init/Kconfig

   1 config ARCH
   2         string
   3         option env="ARCH"
   4
   5 config KERNELVERSION
   6         string
   7         option env="KERNELVERSION"
   8
   9 config DEFCONFIG_LIST
  10         string
  11         depends on !UML
  12         option defconfig_list
  13         default "/lib/modules/$UNAME_RELEASE/.config"
  14         default "/etc/kernel-config"
  15         default "/boot/config-$UNAME_RELEASE"
  16         default "$ARCH_DEFCONFIG"
  17         default "arch/$ARCH/defconfig"
  18
  19 menu "General setup"
  20
  21 config EXPERIMENTAL
  22         bool "Prompt for development and/or incomplete code/drivers"
  23         ---help---
  24           Some of the various things that Linux supports (such as network
  25           drivers, file systems, network protocols, etc.) can be in a state
  26           of development where the functionality, stability, or the level of
  27           testing is not yet high enough for general use. This is usually
  28           known as the "alpha-test" phase among developers. If a feature is
  29           currently in alpha-test, then the developers usually discourage
  30           uninformed widespread use of this feature by the general public to
  31           avoid "Why doesn't this work?" type mail messages. However, active
  32           testing and use of these systems is welcomed. Just be aware that it
  33           may not meet the normal level of reliability or it may fail to work
  34           in some special cases. Detailed bug reports from people familiar
  35           with the kernel internals are usually welcomed by the developers
  36           (before submitting bug reports, please read the documents
  37           <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
  38           <file:Documentation/BUG-HUNTING>, and
  39           <file:Documentation/oops-tracing.txt> in the kernel source).
  40
  41           This option will also make obsoleted drivers available. These are
  42           drivers that have been replaced by something else, and/or are
  43           scheduled to be removed in a future kernel release.
  44
  45           Unless you intend to help test and develop a feature or driver that
  46           falls into this category, or you have a situation that requires
  47           using these features, you should probably say N here, which will
  48           cause the configurator to present you with fewer choices. If
  49           you say Y here, you will be offered the choice of using features or
  50           drivers that are currently considered to be in the alpha-test phase.
  51
  52 config BROKEN
  53         bool
  54
  55 config BROKEN_ON_SMP
  56         bool
  57         depends on BROKEN || !SMP
  58         default y
  59
  60 config LOCK_KERNEL
  61         bool
  62         depends on SMP || PREEMPT
  63         default y
  64
  65 config INIT_ENV_ARG_LIMIT
  66         int
  67         default 32 if !UML
  68         default 128 if UML
  69         help
  70           Maximum of each of the number of arguments and environment
  71           variables passed to init from the kernel command line.
  72
  73
  74 config LOCALVERSION
  75         string "Local version - append to kernel release"
  76         help
  77           Append an extra string to the end of your kernel version.
  78           This will show up when you type uname, for example.
  79           The string you set here will be appended after the contents of
  80           any files with a filename matching localversion* in your
  81           object and source tree, in that order.  Your total string can
  82           be a maximum of 64 characters.
  83
  84 config LOCALVERSION_AUTO
  85         bool "Automatically append version information to the version string"
  86         default y
  87         help
  88           This will try to automatically determine if the current tree is a
  89           release tree by looking for git tags that belong to the current
  90           top of tree revision.
  91
  92           A string of the format -gxxxxxxxx will be added to the localversion
  93           if a git-based tree is found.  The string generated by this will be
  94           appended after any matching localversion* files, and after the value
  95           set in CONFIG_LOCALVERSION.
  96
  97           (The actual string used here is the first eight characters produced
  98           by running the command:
  99
 100             $ git rev-parse --verify HEAD
 101
 102           which is done within the script "scripts/setlocalversion".)
 103
 104 config SWAP
 105         bool "Support for paging of anonymous memory (swap)"
 106         depends on MMU && BLOCK
 107         default y
 108         help
 109           This option allows you to choose whether you want to have support
 110           for so called swap devices or swap files in your kernel that are
 111           used to provide more virtual memory than the actual RAM present
 112           in your computer.  If unsure say Y.
 113
 114 config SYSVIPC
 115         bool "System V IPC"
 116         ---help---
 117           Inter Process Communication is a suite of library functions and
 118           system calls which let processes (running programs) synchronize and
 119           exchange information. It is generally considered to be a good thing,
 120           and some programs won't run unless you say Y here. In particular, if
 121           you want to run the DOS emulator dosemu under Linux (read the
 122           DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
 123           you'll need to say Y here.
 124
 125           You can find documentation about IPC with "info ipc" and also in
 126           section 6.4 of the Linux Programmer's Guide, available from
 127           <http://www.tldp.org/guides.html>.
 128
 129 config SYSVIPC_SYSCTL
 130         bool
 131         depends on SYSVIPC
 132         depends on SYSCTL
 133         default y
 134
 135 config POSIX_MQUEUE
 136         bool "POSIX Message Queues"
 137         depends on NET && EXPERIMENTAL
 138         ---help---
 139           POSIX variant of message queues is a part of IPC. In POSIX message
 140           queues every message has a priority which decides about succession
 141           of receiving it by a process. If you want to compile and run
 142           programs written e.g. for Solaris with use of its POSIX message
 143           queues (functions mq_*) say Y here.
 144
 145           POSIX message queues are visible as a filesystem called 'mqueue'
 146           and can be mounted somewhere if you want to do filesystem
 147           operations on message queues.
 148
 149           If unsure, say Y.
 150
 151 config BSD_PROCESS_ACCT
 152         bool "BSD Process Accounting"
 153         help
 154           If you say Y here, a user level program will be able to instruct the
 155           kernel (via a special system call) to write process accounting
 156           information to a file: whenever a process exits, information about
 157           that process will be appended to the file by the kernel.  The
 158           information includes things such as creation time, owning user,
 159           command name, memory usage, controlling terminal etc. (the complete
 160           list is in the struct acct in <file:include/linux/acct.h>).  It is
 161           up to the user level program to do useful things with this
 162           information.  This is generally a good idea, so say Y.
 163
 164 config BSD_PROCESS_ACCT_V3
 165         bool "BSD Process Accounting version 3 file format"
 166         depends on BSD_PROCESS_ACCT
 167         default n
 168         help
 169           If you say Y here, the process accounting information is written
 170           in a new file format that also logs the process IDs of each
 171           process and it's parent. Note that this file format is incompatible
 172           with previous v0/v1/v2 file formats, so you will need updated tools
 173           for processing it. A preliminary version of these tools is available
 174           at <http://www.gnu.org/software/acct/>.
 175
 176 config TASKSTATS
 177         bool "Export task/process statistics through netlink (EXPERIMENTAL)"
 178         depends on NET
 179         default n
 180         help
 181           Export selected statistics for tasks/processes through the
 182           generic netlink interface. Unlike BSD process accounting, the
 183           statistics are available during the lifetime of tasks/processes as
 184           responses to commands. Like BSD accounting, they are sent to user
 185           space on task exit.
 186
 187           Say N if unsure.
 188
 189 config TASK_DELAY_ACCT
 190         bool "Enable per-task delay accounting (EXPERIMENTAL)"
 191         depends on TASKSTATS
 192         help
 193           Collect information on time spent by a task waiting for system
 194           resources like cpu, synchronous block I/O completion and swapping
 195           in pages. Such statistics can help in setting a task's priorities
 196           relative to other tasks for cpu, io, rss limits etc.
 197
 198           Say N if unsure.
 199
 200 config TASK_XACCT
 201         bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
 202         depends on TASKSTATS
 203         help
 204           Collect extended task accounting data and send the data
 205           to userland for processing over the taskstats interface.
 206
 207           Say N if unsure.
 208
 209 config TASK_IO_ACCOUNTING
 210         bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
 211         depends on TASK_XACCT
 212         help
 213           Collect information on the number of bytes of storage I/O which this
 214           task has caused.
 215
 216           Say N if unsure.
 217
 218 config AUDIT
 219         bool "Auditing support"
 220         depends on NET
 221         help
 222           Enable auditing infrastructure that can be used with another
 223           kernel subsystem, such as SELinux (which requires this for
 224           logging of avc messages output).  Does not do system-call
 225           auditing without CONFIG_AUDITSYSCALL.
 226
 227 config AUDITSYSCALL
 228         bool "Enable system-call auditing support"
 229         depends on AUDIT && (X86 || PPC || PPC64 || S390 || IA64 || UML || SPARC64|| SUPERH)
 230         default y if SECURITY_SELINUX
 231         help
 232           Enable low-overhead system-call auditing infrastructure that
 233           can be used independently or with another kernel subsystem,
 234           such as SELinux.  To use audit's filesystem watch feature, please
 235           ensure that INOTIFY is configured.
 236
 237 config AUDIT_TREE
 238         def_bool y
 239         depends on AUDITSYSCALL && INOTIFY
 240
 241 config IKCONFIG
 242         tristate "Kernel .config support"
 243         ---help---
 244           This option enables the complete Linux kernel ".config" file
 245           contents to be saved in the kernel. It provides documentation
 246           of which kernel options are used in a running kernel or in an
 247           on-disk kernel.  This information can be extracted from the kernel
 248           image file with the script scripts/extract-ikconfig and used as
 249           input to rebuild the current kernel or to build another kernel.
 250           It can also be extracted from a running kernel by reading
 251           /proc/config.gz if enabled (below).
 252
 253 config IKCONFIG_PROC
 254         bool "Enable access to .config through /proc/config.gz"
 255         depends on IKCONFIG && PROC_FS
 256         ---help---
 257           This option enables access to the kernel configuration file
 258           through /proc/config.gz.
 259
 260 config LOG_BUF_SHIFT
 261         int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
 262         range 12 21
 263         default 17
 264         help
 265           Select kernel log buffer size as a power of 2.
 266           Examples:
 267                      17 => 128 KB
 268                      16 => 64 KB
 269                      15 => 32 KB
 270                      14 => 16 KB
 271                      13 =>  8 KB
 272                      12 =>  4 KB
 273
 274 #
 275 # Architectures with an unreliable sched_clock() should select this:
 276 #
 277 config HAVE_UNSTABLE_SCHED_CLOCK
 278         bool
 279
 280 config GROUP_SCHED
 281         bool "Group CPU scheduler"
 282         depends on EXPERIMENTAL
 283         default n
 284         help
 285           This feature lets CPU scheduler recognize task groups and control CPU
 286           bandwidth allocation to such task groups.
 287           In order to create a group from arbitrary set of processes, use
 288           CONFIG_CGROUPS. (See Control Group support.)
 289
 290 config FAIR_GROUP_SCHED
 291         bool "Group scheduling for SCHED_OTHER"
 292         depends on GROUP_SCHED
 293         default GROUP_SCHED
 294
 295 config RT_GROUP_SCHED
 296         bool "Group scheduling for SCHED_RR/FIFO"
 297         depends on EXPERIMENTAL
 298         depends on GROUP_SCHED
 299         default n
 300         help
 301           This feature lets you explicitly allocate real CPU bandwidth
 302           to users or control groups (depending on the "Basis for grouping tasks"
 303           setting below. If enabled, it will also make it impossible to
 304           schedule realtime tasks for non-root users until you allocate
 305           realtime bandwidth for them.
 306           See Documentation/scheduler/sched-rt-group.txt for more information.
 307
 308 choice
 309         depends on GROUP_SCHED
 310         prompt "Basis for grouping tasks"
 311         default USER_SCHED
 312
 313 config USER_SCHED
 314         bool "user id"
 315         help
 316           This option will choose userid as the basis for grouping
 317           tasks, thus providing equal CPU bandwidth to each user.
 318
 319 config CGROUP_SCHED
 320         bool "Control groups"
 321         depends on CGROUPS
 322         help
 323           This option allows you to create arbitrary task groups
 324           using the "cgroup" pseudo filesystem and control
 325           the cpu bandwidth allocated to each such task group.
 326           Refer to Documentation/cgroups/cgroups.txt for more
 327           information on "cgroup" pseudo filesystem.
 328
 329 endchoice
 330
 331 menuconfig CGROUPS
 332         boolean "Control Group support"
 333         help
 334           This option adds support for grouping sets of processes together, for
 335           use with process control subsystems such as Cpusets, CFS, memory
 336           controls or device isolation.
 337           See
 338                 - Documentation/scheduler/sched-design-CFS.txt  (CFS)
 339                 - Documentation/cgroups/ (features for grouping, isolation
 340                                           and resource control)
 341
 342           Say N if unsure.
 343
 344 if CGROUPS
 345
 346 config CGROUP_DEBUG
 347         bool "Example debug cgroup subsystem"
 348         depends on CGROUPS
 349         default n
 350         help
 351           This option enables a simple cgroup subsystem that
 352           exports useful debugging information about the cgroups
 353           framework.
 354
 355           Say N if unsure.
 356
 357 config CGROUP_NS
 358         bool "Namespace cgroup subsystem"
 359         depends on CGROUPS
 360         help
 361           Provides a simple namespace cgroup subsystem to
 362           provide hierarchical naming of sets of namespaces,
 363           for instance virtual servers and checkpoint/restart
 364           jobs.
 365
 366 config CGROUP_FREEZER
 367         bool "Freezer cgroup subsystem"
 368         depends on CGROUPS
 369         help
 370           Provides a way to freeze and unfreeze all tasks in a
 371           cgroup.
 372
 373 config CGROUP_DEVICE
 374         bool "Device controller for cgroups"
 375         depends on CGROUPS && EXPERIMENTAL
 376         help
 377           Provides a cgroup implementing whitelists for devices which
 378           a process in the cgroup can mknod or open.
 379
 380 config CPUSETS
 381         bool "Cpuset support"
 382         depends on SMP && CGROUPS
 383         help
 384           This option will let you create and manage CPUSETs which
 385           allow dynamically partitioning a system into sets of CPUs and
 386           Memory Nodes and assigning tasks to run only within those sets.
 387           This is primarily useful on large SMP or NUMA systems.
 388
 389           Say N if unsure.
 390
 391 config PROC_PID_CPUSET
 392         bool "Include legacy /proc/<pid>/cpuset file"
 393         depends on CPUSETS
 394         default y
 395
 396 config CGROUP_CPUACCT
 397         bool "Simple CPU accounting cgroup subsystem"
 398         depends on CGROUPS
 399         help
 400           Provides a simple Resource Controller for monitoring the
 401           total CPU consumed by the tasks in a cgroup.
