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Building Linux with Clang/LLVM
This document covers how to build the Linux kernel with Clang and LLVM
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."
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
clang --target aarch64-linux-gnu foo.c
LLVM Utilities
LLVM has substitutes for GNU binutils utilities. Kbuild supports `LLVM=1`
to enable them.
make LLVM=1
They can be enabled individually. The full list of the parameters:
make CC=clang LD=ld.lld AR=llvm-ar NM=llvm-nm STRIP=llvm-strip \\
OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump OBJSIZE=llvm-size \\
READELF=llvm-readelf HOSTCC=clang HOSTCXX=clang++ HOSTAR=llvm-ar \\
Currently, the integrated assembler is disabled by default. You can pass
`LLVM_IAS=1` to enable it.
Getting Help
- `Website <>`_
- `Mailing List <!forum/clang-built-linux>`_: <>
- `Issue Tracker <>`_
- IRC: #clangbuiltlinux on
- `Telegram <>`_: @ClangBuiltLinux
- `Wiki <>`_
- `Beginner Bugs <>`_
Getting LLVM