linux-kernel - Re: [PATCH 03/10] ptrace: implement PTRACE

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Message-ID: <20110520093111.GG31426@htj.dyndns.org>
Date:	Fri, 20 May 2011 11:31:11 +0200
From:	Tejun Heo <tj@...nel.org>
To:	Pedro Alves <pedro@...esourcery.com>
Cc:	Denys Vlasenko <vda.linux@...glemail.com>, oleg@...hat.com,
	jan.kratochvil@...hat.com, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	indan@....nu, bdonlan@...il.com
Subject: Re: [PATCH 03/10] ptrace: implement PTRACE_SEIZE

Hello, Pedro.

On Fri, May 20, 2011 at 10:27:35AM +0100, Pedro Alves wrote:
> > Does it matter?  The order of execution isn't even well defined
> > without synchronization border.  If you want full synchronization, you
> > can INTERRUPT tracee.
> 
> The point I was trying to raise was not about the order of
> execution, but about letting the old pre-nice PTRACE_EVENT_
> events quirks stick through.

I see.

> > Yes, SIGTRAP on exec(2) is nasty but also is scheduled to be removed
> > if SEIZED.
> 
> Okay, good to hear that.  Looks like the tracer can do:
> 
>  SEIZE,execve,SETOPTS,'readlink /proc/pid/exe'
> 
> and pretend it SEIZED after the execve.

Yeap, and I was trying to say that if tracer and tracee are running on
different CPUs, the order between SEIZE and execve isn't even well
defined (sans the nasty automatic SIGTRAP).

> I'm happy for now.

Awesome, thanks.

-- 
tejun
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