f3edca46e5
This patch adds BPF STRUCT_OPS support to libbpf.
The only sec_name convention is SEC(".struct_ops") to identify the
struct_ops implemented in BPF,
e.g. To implement a tcp_congestion_ops:
SEC(".struct_ops")
struct tcp_congestion_ops dctcp = {
.init = (void *)dctcp_init, /* <-- a bpf_prog */
/* ... some more func prts ... */
.name = "bpf_dctcp",
};
Each struct_ops is defined as a global variable under SEC(".struct_ops")
as above. libbpf creates a map for each variable and the variable name
is the map's name. Multiple struct_ops is supported under
SEC(".struct_ops").
In the bpf_object__open phase, libbpf will look for the SEC(".struct_ops")
section and find out what is the btf-type the struct_ops is
implementing. Note that the btf-type here is referring to
a type in the bpf_prog.o's btf. A "struct bpf_map" is added
by bpf_object__add_map() as other maps do. It will then
collect (through SHT_REL) where are the bpf progs that the
func ptrs are referring to. No btf_vmlinux is needed in
the open phase.
In the bpf_object__load phase, the map-fields, which depend
on the btf_vmlinux, are initialized (in bpf_map__init_kern_struct_ops()).
It will also set the prog->type, prog->attach_btf_id, and
prog->expected_attach_type. Thus, the prog's properties do
not rely on its section name.
[ Currently, the bpf_prog's btf-type ==> btf_vmlinux's btf-type matching
process is as simple as: member-name match + btf-kind match + size match.
If these matching conditions fail, libbpf will reject.
The current targeting support is "struct tcp_congestion_ops" which
most of its members are function pointers.
The member ordering of the bpf_prog's btf-type can be different from
the btf_vmlinux's btf-type. ]
Then, all obj->maps are created as usual (in bpf_object__create_maps()).
Once the maps are created and prog's properties are all set,
the libbpf will proceed to load all the progs.
bpf_map__attach_struct_ops() is added to register a struct_ops
map to a kernel subsystem.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200109003514.3856730-1-kafai@fb.com
This is a mirror of bpf-next linux tree's
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.hinclude/uapi/linux/bpf.h<->bpf-next/tools/include/uapi/linux/bpf.hinclude/uapi/linux/btf.h<->bpf-next/tools/include/uapi/linux/btf.hinclude/uapi/linux/if_link.h<->bpf-next/tools/include/uapi/linux/if_link.hinclude/uapi/linux/if_xdp.h<->bpf-next/tools/include/uapi/linux/if_xdp.hinclude/uapi/linux/netlink.h<->bpf-next/tools/include/uapi/linux/netlink.hinclude/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's 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
License
This work is dual-licensed under BSD 2-clause license and GNU LGPL v2.1 license. You can choose between one of them if you use this work.
SPDX-License-Identifier: BSD-2-Clause OR LGPL-2.1