[S390] Make user-copy operations run-time configurable.

Introduces a struct uaccess_ops which allows setting user-copy
operations at run-time.

Signed-off-by: Gerald Schaefer <geraldsc@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index f2a9165..e229af5 100644
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -51,6 +51,12 @@
 #include <asm/sections.h>
 
 /*
+ * User copy operations.
+ */
+struct uaccess_ops uaccess;
+EXPORT_SYMBOL_GPL(uaccess);
+
+/*
  * Machine setup..
  */
 unsigned int console_mode = 0;
@@ -641,6 +647,7 @@
 
 	memory_end = memory_size;
 
+	memcpy(&uaccess, &uaccess_std, sizeof(uaccess));
 	parse_early_param();
 
 #ifndef CONFIG_64BIT