Re: pkeys on POWER: Access rights not reset on execve

On Fri, 8 Jun 2018 12:44:53 +0200
Florian Weimer [off-list ref] wrote:

On 06/08/2018 12:15 PM, Michal Such=C3=A1nek wrote:

quoted

On Fri, 8 Jun 2018 07:53:51 +0200
Florian Weimer [off-list ref] wrote:
 =20

quoted

On 06/08/2018 04:34 AM, Ram Pai wrote: =20

quoted

quoted

So the remaining question at this point is whether the Intel
behavior (default-deny instead of default-allow) is preferable. =20

Florian, remind me what behavior needs to fixed? =20

See the other thread.  The Intel register equivalent to the AMR by
default disallows access to yet-unallocated keys, so that threads
which are created before key allocation do not magically gain
access to a key allocated by another thread.
=20

=20
That does not make any sense. The threads share the address space so
they should also share the keys.
=20
Or in other words the keys are supposed to be acceleration of
mprotect() so if mprotect() magically gives access to threads that
did not call it so should pkey functions. If they cannot do that
then they fail the primary purpose. =20

=20
That's not how protection keys work.  The access rights are=20
thread-specific, so that you can change them locally, without=20
synchronization and expensive inter-node communication.
=20

And the association of a key with part of the address space is
thread-local as well?

Thanks

Michal