s390/kasan: double the stack size

Kasan stack instrumentation pads stack variables with redzones, which
increases stack frames size significantly. Stack sizes are increased
from 16k to 32k in the code, as well as for the kernel stack overflow
detection option (CHECK_STACK).
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>

arch/s390/Makefile

@@ -27,7 +27,7 @@ KBUILD_CFLAGS_DECOMPRESSOR += $(call cc-option,-ffreestanding)
 KBUILD_CFLAGS_DECOMPRESSOR += $(if $(CONFIG_DEBUG_INFO),-g)
 KBUILD_CFLAGS_DECOMPRESSOR += $(if $(CONFIG_DEBUG_INFO_DWARF4), $(call cc-option, -gdwarf-4,))
 UTS_MACHINE	:= s390x
-STACK_SIZE	:= 16384
+STACK_SIZE	:= $(if $(CONFIG_KASAN),32768,16384)
 CHECKFLAGS	+= -D__s390__ -D__s390x__
 
 export LD_BFD

arch/s390/include/asm/thread_info.h

@@ -13,7 +13,11 @@
 /*
  * General size of kernel stacks
  */
+#ifdef CONFIG_KASAN
+#define THREAD_SIZE_ORDER 3
+#else
 #define THREAD_SIZE_ORDER 2
+#endif
 #define THREAD_SIZE (PAGE_SIZE << THREAD_SIZE_ORDER)
 
 #ifndef __ASSEMBLY__