linux-kernel - Re: [RFC][PATCH 0/3] fork: Add the ability to create tasks with given pids

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Message-Id: <201111231620.45440.pedro@codesourcery.com>
Date:	Wed, 23 Nov 2011 16:20:44 +0000
From:	Pedro Alves <pedro@...esourcery.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Pavel Emelyanov <xemul@...allels.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alan Cox <alan@...ux.intel.com>,
	Roland McGrath <roland@...k.frob.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	James Bottomley <jbottomley@...allels.com>
Subject: Re: [RFC][PATCH 0/3] fork: Add the ability to create tasks with given pids

Hello Tejun,

On Tuesday 22 November 2011 15:33:26, Tejun Heo wrote:
> Hello,
> 
> On Tue, Nov 22, 2011 at 12:04:38PM +0000, Pedro Alves wrote:
> > This whole userspace C/R stuff and being able to set the child's pid has potential
> > of being very useful for GDB too, allowing a much better reimplementation of its
> > old checkpointing feature [*], and allowing for a faster reverse debugging
> > implementation, by being able to do faster rewinding -- restore snapshot and replay
> > instructions up to N (by single stepping or running to breakpoint), rather than
> > manually undoing the effects of each instruction, one by one.
> > 
> > IOW, root only would be a shame from GDB's perspective.
> 
> Would CAP_CHECKPOINT be a shame too?  

I think CAP_CHECKPOINT (or something through some LSM) would be
definitely better.

> I'm reluctant about priviledge
> through fd inheritance mostly because of its unusualness.  I don't
> think priv management is a good problem space for small creative
> solutions.  We're much better off with mundane mechanisms which people
> are already familiar with and is easy to account for.

fd inheritance wouldn't work for gdb; a user spawned gdb
wouldn't inherit an open fd to kernel.ns_last_pid from anywhere.

-- 
Pedro Alves
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