Re: [PATCH 3/7] x86, LLVM: suppress clang warnings about unaligned accesses

From	Matthias Kaehlcke <mka@chromium.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 3/7] x86, LLVM: suppress clang warnings about unaligned accesses
Date	2017-04-14 01:20 +0200
Message-ID	<tvWbU-1xv-7@gated-at.bofh.it> (permalink)
References	<tlNWh-6eK-9@gated-at.bofh.it> <tlNWh-6eK-7@gated-at.bofh.it> <tm9WN-5YC-7@gated-at.bofh.it> <tsjgJ-4ZI-13@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

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

Back to linux.kernel | Previous | Next — Next in thread | Find similar | Unroll thread

Thread

Re: [PATCH 3/7] x86, LLVM: suppress clang warnings about unaligned  accesses Matthias Kaehlcke <mka@chromium.org> - 2017-04-14 01:20 +0200
  Re: [PATCH 3/7] x86, LLVM: suppress clang warnings about unaligned  accesses "H. Peter Anvin" <hpa@zytor.com> - 2017-04-14 02:00 +0200
    Re: [PATCH 3/7] x86, LLVM: suppress clang warnings about unaligned  accesses Matthias Kaehlcke <mka@chromium.org> - 2017-04-14 02:30 +0200
      Re: [PATCH 3/7] x86, LLVM: suppress clang warnings about unaligned accesses hpa@zytor.com - 2017-04-14 07:40 +0200

csiph-web