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Date: Mon, 7 Jul 2025 12:03:17 +0100
From: Dave Martin <Dave.Martin@arm.com>
To: Kees Cook <kees@kernel.org>
Cc: linux-kernel@vger.kernel.org, Oleg Nesterov <oleg@redhat.com>,
	Akihiko Odaki <akihiko.odaki@daynix.com>
Subject: Re: [PATCH 23/23] binfmt_elf: Warn on missing or suspicious regset
 note names
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References: <20250701135616.29630-1-Dave.Martin@arm.com>
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 <D620FCC4-4A72-45CB-AF16-456E2B49B5C8@kernel.org>
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In-Reply-To: <D620FCC4-4A72-45CB-AF16-456E2B49B5C8@kernel.org>

On Sat, Jul 05, 2025 at 08:14:33AM -0700, Kees Cook wrote:
> 
> 
> On July 1, 2025 6:56:16 AM PDT, Dave Martin <Dave.Martin@arm.com> wrote:
> >Un-migrated arches will trigger WARNs with this patch applied, and
> >arches that don't specify codedump note names will always get
> >"LINUX" -- since the whole point is to stop guessing the note name in
> >the core code.
> >
> >On _unpatched_ arches (only) this is a potential ABI break for the
> >NT_PRFPREG note (which, for historical reasons, is a "CORE" note even
> >though it is OS-specific on most or all arches).
> 
> After all your arch patches, aren't all the archs using the correct
> values? Is the WARN for new or out-of-tree archs?
> 
> -Kees

[...]

If there are in-flight series where someone adds a new arch (?) or more
likely adds a new regset to an existing arch, then we might hit this.

In practice, all per-arch regsets apart from NT_PRFPREG use the name
"LINUX", so defaulting to this if the name is not specified will hardly
ever be a problem -- unless there really is a new arch out of tree that
is going to merge imminently.

I'm happy to simplify the check here if people prefer.

Cheers
---Dave