1# SPDX-License-Identifier: GPL-2.0-only 2config CC_VERSION_TEXT 3 string 4 default "$(CC_VERSION_TEXT)" 5 help 6 This is used in unclear ways: 7 8 - Re-run Kconfig when the compiler is updated 9 The 'default' property references the environment variable, 10 CC_VERSION_TEXT so it is recorded in include/config/auto.conf.cmd. 11 When the compiler is updated, Kconfig will be invoked. 12 13 - Ensure full rebuild when the compiler is updated 14 include/linux/compiler-version.h contains this option in the comment 15 line so fixdep adds include/config/CC_VERSION_TEXT into the 16 auto-generated dependency. When the compiler is updated, syncconfig 17 will touch it and then every file will be rebuilt. 18 19config CC_IS_GCC 20 def_bool $(success,test "$(cc-name)" = GCC) 21 22config GCC_VERSION 23 int 24 default $(cc-version) if CC_IS_GCC 25 default 0 26 27config CC_IS_CLANG 28 def_bool $(success,test "$(cc-name)" = Clang) 29 30config CLANG_VERSION 31 int 32 default $(cc-version) if CC_IS_CLANG 33 default 0 34 35config AS_IS_GNU 36 def_bool $(success,test "$(as-name)" = GNU) 37 38config AS_IS_LLVM 39 def_bool $(success,test "$(as-name)" = LLVM) 40 41config AS_VERSION 42 int 43 # Use clang version if this is the integrated assembler 44 default CLANG_VERSION if AS_IS_LLVM 45 default $(as-version) 46 47config LD_IS_BFD 48 def_bool $(success,test "$(ld-name)" = BFD) 49 50config LD_VERSION 51 int 52 default $(ld-version) if LD_IS_BFD 53 default 0 54 55config LD_IS_LLD 56 def_bool $(success,test "$(ld-name)" = LLD) 57 58config LLD_VERSION 59 int 60 default $(ld-version) if LD_IS_LLD 61 default 0 62 63config RUST_IS_AVAILABLE 64 def_bool $(success,$(srctree)/scripts/rust_is_available.sh) 65 help 66 This shows whether a suitable Rust toolchain is available (found). 67 68 Please see Documentation/rust/quick-start.rst for instructions on how 69 to satify the build requirements of Rust support. 70 71 In particular, the Makefile target 'rustavailable' is useful to check 72 why the Rust toolchain is not being detected. 73 74config CC_CAN_LINK 75 bool 76 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT 77 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag)) 78 79config CC_CAN_LINK_STATIC 80 bool 81 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag) -static) if 64BIT 82 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag) -static) 83 84config CC_HAS_ASM_GOTO_OUTPUT 85 def_bool $(success,echo 'int foo(int x) { asm goto ("": "=r"(x) ::: bar); return x; bar: return 0; }' | $(CC) -x c - -c -o /dev/null) 86 87config CC_HAS_ASM_GOTO_TIED_OUTPUT 88 depends on CC_HAS_ASM_GOTO_OUTPUT 89 # Detect buggy gcc and clang, fixed in gcc-11 clang-14. 90 def_bool $(success,echo 'int foo(int *x) { asm goto (".long (%l[bar]) - .\n": "+m"(*x) ::: bar); return *x; bar: return 0; }' | $CC -x c - -c -o /dev/null) 91 92config TOOLS_SUPPORT_RELR 93 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 94 95config CC_HAS_ASM_INLINE 96 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 97 98config CC_HAS_NO_PROFILE_FN_ATTR 99 def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror) 100 101config PAHOLE_VERSION 102 int 103 default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE)) 104 105config CONSTRUCTORS 106 bool 107 108config IRQ_WORK 109 bool 110 111config BUILDTIME_TABLE_SORT 112 bool 113 114config THREAD_INFO_IN_TASK 115 bool 116 help 117 Select this to move thread_info off the stack into task_struct. To 118 make this work, an arch will need to remove all thread_info fields 119 except flags and fix any runtime bugs. 120 121 One subtle change that will be needed is to use try_get_task_stack() 122 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 123 124menu "General setup" 125 126config BROKEN 127 bool 128 129config BROKEN_ON_SMP 130 bool 131 depends on BROKEN || !SMP 132 default y 133 134config INIT_ENV_ARG_LIMIT 135 int 136 default 32 if !UML 137 default 128 if UML 138 help 139 Maximum of each of the number of arguments and environment 140 variables passed to init from the kernel command line. 141 142config COMPILE_TEST 143 bool "Compile also drivers which will not load" 144 depends on HAS_IOMEM 145 help 146 Some drivers can be compiled on a different platform than they are 147 intended to be run on. Despite they cannot be loaded there (or even 148 when they load they cannot be used due to missing HW support), 149 developers still, opposing to distributors, might want to build such 150 drivers to compile-test them. 151 152 If you are a developer and want to build everything available, say Y 153 here. If you are a user/distributor, say N here to exclude useless 154 drivers to be distributed. 155 156config WERROR 157 bool "Compile the kernel with warnings as errors" 158 default COMPILE_TEST 159 help 160 A kernel build should not cause any compiler warnings, and this 161 enables the '-Werror' (for C) and '-Dwarnings' (for Rust) flags 162 to enforce that rule by default. 163 164 However, if you have a new (or very old) compiler with odd and 165 unusual warnings, or you have some architecture with problems, 166 you may need to disable this config option in order to 167 successfully build the kernel. 168 169 If in doubt, say Y. 170 171config UAPI_HEADER_TEST 172 bool "Compile test UAPI headers" 173 depends on HEADERS_INSTALL && CC_CAN_LINK 174 help 175 Compile test headers exported to user-space to ensure they are 176 self-contained, i.e. compilable as standalone units. 177 178 If you are a developer or tester and want to ensure the exported 179 headers are self-contained, say Y here. Otherwise, choose N. 180 181config LOCALVERSION 182 string "Local version - append to kernel release" 183 help 184 Append an extra string to the end of your kernel version. 185 This will show up when you type uname, for example. 186 The string you set here will be appended after the contents of 187 any files with a filename matching localversion* in your 188 object and source tree, in that order. Your total string can 189 be a maximum of 64 characters. 190 191config LOCALVERSION_AUTO 192 bool "Automatically append version information to the version string" 193 default y 194 depends on !COMPILE_TEST 195 help 196 This will try to automatically determine if the current tree is a 197 release tree by looking for git tags that belong to the current 198 top of tree revision. 199 200 A string of the format -gxxxxxxxx will be added to the localversion 201 if a git-based tree is found. The string generated by this will be 202 appended after any matching localversion* files, and after the value 203 set in CONFIG_LOCALVERSION. 204 205 (The actual string used here is the first eight characters produced 206 by running the command: 207 208 $ git rev-parse --verify HEAD 209 210 which is done within the script "scripts/setlocalversion".) 211 212config BUILD_SALT 213 string "Build ID Salt" 214 default "" 215 help 216 The build ID is used to link binaries and their debug info. Setting 217 this option will use the value in the calculation of the build id. 218 This is mostly useful for distributions which want to ensure the 219 build is unique between builds. It's safe to leave the default. 220 221config HAVE_KERNEL_GZIP 222 bool 223 224config HAVE_KERNEL_BZIP2 225 bool 226 227config HAVE_KERNEL_LZMA 228 bool 229 230config HAVE_KERNEL_XZ 231 bool 232 233config HAVE_KERNEL_LZO 234 bool 235 236config HAVE_KERNEL_LZ4 237 bool 238 239config HAVE_KERNEL_ZSTD 240 bool 241 242config HAVE_KERNEL_UNCOMPRESSED 243 bool 244 245choice 246 prompt "Kernel compression mode" 247 default KERNEL_GZIP 248 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_ZSTD || HAVE_KERNEL_UNCOMPRESSED 249 help 250 The linux kernel is a kind of self-extracting executable. 251 Several compression algorithms are available, which differ 252 in efficiency, compression and decompression speed. 253 Compression speed is only relevant when building a kernel. 254 Decompression speed is relevant at each boot. 255 256 If you have any problems with bzip2 or lzma compressed 257 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 258 version of this functionality (bzip2 only), for 2.4, was 259 supplied by Christian Ludwig) 260 261 High compression options are mostly useful for users, who 262 are low on disk space (embedded systems), but for whom ram 263 size matters less. 264 265 If in doubt, select 'gzip' 266 267config KERNEL_GZIP 268 bool "Gzip" 269 depends on HAVE_KERNEL_GZIP 270 help 271 The old and tried gzip compression. It provides a good balance 272 between compression ratio and decompression speed. 273 274config KERNEL_BZIP2 275 bool "Bzip2" 276 depends on HAVE_KERNEL_BZIP2 277 help 278 Its compression ratio and speed is intermediate. 