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 config CONSTRUCTORS
  20         bool
  21         depends on !UML
  22         default y
  23
  24 menu "General setup"
  25
  26 config EXPERIMENTAL
  27         bool "Prompt for development and/or incomplete code/drivers"
  28         ---help---
  29           Some of the various things that Linux supports (such as network
  30           drivers, file systems, network protocols, etc.) can be in a state
  31           of development where the functionality, stability, or the level of
  32           testing is not yet high enough for general use. This is usually
  33           known as the "alpha-test" phase among developers. If a feature is
  34           currently in alpha-test, then the developers usually discourage
  35           uninformed widespread use of this feature by the general public to
  36           avoid "Why doesn't this work?" type mail messages. However, active
  37           testing and use of these systems is welcomed. Just be aware that it
  38           may not meet the normal level of reliability or it may fail to work
  39           in some special cases. Detailed bug reports from people familiar
  40           with the kernel internals are usually welcomed by the developers
  41           (before submitting bug reports, please read the documents
  42           <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
  43           <file:Documentation/BUG-HUNTING>, and
  44           <file:Documentation/oops-tracing.txt> in the kernel source).
  45
  46           This option will also make obsoleted drivers available. These are
  47           drivers that have been replaced by something else, and/or are
  48           scheduled to be removed in a future kernel release.
  49
  50           Unless you intend to help test and develop a feature or driver that
  51           falls into this category, or you have a situation that requires
  52           using these features, you should probably say N here, which will
  53           cause the configurator to present you with fewer choices. If
  54           you say Y here, you will be offered the choice of using features or
  55           drivers that are currently considered to be in the alpha-test phase.
  56
  57 config BROKEN
  58         bool
  59
  60 config BROKEN_ON_SMP
  61         bool
  62         depends on BROKEN || !SMP
  63         default y
  64
  65 config LOCK_KERNEL
  66         bool
  67         depends on SMP || PREEMPT
  68         default y
  69
  70 config INIT_ENV_ARG_LIMIT
  71         int
  72         default 32 if !UML
  73         default 128 if UML
  74         help
  75           Maximum of each of the number of arguments and environment
  76           variables passed to init from the kernel command line.
  77
  78
  79 config LOCALVERSION
  80         string "Local version - append to kernel release"
  81         help
  82           Append an extra string to the end of your kernel version.
  83           This will show up when you type uname, for example.
  84           The string you set here will be appended after the contents of
  85           any files with a filename matching localversion* in your
  86           object and source tree, in that order.  Your total string can
  87           be a maximum of 64 characters.
  88
  89 config LOCALVERSION_AUTO
  90         bool "Automatically append version information to the version string"
  91         default y
  92         help
  93           This will try to automatically determine if the current tree is a
  94           release tree by looking for git tags that belong to the current
  95           top of tree revision.
  96
  97           A string of the format -gxxxxxxxx will be added to the localversion
  98           if a git-based tree is found.  The string generated by this will be
  99           appended after any matching localversion* files, and after the value
 100           set in CONFIG_LOCALVERSION.
 101
 102           (The actual string used here is the first eight characters produced
 103           by running the command:
 104
 105             $ git rev-parse --verify HEAD
 106
 107           which is done within the script "scripts/setlocalversion".)
 108
 109 config HAVE_KERNEL_GZIP
 110         bool
 111
 112 config HAVE_KERNEL_BZIP2
 113         bool
 114
 115 config HAVE_KERNEL_LZMA
 116         bool
 117
 118 choice
 119         prompt "Kernel compression mode"
 120         default KERNEL_GZIP
 121         depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA
 122         help
 123           The linux kernel is a kind of self-extracting executable.
 124           Several compression algorithms are available, which differ
 125           in efficiency, compression and decompression speed.
 126           Compression speed is only relevant when building a kernel.
 127           Decompression speed is relevant at each boot.
 128
 129           If you have any problems with bzip2 or lzma compressed
 130           kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
 131           version of this functionality (bzip2 only), for 2.4, was
 132           supplied by Christian Ludwig)
 133
 134           High compression options are mostly useful for users, who
 135           are low on disk space (embedded systems), but for whom ram
 136           size matters less.
 137
 138           If in doubt, select 'gzip'
 139
 140 config KERNEL_GZIP
 141         bool "Gzip"
 142         depends on HAVE_KERNEL_GZIP
 143         help
 144           The old and tried gzip compression. Its compression ratio is
 145           the poorest among the 3 choices; however its speed (both
 146           compression and decompression) is the fastest.
 147
 148 config KERNEL_BZIP2
 149         bool "Bzip2"
 150         depends on HAVE_KERNEL_BZIP2
 151         help
 152           Its compression ratio and speed is intermediate.
 153           Decompression speed is slowest among the three.  The kernel
 154           size is about 10% smaller with bzip2, in comparison to gzip.
 155           Bzip2 uses a large amount of memory. For modern kernels you
 156           will need at least 8MB RAM or more for booting.
 157
 158 config KERNEL_LZMA
 159         bool "LZMA"
 160         depends on HAVE_KERNEL_LZMA
 161         help
 162           The most recent compression algorithm.
 163           Its ratio is best, decompression speed is between the other
 164           two. Compression is slowest.  The kernel size is about 33%
 165           smaller with LZMA in comparison to gzip.
