init/Kconfig

   1 config ARCH
   2         string
   3         option env="ARCH"
   4
   5 config KERNELVERSION
   6         string
   7         option env="KERNELVERSION"
   8
   9 config DEFCONFIG_LIST
  10         string
  11         depends on !UML
  12         option defconfig_list
  13         default "/lib/modules/$UNAME_RELEASE/.config"
  14         default "/etc/kernel-config"
  15         default "/boot/config-$UNAME_RELEASE"
  16         default "$ARCH_DEFCONFIG"
  17         default "arch/$ARCH/defconfig"
  18
  19 config CONSTRUCTORS
  20         bool
  21         depends on !UML
  22         default y
  23
  24 menu "General setup"
  25
  26 config EXPERIMENTAL
  27         bool "Prompt for development and/or incomplete code/drivers"
  28         ---help---
  29           Some of the various things that Linux supports (such as network
  30           drivers, file systems, network protocols, etc.) can be in a state
  31           of development where the functionality, stability, or the level of
  32           testing is not yet high enough for general use. This is usually
  33           known as the "alpha-test" phase among developers. If a feature is
  34           currently in alpha-test, then the developers usually discourage
  35           uninformed widespread use of this feature by the general public to
  36           avoid "Why doesn't this work?" type mail messages. However, active
  37           testing and use of these systems is welcomed. Just be aware that it
  38           may not meet the normal level of reliability or it may fail to work
  39           in some special cases. Detailed bug reports from people familiar
  40           with the kernel internals are usually welcomed by the developers
  41           (before submitting bug reports, please read the documents
  42           <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
  43           <file:Documentation/BUG-HUNTING>, and
  44           <file:Documentation/oops-tracing.txt> in the kernel source).
  45
  46           This option will also make obsoleted drivers available. These are
  47           drivers that have been replaced by something else, and/or are
  48           scheduled to be removed in a future kernel release.
  49
  50           Unless you intend to help test and develop a feature or driver that
  51           falls into this category, or you have a situation that requires
  52           using these features, you should probably say N here, which will
  53           cause the configurator to present you with fewer choices. If
  54           you say Y here, you will be offered the choice of using features or
  55           drivers that are currently considered to be in the alpha-test phase.
  56
  57 config BROKEN
  58         bool
  59
  60 config BROKEN_ON_SMP
  61         bool
  62         depends on BROKEN || !SMP
  63         default y
  64
  65 config LOCK_KERNEL
  66         bool
  67         depends on SMP || PREEMPT
  68         default y
  69
  70 config INIT_ENV_ARG_LIMIT
  71         int
  72         default 32 if !UML
  73         default 128 if UML
  74         help
  75           Maximum of each of the number of arguments and environment
  76           variables passed to init from the kernel command line.
  77
  78
  79 config LOCALVERSION
  80         string "Local version - append to kernel release"
  81         help
  82           Append an extra string to the end of your kernel version.
  83           This will show up when you type uname, for example.
  84           The string you set here will be appended after the contents of
  85           any files with a filename matching localversion* in your
  86           object and source tree, in that order.  Your total string can
  87           be a maximum of 64 characters.
  88
  89 config LOCALVERSION_AUTO
  90         bool "Automatically append version information to the version string"
  91         default y
  92         help
  93           This will try to automatically determine if the current tree is a
  94           release tree by looking for git tags that belong to the current
  95           top of tree revision.
  96
  97           A string of the format -gxxxxxxxx will be added to the localversion
  98           if a git-based tree is found.  The string generated by this will be
  99           appended after any matching localversion* files, and after the value
 100           set in CONFIG_LOCALVERSION.
 101
 102           (The actual string used here is the first eight characters produced
 103           by running the command:
 104
 105             $ git rev-parse --verify HEAD
 106
 107           which is done within the script "scripts/setlocalversion".)
 108
 109 config HAVE_KERNEL_GZIP
 110         bool
 111
 112 config HAVE_KERNEL_BZIP2
 113         bool
 114
 115 config HAVE_KERNEL_LZMA
 116         bool
 117
 118 choice
 119         prompt "Kernel compression mode"
 120         default KERNEL_GZIP
 121         depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA
 122         help
 123           The linux kernel is a kind of self-extracting executable.
 124           Several compression algorithms are available, which differ
 125           in efficiency, compression and decompression speed.
 126           Compression speed is only relevant when building a kernel.
 127           Decompression speed is relevant at each boot.
 128
 129           If you have any problems with bzip2 or lzma compressed
 130           kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
 131           version of this functionality (bzip2 only), for 2.4, was
 132           supplied by Christian Ludwig)
 133
 134           High compression options are mostly useful for users, who
 135           are low on disk space (embedded systems), but for whom ram
 136           size matters less.
