An Event-based Formal Framework for Dynamic Software Update

Dynamic Software Update (DSU) is a technique to upgrade running programs without shutting them down. DSU can improve system availability and maintenance flexibility. However, its adoption in practice is still limited due to the risk of system misbehavior that careless DSU may bring. To reduce this risk we propose a formal framework for the specification and verification of DSU. Different from previous approaches where DSU is described from the viewpoint of program's internal state transitions, our framework focuses on program's external behavior and its effect on its environment. This more abstract view avoids over specification of DSU and allows for better DSU flexibility. Based on this framework, we also devise a mechanism that automatically synthesizes runtime monitors to improve DSU timeliness without compromising its safety.