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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
7Note that the XDP-specific samples have been removed from this directory and
8moved to the xdp-tools repository: https://github.com/xdp-project/xdp-tools
9See the commit messages removing each tool from this directory for how to
10convert specific command invocations between the old samples and the utilities
11in xdp-tools.
12
13Build dependencies
14==================
15
16Compiling requires having installed:
17 * clang
18 * llvm
19 * pahole
20
21Consult :ref:`Documentation/process/changes.rst <changes>` for the minimum
22version numbers required and how to update them. Note that LLVM's tool
23'llc' must support target 'bpf', list version and supported targets with
24command: ``llc --version``
25
26Clean and configuration
27-----------------------
28
29It can be needed to clean tools, samples or kernel before trying new arch or
30after some changes (on demand)::
31
32 make -C tools clean
33 make -C samples/bpf clean
34 make clean
35
36Configure kernel, defconfig for instance
37(see "tools/testing/selftests/bpf/config" for a reference config)::
38
39 make defconfig
40
41Kernel headers
42--------------
43
44There are usually dependencies to header files of the current kernel.
45To avoid installing devel kernel headers system wide, as a normal
46user, simply call::
47
48 make headers_install
49
50This will create a local "usr/include" directory in the git/build top
51level directory, that the make system will automatically pick up first.
52
53Compiling
54=========
55
56For building the BPF samples, issue the below command from the kernel
57top level directory::
58
59 make M=samples/bpf
60
61It is also possible to call make from this directory. This will just
62hide the invocation of make as above.
63
64Manually compiling LLVM with 'bpf' support
65------------------------------------------
66
67Since version 3.7.0, LLVM adds a proper LLVM backend target for the
68BPF bytecode architecture.
69
70By default llvm will build all non-experimental backends including bpf.
71To generate a smaller llc binary one can use::
72
73 -DLLVM_TARGETS_TO_BUILD="BPF"
74
75We recommend that developers who want the fastest incremental builds
76use the Ninja build system, you can find it in your system's package
77manager, usually the package is ninja or ninja-build.
78
79Quick 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
91It 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
96Cross compiling samples
97-----------------------
98In order to cross-compile, say for arm64 targets, export CROSS_COMPILE and ARCH
99environment variables before calling make. But do this before clean,
100configuration and header install steps described above. This will direct make to
101build samples for the cross target::
102
103 export ARCH=arm64
104 export CROSS_COMPILE="aarch64-linux-gnu-"
105
106Headers can be also installed on RFS of target board if need to keep them in
107sync (not necessarily and it creates a local "usr/include" directory also)::
108
109 make INSTALL_HDR_PATH=~/some_sysroot/usr headers_install
110
111Pointing LLC and CLANG is not necessarily if it's installed on HOST and have
112in its targets appropriate arm64 arch (usually it has several arches).
113Build samples::
114
115 make M=samples/bpf
116
117Or build samples with SYSROOT if some header or library is absent in toolchain,
118say libelf, providing address to file system containing headers and libs,
119can be RFS of target board::
120
121 make M=samples/bpf SYSROOT=~/some_sysroot
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 >= version 3.4.0
12 * llvm >= version 3.7.1
13
14Note that LLVM's tool 'llc' must support target 'bpf', list version
15and supported targets with command: ``llc --version``
16
17Kernel headers
18--------------
19
20There are usually dependencies to header files of the current kernel.
21To avoid installing devel kernel headers system wide, as a normal
22user, simply call::
23
24 make headers_install
25
26This will creates a local "usr/include" directory in the git/build top
27level directory, that the make system automatically pickup first.
28
29Compiling
30=========
31
32For building the BPF samples, issue the below command from the kernel
33top level directory::
34
35 make samples/bpf/
36
37Do notice the "/" slash after the directory name.
38
39It is also possible to call make from this directory. This will just
40hide the the invocation of make as above with the appended "/".
41
42Manually compiling LLVM with 'bpf' support
43------------------------------------------
44
45Since version 3.7.0, LLVM adds a proper LLVM backend target for the
46BPF bytecode architecture.
47
48By default llvm will build all non-experimental backends including bpf.
49To generate a smaller llc binary one can use::
50
51 -DLLVM_TARGETS_TO_BUILD="BPF"
52
53Quick sniplet for manually compiling LLVM and clang
54(build dependencies are cmake and gcc-c++)::
55
56 $ git clone http://llvm.org/git/llvm.git
57 $ cd llvm/tools
58 $ git clone --depth 1 http://llvm.org/git/clang.git
59 $ cd ..; mkdir build; cd build
60 $ cmake .. -DLLVM_TARGETS_TO_BUILD="BPF;X86"
61 $ make -j $(getconf _NPROCESSORS_ONLN)
62
63It is also possible to point make to the newly compiled 'llc' or
64'clang' command via redefining LLC or CLANG on the make command line::
65
66 make samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang
67
68Cross compiling samples
69-----------------------
70In order to cross-compile, say for arm64 targets, export CROSS_COMPILE and ARCH
71environment variables before calling make. This will direct make to build
72samples for the cross target.
73
74export ARCH=arm64
75export CROSS_COMPILE="aarch64-linux-gnu-"
76make samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang