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=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 5BE48C433B4 for ; Fri, 23 Apr 2021 14:34:21 +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 109826115C for ; Fri, 23 Apr 2021 14:34:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 109826115C 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]:43674 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lZwst-00047l-Uq for qemu-devel@archiver.kernel.org; Fri, 23 Apr 2021 10:34:19 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:50936) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lZwru-0003MR-Hm for qemu-devel@nongnu.org; Fri, 23 Apr 2021 10:33:18 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:23474) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lZwrq-0005RV-Sf for qemu-devel@nongnu.org; Fri, 23 Apr 2021 10:33:18 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619188393; 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=leC3OjvEZfcCPbh74Lvqu9saVT5Lt0iECjsegCCRKkc=; b=goorkiBYpGfvrcpgQlycQDa3xYnOEiCvCInI1zHE8J7/1PHg21hgW6jpx9aS0a+aoql1vi HC72ISzGrCnUQFUklNm+/7CXx2QOLaCG1frETA+w8ZXh1NWfmFRN2JhRzhiKvIC2r2PdRT VoSi91ktpfv2aZDsThAI7Xx5WkkZYwI= 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-516-KiJSGiTfMVO3OHqDkXdYSg-1; Fri, 23 Apr 2021 10:33:12 -0400 X-MC-Unique: KiJSGiTfMVO3OHqDkXdYSg-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 18588839A42; Fri, 23 Apr 2021 14:33:11 +0000 (UTC) Received: from gondolin.fritz.box (ovpn-113-167.ams2.redhat.com [10.36.113.167]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5B96D60C4A; Fri, 23 Apr 2021 14:33:09 +0000 (UTC) Date: Fri, 23 Apr 2021 16:33:06 +0200 From: Cornelia Huck To: Thomas Huth Subject: Re: [PATCH v2] pc-bios/s390-ccw: Use reset_psw pointer instead of hard-coded null pointer Message-ID: <20210423163306.727230ed.cohuck@redhat.com> In-Reply-To: <20210423142440.582188-1-thuth@redhat.com> References: <20210423142440.582188-1-thuth@redhat.com> Organization: Red Hat GmbH MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=cohuck@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=170.10.133.124; envelope-from=cohuck@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, 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=unavailable 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: Christian Borntraeger , qemu-s390x@nongnu.org, Philippe =?UTF-8?B?TWF0aGlldS1EYXVkw6k=?= , qemu-devel@nongnu.org, Janosch Frank Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, 23 Apr 2021 16:24:40 +0200 Thomas Huth wrote: > When compiling the s390-ccw bios with clang, it emits a warning like this= : >=20 > pc-bios/s390-ccw/jump2ipl.c:86:9: warning: indirection of non-volatile n= ull > pointer will be deleted, not trap [-Wnull-dereference] > if (*((uint64_t *)0) & RESET_PSW_MASK) { > ^~~~~~~~~~~~~~~~ > pc-bios/s390-ccw/jump2ipl.c:86:9: note: consider using __builtin_trap() = or > qualifying pointer with 'volatile' >=20 > We could add a "volatile" here to shut it up, but on the other hand, > we also have a pointer variable called "reset_psw" in this file already > that points to the PSW at address 0, so we can simply use that pointer > variable instead. >=20 > Reviewed-by: Philippe Mathieu-Daud=C3=A9 > Signed-off-by: Thomas Huth > --- > v2: Extend comment as suggested by Cornelia Thanks for helping my poor brain :) >=20 > pc-bios/s390-ccw/jump2ipl.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) >=20 > diff --git a/pc-bios/s390-ccw/jump2ipl.c b/pc-bios/s390-ccw/jump2ipl.c > index b9c70d64a5..73e4367e09 100644 > --- a/pc-bios/s390-ccw/jump2ipl.c > +++ b/pc-bios/s390-ccw/jump2ipl.c > @@ -82,8 +82,8 @@ void jump_to_low_kernel(void) > jump_to_IPL_code(KERN_IMAGE_START); > } > =20 > - /* Trying to get PSW at zero address */ > - if (*((uint64_t *)0) & RESET_PSW_MASK) { > + /* Trying to get PSW at zero address (pointed to by reset_psw) */ > + if (*reset_psw & RESET_PSW_MASK) { > /* > * Surely nobody will try running directly from lowcore, so > * let's use 0 as an indication that we want to load the reset Reviewed-by: Cornelia Huck