linux-kernel - Re: [PATCH] efivarfs: Iterate variables with increasing name buffer sizes

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Message-ID: <CA+g+hrh_REk-bcTt-D+eSngofxdejeRXuXKhf1O15wzn+qMy6Q@mail.gmail.com>
Date: Wed, 24 Jan 2024 16:25:24 -0500
From: Peter Jones <pjones@...hat.com>
To: Tim Schumacher <timschumi@....de>
Cc: Ard Biesheuvel <ardb@...nel.org>, Matthew Garrett <mjg59@...f.ucam.org>, linux-efi@...r.kernel.org, 
	Jeremy Kerr <jk@...abs.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] efivarfs: Iterate variables with increasing name buffer sizes

On Tue, Jan 23, 2024 at 12:33 PM Tim Schumacher <timschumi@....de> wrote:
>
> On 23.01.24 15:09, Ard Biesheuvel wrote:
> > On Tue, 23 Jan 2024 at 14:55, Tim Schumacher <timschumi@....de> wrote:
> >>
> >> I'd rather avoid introducing deviations from the specifications on the
> >> kernel side as well.
> >
> > Which specification would this deviate from?
>
> The preexisting comment claims "Per EFI spec", and it appears that I got
> mislead by that. Neither the UEFI specification, nor the newest revision
> of the EFI specification (which I guess is what would have been current
> back in 2004, when this comment was introduced) seem to make any mention
> of a maximum length for the variable name.

Curiously, I can't find it in the 1.02 spec (the oldest I can find)
either.  When I inherited efibootmgr around 2013, this was a
limitation there, but I don't see anything in that tree that claims
it's a spec limitation either.  My suspicion is this is a former
Itanium firmware limit that got promoted to "the spec says" by word of
mouth, or was in some very early ia64 implementation spec.

-- Peter