From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 30D21C432BE for ; Tue, 27 Jul 2021 14:16:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0EB6D61057 for ; Tue, 27 Jul 2021 14:16:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236734AbhG0OQN (ORCPT ); Tue, 27 Jul 2021 10:16:13 -0400 Received: from out03.mta.xmission.com ([166.70.13.233]:34630 "EHLO out03.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232437AbhG0OQK (ORCPT ); Tue, 27 Jul 2021 10:16:10 -0400 Received: from in02.mta.xmission.com ([166.70.13.52]:49264) by out03.mta.xmission.com with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1m8NsP-00DgF3-2x; Tue, 27 Jul 2021 08:16:09 -0600 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95]:48960 helo=email.xmission.com) by in02.mta.xmission.com with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1m8NsN-003YiR-R6; Tue, 27 Jul 2021 08:16:08 -0600 From: ebiederm@xmission.com (Eric W. Biederman) To: Masahiro Yamada Cc: Arnd Bergmann , Linus Torvalds , Nick Desaulniers , Miguel Ojeda , Fangrui Song , Michal Marek , Linux Kernel Mailing List , Linux Kbuild mailing list , clang-built-linux , Geert Uytterhoeven , Christoph Hellwig , Nathan Chancellor References: <20210708232522.3118208-1-ndesaulniers@google.com> <20210708232522.3118208-3-ndesaulniers@google.com> <87r1fkizxl.fsf@disp2133> Date: Tue, 27 Jul 2021 09:16:01 -0500 In-Reply-To: (Masahiro Yamada's message of "Tue, 27 Jul 2021 19:10:02 +0900") Message-ID: <87v94vg7vi.fsf@disp2133> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1m8NsN-003YiR-R6;;;mid=<87v94vg7vi.fsf@disp2133>;;;hst=in02.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1/A0yNJecA7Q20Vto//jCC4YwhQhHttrn4= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCH v2 2/2] Makefile: infer CROSS_COMPILE from SRCARCH for LLVM=1 LLVM_IAS=1 X-SA-Exim-Version: 4.2.1 (built Sat, 08 Feb 2020 21:53:50 +0000) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Masahiro Yamada writes: > On Tue, Jul 27, 2021 at 5:27 AM Eric W. Biederman wrote: >> >> Masahiro Yamada writes: >> >> > On Wed, Jul 21, 2021 at 4:58 AM Arnd Bergmann wrote: >> >> >> >> On Tue, Jul 20, 2021 at 7:43 PM Linus Torvalds >> >> wrote: >> >> > On Tue, Jul 20, 2021 at 1:05 AM Masahiro Yamada wrote: >> >> > >> >> > We do most of the other heavy lifting in this area in Kconfig anyway, >> >> > why not add that compiler choice? >> >> > >> >> > Obviously it would be gated by the tests to see which compilers are >> >> > _installed_ (and that they are valid versions), so that it doesn't ask >> >> > stupid things ("do you want gcc or clang" when only one of them is >> >> > installed and/or viable). >> >> >> >> I don't see a good way of making Kconfig options both select the >> >> compiler and defining variables based on the compiler, since that >> >> would mean teaching Kconfig about re-evaluating all compiler >> >> dependent settings whenever the first option changes. >> >> >> >> I do have another idea that I think would work though. >> >> >> >> > Hmm? So then any "LLVM=1" thing would be about the "make config" >> >> > stage, not the actual build stage. >> >> > >> >> > (It has annoyed me for years that if you want to cross-compile, you >> >> > first have to do "make ARCH=xyz config" and then remember to do "make >> >> > ARCH=xyz" for the build too, but I cross-compile so seldom that I've >> >> > never really cared). >> >> >> >> The best thing that I have come up with is a pre-configure step, where >> >> an object tree gets seeded with a makefile fragment that gets included >> >> for any 'make' invocation. This would set 'ARCH=', 'CROSS_COMPILE', >> >> 'CC=' and possibly any other option that gets passed to 'make' as >> >> a variable and has to exist before calling 'make *config'. >> > >> > >> > There is no need to add a hook to include such makefile fragment(s). >> > >> > Quite opposite, you can put your Makefile (in a different filename) >> > that includes the top Makefile. >> > >> > >> > I think this is what people are already doing: >> > >> > >> > GNU Make looks for 'GNUmakefile', 'makefile', and 'Makefile' >> > in this order. >> > >> > >> > So, you can put 'GNUmakefile' with your favorite setups. >> > >> > >> > $ cat GNUmakefile >> > ARCH=arm64 >> > CROSS_COMPILE=aarch64-linux-gnu- >> > CC=clang >> > include Makefile >> >> Very weird. >> >> I just tested this and it does not work. >> I did this: >> >> $ cat GNUmakefile >> ARCH = alpha >> CROSS_COMPILE = $(arch-prefix alpha) >> include Makefile >> >> In one of my build directories and the main makefile simply does not see >> the value of ARCH or CROSS_COMPILE I set. I have confirmed that my >> GNUmakefile is being read, because everything breaks if I remove the >> include line. >> >> Does anyone have any ideas? >> >> Something so we don't have to specify all of these variables on the make >> command line would be nice. >> >> Eric > > > Worked for me. > > Could you tell me the exact steps you did? > > > This is my case: > > My kernel source tree is located at $HOME/ref/linux > alpha tool chains are located at $HOME/tools/alpha-10.1.0/bin > > > > I tried a simple GNUmakefile with 3 lines. > > You can see 'make' is building the alpha kernel > > > Please see below: Interesting. That appears to work if I don't specify a build directory. Once I specify a build directory with O= it does not work. When I am working on a change that affects multiple architectures I really want a build directory that is not my source tree so I can test small changes on multiple architectures without needing to rebuild everything. Eric