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

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Message-ID: <CANpmjNN5q0r6FEph2P1E2DvBTgFrWFgWkV_kyxiUQwbouLj4+g@mail.gmail.com>
Date: Wed, 28 Jan 2026 00:21:07 +0100
From: Marco Elver <elver@...gle.com>
To: Segher Boessenkool <segher@...nel.crashing.org>
Cc: Peter Zijlstra <peterz@...radead.org>, 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 13:54, Segher Boessenkool
<segher@...nel.crashing.org> wrote:
>
> Hi!
>
> On Thu, Dec 18, 2025 at 01:18:13PM +0100, Peter Zijlstra wrote:
> > On Thu, Dec 18, 2025 at 05:58:44AM -0600, Segher Boessenkool wrote:
> >
> > > You might have more success getting the stuff backported to some
> > > distro(s) you care about?  Or get people to use newer compilers more
> > > quickly of course, "five years" before people have it is pretty
> > > ridiculous, two years is at the tail end of things already.
> >
> > There is a difference between having and requiring it :/ Our current
> > minimum compiler version is gcc-8 or clang-15 (IIRC).
>
> Very much so.  If you have good reasons for requiring it, make sure you
> voice that with your backport request!
>
> Nothing we (again, GCC) do is *only* motivated by procedures.  We can do
> unusual things in unusual situations.  But you need extraordinary
> evidence for why extraordinary things would be needed, of course.  Does
> that apply here, you think?
>
> > On the bright side, I think we can be more aggressively with compiler
> > versions for debug builds vs regular builds. Not being able to build a
> > KASAN/UBSAN/whateverSAN kernel isn't too big of a problem (IMO).
>
> Absolutely.  Just document the feature as needing a recent compiler!

For future reference:
https://discourse.llvm.org/t/explicit-sanitizer-checks-with-builtin-allow-sanitize-check/89383
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123442

Clang 22 should have the builtin.