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  47           drivers that have been replaced by something else, and/or are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 CROSS_COMPILE
  80         string "Cross-compiler tool prefix"
  81         help
  82           Same as running 'make CROSS_COMPILE=prefix-' but stored for
  83           default make runs in this kernel build directory.  You don't
  84           need to set this unless you want the configured kernel build
  85           directory to select the cross-compiler automatically.
  86
  87 config LOCALVERSION
  88         string "Local version - append to kernel release"
  89         help
  90           Append an extra string to the end of your kernel version.
  91           This will show up when you type uname, for example.
  92           The string you set here will be appended after the contents of
  93           any files with a filename matching localversion* in your
  94           object and source tree, in that order.  Your total string can
  95           be a maximum of 64 characters.
  96
  97 config LOCALVERSION_AUTO
  98         bool "Automatically append version information to the version string"
  99         default y
 100         help
 101           This will try to automatically determine if the current tree is a
 102           release tree by looking for git tags that belong to the current
 103           top of tree revision.
 104
 105           A string of the format -gxxxxxxxx will be added to the localversion
 106           if a git-based tree is found.  The string generated by this will be
 107           appended after any matching localversion* files, and after the value
 108           set in CONFIG_LOCALVERSION.
 109
 110           (The actual string used here is the first eight characters produced
 111           by running the command:
 112
 113             $ git rev-parse --verify HEAD
 114
 115           which is done within the script "scripts/setlocalversion".)
 116
 117 config HAVE_KERNEL_GZIP
 118         bool
 119
 120 config HAVE_KERNEL_BZIP2
 121         bool
 122
 123 config HAVE_KERNEL_LZMA
 124         bool
 125
 126 config HAVE_KERNEL_LZO
 127         bool
 128
 129 choice
 130         prompt "Kernel compression mode"
 131         default KERNEL_GZIP
 132         depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_LZO
 133         help
 134           The linux kernel is a kind of self-extracting executable.
 135           Several compression algorithms are available, which differ
 136           in efficiency, compression and decompression speed.
 137           Compression speed is only relevant when building a kernel.
 138           Decompression speed is relevant at each boot.
 139
 140           If you have any problems with bzip2 or lzma compressed
 141           kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
 142           version of this functionality (bzip2 only), for 2.4, was
 143           supplied by Christian Ludwig)
 144
 145           High compression options are mostly useful for users, who
 146           are low on disk space (embedded systems), but for whom ram
 147           size matters less.
 148
 149           If in doubt, select 'gzip'
 150
 151 config KERNEL_GZIP
 152         bool "Gzip"
 153         depends on HAVE_KERNEL_GZIP
 154         help
 155           The old and tried gzip compression. It provides a good balance
 156           between compression ratio and decompression speed.
 157
 158 config KERNEL_BZIP2
 159         bool "Bzip2"
 160         depends on HAVE_KERNEL_BZIP2
 161         help
 162           Its compression ratio and speed is intermediate.
 163           Decompression speed is slowest among the three.  The kernel
 164           size is about 10% smaller with bzip2, in comparison to gzip.
 165           Bzip2 uses a large amount of memory. For modern kernels you
 166           will need at least 8MB RAM or more for booting.
 167
 168 config KERNEL_LZMA
 169         bool "LZMA"
 170         depends on HAVE_KERNEL_LZMA
 171         help
 172           The most recent compression algorithm.
 173           Its ratio is best, decompression speed is between the other
 174           two. Compression is slowest.  The kernel size is about 33%
 175           smaller with LZMA in comparison to gzip.
 176
 177 config KERNEL_LZO
 178         bool "LZO"
 179         depends on HAVE_KERNEL_LZO
 180         help
 181           Its compression ratio is the poorest among the 4. The kernel
 182           size is about about 10% bigger than gzip; however its speed
 183           (both compression and decompression) is the fastest.
 184
 185 endchoice
 186
 187 config SWAP
 188         bool "Support for paging of anonymous memory (swap)"
 189         depends on MMU && BLOCK
 190         default y
 191         help
 192           This option allows you to choose whether you want to have support
 193           for so called swap devices or swap files in your kernel that are
 194           used to provide more virtual memory than the actual RAM present
 195           in your computer.  If unsure say Y.
 196
 197 config SYSVIPC
 198         bool "System V IPC"
 199         ---help---
 200           Inter Process Communication is a suite of library functions and
 201           system calls which let processes (running programs) synchronize and
 202           exchange information. It is generally considered to be a good thing,
 203           and some programs won't run unless you say Y here. In particular, if
 204           you want to run the DOS emulator dosemu under Linux (read the
 205           DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
 206           you'll need to say Y here.
 207
 208           You can find documentation about IPC with "info ipc" and also in
 209           section 6.4 of the Linux Programmer's Guide, available from
 210           <http://www.tldp.org/guides.html>.
 211
 212 config SYSVIPC_SYSCTL
 213         bool
 214         depends on SYSVIPC
 215         depends on SYSCTL
 216         default y
 217
 218 config POSIX_MQUEUE
 219         bool "POSIX Message Queues"
 220         depends on NET && EXPERIMENTAL
 221         ---help---
 222           POSIX variant of message queues is a part of IPC. In POSIX message
 223           queues every message has a priority which decides about succession
 224           of receiving it by a process. If you want to compile and run
 225           programs written e.g. for Solaris with use of its POSIX message
 226           queues (functions mq_*) say Y here.
