[PATCH v3 0/7] efi: CapsuleUpdate: support for dynamic UUIDs

[Caleb Connolly]

As more boards adopt support for the EFI CapsuleUpdate mechanism, there
is a growing issue of being able to target updates to them properly. The
current mechanism of hardcoding UUIDs for each board at compile time is
unsustainable, and maintaining lists of GUIDs is similarly cumbersome.

In this series, I propose that we adopt v5 GUIDs, these are generated
by using a well-known salt GUID as well as board specific information
(like the model/revision), these are hashed together and the result is
truncated to form a new UUID.

The well-known salt GUID can be specific to the architecture (SoC
vendor), or OEM. It is defined in the board defconfig so that vendors
can easily bring their own.

Specifically, the following fields are used to generate a GUID for a
particular fw_image:

* namespace salt
* board compatible (usually the first entry in the dt root compatible
  array).
* fw_image name (the string identifying the specific image, especially
  relevant for board that can update multiple images).

== Usage ==

Boards can integrate dynamic UUID support as follows:

1. Adjust Kconfig to depend on EFI_CAPSULE_DYNAMIC_UUIDS if
   EFI_HAVE_CAPSULE_SUPPORT.
2. Skip setting the fw_images image_type_id property.
3. Generate a UUID and set CONFIG_EFI_CAPSULE_NAMESPACE_UUID in your
   defconfig.

== Limitations ==

* Changing GUIDs

The primary limitation with this approach is that if any of the source
fields change, so will the GUID for the board. It is therefore pretty
important to ensure that GUID changes are caught during development.

* Supporting multiple boards with a single image

This now requires having an entry with the GUID for every board which
might lead to larger UpdateCapsule images.

== Tooling ==

This series introduces a new tool: genguid. This can be used to generate
the same GUIDs that the board would at runtime.

This series follows a related discussion started by Ilias:
https://lore.kernel.org/u-boot/CAC_iWjJNHa4gMF897MqYZNdbgjFG8K4kwGsTXWuy72WkYLizrw@mail.gmail.com/

---
Changes in v3:
- Add manpage for genguid
- Add dedicated CONFIG_TOOLS_GENGUID option
- Minor code fixes addressing v2 feedback
- Link to v2: https://lore.kernel.org/r/20240529-b4-dynamic-uuid-v2-0-c26f31057bbe@linaro.org

Changes in v2:
- Move namespace UUID to be defined in defconfig
- Add tests and tooling
- Only use the first board compatible to generate UUID.
- Link to v1: https://lore.kernel.org/r/20240426-b4-dynamic-uuid-v1-0-e8154e00ec44@linaro.org

---
Caleb Connolly (7):
      lib: uuid: add UUID v5 support
      efi: add a helper to generate dynamic UUIDs
      doc: uefi: document dynamic UUID generation
      sandbox: switch to dynamic UUIDs
      lib: uuid: supporting building as part of host tools
      tools: add genguid tool
      test: lib/uuid: add unit tests for dynamic UUIDs

 arch/Kconfig                                       |   1 +
 board/sandbox/sandbox.c                            |  16 ---
 configs/sandbox_defconfig                          |   1 +
 configs/sandbox_flattree_defconfig                 |   1 +
 doc/develop/uefi/uefi.rst                          |  31 +++++
 doc/genguid.1                                      |  52 +++++++
 include/sandbox_efi_capsule.h                      |   6 +-
 include/uuid.h                                     |  21 ++-
 lib/Kconfig                                        |   8 ++
 lib/efi_loader/Kconfig                             |  23 +++
 lib/efi_loader/efi_capsule.c                       |   1 +
 lib/efi_loader/efi_firmware.c                      |  66 +++++++++
 lib/uuid.c                                         |  81 +++++++++--
 test/lib/uuid.c                                    |  88 ++++++++++++
 .../test_efi_capsule/test_capsule_firmware_fit.py  |   2 +-
 .../test_efi_capsule/test_capsule_firmware_raw.py  |   8 +-
 .../test_capsule_firmware_signed_fit.py            |   2 +-
 .../test_capsule_firmware_signed_raw.py            |   4 +-
 test/py/tests/test_efi_capsule/version.dts         |   6 +-
 tools/Kconfig                                      |   7 +
 tools/Makefile                                     |   3 +
 tools/binman/etype/efi_capsule.py                  |   2 +-
 tools/binman/ftest.py                              |   2 +-
 tools/genguid.c                                    | 154 +++++++++++++++++++++
 24 files changed, 538 insertions(+), 48 deletions(-)
---
change-id: 20240422-b4-dynamic-uuid-1a5ab1486c27
base-commit: 2e682a4a406fc81ef32e05c28542cc8067f1e15f

// Caleb (they/them)