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_PROC 584 tristate "Enable kernel header artifacts through /proc/kheaders.tar.xz" 585 depends on PROC_FS 586 help 587 This option enables access to the kernel header and other artifacts that 588 are generated during the build process. These can be used to build eBPF 589 tracing programs, or similar programs. If you build the headers as a 590 module, a module called kheaders.ko is built which can be loaded on-demand 591 to get access to the headers. 592 593config LOG_BUF_SHIFT 594 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 595 range 12 25 596 default 17 597 depends on PRINTK 598 help 599 Select the minimal kernel log buffer size as a power of 2. 600 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 601 parameter, see below. Any higher size also might be forced 602 by "log_buf_len" boot parameter. 603 604 Examples: 605 17 => 128 KB 606 16 => 64 KB 607 15 => 32 KB 608 14 => 16 KB 609 13 => 8 KB 610 12 => 4 KB 611 612config LOG_CPU_MAX_BUF_SHIFT 613 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 614 depends on SMP 615 range 0 21 616 default 12 if !BASE_SMALL 617 default 0 if BASE_SMALL 618 depends on PRINTK 619 help 620 This option allows to increase the default ring buffer size 621 according to the number of CPUs. The value defines the contribution 622 of each CPU as a power of 2. The used space is typically only few 623 lines however it might be much more when problems are reported, 624 e.g. backtraces. 625 626 The increased size means that a new buffer has to be allocated and 627 the original static one is unused. It makes sense only on systems 628 with more CPUs. Therefore this value is used only when the sum of 629 contributions is greater than the half of the default kernel ring 630 buffer as defined by LOG_BUF_SHIFT. The default values are set 631 so that more than 64 CPUs are needed to trigger the allocation. 632 633 Also this option is ignored when "log_buf_len" kernel parameter is 634 used as it forces an exact (power of two) size of the ring buffer. 635 636 The number of possible CPUs is used for this computation ignoring 637 hotplugging making the computation optimal for the worst case 638 scenario while allowing a simple algorithm to be used from bootup. 639 640 Examples shift values and their meaning: 641 17 => 128 KB for each CPU 642 16 => 64 KB for each CPU 643 15 => 32 KB for each CPU 644 14 => 16 KB for each CPU 645 13 => 8 KB for each CPU 646 12 => 4 KB for each CPU 647 648config PRINTK_SAFE_LOG_BUF_SHIFT 649 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 650 range 10 21 651 default 13 652 depends on PRINTK 653 help 654 Select the size of an alternate printk per-CPU buffer where messages 655 printed from usafe contexts are temporary stored. One example would 656 be NMI messages, another one - printk recursion. The messages are 657 copied to the main log buffer in a safe context to avoid a deadlock. 658 The value defines the size as a power of 2. 659 660 Those messages are rare and limited. The largest one is when 661 a backtrace is printed. It usually fits into 4KB. Select 662 8KB if you want to be on the safe side. 663 664 Examples: 665 17 => 128 KB for each CPU 666 16 => 64 KB for each CPU 667 15 => 32 KB for each CPU 668 14 => 16 KB for each CPU 669 13 => 8 KB for each CPU 670 12 => 4 KB for each CPU 671 672# 673# Architectures with an unreliable sched_clock() should select this: 674# 675config HAVE_UNSTABLE_SCHED_CLOCK 676 bool 677 678config GENERIC_SCHED_CLOCK 679 bool 680 681# 682# For architectures that want to enable the support for NUMA-affine scheduler 683# balancing logic: 684# 685config ARCH_SUPPORTS_NUMA_BALANCING 686 bool 687 688# 689# For architectures that prefer to flush all TLBs after a number of pages 690# are unmapped instead of sending one IPI per page to flush. The architecture 691# must provide guarantees on what happens if a clean TLB cache entry is 692# written after the unmap. Details are in mm/rmap.c near the check for 693# should_defer_flush. The architecture should also consider if the full flush 694# and the refill costs are offset by the savings of sending fewer IPIs. 695config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 696 bool 697 698# 699# For architectures that know their GCC __int128 support is sound 700# 701config ARCH_SUPPORTS_INT128 702 bool 703 704# For architectures that (ab)use NUMA to represent different memory regions 705# all cpu-local but of different latencies, such as SuperH. 706# 707config ARCH_WANT_NUMA_VARIABLE_LOCALITY 708 bool 709 710config NUMA_BALANCING 711 bool "Memory placement aware NUMA scheduler" 712 depends on ARCH_SUPPORTS_NUMA_BALANCING 713 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 714 depends on SMP && NUMA && MIGRATION 715 help 716 This option adds support for automatic NUMA aware memory/task placement. 717 The mechanism is quite primitive and is based on migrating memory when 718 it has references to the node the task is running on. 719 720 This system will be inactive on UMA systems. 721 722config NUMA_BALANCING_DEFAULT_ENABLED 723 bool "Automatically enable NUMA aware memory/task placement" 724 default y 725 depends on NUMA_BALANCING 726 help 727 If set, automatic NUMA balancing will be enabled if running on a NUMA 728 machine. 729 730menuconfig CGROUPS 731 bool "Control Group support" 732 select KERNFS 733 help 734 This option adds support for grouping sets of processes together, for 735 use with process control subsystems such as Cpusets, CFS, memory 736 controls or device isolation. 737 See 738 - Documentation/scheduler/sched-design-CFS.txt (CFS) 739 - Documentation/cgroup-v1/ (features for grouping, isolation 740 and resource control) 741 742 Say N if unsure. 743 744if CGROUPS 745 746config PAGE_COUNTER 747 bool 748 749config MEMCG 750 bool "Memory controller" 751 select PAGE_COUNTER 752 select EVENTFD 753 help 754 Provides control over the memory footprint of tasks in a cgroup. 755 756config MEMCG_SWAP 757 bool "Swap controller" 758 depends on MEMCG && SWAP 759 help 760 Provides control over the swap space consumed by tasks in a cgroup. 761 762config MEMCG_SWAP_ENABLED 763 bool "Swap controller enabled by default" 764 depends on MEMCG_SWAP 765 default y 766 help 767 Memory Resource Controller Swap Extension comes with its price in 768 a bigger memory consumption. General purpose distribution kernels 769 which want to enable the feature but keep it disabled by default 770 and let the user enable it by swapaccount=1 boot command line 771 parameter should have this option unselected. 