linux-stable/Documentation/ABI
Jakub Kicinski 07cbce2e46 Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next
Daniel Borkmann says:

====================
pull-request: bpf-next 2020-11-14

1) Add BTF generation for kernel modules and extend BTF infra in kernel
   e.g. support for split BTF loading and validation, from Andrii Nakryiko.

2) Support for pointers beyond pkt_end to recognize LLVM generated patterns
   on inlined branch conditions, from Alexei Starovoitov.

3) Implements bpf_local_storage for task_struct for BPF LSM, from KP Singh.

4) Enable FENTRY/FEXIT/RAW_TP tracing program to use the bpf_sk_storage
   infra, from Martin KaFai Lau.

5) Add XDP bulk APIs that introduce a defer/flush mechanism to optimize the
   XDP_REDIRECT path, from Lorenzo Bianconi.

6) Fix a potential (although rather theoretical) deadlock of hashtab in NMI
   context, from Song Liu.

7) Fixes for cross and out-of-tree build of bpftool and runqslower allowing build
   for different target archs on same source tree, from Jean-Philippe Brucker.

8) Fix error path in htab_map_alloc() triggered from syzbot, from Eric Dumazet.

9) Move functionality from test_tcpbpf_user into the test_progs framework so it
   can run in BPF CI, from Alexander Duyck.

10) Lift hashtab key_size limit to be larger than MAX_BPF_STACK, from Florian Lehner.

Note that for the fix from Song we have seen a sparse report on context
imbalance which requires changes in sparse itself for proper annotation
detection where this is currently being discussed on linux-sparse among
developers [0]. Once we have more clarification/guidance after their fix,
Song will follow-up.

  [0] https://lore.kernel.org/linux-sparse/CAHk-=wh4bx8A8dHnX612MsDO13st6uzAz1mJ1PaHHVevJx_ZCw@mail.gmail.com/T/
      https://lore.kernel.org/linux-sparse/20201109221345.uklbp3lzgq6g42zb@ltop.local/T/

* git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (66 commits)
  net: mlx5: Add xdp tx return bulking support
  net: mvpp2: Add xdp tx return bulking support
  net: mvneta: Add xdp tx return bulking support
  net: page_pool: Add bulk support for ptr_ring
  net: xdp: Introduce bulking for xdp tx return path
  bpf: Expose bpf_d_path helper to sleepable LSM hooks
  bpf: Augment the set of sleepable LSM hooks
  bpf: selftest: Use bpf_sk_storage in FENTRY/FEXIT/RAW_TP
  bpf: Allow using bpf_sk_storage in FENTRY/FEXIT/RAW_TP
  bpf: Rename some functions in bpf_sk_storage
  bpf: Folding omem_charge() into sk_storage_charge()
  selftests/bpf: Add asm tests for pkt vs pkt_end comparison.
  selftests/bpf: Add skb_pkt_end test
  bpf: Support for pointers beyond pkt_end.
  tools/bpf: Always run the *-clean recipes
  tools/bpf: Add bootstrap/ to .gitignore
  bpf: Fix NULL dereference in bpf_task_storage
  tools/bpftool: Fix build slowdown
  tools/runqslower: Build bpftool using HOSTCC
  tools/runqslower: Enable out-of-tree build
  ...
====================

Link: https://lore.kernel.org/r/20201114020819.29584-1-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2020-11-14 09:13:41 -08:00
..
obsolete docs: ABI: cleanup several ABI documents 2020-10-30 13:14:29 +01:00
removed docs: ABI: cleanup several ABI documents 2020-10-30 13:14:29 +01:00
stable docs: ABI: sysfs-driver-dma-ioatdma: what starts with /sys 2020-11-02 13:45:37 +01:00
testing Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 2020-11-14 09:13:41 -08:00
README docs: ABI: README: specify that files should be ReST compatible 2020-10-30 13:07:01 +01:00

This directory attempts to document the ABI between the Linux kernel and
userspace, and the relative stability of these interfaces.  Due to the
everchanging nature of Linux, and the differing maturity levels, these
interfaces should be used by userspace programs in different ways.

We have four different levels of ABI stability, as shown by the four
different subdirectories in this location.  Interfaces may change levels
of stability according to the rules described below.

The different levels of stability are:

  stable/
	This directory documents the interfaces that the developer has
	defined to be stable.  Userspace programs are free to use these
	interfaces with no restrictions, and backward compatibility for
	them will be guaranteed for at least 2 years.  Most interfaces
	(like syscalls) are expected to never change and always be
	available.

  testing/
	This directory documents interfaces that are felt to be stable,
	as the main development of this interface has been completed.
	The interface can be changed to add new features, but the
	current interface will not break by doing this, unless grave
	errors or security problems are found in them.  Userspace
	programs can start to rely on these interfaces, but they must be
	aware of changes that can occur before these interfaces move to
	be marked stable.  Programs that use these interfaces are
	strongly encouraged to add their name to the description of
	these interfaces, so that the kernel developers can easily
	notify them if any changes occur (see the description of the
	layout of the files below for details on how to do this.)

  obsolete/
	This directory documents interfaces that are still remaining in
	the kernel, but are marked to be removed at some later point in
	time.  The description of the interface will document the reason
	why it is obsolete and when it can be expected to be removed.

  removed/
	This directory contains a list of the old interfaces that have
	been removed from the kernel.

Every file in these directories will contain the following information:

What:		Short description of the interface
Date:		Date created
KernelVersion:	Kernel version this feature first showed up in.
Contact:	Primary contact for this interface (may be a mailing list)
Description:	Long description of the interface and how to use it.
Users:		All users of this interface who wish to be notified when
		it changes.  This is very important for interfaces in
		the "testing" stage, so that kernel developers can work
		with userspace developers to ensure that things do not
		break in ways that are unacceptable.  It is also
		important to get feedback for these interfaces to make
		sure they are working in a proper way and do not need to
		be changed further.


Note:
   The fields should be use a simple notation, compatible with ReST markup.
   Also, the file **should not** have a top-level index, like::

	===
	foo
	===

How things move between levels:

Interfaces in stable may move to obsolete, as long as the proper
notification is given.

Interfaces may be removed from obsolete and the kernel as long as the
documented amount of time has gone by.

Interfaces in the testing state can move to the stable state when the
developers feel they are finished.  They cannot be removed from the
kernel tree without going through the obsolete state first.

It's up to the developer to place their interfaces in the category they
wish for it to start out in.


Notable bits of non-ABI, which should not under any circumstances be considered
stable:

- Kconfig.  Userspace should not rely on the presence or absence of any
  particular Kconfig symbol, in /proc/config.gz, in the copy of .config
  commonly installed to /boot, or in any invocation of the kernel build
  process.

- Kernel-internal symbols.  Do not rely on the presence, absence, location, or
  type of any kernel symbol, either in System.map files or the kernel binary
  itself.  See Documentation/process/stable-api-nonsense.rst.