[RFC v5 12/38] mm: ability to disable execute permission on a key at creation

Dave Hansen dave.hansen at intel.com
Wed Jul 12 08:19:31 AEST 2017

On 07/11/2017 03:14 PM, Ram Pai wrote:
> Now how many does the kernel use to reserve for itself is something
> the kernel knows too and hence can expose it, though the information
> may change dynamically as the kernel reserves and releases the key
> based on its internal needs. 
> So i think we can expose this informaton through procfs/sysfs and let
> the application decide how it wants to use the information.

Why bother?  On x86, you'll be told either 14 or 15 depending on whether
you tried to create a mapping in the process without execute permission.
 You can't use all 14 or 15 unless you actually call pkey_alloc() anyway
because the /proc check is inherently racy.

I'm just not sure I see the value in creating a new ABI for it.

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