Fix bug in handling of E cheat opcode, add cheat support for all remaining games

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

@@ -1,4 +1,5 @@
 #include "common.h"
+#include "thumbInstructions.h"
 #include "CheatEnginePatchCode.h"
 #include "CheatEnginePatch.h"
 
@@ -7,6 +8,10 @@ static const u32 sVBlankIntrPatternArm0[] = { 0xE92D4000u, 0xE24DD004u, 0xE59F00
 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
+static const u32 sVBlankIntrPatternThumb2[] = { 0x46C04718u, 0x0000FFFFu, 0x4804B508u, 0x28006800u }; // +8
+static const u32 sVBlankIntrPatternThumb3[] = { 0xE51FF004u, 0x037FD67Cu, 0x4804B508u, 0x28006800u }; // +8
+static const u32 sVBlankIntrPatternThumb4[] = { 0x46C04770u, 0x02FFFE1Du, 0x4804B508u, 0x28006800u }; // +8
+static const u32 sVBlankIntrPatternThumb5[] = { 0xE51FF004u, 0x037FA868u, 0x4804B508u, 0x28006800u }; // +8
 
 bool CheatEnginePatch::FindPatchTarget(PatchContext& patchContext)
 {
@@ -41,6 +46,42 @@ bool CheatEnginePatch::FindPatchTarget(PatchContext& patchContext)
             _vblankIrqHandler += 2;
         }
     }
+    if (!_vblankIrqHandler)
+    {
+        _vblankIrqHandler = patchContext.FindPattern32(sVBlankIntrPatternThumb2, sizeof(sVBlankIntrPatternThumb2));
+        if (_vblankIrqHandler)
+        {
+            _foundPattern = sVBlankIntrPatternThumb2;
+            _vblankIrqHandler += 2;
+        }
+    }
+    if (!_vblankIrqHandler)
+    {
+        _vblankIrqHandler = patchContext.FindPattern32(sVBlankIntrPatternThumb3, sizeof(sVBlankIntrPatternThumb3));
+        if (_vblankIrqHandler)
+        {
+            _foundPattern = sVBlankIntrPatternThumb3;
+            _vblankIrqHandler += 2;
+        }
+    }
+    if (!_vblankIrqHandler)
+    {
+        _vblankIrqHandler = patchContext.FindPattern32(sVBlankIntrPatternThumb4, sizeof(sVBlankIntrPatternThumb4));
+        if (_vblankIrqHandler)
+        {
+            _foundPattern = sVBlankIntrPatternThumb4;
+            _vblankIrqHandler += 2;
+        }
+    }
+    if (!_vblankIrqHandler)
+    {
+        _vblankIrqHandler = patchContext.FindPattern32(sVBlankIntrPatternThumb5, sizeof(sVBlankIntrPatternThumb5));
+        if (_vblankIrqHandler)
+        {
+            _foundPattern = sVBlankIntrPatternThumb5;
+            _vblankIrqHandler += 2;
+        }
+    }
 
     if (_vblankIrqHandler)
     {
@@ -89,6 +130,8 @@ void CheatEnginePatch::ApplyPatch(PatchContext& patchContext)
         // 1:
         // pop {r3,lr}
         // bx lr
+        _vblankIrqHandler[6] = 0xE51FF004; // ldr pc,= address
+        _vblankIrqHandler[7] = (u32)cheatEnginePatchCode->GetCheatEngineFunctionArm(); // address
     }
     else if (_foundPattern == sVBlankIntrPatternThumb0)
     {
@@ -104,8 +147,15 @@ void CheatEnginePatch::ApplyPatch(PatchContext& patchContext)
         // pop {r3}
         // bx r3
         // nop
+        ((u16*)_vblankIrqHandler)[8] = THUMB_LDR_PC_IMM(THUMB_R1, 0); // ldr r1,= address
+        ((u16*)_vblankIrqHandler)[9] = THUMB_BX(THUMB_R1); // bx r1
+        _vblankIrqHandler[10 >> 1] = (u32)cheatEnginePatchCode->GetCheatEngineFunction(); // address
     }
-    else if (_foundPattern == sVBlankIntrPatternThumb1)
+    else if (_foundPattern == sVBlankIntrPatternThumb1
+        || _foundPattern == sVBlankIntrPatternThumb2
+        || _foundPattern == sVBlankIntrPatternThumb3
+        || _foundPattern == sVBlankIntrPatternThumb4
+        || _foundPattern == sVBlankIntrPatternThumb5)
     {
         // push {r3,lr}
         // ldr r0,=
@@ -117,6 +167,23 @@ void CheatEnginePatch::ApplyPatch(PatchContext& patchContext)
         // pop {r3}
         // pop {r3}
         // bx r3
+
+        // rewrite the function to
+        // add r1, pc, #4
+        // ldr r0,=
+        // ldr r2,= cheatengine_entry_thumb_replace
+        // bx r2
+        // beq 1f
+        // bl
+        // 1:
+        // mov pc, r4
+        // .word cheatengine_entry_thumb_replace
+
+        ((u16*)_vblankIrqHandler)[0] = THUMB_ADD_PC_IMM(THUMB_R1, 4); // add r1, pc, #4
+        ((u16*)_vblankIrqHandler)[2] = THUMB_LDR_PC_IMM(THUMB_R2, 8); // ldr r2,= cheatengine_entry_thumb_replace
+        ((u16*)_vblankIrqHandler)[3] = THUMB_BX(THUMB_R2); // bx r2
+        ((u16*)_vblankIrqHandler)[7] = THUMB_MOV_HIREG(THUMB_HI_PC, THUMB_R4); // mov pc, r4
+        _vblankIrqHandler[8 >> 1] = (u32)cheatEnginePatchCode->GetCheatEngineFunctionThumbReplace(); // .word cheatengine_entry_thumb_replace
     }
     else
     {

