1# SPDX-License-Identifier: GPL-2.0-only 2config DEFCONFIG_LIST 3 string 4 depends on !UML 5 option defconfig_list 6 default "/lib/modules/$(shell,uname -r)/.config" 7 default "/etc/kernel-config" 8 default "/boot/config-$(shell,uname -r)" 9 default ARCH_DEFCONFIG 10 default "arch/$(ARCH)/defconfig" 11 12config CC_IS_GCC 13 def_bool $(success,$(CC) --version | head -n 1 | grep -q gcc) 14 15config GCC_VERSION 16 int 17 default $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) if CC_IS_GCC 18 default 0 19 20config CC_IS_CLANG 21 def_bool $(success,$(CC) --version | head -n 1 | grep -q clang) 22 23config CLANG_VERSION 24 int 25 default $(shell,$(srctree)/scripts/clang-version.sh $(CC)) 26 27config CC_HAS_ASM_GOTO 28 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) 29 30config CC_HAS_WARN_MAYBE_UNINITIALIZED 31 def_bool $(cc-option,-Wmaybe-uninitialized) 32 help 33 GCC >= 4.7 supports this option. 34 35config CC_DISABLE_WARN_MAYBE_UNINITIALIZED 36 bool 37 depends on CC_HAS_WARN_MAYBE_UNINITIALIZED 38 default CC_IS_GCC && GCC_VERSION < 40900 # unreliable for GCC < 4.9 39 help 40 GCC's -Wmaybe-uninitialized is not reliable by definition. 41 Lots of false positive warnings are produced in some cases. 42 43 If this option is enabled, -Wno-maybe-uninitialzed is passed 44 to the compiler to suppress maybe-uninitialized warnings. 45 46config CONSTRUCTORS 47 bool 48 depends on !UML 49 50config IRQ_WORK 51 bool 52 53config BUILDTIME_EXTABLE_SORT 54 bool 55 56config THREAD_INFO_IN_TASK 57 bool 58 help 59 Select this to move thread_info off the stack into task_struct. To 60 make this work, an arch will need to remove all thread_info fields 61 except flags and fix any runtime bugs. 62 63 One subtle change that will be needed is to use try_get_task_stack() 64 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 65 66menu "General setup" 67 68config BROKEN 69 bool 70 71config BROKEN_ON_SMP 72 bool 73 depends on BROKEN || !SMP 74 default y 75 76config INIT_ENV_ARG_LIMIT 77 int 78 default 32 if !UML 79 default 128 if UML 80 help 81 Maximum of each of the number of arguments and environment 82 variables passed to init from the kernel command line. 83 84config COMPILE_TEST 85 bool "Compile also drivers which will not load" 86 depends on !UML 87 default n 88 help 89 Some drivers can be compiled on a different platform than they are 90 intended to be run on. Despite they cannot be loaded there (or even 91 when they load they cannot be used due to missing HW support), 92 developers still, opposing to distributors, might want to build such 93 drivers to compile-test them. 94 95 If you are a developer and want to build everything available, say Y 96 here. If you are a user/distributor, say N here to exclude useless 97 drivers to be distributed. 98 99config LOCALVERSION 100 string "Local version - append to kernel release" 101 help 102 Append an extra string to the end of your kernel version. 103 This will show up when you type uname, for example. 104 The string you set here will be appended after the contents of 105 any files with a filename matching localversion* in your 106 object and source tree, in that order. Your total string can 107 be a maximum of 64 characters. 108 109config LOCALVERSION_AUTO 110 bool "Automatically append version information to the version string" 111 default y 112 depends on !COMPILE_TEST 113 help 114 This will try to automatically determine if the current tree is a 115 release tree by looking for git tags that belong to the current 116 top of tree revision. 117 118 A string of the format -gxxxxxxxx will be added to the localversion 119 if a git-based tree is found. The string generated by this will be 120 appended after any matching localversion* files, and after the value 121 set in CONFIG_LOCALVERSION. 122 123 (The actual string used here is the first eight characters produced 124 by running the command: 125 126 $ git rev-parse --verify HEAD 127 128 which is done within the script "scripts/setlocalversion".) 129 130config BUILD_SALT 131 string "Build ID Salt" 132 default "" 133 help 134 The build ID is used to link binaries and their debug info. Setting 135 this option will use the value in the calculation of the build id. 136 This is mostly useful for distributions which want to ensure the 137 build is unique between builds. It's safe to leave the default. 138 139config HAVE_KERNEL_GZIP 140 bool 141 142config HAVE_KERNEL_BZIP2 143 bool 144 145config HAVE_KERNEL_LZMA 146 bool 147 148config HAVE_KERNEL_XZ 149 bool 150 151config HAVE_KERNEL_LZO 152 bool 153 154config HAVE_KERNEL_LZ4 155 bool 156 157config HAVE_KERNEL_UNCOMPRESSED 158 bool 159 160choice 161 prompt "Kernel compression mode" 162 default KERNEL_GZIP 163 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED 164 help 165 The linux kernel is a kind of self-extracting executable. 166 Several compression algorithms are available, which differ 167 in efficiency, compression and decompression speed. 168 Compression speed is only relevant when building a kernel. 169 Decompression speed is relevant at each boot. 170 171 If you have any problems with bzip2 or lzma compressed 172 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 173 version of this functionality (bzip2 only), for 2.4, was 174 supplied by Christian Ludwig) 175 176 High compression options are mostly useful for users, who 177 are low on disk space (embedded systems), but for whom ram 178 size matters less. 179 180 If in doubt, select 'gzip' 181 182config KERNEL_GZIP 183 bool "Gzip" 184 depends on HAVE_KERNEL_GZIP 185 help 186 The old and tried gzip compression. It provides a good balance 187 between compression ratio and decompression speed. 188 189config KERNEL_BZIP2 190 bool "Bzip2" 191 depends on HAVE_KERNEL_BZIP2 192 help 193 Its compression ratio and speed is intermediate. 194 Decompression speed is slowest among the choices. The kernel 195 size is about 10% smaller with bzip2, in comparison to gzip. 196 Bzip2 uses a large amount of memory. For modern kernels you 197 will need at least 8MB RAM or more for booting. 198 199config KERNEL_LZMA 200 bool "LZMA" 201 depends on HAVE_KERNEL_LZMA 202 help 203 This compression algorithm's ratio is best. Decompression speed 204 is between gzip and bzip2. Compression is slowest. 205 The kernel size is about 33% smaller with LZMA in comparison to gzip. 206 207config KERNEL_XZ 208 bool "XZ" 209 depends on HAVE_KERNEL_XZ 210 help 211 XZ uses the LZMA2 algorithm and instruction set specific 212 BCJ filters which can improve compression ratio of executable 213 code. The size of the kernel is about 30% smaller with XZ in 214 comparison to gzip. On architectures for which there is a BCJ 215 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 216 will create a few percent smaller kernel than plain LZMA. 217 218 The speed is about the same as with LZMA: The decompression 219 speed of XZ is better than that of bzip2 but worse than gzip 220 and LZO. Compression is slow. 221 222config KERNEL_LZO 223 bool "LZO" 224 depends on HAVE_KERNEL_LZO 225 help 226 Its compression ratio is the poorest among the choices. The kernel 227 size is about 10% bigger than gzip; however its speed 228 (both compression and decompression) is the fastest. 229 230config KERNEL_LZ4 231 bool "LZ4" 232 depends on HAVE_KERNEL_LZ4 233 help 234 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 235 A preliminary version of LZ4 de/compression tool is available at 236 <https://code.google.com/p/lz4/>. 237 238 Its compression ratio is worse than LZO. The size of the kernel 239 is about 8% bigger than LZO. But the decompression speed is 240 faster than LZO. 241 242config KERNEL_UNCOMPRESSED 243 bool "None" 244 depends on HAVE_KERNEL_UNCOMPRESSED 245 help 246 Produce uncompressed kernel image. This option is usually not what 247 you want. It is useful for debugging the kernel in slow simulation 248 environments, where decompressing and moving the kernel is awfully 249 slow. This option allows early boot code to skip the decompressor 250 and jump right at uncompressed kernel image. 251 252endchoice 253 254config DEFAULT_HOSTNAME 255 string "Default hostname" 256 default "(none)" 257 help 258 This option determines the default system hostname before userspace 259 calls sethostname(2). The kernel traditionally uses "(none)" here, 260 but you may wish to use a different default here to make a minimal 261 system more usable with less configuration. 262 263# 264# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can 265# add proper SWAP support to them, in which case this can be remove. 266# 267config ARCH_NO_SWAP 268 bool 269 270config SWAP 271 bool "Support for paging of anonymous memory (swap)" 272 depends on MMU && BLOCK && !ARCH_NO_SWAP 273 default y 274 help 275 This option allows you to choose whether you want to have support 276 for so called swap devices or swap files in your kernel that are 277 used to provide more virtual memory than the actual RAM present 278 in your computer. If unsure say Y. 279 280config SYSVIPC 281 bool "System V IPC" 282 ---help--- 283 Inter Process Communication is a suite of library functions and 284 system calls which let processes (running programs) synchronize and 285 exchange information. It is generally considered to be a good thing, 286 and some programs won't run unless you say Y here. In particular, if 287 you want to run the DOS emulator dosemu under Linux (read the 288 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 289 you'll need to say Y here. 290 291 You can find documentation about IPC with "info ipc" and also in 292 section 6.4 of the Linux Programmer's Guide, available from 293 <http://www.tldp.org/guides.html>. 