1 files changed, 53 insertions, 16 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 8fef1d99bbbf..dcce0bf9c84d 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -91,6 +91,7 @@ static struct ftrace_ops *ftrace_list __read_mostly = &ftrace_list_end;
 ftrace_func_t ftrace_trace_function __read_mostly = ftrace_stub;
 ftrace_func_t __ftrace_trace_function __read_mostly = ftrace_stub;
 ftrace_func_t ftrace_pid_function __read_mostly = ftrace_stub;
+static struct ftrace_ops global_ops;
 
 /*
  * Traverse the ftrace_list, invoking all entries.  The reason that we
@@ -153,7 +154,7 @@ static void ftrace_test_stop_func(unsigned long ip, unsigned long parent_ip)
 }
 #endif
 
-static void update_ftrace_function(void)
+static void update_global_ops(void)
 {
         ftrace_func_t func;
 
@@ -173,6 +174,18 @@ static void update_ftrace_function(void)
                 set_ftrace_pid_function(func);
                 func = ftrace_pid_func;
         }
+
+        global_ops.func = func;
+}
+
+static void update_ftrace_function(void)
+{
+        ftrace_func_t func;
+
+        update_global_ops();
+
+        func = global_ops.func;
+
 #ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
         ftrace_trace_function = func;
 #else
@@ -181,24 +194,19 @@ static void update_ftrace_function(void)
 #endif
 }
 
-static int __register_ftrace_function(struct ftrace_ops *ops)
+static void add_ftrace_ops(struct ftrace_ops **list, struct ftrace_ops *ops)
 {
-        ops->next = ftrace_list;
+        ops->next = *list;
         /*
          * We are entering ops into the ftrace_list but another
          * CPU might be walking that list. We need to make sure
          * the ops->next pointer is valid before another CPU sees
          * the ops pointer included into the ftrace_list.
          */
-        rcu_assign_pointer(ftrace_list, ops);
-
-        if (ftrace_enabled)
-                update_ftrace_function();
-
-        return 0;
+        rcu_assign_pointer(*list, ops);
 }
 
-static int __unregister_ftrace_function(struct ftrace_ops *ops)
+static int remove_ftrace_ops(struct ftrace_ops **list, struct ftrace_ops *ops)
 {
         struct ftrace_ops **p;
 
@@ -206,13 +214,12 @@ static int __unregister_ftrace_function(struct ftrace_ops *ops)
          * If we are removing the last function, then simply point
          * to the ftrace_stub.
          */
-        if (ftrace_list == ops && ops->next == &ftrace_list_end) {
-                ftrace_trace_function = ftrace_stub;
-                ftrace_list = &ftrace_list_end;
+        if (*list == ops && ops->next == &ftrace_list_end) {
+                *list = &ftrace_list_end;
                 return 0;
         }
 
-        for (p = &ftrace_list; *p != &ftrace_list_end; p = &(*p)->next)
+        for (p = list; *p != &ftrace_list_end; p = &(*p)->next)
                 if (*p == ops)
                         break;
 
@@ -220,7 +227,37 @@ static int __unregister_ftrace_function(struct ftrace_ops *ops)
                 return -1;
 
         *p = (*p)->next;
+        return 0;
+}
+
+static int __register_ftrace_function(struct ftrace_ops *ops)
+{
+        if (ftrace_disabled)
+                return -ENODEV;
+
+        if (FTRACE_WARN_ON(ops == &global_ops))
+                return -EINVAL;
+
+        add_ftrace_ops(&ftrace_list, ops);
+        if (ftrace_enabled)
+                update_ftrace_function();
+
+        return 0;
+}
 
+static int __unregister_ftrace_function(struct ftrace_ops *ops)
+{
+        int ret;
+
+        if (ftrace_disabled)
+                return -ENODEV;
+
+        if (FTRACE_WARN_ON(ops == &global_ops))
+                return -EINVAL;
+
+        ret = remove_ftrace_ops(&ftrace_list, ops);
+        if (ret < 0)
+                return ret;
         if (ftrace_enabled)
                 update_ftrace_function();
 
@@ -894,7 +931,7 @@ enum {
         FTRACE_OPS_FL_ENABLED           = 1,
 };
 
-struct ftrace_ops global_ops = {
+static struct ftrace_ops global_ops = {
         .func                   = ftrace_stub,
         .notrace_hash           = EMPTY_HASH,
         .filter_hash            = EMPTY_HASH,
@@ -3263,7 +3300,7 @@ void __init ftrace_init(void)
 
 #else
 
-struct ftrace_ops global_ops = {
+static struct ftrace_ops global_ops = {
         .func                   = ftrace_stub,
 };