Documentation/llvm: add documentation on building w/ Clang/LLVM

[linux.git] / init / Kconfig

# SPDX-License-Identifier: GPL-2.0-only
config DEFCONFIG_LIST
	string
	depends on !UML
	option defconfig_list
	default "/lib/modules/$(shell,uname -r)/.config"
	default "/etc/kernel-config"
	default "/boot/config-$(shell,uname -r)"
	default ARCH_DEFCONFIG
	default "arch/$(ARCH)/defconfig"

config CC_IS_GCC
	def_bool $(success,$(CC) --version | head -n 1 | grep -q gcc)

config GCC_VERSION
	int
	default $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) if CC_IS_GCC
	default 0

config CC_IS_CLANG
	def_bool $(success,$(CC) --version | head -n 1 | grep -q clang)

config CLANG_VERSION
	int
	default $(shell,$(srctree)/scripts/clang-version.sh $(CC))

config CC_CAN_LINK
	def_bool $(success,$(srctree)/scripts/cc-can-link.sh $(CC))

config CC_HAS_ASM_GOTO
	def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))

config TOOLS_SUPPORT_RELR
	def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)

config CC_HAS_ASM_INLINE
	def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)

config CC_HAS_WARN_MAYBE_UNINITIALIZED
	def_bool $(cc-option,-Wmaybe-uninitialized)
	help
	  GCC >= 4.7 supports this option.

config CC_DISABLE_WARN_MAYBE_UNINITIALIZED
	bool
	depends on CC_HAS_WARN_MAYBE_UNINITIALIZED
	default CC_IS_GCC && GCC_VERSION < 40900  # unreliable for GCC < 4.9
	help
	  GCC's -Wmaybe-uninitialized is not reliable by definition.
	  Lots of false positive warnings are produced in some cases.

	  If this option is enabled, -Wno-maybe-uninitialzed is passed
	  to the compiler to suppress maybe-uninitialized warnings.

config CONSTRUCTORS
	bool
	depends on !UML

config IRQ_WORK
	bool

config BUILDTIME_TABLE_SORT
	bool

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.

	  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().

menu "General setup"

config BROKEN
	bool

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

config INIT_ENV_ARG_LIMIT
	int
	default 32 if !UML
	default 128 if UML
	help
	  Maximum of each of the number of arguments and environment
	  variables passed to init from the kernel command line.

config COMPILE_TEST
	bool "Compile also drivers which will not load"
	depends on !UML
	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.

config UAPI_HEADER_TEST
	bool "Compile test UAPI headers"
	depends on HEADERS_INSTALL && CC_CAN_LINK
	help
	  Compile test headers exported to user-space to ensure they are
	  self-contained, i.e. compilable as standalone units.

	  If you are a developer or tester and want to ensure the exported
	  headers are self-contained, say Y here. Otherwise, choose N.

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.

config LOCALVERSION_AUTO
	bool "Automatically append version information to the version string"
	default y
	depends on !COMPILE_TEST
	help
	  This will try to automatically determine if the current tree is a
	  release tree by looking for git tags that belong to the current
	  top of tree revision.

	  A string of the format -gxxxxxxxx will be added to the localversion
	  if a git-based tree is found.  The string generated by this will be
	  appended after any matching localversion* files, and after the value
	  set in CONFIG_LOCALVERSION.

	  (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".)

config BUILD_SALT
	string "Build ID Salt"
	default ""
	help
	  The build ID is used to link binaries and their debug info. Setting
	  this option will use the value in the calculation of the build id.
	  This is mostly useful for distributions which want to ensure the
	  build is unique between builds. It's safe to leave the default.

config HAVE_KERNEL_GZIP
	bool

config HAVE_KERNEL_BZIP2
	bool

config HAVE_KERNEL_LZMA
	bool

config HAVE_KERNEL_XZ
	bool

config HAVE_KERNEL_LZO
	bool

config HAVE_KERNEL_LZ4
	bool

config HAVE_KERNEL_UNCOMPRESSED
	bool

choice
	prompt "Kernel compression mode"
	default KERNEL_GZIP
	depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED
	help
	  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) <[email protected]>. (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
	bool "Gzip"
	depends on HAVE_KERNEL_GZIP
	help
	  The old and tried gzip compression. It provides a good balance
	  between compression ratio and decompression speed.

config KERNEL_BZIP2
	bool "Bzip2"
	depends on HAVE_KERNEL_BZIP2
	help
	  Its compression ratio and speed is intermediate.
	  Decompression speed is slowest among the choices.  The kernel
	  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.

config KERNEL_LZMA
	bool "LZMA"
	depends on HAVE_KERNEL_LZMA
	help
	  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.

