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Documentation: add minimum clang/llvm version Based on a vote at the LLVM BoF at Plumbers 2020, we decided to start small, supporting just one formal upstream release of LLVM for now. We can probably widen the support window of supported versions over time. Also, note that LLVM's release process is different than GCC's. GCC tends to have 1 major release per year while releasing minor updates to the past 3 major versions. LLVM tends to support one major release and one minor release every six months. Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Tested-by: Gustavo A. R. Silva <gustavoars@kernel.org> Tested-by: Nathan Chancellor <natechancellor@gmail.com> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com> Reviewed-by: Masahiro Yamada <masahiroy@kernel.org> Acked-by: Will Deacon <will@kernel.org> Link: https://lore.kernel.org/r/20200826191555.3350406-1-ndesaulniers@google.com Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2020-08-27 03:15:55 +08:00
.. _kbuild_llvm:
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>
2020-02-27 07:23:36 +08:00
==============================
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
Documentation/llvm: add Chimera Linux, Google and Meta datacenters Chimera Linux is a Linux distribution from 2021 that builds its kernels with Clang. Google transitioned its data center fleet to run Clang built kernels in 2021, and Meta did so as well in 2022. Meta talked about this at LPC 2022 at a talk titled Kernel Live Patching at Scale. These were important milestones for building the kernel with Clang. Making note of them helps improve confidence in the project. Reviewed-by: Tom Rix <trix@redhat.com> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Reviewed-by: Sedat Dilek <sedat.dilek@gmail.com> Co-developed-by: Yonghong Song <yhs@fb.com> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-02-03 02:05:48 +08:00
<https://www.chromium.org/chromium-os>`_, `OpenMandriva
<https://www.openmandriva.org/>`_, and `Chimera Linux
<https://chimera-linux.org/>`_ use Clang built kernels. Google's and Meta's
datacenter fleets also run kernels built with Clang.
`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."
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>
2020-02-27 07:23:36 +08:00
Documentation/llvm: refresh docs Recent fixes for an embargoed hardware security vulnerability failed to link with ld.lld (LLVM's linker). [0] To be fair, our documentation mentions ``CC=clang`` foremost with ``LLVM=1`` being buried "below the fold." We want to encourage the use of ``LLVM=1`` rather than just ``CC=clang``. Make that suggestion "above the fold" and "front and center" in our docs. While here, the following additional changes were made: - remove the bit about CROSS_COMPILE setting --target=, that's no longer true. - Add ARCH=loongarch to the list of maintained targets (though we're still working on getting defconfig building cleanly at the moment; we're pretty close). - Bump ARCH=powerpc from CC=clang to LLVM=1 status. - Promote ARCH=riscv from being Maintained to being Supported. Android is working towards supporting RISC-V, and we have excellent support from multiple companies in this regard. - Note that the toolchain distribution on kernel.org has been built with profile data from kernel builds. - Note how to use ccache with clang. Link: https://github.com/ClangBuiltLinux/linux/issues/1907 [0] Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-08-26 01:38:01 +08:00
Building with LLVM
------------------
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>
2020-02-27 07:23:36 +08:00
Documentation/llvm: refresh docs Recent fixes for an embargoed hardware security vulnerability failed to link with ld.lld (LLVM's linker). [0] To be fair, our documentation mentions ``CC=clang`` foremost with ``LLVM=1`` being buried "below the fold." We want to encourage the use of ``LLVM=1`` rather than just ``CC=clang``. Make that suggestion "above the fold" and "front and center" in our docs. While here, the following additional changes were made: - remove the bit about CROSS_COMPILE setting --target=, that's no longer true. - Add ARCH=loongarch to the list of maintained targets (though we're still working on getting defconfig building cleanly at the moment; we're pretty close). - Bump ARCH=powerpc from CC=clang to LLVM=1 status. - Promote ARCH=riscv from being Maintained to being Supported. Android is working towards supporting RISC-V, and we have excellent support from multiple companies in this regard. - Note that the toolchain distribution on kernel.org has been built with profile data from kernel builds. - Note how to use ccache with clang. Link: https://github.com/ClangBuiltLinux/linux/issues/1907 [0] Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-08-26 01:38:01 +08:00
Invoke ``make`` via::
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>
2020-02-27 07:23:36 +08:00
Documentation/llvm: refresh docs Recent fixes for an embargoed hardware security vulnerability failed to link with ld.lld (LLVM's linker). [0] To be fair, our documentation mentions ``CC=clang`` foremost with ``LLVM=1`` being buried "below the fold." We want to encourage the use of ``LLVM=1`` rather than just ``CC=clang``. Make that suggestion "above the fold" and "front and center" in our docs. While here, the following additional changes were made: - remove the bit about CROSS_COMPILE setting --target=, that's no longer true. - Add ARCH=loongarch to the list of maintained targets (though we're still working on getting defconfig building cleanly at the moment; we're pretty close). - Bump ARCH=powerpc from CC=clang to LLVM=1 status. - Promote ARCH=riscv from being Maintained to being Supported. Android is working towards supporting RISC-V, and we have excellent support from multiple companies in this regard. - Note that the toolchain distribution on kernel.org has been built with profile data from kernel builds. - Note how to use ccache with clang. Link: https://github.com/ClangBuiltLinux/linux/issues/1907 [0] Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-08-26 01:38:01 +08:00
make LLVM=1
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>
2020-02-27 07:23:36 +08:00
Documentation/llvm: refresh docs Recent fixes for an embargoed hardware security vulnerability failed to link with ld.lld (LLVM's linker). [0] To be fair, our documentation mentions ``CC=clang`` foremost with ``LLVM=1`` being buried "below the fold." We want to encourage the use of ``LLVM=1`` rather than just ``CC=clang``. Make that suggestion "above the fold" and "front and center" in our docs. While here, the following additional changes were made: - remove the bit about CROSS_COMPILE setting --target=, that's no longer true. - Add ARCH=loongarch to the list of maintained targets (though we're still working on getting defconfig building cleanly at the moment; we're pretty close). - Bump ARCH=powerpc from CC=clang to LLVM=1 status. - Promote ARCH=riscv from being Maintained to being Supported. Android is working towards supporting RISC-V, and we have excellent support from multiple companies in this regard. - Note that the toolchain distribution on kernel.org has been built with profile data from kernel builds. - Note how to use ccache with clang. Link: https://github.com/ClangBuiltLinux/linux/issues/1907 [0] Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-08-26 01:38:01 +08:00
