Perf tries to find probe function addresses from map when debuginfo
could not be found.

To the first added function, the value of ref_reloc_sym was set in
maps__set_kallsyms_ref_reloc_sym() and can be obtained from
host_machine->kmaps->maps. After that, new maps are added to
host_machine->kmaps->maps in dso__load_kcore(), all these new added maps
do not have a valid ref_reloc_sym.

When adding a second function, get_target_map() may get a map without
valid ref_reloc_sym, and raise the error "Relocated base symbol is not
found".

Fix this by using kernel_get_ref_reloc_sym() to get ref_reloc_sym.

This problem can be reproduced as following:

  $ perf probe --add='sys_write' --add='sys_open'
  Relocated base symbol is not found!
    Error: Failed to add events.

After this patch:

  $ perf probe --add='sys_write' --add='sys_open'
  Added new event:
    probe:sys_write      (on sys_write)

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

      perf record -e probe:sys_write -aR sleep 1

  Added new event:
    probe:sys_open       (on sys_open)

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

      perf record -e probe:sys_open -aR sleep 1
Signed-off-by: He Kuang <hekuang@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1426816616-2394-1-git-send-email-hekuang@huawei.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>