linux/init/Kconfig
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   1config ARCH
   2        string
   3        option env="ARCH"
   4
   5config KERNELVERSION
   6        string
   7        option env="KERNELVERSION"
   8
   9config 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
  19config CONSTRUCTORS
  20        bool
  21        depends on !UML
  22
  23config HAVE_IRQ_WORK
  24        bool
  25
  26config IRQ_WORK
  27        bool
  28        depends on HAVE_IRQ_WORK
  29
  30config BUILDTIME_EXTABLE_SORT
  31        bool
  32
  33menu "General setup"
  34
  35config EXPERIMENTAL
  36        bool "Prompt for development and/or incomplete code/drivers"
  37        ---help---
  38          Some of the various things that Linux supports (such as network
  39          drivers, file systems, network protocols, etc.) can be in a state
  40          of development where the functionality, stability, or the level of
  41          testing is not yet high enough for general use. This is usually
  42          known as the "alpha-test" phase among developers. If a feature is
  43          currently in alpha-test, then the developers usually discourage
  44          uninformed widespread use of this feature by the general public to
  45          avoid "Why doesn't this work?" type mail messages. However, active
  46          testing and use of these systems is welcomed. Just be aware that it
  47          may not meet the normal level of reliability or it may fail to work
  48          in some special cases. Detailed bug reports from people familiar
  49          with the kernel internals are usually welcomed by the developers
  50          (before submitting bug reports, please read the documents
  51          <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
  52          <file:Documentation/BUG-HUNTING>, and
  53          <file:Documentation/oops-tracing.txt> in the kernel source).
  54
  55          This option will also make obsoleted drivers available. These are
  56          drivers that have been replaced by something else, and/or are
  57          scheduled to be removed in a future kernel release.
  58
  59          Unless you intend to help test and develop a feature or driver that
  60          falls into this category, or you have a situation that requires
  61          using these features, you should probably say N here, which will
  62          cause the configurator to present you with fewer choices. If
  63          you say Y here, you will be offered the choice of using features or
  64          drivers that are currently considered to be in the alpha-test phase.
  65
  66config BROKEN
  67        bool
  68
  69config BROKEN_ON_SMP
  70        bool
  71        depends on BROKEN || !SMP
  72        default y
  73
  74config INIT_ENV_ARG_LIMIT
  75        int
  76        default 32 if !UML
  77        default 128 if UML
  78        help
  79          Maximum of each of the number of arguments and environment
  80          variables passed to init from the kernel command line.
  81
  82
  83config CROSS_COMPILE
  84        string "Cross-compiler tool prefix"
  85        help
  86          Same as running 'make CROSS_COMPILE=prefix-' but stored for
  87          default make runs in this kernel build directory.  You don't
  88          need to set this unless you want the configured kernel build
  89          directory to select the cross-compiler automatically.
  90
  91config LOCALVERSION
  92        string "Local version - append to kernel release"
  93        help
  94          Append an extra string to the end of your kernel version.
  95          This will show up when you type uname, for example.
  96          The string you set here will be appended after the contents of
  97          any files with a filename matching localversion* in your
  98          object and source tree, in that order.  Your total string can
  99          be a maximum of 64 characters.
 100
 101config LOCALVERSION_AUTO
 102        bool "Automatically append version information to the version string"
 103        default y
 104        help
 105          This will try to automatically determine if the current tree is a
 106          release tree by looking for git tags that belong to the current
 107          top of tree revision.
 108
 109          A string of the format -gxxxxxxxx will be added to the localversion
 110          if a git-based tree is found.  The string generated by this will be
 111          appended after any matching localversion* files, and after the value
 112          set in CONFIG_LOCALVERSION.
 113
 114          (The actual string used here is the first eight characters produced
 115          by running the command:
 116
 117            $ git rev-parse --verify HEAD
 118
 119          which is done within the script "scripts/setlocalversion".)
 120
 121config HAVE_KERNEL_GZIP
 122        bool
 123
 124config HAVE_KERNEL_BZIP2
 125        bool
 126
 127config HAVE_KERNEL_LZMA
 128        bool
 129
 130config HAVE_KERNEL_XZ
 131        bool
 132
 133config HAVE_KERNEL_LZO
 134        bool
 135
 136choice
 137        prompt "Kernel compression mode"
 138        default KERNEL_GZIP
 139        depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO
 140        help
 141          The linux kernel is a kind of self-extracting executable.
 142          Several compression algorithms are available, which differ
 143          in efficiency, compression and decompression speed.
 144          Compression speed is only relevant when building a kernel.
 145          Decompression speed is relevant at each boot.
 146
 147          If you have any problems with bzip2 or lzma compressed
 148          kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
 149          version of this functionality (bzip2 only), for 2.4, was
 150          supplied by Christian Ludwig)
 151
 152          High compression options are mostly useful for users, who
 153          are low on disk space (embedded systems), but for whom ram
 154          size matters less.
 155
 156          If in doubt, select 'gzip'
 157
 158config KERNEL_GZIP
 159        bool "Gzip"
 160        depends on HAVE_KERNEL_GZIP
 161        help
 162          The old and tried gzip compression. It provides a good balance
 163          between compression ratio and decompression speed.
 164
 165config KERNEL_BZIP2
 166        bool "Bzip2"
 167        depends on HAVE_KERNEL_BZIP2
 168        help
 169          Its compression ratio and speed is intermediate.
 170          Decompression speed is slowest among the choices.  The kernel
 171          size is about 10% smaller with bzip2, in comparison to gzip.
 172          Bzip2 uses a large amount of memory. For modern kernels you
 173          will need at least 8MB RAM or more for booting.
 174
 175config KERNEL_LZMA
 176        bool "LZMA"
 177        depends on HAVE_KERNEL_LZMA
 178        help
 179          This compression algorithm's ratio is best.  Decompression speed
 180          is between gzip and bzip2.  Compression is slowest.
 181          The kernel size is about 33% smaller with LZMA in comparison to gzip.
 182
 183config KERNEL_XZ
 184        bool "XZ"
 185        depends on HAVE_KERNEL_XZ
 186        help
 187          XZ uses the LZMA2 algorithm and instruction set specific
 188          BCJ filters which can improve compression ratio of executable
 189          code. The size of the kernel is about 30% smaller with XZ in
 190          comparison to gzip. On architectures for which there is a BCJ
 191          filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
 192          will create a few percent smaller kernel than plain LZMA.
 193
 194          The speed is about the same as with LZMA: The decompression
 195          speed of XZ is better than that of bzip2 but worse than gzip
 196          and LZO. Compression is slow.
 197
 198config KERNEL_LZO
 199        bool "LZO"
 200        depends on HAVE_KERNEL_LZO
 201        help
 202          Its compression ratio is the poorest among the choices. The kernel
 203          size is about 10% bigger than gzip; however its speed
 204          (both compression and decompression) is the fastest.
 205
 206endchoice
 207
 208config DEFAULT_HOSTNAME
 209        string "Default hostname"
 210        default "(none)"
 211        help
 212          This option determines the default system hostname before userspace
 213          calls sethostname(2). The kernel traditionally uses "(none)" here,
 214          but you may wish to use a different default here to make a minimal
 215          system more usable with less configuration.
 216
 217config SWAP
 218        bool "Support for paging of anonymous memory (swap)"
 219        depends on MMU && BLOCK
 220        default y
 221        help
 222          This option allows you to choose whether you want to have support
 223          for so called swap devices or swap files in your kernel that are
 224          used to provide more virtual memory than the actual RAM present
 225          in your computer.  If unsure say Y.
