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  42           drivers that have been replaced by something else, and/or are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.txt for more information
 327           on "cgroup" pseudo filesystem.
 328
 329 endchoice
 330
 331 menu "Control Group support"
 332 config CGROUPS
 333         bool "Control Group support"
 334         help
 335           This option add support for grouping sets of processes together, for
 336           use with process control subsystems such as Cpusets, CFS, memory
 337           controls or device isolation.
 338           See
 339                 - Documentation/cpusets.txt     (Cpusets)
 340                 - Documentation/scheduler/sched-design-CFS.txt  (CFS)
 341                 - Documentation/cgroups/ (features for grouping, isolation)
 342                 - Documentation/controllers/ (features for resource control)
 343
 344           Say N if unsure.
 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 "control group freezer 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 CGROUP_CPUACCT
 392         bool "Simple CPU accounting cgroup subsystem"
 393         depends on CGROUPS
 394         help
 395           Provides a simple Resource Controller for monitoring the
 396           total CPU consumed by the tasks in a cgroup
 397
 398 config RESOURCE_COUNTERS
 399         bool "Resource counters"
 400         help
 401           This option enables controller independent resource accounting
 402           infrastructure that works with cgroups
 403         depends on CGROUPS
 404
 405 config CGROUP_MEM_RES_CTLR
 406         bool "Memory Resource Controller for Control Groups"
 407         depends on CGROUPS && RESOURCE_COUNTERS
 408         select MM_OWNER
 409         help
 410           Provides a memory resource controller that manages both anonymous
 411           memory and page cache. (See Documentation/controllers/memory.txt)
 412
 413           Note that setting this option increases fixed memory overhead
 414           associated with each page of memory in the system. By this,
 415           20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
 416           usage tracking struct at boot. Total amount of this is printed out
 417           at boot.
 418
 419           Only enable when you're ok with these trade offs and really
 420           sure you need the memory resource controller. Even when you enable
 421           this, you can set "cgroup_disable=memory" at your boot option to
 422           disable memory resource controller and you can avoid overheads.
 423           (and lose benefits of memory resource controller)
 424
 425           This config option also selects MM_OWNER config option, which
 426           could in turn add some fork/exit overhead.
 427
 428 config MM_OWNER
 429         bool
 430
 431 config CGROUP_MEM_RES_CTLR_SWAP
 432         bool "Memory Resource Controller Swap Extension(EXPERIMENTAL)"
 433         depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL
 434         help
 435           Add swap management feature to memory resource controller. When you
 436           enable this, you can limit mem+swap usage per cgroup. In other words,
 437           when you disable this, memory resource controller has no cares to
 438           usage of swap...a process can exhaust all of the swap. This extension
 439           is useful when you want to avoid exhaustion swap but this itself
 440           adds more overheads and consumes memory for remembering information.
 441           Especially if you use 32bit system or small memory system, please
 442           be careful about enabling this. When memory resource controller
 443           is disabled by boot option, this will be automatically disabled and
 444           there will be no overhead from this. Even when you set this config=y,
 445           if boot option "noswapaccount" is set, swap will not be accounted.
 446
 447
 448 endmenu
 449
 450 config SYSFS_DEPRECATED
 451         bool
 452
 453 config SYSFS_DEPRECATED_V2
 454         bool "Create deprecated sysfs layout for older userspace tools"
 455         depends on SYSFS
 456         default y
 457         select SYSFS_DEPRECATED
 458         help
 459           This option switches the layout of sysfs to the deprecated
 460           version.
 461
 462           The current sysfs layout features a unified device tree at
 463           /sys/devices/, which is able to express a hierarchy between
 464           class devices. If the deprecated option is set to Y, the
 465           unified device tree is split into a bus device tree at
 466           /sys/devices/ and several individual class device trees at
 467           /sys/class/. The class and bus devices will be connected by
 468           "<subsystem>:<name>" and the "device" links. The "block"
 469           class devices, will not show up in /sys/class/block/. Some
 470           subsystems will suppress the creation of some devices which
 471           depend on the unified device tree.
