Kconfig 67.1 KB
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config ARCH
	string
	option env="ARCH"

config KERNELVERSION
	string
	option env="KERNELVERSION"

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config DEFCONFIG_LIST
	string
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	depends on !UML
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	option defconfig_list
	default "/lib/modules/$UNAME_RELEASE/.config"
	default "/etc/kernel-config"
	default "/boot/config-$UNAME_RELEASE"
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	default "$ARCH_DEFCONFIG"
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	default "arch/$ARCH/defconfig"

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config CONSTRUCTORS
	bool
	depends on !UML

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config IRQ_WORK
	bool

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config BUILDTIME_EXTABLE_SORT
	bool

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config THREAD_INFO_IN_TASK
	bool
	help
	  Select this to move thread_info off the stack into task_struct.  To
	  make this work, an arch will need to remove all thread_info fields
	  except flags and fix any runtime bugs.

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	  One subtle change that will be needed is to use try_get_task_stack()
	  and put_task_stack() in save_thread_stack_tsk() and get_wchan().

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menu "General setup"
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config BROKEN
	bool

config BROKEN_ON_SMP
	bool
	depends on BROKEN || !SMP
	default y

config INIT_ENV_ARG_LIMIT
	int
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	default 32 if !UML
	default 128 if UML
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	help
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	  Maximum of each of the number of arguments and environment
	  variables passed to init from the kernel command line.
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config CROSS_COMPILE
	string "Cross-compiler tool prefix"
	help
	  Same as running 'make CROSS_COMPILE=prefix-' but stored for
	  default make runs in this kernel build directory.  You don't
	  need to set this unless you want the configured kernel build
	  directory to select the cross-compiler automatically.

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config COMPILE_TEST
	bool "Compile also drivers which will not load"
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	depends on !UML
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	default n
	help
	  Some drivers can be compiled on a different platform than they are
	  intended to be run on. Despite they cannot be loaded there (or even
	  when they load they cannot be used due to missing HW support),
	  developers still, opposing to distributors, might want to build such
	  drivers to compile-test them.

	  If you are a developer and want to build everything available, say Y
	  here. If you are a user/distributor, say N here to exclude useless
	  drivers to be distributed.

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config LOCALVERSION
	string "Local version - append to kernel release"
	help
	  Append an extra string to the end of your kernel version.
	  This will show up when you type uname, for example.
	  The string you set here will be appended after the contents of
	  any files with a filename matching localversion* in your
	  object and source tree, in that order.  Your total string can
	  be a maximum of 64 characters.

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config LOCALVERSION_AUTO
	bool "Automatically append version information to the version string"
	default y
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	depends on !COMPILE_TEST
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	help
	  This will try to automatically determine if the current tree is a
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	  release tree by looking for git tags that belong to the current
	  top of tree revision.
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	  A string of the format -gxxxxxxxx will be added to the localversion
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	  if a git-based tree is found.  The string generated by this will be
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	  appended after any matching localversion* files, and after the value
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	  set in CONFIG_LOCALVERSION.
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	  (The actual string used here is the first eight characters produced
	  by running the command:

	    $ git rev-parse --verify HEAD

	  which is done within the script "scripts/setlocalversion".)
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config HAVE_KERNEL_GZIP
	bool

config HAVE_KERNEL_BZIP2
	bool

config HAVE_KERNEL_LZMA
	bool

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config HAVE_KERNEL_XZ
	bool

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config HAVE_KERNEL_LZO
	bool

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config HAVE_KERNEL_LZ4
	bool

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choice
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	prompt "Kernel compression mode"
	default KERNEL_GZIP
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	depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4
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	help
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	  The linux kernel is a kind of self-extracting executable.
	  Several compression algorithms are available, which differ
	  in efficiency, compression and decompression speed.
	  Compression speed is only relevant when building a kernel.
	  Decompression speed is relevant at each boot.

	  If you have any problems with bzip2 or lzma compressed
	  kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
	  version of this functionality (bzip2 only), for 2.4, was
	  supplied by Christian Ludwig)

	  High compression options are mostly useful for users, who
	  are low on disk space (embedded systems), but for whom ram
	  size matters less.

	  If in doubt, select 'gzip'

config KERNEL_GZIP
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	bool "Gzip"
	depends on HAVE_KERNEL_GZIP
	help
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	  The old and tried gzip compression. It provides a good balance
	  between compression ratio and decompression speed.
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config KERNEL_BZIP2
	bool "Bzip2"
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	depends on HAVE_KERNEL_BZIP2
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	help
	  Its compression ratio and speed is intermediate.
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	  Decompression speed is slowest among the choices.  The kernel
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	  size is about 10% smaller with bzip2, in comparison to gzip.
	  Bzip2 uses a large amount of memory. For modern kernels you
	  will need at least 8MB RAM or more for booting.
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config KERNEL_LZMA
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	bool "LZMA"
	depends on HAVE_KERNEL_LZMA
	help
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	  This compression algorithm's ratio is best.  Decompression speed
	  is between gzip and bzip2.  Compression is slowest.
	  The kernel size is about 33% smaller with LZMA in comparison to gzip.
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config KERNEL_XZ
	bool "XZ"
	depends on HAVE_KERNEL_XZ
	help
	  XZ uses the LZMA2 algorithm and instruction set specific
	  BCJ filters which can improve compression ratio of executable
	  code. The size of the kernel is about 30% smaller with XZ in
	  comparison to gzip. On architectures for which there is a BCJ
	  filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
	  will create a few percent smaller kernel than plain LZMA.

	  The speed is about the same as with LZMA: The decompression
	  speed of XZ is better than that of bzip2 but worse than gzip
	  and LZO. Compression is slow.

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config KERNEL_LZO
	bool "LZO"
	depends on HAVE_KERNEL_LZO
	help
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	  Its compression ratio is the poorest among the choices. The kernel
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	  size is about 10% bigger than gzip; however its speed
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	  (both compression and decompression) is the fastest.

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config KERNEL_LZ4
	bool "LZ4"
	depends on HAVE_KERNEL_LZ4
	help
	  LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
	  A preliminary version of LZ4 de/compression tool is available at
	  <https://code.google.com/p/lz4/>.

	  Its compression ratio is worse than LZO. The size of the kernel
	  is about 8% bigger than LZO. But the decompression speed is
	  faster than LZO.

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endchoice

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config DEFAULT_HOSTNAME
	string "Default hostname"
	default "(none)"
	help
	  This option determines the default system hostname before userspace
	  calls sethostname(2). The kernel traditionally uses "(none)" here,
	  but you may wish to use a different default here to make a minimal
	  system more usable with less configuration.

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config SWAP
	bool "Support for paging of anonymous memory (swap)"
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	depends on MMU && BLOCK
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	default y
	help
	  This option allows you to choose whether you want to have support
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	  for so called swap devices or swap files in your kernel that are
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	  used to provide more virtual memory than the actual RAM present
	  in your computer.  If unsure say Y.

config SYSVIPC
	bool "System V IPC"
	---help---
	  Inter Process Communication is a suite of library functions and
	  system calls which let processes (running programs) synchronize and
	  exchange information. It is generally considered to be a good thing,
	  and some programs won't run unless you say Y here. In particular, if
	  you want to run the DOS emulator dosemu under Linux (read the
	  DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
	  you'll need to say Y here.

	  You can find documentation about IPC with "info ipc" and also in
	  section 6.4 of the Linux Programmer's Guide, available from
	  <http://www.tldp.org/guides.html>.

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config SYSVIPC_SYSCTL
	bool
	depends on SYSVIPC
	depends on SYSCTL
	default y

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config POSIX_MQUEUE
	bool "POSIX Message Queues"
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	depends on NET
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	---help---
	  POSIX variant of message queues is a part of IPC. In POSIX message
	  queues every message has a priority which decides about succession
	  of receiving it by a process. If you want to compile and run
	  programs written e.g. for Solaris with use of its POSIX message
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	  queues (functions mq_*) say Y here.
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	  POSIX message queues are visible as a filesystem called 'mqueue'
	  and can be mounted somewhere if you want to do filesystem
	  operations on message queues.

	  If unsure, say Y.

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config POSIX_MQUEUE_SYSCTL
	bool
	depends on POSIX_MQUEUE
	depends on SYSCTL
	default y

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config CROSS_MEMORY_ATTACH
	bool "Enable process_vm_readv/writev syscalls"
	depends on MMU
	default y
	help
	  Enabling this option adds the system calls process_vm_readv and
	  process_vm_writev which allow a process with the correct privileges
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	  to directly read from or write to another process' address space.
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	  See the man page for more details.

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config FHANDLE
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	bool "open by fhandle syscalls" if EXPERT
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	select EXPORTFS
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	default y
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	help
	  If you say Y here, a user level program will be able to map
	  file names to handle and then later use the handle for
	  different file system operations. This is useful in implementing
	  userspace file servers, which now track files using handles instead
	  of names. The handle would remain the same even if file names
	  get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
	  syscalls.

