typedef struct vm_impl<Impl, Isa> impl vm{
    __code kpt_alloc_check_impl(Type* vm_impl, __code next(...));
    __code loaduvm_ptesize_check(Type* vm_impl, __code next(int ret, ...));
    __code loaduvm_loop(Type* vm_impl, uint i, pte_t* pte, uint sz, __code next(int ret, ...));
    __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 uva2ka_check_pe_types(Type* vm_impl, pde_t* pgdir, char* uva, __code next(...));
    __code paging_intvm_impl(Type* vm_impl, uint phy_low, uint phy_hi, __code next(...));
    __code copyout_loopvm_impl(Type* vm_impl, pde_t* pgdir, uint va, void* pp, uint len, __code next(...));
    __code switchuvm_check_pgdirvm_impl(Type* vm_impl, proc_struct* p, __code next(...));
    __code init_inituvm_check_sz(Type* vm_impl, pde_t* pgdir, char* init, uint sz, __code next(...));
    __code void_ret(Type* vm_impl);
    __code next(...);
} vm_impl;