linux-kernel - [tip:core/urgent] objtool: Fix bytes check of lea's rex

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Date:   Tue, 6 Dec 2016 02:10:48 -0800
From:   tip-bot for Jiri Slaby <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     luto@...nel.org, jslaby@...e.cz, peterz@...radead.org,
        jpoimboe@...hat.com, mingo@...nel.org, tglx@...utronix.de,
        brgerst@...il.com, hpa@...or.com, dvlasenk@...hat.com,
        torvalds@...ux-foundation.org, bp@...en8.de,
        linux-kernel@...r.kernel.org
Subject: [tip:core/urgent] objtool: Fix bytes check of lea's rex_prefix

Commit-ID:  69042bf2001b44e81cd86ab11a4637b9d9a14c5a
Gitweb:     http://git.kernel.org/tip/69042bf2001b44e81cd86ab11a4637b9d9a14c5a
Author:     Jiri Slaby <jslaby@...e.cz>
AuthorDate: Mon, 5 Dec 2016 11:55:51 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 6 Dec 2016 09:20:59 +0100

objtool: Fix bytes check of lea's rex_prefix

For the "lea %(rsp), %rbp" case, we check if there is a rex_prefix.
But we check 'bytes' which is insn_byte_t[4] in rex_prefix (insn_field
structure). Therefore, the check is always true.

Instead, check 'nbytes' which is the right one.

Signed-off-by: Jiri Slaby <jslaby@...e.cz>
Acked-by: Josh Poimboeuf <jpoimboe@...hat.com>
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: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/20161205105551.25917-1-jslaby@suse.cz
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 tools/objtool/arch/x86/decode.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index b63a31b..5e0dea2 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -99,7 +99,7 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
 		break;
 
 	case 0x8d:
-		if (insn.rex_prefix.bytes &&
+		if (insn.rex_prefix.nbytes &&
 		    insn.rex_prefix.bytes[0] == 0x48 &&
 		    insn.modrm.nbytes && insn.modrm.bytes[0] == 0x2c &&
 		    insn.sib.nbytes && insn.sib.bytes[0] == 0x24)