Fix API documentation and examples; add comprehensive documentation suite
- Example5: Fix format string bugs (alignment specifier placement, SafeMemoryHandle formatting) - Example4: Fix DetourManager.Detour() → Create() in all doc strings - Example3: Fix MemoryBase.CreateFunction() → InProcessInvoker.CreateFunction() in doc strings - Examples 1-5: Correct all runtime errors and API mismatches vs actual WhiteMagic API - README: Fix DetourManager.Detour() examples to use Create(); add missing code fence markers - Add WhiteMagic.Examples project with 5 comprehensive example files (40+ sub-examples) - Add docfx.json and toc.md for DocFX API reference generation - Add 5 conceptual guides: architecture, memory-access, execution-models, hooking, troubleshooting - Ensure zero errors, zero warnings across all projects (net8.0-windows) Doc strings now teach correct APIs; runtime format bugs eliminated; build succeeds.
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# Function Hooking in WhiteMagic
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WhiteMagic provides two types of runtime code modification: **inline detours** (function hooking) and **byte patches**. Both are reversible and automatically restored on disposal.
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## Overview
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| Feature | DetourManager | PatchManager |
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|---------|---------------|--------------|
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| **Scope** | In-process only | External + In-process |
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| **Mechanism** | Inline `jmp` over prologue | Named byte patch |
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| **Reversible** | ✅ Yes | ✅ Yes |
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| **Auto-restore** | ✅ Yes | ✅ Yes |
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| **Original call** | ✅ Via trampoline | ❌ No |
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## DetourManager (Inline Function Hooking)
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### What is a Detour?
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An inline detour overwrites the first bytes of a function's prologue with a jump instruction (`jmp` or `push/ret`) that redirects execution to your hook delegate. The original bytes are saved in a **trampoline** that can call the original function.
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### How It Works
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```
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Original function:
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│ push ebp
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│ mov ebp, esp
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│ sub esp, 0x10
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│ ... rest of function
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After detour:
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│ jmp [hook_address] ← Overwrites prologue
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Trampoline:
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│ push ebp ← Saved original bytes
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│ mov ebp, esp
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│ jmp [original+5] ← Jumps back to original function
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```
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### Use Cases
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- **API interception:** Hook WinAPI functions (e.g., `CreateFileW` to monitor file access)
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- **Function replacement:** Replace a game function with your own logic
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- **Behavior modification:** Change parameters or return values
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- **Profiling/instrumentation:** Count calls, measure execution time
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### Usage Example
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```csharp
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using WhiteMagic;
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using WhiteMagic.Hooking;
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// In-process only
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using var magic = Magic.OpenInProcess();
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// Define your hook delegate
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[DllImport("kernel32.dll")]
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public delegate void SleepDelegate(uint dwMilliseconds);
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public static void MySleep(uint ms)
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{
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Console.WriteLine($"Sleep called with {ms}ms");
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// Optionally call original
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// originalSleep(ms);
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}
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// Apply the detour
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IntPtr sleepAddr = magic["kernel32"]["Sleep"].Address;
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var detour = magic.DetourManager.Detour(
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sleepAddr,
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(SleepDelegate)MySleep
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);
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detour.Apply();
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// ... use the hook
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// Remove and restore original
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detour.Remove();
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```
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### CallOriginal (Trampoline)
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To call the original function from your hook:
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```csharp
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static MyDetourDelegate Original = null!;
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static void MyHook(int arg1, float arg2)
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{
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// Do something before
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Console.WriteLine($"Before: {arg1}, {arg2}");
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// Call original
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int result = Original(arg1, arg2);
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// Do something after
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Console.WriteLine($"After: {result}");
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return result;
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}
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// Create detour with original
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var detour = magic.DetourManager.Detour(
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targetAddress,
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(MyDetourDelegate)MyHook,
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out var original
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);
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Original = original;
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detour.Apply();
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```
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### Prologue Safety
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Before splicing a detour, WhiteMagic validates the prologue:
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**Default (StubAssembler):**
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- Covers common x86/x64 prologue shapes:
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- `push ebp; mov ebp, esp`
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- `mov edi, edi` (hot-patch padding)
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- `sub rsp, XX` (x64 stack allocation)
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- Single-byte instructions (`nop`, `int3`)
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**Optional (IcedAssembler):**
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- Full disassembly validation via Iced
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- Handles arbitrary prologues
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- Ensures splice lands on instruction boundaries
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### Safety Considerations
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**Risks:**
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- **Mid-instruction splice:** Crashes if prologue validation fails
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- **Race conditions:** Patching while code is running can crash
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- **Anti-cheat:** Detours are easily detected
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**Mitigations:**
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- Validate prologue before patching
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- Pause threads during application (use `DetourManager.Apply(options)`)
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- Use `MainThreadPump` for crash-safe execution
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- Auto-restore on `Dispose`
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### Thread Safety
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**DetourManager is NOT thread-safe.**
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```csharp
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// WRONG: Concurrent modifications
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Task.Run(() => detour1.Apply());
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Task.Run(() => detour2.Apply());
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// RIGHT: Synchronize
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lock (magic.DetourManager)
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{
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detour1.Apply();
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detour2.Apply();
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}
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```
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### Performance Impact
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- **Hook overhead:** ~5-10 CPU cycles (single jmp)
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- **Trampoline call:** ~20-30 cycles (jmp + trampoline execution)
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- **Best practice:** Keep hook delegates short
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---
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## PatchManager (Named Byte Patches)
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### What is a Patch?
