GNU bug report logs - #59695
ESP partition uses 1024 byte sectors

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Efraim Flashner <efraim <at> flashner.co.il>
To: bug-guix <at> gnu.org
Subject: ESP partition uses 1024 byte sectors
Date: Tue, 29 Nov 2022 22:51:42 +0200

[Message part 1 (text/plain, inline)]

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

-- 
Efraim Flashner   <efraim <at> flashner.co.il>   אפרים פלשנר
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Message #8 received at 59695 <at> debbugs.gnu.org (full text, mbox):

From: Efraim Flashner <efraim <at> flashner.co.il>
To: 59695 <at> debbugs.gnu.org
Subject: Re: bug#59695: ESP partition uses 1024 byte sectors
Date: Thu, 1 Dec 2022 10:24:17 +0200

[Message part 1 (text/plain, inline)]

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

-- 
Efraim Flashner   <efraim <at> flashner.co.il>   אפרים פלשנר
GPG key = A28B F40C 3E55 1372 662D  14F7 41AA E7DC CA3D 8351
Confidentiality cannot be guaranteed on emails sent or received unencrypted

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