1eBPF sample programs 2==================== 3 4This directory contains a test stubs, verifier test-suite and examples 5for using eBPF. The examples use libbpf from tools/lib/bpf. 6 7Build dependencies 8================== 9 10Compiling requires having installed: 11 * clang 12 * llvm 13 * pahole 14 15Consult :ref:`Documentation/process/changes.rst <changes>` for the minimum 16version numbers required and how to update them. Note that LLVM's tool 17'llc' must support target 'bpf', list version and supported targets with 18command: ``llc --version`` 19 20Clean and configuration 21----------------------- 22 23It can be needed to clean tools, samples or kernel before trying new arch or 24after some changes (on demand):: 25 26 make -C tools clean 27 make -C samples/bpf clean 28 make clean 29 30Configure kernel, defconfig for instance 31(see "tools/testing/selftests/bpf/config" for a reference config):: 32 33 make defconfig 34 35Kernel headers 36-------------- 37 38There are usually dependencies to header files of the current kernel. 39To avoid installing devel kernel headers system wide, as a normal 40user, simply call:: 41 42 make headers_install 43 44This will create a local "usr/include" directory in the git/build top 45level directory, that the make system will automatically pick up first. 46 47Compiling 48========= 49 50For building the BPF samples, issue the below command from the kernel 51top level directory:: 52 53 make M=samples/bpf 54 55It is also possible to call make from this directory. This will just 56hide the invocation of make as above. 57 58Manually compiling LLVM with 'bpf' support 59------------------------------------------ 60 61Since version 3.7.0, LLVM adds a proper LLVM backend target for the 62BPF bytecode architecture. 63 64By default llvm will build all non-experimental backends including bpf. 65To generate a smaller llc binary one can use:: 66 67 -DLLVM_TARGETS_TO_BUILD="BPF" 68 69We recommend that developers who want the fastest incremental builds 70use the Ninja build system, you can find it in your system's package 71manager, usually the package is ninja or ninja-build. 72 73Quick sniplet for manually compiling LLVM and clang 74(build dependencies are ninja, cmake and gcc-c++):: 75 76 $ git clone https://github.com/llvm/llvm-project.git 77 $ mkdir -p llvm-project/llvm/build 78 $ cd llvm-project/llvm/build 79 $ cmake .. -G "Ninja" -DLLVM_TARGETS_TO_BUILD="BPF;X86" \ 80 -DLLVM_ENABLE_PROJECTS="clang" \ 81 -DCMAKE_BUILD_TYPE=Release \ 82 -DLLVM_BUILD_RUNTIME=OFF 83 $ ninja 84 85It is also possible to point make to the newly compiled 'llc' or 86'clang' command via redefining LLC or CLANG on the make command line:: 87 88 make M=samples/bpf LLC=~/git/llvm-project/llvm/build/bin/llc CLANG=~/git/llvm-project/llvm/build/bin/clang 89 90Cross compiling samples 91----------------------- 92In order to cross-compile, say for arm64 targets, export CROSS_COMPILE and ARCH 93environment variables before calling make. But do this before clean, 94configuration and header install steps described above. This will direct make to 95build samples for the cross target:: 96 97 export ARCH=arm64 98 export CROSS_COMPILE="aarch64-linux-gnu-" 99 100Headers can be also installed on RFS of target board if need to keep them in 101sync (not necessarily and it creates a local "usr/include" directory also):: 102 103 make INSTALL_HDR_PATH=~/some_sysroot/usr headers_install 104 105Pointing LLC and CLANG is not necessarily if it's installed on HOST and have 106in its targets appropriate arm64 arch (usually it has several arches). 107Build samples:: 108 109 make M=samples/bpf 110 111Or build samples with SYSROOT if some header or library is absent in toolchain, 112say libelf, providing address to file system containing headers and libs, 113can be RFS of target board:: 114 115 make M=samples/bpf SYSROOT=~/some_sysroot 116