 226
 227config SYSVIPC
 228        bool "System V IPC"
 229        ---help---
 230          Inter Process Communication is a suite of library functions and
 231          system calls which let processes (running programs) synchronize and
 232          exchange information. It is generally considered to be a good thing,
 233          and some programs won't run unless you say Y here. In particular, if
 234          you want to run the DOS emulator dosemu under Linux (read the
 235          DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
 236          you'll need to say Y here.
 237
 238          You can find documentation about IPC with "info ipc" and also in
 239          section 6.4 of the Linux Programmer's Guide, available from
 240          <http://www.tldp.org/guides.html>.
 241
 242config SYSVIPC_SYSCTL
 243        bool
 244        depends on SYSVIPC
 245        depends on SYSCTL
 246        default y
 247
 248config POSIX_MQUEUE
 249        bool "POSIX Message Queues"
 250        depends on NET && EXPERIMENTAL
 251        ---help---
 252          POSIX variant of message queues is a part of IPC. In POSIX message
 253          queues every message has a priority which decides about succession
 254          of receiving it by a process. If you want to compile and run
 255          programs written e.g. for Solaris with use of its POSIX message
 256          queues (functions mq_*) say Y here.
 257
 258          POSIX message queues are visible as a filesystem called 'mqueue'
 259          and can be mounted somewhere if you want to do filesystem
 260          operations on message queues.
 261
 262          If unsure, say Y.
 263
 264config POSIX_MQUEUE_SYSCTL
 265        bool
 266        depends on POSIX_MQUEUE
 267        depends on SYSCTL
 268        default y
 269
 270config FHANDLE
 271        bool "open by fhandle syscalls"
 272        select EXPORTFS
 273        help
 274          If you say Y here, a user level program will be able to map
 275          file names to handle and then later use the handle for
 276          different file system operations. This is useful in implementing
 277          userspace file servers, which now track files using handles instead
 278          of names. The handle would remain the same even if file names
 279          get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
 280          syscalls.
 281
 282config AUDIT
 283        bool "Auditing support"
 284        depends on NET
 285        help
 286          Enable auditing infrastructure that can be used with another
 287          kernel subsystem, such as SELinux (which requires this for
 288          logging of avc messages output).  Does not do system-call
 289          auditing without CONFIG_AUDITSYSCALL.
 290
 291config AUDITSYSCALL
 292        bool "Enable system-call auditing support"
 293        depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH || (ARM && AEABI && !OABI_COMPAT))
 294        default y if SECURITY_SELINUX
 295        help
 296          Enable low-overhead system-call auditing infrastructure that
 297          can be used independently or with another kernel subsystem,
 298          such as SELinux.
 299
 300config AUDIT_WATCH
 301        def_bool y
 302        depends on AUDITSYSCALL
 303        select FSNOTIFY
 304
 305config AUDIT_TREE
 306        def_bool y
 307        depends on AUDITSYSCALL
 308        select FSNOTIFY
 309
 310config AUDIT_LOGINUID_IMMUTABLE
 311        bool "Make audit loginuid immutable"
 312        depends on AUDIT
 313        help
 314          The config option toggles if a task setting its loginuid requires
 315          CAP_SYS_AUDITCONTROL or if that task should require no special permissions
 316          but should instead only allow setting its loginuid if it was never
 317          previously set.  On systems which use systemd or a similar central
 318          process to restart login services this should be set to true.  On older
 319          systems in which an admin would typically have to directly stop and
 320          start processes this should be set to false.  Setting this to true allows
 321          one to drop potentially dangerous capabilites from the login tasks,
 322          but may not be backwards compatible with older init systems.
 323
 324source "kernel/irq/Kconfig"
 325source "kernel/time/Kconfig"
 326
 327menu "CPU/Task time and stats accounting"
 328
 329choice
 330        prompt "Cputime accounting"
 331        default TICK_CPU_ACCOUNTING if !PPC64
 332        default VIRT_CPU_ACCOUNTING if PPC64
 333
 334# Kind of a stub config for the pure tick based cputime accounting
 335config TICK_CPU_ACCOUNTING
 336        bool "Simple tick based cputime accounting"
 337        depends on !S390
 338        help
 339          This is the basic tick based cputime accounting that maintains
 340          statistics about user, system and idle time spent on per jiffies
 341          granularity.
 342
 343          If unsure, say Y.
 344
 345config VIRT_CPU_ACCOUNTING
 346        bool "Deterministic task and CPU time accounting"
 347        depends on HAVE_VIRT_CPU_ACCOUNTING
 348        help
 349          Select this option to enable more accurate task and CPU time
 350          accounting.  This is done by reading a CPU counter on each
 351          kernel entry and exit and on transitions within the kernel
 352          between system, softirq and hardirq state, so there is a
 353          small performance impact.  In the case of s390 or IBM POWER > 5,
 354          this also enables accounting of stolen time on logically-partitioned
 355          systems.
 356
 357config IRQ_TIME_ACCOUNTING
 358        bool "Fine granularity task level IRQ time accounting"
 359        depends on HAVE_IRQ_TIME_ACCOUNTING
 360        help
 361          Select this option to enable fine granularity task irq time
 362          accounting. This is done by reading a timestamp on each
 363          transitions between softirq and hardirq state, so there can be a
 364          small performance impact.
 365
 366          If in doubt, say N here.
 367
 368endchoice
 369
 370config BSD_PROCESS_ACCT
 371        bool "BSD Process Accounting"
 372        help
 373          If you say Y here, a user level program will be able to instruct the
 374          kernel (via a special system call) to write process accounting
 375          information to a file: whenever a process exits, information about
 376          that process will be appended to the file by the kernel.  The
 377          information includes things such as creation time, owning user,
 378          command name, memory usage, controlling terminal etc. (the complete
 379          list is in the struct acct in <file:include/linux/acct.h>).  It is
 380          up to the user level program to do useful things with this
 381          information.  This is generally a good idea, so say Y.
 382
 383config BSD_PROCESS_ACCT_V3
 384        bool "BSD Process Accounting version 3 file format"
 385        depends on BSD_PROCESS_ACCT
 386        default n
 387        help
 388          If you say Y here, the process accounting information is written
 389          in a new file format that also logs the process IDs of each
 390          process and it's parent. Note that this file format is incompatible
 391          with previous v0/v1/v2 file formats, so you will need updated tools
 392          for processing it. A preliminary version of these tools is available
 393          at <http://www.gnu.org/software/acct/>.
 394
 395config TASKSTATS
 396        bool "Export task/process statistics through netlink (EXPERIMENTAL)"
 397        depends on NET
 398        default n
 399        help
 400          Export selected statistics for tasks/processes through the
 401          generic netlink interface. Unlike BSD process accounting, the
 402          statistics are available during the lifetime of tasks/processes as
 403          responses to commands. Like BSD accounting, they are sent to user
 404          space on task exit.
 405
 406          Say N if unsure.
 407
 408config TASK_DELAY_ACCT
 409        bool "Enable per-task delay accounting (EXPERIMENTAL)"
 410        depends on TASKSTATS
 411        help
 412          Collect information on time spent by a task waiting for system
 413          resources like cpu, synchronous block I/O completion and swapping
 414          in pages. Such statistics can help in setting a task's priorities
 415          relative to other tasks for cpu, io, rss limits etc.
