[Bug 1876737] Re: GRUB refuses to boot a 32-bit kernel when in EFI mode

[Hamish McIntyre-Bhatty]

I feel like this is maybe missing the point. These things seem clear to
me:

1. Loading 64-bit kernels on 32-bit UEFIs is a useful feature to have
and I'm glad it was added.

2. AFAICT, the patch was not intended to break loading 32-bit kernels on
64-bit systems (and also what would be the point of such a change?), but
if it was, I don't understand the reasoning behind doing this.

3. Of course booting a 64-bit kernel would work, but why should we be
pushing updates that break existing installations due to what seems to
be either an unintended consequence, or a "computer says no" type error
even though the kernel is perfectly capable of booting. The error is
misleading at best.

As such, I feel like this issue still needs to be fixed.

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https://bugs.launchpad.net/bugs/1876737

Title:
  GRUB refuses to boot a 32-bit kernel when in EFI mode

Status in grub2 package in Ubuntu:
  Triaged

Bug description:
  Also reported at https://savannah.gnu.org/bugs/index.php?58300, but
  doesn't occur in Debian's v2.04 from Bulleye, and only occurred in the
  last few months, so it might be an Ubuntu bug.

  This is grub version 2.02-2ubuntu8.15 as reported by "apt show grub-
  efi"

  GRUB2 fails to boot a 32-bit kernel when started in EFI mode (64-bit
  EFI) on a 64-bit x86 CPU, and gives the message:

  "error: kernel doesn't support 64-bit CPUs"

  However, when a bios grub image made by the same version of grub is
  used, with the same kernel, on the same CPU, everything is normal and
  the kernel boots as expected.

  Hence, I know this kernel will boot on a 64-bit CPU, and with a
  previous version of GRUB 2 (unfortunately I don't know which version),
  it also booted fine in 64-bit mode using GRUB-EFI.

  Running with debug=all doesn't seem to provide any extra useful
  information, as far as I can tell - it just lists sectors being read
  and then freed.

  Any ideas as to what's going on?

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