Ryan Houdek
df2f1ad074
Only a partial fix for #1330, still needs preemption disabled to work. On x86-64 hosts the Linux kernel resides in the top bit of VA which isn't mapped in to userspace. This means that userspace will never receive pointers living with that top bit set unless you're running a 57bit VA host. This results in userspace pointers never needing to do the sign extending pointer canonicalization. But additionally some applications actually don't understand the pointer canonicalization. This results in bugs like: https://github.com/golang/go/issues/49405 Now if you're running on a 57bit VA host, this will end up behaving like FEX but it seems like no one in golang land has really messed with 57bit VA yet. In AArch64, when configured with a 48bit VA, the userspace gets the full 48bit VA space and on EL mode switch has the full address range change to the kernel's 48bit VA. This means that we will /very/ likely allocate pointers in the high 48bit space since Linux currently allocates top-down. So behave more like x86-64, hide the top 128TB of memory space from the guest before boot. Testing: Took the M1Max 15ms to 21ms allocate the top 128TB.
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.
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.
Dependencies
- cmake (version 3.14 minimum)
- ninja-build
- clang (version 10 minimum for C++20)
- libglfw3-dev (For GUI)
- libsdl2-dev (For GUI)
- libepoxy-dev (For GUI)
- g++-x86-64-linux-gnu (For building thunks)
- nasm (only if building tests)
Building FEX
After installing the dependencies you can now build FEX.
git clone https://github.com/FEX-Emu/FEX.git
cd FEX
git submodule update --init
mkdir Build
cd Build
CC=clang CXX=clang++ cmake -DCMAKE_INSTALL_PREFIX=/usr -DCMAKE_BUILD_TYPE=Release -DENABLE_LTO=True -DBUILD_TESTS=False -G Ninja ..
ninja
Installation
sudo ninja install
On AArch64 Hosts
You can install a binfmt_misc handler for both 32bit and 64bit x86 execution directly from the environment. If you already have box86's 32bit binfmt_misc handler installed then I don't recommend installing FEX's until it is useful. Make sure to have run install prior to this, otherwise binfmt_misc will install an old handler even if the executable has been updated.
sudo ninja binfmt_misc_32
sudo ninja binfmt_misc_64
More information
This wiki page can contain more information about setting up FEX on your device https://wiki.fex-emu.org/index.php/Development:Setting_up_FEX
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.org/index.php/Development:Setting_up_RootFS
