mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-26 01:05:37 +07:00
140 lines
4.5 KiB
ReStructuredText
140 lines
4.5 KiB
ReStructuredText
|
.. SPDX-License-Identifier: GPL-2.0
|
||
|
|
||
|
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_``.
|
||
|
|
||
|
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``.
|
||
|
|
||
|
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.
|
||
|
|
||
|
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].
|
||
|
|
||
|
Links
|
||
|
=====
|
||
|
|
||
|
[1] https://www.akkadia.org/drepper/dsohowto.pdf
|
||
|
(Chapter 3. Maintaining APIs and ABIs).
|