From nobody Mon Feb 9 16:53:54 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9ED09EB64DC for ; Tue, 11 Jul 2023 16:09:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233119AbjGKQJM (ORCPT ); Tue, 11 Jul 2023 12:09:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43314 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232876AbjGKQJE (ORCPT ); Tue, 11 Jul 2023 12:09:04 -0400 Received: from pegase1.c-s.fr (pegase1.c-s.fr [93.17.236.30]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2EFA810F9 for ; Tue, 11 Jul 2023 09:09:02 -0700 (PDT) Received: from localhost (mailhub3.si.c-s.fr [192.168.12.233]) by localhost (Postfix) with ESMTP id 4R0m5H4xHSz9sFC; Tue, 11 Jul 2023 18:08:51 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id sJunrGwSK_vC; Tue, 11 Jul 2023 18:08:51 +0200 (CEST) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 4R0m5C3qNTz9sFG; Tue, 11 Jul 2023 18:08:47 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 7F2228B763; Tue, 11 Jul 2023 18:08:47 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id 9d1NI2BXQpaT; Tue, 11 Jul 2023 18:08:47 +0200 (CEST) Received: from PO20335.IDSI0.si.c-s.fr (unknown [192.168.233.184]) by messagerie.si.c-s.fr (Postfix) with ESMTP id D14788B77B; Tue, 11 Jul 2023 18:08:46 +0200 (CEST) Received: from PO20335.IDSI0.si.c-s.fr (localhost [127.0.0.1]) by PO20335.IDSI0.si.c-s.fr (8.17.1/8.16.1) with ESMTPS id 36BG8iwe3696820 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Tue, 11 Jul 2023 18:08:44 +0200 Received: (from chleroy@localhost) by PO20335.IDSI0.si.c-s.fr (8.17.1/8.17.1/Submit) id 36BG8iCY3696819; Tue, 11 Jul 2023 18:08:44 +0200 X-Authentication-Warning: PO20335.IDSI0.si.c-s.fr: chleroy set sender to christophe.leroy@csgroup.eu using -f From: Christophe Leroy To: Michael Ellerman , Nicholas Piggin , Josh Poimboeuf , Peter Zijlstra , Sathvika Vasireddy , Naveen N Rao Cc: Christophe Leroy , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: [PATCH v4 05/15] objtool: Add INSN_RETURN_CONDITIONAL Date: Tue, 11 Jul 2023 18:08:31 +0200 Message-ID: <0b907f1cb4b85cba39b6c2b727c80d29e096e977.1689091394.git.christophe.leroy@csgroup.eu> X-Mailer: git-send-email 2.41.0 In-Reply-To: References: MIME-Version: 1.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1689091705; l=3391; i=christophe.leroy@csgroup.eu; s=20211009; h=from:subject:message-id; bh=RQvNZ3u/NPHor4suqgxX3vAfJ2dn/X79t365w/+p2nc=; b=B9G86bIXes9pIEokdlznNuX5AWjjZ0vaHIsr9dwCR0WD/GmjAkq4cSlQILjBFCpwqKqfNi2Vp F0BbI3cK4UZCuaFCjC7L8IJQ8BTZke0RpQbRghX+b2JMqDYRuFXOm7J X-Developer-Key: i=christophe.leroy@csgroup.eu; a=ed25519; pk=HIzTzUj91asvincQGOFx6+ZF5AoUuP9GdOtQChs7Mm0= Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Most functions have an unconditional return at the end, like this one: 00000000 : 0: 81 22 04 d0 lwz r9,1232(r2) 4: 38 60 00 00 li r3,0 8: 2c 09 00 00 cmpwi r9,0 c: 4d 82 00 20 beqlr <=3D=3D Conditional return 10: 80 69 00 a0 lwz r3,160(r9) 14: 54 63 00 36 clrrwi r3,r3,4 18: 68 63 04 00 xori r3,r3,1024 1c: 7c 63 00 34 cntlzw r3,r3 20: 54 63 d9 7e srwi r3,r3,5 24: 4e 80 00 20 blr <=3D=3D Unconditional return But other functions like this other one below only have conditional returns: 00000028 : 28: 81 25 00 00 lwz r9,0(r5) 2c: 2c 08 00 00 cmpwi r8,0 30: 7d 29 30 78 andc r9,r9,r6 34: 7d 27 3b 78 or r7,r9,r7 38: 54 84 65 3a rlwinm r4,r4,12,20,29 3c: 81 23 00 18 lwz r9,24(r3) 40: 41 82 00 58 beq 98 44: 7d 29 20 2e lwzx r9,r9,r4 48: 55 29 07 3a rlwinm r9,r9,0,28,29 4c: 2c 09 00 0c cmpwi r9,12 50: 41 82 00 08 beq 58 54: 39 00 00 80 li r8,128 58: 2c 08 00 01 cmpwi r8,1 5c: 90 e5 00 00 stw r7,0(r5) 60: 4d a2 00 20 beqlr+ <=3D=3D Conditional return 64: 7c e9 3b 78 mr r9,r7 68: 39 40 00 00 li r10,0 6c: 39 4a 00 04 addi r10,r10,4 70: 7c 0a 40 00 cmpw r10,r8 74: 91 25 00 04 stw r9,4(r5) 78: 91 25 00 08 stw r9,8(r5) 7c: 38 a5 00 10 addi r5,r5,16 80: 91 25 ff fc stw r9,-4(r5) 84: 4c 80 00 20 bgelr <=3D=3D Conditional return 88: 55 49 60 26 slwi r9,r10,12 8c: 7d 29 3a 14 add r9,r9,r7 90: 91 25 00 00 stw r9,0(r5) 94: 4b ff ff d8 b 6c 98: 39 00 00 04 li r8,4 9c: 4b ff ff bc b 58 If conditional returns are decoded as INSN_OTHER, objtool considers that the second function never returns. If conditional returns are decoded as INSN_RETURN, objtool considers that code after that conditional return is dead. To overcome this situation, introduce INSN_RETURN_CONDITIONAL which is taken as a confirmation that a function is not noreturn but still sees following code as reachable. Signed-off-by: Christophe Leroy Acked-by: Peter Zijlstra (Intel) --- tools/objtool/check.c | 2 +- tools/objtool/include/objtool/arch.h | 1 + 2 files changed, 2 insertions(+), 1 deletion(-) diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 25f6df4713ed..ae0019412123 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -219,7 +219,7 @@ static bool __dead_end_function(struct objtool_file *fi= le, struct symbol *func, func_for_each_insn(file, func, insn) { empty =3D false; =20 - if (insn->type =3D=3D INSN_RETURN) + if (insn->type =3D=3D INSN_RETURN || insn->type =3D=3D INSN_RETURN_CONDI= TIONAL) return false; } =20 diff --git a/tools/objtool/include/objtool/arch.h b/tools/objtool/include/o= bjtool/arch.h index 2b6d2ce4f9a5..84ba75112934 100644 --- a/tools/objtool/include/objtool/arch.h +++ b/tools/objtool/include/objtool/arch.h @@ -19,6 +19,7 @@ enum insn_type { INSN_CALL, INSN_CALL_DYNAMIC, INSN_RETURN, + INSN_RETURN_CONDITIONAL, INSN_CONTEXT_SWITCH, INSN_BUG, INSN_NOP, --=20 2.41.0