perf probe: Fix to use symtab only if no debuginfo

Fix perf probe to use symtab only if there is no debuginfo, because debuginfo
has more information than symtab.

If we can't find a function in debuginfo, we never find it in symtab.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
LKML-Reference: <20100421195624.24664.46214.stgit@localhost6.localdomain6>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/probe-event.c

@@ -180,15 +180,16 @@ static int try_to_find_kprobe_trace_events(struct perf_probe_event *pev,
 		return -ENOENT;
 	}
 	/* Error path : ntevs < 0 */
-	if (need_dwarf) {
-		if (ntevs == -EBADF)
-			pr_warning("No dwarf info found in the vmlinux - "
-				"please rebuild with CONFIG_DEBUG_INFO=y.\n");
-		return ntevs;
+	pr_debug("An error occurred in debuginfo analysis (%d).\n", ntevs);
+	if (ntevs == -EBADF) {
+		pr_warning("Warning: No dwarf info found in the vmlinux - "
+			"please rebuild kernel with CONFIG_DEBUG_INFO=y.\n");
+		if (!need_dwarf) {
+			pr_debug("Trying to use symbols.\nn");
+			return 0;
+		}
 	}
-	pr_debug("An error occurred in debuginfo analysis."
-		 " Try to use symbols.\n");
-	return 0;
+	return ntevs;
 }
 
 #define LINEBUF_SIZE 256