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.

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

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.

config KERNEL_UNCOMPRESSED
	bool "None"
	depends on HAVE_KERNEL_UNCOMPRESSED
	help
	  Produce uncompressed kernel image. This option is usually not what
	  you want. It is useful for debugging the kernel in slow simulation
	  environments, where decompressing and moving the kernel is awfully
	  slow. This option allows early boot code to skip the decompressor
	  and jump right at uncompressed kernel image.

endchoice

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.

#
# For some reason microblaze and nios2 hard code SWAP=n.  Hopefully we can
# add proper SWAP support to them, in which case this can be remove.
#
config ARCH_NO_SWAP
	bool

config SWAP
	bool "Support for paging of anonymous memory (swap)"
	depends on MMU && BLOCK && !ARCH_NO_SWAP
	default y
	help
	  This option allows you to choose whether you want to have support
	  for so called swap devices or swap files in your kernel that are
	  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>.

config SYSVIPC_SYSCTL
	bool
	depends on SYSVIPC
	depends on SYSCTL
	default y

config POSIX_MQUEUE
	bool "POSIX Message Queues"
	depends on NET
	---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
	  queues (functions mq_*) say Y here.

	  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.

config POSIX_MQUEUE_SYSCTL
	bool
	depends on POSIX_MQUEUE
	depends on SYSCTL
	default y

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
	  to directly read from or write to another process' address space.
	  See the man page for more details.

config USELIB
	bool "uselib syscall"
	def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
	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.

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
	  logging of avc messages output).  System call auditing is included
	  on architectures which support it.

config HAVE_ARCH_AUDITSYSCALL
	bool

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

source "kernel/irq/Kconfig"
source "kernel/time/Kconfig"
source "kernel/Kconfig.preempt"

menu "CPU/Task time and stats accounting"

config VIRT_CPU_ACCOUNTING
	bool

choice
	prompt "Cputime accounting"
	default TICK_CPU_ACCOUNTING if !PPC64
	default VIRT_CPU_ACCOUNTING_NATIVE if PPC64

# Kind of a stub config for the pure tick based cputime accounting
config TICK_CPU_ACCOUNTING
	bool "Simple tick based cputime accounting"
	depends on !S390 && !NO_HZ_FULL
	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.

config VIRT_CPU_ACCOUNTING_NATIVE
	bool "Deterministic task and CPU time accounting"
	depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
	select VIRT_CPU_ACCOUNTING
	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.

config VIRT_CPU_ACCOUNTING_GEN
	bool "Full dynticks CPU time accounting"
	depends on HAVE_CONTEXT_TRACKING
	depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
	depends on GENERIC_CLOCKEVENTS
	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.

endchoice

config IRQ_TIME_ACCOUNTING
	bool "Fine granularity task level IRQ time accounting"
	depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
	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.

config HAVE_SCHED_AVG_IRQ
	def_bool y
	depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
	depends on SMP

config BSD_PROCESS_ACCT
	bool "BSD Process Accounting"
	depends on MULTIUSER
	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 its 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
	  at <http://www.gnu.org/software/acct/>.

config TASKSTATS
	bool "Export task/process statistics through netlink"
	depends on NET
	depends on MULTIUSER
	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.

config TASK_DELAY_ACCT
	bool "Enable per-task delay accounting"
	depends on TASKSTATS
	select SCHED_INFO
	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.

config TASK_XACCT
	bool "Enable extended accounting over taskstats"
	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
	bool "Enable per-task storage I/O accounting"
	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.

config PSI
	bool "Pressure stall information tracking"
	help
	  Collect metrics that indicate how overcommitted the CPU, memory,
	  and IO capacity are in the system.

	  If you say Y here, the kernel will create /proc/pressure/ with the
	  pressure statistics files cpu, memory, and io. These will indicate
	  the share of walltime in which some or all tasks in the system are
	  delayed due to contention of the respective resource.

	  In kernels with cgroup support, cgroups (cgroup2 only) will
	  have cpu.pressure, memory.pressure, and io.pressure files,
	  which aggregate pressure stalls for the grouped tasks only.

