From patchwork Mon May 10 07:35:18 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Thomas Huth X-Patchwork-Id: 1476207 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=SfplR/CO; dkim-atps=neutral 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 ozlabs.org (Postfix) with ESMTPS id 4FdtFZ10kMz9s1l for ; Mon, 10 May 2021 17:38:10 +1000 (AEST) Received: from localhost ([::1]:54860 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lg0US-000760-3Y for incoming@patchwork.ozlabs.org; Mon, 10 May 2021 03:38:08 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:40352) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lg0SB-0001WI-Mi for qemu-devel@nongnu.org; Mon, 10 May 2021 03:35:50 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:51268) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lg0S2-0003cL-NN for qemu-devel@nongnu.org; Mon, 10 May 2021 03:35:45 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1620632138; 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=QalkaH9xjNaMN2pKTqKYyYDUvbEsE5qtxlc6rdSgBjk=; b=SfplR/COAg9wZp3YX/7PvKlU23nIvQ9Zen2Ew/hj4bgCLVumiB41f/2A6HzdXWMAFgY96a CSpNQk3Rb3/5DCfy6TfxCr1vg4aPb4wLF3T9JZLR7UbC5TnUaGwpTDqdJislANCmRahnwJ 8cCf6zfLzmLhWqsI2lLjNolDEMcl2mY= 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-520-17jwwQKtPr-Fv4QWG511RA-1; Mon, 10 May 2021 03:35:35 -0400 X-MC-Unique: 17jwwQKtPr-Fv4QWG511RA-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 937878BEDA9; Mon, 10 May 2021 07:35:34 +0000 (UTC) Received: from thuth.com (ovpn-112-84.ams2.redhat.com [10.36.112.84]) by smtp.corp.redhat.com (Postfix) with ESMTP id 21DA517A9B; Mon, 10 May 2021 07:35:32 +0000 (UTC) From: Thomas Huth To: qemu-devel@nongnu.org, Peter Maydell Subject: [PULL 3/9] pc-bios/s390-ccw: Use reset_psw pointer instead of hard-coded null pointer Date: Mon, 10 May 2021 09:35:18 +0200 Message-Id: <20210510073524.85951-4-thuth@redhat.com> In-Reply-To: <20210510073524.85951-1-thuth@redhat.com> References: <20210510073524.85951-1-thuth@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 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 Received-SPF: pass client-ip=170.10.133.124; envelope-from=thuth@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.699, 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=-0.01, RCVD_IN_MSPIKE_WL=-0.01, 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: Christian Borntraeger , qemu-s390x@nongnu.org, cohuck@redhat.com Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.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 Message-Id: <20210423142440.582188-1-thuth@redhat.com> Reviewed-by: Janosch Frank Signed-off-by: Thomas Huth --- 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