Getting started with using examples in samples/bpf/ is not straightforward. There are several dependencies, and specific versions of these dependencies. Just compiling the example tool is also slightly obscure, e.g. one need to call make like: make samples/bpf/ Do notice the "/" slash after the directory name. Signed-off-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx> --- samples/bpf/README.rst | 77 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 77 insertions(+) create mode 100644 samples/bpf/README.rst diff --git a/samples/bpf/README.rst b/samples/bpf/README.rst new file mode 100644 index 000000000000..c7ccf553af0d --- /dev/null +++ b/samples/bpf/README.rst @@ -0,0 +1,77 @@ +eBPF sample programs +==================== + +This kernel samples/bpf directory contains a mini eBPF library, test +stubs, verifier test-suite and examples for using eBPF. + +Build dependencies +================== + +Compiling requires having installed: + * clang + * llvm >= version 3.7.1 + +Note that LLVM's tool 'llc' must support target 'bpf', list with command:: + + $ llc --version + LLVM (http://llvm.org/): + LLVM version 3.x.y + [...] + Host CPU: xxx + + Registered Targets: + [...] + bpf - BPF (host endian) + bpfeb - BPF (big endian) + bpfel - BPF (little endian) + [...] + +Kernel headers +-------------- + +There are usually dependencies to header files of the current kernel. +To avoid installing devel kernel headers system wide, as a normal +user, simply call:: + + make headers_install + +This will creates a local "usr/include" directory in the git/build top +level directory, that the make system automatically pickup first. + +Compiling +========= + +For compiling goto kernel top level build directory and run make like:: + + make samples/bpf/ + +Do notice the "/" slash after the directory name. + +Manually compiling LLVM with 'bpf' support +------------------------------------------ + +In some LLVM versions the BPF target were marked experimental. They +needed the 'cmake .. -DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD=BPF'. Since +version 3.7.1, LLVM adds a proper LLVM backend target for the BPF +bytecode architecture. + +By default llvm will build all non-experimental backends including bpf. +To generate a smaller llc binary one can use:: + + -DLLVM_TARGETS_TO_BUILD="BPF;X86" + +Quick sniplet for manually compiling LLVM and clang +(build dependencies are cmake and gcc-c++):: + + $ git clone http://llvm.org/git/llvm.git + $ cd llvm/tools + $ git clone --depth 1 http://llvm.org/git/clang.git + $ cd ..; mkdir build; cd build + $ cmake .. -DLLVM_TARGETS_TO_BUILD="BPF;X86" + $ make -j $(getconf _NPROCESSORS_ONLN) + +It is also possible to point make to the newly compile 'llc' command +via redefining LLC on the make command line:: + + make samples/bpf/ LLC=~/git/llvm/build/bin/llc + -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