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config USELIB
	bool "uselib syscall"
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	def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
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	help
	  This option enables the uselib syscall, a system call used in the
	  dynamic linker from libc5 and earlier.  glibc does not use this
	  system call.  If you intend to run programs built on libc5 or
	  earlier, you may need to enable this syscall.  Current systems
	  running glibc can safely disable this.

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config AUDIT
	bool "Auditing support"
	depends on NET
	help
	  Enable auditing infrastructure that can be used with another
	  kernel subsystem, such as SELinux (which requires this for
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	  logging of avc messages output).  System call auditing is included
	  on architectures which support it.
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config HAVE_ARCH_AUDITSYSCALL
	bool

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config AUDITSYSCALL
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	def_bool y
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	depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
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config AUDIT_WATCH
	def_bool y
	depends on AUDITSYSCALL
	select FSNOTIFY

config AUDIT_TREE
	def_bool y
	depends on AUDITSYSCALL
	select FSNOTIFY

source "kernel/irq/Kconfig"
source "kernel/time/Kconfig"

menu "CPU/Task time and stats accounting"

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config VIRT_CPU_ACCOUNTING
	bool

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choice
	prompt "Cputime accounting"
	default TICK_CPU_ACCOUNTING if !PPC64
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	default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
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# Kind of a stub config for the pure tick based cputime accounting
config TICK_CPU_ACCOUNTING
	bool "Simple tick based cputime accounting"
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	depends on !S390 && !NO_HZ_FULL
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	help
	  This is the basic tick based cputime accounting that maintains
	  statistics about user, system and idle time spent on per jiffies
	  granularity.

	  If unsure, say Y.

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config VIRT_CPU_ACCOUNTING_NATIVE
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	bool "Deterministic task and CPU time accounting"
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	depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
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	select VIRT_CPU_ACCOUNTING
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	help
	  Select this option to enable more accurate task and CPU time
	  accounting.  This is done by reading a CPU counter on each
	  kernel entry and exit and on transitions within the kernel
	  between system, softirq and hardirq state, so there is a
	  small performance impact.  In the case of s390 or IBM POWER > 5,
	  this also enables accounting of stolen time on logically-partitioned
	  systems.

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config VIRT_CPU_ACCOUNTING_GEN
	bool "Full dynticks CPU time accounting"
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	depends on HAVE_CONTEXT_TRACKING
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	depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
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	select VIRT_CPU_ACCOUNTING
	select CONTEXT_TRACKING
	help
	  Select this option to enable task and CPU time accounting on full
	  dynticks systems. This accounting is implemented by watching every
	  kernel-user boundaries using the context tracking subsystem.
	  The accounting is thus performed at the expense of some significant
	  overhead.

	  For now this is only useful if you are working on the full
	  dynticks subsystem development.

	  If unsure, say N.

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endchoice

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config IRQ_TIME_ACCOUNTING
	bool "Fine granularity task level IRQ time accounting"
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	depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
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	help
	  Select this option to enable fine granularity task irq time
	  accounting. This is done by reading a timestamp on each
	  transitions between softirq and hardirq state, so there can be a
	  small performance impact.

	  If in doubt, say N here.

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config BSD_PROCESS_ACCT
	bool "BSD Process Accounting"
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	depends on MULTIUSER
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	help
	  If you say Y here, a user level program will be able to instruct the
	  kernel (via a special system call) to write process accounting
	  information to a file: whenever a process exits, information about
	  that process will be appended to the file by the kernel.  The
	  information includes things such as creation time, owning user,
	  command name, memory usage, controlling terminal etc. (the complete
	  list is in the struct acct in <file:include/linux/acct.h>).  It is
	  up to the user level program to do useful things with this
	  information.  This is generally a good idea, so say Y.

config BSD_PROCESS_ACCT_V3
	bool "BSD Process Accounting version 3 file format"
	depends on BSD_PROCESS_ACCT
	default n
	help
	  If you say Y here, the process accounting information is written
	  in a new file format that also logs the process IDs of each
	  process and it's parent. Note that this file format is incompatible
	  with previous v0/v1/v2 file formats, so you will need updated tools
	  for processing it. A preliminary version of these tools is available
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	  at <http://www.gnu.org/software/acct/>.
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config TASKSTATS
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	bool "Export task/process statistics through netlink"
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	depends on NET
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	depends on MULTIUSER
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	default n
	help
	  Export selected statistics for tasks/processes through the
	  generic netlink interface. Unlike BSD process accounting, the
	  statistics are available during the lifetime of tasks/processes as
	  responses to commands. Like BSD accounting, they are sent to user
	  space on task exit.

	  Say N if unsure.

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config TASK_DELAY_ACCT
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	bool "Enable per-task delay accounting"
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	depends on TASKSTATS
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	select SCHED_INFO
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	help
	  Collect information on time spent by a task waiting for system
	  resources like cpu, synchronous block I/O completion and swapping
	  in pages. Such statistics can help in setting a task's priorities
	  relative to other tasks for cpu, io, rss limits etc.

	  Say N if unsure.

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config TASK_XACCT
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	bool "Enable extended accounting over taskstats"
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	depends on TASKSTATS
	help
	  Collect extended task accounting data and send the data
	  to userland for processing over the taskstats interface.

	  Say N if unsure.

config TASK_IO_ACCOUNTING
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	bool "Enable per-task storage I/O accounting"
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	depends on TASK_XACCT
	help
	  Collect information on the number of bytes of storage I/O which this
	  task has caused.

	  Say N if unsure.

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endmenu # "CPU/Task time and stats accounting"
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menu "RCU Subsystem"

config TREE_RCU
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	bool
	default y if !PREEMPT && SMP
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	help
	  This option selects the RCU implementation that is
	  designed for very large SMP system with hundreds or
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	  thousands of CPUs.  It also scales down nicely to
	  smaller systems.
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config PREEMPT_RCU
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	bool
	default y if PREEMPT
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	help
	  This option selects the RCU implementation that is
	  designed for very large SMP systems with hundreds or
	  thousands of CPUs, but for which real-time response
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	  is also required.  It also scales down nicely to
	  smaller systems.
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	  Select this option if you are unsure.

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config TINY_RCU
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	bool
	default y if !PREEMPT && !SMP
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	help
	  This option selects the RCU implementation that is
	  designed for UP systems from which real-time response
	  is not required.  This option greatly reduces the
	  memory footprint of RCU.

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config RCU_EXPERT
	bool "Make expert-level adjustments to RCU configuration"
	default n
	help
	  This option needs to be enabled if you wish to make
	  expert-level adjustments to RCU configuration.  By default,
	  no such adjustments can be made, which has the often-beneficial
	  side-effect of preventing "make oldconfig" from asking you all
	  sorts of detailed questions about how you would like numerous
	  obscure RCU options to be set up.

	  Say Y if you need to make expert-level adjustments to RCU.

	  Say N if you are unsure.

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config SRCU
	bool
	help
	  This option selects the sleepable version of RCU. This version
	  permits arbitrary sleeping or blocking within RCU read-side critical
	  sections.

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config TASKS_RCU
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	bool
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	default n
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	depends on !UML
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	select SRCU
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	help
	  This option enables a task-based RCU implementation that uses
	  only voluntary context switch (not preemption!), idle, and
	  user-mode execution as quiescent states.

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config RCU_STALL_COMMON
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	def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
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	help
	  This option enables RCU CPU stall code that is common between
	  the TINY and TREE variants of RCU.  The purpose is to allow
	  the tiny variants to disable RCU CPU stall warnings, while
	  making these warnings mandatory for the tree variants.

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config CONTEXT_TRACKING
       bool

config CONTEXT_TRACKING_FORCE
	bool "Force context tracking"
	depends on CONTEXT_TRACKING
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	default y if !NO_HZ_FULL
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	help
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	  The major pre-requirement for full dynticks to work is to
	  support the context tracking subsystem. But there are also
	  other dependencies to provide in order to make the full
	  dynticks working.

	  This option stands for testing when an arch implements the
	  context tracking backend but doesn't yet fullfill all the
	  requirements to make the full dynticks feature working.
	  Without the full dynticks, there is no way to test the support
	  for context tracking and the subsystems that rely on it: RCU
	  userspace extended quiescent state and tickless cputime
	  accounting. This option copes with the absence of the full
	  dynticks subsystem by forcing the context tracking on all
	  CPUs in the system.

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	  Say Y only if you're working on the development of an
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	  architecture backend for the context tracking.

	  Say N otherwise, this option brings an overhead that you
	  don't want in production.