 137
 138           If in doubt, select 'gzip'
 139
 140 config KERNEL_GZIP
 141         bool "Gzip"
 142         depends on HAVE_KERNEL_GZIP
 143         help
 144           The old and tried gzip compression. Its compression ratio is
 145           the poorest among the 3 choices; however its speed (both
 146           compression and decompression) is the fastest.
 147
 148 config KERNEL_BZIP2
 149         bool "Bzip2"
 150         depends on HAVE_KERNEL_BZIP2
 151         help
 152           Its compression ratio and speed is intermediate.
 153           Decompression speed is slowest among the three.  The kernel
 154           size is about 10% smaller with bzip2, in comparison to gzip.
 155           Bzip2 uses a large amount of memory. For modern kernels you
 156           will need at least 8MB RAM or more for booting.
 157
 158 config KERNEL_LZMA
 159         bool "LZMA"
 160         depends on HAVE_KERNEL_LZMA
 161         help
 162           The most recent compression algorithm.
 163           Its ratio is best, decompression speed is between the other
 164           two. Compression is slowest.  The kernel size is about 33%
 165           smaller with LZMA in comparison to gzip.
 166
 167 endchoice
 168
 169 config SWAP
 170         bool "Support for paging of anonymous memory (swap)"
 171         depends on MMU && BLOCK
 172         default y
 173         help
 174           This option allows you to choose whether you want to have support
 175           for so called swap devices or swap files in your kernel that are
 176           used to provide more virtual memory than the actual RAM present
 177           in your computer.  If unsure say Y.
 178
 179 config SYSVIPC
 180         bool "System V IPC"
 181         ---help---
 182           Inter Process Communication is a suite of library functions and
 183           system calls which let processes (running programs) synchronize and
 184           exchange information. It is generally considered to be a good thing,
 185           and some programs won't run unless you say Y here. In particular, if
 186           you want to run the DOS emulator dosemu under Linux (read the
 187           DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
 188           you'll need to say Y here.
 189
 190           You can find documentation about IPC with "info ipc" and also in
 191           section 6.4 of the Linux Programmer's Guide, available from
 192           <http://www.tldp.org/guides.html>.
 193
 194 config SYSVIPC_SYSCTL
 195         bool
 196         depends on SYSVIPC
 197         depends on SYSCTL
 198         default y
 199
 200 config POSIX_MQUEUE
 201         bool "POSIX Message Queues"
 202         depends on NET && EXPERIMENTAL
 203         ---help---
 204           POSIX variant of message queues is a part of IPC. In POSIX message
 205           queues every message has a priority which decides about succession
 206           of receiving it by a process. If you want to compile and run
 207           programs written e.g. for Solaris with use of its POSIX message
 208           queues (functions mq_*) say Y here.
 209
 210           POSIX message queues are visible as a filesystem called 'mqueue'
 211           and can be mounted somewhere if you want to do filesystem
 212           operations on message queues.
 213
 214           If unsure, say Y.
 215
 216 config POSIX_MQUEUE_SYSCTL
 217         bool
 218         depends on POSIX_MQUEUE
 219         depends on SYSCTL
 220         default y
 221
 222 config BSD_PROCESS_ACCT
 223         bool "BSD Process Accounting"
 224         help
 225           If you say Y here, a user level program will be able to instruct the
 226           kernel (via a special system call) to write process accounting
 227           information to a file: whenever a process exits, information about
 228           that process will be appended to the file by the kernel.  The
 229           information includes things such as creation time, owning user,
 230           command name, memory usage, controlling terminal etc. (the complete
 231           list is in the struct acct in <file:include/linux/acct.h>).  It is
 232           up to the user level program to do useful things with this
 233           information.  This is generally a good idea, so say Y.
 234
 235 config BSD_PROCESS_ACCT_V3
 236         bool "BSD Process Accounting version 3 file format"
 237         depends on BSD_PROCESS_ACCT
 238         default n
 239         help
 240           If you say Y here, the process accounting information is written
 241           in a new file format that also logs the process IDs of each
 242           process and it's parent. Note that this file format is incompatible
 243           with previous v0/v1/v2 file formats, so you will need updated tools
 244           for processing it. A preliminary version of these tools is available
 245           at <http://www.gnu.org/software/acct/>.
 246
 247 config TASKSTATS
 248         bool "Export task/process statistics through netlink (EXPERIMENTAL)"
 249         depends on NET
 250         default n
 251         help
 252           Export selected statistics for tasks/processes through the
 253           generic netlink interface. Unlike BSD process accounting, the
 254           statistics are available during the lifetime of tasks/processes as
 255           responses to commands. Like BSD accounting, they are sent to user
 256           space on task exit.
 257
 258           Say N if unsure.
 259
 260 config TASK_DELAY_ACCT
 261         bool "Enable per-task delay accounting (EXPERIMENTAL)"
 262         depends on TASKSTATS
 263         help
 264           Collect information on time spent by a task waiting for system
 265           resources like cpu, synchronous block I/O completion and swapping
 266           in pages. Such statistics can help in setting a task's priorities
 267           relative to other tasks for cpu, io, rss limits etc.
