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 satisfy 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]) - .": "+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. Certain warnings from other tools 163 such as the linker may be upgraded to errors with this option as 164 well. 165 166 However, if you have a new (or very old) compiler or linker with odd 167 and unusual warnings, or you have some architecture with problems, 168 you may need to disable this config option in order to 169 successfully build the kernel. 170 171 If in doubt, say Y. 172 173config UAPI_HEADER_TEST 174 bool "Compile test UAPI headers" 175 depends on HEADERS_INSTALL && CC_CAN_LINK 176 help 177 Compile test headers exported to user-space to ensure they are 178 self-contained, i.e. compilable as standalone units. 179 180 If you are a developer or tester and want to ensure the exported 181 headers are self-contained, say Y here. Otherwise, choose N. 182 183config LOCALVERSION 184 string "Local version - append to kernel release" 185 help 186 Append an extra string to the end of your kernel version. 187 This will show up when you type uname, for example. 188 The string you set here will be appended after the contents of 189 any files with a filename matching localversion* in your 190 object and source tree, in that order. Your total string can 191 be a maximum of 64 characters. 192 193config LOCALVERSION_AUTO 194 bool "Automatically append version information to the version string" 195 default y 196 depends on !COMPILE_TEST 197 help 198 This will try to automatically determine if the current tree is a 199 release tree by looking for git tags that belong to the current 200 top of tree revision. 201 202 A string of the format -gxxxxxxxx will be added to the localversion 203 if a git-based tree is found. The string generated by this will be 204 appended after any matching localversion* files, and after the value 205 set in CONFIG_LOCALVERSION. 206 207 (The actual string used here is the first 12 characters produced 208 by running the command: 209 210 $ git rev-parse --verify HEAD 211 212 which is done within the script "scripts/setlocalversion".) 213 214config BUILD_SALT 215 string "Build ID Salt" 216 default "" 217 help 218 The build ID is used to link binaries and their debug info. Setting 219 this option will use the value in the calculation of the build id. 220 This is mostly useful for distributions which want to ensure the 221 build is unique between builds. It's safe to leave the default. 222 223config HAVE_KERNEL_GZIP 224 bool 225 226config HAVE_KERNEL_BZIP2 227 bool 228 229config HAVE_KERNEL_LZMA 230 bool 231 232config HAVE_KERNEL_XZ 233 bool 234 235config HAVE_KERNEL_LZO 236 bool 237 238config HAVE_KERNEL_LZ4 239 bool 240 241config HAVE_KERNEL_ZSTD 242 bool 243 244config HAVE_KERNEL_UNCOMPRESSED 245 bool 246 247choice 248 prompt "Kernel compression mode" 249 default KERNEL_GZIP 250 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 251 help 252 The linux kernel is a kind of self-extracting executable. 253 Several compression algorithms are available, which differ 254 in efficiency, compression and decompression speed. 255 Compression speed is only relevant when building a kernel. 256 Decompression speed is relevant at each boot. 257 258 If you have any problems with bzip2 or lzma compressed 259 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 260 version of this functionality (bzip2 only), for 2.4, was 261 supplied by Christian Ludwig) 262 263 High compression options are mostly useful for users, who 264 are low on disk space (embedded systems), but for whom ram 265 size matters less. 266 267 If in doubt, select 'gzip' 268 269config KERNEL_GZIP 270 bool "Gzip" 271 depends on HAVE_KERNEL_GZIP 272 help 273 The old and tried gzip compression. It provides a good balance 274 between compression ratio and decompression speed. 275 276config KERNEL_BZIP2 277 bool "Bzip2" 278 depends on HAVE_KERNEL_BZIP2 279 help 280 Its compression ratio and speed is intermediate. 281 Decompression speed is slowest among the choices. The kernel 282 size is about 10% smaller with bzip2, in comparison to gzip. 283 Bzip2 uses a large amount of memory. For modern kernels you 284 will need at least 8MB RAM or more for booting. 285 286config KERNEL_LZMA 287 bool "LZMA" 288 depends on HAVE_KERNEL_LZMA 289 help 290 This compression algorithm's ratio is best. Decompression speed 291 is between gzip and bzip2. Compression is slowest. 292 The kernel size is about 33% smaller with LZMA in comparison to gzip. 293 294config KERNEL_XZ 295 bool "XZ" 296 depends on HAVE_KERNEL_XZ 297 help 298 XZ uses the LZMA2 algorithm and instruction set specific 299 BCJ filters which can improve compression ratio of executable 300 code. The size of the kernel is about 30% smaller with XZ in 301 comparison to gzip. On architectures for which there is a BCJ 302 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 303 will create a few percent smaller kernel than plain LZMA. 304 305 The speed is about the same as with LZMA: The decompression 306 speed of XZ is better than that of bzip2 but worse than gzip 307 and LZO. Compression is slow. 308 309config KERNEL_LZO 310 bool "LZO" 311 depends on HAVE_KERNEL_LZO 312 help 313 Its compression ratio is the poorest among the choices. The kernel 314 size is about 10% bigger than gzip; however its speed 315 (both compression and decompression) is the fastest. 316 317config KERNEL_LZ4 318 bool "LZ4" 319 depends on HAVE_KERNEL_LZ4 320 help 321 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 322 A preliminary version of LZ4 de/compression tool is available at 323 <https://code.google.com/p/lz4/>. 324 325 Its compression ratio is worse than LZO. The size of the kernel 326 is about 8% bigger than LZO. But the decompression speed is 327 faster than LZO. 328 329config KERNEL_ZSTD 330 bool "ZSTD" 331 depends on HAVE_KERNEL_ZSTD 332 help 333 ZSTD is a compression algorithm targeting intermediate compression 334 with fast decompression speed. It will compress better than GZIP and 335 decompress around the same speed as LZO, but slower than LZ4. You 336 will need at least 192 KB RAM or more for booting. The zstd command 337 line tool is required for compression. 338 339config KERNEL_UNCOMPRESSED 340 bool "None" 341 depends on HAVE_KERNEL_UNCOMPRESSED 342 help 343 Produce uncompressed kernel image. This option is usually not what 344 you want. It is useful for debugging the kernel in slow simulation 345 environments, where decompressing and moving the kernel is awfully 346 slow. This option allows early boot code to skip the decompressor 347 and jump right at uncompressed kernel image. 348 349endchoice 350 351config DEFAULT_INIT 352 string "Default init path" 353 default "" 354 help 355 This option determines the default init for the system if no init= 356 option is passed on the kernel command line. If the requested path is 357 not present, we will still then move on to attempting further 358 locations (e.g. /sbin/init, etc). If this is empty, we will just use 359 the fallback list when init= is not passed. 