Research On Key Technology Of Reverse Engineering For DSP Processor

With the rapid development of information technology and the frequent emergence of processor vulnerabilities,general processor security issues have gradually attracted our widespread attentions.Digital signal processor(DSP),as a special-purpose processor in the field of digital signal processing,is widely used in important fields such as communication,precise navigation,and automatic control,but there are few studies on its security.At present,the main difficulty in conducting security research on DSP processors is the lack of reverse engineering methods for DSP processors.In addition,it is unknown what kind of security problems the DSP processors will have.Under this background,we proposed reverse engineering technology named disassembly technology which is suitable for DSP processor according to the characteristics of DSP processor.At the same time,in the light of the undocumented instructions,which is a security problem existed in general-purpose processors,the security research of DSP processors is carried out.The main work of this paper is as follows:(1)A reverse engineering technology framework for DSP processors is proposed:This paper studies the existing disassembly technology for general-purpose processors,and combines the architecture characteristics of DSP processors,and proposes a reverse engineering technology framework suitable for DSP processors.The proposed framework can provide a certain reference for the reverse research of DSP processors.(2)A reverse engineering tool based on the TMS320C64x/C64x+ instruction system is established:According to the reverse engineering technology framework of DSP processor proposed in this paper,a reverse engineering tool based on TMS320C64x/C64x+ instruction system was established and its reliability test was carried out.This tool is divided into three parts: data processing module,database,disassembly module.In the data processing module,we put forward the establishment method of the program segment.We have studied the TMS320C64x/C64x+ instruction set and proposed an efficient instruction set database establishment method.In the disassembly module,we give specific methods and steps of instruction translation.Through this tool,we can complete the disassembly work from machine code to assembly instructions.Finally,experimental verification shows that this tool can achieve a good disassembly effect.(3)An undocumented instruction search method suitable for DSP processors is proposed:With the support of reverse engineering tools,a search method for undocumented instructions based on DSP processors is proposed.This method reduces the search space of the instruction by identifying the instruction format and skipping the inefficient part of the instruction,which greatly improves the work efficiency.Through this search method,we found the undocumented instructions present in the processor.Combined with the structure of the machine code,the structure of the undocumented instructions is analyzed,and the composition of the machine code is given.