linux-kernel - Re: [PATCH resend] x86: Fix detection of GCC -mpreferred-stack-boundary support

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Date:	Wed, 22 Jul 2015 10:04:36 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Andy Lutomirski <luto@...nel.org>
Cc:	x86@...nel.org, linux-kernel@...r.kernel.org,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jan Kara <jack@...e.cz>, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH resend] x86: Fix detection of GCC
 -mpreferred-stack-boundary support

On Tue, Jul 21, 2015 at 09:27:18AM -0700, Andy Lutomirski wrote:
> +# prevent gcc from generating any FP code by mistake
> +# This must be before we try -mpreferred-stack-boundary -- see
> +# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53383
> +KBUILD_CFLAGS += -mno-sse -mno-mmx -mno-sse2 -mno-3dnow
> +KBUILD_CFLAGS += $(call cc-option,-mno-avx,)

Should we unify all FPU-generating switches to one place? I've added
this

        # Don't autogenerate traditional x87 instructions
        KBUILD_CFLAGS += $(call cc-option,-mno-80387)
        KBUILD_CFLAGS += $(call cc-option,-mno-fp-ret-in-387)

to the 64-bit build a while back but I don't see why it shouldn't be in
the generic part of the Makefile...

Also, 32-bit has -msoft-float which, according to the gcc manpage is
ignored but I guess should be kept for older gccs...

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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