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# SPDX-License-Identifier: GPL-2.0-only
config CC_VERSION_TEXT
string
default "$(CC_VERSION_TEXT)"
help
This is used in unclear ways:
- Re-run Kconfig when the compiler is updated
The 'default' property references the environment variable,
CC_VERSION_TEXT so it is recorded in include/config/auto.conf.cmd.
When the compiler is updated, Kconfig will be invoked.
- Ensure full rebuild when the compiler is updated
include/linux/compiler-version.h contains this option in the comment
line so fixdep adds include/config/CC_VERSION_TEXT into the
auto-generated dependency. When the compiler is updated, syncconfig
will touch it and then every file will be rebuilt.
config CC_IS_GCC
def_bool $(success,test "$(cc-name)" = GCC)
config GCC_VERSION
int
default $(cc-version) if CC_IS_GCC
default 0
config CC_IS_CLANG
def_bool $(success,test "$(cc-name)" = Clang)
config CLANG_VERSION
int
default $(cc-version) if CC_IS_CLANG
default 0
config AS_IS_GNU
def_bool $(success,test "$(as-name)" = GNU)
config AS_IS_LLVM
def_bool $(success,test "$(as-name)" = LLVM)
config AS_VERSION
int
# Use clang version if this is the integrated assembler
default CLANG_VERSION if AS_IS_LLVM
default $(as-version)
config LD_IS_BFD
def_bool $(success,test "$(ld-name)" = BFD)
config LD_VERSION
int
default $(ld-version) if LD_IS_BFD
default 0
config LD_IS_LLD
def_bool $(success,test "$(ld-name)" = LLD)
config LLD_VERSION
int
default $(ld-version) if LD_IS_LLD
default 0
config RUSTC_VERSION
int
default $(shell,$(srctree)/scripts/rustc-version.sh $(RUSTC))
help
It does not depend on `RUST` since that one may need to use the version
in a `depends on`.
config RUST_IS_AVAILABLE
def_bool $(success,$(srctree)/scripts/rust_is_available.sh)
help
This shows whether a suitable Rust toolchain is available (found).
Please see Documentation/rust/quick-start.rst for instructions on how
to satisfy the build requirements of Rust support.
In particular, the Makefile target 'rustavailable' is useful to check
why the Rust toolchain is not being detected.
config CC_CAN_LINK
bool
default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT
default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag))
config CC_CAN_LINK_STATIC
bool
default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag) -static) if 64BIT
default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag) -static)
# Fixed in GCC 14, 13.3, 12.4 and 11.5
# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113921
config GCC_ASM_GOTO_OUTPUT_BROKEN
bool
depends on CC_IS_GCC
default y if GCC_VERSION < 110500
default y if GCC_VERSION >= 120000 && GCC_VERSION < 120400
default y if GCC_VERSION >= 130000 && GCC_VERSION < 130300
config CC_HAS_ASM_GOTO_OUTPUT
def_bool y
depends on !GCC_ASM_GOTO_OUTPUT_BROKEN
depends on $(success,echo 'int foo(int x) { asm goto ("": "=r"(x) ::: bar); return x; bar: return 0; }' | $(CC) -x c - -c -o /dev/null)
config CC_HAS_ASM_GOTO_TIED_OUTPUT
depends on CC_HAS_ASM_GOTO_OUTPUT
# Detect buggy gcc and clang, fixed in gcc-11 clang-14.
def_bool $(success,echo 'int foo(int *x) { asm goto (".long (%l[bar]) - .": "+m"(*x) ::: bar); return *x; bar: return 0; }' | $CC -x c - -c -o /dev/null)
config TOOLS_SUPPORT_RELR
def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
config CC_HAS_ASM_INLINE
def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
config CC_HAS_NO_PROFILE_FN_ATTR
def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror)
config PAHOLE_VERSION
int
default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE))
config CONSTRUCTORS
bool
config IRQ_WORK
def_bool y if SMP
config BUILDTIME_TABLE_SORT
bool
config THREAD_INFO_IN_TASK
bool
help
Select this to move thread_info off the stack into task_struct. To
make this work, an arch will need to remove all thread_info fields
except flags and fix any runtime bugs.
One subtle change that will be needed is to use try_get_task_stack()
and put_task_stack() in save_thread_stack_tsk() and get_wchan().
menu "General setup"
config BROKEN
bool
config BROKEN_ON_SMP
bool
depends on BROKEN || !SMP
default y
config INIT_ENV_ARG_LIMIT
int
default 32 if !UML
default 128 if UML
help
Maximum of each of the number of arguments and environment
variables passed to init from the kernel command line.
config COMPILE_TEST
bool "Compile also drivers which will not load"
depends on HAS_IOMEM
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 WERROR
bool "Compile the kernel with warnings as errors"
default y
help
A kernel build should not cause any compiler warnings, and this
enables the '-Werror' (for C) and '-Dwarnings' (for Rust) flags
to enforce that rule by default. Certain warnings from other tools
such as the linker may be upgraded to errors with this option as
well.
