vm_startcopy
bzero(&vm->vm_startcopy,
(char *)&vm->vm_endcopy - (char *)&vm->vm_startcopy);
bcopy(&vm1->vm_startcopy, &vm2->vm_startcopy,
(caddr_t)&vm1->vm_endcopy - (caddr_t)&vm1->vm_startcopy);
bcopy(&oldvmspace->vm_startcopy, &newvmspace->vm_startcopy,
(caddr_t)&oldvmspace->vm_startcopy);