linux/tools/lib/bpf
Toke Høiland-Jørgensen 1e891e513e libbpf: Fix map index used in error message
The error message emitted by bpf_object__init_user_btf_maps() was using the
wrong section ID.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200819110534.9058-1-toke@redhat.com
2020-08-20 16:21:27 +02:00
..
.gitignore .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
Build libbpf: Add BPF ring buffer support 2020-06-01 14:38:22 -07:00
Makefile libbpf: Use .so dynamic symbols for abi check 2020-06-01 14:38:20 -07:00
README.rst libbpf: add perf_buffer_ prefix to README 2019-07-08 15:35:43 +02:00
bpf.c tools/bpf: Support new uapi for map element bpf iterator 2020-08-06 16:39:14 -07:00
bpf.h tools/bpf: Support new uapi for map element bpf iterator 2020-08-06 16:39:14 -07:00
bpf_core_read.h libbpf: Wrap source argument of BPF_CORE_READ macro in parentheses 2020-06-22 17:01:48 -07:00
bpf_endian.h libbpf: Make bpf_endian co-exist with vmlinux.h 2020-07-01 09:06:12 +02:00
bpf_helpers.h libbpf: Do not use __builtin_offsetof for offsetof 2020-08-11 15:11:07 +02:00
bpf_prog_linfo.c libbpf: Poison kernel-only integer types 2020-01-10 10:38:00 -08:00
bpf_tracing.h libbpf: Fix register in PT_REGS MIPS macros 2020-07-31 17:20:49 +02:00
btf.c libbpf: Handle BTF pointer sizes more carefully 2020-08-13 16:45:41 -07:00
btf.h libbpf: Handle BTF pointer sizes more carefully 2020-08-13 16:45:41 -07:00
btf_dump.c libbpf: Fix build on ppc64le architecture 2020-08-18 10:02:52 -07:00
hashmap.c libbpf, hashmap: Fix signedness warnings 2020-05-16 01:06:05 +02:00
hashmap.h libbpf: Fix libbpf hashmap on (I)LP32 architectures 2020-07-09 19:38:55 -07:00
libbpf.c libbpf: Fix map index used in error message 2020-08-20 16:21:27 +02:00
libbpf.h tools/bpf: Support new uapi for map element bpf iterator 2020-08-06 16:39:14 -07:00
libbpf.map libbpf: Handle BTF pointer sizes more carefully 2020-08-13 16:45:41 -07:00
libbpf.pc.template libbpf: Add zlib as a dependency in pkg-config template 2019-12-16 14:55:29 -08:00
libbpf_common.h libbpf: Fix libbpf_common.h when installing libbpf through 'make install' 2019-12-18 00:19:31 +01:00
libbpf_errno.c libbpf: Poison kernel-only integer types 2020-01-10 10:38:00 -08:00
libbpf_internal.h bpf, libbpf: Replace zero-length array with flexible-array 2020-05-11 16:56:47 +02:00
libbpf_probes.c libbpf: Add support for SK_LOOKUP program type 2020-07-17 20:18:17 -07:00
libbpf_util.h libbpf: move logging helpers into libbpf_internal.h 2019-05-16 12:47:47 -07:00
netlink.c libbpf: Only check mode flags in get_xdp_id 2020-04-22 22:07:22 -07:00
nlattr.c libbpf: Poison kernel-only integer types 2020-01-10 10:38:00 -08:00
nlattr.h libbpf: relicense libbpf as LGPL-2.1 OR BSD-2-Clause 2018-10-08 10:09:48 +02:00
ringbuf.c libbpf: Add _GNU_SOURCE for reallocarray to ringbuf.c 2020-06-01 15:13:04 -07:00
str_error.c libbpf: Poison kernel-only integer types 2020-01-10 10:38:00 -08:00
str_error.h libbpf: relicense libbpf as LGPL-2.1 OR BSD-2-Clause 2018-10-08 10:09:48 +02:00
xsk.c libbpf, xsk: Init all ring members in xsk_umem__create and xsk_socket__create 2020-03-28 17:12:56 +01:00
xsk.h libbpf: add flags to umem config 2019-08-31 01:08:26 +02:00

README.rst

.. SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)

libbpf API naming convention
============================

libbpf API provides access to a few logically separated groups of
functions and types. Every group has its own naming convention
described here. It's recommended to follow these conventions whenever a
new function or type is added to keep libbpf API clean and consistent.

All types and functions provided by libbpf API should have one of the
following prefixes: ``bpf_``, ``btf_``, ``libbpf_``, ``xsk_``,
``perf_buffer_``.