772 For those who want to have the feature enabled by default should 773 select this option (if, for some reason, they need to disable it 774 then swapaccount=0 does the trick). 775 776config MEMCG_KMEM 777 bool 778 depends on MEMCG && !SLOB 779 default y 780 781config BLK_CGROUP 782 bool "IO controller" 783 depends on BLOCK 784 default n 785 ---help--- 786 Generic block IO controller cgroup interface. This is the common 787 cgroup interface which should be used by various IO controlling 788 policies. 789 790 Currently, CFQ IO scheduler uses it to recognize task groups and 791 control disk bandwidth allocation (proportional time slice allocation) 792 to such task groups. It is also used by bio throttling logic in 793 block layer to implement upper limit in IO rates on a device. 794 795 This option only enables generic Block IO controller infrastructure. 796 One needs to also enable actual IO controlling logic/policy. For 797 enabling proportional weight division of disk bandwidth in CFQ, set 798 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 799 CONFIG_BLK_DEV_THROTTLING=y. 800 801 See Documentation/cgroup-v1/blkio-controller.txt for more information. 802 803config DEBUG_BLK_CGROUP 804 bool "IO controller debugging" 805 depends on BLK_CGROUP 806 default n 807 ---help--- 808 Enable some debugging help. Currently it exports additional stat 809 files in a cgroup which can be useful for debugging. 810 811config CGROUP_WRITEBACK 812 bool 813 depends on MEMCG && BLK_CGROUP 814 default y 815 816menuconfig CGROUP_SCHED 817 bool "CPU controller" 818 default n 819 help 820 This feature lets CPU scheduler recognize task groups and control CPU 821 bandwidth allocation to such task groups. It uses cgroups to group 822 tasks. 823 824if CGROUP_SCHED 825config FAIR_GROUP_SCHED 826 bool "Group scheduling for SCHED_OTHER" 827 depends on CGROUP_SCHED 828 default CGROUP_SCHED 829 830config CFS_BANDWIDTH 831 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 832 depends on FAIR_GROUP_SCHED 833 default n 834 help 835 This option allows users to define CPU bandwidth rates (limits) for 836 tasks running within the fair group scheduler. Groups with no limit 837 set are considered to be unconstrained and will run with no 838 restriction. 839 See Documentation/scheduler/sched-bwc.txt for more information. 840 841config RT_GROUP_SCHED 842 bool "Group scheduling for SCHED_RR/FIFO" 843 depends on CGROUP_SCHED 844 default n 845 help 846 This feature lets you explicitly allocate real CPU bandwidth 847 to task groups. If enabled, it will also make it impossible to 848 schedule realtime tasks for non-root users until you allocate 849 realtime bandwidth for them. 850 See Documentation/scheduler/sched-rt-group.txt for more information. 851 852endif #CGROUP_SCHED 853 854config CGROUP_PIDS 855 bool "PIDs controller" 856 help 857 Provides enforcement of process number limits in the scope of a 858 cgroup. Any attempt to fork more processes than is allowed in the 859 cgroup will fail. PIDs are fundamentally a global resource because it 860 is fairly trivial to reach PID exhaustion before you reach even a 861 conservative kmemcg limit. As a result, it is possible to grind a 862 system to halt without being limited by other cgroup policies. The 863 PIDs controller is designed to stop this from happening. 864 865 It should be noted that organisational operations (such as attaching 866 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 867 since the PIDs limit only affects a process's ability to fork, not to 868 attach to a cgroup. 869 870config CGROUP_RDMA 871 bool "RDMA controller" 872 help 873 Provides enforcement of RDMA resources defined by IB stack. 874 It is fairly easy for consumers to exhaust RDMA resources, which 875 can result into resource unavailability to other consumers. 876 RDMA controller is designed to stop this from happening. 877 Attaching processes with active RDMA resources to the cgroup 878 hierarchy is allowed even if can cross the hierarchy's limit. 879 880config CGROUP_FREEZER 881 bool "Freezer controller" 882 help 883 Provides a way to freeze and unfreeze all tasks in a 884 cgroup. 885 886 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 887 controller includes important in-kernel memory consumers per default. 888 889 If you're using cgroup2, say N. 890 891config CGROUP_HUGETLB 892 bool "HugeTLB controller" 893 depends on HUGETLB_PAGE 894 select PAGE_COUNTER 895 default n 896 help 897 Provides a cgroup controller for HugeTLB pages. 898 When you enable this, you can put a per cgroup limit on HugeTLB usage. 899 The limit is enforced during page fault. Since HugeTLB doesn't 900 support page reclaim, enforcing the limit at page fault time implies 901 that, the application will get SIGBUS signal if it tries to access 902 HugeTLB pages beyond its limit. This requires the application to know 903 beforehand how much HugeTLB pages it would require for its use. The 904 control group is tracked in the third page lru pointer. This means 905 that we cannot use the controller with huge page less than 3 pages. 906 907config CPUSETS 908 bool "Cpuset controller" 909 depends on SMP 910 help 911 This option will let you create and manage CPUSETs which 912 allow dynamically partitioning a system into sets of CPUs and 913 Memory Nodes and assigning tasks to run only within those sets. 914 This is primarily useful on large SMP or NUMA systems. 915 916 Say N if unsure. 917 918config PROC_PID_CPUSET 919 bool "Include legacy /proc/<pid>/cpuset file" 920 depends on CPUSETS 921 default y 922 923config CGROUP_DEVICE 924 bool "Device controller" 925 help 926 Provides a cgroup controller implementing whitelists for 927 devices which a process in the cgroup can mknod or open. 928 929config CGROUP_CPUACCT 930 bool "Simple CPU accounting controller" 931 help 932 Provides a simple controller for monitoring the 933 total CPU consumed by the tasks in a cgroup. 934 935config CGROUP_PERF 936 bool "Perf controller" 937 depends on PERF_EVENTS 938 help 939 This option extends the perf per-cpu mode to restrict monitoring 940 to threads which belong to the cgroup specified and run on the 941 designated cpu. 942 943 Say N if unsure. 944 945config CGROUP_BPF 946 bool "Support for eBPF programs attached to cgroups" 947 depends on BPF_SYSCALL 948 select SOCK_CGROUP_DATA 949 help 950 Allow attaching eBPF programs to a cgroup using the bpf(2) 951 syscall command BPF_PROG_ATTACH. 952 953 In which context these programs are accessed depends on the type 954 of attachment. For instance, programs that are attached using 955 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 956 inet sockets. 