1config ARCH
   2        string
   3        option env="ARCH"
   6        string
   7        option env="KERNELVERSION"
  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"
  20        bool
  21        depends on !UML
  23config IRQ_WORK
  24        bool
  27        bool
  29menu "General setup"
  31config BROKEN
  32        bool
  34config BROKEN_ON_SMP
  35        bool
  36        depends on BROKEN || !SMP
  37        default y
  40        int
  41        default 32 if !UML
  42        default 128 if UML
  43        help
  44          Maximum of each of the number of arguments and environment
  45          variables passed to init from the kernel command line.
  48config CROSS_COMPILE
  49        string "Cross-compiler tool prefix"
  50        help
  51          Same as running 'make CROSS_COMPILE=prefix-' but stored for
  52          default make runs in this kernel build directory.  You don't
  53          need to set this unless you want the configured kernel build
  54          directory to select the cross-compiler automatically.
  56config COMPILE_TEST
  57        bool "Compile also drivers which will not load"
  58        default n
  59        help
  60          Some drivers can be compiled on a different platform than they are
  61          intended to be run on. Despite they cannot be loaded there (or even
  62          when they load they cannot be used due to missing HW support),
  63          developers still, opposing to distributors, might want to build such
  64          drivers to compile-test them.
  66          If you are a developer and want to build everything available, say Y
  67          here. If you are a user/distributor, say N here to exclude useless
  68          drivers to be distributed.
  71        string "Local version - append to kernel release"
  72        help
  73          Append an extra string to the end of your kernel version.
  74          This will show up when you type uname, for example.
  75          The string you set here will be appended after the contents of
  76          any files with a filename matching localversion* in your
  77          object and source tree, in that order.  Your total string can
  78          be a maximum of 64 characters.
  81        bool "Automatically append version information to the version string"
  82        default y
  83        help
  84          This will try to automatically determine if the current tree is a
  85          release tree by looking for git tags that belong to the current
  86          top of tree revision.
  88          A string of the format -gxxxxxxxx will be added to the localversion
  89          if a git-based tree is found.  The string generated by this will be
  90          appended after any matching localversion* files, and after the value
  91          set in CONFIG_LOCALVERSION.
  93          (The actual string used here is the first eight characters produced
  94          by running the command:
  96            $ git rev-parse --verify HEAD
  98          which is done within the script "scripts/setlocalversion".)
 101        bool
 103config HAVE_KERNEL_BZIP2
 104        bool
 107        bool
 109config HAVE_KERNEL_XZ
 110        bool
 112config HAVE_KERNEL_LZO
 113        bool
 115config HAVE_KERNEL_LZ4
 116        bool
 119        prompt "Kernel compression mode"
 120        default KERNEL_GZIP
 122        help
 123          The linux kernel is a kind of self-extracting executable.
 124          Several compression algorithms are available, which differ
 125          in efficiency, compression and decompression speed.
 126          Compression speed is only relevant when building a kernel.
 127          Decompression speed is relevant at each boot.
 129          If you have any problems with bzip2 or lzma compressed
 130          kernels, mail me (Alain Knaff) <>. (An older
 131          version of this functionality (bzip2 only), for 2.4, was
 132          supplied by Christian Ludwig)
 134          High compression options are mostly useful for users, who
 135          are low on disk space (embedded systems), but for whom ram
 136          size matters less.
 138          If in doubt, select 'gzip'
 140config KERNEL_GZIP
 141        bool "Gzip"
 142        depends on HAVE_KERNEL_GZIP
 143        help
 144          The old and tried gzip compression. It provides a good balance
 145          between compression ratio and decompression speed.
 147config KERNEL_BZIP2
 148        bool "Bzip2"
 149        depends on HAVE_KERNEL_BZIP2
 150        help
 151          Its compression ratio and speed is intermediate.
 152          Decompression speed is slowest among the choices.  The kernel
 153          size is about 10% smaller with bzip2, in comparison to gzip.
 154          Bzip2 uses a large amount of memory. For modern kernels you
 155          will need at least 8MB RAM or more for booting.
 157config KERNEL_LZMA
 158        bool "LZMA"
 159        depends on HAVE_KERNEL_LZMA
 160        help
 161          This compression algorithm's ratio is best.  Decompression speed
 162          is between gzip and bzip2.  Compression is slowest.
 163          The kernel size is about 33% smaller with LZMA in comparison to gzip.
 165config KERNEL_XZ
 166        bool "XZ"
 167        depends on HAVE_KERNEL_XZ
 168        help
 169          XZ uses the LZMA2 algorithm and instruction set specific
 170          BCJ filters which can improve compression ratio of executable
 171          code. The size of the kernel is about 30% smaller with XZ in
 172          comparison to gzip. On architectures for which there is a BCJ
 173          filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
 174          will create a few percent smaller kernel than plain LZMA.
 176          The speed is about the same as with LZMA: The decompression
 177          speed of XZ is better than that of bzip2 but worse than gzip
 178          and LZO. Compression is slow.
 180config KERNEL_LZO
 181        bool "LZO"
 182        depends on HAVE_KERNEL_LZO
 183        help
 184          Its compression ratio is the poorest among the choices. The kernel
 185          size is about 10% bigger than gzip; however its speed
 186          (both compression and decompression) is the fastest.
 188config KERNEL_LZ4
 189        bool "LZ4"
 190        depends on HAVE_KERNEL_LZ4
 191        help
 192          LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
 193          A preliminary version of LZ4 de/compression tool is available at
 194          <>.
 196          Its compression ratio is worse than LZO. The size of the kernel
 197          is about 8% bigger than LZO. But the decompression speed is
 198          faster than LZO.
 203        string "Default hostname"
 204        default "(none)"
 205        help
 206          This option determines the default system hostname before userspace
 207          calls sethostname(2). The kernel traditionally uses "(none)" here,
 208          but you may wish to use a different default here to make a minimal
 209          system more usable with less configuration.
 211config SWAP
 212        bool "Support for paging of anonymous memory (swap)"
 213        depends on MMU && BLOCK
 214        default y
 215        help
 216          This option allows you to choose whether you want to have support
 217          for so called swap devices or swap files in your kernel that are
 218          used to provide more virtual memory than the actual RAM present
 219          in your computer.  If unsure say Y.
 221config SYSVIPC
 222        bool "System V IPC"
 223        ---help---
 224          Inter Process Communication is a suite of library functions and
 225          system calls which let processes (running programs) synchronize and
 226          exchange information. It is generally considered to be a good thing,
 227          and some programs won't run unless you say Y here. In particular, if
 228          you want to run the DOS emulator dosemu under Linux (read the
 229          DOSEMU-HOWTO, available from <>),
 230          you'll need to say Y here.
 232          You can find documentation about IPC with "info ipc" and also in
 233          section 6.4 of the Linux Programmer's Guide, available from
 234          <>.
 237        bool
 238        depends on SYSVIPC
 239        depends on SYSCTL
 240        default y
 242config POSIX_MQUEUE
 243        bool "POSIX Message Queues"
 244        depends on NET
 245        ---help---
 246          POSIX variant of message queues is a part of IPC. In POSIX message
 247          queues every message has a priority which decides about succession
 248          of receiving it by a process. If you want to compile and run
 249          programs written e.g. for Solaris with use of its POSIX message
 250          queues (functions mq_*) say Y here.
 252          POSIX message queues are visible as a filesystem called 'mqueue'
 253          and can be mounted somewhere if you want to do filesystem
 254          operations on message queues.
 256          If unsure, say Y.
 259        bool
 260        depends on POSIX_MQUEUE
 261        depends on SYSCTL
 262        default y
 265        bool "Enable process_vm_readv/writev syscalls"
 266        depends on MMU
 267        default y
 268        help
 269          Enabling this option adds the system calls process_vm_readv and
 270          process_vm_writev which allow a process with the correct privileges
 271          to directly read from or write to another process' address space.
 272          See the man page for more details.
 274config FHANDLE
 275        bool "open by fhandle syscalls" if EXPERT
 276        select EXPORTFS
 277        default y
 278        help
 279          If you say Y here, a user level program will be able to map
 280          file names to handle and then later use the handle for
 281          different file system operations. This is useful in implementing
 282          userspace file servers, which now track files using handles instead
 283          of names. The handle would remain the same even if file names
 284          get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
 285          syscalls.