 402
 403 config RESOURCE_COUNTERS
 404         bool "Resource counters"
 405         help
 406           This option enables controller independent resource accounting
 407           infrastructure that works with cgroups.
 408         depends on CGROUPS
 409
 410 config CGROUP_MEM_RES_CTLR
 411         bool "Memory Resource Controller for Control Groups"
 412         depends on CGROUPS && RESOURCE_COUNTERS
 413         select MM_OWNER
 414         help
 415           Provides a memory resource controller that manages both anonymous
 416           memory and page cache. (See Documentation/controllers/memory.txt)
 417
 418           Note that setting this option increases fixed memory overhead
 419           associated with each page of memory in the system. By this,
 420           20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
 421           usage tracking struct at boot. Total amount of this is printed out
 422           at boot.
 423
 424           Only enable when you're ok with these trade offs and really
 425           sure you need the memory resource controller. Even when you enable
 426           this, you can set "cgroup_disable=memory" at your boot option to
 427           disable memory resource controller and you can avoid overheads.
 428           (and lose benefits of memory resource controller)
 429
 430           This config option also selects MM_OWNER config option, which
 431           could in turn add some fork/exit overhead.
 432
 433 config CGROUP_MEM_RES_CTLR_SWAP
 434         bool "Memory Resource Controller Swap Extension(EXPERIMENTAL)"
 435         depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL
 436         help
 437           Add swap management feature to memory resource controller. When you
 438           enable this, you can limit mem+swap usage per cgroup. In other words,
 439           when you disable this, memory resource controller has no cares to
 440           usage of swap...a process can exhaust all of the swap. This extension
 441           is useful when you want to avoid exhaustion swap but this itself
 442           adds more overheads and consumes memory for remembering information.
 443           Especially if you use 32bit system or small memory system, please
 444           be careful about enabling this. When memory resource controller
 445           is disabled by boot option, this will be automatically disabled and
 446           there will be no overhead from this. Even when you set this config=y,
 447           if boot option "noswapaccount" is set, swap will not be accounted.
 448
 449 endif # CGROUPS
 450
 451 config MM_OWNER
 452         bool
 453
 454 config SYSFS_DEPRECATED
 455         bool
 456
 457 config SYSFS_DEPRECATED_V2
 458         bool "Create deprecated sysfs layout for older userspace tools"
 459         depends on SYSFS
 460         default y
 461         select SYSFS_DEPRECATED
 462         help
 463           This option switches the layout of sysfs to the deprecated
 464           version.
 465
 466           The current sysfs layout features a unified device tree at
 467           /sys/devices/, which is able to express a hierarchy between
 468           class devices. If the deprecated option is set to Y, the
 469           unified device tree is split into a bus device tree at
 470           /sys/devices/ and several individual class device trees at
 471           /sys/class/. The class and bus devices will be connected by
 472           "<subsystem>:<name>" and the "device" links. The "block"
 473           class devices, will not show up in /sys/class/block/. Some
 474           subsystems will suppress the creation of some devices which
 475           depend on the unified device tree.
 476
 477           This option is not a pure compatibility option that can
 478           be safely enabled on newer distributions. It will change the
 479           layout of sysfs to the non-extensible deprecated version,
 480           and disable some features, which can not be exported without
 481           confusing older userspace tools. Since 2007/2008 all major
 482           distributions do not enable this option, and ship no tools which
 483           depend on the deprecated layout or this option.
 484
 485           If you are using a new kernel on an older distribution, or use
 486           older userspace tools, you might need to say Y here. Do not say Y,
 487           if the original kernel, that came with your distribution, has
 488           this option set to N.
 489
 490 config RELAY
 491         bool "Kernel->user space relay support (formerly relayfs)"
 492         help
 493           This option enables support for relay interface support in
 494           certain file systems (such as debugfs).
 495           It is designed to provide an efficient mechanism for tools and
 496           facilities to relay large amounts of data from kernel space to
 497           user space.
 498
 499           If unsure, say N.
 500
 501 config NAMESPACES
 502         bool "Namespaces support" if EMBEDDED
 503         default !EMBEDDED
 504         help
 505           Provides the way to make tasks work with different objects using
 506           the same id. For example same IPC id may refer to different objects
 507           or same user id or pid may refer to different tasks when used in
 508           different namespaces.
