Internet-of-Things devices such as autonomous vehicular sensors, medical devices, and industrial cyber-physical systems commonly rely on small, resource-constrained microcontrollers (MCUs). MCU software is typically written in C and is prone to memory safety vulnerabilities that are exploitable by remote attackers to launch code reuse attacks and code/control data leakage attacks.

Speculative execution is one of the key techniques that modern processors use to boost performance. However, recent research shows that speculative execution can be used to steal sensitive data. We present a software-based solution to mitigate Spectre attacks by restricting the control flow of speculatively-executed instructions.