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From: Matthias Kaehlcke <mka@chromium.org>
To: hpa@zytor.com
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 16:14:39 -0700	[thread overview]
Message-ID: <20170413231439.GG28657@google.com> (raw)
In-Reply-To: <20170403230158.GA145051@google.com>

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.

Cheers

Matthias

  reply	other threads:[~2017-04-13 23:14 UTC|newest]

Thread overview: 50+ 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
2017-04-21  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 [this message]
2017-04-13 23:55         ` H. Peter Anvin
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 19:26                   ` 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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