 287config USELIB
 288        bool "uselib syscall"
 289        def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
 290        help
 291          This option enables the uselib syscall, a system call used in the
 292          dynamic linker from libc5 and earlier.  glibc does not use this
 293          system call.  If you intend to run programs built on libc5 or
 294          earlier, you may need to enable this syscall.  Current systems
 295          running glibc can safely disable this.
 297config AUDIT
 298        bool "Auditing support"
 299        depends on NET
 300        help
 301          Enable auditing infrastructure that can be used with another
 302          kernel subsystem, such as SELinux (which requires this for
 303          logging of avc messages output).  System call auditing is included
 304          on architectures which support it.
 307        bool
 310        def_bool y
 311        depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
 313config AUDIT_WATCH
 314        def_bool y
 315        depends on AUDITSYSCALL
 316        select FSNOTIFY
 318config AUDIT_TREE
 319        def_bool y
 320        depends on AUDITSYSCALL
 321        select FSNOTIFY
 323source "kernel/irq/Kconfig"
 324source "kernel/time/Kconfig"
 326menu "CPU/Task time and stats accounting"
 329        bool
 332        prompt "Cputime accounting"
 333        default TICK_CPU_ACCOUNTING if !PPC64
 334        default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
 336# Kind of a stub config for the pure tick based cputime accounting
 338        bool "Simple tick based cputime accounting"
 339        depends on !S390 && !NO_HZ_FULL
 340        help
 341          This is the basic tick based cputime accounting that maintains
 342          statistics about user, system and idle time spent on per jiffies
 343          granularity.
 345          If unsure, say Y.
 348        bool "Deterministic task and CPU time accounting"
 349        depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
 350        select VIRT_CPU_ACCOUNTING
 351        help
 352          Select this option to enable more accurate task and CPU time
 353          accounting.  This is done by reading a CPU counter on each
 354          kernel entry and exit and on transitions within the kernel
 355          between system, softirq and hardirq state, so there is a
 356          small performance impact.  In the case of s390 or IBM POWER > 5,
 357          this also enables accounting of stolen time on logically-partitioned
 358          systems.
 361        bool "Full dynticks CPU time accounting"
 362        depends on HAVE_CONTEXT_TRACKING
 363        depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
 364        select VIRT_CPU_ACCOUNTING
 365        select CONTEXT_TRACKING
 366        help
 367          Select this option to enable task and CPU time accounting on full
 368          dynticks systems. This accounting is implemented by watching every
 369          kernel-user boundaries using the context tracking subsystem.
 370          The accounting is thus performed at the expense of some significant
 371          overhead.
 373          For now this is only useful if you are working on the full
 374          dynticks subsystem development.
 376          If unsure, say N.
 379        bool "Fine granularity task level IRQ time accounting"
 380        depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL
 381        help
 382          Select this option to enable fine granularity task irq time
 383          accounting. This is done by reading a timestamp on each
 384          transitions between softirq and hardirq state, so there can be a
 385          small performance impact.
 387          If in doubt, say N here.
 392        bool "BSD Process Accounting"
 393        depends on MULTIUSER
 394        help
 395          If you say Y here, a user level program will be able to instruct the
 396          kernel (via a special system call) to write process accounting
 397          information to a file: whenever a process exits, information about
 398          that process will be appended to the file by the kernel.  The
 399          information includes things such as creation time, owning user,
 400          command name, memory usage, controlling terminal etc. (the complete
 401          list is in the struct acct in <file:include/linux/acct.h>).  It is
 402          up to the user level program to do useful things with this
 403          information.  This is generally a good idea, so say Y.
 405config BSD_PROCESS_ACCT_V3
 406        bool "BSD Process Accounting version 3 file format"
 407        depends on BSD_PROCESS_ACCT
 408        default n
 409        help
 410          If you say Y here, the process accounting information is written
 411          in a new file format that also logs the process IDs of each
 412          process and it's parent. Note that this file format is incompatible
 413          with previous v0/v1/v2 file formats, so you will need updated tools
 414          for processing it. A preliminary version of these tools is available
 415          at <>.
 417config TASKSTATS
 418        bool "Export task/process statistics through netlink"
 419        depends on NET
 420        depends on MULTIUSER
 421        default n
 422        help
 423          Export selected statistics for tasks/processes through the
 424          generic netlink interface. Unlike BSD process accounting, the
 425          statistics are available during the lifetime of tasks/processes as
 426          responses to commands. Like BSD accounting, they are sent to user
 427          space on task exit.
 429          Say N if unsure.
 431config TASK_DELAY_ACCT
 432        bool "Enable per-task delay accounting"
 433        depends on TASKSTATS
 434        select SCHED_INFO
 435        help
 436          Collect information on time spent by a task waiting for system
 437          resources like cpu, synchronous block I/O completion and swapping
 438          in pages. Such statistics can help in setting a task's priorities
 439          relative to other tasks for cpu, io, rss limits etc.
 441          Say N if unsure.
 443config TASK_XACCT
 444        bool "Enable extended accounting over taskstats"
 445        depends on TASKSTATS
 446        help
 447          Collect extended task accounting data and send the data
 448          to userland for processing over the taskstats interface.
 450          Say N if unsure.
 453        bool "Enable per-task storage I/O accounting"
 454        depends on TASK_XACCT
 455        help
 456          Collect information on the number of bytes of storage I/O which this
 457          task has caused.
 459          Say N if unsure.
 461endmenu # "CPU/Task time and stats accounting"
 463menu "RCU Subsystem"
 465config TREE_RCU
 466        bool
 467        default y if !PREEMPT && SMP
 468        help
 469          This option selects the RCU implementation that is
 470          designed for very large SMP system with hundreds or
 471          thousands of CPUs.  It also scales down nicely to
 472          smaller systems.
 474config PREEMPT_RCU
 475        bool
 476        default y if PREEMPT
 477        help
 478          This option selects the RCU implementation that is
 479          designed for very large SMP systems with hundreds or
 480          thousands of CPUs, but for which real-time response
 481          is also required.  It also scales down nicely to
 482          smaller systems.
 484          Select this option if you are unsure.
 486config TINY_RCU
 487        bool
 488        default y if !PREEMPT && !SMP
 489        help
 490          This option selects the RCU implementation that is
 491          designed for UP systems from which real-time response
 492          is not required.  This option greatly reduces the
 493          memory footprint of RCU.
 495config RCU_EXPERT
 496        bool "Make expert-level adjustments to RCU configuration"
 497        default n
 498        help
 499          This option needs to be enabled if you wish to make
 500          expert-level adjustments to RCU configuration.  By default,
 501          no such adjustments can be made, which has the often-beneficial
 502          side-effect of preventing "make oldconfig" from asking you all
 503          sorts of detailed questions about how you would like numerous
 504          obscure RCU options to be set up.
 506          Say Y if you need to make expert-level adjustments to RCU.
 508          Say N if you are unsure.
 510config SRCU
 511        bool
 512        help
 513          This option selects the sleepable version of RCU. This version
 514          permits arbitrary sleeping or blocking within RCU read-side critical
 515          sections.
 517config TASKS_RCU
 518        bool
 519        default n
 520        select SRCU
 521        help
 522          This option enables a task-based RCU implementation that uses
 523          only voluntary context switch (not preemption!), idle, and
 524          user-mode execution as quiescent states.
 527        def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
 528        help
 529          This option enables RCU CPU stall code that is common between
 530          the TINY and TREE variants of RCU.  The purpose is to allow
 531          the tiny variants to disable RCU CPU stall warnings, while
 532          making these warnings mandatory for the tree variants.
 535       bool
 538        bool "Force context tracking"
 539        depends on CONTEXT_TRACKING
 540        default y if !NO_HZ_FULL
 541        help
 542          The major pre-requirement for full dynticks to work is to
 543          support the context tracking subsystem. But there are also
 544          other dependencies to provide in order to make the full
 545          dynticks working.
 547          This option stands for testing when an arch implements the
 548          context tracking backend but doesn't yet fullfill all the
 549          requirements to make the full dynticks feature working.
