Implementation of Control Flow Checking—A New Perspective Adopting Model-Based Software Design

A common requirement of embedded software in charge of safety tasks is to guarantee the identification of random hardware failures (RHFs) that can affect digital components. RHFs are unavoidable. For this reason, the functional safety standard devoted to automotive applications requires embedded software designs able to detect and eventually mitigate them. For this purpose, various software-based error detection techniques have been proposed over the years, focusing mainly on detecting control flow errors. Many control flow checking (CFC) algorithms have been proposed to accomplish this task. However, applying these approaches can be difficult because their respective literature gives little guidance on their practical implementation in high-level programming languages, and they have to be implemented in low-level code, e.g., assembly. Moreover, the current trend in the automotive industry is to adopt the so-called model-based software design approach, where an executable algorithm model is automatically translated into C or C++ source code. This paper presents two novelties: firstly, the compliance of the experimental data on the capabilities of control flow checking (CFC) algorithms with the ISO 26262 automotive functional safety standard; secondly, by implementing the CFC algorithm in the application behavioral model, the off-the-shelves code generator seamlessly produces the hardened source code of the application. The assessment was performed using a novel fault injection environment targeting a RISC-V (RV32I) microcontroller.