Continuous signature monitoring: low-cost concurrent detection of processor control errors

A low-cost approach to concurrent detection of processor control errors is presented that uses a simple hardware monitor and signatures embedded into the executing program. Existing signature-monitoring techniques detect a large portion of processor control errors at a fraction of the cost of duplication. Analytical methods developed in this study show that the new approach, continuous signature monitoring (CSM), makes major advances beyond existing techniques. CSM reduces the fraction of undetected control-flow errors by orders of magnitude, to less than 10/sup -6/, while the number of signatures reaches a theoretical minimum, being lowered by as much as three times to a range of 4-11%. Signature cost is reduced by placing CSM signatures at locations that minimize performance loss and (for some architectures) memory overhead. CSM exploits the program memory's SEC/DED code to decrease error-detection latency by as much as 1000 times, to 0.016 program memory cycles, without increasing memory overhead. This short latency allows transient faults to be tolerated. >