From: Marco Elver <elver@google.com>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Stephen Rothwell <sfr@canb.auug.org.au>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux Next Mailing List <linux-next@vger.kernel.org>,
Alexander Potapenko <glider@google.com>,
Andrey Konovalov <andreyknvl@google.com>,
kasan-dev <kasan-dev@googlegroups.com>,
Kees Cook <keescook@google.com>
Subject: Re: linux-next: build warning after merge of the akpm tree
Date: Mon, 7 Dec 2020 13:52:03 +0100 [thread overview]
Message-ID: <CANpmjNObNia7mFFJDz6ofG06QOTzad=iU=b_C=E97nV2hB-hng@mail.gmail.com> (raw)
In-Reply-To: <CACT4Y+bPPSQ1OgZ1NmUckOO2=07RE3C=deW6BpF0cOR9wnJsoA@mail.gmail.com>
On Mon, 7 Dec 2020 at 13:38, 'Dmitry Vyukov' via kasan-dev
<kasan-dev@googlegroups.com> wrote:
> On Mon, Dec 7, 2020 at 1:08 PM Dmitry Vyukov <dvyukov@google.com> wrote:
> > > > Hi all,
> > > >
> > > > After merging the akpm tree, today's linux-next build (powerpc
> > > > allyesconfig) produced warnings like this:
> > > >
> > > > kernel/kcov.c:296:14: warning: conflicting types for built-in function '__sanitizer_cov_trace_switch'; expected 'void(long unsigned int, void *)' [-Wbuiltin-declaration-mismatch]
> > > > 296 | void notrace __sanitizer_cov_trace_switch(u64 val, u64 *cases)
> > > > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > >
> > > Odd. clang wants that signature, according to
> > > https://clang.llvm.org/docs/SanitizerCoverage.html. But gcc seems to
> > > want a different signature. Beats me - best I can do is to cc various
> > > likely culprits ;)
> > >
> > > Which gcc version? Did you recently update gcc?
> > >
> > > > ld: warning: orphan section `.data..Lubsan_data177' from `arch/powerpc/oprofile/op_model_pa6t.o' being placed in section `.data..Lubsan_data177'
> > > >
> > > > (lots of these latter ones)
> > > >
> > > > I don't know what produced these, but it is in the akpm-current or
> > > > akpm trees.
> >
> > I can reproduce this in x86_64 build as well but only if I enable
> > UBSAN as well. There were some recent UBSAN changes by Kees, so maybe
> > that's what affected the warning.
> > Though, the warning itself looks legit and unrelated to UBSAN. In
> > fact, if the compiler expects long and we accept u64, it may be broken
> > on 32-bit arches...
>
> No, I think it works, the argument should be uint64.
>
> I think both gcc and clang signatures are correct and both want
> uint64_t. The question is just how uint64_t is defined :) The old
> printf joke that one can't write portable format specifier for
> uint64_t.
>
> What I know so far:
> clang 11 does not produce this warning even with obviously wrong
> signatures (e.g. short).
> I wasn't able to trigger it with gcc on 32-bits at all. KCOV is not
> supported on i386 and on arm I got no warnings even with obviously
> wrong signatures (e.g. short).
> Using "(unsigned long val, void *cases)" fixes the warning on x86_64.
>
> I am still puzzled why gcc considers this as a builtin because we
> don't enable -fsanitizer-coverage on this file. I am also puzzled how
> UBSAN affects things.
It might be some check-for-builtins check gone wrong if it enables any
one of the sanitizers. That would be confirmed if it works with
UBSAN_SANITIZE_kcov.o := n
> We could change the signature to long, but it feels wrong/dangerous
> because the variable should really be 64-bits (long is broken on
> 32-bits).
> Or we could introduce a typedef that is long on 64-bits and 'long
> long' on 32-bits.
next prev parent reply other threads:[~2020-12-07 12:53 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-04 10:00 linux-next: build warning after merge of the akpm tree Stephen Rothwell
2020-12-05 5:19 ` Andrew Morton
2020-12-05 9:37 ` Stephen Rothwell
2020-12-07 12:08 ` Dmitry Vyukov
2020-12-07 12:38 ` Dmitry Vyukov
2020-12-07 12:52 ` Marco Elver [this message]
2020-12-09 10:06 ` Dmitry Vyukov
2020-12-08 12:01 ` Stephen Rothwell
2020-12-09 4:44 ` Michael Ellerman
2020-12-09 7:07 ` Stephen Rothwell
2020-12-10 0:19 ` Michael Ellerman
2020-12-10 21:17 ` Stephen Rothwell
2020-12-09 10:33 ` Stephen Rothwell
2020-12-09 18:56 ` Kees Cook
-- strict thread matches above, loose matches on Subject: below --
2021-01-28 8:46 Stephen Rothwell
2021-02-01 7:14 ` Vijayanand Jitta
2020-02-28 4:35 Stephen Rothwell
2020-02-28 5:23 ` Arjun Roy
2020-01-06 6:11 Stephen Rothwell
2020-01-06 6:07 Stephen Rothwell
2020-01-07 23:11 ` Andrew Morton
2020-01-08 14:52 ` Steven Price
2018-11-30 5:40 Stephen Rothwell
2018-11-30 14:52 ` Dave Rodgman
2017-08-01 6:02 Stephen Rothwell
2017-08-01 6:15 ` Huang, Ying
2017-08-01 21:15 ` Arnd Bergmann
2017-06-26 6:30 Stephen Rothwell
2017-06-26 23:57 ` Wei Yang
2014-05-19 8:13 Stephen Rothwell
2014-05-19 15:13 ` Davidlohr Bueso
2014-05-19 19:48 ` Andrew Morton
2014-05-19 20:56 ` Davidlohr Bueso
2014-05-19 21:17 ` Andrew Morton
2014-05-19 21:36 ` Stephen Rothwell
2014-05-19 22:38 ` Davidlohr Bueso
2013-04-18 8:03 Stephen Rothwell
2013-04-10 8:33 Stephen Rothwell
2013-04-10 8:18 Stephen Rothwell
2013-02-20 6:34 Stephen Rothwell
2013-02-20 14:37 ` Peter Jones
2013-01-23 6:33 Stephen Rothwell
2013-01-23 6:43 ` Tang Chen
2012-11-09 3:43 Stephen Rothwell
2012-11-09 10:00 ` Grant Likely
2012-10-25 3:35 Stephen Rothwell
2012-04-27 5:44 Stephen Rothwell
2012-04-27 6:22 ` Cyrill Gorcunov
2012-04-27 6:28 ` Stephen Rothwell
2012-04-27 6:40 ` Cyrill Gorcunov
2011-08-10 2:13 Stephen Rothwell
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