Memory Monitor Module Design Based On Leon3 Processor

The embedded system is easily to be attacked by hostile software because of its own disadvantage. The buffer overflow attack is the most popular attack method and causes enormous economic lost every year. Based on the analysis of various methods defending buffer overflow attack, we find that these methods either protect the program stack data section or the heap data section but always ignore the global data section. Some may protects all data section but can hardly be implemented by the reason that it relys on the source code seriously or has program compatibility problems. We can also figure out that how much bound information can we get decides the complication degree and defending granularity of the security module we construct.In this paper, based on studying the security running mechanism of embedded processor in an instruction level, we will design a hardware memory monitor module, which mainly aims at buffer overflow attack. The memory monitor module includes three function units ,which are stack protection module ,heap protection module and global data protection module. Each unit extracts necessary information from processor pipeline and then uses these information to check whether the program behavior is legal. We adopt a opening source processor leon3 as our experiment platform. According to the characteristic of leon3, the memory monitor module is combined with the leon3 processor and check whether the memory operation is legal in real time . The experiment results on FPGA board shows that our memory monitor module can effectively defend majority buffer overflow attacks. The monitor module brings 5% hardware overhead and 0.1% performance overhead.The innovation of our work is that the functionality's implementation of our memory monitor module does not rely on the source code and can perform security checking through dynamic method completely. The monitor realizes protection to all program's data space, not only part of it, like other defending method does, and can prevents majority buffer overflow attacks presently. It functions parallel to the embedded processor, so has neglectable performance influence to the original system.