A Parametric Rely-Guarantee Reasoning Framework for Concurrent Reactive Systems

Reactive systems are composed of a well defined set of event handlers by which the system responds to environment stimulus. In concurrent environments, event handlers can interact with the execution of other handlers such as hardware interruptions in preemptive systems, or other instances of the reactive system in multicore architectures. The rely-guarantee technique is a suitable approach for the specification and verification of reactive systems. However, the languages in existing rely-guarantee implementations are designed only for “pure programs”, simulating reactive systems makes the program and rely-guarantee conditions unnecessary complicated. In this paper, we decouple the system reactions and programs using a rely-guarantee interface, and develop PiCore, a parametric rely-guarantee framework for concurrent reactive systems. PiCore has a two-level inference system to reason on events and programs associated to events. The rely-guarantee interface between the two levels allows the reusability of existing languages and their rely-guarantee proof systems for programs. In this work we show how to integrate in PiCore two existing rely-guarantee proof systems. This work has been fully mechanized in Isabelle/HOL. As a case study, we have applied PiCore to the concurrent buddy memory allocation of a real-world OS, providing a verified low-level specification and revealing bugs in the C code.