360 361config DEFAULT_HOSTNAME 362 string "Default hostname" 363 default "(none)" 364 help 365 This option determines the default system hostname before userspace 366 calls sethostname(2). The kernel traditionally uses "(none)" here, 367 but you may wish to use a different default here to make a minimal 368 system more usable with less configuration. 369 370config SYSVIPC 371 bool "System V IPC" 372 help 373 Inter Process Communication is a suite of library functions and 374 system calls which let processes (running programs) synchronize and 375 exchange information. It is generally considered to be a good thing, 376 and some programs won't run unless you say Y here. In particular, if 377 you want to run the DOS emulator dosemu under Linux (read the 378 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 379 you'll need to say Y here. 380 381 You can find documentation about IPC with "info ipc" and also in 382 section 6.4 of the Linux Programmer's Guide, available from 383 <http://www.tldp.org/guides.html>. 384 385config SYSVIPC_SYSCTL 386 bool 387 depends on SYSVIPC 388 depends on SYSCTL 389 default y 390 391config SYSVIPC_COMPAT 392 def_bool y 393 depends on COMPAT && SYSVIPC 394 395config POSIX_MQUEUE 396 bool "POSIX Message Queues" 397 depends on NET 398 help 399 POSIX variant of message queues is a part of IPC. In POSIX message 400 queues every message has a priority which decides about succession 401 of receiving it by a process. If you want to compile and run 402 programs written e.g. for Solaris with use of its POSIX message 403 queues (functions mq_*) say Y here. 404 405 POSIX message queues are visible as a filesystem called 'mqueue' 406 and can be mounted somewhere if you want to do filesystem 407 operations on message queues. 408 409 If unsure, say Y. 410 411config POSIX_MQUEUE_SYSCTL 412 bool 413 depends on POSIX_MQUEUE 414 depends on SYSCTL 415 default y 416 417config WATCH_QUEUE 418 bool "General notification queue" 419 default n 420 help 421 422 This is a general notification queue for the kernel to pass events to 423 userspace by splicing them into pipes. It can be used in conjunction 424 with watches for key/keyring change notifications and device 425 notifications. 426 427 See Documentation/core-api/watch_queue.rst 428 429config CROSS_MEMORY_ATTACH 430 bool "Enable process_vm_readv/writev syscalls" 431 depends on MMU 432 default y 433 help 434 Enabling this option adds the system calls process_vm_readv and 435 process_vm_writev which allow a process with the correct privileges 436 to directly read from or write to another process' address space. 437 See the man page for more details. 438 439config USELIB 440 bool "uselib syscall (for libc5 and earlier)" 441 default ALPHA || M68K || SPARC 442 help 443 This option enables the uselib syscall, a system call used in the 444 dynamic linker from libc5 and earlier. glibc does not use this 445 system call. If you intend to run programs built on libc5 or 446 earlier, you may need to enable this syscall. Current systems 447 running glibc can safely disable this. 448 449config AUDIT 450 bool "Auditing support" 451 depends on NET 452 help 453 Enable auditing infrastructure that can be used with another 454 kernel subsystem, such as SELinux (which requires this for 455 logging of avc messages output). System call auditing is included 456 on architectures which support it. 457 458config HAVE_ARCH_AUDITSYSCALL 459 bool 460 461config AUDITSYSCALL 462 def_bool y 463 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 464 select FSNOTIFY 465 466source "kernel/irq/Kconfig" 467source "kernel/time/Kconfig" 468source "kernel/bpf/Kconfig" 469source "kernel/Kconfig.preempt" 470 471menu "CPU/Task time and stats accounting" 472 473config VIRT_CPU_ACCOUNTING 474 bool 475 476choice 477 prompt "Cputime accounting" 478 default TICK_CPU_ACCOUNTING 479 480# Kind of a stub config for the pure tick based cputime accounting 481config TICK_CPU_ACCOUNTING 482 bool "Simple tick based cputime accounting" 483 depends on !S390 && !NO_HZ_FULL 484 help 485 This is the basic tick based cputime accounting that maintains 486 statistics about user, system and idle time spent on per jiffies 487 granularity. 488 489 If unsure, say Y. 490 491config VIRT_CPU_ACCOUNTING_NATIVE 492 bool "Deterministic task and CPU time accounting" 493 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 494 select VIRT_CPU_ACCOUNTING 495 help 496 Select this option to enable more accurate task and CPU time 497 accounting. This is done by reading a CPU counter on each 498 kernel entry and exit and on transitions within the kernel 499 between system, softirq and hardirq state, so there is a 500 small performance impact. In the case of s390 or IBM POWER > 5, 501 this also enables accounting of stolen time on logically-partitioned 502 systems. 503 504config VIRT_CPU_ACCOUNTING_GEN 505 bool "Full dynticks CPU time accounting" 506 depends on HAVE_CONTEXT_TRACKING_USER 507 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 508 depends on GENERIC_CLOCKEVENTS 509 select VIRT_CPU_ACCOUNTING 510 select CONTEXT_TRACKING_USER 511 help 512 Select this option to enable task and CPU time accounting on full 513 dynticks systems. This accounting is implemented by watching every 514 kernel-user boundaries using the context tracking subsystem. 515 The accounting is thus performed at the expense of some significant 516 overhead. 517 518 For now this is only useful if you are working on the full 519 dynticks subsystem development. 520 521 If unsure, say N. 522 523endchoice 524 525config IRQ_TIME_ACCOUNTING 526 bool "Fine granularity task level IRQ time accounting" 527 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 528 help 529 Select this option to enable fine granularity task irq time 530 accounting. This is done by reading a timestamp on each 531 transitions between softirq and hardirq state, so there can be a 532 small performance impact. 533 534 If in doubt, say N here. 535 536config HAVE_SCHED_AVG_IRQ 537 def_bool y 538 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 539 depends on SMP 540 541config SCHED_THERMAL_PRESSURE 542 bool 543 default y if ARM && ARM_CPU_TOPOLOGY 544 default y if ARM64 545 depends on SMP 546 depends on CPU_FREQ_THERMAL 547 help 548 Select this option to enable thermal pressure accounting in the 549 scheduler. Thermal pressure is the value conveyed to the scheduler 550 that reflects the reduction in CPU compute capacity resulted from 551 thermal throttling. Thermal throttling occurs when the performance of 552 a CPU is capped due to high operating temperatures. 553 554 If selected, the scheduler will be able to balance tasks accordingly, 555 i.e. put less load on throttled CPUs than on non/less throttled ones. 556 557 This requires the architecture to implement 558 arch_update_thermal_pressure() and arch_scale_thermal_pressure(). 