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. Cheers /Ilias > > > > > >> I am not sure what the intention of the current api is tbh. The event > > >> log basically documents when and how PCR registers were extended. We > > >> have to build that log ourselves as the TPM doesn't do it for us. The > > >> api weirdly allows to have partial local logs even though there's only > > >> one set of PCR registers. > > > > > > Where? > > > > The elog parameters of tcg2_log_prepare_buffer() and tcg2_measure_data() > > are not related to the dev parameter. So it looks like the intention is > > to be able to call it on the same tpm but with different event logs. > > Ah no. The reason was that the non EFI code was retrofitted way later, > and it was eiaster to just allocate the buffer on the spot. I always > had the idea of abstracting this even more in the future > > Cheers > /Ilias > > > > cu > > Ludwig > > > > -- > > Ludwig Nussel > > Siemens AG > > www.siemens.com
