On 6/15/26 15:25, Ilias Apalodimas wrote:
On Mon, 15 Jun 2026 at 16:09, Ilias Apalodimas
<[email protected]> wrote:
Hi Ludwig,
[...]
I'd like the eventlog to be initialized before calling this (look below).
What if I removed the log parameter from those tcg2_* functions instead?
The event log belongs to the tpm device IMO, so should be initialized
with the device.
Measured boot EventLogs etc are primarily described by the TCG specs &
EFI and we only have a specification for it there. The DT describes on
how to pass it over to linux with sml-base etc.
However, in the EFI case the Eventlog is allocated as ACPI memory. So
you cannot allocate the EventLog a priori, until you figure out what
method you are using to boot. We also have use cases people using it
only for RNG, due to limited memory, so we can't just allocate it on
the device bringup. And lastly... Some first stage bootloaders do not
initialize the TPM & drivers. What they do is prepare an EventLog and
expect U-Boot to replay it once the TPM is up and running. In that
case we obviously need to preserve what we have instead of starting
from scratch.
Ack, we are on the same page here.
My main concern is that I *don't* want the EFI and non-EFI code to
deviate. I have some patches that I am playing around for quite some
time and rebased them last week for this reason [1]. If you think
those help your use case or make your life easier feel free to include
them.
Good idea and orthogonal to what I am doing I think. This duplication in
EFI stressed my brain too but I can't care about EFI right now :-)
It is, but the deviation in EFI is pretty minimal atm.
- EFI calls tcg2_log_prepare_buffer instead of tcg2_measurement_init()
-- That's what my patches fix
- EFI has it's own version of tcg2_measure_event() -- That's easy to
fix as well,.
IIUC you are centering the change around calling
tcg2_log_prepare_buffer() in efi_init_event_log(). What do you think
about aiming for tcg2_measurement_init() as central starting point
instead?
That would allow to remove even more duplicated code.
It should be sufficient to have tcg2_measurement_init() accept an
optional pointer to pre-allocated log buffer memory. Attached patch
maybe explains the idea better (just as idea, won't compile).
I agree. In fact I mistyped the functions names on my previous
email.... I really meant tcg2_measurement_init(). The patchset I
pointed you to already converts tcg2_log_prepare_buffer() to static.
Replying to myself here, but.. In order to do that you do need the
unification patches. tcg2_measurement_init() will need to allocate the
appropriate buffer depending on EFI or not.
So this is how it would look like with your patches on top:
https://github.com/u-boot/u-boot/compare/master...lnussel:u-boot:tpm-with-ilias-patches
IMO the untangle patch is not needed. Does that look sensible?
cu
Ludwig
--
Ludwig Nussel
Siemens AG
www.siemens.com
