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The privileged ring concept is implemented by intel in its hardware.
In Intel's developers manual there are around 15 instructions that need for sure ring 0 to execute .
In OS-books and other resources you can read that most of kernel code is running at ring 0. But it is difficult to understand that the most of these kernel code, is of these 15 instructions.
Will that say that an operating system implement his own virtual protection rings ? (by example, maybe you can see virtual memory management as an component of this) Or more important, what triggers the RPL register to 0 ?
hope you can understand and eventually help,
Thx in advance
1You imply the wrong way. It’s not “ring 0 => one of the 15 instructions” but rather “one of the 15 instructions => ring 0”. It does not make any statement about other instructions. – Daniel B – 2018-01-10T06:44:28.870
@DanielB don't think thats what the asker is trying to say. English doesn't seem to be their first language. – jdwolf – 2018-01-10T07:01:32.290