279 Decompression speed is slowest among the choices. The kernel 280 size is about 10% smaller with bzip2, in comparison to gzip. 281 Bzip2 uses a large amount of memory. For modern kernels you 282 will need at least 8MB RAM or more for booting. 283 284config KERNEL_LZMA 285 bool "LZMA" 286 depends on HAVE_KERNEL_LZMA 287 help 288 This compression algorithm's ratio is best. Decompression speed 289 is between gzip and bzip2. Compression is slowest. 290 The kernel size is about 33% smaller with LZMA in comparison to gzip. 291 292config KERNEL_XZ 293 bool "XZ" 294 depends on HAVE_KERNEL_XZ 295 help 296 XZ uses the LZMA2 algorithm and instruction set specific 297 BCJ filters which can improve compression ratio of executable 298 code. The size of the kernel is about 30% smaller with XZ in 299 comparison to gzip. On architectures for which there is a BCJ 300 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 301 will create a few percent smaller kernel than plain LZMA. 302 303 The speed is about the same as with LZMA: The decompression 304 speed of XZ is better than that of bzip2 but worse than gzip 305 and LZO. Compression is slow. 306 307config KERNEL_LZO 308 bool "LZO" 309 depends on HAVE_KERNEL_LZO 310 help 311 Its compression ratio is the poorest among the choices. The kernel 312 size is about 10% bigger than gzip; however its speed 313 (both compression and decompression) is the fastest. 314 315config KERNEL_LZ4 316 bool "LZ4" 317 depends on HAVE_KERNEL_LZ4 318 help 319 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 320 A preliminary version of LZ4 de/compression tool is available at 321 <https://code.google.com/p/lz4/>. 322 323 Its compression ratio is worse than LZO. The size of the kernel 324 is about 8% bigger than LZO. But the decompression speed is 325 faster than LZO. 326 327config KERNEL_ZSTD 328 bool "ZSTD" 329 depends on HAVE_KERNEL_ZSTD 330 help 331 ZSTD is a compression algorithm targeting intermediate compression 332 with fast decompression speed. It will compress better than GZIP and 333 decompress around the same speed as LZO, but slower than LZ4. You 334 will need at least 192 KB RAM or more for booting. The zstd command 335 line tool is required for compression. 336 337config KERNEL_UNCOMPRESSED 338 bool "None" 339 depends on HAVE_KERNEL_UNCOMPRESSED 340 help 341 Produce uncompressed kernel image. This option is usually not what 342 you want. It is useful for debugging the kernel in slow simulation 343 environments, where decompressing and moving the kernel is awfully 344 slow. This option allows early boot code to skip the decompressor 345 and jump right at uncompressed kernel image. 346 347endchoice 348 349config DEFAULT_INIT 350 string "Default init path" 351 default "" 352 help 353 This option determines the default init for the system if no init= 354 option is passed on the kernel command line. If the requested path is 355 not present, we will still then move on to attempting further 356 locations (e.g. /sbin/init, etc). If this is empty, we will just use 357 the fallback list when init= is not passed. 358 359config DEFAULT_HOSTNAME 360 string "Default hostname" 361 default "(none)" 362 help 363 This option determines the default system hostname before userspace 364 calls sethostname(2). The kernel traditionally uses "(none)" here, 365 but you may wish to use a different default here to make a minimal 366 system more usable with less configuration. 367 368config SYSVIPC 369 bool "System V IPC" 370 help 371 Inter Process Communication is a suite of library functions and 372 system calls which let processes (running programs) synchronize and 373 exchange information. It is generally considered to be a good thing, 374 and some programs won't run unless you say Y here. In particular, if 375 you want to run the DOS emulator dosemu under Linux (read the 376 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 377 you'll need to say Y here. 378 379 You can find documentation about IPC with "info ipc" and also in 380 section 6.4 of the Linux Programmer's Guide, available from 381 <http://www.tldp.org/guides.html>. 382 383config SYSVIPC_SYSCTL 384 bool 385 depends on SYSVIPC 386 depends on SYSCTL 387 default y 388 389config SYSVIPC_COMPAT 390 def_bool y 391 depends on COMPAT && SYSVIPC 392 393config POSIX_MQUEUE 394 bool "POSIX Message Queues" 395 depends on NET 396 help 397 POSIX variant of message queues is a part of IPC. In POSIX message 398 queues every message has a priority which decides about succession 399 of receiving it by a process. If you want to compile and run 400 programs written e.g. for Solaris with use of its POSIX message 401 queues (functions mq_*) say Y here. 402 403 POSIX message queues are visible as a filesystem called 'mqueue' 404 and can be mounted somewhere if you want to do filesystem 405 operations on message queues. 406 407 If unsure, say Y. 408 409config POSIX_MQUEUE_SYSCTL 410 bool 411 depends on POSIX_MQUEUE 412 depends on SYSCTL 413 default y 414 415config WATCH_QUEUE 416 bool "General notification queue" 417 default n 418 help 419 420 This is a general notification queue for the kernel to pass events to 421 userspace by splicing them into pipes. It can be used in conjunction 422 with watches for key/keyring change notifications and device 423 notifications. 424 425 See Documentation/core-api/watch_queue.rst 426 427config CROSS_MEMORY_ATTACH 428 bool "Enable process_vm_readv/writev syscalls" 429 depends on MMU 430 default y 431 help 432 Enabling this option adds the system calls process_vm_readv and 433 process_vm_writev which allow a process with the correct privileges 434 to directly read from or write to another process' address space. 435 See the man page for more details. 436 437config USELIB 438 bool "uselib syscall (for libc5 and earlier)" 439 default ALPHA || M68K || SPARC 440 help 441 This option enables the uselib syscall, a system call used in the 442 dynamic linker from libc5 and earlier. glibc does not use this 443 system call. If you intend to run programs built on libc5 or 444 earlier, you may need to enable this syscall. Current systems 445 running glibc can safely disable this. 446 447config AUDIT 448 bool "Auditing support" 449 depends on NET 450 help 451 Enable auditing infrastructure that can be used with another 452 kernel subsystem, such as SELinux (which requires this for 453 logging of avc messages output). System call auditing is included 454 on architectures which support it. 455 456config HAVE_ARCH_AUDITSYSCALL 457 bool 458 459config AUDITSYSCALL 460 def_bool y 461 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 462 select FSNOTIFY 463 464source "kernel/irq/Kconfig" 465source "kernel/time/Kconfig" 466source "kernel/bpf/Kconfig" 467source "kernel/Kconfig.preempt" 468 469menu "CPU/Task time and stats accounting" 470 471config VIRT_CPU_ACCOUNTING 472 bool 473 474choice 475 prompt "Cputime accounting" 476 default TICK_CPU_ACCOUNTING if !PPC64 477 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 478 479# Kind of a stub config for the pure tick based cputime accounting 480config TICK_CPU_ACCOUNTING 481 bool "Simple tick based cputime accounting" 482 depends on !S390 && !NO_HZ_FULL 483 help 484 This is the basic tick based cputime accounting that maintains 485 statistics about user, system and idle time spent on per jiffies 486 granularity. 487 488 If unsure, say Y. 489 490config VIRT_CPU_ACCOUNTING_NATIVE 491 bool "Deterministic task and CPU time accounting" 492 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 493 select VIRT_CPU_ACCOUNTING 494 help 495 Select this option to enable more accurate task and CPU time 496 accounting. This is done by reading a CPU counter on each 497 kernel entry and exit and on transitions within the kernel 498 between system, softirq and hardirq state, so there is a 499 small performance impact. In the case of s390 or IBM POWER > 5, 500 this also enables accounting of stolen time on logically-partitioned 501 systems. 502 503config VIRT_CPU_ACCOUNTING_GEN 504 bool "Full dynticks CPU time accounting" 505 depends on HAVE_CONTEXT_TRACKING_USER 506 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 507 depends on GENERIC_CLOCKEVENTS 508 select VIRT_CPU_ACCOUNTING 509 select CONTEXT_TRACKING_USER 510 help 511 Select this option to enable task and CPU time accounting on full 512 dynticks systems. This accounting is implemented by watching every 513 kernel-user boundaries using the context tracking subsystem. 514 The accounting is thus performed at the expense of some significant 515 overhead. 516 517 For now this is only useful if you are working on the full 518 dynticks subsystem development. 