BepInEx/Runtimes/NET/BepInEx.NET.Framework.Launcher/NetPreloader.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Runtime.InteropServices;
using BepInEx.Bootstrap;
using BepInEx.Configuration;
using BepInEx.Logging;
using BepInEx.NET.Common;
using BepInEx.NET.Framework.Launcher.RuntimeFixes;
using BepInEx.Preloader.Core;
using BepInEx.Preloader.Core.Logging;
using BepInEx.Preloader.Core.Patching;
using HarmonyLib;
using Mono.Cecil;
using MonoMod.Utils;

namespace BepInEx.NET.Framework.Launcher;

public static class NetPreloader
{
    private static readonly ManualLogSource Log = PreloaderLogger.Log;

    #region Config

    private static readonly ConfigEntry<string> ConfigEntrypointExecutable = ConfigFile.CoreConfig.Bind<string>(
     "Preloader.Entrypoint", "Assembly",
     null,
     "The local filename of the .NET executable to target.");

    #endregion

    [DllImport("Kernel32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
    private static extern bool SetDllDirectory(string lpPathName);

    [DllImport("Kernel32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
    private static extern bool AddDllDirectory(string lpPathName);


    public static void Start(string[] args)
    {
        var preloaderListener = new PreloaderConsoleListener();
        Logger.Listeners.Add(preloaderListener);

        if (string.IsNullOrEmpty(ConfigEntrypointExecutable.Value))
        {
            Log.Log(LogLevel.Fatal,
                    $"Entry executable was not set. Please set this in your config before launching the application");
            Program.ReadExit();
            return;
        }

        var executablePath = Path.GetFullPath(ConfigEntrypointExecutable.Value);

        if (!File.Exists(executablePath))
        {
            Log.Log(LogLevel.Fatal, $"Unable to locate executable: {ConfigEntrypointExecutable.Value}");
            Program.ReadExit();
            return;
        }


        Paths.SetExecutablePath(executablePath);
        Program.ResolveDirectories.Add(Paths.GameRootPath);

        foreach (var searchDir in Program.ResolveDirectories)
            TypeLoader.SearchDirectories.Add(searchDir);

        if (PlatformHelper.Is(Platform.Windows))
        {
            AddDllDirectory(Paths.GameRootPath);
            SetDllDirectory(Paths.GameRootPath);
        }


        Logger.Sources.Add(TraceLogSource.CreateSource());

        ChainloaderLogHelper.PrintLogInfo(Log);

        Log.Log(LogLevel.Info, $"CLR runtime version: {Environment.Version}");


        AssemblyBuildInfo executableInfo, launcherInfo;

        using (var executableAssembly = AssemblyDefinition.ReadAssembly(executablePath))
            executableInfo = AssemblyBuildInfo.DetermineInfo(executableAssembly);

        using (var launcherAssembly = AssemblyDefinition.ReadAssembly(typeof(NetPreloader).Assembly.Location))
            launcherInfo = AssemblyBuildInfo.DetermineInfo(launcherAssembly);

        // we don't particularly care about AnyCPU here since the fallback bitness is almost never the case
        if (executableInfo.Is64Bit != launcherInfo.Is64Bit)
        {
            Log.LogError($"Game executable is {(executableInfo.Is64Bit ? "64" : "32")}-bit while BepInEx has been compiled as {(launcherInfo.Is64Bit ? "64" : "32")}-bit. Expect crashes");
        }

        if (executableInfo.NetFrameworkVersion != launcherInfo.NetFrameworkVersion ||
            executableInfo.AssemblyFrameworkType != launcherInfo.AssemblyFrameworkType)
        {
            Log.LogWarning($"Game executable has been compiled as {executableInfo}, while BepInEx has been compiled as {launcherInfo}. There may be issues within the game caused by this");
        }

        Log.LogInfo($"Game executable build architecture: {executableInfo}");
        Log.LogInfo($"BepInEx launcher build architecture: {launcherInfo}");

        Log.Log(LogLevel.Message, "Preloader started");

        Assembly entrypointAssembly;

        using (var assemblyPatcher = new AssemblyPatcher((data, _) => Assembly.Load(data)))
        {
            assemblyPatcher.AddPatchersFromProviders();

            Log.Log(LogLevel.Info,
                    $"{assemblyPatcher.PatcherContext.PatchDefinitions.Count} patcher definition(s) loaded");

            assemblyPatcher.LoadAssemblyDirectories(new[] { Paths.GameRootPath }, new[] { "dll", "exe" });

            Log.Log(LogLevel.Info, $"{assemblyPatcher.PatcherContext.AvailableAssemblies.Count} assemblies discovered");

            assemblyPatcher.PatchAndLoad();


            var assemblyName = AssemblyName.GetAssemblyName(executablePath);

            entrypointAssembly =
                assemblyPatcher.PatcherContext.LoadedAssemblies.Values.FirstOrDefault(x => x.FullName ==
                    assemblyName.FullName);

            foreach (var loadedAssembly in assemblyPatcher.PatcherContext.LoadedAssemblies)
            {
                // TODO: Need full paths for loaded assemblies
                var assemblyPath = Path.Combine(Paths.GameRootPath, loadedAssembly.Key);

                Log.LogDebug($"Registering '{assemblyPath}' as a loaded assembly");
                AssemblyFixes.AssemblyLocations[loadedAssembly.Value.FullName] = assemblyPath;
            }

            if (entrypointAssembly != null)
            {
                Log.LogDebug("Found patched entrypoint assembly! Using it");
            }
            else
            {
                Log.LogDebug("Using entrypoint assembly from disk");
                entrypointAssembly = Assembly.LoadFrom(executablePath);
            }
        }

        Log.LogMessage("Preloader finished");

        Logger.Listeners.Remove(preloaderListener);

        var chainloader = new NetChainloader();
        chainloader.Initialize();
        chainloader.Execute();


        AssemblyFixes.Execute(entrypointAssembly);

        try
        {
            var argList = new List<object>();

            var paramTypes = entrypointAssembly.EntryPoint.GetParameters();

            if (paramTypes.Length == 1 && paramTypes[0].ParameterType == typeof(string[]))
            {
                argList.Add(args);
            }
            else if (paramTypes.Length == 1 && paramTypes[0].ParameterType == typeof(string))
            {
                argList.Add(string.Join(" ", args));
            }
            else if (paramTypes.Length != 0)
            {
                // Only other entrypoint signatures I can think of that .NET supports is Task / Task<int>
                //   async entrypoints. That's a can of worms for another time though

                Log.LogFatal($"Could not figure out how to handle entrypoint method with this signature: {entrypointAssembly.EntryPoint.FullDescription()}");
                return;
            }

            entrypointAssembly.EntryPoint.Invoke(null, argList.ToArray());
        }
        catch (Exception ex)
        {
            Log.LogFatal($"Unhandled exception: {ex}");
        }
    }
}