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Fri, 23 Apr 2021 10:24:50 -0400 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 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) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619187888; 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; bh=03DIq11kpQC0Pqfqn28D8zlYMm447Co+zegpdlEdM50=; b=J0yQJMeN4HkLhuU9w/7hWlvtBTXeZoF4so+rlvzqHdyg8VoDiR4TIcziRW/zFmmt780yM4 1d4RpnXx2XoLsEXERyyNycblHsCauVahxB8D/df3Y1yTe75bUuQeAV95opmlfZ3KeWRHrI L8xcHGtYiuBfeZ5b/ty0RGOFCPE346w= X-MC-Unique: CmEQQjAKM1Kt2FpDcGWlZg-1 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: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; 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+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) 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-Daud=C3=A9 Signed-off-by: Thomas Huth Reviewed-by: Cornelia Huck Reviewed-by: Janosch Frank --- 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); } =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 --=20 2.27.0