 509
 510 config UTS_NS
 511         bool "UTS namespace"
 512         depends on NAMESPACES
 513         help
 514           In this namespace tasks see different info provided with the
 515           uname() system call
 516
 517 config IPC_NS
 518         bool "IPC namespace"
 519         depends on NAMESPACES && SYSVIPC
 520         help
 521           In this namespace tasks work with IPC ids which correspond to
 522           different IPC objects in different namespaces
 523
 524 config USER_NS
 525         bool "User namespace (EXPERIMENTAL)"
 526         depends on NAMESPACES && EXPERIMENTAL
 527         help
 528           This allows containers, i.e. vservers, to use user namespaces
 529           to provide different user info for different servers.
 530           If unsure, say N.
 531
 532 config PID_NS
 533         bool "PID Namespaces (EXPERIMENTAL)"
 534         default n
 535         depends on NAMESPACES && EXPERIMENTAL
 536         help
 537           Support process id namespaces.  This allows having multiple
 538           process with the same pid as long as they are in different
 539           pid namespaces.  This is a building block of containers.
 540
 541           Unless you want to work with an experimental feature
 542           say N here.
 543
 544 config NET_NS
 545         bool "Network namespace"
 546         default n
 547         depends on NAMESPACES && EXPERIMENTAL && NET
 548         help
 549           Allow user space to create what appear to be multiple instances
 550           of the network stack.
 551
 552 config BLK_DEV_INITRD
 553         bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
 554         depends on BROKEN || !FRV
 555         help
 556           The initial RAM filesystem is a ramfs which is loaded by the
 557           boot loader (loadlin or lilo) and that is mounted as root
 558           before the normal boot procedure. It is typically used to
 559           load modules needed to mount the "real" root file system,
 560           etc. See <file:Documentation/initrd.txt> for details.
 561
 562           If RAM disk support (BLK_DEV_RAM) is also included, this
 563           also enables initial RAM disk (initrd) support and adds
 564           15 Kbytes (more on some other architectures) to the kernel size.
 565
 566           If unsure say Y.
 567
 568 if BLK_DEV_INITRD
 569
 570 source "usr/Kconfig"
 571
 572 endif
 573
 574 config CC_OPTIMIZE_FOR_SIZE
 575         bool "Optimize for size"
 576         default y
 577         help
 578           Enabling this option will pass "-Os" instead of "-O2" to gcc
 579           resulting in a smaller kernel.
 580
 581           If unsure, say Y.
 582
 583 config SYSCTL
 584         bool
 585
 586 menuconfig EMBEDDED
 587         bool "Configure standard kernel features (for small systems)"
 588         help
 589           This option allows certain base kernel options and settings
 590           to be disabled or tweaked. This is for specialized
 591           environments which can tolerate a "non-standard" kernel.
 592           Only use this if you really know what you are doing.
 593
 594 config UID16
 595         bool "Enable 16-bit UID system calls" if EMBEDDED
 596         depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
 597         default y
 598         help
 599           This enables the legacy 16-bit UID syscall wrappers.
 600
 601 config SYSCTL_SYSCALL
 602         bool "Sysctl syscall support" if EMBEDDED
 603         default y
 604         select SYSCTL
 605         ---help---
 606           sys_sysctl uses binary paths that have been found challenging
 607           to properly maintain and use.  The interface in /proc/sys
 608           using paths with ascii names is now the primary path to this
 609           information.
 610
 611           Almost nothing using the binary sysctl interface so if you are
 612           trying to save some space it is probably safe to disable this,
 613           making your kernel marginally smaller.
 614
 615           If unsure say Y here.
 616
 617 config KALLSYMS
 618          bool "Load all symbols for debugging/ksymoops" if EMBEDDED
 619          default y
 620          help
 621            Say Y here to let the kernel print out symbolic crash information and
 622            symbolic stack backtraces. This increases the size of the kernel
 623            somewhat, as all symbols have to be loaded into the kernel image.
 624
 625 config KALLSYMS_ALL
 626         bool "Include all symbols in kallsyms"
 627         depends on DEBUG_KERNEL && KALLSYMS
 628         help
 629            Normally kallsyms only contains the symbols of functions, for nicer
 630            OOPS messages.  Some debuggers can use kallsyms for other
 631            symbols too: say Y here to include all symbols, if you need them
 632            and you don't care about adding 300k to the size of your kernel.
 633
 634            Say N.
 635
 636 config KALLSYMS_STRIP_GENERATED
 637         bool "Strip machine generated symbols from kallsyms"
 638         depends on KALLSYMS_ALL
 639         default y
 640         help
 641           Say N if you want kallsyms to retain even machine generated symbols.
 642
 643 config KALLSYMS_EXTRA_PASS
 644         bool "Do an extra kallsyms pass"
 645         depends on KALLSYMS
 646         help
 647            If kallsyms is not working correctly, the build will fail with
 648            inconsistent kallsyms data.  If that occurs, log a bug report and
 649            turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
 650            Always say N here unless you find a bug in kallsyms, which must be
 651            reported.  KALLSYMS_EXTRA_PASS is only a temporary workaround while
 652            you wait for kallsyms to be fixed.
