Re: pkeys: Support setting access rights for signal handlers

From: Florian Weimer <fweimer@redhat.com>
To: Ram Pai <linuxram@us.ibm.com>
Cc: Dave Hansen <dave.hansen@intel.com>,
	linux-mm <linux-mm@kvack.org>,
	x86@kernel.org, linux-arch <linux-arch@vger.kernel.org>,
	linux-x86_64@vger.kernel.org,
	Linux API <linux-api@vger.kernel.org>
Subject: Re: pkeys: Support setting access rights for signal handlers
Date: Mon, 18 Dec 2017 12:00:30 +0100	[thread overview]
Message-ID: <7ab875c5-dc7c-b36e-8612-3d4aaf86a15c@redhat.com> (raw)
In-Reply-To: <20171216172026.GC5461@ram.oc3035372033.ibm.com>

On 12/16/2017 06:20 PM, Ram Pai wrote:
> Ok. Sounds like I do not have much to do. My patches in its current form
> will continue to work and provide the semantics you envision.

Thanks for confirming.

>> I'm open to a different way towards conveying this information to
>> userspace.  I don't want to probe for the behavior by sending a
>> signal because that is quite involved and would also be visible in
>> debuggers, confusing programmers.

> I am fine with your proposal.

So how can we move this forward?  Should I submit a single new patch 
with the new flag with a more appropriate name (PKEY_ALLOC_SIGNALINHERIT 
comes to my mind) and the signal inheritance change?

Dave, do you still want to wait for feedback from the x86 maintainer 
regarding a general interface?  Is this really feasible without detailed 
knowledge of the XSAVE output structure?  Otherwise, there probably 
isn't a way around code which explicitly copies the bits we want to 
preserve from the interrupted CPU context to the signal handler context.

Thanks,
Florian