From mboxrd@z Thu Jan  1 00:00:00 1970
From: "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: Compat 32-bit syscall entry from 64-bit task!?
Date: Wed, 18 Jan 2012 13:30:25 -0800
Message-ID: <4F1739F1.2070902@zytor.com>
References: <20120116183730.GB21112@redhat.com> <20120117170512.GB17070@redhat.com> <CAObL_7EA-Z8yBbr1+-VW0v8k1okdcMfjRe5LgWo8YL5uvOkXbQ@mail.gmail.com> <49017bd7edab7010cd9ac767e39d99e4.squirrel@webmail.greenhost.nl> <20120118015013.GR11715@one.firstfloor.org> <20120118020453.GL7180@jl-vm1.vm.bytemark.co.uk> <20120118022217.GS11715@one.firstfloor.org> <fc8f165e541482d136ff8fc115fe6875.squirrel@webmail.greenhost.nl> <CA+55aFysH3h8sLHwNcaLnYMsgA28vmHgd3DSLPVw-=TzgfBrbg@mail.gmail.com> <CA+55aFzk6OOHoQ_e3pPQNUGN80tjXT7vYTNaRjXbWiQUnNRiTA@mail.gmail.com> <fd4ccb42a25876131e411299d24d9151.squirrel@webmail.greenhost.nl> <CA+55aFzcSVmdDj9Lh_gdbz1OzHyEm6ZrGPBDAJnywm2LF_eVyg@mail.gmail.com> <CA+55aFwMd8MMrcfG5f0zg=qjrBzUhgY1HgJx6QFcnpMQsW1PNg@mail.gmail.com> <4F1731C1.4050007@zytor.com> <CA+55aFwn
 vOxT_K7HFOkjCbfDtYkAVkvF+a7r-0=T6gga_x9t-g@mail.gmail.com> <4F1733DF.7040905@zytor.com> <CA+55aFzrHaJUKgUCx1uaeuqcyzZuUwQLiGj9dP5D3m-xt6v2SA@mail.gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Cc: Indan Zupancic <indan@nul.nu>, Andi Kleen <andi@firstfloor.org>,
	Jamie Lokier <jamie@shareable.org>,
	Andrew Lutomirski <luto@mit.edu>,
	Oleg Nesterov <oleg@redhat.com>,
	Will Drewry <wad@chromium.org>, linux-kernel@vger.kernel.org,
	keescook@chromium.org, john.johansen@canonical.com,
	serge.hallyn@canonical.com, coreyb@linux.vnet.ibm.com,
	pmoore@redhat.com, eparis@redhat.com, djm@mindrot.org,
	segoon@openwall.com, rostedt@goodmis.org, jmorris@namei.org,
	scarybeasts@gmail.com, avi@redhat.com, penberg@cs.helsinki.fi,
	viro@zeniv.linux.org.uk, mingo@elte.hu, akpm@linux-foundation.org,
	khilman@ti.com, borislav.petkov@amd.com, amwang@redhat.com,
	ak@linux.intel.com, eric.dumazet@gmail.com, gregkh@suse.de,
	dhowells@redhat.com, daniel.lezcano@free.fr,
	linux-fsdevel@vger.kernel.org,
	linux-security-module@vger.kernel.org, olofj@chromium.org,
	mhalcrow@google.com, dlaor@redhat.com,
	Ro
To: Linus Torvalds <torvalds@linux-foundation.org>
Return-path: <linux-security-module-owner@vger.kernel.org>
In-Reply-To: <CA+55aFzrHaJUKgUCx1uaeuqcyzZuUwQLiGj9dP5D3m-xt6v2SA@mail.gmail.com>
Sender: linux-security-module-owner@vger.kernel.org
List-Id: linux-fsdevel.vger.kernel.org

On 01/18/2012 01:26 PM, Linus Torvalds wrote:
> On Wed, Jan 18, 2012 at 1:04 PM, H. Peter Anvin <hpa@zytor.com> wrote:
>>
>> Fair enough.  Sigh.  I still think an actual pseudo-register would be
>> better.
> 
> .. and that breaks existing binaries too, because the indexing is
> based on offsets into "struct pt_regs", and while we *could* change
> that - leave pt_regs untouched but add a new virtual register - it
> would be problematic.
> 
> We could add a whole new ptrace() access command (eg
> PTRACE_GETSYSTEMREGSET), of course. But that's a lot of effort for
> very little gain.
> 
> So on the whole, putting it in eflags seemed like the *much* simpler approach.
> 

I would have assumed it would be a new register set (which could be
expanded in the future if we have additional system information to provide.)

	-hpa