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 eight 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 BUILD_BIN2C 686 bool 687 default n 688 689config IKCONFIG 690 tristate "Kernel .config support" 691 help 692 This option enables the complete Linux kernel ".config" file 693 contents to be saved in the kernel. It provides documentation 694 of which kernel options are used in a running kernel or in an 695 on-disk kernel. This information can be extracted from the kernel 696 image file with the script scripts/extract-ikconfig and used as 697 input to rebuild the current kernel or to build another kernel. 698 It can also be extracted from a running kernel by reading 699 /proc/config.gz if enabled (below). 700 701config IKCONFIG_PROC 702 bool "Enable access to .config through /proc/config.gz" 703 depends on IKCONFIG && PROC_FS 704 help 705 This option enables access to the kernel configuration file 706 through /proc/config.gz. 707 708config IKHEADERS 709 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 710 depends on SYSFS 711 help 712 This option enables access to the in-kernel headers that are generated during 713 the build process. These can be used to build eBPF tracing programs, 714 or similar programs. If you build the headers as a module, a module called 715 kheaders.ko is built which can be loaded on-demand to get access to headers. 716 717config LOG_BUF_SHIFT 718 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 719 range 12 25 720 default 17 721 depends on PRINTK 722 help 723 Select the minimal kernel log buffer size as a power of 2. 724 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 725 parameter, see below. Any higher size also might be forced 726 by "log_buf_len" boot parameter. 727 728 Examples: 729 17 => 128 KB 730 16 => 64 KB 731 15 => 32 KB 732 14 => 16 KB 733 13 => 8 KB 734 12 => 4 KB 735 736config LOG_CPU_MAX_BUF_SHIFT 737 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 738 depends on SMP 739 range 0 21 740 default 12 if !BASE_SMALL 741 default 0 if BASE_SMALL 742 depends on PRINTK 743 help 744 This option allows to increase the default ring buffer size 745 according to the number of CPUs. The value defines the contribution 746 of each CPU as a power of 2. The used space is typically only few 747 lines however it might be much more when problems are reported, 748 e.g. backtraces. 749 750 The increased size means that a new buffer has to be allocated and 751 the original static one is unused. It makes sense only on systems 752 with more CPUs. Therefore this value is used only when the sum of 753 contributions is greater than the half of the default kernel ring 754 buffer as defined by LOG_BUF_SHIFT. The default values are set 755 so that more than 16 CPUs are needed to trigger the allocation. 756 757 Also this option is ignored when "log_buf_len" kernel parameter is 758 used as it forces an exact (power of two) size of the ring buffer. 759 760 The number of possible CPUs is used for this computation ignoring 761 hotplugging making the computation optimal for the worst case 762 scenario while allowing a simple algorithm to be used from bootup. 763 764 Examples shift values and their meaning: 765 17 => 128 KB for each CPU 766 16 => 64 KB for each CPU 767 15 => 32 KB for each CPU 768 14 => 16 KB for each CPU 769 13 => 8 KB for each CPU 770 12 => 4 KB for each CPU 771 772config PRINTK_SAFE_LOG_BUF_SHIFT 773 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 774 range 10 21 775 default 13 776 depends on PRINTK 777 help 778 Select the size of an alternate printk per-CPU buffer where messages 779 printed from usafe contexts are temporary stored. One example would 780 be NMI messages, another one - printk recursion. The messages are 781 copied to the main log buffer in a safe context to avoid a deadlock. 782 The value defines the size as a power of 2. 783 784 Those messages are rare and limited. The largest one is when 785 a backtrace is printed. It usually fits into 4KB. Select 786 8KB if you want to be on the safe side. 787 788 Examples: 789 17 => 128 KB for each CPU 790 16 => 64 KB for each CPU 791 15 => 32 KB for each CPU 792 14 => 16 KB for each CPU 793 13 => 8 KB for each CPU 794 12 => 4 KB for each CPU 795 796config PRINTK_INDEX 797 bool "Printk indexing debugfs interface" 798 depends on PRINTK && DEBUG_FS 799 help 800 Add support for indexing of all printk formats known at compile time 801 at <debugfs>/printk/index/<module>. 802 803 This can be used as part of maintaining daemons which monitor 804 /dev/kmsg, as it permits auditing the printk formats present in a 805 kernel, allowing detection of cases where monitored printks are 806 changed or no longer present. 807 808 There is no additional runtime cost to printk with this enabled. 