From mboxrd@z Thu Jan  1 00:00:00 1970
From: Denys Vlasenko <vda.linux@googlemail.com>
Subject: Re: Compat 32-bit syscall entry from 64-bit task!?
Date: Thu, 26 Jan 2012 00:36:35 +0100
Message-ID: <201201260036.35805.vda.linux@googlemail.com>
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Cc: Oleg Nesterov <oleg@redhat.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Indan Zupancic <indan@nul.nu>,
	Andi Kleen <andi@firstfloor.org>,
	Jamie Lokier <jamie@shareable.org>,
	Andrew Lutomirski <luto@mit.edu>,
	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@chromiu
To: Pedro Alves <palves@redhat.com>
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On Wednesday 25 January 2012 21:20, Pedro Alves wrote:
> On 01/25/2012 07:36 PM, Oleg Nesterov wrote:
> > 
> > Not sure this is really better, but there is another idea. Currently we
> > have PTRACE_O_TRACESYSGOOD to avoid the confusion with the real SIGTRAP.
> > Perhaps we can add PTRACE_O_TRACESYS_VERY_GOOD (or we can look at
> > PT_SEIZED instead) and report TS_COMPAT via ptrace_report_syscall ?
> 
> May I beg to don't rely on PTRACE_SYSCALL for anything new?

This doesn't *add* anything new. All the same ptrace stops will happen
at exactly the same moments. No new stops added. We only add a value
into upper half of waitpid status: (status >> 16) used to be 0
on syscall entry. Now it will be PTRACE_EVENT_SYSCALL_ENTRY[1].
That's all.

> You can't PTRACE_SINGLESTEP and PTRACE_SYSCALL simultaneously.

This is an orthogonal problem.

-- 
vda