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Subject: Re: [PATCH] tpm: Document UEFI event log quirks
To:     Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
        linux-kernel@vger.kernel.org, linux-integrity@vger.kernel.org,
        linux-doc@vger.kernel.org
Cc:     tweek@google.com, matthewgarrett@google.com,
        Jonathan Corbet <corbet@lwn.net>
References: <20190703161109.22935-1-jarkko.sakkinen@linux.intel.com>
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 <a8ee93721a674434e22d31fd1d10bf9472c1c739.camel@linux.intel.com>
From:   Randy Dunlap <rdunlap@infradead.org>
Message-ID: <ec274596-6bc8-07a0-d09b-1d191646c5cd@infradead.org>
Date:   Sun, 7 Jul 2019 12:33:31 -0700
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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?

-- 
~Randy