294 295config SYSVIPC_SYSCTL 296 bool 297 depends on SYSVIPC 298 depends on SYSCTL 299 default y 300 301config POSIX_MQUEUE 302 bool "POSIX Message Queues" 303 depends on NET 304 ---help--- 305 POSIX variant of message queues is a part of IPC. In POSIX message 306 queues every message has a priority which decides about succession 307 of receiving it by a process. If you want to compile and run 308 programs written e.g. for Solaris with use of its POSIX message 309 queues (functions mq_*) say Y here. 310 311 POSIX message queues are visible as a filesystem called 'mqueue' 312 and can be mounted somewhere if you want to do filesystem 313 operations on message queues. 314 315 If unsure, say Y. 316 317config POSIX_MQUEUE_SYSCTL 318 bool 319 depends on POSIX_MQUEUE 320 depends on SYSCTL 321 default y 322 323config CROSS_MEMORY_ATTACH 324 bool "Enable process_vm_readv/writev syscalls" 325 depends on MMU 326 default y 327 help 328 Enabling this option adds the system calls process_vm_readv and 329 process_vm_writev which allow a process with the correct privileges 330 to directly read from or write to another process' address space. 331 See the man page for more details. 332 333config USELIB 334 bool "uselib syscall" 335 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION 336 help 337 This option enables the uselib syscall, a system call used in the 338 dynamic linker from libc5 and earlier. glibc does not use this 339 system call. If you intend to run programs built on libc5 or 340 earlier, you may need to enable this syscall. Current systems 341 running glibc can safely disable this. 342 343config AUDIT 344 bool "Auditing support" 345 depends on NET 346 help 347 Enable auditing infrastructure that can be used with another 348 kernel subsystem, such as SELinux (which requires this for 349 logging of avc messages output). System call auditing is included 350 on architectures which support it. 351 352config HAVE_ARCH_AUDITSYSCALL 353 bool 354 355config AUDITSYSCALL 356 def_bool y 357 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 358 select FSNOTIFY 359 360source "kernel/irq/Kconfig" 361source "kernel/time/Kconfig" 362source "kernel/Kconfig.preempt" 363 364menu "CPU/Task time and stats accounting" 365 366config VIRT_CPU_ACCOUNTING 367 bool 368 369choice 370 prompt "Cputime accounting" 371 default TICK_CPU_ACCOUNTING if !PPC64 372 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 373 374# Kind of a stub config for the pure tick based cputime accounting 375config TICK_CPU_ACCOUNTING 376 bool "Simple tick based cputime accounting" 377 depends on !S390 && !NO_HZ_FULL 378 help 379 This is the basic tick based cputime accounting that maintains 380 statistics about user, system and idle time spent on per jiffies 381 granularity. 382 383 If unsure, say Y. 384 385config VIRT_CPU_ACCOUNTING_NATIVE 386 bool "Deterministic task and CPU time accounting" 387 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 388 select VIRT_CPU_ACCOUNTING 389 help 390 Select this option to enable more accurate task and CPU time 391 accounting. This is done by reading a CPU counter on each 392 kernel entry and exit and on transitions within the kernel 393 between system, softirq and hardirq state, so there is a 394 small performance impact. In the case of s390 or IBM POWER > 5, 395 this also enables accounting of stolen time on logically-partitioned 396 systems. 397 398config VIRT_CPU_ACCOUNTING_GEN 399 bool "Full dynticks CPU time accounting" 400 depends on HAVE_CONTEXT_TRACKING 401 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 402 depends on GENERIC_CLOCKEVENTS 403 select VIRT_CPU_ACCOUNTING 404 select CONTEXT_TRACKING 405 help 406 Select this option to enable task and CPU time accounting on full 407 dynticks systems. This accounting is implemented by watching every 408 kernel-user boundaries using the context tracking subsystem. 409 The accounting is thus performed at the expense of some significant 410 overhead. 411 412 For now this is only useful if you are working on the full 413 dynticks subsystem development. 414 415 If unsure, say N. 416 417endchoice 418 419config IRQ_TIME_ACCOUNTING 420 bool "Fine granularity task level IRQ time accounting" 421 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 422 help 423 Select this option to enable fine granularity task irq time 424 accounting. This is done by reading a timestamp on each 425 transitions between softirq and hardirq state, so there can be a 426 small performance impact. 427 428 If in doubt, say N here. 429 430config HAVE_SCHED_AVG_IRQ 431 def_bool y 432 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 433 depends on SMP 434 435config BSD_PROCESS_ACCT 436 bool "BSD Process Accounting" 437 depends on MULTIUSER 438 help 439 If you say Y here, a user level program will be able to instruct the 440 kernel (via a special system call) to write process accounting 441 information to a file: whenever a process exits, information about 442 that process will be appended to the file by the kernel. The 443 information includes things such as creation time, owning user, 444 command name, memory usage, controlling terminal etc. (the complete 445 list is in the struct acct in <file:include/linux/acct.h>). It is 446 up to the user level program to do useful things with this 447 information. This is generally a good idea, so say Y. 448 449config BSD_PROCESS_ACCT_V3 450 bool "BSD Process Accounting version 3 file format" 451 depends on BSD_PROCESS_ACCT 452 default n 453 help 454 If you say Y here, the process accounting information is written 455 in a new file format that also logs the process IDs of each 456 process and its parent. Note that this file format is incompatible 457 with previous v0/v1/v2 file formats, so you will need updated tools 458 for processing it. A preliminary version of these tools is available 459 at <http://www.gnu.org/software/acct/>. 460 461config TASKSTATS 462 bool "Export task/process statistics through netlink" 463 depends on NET 464 depends on MULTIUSER 465 default n 466 help 467 Export selected statistics for tasks/processes through the 468 generic netlink interface. Unlike BSD process accounting, the 469 statistics are available during the lifetime of tasks/processes as 470 responses to commands. Like BSD accounting, they are sent to user 471 space on task exit. 472 473 Say N if unsure. 474 475config TASK_DELAY_ACCT 476 bool "Enable per-task delay accounting" 477 depends on TASKSTATS 478 select SCHED_INFO 479 help 480 Collect information on time spent by a task waiting for system 481 resources like cpu, synchronous block I/O completion and swapping 482 in pages. Such statistics can help in setting a task's priorities 483 relative to other tasks for cpu, io, rss limits etc. 484 485 Say N if unsure. 486 487config TASK_XACCT 488 bool "Enable extended accounting over taskstats" 489 depends on TASKSTATS 490 help 491 Collect extended task accounting data and send the data 492 to userland for processing over the taskstats interface. 493 494 Say N if unsure. 495 496config TASK_IO_ACCOUNTING 497 bool "Enable per-task storage I/O accounting" 498 depends on TASK_XACCT 499 help 500 Collect information on the number of bytes of storage I/O which this 501 task has caused. 502 503 Say N if unsure. 504 505config PSI 506 bool "Pressure stall information tracking" 507 help 508 Collect metrics that indicate how overcommitted the CPU, memory, 509 and IO capacity are in the system. 510 511 If you say Y here, the kernel will create /proc/pressure/ with the 512 pressure statistics files cpu, memory, and io. These will indicate 513 the share of walltime in which some or all tasks in the system are 514 delayed due to contention of the respective resource. 515 516 In kernels with cgroup support, cgroups (cgroup2 only) will 517 have cpu.pressure, memory.pressure, and io.pressure files, 518 which aggregate pressure stalls for the grouped tasks only. 519 520 For more details see Documentation/accounting/psi.txt. 521 522 Say N if unsure. 523 524config PSI_DEFAULT_DISABLED 525 bool "Require boot parameter to enable pressure stall information tracking" 526 default n 527 depends on PSI 528 help 529 If set, pressure stall information tracking will be disabled 530 per default but can be enabled through passing psi=1 on the 531 kernel commandline during boot. 532 533 This feature adds some code to the task wakeup and sleep 534 paths of the scheduler. The overhead is too low to affect 535 common scheduling-intense workloads in practice (such as 536 webservers, memcache), but it does show up in artificial 537 scheduler stress tests, such as hackbench. 538 539 If you are paranoid and not sure what the kernel will be 540 used for, say Y. 541 542 Say N if unsure. 543 544endmenu # "CPU/Task time and stats accounting" 545 546config CPU_ISOLATION 547 bool "CPU isolation" 548 depends on SMP || COMPILE_TEST 549 default y 550 help 551 Make sure that CPUs running critical tasks are not disturbed by 552 any source of "noise" such as unbound workqueues, timers, kthreads... 