519 520 If unsure, say N. 521 522endchoice 523 524config IRQ_TIME_ACCOUNTING 525 bool "Fine granularity task level IRQ time accounting" 526 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 527 help 528 Select this option to enable fine granularity task irq time 529 accounting. This is done by reading a timestamp on each 530 transitions between softirq and hardirq state, so there can be a 531 small performance impact. 532 533 If in doubt, say N here. 534 535config HAVE_SCHED_AVG_IRQ 536 def_bool y 537 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 538 depends on SMP 539 540config SCHED_THERMAL_PRESSURE 541 bool 542 default y if ARM && ARM_CPU_TOPOLOGY 543 default y if ARM64 544 depends on SMP 545 depends on CPU_FREQ_THERMAL 546 help 547 Select this option to enable thermal pressure accounting in the 548 scheduler. Thermal pressure is the value conveyed to the scheduler 549 that reflects the reduction in CPU compute capacity resulted from 550 thermal throttling. Thermal throttling occurs when the performance of 551 a CPU is capped due to high operating temperatures. 552 553 If selected, the scheduler will be able to balance tasks accordingly, 554 i.e. put less load on throttled CPUs than on non/less throttled ones. 555 556 This requires the architecture to implement 557 arch_update_thermal_pressure() and arch_scale_thermal_pressure(). 558 559config BSD_PROCESS_ACCT 560 bool "BSD Process Accounting" 561 depends on MULTIUSER 562 help 563 If you say Y here, a user level program will be able to instruct the 564 kernel (via a special system call) to write process accounting 565 information to a file: whenever a process exits, information about 566 that process will be appended to the file by the kernel. The 567 information includes things such as creation time, owning user, 568 command name, memory usage, controlling terminal etc. (the complete 569 list is in the struct acct in <file:include/linux/acct.h>). It is 570 up to the user level program to do useful things with this 571 information. This is generally a good idea, so say Y. 572 573config BSD_PROCESS_ACCT_V3 574 bool "BSD Process Accounting version 3 file format" 575 depends on BSD_PROCESS_ACCT 576 default n 577 help 578 If you say Y here, the process accounting information is written 579 in a new file format that also logs the process IDs of each 580 process and its parent. Note that this file format is incompatible 581 with previous v0/v1/v2 file formats, so you will need updated tools 582 for processing it. A preliminary version of these tools is available 583 at <http://www.gnu.org/software/acct/>. 584 585config TASKSTATS 586 bool "Export task/process statistics through netlink" 587 depends on NET 588 depends on MULTIUSER 589 default n 590 help 591 Export selected statistics for tasks/processes through the 592 generic netlink interface. Unlike BSD process accounting, the 593 statistics are available during the lifetime of tasks/processes as 594 responses to commands. Like BSD accounting, they are sent to user 595 space on task exit. 596 597 Say N if unsure. 598 599config TASK_DELAY_ACCT 600 bool "Enable per-task delay accounting" 601 depends on TASKSTATS 602 select SCHED_INFO 603 help 604 Collect information on time spent by a task waiting for system 605 resources like cpu, synchronous block I/O completion and swapping 606 in pages. Such statistics can help in setting a task's priorities 607 relative to other tasks for cpu, io, rss limits etc. 608 609 Say N if unsure. 610 611config TASK_XACCT 612 bool "Enable extended accounting over taskstats" 613 depends on TASKSTATS 614 help 615 Collect extended task accounting data and send the data 616 to userland for processing over the taskstats interface. 617 618 Say N if unsure. 619 620config TASK_IO_ACCOUNTING 621 bool "Enable per-task storage I/O accounting" 622 depends on TASK_XACCT 623 help 624 Collect information on the number of bytes of storage I/O which this 625 task has caused. 626 627 Say N if unsure. 628 629config PSI 630 bool "Pressure stall information tracking" 631 help 632 Collect metrics that indicate how overcommitted the CPU, memory, 633 and IO capacity are in the system. 634 635 If you say Y here, the kernel will create /proc/pressure/ with the 636 pressure statistics files cpu, memory, and io. These will indicate 637 the share of walltime in which some or all tasks in the system are 638 delayed due to contention of the respective resource. 639 640 In kernels with cgroup support, cgroups (cgroup2 only) will 641 have cpu.pressure, memory.pressure, and io.pressure files, 642 which aggregate pressure stalls for the grouped tasks only. 643 644 For more details see Documentation/accounting/psi.rst. 645 646 Say N if unsure. 647 648config PSI_DEFAULT_DISABLED 649 bool "Require boot parameter to enable pressure stall information tracking" 650 default n 651 depends on PSI 652 help 653 If set, pressure stall information tracking will be disabled 654 per default but can be enabled through passing psi=1 on the 655 kernel commandline during boot. 656 657 This feature adds some code to the task wakeup and sleep 658 paths of the scheduler. The overhead is too low to affect 659 common scheduling-intense workloads in practice (such as 660 webservers, memcache), but it does show up in artificial 661 scheduler stress tests, such as hackbench. 662 663 If you are paranoid and not sure what the kernel will be 664 used for, say Y. 665 666 Say N if unsure. 667 668endmenu # "CPU/Task time and stats accounting" 669 670config CPU_ISOLATION 671 bool "CPU isolation" 672 depends on SMP || COMPILE_TEST 673 default y 674 help 675 Make sure that CPUs running critical tasks are not disturbed by 676 any source of "noise" such as unbound workqueues, timers, kthreads... 677 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 678 the "isolcpus=" boot parameter. 679 680 Say Y if unsure. 681 682source "kernel/rcu/Kconfig" 683 684config BUILD_BIN2C 685 bool 686 default n 687 688config IKCONFIG 689 tristate "Kernel .config support" 690 help 691 This option enables the complete Linux kernel ".config" file 692 contents to be saved in the kernel. It provides documentation 693 of which kernel options are used in a running kernel or in an 694 on-disk kernel. This information can be extracted from the kernel 695 image file with the script scripts/extract-ikconfig and used as 696 input to rebuild the current kernel or to build another kernel. 697 It can also be extracted from a running kernel by reading 698 /proc/config.gz if enabled (below). 699 700config IKCONFIG_PROC 701 bool "Enable access to .config through /proc/config.gz" 702 depends on IKCONFIG && PROC_FS 703 help 704 This option enables access to the kernel configuration file 705 through /proc/config.gz. 706 707config IKHEADERS 708 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 709 depends on SYSFS 710 help 711 This option enables access to the in-kernel headers that are generated during 712 the build process. These can be used to build eBPF tracing programs, 713 or similar programs. If you build the headers as a module, a module called 714 kheaders.ko is built which can be loaded on-demand to get access to headers. 715 716config LOG_BUF_SHIFT 717 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 718 range 12 25 719 default 17 720 depends on PRINTK 721 help 722 Select the minimal kernel log buffer size as a power of 2. 723 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 724 parameter, see below. Any higher size also might be forced 725 by "log_buf_len" boot parameter. 726 727 Examples: 728 17 => 128 KB 729 16 => 64 KB 730 15 => 32 KB 731 14 => 16 KB 732 13 => 8 KB 733 12 => 4 KB 734 735config LOG_CPU_MAX_BUF_SHIFT 736 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 737 depends on SMP 738 range 0 21 739 default 12 if !BASE_SMALL 740 default 0 if BASE_SMALL 741 depends on PRINTK 742 help 743 This option allows to increase the default ring buffer size 744 according to the number of CPUs. The value defines the contribution 745 of each CPU as a power of 2. The used space is typically only few 746 lines however it might be much more when problems are reported, 747 e.g. backtraces. 748 749 The increased size means that a new buffer has to be allocated and 750 the original static one is unused. It makes sense only on systems 751 with more CPUs. Therefore this value is used only when the sum of 752 contributions is greater than the half of the default kernel ring 753 buffer as defined by LOG_BUF_SHIFT. The default values are set 754 so that more than 16 CPUs are needed to trigger the allocation. 