 653
 654
 655 config HOTPLUG
 656         bool "Support for hot-pluggable devices" if EMBEDDED
 657         default y
 658         help
 659           This option is provided for the case where no hotplug or uevent
 660           capabilities is wanted by the kernel.  You should only consider
 661           disabling this option for embedded systems that do not use modules, a
 662           dynamic /dev tree, or dynamic device discovery.  Just say Y.
 663
 664 config PRINTK
 665         default y
 666         bool "Enable support for printk" if EMBEDDED
 667         help
 668           This option enables normal printk support. Removing it
 669           eliminates most of the message strings from the kernel image
 670           and makes the kernel more or less silent. As this makes it
 671           very difficult to diagnose system problems, saying N here is
 672           strongly discouraged.
 673
 674 config BUG
 675         bool "BUG() support" if EMBEDDED
 676         default y
 677         help
 678           Disabling this option eliminates support for BUG and WARN, reducing
 679           the size of your kernel image and potentially quietly ignoring
 680           numerous fatal conditions. You should only consider disabling this
 681           option for embedded systems with no facilities for reporting errors.
 682           Just say Y.
 683
 684 config ELF_CORE
 685         default y
 686         bool "Enable ELF core dumps" if EMBEDDED
 687         help
 688           Enable support for generating core dumps. Disabling saves about 4k.
 689
 690 config PCSPKR_PLATFORM
 691         bool "Enable PC-Speaker support" if EMBEDDED
 692         depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
 693         default y
 694         help
 695           This option allows to disable the internal PC-Speaker
 696           support, saving some memory.
 697
 698 config COMPAT_BRK
 699         bool "Disable heap randomization"
 700         default y
 701         help
 702           Randomizing heap placement makes heap exploits harder, but it
 703           also breaks ancient binaries (including anything libc5 based).
 704           This option changes the bootup default to heap randomization
 705           disabled, and can be overriden runtime by setting
 706           /proc/sys/kernel/randomize_va_space to 2.
 707
 708           On non-ancient distros (post-2000 ones) N is usually a safe choice.
 709
 710 config BASE_FULL
 711         default y
 712         bool "Enable full-sized data structures for core" if EMBEDDED
 713         help
 714           Disabling this option reduces the size of miscellaneous core
 715           kernel data structures. This saves memory on small machines,
 716           but may reduce performance.
 717
 718 config FUTEX
 719         bool "Enable futex support" if EMBEDDED
 720         default y
 721         select RT_MUTEXES
 722         help
 723           Disabling this option will cause the kernel to be built without
 724           support for "fast userspace mutexes".  The resulting kernel may not
 725           run glibc-based applications correctly.
 726
 727 config ANON_INODES
 728         bool
 729
 730 config EPOLL
 731         bool "Enable eventpoll support" if EMBEDDED
 732         default y
 733         select ANON_INODES
 734         help
 735           Disabling this option will cause the kernel to be built without
 736           support for epoll family of system calls.
 737
 738 config SIGNALFD
 739         bool "Enable signalfd() system call" if EMBEDDED
 740         select ANON_INODES
 741         default y
 742         help
 743           Enable the signalfd() system call that allows to receive signals
 744           on a file descriptor.
 745
 746           If unsure, say Y.
 747
 748 config TIMERFD
 749         bool "Enable timerfd() system call" if EMBEDDED
 750         select ANON_INODES
 751         default y
 752         help
 753           Enable the timerfd() system call that allows to receive timer
 754           events on a file descriptor.
 755
 756           If unsure, say Y.
 757
 758 config EVENTFD
 759         bool "Enable eventfd() system call" if EMBEDDED
 760         select ANON_INODES
 761         default y
 762         help
 763           Enable the eventfd() system call that allows to receive both
 764           kernel notification (ie. KAIO) or userspace notifications.
 765
 766           If unsure, say Y.
 767
 768 config SHMEM
 769         bool "Use full shmem filesystem" if EMBEDDED
 770         default y
 771         depends on MMU
 772         help
 773           The shmem is an internal filesystem used to manage shared memory.
 774           It is backed by swap and manages resource limits. It is also exported
 775           to userspace as tmpfs if TMPFS is enabled. Disabling this
 776           option replaces shmem and tmpfs with the much simpler ramfs code,
 777           which may be appropriate on small systems without swap.
 778
 779 config AIO
 780         bool "Enable AIO support" if EMBEDDED
 781         default y
 782         help
 783           This option enables POSIX asynchronous I/O which may by used
 784           by some high performance threaded applications. Disabling
 785           this option saves about 7k.
 786
 787 config VM_EVENT_COUNTERS
 788         default y
 789         bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
 790         help
 791           VM event counters are needed for event counts to be shown.
 792           This option allows the disabling of the VM event counters
 793           on EMBEDDED systems.  /proc/vmstat will only show page counts
 794           if VM event counters are disabled.