However, if you have a new (or very old) compiler or linker with odd
and unusual warnings, or you have some architecture with problems,
you may need to disable this config option in order to
successfully build the kernel.
If in doubt, say Y.
config UAPI_HEADER_TEST
bool "Compile test UAPI headers"
depends on HEADERS_INSTALL && CC_CAN_LINK
help
Compile test headers exported to user-space to ensure they are
self-contained, i.e. compilable as standalone units.
If you are a developer or tester and want to ensure the exported
headers are self-contained, say Y here. Otherwise, choose N.
config LOCALVERSION
string "Local version - append to kernel release"
help
Append an extra string to the end of your kernel version.
This will show up when you type uname, for example.
The string you set here will be appended after the contents of
any files with a filename matching localversion* in your
object and source tree, in that order. Your total string can
be a maximum of 64 characters.
config LOCALVERSION_AUTO
bool "Automatically append version information to the version string"
default y
depends on !COMPILE_TEST
help
This will try to automatically determine if the current tree is a
release tree by looking for git tags that belong to the current
top of tree revision.
A string of the format -gxxxxxxxx will be added to the localversion
if a git-based tree is found. The string generated by this will be
appended after any matching localversion* files, and after the value
set in CONFIG_LOCALVERSION.
(The actual string used here is the first 12 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_ZSTD
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_ZSTD || 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, ARM64, RISC-V, big endian 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_ZSTD
bool "ZSTD"
depends on HAVE_KERNEL_ZSTD
help
ZSTD is a compression algorithm targeting intermediate compression
with fast decompression speed. It will compress better than GZIP and
decompress around the same speed as LZO, but slower than LZ4. You
will need at least 192 KB RAM or more for booting. The zstd command
line tool is required for compression.
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_INIT
string "Default init path"
default ""
help
This option determines the default init for the system if no init=
option is passed on the kernel command line. If the requested path is
not present, we will still then move on to attempting further
locations (e.g. /sbin/init, etc). If this is empty, we will just use
the fallback list when init= is not passed.
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.
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 SYSVIPC_COMPAT
def_bool y
depends on COMPAT && SYSVIPC
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 WATCH_QUEUE
bool "General notification queue"
default n
help
This is a general notification queue for the kernel to pass events to
userspace by splicing them into pipes. It can be used in conjunction
with watches for key/keyring change notifications and device
notifications.
See Documentation/core-api/watch_queue.rst
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 (for libc5 and earlier)"
default ALPHA || M68K || SPARC
help
This option enables the uselib syscall, a system call used in the
dynamic linker from libc5 and earlier. glibc does not use this
system call. If you intend to run programs built on libc5 or
earlier, you may need to enable this syscall. Current systems
running glibc can safely disable this.
config AUDIT
bool "Auditing support"
depends on NET
help
Enable auditing infrastructure that can be used with another
kernel subsystem, such as SELinux (which requires this for
logging of avc messages output). System call auditing is included
on architectures which support it.
config HAVE_ARCH_AUDITSYSCALL
bool
config AUDITSYSCALL
def_bool y
depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
select FSNOTIFY
source "kernel/irq/Kconfig"
source "kernel/time/Kconfig"
source "kernel/bpf/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
# 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_USER
depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
depends on GENERIC_CLOCKEVENTS
select VIRT_CPU_ACCOUNTING
select CONTEXT_TRACKING_USER
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 SCHED_HW_PRESSURE
bool
default y if ARM && ARM_CPU_TOPOLOGY
default y if ARM64
depends on SMP
depends on CPU_FREQ_THERMAL
help
Select this option to enable HW pressure accounting in the
scheduler. HW pressure is the value conveyed to the scheduler
that reflects the reduction in CPU compute capacity resulted from
HW throttling. HW throttling occurs when the performance of
a CPU is capped due to high operating temperatures as an example.
If selected, the scheduler will be able to balance tasks accordingly,
i.e. put less load on throttled CPUs than on non/less throttled ones.
This requires the architecture to implement
arch_update_hw_pressure() and arch_scale_thermal_pressure().
config BSD_PROCESS_ACCT
bool "BSD Process Accounting"
depends on MULTIUSER
help
If you say Y here, a user level program will be able to instruct the
kernel (via a special system call) to write process accounting
information to a file: whenever a process exits, information about
that process will be appended to the file by the kernel. The
information includes things such as creation time, owning user,
command name, memory usage, controlling terminal etc. (the complete
list is in the struct acct in <file:include/linux/acct.h>). It is
up to the user level program to do useful things with this
information. This is generally a good idea, so say Y.
config BSD_PROCESS_ACCT_V3
bool "BSD Process Accounting version 3 file format"
depends on BSD_PROCESS_ACCT
default n
help
If you say Y here, the process accounting information is written
in a new file format that also logs the process IDs of each
process and its parent. Note that this file format is incompatible
with previous v0/v1/v2 file formats, so you will need updated tools
for processing it. A preliminary version of these tools is available
at <http://www.gnu.org/software/acct/>.
config TASKSTATS
bool "Export task/process statistics through netlink"
depends on NET
depends on MULTIUSER
default n
help
Export selected statistics for tasks/processes through the
generic netlink interface. Unlike BSD process accounting, the
statistics are available during the lifetime of tasks/processes as
responses to commands. Like BSD accounting, they are sent to user
space on task exit.
