Zentool is an AMD Zen microcode manipulation utility that allows users to analyze, manipulate, and generate microcode patches for AMD Zen processors. The package includes tools such as mcas, a simple assembler, and mcop, a simple disassembler. Notably, users can modify microcode updates, compensate for changes made, and apply updates to processors. The tool offers advanced features like examining structures in microcode files, disassembling instruction quads, and customizing microcode patches. Zentool also provides support for debugging with utilities like mcop and mcas. The development of Zentool was influenced by members of the Google Hardware Security Team and research from Ruhr-Univeritat Bochum researchers.
https://github.com/google/security-research/blob/master/pocs/cpus/entrysign/zentool/README.md