[RFC v7 24/25] powerpc: Deliver SEGV signal on pkey violation

[Ram Pai]

On Sat, Aug 19, 2017 at 07:54:20AM +1000, Benjamin Herrenschmidt wrote:
> On Fri, 2017-08-18 at 10:04 -0700, Ram Pai wrote:
> > Assume two threads of a task.
> > 
> > T1:  mprotect_key(foo, PAGE_SIZE, pkey=4);
> > T1:  set AMR to disable access for pkey 4;
> > T1:  key fault
> >     T2: set AMR to enable access to pkey 4;
> > T1:  fault handler called.
> >         This fault handler will see the new AMR and not the
> >         one at the time of the fault.
> 
> You aren't context switching AMR with the threads ? Ugh... something is
> very wrong then.

I do store and restore AMR accross context switch. So nevermind; the
above problem cannot happen.

RP