957 958config CGROUP_DEBUG 959 bool "Debug controller" 960 default n 961 depends on DEBUG_KERNEL 962 help 963 This option enables a simple controller that exports 964 debugging information about the cgroups framework. This 965 controller is for control cgroup debugging only. Its 966 interfaces are not stable. 967 968 Say N. 969 970config SOCK_CGROUP_DATA 971 bool 972 default n 973 974endif # CGROUPS 975 976menuconfig NAMESPACES 977 bool "Namespaces support" if EXPERT 978 depends on MULTIUSER 979 default !EXPERT 980 help 981 Provides the way to make tasks work with different objects using 982 the same id. For example same IPC id may refer to different objects 983 or same user id or pid may refer to different tasks when used in 984 different namespaces. 985 986if NAMESPACES 987 988config UTS_NS 989 bool "UTS namespace" 990 default y 991 help 992 In this namespace tasks see different info provided with the 993 uname() system call 994 995config IPC_NS 996 bool "IPC namespace" 997 depends on (SYSVIPC || POSIX_MQUEUE) 998 default y 999 help 1000 In this namespace tasks work with IPC ids which correspond to 1001 different IPC objects in different namespaces. 1002 1003config USER_NS 1004 bool "User namespace" 1005 default n 1006 help 1007 This allows containers, i.e. vservers, to use user namespaces 1008 to provide different user info for different servers. 1009 1010 When user namespaces are enabled in the kernel it is 1011 recommended that the MEMCG option also be enabled and that 1012 user-space use the memory control groups to limit the amount 1013 of memory a memory unprivileged users can use. 1014 1015 If unsure, say N. 1016 1017config PID_NS 1018 bool "PID Namespaces" 1019 default y 1020 help 1021 Support process id namespaces. This allows having multiple 1022 processes with the same pid as long as they are in different 1023 pid namespaces. This is a building block of containers. 1024 1025config NET_NS 1026 bool "Network namespace" 1027 depends on NET 1028 default y 1029 help 1030 Allow user space to create what appear to be multiple instances 1031 of the network stack. 1032 1033endif # NAMESPACES 1034 1035config CHECKPOINT_RESTORE 1036 bool "Checkpoint/restore support" 1037 select PROC_CHILDREN 1038 default n 1039 help 1040 Enables additional kernel features in a sake of checkpoint/restore. 1041 In particular it adds auxiliary prctl codes to setup process text, 1042 data and heap segment sizes, and a few additional /proc filesystem 1043 entries. 1044 1045 If unsure, say N here. 1046 1047config SCHED_AUTOGROUP 1048 bool "Automatic process group scheduling" 1049 select CGROUPS 1050 select CGROUP_SCHED 1051 select FAIR_GROUP_SCHED 1052 help 1053 This option optimizes the scheduler for common desktop workloads by 1054 automatically creating and populating task groups. This separation 1055 of workloads isolates aggressive CPU burners (like build jobs) from 1056 desktop applications. Task group autogeneration is currently based 1057 upon task session. 1058 1059config SYSFS_DEPRECATED 1060 bool "Enable deprecated sysfs features to support old userspace tools" 1061 depends on SYSFS 1062 default n 1063 help 1064 This option adds code that switches the layout of the "block" class 1065 devices, to not show up in /sys/class/block/, but only in 1066 /sys/block/. 1067 1068 This switch is only active when the sysfs.deprecated=1 boot option is 1069 passed or the SYSFS_DEPRECATED_V2 option is set. 1070 1071 This option allows new kernels to run on old distributions and tools, 1072 which might get confused by /sys/class/block/. Since 2007/2008 all 1073 major distributions and tools handle this just fine. 1074 1075 Recent distributions and userspace tools after 2009/2010 depend on 1076 the existence of /sys/class/block/, and will not work with this 1077 option enabled. 1078 1079 Only if you are using a new kernel on an old distribution, you might 1080 need to say Y here. 1081 1082config SYSFS_DEPRECATED_V2 1083 bool "Enable deprecated sysfs features by default" 1084 default n 1085 depends on SYSFS 1086 depends on SYSFS_DEPRECATED 1087 help 1088 Enable deprecated sysfs by default. 1089 1090 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1091 option. 1092 1093 Only if you are using a new kernel on an old distribution, you might 1094 need to say Y here. Even then, odds are you would not need it 1095 enabled, you can always pass the boot option if absolutely necessary. 1096 1097config RELAY 1098 bool "Kernel->user space relay support (formerly relayfs)" 1099 select IRQ_WORK 1100 help 1101 This option enables support for relay interface support in 1102 certain file systems (such as debugfs). 1103 It is designed to provide an efficient mechanism for tools and 1104 facilities to relay large amounts of data from kernel space to 1105 user space. 1106 1107 If unsure, say N. 1108 1109config BLK_DEV_INITRD 1110 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1111 help 1112 The initial RAM filesystem is a ramfs which is loaded by the 1113 boot loader (loadlin or lilo) and that is mounted as root 1114 before the normal boot procedure. It is typically used to 1115 load modules needed to mount the "real" root file system, 1116 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1117 1118 If RAM disk support (BLK_DEV_RAM) is also included, this 1119 also enables initial RAM disk (initrd) support and adds 1120 15 Kbytes (more on some other architectures) to the kernel size. 1121 1122 If unsure say Y. 1123 1124if BLK_DEV_INITRD 1125 1126source "usr/Kconfig" 1127 1128endif 1129 1130choice 1131 prompt "Compiler optimization level" 1132 default CC_OPTIMIZE_FOR_PERFORMANCE 1133 1134config CC_OPTIMIZE_FOR_PERFORMANCE 1135 bool "Optimize for performance" 1136 help 1137 This is the default optimization level for the kernel, building 1138 with the "-O2" compiler flag for best performance and most 1139 helpful compile-time warnings. 1140 1141config CC_OPTIMIZE_FOR_SIZE 1142 bool "Optimize for size" 1143 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives 1144 help 1145 Enabling this option will pass "-Os" instead of "-O2" to 1146 your compiler resulting in a smaller kernel. 1147 1148 If unsure, say N. 1149 1150endchoice 1151 1152config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1153 bool 1154 help 1155 This requires that the arch annotates or otherwise protects 1156 its external entry points from being discarded. Linker scripts 1157 must also merge .text.*, .data.*, and .bss.* correctly into 1158 output sections. Care must be taken not to pull in unrelated 1159 sections (e.g., '.text.init'). Typically '.' in section names 1160 is used to distinguish them from label names / C identifiers. 