 166
 167 endchoice
 168
 169 config SWAP
 170         bool "Support for paging of anonymous memory (swap)"
 171         depends on MMU && BLOCK
 172         default y
 173         help
 174           This option allows you to choose whether you want to have support
 175           for so called swap devices or swap files in your kernel that are
 176           used to provide more virtual memory than the actual RAM present
 177           in your computer.  If unsure say Y.
 178
 179 config SYSVIPC
 180         bool "System V IPC"
 181         ---help---
 182           Inter Process Communication is a suite of library functions and
 183           system calls which let processes (running programs) synchronize and
 184           exchange information. It is generally considered to be a good thing,
 185           and some programs won't run unless you say Y here. In particular, if
 186           you want to run the DOS emulator dosemu under Linux (read the
 187           DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
 188           you'll need to say Y here.
 189
 190           You can find documentation about IPC with "info ipc" and also in
 191           section 6.4 of the Linux Programmer's Guide, available from
 192           <http://www.tldp.org/guides.html>.
 193
 194 config SYSVIPC_SYSCTL
 195         bool
 196         depends on SYSVIPC
 197         depends on SYSCTL
 198         default y
 199
 200 config POSIX_MQUEUE
 201         bool "POSIX Message Queues"
 202         depends on NET && EXPERIMENTAL
 203         ---help---
 204           POSIX variant of message queues is a part of IPC. In POSIX message
 205           queues every message has a priority which decides about succession
 206           of receiving it by a process. If you want to compile and run
 207           programs written e.g. for Solaris with use of its POSIX message
 208           queues (functions mq_*) say Y here.
 209
 210           POSIX message queues are visible as a filesystem called 'mqueue'
 211           and can be mounted somewhere if you want to do filesystem
 212           operations on message queues.
 213
 214           If unsure, say Y.
 215
 216 config POSIX_MQUEUE_SYSCTL
 217         bool
 218         depends on POSIX_MQUEUE
 219         depends on SYSCTL
 220         default y
 221
 222 config BSD_PROCESS_ACCT
 223         bool "BSD Process Accounting"
 224         help
 225           If you say Y here, a user level program will be able to instruct the
 226           kernel (via a special system call) to write process accounting
 227           information to a file: whenever a process exits, information about
 228           that process will be appended to the file by the kernel.  The
 229           information includes things such as creation time, owning user,
 230           command name, memory usage, controlling terminal etc. (the complete
 231           list is in the struct acct in <file:include/linux/acct.h>).  It is
 232           up to the user level program to do useful things with this
 233           information.  This is generally a good idea, so say Y.
 234
 235 config BSD_PROCESS_ACCT_V3
 236         bool "BSD Process Accounting version 3 file format"
 237         depends on BSD_PROCESS_ACCT
 238         default n
 239         help
 240           If you say Y here, the process accounting information is written
 241           in a new file format that also logs the process IDs of each
 242           process and it's parent. Note that this file format is incompatible
 243           with previous v0/v1/v2 file formats, so you will need updated tools
 244           for processing it. A preliminary version of these tools is available
 245           at <http://www.gnu.org/software/acct/>.
 246
 247 config TASKSTATS
 248         bool "Export task/process statistics through netlink (EXPERIMENTAL)"
 249         depends on NET
 250         default n
 251         help
 252           Export selected statistics for tasks/processes through the
 253           generic netlink interface. Unlike BSD process accounting, the
 254           statistics are available during the lifetime of tasks/processes as
 255           responses to commands. Like BSD accounting, they are sent to user
 256           space on task exit.
 257
 258           Say N if unsure.
 259
 260 config TASK_DELAY_ACCT
 261         bool "Enable per-task delay accounting (EXPERIMENTAL)"
 262         depends on TASKSTATS
 263         help
 264           Collect information on time spent by a task waiting for system
 265           resources like cpu, synchronous block I/O completion and swapping
 266           in pages. Such statistics can help in setting a task's priorities
 267           relative to other tasks for cpu, io, rss limits etc.
 268
 269           Say N if unsure.
 270
 271 config TASK_XACCT
 272         bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
 273         depends on TASKSTATS
 274         help
 275           Collect extended task accounting data and send the data
 276           to userland for processing over the taskstats interface.
 277
 278           Say N if unsure.
 279
 280 config TASK_IO_ACCOUNTING
 281         bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
 282         depends on TASK_XACCT
 283         help
 284           Collect information on the number of bytes of storage I/O which this
 285           task has caused.
 286
 287           Say N if unsure.
 288
 289 config AUDIT
 290         bool "Auditing support"
 291         depends on NET
 292         help
 293           Enable auditing infrastructure that can be used with another
 294           kernel subsystem, such as SELinux (which requires this for
 295           logging of avc messages output).  Does not do system-call
 296           auditing without CONFIG_AUDITSYSCALL.
 297
 298 config AUDITSYSCALL
 299         bool "Enable system-call auditing support"
 300         depends on AUDIT && (X86 || PPC || PPC64 || S390 || IA64 || UML || SPARC64|| SUPERH)
 301         default y if SECURITY_SELINUX
 302         help
 303           Enable low-overhead system-call auditing infrastructure that
 304           can be used independently or with another kernel subsystem,
 305           such as SELinux.  To use audit's filesystem watch feature, please
 306           ensure that INOTIFY is configured.