559 560config BSD_PROCESS_ACCT 561 bool "BSD Process Accounting" 562 depends on MULTIUSER 563 help 564 If you say Y here, a user level program will be able to instruct the 565 kernel (via a special system call) to write process accounting 566 information to a file: whenever a process exits, information about 567 that process will be appended to the file by the kernel. The 568 information includes things such as creation time, owning user, 569 command name, memory usage, controlling terminal etc. (the complete 570 list is in the struct acct in <file:include/linux/acct.h>). It is 571 up to the user level program to do useful things with this 572 information. This is generally a good idea, so say Y. 573 574config BSD_PROCESS_ACCT_V3 575 bool "BSD Process Accounting version 3 file format" 576 depends on BSD_PROCESS_ACCT 577 default n 578 help 579 If you say Y here, the process accounting information is written 580 in a new file format that also logs the process IDs of each 581 process and its parent. Note that this file format is incompatible 582 with previous v0/v1/v2 file formats, so you will need updated tools 583 for processing it. A preliminary version of these tools is available 584 at <http://www.gnu.org/software/acct/>. 585 586config TASKSTATS 587 bool "Export task/process statistics through netlink" 588 depends on NET 589 depends on MULTIUSER 590 default n 591 help 592 Export selected statistics for tasks/processes through the 593 generic netlink interface. Unlike BSD process accounting, the 594 statistics are available during the lifetime of tasks/processes as 595 responses to commands. Like BSD accounting, they are sent to user 596 space on task exit. 597 598 Say N if unsure. 599 600config TASK_DELAY_ACCT 601 bool "Enable per-task delay accounting" 602 depends on TASKSTATS 603 select SCHED_INFO 604 help 605 Collect information on time spent by a task waiting for system 606 resources like cpu, synchronous block I/O completion and swapping 607 in pages. Such statistics can help in setting a task's priorities 608 relative to other tasks for cpu, io, rss limits etc. 609 610 Say N if unsure. 611 612config TASK_XACCT 613 bool "Enable extended accounting over taskstats" 614 depends on TASKSTATS 615 help 616 Collect extended task accounting data and send the data 617 to userland for processing over the taskstats interface. 618 619 Say N if unsure. 620 621config TASK_IO_ACCOUNTING 622 bool "Enable per-task storage I/O accounting" 623 depends on TASK_XACCT 624 help 625 Collect information on the number of bytes of storage I/O which this 626 task has caused. 627 628 Say N if unsure. 629 630config PSI 631 bool "Pressure stall information tracking" 632 help 633 Collect metrics that indicate how overcommitted the CPU, memory, 634 and IO capacity are in the system. 635 636 If you say Y here, the kernel will create /proc/pressure/ with the 637 pressure statistics files cpu, memory, and io. These will indicate 638 the share of walltime in which some or all tasks in the system are 639 delayed due to contention of the respective resource. 640 641 In kernels with cgroup support, cgroups (cgroup2 only) will 642 have cpu.pressure, memory.pressure, and io.pressure files, 643 which aggregate pressure stalls for the grouped tasks only. 644 645 For more details see Documentation/accounting/psi.rst. 646 647 Say N if unsure. 648 649config PSI_DEFAULT_DISABLED 650 bool "Require boot parameter to enable pressure stall information tracking" 651 default n 652 depends on PSI 653 help 654 If set, pressure stall information tracking will be disabled 655 per default but can be enabled through passing psi=1 on the 656 kernel commandline during boot. 657 658 This feature adds some code to the task wakeup and sleep 659 paths of the scheduler. The overhead is too low to affect 660 common scheduling-intense workloads in practice (such as 661 webservers, memcache), but it does show up in artificial 662 scheduler stress tests, such as hackbench. 663 664 If you are paranoid and not sure what the kernel will be 665 used for, say Y. 666 667 Say N if unsure. 668 669endmenu # "CPU/Task time and stats accounting" 670 671config CPU_ISOLATION 672 bool "CPU isolation" 673 depends on SMP || COMPILE_TEST 674 default y 675 help 676 Make sure that CPUs running critical tasks are not disturbed by 677 any source of "noise" such as unbound workqueues, timers, kthreads... 678 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 679 the "isolcpus=" boot parameter. 680 681 Say Y if unsure. 682 683source "kernel/rcu/Kconfig" 684 685config IKCONFIG 686 tristate "Kernel .config support" 687 help 688 This option enables the complete Linux kernel ".config" file 689 contents to be saved in the kernel. It provides documentation 690 of which kernel options are used in a running kernel or in an 691 on-disk kernel. This information can be extracted from the kernel 692 image file with the script scripts/extract-ikconfig and used as 693 input to rebuild the current kernel or to build another kernel. 694 It can also be extracted from a running kernel by reading 695 /proc/config.gz if enabled (below). 696 697config IKCONFIG_PROC 698 bool "Enable access to .config through /proc/config.gz" 699 depends on IKCONFIG && PROC_FS 700 help 701 This option enables access to the kernel configuration file 702 through /proc/config.gz. 703 704config IKHEADERS 705 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 706 depends on SYSFS 707 help 708 This option enables access to the in-kernel headers that are generated during 709 the build process. These can be used to build eBPF tracing programs, 710 or similar programs. If you build the headers as a module, a module called 711 kheaders.ko is built which can be loaded on-demand to get access to headers. 712 713config LOG_BUF_SHIFT 714 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 715 range 12 25 716 default 17 717 depends on PRINTK 718 help 719 Select the minimal kernel log buffer size as a power of 2. 720 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 721 parameter, see below. Any higher size also might be forced 722 by "log_buf_len" boot parameter. 723 724 Examples: 725 17 => 128 KB 726 16 => 64 KB 727 15 => 32 KB 728 14 => 16 KB 729 13 => 8 KB 730 12 => 4 KB 731 732config LOG_CPU_MAX_BUF_SHIFT 733 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 734 depends on SMP 735 range 0 21 736 default 12 if !BASE_SMALL 737 default 0 if BASE_SMALL 738 depends on PRINTK 739 help 740 This option allows to increase the default ring buffer size 741 according to the number of CPUs. The value defines the contribution 742 of each CPU as a power of 2. The used space is typically only few 743 lines however it might be much more when problems are reported, 744 e.g. backtraces. 745 746 The increased size means that a new buffer has to be allocated and 747 the original static one is unused. It makes sense only on systems 748 with more CPUs. Therefore this value is used only when the sum of 749 contributions is greater than the half of the default kernel ring 750 buffer as defined by LOG_BUF_SHIFT. The default values are set 751 so that more than 16 CPUs are needed to trigger the allocation. 