From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964974AbbEMAxt (ORCPT ); Tue, 12 May 2015 20:53:49 -0400 Received: from relay3-d.mail.gandi.net ([217.70.183.195]:48213 "EHLO relay3-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933877AbbEMAxp (ORCPT ); Tue, 12 May 2015 20:53:45 -0400 Date: Tue, 12 May 2015 17:53:37 -0700 From: josh@joshtriplett.org To: Andrew Morton Cc: Andy Lutomirski , Ingo Molnar , "H. Peter Anvin" , Peter Zijlstra , Thomas Gleixner , Linus Torvalds , linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org Subject: Re: [PATCHv2 1/2] clone: Support passing tls argument via C rather than pt_regs magic Message-ID: <20150513005337.GB14292@cloud> References: <20150511192918.GA11361@jtriplet-mobl1> <20150512142250.dcb053da81855ae1b5861173@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150512142250.dcb053da81855ae1b5861173@linux-foundation.org> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 12, 2015 at 02:22:50PM -0700, Andrew Morton wrote: > On Mon, 11 May 2015 12:29:19 -0700 Josh Triplett wrote: > > > Introduce a new CONFIG_HAVE_COPY_THREAD_TLS for architectures to opt > > into, and a new copy_thread_tls that accepts the tls parameter as an > > additional unsigned long (syscall-argument-sized) argument. > > Change sys_clone's tls argument to an unsigned long (which does > > not change the ABI), and pass that down to copy_thread_tls. > > > > Architectures that don't opt into copy_thread_tls will continue to > > ignore the C argument to sys_clone in favor of the pt_regs captured at > > kernel entry, and thus will be unable to introduce new versions of the > > clone syscall. > > What happens quite frequently is that we do something for x86 with the > expectation that other architectures will follow along, but this > doesn't happen. The arch maintainers simply didn't know about it or > nobody nags them. Nothing happens and inconsistencies hang around for > years. eg, http://lkml.iu.edu/hypermail/linux/kernel/1504.2/04993.html In this case, there will be a very clear incentive to switch to CONFIG_HAVE_COPY_THREAD_TLS: if you don't, you can't enable new syscalls. - Josh Triplett From mboxrd@z Thu Jan 1 00:00:00 1970 From: josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org Subject: Re: [PATCHv2 1/2] clone: Support passing tls argument via C rather than pt_regs magic Date: Tue, 12 May 2015 17:53:37 -0700 Message-ID: <20150513005337.GB14292@cloud> References: <20150511192918.GA11361@jtriplet-mobl1> <20150512142250.dcb053da81855ae1b5861173@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20150512142250.dcb053da81855ae1b5861173-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Andrew Morton Cc: Andy Lutomirski , Ingo Molnar , "H. Peter Anvin" , Peter Zijlstra , Thomas Gleixner , Linus Torvalds , linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org List-Id: linux-api@vger.kernel.org On Tue, May 12, 2015 at 02:22:50PM -0700, Andrew Morton wrote: > On Mon, 11 May 2015 12:29:19 -0700 Josh Triplett wrote: > > > Introduce a new CONFIG_HAVE_COPY_THREAD_TLS for architectures to opt > > into, and a new copy_thread_tls that accepts the tls parameter as an > > additional unsigned long (syscall-argument-sized) argument. > > Change sys_clone's tls argument to an unsigned long (which does > > not change the ABI), and pass that down to copy_thread_tls. > > > > Architectures that don't opt into copy_thread_tls will continue to > > ignore the C argument to sys_clone in favor of the pt_regs captured at > > kernel entry, and thus will be unable to introduce new versions of the > > clone syscall. > > What happens quite frequently is that we do something for x86 with the > expectation that other architectures will follow along, but this > doesn't happen. The arch maintainers simply didn't know about it or > nobody nags them. Nothing happens and inconsistencies hang around for > years. eg, http://lkml.iu.edu/hypermail/linux/kernel/1504.2/04993.html In this case, there will be a very clear incentive to switch to CONFIG_HAVE_COPY_THREAD_TLS: if you don't, you can't enable new syscalls. - Josh Triplett