The provided link leads to a 404. Maybe replace with https://github.com/spencertipping/jit-tutorial ?
There are plenty of tutorials like this out there. Some are cross-platform, this one is Linux-only and omits the W^X limit that’s wanted these days. Most of these write hexadecimals into a buffer and then call it.
I’m a bit tired to seeing clones from the same story. It’d be nice if people writing new tutorials would sometimes continue from someone else’s tutorial.