A Model-Based Concept for RTOS Portability

The amount and diversity of connected computing platforms in the Internet of Things (IoT) is expected to increase exponentially throughout the next years, together with their dependability requirements. This imposes many challenges to software and hardware developers and calls for safe and secure real-time operating systems (RTOSs) that are portable to different or changing hardware. Middleware ports, including RTOS ports, must keep functional and non-functional behavior constant towards the application. Current middleware portability approaches for embedded systems, however, are arduous and error prone. We present a novel approach towards portability of embedded RTOSs based on the formal, hardware-independent and detailed specification of RTOS kernels. With additional models of relevant MCU properties and instruction set architectures (ISA), we are able to generate low level RTOS code for different target architectures. This paper focuses on the hardware-independent model of the context switch within a multi-tasking RTOS. With the general approach, we expect to (1) reduce the effort for maintaining and porting RTOS code, as well as the (2) likeliness for errors, (3) make it easier to test new kernel concepts during OS development, (4) improve security by modeling different levels of access permissions for memory or peripherals depending on the execution mode, and (5) improve safety by formally proving the correctness and consistency of the models.