809 810# 811# Architectures with an unreliable sched_clock() should select this: 812# 813config HAVE_UNSTABLE_SCHED_CLOCK 814 bool 815 816config GENERIC_SCHED_CLOCK 817 bool 818 819menu "Scheduler features" 820 821config UCLAMP_TASK 822 bool "Enable utilization clamping for RT/FAIR tasks" 823 depends on CPU_FREQ_GOV_SCHEDUTIL 824 help 825 This feature enables the scheduler to track the clamped utilization 826 of each CPU based on RUNNABLE tasks scheduled on that CPU. 827 828 With this option, the user can specify the min and max CPU 829 utilization allowed for RUNNABLE tasks. The max utilization defines 830 the maximum frequency a task should use while the min utilization 831 defines the minimum frequency it should use. 832 833 Both min and max utilization clamp values are hints to the scheduler, 834 aiming at improving its frequency selection policy, but they do not 835 enforce or grant any specific bandwidth for tasks. 836 837 If in doubt, say N. 838 839config UCLAMP_BUCKETS_COUNT 840 int "Number of supported utilization clamp buckets" 841 range 5 20 842 default 5 843 depends on UCLAMP_TASK 844 help 845 Defines the number of clamp buckets to use. The range of each bucket 846 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 847 number of clamp buckets the finer their granularity and the higher 848 the precision of clamping aggregation and tracking at run-time. 849 850 For example, with the minimum configuration value we will have 5 851 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 852 be refcounted in the [20..39]% bucket and will set the bucket clamp 853 effective value to 25%. 854 If a second 30% boosted task should be co-scheduled on the same CPU, 855 that task will be refcounted in the same bucket of the first task and 856 it will boost the bucket clamp effective value to 30%. 857 The clamp effective value of a bucket is reset to its nominal value 858 (20% in the example above) when there are no more tasks refcounted in 859 that bucket. 860 861 An additional boost/capping margin can be added to some tasks. In the 862 example above the 25% task will be boosted to 30% until it exits the 863 CPU. If that should be considered not acceptable on certain systems, 864 it's always possible to reduce the margin by increasing the number of 865 clamp buckets to trade off used memory for run-time tracking 866 precision. 867 868 If in doubt, use the default value. 869 870endmenu 871 872# 873# For architectures that want to enable the support for NUMA-affine scheduler 874# balancing logic: 875# 876config ARCH_SUPPORTS_NUMA_BALANCING 877 bool 878 879# 880# For architectures that prefer to flush all TLBs after a number of pages 881# are unmapped instead of sending one IPI per page to flush. The architecture 882# must provide guarantees on what happens if a clean TLB cache entry is 883# written after the unmap. Details are in mm/rmap.c near the check for 884# should_defer_flush. The architecture should also consider if the full flush 885# and the refill costs are offset by the savings of sending fewer IPIs. 886config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 887 bool 888 889config CC_HAS_INT128 890 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 891 892config CC_IMPLICIT_FALLTHROUGH 893 string 894 default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5) 895 default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough) 896 897# Currently, disable gcc-12 array-bounds globally. 898# We may want to target only particular configurations some day. 899config GCC12_NO_ARRAY_BOUNDS 900 def_bool y 901 902config CC_NO_ARRAY_BOUNDS 903 bool 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 UCLAMP_TASK_GROUP 1045 bool "Utilization clamping per group of tasks" 1046 depends on CGROUP_SCHED 1047 depends on UCLAMP_TASK 1048 default n 1049 help 1050 This feature enables the scheduler to track the clamped utilization 1051 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 1052 1053 When this option is enabled, the user can specify a min and max 1054 CPU bandwidth which is allowed for each single task in a group. 1055 The max bandwidth allows to clamp the maximum frequency a task 1056 can use, while the min bandwidth allows to define a minimum 1057 frequency a task will always use. 1058 1059 When task group based utilization clamping is enabled, an eventually 1060 specified task-specific clamp value is constrained by the cgroup 1061 specified clamp value. Both minimum and maximum task clamping cannot 1062 be bigger than the corresponding clamping defined at task group level. 1063 1064 If in doubt, say N. 1065 1066config CGROUP_PIDS 1067 bool "PIDs controller" 1068 help 1069 Provides enforcement of process number limits in the scope of a 1070 cgroup. Any attempt to fork more processes than is allowed in the 1071 cgroup will fail. PIDs are fundamentally a global resource because it 1072 is fairly trivial to reach PID exhaustion before you reach even a 1073 conservative kmemcg limit. As a result, it is possible to grind a 1074 system to halt without being limited by other cgroup policies. The 1075 PIDs controller is designed to stop this from happening. 