Have you ever thought how transitions between different rings performed? Well, SYSENTER & SYSCALL used in modern OSs for transitioning between ring 3 to ring 0 but if there are other rings, then what’s Intel solution for entering them? The answer is call gates. The rest of this topic described how to use call gates in modern processors. 80386 and its successors have 4 levels protections which isolate and protect user programs from each other and the operating system. It…