linux/tools/lib/bpf
Andrii Nakryiko 39529a9948 libbpf: Teach btf_dumper to emit stand-alone anonymous enum definitions
BTF-to-C converter previously skipped anonymous enums in an assumption
that those are embedded in struct's field definitions. This is not
always the case and a lot of kernel constants are defined as part of
anonymous enums. This change fixes the logic by eagerly marking all
types as either referenced by any other type or not. This is enough to
distinguish two classes of anonymous enums and emit previously omitted
enum definitions.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20190925203745.3173184-1-andriin@fb.com
2019-09-26 14:38:29 +02:00
..
.gitignore Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-05-02 22:14:21 -04:00
bpf_prog_linfo.c libbpf: add common min/max macro to libbpf_internal.h 2019-06-18 00:08:54 +02:00
bpf.c libbpf: add bpf_btf_get_next_id() to cycle through BTF objects 2019-08-20 09:51:06 -07:00
bpf.h libbpf: add bpf_btf_get_next_id() to cycle through BTF objects 2019-08-20 09:51:06 -07:00
btf_dump.c libbpf: Teach btf_dumper to emit stand-alone anonymous enum definitions 2019-09-26 14:38:29 +02:00
btf.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 2019-08-13 16:24:57 -07:00
btf.h libbpf: add .BTF.ext offset relocation section loading 2019-08-07 14:43:49 -07:00
Build libbpf: add btf_dump API for BTF-to-C conversion 2019-05-24 14:05:58 -07:00
hashmap.c libbpf: add resizable non-thread safe internal hashmap 2019-05-24 14:05:57 -07:00
hashmap.h libbpf: fix missing __WORDSIZE definition 2019-07-29 10:18:08 -03:00
libbpf_errno.c tools/bpf: make libbpf _GNU_SOURCE friendly 2018-11-30 02:41:02 +01:00
libbpf_internal.h libbpf: add .BTF.ext offset relocation section loading 2019-08-07 14:43:49 -07:00
libbpf_probes.c tools/libbpf_probes: Add new devmap_hash type 2019-07-29 13:50:48 -07:00
libbpf_util.h libbpf: move logging helpers into libbpf_internal.h 2019-05-16 12:47:47 -07:00
libbpf.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-08-19 11:54:03 -07:00
libbpf.h libbpf: implement BPF CO-RE offset relocation algorithm 2019-08-07 14:43:49 -07:00
libbpf.map libbpf: add flags to umem config 2019-08-31 01:08:26 +02:00
libbpf.pc.template tools/bpf: generate pkg-config file for libbpf 2019-03-28 17:06:03 +01:00
Makefile libbpf: add flags to umem config 2019-08-31 01:08:26 +02:00
netlink.c libbpf: Add a support for getting xdp prog id on ifindex 2019-02-01 23:37:51 +01:00
nlattr.c libbpf: relicense libbpf as LGPL-2.1 OR BSD-2-Clause 2018-10-08 10:09:48 +02:00
nlattr.h libbpf: relicense libbpf as LGPL-2.1 OR BSD-2-Clause 2018-10-08 10:09:48 +02:00
README.rst libbpf: add perf_buffer_ prefix to README 2019-07-08 15:35:43 +02:00
str_error.c libbpf: make libbpf_strerror_r agnostic to sign of error 2019-07-05 22:37:30 +02:00
str_error.h libbpf: relicense libbpf as LGPL-2.1 OR BSD-2-Clause 2018-10-08 10:09:48 +02:00
test_libbpf.cpp tools/bpf: simplify libbpf API function libbpf_set_print() 2019-02-04 09:40:59 -08:00
xsk.c libbpf: Remove getsockopt() check for XDP_OPTIONS 2019-09-19 14:22:18 +02:00
xsk.h libbpf: add flags to umem config 2019-08-31 01:08:26 +02:00

.. 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).