hat_setup
(void) hat_setup(as->a_hat, HAT_ALLOC);
(void) hat_setup(p->p_as->a_hat, HAT_INIT);
void hat_setup(struct hat *, int);
hat_setup(save_as->a_hat, 0); /* switch back from kernel hat */
hat_setup(kas.a_hat, 0); /* switch to kernel-only hat */