 795
 796 config PCI_QUIRKS
 797         default y
 798         bool "Enable PCI quirk workarounds" if EMBEDDED
 799         depends on PCI
 800         help
 801           This enables workarounds for various PCI chipset
 802           bugs/quirks. Disable this only if your target machine is
 803           unaffected by PCI quirks.
 804
 805 config SLUB_DEBUG
 806         default y
 807         bool "Enable SLUB debugging support" if EMBEDDED
 808         depends on SLUB && SYSFS
 809         help
 810           SLUB has extensive debug support features. Disabling these can
 811           result in significant savings in code size. This also disables
 812           SLUB sysfs support. /sys/slab will not exist and there will be
 813           no support for cache validation etc.
 814
 815 choice
 816         prompt "Choose SLAB allocator"
 817         default SLUB
 818         help
 819            This option allows to select a slab allocator.
 820
 821 config SLAB
 822         bool "SLAB"
 823         help
 824           The regular slab allocator that is established and known to work
 825           well in all environments. It organizes cache hot objects in
 826           per cpu and per node queues.
 827
 828 config SLUB
 829         bool "SLUB (Unqueued Allocator)"
 830         help
 831            SLUB is a slab allocator that minimizes cache line usage
 832            instead of managing queues of cached objects (SLAB approach).
 833            Per cpu caching is realized using slabs of objects instead
 834            of queues of objects. SLUB can use memory efficiently
 835            and has enhanced diagnostics. SLUB is the default choice for
 836            a slab allocator.
 837
 838 config SLOB
 839         depends on EMBEDDED
 840         bool "SLOB (Simple Allocator)"
 841         help
 842            SLOB replaces the stock allocator with a drastically simpler
 843            allocator. SLOB is generally more space efficient but
 844            does not perform as well on large systems.
 845
 846 endchoice
 847
 848 config PROFILING
 849         bool "Profiling support (EXPERIMENTAL)"
 850         help
 851           Say Y here to enable the extended profiling support mechanisms used
 852           by profilers such as OProfile.
 853
 854 #
 855 # Place an empty function call at each tracepoint site. Can be
 856 # dynamically changed for a probe function.
 857 #
 858 config TRACEPOINTS
 859         bool
 860
 861 config MARKERS
 862         bool "Activate markers"
 863         depends on TRACEPOINTS
 864         help
 865           Place an empty function call at each marker site. Can be
 866           dynamically changed for a probe function.
 867
 868 source "arch/Kconfig"
 869
 870 endmenu         # General setup
 871
 872 config HAVE_GENERIC_DMA_COHERENT
 873         bool
 874         default n
 875
 876 config SLABINFO
 877         bool
 878         depends on PROC_FS
 879         depends on SLAB || SLUB_DEBUG
 880         default y
 881
 882 config RT_MUTEXES
 883         boolean
 884         select PLIST
 885
 886 config BASE_SMALL
 887         int
 888         default 0 if BASE_FULL
 889         default 1 if !BASE_FULL
 890
 891 menuconfig MODULES
 892         bool "Enable loadable module support"
 893         help
 894           Kernel modules are small pieces of compiled code which can
 895           be inserted in the running kernel, rather than being
 896           permanently built into the kernel.  You use the "modprobe"
 897           tool to add (and sometimes remove) them.  If you say Y here,
 898           many parts of the kernel can be built as modules (by
 899           answering M instead of Y where indicated): this is most
 900           useful for infrequently used options which are not required
 901           for booting.  For more information, see the man pages for
 902           modprobe, lsmod, modinfo, insmod and rmmod.
 903
 904           If you say Y here, you will need to run "make
 905           modules_install" to put the modules under /lib/modules/
 906           where modprobe can find them (you may need to be root to do
 907           this).
 908
 909           If unsure, say Y.
 910
 911 if MODULES
 912
 913 config MODULE_FORCE_LOAD
 914         bool "Forced module loading"
 915         default n
 916         help
 917           Allow loading of modules without version information (ie. modprobe
 918           --force).  Forced module loading sets the 'F' (forced) taint flag and
 919           is usually a really bad idea.
 920
 921 config MODULE_UNLOAD
 922         bool "Module unloading"
 923         help
 924           Without this option you will not be able to unload any
 925           modules (note that some modules may not be unloadable
 926           anyway), which makes your kernel smaller, faster
 927           and simpler.  If unsure, say Y.
 928
 929 config MODULE_FORCE_UNLOAD
 930         bool "Forced module unloading"
 931         depends on MODULE_UNLOAD && EXPERIMENTAL
 932         help
 933           This option allows you to force a module to unload, even if the
 934           kernel believes it is unsafe: the kernel will remove the module
 935           without waiting for anyone to stop using it (using the -f option to
 936           rmmod).  This is mainly for kernel developers and desperate users.
