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  42           drivers that have been replaced by something else, and/or are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 BLK_DEV_INITRD
 545         bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
 546         depends on BROKEN || !FRV
 547         help
 548           The initial RAM filesystem is a ramfs which is loaded by the
 549           boot loader (loadlin or lilo) and that is mounted as root
 550           before the normal boot procedure. It is typically used to
 551           load modules needed to mount the "real" root file system,
 552           etc. See <file:Documentation/initrd.txt> for details.
 553
 554           If RAM disk support (BLK_DEV_RAM) is also included, this
 555           also enables initial RAM disk (initrd) support and adds
 556           15 Kbytes (more on some other architectures) to the kernel size.
 557
 558           If unsure say Y.
 559
 560 if BLK_DEV_INITRD
 561
 562 source "usr/Kconfig"
 563
 564 endif
 565
 566 config CC_OPTIMIZE_FOR_SIZE
 567         bool "Optimize for size"
 568         default y
 569         help
 570           Enabling this option will pass "-Os" instead of "-O2" to gcc
 571           resulting in a smaller kernel.
 572
 573           If unsure, say Y.
 574
 575 config SYSCTL
 576         bool
 577
 578 menuconfig EMBEDDED
 579         bool "Configure standard kernel features (for small systems)"
 580         help
 581           This option allows certain base kernel options and settings
 582           to be disabled or tweaked. This is for specialized
 583           environments which can tolerate a "non-standard" kernel.
 584           Only use this if you really know what you are doing.
 585
 586 config UID16
 587         bool "Enable 16-bit UID system calls" if EMBEDDED
 588         depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
 589         default y
 590         help
 591           This enables the legacy 16-bit UID syscall wrappers.
 592
 593 config SYSCTL_SYSCALL
 594         bool "Sysctl syscall support" if EMBEDDED
 595         default y
 596         select SYSCTL
 597         ---help---
 598           sys_sysctl uses binary paths that have been found challenging
 599           to properly maintain and use.  The interface in /proc/sys
 600           using paths with ascii names is now the primary path to this
 601           information.
 602
 603           Almost nothing using the binary sysctl interface so if you are
 604           trying to save some space it is probably safe to disable this,
 605           making your kernel marginally smaller.
 606
 607           If unsure say Y here.
 608
 609 config KALLSYMS
 610          bool "Load all symbols for debugging/ksymoops" if EMBEDDED
 611          default y
 612          help
 613            Say Y here to let the kernel print out symbolic crash information and
 614            symbolic stack backtraces. This increases the size of the kernel
 615            somewhat, as all symbols have to be loaded into the kernel image.
 616
 617 config KALLSYMS_ALL
 618         bool "Include all symbols in kallsyms"
 619         depends on DEBUG_KERNEL && KALLSYMS
 620         help
 621            Normally kallsyms only contains the symbols of functions, for nicer
 622            OOPS messages.  Some debuggers can use kallsyms for other
 623            symbols too: say Y here to include all symbols, if you need them
 624            and you don't care about adding 300k to the size of your kernel.
 625
 626            Say N.
 627
 628 config KALLSYMS_STRIP_GENERATED
 629         bool "Strip machine generated symbols from kallsyms"
 630         depends on KALLSYMS_ALL
 631         default y
 632         help
 633           Say N if you want kallsyms to retain even machine generated symbols.
 634
 635 config KALLSYMS_EXTRA_PASS
 636         bool "Do an extra kallsyms pass"
 637         depends on KALLSYMS
 638         help
 639            If kallsyms is not working correctly, the build will fail with
 640            inconsistent kallsyms data.  If that occurs, log a bug report and
 641            turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
 642            Always say N here unless you find a bug in kallsyms, which must be
 643            reported.  KALLSYMS_EXTRA_PASS is only a temporary workaround while
 644            you wait for kallsyms to be fixed.
 645
 646
 647 config HOTPLUG
 648         bool "Support for hot-pluggable devices" if EMBEDDED
 649         default y
 650         help
 651           This option is provided for the case where no hotplug or uevent
 652           capabilities is wanted by the kernel.  You should only consider
 653           disabling this option for embedded systems that do not use modules, a
 654           dynamic /dev tree, or dynamic device discovery.  Just say Y.
 655
 656 config PRINTK
 657         default y
 658         bool "Enable support for printk" if EMBEDDED
 659         help
 660           This option enables normal printk support. Removing it
 661           eliminates most of the message strings from the kernel image
 662           and makes the kernel more or less silent. As this makes it
 663           very difficult to diagnose system problems, saying N here is
 664           strongly discouraged.
