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.txt (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 DEBUG_BLK_CGROUP 856 bool "IO controller debugging" 857 depends on BLK_CGROUP 858 default n 859 ---help--- 860 Enable some debugging help. Currently it exports additional stat 861 files in a cgroup which can be useful for debugging. 862 863config CGROUP_WRITEBACK 864 bool 865 depends on MEMCG && BLK_CGROUP 866 default y 867 868menuconfig CGROUP_SCHED 869 bool "CPU controller" 870 default n 871 help 872 This feature lets CPU scheduler recognize task groups and control CPU 873 bandwidth allocation to such task groups. It uses cgroups to group 874 tasks. 875 876if CGROUP_SCHED 877config FAIR_GROUP_SCHED 878 bool "Group scheduling for SCHED_OTHER" 879 depends on CGROUP_SCHED 880 default CGROUP_SCHED 881 882config CFS_BANDWIDTH 883 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 884 depends on FAIR_GROUP_SCHED 885 default n 886 help 887 This option allows users to define CPU bandwidth rates (limits) for 888 tasks running within the fair group scheduler. Groups with no limit 889 set are considered to be unconstrained and will run with no 890 restriction. 891 See Documentation/scheduler/sched-bwc.txt for more information. 892 893config RT_GROUP_SCHED 894 bool "Group scheduling for SCHED_RR/FIFO" 895 depends on CGROUP_SCHED 896 default n 897 help 898 This feature lets you explicitly allocate real CPU bandwidth 899 to task groups. If enabled, it will also make it impossible to 900 schedule realtime tasks for non-root users until you allocate 901 realtime bandwidth for them. 902 See Documentation/scheduler/sched-rt-group.txt for more information. 903 904endif #CGROUP_SCHED 905 906config CGROUP_PIDS 907 bool "PIDs controller" 908 help 909 Provides enforcement of process number limits in the scope of a 910 cgroup. Any attempt to fork more processes than is allowed in the 911 cgroup will fail. PIDs are fundamentally a global resource because it 912 is fairly trivial to reach PID exhaustion before you reach even a 913 conservative kmemcg limit. As a result, it is possible to grind a 914 system to halt without being limited by other cgroup policies. The 915 PIDs controller is designed to stop this from happening. 916 917 It should be noted that organisational operations (such as attaching 918 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 919 since the PIDs limit only affects a process's ability to fork, not to 920 attach to a cgroup. 921 922config CGROUP_RDMA 923 bool "RDMA controller" 924 help 925 Provides enforcement of RDMA resources defined by IB stack. 926 It is fairly easy for consumers to exhaust RDMA resources, which 927 can result into resource unavailability to other consumers. 928 RDMA controller is designed to stop this from happening. 929 Attaching processes with active RDMA resources to the cgroup 930 hierarchy is allowed even if can cross the hierarchy's limit. 931 932config CGROUP_FREEZER 933 bool "Freezer controller" 934 help 935 Provides a way to freeze and unfreeze all tasks in a 936 cgroup. 937 938 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 939 controller includes important in-kernel memory consumers per default. 940 941 If you're using cgroup2, say N. 942 943config CGROUP_HUGETLB 944 bool "HugeTLB controller" 945 depends on HUGETLB_PAGE 946 select PAGE_COUNTER 947 default n 948 help 949 Provides a cgroup controller for HugeTLB pages. 950 When you enable this, you can put a per cgroup limit on HugeTLB usage. 951 The limit is enforced during page fault. Since HugeTLB doesn't 952 support page reclaim, enforcing the limit at page fault time implies 953 that, the application will get SIGBUS signal if it tries to access 954 HugeTLB pages beyond its limit. This requires the application to know 955 beforehand how much HugeTLB pages it would require for its use. The 956 control group is tracked in the third page lru pointer. This means 957 that we cannot use the controller with huge page less than 3 pages. 958 959config CPUSETS 960 bool "Cpuset controller" 961 depends on SMP 962 help 963 This option will let you create and manage CPUSETs which 964 allow dynamically partitioning a system into sets of CPUs and 965 Memory Nodes and assigning tasks to run only within those sets. 966 This is primarily useful on large SMP or NUMA systems. 967 968 Say N if unsure. 969 970config PROC_PID_CPUSET 971 bool "Include legacy /proc/<pid>/cpuset file" 972 depends on CPUSETS 973 default y 974 975config CGROUP_DEVICE 976 bool "Device controller" 977 help 978 Provides a cgroup controller implementing whitelists for 979 devices which a process in the cgroup can mknod or open. 980 981config CGROUP_CPUACCT 982 bool "Simple CPU accounting controller" 983 help 984 Provides a simple controller for monitoring the 985 total CPU consumed by the tasks in a cgroup. 986 987config CGROUP_PERF 988 bool "Perf controller" 989 depends on PERF_EVENTS 990 help 991 This option extends the perf per-cpu mode to restrict monitoring 992 to threads which belong to the cgroup specified and run on the 993 designated cpu. 994 995 Say N if unsure. 996 997config CGROUP_BPF 998 bool "Support for eBPF programs attached to cgroups" 999 depends on BPF_SYSCALL 1000 select SOCK_CGROUP_DATA 1001 help 1002 Allow attaching eBPF programs to a cgroup using the bpf(2) 1003 syscall command BPF_PROG_ATTACH. 1004 1005 In which context these programs are accessed depends on the type 1006 of attachment. For instance, programs that are attached using 1007 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1008 inet sockets. 