swrand_get_entropy
static int swrand_get_entropy(uint8_t *ptr, size_t len, boolean_t);
(void) swrand_get_entropy((uint8_t *)swrand_XKEY, HASHSIZE, B_TRUE);
(void) swrand_get_entropy(buf, len, B_TRUE);
(void) swrand_get_entropy(buf, len, B_FALSE);