This code was forked from the Xen hypervisor version 4.5.1, and modified by Stephen Kell for use as a simple instruction decoder. BEWARE: this code has a history of security vulnerabilities when used in security-critical applications (e.g. inside the hypervisor, emulating instructions). Use it at your own risk. My interest in the code is that it's the most compact implementation of x86 I'm aware of, and that it's written in C with no external dependencies. I currently use it in my libsystrap project, only for decode, and in user processes (a much safer proposition than in-hypervisor emulation!). The intention is to backport later changes from Xen (whose version 4.5.1 dates from mid-2016), restore emulation capability, and add some very basic/limited symbolic execution support for a subset of instructions, to support a few binary analysis applications. Patches in support of the above are welcome. Again, a key goal is to keep things simple enough that the code can easily be linked in to a tool or runtime written in C, in contrast to full-scale binary analysis systems like BAP. Like Xen, the licence is "GPLv2 or later". See LICENSE.gpl2. I might be able to license my changes differently if that would help you (thought I doubt it). Stephen Kell 7th April 2020