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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 28EDCC433DF for ; Mon, 6 Jul 2020 08:39:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 015CF206E9 for ; Mon, 6 Jul 2020 08:39:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="NAUrJJLo" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728397AbgGFIjJ (ORCPT ); Mon, 6 Jul 2020 04:39:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58042 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728188AbgGFIjJ (ORCPT ); Mon, 6 Jul 2020 04:39:09 -0400 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 103C0C061794 for ; Mon, 6 Jul 2020 01:39:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=hQtxiKLfzE/x9Sg6QTa2n1RkY6u3HrYEtMHaJwO31ZI=; b=NAUrJJLoSJovF0sBrKzhye0fWI U2oiLykG4uyH6CzOQgoKWxa4xeHWzaul6dG2cRVdbxpePsvAAGZhl7GI7ZHt9VEY1rVZ7Q4Spki88 8SUYFU+545f0WZEllcMNKoDPDuEj+aQryGRhrN5SKIJqPk99T7h8JKCE85qDIXNztsPFo52oZ/EAV kMm1Ctc23i4nAyq11HV1yAjLVSVdCJsqVDkDOsFhtcMN163orWzLIiifxOycFvxCyA26uYXdKYqln Rsnh7w6Hwvf+GJ68nyUTT8PSWsWp0bx0Rt48yd9Q+Ki13MY7JDw+vMegTSsobNZzfec1dpWZgZHi4 kyfXPjFg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jsMeV-0007ks-RK; Mon, 06 Jul 2020 08:39:04 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 998103028C8; Mon, 6 Jul 2020 10:39:00 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 824F82025890A; Mon, 6 Jul 2020 10:39:00 +0200 (CEST) Date: Mon, 6 Jul 2020 10:39:00 +0200 From: Peter Zijlstra To: Sedat Dilek Cc: Josh Poimboeuf , x86@kernel.org, linux-kernel@vger.kernel.org, mbenes@suse.cz Subject: Re: [Linux v5.8-rc4] objtool warnings with gcc-10 Message-ID: <20200706083900.GC4800@hirez.programming.kicks-ass.net> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 06, 2020 at 09:09:55AM +0200, Sedat Dilek wrote: > [ Please CC me I am not subscribed to this mailing-list ] > > Hi Josh and Peter, > > today I switched over from Linux v5.7.y to Linux v5.8-rc4 and built > the first time with GCC version 10 on Debian/testing AMD64. > > $ cat /proc/version > Linux version 5.8.0-rc4-1-amd64-gcc10 (sedat.dilek@gmail.com@iniza) > (gcc-10 (Debian 10.1.0-4) 10.1.0, GNU ld (GNU Binutils for Debian) > 2.34) #1~bullseye+dileks1 SMP 2020-07-06 > > I see these objtool warnings (which are new to me): > > $ grep warning: build-log_5.8.0-rc4-1-amd64-gcc10.txt | sort > arch/x86/kernel/cpu/mce/core.o: warning: objtool: mce_panic()+0x118: unreachable instruction > drivers/atm/horizon.o: warning: objtool: interrupt_handler()+0x19f: unreachable instruction > drivers/message/fusion/mptbase.o: warning: objtool: mpt_Soft_Hard_ResetHandler()+0x33a: unreachable instruction > drivers/scsi/aic7xxx/aic79xx_core.o: warning: objtool: ahd_intr.part.0()+0x10f: unreachable instruction > drivers/scsi/pcmcia/aha152x_core.o: warning: objtool: run()+0x4c0: unreachable instruction > fs/btrfs/backref.o: warning: objtool: btrfs_backref_finish_upper_links()+0x309: unreachable instruction > fs/btrfs/extent_io.o: warning: objtool: __set_extent_bit.cold()+0xc: unreachable instruction > fs/btrfs/relocation.o: warning: objtool: update_backref_cache.part.0()+0x1de: unreachable instruction > kernel/exit.o: warning: objtool: __x64_sys_exit_group()+0x14: unreachable instruction > net/core/skbuff.o: warning: objtool: skb_push.cold()+0x15: unreachable instruction That's more CONFIG_LIVEPATCH=y wreckage I expect. The problem is that GCC -flive-patching= thing wreck the propagation of the noreturn. This really is a compiler issue and we've not managed a sensible work-around in objtool.