[tip: x86/core] objtool: Default ignore INT3 for unreachable

[tip-bot2 for Peter Zijlstra]

The following commit has been merged into the x86/core branch of tip:

Commit-ID:     def466688a10fe8a2e1da7d3a72b4a29ff6b1a9e
Gitweb:        https://git.kernel.org/tip/def466688a10fe8a2e1da7d3a72b4a29ff6b1a9e
Author:        Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate:    Tue, 08 Mar 2022 16:30:14 +01:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Tue, 08 Mar 2022 23:53:27 +01:00

objtool: Default ignore INT3 for unreachable

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@xxxxxxxxxxxxx>
Acked-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20220308154317.343312938@xxxxxxxxxxxxx
---
 tools/objtool/check.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 7c33ec6..311bfc6 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -3115,9 +3115,8 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
 		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);
 			}
@@ -3164,9 +3163,8 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
 			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);
 			}
@@ -3337,7 +3335,7 @@ static bool ignore_unreachable_insn(struct objtool_file *file, struct instructio
 	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;
 
 	/*