linux-stable/Documentation/core-api/kernel-api.rst
Linus Torvalds 48ea09cdda hardening updates for v6.2-rc1
- Convert flexible array members, fix -Wstringop-overflow warnings,
   and fix KCFI function type mismatches that went ignored by
   maintainers (Gustavo A. R. Silva, Nathan Chancellor, Kees Cook).
 
 - Remove the remaining side-effect users of ksize() by converting
   dma-buf, btrfs, and coredump to using kmalloc_size_roundup(),
   add more __alloc_size attributes, and introduce full testing
   of all allocator functions. Finally remove the ksize() side-effect
   so that each allocation-aware checker can finally behave without
   exceptions.
 
 - Introduce oops_limit (default 10,000) and warn_limit (default off)
   to provide greater granularity of control for panic_on_oops and
   panic_on_warn (Jann Horn, Kees Cook).
 
 - Introduce overflows_type() and castable_to_type() helpers for
   cleaner overflow checking.
 
 - Improve code generation for strscpy() and update str*() kern-doc.
 
 - Convert strscpy and sigphash tests to KUnit, and expand memcpy
   tests.
 
 - Always use a non-NULL argument for prepare_kernel_cred().
 
 - Disable structleak plugin in FORTIFY KUnit test (Anders Roxell).
 
 - Adjust orphan linker section checking to respect CONFIG_WERROR
   (Xin Li).
 
 - Make sure siginfo is cleared for forced SIGKILL (haifeng.xu).
 
 - Fix um vs FORTIFY warnings for always-NULL arguments.
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Merge tag 'hardening-v6.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull kernel hardening updates from Kees Cook:

 - Convert flexible array members, fix -Wstringop-overflow warnings, and
   fix KCFI function type mismatches that went ignored by maintainers
   (Gustavo A. R. Silva, Nathan Chancellor, Kees Cook)

 - Remove the remaining side-effect users of ksize() by converting
   dma-buf, btrfs, and coredump to using kmalloc_size_roundup(), add
   more __alloc_size attributes, and introduce full testing of all
   allocator functions. Finally remove the ksize() side-effect so that
   each allocation-aware checker can finally behave without exceptions

 - Introduce oops_limit (default 10,000) and warn_limit (default off) to
   provide greater granularity of control for panic_on_oops and
   panic_on_warn (Jann Horn, Kees Cook)

 - Introduce overflows_type() and castable_to_type() helpers for cleaner
   overflow checking

 - Improve code generation for strscpy() and update str*() kern-doc

 - Convert strscpy and sigphash tests to KUnit, and expand memcpy tests

 - Always use a non-NULL argument for prepare_kernel_cred()

 - Disable structleak plugin in FORTIFY KUnit test (Anders Roxell)

 - Adjust orphan linker section checking to respect CONFIG_WERROR (Xin
   Li)

 - Make sure siginfo is cleared for forced SIGKILL (haifeng.xu)

 - Fix um vs FORTIFY warnings for always-NULL arguments

* tag 'hardening-v6.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: (31 commits)
  ksmbd: replace one-element arrays with flexible-array members
  hpet: Replace one-element array with flexible-array member
  um: virt-pci: Avoid GCC non-NULL warning
  signal: Initialize the info in ksignal
  lib: fortify_kunit: build without structleak plugin
  panic: Expose "warn_count" to sysfs
  panic: Introduce warn_limit
  panic: Consolidate open-coded panic_on_warn checks
  exit: Allow oops_limit to be disabled
  exit: Expose "oops_count" to sysfs
  exit: Put an upper limit on how often we can oops
  panic: Separate sysctl logic from CONFIG_SMP
  mm/pgtable: Fix multiple -Wstringop-overflow warnings
  mm: Make ksize() a reporting-only function
  kunit/fortify: Validate __alloc_size attribute results
  drm/sti: Fix return type of sti_{dvo,hda,hdmi}_connector_mode_valid()
  drm/fsl-dcu: Fix return type of fsl_dcu_drm_connector_mode_valid()
  driver core: Add __alloc_size hint to devm allocators
  overflow: Introduce overflows_type() and castable_to_type()
  coredump: Proactively round up to kmalloc bucket size
  ...
2022-12-14 12:20:00 -08:00

