Hi Trevor,
On 3/2/26 19:00, Trevor Gamblin wrote:
On 2026-03-01 16:17, Francesco Valla via lists.openembedded.org wrote:
Allow a user to insert additional, arbitrary loadables in a FIT image.
The loadables can be specified through the FIT_LOADABLES variable as
a list, with parameters defined by flags on dedicated FIT_LOADABLE_*
variables; they will be included in all configurations.
Sensible defaults will be used for some parameters (type, compression,
description, arch, os) if the corresponding flag is not set, while
others (load address and entry point) will be omitted in the final FIT
image.
As an example, the following configuration can be specified to add as
loadables a TF-A BL31 firmware and a (compressed) TEE firmware, to be
loaded respectively at 0x204E0000 and 0x96000000:
FIT_LOADABLES = "atf tee"
FIT_LOADABLE_FILENAME[atf] = "bl31.bin"
FIT_LOADABLE_TYPE[atf] = "tfa-bl31"
FIT_LOADABLE_ARCH[atf] = "arm64"
FIT_LOADABLE_OS[atf] = "arm-trusted-firmware"
FIT_LOADABLE_LOADADDRESS[atf] = "0x204E0000"
FIT_LOADABLE_FILENAME[tee] = "tee.bin.gz"
FIT_LOADABLE_COMPRESSSION[tee] = "gzip"
FIT_LOADABLE_TYPE[tee] = "tee"
FIT_LOADABLE_OS[tee] = "tee"
FIT_LOADABLE_LOADADDRESS[tee] = "0x21000000"
Signed-off-by: Francesco Valla <[email protected]>
---
Hello,
(sending this shortly after the v1 because that one had a wrong approach
to testing - sorry for the noise)
this patchset adds the possibility to include arbitrary loadables in a
kernel FIT image and to define all associated parameters (description,
compression, type, arch, os, load address and entry address) through
variables.
The idea behind the proposal is to be able to generate FIT images for
complex boot flows, in which components beyond the Linux kernel, its FDT
and an initramfs need to be loaded before the aforementioned Linux
kernel is up and running.
As an example, the setup propose by Marek Vasut in [1] (boot of the
kernel through OP-TEE, with both components being loaded from a single
FIT by U-Boot) could be simply obtained with:
FIT_LOADABLES = "tee"
FIT_LOADABLE_DESCRIPTION[tee] = "OP-TEE"
FIT_LOADABLE_TYPE[tee] = "tee"
FIT_LOADABLE_ARCH = "arm"
FIT_LOADABLE_OS[tee] = "tee"
FIT_LOADABLE_LOADADDRESS[tee] = "0xde000000"
FIT_LOADABLE_ENTRYPOINT[tee] = "0xde000000"
while a more complex flow I'm experimenting on (boot of the OP-TEE and
the kernel through TF-A on the i.MX93, with all components being loaded
from a single FIT by U-Boot SPL after verification) as:
FIT_LOADABLES = "atf tee"
FIT_LOADABLE_FILENAME[atf] = "bl31-imx93.bin-optee"
FIT_LOADABLE_DESCRIPTION[atf] = "TF-A Firmware"
FIT_LOADABLE_TYPE[atf] = "tfa-bl31"
FIT_LOADABLE_OS[atf] = "arm-trusted-firmware"
FIT_LOADABLE_LOADADDRESS[atf] = "0x204E0000"
FIT_LOADABLE_FILENAME[tee] = "tee.bin"
FIT_LOADABLE_DESCRIPTION[tee] = "OP-TEE"
FIT_LOADABLE_TYPE[tee] = "tee"
FIT_LOADABLE_OS[tee] = "tee"
FIT_LOADABLE_LOADADDRESS[tee] = "0x96000000"
Being inside the FIT image, and part of all configurations, the
loadables can be in this way hashed and (optionally) signed and/or
encrypted with the same flow and key(s) already in place for the kernel.
The generated FIT image is compatible with the U-Boot FIT "full" boot
flow, which loads any component part of the "loadables" group after the
kernel, the fdt and the initramfs.
Regards,
Francesco Valla
Hi,
Thanks for submitting this. LGTM, but it'd be nice to have it
documented as well.
Could you add some details to the Yocto Project docs (e.g. in the
"Variables Glossary" section) and submit it to
[email protected]?
Yes, documentation here is pretty much necessary to understand how this
shall be used.
I'll work on it as soon as possible.
Thanks,
Trevor
Regards,
Francesco
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