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

[Alkis Georgopoulos]

This problem is Ubuntu-specific, caused by that line:
https://git.launchpad.net/ubuntu/+source/grub2/tree/debian/patches/ubuntu-linuxefi.patch#n2105

That line was added by that commit:
https://git.launchpad.net/ubuntu/+source/grub2/commit/?id=6a814c759e10feafb40c3669be30aa51eb5ce39b

@cyphermox, this prohibits loading 32bit kernels under UEFI, would it be possible to revert it?
For example, before this patch, I was able to boot lubuntu-18.04-desktop-i386.iso under UEFI using https://github.com/alkisg/liveusb; after the patch, I can't.

True, the use cases for booting 32bit kernels under UEFI are limited,
but is there a reason to have an Ubuntu-specific patch to block it when
it works fine?

** Changed in: grub2 (Ubuntu)
   Importance: Undecided => Low

** Changed in: grub2 (Ubuntu)
       Status: New => Triaged

** Changed in: grub2 (Ubuntu)
     Assignee: (unassigned) => Mathieu Trudel-Lapierre (cyphermox)

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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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