 550          Without the full dynticks, there is no way to test the support
 551          for context tracking and the subsystems that rely on it: RCU
 552          userspace extended quiescent state and tickless cputime
 553          accounting. This option copes with the absence of the full
 554          dynticks subsystem by forcing the context tracking on all
 555          CPUs in the system.
 557          Say Y only if you're working on the development of an
 558          architecture backend for the context tracking.
 560          Say N otherwise, this option brings an overhead that you
 561          don't want in production.
 564config RCU_FANOUT
 565        int "Tree-based hierarchical RCU fanout value"
 566        range 2 64 if 64BIT
 567        range 2 32 if !64BIT
 568        depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
 569        default 64 if 64BIT
 570        default 32 if !64BIT
 571        help
 572          This option controls the fanout of hierarchical implementations
 573          of RCU, allowing RCU to work efficiently on machines with
 574          large numbers of CPUs.  This value must be at least the fourth
 575          root of NR_CPUS, which allows NR_CPUS to be insanely large.
 576          The default value of RCU_FANOUT should be used for production
 577          systems, but if you are stress-testing the RCU implementation
 578          itself, small RCU_FANOUT values allow you to test large-system
 579          code paths on small(er) systems.
 581          Select a specific number if testing RCU itself.
 582          Take the default if unsure.
 584config RCU_FANOUT_LEAF
 585        int "Tree-based hierarchical RCU leaf-level fanout value"
 586        range 2 64 if 64BIT
 587        range 2 32 if !64BIT
 588        depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
 589        default 16
 590        help
 591          This option controls the leaf-level fanout of hierarchical
 592          implementations of RCU, and allows trading off cache misses
 593          against lock contention.  Systems that synchronize their
 594          scheduling-clock interrupts for energy-efficiency reasons will
 595          want the default because the smaller leaf-level fanout keeps
 596          lock contention levels acceptably low.  Very large systems
 597          (hundreds or thousands of CPUs) will instead want to set this
 598          value to the maximum value possible in order to reduce the
 599          number of cache misses incurred during RCU's grace-period
 600          initialization.  These systems tend to run CPU-bound, and thus
 601          are not helped by synchronized interrupts, and thus tend to
 602          skew them, which reduces lock contention enough that large
 603          leaf-level fanouts work well.
 605          Select a specific number if testing RCU itself.
 607          Select the maximum permissible value for large systems.
 609          Take the default if unsure.
 611config RCU_FAST_NO_HZ
 612        bool "Accelerate last non-dyntick-idle CPU's grace periods"
 613        depends on NO_HZ_COMMON && SMP && RCU_EXPERT
 614        default n
 615        help
 616          This option permits CPUs to enter dynticks-idle state even if
 617          they have RCU callbacks queued, and prevents RCU from waking
 618          these CPUs up more than roughly once every four jiffies (by
 619          default, you can adjust this using the rcutree.rcu_idle_gp_delay
 620          parameter), thus improving energy efficiency.  On the other
 621          hand, this option increases the duration of RCU grace periods,
 622          for example, slowing down synchronize_rcu().
 624          Say Y if energy efficiency is critically important, and you
 625                don't care about increased grace-period durations.
 627          Say N if you are unsure.
 629config TREE_RCU_TRACE
 630        def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
 631        select DEBUG_FS
 632        help
 633          This option provides tracing for the TREE_RCU and
 634          PREEMPT_RCU implementations, permitting Makefile to
 635          trivially select kernel/rcutree_trace.c.
 637config RCU_BOOST
 638        bool "Enable RCU priority boosting"
 639        depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT
 640        default n
 641        help
 642          This option boosts the priority of preempted RCU readers that
 643          block the current preemptible RCU grace period for too long.
 644          This option also prevents heavy loads from blocking RCU
 645          callback invocation for all flavors of RCU.
 647          Say Y here if you are working with real-time apps or heavy loads
 648          Say N here if you are unsure.
 651        int "Real-time priority to use for RCU worker threads"
 652        range 1 99 if RCU_BOOST
 653        range 0 99 if !RCU_BOOST
 654        default 1 if RCU_BOOST
 655        default 0 if !RCU_BOOST
 656        depends on RCU_EXPERT
 657        help
 658          This option specifies the SCHED_FIFO priority value that will be
 659          assigned to the rcuc/n and rcub/n threads and is also the value
 660          used for RCU_BOOST (if enabled). If you are working with a
 661          real-time application that has one or more CPU-bound threads
 662          running at a real-time priority level, you should set
 663          RCU_KTHREAD_PRIO to a priority higher than the highest-priority
 664          real-time CPU-bound application thread.  The default RCU_KTHREAD_PRIO
 665          value of 1 is appropriate in the common case, which is real-time
 666          applications that do not have any CPU-bound threads.
 668          Some real-time applications might not have a single real-time
 669          thread that saturates a given CPU, but instead might have
 670          multiple real-time threads that, taken together, fully utilize
 671          that CPU.  In this case, you should set RCU_KTHREAD_PRIO to
 672          a priority higher than the lowest-priority thread that is
 673          conspiring to prevent the CPU from running any non-real-time
 674          tasks.  For example, if one thread at priority 10 and another
 675          thread at priority 5 are between themselves fully consuming
 676          the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
 677          set to priority 6 or higher.
 679          Specify the real-time priority, or take the default if unsure.
 681config RCU_BOOST_DELAY
 682        int "Milliseconds to delay boosting after RCU grace-period start"
 683        range 0 3000
 684        depends on RCU_BOOST
 685        default 500
 686        help
 687          This option specifies the time to wait after the beginning of
 688          a given grace period before priority-boosting preempted RCU
 689          readers blocking that grace period.  Note that any RCU reader
 690          blocking an expedited RCU grace period is boosted immediately.
 692          Accept the default if unsure.
 694config RCU_NOCB_CPU
 695        bool "Offload RCU callback processing from boot-selected CPUs"
 696        depends on TREE_RCU || PREEMPT_RCU
 697        depends on RCU_EXPERT || NO_HZ_FULL
 698        default n
 699        help
 700          Use this option to reduce OS jitter for aggressive HPC or
 701          real-time workloads.  It can also be used to offload RCU
 702          callback invocation to energy-efficient CPUs in battery-powered
 703          asymmetric multiprocessors.
 705          This option offloads callback invocation from the set of
 706          CPUs specified at boot time by the rcu_nocbs parameter.
 707          For each such CPU, a kthread ("rcuox/N") will be created to
 708          invoke callbacks, where the "N" is the CPU being offloaded,
 709          and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
 710          "s" for RCU-sched.  Nothing prevents this kthread from running
 711          on the specified CPUs, but (1) the kthreads may be preempted
 712          between each callback, and (2) affinity or cgroups can be used
 713          to force the kthreads to run on whatever set of CPUs is desired.
 715          Say Y here if you want to help to debug reduced OS jitter.
 716          Say N here if you are unsure.
 719        prompt "Build-forced no-CBs CPUs"
 720        default RCU_NOCB_CPU_NONE
 721        depends on RCU_NOCB_CPU
 722        help
 723          This option allows no-CBs CPUs (whose RCU callbacks are invoked
 724          from kthreads rather than from softirq context) to be specified
 725          at build time.  Additional no-CBs CPUs may be specified by
 726          the rcu_nocbs= boot parameter.
 728config RCU_NOCB_CPU_NONE
 729        bool "No build_forced no-CBs CPUs"
 730        help
 731          This option does not force any of the CPUs to be no-CBs CPUs.
 732          Only CPUs designated by the rcu_nocbs= boot parameter will be
 733          no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
 734          kthreads whose names begin with "rcuo".  All other CPUs will
 735          invoke their own RCU callbacks in softirq context.
 737          Select this option if you want to choose no-CBs CPUs at
 738          boot time, for example, to allow testing of different no-CBs
 739          configurations without having to rebuild the kernel each time.
 741config RCU_NOCB_CPU_ZERO
 742        bool "CPU 0 is a build_forced no-CBs CPU"
 743        help
 744          This option forces CPU 0 to be a no-CBs CPU, so that its RCU
 745          callbacks are invoked by a per-CPU kthread whose name begins
 746          with "rcuo".  Additional CPUs may be designated as no-CBs
 747          CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
 748          All other CPUs will invoke their own RCU callbacks in softirq
 749          context.
