init/Kconfig

   1 config DEFCONFIG_LIST
   2         string
   3         depends on !UML
   4         option defconfig_list
   5         default "/lib/modules/$UNAME_RELEASE/.config"
   6         default "/etc/kernel-config"
   7         default "/boot/config-$UNAME_RELEASE"
   8         default "arch/$ARCH/defconfig"
   9
  10 menu "Code maturity level options"
  11
  12 config EXPERIMENTAL
  13         bool "Prompt for development and/or incomplete code/drivers"
  14         ---help---
  15           Some of the various things that Linux supports (such as network
  16           drivers, file systems, network protocols, etc.) can be in a state
  17           of development where the functionality, stability, or the level of
  18           testing is not yet high enough for general use. This is usually
  19           known as the "alpha-test" phase among developers. If a feature is
  20           currently in alpha-test, then the developers usually discourage
  21           uninformed widespread use of this feature by the general public to
  22           avoid "Why doesn't this work?" type mail messages. However, active
  23           testing and use of these systems is welcomed. Just be aware that it
  24           may not meet the normal level of reliability or it may fail to work
  25           in some special cases. Detailed bug reports from people familiar
  26           with the kernel internals are usually welcomed by the developers
  27           (before submitting bug reports, please read the documents
  28           <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
  29           <file:Documentation/BUG-HUNTING>, and
  30           <file:Documentation/oops-tracing.txt> in the kernel source).
  31
  32           This option will also make obsoleted drivers available. These are
  33           drivers that have been replaced by something else, and/or are
  34           scheduled to be removed in a future kernel release.
  35
  36           Unless you intend to help test and develop a feature or driver that
  37           falls into this category, or you have a situation that requires
  38           using these features, you should probably say N here, which will
  39           cause the configurator to present you with fewer choices. If
  40           you say Y here, you will be offered the choice of using features or
  41           drivers that are currently considered to be in the alpha-test phase.
  42
  43 config BROKEN
  44         bool
  45
  46 config BROKEN_ON_SMP
  47         bool
  48         depends on BROKEN || !SMP
  49         default y
  50
  51 config LOCK_KERNEL
  52         bool
  53         depends on SMP || PREEMPT
  54         default y
  55
  56 config INIT_ENV_ARG_LIMIT
  57         int
  58         default 32 if !UML
  59         default 128 if UML
  60         help
  61           Maximum of each of the number of arguments and environment
  62           variables passed to init from the kernel command line.
  63
  64 endmenu
  65
  66 menu "General setup"
  67
  68 config LOCALVERSION
  69         string "Local version - append to kernel release"
  70         help
  71           Append an extra string to the end of your kernel version.
  72           This will show up when you type uname, for example.
  73           The string you set here will be appended after the contents of
  74           any files with a filename matching localversion* in your
  75           object and source tree, in that order.  Your total string can
  76           be a maximum of 64 characters.
  77
  78 config LOCALVERSION_AUTO
  79         bool "Automatically append version information to the version string"
  80         default y
  81         help
  82           This will try to automatically determine if the current tree is a
  83           release tree by looking for git tags that belong to the current
  84           top of tree revision.
  85
  86           A string of the format -gxxxxxxxx will be added to the localversion
  87           if a git-based tree is found.  The string generated by this will be
  88           appended after any matching localversion* files, and after the value
  89           set in CONFIG_LOCALVERSION.
  90
  91           (The actual string used here is the first eight characters produced
  92           by running the command:
  93
  94             $ git rev-parse --verify HEAD
  95
  96           which is done within the script "scripts/setlocalversion".)
  97
  98 config SWAP
  99         bool "Support for paging of anonymous memory (swap)"
 100         depends on MMU && BLOCK
 101         default y
 102         help
 103           This option allows you to choose whether you want to have support
 104           for so called swap devices or swap files in your kernel that are
 105           used to provide more virtual memory than the actual RAM present
 106           in your computer.  If unsure say Y.
 107
 108 config SYSVIPC
 109         bool "System V IPC"
 110         ---help---
 111           Inter Process Communication is a suite of library functions and
 112           system calls which let processes (running programs) synchronize and
 113           exchange information. It is generally considered to be a good thing,
 114           and some programs won't run unless you say Y here. In particular, if
 115           you want to run the DOS emulator dosemu under Linux (read the
 116           DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
 117           you'll need to say Y here.
 118
 119           You can find documentation about IPC with "info ipc" and also in
 120           section 6.4 of the Linux Programmer's Guide, available from
 121           <http://www.tldp.org/guides.html>.
 122
 123 config IPC_NS
 124         bool "IPC Namespaces"
 125         depends on SYSVIPC
 126         default n
 127         help
 128           Support ipc namespaces.  This allows containers, i.e. virtual
 129           environments, to use ipc namespaces to provide different ipc
 130           objects for different servers.  If unsure, say N.
 131
 132 config SYSVIPC_SYSCTL
 133         bool
 134         depends on SYSVIPC
 135         depends on SYSCTL
 136         default y
 137
 138 config POSIX_MQUEUE
 139         bool "POSIX Message Queues"
 140         depends on NET && EXPERIMENTAL
 141         ---help---
 142           POSIX variant of message queues is a part of IPC. In POSIX message
 143           queues every message has a priority which decides about succession
 144           of receiving it by a process. If you want to compile and run
 145           programs written e.g. for Solaris with use of its POSIX message
 146           queues (functions mq_*) say Y here. To use this feature you will
 147           also need mqueue library, available from
 148           <http://www.mat.uni.torun.pl/~wrona/posix_ipc/>
 149
 150           POSIX message queues are visible as a filesystem called 'mqueue'
 151           and can be mounted somewhere if you want to do filesystem
 152           operations on message queues.
 153
 154           If unsure, say Y.
 155
 156 config BSD_PROCESS_ACCT
 157         bool "BSD Process Accounting"
 158         help
 159           If you say Y here, a user level program will be able to instruct the
 160           kernel (via a special system call) to write process accounting
 161           information to a file: whenever a process exits, information about
 162           that process will be appended to the file by the kernel.  The
 163           information includes things such as creation time, owning user,
 164           command name, memory usage, controlling terminal etc. (the complete
 165           list is in the struct acct in <file:include/linux/acct.h>).  It is
 166           up to the user level program to do useful things with this
 167           information.  This is generally a good idea, so say Y.
 168
 169 config BSD_PROCESS_ACCT_V3
 170         bool "BSD Process Accounting version 3 file format"
 171         depends on BSD_PROCESS_ACCT
 172         default n
 173         help
 174           If you say Y here, the process accounting information is written
 175           in a new file format that also logs the process IDs of each
 176           process and it's parent. Note that this file format is incompatible
 177           with previous v0/v1/v2 file formats, so you will need updated tools
 178           for processing it. A preliminary version of these tools is available
 179           at <http://www.physik3.uni-rostock.de/tim/kernel/utils/acct/>.
 180
 181 config TASKSTATS
 182         bool "Export task/process statistics through netlink (EXPERIMENTAL)"
 183         depends on NET
 184         default n
 185         help
 186           Export selected statistics for tasks/processes through the
 187           generic netlink interface. Unlike BSD process accounting, the
 188           statistics are available during the lifetime of tasks/processes as
 189           responses to commands. Like BSD accounting, they are sent to user
 190           space on task exit.
 191
 192           Say N if unsure.
 193
 194 config TASK_DELAY_ACCT
 195         bool "Enable per-task delay accounting (EXPERIMENTAL)"
 196         depends on TASKSTATS
 197         help
 198           Collect information on time spent by a task waiting for system
 199           resources like cpu, synchronous block I/O completion and swapping
 200           in pages. Such statistics can help in setting a task's priorities
 201           relative to other tasks for cpu, io, rss limits etc.
 202
 203           Say N if unsure.
 204
 205 config TASK_XACCT
 206         bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
 207         depends on TASKSTATS
 208         help
 209           Collect extended task accounting data and send the data
 210           to userland for processing over the taskstats interface.
 211
 212           Say N if unsure.
 213
 214 config TASK_IO_ACCOUNTING
 215         bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
 216         depends on TASK_XACCT
 217         help
 218           Collect information on the number of bytes of storage I/O which this
 219           task has caused.
 220
 221           Say N if unsure.
 222
 223 config UTS_NS
 224         bool "UTS Namespaces"
 225         default n
 226         help
 227           Support uts namespaces.  This allows containers, i.e.
 228           vservers, to use uts namespaces to provide different
 229           uts info for different servers.  If unsure, say N.
 230
 231 config AUDIT
 232         bool "Auditing support"
 233         depends on NET
 234         help
 235           Enable auditing infrastructure that can be used with another
 236           kernel subsystem, such as SELinux (which requires this for
 237           logging of avc messages output).  Does not do system-call
 238           auditing without CONFIG_AUDITSYSCALL.
 239
 240 config AUDITSYSCALL
 241         bool "Enable system-call auditing support"
 242         depends on AUDIT && (X86 || PPC || PPC64 || S390 || IA64 || UML || SPARC64)
 243         default y if SECURITY_SELINUX
 244         help
 245           Enable low-overhead system-call auditing infrastructure that
 246           can be used independently or with another kernel subsystem,
 247           such as SELinux.  To use audit's filesystem watch feature, please
 248           ensure that INOTIFY is configured.
 249
 250 config IKCONFIG
 251         tristate "Kernel .config support"
 252         ---help---
 253           This option enables the complete Linux kernel ".config" file
 254           contents to be saved in the kernel. It provides documentation
 255           of which kernel options are used in a running kernel or in an
 256           on-disk kernel.  This information can be extracted from the kernel
 257           image file with the script scripts/extract-ikconfig and used as
 258           input to rebuild the current kernel or to build another kernel.
 259           It can also be extracted from a running kernel by reading
 260           /proc/config.gz if enabled (below).
 261
 262 config IKCONFIG_PROC
 263         bool "Enable access to .config through /proc/config.gz"
 264         depends on IKCONFIG && PROC_FS
 265         ---help---
 266           This option enables access to the kernel configuration file
 267           through /proc/config.gz.
 268
 269 config LOG_BUF_SHIFT
 270         int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
 271         range 12 21
 272         default 17 if S390 || LOCKDEP
 273         default 16 if X86_NUMAQ || IA64
 274         default 15 if SMP
 275         default 14
 276         help
 277           Select kernel log buffer size as a power of 2.
 278           Defaults and Examples:
 279                      17 => 128 KB for S/390
 280                      16 => 64 KB for x86 NUMAQ or IA-64
 281                      15 => 32 KB for SMP
 282                      14 => 16 KB for uniprocessor
 283                      13 =>  8 KB
 284                      12 =>  4 KB
 285
 286 config CPUSETS
 287         bool "Cpuset support"
 288         depends on SMP
 289         help
 290           This option will let you create and manage CPUSETs which
 291           allow dynamically partitioning a system into sets of CPUs and
 292           Memory Nodes and assigning tasks to run only within those sets.
 293           This is primarily useful on large SMP or NUMA systems.
 294
 295           Say N if unsure.
 296
 297 config SYSFS_DEPRECATED
 298         bool "Create deprecated sysfs files"
 299         default y
 300         help
 301           This option creates deprecated symlinks such as the
 302           "device"-link, the <subsystem>:<name>-link, and the
 303           "bus"-link. It may also add deprecated key in the
 304           uevent environment.
 305           None of these features or values should be used today, as
 306           they export driver core implementation details to userspace
 307           or export properties which can't be kept stable across kernel
 308           releases.
 309
 310           If enabled, this option will also move any device structures
 311           that belong to a class, back into the /sys/class hierarchy, in
 312           order to support older versions of udev.
 313
 314           If you are using a distro that was released in 2006 or later,
 315           it should be safe to say N here.
 316
 317 config RELAY
 318         bool "Kernel->user space relay support (formerly relayfs)"
 319         help
 320           This option enables support for relay interface support in
 321           certain file systems (such as debugfs).
 322           It is designed to provide an efficient mechanism for tools and
 323           facilities to relay large amounts of data from kernel space to
 324           user space.
 325
 326           If unsure, say N.
 327
 328 config BLK_DEV_INITRD
 329         bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
 330         depends on BROKEN || !FRV
 331         help
 332           The initial RAM filesystem is a ramfs which is loaded by the
 333           boot loader (loadlin or lilo) and that is mounted as root
 334           before the normal boot procedure. It is typically used to
 335           load modules needed to mount the "real" root file system,
 336           etc. See <file:Documentation/initrd.txt> for details.
 337
 338           If RAM disk support (BLK_DEV_RAM) is also included, this
 339           also enables initial RAM disk (initrd) support and adds
 340           15 Kbytes (more on some other architectures) to the kernel size.
 341
 342           If unsure say Y.
 343
 344 if BLK_DEV_INITRD
 345
 346 source "usr/Kconfig"
 347
 348 endif
 349
 350 config CC_OPTIMIZE_FOR_SIZE
 351         bool "Optimize for size (Look out for broken compilers!)"
 352         default y
 353         depends on ARM || H8300 || EXPERIMENTAL
 354         help
 355           Enabling this option will pass "-Os" instead of "-O2" to gcc
 356           resulting in a smaller kernel.
 357
 358           WARNING: some versions of gcc may generate incorrect code with this
 359           option.  If problems are observed, a gcc upgrade may be needed.
 360
 361           If unsure, say N.
 362
 363 config SYSCTL
 364         bool
 365
 366 menuconfig EMBEDDED
 367         bool "Configure standard kernel features (for small systems)"
 368         help
 369           This option allows certain base kernel options and settings
 370           to be disabled or tweaked. This is for specialized
 371           environments which can tolerate a "non-standard" kernel.
 372           Only use this if you really know what you are doing.
 373
 374 config UID16
 375         bool "Enable 16-bit UID system calls" if EMBEDDED
 376         depends on ARM || BFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && SPARC32_COMPAT) || UML || (X86_64 && IA32_EMULATION)
 377         default y
 378         help
 379           This enables the legacy 16-bit UID syscall wrappers.
 380
 381 config SYSCTL_SYSCALL
 382         bool "Sysctl syscall support" if EMBEDDED
 383         default y
 384         select SYSCTL
 385         ---help---
 386           sys_sysctl uses binary paths that have been found challenging
 387           to properly maintain and use.  The interface in /proc/sys
 388           using paths with ascii names is now the primary path to this
 389           information.
 390
 391           Almost nothing using the binary sysctl interface so if you are
 392           trying to save some space it is probably safe to disable this,
 393           making your kernel marginally smaller.
 394
 395           If unsure say Y here.
 396
 397 config KALLSYMS
 398          bool "Load all symbols for debugging/ksymoops" if EMBEDDED
 399          default y
 400          help
 401            Say Y here to let the kernel print out symbolic crash information and
 402            symbolic stack backtraces. This increases the size of the kernel
 403            somewhat, as all symbols have to be loaded into the kernel image.
 404
 405 config KALLSYMS_ALL
 406         bool "Include all symbols in kallsyms"
 407         depends on DEBUG_KERNEL && KALLSYMS
 408         help
 409            Normally kallsyms only contains the symbols of functions, for nicer
 410            OOPS messages.  Some debuggers can use kallsyms for other
 411            symbols too: say Y here to include all symbols, if you need them
 412            and you don't care about adding 300k to the size of your kernel.
 413
 414            Say N.
 415
 416 config KALLSYMS_EXTRA_PASS
 417         bool "Do an extra kallsyms pass"
 418         depends on KALLSYMS
 419         help
 420            If kallsyms is not working correctly, the build will fail with
 421            inconsistent kallsyms data.  If that occurs, log a bug report and
 422            turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
 423            Always say N here unless you find a bug in kallsyms, which must be
 424            reported.  KALLSYMS_EXTRA_PASS is only a temporary workaround while
 425            you wait for kallsyms to be fixed.
 426
 427
 428 config HOTPLUG
 429         bool "Support for hot-pluggable devices" if EMBEDDED
 430         default y
 431         help
 432           This option is provided for the case where no hotplug or uevent
 433           capabilities is wanted by the kernel.  You should only consider
 434           disabling this option for embedded systems that do not use modules, a
 435           dynamic /dev tree, or dynamic device discovery.  Just say Y.
 436
 437 config PRINTK
 438         default y
 439         bool "Enable support for printk" if EMBEDDED
 440         help
 441           This option enables normal printk support. Removing it
 442           eliminates most of the message strings from the kernel image
 443           and makes the kernel more or less silent. As this makes it
 444           very difficult to diagnose system problems, saying N here is
 445           strongly discouraged.
 446
 447 config BUG
 448         bool "BUG() support" if EMBEDDED
 449         default y
 450         help
 451           Disabling this option eliminates support for BUG and WARN, reducing
 452           the size of your kernel image and potentially quietly ignoring
 453           numerous fatal conditions. You should only consider disabling this
 454           option for embedded systems with no facilities for reporting errors.
 455           Just say Y.
 456
 457 config ELF_CORE
 458         default y
 459         bool "Enable ELF core dumps" if EMBEDDED
 460         help
 461           Enable support for generating core dumps. Disabling saves about 4k.
 462
 463 config BASE_FULL
 464         default y
 465         bool "Enable full-sized data structures for core" if EMBEDDED
 466         help
 467           Disabling this option reduces the size of miscellaneous core
 468           kernel data structures. This saves memory on small machines,
 469           but may reduce performance.
 470
 471 config FUTEX
 472         bool "Enable futex support" if EMBEDDED
 473         default y
 474         select RT_MUTEXES
 475         help
 476           Disabling this option will cause the kernel to be built without
 477           support for "fast userspace mutexes".  The resulting kernel may not
 478           run glibc-based applications correctly.
 479
 480 config EPOLL
 481         bool "Enable eventpoll support" if EMBEDDED
 482         default y
 483         help
 484           Disabling this option will cause the kernel to be built without
 485           support for epoll family of system calls.
 486
 487 config SHMEM
 488         bool "Use full shmem filesystem" if EMBEDDED
 489         default y
 490         depends on MMU
 491         help
 492           The shmem is an internal filesystem used to manage shared memory.
 493           It is backed by swap and manages resource limits. It is also exported
 494           to userspace as tmpfs if TMPFS is enabled. Disabling this
 495           option replaces shmem and tmpfs with the much simpler ramfs code,
 496           which may be appropriate on small systems without swap.
 497
 498 config VM_EVENT_COUNTERS
 499         default y
 500         bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
 501         help
 502           VM event counters are needed for event counts to be shown.
 503           This option allows the disabling of the VM event counters
 504           on EMBEDDED systems.  /proc/vmstat will only show page counts
 505           if VM event counters are disabled.
 506
 507 choice
 508         prompt "Choose SLAB allocator"
 509         default SLAB
 510         help
 511            This option allows to select a slab allocator.
 512
 513 config SLAB
 514         bool "SLAB"
 515         help
 516           The regular slab allocator that is established and known to work
 517           well in all environments. It organizes chache hot objects in
 518           per cpu and per node queues. SLAB is the default choice for
 519           slab allocator.
 520
 521 config SLUB
 522         depends on EXPERIMENTAL && !ARCH_USES_SLAB_PAGE_STRUCT
 523         bool "SLUB (Unqueued Allocator)"
 524         help
 525            SLUB is a slab allocator that minimizes cache line usage
 526            instead of managing queues of cached objects (SLAB approach).
 527            Per cpu caching is realized using slabs of objects instead
 528            of queues of objects. SLUB can use memory efficiently
 529            way and has enhanced diagnostics.
 530
 531 config SLOB
 532 #
 533 #       SLOB cannot support SMP because SLAB_DESTROY_BY_RCU does not work
 534 #       properly.
 535 #
 536         depends on EMBEDDED && !SMP && !SPARSEMEM
 537         bool "SLOB (Simple Allocator)"
 538         help
 539            SLOB replaces the SLAB allocator with a drastically simpler
 540            allocator.  SLOB is more space efficient that SLAB but does not
 541            scale well (single lock for all operations) and is more susceptible
 542            to fragmentation. SLOB it is a great choice to reduce
 543            memory usage and code size for embedded systems.
 544
 545 endchoice
 546
 547 endmenu         # General setup
 548
 549 config RT_MUTEXES
 550         boolean
 551         select PLIST
 552
 553 config TINY_SHMEM
 554         default !SHMEM
 555         bool
 556
 557 config BASE_SMALL
 558         int
 559         default 0 if BASE_FULL
 560         default 1 if !BASE_FULL
 561
 562 menu "Loadable module support"
 563
 564 config MODULES
 565         bool "Enable loadable module support"
 566         help
 567           Kernel modules are small pieces of compiled code which can
 568           be inserted in the running kernel, rather than being
 569           permanently built into the kernel.  You use the "modprobe"
 570           tool to add (and sometimes remove) them.  If you say Y here,
 571           many parts of the kernel can be built as modules (by
 572           answering M instead of Y where indicated): this is most
 573           useful for infrequently used options which are not required
 574           for booting.  For more information, see the man pages for
 575           modprobe, lsmod, modinfo, insmod and rmmod.
 576
 577           If you say Y here, you will need to run "make
 578           modules_install" to put the modules under /lib/modules/
 579           where modprobe can find them (you may need to be root to do
 580           this).
 581
 582           If unsure, say Y.
 583
 584 config MODULE_UNLOAD
 585         bool "Module unloading"
 586         depends on MODULES
 587         help
 588           Without this option you will not be able to unload any
 589           modules (note that some modules may not be unloadable
 590           anyway), which makes your kernel slightly smaller and
 591           simpler.  If unsure, say Y.
 592
 593 config MODULE_FORCE_UNLOAD
 594         bool "Forced module unloading"
 595         depends on MODULE_UNLOAD && EXPERIMENTAL
 596         help
 597           This option allows you to force a module to unload, even if the
 598           kernel believes it is unsafe: the kernel will remove the module
 599           without waiting for anyone to stop using it (using the -f option to
 600           rmmod).  This is mainly for kernel developers and desperate users.
 601           If unsure, say N.
 602
 603 config MODVERSIONS
 604         bool "Module versioning support"
 605         depends on MODULES
 606         help
 607           Usually, you have to use modules compiled with your kernel.
 608           Saying Y here makes it sometimes possible to use modules
 609           compiled for different kernels, by adding enough information
 610           to the modules to (hopefully) spot any changes which would
 611           make them incompatible with the kernel you are running.  If
 612           unsure, say N.
 613
 614 config MODULE_SRCVERSION_ALL
 615         bool "Source checksum for all modules"
 616         depends on MODULES
 617         help
 618           Modules which contain a MODULE_VERSION get an extra "srcversion"
 619           field inserted into their modinfo section, which contains a
 620           sum of the source files which made it.  This helps maintainers
 621           see exactly which source was used to build a module (since
 622           others sometimes change the module source without updating
 623           the version).  With this option, such a "srcversion" field
 624           will be created for all modules.  If unsure, say N.
 625
 626 config KMOD
 627         bool "Automatic kernel module loading"
 628         depends on MODULES
 629         help
 630           Normally when you have selected some parts of the kernel to
 631           be created as kernel modules, you must load them (using the
 632           "modprobe" command) before you can use them. If you say Y
 633           here, some parts of the kernel will be able to load modules
 634           automatically: when a part of the kernel needs a module, it
 635           runs modprobe with the appropriate arguments, thereby
 636           loading the module if it is available.  If unsure, say Y.
 637
 638 config STOP_MACHINE
 639         bool
 640         default y
 641         depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
 642         help
 643           Need stop_machine() primitive.
 644 endmenu
 645
 646 menu "Block layer"
 647 source "block/Kconfig"
 648 endmenu