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=-15.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 02369C433E3 for ; Tue, 21 Jul 2020 22:15:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CF62820717 for ; Tue, 21 Jul 2020 22:15:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595369757; bh=keTbomrf4zknktam/LM8fhy2QKlR/GqqXEwH7QR0xf0=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=qd8/yZqnaxaCUcpXwBM3dZz1RnhAjRQF4LvobEvd4sLeHnZda/19zBbPbEIo5/VNe OOWxb5fj1jzSDoSLM1LDzhqZBBHGUAkSKY+XnnPtztmWOM9lLjowTfa4NgapPwAPwO pWG9j0s5qk84VSa8HYoqyMvPJ0EzrlJQ4EUsAJrk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729039AbgGUWP4 (ORCPT ); Tue, 21 Jul 2020 18:15:56 -0400 Received: from conssluserg-04.nifty.com ([210.131.2.83]:64746 "EHLO conssluserg-04.nifty.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726658AbgGUWP4 (ORCPT ); Tue, 21 Jul 2020 18:15:56 -0400 Received: from mail-ua1-f45.google.com (mail-ua1-f45.google.com [209.85.222.45]) (authenticated) by conssluserg-04.nifty.com with ESMTP id 06LMFG4v024349; Wed, 22 Jul 2020 07:15:17 +0900 DKIM-Filter: OpenDKIM Filter v2.10.3 conssluserg-04.nifty.com 06LMFG4v024349 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nifty.com; s=dec2015msa; t=1595369718; bh=vR1Y8P9QQm4CTezIGezqaKkPlD5HSAJvtH4tLGcsSBI=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=Eac1OkjRpXczpVkoHps5q00SjaAGdrQ3pmDGHflV2eWLHwS9LUnXYJosQBVz0UOFJ atSqHwrjAyEqKhhMCDEp8gwAke30wrqbqvvi4lNmMa7gumSCpmUVL/vLMchR8jjKyq xbDGV9JH2i3/zqvStgXRklaXyKjGDbNGh3yQ9HK03urpCmxPAhwXQdZ4eou/4l+Esb Vqij88PKHqQRSj9ZyeZiCqK8drr6KjJKQsZWrvfWZLE4cVET/n6SYbK9Va4ZDFNiP5 KCPX+0qwTVEPdYdDJVfO2+1vCzS/ra4OaFB36trWx5dGdyr6f2GQJDUL8eWZZzbjnY RQ3dTkGUPMDYg== X-Nifty-SrcIP: [209.85.222.45] Received: by mail-ua1-f45.google.com with SMTP id o25so2610uar.1; Tue, 21 Jul 2020 15:15:17 -0700 (PDT) X-Gm-Message-State: AOAM530IRbG3+lOvgD6rulQC2H99mTIThdfVnrbgoQQHaaNDc1HgkrWH J/CFyn1P1aUdWOesoDNxGKsM+c88iGicZCAbpy4= X-Google-Smtp-Source: ABdhPJyfvusDeLSk02B9TNvScFemIglbaRo6s+sUXc0hUvfsW+NlwIYAiHd3h/00MalC6DXvqL7qEYtSs9IWJGdOHqk= X-Received: by 2002:ab0:48:: with SMTP id 66mr22845681uai.40.1595369716204; Tue, 21 Jul 2020 15:15:16 -0700 (PDT) MIME-Version: 1.0 References: <20200721173125.1273884-1-maskray@google.com> In-Reply-To: <20200721173125.1273884-1-maskray@google.com> From: Masahiro Yamada Date: Wed, 22 Jul 2020 07:14:39 +0900 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v3] Makefile: Fix GCC_TOOLCHAIN_DIR prefix for Clang cross compilation To: Fangrui Song Cc: Michal Marek , Linux Kbuild mailing list , Linux Kernel Mailing List , clang-built-linux , Jian Cai , Bill Wendling , Manoj Gupta , stable , Nathan Chancellor , Nick Desaulniers Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 22, 2020 at 2:31 AM 'Fangrui Song' via Clang Built Linux wrote: > > When CROSS_COMPILE is set (e.g. aarch64-linux-gnu-), if > $(CROSS_COMPILE)elfedit is found at /usr/bin/aarch64-linux-gnu-elfedit, > GCC_TOOLCHAIN_DIR will be set to /usr/bin/. --prefix= will be set to > /usr/bin/ and Clang as of 11 will search for both > $(prefix)aarch64-linux-gnu-$needle and $(prefix)$needle. > > GCC searchs for $(prefix)aarch64-linux-gnu/$version/$needle, > $(prefix)aarch64-linux-gnu/$needle and $(prefix)$needle. In practice, > $(prefix)aarch64-linux-gnu/$needle rarely contains executables. > > To better model how GCC's -B/--prefix takes in effect in practice, newer > Clang (since > https://github.com/llvm/llvm-project/commit/3452a0d8c17f7166f479706b293caf6ac76ffd90) > only searches for $(prefix)$needle. Currently it will find /usr/bin/as > instead of /usr/bin/aarch64-linux-gnu-as. > > Set --prefix= to $(GCC_TOOLCHAIN_DIR)$(CROSS_COMPILE) > (/usr/bin/aarch64-linux-gnu-) so that newer Clang can find the > appropriate cross compiling GNU as (when -no-integrated-as is in > effect). > > Cc: stable@vger.kernel.org > Reported-by: Nathan Chancellor > Signed-off-by: Fangrui Song > Reviewed-by: Nathan Chancellor > Tested-by: Nathan Chancellor > Tested-by: Nick Desaulniers > Link: https://github.com/ClangBuiltLinux/linux/issues/1099 > --- > Changes in v2: > * Updated description to add tags and the llvm-project commit link. > * Fixed a typo. > > Changes in v3: > * Add Cc: stable@vger.kernel.org > --- > Makefile | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/Makefile b/Makefile > index 0b5f8538bde5..3ac83e375b61 100644 > --- a/Makefile > +++ b/Makefile > @@ -567,7 +567,7 @@ ifneq ($(shell $(CC) --version 2>&1 | head -n 1 | grep clang),) > ifneq ($(CROSS_COMPILE),) > CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%)) > GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit)) > -CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR) > +CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)$(CROSS_COMPILE) CROSS_COMPILE may contain the directory path to the cross toolchains. For example, I use aarch64-linux-gnu-* installed in /home/masahiro/tools/aarch64-linaro-7.5/bin Basically, there are two ways to use it. [1] PATH=$PATH:/home/masahiro/tools/aarch64-linaro-7.5/bin CROSS_COMPILE=aarch64-linux-gnu- [2] Without setting PATH, CROSS_COMPILE=~/tools/aarch64-linaro-7.5/bin/aarch64-linux-gnu- I usually do [2] (and so does intel's 0day bot). This patch works for the use-case [1] but if I do [2], --prefix is set to a strange path: --prefix=/home/masahiro/tools/aarch64-linaro-7.5/bin//home/masahiro/tools/aarch64-linaro-7.5/bin/aarch64-linux-gnu- Interestingly, the build is still successful. Presumably Clang searches for more paths when $(prefix)$needle is not found ? I applied your patch and added -v option to see which assembler was internally invoked: "/home/masahiro/tools/aarch64-linaro-7.5/lib/gcc/aarch64-linux-gnu/7.5.0/../../../../aarch64-linux-gnu/bin/as" -EL -I ./arch/arm64/include -I ./arch/arm64/include/generated -I ./include -I ./arch/arm64/include/uapi -I ./arch/arm64/include/generated/uapi -I ./include/uapi -I ./include/generated/uapi -o kernel/smp.o /tmp/smp-2ec2c7.s Ok, it looks like Clang found an alternative path to the correct 'as'. But, to keep the original behavior for both [1] and [2], how about this? CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE)) Then, I can get this: "/home/masahiro/tools/aarch64-linaro-7.5/bin/aarch64-linux-gnu-as" -EL -I ./arch/arm64/include -I ./arch/arm64/include/generated -I ./include -I ./arch/arm64/include/uapi -I ./arch/arm64/include/generated/uapi -I ./include/uapi -I ./include/generated/uapi -o kernel/smp.o /tmp/smp-16d76f.s > GCC_TOOLCHAIN := $(realpath $(GCC_TOOLCHAIN_DIR)/..) > endif > ifneq ($(GCC_TOOLCHAIN),) > -- > 2.28.0.rc0.105.gf9edc3c819-goog > > -- > You received this message because you are subscribed to the Google Groups "Clang Built Linux" group. > To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@googlegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/20200721173125.1273884-1-maskray%40google.com. -- Best Regards Masahiro Yamada