Add exports to get the return value of functions from return hooks (#116)

Author: Mr-Wiseguy

librecomp/include/librecomp/mods.hpp

@@ -591,6 +591,7 @@ namespace recomp {
         void finish_event_setup(const ModContext& context);
         void finish_hook_setup(const ModContext& context);
         void reset_hooks();
+        void register_hook_exports();
         void run_hook(uint8_t* rdram, recomp_context* ctx, size_t hook_slot_index);
 
         ModOpenError parse_manifest(ModManifest &ret, const std::vector<char> &manifest_data, std::string &error_param);

librecomp/src/mod_hooks.cpp

@@ -21,6 +21,10 @@ struct HookTableEntry {
 // Vector of individual hooks for each hook slot.
 std::vector<HookTableEntry> hook_table{};
 
+// Holds the recomp context to restore after running each hook. This is a vector because a hook may end up calling another hooked function,
+// so this acts as a stack of contexts to handle that recursion.
+thread_local std::vector<recomp_context> hook_contexts = { recomp_context{} };
+
 void recomp::mods::run_hook(uint8_t* rdram, recomp_context* ctx, size_t hook_slot_index) {
     // Sanity check the hook slot index.
     if (hook_slot_index >= hook_table.size()) {
@@ -31,7 +35,7 @@ void recomp::mods::run_hook(uint8_t* rdram, recomp_context* ctx, size_t hook_slo
     }
 
     // Copy the initial context state to restore it after running each callback.
-    recomp_context initial_context = *ctx;
+    hook_contexts.emplace_back(*ctx);
 
     // Call every hook attached to the hook slot.
     const std::vector<HookEntry>& hooks = hook_table[hook_slot_index].hooks;
@@ -44,8 +48,11 @@ void recomp::mods::run_hook(uint8_t* rdram, recomp_context* ctx, size_t hook_slo
         }, hook.func);
 
         // Restore the original context.
-        *ctx = initial_context;
+        *ctx = hook_contexts.back();
     }
+
+    // Pop the context after the hook is done.
+    hook_contexts.pop_back();
 }
 
 void recomp::mods::setup_hooks(size_t num_hook_slots) {
@@ -85,3 +92,65 @@ void recomp::mods::finish_hook_setup(const ModContext& context) {
 void recomp::mods::reset_hooks() {
     hook_table.clear();
 }
+
+void recomphook_get_return_s32(uint8_t* rdram, recomp_context* ctx) {
+    ctx->r2 = (gpr)(int32_t)hook_contexts.back().r2;
+}
+
+void recomphook_get_return_u32(uint8_t* rdram, recomp_context* ctx) {
+    recomphook_get_return_s32(rdram, ctx);
+}
+
+void recomphook_get_return_ptr(uint8_t* rdram, recomp_context* ctx) {
+    recomphook_get_return_s32(rdram, ctx);
+}
+
+void recomphook_get_return_s16(uint8_t* rdram, recomp_context* ctx) {
+    ctx->r2 = (gpr)(int16_t)hook_contexts.back().r2;
+}
+
+void recomphook_get_return_u16(uint8_t* rdram, recomp_context* ctx) {
+    ctx->r2 = (gpr)(uint16_t)hook_contexts.back().r2;
+}
+
+void recomphook_get_return_s8(uint8_t* rdram, recomp_context* ctx) {
+    ctx->r2 = (gpr)(int8_t)hook_contexts.back().r2;
+}
+
+void recomphook_get_return_u8(uint8_t* rdram, recomp_context* ctx) {
+    ctx->r2 = (gpr)(uint8_t)hook_contexts.back().r2;
+}
+
+void recomphook_get_return_s64(uint8_t* rdram, recomp_context* ctx) {
+    ctx->r2 = (gpr)(int32_t)hook_contexts.back().r2;
+    ctx->r3 = (gpr)(int32_t)hook_contexts.back().r3;
+}
+
+void recomphook_get_return_u64(uint8_t* rdram, recomp_context* ctx) {
+    recomphook_get_return_s64(rdram, ctx);
+}
+
+void recomphook_get_return_float(uint8_t* rdram, recomp_context* ctx) {
+    ctx->f0.fl = hook_contexts.back().f0.fl;
+}
+
+void recomphook_get_return_double(uint8_t* rdram, recomp_context* ctx) {
+    ctx->f0.fl = (gpr)(uint8_t)hook_contexts.back().f0.fl;
+    ctx->f1.fl = (gpr)(uint8_t)hook_contexts.back().f1.fl;
+}
+
+#define REGISTER_FUNC(name) recomp::overlays::register_base_export(#name, name)
+
+void recomp::mods::register_hook_exports() {
+    REGISTER_FUNC(recomphook_get_return_s32);
+    REGISTER_FUNC(recomphook_get_return_u32);
+    REGISTER_FUNC(recomphook_get_return_ptr);
+    REGISTER_FUNC(recomphook_get_return_s16);
+    REGISTER_FUNC(recomphook_get_return_u16);
+    REGISTER_FUNC(recomphook_get_return_s8);
+    REGISTER_FUNC(recomphook_get_return_u8);
+    REGISTER_FUNC(recomphook_get_return_s64);
+    REGISTER_FUNC(recomphook_get_return_u64);
+    REGISTER_FUNC(recomphook_get_return_float);
+    REGISTER_FUNC(recomphook_get_return_double);
+}

librecomp/src/recomp.cpp

@@ -780,6 +780,7 @@ void recomp::start(
 
     recomp::register_heap_exports();
     recomp::mods::register_config_exports();
+    recomp::mods::register_hook_exports();
 
     std::thread game_thread{[](ultramodern::renderer::WindowHandle window_handle, uint8_t* rdram) {
         debug_printf("[Recomp] Starting\n");