linux-kernel - [PATCH 1/2] x86/purgatory: add -mno-sse, -mno-mmx, -mno-sse2 to Makefile

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Date:   Wed, 17 Jul 2019 17:02:05 -0700
From:   Vaibhav Rustagi <vaibhavrustagi@...gle.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Vivek Goyal <vgoyal@...hat.com>,
        Vaibhav Rustagi <vaibhavrustagi@...gle.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        stable@...r.kernel.org
Subject: [PATCH 1/2] x86/purgatory: add -mno-sse, -mno-mmx, -mno-sse2 to Makefile

Compiling the purgatory code with clang results in using of mmx
registers.

$ objdump -d arch/x86/purgatory/purgatory.ro | grep xmm

     112:	0f 28 00             	movaps (%rax),%xmm0
     115:	0f 11 07             	movups %xmm0,(%rdi)
     122:	0f 28 00             	movaps (%rax),%xmm0
     125:	0f 11 47 10          	movups %xmm0,0x10(%rdi)

Add -mno-sse, -mno-mmx, -mno-sse2 to avoid generating SSE instructions.

Signed-off-by: Vaibhav Rustagi <vaibhavrustagi@...gle.com>
---
 arch/x86/purgatory/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile
index 3cf302b26332..3589ec4a28c7 100644
--- a/arch/x86/purgatory/Makefile
+++ b/arch/x86/purgatory/Makefile
@@ -20,6 +20,7 @@ KCOV_INSTRUMENT := n
 # sure how to relocate those. Like kexec-tools, use custom flags.
 
 KBUILD_CFLAGS := -fno-strict-aliasing -Wall -Wstrict-prototypes -fno-zero-initialized-in-bss -fno-builtin -ffreestanding -c -Os -mcmodel=large
+KBUILD_CFLAGS += -mno-mmx -mno-sse -mno-sse2
 KBUILD_CFLAGS += -m$(BITS)
 KBUILD_CFLAGS += $(call cc-option,-fno-PIE)
 
-- 
2.22.0.510.g264f2c817a-goog