v4.19.13 snapshot.
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+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 -p $(CC) | sed 's/^0*//') 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 CONSTRUCTORS
+ bool
+ depends on !UML
+
+config IRQ_WORK
+ bool
+
+config BUILDTIME_EXTABLE_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 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) <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
+ 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
+
+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"
+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
+ 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.
+
+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"
+ select BUILD_BIN2C
+ ---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 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
+
+#
+# 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
+
+#
+# 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.txt (CFS)
+ - Documentation/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/cgroup-v1/blkio-controller.txt for more information.
+
+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
+
+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.txt 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.txt for more information.
+
+endif #CGROUP_SCHED
+
+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 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
+
+choice
+ prompt "Compiler optimization level"
+ default 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.
+
+config CC_OPTIMIZE_FOR_SIZE
+ bool "Optimize for size"
+ help
+ Enabling this option will pass "-Os" instead of "-O2" to
+ your compiler resulting in a smaller kernel.
+
+ If unsure, say N.
+
+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 $(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 ANON_INODES
+ 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 SYSCTL_SYSCALL
+ bool "Sysctl syscall support" if EXPERT
+ depends on PROC_SYSCTL
+ default n
+ select SYSCTL
+ ---help---
+ 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.
+
+ 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.
+
+ If unsure say N 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
+ select ANON_INODES
+ 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
+ select ANON_INODES
+ 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
+ select ANON_INODES
+ 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
+ select ANON_INODES
+ 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 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 ANON_INODES
+ 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 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 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.
+
+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 ANON_INODES
+ 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
+ sacrifies to harden the kernel slab allocator against common
+ freelist exploit methods.
+
+config SLUB_CPU_PARTIAL
+ default y
+ depends on SLUB && SMP
+ 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.
+
+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
+
+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 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"
+ depends on MODULES
+ select SYSTEM_DATA_VERIFICATION
+ 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.
+
+ !!!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"
+ depends on MODULES
+ 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 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.
+
+ 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