linux-kernel - Re: [tpmdd-devel] [PATCH v2 0/3] Call GetEventLog before ExitBootServices

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Date:   Thu, 14 Sep 2017 12:21:59 +0200
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     Thiebaud Weksteen <tweek@...gle.com>, linux-efi@...r.kernel.org
Cc:     ard.biesheuvel@...aro.org, matt@...eblueprint.co.uk,
        linux-kernel@...r.kernel.org, mjg59@...gle.com,
        jgunthorpe@...idianresearch.com, tpmdd-devel@...ts.sourceforge.net,
        jarkko.sakkinen@...ux.intel.com, Peter Jones <pjones@...hat.com>
Subject: Re: [tpmdd-devel] [PATCH v2 0/3] Call GetEventLog before
 ExitBootServices

Hello Thiebaud,

On 09/11/2017 12:00 PM, Thiebaud Weksteen via tpmdd-devel wrote:
> With TPM 1.2, the ACPI table ("TCPA") has two fields to recover the Event Log
> Area (LAML and LASA). These logs are useful to understand and rebuild the
> final values of PCRs.
> 
> With TPM 2.0, the ACPI table ("TPM2") does not contain these fields anymore.
> The recommended method is now to call the GetEventLog EFI protocol before
> ExitBootServices.
> 
> Implement this method within the EFI stub and create copy of the logs for the
> TPM device. This will create /sys/kernel/security/tpm0/binary_bios_measurements
> for TPM 2.0 devices (similarly to the current behaviour for TPM 1.2 devices).
> 

I've tested your patches on a system with an Intel PTT firmware based TPM2.0 and
the measurements securityfs entry was correctly created and was able to read it:

$ cat /sys/class/tpm/tpm0/device/description
TPM 2.0 Device

$ hexdump /sys/kernel/security/tpm0/binary_bios_measurements | head -n2
0000000 0000 0000 0008 0000 f504 15a0 1810 bf44
0000010 63d0 4fdb b8a4 f278 8dc7 c8aa 0014 0000

So please feel free to add:

Tested-by: Javier Martinez Canillas <javierm@...hat.com>

I also reviewed the patches and look good to me, I have just one question for
patch #2, but I'll comment there.

Best regards,
-- 
Javier Martinez Canillas
Software Engineer - Desktop Hardware Enablement
Red Hat