Say N if unsure.
config TASK_DELAY_ACCT
bool "Enable per-task delay accounting"
depends on TASKSTATS
select SCHED_INFO
help
Collect information on time spent by a task waiting for system
resources like cpu, synchronous block I/O completion and swapping
in pages. Such statistics can help in setting a task's priorities
relative to other tasks for cpu, io, rss limits etc.
Say N if unsure.
config TASK_XACCT
bool "Enable extended accounting over taskstats"
depends on TASKSTATS
help
Collect extended task accounting data and send the data
to userland for processing over the taskstats interface.
Say N if unsure.
config TASK_IO_ACCOUNTING
bool "Enable per-task storage I/O accounting"
depends on TASK_XACCT
help
Collect information on the number of bytes of storage I/O which this
task has caused.
Say N if unsure.
config PSI
bool "Pressure stall information tracking"
select KERNFS
help
Collect metrics that indicate how overcommitted the CPU, memory,
and IO capacity are in the system.
If you say Y here, the kernel will create /proc/pressure/ with the
pressure statistics files cpu, memory, and io. These will indicate
the share of walltime in which some or all tasks in the system are
delayed due to contention of the respective resource.
In kernels with cgroup support, cgroups (cgroup2 only) will
have cpu.pressure, memory.pressure, and io.pressure files,
which aggregate pressure stalls for the grouped tasks only.
For more details see Documentation/accounting/psi.rst.
Say N if unsure.
config PSI_DEFAULT_DISABLED
bool "Require boot parameter to enable pressure stall information tracking"
default n
depends on PSI
help
If set, pressure stall information tracking will be disabled
per default but can be enabled through passing psi=1 on the
kernel commandline during boot.
This feature adds some code to the task wakeup and sleep
paths of the scheduler. The overhead is too low to affect
common scheduling-intense workloads in practice (such as
webservers, memcache), but it does show up in artificial
scheduler stress tests, such as hackbench.
If you are paranoid and not sure what the kernel will be
used for, say Y.
Say N if unsure.
endmenu # "CPU/Task time and stats accounting"
config CPU_ISOLATION
bool "CPU isolation"
depends on SMP || COMPILE_TEST
default y
help
Make sure that CPUs running critical tasks are not disturbed by
any source of "noise" such as unbound workqueues, timers, kthreads...
Unbound jobs get offloaded to housekeeping CPUs. This is driven by
the "isolcpus=" boot parameter.
Say Y if unsure.
source "kernel/rcu/Kconfig"
config IKCONFIG
tristate "Kernel .config support"
help
This option enables the complete Linux kernel ".config" file
contents to be saved in the kernel. It provides documentation
of which kernel options are used in a running kernel or in an
on-disk kernel. This information can be extracted from the kernel
image file with the script scripts/extract-ikconfig and used as
input to rebuild the current kernel or to build another kernel.
It can also be extracted from a running kernel by reading
/proc/config.gz if enabled (below).
config IKCONFIG_PROC
bool "Enable access to .config through /proc/config.gz"
depends on IKCONFIG && PROC_FS
help
This option enables access to the kernel configuration file
through /proc/config.gz.
config IKHEADERS
tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
depends on SYSFS
help
This option enables access to the in-kernel headers that are generated during
the build process. These can be used to build eBPF tracing programs,
or similar programs. If you build the headers as a module, a module called
kheaders.ko is built which can be loaded on-demand to get access to headers.
config LOG_BUF_SHIFT
int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
range 12 25
default 17
depends on PRINTK
help
Select the minimal kernel log buffer size as a power of 2.
The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
parameter, see below. Any higher size also might be forced
by "log_buf_len" boot parameter.
Examples:
17 => 128 KB
16 => 64 KB
15 => 32 KB
14 => 16 KB
13 => 8 KB
12 => 4 KB
config LOG_CPU_MAX_BUF_SHIFT
int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
depends on SMP
range 0 21
default 0 if BASE_SMALL
default 12
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 16 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_INDEX
bool "Printk indexing debugfs interface"
depends on PRINTK && DEBUG_FS
help
Add support for indexing of all printk formats known at compile time
at <debugfs>/printk/index/<module>.
This can be used as part of maintaining daemons which monitor
/dev/kmsg, as it permits auditing the printk formats present in a
kernel, allowing detection of cases where monitored printks are
changed or no longer present.
There is no additional runtime cost to printk with this enabled.
