Re: [PATCH v8 00/14] kasan: x86: arm64: KASAN tag-based mode for x86

[Andrey Konovalov <andreyknvl@gmail.com>]

On Mon, Jan 12, 2026 at 9:53 PM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Mon, 12 Jan 2026 20:08:23 +0000 Maciej Wieczór-Retman <m.wieczorretman@pm.me> wrote:
>
> > >OK, known issues and they are understandable.  With this patchset is
> > >there any way in which our testers can encounter these things?  If so
> > >can we make changes to protect them from hitting known issues?
> >
> > The gcc documentation states that the -fsanitize=kernel-hwaddress is
> > similar to -fsanitize=hwaddress, which only works on AArch64. So that
> > hints that it shouldn't work.
> >
> > But while with KASAN sw_tags enabled the kernel compiles fine with gcc,
> > at least in my patched qemu it doesn't run. I remember Ada Couprie Diaz
> > mention that passing -march=arrowlake might help since the tag support
> > seems to be based on arch.

FYI, there are some known GCC issues with arm64 SW_TAGS mode as well:
https://bugzilla.kernel.org/show_bug.cgi?id=218043#c3.

> >
> > I'll check if there's a non-hacky way to have gcc work too, but perhaps
> > to minimize hitting known issue, for now HAVE_ARCH_KASAN_SW_TAGS should
> > be locked behind both ADDRESS_MASKING and CC_IS_CLANG in the Kconfig?
>
> Yes please - my main concern is that we avoid causing any disruption to
> testers/buildbots/fuzzers/etc.

I left some comments, but from my/KASAN point of view, the series is
ready for linux-next (but this could wait for a week and maybe the
next version of the series).

I wouldn't think there would be disruption issues: one would need to
deliberately enable the SW_TAGS mode for x86 (as GENERIC is the
default mode when just enabling KASAN). But I don't mind locking down
x86 SW_TAGS to be Clang-only for now if GCC is known not to work at
all.