1009 1010config CGROUP_DEBUG 1011 bool "Debug controller" 1012 default n 1013 depends on DEBUG_KERNEL 1014 help 1015 This option enables a simple controller that exports 1016 debugging information about the cgroups framework. This 1017 controller is for control cgroup debugging only. Its 1018 interfaces are not stable. 1019 1020 Say N. 1021 1022config SOCK_CGROUP_DATA 1023 bool 1024 default n 1025 1026endif # CGROUPS 1027 1028menuconfig NAMESPACES 1029 bool "Namespaces support" if EXPERT 1030 depends on MULTIUSER 1031 default !EXPERT 1032 help 1033 Provides the way to make tasks work with different objects using 1034 the same id. For example same IPC id may refer to different objects 1035 or same user id or pid may refer to different tasks when used in 1036 different namespaces. 1037 1038if NAMESPACES 1039 1040config UTS_NS 1041 bool "UTS namespace" 1042 default y 1043 help 1044 In this namespace tasks see different info provided with the 1045 uname() system call 1046 1047config IPC_NS 1048 bool "IPC namespace" 1049 depends on (SYSVIPC || POSIX_MQUEUE) 1050 default y 1051 help 1052 In this namespace tasks work with IPC ids which correspond to 1053 different IPC objects in different namespaces. 1054 1055config USER_NS 1056 bool "User namespace" 1057 default n 1058 help 1059 This allows containers, i.e. vservers, to use user namespaces 1060 to provide different user info for different servers. 1061 1062 When user namespaces are enabled in the kernel it is 1063 recommended that the MEMCG option also be enabled and that 1064 user-space use the memory control groups to limit the amount 1065 of memory a memory unprivileged users can use. 1066 1067 If unsure, say N. 1068 1069config PID_NS 1070 bool "PID Namespaces" 1071 default y 1072 help 1073 Support process id namespaces. This allows having multiple 1074 processes with the same pid as long as they are in different 1075 pid namespaces. This is a building block of containers. 1076 1077config NET_NS 1078 bool "Network namespace" 1079 depends on NET 1080 default y 1081 help 1082 Allow user space to create what appear to be multiple instances 1083 of the network stack. 1084 1085endif # NAMESPACES 1086 1087config CHECKPOINT_RESTORE 1088 bool "Checkpoint/restore support" 1089 select PROC_CHILDREN 1090 default n 1091 help 1092 Enables additional kernel features in a sake of checkpoint/restore. 1093 In particular it adds auxiliary prctl codes to setup process text, 1094 data and heap segment sizes, and a few additional /proc filesystem 1095 entries. 1096 1097 If unsure, say N here. 1098 1099config SCHED_AUTOGROUP 1100 bool "Automatic process group scheduling" 1101 select CGROUPS 1102 select CGROUP_SCHED 1103 select FAIR_GROUP_SCHED 1104 help 1105 This option optimizes the scheduler for common desktop workloads by 1106 automatically creating and populating task groups. This separation 1107 of workloads isolates aggressive CPU burners (like build jobs) from 1108 desktop applications. Task group autogeneration is currently based 1109 upon task session. 1110 1111config SYSFS_DEPRECATED 1112 bool "Enable deprecated sysfs features to support old userspace tools" 1113 depends on SYSFS 1114 default n 1115 help 1116 This option adds code that switches the layout of the "block" class 1117 devices, to not show up in /sys/class/block/, but only in 1118 /sys/block/. 1119 1120 This switch is only active when the sysfs.deprecated=1 boot option is 1121 passed or the SYSFS_DEPRECATED_V2 option is set. 1122 1123 This option allows new kernels to run on old distributions and tools, 1124 which might get confused by /sys/class/block/. Since 2007/2008 all 1125 major distributions and tools handle this just fine. 1126 1127 Recent distributions and userspace tools after 2009/2010 depend on 1128 the existence of /sys/class/block/, and will not work with this 1129 option enabled. 1130 1131 Only if you are using a new kernel on an old distribution, you might 1132 need to say Y here. 1133 1134config SYSFS_DEPRECATED_V2 1135 bool "Enable deprecated sysfs features by default" 1136 default n 1137 depends on SYSFS 1138 depends on SYSFS_DEPRECATED 1139 help 1140 Enable deprecated sysfs by default. 1141 1142 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1143 option. 1144 1145 Only if you are using a new kernel on an old distribution, you might 1146 need to say Y here. Even then, odds are you would not need it 1147 enabled, you can always pass the boot option if absolutely necessary. 1148 1149config RELAY 1150 bool "Kernel->user space relay support (formerly relayfs)" 1151 select IRQ_WORK 1152 help 1153 This option enables support for relay interface support in 1154 certain file systems (such as debugfs). 1155 It is designed to provide an efficient mechanism for tools and 1156 facilities to relay large amounts of data from kernel space to 1157 user space. 1158 1159 If unsure, say N. 1160 1161config BLK_DEV_INITRD 1162 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1163 help 1164 The initial RAM filesystem is a ramfs which is loaded by the 1165 boot loader (loadlin or lilo) and that is mounted as root 1166 before the normal boot procedure. It is typically used to 1167 load modules needed to mount the "real" root file system, 1168 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1169 1170 If RAM disk support (BLK_DEV_RAM) is also included, this 1171 also enables initial RAM disk (initrd) support and adds 1172 15 Kbytes (more on some other architectures) to the kernel size. 1173 1174 If unsure say Y. 1175 1176if BLK_DEV_INITRD 1177 1178source "usr/Kconfig" 1179 1180endif 1181 1182choice 1183 prompt "Compiler optimization level" 1184 default CC_OPTIMIZE_FOR_PERFORMANCE 1185 1186config CC_OPTIMIZE_FOR_PERFORMANCE 1187 bool "Optimize for performance" 1188 help 1189 This is the default optimization level for the kernel, building 1190 with the "-O2" compiler flag for best performance and most 1191 helpful compile-time warnings. 