s390/stack: merge empty stack frame slots

Merge empty1 and empty2 arrays within the stack frame to one single
array. This is possible since with commit 42b01a55 ("s390: always
use the packed stack layout") the alternative stack frame layout is
gone.
Reviewed-by: Nico Boehr <nrb@linux.ibm.com>
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

arch/s390/include/asm/stacktrace.h

@@ -39,8 +39,7 @@ static inline bool on_stack(struct stack_info *info,
  * Kernel uses the packed stack layout (-mpacked-stack).
  */
 struct stack_frame {
-	unsigned long empty1[5];
-	unsigned int  empty2[8];
+	unsigned long empty[9];
 	unsigned long gprs[10];
 	unsigned long back_chain;
 };

arch/s390/kernel/asm-offsets.c

@@ -57,11 +57,11 @@ int main(void)
 	/* stack_frame offsets */
 	OFFSET(__SF_BACKCHAIN, stack_frame, back_chain);
 	OFFSET(__SF_GPRS, stack_frame, gprs);
-	OFFSET(__SF_EMPTY, stack_frame, empty1[0]);
-	OFFSET(__SF_SIE_CONTROL, stack_frame, empty1[1]);
-	OFFSET(__SF_SIE_SAVEAREA, stack_frame, empty1[2]);
-	OFFSET(__SF_SIE_REASON, stack_frame, empty1[3]);
-	OFFSET(__SF_SIE_FLAGS, stack_frame, empty1[4]);
+	OFFSET(__SF_EMPTY, stack_frame, empty[0]);
+	OFFSET(__SF_SIE_CONTROL, stack_frame, empty[1]);
+	OFFSET(__SF_SIE_SAVEAREA, stack_frame, empty[2]);
+	OFFSET(__SF_SIE_REASON, stack_frame, empty[3]);
+	OFFSET(__SF_SIE_FLAGS, stack_frame, empty[4]);
 	DEFINE(STACK_FRAME_OVERHEAD, sizeof(struct stack_frame));
 	BLANK();
 	/* idle data offsets */

arch/s390/kernel/perf_event.c

@@ -30,7 +30,7 @@ static struct kvm_s390_sie_block *sie_block(struct pt_regs *regs)
 	if (!stack)
 		return NULL;
 
-	return (struct kvm_s390_sie_block *)stack->empty1[1];
+	return (struct kvm_s390_sie_block *)stack->empty[1];
 }
 
 static bool is_in_guest(struct pt_regs *regs)