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Groups > linux.kernel > #1455436

perf test BPF failing on f24: fix

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Hi Wang,

	Something changed and a function used in a perf test for BPF is
not anymore appearing on vmlinux, albeit still available on
/proc/kallsyms:

# readelf -wi /lib/modules/4.7.0+/build/vmlinux | grep -w sys_epoll_wait
#

But:

[root@jouet ~]# grep -i sys_epoll_wait /proc/kallsyms 
ffffffffbd295b50 T SyS_epoll_wait
ffffffffbd295b50 T sys_epoll_wait
[root@jouet ~]#

I noticed that it is some sort of aliasing so I checked the other
variant:

[root@jouet ~]# readelf -wi /lib/modules/4.7.0+/build/vmlinux | grep -w SyS_epoll_wait
    <2bc9b85>   DW_AT_name        : (indirect string, offset: 0xe7524): SyS_epoll_wait
[root@jouet ~]# 

Trying to use perf probe also produces the same resuls I notice when
running the perf test that is failing:

[root@jouet ~]# perf probe sys_epoll_wait
Failed to find debug information for address ffffffffbd295b50
Probe point 'sys_epoll_wait' not found.
  Error: Failed to add events.
[root@jouet ~]# perf probe SyS_epoll_wait
Added new events:
  probe:SyS_epoll_wait (on SyS_epoll_wait)
  probe:SyS_epoll_wait_1 (on SyS_epoll_wait)
  probe:SyS_epoll_wait_2 (on SyS_epoll_wait)

You can now use it in all perf tools, such as:

	perf record -e probe:SyS_epoll_wait_2 -aR sleep 1

[root@jouet ~]# 

So I am changing the BPF perf test to use the CamelCase notation alias:

Failing (with sys_epoll_wait):

[root@jouet ~]# perf test BPF
37: Test BPF filter                                          :
37.1: Test basic BPF filtering                               : FAILED!
37.2: Test BPF prologue generation                           : Skip
37.3: Test BPF relocation checker                            : Skip
[root@jouet ~]#

Changing to (SyS_epoll_wait):

[root@jouet ~]# perf test BPF
37: Test BPF filter                                          :
37.1: Test basic BPF filtering                               : Ok
37.2: Test BPF prologue generation                           : Ok
37.3: Test BPF relocation checker                            : Ok
[root@jouet ~]#

I'm adding a fix that just makes it use SyS_epoll_wait.

- Arnaldo

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Thread

perf test BPF failing on f24: fix Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-08-02 22:00 +0200
  Re: perf test BPF failing on f24: fix Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2016-08-03 01:00 +0200
    Re: perf test BPF failing on f24: fix Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-08-03 04:20 +0200
      Re: perf test BPF failing on f24: fix Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2016-08-03 05:00 +0200
  Re: perf test BPF failing on f24: fix "Wangnan (F)" <wangnan0@huawei.com> - 2016-08-03 05:00 +0200
    Re: perf test BPF failing on f24: fix "Wangnan (F)" <wangnan0@huawei.com> - 2016-08-03 05:50 +0200
  Re: perf test BPF failing on f24: fix "Wangnan (F)" <wangnan0@huawei.com> - 2016-08-03 10:30 +0200
    Re: perf test BPF failing on f24: fix Masami Hiramatsu <mhiramat@kernel.org> - 2016-08-03 16:50 +0200
      Re: perf test BPF failing on f24: fix Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-08-03 22:10 +0200
        Re: perf test BPF failing on f24: fix Masami Hiramatsu <mhiramat@kernel.org> - 2016-08-04 08:50 +0200
          Re: perf test BPF failing on f24: fix Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-08-04 14:50 +0200
            Re: perf test BPF failing on f24: fix Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-08-04 21:40 +0200
              Re: perf test BPF failing on f24: fix Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-08-04 23:50 +0200
                Re: perf test BPF failing on f24: fix Masami Hiramatsu <mhiramat@kernel.org> - 2016-08-05 11:50 +0200
                Re: perf test BPF failing on f24: fix Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-08-05 16:40 +0200
                Re: perf test BPF failing on f24: fix Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-08-05 18:00 +0200
                Re: perf test BPF failing on f24: fix Masami Hiramatsu <mhiramat@kernel.org> - 2016-08-06 23:10 +0200
                Re: perf test BPF failing on f24: fix Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-08-08 21:40 +0200
                [tip:perf/urgent] perf probe: Adjust map->reloc offset when finding  kernel symbol from map tip-bot for Masami Hiramatsu <tipbot@zytor.com> - 2016-08-09 21:20 +0200
      Re: perf test BPF failing on f24: fix Masami Hiramatsu <mhiramat@kernel.org> - 2016-08-04 01:10 +0200
        Re: perf test BPF failing on f24: fix "Wangnan (F)" <wangnan0@huawei.com> - 2016-08-04 04:00 +0200
          Re: perf test BPF failing on f24: fix Masami Hiramatsu <mhiramat@kernel.org> - 2016-08-04 11:00 +0200

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