Merge 216da0b7 (automated)

1 files changed, 293 insertions, 0 deletions

diff --git a/pkg/sentry/syscalls/linux/sys_splice.go b/pkg/sentry/syscalls/linux/sys_splice.go
new file mode 100644
index 000000000..37303606f
--- /dev/null
+++ b/pkg/sentry/syscalls/linux/sys_splice.go
@@ -0,0 +1,293 @@
+// 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 linux
+
+import (
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/kdefs"
+	"gvisor.googlesource.com/gvisor/pkg/syserror"
+	"gvisor.googlesource.com/gvisor/pkg/waiter"
+)
+
+// doSplice implements a blocking splice operation.
+func doSplice(t *kernel.Task, outFile, inFile *fs.File, opts fs.SpliceOpts, nonBlocking bool) (int64, error) {
+	var (
+		total int64
+		n     int64
+		err   error
+		ch    chan struct{}
+		inW   bool
+		outW  bool
+	)
+	for opts.Length > 0 {
+		n, err = fs.Splice(t, outFile, inFile, opts)
+		opts.Length -= n
+		total += n
+		if err != syserror.ErrWouldBlock {
+			break
+		} else if err == syserror.ErrWouldBlock && nonBlocking {
+			break
+		}
+
+		// Are we a registered waiter?
+		if ch == nil {
+			ch = make(chan struct{}, 1)
+		}
+		if !inW && inFile.Readiness(EventMaskRead) == 0 && !inFile.Flags().NonBlocking {
+			w, _ := waiter.NewChannelEntry(ch)
+			inFile.EventRegister(&w, EventMaskRead)
+			defer inFile.EventUnregister(&w)
+			inW = true // Registered.
+		} else if !outW && outFile.Readiness(EventMaskWrite) == 0 && !outFile.Flags().NonBlocking {
+			w, _ := waiter.NewChannelEntry(ch)
+			outFile.EventRegister(&w, EventMaskWrite)
+			defer outFile.EventUnregister(&w)
+			outW = true // Registered.
+		}
+
+		// Was anything registered? If no, everything is non-blocking.
+		if !inW && !outW {
+			break
+		}
+
+		// Block until there's data.
+		if err = t.Block(ch); err != nil {
+			break
+		}
+	}
+
+	return total, err
+}
+
+// Sendfile implements linux system call sendfile(2).
+func Sendfile(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	outFD := kdefs.FD(args[0].Int())
+	inFD := kdefs.FD(args[1].Int())
+	offsetAddr := args[2].Pointer()
+	count := int64(args[3].SizeT())
+
+	// Don't send a negative number of bytes.
+	if count < 0 {
+		return 0, nil, syserror.EINVAL
+	}
+
+	// Get files.
+	outFile := t.FDMap().GetFile(outFD)
+	if outFile == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer outFile.DecRef()
+
+	inFile := t.FDMap().GetFile(inFD)
+	if inFile == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer inFile.DecRef()
+
+	// Verify that the outfile Append flag is not set. Note that fs.Splice
+	// itself validates that the output file is writable.
+	if outFile.Flags().Append {
+		return 0, nil, syserror.EBADF
+	}
+
+	// Verify that we have a regular infile. This is a requirement; the
+	// same check appears in Linux (fs/splice.c:splice_direct_to_actor).
+	if !fs.IsRegular(inFile.Dirent.Inode.StableAttr) {
+		return 0, nil, syserror.EINVAL
+	}
+
+	var (
+		n   int64
+		err error
+	)
+	if offsetAddr != 0 {
+		// Verify that when offset address is not null, infile must be
+		// seekable. The fs.Splice routine itself validates basic read.
+		if !inFile.Flags().Pread {
+			return 0, nil, syserror.ESPIPE
+		}
+
+		// Copy in the offset.
+		var offset int64
+		if _, err := t.CopyIn(offsetAddr, &offset); err != nil {
+			return 0, nil, err
+		}
+
+		// The offset must be valid.
+		if offset < 0 {
+			return 0, nil, syserror.EINVAL
+		}
+
+		// Do the splice.
+		n, err = doSplice(t, outFile, inFile, fs.SpliceOpts{
+			Length:    count,
+			SrcOffset: true,
+			SrcStart:  offset,
+		}, false)
+
+		// Copy out the new offset.
+		if _, err := t.CopyOut(offsetAddr, n+offset); err != nil {
+			return 0, nil, err
+		}
+	} else {
+		// Send data using splice.
+		n, err = doSplice(t, outFile, inFile, fs.SpliceOpts{
+			Length: count,
+		}, false)
+	}
+
+	// We can only pass a single file to handleIOError, so pick inFile
+	// arbitrarily. This is used only for debugging purposes.
