Ryan Houdek
e2db607769
In the case that the symlink following would immediately fail (Due to the first query not existing or not being a symlink), then FEX would immediately return the first query. Then the resulting syscall using this result would try to run the syscall on that file, immediately error, and try again on the file outside of the rootfs. This gives us three syscalls for the price of one. This adds an additional syscall cost to every syscall that that takes the `FollowSymlink` code path, which is quite a few. Instead now, check to see if the filepath exists at all, and if the filepath doesn't even exist for the first fstatat, return a `NoEntry` immediately. This will cause the resulting syscall waiting for the result to skip the EmulatedFDPath check and run regular syscall. If the filepath is symlink it will still loop to track through the entire symlink tree to find the one that is in the rootfs. If the filepath is just a file, then the `IsLink` step will fail, returning the filepath to the file inside of the rootfs. (Getting this step wrong will make wine/proton immediately break). With this resolved, this converts a lot of three syscall operations down to two.
FEX - Fast x86 emulation frontend
FEX allows you to run x86 and x86-64 binaries on an AArch64 host, similar to qemu-user and box86. It has native support for a rootfs overlay, so you don't need to chroot, as well as some thunklibs so it can forward things like GL to the host. FEX presents a Linux 5.0 interface to the guest, and supports both AArch64 and x86-64 as hosts. FEX is very much work in progress, so expect things to change.
Quick start guide
For Ubuntu 20.04, 21.04, 21.10, 22.04
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 --output /tmp/InstallFEX.py && python3 /tmp/InstallFEX.py && rm /tmp/InstallFEX.py
This command will walk you through installing FEX through a PPA, and downloading a RootFS for use with FEX.
Ubuntu PPA is updated with our monthly releases.
For everyone else
Please see Building FEX.
Getting Started
FEX has been tested to build and run on ARMv8.0, ARMv8.1+, and x86-64(AVX or newer) hardware. ARMv7 and older x86 hardware will not work. Expected operating system usage is Linux. FEX has been tested with Ubuntu 20.04, 20.10, and 21.04. Also Arch Linux.
On AArch64 hosts the user MUST have an x86-64 RootFS Creating a RootFS.
Navigating the Source
See the Source Outline for more information.
Building FEX
Follow the guide on the official FEX-Emu Wiki here.
RootFS generation
AArch64 hosts require a rootfs for running applications. Follow the guide on the wiki page for seeing how to set up the rootfs from scratch https://wiki.fex-emu.com/index.php/Development:Setting_up_RootFS
