参照元

説明

引数

返り値

参考

実装

int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds,
		struct timespec *end_time)
{
	struct poll_wqueues table;
 	int err = -EFAULT, fdcount, len, size;
	/* Allocate small arguments on the stack to save memory and be
	   faster - use long to make sure the buffer is aligned properly
	   on 64 bit archs to avoid unaligned access */
	long stack_pps[POLL_STACK_ALLOC/sizeof(long)];
	struct poll_list *const head = (struct poll_list *)stack_pps;
 	struct poll_list *walk = head;
 	unsigned long todo = nfds;
	if (nfds > rlimit(RLIMIT_NOFILE))
		return -EINVAL;
	len = min_t(unsigned int, nfds, N_STACK_PPS);
	for (;;) {
		walk->next = NULL;
		walk->len = len;
		if (!len)
			break;

		if (copy_from_user(walk->entries, ufds + nfds-todo,
					sizeof(struct pollfd) * walk->len))
			goto out_fds;
		todo -= walk->len;
		if (!todo)
			break;

		len = min(todo, POLLFD_PER_PAGE);
		size = sizeof(struct poll_list) + sizeof(struct pollfd) * len;
		walk = walk->next = kmalloc(size, GFP_KERNEL);
		if (!walk) {
			err = -ENOMEM;
			goto out_fds;
		}
	}

	poll_initwait(&table);
	fdcount = do_poll(nfds, head, &table, end_time);
	poll_freewait(&table);
	for (walk = head; walk; walk = walk->next) {
		struct pollfd *fds = walk->entries;
		int j;

		for (j = 0; j < walk->len; j++, ufds++)
			if (__put_user(fds[j].revents, &ufds->revents))
				goto out_fds;
  	}
	err = fdcount;
out_fds:
	walk = head->next;
	while (walk) {
		struct poll_list *pos = walk;
		walk = walk->next;
		kfree(pos);
	}
	return err;
}

コメント


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Last-modified: 2018-01-11 (木) 16:20:11