1 ==============================
2 Building Linux with Clang/LLVM
3 ==============================
5 This document covers how to build the Linux kernel with Clang and LLVM
11 The Linux kernel has always traditionally been compiled with GNU toolchains
12 such as GCC and binutils. Ongoing work has allowed for `Clang
13 <https://clang.llvm.org/>`_ and `LLVM <https://llvm.org/>`_ utilities to be
14 used as viable substitutes. Distributions such as `Android
15 <https://www.android.com/>`_, `ChromeOS
16 <https://www.chromium.org/chromium-os>`_, and `OpenMandriva
17 <https://www.openmandriva.org/>`_ use Clang built kernels. `LLVM is a
18 collection of toolchain components implemented in terms of C++ objects
19 <https://www.aosabook.org/en/llvm.html>`_. Clang is a front-end to LLVM that
20 supports C and the GNU C extensions required by the kernel, and is pronounced
21 "klang," not "see-lang."
26 The compiler used can be swapped out via `CC=` command line argument to `make`.
27 `CC=` should be set when selecting a config and during a build.
29 make CC=clang defconfig
36 A single Clang compiler binary will typically contain all supported backends,
37 which can help simplify cross compiling.
39 ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make CC=clang
41 `CROSS_COMPILE` is not used to prefix the Clang compiler binary, instead
42 `CROSS_COMPILE` is used to set a command line flag: `--target <triple>`. For
45 clang --target aarch64-linux-gnu foo.c
50 LLVM has substitutes for GNU binutils utilities. These can be invoked as
51 additional parameters to `make`.
53 make CC=clang AS=clang LD=ld.lld AR=llvm-ar NM=llvm-nm STRIP=llvm-strip \\
54 OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump OBJSIZE=llvm-objsize \\
55 READELF=llvm-readelf HOSTCC=clang HOSTCXX=clang++ HOSTAR=llvm-ar \\
61 - `Website <https://clangbuiltlinux.github.io/>`_
62 - `Mailing List <https://groups.google.com/forum/#!forum/clang-built-linux>`_: <clang-built-linux@googlegroups.com>
63 - `Issue Tracker <https://github.com/ClangBuiltLinux/linux/issues>`_
64 - IRC: #clangbuiltlinux on chat.freenode.net
65 - `Telegram <https://t.me/ClangBuiltLinux>`_: @ClangBuiltLinux
66 - `Wiki <https://github.com/ClangBuiltLinux/linux/wiki>`_
67 - `Beginner Bugs <https://github.com/ClangBuiltLinux/linux/issues?q=is%3Aopen+is%3Aissue+label%3A%22good+first+issue%22>`_
72 - http://releases.llvm.org/download.html
73 - https://github.com/llvm/llvm-project
74 - https://llvm.org/docs/GettingStarted.html
75 - https://llvm.org/docs/CMake.html
76 - https://apt.llvm.org/
77 - https://www.archlinux.org/packages/extra/x86_64/llvm/
78 - https://github.com/ClangBuiltLinux/tc-build
79 - https://github.com/ClangBuiltLinux/linux/wiki/Building-Clang-from-source
80 - https://android.googlesource.com/platform/prebuilts/clang/host/linux-x86/