553 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 554 the "isolcpus=" boot parameter. 555 556 Say Y if unsure. 557 558source "kernel/rcu/Kconfig" 559 560config BUILD_BIN2C 561 bool 562 default n 563 564config IKCONFIG 565 tristate "Kernel .config support" 566 ---help--- 567 This option enables the complete Linux kernel ".config" file 568 contents to be saved in the kernel. It provides documentation 569 of which kernel options are used in a running kernel or in an 570 on-disk kernel. This information can be extracted from the kernel 571 image file with the script scripts/extract-ikconfig and used as 572 input to rebuild the current kernel or to build another kernel. 573 It can also be extracted from a running kernel by reading 574 /proc/config.gz if enabled (below). 575 576config IKCONFIG_PROC 577 bool "Enable access to .config through /proc/config.gz" 578 depends on IKCONFIG && PROC_FS 579 ---help--- 580 This option enables access to the kernel configuration file 581 through /proc/config.gz. 582 583config IKHEADERS 584 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 585 depends on SYSFS 586 help 587 This option enables access to the in-kernel headers that are generated during 588 the build process. These can be used to build eBPF tracing programs, 589 or similar programs. If you build the headers as a module, a module called 590 kheaders.ko is built which can be loaded on-demand to get access to headers. 591 592config LOG_BUF_SHIFT 593 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 594 range 12 25 595 default 17 596 depends on PRINTK 597 help 598 Select the minimal kernel log buffer size as a power of 2. 599 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 600 parameter, see below. Any higher size also might be forced 601 by "log_buf_len" boot parameter. 602 603 Examples: 604 17 => 128 KB 605 16 => 64 KB 606 15 => 32 KB 607 14 => 16 KB 608 13 => 8 KB 609 12 => 4 KB 610 611config LOG_CPU_MAX_BUF_SHIFT 612 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 613 depends on SMP 614 range 0 21 615 default 12 if !BASE_SMALL 616 default 0 if BASE_SMALL 617 depends on PRINTK 618 help 619 This option allows to increase the default ring buffer size 620 according to the number of CPUs. The value defines the contribution 621 of each CPU as a power of 2. The used space is typically only few 622 lines however it might be much more when problems are reported, 623 e.g. backtraces. 624 625 The increased size means that a new buffer has to be allocated and 626 the original static one is unused. It makes sense only on systems 627 with more CPUs. Therefore this value is used only when the sum of 628 contributions is greater than the half of the default kernel ring 629 buffer as defined by LOG_BUF_SHIFT. The default values are set 630 so that more than 64 CPUs are needed to trigger the allocation. 631 632 Also this option is ignored when "log_buf_len" kernel parameter is 633 used as it forces an exact (power of two) size of the ring buffer. 634 635 The number of possible CPUs is used for this computation ignoring 636 hotplugging making the computation optimal for the worst case 637 scenario while allowing a simple algorithm to be used from bootup. 638 639 Examples shift values and their meaning: 640 17 => 128 KB for each CPU 641 16 => 64 KB for each CPU 642 15 => 32 KB for each CPU 643 14 => 16 KB for each CPU 644 13 => 8 KB for each CPU 645 12 => 4 KB for each CPU 646 647config PRINTK_SAFE_LOG_BUF_SHIFT 648 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 649 range 10 21 650 default 13 651 depends on PRINTK 652 help 653 Select the size of an alternate printk per-CPU buffer where messages 654 printed from usafe contexts are temporary stored. One example would 655 be NMI messages, another one - printk recursion. The messages are 656 copied to the main log buffer in a safe context to avoid a deadlock. 657 The value defines the size as a power of 2. 658 659 Those messages are rare and limited. The largest one is when 660 a backtrace is printed. It usually fits into 4KB. Select 661 8KB if you want to be on the safe side. 662 663 Examples: 664 17 => 128 KB for each CPU 665 16 => 64 KB for each CPU 666 15 => 32 KB for each CPU 667 14 => 16 KB for each CPU 668 13 => 8 KB for each CPU 669 12 => 4 KB for each CPU 670 671# 672# Architectures with an unreliable sched_clock() should select this: 673# 674config HAVE_UNSTABLE_SCHED_CLOCK 675 bool 676 677config GENERIC_SCHED_CLOCK 678 bool 679 680menu "Scheduler features" 681 682config UCLAMP_TASK 683 bool "Enable utilization clamping for RT/FAIR tasks" 684 depends on CPU_FREQ_GOV_SCHEDUTIL 685 help 686 This feature enables the scheduler to track the clamped utilization 687 of each CPU based on RUNNABLE tasks scheduled on that CPU. 688 689 With this option, the user can specify the min and max CPU 690 utilization allowed for RUNNABLE tasks. The max utilization defines 691 the maximum frequency a task should use while the min utilization 692 defines the minimum frequency it should use. 693 694 Both min and max utilization clamp values are hints to the scheduler, 695 aiming at improving its frequency selection policy, but they do not 696 enforce or grant any specific bandwidth for tasks. 697 698 If in doubt, say N. 699 700config UCLAMP_BUCKETS_COUNT 701 int "Number of supported utilization clamp buckets" 702 range 5 20 703 default 5 704 depends on UCLAMP_TASK 705 help 706 Defines the number of clamp buckets to use. The range of each bucket 707 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 708 number of clamp buckets the finer their granularity and the higher 709 the precision of clamping aggregation and tracking at run-time. 710 711 For example, with the minimum configuration value we will have 5 712 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 713 be refcounted in the [20..39]% bucket and will set the bucket clamp 714 effective value to 25%. 715 If a second 30% boosted task should be co-scheduled on the same CPU, 716 that task will be refcounted in the same bucket of the first task and 717 it will boost the bucket clamp effective value to 30%. 718 The clamp effective value of a bucket is reset to its nominal value 719 (20% in the example above) when there are no more tasks refcounted in 720 that bucket. 721 722 An additional boost/capping margin can be added to some tasks. In the 723 example above the 25% task will be boosted to 30% until it exits the 724 CPU. If that should be considered not acceptable on certain systems, 725 it's always possible to reduce the margin by increasing the number of 726 clamp buckets to trade off used memory for run-time tracking 727 precision. 728 729 If in doubt, use the default value. 730 731endmenu 732 733# 734# For architectures that want to enable the support for NUMA-affine scheduler 735# balancing logic: 736# 737config ARCH_SUPPORTS_NUMA_BALANCING 738 bool 739 740# 741# For architectures that prefer to flush all TLBs after a number of pages 742# are unmapped instead of sending one IPI per page to flush. The architecture 743# must provide guarantees on what happens if a clean TLB cache entry is 744# written after the unmap. Details are in mm/rmap.c near the check for 745# should_defer_flush. The architecture should also consider if the full flush 746# and the refill costs are offset by the savings of sending fewer IPIs. 747config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 748 bool 749 750# 751# For architectures that know their GCC __int128 support is sound 752# 753config ARCH_SUPPORTS_INT128 754 bool 755 756# For architectures that (ab)use NUMA to represent different memory regions 757# all cpu-local but of different latencies, such as SuperH. 758# 759config ARCH_WANT_NUMA_VARIABLE_LOCALITY 760 bool 761 762config NUMA_BALANCING 763 bool "Memory placement aware NUMA scheduler" 764 depends on ARCH_SUPPORTS_NUMA_BALANCING 765 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 766 depends on SMP && NUMA && MIGRATION 767 help 768 This option adds support for automatic NUMA aware memory/task placement. 769 The mechanism is quite primitive and is based on migrating memory when 770 it has references to the node the task is running on. 771 772 This system will be inactive on UMA systems. 773 774config NUMA_BALANCING_DEFAULT_ENABLED 775 bool "Automatically enable NUMA aware memory/task placement" 776 default y 777 depends on NUMA_BALANCING 778 help 779 If set, automatic NUMA balancing will be enabled if running on a NUMA 780 machine. 781 782menuconfig CGROUPS 783 bool "Control Group support" 784 select KERNFS 785 help 786 This option adds support for grouping sets of processes together, for 787 use with process control subsystems such as Cpusets, CFS, memory 788 controls or device isolation. 789 See 790 - Documentation/scheduler/sched-design-CFS.rst (CFS) 791 - Documentation/cgroup-v1/ (features for grouping, isolation 792 and resource control) 793 794 Say N if unsure. 795 796if CGROUPS 797 798config PAGE_COUNTER 799 bool 800 801config MEMCG 802 bool "Memory controller" 803 select PAGE_COUNTER 804 select EVENTFD 805 help 806 Provides control over the memory footprint of tasks in a cgroup. 807 808config MEMCG_SWAP 809 bool "Swap controller" 810 depends on MEMCG && SWAP 811 help 812 Provides control over the swap space consumed by tasks in a cgroup. 