 751          Select this if CPU 0 needs to be a no-CBs CPU for real-time
 752          or energy-efficiency reasons, but the real reason it exists
 753          is to ensure that randconfig testing covers mixed systems.
 755config RCU_NOCB_CPU_ALL
 756        bool "All CPUs are build_forced no-CBs CPUs"
 757        help
 758          This option forces all CPUs to be no-CBs CPUs.  The rcu_nocbs=
 759          boot parameter will be ignored.  All CPUs' RCU callbacks will
 760          be executed in the context of per-CPU rcuo kthreads created for
 761          this purpose.  Assuming that the kthreads whose names start with
 762          "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
 763          on the remaining CPUs, but might decrease memory locality during
 764          RCU-callback invocation, thus potentially degrading throughput.
 766          Select this if all CPUs need to be no-CBs CPUs for real-time
 767          or energy-efficiency reasons.
 772        bool
 773        default n
 774        help
 775          This option enables expedited grace periods at boot time,
 776          as if rcu_expedite_gp() had been invoked early in boot.
 777          The corresponding rcu_unexpedite_gp() is invoked from
 778          rcu_end_inkernel_boot(), which is intended to be invoked
 779          at the end of the kernel-only boot sequence, just before
 780          init is exec'ed.
 782          Accept the default if unsure.
 784endmenu # "RCU Subsystem"
 786config BUILD_BIN2C
 787        bool
 788        default n
 790config IKCONFIG
 791        tristate "Kernel .config support"
 792        select BUILD_BIN2C
 793        ---help---
 794          This option enables the complete Linux kernel ".config" file
 795          contents to be saved in the kernel. It provides documentation
 796          of which kernel options are used in a running kernel or in an
 797          on-disk kernel.  This information can be extracted from the kernel
 798          image file with the script scripts/extract-ikconfig and used as
 799          input to rebuild the current kernel or to build another kernel.
 800          It can also be extracted from a running kernel by reading
 801          /proc/config.gz if enabled (below).
 803config IKCONFIG_PROC
 804        bool "Enable access to .config through /proc/config.gz"
 805        depends on IKCONFIG && PROC_FS
 806        ---help---
 807          This option enables access to the kernel configuration file
 808          through /proc/config.gz.
 810config LOG_BUF_SHIFT
 811        int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
 812        range 12 25
 813        default 17
 814        depends on PRINTK
 815        help
 816          Select the minimal kernel log buffer size as a power of 2.
 817          The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
 818          parameter, see below. Any higher size also might be forced
 819          by "log_buf_len" boot parameter.
 821          Examples:
 822                     17 => 128 KB
 823                     16 => 64 KB
 824                     15 => 32 KB
 825                     14 => 16 KB
 826                     13 =>  8 KB
 827                     12 =>  4 KB
 830        int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
 831        depends on SMP
 832        range 0 21
 833        default 12 if !BASE_SMALL
 834        default 0 if BASE_SMALL
 835        depends on PRINTK
 836        help
 837          This option allows to increase the default ring buffer size
 838          according to the number of CPUs. The value defines the contribution
 839          of each CPU as a power of 2. The used space is typically only few
 840          lines however it might be much more when problems are reported,
 841          e.g. backtraces.
 843          The increased size means that a new buffer has to be allocated and
 844          the original static one is unused. It makes sense only on systems
 845          with more CPUs. Therefore this value is used only when the sum of
 846          contributions is greater than the half of the default kernel ring
 847          buffer as defined by LOG_BUF_SHIFT. The default values are set
 848          so that more than 64 CPUs are needed to trigger the allocation.
 850          Also this option is ignored when "log_buf_len" kernel parameter is
 851          used as it forces an exact (power of two) size of the ring buffer.
 853          The number of possible CPUs is used for this computation ignoring
 854          hotplugging making the compuation optimal for the the worst case
 855          scenerio while allowing a simple algorithm to be used from bootup.
 857          Examples shift values and their meaning:
 858                     17 => 128 KB for each CPU
 859                     16 =>  64 KB for each CPU
 860                     15 =>  32 KB for each CPU
 861                     14 =>  16 KB for each CPU
 862                     13 =>   8 KB for each CPU
 863                     12 =>   4 KB for each CPU
 866# Architectures with an unreliable sched_clock() should select this:
 869        bool
 872        bool
 875# For architectures that want to enable the support for NUMA-affine scheduler
 876# balancing logic:
 879        bool
 882# For architectures that prefer to flush all TLBs after a number of pages
 883# are unmapped instead of sending one IPI per page to flush. The architecture
 884# must provide guarantees on what happens if a clean TLB cache entry is
 885# written after the unmap. Details are in mm/rmap.c near the check for
 886# should_defer_flush. The architecture should also consider if the full flush
 887# and the refill costs are offset by the savings of sending fewer IPIs.
 889        bool
 892# For architectures that know their GCC __int128 support is sound
 894config ARCH_SUPPORTS_INT128
 895        bool
 897# For architectures that (ab)use NUMA to represent different memory regions
 898# all cpu-local but of different latencies, such as SuperH.
 901        bool
 904        bool "Memory placement aware NUMA scheduler"
 905        depends on ARCH_SUPPORTS_NUMA_BALANCING
 906        depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
 907        depends on SMP && NUMA && MIGRATION
 908        help
 909          This option adds support for automatic NUMA aware memory/task placement.
 910          The mechanism is quite primitive and is based on migrating memory when
 911          it has references to the node the task is running on.
 913          This system will be inactive on UMA systems.
 916        bool "Automatically enable NUMA aware memory/task placement"
 917        default y
 918        depends on NUMA_BALANCING
 919        help
 920          If set, automatic NUMA balancing will be enabled if running on a NUMA
 921          machine.
 923menuconfig CGROUPS
 924        bool "Control Group support"
 925        select KERNFS
 926        help
 927          This option adds support for grouping sets of processes together, for
 928          use with process control subsystems such as Cpusets, CFS, memory
 929          controls or device isolation.
 930          See
 931                - Documentation/scheduler/sched-design-CFS.txt  (CFS)
 932                - Documentation/cgroups/ (features for grouping, isolation
 933                                          and resource control)
 935          Say N if unsure.
 937if CGROUPS
 939config PAGE_COUNTER
 940       bool
 942config MEMCG
 943        bool "Memory controller"
 944        select PAGE_COUNTER
 945        select EVENTFD
 946        help
 947          Provides control over the memory footprint of tasks in a cgroup.
 949config MEMCG_SWAP
 950        bool "Swap controller"
 951        depends on MEMCG && SWAP
 952        help
 953          Provides control over the swap space consumed by tasks in a cgroup.
 956        bool "Swap controller enabled by default"
 957        depends on MEMCG_SWAP
 958        default y
 959        help
 960          Memory Resource Controller Swap Extension comes with its price in
 961          a bigger memory consumption. General purpose distribution kernels
 962          which want to enable the feature but keep it disabled by default
 963          and let the user enable it by swapaccount=1 boot command line
 964          parameter should have this option unselected.
 965          For those who want to have the feature enabled by default should
 966          select this option (if, for some reason, they need to disable it
 967          then swapaccount=0 does the trick).
 969config BLK_CGROUP
 970        bool "IO controller"
 971        depends on BLOCK
 972        default n
 973        ---help---
 974        Generic block IO controller cgroup interface. This is the common
 975        cgroup interface which should be used by various IO controlling
 976        policies.
 978        Currently, CFQ IO scheduler uses it to recognize task groups and
 979        control disk bandwidth allocation (proportional time slice allocation)
 980        to such task groups. It is also used by bio throttling logic in
 981        block layer to implement upper limit in IO rates on a device.
 983        This option only enables generic Block IO controller infrastructure.
 984        One needs to also enable actual IO controlling logic/policy. For
 985        enabling proportional weight division of disk bandwidth in CFQ, set
 986        CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
 989        See Documentation/cgroups/blkio-controller.txt for more information.
 992        bool "IO controller debugging"
 993        depends on BLK_CGROUP
 994        default n
 995        ---help---
 996        Enable some debugging help. Currently it exports additional stat
 997        files in a cgroup which can be useful for debugging.