 268
 269           Say N if unsure.
 270
 271 config TASK_XACCT
 272         bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
 273         depends on TASKSTATS
 274         help
 275           Collect extended task accounting data and send the data
 276           to userland for processing over the taskstats interface.
 277
 278           Say N if unsure.
 279
 280 config TASK_IO_ACCOUNTING
 281         bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
 282         depends on TASK_XACCT
 283         help
 284           Collect information on the number of bytes of storage I/O which this
 285           task has caused.
 286
 287           Say N if unsure.
 288
 289 config AUDIT
 290         bool "Auditing support"
 291         depends on NET
 292         help
 293           Enable auditing infrastructure that can be used with another
 294           kernel subsystem, such as SELinux (which requires this for
 295           logging of avc messages output).  Does not do system-call
 296           auditing without CONFIG_AUDITSYSCALL.
 297
 298 config AUDITSYSCALL
 299         bool "Enable system-call auditing support"
 300         depends on AUDIT && (X86 || PPC || PPC64 || S390 || IA64 || UML || SPARC64|| SUPERH)
 301         default y if SECURITY_SELINUX
 302         help
 303           Enable low-overhead system-call auditing infrastructure that
 304           can be used independently or with another kernel subsystem,
 305           such as SELinux.  To use audit's filesystem watch feature, please
 306           ensure that INOTIFY is configured.
 307
 308 config AUDIT_TREE
 309         def_bool y
 310         depends on AUDITSYSCALL
 311         select INOTIFY
 312
 313 menu "RCU Subsystem"
 314
 315 choice
 316         prompt "RCU Implementation"
 317         default TREE_RCU
 318
 319 config TREE_RCU
 320         bool "Tree-based hierarchical RCU"
 321         help
 322           This option selects the RCU implementation that is
 323           designed for very large SMP system with hundreds or
 324           thousands of CPUs.  It also scales down nicely to
 325           smaller systems.
 326
 327 config TREE_PREEMPT_RCU
 328         bool "Preemptable tree-based hierarchical RCU"
 329         depends on PREEMPT
 330         help
 331           This option selects the RCU implementation that is
 332           designed for very large SMP systems with hundreds or
 333           thousands of CPUs, but for which real-time response
 334           is also required.
 335
 336 endchoice
 337
 338 config RCU_TRACE
 339         bool "Enable tracing for RCU"
 340         depends on TREE_RCU || TREE_PREEMPT_RCU
 341         help
 342           This option provides tracing in RCU which presents stats
 343           in debugfs for debugging RCU implementation.
 344
 345           Say Y here if you want to enable RCU tracing
 346           Say N if you are unsure.
 347
 348 config RCU_FANOUT
 349         int "Tree-based hierarchical RCU fanout value"
 350         range 2 64 if 64BIT
 351         range 2 32 if !64BIT
 352         depends on TREE_RCU || TREE_PREEMPT_RCU
 353         default 64 if 64BIT
 354         default 32 if !64BIT
 355         help
 356           This option controls the fanout of hierarchical implementations
 357           of RCU, allowing RCU to work efficiently on machines with
 358           large numbers of CPUs.  This value must be at least the cube
 359           root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
 360           systems and up to 262,144 for 64-bit systems.
 361
 362           Select a specific number if testing RCU itself.
 363           Take the default if unsure.
 364
 365 config RCU_FANOUT_EXACT
 366         bool "Disable tree-based hierarchical RCU auto-balancing"
 367         depends on TREE_RCU || TREE_PREEMPT_RCU
 368         default n
 369         help
 370           This option forces use of the exact RCU_FANOUT value specified,
 371           regardless of imbalances in the hierarchy.  This is useful for
 372           testing RCU itself, and might one day be useful on systems with
 373           strong NUMA behavior.
 374
 375           Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
 376
 377           Say N if unsure.
 378
 379 config TREE_RCU_TRACE
 380         def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
 381         select DEBUG_FS
 382         help
 383           This option provides tracing for the TREE_RCU and
 384           TREE_PREEMPT_RCU implementations, permitting Makefile to
 385           trivially select kernel/rcutree_trace.c.
 386
 387 endmenu # "RCU Subsystem"
 388
 389 config IKCONFIG
 390         tristate "Kernel .config support"
 391         ---help---
 392           This option enables the complete Linux kernel ".config" file
 393           contents to be saved in the kernel. It provides documentation
 394           of which kernel options are used in a running kernel or in an
 395           on-disk kernel.  This information can be extracted from the kernel
 396           image file with the script scripts/extract-ikconfig and used as
 397           input to rebuild the current kernel or to build another kernel.
 398           It can also be extracted from a running kernel by reading
 399           /proc/config.gz if enabled (below).