813 814config MEMCG_SWAP_ENABLED 815 bool "Swap controller enabled by default" 816 depends on MEMCG_SWAP 817 default y 818 help 819 Memory Resource Controller Swap Extension comes with its price in 820 a bigger memory consumption. General purpose distribution kernels 821 which want to enable the feature but keep it disabled by default 822 and let the user enable it by swapaccount=1 boot command line 823 parameter should have this option unselected. 824 For those who want to have the feature enabled by default should 825 select this option (if, for some reason, they need to disable it 826 then swapaccount=0 does the trick). 827 828config MEMCG_KMEM 829 bool 830 depends on MEMCG && !SLOB 831 default y 832 833config BLK_CGROUP 834 bool "IO controller" 835 depends on BLOCK 836 default n 837 ---help--- 838 Generic block IO controller cgroup interface. This is the common 839 cgroup interface which should be used by various IO controlling 840 policies. 841 842 Currently, CFQ IO scheduler uses it to recognize task groups and 843 control disk bandwidth allocation (proportional time slice allocation) 844 to such task groups. It is also used by bio throttling logic in 845 block layer to implement upper limit in IO rates on a device. 846 847 This option only enables generic Block IO controller infrastructure. 848 One needs to also enable actual IO controlling logic/policy. For 849 enabling proportional weight division of disk bandwidth in CFQ, set 850 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 851 CONFIG_BLK_DEV_THROTTLING=y. 852 853 See Documentation/cgroup-v1/blkio-controller.rst for more information. 854 855config CGROUP_WRITEBACK 856 bool 857 depends on MEMCG && BLK_CGROUP 858 default y 859 860menuconfig CGROUP_SCHED 861 bool "CPU controller" 862 default n 863 help 864 This feature lets CPU scheduler recognize task groups and control CPU 865 bandwidth allocation to such task groups. It uses cgroups to group 866 tasks. 867 868if CGROUP_SCHED 869config FAIR_GROUP_SCHED 870 bool "Group scheduling for SCHED_OTHER" 871 depends on CGROUP_SCHED 872 default CGROUP_SCHED 873 874config CFS_BANDWIDTH 875 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 876 depends on FAIR_GROUP_SCHED 877 default n 878 help 879 This option allows users to define CPU bandwidth rates (limits) for 880 tasks running within the fair group scheduler. Groups with no limit 881 set are considered to be unconstrained and will run with no 882 restriction. 883 See Documentation/scheduler/sched-bwc.rst for more information. 884 885config RT_GROUP_SCHED 886 bool "Group scheduling for SCHED_RR/FIFO" 887 depends on CGROUP_SCHED 888 default n 889 help 890 This feature lets you explicitly allocate real CPU bandwidth 891 to task groups. If enabled, it will also make it impossible to 892 schedule realtime tasks for non-root users until you allocate 893 realtime bandwidth for them. 894 See Documentation/scheduler/sched-rt-group.rst for more information. 895 896endif #CGROUP_SCHED 897 898config CGROUP_PIDS 899 bool "PIDs controller" 900 help 901 Provides enforcement of process number limits in the scope of a 902 cgroup. Any attempt to fork more processes than is allowed in the 903 cgroup will fail. PIDs are fundamentally a global resource because it 904 is fairly trivial to reach PID exhaustion before you reach even a 905 conservative kmemcg limit. As a result, it is possible to grind a 906 system to halt without being limited by other cgroup policies. The 907 PIDs controller is designed to stop this from happening. 908 909 It should be noted that organisational operations (such as attaching 910 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 911 since the PIDs limit only affects a process's ability to fork, not to 912 attach to a cgroup. 913 914config CGROUP_RDMA 915 bool "RDMA controller" 916 help 917 Provides enforcement of RDMA resources defined by IB stack. 918 It is fairly easy for consumers to exhaust RDMA resources, which 919 can result into resource unavailability to other consumers. 920 RDMA controller is designed to stop this from happening. 921 Attaching processes with active RDMA resources to the cgroup 922 hierarchy is allowed even if can cross the hierarchy's limit. 923 924config CGROUP_FREEZER 925 bool "Freezer controller" 926 help 927 Provides a way to freeze and unfreeze all tasks in a 928 cgroup. 929 930 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 931 controller includes important in-kernel memory consumers per default. 932 933 If you're using cgroup2, say N. 934 935config CGROUP_HUGETLB 936 bool "HugeTLB controller" 937 depends on HUGETLB_PAGE 938 select PAGE_COUNTER 939 default n 940 help 941 Provides a cgroup controller for HugeTLB pages. 942 When you enable this, you can put a per cgroup limit on HugeTLB usage. 943 The limit is enforced during page fault. Since HugeTLB doesn't 944 support page reclaim, enforcing the limit at page fault time implies 945 that, the application will get SIGBUS signal if it tries to access 946 HugeTLB pages beyond its limit. This requires the application to know 947 beforehand how much HugeTLB pages it would require for its use. The 948 control group is tracked in the third page lru pointer. This means 949 that we cannot use the controller with huge page less than 3 pages. 950 951config CPUSETS 952 bool "Cpuset controller" 953 depends on SMP 954 help 955 This option will let you create and manage CPUSETs which 956 allow dynamically partitioning a system into sets of CPUs and 957 Memory Nodes and assigning tasks to run only within those sets. 958 This is primarily useful on large SMP or NUMA systems. 959 960 Say N if unsure. 961 962config PROC_PID_CPUSET 963 bool "Include legacy /proc/<pid>/cpuset file" 964 depends on CPUSETS 965 default y 966 967config CGROUP_DEVICE 968 bool "Device controller" 969 help 970 Provides a cgroup controller implementing whitelists for 971 devices which a process in the cgroup can mknod or open. 972 973config CGROUP_CPUACCT 974 bool "Simple CPU accounting controller" 975 help 976 Provides a simple controller for monitoring the 977 total CPU consumed by the tasks in a cgroup. 978 979config CGROUP_PERF 980 bool "Perf controller" 981 depends on PERF_EVENTS 982 help 983 This option extends the perf per-cpu mode to restrict monitoring 984 to threads which belong to the cgroup specified and run on the 985 designated cpu. 986 987 Say N if unsure. 988 989config CGROUP_BPF 990 bool "Support for eBPF programs attached to cgroups" 991 depends on BPF_SYSCALL 992 select SOCK_CGROUP_DATA 993 help 994 Allow attaching eBPF programs to a cgroup using the bpf(2) 995 syscall command BPF_PROG_ATTACH. 996 997 In which context these programs are accessed depends on the type 998 of attachment. For instance, programs that are attached using 999 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1000 inet sockets. 1001 1002config CGROUP_DEBUG 1003 bool "Debug controller" 1004 default n 1005 depends on DEBUG_KERNEL 1006 help 1007 This option enables a simple controller that exports 1008 debugging information about the cgroups framework. This 1009 controller is for control cgroup debugging only. Its 1010 interfaces are not stable. 1011 1012 Say N. 1013 1014config SOCK_CGROUP_DATA 1015 bool 1016 default n 1017 1018endif # CGROUPS 1019 1020menuconfig NAMESPACES 1021 bool "Namespaces support" if EXPERT 1022 depends on MULTIUSER 1023 default !EXPERT 1024 help 1025 Provides the way to make tasks work with different objects using 1026 the same id. For example same IPC id may refer to different objects 1027 or same user id or pid may refer to different tasks when used in 1028 different namespaces. 1029 1030if NAMESPACES 1031 1032config UTS_NS 1033 bool "UTS namespace" 1034 default y 1035 help 1036 In this namespace tasks see different info provided with the 1037 uname() system call 1038 1039config IPC_NS 1040 bool "IPC namespace" 1041 depends on (SYSVIPC || POSIX_MQUEUE) 1042 default y 1043 help 1044 In this namespace tasks work with IPC ids which correspond to 1045 different IPC objects in different namespaces. 1046 1047config USER_NS 1048 bool "User namespace" 1049 default n 1050 help 1051 This allows containers, i.e. vservers, to use user namespaces 1052 to provide different user info for different servers. 1053 1054 When user namespaces are enabled in the kernel it is 1055 recommended that the MEMCG option also be enabled and that 1056 user-space use the memory control groups to limit the amount 1057 of memory a memory unprivileged users can use. 1058 1059 If unsure, say N. 1060 1061config PID_NS 1062 bool "PID Namespaces" 1063 default y 1064 help 1065 Support process id namespaces. This allows having multiple 1066 processes with the same pid as long as they are in different 1067 pid namespaces. This is a building block of containers. 1068 1069config NET_NS 1070 bool "Network namespace" 1071 depends on NET 1072 default y 1073 help 1074 Allow user space to create what appear to be multiple instances 1075 of the network stack. 1076 1077endif # NAMESPACES 1078 1079config CHECKPOINT_RESTORE 1080 bool "Checkpoint/restore support" 1081 select PROC_CHILDREN 1082 default n 1083 help 1084 Enables additional kernel features in a sake of checkpoint/restore. 1085 In particular it adds auxiliary prctl codes to setup process text, 1086 data and heap segment sizes, and a few additional /proc filesystem 1087 entries. 