 665
 666 config BUG
 667         bool "BUG() support" if EMBEDDED
 668         default y
 669         help
 670           Disabling this option eliminates support for BUG and WARN, reducing
 671           the size of your kernel image and potentially quietly ignoring
 672           numerous fatal conditions. You should only consider disabling this
 673           option for embedded systems with no facilities for reporting errors.
 674           Just say Y.
 675
 676 config ELF_CORE
 677         default y
 678         bool "Enable ELF core dumps" if EMBEDDED
 679         help
 680           Enable support for generating core dumps. Disabling saves about 4k.
 681
 682 config PCSPKR_PLATFORM
 683         bool "Enable PC-Speaker support" if EMBEDDED
 684         depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
 685         default y
 686         help
 687           This option allows to disable the internal PC-Speaker
 688           support, saving some memory.
 689
 690 config COMPAT_BRK
 691         bool "Disable heap randomization"
 692         default y
 693         help
 694           Randomizing heap placement makes heap exploits harder, but it
 695           also breaks ancient binaries (including anything libc5 based).
 696           This option changes the bootup default to heap randomization
 697           disabled, and can be overriden runtime by setting
 698           /proc/sys/kernel/randomize_va_space to 2.
 699
 700           On non-ancient distros (post-2000 ones) N is usually a safe choice.
 701
 702 config BASE_FULL
 703         default y
 704         bool "Enable full-sized data structures for core" if EMBEDDED
 705         help
 706           Disabling this option reduces the size of miscellaneous core
 707           kernel data structures. This saves memory on small machines,
 708           but may reduce performance.
 709
 710 config FUTEX
 711         bool "Enable futex support" if EMBEDDED
 712         default y
 713         select RT_MUTEXES
 714         help
 715           Disabling this option will cause the kernel to be built without
 716           support for "fast userspace mutexes".  The resulting kernel may not
 717           run glibc-based applications correctly.
 718
 719 config ANON_INODES
 720         bool
 721
 722 config EPOLL
 723         bool "Enable eventpoll support" if EMBEDDED
 724         default y
 725         select ANON_INODES
 726         help
 727           Disabling this option will cause the kernel to be built without
 728           support for epoll family of system calls.
 729
 730 config SIGNALFD
 731         bool "Enable signalfd() system call" if EMBEDDED
 732         select ANON_INODES
 733         default y
 734         help
 735           Enable the signalfd() system call that allows to receive signals
 736           on a file descriptor.
 737
 738           If unsure, say Y.
 739
 740 config TIMERFD
 741         bool "Enable timerfd() system call" if EMBEDDED
 742         select ANON_INODES
 743         default y
 744         help
 745           Enable the timerfd() system call that allows to receive timer
 746           events on a file descriptor.
 747
 748           If unsure, say Y.
 749
 750 config EVENTFD
 751         bool "Enable eventfd() system call" if EMBEDDED
 752         select ANON_INODES
 753         default y
 754         help
 755           Enable the eventfd() system call that allows to receive both
 756           kernel notification (ie. KAIO) or userspace notifications.
 757
 758           If unsure, say Y.
 759
 760 config SHMEM
 761         bool "Use full shmem filesystem" if EMBEDDED
 762         default y
 763         depends on MMU
 764         help
 765           The shmem is an internal filesystem used to manage shared memory.
 766           It is backed by swap and manages resource limits. It is also exported
 767           to userspace as tmpfs if TMPFS is enabled. Disabling this
 768           option replaces shmem and tmpfs with the much simpler ramfs code,
 769           which may be appropriate on small systems without swap.
 770
 771 config AIO
 772         bool "Enable AIO support" if EMBEDDED
 773         default y
 774         help
 775           This option enables POSIX asynchronous I/O which may by used
 776           by some high performance threaded applications. Disabling
 777           this option saves about 7k.
 778
 779 config VM_EVENT_COUNTERS
 780         default y
 781         bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
 782         help
 783           VM event counters are needed for event counts to be shown.
 784           This option allows the disabling of the VM event counters
 785           on EMBEDDED systems.  /proc/vmstat will only show page counts
 786           if VM event counters are disabled.
 787
 788 config PCI_QUIRKS
 789         default y
 790         bool "Enable PCI quirk workarounds" if EMBEDDED
 791         depends on PCI
 792         help
 793           This enables workarounds for various PCI chipset
 794           bugs/quirks. Disable this only if your target machine is
 795           unaffected by PCI quirks.
