package main import ( "encoding/binary" "encoding/hex" "hash/crc32" "strings" "time" "lukeshu.com/btrfs-tools/pkg/binstruct" ) type ( PhysicalAddr int64 LogicalAddr int64 ObjID int64 CSum [0x20]byte UUID [16]byte ) func (uuid UUID) String() string { str := hex.EncodeToString(uuid[:]) return strings.Join([]string{ str[:8], str[8:12], str[12:16], str[16:20], str[20:32], }, "-") } func crc32c(data []byte) CSum { sum := crc32.Update(0xFFFFFFFF, crc32.MakeTable(0x1EDC6F41), data) var buf CSum binary.LittleEndian.PutUint32(buf[:], sum) return buf } type Key struct { ObjectID ObjID `bin:"off=0, siz=8, desc=Object ID. Each tree has its own set of Object IDs."` ItemType uint8 `bin:"off=8, siz=1, desc=Item type."` Offset uint64 `bin:"off=9, siz=8, desc=Offset. The meaning depends on the item type."` binstruct.End `bin:"off=11"` } type Time struct { Sec int64 `bin:"off=0, siz=8, desc=Number of seconds since 1970-01-01T00:00:00Z."` NSec uint64 `bin:"off=8, siz=4, desc=Number of nanoseconds since the beginning of the second."` binstruct.End `bin:"off=c"` } func (t Time) ToStd() time.Time { return time.Unix(t.Sec, int64(t.NSec)) } type Superblock struct { Checksum CSum `bin:"off=0, siz=20, desc=Checksum of everything past this field (from 20 to 1000)"` FSUUID UUID `bin:"off=20, siz=10, desc=FS UUID"` Self PhysicalAddr `bin:"off=30, siz=8, desc=physical address of this block (different for mirrors)"` Flags uint64 `bin:"off=38, siz=8, desc=flags"` Magic [8]byte `bin:"off=40, siz=8, desc=magic ('_BHRfS_M')"` Generation uint64 `bin:"off=48, siz=8, desc=generation"` RootTree LogicalAddr `bin:"off=50, siz=8, desc=logical address of the root tree root"` ChunkTree LogicalAddr `bin:"off=58, siz=8, desc=logical address of the chunk tree root"` LogTree LogicalAddr `bin:"off=60, siz=8, desc=logical address of the log tree root"` LogRootTransID uint64 `bin:"off=68, siz=8, desc=log_root_transid"` TotalBytes uint64 `bin:"off=70, siz=8, desc=total_bytes"` BytesUsed uint64 `bin:"off=78, siz=8, desc=bytes_used"` RootDirObjectID uint64 `bin:"off=80, siz=8, desc=root_dir_objectid (usually 6)"` NumDevices uint64 `bin:"off=88, siz=8, desc=num_devices"` SectorSize uint32 `bin:"off=90, siz=4, desc=sectorsize"` NodeSize uint32 `bin:"off=94, siz=4, desc=nodesize"` LeafSize uint32 `bin:"off=98, siz=4, desc=leafsize"` StripeSize uint32 `bin:"off=9c, siz=4, desc=stripesize"` SysChunkArraySize uint32 `bin:"off=a0, siz=4, desc=sys_chunk_array_size"` ChunkRootGeneration uint64 `bin:"off=a4, siz=8, desc=chunk_root_generation"` CompatFlags uint64 `bin:"off=ac, siz=8, desc=compat_flags"` CompatROFlags uint64 `bin:"off=b4, siz=8, desc=compat_ro_flags - only implementations that support the flags can write to the filesystem"` IncompatFlags uint64 `bin:"off=bc, siz=8, desc=incompat_flags - only implementations that support the flags can use the filesystem"` ChecksumType uint16 `bin:"off=c4, siz=2, desc=csum_type - Btrfs currently uses the CRC32c little-endian hash function with seed -1."