Architectural support for security and reliability in embedded processors

Security and reliability in processor based systems are concerns requiring adroit solutions. Security is often compromised by code injection attacks, jeopardizing even trusted software . Reliability is of concern, where unintended code is executed in modern processors with ever smaller feature sizes and low voltage swings causing bit flips. Countermeasures by software-only approaches increase code size and therefore significantly reduce performance. Hardware assisted approaches use additional hardware monitors and thus incur considerably high hardware cost and have scalability problems. Considering reliability and security issues during the design of an embedded system has its advantages as this overcomes the limitations of existing solutions. The research work presented in this thesis combines two elements: one, defining a hardware software design framework for reliability and security monitoring at the granularity of micro-instructions, and two, applying this framework for real world problems. At a given time, a processor executes only a few instructions and large part of the processor is idle. Utilizing these idling hardware components by sharing them with the monitoring hardware, to perform security and reliability monitoring reduces the impact of the monitors on hardware cost. Using micro-instruction routines within the machine instructions, allows us to share most of the monitoring hardware. Therefore, our technique requires little hardware overhead in comparison to having additional hardware blocks outside the processor. This reduction in overhead is due to maximal sharing of hardware resources of the processor. Our framework is superior to software-only techniques as the monitoring routines are formed with micro-instructions and therefore reduces code size and execution time overheads, since they occur in parallel with machine instructions. This dissertation makes four significant contributions to the field of security and reliability on embedded processor research and they are: (i) proposed a security ...