	  For more details see Documentation/accounting/psi.rst.

	  Say N if unsure.

config PSI_DEFAULT_DISABLED
	bool "Require boot parameter to enable pressure stall information tracking"
	default n
	depends on PSI
	help
	  If set, pressure stall information tracking will be disabled
	  per default but can be enabled through passing psi=1 on the
	  kernel commandline during boot.

	  This feature adds some code to the task wakeup and sleep
	  paths of the scheduler. The overhead is too low to affect
	  common scheduling-intense workloads in practice (such as
	  webservers, memcache), but it does show up in artificial
	  scheduler stress tests, such as hackbench.

	  If you are paranoid and not sure what the kernel will be
	  used for, say Y.

	  Say N if unsure.

endmenu # "CPU/Task time and stats accounting"

config CPU_ISOLATION
	bool "CPU isolation"
	depends on SMP || COMPILE_TEST
	default y
	help
	  Make sure that CPUs running critical tasks are not disturbed by
	  any source of "noise" such as unbound workqueues, timers, kthreads...
	  Unbound jobs get offloaded to housekeeping CPUs. This is driven by
	  the "isolcpus=" boot parameter.

	  Say Y if unsure.

source "kernel/rcu/Kconfig"

config BUILD_BIN2C
	bool
	default n

config IKCONFIG
	tristate "Kernel .config support"
	---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.

config IKHEADERS
	tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
	depends on SYSFS
	help
	  This option enables access to the in-kernel headers that are generated during
	  the build process. These can be used to build eBPF tracing programs,
	  or similar programs.  If you build the headers as a module, a module called
	  kheaders.ko is built which can be loaded on-demand to get access to headers.

config LOG_BUF_SHIFT
	int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
	range 12 25
	default 17
	depends on PRINTK
	help
	  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.

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

config LOG_CPU_MAX_BUF_SHIFT
	int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
	depends on SMP
	range 0 21
	default 12 if !BASE_SMALL
	default 0 if BASE_SMALL
	depends on PRINTK
	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
	  hotplugging making the computation optimal for the worst case
	  scenario while allowing a simple algorithm to be used from bootup.

	  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

config PRINTK_SAFE_LOG_BUF_SHIFT
	int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
	range 10 21
	default 13
	depends on PRINTK
	help
	  Select the size of an alternate printk per-CPU buffer where messages
	  printed from usafe contexts are temporary stored. One example would
	  be NMI messages, another one - printk recursion. The messages 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.

	  Those 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

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

config GENERIC_SCHED_CLOCK
	bool

menu "Scheduler features"

config UCLAMP_TASK
	bool "Enable utilization clamping for RT/FAIR tasks"
	depends on CPU_FREQ_GOV_SCHEDUTIL
	help
	  This feature enables the scheduler to track the clamped utilization
	  of each CPU based on RUNNABLE tasks scheduled on that CPU.

	  With this option, the user can specify the min and max CPU
	  utilization allowed for RUNNABLE tasks. The max utilization defines
	  the maximum frequency a task should use while the min utilization
	  defines the minimum frequency it should use.

	  Both min and max utilization clamp values are hints to the scheduler,
	  aiming at improving its frequency selection policy, but they do not
	  enforce or grant any specific bandwidth for tasks.

	  If in doubt, say N.

config UCLAMP_BUCKETS_COUNT
	int "Number of supported utilization clamp buckets"
	range 5 20
	default 5
	depends on UCLAMP_TASK
	help
	  Defines the number of clamp buckets to use. The range of each bucket
	  will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
	  number of clamp buckets the finer their granularity and the higher
	  the precision of clamping aggregation and tracking at run-time.

	  For example, with the minimum configuration value we will have 5
	  clamp buckets tracking 20% utilization each. A 25% boosted tasks will
	  be refcounted in the [20..39]% bucket and will set the bucket clamp
	  effective value to 25%.
	  If a second 30% boosted task should be co-scheduled on the same CPU,
	  that task will be refcounted in the same bucket of the first task and
	  it will boost the bucket clamp effective value to 30%.
	  The clamp effective value of a bucket is reset to its nominal value
	  (20% in the example above) when there are no more tasks refcounted in
	  that bucket.

	  An additional boost/capping margin can be added to some tasks. In the
	  example above the 25% task will be boosted to 30% until it exits the
	  CPU. If that should be considered not acceptable on certain systems,
	  it's always possible to reduce the margin by increasing the number of
	  clamp buckets to trade off used memory for run-time tracking
	  precision.

