ReIFunc: Identifying Recurring Inline Functions in Binary Code

Function inlining, although a common phenomenon, can greatly hinder the readability of the binary code obtained through decompilation. Identifying inline functions in the binary code is additionally challenging as there is no clear boundary between an inlined function and its caller function, the instructions of the same function might differ during inline expansion, and existing graph-schema methods for inline function identification cannot handle the vast number of functions involved due to their complexity. To address the challenge, in this paper, we propose an effective inline function identification solution named ReIFunc, which combines subgraph isomorphism and deep learning to identify these recurring inline functions (RIFs). Our evaluation shows that ReIFunc can effectively match functions within a broad candidate set with a high precision rate exceeding 99% while maintaining an acceptable recall, thus getting rid of the constraints imposed by the limited size of the candidate set.