 227
 228           POSIX message queues are visible as a filesystem called 'mqueue'
 229           and can be mounted somewhere if you want to do filesystem
 230           operations on message queues.
 231
 232           If unsure, say Y.
 233
 234 config POSIX_MQUEUE_SYSCTL
 235         bool
 236         depends on POSIX_MQUEUE
 237         depends on SYSCTL
 238         default y
 239
 240 config BSD_PROCESS_ACCT
 241         bool "BSD Process Accounting"
 242         help
 243           If you say Y here, a user level program will be able to instruct the
 244           kernel (via a special system call) to write process accounting
 245           information to a file: whenever a process exits, information about
 246           that process will be appended to the file by the kernel.  The
 247           information includes things such as creation time, owning user,
 248           command name, memory usage, controlling terminal etc. (the complete
 249           list is in the struct acct in <file:include/linux/acct.h>).  It is
 250           up to the user level program to do useful things with this
 251           information.  This is generally a good idea, so say Y.
 252
 253 config BSD_PROCESS_ACCT_V3
 254         bool "BSD Process Accounting version 3 file format"
 255         depends on BSD_PROCESS_ACCT
 256         default n
 257         help
 258           If you say Y here, the process accounting information is written
 259           in a new file format that also logs the process IDs of each
 260           process and it's parent. Note that this file format is incompatible
 261           with previous v0/v1/v2 file formats, so you will need updated tools
 262           for processing it. A preliminary version of these tools is available
 263           at <http://www.gnu.org/software/acct/>.
 264
 265 config TASKSTATS
 266         bool "Export task/process statistics through netlink (EXPERIMENTAL)"
 267         depends on NET
 268         default n
 269         help
 270           Export selected statistics for tasks/processes through the
 271           generic netlink interface. Unlike BSD process accounting, the
 272           statistics are available during the lifetime of tasks/processes as
 273           responses to commands. Like BSD accounting, they are sent to user
 274           space on task exit.
 275
 276           Say N if unsure.
 277
 278 config TASK_DELAY_ACCT
 279         bool "Enable per-task delay accounting (EXPERIMENTAL)"
 280         depends on TASKSTATS
 281         help
 282           Collect information on time spent by a task waiting for system
 283           resources like cpu, synchronous block I/O completion and swapping
 284           in pages. Such statistics can help in setting a task's priorities
 285           relative to other tasks for cpu, io, rss limits etc.
 286
 287           Say N if unsure.
 288
 289 config TASK_XACCT
 290         bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
 291         depends on TASKSTATS
 292         help
 293           Collect extended task accounting data and send the data
 294           to userland for processing over the taskstats interface.
 295
 296           Say N if unsure.
 297
 298 config TASK_IO_ACCOUNTING
 299         bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
 300         depends on TASK_XACCT
 301         help
 302           Collect information on the number of bytes of storage I/O which this
 303           task has caused.
 304
 305           Say N if unsure.
 306
 307 config AUDIT
 308         bool "Auditing support"
 309         depends on NET
 310         help
 311           Enable auditing infrastructure that can be used with another
 312           kernel subsystem, such as SELinux (which requires this for
 313           logging of avc messages output).  Does not do system-call
 314           auditing without CONFIG_AUDITSYSCALL.
 315
 316 config AUDITSYSCALL
 317         bool "Enable system-call auditing support"
 318         depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH)
 319         default y if SECURITY_SELINUX
 320         help
 321           Enable low-overhead system-call auditing infrastructure that
 322           can be used independently or with another kernel subsystem,
 323           such as SELinux.
 324
 325 config AUDIT_WATCH
 326         def_bool y
 327         depends on AUDITSYSCALL
 328         select FSNOTIFY
 329
 330 config AUDIT_TREE
 331         def_bool y
 332         depends on AUDITSYSCALL
 333         select FSNOTIFY
 334
 335 source "kernel/irq/Kconfig"
 336
 337 menu "RCU Subsystem"
 338
 339 choice
 340         prompt "RCU Implementation"
 341         default TREE_RCU
 342
 343 config TREE_RCU
 344         bool "Tree-based hierarchical RCU"
 345         help
 346           This option selects the RCU implementation that is
 347           designed for very large SMP system with hundreds or
 348           thousands of CPUs.  It also scales down nicely to
 349           smaller systems.
 350
 351 config TREE_PREEMPT_RCU
 352         bool "Preemptable tree-based hierarchical RCU"
 353         depends on PREEMPT
 354         help
 355           This option selects the RCU implementation that is
 356           designed for very large SMP systems with hundreds or
 357           thousands of CPUs, but for which real-time response
 358           is also required.  It also scales down nicely to
 359           smaller systems.
 360
 361 config TINY_RCU
 362         bool "UP-only small-memory-footprint RCU"
 363         depends on !SMP
 364         help
 365           This option selects the RCU implementation that is
 366           designed for UP systems from which real-time response
 367           is not required.  This option greatly reduces the
 368           memory footprint of RCU.
 369
 370 endchoice
 371
 372 config RCU_TRACE
 373         bool "Enable tracing for RCU"
 374         depends on TREE_RCU || TREE_PREEMPT_RCU
 375         help
 376           This option provides tracing in RCU which presents stats
 377           in debugfs for debugging RCU implementation.
 378
 379           Say Y here if you want to enable RCU tracing
 380           Say N if you are unsure.
 381
 382 config RCU_FANOUT
 383         int "Tree-based hierarchical RCU fanout value"
 384         range 2 64 if 64BIT
 385         range 2 32 if !64BIT
 386         depends on TREE_RCU || TREE_PREEMPT_RCU
 387         default 64 if 64BIT
 388         default 32 if !64BIT
 389         help
 390           This option controls the fanout of hierarchical implementations
 391           of RCU, allowing RCU to work efficiently on machines with
 392           large numbers of CPUs.  This value must be at least the cube
 393           root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
 394           systems and up to 262,144 for 64-bit systems.
 395
 396           Select a specific number if testing RCU itself.
 397           Take the default if unsure.
 398
 399 config RCU_FANOUT_EXACT
 400         bool "Disable tree-based hierarchical RCU auto-balancing"
 401         depends on TREE_RCU || TREE_PREEMPT_RCU
 402         default n
 403         help
 404           This option forces use of the exact RCU_FANOUT value specified,
 405           regardless of imbalances in the hierarchy.  This is useful for
 406           testing RCU itself, and might one day be useful on systems with
 407           strong NUMA behavior.
 408
 409           Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
 410
 411           Say N if unsure.
 412
 413 config RCU_FAST_NO_HZ
 414         bool "Accelerate last non-dyntick-idle CPU's grace periods"
 415         depends on TREE_RCU && NO_HZ && SMP
 416         default n
 417         help
 418           This option causes RCU to attempt to accelerate grace periods
 419           in order to allow the final CPU to enter dynticks-idle state
 420           more quickly.  On the other hand, this option increases the
 421           overhead of the dynticks-idle checking, particularly on systems
 422           with large numbers of CPUs.
 423
 424           Say Y if energy efficiency is critically important, particularly
 425                 if you have relatively few CPUs.
 426
 427           Say N if you are unsure.
 428
 429 config TREE_RCU_TRACE
 430         def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
 431         select DEBUG_FS
 432         help
 433           This option provides tracing for the TREE_RCU and
 434           TREE_PREEMPT_RCU implementations, permitting Makefile to
 435           trivially select kernel/rcutree_trace.c.
 436
 437 endmenu # "RCU Subsystem"
 438
 439 config IKCONFIG
 440         tristate "Kernel .config support"
 441         ---help---
 442           This option enables the complete Linux kernel ".config" file
 443           contents to be saved in the kernel. It provides documentation
 444           of which kernel options are used in a running kernel or in an
 445           on-disk kernel.  This information can be extracted from the kernel
 446           image file with the script scripts/extract-ikconfig and used as
 447           input to rebuild the current kernel or to build another kernel.
 448           It can also be extracted from a running kernel by reading
 449           /proc/config.gz if enabled (below).
 450
 451 config IKCONFIG_PROC
 452         bool "Enable access to .config through /proc/config.gz"
 453         depends on IKCONFIG && PROC_FS
 454         ---help---
 455           This option enables access to the kernel configuration file
 456           through /proc/config.gz.
 457
 458 config LOG_BUF_SHIFT
 459         int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
 460         range 12 21
 461         default 17
 462         help
 463           Select kernel log buffer size as a power of 2.
 464           Examples:
 465                      17 => 128 KB
 466                      16 => 64 KB
 467                      15 => 32 KB
 468                      14 => 16 KB
 469                      13 =>  8 KB
 470                      12 =>  4 KB
 471
 472 #
 473 # Architectures with an unreliable sched_clock() should select this:
 474 #
 475 config HAVE_UNSTABLE_SCHED_CLOCK
 476         bool
 477
 478 menuconfig CGROUPS
 479         boolean "Control Group support"
 480         depends on EVENTFD
 481         help
 482           This option adds support for grouping sets of processes together, for
 483           use with process control subsystems such as Cpusets, CFS, memory
 484           controls or device isolation.
 485           See
 486                 - Documentation/scheduler/sched-design-CFS.txt  (CFS)
 487                 - Documentation/cgroups/ (features for grouping, isolation
 488                                           and resource control)
 489
 490           Say N if unsure.
 491
 492 if CGROUPS
 493
 494 config CGROUP_DEBUG
 495         bool "Example debug cgroup subsystem"
 496         depends on CGROUPS
 497         default n
 498         help
 499           This option enables a simple cgroup subsystem that
 500           exports useful debugging information about the cgroups
 501           framework.
 502
 503           Say N if unsure.
 504
 505 config CGROUP_NS
 506         bool "Namespace cgroup subsystem"
 507         depends on CGROUPS
 508         help
 509           Provides a simple namespace cgroup subsystem to
 510           provide hierarchical naming of sets of namespaces,
 511           for instance virtual servers and checkpoint/restart
 512           jobs.
 513
 514 config CGROUP_FREEZER
 515         bool "Freezer cgroup subsystem"
 516         depends on CGROUPS
 517         help
 518           Provides a way to freeze and unfreeze all tasks in a
 519           cgroup.
 520
 521 config CGROUP_DEVICE
 522         bool "Device controller for cgroups"
 523         depends on CGROUPS && EXPERIMENTAL
 524         help
 525           Provides a cgroup implementing whitelists for devices which
 526           a process in the cgroup can mknod or open.
