81 lines
2.8 KiB
ReStructuredText
81 lines
2.8 KiB
ReStructuredText
|
==============================
|
||
|
|
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
|
||
|
|
<https://clang.llvm.org/>`_ and `LLVM <https://llvm.org/>`_ utilities to be
|
||
|
|
used as viable substitutes. Distributions such as `Android
|
||
|
|
<https://www.android.com/>`_, `ChromeOS
|
||
|
|
<https://www.chromium.org/chromium-os>`_, and `OpenMandriva
|
||
|
|
<https://www.openmandriva.org/>`_ use Clang built kernels. `LLVM is a
|
||
|
|
collection of toolchain components implemented in terms of C++ objects
|
||
|
|
<https://www.aosabook.org/en/llvm.html>`_. 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 <triple>`. 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 <https://clangbuiltlinux.github.io/>`_
|
||
|
|
- `Mailing List <https://groups.google.com/forum/#!forum/clang-built-linux>`_: <clang-built-linux@googlegroups.com>
|
||
|
|
- `Issue Tracker <https://github.com/ClangBuiltLinux/linux/issues>`_
|
||
|
|
- IRC: #clangbuiltlinux on chat.freenode.net
|
||
|
|
- `Telegram <https://t.me/ClangBuiltLinux>`_: @ClangBuiltLinux
|
||
|
|
- `Wiki <https://github.com/ClangBuiltLinux/linux/wiki>`_
|
||
|
|
- `Beginner Bugs <https://github.com/ClangBuiltLinux/linux/issues?q=is%3Aopen+is%3Aissue+label%3A%22good+first+issue%22>`_
|
||
|
|
|
||
|
|
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/
|