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/ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>