Re: [LI] user space, kernel space and .........

[Arun Sharma <adsharma@xxxxxxxxxxxxxxx>]

On Wed, Jan 12, 2000 at 07:02:12PM +0530, skhader@xxxxxxxxxx wrote:
> And can anybody elaborate why Unix uses only two levels and
> why not all the four ?? And anybody here knows what are the four levels in
> the Intel
> processors.

Intel processors have 4 level aka "rings". The idea was to isolate 
untrusted third party code within the kernel - device drivers for
example.

UNIX uses only two because of historical reasons and no one has found
a reason to change it. All users including root run at ring 4 and the
kernel and device drivers run at ring 0.

	-Arun

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