Processor Control Flow Monitoring Using Signatured Instruction Streams

This paper presents an innovative approach, called signatured instruction streams (SIS), to the on-line detection of control flow errors caused by transient and intermittent faults. At compile time an application program is appropriately partitioned into smaller subprograms, and cyclic codes, or signatures, characterizing the control flow of each subprogram are generated and embedded in the object code. At runtime, special built-in hardware regenerates these signatures using runtime information and compares them to the precomputed signatures. A mismatch indicates the detection of an error. A demonstration system, based on the MC68000 processor, has been designed and built. Fault insertion experiments have been performed using the demonstration system. The demonstration system, using 17 percent hardware overhead, is able to detect 98 percent of faults affecting the control flow and 82 percent of all randomly inserted faults.