s390/kasan: reipl and kexec support

Some functions from both arch/s390/kernel/ipl.c and
arch/s390/kernel/machine_kexec.c are called without DAT enabled
(or with and without DAT enabled code paths). There is no easy way
to partially disable kasan for those files without a substantial
rework. Disable kasan for both files for now.

To avoid disabling kasan for arch/s390/kernel/diag.c DAT flag is
enabled in diag308 call. pcpu_delegate which disables DAT is marked
with __no_sanitize_address to disable instrumentation for that one
function.
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/processor.h

@@ -242,7 +242,7 @@ static inline unsigned long current_stack_pointer(void)
 	return sp;
 }
 
-static inline unsigned short stap(void)
+static __no_sanitize_address_or_inline unsigned short stap(void)
 {
 	unsigned short cpu_address;
 

arch/s390/kernel/Makefile

@@ -24,6 +24,8 @@ UBSAN_SANITIZE_early.o		:= n
 UBSAN_SANITIZE_early_nobss.o	:= n
 
 KASAN_SANITIZE_early_nobss.o	:= n
+KASAN_SANITIZE_ipl.o		:= n
+KASAN_SANITIZE_machine_kexec.o	:= n
 
 #
 # Passing null pointers is ok for smp code, since we access the lowcore here.

arch/s390/kernel/ipl.c

@@ -156,6 +156,8 @@ static inline int __diag308(unsigned long subcode, void *addr)
 
 int diag308(unsigned long subcode, void *addr)
 {
+	if (IS_ENABLED(CONFIG_KASAN))
+		__arch_local_irq_stosm(0x04); /* enable DAT */
 	diag_stat_inc(DIAG_STAT_X308);
 	return __diag308(subcode, addr);
 }

arch/s390/kernel/smp.c

@@ -313,7 +313,8 @@ static void __pcpu_delegate(void (*func)(void*), void *data)
 	func(data);	/* should not return */
 }
 
-static void pcpu_delegate(struct pcpu *pcpu, void (*func)(void *),
+static void __no_sanitize_address pcpu_delegate(struct pcpu *pcpu,
+						void (*func)(void *),
 						void *data, unsigned long stack)
 {
 	struct lowcore *lc = lowcore_ptr[pcpu - pcpu_devices];