#
# Architectures with an unreliable sched_clock() should select this:
#
config HAVE_UNSTABLE_SCHED_CLOCK
bool
config GENERIC_SCHED_CLOCK
bool
menu "Scheduler features"
config UCLAMP_TASK
bool "Enable utilization clamping for RT/FAIR tasks"
depends on CPU_FREQ_GOV_SCHEDUTIL
help
This feature enables the scheduler to track the clamped utilization
of each CPU based on RUNNABLE tasks scheduled on that CPU.
With this option, the user can specify the min and max CPU
utilization allowed for RUNNABLE tasks. The max utilization defines
the maximum frequency a task should use while the min utilization
defines the minimum frequency it should use.
Both min and max utilization clamp values are hints to the scheduler,
aiming at improving its frequency selection policy, but they do not
enforce or grant any specific bandwidth for tasks.
If in doubt, say N.
config UCLAMP_BUCKETS_COUNT
int "Number of supported utilization clamp buckets"
range 5 20
default 5
depends on UCLAMP_TASK
help
Defines the number of clamp buckets to use. The range of each bucket
will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
number of clamp buckets the finer their granularity and the higher
the precision of clamping aggregation and tracking at run-time.
For example, with the minimum configuration value we will have 5
clamp buckets tracking 20% utilization each. A 25% boosted tasks will
be refcounted in the [20..39]% bucket and will set the bucket clamp
effective value to 25%.
If a second 30% boosted task should be co-scheduled on the same CPU,
that task will be refcounted in the same bucket of the first task and
it will boost the bucket clamp effective value to 30%.
The clamp effective value of a bucket is reset to its nominal value
(20% in the example above) when there are no more tasks refcounted in
that bucket.
An additional boost/capping margin can be added to some tasks. In the
example above the 25% task will be boosted to 30% until it exits the
CPU. If that should be considered not acceptable on certain systems,
it's always possible to reduce the margin by increasing the number of
clamp buckets to trade off used memory for run-time tracking
precision.
If in doubt, use the default value.
endmenu
#
# For architectures that want to enable the support for NUMA-affine scheduler
# balancing logic:
#
config ARCH_SUPPORTS_NUMA_BALANCING
bool
#
# For architectures that prefer to flush all TLBs after a number of pages
# are unmapped instead of sending one IPI per page to flush. The architecture
# must provide guarantees on what happens if a clean TLB cache entry is
# written after the unmap. Details are in mm/rmap.c near the check for
# should_defer_flush. The architecture should also consider if the full flush
# and the refill costs are offset by the savings of sending fewer IPIs.
config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
bool
config CC_HAS_INT128
def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
config CC_IMPLICIT_FALLTHROUGH
string
default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5)
default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough)
# Currently, disable gcc-10+ array-bounds globally.
# It's still broken in gcc-13, so no upper bound yet.
config GCC10_NO_ARRAY_BOUNDS
def_bool y
config CC_NO_ARRAY_BOUNDS
bool
default y if CC_IS_GCC && GCC_VERSION >= 90000 && GCC10_NO_ARRAY_BOUNDS
# Currently, disable -Wstringop-overflow for GCC globally.
config GCC_NO_STRINGOP_OVERFLOW
def_bool y
config CC_NO_STRINGOP_OVERFLOW
bool
default y if CC_IS_GCC && GCC_NO_STRINGOP_OVERFLOW
config CC_STRINGOP_OVERFLOW
bool
default y if CC_IS_GCC && !CC_NO_STRINGOP_OVERFLOW
#
# 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 && !PREEMPT_RT
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.
config SLAB_OBJ_EXT
bool
menuconfig CGROUPS
bool "Control Group support"
select KERNFS
help
This option adds support for grouping sets of processes together, for
use with process control subsystems such as Cpusets, CFS, memory
controls or device isolation.
See
- Documentation/scheduler/sched-design-CFS.rst (CFS)
- Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
and resource control)
Say N if unsure.
if CGROUPS
config PAGE_COUNTER
bool
config CGROUP_FAVOR_DYNMODS
bool "Favor dynamic modification latency reduction by default"
help
This option enables the "favordynmods" mount option by default
which reduces the latencies of dynamic cgroup modifications such
as task migrations and controller on/offs at the cost of making
hot path operations such as forks and exits more expensive.
Say N if unsure.
config MEMCG
bool "Memory controller"
select PAGE_COUNTER
select EVENTFD
select SLAB_OBJ_EXT
help
Provides control over the memory footprint of tasks in a cgroup.
config MEMCG_V1
bool "Legacy cgroup v1 memory controller"
depends on MEMCG
default n
help
Legacy cgroup v1 memory controller which has been deprecated by
cgroup v2 implementation. The v1 is there for legacy applications
which haven't migrated to the new cgroup v2 interface yet. If you
do not have any such application then you are completely fine leaving
this option disabled.
Please note that feature set of the legacy memory controller is likely
going to shrink due to deprecation process. New deployments with v1
controller are highly discouraged.
Say N if unsure.
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_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
CONFIG_BLK_DEV_THROTTLING=y.
