1 files changed, 269 insertions, 0 deletions
diff --git a/pkg/sentry/syscalls/linux/sys_getdents.go b/pkg/sentry/syscalls/linux/sys_getdents.go
new file mode 100644
index 000000000..178714b07
--- /dev/null
+++ b/pkg/sentry/syscalls/linux/sys_getdents.go
@@ -0,0 +1,269 @@
+// 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 linux
+
+import (
+	"bytes"
+	"io"
+	"syscall"
+
+	"gvisor.googlesource.com/gvisor/pkg/binary"
+	"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/sentry/usermem"
+	"gvisor.googlesource.com/gvisor/pkg/syserror"
+)
+
+// Getdents implements linux syscall getdents(2) for 64bit systems.
+func Getdents(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := kdefs.FD(args[0].Int())
+	addr := args[1].Pointer()
+	size := int(args[2].Uint())
+
+	minSize := int(smallestDirent(t.Arch()))
+	if size < minSize {
+		// size is smaller than smallest possible dirent.
+		return 0, nil, syserror.EINVAL
+	}
+
+	n, err := getdents(t, fd, addr, size, (*dirent).Serialize)
+	return n, nil, err
+}
+
+// Getdents64 implements linux syscall getdents64(2).
+func Getdents64(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := kdefs.FD(args[0].Int())
+	addr := args[1].Pointer()
+	size := int(args[2].Uint())
+
+	minSize := int(smallestDirent64(t.Arch()))
+	if size < minSize {
+		// size is smaller than smallest possible dirent.
+		return 0, nil, syserror.EINVAL
+	}
+
+	n, err := getdents(t, fd, addr, size, (*dirent).Serialize64)
+	return n, nil, err
+}
+
+// getdents implements the core of getdents(2)/getdents64(2).
+// f is the syscall implementation dirent serialization function.
+func getdents(t *kernel.Task, fd kdefs.FD, addr usermem.Addr, size int, f func(*dirent, io.Writer) (int, error)) (uintptr, error) {
+	dir := t.FDMap().GetFile(fd)
+	if dir == nil {
+		return 0, syserror.EBADF
+	}
+	defer dir.DecRef()
+
+	w := &usermem.IOReadWriter{
+		Ctx:  t,
+		IO:   t.MemoryManager(),
+		Addr: addr,
+		Opts: usermem.IOOpts{
+			AddressSpaceActive: true,
+		},
+	}
+
+	ds := newDirentSerializer(f, w, t.Arch(), size)
+	rerr := dir.Readdir(t, ds)
+
+	switch err := handleIOError(t, ds.Written() > 0, rerr, kernel.ERESTARTSYS, "getdents", dir); err {
+	case nil:
+		dir.Dirent.InotifyEvent(syscall.IN_ACCESS, 0)
+		return uintptr(ds.Written()), nil
+	case io.EOF:
+		return 0, nil
+	default:
+		return 0, err
+	}
+}
+
+// oldDirentHdr is a fixed sized header matching the fixed size
+// fields found in the old linux dirent struct.
+type oldDirentHdr struct {
+	Ino    uint64
+	Off    uint64
+	Reclen uint16
+}
+
+// direntHdr is a fixed sized header matching the fixed size
+// fields found in the new linux dirent struct.
+type direntHdr struct {
+	OldHdr oldDirentHdr
+	Typ    uint8
+}
+
+// dirent contains the data pointed to by a new linux dirent struct.
+type dirent struct {
+	Hdr  direntHdr
+	Name []byte
+}
+
+// newDirent returns a dirent from an fs.InodeOperationsInfo.
+func newDirent(width uint, name string, attr fs.DentAttr, offset uint64) *dirent {
+	d := &dirent{
+		Hdr: direntHdr{
+			OldHdr: oldDirentHdr{
+				Ino: attr.InodeID,
+				Off: offset,
+			},
+			Typ: toType(attr.Type),
+		},
+		Name: []byte(name),
+	}
+	d.Hdr.OldHdr.Reclen = d.padRec(int(width))
+	return d
+}
+
+// smallestDirent returns the size of the smallest possible dirent using
+// the old linux dirent format.
+func smallestDirent(a arch.Context) uint {
+	d := dirent{}
+	return uint(binary.Size(d.Hdr.OldHdr)) + a.Width() + 1
+}
+
+// smallestDirent64 returns the size of the smallest possible dirent using
+// the new linux dirent format.