to compile for the host target. For cross compiling::
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>
2020-02-27 07:23:36 +08:00
Documentation/llvm: refresh docs Recent fixes for an embargoed hardware security vulnerability failed to link with ld.lld (LLVM's linker). [0] To be fair, our documentation mentions ``CC=clang`` foremost with ``LLVM=1`` being buried "below the fold." We want to encourage the use of ``LLVM=1`` rather than just ``CC=clang``. Make that suggestion "above the fold" and "front and center" in our docs. While here, the following additional changes were made: - remove the bit about CROSS_COMPILE setting --target=, that's no longer true. - Add ARCH=loongarch to the list of maintained targets (though we're still working on getting defconfig building cleanly at the moment; we're pretty close). - Bump ARCH=powerpc from CC=clang to LLVM=1 status. - Promote ARCH=riscv from being Maintained to being Supported. Android is working towards supporting RISC-V, and we have excellent support from multiple companies in this regard. - Note that the toolchain distribution on kernel.org has been built with profile data from kernel builds. - Note how to use ccache with clang. Link: https://github.com/ClangBuiltLinux/linux/issues/1907 [0] Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-08-26 01:38:01 +08:00
make LLVM=1 ARCH=arm64
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>
2020-02-27 07:23:36 +08:00
Documentation/llvm: refresh docs Recent fixes for an embargoed hardware security vulnerability failed to link with ld.lld (LLVM's linker). [0] To be fair, our documentation mentions ``CC=clang`` foremost with ``LLVM=1`` being buried "below the fold." We want to encourage the use of ``LLVM=1`` rather than just ``CC=clang``. Make that suggestion "above the fold" and "front and center" in our docs. While here, the following additional changes were made: - remove the bit about CROSS_COMPILE setting --target=, that's no longer true. - Add ARCH=loongarch to the list of maintained targets (though we're still working on getting defconfig building cleanly at the moment; we're pretty close). - Bump ARCH=powerpc from CC=clang to LLVM=1 status. - Promote ARCH=riscv from being Maintained to being Supported. Android is working towards supporting RISC-V, and we have excellent support from multiple companies in this regard. - Note that the toolchain distribution on kernel.org has been built with profile data from kernel builds. - Note how to use ccache with clang. Link: https://github.com/ClangBuiltLinux/linux/issues/1907 [0] Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-08-26 01:38:01 +08:00
The LLVM= argument
------------------
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>
2020-02-27 07:23:36 +08:00
Documentation/llvm: refresh docs Recent fixes for an embargoed hardware security vulnerability failed to link with ld.lld (LLVM's linker). [0] To be fair, our documentation mentions ``CC=clang`` foremost with ``LLVM=1`` being buried "below the fold." We want to encourage the use of ``LLVM=1`` rather than just ``CC=clang``. Make that suggestion "above the fold" and "front and center" in our docs. While here, the following additional changes were made: - remove the bit about CROSS_COMPILE setting --target=, that's no longer true. - Add ARCH=loongarch to the list of maintained targets (though we're still working on getting defconfig building cleanly at the moment; we're pretty close). - Bump ARCH=powerpc from CC=clang to LLVM=1 status. - Promote ARCH=riscv from being Maintained to being Supported. Android is working towards supporting RISC-V, and we have excellent support from multiple companies in this regard. - Note that the toolchain distribution on kernel.org has been built with profile data from kernel builds. - Note how to use ccache with clang. Link: https://github.com/ClangBuiltLinux/linux/issues/1907 [0] Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-08-26 01:38:01 +08:00
LLVM has substitutes for GNU binutils utilities. They can be enabled
individually. The full list of supported make variables::
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>
2020-02-27 07:23:36 +08:00
Documentation/llvm: Improve formatting of commands, variables, and arguments While reviewing a separate patch, I noticed that the formatting of the commands, variables, and arguments was not in a monospaced font like the rest of the Kbuild documentation (see kbuild/kconfig.rst for an example). This is due to a lack of "::" before indented command blocks and single backticks instead of double backticks for inline formatting. Add those so that the document looks nicer in an HTML format, while not ruining the look in plain text. As a result of this, we can remove the escaped backslashes in the last code block and move them to single backslashes. Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2020-08-26 07:14:38 +08:00
make CC=clang LD=ld.lld AR=llvm-ar NM=llvm-nm STRIP=llvm-strip \
kbuild: remove unused OBJSIZE The "size" tool has been solely used by s390 to enforce .bss section usage restrictions in early startup code. Since commit 980d5f9ab36b ("s390/boot: enable .bss section for compressed kernel") and commit 2e83e0eb85ca ("s390: clean .bss before running uncompressed kernel") these restrictions have been lifted for the decompressor and uncompressed kernel and the size tool is now unused. Signed-off-by: Vasily Gorbik <gor@linux.ibm.com> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2020-10-23 19:57:32 +08:00
OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump READELF=llvm-readelf \
HOSTCC=clang HOSTCXX=clang++ HOSTAR=llvm-ar HOSTLD=ld.lld
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>
2020-02-27 07:23:36 +08:00
Documentation/llvm: refresh docs Recent fixes for an embargoed hardware security vulnerability failed to link with ld.lld (LLVM's linker). [0] To be fair, our documentation mentions ``CC=clang`` foremost with ``LLVM=1`` being buried "below the fold." We want to encourage the use of ``LLVM=1`` rather than just ``CC=clang``. Make that suggestion "above the fold" and "front and center" in our docs. While here, the following additional changes were made: - remove the bit about CROSS_COMPILE setting --target=, that's no longer true. - Add ARCH=loongarch to the list of maintained targets (though we're still working on getting defconfig building cleanly at the moment; we're pretty close). - Bump ARCH=powerpc from CC=clang to LLVM=1 status. - Promote ARCH=riscv from being Maintained to being Supported. Android is working towards supporting RISC-V, and we have excellent support from multiple companies in this regard. - Note that the toolchain distribution on kernel.org has been built with profile data from kernel builds. - Note how to use ccache with clang. Link: https://github.com/ClangBuiltLinux/linux/issues/1907 [0] Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-08-26 01:38:01 +08:00
``LLVM=1`` expands to the above.