 307
 308 config AUDIT_TREE
 309         def_bool y
 310         depends on AUDITSYSCALL
 311         select INOTIFY
 312
 313 menu "RCU Subsystem"
 314
 315 choice
 316         prompt "RCU Implementation"
 317         default TREE_RCU
 318
 319 config CLASSIC_RCU
 320         bool "Classic RCU"
 321         help
 322           This option selects the classic RCU implementation that is
 323           designed for best read-side performance on non-realtime
 324           systems.
 325
 326           Select this option if you are unsure.
 327
 328 config TREE_RCU
 329         bool "Tree-based hierarchical RCU"
 330         help
 331           This option selects the RCU implementation that is
 332           designed for very large SMP system with hundreds or
 333           thousands of CPUs.
 334
 335 config PREEMPT_RCU
 336         bool "Preemptible RCU"
 337         depends on PREEMPT
 338         help
 339           This option reduces the latency of the kernel by making certain
 340           RCU sections preemptible. Normally RCU code is non-preemptible, if
 341           this option is selected then read-only RCU sections become
 342           preemptible. This helps latency, but may expose bugs due to
 343           now-naive assumptions about each RCU read-side critical section
 344           remaining on a given CPU through its execution.
 345
 346 endchoice
 347
 348 config RCU_TRACE
 349         bool "Enable tracing for RCU"
 350         depends on TREE_RCU || PREEMPT_RCU
 351         help
 352           This option provides tracing in RCU which presents stats
 353           in debugfs for debugging RCU implementation.
 354
 355           Say Y here if you want to enable RCU tracing
 356           Say N if you are unsure.
 357
 358 config RCU_FANOUT
 359         int "Tree-based hierarchical RCU fanout value"
 360         range 2 64 if 64BIT
 361         range 2 32 if !64BIT
 362         depends on TREE_RCU
 363         default 64 if 64BIT
 364         default 32 if !64BIT
 365         help
 366           This option controls the fanout of hierarchical implementations
 367           of RCU, allowing RCU to work efficiently on machines with
 368           large numbers of CPUs.  This value must be at least the cube
 369           root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
 370           systems and up to 262,144 for 64-bit systems.
 371
 372           Select a specific number if testing RCU itself.
 373           Take the default if unsure.
 374
 375 config RCU_FANOUT_EXACT
 376         bool "Disable tree-based hierarchical RCU auto-balancing"
 377         depends on TREE_RCU
 378         default n
 379         help
 380           This option forces use of the exact RCU_FANOUT value specified,
 381           regardless of imbalances in the hierarchy.  This is useful for
 382           testing RCU itself, and might one day be useful on systems with
 383           strong NUMA behavior.
 384
 385           Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
 386
 387           Say N if unsure.
 388
 389 config TREE_RCU_TRACE
 390         def_bool RCU_TRACE && TREE_RCU
 391         select DEBUG_FS
 392         help
 393           This option provides tracing for the TREE_RCU implementation,
 394           permitting Makefile to trivially select kernel/rcutree_trace.c.
 395
 396 config PREEMPT_RCU_TRACE
 397         def_bool RCU_TRACE && PREEMPT_RCU
 398         select DEBUG_FS
 399         help
 400           This option provides tracing for the PREEMPT_RCU implementation,
 401           permitting Makefile to trivially select kernel/rcupreempt_trace.c.
 402
 403 endmenu # "RCU Subsystem"
 404
 405 config IKCONFIG
 406         tristate "Kernel .config support"
 407         ---help---
 408           This option enables the complete Linux kernel ".config" file
 409           contents to be saved in the kernel. It provides documentation
 410           of which kernel options are used in a running kernel or in an
 411           on-disk kernel.  This information can be extracted from the kernel
 412           image file with the script scripts/extract-ikconfig and used as
 413           input to rebuild the current kernel or to build another kernel.
 414           It can also be extracted from a running kernel by reading
 415           /proc/config.gz if enabled (below).
 416
 417 config IKCONFIG_PROC
 418         bool "Enable access to .config through /proc/config.gz"
 419         depends on IKCONFIG && PROC_FS
 420         ---help---
 421           This option enables access to the kernel configuration file
 422           through /proc/config.gz.
 423
 424 config LOG_BUF_SHIFT
 425         int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
 426         range 12 21
 427         default 17
 428         help
 429           Select kernel log buffer size as a power of 2.
 430           Examples:
 431                      17 => 128 KB
 432                      16 => 64 KB
 433                      15 => 32 KB
 434                      14 => 16 KB
 435                      13 =>  8 KB
 436                      12 =>  4 KB
 437
 438 #
 439 # Architectures with an unreliable sched_clock() should select this:
 440 #
 441 config HAVE_UNSTABLE_SCHED_CLOCK
 442         bool
 443
 444 config GROUP_SCHED
 445         bool "Group CPU scheduler"
 446         depends on EXPERIMENTAL
 447         default n
 448         help
 449           This feature lets CPU scheduler recognize task groups and control CPU
 450           bandwidth allocation to such task groups.
