Core-Local Reasoning and Predictable Cross-Core Communication with M3

Modern cyber-physical systems often require security, heterogeneity, and real-time operation from their hardware platform and operating system. However, highly predictable real-time operating systems such as FreeRTOS do not employ strong component isolation required for platform security. Microkernels implement such isolation using virtual memory and code running in the privileged CPU mode, complicating real-time analysis. In this work, we start with a different architectural approach: M3 is an existing hardware/software co-design for heterogeneous systems that features strong isolation between cores. However, the real-time properties of this platform have not been investigated. We first survey M3{\prime}s current state for real-time applicability and study both the communication latencies in comparison to other systems and M3's different approach to task priorities. Furthermore we improve M3's real-time applicability by adding a network-on-chip traffic regulation and enabling the enforcement of resource limits. With these additions, M3 enables local reasoning about application execution. We perform the evaluation with an FPGA-based hardware prototype and in simulation based on gem5.