bootstd: Support for distro specific EFI folders

[Shantur Rathore]

On Thu, Nov 16, 2023 at 6:15 PM Heinrich Schuchardt
<heinrich.schuchardt at canonical.com> wrote:
>
> 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.
>

Thanks for correcting me.

> >
> > 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.

So, I am building a new RockPro64 based cluster and using Canonical
MAAS to set them up automatically, booting them up using DHCP and
installing them over the network.
I configured an Armbian image using Packer to be compatible with MAAS
and it happily installs it. As part of installation process, a
grub-install is run which installs the grub efi,
this EFI ends up in EFI/debian instead of expected EFI/boot.
To be able to make it boot, I have to add commands to move it to
EFI/boot. I am trying to find a way in U-Boot that would allow me to
skip this step.
With eficonfig if I understand correctly, it would need manual
intervention to create boot entries.

>
> 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.kojima@linaro.org/
>

Would it be possible to save it in SPI Flash as the U-Boot environment ?

Kind regards,
Shantur

> Best regards
>
> Heinrich