tracing: have event_trace_printk use static tracer

Impact: speed up on event tracing

The event_trace_printk is currently a wrapper function that calls
trace_vprintk. Because it uses a variable for the fmt it misses out
on the optimization of using the binary printk.

This patch makes event_trace_printk into a macro wrapper to use the
fmt as the same as the trace_printks.

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

kernel/trace/trace.h

@@ -773,4 +773,21 @@ void event_trace_printk(unsigned long ip, const char *fmt, ...);
 extern struct ftrace_event_call __start_ftrace_events[];
 extern struct ftrace_event_call __stop_ftrace_events[];
 
+extern const char *__start___trace_bprintk_fmt[];
+extern const char *__stop___trace_bprintk_fmt[];
+
+#define event_trace_printk(ip, fmt, args...)				\
+do {									\
+	__trace_printk_check_format(fmt, ##args);			\
+	tracing_record_cmdline(current);				\
+	if (__builtin_constant_p(fmt)) {				\
+		static const char *trace_printk_fmt			\
+		  __attribute__((section("__trace_printk_fmt"))) =	\
+			__builtin_constant_p(fmt) ? fmt : NULL;		\
+									\
+		__trace_bprintk(ip, trace_printk_fmt, ##args);		\
+	} else								\
+		__trace_printk(ip, fmt, ##args);			\
+} while (0)
+
 #endif /* _LINUX_KERNEL_TRACE_H */

kernel/trace/trace_events.c

@@ -24,16 +24,6 @@ static DEFINE_MUTEX(event_mutex);
 	     (unsigned long)event < (unsigned long)__stop_ftrace_events; \
 	     event++)
 
-void event_trace_printk(unsigned long ip, const char *fmt, ...)
-{
-	va_list ap;
-
-	va_start(ap, fmt);
-	tracing_record_cmdline(current);
-	trace_vprintk(ip, task_curr_ret_stack(current), fmt, ap);
-	va_end(ap);
-}
-
 static void ftrace_clear_events(void)
 {
 	struct ftrace_event_call *call = (void *)__start_ftrace_events;