ESP partition uses 1024 byte sectors

Efraim Flashner wrote on 29 Nov 2022 21:51

Recipients:(address . bug-guix@gnu.org)

Message-ID:Y4Zw3gQWuqtEQ7Py@3900XT

I was working on using a grub-efi system image for aarch64 and I got the
following error:
'Error: FAT sector size mismatch (fs=1024, dev=512)'
I traced it back to u-boot¹. u-boot wouldn't chainload grub if the
device block size and the filesystem sector size doesn't line up. I
changed the line in (gnu build image) in make-vfat-image to use '-S 512'
for esp partitions and was able to load the grub menu from u-boot.

I spent some time looking through the git history but I wasn't able to
find anything to suggest why we have 1024 byte sectors there
specifically.

¹ https://source.denx.de/u-boot/u-boot/-/blob/master/fs/fat/fat.c#L589

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Efraim Flashner wrote on 1 Dec 2022 09:24

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Message-ID:Y4hksd7ae7PPiZUd@3900XT

On Tue, Nov 29, 2022 at 10:51:42PM +0200, Efraim Flashner wrote:

Toggle quote (14 lines)> I was working on using a grub-efi system image for aarch64 and I got the
> following error:
> 'Error: FAT sector size mismatch (fs=1024, dev=512)'
> I traced it back to u-boot¹. u-boot wouldn't chainload grub if the
> device block size and the filesystem sector size doesn't line up. I
> changed the line in (gnu build image) in make-vfat-image to use '-S 512'
> for esp partitions and was able to load the grub menu from u-boot.
> 
> I spent some time looking through the git history but I wasn't able to
> find anything to suggest why we have 1024 byte sectors there
> specifically.
> 
> ¹ https://source.denx.de/u-boot/u-boot/-/blob/master/fs/fat/fat.c#L589

Normally I'd be ok with hardcoding 512 for the sector size to fix this,

but then I remembered that there are 4k block size disks which actually

declare themselves as having 4k blocks and not emulating 512 byte

blocks.

What do you think? I suppose one option would be to patch u-boot to not

demand they be equal, but that only works with guix build u-boot. We

could force 512, u-boot is the only thing I've come across so far that

cares and most people² use µSD cards which advertise 512 byte blocks.

Maybe change it to 512 and add a TODO to revisit it later as needed?

² citation needed

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