Arnaldo Carvalho de Melo ee12996c9d samples/bpf sock_example: Avoid getting ethhdr from two includes
To avoid the following build failure on Alpine Linux 3.4, that has
clang-3.8 with the bpf target:

    HOSTCC  samples/bpf/sock_example.o
  In file included from /usr/include/net/ethernet.h:10:0,
                   from /git/linux/samples/bpf/sock_example.h:7,
                   from /git/linux/samples/bpf/sock_example.c:30:
  /usr/include/netinet/if_ether.h:96:8: error: redefinition of 'struct
  ethhdr'
   struct ethhdr {
          ^
  In file included from /git/linux/samples/bpf/sock_example.c:26:0:
  ./usr/include/linux/if_ether.h:144:8: note: originally defined here
   struct ethhdr {
          ^
  scripts/Makefile.host:124: recipe for target
  'samples/bpf/sock_example.o' failed
  make[2]: *** [samples/bpf/sock_example.o] Error 1
  /git/linux/Makefile:1658: recipe for target 'samples/bpf/' failed

So include net/if_ether.h for the needs of sock_example.h, using the
same include that sock_example.c uses.

Cc: Alexei Starovoitov <ast@fb.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Joe Stringer <joe@ovn.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-m9avekl1b651qe1r1zd5tzz9@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2016-12-27 21:49:17 -03:00
..
2015-06-23 06:09:58 -07:00
2016-12-20 12:00:38 -03:00

eBPF sample programs
====================

This directory contains a test stubs, verifier test-suite and examples
for using eBPF. The examples use libbpf from tools/lib/bpf.

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.

It is also possible to call make from this directory.  This will just
hide the the invocation of make as above with the appended "/".

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' or
'clang' command via redefining LLC or CLANG on the make command line::

 make samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang