Re: x86 architecture questions

From: Grumble (invalid_at_kma.eu.org)
Date: 04/25/04 

Date: Sun, 25 Apr 2004 20:10:02 +0000 (UTC)

Matt Taylor wrote:

> It is worth pointing out that this is why the privilege levels are
> so useless. A tiered protection scheme would be very helpful for
> protecting OS structures from drivers and still allowing drivers to
> do their job. Instead, rings 0, 1, and 2 are treated equally by the
> paging mechanism.

Matt,

Are you saying that privilege levels 1 and 2 on IA-32 are useless? Or
do you mean that privilege levels are useless altogether?

Is it even possible to write a POSIX-compliant OS for a CPU that does
not implement privilege levels? Where any application can execute what
we now consider privileged instructions.

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