futex: Make syscall entry points less convoluted

The futex and the compat syscall entry points do pretty much the same
except for the timespec data types and the corresponding copy from
user function.

Split out the rest into inline functions and share the functionality.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210422194705.244476369@linutronix.de

kernel/futex.c

@@ -3760,30 +3760,48 @@ long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
 	return -ENOSYS;
 }
 
+static __always_inline bool futex_cmd_has_timeout(u32 cmd)
+{
+	switch (cmd) {
+	case FUTEX_WAIT:
+	case FUTEX_LOCK_PI:
+	case FUTEX_WAIT_BITSET:
+	case FUTEX_WAIT_REQUEUE_PI:
+		return true;
+	}
+	return false;
+}
+
+static __always_inline int
+futex_init_timeout(u32 cmd, u32 op, struct timespec64 *ts, ktime_t *t)
+{
+	if (!timespec64_valid(ts))
+		return -EINVAL;
+
+	*t = timespec64_to_ktime(*ts);
+	if (cmd == FUTEX_WAIT)
+		*t = ktime_add_safe(ktime_get(), *t);
+	else if (cmd != FUTEX_LOCK_PI && !(op & FUTEX_CLOCK_REALTIME))
+		*t = timens_ktime_to_host(CLOCK_MONOTONIC, *t);
+	return 0;
+}
 
 SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
 		struct __kernel_timespec __user *, utime, u32 __user *, uaddr2,
 		u32, val3)
 {
-	struct timespec64 ts;
+	int ret, cmd = op & FUTEX_CMD_MASK;
 	ktime_t t, *tp = NULL;
-	int cmd = op & FUTEX_CMD_MASK;
+	struct timespec64 ts;
 
-	if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
-		      cmd == FUTEX_WAIT_BITSET ||
-		      cmd == FUTEX_WAIT_REQUEUE_PI)) {
+	if (utime && futex_cmd_has_timeout(cmd)) {
 		if (unlikely(should_fail_futex(!(op & FUTEX_PRIVATE_FLAG))))
 			return -EFAULT;
 		if (get_timespec64(&ts, utime))
 			return -EFAULT;
-		if (!timespec64_valid(&ts))
-			return -EINVAL;
-
-		t = timespec64_to_ktime(ts);
-		if (cmd == FUTEX_WAIT)
-			t = ktime_add_safe(ktime_get(), t);
-		else if (cmd != FUTEX_LOCK_PI && !(op & FUTEX_CLOCK_REALTIME))
-			t = timens_ktime_to_host(CLOCK_MONOTONIC, t);
+		ret = futex_init_timeout(cmd, op, &ts, &t);
+		if (ret)
+			return ret;
 		tp = &t;
 	}
 
@@ -3953,23 +3971,16 @@ SYSCALL_DEFINE6(futex_time32, u32 __user *, uaddr, int, op, u32, val,
 		struct old_timespec32 __user *, utime, u32 __user *, uaddr2,
 		u32, val3)
 {
-	struct timespec64 ts;
+	int ret, cmd = op & FUTEX_CMD_MASK;
 	ktime_t t, *tp = NULL;
-	int cmd = op & FUTEX_CMD_MASK;
+	struct timespec64 ts;
 
-	if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
-		      cmd == FUTEX_WAIT_BITSET ||
-		      cmd == FUTEX_WAIT_REQUEUE_PI)) {
+	if (utime && futex_cmd_has_timeout(cmd)) {
 		if (get_old_timespec32(&ts, utime))
 			return -EFAULT;
-		if (!timespec64_valid(&ts))
-			return -EINVAL;
-
-		t = timespec64_to_ktime(ts);
-		if (cmd == FUTEX_WAIT)
-			t = ktime_add_safe(ktime_get(), t);
-		else if (cmd != FUTEX_LOCK_PI && !(op & FUTEX_CLOCK_REALTIME))
-			t = timens_ktime_to_host(CLOCK_MONOTONIC, t);
+		ret = futex_init_timeout(cmd, op, &ts, &t);
+		if (ret)
+			return ret;
 		tp = &t;
 	}