Messages in this thread | | | Subject | Re: [PATCH 26/34] mm: implement new mprotect_key() system call | From | Dave Hansen <> | Date | Wed, 9 Dec 2015 09:05:06 -0800 |
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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.
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