Fault Injection and selective Hardening of Real Time Operating Systems

Real-Time operating systems provide deterministic behavior for systems operating under strict deadline requirements. Beyond managing tasks and resources, operating systems offer a hardware abstraction layer that enables developers to concentrate on application logic instead of low-level hardware details. However, both systems with and without operating system support are vulnerable to ionizing radiation from sources such as cosmic rays, solar wind, electromagnetic interference, and other deep space phenomena. These radiation effects can lead to unintended, often catastrophic, failures ranging from system malfunctions to complete device breakdowns. Real-Time operating systems are commonly deployed in safety-critical applications including railway systems, military drones, medical devices and transportation systems in cars and airplanes; where even a minor failure could have dire consequences for human life. Thus, it is crucial to investigate mitigation techniques at both the hardware and software levels. This thesis focuses exclusively on software-based mitigation strategies within an RTOS environment, specifically using FreeRTOS as the platform under study. More precisely, the work targets the FreeRTOS port for posix and Windows, which allows a complete FreeRTOS operating system to run as a hosted user-space application on general-purpose operating systems such as gnu/Linux, FreeBSD, Solaris, Mac OS or Windows. For the purposes of this thesis, the system of choice is gnu/Linux. The study begins with a fault injection investigation designed to identify critical components of the rtos that may compromise its expected behavior under radiation-induced disturbances. This research employs a software fault injection technique to emulate the effects of radiation on electronic devices, focusing on two primary error types: the seu, which causes random bit flips in memory; and the sehe, which results in permanent "stuck-at" memory states. Software fault injection offers a cost-effective alternative to specialized radiation testing facilities while still providing meaningful insights. Based on the data collected from this investigation, the objective of this thesis is to implement a targeted, selective hardening strategy to reinforce the identified vulnerable areas of the rtos under study.