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====================
The Linux Kernel API
====================
List Management Functions
=========================
.. kernel-doc:: include/linux/list.h
:internal:
Basic C Library Functions
=========================
When writing drivers, you cannot in general use routines which are from
the C Library. Some of the functions have been found generally useful
and they are listed below. The behaviour of these functions may vary
slightly from those defined by ANSI, and these deviations are noted in
the text.
String Conversions
------------------
.. kernel-doc:: lib/vsprintf.c
:export:
.. kernel-doc:: include/linux/kstrtox.h
:functions: kstrtol kstrtoul
.. kernel-doc:: lib/kstrtox.c
:export:
.. kernel-doc:: lib/string_helpers.c
:export:
String Manipulation
-------------------
.. kernel-doc:: include/linux/fortify-string.h
:internal:
.. kernel-doc:: lib/string.c
:export:
.. kernel-doc:: include/linux/string.h
:internal:
.. kernel-doc:: mm/util.c
:functions: kstrdup kstrdup_const kstrndup kmemdup kmemdup_nul memdup_user
vmemdup_user strndup_user memdup_user_nul
Basic Kernel Library Functions
==============================
The Linux kernel provides more basic utility functions.
Bit Operations
--------------
.. kernel-doc:: include/asm-generic/bitops/instrumented-atomic.h
:internal:
.. kernel-doc:: include/asm-generic/bitops/instrumented-non-atomic.h
:internal:
.. kernel-doc:: include/asm-generic/bitops/instrumented-lock.h
:internal:
Bitmap Operations
-----------------
.. kernel-doc:: lib/bitmap.c
:doc: bitmap introduction
.. kernel-doc:: include/linux/bitmap.h
:doc: declare bitmap
.. kernel-doc:: include/linux/bitmap.h
:doc: bitmap overview
.. kernel-doc:: include/linux/bitmap.h
:doc: bitmap bitops
.. kernel-doc:: lib/bitmap.c
:export:
.. kernel-doc:: lib/bitmap.c
:internal:
.. kernel-doc:: include/linux/bitmap.h
:internal:
Command-line Parsing
--------------------
.. kernel-doc:: lib/cmdline.c
:export:
Sorting
-------
.. kernel-doc:: lib/sort.c
:export:
.. kernel-doc:: lib/list_sort.c
:export:
Text Searching
--------------
.. kernel-doc:: lib/textsearch.c
:doc: ts_intro
.. kernel-doc:: lib/textsearch.c
:export:
.. kernel-doc:: include/linux/textsearch.h
:functions: textsearch_find textsearch_next \
textsearch_get_pattern textsearch_get_pattern_len
CRC and Math Functions in Linux
===============================
Arithmetic Overflow Checking
----------------------------
.. kernel-doc:: include/linux/overflow.h
:internal:
CRC Functions
-------------
.. kernel-doc:: lib/crc4.c
:export:
.. kernel-doc:: lib/crc7.c
:export:
.. kernel-doc:: lib/crc8.c
:export:
.. kernel-doc:: lib/crc16.c
:export:
.. kernel-doc:: lib/crc32.c
.. kernel-doc:: lib/crc-ccitt.c
:export:
.. kernel-doc:: lib/crc-itu-t.c
:export:
Base 2 log and power Functions
------------------------------
.. kernel-doc:: include/linux/log2.h
:internal:
Integer power Functions
-----------------------
.. kernel-doc:: lib/math/int_pow.c
:export:
.. kernel-doc:: lib/math/int_sqrt.c
:export:
Division Functions
------------------
.. kernel-doc:: include/asm-generic/div64.h
:functions: do_div
.. kernel-doc:: include/linux/math64.h
:internal:
.. kernel-doc:: lib/math/gcd.c
:export:
UUID/GUID
---------
.. kernel-doc:: lib/uuid.c
:export:
Kernel IPC facilities
=====================
IPC utilities
-------------
.. kernel-doc:: ipc/util.c
:internal:
FIFO Buffer
===========
kfifo interface
---------------
.. kernel-doc:: include/linux/kfifo.h
:internal:
relay interface support
=======================
Relay interface support is designed to provide an efficient mechanism
for tools and facilities to relay large amounts of data from kernel
space to user space.
relay interface
---------------
.. kernel-doc:: kernel/relay.c
:export:
.. kernel-doc:: kernel/relay.c
:internal:
Module Support
==============
Module Loading
--------------
.. kernel-doc:: kernel/kmod.c
:export:
Inter Module support
--------------------
