This paper describes a novel approach to assess detection mechanisms and their diagnostic coverage, implemented using embedded software, designed to identify random hardware failures affecting digital components. In the literature, many proposals adopting fault injection methods are available, with most of them focusing on transient faults and not considering the functional safety standards requirements. This kind of proposal can benefit developers involved in the automotive market, where strict safety and cost requirements make the adoption of software-only strategies convenient. Hence, we have focused our efforts on compliance with the ISO 26262 automotive functional safety standard. The approach concerns permanent faults affecting microcontrollers and it provides a mapping between the failure mode described in part 11 of the Standard and the chosen fault models. We propose a test bench designed to inject permanent failures into an emulated microcontroller and determine which of them are detected by the embedded software. The main contribution of this paper is a novel fault injection manager integrated with the open-source software GCC, GDB, and QEMU. This test bench manages all the assessment phases, from fault generation to fault injection and the ISA emulation management, up to the classification of the simulation results.

As system designers are transitioning to the usage of pre-existing software architectural elements to reduce time-to-market and costs, they face challenges in safety-critical applications. Pre-existing software may have been implemented without following any safety and/or quality standard, and its documentation may be incomplete or unclear. As recommended by part 6 of the functional safety standard ISO 26262 (product development at the software level), stringent rules and guidelines must be followed during the implementation of a new software. The qualification of a pre-existing software according to ISO 26262 may hence be very time consuming and expensive if not addressed in a structured way. This work presents STPA for Pre-existing Software (STPA-PES), a new software hazardous behavior analysis approach designed to identify criticalities or abnormal conditions in complex pre-existing software to be mitigated with adequate safety measures. The major challenge in such a process consists in the definition of a model that correctly represents the system under analysis when the architectural design of pre-existing software is not available. As a relevant example, the proposed approach is finally applied to dynamic memory allocator (DynMA) in Linux kernel to show how STPA-PES is able to derive safety requirements of this software architectural element.