ftrace: add ftrace_vprintk

Impact: new helper function

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 2129ab9..2f8ac1f 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2951,6 +2951,15 @@
 }
 EXPORT_SYMBOL_GPL(__ftrace_printk);
 
+int __ftrace_vprintk(unsigned long ip, const char *fmt, va_list ap)
+{
+	if (!(trace_flags & TRACE_ITER_PRINTK))
+		return 0;
+
+	return trace_vprintk(ip, task_curr_ret_stack(current), fmt, ap);
+}
+EXPORT_SYMBOL_GPL(__ftrace_vprintk);
+
 static int trace_panic_handler(struct notifier_block *this,
 			       unsigned long event, void *unused)
 {