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config RCU_FANOUT
	int "Tree-based hierarchical RCU fanout value"
	range 2 64 if 64BIT
	range 2 32 if !64BIT
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	depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
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	default 64 if 64BIT
	default 32 if !64BIT
	help
	  This option controls the fanout of hierarchical implementations
	  of RCU, allowing RCU to work efficiently on machines with
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	  large numbers of CPUs.  This value must be at least the fourth
	  root of NR_CPUS, which allows NR_CPUS to be insanely large.
	  The default value of RCU_FANOUT should be used for production
	  systems, but if you are stress-testing the RCU implementation
	  itself, small RCU_FANOUT values allow you to test large-system
	  code paths on small(er) systems.
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	  Select a specific number if testing RCU itself.
	  Take the default if unsure.

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config RCU_FANOUT_LEAF
	int "Tree-based hierarchical RCU leaf-level fanout value"
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	range 2 64 if 64BIT
	range 2 32 if !64BIT
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	depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
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	default 16
	help
	  This option controls the leaf-level fanout of hierarchical
	  implementations of RCU, and allows trading off cache misses
	  against lock contention.  Systems that synchronize their
	  scheduling-clock interrupts for energy-efficiency reasons will
	  want the default because the smaller leaf-level fanout keeps
	  lock contention levels acceptably low.  Very large systems
	  (hundreds or thousands of CPUs) will instead want to set this
	  value to the maximum value possible in order to reduce the
	  number of cache misses incurred during RCU's grace-period
	  initialization.  These systems tend to run CPU-bound, and thus
	  are not helped by synchronized interrupts, and thus tend to
	  skew them, which reduces lock contention enough that large
	  leaf-level fanouts work well.

	  Select a specific number if testing RCU itself.

	  Select the maximum permissible value for large systems.

	  Take the default if unsure.

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config RCU_FAST_NO_HZ
	bool "Accelerate last non-dyntick-idle CPU's grace periods"
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	depends on NO_HZ_COMMON && SMP && RCU_EXPERT
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	default n
	help
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	  This option permits CPUs to enter dynticks-idle state even if
	  they have RCU callbacks queued, and prevents RCU from waking
	  these CPUs up more than roughly once every four jiffies (by
	  default, you can adjust this using the rcutree.rcu_idle_gp_delay
	  parameter), thus improving energy efficiency.  On the other
	  hand, this option increases the duration of RCU grace periods,
	  for example, slowing down synchronize_rcu().
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	  Say Y if energy efficiency is critically important, and you
	  	don't care about increased grace-period durations.
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	  Say N if you are unsure.

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config TREE_RCU_TRACE
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	def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
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	select DEBUG_FS
	help
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	  This option provides tracing for the TREE_RCU and
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	  PREEMPT_RCU implementations, permitting Makefile to
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	  trivially select kernel/rcutree_trace.c.
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config RCU_BOOST
	bool "Enable RCU priority boosting"
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	depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT
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	default n
	help
	  This option boosts the priority of preempted RCU readers that
	  block the current preemptible RCU grace period for too long.
	  This option also prevents heavy loads from blocking RCU
	  callback invocation for all flavors of RCU.

	  Say Y here if you are working with real-time apps or heavy loads
	  Say N here if you are unsure.

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config RCU_KTHREAD_PRIO
	int "Real-time priority to use for RCU worker threads"
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	range 1 99 if RCU_BOOST
	range 0 99 if !RCU_BOOST
	default 1 if RCU_BOOST
	default 0 if !RCU_BOOST
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	depends on RCU_EXPERT
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	help
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	  This option specifies the SCHED_FIFO priority value that will be
	  assigned to the rcuc/n and rcub/n threads and is also the value
	  used for RCU_BOOST (if enabled). If you are working with a
	  real-time application that has one or more CPU-bound threads
	  running at a real-time priority level, you should set
	  RCU_KTHREAD_PRIO to a priority higher than the highest-priority
	  real-time CPU-bound application thread.  The default RCU_KTHREAD_PRIO
	  value of 1 is appropriate in the common case, which is real-time
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	  applications that do not have any CPU-bound threads.

	  Some real-time applications might not have a single real-time
	  thread that saturates a given CPU, but instead might have
	  multiple real-time threads that, taken together, fully utilize
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	  that CPU.  In this case, you should set RCU_KTHREAD_PRIO to
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	  a priority higher than the lowest-priority thread that is
	  conspiring to prevent the CPU from running any non-real-time
	  tasks.  For example, if one thread at priority 10 and another
	  thread at priority 5 are between themselves fully consuming
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	  the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
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	  set to priority 6 or higher.
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	  Specify the real-time priority, or take the default if unsure.

config RCU_BOOST_DELAY
	int "Milliseconds to delay boosting after RCU grace-period start"
	range 0 3000
	depends on RCU_BOOST
	default 500
	help
	  This option specifies the time to wait after the beginning of
	  a given grace period before priority-boosting preempted RCU
	  readers blocking that grace period.  Note that any RCU reader
	  blocking an expedited RCU grace period is boosted immediately.

	  Accept the default if unsure.

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config RCU_NOCB_CPU
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	bool "Offload RCU callback processing from boot-selected CPUs"
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	depends on TREE_RCU || PREEMPT_RCU
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	depends on RCU_EXPERT || NO_HZ_FULL
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	default n
	help
	  Use this option to reduce OS jitter for aggressive HPC or
	  real-time workloads.	It can also be used to offload RCU
	  callback invocation to energy-efficient CPUs in battery-powered
	  asymmetric multiprocessors.

	  This option offloads callback invocation from the set of
	  CPUs specified at boot time by the rcu_nocbs parameter.
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	  For each such CPU, a kthread ("rcuox/N") will be created to
	  invoke callbacks, where the "N" is the CPU being offloaded,
	  and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
	  "s" for RCU-sched.  Nothing prevents this kthread from running
	  on the specified CPUs, but (1) the kthreads may be preempted
	  between each callback, and (2) affinity or cgroups can be used
	  to force the kthreads to run on whatever set of CPUs is desired.
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	  Say Y here if you want to help to debug reduced OS jitter.
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	  Say N here if you are unsure.

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choice
	prompt "Build-forced no-CBs CPUs"
	default RCU_NOCB_CPU_NONE
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	depends on RCU_NOCB_CPU
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	help
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	  This option allows no-CBs CPUs (whose RCU callbacks are invoked
	  from kthreads rather than from softirq context) to be specified
	  at build time.  Additional no-CBs CPUs may be specified by
	  the rcu_nocbs= boot parameter.
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config RCU_NOCB_CPU_NONE
	bool "No build_forced no-CBs CPUs"
	help
	  This option does not force any of the CPUs to be no-CBs CPUs.
	  Only CPUs designated by the rcu_nocbs= boot parameter will be
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	  no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
	  kthreads whose names begin with "rcuo".  All other CPUs will
	  invoke their own RCU callbacks in softirq context.

	  Select this option if you want to choose no-CBs CPUs at
	  boot time, for example, to allow testing of different no-CBs
	  configurations without having to rebuild the kernel each time.
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config RCU_NOCB_CPU_ZERO
	bool "CPU 0 is a build_forced no-CBs CPU"
	help
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	  This option forces CPU 0 to be a no-CBs CPU, so that its RCU
	  callbacks are invoked by a per-CPU kthread whose name begins
	  with "rcuo".	Additional CPUs may be designated as no-CBs
	  CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
	  All other CPUs will invoke their own RCU callbacks in softirq
	  context.
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	  Select this if CPU 0 needs to be a no-CBs CPU for real-time
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	  or energy-efficiency reasons, but the real reason it exists
	  is to ensure that randconfig testing covers mixed systems.
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config RCU_NOCB_CPU_ALL
	bool "All CPUs are build_forced no-CBs CPUs"
	help
	  This option forces all CPUs to be no-CBs CPUs.  The rcu_nocbs=
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	  boot parameter will be ignored.  All CPUs' RCU callbacks will
	  be executed in the context of per-CPU rcuo kthreads created for
	  this purpose.  Assuming that the kthreads whose names start with
	  "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
	  on the remaining CPUs, but might decrease memory locality during
	  RCU-callback invocation, thus potentially degrading throughput.
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	  Select this if all CPUs need to be no-CBs CPUs for real-time
	  or energy-efficiency reasons.

endchoice

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config RCU_EXPEDITE_BOOT
	bool
	default n
	help
	  This option enables expedited grace periods at boot time,
	  as if rcu_expedite_gp() had been invoked early in boot.
	  The corresponding rcu_unexpedite_gp() is invoked from
	  rcu_end_inkernel_boot(), which is intended to be invoked
	  at the end of the kernel-only boot sequence, just before
	  init is exec'ed.

	  Accept the default if unsure.

