vgetrandom
ssize_t ret = vgetrandom(&val, sizeof(val), 0);
vgetrandom(weird_size, sizeof(weird_size), 0);
ssize_t ret = vgetrandom(weird_size, sizeof(weird_size), 0);
ksft_assert(vgetrandom(weird_size, sizeof(weird_size), 0) == sizeof(weird_size));