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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 CC_HAS_ASM_GOTO
- def_bool $(success,$(srctree)/scripts/gcc-goto.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 !(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 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
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