Duplication-Based Fault Tolerance for RISC-V Embedded Software

Embedded devices play critical roles in security and safety, demanding robust protection against fault injection attacks. Among the myriad of fault effects, the instruction skip fault model stands out due to its recurrent manifestation in silicon devices. Furthermore, the continually evolving landscape of hardware attacks facilitates increasingly sophisticated exploits by achieving multiple instruction skips. In this work, we propose an extension of the RISC-V debug specification which enables efficient fault injection testing of the firmware executed on an FPGA-emulated core under a commonly observed instruction skip fault model. We use insights from a fault injection campaign to harden and protect potentially exploitable instructions and propose an assembly level duplication-based approach for software fault tolerance against instruction skip applied to RISC-V architecture. Additionally, we provide a custom debugger implementation which accelerates fault injection campaign by factor of ten. By combining fault injection testing and a generic instruction duplication technique, our methodology can increase fault tolerance of the reference software while having minimal performance loss and code size overhead.