1000        bool
1001        depends on MEMCG && BLK_CGROUP
1002        default y
1004menuconfig CGROUP_SCHED
1005        bool "CPU controller"
1006        default n
1007        help
1008          This feature lets CPU scheduler recognize task groups and control CPU
1009          bandwidth allocation to such task groups. It uses cgroups to group
1010          tasks.
1014        bool "Group scheduling for SCHED_OTHER"
1015        depends on CGROUP_SCHED
1016        default CGROUP_SCHED
1018config CFS_BANDWIDTH
1019        bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1020        depends on FAIR_GROUP_SCHED
1021        default n
1022        help
1023          This option allows users to define CPU bandwidth rates (limits) for
1024          tasks running within the fair group scheduler.  Groups with no limit
1025          set are considered to be unconstrained and will run with no
1026          restriction.
1027          See tip/Documentation/scheduler/sched-bwc.txt for more information.
1029config RT_GROUP_SCHED
1030        bool "Group scheduling for SCHED_RR/FIFO"
1031        depends on CGROUP_SCHED
1032        default n
1033        help
1034          This feature lets you explicitly allocate real CPU bandwidth
1035          to task groups. If enabled, it will also make it impossible to
1036          schedule realtime tasks for non-root users until you allocate
1037          realtime bandwidth for them.
1038          See Documentation/scheduler/sched-rt-group.txt for more information.
1040endif #CGROUP_SCHED
1042config CGROUP_PIDS
1043        bool "PIDs controller"
1044        help
1045          Provides enforcement of process number limits in the scope of a
1046          cgroup. Any attempt to fork more processes than is allowed in the
1047          cgroup will fail. PIDs are fundamentally a global resource because it
1048          is fairly trivial to reach PID exhaustion before you reach even a
1049          conservative kmemcg limit. As a result, it is possible to grind a
1050          system to halt without being limited by other cgroup policies. The
1051          PIDs controller is designed to stop this from happening.
1053          It should be noted that organisational operations (such as attaching
1054          to a cgroup hierarchy will *not* be blocked by the PIDs controller),
1055          since the PIDs limit only affects a process's ability to fork, not to
1056          attach to a cgroup.
1059        bool "Freezer controller"
1060        help
1061          Provides a way to freeze and unfreeze all tasks in a
1062          cgroup.
1064          This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1065          controller includes important in-kernel memory consumers per default.
1067          If you're using cgroup2, say N.
1070        bool "HugeTLB controller"
1071        depends on HUGETLB_PAGE
1072        select PAGE_COUNTER
1073        default n
1074        help
1075          Provides a cgroup controller for HugeTLB pages.
1076          When you enable this, you can put a per cgroup limit on HugeTLB usage.
1077          The limit is enforced during page fault. Since HugeTLB doesn't
1078          support page reclaim, enforcing the limit at page fault time implies
1079          that, the application will get SIGBUS signal if it tries to access
1080          HugeTLB pages beyond its limit. This requires the application to know
1081          beforehand how much HugeTLB pages it would require for its use. The
1082          control group is tracked in the third page lru pointer. This means
1083          that we cannot use the controller with huge page less than 3 pages.
1085config CPUSETS
1086        bool "Cpuset controller"
1087        help
1088          This option will let you create and manage CPUSETs which
1089          allow dynamically partitioning a system into sets of CPUs and
1090          Memory Nodes and assigning tasks to run only within those sets.
1091          This is primarily useful on large SMP or NUMA systems.
1093          Say N if unsure.
1095config PROC_PID_CPUSET
1096        bool "Include legacy /proc/<pid>/cpuset file"
1097        depends on CPUSETS
1098        default y
1100config CGROUP_DEVICE
1101        bool "Device controller"
1102        help
1103          Provides a cgroup controller implementing whitelists for
1104          devices which a process in the cgroup can mknod or open.
1107        bool "Simple CPU accounting controller"
1108        help
1109          Provides a simple controller for monitoring the
1110          total CPU consumed by the tasks in a cgroup.
1112config CGROUP_PERF
1113        bool "Perf controller"
1114        depends on PERF_EVENTS
1115        help
1116          This option extends the perf per-cpu mode to restrict monitoring
1117          to threads which belong to the cgroup specified and run on the
1118          designated cpu.
1120          Say N if unsure.
1122config CGROUP_DEBUG
1123        bool "Example controller"
1124        default n
1125        help
1126          This option enables a simple controller that exports
1127          debugging information about the cgroups framework.
1129          Say N.
1131endif # CGROUPS
1134        bool "Checkpoint/restore support" if EXPERT
1135        select PROC_CHILDREN
1136        default n
1137        help
1138          Enables additional kernel features in a sake of checkpoint/restore.
1139          In particular it adds auxiliary prctl codes to setup process text,
1140          data and heap segment sizes, and a few additional /proc filesystem
1141          entries.
1143          If unsure, say N here.
1145menuconfig NAMESPACES
1146        bool "Namespaces support" if EXPERT
1147        depends on MULTIUSER
1148        default !EXPERT
1149        help
1150          Provides the way to make tasks work with different objects using
1151          the same id. For example same IPC id may refer to different objects
1152          or same user id or pid may refer to different tasks when used in
1153          different namespaces.
1157config UTS_NS
1158        bool "UTS namespace"
1159        default y
1160        help
1161          In this namespace tasks see different info provided with the
1162          uname() system call
1164config IPC_NS
1165        bool "IPC namespace"
1166        depends on (SYSVIPC || POSIX_MQUEUE)
1167        default y
1168        help
1169          In this namespace tasks work with IPC ids which correspond to
1170          different IPC objects in different namespaces.
1172config USER_NS
1173        bool "User namespace"
1174        default n
1175        help
1176          This allows containers, i.e. vservers, to use user namespaces
1177          to provide different user info for different servers.
1179          When user namespaces are enabled in the kernel it is
1180          recommended that the MEMCG option also be enabled and that
1181          user-space use the memory control groups to limit the amount
1182          of memory a memory unprivileged users can use.
1184          If unsure, say N.
1186config PID_NS
1187        bool "PID Namespaces"
1188        default y
1189        help
1190          Support process id namespaces.  This allows having multiple
1191          processes with the same pid as long as they are in different
1192          pid namespaces.  This is a building block of containers.
1194config NET_NS
1195        bool "Network namespace"
1196        depends on NET
1197        default y
1198        help
1199          Allow user space to create what appear to be multiple instances
1200          of the network stack.
1202endif # NAMESPACES
1205        bool "Automatic process group scheduling"
1206        select CGROUPS
1207        select CGROUP_SCHED
1208        select FAIR_GROUP_SCHED
1209        help
1210          This option optimizes the scheduler for common desktop workloads by
1211          automatically creating and populating task groups.  This separation
1212          of workloads isolates aggressive CPU burners (like build jobs) from
1213          desktop applications.  Task group autogeneration is currently based
1214          upon task session.
1217        bool "Enable deprecated sysfs features to support old userspace tools"
1218        depends on SYSFS
1219        default n
1220        help
1221          This option adds code that switches the layout of the "block" class
1222          devices, to not show up in /sys/class/block/, but only in
1223          /sys/block/.
1225          This switch is only active when the sysfs.deprecated=1 boot option is
1226          passed or the SYSFS_DEPRECATED_V2 option is set.
1228          This option allows new kernels to run on old distributions and tools,
1229          which might get confused by /sys/class/block/. Since 2007/2008 all
1230          major distributions and tools handle this just fine.
1232          Recent distributions and userspace tools after 2009/2010 depend on
1233          the existence of /sys/class/block/, and will not work with this
1234          option enabled.
1236          Only if you are using a new kernel on an old distribution, you might
1237          need to say Y here.
1240        bool "Enable deprecated sysfs features by default"
1241        default n
1242        depends on SYSFS
1243        depends on SYSFS_DEPRECATED
1244        help
1245          Enable deprecated sysfs by default.
1247          See the CONFIG_SYSFS_DEPRECATED option for more details about this
1248          option.
1250          Only if you are using a new kernel on an old distribution, you might
1251          need to say Y here. Even then, odds are you would not need it
1252          enabled, you can always pass the boot option if absolutely necessary.
