From 0a1c70370bef14722daa8e8134887c9a56c0043f Mon Sep 17 00:00:00 2001
From: JoshuaMK <60854312+JoshuaMKW@users.noreply.github.com>
Date: Tue, 14 Apr 2020 15:48:58 -0500
Subject: [PATCH] Added GeckoLoader C source

Compile with godbolt, setting: x86-64 clang 10.0.0, option: -O3 --target=unknown-ppc-eabi
---
 loader.c | 159 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 159 insertions(+)
 create mode 100644 loader.c

diff --git a/loader.c b/loader.c
new file mode 100644
index 0000000..e9a82bd
--- /dev/null
+++ b/loader.c
@@ -0,0 +1,159 @@
+#include "cache.h"
+
+#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))
+
+typedef unsigned int u32;
+typedef unsigned short u16;
+typedef unsigned char u8;
+typedef int BOOL;
+typedef u32 unk32;
+enum { FALSE, TRUE };
+enum { NULL };
+
+struct Info {
+	u32 allocsize;
+	u32 _loaderSize;
+	u32 _loaderFullSize;
+	struct CodeList* _codelistPointer;
+    u32 _wiiVIHook[4];
+    u32 _gcnVIHook[8];
+};
+
+struct CodeList {
+    u16 mBaseASM;
+    u16 mUpperBase;
+    u16 mOffsetASM;
+    u16 mLowerOffset;
+};
+
+struct DiscInfo {
+  u8 mDiscID;
+  u16 mGameCode;
+  u8 mRegionCode;
+  u16 mMakerCode;
+  u8 mDiscNumber;
+  u8 mDiscVersion;
+  u8 mAudioStreaming;
+  u8 mStreamBufferSize;
+  u8 mUnknown[12];
+  u32 mWiiMagic;
+  u32 mGCNMagic;
+  u32 mUnknown2[2];
+  u32 mRAMSize;
+  u32 mUnknown3[2];
+  u32* mHeapPointer;
+  u32 mHeapMirror;
+  u32 mFstSize;
+  u32 mData[(0x3110 - 0x40) / 4];
+  u32 mWiiHeap;
+};
+
+struct Info gInfo = {
+    .allocsize = 0,
+    ._loaderSize = 0,
+    ._loaderFullSize = 0,
+    ._codelistPointer = (struct CodeList*)0x800018F8,
+    ._wiiVIHook = {0x7CE33B78, 0x38870034,
+				   0x38A70038, 0x38C7004C},
+    ._gcnVIHook = {0x7C030034, 0x38830020,
+				   0x5485083C, 0x7C7F2A14,
+				   0xA0030000, 0x7C7D2A14,
+				   0x20A4003F, 0xB0030000},
+};
+
+static inline void flushAddr(void* addr)
+{
+    dcbf(addr);
+    icbi(addr);
+}
+
+static inline void directWrite(u32* addr, u32 ptr) {
+	addr[0] = ptr;
+	flushAddr(addr);
+}
+
+static inline void directBranchEx(void* addr, void* ptr, BOOL link) {
+    directWrite((u32*)(addr),
+    ((((u32)(ptr) - (u32)(addr)) & 0x3ffffff) | 0x48000000 | !!link));
+}
+
+void (*_init_registers)(void) = &gInfo;
+void (*_codeHandler)(void) = &gInfo;
+
+static inline u32* findFunction(u32* hookData, u32* start, u32 end, u32 arrayLength) {
+	u32 index = 0;
+	for (u32 i = 0; (u32)&start[i] < end; ++i) {
+		if (start[i] == hookData[index]) index = index + 1;
+		else index = 0;
+		if (index >= (arrayLength - 1)) {
+            if ((u32)&start[i] < &gInfo || (u32)&start[i] > (u32)&gInfo + 0x100){
+                return &start[i];
+            }
+		}
+	}
+	return NULL;
+}
+
+void hookFunction(u32* start, u32 hookInstruction, u32 hookTo) {
+	int i = 0;
+	while (start[i] != hookInstruction) {
+		++i;
+	}
+	directBranchEx((u32*)(&start[i]), (void*)(hookTo), FALSE);
+}
+
+static inline void overwriteValue(u32* addr, u32 newValue) {
+    addr[0] = newValue;
+    flushAddr(&addr[0]);
+}
+
+void initMods(struct DiscInfo* baseAddress) {
+
+	struct Info* infoPointer = &gInfo;
+	const u32* geckoPointerInit = (u32*)(u32)baseAddress + 0x18F8;
+	u32 sizeDiff = infoPointer->_loaderFullSize - infoPointer->_loaderSize;
+	const u32* sourcePointer = (u32*)(infoPointer);
+
+	if (infoPointer->_codelistPointer) {
+		if (baseAddress->mWiiMagic) {
+			baseAddress->mHeapPointer = (u32)baseAddress->mWiiHeap - infoPointer->allocsize;
+			baseAddress->mWiiHeap = (u32)baseAddress->mHeapPointer;
+		}
+		else if(baseAddress->mGCNMagic) {
+			baseAddress->mHeapPointer = (u32)baseAddress->mHeapPointer - infoPointer->allocsize;
+		}
+
+		if (infoPointer->_loaderFullSize > 0 && infoPointer->_loaderSize > 0) {
+			while (sizeDiff > 0) {
+				sizeDiff = sizeDiff - 4;
+				baseAddress->mHeapPointer[sizeDiff / 4] = sourcePointer[sizeDiff / 4];
+			}
+			infoPointer->_codelistPointer->mUpperBase = ((u32)baseAddress->mHeapPointer >> 16) & 0xFFFF;
+			infoPointer->_codelistPointer->mLowerOffset = (u32)(baseAddress->mHeapPointer) & 0xFFFF;
+			flushAddr(&infoPointer->_codelistPointer->mUpperBase);
+			flushAddr(&infoPointer->_codelistPointer->mLowerOffset);
+
+            u32* functionAddr;
+            if (baseAddress->mWiiMagic) {
+                functionAddr = findFunction((u32*)infoPointer->_wiiVIHook, (u32*)baseAddress, 0x817FFF00, 0x4);
+            }
+            else {
+                functionAddr = findFunction((u32*)infoPointer->_gcnVIHook, (u32*)baseAddress, 0x817FFF00, 0x8);
+            }
+			if (functionAddr) {
+				hookFunction(functionAddr, 0x4E800020, 0x800018A8);
+			}
+		}
+	}
+}
+
+int main() {
+	struct DiscInfo* baseAddress = (struct DiscInfo*)0x80000000;
+	if (baseAddress->mWiiMagic || baseAddress->mGCNMagic) {
+		initMods(baseAddress);
+        (*_codeHandler)();
+	}
+    (*_init_registers)();
+}
\ No newline at end of file