755 756 Also this option is ignored when "log_buf_len" kernel parameter is 757 used as it forces an exact (power of two) size of the ring buffer. 758 759 The number of possible CPUs is used for this computation ignoring 760 hotplugging making the computation optimal for the worst case 761 scenario while allowing a simple algorithm to be used from bootup. 762 763 Examples shift values and their meaning: 764 17 => 128 KB for each CPU 765 16 => 64 KB for each CPU 766 15 => 32 KB for each CPU 767 14 => 16 KB for each CPU 768 13 => 8 KB for each CPU 769 12 => 4 KB for each CPU 770 771config PRINTK_SAFE_LOG_BUF_SHIFT 772 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 773 range 10 21 774 default 13 775 depends on PRINTK 776 help 777 Select the size of an alternate printk per-CPU buffer where messages 778 printed from usafe contexts are temporary stored. One example would 779 be NMI messages, another one - printk recursion. The messages are 780 copied to the main log buffer in a safe context to avoid a deadlock. 781 The value defines the size as a power of 2. 782 783 Those messages are rare and limited. The largest one is when 784 a backtrace is printed. It usually fits into 4KB. Select 785 8KB if you want to be on the safe side. 786 787 Examples: 788 17 => 128 KB for each CPU 789 16 => 64 KB for each CPU 790 15 => 32 KB for each CPU 791 14 => 16 KB for each CPU 792 13 => 8 KB for each CPU 793 12 => 4 KB for each CPU 794 795config PRINTK_INDEX 796 bool "Printk indexing debugfs interface" 797 depends on PRINTK && DEBUG_FS 798 help 799 Add support for indexing of all printk formats known at compile time 800 at <debugfs>/printk/index/<module>. 801 802 This can be used as part of maintaining daemons which monitor 803 /dev/kmsg, as it permits auditing the printk formats present in a 804 kernel, allowing detection of cases where monitored printks are 805 changed or no longer present. 806 807 There is no additional runtime cost to printk with this enabled. 808 809# 810# Architectures with an unreliable sched_clock() should select this: 811# 812config HAVE_UNSTABLE_SCHED_CLOCK 813 bool 814 815config GENERIC_SCHED_CLOCK 816 bool 817 818menu "Scheduler features" 819 820config UCLAMP_TASK 821 bool "Enable utilization clamping for RT/FAIR tasks" 822 depends on CPU_FREQ_GOV_SCHEDUTIL 823 help 824 This feature enables the scheduler to track the clamped utilization 825 of each CPU based on RUNNABLE tasks scheduled on that CPU. 826 827 With this option, the user can specify the min and max CPU 828 utilization allowed for RUNNABLE tasks. The max utilization defines 829 the maximum frequency a task should use while the min utilization 830 defines the minimum frequency it should use. 831 832 Both min and max utilization clamp values are hints to the scheduler, 833 aiming at improving its frequency selection policy, but they do not 834 enforce or grant any specific bandwidth for tasks. 835 836 If in doubt, say N. 837 838config UCLAMP_BUCKETS_COUNT 839 int "Number of supported utilization clamp buckets" 840 range 5 20 841 default 5 842 depends on UCLAMP_TASK 843 help 844 Defines the number of clamp buckets to use. The range of each bucket 845 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 846 number of clamp buckets the finer their granularity and the higher 847 the precision of clamping aggregation and tracking at run-time. 848 849 For example, with the minimum configuration value we will have 5 850 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 851 be refcounted in the [20..39]% bucket and will set the bucket clamp 852 effective value to 25%. 853 If a second 30% boosted task should be co-scheduled on the same CPU, 854 that task will be refcounted in the same bucket of the first task and 855 it will boost the bucket clamp effective value to 30%. 856 The clamp effective value of a bucket is reset to its nominal value 857 (20% in the example above) when there are no more tasks refcounted in 858 that bucket. 859 860 An additional boost/capping margin can be added to some tasks. In the 861 example above the 25% task will be boosted to 30% until it exits the 862 CPU. If that should be considered not acceptable on certain systems, 863 it's always possible to reduce the margin by increasing the number of 864 clamp buckets to trade off used memory for run-time tracking 865 precision. 866 867 If in doubt, use the default value. 868 869endmenu 870 871# 872# For architectures that want to enable the support for NUMA-affine scheduler 873# balancing logic: 874# 875config ARCH_SUPPORTS_NUMA_BALANCING 876 bool 877 878# 879# For architectures that prefer to flush all TLBs after a number of pages 880# are unmapped instead of sending one IPI per page to flush. The architecture 881# must provide guarantees on what happens if a clean TLB cache entry is 882# written after the unmap. Details are in mm/rmap.c near the check for 883# should_defer_flush. The architecture should also consider if the full flush 884# and the refill costs are offset by the savings of sending fewer IPIs. 885config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 886 bool 887 888config CC_HAS_INT128 889 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 890 891config CC_IMPLICIT_FALLTHROUGH 892 string 893 default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5) 894 default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough) 895 896# Currently, disable gcc-12 array-bounds globally. 897# We may want to target only particular configurations some day. 898config GCC12_NO_ARRAY_BOUNDS 899 def_bool y 900 901config CC_NO_ARRAY_BOUNDS 902 bool 903 default y if CC_IS_GCC && GCC_VERSION >= 120000 && GCC_VERSION < 130000 && GCC12_NO_ARRAY_BOUNDS 904 905# 906# For architectures that know their GCC __int128 support is sound 907# 908config ARCH_SUPPORTS_INT128 909 bool 910 911# For architectures that (ab)use NUMA to represent different memory regions 912# all cpu-local but of different latencies, such as SuperH. 913# 914config ARCH_WANT_NUMA_VARIABLE_LOCALITY 915 bool 916 917config NUMA_BALANCING 918 bool "Memory placement aware NUMA scheduler" 919 depends on ARCH_SUPPORTS_NUMA_BALANCING 920 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 921 depends on SMP && NUMA && MIGRATION && !PREEMPT_RT 922 help 923 This option adds support for automatic NUMA aware memory/task placement. 924 The mechanism is quite primitive and is based on migrating memory when 925 it has references to the node the task is running on. 926 927 This system will be inactive on UMA systems. 928 929config NUMA_BALANCING_DEFAULT_ENABLED 930 bool "Automatically enable NUMA aware memory/task placement" 931 default y 932 depends on NUMA_BALANCING 933 help 934 If set, automatic NUMA balancing will be enabled if running on a NUMA 935 machine. 936 937menuconfig CGROUPS 938 bool "Control Group support" 939 select KERNFS 940 help 941 This option adds support for grouping sets of processes together, for 942 use with process control subsystems such as Cpusets, CFS, memory 943 controls or device isolation. 944 See 945 - Documentation/scheduler/sched-design-CFS.rst (CFS) 946 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 947 and resource control) 948 949 Say N if unsure. 950 951if CGROUPS 952 953config PAGE_COUNTER 954 bool 955 956config CGROUP_FAVOR_DYNMODS 957 bool "Favor dynamic modification latency reduction by default" 958 help 959 This option enables the "favordynmods" mount option by default 960 which reduces the latencies of dynamic cgroup modifications such 961 as task migrations and controller on/offs at the cost of making 962 hot path operations such as forks and exits more expensive. 963 964 Say N if unsure. 965 966config MEMCG 967 bool "Memory controller" 968 select PAGE_COUNTER 969 select EVENTFD 970 help 971 Provides control over the memory footprint of tasks in a cgroup. 972 973config MEMCG_SWAP 974 bool 975 depends on MEMCG && SWAP 976 default y 977 978config MEMCG_KMEM 979 bool 980 depends on MEMCG && !SLOB 981 default y 982 983config BLK_CGROUP 984 bool "IO controller" 985 depends on BLOCK 986 default n 987 help 988 Generic block IO controller cgroup interface. This is the common 989 cgroup interface which should be used by various IO controlling 990 policies. 991 992 Currently, CFQ IO scheduler uses it to recognize task groups and 993 control disk bandwidth allocation (proportional time slice allocation) 994 to such task groups. It is also used by bio throttling logic in 995 block layer to implement upper limit in IO rates on a device. 996 997 This option only enables generic Block IO controller infrastructure. 