 451           In order to create a group from arbitrary set of processes, use
 452           CONFIG_CGROUPS. (See Control Group support.)
 453
 454 config FAIR_GROUP_SCHED
 455         bool "Group scheduling for SCHED_OTHER"
 456         depends on GROUP_SCHED
 457         default GROUP_SCHED
 458
 459 config RT_GROUP_SCHED
 460         bool "Group scheduling for SCHED_RR/FIFO"
 461         depends on EXPERIMENTAL
 462         depends on GROUP_SCHED
 463         default n
 464         help
 465           This feature lets you explicitly allocate real CPU bandwidth
 466           to users or control groups (depending on the "Basis for grouping tasks"
 467           setting below. If enabled, it will also make it impossible to
 468           schedule realtime tasks for non-root users until you allocate
 469           realtime bandwidth for them.
 470           See Documentation/scheduler/sched-rt-group.txt for more information.
 471
 472 choice
 473         depends on GROUP_SCHED
 474         prompt "Basis for grouping tasks"
 475         default USER_SCHED
 476
 477 config USER_SCHED
 478         bool "user id"
 479         help
 480           This option will choose userid as the basis for grouping
 481           tasks, thus providing equal CPU bandwidth to each user.
 482
 483 config CGROUP_SCHED
 484         bool "Control groups"
 485         depends on CGROUPS
 486         help
 487           This option allows you to create arbitrary task groups
 488           using the "cgroup" pseudo filesystem and control
 489           the cpu bandwidth allocated to each such task group.
 490           Refer to Documentation/cgroups/cgroups.txt for more
 491           information on "cgroup" pseudo filesystem.
 492
 493 endchoice
 494
 495 menuconfig CGROUPS
 496         boolean "Control Group support"
 497         help
 498           This option adds support for grouping sets of processes together, for
 499           use with process control subsystems such as Cpusets, CFS, memory
 500           controls or device isolation.
 501           See
 502                 - Documentation/scheduler/sched-design-CFS.txt  (CFS)
 503                 - Documentation/cgroups/ (features for grouping, isolation
 504                                           and resource control)
 505
 506           Say N if unsure.
 507
 508 if CGROUPS
 509
 510 config CGROUP_DEBUG
 511         bool "Example debug cgroup subsystem"
 512         depends on CGROUPS
 513         default n
 514         help
 515           This option enables a simple cgroup subsystem that
 516           exports useful debugging information about the cgroups
 517           framework.
 518
 519           Say N if unsure.
 520
 521 config CGROUP_NS
 522         bool "Namespace cgroup subsystem"
 523         depends on CGROUPS
 524         help
 525           Provides a simple namespace cgroup subsystem to
 526           provide hierarchical naming of sets of namespaces,
 527           for instance virtual servers and checkpoint/restart
 528           jobs.
 529
 530 config CGROUP_FREEZER
 531         bool "Freezer cgroup subsystem"
 532         depends on CGROUPS
 533         help
 534           Provides a way to freeze and unfreeze all tasks in a
 535           cgroup.
 536
 537 config CGROUP_DEVICE
 538         bool "Device controller for cgroups"
 539         depends on CGROUPS && EXPERIMENTAL
 540         help
 541           Provides a cgroup implementing whitelists for devices which
 542           a process in the cgroup can mknod or open.
 543
 544 config CPUSETS
 545         bool "Cpuset support"
 546         depends on CGROUPS
 547         help
 548           This option will let you create and manage CPUSETs which
 549           allow dynamically partitioning a system into sets of CPUs and
 550           Memory Nodes and assigning tasks to run only within those sets.
 551           This is primarily useful on large SMP or NUMA systems.
 552
 553           Say N if unsure.
 554
 555 config PROC_PID_CPUSET
 556         bool "Include legacy /proc/<pid>/cpuset file"
 557         depends on CPUSETS
 558         default y
 559
 560 config CGROUP_CPUACCT
 561         bool "Simple CPU accounting cgroup subsystem"
 562         depends on CGROUPS
 563         help
 564           Provides a simple Resource Controller for monitoring the
 565           total CPU consumed by the tasks in a cgroup.
 566
 567 config RESOURCE_COUNTERS
 568         bool "Resource counters"
 569         help
 570           This option enables controller independent resource accounting
 571           infrastructure that works with cgroups.
 572         depends on CGROUPS
 573
 574 config CGROUP_MEM_RES_CTLR
 575         bool "Memory Resource Controller for Control Groups"
 576         depends on CGROUPS && RESOURCE_COUNTERS
 577         select MM_OWNER
 578         help
 579           Provides a memory resource controller that manages both anonymous
 580           memory and page cache. (See Documentation/cgroups/memory.txt)
 581
 582           Note that setting this option increases fixed memory overhead
 583           associated with each page of memory in the system. By this,
 584           20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
 585           usage tracking struct at boot. Total amount of this is printed out
 586           at boot.
 587
 588           Only enable when you're ok with these trade offs and really
 589           sure you need the memory resource controller. Even when you enable
 590           this, you can set "cgroup_disable=memory" at your boot option to
 591           disable memory resource controller and you can avoid overheads.
 592           (and lose benefits of memory resource controller)
 593
 594           This config option also selects MM_OWNER config option, which
 595           could in turn add some fork/exit overhead.
 596
 597 config CGROUP_MEM_RES_CTLR_SWAP
 598         bool "Memory Resource Controller Swap Extension(EXPERIMENTAL)"
 599         depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL
 600         help
 601           Add swap management feature to memory resource controller. When you
 602           enable this, you can limit mem+swap usage per cgroup. In other words,
 603           when you disable this, memory resource controller has no cares to
 604           usage of swap...a process can exhaust all of the swap. This extension
 605           is useful when you want to avoid exhaustion swap but this itself
 606           adds more overheads and consumes memory for remembering information.