 416
 417          Say N if unsure.
 418
 419config TASK_XACCT
 420        bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
 421        depends on TASKSTATS
 422        help
 423          Collect extended task accounting data and send the data
 424          to userland for processing over the taskstats interface.
 425
 426          Say N if unsure.
 427
 428config TASK_IO_ACCOUNTING
 429        bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
 430        depends on TASK_XACCT
 431        help
 432          Collect information on the number of bytes of storage I/O which this
 433          task has caused.
 434
 435          Say N if unsure.
 436
 437endmenu # "CPU/Task time and stats accounting"
 438
 439menu "RCU Subsystem"
 440
 441choice
 442        prompt "RCU Implementation"
 443        default TREE_RCU
 444
 445config TREE_RCU
 446        bool "Tree-based hierarchical RCU"
 447        depends on !PREEMPT && SMP
 448        help
 449          This option selects the RCU implementation that is
 450          designed for very large SMP system with hundreds or
 451          thousands of CPUs.  It also scales down nicely to
 452          smaller systems.
 453
 454config TREE_PREEMPT_RCU
 455        bool "Preemptible tree-based hierarchical RCU"
 456        depends on PREEMPT && SMP
 457        help
 458          This option selects the RCU implementation that is
 459          designed for very large SMP systems with hundreds or
 460          thousands of CPUs, but for which real-time response
 461          is also required.  It also scales down nicely to
 462          smaller systems.
 463
 464config TINY_RCU
 465        bool "UP-only small-memory-footprint RCU"
 466        depends on !PREEMPT && !SMP
 467        help
 468          This option selects the RCU implementation that is
 469          designed for UP systems from which real-time response
 470          is not required.  This option greatly reduces the
 471          memory footprint of RCU.
 472
 473config TINY_PREEMPT_RCU
 474        bool "Preemptible UP-only small-memory-footprint RCU"
 475        depends on PREEMPT && !SMP
 476        help
 477          This option selects the RCU implementation that is designed
 478          for real-time UP systems.  This option greatly reduces the
 479          memory footprint of RCU.
 480
 481endchoice
 482
 483config PREEMPT_RCU
 484        def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
 485        help
 486          This option enables preemptible-RCU code that is common between
 487          the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
 488
 489config RCU_USER_QS
 490        bool "Consider userspace as in RCU extended quiescent state"
 491        depends on HAVE_RCU_USER_QS && SMP
 492        help
 493          This option sets hooks on kernel / userspace boundaries and
 494          puts RCU in extended quiescent state when the CPU runs in
 495          userspace. It means that when a CPU runs in userspace, it is
 496          excluded from the global RCU state machine and thus doesn't
 497          to keep the timer tick on for RCU.
 498
 499          Unless you want to hack and help the development of the full
 500          tickless feature, you shouldn't enable this option. It adds
 501          unnecessary overhead.
 502
 503          If unsure say N
 504
 505config RCU_USER_QS_FORCE
 506        bool "Force userspace extended QS by default"
 507        depends on RCU_USER_QS
 508        help
 509          Set the hooks in user/kernel boundaries by default in order to
 510          test this feature that treats userspace as an extended quiescent
 511          state until we have a real user like a full adaptive nohz option.
 512
 513          Unless you want to hack and help the development of the full
 514          tickless feature, you shouldn't enable this option. It adds
 515          unnecessary overhead.
 516
 517          If unsure say N
 518
 519config RCU_FANOUT
 520        int "Tree-based hierarchical RCU fanout value"
 521        range 2 64 if 64BIT
 522        range 2 32 if !64BIT
 523        depends on TREE_RCU || TREE_PREEMPT_RCU
 524        default 64 if 64BIT
 525        default 32 if !64BIT
 526        help
 527          This option controls the fanout of hierarchical implementations
 528          of RCU, allowing RCU to work efficiently on machines with
 529          large numbers of CPUs.  This value must be at least the fourth
 530          root of NR_CPUS, which allows NR_CPUS to be insanely large.
 531          The default value of RCU_FANOUT should be used for production
 532          systems, but if you are stress-testing the RCU implementation
 533          itself, small RCU_FANOUT values allow you to test large-system
 534          code paths on small(er) systems.
 535
 536          Select a specific number if testing RCU itself.
 537          Take the default if unsure.
 538
 539config RCU_FANOUT_LEAF
 540        int "Tree-based hierarchical RCU leaf-level fanout value"
 541        range 2 RCU_FANOUT if 64BIT
 542        range 2 RCU_FANOUT if !64BIT
 543        depends on TREE_RCU || TREE_PREEMPT_RCU
 544        default 16
 545        help
 546          This option controls the leaf-level fanout of hierarchical
 547          implementations of RCU, and allows trading off cache misses
 548          against lock contention.  Systems that synchronize their
 549          scheduling-clock interrupts for energy-efficiency reasons will
 550          want the default because the smaller leaf-level fanout keeps
 551          lock contention levels acceptably low.  Very large systems
 552          (hundreds or thousands of CPUs) will instead want to set this
 553          value to the maximum value possible in order to reduce the
 554          number of cache misses incurred during RCU's grace-period
 555          initialization.  These systems tend to run CPU-bound, and thus
 556          are not helped by synchronized interrupts, and thus tend to
 557          skew them, which reduces lock contention enough that large
 558          leaf-level fanouts work well.
 559
 560          Select a specific number if testing RCU itself.
 561
 562          Select the maximum permissible value for large systems.
 563
 564          Take the default if unsure.
 565
 566config RCU_FANOUT_EXACT
 567        bool "Disable tree-based hierarchical RCU auto-balancing"
 568        depends on TREE_RCU || TREE_PREEMPT_RCU
 569        default n
 570        help
 571          This option forces use of the exact RCU_FANOUT value specified,
 572          regardless of imbalances in the hierarchy.  This is useful for
 573          testing RCU itself, and might one day be useful on systems with
 574          strong NUMA behavior.
 575
 576          Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
 577
 578          Say N if unsure.
 579
 580config RCU_FAST_NO_HZ
 581        bool "Accelerate last non-dyntick-idle CPU's grace periods"
 582        depends on NO_HZ && SMP
 583        default n
 584        help
 585          This option causes RCU to attempt to accelerate grace periods
 586          in order to allow CPUs to enter dynticks-idle state more
 587          quickly.  On the other hand, this option increases the overhead
 588          of the dynticks-idle checking, particularly on systems with
 589          large numbers of CPUs.
 590
 591          Say Y if energy efficiency is critically important, particularly
 592                if you have relatively few CPUs.
 593
 594          Say N if you are unsure.
 595
 596config TREE_RCU_TRACE
 597        def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
 598        select DEBUG_FS
 599        help
 600          This option provides tracing for the TREE_RCU and
 601          TREE_PREEMPT_RCU implementations, permitting Makefile to
 602          trivially select kernel/rcutree_trace.c.
 603
 604config RCU_BOOST
 605        bool "Enable RCU priority boosting"
 606        depends on RT_MUTEXES && PREEMPT_RCU
 607        default n
 608        help
 609          This option boosts the priority of preempted RCU readers that
 610          block the current preemptible RCU grace period for too long.
 611          This option also prevents heavy loads from blocking RCU
 612          callback invocation for all flavors of RCU.