752 753 Also this option is ignored when "log_buf_len" kernel parameter is 754 used as it forces an exact (power of two) size of the ring buffer. 755 756 The number of possible CPUs is used for this computation ignoring 757 hotplugging making the computation optimal for the worst case 758 scenario while allowing a simple algorithm to be used from bootup. 759 760 Examples shift values and their meaning: 761 17 => 128 KB for each CPU 762 16 => 64 KB for each CPU 763 15 => 32 KB for each CPU 764 14 => 16 KB for each CPU 765 13 => 8 KB for each CPU 766 12 => 4 KB for each CPU 767 768config PRINTK_SAFE_LOG_BUF_SHIFT 769 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 770 range 10 21 771 default 13 772 depends on PRINTK 773 help 774 Select the size of an alternate printk per-CPU buffer where messages 775 printed from unsafe contexts are temporary stored. One example would 776 be NMI messages, another one - printk recursion. The messages are 777 copied to the main log buffer in a safe context to avoid a deadlock. 778 The value defines the size as a power of 2. 779 780 Those messages are rare and limited. The largest one is when 781 a backtrace is printed. It usually fits into 4KB. Select 782 8KB if you want to be on the safe side. 783 784 Examples: 785 17 => 128 KB for each CPU 786 16 => 64 KB for each CPU 787 15 => 32 KB for each CPU 788 14 => 16 KB for each CPU 789 13 => 8 KB for each CPU 790 12 => 4 KB for each CPU 791 792config PRINTK_INDEX 793 bool "Printk indexing debugfs interface" 794 depends on PRINTK && DEBUG_FS 795 help 796 Add support for indexing of all printk formats known at compile time 797 at <debugfs>/printk/index/<module>. 798 799 This can be used as part of maintaining daemons which monitor 800 /dev/kmsg, as it permits auditing the printk formats present in a 801 kernel, allowing detection of cases where monitored printks are 802 changed or no longer present. 803 804 There is no additional runtime cost to printk with this enabled. 805 806# 807# Architectures with an unreliable sched_clock() should select this: 808# 809config HAVE_UNSTABLE_SCHED_CLOCK 810 bool 811 812config GENERIC_SCHED_CLOCK 813 bool 814 815menu "Scheduler features" 816 817config UCLAMP_TASK 818 bool "Enable utilization clamping for RT/FAIR tasks" 819 depends on CPU_FREQ_GOV_SCHEDUTIL 820 help 821 This feature enables the scheduler to track the clamped utilization 822 of each CPU based on RUNNABLE tasks scheduled on that CPU. 823 824 With this option, the user can specify the min and max CPU 825 utilization allowed for RUNNABLE tasks. The max utilization defines 826 the maximum frequency a task should use while the min utilization 827 defines the minimum frequency it should use. 828 829 Both min and max utilization clamp values are hints to the scheduler, 830 aiming at improving its frequency selection policy, but they do not 831 enforce or grant any specific bandwidth for tasks. 832 833 If in doubt, say N. 834 835config UCLAMP_BUCKETS_COUNT 836 int "Number of supported utilization clamp buckets" 837 range 5 20 838 default 5 839 depends on UCLAMP_TASK 840 help 841 Defines the number of clamp buckets to use. The range of each bucket 842 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 843 number of clamp buckets the finer their granularity and the higher 844 the precision of clamping aggregation and tracking at run-time. 845 846 For example, with the minimum configuration value we will have 5 847 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 848 be refcounted in the [20..39]% bucket and will set the bucket clamp 849 effective value to 25%. 850 If a second 30% boosted task should be co-scheduled on the same CPU, 851 that task will be refcounted in the same bucket of the first task and 852 it will boost the bucket clamp effective value to 30%. 853 The clamp effective value of a bucket is reset to its nominal value 854 (20% in the example above) when there are no more tasks refcounted in 855 that bucket. 856 857 An additional boost/capping margin can be added to some tasks. In the 858 example above the 25% task will be boosted to 30% until it exits the 859 CPU. If that should be considered not acceptable on certain systems, 860 it's always possible to reduce the margin by increasing the number of 861 clamp buckets to trade off used memory for run-time tracking 862 precision. 863 864 If in doubt, use the default value. 865 866endmenu 867 868# 869# For architectures that want to enable the support for NUMA-affine scheduler 870# balancing logic: 871# 872config ARCH_SUPPORTS_NUMA_BALANCING 873 bool 874 875# 876# For architectures that prefer to flush all TLBs after a number of pages 877# are unmapped instead of sending one IPI per page to flush. The architecture 878# must provide guarantees on what happens if a clean TLB cache entry is 879# written after the unmap. Details are in mm/rmap.c near the check for 880# should_defer_flush. The architecture should also consider if the full flush 881# and the refill costs are offset by the savings of sending fewer IPIs. 882config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 883 bool 884 885config CC_HAS_INT128 886 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 887 888config CC_IMPLICIT_FALLTHROUGH 889 string 890 default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5) 891 default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough) 892 893# Currently, disable gcc-11,12 array-bounds globally. 894# We may want to target only particular configurations some day. 895config GCC11_NO_ARRAY_BOUNDS 896 def_bool y 897 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 >= 110000 && GCC_VERSION < 120000 && GCC11_NO_ARRAY_BOUNDS 904 default y if CC_IS_GCC && GCC_VERSION >= 120000 && GCC_VERSION < 130000 && GCC12_NO_ARRAY_BOUNDS 905 906# 907# For architectures that know their GCC __int128 support is sound 908# 909config ARCH_SUPPORTS_INT128 910 bool 911 912# For architectures that (ab)use NUMA to represent different memory regions 913# all cpu-local but of different latencies, such as SuperH. 914# 915config ARCH_WANT_NUMA_VARIABLE_LOCALITY 916 bool 917 918config NUMA_BALANCING 919 bool "Memory placement aware NUMA scheduler" 920 depends on ARCH_SUPPORTS_NUMA_BALANCING 921 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 922 depends on SMP && NUMA && MIGRATION && !PREEMPT_RT 923 help 924 This option adds support for automatic NUMA aware memory/task placement. 925 The mechanism is quite primitive and is based on migrating memory when 926 it has references to the node the task is running on. 927 928 This system will be inactive on UMA systems. 929 930config NUMA_BALANCING_DEFAULT_ENABLED 931 bool "Automatically enable NUMA aware memory/task placement" 932 default y 933 depends on NUMA_BALANCING 934 help 935 If set, automatic NUMA balancing will be enabled if running on a NUMA 936 machine. 937 938menuconfig CGROUPS 939 bool "Control Group support" 940 select KERNFS 941 help 942 This option adds support for grouping sets of processes together, for 943 use with process control subsystems such as Cpusets, CFS, memory 944 controls or device isolation. 