Refer to the files in kernel/module/ for more information.
Hardware Interfaces
===================
DMA Channels
------------
.. kernel-doc:: kernel/dma.c
:export:
Resources Management
--------------------
.. kernel-doc:: kernel/resource.c
:internal:
.. kernel-doc:: kernel/resource.c
:export:
MTRR Handling
-------------
.. kernel-doc:: arch/x86/kernel/cpu/mtrr/mtrr.c
:export:
Security Framework
==================
.. kernel-doc:: security/security.c
:internal:
.. kernel-doc:: security/inode.c
:export:
Audit Interfaces
================
.. kernel-doc:: kernel/audit.c
:export:
.. kernel-doc:: kernel/auditsc.c
:internal:
.. kernel-doc:: kernel/auditfilter.c
:internal:
Accounting Framework
====================
.. kernel-doc:: kernel/acct.c
:internal:
Block Devices
=============
.. kernel-doc:: include/linux/bio.h
.. kernel-doc:: block/blk-core.c
:export:
.. kernel-doc:: block/blk-core.c
:internal:
.. kernel-doc:: block/blk-map.c
:export:
.. kernel-doc:: block/blk-sysfs.c
:internal:
.. kernel-doc:: block/blk-settings.c
:export:
.. kernel-doc:: block/blk-flush.c
:export:
.. kernel-doc:: block/blk-lib.c
:export:
.. kernel-doc:: block/blk-integrity.c
:export:
.. kernel-doc:: kernel/trace/blktrace.c
:internal:
.. kernel-doc:: block/genhd.c
:internal:
.. kernel-doc:: block/genhd.c
:export:
.. kernel-doc:: block/bdev.c
:export:
Char devices
============
.. kernel-doc:: fs/char_dev.c
:export:
Clock Framework
===============
The clock framework defines programming interfaces to support software
management of the system clock tree. This framework is widely used with
System-On-Chip (SOC) platforms to support power management and various
devices which may need custom clock rates. Note that these "clocks"
don't relate to timekeeping or real time clocks (RTCs), each of which
have separate frameworks. These :c:type:`struct clk <clk>`
instances may be used to manage for example a 96 MHz signal that is used
to shift bits into and out of peripherals or busses, or otherwise
trigger synchronous state machine transitions in system hardware.
Power management is supported by explicit software clock gating: unused
clocks are disabled, so the system doesn't waste power changing the
state of transistors that aren't in active use. On some systems this may
be backed by hardware clock gating, where clocks are gated without being
disabled in software. Sections of chips that are powered but not clocked
may be able to retain their last state. This low power state is often
called a *retention mode*. This mode still incurs leakage currents,
especially with finer circuit geometries, but for CMOS circuits power is
mostly used by clocked state changes.
Power-aware drivers only enable their clocks when the device they manage
is in active use. Also, system sleep states often differ according to
which clock domains are active: while a "standby" state may allow wakeup
from several active domains, a "mem" (suspend-to-RAM) state may require
a more wholesale shutdown of clocks derived from higher speed PLLs and
oscillators, limiting the number of possible wakeup event sources. A
driver's suspend method may need to be aware of system-specific clock
constraints on the target sleep state.
Some platforms support programmable clock generators. These can be used
by external chips of various kinds, such as other CPUs, multimedia
codecs, and devices with strict requirements for interface clocking.
.. kernel-doc:: include/linux/clk.h
:internal:
Synchronization Primitives
==========================
Read-Copy Update (RCU)
----------------------
.. kernel-doc:: include/linux/rcupdate.h
.. kernel-doc:: kernel/rcu/tree.c
.. kernel-doc:: kernel/rcu/tree_exp.h
.. kernel-doc:: kernel/rcu/update.c
.. kernel-doc:: include/linux/srcu.h
.. kernel-doc:: kernel/rcu/srcutree.c
.. kernel-doc:: include/linux/rculist_bl.h
.. kernel-doc:: include/linux/rculist.h
.. kernel-doc:: include/linux/rculist_nulls.h
.. kernel-doc:: include/linux/rcu_sync.h
.. kernel-doc:: kernel/rcu/sync.c