Patchlings: Safety-Preserving Flash-Based Hotpatching for Automotive Microcontrollers

Abstract: The increasing presence of software in modern automobiles has created a growing need to deliver software updates throughout a vehicle's entire lifespan. Traditional update methods are slow and require months of re-validation to comply with stringent safety standards like ISO 26262. Although hotpatching offers a path to faster updates, existing solutions for real-time embedded systems are unsuitable for the automotive domain: they overlook regulatory compliance, demand extensive safety validation, and lack support for the flash-based Execute-in-Place (XIP) architecture commonly used in automotive electronic control units (ECUs). We introduce Patchlings, the first hotpatching framework designed for compliance, safety, and persistence in automotive systems. It fills the gap in applying hotpatching to automotive systems and fundamentally reduces the mean-time-to-mitigate (MTTM) for vulnerabilities and bugs. We implement and evaluate a complete prototype of Patchlings on an automotive-grade hardware platform, NXP S32K148EVB, with both FreeRTOS and Zephyr. Our results demonstrate low and deterministic overhead (e.g., 3.3 $μ$s when a patch is applied), small firmware size increase (e.g., as low as 6.34%), and successful patching of different types of real CVEs, proving its real-world applicability and effectiveness.