 527
 528 config CPUSETS
 529         bool "Cpuset support"
 530         depends on CGROUPS
 531         help
 532           This option will let you create and manage CPUSETs which
 533           allow dynamically partitioning a system into sets of CPUs and
 534           Memory Nodes and assigning tasks to run only within those sets.
 535           This is primarily useful on large SMP or NUMA systems.
 536
 537           Say N if unsure.
 538
 539 config PROC_PID_CPUSET
 540         bool "Include legacy /proc/<pid>/cpuset file"
 541         depends on CPUSETS
 542         default y
 543
 544 config CGROUP_CPUACCT
 545         bool "Simple CPU accounting cgroup subsystem"
 546         depends on CGROUPS
 547         help
 548           Provides a simple Resource Controller for monitoring the
 549           total CPU consumed by the tasks in a cgroup.
 550
 551 config RESOURCE_COUNTERS
 552         bool "Resource counters"
 553         help
 554           This option enables controller independent resource accounting
 555           infrastructure that works with cgroups.
 556         depends on CGROUPS
 557
 558 config CGROUP_MEM_RES_CTLR
 559         bool "Memory Resource Controller for Control Groups"
 560         depends on CGROUPS && RESOURCE_COUNTERS
 561         select MM_OWNER
 562         help
 563           Provides a memory resource controller that manages both anonymous
 564           memory and page cache. (See Documentation/cgroups/memory.txt)
 565
 566           Note that setting this option increases fixed memory overhead
 567           associated with each page of memory in the system. By this,
 568           20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
 569           usage tracking struct at boot. Total amount of this is printed out
 570           at boot.
 571
 572           Only enable when you're ok with these trade offs and really
 573           sure you need the memory resource controller. Even when you enable
 574           this, you can set "cgroup_disable=memory" at your boot option to
 575           disable memory resource controller and you can avoid overheads.
 576           (and lose benefits of memory resource controller)
 577
 578           This config option also selects MM_OWNER config option, which
 579           could in turn add some fork/exit overhead.
 580
 581 config CGROUP_MEM_RES_CTLR_SWAP
 582         bool "Memory Resource Controller Swap Extension"
 583         depends on CGROUP_MEM_RES_CTLR && SWAP
 584         help
 585           Add swap management feature to memory resource controller. When you
 586           enable this, you can limit mem+swap usage per cgroup. In other words,
 587           when you disable this, memory resource controller has no cares to
 588           usage of swap...a process can exhaust all of the swap. This extension
 589           is useful when you want to avoid exhaustion swap but this itself
 590           adds more overheads and consumes memory for remembering information.
 591           Especially if you use 32bit system or small memory system, please
 592           be careful about enabling this. When memory resource controller
 593           is disabled by boot option, this will be automatically disabled and
 594           there will be no overhead from this. Even when you set this config=y,
 595           if boot option "noswapaccount" is set, swap will not be accounted.
 596           Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
 597           size is 4096bytes, 512k per 1Gbytes of swap.
 598
 599 menuconfig CGROUP_SCHED
 600         bool "Group CPU scheduler"
 601         depends on EXPERIMENTAL && CGROUPS
 602         default n
 603         help
 604           This feature lets CPU scheduler recognize task groups and control CPU
 605           bandwidth allocation to such task groups. It uses cgroups to group
 606           tasks.
 607
 608 if CGROUP_SCHED
 609 config FAIR_GROUP_SCHED
 610         bool "Group scheduling for SCHED_OTHER"
 611         depends on CGROUP_SCHED
 612         default CGROUP_SCHED
 613
 614 config RT_GROUP_SCHED
 615         bool "Group scheduling for SCHED_RR/FIFO"
 616         depends on EXPERIMENTAL
 617         depends on CGROUP_SCHED
 618         default n
 619         help
 620           This feature lets you explicitly allocate real CPU bandwidth
 621           to task groups. If enabled, it will also make it impossible to
 622           schedule realtime tasks for non-root users until you allocate
 623           realtime bandwidth for them.
 624           See Documentation/scheduler/sched-rt-group.txt for more information.
 625
 626 endif #CGROUP_SCHED
 627
 628 config BLK_CGROUP
 629         tristate "Block IO controller"
 630         depends on CGROUPS && BLOCK
 631         default n
 632         ---help---
 633         Generic block IO controller cgroup interface. This is the common
 634         cgroup interface which should be used by various IO controlling
 635         policies.
 636
 637         Currently, CFQ IO scheduler uses it to recognize task groups and
 638         control disk bandwidth allocation (proportional time slice allocation)
 639         to such task groups.
 640
 641         This option only enables generic Block IO controller infrastructure.
 642         One needs to also enable actual IO controlling logic in CFQ for it
 643         to take effect. (CONFIG_CFQ_GROUP_IOSCHED=y).
 644
 645         See Documentation/cgroups/blkio-controller.txt for more information.
 646
 647 config DEBUG_BLK_CGROUP
 648         bool "Enable Block IO controller debugging"
 649         depends on BLK_CGROUP
 650         default n
 651         ---help---
 652         Enable some debugging help. Currently it exports additional stat
 653         files in a cgroup which can be useful for debugging.
