GeckoLoader/loader.cpp

//#include <vector>
//#include <string>

//using std::array;
//using std::memcpy;
//using std::memcmp;
//using std::memset;
//using std::string;

#define dcbst(_val) asm volatile("dcbst 0, %0" \
                                 :             \
                                 : "r"(_val))
#define dcbf(_val) asm volatile("dcbf 0, %0" \
                                :            \
                                : "r"(_val))
#define icbi(_val) asm volatile("icbi 0, %0" \
                                :            \
                                : "r"(_val))

#define call(addr) ((void (*)(...))addr)
#define CODEHANDLER 0x800018A8
#define GCT_MAGIC 0x00D0C0DE

#define __start call(0x4948494C)

using u32 = unsigned int;
using u16 = unsigned short;
using u8 = unsigned char;
using s32 = int;
using s16 = short;
using s8 = char;
using f32 = float;
using f64 = double;

__attribute__((noreturn)) int main();

struct CodeList {

  u16 mBaseASM;
  u16 mUpperBase;
  u16 mOffsetASM;
  u16 mLowerOffset;

};

struct Info {

  const u32 allocsize;
  const u32 loaderSize;
  const u32 handlerSize;
  const u32 codeSize;
  const u32* codehandlerHook;
  const u32 crypted;

};

class DiscHeader {

public:

  enum class TVMODE {
    NTSC,
    PAL,
    DEBUG,
    DEBUGPAL,
    MPAL,
    PAL60
  };
  struct MetaData {

    const u8 mDiscID; //0x0000
    const u16 mGameCode; //0x0001
    const u8 mRegionCode; //0x0003
    const u16 mMakerCode; //0x0004
    const u8 mDiscNumber; //0x0006
    const u8 mDiscVersion; //0x0007
    const u8 mAudioStreaming; //0x0008
    const u8 mStreamBufferSize; //0x0009
    const u8 _00[12]; //0x000A
    const u32 mWiiMagic; //0x0018
    const u32 mGCNMagic; //0x001C
    const u32 mNinBootCode; //0x0020
    const u32 mAppVersion; //0x0024
    const u32 mPhysicalRAMSize; //0x0028
    const u32 mBoardModel; //0x002C
    u8* mOSArenaLo; //0x0030
    u8* mOSArenaHi; //0x0034
    u32* mFstStart; //0x0038
    u32 mFstSize; //0x003C
    u32 mDebuggerPresent; //0x0040
    const u32 mDebuggerExceptionMask; //0x0044
    void* mExceptionHookDest; //0x0048
    const u32 mExceptionReturn; //0x004C
    u32 _01[0x10 / 4]; //0x0050
    u32 mDebuggerHook[0x24 / 4]; //0x0060
    u32 _02[0x3C / 4]; //0x0084
    u32 mCurrentOSContext; //0x00C0
    u32 mPreviousOSMask; //0x00C4
    u32 mCurrentOSMask; //0x00C8
    TVMODE mTVMode; //0x00CC
    u32 mARAMSize; //0x00D0
    void* mCurOSContextLogical; //0x00D4
    void* mDefaultOSThreadLogical; //0x00D8
    u32* mThreadQueueHead; //0x00DC
    u32* mThreadQueueTail; //0x00E0
    u32* mCurrentOSThread; //0x00E4
    u32 mDebuggerSize; //0x00E8
    u32* mDebuggerMonitorLoc; //0x00EC
    u32 mSimulatedMemSize; //0x00F0
    u8* mBi2HeaderLoc; //0x00F4
    u32 mBusClockSpeed; //0x00F8
    u32 mCPUClockSpeed; //00x00FC
    u32 _04[0x3010 / 4];
    u8* mWiiHeap; //0x3110

  };

  static MetaData sMetaData;

  enum class CONSOLETYPE { Gamecube, Wii, Unknown };

  inline u32 getGameID() { return ((u32)sMetaData.mDiscID << 24) | ((u32)sMetaData.mGameCode << 8) | ((u32)sMetaData.mRegionCode); }
  inline u16 getMakerID() { return sMetaData.mMakerCode; }
  inline u8 getDiscNumber() { return sMetaData.mDiscNumber; }
  inline u8 getDiscVersion() { return sMetaData.mDiscVersion; }