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endmenu # "RCU Subsystem"

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config BUILD_BIN2C
	bool
	default n

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config IKCONFIG
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	tristate "Kernel .config support"
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	select BUILD_BIN2C
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	---help---
	  This option enables the complete Linux kernel ".config" file
	  contents to be saved in the kernel. It provides documentation
	  of which kernel options are used in a running kernel or in an
	  on-disk kernel.  This information can be extracted from the kernel
	  image file with the script scripts/extract-ikconfig and used as
	  input to rebuild the current kernel or to build another kernel.
	  It can also be extracted from a running kernel by reading
	  /proc/config.gz if enabled (below).

config IKCONFIG_PROC
	bool "Enable access to .config through /proc/config.gz"
	depends on IKCONFIG && PROC_FS
	---help---
	  This option enables access to the kernel configuration file
	  through /proc/config.gz.

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config LOG_BUF_SHIFT
	int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
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	range 12 25
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	default 17
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	depends on PRINTK
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	help
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	  Select the minimal kernel log buffer size as a power of 2.
	  The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
	  parameter, see below. Any higher size also might be forced
	  by "log_buf_len" boot parameter.

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	  Examples:
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		     17 => 128 KB
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		     16 => 64 KB
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		     15 => 32 KB
		     14 => 16 KB
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		     13 =>  8 KB
		     12 =>  4 KB

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config LOG_CPU_MAX_BUF_SHIFT
	int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
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	depends on SMP
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	range 0 21
	default 12 if !BASE_SMALL
	default 0 if BASE_SMALL
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	depends on PRINTK
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	help
	  This option allows to increase the default ring buffer size
	  according to the number of CPUs. The value defines the contribution
	  of each CPU as a power of 2. The used space is typically only few
	  lines however it might be much more when problems are reported,
	  e.g. backtraces.

	  The increased size means that a new buffer has to be allocated and
	  the original static one is unused. It makes sense only on systems
	  with more CPUs. Therefore this value is used only when the sum of
	  contributions is greater than the half of the default kernel ring
	  buffer as defined by LOG_BUF_SHIFT. The default values are set
	  so that more than 64 CPUs are needed to trigger the allocation.

	  Also this option is ignored when "log_buf_len" kernel parameter is
	  used as it forces an exact (power of two) size of the ring buffer.

	  The number of possible CPUs is used for this computation ignoring
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	  hotplugging making the computation optimal for the worst case
	  scenario while allowing a simple algorithm to be used from bootup.
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	  Examples shift values and their meaning:
		     17 => 128 KB for each CPU
		     16 =>  64 KB for each CPU
		     15 =>  32 KB for each CPU
		     14 =>  16 KB for each CPU
		     13 =>   8 KB for each CPU
		     12 =>   4 KB for each CPU

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config NMI_LOG_BUF_SHIFT
	int "Temporary per-CPU NMI log buffer size (12 => 4KB, 13 => 8KB)"
	range 10 21
	default 13
	depends on PRINTK_NMI
	help
	  Select the size of a per-CPU buffer where NMI messages are temporary
	  stored. They are copied to the main log buffer in a safe context
	  to avoid a deadlock. The value defines the size as a power of 2.

	  NMI messages are rare and limited. The largest one is when
	  a backtrace is printed. It usually fits into 4KB. Select
	  8KB if you want to be on the safe side.

	  Examples:
		     17 => 128 KB for each CPU
		     16 =>  64 KB for each CPU
		     15 =>  32 KB for each CPU
		     14 =>  16 KB for each CPU
		     13 =>   8 KB for each CPU
		     12 =>   4 KB for each CPU

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#
# Architectures with an unreliable sched_clock() should select this:
#
config HAVE_UNSTABLE_SCHED_CLOCK
	bool

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config GENERIC_SCHED_CLOCK
	bool

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#
# For architectures that want to enable the support for NUMA-affine scheduler
# balancing logic:
#
config ARCH_SUPPORTS_NUMA_BALANCING
	bool

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#
# For architectures that prefer to flush all TLBs after a number of pages
# are unmapped instead of sending one IPI per page to flush. The architecture
# must provide guarantees on what happens if a clean TLB cache entry is
# written after the unmap. Details are in mm/rmap.c near the check for
# should_defer_flush. The architecture should also consider if the full flush
# and the refill costs are offset by the savings of sending fewer IPIs.
config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
	bool

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#
# For architectures that know their GCC __int128 support is sound
#
config ARCH_SUPPORTS_INT128
	bool

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# For architectures that (ab)use NUMA to represent different memory regions
# all cpu-local but of different latencies, such as SuperH.
#
config ARCH_WANT_NUMA_VARIABLE_LOCALITY
	bool

config NUMA_BALANCING
	bool "Memory placement aware NUMA scheduler"
	depends on ARCH_SUPPORTS_NUMA_BALANCING
	depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
	depends on SMP && NUMA && MIGRATION
	help
	  This option adds support for automatic NUMA aware memory/task placement.
	  The mechanism is quite primitive and is based on migrating memory when
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	  it has references to the node the task is running on.
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	  This system will be inactive on UMA systems.

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config NUMA_BALANCING_DEFAULT_ENABLED
	bool "Automatically enable NUMA aware memory/task placement"
	default y
	depends on NUMA_BALANCING
	help
	  If set, automatic NUMA balancing will be enabled if running on a NUMA
	  machine.

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menuconfig CGROUPS
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	bool "Control Group support"
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	select KERNFS
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	help
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	  This option adds support for grouping sets of processes together, for
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	  use with process control subsystems such as Cpusets, CFS, memory
	  controls or device isolation.
	  See
		- Documentation/scheduler/sched-design-CFS.txt	(CFS)
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		- Documentation/cgroup-v1/ (features for grouping, isolation
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					  and resource control)
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	  Say N if unsure.

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if CGROUPS

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config PAGE_COUNTER
       bool

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config MEMCG
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	bool "Memory controller"
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	select PAGE_COUNTER
980
	select EVENTFD
981
	help
982
	  Provides control over the memory footprint of tasks in a cgroup.
983

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config MEMCG_SWAP
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	bool "Swap controller"
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	depends on MEMCG && SWAP
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	help
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	  Provides control over the swap space consumed by tasks in a cgroup.

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config MEMCG_SWAP_ENABLED
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	bool "Swap controller enabled by default"
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	depends on MEMCG_SWAP
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	default y
	help
	  Memory Resource Controller Swap Extension comes with its price in
	  a bigger memory consumption. General purpose distribution kernels
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	  which want to enable the feature but keep it disabled by default
998
	  and let the user enable it by swapaccount=1 boot command line
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	  parameter should have this option unselected.
	  For those who want to have the feature enabled by default should
	  select this option (if, for some reason, they need to disable it
1002
	  then swapaccount=0 does the trick).
1003

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config BLK_CGROUP
	bool "IO controller"
	depends on BLOCK
1007
	default n
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	---help---
	Generic block IO controller cgroup interface. This is the common
	cgroup interface which should be used by various IO controlling
	policies.
1012

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	Currently, CFQ IO scheduler uses it to recognize task groups and
	control disk bandwidth allocation (proportional time slice allocation)
	to such task groups. It is also used by bio throttling logic in
	block layer to implement upper limit in IO rates on a device.
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	This option only enables generic Block IO controller infrastructure.
	One needs to also enable actual IO controlling logic/policy. For
	enabling proportional weight division of disk bandwidth in CFQ, set
	CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
	CONFIG_BLK_DEV_THROTTLING=y.

1024
	See Documentation/cgroup-v1/blkio-controller.txt for more information.
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config DEBUG_BLK_CGROUP
	bool "IO controller debugging"
	depends on BLK_CGROUP
	default n
	---help---
	Enable some debugging help. Currently it exports additional stat
	files in a cgroup which can be useful for debugging.

config CGROUP_WRITEBACK
	bool
	depends on MEMCG && BLK_CGROUP
	default y
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menuconfig CGROUP_SCHED
1040
	bool "CPU controller"
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	default n
	help
	  This feature lets CPU scheduler recognize task groups and control CPU
	  bandwidth allocation to such task groups. It uses cgroups to group
	  tasks.

if CGROUP_SCHED
config FAIR_GROUP_SCHED
	bool "Group scheduling for SCHED_OTHER"
	depends on CGROUP_SCHED
	default CGROUP_SCHED

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config CFS_BANDWIDTH
	bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
	depends on FAIR_GROUP_SCHED
	default n
	help
	  This option allows users to define CPU bandwidth rates (limits) for
	  tasks running within the fair group scheduler.  Groups with no limit
	  set are considered to be unconstrained and will run with no
	  restriction.
	  See tip/Documentation/scheduler/sched-bwc.txt for more information.

