RE: [PATCH] efi/libstub/arm64: avoid image_base value from efi_loaded_image

[Michael Kelley <mikelley@microsoft.com>]

From: Michael Kelley  Sent: Tuesday, March 31, 2020 6:38 AM
> 
> From: Ard Biesheuvel <ardb@kernel.org>  Sent: Tuesday, March 31, 2020 12:56 AM
> >
> > On Mon, 30 Mar 2020 at 20:24, Ard Biesheuvel <ardb@kernel.org> wrote:
> > >
> > > On Mon, 30 Mar 2020 at 20:12, Michael Kelley <mikelley@microsoft.com> wrote:
> > > >
> > > > From: Ard Biesheuvel <ardb@kernel.org>  Sent: Monday, March 30, 2020 12:51 AM
> > > > >
> > > > > On Mon, 30 Mar 2020 at 09:50, Ard Biesheuvel <ardb@kernel.org> wrote:
> > > > > >
> > > > > > On Mon, 30 Mar 2020 at 09:47, Leif Lindholm <leif@nuviainc.com> wrote:
> > > > > > >
> > > > > > > On Sat, Mar 28, 2020 at 21:58:09 +0100, Ard Biesheuvel wrote:
> > > > > > > > Commit 9f9223778ef3 ("efi/libstub/arm: Make efi_entry() an ordinary
> > > > > > > > PE/COFF entrypoint") did some code refactoring to get rid of the
> > > > > > > > EFI entry point assembler code, and in the process, it got rid of the
> > > > > > > > assignment of image_addr to the value of _text. Instead, it switched
> > > > > > > > to using the image_base field of the efi_loaded_image struct provided
> > > > > > > > by UEFI, which should contain the same value.
> > > > > > > >
> > > > > > > > However, Michael reports that this is not the case: older GRUB builds
> > > > > > > > corrupt this value in some way, and since we can easily switch back to
> > > > > > > > referring to _text to discover this value, let's simply do that.
> > > > > > >
> > > > > > > It is not clear to me how "older GRUB builds" would differ here.
> > > > > > > I think more investigation is needed before making that claim.
> > > > > > > My suspicion is that some (old) version of non-upstream, shim-enabled
> > > > > > > distro-specific build is playing a part.
> > > > > > >
> > > > > > > So, do we have the option for more detailed investigations, or can we
> > > > > > > vague the claim up to say "some GRUB builds seen in the wild, based
> > > > > > > on an upstream 2.02" or suchlike?
> > > > > > >
> > > > > >
> > > > > > I've queued a fix that prints a nastygram if the value deviates from
> > > > > > the expected one. Let's see if this triggers any reports.
> > > > >
> > > > > (/me looks at context)
> > > > >
> > > > > *This* is the fix that prints a nastygram.
> > > >
> > > > FWIW, I pulled the BOOTAA64.EFI and grubaa64.efi files from CentOS 7.6
> > > > and CentOS 8.0 binary packages and tested both in my Hyper-V VM.
> > > > Using strings | grep '2\.' to get version info, the CentOS 7.6 grubaa64.efi
> > > > shows:
> > > >
> > > >         User-Agent: GRUB 2.02~beta2
> > > >
> > > > The CentOS 8.0 grubaa64.efi shows:
> > > >
> > > >         User-Agent: GRUB 2.03
> > > >
> > > > Both versions produce the FIRMWARE BUG warning when using Ard's
> > > > latest patch.  I'll assume the equivalent RHEL versions are the same.
> > > > So we've got official distro releases that show the problem.
> > > >
> > > > As reported earlier, the BOOTAA64.EFI and grubaa64.efi from a
> > > > Debian release (not exactly sure which one) do not produce the
> > > > FIRMWARE BUG warning.  The grubaa64.efi reports as 2.04-4.
> > > >
> > >
> > > Thanks a lot Michael, that is really helpful.
> >
> > I could not reproduce the issue with Debian Stretch's
> > 2.02~beta3-5+deb9u2, so it does appear to be RedHat's value add that
> > is to blame here.
> >
> > @Laszlo: TL;DR RedHat's GRUB for arm64 appears to clobber the
> > image_base field of the efi_loaded_image struct passed to the kernel.
> > Could you please recommend a way to report this?
> 
> Or there could be something weird about my Hyper-V VM.  I have a
> couple of ARM64 bare metal machines, but they are in the office
> with no remote access, and we're on the work-from-home plan for
> now.  But I may be able to get into the office later this week and
> try it.  I'd like to rule out anything related to Hyper-V, and will
> update this thread if I can.
> 

I have tried this scenario on bare metal running RHEL 7.4, and the
problem reproduces as described above.  So this is *not* related to
running in a Hyper-V VM, which is what I wanted to make sure of.

Michael
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel