xref: /openbmc/linux/init/Kconfig (revision 34a1a63e)

menu "Code maturity level options"

config EXPERIMENTAL
	bool "Prompt for development and/or incomplete code/drivers"
	---help---
	  Some of the various things that Linux supports (such as network
	  drivers, file systems, network protocols, etc.) can be in a state
	  of development where the functionality, stability, or the level of
	  testing is not yet high enough for general use. This is usually
	  known as the "alpha-test" phase among developers. If a feature is
	  currently in alpha-test, then the developers usually discourage
	  uninformed widespread use of this feature by the general public to
	  avoid "Why doesn't this work?" type mail messages. However, active
	  testing and use of these systems is welcomed. Just be aware that it
	  may not meet the normal level of reliability or it may fail to work
	  in some special cases. Detailed bug reports from people familiar
	  with the kernel internals are usually welcomed by the developers
	  (before submitting bug reports, please read the documents
	  <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
	  <file:Documentation/BUG-HUNTING>, and
	  <file:Documentation/oops-tracing.txt> in the kernel source).

	  This option will also make obsoleted drivers available. These are
	  drivers that have been replaced by something else, and/or are
	  scheduled to be removed in a future kernel release.

	  Unless you intend to help test and develop a feature or driver that
	  falls into this category, or you have a situation that requires
	  using these features, you should probably say N here, which will
	  cause the configurator to present you with fewer choices. If
	  you say Y here, you will be offered the choice of using features or
	  drivers that are currently considered to be in the alpha-test phase.

config CLEAN_COMPILE
	bool "Select only drivers expected to compile cleanly" if EXPERIMENTAL
	default y
	help
	  Select this option if you don't even want to see the option
	  to configure known-broken drivers.

	  If unsure, say Y

config BROKEN
	bool
	depends on !CLEAN_COMPILE
	default y

config BROKEN_ON_SMP
	bool
	depends on BROKEN || !SMP
	default y

config LOCK_KERNEL
	bool
	depends on SMP || PREEMPT
	default y

config INIT_ENV_ARG_LIMIT
	int
	default 32 if !USERMODE
	default 128 if USERMODE
	help
	  This is the value of the two limits on the number of argument and of
	  env.var passed to init from the kernel command line.

endmenu

menu "General setup"

config LOCALVERSION
	string "Local version - append to kernel release"
	help
	  Append an extra string to the end of your kernel version.
	  This will show up when you type uname, for example.
	  The string you set here will be appended after the contents of
	  any files with a filename matching localversion* in your
	  object and source tree, in that order.  Your total string can
	  be a maximum of 64 characters.

config SWAP
	bool "Support for paging of anonymous memory (swap)"
	depends on MMU
	default y
	help
	  This option allows you to choose whether you want to have support
	  for socalled swap devices or swap files in your kernel that are
	  used to provide more virtual memory than the actual RAM present
	  in your computer.  If unsure say Y.

config SYSVIPC
	bool "System V IPC"
	depends on MMU
	---help---
	  Inter Process Communication is a suite of library functions and
	  system calls which let processes (running programs) synchronize and
	  exchange information. It is generally considered to be a good thing,
	  and some programs won't run unless you say Y here. In particular, if
	  you want to run the DOS emulator dosemu under Linux (read the
	  DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
	  you'll need to say Y here.

	  You can find documentation about IPC with "info ipc" and also in
	  section 6.4 of the Linux Programmer's Guide, available from
	  <http://www.tldp.org/guides.html>.

config POSIX_MQUEUE
	bool "POSIX Message Queues"
	depends on NET && EXPERIMENTAL
	---help---
	  POSIX variant of message queues is a part of IPC. In POSIX message
	  queues every message has a priority which decides about succession
	  of receiving it by a process. If you want to compile and run
	  programs written e.g. for Solaris with use of its POSIX message
	  queues (functions mq_*) say Y here. To use this feature you will
	  also need mqueue library, available from
	  <http://www.mat.uni.torun.pl/~wrona/posix_ipc/>

	  POSIX message queues are visible as a filesystem called 'mqueue'
	  and can be mounted somewhere if you want to do filesystem
	  operations on message queues.

	  If unsure, say Y.

config BSD_PROCESS_ACCT
	bool "BSD Process Accounting"
	help
	  If you say Y here, a user level program will be able to instruct the
	  kernel (via a special system call) to write process accounting
	  information to a file: whenever a process exits, information about
	  that process will be appended to the file by the kernel.  The
	  information includes things such as creation time, owning user,
	  command name, memory usage, controlling terminal etc. (the complete
	  list is in the struct acct in <file:include/linux/acct.h>).  It is
	  up to the user level program to do useful things with this
	  information.  This is generally a good idea, so say Y.

config BSD_PROCESS_ACCT_V3
	bool "BSD Process Accounting version 3 file format"
	depends on BSD_PROCESS_ACCT
	default n
	help
	  If you say Y here, the process accounting information is written
	  in a new file format that also logs the process IDs of each
	  process and it's parent. Note that this file format is incompatible
	  with previous v0/v1/v2 file formats, so you will need updated tools
	  for processing it. A preliminary version of these tools is available
	  at <http://www.physik3.uni-rostock.de/tim/kernel/utils/acct/>.

config SYSCTL
	bool "Sysctl support"
	---help---
	  The sysctl interface provides a means of dynamically changing
	  certain kernel parameters and variables on the fly without requiring
	  a recompile of the kernel or reboot of the system.  The primary
	  interface consists of a system call, but if you say Y to "/proc
	  file system support", a tree of modifiable sysctl entries will be
	  generated beneath the /proc/sys directory. They are explained in the
	  files in <file:Documentation/sysctl/>.  Note that enabling this
	  option will enlarge the kernel by at least 8 KB.

	  As it is generally a good thing, you should say Y here unless
	  building a kernel for install/rescue disks or your system is very
	  limited in memory.

config AUDIT
	bool "Auditing support"
	default y if SECURITY_SELINUX
	help
	  Enable auditing infrastructure that can be used with another
	  kernel subsystem, such as SELinux (which requires this for
	  logging of avc messages output).  Does not do system-call
	  auditing without CONFIG_AUDITSYSCALL.

config AUDITSYSCALL
	bool "Enable system-call auditing support"
	depends on AUDIT && (X86 || PPC64 || ARCH_S390 || IA64 || UML)
	default y if SECURITY_SELINUX
	help
	  Enable low-overhead system-call auditing infrastructure that
	  can be used independently or with another kernel subsystem,
	  such as SELinux.

config HOTPLUG
	bool "Support for hot-pluggable devices" if !ARCH_S390
	default ARCH_S390
	help
	  This option is provided for the case where no in-kernel-tree
	  modules require HOTPLUG functionality, but a module built
	  outside the kernel tree does. Such modules require Y here.

config KOBJECT_UEVENT
	bool "Kernel Userspace Events"
	depends on NET
	default y
	help
	  This option enables the kernel userspace event layer, which is a
	  simple mechanism for kernel-to-user communication over a netlink
	  socket.
	  The goal of the kernel userspace events layer is to provide a simple
	  and efficient events system, that notifies userspace about kobject
	  state changes. This will enable applications to just listen for
	  events instead of polling system devices and files.
	  Hotplug events (kobject addition and removal) are also available on
	  the netlink socket in addition to the execution of /sbin/hotplug if
	  CONFIG_HOTPLUG is enabled.

	  Say Y, unless you are building a system requiring minimal memory
	  consumption.

config IKCONFIG
	bool "Kernel .config support"
	---help---
	  This option enables the complete Linux kernel ".config" file
	  contents to be saved in the kernel. It provides documentation
	  of which kernel options are used in a running kernel or in an
	  on-disk kernel.  This information can be extracted from the kernel
	  image file with the script scripts/extract-ikconfig and used as
	  input to rebuild the current kernel or to build another kernel.
	  It can also be extracted from a running kernel by reading
	  /proc/config.gz if enabled (below).

config IKCONFIG_PROC
	bool "Enable access to .config through /proc/config.gz"
	depends on IKCONFIG && PROC_FS
	---help---
	  This option enables access to the kernel configuration file
	  through /proc/config.gz.

config CPUSETS
	bool "Cpuset support"
	depends on SMP
	help
	  This options will let you create and manage CPUSET's which
	  allow dynamically partitioning a system into sets of CPUs and
	  Memory Nodes and assigning tasks to run only within those sets.
	  This is primarily useful on large SMP or NUMA systems.

