linux-kernel - [PATCH 5.15 21/78] objtool: Default ignore INT3 for unreachable

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Message-Id: <20220712183239.696980857@linuxfoundation.org>
Date:   Tue, 12 Jul 2022 20:38:51 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
Subject: [PATCH 5.15 21/78] objtool: Default ignore INT3 for unreachable

From: Peter Zijlstra <peterz@...radead.org>

commit 1ffbe4e935f9b7308615c75be990aec07464d1e7 upstream.

Ignore all INT3 instructions for unreachable code warnings, similar to NOP.
This allows using INT3 for various paddings instead of NOPs.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Josh Poimboeuf <jpoimboe@...hat.com>
Link: https://lore.kernel.org/r/20220308154317.343312938@infradead.org
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 tools/objtool/check.c |   12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2965,9 +2965,8 @@ static int validate_branch(struct objtoo
 		switch (insn->type) {
 
 		case INSN_RETURN:
-			if (next_insn && next_insn->type == INSN_TRAP) {
-				next_insn->ignore = true;
-			} else if (sls && !insn->retpoline_safe) {
+			if (sls && !insn->retpoline_safe &&
+			    next_insn && next_insn->type != INSN_TRAP) {
 				WARN_FUNC("missing int3 after ret",
 					  insn->sec, insn->offset);
 			}
@@ -3014,9 +3013,8 @@ static int validate_branch(struct objtoo
 			break;
 
 		case INSN_JUMP_DYNAMIC:
-			if (next_insn && next_insn->type == INSN_TRAP) {
-				next_insn->ignore = true;
-			} else if (sls && !insn->retpoline_safe) {
+			if (sls && !insn->retpoline_safe &&
+			    next_insn && next_insn->type != INSN_TRAP) {
 				WARN_FUNC("missing int3 after indirect jump",
 					  insn->sec, insn->offset);
 			}
@@ -3187,7 +3185,7 @@ static bool ignore_unreachable_insn(stru
 	int i;
 	struct instruction *prev_insn;
 
-	if (insn->ignore || insn->type == INSN_NOP)
+	if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP)
 		return true;
 
 	/*