fujsu

A minimal APK embedded native mod loader for Unity IL2CPP on Android (ARM64 only).

Why?

QuestLoader and/or scotland2 (I don't know the difference) was too fancy for my needs, so I figured I'd make my own very basic loader.

How?

Fujsu does very little by itself. The project has two sections, main and fujsu.

main is a replacement for the built-in Unity libmain.so. It allows the original game data to load, while also loading fujsu.

fujsu is the actual mod loader. Simply put, it reads a configuration embedded into the APK which defines which libraries (mods) to load. From there it loads the mods, calls the load() function, hooks il2cpp_init, then once that is called, it calls every mod's il2cpp_ready() function.

Installation

Installation is meant to be mostly painless.

1. Once compiled, put libfujsu.so and libmain.so inside the APK's ARM64 library folder (replacing the original libmain.so).
2. Download libdobby.so from here and place it alongside the others.
   • Dobby is required to hook il2cpp_init.
3. Place any mods inside that directory.
4. Create a fujsu.toml inside the assets folder.
5. Inside of the config, you only need to define a list of mods.

mods = [
    "libmod1.so",
    "libmod2.so"
]

6. Recompile the APK

Fujsu, and your mod(s), should automatically be loaded into the game.

Mod Development

Fujsu is intended to be used with cordl and my fork of beatsaber-hook, though neither are required. If you don't want to use either, but want the other functions from fujsu.h, add add_compile_definitions(NO_CORDL) to CMakeLists.txt.

cordl is the tool that generates C++ headers based on IL2CPP data and my fork of beatsaber-hook is a heavily stripped down version that only provides IL2CPP functions/utilities.

To create a mod, you can use the base mod_template project which defines the basics for a project to compile and run. I use the project with CLion with the following CMake options -DCMAKE_TOOLCHAIN_FILE={NDK}/build/cmake/android.toolchain.cmake -DANDROID_ABI=arm64-v8a -DANDROID_NATIVE_API_LEVEL=23.

Here is another example using cordl and the macros in fujsu.h to hook a function.

#include "core.h"
#include "fujsu.h"

CREATE_HOOK(UIIncrementHook, &GlobalNamespace::UIController::IncrementPressed, void, GlobalNamespace::UIController* self) {
    self->count += 9; // counter adds 1 by default
    fujsu::info("Hello, world. - from UIIncrementHook macro; UIController Instance ID: %d", self->GetInstanceID());
    UIIncrementHook(self);
}

extern "C" void load() {
    fujsu::info("load()");
}

extern "C" void il2cpp_ready() {
    fujsu::info("il2cpp_ready()");

    il2cpp_functions::Init(); // required for beatsaber-hook

    INSTALL_HOOK(UIIncrementHook);
}

Console

It can be viewed with adb logcat. If you want a filtered version, this following works.

adb logcat -v time main:D fujsu:D Dobby:D Zygote:D DEBUG:D Unity:D Binder:D AndroidRuntime:D *:S

Thanks and Licenses

• Millzy
• Someone Somewhere
• zCubed
• RinLovesYou
• A lot of the Beat Saber for Quest modders.
• Some code was based on (or directly taken from) beatsaber-hook under the MIT License. The full license is available here.