A semantic model of types and machine instructions for proof-carrying code

Proof-carrying code is a framework for proving the safety of machine-language programs with a machine-checkable proof. Previous PCC frameworks have defined type-checking rules as part of the logic. We show a universal type framework for proof-carrying code that will allow a code producer to choose a programming language, prove the type rules for that language as lemmas in higher-order logic, then use those lemmas to prove the safety of a particular program. We show how to handle traversal, allocation, and initialization of values in a wide variety of types, including functions, records, unions, existentials, and covariant recursive types.