1076 1077 It should be noted that organisational operations (such as attaching 1078 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 1079 since the PIDs limit only affects a process's ability to fork, not to 1080 attach to a cgroup. 1081 1082config CGROUP_RDMA 1083 bool "RDMA controller" 1084 help 1085 Provides enforcement of RDMA resources defined by IB stack. 1086 It is fairly easy for consumers to exhaust RDMA resources, which 1087 can result into resource unavailability to other consumers. 1088 RDMA controller is designed to stop this from happening. 1089 Attaching processes with active RDMA resources to the cgroup 1090 hierarchy is allowed even if can cross the hierarchy's limit. 1091 1092config CGROUP_FREEZER 1093 bool "Freezer controller" 1094 help 1095 Provides a way to freeze and unfreeze all tasks in a 1096 cgroup. 1097 1098 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1099 controller includes important in-kernel memory consumers per default. 1100 1101 If you're using cgroup2, say N. 1102 1103config CGROUP_HUGETLB 1104 bool "HugeTLB controller" 1105 depends on HUGETLB_PAGE 1106 select PAGE_COUNTER 1107 default n 1108 help 1109 Provides a cgroup controller for HugeTLB pages. 1110 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1111 The limit is enforced during page fault. Since HugeTLB doesn't 1112 support page reclaim, enforcing the limit at page fault time implies 1113 that, the application will get SIGBUS signal if it tries to access 1114 HugeTLB pages beyond its limit. This requires the application to know 1115 beforehand how much HugeTLB pages it would require for its use. The 1116 control group is tracked in the third page lru pointer. This means 1117 that we cannot use the controller with huge page less than 3 pages. 1118 1119config CPUSETS 1120 bool "Cpuset controller" 1121 depends on SMP 1122 help 1123 This option will let you create and manage CPUSETs which 1124 allow dynamically partitioning a system into sets of CPUs and 1125 Memory Nodes and assigning tasks to run only within those sets. 1126 This is primarily useful on large SMP or NUMA systems. 1127 1128 Say N if unsure. 1129 1130config PROC_PID_CPUSET 1131 bool "Include legacy /proc/<pid>/cpuset file" 1132 depends on CPUSETS 1133 default y 1134 1135config CGROUP_DEVICE 1136 bool "Device controller" 1137 help 1138 Provides a cgroup controller implementing whitelists for 1139 devices which a process in the cgroup can mknod or open. 1140 1141config CGROUP_CPUACCT 1142 bool "Simple CPU accounting controller" 1143 help 1144 Provides a simple controller for monitoring the 1145 total CPU consumed by the tasks in a cgroup. 1146 1147config CGROUP_PERF 1148 bool "Perf controller" 1149 depends on PERF_EVENTS 1150 help 1151 This option extends the perf per-cpu mode to restrict monitoring 1152 to threads which belong to the cgroup specified and run on the 1153 designated cpu. Or this can be used to have cgroup ID in samples 1154 so that it can monitor performance events among cgroups. 1155 1156 Say N if unsure. 1157 1158config CGROUP_BPF 1159 bool "Support for eBPF programs attached to cgroups" 1160 depends on BPF_SYSCALL 1161 select SOCK_CGROUP_DATA 1162 help 1163 Allow attaching eBPF programs to a cgroup using the bpf(2) 1164 syscall command BPF_PROG_ATTACH. 1165 1166 In which context these programs are accessed depends on the type 1167 of attachment. For instance, programs that are attached using 1168 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1169 inet sockets. 1170 1171config CGROUP_MISC 1172 bool "Misc resource controller" 1173 default n 1174 help 1175 Provides a controller for miscellaneous resources on a host. 1176 1177 Miscellaneous scalar resources are the resources on the host system 1178 which cannot be abstracted like the other cgroups. This controller 1179 tracks and limits the miscellaneous resources used by a process 1180 attached to a cgroup hierarchy. 1181 1182 For more information, please check misc cgroup section in 1183 /Documentation/admin-guide/cgroup-v2.rst. 1184 1185config CGROUP_DEBUG 1186 bool "Debug controller" 1187 default n 1188 depends on DEBUG_KERNEL 1189 help 1190 This option enables a simple controller that exports 1191 debugging information about the cgroups framework. This 1192 controller is for control cgroup debugging only. Its 1193 interfaces are not stable. 1194 1195 Say N. 1196 1197config SOCK_CGROUP_DATA 1198 bool 1199 default n 1200 1201endif # CGROUPS 1202 1203menuconfig NAMESPACES 1204 bool "Namespaces support" if EXPERT 1205 depends on MULTIUSER 1206 default !EXPERT 1207 help 1208 Provides the way to make tasks work with different objects using 1209 the same id. For example same IPC id may refer to different objects 1210 or same user id or pid may refer to different tasks when used in 1211 different namespaces. 