1161 1162config LD_DEAD_CODE_DATA_ELIMINATION 1163 bool "Dead code and data elimination (EXPERIMENTAL)" 1164 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1165 depends on EXPERT 1166 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800) 1167 depends on $(cc-option,-ffunction-sections -fdata-sections) 1168 depends on $(ld-option,--gc-sections) 1169 help 1170 Enable this if you want to do dead code and data elimination with 1171 the linker by compiling with -ffunction-sections -fdata-sections, 1172 and linking with --gc-sections. 1173 1174 This can reduce on disk and in-memory size of the kernel 1175 code and static data, particularly for small configs and 1176 on small systems. This has the possibility of introducing 1177 silently broken kernel if the required annotations are not 1178 present. This option is not well tested yet, so use at your 1179 own risk. 1180 1181config SYSCTL 1182 bool 1183 1184config HAVE_UID16 1185 bool 1186 1187config SYSCTL_EXCEPTION_TRACE 1188 bool 1189 help 1190 Enable support for /proc/sys/debug/exception-trace. 1191 1192config SYSCTL_ARCH_UNALIGN_NO_WARN 1193 bool 1194 help 1195 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1196 Allows arch to define/use @no_unaligned_warning to possibly warn 1197 about unaligned access emulation going on under the hood. 1198 1199config SYSCTL_ARCH_UNALIGN_ALLOW 1200 bool 1201 help 1202 Enable support for /proc/sys/kernel/unaligned-trap 1203 Allows arches to define/use @unaligned_enabled to runtime toggle 1204 the unaligned access emulation. 1205 see arch/parisc/kernel/unaligned.c for reference 1206 1207config HAVE_PCSPKR_PLATFORM 1208 bool 1209 1210# interpreter that classic socket filters depend on 1211config BPF 1212 bool 1213 1214menuconfig EXPERT 1215 bool "Configure standard kernel features (expert users)" 1216 # Unhide debug options, to make the on-by-default options visible 1217 select DEBUG_KERNEL 1218 help 1219 This option allows certain base kernel options and settings 1220 to be disabled or tweaked. This is for specialized 1221 environments which can tolerate a "non-standard" kernel. 1222 Only use this if you really know what you are doing. 1223 1224config UID16 1225 bool "Enable 16-bit UID system calls" if EXPERT 1226 depends on HAVE_UID16 && MULTIUSER 1227 default y 1228 help 1229 This enables the legacy 16-bit UID syscall wrappers. 1230 1231config MULTIUSER 1232 bool "Multiple users, groups and capabilities support" if EXPERT 1233 default y 1234 help 1235 This option enables support for non-root users, groups and 1236 capabilities. 1237 1238 If you say N here, all processes will run with UID 0, GID 0, and all 1239 possible capabilities. Saying N here also compiles out support for 1240 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1241 setgid, and capset. 1242 1243 If unsure, say Y here. 1244 1245config SGETMASK_SYSCALL 1246 bool "sgetmask/ssetmask syscalls support" if EXPERT 1247 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1248 ---help--- 1249 sys_sgetmask and sys_ssetmask are obsolete system calls 1250 no longer supported in libc but still enabled by default in some 1251 architectures. 1252 1253 If unsure, leave the default option here. 1254 1255config SYSFS_SYSCALL 1256 bool "Sysfs syscall support" if EXPERT 1257 default y 1258 ---help--- 1259 sys_sysfs is an obsolete system call no longer supported in libc. 1260 Note that disabling this option is more secure but might break 1261 compatibility with some systems. 1262 1263 If unsure say Y here. 1264 1265config SYSCTL_SYSCALL 1266 bool "Sysctl syscall support" if EXPERT 1267 depends on PROC_SYSCTL 1268 default n 1269 select SYSCTL 1270 ---help--- 1271 sys_sysctl uses binary paths that have been found challenging 1272 to properly maintain and use. The interface in /proc/sys 1273 using paths with ascii names is now the primary path to this 1274 information. 1275 1276 Almost nothing using the binary sysctl interface so if you are 1277 trying to save some space it is probably safe to disable this, 1278 making your kernel marginally smaller. 1279 1280 If unsure say N here. 1281 1282config FHANDLE 1283 bool "open by fhandle syscalls" if EXPERT 1284 select EXPORTFS 1285 default y 1286 help 1287 If you say Y here, a user level program will be able to map 1288 file names to handle and then later use the handle for 1289 different file system operations. This is useful in implementing 1290 userspace file servers, which now track files using handles instead 1291 of names. The handle would remain the same even if file names 1292 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1293 syscalls. 1294 1295config POSIX_TIMERS 1296 bool "Posix Clocks & timers" if EXPERT 1297 default y 1298 help 1299 This includes native support for POSIX timers to the kernel. 1300 Some embedded systems have no use for them and therefore they 1301 can be configured out to reduce the size of the kernel image. 1302 1303 When this option is disabled, the following syscalls won't be 1304 available: timer_create, timer_gettime: timer_getoverrun, 1305 timer_settime, timer_delete, clock_adjtime, getitimer, 1306 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1307 clock_getres and clock_nanosleep syscalls will be limited to 1308 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1309 1310 If unsure say y. 1311 1312config PRINTK 1313 default y 1314 bool "Enable support for printk" if EXPERT 1315 select IRQ_WORK 1316 help 1317 This option enables normal printk support. Removing it 1318 eliminates most of the message strings from the kernel image 1319 and makes the kernel more or less silent. As this makes it 1320 very difficult to diagnose system problems, saying N here is 1321 strongly discouraged. 1322 1323config PRINTK_NMI 1324 def_bool y 1325 depends on PRINTK 1326 depends on HAVE_NMI 1327 1328config BUG 1329 bool "BUG() support" if EXPERT 1330 default y 1331 help 1332 Disabling this option eliminates support for BUG and WARN, reducing 1333 the size of your kernel image and potentially quietly ignoring 1334 numerous fatal conditions. You should only consider disabling this 1335 option for embedded systems with no facilities for reporting errors. 1336 Just say Y. 1337 1338config ELF_CORE 1339 depends on COREDUMP 1340 default y 1341 bool "Enable ELF core dumps" if EXPERT 1342 help 1343 Enable support for generating core dumps. Disabling saves about 4k. 1344 1345 1346config PCSPKR_PLATFORM 1347 bool "Enable PC-Speaker support" if EXPERT 1348 depends on HAVE_PCSPKR_PLATFORM 1349 select I8253_LOCK 1350 default y 1351 help 1352 This option allows to disable the internal PC-Speaker 1353 support, saving some memory. 