 472
 473           This option is not a pure compatibility option that can
 474           be safely enabled on newer distributions. It will change the
 475           layout of sysfs to the non-extensible deprecated version,
 476           and disable some features, which can not be exported without
 477           confusing older userspace tools. Since 2007/2008 all major
 478           distributions do not enable this option, and ship no tools which
 479           depend on the deprecated layout or this option.
 480
 481           If you are using a new kernel on an older distribution, or use
 482           older userspace tools, you might need to say Y here. Do not say Y,
 483           if the original kernel, that came with your distribution, has
 484           this option set to N.
 485
 486 config PROC_PID_CPUSET
 487         bool "Include legacy /proc/<pid>/cpuset file"
 488         depends on CPUSETS
 489         default y
 490
 491 config RELAY
 492         bool "Kernel->user space relay support (formerly relayfs)"
 493         help
 494           This option enables support for relay interface support in
 495           certain file systems (such as debugfs).
 496           It is designed to provide an efficient mechanism for tools and
 497           facilities to relay large amounts of data from kernel space to
 498           user space.
 499
 500           If unsure, say N.
 501
 502 config NAMESPACES
 503         bool "Namespaces support" if EMBEDDED
 504         default !EMBEDDED
 505         help
 506           Provides the way to make tasks work with different objects using
 507           the same id. For example same IPC id may refer to different objects
 508           or same user id or pid may refer to different tasks when used in
 509           different namespaces.
 510
 511 config UTS_NS
 512         bool "UTS namespace"
 513         depends on NAMESPACES
 514         help
 515           In this namespace tasks see different info provided with the
 516           uname() system call
 517
 518 config IPC_NS
 519         bool "IPC namespace"
 520         depends on NAMESPACES && SYSVIPC
 521         help
 522           In this namespace tasks work with IPC ids which correspond to
 523           different IPC objects in different namespaces
 524
 525 config USER_NS
 526         bool "User namespace (EXPERIMENTAL)"
 527         depends on NAMESPACES && EXPERIMENTAL
 528         help
 529           This allows containers, i.e. vservers, to use user namespaces
 530           to provide different user info for different servers.
 531           If unsure, say N.
 532
 533 config PID_NS
 534         bool "PID Namespaces (EXPERIMENTAL)"
 535         default n
 536         depends on NAMESPACES && EXPERIMENTAL
 537         help
 538           Support process id namespaces.  This allows having multiple
 539           process with the same pid as long as they are in different
 540           pid namespaces.  This is a building block of containers.
 541
 542           Unless you want to work with an experimental feature
 543           say N here.
 544
 545 config BLK_DEV_INITRD
 546         bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
 547         depends on BROKEN || !FRV
 548         help
 549           The initial RAM filesystem is a ramfs which is loaded by the
 550           boot loader (loadlin or lilo) and that is mounted as root
 551           before the normal boot procedure. It is typically used to
 552           load modules needed to mount the "real" root file system,
 553           etc. See <file:Documentation/initrd.txt> for details.
 554
 555           If RAM disk support (BLK_DEV_RAM) is also included, this
 556           also enables initial RAM disk (initrd) support and adds
 557           15 Kbytes (more on some other architectures) to the kernel size.
 558
 559           If unsure say Y.
 560
 561 if BLK_DEV_INITRD
 562
 563 source "usr/Kconfig"
 564
 565 endif
 566
 567 config CC_OPTIMIZE_FOR_SIZE
 568         bool "Optimize for size"
 569         default y
 570         help
 571           Enabling this option will pass "-Os" instead of "-O2" to gcc
 572           resulting in a smaller kernel.
 573
 574           If unsure, say Y.
 575
 576 config SYSCTL
 577         bool
 578
 579 menuconfig EMBEDDED
 580         bool "Configure standard kernel features (for small systems)"
 581         help
 582           This option allows certain base kernel options and settings
 583           to be disabled or tweaked. This is for specialized
 584           environments which can tolerate a "non-standard" kernel.
