From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752796AbcHHTdr (ORCPT ); Mon, 8 Aug 2016 15:33:47 -0400 Received: from mail.kernel.org ([198.145.29.136]:42252 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932290AbcHHTdn (ORCPT ); Mon, 8 Aug 2016 15:33:43 -0400 Date: Mon, 8 Aug 2016 16:33:21 -0300 From: Arnaldo Carvalho de Melo To: Masami Hiramatsu Cc: Arnaldo Carvalho de Melo , "Wangnan (F)" , Alexei Starovoitov , Linux Kernel Mailing List Subject: Re: perf test BPF failing on f24: fix Message-ID: <20160808193321.GA3192@kernel.org> References: <57A1A913.6000307@huawei.com> <20160803234557.29f43f755b7e14c634a54a9a@kernel.org> <20160803200415.GG14639@kernel.org> <20160804153221.8aa29dfc5533b14089bd7470@kernel.org> <20160804124857.GH14639@kernel.org> <20160804193656.GK14639@kernel.org> <20160804214724.GL14639@kernel.org> <20160805184550.33ffa7a6989fad3940187d7e@kernel.org> <20160805143532.GO14639@kernel.org> <20160806192948.e366f3fbc4b194de600f8326@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160806192948.e366f3fbc4b194de600f8326@kernel.org> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.6.2 (2016-07-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em Sat, Aug 06, 2016 at 07:29:48PM +0900, Masami Hiramatsu escreveu: > On Fri, 5 Aug 2016 11:35:32 -0300 > Arnaldo Carvalho de Melo wrote: > > > Em Fri, Aug 05, 2016 at 06:45:50PM +0900, Masami Hiramatsu escreveu: > > > On Thu, 4 Aug 2016 18:47:24 -0300 > > > Arnaldo Carvalho de Melo wrote: > > > > > > > Em Thu, Aug 04, 2016 at 04:36:56PM -0300, Arnaldo Carvalho de Melo escreveu: > > > > > So: > > > > > > > > > > int err = debuginfo__get_text_offset(dbg, &baseaddr); > > > > > > > > > > is returning 0, no relocation, its dwarf_addrdie() that is not finding > > > > > SyS_epoll_wait from its address. > > > > > > > > > > Trying to figure out why dwarf_addrdie(0xffffffffbd295b50) fails... > > > > > > > > So, trying to use that vmlinux with objdump to do disassembly I found > > > > that I need to do some offsetting, and after calculating it, this made > > > > things works for me: > > > > > > > > diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c > > > > index f2d9ff064e2d..9b95754f28ed 100644 > > > > --- a/tools/perf/util/probe-finder.c > > > > +++ b/tools/perf/util/probe-finder.c > > > > @@ -1486,6 +1486,8 @@ retry: > > > > /* Find cu die */ > > > > if (!dwarf_addrdie(dbg->dbg, (Dwarf_Addr)addr, &cudie)) { > > > > if (!reloc && debuginfo__get_text_offset(dbg, &baseaddr) == 0) { > > > > + if (baseaddr == 0) > > > > + baseaddr = -0x3c000000; > > > > > > Hmm, strange... what's this magic number ...? > > > Actually debuginfo__get_text_offset() is for kernel modules and it relocate the offset. > > I've found "commit f90acac75713cc6f18a4b2f1b9162bc1cd893c20" > > Actually, I forgot to count the relocation at find_alternative_probe_point(). > Could you try the patch below? > > ------ > perf-probe: Adjust map->reloc offset when finding kernel symbol from map Does the trick, booting with a kernel built from what is in tip/perf/urgent, and with CONFIG_RANDOMIZE_BASE=y, before this fix: [root@jouet ~]# perf probe -v sys_epoll_wait probe-definition(0): sys_epoll_wait symbol:sys_epoll_wait file:(null) line:0 offset:0 return:0 lazy:(null) 0 arguments Failed to get sdt note: -9 Failed to update/scan SDT cache for (null) Looking at the vmlinux_path (8 entries long) Using /lib/modules/4.7.0+/build/vmlinux for symbols Open Debuginfo file: /lib/modules/4.7.0+/build/vmlinux Try to find probe point from debuginfo. Symbol sys_epoll_wait address found : ffffffffac296900 Failed to find debug information for address ffffffffac296900 Probe point 'sys_epoll_wait' not found. Error: Failed to add events. Reason: No such file or directory (Code: -2) [root@jouet ~]# [root@jouet ~]# After the fix: [root@jouet ~]# perf probe -v sys_epoll_wait probe-definition(0): sys_epoll_wait symbol:sys_epoll_wait file:(null) line:0 offset:0 return:0 lazy:(null) 0 arguments Looking at the vmlinux_path (8 entries long) Using /lib/modules/4.7.0+/build/vmlinux for symbols Open Debuginfo file: /lib/modules/4.7.0+/build/vmlinux Try to find probe point from debuginfo. Symbol sys_epoll_wait address found : ffffffff81296900 Matched function: SyS_epoll_wait found inline addr: 0xffffffff81296c97 Probe point found: compat_SyS_epoll_pwait+151 found inline addr: 0xffffffff81296a7a Probe point found: SyS_epoll_pwait+138 found inline addr: 0xffffffff81296900 Probe point found: SyS_epoll_wait+0 Found 3 probe_trace_events. Opening /sys/kernel/debug/tracing//kprobe_events write=1 Writing event: p:probe/sys_epoll_wait _text+2714775 Writing event: p:probe/sys_epoll_wait_1 _text+2714234 Writing event: p:probe/sys_epoll_wait_2 _text+2713856 Added new events: probe:sys_epoll_wait (on sys_epoll_wait) probe:sys_epoll_wait_1 (on sys_epoll_wait) probe:sys_epoll_wait_2 (on sys_epoll_wait) You can now use it in all perf tools, such as: perf record -e probe:sys_epoll_wait_2 -aR sleep 1 [root@jouet ~]#