 654
 655 endif # CGROUPS
 656
 657 config MM_OWNER
 658         bool
 659
 660 config SYSFS_DEPRECATED
 661         bool
 662
 663 config SYSFS_DEPRECATED_V2
 664         bool "enable deprecated sysfs features to support old userspace tools"
 665         depends on SYSFS
 666         default n
 667         select SYSFS_DEPRECATED
 668         help
 669           This option switches the layout of sysfs to the deprecated
 670           version. Do not use it on recent distributions.
 671
 672           The current sysfs layout features a unified device tree at
 673           /sys/devices/, which is able to express a hierarchy between
 674           class devices. If the deprecated option is set to Y, the
 675           unified device tree is split into a bus device tree at
 676           /sys/devices/ and several individual class device trees at
 677           /sys/class/. The class and bus devices will be connected by
 678           "<subsystem>:<name>" and the "device" links. The "block"
 679           class devices, will not show up in /sys/class/block/. Some
 680           subsystems will suppress the creation of some devices which
 681           depend on the unified device tree.
 682
 683           This option is not a pure compatibility option that can
 684           be safely enabled on newer distributions. It will change the
 685           layout of sysfs to the non-extensible deprecated version,
 686           and disable some features, which can not be exported without
 687           confusing older userspace tools. Since 2007/2008 all major
 688           distributions do not enable this option, and ship no tools which
 689           depend on the deprecated layout or this option.
 690
 691           If you are using a new kernel on an older distribution, or use
 692           older userspace tools, you might need to say Y here. Do not say Y,
 693           if the original kernel, that came with your distribution, has
 694           this option set to N.
 695
 696 config RELAY
 697         bool "Kernel->user space relay support (formerly relayfs)"
 698         help
 699           This option enables support for relay interface support in
 700           certain file systems (such as debugfs).
 701           It is designed to provide an efficient mechanism for tools and
 702           facilities to relay large amounts of data from kernel space to
 703           user space.
 704
 705           If unsure, say N.
 706
 707 config NAMESPACES
 708         bool "Namespaces support" if EMBEDDED
 709         default !EMBEDDED
 710         help
 711           Provides the way to make tasks work with different objects using
 712           the same id. For example same IPC id may refer to different objects
 713           or same user id or pid may refer to different tasks when used in
 714           different namespaces.
 715
 716 config UTS_NS
 717         bool "UTS namespace"
 718         depends on NAMESPACES
 719         help
 720           In this namespace tasks see different info provided with the
 721           uname() system call
 722
 723 config IPC_NS
 724         bool "IPC namespace"
 725         depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
 726         help
 727           In this namespace tasks work with IPC ids which correspond to
 728           different IPC objects in different namespaces.
 729
 730 config USER_NS
 731         bool "User namespace (EXPERIMENTAL)"
 732         depends on NAMESPACES && EXPERIMENTAL
 733         help
 734           This allows containers, i.e. vservers, to use user namespaces
 735           to provide different user info for different servers.
 736           If unsure, say N.
 737
 738 config PID_NS
 739         bool "PID Namespaces (EXPERIMENTAL)"
 740         default n
 741         depends on NAMESPACES && EXPERIMENTAL
 742         help
 743           Support process id namespaces.  This allows having multiple
 744           processes with the same pid as long as they are in different
 745           pid namespaces.  This is a building block of containers.
 746
 747           Unless you want to work with an experimental feature
 748           say N here.
 749
 750 config NET_NS
 751         bool "Network namespace"
 752         default n
 753         depends on NAMESPACES && EXPERIMENTAL && NET
 754         help
 755           Allow user space to create what appear to be multiple instances
 756           of the network stack.
 757
 758 config BLK_DEV_INITRD
 759         bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
 760         depends on BROKEN || !FRV
 761         help
 762           The initial RAM filesystem is a ramfs which is loaded by the
 763           boot loader (loadlin or lilo) and that is mounted as root
 764           before the normal boot procedure. It is typically used to
 765           load modules needed to mount the "real" root file system,
 766           etc. See <file:Documentation/initrd.txt> for details.
 767
 768           If RAM disk support (BLK_DEV_RAM) is also included, this
 769           also enables initial RAM disk (initrd) support and adds
 770           15 Kbytes (more on some other architectures) to the kernel size.
 771
 772           If unsure say Y.
 773
 774 if BLK_DEV_INITRD
 775
 776 source "usr/Kconfig"
 777
 778 endif
 779
 780 config CC_OPTIMIZE_FOR_SIZE
 781         bool "Optimize for size"
 782         default y
 783         help
 784           Enabling this option will pass "-Os" instead of "-O2" to gcc
 785           resulting in a smaller kernel.
 786
 787           If unsure, say Y.
 788
 789 config SYSCTL
 790         bool
 791
 792 config ANON_INODES
 793         bool
 794
 795 menuconfig EMBEDDED
 796         bool "Configure standard kernel features (for small systems)"
 797         help
 798           This option allows certain base kernel options and settings
 799           to be disabled or tweaked. This is for specialized
 800           environments which can tolerate a "non-standard" kernel.
 801           Only use this if you really know what you are doing.
 802
 803 config UID16
 804         bool "Enable 16-bit UID system calls" if EMBEDDED
 805         depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
 806         default y
 807         help
 808           This enables the legacy 16-bit UID syscall wrappers.
 809
 810 config SYSCTL_SYSCALL
 811         bool "Sysctl syscall support" if EMBEDDED
 812         depends on PROC_SYSCTL
 813         default y
 814         select SYSCTL
 815         ---help---
 816           sys_sysctl uses binary paths that have been found challenging
 817           to properly maintain and use.  The interface in /proc/sys
 818           using paths with ascii names is now the primary path to this
 819           information.
