perf symbols: Add dso__last_symbol()

Add a function to find the last symbol in a DSO. This will be used when
parsing address filters to calculate a region that includes the entire
DSO.

Signed-off-by: Adrian Hunter <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Masami Hiramatsu <[e-mail]>
Cc: Mathieu Poirier <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/symbol.c

···
 	return NULL;
 }
 
+static struct symbol *symbols__last(struct rb_root *symbols)
+{
+	struct rb_node *n = rb_last(symbols);
+
+	if (n)
+		return rb_entry(n, struct symbol, rb_node);
+
+	return NULL;
+}
+
 static struct symbol *symbols__next(struct symbol *sym)
 {
 	struct rb_node *n = rb_next(&sym->rb_node);
···
 struct symbol *dso__first_symbol(struct dso *dso, enum map_type type)
 {
 	return symbols__first(&dso->symbols[type]);
+}
+
+struct symbol *dso__last_symbol(struct dso *dso, enum map_type type)
+{
+	return symbols__last(&dso->symbols[type]);
 }
 
 struct symbol *dso__next_symbol(struct symbol *sym)

tools/perf/util/symbol.h

···
 struct symbol *symbol__next_by_name(struct symbol *sym);
 
 struct symbol *dso__first_symbol(struct dso *dso, enum map_type type);
+struct symbol *dso__last_symbol(struct dso *dso, enum map_type type);
 struct symbol *dso__next_symbol(struct symbol *sym);
 
 enum dso_type dso__type_fd(int fd);