• Masami Hiramatsu's avatar
    perf probe: Support basic dwarf-based operations on uprobe events · fb7345bb
    Masami Hiramatsu authored
    Support basic dwarf(debuginfo) based operations for uprobe events.  With
    this change, perf probe can analyze debuginfo of user application binary
    to set up new uprobe event.
    
    This allows perf-probe --add(with local variables, line numbers) and
    --line works with -x option.  (Actually, --vars has already accepted -x
    option)
    
    For example, the following command shows the probe-able lines of a given
    user space function. Something that so far was only available in the
    'perf probe' tool for kernel space functions:
    
      # ./perf probe -x perf --line map__load
      <map__load@/home/fedora/ksrc/linux-2.6/tools/perf/util/map.c:0>
            0  int map__load(struct map *map, symbol_filter_t filter)
            1  {
            2         const char *name = map->dso->long_name;
                      int nr;
    
            5         if (dso__loaded(map->dso, map->type))
            6                 return 0;
    
            8         nr = dso__load(map->dso, map, filter);
            9         if (nr < 0) {
           10                 if (map->dso->has_build_id) {
    
    And this shows the available variables at the given line of the
    function.
    
      # ./perf probe -x perf --vars map__load:8
      Available variables at map__load:8
              @<map__load+96>
                      char*   name
                      struct map*     map
                      symbol_filter_t filter
              @<map__find_symbol+112>
                      char*   name
                      symbol_filter_t filter
              @<map__find_symbol_by_name+136>
                      char*   name
                      symbol_filter_t filter
              @<map_groups__find_symbol_by_name+176>
                      char*   name
                      struct map*     map
                      symbol_filter_t filter
    
    And lastly, we can now define probe(s) with all available
    variables on the given line:
    
      # ./perf probe -x perf --add 'map__load:8 $vars'
    
      Added new events:
        probe_perf:map__load (on map__load:8 with $vars)
        probe_perf:map__load_1 (on map__load:8 with $vars)
        probe_perf:map__load_2 (on map__load:8 with $vars)
        probe_perf:map__load_3 (on map__load:8 with $vars)
    
      You can now use it in all perf tools, such as:
    
              perf record -e probe_perf:map__load_3 -aR sleep 1
    
      Changes from previous version:
       - Add examples in the patch description.
       - Use .text section start address and dwarf symbol address
         for calculating the offset of given symbol, instead of
         searching the symbol in symtab again.
         With this change, we can safely handle multiple local
         function instances (e.g. scnprintf in perf).
    Signed-off-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
    Cc: David Ahern <dsahern@gmail.com>
    Cc: David A. Long <dave.long@linaro.org>
    Cc: Ingo Molnar <mingo@kernel.org>
    Cc: Namhyung Kim <namhyung@kernel.org>
    Cc: Oleg Nesterov <oleg@redhat.com>
    Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
    Cc: Steven Rostedt <rostedt@goodmis.org>
    Cc: systemtap@sourceware.org
    Cc: yrl.pp-manager.tt@hitachi.com
    Link: http://lkml.kernel.org/r/20131226054152.22364.47021.stgit@kbuild-fedora.novalocalSigned-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
    fb7345bb
probe-finder.c 41.8 KB