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=-15.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT 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 E7F5EC4363D for ; Fri, 25 Sep 2020 12:54:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AD7872075E for ; Fri, 25 Sep 2020 12:54:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601038463; bh=JFrCt+vGTBVOxHL+wcCyG0sxMyL/8clo5DWfoflr+d8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=F/O0vMrkGz71/rrDzTNv37GEdYb529ywopb0yi1H8ZP5I4Llq8kY99hsXvj19fNRY dtdkp6G4C4+Ya2m5RB4gxAT8Kj02louhFgDZsc4sJbREplvq0W+IpacpNSPH1VU/Jn NzYQcZF2qQPekqyvbUw5dnSokKGSMiH6eCKjeCBg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729556AbgIYMyW (ORCPT ); Fri, 25 Sep 2020 08:54:22 -0400 Received: from mail.kernel.org ([198.145.29.99]:60874 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728430AbgIYMyT (ORCPT ); Fri, 25 Sep 2020 08:54:19 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 00D4A2072E; Fri, 25 Sep 2020 12:54:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601038458; bh=JFrCt+vGTBVOxHL+wcCyG0sxMyL/8clo5DWfoflr+d8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SaKnPBmHmwcodZv8nZLvEPryLWMyK+9V0I50E0uc0qNpBLfr/UmfyTT2v35P8sEKC PXjrOwKmO5a1VZqLIOTIMa7SEnowNiPta6rMHFO+HfHx/myZj7H8UdxGz7iZOl31Bp rDWgOsj+wSbnyF3da1KVeEWfT8t0H5zdhVYhecGs= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Kees Cook , Nathan Chancellor , Sedat Dilek , Nick Desaulniers , Masahiro Yamada Subject: [PATCH 4.19 26/37] Documentation/llvm: add documentation on building w/ Clang/LLVM Date: Fri, 25 Sep 2020 14:48:54 +0200 Message-Id: <20200925124724.908634664@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200925124720.972208530@linuxfoundation.org> References: <20200925124720.972208530@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Nick Desaulniers commit fcf1b6a35c16ac500fa908a4022238e5d666eabf upstream. added to kbuild documentation. Provides more official info on building kernels with Clang and LLVM than our wiki. Suggested-by: Kees Cook Reviewed-by: Kees Cook Reviewed-by: Nathan Chancellor Reviewed-by: Sedat Dilek Signed-off-by: Nick Desaulniers Signed-off-by: Masahiro Yamada [nd: hunk against Documentation/kbuild/index.rst dropped due to not backporting commit cd238effefa2 ("docs: kbuild: convert docs to ReST and rename to *.rst")] Signed-off-by: Greg Kroah-Hartman --- Documentation/kbuild/llvm.rst | 80 ++++++++++++++++++++++++++++++++++++++++++ MAINTAINERS | 1 2 files changed, 81 insertions(+) create mode 100644 Documentation/kbuild/llvm.rst --- /dev/null +++ b/Documentation/kbuild/llvm.rst @@ -0,0 +1,80 @@ +============================== +Building Linux with Clang/LLVM +============================== + +This document covers how to build the Linux kernel with Clang and LLVM +utilities. + +About +----- + +The Linux kernel has always traditionally been compiled with GNU toolchains +such as GCC and binutils. Ongoing work has allowed for `Clang +`_ and `LLVM `_ utilities to be +used as viable substitutes. Distributions such as `Android +`_, `ChromeOS +`_, and `OpenMandriva +`_ use Clang built kernels. `LLVM is a +collection of toolchain components implemented in terms of C++ objects +`_. Clang is a front-end to LLVM that +supports C and the GNU C extensions required by the kernel, and is pronounced +"klang," not "see-lang." + +Clang +----- + +The compiler used can be swapped out via `CC=` command line argument to `make`. +`CC=` should be set when selecting a config and during a build. + + make CC=clang defconfig + + make CC=clang + +Cross Compiling +--------------- + +A single Clang compiler binary will typically contain all supported backends, +which can help simplify cross compiling. + + ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make CC=clang + +`CROSS_COMPILE` is not used to prefix the Clang compiler binary, instead +`CROSS_COMPILE` is used to set a command line flag: `--target `. For +example: + + clang --target aarch64-linux-gnu foo.c + +LLVM Utilities +-------------- + +LLVM has substitutes for GNU binutils utilities. These can be invoked as +additional parameters to `make`. + + make CC=clang AS=clang LD=ld.lld AR=llvm-ar NM=llvm-nm STRIP=llvm-strip \\ + OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump OBJSIZE=llvm-objsize \\ + READELF=llvm-readelf HOSTCC=clang HOSTCXX=clang++ HOSTAR=llvm-ar \\ + HOSTLD=ld.lld + +Getting Help +------------ + +- `Website `_ +- `Mailing List `_: +- `Issue Tracker `_ +- IRC: #clangbuiltlinux on chat.freenode.net +- `Telegram `_: @ClangBuiltLinux +- `Wiki `_ +- `Beginner Bugs `_ + +Getting LLVM +------------- + +- http://releases.llvm.org/download.html +- https://github.com/llvm/llvm-project +- https://llvm.org/docs/GettingStarted.html +- https://llvm.org/docs/CMake.html +- https://apt.llvm.org/ +- https://www.archlinux.org/packages/extra/x86_64/llvm/ +- https://github.com/ClangBuiltLinux/tc-build +- https://github.com/ClangBuiltLinux/linux/wiki/Building-Clang-from-source +- https://android.googlesource.com/platform/prebuilts/clang/host/linux-x86/ --- a/MAINTAINERS +++ b/MAINTAINERS @@ -3620,6 +3620,7 @@ B: https://github.com/ClangBuiltLinux/li C: irc://chat.freenode.net/clangbuiltlinux S: Supported K: \b(?i:clang|llvm)\b +F: Documentation/kbuild/llvm.rst CLEANCACHE API M: Konrad Rzeszutek Wilk