Em Mon, Mar 30, 2015 at 07:46:55PM +0200, Jiri Olsa escreveu:
> hi,
> Martin found out following issue.. having following ex binary:
>
> ---
> int main(void)
> {
> return 0;
> }
> ---
>
> following will create uprobe on main:
>
> [root@dell-per510-01 perf]# gcc -g -o ex ex.c
> [root@dell-per510-01 perf]# ./perf probe -x ./ex -a main
> Added new event:
> probe_ex:main (on main in /root/linux/tools/perf/ex)
>
> You can now use it in all perf tools, such as:
>
> perf record -e probe_ex:main -aR sleep 1
>
> [root@dell-per510-01 perf]# cat /sys/kernel/debug/tracing/uprobe_events
> p:probe_ex/main /root/linux/tools/perf/ex:0x00000000000004f6
>
>
> while following will create (?) kprobe with complain in dmesg:
Right, it looks like it will create the probe on the currently selected
DSO, which, if you have none, will be the kernel, thus the kprobe
(probe:main), while if you do a '-x ./ex -a main' you are selecting the
'ex' DSO and then asking for the probe to be added to a function named
'main', on that DSO, that 'perf probe' realizes is a userspace binary,
thus creates a uprobe: probe_%DSONAME:%FUNCTIONAME.
I wonder if I can do:
[root@ssdandy acme]# perf probe -a icmp_rcv -x ./ex -a main
Probe point 'icmp_rcv' not found.
Error: Failed to add events.
No, I can't, I'd say we should support that, i.e. inserting multiple
probes per command line, for different DSOs, etc. I.e. the above would
be equivalent to these two calls:
[root@ssdandy acme]# perf probe -a icmp_rcv
Added new event:
probe:icmp_rcv (on icmp_rcv)
You can now use it in all perf tools, such as:
perf record -e probe:icmp_rcv -aR sleep 1
[root@ssdandy acme]# perf probe -x ./ex -a main
Added new event:
probe_ex:main (on main in /home/acme/ex)
You can now use it in all perf tools, such as:
perf record -e probe_ex:main -aR sleep 1
[root@ssdandy acme]#
But it isn't like that, so, yes, what you report is a bug, both for your
expectation (that I think is that it should put a uprobes with both your
examples) and for mine (that it would add the first to the kernel, and
the second to the selected DSO via -x).
- Arnaldo
> [root@dell-per510-01 perf]# gcc -g -o ex ex.c
> [root@dell-per510-01 perf]# ./perf probe -a main -x ./ex
> Added new event:
> probe:main (on main in ex)
>
> You can now use it in all perf tools, such as:
>
> perf record -e probe:main -aR sleep 1
>
> [root@dell-per510-01 perf]# dmesg | tail -2
> [16986.182159] Could not insert probe at ex:main+0: -2
> [16986.187030] This probe might be able to register aftertarget module is
> loaded. Continue.
>
>
> that does not seem as an expected behaviour, or am I missing something?
>
> thanks,
> jirka
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