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=-5.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 2049CC433B4 for ; Thu, 22 Apr 2021 04:49:59 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id CBED561448 for ; Thu, 22 Apr 2021 04:49:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CBED561448 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:32984 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lZRHp-0002rl-TG for qemu-devel@archiver.kernel.org; Thu, 22 Apr 2021 00:49:57 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:47722) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lZRFf-0001Od-Go for qemu-devel@nongnu.org; Thu, 22 Apr 2021 00:47:43 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:23532) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lZRFc-0006zr-IR for qemu-devel@nongnu.org; Thu, 22 Apr 2021 00:47:42 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619066859; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=YycjBmv4F0+nju3HHWEounKS9MOpDZN6nFI9gI/i1+0=; b=BkppA+lFmIpz0lPXMrE2Nta99elNOvKH4AASZjxKcT7NH386iCzmkjeIB/cv6yM125/GAm gricMPZLFyNUzfJjlTGceBcdb6U39FxGW83uldQU5/Pdm1TblUrvgrAJM9jeTF4JDW4ljl vbU/b5Il9x/CTYzeLS9f4KwUcyVBFJo= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-237-GUFsiE4fPbG6aWeYRnbDSg-1; Thu, 22 Apr 2021 00:47:37 -0400 X-MC-Unique: GUFsiE4fPbG6aWeYRnbDSg-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5DB2E18397A3; Thu, 22 Apr 2021 04:47:36 +0000 (UTC) Received: from thuth.remote.csb (ovpn-112-48.ams2.redhat.com [10.36.112.48]) by smtp.corp.redhat.com (Postfix) with ESMTP id 206EC60C05; Thu, 22 Apr 2021 04:47:33 +0000 (UTC) Subject: Re: s390-ccw: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=] To: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , "Daniel P . Berrange" , Stefano Garzarella , Christian Borntraeger , Cornelia Huck , Janosch Frank References: <4e327c80-8f5d-c848-b524-7f2c75255da4@redhat.com> From: Thomas Huth Message-ID: <485773db-fca2-03ca-c6e8-90ef313fb8f1@redhat.com> Date: Thu, 22 Apr 2021 06:47:30 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.9.1 MIME-Version: 1.0 In-Reply-To: <4e327c80-8f5d-c848-b524-7f2c75255da4@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=thuth@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=thuth@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-s390x , Richard Henderson , qemu-devel Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 22/04/2021 06.18, Philippe Mathieu-Daudé wrote: > Hi Thomas, Daniel, Stefano, > > Regarding the following warning (GCC 11 on Fedora 34): > > In file included from pc-bios/s390-ccw/main.c:11: > > In function ‘memset’, > > inlined from ‘boot_setup’ at pc-bios/s390-ccw/main.c:185:5, > > inlined from ‘main’ at pc-bios/s390-ccw/main.c:288:5: > > pc-bios/s390-ccw/libc.h:28:14: warning: writing 1 byte into a region of > size 0 [-Wstringop-overflow=] > > 28 | p[i] = c; > > | ~~~~~^~~ > > Daniel were right on IRC: > > danpb: it is from a call memset((char *)S390EP, 0, 6) where S390EP > is just a constant address 0x10008 > danpb: the compiler doesn't now how big that is, so it seems to assume > it is zero length > > This is a known GCC issue: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99578 > "gcc-11 -Warray-bounds or -Wstringop-overread warning when accessing a > pointer from integer literal" Hi Philippe, thanks for following up with the gcc bugzilla! ... so the problem is that GCC thinks we're in fact dereferencing a NULL pointer at offset 0x10008 here? Wow, that's ... crazy. Not sure what to do now - wait for the bug to get resolved? Compile the s390-ccw bios with -Wno-stringop-overread ? Add "volatiles" here and there to hope that these silence the compiler warnings? ... I tend to wait for the bug ticket to see whether the GCC folks change the behavior of the compiler again, but I'm open for other suggestions. Thomas