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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Thu, 7 Feb 2019 06:59:59 -0000 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x176xwPL60358674 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 7 Feb 2019 06:59:58 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C35A4AE045; Thu, 7 Feb 2019 06:59:58 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 683DBAE04D; Thu, 7 Feb 2019 06:59:58 +0000 (GMT) Received: from ozlabs.au.ibm.com (unknown [9.192.253.14]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Thu, 7 Feb 2019 06:59:58 +0000 (GMT) Received: from [10.61.2.125] (haven.au.ibm.com [9.192.254.114]) (using TLSv1.2 with cipher AES128-SHA (128/128 bits)) (No client certificate requested) by ozlabs.au.ibm.com (Postfix) with ESMTPSA id F012FA01B6; Thu, 7 Feb 2019 17:59:53 +1100 (AEDT) Subject: Re: [PATCH 1/2] powerpc/64s: Work around spurious warning on old gccs with -fsanitize-coverage To: Segher Boessenkool References: <20190207053324.17541-1-andrew.donnellan@au1.ibm.com> <20190207063736.GS14180@gate.crashing.org> From: Andrew Donnellan Date: Thu, 7 Feb 2019 17:59:48 +1100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190207063736.GS14180@gate.crashing.org> Content-Language: en-AU X-TM-AS-GCONF: 00 x-cbid: 19020707-0020-0000-0000-00000313D454 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19020706-0021-0000-0000-00002164DAF4 Message-Id: <630e392b-e9a7-6b1e-e3d8-c5382f94e5d7@au1.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-02-07_05:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=578 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1902070054 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: syzkaller@googlegroups.com, linuxppc-dev@lists.ozlabs.org, dvyukov@google.com Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 7/2/19 5:37 pm, Segher Boessenkool wrote: > On Thu, Feb 07, 2019 at 04:33:23PM +1100, Andrew Donnellan wrote: >> Some older gccs (> cause a spurious uninitialised variable warning in dt_cpu_ftrs.c: >> >> arch/powerpc/kernel/dt_cpu_ftrs.c: In function ‘cpufeatures_process_feature’: >> arch/powerpc/kernel/dt_cpu_ftrs.c:686:7: warning: ‘m’ may be used uninitialized in this function [-Wmaybe-uninitialized] >> if (m->cpu_ftr_bit_mask) > > It seems to me the warning is correct? If enable_unknown is false and no > cpu_feature is found, it will in > > if (m->cpu_ftr_bit_mask) > cur_cpu_spec->cpu_features |= m->cpu_ftr_bit_mask; > > enable random features (whatever was last in the table), or indeed access > via NULL if the table is length 0? So maybe this should be > > if (known && m->cpu_ftr_bit_mask) > cur_cpu_spec->cpu_features |= m->cpu_ftr_bit_mask; > > instead? (The code would be much clearer if all the known vs. !known > codepath was fully separated here). The table is never length 0, it's a statically defined array. > > > Segher > -- Andrew Donnellan OzLabs, ADL Canberra andrew.donnellan@au1.ibm.com IBM Australia Limited