1254config RELAY
1255        bool "Kernel->user space relay support (formerly relayfs)"
1256        help
1257          This option enables support for relay interface support in
1258          certain file systems (such as debugfs).
1259          It is designed to provide an efficient mechanism for tools and
1260          facilities to relay large amounts of data from kernel space to
1261          user space.
1263          If unsure, say N.
1265config BLK_DEV_INITRD
1266        bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1267        depends on BROKEN || !FRV
1268        help
1269          The initial RAM filesystem is a ramfs which is loaded by the
1270          boot loader (loadlin or lilo) and that is mounted as root
1271          before the normal boot procedure. It is typically used to
1272          load modules needed to mount the "real" root file system,
1273          etc. See <file:Documentation/initrd.txt> for details.
1275          If RAM disk support (BLK_DEV_RAM) is also included, this
1276          also enables initial RAM disk (initrd) support and adds
1277          15 Kbytes (more on some other architectures) to the kernel size.
1279          If unsure say Y.
1283source "usr/Kconfig"
1288        bool "Optimize for size"
1289        help
1290          Enabling this option will pass "-Os" instead of "-O2" to
1291          your compiler resulting in a smaller kernel.
1293          If unsure, say N.
1295config SYSCTL
1296        bool
1298config ANON_INODES
1299        bool
1301config HAVE_UID16
1302        bool
1305        bool
1306        help
1307          Enable support for /proc/sys/debug/exception-trace.
1310        bool
1311        help
1312          Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1313          Allows arch to define/use @no_unaligned_warning to possibly warn
1314          about unaligned access emulation going on under the hood.
1317        bool
1318        help
1319          Enable support for /proc/sys/kernel/unaligned-trap
1320          Allows arches to define/use @unaligned_enabled to runtime toggle
1321          the unaligned access emulation.
1322          see arch/parisc/kernel/unaligned.c for reference
1325        bool
1327# interpreter that classic socket filters depend on
1328config BPF
1329        bool
1331menuconfig EXPERT
1332        bool "Configure standard kernel features (expert users)"
1333        # Unhide debug options, to make the on-by-default options visible
1334        select DEBUG_KERNEL
1335        help
1336          This option allows certain base kernel options and settings
1337          to be disabled or tweaked. This is for specialized
1338          environments which can tolerate a "non-standard" kernel.
1339          Only use this if you really know what you are doing.
1341config UID16
1342        bool "Enable 16-bit UID system calls" if EXPERT
1343        depends on HAVE_UID16 && MULTIUSER
1344        default y
1345        help
1346          This enables the legacy 16-bit UID syscall wrappers.
1348config MULTIUSER
1349        bool "Multiple users, groups and capabilities support" if EXPERT
1350        default y
1351        help
1352          This option enables support for non-root users, groups and
1353          capabilities.
1355          If you say N here, all processes will run with UID 0, GID 0, and all
1356          possible capabilities.  Saying N here also compiles out support for
1357          system calls related to UIDs, GIDs, and capabilities, such as setuid,
1358          setgid, and capset.
1360          If unsure, say Y here.
1363        bool "sgetmask/ssetmask syscalls support" if EXPERT
1364        def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1365        ---help---
1366          sys_sgetmask and sys_ssetmask are obsolete system calls
1367          no longer supported in libc but still enabled by default in some
1368          architectures.
1370          If unsure, leave the default option here.
1372config SYSFS_SYSCALL
1373        bool "Sysfs syscall support" if EXPERT
1374        default y
1375        ---help---
1376          sys_sysfs is an obsolete system call no longer supported in libc.
1377          Note that disabling this option is more secure but might break
1378          compatibility with some systems.
1380          If unsure say Y here.
1383        bool "Sysctl syscall support" if EXPERT
1384        depends on PROC_SYSCTL
1385        default n
1386        select SYSCTL
1387        ---help---
1388          sys_sysctl uses binary paths that have been found challenging
1389          to properly maintain and use.  The interface in /proc/sys
1390          using paths with ascii names is now the primary path to this
1391          information.
1393          Almost nothing using the binary sysctl interface so if you are
1394          trying to save some space it is probably safe to disable this,
1395          making your kernel marginally smaller.
1397          If unsure say N here.
1399config KALLSYMS
1400         bool "Load all symbols for debugging/ksymoops" if EXPERT
1401         default y
1402         help
1403           Say Y here to let the kernel print out symbolic crash information and
1404           symbolic stack backtraces. This increases the size of the kernel
1405           somewhat, as all symbols have to be loaded into the kernel image.
1407config KALLSYMS_ALL
1408        bool "Include all symbols in kallsyms"
1409        depends on DEBUG_KERNEL && KALLSYMS
1410        help
1411           Normally kallsyms only contains the symbols of functions for nicer
1412           OOPS messages and backtraces (i.e., symbols from the text and inittext
1413           sections). This is sufficient for most cases. And only in very rare
1414           cases (e.g., when a debugger is used) all symbols are required (e.g.,
1415           names of variables from the data sections, etc).
1417           This option makes sure that all symbols are loaded into the kernel
1418           image (i.e., symbols from all sections) in cost of increased kernel
1419           size (depending on the kernel configuration, it may be 300KiB or
1420           something like this).
1422           Say N unless you really need all symbols.
1425        bool
1426        default X86_64 && SMP
1429        bool
1430        depends on KALLSYMS
1431        default !IA64 && !(TILE && 64BIT)
1432        help
1433          Instead of emitting them as absolute values in the native word size,
1434          emit the symbol references in the kallsyms table as 32-bit entries,
1435          each containing a relative value in the range [base, base + U32_MAX]
1436          or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1437          an absolute value in the range [0, S32_MAX] or a relative value in the
1438          range [base, base + S32_MAX], where base is the lowest relative symbol
1439          address encountered in the image.
1441          On 64-bit builds, this reduces the size of the address table by 50%,
1442          but more importantly, it results in entries whose values are build
1443          time constants, and no relocation pass is required at runtime to fix
1444          up the entries based on the runtime load address of the kernel.
1446config PRINTK
1447        default y
1448        bool "Enable support for printk" if EXPERT
1449        select IRQ_WORK
1450        help
1451          This option enables normal printk support. Removing it
1452          eliminates most of the message strings from the kernel image
1453          and makes the kernel more or less silent. As this makes it
1454          very difficult to diagnose system problems, saying N here is
1455          strongly discouraged.
1457config BUG
1458        bool "BUG() support" if EXPERT
1459        default y
1460        help
1461          Disabling this option eliminates support for BUG and WARN, reducing
1462          the size of your kernel image and potentially quietly ignoring
1463          numerous fatal conditions. You should only consider disabling this
1464          option for embedded systems with no facilities for reporting errors.
1465          Just say Y.
1467config ELF_CORE
1468        depends on COREDUMP
1469        default y
1470        bool "Enable ELF core dumps" if EXPERT
1471        help
1472          Enable support for generating core dumps. Disabling saves about 4k.
1476        bool "Enable PC-Speaker support" if EXPERT
1477        depends on HAVE_PCSPKR_PLATFORM
1478        select I8253_LOCK
1479        default y
1480        help
1481          This option allows to disable the internal PC-Speaker
1482          support, saving some memory.
1484config BASE_FULL
1485        default y
1486        bool "Enable full-sized data structures for core" if EXPERT
1487        help
1488          Disabling this option reduces the size of miscellaneous core
1489          kernel data structures. This saves memory on small machines,
1490          but may reduce performance.
1492config FUTEX
1493        bool "Enable futex support" if EXPERT
1494        default y
1495        select RT_MUTEXES
1496        help
1497          Disabling this option will cause the kernel to be built without
1498          support for "fast userspace mutexes".  The resulting kernel may not
1499          run glibc-based applications correctly.
1502        bool
1503        depends on FUTEX
1504        help
1505          Architectures should select this if futex_atomic_cmpxchg_inatomic()
1506          is implemented and always working. This removes a couple of runtime
1507          checks.
1509config EPOLL
1510        bool "Enable eventpoll support" if EXPERT
1511        default y
1512        select ANON_INODES
1513        help
1514          Disabling this option will cause the kernel to be built without
1515          support for epoll family of system calls.