 607           Especially if you use 32bit system or small memory system, please
 608           be careful about enabling this. When memory resource controller
 609           is disabled by boot option, this will be automatically disabled and
 610           there will be no overhead from this. Even when you set this config=y,
 611           if boot option "noswapaccount" is set, swap will not be accounted.
 612           Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
 613           size is 4096bytes, 512k per 1Gbytes of swap.
 614
 615 endif # CGROUPS
 616
 617 config MM_OWNER
 618         bool
 619
 620 config SYSFS_DEPRECATED
 621         bool
 622
 623 config SYSFS_DEPRECATED_V2
 624         bool "remove sysfs features which may confuse old userspace tools"
 625         depends on SYSFS
 626         default n
 627         select SYSFS_DEPRECATED
 628         help
 629           This option switches the layout of sysfs to the deprecated
 630           version. Do not use it on recent distributions.
 631
 632           The current sysfs layout features a unified device tree at
 633           /sys/devices/, which is able to express a hierarchy between
 634           class devices. If the deprecated option is set to Y, the
 635           unified device tree is split into a bus device tree at
 636           /sys/devices/ and several individual class device trees at
 637           /sys/class/. The class and bus devices will be connected by
 638           "<subsystem>:<name>" and the "device" links. The "block"
 639           class devices, will not show up in /sys/class/block/. Some
 640           subsystems will suppress the creation of some devices which
 641           depend on the unified device tree.
 642
 643           This option is not a pure compatibility option that can
 644           be safely enabled on newer distributions. It will change the
 645           layout of sysfs to the non-extensible deprecated version,
 646           and disable some features, which can not be exported without
 647           confusing older userspace tools. Since 2007/2008 all major
 648           distributions do not enable this option, and ship no tools which
 649           depend on the deprecated layout or this option.
 650
 651           If you are using a new kernel on an older distribution, or use
 652           older userspace tools, you might need to say Y here. Do not say Y,
 653           if the original kernel, that came with your distribution, has
 654           this option set to N.
 655
 656 config RELAY
 657         bool "Kernel->user space relay support (formerly relayfs)"
 658         help
 659           This option enables support for relay interface support in
 660           certain file systems (such as debugfs).
 661           It is designed to provide an efficient mechanism for tools and
 662           facilities to relay large amounts of data from kernel space to
 663           user space.
 664
 665           If unsure, say N.
 666
 667 config NAMESPACES
 668         bool "Namespaces support" if EMBEDDED
 669         default !EMBEDDED
 670         help
 671           Provides the way to make tasks work with different objects using
 672           the same id. For example same IPC id may refer to different objects
 673           or same user id or pid may refer to different tasks when used in
 674           different namespaces.
 675
 676 config UTS_NS
 677         bool "UTS namespace"
 678         depends on NAMESPACES
 679         help
 680           In this namespace tasks see different info provided with the
 681           uname() system call
 682
 683 config IPC_NS
 684         bool "IPC namespace"
 685         depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
 686         help
 687           In this namespace tasks work with IPC ids which correspond to
 688           different IPC objects in different namespaces.
 689
 690 config USER_NS
 691         bool "User namespace (EXPERIMENTAL)"
 692         depends on NAMESPACES && EXPERIMENTAL
 693         help
 694           This allows containers, i.e. vservers, to use user namespaces
 695           to provide different user info for different servers.
 696           If unsure, say N.
 697
 698 config PID_NS
 699         bool "PID Namespaces (EXPERIMENTAL)"
 700         default n
 701         depends on NAMESPACES && EXPERIMENTAL
 702         help
 703           Support process id namespaces.  This allows having multiple
 704           processes with the same pid as long as they are in different
 705           pid namespaces.  This is a building block of containers.
 706
 707           Unless you want to work with an experimental feature
 708           say N here.
 709
 710 config NET_NS
 711         bool "Network namespace"
 712         default n
 713         depends on NAMESPACES && EXPERIMENTAL && NET
 714         help
 715           Allow user space to create what appear to be multiple instances
 716           of the network stack.
 717
 718 config BLK_DEV_INITRD
 719         bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
 720         depends on BROKEN || !FRV
 721         help
 722           The initial RAM filesystem is a ramfs which is loaded by the
 723           boot loader (loadlin or lilo) and that is mounted as root
 724           before the normal boot procedure. It is typically used to
 725           load modules needed to mount the "real" root file system,
 726           etc. See <file:Documentation/initrd.txt> for details.
 727
 728           If RAM disk support (BLK_DEV_RAM) is also included, this
 729           also enables initial RAM disk (initrd) support and adds
 730           15 Kbytes (more on some other architectures) to the kernel size.
 731
 732           If unsure say Y.
 733
 734 if BLK_DEV_INITRD
 735
 736 source "usr/Kconfig"
 737
 738 endif
 739
 740 config CC_OPTIMIZE_FOR_SIZE
 741         bool "Optimize for size"
 742         default y
 743         help
 744           Enabling this option will pass "-Os" instead of "-O2" to gcc
 745           resulting in a smaller kernel.
