Undocumented x86 instructions to control the CPU at the microarchitecture level in modern Intel processors

Undocumented x86 instructions to control the CPU at the microarchitecture level in modern Intel processors

연구 분야: Analysis

학회: Journal of Computer Virology and Hacking Techniques

At the beginning of 2020, we discovered the Red Unlock technique that allows extracting Intel Atom CPUs microcode. Using the technique we were able to research the internal structure of the microcode and then x86 instructions implementation. We found two undocumented x86 instructions which are intendent to control the microarhitecture for debug purposes. In this paper we are going to introduce these instructions and explain the conditions under which they can be used on public-available platforms. We believe, this is a unique opportunity for third-party researchers to better understand the x86 architecture.