Re: [RFC] Using SimpleDRM in the initramfs

From	Askar Safin <safinaskar@gmail.com>
Newsgroups	linux.debian.kernel, linux.debian.maint.boot
Subject	Re: [RFC] Using SimpleDRM in the initramfs
Date	2026-05-11 16:50 +0200
Message-ID	<MTA7f-4mTj-1@gated-at.bofh.it> (permalink)
References	<MThnX-49Ww-1@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Cross-posted to 2 groups.

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Ben Hutchings <benh@debian.org>:
> - In the kernel, we cannot assume that an EFI framebuffer is always
>   usable.  In particular, older versions of GRUB may break it by using
>   a native graphics driver, but without clearing whatever signals the
>   kernel that it is available.  This was fixed upstream in the default
>   config for GRUB 2.14 but we cannot assume that the config change
>   actually gets applied to existing installations.

It WILL be applied to existing installations.

Here is upstream commit in question:
https://cgit.git.savannah.gnu.org/cgit/grub.git/commit/?id=ea0b76dc4a003f2b7f828ef0c24cc8227148b2f8

It changed file util/grub.d/00_header.in in the repo. It corresponds to
/etc/grub.d/00_header in installed system. It is script, which is used
when generating /boot/grub/grub.cfg .

/etc/grub.d/00_header is present in output of
"dpkg-query -W -f='${Conffiles}\n' grub-*", but I think that this is
highly unlikely that users manually edited that file.

So the file will be simply replaced on upgrade, and then new /boot/grub/grub.cfg
will be generated from it.

Also note that I only was able to reproduce that GRUB bug in Qemu only.
And I was not able to reproduce it on real hardware. The original bug
report by Cyril Brulebois also talks about Qemu:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1036019 .

Here is output of "ls /boot/grub/x86_64-efi/video*.mod" on my machine:

/boot/grub/x86_64-efi/video_bochs.mod
/boot/grub/x86_64-efi/video_cirrus.mod
/boot/grub/x86_64-efi/video_colors.mod
/boot/grub/x86_64-efi/video_fb.mod
/boot/grub/x86_64-efi/videoinfo.mod
/boot/grub/x86_64-efi/video.mod
/boot/grub/x86_64-efi/videotest_checksum.mod
/boot/grub/x86_64-efi/videotest.mod

As you can see, there is no mention of Intel, AMD or Nvidia. So usual
desktop computers should not be affected by that GRUB bug. But
there are mentions of Bochs and Cirrus, which are videocards emulated
by Qemu.

==
Askar Safin

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Thread

[RFC] Using SimpleDRM in the initramfs Ben Hutchings <benh@debian.org> - 2026-05-10 20:50 +0200
  Re: [RFC] Using SimpleDRM in the initramfs Askar Safin <safinaskar@gmail.com> - 2026-05-11 16:50 +0200
    Re: [RFC] Using SimpleDRM in the initramfs Ben Hutchings <benh@debian.org> - 2026-05-11 19:00 +0200
  Re: [RFC] Using SimpleDRM in the initramfs Askar Safin <safinaskar@gmail.com> - 2026-05-11 18:30 +0200
    Re: [RFC] Using SimpleDRM in the initramfs Ben Hutchings <benh@debian.org> - 2026-05-11 19:10 +0200

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