1192 1193config CC_OPTIMIZE_FOR_SIZE 1194 bool "Optimize for size" 1195 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives 1196 help 1197 Enabling this option will pass "-Os" instead of "-O2" to 1198 your compiler resulting in a smaller kernel. 1199 1200 If unsure, say N. 1201 1202endchoice 1203 1204config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1205 bool 1206 help 1207 This requires that the arch annotates or otherwise protects 1208 its external entry points from being discarded. Linker scripts 1209 must also merge .text.*, .data.*, and .bss.* correctly into 1210 output sections. Care must be taken not to pull in unrelated 1211 sections (e.g., '.text.init'). Typically '.' in section names 1212 is used to distinguish them from label names / C identifiers. 1213 1214config LD_DEAD_CODE_DATA_ELIMINATION 1215 bool "Dead code and data elimination (EXPERIMENTAL)" 1216 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1217 depends on EXPERT 1218 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800) 1219 depends on $(cc-option,-ffunction-sections -fdata-sections) 1220 depends on $(ld-option,--gc-sections) 1221 help 1222 Enable this if you want to do dead code and data elimination with 1223 the linker by compiling with -ffunction-sections -fdata-sections, 1224 and linking with --gc-sections. 1225 1226 This can reduce on disk and in-memory size of the kernel 1227 code and static data, particularly for small configs and 1228 on small systems. This has the possibility of introducing 1229 silently broken kernel if the required annotations are not 1230 present. This option is not well tested yet, so use at your 1231 own risk. 1232 1233config SYSCTL 1234 bool 1235 1236config HAVE_UID16 1237 bool 1238 1239config SYSCTL_EXCEPTION_TRACE 1240 bool 1241 help 1242 Enable support for /proc/sys/debug/exception-trace. 1243 1244config SYSCTL_ARCH_UNALIGN_NO_WARN 1245 bool 1246 help 1247 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1248 Allows arch to define/use @no_unaligned_warning to possibly warn 1249 about unaligned access emulation going on under the hood. 1250 1251config SYSCTL_ARCH_UNALIGN_ALLOW 1252 bool 1253 help 1254 Enable support for /proc/sys/kernel/unaligned-trap 1255 Allows arches to define/use @unaligned_enabled to runtime toggle 1256 the unaligned access emulation. 1257 see arch/parisc/kernel/unaligned.c for reference 1258 1259config HAVE_PCSPKR_PLATFORM 1260 bool 1261 1262# interpreter that classic socket filters depend on 1263config BPF 1264 bool 1265 1266menuconfig EXPERT 1267 bool "Configure standard kernel features (expert users)" 1268 # Unhide debug options, to make the on-by-default options visible 1269 select DEBUG_KERNEL 1270 help 1271 This option allows certain base kernel options and settings 1272 to be disabled or tweaked. This is for specialized 1273 environments which can tolerate a "non-standard" kernel. 1274 Only use this if you really know what you are doing. 1275 1276config UID16 1277 bool "Enable 16-bit UID system calls" if EXPERT 1278 depends on HAVE_UID16 && MULTIUSER 1279 default y 1280 help 1281 This enables the legacy 16-bit UID syscall wrappers. 1282 1283config MULTIUSER 1284 bool "Multiple users, groups and capabilities support" if EXPERT 1285 default y 1286 help 1287 This option enables support for non-root users, groups and 1288 capabilities. 1289 1290 If you say N here, all processes will run with UID 0, GID 0, and all 1291 possible capabilities. Saying N here also compiles out support for 1292 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1293 setgid, and capset. 1294 1295 If unsure, say Y here. 1296 1297config SGETMASK_SYSCALL 1298 bool "sgetmask/ssetmask syscalls support" if EXPERT 1299 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1300 ---help--- 1301 sys_sgetmask and sys_ssetmask are obsolete system calls 1302 no longer supported in libc but still enabled by default in some 1303 architectures. 1304 1305 If unsure, leave the default option here. 1306 1307config SYSFS_SYSCALL 1308 bool "Sysfs syscall support" if EXPERT 1309 default y 1310 ---help--- 1311 sys_sysfs is an obsolete system call no longer supported in libc. 1312 Note that disabling this option is more secure but might break 1313 compatibility with some systems. 1314 1315 If unsure say Y here. 1316 1317config SYSCTL_SYSCALL 1318 bool "Sysctl syscall support" if EXPERT 1319 depends on PROC_SYSCTL 1320 default n 1321 select SYSCTL 1322 ---help--- 1323 sys_sysctl uses binary paths that have been found challenging 1324 to properly maintain and use. The interface in /proc/sys 1325 using paths with ascii names is now the primary path to this 1326 information. 1327 1328 Almost nothing using the binary sysctl interface so if you are 1329 trying to save some space it is probably safe to disable this, 1330 making your kernel marginally smaller. 1331 1332 If unsure say N here. 1333 1334config FHANDLE 1335 bool "open by fhandle syscalls" if EXPERT 1336 select EXPORTFS 1337 default y 1338 help 1339 If you say Y here, a user level program will be able to map 1340 file names to handle and then later use the handle for 1341 different file system operations. This is useful in implementing 1342 userspace file servers, which now track files using handles instead 1343 of names. The handle would remain the same even if file names 1344 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1345 syscalls. 1346 1347config POSIX_TIMERS 1348 bool "Posix Clocks & timers" if EXPERT 1349 default y 1350 help 1351 This includes native support for POSIX timers to the kernel. 