diff options
Diffstat (limited to 'pkg/sentry')
| -rw-r--r-- | pkg/sentry/fs/ext4/disklayout/BUILD | 21 | ||||
| -rw-r--r-- | pkg/sentry/fs/ext4/disklayout/block_group.go | 135 | ||||
| -rw-r--r-- | pkg/sentry/fs/ext4/disklayout/block_group_32.go | 75 | ||||
| -rw-r--r-- | pkg/sentry/fs/ext4/disklayout/block_group_64.go | 93 | ||||
| -rw-r--r-- | pkg/sentry/fs/ext4/disklayout/block_group_test.go | 34 |
5 files changed, 358 insertions, 0 deletions
diff --git a/pkg/sentry/fs/ext4/disklayout/BUILD b/pkg/sentry/fs/ext4/disklayout/BUILD new file mode 100644 index 000000000..2fb1d5b37 --- /dev/null +++ b/pkg/sentry/fs/ext4/disklayout/BUILD @@ -0,0 +1,21 @@ +package(licenses = ["notice"]) + +load("//tools/go_stateify:defs.bzl", "go_library", "go_test") + +go_library( + name = "disklayout", + srcs = [ + "block_group.go", + "block_group_32.go", + "block_group_64.go", + ], + importpath = "gvisor.dev/gvisor/pkg/sentry/fs/ext4/disklayout", +) + +go_test( + name = "disklayout_test", + size = "small", + srcs = ["block_group_test.go"], + embed = [":disklayout"], + deps = ["//pkg/binary"], +) diff --git a/pkg/sentry/fs/ext4/disklayout/block_group.go b/pkg/sentry/fs/ext4/disklayout/block_group.go new file mode 100644 index 000000000..7359df5b9 --- /dev/null +++ b/pkg/sentry/fs/ext4/disklayout/block_group.go @@ -0,0 +1,135 @@ +// 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 provides ext4 disk level structures which can be directly +// filled with bytes from the underlying device. All structures on disk are in +// little-endian order. Only jbd2 (journal) structures are in big-endian order. +// Structs aim to emulate structures `exactly` how they are layed out on disk. +// +// Note: All fields in these structs are exported because binary.Read would +// panic otherwise. +package disklayout + +// BlockGroup represents Linux struct ext4_group_desc which is internally +// called a block group descriptor. An ext4 file system is split into a series +// of block groups. This provides an access layer to information needed to +// access and use a block group. +// +// See https://www.kernel.org/doc/html/latest/filesystems/ext4/globals.html#block-group-descriptors. +type BlockGroup interface { + // InodeTable returns the absolute block number of the block containing the + // inode table. This points to an array of Inode structs. Inode tables are + // statically allocated at mkfs time. The superblock records the number of + // inodes per group (length of this table). + InodeTable() uint64 + + // BlockBitmap returns the absolute block number of the block containing the + // block bitmap. This bitmap tracks the usage of data blocks within this block + // group and has its own checksum. + BlockBitmap() uint64 + + // InodeBitmap returns the absolute block number of the block containing the + // inode bitmap. This bitmap tracks the usage of this group's inode table + // entries and has its own checksum. + InodeBitmap() uint64 + + // ExclusionBitmap returns the absolute block number of the snapshot exclusion + // bitmap. + ExclusionBitmap() uint64 + + // FreeBlocksCount returns the number of free blocks in the group. + FreeBlocksCount() uint32 + + // FreeInodesCount returns the number of free inodes in the group. + FreeInodesCount() uint32 + + // DirectoryCount returns the number of inodes that represent directories + // under this block group. + DirectoryCount() uint32 + + // UnusedInodeCount returns the number of unused inodes beyond the last used + // inode in this group's inode table. As a result, we needn’t scan past the + // (InodesPerGroup - UnusedInodeCount())th entry in the inode table. + UnusedInodeCount() uint32 + + // BlockBitmapChecksum returns the block bitmap checksum. This is calculated + // using crc32c(FS UUID + group number + entire bitmap). + BlockBitmapChecksum() uint32 + + // InodeBitmapChecksum returns the inode bitmap checksum. This is calculated + // using crc32c(FS UUID + group number + entire bitmap). + InodeBitmapChecksum() uint32 + + // Checksum returns this block group's checksum. + // + // If RO_COMPAT_METADATA_CSUM feature is set: + // - checksum is crc32c(FS UUID + group number + group descriptor + // structure) & 