Securing Network Information System Design: An Efficient Tool for DSP Undocumented Instruction Mining

As recently studied, the undocumented instructions in embedded processors that may cause catastrophic results for devices have become one of the main threats to system security. To tackle this issue, in this paper, we propose an undocumented instruction mining tool for digital signal processors named DSPUIM that can find out the undocumented instructions from the frequently used Digital Signal Processors (DSP) in network information systems. First, we analyzed the characteristics of the DSP instruction format to compress the instruction search space and improve the instruction search speed. Second, according to the public instruction set of DSPs, we built an instruction disassembly framework that helped us to identify all the undefined instructions. Finally, by testing the executability of undefined instructions automatically, we obtained the undocumented instructions for target DSPs. To demonstrate the effectiveness of our tool, we applied it on ten DSP processors of Texas Instruments (TI) and mined 335 undocumented instructions from them within 5 min. Some undocumented instructions have malicious functions, such as changing registers and denial of service, posing a security threat to the network devices using DSPs.