[tip:core/urgent] objtool: Fix bytes check of lea's rex_prefix

[tip-bot for Jiri Slaby]

Commit-ID:  69042bf2001b44e81cd86ab11a4637b9d9a14c5a
Gitweb:     http://git.kernel.org/tip/69042bf2001b44e81cd86ab11a4637b9d9a14c5a
Author:     Jiri Slaby <jslaby@xxxxxxx>
AuthorDate: Mon, 5 Dec 2016 11:55:51 +0100
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
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@xxxxxxx>
Acked-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20161205105551.25917-1-jslaby@xxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 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)