1088 1089 If unsure, say N here. 1090 1091config SCHED_AUTOGROUP 1092 bool "Automatic process group scheduling" 1093 select CGROUPS 1094 select CGROUP_SCHED 1095 select FAIR_GROUP_SCHED 1096 help 1097 This option optimizes the scheduler for common desktop workloads by 1098 automatically creating and populating task groups. This separation 1099 of workloads isolates aggressive CPU burners (like build jobs) from 1100 desktop applications. Task group autogeneration is currently based 1101 upon task session. 1102 1103config SYSFS_DEPRECATED 1104 bool "Enable deprecated sysfs features to support old userspace tools" 1105 depends on SYSFS 1106 default n 1107 help 1108 This option adds code that switches the layout of the "block" class 1109 devices, to not show up in /sys/class/block/, but only in 1110 /sys/block/. 1111 1112 This switch is only active when the sysfs.deprecated=1 boot option is 1113 passed or the SYSFS_DEPRECATED_V2 option is set. 1114 1115 This option allows new kernels to run on old distributions and tools, 1116 which might get confused by /sys/class/block/. Since 2007/2008 all 1117 major distributions and tools handle this just fine. 1118 1119 Recent distributions and userspace tools after 2009/2010 depend on 1120 the existence of /sys/class/block/, and will not work with this 1121 option enabled. 1122 1123 Only if you are using a new kernel on an old distribution, you might 1124 need to say Y here. 1125 1126config SYSFS_DEPRECATED_V2 1127 bool "Enable deprecated sysfs features by default" 1128 default n 1129 depends on SYSFS 1130 depends on SYSFS_DEPRECATED 1131 help 1132 Enable deprecated sysfs by default. 1133 1134 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1135 option. 1136 1137 Only if you are using a new kernel on an old distribution, you might 1138 need to say Y here. Even then, odds are you would not need it 1139 enabled, you can always pass the boot option if absolutely necessary. 1140 1141config RELAY 1142 bool "Kernel->user space relay support (formerly relayfs)" 1143 select IRQ_WORK 1144 help 1145 This option enables support for relay interface support in 1146 certain file systems (such as debugfs). 1147 It is designed to provide an efficient mechanism for tools and 1148 facilities to relay large amounts of data from kernel space to 1149 user space. 1150 1151 If unsure, say N. 1152 1153config BLK_DEV_INITRD 1154 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1155 help 1156 The initial RAM filesystem is a ramfs which is loaded by the 1157 boot loader (loadlin or lilo) and that is mounted as root 1158 before the normal boot procedure. It is typically used to 1159 load modules needed to mount the "real" root file system, 1160 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1161 1162 If RAM disk support (BLK_DEV_RAM) is also included, this 1163 also enables initial RAM disk (initrd) support and adds 1164 15 Kbytes (more on some other architectures) to the kernel size. 1165 1166 If unsure say Y. 1167 1168if BLK_DEV_INITRD 1169 1170source "usr/Kconfig" 1171 1172endif 1173 1174choice 1175 prompt "Compiler optimization level" 1176 default CC_OPTIMIZE_FOR_PERFORMANCE 1177 1178config CC_OPTIMIZE_FOR_PERFORMANCE 1179 bool "Optimize for performance" 1180 help 1181 This is the default optimization level for the kernel, building 1182 with the "-O2" compiler flag for best performance and most 1183 helpful compile-time warnings. 1184 1185config CC_OPTIMIZE_FOR_SIZE 1186 bool "Optimize for size" 1187 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives 1188 help 1189 Enabling this option will pass "-Os" instead of "-O2" to 1190 your compiler resulting in a smaller kernel. 1191 1192 If unsure, say N. 1193 1194endchoice 1195 1196config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1197 bool 1198 help 1199 This requires that the arch annotates or otherwise protects 1200 its external entry points from being discarded. Linker scripts 1201 must also merge .text.*, .data.*, and .bss.* correctly into 1202 output sections. Care must be taken not to pull in unrelated 1203 sections (e.g., '.text.init'). Typically '.' in section names 1204 is used to distinguish them from label names / C identifiers. 1205 1206config LD_DEAD_CODE_DATA_ELIMINATION 1207 bool "Dead code and data elimination (EXPERIMENTAL)" 1208 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1209 depends on EXPERT 1210 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800) 1211 depends on $(cc-option,-ffunction-sections -fdata-sections) 1212 depends on $(ld-option,--gc-sections) 1213 help 1214 Enable this if you want to do dead code and data elimination with 1215 the linker by compiling with -ffunction-sections -fdata-sections, 1216 and linking with --gc-sections. 1217 1218 This can reduce on disk and in-memory size of the kernel 1219 code and static data, particularly for small configs and 1220 on small systems. This has the possibility of introducing 1221 silently broken kernel if the required annotations are not 1222 present. This option is not well tested yet, so use at your 1223 own risk. 1224 1225config SYSCTL 1226 bool 1227 1228config HAVE_UID16 1229 bool 1230 1231config SYSCTL_EXCEPTION_TRACE 1232 bool 1233 help 1234 Enable support for /proc/sys/debug/exception-trace. 1235 1236config SYSCTL_ARCH_UNALIGN_NO_WARN 1237 bool 1238 help 1239 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1240 Allows arch to define/use @no_unaligned_warning to possibly warn 1241 about unaligned access emulation going on under the hood. 1242 1243config SYSCTL_ARCH_UNALIGN_ALLOW 1244 bool 1245 help 1246 Enable support for /proc/sys/kernel/unaligned-trap 1247 Allows arches to define/use @unaligned_enabled to runtime toggle 1248 the unaligned access emulation. 1249 see arch/parisc/kernel/unaligned.c for reference 1250 1251config HAVE_PCSPKR_PLATFORM 1252 bool 1253 1254# interpreter that classic socket filters depend on 1255config BPF 1256 bool 1257 1258menuconfig EXPERT 1259 bool "Configure standard kernel features (expert users)" 1260 # Unhide debug options, to make the on-by-default options visible 1261 select DEBUG_KERNEL 1262 help 1263 This option allows certain base kernel options and settings 1264 to be disabled or tweaked. This is for specialized 1265 environments which can tolerate a "non-standard" kernel. 1266 Only use this if you really know what you are doing. 1267 1268config UID16 1269 bool "Enable 16-bit UID system calls" if EXPERT 1270 depends on HAVE_UID16 && MULTIUSER 1271 default y 1272 help 1273 This enables the legacy 16-bit UID syscall wrappers. 1274 1275config MULTIUSER 1276 bool "Multiple users, groups and capabilities support" if EXPERT 1277 default y 1278 help 1279 This option enables support for non-root users, groups and 1280 capabilities. 1281 1282 If you say N here, all processes will run with UID 0, GID 0, and all 1283 possible capabilities. Saying N here also compiles out support for 1284 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1285 setgid, and capset. 1286 1287 If unsure, say Y here. 1288 1289config SGETMASK_SYSCALL 1290 bool "sgetmask/ssetmask syscalls support" if EXPERT 1291 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1292 ---help--- 1293 sys_sgetmask and sys_ssetmask are obsolete system calls 1294 no longer supported in libc but still enabled by default in some 1295 architectures. 1296 1297 If unsure, leave the default option here. 1298 1299config SYSFS_SYSCALL 1300 bool "Sysfs syscall support" if EXPERT 1301 default y 1302 ---help--- 1303 sys_sysfs is an obsolete system call no longer supported in libc. 1304 Note that disabling this option is more secure but might break 1305 compatibility with some systems. 1306 1307 If unsure say Y here. 1308 1309config SYSCTL_SYSCALL 1310 bool "Sysctl syscall support" if EXPERT 1311 depends on PROC_SYSCTL 1312 default n 1313 select SYSCTL 1314 ---help--- 1315 sys_sysctl uses binary paths that have been found challenging 1316 to properly maintain and use. The interface in /proc/sys 1317 using paths with ascii names is now the primary path to this 1318 information. 1319 1320 Almost nothing using the binary sysctl interface so if you are 1321 trying to save some space it is probably safe to disable this, 1322 making your kernel marginally smaller. 1323 1324 If unsure say N here. 1325 1326config FHANDLE 1327 bool "open by fhandle syscalls" if EXPERT 1328 select EXPORTFS 1329 default y 1330 help 1331 If you say Y here, a user level program will be able to map 1332 file names to handle and then later use the handle for 1333 different file system operations. This is useful in implementing 1334 userspace file servers, which now track files using handles instead 1335 of names. The handle would remain the same even if file names 1336 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1337 syscalls. 1338 1339config POSIX_TIMERS 1340 bool "Posix Clocks & timers" if EXPERT 1341 default y 1342 help 1343 This includes native support for POSIX timers to the kernel. 1344 Some embedded systems have no use for them and therefore they 1345 can be configured out to reduce the size of the kernel image. 