Further work on implementing support for cheats

arm7/source/loader/NdsLoader.cpp

@@ -522,7 +522,13 @@ void NdsLoader::HandleHomebrewPatching()
 void NdsLoader::ApplyArm7Patches()
 {
     sendToArm9(IPC_COMMAND_ARM9_APPLY_ARM7_PATCHES);
+    sendToArm9(_cheats ? _cheats->length : 0);
     void* patchSpaceStart = (void*)receiveFromArm9();
+    void* cheatsPtr = (void*)receiveFromArm9();
+    if (cheatsPtr != nullptr && _cheats != nullptr)
+    {
+        memcpy(cheatsPtr, _cheats, _cheats->length);
+    }
     if (patchSpaceStart)
     {
         u32 mbk6 = 0;

arm7/source/loader/NdsLoader.h

@@ -42,6 +42,13 @@ public:
         _argumentsLength = argumentsLength;
     }
 
+    /// @brief Sets the cheats to apply to the rom.
+    /// @param cheats The cheats.
+    void SetCheats(const pload_cheats_t* cheats)
+    {
+        _cheats = cheats;
+    }
+
     /// @brief Loads the rom according to the specified \p bootMode.
     /// @param bootMode The boot mode.
     void Load(BootMode bootMode);
@@ -53,6 +60,7 @@ private:
     const TCHAR* _launcherPath = nullptr;
     u32 _argumentsLength = 0;
     const char* _arguments = nullptr;
+    const pload_cheats_t* _cheats = nullptr;
     nds_header_twl_t _romHeader;
     DsiWareSaveResult _dsiwareSaveResult;
 

arm7/source/main.cpp

@@ -219,10 +219,19 @@ extern "C" void loaderMain()
     }
     else
     {
+        pload_cheats_t* cheats = nullptr;
+        if (gLoaderHeader.v3.cheats != nullptr && gLoaderHeader.v3.cheats->numberOfCheats != 0)
+        {
+            // Copy cheats to vram
+            cheats = (pload_cheats_t*)malloc(gLoaderHeader.v3.cheats->length);
+            memcpy(cheats, gLoaderHeader.v3.cheats, gLoaderHeader.v3.cheats->length);
+        }
+
         sLoader.SetRomPath(gLoaderHeader.loadParams.romPath);
         handleSavePath();
         sLoader.SetArguments(gLoaderHeader.loadParams.arguments, gLoaderHeader.loadParams.argumentsLength);
         sLoader.SetLauncherPath(gLoaderHeader.v2.launcherPath);
+        sLoader.SetCheats(cheats);
         sLoader.Load(BootMode::Normal);
     }
 

arm9/source/Arm7Patcher.cpp

@@ -15,10 +15,12 @@
 #include "patches/arm7/DisableArm7WramClearPatch.h"
 #include "patches/arm7/sdk5/Sdk5DsiSdCardRedirectPatch.h"
 #include "patches/arm7/PokemonDownloaderArm7Patch.h"
+#include "patches/arm7/cheats/CheatEnginePatch.h"
 #include "Arm7Patcher.h"
 
-void* Arm7Patcher::ApplyPatches(const LoaderPlatform* loaderPlatform) const
+void* Arm7Patcher::ApplyPatches(const LoaderPlatform* loaderPlatform, u32 cheatsLength, void*& cheatsPtr) const
 {
+    cheatsPtr = nullptr;
     auto romHeader = (const nds_header_ntr_t*)TWL_SHARED_MEMORY->ntrSharedMem.romHeader;
     auto twlRomHeader = (const nds_header_twl_t*)TWL_SHARED_MEMORY->twlRomHeader;
     ModuleParamsLocator moduleParamsLocator;
@@ -91,10 +93,18 @@ void* Arm7Patcher::ApplyPatches(const LoaderPlatform* loaderPlatform) const
             patchCollection.AddPatch(new PokemonDownloaderArm7Patch());
         }
 
