On 04/26/2016 01:09 PM, Jesper Dangaard Brouer wrote:
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 | 67 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 67 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..3e1ac05d8e7c --- /dev/null +++ b/samples/bpf/README.rst @@ -0,0 +1,67 @@ +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 3.7.0 + +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. To +compile LLVM manually and enable BPF target run (build dependencies +are cmake and gcc-c++):: + + $ git clone http://llvm.org/git/llvm.git + $ cd llvm + $ mkdir build; cd build + $ cmake .. -DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD=BPF + $ make
That's perhaps a bit misleading in the sense that when you clone the tree from git, you'd nowadays invoke cmake normally with LLVM_TARGETS_TO_BUILD instead of LLVM_EXPERIMENTAL_TARGETS_TO_BUILD for BPF, as BPF is not an experimental target anymore. It's probably also recommended to clone clang into tools/ dir as well under your llvm/ repo when you compile from scratch anyways.
+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 +
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