netdev - [net-next PATCH V4 3/5] samples/bpf: add a README file to get users started

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Message-ID: <20160428122103.16807.41837.stgit@firesoul>
Date:	Thu, 28 Apr 2016 14:21:04 +0200
From:	Jesper Dangaard Brouer <brouer@...hat.com>
To:	netdev@...r.kernel.org
Cc:	linux-kbuild@...r.kernel.org, bblanco@...mgrid.com,
	Jesper Dangaard Brouer <brouer@...hat.com>,
	naveen.n.rao@...ux.vnet.ibm.com, borkmann@...earbox.net,
	alexei.starovoitov@...il.com
Subject: [net-next PATCH V4 3/5] samples/bpf: add a README file to get users
 started

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@...hat.com>
---
 samples/bpf/README.rst |   64 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 64 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..993d280184fa
--- /dev/null
+++ b/samples/bpf/README.rst
@@ -0,0 +1,64 @@
+eBPF sample programs
+====================
+
+This directory contains a mini eBPF library, test stubs, verifier
+test-suite and examples for using eBPF.
+
+Build dependencies
+==================
+
+Compiling requires having installed:
+ * clang >= version 3.4.0
+ * llvm >= version 3.7.1
+
+Note that LLVM's tool 'llc' must support target 'bpf', list version
+and supported targets with command: ``llc --version``
+
+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 building the BPF samples, issue the below command from the kernel
+top level directory::
+
+ make samples/bpf/
+
+Do notice the "/" slash after the directory name.
+
+Manually compiling LLVM with 'bpf' support
+------------------------------------------
+
+Since version 3.7.0, 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"
+
+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 compiled 'llc' command
+via redefining LLC on the make command line::
+
+ make samples/bpf/ LLC=~/git/llvm/build/bin/llc
+