Inverse-engineering a simple real-time program

Reverse engineering of interrupt-driven real-time programs with timing constraints is a particularly challenging research area, because the functional behaviour of a program, and the non-functional timing requirements, are implicit and can be very difficult to discover. However, in this paper we present a significant advance in this area, which is achieved by modelling real-time programs with interrupts in the wide spectrum language WSL. A small example program is modelled in this way, and formal program transformations are used to derive various timing constraints and to “inverse engineer” a formal specification of the program. (We use the term “inverse engineering” to mean “reverse engineering achieved by formal program transformations).