	  If in doubt, use the default value.

endmenu

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

#
# 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

config CC_HAS_INT128
	def_bool y
	depends on !$(cc-option,-D__SIZEOF_INT128__=0)

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

# 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
	  it has references to the node the task is running on.

	  This system will be inactive on UMA systems.

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.

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

	  Say N if unsure.

if CGROUPS

config PAGE_COUNTER
	bool

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

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

config MEMCG_SWAP_ENABLED
	bool "Swap controller enabled by default"
	depends on MEMCG_SWAP
	default y
	help
	  Memory Resource Controller Swap Extension comes with its price in
	  a bigger memory consumption. General purpose distribution kernels
	  which want to enable the feature but keep it disabled by default
	  and let the user enable it by swapaccount=1 boot command line
	  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
	  then swapaccount=0 does the trick).

config MEMCG_KMEM
	bool
	depends on MEMCG && !SLOB
	default y

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

	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.

	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.

	See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.

config CGROUP_WRITEBACK
	bool
	depends on MEMCG && BLK_CGROUP
	default y

menuconfig CGROUP_SCHED
	bool "CPU controller"
	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

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 Documentation/scheduler/sched-bwc.rst for more information.

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
	  to task groups. If enabled, it will also make it impossible to
	  schedule realtime tasks for non-root users until you allocate
	  realtime bandwidth for them.
	  See Documentation/scheduler/sched-rt-group.rst for more information.

endif #CGROUP_SCHED

config UCLAMP_TASK_GROUP
	bool "Utilization clamping per group of tasks"
	depends on CGROUP_SCHED
	depends on UCLAMP_TASK
	default n
	help
	  This feature enables the scheduler to track the clamped utilization
	  of each CPU based on RUNNABLE tasks currently scheduled on that CPU.

	  When this option is enabled, the user can specify a min and max
	  CPU bandwidth which is allowed for each single task in a group.
	  The max bandwidth allows to clamp the maximum frequency a task
	  can use, while the min bandwidth allows to define a minimum
	  frequency a task will always use.

	  When task group based utilization clamping is enabled, an eventually
	  specified task-specific clamp value is constrained by the cgroup
	  specified clamp value. Both minimum and maximum task clamping cannot
	  be bigger than the corresponding clamping defined at task group level.

	  If in doubt, say N.

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
	  PIDs controller is designed to stop this from happening.

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

config CGROUP_RDMA
	bool "RDMA controller"
	help
	  Provides enforcement of RDMA resources defined by IB stack.
	  It is fairly easy for consumers to exhaust RDMA resources, which
	  can result into resource unavailability to other consumers.
	  RDMA controller is designed to stop this from happening.
	  Attaching processes with active RDMA resources to the cgroup
	  hierarchy is allowed even if can cross the hierarchy's limit.

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

	  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.

config CGROUP_HUGETLB
	bool "HugeTLB controller"
	depends on HUGETLB_PAGE
	select PAGE_COUNTER
	default n
	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.

config CPUSETS
	bool "Cpuset controller"
	depends on SMP
	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.

	  Say N if unsure.

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

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_BPF
	bool "Support for eBPF programs attached to cgroups"
	depends on BPF_SYSCALL
	select SOCK_CGROUP_DATA
	help
	  Allow attaching eBPF programs to a cgroup using the bpf(2)
	  syscall command BPF_PROG_ATTACH.

	  In which context these programs are accessed depends on the type
	  of attachment. For instance, programs that are attached using
	  BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
	  inet sockets.

config CGROUP_DEBUG
	bool "Debug controller"
	default n
	depends on DEBUG_KERNEL
	help
	  This option enables a simple controller that exports
	  debugging information about the cgroups framework. This
	  controller is for control cgroup debugging only. Its
	  interfaces are not stable.

	  Say N.

config SOCK_CGROUP_DATA
	bool
	default n

endif # CGROUPS

menuconfig NAMESPACES
	bool "Namespaces support" if EXPERT
	depends on MULTIUSER
	default !EXPERT
	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.

if NAMESPACES

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

config TIME_NS
	bool "TIME namespace"
	depends on GENERIC_VDSO_TIME_NS
	default y
	help
	  In this namespace boottime and monotonic clocks can be set.
	  The time will keep going with the same pace.

