Multimode Security-Aware Real-Time Scheduling on Multiprocessors

Embedded real-time systems generally execute in a predictable and deterministic manner to deliver critical functionality within stringent timing constraints. However, the predictable execution behavior leaves the system vulnerable to schedule-based attacks. In this article, we present a multimode security-aware real-time scheduling scheme to counteract schedule-based attacks on multiprocessor real-time systems. To mitigate the vulnerability to the schedule-based attack, we propose a multimode scheduling method to reduce the accumulative attack effective window (AEW) of multiple victim tasks and prevent the untrusted tasks from executing during the AEW by distinctively scheduling mixed-trust tasks according to the system mode. To avoid the protection degradation due to the excessive blocking of untrusted tasks, we introduce a protection window for multiple victims on multiprocessors by analyzing the system protection capability limit under the system schedulability constraint. Furthermore, to maximize the protection capability of the multimode security-aware scheduling strategy on a multiprocessor platform, we also propose a security-aware packing algorithm to balance the workloads of mixed-trust tasks on different processors using a mixed-trust worst-fit decreasing heuristic strategy. The experimental results demonstrate that our proposed approach significantly outperforms the state-of-the-art method. Specifically, the AEW ratio and the AEW untrusted execution time ratio are reduced by 18.8% and 62.8%, respectively, while the defense success rate against ScheduLeak attack is improved by 16.3%.