diff options
| -rw-r--r-- | pkg/sentry/fs/ext4/disklayout/BUILD | 5 | ||||
| -rw-r--r-- | pkg/sentry/fs/ext4/disklayout/dirent.go | 69 | ||||
| -rw-r--r-- | pkg/sentry/fs/ext4/disklayout/dirent_new.go | 61 | ||||
| -rw-r--r-- | pkg/sentry/fs/ext4/disklayout/dirent_old.go | 50 | ||||
| -rw-r--r-- | pkg/sentry/fs/ext4/disklayout/dirent_test.go | 28 |
5 files changed, 213 insertions, 0 deletions
diff --git a/pkg/sentry/fs/ext4/disklayout/BUILD b/pkg/sentry/fs/ext4/disklayout/BUILD index d1cbab275..2920bfb52 100644 --- a/pkg/sentry/fs/ext4/disklayout/BUILD +++ b/pkg/sentry/fs/ext4/disklayout/BUILD @@ -8,6 +8,9 @@ go_library( "block_group.go", "block_group_32.go", "block_group_64.go", + "dirent.go", + "dirent_new.go", + "dirent_old.go", "disklayout.go", "inode.go", "inode_new.go", @@ -22,6 +25,7 @@ go_library( deps = [ "//pkg/abi/linux", "//pkg/binary", + "//pkg/sentry/fs", "//pkg/sentry/kernel/auth", "//pkg/sentry/kernel/time", ], @@ -32,6 +36,7 @@ go_test( size = "small", srcs = [ "block_group_test.go", + "dirent_test.go", "inode_test.go", "superblock_test.go", ], diff --git a/pkg/sentry/fs/ext4/disklayout/dirent.go b/pkg/sentry/fs/ext4/disklayout/dirent.go new file mode 100644 index 000000000..685bf57b8 --- /dev/null +++ b/pkg/sentry/fs/ext4/disklayout/dirent.go @@ -0,0 +1,69 @@ +// 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 disklayout + +import ( + "gvisor.dev/gvisor/pkg/sentry/fs" +) + +const ( + // MaxFileName is the maximum length of an ext fs file's name. + MaxFileName = 255 +) + +var ( + // inodeTypeByFileType maps ext4 file types to vfs inode types. + // + // See https://www.kernel.org/doc/html/latest/filesystems/ext4/dynamic.html#ftype. + inodeTypeByFileType = map[uint8]fs.InodeType{ + 0: fs.Anonymous, + 1: fs.RegularFile, + 2: fs.Directory, + 3: fs.CharacterDevice, + 4: fs.BlockDevice, + 5: fs.Pipe, + 6: fs.Socket, + 7: fs.Symlink, + } +) + +// The Dirent interface should be implemented by structs representing ext +// directory entries. These are for the linear classical directories which +// just store a list of dirent structs. A directory is a series of data blocks +// where is each data block contains a linear array of dirents. The last entry +// of the block has a record size that takes it to the end of the block. The +// end of the directory is when you read dirInode.Size() bytes from the blocks. +// +// See https://www.kernel.org/doc/html/latest/filesystems/ext4/dynamic.html#linear-classic-directories. +type Dirent interface { + // Inode returns the absolute inode number of the underlying inode. + // Inode number 0 signifies an unused dirent. + Inode() uint32 + + // RecordSize returns the record length of this dirent on disk. The next + // dirent in the dirent list should be read after these many bytes from + // the current dirent. Must be a multiple of 4. + RecordSize() uint16 + + // FileName returns the name of the file. Can be at most 255 is length. + FileName() string + + // FileType returns the inode type of the underlying inode. This is a + // performance hack so that we do not have to read the underlying inode struct + // to know the type of inode. This will only work when the SbDirentFileType + // feature is set. If not, the second returned value will be false indicating + // that user code has to use the inode mode to extract the file type. + FileType() (fs.InodeType, bool) +} diff --git a/pkg/sentry/fs/ext4/disklayout/dirent_new.go b/pkg/sentry/fs/ext4/disklayout/dirent_new.go new file mode 100644 index 000000000..29ae4a5c2 --- /dev/null +++ b/pkg/sentry/fs/ext4/disklayout/dirent_new.go @@ -0,0 +1,61 @@ +// 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 disklayout + +import ( + "fmt" + + "gvisor.dev/gvisor/pkg/sentry/fs" +) + +// DirentNew represents the ext4 directory entry struct. This emulates Linux's +// ext4_dir_entry_2 struct. The FileName can not be more than 255 bytes so we +// only need 8 bits to store the NameLength. As a result, NameLength has been +// shortened and the other 8 bits are used to encode the file type. Use the +// FileTypeRaw field only if the SbDirentFileType feature is set. +// +// Note: This struct can be of variable size on disk. The one described below +// is of maximum size and the FileName beyond NameLength bytes might contain +// garbage. +type DirentNew struct { + InodeNumber uint32 + RecordLength uint16 + NameLength uint8 + FileTypeRaw uint8 + FileNameRaw [MaxFileName]byte +} + +// Compiles only if DirentNew implements Dirent. +var _ Dirent = (*DirentNew)(nil) + +// Inode implements Dirent.Inode. +func (d *DirentNew) Inode() uint32 { return d.InodeNumber } + +// RecordSize implements Dirent.RecordSize. +func (d *DirentNew) RecordSize() uint16 { return d.RecordLength } + +// FileName implements Dirent.FileName. +func (d *DirentNew) FileName() string { + return string(d.FileNameRaw[:d.NameLength]) +} + +// FileType implements Dirent.FileType. +func (d *DirentNew) FileType() (fs.InodeType, bool) { + if inodeType, ok := inodeTypeByFileType[d.FileTypeRaw]; ok { + return inodeType, true + } + + panic(fmt.Sprintf("unknown file type %v", d.FileTypeRaw)) +} diff --git a/pkg/sentry/fs/ext4/disklayout/dirent_old.go b/pkg/sentry/fs/ext4/disklayout/dirent_old.go new file mode 100644 index 000000000..2e0f9c812 --- /dev/null +++ b/pkg/sentry/fs/ext4/disklayout/dirent_old.go @@ -0,0 +1,50 @@ +// 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 disklayout + +import "gvisor.dev/gvisor/pkg/sentry/fs" + +// DirentOld represents the old directory entry struct which does not contain +// the file type. This emulates Linux's ext4_dir_entry struct. This is used in +// ext2, ext3 and sometimes in ext4. +// +// Note: This struct can be of variable size on disk. The one described below +// is of maximum size and the FileName beyond NameLength bytes might contain +// garbage. +type DirentOld struct { + InodeNumber uint32 + RecordLength uint16 + NameLength uint16 + FileNameRaw [MaxFileName]byte +} + +// Compiles only if DirentOld implements Dirent. +var _ Dirent = (*DirentOld)(nil) + +// Inode implements Dirent.Inode. +func (d *DirentOld) Inode() uint32 { return d.InodeNumber } + +// RecordSize implements Dirent.RecordSize. +func (d *DirentOld) RecordSize() uint16 { return d.RecordLength } + +// FileName implements Dirent.FileName. +func (d *DirentOld) FileName() string { + return string(d.FileNameRaw[:d.NameLength]) +} + +// FileType implements Dirent.FileType. +func (d *DirentOld) FileType() (fs.InodeType, bool) { + return fs.Anonymous, false +} diff --git a/pkg/sentry/fs/ext4/disklayout/dirent_test.go b/pkg/sentry/fs/ext4/disklayout/dirent_test.go new file mode 100644 index 000000000..cc6dff2c9 --- /dev/null +++ b/pkg/sentry/fs/ext4/disklayout/dirent_test.go @@ -0,0 +1,28 @@ +// 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 disklayout + +import ( + "testing" +) + +// TestDirentSize tests that the dirent structs are of the correct +// size. +func TestDirentSize(t *testing.T) { + want := uintptr(263) + + assertSize(t, DirentOld{}, want) + assertSize(t, DirentNew{}, want) +} |