x86_64 UEFI system needs GRUB2_IMAGE_FORMAT=x86_64-efi

[jsmeix]

This is related to the changes in
#3157

On my openSUSE Leap 15.5 x86_64 UEFI system
with current GitHub master code with
3db2724
that makes "rear mkrescue" fail with

++ test
++ LogPrintError 'grub2-mkstandalone may fail to make a bootable EFI image of GRUB2 (no /usr/*/grub*/i386-efi/moddep.lst file)'
...
++ grub2-mkstandalone -v '--modules=cryptodisk ext2 fat gcry_rijndael gcry_sha256 luks part_gpt part_msdos' -O i386-efi -o /var/tmp/rear.t0eFjv7bA3CjENy/tmp/mnt/EFI/BOOT/BOOTX64.efi /boot/
grub/grub.cfg=/var/tmp/rear.t0eFjv7bA3CjENy/tmp/mnt/EFI/BOOT/grub.cfg
grub2-mkstandalone: error: /usr/share/grub2/i386-efi/modinfo.sh doesn't exist. Please specify --target or --directory.

because I have

# uname -m
x86_64

# find /usr -type f | grep 'moddep.lst'
/usr/share/grub2/x86_64-efi/moddep.lst
/usr/share/grub2/i386-pc/moddep.lst

# find /usr -type f | grep 'modinfo.sh'
/usr/share/grub2/x86_64-efi/modinfo.sh
/usr/share/grub2/i386-pc/modinfo.sh

so I need GRUB2_IMAGE_FORMAT=x86_64-efi in
usr/share/rear/prep/Linux-i386/330_set_efi_arch.sh

--- a/usr/share/rear/prep/Linux-i386/330_set_efi_arch.sh
+++ b/usr/share/rear/prep/Linux-i386/330_set_efi_arch.sh
@@ -16,7 +16,8 @@ case "$REAL_MACHINE" in
         ;;
     (x86_64)
         EFI_ARCH=x64
-        GRUB2_IMAGE_FORMAT=i386-efi
+        # GRUB2_IMAGE_FORMAT=i386-efi
+        GRUB2_IMAGE_FORMAT=x86_64-efi
         ;;
     (*)
         BugError "Unknown architecture $REAL_MACHINE"

[jsmeix]

@pcahyna
for now this is just a quick issue report
so that it is not forgotten.
I will have a closer look tomorrow.

At first glance in
usr/share/rear/prep/Linux-i386/330_set_efi_arch.sh
https://github.com/rear/rear/blob/master/usr/share/rear/prep/Linux-i386/330_set_efi_arch.sh
it looks like a typo

   (i686|i586|i386)
        ...
        GRUB2_IMAGE_FORMAT=x86_64-efi
   (x86_64)
        ...
        GRUB2_IMAGE_FORMAT=i386-efi

to set GRUB2_IMAGE_FORMAT
to x86_64... in case of i686|i586|i386
and to i386... in case of x86_64.

@pcahyna
is this a typo or even intentional?

[pcahyna]

@jsmeix Oops, I must have swapped the two! Really sorry. It is curious how even a simplest change can break things.

[jsmeix]

I am confused when looking at
usr/share/rear/prep/Linux-i386/330_set_efi_arch.sh
because it sets the GRUB2_IMAGE_FORMAT variable
only to grub-mkstandalone --format values
for EFI ('x86_64-efi' and 'i386-efi')
regardless that prep/Linux-i386/330_set_efi_arch.sh
is run for EFI and BIOS systems.

So on a BIOS system GRUB2_IMAGE_FORMAT
is set to a value for EFI systems
which is a contradiction.

The prep/Linux-*/330_set_efi_arch.sh scripts tell [sic!]

# Se the variables even if USING_UEFI_BOOTLOADER empty or no explicit 'true' value

so that is intentional but it does not tell why.

As far as I see it works currently only because
the generic GRUB2_IMAGE_FORMAT variable
is only used in case of EFI

# find usr/sbin/rear usr/share/rear/ -type f | xargs grep -l 'GRUB2_IMAGE_FORMAT'

usr/share/rear/prep/Linux-i386/330_set_efi_arch.sh
usr/share/rear/prep/Linux-arm/330_set_efi_arch.sh
usr/share/rear/prep/Linux-ia64/330_set_efi_arch.sh
usr/share/rear/lib/uefi-functions.sh
usr/share/rear/output/RAWDISK/Linux-i386/270_create_grub2_efi_bootloader.sh

but things will fail if GRUB2_IMAGE_FORMAT
will be also used for BIOS systems in the future.

@pcahyna
could you explain the intent behind why on a BIOS system
GRUB2_IMAGE_FORMAT is set to a value for EFI systems?

[jsmeix]

This issue does not depend on openSUSE Leap 15.5
but (probably) happens on all x86_64 UEFI systems.

[pcahyna]

I am confused when looking at usr/share/rear/prep/Linux-i386/330_set_efi_arch.sh because it sets the GRUB2_IMAGE_FORMAT variable only to grub-mkstandalone --format values for EFI ('x86_64-efi' and 'i386-efi') regardless that prep/Linux-i386/330_set_efi_arch.sh is run for EFI and BIOS systems.

So on a BIOS system GRUB2_IMAGE_FORMAT is set to a value for EFI systems which is a contradiction.

The intent of the variable is to hold the image format for EFI GRUB on the platform, so the variable is simply misnamed. I should have called it GRUB2_EFI_IMAGE_FORMAT.

The prep/Linux-*/330_set_efi_arch.sh scripts tell [sic!]

# Se the variables even if USING_UEFI_BOOTLOADER empty or no explicit 'true' value

so that is intentional but it does not tell why.

My bad, I should have indicated why and I don't even recall exactly, but I believe it has referred to the EFI_ARCH* variables and not to GRUB2_IMAGE_FORMAT originally. I think I did not want to audit all uses of EFI_ARCH* whether they are protected by a test of for USING_UEFI_BOOTLOADER (we don't want to refer to an undefined variable and to prevent it the easiest way is to define it always). Actually I see at least some use of EFI_ARCH* that is not conditional on USING_UEFI_BOOTLOADER: usr/share/rear/output/RAWDISK/Linux-i386/{270_create_grub2_efi_bootloader.sh,260_create_syslinux_efi_bootloader.sh}, so setting the variable always is the right thing already.

As far as I see it works currently only because the generic GRUB2_IMAGE_FORMAT variable is only used in case of EFI

# find usr/sbin/rear usr/share/rear/ -type f | xargs grep -l 'GRUB2_IMAGE_FORMAT'

usr/share/rear/prep/Linux-i386/330_set_efi_arch.sh
usr/share/rear/prep/Linux-arm/330_set_efi_arch.sh
usr/share/rear/prep/Linux-ia64/330_set_efi_arch.sh
usr/share/rear/lib/uefi-functions.sh
usr/share/rear/output/RAWDISK/Linux-i386/270_create_grub2_efi_bootloader.sh

but things will fail if GRUB2_IMAGE_FORMAT will be also used for BIOS systems in the future.

Another variable will have to be introduced then. You may wonder why not to have just one variable that holds the correct image format for the given situation, regardless of whether it is UEFI or BIOS. I believe it is better to keep it separated for the case when we need to handle a hybrid boot setup. I think we are already creating bootable media with ESP even on BIOS systems and we may be able to create hybrid boot media in the future (maybe we are already able to do that in some situations). We are also already capable of restoring hybrid bootloader setups.