 400
 401 config IKCONFIG_PROC
 402         bool "Enable access to .config through /proc/config.gz"
 403         depends on IKCONFIG && PROC_FS
 404         ---help---
 405           This option enables access to the kernel configuration file
 406           through /proc/config.gz.
 407
 408 config LOG_BUF_SHIFT
 409         int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
 410         range 12 21
 411         default 17
 412         help
 413           Select kernel log buffer size as a power of 2.
 414           Examples:
 415                      17 => 128 KB
 416                      16 => 64 KB
 417                      15 => 32 KB
 418                      14 => 16 KB
 419                      13 =>  8 KB
 420                      12 =>  4 KB
 421
 422 #
 423 # Architectures with an unreliable sched_clock() should select this:
 424 #
 425 config HAVE_UNSTABLE_SCHED_CLOCK
 426         bool
 427
 428 config GROUP_SCHED
 429         bool "Group CPU scheduler"
 430         depends on EXPERIMENTAL
 431         default n
 432         help
 433           This feature lets CPU scheduler recognize task groups and control CPU
 434           bandwidth allocation to such task groups.
 435           In order to create a group from arbitrary set of processes, use
 436           CONFIG_CGROUPS. (See Control Group support.)
 437
 438 config FAIR_GROUP_SCHED
 439         bool "Group scheduling for SCHED_OTHER"
 440         depends on GROUP_SCHED
 441         default GROUP_SCHED
 442
 443 config RT_GROUP_SCHED
 444         bool "Group scheduling for SCHED_RR/FIFO"
 445         depends on EXPERIMENTAL
 446         depends on GROUP_SCHED
 447         default n
 448         help
 449           This feature lets you explicitly allocate real CPU bandwidth
 450           to users or control groups (depending on the "Basis for grouping tasks"
 451           setting below. If enabled, it will also make it impossible to
 452           schedule realtime tasks for non-root users until you allocate
 453           realtime bandwidth for them.
 454           See Documentation/scheduler/sched-rt-group.txt for more information.
 455
 456 choice
 457         depends on GROUP_SCHED
 458         prompt "Basis for grouping tasks"
 459         default USER_SCHED
 460
 461 config USER_SCHED
 462         bool "user id"
 463         help
 464           This option will choose userid as the basis for grouping
 465           tasks, thus providing equal CPU bandwidth to each user.
 466
 467 config CGROUP_SCHED
 468         bool "Control groups"
 469         depends on CGROUPS
 470         help
 471           This option allows you to create arbitrary task groups
 472           using the "cgroup" pseudo filesystem and control
 473           the cpu bandwidth allocated to each such task group.
 474           Refer to Documentation/cgroups/cgroups.txt for more
 475           information on "cgroup" pseudo filesystem.
 476
 477 endchoice
 478
 479 menuconfig CGROUPS
 480         boolean "Control Group support"
 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(EXPERIMENTAL)"
 583         depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL
 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 endif # CGROUPS
 600
 601 config MM_OWNER
 602         bool
 603
 604 config SYSFS_DEPRECATED
 605         bool
 606
 607 config SYSFS_DEPRECATED_V2
 608         bool "remove sysfs features which may confuse old userspace tools"
 609         depends on SYSFS
 610         default n
 611         select SYSFS_DEPRECATED
 612         help
 613           This option switches the layout of sysfs to the deprecated
 614           version. Do not use it on recent distributions.
 615
 616           The current sysfs layout features a unified device tree at
 617           /sys/devices/, which is able to express a hierarchy between
 618           class devices. If the deprecated option is set to Y, the
 619           unified device tree is split into a bus device tree at
 620           /sys/devices/ and several individual class device trees at
 621           /sys/class/. The class and bus devices will be connected by
 622           "<subsystem>:<name>" and the "device" links. The "block"
 623           class devices, will not show up in /sys/class/block/. Some
 624           subsystems will suppress the creation of some devices which
 625           depend on the unified device tree.
 626
 627           This option is not a pure compatibility option that can
 628           be safely enabled on newer distributions. It will change the
 629           layout of sysfs to the non-extensible deprecated version,
 630           and disable some features, which can not be exported without
 631           confusing older userspace tools. Since 2007/2008 all major
 632           distributions do not enable this option, and ship no tools which
 633           depend on the deprecated layout or this option.
 634
 635           If you are using a new kernel on an older distribution, or use
 636           older userspace tools, you might need to say Y here. Do not say Y,
 637           if the original kernel, that came with your distribution, has
 638           this option set to N.
 639
 640 config RELAY
 641         bool "Kernel->user space relay support (formerly relayfs)"
 642         help
 643           This option enables support for relay interface support in
 644           certain file systems (such as debugfs).
 645           It is designed to provide an efficient mechanism for tools and
 646           facilities to relay large amounts of data from kernel space to
 647           user space.
