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

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Message-ID: <20110520091256.GD31426@htj.dyndns.org>
Date:	Fri, 20 May 2011 11:12:56 +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,

On Fri, May 20, 2011 at 09:56:22AM +0100, Pedro Alves wrote:
> > Ptrace API never allowed poking of running tracees.
> 
> Which is a bit lame.

Lame as it may be, it would be quite challenging to change that.

> > You need to stop it first.
> 
> That was my point...  I was just pointing out that GDB will end
> up PTRACE_INTERRUPTing the target anyway.  Maybe we could extend
> GDB's "observer" mode to be even more observer-only, and delay
> reading the DSO list and whatever else GDB does on attach until
> the first stop, or to user request.  Some archs need reading
> registers as soon as possible in order to actually know which
> arch variant we've attached to.  Anyway, this is GDBs business.
> SEIZE not interrupting won't hurt GDB, and is obviously useful for
> some use cases and tracers, _provided the race with SETOPTS is fixed_.

Other than the to-be-removed SIGTRAP, I don't think the trace is
observable from userland.  Do you have anything specific on mind?

Thanks.

-- 
tejun
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