linux-kernel - [PATCH v2 16/22] objtool: Do frame pointer check before dead end check

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Message-Id: <aed62fbd60e239280218be623f751a433658e896.1563413318.git.jpoimboe@redhat.com>
Date:   Wed, 17 Jul 2019 20:36:51 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Arnd Bergmann <arnd@...db.de>, Jann Horn <jannh@...gle.com>,
        Randy Dunlap <rdunlap@...radead.org>
Subject: [PATCH v2 16/22] objtool: Do frame pointer check before dead end check

Even calls to __noreturn functions need the frame pointer setup first.
Such functions often dump the stack.

Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Tested-by: Nick Desaulniers <ndesaulniers@...gle.com>
---
 tools/objtool/check.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 970dfeac841d..3fb656ea96b9 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -133,6 +133,9 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
 		"rewind_stack_do_exit",
 	};
 
+	if (!func)
+		return false;
+
 	if (func->bind == STB_WEAK)
 		return false;
 
@@ -2071,19 +2074,16 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
 			if (ret)
 				return ret;
 
-			if (insn->type == INSN_CALL) {
-				if (is_fentry_call(insn))
-					break;
-
-				if (dead_end_function(file, insn->call_dest))
-					return 0;
-			}
-
-			if (!no_fp && func && !has_valid_stack_frame(&state)) {
+			if (!no_fp && func && !is_fentry_call(insn) &&
+			    !has_valid_stack_frame(&state)) {
 				WARN_FUNC("call without frame pointer save/setup",
 					  sec, insn->offset);
 				return 1;
 			}
+
+			if (dead_end_function(file, insn->call_dest))
+				return 0;
+
 			break;
 
 		case INSN_JUMP_CONDITIONAL:
-- 
2.20.1