 648
 649           If unsure, say N.
 650
 651 config NAMESPACES
 652         bool "Namespaces support" if EMBEDDED
 653         default !EMBEDDED
 654         help
 655           Provides the way to make tasks work with different objects using
 656           the same id. For example same IPC id may refer to different objects
 657           or same user id or pid may refer to different tasks when used in
 658           different namespaces.
 659
 660 config UTS_NS
 661         bool "UTS namespace"
 662         depends on NAMESPACES
 663         help
 664           In this namespace tasks see different info provided with the
 665           uname() system call
 666
 667 config IPC_NS
 668         bool "IPC namespace"
 669         depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
 670         help
 671           In this namespace tasks work with IPC ids which correspond to
 672           different IPC objects in different namespaces.
 673
 674 config USER_NS
 675         bool "User namespace (EXPERIMENTAL)"
 676         depends on NAMESPACES && EXPERIMENTAL
 677         help
 678           This allows containers, i.e. vservers, to use user namespaces
 679           to provide different user info for different servers.
 680           If unsure, say N.
 681
 682 config PID_NS
 683         bool "PID Namespaces (EXPERIMENTAL)"
 684         default n
 685         depends on NAMESPACES && EXPERIMENTAL
 686         help
 687           Support process id namespaces.  This allows having multiple
 688           processes with the same pid as long as they are in different
 689           pid namespaces.  This is a building block of containers.
 690
 691           Unless you want to work with an experimental feature
 692           say N here.
 693
 694 config NET_NS
 695         bool "Network namespace"
 696         default n
 697         depends on NAMESPACES && EXPERIMENTAL && NET
 698         help
 699           Allow user space to create what appear to be multiple instances
 700           of the network stack.
 701
 702 config BLK_DEV_INITRD
 703         bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
 704         depends on BROKEN || !FRV
 705         help
 706           The initial RAM filesystem is a ramfs which is loaded by the
 707           boot loader (loadlin or lilo) and that is mounted as root
 708           before the normal boot procedure. It is typically used to
 709           load modules needed to mount the "real" root file system,
 710           etc. See <file:Documentation/initrd.txt> for details.
 711
 712           If RAM disk support (BLK_DEV_RAM) is also included, this
 713           also enables initial RAM disk (initrd) support and adds
 714           15 Kbytes (more on some other architectures) to the kernel size.
 715
 716           If unsure say Y.
 717
 718 if BLK_DEV_INITRD
 719
 720 source "usr/Kconfig"
 721
 722 endif
 723
 724 config CC_OPTIMIZE_FOR_SIZE
 725         bool "Optimize for size"
 726         default y
 727         help
 728           Enabling this option will pass "-Os" instead of "-O2" to gcc
 729           resulting in a smaller kernel.
 730
 731           If unsure, say Y.
 732
 733 config SYSCTL
 734         bool
 735
 736 config ANON_INODES
 737         bool
 738
 739 menuconfig EMBEDDED
 740         bool "Configure standard kernel features (for small systems)"
 741         help
 742           This option allows certain base kernel options and settings
 743           to be disabled or tweaked. This is for specialized
 744           environments which can tolerate a "non-standard" kernel.
 745           Only use this if you really know what you are doing.
 746
 747 config UID16
 748         bool "Enable 16-bit UID system calls" if EMBEDDED
 749         depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
 750         default y
 751         help
 752           This enables the legacy 16-bit UID syscall wrappers.
 753
 754 config SYSCTL_SYSCALL
 755         bool "Sysctl syscall support" if EMBEDDED
 756         default y
 757         select SYSCTL
 758         ---help---
 759           sys_sysctl uses binary paths that have been found challenging
 760           to properly maintain and use.  The interface in /proc/sys
 761           using paths with ascii names is now the primary path to this
 762           information.
 763
 764           Almost nothing using the binary sysctl interface so if you are
 765           trying to save some space it is probably safe to disable this,
 766           making your kernel marginally smaller.
 767
 768           If unsure say Y here.
 769
 770 config KALLSYMS
 771          bool "Load all symbols for debugging/ksymoops" if EMBEDDED
 772          default y
 773          help
 774            Say Y here to let the kernel print out symbolic crash information and
 775            symbolic stack backtraces. This increases the size of the kernel
 776            somewhat, as all symbols have to be loaded into the kernel image.
 777
 778 config KALLSYMS_ALL
 779         bool "Include all symbols in kallsyms"
 780         depends on DEBUG_KERNEL && KALLSYMS
 781         help
 782            Normally kallsyms only contains the symbols of functions, for nicer
 783            OOPS messages.  Some debuggers can use kallsyms for other
 784            symbols too: say Y here to include all symbols, if you need them
 785            and you don't care about adding 300k to the size of your kernel.