1352 Some embedded systems have no use for them and therefore they 1353 can be configured out to reduce the size of the kernel image. 1354 1355 When this option is disabled, the following syscalls won't be 1356 available: timer_create, timer_gettime: timer_getoverrun, 1357 timer_settime, timer_delete, clock_adjtime, getitimer, 1358 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1359 clock_getres and clock_nanosleep syscalls will be limited to 1360 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1361 1362 If unsure say y. 1363 1364config PRINTK 1365 default y 1366 bool "Enable support for printk" if EXPERT 1367 select IRQ_WORK 1368 help 1369 This option enables normal printk support. Removing it 1370 eliminates most of the message strings from the kernel image 1371 and makes the kernel more or less silent. As this makes it 1372 very difficult to diagnose system problems, saying N here is 1373 strongly discouraged. 1374 1375config PRINTK_NMI 1376 def_bool y 1377 depends on PRINTK 1378 depends on HAVE_NMI 1379 1380config BUG 1381 bool "BUG() support" if EXPERT 1382 default y 1383 help 1384 Disabling this option eliminates support for BUG and WARN, reducing 1385 the size of your kernel image and potentially quietly ignoring 1386 numerous fatal conditions. You should only consider disabling this 1387 option for embedded systems with no facilities for reporting errors. 1388 Just say Y. 1389 1390config ELF_CORE 1391 depends on COREDUMP 1392 default y 1393 bool "Enable ELF core dumps" if EXPERT 1394 help 1395 Enable support for generating core dumps. Disabling saves about 4k. 1396 1397 1398config PCSPKR_PLATFORM 1399 bool "Enable PC-Speaker support" if EXPERT 1400 depends on HAVE_PCSPKR_PLATFORM 1401 select I8253_LOCK 1402 default y 1403 help 1404 This option allows to disable the internal PC-Speaker 1405 support, saving some memory. 1406 1407config BASE_FULL 1408 default y 1409 bool "Enable full-sized data structures for core" if EXPERT 1410 help 1411 Disabling this option reduces the size of miscellaneous core 1412 kernel data structures. This saves memory on small machines, 1413 but may reduce performance. 1414 1415config FUTEX 1416 bool "Enable futex support" if EXPERT 1417 default y 1418 imply RT_MUTEXES 1419 help 1420 Disabling this option will cause the kernel to be built without 1421 support for "fast userspace mutexes". The resulting kernel may not 1422 run glibc-based applications correctly. 1423 1424config FUTEX_PI 1425 bool 1426 depends on FUTEX && RT_MUTEXES 1427 default y 1428 1429config HAVE_FUTEX_CMPXCHG 1430 bool 1431 depends on FUTEX 1432 help 1433 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1434 is implemented and always working. This removes a couple of runtime 1435 checks. 1436 1437config EPOLL 1438 bool "Enable eventpoll support" if EXPERT 1439 default y 1440 help 1441 Disabling this option will cause the kernel to be built without 1442 support for epoll family of system calls. 1443 1444config SIGNALFD 1445 bool "Enable signalfd() system call" if EXPERT 1446 default y 1447 help 1448 Enable the signalfd() system call that allows to receive signals 1449 on a file descriptor. 1450 1451 If unsure, say Y. 1452 1453config TIMERFD 1454 bool "Enable timerfd() system call" if EXPERT 1455 default y 1456 help 1457 Enable the timerfd() system call that allows to receive timer 1458 events on a file descriptor. 1459 1460 If unsure, say Y. 1461 1462config EVENTFD 1463 bool "Enable eventfd() system call" if EXPERT 1464 default y 1465 help 1466 Enable the eventfd() system call that allows to receive both 1467 kernel notification (ie. KAIO) or userspace notifications. 1468 1469 If unsure, say Y. 1470 1471config SHMEM 1472 bool "Use full shmem filesystem" if EXPERT 1473 default y 1474 depends on MMU 1475 help 1476 The shmem is an internal filesystem used to manage shared memory. 1477 It is backed by swap and manages resource limits. It is also exported 1478 to userspace as tmpfs if TMPFS is enabled. Disabling this 1479 option replaces shmem and tmpfs with the much simpler ramfs code, 1480 which may be appropriate on small systems without swap. 1481 1482config AIO 1483 bool "Enable AIO support" if EXPERT 1484 default y 1485 help 1486 This option enables POSIX asynchronous I/O which may by used 1487 by some high performance threaded applications. Disabling 1488 this option saves about 7k. 1489 1490config IO_URING 1491 bool "Enable IO uring support" if EXPERT 1492 select ANON_INODES 1493 default y 1494 help 1495 This option enables support for the io_uring interface, enabling 1496 applications to submit and complete IO through submission and 1497 completion rings that are shared between the kernel and application. 1498 1499config ADVISE_SYSCALLS 1500 bool "Enable madvise/fadvise syscalls" if EXPERT 1501 default y 1502 help 1503 This option enables the madvise and fadvise syscalls, used by 1504 applications to advise the kernel about their future memory or file 1505 usage, improving performance. If building an embedded system where no 1506 applications use these syscalls, you can disable this option to save 1507 space. 1508 1509config MEMBARRIER 1510 bool "Enable membarrier() system call" if EXPERT 1511 default y 1512 help 1513 Enable the membarrier() system call that allows issuing memory 1514 barriers across all running threads, which can be used to distribute 1515 the cost of user-space memory barriers asymmetrically by transforming 1516 pairs of memory barriers into pairs consisting of membarrier() and a 1517 compiler barrier. 