public void Inject()
{
EnsureNotDisposed();
if (_injected)
{
throw new InvalidOperationException();
}
// TODO: atomic substitute
if (CanMakeRelativeJump(_target, _subst))
{
const int jmpSize = 5;
int jmpDistance = GetRelativeJumpDistance(_target, _subst);
var ptr = Utils.FindNearestOp(_target, jmpSize);
_size = (int)(ptr.ToInt64() - _target.ToInt64());
Debug.Assert(_size <= 16);
_oldCode = CodeBlock.FromPtr(_target, _size);
var reJmp = new CodeBlock(_oldCode);
reJmp.Append(0xE9);
reJmp.AppendInt(GetRelativeJumpDistance(_relocated, _target));
reJmp.WriteTo(_relocated);
var jmp = new CodeBlock();
jmp.Append(0xE9);
jmp.AppendInt(jmpDistance);
for (int i = 0; i < _size - jmpSize; ++i)
{
jmp.Append(0x90);
}
Debug.Assert(jmp.Length == _size);
jmp.WriteTo(_target);
}
else
{
// TODO: absolute jmp to subst code
throw new NotImplementedException();
}
_injected = true;
}
private static void WriteCode(MemoryBlock mem, IntPtr md)
{
// DoPreStub uses __fastcall
// so we need to put it's first argument (methodDesc) in rcx/ecx
// and the second (methodTable, should be NULL) in rdx/edx
var code = new CodeBlock();
// mov rax, DoPreStubAdderss
code.Append(0x48).Append(0xB8).AppendLong(_doPreStubPtr.Value.ToInt64());
// mov rcx, methodDesc
code.Append(0x48).Append(0xB9).AppendLong(md.ToInt64());
// xor rdx, rdx
code.Append(0x48).Append(0x31).Append(0xD2);
// jmp rax
code.Append(0xFF).Append(0xE0);
code.WriteTo(mem.Address);
}