 786
 787            Say N.
 788
 789 config KALLSYMS_EXTRA_PASS
 790         bool "Do an extra kallsyms pass"
 791         depends on KALLSYMS
 792         help
 793            If kallsyms is not working correctly, the build will fail with
 794            inconsistent kallsyms data.  If that occurs, log a bug report and
 795            turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
 796            Always say N here unless you find a bug in kallsyms, which must be
 797            reported.  KALLSYMS_EXTRA_PASS is only a temporary workaround while
 798            you wait for kallsyms to be fixed.
 799
 800
 801 config HOTPLUG
 802         bool "Support for hot-pluggable devices" if EMBEDDED
 803         default y
 804         help
 805           This option is provided for the case where no hotplug or uevent
 806           capabilities is wanted by the kernel.  You should only consider
 807           disabling this option for embedded systems that do not use modules, a
 808           dynamic /dev tree, or dynamic device discovery.  Just say Y.
 809
 810 config PRINTK
 811         default y
 812         bool "Enable support for printk" if EMBEDDED
 813         help
 814           This option enables normal printk support. Removing it
 815           eliminates most of the message strings from the kernel image
 816           and makes the kernel more or less silent. As this makes it
 817           very difficult to diagnose system problems, saying N here is
 818           strongly discouraged.
 819
 820 config BUG
 821         bool "BUG() support" if EMBEDDED
 822         default y
 823         help
 824           Disabling this option eliminates support for BUG and WARN, reducing
 825           the size of your kernel image and potentially quietly ignoring
 826           numerous fatal conditions. You should only consider disabling this
 827           option for embedded systems with no facilities for reporting errors.
 828           Just say Y.
 829
 830 config ELF_CORE
 831         default y
 832         bool "Enable ELF core dumps" if EMBEDDED
 833         help
 834           Enable support for generating core dumps. Disabling saves about 4k.
 835
 836 config PCSPKR_PLATFORM
 837         bool "Enable PC-Speaker support" if EMBEDDED
 838         depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
 839         default y
 840         help
 841           This option allows to disable the internal PC-Speaker
 842           support, saving some memory.
 843
 844 config BASE_FULL
 845         default y
 846         bool "Enable full-sized data structures for core" if EMBEDDED
 847         help
 848           Disabling this option reduces the size of miscellaneous core
 849           kernel data structures. This saves memory on small machines,
 850           but may reduce performance.
 851
 852 config FUTEX
 853         bool "Enable futex support" if EMBEDDED
 854         default y
 855         select RT_MUTEXES
 856         help
 857           Disabling this option will cause the kernel to be built without
 858           support for "fast userspace mutexes".  The resulting kernel may not
 859           run glibc-based applications correctly.
 860
 861 config EPOLL
 862         bool "Enable eventpoll support" if EMBEDDED
 863         default y
 864         select ANON_INODES
 865         help
 866           Disabling this option will cause the kernel to be built without
 867           support for epoll family of system calls.
 868
 869 config SIGNALFD
 870         bool "Enable signalfd() system call" if EMBEDDED
 871         select ANON_INODES
 872         default y
 873         help
 874           Enable the signalfd() system call that allows to receive signals
 875           on a file descriptor.
 876
 877           If unsure, say Y.
 878
 879 config TIMERFD
 880         bool "Enable timerfd() system call" if EMBEDDED
 881         select ANON_INODES
 882         default y
 883         help
 884           Enable the timerfd() system call that allows to receive timer
 885           events on a file descriptor.
 886
 887           If unsure, say Y.
 888
 889 config EVENTFD
 890         bool "Enable eventfd() system call" if EMBEDDED
 891         select ANON_INODES
 892         default y
 893         help
 894           Enable the eventfd() system call that allows to receive both
 895           kernel notification (ie. KAIO) or userspace notifications.
 896
 897           If unsure, say Y.
 898
 899 config SHMEM
 900         bool "Use full shmem filesystem" if EMBEDDED
 901         default y
 902         depends on MMU
 903         help
 904           The shmem is an internal filesystem used to manage shared memory.
 905           It is backed by swap and manages resource limits. It is also exported
 906           to userspace as tmpfs if TMPFS is enabled. Disabling this
 907           option replaces shmem and tmpfs with the much simpler ramfs code,
 908           which may be appropriate on small systems without swap.
 909
 910 config AIO
 911         bool "Enable AIO support" if EMBEDDED
 912         default y
 913         help
 914           This option enables POSIX asynchronous I/O which may by used
 915           by some high performance threaded applications. Disabling
 916           this option saves about 7k.
 917
 918 config HAVE_PERF_EVENTS
 919         bool
 920         help
 921           See tools/perf/design.txt for details.
 922
 923 menu "Kernel Performance Events And Counters"
 924
 925 config PERF_EVENTS
 926         bool "Kernel performance events and counters"
 927         default y if (PROFILING || PERF_COUNTERS)
 928         depends on HAVE_PERF_EVENTS
 929         select ANON_INODES
 930         help
 931           Enable kernel support for various performance events provided
 932           by software and hardware.