1354 1355config BASE_FULL 1356 default y 1357 bool "Enable full-sized data structures for core" if EXPERT 1358 help 1359 Disabling this option reduces the size of miscellaneous core 1360 kernel data structures. This saves memory on small machines, 1361 but may reduce performance. 1362 1363config FUTEX 1364 bool "Enable futex support" if EXPERT 1365 default y 1366 imply RT_MUTEXES 1367 help 1368 Disabling this option will cause the kernel to be built without 1369 support for "fast userspace mutexes". The resulting kernel may not 1370 run glibc-based applications correctly. 1371 1372config FUTEX_PI 1373 bool 1374 depends on FUTEX && RT_MUTEXES 1375 default y 1376 1377config HAVE_FUTEX_CMPXCHG 1378 bool 1379 depends on FUTEX 1380 help 1381 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1382 is implemented and always working. This removes a couple of runtime 1383 checks. 1384 1385config EPOLL 1386 bool "Enable eventpoll support" if EXPERT 1387 default y 1388 help 1389 Disabling this option will cause the kernel to be built without 1390 support for epoll family of system calls. 1391 1392config SIGNALFD 1393 bool "Enable signalfd() system call" if EXPERT 1394 default y 1395 help 1396 Enable the signalfd() system call that allows to receive signals 1397 on a file descriptor. 1398 1399 If unsure, say Y. 1400 1401config TIMERFD 1402 bool "Enable timerfd() system call" if EXPERT 1403 default y 1404 help 1405 Enable the timerfd() system call that allows to receive timer 1406 events on a file descriptor. 1407 1408 If unsure, say Y. 1409 1410config EVENTFD 1411 bool "Enable eventfd() system call" if EXPERT 1412 default y 1413 help 1414 Enable the eventfd() system call that allows to receive both 1415 kernel notification (ie. KAIO) or userspace notifications. 1416 1417 If unsure, say Y. 1418 1419config SHMEM 1420 bool "Use full shmem filesystem" if EXPERT 1421 default y 1422 depends on MMU 1423 help 1424 The shmem is an internal filesystem used to manage shared memory. 1425 It is backed by swap and manages resource limits. It is also exported 1426 to userspace as tmpfs if TMPFS is enabled. Disabling this 1427 option replaces shmem and tmpfs with the much simpler ramfs code, 1428 which may be appropriate on small systems without swap. 1429 1430config AIO 1431 bool "Enable AIO support" if EXPERT 1432 default y 1433 help 1434 This option enables POSIX asynchronous I/O which may by used 1435 by some high performance threaded applications. Disabling 1436 this option saves about 7k. 1437 1438config IO_URING 1439 bool "Enable IO uring support" if EXPERT 1440 select ANON_INODES 1441 default y 1442 help 1443 This option enables support for the io_uring interface, enabling 1444 applications to submit and complete IO through submission and 1445 completion rings that are shared between the kernel and application. 1446 1447config ADVISE_SYSCALLS 1448 bool "Enable madvise/fadvise syscalls" if EXPERT 1449 default y 1450 help 1451 This option enables the madvise and fadvise syscalls, used by 1452 applications to advise the kernel about their future memory or file 1453 usage, improving performance. If building an embedded system where no 1454 applications use these syscalls, you can disable this option to save 1455 space. 1456 1457config MEMBARRIER 1458 bool "Enable membarrier() system call" if EXPERT 1459 default y 1460 help 1461 Enable the membarrier() system call that allows issuing memory 1462 barriers across all running threads, which can be used to distribute 1463 the cost of user-space memory barriers asymmetrically by transforming 1464 pairs of memory barriers into pairs consisting of membarrier() and a 1465 compiler barrier. 1466 1467 If unsure, say Y. 1468 1469config KALLSYMS 1470 bool "Load all symbols for debugging/ksymoops" if EXPERT 1471 default y 1472 help 1473 Say Y here to let the kernel print out symbolic crash information and 1474 symbolic stack backtraces. This increases the size of the kernel 1475 somewhat, as all symbols have to be loaded into the kernel image. 1476 1477config KALLSYMS_ALL 1478 bool "Include all symbols in kallsyms" 1479 depends on DEBUG_KERNEL && KALLSYMS 1480 help 1481 Normally kallsyms only contains the symbols of functions for nicer 1482 OOPS messages and backtraces (i.e., symbols from the text and inittext 1483 sections). This is sufficient for most cases. And only in very rare 1484 cases (e.g., when a debugger is used) all symbols are required (e.g., 1485 names of variables from the data sections, etc). 1486 1487 This option makes sure that all symbols are loaded into the kernel 1488 image (i.e., symbols from all sections) in cost of increased kernel 1489 size (depending on the kernel configuration, it may be 300KiB or 1490 something like this). 1491 1492 Say N unless you really need all symbols. 1493 1494config KALLSYMS_ABSOLUTE_PERCPU 1495 bool 1496 depends on KALLSYMS 1497 default X86_64 && SMP 1498 1499config KALLSYMS_BASE_RELATIVE 1500 bool 1501 depends on KALLSYMS 1502 default !IA64 1503 help 1504 Instead of emitting them as absolute values in the native word size, 1505 emit the symbol references in the kallsyms table as 32-bit entries, 1506 each containing a relative value in the range [base, base + U32_MAX] 1507 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1508 an absolute value in the range [0, S32_MAX] or a relative value in the 1509 range [base, base + S32_MAX], where base is the lowest relative symbol 1510 address encountered in the image. 1511 1512 On 64-bit builds, this reduces the size of the address table by 50%, 1513 but more importantly, it results in entries whose values are build 1514 time constants, and no relocation pass is required at runtime to fix 1515 up the entries based on the runtime load address of the kernel. 1516 1517# end of the "standard kernel features (expert users)" menu 1518 1519# syscall, maps, verifier 1520config BPF_SYSCALL 1521 bool "Enable bpf() system call" 1522 select BPF 1523 select IRQ_WORK 1524 default n 1525 help 1526 Enable the bpf() system call that allows to manipulate eBPF 1527 programs and maps via file descriptors. 1528 1529config BPF_JIT_ALWAYS_ON 1530 bool "Permanently enable BPF JIT and remove BPF interpreter" 1531 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1532 help 1533 Enables BPF JIT and removes BPF interpreter to avoid 1534 speculative execution of BPF instructions by the interpreter 1535 1536config USERFAULTFD 1537 bool "Enable userfaultfd() system call" 1538 depends on MMU 1539 help 1540 Enable the userfaultfd() system call that allows to intercept and 1541 handle page faults in userland. 