kbuild: Make $(LLVM) more flexible The LLVM make variable allows a developer to quickly switch between the GNU and LLVM tools. However, it does not handle versioned binaries, such as the ones shipped by Debian, as LLVM=1 just defines the tool variables with the unversioned binaries. There was some discussion during the review of the patch that introduces LLVM=1 around versioned binaries, ultimately coming to the conclusion that developers can just add the folder that contains the unversioned binaries to their PATH, as Debian's versioned suffixed binaries are really just symlinks to the unversioned binaries in /usr/lib/llvm-#/bin: $ realpath /usr/bin/clang-14 /usr/lib/llvm-14/bin/clang $ PATH=/usr/lib/llvm-14/bin:$PATH make ... LLVM=1 However, that can be cumbersome to developers who are constantly testing series with different toolchains and versions. It is simple enough to support these versioned binaries directly in the Kbuild system by allowing the developer to specify the version suffix with LLVM=, which is shorter than the above suggestion: $ make ... LLVM=-14 It does not change the meaning of LLVM=1 (which will continue to use unversioned binaries) and it does not add too much additional complexity to the existing $(LLVM) code, while allowing developers to quickly test their series with different versions of the whole LLVM suite of tools. Some developers may build LLVM from source but not add the binaries to their PATH, as they may not want to use that toolchain systemwide. Support those developers by allowing them to supply the directory that the LLVM tools are available in, as it is no more complex to support than the version suffix change above. $ make ... LLVM=/path/to/llvm/ Update and reorder the documentation to reflect these new additions. At the same time, notate that LLVM=0 is not the same as just omitting it altogether, which has confused people in the past. Link: https://lore.kernel.org/r/20200317215515.226917-1-ndesaulniers@google.com/ Link: https://lore.kernel.org/r/20220224151322.072632223@infradead.org/ Suggested-by: Masahiro Yamada <masahiroy@kernel.org> Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Nathan Chancellor <nathan@kernel.org> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2022-03-05 01:08:14 +08:00
If your LLVM tools are not available in your PATH, you can supply their
location using the LLVM variable with a trailing slash::
make LLVM=/path/to/llvm/
Documentation/llvm: refresh docs Recent fixes for an embargoed hardware security vulnerability failed to link with ld.lld (LLVM's linker). [0] To be fair, our documentation mentions ``CC=clang`` foremost with ``LLVM=1`` being buried "below the fold." We want to encourage the use of ``LLVM=1`` rather than just ``CC=clang``. Make that suggestion "above the fold" and "front and center" in our docs. While here, the following additional changes were made: - remove the bit about CROSS_COMPILE setting --target=, that's no longer true. - Add ARCH=loongarch to the list of maintained targets (though we're still working on getting defconfig building cleanly at the moment; we're pretty close). - Bump ARCH=powerpc from CC=clang to LLVM=1 status. - Promote ARCH=riscv from being Maintained to being Supported. Android is working towards supporting RISC-V, and we have excellent support from multiple companies in this regard. - Note that the toolchain distribution on kernel.org has been built with profile data from kernel builds. - Note how to use ccache with clang. Link: https://github.com/ClangBuiltLinux/linux/issues/1907 [0] Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-08-26 01:38:01 +08:00
which will use ``/path/to/llvm/clang``, ``/path/to/llvm/ld.lld``, etc. The
following may also be used::
PATH=/path/to/llvm:$PATH make LLVM=1
kbuild: Make $(LLVM) more flexible The LLVM make variable allows a developer to quickly switch between the GNU and LLVM tools. However, it does not handle versioned binaries, such as the ones shipped by Debian, as LLVM=1 just defines the tool variables with the unversioned binaries. There was some discussion during the review of the patch that introduces LLVM=1 around versioned binaries, ultimately coming to the conclusion that developers can just add the folder that contains the unversioned binaries to their PATH, as Debian's versioned suffixed binaries are really just symlinks to the unversioned binaries in /usr/lib/llvm-#/bin: $ realpath /usr/bin/clang-14 /usr/lib/llvm-14/bin/clang $ PATH=/usr/lib/llvm-14/bin:$PATH make ... LLVM=1 However, that can be cumbersome to developers who are constantly testing series with different toolchains and versions. It is simple enough to support these versioned binaries directly in the Kbuild system by allowing the developer to specify the version suffix with LLVM=, which is shorter than the above suggestion: $ make ... LLVM=-14 It does not change the meaning of LLVM=1 (which will continue to use unversioned binaries) and it does not add too much additional complexity to the existing $(LLVM) code, while allowing developers to quickly test their series with different versions of the whole LLVM suite of tools. Some developers may build LLVM from source but not add the binaries to their PATH, as they may not want to use that toolchain systemwide. Support those developers by allowing them to supply the directory that the LLVM tools are available in, as it is no more complex to support than the version suffix change above. $ make ... LLVM=/path/to/llvm/ Update and reorder the documentation to reflect these new additions. At the same time, notate that LLVM=0 is not the same as just omitting it altogether, which has confused people in the past. Link: https://lore.kernel.org/r/20200317215515.226917-1-ndesaulniers@google.com/ Link: https://lore.kernel.org/r/20220224151322.072632223@infradead.org/ Suggested-by: Masahiro Yamada <masahiroy@kernel.org> Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Nathan Chancellor <nathan@kernel.org> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2022-03-05 01:08:14 +08:00
If your LLVM tools have a version suffix and you want to test with that
explicit version rather than the unsuffixed executables like ``LLVM=1``, you
can pass the suffix using the ``LLVM`` variable::
make LLVM=-14
which will use ``clang-14``, ``ld.lld-14``, etc.
Documentation/llvm: refresh docs Recent fixes for an embargoed hardware security vulnerability failed to link with ld.lld (LLVM's linker). [0] To be fair, our documentation mentions ``CC=clang`` foremost with ``LLVM=1`` being buried "below the fold." We want to encourage the use of ``LLVM=1`` rather than just ``CC=clang``. Make that suggestion "above the fold" and "front and center" in our docs. While here, the following additional changes were made: - remove the bit about CROSS_COMPILE setting --target=, that's no longer true. - Add ARCH=loongarch to the list of maintained targets (though we're still working on getting defconfig building cleanly at the moment; we're pretty close). - Bump ARCH=powerpc from CC=clang to LLVM=1 status. - Promote ARCH=riscv from being Maintained to being Supported. Android is working towards supporting RISC-V, and we have excellent support from multiple companies in this regard. - Note that the toolchain distribution on kernel.org has been built with profile data from kernel builds. - Note how to use ccache with clang. Link: https://github.com/ClangBuiltLinux/linux/issues/1907 [0] Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-08-26 01:38:01 +08:00
To support combinations of out of tree paths with version suffixes, we
recommend::
PATH=/path/to/llvm/:$PATH make LLVM=-14
kbuild: Make $(LLVM) more flexible The LLVM make variable allows a developer to quickly switch between the GNU and LLVM tools. However, it does not handle versioned binaries, such as the ones shipped by Debian, as LLVM=1 just defines the tool variables with the unversioned binaries. There was some discussion during the review of the patch that introduces LLVM=1 around versioned binaries, ultimately coming to the conclusion that developers can just add the folder that contains the unversioned binaries to their PATH, as Debian's versioned suffixed binaries are really just symlinks to the unversioned binaries in /usr/lib/llvm-#/bin: $ realpath /usr/bin/clang-14 /usr/lib/llvm-14/bin/clang $ PATH=/usr/lib/llvm-14/bin:$PATH make ... LLVM=1 However, that can be cumbersome to developers who are constantly testing series with different toolchains and versions. It is simple enough to support these versioned binaries directly in the Kbuild system by allowing the developer to specify the version suffix with LLVM=, which is shorter than the above suggestion: $ make ... LLVM=-14 It does not change the meaning of LLVM=1 (which will continue to use unversioned binaries) and it does not add too much additional complexity to the existing $(LLVM) code, while allowing developers to quickly test their series with different versions of the whole LLVM suite of tools. Some developers may build LLVM from source but not add the binaries to their PATH, as they may not want to use that toolchain systemwide. Support those developers by allowing them to supply the directory that the LLVM tools are available in, as it is no more complex to support than the version suffix change above. $ make ... LLVM=/path/to/llvm/ Update and reorder the documentation to reflect these new additions. At the same time, notate that LLVM=0 is not the same as just omitting it altogether, which has confused people in the past. Link: https://lore.kernel.org/r/20200317215515.226917-1-ndesaulniers@google.com/ Link: https://lore.kernel.org/r/20220224151322.072632223@infradead.org/ Suggested-by: Masahiro Yamada <masahiroy@kernel.org> Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Nathan Chancellor <nathan@kernel.org> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2022-03-05 01:08:14 +08:00
``LLVM=0`` is not the same as omitting ``LLVM`` altogether, it will behave like
Documentation/llvm: refresh docs Recent fixes for an embargoed hardware security vulnerability failed to link with ld.lld (LLVM's linker). [0] To be fair, our documentation mentions ``CC=clang`` foremost with ``LLVM=1`` being buried "below the fold." We want to encourage the use of ``LLVM=1`` rather than just ``CC=clang``. Make that suggestion "above the fold" and "front and center" in our docs. While here, the following additional changes were made: - remove the bit about CROSS_COMPILE setting --target=, that's no longer true. - Add ARCH=loongarch to the list of maintained targets (though we're still working on getting defconfig building cleanly at the moment; we're pretty close). - Bump ARCH=powerpc from CC=clang to LLVM=1 status. - Promote ARCH=riscv from being Maintained to being Supported. Android is working towards supporting RISC-V, and we have excellent support from multiple companies in this regard. - Note that the toolchain distribution on kernel.org has been built with profile data from kernel builds. - Note how to use ccache with clang. Link: https://github.com/ClangBuiltLinux/linux/issues/1907 [0] Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-08-26 01:38:01 +08:00
``LLVM=1``. If you only wish to use certain LLVM utilities, use their
respective make variables.