See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
config CGROUP_WRITEBACK
bool
depends on MEMCG && BLK_CGROUP
default y
menuconfig CGROUP_SCHED
bool "CPU controller"
default n
help
This feature lets CPU scheduler recognize task groups and control CPU
bandwidth allocation to such task groups. It uses cgroups to group
tasks.
if CGROUP_SCHED
config GROUP_SCHED_WEIGHT
def_bool n
config FAIR_GROUP_SCHED
bool "Group scheduling for SCHED_OTHER"
depends on CGROUP_SCHED
select GROUP_SCHED_WEIGHT
default CGROUP_SCHED
config CFS_BANDWIDTH
bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
depends on FAIR_GROUP_SCHED
default n
help
This option allows users to define CPU bandwidth rates (limits) for
tasks running within the fair group scheduler. Groups with no limit
set are considered to be unconstrained and will run with no
restriction.
See Documentation/scheduler/sched-bwc.rst for more information.
config RT_GROUP_SCHED
bool "Group scheduling for SCHED_RR/FIFO"
depends on CGROUP_SCHED
default n
help
This feature lets you explicitly allocate real CPU bandwidth
to task groups. If enabled, it will also make it impossible to
schedule realtime tasks for non-root users until you allocate
realtime bandwidth for them.
See Documentation/scheduler/sched-rt-group.rst for more information.
config EXT_GROUP_SCHED
bool
depends on SCHED_CLASS_EXT && CGROUP_SCHED
select GROUP_SCHED_WEIGHT
default y
endif #CGROUP_SCHED
config SCHED_MM_CID
def_bool y
depends on SMP && RSEQ
config UCLAMP_TASK_GROUP
bool "Utilization clamping per group of tasks"
depends on CGROUP_SCHED
depends on UCLAMP_TASK
default n
help
This feature enables the scheduler to track the clamped utilization
of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
When this option is enabled, the user can specify a min and max
CPU bandwidth which is allowed for each single task in a group.
The max bandwidth allows to clamp the maximum frequency a task
can use, while the min bandwidth allows to define a minimum
frequency a task will always use.
When task group based utilization clamping is enabled, an eventually
specified task-specific clamp value is constrained by the cgroup
specified clamp value. Both minimum and maximum task clamping cannot
be bigger than the corresponding clamping defined at task group level.
If in doubt, say N.
config CGROUP_PIDS
bool "PIDs controller"
help
Provides enforcement of process number limits in the scope of a
cgroup. Any attempt to fork more processes than is allowed in the
cgroup will fail. PIDs are fundamentally a global resource because it
is fairly trivial to reach PID exhaustion before you reach even a
conservative kmemcg limit. As a result, it is possible to grind a
system to halt without being limited by other cgroup policies. The
PIDs controller is designed to stop this from happening.
It should be noted that organisational operations (such as attaching
to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
since the PIDs limit only affects a process's ability to fork, not to
attach to a cgroup.
config CGROUP_RDMA
bool "RDMA controller"
help
Provides enforcement of RDMA resources defined by IB stack.
It is fairly easy for consumers to exhaust RDMA resources, which
can result into resource unavailability to other consumers.
RDMA controller is designed to stop this from happening.
Attaching processes with active RDMA resources to the cgroup
hierarchy is allowed even if can cross the hierarchy's limit.
config CGROUP_FREEZER
bool "Freezer controller"
help
Provides a way to freeze and unfreeze all tasks in a
cgroup.
This option affects the ORIGINAL cgroup interface. The cgroup2 memory
controller includes important in-kernel memory consumers per default.
If you're using cgroup2, say N.
config CGROUP_HUGETLB
bool "HugeTLB controller"
depends on HUGETLB_PAGE
select PAGE_COUNTER
default n
help
Provides a cgroup controller for HugeTLB pages.
When you enable this, you can put a per cgroup limit on HugeTLB usage.
The limit is enforced during page fault. Since HugeTLB doesn't
support page reclaim, enforcing the limit at page fault time implies
that, the application will get SIGBUS signal if it tries to access
HugeTLB pages beyond its limit. This requires the application to know
beforehand how much HugeTLB pages it would require for its use. The
control group is tracked in the third page lru pointer. This means
that we cannot use the controller with huge page less than 3 pages.
config CPUSETS
bool "Cpuset controller"
depends on SMP
help
This option will let you create and manage CPUSETs which
allow dynamically partitioning a system into sets of CPUs and
Memory Nodes and assigning tasks to run only within those sets.
This is primarily useful on large SMP or NUMA systems.
Say N if unsure.
config CPUSETS_V1
bool "Legacy cgroup v1 cpusets controller"
depends on CPUSETS
default n
help
Legacy cgroup v1 cpusets controller which has been deprecated by
cgroup v2 implementation. The v1 is there for legacy applications
which haven't migrated to the new cgroup v2 interface yet. If you
do not have any such application then you are completely fine leaving
this option disabled.
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. Or this can be used to have cgroup ID in samples
so that it can monitor performance events among cgroups.
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_MISC
bool "Misc resource controller"
default n
help
Provides a controller for miscellaneous resources on a host.
Miscellaneous scalar resources are the resources on the host system
which cannot be abstracted like the other cgroups. This controller
tracks and limits the miscellaneous resources used by a process
attached to a cgroup hierarchy.
For more information, please check misc cgroup section in
/Documentation/admin-guide/cgroup-v2.rst.
config CGROUP_DEBUG
bool "Debug controller"
default n
depends on DEBUG_KERNEL
help
This option enables a simple controller that exports
debugging information about the cgroups framework. This
controller is for control cgroup debugging only. Its
interfaces are not stable.
Say N.
config SOCK_CGROUP_DATA
bool
default n
endif # CGROUPS
menuconfig NAMESPACES
bool "Namespaces support" if EXPERT
depends on MULTIUSER
default !EXPERT
help
Provides the way to make tasks work with different objects using
the same id. For example same IPC id may refer to different objects
or same user id or pid may refer to different tasks when used in
different namespaces.
if NAMESPACES
config UTS_NS
bool "UTS namespace"
default y
help
In this namespace tasks see different info provided with the
uname() system call
config TIME_NS
bool "TIME namespace"
depends on GENERIC_VDSO_TIME_NS
default y
help
In this namespace boottime and monotonic clocks can be set.
The time will keep going with the same pace.
config IPC_NS
bool "IPC namespace"
depends on (SYSVIPC || POSIX_MQUEUE)
default y
help
In this namespace tasks work with IPC ids which correspond to
different IPC objects in different namespaces.
config USER_NS
bool "User namespace"
default n
help
This allows containers, i.e. vservers, to use user namespaces
to provide different user info for different servers.
When user namespaces are enabled in the kernel it is
recommended that the MEMCG option also be enabled and that
user-space use the memory control groups to limit the amount
of memory a memory unprivileged users can use.
If unsure, say N.
config PID_NS
bool "PID Namespaces"
default y
help
Support process id namespaces. This allows having multiple
processes with the same pid as long as they are in different
pid namespaces. This is a building block of containers.
config NET_NS
bool "Network namespace"
depends on NET
default y
help
Allow user space to create what appear to be multiple instances
of the network stack.
endif # NAMESPACES
config CHECKPOINT_RESTORE
bool "Checkpoint/restore support"
depends on PROC_FS
select PROC_CHILDREN
select KCMP
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 RELAY
bool "Kernel->user space relay support (formerly relayfs)"
select IRQ_WORK
help
This option enables support for relay interface support in
certain file systems (such as debugfs).
It is designed to provide an efficient mechanism for tools and
facilities to relay large amounts of data from kernel space to
user space.
If unsure, say N.
config BLK_DEV_INITRD
bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
help
The initial RAM filesystem is a ramfs which is loaded by the
boot loader (loadlin or lilo) and that is mounted as root
before the normal boot procedure. It is typically used to
load modules needed to mount the "real" root file system,
etc. See <file:Documentation/admin-guide/initrd.rst> for details.
If RAM disk support (BLK_DEV_RAM) is also included, this
also enables initial RAM disk (initrd) support and adds
15 Kbytes (more on some other architectures) to the kernel size.
If unsure say Y.
if BLK_DEV_INITRD
source "usr/Kconfig"
endif
config BOOT_CONFIG
bool "Boot config support"
select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED
help
Extra boot config allows system admin to pass a config file as
complemental extension of kernel cmdline when booting.
The boot config file must be attached at the end of initramfs
with checksum, size and magic word.
See <file:Documentation/admin-guide/bootconfig.rst> for details.
If unsure, say Y.
config BOOT_CONFIG_FORCE
bool "Force unconditional bootconfig processing"
depends on BOOT_CONFIG
default y if BOOT_CONFIG_EMBED
help
With this Kconfig option set, BOOT_CONFIG processing is carried
out even when the "bootconfig" kernel-boot parameter is omitted.
In fact, with this Kconfig option set, there is no way to
make the kernel ignore the BOOT_CONFIG-supplied kernel-boot
parameters.
If unsure, say N.
config BOOT_CONFIG_EMBED
bool "Embed bootconfig file in the kernel"
depends on BOOT_CONFIG
help
Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the
kernel. Usually, the bootconfig file is loaded with the initrd
image. But if the system doesn't support initrd, this option will
help you by embedding a bootconfig file while building the kernel.
If unsure, say N.
config BOOT_CONFIG_EMBED_FILE
string "Embedded bootconfig file path"
depends on BOOT_CONFIG_EMBED
help
Specify a bootconfig file which will be embedded to the kernel.
This bootconfig will be used if there is no initrd or no other
bootconfig in the initrd.
config INITRAMFS_PRESERVE_MTIME
bool "Preserve cpio archive mtimes in initramfs"
default y
help
Each entry in an initramfs cpio archive carries an mtime value. When
enabled, extracted cpio items take this mtime, with directory mtime
setting deferred until after creation of any child entries.
If unsure, say Y.
choice
prompt "Compiler optimization level"
default CC_OPTIMIZE_FOR_PERFORMANCE
config CC_OPTIMIZE_FOR_PERFORMANCE
bool "Optimize for performance (-O2)"
help
This is the default optimization level for the kernel, building
with the "-O2" compiler flag for best performance and most
helpful compile-time warnings.
config CC_OPTIMIZE_FOR_SIZE
bool "Optimize for size (-Os)"
help
Choosing this option will pass "-Os" to your compiler resulting
in a smaller kernel.
endchoice
config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
bool
help
This requires that the arch annotates or otherwise protects
its external entry points from being discarded. Linker scripts
must also merge .text.*, .data.*, and .bss.* correctly into
output sections. Care must be taken not to pull in unrelated
sections (e.g., '.text.init'). Typically '.' in section names
is used to distinguish them from label names / C identifiers.
config LD_DEAD_CODE_DATA_ELIMINATION
bool "Dead code and data elimination (EXPERIMENTAL)"
depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
depends on EXPERT
depends on $(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 LD_ORPHAN_WARN
def_bool y
depends on ARCH_WANT_LD_ORPHAN_WARN
depends on $(ld-option,--orphan-handling=warn)
depends on $(ld-option,--orphan-handling=error)
config LD_ORPHAN_WARN_LEVEL
string
depends on LD_ORPHAN_WARN
default "error" if WERROR
default "warn"
config SYSCTL
bool
config HAVE_UID16
bool
config SYSCTL_EXCEPTION_TRACE
bool
help
Enable support for /proc/sys/debug/exception-trace.
config SYSCTL_ARCH_UNALIGN_NO_WARN
bool
help
Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
Allows arch to define/use @no_unaligned_warning to possibly warn
about unaligned access emulation going on under the hood.
config SYSCTL_ARCH_UNALIGN_ALLOW
bool
help
Enable support for /proc/sys/kernel/unaligned-trap
Allows arches to define/use @unaligned_enabled to runtime toggle
the unaligned access emulation.
see arch/parisc/kernel/unaligned.c for reference
config HAVE_PCSPKR_PLATFORM
bool
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
default PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
help
sys_sgetmask and sys_ssetmask are obsolete system calls
no longer supported in libc but still enabled by default in some
architectures.
If unsure, leave the default option here.
config SYSFS_SYSCALL
bool "Sysfs syscall support" if EXPERT
default y
help
sys_sysfs is an obsolete system call no longer supported in libc.
Note that disabling this option is more secure but might break
compatibility with some systems.
If unsure say Y here.
config FHANDLE
bool "open by fhandle syscalls" if EXPERT
select EXPORTFS
default y
help
If you say Y here, a user level program will be able to map
file names to handle and then later use the handle for
different file system operations. This is useful in implementing
userspace file servers, which now track files using handles instead
of names. The handle would remain the same even if file names
get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
syscalls.
config POSIX_TIMERS
bool "Posix Clocks & timers" if EXPERT
default y
help
This includes native support for POSIX timers to the kernel.
Some embedded systems have no use for them and therefore they
can be configured out to reduce the size of the kernel image.
When this option is disabled, the following syscalls won't be
available: timer_create, timer_gettime: timer_getoverrun,
timer_settime, timer_delete, clock_adjtime, getitimer,
setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
clock_getres and clock_nanosleep syscalls will be limited to
CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
If unsure say y.
config PRINTK
default y
bool "Enable support for printk" if EXPERT
select IRQ_WORK
help
This option enables normal printk support. Removing it
eliminates most of the message strings from the kernel image
and makes the kernel more or less silent. As this makes it
very difficult to diagnose system problems, saying N here is
strongly discouraged.
config 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_SMALL
bool "Enable smaller-sized data structures for core" if EXPERT
help
Enabling 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
depends on !(SPARC32 && SMP)
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 EPOLL
bool "Enable eventpoll support" if EXPERT
default y
help
Disabling this option will cause the kernel to be built without
support for epoll family of system calls.
config SIGNALFD
bool "Enable signalfd() system call" if EXPERT
default y
help
Enable the signalfd() system call that allows to receive signals
on a file descriptor.
If unsure, say Y.
config TIMERFD
bool "Enable timerfd() system call" if EXPERT
default y
help
Enable the timerfd() system call that allows to receive timer
events on a file descriptor.
If unsure, say Y.
config EVENTFD
bool "Enable eventfd() system call" if EXPERT
default y
help
Enable the eventfd() system call that allows to receive both
kernel notification (ie. KAIO) or userspace notifications.
If unsure, say Y.
config SHMEM
bool "Use full shmem filesystem" if EXPERT
default y
depends on MMU
help
The shmem is an internal filesystem used to manage shared memory.