 746
 747           If unsure, say Y.
 748
 749 config SYSCTL
 750         bool
 751
 752 config ANON_INODES
 753         bool
 754
 755 menuconfig EMBEDDED
 756         bool "Configure standard kernel features (for small systems)"
 757         help
 758           This option allows certain base kernel options and settings
 759           to be disabled or tweaked. This is for specialized
 760           environments which can tolerate a "non-standard" kernel.
 761           Only use this if you really know what you are doing.
 762
 763 config UID16
 764         bool "Enable 16-bit UID system calls" if EMBEDDED
 765         depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
 766         default y
 767         help
 768           This enables the legacy 16-bit UID syscall wrappers.
 769
 770 config SYSCTL_SYSCALL
 771         bool "Sysctl syscall support" if EMBEDDED
 772         default y
 773         select SYSCTL
 774         ---help---
 775           sys_sysctl uses binary paths that have been found challenging
 776           to properly maintain and use.  The interface in /proc/sys
 777           using paths with ascii names is now the primary path to this
 778           information.
 779
 780           Almost nothing using the binary sysctl interface so if you are
 781           trying to save some space it is probably safe to disable this,
 782           making your kernel marginally smaller.
 783
 784           If unsure say Y here.
 785
 786 config KALLSYMS
 787          bool "Load all symbols for debugging/ksymoops" if EMBEDDED
 788          default y
 789          help
 790            Say Y here to let the kernel print out symbolic crash information and
 791            symbolic stack backtraces. This increases the size of the kernel
 792            somewhat, as all symbols have to be loaded into the kernel image.
 793
 794 config KALLSYMS_ALL
 795         bool "Include all symbols in kallsyms"
 796         depends on DEBUG_KERNEL && KALLSYMS
 797         help
 798            Normally kallsyms only contains the symbols of functions, for nicer
 799            OOPS messages.  Some debuggers can use kallsyms for other
 800            symbols too: say Y here to include all symbols, if you need them
 801            and you don't care about adding 300k to the size of your kernel.
 802
 803            Say N.
 804
 805 config KALLSYMS_EXTRA_PASS
 806         bool "Do an extra kallsyms pass"
 807         depends on KALLSYMS
 808         help
 809            If kallsyms is not working correctly, the build will fail with
 810            inconsistent kallsyms data.  If that occurs, log a bug report and
 811            turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
 812            Always say N here unless you find a bug in kallsyms, which must be
 813            reported.  KALLSYMS_EXTRA_PASS is only a temporary workaround while
 814            you wait for kallsyms to be fixed.
 815
 816
 817 config HOTPLUG
 818         bool "Support for hot-pluggable devices" if EMBEDDED
 819         default y
 820         help
 821           This option is provided for the case where no hotplug or uevent
 822           capabilities is wanted by the kernel.  You should only consider
 823           disabling this option for embedded systems that do not use modules, a
 824           dynamic /dev tree, or dynamic device discovery.  Just say Y.
 825
 826 config PRINTK
 827         default y
 828         bool "Enable support for printk" if EMBEDDED
 829         help
 830           This option enables normal printk support. Removing it
 831           eliminates most of the message strings from the kernel image
 832           and makes the kernel more or less silent. As this makes it
 833           very difficult to diagnose system problems, saying N here is
 834           strongly discouraged.
 835
 836 config BUG
 837         bool "BUG() support" if EMBEDDED
 838         default y
 839         help
 840           Disabling this option eliminates support for BUG and WARN, reducing
 841           the size of your kernel image and potentially quietly ignoring
 842           numerous fatal conditions. You should only consider disabling this
 843           option for embedded systems with no facilities for reporting errors.
 844           Just say Y.
 845
 846 config ELF_CORE
 847         default y
 848         bool "Enable ELF core dumps" if EMBEDDED
 849         help
 850           Enable support for generating core dumps. Disabling saves about 4k.
 851
 852 config PCSPKR_PLATFORM
 853         bool "Enable PC-Speaker support" if EMBEDDED
 854         depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
 855         default y
 856         help
 857           This option allows to disable the internal PC-Speaker
 858           support, saving some memory.
 859
 860 config BASE_FULL
 861         default y
 862         bool "Enable full-sized data structures for core" if EMBEDDED
 863         help
 864           Disabling this option reduces the size of miscellaneous core
 865           kernel data structures. This saves memory on small machines,
 866           but may reduce performance.
 867
 868 config FUTEX
 869         bool "Enable futex support" if EMBEDDED
 870         default y
 871         select RT_MUTEXES
 872         help
 873           Disabling this option will cause the kernel to be built without
 874           support for "fast userspace mutexes".  The resulting kernel may not
 875           run glibc-based applications correctly.
 876
 877 config EPOLL
 878         bool "Enable eventpoll support" if EMBEDDED
 879         default y
 880         select ANON_INODES
 881         help
 882           Disabling this option will cause the kernel to be built without
 883           support for epoll family of system calls.
 884
 885 config SIGNALFD
 886         bool "Enable signalfd() system call" if EMBEDDED
 887         select ANON_INODES
 888         default y
 889         help
 890           Enable the signalfd() system call that allows to receive signals
 891           on a file descriptor.
 892
 893           If unsure, say Y.
 894
 895 config TIMERFD
 896         bool "Enable timerfd() system call" if EMBEDDED
 897         select ANON_INODES
 898         default y
 899         help
 900           Enable the timerfd() system call that allows to receive timer
 901           events on a file descriptor.
