Re: pkeys: Reserve PKEY_DISABLE_READ

[Florian Weimer <fweimer@redhat.com>]

* Dave Hansen:

> On 11/8/18 4:05 AM, Florian Weimer wrote:
>> Would it be possible to reserve a bit for PKEY_DISABLE_READ?
>> 
>> I think the POWER implementation can disable read access at the hardware
>> level, but not write access, and that cannot be expressed with the
>> current PKEY_DISABLE_ACCESS and PKEY_DISABLE_WRITE bits.
>
> Do you just mean in the syscall interfaces?  What would we need to do on
> x86 if we see the bit?  Would we just say it's invalid on x86, or would
> we make sure that PKEY_DISABLE_ACCESS==PKEY_DISABLE_READ?

Ideally, PKEY_DISABLE_READ | PKEY_DISABLE_WRITE and PKEY_DISABLE_READ |
PKEY_DISABLE_ACCESS would be treated as PKEY_DISABLE_ACCESS both, and a
line PKEY_DISABLE_READ would result in an EINVAL failure.

Thanks,
Florian