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From:   Alexander Potapenko <glider@google.com>
Date:   Thu, 16 Nov 2023 10:05:14 +0100
Message-ID: <CAG_fn=XftAnT0=kxkjGrtn9QEye1Xayg_jw3Fk_cy6SforMTpg@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 Thu, Nov 16, 2023 at 10:04=E2=80=AFAM Alexander Potapenko <glider@google=
.com> wrote:
>
> On Wed, Nov 15, 2023 at 9:35=E2=80=AFPM Ilya Leoshkevich <iii@linux.ibm.c=
om> 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_sta=
te *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.

Apart from that,

Reviewed-by: Alexander Potapenko <glider@google.com>


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Alexander Potapenko
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