1346 1347 When this option is disabled, the following syscalls won't be 1348 available: timer_create, timer_gettime: timer_getoverrun, 1349 timer_settime, timer_delete, clock_adjtime, getitimer, 1350 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1351 clock_getres and clock_nanosleep syscalls will be limited to 1352 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1353 1354 If unsure say y. 1355 1356config PRINTK 1357 default y 1358 bool "Enable support for printk" if EXPERT 1359 select IRQ_WORK 1360 help 1361 This option enables normal printk support. Removing it 1362 eliminates most of the message strings from the kernel image 1363 and makes the kernel more or less silent. As this makes it 1364 very difficult to diagnose system problems, saying N here is 1365 strongly discouraged. 1366 1367config PRINTK_NMI 1368 def_bool y 1369 depends on PRINTK 1370 depends on HAVE_NMI 1371 1372config BUG 1373 bool "BUG() support" if EXPERT 1374 default y 1375 help 1376 Disabling this option eliminates support for BUG and WARN, reducing 1377 the size of your kernel image and potentially quietly ignoring 1378 numerous fatal conditions. You should only consider disabling this 1379 option for embedded systems with no facilities for reporting errors. 1380 Just say Y. 1381 1382config ELF_CORE 1383 depends on COREDUMP 1384 default y 1385 bool "Enable ELF core dumps" if EXPERT 1386 help 1387 Enable support for generating core dumps. Disabling saves about 4k. 1388 1389 1390config PCSPKR_PLATFORM 1391 bool "Enable PC-Speaker support" if EXPERT 1392 depends on HAVE_PCSPKR_PLATFORM 1393 select I8253_LOCK 1394 default y 1395 help 1396 This option allows to disable the internal PC-Speaker 1397 support, saving some memory. 1398 1399config BASE_FULL 1400 default y 1401 bool "Enable full-sized data structures for core" if EXPERT 1402 help 1403 Disabling this option reduces the size of miscellaneous core 1404 kernel data structures. This saves memory on small machines, 1405 but may reduce performance. 1406 1407config FUTEX 1408 bool "Enable futex support" if EXPERT 1409 default y 1410 imply RT_MUTEXES 1411 help 1412 Disabling this option will cause the kernel to be built without 1413 support for "fast userspace mutexes". The resulting kernel may not 1414 run glibc-based applications correctly. 1415 1416config FUTEX_PI 1417 bool 1418 depends on FUTEX && RT_MUTEXES 1419 default y 1420 1421config HAVE_FUTEX_CMPXCHG 1422 bool 1423 depends on FUTEX 1424 help 1425 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1426 is implemented and always working. This removes a couple of runtime 1427 checks. 1428 1429config EPOLL 1430 bool "Enable eventpoll support" if EXPERT 1431 default y 1432 help 1433 Disabling this option will cause the kernel to be built without 1434 support for epoll family of system calls. 1435 1436config SIGNALFD 1437 bool "Enable signalfd() system call" if EXPERT 1438 default y 1439 help 1440 Enable the signalfd() system call that allows to receive signals 1441 on a file descriptor. 1442 1443 If unsure, say Y. 1444 1445config TIMERFD 1446 bool "Enable timerfd() system call" if EXPERT 1447 default y 1448 help 1449 Enable the timerfd() system call that allows to receive timer 1450 events on a file descriptor. 1451 1452 If unsure, say Y. 1453 1454config EVENTFD 1455 bool "Enable eventfd() system call" if EXPERT 1456 default y 1457 help 1458 Enable the eventfd() system call that allows to receive both 1459 kernel notification (ie. KAIO) or userspace notifications. 1460 1461 If unsure, say Y. 1462 1463config SHMEM 1464 bool "Use full shmem filesystem" if EXPERT 1465 default y 1466 depends on MMU 1467 help 1468 The shmem is an internal filesystem used to manage shared memory. 1469 It is backed by swap and manages resource limits. It is also exported 1470 to userspace as tmpfs if TMPFS is enabled. Disabling this 1471 option replaces shmem and tmpfs with the much simpler ramfs code, 1472 which may be appropriate on small systems without swap. 1473 1474config AIO 1475 bool "Enable AIO support" if EXPERT 1476 default y 1477 help 1478 This option enables POSIX asynchronous I/O which may by used 1479 by some high performance threaded applications. Disabling 1480 this option saves about 7k. 1481 1482config IO_URING 1483 bool "Enable IO uring support" if EXPERT 1484 select ANON_INODES 1485 default y 1486 help 1487 This option enables support for the io_uring interface, enabling 1488 applications to submit and complete IO through submission and 1489 completion rings that are shared between the kernel and application. 1490 1491config ADVISE_SYSCALLS 1492 bool "Enable madvise/fadvise syscalls" if EXPERT 1493 default y 1494 help 1495 This option enables the madvise and fadvise syscalls, used by 1496 applications to advise the kernel about their future memory or file 1497 usage, improving performance. If building an embedded system where no 1498 applications use these syscalls, you can disable this option to save 1499 space. 1500 1501config MEMBARRIER 1502 bool "Enable membarrier() system call" if EXPERT 1503 default y 1504 help 1505 Enable the membarrier() system call that allows issuing memory 1506 barriers across all running threads, which can be used to distribute 1507 the cost of user-space memory barriers asymmetrically by transforming 1508 pairs of memory barriers into pairs consisting of membarrier() and a 1509 compiler barrier. 1510 1511 If unsure, say Y. 1512 1513config KALLSYMS 1514 bool "Load all symbols for debugging/ksymoops" if EXPERT 1515 default y 1516 help 1517 Say Y here to let the kernel print out symbolic crash information and 1518 symbolic stack backtraces. This increases the size of the kernel 1519 somewhat, as all symbols have to be loaded into the kernel image. 1520 1521config KALLSYMS_ALL 1522 bool "Include all symbols in kallsyms" 1523 depends on DEBUG_KERNEL && KALLSYMS 1524 help 1525 Normally kallsyms only contains the symbols of functions for nicer 1526 OOPS messages and backtraces (i.e., symbols from the text and inittext 1527 sections). This is sufficient for most cases. And only in very rare 1528 cases (e.g., when a debugger is used) all symbols are required (e.g., 1529 names of variables from the data sections, etc). 1530 1531 This option makes sure that all symbols are loaded into the kernel 1532 image (i.e., symbols from all sections) in cost of increased kernel 1533 size (depending on the kernel configuration, it may be 300KiB or 1534 something like this). 1535 1536 Say N unless you really need all symbols. 1537 1538config KALLSYMS_ABSOLUTE_PERCPU 1539 bool 1540 depends on KALLSYMS 1541 default X86_64 && SMP 1542 1543config KALLSYMS_BASE_RELATIVE 1544 bool 1545 depends on KALLSYMS 1546 default !IA64 1547 help 1548 Instead of emitting them as absolute values in the native word size, 1549 emit the symbol references in the kallsyms table as 32-bit entries, 1550 each containing a relative value in the range [base, base + U32_MAX] 1551 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1552 an absolute value in the range [0, S32_MAX] or a relative value in the 1553 range [base, base + S32_MAX], where base is the lowest relative symbol 1554 address encountered in the image. 1555 1556 On 64-bit builds, this reduces the size of the address table by 50%, 1557 but more importantly, it results in entries whose values are build 1558 time constants, and no relocation pass is required at runtime to fix 1559 up the entries based on the runtime load address of the kernel. 1560 1561# end of the "standard kernel features (expert users)" menu 1562 1563# syscall, maps, verifier 1564config BPF_SYSCALL 1565 bool "Enable bpf() system call" 1566 select BPF 1567 select IRQ_WORK 1568 default n 1569 help 1570 Enable the bpf() system call that allows to manipulate eBPF 1571 programs and maps via file descriptors. 1572 1573config BPF_JIT_ALWAYS_ON 1574 bool "Permanently enable BPF JIT and remove BPF interpreter" 1575 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1576 help 1577 Enables BPF JIT and removes BPF interpreter to avoid 1578 speculative execution of BPF instructions by the interpreter 1579 1580config USERFAULTFD 1581 bool "Enable userfaultfd() system call" 1582 depends on MMU 1583 help 1584 Enable the userfaultfd() system call that allows to intercept and 1585 handle page faults in userland. 1586 1587config ARCH_HAS_MEMBARRIER_CALLBACKS 1588 bool 1589 1590config ARCH_HAS_MEMBARRIER_SYNC_CORE 1591 bool 1592 1593config RSEQ 1594 bool "Enable rseq() system call" if EXPERT 1595 default y 1596 depends on HAVE_RSEQ 1597 select MEMBARRIER 1598 help 1599 Enable the restartable sequences system call. It provides a 1600 user-space cache for the current CPU number value, which 1601 speeds up getting the current CPU number from user-space, 1602 as well as an ABI to speed up user-space operations on 1603 per-CPU data. 1604 1605 If unsure, say Y. 1606 1607config DEBUG_RSEQ 1608 default n 1609 bool "Enabled debugging of rseq() system call" if EXPERT 1610 depends on RSEQ && DEBUG_KERNEL 1611 help 1612 Enable extra debugging checks for the rseq system call. 1613 1614 If unsure, say N. 1615 1616config EMBEDDED 1617 bool "Embedded system" 1618 option allnoconfig_y 1619 select EXPERT 1620 help 1621 This option should be enabled if compiling the kernel for 1622 an embedded system so certain expert options are available 1623 for configuration. 1624 1625config HAVE_PERF_EVENTS 1626 bool 1627 help 1628 See tools/perf/design.txt for details. 