  CONSOLETYPE detectHomeConsole()
  {
    if (sMetaData.mGCNMagic) {
      return CONSOLETYPE::Gamecube;
    }
    else if (sMetaData.mWiiMagic) {
      return CONSOLETYPE::Wii;
    }

    return CONSOLETYPE::Unknown;
  }

  inline void setHeap(u32 alloc)
  {
    if (sMetaData.mBi2HeaderLoc < sMetaData.mOSArenaHi) {
      sMetaData.mOSArenaHi = sMetaData.mBi2HeaderLoc - alloc;
      if (this->detectHomeConsole() == DiscHeader::CONSOLETYPE::Wii) {
        sMetaData.mWiiHeap = sMetaData.mBi2HeaderLoc - alloc;
      }
    }
    else {
      sMetaData.mOSArenaHi = sMetaData.mWiiHeap - alloc;
      if (this->detectHomeConsole() == DiscHeader::CONSOLETYPE::Wii) {
        sMetaData.mWiiHeap -= alloc;
      }
    }
  }
};

static DiscHeader sDisc;
Info gpModInfo = {
  0x48454150,
  0x4C53495A,
  0x4853495A,
  0x4353495A,
  (const u32*)0x484F4F4B,
  0x43525054,
};

inline u32 extractBranchAddr(u32* bAddr) {
  s32 offset;
  if (*bAddr & 0x2000000)
    offset = (*bAddr & 0x3FFFFFD) - 0x4000000;
  else
    offset = *bAddr & 0x3FFFFFD;
  return (u32)bAddr + offset;
}

namespace Memory {

  static void memcpy(u8* to, u8* from, s32 size)
  {
    for (s32 i = 0; i < size; ++i) {
      *to++ = *from++;
    }
  }

  namespace Cache {

    static inline void flushAddr(void* addr)
    {
      dcbf(addr);
      icbi(addr);
    }

    static void flushRange(u8* addr, s32 size)
    {
      size += 31 + (((u32)addr & 31) > 0);

      for (u32 i = 0; i < (size >> 5); ++i) {
        flushAddr((void*)(addr + (i << 5)));
      }
    }

    static void storeAddr(void* addr)
    {
      dcbst(addr);
      icbi(addr);
    }

    static void storeRange(u8* addr, s32 size)
    {
      size += 31 + (((u32)addr & 31) > 0);

      for (u32 i = 0; i < (size >> 5); ++i) {
        storeAddr((void*)(addr + (i << 5)));
      }
    }

  }

  namespace Direct {

    template <typename T>
    static inline void write(T* addr, T value)
    {
      *addr = value;
      Cache::flushAddr(addr);
    }

    /*This constructs a branch instruction. &TO = ((TO - FROM) & MAX_OFFSET) | BRANCH_TYPE | !!isLink*/
    static inline void branch(void* addr, void* to, bool lk)
    {
      Direct::write<u32>((u32*)(addr), ((((u32)(to)-(u32)(addr)) & 0x3ffffff) | 0x48000000 | lk));
    }

  }

  namespace Search {

    static u32* array(u32* start, u32* end, u32 arrayLength, const u32* hookData)
    {
      u32 index = 0;

      /*Loop through the games RAM, make sure we don't find our own hook data by accident*/
      for (u32 i = 0; &start[i] < end; ++i) {
        /*If the data matches, increase the index counter and continue search,
        else set index to 0 and continue searching*/
        if (start[i] == hookData[index])
          ++index;
        else
          index = 0;

        /*If the data has matched the whole array, return the address of the match*/
        if (index >= (arrayLength) && (&start[i] < (u32*)&gpModInfo || &start[i] > (u32*) & gpModInfo + sizeof(Info)))
          return &start[i];
      }
      return nullptr;
    }

    template <typename T>
    static T* single(T* start, T* end, T match)
    {
      for (u32 i = 0; &start[i] < end; ++i) {
        if (start[i] == match) {
          return &start[i];
        }
      }
      return nullptr;
    }

    /*Call this after viHook, finds the address of the first instance
    of targetVal, and hooks it to the pointer hookTo*/
    static inline void hookFunction(u32* start, u32 targetVal, void* hookTo, bool lk)
    {
      Direct::branch(Search::single<u32>(start, start + 0x500, targetVal), hookTo, lk);
    }

