From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DBFC4C2BA19 for ; Tue, 14 Apr 2020 10:41:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BC97220644 for ; Tue, 14 Apr 2020 10:41:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2438486AbgDNKlj (ORCPT ); Tue, 14 Apr 2020 06:41:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58330 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S2438403AbgDNKeL (ORCPT ); Tue, 14 Apr 2020 06:34:11 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 37778C0610D6; Tue, 14 Apr 2020 03:34:11 -0700 (PDT) Received: from [5.158.153.53] (helo=tip-bot2.lab.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1jOItI-0008Ti-9o; Tue, 14 Apr 2020 12:34:04 +0200 Received: from [127.0.1.1] (localhost [IPv6:::1]) by tip-bot2.lab.linutronix.de (Postfix) with ESMTP id E6D5D1C0086; Tue, 14 Apr 2020 12:34:03 +0200 (CEST) Date: Tue, 14 Apr 2020 10:34:03 -0000 From: "tip-bot2 for Josh Poimboeuf" Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/urgent] objtool: Fix CONFIG_UBSAN_TRAP unreachable warnings Cc: Randy Dunlap , Josh Poimboeuf , Borislav Petkov , Kees Cook , Miroslav Benes , "Peter Zijlstra (Intel)" , x86 , LKML In-Reply-To: <6653ad73c6b59c049211bd7c11ed3809c20ee9f5.1585761021.git.jpoimboe@redhat.com> References: <6653ad73c6b59c049211bd7c11ed3809c20ee9f5.1585761021.git.jpoimboe@redhat.com> MIME-Version: 1.0 Message-ID: <158686044342.28353.9170954952502687843.tip-bot2@tip-bot2> X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the x86/urgent branch of tip: Commit-ID: bd841d6154f5f41f8a32d3c1b0bc229e326e640a Gitweb: https://git.kernel.org/tip/bd841d6154f5f41f8a32d3c1b0bc229e326e640a Author: Josh Poimboeuf AuthorDate: Wed, 01 Apr 2020 13:23:25 -05:00 Committer: Borislav Petkov CommitterDate: Tue, 14 Apr 2020 11:55:09 +02:00 objtool: Fix CONFIG_UBSAN_TRAP unreachable warnings CONFIG_UBSAN_TRAP causes GCC to emit a UD2 whenever it encounters an unreachable code path. This includes __builtin_unreachable(). Because the BUG() macro uses __builtin_unreachable() after it emits its own UD2, this results in a double UD2. In this case objtool rightfully detects that the second UD2 is unreachable: init/main.o: warning: objtool: repair_env_string()+0x1c8: unreachable instruction We weren't able to figure out a way to get rid of the double UD2s, so just silence the warning. Reported-by: Randy Dunlap Signed-off-by: Josh Poimboeuf Signed-off-by: Borislav Petkov Reviewed-by: Kees Cook Reviewed-by: Miroslav Benes Acked-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/6653ad73c6b59c049211bd7c11ed3809c20ee9f5.1585761021.git.jpoimboe@redhat.com --- tools/objtool/check.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 8dd01f9..4811325 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -2364,14 +2364,27 @@ static bool ignore_unreachable_insn(struct instruction *insn) !strcmp(insn->sec->name, ".altinstr_aux")) return true; + if (!insn->func) + return false; + + /* + * CONFIG_UBSAN_TRAP inserts a UD2 when it sees + * __builtin_unreachable(). The BUG() macro has an unreachable() after + * the UD2, which causes GCC's undefined trap logic to emit another UD2 + * (or occasionally a JMP to UD2). + */ + if (list_prev_entry(insn, list)->dead_end && + (insn->type == INSN_BUG || + (insn->type == INSN_JUMP_UNCONDITIONAL && + insn->jump_dest && insn->jump_dest->type == INSN_BUG))) + return true; + /* * Check if this (or a subsequent) instruction is related to * CONFIG_UBSAN or CONFIG_KASAN. * * End the search at 5 instructions to avoid going into the weeds. */ - if (!insn->func) - return false; for (i = 0; i < 5; i++) { if (is_kasan_insn(insn) || is_ubsan_insn(insn))