Package: systemd-boot
Version: 257.2-3
Hi,
systemd-boot's postinst script creates the CSV file for shim's fallback
helper with the following line:
echo "shim${efi_arch}.efi,${vendor},,This is the boot entry for
${vendor}" > "${esp_path}/EFI/${vendor}/BOOT${efi_arch_upper}.CSV"
This won't work for several reasons:
1/ This creates a file with ASCII text, whereas fb${efi_arch}.efi
expects UCS-2 text
2/ There is no parameter for shim${efi_arch}.efi to know what to
chainload, so it will try to load grub${efi_arch}.efi, which won't exist
anymore (since the whole stanza will only run if GRUB is removed)
3/ The copy of shim${efi_arch}.efi in \EFI\BOOT is useless by itself,
since without any parameter or fb{efi_arch}.efi, it will also try to
chainload a missing grub${efi_arch}.efi (note that this theoretically
also applies to GRUB, see below)
All necessary information about shim's fallback helper can be found here:
https://github.com/rhboot/shim/blob/main/README.fallback
So systemd-boot's postinst script can be fixed by:
- Also copy fb{efi_arch}.efi to \EFI\BOOT (in addition of shim)
- Create the CSV file with something like:
echo
"shim${efi_arch}.efi,${vendor_upper},\\EFI\systemd\systemd-boot${efi_arch}.efi
\\0,This is the boot entry for ${vendor_upper}" | iconv -t UCS-2 >
"${esp_path}/EFI/${vendor}/BOOT${efi_arch_upper}.CSV"
With these modifications, shim's fallback helper would re-create an UEFI
boot entry almost identical to the one that the current postinst creates
with `efibootmgr` (it will prepend shim's path with a backslash, maybe
it should also be done in the `efibootmgr` command to more closely
follow shim's behavior, although it currently works as-is) which
actually works as intended.
To test it, after applying those two modifications, delete the UEFI boot
entry that was created with `efibootmgr`, use the firmware's boot menu
to boot from the hard disk, wait for the countdown, and the fallback
helper will re-create an UEFI boot entry identical to the one created by
the postinst's `efibootmgr` command.
Regards,
--
Raphaël Halimi