1518 1519 If unsure, say Y. 1520 1521config KALLSYMS 1522 bool "Load all symbols for debugging/ksymoops" if EXPERT 1523 default y 1524 help 1525 Say Y here to let the kernel print out symbolic crash information and 1526 symbolic stack backtraces. This increases the size of the kernel 1527 somewhat, as all symbols have to be loaded into the kernel image. 1528 1529config KALLSYMS_ALL 1530 bool "Include all symbols in kallsyms" 1531 depends on DEBUG_KERNEL && KALLSYMS 1532 help 1533 Normally kallsyms only contains the symbols of functions for nicer 1534 OOPS messages and backtraces (i.e., symbols from the text and inittext 1535 sections). This is sufficient for most cases. And only in very rare 1536 cases (e.g., when a debugger is used) all symbols are required (e.g., 1537 names of variables from the data sections, etc). 1538 1539 This option makes sure that all symbols are loaded into the kernel 1540 image (i.e., symbols from all sections) in cost of increased kernel 1541 size (depending on the kernel configuration, it may be 300KiB or 1542 something like this). 1543 1544 Say N unless you really need all symbols. 1545 1546config KALLSYMS_ABSOLUTE_PERCPU 1547 bool 1548 depends on KALLSYMS 1549 default X86_64 && SMP 1550 1551config KALLSYMS_BASE_RELATIVE 1552 bool 1553 depends on KALLSYMS 1554 default !IA64 1555 help 1556 Instead of emitting them as absolute values in the native word size, 1557 emit the symbol references in the kallsyms table as 32-bit entries, 1558 each containing a relative value in the range [base, base + U32_MAX] 1559 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1560 an absolute value in the range [0, S32_MAX] or a relative value in the 1561 range [base, base + S32_MAX], where base is the lowest relative symbol 1562 address encountered in the image. 1563 1564 On 64-bit builds, this reduces the size of the address table by 50%, 1565 but more importantly, it results in entries whose values are build 1566 time constants, and no relocation pass is required at runtime to fix 1567 up the entries based on the runtime load address of the kernel. 1568 1569# end of the "standard kernel features (expert users)" menu 1570 1571# syscall, maps, verifier 1572config BPF_SYSCALL 1573 bool "Enable bpf() system call" 1574 select BPF 1575 select IRQ_WORK 1576 default n 1577 help 1578 Enable the bpf() system call that allows to manipulate eBPF 1579 programs and maps via file descriptors. 1580 1581config BPF_JIT_ALWAYS_ON 1582 bool "Permanently enable BPF JIT and remove BPF interpreter" 1583 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1584 help 1585 Enables BPF JIT and removes BPF interpreter to avoid 1586 speculative execution of BPF instructions by the interpreter 1587 1588config USERFAULTFD 1589 bool "Enable userfaultfd() system call" 1590 depends on MMU 1591 help 1592 Enable the userfaultfd() system call that allows to intercept and 1593 handle page faults in userland. 1594 1595config ARCH_HAS_MEMBARRIER_CALLBACKS 1596 bool 1597 1598config ARCH_HAS_MEMBARRIER_SYNC_CORE 1599 bool 1600 1601config RSEQ 1602 bool "Enable rseq() system call" if EXPERT 1603 default y 1604 depends on HAVE_RSEQ 1605 select MEMBARRIER 1606 help 1607 Enable the restartable sequences system call. It provides a 1608 user-space cache for the current CPU number value, which 1609 speeds up getting the current CPU number from user-space, 1610 as well as an ABI to speed up user-space operations on 1611 per-CPU data. 1612 1613 If unsure, say Y. 1614 1615config DEBUG_RSEQ 1616 default n 1617 bool "Enabled debugging of rseq() system call" if EXPERT 1618 depends on RSEQ && DEBUG_KERNEL 1619 help 1620 Enable extra debugging checks for the rseq system call. 1621 1622 If unsure, say N. 1623 1624config EMBEDDED 1625 bool "Embedded system" 1626 option allnoconfig_y 1627 select EXPERT 1628 help 1629 This option should be enabled if compiling the kernel for 1630 an embedded system so certain expert options are available 1631 for configuration. 1632 1633config HAVE_PERF_EVENTS 1634 bool 1635 help 1636 See tools/perf/design.txt for details. 1637 1638config PERF_USE_VMALLOC 1639 bool 1640 help 1641 See tools/perf/design.txt for details 1642 1643config PC104 1644 bool "PC/104 support" if EXPERT 1645 help 1646 Expose PC/104 form factor device drivers and options available for 1647 selection and configuration. Enable this option if your target 1648 machine has a PC/104 bus. 1649 1650menu "Kernel Performance Events And Counters" 1651 1652config PERF_EVENTS 1653 bool "Kernel performance events and counters" 1654 default y if PROFILING 1655 depends on HAVE_PERF_EVENTS 1656 select IRQ_WORK 1657 select SRCU 1658 help 1659 Enable kernel support for various performance events provided 1660 by software and hardware. 1661 1662 Software events are supported either built-in or via the 1663 use of generic tracepoints. 1664 1665 Most modern CPUs support performance events via performance 1666 counter registers. These registers count the number of certain 1667 types of hw events: such as instructions executed, cachemisses 1668 suffered, or branches mis-predicted - without slowing down the 1669 kernel or applications. These registers can also trigger interrupts 1670 when a threshold number of events have passed - and can thus be 1671 used to profile the code that runs on that CPU. 1672 1673 The Linux Performance Event subsystem provides an abstraction of 1674 these software and hardware event capabilities, available via a 1675 system call and used by the "perf" utility in tools/perf/. It 1676 provides per task and per CPU counters, and it provides event 1677 capabilities on top of those. 1678 1679 Say Y if unsure. 1680 1681config DEBUG_PERF_USE_VMALLOC 1682 default n 1683 bool "Debug: use vmalloc to back perf mmap() buffers" 1684 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1685 select PERF_USE_VMALLOC 1686 help 1687 Use vmalloc memory to back perf mmap() buffers. 