+        CheatEnginePatch* cheatEnginePatch = nullptr;
+        if (cheatsLength > 0)
+        {
+            cheatEnginePatch = new CheatEnginePatch();
+            patchCollection.AddPatch(cheatEnginePatch);
+        }
+
         if (arm7ArenaPatch->FindPatchTarget(patchContext))
         {
             const u32 arm7PatchSpaceSize = 0x800;
             void* privateWramHeapStart = arm7ArenaPatch->GetArm7PrivateWramArenaLo();
+            u32 mainMemoryArenaLo = (u32)arm7ArenaPatch->GetMainMemoryArenaLo();
             if (0x0380F780 - (u32)privateWramHeapStart - 0x2100 >= arm7PatchSpaceSize)
             {
                 patchSpaceStart = privateWramHeapStart;
@@ -103,7 +113,6 @@ void* Arm7Patcher::ApplyPatches(const LoaderPlatform* loaderPlatform) const
             else
             {
                 LOG_DEBUG("Arm 7 patches placed in main memory\n");
-                u32 mainMemoryArenaLo = (u32)arm7ArenaPatch->GetMainMemoryArenaLo();
                 if (gIsDsiMode && romHeader->unitCode == 0)
                 {
                     patchSpaceStart = (void*)(mainMemoryArenaLo & ~0xC00000); // 0x023...
@@ -112,8 +121,24 @@ void* Arm7Patcher::ApplyPatches(const LoaderPlatform* loaderPlatform) const
                 {
                     patchSpaceStart = (void*)(mainMemoryArenaLo | 0x800000); // make sure it ends up in the right place while in 16MB mode
                 }
-                arm7ArenaPatch->SetMainMemoryArenaLo((u8*)mainMemoryArenaLo + arm7PatchSpaceSize);
+                mainMemoryArenaLo += arm7PatchSpaceSize;
             }
+            if (cheatsLength > 0)
+            {
+                void* cheats;
+                if (gIsDsiMode && romHeader->unitCode == 0)
+                {
+                    cheats = (void*)(mainMemoryArenaLo & ~0xC00000); // 0x023...
+                }
+                else
+                {
+                    cheats = (void*)(mainMemoryArenaLo | 0x800000); // make sure it ends up in the right place while in 16MB mode
+                }
+                cheatsPtr = cheats;
+                cheatEnginePatch->SetCheats(cheats);
+                mainMemoryArenaLo += cheatsLength;
+            }
+            arm7ArenaPatch->SetMainMemoryArenaLo((void*)mainMemoryArenaLo);
             patchContext.GetPatchHeap().AddFreeSpace(patchSpaceStart, arm7PatchSpaceSize);
         }
 

arm9/source/Arm7Patcher.h

@@ -8,6 +8,8 @@ class Arm7Patcher
 public:
     /// @brief Applies arm7 patches using the given \p loaderPlatform.
     /// @param loaderPlatform The loader platform to use.
+    /// @param cheatsLength The length of the cheats data, or zero when there are no cheats.
+    /// @param cheatsPtr Pointer to where the cheats need to be stored, or \c nullptr when there are no cheats.
     /// @return A pointer to the patch space in IWRAM, or \c nullptr if the patches have been placed in main memory.
-    void* ApplyPatches(const LoaderPlatform* loaderPlatform) const;
+    void* ApplyPatches(const LoaderPlatform* loaderPlatform, u32 cheatsLength, void*& cheatsPtr) const;
 };

arm9/source/main.cpp

@@ -155,10 +155,12 @@ static void handleApplyArm9PatchesCommand()
     ipc_sendWordDirect(1);
 }
 
-static void handleApplyArm7PatchesCommand()
+static void handleApplyArm7PatchesCommand(u32 cheatsLength)
 {
-    void* patchSpaceStart = Arm7Patcher().ApplyPatches(sLoaderPlatform);
+    void* cheats = nullptr;
+    void* patchSpaceStart = Arm7Patcher().ApplyPatches(sLoaderPlatform, cheatsLength, cheats);
     ipc_sendWordDirect((u32)patchSpaceStart);
+    ipc_sendWordDirect((u32)cheats);
 }
 
 static void handleSetAPInfoCommand()
@@ -289,7 +291,8 @@ static void handleArm7Command(u32 command)
         }
         case IPC_COMMAND_ARM9_APPLY_ARM7_PATCHES:
         {
-            handleApplyArm7PatchesCommand();
+            u32 cheatsLength = receiveFromArm7();
+            handleApplyArm7PatchesCommand(cheatsLength);
             break;
         }
         case IPC_COMMAND_ARM9_SET_AP_INFO:

arm9/source/patches/arm7/cheats/CheatEnginePatch.cpp

@@ -0,0 +1,125 @@
+#include "common.h"
+#include "CheatEnginePatchCode.h"
+#include "CheatEnginePatch.h"
+
+// sdk2-4
+static const u32 sVBlankIntrPatternArm0[] = { 0xE92D4000u, 0xE24DD004u, 0xE59F0018u, 0xE5900000u };
+static const u32 sVBlankIntrPatternArm1[] = { 0xE92D4008u, 0xE59F0014u, 0xE5900000u, 0xE3500000u };
+static const u32 sVBlankIntrPatternThumb0[] = { 0x00000000u, 0xB081B500u, 0x68004804u, 0xD0012800u }; // +4
+static const u32 sVBlankIntrPatternThumb1[] = { 0x46C04770u, 0x027FFE1Du, 0x4804B508u, 0x28006800u }; // +8
+
+bool CheatEnginePatch::FindPatchTarget(PatchContext& patchContext)
+{
+    _vblankIrqHandler = patchContext.FindPattern32(sVBlankIntrPatternArm0, sizeof(sVBlankIntrPatternArm0));
+    if (_vblankIrqHandler)
+    {
+        _foundPattern = sVBlankIntrPatternArm0;
+    }
+    if (!_vblankIrqHandler)
+    {
+        _vblankIrqHandler = patchContext.FindPattern32(sVBlankIntrPatternArm1, sizeof(sVBlankIntrPatternArm1));
+        if (_vblankIrqHandler)
+        {
+            _foundPattern = sVBlankIntrPatternArm1;
+        }
+    }
+    if (!_vblankIrqHandler)
+    {
+        _vblankIrqHandler = patchContext.FindPattern32(sVBlankIntrPatternThumb0, sizeof(sVBlankIntrPatternThumb0));
+        if (_vblankIrqHandler)
+        {
+            _foundPattern = sVBlankIntrPatternThumb0;
+            _vblankIrqHandler += 1;
+        }
+    }
+    if (!_vblankIrqHandler)
+    {
+        _vblankIrqHandler = patchContext.FindPattern32(sVBlankIntrPatternThumb1, sizeof(sVBlankIntrPatternThumb1));
+        if (_vblankIrqHandler)
+        {
+            _foundPattern = sVBlankIntrPatternThumb1;
+            _vblankIrqHandler += 2;
+        }
+    }
+
+    if (_vblankIrqHandler)
+    {
+        LOG_DEBUG("ARM7 VBlankIntr found at 0x%p\n", _vblankIrqHandler);
+    }
+
+    return _vblankIrqHandler != nullptr;
+}
+
+void CheatEnginePatch::ApplyPatch(PatchContext& patchContext)
+{
+    if (!_vblankIrqHandler || !_cheats)
+        return;
+
+    auto cheatEnginePatchCode = patchContext.GetPatchCodeCollection().AddUniquePatchCode<CheatEnginePatchCode>
+    (
+        patchContext.GetPatchHeap(),
+        _cheats
+    );
+
+    if (_foundPattern == sVBlankIntrPatternArm0)
+    {
+        // push {lr}
+        // sub sp, sp, #4
+        // ldr r0,=
+        // ldr r0, [r0]
+        // cmp r0, #0
+        // beq 1f
+        // bl
+        // 1:
+        // add sp, sp, #4
+        // pop {lr}
+        // bx lr
+        _vblankIrqHandler[7] = 0xE59F0000; // ldr r0,= address
+        _vblankIrqHandler[8] = 0xE12FFF10; // bx r0
+        _vblankIrqHandler[9] = (u32)cheatEnginePatchCode->GetCheatEngineFunction(); // address
+    }
+    else if (_foundPattern == sVBlankIntrPatternArm1)
+    {
+        // push {r3,lr}
+        // ldr r0,=
+        // ldr r0, [r0]
+        // cmp r0, #0
+        // beq 1f
+        // bl
+        // 1:
+        // pop {r3,lr}
+        // bx lr
+    }
+    else if (_foundPattern == sVBlankIntrPatternThumb0)
+    {
+        // push {lr}
+        // sub sp, sp, #4
+        // ldr r0,=
+        // ldr r0, [r0]
+        // cmp r0, #0
+        // beq 1f
+        // bl
+        // 1:
+        // add sp, sp, #4
+        // pop {r3}
+        // bx r3
+        // nop
+    }
+    else if (_foundPattern == sVBlankIntrPatternThumb1)
+    {
+        // push {r3,lr}
+        // ldr r0,=
+        // ldr r0, [r0]
+        // cmp r0, #0
+        // beq 1f
+        // bl
+        // 1:
+        // pop {r3}
+        // pop {r3}
+        // bx r3
+    }
+    else
+    {
+        LOG_ERROR("ARM7 VBlankIntr signature not implemented\n");
+    }
+}

arm9/source/patches/arm7/cheats/CheatEnginePatch.h

@@ -0,0 +1,20 @@
+#pragma once
+#include "patches/Patch.h"
+
+/// @brief Arm7 patch for injecting the cheat engine in the vblank interrupt handler.
+class CheatEnginePatch : public Patch
+{
+public:
+    bool FindPatchTarget(PatchContext& patchContext) override;
+    void ApplyPatch(PatchContext& patchContext) override;
+
+    void SetCheats(const void* cheats)
+    {
+        _cheats = cheats;
+    }
+
+private:
+    const void* _cheats = nullptr;
+    u32* _vblankIrqHandler = nullptr;
+    const u32* _foundPattern = nullptr;
+};

