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Diffstat (limited to 'Documentation/bpf/libbpf')
| -rw-r--r-- | Documentation/bpf/libbpf/index.rst | 24 | ||||
| -rw-r--r-- | Documentation/bpf/libbpf/libbpf_build.rst | 37 | ||||
| -rw-r--r-- | Documentation/bpf/libbpf/libbpf_naming_convention.rst | 193 | ||||
| -rw-r--r-- | Documentation/bpf/libbpf/program_types.rst | 203 |
4 files changed, 457 insertions, 0 deletions
diff --git a/Documentation/bpf/libbpf/index.rst b/Documentation/bpf/libbpf/index.rst new file mode 100644 index 000000000..f9b3b252e --- /dev/null +++ b/Documentation/bpf/libbpf/index.rst @@ -0,0 +1,24 @@ +.. SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) + +.. _libbpf: + +libbpf +====== + +.. toctree:: + :maxdepth: 1 + + API Documentation <https://libbpf.readthedocs.io/en/latest/api.html> + program_types + libbpf_naming_convention + libbpf_build + +This is documentation for libbpf, a userspace library for loading and +interacting with bpf programs. + +All general BPF questions, including kernel functionality, libbpf APIs and +their application, should be sent to bpf@vger.kernel.org mailing list. +You can `subscribe <http://vger.kernel.org/vger-lists.html#bpf>`_ to the +mailing list search its `archive <https://lore.kernel.org/bpf/>`_. +Please search the archive before asking new questions. It very well might +be that this was already addressed or answered before. diff --git a/Documentation/bpf/libbpf/libbpf_build.rst b/Documentation/bpf/libbpf/libbpf_build.rst new file mode 100644 index 000000000..8e8c23e80 --- /dev/null +++ b/Documentation/bpf/libbpf/libbpf_build.rst @@ -0,0 +1,37 @@ +.. SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) + +Building libbpf +=============== + +libelf and zlib are internal dependencies of libbpf and thus are 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: + +.. code-block:: bash + + $ 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/: + +.. code-block:: bash + + $ 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/: + +.. code-block:: bash + + $ cd src + $ PKG_CONFIG_PATH=/build/root/lib64/pkgconfig DESTDIR=/build/root make
\ No newline at end of file diff --git a/Documentation/bpf/libbpf/libbpf_naming_convention.rst b/Documentation/bpf/libbpf/libbpf_naming_convention.rst new file mode 100644 index 000000000..b5b41b61b --- /dev/null +++ b/Documentation/bpf/libbpf/libbpf_naming_convention.rst @@ -0,0 +1,193 @@ +.. SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) + +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_``, ``btf_dump_``, +``ring_buffer_``, ``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 to 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. + +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``. + +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 versioning +-------------- + +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:: none + + 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:: none + + 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. + + +API documentation convention +============================ + +The libbpf API is documented via comments above definitions in +header files. These comments can be rendered by doxygen and sphinx +for well organized html output. This section describes the +convention in which these comments should be formatted. + +Here is an example from btf.h: + +.. code-block:: c + + /** + * @brief **btf__new()** creates a new instance of a BTF object from the raw + * bytes of an ELF's BTF section + * @param data raw bytes + * @param size number of bytes passed in `data` + * @return new BTF object instance which has to be eventually freed with + * **btf__free()** + * + * On error, error-code-encoded-as-pointer is returned, not a NULL. To extract + * error code from such a pointer `libbpf_get_error()` should be used. If + * `libbpf_set_strict_mode(LIBBPF_STRICT_CLEAN_PTRS)` is enabled, NULL is + * returned on error instead. In both cases thread-local `errno` variable is + * always set to error code as well. + */ + +The comment must start with a block comment of the form '/\*\*'. + +The documentation always starts with a @brief directive. This line is a short +description about this API. It starts with the name of the API, denoted in bold +like so: **api_name**. Please include an open and close parenthesis if this is a +function. Follow with the short description of the API. A longer form description +can be added below the last directive, at the bottom of the comment. + +Parameters are denoted with the @param directive, there should be one for each +parameter. If this is a function with a non-void return, use the @return directive +to document it. + +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). diff --git a/Documentation/bpf/libbpf/program_types.rst b/Documentation/bpf/libbpf/program_types.rst new file mode 100644 index 000000000..ad4d4d5ee --- /dev/null +++ b/Documentation/bpf/libbpf/program_types.rst @@ -0,0 +1,203 @@ +.. SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) + +.. _program_types_and_elf: + +Program Types and ELF Sections +============================== + +The table below lists the program types, their attach types where relevant and the ELF section +names supported by libbpf for them. The ELF section names follow these rules: + +- ``type`` is an exact match, e.g. ``SEC("socket")`` +- ``type+`` means it can be either exact ``SEC("type")`` or well-formed ``SEC("type/extras")`` + with a '``/``' separator between ``type`` and ``extras``. + +When ``extras`` are specified, they provide details of how to auto-attach the BPF program. The +format of ``extras`` depends on the program type, e.g. ``SEC("tracepoint/<category>/<name>")`` +for tracepoints or ``SEC("usdt/<path>:<provider>:<name>")`` for USDT probes. The extras are +described in more detail in the footnotes. + + ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| Program Type | Attach Type | ELF Section Name | Sleepable | ++===========================================+========================================+==================================+===========+ +| ``BPF_PROG_TYPE_CGROUP_DEVICE`` | ``BPF_CGROUP_DEVICE`` | ``cgroup/dev`` | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_CGROUP_SKB`` | | ``cgroup/skb`` | | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_CGROUP_INET_EGRESS`` | ``cgroup_skb/egress`` | | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_CGROUP_INET_INGRESS`` | ``cgroup_skb/ingress`` | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_CGROUP_SOCKOPT`` | ``BPF_CGROUP_GETSOCKOPT`` | ``cgroup/getsockopt`` | | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_CGROUP_SETSOCKOPT`` | ``cgroup/setsockopt`` | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_CGROUP_SOCK_ADDR`` | ``BPF_CGROUP_INET4_BIND`` | ``cgroup/bind4`` | | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_CGROUP_INET4_CONNECT`` | ``cgroup/connect4`` | | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_CGROUP_INET4_GETPEERNAME`` | ``cgroup/getpeername4`` | | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_CGROUP_INET4_GETSOCKNAME`` | ``cgroup/getsockname4`` | | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_CGROUP_INET6_BIND`` | ``cgroup/bind6`` | | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_CGROUP_INET6_CONNECT`` | ``cgroup/connect6`` | | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_CGROUP_INET6_GETPEERNAME`` | ``cgroup/getpeername6`` | | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_CGROUP_INET6_GETSOCKNAME`` | ``cgroup/getsockname6`` | | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_CGROUP_UDP4_RECVMSG`` | ``cgroup/recvmsg4`` | | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_CGROUP_UDP4_SENDMSG`` | ``cgroup/sendmsg4`` | | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_CGROUP_UDP6_RECVMSG`` | ``cgroup/recvmsg6`` | | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_CGROUP_UDP6_SENDMSG`` | ``cgroup/sendmsg6`` | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_CGROUP_SOCK`` | ``BPF_CGROUP_INET4_POST_BIND`` | ``cgroup/post_bind4`` | | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_CGROUP_INET6_POST_BIND`` | ``cgroup/post_bind6`` | | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_CGROUP_INET_SOCK_CREATE`` | ``cgroup/sock_create`` | | ++ + +----------------------------------+-----------+ +| | | ``cgroup/sock`` | | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_CGROUP_INET_SOCK_RELEASE`` | ``cgroup/sock_release`` | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_CGROUP_SYSCTL`` | ``BPF_CGROUP_SYSCTL`` | ``cgroup/sysctl`` | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_EXT`` | | ``freplace+`` [#fentry]_ | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_FLOW_DISSECTOR`` | ``BPF_FLOW_DISSECTOR`` | ``flow_dissector`` | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_KPROBE`` | | ``kprobe+`` [#kprobe]_ | | ++ + +----------------------------------+-----------+ +| | | ``kretprobe+`` [#kprobe]_ | | ++ + +----------------------------------+-----------+ +| | | ``ksyscall+`` [#ksyscall]_ | | ++ + +----------------------------------+-----------+ +| | | ``kretsyscall+`` [#ksyscall]_ | | ++ + +----------------------------------+-----------+ +| | | ``uprobe+`` [#uprobe]_ | | ++ + +----------------------------------+-----------+ +| | | ``uprobe.s+`` [#uprobe]_ | Yes | ++ + +----------------------------------+-----------+ +| | | ``uretprobe+`` [#uprobe]_ | | ++ + +----------------------------------+-----------+ +| | | ``uretprobe.s+`` [#uprobe]_ | Yes | ++ + +----------------------------------+-----------+ +| | | ``usdt+`` [#usdt]_ | | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_TRACE_KPROBE_MULTI`` | ``kprobe.multi+`` [#kpmulti]_ | | ++ + +----------------------------------+-----------+ +| | | ``kretprobe.multi+`` [#kpmulti]_ | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_LIRC_MODE2`` | ``BPF_LIRC_MODE2`` | ``lirc_mode2`` | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_LSM`` | ``BPF_LSM_CGROUP`` | ``lsm_cgroup+`` | | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_LSM_MAC`` | ``lsm+`` [#lsm]_ | | ++ + +----------------------------------+-----------+ +| | | ``lsm.s+`` [#lsm]_ | Yes | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_LWT_IN`` | | ``lwt_in`` | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_LWT_OUT`` | | ``lwt_out`` | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_LWT_SEG6LOCAL`` | | ``lwt_seg6local`` | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_LWT_XMIT`` | | ``lwt_xmit`` | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_PERF_EVENT`` | | ``perf_event`` | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE`` | | ``raw_tp.w+`` [#rawtp]_ | | ++ + +----------------------------------+-----------+ +| | | ``raw_tracepoint.w+`` | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_RAW_TRACEPOINT`` | | ``raw_tp+`` [#rawtp]_ | | ++ + +----------------------------------+-----------+ +| | | ``raw_tracepoint+`` | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_SCHED_ACT`` | | ``action`` | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_SCHED_CLS`` | | ``classifier`` | | ++ + +----------------------------------+-----------+ +| | | ``tc`` | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_SK_LOOKUP`` | ``BPF_SK_LOOKUP`` | ``sk_lookup`` | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_SK_MSG`` | ``BPF_SK_MSG_VERDICT`` | ``sk_msg`` | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_SK_REUSEPORT`` | ``BPF_SK_REUSEPORT_SELECT_OR_MIGRATE`` | ``sk_reuseport/migrate`` | | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_SK_REUSEPORT_SELECT`` | ``sk_reuseport`` | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_SK_SKB`` | | ``sk_skb`` | | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_SK_SKB_STREAM_PARSER`` | ``sk_skb/stream_parser`` | | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_SK_SKB_STREAM_VERDICT`` | ``sk_skb/stream_verdict`` | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_SOCKET_FILTER`` | | ``socket`` | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_SOCK_OPS`` | ``BPF_CGROUP_SOCK_OPS`` | ``sockops`` | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_STRUCT_OPS`` | | ``struct_ops+`` | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_SYSCALL`` | | ``syscall`` | Yes | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_TRACEPOINT`` | | ``tp+`` [#tp]_ | | ++ + +----------------------------------+-----------+ +| | | ``tracepoint+`` [#tp]_ | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_TRACING`` | ``BPF_MODIFY_RETURN`` | ``fmod_ret+`` [#fentry]_ | | ++ + +----------------------------------+-----------+ +| | | ``fmod_ret.s+`` [#fentry]_ | Yes | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_TRACE_FENTRY`` | ``fentry+`` [#fentry]_ | | ++ + +----------------------------------+-----------+ +| | | ``fentry.s+`` [#fentry]_ | Yes | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_TRACE_FEXIT`` | ``fexit+`` [#fentry]_ | | ++ + +----------------------------------+-----------+ +| | | ``fexit.s+`` [#fentry]_ | Yes | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_TRACE_ITER`` | ``iter+`` [#iter]_ | | ++ + +----------------------------------+-----------+ +| | | ``iter.s+`` [#iter]_ | Yes | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_TRACE_RAW_TP`` | ``tp_btf+`` [#fentry]_ | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ +| ``BPF_PROG_TYPE_XDP`` | ``BPF_XDP_CPUMAP`` | ``xdp.frags/cpumap`` | | ++ + +----------------------------------+-----------+ +| | | ``xdp/cpumap`` | | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_XDP_DEVMAP`` | ``xdp.frags/devmap`` | | ++ + +----------------------------------+-----------+ +| | | ``xdp/devmap`` | | ++ +----------------------------------------+----------------------------------+-----------+ +| | ``BPF_XDP`` | ``xdp.frags`` | | ++ + +----------------------------------+-----------+ +| | | ``xdp`` | | ++-------------------------------------------+----------------------------------------+----------------------------------+-----------+ + + +.. rubric:: Footnotes + +.. [#fentry] The ``fentry`` attach format is ``fentry[.s]/<function>``. +.. [#kprobe] The ``kprobe`` attach format is ``kprobe/<function>[+<offset>]``. Valid + characters for ``function`` are ``a-zA-Z0-9_.`` and ``offset`` must be a valid + non-negative integer. +.. [#ksyscall] The ``ksyscall`` attach format is ``ksyscall/<syscall>``. +.. [#uprobe] The ``uprobe`` attach format is ``uprobe[.s]/<path>:<function>[+<offset>]``. +.. [#usdt] The ``usdt`` attach format is ``usdt/<path>:<provider>:<name>``. +.. [#kpmulti] The ``kprobe.multi`` attach format is ``kprobe.multi/<pattern>`` where ``pattern`` + supports ``*`` and ``?`` wildcards. Valid characters for pattern are + ``a-zA-Z0-9_.*?``. +.. [#lsm] The ``lsm`` attachment format is ``lsm[.s]/<hook>``. +.. [#rawtp] The ``raw_tp`` attach format is ``raw_tracepoint[.w]/<tracepoint>``. +.. [#tp] The ``tracepoint`` attach format is ``tracepoint/<category>/<name>``. +.. [#iter] The ``iter`` attach format is ``iter[.s]/<struct-name>``. |