bepin/BepInEx.Preloader/Preloader.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.IO;
using System.Linq;
using BepInEx.Configuration;
using BepInEx.Logging;
using BepInEx.Preloader.Patching;
using BepInEx.Preloader.RuntimeFixes;
using HarmonyLib;
using Mono.Cecil;
using Mono.Cecil.Cil;
using MonoMod.Utils;
using MethodAttributes = Mono.Cecil.MethodAttributes;

namespace BepInEx.Preloader
{
	/// <summary>
	///     The main entrypoint of BepInEx, and initializes all patchers and the chainloader.
	/// </summary>
	internal static class Preloader
	{
		/// <summary>
		///     The log writer that is specific to the preloader.
		/// </summary>
		private static PreloaderConsoleListener PreloaderLog { get; set; }

		public static bool IsPostUnity2017 { get; } = File.Exists(Path.Combine(Paths.ManagedPath, "UnityEngine.CoreModule.dll"));

		public static void Run()
		{
			try
			{
				InitializeHarmony();

				ConsoleManager.Initialize(false);
				AllocateConsole();

				Utility.TryDo(() =>
				{
					if (ConfigApplyRuntimePatches.Value)
						UnityPatches.Apply();
				}, out var runtimePatchException);

				Logger.InitializeInternalLoggers();
				Logger.Sources.Add(TraceLogSource.CreateSource());
				
				PreloaderLog = new PreloaderConsoleListener();
				Logger.Listeners.Add(PreloaderLog);

				string consoleTile = $"BepInEx {typeof(Paths).Assembly.GetName().Version} - {Paths.ProcessName}";

				if (ConsoleManager.ConsoleActive)
					ConsoleManager.SetConsoleTitle(consoleTile);

				Logger.LogMessage(consoleTile);

				//See BuildInfoAttribute for more information about this section.
				object[] attributes = typeof(BuildInfoAttribute).Assembly.GetCustomAttributes(typeof(BuildInfoAttribute), false);

				if (attributes.Length > 0)
				{
					var attribute = (BuildInfoAttribute)attributes[0];
					Logger.LogMessage(attribute.Info);
				}

				Logger.LogInfo($"Running under Unity v{GetUnityVersion()}");
				Logger.LogInfo($"CLR runtime version: {Environment.Version}");
				Logger.LogInfo($"Supports SRE: {Utility.CLRSupportsDynamicAssemblies}");
				Logger.LogInfo($"System platform: {PlatformHelper.Current}");

				if (runtimePatchException != null)
					Logger.LogWarning($"Failed to apply runtime patches for Mono. See more info in the output log. Error message: {runtimePatchException.Message}");

				Logger.LogMessage("Preloader started");

				AssemblyPatcher.AddPatcher(new PatcherPlugin
				{
					TargetDLLs = () => new[] { ConfigEntrypointAssembly.Value },
					Patcher = PatchEntrypoint,
					TypeName = "BepInEx.Chainloader"
				});

				AssemblyPatcher.AddPatchersFromDirectory(Paths.PatcherPluginPath);

				Logger.LogInfo($"{AssemblyPatcher.PatcherPlugins.Count} patcher plugin{(AssemblyPatcher.PatcherPlugins.Count == 1 ? "" : "s")} loaded");

				AssemblyPatcher.PatchAndLoad(Paths.ManagedPath);
				AssemblyPatcher.DisposePatchers();

				Logger.LogMessage("Preloader finished");

				Logger.Listeners.Remove(PreloaderLog);

				PreloaderLog.Dispose();
			}
			catch (Exception ex)
			{
				try
				{
					Logger.LogFatal("Could not run preloader!");
					Logger.LogFatal(ex);

					if (!ConsoleManager.ConsoleActive)
					{
						//if we've already attached the console, then the log will already be written to the console
						AllocateConsole();
						Console.Write(PreloaderLog);
					}
				}
				catch { }

				string log = string.Empty;

				try
				{
					// We could use platform-dependent newlines, however the developers use Windows so this will be easier to read :)

					log = string.Join("\r\n", PreloaderConsoleListener.LogEvents.Select(x => x.ToString()).ToArray());
					log += "\r\n";

					PreloaderLog?.Dispose();
					PreloaderLog = null;
				}
				catch { }

				File.WriteAllText(
					Path.Combine(Paths.GameRootPath, $"preloader_{DateTime.Now:yyyyMMdd_HHmmss_fff}.log"),
					log + ex);
			}
		}

		/// <summary>
		///     Inserts BepInEx's own chainloader entrypoint into UnityEngine.
		/// </summary>
		/// <param name="assembly">The assembly that will be attempted to be patched.</param>
		public static void PatchEntrypoint(ref AssemblyDefinition assembly)
		{
			if (assembly.MainModule.AssemblyReferences.Any(x => x.Name.Contains("BepInEx")))
				throw new Exception("BepInEx has been detected to be patched! Please unpatch before using a patchless variant!");

			string entrypointType = ConfigEntrypointType.Value;
			string entrypointMethod = ConfigEntrypointMethod.Value;

			bool isCctor = entrypointMethod.IsNullOrWhiteSpace() || entrypointMethod == ".cctor";


			var entryType = assembly.MainModule.Types.FirstOrDefault(x => x.Name == entrypointType);

			if (entryType == null)
				throw new Exception("The entrypoint type is invalid! Please check your config/BepInEx.cfg file");

			using (var injected = AssemblyDefinition.ReadAssembly(Paths.BepInExAssemblyPath))
			{
				var originalInitMethod = injected.MainModule.Types.First(x => x.Name == "Chainloader").Methods
												 .First(x => x.Name == "Initialize");