 585           Only use this if you really know what you are doing.
 586
 587 config UID16
 588         bool "Enable 16-bit UID system calls" if EMBEDDED
 589         depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
 590         default y
 591         help
 592           This enables the legacy 16-bit UID syscall wrappers.
 593
 594 config SYSCTL_SYSCALL
 595         bool "Sysctl syscall support" if EMBEDDED
 596         default y
 597         select SYSCTL
 598         ---help---
 599           sys_sysctl uses binary paths that have been found challenging
 600           to properly maintain and use.  The interface in /proc/sys
 601           using paths with ascii names is now the primary path to this
 602           information.
 603
 604           Almost nothing using the binary sysctl interface so if you are
 605           trying to save some space it is probably safe to disable this,
 606           making your kernel marginally smaller.
 607
 608           If unsure say Y here.
 609
 610 config KALLSYMS
 611          bool "Load all symbols for debugging/ksymoops" if EMBEDDED
 612          default y
 613          help
 614            Say Y here to let the kernel print out symbolic crash information and
 615            symbolic stack backtraces. This increases the size of the kernel
 616            somewhat, as all symbols have to be loaded into the kernel image.
 617
 618 config KALLSYMS_ALL
 619         bool "Include all symbols in kallsyms"
 620         depends on DEBUG_KERNEL && KALLSYMS
 621         help
 622            Normally kallsyms only contains the symbols of functions, for nicer
 623            OOPS messages.  Some debuggers can use kallsyms for other
 624            symbols too: say Y here to include all symbols, if you need them
 625            and you don't care about adding 300k to the size of your kernel.
 626
 627            Say N.
 628
 629 config KALLSYMS_EXTRA_PASS
 630         bool "Do an extra kallsyms pass"
 631         depends on KALLSYMS
 632         help
 633            If kallsyms is not working correctly, the build will fail with
 634            inconsistent kallsyms data.  If that occurs, log a bug report and
 635            turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
 636            Always say N here unless you find a bug in kallsyms, which must be
 637            reported.  KALLSYMS_EXTRA_PASS is only a temporary workaround while
 638            you wait for kallsyms to be fixed.
 639
 640
 641 config HOTPLUG
 642         bool "Support for hot-pluggable devices" if EMBEDDED
 643         default y
 644         help
 645           This option is provided for the case where no hotplug or uevent
 646           capabilities is wanted by the kernel.  You should only consider
 647           disabling this option for embedded systems that do not use modules, a
 648           dynamic /dev tree, or dynamic device discovery.  Just say Y.
 649
 650 config PRINTK
 651         default y
 652         bool "Enable support for printk" if EMBEDDED
 653         help
 654           This option enables normal printk support. Removing it
 655           eliminates most of the message strings from the kernel image
 656           and makes the kernel more or less silent. As this makes it
 657           very difficult to diagnose system problems, saying N here is
 658           strongly discouraged.
 659
 660 config BUG
 661         bool "BUG() support" if EMBEDDED
 662         default y
 663         help
 664           Disabling this option eliminates support for BUG and WARN, reducing
 665           the size of your kernel image and potentially quietly ignoring
 666           numerous fatal conditions. You should only consider disabling this
 667           option for embedded systems with no facilities for reporting errors.
 668           Just say Y.
 669
 670 config ELF_CORE
 671         default y
 672         bool "Enable ELF core dumps" if EMBEDDED
 673         help
 674           Enable support for generating core dumps. Disabling saves about 4k.
 675
 676 config PCSPKR_PLATFORM
 677         bool "Enable PC-Speaker support" if EMBEDDED
 678         depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
 679         default y
 680         help
 681           This option allows to disable the internal PC-Speaker
 682           support, saving some memory.
 683
 684 config COMPAT_BRK
 685         bool "Disable heap randomization"
 686         default y
 687         help
 688           Randomizing heap placement makes heap exploits harder, but it
 689           also breaks ancient binaries (including anything libc5 based).
 690           This option changes the bootup default to heap randomization
 691           disabled, and can be overriden runtime by setting
 692           /proc/sys/kernel/randomize_va_space to 2.