0xFFFF. + // + // If RO_COMPAT_GDT_CSUM feature is set: + // - checksum is crc16(FS UUID + group number + group descriptor + // structure). + // + // RO_COMPAT_METADATA_CSUM and RO_COMPAT_GDT_CSUM should not be both set. + // If they are, Linux warns and asks to run fsck. + Checksum() uint16 + + // Flags returns BGFlags which represents the block group flags. + Flags() BGFlags +} + +// These are the different block group flags. +const ( + // BgInodeUninit indicates that inode table and bitmap are not initialized. + BgInodeUninit uint16 = 0x1 + + // BgBlockUninit indicates that block bitmap is not initialized. + BgBlockUninit uint16 = 0x2 + + // BgInodeZeroed indicates that inode table is zeroed. + BgInodeZeroed uint16 = 0x4 +) + +// BGFlags represents all the different combinations of block group flags. +type BGFlags struct { + InodeUninit bool + BlockUninit bool + InodeZeroed bool +} + +// ToInt converts a BGFlags struct back to its 16-bit representation. +func (f BGFlags) ToInt() uint16 { + var res uint16 + + if f.InodeUninit { + res |= BgInodeUninit + } + if f.BlockUninit { + res |= BgBlockUninit + } + if f.InodeZeroed { + res |= BgInodeZeroed + } + + return res +} + +// BGFlagsFromInt converts the 16-bit flag representation to a BGFlags struct. +func BGFlagsFromInt(flags uint16) BGFlags { + return BGFlags{ + InodeUninit: (flags & BgInodeUninit) > 0, + BlockUninit: (flags & BgBlockUninit) > 0, + InodeZeroed: (flags & BgInodeZeroed) > 0, + } +} diff --git a/pkg/sentry/fs/ext4/disklayout/block_group_32.go b/pkg/sentry/fs/ext4/disklayout/block_group_32.go new file mode 100644 index 000000000..087f1fb4a --- /dev/null +++ b/pkg/sentry/fs/ext4/disklayout/block_group_32.go @@ -0,0 +1,75 @@ +// 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 + +// BlockGroup32Bit emulates the first half of struct ext4_group_desc in +// fs/ext4/ext4.h. It is the block group descriptor struct for 32-bit ext4 +// filesystems. It implements BlockGroup interface. +// +// The suffix `Lo` here stands for lower bits because this is also used in the +// 64-bit version where these fields represent the lower half of the fields. +// The suffix `Raw` has been added to indicate that the field does not have a +// counterpart in the 64-bit version and to resolve name collision with the +// interface. +type BlockGroup32Bit struct { + BlockBitmapLo uint32 + InodeBitmapLo uint32 + InodeTableLo uint32 + FreeBlocksCountLo uint16 + FreeInodesCountLo uint16 + UsedDirsCountLo uint16 + FlagsRaw uint16 + ExcludeBitmapLo uint32 + BlockBitmapChecksumLo uint16 + InodeBitmapChecksumLo uint16 + ItableUnusedLo uint16 + ChecksumRaw uint16 +} + +// InodeTable implements BlockGroup.InodeTable. +func (bg *BlockGroup32Bit) InodeTable() uint64 { return uint64(bg.InodeTableLo) } + +// BlockBitmap implements BlockGroup.BlockBitmap. +func (bg *BlockGroup32Bit) BlockBitmap() uint64 { return uint64(bg.BlockBitmapLo) } + +// InodeBitmap implements BlockGroup.InodeBitmap. +func (bg *BlockGroup32Bit) InodeBitmap() uint64 { return uint64(bg.InodeBitmapLo) } + +// ExclusionBitmap implements BlockGroup.ExclusionBitmap. +func (bg *BlockGroup32Bit) ExclusionBitmap() uint64 { return uint64(bg.ExcludeBitmapLo) } + +// FreeBlocksCount implements BlockGroup.FreeBlocksCount. +func (bg *BlockGroup32Bit) FreeBlocksCount() uint32 { return uint32(bg.FreeBlocksCountLo) } + +// FreeInodesCount implements BlockGroup.FreeInodesCount. +func (bg *BlockGroup32Bit) FreeInodesCount() uint32 { return uint32(bg.FreeInodesCountLo) } + +// DirectoryCount implements BlockGroup.DirectoryCount. +func (bg *BlockGroup32Bit) DirectoryCount() uint32 { return uint32(bg.UsedDirsCountLo) } + +// UnusedInodeCount implements BlockGroup.UnusedInodeCount. +func (bg *BlockGroup32Bit) UnusedInodeCount() uint32 { return uint32(bg.ItableUnusedLo) } + +// BlockBitmapChecksum implements BlockGroup.BlockBitmapChecksum. +func (bg *BlockGroup32Bit) BlockBitmapChecksum() uint32 { return uint32(bg.BlockBitmapChecksumLo) } + +// InodeBitmapChecksum implements BlockGroup.InodeBitmapChecksum. +func (bg *BlockGroup32Bit) InodeBitmapChecksum() uint32 { return uint32(bg.InodeBitmapChecksumLo) } + +// Checksum implements BlockGroup.Checksum. +func (bg *BlockGroup32Bit) Checksum() uint16 { return bg.ChecksumRaw } + +// Flags implements BlockGroup.Flags. +func (bg *BlockGroup32Bit) Flags() BGFlags { return BGFlagsFromInt(bg.FlagsRaw) } diff --git a/pkg/sentry/fs/ext4/disklayout/block_group_64.go b/pkg/sentry/fs/ext4/disklayout/block_group_64.go new file mode 100644 index 000000000..27de3990d --- /dev/null +++ b/pkg/sentry/fs/ext4/disklayout/block_group_64.go @@ -0,0 +1,93 @@ +// 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 + +// BlockGroup64Bit emulates struct ext4_group_desc in fs/ext4/ext4.h. +// It is the block group descriptor struct for 64-bit ext4 filesystems. +// It implements BlockGroup interface. It is an extension of the 32-bit +// version of BlockGroup. +// +// The suffix `Hi` here stands for upper bits because they represent the upper +// half of the fields. +type BlockGroup64Bit struct { + // We embed the 32-bit struct here because 64-bit version is just an extension + // of the 32-bit version. + BlockGroup32Bit + + // 64-bit specific fields. + BlockBitmapHi uint32 + InodeBitmapHi uint32 + InodeTableHi uint32 + FreeBlocksCountHi uint16 + FreeInodesCountHi uint16 + UsedDirsCountHi uint16 + ItableUnusedHi uint16 + ExcludeBitmapHi uint32 + BlockBitmapChecksumHi uint16 + InodeBitmapChecksumHi uint16 + _ uint32 // Padding to 64 bytes. +} + +// Methods to override. Checksum() and Flags() are not overridden. + +// InodeTable implements BlockGroup.InodeTable. +func (bg *BlockGroup64Bit) InodeTable() uint64 { + return (uint64(bg.InodeTableHi) << 32) | uint64(bg.InodeTableLo) +} + +// BlockBitmap implements BlockGroup.BlockBitmap. +func (bg *BlockGroup64Bit) BlockBitmap() uint64 { + return (uint64(bg.BlockBitmapHi) << 32) | uint64(bg.BlockBitmapLo) +} + +// InodeBitmap implements BlockGroup.InodeBitmap. +func (bg *BlockGroup64Bit) InodeBitmap() uint64 { + return (uint64(bg.InodeBitmapHi) << 32) | uint64(bg.InodeBitmapLo) +} + +// ExclusionBitmap implements BlockGroup.ExclusionBitmap. +func (bg *BlockGroup64Bit) ExclusionBitmap() uint64 { + return (uint64(bg.ExcludeBitmapHi) << 32) | uint64(bg.ExcludeBitmapLo) +} + +// FreeBlocksCount implements BlockGroup.FreeBlocksCount. +func (bg *BlockGroup64Bit) FreeBlocksCount() uint32 { + return (uint32(bg.FreeBlocksCountHi) << 16) | uint32(bg.FreeBlocksCountLo) +} + +// FreeInodesCount implements BlockGroup.FreeInodesCount. +func (bg *BlockGroup64Bit) FreeInodesCount() uint32 { + return (uint32(bg.FreeInodesCountHi) << 16) | uint32(bg.FreeInodesCountLo) +} + +// DirectoryCount implements BlockGroup.DirectoryCount. +func (bg *BlockGroup64Bit) DirectoryCount() uint32 { + return (uint32(bg.UsedDirsCountHi) << 16) | uint32(bg.UsedDirsCountLo) +} + +// UnusedInodeCount implements BlockGroup.UnusedInodeCount. +func (bg *BlockGroup64Bit) UnusedInodeCount() uint32 { + return (uint32(bg.ItableUnusedHi) << 16) | uint32(bg.ItableUnusedLo) +} + +// BlockBitmapChecksum implements BlockGroup.BlockBitmapChecksum. +func (bg *BlockGroup64Bit) BlockBitmapChecksum() uint32 { + return (uint32(bg.BlockBitmapChecksumHi) << 16) | uint32(bg.BlockBitmapChecksumLo) +} + +// InodeBitmapChecksum implements BlockGroup.InodeBitmapChecksum. +func (bg *BlockGroup64Bit) InodeBitmapChecksum() uint32 { + return (uint32(bg.InodeBitmapChecksumHi) << 16) | uint32(bg.InodeBitmapChecksumLo) +} diff --git a/pkg/sentry/fs/ext4/disklayout/block_group_test.go b/pkg/sentry/fs/ext4/disklayout/block_group_test.go new file mode 100644 index 000000000..794ae99cc --- /dev/null +++ b/pkg/sentry/fs/ext4/disklayout/block_group_test.go @@ -0,0 +1,34 @@ +// 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" + + "gvisor.dev/gvisor/pkg/binary" +) + +// TestBlockGroupSize tests the fact that the block group struct for +// 32-bit ext filesystems should be exactly 32 bytes big and for 64-bit fs it +// should be 64 bytes. +func TestBlockGroupSize(t *testing.T) { + if got, want := int(binary.Size(BlockGroup32Bit{})), 32; got != want { + t.Errorf("BlockGroup32Bit should be exactly 32 bytes but is %d bytes", got) + } + + if got, want := int(binary.Size(BlockGroup64Bit{})), 64; got != want { + t.Errorf("BlockGroup64Bit should be exactly 64 bytes but is %d bytes", got) + } +} |