998 One needs to also enable actual IO controlling logic/policy. For 999 enabling proportional weight division of disk bandwidth in CFQ, set 1000 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 1001 CONFIG_BLK_DEV_THROTTLING=y. 1002 1003 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 1004 1005config CGROUP_WRITEBACK 1006 bool 1007 depends on MEMCG && BLK_CGROUP 1008 default y 1009 1010menuconfig CGROUP_SCHED 1011 bool "CPU controller" 1012 default n 1013 help 1014 This feature lets CPU scheduler recognize task groups and control CPU 1015 bandwidth allocation to such task groups. It uses cgroups to group 1016 tasks. 1017 1018if CGROUP_SCHED 1019config FAIR_GROUP_SCHED 1020 bool "Group scheduling for SCHED_OTHER" 1021 depends on CGROUP_SCHED 1022 default CGROUP_SCHED 1023 1024config CFS_BANDWIDTH 1025 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 1026 depends on FAIR_GROUP_SCHED 1027 default n 1028 help 1029 This option allows users to define CPU bandwidth rates (limits) for 1030 tasks running within the fair group scheduler. Groups with no limit 1031 set are considered to be unconstrained and will run with no 1032 restriction. 1033 See Documentation/scheduler/sched-bwc.rst for more information. 1034 1035config RT_GROUP_SCHED 1036 bool "Group scheduling for SCHED_RR/FIFO" 1037 depends on CGROUP_SCHED 1038 default n 1039 help 1040 This feature lets you explicitly allocate real CPU bandwidth 1041 to task groups. If enabled, it will also make it impossible to 1042 schedule realtime tasks for non-root users until you allocate 1043 realtime bandwidth for them. 1044 See Documentation/scheduler/sched-rt-group.rst for more information. 1045 1046endif #CGROUP_SCHED 1047 1048config UCLAMP_TASK_GROUP 1049 bool "Utilization clamping per group of tasks" 1050 depends on CGROUP_SCHED 1051 depends on UCLAMP_TASK 1052 default n 1053 help 1054 This feature enables the scheduler to track the clamped utilization 1055 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 1056 1057 When this option is enabled, the user can specify a min and max 1058 CPU bandwidth which is allowed for each single task in a group. 1059 The max bandwidth allows to clamp the maximum frequency a task 1060 can use, while the min bandwidth allows to define a minimum 1061 frequency a task will always use. 1062 1063 When task group based utilization clamping is enabled, an eventually 1064 specified task-specific clamp value is constrained by the cgroup 1065 specified clamp value. Both minimum and maximum task clamping cannot 1066 be bigger than the corresponding clamping defined at task group level. 1067 1068 If in doubt, say N. 1069 1070config CGROUP_PIDS 1071 bool "PIDs controller" 1072 help 1073 Provides enforcement of process number limits in the scope of a 1074 cgroup. Any attempt to fork more processes than is allowed in the 1075 cgroup will fail. PIDs are fundamentally a global resource because it 1076 is fairly trivial to reach PID exhaustion before you reach even a 1077 conservative kmemcg limit. As a result, it is possible to grind a 1078 system to halt without being limited by other cgroup policies. The 1079 PIDs controller is designed to stop this from happening. 1080 1081 It should be noted that organisational operations (such as attaching 1082 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 1083 since the PIDs limit only affects a process's ability to fork, not to 1084 attach to a cgroup. 1085 1086config CGROUP_RDMA 1087 bool "RDMA controller" 1088 help 1089 Provides enforcement of RDMA resources defined by IB stack. 1090 It is fairly easy for consumers to exhaust RDMA resources, which 1091 can result into resource unavailability to other consumers. 1092 RDMA controller is designed to stop this from happening. 1093 Attaching processes with active RDMA resources to the cgroup 1094 hierarchy is allowed even if can cross the hierarchy's limit. 1095 1096config CGROUP_FREEZER 1097 bool "Freezer controller" 1098 help 1099 Provides a way to freeze and unfreeze all tasks in a 1100 cgroup. 1101 1102 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1103 controller includes important in-kernel memory consumers per default. 1104 1105 If you're using cgroup2, say N. 1106 1107config CGROUP_HUGETLB 1108 bool "HugeTLB controller" 1109 depends on HUGETLB_PAGE 1110 select PAGE_COUNTER 1111 default n 1112 help 1113 Provides a cgroup controller for HugeTLB pages. 1114 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1115 The limit is enforced during page fault. Since HugeTLB doesn't 1116 support page reclaim, enforcing the limit at page fault time implies 1117 that, the application will get SIGBUS signal if it tries to access 1118 HugeTLB pages beyond its limit. This requires the application to know 1119 beforehand how much HugeTLB pages it would require for its use. The 1120 control group is tracked in the third page lru pointer. This means 1121 that we cannot use the controller with huge page less than 3 pages. 1122 1123config CPUSETS 1124 bool "Cpuset controller" 1125 depends on SMP 1126 help 1127 This option will let you create and manage CPUSETs which 1128 allow dynamically partitioning a system into sets of CPUs and 1129 Memory Nodes and assigning tasks to run only within those sets. 1130 This is primarily useful on large SMP or NUMA systems. 1131 1132 Say N if unsure. 1133 1134config PROC_PID_CPUSET 1135 bool "Include legacy /proc/<pid>/cpuset file" 1136 depends on CPUSETS 1137 default y 1138 1139config CGROUP_DEVICE 1140 bool "Device controller" 1141 help 1142 Provides a cgroup controller implementing whitelists for 1143 devices which a process in the cgroup can mknod or open. 1144 1145config CGROUP_CPUACCT 1146 bool "Simple CPU accounting controller" 1147 help 1148 Provides a simple controller for monitoring the 1149 total CPU consumed by the tasks in a cgroup. 1150 1151config CGROUP_PERF 1152 bool "Perf controller" 1153 depends on PERF_EVENTS 1154 help 1155 This option extends the perf per-cpu mode to restrict monitoring 1156 to threads which belong to the cgroup specified and run on the 1157 designated cpu. Or this can be used to have cgroup ID in samples 1158 so that it can monitor performance events among cgroups. 1159 1160 Say N if unsure. 1161 1162config CGROUP_BPF 1163 bool "Support for eBPF programs attached to cgroups" 1164 depends on BPF_SYSCALL 1165 select SOCK_CGROUP_DATA 1166 help 1167 Allow attaching eBPF programs to a cgroup using the bpf(2) 1168 syscall command BPF_PROG_ATTACH. 1169 1170 In which context these programs are accessed depends on the type 1171 of attachment. For instance, programs that are attached using 1172 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1173 inet sockets. 1174 1175config CGROUP_MISC 1176 bool "Misc resource controller" 1177 default n 1178 help 1179 Provides a controller for miscellaneous resources on a host. 1180 1181 Miscellaneous scalar resources are the resources on the host system 1182 which cannot be abstracted like the other cgroups. This controller 1183 tracks and limits the miscellaneous resources used by a process 1184 attached to a cgroup hierarchy. 1185 1186 For more information, please check misc cgroup section in 1187 /Documentation/admin-guide/cgroup-v2.rst. 1188 1189config CGROUP_DEBUG 1190 bool "Debug controller" 1191 default n 1192 depends on DEBUG_KERNEL 1193 help 1194 This option enables a simple controller that exports 1195 debugging information about the cgroups framework. This 1196 controller is for control cgroup debugging only. Its 1197 interfaces are not stable. 1198 1199 Say N. 1200 1201config SOCK_CGROUP_DATA 1202 bool 1203 default n 1204 1205endif # CGROUPS 1206 1207menuconfig NAMESPACES 1208 bool "Namespaces support" if EXPERT 1209 depends on MULTIUSER 1210 default !EXPERT 1211 help 1212 Provides the way to make tasks work with different objects using 1213 the same id. For example same IPC id may refer to different objects 1214 or same user id or pid may refer to different tasks when used in 1215 different namespaces. 1216 1217if NAMESPACES 1218 1219config UTS_NS 1220 bool "UTS namespace" 1221 default y 1222 help 1223 In this namespace tasks see different info provided with the 1224 uname() system call 1225 1226config TIME_NS 1227 bool "TIME namespace" 1228 depends on GENERIC_VDSO_TIME_NS 1229 default y 1230 help 1231 In this namespace boottime and monotonic clocks can be set. 1232 The time will keep going with the same pace. 1233 1234config IPC_NS 1235 bool "IPC namespace" 1236 depends on (SYSVIPC || POSIX_MQUEUE) 1237 default y 1238 help 1239 In this namespace tasks work with IPC ids which correspond to 1240 different IPC objects in different namespaces. 