On Mon, Jun 29, 2015 at 12:00:38PM -0300, Arnaldo Carvalho de Melo wrote:
>Em Sun, Jun 28, 2015 at 05:46:51PM +0200, Benjamin King escreveu:
>> >Is there a trick to getting perf to probe a user-level address without
>> >debuginfo? Eg (on Linux 4.0):
>> >[...]
>> >I can do this using ftrace ok, eg, "p:tick_0x583 /root/tick:0x583"
>> >works. Thanks,
>>
>> Not quite what you have asked for, but you can add the probe via ftrace and
>> then use it from perf. Probes from /sys/kernel/debug/tracing/uprobe_events
>> will show up in 'perf list' as well.
>
>Masami,
>
>	Is this already possible?

Hi Arnaldo,

for me this works in 3.19.0. I'm using the attached script to help me add
probes to /sys/kernel/debug/tracing/uprobe_events which I can then see with
'sudo perf list' and use from the other perf subcommands. Tracing arguments is
also working fine:

--- snip ---
$ uprobe /lib/x86_64-linux-gnu/libc.so.6 malloc %di
$ sudo perf stat  -e uprobes:* ls
...
 Performance counter stats for 'ls':
...
               218      uprobes:malloc_1                                            
$ sudo perf record -euprobes:malloc_1 ls >/dev/null 2>&1
$ sudo perf script
              ls 21084 [003] 10825.526815: uprobes:malloc_1: (7f772bfc2700) arg1=0x238
              ls 21084 [003] 10825.526917: uprobes:malloc_1: (7f772bfc2700) arg1=0x238
              ls 21084 [003] 10825.526968: uprobes:malloc_1: (7f772bfc2700) arg1=0x78
              ls 21084 [003] 10825.527089: uprobes:malloc_1: (7f772bfc2700) arg1=0x5
              ls 21084 [003] 10825.527132: uprobes:malloc_1: (7f772bfc2700) arg1=0x78
...
--- snip ---

This is superuseful to me, so thank you all for working on perf!

I failed to manage placing proper probes in C++-Code with perf probe, so I
hacked the script together after reading Brendans ftrace article on LWN.

Cheers,
  Benjamin