Bridging the Gap between RTL and Software Fault Injection

Protecting programs against hardware fault injection requires accurate software fault models. However, typical models, such as the instruction skip, do not take into account the microarchitecture specificities of a processor. We propose in this article an approach to study the relation between faults at the Register Transfer Level (RTL) and faults at the software level. The goal is twofold: accurately model RTL faults at the software level and materialize software fault models to actual RTL injections. These goals lead to a better understanding of a system's security against hardware fault injection, which is important to design effective and cost-efficient countermeasures. Our approach is based on the comparison between results from RTL simulations and software injections (using a program mutation tool). Various analyses are included in this article to give insight on the relevance of software fault models, such as the computation of a coverage and fidelity metric, and to link software fault models to hardware RTL descriptions. These analyses are applied on various single-bit and multiple-bit injection campaigns to study the faulty behaviors of a RISC-V processor.