[SeaBIOS] [PATCH 4/8] tpm: Use pcpes->event[] to pass data to tpm_extend_acpi_log()

Stefan Berger stefanb at linux.vnet.ibm.com
Mon Nov 23 04:06:35 CET 2015

On 11/22/2015 08:52 PM, Kevin O'Connor wrote:
> On Sun, Nov 22, 2015 at 08:31:43PM -0500, Stefan Berger wrote:
>> On 11/22/2015 08:02 PM, Kevin O'Connor wrote:
>>> Instead of passing in the event data to tpm_extend_acpi_log() via
>>> parameters, use the event[] field in the pcpes.  Update those callers
>>> that don't populate the pcpes->event to do so prior to calling
>>> tpm_extend_acpi_log().
> [...]
>> You are undoing a previous change now. I had tried to prevent having this
>> event buffer (on the stack) but allow higher layers to pass arbitrary-length
>> event buffers around that get copied into the log at the very end. This was
>> to avoid having to append them here.
> Okay, that was dumb on my part.  I only looked deeper into the code
> after your cleanup series from the 17th, and it looks like I undid a
> bunch of changes you just made.
> I agree that we don't want the internal code to be dependent on the
> external bios interface.  The pcpes is ultimately what goes into the
> ACPI table though, and so it doesn't seem so bad to use its layout
> when figuring out what to add to the ACPI table.  What's the rational
> for sending both a pcpes and the content of the pcpes to the lower
> functions?  (The tpm_add_measurement_to_log() code is only ever called

The change was driven by trying to avoid that one buffer for the event.

> by internal functions that only use a small amount of data, so there
> is no fear of it overflowing - at least in the current code.)
> It looks like I also undid the change to build_and_send_cmd() - it
> would be nice to have transmit() just take a single buffer instead of
> having to use the iovec[] stuff.



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