Buffer overflow attacks have been causing serious security problems for decades. With more embedded systems networked, it becomes an important research problem to defend embedded systems against buffer overflow attacks. In this paper, we propose the Hardware/Software Address Protection (HSAP) technique to solve this problem. We first classify buffer overflow attacks into two categories (stack smashing attacks and function pointer attacks) and then provide two corresponding defending strategies. In our technique, hardware boundary check method and function pointer XOR method are used to protect a system against stack smashing attacks and function pointer attacks, respectively. Although the focus of the HSAP technique is on embedded systems because of the availability of hardware support, we show that the HSAP technique can be applied to any type of processors to defend against buffer overflow attacks. We use four classes of processors to illustrate that the applicability of our technique is independent of architectures. We experiment with our HSAP technique in ARM Evaluator-7T simulation development environments. The results show that our HSAP technique can defend a system against more types of buffer overflow attacks with little overhead than the previous work.