				var originalStartMethod = injected.MainModule.Types.First(x => x.Name == "Chainloader").Methods
												  .First(x => x.Name == "Start");

				var initMethod = assembly.MainModule.ImportReference(originalInitMethod);
				var startMethod = assembly.MainModule.ImportReference(originalStartMethod);

				var methods = new List<MethodDefinition>();

				if (isCctor)
				{
					var cctor = entryType.Methods.FirstOrDefault(m => m.IsConstructor && m.IsStatic);

					if (cctor == null)
					{
						cctor = new MethodDefinition(".cctor",
							MethodAttributes.Static | MethodAttributes.Private | MethodAttributes.HideBySig
							| MethodAttributes.SpecialName | MethodAttributes.RTSpecialName,
							assembly.MainModule.ImportReference(typeof(void)));

						entryType.Methods.Add(cctor);
						var il = cctor.Body.GetILProcessor();
						il.Append(il.Create(OpCodes.Ret));
					}

					methods.Add(cctor);
				}
				else
				{
					methods.AddRange(entryType.Methods.Where(x => x.Name == entrypointMethod));
				}

				if (!methods.Any())
					throw new Exception("The entrypoint method is invalid! Please check your config.ini");

				foreach (var method in methods)
				{
					var il = method.Body.GetILProcessor();

					var ins = il.Body.Instructions.First();

					il.InsertBefore(ins,
						il.Create(OpCodes.Ldnull)); // gameExePath (always null, we initialize the Paths class in Entrypoint

					il.InsertBefore(ins,
						il.Create(OpCodes.Ldc_I4_0)); //startConsole (always false, we already load the console in Preloader)

					il.InsertBefore(ins,
						il.Create(OpCodes.Call, assembly.MainModule.ImportReference(
							AccessTools.PropertyGetter(typeof(PreloaderConsoleListener), nameof(PreloaderConsoleListener.LogEvents))))); // preloaderLogEvents (load from Preloader.PreloaderLog.LogEvents)

                    il.InsertBefore(ins,
						il.Create(OpCodes.Call, initMethod)); // Chainloader.Initialize(string gamePath, string managedPath = null, bool startConsole = true)

					il.InsertBefore(ins,
						il.Create(OpCodes.Call, startMethod));
				}
			}
		}

		/// <summary>
		///     Allocates a console window for use by BepInEx safely.
		/// </summary>
		public static void AllocateConsole()
		{
			if (!ConsoleManager.ConfigConsoleEnabled.Value)
				return;

			try
			{
				ConsoleManager.CreateConsole();
				Logger.Listeners.Add(new ConsoleLogListener());
			}
			catch (Exception ex)
			{
				Logger.LogError("Failed to allocate console!");
				Logger.LogError(ex);
			}
		}

		public static string GetUnityVersion()
		{
			if (PlatformHelper.Is(Platform.Windows))
				return FileVersionInfo.GetVersionInfo(Paths.ExecutablePath).FileVersion;

			return $"Unknown ({(IsPostUnity2017 ? "post" : "pre")}-2017)";
		}

		private static void InitializeHarmony()
		{
			switch (HarmonyBackend.Value)
			{
				case MonoModBackend.auto:
					break;
				case MonoModBackend.dynamicmethod:
				case MonoModBackend.methodbuilder:
				case MonoModBackend.cecil:
					Environment.SetEnvironmentVariable("MONOMOD_DMD_TYPE", HarmonyBackend.Value.ToString());
					break;
				default:
					throw new ArgumentOutOfRangeException(nameof(HarmonyBackend), HarmonyBackend.Value, "Unknown backend");
			}
		}

		private enum MonoModBackend
		{
			// Enum names are important!
			[Description("Auto")] auto = 0,
			[Description("DynamicMethod")] dynamicmethod,
			[Description("MethodBuilder")] methodbuilder,
			[Description("Cecil")] cecil
		}

		#region Config

		private static readonly ConfigEntry<string> ConfigEntrypointAssembly = ConfigFile.CoreConfig.Bind(
			"Preloader.Entrypoint", "Assembly",
			IsPostUnity2017 ? "UnityEngine.CoreModule.dll" : "UnityEngine.dll",
			"The local filename of the assembly to target.");

		private static readonly ConfigEntry<string> ConfigEntrypointType = ConfigFile.CoreConfig.Bind(
			"Preloader.Entrypoint", "Type",
			"Application",
			"The name of the type in the entrypoint assembly to search for the entrypoint method.");

		private static readonly ConfigEntry<string> ConfigEntrypointMethod = ConfigFile.CoreConfig.Bind(
			"Preloader.Entrypoint", "Method",
			".cctor",
			"The name of the method in the specified entrypoint assembly and type to hook and load Chainloader from.");

		internal static readonly ConfigEntry<bool> ConfigApplyRuntimePatches = ConfigFile.CoreConfig.Bind(
			"Preloader", "ApplyRuntimePatches",
			true,
			"Enables or disables runtime patches.\nThis should always be true, unless you cannot start the game due to a Harmony related issue (such as running .NET Standard runtime) or you know what you're doing.");

		private static readonly ConfigEntry<MonoModBackend> HarmonyBackend = ConfigFile.CoreConfig.Bind(
			"Preloader",
			"HarmonyBackend",
			MonoModBackend.auto,
			"Specifies which MonoMod backend to use for Harmony patches. Auto uses the best available backend.\nThis setting should only be used for development purposes (e.g. debugging in dnSpy). Other code might override this setting.");

		#endregion
	}
}