Re: [PATCH] tpm: Document UEFI event log quirks

[Jarkko Sakkinen]

On Sun, 2019-07-07 at 12:33 -0700, Randy Dunlap wrote:
> On 7/5/19 3:15 AM, Jarkko Sakkinen wrote:
> > On Wed, 2019-07-03 at 09:45 -0700, Randy Dunlap wrote:
> > > > +This introduces another problem: nothing guarantees that it is not
> > > > +called before the stub gets to run. Thus, it needs to copy the final
> > > > +events table preboot size to the custom configuration table so that
> > > > +kernel offset it later on.
> 
>      (so that)
>      the kernel can use that final table preboot size as an events table
>      offset later on.
> 
> > > ?  kernel can offset it later on.
> > 
> > EFI stub calculates the total size of the events in the final events
> > table at the time.
> > 
> > Later on, TPM driver uses this offset to copy only the events that
> > were actually generated after ExitBootServices():
> > 
> > /*
> >  * Copy any of the final events log that didn't also end up in the
> >  * main log. Events can be logged in both if events are generated
> >  * between GetEventLog() and ExitBootServices().
> >  */
> > memcpy((void *)log->bios_event_log + log_size,
> >        final_tbl->events + log_tbl->final_events_preboot_size,
> >        efi_tpm_final_log_size);
> > 
> > What would be a better way to describe this?
> 
> Yeah, I think I see what it's doing, how it's using that.
> See above.
> 
> OK?

Your propsal looks legit, thank you. I'll send an update that
tries to address yours and Jordan's feedback.

/Jarkko