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 CAE1C7D043 for ; Sat, 16 Jun 2018 15:07:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754086AbeFPPHk (ORCPT ); Sat, 16 Jun 2018 11:07:40 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:45008 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754005AbeFPPHj (ORCPT ); Sat, 16 Jun 2018 11:07:39 -0400 Received: from pps.filterd (m0098421.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w5GF4MZG009209 for ; Sat, 16 Jun 2018 11:07:38 -0400 Received: from e06smtp03.uk.ibm.com (e06smtp03.uk.ibm.com [195.75.94.99]) by mx0a-001b2d01.pphosted.com with ESMTP id 2jmxjbhknh-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Sat, 16 Jun 2018 11:07:38 -0400 Received: from localhost by e06smtp03.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) Sat, 16 Jun 2018 16:07:32 +0100 Received: from d06av25.portsmouth.uk.ibm.com (d06av25.portsmouth.uk.ibm.com [9.149.105.61]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w5GF7Vfs28967014 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Sat, 16 Jun 2018 15:07:31 GMT Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 748D911C04C; Sat, 16 Jun 2018 15:58:01 +0100 (BST) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E5BEA11C050; Sat, 16 Jun 2018 15:57:55 +0100 (BST) Received: from [9.78.192.161] (unknown [9.78.192.161]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Sat, 16 Jun 2018 15:57:55 +0100 (BST) Subject: Re: [PATCH 0/7] Uprobes: Support SDT markers having reference count (semaphore) To: Masami Hiramatsu Cc: oleg@redhat.com, srikar@linux.vnet.ibm.com, rostedt@goodmis.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, Ravi Bangoria References: <20180606083344.31320-1-ravi.bangoria@linux.ibm.com> <20180608101023.cbf20db485026213d490cb7c@kernel.org> <0d487b32-3141-ec30-6cca-eba7159d70b0@linux.ibm.com> <20180608141431.c0196a2c80a8d4701bc9db58@kernel.org> <71f19b63-a641-1705-f087-a39b8b81c4be@linux.ibm.com> <20180609004549.ea7b1854772217598bb1cdfd@kernel.org> <6225481e-fa00-a242-2b57-223559e3c488@linux.ibm.com> <20180616225032.3fc9a027dca76926ff198ff8@kernel.org> From: Ravi Bangoria Date: Sat, 16 Jun 2018 20:37:24 +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: <20180616225032.3fc9a027dca76926ff198ff8@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 18061615-0012-0000-0000-000002801ED1 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18061615-0013-0000-0000-000020B14BAE Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-06-16_08:,, 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=887 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1805220000 definitions=main-1806160183 Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org Hi Masami, On 06/16/2018 07:20 PM, Masami Hiramatsu wrote: > Hi Ravi, > > Sorry for replying later. No issues :) > > On Mon, 11 Jun 2018 10:01:58 +0530 > Ravi Bangoria wrote: > >> Hi Masami, >> >>>>> Hmm, it sounds simple... maybe we can increment refctr in install_breakpoint/ >>>>> remove_breakpoint? >>>> >>>> Not really, it would be simpler if I can put it inside install_breakpoint(). >>>> Consider an mmap() case. Probed instruction resides in the text section whereas >>>> reference counter resides in the data section. These sections gets mapped using >>>> separate mmap() calls. So, when process mmaps the text section we will change the >>>> instruction, but section holding the reference counter may not have been mapped >>>> yet in the virtual memory. If so, we will fail to update the reference counter. >>> >>> Got it. >>> In such case, maybe we can hook the target page mmapped and do install_breakpoint() >>> at that point. Since the instruction is protected by a refctr, unless mmap the >>> page on where the refctr is, the program doesn't reach the tracepoint. Is that right? >>> >> >> You mean, when mmap(text) happens, save the target page somewhere and when >> mmap(data) happens, update both instruction and ref_ctr? > > Yes. I think you can just clone the target(text) page but not install > breakpoint, and if mmap(data) happens, update both. I'm preparing a prototype according to this. The only difference in my approach is, I'm not delaying instruction update. I.e. let instruction update happen as it is, just mark that uprobe as delayed. Whenever vma holding reference counter gets mapped, update the reference counter. Will post the series soon. Thanks for the reply, 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