 613
 614          Say Y here if you are working with real-time apps or heavy loads
 615          Say N here if you are unsure.
 616
 617config RCU_BOOST_PRIO
 618        int "Real-time priority to boost RCU readers to"
 619        range 1 99
 620        depends on RCU_BOOST
 621        default 1
 622        help
 623          This option specifies the real-time priority to which long-term
 624          preempted RCU readers are to be boosted.  If you are working
 625          with a real-time application that has one or more CPU-bound
 626          threads running at a real-time priority level, you should set
 627          RCU_BOOST_PRIO to a priority higher then the highest-priority
 628          real-time CPU-bound thread.  The default RCU_BOOST_PRIO value
 629          of 1 is appropriate in the common case, which is real-time
 630          applications that do not have any CPU-bound threads.
 631
 632          Some real-time applications might not have a single real-time
 633          thread that saturates a given CPU, but instead might have
 634          multiple real-time threads that, taken together, fully utilize
 635          that CPU.  In this case, you should set RCU_BOOST_PRIO to
 636          a priority higher than the lowest-priority thread that is
 637          conspiring to prevent the CPU from running any non-real-time
 638          tasks.  For example, if one thread at priority 10 and another
 639          thread at priority 5 are between themselves fully consuming
 640          the CPU time on a given CPU, then RCU_BOOST_PRIO should be
 641          set to priority 6 or higher.
 642
 643          Specify the real-time priority, or take the default if unsure.
 644
 645config RCU_BOOST_DELAY
 646        int "Milliseconds to delay boosting after RCU grace-period start"
 647        range 0 3000
 648        depends on RCU_BOOST
 649        default 500
 650        help
 651          This option specifies the time to wait after the beginning of
 652          a given grace period before priority-boosting preempted RCU
 653          readers blocking that grace period.  Note that any RCU reader
 654          blocking an expedited RCU grace period is boosted immediately.
 655
 656          Accept the default if unsure.
 657
 658endmenu # "RCU Subsystem"
 659
 660config IKCONFIG
 661        tristate "Kernel .config support"
 662        ---help---
 663          This option enables the complete Linux kernel ".config" file
 664          contents to be saved in the kernel. It provides documentation
 665          of which kernel options are used in a running kernel or in an
 666          on-disk kernel.  This information can be extracted from the kernel
 667          image file with the script scripts/extract-ikconfig and used as
 668          input to rebuild the current kernel or to build another kernel.
 669          It can also be extracted from a running kernel by reading
 670          /proc/config.gz if enabled (below).
 671
 672config IKCONFIG_PROC
 673        bool "Enable access to .config through /proc/config.gz"
 674        depends on IKCONFIG && PROC_FS
 675        ---help---
 676          This option enables access to the kernel configuration file
 677          through /proc/config.gz.
 678
 679config LOG_BUF_SHIFT
 680        int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
 681        range 12 21
 682        default 17
 683        help
 684          Select kernel log buffer size as a power of 2.
 685          Examples:
 686                     17 => 128 KB
 687                     16 => 64 KB
 688                     15 => 32 KB
 689                     14 => 16 KB
 690                     13 =>  8 KB
 691                     12 =>  4 KB
 692
 693#
 694# Architectures with an unreliable sched_clock() should select this:
 695#
 696config HAVE_UNSTABLE_SCHED_CLOCK
 697        bool
 698
 699menuconfig CGROUPS
 700        boolean "Control Group support"
 701        depends on EVENTFD
 702        help
 703          This option adds support for grouping sets of processes together, for
 704          use with process control subsystems such as Cpusets, CFS, memory
 705          controls or device isolation.
 706          See
 707                - Documentation/scheduler/sched-design-CFS.txt  (CFS)
 708                - Documentation/cgroups/ (features for grouping, isolation
 709                                          and resource control)
 710
 711          Say N if unsure.
 712
 713if CGROUPS
 714
 715config CGROUP_DEBUG
 716        bool "Example debug cgroup subsystem"
 717        default n
 718        help
 719          This option enables a simple cgroup subsystem that
 720          exports useful debugging information about the cgroups
 721          framework.
 722
 723          Say N if unsure.
 724
 725config CGROUP_FREEZER
 726        bool "Freezer cgroup subsystem"
 727        help
 728          Provides a way to freeze and unfreeze all tasks in a
 729          cgroup.
 730
 731config CGROUP_DEVICE
 732        bool "Device controller for cgroups"
 733        help
 734          Provides a cgroup implementing whitelists for devices which
 735          a process in the cgroup can mknod or open.
 736
 737config CPUSETS
 738        bool "Cpuset support"
 739        help
 740          This option will let you create and manage CPUSETs which
 741          allow dynamically partitioning a system into sets of CPUs and
 742          Memory Nodes and assigning tasks to run only within those sets.
 743          This is primarily useful on large SMP or NUMA systems.
 744
 745          Say N if unsure.
 746
 747config PROC_PID_CPUSET
 748        bool "Include legacy /proc/<pid>/cpuset file"
 749        depends on CPUSETS
 750        default y
 751
 752config CGROUP_CPUACCT
 753        bool "Simple CPU accounting cgroup subsystem"
 754        help
 755          Provides a simple Resource Controller for monitoring the
 756          total CPU consumed by the tasks in a cgroup.
 757
 758config RESOURCE_COUNTERS
 759        bool "Resource counters"
 760        help
 761          This option enables controller independent resource accounting
 762          infrastructure that works with cgroups.
 763
 764config MEMCG
 765        bool "Memory Resource Controller for Control Groups"
 766        depends on RESOURCE_COUNTERS
 767        select MM_OWNER
 768        help
 769          Provides a memory resource controller that manages both anonymous
 770          memory and page cache. (See Documentation/cgroups/memory.txt)
 771
 772          Note that setting this option increases fixed memory overhead
 773          associated with each page of memory in the system. By this,
 774          20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
 775          usage tracking struct at boot. Total amount of this is printed out
 776          at boot.
 777
 778          Only enable when you're ok with these trade offs and really
 779          sure you need the memory resource controller. Even when you enable
 780          this, you can set "cgroup_disable=memory" at your boot option to
 781          disable memory resource controller and you can avoid overheads.
 782          (and lose benefits of memory resource controller)
 783
 784          This config option also selects MM_OWNER config option, which
 785          could in turn add some fork/exit overhead.
 786
 787config MEMCG_SWAP
 788        bool "Memory Resource Controller Swap Extension"
 789        depends on MEMCG && SWAP
 790        help
 791          Add swap management feature to memory resource controller. When you
 792          enable this, you can limit mem+swap usage per cgroup. In other words,
 793          when you disable this, memory resource controller has no cares to
 794          usage of swap...a process can exhaust all of the swap. This extension
 795          is useful when you want to avoid exhaustion swap but this itself
 796          adds more overheads and consumes memory for remembering information.
 797          Especially if you use 32bit system or small memory system, please
 798          be careful about enabling this. When memory resource controller
 799          is disabled by boot option, this will be automatically disabled and
 800          there will be no overhead from this. Even when you set this config=y,
 801          if boot option "swapaccount=0" is set, swap will not be accounted.
 802          Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
 803          size is 4096bytes, 512k per 1Gbytes of swap.
 804config MEMCG_SWAP_ENABLED
 805        bool "Memory Resource Controller Swap Extension enabled by default"
 806        depends on MEMCG_SWAP
 807        default y
 808        help
 809          Memory Resource Controller Swap Extension comes with its price in
 810          a bigger memory consumption. General purpose distribution kernels
 811          which want to enable the feature but keep it disabled by default
 812          and let the user enable it by swapaccount boot command line
 813          parameter should have this option unselected.
 814          For those who want to have the feature enabled by default should
 815          select this option (if, for some reason, they need to disable it
 816          then swapaccount=0 does the trick).