 820
 821           Almost nothing using the binary sysctl interface so if you are
 822           trying to save some space it is probably safe to disable this,
 823           making your kernel marginally smaller.
 824
 825           If unsure say Y here.
 826
 827 config KALLSYMS
 828          bool "Load all symbols for debugging/ksymoops" if EMBEDDED
 829          default y
 830          help
 831            Say Y here to let the kernel print out symbolic crash information and
 832            symbolic stack backtraces. This increases the size of the kernel
 833            somewhat, as all symbols have to be loaded into the kernel image.
 834
 835 config KALLSYMS_ALL
 836         bool "Include all symbols in kallsyms"
 837         depends on DEBUG_KERNEL && KALLSYMS
 838         help
 839            Normally kallsyms only contains the symbols of functions, for nicer
 840            OOPS messages.  Some debuggers can use kallsyms for other
 841            symbols too: say Y here to include all symbols, if you need them
 842            and you don't care about adding 300k to the size of your kernel.
 843
 844            Say N.
 845
 846 config KALLSYMS_EXTRA_PASS
 847         bool "Do an extra kallsyms pass"
 848         depends on KALLSYMS
 849         help
 850            If kallsyms is not working correctly, the build will fail with
 851            inconsistent kallsyms data.  If that occurs, log a bug report and
 852            turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
 853            Always say N here unless you find a bug in kallsyms, which must be
 854            reported.  KALLSYMS_EXTRA_PASS is only a temporary workaround while
 855            you wait for kallsyms to be fixed.
 856
 857
 858 config HOTPLUG
 859         bool "Support for hot-pluggable devices" if EMBEDDED
 860         default y
 861         help
 862           This option is provided for the case where no hotplug or uevent
 863           capabilities is wanted by the kernel.  You should only consider
 864           disabling this option for embedded systems that do not use modules, a
 865           dynamic /dev tree, or dynamic device discovery.  Just say Y.
 866
 867 config PRINTK
 868         default y
 869         bool "Enable support for printk" if EMBEDDED
 870         help
 871           This option enables normal printk support. Removing it
 872           eliminates most of the message strings from the kernel image
 873           and makes the kernel more or less silent. As this makes it
 874           very difficult to diagnose system problems, saying N here is
 875           strongly discouraged.
 876
 877 config BUG
 878         bool "BUG() support" if EMBEDDED
 879         default y
 880         help
 881           Disabling this option eliminates support for BUG and WARN, reducing
 882           the size of your kernel image and potentially quietly ignoring
 883           numerous fatal conditions. You should only consider disabling this
 884           option for embedded systems with no facilities for reporting errors.
 885           Just say Y.
 886
 887 config ELF_CORE
 888         default y
 889         bool "Enable ELF core dumps" if EMBEDDED
 890         help
 891           Enable support for generating core dumps. Disabling saves about 4k.
 892
 893 config PCSPKR_PLATFORM
 894         bool "Enable PC-Speaker support" if EMBEDDED
 895         depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
 896         default y
 897         help
 898           This option allows to disable the internal PC-Speaker
 899           support, saving some memory.
 900
 901 config BASE_FULL
 902         default y
 903         bool "Enable full-sized data structures for core" if EMBEDDED
 904         help
 905           Disabling this option reduces the size of miscellaneous core
 906           kernel data structures. This saves memory on small machines,
 907           but may reduce performance.
 908
 909 config FUTEX
 910         bool "Enable futex support" if EMBEDDED
 911         default y
 912         select RT_MUTEXES
 913         help
 914           Disabling this option will cause the kernel to be built without
 915           support for "fast userspace mutexes".  The resulting kernel may not
 916           run glibc-based applications correctly.
 917
 918 config EPOLL
 919         bool "Enable eventpoll support" if EMBEDDED
 920         default y
 921         select ANON_INODES
 922         help
 923           Disabling this option will cause the kernel to be built without
 924           support for epoll family of system calls.
 925
 926 config SIGNALFD
 927         bool "Enable signalfd() system call" if EMBEDDED
 928         select ANON_INODES
 929         default y
 930         help
 931           Enable the signalfd() system call that allows to receive signals
 932           on a file descriptor.
 933
 934           If unsure, say Y.
 935
 936 config TIMERFD
 937         bool "Enable timerfd() system call" if EMBEDDED
 938         select ANON_INODES
 939         default y
 940         help
 941           Enable the timerfd() system call that allows to receive timer
 942           events on a file descriptor.
 943
 944           If unsure, say Y.
 945
 946 config EVENTFD
 947         bool "Enable eventfd() system call" if EMBEDDED
 948         select ANON_INODES
 949         default y
 950         help
 951           Enable the eventfd() system call that allows to receive both
 952           kernel notification (ie. KAIO) or userspace notifications.
 953
 954           If unsure, say Y.
 955
 956 config SHMEM
 957         bool "Use full shmem filesystem" if EMBEDDED
 958         default y
 959         depends on MMU
 960         help
 961           The shmem is an internal filesystem used to manage shared memory.
 962           It is backed by swap and manages resource limits. It is also exported
 963           to userspace as tmpfs if TMPFS is enabled. Disabling this
 964           option replaces shmem and tmpfs with the much simpler ramfs code,
 965           which may be appropriate on small systems without swap.