+func smallestDirent64(a arch.Context) uint {
+	d := dirent{}
+	return uint(binary.Size(d.Hdr)) + a.Width()
+}
+
+// toType converts an fs.InodeOperationsInfo to a linux dirent typ field.
+func toType(nodeType fs.InodeType) uint8 {
+	switch nodeType {
+	case fs.RegularFile, fs.SpecialFile:
+		return syscall.DT_REG
+	case fs.Symlink:
+		return syscall.DT_LNK
+	case fs.Directory:
+		return syscall.DT_DIR
+	case fs.Pipe:
+		return syscall.DT_FIFO
+	case fs.CharacterDevice:
+		return syscall.DT_CHR
+	case fs.BlockDevice:
+		return syscall.DT_BLK
+	case fs.Socket:
+		return syscall.DT_SOCK
+	default:
+		return syscall.DT_UNKNOWN
+	}
+}
+
+// padRec pads the name field until the rec length is a multiple of the width,
+// which must be a power of 2. It returns the padded rec length.
+func (d *dirent) padRec(width int) uint16 {
+	a := int(binary.Size(d.Hdr)) + len(d.Name)
+	r := (a + width) &^ (width - 1)
+	padding := r - a
+	d.Name = append(d.Name, make([]byte, padding)...)
+	return uint16(r)
+}
+
+// Serialize64 serializes a Dirent struct to a byte slice, keeping the new
+// linux dirent format. Returns the number of bytes serialized or an error.
+func (d *dirent) Serialize64(w io.Writer) (int, error) {
+	n1, err := w.Write(binary.Marshal(nil, usermem.ByteOrder, d.Hdr))
+	if err != nil {
+		return 0, err
+	}
+	n2, err := w.Write(d.Name)
+	if err != nil {
+		return 0, err
+	}
+	return n1 + n2, nil
+}
+
+// Serialize serializes a Dirent struct to a byte slice, using the old linux
+// dirent format.
+// Returns the number of bytes serialized or an error.
+func (d *dirent) Serialize(w io.Writer) (int, error) {
+	n1, err := w.Write(binary.Marshal(nil, usermem.ByteOrder, d.Hdr.OldHdr))
+	if err != nil {
+		return 0, err
+	}
+	n2, err := w.Write(d.Name)
+	if err != nil {
+		return 0, err
+	}
+	n3, err := w.Write([]byte{d.Hdr.Typ})
+	if err != nil {
+		return 0, err
+	}
+	return n1 + n2 + n3, nil
+}
+
+// direntSerializer implements fs.InodeOperationsInfoSerializer, serializing dirents to an
+// io.Writer.
+type direntSerializer struct {
+	serialize func(*dirent, io.Writer) (int, error)
+	w         io.Writer
+	// width is the arch native value width.
+	width uint
+	// offset is the current dirent offset.
+	offset uint64
+	// written is the total bytes serialized.
+	written int
+	// size is the size of the buffer to serialize into.
+	size int
+}
+
+func newDirentSerializer(f func(d *dirent, w io.Writer) (int, error), w io.Writer, ac arch.Context, size int) *direntSerializer {
+	return &direntSerializer{
+		serialize: f,
+		w:         w,
+		width:     ac.Width(),
+		size:      size,
+	}
+}
+
+// CopyOut implements fs.InodeOperationsInfoSerializer.CopyOut.
+// It serializes and writes the fs.DentAttr to the direntSerializer io.Writer.
+func (ds *direntSerializer) CopyOut(name string, attr fs.DentAttr) error {
+	ds.offset++
+
+	d := newDirent(ds.width, name, attr, ds.offset)
+
+	// Serialize dirent into a temp buffer.
+	var b bytes.Buffer
+	n, err := ds.serialize(d, &b)
+	if err != nil {
+		ds.offset--
+		return err
+	}
+
+	// Check that we have enough room remaining to write the dirent.
+	if n > (ds.size - ds.written) {
+		ds.offset--
+		return io.EOF
+	}
+
+	// Write out the temp buffer.
+	if _, err := b.WriteTo(ds.w); err != nil {
+		ds.offset--
+		return err
+	}
+
+	ds.written += n
+	return nil
+}
+
+// Written returns the total number of bytes written.
+func (ds *direntSerializer) Written() int {
+	return ds.written
+}