linux-kernel - Re: Compat 32-bit syscall entry from 64-bit task!?

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Message-ID: <29acd271cd920259e9703c438295d7b3.squirrel@webmail.greenhost.nl>
Date:	Thu, 26 Jan 2012 12:19:42 +0100
From:	"Indan Zupancic" <indan@....nu>
To:	"Denys Vlasenko" <vda.linux@...glemail.com>
Cc:	"Jamie Lokier" <jamie@...reable.org>,
	"Oleg Nesterov" <oleg@...hat.com>,
	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"Andi Kleen" <andi@...stfloor.org>,
	"Andrew Lutomirski" <luto@....edu>,
	"Will Drewry" <wad@...omium.org>, linux-kernel@...r.kernel.org,
	keescook@...omium.org, john.johansen@...onical.com,
	serge.hallyn@...onical.com, coreyb@...ux.vnet.ibm.com,
	pmoore@...hat.com, eparis@...hat.com, djm@...drot.org,
	segoon@...nwall.com, rostedt@...dmis.org, jmorris@...ei.org,
	scarybeasts@...il.com, avi@...hat.com, penberg@...helsinki.fi,
	viro@...iv.linux.org.uk, mingo@...e.hu, akpm@...ux-foundation.org,
	khilman@...com, borislav.petkov@....com, amwang@...hat.com,
	ak@...ux.intel.com, eric.dumazet@...il.com, gregkh@...e.de,
	dhowells@...hat.com, daniel.lezcano@...e.fr,
	linux-fsdevel@...r.kernel.org,
	linux-security-module@...r.kernel.org, olofj@...omium.org,
	mhalcrow@...gle.com, dlaor@...hat.com,
	"Roland McGrath" <mcgrathr@...omium.org>
Subject: Re: Compat 32-bit syscall entry from 64-bit task!?

On Thu, January 26, 2012 11:40, Denys Vlasenko wrote:
> On Thu, Jan 26, 2012 at 11:31 AM, Jamie Lokier <jamie@...reable.org> wrote:
>> Indan Zupancic wrote:
>>> On Thu, January 26, 2012 02:08, Jamie Lokier wrote:
>>> > Is it disambiguated by PTRACE_EVENT_EXEC happening before the execve
>>> > returns, and you knowing the TID always changes to the PID? �I haven't
>>> > yet checked which TID gets the PTRACE_EVENT_EXEC event, but if it's
>>> > not the old one, perhaps that could be changed.
>>>
>>> Please don't ever change the behaviour of PTRACE_EVENT_EXEC, it's
>>> barely documented already, but if if ever changes it will be also
>>> unreliable.
>>>
>>> It's still unclear if the PTRACE_EVENT_EXEC comes before or after
>>> or instead of the post-execve ptrace event.
>
> Denis <- confused.
> Was ist das "post-execve ptrace event"? I know no such thing.
> I know about PTRACE_EVENT_EXEC, and "post-execve SIGTRAP".

I mean the second SIGTRAP | 0x80 event, the syscall return of execve.

> All ptrace stops (events and other stops) are synchronous.
> Tracee stops, tracer notices it, tracer restarts tracee,
> and only after this tracee can generate next event.
> Therefore ptrace stops can't get reordered.

That's good to know and what I expected.

Since which kernel version does the PTRACE_GETEVENTMSG work and
is there a way to find out before it returns zero?

Greetings,

Indan


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