Re: Page Protection , rings 0-4, and Supervisor/User mode

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On Tue, Apr 26, 2005 at 09:55:03AM +0300, sting sting wrote:
> I had tried to see if in IA-64 we have the same structure of four rings,and 
> the same supervisor mode/user mode.

Yes, similar, you might find more from looking up "current privilege
level"

> I had looked at Intel Itanium Architecture Software Developer Manual.
> (Vol 2: System Architecture).

That's a good start.

> I saw that there is something which is called "protection keys" but I do 
> not know if it is relevant.

Protection keys aren't really directly relevant to what you're talking
about.  You can think of a protection key as a way of tagging TLB
entries with smaller granularity than an ASID (for example, the code
for a library could be given a key and then shared amongst processes
that use that library).  Linux currently doesn't use protection keys.

> There is a paragraph in this manual titled "Privilege levels" which
> says there are 4 privilege levels (0-3) but it talks about
> instructions and registers permissions and not about memory.

Yep, but if you have a look at the TLB insertion format section, you
can see the privilege level is set on insert.  Later on there is
documentation on page access rights which should answer your
questions.

There are a couple of other lists you might like to try with
questions, namely :

https://www.gelato.unsw.edu.au/mailman/listinfo/gelato-technical
https://www.gelato.unsw.edu.au/mailman/listinfo/ia64-technical

-i
[email protected]
http://www.gelato.unsw.edu.au

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