s390/ptrace: guarded storage regset for the current task

The regset functions for guarded storage are supposed to work on
the current task as well. For task == current add the required
load and store instructions for the guarded storage control block.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/ptrace.c

@@ -1160,6 +1160,8 @@ static int s390_gs_cb_get(struct task_struct *target,
 		return -ENODEV;
 	if (!data)
 		return -ENODATA;
+	if (target == current)
+		save_gs_cb(data);
 	return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
 				   data, 0, sizeof(struct gs_cb));
 }
@@ -1170,6 +1172,7 @@ static int s390_gs_cb_set(struct task_struct *target,
 			  const void *kbuf, const void __user *ubuf)
 {
 	struct gs_cb *data = target->thread.gs_cb;
+	int rc;
 
 	if (!MACHINE_HAS_GS)
 		return -ENODEV;
@@ -1177,10 +1180,18 @@ static int s390_gs_cb_set(struct task_struct *target,
 		data = kzalloc(sizeof(*data), GFP_KERNEL);
 		if (!data)
 			return -ENOMEM;
+		data->gsd = 25;
 		target->thread.gs_cb = data;
+		if (target == current)
+			__ctl_set_bit(2, 4);
+	} else if (target == current) {
+		save_gs_cb(data);
 	}
-	return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
-				  data, 0, sizeof(struct gs_cb));
+	rc = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
+				data, 0, sizeof(struct gs_cb));
+	if (target == current)
+		restore_gs_cb(data);
+	return rc;
 }
 
 static int s390_gs_bc_get(struct task_struct *target,