s390/kasan: enable stack and global variables access checks

By defining KASAN_SHADOW_OFFSET in Kconfig stack and global variables
memory access check instrumentation is enabled. gcc version 4.9.2 or
newer is also required.

Reviewed-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 95fff77..2458625 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -56,6 +56,11 @@
 config ARCH_SUPPORTS_UPROBES
 	def_bool y
 
+config KASAN_SHADOW_OFFSET
+	hex
+	depends on KASAN
+	default 0x30000000000
+
 config S390
 	def_bool y
 	select ARCH_BINFMT_ELF_STATE