1688 1689 Mostly useful for debugging the vmalloc code on platforms 1690 that don't require it. 1691 1692 Say N if unsure. 1693 1694endmenu 1695 1696config VM_EVENT_COUNTERS 1697 default y 1698 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1699 help 1700 VM event counters are needed for event counts to be shown. 1701 This option allows the disabling of the VM event counters 1702 on EXPERT systems. /proc/vmstat will only show page counts 1703 if VM event counters are disabled. 1704 1705config SLUB_DEBUG 1706 default y 1707 bool "Enable SLUB debugging support" if EXPERT 1708 depends on SLUB && SYSFS 1709 help 1710 SLUB has extensive debug support features. Disabling these can 1711 result in significant savings in code size. This also disables 1712 SLUB sysfs support. /sys/slab will not exist and there will be 1713 no support for cache validation etc. 1714 1715config SLUB_MEMCG_SYSFS_ON 1716 default n 1717 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1718 depends on SLUB && SYSFS && MEMCG 1719 help 1720 SLUB creates a directory under /sys/kernel/slab for each 1721 allocation cache to host info and debug files. If memory 1722 cgroup is enabled, each cache can have per memory cgroup 1723 caches. SLUB can create the same sysfs directories for these 1724 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1725 to a very high number of debug files being created. This is 1726 controlled by slub_memcg_sysfs boot parameter and this 1727 config option determines the parameter's default value. 1728 1729config COMPAT_BRK 1730 bool "Disable heap randomization" 1731 default y 1732 help 1733 Randomizing heap placement makes heap exploits harder, but it 1734 also breaks ancient binaries (including anything libc5 based). 1735 This option changes the bootup default to heap randomization 1736 disabled, and can be overridden at runtime by setting 1737 /proc/sys/kernel/randomize_va_space to 2. 1738 1739 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1740 1741choice 1742 prompt "Choose SLAB allocator" 1743 default SLUB 1744 help 1745 This option allows to select a slab allocator. 1746 1747config SLAB 1748 bool "SLAB" 1749 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1750 help 1751 The regular slab allocator that is established and known to work 1752 well in all environments. It organizes cache hot objects in 1753 per cpu and per node queues. 1754 1755config SLUB 1756 bool "SLUB (Unqueued Allocator)" 1757 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1758 help 1759 SLUB is a slab allocator that minimizes cache line usage 1760 instead of managing queues of cached objects (SLAB approach). 1761 Per cpu caching is realized using slabs of objects instead 1762 of queues of objects. SLUB can use memory efficiently 1763 and has enhanced diagnostics. SLUB is the default choice for 1764 a slab allocator. 1765 1766config SLOB 1767 depends on EXPERT 1768 bool "SLOB (Simple Allocator)" 1769 help 1770 SLOB replaces the stock allocator with a drastically simpler 1771 allocator. SLOB is generally more space efficient but 1772 does not perform as well on large systems. 1773 1774endchoice 1775 1776config SLAB_MERGE_DEFAULT 1777 bool "Allow slab caches to be merged" 1778 default y 1779 help 1780 For reduced kernel memory fragmentation, slab caches can be 1781 merged when they share the same size and other characteristics. 1782 This carries a risk of kernel heap overflows being able to 1783 overwrite objects from merged caches (and more easily control 1784 cache layout), which makes such heap attacks easier to exploit 1785 by attackers. By keeping caches unmerged, these kinds of exploits 1786 can usually only damage objects in the same cache. To disable 1787 merging at runtime, "slab_nomerge" can be passed on the kernel 1788 command line. 1789 1790config SLAB_FREELIST_RANDOM 1791 default n 1792 depends on SLAB || SLUB 1793 bool "SLAB freelist randomization" 1794 help 1795 Randomizes the freelist order used on creating new pages. This 1796 security feature reduces the predictability of the kernel slab 1797 allocator against heap overflows. 1798 1799config SLAB_FREELIST_HARDENED 1800 bool "Harden slab freelist metadata" 1801 depends on SLUB 1802 help 1803 Many kernel heap attacks try to target slab cache metadata and 1804 other infrastructure. This options makes minor performance 1805 sacrifies to harden the kernel slab allocator against common 1806 freelist exploit methods. 1807 1808config SHUFFLE_PAGE_ALLOCATOR 1809 bool "Page allocator randomization" 1810 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1811 help 1812 Randomization of the page allocator improves the average 1813 utilization of a direct-mapped memory-side-cache. See section 1814 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1815 6.2a specification for an example of how a platform advertises 1816 the presence of a memory-side-cache. There are also incidental 1817 security benefits as it reduces the predictability of page 1818 allocations to compliment SLAB_FREELIST_RANDOM, but the 1819 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1820 10th order of pages is selected based on cache utilization 1821 benefits on x86. 1822 1823 While the randomization improves cache utilization it may 1824 negatively impact workloads on platforms without a cache. For 1825 this reason, by default, the randomization is enabled only 1826 after runtime detection of a direct-mapped memory-side-cache. 1827 Otherwise, the randomization may be force enabled with the 1828 'page_alloc.shuffle' kernel command line parameter. 1829 1830 Say Y if unsure. 