Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S981007AbdDYGp4 (ORCPT ); Tue, 25 Apr 2017 02:45:56 -0400 Received: from hauke-m.de ([5.39.93.123]:35592 "EHLO mail.hauke-m.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932761AbdDYGps (ORCPT ); Tue, 25 Apr 2017 02:45:48 -0400 Subject: Re: [musl] Re: [PATCH resent] uapi libc compat: allow non-glibc to opt out of uapi definitions To: musl@lists.openwall.com, David Woodhouse , Felix Janda , linux-kernel@vger.kernel.org References: <20161111120820.GA435@nyan> <1488977188.4347.134.camel@infradead.org> <459a8faf-4585-5063-3d94-3a1fecfa8289@redhat.com> Cc: "David S. Miller" , linux-api@vger.kernel.org From: Hauke Mehrtens Message-ID: <21e624b9-7ab1-dcf9-fb1e-c31dd564a283@hauke-m.de> Date: Tue, 25 Apr 2017 08:45:43 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: <459a8faf-4585-5063-3d94-3a1fecfa8289@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1200 Lines: 23 On 03/08/2017 05:39 PM, Carlos O'Donell wrote: > Any header needing compat with a libc includes libc-compat.h (per the > documented way the model works). With this patch any included linux kernel > header that also includes libc-compat.h would immediately define all > the __UAPI_DEF_* constants to 1 as-if it had defined those structures, > but it has not. > > For example, with these two patches applied, the inclusion of linux/if.h > would define __UAPI_DEF_XATTR to 1, but linux/if.h has not defined > XATTR_CREATE or other constants, so a subsequent inclusion sys/xattrs.h > from userspace would _not_ define XATTR_CREATE because __UAPI_DEF_XATTR set > to 1 indicates the kernel has. > > I don't want to read into the model you are proposing and would rather you > document the semantics clearly so we can all see what you mean. What about moving the code from libc-comapt.h into the specific header files? This way including linux/if.h would not have an impact on __UAPI_DEF_XATTR, because this is defined in linux/xattr.h. We would still have a problem when the specific Linux header file gets included before the libc header file, but at least musl does not support this anyway. Hauke