From patchwork Wed Jan 21 11:54:46 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Markus Armbruster X-Patchwork-Id: 431447 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 36B07140293 for ; Wed, 21 Jan 2015 22:55:29 +1100 (AEDT) Received: from localhost ([::1]:47620 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YDtsd-0004OU-93 for incoming@patchwork.ozlabs.org; Wed, 21 Jan 2015 06:55:27 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54026) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YDtsC-0003iP-AI for qemu-devel@nongnu.org; Wed, 21 Jan 2015 06:55:01 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YDts9-0008Pz-4K for qemu-devel@nongnu.org; Wed, 21 Jan 2015 06:55:00 -0500 Received: from mx1.redhat.com ([209.132.183.28]:39275) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YDts8-0008Pr-U3 for qemu-devel@nongnu.org; Wed, 21 Jan 2015 06:54:57 -0500 Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id t0LBsndg029222 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Wed, 21 Jan 2015 06:54:50 -0500 Received: from blackfin.pond.sub.org (ovpn-116-46.ams2.redhat.com [10.36.116.46]) by int-mx14.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t0LBslTv010922 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Wed, 21 Jan 2015 06:54:49 -0500 Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 0722030A4C13; Wed, 21 Jan 2015 12:54:46 +0100 (CET) From: Markus Armbruster To: Frank Blaschka References: <1420790680-3266-1-git-send-email-blaschka@linux.vnet.ibm.com> <1420790680-3266-3-git-send-email-blaschka@linux.vnet.ibm.com> <87h9vln5tm.fsf@blackfin.pond.sub.org> <20150120110348.66afc423.cornelia.huck@de.ibm.com> <87ppa9iqco.fsf@blackfin.pond.sub.org> <87bnlthaqe.fsf@blackfin.pond.sub.org> <20150120142052.GA44419@tuxmaker.boeblingen.de.ibm.com> <87bnltryii.fsf@blackfin.pond.sub.org> Date: Wed, 21 Jan 2015 12:54:46 +0100 In-Reply-To: <87bnltryii.fsf@blackfin.pond.sub.org> (Markus Armbruster's message of "Tue, 20 Jan 2015 21:24:37 +0100") Message-ID: <87twzkmjqx.fsf@blackfin.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.68 on 10.5.11.27 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: Cornelia Huck , borntraeger@de.ibm.com, Frank Blaschka , qemu-devel@nongnu.org Subject: Re: [Qemu-devel] [PATCH 2/3 V3] s390: implement pci instructions X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Markus Armbruster writes: > Frank Blaschka writes: > >> On Tue, Jan 20, 2015 at 01:56:09PM +0100, Markus Armbruster wrote: >>> Markus Armbruster writes: >>> >>> > Cornelia Huck writes: >>> > >>> >> On Tue, 20 Jan 2015 10:45:41 +0100 >>> >> Markus Armbruster wrote: >>> >> >>> >>> This patch makes Coverity unhappy: >>> >>> >>> >>> *** CID 1264326: Unintended sign extension (SIGN_EXTENSION) >>> >>> /hw/s390x/s390-pci-inst.c: 787 in stpcifc_service_call() >>> >>> 781 stq_p(&fib.pal, pbdev->pal); >>> >>> 782 stq_p(&fib.iota, pbdev->g_iota); >>> >>> 783 stq_p(&fib.aibv, pbdev->routes.adapter.ind_addr); >>> >>> 784 stq_p(&fib.aisb, pbdev->routes.adapter.summary_addr); >>> >>> 785 stq_p(&fib.fmb_addr, pbdev->fmb_addr); >>> >>> 786 >>> >>> >>> CID 1264326: Unintended sign extension (SIGN_EXTENSION) >>> >>> >>> Suspicious implicit sign extension: "pbdev->isc" with type >>> >>> >>> "unsigned char" (8 bits, unsigned) is promoted in "(pbdev->isc << >>> >>> >>> 28) | (pbdev->noi << 16)" to type "int" (32 bits, signed), then >>> >>> >>> sign-extended to type "unsigned long" (64 bits, unsigned). If >>> >>> >>> "(pbdev->isc << 28) | (pbdev->noi << 16)" is greater than >>> >>> >>> 0x7FFFFFFF, the upper bits of the result will all be 1. >>> >>> 787 data = (pbdev->isc << 28) | (pbdev->noi << 16) | >>> >>> 788 (pbdev->routes.adapter.ind_offset << 8) | (pbdev->sum << 7) | >>> >>> 789 pbdev->routes.adapter.summary_offset; >>> >>> 790 stw_p(&fib.data, data); >>> >>> 791 >>> >>> 792 if (pbdev->fh >> ENABLE_BIT_OFFSET) { >>> >> >>> >> There's a fix for this (and the memory leak): >>> >> >>> >> http://marc.info/?l=qemu-devel&m=142124886620078&w=2 >>> >> >>> >> The patch is sitting in my queue, will send with the next pile of s390x >>> >> updates. >>> > >>> > I can't see how >>> > >>> > @@ -787,7 +787,7 @@ int stpcifc_service_call(S390CPU *cpu, uint8_t r1, uint64_t fiba) >>> > data = (pbdev->isc << 28) | (pbdev->noi << 16) | >>> > (pbdev->routes.adapter.ind_offset << 8) | (pbdev->sum << 7) | >>> > pbdev->routes.adapter.summary_offset; >>> > - stw_p(&fib.data, data); >>> > + stl_p(&fib.data, data); >>> > >>> > if (pbdev->fh >> ENABLE_BIT_OFFSET) { >>> > fib.fc |= 0x80; >>> > >>> > fixes the implicit sign extension within the assignment preceding it. >>> > Let me explain it again real slow: >>> > >>> > 1. pbdev->isc gets promoted from uint8_t to int as operand of binary << >>> > (usual arithmetic conversions ISO/IEC 9899:1999 6.3.1.8) >>> > >>> > 2. The int result is shifted left 28 bits. This can set the MSB. >>> > >>> > 3. Likewise: pbdev->noi gets promoted from uint64_t to int, and shifted >>> > left 16 bits. >> uint16_t to int > > Yes, that's what I meant :) > >>> > >>> > 4. The two shift results stay int and get ored. >>> > >>> > 5. pbdev->routes.adapter.ind_offset stays uint64_t, and is shifted left >>> > 8 bits. >>> > >>> > 6. The next or's left operand is the int result of 4 and the right >>> > operant is the uint64_t result of 5. Therefore, the left operand is >>> > *sign-extended* from int to uint64_t. This copies bit#7 of >>> > pbdev->isc to bits#31..63. Whoops. >>> >>> I neglected to say: we don't currently use the upper 32 bits, and as >>> long as we do that, the sign extension is harmless. I'd recommend to >>> avoid it all the same, for robustness, and to hush up Coverity. >>> >> >> Hi Markus, >> >> thx for your explanation. I did not see a problem since ISC is not bigger >> than 0x7 so MSB is never set. But the time I wrote the code I was not aware of >> ind_offset is uint64_t since zpci defines only a 6 bit field for this value. > > Okay. > >> How can I avoid the sign extension and make Coverity happy? > > Casting pbdev->routes.adapter.ind_offset to uint32_t should do. Then, > all operands of | are either int (promoted from narrower unsigned type) > or uint32_t (type cast). Conversion from int to uint32_t won't > sign-extend as long as int is at least 32 bits. Surely the case for > anything that can run QEMU. Yup, it hushes up Coverity (I checked). diff --git a/hw/s390x/s390-pci-inst.c b/hw/s390x/s390-pci-inst.c index 5ea13e5..2bed3f5 100644 --- a/hw/s390x/s390-pci-inst.c +++ b/hw/s390x/s390-pci-inst.c @@ -785,8 +785,8 @@ int stpcifc_service_call(S390CPU *cpu, uint8_t r1, uint64_t fiba) stq_p(&fib.fmb_addr, pbdev->fmb_addr); data = (pbdev->isc << 28) | (pbdev->noi << 16) | - (pbdev->routes.adapter.ind_offset << 8) | (pbdev->sum << 7) | - pbdev->routes.adapter.summary_offset; + ((uint32_t)pbdev->routes.adapter.ind_offset << 8) | + (pbdev->sum << 7) | pbdev->routes.adapter.summary_offset; stw_p(&fib.data, data); if (pbdev->fh >> ENABLE_BIT_OFFSET) {