945 See 946 - Documentation/scheduler/sched-design-CFS.rst (CFS) 947 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 948 and resource control) 949 950 Say N if unsure. 951 952if CGROUPS 953 954config PAGE_COUNTER 955 bool 956 957config CGROUP_FAVOR_DYNMODS 958 bool "Favor dynamic modification latency reduction by default" 959 help 960 This option enables the "favordynmods" mount option by default 961 which reduces the latencies of dynamic cgroup modifications such 962 as task migrations and controller on/offs at the cost of making 963 hot path operations such as forks and exits more expensive. 964 965 Say N if unsure. 966 967config MEMCG 968 bool "Memory controller" 969 select PAGE_COUNTER 970 select EVENTFD 971 help 972 Provides control over the memory footprint of tasks in a cgroup. 973 974config MEMCG_KMEM 975 bool 976 depends on MEMCG && !SLOB 977 default y 978 979config BLK_CGROUP 980 bool "IO controller" 981 depends on BLOCK 982 default n 983 help 984 Generic block IO controller cgroup interface. This is the common 985 cgroup interface which should be used by various IO controlling 986 policies. 987 988 Currently, CFQ IO scheduler uses it to recognize task groups and 989 control disk bandwidth allocation (proportional time slice allocation) 990 to such task groups. It is also used by bio throttling logic in 991 block layer to implement upper limit in IO rates on a device. 992 993 This option only enables generic Block IO controller infrastructure. 994 One needs to also enable actual IO controlling logic/policy. For 995 enabling proportional weight division of disk bandwidth in CFQ, set 996 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 997 CONFIG_BLK_DEV_THROTTLING=y. 998 999 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 1000 1001config CGROUP_WRITEBACK 1002 bool 1003 depends on MEMCG && BLK_CGROUP 1004 default y 1005 1006menuconfig CGROUP_SCHED 1007 bool "CPU controller" 1008 default n 1009 help 1010 This feature lets CPU scheduler recognize task groups and control CPU 1011 bandwidth allocation to such task groups. It uses cgroups to group 1012 tasks. 1013 1014if CGROUP_SCHED 1015config FAIR_GROUP_SCHED 1016 bool "Group scheduling for SCHED_OTHER" 1017 depends on CGROUP_SCHED 1018 default CGROUP_SCHED 1019 1020config CFS_BANDWIDTH 1021 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 1022 depends on FAIR_GROUP_SCHED 1023 default n 1024 help 1025 This option allows users to define CPU bandwidth rates (limits) for 1026 tasks running within the fair group scheduler. Groups with no limit 1027 set are considered to be unconstrained and will run with no 1028 restriction. 1029 See Documentation/scheduler/sched-bwc.rst for more information. 1030 1031config RT_GROUP_SCHED 1032 bool "Group scheduling for SCHED_RR/FIFO" 1033 depends on CGROUP_SCHED 1034 default n 1035 help 1036 This feature lets you explicitly allocate real CPU bandwidth 1037 to task groups. If enabled, it will also make it impossible to 1038 schedule realtime tasks for non-root users until you allocate 1039 realtime bandwidth for them. 1040 See Documentation/scheduler/sched-rt-group.rst for more information. 1041 1042endif #CGROUP_SCHED 1043 1044config SCHED_MM_CID 1045 def_bool y 1046 depends on SMP && RSEQ 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 depends on PROC_FS 1277 select PROC_CHILDREN 1278 select KCMP 1279 default n 1280 help 1281 Enables additional kernel features in a sake of checkpoint/restore. 1282 In particular it adds auxiliary prctl codes to setup process text, 1283 data and heap segment sizes, and a few additional /proc filesystem 1284 entries. 1285 1286 If unsure, say N here. 1287 1288config SCHED_AUTOGROUP 1289 bool "Automatic process group scheduling" 1290 select CGROUPS 1291 select CGROUP_SCHED 1292 select FAIR_GROUP_SCHED 1293 help 1294 This option optimizes the scheduler for common desktop workloads by 1295 automatically creating and populating task groups. This separation 1296 of workloads isolates aggressive CPU burners (like build jobs) from 1297 desktop applications. Task group autogeneration is currently based 1298 upon task session. 1299 1300config RELAY 1301 bool "Kernel->user space relay support (formerly relayfs)" 1302 select IRQ_WORK 1303 help 1304 This option enables support for relay interface support in 1305 certain file systems (such as debugfs). 1306 It is designed to provide an efficient mechanism for tools and 1307 facilities to relay large amounts of data from kernel space to 1308 user space. 1309 1310 If unsure, say N. 1311 1312config BLK_DEV_INITRD 1313 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1314 help 1315 The initial RAM filesystem is a ramfs which is loaded by the 1316 boot loader (loadlin or lilo) and that is mounted as root 1317 before the normal boot procedure. It is typically used to 1318 load modules needed to mount the "real" root file system, 1319 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1320 1321 If RAM disk support (BLK_DEV_RAM) is also included, this 1322 also enables initial RAM disk (initrd) support and adds 1323 15 Kbytes (more on some other architectures) to the kernel size. 1324 1325 If unsure say Y. 1326 1327if BLK_DEV_INITRD 1328 1329source "usr/Kconfig" 1330 1331endif 1332 1333config BOOT_CONFIG 1334 bool "Boot config support" 1335 select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED 1336 help 1337 Extra boot config allows system admin to pass a config file as 1338 complemental extension of kernel cmdline when booting. 1339 The boot config file must be attached at the end of initramfs 1340 with checksum, size and magic word. 1341 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1342 1343 If unsure, say Y. 1344 1345config BOOT_CONFIG_FORCE 1346 bool "Force unconditional bootconfig processing" 1347 depends on BOOT_CONFIG 1348 default y if BOOT_CONFIG_EMBED 1349 help 1350 With this Kconfig option set, BOOT_CONFIG processing is carried 1351 out even when the "bootconfig" kernel-boot parameter is omitted. 1352 In fact, with this Kconfig option set, there is no way to 1353 make the kernel ignore the BOOT_CONFIG-supplied kernel-boot 1354 parameters. 1355 1356 If unsure, say N. 1357 1358config BOOT_CONFIG_EMBED 1359 bool "Embed bootconfig file in the kernel" 1360 depends on BOOT_CONFIG 1361 help 1362 Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the 1363 kernel. Usually, the bootconfig file is loaded with the initrd 1364 image. But if the system doesn't support initrd, this option will 1365 help you by embedding a bootconfig file while building the kernel. 1366 1367 If unsure, say N. 1368 1369config BOOT_CONFIG_EMBED_FILE 1370 string "Embedded bootconfig file path" 1371 depends on BOOT_CONFIG_EMBED 1372 help 1373 Specify a bootconfig file which will be embedded to the kernel. 1374 This bootconfig will be used if there is no initrd or no other 1375 bootconfig in the initrd. 