Andrew Gunnerson
0a1888ad94
Newer Magisk versions no longer try to autodetect a writable ext4 partition for storing SELinux rules during boot. Instead, the block device is detected during boot image patching and is stored in the ramdisk's `.backup/.magisk` as `makedev(rdev_maj, rdev_min)`. This unfortunately complicates the patching process for avbroot. Even if we replicate Magisk's algorithm for finding a suitable partition, there's no way to find the block device's rdev for it with the information contained in the OTA package. This is the first change that adds a hard dependency on information only attainable from a running device. For these newer Magisk versions, the user will have to patch the boot image once in the Magisk app (must be on the target device) and then run `avbroot magisk-info` to show the computed device ID. Then, avbroot can use this during patching via `--magisk-rules-device`. If the user's device is unable to run the Magisk app prior to patching (eg. unbootable), they'll have to go through the patching process twice, once with `--ignore-magisk-warnings` and a second time with the proper device ID specified. When using `--ignore-magisk-warnings`, root still works, but there will be subtle issues, like certain modules failing to load. Signed-off-by: Andrew Gunnerson <accounts+github@chiller3.com>
avbroot extra
This directory contains some extra scripts that aren't required for avbroot's operation, but may be useful for troubleshooting.
bootimagetool
This is a frontend to the avbroot/formats/bootimage.py library for working with boot images.
Unpacking a boot image
python bootimagetool.py unpack <input boot image>
This subcommand unpacks all of the components of the boot image into the current directory by default (see --help). The header fields are saved to header.json and each blob section is saved to a separate file. Each blob is written to disk as-is, without decompression.
Packing a boot image
python bootimagetool.py pack <output boot image>
This subcommand packs a new boot image from the individual components in the current directory by default (see --help). The default input filenames are the same as the output filenames for the unpack subcommand.
Repacking a boot image
python bootimagetool.py repack <input boot image> <output boot image>
This subcommand repacks a boot image without writing the individual components to disk first. This is useful for roundtrip testing of avbroot's boot image parser. The output should be identical to the input, minus any footers, like the AVB footer. The only exception is the VTS signature for v4 boot images, which is always stripped out.
cpiotool
This is a frontend to the avbroot/formats/compression.py and avbroot/formats/cpio.py libraries. It is useful for inspecting compressed and uncompressed cpio archives.
Dumping a cpio archive
python cpiotool.py dump <cpio archive>
This subcommand dumps all information about a cpio archive to stdout. This includes the compression format, all header fields (including the trailer entry), and all data. If an entry's data can be decoded as UTF-8, then it is printed out as text. Otherwise, the binary data is printed out base64-encoded. The base64-encoded data is truncated to 5 lines by default to avoid outputting too much data, but this behavior can be disabled with --no-truncate.
Repacking a cpio archive
python cpiotool.py repack <input cpio archive> <output cpio archive>
This subcommand repacks a cpio archive, including recompression if needed. This is useful for roundtrip testing of avbroot's cpio parser and compression handling. The uncompressed output should be identical to the uncompressed input, except:
- files are sorted by name
- inodes are reassigned, starting from 300000
- there is no excess padding at the end of the file
The compressed output may differ from what other tools produce because:
- LZ4 legacy chunks are packed to exactly 8 MiB, except for the last chunk, which may be smaller.
- LZ4 legacy uses the high compression mode with a compression level of 12.
- The GZIP header has the modification timestamp set to 0 (Unix epoch time).
- GZIP uses a compression level of 9.