From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751516AbcGRCdv (ORCPT ); Sun, 17 Jul 2016 22:33:51 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41806 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751016AbcGRCdq (ORCPT ); Sun, 17 Jul 2016 22:33:46 -0400 Date: Mon, 18 Jul 2016 10:33:39 +0800 From: Dave Young To: Vivek Goyal Cc: AKASHI Takahiro , ebiederm@xmission.com, bhe@redhat.com, bauerman@linux.vnet.ibm.com, arnd@arndb.de, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [RFC 3/3] kexec: extend kexec_file_load system call Message-ID: <20160718023339.GC6310@dhcp-128-65.nay.redhat.com> References: <20160712014201.11456-1-takahiro.akashi@linaro.org> <20160712014201.11456-4-takahiro.akashi@linaro.org> <20160715130955.GC23514@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160715130955.GC23514@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Mon, 18 Jul 2016 02:33:46 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/15/16 at 09:09am, Vivek Goyal wrote: > On Tue, Jul 12, 2016 at 10:42:01AM +0900, AKASHI Takahiro wrote: > > [..] > > -SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd, > > +SYSCALL_DEFINE6(kexec_file_load, int, kernel_fd, int, initrd_fd, > > unsigned long, cmdline_len, const char __user *, cmdline_ptr, > > - unsigned long, flags) > > + unsigned long, flags, const struct kexec_fdset __user *, ufdset) > > Can one add more parameters to existing syscall. Can it break existing > programs with new kernel? I was of the impression that one can't do that. > But may be I am missing something. It will not break existing programs because we can use the new param only when the new flag is set. But we have a case below, but I think it is fine? Originally kexec_file_load with the new flags will fail, but now it will succeed and will access the new argument. Thanks Dave