tracepoints: Add check trace callback type

This check is meant to be used by tracepoint users which do a direct cast of
callbacks to (void *) for direct registration, thus bypassing the
register_trace_##name and unregister_trace_##name checks.

This permits to ensure that the callback type matches the function type at the
call site, but without generating any code.

Acked-by: Masami Hiramatsu <mhiramat@redhat.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
LKML-Reference: <20100430165959.GA25605@Krystal>
CC: Ingo Molnar <mingo@elte.hu>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Peter Zijlstra <peterz@infradead.org>
CC: Arnaldo Carvalho de Melo <acme@redhat.com>
CC: Lai Jiangshan <laijs@cn.fujitsu.com>
CC: Li Zefan <lizf@cn.fujitsu.com>
CC: Christoph Hellwig <hch@lst.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

include/linux/tracepoint.h

@@ -137,9 +137,11 @@ static inline void tracepoint_update_probe_range(struct tracepoint *begin,
 	static inline int unregister_trace_##name(void (*probe)(proto))	\
 	{								\
 		return tracepoint_probe_unregister(#name, (void *)probe);\
+	}								\
+	static inline void check_trace_callback_type_##name(void (*cb)(proto)) \
+	{								\
 	}
 
-
 #define DEFINE_TRACE_FN(name, reg, unreg)				\
 	static const char __tpstrtab_##name[]				\
 	__attribute__((section("__tracepoints_strings"))) = #name;	\
@@ -168,6 +170,9 @@ static inline void tracepoint_update_probe_range(struct tracepoint *begin,
 	static inline int unregister_trace_##name(void (*probe)(proto))	\
 	{								\
 		return -ENOSYS;						\
+	}								\
+	static inline void check_trace_callback_type_##name(void (*cb)(proto)) \
+	{								\
 	}
 
 #define DEFINE_TRACE_FN(name, reg, unreg)