From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757720AbcGKIMI (ORCPT ); Mon, 11 Jul 2016 04:12:08 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:15024 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752160AbcGKIMF (ORCPT ); Mon, 11 Jul 2016 04:12:05 -0400 X-IBM-Helo: d03dlp01.boulder.ibm.com X-IBM-MailFrom: gongss@linux.vnet.ibm.com Subject: Re: [PATCH] [RFC V1]s390/perf: fix 'start' address of module's map To: Jiri Olsa References: <1467856176-8712-1-git-send-email-gongss@linux.vnet.ibm.com> <20160708151836.GG31763@krava> Cc: acme@kernel.org, jolsa@kernel.org, dsahern@gmail.com, linux-kernel@vger.kernel.org From: Songshan Gong Date: Mon, 11 Jul 2016 16:11:55 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <20160708151836.GG31763@krava> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16071108-0016-0000-0000-000004267711 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16071108-0017-0000-0000-000030FDDBB7 Message-Id: <71b0ebd9-a50d-faef-933d-2258ae19236e@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-07-11_04:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1604210000 definitions=main-1607110089 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 7/8/2016 11:18 PM, Jiri Olsa 写道: > On Thu, Jul 07, 2016 at 09:49:36AM +0800, Song Shan Gong wrote: >> At preset, when creating module's map, perf gets 'start' address by parsing >> 'proc/modules', but it's module base address, isn't the start address of >> '.text' section. In most archs, it's OK. But for s390, it places 'GOT' and >> 'PLT' relocations before '.text' section. So there exists an offset between >> module base address and '.text' section, which will incur wrong symbol >> resolution for modules. >> >> Fix this bug by getting 'start' address of module's map from parsing >> '/sys/module/[module name]/sections/.text', not from '/proc/modules'. > > cool, does this fix the 'perf test 1' for s390? that'd be great I've checked, 'perf test 1' is still failed. But the test is for testing whether 'vmlinux symtab matches kallsyms'. For vmlinux, it's built when compiling linux-kernel, so there's no any symbol info about module. For kallsyms, when loading, it also splits kernel symbols with module symbols. But this patch is intended to fix wrong symbol resolution for modules, so I think there's no relationship between this patch and the testcase 'perf test 1'. I also debuged the reason why 'perf test 1' fails, there are two reasons at least: 1. perf gets kernel start address by finding the first no-zero value of symbols {'_text', '_stext'} in /proc/kallsyms; for s390, it's always '_stext', but actually, '_stext' is not the first symbol in s390, there are other symbols before '_stext', for example 'iplstart'. 2. In addition, when loading by parsing /proc/kallsyms, if the kernel map start value is a non-zero value getting from '_stext', because '_text' is zero, it will not be included in kernel map; but for vmlinux, it always add '_text' to kernel map whether '_text' is zero or not. So if '_text' is zero, whether adding '_text' to kernel map, it's non-consistent for loading by /proc/kallsyms and vmlinux. I'll try to fix this bug later. Thanks for your comments. > I'll send few coments shortly > > thanks, > jirka > -- SongShan Gong