 937           If unsure, say N.
 938
 939 config MODVERSIONS
 940         bool "Module versioning support"
 941         help
 942           Usually, you have to use modules compiled with your kernel.
 943           Saying Y here makes it sometimes possible to use modules
 944           compiled for different kernels, by adding enough information
 945           to the modules to (hopefully) spot any changes which would
 946           make them incompatible with the kernel you are running.  If
 947           unsure, say N.
 948
 949 config MODULE_SRCVERSION_ALL
 950         bool "Source checksum for all modules"
 951         help
 952           Modules which contain a MODULE_VERSION get an extra "srcversion"
 953           field inserted into their modinfo section, which contains a
 954           sum of the source files which made it.  This helps maintainers
 955           see exactly which source was used to build a module (since
 956           others sometimes change the module source without updating
 957           the version).  With this option, such a "srcversion" field
 958           will be created for all modules.  If unsure, say N.
 959
 960 endif # MODULES
 961
 962 config INIT_ALL_POSSIBLE
 963         bool
 964         help
 965           Back when each arch used to define their own cpu_online_map and
 966           cpu_possible_map, some of them chose to initialize cpu_possible_map
 967           with all 1s, and others with all 0s.  When they were centralised,
 968           it was better to provide this option than to break all the archs
 969           and have several arch maintainers persuing me down dark alleys.
 970
 971 config STOP_MACHINE
 972         bool
 973         default y
 974         depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
 975         help
 976           Need stop_machine() primitive.
 977
 978 source "block/Kconfig"
 979
 980 config PREEMPT_NOTIFIERS
 981         bool
 982
 983 choice
 984         prompt "RCU Implementation"
 985         default CLASSIC_RCU
 986
 987 config CLASSIC_RCU
 988         bool "Classic RCU"
 989         help
 990           This option selects the classic RCU implementation that is
 991           designed for best read-side performance on non-realtime
 992           systems.
 993
 994           Select this option if you are unsure.
 995
 996 config TREE_RCU
 997         bool "Tree-based hierarchical RCU"
 998         help
 999           This option selects the RCU implementation that is
1000           designed for very large SMP system with hundreds or
1001           thousands of CPUs.
1002
1003 config PREEMPT_RCU
1004         bool "Preemptible RCU"
1005         depends on PREEMPT
1006         help
1007           This option reduces the latency of the kernel by making certain
1008           RCU sections preemptible. Normally RCU code is non-preemptible, if
1009           this option is selected then read-only RCU sections become
1010           preemptible. This helps latency, but may expose bugs due to
1011           now-naive assumptions about each RCU read-side critical section
1012           remaining on a given CPU through its execution.
1013
1014 endchoice
1015
1016 config RCU_TRACE
1017         bool "Enable tracing for RCU"
1018         depends on TREE_RCU || PREEMPT_RCU
1019         help
1020           This option provides tracing in RCU which presents stats
1021           in debugfs for debugging RCU implementation.
1022
1023           Say Y here if you want to enable RCU tracing
1024           Say N if you are unsure.
1025
1026 config RCU_FANOUT
1027         int "Tree-based hierarchical RCU fanout value"
1028         range 2 64 if 64BIT
1029         range 2 32 if !64BIT
1030         depends on TREE_RCU
1031         default 64 if 64BIT
1032         default 32 if !64BIT
1033         help
1034           This option controls the fanout of hierarchical implementations
1035           of RCU, allowing RCU to work efficiently on machines with
1036           large numbers of CPUs.  This value must be at least the cube
1037           root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
1038           systems and up to 262,144 for 64-bit systems.
1039
1040           Select a specific number if testing RCU itself.
1041           Take the default if unsure.
1042
1043 config RCU_FANOUT_EXACT
1044         bool "Disable tree-based hierarchical RCU auto-balancing"
1045         depends on TREE_RCU
1046         default n
1047         help
1048           This option forces use of the exact RCU_FANOUT value specified,
1049           regardless of imbalances in the hierarchy.  This is useful for
1050           testing RCU itself, and might one day be useful on systems with
1051           strong NUMA behavior.
1052
1053           Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
1054
1055           Say N if unsure.
1056
1057 config TREE_RCU_TRACE
1058         def_bool RCU_TRACE && TREE_RCU
1059         select DEBUG_FS
1060         help
1061           This option provides tracing for the TREE_RCU implementation,
1062           permitting Makefile to trivially select kernel/rcutree_trace.c.
1063
1064 config PREEMPT_RCU_TRACE
1065         def_bool RCU_TRACE && PREEMPT_RCU
1066         select DEBUG_FS
1067         help
1068           This option provides tracing for the PREEMPT_RCU implementation,
1069           permitting Makefile to trivially select kernel/rcupreempt_trace.c.