A Formal Modeling Approach for Portable Low-Level OS Functionality

The increasing dependability requirements and hardware diversity of the Internet of Things (IoT) pose a challenge to developers. New approaches for software development that guarantee correct implementations will become indispensable. Specially for Real Time Operating Systems (RTOSs), automatic porting for all current and future devices will also be required. As part of our framework for embedded RTOS portability, based on formal methods and code generation, we present our approach to formally model low-level operating-system functionality using Event-B. We show the part of our RTOS model where the switch into the kernel and back to a task happens, and prove that the model is correct according to the specification. Hardware details are only introduced in late refinements, which allows us to reuse most of the RTOS model and proofs for several target platforms. As a proof of concept, we refine the generic model to two different architectures and prove safety and liveness properties of the models.