How does Windows protect transition into kernel mode?

Question

How does Windows protect against a user-mode thread from arbitrarily transitioning the CPU to kernel-mode?

I understand these things are true:

1. User-mode th

Answer 1

I think (I may be wrong) that the mechanism which it uses for transition is simple:

• User-mode code executes a software interrupt
• This (interrupt) causes a branch to a location specified in the interrupt descriptor table (IDT)

The thing that prevents user-mode code from usurping this is as follows: you need to be priviledged to write to the IDT; so only the kernel is able to specify what happens when an interrupt is executed.