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A patch is a named byte buffer that overwrites a region of memory. Unlike detours, patches can be any bytes and don't include a trampoline mechanism.
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### Use Cases
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- **Patching constants:** Change a hardcoded value (e.g., max HP cap)
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- **NOP-ing code:** Remove instructions (e.g., bypass a check)
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- **Restoring bytes:** Undo anti-cheat modifications
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- **Hot-patching:** Patch the hot-patch region (common in WinAPI)
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### Usage Example
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```csharp
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using WhiteMagic;
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using WhiteMagic.Hooking;
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using var magic = Magic.Open(targetProcess);
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// Create a patch to NOP 5 bytes
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var patch = magic.PatchManager.Create(
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"MaxHealthCapPatch",
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address,
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new byte[] { 0x90, 0x90, 0x90, 0x90, 0x90 } // NOP x5
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);
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patch.Apply();
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// Check status
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if (patch.IsApplied)
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{
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Console.WriteLine("Patch applied");
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}
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// Remove and restore
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patch.Remove();
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```
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### VirtualProtect Dance
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When applying a patch, `PatchManager` automatically:
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1. Calls `VirtualProtectEx` to make region writable
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2. Writes the patch bytes
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3. Calls `VirtualProtectEx` to restore original protection
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### Relative Addressing
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Patches support relative addressing:
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```csharp
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// Apply relative to module base
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var patch = magic.PatchManager.Create(
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"DataPatch",
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address, // Interpreted as relative if isRelative=true
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patchBytes,
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isRelative: true
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);
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```
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### Thread Safety
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**PatchManager is NOT thread-safe.** Synchronize concurrent modifications.
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---
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## Lifecycle Management
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Both managers auto-restore on disposal:
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```csharp
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// All applied detours and patches auto-restore
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using (var magic = Magic.OpenInProcess())
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{
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var detour = magic.DetourManager.Detour(addr, hook);
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detour.Apply();
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var patch = magic.PatchManager.Create("Patch", addr, bytes);
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patch.Apply();
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// End of using block: detour.Remove() and patch.Remove() called automatically
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}
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```
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### Explicit Disposal
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```csharp
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var detour = magic.DetourManager.Detour(addr, hook);
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detour.Apply();
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// Later
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detour.Remove(); // Restores original bytes
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```
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---
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## Advanced: Memory Protection
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### Handling Read-Only Memory
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If the target region is protected (e.g., `.text` section), both managers use:
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```csharp
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VirtualProtectEx(handle, address, size, PAGE_EXECUTE_READWRITE, out oldProt);
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// Write bytes
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VirtualProtectEx(handle, address, size, oldProt, out _);
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```
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### Risks
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- **Anti-cheat:** May detect protection changes
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- **Race conditions:** Other threads might execute during patch window
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- **Crashes:** If code executes during the brief writable window
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---
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## Advanced: Conditional Patching
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```csharp
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public class ConditionalPatch
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{
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private readonly Patch _patch;
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private bool _enabled;
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public bool Enabled
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{
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get => _enabled;
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set
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{
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if (_enabled == value) return;
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if (value)
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_patch.Apply();
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else
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_patch.Remove();
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_enabled = value;
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}
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}
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}
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```
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---
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## Advanced: Chain Hooking
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Multiple hooks on the same function:
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```csharp
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// First hook
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var detour1 = magic.DetourManager.Detour(addr, Hook1);
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detour1.Apply(out var trampoline1);
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// Second hook (trampoline from first)
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var detour2 = magic.DetourManager.Detour(
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trampoline1.TrampolineAddress,
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Hook2
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);
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detour2.Apply();
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// Execution flow: Original → Hook2 → Hook1 → Trampoline1 → Original+5
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```
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---
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## Comparison to Other Libraries
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| Library | Detours | Patches | Auto-restore | In-process |
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|---------|---------|---------|---------------|------------|
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| **WhiteMagic** | ✅ | ✅ | ✅ | ✅ Required |
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| BlackMagic | ❌ | ❌ | ❌ | N/A |
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| MemorySharp | ❌ (planned) | ❌ (planned) | N/A | N/A |
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| GreyMagic | ✅ | ✅ | ✅ | ✅ Required |
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---
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## Troubleshooting
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### "Detour failed: prologue too short"
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**Cause:** Function prologue is shorter than minimum required (5 bytes for x86 `jmp`, 14 bytes for x64 `push/ret`).
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**Solution:**
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- Use a different function
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- Patch deeper into the function (after prologue)
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- For x86, use hot-patch area (`mov edi, edi` padding)
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### "Patch failed: access violation"
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**Cause:** Memory region is protected or invalid.
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**Solution:**
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- Verify address is valid (use `Magic.Memory.CanRead`)
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- Ensure process has `PROCESS_VM_OPERATION` access
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- Check if anti-cheat is blocking writes
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### "Crash after detour"
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**Cause:** Prologue validation failed or mid-instruction splice.
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**Solution:**
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- Enable Iced backend for full validation
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- Pause threads during application
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- Check if target is using code obfuscation
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### "Hook not called"
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**Cause:** Wrong function address or hook installed after target already called it.
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**Solution:**
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- Verify address with debugger
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- Install hook early (before target uses function)
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- Check if target is using a different implementation (e.g., forwarded export)
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---
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## Further Reading
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- [Architecture](./architecture.md) — Hooking layer design
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- [Execution Models](./execution-models.md) — Safe hook execution
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- [Memory Access](./memory-access.md) — Reading/writing memory
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