vmspace_fork
vmres->vr_vmspace = vmspace_fork(p->p_vmspace, NULL, NULL); /* XXX order */
struct vmspace *vmspace_fork(struct vmspace *origvm,
p2->p_vmspace = vmspace_fork(p1->p_vmspace, p2, lp2);
newvmspace = vmspace_fork(vmcopy, NULL, NULL);
newvmspace = vmspace_fork(oldvmspace, NULL, NULL);