Real-Time OS with Memory Protection using Static Memory Layout

Abstract

These days, memory protection is an important feature for embedded and real-time systems. Some embedded processors, therefore, have a memory protection unit (MPU), which is a hardware designed exclusively for memory protection. A MPU has limited number of region to set memory protection attributes. So when using a MPU, it needs to perform memory layout statically so that memory regions having the same memory protection attribute are located successively. In this paper, we describe TOPPERS/HRP2 kernel, which is a real-time OS with memory protection. HRP2 kernel performs memory layout statically in static configuration. Then HRP2 kernel supports memory protection using a MPU. We evaluated the overhead caused by memory protection in HRP2 kernel, by comparison with a real-time OS without memory protection.