linux-kernel - [tip:x86/asm] objtool: Fix '-mtune=atom' decoding support in objtool 2.0

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Date:   Fri, 28 Jul 2017 00:37:55 -0700
From:   tip-bot for Josh Poimboeuf <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     tglx@...utronix.de, linux-kernel@...r.kernel.org,
        jpoimboe@...hat.com, peterz@...radead.org, mingo@...nel.org,
        torvalds@...ux-foundation.org, hpa@...or.com, arnd@...db.de
Subject: [tip:x86/asm] objtool: Fix '-mtune=atom' decoding support in
 objtool 2.0

Commit-ID:  5b8de48e82ba322483c925ce33f193e28e59a5fd
Gitweb:     http://git.kernel.org/tip/5b8de48e82ba322483c925ce33f193e28e59a5fd
Author:     Josh Poimboeuf <jpoimboe@...hat.com>
AuthorDate: Thu, 27 Jul 2017 15:56:55 -0500
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Fri, 28 Jul 2017 08:33:32 +0200

objtool: Fix '-mtune=atom' decoding support in objtool 2.0

With '-mtune=atom', which is enabled with CONFIG_MATOM=y, GCC uses some
unusual instructions for setting up the stack.

Instead of:

  mov %rsp, %rbp

it does:

  lea (%rsp), %rbp

And instead of:

  add imm, %rsp

it does:

  lea disp(%rsp), %rsp

Add support for these instructions to the objtool decoder.

Reported-by: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Fixes: baa41469a7b9 ("objtool: Implement stack validation 2.0")
Link: http://lkml.kernel.org/r/4ea1db896e821226efe1f8e09f270771bde47e65.1501188854.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 tools/objtool/arch/x86/decode.c | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index e4b400b..7841e5d 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -271,7 +271,7 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
 	case 0x8d:
 		if (rex == 0x48 && modrm == 0x65) {
 
-			/* lea -disp(%rbp), %rsp */
+			/* lea disp(%rbp), %rsp */
 			*type = INSN_STACK;
 			op->src.type = OP_SRC_ADD;
 			op->src.reg = CFI_BP;
@@ -281,6 +281,30 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
 			break;
 		}
 
+		if (rex == 0x48 && (modrm == 0xa4 || modrm == 0x64) &&
+		    sib == 0x24) {
+
+			/* lea disp(%rsp), %rsp */
+			*type = INSN_STACK;
+			op->src.type = OP_SRC_ADD;
+			op->src.reg = CFI_SP;
+			op->src.offset = insn.displacement.value;
+			op->dest.type = OP_DEST_REG;
+			op->dest.reg = CFI_SP;
+			break;
+		}
+
+		if (rex == 0x48 && modrm == 0x2c && sib == 0x24) {
+
+			/* lea (%rsp), %rbp */
+			*type = INSN_STACK;
+			op->src.type = OP_SRC_REG;
+			op->src.reg = CFI_SP;
+			op->dest.type = OP_DEST_REG;
+			op->dest.reg = CFI_BP;
+			break;
+		}
+
 		if (rex == 0x4c && modrm == 0x54 && sib == 0x24 &&
 		    insn.displacement.value == 8) {