Inherent Diversity in Replicated Architectures

In this paper, we report our ongoing investigations of the inherent non-determinism in contemporary execution environments that can potentially lead to divergence in state of a multi-channel hardware/software system. Our approach involved setting up of experiments to study execution path variability of a simple program by tracing its execution at the kernel level. In the first of the two experiments, we analyzed the execution path by repeated execution of the program. In the second, we executed in parallel two instances of the same program, each pinned to a separate processor core. Our results show that for a program executing in a contemporary hardware/software platform, there is sufcient path non-determinism in kernel space that can potentially lead to diversity in replicated architectures. We believe the execution non-determinism can impact the activation of residual systematic faults in software. If this is true, then the inherent diversity can be used together with architectural means to protect safety related systems against residual systematic faults in the operating systems.