Commit f801073f authored by Darren Hart's avatar Darren Hart Committed by Thomas Gleixner
Browse files

futex: split out futex value validation code 



Refactor the code to validate the expected futex value in order to
reuse it with the requeue_pi code.

Signed-off-by: default avatarDarren Hart <dvhltc@us.ibm.com>
Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 9121e478

kernel/futex.c

+72 −44
Original line number Diff line number Diff line
@@ -1398,42 +1398,29 @@ static void futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q *q, 
	__set_current_state(TASK_RUNNING);

}



static int futex_wait(u32 __user *uaddr, int fshared,

		      u32 val, ktime_t *abs_time, u32 bitset, int clockrt)

/**

 * futex_wait_setup() - Prepare to wait on a futex

 * @uaddr:	the futex userspace address

 * @val:	the expected value

 * @fshared:	whether the futex is shared (1) or not (0)

 * @q:		the associated futex_q

 * @hb:		storage for hash_bucket pointer to be returned to caller

 *

 * Setup the futex_q and locate the hash_bucket.  Get the futex value and

 * compare it with the expected value.  Handle atomic faults internally.

 * Return with the hb lock held and a q.key reference on success, and unlocked

 * with no q.key reference on failure.

 *

 * Returns:

 *  0 - uaddr contains val and hb has been locked

 * <1 - -EFAULT or -EWOULDBLOCK (uaddr does not contain val) and hb is unlcoked

 */

static int futex_wait_setup(u32 __user *uaddr, u32 val, int fshared,

			   struct futex_q *q, struct futex_hash_bucket **hb)

{

	struct hrtimer_sleeper timeout, *to = NULL;

	DECLARE_WAITQUEUE(wait, current);

	struct restart_block *restart;

	struct futex_hash_bucket *hb;

	struct futex_q q;

	u32 uval;

	int ret;



	if (!bitset)

		return -EINVAL;



	q.pi_state = NULL;

	q.bitset = bitset;



	if (abs_time) {

		to = &timeout;



		hrtimer_init_on_stack(&to->timer, clockrt ? CLOCK_REALTIME :

				      CLOCK_MONOTONIC, HRTIMER_MODE_ABS);

		hrtimer_init_sleeper(to, current);

		hrtimer_set_expires_range_ns(&to->timer, *abs_time,

					     current->timer_slack_ns);

	}



retry:

	q.key = FUTEX_KEY_INIT;

	ret = get_futex_key(uaddr, fshared, &q.key);

	if (unlikely(ret != 0))

		goto out;



retry_private:

	hb = queue_lock(&q);



	/*

	 * Access the page AFTER the hash-bucket is locked.

	 * Order is important:
@@ -1450,33 +1437,74 @@ static int futex_wait(u32 __user *uaddr, int fshared, 
	 * A consequence is that futex_wait() can return zero and absorb

	 * a wakeup when *uaddr != val on entry to the syscall.  This is

	 * rare, but normal.

	 *

	 * For shared futexes, we hold the mmap semaphore, so the mapping

	 * cannot have changed since we looked it up in get_futex_key.

	 */

retry:

	q->key = FUTEX_KEY_INIT;

	ret = get_futex_key(uaddr, fshared, &q->key);

	if (unlikely(ret != 0))

		goto out;



retry_private:

	*hb = queue_lock(q);



	ret = get_futex_value_locked(&uval, uaddr);



	if (unlikely(ret)) {

		queue_unlock(&q, hb);

	if (ret) {

		queue_unlock(q, *hb);



		ret = get_user(uval, uaddr);

		if (ret)

			goto out_put_key;

			goto out;



		if (!fshared)

			goto retry_private;



		put_futex_key(fshared, &q.key);

		put_futex_key(fshared, &q->key);

		goto retry;

	}



	if (uval != val) {

		queue_unlock(q, *hb);

		ret = -EWOULDBLOCK;

	}



	/* Only actually queue if *uaddr contained val.  */

	if (unlikely(uval != val)) {

		queue_unlock(&q, hb);

		goto out_put_key;

out:

	if (ret)

		put_futex_key(fshared, &q->key);

	return ret;

}



static int futex_wait(u32 __user *uaddr, int fshared,

		      u32 val, ktime_t *abs_time, u32 bitset, int clockrt)

{

	struct hrtimer_sleeper timeout, *to = NULL;

	DECLARE_WAITQUEUE(wait, current);

	struct restart_block *restart;

	struct futex_hash_bucket *hb;

	struct futex_q q;

	int ret;



	if (!bitset)

		return -EINVAL;



	q.pi_state = NULL;

	q.bitset = bitset;



	if (abs_time) {

		to = &timeout;



		hrtimer_init_on_stack(&to->timer, clockrt ? CLOCK_REALTIME :

				      CLOCK_MONOTONIC, HRTIMER_MODE_ABS);

		hrtimer_init_sleeper(to, current);

		hrtimer_set_expires_range_ns(&to->timer, *abs_time,

					     current->timer_slack_ns);

	}



	/* Prepare to wait on uaddr. */

	ret = futex_wait_setup(uaddr, val, fshared, &q, &hb);

	if (ret)

		goto out;



	/* queue_me and wait for wakeup, timeout, or a signal. */

	futex_wait_queue_me(hb, &q, to, &wait);