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|
package btrfs
import (
"fmt"
"os"
"lukeshu.com/btrfs-tools/pkg/binstruct"
)
type Img struct {
*os.File
}
func (img *Img) Size() (int64, error) {
fi, err := img.Stat()
if err != nil {
return 0, err
}
return fi.Size(), nil
}
type Ref[T any] struct {
img *Img
addr int64
Data T
}
func (r *Ref[T]) Read() error {
size, err := binstruct.Size(r.Data)
if err != nil {
return err
}
buf := make([]byte, size)
if _, err := r.img.ReadAt(buf, r.addr); err != nil {
return err
}
return binstruct.Unmarshal(buf, &r.Data)
}
var superblockAddrs = []int64{
0x00_0001_0000, // 64KiB
0x00_0400_0000, // 64MiB
0x40_0000_0000, // 256GiB
}
func (img *Img) Superblocks() ([]Ref[Superblock], error) {
const superblockSize = 0x1000
sz, err := img.Size()
if err != nil {
return nil, err
}
var ret []Ref[Superblock]
for i, addr := range superblockAddrs {
if addr+superblockSize <= sz {
superblock := Ref[Superblock]{
img: img,
addr: addr,
}
if err := superblock.Read(); err != nil {
return nil, fmt.Errorf("superblock %d: %w", i, err)
}
ret = append(ret, superblock)
}
}
if len(ret) == 0 {
return nil, fmt.Errorf("no superblocks")
}
return ret, nil
}
// ScanForNodes mimics btrfs-progs
// cmds/rescue-chunk-recover.c:scan_one_device(), except it doesn't do
// anything but log when it finds a node.
func (img *Img) ScanForNodes(sb Superblock) error {
devSize, err := img.Size()
if err != nil {
return err
}
if sb.NodeSize < sb.SectorSize {
return fmt.Errorf("node_size(%d) < sector_size(%d)",
sb.NodeSize, sb.SectorSize)
}
nodeBuf := make([]byte, sb.NodeSize)
for pos := int64(0); pos < devSize; pos += int64(sb.SectorSize) {
if inSlice(pos, superblockAddrs) {
fmt.Printf("sector@%d is a superblock\n", pos)
continue
}
if _, err := img.ReadAt(nodeBuf, pos); err != nil {
return fmt.Errorf("sector@%d: %w", pos, err)
}
var nodeHeader NodeHeader
if err := binstruct.Unmarshal(nodeBuf, &nodeHeader); err != nil {
return fmt.Errorf("sector@%d: %w", pos, err)
}
if !nodeHeader.MetadataUUID.Equal(sb.EffectiveMetadataUUID()) {
//fmt.Printf("sector@%d does not look like a node\n", pos)
continue
}
if !nodeHeader.Checksum.Equal(CRC32c(nodeBuf[0x20:])) {
fmt.Printf("sector@%d looks like a node but is corrupt (checksum doesn't match)\n", pos)
continue
}
fmt.Printf("node@%d: physical_addr=0x%0X logical_addr=0x%0X generation=%d owner_tree=%v level=%d\n",
pos, pos, nodeHeader.Addr, nodeHeader.Generation, nodeHeader.OwnerTree, nodeHeader.Level)
pos += int64(sb.NodeSize) - int64(sb.SectorSize)
}
return nil
}
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