tracing: add event trace infrastructure

This patch creates the event tracing infrastructure of ftrace.
It will create the files:

 /debug/tracing/available_events
 /debug/tracing/set_event

The available_events will list the trace points that have been
registered with the event tracer.

set_events will allow the user to enable or disable an event hook.

example:

 # echo sched_wakeup > /debug/tracing/set_event

Will enable the sched_wakeup event (if it is registered).

 # echo "!sched_wakeup" >> /debug/tracing/set_event

Will disable the sched_wakeup event (and only that event).

 # echo > /debug/tracing/set_event

Will disable all events (notice the '>')

 # cat /debug/tracing/available_events > /debug/tracing/set_event

Will enable all registered event hooks.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>

1 files changed, 52 insertions, 0 deletions

diff --git a/kernel/trace/trace_events.h b/kernel/trace/trace_events.h
new file mode 100644
index 00000000000..39342f86db2
--- /dev/null
+++ b/kernel/trace/trace_events.h
@@ -0,0 +1,52 @@
+#ifndef _LINUX_KERNEL_TRACE_EVENTS_H
+#define _LINUX_KERNEL_TRACE_EVENTS_H
+
+#include <linux/ftrace.h>
+#include "trace.h"
+
+struct ftrace_event_call {
+	char		*name;
+	int		enabled;
+	int		(*regfunc)(void);
+	void		(*unregfunc)(void);
+};
+
+
+#undef TPFMT
+#define TPFMT(fmt, args...)	fmt "\n", ##args
+
+#undef DEFINE_TRACE_FMT
+#define DEFINE_TRACE_FMT(call, proto, args, fmt)			\
+static void ftrace_event_##call(proto)					\
+{									\
+	event_trace_printk(_RET_IP_, "(" #call ") " fmt);		\
+}									\
+									\
+static int ftrace_reg_event_##call(void)				\
+{									\
+	int ret;							\
+									\
+	ret = register_trace_##call(ftrace_event_##call);		\
+	if (!ret)							\
+		pr_info("event trace: Could not activate trace point "	\
+			"probe to " #call);				\
+	return ret;							\
+}									\
+									\
+static void ftrace_unreg_event_##call(void)				\
+{									\
+	unregister_trace_##call(ftrace_event_##call);			\
+}									\
+									\
+static struct ftrace_event_call __used					\
+__attribute__((section("_ftrace_events"))) event_##call = {		\
+	.name 			= #call,				\
+	.regfunc		= ftrace_reg_event_##call,		\
+	.unregfunc		= ftrace_unreg_event_##call,		\
+}
+
+void event_trace_printk(unsigned long ip, const char *fmt, ...);
+extern unsigned long __start_ftrace_events[];
+extern unsigned long __stop_ftrace_events[];
+
+#endif /* _LINUX_KERNEL_TRACE_EVENTS_H */