linux-kernel - Re: [PATCH 0/2] Noinstr fixes for K[CA]SAN with GCOV

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Message-ID: <CANpmjNOQJVRf5Ffk0-WMcFkTfAuh5J-ZoPHC+4BdXgLLf22Rjg@mail.gmail.com>
Date: Thu, 18 Dec 2025 10:56:48 +0100
From: Marco Elver <elver@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Ard Biesheuvel <ardb@...nel.org>, Kees Cook <kees@...nel.org>, 
	Brendan Jackman <jackmanb@...gle.com>, Andrey Ryabinin <ryabinin.a.a@...il.com>, 
	Alexander Potapenko <glider@...gle.com>, Andrey Konovalov <andreyknvl@...il.com>, 
	Dmitry Vyukov <dvyukov@...gle.com>, Vincenzo Frascino <vincenzo.frascino@....com>, 
	kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org, 
	linux-toolchains@...r.kernel.org
Subject: Re: [PATCH 0/2] Noinstr fixes for K[CA]SAN with GCOV

On Thu, 18 Dec 2025 at 10:51, Peter Zijlstra <peterz@...radead.org> wrote:
> On Sat, Dec 13, 2025 at 08:59:44AM +0900, Ard Biesheuvel wrote:
>
> > > After that I sat down and finally got around to implement the builtin
> > > that should solve this once and for all, regardless of where it's
> > > called: https://github.com/llvm/llvm-project/pull/172030
> > > What this will allow us to do is to remove the
> > > "K[AC]SAN_SANITIZE_noinstr.o := n" lines from the Makefile, and purely
> > > rely on the noinstr attribute, even in the presence of explicit
> > > instrumentation calls.
> > >
> >
> > Excellent! Thanks for the quick fix. Happy to test and/or look into
> > the kernel side of this once this lands.
>
> Well, would not GCC need to grow the same thing and then we must wait
> until these versions are the minimum supported versions for sanitizer
> builds.
>
> I mean, the extension is nice, but I'm afraid we can't really use it
> until much later :/

Unfortunately, yes. But let's try to get the builtin into Clang and
GCC now (for the latter, need to Cc GCC folks to help).

Then we wait for 5 years. :-)

There's a possibility to try and backport it to stable Clang and GCC
versions, but it's a long stretch (extremely unlikely).