linux-kernel - Re: 5.3 boot regression caused by 5.3 TPM changes

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Date:   Wed, 7 Aug 2019 23:55:26 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     Matthew Garrett <mjg59@...gle.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Peter Huewe <peterhuewe@....de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        linux-integrity <linux-integrity@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-efi <linux-efi@...r.kernel.org>
Subject: Re: 5.3 boot regression caused by 5.3 TPM changes

Hi,

On 05-08-19 18:01, Ard Biesheuvel wrote:
> On Sun, 4 Aug 2019 at 19:12, Hans de Goede <hdegoede@...hat.com> wrote:
>>
>> Hi,
>>
>> On 04-08-19 17:33, Ard Biesheuvel wrote:
>>> Hi Hans,
>>>
>>> On Sun, 4 Aug 2019 at 13:00, Hans de Goede <hdegoede@...hat.com> wrote:
>>>>
>>>> Hi All,
>>>>
>>>> While testing 5.3-rc2 on an Irbis TW90 Intel Cherry Trail based
>>>> tablet I noticed that it does not boot on this device.
>>>>
>>>> A git bisect points to commit 166a2809d65b ("tpm: Don't duplicate
>>>> events from the final event log in the TCG2 log")
>>>>
>>>> And I can confirm that reverting just that single commit makes
>>>> the TW90 boot again.
>>>>
>>>> This machine uses AptIO firmware with base component versions
>>>> of: UEFI 2.4 PI 1.3. I've tried to reproduce the problem on
>>>> a Teclast X80 Pro which is also CHT based and also uses AptIO
>>>> firmware with the same base components. But it does not reproduce
>>>> there. Neither does the problem reproduce on a CHT tablet using
>>>> InsideH20 based firmware.
>>>>
>>>> Note that these devices have a software/firmware TPM-2.0
>>>> implementation, they do not have an actual TPM chip.
>>>>
>>>> Comparing TPM firmware setting between the 2 AptIO based
>>>> tablets the settings are identical, but the troublesome
>>>> TW90 does have some more setting then the X80, it has
>>>> the following settings which are not shown on the X80:
>>>>
>>>> Active PCR banks:           SHA-1         (read only)
>>>> Available PCR banks:        SHA-1,SHA256  (read only)
>>>> TPM2.0 UEFI SPEC version:   TCG_2         (other possible setting: TCG_1_2
>>>> Physical Presence SPEC ver: 1.2           (other possible setting: 1.3)
>>>>
>>>> I have the feeling that at least the first 2 indicate that
>>>> the previous win10 installation has actually used the
>>>> TPM, where as on the X80 the TPM is uninitialized.
>>>> Note this is just a hunch I could be completely wrong.
>>>>
>>>> I would be happy to run any commands to try and debug this
>>>> or to build a kernel with some patches to gather more info.
>>>>
>>>> Note any kernel patches to printk some debug stuff need
>>>> to be based on 5.3 with 166a2809d65b reverted, without that
>>>> reverted the device will not boot, and thus I cannot collect
>>>> logs without it reverted.
>>>>
>>>
>>> Are you booting a 64-bit kernel on 32-bit firmware?
>>
>> Yes you are right, I must say that this is somewhat surprising
>> most Cherry Trail devices do use 64 bit firmware (where as Bay Trail
>> typically uses 32 bit). But I just checked efibootmgr output and it
>> says it is booting: \EFI\FEDORA\SHIMIA32.EFI so yeah 32 bit firmware.
>>
>> Recent Fedora releases take care of this so seamlessly I did not
>> even realize...
>>
> 
> OK, so we'll have to find out how this patch affects 64-bit code
> running on 32-bit firmware. The only EFI call in that patch is
> get_config_table(), which is not actually a EFI boot service call but
> a EFI stub helper that parses the config table array in the EFI system
> table.

Ok, the problem indeed is the new get_efi_config_table() helper, it
does not make any calls, but it does interpret some structs which
have different sized members depending on if the firmware is 32 or 64 bit.

I've prepared a patch fixing this which I will send out after this mail.

Regards,

Hans