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

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Message-ID: <CAKv+Gu9nEM5D877YD+N8tSN0sON6rR3f+Tc-9bg5u==+9Q2meA@mail.gmail.com>
Date:   Mon, 5 Aug 2019 19:01:20 +0300
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Hans de Goede <hdegoede@...hat.com>
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

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.