1629 1630config PERF_USE_VMALLOC 1631 bool 1632 help 1633 See tools/perf/design.txt for details 1634 1635config PC104 1636 bool "PC/104 support" if EXPERT 1637 help 1638 Expose PC/104 form factor device drivers and options available for 1639 selection and configuration. Enable this option if your target 1640 machine has a PC/104 bus. 1641 1642menu "Kernel Performance Events And Counters" 1643 1644config PERF_EVENTS 1645 bool "Kernel performance events and counters" 1646 default y if PROFILING 1647 depends on HAVE_PERF_EVENTS 1648 select IRQ_WORK 1649 select SRCU 1650 help 1651 Enable kernel support for various performance events provided 1652 by software and hardware. 1653 1654 Software events are supported either built-in or via the 1655 use of generic tracepoints. 1656 1657 Most modern CPUs support performance events via performance 1658 counter registers. These registers count the number of certain 1659 types of hw events: such as instructions executed, cachemisses 1660 suffered, or branches mis-predicted - without slowing down the 1661 kernel or applications. These registers can also trigger interrupts 1662 when a threshold number of events have passed - and can thus be 1663 used to profile the code that runs on that CPU. 1664 1665 The Linux Performance Event subsystem provides an abstraction of 1666 these software and hardware event capabilities, available via a 1667 system call and used by the "perf" utility in tools/perf/. It 1668 provides per task and per CPU counters, and it provides event 1669 capabilities on top of those. 1670 1671 Say Y if unsure. 1672 1673config DEBUG_PERF_USE_VMALLOC 1674 default n 1675 bool "Debug: use vmalloc to back perf mmap() buffers" 1676 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1677 select PERF_USE_VMALLOC 1678 help 1679 Use vmalloc memory to back perf mmap() buffers. 1680 1681 Mostly useful for debugging the vmalloc code on platforms 1682 that don't require it. 1683 1684 Say N if unsure. 1685 1686endmenu 1687 1688config VM_EVENT_COUNTERS 1689 default y 1690 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1691 help 1692 VM event counters are needed for event counts to be shown. 1693 This option allows the disabling of the VM event counters 1694 on EXPERT systems. /proc/vmstat will only show page counts 1695 if VM event counters are disabled. 1696 1697config SLUB_DEBUG 1698 default y 1699 bool "Enable SLUB debugging support" if EXPERT 1700 depends on SLUB && SYSFS 1701 help 1702 SLUB has extensive debug support features. Disabling these can 1703 result in significant savings in code size. This also disables 1704 SLUB sysfs support. /sys/slab will not exist and there will be 1705 no support for cache validation etc. 1706 1707config SLUB_MEMCG_SYSFS_ON 1708 default n 1709 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1710 depends on SLUB && SYSFS && MEMCG 1711 help 1712 SLUB creates a directory under /sys/kernel/slab for each 1713 allocation cache to host info and debug files. If memory 1714 cgroup is enabled, each cache can have per memory cgroup 1715 caches. SLUB can create the same sysfs directories for these 1716 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1717 to a very high number of debug files being created. This is 1718 controlled by slub_memcg_sysfs boot parameter and this 1719 config option determines the parameter's default value. 1720 1721config COMPAT_BRK 1722 bool "Disable heap randomization" 1723 default y 1724 help 1725 Randomizing heap placement makes heap exploits harder, but it 1726 also breaks ancient binaries (including anything libc5 based). 1727 This option changes the bootup default to heap randomization 1728 disabled, and can be overridden at runtime by setting 1729 /proc/sys/kernel/randomize_va_space to 2. 1730 1731 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1732 1733choice 1734 prompt "Choose SLAB allocator" 1735 default SLUB 1736 help 1737 This option allows to select a slab allocator. 1738 1739config SLAB 1740 bool "SLAB" 1741 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1742 help 1743 The regular slab allocator that is established and known to work 1744 well in all environments. It organizes cache hot objects in 1745 per cpu and per node queues. 1746 1747config SLUB 1748 bool "SLUB (Unqueued Allocator)" 1749 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1750 help 1751 SLUB is a slab allocator that minimizes cache line usage 1752 instead of managing queues of cached objects (SLAB approach). 1753 Per cpu caching is realized using slabs of objects instead 1754 of queues of objects. SLUB can use memory efficiently 1755 and has enhanced diagnostics. SLUB is the default choice for 1756 a slab allocator. 1757 1758config SLOB 1759 depends on EXPERT 1760 bool "SLOB (Simple Allocator)" 1761 help 1762 SLOB replaces the stock allocator with a drastically simpler 1763 allocator. SLOB is generally more space efficient but 1764 does not perform as well on large systems. 1765 1766endchoice 1767 1768config SLAB_MERGE_DEFAULT 1769 bool "Allow slab caches to be merged" 1770 default y 1771 help 1772 For reduced kernel memory fragmentation, slab caches can be 1773 merged when they share the same size and other characteristics. 1774 This carries a risk of kernel heap overflows being able to 1775 overwrite objects from merged caches (and more easily control 1776 cache layout), which makes such heap attacks easier to exploit 1777 by attackers. By keeping caches unmerged, these kinds of exploits 1778 can usually only damage objects in the same cache. To disable 1779 merging at runtime, "slab_nomerge" can be passed on the kernel 1780 command line. 1781 1782config SLAB_FREELIST_RANDOM 1783 default n 1784 depends on SLAB || SLUB 1785 bool "SLAB freelist randomization" 1786 help 1787 Randomizes the freelist order used on creating new pages. This 1788 security feature reduces the predictability of the kernel slab 1789 allocator against heap overflows. 1790 1791config SLAB_FREELIST_HARDENED 1792 bool "Harden slab freelist metadata" 1793 depends on SLUB 1794 help 1795 Many kernel heap attacks try to target slab cache metadata and 1796 other infrastructure. This options makes minor performance 1797 sacrifies to harden the kernel slab allocator against common 1798 freelist exploit methods. 1799 1800config SHUFFLE_PAGE_ALLOCATOR 1801 bool "Page allocator randomization" 1802 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1803 help 1804 Randomization of the page allocator improves the average 1805 utilization of a direct-mapped memory-side-cache. See section 1806 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1807 6.2a specification for an example of how a platform advertises 1808 the presence of a memory-side-cache. There are also incidental 1809 security benefits as it reduces the predictability of page 1810 allocations to compliment SLAB_FREELIST_RANDOM, but the 1811 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1812 10th order of pages is selected based on cache utilization 1813 benefits on x86. 1814 1815 While the randomization improves cache utilization it may 1816 negatively impact workloads on platforms without a cache. For 1817 this reason, by default, the randomization is enabled only 1818 after runtime detection of a direct-mapped memory-side-cache. 1819 Otherwise, the randomization may be force enabled with the 1820 'page_alloc.shuffle' kernel command line parameter. 1821 1822 Say Y if unsure. 1823 1824config SLUB_CPU_PARTIAL 1825 default y 1826 depends on SLUB && SMP 1827 bool "SLUB per cpu partial cache" 1828 help 1829 Per cpu partial caches accellerate objects allocation and freeing 1830 that is local to a processor at the price of more indeterminism 1831 in the latency of the free. On overflow these caches will be cleared 1832 which requires the taking of locks that may cause latency spikes. 1833 Typically one would choose no for a realtime system. 1834 1835config MMAP_ALLOW_UNINITIALIZED 1836 bool "Allow mmapped anonymous memory to be uninitialized" 1837 depends on EXPERT && !MMU 1838 default n 1839 help 1840 Normally, and according to the Linux spec, anonymous memory obtained 1841 from mmap() has its contents cleared before it is passed to 1842 userspace. Enabling this config option allows you to request that 1843 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1844 providing a huge performance boost. If this option is not enabled, 1845 then the flag will be ignored. 1846 1847 This is taken advantage of by uClibc's malloc(), and also by 1848 ELF-FDPIC binfmt's brk and stack allocator. 1849 1850 Because of the obvious security issues, this option should only be 1851 enabled on embedded devices where you control what is run in 1852 userspace. Since that isn't generally a problem on no-MMU systems, 1853 it is normally safe to say Y here. 1854 1855 See Documentation/nommu-mmap.txt for more information. 1856 1857config SYSTEM_DATA_VERIFICATION 1858 def_bool n 1859 select SYSTEM_TRUSTED_KEYRING 1860 select KEYS 1861 select CRYPTO 1862 select CRYPTO_RSA 1863 select ASYMMETRIC_KEY_TYPE 1864 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1865 select ASN1 1866 select OID_REGISTRY 1867 select X509_CERTIFICATE_PARSER 1868 select PKCS7_MESSAGE_PARSER 1869 help 1870 Provide PKCS#7 message verification using the contents of the system 1871 trusted keyring to provide public keys. This then can be used for 1872 module verification, kexec image verification and firmware blob 1873 verification. 