 693
 694           On non-ancient distros (post-2000 ones) N is usually a safe choice.
 695
 696 config BASE_FULL
 697         default y
 698         bool "Enable full-sized data structures for core" if EMBEDDED
 699         help
 700           Disabling this option reduces the size of miscellaneous core
 701           kernel data structures. This saves memory on small machines,
 702           but may reduce performance.
 703
 704 config FUTEX
 705         bool "Enable futex support" if EMBEDDED
 706         default y
 707         select RT_MUTEXES
 708         help
 709           Disabling this option will cause the kernel to be built without
 710           support for "fast userspace mutexes".  The resulting kernel may not
 711           run glibc-based applications correctly.
 712
 713 config ANON_INODES
 714         bool
 715
 716 config EPOLL
 717         bool "Enable eventpoll support" if EMBEDDED
 718         default y
 719         select ANON_INODES
 720         help
 721           Disabling this option will cause the kernel to be built without
 722           support for epoll family of system calls.
 723
 724 config SIGNALFD
 725         bool "Enable signalfd() system call" if EMBEDDED
 726         select ANON_INODES
 727         default y
 728         help
 729           Enable the signalfd() system call that allows to receive signals
 730           on a file descriptor.
 731
 732           If unsure, say Y.
 733
 734 config TIMERFD
 735         bool "Enable timerfd() system call" if EMBEDDED
 736         select ANON_INODES
 737         default y
 738         help
 739           Enable the timerfd() system call that allows to receive timer
 740           events on a file descriptor.
 741
 742           If unsure, say Y.
 743
 744 config EVENTFD
 745         bool "Enable eventfd() system call" if EMBEDDED
 746         select ANON_INODES
 747         default y
 748         help
 749           Enable the eventfd() system call that allows to receive both
 750           kernel notification (ie. KAIO) or userspace notifications.
 751
 752           If unsure, say Y.
 753
 754 config SHMEM
 755         bool "Use full shmem filesystem" if EMBEDDED
 756         default y
 757         depends on MMU
 758         help
 759           The shmem is an internal filesystem used to manage shared memory.
 760           It is backed by swap and manages resource limits. It is also exported
 761           to userspace as tmpfs if TMPFS is enabled. Disabling this
 762           option replaces shmem and tmpfs with the much simpler ramfs code,
 763           which may be appropriate on small systems without swap.
 764
 765 config AIO
 766         bool "Enable AIO support" if EMBEDDED
 767         default y
 768         help
 769           This option enables POSIX asynchronous I/O which may by used
 770           by some high performance threaded applications. Disabling
 771           this option saves about 7k.
 772
 773 config VM_EVENT_COUNTERS
 774         default y
 775         bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
 776         help
 777           VM event counters are needed for event counts to be shown.
 778           This option allows the disabling of the VM event counters
 779           on EMBEDDED systems.  /proc/vmstat will only show page counts
 780           if VM event counters are disabled.
 781
 782 config PCI_QUIRKS
 783         default y
 784         bool "Enable PCI quirk workarounds" if EMBEDDED
 785         depends on PCI
 786         help
 787           This enables workarounds for various PCI chipset
 788           bugs/quirks. Disable this only if your target machine is
 789           unaffected by PCI quirks.
 790
 791 config SLUB_DEBUG
 792         default y
 793         bool "Enable SLUB debugging support" if EMBEDDED
 794         depends on SLUB && SYSFS
 795         help
 796           SLUB has extensive debug support features. Disabling these can
 797           result in significant savings in code size. This also disables
 798           SLUB sysfs support. /sys/slab will not exist and there will be
 799           no support for cache validation etc.
 800
 801 choice
 802         prompt "Choose SLAB allocator"
 803         default SLUB
 804         help
 805            This option allows to select a slab allocator.
 806
 807 config SLAB
 808         bool "SLAB"
 809         help
 810           The regular slab allocator that is established and known to work
 811           well in all environments. It organizes cache hot objects in
 812           per cpu and per node queues.
 813
 814 config SLUB
 815         bool "SLUB (Unqueued Allocator)"
 816         help
 817            SLUB is a slab allocator that minimizes cache line usage
 818            instead of managing queues of cached objects (SLAB approach).