	  Say N if unsure.

menuconfig EMBEDDED
	bool "Configure standard kernel features (for small systems)"
	help
	  This option allows certain base kernel options and settings
          to be disabled or tweaked. This is for specialized
          environments which can tolerate a "non-standard" kernel.
          Only use this if you really know what you are doing.

config KALLSYMS
	 bool "Load all symbols for debugging/kksymoops" if EMBEDDED
	 default y
	 help
	   Say Y here to let the kernel print out symbolic crash information and
	   symbolic stack backtraces. This increases the size of the kernel
	   somewhat, as all symbols have to be loaded into the kernel image.

config KALLSYMS_ALL
	bool "Include all symbols in kallsyms"
	depends on DEBUG_KERNEL && KALLSYMS
	help
	   Normally kallsyms only contains the symbols of functions, for nicer
	   OOPS messages.  Some debuggers can use kallsyms for other
	   symbols too: say Y here to include all symbols, and you
	   don't care about adding 300k to the size of your kernel.

	   Say N.

config KALLSYMS_EXTRA_PASS
	bool "Do an extra kallsyms pass"
	depends on KALLSYMS
	help
	   If kallsyms is not working correctly, the build will fail with
	   inconsistent kallsyms data.  If that occurs, log a bug report and
	   turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
	   Always say N here unless you find a bug in kallsyms, which must be
	   reported.  KALLSYMS_EXTRA_PASS is only a temporary workaround while
	   you wait for kallsyms to be fixed.


config PRINTK
	default y
	bool "Enable support for printk" if EMBEDDED
	help
	  This option enables normal printk support. Removing it
	  eliminates most of the message strings from the kernel image
	  and makes the kernel more or less silent. As this makes it
	  very difficult to diagnose system problems, saying N here is
	  strongly discouraged.

config BUG
	bool "BUG() support" if EMBEDDED
	default y
	help
          Disabling this option eliminates support for BUG and WARN, reducing
          the size of your kernel image and potentially quietly ignoring
          numerous fatal conditions. You should only consider disabling this
          option for embedded systems with no facilities for reporting errors.
          Just say Y.

config BASE_FULL
	default y
	bool "Enable full-sized data structures for core" if EMBEDDED
	help
	  Disabling this option reduces the size of miscellaneous core
	  kernel data structures. This saves memory on small machines,
	  but may reduce performance.

config FUTEX
	bool "Enable futex support" if EMBEDDED
	default y
	help
	  Disabling this option will cause the kernel to be built without
	  support for "fast userspace mutexes".  The resulting kernel may not
	  run glibc-based applications correctly.

config EPOLL
	bool "Enable eventpoll support" if EMBEDDED
	default y
	help
	  Disabling this option will cause the kernel to be built without
	  support for epoll family of system calls.

config CC_OPTIMIZE_FOR_SIZE
	bool "Optimize for size" if EMBEDDED
	default y if ARM || H8300
	help
	  Enabling this option will pass "-Os" instead of "-O2" to gcc
	  resulting in a smaller kernel.

	  WARNING: some versions of gcc may generate incorrect code with this
	  option.  If problems are observed, a gcc upgrade may be needed.

	  If unsure, say N.

config SHMEM
	bool "Use full shmem filesystem" if EMBEDDED
	default y
	depends on MMU
	help
	  The shmem is an internal filesystem used to manage shared memory.
	  It is backed by swap and manages resource limits. It is also exported
	  to userspace as tmpfs if TMPFS is enabled. Disabling this
	  option replaces shmem and tmpfs with the much simpler ramfs code,
	  which may be appropriate on small systems without swap.

config CC_ALIGN_FUNCTIONS
	int "Function alignment" if EMBEDDED
	default 0
	help
	  Align the start of functions to the next power-of-two greater than n,
	  skipping up to n bytes.  For instance, 32 aligns functions
	  to the next 32-byte boundary, but 24 would align to the next
	  32-byte boundary only if this can be done by skipping 23 bytes or less.
	  Zero means use compiler's default.

config CC_ALIGN_LABELS
	int "Label alignment" if EMBEDDED
	default 0
	help
	  Align all branch targets to a power-of-two boundary, skipping
	  up to n bytes like ALIGN_FUNCTIONS.  This option can easily
	  make code slower, because it must insert dummy operations for
	  when the branch target is reached in the usual flow of the code.
	  Zero means use compiler's default.

config CC_ALIGN_LOOPS
	int "Loop alignment" if EMBEDDED
	default 0
	help
	  Align loops to a power-of-two boundary, skipping up to n bytes.
	  Zero means use compiler's default.

config CC_ALIGN_JUMPS
	int "Jump alignment" if EMBEDDED
	default 0
	help
	  Align branch targets to a power-of-two boundary, for branch
	  targets where the targets can only be reached by jumping,
	  skipping up to n bytes like ALIGN_FUNCTIONS.  In this case,
	  no dummy operations need be executed.
	  Zero means use compiler's default.

endmenu		# General setup

config TINY_SHMEM
	default !SHMEM
	bool

config BASE_SMALL
	int
	default 0 if BASE_FULL
	default 1 if !BASE_FULL

menu "Loadable module support"

config MODULES
	bool "Enable loadable module support"
	help
	  Kernel modules are small pieces of compiled code which can
	  be inserted in the running kernel, rather than being
	  permanently built into the kernel.  You use the "modprobe"
	  tool to add (and sometimes remove) them.  If you say Y here,
	  many parts of the kernel can be built as modules (by
	  answering M instead of Y where indicated): this is most
	  useful for infrequently used options which are not required
	  for booting.  For more information, see the man pages for
	  modprobe, lsmod, modinfo, insmod and rmmod.

	  If you say Y here, you will need to run "make
	  modules_install" to put the modules under /lib/modules/
	  where modprobe can find them (you may need to be root to do
	  this).

	  If unsure, say Y.

config MODULE_UNLOAD
	bool "Module unloading"
	depends on MODULES
	help
	  Without this option you will not be able to unload any
	  modules (note that some modules may not be unloadable
	  anyway), which makes your kernel slightly smaller and
	  simpler.  If unsure, say Y.

config MODULE_FORCE_UNLOAD
	bool "Forced module unloading"
	depends on MODULE_UNLOAD && EXPERIMENTAL
	help
	  This option allows you to force a module to unload, even if the
	  kernel believes it is unsafe: the kernel will remove the module
	  without waiting for anyone to stop using it (using the -f option to
	  rmmod).  This is mainly for kernel developers and desperate users.
	  If unsure, say N.

config OBSOLETE_MODPARM
	bool
	default y
	depends on MODULES
	help
	  You need this option to use module parameters on modules which
	  have not been converted to the new module parameter system yet.
	  If unsure, say Y.

config MODVERSIONS
	bool "Module versioning support (EXPERIMENTAL)"
	depends on MODULES && EXPERIMENTAL
	help
	  Usually, you have to use modules compiled with your kernel.
	  Saying Y here makes it sometimes possible to use modules
	  compiled for different kernels, by adding enough information
	  to the modules to (hopefully) spot any changes which would
	  make them incompatible with the kernel you are running.  If
	  unsure, say N.

config MODULE_SRCVERSION_ALL
	bool "Source checksum for all modules"
	depends on MODULES
	help
	  Modules which contain a MODULE_VERSION get an extra "srcversion"
	  field inserted into their modinfo section, which contains a
    	  sum of the source files which made it.  This helps maintainers
	  see exactly which source was used to build a module (since
	  others sometimes change the module source without updating
	  the version).  With this option, such a "srcversion" field
	  will be created for all modules.  If unsure, say N.

config KMOD
	bool "Automatic kernel module loading"
	depends on MODULES
	help
	  Normally when you have selected some parts of the kernel to
	  be created as kernel modules, you must load them (using the
	  "modprobe" command) before you can use them. If you say Y
	  here, some parts of the kernel will be able to load modules
	  automatically: when a part of the kernel needs a module, it
	  runs modprobe with the appropriate arguments, thereby
	  loading the module if it is available.  If unsure, say Y.

config STOP_MACHINE
	bool
	default y
	depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
	help
	  Need stop_machine() primitive.
endmenu