From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-5.8 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham autolearn_force=no version=3.4.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id 17F6B7D09E for ; Tue, 3 Jul 2018 07:51:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933171AbeGCHup (ORCPT ); Tue, 3 Jul 2018 03:50:45 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:44764 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933589AbeGCHun (ORCPT ); Tue, 3 Jul 2018 03:50:43 -0400 Received: from pps.filterd (m0098394.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w637mVEE009810 for ; Tue, 3 Jul 2018 03:50:42 -0400 Received: from e06smtp02.uk.ibm.com (e06smtp02.uk.ibm.com [195.75.94.98]) by mx0a-001b2d01.pphosted.com with ESMTP id 2k03a7m72k-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 03 Jul 2018 03:50:42 -0400 Received: from localhost by e06smtp02.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 3 Jul 2018 08:50:34 +0100 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w637oXwS39715058 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Tue, 3 Jul 2018 07:50:33 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 65FC2AE045; Tue, 3 Jul 2018 10:50:36 +0100 (BST) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2B27BAE053; Tue, 3 Jul 2018 10:50:33 +0100 (BST) Received: from [9.124.31.159] (unknown [9.124.31.159]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 3 Jul 2018 10:50:32 +0100 (BST) Subject: Re: [PATCH v5 09/10] Uprobes/sdt: Document about reference counter To: Srikar Dronamraju Cc: oleg@redhat.com, rostedt@goodmis.org, mhiramat@kernel.org, peterz@infradead.org, mingo@redhat.com, acme@kernel.org, alexander.shishkin@linux.intel.com, jolsa@redhat.com, namhyung@kernel.org, linux-kernel@vger.kernel.org, corbet@lwn.net, linux-doc@vger.kernel.org, ananth@linux.vnet.ibm.com, alexis.berlemont@gmail.com, naveen.n.rao@linux.vnet.ibm.com, linux-arm-kernel@lists.infradead.org, linux-mips@linux-mips.org, linux@armlinux.org.uk, ralf@linux-mips.org, paul.burton@mips.com, Ravi Bangoria References: <20180628052209.13056-1-ravi.bangoria@linux.ibm.com> <20180628052209.13056-10-ravi.bangoria@linux.ibm.com> <20180702145444.GB65296@linux.vnet.ibm.com> From: Ravi Bangoria Date: Tue, 3 Jul 2018 13:20:29 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <20180702145444.GB65296@linux.vnet.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 18070307-0008-0000-0000-0000024F1611 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18070307-0009-0000-0000-000021B522F1 Message-Id: <0110cd8a-9785-c761-e2a5-ba8ab92745e9@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-07-03_03:,, 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=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1806210000 definitions=main-1807030090 Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org Hi Srikar, On 07/02/2018 08:24 PM, Srikar Dronamraju wrote: > * Ravi Bangoria [2018-06-28 10:52:08]: > >> Reference counter gate the invocation of probe. If present, >> by default reference count is 0. Kernel needs to increment >> it before tracing the probe and decrement it when done. This >> is identical to semaphore in Userspace Statically Defined >> Tracepoints (USDT). >> >> Document usage of reference counter. >> >> Signed-off-by: Ravi Bangoria >> Acked-by: Masami Hiramatsu > > Unlike perf, this mechanism cannot detect ref count and depends on the > users data. What happens if the user mistakenly provides a wrong location? > I guess he can corrupt some other data structures? Yes, if user is giving wrong ref_ctr_offset, uprobe infrastructure will corrupt some user data. > > Hence I would think twice of advertising this mechanism. i.e keep this > as an undocumented feature. > I don't mind. Thanks, Ravi -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html