linux-kernel - [tip:x86/pti] x86/asm: Pad assembly functions with INT3 instructions

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Date:   Mon, 14 May 2018 05:53:19 -0700
From:   tip-bot for Alexey Dobriyan <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     mingo@...nel.org, tglx@...utronix.de, luto@...nel.org,
        peterz@...radead.org, jpoimboe@...hat.com, adobriyan@...il.com,
        torvalds@...ux-foundation.org, dvlasenk@...hat.com,
        linux-kernel@...r.kernel.org, h.peter.anvin@...el.com,
        bp@...en8.de, brgerst@...il.com, hpa@...or.com
Subject: [tip:x86/pti] x86/asm: Pad assembly functions with INT3
 instructions

Commit-ID:  51bad67ffbce0aaa44579f84ef5d05597054ec6a
Gitweb:     https://git.kernel.org/tip/51bad67ffbce0aaa44579f84ef5d05597054ec6a
Author:     Alexey Dobriyan <adobriyan@...il.com>
AuthorDate: Tue, 8 May 2018 00:37:55 +0300
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Mon, 14 May 2018 11:43:03 +0200

x86/asm: Pad assembly functions with INT3 instructions

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>
Acked-by: H. Peter Anvin <h.peter.anvin@...el.com>
Acked-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Link: http://lkml.kernel.org/r/20180507213755.GA32406@avx2
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/include/asm/linkage.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/linkage.h b/arch/x86/include/asm/linkage.h
index 14caa9d9fb7f..c0b70bc1e659 100644
--- 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