Exceptional behavior: the Windows 8.1 X64 SEH Implementation

In my last post, you may remember how the latest Uroburos rootkit was able to disarm Patchguard on Windows 7. I was recently looking into how Patchguard is implemented in Windows 8.1 and decided to dig into Exception Handling on x64. As a matter of fact, all the new 64-bit Windows operating systems have entirely changed the way they manage error conditions from their state in older 32-bit versions of Windows (C++ exceptions and OS Structured Exception handling). There are a lot of papers available on 64-bit Windows exception handling on the web, but I decided to increase my knowledge on this topic with the goal to understand how it is implemented and to correctly characterize some strange behavior associated with the implementation of Patchguard on Windows 8.1.