tracing/filters: add TRACE_EVENT_FORMAT_NOFILTER event macro

Frederic Weisbecker suggested that the trace_special event shouldn't be
filterable; this patch adds a TRACE_EVENT_FORMAT_NOFILTER event macro
that allows an event format to be exported without having a filter
attached, and removes filtering from the trace_special event.
Signed-off-by: NTom Zanussi <tzanussi@gmail.com>
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

kernel/trace/trace.c

@@ -1064,7 +1064,6 @@ ftrace_trace_special(void *__tr,
 		     unsigned long arg1, unsigned long arg2, unsigned long arg3,
 		     int pc)
 {
-	struct ftrace_event_call *call = &event_special;
 	struct ring_buffer_event *event;
 	struct trace_array *tr = __tr;
 	struct special_entry *entry;
@@ -1077,7 +1076,6 @@ ftrace_trace_special(void *__tr,
 	entry->arg1			= arg1;
 	entry->arg2			= arg2;
 	entry->arg3			= arg3;
-	filter_check_discard(call, entry, event);
 	trace_buffer_unlock_commit(tr, event, 0, pc);
 }
 

kernel/trace/trace.h

@@ -915,6 +915,8 @@ do {									\
 #undef TRACE_EVENT_FORMAT
 #define TRACE_EVENT_FORMAT(call, proto, args, fmt, tstruct, tpfmt)	\
 	extern struct ftrace_event_call event_##call;
+#undef TRACE_EVENT_FORMAT_NOFILTER
+#define TRACE_EVENT_FORMAT_NOFILTER(call, proto, args, fmt, tstruct, tpfmt)
 #include "trace_event_types.h"
 
 #endif /* _LINUX_KERNEL_TRACE_H */

kernel/trace/trace_event_types.h

@@ -57,7 +57,7 @@ TRACE_EVENT_FORMAT(context_switch, TRACE_CTX, ctx_switch_entry, ignore,
 	TP_RAW_FMT("%u:%u:%u  ==+ %u:%u:%u [%03u]")
 );
 
-TRACE_EVENT_FORMAT(special, TRACE_SPECIAL, special_entry, ignore,
+TRACE_EVENT_FORMAT_NOFILTER(special, TRACE_SPECIAL, special_entry, ignore,
 	TRACE_STRUCT(
 		TRACE_FIELD(unsigned long, arg1, arg1)
 		TRACE_FIELD(unsigned long, arg2, arg2)

kernel/trace/trace_export.c

@@ -65,6 +65,22 @@ ftrace_format_##call(struct trace_seq *s)				\
 	return ret;							\
 }
 
+#undef TRACE_EVENT_FORMAT_NOFILTER
+#define TRACE_EVENT_FORMAT_NOFILTER(call, proto, args, fmt, tstruct,	\
+				    tpfmt)				\
+static int								\
+ftrace_format_##call(struct trace_seq *s)				\
+{									\
+	struct args field;						\
+	int ret;							\
+									\
+	tstruct;							\
+									\
+	trace_seq_printf(s, "\nprint fmt: \"%s\"\n", tpfmt);		\
+									\
+	return ret;							\
+}
+
 #include "trace_event_types.h"
 
 #undef TRACE_ZERO_CHAR
@@ -109,6 +125,19 @@ static int ftrace_raw_init_event_##call(void)				\
 	return 0;							\
 }									\
 
+#undef TRACE_EVENT_FORMAT_NOFILTER
+#define TRACE_EVENT_FORMAT_NOFILTER(call, proto, args, fmt, tstruct,	\
+				    tpfmt)				\
+									\
+struct ftrace_event_call __used						\
+__attribute__((__aligned__(4)))						\
+__attribute__((section("_ftrace_events"))) event_##call = {		\
+	.name			= #call,				\
+	.id			= proto,				\
+	.system			= __stringify(TRACE_SYSTEM),		\
+	.show_format		= ftrace_format_##call,			\
+};
+
 #include "trace_event_types.h"
 
 #undef TRACE_FIELD
@@ -150,4 +179,8 @@ ftrace_define_fields_##call(void)					\
 	return ret;							\
 }
 
+#undef TRACE_EVENT_FORMAT_NOFILTER
+#define TRACE_EVENT_FORMAT_NOFILTER(call, proto, args, fmt, tstruct,	\
+				    tpfmt)
+
 #include "trace_event_types.h"