1212 1213if NAMESPACES 1214 1215config UTS_NS 1216 bool "UTS namespace" 1217 default y 1218 help 1219 In this namespace tasks see different info provided with the 1220 uname() system call 1221 1222config TIME_NS 1223 bool "TIME namespace" 1224 depends on GENERIC_VDSO_TIME_NS 1225 default y 1226 help 1227 In this namespace boottime and monotonic clocks can be set. 1228 The time will keep going with the same pace. 1229 1230config IPC_NS 1231 bool "IPC namespace" 1232 depends on (SYSVIPC || POSIX_MQUEUE) 1233 default y 1234 help 1235 In this namespace tasks work with IPC ids which correspond to 1236 different IPC objects in different namespaces. 1237 1238config USER_NS 1239 bool "User namespace" 1240 default n 1241 help 1242 This allows containers, i.e. vservers, to use user namespaces 1243 to provide different user info for different servers. 1244 1245 When user namespaces are enabled in the kernel it is 1246 recommended that the MEMCG option also be enabled and that 1247 user-space use the memory control groups to limit the amount 1248 of memory a memory unprivileged users can use. 1249 1250 If unsure, say N. 1251 1252config PID_NS 1253 bool "PID Namespaces" 1254 default y 1255 help 1256 Support process id namespaces. This allows having multiple 1257 processes with the same pid as long as they are in different 1258 pid namespaces. This is a building block of containers. 1259 1260config NET_NS 1261 bool "Network namespace" 1262 depends on NET 1263 default y 1264 help 1265 Allow user space to create what appear to be multiple instances 1266 of the network stack. 1267 1268endif # NAMESPACES 1269 1270config CHECKPOINT_RESTORE 1271 bool "Checkpoint/restore support" 1272 depends on PROC_FS 1273 select PROC_CHILDREN 1274 select KCMP 1275 default n 1276 help 1277 Enables additional kernel features in a sake of checkpoint/restore. 1278 In particular it adds auxiliary prctl codes to setup process text, 1279 data and heap segment sizes, and a few additional /proc filesystem 1280 entries. 1281 1282 If unsure, say N here. 1283 1284config SCHED_AUTOGROUP 1285 bool "Automatic process group scheduling" 1286 select CGROUPS 1287 select CGROUP_SCHED 1288 select FAIR_GROUP_SCHED 1289 help 1290 This option optimizes the scheduler for common desktop workloads by 1291 automatically creating and populating task groups. This separation 1292 of workloads isolates aggressive CPU burners (like build jobs) from 1293 desktop applications. Task group autogeneration is currently based 1294 upon task session. 1295 1296config SYSFS_DEPRECATED 1297 bool "Enable deprecated sysfs features to support old userspace tools" 1298 depends on SYSFS 1299 default n 1300 help 1301 This option adds code that switches the layout of the "block" class 1302 devices, to not show up in /sys/class/block/, but only in 1303 /sys/block/. 1304 1305 This switch is only active when the sysfs.deprecated=1 boot option is 1306 passed or the SYSFS_DEPRECATED_V2 option is set. 1307 1308 This option allows new kernels to run on old distributions and tools, 1309 which might get confused by /sys/class/block/. Since 2007/2008 all 1310 major distributions and tools handle this just fine. 1311 1312 Recent distributions and userspace tools after 2009/2010 depend on 1313 the existence of /sys/class/block/, and will not work with this 1314 option enabled. 1315 1316 Only if you are using a new kernel on an old distribution, you might 1317 need to say Y here. 1318 1319config SYSFS_DEPRECATED_V2 1320 bool "Enable deprecated sysfs features by default" 1321 default n 1322 depends on SYSFS 1323 depends on SYSFS_DEPRECATED 1324 help 1325 Enable deprecated sysfs by default. 1326 1327 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1328 option. 1329 1330 Only if you are using a new kernel on an old distribution, you might 1331 need to say Y here. Even then, odds are you would not need it 1332 enabled, you can always pass the boot option if absolutely necessary. 1333 1334config RELAY 1335 bool "Kernel->user space relay support (formerly relayfs)" 1336 select IRQ_WORK 1337 help 1338 This option enables support for relay interface support in 1339 certain file systems (such as debugfs). 1340 It is designed to provide an efficient mechanism for tools and 1341 facilities to relay large amounts of data from kernel space to 1342 user space. 