linux-kernel - Re: [PATCH] x86: prevent gcc from emitting SSE into boot code

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Message-ID: <CACT4Y+b8WC8NaWgtjbeY+Ach8ZOyy-r_dvzWrNU34fSMRhuHFQ@mail.gmail.com>
Date:	Wed, 22 Jun 2016 22:17:01 +0200
From:	Dmitry Vyukov <dvyukov@...gle.com>
To:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"x86@...nel.org" <x86@...nel.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Alexander Potapenko <glider@...gle.com>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	kasan-dev <kasan-dev@...glegroups.com>,
	Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH] x86: prevent gcc from emitting SSE into boot code

On Wed, Jun 22, 2016 at 7:37 PM, Dmitry Vyukov <dvyukov@...gle.com> wrote:
> Latest gcc manages to emit MOVDQA into boot code
> which leads to crashes. Add more -mno-see flags.
>
> Signed-off-by: Dmitry Vyukov <dvyukov@...gle.com>
> ---
>  arch/x86/boot/compressed/Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
> index f135688..7eaafb8 100644
> --- a/arch/x86/boot/compressed/Makefile
> +++ b/arch/x86/boot/compressed/Makefile
> @@ -31,7 +31,7 @@ KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING
>  cflags-$(CONFIG_X86_32) := -march=i386
>  cflags-$(CONFIG_X86_64) := -mcmodel=small
>  KBUILD_CFLAGS += $(cflags-y)
> -KBUILD_CFLAGS += -mno-mmx -mno-sse
> +KBUILD_CFLAGS += -mno-mmx -mno-sse -mno-sse2 -mno-sse3
>  KBUILD_CFLAGS += $(call cc-option,-ffreestanding)
>  KBUILD_CFLAGS += $(call cc-option,-fno-stack-protector)
>
> --
> 2.8.0.rc3.226.g39d4020


I withdraw this patch.

>From off-list discussion:

"-mno-sse alone should disable all SSE/AVX instructions. If not,
please file a GCC bug report".