1517config SIGNALFD
1518        bool "Enable signalfd() system call" if EXPERT
1519        select ANON_INODES
1520        default y
1521        help
1522          Enable the signalfd() system call that allows to receive signals
1523          on a file descriptor.
1525          If unsure, say Y.
1527config TIMERFD
1528        bool "Enable timerfd() system call" if EXPERT
1529        select ANON_INODES
1530        default y
1531        help
1532          Enable the timerfd() system call that allows to receive timer
1533          events on a file descriptor.
1535          If unsure, say Y.
1537config EVENTFD
1538        bool "Enable eventfd() system call" if EXPERT
1539        select ANON_INODES
1540        default y
1541        help
1542          Enable the eventfd() system call that allows to receive both
1543          kernel notification (ie. KAIO) or userspace notifications.
1545          If unsure, say Y.
1547# syscall, maps, verifier
1548config BPF_SYSCALL
1549        bool "Enable bpf() system call"
1550        select ANON_INODES
1551        select BPF
1552        default n
1553        help
1554          Enable the bpf() system call that allows to manipulate eBPF
1555          programs and maps via file descriptors.
1557config SHMEM
1558        bool "Use full shmem filesystem" if EXPERT
1559        default y
1560        depends on MMU
1561        help
1562          The shmem is an internal filesystem used to manage shared memory.
1563          It is backed by swap and manages resource limits. It is also exported
1564          to userspace as tmpfs if TMPFS is enabled. Disabling this
1565          option replaces shmem and tmpfs with the much simpler ramfs code,
1566          which may be appropriate on small systems without swap.
1568config AIO
1569        bool "Enable AIO support" if EXPERT
1570        default y
1571        help
1572          This option enables POSIX asynchronous I/O which may by used
1573          by some high performance threaded applications. Disabling
1574          this option saves about 7k.
1577        bool "Enable madvise/fadvise syscalls" if EXPERT
1578        default y
1579        help
1580          This option enables the madvise and fadvise syscalls, used by
1581          applications to advise the kernel about their future memory or file
1582          usage, improving performance. If building an embedded system where no
1583          applications use these syscalls, you can disable this option to save
1584          space.
1586config USERFAULTFD
1587        bool "Enable userfaultfd() system call"
1588        select ANON_INODES
1589        depends on MMU
1590        help
1591          Enable the userfaultfd() system call that allows to intercept and
1592          handle page faults in userland.
1594config PCI_QUIRKS
1595        default y
1596        bool "Enable PCI quirk workarounds" if EXPERT
1597        depends on PCI
1598        help
1599          This enables workarounds for various PCI chipset
1600          bugs/quirks. Disable this only if your target machine is
1601          unaffected by PCI quirks.
1603config MEMBARRIER
1604        bool "Enable membarrier() system call" if EXPERT
1605        default y
1606        help
1607          Enable the membarrier() system call that allows issuing memory
1608          barriers across all running threads, which can be used to distribute
1609          the cost of user-space memory barriers asymmetrically by transforming
1610          pairs of memory barriers into pairs consisting of membarrier() and a
1611          compiler barrier.
1613          If unsure, say Y.
1615config EMBEDDED
1616        bool "Embedded system"
1617        option allnoconfig_y
1618        select EXPERT
1619        help
1620          This option should be enabled if compiling the kernel for
1621          an embedded system so certain expert options are available
1622          for configuration.
1625        bool
1626        help
1627          See tools/perf/design.txt for details.
1630        bool
1631        help
1632          See tools/perf/design.txt for details
1634menu "Kernel Performance Events And Counters"
1636config PERF_EVENTS
1637        bool "Kernel performance events and counters"
1638        default y if PROFILING
1639        depends on HAVE_PERF_EVENTS
1640        select ANON_INODES
1641        select IRQ_WORK
1642        select SRCU
1643        help
1644          Enable kernel support for various performance events provided
1645          by software and hardware.
1647          Software events are supported either built-in or via the
1648          use of generic tracepoints.
1650          Most modern CPUs support performance events via performance
1651          counter registers. These registers count the number of certain
1652          types of hw events: such as instructions executed, cachemisses
1653          suffered, or branches mis-predicted - without slowing down the
1654          kernel or applications. These registers can also trigger interrupts
1655          when a threshold number of events have passed - and can thus be
1656          used to profile the code that runs on that CPU.
1658          The Linux Performance Event subsystem provides an abstraction of
1659          these software and hardware event capabilities, available via a
1660          system call and used by the "perf" utility in tools/perf/. It
1661          provides per task and per CPU counters, and it provides event
1662          capabilities on top of those.
1664          Say Y if unsure.
1667        default n
1668        bool "Debug: use vmalloc to back perf mmap() buffers"
1669        depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1670        select PERF_USE_VMALLOC
1671        help
1672         Use vmalloc memory to back perf mmap() buffers.
1674         Mostly useful for debugging the vmalloc code on platforms
1675         that don't require it.
1677         Say N if unsure.
1682        default y
1683        bool "Enable VM event counters for /proc/vmstat" if EXPERT
1684        help
1685          VM event counters are needed for event counts to be shown.
1686          This option allows the disabling of the VM event counters
1687          on EXPERT systems.  /proc/vmstat will only show page counts
1688          if VM event counters are disabled.
1690config SLUB_DEBUG
1691        default y
1692        bool "Enable SLUB debugging support" if EXPERT
1693        depends on SLUB && SYSFS
1694        help
1695          SLUB has extensive debug support features. Disabling these can
1696          result in significant savings in code size. This also disables
1697          SLUB sysfs support. /sys/slab will not exist and there will be
1698          no support for cache validation etc.
1700config COMPAT_BRK
1701        bool "Disable heap randomization"
1702        default y
1703        help
1704          Randomizing heap placement makes heap exploits harder, but it
1705          also breaks ancient binaries (including anything libc5 based).
1706          This option changes the bootup default to heap randomization
1707          disabled, and can be overridden at runtime by setting
1708          /proc/sys/kernel/randomize_va_space to 2.
1710          On non-ancient distros (post-2000 ones) N is usually a safe choice.
1713        prompt "Choose SLAB allocator"
1714        default SLUB
1715        help
1716           This option allows to select a slab allocator.
1718config SLAB
1719        bool "SLAB"
1720        help
1721          The regular slab allocator that is established and known to work
1722          well in all environments. It organizes cache hot objects in
1723          per cpu and per node queues.
1725config SLUB
1726        bool "SLUB (Unqueued Allocator)"
1727        help
1728           SLUB is a slab allocator that minimizes cache line usage
1729           instead of managing queues of cached objects (SLAB approach).
1730           Per cpu caching is realized using slabs of objects instead
1731           of queues of objects. SLUB can use memory efficiently
1732           and has enhanced diagnostics. SLUB is the default choice for
1733           a slab allocator.
1735config SLOB
1736        depends on EXPERT
1737        bool "SLOB (Simple Allocator)"
1738        help
1739           SLOB replaces the stock allocator with a drastically simpler
1740           allocator. SLOB is generally more space efficient but
1741           does not perform as well on large systems.
1746        default y
1747        depends on SLUB && SMP
1748        bool "SLUB per cpu partial cache"
1749        help
1750          Per cpu partial caches accellerate objects allocation and freeing
1751          that is local to a processor at the price of more indeterminism
1752          in the latency of the free. On overflow these caches will be cleared
1753          which requires the taking of locks that may cause latency spikes.
1754          Typically one would choose no for a realtime system.
1757        bool "Allow mmapped anonymous memory to be uninitialized"
1758        depends on EXPERT && !MMU
1759        default n
1760        help
1761          Normally, and according to the Linux spec, anonymous memory obtained
1762          from mmap() has it's contents cleared before it is passed to
1763          userspace.  Enabling this config option allows you to request that
1764          mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1765          providing a huge performance boost.  If this option is not enabled,
1766          then the flag will be ignored.
1768          This is taken advantage of by uClibc's malloc(), and also by
1769          ELF-FDPIC binfmt's brk and stack allocator.
1771          Because of the obvious security issues, this option should only be
1772          enabled on embedded devices where you control what is run in
1773          userspace.  Since that isn't generally a problem on no-MMU systems,
1774          it is normally safe to say Y here.