1542 1543config ARCH_HAS_MEMBARRIER_CALLBACKS 1544 bool 1545 1546config ARCH_HAS_MEMBARRIER_SYNC_CORE 1547 bool 1548 1549config RSEQ 1550 bool "Enable rseq() system call" if EXPERT 1551 default y 1552 depends on HAVE_RSEQ 1553 select MEMBARRIER 1554 help 1555 Enable the restartable sequences system call. It provides a 1556 user-space cache for the current CPU number value, which 1557 speeds up getting the current CPU number from user-space, 1558 as well as an ABI to speed up user-space operations on 1559 per-CPU data. 1560 1561 If unsure, say Y. 1562 1563config DEBUG_RSEQ 1564 default n 1565 bool "Enabled debugging of rseq() system call" if EXPERT 1566 depends on RSEQ && DEBUG_KERNEL 1567 help 1568 Enable extra debugging checks for the rseq system call. 1569 1570 If unsure, say N. 1571 1572config EMBEDDED 1573 bool "Embedded system" 1574 option allnoconfig_y 1575 select EXPERT 1576 help 1577 This option should be enabled if compiling the kernel for 1578 an embedded system so certain expert options are available 1579 for configuration. 1580 1581config HAVE_PERF_EVENTS 1582 bool 1583 help 1584 See tools/perf/design.txt for details. 1585 1586config PERF_USE_VMALLOC 1587 bool 1588 help 1589 See tools/perf/design.txt for details 1590 1591config PC104 1592 bool "PC/104 support" if EXPERT 1593 help 1594 Expose PC/104 form factor device drivers and options available for 1595 selection and configuration. Enable this option if your target 1596 machine has a PC/104 bus. 1597 1598menu "Kernel Performance Events And Counters" 1599 1600config PERF_EVENTS 1601 bool "Kernel performance events and counters" 1602 default y if PROFILING 1603 depends on HAVE_PERF_EVENTS 1604 select IRQ_WORK 1605 select SRCU 1606 help 1607 Enable kernel support for various performance events provided 1608 by software and hardware. 1609 1610 Software events are supported either built-in or via the 1611 use of generic tracepoints. 1612 1613 Most modern CPUs support performance events via performance 1614 counter registers. These registers count the number of certain 1615 types of hw events: such as instructions executed, cachemisses 1616 suffered, or branches mis-predicted - without slowing down the 1617 kernel or applications. These registers can also trigger interrupts 1618 when a threshold number of events have passed - and can thus be 1619 used to profile the code that runs on that CPU. 1620 1621 The Linux Performance Event subsystem provides an abstraction of 1622 these software and hardware event capabilities, available via a 1623 system call and used by the "perf" utility in tools/perf/. It 1624 provides per task and per CPU counters, and it provides event 1625 capabilities on top of those. 1626 1627 Say Y if unsure. 1628 1629config DEBUG_PERF_USE_VMALLOC 1630 default n 1631 bool "Debug: use vmalloc to back perf mmap() buffers" 1632 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1633 select PERF_USE_VMALLOC 1634 help 1635 Use vmalloc memory to back perf mmap() buffers. 1636 1637 Mostly useful for debugging the vmalloc code on platforms 1638 that don't require it. 1639 1640 Say N if unsure. 1641 1642endmenu 1643 1644config VM_EVENT_COUNTERS 1645 default y 1646 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1647 help 1648 VM event counters are needed for event counts to be shown. 1649 This option allows the disabling of the VM event counters 1650 on EXPERT systems. /proc/vmstat will only show page counts 1651 if VM event counters are disabled. 1652 1653config SLUB_DEBUG 1654 default y 1655 bool "Enable SLUB debugging support" if EXPERT 1656 depends on SLUB && SYSFS 1657 help 1658 SLUB has extensive debug support features. Disabling these can 1659 result in significant savings in code size. This also disables 1660 SLUB sysfs support. /sys/slab will not exist and there will be 1661 no support for cache validation etc. 1662 1663config SLUB_MEMCG_SYSFS_ON 1664 default n 1665 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1666 depends on SLUB && SYSFS && MEMCG 1667 help 1668 SLUB creates a directory under /sys/kernel/slab for each 1669 allocation cache to host info and debug files. If memory 1670 cgroup is enabled, each cache can have per memory cgroup 1671 caches. SLUB can create the same sysfs directories for these 1672 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1673 to a very high number of debug files being created. This is 1674 controlled by slub_memcg_sysfs boot parameter and this 1675 config option determines the parameter's default value. 1676 1677config COMPAT_BRK 1678 bool "Disable heap randomization" 1679 default y 1680 help 1681 Randomizing heap placement makes heap exploits harder, but it 1682 also breaks ancient binaries (including anything libc5 based). 1683 This option changes the bootup default to heap randomization 1684 disabled, and can be overridden at runtime by setting 1685 /proc/sys/kernel/randomize_va_space to 2. 1686 1687 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1688 1689choice 1690 prompt "Choose SLAB allocator" 1691 default SLUB 1692 help 1693 This option allows to select a slab allocator. 1694 1695config SLAB 1696 bool "SLAB" 1697 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1698 help 1699 The regular slab allocator that is established and known to work 1700 well in all environments. It organizes cache hot objects in 1701 per cpu and per node queues. 1702 1703config SLUB 1704 bool "SLUB (Unqueued Allocator)" 1705 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1706 help 1707 SLUB is a slab allocator that minimizes cache line usage 1708 instead of managing queues of cached objects (SLAB approach). 1709 Per cpu caching is realized using slabs of objects instead 1710 of queues of objects. SLUB can use memory efficiently 1711 and has enhanced diagnostics. SLUB is the default choice for 1712 a slab allocator. 1713 1714config SLOB 1715 depends on EXPERT 1716 bool "SLOB (Simple Allocator)" 1717 help 1718 SLOB replaces the stock allocator with a drastically simpler 1719 allocator. SLOB is generally more space efficient but 1720 does not perform as well on large systems. 1721 1722endchoice 1723 1724config SLAB_MERGE_DEFAULT 1725 bool "Allow slab caches to be merged" 1726 default y 1727 help 1728 For reduced kernel memory fragmentation, slab caches can be 1729 merged when they share the same size and other characteristics. 1730 This carries a risk of kernel heap overflows being able to 1731 overwrite objects from merged caches (and more easily control 1732 cache layout), which makes such heap attacks easier to exploit 1733 by attackers. By keeping caches unmerged, these kinds of exploits 1734 can usually only damage objects in the same cache. To disable 1735 merging at runtime, "slab_nomerge" can be passed on the kernel 1736 command line. 1737 1738config SLAB_FREELIST_RANDOM 1739 default n 1740 depends on SLAB || SLUB 1741 bool "SLAB freelist randomization" 1742 help 1743 Randomizes the freelist order used on creating new pages. This 1744 security feature reduces the predictability of the kernel slab 1745 allocator against heap overflows. 