linux-kernel - [PATCH] objtool: ignore INT3 padding

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Date:   Tue, 15 May 2018 01:35:04 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     jpoimboe@...hat.com, peterz@...radead.org, mingo@...nel.org
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH] objtool: ignore INT3 padding

NOP padding doesn't count as unreachable instruction
neither should INT3.

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

 tools/objtool/arch.h            |    3 ++-
 tools/objtool/arch/x86/decode.c |    4 ++++
 tools/objtool/check.c           |    3 +++
 3 files changed, 9 insertions(+), 1 deletion(-)

--- a/tools/objtool/arch.h
+++ b/tools/objtool/arch.h
@@ -34,7 +34,8 @@
 #define INSN_BUG		9
 #define INSN_NOP		10
 #define INSN_OTHER		11
-#define INSN_LAST		INSN_OTHER
+#define INSN_INT3		12
+#define INSN_LAST		INSN_INT3
 
 enum op_dest_type {
 	OP_DEST_REG,
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -440,6 +440,10 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
 		*type = INSN_CONTEXT_SWITCH;
 		break;
 
+	case 0xcc:
+		*type = INSN_INT3;
+		break;
+
 	case 0xe8:
 		*type = INSN_CALL;
 		break;
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1998,6 +1998,9 @@ static bool ignore_unreachable_insn(struct instruction *insn)
 
 	if (insn->ignore || insn->type == INSN_NOP)
 		return true;
+	/* Inter-function padding. */
+	if (insn->type == INSN_INT3)
+		return true;
 
 	/*
 	 * Ignore any unused exceptions.  This can happen when a whitelisted