 817config MEMCG_KMEM
 818        bool "Memory Resource Controller Kernel Memory accounting (EXPERIMENTAL)"
 819        depends on MEMCG && EXPERIMENTAL
 820        default n
 821        help
 822          The Kernel Memory extension for Memory Resource Controller can limit
 823          the amount of memory used by kernel objects in the system. Those are
 824          fundamentally different from the entities handled by the standard
 825          Memory Controller, which are page-based, and can be swapped. Users of
 826          the kmem extension can use it to guarantee that no group of processes
 827          will ever exhaust kernel resources alone.
 828
 829config CGROUP_HUGETLB
 830        bool "HugeTLB Resource Controller for Control Groups"
 831        depends on RESOURCE_COUNTERS && HUGETLB_PAGE && EXPERIMENTAL
 832        default n
 833        help
 834          Provides a cgroup Resource Controller for HugeTLB pages.
 835          When you enable this, you can put a per cgroup limit on HugeTLB usage.
 836          The limit is enforced during page fault. Since HugeTLB doesn't
 837          support page reclaim, enforcing the limit at page fault time implies
 838          that, the application will get SIGBUS signal if it tries to access
 839          HugeTLB pages beyond its limit. This requires the application to know
 840          beforehand how much HugeTLB pages it would require for its use. The
 841          control group is tracked in the third page lru pointer. This means
 842          that we cannot use the controller with huge page less than 3 pages.
 843
 844config CGROUP_PERF
 845        bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
 846        depends on PERF_EVENTS && CGROUPS
 847        help
 848          This option extends the per-cpu mode to restrict monitoring to
 849          threads which belong to the cgroup specified and run on the
 850          designated cpu.
 851
 852          Say N if unsure.
 853
 854menuconfig CGROUP_SCHED
 855        bool "Group CPU scheduler"
 856        default n
 857        help
 858          This feature lets CPU scheduler recognize task groups and control CPU
 859          bandwidth allocation to such task groups. It uses cgroups to group
 860          tasks.
 861
 862if CGROUP_SCHED
 863config FAIR_GROUP_SCHED
 864        bool "Group scheduling for SCHED_OTHER"
 865        depends on CGROUP_SCHED
 866        default CGROUP_SCHED
 867
 868config CFS_BANDWIDTH
 869        bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
 870        depends on EXPERIMENTAL
 871        depends on FAIR_GROUP_SCHED
 872        default n
 873        help
 874          This option allows users to define CPU bandwidth rates (limits) for
 875          tasks running within the fair group scheduler.  Groups with no limit
 876          set are considered to be unconstrained and will run with no
 877          restriction.
 878          See tip/Documentation/scheduler/sched-bwc.txt for more information.
 879
 880config RT_GROUP_SCHED
 881        bool "Group scheduling for SCHED_RR/FIFO"
 882        depends on EXPERIMENTAL
 883        depends on CGROUP_SCHED
 884        default n
 885        help
 886          This feature lets you explicitly allocate real CPU bandwidth
 887          to task groups. If enabled, it will also make it impossible to
 888          schedule realtime tasks for non-root users until you allocate
 889          realtime bandwidth for them.
 890          See Documentation/scheduler/sched-rt-group.txt for more information.
 891
 892endif #CGROUP_SCHED
 893
 894config BLK_CGROUP
 895        bool "Block IO controller"
 896        depends on BLOCK
 897        default n
 898        ---help---
 899        Generic block IO controller cgroup interface. This is the common
 900        cgroup interface which should be used by various IO controlling
 901        policies.
 902
 903        Currently, CFQ IO scheduler uses it to recognize task groups and
 904        control disk bandwidth allocation (proportional time slice allocation)
 905        to such task groups. It is also used by bio throttling logic in
 906        block layer to implement upper limit in IO rates on a device.
 907
 908        This option only enables generic Block IO controller infrastructure.
 909        One needs to also enable actual IO controlling logic/policy. For
 910        enabling proportional weight division of disk bandwidth in CFQ, set
 911        CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
 912        CONFIG_BLK_DEV_THROTTLING=y.
 913
 914        See Documentation/cgroups/blkio-controller.txt for more information.
 915
 916config DEBUG_BLK_CGROUP
 917        bool "Enable Block IO controller debugging"
 918        depends on BLK_CGROUP
 919        default n
 920        ---help---
 921        Enable some debugging help. Currently it exports additional stat
 922        files in a cgroup which can be useful for debugging.
 923
 924endif # CGROUPS
 925
 926config CHECKPOINT_RESTORE
 927        bool "Checkpoint/restore support" if EXPERT
 928        default n
 929        help
 930          Enables additional kernel features in a sake of checkpoint/restore.
 931          In particular it adds auxiliary prctl codes to setup process text,
 932          data and heap segment sizes, and a few additional /proc filesystem
 933          entries.
 934
 935          If unsure, say N here.
 936
 937menuconfig NAMESPACES
 938        bool "Namespaces support" if EXPERT
 939        default !EXPERT
 940        help
 941          Provides the way to make tasks work with different objects using
 942          the same id. For example same IPC id may refer to different objects
 943          or same user id or pid may refer to different tasks when used in
 944          different namespaces.
 945
 946if NAMESPACES
 947
 948config UTS_NS
 949        bool "UTS namespace"
 950        default y
 951        help
 952          In this namespace tasks see different info provided with the
 953          uname() system call
 954
 955config IPC_NS
 956        bool "IPC namespace"
 957        depends on (SYSVIPC || POSIX_MQUEUE)
 958        default y
 959        help
 960          In this namespace tasks work with IPC ids which correspond to
 961          different IPC objects in different namespaces.
 962
 963config USER_NS
 964        bool "User namespace (EXPERIMENTAL)"
 965        depends on EXPERIMENTAL
 966        depends on UIDGID_CONVERTED
 967        select UIDGID_STRICT_TYPE_CHECKS
 968
 969        default n
 970        help
 971          This allows containers, i.e. vservers, to use user namespaces
 972          to provide different user info for different servers.
 973          If unsure, say N.
 974
 975config PID_NS
 976        bool "PID Namespaces"
 977        default y
 978        help
 979          Support process id namespaces.  This allows having multiple
 980          processes with the same pid as long as they are in different
 981          pid namespaces.  This is a building block of containers.
 982
 983config NET_NS
 984        bool "Network namespace"
 985        depends on NET
 986        default y
 987        help
 988          Allow user space to create what appear to be multiple instances
 989          of the network stack.
 990
 991endif # NAMESPACES
 992
 993config UIDGID_CONVERTED
 994        # True if all of the selected software conmponents are known
 995        # to have uid_t and gid_t converted to kuid_t and kgid_t
 996        # where appropriate and are otherwise safe to use with
 997        # the user namespace.
 998        bool
 999        default y
1000
1001        # Networking
1002        depends on NET_9P = n
1003
1004        # Filesystems
1005        depends on 9P_FS = n
1006        depends on AFS_FS = n
1007        depends on AUTOFS4_FS = n
1008        depends on CEPH_FS = n
1009        depends on CIFS = n
1010        depends on CODA_FS = n
1011        depends on FUSE_FS = n
1012        depends on GFS2_FS = n
1013        depends on NCP_FS = n
1014        depends on NFSD = n
1015        depends on NFS_FS = n
1016        depends on OCFS2_FS = n
1017        depends on XFS_FS = n
1018
1019config UIDGID_STRICT_TYPE_CHECKS
1020        bool "Require conversions between uid/gids and their internal representation"
1021        depends on UIDGID_CONVERTED
1022        default n
1023        help
1024         While the nececessary conversions are being added to all subsystems this option allows
1025         the code to continue to build for unconverted subsystems.
