Re: [PATCH] pkeys: Introduce PKEY_ALLOC_SIGNALINHERIT and change signal semantics

On 05/09/2018 04:41 PM, Andy Lutomirski wrote:

Hmm.  I can get on board with the idea that fork() / clone() /
pthread_create() are all just special cases of the idea that the thread
that*calls*  them should have the right pkey values, and the latter is
already busted given our inability to asynchronously propagate the new mode
in pkey_alloc().  So let's so PKEY_ALLOC_SETSIGNAL as a starting point.

Ram, any suggestions for implementing this on POWER?

One thing we could do, though: the current initual state on process
creation is all access blocked on all keys.  We could change it so that
half the keys are fully blocked and half are read-only.  Then we could add
a PKEY_ALLOC_STRICT or similar that allocates a key with the correct
initial state*and*  does the setsignal thing.  If there are no keys left
with the correct initial state, then it fails.

The initial PKRU value can currently be configured by the system 
administrator.  I fear this approach has too many moving parts to be viable.

Thanks,
Florian