Re: 5.3 boot regression caused by 5.3 TPM changes

[Hans de Goede]

Hi,

On 05-08-19 18:01, Ard Biesheuvel wrote:
> On Sun, 4 Aug 2019 at 19:12, Hans de Goede <hdegoede@xxxxxxxxxx> 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@xxxxxxxxxx> 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