linux-kernel - Re: Regression from efi: call get_event

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Message-ID: <185d1c06-c379-ee7d-496b-2f4e49f8c9a3@redhat.com>
Date:   Wed, 7 Mar 2018 12:16:23 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Thiebaud Weksteen <tweek@...gle.com>, jeremy@...ine.org
Cc:     Javier Martinez Canillas <javierm@...hat.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        linux-efi@...r.kernel.org, linux-integrity@...r.kernel.org,
        tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: Regression from efi: call get_event_log before ExitBootServices

Hi,

On 07-03-18 09:41, Thiebaud Weksteen wrote:
> Hi,
> 
> Thanks for testing and sending this report! This patch relies heavily on
> the functions exposed by the firmware. My first guess would be that some of
> these may not be implemented correctly by the manufacturer.
> 
> Could you share more information on this specific device?

I've the same device as Jeremy, but I just tried a 4.16-rc3 kernel
and I'm not seeing this problem, BIOS settings all default (I loaded
the BIOS defaults to make sure).

> Do you have any link to the manufacturer website (I found [1] but it is
> based on an ARM CPU)?
> Do you have the option to update your firmware? Is a copy of the firmware
> available from the manufacturer?

This is a really cheap Windows tablet which was given away for free in
the Netherlands with some home-schooling language courses, or something
similar.

Both mine and Jeremy tablets come from a website in the Netherlands
where people can buy/sell used goods.

Most relevant for this discussion I guess is that this device is
based on a Bay Trail Z3735G SoC, on which according to the internets:
https://embedded.communities.intel.com/thread/7868

The TPM 2.0 it contains is implemented as part of the TXE firmware.

Since I cannot reproduce I'm thinking that maybe Jeremy actually has
some log messages in the TPM log, where as mine is empty.  Is there a
way to make sure some messages are in there?

Regards,

Hans



> On your side, I assume no error message got displayed on the screen when
> booting. Would you be able to try to boot in an UEFI shell [2] and execute
> the command "dh -v"?
> 
> Thanks,
> Thiebaud
> 
> [1] https://www.gp-electronic.nl/product/7inchtablet
> [2]
> https://wiki.archlinux.org/index.php/Unified_Extensible_Firmware_Interface#UEFI_Shell
> 
> On Tue, Mar 6, 2018 at 5:00 PM Jeremy Cline <jeremy@...ine.org> wrote:
> 
>> Hi folks,
> 
>> Commit 33b6d03469b2 ("efi: call get_event_log before ExitBootServices")
>> causes my GP-electronic T701 tablet to hang when booting. Reverting the
>> patch series or hiding the TPM in the BIOS fixes the problem.
> 
>> I've never fiddled with TPMs before so I'm not sure what what debugging
>> information to provide. It's got an Atom Z3735G and the UEFI firmware is
>> InsydeH20 version BYT70A.YNCHENG.WIN.007.
> 
> 
>> Regards,
>> Jeremy