Machine instruction syntax and semantics in higher order logic

Proof-carrying code and other applications in computer security require machine-checkable proofs of properties of machine-language programs. These in turn require axioms about the opcode/operand encoding of machine instructions and the semantics of the encoded instructions. We show how to specify instruction encodings and semantics in higher-order logic, in a way that preserves the factoring of similar instructions in real machine architectures. We show how to automatically generate proofs of instruction decodings, global invariants from local invariants, Floyd-Hoare rules and predicate transformers. all from the specification of the instruction semantics. Our work is implemented in ML and Twelf, and all the theorems are checked in Twelf.