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@xxxxxxxxxx> Reviewed-by: Fangrui Song <maskray@xxxxxxxxxx> Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> --- Changes v5 -> v6: * Pick up Fangrui's RB tag. * Change use of env vars to command line parameters for consistency. Documentation/kbuild/llvm.rst | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) diff --git a/Documentation/kbuild/llvm.rst b/Documentation/kbuild/llvm.rst index b18401d2ba82..f8a360958f4c 100644 --- a/Documentation/kbuild/llvm.rst +++ b/Documentation/kbuild/llvm.rst @@ -38,7 +38,7 @@ 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 + make ARCH=arm64 CC=clang CROSS_COMPILE=aarch64-linux-gnu- ``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 @@ -63,6 +63,23 @@ They can be enabled individually. The full list of the parameters: :: Currently, the integrated assembler is disabled by default. You can pass ``LLVM_IAS=1`` to enable it. +Omitting CROSS_COMPILE +---------------------- + +As explained above, ``CROSS_COMPILE`` is used to set ``--target=<triple>``. + +Unless ``LLVM_IAS=1`` is specified, ``CROSS_COMPILE`` is also used to derive +``--prefix=<path>`` to search for the GNU assembler and linker. + +If ``CROSS_COMPILE`` is not specified, the ``--target=<triple>`` is inferred +from ``ARCH``. + +That means if you use only LLVM tools, ``CROSS_COMPILE`` becomes unnecessary. + +For example, to cross-compile the arm64 kernel:: + + make ARCH=arm64 LLVM=1 LLVM_IAS=1 + Supported Architectures ----------------------- -- 2.32.0.554.ge1b32706d8-goog
