summaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
authorNick Desaulniers <ndesaulniers@google.com>2020-02-26 15:23:36 -0800
committerMasahiro Yamada <masahiroy@kernel.org>2020-03-03 20:49:21 +0900
commitfcf1b6a35c16ac500fa908a4022238e5d666eabf (patch)
tree8431da6b4f50c4ed86ec42d66cd292d49285a596
parenta1af8d71f0e4c6c23eb809de559150bbff296f4d (diff)
downloadlinux-fcf1b6a35c16ac500fa908a4022238e5d666eabf.tar.bz2
Documentation/llvm: add documentation on building w/ Clang/LLVM
Added to kbuild documentation. Provides more official info on building kernels with Clang and LLVM than our wiki. Suggested-by: Kees Cook <keescook@chromium.org> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com> Reviewed-by: Sedat Dilek <sedat.dilek@gmail.com> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
-rw-r--r--Documentation/kbuild/index.rst1
-rw-r--r--Documentation/kbuild/llvm.rst80
-rw-r--r--MAINTAINERS1
3 files changed, 82 insertions, 0 deletions
diff --git a/Documentation/kbuild/index.rst b/Documentation/kbuild/index.rst
index 0f144fad99a6..3882bd5f7728 100644
--- a/Documentation/kbuild/index.rst
+++ b/Documentation/kbuild/index.rst
@@ -19,6 +19,7 @@ Kernel Build System
issues
reproducible-builds
+ llvm
.. only:: subproject and html
diff --git a/Documentation/kbuild/llvm.rst b/Documentation/kbuild/llvm.rst
new file mode 100644
index 000000000000..d6c79eb4e23e
--- /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
+<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/
diff --git a/MAINTAINERS b/MAINTAINERS
index 6158a143a13e..b6c6f3eee93c 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4119,6 +4119,7 @@ B: https://github.com/ClangBuiltLinux/linux/issues
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 <konrad.wilk@oracle.com>