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

config USER_NS
	bool "User namespace"
	default n
	help
	  This allows containers, i.e. vservers, to use user namespaces
	  to provide different user info for different servers.

	  When user namespaces are enabled in the kernel it is
	  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.

	  If unsure, say N.

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

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

endif # NAMESPACES

config CHECKPOINT_RESTORE
	bool "Checkpoint/restore support"
	select PROC_CHILDREN
	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.

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.

config SYSFS_DEPRECATED
	bool "Enable deprecated sysfs features to support old userspace tools"
	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
	bool "Enable deprecated sysfs features by default"
	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)"
	select IRQ_WORK
	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.

config BLK_DEV_INITRD
	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
	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/admin-guide/initrd.rst> 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.

if BLK_DEV_INITRD

source "usr/Kconfig"

endif

config BOOT_CONFIG
	bool "Boot config support"
	select BLK_DEV_INITRD
	help
	  Extra boot config allows system admin to pass a config file as
	  complemental extension of kernel cmdline when booting.
	  The boot config file must be attached at the end of initramfs
	  with checksum, size and magic word.
	  See <file:Documentation/admin-guide/bootconfig.rst> for details.

	  If unsure, say Y.

choice
	prompt "Compiler optimization level"
	default CC_OPTIMIZE_FOR_PERFORMANCE

config CC_OPTIMIZE_FOR_PERFORMANCE
	bool "Optimize for performance (-O2)"
	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.

config CC_OPTIMIZE_FOR_PERFORMANCE_O3
	bool "Optimize more for performance (-O3)"
	depends on ARC
	imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED  # avoid false positives
	help
	  Choosing this option will pass "-O3" to your compiler to optimize
	  the kernel yet more for performance.

config CC_OPTIMIZE_FOR_SIZE
	bool "Optimize for size (-Os)"
	imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED  # avoid false positives
	help
	  Choosing this option will pass "-Os" to your compiler resulting
	  in a smaller kernel.

endchoice

config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
	bool
	help
	  This requires that the arch annotates or otherwise protects
	  its external entry points from being discarded. Linker scripts
	  must also merge .text.*, .data.*, and .bss.* correctly into
	  output sections. Care must be taken not to pull in unrelated
	  sections (e.g., '.text.init'). Typically '.' in section names
	  is used to distinguish them from label names / C identifiers.

config LD_DEAD_CODE_DATA_ELIMINATION
	bool "Dead code and data elimination (EXPERIMENTAL)"
	depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
	depends on EXPERT
	depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800)
	depends on $(cc-option,-ffunction-sections -fdata-sections)
	depends on $(ld-option,--gc-sections)
	help
	  Enable this if you want to do dead code and data elimination with
	  the linker by compiling with -ffunction-sections -fdata-sections,
	  and linking with --gc-sections.

	  This can reduce on disk and in-memory size of the kernel
	  code and static data, particularly for small configs and
	  on small systems. This has the possibility of introducing
	  silently broken kernel if the required annotations are not
	  present. This option is not well tested yet, so use at your
	  own risk.

config SYSCTL
	bool

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

# interpreter that classic socket filters depend on
config BPF
	bool

menuconfig EXPERT
	bool "Configure standard kernel features (expert users)"
	# Unhide debug options, to make the on-by-default options visible
	select DEBUG_KERNEL
	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.

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

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.

config SGETMASK_SYSCALL
	bool "sgetmask/ssetmask syscalls support" if EXPERT
	def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || 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.

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.

config FHANDLE
	bool "open by fhandle syscalls" if EXPERT
	select EXPORTFS
	default y
	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.

config POSIX_TIMERS
	bool "Posix Clocks & timers" if EXPERT
	default y
	help
	  This includes native support for POSIX timers to the kernel.
	  Some embedded systems have no use for them and therefore they
	  can be configured out to reduce the size of the kernel image.

	  When this option is disabled, the following syscalls won't be
	  available: timer_create, timer_gettime: timer_getoverrun,
	  timer_settime, timer_delete, clock_adjtime, getitimer,
	  setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
	  clock_getres and clock_nanosleep syscalls will be limited to
	  CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.

	  If unsure say y.

config PRINTK
	default y
	bool "Enable support for printk" if EXPERT
	select IRQ_WORK
	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.

config PRINTK_NMI
	def_bool y
	depends on PRINTK
	depends on HAVE_NMI

config BUG
	bool "BUG() support" if EXPERT
	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.

config ELF_CORE
	depends on COREDUMP
	default y
	bool "Enable ELF core dumps" if EXPERT
	help
	  Enable support for generating core dumps. Disabling saves about 4k.