1874 1875config PROFILING 1876 bool "Profiling support" 1877 help 1878 Say Y here to enable the extended profiling support mechanisms used 1879 by profilers such as OProfile. 1880 1881# 1882# Place an empty function call at each tracepoint site. Can be 1883# dynamically changed for a probe function. 1884# 1885config TRACEPOINTS 1886 bool 1887 1888endmenu # General setup 1889 1890source "arch/Kconfig" 1891 1892config RT_MUTEXES 1893 bool 1894 1895config BASE_SMALL 1896 int 1897 default 0 if BASE_FULL 1898 default 1 if !BASE_FULL 1899 1900menuconfig MODULES 1901 bool "Enable loadable module support" 1902 option modules 1903 help 1904 Kernel modules are small pieces of compiled code which can 1905 be inserted in the running kernel, rather than being 1906 permanently built into the kernel. You use the "modprobe" 1907 tool to add (and sometimes remove) them. If you say Y here, 1908 many parts of the kernel can be built as modules (by 1909 answering M instead of Y where indicated): this is most 1910 useful for infrequently used options which are not required 1911 for booting. For more information, see the man pages for 1912 modprobe, lsmod, modinfo, insmod and rmmod. 1913 1914 If you say Y here, you will need to run "make 1915 modules_install" to put the modules under /lib/modules/ 1916 where modprobe can find them (you may need to be root to do 1917 this). 1918 1919 If unsure, say Y. 1920 1921if MODULES 1922 1923config MODULE_FORCE_LOAD 1924 bool "Forced module loading" 1925 default n 1926 help 1927 Allow loading of modules without version information (ie. modprobe 1928 --force). Forced module loading sets the 'F' (forced) taint flag and 1929 is usually a really bad idea. 1930 1931config MODULE_UNLOAD 1932 bool "Module unloading" 1933 help 1934 Without this option you will not be able to unload any 1935 modules (note that some modules may not be unloadable 1936 anyway), which makes your kernel smaller, faster 1937 and simpler. If unsure, say Y. 1938 1939config MODULE_FORCE_UNLOAD 1940 bool "Forced module unloading" 1941 depends on MODULE_UNLOAD 1942 help 1943 This option allows you to force a module to unload, even if the 1944 kernel believes it is unsafe: the kernel will remove the module 1945 without waiting for anyone to stop using it (using the -f option to 1946 rmmod). This is mainly for kernel developers and desperate users. 1947 If unsure, say N. 1948 1949config MODVERSIONS 1950 bool "Module versioning support" 1951 help 1952 Usually, you have to use modules compiled with your kernel. 1953 Saying Y here makes it sometimes possible to use modules 1954 compiled for different kernels, by adding enough information 1955 to the modules to (hopefully) spot any changes which would 1956 make them incompatible with the kernel you are running. If 1957 unsure, say N. 1958 1959config MODULE_REL_CRCS 1960 bool 1961 depends on MODVERSIONS 1962 1963config MODULE_SRCVERSION_ALL 1964 bool "Source checksum for all modules" 1965 help 1966 Modules which contain a MODULE_VERSION get an extra "srcversion" 1967 field inserted into their modinfo section, which contains a 1968 sum of the source files which made it. This helps maintainers 1969 see exactly which source was used to build a module (since 1970 others sometimes change the module source without updating 1971 the version). With this option, such a "srcversion" field 1972 will be created for all modules. If unsure, say N. 1973 1974config MODULE_SIG 1975 bool "Module signature verification" 1976 depends on MODULES 1977 select SYSTEM_DATA_VERIFICATION 1978 help 1979 Check modules for valid signatures upon load: the signature 1980 is simply appended to the module. For more information see 1981 <file:Documentation/admin-guide/module-signing.rst>. 1982 1983 Note that this option adds the OpenSSL development packages as a 1984 kernel build dependency so that the signing tool can use its crypto 1985 library. 1986 1987 !!!WARNING!!! If you enable this option, you MUST make sure that the 1988 module DOES NOT get stripped after being signed. This includes the 1989 debuginfo strip done by some packagers (such as rpmbuild) and 1990 inclusion into an initramfs that wants the module size reduced. 1991 1992config MODULE_SIG_FORCE 1993 bool "Require modules to be validly signed" 1994 depends on MODULE_SIG 1995 help 1996 Reject unsigned modules or signed modules for which we don't have a 1997 key. Without this, such modules will simply taint the kernel. 1998 1999config MODULE_SIG_ALL 2000 bool "Automatically sign all modules" 2001 default y 2002 depends on MODULE_SIG 2003 help 2004 Sign all modules during make modules_install. Without this option, 2005 modules must be signed manually, using the scripts/sign-file tool. 2006 2007comment "Do not forget to sign required modules with scripts/sign-file" 2008 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2009 2010choice 2011 prompt "Which hash algorithm should modules be signed with?" 2012 depends on MODULE_SIG 2013 help 2014 This determines which sort of hashing algorithm will be used during 2015 signature generation. This algorithm _must_ be built into the kernel 2016 directly so that signature verification can take place. It is not 2017 possible to load a signed module containing the algorithm to check 2018 the signature on that module. 2019 2020config MODULE_SIG_SHA1 2021 bool "Sign modules with SHA-1" 2022 select CRYPTO_SHA1 2023 2024config MODULE_SIG_SHA224 2025 bool "Sign modules with SHA-224" 2026 select CRYPTO_SHA256 2027 2028config MODULE_SIG_SHA256 2029 bool "Sign modules with SHA-256" 2030 select CRYPTO_SHA256 2031 2032config MODULE_SIG_SHA384 2033 bool "Sign modules with SHA-384" 2034 select CRYPTO_SHA512 2035 2036config MODULE_SIG_SHA512 2037 bool "Sign modules with SHA-512" 2038 select CRYPTO_SHA512 2039 2040endchoice 2041 2042config MODULE_SIG_HASH 2043 string 2044 depends on MODULE_SIG 2045 default "sha1" if MODULE_SIG_SHA1 2046 default "sha224" if MODULE_SIG_SHA224 2047 default "sha256" if MODULE_SIG_SHA256 2048 default "sha384" if MODULE_SIG_SHA384 2049 default "sha512" if MODULE_SIG_SHA512 2050 2051config MODULE_COMPRESS 2052 bool "Compress modules on installation" 2053 depends on MODULES 2054 help 2055 2056 Compresses kernel modules when 'make modules_install' is run; gzip or 2057 xz depending on "Compression algorithm" below. 2058 2059 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 2060 2061 Out-of-tree kernel modules installed using Kbuild will also be 2062 compressed upon installation. 2063 2064 Note: for modules inside an initrd or initramfs, it's more efficient 2065 to compress the whole initrd or initramfs instead. 2066 2067 Note: This is fully compatible with signed modules. 2068 2069 If in doubt, say N. 2070 2071choice 2072 prompt "Compression algorithm" 2073 depends on MODULE_COMPRESS 2074 default MODULE_COMPRESS_GZIP 2075 help 2076 This determines which sort of compression will be used during 2077 'make modules_install'. 2078 2079 GZIP (default) and XZ are supported. 2080 2081config MODULE_COMPRESS_GZIP 2082 bool "GZIP" 2083 2084config MODULE_COMPRESS_XZ 2085 bool "XZ" 2086 2087endchoice 2088 2089config TRIM_UNUSED_KSYMS 2090 bool "Trim unused exported kernel symbols" 2091 depends on MODULES && !UNUSED_SYMBOLS 2092 help 2093 The kernel and some modules make many symbols available for 2094 other modules to use via EXPORT_SYMBOL() and variants. Depending 2095 on the set of modules being selected in your kernel configuration, 2096 many of those exported symbols might never be used. 2097 2098 This option allows for unused exported symbols to be dropped from 2099 the build. In turn, this provides the compiler more opportunities 2100 (especially when using LTO) for optimizing the code and reducing 2101 binary size. This might have some security advantages as well. 2102 2103 If unsure, or if you need to build out-of-tree modules, say N. 2104 2105endif # MODULES 2106 2107config MODULES_TREE_LOOKUP 2108 def_bool y 2109 depends on PERF_EVENTS || TRACING 2110 2111config INIT_ALL_POSSIBLE 2112 bool 2113 help 2114 Back when each arch used to define their own cpu_online_mask and 2115 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2116 with all 1s, and others with all 0s. When they were centralised, 2117 it was better to provide this option than to break all the archs 2118 and have several arch maintainers pursuing me down dark alleys. 2119 2120source "block/Kconfig" 2121 2122config PREEMPT_NOTIFIERS 2123 bool 2124 2125config PADATA 2126 depends on SMP 2127 bool 2128 2129config ASN1 2130 tristate 2131 help 2132 Build a simple ASN.1 grammar compiler that produces a bytecode output 2133 that can be interpreted by the ASN.1 stream decoder and used to 2134 inform it as to what tags are to be expected in a stream and what 2135 functions to call on what tags. 2136 2137source "kernel/Kconfig.locks" 2138 2139config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2140 bool 2141 2142# It may be useful for an architecture to override the definitions of the 2143# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2144# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2145# different calling convention for syscalls. They can also override the 2146# macros for not-implemented syscalls in kernel/sys_ni.c and 2147# kernel/time/posix-stubs.c. All these overrides need to be available in 2148# <asm/syscall_wrapper.h>. 2149config ARCH_HAS_SYSCALL_WRAPPER 2150 def_bool n 2151