Modular Verification of Assembly Code with Stack-Based Control Abstractions
Last modified: Wed Nov 22 20:51:15 2006 GMT.
AbstractRuntime stacks are critical components of any modern software---they are used to implement powerful control structures such as function call/return, stack cutting and unwinding, coroutines, and thread context switch. Stack operations, however, are very hard to reason about: there are no known formal specifications for certifying C-style setjmp/longjmp, stack cutting and unwinding, or weak continuations (in C--). In many proof-carrying code (PCC) systems, return code pointers and exception handlers are treated as general first-class functions (as in continuation-passing style) even though both should have more limited scopes.
In this paper we show that stack-based control abstractions follow a much simpler pattern than general first-class code pointers. We present a simple but flexible Hoare-style framework for modular verification of assembly code with all kinds of stack-based control abstractions, including function call/return, tail call, setjmp/longjmp, weak continuation, stack cutting, stack unwinding, multi-return function call, coroutines, and thread context switch. Instead of presenting a specific logic for each control structure, we develop all reasoning systems as instances of a generic framework. This allows program modules and their proofs developed in different PCC systems to be linked together. Our system is fully mechanized. We give the complete soundness proof and a full verification of several examples in the Coq proof assistant.
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