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

config BASE_FULL
	default y
	bool "Enable full-sized data structures for core" if EXPERT
	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
	bool "Enable futex support" if EXPERT
	default y
	imply RT_MUTEXES
	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.

config FUTEX_PI
	bool
	depends on FUTEX && RT_MUTEXES
	default y

config HAVE_FUTEX_CMPXCHG
	bool
	depends on FUTEX
	help
	  Architectures should select this if futex_atomic_cmpxchg_inatomic()
	  is implemented and always working. This removes a couple of runtime
	  checks.

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

config SIGNALFD
	bool "Enable signalfd() system call" if EXPERT
	default y
	help
	  Enable the signalfd() system call that allows to receive signals
	  on a file descriptor.

	  If unsure, say Y.

config TIMERFD
	bool "Enable timerfd() system call" if EXPERT
	default y
	help
	  Enable the timerfd() system call that allows to receive timer
	  events on a file descriptor.

	  If unsure, say Y.

config EVENTFD
	bool "Enable eventfd() system call" if EXPERT
	default y
	help
	  Enable the eventfd() system call that allows to receive both
	  kernel notification (ie. KAIO) or userspace notifications.

	  If unsure, say Y.

config SHMEM
	bool "Use full shmem filesystem" if EXPERT
	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.

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

config IO_URING
	bool "Enable IO uring support" if EXPERT
	select ANON_INODES
	select IO_WQ
	default y
	help
	  This option enables support for the io_uring interface, enabling
	  applications to submit and complete IO through submission and
	  completion rings that are shared between the kernel and application.

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.

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.

config KALLSYMS
	bool "Load all symbols for debugging/ksymoops" if EXPERT
	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
	  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.

config KALLSYMS_ABSOLUTE_PERCPU
	bool
	depends on KALLSYMS
	default X86_64 && SMP

config KALLSYMS_BASE_RELATIVE
	bool
	depends on KALLSYMS
	default !IA64
	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.

# end of the "standard kernel features (expert users)" menu

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

config ARCH_WANT_DEFAULT_BPF_JIT
	bool

config BPF_JIT_ALWAYS_ON
	bool "Permanently enable BPF JIT and remove BPF interpreter"
	depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
	help
	  Enables BPF JIT and removes BPF interpreter to avoid
	  speculative execution of BPF instructions by the interpreter

config BPF_JIT_DEFAULT_ON
	def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON
	depends on HAVE_EBPF_JIT && BPF_JIT

config USERFAULTFD
	bool "Enable userfaultfd() system call"
	depends on MMU
	help
	  Enable the userfaultfd() system call that allows to intercept and
	  handle page faults in userland.

config ARCH_HAS_MEMBARRIER_CALLBACKS
	bool

config ARCH_HAS_MEMBARRIER_SYNC_CORE
	bool

config RSEQ
	bool "Enable rseq() system call" if EXPERT
	default y
	depends on HAVE_RSEQ
	select MEMBARRIER
	help
	  Enable the restartable sequences system call. It provides a
	  user-space cache for the current CPU number value, which
	  speeds up getting the current CPU number from user-space,
	  as well as an ABI to speed up user-space operations on
	  per-CPU data.

	  If unsure, say Y.

config DEBUG_RSEQ
	default n
	bool "Enabled debugging of rseq() system call" if EXPERT
	depends on RSEQ && DEBUG_KERNEL
	help
	  Enable extra debugging checks for the rseq system call.

	  If unsure, say N.

config EMBEDDED
	bool "Embedded system"
	option allnoconfig_y
	select EXPERT
	help
	  This option should be enabled if compiling the kernel for
	  an embedded system so certain expert options are available
	  for configuration.

config HAVE_PERF_EVENTS
	bool
	help
	  See tools/perf/design.txt for details.

config PERF_USE_VMALLOC
	bool
	help
	  See tools/perf/design.txt for details

config PC104
	bool "PC/104 support" if EXPERT
	help
	  Expose PC/104 form factor device drivers and options available for
	  selection and configuration. Enable this option if your target
	  machine has a PC/104 bus.

menu "Kernel Performance Events And Counters"

config PERF_EVENTS
	bool "Kernel performance events and counters"
	default y if PROFILING
	depends on HAVE_PERF_EVENTS
	select IRQ_WORK
	select SRCU
	help
	  Enable kernel support for various performance events provided
	  by software and hardware.

