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 544D7C433B4 for ; Fri, 23 Apr 2021 14:25:46 +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 BFA3661450 for ; Fri, 23 Apr 2021 14:25:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BFA3661450 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; 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bh=03DIq11kpQC0Pqfqn28D8zlYMm447Co+zegpdlEdM50=; b=J0yQJMeN4HkLhuU9w/7hWlvtBTXeZoF4so+rlvzqHdyg8VoDiR4TIcziRW/zFmmt780yM4 1d4RpnXx2XoLsEXERyyNycblHsCauVahxB8D/df3Y1yTe75bUuQeAV95opmlfZ3KeWRHrI L8xcHGtYiuBfeZ5b/ty0RGOFCPE346w= 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-527-CmEQQjAKM1Kt2FpDcGWlZg-1; Fri, 23 Apr 2021 10:24:46 -0400 X-MC-Unique: CmEQQjAKM1Kt2FpDcGWlZg-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 D2E7A802575; Fri, 23 Apr 2021 14:24:44 +0000 (UTC) Received: from thuth.com (ovpn-115-143.ams2.redhat.com [10.36.115.143]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4AFB060BE5; Fri, 23 Apr 2021 14:24:43 +0000 (UTC) From: Thomas Huth To: qemu-devel@nongnu.org, Cornelia Huck , Christian Borntraeger Subject: [PATCH v2] pc-bios/s390-ccw: Use reset_psw pointer instead of hard-coded null pointer Date: Fri, 23 Apr 2021 16:24:40 +0200 Message-Id: <20210423142440.582188-1-thuth@redhat.com> 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=thuth@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=UTF-8 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, 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: qemu-s390x@nongnu.org, =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , Janosch Frank Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" When compiling the s390-ccw bios with clang, it emits a warning like this: pc-bios/s390-ccw/jump2ipl.c:86:9: warning: indirection of non-volatile null 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' 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. Reviewed-by: Philippe Mathieu-Daudé Signed-off-by: Thomas Huth --- v2: Extend comment as suggested by Cornelia pc-bios/s390-ccw/jump2ipl.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) 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); } - /* 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 -- 2.27.0