 933
 934           Software events are supported either build-in or via the
 935           use of generic tracepoints.
 936
 937           Most modern CPUs support performance events via performance
 938           counter registers. These registers count the number of certain
 939           types of hw events: such as instructions executed, cachemisses
 940           suffered, or branches mis-predicted - without slowing down the
 941           kernel or applications. These registers can also trigger interrupts
 942           when a threshold number of events have passed - and can thus be
 943           used to profile the code that runs on that CPU.
 944
 945           The Linux Performance Event subsystem provides an abstraction of
 946           these software and hardware cevent apabilities, available via a
 947           system call and used by the "perf" utility in tools/perf/. It
 948           provides per task and per CPU counters, and it provides event
 949           capabilities on top of those.
 950
 951           Say Y if unsure.
 952
 953 config EVENT_PROFILE
 954         bool "Tracepoint profiling sources"
 955         depends on PERF_EVENTS && EVENT_TRACING
 956         default y
 957         help
 958          Allow the use of tracepoints as software performance events.
 959
 960          When this is enabled, you can create perf events based on
 961          tracepoints using PERF_TYPE_TRACEPOINT and the tracepoint ID
 962          found in debugfs://tracing/events/*/*/id. (The -e/--events
 963          option to the perf tool can parse and interpret symbolic
 964          tracepoints, in the subsystem:tracepoint_name format.)
 965
 966 config PERF_COUNTERS
 967         bool "Kernel performance counters (old config option)"
 968         depends on HAVE_PERF_EVENTS
 969         help
 970           This config has been obsoleted by the PERF_EVENTS
 971           config option - please see that one for details.
 972
 973           It has no effect on the kernel whether you enable
 974           it or not, it is a compatibility placeholder.
 975
 976           Say N if unsure.
 977
 978 endmenu
 979
 980 config VM_EVENT_COUNTERS
 981         default y
 982         bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
 983         help
 984           VM event counters are needed for event counts to be shown.
 985           This option allows the disabling of the VM event counters
 986           on EMBEDDED systems.  /proc/vmstat will only show page counts
 987           if VM event counters are disabled.
 988
 989 config PCI_QUIRKS
 990         default y
 991         bool "Enable PCI quirk workarounds" if EMBEDDED
 992         depends on PCI
 993         help
 994           This enables workarounds for various PCI chipset
 995           bugs/quirks. Disable this only if your target machine is
 996           unaffected by PCI quirks.
 997
 998 config SLUB_DEBUG
 999         default y
1000         bool "Enable SLUB debugging support" if EMBEDDED
1001         depends on SLUB && SYSFS
1002         help
1003           SLUB has extensive debug support features. Disabling these can
1004           result in significant savings in code size. This also disables
1005           SLUB sysfs support. /sys/slab will not exist and there will be
1006           no support for cache validation etc.
1007
1008 config STRIP_ASM_SYMS
1009         bool "Strip assembler-generated symbols during link"
1010         default n
1011         help
1012           Strip internal assembler-generated symbols during a link (symbols
1013           that look like '.Lxxx') so they don't pollute the output of
1014           get_wchan() and suchlike.
1015
1016 config COMPAT_BRK
1017         bool "Disable heap randomization"
1018         default y
1019         help
1020           Randomizing heap placement makes heap exploits harder, but it
1021           also breaks ancient binaries (including anything libc5 based).
1022           This option changes the bootup default to heap randomization
1023           disabled, and can be overridden at runtime by setting
1024           /proc/sys/kernel/randomize_va_space to 2.
1025
1026           On non-ancient distros (post-2000 ones) N is usually a safe choice.
1027
1028 choice
1029         prompt "Choose SLAB allocator"
1030         default SLUB
1031         help
1032            This option allows to select a slab allocator.
1033
1034 config SLAB
1035         bool "SLAB"
1036         help
1037           The regular slab allocator that is established and known to work
1038           well in all environments. It organizes cache hot objects in
1039           per cpu and per node queues.
1040
1041 config SLUB
1042         bool "SLUB (Unqueued Allocator)"
1043         help
1044            SLUB is a slab allocator that minimizes cache line usage
1045            instead of managing queues of cached objects (SLAB approach).
1046            Per cpu caching is realized using slabs of objects instead
1047            of queues of objects. SLUB can use memory efficiently
1048            and has enhanced diagnostics. SLUB is the default choice for
1049            a slab allocator.
1050
1051 config SLOB
1052         depends on EMBEDDED
1053         bool "SLOB (Simple Allocator)"
1054         help
1055            SLOB replaces the stock allocator with a drastically simpler
1056            allocator. SLOB is generally more space efficient but
1057            does not perform as well on large systems.
1058
1059 endchoice
1060
1061 config PROFILING
1062         bool "Profiling support (EXPERIMENTAL)"
1063         help
1064           Say Y here to enable the extended profiling support mechanisms used
1065           by profilers such as OProfile.
