va0               369 vm.c             uint n, va0;
va0               373 vm.c               va0 = (uint)PGROUNDDOWN(va);
va0               374 vm.c               pa0 = uva2ka(pgdir, (char*)va0);
va0               377 vm.c               n = PGSIZE - (va - va0);
va0               380 vm.c               memmove(pa0 + (va - va0), buf, n);
va0               383 vm.c               va = va0 + PGSIZE;