linux-kernel - Re: Re: [PATCH] perf probe: Fix --line option behavior

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Message-ID: <533A6D5D.60306@hitachi.com>
Date:	Tue, 01 Apr 2014 16:40:13 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...nel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Namhyung Kim <namhyung.kim@....com>,
	LKML <linux-kernel@...r.kernel.org>, Jiri Olsa <jolsa@...hat.com>
Subject: Re: Re: [PATCH] perf probe: Fix --line option behavior

(2014/04/01 16:21), Namhyung Kim wrote:
> Hi Masami,
> 
> (Also adding Jiri in CC and changing email of acme)
> 
> On Tue, Apr 1, 2014 at 5:01 AM, Masami Hiramatsu
> <masami.hiramatsu.pt@...achi.com> wrote:
>> (2014/04/01 13:47), Namhyung Kim wrote:
>>> The commit 5a62257a3ddd1 ("perf probe: Replace line_list with
>>> intlist") replaced line_list to intlist but it has a problem that if a
>>> same line was added again, it'd return -EEXIST rather than 1.
>>
>> Ah, right! that's a different behavior.
>>
>>> Since line_range_walk_cb() only checks the result being negative, it
>>> resulted in failure or segfault sometimes.
>>
>> Could you give me an example input of the segfault? I'd like to trace
>> it down.
> 
> Just used current acme/perf/core.
> 
> $ git log -1
> commit 28b5724a61cc9d84f2cbef6675e8a85ae4b1bc57
> Author: Arnaldo Carvalho de Melo <acme@...hat.com>
> Date:   Thu Mar 27 17:36:14 2014 -0300
> 
>     MAINTAINERS: Change e-mail to kernel.org one
> 
>     Leaving ghostprotocols.net for old networking stuff.
> 
> ...
> 
> $ perf --version
> perf version 3.14.rc6.g28b572
> 
> $ perf probe -x ./perf -v -L map__load
> Open Debuginfo file: /home/namhyung/project/linux/tools/perf/perf
> fname: util/map.c, lineno:153
> New line range: 153 to 2147483647
> path: (null)
> Segmentation fault (core dumped)
> 
> 
> It seems like find_line_range_by_line() called for multiple times,
> line_range_walk_cb returns 0 at first but as line_range_add_line()
> returns -EEXIST, it freed lr->path and __show_line_range() ended up
> accessing to NULL path.

OK, thanks for this nice report!
Hmm, line_range_inline_cb() must check the result of
find_line_range_by_line() but ignored. That should be fixed too...

Thank you,

> 
> 
> (gdb) bt
> #0  get_real_path (new_path=0x839ff8 <params+9272>,
>     comp_dir=0x1f994f0 "/home/namhyung/project/linux/tools/perf",
>     raw_path=0x0) at util/probe-event.c:518
> #1  __show_line_range (module=<optimized out>, lr=0x839fd8 <params+9240>)
>     at util/probe-event.c:641
> #2  show_line_range (lr=lr@...ry=0x839fd8 <params+9240>,
>     module=<optimized out>) at util/probe-event.c:699
> #3  0x000000000044667b in __cmd_probe (argc=<optimized out>,
>     argv=argv@...ry=0x7fff7a770ba0, prefix=<optimized out>)
>     at builtin-probe.c:465
> #4  0x00000000004469f4 in cmd_probe (argc=<optimized out>,
>     argv=0x7fff7a770ba0, prefix=<optimized out>) at builtin-probe.c:520
> #5  0x00000000004241b5 in run_builtin (p=p@...ry=0x7ebde0 <commands+384>,
>     argc=argc@...ry=6, argv=argv@...ry=0x7fff7a770ba0) at perf.c:319
> #6  0x0000000000423a29 in handle_internal_command (argv=0x7fff7a770ba0,
>     argc=6) at perf.c:376
> #7  run_argv (argv=0x7fff7a7709a0, argcp=0x7fff7a7709ac) at perf.c:420
> #8  main (argc=6, argv=0x7fff7a770ba0) at perf.c:529
> 
> 
> Thanks,
> Namhyung
> --
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-- 
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com


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