--- a/src/impl/vm_impl.cbc	Fri Jan 24 15:22:44 2020 +0900
+++ b/src/impl/vm_impl.cbc	Fri Jan 24 16:17:25 2020 +0900
@@ -28,6 +28,8 @@
     vm_impl->loaduvm_loop = C_loaduvm_loopvm_impl;
     vm_impl->allocuvm_check_newsz = C_allocuvm_check_newszvm_impl;
     vm_impl->allocuvm_loop = C_allocuvm_loopvm_impl;
+    vm_impl->copyuvm_check_null = C_copyuvm_check_nullvm_impl;
+    vm_impl->copyuvm_loop = C_copyuvm_loopvm_impl;
     vm->init_vmm = C_init_vmmvm_impl;
     vm->kpt_freerange = C_kpt_freerangevm_impl;
     vm->kpt_alloc = C_kpt_allocvm_impl;
@@ -118,7 +120,7 @@
 
 __code copyuvmvm_impl(struct vm_impl* vm, pde_t* pgdir, uint sz, __code next(...)) {
 
-    goto next(...);
+    goto copyuvm_check_nullvm_impl(vm, pgdir, sz, __code next(...));
 }
 
 __code uva2kavm_impl(struct vm_impl* vm, pde_t* pgdir, char* uva, __code next(...)) {

--- a/src/impl/vm_impl.h	Fri Jan 24 15:22:44 2020 +0900
+++ b/src/impl/vm_impl.h	Fri Jan 24 16:17:25 2020 +0900
@@ -15,15 +15,18 @@
     int ret;
     char* mem;
     char* uva;
+    pde_t* d;
+    uint ap;
 
     __code kpt_alloc_check_impl(Type* vm_impl, __code next(...));
     __code loaduvm_ptesize_check(Type* vm_impl, __code next(...));
     __code loaduvm_loop(Type* vm_impl, uint i, pte_t* pte, uint sz, __code next(...));
     __code allocuvm_check_newsz(Type* vm_impl, pde_t* pgdir, uint oldsz, uint newsz, __code next(...));
     __code allocuvm_loop(Type* vm_impl, pde_t* pgdir, uint oldsz, uint newsz, uint a, __code next(...));
+    __code copyuvm_check_null(Type* vm_impl, pde_t* pgdir, uint sz, __code next(...));
+    __code copyuvm_loop(Type* vm_impl,pde_t* pgdir, uint sz, pde_t* d, pte_t* pte, uint pa, uint i, uint ap, char* mem, __code next(int ret, ...));
     __code clearpteu_check_ptevm_impl(Type* vm_impl, pde_t* pgdir, char* uva,  __code next(...));
     __code next(...);
- 
 
 } vm_impl;
 

--- a/src/impl/vm_impl_private.cbc	Fri Jan 24 15:22:44 2020 +0900
+++ b/src/impl/vm_impl_private.cbc	Fri Jan 24 16:17:25 2020 +0900
@@ -213,3 +213,59 @@
 
     goto next(ret, ...);
 }
+
+__code copyuvm_check_nullvm_impl(struct vm_impl* vm_impl, pde_t* pgdir, uint sz, __code next(int ret, ...)) {
+    pde_t *d;
+    pte_t *pte;
+    uint pa, i, ap;
+    char *mem;
+
+    // allocate a new first level page directory
+    d = kpt_alloc();
+    if (d == NULL ) {
+        ret = NULL;
+        goto next(ret, ...);
+    }
+    i = 0;
+
+    goto copyuvm_loopvm_impl(vm_impl, pgdir, sz, *d, *pte, pa, i, ap, *mem, next(ret, ...));
+}
+
+__code copyuvm_loopvm_impl(struct vm_impl* vm_impl, pde_t* pgdir, uint sz, pde_t* d, pte_t* pte, uint pa, uint i, uint ap, char* mem, __code next(int ret, ...)) {
+
+    if (i < sz) { 
+        if ((pte = walkpgdir(pgdir, (void *) i, 0)) == 0) {
+            panic("copyuvm: pte should exist");
+        }
+
+        if (!(*pte & PE_TYPES)) {
+            panic("copyuvm: page not present");
+        }
+
+        pa = PTE_ADDR (*pte);
+        ap = PTE_AP (*pte);
+
+        if ((mem = alloc_page()) == 0) {
+            goto copyuvm_loop_bad(vm_impl, d, next(...));
+        }
+
+        memmove(mem, (char*) p2v(pa), PTE_SZ);
+
+        if (mappages(d, (void*) i, PTE_SZ, v2p(mem), ap) < 0) {
+            goto copyuvm_loop_bad(vm_impl, d, next(...));
+        }
+        goto copyuvm_loopvm_impl(vm_impl, pgdir, sz, d, pte, pa, i + PTE_SZ, ap, mem, next(ret, ...));
+    }
+    ret = d;
+    goto next(ret, ...);
+}
+
+__code copyuvm_loop_check_walkpgdir() {
+
+}
+
+__code copyuvm_loop_bad(struct vm_impl* vm_impl, pde_t* d, __code next(int ret, ...)) {
+    freevm(d);
+    ret = 0;
+    goto next(ret, ...);
+}