linux-kernel - [PATCH] x86: pad assembly functions with INT3

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Date:   Tue, 8 May 2018 00:37:55 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     tglx@...utronix.de, mingo@...hat.com, hpa@...or.com
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org
Subject: [PATCH] x86: pad assembly functions with INT3

Use INT3 instead of NOP. All that padding between functions is
an illegal area, no legitimate code should jump into it.

I've checked x86_64 allyesconfig disassembly, all changes looks sane:
INT3 is only used after RET or unconditional JMP.

Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
---

 arch/x86/include/asm/linkage.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/include/asm/linkage.h
+++ b/arch/x86/include/asm/linkage.h
@@ -18,7 +18,7 @@
 	name:
 
 #if defined(CONFIG_X86_64) || defined(CONFIG_X86_ALIGNMENT_16)
-#define __ALIGN		.p2align 4, 0x90
+#define __ALIGN		.p2align 4, 0xCC
 #define __ALIGN_STR	__stringify(__ALIGN)
 #endif