ftrace: Have ftrace_startup() return failure code

The register_ftrace_function() returns an error code on failure
except if the call to ftrace_startup() fails. Add a error return to
ftrace_startup() if it fails to start, allowing register_ftrace_funtion()
to return a proper error value.

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

1 files changed, 8 insertions, 6 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index d017c2c82c44..bebbc959ee8c 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1638,12 +1638,12 @@ static void ftrace_startup_enable(int command)
         ftrace_run_update_code(command);
 }
 
-static void ftrace_startup(struct ftrace_ops *ops, int command)
+static int ftrace_startup(struct ftrace_ops *ops, int command)
 {
         bool hash_enable = true;
 
         if (unlikely(ftrace_disabled))
-                return;
+                return -ENODEV;
 
         ftrace_start_up++;
         command |= FTRACE_ENABLE_CALLS;
@@ -1662,6 +1662,8 @@ static void ftrace_startup(struct ftrace_ops *ops, int command)
                 ftrace_hash_rec_enable(ops, 1);
 
         ftrace_startup_enable(command);
+
+        return 0;
 }
 
 static void ftrace_shutdown(struct ftrace_ops *ops, int command)
@@ -2501,7 +2503,7 @@ static void __enable_ftrace_function_probe(void)
 
         ret = __register_ftrace_function(&trace_probe_ops);
         if (!ret)
-                ftrace_startup(&trace_probe_ops, 0);
+                ret = ftrace_startup(&trace_probe_ops, 0);
 
         ftrace_probe_registered = 1;
 }
@@ -3466,7 +3468,7 @@ device_initcall(ftrace_nodyn_init);
 static inline int ftrace_init_dyn_debugfs(struct dentry *d_tracer) { return 0; }
 static inline void ftrace_startup_enable(int command) { }
 /* Keep as macros so we do not need to define the commands */
-# define ftrace_startup(ops, command)   do { } while (0)
+# define ftrace_startup(ops, command)   ({0;})
 # define ftrace_shutdown(ops, command)  do { } while (0)
 # define ftrace_startup_sysctl()        do { } while (0)
 # define ftrace_shutdown_sysctl()       do { } while (0)
@@ -3799,7 +3801,7 @@ int register_ftrace_function(struct ftrace_ops *ops)
 
         ret = __register_ftrace_function(ops);
         if (!ret)
-                ftrace_startup(ops, 0);
+                ret = ftrace_startup(ops, 0);
 
 
  out_unlock:
@@ -4045,7 +4047,7 @@ int register_ftrace_graph(trace_func_graph_ret_t retfunc,
         ftrace_graph_return = retfunc;
         ftrace_graph_entry = entryfunc;
 
-        ftrace_startup(&global_ops, FTRACE_START_FUNC_RET);
+        ret = ftrace_startup(&global_ops, FTRACE_START_FUNC_RET);
 
 out:
         mutex_unlock(&ftrace_lock);