Security-Aware Scheduling of Real-Time Tasks on Multi-core Processors

Abstract

Modern real-time systems are increasingly exposed to timing-based security threats due to their predictable task scheduling. When scheduling tasks for real-time execution, a predictable execution pattern is needed to ensure all tasks will meet their deadlines. A common practice is to employ a fixed-priority scheduler, a deterministic scheduling algorithm always choosing the same task to execute every time it’s given the same conditions. Schedule-based attacks exploit this determinism, enabling adversaries to manipulate or extract sensitive information by aligning their execution with critical tasks. To counter this, schedule randomization has emerged as a potential solution, introducing controlled unpredictability into task execution.

This thesis investigates the application of schedule randomization in multi-core realtime systems, particularly when tasks are pre-allocated to specific cores. The study builds upon TaskShuffler, an already existing algorithm that introduces randomness into the previously deterministic fixed priority scheduler. This algorithm, designed for single-core systems, is now extended for multi-core use. Further, we examine techniques to mitigate or circumvent schedule-based attacks targeting multi-core systems. We also extend the concept of schedule entropy, a “randomness” metric, to better suit multi-core systems, as well as introduce new security-aware metric to capture the risk of common types of targeted attacks. We evaluate the security and performance impact of our methods by by simulating tasks execution on multi-core processors under different task sets and configurations. This provides insights into how core assignment and priority relations affect the system’s exposure to schedulebased attacks. Such insights may help the system designer to strengthen the security of the systems by allocating or not allocating certain tasks to certain cores at design time.