On 11/16/23 17:52, Shantur Rathore wrote:
Hi Simon,
Currently bootstd - bootmethod_efi only looks for the default
bootxx64.efi in /EFI/boot folder only.
Generally many distros end up putting their bootloaders in
EFI/<distro> folders like EFI/ubuntu and EFI/debian etc.
In x86 worlds, the NVRAM is modified and new boot entries are added to
support these but in the U-boot world the NVRAM variables are
read-only.
I guess you are referring to UEFI boot options. These typically are not
stored in non-volatile RAM but on a SPI flash device.
What would be the best way to implement this?
I was thinking of having a "efi_prefixes" environment variable which
can be set to "ubuntu debian centos" etc and bootmethod_efi can try
all of them. Will bootmethod_efi be able to support multiple entries (
thinking of multiboot ) ?
On my laptop I have:
EFI/Microsoft/Boot/bootmgr.efi
EFI/Microsoft/Boot/memtest.efi
EFI/Boot/bootx64.efi
EFI/Boot/fbx64.efi
EFI/Boot/mmx64.efi
EFI/debian/shimx64.efi
EFI/debian/grubx64.efi
EFI/debian/mmx64.efi
EFI/debian/fbx64.efi
EFI/ubuntu/grubx64.efi
EFI/ubuntu/shimx64.efi
EFI/ubuntu/mmx64.efi
Obviously each installed operating system provides multiple EFI binaries
and non uses the fallback file name BOOT<ARCH>.EFI. A value "ubuntu
debian centos" would not be able to describe which file you are looking
for.
We already have the U-Boot command line eficonfig and efidebug commands
to set up UEFI boot options which can describe which EFI binary to load
and which command line to pass to it. These are considered by the
existing boot flows.
If you are installing the shim-signed package on Ubuntu, the EFI boot
option for Ubuntu is set up by EFI/BOOT/BOOT<ARCH>.EFI using the content
of EFI/ubuntu/BOOT<ARCH>.CSV. This is done before ExitBootServices() and
therefore should work with current U-Boot.
Patches are pending upstream to make EFI variables writable from Linux
if they are stored in the RPMB partition in the eMMC. See this series:
https://lore.kernel.org/linux-efi/20231107054057.1893-2-masahisa.koj...@linaro.org/
Best regards
Heinrich
