Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1455523

Re: perf test BPF failing on f24: fix

From Alexei Starovoitov <alexei.starovoitov@gmail.com>
Newsgroups linux.kernel
Subject Re: perf test BPF failing on f24: fix
Date 2016-08-03 01:00 +0200
Message-ID <s1QPg-2oO-9@gated-at.bofh.it> (permalink)
References <s1O13-Er-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

Show all headers | View raw

On Tue, Aug 02, 2016 at 04:51:02PM -0300, Arnaldo Carvalho de Melo wrote:
> 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)

that change will break all sorts of scripts that relying on syscalls to start
with sys_
I guess we can workaround in user space, but what was the motivation to
disable kprobe attach on sys_* while it's still in kallsyms?

> 
> 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

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

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

csiph-web