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config RT_GROUP_SCHED
	bool "Group scheduling for SCHED_RR/FIFO"
	depends on CGROUP_SCHED
	default n
	help
	  This feature lets you explicitly allocate real CPU bandwidth
1070
	  to task groups. If enabled, it will also make it impossible to
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	  schedule realtime tasks for non-root users until you allocate
	  realtime bandwidth for them.
	  See Documentation/scheduler/sched-rt-group.txt for more information.

endif #CGROUP_SCHED

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config CGROUP_PIDS
	bool "PIDs controller"
	help
	  Provides enforcement of process number limits in the scope of a
	  cgroup. Any attempt to fork more processes than is allowed in the
	  cgroup will fail. PIDs are fundamentally a global resource because it
	  is fairly trivial to reach PID exhaustion before you reach even a
	  conservative kmemcg limit. As a result, it is possible to grind a
	  system to halt without being limited by other cgroup policies. The
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	  PIDs controller is designed to stop this from happening.
1087 1088

	  It should be noted that organisational operations (such as attaching
1089
	  to a cgroup hierarchy will *not* be blocked by the PIDs controller),
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	  since the PIDs limit only affects a process's ability to fork, not to
	  attach to a cgroup.

config CGROUP_FREEZER
	bool "Freezer controller"
	help
	  Provides a way to freeze and unfreeze all tasks in a
	  cgroup.

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	  This option affects the ORIGINAL cgroup interface. The cgroup2 memory
	  controller includes important in-kernel memory consumers per default.

	  If you're using cgroup2, say N.

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config CGROUP_HUGETLB
	bool "HugeTLB controller"
	depends on HUGETLB_PAGE
	select PAGE_COUNTER
1108
	default n
1109 1110 1111 1112 1113 1114 1115 1116 1117 1118
	help
	  Provides a cgroup controller for HugeTLB pages.
	  When you enable this, you can put a per cgroup limit on HugeTLB usage.
	  The limit is enforced during page fault. Since HugeTLB doesn't
	  support page reclaim, enforcing the limit at page fault time implies
	  that, the application will get SIGBUS signal if it tries to access
	  HugeTLB pages beyond its limit. This requires the application to know
	  beforehand how much HugeTLB pages it would require for its use. The
	  control group is tracked in the third page lru pointer. This means
	  that we cannot use the controller with huge page less than 3 pages.
1119

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config CPUSETS
	bool "Cpuset controller"
	help
	  This option will let you create and manage CPUSETs which
	  allow dynamically partitioning a system into sets of CPUs and
	  Memory Nodes and assigning tasks to run only within those sets.
	  This is primarily useful on large SMP or NUMA systems.
1127

1128
	  Say N if unsure.
1129

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config PROC_PID_CPUSET
	bool "Include legacy /proc/<pid>/cpuset file"
	depends on CPUSETS
	default y
1134

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config CGROUP_DEVICE
	bool "Device controller"
	help
	  Provides a cgroup controller implementing whitelists for
	  devices which a process in the cgroup can mknod or open.

config CGROUP_CPUACCT
	bool "Simple CPU accounting controller"
	help
	  Provides a simple controller for monitoring the
	  total CPU consumed by the tasks in a cgroup.

config CGROUP_PERF
	bool "Perf controller"
	depends on PERF_EVENTS
	help
	  This option extends the perf per-cpu mode to restrict monitoring
	  to threads which belong to the cgroup specified and run on the
	  designated cpu.

	  Say N if unsure.

config CGROUP_DEBUG
	bool "Example controller"
1159
	default n
1160 1161 1162
	help
	  This option enables a simple controller that exports
	  debugging information about the cgroups framework.
1163

1164
	  Say N.
1165

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endif # CGROUPS
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config CHECKPOINT_RESTORE
	bool "Checkpoint/restore support" if EXPERT
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	select PROC_CHILDREN
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	default n
	help
	  Enables additional kernel features in a sake of checkpoint/restore.
	  In particular it adds auxiliary prctl codes to setup process text,
	  data and heap segment sizes, and a few additional /proc filesystem
	  entries.

	  If unsure, say N here.

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menuconfig NAMESPACES
1181
	bool "Namespaces support" if EXPERT
1182
	depends on MULTIUSER
1183
	default !EXPERT
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	help
	  Provides the way to make tasks work with different objects using
	  the same id. For example same IPC id may refer to different objects
	  or same user id or pid may refer to different tasks when used in
	  different namespaces.

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if NAMESPACES

1192 1193
config UTS_NS
	bool "UTS namespace"
1194
	default y
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	help
	  In this namespace tasks see different info provided with the
	  uname() system call

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config IPC_NS
	bool "IPC namespace"
1201
	depends on (SYSVIPC || POSIX_MQUEUE)
1202
	default y
1203 1204
	help
	  In this namespace tasks work with IPC ids which correspond to
1205
	  different IPC objects in different namespaces.
1206

1207
config USER_NS
1208
	bool "User namespace"
1209
	default n
1210 1211 1212
	help
	  This allows containers, i.e. vservers, to use user namespaces
	  to provide different user info for different servers.
1213 1214

	  When user namespaces are enabled in the kernel it is
1215 1216 1217
	  recommended that the MEMCG option also be enabled and that
	  user-space use the memory control groups to limit the amount
	  of memory a memory unprivileged users can use.
1218

1219 1220
	  If unsure, say N.

1221
config PID_NS
1222
	bool "PID Namespaces"
1223
	default y
1224
	help
1225
	  Support process id namespaces.  This allows having multiple
1226
	  processes with the same pid as long as they are in different
1227 1228
	  pid namespaces.  This is a building block of containers.

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config NET_NS
	bool "Network namespace"
1231
	depends on NET
1232
	default y
1233 1234 1235 1236
	help
	  Allow user space to create what appear to be multiple instances
	  of the network stack.

1237 1238
endif # NAMESPACES

1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250
config SCHED_AUTOGROUP
	bool "Automatic process group scheduling"
	select CGROUPS
	select CGROUP_SCHED
	select FAIR_GROUP_SCHED
	help
	  This option optimizes the scheduler for common desktop workloads by
	  automatically creating and populating task groups.  This separation
	  of workloads isolates aggressive CPU burners (like build jobs) from
	  desktop applications.  Task group autogeneration is currently based
	  upon task session.

1251
config SYSFS_DEPRECATED
1252
	bool "Enable deprecated sysfs features to support old userspace tools"
1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274
	depends on SYSFS
	default n
	help
	  This option adds code that switches the layout of the "block" class
	  devices, to not show up in /sys/class/block/, but only in
	  /sys/block/.

	  This switch is only active when the sysfs.deprecated=1 boot option is
	  passed or the SYSFS_DEPRECATED_V2 option is set.

	  This option allows new kernels to run on old distributions and tools,
	  which might get confused by /sys/class/block/. Since 2007/2008 all
	  major distributions and tools handle this just fine.

	  Recent distributions and userspace tools after 2009/2010 depend on
	  the existence of /sys/class/block/, and will not work with this
	  option enabled.

	  Only if you are using a new kernel on an old distribution, you might
	  need to say Y here.

config SYSFS_DEPRECATED_V2
1275
	bool "Enable deprecated sysfs features by default"
1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290
	default n
	depends on SYSFS
	depends on SYSFS_DEPRECATED
	help
	  Enable deprecated sysfs by default.

	  See the CONFIG_SYSFS_DEPRECATED option for more details about this
	  option.

	  Only if you are using a new kernel on an old distribution, you might
	  need to say Y here. Even then, odds are you would not need it
	  enabled, you can always pass the boot option if absolutely necessary.

config RELAY
	bool "Kernel->user space relay support (formerly relayfs)"
1291
	select IRQ_WORK
1292 1293 1294 1295 1296 1297 1298 1299 1300
	help
	  This option enables support for relay interface support in
	  certain file systems (such as debugfs).
	  It is designed to provide an efficient mechanism for tools and
	  facilities to relay large amounts of data from kernel space to
	  user space.

	  If unsure, say N.

1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316
config BLK_DEV_INITRD
	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
	depends on BROKEN || !FRV
	help
	  The initial RAM filesystem is a ramfs which is loaded by the
	  boot loader (loadlin or lilo) and that is mounted as root
	  before the normal boot procedure. It is typically used to
	  load modules needed to mount the "real" root file system,
	  etc. See <file:Documentation/initrd.txt> for details.

	  If RAM disk support (BLK_DEV_RAM) is also included, this
	  also enables initial RAM disk (initrd) support and adds
	  15 Kbytes (more on some other architectures) to the kernel size.

	  If unsure say Y.

1317 1318
if BLK_DEV_INITRD

1319 1320
source "usr/Kconfig"

1321 1322
endif

1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333
choice
	prompt "Compiler optimization level"
	default CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE

config CC_OPTIMIZE_FOR_PERFORMANCE
	bool "Optimize for performance"
	help
	  This is the default optimization level for the kernel, building
	  with the "-O2" compiler flag for best performance and most
	  helpful compile-time warnings.

