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=-22.6 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 0B37CC433E1 for ; Wed, 22 Jul 2020 00:14:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CADCF20771 for ; Wed, 22 Jul 2020 00:14:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="rBfa1OHr" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728246AbgGVAO3 (ORCPT ); Tue, 21 Jul 2020 20:14:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60898 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726468AbgGVAO2 (ORCPT ); Tue, 21 Jul 2020 20:14:28 -0400 Received: from mail-pf1-x443.google.com (mail-pf1-x443.google.com [IPv6:2607:f8b0:4864:20::443]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6A268C061794 for ; Tue, 21 Jul 2020 17:14:28 -0700 (PDT) Received: by mail-pf1-x443.google.com with SMTP id x72so247274pfc.6 for ; Tue, 21 Jul 2020 17:14:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=9qebLmGY/4gEoVD5iagvEbtSEoeLp/rn7yyW5dBLp+g=; b=rBfa1OHrzErPK/ONQUP8CbcQunwM1IE/O/X+DkvbhC97maUcc0QhXPg5KgY+bBd34B sy/oZcUVUqcOHqnl9FneUGu20jN9QMtGanI+3VN5mQiWq+W+mobBvlTyVg+BHvrwH7kX tKVX7UN7C5neEmOdS4GJMCCb2lbDLmMmRAXKmKh3aoXW95u71P4piCNW2zMqfE94VFtI 2iGkwPflJzEP6DqNiyXyYM+a0tvtiXY+8xbFpQStdrNJwBcknEwv4sqQdYYUEWiUtwao 4Wcbn11+Dqsh+6i6symRbuK0KuDMFPGcS5hXwS6ISaKxcGKCqPhGaTmkikHFJe+yXfkn MjQA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=9qebLmGY/4gEoVD5iagvEbtSEoeLp/rn7yyW5dBLp+g=; b=ONEAh3qTWVEnvnsd0BIQoMhLwMgBDHtRCkmYDbCLVvk9epgmqOc7Flc7dbef+Y2uCV AM8kZkTR7SReL83DT0U0sdky7dT7k1NJBgujR7spRcNjtMqNemcFPG2oQqM2HZPufcw3 J1V1dZmVTPICOEQZ2A33VC0R1692rdGQKCsiomqlaWE/dWMaXC+MuuSgvRX3m/BGaAgj HYXyBvh4xFURMxHZWHKw2+T2g41iwgIeC05Qznv/e1r4HPLlIQruXtttbeXAywRzy2HE mw1RcCtDGuWGB/60J96+CSu2pzviSgse6CHLSY+H60rUKB+BgSZQmA+waRu0oqL9f2z4 WdUA== X-Gm-Message-State: AOAM532sHkHMu5IrKN5bQ5RZkeQOvbV5qqaFDSjGi3jqm1StOEGXou8R GK0AdYH78iNL0A4MWW/4wQXrSw== X-Google-Smtp-Source: ABdhPJxpClug0jSxEuFfQ647WlLMd6xqykRwn3bkE3najs66S1jKCsrsPBbTOOKCoN3nuLlYWQrRsQ== X-Received: by 2002:a62:f241:: with SMTP id y1mr26305365pfl.136.1595376867468; Tue, 21 Jul 2020 17:14:27 -0700 (PDT) Received: from google.com ([2620:15c:2ce:0:a6ae:11ff:fe11:4abb]) by smtp.gmail.com with ESMTPSA id t1sm4438981pje.55.2020.07.21.17.14.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Jul 2020 17:14:26 -0700 (PDT) Date: Tue, 21 Jul 2020 17:14:24 -0700 From: Fangrui Song To: Masahiro Yamada 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 Subject: Re: [PATCH v3] Makefile: Fix GCC_TOOLCHAIN_DIR prefix for Clang cross compilation Message-ID: <20200722001424.qor3up6357jjsbia@google.com> References: <20200721173125.1273884-1-maskray@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020-07-22, Masahiro Yamada wrote: >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=$PATH:/home/masahiro/tools/aarch64-linaro-7.5/bin >CROSS_COMPILE=aarch64-linux-gnu- > > >[2] >Without setting PATH, >CROSS_COMPILE=~/tools/aarch64-linaro-7.5/bin/aarch64-linux-gnu- > > > >I usually do [2] (and so does intel's 0day bot). > > > >This patch works for the use-case [1] >but if I do [2], --prefix is set to a strange path: > >--prefix=/home/masahiro/tools/aarch64-linaro-7.5/bin//home/masahiro/tools/aarch64-linaro-7.5/bin/aarch64-linux-gnu- Thanks. I did not know the use-case [2]. This explains why there is a `$(notdir ...)` in `CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%))` > > >Interestingly, the build is still successful. >Presumably Clang searches for more paths >when $(prefix)$needle is not found ? The priority order is: -B(--prefix), COMPILER_PATH, detected gcc-cross paths (In GCC, -B paths get prepended to the COMPILER_PATH list. Clang<=11 incorrectly adds -B to the COMPILER_PATH list. I have fixed it for 12.0.0) If -B fails, the detected gcc-cross paths may still be able to find /usr/bin/aarch64-linux-gnu- For example, on my machine (a variant of Debian testing), Clang finds $(realpath /usr/lib/gcc-cross/aarch64-linux-gnu/9/../../../../aarch64-linux-gnu/bin/as), which is /usr/bin/aarch64-linux-gnu-as > >I applied your patch and added -v option >to see which assembler was internally invoked: > > "/home/masahiro/tools/aarch64-linaro-7.5/lib/gcc/aarch64-linux-gnu/7.5.0/../../../../aarch64-linux-gnu/bin/as" >-EL -I ./arch/arm64/include -I ./arch/arm64/include/generated -I >./include -I ./arch/arm64/include/uapi -I >./arch/arm64/include/generated/uapi -I ./include/uapi -I >./include/generated/uapi -o kernel/smp.o /tmp/smp-2ec2c7.s > > >Ok, it looks like Clang found an alternative path >to the correct 'as'. > > > > >But, to keep the original behavior for both [1] and [2], >how about this? > >CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE)) > > > >Then, I can get this: > > "/home/masahiro/tools/aarch64-linaro-7.5/bin/aarch64-linux-gnu-as" >-EL -I ./arch/arm64/include -I ./arch/arm64/include/generated -I >./include -I ./arch/arm64/include/uapi -I >./arch/arm64/include/generated/uapi -I ./include/uapi -I >./include/generated/uapi -o kernel/smp.o /tmp/smp-16d76f.s This looks good. Agreed that `--prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE))` should work for both [1] and [2]. Shall I send a v4? Or you are kind enough that you'll just add your Signed-off-by: tag and fix that for me? :) > > >> 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