1026
1027         Say Y here if you want the strict type checking enabled
1028
1029config SCHED_AUTOGROUP
1030        bool "Automatic process group scheduling"
1031        select EVENTFD
1032        select CGROUPS
1033        select CGROUP_SCHED
1034        select FAIR_GROUP_SCHED
1035        help
1036          This option optimizes the scheduler for common desktop workloads by
1037          automatically creating and populating task groups.  This separation
1038          of workloads isolates aggressive CPU burners (like build jobs) from
1039          desktop applications.  Task group autogeneration is currently based
1040          upon task session.
1041
1042config MM_OWNER
1043        bool
1044
1045config SYSFS_DEPRECATED
1046        bool "Enable deprecated sysfs features to support old userspace tools"
1047        depends on SYSFS
1048        default n
1049        help
1050          This option adds code that switches the layout of the "block" class
1051          devices, to not show up in /sys/class/block/, but only in
1052          /sys/block/.
1053
1054          This switch is only active when the sysfs.deprecated=1 boot option is
1055          passed or the SYSFS_DEPRECATED_V2 option is set.
1056
1057          This option allows new kernels to run on old distributions and tools,
1058          which might get confused by /sys/class/block/. Since 2007/2008 all
1059          major distributions and tools handle this just fine.
1060
1061          Recent distributions and userspace tools after 2009/2010 depend on
1062          the existence of /sys/class/block/, and will not work with this
1063          option enabled.
1064
1065          Only if you are using a new kernel on an old distribution, you might
1066          need to say Y here.
1067
1068config SYSFS_DEPRECATED_V2
1069        bool "Enable deprecated sysfs features by default"
1070        default n
1071        depends on SYSFS
1072        depends on SYSFS_DEPRECATED
1073        help
1074          Enable deprecated sysfs by default.
1075
1076          See the CONFIG_SYSFS_DEPRECATED option for more details about this
1077          option.
1078
1079          Only if you are using a new kernel on an old distribution, you might
1080          need to say Y here. Even then, odds are you would not need it
1081          enabled, you can always pass the boot option if absolutely necessary.
1082
1083config RELAY
1084        bool "Kernel->user space relay support (formerly relayfs)"
1085        help
1086          This option enables support for relay interface support in
1087          certain file systems (such as debugfs).
1088          It is designed to provide an efficient mechanism for tools and
1089          facilities to relay large amounts of data from kernel space to
1090          user space.
1091
1092          If unsure, say N.
1093
1094config BLK_DEV_INITRD
1095        bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1096        depends on BROKEN || !FRV
1097        help
1098          The initial RAM filesystem is a ramfs which is loaded by the
1099          boot loader (loadlin or lilo) and that is mounted as root
1100          before the normal boot procedure. It is typically used to
1101          load modules needed to mount the "real" root file system,
1102          etc. See <file:Documentation/initrd.txt> for details.
1103
1104          If RAM disk support (BLK_DEV_RAM) is also included, this
1105          also enables initial RAM disk (initrd) support and adds
1106          15 Kbytes (more on some other architectures) to the kernel size.
1107
1108          If unsure say Y.
1109
1110if BLK_DEV_INITRD
1111
1112source "usr/Kconfig"
1113
1114endif
1115
1116config CC_OPTIMIZE_FOR_SIZE
1117        bool "Optimize for size"
1118        help
1119          Enabling this option will pass "-Os" instead of "-O2" to gcc
1120          resulting in a smaller kernel.
1121
1122          If unsure, say Y.
1123
1124config SYSCTL
1125        bool
1126
1127config ANON_INODES
1128        bool
1129
1130menuconfig EXPERT
1131        bool "Configure standard kernel features (expert users)"
1132        # Unhide debug options, to make the on-by-default options visible
1133        select DEBUG_KERNEL
1134        help
1135          This option allows certain base kernel options and settings
1136          to be disabled or tweaked. This is for specialized
1137          environments which can tolerate a "non-standard" kernel.
1138          Only use this if you really know what you are doing.
1139
1140config HAVE_UID16
1141        bool
1142
1143config UID16
1144        bool "Enable 16-bit UID system calls" if EXPERT
1145        depends on HAVE_UID16
1146        default y
1147        help
1148          This enables the legacy 16-bit UID syscall wrappers.
1149
1150config SYSCTL_SYSCALL
1151        bool "Sysctl syscall support" if EXPERT
1152        depends on PROC_SYSCTL
1153        default n
1154        select SYSCTL
1155        ---help---
1156          sys_sysctl uses binary paths that have been found challenging
1157          to properly maintain and use.  The interface in /proc/sys
1158          using paths with ascii names is now the primary path to this
1159          information.
1160
1161          Almost nothing using the binary sysctl interface so if you are
1162          trying to save some space it is probably safe to disable this,
1163          making your kernel marginally smaller.
1164
1165          If unsure say N here.
1166
1167config SYSCTL_EXCEPTION_TRACE
1168        bool
1169        help
1170          Enable support for /proc/sys/debug/exception-trace.
1171
1172config KALLSYMS
1173         bool "Load all symbols for debugging/ksymoops" if EXPERT
1174         default y
1175         help
1176           Say Y here to let the kernel print out symbolic crash information and
1177           symbolic stack backtraces. This increases the size of the kernel
1178           somewhat, as all symbols have to be loaded into the kernel image.
1179
1180config KALLSYMS_ALL
1181        bool "Include all symbols in kallsyms"
1182        depends on DEBUG_KERNEL && KALLSYMS
1183        help
1184           Normally kallsyms only contains the symbols of functions for nicer
1185           OOPS messages and backtraces (i.e., symbols from the text and inittext
1186           sections). This is sufficient for most cases. And only in very rare
1187           cases (e.g., when a debugger is used) all symbols are required (e.g.,
1188           names of variables from the data sections, etc).
1189
1190           This option makes sure that all symbols are loaded into the kernel
1191           image (i.e., symbols from all sections) in cost of increased kernel
1192           size (depending on the kernel configuration, it may be 300KiB or
1193           something like this).
1194
1195           Say N unless you really need all symbols.
1196
1197config HOTPLUG
1198        def_bool y
1199
1200config PRINTK
1201        default y
1202        bool "Enable support for printk" if EXPERT
1203        help
1204          This option enables normal printk support. Removing it
1205          eliminates most of the message strings from the kernel image
1206          and makes the kernel more or less silent. As this makes it
1207          very difficult to diagnose system problems, saying N here is
1208          strongly discouraged.
1209
1210config BUG
1211        bool "BUG() support" if EXPERT
1212        default y
1213        help
1214          Disabling this option eliminates support for BUG and WARN, reducing
1215          the size of your kernel image and potentially quietly ignoring
1216          numerous fatal conditions. You should only consider disabling this
1217          option for embedded systems with no facilities for reporting errors.
1218          Just say Y.
1219
1220config ELF_CORE
1221        depends on COREDUMP
1222        default y
1223        bool "Enable ELF core dumps" if EXPERT
1224        help
1225          Enable support for generating core dumps. Disabling saves about 4k.
1226
1227
1228config PCSPKR_PLATFORM
1229        bool "Enable PC-Speaker support" if EXPERT
1230        depends on HAVE_PCSPKR_PLATFORM
1231        select I8253_LOCK
1232        default y
1233        help
1234          This option allows to disable the internal PC-Speaker
1235          support, saving some memory.
