Merge tag 'trace-fixes-v3.13-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing fixes from Steven Rostedt:
"This includes two fixes.

1) is a bug fix that happens when root does the following:

echo function_graph > current_tracer
modprobe foo
echo nop > current_tracer

This causes the ftrace internal accounting to get screwed up and
crashes ftrace, preventing the user from using the function tracer
after that.

2) if a TRACE_EVENT has a string field, and NULL is given for it.

The internal trace event code does a strlen() and strcpy() on the
source of field. If it is NULL it causes the system to oops.

This bug has been there since 2.6.31, but no TRACE_EVENT ever passed
in a NULL to the string field, until now"

* tag 'trace-fixes-v3.13-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
ftrace: Fix function graph with loading of modules
tracing: Allow events to have NULL strings

include/trace/ftrace.h

···
 	__data_size += (len) * sizeof(type);
 
 #undef __string
-#define __string(item, src) __dynamic_array(char, item, strlen(src) + 1)
+#define __string(item, src) __dynamic_array(char, item,			\
+		    strlen((src) ? (const char *)(src) : "(null)") + 1)
 
 #undef DECLARE_EVENT_CLASS
 #define DECLARE_EVENT_CLASS(call, proto, args, tstruct, assign, print)	\
···
 
 #undef __assign_str
 #define __assign_str(dst, src)						\
-	strcpy(__get_str(dst), src);
+	strcpy(__get_str(dst), (src) ? (const char *)(src) : "(null)");
 
 #undef TP_fast_assign
 #define TP_fast_assign(args...) args

kernel/trace/ftrace.c

···
 
 static int __register_ftrace_function(struct ftrace_ops *ops)
 {
-	if (unlikely(ftrace_disabled))
-		return -ENODEV;
-
 	if (FTRACE_WARN_ON(ops == &global_ops))
 		return -EINVAL;
 
···
 static int __unregister_ftrace_function(struct ftrace_ops *ops)
 {
 	int ret;
-
-	if (ftrace_disabled)
-		return -ENODEV;
 
 	if (WARN_ON(!(ops->flags & FTRACE_OPS_FL_ENABLED)))
 		return -EBUSY;
···
 static int ftrace_startup(struct ftrace_ops *ops, int command)
 {
 	bool hash_enable = true;
+	int ret;
 
 	if (unlikely(ftrace_disabled))
 		return -ENODEV;
+
+	ret = __register_ftrace_function(ops);
+	if (ret)
+		return ret;
 
 	ftrace_start_up++;
 	command |= FTRACE_UPDATE_CALLS;
···
 	return 0;
 }
 
-static void ftrace_shutdown(struct ftrace_ops *ops, int command)
+static int ftrace_shutdown(struct ftrace_ops *ops, int command)
 {
 	bool hash_disable = true;
+	int ret;
 
 	if (unlikely(ftrace_disabled))
-		return;
+		return -ENODEV;
+
+	ret = __unregister_ftrace_function(ops);
+	if (ret)
+		return ret;
 
 	ftrace_start_up--;
 	/*
···
 	}
 
 	if (!command || !ftrace_enabled)
-		return;
+		return 0;
 
 	ftrace_run_update_code(command);
+	return 0;
 }
 
 static void ftrace_startup_sysctl(void)
···
 	if (i == FTRACE_FUNC_HASHSIZE)
 		return;
 
-	ret = __register_ftrace_function(&trace_probe_ops);
-	if (!ret)
-		ret = ftrace_startup(&trace_probe_ops, 0);
+	ret = ftrace_startup(&trace_probe_ops, 0);
 
 	ftrace_probe_registered = 1;
 }
 
 static void __disable_ftrace_function_probe(void)
 {
-	int ret;
 	int i;
 
 	if (!ftrace_probe_registered)
···
 	}
 
 	/* no more funcs left */
-	ret = __unregister_ftrace_function(&trace_probe_ops);
-	if (!ret)
-		ftrace_shutdown(&trace_probe_ops, 0);
+	ftrace_shutdown(&trace_probe_ops, 0);
 
 	ftrace_probe_registered = 0;
 }
···
 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)			\
-	({						\
-		(ops)->flags |= FTRACE_OPS_FL_ENABLED;	\
-		0;					\
+# define ftrace_startup(ops, command)					\
+	({								\
+		int ___ret = __register_ftrace_function(ops);		\
+		if (!___ret)						\
+			(ops)->flags |= FTRACE_OPS_FL_ENABLED;		\
+		___ret;							\
 	})
-# define ftrace_shutdown(ops, command)	do { } while (0)
+# define ftrace_shutdown(ops, command) __unregister_ftrace_function(ops)
+
 # define ftrace_startup_sysctl()	do { } while (0)
 # define ftrace_shutdown_sysctl()	do { } while (0)
 
···
 
 	mutex_lock(&ftrace_lock);
 
-	ret = __register_ftrace_function(ops);
-	if (!ret)
-		ret = ftrace_startup(ops, 0);
+	ret = ftrace_startup(ops, 0);
 
 	mutex_unlock(&ftrace_lock);
 
···
 	int ret;
 
 	mutex_lock(&ftrace_lock);
-	ret = __unregister_ftrace_function(ops);
-	if (!ret)
-		ftrace_shutdown(ops, 0);
+	ret = ftrace_shutdown(ops, 0);
 	mutex_unlock(&ftrace_lock);
 
 	return ret;
···
 	return NOTIFY_DONE;
 }
 
+/* Just a place holder for function graph */
+static struct ftrace_ops fgraph_ops __read_mostly = {
+	.func		= ftrace_stub,
+	.flags		= FTRACE_OPS_FL_STUB | FTRACE_OPS_FL_GLOBAL |
+				FTRACE_OPS_FL_RECURSION_SAFE,
+};
+
 int register_ftrace_graph(trace_func_graph_ret_t retfunc,
 			trace_func_graph_ent_t entryfunc)
 {
···
 	ftrace_graph_return = retfunc;
 	ftrace_graph_entry = entryfunc;
 
-	ret = ftrace_startup(&global_ops, FTRACE_START_FUNC_RET);
+	ret = ftrace_startup(&fgraph_ops, FTRACE_START_FUNC_RET);
 
 out:
 	mutex_unlock(&ftrace_lock);
···
 	ftrace_graph_active--;
 	ftrace_graph_return = (trace_func_graph_ret_t)ftrace_stub;
 	ftrace_graph_entry = ftrace_graph_entry_stub;
-	ftrace_shutdown(&global_ops, FTRACE_STOP_FUNC_RET);
+	ftrace_shutdown(&fgraph_ops, FTRACE_STOP_FUNC_RET);
 	unregister_pm_notifier(&ftrace_suspend_notifier);
 	unregister_trace_sched_switch(ftrace_graph_probe_sched_switch, NULL);