Further work on implementing support for cheats

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
-    cmp r0, #0
-    beq entry_end
+    subs r5, #1
+    bmi 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