1241 1242config USER_NS 1243 bool "User namespace" 1244 default n 1245 help 1246 This allows containers, i.e. vservers, to use user namespaces 1247 to provide different user info for different servers. 1248 1249 When user namespaces are enabled in the kernel it is 1250 recommended that the MEMCG option also be enabled and that 1251 user-space use the memory control groups to limit the amount 1252 of memory a memory unprivileged users can use. 1253 1254 If unsure, say N. 1255 1256config PID_NS 1257 bool "PID Namespaces" 1258 default y 1259 help 1260 Support process id namespaces. This allows having multiple 1261 processes with the same pid as long as they are in different 1262 pid namespaces. This is a building block of containers. 1263 1264config NET_NS 1265 bool "Network namespace" 1266 depends on NET 1267 default y 1268 help 1269 Allow user space to create what appear to be multiple instances 1270 of the network stack. 1271 1272endif # NAMESPACES 1273 1274config CHECKPOINT_RESTORE 1275 bool "Checkpoint/restore support" 1276 select PROC_CHILDREN 1277 select KCMP 1278 default n 1279 help 1280 Enables additional kernel features in a sake of checkpoint/restore. 1281 In particular it adds auxiliary prctl codes to setup process text, 1282 data and heap segment sizes, and a few additional /proc filesystem 1283 entries. 1284 1285 If unsure, say N here. 1286 1287config SCHED_AUTOGROUP 1288 bool "Automatic process group scheduling" 1289 select CGROUPS 1290 select CGROUP_SCHED 1291 select FAIR_GROUP_SCHED 1292 help 1293 This option optimizes the scheduler for common desktop workloads by 1294 automatically creating and populating task groups. This separation 1295 of workloads isolates aggressive CPU burners (like build jobs) from 1296 desktop applications. Task group autogeneration is currently based 1297 upon task session. 1298 1299config SYSFS_DEPRECATED 1300 bool "Enable deprecated sysfs features to support old userspace tools" 1301 depends on SYSFS 1302 default n 1303 help 1304 This option adds code that switches the layout of the "block" class 1305 devices, to not show up in /sys/class/block/, but only in 1306 /sys/block/. 1307 1308 This switch is only active when the sysfs.deprecated=1 boot option is 1309 passed or the SYSFS_DEPRECATED_V2 option is set. 1310 1311 This option allows new kernels to run on old distributions and tools, 1312 which might get confused by /sys/class/block/. Since 2007/2008 all 1313 major distributions and tools handle this just fine. 1314 1315 Recent distributions and userspace tools after 2009/2010 depend on 1316 the existence of /sys/class/block/, and will not work with this 1317 option enabled. 1318 1319 Only if you are using a new kernel on an old distribution, you might 1320 need to say Y here. 1321 1322config SYSFS_DEPRECATED_V2 1323 bool "Enable deprecated sysfs features by default" 1324 default n 1325 depends on SYSFS 1326 depends on SYSFS_DEPRECATED 1327 help 1328 Enable deprecated sysfs by default. 1329 1330 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1331 option. 1332 1333 Only if you are using a new kernel on an old distribution, you might 1334 need to say Y here. Even then, odds are you would not need it 1335 enabled, you can always pass the boot option if absolutely necessary. 1336 1337config RELAY 1338 bool "Kernel->user space relay support (formerly relayfs)" 1339 select IRQ_WORK 1340 help 1341 This option enables support for relay interface support in 1342 certain file systems (such as debugfs). 1343 It is designed to provide an efficient mechanism for tools and 1344 facilities to relay large amounts of data from kernel space to 1345 user space. 1346 1347 If unsure, say N. 1348 1349config BLK_DEV_INITRD 1350 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1351 help 1352 The initial RAM filesystem is a ramfs which is loaded by the 1353 boot loader (loadlin or lilo) and that is mounted as root 1354 before the normal boot procedure. It is typically used to 1355 load modules needed to mount the "real" root file system, 1356 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1357 1358 If RAM disk support (BLK_DEV_RAM) is also included, this 1359 also enables initial RAM disk (initrd) support and adds 1360 15 Kbytes (more on some other architectures) to the kernel size. 1361 1362 If unsure say Y. 1363 1364if BLK_DEV_INITRD 1365 1366source "usr/Kconfig" 1367 1368endif 1369 1370config BOOT_CONFIG 1371 bool "Boot config support" 1372 select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED 1373 help 1374 Extra boot config allows system admin to pass a config file as 1375 complemental extension of kernel cmdline when booting. 1376 The boot config file must be attached at the end of initramfs 1377 with checksum, size and magic word. 1378 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1379 1380 If unsure, say Y. 1381 1382config BOOT_CONFIG_EMBED 1383 bool "Embed bootconfig file in the kernel" 1384 depends on BOOT_CONFIG 1385 help 1386 Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the 1387 kernel. Usually, the bootconfig file is loaded with the initrd 1388 image. But if the system doesn't support initrd, this option will 1389 help you by embedding a bootconfig file while building the kernel. 1390 1391 If unsure, say N. 1392 1393config BOOT_CONFIG_EMBED_FILE 1394 string "Embedded bootconfig file path" 1395 depends on BOOT_CONFIG_EMBED 1396 help 1397 Specify a bootconfig file which will be embedded to the kernel. 1398 This bootconfig will be used if there is no initrd or no other 1399 bootconfig in the initrd. 1400 1401config INITRAMFS_PRESERVE_MTIME 1402 bool "Preserve cpio archive mtimes in initramfs" 1403 default y 1404 help 1405 Each entry in an initramfs cpio archive carries an mtime value. When 1406 enabled, extracted cpio items take this mtime, with directory mtime 1407 setting deferred until after creation of any child entries. 1408 1409 If unsure, say Y. 1410 1411choice 1412 prompt "Compiler optimization level" 1413 default CC_OPTIMIZE_FOR_PERFORMANCE 1414 1415config CC_OPTIMIZE_FOR_PERFORMANCE 1416 bool "Optimize for performance (-O2)" 1417 help 1418 This is the default optimization level for the kernel, building 1419 with the "-O2" compiler flag for best performance and most 1420 helpful compile-time warnings. 1421 1422config CC_OPTIMIZE_FOR_SIZE 1423 bool "Optimize for size (-Os)" 1424 help 1425 Choosing this option will pass "-Os" to your compiler resulting 1426 in a smaller kernel. 1427 1428endchoice 1429 1430config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1431 bool 1432 help 1433 This requires that the arch annotates or otherwise protects 1434 its external entry points from being discarded. Linker scripts 1435 must also merge .text.*, .data.*, and .bss.* correctly into 1436 output sections. Care must be taken not to pull in unrelated 1437 sections (e.g., '.text.init'). Typically '.' in section names 1438 is used to distinguish them from label names / C identifiers. 1439 1440config LD_DEAD_CODE_DATA_ELIMINATION 1441 bool "Dead code and data elimination (EXPERIMENTAL)" 1442 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1443 depends on EXPERT 1444 depends on $(cc-option,-ffunction-sections -fdata-sections) 1445 depends on $(ld-option,--gc-sections) 1446 help 1447 Enable this if you want to do dead code and data elimination with 1448 the linker by compiling with -ffunction-sections -fdata-sections, 1449 and linking with --gc-sections. 1450 1451 This can reduce on disk and in-memory size of the kernel 1452 code and static data, particularly for small configs and 1453 on small systems. This has the possibility of introducing 1454 silently broken kernel if the required annotations are not 1455 present. This option is not well tested yet, so use at your 1456 own risk. 1457 1458config LD_ORPHAN_WARN 1459 def_bool y 1460 depends on ARCH_WANT_LD_ORPHAN_WARN 1461 depends on $(ld-option,--orphan-handling=warn) 1462 1463config SYSCTL 1464 bool 1465 1466config HAVE_UID16 1467 bool 1468 1469config SYSCTL_EXCEPTION_TRACE 1470 bool 1471 help 1472 Enable support for /proc/sys/debug/exception-trace. 1473 1474config SYSCTL_ARCH_UNALIGN_NO_WARN 1475 bool 1476 help 1477 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1478 Allows arch to define/use @no_unaligned_warning to possibly warn 1479 about unaligned access emulation going on under the hood. 1480 1481config SYSCTL_ARCH_UNALIGN_ALLOW 1482 bool 1483 help 1484 Enable support for /proc/sys/kernel/unaligned-trap 1485 Allows arches to define/use @unaligned_enabled to runtime toggle 1486 the unaligned access emulation. 