1343 1344 If unsure, say N. 1345 1346config BLK_DEV_INITRD 1347 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1348 help 1349 The initial RAM filesystem is a ramfs which is loaded by the 1350 boot loader (loadlin or lilo) and that is mounted as root 1351 before the normal boot procedure. It is typically used to 1352 load modules needed to mount the "real" root file system, 1353 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1354 1355 If RAM disk support (BLK_DEV_RAM) is also included, this 1356 also enables initial RAM disk (initrd) support and adds 1357 15 Kbytes (more on some other architectures) to the kernel size. 1358 1359 If unsure say Y. 1360 1361if BLK_DEV_INITRD 1362 1363source "usr/Kconfig" 1364 1365endif 1366 1367config BOOT_CONFIG 1368 bool "Boot config support" 1369 select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED 1370 help 1371 Extra boot config allows system admin to pass a config file as 1372 complemental extension of kernel cmdline when booting. 1373 The boot config file must be attached at the end of initramfs 1374 with checksum, size and magic word. 1375 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1376 1377 If unsure, say Y. 1378 1379config BOOT_CONFIG_EMBED 1380 bool "Embed bootconfig file in the kernel" 1381 depends on BOOT_CONFIG 1382 help 1383 Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the 1384 kernel. Usually, the bootconfig file is loaded with the initrd 1385 image. But if the system doesn't support initrd, this option will 1386 help you by embedding a bootconfig file while building the kernel. 1387 1388 If unsure, say N. 1389 1390config BOOT_CONFIG_EMBED_FILE 1391 string "Embedded bootconfig file path" 1392 depends on BOOT_CONFIG_EMBED 1393 help 1394 Specify a bootconfig file which will be embedded to the kernel. 1395 This bootconfig will be used if there is no initrd or no other 1396 bootconfig in the initrd. 1397 1398config INITRAMFS_PRESERVE_MTIME 1399 bool "Preserve cpio archive mtimes in initramfs" 1400 default y 1401 help 1402 Each entry in an initramfs cpio archive carries an mtime value. When 1403 enabled, extracted cpio items take this mtime, with directory mtime 1404 setting deferred until after creation of any child entries. 1405 1406 If unsure, say Y. 1407 1408choice 1409 prompt "Compiler optimization level" 1410 default CC_OPTIMIZE_FOR_PERFORMANCE 1411 1412config CC_OPTIMIZE_FOR_PERFORMANCE 1413 bool "Optimize for performance (-O2)" 1414 help 1415 This is the default optimization level for the kernel, building 1416 with the "-O2" compiler flag for best performance and most 1417 helpful compile-time warnings. 1418 1419config CC_OPTIMIZE_FOR_SIZE 1420 bool "Optimize for size (-Os)" 1421 help 1422 Choosing this option will pass "-Os" to your compiler resulting 1423 in a smaller kernel. 1424 1425endchoice 1426 1427config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1428 bool 1429 help 1430 This requires that the arch annotates or otherwise protects 1431 its external entry points from being discarded. Linker scripts 1432 must also merge .text.*, .data.*, and .bss.* correctly into 1433 output sections. Care must be taken not to pull in unrelated 1434 sections (e.g., '.text.init'). Typically '.' in section names 1435 is used to distinguish them from label names / C identifiers. 1436 1437config LD_DEAD_CODE_DATA_ELIMINATION 1438 bool "Dead code and data elimination (EXPERIMENTAL)" 1439 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1440 depends on EXPERT 1441 depends on $(cc-option,-ffunction-sections -fdata-sections) 1442 depends on $(ld-option,--gc-sections) 1443 help 1444 Enable this if you want to do dead code and data elimination with 1445 the linker by compiling with -ffunction-sections -fdata-sections, 1446 and linking with --gc-sections. 1447 1448 This can reduce on disk and in-memory size of the kernel 1449 code and static data, particularly for small configs and 1450 on small systems. This has the possibility of introducing 1451 silently broken kernel if the required annotations are not 1452 present. This option is not well tested yet, so use at your 1453 own risk. 1454 1455config LD_ORPHAN_WARN 1456 def_bool y 1457 depends on ARCH_WANT_LD_ORPHAN_WARN 1458 depends on $(ld-option,--orphan-handling=warn) 1459 depends on $(ld-option,--orphan-handling=error) 1460 1461config LD_ORPHAN_WARN_LEVEL 1462 string 1463 depends on LD_ORPHAN_WARN 1464 default "error" if WERROR 1465 default "warn" 1466 1467config SYSCTL 1468 bool 1469 1470config HAVE_UID16 1471 bool 1472 1473config SYSCTL_EXCEPTION_TRACE 1474 bool 1475 help 1476 Enable support for /proc/sys/debug/exception-trace. 1477 1478config SYSCTL_ARCH_UNALIGN_NO_WARN 1479 bool 1480 help 1481 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1482 Allows arch to define/use @no_unaligned_warning to possibly warn 1483 about unaligned access emulation going on under the hood. 1484 1485config SYSCTL_ARCH_UNALIGN_ALLOW 1486 bool 1487 help 1488 Enable support for /proc/sys/kernel/unaligned-trap 1489 Allows arches to define/use @unaligned_enabled to runtime toggle 1490 the unaligned access emulation. 