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  47           drivers that have been replaced by something else, and/or are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