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, 9 insertions, 0 deletions

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 07877f4b5233..999c6a2485df 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -159,6 +159,15 @@ config CONTEXT_SWITCH_TRACER
           This tracer gets called from the context switch and records
           all switching of tasks.
 
+config EVENT_TRACER
+        bool "Trace various events in the kernel"
+        depends on DEBUG_KERNEL
+        select TRACING
+        help
+          This tracer hooks to various trace points in the kernel
+          allowing the user to pick and choose which trace point they
+          want to trace.
+
 config BOOT_TRACER
         bool "Trace boot initcalls"
         depends on DEBUG_KERNEL