[S390] ftrace: add dynamic ftrace support

Dynamic ftrace support for s390.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/early.c

@@ -11,6 +11,7 @@
 #include <linux/errno.h>
 #include <linux/string.h>
 #include <linux/ctype.h>
+#include <linux/ftrace.h>
 #include <linux/lockdep.h>
 #include <linux/module.h>
 #include <linux/pfn.h>
@@ -410,5 +411,8 @@ void __init startup_init(void)
 	sclp_facilities_detect();
 	detect_memory_layout(memory_chunk);
 	S390_lowcore.machine_flags = machine_flags;
+#ifdef CONFIG_DYNAMIC_FTRACE
+	S390_lowcore.ftrace_func = (unsigned long)ftrace_caller;
+#endif
 	lockdep_on();
 }