SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events,
		int, maxevents, int, timeout)
{
	int error;
	struct file *file;
	struct eventpoll *ep;

	/* The maximum number of event must be greater than zero */
	if (maxevents <= 0 || maxevents > EP_MAX_EVENTS)
		return -EINVAL;

	/* Verify that the area passed by the user is writeable */
	if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event))) {
		error = -EFAULT;
		goto error_return;
	}

	/* Get the "struct file *" for the eventpoll file */
	error = -EBADF;
	file = fget(epfd);
	if (!file)
		goto error_return;

	/*
	 * We have to check that the file structure underneath the fd
	 * the user passed to us _is_ an eventpoll file.
	 */
	error = -EINVAL;
	if (!is_file_epoll(file))
		goto error_fput;

	/*
	 * At this point it is safe to assume that the "private_data" contains
	 * our own data structure.
	 */
	ep = file->private_data;

	/* Time to fish for events ... */
	error = ep_poll(ep, events, maxevents, timeout);

error_fput:
	fput(file);
error_return:

	return error;
}

Unknown