 966
 967 config AIO
 968         bool "Enable AIO support" if EMBEDDED
 969         default y
 970         help
 971           This option enables POSIX asynchronous I/O which may by used
 972           by some high performance threaded applications. Disabling
 973           this option saves about 7k.
 974
 975 config HAVE_PERF_EVENTS
 976         bool
 977         help
 978           See tools/perf/design.txt for details.
 979
 980 config PERF_USE_VMALLOC
 981         bool
 982         help
 983           See tools/perf/design.txt for details
 984
 985 menu "Kernel Performance Events And Counters"
 986
 987 config PERF_EVENTS
 988         bool "Kernel performance events and counters"
 989         default y if (PROFILING || PERF_COUNTERS)
 990         depends on HAVE_PERF_EVENTS
 991         select ANON_INODES
 992         help
 993           Enable kernel support for various performance events provided
 994           by software and hardware.
 995
 996           Software events are supported either built-in or via the
 997           use of generic tracepoints.
 998
 999           Most modern CPUs support performance events via performance
1000           counter registers. These registers count the number of certain
1001           types of hw events: such as instructions executed, cachemisses
1002           suffered, or branches mis-predicted - without slowing down the
1003           kernel or applications. These registers can also trigger interrupts
1004           when a threshold number of events have passed - and can thus be
1005           used to profile the code that runs on that CPU.
1006
1007           The Linux Performance Event subsystem provides an abstraction of
1008           these software and hardware event capabilities, available via a
1009           system call and used by the "perf" utility in tools/perf/. It
1010           provides per task and per CPU counters, and it provides event
1011           capabilities on top of those.
1012
1013           Say Y if unsure.
1014
1015 config PERF_COUNTERS
1016         bool "Kernel performance counters (old config option)"
1017         depends on HAVE_PERF_EVENTS
1018         help
1019           This config has been obsoleted by the PERF_EVENTS
1020           config option - please see that one for details.
1021
1022           It has no effect on the kernel whether you enable
1023           it or not, it is a compatibility placeholder.
1024
1025           Say N if unsure.
1026
1027 config DEBUG_PERF_USE_VMALLOC
1028         default n
1029         bool "Debug: use vmalloc to back perf mmap() buffers"
1030         depends on PERF_EVENTS && DEBUG_KERNEL
1031         select PERF_USE_VMALLOC
1032         help
1033          Use vmalloc memory to back perf mmap() buffers.
1034
1035          Mostly useful for debugging the vmalloc code on platforms
1036          that don't require it.
1037
1038          Say N if unsure.
1039
1040 endmenu
1041
1042 config VM_EVENT_COUNTERS
1043         default y
1044         bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
1045         help
1046           VM event counters are needed for event counts to be shown.
1047           This option allows the disabling of the VM event counters
1048           on EMBEDDED systems.  /proc/vmstat will only show page counts
1049           if VM event counters are disabled.
1050
1051 config PCI_QUIRKS
1052         default y
1053         bool "Enable PCI quirk workarounds" if EMBEDDED
1054         depends on PCI
1055         help
1056           This enables workarounds for various PCI chipset
1057           bugs/quirks. Disable this only if your target machine is
1058           unaffected by PCI quirks.
1059
1060 config SLUB_DEBUG
1061         default y
1062         bool "Enable SLUB debugging support" if EMBEDDED
1063         depends on SLUB && SYSFS
1064         help
1065           SLUB has extensive debug support features. Disabling these can
1066           result in significant savings in code size. This also disables
1067           SLUB sysfs support. /sys/slab will not exist and there will be
1068           no support for cache validation etc.
1069
1070 config COMPAT_BRK
1071         bool "Disable heap randomization"
1072         default y
1073         help
1074           Randomizing heap placement makes heap exploits harder, but it
1075           also breaks ancient binaries (including anything libc5 based).
1076           This option changes the bootup default to heap randomization
1077           disabled, and can be overridden at runtime by setting
1078           /proc/sys/kernel/randomize_va_space to 2.
1079
1080           On non-ancient distros (post-2000 ones) N is usually a safe choice.
1081
1082 choice
1083         prompt "Choose SLAB allocator"
1084         default SLUB
1085         help
1086            This option allows to select a slab allocator.
1087
1088 config SLAB
1089         bool "SLAB"
1090         help
1091           The regular slab allocator that is established and known to work
1092           well in all environments. It organizes cache hot objects in
1093           per cpu and per node queues.
1094
1095 config SLUB
1096         bool "SLUB (Unqueued Allocator)"
1097         help
1098            SLUB is a slab allocator that minimizes cache line usage
1099            instead of managing queues of cached objects (SLAB approach).
1100            Per cpu caching is realized using slabs of objects instead
1101            of queues of objects. SLUB can use memory efficiently
1102            and has enhanced diagnostics. SLUB is the default choice for
1103            a slab allocator.
1104
1105 config SLOB
1106         depends on EMBEDDED
1107         bool "SLOB (Simple Allocator)"
1108         help
1109            SLOB replaces the stock allocator with a drastically simpler
1110            allocator. SLOB is generally more space efficient but
1111            does not perform as well on large systems.
