关键词: 可编程逻辑控制器, 控制流, 中间表示, 程序理解, 安全性

Abstract: Programmable Logic Controller (PLC) is one of the most important components of industrial control system, which controls varieties of physical equipment and production process. The faults of PLC programs caused by malicious tempering or programming mistakes could seriously threat equipment safety and personal safety in industrial field. To solve this problem, this paper proposed a control flow analysis approach of PLC program. Firstly, this approach analyzed the lexical and syntactic structure of the source code. Then it generates and optimizes the intermediate representation without side effects by analyzing the abstract syntax tree. Finally, the basic blocks are divided on the basis of the intermediate representation, and the control flow graph of the program is constructed. The result of the experiments proves that the proposed method can restore the control flow structure of PLC program which is the basis of program understanding and security analysis.

Key words: Programmable Logic Controller (PLC), control flow, intermediate representation, program understanding, security