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

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Message-Id: <20170616191041.GA17588@ram.oc3035372033.ibm.com>
Date:   Fri, 16 Jun 2017 12:10:41 -0700
From:   Ram Pai <linuxram@...ibm.com>
To:     Anshuman Khandual <khandual@...ux.vnet.ibm.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        dave.hansen@...el.com, paulus@...ba.org,
        aneesh.kumar@...ux.vnet.ibm.com
Subject: Re: [RFC PATCH 7/7 v1]powerpc: Deliver SEGV signal on protection key
 violation.

On Fri, Jun 16, 2017 at 02:50:13PM +0530, Anshuman Khandual wrote:
> On 06/06/2017 06:35 AM, Ram Pai wrote:
> > 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 ?

It should not be available in uctxt->uc_mcontext.regs->amr.
In fact that field itself should not be there.

The ideas was to use one of the unused fields in gp_regs; without
extending gp_regs, to provide the contents of AMR. the 
PT_AMR offset in gp_regs is currently not used, which I am using
in this patch.

However this patch needs to be modified not to extend pt_regs,
or uctxt->uc_mcontext.regs

Thanks for initiating this concern.
RP

-- 
Ram Pai