	  Software events are supported either built-in or via the
	  use of generic tracepoints.

	  Most modern CPUs support performance events via performance
	  counter registers. These registers count the number of certain
	  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.

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

	  Say Y if unsure.

config DEBUG_PERF_USE_VMALLOC
	default n
	bool "Debug: use vmalloc to back perf mmap() buffers"
	depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
	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.

endmenu

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

config SLUB_DEBUG
	default y
	bool "Enable SLUB debugging support" if EXPERT
	depends on SLUB && SYSFS
	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.

config SLUB_MEMCG_SYSFS_ON
	default n
	bool "Enable memcg SLUB sysfs support by default" if EXPERT
	depends on SLUB && SYSFS && MEMCG
	help
	  SLUB creates a directory under /sys/kernel/slab for each
	  allocation cache to host info and debug files. If memory
	  cgroup is enabled, each cache can have per memory cgroup
	  caches. SLUB can create the same sysfs directories for these
	  caches under /sys/kernel/slab/CACHE/cgroup but it can lead
	  to a very high number of debug files being created. This is
	  controlled by slub_memcg_sysfs boot parameter and this
	  config option determines the parameter's default value.

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
	  disabled, and can be overridden at runtime by setting
	  /proc/sys/kernel/randomize_va_space to 2.

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

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

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

config SLUB
	bool "SLUB (Unqueued Allocator)"
	select HAVE_HARDENED_USERCOPY_ALLOCATOR
	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
	   and has enhanced diagnostics. SLUB is the default choice for
	   a slab allocator.

config SLOB
	depends on EXPERT
	bool "SLOB (Simple Allocator)"
	help
	   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.

endchoice

config SLAB_MERGE_DEFAULT
	bool "Allow slab caches to be merged"
	default y
	help
	  For reduced kernel memory fragmentation, slab caches can be
	  merged when they share the same size and other characteristics.
	  This carries a risk of kernel heap overflows being able to
	  overwrite objects from merged caches (and more easily control
	  cache layout), which makes such heap attacks easier to exploit
	  by attackers. By keeping caches unmerged, these kinds of exploits
	  can usually only damage objects in the same cache. To disable
	  merging at runtime, "slab_nomerge" can be passed on the kernel
	  command line.

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

config SLAB_FREELIST_HARDENED
	bool "Harden slab freelist metadata"
	depends on SLUB
	help
	  Many kernel heap attacks try to target slab cache metadata and
	  other infrastructure. This options makes minor performance
	  sacrifices to harden the kernel slab allocator against common
	  freelist exploit methods.

config SHUFFLE_PAGE_ALLOCATOR
	bool "Page allocator randomization"
	default SLAB_FREELIST_RANDOM && ACPI_NUMA
	help
	  Randomization of the page allocator improves the average
	  utilization of a direct-mapped memory-side-cache. See section
	  5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
	  6.2a specification for an example of how a platform advertises
	  the presence of a memory-side-cache. There are also incidental
	  security benefits as it reduces the predictability of page
	  allocations to compliment SLAB_FREELIST_RANDOM, but the
	  default granularity of shuffling on the "MAX_ORDER - 1" i.e,
	  10th order of pages is selected based on cache utilization
	  benefits on x86.

	  While the randomization improves cache utilization it may
	  negatively impact workloads on platforms without a cache. For
	  this reason, by default, the randomization is enabled only
	  after runtime detection of a direct-mapped memory-side-cache.
	  Otherwise, the randomization may be force enabled with the
	  'page_alloc.shuffle' kernel command line parameter.

	  Say Y if unsure.

config SLUB_CPU_PARTIAL
	default y
	depends on SLUB && SMP
	bool "SLUB per cpu partial cache"
	help
	  Per cpu partial caches accelerate 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.

config MMAP_ALLOW_UNINITIALIZED
	bool "Allow mmapped anonymous memory to be uninitialized"
	depends on EXPERT && !MMU
	default n
	help
	  Normally, and according to the Linux spec, anonymous memory obtained
	  from mmap() has its 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.

config SYSTEM_DATA_VERIFICATION
	def_bool n
	select SYSTEM_TRUSTED_KEYRING
	select KEYS
	select CRYPTO
	select CRYPTO_RSA
	select ASYMMETRIC_KEY_TYPE
	select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
	select ASN1
	select OID_REGISTRY
	select X509_CERTIFICATE_PARSER
	select PKCS7_MESSAGE_PARSER
	help
	  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.

config PROFILING
	bool "Profiling support"
	help
	  Say Y here to enable the extended profiling support mechanisms used
	  by profilers such as OProfile.

