sched_rr_get_interval(): move compat to native, get rid of set_fs()

switch to using timespec64 internally, while we are at it
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

kernel/compat.c

@@ -562,22 +562,6 @@ COMPAT_SYSCALL_DEFINE4(migrate_pages, compat_pid_t, pid,
 }
 #endif
 
-COMPAT_SYSCALL_DEFINE2(sched_rr_get_interval,
-		       compat_pid_t, pid,
-		       struct compat_timespec __user *, interval)
-{
-	struct timespec t;
-	int ret;
-	mm_segment_t old_fs = get_fs();
-
-	set_fs(KERNEL_DS);
-	ret = sys_sched_rr_get_interval(pid, (struct timespec __user *)&t);
-	set_fs(old_fs);
-	if (compat_put_timespec(&t, interval))
-		return -EFAULT;
-	return ret;
-}
-
 /*
  * Allocate user-space memory for the duration of a single system call,
  * in order to marshall parameters inside a compat thunk.

kernel/sched/core.c

@@ -16,6 +16,7 @@
 #include <linux/init_task.h>
 #include <linux/context_tracking.h>
 #include <linux/rcupdate_wait.h>
+#include <linux/compat.h>
 
 #include <linux/blkdev.h>
 #include <linux/kprobes.h>
@@ -5098,13 +5099,11 @@ SYSCALL_DEFINE1(sched_get_priority_min, int, policy)
  * Return: On success, 0 and the timeslice is in @interval. Otherwise,
  * an error code.
  */
-SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid,
-		struct timespec __user *, interval)
+static int sched_rr_get_interval(pid_t pid, struct timespec64 *t)
 {
 	struct task_struct *p;
 	unsigned int time_slice;
 	struct rq_flags rf;
-	struct timespec t;
 	struct rq *rq;
 	int retval;
 
@@ -5128,15 +5127,40 @@ SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid,
 	task_rq_unlock(rq, p, &rf);
 
 	rcu_read_unlock();
-	jiffies_to_timespec(time_slice, &t);
-	retval = copy_to_user(interval, &t, sizeof(t)) ? -EFAULT : 0;
-	return retval;
+	jiffies_to_timespec64(time_slice, t);
+	return 0;
 
 out_unlock:
 	rcu_read_unlock();
 	return retval;
 }
 
+SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid,
+		struct timespec __user *, interval)
+{
+	struct timespec64 t;
+	int retval = sched_rr_get_interval(pid, &t);
+
+	if (retval == 0)
+		retval = put_timespec64(&t, interval);
+
+	return retval;
+}
+
+#ifdef CONFIG_COMPAT
+COMPAT_SYSCALL_DEFINE2(sched_rr_get_interval,
+		       compat_pid_t, pid,
+		       struct compat_timespec __user *, interval)
+{
+	struct timespec64 t;
+	int retval = sched_rr_get_interval(pid, &t);
+
+	if (retval == 0)
+		retval = compat_put_timespec64(&t, interval);
+	return retval;
+}
+#endif
+
 void sched_show_task(struct task_struct *p)
 {
 	unsigned long free = 0;