Automating Object Transformations for Dynamic Software Updating

Dynamic software updating (DSU) systems eliminate costly downtime by dynamically fixing bugs and adding features to executing programs. Given a static code patch, most DSU systems can construct the run-time code changes automatically. However, a dynamic update must also specify how to change the running program’s execution state, e.g., its stack and heap, to be compatible with the new code. Constructing such state transformations correctly and automatically remains an open problem. This paper presents a solution called Targeted Object Synthesis (TOS). TOS first executes the same tests on the old and new program versions separately, observing the program state at key points. Given two corresponding states, TOS matches corresponding objects between the two versions, and synthesizes the simplest-possible function to transform old version objects to their corresponding new versions. We show the efficacy of TOS by inferring transformation functions for actual updates to four open-source server programs.