Ram Pai <linuxram@xxxxxxxxxx> writes: > On Fri, Aug 11, 2017 at 02:34:43PM -0300, Thiago Jung Bauermann wrote: >> Expose useful information for programs using memory protection keys. >> Provide implementation for powerpc and x86. >> >> On a powerpc system with pkeys support, here is what is shown: >> >> $ head /sys/kernel/mm/protection_keys/* >> ==> /sys/kernel/mm/protection_keys/disable_execute_supported <== >> true > > We should not just call out disable_execute_supported. > disable_access_supported and disable_write_supported should also > be called out. Ok, will do in the next version. >> ==> /sys/kernel/mm/protection_keys/total_keys <== >> 32 >> > >> ==> /sys/kernel/mm/protection_keys/usable_keys <== >> 30 > > This is little nebulous. It depends on how we define > usable as. Is it the number of keys that are available > to the app? If that is the case that value is dynamic. > Sometime the OS steals one key for execute-only key. > And anything that is dynamic can be inherently racy. > So I think we should define 'usable' as guaranteed number > of keys available to the app Yes, that is how I defined it: the difference between the number of keys provided by the platform and the keys reserved by the OS. I do need to spell it out somewhere inside Documentation/ though. > and display a value that is one less than what is available. > > in the above example the value should be 29. Good point, I didn't account for the execute-only key. I will make that change in the next version. -- Thiago Jung Bauermann IBM Linux Technology Center -- 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>
