Abstract. Online testing of computer systems is crucial in contexts such as the safety-critical domain, where the software is usually made of functional code, which is the code implementing the application-specific functionalities, and non-functional code, which implements auxiliary functionalities, e.g., test routines. By periodically running a test routine it is possible to satisfy the high dependability requirements mandated by regulators, and defined in safety standards such as ISO26262, IEC61508, and CENELEC EN 5012X. Self-Test Libraries (STLs) are a form of software-based self-test, widely used in safety-related applications. The main drawback of this safety mechanism is the overhead imposed on the execution of the functional code, and reducing this overhead is a well-known challenge in research. We propose here HUSTLE, a Hardware Unit for STL Efficient execution, which can be integrated into the chip design with no modification to the CPU’s internal logic. We also propose a scheduling mechanism that allows HUSTLE to efficiently execute self-tests, by exploiting the CPU’s idle time. This is achieved by storing test code in a separate memory and sending instructions to the CPU, bypassing the Instruction Cache, thus allowing to reduce the overall execution time and the cache interference of STL, while CPU utilization increases.

Keywords: Software-Based Self-Test, Safety-Critical Systems, Embedded Systems Testing.