1376 1377config INITRAMFS_PRESERVE_MTIME 1378 bool "Preserve cpio archive mtimes in initramfs" 1379 default y 1380 help 1381 Each entry in an initramfs cpio archive carries an mtime value. When 1382 enabled, extracted cpio items take this mtime, with directory mtime 1383 setting deferred until after creation of any child entries. 1384 1385 If unsure, say Y. 1386 1387choice 1388 prompt "Compiler optimization level" 1389 default CC_OPTIMIZE_FOR_PERFORMANCE 1390 1391config CC_OPTIMIZE_FOR_PERFORMANCE 1392 bool "Optimize for performance (-O2)" 1393 help 1394 This is the default optimization level for the kernel, building 1395 with the "-O2" compiler flag for best performance and most 1396 helpful compile-time warnings. 1397 1398config CC_OPTIMIZE_FOR_SIZE 1399 bool "Optimize for size (-Os)" 1400 help 1401 Choosing this option will pass "-Os" to your compiler resulting 1402 in a smaller kernel. 1403 1404endchoice 1405 1406config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1407 bool 1408 help 1409 This requires that the arch annotates or otherwise protects 1410 its external entry points from being discarded. Linker scripts 1411 must also merge .text.*, .data.*, and .bss.* correctly into 1412 output sections. Care must be taken not to pull in unrelated 1413 sections (e.g., '.text.init'). Typically '.' in section names 1414 is used to distinguish them from label names / C identifiers. 1415 1416config LD_DEAD_CODE_DATA_ELIMINATION 1417 bool "Dead code and data elimination (EXPERIMENTAL)" 1418 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1419 depends on EXPERT 1420 depends on $(cc-option,-ffunction-sections -fdata-sections) 1421 depends on $(ld-option,--gc-sections) 1422 help 1423 Enable this if you want to do dead code and data elimination with 1424 the linker by compiling with -ffunction-sections -fdata-sections, 1425 and linking with --gc-sections. 1426 1427 This can reduce on disk and in-memory size of the kernel 1428 code and static data, particularly for small configs and 1429 on small systems. This has the possibility of introducing 1430 silently broken kernel if the required annotations are not 1431 present. This option is not well tested yet, so use at your 1432 own risk. 1433 1434config LD_ORPHAN_WARN 1435 def_bool y 1436 depends on ARCH_WANT_LD_ORPHAN_WARN 1437 depends on $(ld-option,--orphan-handling=warn) 1438 depends on $(ld-option,--orphan-handling=error) 1439 1440config LD_ORPHAN_WARN_LEVEL 1441 string 1442 depends on LD_ORPHAN_WARN 1443 default "error" if WERROR 1444 default "warn" 1445 1446config SYSCTL 1447 bool 1448 1449config HAVE_UID16 1450 bool 1451 1452config SYSCTL_EXCEPTION_TRACE 1453 bool 1454 help 1455 Enable support for /proc/sys/debug/exception-trace. 1456 1457config SYSCTL_ARCH_UNALIGN_NO_WARN 1458 bool 1459 help 1460 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1461 Allows arch to define/use @no_unaligned_warning to possibly warn 1462 about unaligned access emulation going on under the hood. 1463 1464config SYSCTL_ARCH_UNALIGN_ALLOW 1465 bool 1466 help 1467 Enable support for /proc/sys/kernel/unaligned-trap 1468 Allows arches to define/use @unaligned_enabled to runtime toggle 1469 the unaligned access emulation. 1470 see arch/parisc/kernel/unaligned.c for reference 1471 1472config HAVE_PCSPKR_PLATFORM 1473 bool 1474 1475# interpreter that classic socket filters depend on 1476config BPF 1477 bool 1478 select CRYPTO_LIB_SHA1 1479 1480menuconfig EXPERT 1481 bool "Configure standard kernel features (expert users)" 1482 # Unhide debug options, to make the on-by-default options visible 1483 select DEBUG_KERNEL 1484 help 1485 This option allows certain base kernel options and settings 1486 to be disabled or tweaked. This is for specialized 1487 environments which can tolerate a "non-standard" kernel. 1488 Only use this if you really know what you are doing. 1489 1490config UID16 1491 bool "Enable 16-bit UID system calls" if EXPERT 1492 depends on HAVE_UID16 && MULTIUSER 1493 default y 1494 help 1495 This enables the legacy 16-bit UID syscall wrappers. 1496 1497config MULTIUSER 1498 bool "Multiple users, groups and capabilities support" if EXPERT 1499 default y 1500 help 1501 This option enables support for non-root users, groups and 1502 capabilities. 1503 1504 If you say N here, all processes will run with UID 0, GID 0, and all 1505 possible capabilities. Saying N here also compiles out support for 1506 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1507 setgid, and capset. 1508 1509 If unsure, say Y here. 1510 1511config SGETMASK_SYSCALL 1512 bool "sgetmask/ssetmask syscalls support" if EXPERT 1513 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1514 help 1515 sys_sgetmask and sys_ssetmask are obsolete system calls 1516 no longer supported in libc but still enabled by default in some 1517 architectures. 1518 1519 If unsure, leave the default option here. 1520 1521config SYSFS_SYSCALL 1522 bool "Sysfs syscall support" if EXPERT 1523 default y 1524 help 1525 sys_sysfs is an obsolete system call no longer supported in libc. 1526 Note that disabling this option is more secure but might break 1527 compatibility with some systems. 1528 1529 If unsure say Y here. 1530 1531config FHANDLE 1532 bool "open by fhandle syscalls" if EXPERT 1533 select EXPORTFS 1534 default y 1535 help 1536 If you say Y here, a user level program will be able to map 1537 file names to handle and then later use the handle for 1538 different file system operations. This is useful in implementing 1539 userspace file servers, which now track files using handles instead 1540 of names. The handle would remain the same even if file names 1541 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1542 syscalls. 1543 1544config POSIX_TIMERS 1545 bool "Posix Clocks & timers" if EXPERT 1546 default y 1547 help 1548 This includes native support for POSIX timers to the kernel. 1549 Some embedded systems have no use for them and therefore they 1550 can be configured out to reduce the size of the kernel image. 1551 1552 When this option is disabled, the following syscalls won't be 1553 available: timer_create, timer_gettime: timer_getoverrun, 1554 timer_settime, timer_delete, clock_adjtime, getitimer, 1555 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1556 clock_getres and clock_nanosleep syscalls will be limited to 1557 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1558 1559 If unsure say y. 1560 1561config PRINTK 1562 default y 1563 bool "Enable support for printk" if EXPERT 1564 select IRQ_WORK 1565 help 1566 This option enables normal printk support. Removing it 1567 eliminates most of the message strings from the kernel image 1568 and makes the kernel more or less silent. As this makes it 1569 very difficult to diagnose system problems, saying N here is 1570 strongly discouraged. 1571 1572config BUG 1573 bool "BUG() support" if EXPERT 1574 default y 1575 help 1576 Disabling this option eliminates support for BUG and WARN, reducing 1577 the size of your kernel image and potentially quietly ignoring 1578 numerous fatal conditions. You should only consider disabling this 1579 option for embedded systems with no facilities for reporting errors. 