diff options
author | Andrey Zhizhikin <andrey.zhizhikin@leica-geosystems.com> | 2020-08-26 15:29:05 +0000 |
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committer | Andrey Zhizhikin <andrey.zhizhikin@leica-geosystems.com> | 2020-08-26 15:29:05 +0000 |
commit | 498d6443146f2a1576e222ce8b50fafc0c604954 (patch) | |
tree | bf4286db07a3c5c6b4dff8302e56b2d53f5980df /Documentation | |
parent | 952671071125edd74e401656820e52b3f87db446 (diff) | |
parent | 6576d69aac94cd8409636dfa86e0df39facdf0d2 (diff) |
Merge tag 'v5.4.61' into 5.4-2.1.x-imx
This is the 5.4.61 stable release
Conflicts (manual resolve, upstream version taken):
- drivers/xen/swiotlb-xen.c
Port upstream commit cca58a166920a to NXP tree, manual hunk was
resolved during merge.
Signed-off-by: Andrey Zhizhikin <andrey.zhizhikin@leica-geosystems.com>
Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/kbuild/index.rst | 1 | ||||
-rw-r--r-- | Documentation/kbuild/kbuild.rst | 5 | ||||
-rw-r--r-- | Documentation/kbuild/llvm.rst | 87 |
3 files changed, 93 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/kbuild.rst b/Documentation/kbuild/kbuild.rst index f1e5dce86af7..852ccc551bb3 100644 --- a/Documentation/kbuild/kbuild.rst +++ b/Documentation/kbuild/kbuild.rst @@ -262,3 +262,8 @@ KBUILD_BUILD_USER, KBUILD_BUILD_HOST These two variables allow to override the user@host string displayed during boot and in /proc/version. The default value is the output of the commands whoami and host, respectively. + +LLVM +---- +If this variable is set to 1, Kbuild will use Clang and LLVM utilities instead +of GCC and GNU binutils to build the kernel. diff --git a/Documentation/kbuild/llvm.rst b/Documentation/kbuild/llvm.rst new file mode 100644 index 000000000000..c776b6eee969 --- /dev/null +++ b/Documentation/kbuild/llvm.rst @@ -0,0 +1,87 @@ +============================== +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. 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 \\ + HOSTLD=ld.lld + +Currently, the integrated assembler is disabled by default. You can pass +`LLVM_IAS=1` to enable it. + +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/ |