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

@@ -4,6 +4,8 @@
 
 DEFINE_SECTION_SYMBOLS(patch_cheatengine);
 
+extern "C" void cheatengine_entry_arm(void);
+extern "C" void cheatengine_entry_thumb_replace(void);
 extern "C" void cheatengine_entry(void);
 
 extern const void* cheatengine_cheatsPtr;
@@ -21,4 +23,14 @@ public:
     {
         return GetAddressAtTarget((void*)cheatengine_entry);
     }
+
+    const void* GetCheatEngineFunctionArm() const
+    {
+        return GetAddressAtTarget((void*)cheatengine_entry_arm);
+    }
+
+    const void* GetCheatEngineFunctionThumbReplace() const
+    {
+        return GetAddressAtTarget((void*)cheatengine_entry_thumb_replace);
+    }
 };

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

@@ -1,12 +1,34 @@
 .cpu arm7tdmi
 .section "patch_cheatengine", "ax"
 .syntax unified
-.thumb
 
 // For reference on how Action Replay codes work for the DS
 // - https://problemkaputt.de/gbatek-ds-cart-cheat-action-replay-ds.htm
 // - https://github.com/melonDS-emu/melonDS/blob/master/src/AREngine.cpp
 
+.arm
+.global cheatengine_entry_arm
+.type cheatengine_entry_arm, %function
+cheatengine_entry_arm:
+    adr r12, cheatengine_entry + 1
+    bx r12
+
+.thumb
+.global cheatengine_entry_thumb_replace
+.type cheatengine_entry_thumb_replace, %function
+cheatengine_entry_thumb_replace:
+    push {r4, r5, lr} // r5 is a dummy
+    ldr r0, [r0]
+    adr r4, cheatengine_entry_thumb_replace_return
+    cmp r0, #0
+    mov pc, r1
+
+.balign 4
+
+cheatengine_entry_thumb_replace_return:
+    pop {r4}
+    nop
+
 .global cheatengine_entry
 .type cheatengine_entry, %function
 cheatengine_entry:
@@ -79,7 +101,7 @@ runCheat_opcode_loop:
     cmp r3, #0xE0
     bne runCheat_opcode_loop
 
-    // opcode E0 has a dynamic length
+    // opcode E has a dynamic length
     adds r2, #7
     movs r3, #7
     bics r2, r3 // pad length to multiple of 8
@@ -385,10 +407,11 @@ opcode_DC: // offset += b
 opcode_EX: // copy b param bytes to address a+offset
     push {r0}
 
-    adds r0, r2
-    adds r0, #7
-    movs r3, #7
-    bics r0, r3 // pad length to multiple of 8
+    // pad length to multiple of 8
+    adds r3, r2, #7
+    lsrs r3, r3, #3
+    lsls r3, r3, #3
+    adds r0, r3
 
     pop {r3}
     push {r0}

common/thumbInstructions.h

@@ -32,4 +32,5 @@
 #define THUMB_STR_IMM(rd, rb, imm)  (0x6000 | (((imm) >> 2) << 6) | ((rb) << 3) | (rd))
 #define THUMB_STR_SP_IMM(rd, imm)   (0x9000 | ((rd) << 8) | (((imm) >> 2) & 0xFF))
 #define THUMB_LDR_SP_IMM(rd, imm)   (0x9800 | ((rd) << 8) | (((imm) >> 2) & 0xFF))
+#define THUMB_ADD_PC_IMM(rd, imm)   (0xA000 | ((rd) << 8) | (((imm) >> 2) & 0xFF))
 #define THUMB_SVC(x)                (0xDF00 | (x))