  }

  class Crypt {

  private:
    u32 key;

    u32 getKey()
    {
      u32 b1 = (this->key >> 24) & 0xFF;
      u32 b2 = (this->key >> 16) & 0xFF;
      u32 b3 = (this->key >> 8) & 0xFF;
      u32 b4 = this->key & 0xFF;
      b1 ^= b2;
      b2 ^= b3;
      b3 ^= b4;
      return (b4 << 24) | (b3 << 16) | (b2 << 8) | b1;
    }

    void setKey(u32 key)
    {
      u32 b1 = key & 0xFF;
      u32 b2 = (key >> 8) & 0xFF;
      u32 b3 = (key >> 16) & 0xFF;
      u32 b4 = (key >> 24) & 0xFF;
      b3 ^= b4;
      b2 ^= b3;
      b1 ^= b2;
      this->key = (b1 << 24) | (b2 << 16) | (b3 << 8) | b4;
    }

  public:
    Crypt(u32 key)
    {
      this->key = key;
    }

    inline void xorCrypt(u32* dest, u32* buffer, u32 size)
    {
      auto key = this->getKey();

      for (u32 i = 0; i < size; ++i) {
        dest[i] = buffer[i] ^ key;
        key += i << 3;
      }
    }
  };

  enum class Space : u32 { Start = 0x80000000, End = 0x81800000, Size = 0x1800000 };

}

Memory::Crypt gpCryptor = { 0x43595054 };

static void initMods()
{
  sDisc.setHeap(gpModInfo.allocsize); /*Reallocate the internal heap*/

  /*Change codelist pointer to the new address in the allocation*/
  CodeList* codelistPointer = (CodeList*)((u32)&gpModInfo + sizeof(Info) + 0xFC);
  codelistPointer->mUpperBase = (((u32)sDisc.sMetaData.mOSArenaHi + gpModInfo.handlerSize) >> 16) & 0xFFFF;
  codelistPointer->mLowerOffset = ((u32)sDisc.sMetaData.mOSArenaHi + gpModInfo.handlerSize) & 0xFFFF;

  /*Copy codelist to the new allocation*/
  if (gpModInfo.crypted) {
    Memory::memcpy(sDisc.sMetaData.mOSArenaHi, (u8*)&gpModInfo + sizeof(Info) + 4, gpModInfo.handlerSize);
    gpCryptor.xorCrypt((u32*)(sDisc.sMetaData.mOSArenaHi + gpModInfo.handlerSize), (u32*)((u8*)&gpModInfo + sizeof(Info) + gpModInfo.handlerSize + 4), gpModInfo.codeSize >> 2);
  }
  else {
    Memory::memcpy(sDisc.sMetaData.mOSArenaHi, (u8*)&gpModInfo + sizeof(Info) + 4, gpModInfo.handlerSize + gpModInfo.codeSize);
  }

  /*Get codehandler hook resources*/
  auto fillInField = Memory::Search::single<u32>((u32*)sDisc.sMetaData.mOSArenaHi, (u32*)(sDisc.sMetaData.mOSArenaHi + 0x600), 0x00DEDEDE);
  auto returnAddress = extractBranchAddr((u32*)gpModInfo.codehandlerHook);
  auto ppc = *gpModInfo.codehandlerHook;

  
  /*Write hook branch*/
  Memory::Direct::branch((void*)gpModInfo.codehandlerHook, (void*)((u32)sDisc.sMetaData.mOSArenaHi + 0xA8), false); //entryhook

  /*Temporary nop*/
  *fillInField = 0x60000000;
  
  /*Flush the cache so that the instructions update*/
  Memory::Cache::flushRange((u8*)sDisc.sMetaData.mOSArenaHi, gpModInfo.handlerSize + gpModInfo.codeSize);

  /*Call the codehandler*/
  call((void*)((u32)(sDisc.sMetaData.mOSArenaHi) + 0xA8))();

  /*Write original instruction or translate offset data if a branch*/
  if (((ppc >> 24) & 0xFF) > 0x47 && ((ppc >> 24) & 0xFF) < 0x4C) {
    Memory::Direct::branch((void*)fillInField, (void*)returnAddress, ppc & 1);
  } else {
    Memory::Direct::write(fillInField, ppc);
  }

  /*Write branch back to the hook address + 4*/
  Memory::Direct::branch((void*)&fillInField[1], (void*)(&gpModInfo.codehandlerHook[1]), false); //return

}

int main()
{
  if (sDisc.detectHomeConsole() != DiscHeader::CONSOLETYPE::Unknown) {
    initMods();
  }
  __start();
}