[PATCH v3 0/7] fit: dm-verity support

[Daniel Golle <daniel@makrotopia.org>]

This series adds dm-verity support to U-Boot's FIT image infrastructure.
It is the first logical subset of the larger OpenWrt boot method series
posted as an RFC in February 2026 [1], extracted here for independent
review and merging.

OpenWrt's firmware model embeds a read-only squashfs or erofs root
filesystem directly inside a uImage.FIT container as a FILESYSTEM-type
loadable FIT image. At boot the kernel maps this sub-image directly from
the underlying block device via the fitblk driver (/dev/fit0, /dev/fit1,
...), the goal is that the bootloader never even copies it to RAM.

dm-verity enables the kernel to verify the integrity of those mapped
filesystems at read time, with a Merkle hash tree stored contiguously in
the same sub-image just after the data. Two kernel command-line
parameters are required:

  dm-mod.create=   -- the device-mapper target table for the verity device
  dm-mod.waitfor=  -- a comma-separated list of block devices to wait for
                      before dm-init sets up the targets (needed when fitblk
                      probes late, e.g. because it depends on NVMEM
                      calibration data)

The FIT dm-verity node schema was upstreamed into the flat-image-tree
specification [2], which this implementation tries to follow exactly.

The runtime feature is guarded behind CONFIG_FIT_VERITY. If not
enabled the resulting binary size remains unchanged. If enabled the
binary size increases by about 3kB.

[1] previous submissions:
    RFC: https://www.mail-archive.com/u-boot@lists.denx.de/msg565945.html
    v1:  https://www.mail-archive.com/u-boot@lists.denx.de/msg569472.html
    v2:  https://www.mail-archive.com/u-boot@lists.denx.de/msg570599.html
[2] flat-image-tree dm-verity node spec:
    https://github.com/open-source-firmware/flat-image-tree/commit/795fd5fd7f0121d0cb03efb1900aafc61c704771

v3: address comments by Heinrich Schuchardt and Simon Glass
 * use unsigned int instead of int for data-block-size and hash-block-size
 * replace printf() with log_err() for the "broken dm-verity metadata"
   diagnostic
 * use FIT_VERITY_*_PROP, FIT_TYPE_PROP and FIT_LOADABLE_PROP constants
   in the unit test instead of literal strings
 * extend the mkimage block-count overflow check to also cover
   hash_start_block (matters when hash-block-size < data-block-size)
 * doc: clarify that hash-start-block only equals num-data-blocks when
   data-block-size == hash-block-size
 * pytest: drop unused 'struct' import and the home-rolled
   have_veritysetup() helper in favour of
   @pytest.mark.requiredtool('veritysetup')

v2: address comments by Simon Glass
 * use is_power_of_2() for pre-boot sanity check
 * let fit_verity_build_cmdline() return 0 on success
 * add comment explaining why bootm_start() calls fit_verity_free()
 * use existing hex2bin() (and adapt it to be usable for host-tools)
 * fix stale comment still including superblock despite veritysetup
   being called with --no-superblock
 * add power-of-two check for data-block-size and hash-block-size to
   mkimage
 * don't ignore return value of fdt_delprop()
 * various documentation fixes, minimal example
 * add pytest for mkimage part
 * add run-time unit test for cmdline generation part

Daniel Golle (7):
  image: fit: add dm-verity property name constants
  boot: fit: support generating DM verity cmdline parameters
  include: hexdump: make hex2bin() usable from host tools
  tools: mkimage: add dm-verity Merkle-tree generation
  doc: fit: add dm-verity boot parameter documentation
  test: boot: add runtime unit test for fit_verity_build_cmdline()
  test: py: add mkimage dm-verity round-trip test

 boot/Kconfig                     |  20 ++
 boot/bootm.c                     |  13 ++
 boot/image-board.c               |   5 +
 boot/image-fit.c                 | 337 +++++++++++++++++++++++++++++
 doc/usage/fit/dm-verity.rst      | 284 +++++++++++++++++++++++++
 doc/usage/fit/index.rst          |   1 +
 include/hexdump.h                |   8 +-
 include/image.h                  |  97 ++++++++-
 test/boot/Makefile               |   1 +
 test/boot/fit_verity.c           | 306 +++++++++++++++++++++++++++
 test/cmd_ut.c                    |   2 +
 test/py/tests/test_fit_verity.py | 145 +++++++++++++
 tools/fit_image.c                | 116 +++++++++-
 tools/image-host.c               | 350 ++++++++++++++++++++++++++++++-
 14 files changed, 1672 insertions(+), 13 deletions(-)
 create mode 100644 doc/usage/fit/dm-verity.rst
 create mode 100644 test/boot/fit_verity.c
 create mode 100644 test/py/tests/test_fit_verity.py

-- 
2.54.0