1831 1832config SLUB_CPU_PARTIAL 1833 default y 1834 depends on SLUB && SMP 1835 bool "SLUB per cpu partial cache" 1836 help 1837 Per cpu partial caches accellerate objects allocation and freeing 1838 that is local to a processor at the price of more indeterminism 1839 in the latency of the free. On overflow these caches will be cleared 1840 which requires the taking of locks that may cause latency spikes. 1841 Typically one would choose no for a realtime system. 1842 1843config MMAP_ALLOW_UNINITIALIZED 1844 bool "Allow mmapped anonymous memory to be uninitialized" 1845 depends on EXPERT && !MMU 1846 default n 1847 help 1848 Normally, and according to the Linux spec, anonymous memory obtained 1849 from mmap() has its contents cleared before it is passed to 1850 userspace. Enabling this config option allows you to request that 1851 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1852 providing a huge performance boost. If this option is not enabled, 1853 then the flag will be ignored. 1854 1855 This is taken advantage of by uClibc's malloc(), and also by 1856 ELF-FDPIC binfmt's brk and stack allocator. 1857 1858 Because of the obvious security issues, this option should only be 1859 enabled on embedded devices where you control what is run in 1860 userspace. Since that isn't generally a problem on no-MMU systems, 1861 it is normally safe to say Y here. 1862 1863 See Documentation/nommu-mmap.txt for more information. 1864 1865config SYSTEM_DATA_VERIFICATION 1866 def_bool n 1867 select SYSTEM_TRUSTED_KEYRING 1868 select KEYS 1869 select CRYPTO 1870 select CRYPTO_RSA 1871 select ASYMMETRIC_KEY_TYPE 1872 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1873 select ASN1 1874 select OID_REGISTRY 1875 select X509_CERTIFICATE_PARSER 1876 select PKCS7_MESSAGE_PARSER 1877 help 1878 Provide PKCS#7 message verification using the contents of the system 1879 trusted keyring to provide public keys. This then can be used for 1880 module verification, kexec image verification and firmware blob 1881 verification. 1882 1883config PROFILING 1884 bool "Profiling support" 1885 help 1886 Say Y here to enable the extended profiling support mechanisms used 1887 by profilers such as OProfile. 1888 1889# 1890# Place an empty function call at each tracepoint site. Can be 1891# dynamically changed for a probe function. 1892# 1893config TRACEPOINTS 1894 bool 1895 1896endmenu # General setup 1897 1898source "arch/Kconfig" 1899 1900config RT_MUTEXES 1901 bool 1902 1903config BASE_SMALL 1904 int 1905 default 0 if BASE_FULL 1906 default 1 if !BASE_FULL 1907 1908menuconfig MODULES 1909 bool "Enable loadable module support" 1910 option modules 1911 help 1912 Kernel modules are small pieces of compiled code which can 1913 be inserted in the running kernel, rather than being 1914 permanently built into the kernel. You use the "modprobe" 1915 tool to add (and sometimes remove) them. If you say Y here, 1916 many parts of the kernel can be built as modules (by 1917 answering M instead of Y where indicated): this is most 1918 useful for infrequently used options which are not required 1919 for booting. For more information, see the man pages for 1920 modprobe, lsmod, modinfo, insmod and rmmod. 1921 1922 If you say Y here, you will need to run "make 1923 modules_install" to put the modules under /lib/modules/ 1924 where modprobe can find them (you may need to be root to do 1925 this). 1926 1927 If unsure, say Y. 1928 1929if MODULES 1930 1931config MODULE_FORCE_LOAD 1932 bool "Forced module loading" 1933 default n 1934 help 1935 Allow loading of modules without version information (ie. modprobe 1936 --force). Forced module loading sets the 'F' (forced) taint flag and 1937 is usually a really bad idea. 1938 1939config MODULE_UNLOAD 1940 bool "Module unloading" 1941 help 1942 Without this option you will not be able to unload any 1943 modules (note that some modules may not be unloadable 1944 anyway), which makes your kernel smaller, faster 1945 and simpler. If unsure, say Y. 1946 1947config MODULE_FORCE_UNLOAD 1948 bool "Forced module unloading" 1949 depends on MODULE_UNLOAD 1950 help 1951 This option allows you to force a module to unload, even if the 1952 kernel believes it is unsafe: the kernel will remove the module 1953 without waiting for anyone to stop using it (using the -f option to 1954 rmmod). This is mainly for kernel developers and desperate users. 1955 If unsure, say N. 1956 1957config MODVERSIONS 1958 bool "Module versioning support" 1959 help 1960 Usually, you have to use modules compiled with your kernel. 1961 Saying Y here makes it sometimes possible to use modules 1962 compiled for different kernels, by adding enough information 1963 to the modules to (hopefully) spot any changes which would 1964 make them incompatible with the kernel you are running. If 1965 unsure, say N. 1966 1967config MODULE_REL_CRCS 1968 bool 1969 depends on MODVERSIONS 1970 1971config MODULE_SRCVERSION_ALL 1972 bool "Source checksum for all modules" 1973 help 1974 Modules which contain a MODULE_VERSION get an extra "srcversion" 1975 field inserted into their modinfo section, which contains a 1976 sum of the source files which made it. This helps maintainers 1977 see exactly which source was used to build a module (since 1978 others sometimes change the module source without updating 1979 the version). With this option, such a "srcversion" field 1980 will be created for all modules. If unsure, say N. 1981 1982config MODULE_SIG 1983 bool "Module signature verification" 1984 depends on MODULES 1985 select SYSTEM_DATA_VERIFICATION 1986 help 1987 Check modules for valid signatures upon load: the signature 1988 is simply appended to the module. For more information see 1989 <file:Documentation/admin-guide/module-signing.rst>. 