Ryan Houdek
4516e4e9f6
This nearly gets FEX's TestHarnessRunner to be self-hosting inside of FEX. The only thing blocking it currently is that our SBRK emulation reserves the whole region, when it should be "soft-reserved" and mmap with MAP_FIXED_NOREPLACE can override it. Plus an assert in OpcodeDispatcher preventing any 32-bit code from running from a 64-bit process. In the most simple terms, gdt and ldt are setup to be unique per thread, and modify_ldt then modifies that thread's ldt entry. On thread creation, these values get inherited as a copy. This allows installation of 32-bit code entries, which with the previous PRs merged allows the code to attempt jumping to that 32-bit code entry. It then will immediately explode with an assert in our OpcodeDispatcher. We can't allow 32-bit code jumping yet until our OpDispatcher/X86Tables allows runtime selection of 64-bit and 32-bit code entries which is still a ways away. With the assert removed and the SBRK code handling hacked out, /technically/ the TestHarnessRunner can run some code, albeit anything that changes behaviour between bitness is completely incorrect.
FEX: Emulate x86 Programs on ARM64
FEX allows you to run x86 applications on ARM64 Linux devices, similar to qemu-user and box64. It offers broad compatibility with both 32-bit and 64-bit binaries, and it can be used alongside Wine/Proton to play Windows games.
It supports forwarding API calls to host system libraries like OpenGL or Vulkan to reduce emulation overhead. An experimental code cache helps minimize in-game stuttering as much as possible. Furthermore, a per-app configuration system allows tweaking performance per game, e.g. by skipping costly memory model emulation. We also provide a user-friendly FEXConfig GUI to explore and change these settings.
Prerequisites
FEX requires ARMv8.0+ hardware. It has been tested with the following Linux distributions, though others are likely to work as well:
- Arch Linux
- Fedora Linux
- openSUSE
- Ubuntu 22.04/24.04/24.10/25.04
An x86-64 RootFS is required and can be downloaded using our FEXRootFSFetcher tool for many distributions.
For other distributions you will need to generate your own RootFS (our wiki page might help).
Quick Start
For Ubuntu 22.04, 24.04, 24.10 and 25.04
Execute the following command in the terminal to install FEX through a PPA.
curl --silent https://raw.githubusercontent.com/FEX-Emu/FEX/main/Scripts/InstallFEX.py | python3
This command will walk you through installing FEX through a PPA, and downloading a RootFS for use with FEX.
For other Distributions
Follow the guide on the official FEX-Emu Wiki here.
Navigating the Source
See the Source Outline for more information.