The same value used for ``LLVM=`` should be set for each invocation of ``make``
if configuring and building via distinct commands. ``LLVM=`` should also be set
as an environment variable when running scripts that will eventually run
``make``.
kbuild: Make $(LLVM) more flexible The LLVM make variable allows a developer to quickly switch between the GNU and LLVM tools. However, it does not handle versioned binaries, such as the ones shipped by Debian, as LLVM=1 just defines the tool variables with the unversioned binaries. There was some discussion during the review of the patch that introduces LLVM=1 around versioned binaries, ultimately coming to the conclusion that developers can just add the folder that contains the unversioned binaries to their PATH, as Debian's versioned suffixed binaries are really just symlinks to the unversioned binaries in /usr/lib/llvm-#/bin: $ realpath /usr/bin/clang-14 /usr/lib/llvm-14/bin/clang $ PATH=/usr/lib/llvm-14/bin:$PATH make ... LLVM=1 However, that can be cumbersome to developers who are constantly testing series with different toolchains and versions. It is simple enough to support these versioned binaries directly in the Kbuild system by allowing the developer to specify the version suffix with LLVM=, which is shorter than the above suggestion: $ make ... LLVM=-14 It does not change the meaning of LLVM=1 (which will continue to use unversioned binaries) and it does not add too much additional complexity to the existing $(LLVM) code, while allowing developers to quickly test their series with different versions of the whole LLVM suite of tools. Some developers may build LLVM from source but not add the binaries to their PATH, as they may not want to use that toolchain systemwide. Support those developers by allowing them to supply the directory that the LLVM tools are available in, as it is no more complex to support than the version suffix change above. $ make ... LLVM=/path/to/llvm/ Update and reorder the documentation to reflect these new additions. At the same time, notate that LLVM=0 is not the same as just omitting it altogether, which has confused people in the past. Link: https://lore.kernel.org/r/20200317215515.226917-1-ndesaulniers@google.com/ Link: https://lore.kernel.org/r/20220224151322.072632223@infradead.org/ Suggested-by: Masahiro Yamada <masahiroy@kernel.org> Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Nathan Chancellor <nathan@kernel.org> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2022-03-05 01:08:14 +08:00
Documentation/llvm: refresh docs Recent fixes for an embargoed hardware security vulnerability failed to link with ld.lld (LLVM's linker). [0] To be fair, our documentation mentions ``CC=clang`` foremost with ``LLVM=1`` being buried "below the fold." We want to encourage the use of ``LLVM=1`` rather than just ``CC=clang``. Make that suggestion "above the fold" and "front and center" in our docs. While here, the following additional changes were made: - remove the bit about CROSS_COMPILE setting --target=, that's no longer true. - Add ARCH=loongarch to the list of maintained targets (though we're still working on getting defconfig building cleanly at the moment; we're pretty close). - Bump ARCH=powerpc from CC=clang to LLVM=1 status. - Promote ARCH=riscv from being Maintained to being Supported. Android is working towards supporting RISC-V, and we have excellent support from multiple companies in this regard. - Note that the toolchain distribution on kernel.org has been built with profile data from kernel builds. - Note how to use ccache with clang. Link: https://github.com/ClangBuiltLinux/linux/issues/1907 [0] Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-08-26 01:38:01 +08:00
Cross Compiling
---------------
kbuild: replace AS=clang with LLVM_IAS=1 The 'AS' variable is unused for building the kernel. Only the remaining usage is to turn on the integrated assembler. A boolean flag is a better fit for this purpose. AS=clang was added for experts. So, I replaced it with LLVM_IAS=1, breaking the backward compatibility. Suggested-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
2020-04-08 09:36:22 +08:00
Documentation/llvm: refresh docs Recent fixes for an embargoed hardware security vulnerability failed to link with ld.lld (LLVM's linker). [0] To be fair, our documentation mentions ``CC=clang`` foremost with ``LLVM=1`` being buried "below the fold." We want to encourage the use of ``LLVM=1`` rather than just ``CC=clang``. Make that suggestion "above the fold" and "front and center" in our docs. While here, the following additional changes were made: - remove the bit about CROSS_COMPILE setting --target=, that's no longer true. - Add ARCH=loongarch to the list of maintained targets (though we're still working on getting defconfig building cleanly at the moment; we're pretty close). - Bump ARCH=powerpc from CC=clang to LLVM=1 status. - Promote ARCH=riscv from being Maintained to being Supported. Android is working towards supporting RISC-V, and we have excellent support from multiple companies in this regard. - Note that the toolchain distribution on kernel.org has been built with profile data from kernel builds. - Note how to use ccache with clang. Link: https://github.com/ClangBuiltLinux/linux/issues/1907 [0] Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-08-26 01:38:01 +08:00
A single Clang compiler binary (and corresponding LLVM utilities) will
typically contain all supported back ends, which can help simplify cross
compiling especially when ``LLVM=1`` is used. If you use only LLVM tools,
``CROSS_COMPILE`` or target-triple-prefixes become unnecessary. Example::
make LLVM=1 ARCH=arm64
As an example of mixing LLVM and GNU utilities, for a target like ``ARCH=s390``
which does not yet have ``ld.lld`` or ``llvm-objcopy`` support, you could
invoke ``make`` via::
make LLVM=1 ARCH=s390 LD=s390x-linux-gnu-ld.bfd \
OBJCOPY=s390x-linux-gnu-objcopy
This example will invoke ``s390x-linux-gnu-ld.bfd`` as the linker and
``s390x-linux-gnu-objcopy``, so ensure those are reachable in your ``$PATH``.