1491 see arch/parisc/kernel/unaligned.c for reference 1492 1493config HAVE_PCSPKR_PLATFORM 1494 bool 1495 1496# interpreter that classic socket filters depend on 1497config BPF 1498 bool 1499 select CRYPTO_LIB_SHA1 1500 1501menuconfig EXPERT 1502 bool "Configure standard kernel features (expert users)" 1503 # Unhide debug options, to make the on-by-default options visible 1504 select DEBUG_KERNEL 1505 help 1506 This option allows certain base kernel options and settings 1507 to be disabled or tweaked. This is for specialized 1508 environments which can tolerate a "non-standard" kernel. 1509 Only use this if you really know what you are doing. 1510 1511config UID16 1512 bool "Enable 16-bit UID system calls" if EXPERT 1513 depends on HAVE_UID16 && MULTIUSER 1514 default y 1515 help 1516 This enables the legacy 16-bit UID syscall wrappers. 1517 1518config MULTIUSER 1519 bool "Multiple users, groups and capabilities support" if EXPERT 1520 default y 1521 help 1522 This option enables support for non-root users, groups and 1523 capabilities. 1524 1525 If you say N here, all processes will run with UID 0, GID 0, and all 1526 possible capabilities. Saying N here also compiles out support for 1527 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1528 setgid, and capset. 1529 1530 If unsure, say Y here. 1531 1532config SGETMASK_SYSCALL 1533 bool "sgetmask/ssetmask syscalls support" if EXPERT 1534 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1535 help 1536 sys_sgetmask and sys_ssetmask are obsolete system calls 1537 no longer supported in libc but still enabled by default in some 1538 architectures. 1539 1540 If unsure, leave the default option here. 1541 1542config SYSFS_SYSCALL 1543 bool "Sysfs syscall support" if EXPERT 1544 default y 1545 help 1546 sys_sysfs is an obsolete system call no longer supported in libc. 1547 Note that disabling this option is more secure but might break 1548 compatibility with some systems. 1549 1550 If unsure say Y here. 1551 1552config FHANDLE 1553 bool "open by fhandle syscalls" if EXPERT 1554 select EXPORTFS 1555 default y 1556 help 1557 If you say Y here, a user level program will be able to map 1558 file names to handle and then later use the handle for 1559 different file system operations. This is useful in implementing 1560 userspace file servers, which now track files using handles instead 1561 of names. The handle would remain the same even if file names 1562 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1563 syscalls. 1564 1565config POSIX_TIMERS 1566 bool "Posix Clocks & timers" if EXPERT 1567 default y 1568 help 1569 This includes native support for POSIX timers to the kernel. 1570 Some embedded systems have no use for them and therefore they 1571 can be configured out to reduce the size of the kernel image. 1572 1573 When this option is disabled, the following syscalls won't be 1574 available: timer_create, timer_gettime: timer_getoverrun, 1575 timer_settime, timer_delete, clock_adjtime, getitimer, 1576 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1577 clock_getres and clock_nanosleep syscalls will be limited to 1578 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1579 1580 If unsure say y. 1581 1582config PRINTK 1583 default y 1584 bool "Enable support for printk" if EXPERT 1585 select IRQ_WORK 1586 help 1587 This option enables normal printk support. Removing it 1588 eliminates most of the message strings from the kernel image 1589 and makes the kernel more or less silent. As this makes it 1590 very difficult to diagnose system problems, saying N here is 1591 strongly discouraged. 1592 1593config BUG 1594 bool "BUG() support" if EXPERT 1595 default y 1596 help 1597 Disabling this option eliminates support for BUG and WARN, reducing 1598 the size of your kernel image and potentially quietly ignoring 1599 numerous fatal conditions. You should only consider disabling this 1600 option for embedded systems with no facilities for reporting errors. 1601 Just say Y. 1602 1603config ELF_CORE 1604 depends on COREDUMP 1605 default y 1606 bool "Enable ELF core dumps" if EXPERT 1607 help 1608 Enable support for generating core dumps. Disabling saves about 4k. 1609 1610 1611config PCSPKR_PLATFORM 1612 bool "Enable PC-Speaker support" if EXPERT 1613 depends on HAVE_PCSPKR_PLATFORM 1614 select I8253_LOCK 1615 default y 1616 help 1617 This option allows to disable the internal PC-Speaker 1618 support, saving some memory. 1619 1620config BASE_FULL 1621 default y 1622 bool "Enable full-sized data structures for core" if EXPERT 1623 help 1624 Disabling this option reduces the size of miscellaneous core 1625 kernel data structures. This saves memory on small machines, 1626 but may reduce performance. 1627 1628config FUTEX 1629 bool "Enable futex support" if EXPERT 1630 depends on !(SPARC32 && SMP) 1631 default y 1632 imply RT_MUTEXES 1633 help 1634 Disabling this option will cause the kernel to be built without 1635 support for "fast userspace mutexes". The resulting kernel may not 1636 run glibc-based applications correctly. 