perf probe: Use existing routine to look for a kernel module by dso->…

…short_name

We have map_groups__find_by_name() to look at the list of modules that
are in place for a given machine, so use it instead of traversing the
machine dso list, which also includes DSOs for userspace.

When merging the user and kernel DSO lists a bug was introduced where
'perf probe' stopped being able to add probes to modules using its short
name:

  # perf probe -m usbnet --add usbnet_start_xmit
  usbnet_start_xmit is out of .text, skip it.
    Error: Failed to add events.
  #

With this fix it works again:

  # perf probe -m usbnet --add usbnet_start_xmit
  Added new event:
    probe:usbnet_start_xmit (on usbnet_start_xmit in usbnet)

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

  	perf record -e probe:usbnet_start_xmit -aR sleep 1
  #

Reported-by: Wang Nan <[email protected]>
Acked-by: Masami Hiramatsu <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Stephane Eranian <[email protected]>
Fixes: 3d39ac5 ("perf machine: No need to have two DSOs lists")
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

tools/perf/util/probe-event.c

@@ -270,12 +270,13 @@ static int kernel_get_module_dso(const char *module, struct dso **pdso)
 	int ret = 0;
 
 	if (module) {
-		list_for_each_entry(dso, &host_machine->dsos.head, node) {
-			if (!dso->kernel)
-				continue;
-			if (strncmp(dso->short_name + 1, module,
-				    dso->short_name_len - 2) == 0)
-				goto found;
+		char module_name[128];
+
+		snprintf(module_name, sizeof(module_name), "[%s]", module);
+		map = map_groups__find_by_name(&host_machine->kmaps, MAP__FUNCTION, module_name);
+		if (map) {
+			dso = map->dso;
+			goto found;
 		}
 		pr_debug("Failed to find module %s.\n", module);
 		return -ENOENT;