+	return uintptr(n), nil, handleIOError(t, n != 0, err, kernel.ERESTARTSYS, "sendfile", inFile)
+}
+
+// Splice implements splice(2).
+func Splice(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	inFD := kdefs.FD(args[0].Int())
+	inOffset := args[1].Pointer()
+	outFD := kdefs.FD(args[2].Int())
+	outOffset := args[3].Pointer()
+	count := int64(args[4].SizeT())
+	flags := args[5].Int()
+
+	// 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
+	}
+
+	// Only non-blocking is meaningful. Note that unlike in Linux, this
+	// flag is applied consistently. We will have either fully blocking or
+	// non-blocking behavior below, regardless of the underlying files
+	// being spliced to. It's unclear if this is a bug or not yet.
+	nonBlocking := (flags & linux.SPLICE_F_NONBLOCK) != 0
+
+	// Get files.
+	outFile := t.FDMap().GetFile(outFD)
+	if outFile == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer outFile.DecRef()
+
+	inFile := t.FDMap().GetFile(inFD)
+	if inFile == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer inFile.DecRef()
+
+	// Construct our options.
+	//
+	// Note that exactly one of the underlying buffers must be a pipe. We
+	// don't actually have this constraint internally, but we enforce it
+	// for the semantics of the call.
+	opts := fs.SpliceOpts{
+		Length: count,
+	}
+	switch {
+	case fs.IsPipe(inFile.Dirent.Inode.StableAttr) && !fs.IsPipe(outFile.Dirent.Inode.StableAttr):
+		if inOffset != 0 {
+			return 0, nil, syserror.ESPIPE
+		}
+		if outOffset != 0 {
+			var offset int64
+			if _, err := t.CopyIn(outOffset, &offset); err != nil {
+				return 0, nil, err
+			}
+			// Use the destination offset.
+			opts.DstOffset = true
+			opts.DstStart = offset
+		}
+	case !fs.IsPipe(inFile.Dirent.Inode.StableAttr) && fs.IsPipe(outFile.Dirent.Inode.StableAttr):
+		if outOffset != 0 {
+			return 0, nil, syserror.ESPIPE
+		}
+		if inOffset != 0 {
+			var offset int64
+			if _, err := t.CopyIn(inOffset, &offset); err != nil {
+				return 0, nil, err
+			}
+			// Use the source offset.
+			opts.SrcOffset = true
+			opts.SrcStart = offset
+		}
+	case fs.IsPipe(inFile.Dirent.Inode.StableAttr) && fs.IsPipe(outFile.Dirent.Inode.StableAttr):
+		if inOffset != 0 || outOffset != 0 {
+			return 0, nil, syserror.ESPIPE
+		}
+	default:
+		return 0, nil, syserror.EINVAL
+	}
+
+	// We may not refer to the same pipe; otherwise it's a continuous loop.
+	if inFile.Dirent.Inode.StableAttr.InodeID == outFile.Dirent.Inode.StableAttr.InodeID {
+		return 0, nil, syserror.EINVAL
+	}
+
+	// Splice data.
+	n, err := doSplice(t, outFile, inFile, opts, nonBlocking)
+
+	// See above; inFile is chosen arbitrarily here.
+	return uintptr(n), nil, handleIOError(t, n != 0, err, kernel.ERESTARTSYS, "splice", inFile)
+}
+
+// Tee imlements tee(2).
+func Tee(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	inFD := kdefs.FD(args[0].Int())
+	outFD := kdefs.FD(args[1].Int())
+	count := int64(args[2].SizeT())
+	flags := args[3].Int()
+
+	// 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
+	}
+
+	// Only non-blocking is meaningful.
+	nonBlocking := (flags & linux.SPLICE_F_NONBLOCK) != 0
+
+	// Get files.
+	outFile := t.FDMap().GetFile(outFD)
+	if outFile == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer outFile.DecRef()
+
+	inFile := t.FDMap().GetFile(inFD)
+	if inFile == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer inFile.DecRef()
+
+	// All files must be pipes.
+	if !fs.IsPipe(inFile.Dirent.Inode.StableAttr) || !fs.IsPipe(outFile.Dirent.Inode.StableAttr) {
+		return 0, nil, syserror.EINVAL
+	}
+
+	// We may not refer to the same pipe; see above.
+	if inFile.Dirent.Inode.StableAttr.InodeID == outFile.Dirent.Inode.StableAttr.InodeID {
+		return 0, nil, syserror.EINVAL
+	}
+
+	// Splice data.
+	n, err := doSplice(t, outFile, inFile, fs.SpliceOpts{
+		Length: count,
+		Dup:    true,
+	}, nonBlocking)
+
+	// See above; inFile is chosen arbitrarily here.
+	return uintptr(n), nil, handleIOError(t, n != 0, err, kernel.ERESTARTSYS, "tee", inFile)
+}