Em Tue, Nov 24, 2015 at 11:54:24AM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Tue, Nov 24, 2015 at 12:18:22PM +0100, Michael Petlan escreveu:
> > I have been playing with perf-probe tool and I found out that some bogus
> > values of a function argument are obtained by perf-record.
> > How to reproduce:
> > gcc -O0 -g -o dummy dummy.c
> > perf probe -x ./dummy --add 'isprime a'
> > perf record -e probe_dummy:isprime ./dummy
> > perf script
> Checking this here, but as non root I get:
> [acme@zoo ~]$ gcc -O0 -g -o isprime isprime.c
> [acme@zoo ~]$ perf probe -x ./isprime --add 'isprime a'
> Mapping for the register number 4113 missing on this architecture.
> Sorry, we don't support this variable location yet.
> Error: Failed to add events.
> [acme@zoo ~]$
Bisected it down to:
[acme@zoo linux]$ git bisect good
05c8d802fa52ef17dbcce21c38b72b4a313eb036 is the first bad commit
commit 05c8d802fa52ef17dbcce21c38b72b4a313eb036
Author: Masami Hiramatsu <masami.hiramatsu...@hitachi.com>
Date: Wed Nov 18 15:40:12 2015 +0900
perf probe: Fix to free temporal Dwarf_Frame
Since dwarf_cfi_addrframe returns malloc'd Dwarf_Frame object, it has to
be freed after it is used.
Signed-off-by: Masami Hiramatsu <masami.hiramatsu...@hitachi.com>
Cc: Adrian Hunter <adrian.hun...@intel.com>
Cc: Jiri Olsa <jo...@redhat.com>
Cc: Namhyung Kim <namhy...@kernel.org>
Cc: Peter Zijlstra <a.p.zijls...@chello.nl>
Link:
http://lkml.kernel.org/r/20151118064011.30709.65674.stgit@localhost.localdomain
Signed-off-by: Arnaldo Carvalho de Melo <a...@redhat.com>
:040000 040000 6438a0b3a7817ecbfc61eb00af9c62e54c405bcb
62ca7f05ff3ec7202d4c47f9cd2e2cb183060725 M tools
[acme@zoo linux]$
If I just do a:
[acme@zoo linux]$ git revert 05c8d802fa52ef17dbcce21c38b72b4a313eb036
[perf/core 15ef27d95f5c] Revert "perf probe: Fix to free temporal Dwarf_Frame"
1 file changed, 3 insertions(+), 6 deletions(-)
[acme@zoo linux]$
It works again, i.e. it goes from:
[acme@zoo linux]$ perf probe -x ~/isprime --add 'isprime a'
Mapping for the register number 4113 missing on this architecture.
Sorry, we don't support this variable location yet.
Error: Failed to add events.
[acme@zoo linux]$
To, after the revert:
[acme@zoo linux]$ perf probe -x ~/isprime --add 'isprime a'
Failed to open uprobe_events: Permission denied
Error: Failed to add events.
And, as root:
[root@zoo acme]# perf probe -x ./isprime --add 'isprime a'
Added new event:
probe_isprime:isprime (on isprime in /home/acme/isprime with a)
You can now use it in all perf tools, such as:
perf record -e probe_isprime:isprime -aR sleep 1
[root@zoo acme]# perf record -e probe_isprime:isprime ./isprime
2 is prime
3 is prime
4 is not prime
5 is prime
6 is not prime
7 is prime
13 is prime
17 is prime
19 is prime
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.018 MB perf.data (9 samples) ]
[root@zoo acme]#
[root@zoo acme]# perf script
isprime 27687 [003] 184735.650141: probe_isprime:isprime: (400536) a=0
isprime 27687 [003] 184735.650204: probe_isprime:isprime: (400536)
a=32570
isprime 27687 [003] 184735.650209: probe_isprime:isprime: (400536) a=3
isprime 27687 [003] 184735.650212: probe_isprime:isprime: (400536) a=4
isprime 27687 [003] 184735.650215: probe_isprime:isprime: (400536) a=5
isprime 27687 [003] 184735.650218: probe_isprime:isprime: (400536) a=6
isprime 27687 [003] 184735.650222: probe_isprime:isprime: (400536) a=7
isprime 27687 [003] 184735.650225: probe_isprime:isprime: (400536) a=13
isprime 27687 [003] 184735.650229: probe_isprime:isprime: (400536) a=17
[root@zoo acme]#
I.e. bogus values for some of the samples, as Michael reported.
Ah, using 'perf trace', or 'trace' to type less, we can combine 'record' +
'script',
only to end at the same bogus values for some of the captured 'a' variable
contents:
[root@zoo acme]# trace --no-sys --ev probe_isprime:isprime ./isprime
2 is prime
3 is prime
4 is not prime
5 is prime
6 is not prime
7 is prime
13 is prime
17 is prime
19 is prime
0.264 probe_isprime:isprime:(400536) a=0)
0.332 probe_isprime:isprime:(400536) a=32562)
0.363 probe_isprime:isprime:(400536) a=3)
0.395 probe_isprime:isprime:(400536) a=4)
0.429 probe_isprime:isprime:(400536) a=5)
0.463 probe_isprime:isprime:(400536) a=6)
0.497 probe_isprime:isprime:(400536) a=7)
0.532 probe_isprime:isprime:(400536) a=13)
0.566 probe_isprime:isprime:(400536) a=17)
[root@zoo acme]#
- Arnaldo
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