From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966041AbcHDVsn (ORCPT ); Thu, 4 Aug 2016 17:48:43 -0400 Received: from mail.kernel.org ([198.145.29.136]:53296 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934199AbcHDVsV (ORCPT ); Thu, 4 Aug 2016 17:48:21 -0400 Date: Thu, 4 Aug 2016 18:47:24 -0300 From: Arnaldo Carvalho de Melo To: Arnaldo Carvalho de Melo Cc: Masami Hiramatsu , "Wangnan (F)" , Alexei Starovoitov , Linux Kernel Mailing List Subject: Re: perf test BPF failing on f24: fix Message-ID: <20160804214724.GL14639@kernel.org> References: <20160802195102.GD14639@kernel.org> <57A1A913.6000307@huawei.com> <20160803234557.29f43f755b7e14c634a54a9a@kernel.org> <20160803200415.GG14639@kernel.org> <20160804153221.8aa29dfc5533b14089bd7470@kernel.org> <20160804124857.GH14639@kernel.org> <20160804193656.GK14639@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160804193656.GK14639@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 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; addr += baseaddr; reloc = true; goto retry; ---------------- With it, which is not a proper fix, of course, we get: [root@jouet ~]# perf probe sys_epoll_wait 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 ~]# Which, using -v shows it "finding" the alias: [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 : ffffffffbd295b50 Matched function: SyS_epoll_wait found inline addr: 0xffffffff81295ee7 Probe point found: compat_SyS_epoll_pwait+151 found inline addr: 0xffffffff81295cca Probe point found: SyS_epoll_pwait+138 found inline addr: 0xffffffff81295b50 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+2711271 Writing event: p:probe/sys_epoll_wait_1 _text+2710730 Writing event: p:probe/sys_epoll_wait_2 _text+2710352 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 ~]# ---------- Now to figure out why baseaddr is returning as zero... - Arnaldo