1776          See Documentation/nommu-mmap.txt for more information.
1779        def_bool n
1780        select SYSTEM_TRUSTED_KEYRING
1781        select KEYS
1782        select CRYPTO
1783        select CRYPTO_RSA
1784        select ASYMMETRIC_KEY_TYPE
1786        select ASN1
1787        select OID_REGISTRY
1788        select X509_CERTIFICATE_PARSER
1789        select PKCS7_MESSAGE_PARSER
1790        help
1791          Provide PKCS#7 message verification using the contents of the system
1792          trusted keyring to provide public keys.  This then can be used for
1793          module verification, kexec image verification and firmware blob
1794          verification.
1796config PROFILING
1797        bool "Profiling support"
1798        help
1799          Say Y here to enable the extended profiling support mechanisms used
1800          by profilers such as OProfile.
1803# Place an empty function call at each tracepoint site. Can be
1804# dynamically changed for a probe function.
1806config TRACEPOINTS
1807        bool
1809source "arch/Kconfig"
1811endmenu         # General setup
1814        bool
1815        default n
1817config SLABINFO
1818        bool
1819        depends on PROC_FS
1820        depends on SLAB || SLUB_DEBUG
1821        default y
1823config RT_MUTEXES
1824        bool
1826config BASE_SMALL
1827        int
1828        default 0 if BASE_FULL
1829        default 1 if !BASE_FULL
1831menuconfig MODULES
1832        bool "Enable loadable module support"
1833        option modules
1834        help
1835          Kernel modules are small pieces of compiled code which can
1836          be inserted in the running kernel, rather than being
1837          permanently built into the kernel.  You use the "modprobe"
1838          tool to add (and sometimes remove) them.  If you say Y here,
1839          many parts of the kernel can be built as modules (by
1840          answering M instead of Y where indicated): this is most
1841          useful for infrequently used options which are not required
1842          for booting.  For more information, see the man pages for
1843          modprobe, lsmod, modinfo, insmod and rmmod.
1845          If you say Y here, you will need to run "make
1846          modules_install" to put the modules under /lib/modules/
1847          where modprobe can find them (you may need to be root to do
1848          this).
1850          If unsure, say Y.
1852if MODULES
1855        bool "Forced module loading"
1856        default n
1857        help
1858          Allow loading of modules without version information (ie. modprobe
1859          --force).  Forced module loading sets the 'F' (forced) taint flag and
1860          is usually a really bad idea.
1862config MODULE_UNLOAD
1863        bool "Module unloading"
1864        help
1865          Without this option you will not be able to unload any
1866          modules (note that some modules may not be unloadable
1867          anyway), which makes your kernel smaller, faster
1868          and simpler.  If unsure, say Y.
1871        bool "Forced module unloading"
1872        depends on MODULE_UNLOAD
1873        help
1874          This option allows you to force a module to unload, even if the
1875          kernel believes it is unsafe: the kernel will remove the module
1876          without waiting for anyone to stop using it (using the -f option to
1877          rmmod).  This is mainly for kernel developers and desperate users.
1878          If unsure, say N.
1880config MODVERSIONS
1881        bool "Module versioning support"
1882        help
1883          Usually, you have to use modules compiled with your kernel.
1884          Saying Y here makes it sometimes possible to use modules
1885          compiled for different kernels, by adding enough information
1886          to the modules to (hopefully) spot any changes which would
1887          make them incompatible with the kernel you are running.  If
1888          unsure, say N.
1891        bool "Source checksum for all modules"
1892        help
1893          Modules which contain a MODULE_VERSION get an extra "srcversion"
1894          field inserted into their modinfo section, which contains a
1895          sum of the source files which made it.  This helps maintainers
1896          see exactly which source was used to build a module (since
1897          others sometimes change the module source without updating
1898          the version).  With this option, such a "srcversion" field
1899          will be created for all modules.  If unsure, say N.
1901config MODULE_SIG
1902        bool "Module signature verification"
1903        depends on MODULES
1905        help
1906          Check modules for valid signatures upon load: the signature
1907          is simply appended to the module. For more information see
1908          Documentation/module-signing.txt.
1910          Note that this option adds the OpenSSL development packages as a
1911          kernel build dependency so that the signing tool can use its crypto
1912          library.
1914          !!!WARNING!!!  If you enable this option, you MUST make sure that the
1915          module DOES NOT get stripped after being signed.  This includes the
1916          debuginfo strip done by some packagers (such as rpmbuild) and
1917          inclusion into an initramfs that wants the module size reduced.
1920        bool "Require modules to be validly signed"
1921        depends on MODULE_SIG
1922        help
1923          Reject unsigned modules or signed modules for which we don't have a
1924          key.  Without this, such modules will simply taint the kernel.
1926config MODULE_SIG_ALL
1927        bool "Automatically sign all modules"
1928        default y
1929        depends on MODULE_SIG
1930        help
1931          Sign all modules during make modules_install. Without this option,
1932          modules must be signed manually, using the scripts/sign-file tool.
1934comment "Do not forget to sign required modules with scripts/sign-file"
1935        depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1938        prompt "Which hash algorithm should modules be signed with?"
1939        depends on MODULE_SIG
1940        help
1941          This determines which sort of hashing algorithm will be used during
1942          signature generation.  This algorithm _must_ be built into the kernel
1943          directly so that signature verification can take place.  It is not
1944          possible to load a signed module containing the algorithm to check
1945          the signature on that module.
1947config MODULE_SIG_SHA1
1948        bool "Sign modules with SHA-1"
1949        select CRYPTO_SHA1
1951config MODULE_SIG_SHA224
1952        bool "Sign modules with SHA-224"
1953        select CRYPTO_SHA256
1955config MODULE_SIG_SHA256
1956        bool "Sign modules with SHA-256"
1957        select CRYPTO_SHA256
1959config MODULE_SIG_SHA384
1960        bool "Sign modules with SHA-384"
1961        select CRYPTO_SHA512
1963config MODULE_SIG_SHA512
1964        bool "Sign modules with SHA-512"
1965        select CRYPTO_SHA512
1969config MODULE_SIG_HASH
1970        string
1971        depends on MODULE_SIG
1972        default "sha1" if MODULE_SIG_SHA1
1973        default "sha224" if MODULE_SIG_SHA224
1974        default "sha256" if MODULE_SIG_SHA256
1975        default "sha384" if MODULE_SIG_SHA384
1976        default "sha512" if MODULE_SIG_SHA512
1979        bool "Compress modules on installation"
1980        depends on MODULES
1981        help
1983          Compresses kernel modules when 'make modules_install' is run; gzip or
1984          xz depending on "Compression algorithm" below.
1986          module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
1988          Out-of-tree kernel modules installed using Kbuild will also be
1989          compressed upon installation.
1991          Note: for modules inside an initrd or initramfs, it's more efficient
1992          to compress the whole initrd or initramfs instead.
1994          Note: This is fully compatible with signed modules.
1996          If in doubt, say N.
1999        prompt "Compression algorithm"
2000        depends on MODULE_COMPRESS
2001        default MODULE_COMPRESS_GZIP
2002        help
2003          This determines which sort of compression will be used during
2004          'make modules_install'.
2006          GZIP (default) and XZ are supported.
2009        bool "GZIP"
2012        bool "XZ"
2016endif # MODULES
2019        def_bool y
2020        depends on PERF_EVENTS || TRACING
2023        bool
2024        help
2025          Back when each arch used to define their own cpu_online_mask and
2026          cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2027          with all 1s, and others with all 0s.  When they were centralised,
2028          it was better to provide this option than to break all the archs
2029          and have several arch maintainers pursuing me down dark alleys.
2031source "block/Kconfig"
2034        bool
2036config PADATA
2037        depends on SMP
2038        bool
2040# Can be selected by architectures with broken toolchains
2041# that get confused by correct const<->read_only section
2042# mappings
2043config BROKEN_RODATA
2044        bool
2046config ASN1
2047        tristate
2048        help
2049          Build a simple ASN.1 grammar compiler that produces a bytecode output
2050          that can be interpreted by the ASN.1 stream decoder and used to
2051          inform it as to what tags are to be expected in a stream and what
2052          functions to call on what tags.
2054source "kernel/Kconfig.locks"