perf probe: Warn unmatched function filter correctly

Warn unmatched function filter correctly instead of warning
"symbol-loading error", since that can be a filter issue.

From the technical point of view, this adds a filter chech in map__load
and if there is a filter, it returns -2 (filter-out), instead of -1
(error), and perf-probe checks it and change message.

E.g. without this fix:

  # perf probe -F rt_sp*
  no symbols found in [kernel.kallsyms], maybe install a debug package?
  Failed to load symbols in kernel

With this fix:

  # perf probe -F rt_sp*
  no symbols passed the given filter.
  Failed to find symbols matched to "rt_sp*"
    Error: Failed to show functions.

Reported-and-Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/146885835596.16106.2293540792775552481.stgit@devbox
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

2 files changed, 13 insertions, 2 deletions

diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
index b39b12a1208d..728129ac653a 100644
--- a/tools/perf/util/map.c
+++ b/tools/perf/util/map.c
@@ -312,6 +312,9 @@ int map__load(struct map *map, symbol_filter_t filter)
                         pr_warning("%.*s was updated (is prelink enabled?). "
                                 "Restart the long running apps that use it!\n",
                                    (int)real_len, name);
+                } else if (filter) {
+                        pr_warning("no symbols passed the given filter.\n");
+                        return -2;      /* Empty but maybe by the filter */
                 } else {
                         pr_warning("no symbols found in %s, maybe install "
                                    "a debug package?\n", name);
diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index d4f8835c0a27..953dc1ab2ed7 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -3312,8 +3312,16 @@ int show_available_funcs(const char *target, struct strfilter *_filter,
 
         /* Load symbols with given filter */
         available_func_filter = _filter;
-        if (map__load(map, filter_available_functions)) {
-                pr_err("Failed to load symbols in %s\n", (target) ? : "kernel");
+        ret = map__load(map, filter_available_functions);
+        if (ret) {
+                if (ret == -2) {
+                        char *str = strfilter__string(_filter);
+                        pr_err("Failed to find symbols matched to \"%s\"\n",
+                               str);
+                        free(str);
+                } else
+                        pr_err("Failed to load symbols in %s\n",
+                               (target) ? : "kernel");
                 goto end;
         }
         if (!dso__sorted_by_name(map->dso, map->type))