 902
 903           If unsure, say Y.
 904
 905 config EVENTFD
 906         bool "Enable eventfd() system call" if EMBEDDED
 907         select ANON_INODES
 908         default y
 909         help
 910           Enable the eventfd() system call that allows to receive both
 911           kernel notification (ie. KAIO) or userspace notifications.
 912
 913           If unsure, say Y.
 914
 915 config SHMEM
 916         bool "Use full shmem filesystem" if EMBEDDED
 917         default y
 918         depends on MMU
 919         help
 920           The shmem is an internal filesystem used to manage shared memory.
 921           It is backed by swap and manages resource limits. It is also exported
 922           to userspace as tmpfs if TMPFS is enabled. Disabling this
 923           option replaces shmem and tmpfs with the much simpler ramfs code,
 924           which may be appropriate on small systems without swap.
 925
 926 config AIO
 927         bool "Enable AIO support" if EMBEDDED
 928         default y
 929         help
 930           This option enables POSIX asynchronous I/O which may by used
 931           by some high performance threaded applications. Disabling
 932           this option saves about 7k.
 933
 934 config HAVE_PERF_COUNTERS
 935         bool
 936         help
 937           See tools/perf/design.txt for details.
 938
 939 menu "Performance Counters"
 940
 941 config PERF_COUNTERS
 942         bool "Kernel Performance Counters"
 943         default y if PROFILING
 944         depends on HAVE_PERF_COUNTERS
 945         select ANON_INODES
 946         help
 947           Enable kernel support for performance counter hardware.
 948
 949           Performance counters are special hardware registers available
 950           on most modern CPUs. These registers count the number of certain
 951           types of hw events: such as instructions executed, cachemisses
 952           suffered, or branches mis-predicted - without slowing down the
 953           kernel or applications. These registers can also trigger interrupts
 954           when a threshold number of events have passed - and can thus be
 955           used to profile the code that runs on that CPU.
 956
 957           The Linux Performance Counter subsystem provides an abstraction of
 958           these hardware capabilities, available via a system call. It
 959           provides per task and per CPU counters, and it provides event
 960           capabilities on top of those.
 961
 962           Say Y if unsure.
 963
 964 config EVENT_PROFILE
 965         bool "Tracepoint profiling sources"
 966         depends on PERF_COUNTERS && EVENT_TRACING
 967         default y
 968         help
 969          Allow the use of tracepoints as software performance counters.
 970
 971          When this is enabled, you can create perf counters based on
 972          tracepoints using PERF_TYPE_TRACEPOINT and the tracepoint ID
 973          found in debugfs://tracing/events/*/*/id. (The -e/--events
 974          option to the perf tool can parse and interpret symbolic
 975          tracepoints, in the subsystem:tracepoint_name format.)
 976
 977 endmenu
 978
 979 config VM_EVENT_COUNTERS
 980         default y
 981         bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
 982         help
 983           VM event counters are needed for event counts to be shown.
 984           This option allows the disabling of the VM event counters
 985           on EMBEDDED systems.  /proc/vmstat will only show page counts
 986           if VM event counters are disabled.
 987
 988 config PCI_QUIRKS
 989         default y
 990         bool "Enable PCI quirk workarounds" if EMBEDDED
 991         depends on PCI
 992         help
 993           This enables workarounds for various PCI chipset
 994           bugs/quirks. Disable this only if your target machine is
 995           unaffected by PCI quirks.
 996
 997 config SLUB_DEBUG
 998         default y
 999         bool "Enable SLUB debugging support" if EMBEDDED
1000         depends on SLUB && SYSFS
1001         help
1002           SLUB has extensive debug support features. Disabling these can
1003           result in significant savings in code size. This also disables
1004           SLUB sysfs support. /sys/slab will not exist and there will be
1005           no support for cache validation etc.
1006
1007 config STRIP_ASM_SYMS
1008         bool "Strip assembler-generated symbols during link"
1009         default n
1010         help
1011           Strip internal assembler-generated symbols during a link (symbols
1012           that look like '.Lxxx') so they don't pollute the output of
1013           get_wchan() and suchlike.
1014
1015 config COMPAT_BRK
1016         bool "Disable heap randomization"
1017         default y
1018         help
1019           Randomizing heap placement makes heap exploits harder, but it
1020           also breaks ancient binaries (including anything libc5 based).
1021           This option changes the bootup default to heap randomization
1022           disabled, and can be overridden at runtime by setting
1023           /proc/sys/kernel/randomize_va_space to 2.
1024
1025           On non-ancient distros (post-2000 ones) N is usually a safe choice.
1026
1027 choice
1028         prompt "Choose SLAB allocator"
1029         default SLUB
1030         help
1031            This option allows to select a slab allocator.
1032
1033 config SLAB
1034         bool "SLAB"
1035         help
1036           The regular slab allocator that is established and known to work
1037           well in all environments. It organizes cache hot objects in
1038           per cpu and per node queues.
1039
1040 config SLUB
1041         bool "SLUB (Unqueued Allocator)"
1042         help
1043            SLUB is a slab allocator that minimizes cache line usage
1044            instead of managing queues of cached objects (SLAB approach).
1045            Per cpu caching is realized using slabs of objects instead
1046            of queues of objects. SLUB can use memory efficiently
1047            and has enhanced diagnostics. SLUB is the default choice for
1048            a slab allocator.
