Daniel Borkmann 0c4ac0d576 bpf, libbpf: add support for BTF Var and DataSec
This adds libbpf support for BTF Var and DataSec kinds. Main point
here is that libbpf needs to do some preparatory work before the
whole BTF object can be loaded into the kernel, that is, fixing up
of DataSec size taken from the ELF section size and non-static
variable offset which needs to be taken from the ELF's string section.

Upstream LLVM doesn't fix these up since at time of BTF emission
it is too early in the compilation process thus this information
isn't available yet, hence loader needs to take care of it.

Note, deduplication handling has not been in the scope of this work
and needs to be addressed in a future commit.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://reviews.llvm.org/D59441
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2019-04-10 14:27:33 -07:00

This is a mirror of bpf-next linux tree
(https://kernel.googlesource.com/pub/scm/linux/kernel/git/bpf/bpf-next)
bpf-next/tools/lib/bpf directory plus its supporting header files.

The following files will by sync'ed with bpf-next repo:
  src/ <-> bpf-next/tools/lib/bpf/
  include/uapi/linux/bpf_common.h <-> bpf-next/tools/include/uapi/linux/bpf_common.h
  include/uapi/linux/bpf.h <-> bpf-next/tools/include/uapi/linux/bpf.h
  include/uapi/linux/btf.h <-> bpf-next/tools/include/uapi/linux/btf.h
  include/uapi/linux/if_link.h <-> bpf-next/tools/include/uapi/linux/if_link.h
  include/uapi/linux/if_xdp.h <-> bpf-next/tools/include/uapi/linux/if_xdp.h
  include/uapi/linux/netlink.h <-> bpf-next/tools/include/uapi/linux/netlink.h
  include/tools/libc_compat.h <-> bpf-next/tools/include/tools/libc_compat.h

Other header files at this repo (include/linux/*.h) are reduced versions of
their counterpart files at bpf-next/tools/include/linux/*.h to make compilation
successful.

Build
=====
libelf is an internal dependency of libbpf and thus it is required to link
against and must be installed on the system for applications to work.
pkg-config is used by default to find libelf, and the program called can be
overridden with PKG_CONFIG.
If using pkg-config at build time is not desired, it can be disabled by setting
NO_PKG_CONFIG=1 when calling make.

To build both static libbpf.a and shared libbpf.so:
  cd src
  make

To build only static libbpf.a library in directory
build/ and install them together with libbpf headers in a staging directory
root/:
  cd src
  mkdir build root
  BUILD_STATIC_ONLY=y OBJDIR=build DESTDIR=root make install

To build both static libbpf.a and shared libbpf.so against a custom libelf
dependency installed in /build/root/ and install them together with libbpf
headers in a build directory /build/root/:

  cd src
  PKG_CONFIG_PATH=/build/root/lib64/pkgconfig DESTDIR=/build/root make install
Description
Automated upstream mirror for libbpf stand-alone build.
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