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

On Fri, Jun 16, 2017 at 08:33:01PM +1000, Benjamin Herrenschmidt wrote:

On Fri, 2017-06-16 at 14:50 +0530, Anshuman Khandual wrote:

quoted

On 06/06/2017 06:35 AM, Ram Pai wrote:

quoted

The value of the AMR register at the time of the exception
is made available in gp_regs[PT_AMR] of the siginfo.

But its already available there in uctxt->uc_mcontext.regs->amr
while inside the signal delivery context in the user space. The
pt_regs already got updated with new AMR register. Then why we
need gp_regs to also contain AMR as well ?

Also changing gp_regs layout/size is a major ABI issue...

Ben,
	
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?
RP

Ben.

-- 
Ram Pai