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bh=YOCC8ZGy7RuMXEQpsV5ygc1b9UdL8+97WFggzRf53UU=; b=NoSz+SIwG/KBRLpCu8ZENYp6F00d21ASZj2T7Ln15iONeCqtc9amESZjTNPkp9q/IOgR3I yQYDtWMZ7HZkEl9Ux9UdhkZrYZgXAOJCADyU1SC7+0SdzdvoEqm6PjDPudWwDm1WQsehQD yLUt1PEro9RvyULrQoZxVJXR4t/m7Rc= 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-514-3VJh6e9lPzKLP2Qi_ezq-w-1; Fri, 23 Apr 2021 06:10:31 -0400 X-MC-Unique: 3VJh6e9lPzKLP2Qi_ezq-w-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5A0216414C; Fri, 23 Apr 2021 10:10:30 +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 D9A425D745; Fri, 23 Apr 2021 10:10:28 +0000 (UTC) Date: Fri, 23 Apr 2021 12:10:26 +0200 From: Cornelia Huck To: Thomas Huth Subject: Re: [PATCH] pc-bios/s390-ccw: Use reset_psw pointer instead of hard-coded null pointer Message-ID: <20210423121026.4aed1b54.cohuck@redhat.com> In-Reply-To: <20210423083604.526367-1-thuth@redhat.com> References: <20210423083604.526367-1-thuth@redhat.com> Organization: Red Hat GmbH MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 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=US-ASCII Content-Transfer-Encoding: 7bit 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=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, 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 10:36:04 +0200 Thomas Huth wrote: > 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. > > Signed-off-by: Thomas Huth > --- > pc-bios/s390-ccw/jump2ipl.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/pc-bios/s390-ccw/jump2ipl.c b/pc-bios/s390-ccw/jump2ipl.c > index b9c70d64a5..de1541ea5d 100644 > --- a/pc-bios/s390-ccw/jump2ipl.c > +++ b/pc-bios/s390-ccw/jump2ipl.c > @@ -83,7 +83,7 @@ void jump_to_low_kernel(void) > } > > /* Trying to get PSW at zero address */ Maybe make this /* Trying to get PSW at zero address (pointed to by reset_psw) */ I'm always getting a headache when I'm reading this file, so let's make it easy :) > - if (*((uint64_t *)0) & RESET_PSW_MASK) { > + 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