From mboxrd@z Thu Jan 1 00:00:00 1970 From: sukadev@us.ibm.com Subject: Re: [PATCH 0/3] clone64() and unshare64() system calls Date: Wed, 9 Apr 2008 18:07:17 -0700 Message-ID: <20080410010717.GA28477@us.ibm.com> References: <20080409222611.GA28087@us.ibm.com> <47FD5899.2040206@zytor.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <47FD5899.2040206@zytor.com> Sender: linux-kernel-owner@vger.kernel.org To: "H. Peter Anvin" Cc: Andrew Morton , clg@fr.ibm.com, serue@us.ibm.com, "David C. Hansen" , Pavel Emelyanov , Containers , linux-kernel@vger.kernel.org List-Id: containers.vger.kernel.org H. Peter Anvin [hpa@zytor.com] wrote: > sukadev@us.ibm.com wrote: >> This is a resend of the patch set Cedric had sent earlier. I ported >> the patch set to 2.6.25-rc8-mm1 and tested on x86 and x86_64. >> --- >> We have run out of the 32 bits in clone_flags ! >> This patchset introduces 2 new system calls which support 64bit >> clone-flags. >> long sys_clone64(unsigned long flags_high, unsigned long flags_low, >> unsigned long newsp); >> long sys_unshare64(unsigned long flags_high, unsigned long >> flags_low); >> The current version of clone64() does not support CLONE_PARENT_SETTID and >> CLONE_CHILD_CLEARTID because we would exceed the 6 registers limit of some >> arches. It's possible to get around this limitation but we might not >> need it as we already have clone() > > I really dislike this interface. > > If you're going to make it a 64-bit pass it in as a 64-bit number, instead > of breaking it into two numbers. Maybe I am missing your point. The glibc interface could take a 64bit parameter, but don't we need to pass 32-bit values into the system call on 32 bit systems ? > Better yet, IMO, would be to pass a pointer to a structure like: > > struct shared { > unsigned long nwords; > unsigned long flags[]; > }; > > ... which can be expanded indefinitely. Yes, this was discussed before in the context of Pavel Emelyanov's patch http://lkml.org/lkml/2008/1/16/109 along with sys_indirect(). While there was no consensus, it looked like adding a new system call was better than open ended interfaces.