From c0954035da25d040ff32b24eefb46fa3e4fed512 Mon Sep 17 00:00:00 2001
From: Soreepeong <soreepeong@gmail.com>
Date: Fri, 10 Mar 2023 13:12:54 +0900
Subject: [PATCH] Fail fast on trying to dispose import hook that has been
 overwritten by something else

---
 .../Internal/FunctionPointerVariableHook.cs     | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/Dalamud/Hooking/Internal/FunctionPointerVariableHook.cs b/Dalamud/Hooking/Internal/FunctionPointerVariableHook.cs
index 3272f50b3..80bd65cf6 100644
--- a/Dalamud/Hooking/Internal/FunctionPointerVariableHook.cs
+++ b/Dalamud/Hooking/Internal/FunctionPointerVariableHook.cs
@@ -13,10 +13,12 @@ namespace Dalamud.Hooking.Internal;
 /// <typeparam name="T">Delegate type to represents a function prototype. This must be the same prototype as original function do.</typeparam>
 internal class FunctionPointerVariableHook<T> : Hook<T> where T : Delegate
 {
-    private readonly IntPtr pfnOriginal;
-    private readonly T originalDelegate;
+    private readonly nint pfnDetour;
     private readonly T detourDelegate;
 
+    private nint pfnOriginal;
+    private T? originalDelegate;
+
     private bool enabled = false;
 
     /// <summary>
@@ -40,9 +42,8 @@ internal class FunctionPointerVariableHook<T> : Hook<T> where T : Delegate
             if (!HookManager.MultiHookTracker.TryGetValue(this.Address, out var indexList))
                 indexList = HookManager.MultiHookTracker[this.Address] = new();
 
-            this.pfnOriginal = Marshal.ReadIntPtr(this.Address);
-            this.originalDelegate = Marshal.GetDelegateForFunctionPointer<T>(this.pfnOriginal);
             this.detourDelegate = detour;
+            this.pfnDetour = Marshal.GetFunctionPointerForDelegate(detour);
 
             // Add afterwards, so the hookIdent starts at 0.
             indexList.Add(this);
@@ -100,7 +101,10 @@ internal class FunctionPointerVariableHook<T> : Hook<T> where T : Delegate
                 if (!NativeFunctions.VirtualProtect(this.Address, (UIntPtr)Marshal.SizeOf<IntPtr>(), MemoryProtection.ExecuteReadWrite, out var oldProtect))
                     throw new Win32Exception(Marshal.GetLastWin32Error());
 
-                Marshal.WriteIntPtr(this.Address, Marshal.GetFunctionPointerForDelegate(this.detourDelegate));
+                this.pfnOriginal = Marshal.ReadIntPtr(this.Address);
+                this.originalDelegate = Marshal.GetDelegateForFunctionPointer<T>(this.pfnOriginal);
+                Marshal.WriteIntPtr(this.Address, this.pfnDetour);
+
                 NativeFunctions.VirtualProtect(this.Address, (UIntPtr)Marshal.SizeOf<IntPtr>(), oldProtect, out _);
             }
         }
@@ -118,6 +122,9 @@ internal class FunctionPointerVariableHook<T> : Hook<T> where T : Delegate
                 if (!NativeFunctions.VirtualProtect(this.Address, (UIntPtr)Marshal.SizeOf<IntPtr>(), MemoryProtection.ExecuteReadWrite, out var oldProtect))
                     throw new Win32Exception(Marshal.GetLastWin32Error());
 
+                if (Marshal.ReadIntPtr(this.Address) != this.pfnOriginal)
+                    Environment.FailFast("Cannot disable this hook in a sane manner.");
+
                 Marshal.WriteIntPtr(this.Address, this.pfnOriginal);
                 NativeFunctions.VirtualProtect(this.Address, (UIntPtr)Marshal.SizeOf<IntPtr>(), oldProtect, out _);
             }