From patchwork Fri May 1 13:22:18 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 226528 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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=unavailable 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 E9D40C4724C for ; Fri, 1 May 2020 13:54:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CB19B2051A for ; Fri, 1 May 2020 13:54:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588341280; bh=RpCOqBR4v3FHWcOXyUprhr2wJAYbPKCXR2v4g0MUhGw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=uV1VPtTXjHQImyWjROtEsE8/vJUCbD9gVNMSCuujDNNy2Iaxljmzzih6s/eD+z38W qQD0zxtSfkNZs4+mo5yzqIeX0Csexh0tTejZhvPkGTmoL02nfihHPAN38yhsZtz/zX LuDr8oJwGLpgTakvuY7jUGSyU265go5wxwjfwSyQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730183AbgEANex (ORCPT ); Fri, 1 May 2020 09:34:53 -0400 Received: from mail.kernel.org ([198.145.29.99]:32966 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729793AbgEANeu (ORCPT ); Fri, 1 May 2020 09:34:50 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 77CF0216FD; Fri, 1 May 2020 13:34:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588340089; bh=RpCOqBR4v3FHWcOXyUprhr2wJAYbPKCXR2v4g0MUhGw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=W+9W9JhLsyTMBj+U7WwXpICNhq2F5IucaM5dnMVlIpiPad8XdxRIM+tJ7iMyT+/y7 A3KhdHvE3XR2sUuo3MUGJIpexcj2y+UHANfObE5Ty1lHG0vQGCfwpieurpf69fnAnC /HOVzNYf7MlM+zNKmIQ4yZ+5RSTaUVB3P5VCmwG4= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Randy Dunlap , Josh Poimboeuf , Borislav Petkov , Kees Cook , Miroslav Benes , "Peter Zijlstra (Intel)" , Sasha Levin Subject: [PATCH 4.14 102/117] objtool: Fix CONFIG_UBSAN_TRAP unreachable warnings Date: Fri, 1 May 2020 15:22:18 +0200 Message-Id: <20200501131557.685691506@linuxfoundation.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200501131544.291247695@linuxfoundation.org> References: <20200501131544.291247695@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Josh Poimboeuf [ Upstream commit bd841d6154f5f41f8a32d3c1b0bc229e326e640a ] 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 Signed-off-by: Sasha Levin --- 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 ccd5319d1284c..04fc04b4ab67e 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -2062,14 +2062,27 @@ 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))