All of lore.kernel.org
 help / color / mirror / Atom feed
From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	LKML <linux-kernel@vger.kernel.org>,
	David Ahern <dsahern@gmail.com>
Subject: Re: Re: [PATCH 3/4] perf probe: Fix probing kretprobes
Date: Mon, 12 Jan 2015 21:08:53 +0900	[thread overview]
Message-ID: <54B3B955.80105@hitachi.com> (raw)
In-Reply-To: <20150112112604.GA4811@krava.brq.redhat.com>

(2015/01/12 20:26), Jiri Olsa wrote:
> On Sat, Jan 10, 2015 at 07:33:47PM +0900, 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.
> 
> with your patchset on top of current Arnaldo's perf/core,
> I'm still getting the same error:
> 
> 
> [root@krava perf]# ./perf probe -a fork_exit=do_fork%return
> Added new event:
> Failed to write event: Invalid argument
>   Error: Failed to add events.
> [root@krava perf]# ./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
> Using /root/.debug/.build-id/60/4c5fd8a6c9202acac3a9e82ecd34b22b8caef6 for symbols
> Open Debuginfo file: /root/.debug/.build-id/60/4c5fd8a6c9202acac3a9e82ecd34b22b8caef6
> Try to find probe point from debuginfo.
> Probe point found: do_fork+0
> Found 1 probe_trace_events.
> Opening /sys/kernel/debug/tracing/kprobe_events write=1
> Added new event:
> Writing event: r:probe/do_fork _text+597840
> Failed to write event: Invalid argument
>   Error: Failed to add events. Reason: Invalid argument (Code: -22)
> [root@krava perf]# dmesg | tail -1
> [113205.738833] Return probe must be used without offset.

Yes, it seems that Namhyung's patch fixes a half of the code path.
We should fix post_process_probe_trace_events() to skip symbol
conversion or we shouldn't use debuginfo when %return is given.
Even if we find inlined function for retprobe, we can't use it
for retprobe...

Thank you,

-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com



  reply	other threads:[~2015-01-12 12:09 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-10 10:33 [PATCH 1/4] perf tools: Allow use of an exclusive option more than once Namhyung Kim
2015-01-10 10:33 ` [PATCH 2/4] perf probe: Do not rely on map__load() filter to find symbols Namhyung Kim
2015-01-12 12:31   ` Masami Hiramatsu
2015-01-14  1:45     ` Namhyung Kim
2015-01-14  8:42       ` Masami Hiramatsu
2015-01-10 10:33 ` [PATCH 3/4] perf probe: Fix probing kretprobes Namhyung Kim
2015-01-12 11:26   ` Jiri Olsa
2015-01-12 12:08     ` Masami Hiramatsu [this message]
2015-01-12 12:22   ` Masami Hiramatsu
2015-01-14  1:59     ` Namhyung Kim
2015-01-10 10:33 ` [PATCH 4/4] perf probe: Propagate error code when write(2) failed Namhyung Kim
2015-01-12 11:17   ` Masami Hiramatsu
2015-01-12 14:03     ` Arnaldo Carvalho de Melo
2015-01-17 10:10   ` [tip:perf/urgent] " tip-bot for Namhyung Kim
2015-01-12 11:44 ` [PATCH 1/4] perf tools: Allow use of an exclusive option more than once Masami Hiramatsu
2015-01-12 14:02   ` Arnaldo Carvalho de Melo
2015-01-28 15:06 ` [tip:perf/core] " tip-bot for Namhyung Kim

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=54B3B955.80105@hitachi.com \
    --to=masami.hiramatsu.pt@hitachi.com \
    --cc=a.p.zijlstra@chello.nl \
    --cc=acme@kernel.org \
    --cc=dsahern@gmail.com \
    --cc=jolsa@redhat.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@kernel.org \
    --cc=namhyung@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.