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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Tue, 9 Jul 2019 21:35:34 +0200
Message-ID: <CAK8P3a1SQaEymLpvTaX0_YDsGcKt=ys6_KwceC7mpkFJzhpQ=g@mail.gmail.com>
Subject: Re: [PATCH] mm/kasan: fix kasan_check_read() compiler warning
To:     Marco Elver <elver@google.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Alexander Potapenko <glider@google.com>,
        Andrey Konovalov <andreyknvl@google.com>,
        Christoph Lameter <cl@linux.com>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Kees Cook <keescook@chromium.org>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
        "ndesaulniers@google.com" <ndesaulniers@google.com>,
        Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
        Ingo Molnar <mingo@kernel.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        LKML <linux-kernel@vger.kernel.org>
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On Tue, Jul 9, 2019 at 8:46 PM Marco Elver <elver@google.com> wrote:
>
> On Tue, 9 Jul 2019 at 20:36, Arnd Bergmann <arnd@arndb.de> wrote:
> >
> > The kasan_check_read() is marked 'inline', which usually includes
> > the 'always_inline' attribute. In some configuration, gcc decides that
> > it cannot inline this, causing a build failure:
> >
> > In file included from include/linux/compiler.h:257,
> >                  from arch/x86/include/asm/current.h:5,
> >                  from include/linux/sched.h:12,
> >                  from include/linux/ratelimit.h:6,
> >                  from fs/dcache.c:18:
> > include/linux/compiler.h: In function 'read_word_at_a_time':
> > include/linux/kasan-checks.h:31:20: error: inlining failed in call to always_inline 'kasan_check_read': function attribute mismatch
> >  static inline bool kasan_check_read(const volatile void *p, unsigned int size)
> >                     ^~~~~~~~~~~~~~~~
> > In file included from arch/x86/include/asm/current.h:5,
> >                  from include/linux/sched.h:12,
> >                  from include/linux/ratelimit.h:6,
> >                  from fs/dcache.c:18:
> > include/linux/compiler.h:280:2: note: called from here
> >   kasan_check_read(addr, 1);
> >   ^~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > While I have no idea why it does this, but changing the call to the
> > internal __kasan_check_read() fixes the issue.
>
> Thanks, this was fixed more generally in v5:
> http://lkml.kernel.org/r/20190708170706.174189-1-elver@google.com

Ok, that looks like a better solution indeed. I tried something
similar at first but got it wrong.

      Arnd