1 eBPF sample programs 2 ==================== 3 4 This directory contains a test stubs, verifier test-suite and examples 5 for using eBPF. The examples use libbpf from tools/lib/bpf. 6 7 Note that the XDP-specific samples have been removed from this directory and 8 moved to the xdp-tools repository: https://github.com/xdp-project/xdp-tools 9 See the commit messages removing each tool from this directory for how to 10 convert specific command invocations between the old samples and the utilities 11 in xdp-tools. 12 13 Build dependencies 14 ================== 15 16 Compiling requires having installed: 17 * clang 18 * llvm 19 * pahole 20 21 Consult :ref:`Documentation/process/changes.rst <changes>` for the minimum 22 version numbers required and how to update them. Note that LLVM's tool 23 'llc' must support target 'bpf', list version and supported targets with 24 command: ``llc --version`` 25 26 Clean and configuration 27 ----------------------- 28 29 It can be needed to clean tools, samples or kernel before trying new arch or 30 after some changes (on demand):: 31 32 make -C tools clean 33 make -C samples/bpf clean 34 make clean 35 36 Configure kernel, defconfig for instance 37 (see "tools/testing/selftests/bpf/config" for a reference config):: 38 39 make defconfig 40 41 Kernel headers 42 -------------- 43 44 There are usually dependencies to header files of the current kernel. 45 To avoid installing devel kernel headers system wide, as a normal 46 user, simply call:: 47 48 make headers_install 49 50 This will create a local "usr/include" directory in the git/build top 51 level directory, that the make system will automatically pick up first. 52 53 Compiling 54 ========= 55 56 For building the BPF samples, issue the below command from the kernel 57 top level directory:: 58 59 make M=samples/bpf 60 61 It is also possible to call make from this directory. This will just 62 hide the invocation of make as above. 63 64 Manually compiling LLVM with 'bpf' support 65 ------------------------------------------ 66 67 Since version 3.7.0, LLVM adds a proper LLVM backend target for the 68 BPF bytecode architecture. 69 70 By default llvm will build all non-experimental backends including bpf. 71 To generate a smaller llc binary one can use:: 72 73 -DLLVM_TARGETS_TO_BUILD="BPF" 74 75 We recommend that developers who want the fastest incremental builds 76 use the Ninja build system, you can find it in your system's package 77 manager, usually the package is ninja or ninja-build. 78 79 Quick sniplet for manually compiling LLVM and clang 80 (build dependencies are ninja, cmake and gcc-c++):: 81 82 $ git clone https://github.com/llvm/llvm-project.git 83 $ mkdir -p llvm-project/llvm/build 84 $ cd llvm-project/llvm/build 85 $ cmake .. -G "Ninja" -DLLVM_TARGETS_TO_BUILD="BPF;X86" \ 86 -DLLVM_ENABLE_PROJECTS="clang" \ 87 -DCMAKE_BUILD_TYPE=Release \ 88 -DLLVM_BUILD_RUNTIME=OFF 89 $ ninja 90 91 It is also possible to point make to the newly compiled 'llc' or 92 'clang' command via redefining LLC or CLANG on the make command line:: 93 94 make M=samples/bpf LLC=~/git/llvm-project/llvm/build/bin/llc CLANG=~/git/llvm-project/llvm/build/bin/clang 95 96 Cross compiling samples 97 ----------------------- 98 In order to cross-compile, say for arm64 targets, export CROSS_COMPILE and ARCH 99 environment variables before calling make. But do this before clean, 100 configuration and header install steps described above. This will direct make to 101 build samples for the cross target:: 102 103 export ARCH=arm64 104 export CROSS_COMPILE="aarch64-linux-gnu-" 105 106 Headers can be also installed on RFS of target board if need to keep them in 107 sync (not necessarily and it creates a local "usr/include" directory also):: 108 109 make INSTALL_HDR_PATH=~/some_sysroot/usr headers_install 110 111 Pointing LLC and CLANG is not necessarily if it's installed on HOST and have 112 in its targets appropriate arm64 arch (usually it has several arches). 113 Build samples:: 114 115 make M=samples/bpf 116 117 Or build samples with SYSROOT if some header or library is absent in toolchain, 118 say libelf, providing address to file system containing headers and libs, 119 can be RFS of target board:: 120 121 make M=samples/bpf SYSROOT=~/some_sysroot
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