From: Andrey Ryabinin <aryabinin@virtuozzo•com>
To: Stephen Rothwell <sfr@canb•auug.org.au>
Cc: linux-kernel@vger•kernel.org, Ingo Molnar <mingo@kernel•org>,
Thomas Gleixner <tglx@linutronix•de>,
"H. Peter Anvin" <hpa@zytor•com>,
x86@kernel•org, Andrew Morton <akpm@linux-foundation•org>,
Andy Lutomirski <luto@amacapital•net>,
Andrey Konovalov <andreyknvl@google•com>,
Kostya Serebryany <kcc@google•com>,
Alexander Potapenko <glider@google•com>,
kasan-dev <kasan-dev@googlegroups•com>,
Borislav Petkov <bp@alien8•de>,
Denys Vlasenko <dvlasenk@redhat•com>,
Andi Kleen <ak@linux•intel.com>,
Dmitry Vyukov <dvyukov@google•com>,
Sasha Levin <sasha.levin@oracle•com>,
Wolfram Gloger <wmglo@dent•med.uni-muenchen.de>,
linux-next@vger•kernel.org
Subject: Re: linux-next: build problems (Was: [PATCH v3 1/2] Provide READ_ONCE_NOCHECK())
Date: Thu, 15 Oct 2015 13:03:11 +0300 [thread overview]
Message-ID: <561F79DF.3000402@virtuozzo.com> (raw)
In-Reply-To: <20151015201834.350258bf@canb.auug.org.au>
On 10/15/2015 12:18 PM, Stephen Rothwell wrote:
> Hi Andrey,
>
> On Tue, 13 Oct 2015 18:28:07 +0300 Andrey Ryabinin <aryabinin@virtuozzo•com> wrote:
>>
>> Some code may perform racy by design memory reads. This could be harmless,
>> yet such code may produce KASAN warnings.
>>
>> To hide such accesses from KASAN this patch introduces READ_ONCE_NOCHECK()
>> macro. KASAN will not check the memory accessed by READ_ONCE_NOCHECK().
>>
>> This patch creates __read_once_size_nocheck() a clone of
>> __read_once_size_check() (renamed __read_once_size()).
>> The only difference between them is 'no_sanitized_address' attribute
>> appended to '*_nocheck' function. This attribute tells the compiler that
>> instrumentation of memory accesses should not be applied to that function.
>> We declare it as static '__maybe_unsed' because GCC is not capable to
>> inline such function: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
>>
>> With KASAN=n READ_ONCE_NOCHECK() is just a clone of READ_ONCE().
>>
>> Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo•com>
>> ---
>> include/linux/compiler-gcc.h | 13 ++++++++++
>> include/linux/compiler.h | 60 ++++++++++++++++++++++++++++++++++----------
>> 2 files changed, 60 insertions(+), 13 deletions(-)
>
> I am pretty sure that this patch is causing quite a bit of compile
> breakage in linux-next today. During the day I compile with gcc 4.9.0
> and did not see any problems with c86_64 allmodconfig, or i386
> defconfig etc, but overnight we compile with older compilers (gcc 4.6.3
> in particular) and are getting quite a few errors:
>
Looks like that older GCC doesn't like __alias (or combination of static __always_inline __alias).
It creates outline and unused copy of __read_once_size_check() function in the object file.
Should be easy to work around this.
> From an i386 allnoconfig build:
>
> arch/x86/entry/vdso/vdso32.so.dbg: undefined symbols found
> /home/kisskb/slave/src/arch/x86/entry/vdso/Makefile:154: recipe for target 'arch/x86/entry/vdso/vdso32.so.dbg' failed
>
> From an x86_64 allnoconfig build:
>
> arch/x86/entry/vdso/vclock_gettime.o: In function `__read_once_size_check':
> vclock_gettime.c:(.text+0x5f): undefined reference to `memcpy'
> arch/x86/entry/vdso/vgetcpu.o: In function `__read_once_size_check':
> vgetcpu.c:(.text+0x2f): undefined reference to `memcpy'
>
> and several others ...
>
next prev parent reply other threads:[~2015-10-15 10:03 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1444739750-29241-1-git-send-email-aryabinin@virtuozzo.com>
[not found] ` <1444750088-24444-1-git-send-email-aryabinin@virtuozzo.com>
[not found] ` <1444750088-24444-2-git-send-email-aryabinin@virtuozzo.com>
2015-10-15 9:18 ` linux-next: build problems (Was: [PATCH v3 1/2] Provide READ_ONCE_NOCHECK()) Stephen Rothwell
2015-10-15 10:03 ` Andrey Ryabinin [this message]
2015-10-15 10:19 ` [PATCH] compiler, READ_ONCE: Fix build failure with some older GCC Andrey Ryabinin
2015-10-15 11:30 ` Ingo Molnar
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