset if it exists.
+ offset := int64(-1)
+ if offsetAddr != 0 {
+ if inFile.Options().DenyPRead {
+ return 0, nil, syserror.ESPIPE
+ }
+ if _, err := t.CopyIn(offsetAddr, &offset); err != nil {
+ return 0, nil, err
+ }
+ if offset < 0 {
+ return 0, nil, syserror.EINVAL
+ }
+ if offset+count < 0 {
+ return 0, nil, syserror.EINVAL
+ }
+ }
+
+ // Validate count. This must come after offset checks.
+ if count < 0 {
+ return 0, nil, syserror.EINVAL
+ }
+ if count == 0 {
+ return 0, nil, nil
+ }
+ if count > int64(kernel.MAX_RW_COUNT) {
+ count = int64(kernel.MAX_RW_COUNT)
+ }
+
+ // Copy data.
+ var (
+ n int64
+ err error
+ )
+ dw := dualWaiter{
+ inFile: inFile,
+ outFile: outFile,
+ }
+ defer dw.destroy()
+ outPipeFD, outIsPipe := outFile.Impl().(*pipe.VFSPipeFD)
+ // Reading from input file should never block, since it is regular or
+ // block device. We only need to check if writing to the output file
+ // can block.
+ nonBlock := outFile.StatusFlags()&linux.O_NONBLOCK != 0
+ if outIsPipe {
+ for n < count {
+ var spliceN int64
+ if offset != -1 {
+ spliceN, err = inFile.PRead(t, outPipeFD.IOSequence(count), offset, vfs.ReadOptions{})
+ offset += spliceN
+ } else {
+ spliceN, err = inFile.Read(t, outPipeFD.IOSequence(count), vfs.ReadOptions{})
+ }
+ if spliceN == 0 && err == io.EOF {
+ // We reached the end of the file. Eat the error and exit the loop.
+ err = nil
+ break
+ }
+ n += spliceN
+ if err == syserror.ErrWouldBlock && !nonBlock {
+ err = dw.waitForBoth(t)
+ }
+ if err != nil {
+ break
+ }
+ }
+ } else {
+ // Read inFile to buffer, then write the contents to outFile.
+ buf := make([]byte, count)
+ for n < count {
+ var readN int64
+ if offset != -1 {
+ readN, err = inFile.PRead(t, usermem.BytesIOSequence(buf), offset, vfs.ReadOptions{})
+ offset += readN
+ } else {
+ readN, err = inFile.Read(t, usermem.BytesIOSequence(buf), vfs.ReadOptions{})
+ }
+ if readN == 0 && err == io.EOF {
+ // We reached the end of the file. Eat the error and exit the loop.
+ err = nil
+ break
+ }
+ n += readN
+ if err != nil {
+ break
+ }
+
+ // Write all of the bytes that we read. This may need
+ // multiple write calls to complete.
+ wbuf := buf[:n]
+ for len(wbuf) > 0 {
+ var writeN int64
+ writeN, err = outFile.Write(t, usermem.BytesIOSequence(wbuf), vfs.WriteOptions{})
+ wbuf = wbuf[writeN:]
+ if err == syserror.ErrWouldBlock && !nonBlock {
+ err = dw.waitForOut(t)
+ }
+ if err != nil {
+ // We didn't complete the write. Only
+ // report the bytes that were actually
+ // written, and rewind the offset.
+ notWritten := int64(len(wbuf))
+ n -= notWritten
+ if offset != -1 {
+ offset -= notWritten
+ }
+ break
+ }
+ }
+ if err == syserror.ErrWouldBlock && !nonBlock {
+ err = dw.waitForBoth(t)
+ }
+ if err != nil {
+ break
+ }
+ }
+ }
+
+ if offsetAddr != 0 {
+ // Copy out the new offset.
+ if _, err := t.CopyOut(offsetAddr, offset); err != nil {
+ return 0, nil, err
+ }
+ }
+
+ if n == 0 {
+ return 0, nil, err
+ }
+
+ inFile.Dentry().InotifyWithParent(t, linux.IN_ACCESS, 0, vfs.PathEvent)
+ outFile.Dentry().InotifyWithParent(t, linux.IN_MODIFY, 0, vfs.PathEvent)
+ return uintptr(n), nil, nil
+}
+
+// dualWaiter is used to wait on one or both vfs.FileDescriptions. It is not
+// thread-safe, and does not take a reference on the vfs.FileDescriptions.
+//
+// Users must call destroy() when finished.
+type dualWaiter struct {
+ inFile *vfs.FileDescription
+ outFile *vfs.FileDescription
+
+ inW waiter.Entry
+ inCh chan struct{}
+ outW waiter.Entry
+ outCh chan struct{}
+}
+
+// waitForBoth waits for both dw.inFile and dw.outFile to be ready.
+func (dw *dualWaiter) waitForBoth(t *kernel.Task) error {
+ if dw.inFile.Readiness(eventMaskRead)&eventMaskRead == 0 {
+ if dw.inCh == nil {
+ dw.inW, dw.inCh = waiter.NewChannelEntry(nil)
+ dw.inFile.EventRegister(&dw.inW, eventMaskRead)
+ // We might be ready now. Try again before blocking.
+ return nil
+ }
+ if err := t.Block(dw.inCh); err != nil {
+ return err
+ }
+ }
+ return dw.waitForOut(t)
+}
+
+// waitForOut waits for dw.outfile to be read.
+func (dw *dualWaiter) waitForOut(t *kernel.Task) error {
+ if dw.outFile.Readiness(eventMaskWrite)&eventMaskWrite == 0 {
+ if dw.outCh == nil {
+ dw.outW, dw.outCh = waiter.NewChannelEntry(nil)
+ dw.outFile.EventRegister(&dw.outW, eventMaskWrite)
+ // We might be ready now. Try again before blocking.
+ return nil
+ }
+ if err := t.Block(dw.outCh); err != nil {
+ return err
+ }
+ }
+ return nil
+}
+
+// destroy cleans up resources help by dw. No more calls to wait* can occur
+// after destroy is called.
+func (dw *dualWaiter) destroy() {
+ if dw.inCh != nil {
+ dw.inFile.EventUnregister(&dw.inW)
+ dw.inCh = nil
+ }
+ if dw.outCh != nil {
+ dw.outFile.EventUnregister(&dw.outW)
+ dw.outCh = nil
+ }
+ dw.inFile = nil
+ dw.outFile = nil
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-17 03:27:11 +0000