System call wrappers
--------------------

System call wrappers are simple wrappers for commands supported by
sys_bpf system call. These wrappers should go to ``bpf.h`` header file
and map one-on-one to corresponding commands.

For example ``bpf_map_lookup_elem`` wraps ``BPF_MAP_LOOKUP_ELEM``
command of sys_bpf, ``bpf_prog_attach`` wraps ``BPF_PROG_ATTACH``, etc.

Objects
-------

Another class of types and functions provided by libbpf API is "objects"
and functions to work with them. Objects are high-level abstractions
such as BPF program or BPF map. They're represented by corresponding
structures such as ``struct bpf_object``, ``struct bpf_program``,
``struct bpf_map``, etc.

Structures are forward declared and access to their fields should be
provided via corresponding getters and setters rather than directly.

These objects are associated with corresponding parts of ELF object that
contains compiled BPF programs.

For example ``struct bpf_object`` represents ELF object itself created
from an ELF file or from a buffer, ``struct bpf_program`` represents a
program in ELF object and ``struct bpf_map`` is a map.

Functions that work with an object have names built from object name,
double underscore and part that describes function purpose.

For example ``bpf_object__open`` consists of the name of corresponding
object, ``bpf_object``, double underscore and ``open`` that defines the
purpose of the function to open ELF file and create ``bpf_object`` from
it.

Another example: ``bpf_program__load`` is named for corresponding
object, ``bpf_program``, that is separated from other part of the name
by double underscore.

All objects and corresponding functions other than BTF related should go
to ``libbpf.h``. BTF types and functions should go to ``btf.h``.

Auxiliary functions
-------------------

Auxiliary functions and types that don't fit well in any of categories
described above should have ``libbpf_`` prefix, e.g.
``libbpf_get_error`` or ``libbpf_prog_type_by_name``.

AF_XDP functions
-------------------

AF_XDP functions should have an ``xsk_`` prefix, e.g.
``xsk_umem__get_data`` or ``xsk_umem__create``. The interface consists
of both low-level ring access functions and high-level configuration
functions. These can be mixed and matched. Note that these functions
are not reentrant for performance reasons.

Please take a look at Documentation/networking/af_xdp.rst in the Linux
kernel source tree on how to use XDP sockets and for some common
mistakes in case you do not get any traffic up to user space.

libbpf ABI
==========

libbpf can be both linked statically or used as DSO. To avoid possible
conflicts with other libraries an application is linked with, all
non-static libbpf symbols should have one of the prefixes mentioned in
API documentation above. See API naming convention to choose the right
name for a new symbol.

Symbol visibility
-----------------

libbpf follow the model when all global symbols have visibility "hidden"
by default and to make a symbol visible it has to be explicitly
attributed with ``LIBBPF_API`` macro. For example:

.. code-block:: c

        LIBBPF_API int bpf_prog_get_fd_by_id(__u32 id);

This prevents from accidentally exporting a symbol, that is not supposed
to be a part of ABI what, in turn, improves both libbpf developer- and
user-experiences.

ABI versionning
---------------

To make future ABI extensions possible libbpf ABI is versioned.
Versioning is implemented by ``libbpf.map`` version script that is
passed to linker.

Version name is ``LIBBPF_`` prefix + three-component numeric version,
starting from ``0.0.1``.

Every time ABI is being changed, e.g. because a new symbol is added or
semantic of existing symbol is changed, ABI version should be bumped.
This bump in ABI version is at most once per kernel development cycle.

For example, if current state of ``libbpf.map`` is:

.. code-block::
        LIBBPF_0.0.1 {
        	global:
                        bpf_func_a;
                        bpf_func_b;
        	local:
        		\*;
        };

, and a new symbol ``bpf_func_c`` is being introduced, then
``libbpf.map`` should be changed like this:

.. code-block::
        LIBBPF_0.0.1 {
        	global:
                        bpf_func_a;
                        bpf_func_b;
        	local:
        		\*;
        };
        LIBBPF_0.0.2 {
                global:
                        bpf_func_c;
        } LIBBPF_0.0.1;

, where new version ``LIBBPF_0.0.2`` depends on the previous
``LIBBPF_0.0.1``.

Format of version script and ways to handle ABI changes, including
incompatible ones, described in details in [1].

Stand-alone build
=================

Under https://github.com/libbpf/libbpf there is a (semi-)automated
mirror of the mainline's version of libbpf for a stand-alone build.

However, all changes to libbpf's code base must be upstreamed through
the mainline kernel tree.

License
=======

libbpf is dual-licensed under LGPL 2.1 and BSD 2-Clause.

Links
=====

[1] https://www.akkadia.org/drepper/dsohowto.pdf
    (Chapter 3. Maintaining APIs and ABIs).