` RootLevel uint8 `bin:"off=c6, siz=1, desc=root_level"` ChunkLevel uint8 `bin:"off=c7, siz=1, desc=chunk_root_level"` LogLevel uint8 `bin:"off=c8, siz=1, desc=log_root_level"` DevItem DevItem `bin:"off=c9, siz=62, desc=DEV_ITEM data for this device"` Label [0x100]byte `bin:"off=12b, siz=100, desc=label (may not contain '/' or '\\')"` CacheGeneration uint64 `bin:"off=22b, siz=8, desc=cache_generation"` UUIDTreeGeneration uint64 `bin:"off=233, siz=8, desc=uuid_tree_generation"` Reserved [0xf0]byte `bin:"off=23b, siz=f0, desc=reserved /* future expansion */"` TODOSysChunkArray [0x800]byte `bin:"off=32b, siz=800, desc=sys_chunk_array:(n bytes valid) Contains (KEY . CHUNK_ITEM) pairs for all SYSTEM chunks. This is needed to bootstrap the mapping from logical addresses to physical. "` TODOSuperRoots [0x2a0]byte `bin:"off=b2b, siz=2a0, desc=Contain super_roots (4 btrfs_root_backup)"` Unused [0x235]byte `bin:"off=dcb, siz=235, desc=current unused"` binstruct.End `bin:"off=1000"` } func (sb Superblock) CalculateChecksum() (CSum, error) { data, err := binstruct.Marshal(sb) if err != nil { return CSum{}, err } return crc32c(data[0x20:]), nil } type DevItem struct { DeviceID uint64 `bin:"off=0, siz=8, desc=device id"` NumBytes uint64 `bin:"off=8, siz=8, desc=number of bytes"` NumBytesUsed uint64 `bin:"off=10, siz=8, desc=number of bytes used"` IOOptimalAlign uint32 `bin:"off=18, siz=4, desc=optimal I/O align"` IOOptimalWidth uint32 `bin:"off=1c, siz=4, desc=optimal I/O width"` IOMinSize uint32 `bin:"off=20, siz=4, desc=minimal I/O size (sector size)"` Type uint64 `bin:"off=24, siz=8, desc=type"` Generation uint64 `bin:"off=2c, siz=8, desc=generation"` StartOffset uint64 `bin:"off=34, siz=8, desc=start offset"` DevGroup uint32 `bin:"off=3c, siz=4, desc=dev group"` SeekSpeed uint8 `bin:"off=40, siz=1, desc=seek speed"` Bandwidth uint8 `bin:"off=41, siz=1, desc=bandwidth"` DevUUID UUID `bin:"off=42, siz=10, desc=device UUID"` FSUUID UUID `bin:"off=52, siz=10, desc=FS UUID"` binstruct.End `bin:"off=62"` } type ChunkItem struct { // Maps logical address to physical. Size uint64 `bin:"off=0, siz=8, desc=size of chunk (bytes)"` Root ObjID `bin:"off=8, siz=8, desc=root referencing this chunk (2)"` StripeLen uint64 `bin:"off=10, siz=8, desc=stripe length"` Type uint64 `bin:"off=18, siz=8, desc=type (same as flags for block group?)"` IOOptimalAlign uint32 `bin:"off=20, siz=4, desc=optimal io alignment"` IOOptimalWidth uint32 `bin:"off=24, siz=4, desc=optimal io width"` IoMinSize uint32 `bin:"off=28, siz=4, desc=minimal io size (sector size)"` NumStripes uint16 `bin:"off=2c, siz=2, desc=number of stripes"` SubStripes uint16 `bin:"off=2e, siz=2, desc=sub stripes"` binstruct.End `bin:"off=30"` } type ChunkItemStripe struct { // Stripes follow (for each number of stripes): DeviceID ObjID `bin:"off=0, siz=8, desc=device id"` Offset uint64 `bin:"off=8, siz=8, desc=offset"` DeviceUUID UUID `bin:"off=10, siz=10, desc=device UUID"` binstruct.End `bin:"off=20"` }