tracing/events: add support for modules to TRACE_EVENT

Impact: allow modules to add TRACE_EVENTS on load

This patch adds the final hooks to allow modules to use the TRACE_EVENT
macro. A notifier and a data structure are used to link the TRACE_EVENTs
defined in the module to connect them with the ftrace event tracing system.

It also adds the necessary automated clean ups to the trace events when a
module is removed.

Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

include/linux/ftrace_event.h

@@ -7,6 +7,7 @@
 
 struct trace_array;
 struct tracer;
+struct dentry;
 
 /*
  * The trace entry - the most basic unit of tracing. This is what
@@ -87,6 +88,7 @@ struct ftrace_event_call {
 	char			*name;
 	char			*system;
 	struct dentry		*dir;
+	struct trace_event	*event;
 	int			enabled;
 	int			(*regfunc)(void);
 	void			(*unregfunc)(void);
@@ -97,6 +99,7 @@ struct ftrace_event_call {
 	struct list_head	fields;
 	int			n_preds;
 	struct filter_pred	**preds;
+	void			*mod;
 
 #ifdef CONFIG_EVENT_PROFILE
 	atomic_t	profile_count;

include/linux/module.h

@@ -337,6 +337,10 @@ struct module
 	const char **trace_bprintk_fmt_start;
 	unsigned int num_trace_bprintk_fmt;
 #endif
+#ifdef CONFIG_EVENT_TRACING
+	struct ftrace_event_call *trace_events;
+	unsigned int num_trace_events;
+#endif
 
 #ifdef CONFIG_MODULE_UNLOAD
 	/* What modules depend on me? */

include/linux/trace_seq.h

@@ -1,6 +1,8 @@
 #ifndef _LINUX_TRACE_SEQ_H
 #define _LINUX_TRACE_SEQ_H
 
+#include <linux/fs.h>
+
 /*
  * Trace sequences are used to allow a function to call several other functions
  * to create a string of data to use (up to a max of PAGE_SIZE.