1580 Just say Y. 1581 1582config ELF_CORE 1583 depends on COREDUMP 1584 default y 1585 bool "Enable ELF core dumps" if EXPERT 1586 help 1587 Enable support for generating core dumps. Disabling saves about 4k. 1588 1589 1590config PCSPKR_PLATFORM 1591 bool "Enable PC-Speaker support" if EXPERT 1592 depends on HAVE_PCSPKR_PLATFORM 1593 select I8253_LOCK 1594 default y 1595 help 1596 This option allows to disable the internal PC-Speaker 1597 support, saving some memory. 1598 1599config BASE_FULL 1600 default y 1601 bool "Enable full-sized data structures for core" if EXPERT 1602 help 1603 Disabling this option reduces the size of miscellaneous core 1604 kernel data structures. This saves memory on small machines, 1605 but may reduce performance. 1606 1607config FUTEX 1608 bool "Enable futex support" if EXPERT 1609 depends on !(SPARC32 && SMP) 1610 default y 1611 imply RT_MUTEXES 1612 help 1613 Disabling this option will cause the kernel to be built without 1614 support for "fast userspace mutexes". The resulting kernel may not 1615 run glibc-based applications correctly. 1616 1617config FUTEX_PI 1618 bool 1619 depends on FUTEX && RT_MUTEXES 1620 default y 1621 1622config EPOLL 1623 bool "Enable eventpoll support" if EXPERT 1624 default y 1625 help 1626 Disabling this option will cause the kernel to be built without 1627 support for epoll family of system calls. 1628 1629config SIGNALFD 1630 bool "Enable signalfd() system call" if EXPERT 1631 default y 1632 help 1633 Enable the signalfd() system call that allows to receive signals 1634 on a file descriptor. 1635 1636 If unsure, say Y. 1637 1638config TIMERFD 1639 bool "Enable timerfd() system call" if EXPERT 1640 default y 1641 help 1642 Enable the timerfd() system call that allows to receive timer 1643 events on a file descriptor. 1644 1645 If unsure, say Y. 1646 1647config EVENTFD 1648 bool "Enable eventfd() system call" if EXPERT 1649 default y 1650 help 1651 Enable the eventfd() system call that allows to receive both 1652 kernel notification (ie. KAIO) or userspace notifications. 1653 1654 If unsure, say Y. 1655 1656config SHMEM 1657 bool "Use full shmem filesystem" if EXPERT 1658 default y 1659 depends on MMU 1660 help 1661 The shmem is an internal filesystem used to manage shared memory. 1662 It is backed by swap and manages resource limits. It is also exported 1663 to userspace as tmpfs if TMPFS is enabled. Disabling this 1664 option replaces shmem and tmpfs with the much simpler ramfs code, 1665 which may be appropriate on small systems without swap. 1666 1667config AIO 1668 bool "Enable AIO support" if EXPERT 1669 default y 1670 help 1671 This option enables POSIX asynchronous I/O which may by used 1672 by some high performance threaded applications. Disabling 1673 this option saves about 7k. 1674 1675config IO_URING 1676 bool "Enable IO uring support" if EXPERT 1677 select IO_WQ 1678 default y 1679 help 1680 This option enables support for the io_uring interface, enabling 1681 applications to submit and complete IO through submission and 1682 completion rings that are shared between the kernel and application. 1683 1684config ADVISE_SYSCALLS 1685 bool "Enable madvise/fadvise syscalls" if EXPERT 1686 default y 1687 help 1688 This option enables the madvise and fadvise syscalls, used by 1689 applications to advise the kernel about their future memory or file 1690 usage, improving performance. If building an embedded system where no 1691 applications use these syscalls, you can disable this option to save 1692 space. 1693 1694config MEMBARRIER 1695 bool "Enable membarrier() system call" if EXPERT 1696 default y 1697 help 1698 Enable the membarrier() system call that allows issuing memory 1699 barriers across all running threads, which can be used to distribute 1700 the cost of user-space memory barriers asymmetrically by transforming 1701 pairs of memory barriers into pairs consisting of membarrier() and a 1702 compiler barrier. 1703 1704 If unsure, say Y. 1705 1706config KALLSYMS 1707 bool "Load all symbols for debugging/ksymoops" if EXPERT 1708 default y 1709 help 1710 Say Y here to let the kernel print out symbolic crash information and 1711 symbolic stack backtraces. This increases the size of the kernel 1712 somewhat, as all symbols have to be loaded into the kernel image. 1713 1714config KALLSYMS_SELFTEST 1715 bool "Test the basic functions and performance of kallsyms" 1716 depends on KALLSYMS 1717 default n 1718 help 1719 Test the basic functions and performance of some interfaces, such as 1720 kallsyms_lookup_name. It also calculates the compression rate of the 1721 kallsyms compression algorithm for the current symbol set. 1722 1723 Start self-test automatically after system startup. Suggest executing 1724 "dmesg | grep kallsyms_selftest" to collect test results. "finish" is 1725 displayed in the last line, indicating that the test is complete. 1726 1727config KALLSYMS_ALL 1728 bool "Include all symbols in kallsyms" 1729 depends on DEBUG_KERNEL && KALLSYMS 1730 help 1731 Normally kallsyms only contains the symbols of functions for nicer 1732 OOPS messages and backtraces (i.e., symbols from the text and inittext 1733 sections). This is sufficient for most cases. And only if you want to 1734 enable kernel live patching, or other less common use cases (e.g., 1735 when a debugger is used) all symbols are required (i.e., names of 1736 variables from the data sections, etc). 1737 1738 This option makes sure that all symbols are loaded into the kernel 1739 image (i.e., symbols from all sections) in cost of increased kernel 1740 size (depending on the kernel configuration, it may be 300KiB or 1741 something like this). 1742 1743 Say N unless you really need all symbols, or kernel live patching. 1744 1745config KALLSYMS_ABSOLUTE_PERCPU 1746 bool 1747 depends on KALLSYMS 1748 default X86_64 && SMP 1749 1750config KALLSYMS_BASE_RELATIVE 1751 bool 1752 depends on KALLSYMS 1753 default !IA64 1754 help 1755 Instead of emitting them as absolute values in the native word size, 1756 emit the symbol references in the kallsyms table as 32-bit entries, 1757 each containing a relative value in the range [base, base + U32_MAX] 1758 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1759 an absolute value in the range [0, S32_MAX] or a relative value in the 1760 range [base, base + S32_MAX], where base is the lowest relative symbol 1761 address encountered in the image. 1762 1763 On 64-bit builds, this reduces the size of the address table by 50%, 1764 but more importantly, it results in entries whose values are build 1765 time constants, and no relocation pass is required at runtime to fix 1766 up the entries based on the runtime load address of the kernel. 1767 1768# end of the "standard kernel features (expert users)" menu 1769 1770# syscall, maps, verifier 1771 1772config ARCH_HAS_MEMBARRIER_CALLBACKS 1773 bool 1774 1775config ARCH_HAS_MEMBARRIER_SYNC_CORE 1776 bool 1777 1778config KCMP 1779 bool "Enable kcmp() system call" if EXPERT 1780 help 1781 Enable the kernel resource comparison system call. It provides 1782 user-space with the ability to compare two processes to see if they 1783 share a common resource, such as a file descriptor or even virtual 1784 memory space. 