FirmEE: Firmware Emulation Enhancement via Automated and Dynamic NVRAM Configuration

Qin Si, Lei Cui, Haiqiang Fei, Lin Ji, Lun Li, Hongsong Zhu

Abstract: Firmware emulation is a critical method for re-searching embedded systems. However, current approaches to Non- Volatile Random Access Memory (NVRAM) emulation often face challenges such as strong hardware dependency, complex parameter configuration, and the need for extensive manual intervention, which result in low emulation success rates and poor network reachability. Additionally, the lack of transparency during the firmware execution process makes it difficult to track and analyze the causes of emulation failures. To address these challenges, this paper introduces FirmEE, a firmware emulation enhancement system that leverages NVRAM-Sim, which automates the modeling of NVRAM peripherals and simulates the interaction between firmware and NVRAM hardware during parameter requests and assignments. FirmEE dynamically optimizes parameter configurations by constructing an NVRAM value exploration space, utilizing the number of basic blocks executed during firmware startup as reward. This approach facilitates large-scale automated firmware emulation, significantly improving both emulation success rates and network reachability. Moreover, FirmEE provides fine-grained monitoring of the firmware execution process, offering enhanced transparency and deeper insights into system behavior. Experimental results show that FirmEE increases the emulation success rate to 79.41 % and the network reachability rate to 73.09% on a custom dataset comprising 301 firmware images from four mainstream router vendors, significantly outperforming existing methods.