'UEFI Firmware Settings' in GRUB menu on UEFI installations

[kalle123]

Thought, that I remember having seen this option in the GRUB menu working before. So I was a bit
astonished, this did not work now a days.

Have two ASUS boards here, a PRIME X370-A and a B450 Plus with up to date bios flashed.

Installation Debian 12 on those and hitting 'UEFI Firmware Settings' in GRUB only produced

Reboot > ASUS greeting screen > GRUB menu and after 5' > desktop.

A search in the net did not help , so maybe a problem on my side then. Started a thread in the German forum to see, if anyone could verify that strange behavior, maybe a bug? https://debianforum.de/forum/viewtopic.php?t=187613

There I got a hint, that maybe some board manufactures are prohibiting that shortcut for Linux users.

So I started doing some test by flashing older BIOS versions on both boards here, which ASUS does not seem to like very much. Often you'll be confronted with a nice 'Selected file is not a proper BIOS!' But flashing an older BIOS with ASUS finally seemed to do the trick. Now hitting 'UEFI Firmware Settings' in GRUB gives you Reboot > ASUS greeting screen > UEFI (BIOS) menu.

Strange, that I did not find any discussions on the feature, what about Gigabyte, MSI, Asrock?

If that is not only happening with ASUS boards, I think, I'll make a bug report and ask the developer to delete the 'UEFI Firmware Settings' in GRUB in future ,,,

br KH

[sunrat]

I never use that option nor understood why it exists. Always just hit the keyboard key to enter UEFI Settings which is Delete on my mobo.

[Aki]

Hello,

Thought, that I remember having seen this option in the GRUB menu working before. So I was a bit
astonished, this did not work now a days.
[...]
If that is not only happening with ASUS boards, I think, I'll make a bug report and ask the developer to delete the 'UEFI Firmware Settings' in GRUB in future ,,,

This is an interesting topic that offers the opportunity to explore an UEFI feature used by grub.

This is the grub2 configuration for this boot option [1].

Therefore, grub2 install the fwsetup binary in the Extensible Firmware Interface (ESP) partition if the motherboard's UEFI firmware support a specific feature.

The source code of grub's fwsetup firmware is here [2]

In fact, it turns out that UEFI firmware has a specification that, if supported by the motherboard’s manufacturer, allows the boot loader or the OS to ask the UEFI firmware to activate its setup functions at the time of the next reboot [3]:

7.5.4 Exchanging information between the OS and Firmware
The firmware and an Operating System may exchange information through the
OsIndicationsSupported and the OSIndications variables as follows:

• The OsIndications variable returns a UINT64 bitmask owned by the OS and is used to
  indicate which features the OS wants firmware to enable or which actions the OS wants the
  firmware to take. The OS will supply this data with a SetVariable()call.

• The OsIndicationsSupported variable returns a UINT64 bitmask owned by the
  firmware and indicates which of the OS indication features and actions that the firmware
  supports. This variable is recreated by firmware every boot, and cannot be modified by the OS .

The EFI_OS_INDICATIONS_BOOT_TO_FW_UI bit can be set in the
OsIndicationsSupported variable by the firmware, if the firmware supports OS requests to
stop at a firmware user interface.

The EFI_OS_INDICATIONS_BOOT_TO_FW_UI bit can be set
by the OS in the OsIndications variable, if the OS desires for the firmware to stop at a firmware
user interface on the next boot. Once the firmware consumes this bit in the OsIndications
variable and stops at the firmware user interface, the firmware should clear the bit from the
OsIndications variable in order to acknowledge to the OS that the information was consumed
and, more importantly, to prevent the firmware user interface from showing again on subsequent
boots.

Therefore, the grub2's 'UEFI Firmware Settings' only appears if it is supported by the installed UEFI firmware. If you activate it and the firmware setup does not come up at reboot, it is probably an UEFI firmware issue of that motherboard.

---
[1] https://sources.debian.org/src/grub2/2.06-13/util/grub.d/30_uefi-firmware.in/?hl=40#L40
[2] https://sources.debian.org/src/grub2/2.06-13/grub-core/commands/efi/efifwsetup.c/?hl=1#L1
[3] Unified Extensible Firmware Interface Specification

[kalle123]

Therefore, the grub2's 'UEFI Firmware Settings' only appears if it is supported by the installed UEFI firmware. If you activate it and the firmware setup does not come up at reboot, it is probably an UEFI firmware issue of that motherboard.

I do see that behavior with two ASUS boards with the latest BIOS versions, but what is with the rest?? What mainboards do you have and does that 'issue' show up? Or is that an only ASUS thing?

Regards - KH