 819            Per cpu caching is realized using slabs of objects instead
 820            of queues of objects. SLUB can use memory efficiently
 821            and has enhanced diagnostics. SLUB is the default choice for
 822            a slab allocator.
 823
 824 config SLOB
 825         depends on EMBEDDED
 826         bool "SLOB (Simple Allocator)"
 827         help
 828            SLOB replaces the stock allocator with a drastically simpler
 829            allocator. SLOB is generally more space efficient but
 830            does not perform as well on large systems.
 831
 832 endchoice
 833
 834 config PROFILING
 835         bool "Profiling support (EXPERIMENTAL)"
 836         help
 837           Say Y here to enable the extended profiling support mechanisms used
 838           by profilers such as OProfile.
 839
 840 #
 841 # Place an empty function call at each tracepoint site. Can be
 842 # dynamically changed for a probe function.
 843 #
 844 config TRACEPOINTS
 845         bool
 846
 847 config MARKERS
 848         bool "Activate markers"
 849         depends on TRACEPOINTS
 850         help
 851           Place an empty function call at each marker site. Can be
 852           dynamically changed for a probe function.
 853
 854 source "arch/Kconfig"
 855
 856 endmenu         # General setup
 857
 858 config HAVE_GENERIC_DMA_COHERENT
 859         bool
 860         default n
 861
 862 config SLABINFO
 863         bool
 864         depends on PROC_FS
 865         depends on SLAB || SLUB_DEBUG
 866         default y
 867
 868 config RT_MUTEXES
 869         boolean
 870         select PLIST
 871
 872 config BASE_SMALL
 873         int
 874         default 0 if BASE_FULL
 875         default 1 if !BASE_FULL
 876
 877 menuconfig MODULES
 878         bool "Enable loadable module support"
 879         help
 880           Kernel modules are small pieces of compiled code which can
 881           be inserted in the running kernel, rather than being
 882           permanently built into the kernel.  You use the "modprobe"
 883           tool to add (and sometimes remove) them.  If you say Y here,
 884           many parts of the kernel can be built as modules (by
 885           answering M instead of Y where indicated): this is most
 886           useful for infrequently used options which are not required
 887           for booting.  For more information, see the man pages for
 888           modprobe, lsmod, modinfo, insmod and rmmod.
 889
 890           If you say Y here, you will need to run "make
 891           modules_install" to put the modules under /lib/modules/
 892           where modprobe can find them (you may need to be root to do
 893           this).
 894
 895           If unsure, say Y.
 896
 897 if MODULES
 898
 899 config MODULE_FORCE_LOAD
 900         bool "Forced module loading"
 901         default n
 902         help
 903           Allow loading of modules without version information (ie. modprobe
 904           --force).  Forced module loading sets the 'F' (forced) taint flag and
 905           is usually a really bad idea.
 906
 907 config MODULE_UNLOAD
 908         bool "Module unloading"
 909         help
 910           Without this option you will not be able to unload any
 911           modules (note that some modules may not be unloadable
 912           anyway), which makes your kernel smaller, faster
 913           and simpler.  If unsure, say Y.
 914
 915 config MODULE_FORCE_UNLOAD
 916         bool "Forced module unloading"
 917         depends on MODULE_UNLOAD && EXPERIMENTAL
 918         help
 919           This option allows you to force a module to unload, even if the
 920           kernel believes it is unsafe: the kernel will remove the module
 921           without waiting for anyone to stop using it (using the -f option to
 922           rmmod).  This is mainly for kernel developers and desperate users.
 923           If unsure, say N.
 924
 925 config MODVERSIONS
 926         bool "Module versioning support"
 927         help
 928           Usually, you have to use modules compiled with your kernel.
 929           Saying Y here makes it sometimes possible to use modules
 930           compiled for different kernels, by adding enough information
 931           to the modules to (hopefully) spot any changes which would
 932           make them incompatible with the kernel you are running.  If
 933           unsure, say N.
