From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752234AbbALMWW (ORCPT ); Mon, 12 Jan 2015 07:22:22 -0500 Received: from mail4.hitachi.co.jp ([133.145.228.5]:43510 "EHLO mail4.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751131AbbALMWU (ORCPT ); Mon, 12 Jan 2015 07:22:20 -0500 Message-ID: <54B3BC75.2060500@hitachi.com> Date: Mon, 12 Jan 2015 21:22:13 +0900 From: Masami Hiramatsu Organization: Hitachi, Ltd., Japan User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:13.0) Gecko/20120614 Thunderbird/13.0.1 MIME-Version: 1.0 To: Namhyung Kim Cc: Arnaldo Carvalho de Melo , Ingo Molnar , Peter Zijlstra , Jiri Olsa , LKML , David Ahern Subject: Re: [PATCH 3/4] perf probe: Fix probing kretprobes References: <1420886028-15135-1-git-send-email-namhyung@kernel.org> <1420886028-15135-3-git-send-email-namhyung@kernel.org> In-Reply-To: <1420886028-15135-3-git-send-email-namhyung@kernel.org> Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (2015/01/10 19:33), Namhyung Kim wrote: > The commit dfef99cd0b2c ("perf probe: Use ref_reloc_sym based address > instead of the symbol name") converts kprobes to use ref_reloc_sym > (i.e. _stext) and offset instead of using symbol's name directly. So > on my system, adding do_fork ends up with like below: > > $ sudo perf probe -v --add do_fork%return > probe-definition(0): do_fork%return > symbol:do_fork file:(null) line:0 offset:0 return:1 lazy:(null) > 0 arguments > Looking at the vmlinux_path (7 entries long) > Using /lib/modules/3.17.6-1-ARCH/build/vmlinux for symbols > Could not open debuginfo. Try to use symbols. > Opening /sys/kernel/debug/tracing/kprobe_events write=1 > Added new event: > Writing event: r:probe/do_fork _stext+456136 > Failed to write event: Invalid argument > Error: Failed to add events. Reason: Operation not permitted (Code: -1) > > As you can see, the do_fork was translated to _stext+456136. This was > because to support (local) symbols that have same name. But the > problem is that kretprobe requires to be inserted at function start > point so it simply checks whether it's called with offset 0. And if > not, it'll return with -EINVAL. You can see it with dmesg. > > $ dmesg | tail -1 > [125621.764103] Return probe must be used without offset. > > So we need to use the symbol name instead of ref_reloc_sym in case of > return probes. Thanks, but as I pointed in previous mail, this patch fixes just one code path which doesn't use debuginfo. With debuginfo, perf-probe executes try_to_find_probe_trace_events() to analyze debuginfo. We can just skip calling it for retprobes, but I prefer to keep it works. So just skipping conversion in post_process_probe_trace_events() is better. Thank you, > > Reported-by: Jiri Olsa > Cc: Masami Hiramatsu > Signed-off-by: Namhyung Kim > --- > tools/perf/util/probe-event.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c > index e5af16988791..6fe5aa357efc 100644 > --- a/tools/perf/util/probe-event.c > +++ b/tools/perf/util/probe-event.c > @@ -2321,7 +2321,7 @@ static int find_probe_trace_events_from_map(struct perf_probe_event *pev, > goto out; > } > > - if (!pev->uprobes) { > + if (!pev->uprobes && !pp->retprobe) { > kmap = map__kmap(map); > reloc_sym = kmap->ref_reloc_sym; > if (!reloc_sym) { > -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Research Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com