Abstract Porting software to new target architectures is a common challenge, particularly when dealing with low-level functionality in drivers or OS kernels that interact directly with hardware. Traditionally, adapting code for different hardware platforms has been a manual and error-prone process. However, with the growing demand for dependability and the increasing hardware diversity in systems like the IoT, new software development approaches are essential. This includes rigorous methods for verifying and automatically porting Real-Time Operating Systems (RTOS) to various devices. Our framework addresses this challenge through formal methods and code generation for embedded RTOS. We demonstrate a hardware-specific part of a kernel model in Event-B, ensuring correctness according to the specification. Since hardware details are only added in late modeling stages, we can reuse most of the model and proofs for multiple targets. In a proof of concept, we refine the generic model for two different architectures, also ensuring safety and liveness properties. We then showcase automatic low-level code generation from the model. Finally, a hardware-independent factorial function model illustrates more potential of our approach.

Current approaches for portability of real-time operating systems (RTOSs) for embedded systems are largely based on manual coding, which is arduous and error prone. With increasing dependability requirements for cyber physical systems, specially within the Internet of Things (IoT), along with the expected great diversity of hardware platforms, software platforms will only remain competitive in the long run if they guarantee correct operation and easy deployment to every hardware platform. In this scenario, a new approach to the development and portability of RTOSs that guarantees correct implementations for all current and future devices and hardware architectures becomes indispensable.We present a framework for automatic RTOS portability that integrates model-based design and formal methods into dependable embedded software development. We focus specially on modeling the interaction between software and hardware in order to generate low-level code. This enables automatic portability for hardware-related parts of the OS (i.e., context switching, memory management, security aspects, etc,) as well as for on-chip peripheral drivers (i.e., timers, I/O, etc.).With our framework we will be able to prove the consistency of the refinements as well as that the RTOS model fulfills various functional and non-functional requirements. Automatic code generation guarantees that the model is correctly translated to machine language, avoiding implementation mistakes common to manual coding. Changes on the software, for bug fixes or testing of new concepts, for example, do not require knowledge of the target architectures, since they are done on the model and are immediately reflected in all implementations upon code generation, assuring consistency across platforms.

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.