 934
 935 config MODULE_SRCVERSION_ALL
 936         bool "Source checksum for all modules"
 937         help
 938           Modules which contain a MODULE_VERSION get an extra "srcversion"
 939           field inserted into their modinfo section, which contains a
 940           sum of the source files which made it.  This helps maintainers
 941           see exactly which source was used to build a module (since
 942           others sometimes change the module source without updating
 943           the version).  With this option, such a "srcversion" field
 944           will be created for all modules.  If unsure, say N.
 945
 946 endif # MODULES
 947
 948 config INIT_ALL_POSSIBLE
 949         bool
 950         help
 951           Back when each arch used to define their own cpu_online_map and
 952           cpu_possible_map, some of them chose to initialize cpu_possible_map
 953           with all 1s, and others with all 0s.  When they were centralised,
 954           it was better to provide this option than to break all the archs
 955           and have several arch maintainers persuing me down dark alleys.
 956
 957 config STOP_MACHINE
 958         bool
 959         default y
 960         depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
 961         help
 962           Need stop_machine() primitive.
 963
 964 source "block/Kconfig"
 965
 966 config PREEMPT_NOTIFIERS
 967         bool
 968
 969 choice
 970         prompt "RCU Implementation"
 971         default CLASSIC_RCU
 972
 973 config CLASSIC_RCU
 974         bool "Classic RCU"
 975         help
 976           This option selects the classic RCU implementation that is
 977           designed for best read-side performance on non-realtime
 978           systems.
 979
 980           Select this option if you are unsure.
 981
 982 config TREE_RCU
 983         bool "Tree-based hierarchical RCU"
 984         help
 985           This option selects the RCU implementation that is
 986           designed for very large SMP system with hundreds or
 987           thousands of CPUs.
 988
 989 config PREEMPT_RCU
 990         bool "Preemptible RCU"
 991         depends on PREEMPT
 992         help
 993           This option reduces the latency of the kernel by making certain
 994           RCU sections preemptible. Normally RCU code is non-preemptible, if
 995           this option is selected then read-only RCU sections become
 996           preemptible. This helps latency, but may expose bugs due to
 997           now-naive assumptions about each RCU read-side critical section
 998           remaining on a given CPU through its execution.
 999
1000 endchoice
1001
1002 config RCU_TRACE
1003         bool "Enable tracing for RCU"
1004         depends on TREE_RCU || PREEMPT_RCU
1005         help
1006           This option provides tracing in RCU which presents stats
1007           in debugfs for debugging RCU implementation.
1008
1009           Say Y here if you want to enable RCU tracing
1010           Say N if you are unsure.
1011
1012 config RCU_FANOUT
1013         int "Tree-based hierarchical RCU fanout value"
1014         range 2 64 if 64BIT
1015         range 2 32 if !64BIT
1016         depends on TREE_RCU
1017         default 64 if 64BIT
1018         default 32 if !64BIT
1019         help
1020           This option controls the fanout of hierarchical implementations
1021           of RCU, allowing RCU to work efficiently on machines with
1022           large numbers of CPUs.  This value must be at least the cube
1023           root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
1024           systems and up to 262,144 for 64-bit systems.
1025
1026           Select a specific number if testing RCU itself.
1027           Take the default if unsure.
1028
1029 config RCU_FANOUT_EXACT
1030         bool "Disable tree-based hierarchical RCU auto-balancing"
1031         depends on TREE_RCU
1032         default n
1033         help
1034           This option forces use of the exact RCU_FANOUT value specified,
1035           regardless of imbalances in the hierarchy.  This is useful for
1036           testing RCU itself, and might one day be useful on systems with
1037           strong NUMA behavior.
1038
1039           Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
1040
1041           Say N if unsure.
1042
1043 config TREE_RCU_TRACE
1044         def_bool RCU_TRACE && TREE_RCU
1045         select DEBUG_FS
1046         help
1047           This option provides tracing for the TREE_RCU implementation,
1048           permitting Makefile to trivially select kernel/rcutree_trace.c.
1049
1050 config PREEMPT_RCU_TRACE
1051         def_bool RCU_TRACE && PREEMPT_RCU
1052         select DEBUG_FS
1053         help
1054           This option provides tracing for the PREEMPT_RCU implementation,
1055           permitting Makefile to trivially select kernel/rcupreempt_trace.c.