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* [PATCH] Documentation/llvm: add documentation on building w/ Clang/LLVM
@ 2020-02-24 17:41 Nick Desaulniers
  2020-02-24 21:20 ` Randy Dunlap
                   ` (3 more replies)
  0 siblings, 4 replies; 26+ messages in thread
From: Nick Desaulniers @ 2020-02-24 17:41 UTC (permalink / raw)
  To: corbet, masahiroy
  Cc: Nick Desaulniers, Kees Cook, Nathan Chancellor, Michal Marek,
	linux-kbuild, linux-doc, linux-kernel, clang-built-linux

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: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
 Documentation/kbuild/index.rst |  1 +
 Documentation/kbuild/llvm.rst  | 80 ++++++++++++++++++++++++++++++++++
 2 files changed, 81 insertions(+)
 create mode 100644 Documentation/kbuild/llvm.rst

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..68ae022aebc0
--- /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. On going 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 suffix 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/
-- 
2.25.0.265.gbab2e86ba0-goog


^ permalink raw reply related	[flat|nested] 26+ messages in thread
end of thread, other threads:[~2020-02-27 16:12 UTC | newest]

Thread overview: 26+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-02-24 17:41 [PATCH] Documentation/llvm: add documentation on building w/ Clang/LLVM Nick Desaulniers
2020-02-24 21:20 ` Randy Dunlap
2020-02-25  0:33 ` Masahiro Yamada
2020-02-25 20:52   ` Nick Desaulniers
2020-02-26 12:00     ` Masahiro Yamada
2020-02-26 12:33       ` Sedat Dilek
2020-02-27  4:38         ` Nathan Chancellor
2020-02-25  4:08 ` Kees Cook
2020-02-25  4:16   ` Nathan Chancellor
2020-02-25  4:25     ` Kees Cook
2020-02-25 20:59     ` Nick Desaulniers
2020-02-25 21:56       ` Kees Cook
2020-02-25 22:20         ` Joe Perches
2020-02-26 23:18           ` Nick Desaulniers
2020-02-26 23:23             ` Joe Perches
2020-02-27  4:44       ` Nathan Chancellor
2020-02-25  6:33   ` Sedat Dilek
2020-02-25 21:02 ` [PATCH v2] " Nick Desaulniers
2020-02-26 11:30   ` Masahiro Yamada
2020-02-26 12:29     ` Sedat Dilek
2020-02-26 12:38       ` Masahiro Yamada
2020-02-26 13:02         ` Sedat Dilek
2020-02-26 15:45     ` Randy Dunlap
2020-02-26 23:23   ` [PATCH v3] " Nick Desaulniers
2020-02-27  3:58     ` Masahiro Yamada
2020-02-27 16:11     ` Masahiro Yamada

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