1487 see arch/parisc/kernel/unaligned.c for reference 1488 1489config HAVE_PCSPKR_PLATFORM 1490 bool 1491 1492# interpreter that classic socket filters depend on 1493config BPF 1494 bool 1495 select CRYPTO_LIB_SHA1 1496 1497menuconfig EXPERT 1498 bool "Configure standard kernel features (expert users)" 1499 # Unhide debug options, to make the on-by-default options visible 1500 select DEBUG_KERNEL 1501 help 1502 This option allows certain base kernel options and settings 1503 to be disabled or tweaked. This is for specialized 1504 environments which can tolerate a "non-standard" kernel. 1505 Only use this if you really know what you are doing. 1506 1507config UID16 1508 bool "Enable 16-bit UID system calls" if EXPERT 1509 depends on HAVE_UID16 && MULTIUSER 1510 default y 1511 help 1512 This enables the legacy 16-bit UID syscall wrappers. 1513 1514config MULTIUSER 1515 bool "Multiple users, groups and capabilities support" if EXPERT 1516 default y 1517 help 1518 This option enables support for non-root users, groups and 1519 capabilities. 1520 1521 If you say N here, all processes will run with UID 0, GID 0, and all 1522 possible capabilities. Saying N here also compiles out support for 1523 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1524 setgid, and capset. 1525 1526 If unsure, say Y here. 1527 1528config SGETMASK_SYSCALL 1529 bool "sgetmask/ssetmask syscalls support" if EXPERT 1530 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1531 help 1532 sys_sgetmask and sys_ssetmask are obsolete system calls 1533 no longer supported in libc but still enabled by default in some 1534 architectures. 1535 1536 If unsure, leave the default option here. 1537 1538config SYSFS_SYSCALL 1539 bool "Sysfs syscall support" if EXPERT 1540 default y 1541 help 1542 sys_sysfs is an obsolete system call no longer supported in libc. 1543 Note that disabling this option is more secure but might break 1544 compatibility with some systems. 1545 1546 If unsure say Y here. 1547 1548config FHANDLE 1549 bool "open by fhandle syscalls" if EXPERT 1550 select EXPORTFS 1551 default y 1552 help 1553 If you say Y here, a user level program will be able to map 1554 file names to handle and then later use the handle for 1555 different file system operations. This is useful in implementing 1556 userspace file servers, which now track files using handles instead 1557 of names. The handle would remain the same even if file names 1558 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1559 syscalls. 1560 1561config POSIX_TIMERS 1562 bool "Posix Clocks & timers" if EXPERT 1563 default y 1564 help 1565 This includes native support for POSIX timers to the kernel. 1566 Some embedded systems have no use for them and therefore they 1567 can be configured out to reduce the size of the kernel image. 1568 1569 When this option is disabled, the following syscalls won't be 1570 available: timer_create, timer_gettime: timer_getoverrun, 1571 timer_settime, timer_delete, clock_adjtime, getitimer, 1572 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1573 clock_getres and clock_nanosleep syscalls will be limited to 1574 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1575 1576 If unsure say y. 1577 1578config PRINTK 1579 default y 1580 bool "Enable support for printk" if EXPERT 1581 select IRQ_WORK 1582 help 1583 This option enables normal printk support. Removing it 1584 eliminates most of the message strings from the kernel image 1585 and makes the kernel more or less silent. As this makes it 1586 very difficult to diagnose system problems, saying N here is 1587 strongly discouraged. 1588 1589config BUG 1590 bool "BUG() support" if EXPERT 1591 default y 1592 help 1593 Disabling this option eliminates support for BUG and WARN, reducing 1594 the size of your kernel image and potentially quietly ignoring 1595 numerous fatal conditions. You should only consider disabling this 1596 option for embedded systems with no facilities for reporting errors. 1597 Just say Y. 1598 1599config ELF_CORE 1600 depends on COREDUMP 1601 default y 1602 bool "Enable ELF core dumps" if EXPERT 1603 help 1604 Enable support for generating core dumps. Disabling saves about 4k. 1605 1606 1607config PCSPKR_PLATFORM 1608 bool "Enable PC-Speaker support" if EXPERT 1609 depends on HAVE_PCSPKR_PLATFORM 1610 select I8253_LOCK 1611 default y 1612 help 1613 This option allows to disable the internal PC-Speaker 1614 support, saving some memory. 1615 1616config BASE_FULL 1617 default y 1618 bool "Enable full-sized data structures for core" if EXPERT 1619 help 1620 Disabling this option reduces the size of miscellaneous core 1621 kernel data structures. This saves memory on small machines, 1622 but may reduce performance. 1623 1624config FUTEX 1625 bool "Enable futex support" if EXPERT 1626 depends on !(SPARC32 && SMP) 1627 default y 1628 imply RT_MUTEXES 1629 help 1630 Disabling this option will cause the kernel to be built without 1631 support for "fast userspace mutexes". The resulting kernel may not 1632 run glibc-based applications correctly. 1633 1634config FUTEX_PI 1635 bool 1636 depends on FUTEX && RT_MUTEXES 1637 default y 1638 1639config EPOLL 1640 bool "Enable eventpoll support" if EXPERT 1641 default y 1642 help 1643 Disabling this option will cause the kernel to be built without 1644 support for epoll family of system calls. 1645 1646config SIGNALFD 1647 bool "Enable signalfd() system call" if EXPERT 1648 default y 1649 help 1650 Enable the signalfd() system call that allows to receive signals 1651 on a file descriptor. 1652 1653 If unsure, say Y. 1654 1655config TIMERFD 1656 bool "Enable timerfd() system call" if EXPERT 1657 default y 1658 help 1659 Enable the timerfd() system call that allows to receive timer 1660 events on a file descriptor. 1661 1662 If unsure, say Y. 1663 1664config EVENTFD 1665 bool "Enable eventfd() system call" if EXPERT 1666 default y 1667 help 1668 Enable the eventfd() system call that allows to receive both 1669 kernel notification (ie. KAIO) or userspace notifications. 1670 1671 If unsure, say Y. 1672 1673config SHMEM 1674 bool "Use full shmem filesystem" if EXPERT 1675 default y 1676 depends on MMU 1677 help 1678 The shmem is an internal filesystem used to manage shared memory. 1679 It is backed by swap and manages resource limits. It is also exported 1680 to userspace as tmpfs if TMPFS is enabled. Disabling this 1681 option replaces shmem and tmpfs with the much simpler ramfs code, 1682 which may be appropriate on small systems without swap. 1683 1684config AIO 1685 bool "Enable AIO support" if EXPERT 1686 default y 1687 help 1688 This option enables POSIX asynchronous I/O which may by used 1689 by some high performance threaded applications. Disabling 1690 this option saves about 7k. 1691 1692config IO_URING 1693 bool "Enable IO uring support" if EXPERT 1694 select IO_WQ 1695 default y 1696 help 1697 This option enables support for the io_uring interface, enabling 1698 applications to submit and complete IO through submission and 1699 completion rings that are shared between the kernel and application. 1700 1701config ADVISE_SYSCALLS 1702 bool "Enable madvise/fadvise syscalls" if EXPERT 1703 default y 1704 help 1705 This option enables the madvise and fadvise syscalls, used by 1706 applications to advise the kernel about their future memory or file 1707 usage, improving performance. If building an embedded system where no 1708 applications use these syscalls, you can disable this option to save 1709 space. 1710 1711config MEMBARRIER 1712 bool "Enable membarrier() system call" if EXPERT 1713 default y 1714 help 1715 Enable the membarrier() system call that allows issuing memory 1716 barriers across all running threads, which can be used to distribute 1717 the cost of user-space memory barriers asymmetrically by transforming 1718 pairs of memory barriers into pairs consisting of membarrier() and a 1719 compiler barrier. 1720 1721 If unsure, say Y. 1722 1723config KALLSYMS 1724 bool "Load all symbols for debugging/ksymoops" if EXPERT 1725 default y 1726 help 1727 Say Y here to let the kernel print out symbolic crash information and 1728 symbolic stack backtraces. This increases the size of the kernel 1729 somewhat, as all symbols have to be loaded into the kernel image. 1730 1731config KALLSYMS_ALL 1732 bool "Include all symbols in kallsyms" 1733 depends on DEBUG_KERNEL && KALLSYMS 1734 help 1735 Normally kallsyms only contains the symbols of functions for nicer 1736 OOPS messages and backtraces (i.e., symbols from the text and inittext 1737 sections). This is sufficient for most cases. And only if you want to 1738 enable kernel live patching, or other less common use cases (e.g., 1739 when a debugger is used) all symbols are required (i.e., names of 1740 variables from the data sections, etc). 