From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Gortmaker Subject: Re: [PATCH] Documentation/vDSO: don't build tests when cross compiling Date: Mon, 22 Jun 2015 15:09:42 -0400 Message-ID: <20150622190942.GM16386@windriver.com> References: <1434849028-26733-1-git-send-email-paul.gortmaker@windriver.com> <20150622104124.62299220@lwn.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Return-path: Received: from mail.windriver.com ([147.11.1.11]:35945 "EHLO mail.windriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750900AbbFVTJv (ORCPT ); Mon, 22 Jun 2015 15:09:51 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-next-owner@vger.kernel.org List-ID: To: Andy Lutomirski Cc: Jonathan Corbet , Stephen Rothwell , "linux-kernel@vger.kernel.org" , "linux-doc@vger.kernel.org" , "linux-next@vger.kernel.org" [Re: [PATCH] Documentation/vDSO: don't build tests when cross compiling] On 22/06/2015 (Mon 10:01) Andy Lutomirski wrote: > On Mon, Jun 22, 2015 at 9:41 AM, Jonathan Corbet wrote: > > On Sat, 20 Jun 2015 21:10:28 -0400 > > Paul Gortmaker wrote: > > > >> The following was seen in linux-next build coverage, which is somewhat > >> unique since it uses powerpc host to cross compile x86: > >> > >> Documentation/vDSO/vdso_standalone_test_x86.c:49:2: error: impossible > >> register constraint in 'asm' > >> make[4]: *** [Documentation/vDSO/vdso_standalone_test_x86.o] Error 1 > >> > >> It probably makes sense to just skip building these tests when > >> we are cross compiling. > > > > So I guess I'm not totally averse to applying these; getting rid of build > > errors is a good thing. But I do get the feeling like it's papering over > > the real problem. As a general rule, cross-compiling works; what's > > special about these programs that makes it fail? > > Agreed. What gcc version is this? Just to re-iterate, this is ppc host, cross compiling x86_64 target. The linux-next build I saw the errors in this weekend is here: http://kisskb.ellerman.id.au/kisskb/buildresult/12445538/ According to that, it is gcc 4.6.3 It seems that the assumption is that nobody cross compiles x86, so when people see CONFIG_X86_64 set, they assume HOSTCC can create x86 binaries and will do so by default. Hence the breakdown in creation of some of these sample programs. We've already a similar fix in mainline in e9107f88c985bc ("samples/seccomp/Makefile: do not build tests if cross-compiling for MIPS") I've added linux-next folks to Cc: -- probably should have done that on the original send... they know more about the toolchains used for -next. Paul. -- > > --Andy > > > > > Thanks, > > > > jon > > > > -- > Andy Lutomirski > AMA Capital Management, LLC