From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mark Kettenis <mark.kettenis@xs4all.nl>
Date: Mon, 9 Nov 2020 14:51:13 +0100 (CET)
Subject: [PATCH] efi_loader: improve detection of ESP for storing UEFI
 variables
In-Reply-To: <87lffad5on.fsf@cjr.nz> (message from Paulo Alcantara on Mon, 09
 Nov 2020 10:24:08 -0300)
References: <20201108235855.28788-1-pc@cjr.nz>
 <abe2c884-76b9-be6e-20b5-73e2030dcd8c@gmx.de> <87lffad5on.fsf@cjr.nz>
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> From: Paulo Alcantara <pc@cjr.nz>
> Date: Mon, 09 Nov 2020 10:24:08 -0300
> 
> Heinrich Schuchardt <xypron.glpk@gmx.de> writes:
> 
> > On 09.11.20 00:58, Paulo Alcantara wrote:
> >> The UEFI specification does not restrict on the number and location of
> >> ESPs in a system.  They are discovered as required by looking at the
> >> partition type, but firmware implementations are allowed to support
> >> ESPs which do not contain a valid partition type.
> >
> > I guess you refer to chapter "13.3.3 Number and Location of System
> > Partitions" of the UEFI spec saying: "Further, UEFI implementations
> > may allow the use of conforming FAT partitions which do not use the
> > ESP GUID."
> 
> Yep, sorry.  Thanks for pointing it out!
> 
> > Why should U-Boot support FAT partitions that are not of type FAT 0xef
> > and GPT partition that do not use the ESP GUID?
> 
> In most UEFI (EDK2-based) systems I used, I could boot my OSes and
> diagnostic tools by simply having a supported filesystem (FAT12/16/32)
> and /EFI/BOOT/BOOT{ARCH}.EFI file and never cared about setting the
> partition type at all.  It took me a while for figuring out why I
> couldn't get my UEFI variables loaded from my FAT partition that
> contained /ubootefi.var and /EFI/BOOT/BOOTAA64.efi files.

The OpenBSD installation media for armv7 and arm64 use a FAT partition
of type 0x0c because the Raspberry Pi firmware doesn't support 0xef.
This allows us to have a single FAT partition with the Raspberry Pi
firmware, U-Boot and /EFI/BOOT/BOOT{ARCH}.EFI.

So far this works on all UEFI firmware I've tried (EDK2, U-Boot and
AMI AptioV UEFI).