linux-kernel - Re: [PATCH 30/32] s390/unwind: Disable KMSAN checks

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Date:   Thu, 16 Nov 2023 10:04:48 +0100
From:   Alexander Potapenko <glider@...gle.com>
To:     Ilya Leoshkevich <iii@...ux.ibm.com>
Cc:     Alexander Gordeev <agordeev@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Marco Elver <elver@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Pekka Enberg <penberg@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>,
        kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-s390@...r.kernel.org,
        linux-trace-kernel@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Sven Schnelle <svens@...ux.ibm.com>
Subject: Re: [PATCH 30/32] s390/unwind: Disable KMSAN checks

On Wed, Nov 15, 2023 at 9:35 PM Ilya Leoshkevich <iii@...ux.ibm.com> wrote:
>
> The unwind code can read uninitialized frames. Furthermore, even in
> the good case, KMSAN does not emit shadow for backchains. Therefore
> disable it for the unwinding functions.
>
> Signed-off-by: Ilya Leoshkevich <iii@...ux.ibm.com>
> ---
>  arch/s390/kernel/unwind_bc.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/arch/s390/kernel/unwind_bc.c b/arch/s390/kernel/unwind_bc.c
> index 0ece156fdd7c..7ecaab24783f 100644
> --- a/arch/s390/kernel/unwind_bc.c
> +++ b/arch/s390/kernel/unwind_bc.c
> @@ -49,6 +49,7 @@ static inline bool is_final_pt_regs(struct unwind_state *state,
>                READ_ONCE_NOCHECK(regs->psw.mask) & PSW_MASK_PSTATE;
>  }
>
> +__no_kmsan_checks

Please add some comments to the source file to back this annotation,
so that the intent is not lost in git history.