// Writes push dword ptr [esp+displ]
static void WritePushDwordPtrEspDispl(NativeCodeGenerator code, sbyte displ)
{
code.WriteBytes(0xFF, 0x74);
code.WriteBytes(0x24, (byte)displ);
}
unsafe void CreateOurCode()
{
var code = new NativeCodeGenerator();
// our compileMethod() func
int compileMethodOffset = code.Size;
int numPushedArgs = compileMethodIsThisCall ? 5 : 6;
code.WriteByte(0x51); // push ecx
code.WriteByte(0x50); // push eax
code.WriteByte(0x54); // push esp
for (int i = 0; i < 5; i++)
{
WritePushDwordPtrEspDispl(code, (sbyte)(0xC + numPushedArgs * 4)); // push dword ptr [esp+XXh]
}
if (!compileMethodIsThisCall)
{
WritePushDwordPtrEspDispl(code, (sbyte)(0xC + numPushedArgs * 4)); // push dword ptr [esp+XXh]
}
else
{
code.WriteByte(0x51); // push ecx
}
code.WriteCall(ourCompileMethodInfo.ptr);
code.WriteByte(0x5A); // pop edx
code.WriteByte(0x59); // pop ecx
code.WriteBytes(0x84, 0xD2); // test dl, dl
code.WriteBytes(0x74, 0x03); // jz $+5
code.WriteBytes(0xC2, (ushort)(numPushedArgs * 4)); // retn 14h/18h
for (int i = 0; i < numPushedArgs; i++)
{
WritePushDwordPtrEspDispl(code, (sbyte)(numPushedArgs * 4)); // push dword ptr [esp+XXh]
}
code.WriteCall(origCompileMethod);
code.WriteBytes(0xC2, (ushort)(numPushedArgs * 4)); // retn 14h/18h
// Our callMethod() code. 1st arg is the method to call. stdcall calling convention.
int callMethodOffset = code.Size;
code.WriteByte(0x58); // pop eax (ret addr)
code.WriteByte(0x5A); // pop edx (method to call)
if (compileMethodIsThisCall)
{
code.WriteByte(0x59); // pop ecx (this ptr)
}
code.WriteByte(0x50); // push eax (ret addr)
code.WriteBytes(0xFF, 0xE2); // jmp edx
// Returns token of method
int getMethodTokenOffset = code.Size;
code.WriteCall(returnMethodTokenInfo.ptr);
code.WriteBytes(0xC2, (ushort)(IntPtr.Size * 2));
// Returns name of method
int getMethodNameOffset = code.Size;
code.WriteCall(returnNameOfMethodInfo.ptr);
code.WriteBytes(0xC2, (ushort)(IntPtr.Size * 3));
ourCodeAddr = VirtualAlloc(IntPtr.Zero, new UIntPtr((ulong)code.Size), 0x00001000, PAGE_EXECUTE_READWRITE);
IntPtr baseAddr = ourCodeAddr;
ourCompileMethodInfo.ptrInDll = new IntPtr((byte *)baseAddr + compileMethodOffset);
callMethod = new IntPtr((byte *)baseAddr + callMethodOffset);
returnMethodTokenInfo.ptrInDll = new IntPtr((byte *)baseAddr + getMethodTokenOffset);
returnNameOfMethodInfo.ptrInDll = new IntPtr((byte *)baseAddr + getMethodNameOffset);
byte[] theCode = code.GetCode(baseAddr);
Marshal.Copy(theCode, 0, baseAddr, theCode.Length);
}
