MemMON: run-time off-chip detection for memory access violation in embedded systems

Abstract

To deploy a memory protection mechanism, it requires CPU support hardware components like Memory Management Unit (MMU) or Memory Protection Unit (MPU). However, in embedded system, most of microcontrollers lack to be equipped these features because they cause the system incurred hardware cost and performance penalty. In this paper, a method to detect memory corruption at run-time without incurring hardware cost is proposed. Embedded system processor does not require having MMU or MPU. Off-chip detection based on FPGA by hooking on memory bus to monitor memory access for multitasking Realtime Operating System (RTOS) application is explored. Our solution, called MemMON, by combining hardware/software can detect memory access error such as task's stack overflow, task's reading/writing to code/data segments of the other tasks or memory access violation to OS kernel efficiently. In experimental evaluation, a comparison of realtime schedulability is carried out for both using and not using MemMON. Using our MemMON causes realtime schedulability of the system dropped-off about 3 times.