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samples/bpf: Add preparation steps and sysroot info to readme

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Add couple preparation steps: clean and configuration. Also add newly
added sysroot support info to cross-compile section.

Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20191011002808.28206-16-ivan.khoronzhuk@linaro.org
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Ivan Khoronzhuk 2019-10-11 03:28:08 +03:00 committed by Alexei Starovoitov
parent b2327c107d
commit 1600c9c26f
1 changed files with 36 additions and 5 deletions
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samples/bpf/README.rst
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@ -14,6 +14,20 @@ Compiling requires having installed:
Note that LLVM's tool 'llc' must support target 'bpf', list version
and supported targets with command: ``llc --version``
Clean and configuration
-----------------------
It can be needed to clean tools, samples or kernel before trying new arch or
after some changes (on demand)::
make -C tools clean
make -C samples/bpf clean
make clean
Configure kernel, defconfig for instance::
make defconfig
Kernel headers
--------------
@ -68,9 +82,26 @@ It is also possible to point make to the newly compiled 'llc' or
Cross compiling samples
-----------------------
In order to cross-compile, say for arm64 targets, export CROSS_COMPILE and ARCH
environment variables before calling make. This will direct make to build
samples for the cross target.
environment variables before calling make. But do this before clean,
cofiguration and header install steps described above. This will direct make to
build samples for the cross target::
export ARCH=arm64
export CROSS_COMPILE="aarch64-linux-gnu-"
make samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang
export ARCH=arm64
export CROSS_COMPILE="aarch64-linux-gnu-"
Headers can be also installed on RFS of target board if need to keep them in
sync (not necessarily and it creates a local "usr/include" directory also)::
make INSTALL_HDR_PATH=~/some_sysroot/usr headers_install
Pointing LLC and CLANG is not necessarily if it's installed on HOST and have
in its targets appropriate arm64 arch (usually it has several arches).
Build samples::
make samples/bpf/
Or build samples with SYSROOT if some header or library is absent in toolchain,
say libelf, providing address to file system containing headers and libs,
can be RFS of target board::
make samples/bpf/ SYSROOT=~/some_sysroot