1741 1742 This option makes sure that all symbols are loaded into the kernel 1743 image (i.e., symbols from all sections) in cost of increased kernel 1744 size (depending on the kernel configuration, it may be 300KiB or 1745 something like this). 1746 1747 Say N unless you really need all symbols, or kernel live patching. 1748 1749config KALLSYMS_ABSOLUTE_PERCPU 1750 bool 1751 depends on KALLSYMS 1752 default X86_64 && SMP 1753 1754config KALLSYMS_BASE_RELATIVE 1755 bool 1756 depends on KALLSYMS 1757 default !IA64 1758 help 1759 Instead of emitting them as absolute values in the native word size, 1760 emit the symbol references in the kallsyms table as 32-bit entries, 1761 each containing a relative value in the range [base, base + U32_MAX] 1762 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1763 an absolute value in the range [0, S32_MAX] or a relative value in the 1764 range [base, base + S32_MAX], where base is the lowest relative symbol 1765 address encountered in the image. 1766 1767 On 64-bit builds, this reduces the size of the address table by 50%, 1768 but more importantly, it results in entries whose values are build 1769 time constants, and no relocation pass is required at runtime to fix 1770 up the entries based on the runtime load address of the kernel. 1771 1772# end of the "standard kernel features (expert users)" menu 1773 1774# syscall, maps, verifier 1775 1776config ARCH_HAS_MEMBARRIER_CALLBACKS 1777 bool 1778 1779config ARCH_HAS_MEMBARRIER_SYNC_CORE 1780 bool 1781 1782config KCMP 1783 bool "Enable kcmp() system call" if EXPERT 1784 help 1785 Enable the kernel resource comparison system call. It provides 1786 user-space with the ability to compare two processes to see if they 1787 share a common resource, such as a file descriptor or even virtual 1788 memory space. 1789 1790 If unsure, say N. 1791 1792config RSEQ 1793 bool "Enable rseq() system call" if EXPERT 1794 default y 1795 depends on HAVE_RSEQ 1796 select MEMBARRIER 1797 help 1798 Enable the restartable sequences system call. It provides a 1799 user-space cache for the current CPU number value, which 1800 speeds up getting the current CPU number from user-space, 1801 as well as an ABI to speed up user-space operations on 1802 per-CPU data. 1803 1804 If unsure, say Y. 1805 1806config DEBUG_RSEQ 1807 default n 1808 bool "Enabled debugging of rseq() system call" if EXPERT 1809 depends on RSEQ && DEBUG_KERNEL 1810 help 1811 Enable extra debugging checks for the rseq system call. 1812 1813 If unsure, say N. 1814 1815config EMBEDDED 1816 bool "Embedded system" 1817 select EXPERT 1818 help 1819 This option should be enabled if compiling the kernel for 1820 an embedded system so certain expert options are available 1821 for configuration. 1822 1823config HAVE_PERF_EVENTS 1824 bool 1825 help 1826 See tools/perf/design.txt for details. 1827 1828config GUEST_PERF_EVENTS 1829 bool 1830 depends on HAVE_PERF_EVENTS 1831 1832config PERF_USE_VMALLOC 1833 bool 1834 help 1835 See tools/perf/design.txt for details 1836 1837config PC104 1838 bool "PC/104 support" if EXPERT 1839 help 1840 Expose PC/104 form factor device drivers and options available for 1841 selection and configuration. Enable this option if your target 1842 machine has a PC/104 bus. 1843 1844menu "Kernel Performance Events And Counters" 1845 1846config PERF_EVENTS 1847 bool "Kernel performance events and counters" 1848 default y if PROFILING 1849 depends on HAVE_PERF_EVENTS 1850 select IRQ_WORK 1851 select SRCU 1852 help 1853 Enable kernel support for various performance events provided 1854 by software and hardware. 1855 1856 Software events are supported either built-in or via the 1857 use of generic tracepoints. 1858 1859 Most modern CPUs support performance events via performance 1860 counter registers. These registers count the number of certain 1861 types of hw events: such as instructions executed, cachemisses 1862 suffered, or branches mis-predicted - without slowing down the 1863 kernel or applications. These registers can also trigger interrupts 1864 when a threshold number of events have passed - and can thus be 1865 used to profile the code that runs on that CPU. 1866 1867 The Linux Performance Event subsystem provides an abstraction of 1868 these software and hardware event capabilities, available via a 1869 system call and used by the "perf" utility in tools/perf/. It 1870 provides per task and per CPU counters, and it provides event 1871 capabilities on top of those. 1872 1873 Say Y if unsure. 1874 1875config DEBUG_PERF_USE_VMALLOC 1876 default n 1877 bool "Debug: use vmalloc to back perf mmap() buffers" 1878 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1879 select PERF_USE_VMALLOC 1880 help 1881 Use vmalloc memory to back perf mmap() buffers. 1882 1883 Mostly useful for debugging the vmalloc code on platforms 1884 that don't require it. 1885 1886 Say N if unsure. 1887 1888endmenu 1889 1890config SYSTEM_DATA_VERIFICATION 1891 def_bool n 1892 select SYSTEM_TRUSTED_KEYRING 1893 select KEYS 1894 select CRYPTO 1895 select CRYPTO_RSA 1896 select ASYMMETRIC_KEY_TYPE 1897 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1898 select ASN1 1899 select OID_REGISTRY 1900 select X509_CERTIFICATE_PARSER 1901 select PKCS7_MESSAGE_PARSER 1902 help 1903 Provide PKCS#7 message verification using the contents of the system 1904 trusted keyring to provide public keys. This then can be used for 1905 module verification, kexec image verification and firmware blob 1906 verification. 1907 1908config PROFILING 1909 bool "Profiling support" 1910 help 1911 Say Y here to enable the extended profiling support mechanisms used 1912 by profilers. 1913 1914config RUST 1915 bool "Rust support" 1916 depends on HAVE_RUST 1917 depends on RUST_IS_AVAILABLE 1918 depends on !MODVERSIONS 1919 depends on !GCC_PLUGINS 1920 depends on !RANDSTRUCT 1921 depends on !DEBUG_INFO_BTF 1922 select CONSTRUCTORS 1923 help 1924 Enables Rust support in the kernel. 1925 1926 This allows other Rust-related options, like drivers written in Rust, 1927 to be selected. 1928 1929 It is also required to be able to load external kernel modules 1930 written in Rust. 1931 1932 See Documentation/rust/ for more information. 1933 1934 If unsure, say N. 1935 1936config RUSTC_VERSION_TEXT 1937 string 1938 depends on RUST 1939 default $(shell,command -v $(RUSTC) >/dev/null 2>&1 && $(RUSTC) --version || echo n) 1940 1941config BINDGEN_VERSION_TEXT 1942 string 1943 depends on RUST 1944 default $(shell,command -v $(BINDGEN) >/dev/null 2>&1 && $(BINDGEN) --version || echo n) 1945 1946# 1947# Place an empty function call at each tracepoint site. Can be 1948# dynamically changed for a probe function. 1949# 1950config TRACEPOINTS 1951 bool 1952 1953endmenu # General setup 1954 1955source "arch/Kconfig" 1956 1957config RT_MUTEXES 1958 bool 1959 default y if PREEMPT_RT 1960 1961config BASE_SMALL 1962 int 1963 default 0 if BASE_FULL 1964 default 1 if !BASE_FULL 1965 1966config MODULE_SIG_FORMAT 1967 def_bool n 1968 select SYSTEM_DATA_VERIFICATION 1969 1970source "kernel/module/Kconfig" 1971 1972config INIT_ALL_POSSIBLE 1973 bool 1974 help 1975 Back when each arch used to define their own cpu_online_mask and 1976 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 1977 with all 1s, and others with all 0s. When they were centralised, 1978 it was better to provide this option than to break all the archs 1979 and have several arch maintainers pursuing me down dark alleys. 1980 1981source "block/Kconfig" 1982 1983config PREEMPT_NOTIFIERS 1984 bool 1985 1986config PADATA 1987 depends on SMP 1988 bool 1989 1990config ASN1 1991 tristate 1992 help 1993 Build a simple ASN.1 grammar compiler that produces a bytecode output 1994 that can be interpreted by the ASN.1 stream decoder and used to 1995 inform it as to what tags are to be expected in a stream and what 1996 functions to call on what tags. 1997 1998source "kernel/Kconfig.locks" 1999 2000config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 2001 bool 2002 2003config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2004 bool 2005 2006# It may be useful for an architecture to override the definitions of the 2007# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2008# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2009# different calling convention for syscalls. They can also override the 2010# macros for not-implemented syscalls in kernel/sys_ni.c and 2011# kernel/time/posix-stubs.c. All these overrides need to be available in 2012# <asm/syscall_wrapper.h>. 2013config ARCH_HAS_SYSCALL_WRAPPER 2014 def_bool n 2015