From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f50.google.com ([74.125.83.50]:35539 "EHLO mail-pg0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750987AbdFTRhY (ORCPT ); Tue, 20 Jun 2017 13:37:24 -0400 Received: by mail-pg0-f50.google.com with SMTP id 132so31962755pgb.2 for ; Tue, 20 Jun 2017 10:37:23 -0700 (PDT) Date: Tue, 20 Jun 2017 10:37:21 -0700 From: Matthias Kaehlcke Subject: Re: [PATCH v4 3/3] x86/build: Specify stack alignment for clang Message-ID: <20170620173721.GA52338@google.com> References: <20170619183757.124992-1-mka@chromium.org> <20170619183757.124992-4-mka@chromium.org> <20170619204704.GP141096@google.com> <20170620092054.7d2mgzx6cw3jvgji@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20170620092054.7d2mgzx6cw3jvgji@gmail.com> Sender: linux-kbuild-owner@vger.kernel.org List-ID: To: Ingo Molnar Cc: hpa@zytor.com, Thomas Gleixner , Ingo Molnar , "H . J . Lu" , David Woodhouse , Masahiro Yamada , Michal Marek , x86@kernel.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, Michael Davidson , Greg Hackmann , Nick Desaulniers , Stephen Hines , Kees Cook , Arnd Bergmann , Bernhard.Rosenkranzer@linaro.org, Peter Foley , Behan Webster , Douglas Anderson El Tue, Jun 20, 2017 at 11:20:54AM +0200 Ingo Molnar ha dit: > > * Matthias Kaehlcke wrote: > > > Ingo didn't like the duplication and suggested the use of a variable, which > > kinda implies a check for the compiler name. > > I don't think it implies that: why cannot cc_stack_align_opt probe for the > compiler option and use whichever is available, without hard-coding the compiler > name? We could do this: ifneq ($(call __cc-option, $(CC), -mno-sse, -mpreferred-stack-boundary=3,),) cc_stack_align_opt := -mpreferred-stack-boundary endif ifneq ($(call cc-option, -mstack-alignment=3,),) cc_stack_align_opt := -mstack-alignment endif If preferred cc-option could be used to probe for -mpreferred-stack-boundary , however it would require REALMODE_CFLAGS to be moved further down in the Makefile. Since this solution also won't win a beauty price please let me know if it is acceptable before respinning the patch or if you have other suggestions. > > I also think this is a cleaner solution. [...] > > I concur with hpa: hard-coding compiler is awfully fragile and ugly as well. > > With the proper probing of compiler options it will be possible for compilers to > consolidate their options, and it would be possible for a third compiler to use a > mixture of GCC and Clang options. With hard-coding none of that flexibility is > available. > > > but I'm happy to respin the patch if you have another suggestion that is ok for > > both of you. > > Please do. > > Thanks, > > Ingo