1049
1050 config SLOB
1051         depends on EMBEDDED
1052         bool "SLOB (Simple Allocator)"
1053         help
1054            SLOB replaces the stock allocator with a drastically simpler
1055            allocator. SLOB is generally more space efficient but
1056            does not perform as well on large systems.
1057
1058 endchoice
1059
1060 config PROFILING
1061         bool "Profiling support (EXPERIMENTAL)"
1062         help
1063           Say Y here to enable the extended profiling support mechanisms used
1064           by profilers such as OProfile.
1065
1066 #
1067 # Place an empty function call at each tracepoint site. Can be
1068 # dynamically changed for a probe function.
1069 #
1070 config TRACEPOINTS
1071         bool
1072
1073 config MARKERS
1074         bool "Activate markers"
1075         select TRACEPOINTS
1076         help
1077           Place an empty function call at each marker site. Can be
1078           dynamically changed for a probe function.
1079
1080 source "arch/Kconfig"
1081
1082 config SLOW_WORK
1083         default n
1084         bool
1085         help
1086           The slow work thread pool provides a number of dynamically allocated
1087           threads that can be used by the kernel to perform operations that
1088           take a relatively long time.
1089
1090           An example of this would be CacheFiles doing a path lookup followed
1091           by a series of mkdirs and a create call, all of which have to touch
1092           disk.
1093
1094           See Documentation/slow-work.txt.
1095
1096 endmenu         # General setup
1097
1098 config HAVE_GENERIC_DMA_COHERENT
1099         bool
1100         default n
1101
1102 config SLABINFO
1103         bool
1104         depends on PROC_FS
1105         depends on SLAB || SLUB_DEBUG
1106         default y
1107
1108 config RT_MUTEXES
1109         boolean
1110
1111 config BASE_SMALL
1112         int
1113         default 0 if BASE_FULL
1114         default 1 if !BASE_FULL
1115
1116 menuconfig MODULES
1117         bool "Enable loadable module support"
1118         help
1119           Kernel modules are small pieces of compiled code which can
1120           be inserted in the running kernel, rather than being
1121           permanently built into the kernel.  You use the "modprobe"
1122           tool to add (and sometimes remove) them.  If you say Y here,
1123           many parts of the kernel can be built as modules (by
1124           answering M instead of Y where indicated): this is most
1125           useful for infrequently used options which are not required
1126           for booting.  For more information, see the man pages for
1127           modprobe, lsmod, modinfo, insmod and rmmod.
1128
1129           If you say Y here, you will need to run "make
1130           modules_install" to put the modules under /lib/modules/
1131           where modprobe can find them (you may need to be root to do
1132           this).
1133
1134           If unsure, say Y.
1135
1136 if MODULES
1137
1138 config MODULE_FORCE_LOAD
1139         bool "Forced module loading"
1140         default n
1141         help
1142           Allow loading of modules without version information (ie. modprobe
1143           --force).  Forced module loading sets the 'F' (forced) taint flag and
1144           is usually a really bad idea.
1145
1146 config MODULE_UNLOAD
1147         bool "Module unloading"
1148         help
1149           Without this option you will not be able to unload any
1150           modules (note that some modules may not be unloadable
1151           anyway), which makes your kernel smaller, faster
1152           and simpler.  If unsure, say Y.
1153
1154 config MODULE_FORCE_UNLOAD
1155         bool "Forced module unloading"
1156         depends on MODULE_UNLOAD && EXPERIMENTAL
1157         help
1158           This option allows you to force a module to unload, even if the
1159           kernel believes it is unsafe: the kernel will remove the module
1160           without waiting for anyone to stop using it (using the -f option to
1161           rmmod).  This is mainly for kernel developers and desperate users.
1162           If unsure, say N.
1163
1164 config MODVERSIONS
1165         bool "Module versioning support"
1166         help
1167           Usually, you have to use modules compiled with your kernel.
1168           Saying Y here makes it sometimes possible to use modules
1169           compiled for different kernels, by adding enough information
1170           to the modules to (hopefully) spot any changes which would
1171           make them incompatible with the kernel you are running.  If
1172           unsure, say N.
1173
1174 config MODULE_SRCVERSION_ALL
1175         bool "Source checksum for all modules"
1176         help
1177           Modules which contain a MODULE_VERSION get an extra "srcversion"
1178           field inserted into their modinfo section, which contains a
1179           sum of the source files which made it.  This helps maintainers
1180           see exactly which source was used to build a module (since
1181           others sometimes change the module source without updating
1182           the version).  With this option, such a "srcversion" field
1183           will be created for all modules.  If unsure, say N.
1184
1185 endif # MODULES
1186
1187 config INIT_ALL_POSSIBLE
1188         bool
1189         help
1190           Back when each arch used to define their own cpu_online_map and
1191           cpu_possible_map, some of them chose to initialize cpu_possible_map
1192           with all 1s, and others with all 0s.  When they were centralised,
1193           it was better to provide this option than to break all the archs
1194           and have several arch maintainers pursuing me down dark alleys.
1195
1196 config STOP_MACHINE
1197         bool
1198         default y
1199         depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1200         help
1201           Need stop_machine() primitive.
1202
1203 source "block/Kconfig"
1204
1205 config PREEMPT_NOTIFIERS
1206         bool
1207