Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 15 Aug 2002 22:38:01 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 15 Aug 2002 22:38:01 -0400 Received: from pc-62-30-255-50-az.blueyonder.co.uk ([62.30.255.50]:64224 "EHLO kushida.apsleyroad.org") by vger.kernel.org with ESMTP id ; Thu, 15 Aug 2002 22:37:59 -0400 Date: Thu, 15 Aug 2002 23:38:02 +0100 From: Jamie Lokier To: Linus Torvalds Cc: Ingo Molnar , linux-kernel@vger.kernel.org Subject: [patch] complain about unknown CLONE_* flags Message-ID: <20020815233802.A30018@kushida.apsleyroad.org> References:

Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5.1i In-Reply-To: ; from mingo@elte.hu on Tue, Aug 13, 2002 at 08:32:06PM +0200 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1739 Lines: 44 About new clone() flags... One of the obvious things for a thread library is to: (a) try clone() with lots of snazzy flags (b) if that returns -EINVAL, we must be running on an older kernel; try with fewer flags and more workarounds However, I don't see any code in sys_clone() that rejects a call that specifies unknown flags. So, code that uses e.g. CLONE_SETTID will appear to run perfectly well on an old kernel... except that it will behave incorrectly. That leads to having to write some silly test for each feature prior to using it, instead of trying it and falling back. E.g. I'd need to do the silly signal-blocking workaround when creating the second thread in a program, just to find out whether CLONE_SETTID actually worked. Either that, or check the kernel version. Ingo, how do you handle this sort of backward compatibility in your latest pthreads library, or don't you do backward compatibility? For future-proofing, here's a patch: diff -u linux-2.5/kernel/fork.c.orig linux-2.5/kernel/fork.c --- linux-2.5/kernel/fork.c +++ linux-2.5/kernel/fork.c Thu Aug 15 23:35:00 2002 @@ -619,6 +619,11 @@ struct task_struct *p = NULL; struct completion vfork; + if ((clone_flags & ~(0UL|CSIGNAL|CLONE_VM|CLONE_FS|CLONE_FILES + |CLONE_SIGHAND|CLONE_PID|CLONE_PTRACE|CLONE_VFORK + |CLONE_PARENT|CLONE_THREAD))) + return ERR_PTR (-EINVAL); + if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) return ERR_PTR(-EINVAL); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/