tracepoint: Do not warn for unused event that is exported

There are a few generic events that may only be used by modules. They are
defined and then set with EXPORT_TRACEPOINT*(). Mark events that are
exported as being used, even though they still waste memory in the kernel
proper.

Cc: Masami Hiramatsu <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Mathieu Desnoyers <[e-mail]>
Cc: Andrew Morton <[e-mail]>
Cc: Arnd Bergmann <[e-mail]>
Cc: Masahiro Yamada <[e-mail]>
Cc: Nathan Chancellor <[e-mail]>
Cc: Nicolas Schier <[e-mail]>
Cc: Nick Desaulniers <[e-mail]>
Cc: Catalin Marinas <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Cc: Randy Dunlap <[e-mail]>
Cc: Stephen Rothwell <[e-mail]>
Link: https://lore.kernel.org/[e-mail]
Signed-off-by: Steven Rostedt (Google) <[e-mail]>

include/linux/tracepoint.h

···
  * defined tracepoints are used. It is discarded after the build.
  */
 # define TRACEPOINT_CHECK(name)						\
-	static const char __used __section("__tracepoint_check") __trace_check[] = \
-		#name;
+	static const char __used __section("__tracepoint_check")	\
+	__trace_check_##name[] = #name;
 
 /*
  * Make sure the alignment of the structure in the __tracepoints section will
···
 	__DEFINE_TRACE_EXT(_name, NULL, PARAMS(_proto), PARAMS(_args));
 
 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)				\
+	TRACEPOINT_CHECK(name)						\
 	EXPORT_SYMBOL_GPL(__tracepoint_##name);				\
 	EXPORT_SYMBOL_GPL(__traceiter_##name);				\
 	EXPORT_STATIC_CALL_GPL(tp_func_##name)
 #define EXPORT_TRACEPOINT_SYMBOL(name)					\
+	TRACEPOINT_CHECK(name)						\
 	EXPORT_SYMBOL(__tracepoint_##name);				\
 	EXPORT_SYMBOL(__traceiter_##name);				\
 	EXPORT_STATIC_CALL(tp_func_##name)