Miri is an essential tool for checking unsafe Rust code, but it had always been limited to running that code and no more. Work has been done over the past years to make it possible to perform arbitrary FFI from within it while still detecting almost all UB, enabling more and more real-world code to be validated. Doing so required writing most of a debugger inside Miri, pulling in a disassembler, and making very liberal use of unix signals.