arm9/source/patches/arm7/cheats/CheatEnginePatchCode.h

@@ -0,0 +1,24 @@
+#pragma once
+#include "sections.h"
+#include "patches/PatchCode.h"
+
+DEFINE_SECTION_SYMBOLS(patch_cheatengine);
+
+extern "C" void cheatengine_entry(void);
+
+extern const void* cheatengine_cheatsPtr;
+
+class CheatEnginePatchCode : public PatchCode
+{
+public:
+    CheatEnginePatchCode(PatchHeap& patchHeap, const void* cheatsAddress)
+        : PatchCode(SECTION_START(patch_cheatengine), SECTION_SIZE(patch_cheatengine), patchHeap)
+    {
+        cheatengine_cheatsPtr = cheatsAddress;
+    }
+
+    const void* GetCheatEngineFunction() const
+    {
+        return GetAddressAtTarget((void*)cheatengine_entry);
+    }
+};

arm9/source/patches/arm7/cheats/CheatEnginePatchCode.s

@@ -10,16 +10,22 @@
 .global cheatengine_entry
 .type cheatengine_entry, %function
 cheatengine_entry:
-    push {r4, lr}
+    pop {r0, r1}
+    mov lr, r1
+    push {r4, r5, lr}
     ldr r4, cheatengine_cheatsPtr
+    ldr r5, [r4, #4] // pload_cheats_t::numberOfCheats
+    adds r4, #8
 entry_cheats_loop:
-    ldmia r4!, {r0} // r0 = cheat pointer
+    subs r5, #1
-    cmp r0, #0
+    bmi entry_end
-    beq entry_end
+    movs r0, r4
     bl cheatengine_runCheat
+    ldmia r4!, {r0} // r0 = length of cheat in bytes (pload_cheat_t::length)
+    adds r4, r0
     b entry_cheats_loop
 entry_end:
-    pop {r4}
+    pop {r4, r5}
     pop {r3}
     bx r3
 
@@ -38,7 +44,8 @@ cheatengine_runCheat:
     mov r6, r10
     mov r7, r11
     push {r4, r5, r6, r7} // r8, r9, r10, r11
-    ldr r1, [r0] // r1 = length of cheat code
+
+    ldmia r0!, {r1} // r1 = length of cheat code
     adds r1, r0
     mov r8, r1 // r8 = end of cheat code
     mov r9, r0 // r9 = loop start
@@ -389,7 +396,6 @@ FX_end:
 
 .balign 4
 
-// Pointer to list of pointers to cheat codes. Last pointer should be nullptr to terminate the list.
 .global cheatengine_cheatsPtr
 cheatengine_cheatsPtr:
     .word 0

include/picoLoader7.h

@@ -1,7 +1,7 @@
 #pragma once
 
 /// @brief The Pico Loader API version supported by this header file.
-#define PICO_LOADER_API_VERSION     2
+#define PICO_LOADER_API_VERSION     3
 
 /// @brief Enum to specify the drive to boot from.
 typedef enum
@@ -43,6 +43,46 @@ typedef struct
     char launcherPath[256];
 } pload_header7_v2_t;
 
+/// @brief Struct representing a single Action Replay cheat opcode.
+typedef struct
+{
+    /// @brief The first part of the opcode.
+    u32 a;
+
+    /// @brief The second part of the opcode.
+    u32 b;
+} pload_cheat_opcode_t;
+
+/// @brief Struct representing a single Action Replay cheat.
+typedef struct
+{
+    /// @brief Length of \see opcodes in bytes.
+    u32 length;
+
+    /// @brief The cheat opcodes.
+    pload_cheat_opcode_t opcodes[1];
+} pload_cheat_t;
+
+/// @brief Struct representing one or more cheats. Cheats are adjacent starting from the firstCheat field.
+typedef struct
+{
+    /// @brief Length of this stucture (length field + numberOfCheats field + all cheats).
+    u32 length;
+
+    /// @brief The number of cheats.
+    u32 numberOfCheats;
+
+    /// @brief The first cheat.
+    pload_cheat_t firstCheat;
+} pload_cheats_t;
+
+/// @brief Struct representing the API version 3 part of the header of picoLoader7.bin.
+typedef struct
+{
+    /// @brief Pointer to the cheats, or \c nullptr when there are no cheats.
+    const pload_cheats_t* cheats;
+} pload_header7_v3_t;
+
 /// @brief Struct representing the header of picoLoader7.bin.
 typedef struct
 {
@@ -63,4 +103,7 @@ typedef struct
 
     /// @brief The API version 2 part of the header. Only access this when \see apiVersion >= 2.
     pload_header7_v2_t v2;
+
+    /// @brief The API version 3 part of the header. Only access this when \see apiVersion >= 3.
+    pload_header7_v3_t v3;
 } pload_header7_t;