linux-kernel - Re: [PATCH v2 1/3] acpi: Extend TPM2 ACPI table with missing log fields

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Date:   Mon, 30 Mar 2020 17:26:25 -0400
From:   Stefan Berger <stefanb@...ux.ibm.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Stefan Berger <stefanb@...ux.vnet.ibm.com>
Cc:     linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org, linux-security-module@...r.kernel.org
Subject: Re: [PATCH v2 1/3] acpi: Extend TPM2 ACPI table with missing log
 fields

On 3/30/20 3:28 PM, Jarkko Sakkinen wrote:
> On Mon, Mar 30, 2020 at 11:15:34AM -0400, Stefan Berger wrote:
>> From: Stefan Berger <stefanb@...ux.ibm.com>
>>
>> Recent extensions of the TPM2 ACPI table added 3 more fields
>> including 12 bytes of start method specific parameters and Log Area
>> Minimum Length (u32) and Log Area Start Address (u64). So, we extend
>> the existing structure with these fields to allow non-UEFI systems
>> to access the TPM2's log.
>>
>> The specification that has the new fields is the following:
>>    TCG ACPI Specification
>>    Family "1.2" and "2.0"
>>    Version 1.2, Revision 8
>>
>> Adapt all existing table size calculations to use
>> offsetof(struct acpi_table_tpm2, start_method_specific)
>> [where start_method_specific is a newly added field]
>> rather than sizeof(struct acpi_table_tpm2) so that the addition
>> of the new fields does not affect current systems that may not
>> have them.
>>
> Cc: linux-acpi@...r.kernel.org
>
>> Signed-off-by: Stefan Berger <stefanb@...ux.ibm.com>
> You have this comment:
>
> /* Platform-specific data follows */

You mean there 'was this comment'? I actually removed this comment 
because I didn't know what it meant or what it has to do with 'platform':

-
-       /* Platform-specific data follows */
+       u8  start_method_specific[12];
+       u32 log_area_minimum_length;
+       u64 log_area_start_address;

Specs: 
https://trustedcomputinggroup.org/wp-content/uploads/TCG_ACPIGeneralSpecification_v1.20_r8.pdf

PDF Page 16 / Doc page 10 bottom.

start_method_specific is obviously related to the start_method field. 
The subsequent two fields are optional and show those 2 filelds we know 
from the TCPA ACPI table.

>
> Can you elaborate a bit which platform you are speaking of? It is now
> enabled for everything.
>
> /Jarkko