int getentropy(void *buf, size_t buflen)
{
	int ret;

	if (buflen > 256)
		goto failure;
	ret = getrandom(buf, buflen, 0);
	if (ret < 0)
		return ret;
	if (ret == buflen)
		return 0;
failure:
	errno = EIO;
	return -1;
}