1236
1237config HAVE_PCSPKR_PLATFORM
1238        bool
1239
1240config BASE_FULL
1241        default y
1242        bool "Enable full-sized data structures for core" if EXPERT
1243        help
1244          Disabling this option reduces the size of miscellaneous core
1245          kernel data structures. This saves memory on small machines,
1246          but may reduce performance.
1247
1248config FUTEX
1249        bool "Enable futex support" if EXPERT
1250        default y
1251        select RT_MUTEXES
1252        help
1253          Disabling this option will cause the kernel to be built without
1254          support for "fast userspace mutexes".  The resulting kernel may not
1255          run glibc-based applications correctly.
1256
1257config EPOLL
1258        bool "Enable eventpoll support" if EXPERT
1259        default y
1260        select ANON_INODES
1261        help
1262          Disabling this option will cause the kernel to be built without
1263          support for epoll family of system calls.
1264
1265config SIGNALFD
1266        bool "Enable signalfd() system call" if EXPERT
1267        select ANON_INODES
1268        default y
1269        help
1270          Enable the signalfd() system call that allows to receive signals
1271          on a file descriptor.
1272
1273          If unsure, say Y.
1274
1275config TIMERFD
1276        bool "Enable timerfd() system call" if EXPERT
1277        select ANON_INODES
1278        default y
1279        help
1280          Enable the timerfd() system call that allows to receive timer
1281          events on a file descriptor.
1282
1283          If unsure, say Y.
1284
1285config EVENTFD
1286        bool "Enable eventfd() system call" if EXPERT
1287        select ANON_INODES
1288        default y
1289        help
1290          Enable the eventfd() system call that allows to receive both
1291          kernel notification (ie. KAIO) or userspace notifications.
1292
1293          If unsure, say Y.
1294
1295config SHMEM
1296        bool "Use full shmem filesystem" if EXPERT
1297        default y
1298        depends on MMU
1299        help
1300          The shmem is an internal filesystem used to manage shared memory.
1301          It is backed by swap and manages resource limits. It is also exported
1302          to userspace as tmpfs if TMPFS is enabled. Disabling this
1303          option replaces shmem and tmpfs with the much simpler ramfs code,
1304          which may be appropriate on small systems without swap.
1305
1306config AIO
1307        bool "Enable AIO support" if EXPERT
1308        default y
1309        help
1310          This option enables POSIX asynchronous I/O which may by used
1311          by some high performance threaded applications. Disabling
1312          this option saves about 7k.
1313
1314config EMBEDDED
1315        bool "Embedded system"
1316        select EXPERT
1317        help
1318          This option should be enabled if compiling the kernel for
1319          an embedded system so certain expert options are available
1320          for configuration.
1321
1322config HAVE_PERF_EVENTS
1323        bool
1324        help
1325          See tools/perf/design.txt for details.
1326
1327config PERF_USE_VMALLOC
1328        bool
1329        help
1330          See tools/perf/design.txt for details
1331
1332menu "Kernel Performance Events And Counters"
1333
1334config PERF_EVENTS
1335        bool "Kernel performance events and counters"
1336        default y if PROFILING
1337        depends on HAVE_PERF_EVENTS
1338        select ANON_INODES
1339        select IRQ_WORK
1340        help
1341          Enable kernel support for various performance events provided
1342          by software and hardware.
1343
1344          Software events are supported either built-in or via the
1345          use of generic tracepoints.
1346
1347          Most modern CPUs support performance events via performance
1348          counter registers. These registers count the number of certain
1349          types of hw events: such as instructions executed, cachemisses
1350          suffered, or branches mis-predicted - without slowing down the
1351          kernel or applications. These registers can also trigger interrupts
1352          when a threshold number of events have passed - and can thus be
1353          used to profile the code that runs on that CPU.
1354
1355          The Linux Performance Event subsystem provides an abstraction of
1356          these software and hardware event capabilities, available via a
1357          system call and used by the "perf" utility in tools/perf/. It
1358          provides per task and per CPU counters, and it provides event
1359          capabilities on top of those.
1360
1361          Say Y if unsure.
1362
1363config DEBUG_PERF_USE_VMALLOC
1364        default n
1365        bool "Debug: use vmalloc to back perf mmap() buffers"
1366        depends on PERF_EVENTS && DEBUG_KERNEL
1367        select PERF_USE_VMALLOC
1368        help
1369         Use vmalloc memory to back perf mmap() buffers.
1370
1371         Mostly useful for debugging the vmalloc code on platforms
1372         that don't require it.
1373
1374         Say N if unsure.
1375
1376endmenu
1377
1378config VM_EVENT_COUNTERS
1379        default y
1380        bool "Enable VM event counters for /proc/vmstat" if EXPERT
1381        help
1382          VM event counters are needed for event counts to be shown.
1383          This option allows the disabling of the VM event counters
1384          on EXPERT systems.  /proc/vmstat will only show page counts
1385          if VM event counters are disabled.
1386
1387config PCI_QUIRKS
1388        default y
1389        bool "Enable PCI quirk workarounds" if EXPERT
1390        depends on PCI
1391        help
1392          This enables workarounds for various PCI chipset
1393          bugs/quirks. Disable this only if your target machine is
1394          unaffected by PCI quirks.
1395
1396config SLUB_DEBUG
1397        default y
1398        bool "Enable SLUB debugging support" if EXPERT
1399        depends on SLUB && SYSFS
1400        help
1401          SLUB has extensive debug support features. Disabling these can
1402          result in significant savings in code size. This also disables
1403          SLUB sysfs support. /sys/slab will not exist and there will be
1404          no support for cache validation etc.
1405
1406config COMPAT_BRK
1407        bool "Disable heap randomization"
1408        default y
1409        help
1410          Randomizing heap placement makes heap exploits harder, but it
1411          also breaks ancient binaries (including anything libc5 based).
1412          This option changes the bootup default to heap randomization
1413          disabled, and can be overridden at runtime by setting
1414          /proc/sys/kernel/randomize_va_space to 2.
1415
1416          On non-ancient distros (post-2000 ones) N is usually a safe choice.
1417
1418choice
1419        prompt "Choose SLAB allocator"
1420        default SLUB
1421        help
1422           This option allows to select a slab allocator.
1423
1424config SLAB
1425        bool "SLAB"
1426        help
1427          The regular slab allocator that is established and known to work
1428          well in all environments. It organizes cache hot objects in
1429          per cpu and per node queues.
1430
1431config SLUB
1432        bool "SLUB (Unqueued Allocator)"
1433        help
1434           SLUB is a slab allocator that minimizes cache line usage
1435           instead of managing queues of cached objects (SLAB approach).
1436           Per cpu caching is realized using slabs of objects instead
1437           of queues of objects. SLUB can use memory efficiently
1438           and has enhanced diagnostics. SLUB is the default choice for
1439           a slab allocator.
1440
1441config SLOB
1442        depends on EXPERT
1443        bool "SLOB (Simple Allocator)"
1444        help
1445           SLOB replaces the stock allocator with a drastically simpler
1446           allocator. SLOB is generally more space efficient but
1447           does not perform as well on large systems.
1448
1449endchoice
1450
1451config MMAP_ALLOW_UNINITIALIZED
1452        bool "Allow mmapped anonymous memory to be uninitialized"
1453        depends on EXPERT && !MMU
1454        default n
1455        help
1456          Normally, and according to the Linux spec, anonymous memory obtained
1457          from mmap() has it's contents cleared before it is passed to
1458          userspace.  Enabling this config option allows you to request that
1459          mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1460          providing a huge performance boost.  If this option is not enabled,
1461          then the flag will be ignored.
