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SubjectRe: [PATCH 26/34] mm: implement new mprotect_key() system call
On 12/09/2015 06:05 PM, Dave Hansen wrote:
> On 12/09/2015 08:45 AM, Michael Kerrisk (man-pages) wrote:
>>>>>> * Explanation of what a protection domain is.
>>>>
>>>> A protection domain is a unique view of memory and is represented by the
>>>> value in the PKRU register.
>> Out something about this in pkey(7), but explain what you mean by a
>> "unique view of memory".
>
> Let's say there are only two protection keys: 0 and 1. There are two
> disable bits per protection key (Access and Write Disable), so a two-key
> PKRU looks like:
>
> | PKEY0 | PKEY1 |
> | AD0 | WD0 | AD1 | WD1 |
>
> In this example, there are 16 possible protection domains, one for each
> possible combination of the 4 rights-disable bits.
>
> "Changing a protection domain" would mean changing (setting or clearing)
> the value of any of those 4 bits. Each unique value of PKRU represents
> a view of memory, or unique protection domain.

Again, some of this could make its way into pkey(7). And I guess there
are useful nuggets for that page to be found in Jon's article at
https://lwn.net/Articles/667156/

Thanks,

Michael




--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/


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