linux-kernel - [PATCH v2 32/59] objtool: Allow STT_NOTYPE -> STT

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Message-ID: <20220902130949.683665538@infradead.org>
Date:   Fri, 02 Sep 2022 15:06:57 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org, x86@...nel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Andrew Cooper <Andrew.Cooper3@...rix.com>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Johannes Wikner <kwikner@...z.ch>,
        Alyssa Milburn <alyssa.milburn@...ux.intel.com>,
        Jann Horn <jannh@...gle.com>, "H.J. Lu" <hjl.tools@...il.com>,
        Joao Moreira <joao.moreira@...el.com>,
        Joseph Nuzman <joseph.nuzman@...el.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Juergen Gross <jgross@...e.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        K Prateek Nayak <kprateek.nayak@....com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH v2 32/59] objtool: Allow STT_NOTYPE -> STT_FUNC+0 tail-calls

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

Allow STT_NOTYPE to tail-call into STT_FUNC, per definition STT_NOTYPE
is not a sub-function of the STT_FUNC.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 tools/objtool/check.c |   29 ++++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)

--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1370,6 +1370,16 @@ static void add_return_call(struct objto
 
 static bool same_function(struct instruction *insn1, struct instruction *insn2)
 {
+	if (!insn1->func && !insn2->func)
+		return true;
+
+	/* Allow STT_NOTYPE -> STT_FUNC+0 tail-calls */
+	if (!insn1->func && insn1->func != insn2->func)
+		return false;
+
+	if (!insn2->func)
+		return true;
+
 	return insn1->func->pfunc == insn2->func->pfunc;
 }
 
@@ -1487,18 +1497,19 @@ static int add_jump_destinations(struct
 			    strstr(jump_dest->func->name, ".cold")) {
 				insn->func->cfunc = jump_dest->func;
 				jump_dest->func->pfunc = insn->func;
-
-			} else if (!same_function(insn, jump_dest) &&
-				   is_first_func_insn(file, jump_dest)) {
-				/*
-				 * Internal sibling call without reloc or with
-				 * STT_SECTION reloc.
-				 */
-				add_call_dest(file, insn, jump_dest->func, true);
-				continue;
 			}
 		}
 
+		if (!same_function(insn, jump_dest) &&
+		    is_first_func_insn(file, jump_dest)) {
+			/*
+			 * Internal sibling call without reloc or with
+			 * STT_SECTION reloc.
+			 */
+			add_call_dest(file, insn, jump_dest->func, true);
+			continue;
+		}
+
 		insn->jump_dest = jump_dest;
 	}