1990 1991 Note that this option adds the OpenSSL development packages as a 1992 kernel build dependency so that the signing tool can use its crypto 1993 library. 1994 1995 !!!WARNING!!! If you enable this option, you MUST make sure that the 1996 module DOES NOT get stripped after being signed. This includes the 1997 debuginfo strip done by some packagers (such as rpmbuild) and 1998 inclusion into an initramfs that wants the module size reduced. 1999 2000config MODULE_SIG_FORCE 2001 bool "Require modules to be validly signed" 2002 depends on MODULE_SIG 2003 help 2004 Reject unsigned modules or signed modules for which we don't have a 2005 key. Without this, such modules will simply taint the kernel. 2006 2007config MODULE_SIG_ALL 2008 bool "Automatically sign all modules" 2009 default y 2010 depends on MODULE_SIG 2011 help 2012 Sign all modules during make modules_install. Without this option, 2013 modules must be signed manually, using the scripts/sign-file tool. 2014 2015comment "Do not forget to sign required modules with scripts/sign-file" 2016 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2017 2018choice 2019 prompt "Which hash algorithm should modules be signed with?" 2020 depends on MODULE_SIG 2021 help 2022 This determines which sort of hashing algorithm will be used during 2023 signature generation. This algorithm _must_ be built into the kernel 2024 directly so that signature verification can take place. It is not 2025 possible to load a signed module containing the algorithm to check 2026 the signature on that module. 2027 2028config MODULE_SIG_SHA1 2029 bool "Sign modules with SHA-1" 2030 select CRYPTO_SHA1 2031 2032config MODULE_SIG_SHA224 2033 bool "Sign modules with SHA-224" 2034 select CRYPTO_SHA256 2035 2036config MODULE_SIG_SHA256 2037 bool "Sign modules with SHA-256" 2038 select CRYPTO_SHA256 2039 2040config MODULE_SIG_SHA384 2041 bool "Sign modules with SHA-384" 2042 select CRYPTO_SHA512 2043 2044config MODULE_SIG_SHA512 2045 bool "Sign modules with SHA-512" 2046 select CRYPTO_SHA512 2047 2048endchoice 2049 2050config MODULE_SIG_HASH 2051 string 2052 depends on MODULE_SIG 2053 default "sha1" if MODULE_SIG_SHA1 2054 default "sha224" if MODULE_SIG_SHA224 2055 default "sha256" if MODULE_SIG_SHA256 2056 default "sha384" if MODULE_SIG_SHA384 2057 default "sha512" if MODULE_SIG_SHA512 2058 2059config MODULE_COMPRESS 2060 bool "Compress modules on installation" 2061 depends on MODULES 2062 help 2063 2064 Compresses kernel modules when 'make modules_install' is run; gzip or 2065 xz depending on "Compression algorithm" below. 2066 2067 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 2068 2069 Out-of-tree kernel modules installed using Kbuild will also be 2070 compressed upon installation. 2071 2072 Note: for modules inside an initrd or initramfs, it's more efficient 2073 to compress the whole initrd or initramfs instead. 2074 2075 Note: This is fully compatible with signed modules. 2076 2077 If in doubt, say N. 2078 2079choice 2080 prompt "Compression algorithm" 2081 depends on MODULE_COMPRESS 2082 default MODULE_COMPRESS_GZIP 2083 help 2084 This determines which sort of compression will be used during 2085 'make modules_install'. 2086 2087 GZIP (default) and XZ are supported. 2088 2089config MODULE_COMPRESS_GZIP 2090 bool "GZIP" 2091 2092config MODULE_COMPRESS_XZ 2093 bool "XZ" 2094 2095endchoice 2096 2097config TRIM_UNUSED_KSYMS 2098 bool "Trim unused exported kernel symbols" 2099 depends on MODULES && !UNUSED_SYMBOLS 2100 help 2101 The kernel and some modules make many symbols available for 2102 other modules to use via EXPORT_SYMBOL() and variants. Depending 2103 on the set of modules being selected in your kernel configuration, 2104 many of those exported symbols might never be used. 2105 2106 This option allows for unused exported symbols to be dropped from 2107 the build. In turn, this provides the compiler more opportunities 2108 (especially when using LTO) for optimizing the code and reducing 2109 binary size. This might have some security advantages as well. 2110 2111 If unsure, or if you need to build out-of-tree modules, say N. 2112 2113endif # MODULES 2114 2115config MODULES_TREE_LOOKUP 2116 def_bool y 2117 depends on PERF_EVENTS || TRACING 2118 2119config INIT_ALL_POSSIBLE 2120 bool 2121 help 2122 Back when each arch used to define their own cpu_online_mask and 2123 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2124 with all 1s, and others with all 0s. When they were centralised, 2125 it was better to provide this option than to break all the archs 2126 and have several arch maintainers pursuing me down dark alleys. 2127 2128source "block/Kconfig" 2129 2130config PREEMPT_NOTIFIERS 2131 bool 2132 2133config PADATA 2134 depends on SMP 2135 bool 2136 2137config ASN1 2138 tristate 2139 help 2140 Build a simple ASN.1 grammar compiler that produces a bytecode output 2141 that can be interpreted by the ASN.1 stream decoder and used to 2142 inform it as to what tags are to be expected in a stream and what 2143 functions to call on what tags. 2144 2145source "kernel/Kconfig.locks" 2146 2147config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2148 bool 2149 2150# It may be useful for an architecture to override the definitions of the 2151# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2152# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2153# different calling convention for syscalls. They can also override the 2154# macros for not-implemented syscalls in kernel/sys_ni.c and 2155# kernel/time/posix-stubs.c. All these overrides need to be available in 2156# <asm/syscall_wrapper.h>. 2157config ARCH_HAS_SYSCALL_WRAPPER 2158 def_bool n 2159