From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763088AbXHFGir (ORCPT ); Mon, 6 Aug 2007 02:38:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1762510AbXHFGi0 (ORCPT ); Mon, 6 Aug 2007 02:38:26 -0400 Received: from mail.gmx.net ([213.165.64.20]:39288 "HELO mail.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1762319AbXHFGiZ (ORCPT ); Mon, 6 Aug 2007 02:38:25 -0400 X-Authenticated: #24879014 X-Provags-ID: V01U2FsdGVkX199PspFiv59Bo1y9nu5GH10ZpEbucfgVr0WK+Ts31 w31uLGoucqmreD Message-ID: <46B6C17D.4050201@gmx.net> Date: Mon, 06 Aug 2007 08:36:45 +0200 From: Michael Kerrisk User-Agent: Thunderbird 1.5.0.8 (X11/20060911) MIME-Version: 1.0 To: "Eric W. Biederman" CC: Kirill Korotaev , lkml , Pavel Emelianov , Cedric Le Goater Subject: Re: CLONE_NEWIPC documentation References: <46B599D8.8010003@gmx.net> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Y-GMX-Trusted: 0 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Eric W. Biederman wrote: > Michael Kerrisk writes: > >> Hello Kirill, >> >> In 2.6.19, your patch to add support for CLONE_NEWIPC was included. Is >> there there some for-userland-programmers documentation of this flag >> somewhere? Would you be able to send some documentation to me (ideally as >> a patch to the clone.2 man page, but otherwise some plain text will do). >> >> If this flag is also supported for unshare(), then could you please send me >> a patch/text for that too? > > In case someone else doesn't do better here is a short summary. Thanks Eric. That looks to cover a lot of the essentials. Anyone else see something important that should be documented? And a further question: is CLONE_NEWIPC implemented for unshare()? Cheers, Michael > CLONE_NEWIPC creates a new ipc namespace for the new child and all > of it's children. So far CAP_SYS_ADMIN is required. > > An IPC namespace creates a new context for looking up and listing > SYSV IPC shared memory, message queues, and semaphores. Only allowing > finding of SYSV IPC objects in this namespace. > > For most practical purposes two processes in different SYSV IPC > namespaces might as well be on different machines. As they cannot > find each others SYSV IPC resources, and so cannot interact with > each other that way. > > The implementation is essentially just a lookup of the objects > in a different table when doing name to object translation so > there should be no measurable overhead. > > When the last process in a SYSV IPC namespace exits any remaining > objects in that SYSV IPC namespace are destroyed. > > Eric > -- Michael Kerrisk maintainer of Linux man pages Sections 2, 3, 4, 5, and 7 Want to help with man page maintenance? Grab the latest tarball at http://www.kernel.org/pub/linux/docs/manpages/ read the HOWTOHELP file and grep the source files for 'FIXME'.