From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753016AbbJOLgH (ORCPT ); Thu, 15 Oct 2015 07:36:07 -0400 Received: from mail.kapsi.fi ([217.30.184.167]:56948 "EHLO mail.kapsi.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752690AbbJOLgE (ORCPT ); Thu, 15 Oct 2015 07:36:04 -0400 Date: Thu, 15 Oct 2015 14:35:31 +0300 From: Mikko Rapeli To: David Vrabel Cc: linux-kernel@vger.kernel.org, Stefano Stabellini , Russell King , Konrad Rzeszutek Wilk , Boris Ostrovsky , xen-devel@lists.xenproject.org, linux-arm-kernel@lists.infradead.org, linux-api@vger.kernel.org Subject: Re: [PATCH v4 75/79] include/uapi/xen/privcmd.h: fix compilation in userspace Message-ID: <20151015113531.GX6104@lakka.kapsi.fi> References: <1444888618-4506-1-git-send-email-mikko.rapeli@iki.fi> <1444888618-4506-76-git-send-email-mikko.rapeli@iki.fi> <561F7FF8.9030703@citrix.com> <20151015111801.GW6104@lakka.kapsi.fi> <561F8CF7.9070102@citrix.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <561F8CF7.9070102@citrix.com> X-SA-Exim-Connect-IP: 2001:1bc8:1004::1 X-SA-Exim-Mail-From: mikko.rapeli@iki.fi X-SA-Exim-Scanned: No (on mail.kapsi.fi); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 15, 2015 at 12:24:39PM +0100, David Vrabel wrote: > On 15/10/15 12:18, Mikko Rapeli wrote: > > On Thu, Oct 15, 2015 at 11:29:12AM +0100, David Vrabel wrote: > >> On 15/10/15 06:56, Mikko Rapeli wrote: > >>> xen/interface/xen.h is not exported from kernel headers so remove the > >>> dependency and provide needed defines for domid_t and xen_pfn_t if they > >>> are not already defined by some other e.g. Xen specific headers. > >>> > >>> Suggested by Andrew Cooper on lkml message > >>> <5569F9C9.8000607@citrix.com>. > >>> > >>> The ifdef for ARM is ugly but did not find better solutions for it. > >>> > >>> Fixes userspace compilation error: > >>> > >>> xen/privcmd.h:38:31: fatal error: xen/interface/xen.h: No such file or directory > >> [...] > >>> --- a/include/uapi/xen/privcmd.h > >>> +++ b/include/uapi/xen/privcmd.h > >>> @@ -35,7 +35,19 @@ > >>> > >>> #include > >>> #include > >>> -#include > >>> + > >>> +/* Might be defined by Xen specific headers, but if not */ > >>> +#ifndef domid_t > >>> +typedef __u16 domid_t; > >>> +#endif /* domid_t */ > >> > >> As the kbuild bot points out, this does not work since the existence of > >> a typedef cannot be checked with #ifdef. > > > > Yeah, this hack doesn't cut it. Sorry. Tried to implement these changes: > > http://www.spinics.net/lists/linux-api/msg11048.html > > > >> I'm not really sure what problem you're trying to solve. A user space > >> program making use of this interface gets the domid_t and xen_pfn_t etc > >> typedefs from the headers provided as part of the libxenctrl library. > > > > I'm trying to make sure that kernel headers in userspace compile with minimal > > dependencies which are gcc and libc. > > > > For me it is clear by now that many Linux API's and ABI's like Xen parts do > > not live in the uapi header files and instead there's a separate userspace > > library with needed headers and defines which have embedded copies of > > the needed API and ABI definitions, like header files. > > > > So how could this file be changed so that it compiles in userspace without > > definitions from libxenctrl? > > I don't think anything needs to be changed. > > Instead I would make your compilation check of this header dependent on > the existence of the xen/interface/xen.h header. Or you may exclude the > check of this header entirely. There are not many headers in uapi which require additional userspace headers to compile (I'm not saying that uapi headers represent the full API's/ABI's, it's clear they don't). If there are ~700 headers and just a single one needs an exception and additional dependencies, I would try to make it work without the dependency. I just need some advice and guidance from maintainers how to do this. Or we should start tracking these userspace library dependencies too, at least at linux-headers package levels in distributions. This might be a good idea anyway, but then we might as well move headers like this directly to the userspace library and out of include/uapi. Both would solve the non-compiling uapi header problem. > > I guess I could copy the needed definitions for domid_t and xen_pfn_t from > > xen/interface/xen.h of libxenctrl. That I should have done to begin with > > instead of trying to hack something on my own. > > I do not want definitions duplicated/copied from the hypervisor ABI > headers. This causes problems when support for new architectures is > added (for example). Understood. -Mikko > David