Re: [RFC PATCH 7/7 v1]powerpc: Deliver SEGV signal on protection key violation.

From: Benjamin Herrenschmidt
Date: Fri Jun 16 2017 - 18:55:45 EST

On Fri, 2017-06-16 at 12:15 -0700, Ram Pai wrote:
> gp_regs size is not changed, nor is the layout. A unused field in
> the gp_regs is used to fill in the AMR contents. Old binaries will not
> be knowing about this unused field, and hence should not break.
> New binaries can leverage this already existing but newly defined
> field; to read the contents of AMR.
> Is it still a concern?

Calls to sys_swapcontext with a made-up context will end up with a crap
AMR if done by code who didn't know about that register.