1746 1747config SLAB_FREELIST_HARDENED 1748 bool "Harden slab freelist metadata" 1749 depends on SLUB 1750 help 1751 Many kernel heap attacks try to target slab cache metadata and 1752 other infrastructure. This options makes minor performance 1753 sacrifies to harden the kernel slab allocator against common 1754 freelist exploit methods. 1755 1756config SHUFFLE_PAGE_ALLOCATOR 1757 bool "Page allocator randomization" 1758 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1759 help 1760 Randomization of the page allocator improves the average 1761 utilization of a direct-mapped memory-side-cache. See section 1762 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1763 6.2a specification for an example of how a platform advertises 1764 the presence of a memory-side-cache. There are also incidental 1765 security benefits as it reduces the predictability of page 1766 allocations to compliment SLAB_FREELIST_RANDOM, but the 1767 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1768 10th order of pages is selected based on cache utilization 1769 benefits on x86. 1770 1771 While the randomization improves cache utilization it may 1772 negatively impact workloads on platforms without a cache. For 1773 this reason, by default, the randomization is enabled only 1774 after runtime detection of a direct-mapped memory-side-cache. 1775 Otherwise, the randomization may be force enabled with the 1776 'page_alloc.shuffle' kernel command line parameter. 1777 1778 Say Y if unsure. 1779 1780config SLUB_CPU_PARTIAL 1781 default y 1782 depends on SLUB && SMP 1783 bool "SLUB per cpu partial cache" 1784 help 1785 Per cpu partial caches accellerate objects allocation and freeing 1786 that is local to a processor at the price of more indeterminism 1787 in the latency of the free. On overflow these caches will be cleared 1788 which requires the taking of locks that may cause latency spikes. 1789 Typically one would choose no for a realtime system. 1790 1791config MMAP_ALLOW_UNINITIALIZED 1792 bool "Allow mmapped anonymous memory to be uninitialized" 1793 depends on EXPERT && !MMU 1794 default n 1795 help 1796 Normally, and according to the Linux spec, anonymous memory obtained 1797 from mmap() has its contents cleared before it is passed to 1798 userspace. Enabling this config option allows you to request that 1799 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1800 providing a huge performance boost. If this option is not enabled, 1801 then the flag will be ignored. 1802 1803 This is taken advantage of by uClibc's malloc(), and also by 1804 ELF-FDPIC binfmt's brk and stack allocator. 1805 1806 Because of the obvious security issues, this option should only be 1807 enabled on embedded devices where you control what is run in 1808 userspace. Since that isn't generally a problem on no-MMU systems, 1809 it is normally safe to say Y here. 1810 1811 See Documentation/nommu-mmap.txt for more information. 1812 1813config SYSTEM_DATA_VERIFICATION 1814 def_bool n 1815 select SYSTEM_TRUSTED_KEYRING 1816 select KEYS 1817 select CRYPTO 1818 select CRYPTO_RSA 1819 select ASYMMETRIC_KEY_TYPE 1820 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1821 select ASN1 1822 select OID_REGISTRY 1823 select X509_CERTIFICATE_PARSER 1824 select PKCS7_MESSAGE_PARSER 1825 help 1826 Provide PKCS#7 message verification using the contents of the system 1827 trusted keyring to provide public keys. This then can be used for 1828 module verification, kexec image verification and firmware blob 1829 verification. 1830 1831config PROFILING 1832 bool "Profiling support" 1833 help 1834 Say Y here to enable the extended profiling support mechanisms used 1835 by profilers such as OProfile. 1836 1837# 1838# Place an empty function call at each tracepoint site. Can be 1839# dynamically changed for a probe function. 1840# 1841config TRACEPOINTS 1842 bool 1843 1844endmenu # General setup 1845 1846source "arch/Kconfig" 1847 1848config RT_MUTEXES 1849 bool 1850 1851config BASE_SMALL 1852 int 1853 default 0 if BASE_FULL 1854 default 1 if !BASE_FULL 1855 1856menuconfig MODULES 1857 bool "Enable loadable module support" 1858 option modules 1859 help 1860 Kernel modules are small pieces of compiled code which can 1861 be inserted in the running kernel, rather than being 1862 permanently built into the kernel. You use the "modprobe" 1863 tool to add (and sometimes remove) them. If you say Y here, 1864 many parts of the kernel can be built as modules (by 1865 answering M instead of Y where indicated): this is most 1866 useful for infrequently used options which are not required 1867 for booting. For more information, see the man pages for 1868 modprobe, lsmod, modinfo, insmod and rmmod. 1869 1870 If you say Y here, you will need to run "make 1871 modules_install" to put the modules under /lib/modules/ 1872 where modprobe can find them (you may need to be root to do 1873 this). 1874 1875 If unsure, say Y. 1876 1877if MODULES 1878 1879config MODULE_FORCE_LOAD 1880 bool "Forced module loading" 1881 default n 1882 help 1883 Allow loading of modules without version information (ie. modprobe 1884 --force). Forced module loading sets the 'F' (forced) taint flag and 1885 is usually a really bad idea. 1886 1887config MODULE_UNLOAD 1888 bool "Module unloading" 1889 help 1890 Without this option you will not be able to unload any 1891 modules (note that some modules may not be unloadable 1892 anyway), which makes your kernel smaller, faster 1893 and simpler. If unsure, say Y. 1894 1895config MODULE_FORCE_UNLOAD 1896 bool "Forced module unloading" 1897 depends on MODULE_UNLOAD 1898 help 1899 This option allows you to force a module to unload, even if the 1900 kernel believes it is unsafe: the kernel will remove the module 1901 without waiting for anyone to stop using it (using the -f option to 1902 rmmod). This is mainly for kernel developers and desperate users. 1903 If unsure, say N. 1904 1905config MODVERSIONS 1906 bool "Module versioning support" 1907 help 1908 Usually, you have to use modules compiled with your kernel. 