1637 1638config FUTEX_PI 1639 bool 1640 depends on FUTEX && RT_MUTEXES 1641 default y 1642 1643config EPOLL 1644 bool "Enable eventpoll support" if EXPERT 1645 default y 1646 help 1647 Disabling this option will cause the kernel to be built without 1648 support for epoll family of system calls. 1649 1650config SIGNALFD 1651 bool "Enable signalfd() system call" if EXPERT 1652 default y 1653 help 1654 Enable the signalfd() system call that allows to receive signals 1655 on a file descriptor. 1656 1657 If unsure, say Y. 1658 1659config TIMERFD 1660 bool "Enable timerfd() system call" if EXPERT 1661 default y 1662 help 1663 Enable the timerfd() system call that allows to receive timer 1664 events on a file descriptor. 1665 1666 If unsure, say Y. 1667 1668config EVENTFD 1669 bool "Enable eventfd() system call" if EXPERT 1670 default y 1671 help 1672 Enable the eventfd() system call that allows to receive both 1673 kernel notification (ie. KAIO) or userspace notifications. 1674 1675 If unsure, say Y. 1676 1677config SHMEM 1678 bool "Use full shmem filesystem" if EXPERT 1679 default y 1680 depends on MMU 1681 help 1682 The shmem is an internal filesystem used to manage shared memory. 1683 It is backed by swap and manages resource limits. It is also exported 1684 to userspace as tmpfs if TMPFS is enabled. Disabling this 1685 option replaces shmem and tmpfs with the much simpler ramfs code, 1686 which may be appropriate on small systems without swap. 1687 1688config AIO 1689 bool "Enable AIO support" if EXPERT 1690 default y 1691 help 1692 This option enables POSIX asynchronous I/O which may by used 1693 by some high performance threaded applications. Disabling 1694 this option saves about 7k. 1695 1696config IO_URING 1697 bool "Enable IO uring support" if EXPERT 1698 select IO_WQ 1699 default y 1700 help 1701 This option enables support for the io_uring interface, enabling 1702 applications to submit and complete IO through submission and 1703 completion rings that are shared between the kernel and application. 1704 1705config ADVISE_SYSCALLS 1706 bool "Enable madvise/fadvise syscalls" if EXPERT 1707 default y 1708 help 1709 This option enables the madvise and fadvise syscalls, used by 1710 applications to advise the kernel about their future memory or file 1711 usage, improving performance. If building an embedded system where no 1712 applications use these syscalls, you can disable this option to save 1713 space. 1714 1715config MEMBARRIER 1716 bool "Enable membarrier() system call" if EXPERT 1717 default y 1718 help 1719 Enable the membarrier() system call that allows issuing memory 1720 barriers across all running threads, which can be used to distribute 1721 the cost of user-space memory barriers asymmetrically by transforming 1722 pairs of memory barriers into pairs consisting of membarrier() and a 1723 compiler barrier. 1724 1725 If unsure, say Y. 1726 1727config KALLSYMS 1728 bool "Load all symbols for debugging/ksymoops" if EXPERT 1729 default y 1730 help 1731 Say Y here to let the kernel print out symbolic crash information and 1732 symbolic stack backtraces. This increases the size of the kernel 1733 somewhat, as all symbols have to be loaded into the kernel image. 1734 1735config KALLSYMS_SELFTEST 1736 bool "Test the basic functions and performance of kallsyms" 1737 depends on KALLSYMS 1738 default n 1739 help 1740 Test the basic functions and performance of some interfaces, such as 1741 kallsyms_lookup_name. It also calculates the compression rate of the 1742 kallsyms compression algorithm for the current symbol set. 1743 1744 Start self-test automatically after system startup. Suggest executing 1745 "dmesg | grep kallsyms_selftest" to collect test results. "finish" is 1746 displayed in the last line, indicating that the test is complete. 1747 1748config KALLSYMS_ALL 1749 bool "Include all symbols in kallsyms" 1750 depends on DEBUG_KERNEL && KALLSYMS 1751 help 1752 Normally kallsyms only contains the symbols of functions for nicer 1753 OOPS messages and backtraces (i.e., symbols from the text and inittext 1754 sections). This is sufficient for most cases. And only if you want to 1755 enable kernel live patching, or other less common use cases (e.g., 1756 when a debugger is used) all symbols are required (i.e., names of 1757 variables from the data sections, etc). 1758 1759 This option makes sure that all symbols are loaded into the kernel 1760 image (i.e., symbols from all sections) in cost of increased kernel 1761 size (depending on the kernel configuration, it may be 300KiB or 1762 something like this). 1763 1764 Say N unless you really need all symbols, or kernel live patching. 