From: "H. Peter Anvin" <hpa@zytor.com>
To: Matthias Kaehlcke <mka@chromium.org>
Cc: Michael Davidson <md@google.com>, Michal Marek <mmarek@suse.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
Herbert Xu <herbert@gondor.apana.org.au>,
"David S. Miller" <davem@davemloft.net>,
Shaohua Li <shli@kernel.org>,
Alexander Potapenko <glider@google.com>,
Dmitry Vyukov <dvyukov@google.com>,
x86@kernel.org, linux-kbuild@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org,
linux-raid@vger.kernel.org
Subject: Re: [PATCH 3/7] x86, LLVM: suppress clang warnings about unaligned accesses
Date: Thu, 13 Apr 2017 16:55:00 -0700 [thread overview]
Message-ID: <3b743cf7-3d81-1fd6-b3a9-2f58a3bd8817@zytor.com> (raw)
In-Reply-To: <20170413231439.GG28657@google.com>
On 04/13/17 16:14, Matthias Kaehlcke wrote:
> El Mon, Apr 03, 2017 at 04:01:58PM -0700 Matthias Kaehlcke ha dit:
>
>> El Fri, Mar 17, 2017 at 04:50:19PM -0700 hpa@zytor.com ha dit:
>>
>>> On March 16, 2017 5:15:16 PM PDT, Michael Davidson <md@google.com> wrote:
>>>> Suppress clang warnings about potential unaliged accesses
>>>> to members in packed structs. This gets rid of almost 10,000
>>>> warnings about accesses to the ring 0 stack pointer in the TSS.
>>>>
>>>> Signed-off-by: Michael Davidson <md@google.com>
>>>> ---
>>>> arch/x86/Makefile | 5 +++++
>>>> 1 file changed, 5 insertions(+)
>>>>
>>>> diff --git a/arch/x86/Makefile b/arch/x86/Makefile
>>>> index 894a8d18bf97..7f21703c475d 100644
>>>> --- a/arch/x86/Makefile
>>>> +++ b/arch/x86/Makefile
>>>> @@ -128,6 +128,11 @@ endif
>>>> KBUILD_CFLAGS += $(call cc-option,-maccumulate-outgoing-args)
>>>> endif
>>>>
>>>> +ifeq ($(cc-name),clang)
>>>> +# Suppress clang warnings about potential unaligned accesses.
>>>> +KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
>>>> +endif
>>>> +
>>>> ifdef CONFIG_X86_X32
>>>> x32_ld_ok := $(call try-run,\
>>>> /bin/echo -e '1: .quad 1b' | \
>>>
>>> Why conditional on clang?
>>
>> My understanding is that this warning is clang specific, it is not
>> listed on https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html
>
> Actually this warning affects other platforms besides x86
> (e.g. arm64), I'll submit a patch that disables the warning on all
> platforms.
>
Drop the ifeq ($(cc-name),clang).
You should assume that if you have to add one of those ifeq's then you
are doing something fundamentally wrong.
-hpa
next prev parent reply other threads:[~2017-04-13 23:59 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-17 0:15 [PATCH 0/7] LLVM: make x86_64 kernel build with clang Michael Davidson
2017-03-17 0:15 ` [PATCH 1/7] Makefile, LLVM: add -no-integrated-as to KBUILD_[AC]FLAGS Michael Davidson
2017-04-03 22:49 ` Matthias Kaehlcke
2017-04-21 7:49 ` Masahiro Yamada
2017-03-17 0:15 ` [PATCH 2/7] Makefile, x86, LLVM: disable unsupported optimization flags Michael Davidson
2017-03-17 21:32 ` H. Peter Anvin
2017-03-17 21:34 ` H. Peter Anvin
2017-04-05 18:08 ` Masahiro Yamada
2017-04-05 19:01 ` Matthias Kaehlcke
2017-04-05 19:11 ` Michael Davidson
2017-04-10 14:54 ` Masahiro Yamada
2017-03-17 0:15 ` [PATCH 3/7] x86, LLVM: suppress clang warnings about unaligned accesses Michael Davidson
2017-03-17 23:50 ` hpa
2017-04-03 23:01 ` Matthias Kaehlcke
2017-04-13 23:14 ` Matthias Kaehlcke
2017-04-13 23:55 ` H. Peter Anvin [this message]
2017-04-14 0:23 ` Matthias Kaehlcke
2017-04-14 5:30 ` hpa
2017-03-17 0:15 ` [PATCH 4/7] x86, boot, LLVM: #undef memcpy etc in string.c Michael Davidson
2017-06-22 22:31 ` Matthias Kaehlcke
2017-06-22 22:37 ` H. Peter Anvin
2017-06-30 18:32 ` Matthias Kaehlcke
2017-03-17 0:15 ` [PATCH 5/7] x86, boot, LLVM: Use regparm=0 for memcpy and memset Michael Davidson
2017-03-17 12:08 ` Peter Zijlstra
2017-06-22 22:38 ` H. Peter Anvin
2017-03-17 0:15 ` [PATCH 6/7] md/raid10, LLVM: get rid of variable length array Michael Davidson
2017-03-17 12:08 ` Peter Zijlstra
2017-03-17 12:31 ` Alexander Potapenko
2017-03-17 12:32 ` Alexander Potapenko
2017-03-17 18:03 ` Borislav Petkov
2017-03-17 18:47 ` Dmitry Vyukov
2017-03-17 18:57 ` Borislav Petkov
2017-03-17 19:05 ` Dmitry Vyukov
2017-03-17 19:26 ` Peter Zijlstra
2017-03-17 19:29 ` Peter Zijlstra
2017-03-24 13:50 ` Dmitry Vyukov
2017-03-24 14:10 ` Peter Zijlstra
2017-03-24 14:22 ` Dmitry Vyukov
2017-03-18 0:41 ` Fengguang Wu
2017-03-17 12:44 ` Peter Zijlstra
2017-03-17 18:52 ` Michael Davidson
2017-03-17 19:27 ` Peter Zijlstra
2017-03-17 20:04 ` hpa
2017-03-24 13:47 ` Dmitry Vyukov
2017-03-24 14:09 ` Peter Zijlstra
2017-03-17 0:15 ` [PATCH 7/7] crypto, x86, LLVM: aesni - fix token pasting Michael Davidson
2017-04-03 23:14 ` Matthias Kaehlcke
2017-03-17 8:17 ` [PATCH 0/7] LLVM: make x86_64 kernel build with clang Dmitry Vyukov
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