1112
1113 endchoice
1114
1115 config MMAP_ALLOW_UNINITIALIZED
1116         bool "Allow mmapped anonymous memory to be uninitialized"
1117         depends on EMBEDDED && !MMU
1118         default n
1119         help
1120           Normally, and according to the Linux spec, anonymous memory obtained
1121           from mmap() has it's contents cleared before it is passed to
1122           userspace.  Enabling this config option allows you to request that
1123           mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1124           providing a huge performance boost.  If this option is not enabled,
1125           then the flag will be ignored.
1126
1127           This is taken advantage of by uClibc's malloc(), and also by
1128           ELF-FDPIC binfmt's brk and stack allocator.
1129
1130           Because of the obvious security issues, this option should only be
1131           enabled on embedded devices where you control what is run in
1132           userspace.  Since that isn't generally a problem on no-MMU systems,
1133           it is normally safe to say Y here.
1134
1135           See Documentation/nommu-mmap.txt for more information.
1136
1137 config PROFILING
1138         bool "Profiling support"
1139         help
1140           Say Y here to enable the extended profiling support mechanisms used
1141           by profilers such as OProfile.
1142
1143 #
1144 # Place an empty function call at each tracepoint site. Can be
1145 # dynamically changed for a probe function.
1146 #
1147 config TRACEPOINTS
1148         bool
1149
1150 source "arch/Kconfig"
1151
1152 endmenu         # General setup
1153
1154 config HAVE_GENERIC_DMA_COHERENT
1155         bool
1156         default n
1157
1158 config SLABINFO
1159         bool
1160         depends on PROC_FS
1161         depends on SLAB || SLUB_DEBUG
1162         default y
1163
1164 config RT_MUTEXES
1165         boolean
1166
1167 config BASE_SMALL
1168         int
1169         default 0 if BASE_FULL
1170         default 1 if !BASE_FULL
1171
1172 menuconfig MODULES
1173         bool "Enable loadable module support"
1174         help
1175           Kernel modules are small pieces of compiled code which can
1176           be inserted in the running kernel, rather than being
1177           permanently built into the kernel.  You use the "modprobe"
1178           tool to add (and sometimes remove) them.  If you say Y here,
1179           many parts of the kernel can be built as modules (by
1180           answering M instead of Y where indicated): this is most
1181           useful for infrequently used options which are not required
1182           for booting.  For more information, see the man pages for
1183           modprobe, lsmod, modinfo, insmod and rmmod.
1184
1185           If you say Y here, you will need to run "make
1186           modules_install" to put the modules under /lib/modules/
1187           where modprobe can find them (you may need to be root to do
1188           this).
1189
1190           If unsure, say Y.
1191
1192 if MODULES
1193
1194 config MODULE_FORCE_LOAD
1195         bool "Forced module loading"
1196         default n
1197         help
1198           Allow loading of modules without version information (ie. modprobe
1199           --force).  Forced module loading sets the 'F' (forced) taint flag and
1200           is usually a really bad idea.
1201
1202 config MODULE_UNLOAD
1203         bool "Module unloading"
1204         help
1205           Without this option you will not be able to unload any
1206           modules (note that some modules may not be unloadable
1207           anyway), which makes your kernel smaller, faster
1208           and simpler.  If unsure, say Y.
1209
1210 config MODULE_FORCE_UNLOAD
1211         bool "Forced module unloading"
1212         depends on MODULE_UNLOAD && EXPERIMENTAL
1213         help
1214           This option allows you to force a module to unload, even if the
1215           kernel believes it is unsafe: the kernel will remove the module
1216           without waiting for anyone to stop using it (using the -f option to
1217           rmmod).  This is mainly for kernel developers and desperate users.
1218           If unsure, say N.
1219
1220 config MODVERSIONS
1221         bool "Module versioning support"
1222         help
1223           Usually, you have to use modules compiled with your kernel.
1224           Saying Y here makes it sometimes possible to use modules
1225           compiled for different kernels, by adding enough information
1226           to the modules to (hopefully) spot any changes which would
1227           make them incompatible with the kernel you are running.  If
1228           unsure, say N.
1229
1230 config MODULE_SRCVERSION_ALL
1231         bool "Source checksum for all modules"
1232         help
1233           Modules which contain a MODULE_VERSION get an extra "srcversion"
1234           field inserted into their modinfo section, which contains a
1235           sum of the source files which made it.  This helps maintainers
1236           see exactly which source was used to build a module (since
1237           others sometimes change the module source without updating
1238           the version).  With this option, such a "srcversion" field
1239           will be created for all modules.  If unsure, say N.
1240
1241 endif # MODULES
1242
1243 config INIT_ALL_POSSIBLE
1244         bool
1245         help
1246           Back when each arch used to define their own cpu_online_map and
1247           cpu_possible_map, some of them chose to initialize cpu_possible_map
1248           with all 1s, and others with all 0s.  When they were centralised,
1249           it was better to provide this option than to break all the archs
1250           and have several arch maintainers pursuing me down dark alleys.
1251
1252 config STOP_MACHINE
1253         bool
1254         default y
1255         depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1256         help
1257           Need stop_machine() primitive.
1258
1259 source "block/Kconfig"
1260
1261 config PREEMPT_NOTIFIERS
1262         bool
1263
1264 config PADATA
1265         depends on SMP
1266         bool
1267
1268 source "kernel/Kconfig.locks"