``CROSS_COMPILE`` is not used to prefix the Clang compiler binary (or
corresponding LLVM utilities) as is the case for GNU utilities when ``LLVM=1``
is not set.
The LLVM_IAS= argument
Documentation/llvm: update CROSS_COMPILE inferencing As noted by Masahiro, document how we can generally infer CROSS_COMPILE (and the more specific details about --target and --prefix) based on ARCH. Change use of env vars to command line parameters. Suggested-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Fangrui Song <maskray@google.com> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-08-03 02:39:10 +08:00
----------------------
Documentation/llvm: refresh docs Recent fixes for an embargoed hardware security vulnerability failed to link with ld.lld (LLVM's linker). [0] To be fair, our documentation mentions ``CC=clang`` foremost with ``LLVM=1`` being buried "below the fold." We want to encourage the use of ``LLVM=1`` rather than just ``CC=clang``. Make that suggestion "above the fold" and "front and center" in our docs. While here, the following additional changes were made: - remove the bit about CROSS_COMPILE setting --target=, that's no longer true. - Add ARCH=loongarch to the list of maintained targets (though we're still working on getting defconfig building cleanly at the moment; we're pretty close). - Bump ARCH=powerpc from CC=clang to LLVM=1 status. - Promote ARCH=riscv from being Maintained to being Supported. Android is working towards supporting RISC-V, and we have excellent support from multiple companies in this regard. - Note that the toolchain distribution on kernel.org has been built with profile data from kernel builds. - Note how to use ccache with clang. Link: https://github.com/ClangBuiltLinux/linux/issues/1907 [0] Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-08-26 01:38:01 +08:00
Clang can assemble assembler code. You can pass ``LLVM_IAS=0`` to disable this
behavior and have Clang invoke the corresponding non-integrated assembler
instead. Example::
make LLVM=1 LLVM_IAS=0
``CROSS_COMPILE`` is necessary when cross compiling and ``LLVM_IAS=0``
is used in order to set ``--prefix=`` for the compiler to find the
corresponding non-integrated assembler (typically, you don't want to use the
system assembler when targeting another architecture). Example::
Documentation/llvm: update CROSS_COMPILE inferencing As noted by Masahiro, document how we can generally infer CROSS_COMPILE (and the more specific details about --target and --prefix) based on ARCH. Change use of env vars to command line parameters. Suggested-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Fangrui Song <maskray@google.com> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-08-03 02:39:10 +08:00
Documentation/llvm: refresh docs Recent fixes for an embargoed hardware security vulnerability failed to link with ld.lld (LLVM's linker). [0] To be fair, our documentation mentions ``CC=clang`` foremost with ``LLVM=1`` being buried "below the fold." We want to encourage the use of ``LLVM=1`` rather than just ``CC=clang``. Make that suggestion "above the fold" and "front and center" in our docs. While here, the following additional changes were made: - remove the bit about CROSS_COMPILE setting --target=, that's no longer true. - Add ARCH=loongarch to the list of maintained targets (though we're still working on getting defconfig building cleanly at the moment; we're pretty close). - Bump ARCH=powerpc from CC=clang to LLVM=1 status. - Promote ARCH=riscv from being Maintained to being Supported. Android is working towards supporting RISC-V, and we have excellent support from multiple companies in this regard. - Note that the toolchain distribution on kernel.org has been built with profile data from kernel builds. - Note how to use ccache with clang. Link: https://github.com/ClangBuiltLinux/linux/issues/1907 [0] Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-08-26 01:38:01 +08:00
make LLVM=1 ARCH=arm LLVM_IAS=0 CROSS_COMPILE=arm-linux-gnueabi-
Documentation/llvm: update CROSS_COMPILE inferencing As noted by Masahiro, document how we can generally infer CROSS_COMPILE (and the more specific details about --target and --prefix) based on ARCH. Change use of env vars to command line parameters. Suggested-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Fangrui Song <maskray@google.com> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-08-03 02:39:10 +08:00
Documentation/llvm: refresh docs Recent fixes for an embargoed hardware security vulnerability failed to link with ld.lld (LLVM's linker). [0] To be fair, our documentation mentions ``CC=clang`` foremost with ``LLVM=1`` being buried "below the fold." We want to encourage the use of ``LLVM=1`` rather than just ``CC=clang``. Make that suggestion "above the fold" and "front and center" in our docs. While here, the following additional changes were made: - remove the bit about CROSS_COMPILE setting --target=, that's no longer true. - Add ARCH=loongarch to the list of maintained targets (though we're still working on getting defconfig building cleanly at the moment; we're pretty close). - Bump ARCH=powerpc from CC=clang to LLVM=1 status. - Promote ARCH=riscv from being Maintained to being Supported. Android is working towards supporting RISC-V, and we have excellent support from multiple companies in this regard. - Note that the toolchain distribution on kernel.org has been built with profile data from kernel builds. - Note how to use ccache with clang. Link: https://github.com/ClangBuiltLinux/linux/issues/1907 [0] Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-08-26 01:38:01 +08:00
Ccache
------
Documentation/llvm: update CROSS_COMPILE inferencing As noted by Masahiro, document how we can generally infer CROSS_COMPILE (and the more specific details about --target and --prefix) based on ARCH. Change use of env vars to command line parameters. Suggested-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Fangrui Song <maskray@google.com> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-08-03 02:39:10 +08:00
Documentation/llvm: refresh docs Recent fixes for an embargoed hardware security vulnerability failed to link with ld.lld (LLVM's linker). [0] To be fair, our documentation mentions ``CC=clang`` foremost with ``LLVM=1`` being buried "below the fold." We want to encourage the use of ``LLVM=1`` rather than just ``CC=clang``. Make that suggestion "above the fold" and "front and center" in our docs. While here, the following additional changes were made: - remove the bit about CROSS_COMPILE setting --target=, that's no longer true. - Add ARCH=loongarch to the list of maintained targets (though we're still working on getting defconfig building cleanly at the moment; we're pretty close). - Bump ARCH=powerpc from CC=clang to LLVM=1 status. - Promote ARCH=riscv from being Maintained to being Supported. Android is working towards supporting RISC-V, and we have excellent support from multiple companies in this regard. - Note that the toolchain distribution on kernel.org has been built with profile data from kernel builds. - Note how to use ccache with clang. Link: https://github.com/ClangBuiltLinux/linux/issues/1907 [0] Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-08-26 01:38:01 +08:00
