/// <summary> /// Primitive patching. Inserts a jump to 'target' at 'site'. Works even if both methods' /// callers have already been compiled. /// </summary> /// <param name="site"></param> /// <param name="target"></param> private static RedirectCallsState PatchJumpTo(IntPtr site, IntPtr target) { RedirectCallsState state = new RedirectCallsState(); // R11 is volatile. unsafe { byte* sitePtr = (byte*)site.ToPointer(); state.A = *sitePtr; state.B = *(sitePtr + 1); state.C = *(sitePtr + 10); state.D = *(sitePtr + 11); state.E = *(sitePtr + 12); state.F = *((ulong*)(sitePtr + 2)); *sitePtr = 0x49; // mov r11, target *(sitePtr + 1) = 0xBB; *((ulong*)(sitePtr + 2)) = (ulong)target.ToInt64(); *(sitePtr + 10) = 0x41; // jmp r11 *(sitePtr + 11) = 0xFF; *(sitePtr + 12) = 0xE3; } return state; }
private static void RevertJumpTo(IntPtr site, RedirectCallsState state) { unsafe { byte* sitePtr = (byte*)site.ToPointer(); *sitePtr = state.A; // mov r11, target *(sitePtr + 1) = state.B; *((ulong*)(sitePtr + 2)) = state.F; *(sitePtr + 10) = state.C; // jmp r11 *(sitePtr + 11) = state.D; *(sitePtr + 12) = state.E; } }
public static void RevertRedirect(MethodInfo from, RedirectCallsState state) { var fptr1 = from.MethodHandle.GetFunctionPointer(); RevertJumpTo(fptr1, state); }