typedef struct vm_impl<Impl, Isa> impl vm{
    union Data* vm_impl;
    uint i;
    pte_t* pte;
    uint sz;
    pde_t* pgdir;
    char* addr;
    struct inode* ip;
    uint offset;
    uint pa;
    uint n;
    uint oldsz;
    uint newsz;
    uint a;
    int ret;

    __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 next(...);
 

} vm_impl;