perf symbols: Return the first entry with a given name in find_by_name method

When a dso contains multiple symbols which have same name, current
dso__find_symbol_by_name() only finds an one of them and there's no way
to get the all symbols without going through the rbtree.

So make symbols__find_by_name() return the first entry with the given
name and the next patch in this series will provide a way to iterate
from there, by the name ordered rb_tree, till a suitable symbol is
found.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Link: http://lkml.kernel.org/r/1421234288-22758-2-git-send-email-namhyung@kernel.org
[ Yanked this independent hunk, without changes, from a larger patch  ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/symbol.c

@@ -396,6 +396,7 @@ static struct symbol *symbols__find_by_name(struct rb_root *symbols,
 					    const char *name)
 {
 	struct rb_node *n;
+	struct symbol_name_rb_node *s;
 
 	if (symbols == NULL)
 		return NULL;
@@ -403,7 +404,6 @@ static struct symbol *symbols__find_by_name(struct rb_root *symbols,
 	n = symbols->rb_node;
 
 	while (n) {
-		struct symbol_name_rb_node *s;
 		int cmp;
 
 		s = rb_entry(n, struct symbol_name_rb_node, rb_node);
@@ -414,10 +414,24 @@ static struct symbol *symbols__find_by_name(struct rb_root *symbols,
 		else if (cmp > 0)
 			n = n->rb_right;
 		else
-			return &s->sym;
+			break;
 	}
 
-	return NULL;
+	if (n == NULL)
+		return NULL;
+
+	/* return first symbol that has same name (if any) */
+	for (n = rb_prev(n); n; n = rb_prev(n)) {
+		struct symbol_name_rb_node *tmp;
+
+		tmp = rb_entry(n, struct symbol_name_rb_node, rb_node);
+		if (strcmp(tmp->sym.name, s->sym.name))
+			break;
+
+		s = tmp;
+	}
+
+	return &s->sym;
 }
 
 struct symbol *dso__find_symbol(struct dso *dso,