1909 Saying Y here makes it sometimes possible to use modules 1910 compiled for different kernels, by adding enough information 1911 to the modules to (hopefully) spot any changes which would 1912 make them incompatible with the kernel you are running. If 1913 unsure, say N. 1914 1915config MODULE_REL_CRCS 1916 bool 1917 depends on MODVERSIONS 1918 1919config MODULE_SRCVERSION_ALL 1920 bool "Source checksum for all modules" 1921 help 1922 Modules which contain a MODULE_VERSION get an extra "srcversion" 1923 field inserted into their modinfo section, which contains a 1924 sum of the source files which made it. This helps maintainers 1925 see exactly which source was used to build a module (since 1926 others sometimes change the module source without updating 1927 the version). With this option, such a "srcversion" field 1928 will be created for all modules. If unsure, say N. 1929 1930config MODULE_SIG 1931 bool "Module signature verification" 1932 depends on MODULES 1933 select SYSTEM_DATA_VERIFICATION 1934 help 1935 Check modules for valid signatures upon load: the signature 1936 is simply appended to the module. For more information see 1937 <file:Documentation/admin-guide/module-signing.rst>. 1938 1939 Note that this option adds the OpenSSL development packages as a 1940 kernel build dependency so that the signing tool can use its crypto 1941 library. 1942 1943 !!!WARNING!!! If you enable this option, you MUST make sure that the 1944 module DOES NOT get stripped after being signed. This includes the 1945 debuginfo strip done by some packagers (such as rpmbuild) and 1946 inclusion into an initramfs that wants the module size reduced. 1947 1948config MODULE_SIG_FORCE 1949 bool "Require modules to be validly signed" 1950 depends on MODULE_SIG 1951 help 1952 Reject unsigned modules or signed modules for which we don't have a 1953 key. Without this, such modules will simply taint the kernel. 1954 1955config MODULE_SIG_ALL 1956 bool "Automatically sign all modules" 1957 default y 1958 depends on MODULE_SIG 1959 help 1960 Sign all modules during make modules_install. Without this option, 1961 modules must be signed manually, using the scripts/sign-file tool. 1962 1963comment "Do not forget to sign required modules with scripts/sign-file" 1964 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 1965 1966choice 1967 prompt "Which hash algorithm should modules be signed with?" 1968 depends on MODULE_SIG 1969 help 1970 This determines which sort of hashing algorithm will be used during 1971 signature generation. This algorithm _must_ be built into the kernel 1972 directly so that signature verification can take place. It is not 1973 possible to load a signed module containing the algorithm to check 1974 the signature on that module. 1975 1976config MODULE_SIG_SHA1 1977 bool "Sign modules with SHA-1" 1978 select CRYPTO_SHA1 1979 1980config MODULE_SIG_SHA224 1981 bool "Sign modules with SHA-224" 1982 select CRYPTO_SHA256 1983 1984config MODULE_SIG_SHA256 1985 bool "Sign modules with SHA-256" 1986 select CRYPTO_SHA256 1987 1988config MODULE_SIG_SHA384 1989 bool "Sign modules with SHA-384" 1990 select CRYPTO_SHA512 1991 1992config MODULE_SIG_SHA512 1993 bool "Sign modules with SHA-512" 1994 select CRYPTO_SHA512 1995 1996endchoice 1997 1998config MODULE_SIG_HASH 1999 string 2000 depends on MODULE_SIG 2001 default "sha1" if MODULE_SIG_SHA1 2002 default "sha224" if MODULE_SIG_SHA224 2003 default "sha256" if MODULE_SIG_SHA256 2004 default "sha384" if MODULE_SIG_SHA384 2005 default "sha512" if MODULE_SIG_SHA512 2006 2007config MODULE_COMPRESS 2008 bool "Compress modules on installation" 2009 depends on MODULES 2010 help 2011 2012 Compresses kernel modules when 'make modules_install' is run; gzip or 2013 xz depending on "Compression algorithm" below. 2014 2015 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 2016 2017 Out-of-tree kernel modules installed using Kbuild will also be 2018 compressed upon installation. 2019 2020 Note: for modules inside an initrd or initramfs, it's more efficient 2021 to compress the whole initrd or initramfs instead. 2022 2023 Note: This is fully compatible with signed modules. 2024 2025 If in doubt, say N. 2026 2027choice 2028 prompt "Compression algorithm" 2029 depends on MODULE_COMPRESS 2030 default MODULE_COMPRESS_GZIP 2031 help 2032 This determines which sort of compression will be used during 2033 'make modules_install'. 2034 2035 GZIP (default) and XZ are supported. 2036 2037config MODULE_COMPRESS_GZIP 2038 bool "GZIP" 2039 2040config MODULE_COMPRESS_XZ 2041 bool "XZ" 2042 2043endchoice 2044 2045config TRIM_UNUSED_KSYMS 2046 bool "Trim unused exported kernel symbols" 2047 depends on MODULES && !UNUSED_SYMBOLS 2048 help 2049 The kernel and some modules make many symbols available for 2050 other modules to use via EXPORT_SYMBOL() and variants. Depending 2051 on the set of modules being selected in your kernel configuration, 2052 many of those exported symbols might never be used. 2053 2054 This option allows for unused exported symbols to be dropped from 2055 the build. In turn, this provides the compiler more opportunities 2056 (especially when using LTO) for optimizing the code and reducing 2057 binary size. This might have some security advantages as well. 2058 2059 If unsure, or if you need to build out-of-tree modules, say N. 2060 2061endif # MODULES 2062 2063config MODULES_TREE_LOOKUP 2064 def_bool y 2065 depends on PERF_EVENTS || TRACING 2066 2067config INIT_ALL_POSSIBLE 2068 bool 2069 help 2070 Back when each arch used to define their own cpu_online_mask and 2071 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2072 with all 1s, and others with all 0s. When they were centralised, 2073 it was better to provide this option than to break all the archs 2074 and have several arch maintainers pursuing me down dark alleys. 2075 2076source "block/Kconfig" 2077 2078config PREEMPT_NOTIFIERS 2079 bool 2080 2081config PADATA 2082 depends on SMP 2083 bool 2084 2085config ASN1 2086 tristate 2087 help 2088 Build a simple ASN.1 grammar compiler that produces a bytecode output 2089 that can be interpreted by the ASN.1 stream decoder and used to 2090 inform it as to what tags are to be expected in a stream and what 2091 functions to call on what tags. 2092 2093source "kernel/Kconfig.locks" 2094 2095config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2096 bool 2097 2098# It may be useful for an architecture to override the definitions of the 2099# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2100# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2101# different calling convention for syscalls. They can also override the 2102# macros for not-implemented syscalls in kernel/sys_ni.c and 2103# kernel/time/posix-stubs.c. All these overrides need to be available in 2104# <asm/syscall_wrapper.h>. 2105config ARCH_HAS_SYSCALL_WRAPPER 2106 def_bool n 2107