``ccache`` can be used with ``clang`` to improve subsequent builds, (though
KBUILD_BUILD_TIMESTAMP_ should be set to a deterministic value between builds
in order to avoid 100% cache misses, see Reproducible_builds_ for more info):
scripts/Makefile.clang: default to LLVM_IAS=1 LLVM_IAS=1 controls enabling clang's integrated assembler via -integrated-as. This was an explicit opt in until we could enable assembler support in Clang for more architecures. Now we have support and CI coverage of LLVM_IAS=1 for all architecures except a few more bugs affecting s390 and powerpc. This commit flips the default from opt in via LLVM_IAS=1 to opt out via LLVM_IAS=0. CI systems or developers that were previously doing builds with CC=clang or LLVM=1 without explicitly setting LLVM_IAS must now explicitly opt out via LLVM_IAS=0, otherwise they will be implicitly opted-in. This finally shortens the command line invocation when cross compiling with LLVM to simply: $ make ARCH=arm64 LLVM=1 Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-08-07 01:27:01 +08:00
Documentation/llvm: refresh docs Recent fixes for an embargoed hardware security vulnerability failed to link with ld.lld (LLVM's linker). [0] To be fair, our documentation mentions ``CC=clang`` foremost with ``LLVM=1`` being buried "below the fold." We want to encourage the use of ``LLVM=1`` rather than just ``CC=clang``. Make that suggestion "above the fold" and "front and center" in our docs. While here, the following additional changes were made: - remove the bit about CROSS_COMPILE setting --target=, that's no longer true. - Add ARCH=loongarch to the list of maintained targets (though we're still working on getting defconfig building cleanly at the moment; we're pretty close). - Bump ARCH=powerpc from CC=clang to LLVM=1 status. - Promote ARCH=riscv from being Maintained to being Supported. Android is working towards supporting RISC-V, and we have excellent support from multiple companies in this regard. - Note that the toolchain distribution on kernel.org has been built with profile data from kernel builds. - Note how to use ccache with clang. Link: https://github.com/ClangBuiltLinux/linux/issues/1907 [0] Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-08-26 01:38:01 +08:00
KBUILD_BUILD_TIMESTAMP='' make LLVM=1 CC="ccache clang"
scripts/Makefile.clang: default to LLVM_IAS=1 LLVM_IAS=1 controls enabling clang's integrated assembler via -integrated-as. This was an explicit opt in until we could enable assembler support in Clang for more architecures. Now we have support and CI coverage of LLVM_IAS=1 for all architecures except a few more bugs affecting s390 and powerpc. This commit flips the default from opt in via LLVM_IAS=1 to opt out via LLVM_IAS=0. CI systems or developers that were previously doing builds with CC=clang or LLVM=1 without explicitly setting LLVM_IAS must now explicitly opt out via LLVM_IAS=0, otherwise they will be implicitly opted-in. This finally shortens the command line invocation when cross compiling with LLVM to simply: $ make ARCH=arm64 LLVM=1 Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-08-07 01:27:01 +08:00
Documentation/llvm: refresh docs Recent fixes for an embargoed hardware security vulnerability failed to link with ld.lld (LLVM's linker). [0] To be fair, our documentation mentions ``CC=clang`` foremost with ``LLVM=1`` being buried "below the fold." We want to encourage the use of ``LLVM=1`` rather than just ``CC=clang``. Make that suggestion "above the fold" and "front and center" in our docs. While here, the following additional changes were made: - remove the bit about CROSS_COMPILE setting --target=, that's no longer true. - Add ARCH=loongarch to the list of maintained targets (though we're still working on getting defconfig building cleanly at the moment; we're pretty close). - Bump ARCH=powerpc from CC=clang to LLVM=1 status. - Promote ARCH=riscv from being Maintained to being Supported. Android is working towards supporting RISC-V, and we have excellent support from multiple companies in this regard. - Note that the toolchain distribution on kernel.org has been built with profile data from kernel builds. - Note how to use ccache with clang. Link: https://github.com/ClangBuiltLinux/linux/issues/1907 [0] Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-08-26 01:38:01 +08:00
.. _KBUILD_BUILD_TIMESTAMP: kbuild.html#kbuild-build-timestamp
.. _Reproducible_builds: reproducible-builds.html#timestamps
Documentation/llvm: update CROSS_COMPILE inferencing As noted by Masahiro, document how we can generally infer CROSS_COMPILE (and the more specific details about --target and --prefix) based on ARCH. Change use of env vars to command line parameters. Suggested-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Fangrui Song <maskray@google.com> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-08-03 02:39:10 +08:00
Documentation/llvm: Add a section about supported architectures The most common question around building the Linux kernel with clang is "does it work?" and the answer has always been "it depends on your architecture, configuration, and LLVM version" with no hard answers for users wanting to experiment. LLVM support has significantly improved over the past couple of years, resulting in more architectures and configurations supported, and continuous integration has made it easier to see what works and what does not. Add a section that goes over what architectures are supported in the current kernel version, how they should be built (with just clang or the LLVM utilities as well), and the level of support they receive. This will make it easier for people to try out building their kernel with LLVM and reporting issues that come about from it. Suggested-by: Miguel Ojeda <ojeda@kernel.org> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> Reviewed-by: Nick Desaulniers <ndesaulnier@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-01-14 08:34:47 +08:00
Supported Architectures
-----------------------
LLVM does not target all of the architectures that Linux supports and
just because a target is supported in LLVM does not mean that the kernel
will build or work without any issues. Below is a general summary of
architectures that currently work with ``CC=clang`` or ``LLVM=1``. Level
of support corresponds to "S" values in the MAINTAINERS files. If an
architecture is not present, it either means that LLVM does not target
it or there are known issues. Using the latest stable version of LLVM or
even the development tree will generally yield the best results.
An architecture's ``defconfig`` is generally expected to work well,
certain configurations may have problems that have not been uncovered
yet. Bug reports are always welcome at the issue tracker below!
