ftrace: Add selftest to test function trace recursion protection

Add selftests to test the function tracing recursion protection actually
does work. It also tests if a ftrace_ops states it will perform its own
protection. Although, even if the ftrace_ops states it will protect itself,
the ftrace infrastructure may still provide protection if the arch does
not support all features or another ftrace_ops is registered.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 21 insertions, 0 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index ad765b4ba426..528d997c7f99 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -111,6 +111,27 @@ static void ftrace_ops_no_ops(unsigned long ip, unsigned long parent_ip);
 #define ftrace_ops_list_func ((ftrace_func_t)ftrace_ops_no_ops)
 #endif
 
+/**
+ * ftrace_nr_registered_ops - return number of ops registered
+ *
+ * Returns the number of ftrace_ops registered and tracing functions
+ */
+int ftrace_nr_registered_ops(void)
+{
+        struct ftrace_ops *ops;
+        int cnt = 0;
+
+        mutex_lock(&ftrace_lock);
+
+        for (ops = ftrace_ops_list;
+             ops != &ftrace_list_end; ops = ops->next)
+                cnt++;
+
+        mutex_unlock(&ftrace_lock);
+
+        return cnt;
+}
+
 /*
  * Traverse the ftrace_global_list, invoking all entries.  The reason that we
  * can use rcu_dereference_raw() is that elements removed from this list