 796
 797 config SLUB_DEBUG
 798         default y
 799         bool "Enable SLUB debugging support" if EMBEDDED
 800         depends on SLUB && SYSFS
 801         help
 802           SLUB has extensive debug support features. Disabling these can
 803           result in significant savings in code size. This also disables
 804           SLUB sysfs support. /sys/slab will not exist and there will be
 805           no support for cache validation etc.
 806
 807 choice
 808         prompt "Choose SLAB allocator"
 809         default SLUB
 810         help
 811            This option allows to select a slab allocator.
 812
 813 config SLAB
 814         bool "SLAB"
 815         help
 816           The regular slab allocator that is established and known to work
 817           well in all environments. It organizes cache hot objects in
 818           per cpu and per node queues.
 819
 820 config SLUB
 821         bool "SLUB (Unqueued Allocator)"
 822         help
 823            SLUB is a slab allocator that minimizes cache line usage
 824            instead of managing queues of cached objects (SLAB approach).
 825            Per cpu caching is realized using slabs of objects instead
 826            of queues of objects. SLUB can use memory efficiently
 827            and has enhanced diagnostics. SLUB is the default choice for
 828            a slab allocator.
 829
 830 config SLOB
 831         depends on EMBEDDED
 832         bool "SLOB (Simple Allocator)"
 833         help
 834            SLOB replaces the stock allocator with a drastically simpler
 835            allocator. SLOB is generally more space efficient but
 836            does not perform as well on large systems.
 837
 838 endchoice
 839
 840 config PROFILING
 841         bool "Profiling support (EXPERIMENTAL)"
 842         help
 843           Say Y here to enable the extended profiling support mechanisms used
 844           by profilers such as OProfile.
 845
 846 #
 847 # Place an empty function call at each tracepoint site. Can be
 848 # dynamically changed for a probe function.
 849 #
 850 config TRACEPOINTS
 851         bool
 852
 853 config MARKERS
 854         bool "Activate markers"
 855         depends on TRACEPOINTS
 856         help
 857           Place an empty function call at each marker site. Can be
 858           dynamically changed for a probe function.
 859
 860 source "arch/Kconfig"
 861
 862 endmenu         # General setup
 863
 864 config HAVE_GENERIC_DMA_COHERENT
 865         bool
 866         default n
 867
 868 config SLABINFO
 869         bool
 870         depends on PROC_FS
 871         depends on SLAB || SLUB_DEBUG
 872         default y
 873
 874 config RT_MUTEXES
 875         boolean
 876         select PLIST
 877
 878 config BASE_SMALL
 879         int
 880         default 0 if BASE_FULL
 881         default 1 if !BASE_FULL
 882
 883 menuconfig MODULES
 884         bool "Enable loadable module support"
 885         help
 886           Kernel modules are small pieces of compiled code which can
 887           be inserted in the running kernel, rather than being
 888           permanently built into the kernel.  You use the "modprobe"
 889           tool to add (and sometimes remove) them.  If you say Y here,
 890           many parts of the kernel can be built as modules (by
 891           answering M instead of Y where indicated): this is most
 892           useful for infrequently used options which are not required
 893           for booting.  For more information, see the man pages for
 894           modprobe, lsmod, modinfo, insmod and rmmod.
 895
 896           If you say Y here, you will need to run "make
 897           modules_install" to put the modules under /lib/modules/
 898           where modprobe can find them (you may need to be root to do
 899           this).
 900
 901           If unsure, say Y.
 902
 903 if MODULES
 904
 905 config MODULE_FORCE_LOAD
 906         bool "Forced module loading"
 907         default n
 908         help
 909           Allow loading of modules without version information (ie. modprobe
 910           --force).  Forced module loading sets the 'F' (forced) taint flag and
 911           is usually a really bad idea.
 912
 913 config MODULE_UNLOAD
 914         bool "Module unloading"
 915         help
 916           Without this option you will not be able to unload any
 917           modules (note that some modules may not be unloadable
 918           anyway), which makes your kernel smaller, faster
 919           and simpler.  If unsure, say Y.
 920
 921 config MODULE_FORCE_UNLOAD
 922         bool "Forced module unloading"
 923         depends on MODULE_UNLOAD && EXPERIMENTAL
 924         help
 925           This option allows you to force a module to unload, even if the
 926           kernel believes it is unsafe: the kernel will remove the module
 927           without waiting for anyone to stop using it (using the -f option to
 928           rmmod).  This is mainly for kernel developers and desperate users.
