[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>

arch/s390/kernel/setup.c

@@ -50,6 +50,12 @@
 #include <asm/ptrace.h>
 #include <asm/sections.h>
 
+/*
+ * User copy operations.
+ */
+struct uaccess_ops uaccess;
+EXPORT_SYMBOL_GPL(uaccess);
+
 /*
  * Machine setup..
  */
@@ -641,6 +647,7 @@ setup_arch(char **cmdline_p)
 
 	memory_end = memory_size;
 
+	memcpy(&uaccess, &uaccess_std, sizeof(uaccess));
 	parse_early_param();
 
 #ifndef CONFIG_64BIT