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References: <20211214162050.660953-1-glider@google.com> <20211214162050.660953-40-glider@google.com>
 <87bl1ec32a.ffs@tglx>
In-Reply-To: <87bl1ec32a.ffs@tglx>
From:   Alexander Potapenko <glider@google.com>
Date:   Mon, 20 Dec 2021 15:35:13 +0100
Message-ID: <CAG_fn=VTow8S-H8SQbDNmB8gj+QpBm3RFKeiYhH=CRo0yd_CKg@mail.gmail.com>
Subject: Re: [PATCH 39/43] x86: kmsan: handle register passing from
 uninstrumented code
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     Alexander Viro <viro@zeniv.linux.org.uk>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andrey Konovalov <andreyknvl@google.com>,
        Andy Lutomirski <luto@kernel.org>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Arnd Bergmann <arnd@arndb.de>, Borislav Petkov <bp@alien8.de>,
        Christoph Hellwig <hch@lst.de>,
        Christoph Lameter <cl@linux.com>,
        David Rientjes <rientjes@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Eric Dumazet <edumazet@google.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Ilya Leoshkevich <iii@linux.ibm.com>,
        Ingo Molnar <mingo@redhat.com>, Jens Axboe <axboe@kernel.dk>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Kees Cook <keescook@chromium.org>,
        Marco Elver <elver@google.com>,
        Matthew Wilcox <willy@infradead.org>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Pekka Enberg <penberg@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Petr Mladek <pmladek@suse.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Vegard Nossum <vegard.nossum@oracle.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Linux Memory Management List <linux-mm@kvack.org>,
        Linux-Arch <linux-arch@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Fri, Dec 17, 2021 at 10:51 PM Thomas Gleixner <tglx@linutronix.de> wrote=
:
>
> Alexander,
>
> On Tue, Dec 14 2021 at 17:20, Alexander Potapenko wrote:
> > When calling KMSAN-instrumented functions from non-instrumented
> > functions, function parameters may not be initialized properly, leading
> > to false positive reports. In particular, this happens all the time whe=
n
> > calling interrupt handlers from `noinstr` IDT entries.
> >
> > Fortunately, x86 code has instrumentation_begin() and
>
> It's not only x86 code:
> >  kernel/entry/common.c           | 3 +++

Shall this bit go into a separate patch?

> > @@ -76,6 +77,7 @@ __visible noinstr void do_syscall_64(struct pt_regs *=
regs, int nr)
> >       nr =3D syscall_enter_from_user_mode(regs, nr);
> >
> >       instrumentation_begin();
> > +     kmsan_instrumentation_begin(regs);
>
> Can we please make this something like:
>
>        instrumentation_begin_at_entry(regs);

Fine, will do.
Do you think it would make sense to hide it inside
instrumentation_begin(), or is it ok to have both macros follow each
other?

> or some other sensible name which hides that kmsan gunk and avoids to
> touch all of this again when KFOOSAN comes around?
>
> Thanks,
>
>         tglx
>
>
>


--=20
Alexander Potapenko
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