1334
config CC_OPTIMIZE_FOR_SIZE
1335
	bool "Optimize for size"
1336
	help
1337 1338
	  Enabling this option will pass "-Os" instead of "-O2" to
	  your compiler resulting in a smaller kernel.
1339

1340
	  If unsure, say N.
1341

1342 1343
endchoice

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config SYSCTL
	bool

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config ANON_INODES
	bool

1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375
config HAVE_UID16
	bool

config SYSCTL_EXCEPTION_TRACE
	bool
	help
	  Enable support for /proc/sys/debug/exception-trace.

config SYSCTL_ARCH_UNALIGN_NO_WARN
	bool
	help
	  Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
	  Allows arch to define/use @no_unaligned_warning to possibly warn
	  about unaligned access emulation going on under the hood.

config SYSCTL_ARCH_UNALIGN_ALLOW
	bool
	help
	  Enable support for /proc/sys/kernel/unaligned-trap
	  Allows arches to define/use @unaligned_enabled to runtime toggle
	  the unaligned access emulation.
	  see arch/parisc/kernel/unaligned.c for reference

config HAVE_PCSPKR_PLATFORM
	bool

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# interpreter that classic socket filters depend on
config BPF
	bool

1380 1381
menuconfig EXPERT
	bool "Configure standard kernel features (expert users)"
1382 1383
	# Unhide debug options, to make the on-by-default options visible
	select DEBUG_KERNEL
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	help
	  This option allows certain base kernel options and settings
          to be disabled or tweaked. This is for specialized
          environments which can tolerate a "non-standard" kernel.
          Only use this if you really know what you are doing.

1390
config UID16
1391
	bool "Enable 16-bit UID system calls" if EXPERT
1392
	depends on HAVE_UID16 && MULTIUSER
1393 1394 1395 1396
	default y
	help
	  This enables the legacy 16-bit UID syscall wrappers.

1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410
config MULTIUSER
	bool "Multiple users, groups and capabilities support" if EXPERT
	default y
	help
	  This option enables support for non-root users, groups and
	  capabilities.

	  If you say N here, all processes will run with UID 0, GID 0, and all
	  possible capabilities.  Saying N here also compiles out support for
	  system calls related to UIDs, GIDs, and capabilities, such as setuid,
	  setgid, and capset.

	  If unsure, say Y here.

1411 1412 1413 1414 1415 1416 1417 1418 1419 1420
config SGETMASK_SYSCALL
	bool "sgetmask/ssetmask syscalls support" if EXPERT
	def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
	---help---
	  sys_sgetmask and sys_ssetmask are obsolete system calls
	  no longer supported in libc but still enabled by default in some
	  architectures.

	  If unsure, leave the default option here.

1421 1422 1423 1424 1425 1426 1427 1428 1429 1430
config SYSFS_SYSCALL
	bool "Sysfs syscall support" if EXPERT
	default y
	---help---
	  sys_sysfs is an obsolete system call no longer supported in libc.
	  Note that disabling this option is more secure but might break
	  compatibility with some systems.

	  If unsure say Y here.

1431
config SYSCTL_SYSCALL
1432
	bool "Sysctl syscall support" if EXPERT
1433
	depends on PROC_SYSCTL
1434
	default n
1435
	select SYSCTL
1436
	---help---
1437 1438 1439 1440
	  sys_sysctl uses binary paths that have been found challenging
	  to properly maintain and use.  The interface in /proc/sys
	  using paths with ascii names is now the primary path to this
	  information.
1441

1442 1443 1444
	  Almost nothing using the binary sysctl interface so if you are
	  trying to save some space it is probably safe to disable this,
	  making your kernel marginally smaller.
1445

1446
	  If unsure say N here.
1447

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config KALLSYMS
1449
	 bool "Load all symbols for debugging/ksymoops" if EXPERT
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	 default y
	 help
	   Say Y here to let the kernel print out symbolic crash information and
	   symbolic stack backtraces. This increases the size of the kernel
	   somewhat, as all symbols have to be loaded into the kernel image.

config KALLSYMS_ALL
	bool "Include all symbols in kallsyms"
	depends on DEBUG_KERNEL && KALLSYMS
	help
1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471
	   Normally kallsyms only contains the symbols of functions for nicer
	   OOPS messages and backtraces (i.e., symbols from the text and inittext
	   sections). This is sufficient for most cases. And only in very rare
	   cases (e.g., when a debugger is used) all symbols are required (e.g.,
	   names of variables from the data sections, etc).

	   This option makes sure that all symbols are loaded into the kernel
	   image (i.e., symbols from all sections) in cost of increased kernel
	   size (depending on the kernel configuration, it may be 300KiB or
	   something like this).

	   Say N unless you really need all symbols.
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1473 1474
config KALLSYMS_ABSOLUTE_PERCPU
	bool
1475
	depends on KALLSYMS
1476 1477
	default X86_64 && SMP

1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495
config KALLSYMS_BASE_RELATIVE
	bool
	depends on KALLSYMS
	default !IA64 && !(TILE && 64BIT)
	help
	  Instead of emitting them as absolute values in the native word size,
	  emit the symbol references in the kallsyms table as 32-bit entries,
	  each containing a relative value in the range [base, base + U32_MAX]
	  or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
	  an absolute value in the range [0, S32_MAX] or a relative value in the
	  range [base, base + S32_MAX], where base is the lowest relative symbol
	  address encountered in the image.

	  On 64-bit builds, this reduces the size of the address table by 50%,
	  but more importantly, it results in entries whose values are build
	  time constants, and no relocation pass is required at runtime to fix
	  up the entries based on the runtime load address of the kernel.

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config PRINTK
	default y
1498
	bool "Enable support for printk" if EXPERT
1499
	select IRQ_WORK
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	help
	  This option enables normal printk support. Removing it
	  eliminates most of the message strings from the kernel image
	  and makes the kernel more or less silent. As this makes it
	  very difficult to diagnose system problems, saying N here is
	  strongly discouraged.

1507 1508 1509 1510 1511
config PRINTK_NMI
	def_bool y
	depends on PRINTK
	depends on HAVE_NMI

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config BUG
1513
	bool "BUG() support" if EXPERT
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	default y
	help
          Disabling this option eliminates support for BUG and WARN, reducing
          the size of your kernel image and potentially quietly ignoring
          numerous fatal conditions. You should only consider disabling this
          option for embedded systems with no facilities for reporting errors.
          Just say Y.

1522
config ELF_CORE
1523
	depends on COREDUMP
1524
	default y
1525
	bool "Enable ELF core dumps" if EXPERT
1526 1527 1528
	help
	  Enable support for generating core dumps. Disabling saves about 4k.

1529

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config PCSPKR_PLATFORM
1531
	bool "Enable PC-Speaker support" if EXPERT
1532
	depends on HAVE_PCSPKR_PLATFORM
1533
	select I8253_LOCK
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	default y
	help
          This option allows to disable the internal PC-Speaker
          support, saving some memory.

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config BASE_FULL
	default y
1541
	bool "Enable full-sized data structures for core" if EXPERT
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	help
	  Disabling this option reduces the size of miscellaneous core
	  kernel data structures. This saves memory on small machines,
	  but may reduce performance.

config FUTEX
1548
	bool "Enable futex support" if EXPERT
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	default y
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	select RT_MUTEXES
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	help
	  Disabling this option will cause the kernel to be built without
	  support for "fast userspace mutexes".  The resulting kernel may not
	  run glibc-based applications correctly.

1556 1557
config HAVE_FUTEX_CMPXCHG
	bool
1558
	depends on FUTEX
1559 1560 1561 1562 1563
	help
	  Architectures should select this if futex_atomic_cmpxchg_inatomic()
	  is implemented and always working. This removes a couple of runtime
	  checks.

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config EPOLL
1565
	bool "Enable eventpoll support" if EXPERT
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	default y
1567
	select ANON_INODES
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	help
	  Disabling this option will cause the kernel to be built without
	  support for epoll family of system calls.

1572
config SIGNALFD
1573
	bool "Enable signalfd() system call" if EXPERT
1574
	select ANON_INODES
1575 1576 1577 1578 1579 1580 1581
	default y
	help
	  Enable the signalfd() system call that allows to receive signals
	  on a file descriptor.

	  If unsure, say Y.

1582
config TIMERFD
1583
	bool "Enable timerfd() system call" if EXPERT
1584
	select ANON_INODES
1585 1586 1587 1588 1589 1590 1591
	default y
	help
	  Enable the timerfd() system call that allows to receive timer
	  events on a file descriptor.

	  If unsure, say Y.

1592
config EVENTFD
1593
	bool "Enable eventfd() system call" if EXPERT
1594
	select ANON_INODES
1595 1596 1597 1598 1599 1600 1601
	default y
	help
	  Enable the eventfd() system call that allows to receive both
	  kernel notification (ie. KAIO) or userspace notifications.

	  If unsure, say Y.