.. list-table::
:widths: 10 10 10
:header-rows: 1
* - Architecture
- Level of support
- ``make`` command
* - arm
- Supported
- ``LLVM=1``
* - arm64
- Supported
- ``LLVM=1``
Documentation/llvm: Update Supported Arch table While watching Michael's new talk on Clang-built-Linux, I noticed the arch table in our docs that he refers to is outdated. Add hexagon and User Mode. Bump MIPS and RISCV to LLVM=1. PowerPC is almost LLVM=1 capable; ppc64le works, but ppc64 (big endian) and ppc32 still need more work. Link: https://youtu.be/W4zdEDpvR5c?t=399 Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2022-06-18 00:58:17 +08:00
* - hexagon
- Maintained
- ``LLVM=1``
Documentation/llvm: refresh docs Recent fixes for an embargoed hardware security vulnerability failed to link with ld.lld (LLVM's linker). [0] To be fair, our documentation mentions ``CC=clang`` foremost with ``LLVM=1`` being buried "below the fold." We want to encourage the use of ``LLVM=1`` rather than just ``CC=clang``. Make that suggestion "above the fold" and "front and center" in our docs. While here, the following additional changes were made: - remove the bit about CROSS_COMPILE setting --target=, that's no longer true. - Add ARCH=loongarch to the list of maintained targets (though we're still working on getting defconfig building cleanly at the moment; we're pretty close). - Bump ARCH=powerpc from CC=clang to LLVM=1 status. - Promote ARCH=riscv from being Maintained to being Supported. Android is working towards supporting RISC-V, and we have excellent support from multiple companies in this regard. - Note that the toolchain distribution on kernel.org has been built with profile data from kernel builds. - Note how to use ccache with clang. Link: https://github.com/ClangBuiltLinux/linux/issues/1907 [0] Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-08-26 01:38:01 +08:00
* - loongarch
- Maintained
- ``LLVM=1``
Documentation/llvm: Add a section about supported architectures The most common question around building the Linux kernel with clang is "does it work?" and the answer has always been "it depends on your architecture, configuration, and LLVM version" with no hard answers for users wanting to experiment. LLVM support has significantly improved over the past couple of years, resulting in more architectures and configurations supported, and continuous integration has made it easier to see what works and what does not. Add a section that goes over what architectures are supported in the current kernel version, how they should be built (with just clang or the LLVM utilities as well), and the level of support they receive. This will make it easier for people to try out building their kernel with LLVM and reporting issues that come about from it. Suggested-by: Miguel Ojeda <ojeda@kernel.org> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> Reviewed-by: Nick Desaulniers <ndesaulnier@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-01-14 08:34:47 +08:00
* - mips
- Maintained
Documentation/llvm: Update Supported Arch table While watching Michael's new talk on Clang-built-Linux, I noticed the arch table in our docs that he refers to is outdated. Add hexagon and User Mode. Bump MIPS and RISCV to LLVM=1. PowerPC is almost LLVM=1 capable; ppc64le works, but ppc64 (big endian) and ppc32 still need more work. Link: https://youtu.be/W4zdEDpvR5c?t=399 Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2022-06-18 00:58:17 +08:00
- ``LLVM=1``
Documentation/llvm: Add a section about supported architectures The most common question around building the Linux kernel with clang is "does it work?" and the answer has always been "it depends on your architecture, configuration, and LLVM version" with no hard answers for users wanting to experiment. LLVM support has significantly improved over the past couple of years, resulting in more architectures and configurations supported, and continuous integration has made it easier to see what works and what does not. Add a section that goes over what architectures are supported in the current kernel version, how they should be built (with just clang or the LLVM utilities as well), and the level of support they receive. This will make it easier for people to try out building their kernel with LLVM and reporting issues that come about from it. Suggested-by: Miguel Ojeda <ojeda@kernel.org> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> Reviewed-by: Nick Desaulniers <ndesaulnier@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-01-14 08:34:47 +08:00
* - powerpc
- Maintained
Documentation/llvm: refresh docs Recent fixes for an embargoed hardware security vulnerability failed to link with ld.lld (LLVM's linker). [0] To be fair, our documentation mentions ``CC=clang`` foremost with ``LLVM=1`` being buried "below the fold." We want to encourage the use of ``LLVM=1`` rather than just ``CC=clang``. Make that suggestion "above the fold" and "front and center" in our docs. While here, the following additional changes were made: - remove the bit about CROSS_COMPILE setting --target=, that's no longer true. - Add ARCH=loongarch to the list of maintained targets (though we're still working on getting defconfig building cleanly at the moment; we're pretty close). - Bump ARCH=powerpc from CC=clang to LLVM=1 status. - Promote ARCH=riscv from being Maintained to being Supported. Android is working towards supporting RISC-V, and we have excellent support from multiple companies in this regard. - Note that the toolchain distribution on kernel.org has been built with profile data from kernel builds. - Note how to use ccache with clang. Link: https://github.com/ClangBuiltLinux/linux/issues/1907 [0] Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-08-26 01:38:01 +08:00
- ``LLVM=1``
Documentation/llvm: Add a section about supported architectures The most common question around building the Linux kernel with clang is "does it work?" and the answer has always been "it depends on your architecture, configuration, and LLVM version" with no hard answers for users wanting to experiment. LLVM support has significantly improved over the past couple of years, resulting in more architectures and configurations supported, and continuous integration has made it easier to see what works and what does not. Add a section that goes over what architectures are supported in the current kernel version, how they should be built (with just clang or the LLVM utilities as well), and the level of support they receive. This will make it easier for people to try out building their kernel with LLVM and reporting issues that come about from it. Suggested-by: Miguel Ojeda <ojeda@kernel.org> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> Reviewed-by: Nick Desaulniers <ndesaulnier@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-01-14 08:34:47 +08:00
* - riscv
Documentation/llvm: refresh docs Recent fixes for an embargoed hardware security vulnerability failed to link with ld.lld (LLVM's linker). [0] To be fair, our documentation mentions ``CC=clang`` foremost with ``LLVM=1`` being buried "below the fold." We want to encourage the use of ``LLVM=1`` rather than just ``CC=clang``. Make that suggestion "above the fold" and "front and center" in our docs. While here, the following additional changes were made: - remove the bit about CROSS_COMPILE setting --target=, that's no longer true. - Add ARCH=loongarch to the list of maintained targets (though we're still working on getting defconfig building cleanly at the moment; we're pretty close). - Bump ARCH=powerpc from CC=clang to LLVM=1 status. - Promote ARCH=riscv from being Maintained to being Supported. Android is working towards supporting RISC-V, and we have excellent support from multiple companies in this regard. - Note that the toolchain distribution on kernel.org has been built with profile data from kernel builds. - Note how to use ccache with clang. Link: https://github.com/ClangBuiltLinux/linux/issues/1907 [0] Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-08-26 01:38:01 +08:00
- Supported
Documentation/llvm: Update Supported Arch table While watching Michael's new talk on Clang-built-Linux, I noticed the arch table in our docs that he refers to is outdated. Add hexagon and User Mode. Bump MIPS and RISCV to LLVM=1. PowerPC is almost LLVM=1 capable; ppc64le works, but ppc64 (big endian) and ppc32 still need more work. Link: https://youtu.be/W4zdEDpvR5c?t=399 Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2022-06-18 00:58:17 +08:00