1462
1463          This is taken advantage of by uClibc's malloc(), and also by
1464          ELF-FDPIC binfmt's brk and stack allocator.
1465
1466          Because of the obvious security issues, this option should only be
1467          enabled on embedded devices where you control what is run in
1468          userspace.  Since that isn't generally a problem on no-MMU systems,
1469          it is normally safe to say Y here.
1470
1471          See Documentation/nommu-mmap.txt for more information.
1472
1473config PROFILING
1474        bool "Profiling support"
1475        help
1476          Say Y here to enable the extended profiling support mechanisms used
1477          by profilers such as OProfile.
1478
1479#
1480# Place an empty function call at each tracepoint site. Can be
1481# dynamically changed for a probe function.
1482#
1483config TRACEPOINTS
1484        bool
1485
1486source "arch/Kconfig"
1487
1488endmenu         # General setup
1489
1490config HAVE_GENERIC_DMA_COHERENT
1491        bool
1492        default n
1493
1494config SLABINFO
1495        bool
1496        depends on PROC_FS
1497        depends on SLAB || SLUB_DEBUG
1498        default y
1499
1500config RT_MUTEXES
1501        boolean
1502
1503config BASE_SMALL
1504        int
1505        default 0 if BASE_FULL
1506        default 1 if !BASE_FULL
1507
1508menuconfig MODULES
1509        bool "Enable loadable module support"
1510        help
1511          Kernel modules are small pieces of compiled code which can
1512          be inserted in the running kernel, rather than being
1513          permanently built into the kernel.  You use the "modprobe"
1514          tool to add (and sometimes remove) them.  If you say Y here,
1515          many parts of the kernel can be built as modules (by
1516          answering M instead of Y where indicated): this is most
1517          useful for infrequently used options which are not required
1518          for booting.  For more information, see the man pages for
1519          modprobe, lsmod, modinfo, insmod and rmmod.
1520
1521          If you say Y here, you will need to run "make
1522          modules_install" to put the modules under /lib/modules/
1523          where modprobe can find them (you may need to be root to do
1524          this).
1525
1526          If unsure, say Y.
1527
1528if MODULES
1529
1530config MODULE_FORCE_LOAD
1531        bool "Forced module loading"
1532        default n
1533        help
1534          Allow loading of modules without version information (ie. modprobe
1535          --force).  Forced module loading sets the 'F' (forced) taint flag and
1536          is usually a really bad idea.
1537
1538config MODULE_UNLOAD
1539        bool "Module unloading"
1540        help
1541          Without this option you will not be able to unload any
1542          modules (note that some modules may not be unloadable
1543          anyway), which makes your kernel smaller, faster
1544          and simpler.  If unsure, say Y.
1545
1546config MODULE_FORCE_UNLOAD
1547        bool "Forced module unloading"
1548        depends on MODULE_UNLOAD && EXPERIMENTAL
1549        help
1550          This option allows you to force a module to unload, even if the
1551          kernel believes it is unsafe: the kernel will remove the module
1552          without waiting for anyone to stop using it (using the -f option to
1553          rmmod).  This is mainly for kernel developers and desperate users.
1554          If unsure, say N.
1555
1556config MODVERSIONS
1557        bool "Module versioning support"
1558        help
1559          Usually, you have to use modules compiled with your kernel.
1560          Saying Y here makes it sometimes possible to use modules
1561          compiled for different kernels, by adding enough information
1562          to the modules to (hopefully) spot any changes which would
1563          make them incompatible with the kernel you are running.  If
1564          unsure, say N.
1565
1566config MODULE_SRCVERSION_ALL
1567        bool "Source checksum for all modules"
1568        help
1569          Modules which contain a MODULE_VERSION get an extra "srcversion"
1570          field inserted into their modinfo section, which contains a
1571          sum of the source files which made it.  This helps maintainers
1572          see exactly which source was used to build a module (since
1573          others sometimes change the module source without updating
1574          the version).  With this option, such a "srcversion" field
1575          will be created for all modules.  If unsure, say N.
1576
1577config MODULE_SIG
1578        bool "Module signature verification"
1579        depends on MODULES
1580        select KEYS
1581        select CRYPTO
1582        select ASYMMETRIC_KEY_TYPE
1583        select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1584        select PUBLIC_KEY_ALGO_RSA
1585        select ASN1
1586        select OID_REGISTRY
1587        select X509_CERTIFICATE_PARSER
1588        help
1589          Check modules for valid signatures upon load: the signature
1590          is simply appended to the module. For more information see
1591          Documentation/module-signing.txt.
1592
1593          !!!WARNING!!!  If you enable this option, you MUST make sure that the
1594          module DOES NOT get stripped after being signed.  This includes the
1595          debuginfo strip done by some packagers (such as rpmbuild) and
1596          inclusion into an initramfs that wants the module size reduced.
1597
1598config MODULE_SIG_FORCE
1599        bool "Require modules to be validly signed"
1600        depends on MODULE_SIG
1601        help
1602          Reject unsigned modules or signed modules for which we don't have a
1603          key.  Without this, such modules will simply taint the kernel.
1604
1605choice
1606        prompt "Which hash algorithm should modules be signed with?"
1607        depends on MODULE_SIG
1608        help
1609          This determines which sort of hashing algorithm will be used during
1610          signature generation.  This algorithm _must_ be built into the kernel
1611          directly so that signature verification can take place.  It is not
1612          possible to load a signed module containing the algorithm to check
1613          the signature on that module.
1614
1615config MODULE_SIG_SHA1
1616        bool "Sign modules with SHA-1"
1617        select CRYPTO_SHA1
1618
1619config MODULE_SIG_SHA224
1620        bool "Sign modules with SHA-224"
1621        select CRYPTO_SHA256
1622
1623config MODULE_SIG_SHA256
1624        bool "Sign modules with SHA-256"
1625        select CRYPTO_SHA256
1626
1627config MODULE_SIG_SHA384
1628        bool "Sign modules with SHA-384"
1629        select CRYPTO_SHA512
1630
1631config MODULE_SIG_SHA512
1632        bool "Sign modules with SHA-512"
1633        select CRYPTO_SHA512
1634
1635endchoice
1636
1637endif # MODULES
1638
1639config INIT_ALL_POSSIBLE
1640        bool
1641        help
1642          Back when each arch used to define their own cpu_online_mask and
1643          cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1644          with all 1s, and others with all 0s.  When they were centralised,
1645          it was better to provide this option than to break all the archs
1646          and have several arch maintainers pursuing me down dark alleys.
1647
1648config STOP_MACHINE
1649        bool
1650        default y
1651        depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1652        help
1653          Need stop_machine() primitive.
1654
1655source "block/Kconfig"
1656
1657config PREEMPT_NOTIFIERS
1658        bool
1659
1660config PADATA
1661        depends on SMP
1662        bool
1663
1664# Can be selected by architectures with broken toolchains
1665# that get confused by correct const<->read_only section
1666# mappings
1667config BROKEN_RODATA
1668        bool
1669
1670config ASN1
1671        tristate
1672        help
1673          Build a simple ASN.1 grammar compiler that produces a bytecode output
1674          that can be interpreted by the ASN.1 stream decoder and used to
1675          inform it as to what tags are to be expected in a stream and what
1676          functions to call on what tags.
1677
1678source "kernel/Kconfig.locks"
1679
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