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  47           drivers that have been replaced by something else, and/or are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