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# syscall, maps, verifier
config BPF_SYSCALL
1604
	bool "Enable bpf() system call"
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	select ANON_INODES
	select BPF
	default n
	help
	  Enable the bpf() system call that allows to manipulate eBPF
	  programs and maps via file descriptors.

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config SHMEM
1613
	bool "Use full shmem filesystem" if EXPERT
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	default y
	depends on MMU
	help
	  The shmem is an internal filesystem used to manage shared memory.
	  It is backed by swap and manages resource limits. It is also exported
	  to userspace as tmpfs if TMPFS is enabled. Disabling this
	  option replaces shmem and tmpfs with the much simpler ramfs code,
	  which may be appropriate on small systems without swap.

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config AIO
1624
	bool "Enable AIO support" if EXPERT
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	default y
	help
	  This option enables POSIX asynchronous I/O which may by used
1628 1629 1630
	  by some high performance threaded applications. Disabling
	  this option saves about 7k.

1631 1632 1633 1634 1635 1636 1637 1638 1639 1640
config ADVISE_SYSCALLS
	bool "Enable madvise/fadvise syscalls" if EXPERT
	default y
	help
	  This option enables the madvise and fadvise syscalls, used by
	  applications to advise the kernel about their future memory or file
	  usage, improving performance. If building an embedded system where no
	  applications use these syscalls, you can disable this option to save
	  space.

1641 1642 1643 1644 1645 1646 1647 1648
config USERFAULTFD
	bool "Enable userfaultfd() system call"
	select ANON_INODES
	depends on MMU
	help
	  Enable the userfaultfd() system call that allows to intercept and
	  handle page faults in userland.

1649 1650 1651 1652 1653 1654 1655 1656
config PCI_QUIRKS
	default y
	bool "Enable PCI quirk workarounds" if EXPERT
	depends on PCI
	help
	  This enables workarounds for various PCI chipset
	  bugs/quirks. Disable this only if your target machine is
	  unaffected by PCI quirks.
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1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669
config MEMBARRIER
	bool "Enable membarrier() system call" if EXPERT
	default y
	help
	  Enable the membarrier() system call that allows issuing memory
	  barriers across all running threads, which can be used to distribute
	  the cost of user-space memory barriers asymmetrically by transforming
	  pairs of memory barriers into pairs consisting of membarrier() and a
	  compiler barrier.

	  If unsure, say Y.

1670 1671
config EMBEDDED
	bool "Embedded system"
1672
	option allnoconfig_y
1673 1674 1675 1676 1677 1678
	select EXPERT
	help
	  This option should be enabled if compiling the kernel for
	  an embedded system so certain expert options are available
	  for configuration.

1679
config HAVE_PERF_EVENTS
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	bool
1681 1682
	help
	  See tools/perf/design.txt for details.
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1684 1685 1686 1687 1688
config PERF_USE_VMALLOC
	bool
	help
	  See tools/perf/design.txt for details

I
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1689
menu "Kernel Performance Events And Counters"
T
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1691
config PERF_EVENTS
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1692
	bool "Kernel performance events and counters"
1693
	default y if PROFILING
1694
	depends on HAVE_PERF_EVENTS
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1695
	select ANON_INODES
1696
	select IRQ_WORK
1697
	select SRCU
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	help
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	  Enable kernel support for various performance events provided
	  by software and hardware.
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1701

1702
	  Software events are supported either built-in or via the
I
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1703
	  use of generic tracepoints.
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I
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1705 1706
	  Most modern CPUs support performance events via performance
	  counter registers. These registers count the number of certain
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	  types of hw events: such as instructions executed, cachemisses
	  suffered, or branches mis-predicted - without slowing down the
	  kernel or applications. These registers can also trigger interrupts
	  when a threshold number of events have passed - and can thus be
	  used to profile the code that runs on that CPU.

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	  The Linux Performance Event subsystem provides an abstraction of
1714
	  these software and hardware event capabilities, available via a
I
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	  system call and used by the "perf" utility in tools/perf/. It
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	  provides per task and per CPU counters, and it provides event
	  capabilities on top of those.

	  Say Y if unsure.

1721 1722 1723
config DEBUG_PERF_USE_VMALLOC
	default n
	bool "Debug: use vmalloc to back perf mmap() buffers"
1724
	depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1725 1726 1727 1728 1729 1730 1731 1732 1733
	select PERF_USE_VMALLOC
	help
	 Use vmalloc memory to back perf mmap() buffers.

	 Mostly useful for debugging the vmalloc code on platforms
	 that don't require it.

	 Say N if unsure.

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endmenu

1736 1737
config VM_EVENT_COUNTERS
	default y
1738
	bool "Enable VM event counters for /proc/vmstat" if EXPERT
1739
	help
1740 1741
	  VM event counters are needed for event counts to be shown.
	  This option allows the disabling of the VM event counters
1742
	  on EXPERT systems.  /proc/vmstat will only show page counts
1743
	  if VM event counters are disabled.
1744

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config SLUB_DEBUG
	default y
1747
	bool "Enable SLUB debugging support" if EXPERT
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1748
	depends on SLUB && SYSFS
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1749 1750 1751 1752 1753 1754
	help
	  SLUB has extensive debug support features. Disabling these can
	  result in significant savings in code size. This also disables
	  SLUB sysfs support. /sys/slab will not exist and there will be
	  no support for cache validation etc.

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config COMPAT_BRK
	bool "Disable heap randomization"
	default y
	help
	  Randomizing heap placement makes heap exploits harder, but it
	  also breaks ancient binaries (including anything libc5 based).
	  This option changes the bootup default to heap randomization
1762
	  disabled, and can be overridden at runtime by setting
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	  /proc/sys/kernel/randomize_va_space to 2.

	  On non-ancient distros (post-2000 ones) N is usually a safe choice.

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choice
	prompt "Choose SLAB allocator"
1769
	default SLUB
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	help
	   This option allows to select a slab allocator.

config SLAB
	bool "SLAB"
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	select HAVE_HARDENED_USERCOPY_ALLOCATOR
C
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	help
	  The regular slab allocator that is established and known to work
1778
	  well in all environments. It organizes cache hot objects in
1779
	  per cpu and per node queues.
C
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1780 1781 1782

config SLUB
	bool "SLUB (Unqueued Allocator)"
K
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1783
	select HAVE_HARDENED_USERCOPY_ALLOCATOR
C
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1784 1785 1786 1787 1788
	help
	   SLUB is a slab allocator that minimizes cache line usage
	   instead of managing queues of cached objects (SLAB approach).
	   Per cpu caching is realized using slabs of objects instead
	   of queues of objects. SLUB can use memory efficiently
1789 1790
	   and has enhanced diagnostics. SLUB is the default choice for
	   a slab allocator.
C
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config SLOB
1793
	depends on EXPERT
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1794 1795
	bool "SLOB (Simple Allocator)"
	help
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	   SLOB replaces the stock allocator with a drastically simpler
	   allocator. SLOB is generally more space efficient but
	   does not perform as well on large systems.
C
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endchoice

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config SLAB_FREELIST_RANDOM
	default n
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1804
	depends on SLAB || SLUB
T
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1805 1806
	bool "SLAB freelist randomization"
	help
T
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1807
	  Randomizes the freelist order used on creating new pages. This
T
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1808 1809 1810
	  security feature reduces the predictability of the kernel slab
	  allocator against heap overflows.

1811 1812
config SLUB_CPU_PARTIAL
	default y
1813
	depends on SLUB && SMP
1814 1815 1816 1817 1818 1819 1820 1821
	bool "SLUB per cpu partial cache"
	help
	  Per cpu partial caches accellerate objects allocation and freeing
	  that is local to a processor at the price of more indeterminism
	  in the latency of the free. On overflow these caches will be cleared
	  which requires the taking of locks that may cause latency spikes.
	  Typically one would choose no for a realtime system.

1822 1823
config MMAP_ALLOW_UNINITIALIZED
	bool "Allow mmapped anonymous memory to be uninitialized"
1824
	depends on EXPERT && !MMU
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	default n
	help
	  Normally, and according to the Linux spec, anonymous memory obtained
	  from mmap() has it's contents cleared before it is passed to
	  userspace.  Enabling this config option allows you to request that
	  mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
	  providing a huge performance boost.  If this option is not enabled,
	  then the flag will be ignored.

	  This is taken advantage of by uClibc's malloc(), and also by
	  ELF-FDPIC binfmt's brk and stack allocator.

	  Because of the obvious security issues, this option should only be
	  enabled on embedded devices where you control what is run in
	  userspace.  Since that isn't generally a problem on no-MMU systems,
	  it is normally safe to say Y here.

	  See Documentation/nommu-mmap.txt for more information.

