VmtHook: Have hooks inherit from their targets

cursey · Apr 24, 2023 · 60dd639 · 60dd639
1 parent b4b8abe
commit 60dd639
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Showing 3 changed files with 13 additions and 19 deletions.
diff --git a/include/safetyhook/utility.hpp b/include/safetyhook/utility.hpp
@@ -11,12 +11,6 @@ template <typename T> constexpr void store(uint8_t* address, const T& value) {
 
 template <typename T>
 concept FnPtr = requires(T f) {
-    std::is_pointer_v<T>
-
-    // 32-bit MSVC doesn't seem to think `static __thiscall` functions are functions.
-#if defined(_M_X64)
-        && std::is_function_v<std::remove_pointer_t<T>>
-#endif
-        ;
+    std::is_pointer_v<T> && std::is_function_v<std::remove_pointer_t<T>>;
 };
 } // namespace safetyhook
diff --git a/include/safetyhook/vmt_hook.hpp b/include/safetyhook/vmt_hook.hpp
@@ -72,7 +72,7 @@ class VmtHook final {
 
         ++index; // Skip RTTI pointer.
         hook.m_original_vm = m_new_vmt[index];
-        hook.m_new_vm = reinterpret_cast<uint8_t*>(new_function);
+        store(reinterpret_cast<uint8_t*>(&hook.m_new_vm), new_function);
         hook.m_vmt_entry = &m_new_vmt[index];
         m_new_vmt[index] = hook.m_new_vm;
 

diff --git a/unittest/vmt_hook.cpp b/unittest/vmt_hook.cpp
@@ -18,8 +18,8 @@ TEST_CASE("VMT hook an object instance", "[vmt_hook]") {
     static SafetyHookVmt target_hook{};
     static SafetyHookVm add_42_hook{};
 
-    struct Hook {
-        static int __thiscall add_42(Target* self, int a) { return add_42_hook.thiscall<int>(self, a) + 1337; }
+    struct Hook : Target {
+        int hooked_add_42(int a) { return add_42_hook.thiscall<int>(this, a) + 1337; }
     };
 
     auto vmt_result = SafetyHookVmt::create(target.get());
@@ -28,7 +28,7 @@ TEST_CASE("VMT hook an object instance", "[vmt_hook]") {
 
     target_hook = std::move(*vmt_result);
 
-    auto vm_result = target_hook.hook_method(1, Hook::add_42);
+    auto vm_result = target_hook.hook_method(1, &Hook::hooked_add_42);
 
     REQUIRE(vm_result);
 
@@ -62,9 +62,9 @@ TEST_CASE("Resetting the VMT hook removes all VM hooks for that object", "[vmt_h
     static SafetyHookVm add_42_hook{};
     static SafetyHookVm add_43_hook{};
 
-    struct Hook {
-        static int __thiscall add_42(Target* self, int a) { return add_42_hook.thiscall<int>(self, a) + 1337; }
-        static int __thiscall add_43(Target* self, int a) { return add_43_hook.thiscall<int>(self, a) + 1337; }
+    struct Hook : Target {
+        int hooked_add_42(int a) { return add_42_hook.thiscall<int>(this, a) + 1337; }
+        int hooked_add_43(int a) { return add_43_hook.thiscall<int>(this, a) + 1337; }
     };
 
     auto vmt_result = SafetyHookVmt::create(target.get());
@@ -73,15 +73,15 @@ TEST_CASE("Resetting the VMT hook removes all VM hooks for that object", "[vmt_h
 
     target_hook = std::move(*vmt_result);
 
-    auto vm_result = target_hook.hook_method(1, Hook::add_42);
+    auto vm_result = target_hook.hook_method(1, &Hook::hooked_add_42);
 
     REQUIRE(vm_result);
 
     add_42_hook = std::move(*vm_result);
 
     REQUIRE(target->add_42(1) == 1380);
 
-    vm_result = target_hook.hook_method(2, Hook::add_43);
+    vm_result = target_hook.hook_method(2, &Hook::hooked_add_43);
 
     REQUIRE(vm_result);
 
@@ -113,8 +113,8 @@ TEST_CASE("VMT hooking an object maintains correct RTTI", "[vmt_hook]") {
     static SafetyHookVmt target_hook{};
     static SafetyHookVm add_42_hook{};
 
-    struct Hook {
-        static int __thiscall add_42(Target* self, int a) { return add_42_hook.thiscall<int>(self, a) + 1337; }
+    struct Hook : Target {
+        int hooked_add_42(int a) { return add_42_hook.thiscall<int>(this, a) + 1337; }
     };
 
     auto vmt_result = SafetyHookVmt::create(target.get());
@@ -123,7 +123,7 @@ TEST_CASE("VMT hooking an object maintains correct RTTI", "[vmt_hook]") {
 
     target_hook = std::move(*vmt_result);
 
-    auto vm_result = target_hook.hook_method(1, Hook::add_42);
+    auto vm_result = target_hook.hook_method(1, &Hook::hooked_add_42);
 
     REQUIRE(vm_result);