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

[Hamish McIntyre-Bhatty]

Public bug reported:

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?

** Affects: grub2 (Ubuntu)
     Importance: Undecided
         Status: New

** Description changed:

  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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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:
  New

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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