 929           If unsure, say N.
 930
 931 config MODVERSIONS
 932         bool "Module versioning support"
 933         help
 934           Usually, you have to use modules compiled with your kernel.
 935           Saying Y here makes it sometimes possible to use modules
 936           compiled for different kernels, by adding enough information
 937           to the modules to (hopefully) spot any changes which would
 938           make them incompatible with the kernel you are running.  If
 939           unsure, say N.
 940
 941 config MODULE_SRCVERSION_ALL
 942         bool "Source checksum for all modules"
 943         help
 944           Modules which contain a MODULE_VERSION get an extra "srcversion"
 945           field inserted into their modinfo section, which contains a
 946           sum of the source files which made it.  This helps maintainers
 947           see exactly which source was used to build a module (since
 948           others sometimes change the module source without updating
 949           the version).  With this option, such a "srcversion" field
 950           will be created for all modules.  If unsure, say N.
 951
 952 endif # MODULES
 953
 954 config INIT_ALL_POSSIBLE
 955         bool
 956         help
 957           Back when each arch used to define their own cpu_online_map and
 958           cpu_possible_map, some of them chose to initialize cpu_possible_map
 959           with all 1s, and others with all 0s.  When they were centralised,
 960           it was better to provide this option than to break all the archs
 961           and have several arch maintainers persuing me down dark alleys.
 962
 963 config STOP_MACHINE
 964         bool
 965         default y
 966         depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
 967         help
 968           Need stop_machine() primitive.
 969
 970 source "block/Kconfig"
 971
 972 config PREEMPT_NOTIFIERS
 973         bool
 974
 975 choice
 976         prompt "RCU Implementation"
 977         default CLASSIC_RCU
 978
 979 config CLASSIC_RCU
 980         bool "Classic RCU"
 981         help
 982           This option selects the classic RCU implementation that is
 983           designed for best read-side performance on non-realtime
 984           systems.
 985
 986           Select this option if you are unsure.
 987
 988 config TREE_RCU
 989         bool "Tree-based hierarchical RCU"
 990         help
 991           This option selects the RCU implementation that is
 992           designed for very large SMP system with hundreds or
 993           thousands of CPUs.
 994
 995 config PREEMPT_RCU
 996         bool "Preemptible RCU"
 997         depends on PREEMPT
 998         help
 999           This option reduces the latency of the kernel by making certain
1000           RCU sections preemptible. Normally RCU code is non-preemptible, if
1001           this option is selected then read-only RCU sections become
1002           preemptible. This helps latency, but may expose bugs due to
1003           now-naive assumptions about each RCU read-side critical section
1004           remaining on a given CPU through its execution.
1005
1006 endchoice
1007
1008 config RCU_TRACE
1009         bool "Enable tracing for RCU"
1010         depends on TREE_RCU || PREEMPT_RCU
1011         help
1012           This option provides tracing in RCU which presents stats
1013           in debugfs for debugging RCU implementation.
1014
1015           Say Y here if you want to enable RCU tracing
1016           Say N if you are unsure.
1017
1018 config RCU_FANOUT
1019         int "Tree-based hierarchical RCU fanout value"
1020         range 2 64 if 64BIT
1021         range 2 32 if !64BIT
1022         depends on TREE_RCU
1023         default 64 if 64BIT
1024         default 32 if !64BIT
1025         help
1026           This option controls the fanout of hierarchical implementations
1027           of RCU, allowing RCU to work efficiently on machines with
1028           large numbers of CPUs.  This value must be at least the cube
1029           root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
1030           systems and up to 262,144 for 64-bit systems.
1031
1032           Select a specific number if testing RCU itself.
1033           Take the default if unsure.
1034
1035 config RCU_FANOUT_EXACT
1036         bool "Disable tree-based hierarchical RCU auto-balancing"
1037         depends on TREE_RCU
1038         default n
1039         help
1040           This option forces use of the exact RCU_FANOUT value specified,
1041           regardless of imbalances in the hierarchy.  This is useful for
1042           testing RCU itself, and might one day be useful on systems with
1043           strong NUMA behavior.
1044
1045           Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
1046
1047           Say N if unsure.
1048
1049 config TREE_RCU_TRACE
1050         def_bool RCU_TRACE && TREE_RCU
1051         select DEBUG_FS
1052         help
1053           This option provides tracing for the TREE_RCU implementation,
1054           permitting Makefile to trivially select kernel/rcutree_trace.c.
1055
1056 config PREEMPT_RCU_TRACE
1057         def_bool RCU_TRACE && PREEMPT_RCU
1058         select DEBUG_FS
1059         help
1060           This option provides tracing for the PREEMPT_RCU implementation,
1061           permitting Makefile to trivially select kernel/rcupreempt_trace.c.