1785 1786 If unsure, say N. 1787 1788config RSEQ 1789 bool "Enable rseq() system call" if EXPERT 1790 default y 1791 depends on HAVE_RSEQ 1792 select MEMBARRIER 1793 help 1794 Enable the restartable sequences system call. It provides a 1795 user-space cache for the current CPU number value, which 1796 speeds up getting the current CPU number from user-space, 1797 as well as an ABI to speed up user-space operations on 1798 per-CPU data. 1799 1800 If unsure, say Y. 1801 1802config DEBUG_RSEQ 1803 default n 1804 bool "Enabled debugging of rseq() system call" if EXPERT 1805 depends on RSEQ && DEBUG_KERNEL 1806 help 1807 Enable extra debugging checks for the rseq system call. 1808 1809 If unsure, say N. 1810 1811config EMBEDDED 1812 bool "Embedded system" 1813 select EXPERT 1814 help 1815 This option should be enabled if compiling the kernel for 1816 an embedded system so certain expert options are available 1817 for configuration. 1818 1819config HAVE_PERF_EVENTS 1820 bool 1821 help 1822 See tools/perf/design.txt for details. 1823 1824config GUEST_PERF_EVENTS 1825 bool 1826 depends on HAVE_PERF_EVENTS 1827 1828config PERF_USE_VMALLOC 1829 bool 1830 help 1831 See tools/perf/design.txt for details 1832 1833config PC104 1834 bool "PC/104 support" if EXPERT 1835 help 1836 Expose PC/104 form factor device drivers and options available for 1837 selection and configuration. Enable this option if your target 1838 machine has a PC/104 bus. 1839 1840menu "Kernel Performance Events And Counters" 1841 1842config PERF_EVENTS 1843 bool "Kernel performance events and counters" 1844 default y if PROFILING 1845 depends on HAVE_PERF_EVENTS 1846 select IRQ_WORK 1847 help 1848 Enable kernel support for various performance events provided 1849 by software and hardware. 1850 1851 Software events are supported either built-in or via the 1852 use of generic tracepoints. 1853 1854 Most modern CPUs support performance events via performance 1855 counter registers. These registers count the number of certain 1856 types of hw events: such as instructions executed, cachemisses 1857 suffered, or branches mis-predicted - without slowing down the 1858 kernel or applications. These registers can also trigger interrupts 1859 when a threshold number of events have passed - and can thus be 1860 used to profile the code that runs on that CPU. 1861 1862 The Linux Performance Event subsystem provides an abstraction of 1863 these software and hardware event capabilities, available via a 1864 system call and used by the "perf" utility in tools/perf/. It 1865 provides per task and per CPU counters, and it provides event 1866 capabilities on top of those. 1867 1868 Say Y if unsure. 1869 1870config DEBUG_PERF_USE_VMALLOC 1871 default n 1872 bool "Debug: use vmalloc to back perf mmap() buffers" 1873 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1874 select PERF_USE_VMALLOC 1875 help 1876 Use vmalloc memory to back perf mmap() buffers. 1877 1878 Mostly useful for debugging the vmalloc code on platforms 1879 that don't require it. 1880 1881 Say N if unsure. 1882 1883endmenu 1884 1885config SYSTEM_DATA_VERIFICATION 1886 def_bool n 1887 select SYSTEM_TRUSTED_KEYRING 1888 select KEYS 1889 select CRYPTO 1890 select CRYPTO_RSA 1891 select ASYMMETRIC_KEY_TYPE 1892 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1893 select ASN1 1894 select OID_REGISTRY 1895 select X509_CERTIFICATE_PARSER 1896 select PKCS7_MESSAGE_PARSER 1897 help 1898 Provide PKCS#7 message verification using the contents of the system 1899 trusted keyring to provide public keys. This then can be used for 1900 module verification, kexec image verification and firmware blob 1901 verification. 1902 1903config PROFILING 1904 bool "Profiling support" 1905 help 1906 Say Y here to enable the extended profiling support mechanisms used 1907 by profilers. 1908 1909config RUST 1910 bool "Rust support" 1911 depends on HAVE_RUST 1912 depends on RUST_IS_AVAILABLE 1913 depends on !MODVERSIONS 1914 depends on !GCC_PLUGINS 1915 depends on !RANDSTRUCT 1916 depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE 1917 select CONSTRUCTORS 1918 help 1919 Enables Rust support in the kernel. 1920 1921 This allows other Rust-related options, like drivers written in Rust, 1922 to be selected. 1923 1924 It is also required to be able to load external kernel modules 1925 written in Rust. 1926 1927 See Documentation/rust/ for more information. 1928 1929 If unsure, say N. 1930 1931config RUSTC_VERSION_TEXT 1932 string 1933 depends on RUST 1934 default $(shell,command -v $(RUSTC) >/dev/null 2>&1 && $(RUSTC) --version || echo n) 1935 1936config BINDGEN_VERSION_TEXT 1937 string 1938 depends on RUST 1939 default $(shell,command -v $(BINDGEN) >/dev/null 2>&1 && $(BINDGEN) --version || echo n) 1940 1941# 1942# Place an empty function call at each tracepoint site. Can be 1943# dynamically changed for a probe function. 1944# 1945config TRACEPOINTS 1946 bool 1947 1948endmenu # General setup 1949 1950source "arch/Kconfig" 1951 1952config RT_MUTEXES 1953 bool 1954 default y if PREEMPT_RT 1955 1956config BASE_SMALL 1957 int 1958 default 0 if BASE_FULL 1959 default 1 if !BASE_FULL 1960 1961config MODULE_SIG_FORMAT 1962 def_bool n 1963 select SYSTEM_DATA_VERIFICATION 1964 1965source "kernel/module/Kconfig" 1966 1967config INIT_ALL_POSSIBLE 1968 bool 1969 help 1970 Back when each arch used to define their own cpu_online_mask and 1971 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 1972 with all 1s, and others with all 0s. When they were centralised, 1973 it was better to provide this option than to break all the archs 1974 and have several arch maintainers pursuing me down dark alleys. 1975 1976source "block/Kconfig" 1977 1978config PREEMPT_NOTIFIERS 1979 bool 1980 1981config PADATA 1982 depends on SMP 1983 bool 1984 1985config ASN1 1986 tristate 1987 help 1988 Build a simple ASN.1 grammar compiler that produces a bytecode output 1989 that can be interpreted by the ASN.1 stream decoder and used to 1990 inform it as to what tags are to be expected in a stream and what 1991 functions to call on what tags. 1992 1993source "kernel/Kconfig.locks" 1994 1995config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 1996 bool 1997 1998config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 1999 bool 2000 2001# It may be useful for an architecture to override the definitions of the 2002# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2003# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2004# different calling convention for syscalls. They can also override the 2005# macros for not-implemented syscalls in kernel/sys_ni.c and 2006# kernel/time/posix-stubs.c. All these overrides need to be available in 2007# <asm/syscall_wrapper.h>. 2008config ARCH_HAS_SYSCALL_WRAPPER 2009 def_bool n 2010