=================
BPF Documentation
=================

This directory contains documentation for the BPF (Berkeley Packet
Filter) facility, with a focus on the extended BPF version (eBPF).

This kernel side documentation is still work in progress. The main
textual documentation is (for historical reasons) described in
:ref:`networking-filter`, which describe both classical and extended
BPF instruction-set.
The Cilium project also maintains a `BPF and XDP Reference Guide`_
that goes into great technical depth about the BPF Architecture.

libbpf
======

Documentation/bpf/libbpf/libbpf.rst is a userspace library for loading and interacting with bpf programs.

BPF Type Format (BTF)
=====================

.. toctree::
   :maxdepth: 1

   btf


Frequently asked questions (FAQ)
================================

Two sets of Questions and Answers (Q&A) are maintained.

.. toctree::
   :maxdepth: 1

   bpf_design_QA
   bpf_devel_QA

Syscall API
===========

The primary info for the bpf syscall is available in the `man-pages`_
for `bpf(2)`_. For more information about the userspace API, see
Documentation/userspace-api/ebpf/index.rst.

Helper functions
================

* `bpf-helpers(7)`_ maintains a list of helpers available to eBPF programs.


Program types
=============

.. toctree::
   :maxdepth: 1

   prog_cgroup_sockopt
   prog_cgroup_sysctl
   prog_flow_dissector
   bpf_lsm
   prog_sk_lookup


Map types
=========

.. toctree::
   :maxdepth: 1

   map_cgroup_storage


Testing and debugging BPF
=========================

.. toctree::
   :maxdepth: 1

   drgn
   s390


Other
=====

.. toctree::
   :maxdepth: 1

   ringbuf
   llvm_reloc

.. Links:
.. _networking-filter: ../networking/filter.rst
.. _man-pages: https://www.kernel.org/doc/man-pages/
.. _bpf(2): https://man7.org/linux/man-pages/man2/bpf.2.html
.. _bpf-helpers(7): https://man7.org/linux/man-pages/man7/bpf-helpers.7.html
.. _BPF and XDP Reference Guide: https://docs.cilium.io/en/latest/bpf/