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

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Date:   Tue, 31 Mar 2020 14:55:00 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Stefan Berger <stefanb@...ux.ibm.com>
Cc:     Stefan Berger <stefanb@...ux.vnet.ibm.com>,
        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 Mon, Mar 30, 2020 at 05:26:25PM -0400, Stefan Berger wrote:
> 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.

You should CC the change to linux-acpi because it touches their files.
For this reason preferably this change should be commit of its own.

/Jarkko