1066
1067 #
1068 # Place an empty function call at each tracepoint site. Can be
1069 # dynamically changed for a probe function.
1070 #
1071 config TRACEPOINTS
1072         bool
1073
1074 config MARKERS
1075         bool "Activate markers"
1076         select TRACEPOINTS
1077         help
1078           Place an empty function call at each marker site. Can be
1079           dynamically changed for a probe function.
1080
1081 source "arch/Kconfig"
1082
1083 config SLOW_WORK
1084         default n
1085         bool
1086         help
1087           The slow work thread pool provides a number of dynamically allocated
1088           threads that can be used by the kernel to perform operations that
1089           take a relatively long time.
1090
1091           An example of this would be CacheFiles doing a path lookup followed
1092           by a series of mkdirs and a create call, all of which have to touch
1093           disk.
1094
1095           See Documentation/slow-work.txt.
1096
1097 endmenu         # General setup
1098
1099 config HAVE_GENERIC_DMA_COHERENT
1100         bool
1101         default n
1102
1103 config SLABINFO
1104         bool
1105         depends on PROC_FS
1106         depends on SLAB || SLUB_DEBUG
1107         default y
1108
1109 config RT_MUTEXES
1110         boolean
1111
1112 config BASE_SMALL
1113         int
1114         default 0 if BASE_FULL
1115         default 1 if !BASE_FULL
1116
1117 menuconfig MODULES
1118         bool "Enable loadable module support"
1119         help
1120           Kernel modules are small pieces of compiled code which can
1121           be inserted in the running kernel, rather than being
1122           permanently built into the kernel.  You use the "modprobe"
1123           tool to add (and sometimes remove) them.  If you say Y here,
1124           many parts of the kernel can be built as modules (by
1125           answering M instead of Y where indicated): this is most
1126           useful for infrequently used options which are not required
1127           for booting.  For more information, see the man pages for
1128           modprobe, lsmod, modinfo, insmod and rmmod.
1129
1130           If you say Y here, you will need to run "make
1131           modules_install" to put the modules under /lib/modules/
1132           where modprobe can find them (you may need to be root to do
1133           this).
1134
1135           If unsure, say Y.
1136
1137 if MODULES
1138
1139 config MODULE_FORCE_LOAD
1140         bool "Forced module loading"
1141         default n
1142         help
1143           Allow loading of modules without version information (ie. modprobe
1144           --force).  Forced module loading sets the 'F' (forced) taint flag and
1145           is usually a really bad idea.
1146
1147 config MODULE_UNLOAD
1148         bool "Module unloading"
1149         help
1150           Without this option you will not be able to unload any
1151           modules (note that some modules may not be unloadable
1152           anyway), which makes your kernel smaller, faster
1153           and simpler.  If unsure, say Y.
1154
1155 config MODULE_FORCE_UNLOAD
1156         bool "Forced module unloading"
1157         depends on MODULE_UNLOAD && EXPERIMENTAL
1158         help
1159           This option allows you to force a module to unload, even if the
1160           kernel believes it is unsafe: the kernel will remove the module
1161           without waiting for anyone to stop using it (using the -f option to
1162           rmmod).  This is mainly for kernel developers and desperate users.
1163           If unsure, say N.
1164
1165 config MODVERSIONS
1166         bool "Module versioning support"
1167         help
1168           Usually, you have to use modules compiled with your kernel.
1169           Saying Y here makes it sometimes possible to use modules
1170           compiled for different kernels, by adding enough information
1171           to the modules to (hopefully) spot any changes which would
1172           make them incompatible with the kernel you are running.  If
1173           unsure, say N.
1174
1175 config MODULE_SRCVERSION_ALL
1176         bool "Source checksum for all modules"
1177         help
1178           Modules which contain a MODULE_VERSION get an extra "srcversion"
1179           field inserted into their modinfo section, which contains a
1180           sum of the source files which made it.  This helps maintainers
1181           see exactly which source was used to build a module (since
1182           others sometimes change the module source without updating
1183           the version).  With this option, such a "srcversion" field
1184           will be created for all modules.  If unsure, say N.
1185
1186 endif # MODULES
1187
1188 config INIT_ALL_POSSIBLE
1189         bool
1190         help
1191           Back when each arch used to define their own cpu_online_map and
1192           cpu_possible_map, some of them chose to initialize cpu_possible_map
1193           with all 1s, and others with all 0s.  When they were centralised,
1194           it was better to provide this option than to break all the archs
1195           and have several arch maintainers pursuing me down dark alleys.
1196
1197 config STOP_MACHINE
1198         bool
1199         default y
1200         depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1201         help
1202           Need stop_machine() primitive.
1203
1204 source "block/Kconfig"
1205
1206 config PREEMPT_NOTIFIERS
1207         bool
1208