Federico Reghenzani

Qualifying the ability of integrated circuits to prevent or tolerate radiation-induced faults is essential for their use in the space environment or, in general, in safety-/mission-critical systems. Radiation effects represent a problem at high altitudes or outside of the Earth’s atmosphere, as well as at the ground level, due to package impurities and other manufacturing problems [13]. Therefore, their effects must not be ignored for certain high-integrity terrestrial applications.

Software-Implemented Hardware Fault Tolerance (SIHFT) is a modern approach for tackling random hardware faults of dependable systems employing solely software solutions. This work extends an automatic compiler-based SIHFT hardening tool called ASPIS, enhancing it with novel protection mechanisms and overhead-reduction techniques, also providing an extensive analysis of its compliance with the non-trivial workload of the open-source Real-Time Operating System FreeRTOS. A thorough experimental fault-injection campaign on an STM32 board shows how the system achieves remarkably high tolerance to single-event upsets and a comparison between the SIHFT mechanisms implemented summarises the tradeoff between the overhead introduced and the detection capabilities of the various solutions.

Tolerating hardware faults in modern architectures is becoming a prominent problem due to the miniaturization of the hardware components, their increasing complexity, and the necessity to reduce costs. Software-Implemented Hardware Fault Tolerance approaches have been developed to improve system dependability regarding hardware faults without resorting to custom hardware solutions. However, these come at the expense of making the satisfaction of the timing constraints of the applications/activities harder from a scheduling standpoint. This article surveys the current state-of-the-art of fault tolerance approaches when used in the context of real-time systems, identifying the main challenges and the cross-links between these two topics. We propose a joint scheduling-failure analysis model that highlights the formal interactions among software fault tolerance mechanisms and timing properties. This model allows us to present and discuss many open research questions with the final aim to spur future research activities.

In this position article, we motivate the necessity to introduce three software methods in spacecraft computing platforms in order to enable to use COTS components: SIHFT, mixed-criticality, and probabilistic timing analysis. We investigate the benefits and the drawbacks of these techniques, especially in terms of safety, by also analyzing the standards to identify the current limitations that do not allow such techniques to be used. Finally, we recap current and future works, highlighting possible changes to standards.