ftrace: Add enabled_functions file

Add the enabled_functions file that is used to show all the
functions that have been enabled for tracing as well as their
ref counts. This helps seeing if any function has been registered
and what functions are being traced.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/ftrace.c

@@ -1703,6 +1703,7 @@ enum {
 	FTRACE_ITER_NOTRACE	= (1 << 1),
 	FTRACE_ITER_PRINTALL	= (1 << 2),
 	FTRACE_ITER_HASH	= (1 << 3),
+	FTRACE_ITER_ENABLED	= (1 << 4),
 };
 
 #define FTRACE_BUFF_MAX (KSYM_SYMBOL_LEN+4) /* room for wildcards */
@@ -1842,7 +1843,11 @@ t_next(struct seq_file *m, void *v, loff_t *pos)
 		     !(ftrace_lookup_ip(ops->filter_hash, rec->ip))) ||
 
 		    ((iter->flags & FTRACE_ITER_NOTRACE) &&
-		     !ftrace_lookup_ip(ops->notrace_hash, rec->ip))) {
+		     !ftrace_lookup_ip(ops->notrace_hash, rec->ip)) ||
+
+		    ((iter->flags & FTRACE_ITER_ENABLED) &&
+		     !(rec->flags & ~FTRACE_FL_MASK))) {
+
 			rec = NULL;
 			goto retry;
 		}
@@ -1944,7 +1949,11 @@ static int t_show(struct seq_file *m, void *v)
 	if (!rec)
 		return 0;
 
-	seq_printf(m, "%ps\n", (void *)rec->ip);
+	seq_printf(m, "%ps", (void *)rec->ip);
+	if (iter->flags & FTRACE_ITER_ENABLED)
+		seq_printf(m, " (%ld)",
+			   rec->flags & ~FTRACE_FL_MASK);
+	seq_printf(m, "\n");
 
 	return 0;
 }
@@ -1983,6 +1992,34 @@ ftrace_avail_open(struct inode *inode, struct file *file)
 	return ret;
 }
 
+static int
+ftrace_enabled_open(struct inode *inode, struct file *file)
+{
+	struct ftrace_iterator *iter;
+	int ret;
+
+	if (unlikely(ftrace_disabled))
+		return -ENODEV;
+
+	iter = kzalloc(sizeof(*iter), GFP_KERNEL);
+	if (!iter)
+		return -ENOMEM;
+
+	iter->pg = ftrace_pages_start;
+	iter->flags = FTRACE_ITER_ENABLED;
+
+	ret = seq_open(file, &show_ftrace_seq_ops);
+	if (!ret) {
+		struct seq_file *m = file->private_data;
+
+		m->private = iter;
+	} else {
+		kfree(iter);
+	}
+
+	return ret;
+}
+
 static void ftrace_filter_reset(struct ftrace_hash *hash)
 {
 	mutex_lock(&ftrace_lock);
@@ -2838,6 +2875,13 @@ static const struct file_operations ftrace_avail_fops = {
 	.release = seq_release_private,
 };
 
+static const struct file_operations ftrace_enabled_fops = {
+	.open = ftrace_enabled_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = seq_release_private,
+};
+
 static const struct file_operations ftrace_filter_fops = {
 	.open = ftrace_filter_open,
 	.read = seq_read,
@@ -3069,6 +3113,9 @@ static __init int ftrace_init_dyn_debugfs(struct dentry *d_tracer)
 	trace_create_file("available_filter_functions", 0444,
 			d_tracer, NULL, &ftrace_avail_fops);
 
+	trace_create_file("enabled_functions", 0444,
+			d_tracer, NULL, &ftrace_enabled_fops);
+
 	trace_create_file("set_ftrace_filter", 0644, d_tracer,
 			NULL, &ftrace_filter_fops);