[RFC PATCH 0/4] capsule: Embed the public key ESL as part of build

[Sughosh Ganu]

This is a RFC series which takes a different approach to embedding the
public key EFI Signature List(ESL) needed for capsule authentication
into the platform's DTB.

The earlier approach [1] was using a u-boot.dtsi file to embed the
key. But this approach has a few issues. 1) The path of the incbin file
is not relative to $(srctree), but relative to the directory of the
dts file which is including the dtsi. 2) The u-boot.dtsi file only
gets included in the DTB if there are no other *u-boot.dtsi files
being included. 3) A separate u-boot.dtsi is needed per arch.

To get around these issues, this approach generates a dtsi
file(.capsule_esl.dtsi) with the public key node during build. This
generated dtsi file contains the resolved path to the ESL and is then
included for the DTB generation.

The first patch of the series also cleans up the logic to include the
dtsi files, by collating all the dtsi files to be included into a
single variable.

Since this is a RFC, I have only build tested this on sandbox variants
and not put this through a CI run.

These patches need to be applied on top of the series for generating
the capsules as part of the build [2].

[1] - https://lists.denx.de/pipermail/u-boot/2023-August/526323.html
[2] - https://lore.kernel.org/u-boot/20230812153024.334563-1-sughosh.ganu@linaro.org/T/#m85a50079007acf8943cfe8efcc7d78d23a40db7c


Sughosh Ganu (4):
  scripts/Makefile.lib: Collate all dtsi files for inclusion
  scripts/Makefile.lib: Embed capsule public key in platform's dtb
  sandbox: capsule: Add path to the public key ESL file
  doc: capsule: Document the new mechanism to embed ESL file into dtb

 configs/sandbox_defconfig          |  1 +
 configs/sandbox_flattree_defconfig |  1 +
 doc/develop/uefi/uefi.rst          | 19 +++++--------------
 lib/efi_loader/Kconfig             |  9 +++++++++
 lib/efi_loader/capsule_esl.dtsi.in | 11 +++++++++++
 scripts/Makefile.lib               | 28 ++++++++++++++++++++++++----
 6 files changed, 51 insertions(+), 18 deletions(-)
 create mode 100644 lib/efi_loader/capsule_esl.dtsi.in

-- 
2.34.1