From:   Michael Ellerman <mpe@ellerman.id.au>
To:     Marco Elver <elver@google.com>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     Alexander Potapenko <glider@google.com>,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        Andrey Konovalov <andreyknvl@gmail.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Nicholas Piggin <npiggin@gmail.com>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        Liam Howlett <liam.howlett@oracle.com>,
        kasan-dev@googlegroups.com, linuxppc-dev@lists.ozlabs.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Daniel Axtens <dja@axtens.net>,
        kernel test robot <lkp@intel.com>
Subject: Re: [PATCH mm] kasan, powerpc: Don't rename memintrinsics if
 compiler adds prefixes
In-Reply-To: <CANpmjNNtxW41H8ju6iog=ynMdEE0awa7GYabsuL6ZRihmVYQHw@mail.gmail.com>
References: <20230227094726.3833247-1-elver@google.com>
 <20230227141646.084c9a49fcae018852ca60f5@linux-foundation.org>
 <CANpmjNNtxW41H8ju6iog=ynMdEE0awa7GYabsuL6ZRihmVYQHw@mail.gmail.com>
Date:   Tue, 28 Feb 2023 22:58:03 +1100
Message-ID: <87o7peuhmc.fsf@mpe.ellerman.id.au>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

Marco Elver <elver@google.com> writes:
> On Mon, 27 Feb 2023 at 23:16, Andrew Morton <akpm@linux-foundation.org> wrote:
>>
>> On Mon, 27 Feb 2023 10:47:27 +0100 Marco Elver <elver@google.com> wrote:
>>
>> > With appropriate compiler support [1], KASAN builds use __asan prefixed
>> > meminstrinsics, and KASAN no longer overrides memcpy/memset/memmove.
>> >
>> > If compiler support is detected (CC_HAS_KASAN_MEMINTRINSIC_PREFIX),
>> > define memintrinsics normally (do not prefix '__').
>> >
>> > On powerpc, KASAN is the only user of __mem functions, which are used to
>> > define instrumented memintrinsics. Alias the normal versions for KASAN
>> > to use in its implementation.
>> >
>> > Link: https://lore.kernel.org/all/20230224085942.1791837-1-elver@google.com/ [1]
>> > Link: https://lore.kernel.org/oe-kbuild-all/202302271348.U5lvmo0S-lkp@intel.com/
>> > Reported-by: kernel test robot <lkp@intel.com>
>> > Signed-off-by: Marco Elver <elver@google.com>
>>
>> Seems this is a fix against "kasan: treat meminstrinsic as builtins in
>> uninstrumented files", so I'll plan to fold this patch into that patch.
>
> Yes, that looks right.
>
> If a powerpc maintainer could take a quick look as well would be good.

The patch looks OK to me. It builds for various configs and I did a few
test boots with KASAN enabled, everything seems normal.

Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)


> The maze of memcpy/memmove/memset definitions and redefinitions isn't
> the simplest - I hope in a few years we can delete all the old code
> (before CC_HAS_KASAN_MEMINTRINSIC_PREFIX), and let the compilers just
> "do the right thing".

Yeah that would be nice.

cheers