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References: <20231115203401.2495875-1-iii@linux.ibm.com> <20231115203401.2495875-31-iii@linux.ibm.com>
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From:   Alexander Potapenko <glider@google.com>
Date:   Thu, 16 Nov 2023 10:04:48 +0100
Message-ID: <CAG_fn=WW1BUehMSsbjtPb4gKpakLGi3bF2KFEPxE4dV7n1ToSQ@mail.gmail.com>
Subject: Re: [PATCH 30/32] s390/unwind: Disable KMSAN checks
To:     Ilya Leoshkevich <iii@linux.ibm.com>
Cc:     Alexander Gordeev <agordeev@linux.ibm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Christoph Lameter <cl@linux.com>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Marco Elver <elver@google.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Pekka Enberg <penberg@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Christian Borntraeger <borntraeger@linux.ibm.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Hyeonggon Yoo <42.hyeyoo@gmail.com>,
        kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, linux-s390@vger.kernel.org,
        linux-trace-kernel@vger.kernel.org,
        Mark Rutland <mark.rutland@arm.com>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Sven Schnelle <svens@linux.ibm.com>
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On Wed, Nov 15, 2023 at 9:35=E2=80=AFPM Ilya Leoshkevich <iii@linux.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@linux.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.