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config SYSTEM_DATA_VERIFICATION
	def_bool n
	select SYSTEM_TRUSTED_KEYRING
	select KEYS
	select CRYPTO
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	select CRYPTO_RSA
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	select ASYMMETRIC_KEY_TYPE
	select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
	select ASN1
	select OID_REGISTRY
	select X509_CERTIFICATE_PARSER
	select PKCS7_MESSAGE_PARSER
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	help
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	  Provide PKCS#7 message verification using the contents of the system
	  trusted keyring to provide public keys.  This then can be used for
	  module verification, kexec image verification and firmware blob
	  verification.
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config PROFILING
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	bool "Profiling support"
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	help
	  Say Y here to enable the extended profiling support mechanisms used
	  by profilers such as OProfile.

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#
# Place an empty function call at each tracepoint site. Can be
# dynamically changed for a probe function.
#
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config TRACEPOINTS
1873
	bool
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M
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source "arch/Kconfig"

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endmenu		# General setup

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config HAVE_GENERIC_DMA_COHERENT
	bool
	default n

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config SLABINFO
	bool
	depends on PROC_FS
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	depends on SLAB || SLUB_DEBUG
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	default y

1889
config RT_MUTEXES
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	bool
1891

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config BASE_SMALL
	int
	default 0 if BASE_FULL
	default 1 if !BASE_FULL

1897
menuconfig MODULES
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	bool "Enable loadable module support"
1899
	option modules
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	help
	  Kernel modules are small pieces of compiled code which can
	  be inserted in the running kernel, rather than being
	  permanently built into the kernel.  You use the "modprobe"
	  tool to add (and sometimes remove) them.  If you say Y here,
	  many parts of the kernel can be built as modules (by
	  answering M instead of Y where indicated): this is most
	  useful for infrequently used options which are not required
	  for booting.  For more information, see the man pages for
	  modprobe, lsmod, modinfo, insmod and rmmod.

	  If you say Y here, you will need to run "make
	  modules_install" to put the modules under /lib/modules/
	  where modprobe can find them (you may need to be root to do
	  this).

	  If unsure, say Y.

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if MODULES

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config MODULE_FORCE_LOAD
	bool "Forced module loading"
	default n
	help
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	  Allow loading of modules without version information (ie. modprobe
	  --force).  Forced module loading sets the 'F' (forced) taint flag and
	  is usually a really bad idea.
1927

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config MODULE_UNLOAD
	bool "Module unloading"
	help
	  Without this option you will not be able to unload any
	  modules (note that some modules may not be unloadable
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	  anyway), which makes your kernel smaller, faster
	  and simpler.  If unsure, say Y.
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config MODULE_FORCE_UNLOAD
	bool "Forced module unloading"
1938
	depends on MODULE_UNLOAD
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	help
	  This option allows you to force a module to unload, even if the
	  kernel believes it is unsafe: the kernel will remove the module
	  without waiting for anyone to stop using it (using the -f option to
	  rmmod).  This is mainly for kernel developers and desperate users.
	  If unsure, say N.

config MODVERSIONS
1947
	bool "Module versioning support"
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	help
	  Usually, you have to use modules compiled with your kernel.
	  Saying Y here makes it sometimes possible to use modules
	  compiled for different kernels, by adding enough information
	  to the modules to (hopefully) spot any changes which would
	  make them incompatible with the kernel you are running.  If
	  unsure, say N.

config MODULE_SRCVERSION_ALL
	bool "Source checksum for all modules"
	help
	  Modules which contain a MODULE_VERSION get an extra "srcversion"
	  field inserted into their modinfo section, which contains a
    	  sum of the source files which made it.  This helps maintainers
	  see exactly which source was used to build a module (since
	  others sometimes change the module source without updating
	  the version).  With this option, such a "srcversion" field
	  will be created for all modules.  If unsure, say N.

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config MODULE_SIG
	bool "Module signature verification"
	depends on MODULES
1970
	select SYSTEM_DATA_VERIFICATION
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	help
	  Check modules for valid signatures upon load: the signature
	  is simply appended to the module. For more information see
	  Documentation/module-signing.txt.

1976 1977 1978 1979
	  Note that this option adds the OpenSSL development packages as a
	  kernel build dependency so that the signing tool can use its crypto
	  library.

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	  !!!WARNING!!!  If you enable this option, you MUST make sure that the
	  module DOES NOT get stripped after being signed.  This includes the
	  debuginfo strip done by some packagers (such as rpmbuild) and
	  inclusion into an initramfs that wants the module size reduced.

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config MODULE_SIG_FORCE
	bool "Require modules to be validly signed"
	depends on MODULE_SIG
	help
	  Reject unsigned modules or signed modules for which we don't have a
	  key.  Without this, such modules will simply taint the kernel.
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1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002
config MODULE_SIG_ALL
	bool "Automatically sign all modules"
	default y
	depends on MODULE_SIG
	help
	  Sign all modules during make modules_install. Without this option,
	  modules must be signed manually, using the scripts/sign-file tool.

comment "Do not forget to sign required modules with scripts/sign-file"
	depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL

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2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034
choice
	prompt "Which hash algorithm should modules be signed with?"
	depends on MODULE_SIG
	help
	  This determines which sort of hashing algorithm will be used during
	  signature generation.  This algorithm _must_ be built into the kernel
	  directly so that signature verification can take place.  It is not
	  possible to load a signed module containing the algorithm to check
	  the signature on that module.

config MODULE_SIG_SHA1
	bool "Sign modules with SHA-1"
	select CRYPTO_SHA1

config MODULE_SIG_SHA224
	bool "Sign modules with SHA-224"
	select CRYPTO_SHA256

config MODULE_SIG_SHA256
	bool "Sign modules with SHA-256"
	select CRYPTO_SHA256

config MODULE_SIG_SHA384
	bool "Sign modules with SHA-384"
	select CRYPTO_SHA512

config MODULE_SIG_SHA512
	bool "Sign modules with SHA-512"
	select CRYPTO_SHA512

endchoice

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config MODULE_SIG_HASH
	string
	depends on MODULE_SIG
	default "sha1" if MODULE_SIG_SHA1
	default "sha224" if MODULE_SIG_SHA224
	default "sha256" if MODULE_SIG_SHA256
	default "sha384" if MODULE_SIG_SHA384
	default "sha512" if MODULE_SIG_SHA512

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config MODULE_COMPRESS
	bool "Compress modules on installation"
	depends on MODULES
	help

2049 2050
	  Compresses kernel modules when 'make modules_install' is run; gzip or
	  xz depending on "Compression algorithm" below.
2051

2052
	  module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
2053

2054 2055
	  Out-of-tree kernel modules installed using Kbuild will also be
	  compressed upon installation.
2056

2057 2058
	  Note: for modules inside an initrd or initramfs, it's more efficient
	  to compress the whole initrd or initramfs instead.
2059

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	  Note: This is fully compatible with signed modules.

	  If in doubt, say N.
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choice
	prompt "Compression algorithm"
	depends on MODULE_COMPRESS
	default MODULE_COMPRESS_GZIP
	help
	  This determines which sort of compression will be used during
	  'make modules_install'.

	  GZIP (default) and XZ are supported.

config MODULE_COMPRESS_GZIP
	bool "GZIP"

config MODULE_COMPRESS_XZ
	bool "XZ"

endchoice

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config TRIM_UNUSED_KSYMS
	bool "Trim unused exported kernel symbols"
	depends on MODULES && !UNUSED_SYMBOLS
	help
	  The kernel and some modules make many symbols available for
	  other modules to use via EXPORT_SYMBOL() and variants. Depending
	  on the set of modules being selected in your kernel configuration,
	  many of those exported symbols might never be used.

	  This option allows for unused exported symbols to be dropped from
	  the build. In turn, this provides the compiler more opportunities
	  (especially when using LTO) for optimizing the code and reducing
	  binary size.  This might have some security advantages as well.

2096
	  If unsure, or if you need to build out-of-tree modules, say N.
2097

2098 2099
endif # MODULES

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config MODULES_TREE_LOOKUP
	def_bool y
	depends on PERF_EVENTS || TRACING

2104 2105 2106
config INIT_ALL_POSSIBLE
	bool
	help
2107 2108
	  Back when each arch used to define their own cpu_online_mask and
	  cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2109 2110
	  with all 1s, and others with all 0s.  When they were centralised,
	  it was better to provide this option than to break all the archs
2111
	  and have several arch maintainers pursuing me down dark alleys.
2112

2113
source "block/Kconfig"
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config PREEMPT_NOTIFIERS
	bool
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2117

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config PADATA
	depends on SMP
	bool

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config ASN1
	tristate
	help
	  Build a simple ASN.1 grammar compiler that produces a bytecode output
	  that can be interpreted by the ASN.1 stream decoder and used to
	  inform it as to what tags are to be expected in a stream and what
	  functions to call on what tags.

2130
source "kernel/Kconfig.locks"