os_getrandom
ret = os_getrandom(v, max_longs * sizeof(*v), 0);
ssize_t os_getrandom(void *buf, size_t len, unsigned int flags);
extern ssize_t os_getrandom(void *buf, size_t len, unsigned int flags);
if (os_getrandom(rng_seed, sizeof(rng_seed), 0) == sizeof(rng_seed)) {