- ``LLVM=1``
Documentation/llvm: Add a section about supported architectures The most common question around building the Linux kernel with clang is "does it work?" and the answer has always been "it depends on your architecture, configuration, and LLVM version" with no hard answers for users wanting to experiment. LLVM support has significantly improved over the past couple of years, resulting in more architectures and configurations supported, and continuous integration has made it easier to see what works and what does not. Add a section that goes over what architectures are supported in the current kernel version, how they should be built (with just clang or the LLVM utilities as well), and the level of support they receive. This will make it easier for people to try out building their kernel with LLVM and reporting issues that come about from it. Suggested-by: Miguel Ojeda <ojeda@kernel.org> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> Reviewed-by: Nick Desaulniers <ndesaulnier@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-01-14 08:34:47 +08:00
* - s390
- Maintained
- ``CC=clang``
Documentation/llvm: Update Supported Arch table While watching Michael's new talk on Clang-built-Linux, I noticed the arch table in our docs that he refers to is outdated. Add hexagon and User Mode. Bump MIPS and RISCV to LLVM=1. PowerPC is almost LLVM=1 capable; ppc64le works, but ppc64 (big endian) and ppc32 still need more work. Link: https://youtu.be/W4zdEDpvR5c?t=399 Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2022-06-18 00:58:17 +08:00
* - um (User Mode)
- Maintained
- ``LLVM=1``
Documentation/llvm: Add a section about supported architectures The most common question around building the Linux kernel with clang is "does it work?" and the answer has always been "it depends on your architecture, configuration, and LLVM version" with no hard answers for users wanting to experiment. LLVM support has significantly improved over the past couple of years, resulting in more architectures and configurations supported, and continuous integration has made it easier to see what works and what does not. Add a section that goes over what architectures are supported in the current kernel version, how they should be built (with just clang or the LLVM utilities as well), and the level of support they receive. This will make it easier for people to try out building their kernel with LLVM and reporting issues that come about from it. Suggested-by: Miguel Ojeda <ojeda@kernel.org> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> Reviewed-by: Nick Desaulniers <ndesaulnier@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-01-14 08:34:47 +08:00
* - x86
- Supported
- ``LLVM=1``
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>
2020-02-27 07:23:36 +08:00
Getting Help
------------
- `Website <https://clangbuiltlinux.github.io/>`_
Documentation/llvm: update mailing list We are now at llvm@lists.linux.dev. Link: https://lkml.kernel.org/r/20210825211823.6406-2-nathan@kernel.org Signed-off-by: Nathan Chancellor <nathan@kernel.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Cc: Kees Cook <keescook@chromium.org> Cc: Masahiro Yamada <masahiroy@kernel.org> Cc: Sami Tolvanen <samitolvanen@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-09-08 10:58:27 +08:00
- `Mailing List <https://lore.kernel.org/llvm/>`_: <llvm@lists.linux.dev>
- `Old Mailing List Archives <https://groups.google.com/g/clang-built-linux>`_
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>
2020-02-27 07:23:36 +08:00
- `Issue Tracker <https://github.com/ClangBuiltLinux/linux/issues>`_
Documentation/llvm: update IRC location This should have been done with commit 91ed3ed0f798 ("MAINTAINERS: update ClangBuiltLinux IRC chat") but I did not realize it was in two separate spots. Link: https://lkml.kernel.org/r/20210825211823.6406-3-nathan@kernel.org Signed-off-by: Nathan Chancellor <nathan@kernel.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Cc: Kees Cook <keescook@chromium.org> Cc: Masahiro Yamada <masahiroy@kernel.org> Cc: Sami Tolvanen <samitolvanen@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-09-08 10:58:30 +08:00
- IRC: #clangbuiltlinux on irc.libera.chat
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>
2020-02-27 07:23:36 +08:00
- `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>`_
Documentation: add minimum clang/llvm version Based on a vote at the LLVM BoF at Plumbers 2020, we decided to start small, supporting just one formal upstream release of LLVM for now. We can probably widen the support window of supported versions over time. Also, note that LLVM's release process is different than GCC's. GCC tends to have 1 major release per year while releasing minor updates to the past 3 major versions. LLVM tends to support one major release and one minor release every six months. Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Tested-by: Gustavo A. R. Silva <gustavoars@kernel.org> Tested-by: Nathan Chancellor <natechancellor@gmail.com> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com> Reviewed-by: Masahiro Yamada <masahiroy@kernel.org> Acked-by: Will Deacon <will@kernel.org> Link: https://lore.kernel.org/r/20200826191555.3350406-1-ndesaulniers@google.com Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2020-08-27 03:15:55 +08:00
.. _getting_llvm:
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>
2020-02-27 07:23:36 +08:00
Getting LLVM
-------------
Documentation/llvm: refresh docs Recent fixes for an embargoed hardware security vulnerability failed to link with ld.lld (LLVM's linker). [0] To be fair, our documentation mentions ``CC=clang`` foremost with ``LLVM=1`` being buried "below the fold." We want to encourage the use of ``LLVM=1`` rather than just ``CC=clang``. Make that suggestion "above the fold" and "front and center" in our docs. While here, the following additional changes were made: - remove the bit about CROSS_COMPILE setting --target=, that's no longer true. - Add ARCH=loongarch to the list of maintained targets (though we're still working on getting defconfig building cleanly at the moment; we're pretty close). - Bump ARCH=powerpc from CC=clang to LLVM=1 status. - Promote ARCH=riscv from being Maintained to being Supported. Android is working towards supporting RISC-V, and we have excellent support from multiple companies in this regard. - Note that the toolchain distribution on kernel.org has been built with profile data from kernel builds. - Note how to use ccache with clang. Link: https://github.com/ClangBuiltLinux/linux/issues/1907 [0] Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-08-26 01:38:01 +08:00
We provide prebuilt stable versions of LLVM on `kernel.org
<https://kernel.org/pub/tools/llvm/>`_. These have been optimized with profile
data for building Linux kernels, which should improve kernel build times
relative to other distributions of LLVM.
Documentation/llvm: Add a note about prebuilt kernel.org toolchains I recently started uploading prebuilt stable versions of LLVM to kernel.org, which should make building the kernel with LLVM more accessible to maintainers and developers. Link them in the LLVM documentation to make this more visible. Link: https://lore.kernel.org/20230319235619.GA18547@dev-arch.thelio-3990X/ Suggested-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Bill Wendling <morbo@google.com> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-04-08 05:42:48 +08:00
Below are links that may be useful for building LLVM from source or procuring
it through a distribution's package manager.
kbuild: Replace HTTP links with HTTPS ones Rationale: Reduces attack surface on kernel devs opening the links for MITM as HTTPS traffic is much harder to manipulate. Deterministic algorithm: For each file: If not .svg: For each line: If doesn't contain `\bxmlns\b`: For each link, `\bhttp://[^# \t\r\n]*(?:\w|/)`: If neither `\bgnu\.org/license`, nor `\bmozilla\.org/MPL\b`: If both the HTTP and HTTPS versions return 200 OK and serve the same content: Replace HTTP with HTTPS. Signed-off-by: Alexander A. Klimov <grandmaster@al2klimov.de> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2020-07-20 03:46:02 +08:00
- https://releases.llvm.org/download.html
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>
2020-02-27 07:23:36 +08:00
- 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/
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