It is backed by swap and manages resource limits. It is also exported
to userspace as tmpfs if TMPFS is enabled. Disabling this
option replaces shmem and tmpfs with the much simpler ramfs code,
which may be appropriate on small systems without swap.
config AIO
bool "Enable AIO support" if EXPERT
default y
help
This option enables POSIX asynchronous I/O which may by used
by some high performance threaded applications. Disabling
this option saves about 7k.
config IO_URING
bool "Enable IO uring support" if EXPERT
select IO_WQ
default y
help
This option enables support for the io_uring interface, enabling
applications to submit and complete IO through submission and
completion rings that are shared between the kernel and application.
config GCOV_PROFILE_URING
bool "Enable GCOV profiling on the io_uring subsystem"
depends on GCOV_KERNEL
help
Enable GCOV profiling on the io_uring subsystem, to facilitate
code coverage testing.
If unsure, say N.
Note that this will have a negative impact on the performance of
the io_uring subsystem, hence this should only be enabled for
specific test purposes.
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 KCMP
bool "Enable kcmp() system call" if EXPERT
help
Enable the kernel resource comparison system call. It provides
user-space with the ability to compare two processes to see if they
share a common resource, such as a file descriptor or even virtual
memory space.
If unsure, say N.
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 "Enable 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 CACHESTAT_SYSCALL
bool "Enable cachestat() system call" if EXPERT
default y
help
Enable the cachestat system call, which queries the page cache
statistics of a file (number of cached pages, dirty pages,
pages marked for writeback, (recently) evicted pages).
If unsure say Y here.
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.
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_SELFTEST
bool "Test the basic functions and performance of kallsyms"
depends on KALLSYMS
default n
help
Test the basic functions and performance of some interfaces, such as
kallsyms_lookup_name. It also calculates the compression rate of the
kallsyms compression algorithm for the current symbol set.
Start self-test automatically after system startup. Suggest executing
"dmesg | grep kallsyms_selftest" to collect test results. "finish" is
displayed in the last line, indicating that the test is complete.
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 if you want to
enable kernel live patching, or other less common use cases (e.g.,
when a debugger is used) all symbols are required (i.e., 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, or kernel live patching.
config KALLSYMS_ABSOLUTE_PERCPU
bool
depends on KALLSYMS
default X86_64 && SMP
# end of the "standard kernel features (expert users)" menu
config ARCH_HAS_MEMBARRIER_CALLBACKS
bool
config ARCH_HAS_MEMBARRIER_SYNC_CORE
bool
config HAVE_PERF_EVENTS
bool
help
See tools/perf/design.txt for details.
config GUEST_PERF_EVENTS
bool
depends on HAVE_PERF_EVENTS
config PERF_USE_VMALLOC
bool
help
See tools/perf/design.txt for details
menu "Kernel Performance Events And Counters"
config PERF_EVENTS
bool "Kernel performance events and counters"
default y if PROFILING
depends on HAVE_PERF_EVENTS
select IRQ_WORK
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 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.
config RUST
bool "Rust support"
depends on HAVE_RUST
depends on RUST_IS_AVAILABLE
depends on !MODVERSIONS
depends on !GCC_PLUGIN_RANDSTRUCT
depends on !RANDSTRUCT
depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE
depends on !CFI_CLANG || RUSTC_VERSION >= 107900 && HAVE_CFI_ICALL_NORMALIZE_INTEGERS
select CFI_ICALL_NORMALIZE_INTEGERS if CFI_CLANG
depends on !CALL_PADDING || RUSTC_VERSION >= 108100
depends on !KASAN_SW_TAGS
depends on !(MITIGATION_RETHUNK && KASAN) || RUSTC_VERSION >= 108300
help
Enables Rust support in the kernel.
This allows other Rust-related options, like drivers written in Rust,
to be selected.
It is also required to be able to load external kernel modules
written in Rust.
See Documentation/rust/ for more information.
If unsure, say N.
config RUSTC_VERSION_TEXT
string
depends on RUST
default "$(RUSTC_VERSION_TEXT)"
help
See `CC_VERSION_TEXT`.
config BINDGEN_VERSION_TEXT
string
depends on RUST
# The dummy parameter `workaround-for-0.69.0` is required to support 0.69.0
# (https://github.com/rust-lang/rust-bindgen/pull/2678). It can be removed when
# the minimum version is upgraded past that (0.69.1 already fixed the issue).
default "$(shell,$(BINDGEN) --version workaround-for-0.69.0 2>/dev/null)"
#
# Place an empty function call at each tracepoint site. Can be
# dynamically changed for a probe function.
#
config TRACEPOINTS
bool
source "kernel/Kconfig.kexec"
endmenu # General setup
source "arch/Kconfig"
config RT_MUTEXES
bool
default y if PREEMPT_RT
config MODULE_SIG_FORMAT
def_bool n
select SYSTEM_DATA_VERIFICATION
source "kernel/module/Kconfig"
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_NON_OVERLAPPING_ADDRESS_SPACE
bool
config ARCH_HAS_PREPARE_SYNC_CORE_CMD
bool
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
source "init/Kconfig.gki"