linux/Documentation/ABI
Linus Torvalds 1f6075f990 Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull more perf updates from Ingo Molnar:
 "A second (and last) round of late coming fixes and changes, almost all
  of them in perf tooling:

  User visible tooling changes:

   - Add period data column and make it default in 'perf script' (Jiri
     Olsa)

   - Add a visual cue for toggle zeroing of samples in 'perf top'
     (Taeung Song)

   - Improve callchains when using libunwind (Namhyung Kim)

  Tooling fixes and infrastructure changes:

   - Fix for double free in 'perf stat' when using some specific invalid
     command line combo (Yasser Shalabi)

   - Fix off-by-one bugs in map->end handling (Stephane Eranian)

   - Fix off-by-one bug in maps__find(), also related to map->end
     handling (Namhyung Kim)

   - Make struct symbol->end be the first addr after the symbol range,
     to make it match the convention used for struct map->end.  (Arnaldo
     Carvalho de Melo)

   - Fix perf_evlist__add_pollfd() error handling in 'perf kvm stat
     live' (Jiri Olsa)

   - Fix python test build by moving callchain_param to an object linked
     into the python binding (Jiri Olsa)

   - Document sysfs events/ interfaces (Cody P Schafer)

   - Fix typos in perf/Documentation (Masanari Iida)

   - Add missing 'struct option' forward declaration (Arnaldo Carvalho
     de Melo)

   - Add option to copy events when queuing for sorting across cpu
     buffers and enable it for 'perf kvm stat live', to avoid having
     events left in the queue pointing to the ring buffer be rewritten
     in high volume sessions.  (Alexander Yarygin, improving work done
     by David Ahern):

   - Do not include a struct hists per perf_evsel, untangling the
     histogram code from perf_evsel, to pave the way for exporting a
     minimalistic tools/lib/api/perf/ library usable by tools/perf and
     initially by the rasd daemon being developed by Borislav Petkov,
     Robert Richter and Jean Pihet.  (Arnaldo Carvalho de Melo)

   - Make perf_evlist__open(evlist, NULL, NULL), i.e. without cpu and
     thread maps mean syswide monitoring, reducing the boilerplate for
     tools that only want system wide mode.  (Arnaldo Carvalho de Melo)

   - Move exit stuff from perf_evsel__delete to perf_evsel__exit, delete
     should be just a front end for exit + free (Arnaldo Carvalho de
     Melo)

   - Add support to new style format of kernel PMU event.  (Kan Liang)

  and other misc fixes"

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (45 commits)
  perf script: Add period as a default output column
  perf script: Add period data column
  perf evsel: No need to drag util/cgroup.h
  perf evlist: Add missing 'struct option' forward declaration
  perf evsel: Move exit stuff from __delete to __exit
  kprobes/x86: Remove stale ARCH_SUPPORTS_KPROBES_ON_FTRACE define
  perf kvm stat live: Enable events copying
  perf session: Add option to copy events when queueing
  perf Documentation: Fix typos in perf/Documentation
  perf trace: Use thread_{,_set}_priv helpers
  perf kvm: Use thread_{,_set}_priv helpers
  perf callchain: Create an address space per thread
  perf report: Set callchain_param.record_mode for future use
  perf evlist: Fix for double free in tools/perf stat
  perf test: Add test case for pmu event new style format
  perf tools: Add support to new style format of kernel PMU event
  perf tools: Parse the pmu event prefix and suffix
  Revert "perf tools: Default to cpu// for events v5"
  perf Documentation: Remove Ruplicated docs for powerpc cpu specific events
  perf Documentation: sysfs events/ interfaces
  ...
2014-10-19 11:55:41 -07:00
..
obsolete
removed net_dma: simple removal 2014-09-28 07:05:16 -07:00
stable mm: remove noisy remainder of the scan_unevictable interface 2014-10-09 22:25:55 -04:00
testing Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-10-19 11:55:41 -07:00
README

README

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.


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/stable_api_nonsense.txt.