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Thu, 5 Dec 2019 10:02:33 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by userp3020.oracle.com with ESMTP id 2wpp73usc1-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 05 Dec 2019 10:02:32 +0000 Received: from abhmp0019.oracle.com (abhmp0019.oracle.com [141.146.116.25]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id xB5A2SRk019046; Thu, 5 Dec 2019 10:02:30 GMT Received: from kadam (/129.205.23.165) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 05 Dec 2019 02:02:27 -0800 Date: Thu, 5 Dec 2019 13:02:20 +0300 From: Dan Carpenter To: Peter Zijlstra Cc: Steven Rostedt , Ingo Molnar , linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org Subject: Re: [PATCH] Silence an uninitialized variable warning Message-ID: <20191205100220.GH1765@kadam> References: <20191126121934.kuolgbm55dirfbay@kili.mountain> <20191204092640.692c95af@gandalf.local.home> <20191204184247.GG1765@kadam> <20191205093229.GE2810@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191205093229.GE2810@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.9.4 (2018-02-28) X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9461 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1911140001 definitions=main-1912050080 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9461 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1911140001 definitions=main-1912050080 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 05, 2019 at 10:32:29AM +0100, Peter Zijlstra wrote: > On Wed, Dec 04, 2019 at 09:42:47PM +0300, Dan Carpenter wrote: > > > > The current code has this: > > > > > > static int __init syscall_enter_define_fields(struct trace_event_call *call) > > > { > > > struct syscall_trace_enter trace; > > > struct syscall_metadata *meta = call->data; > > > int ret; > > > int i; > > > int offset = offsetof(typeof(trace), args); > > > > > > ret = trace_define_field(call, SYSCALL_FIELD(int, nr, __syscall_nr), > > > FILTER_OTHER); > > > > In linux-next this ret = trace_define_field() assignment is removed. > > That was commit 60fdad00827c ("ftrace: Rework event_create_dir()"). > > Yep, mea culpa. > > > > if (ret) > > > return ret; > > > > > > for (i = 0; i < meta->nb_args; i++) { > > > ret = trace_define_field(call, meta->types[i], > > > meta->args[i], offset, > > > sizeof(unsigned long), 0, > > > FILTER_OTHER); > > > offset += sizeof(unsigned long); > > > } > > > > > > return ret; > > > } > > > > > > > > > How can ret possibly be uninitialized? > > > > I should have written this commit more carefully and verified whether > > meta->nb_args can actually be zero instead of just assuming it was a > > false positive... > > Right, I'm thinking this is in fact possible. We have syscalls without > arguments (sys_sched_yield for exmaple). Well, it would have triggered a run time bug because of that thing with GCC where it sometimes initializes variables to zero. Let me resend properly with a Fixes tag. regards, dan carpenter