#
# Place an empty function call at each tracepoint site. Can be
# dynamically changed for a probe function.
#
config TRACEPOINTS
	bool

endmenu		# General setup

source "arch/Kconfig"

config RT_MUTEXES
	bool

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

config MODULE_SIG_FORMAT
	def_bool n
	select SYSTEM_DATA_VERIFICATION

menuconfig MODULES
	bool "Enable loadable module support"
	option modules
	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.

if MODULES

config MODULE_FORCE_LOAD
	bool "Forced module loading"
	default n
	help
	  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.

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
	  anyway), which makes your kernel smaller, faster
	  and simpler.  If unsure, say Y.

config MODULE_FORCE_UNLOAD
	bool "Forced module unloading"
	depends on MODULE_UNLOAD
	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
	bool "Module versioning support"
	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 ASM_MODVERSIONS
	bool
	default HAVE_ASM_MODVERSIONS && MODVERSIONS
	help
	  This enables module versioning for exported symbols also from
	  assembly. This can be enabled only when the target architecture
	  supports it.

config MODULE_REL_CRCS
	bool
	depends on MODVERSIONS

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.

config MODULE_SIG
	bool "Module signature verification"
	select MODULE_SIG_FORMAT
	help
	  Check modules for valid signatures upon load: the signature
	  is simply appended to the module. For more information see
	  <file:Documentation/admin-guide/module-signing.rst>.

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

	  You should enable this option if you wish to use either
	  CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via
	  another LSM - otherwise unsigned modules will be loadable regardless
	  of the lockdown policy.

	  !!!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.

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.

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

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

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

config MODULE_COMPRESS
	bool "Compress modules on installation"
	help

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

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

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

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

	  Note: This is fully compatible with signed modules.

	  If in doubt, say N.

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

config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
	bool "Allow loading of modules with missing namespace imports"
	help
	  Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in
	  a namespace. A module that makes use of a symbol exported with such a
	  namespace is required to import the namespace via MODULE_IMPORT_NS().
	  There is no technical reason to enforce correct namespace imports,
	  but it creates consistency between symbols defining namespaces and
	  users importing namespaces they make use of. This option relaxes this
	  requirement and lifts the enforcement when loading a module.

	  If unsure, say N.

config UNUSED_SYMBOLS
	bool "Enable unused/obsolete exported symbols"
	default y if X86
	help
	  Unused but exported symbols make the kernel needlessly bigger.  For
	  that reason most of these unused exports will soon be removed.  This
	  option is provided temporarily to provide a transition period in case
	  some external kernel module needs one of these symbols anyway. If you
	  encounter such a case in your module, consider if you are actually
	  using the right API.  (rationale: since nobody in the kernel is using
	  this in a module, there is a pretty good chance it's actually the
	  wrong interface to use).  If you really need the symbol, please send a
	  mail to the linux kernel mailing list mentioning the symbol and why
	  you really need it, and what the merge plan to the mainline kernel for
	  your module is.

config TRIM_UNUSED_KSYMS
	bool "Trim unused exported kernel symbols"
	depends on !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.

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

endif # MODULES

config MODULES_TREE_LOOKUP
	def_bool y
	depends on PERF_EVENTS || TRACING

config INIT_ALL_POSSIBLE
	bool
	help
	  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
	  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
	  and have several arch maintainers pursuing me down dark alleys.

source "block/Kconfig"

config PREEMPT_NOTIFIERS
	bool

config PADATA
	depends on SMP
	bool

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.

source "kernel/Kconfig.locks"

config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
	bool

# It may be useful for an architecture to override the definitions of the
# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
# and the COMPAT_ variants in <linux/compat.h>, in particular to use a
# different calling convention for syscalls. They can also override the
# macros for not-implemented syscalls in kernel/sys_ni.c and
# kernel/time/posix-stubs.c. All these overrides need to be available in
# <asm/syscall_wrapper.h>.
config ARCH_HAS_SYSCALL_WRAPPER
	def_bool n