112 lines
3.4 KiB
ReStructuredText
112 lines
3.4 KiB
ReStructuredText
eBPF sample programs
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====================
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This directory contains a test stubs, verifier test-suite and examples
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for using eBPF. The examples use libbpf from tools/lib/bpf.
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Build dependencies
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==================
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Compiling requires having installed:
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* clang >= version 3.4.0
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* llvm >= version 3.7.1
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Note that LLVM's tool 'llc' must support target 'bpf', list version
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and supported targets with command: ``llc --version``
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Clean and configuration
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-----------------------
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It can be needed to clean tools, samples or kernel before trying new arch or
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after some changes (on demand)::
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make -C tools clean
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make -C samples/bpf clean
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make clean
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Configure kernel, defconfig for instance::
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make defconfig
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Kernel headers
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--------------
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There are usually dependencies to header files of the current kernel.
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To avoid installing devel kernel headers system wide, as a normal
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user, simply call::
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make headers_install
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This will creates a local "usr/include" directory in the git/build top
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level directory, that the make system automatically pickup first.
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Compiling
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=========
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For building the BPF samples, issue the below command from the kernel
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top level directory::
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make M=samples/bpf
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It is also possible to call make from this directory. This will just
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hide the invocation of make as above.
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Manually compiling LLVM with 'bpf' support
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------------------------------------------
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Since version 3.7.0, LLVM adds a proper LLVM backend target for the
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BPF bytecode architecture.
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By default llvm will build all non-experimental backends including bpf.
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To generate a smaller llc binary one can use::
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-DLLVM_TARGETS_TO_BUILD="BPF"
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We recommend that developers who want the fastest incremental builds
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use the Ninja build system, you can find it in your system's package
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manager, usually the package is ninja or ninja-build.
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Quick sniplet for manually compiling LLVM and clang
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(build dependencies are ninja, cmake and gcc-c++)::
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$ git clone https://github.com/llvm/llvm-project.git
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$ mkdir -p llvm-project/llvm/build
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$ cd llvm-project/llvm/build
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$ cmake .. -G "Ninja" -DLLVM_TARGETS_TO_BUILD="BPF;X86" \
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-DLLVM_ENABLE_PROJECTS="clang" \
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-DCMAKE_BUILD_TYPE=Release \
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-DLLVM_BUILD_RUNTIME=OFF
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$ ninja
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It is also possible to point make to the newly compiled 'llc' or
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'clang' command via redefining LLC or CLANG on the make command line::
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make M=samples/bpf LLC=~/git/llvm-project/llvm/build/bin/llc CLANG=~/git/llvm-project/llvm/build/bin/clang
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Cross compiling samples
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-----------------------
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In order to cross-compile, say for arm64 targets, export CROSS_COMPILE and ARCH
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environment variables before calling make. But do this before clean,
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cofiguration and header install steps described above. This will direct make to
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build samples for the cross target::
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export ARCH=arm64
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export CROSS_COMPILE="aarch64-linux-gnu-"
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Headers can be also installed on RFS of target board if need to keep them in
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sync (not necessarily and it creates a local "usr/include" directory also)::
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make INSTALL_HDR_PATH=~/some_sysroot/usr headers_install
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Pointing LLC and CLANG is not necessarily if it's installed on HOST and have
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in its targets appropriate arm64 arch (usually it has several arches).
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Build samples::
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make M=samples/bpf
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Or build samples with SYSROOT if some header or library is absent in toolchain,
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say libelf, providing address to file system containing headers and libs,
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can be RFS of target board::
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make M=samples/bpf SYSROOT=~/some_sysroot
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