1765 1766config KALLSYMS_ABSOLUTE_PERCPU 1767 bool 1768 depends on KALLSYMS 1769 default X86_64 && SMP 1770 1771config KALLSYMS_BASE_RELATIVE 1772 bool 1773 depends on KALLSYMS 1774 default !IA64 1775 help 1776 Instead of emitting them as absolute values in the native word size, 1777 emit the symbol references in the kallsyms table as 32-bit entries, 1778 each containing a relative value in the range [base, base + U32_MAX] 1779 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1780 an absolute value in the range [0, S32_MAX] or a relative value in the 1781 range [base, base + S32_MAX], where base is the lowest relative symbol 1782 address encountered in the image. 1783 1784 On 64-bit builds, this reduces the size of the address table by 50%, 1785 but more importantly, it results in entries whose values are build 1786 time constants, and no relocation pass is required at runtime to fix 1787 up the entries based on the runtime load address of the kernel. 1788 1789# end of the "standard kernel features (expert users)" menu 1790 1791# syscall, maps, verifier 1792 1793config ARCH_HAS_MEMBARRIER_CALLBACKS 1794 bool 1795 1796config ARCH_HAS_MEMBARRIER_SYNC_CORE 1797 bool 1798 1799config KCMP 1800 bool "Enable kcmp() system call" if EXPERT 1801 help 1802 Enable the kernel resource comparison system call. It provides 1803 user-space with the ability to compare two processes to see if they 1804 share a common resource, such as a file descriptor or even virtual 1805 memory space. 1806 1807 If unsure, say N. 1808 1809config RSEQ 1810 bool "Enable rseq() system call" if EXPERT 1811 default y 1812 depends on HAVE_RSEQ 1813 select MEMBARRIER 1814 help 1815 Enable the restartable sequences system call. It provides a 1816 user-space cache for the current CPU number value, which 1817 speeds up getting the current CPU number from user-space, 1818 as well as an ABI to speed up user-space operations on 1819 per-CPU data. 1820 1821 If unsure, say Y. 1822 1823config DEBUG_RSEQ 1824 default n 1825 bool "Enabled debugging of rseq() system call" if EXPERT 1826 depends on RSEQ && DEBUG_KERNEL 1827 help 1828 Enable extra debugging checks for the rseq system call. 1829 1830 If unsure, say N. 1831 1832config EMBEDDED 1833 bool "Embedded system" 1834 select EXPERT 1835 help 1836 This option should be enabled if compiling the kernel for 1837 an embedded system so certain expert options are available 1838 for configuration. 1839 1840config HAVE_PERF_EVENTS 1841 bool 1842 help 1843 See tools/perf/design.txt for details. 1844 1845config GUEST_PERF_EVENTS 1846 bool 1847 depends on HAVE_PERF_EVENTS 1848 1849config PERF_USE_VMALLOC 1850 bool 1851 help 1852 See tools/perf/design.txt for details 1853 1854config PC104 1855 bool "PC/104 support" if EXPERT 1856 help 1857 Expose PC/104 form factor device drivers and options available for 1858 selection and configuration. Enable this option if your target 1859 machine has a PC/104 bus. 1860 1861menu "Kernel Performance Events And Counters" 1862 1863config PERF_EVENTS 1864 bool "Kernel performance events and counters" 1865 default y if PROFILING 1866 depends on HAVE_PERF_EVENTS 1867 select IRQ_WORK 1868 select SRCU 1869 help 1870 Enable kernel support for various performance events provided 1871 by software and hardware. 1872 1873 Software events are supported either built-in or via the 1874 use of generic tracepoints. 1875 1876 Most modern CPUs support performance events via performance 1877 counter registers. These registers count the number of certain 1878 types of hw events: such as instructions executed, cachemisses 1879 suffered, or branches mis-predicted - without slowing down the 1880 kernel or applications. These registers can also trigger interrupts 1881 when a threshold number of events have passed - and can thus be 1882 used to profile the code that runs on that CPU. 1883 1884 The Linux Performance Event subsystem provides an abstraction of 1885 these software and hardware event capabilities, available via a 1886 system call and used by the "perf" utility in tools/perf/. It 1887 provides per task and per CPU counters, and it provides event 1888 capabilities on top of those. 1889 1890 Say Y if unsure. 1891 1892config DEBUG_PERF_USE_VMALLOC 1893 default n 1894 bool "Debug: use vmalloc to back perf mmap() buffers" 1895 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1896 select PERF_USE_VMALLOC 1897 help 1898 Use vmalloc memory to back perf mmap() buffers. 1899 1900 Mostly useful for debugging the vmalloc code on platforms 1901 that don't require it. 1902 1903 Say N if unsure. 1904 1905endmenu 1906 1907config SYSTEM_DATA_VERIFICATION 1908 def_bool n 1909 select SYSTEM_TRUSTED_KEYRING 1910 select KEYS 1911 select CRYPTO 1912 select CRYPTO_RSA 1913 select ASYMMETRIC_KEY_TYPE 1914 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1915 select ASN1 1916 select OID_REGISTRY 1917 select X509_CERTIFICATE_PARSER 1918 select PKCS7_MESSAGE_PARSER 1919 help 1920 Provide PKCS#7 message verification using the contents of the system 1921 trusted keyring to provide public keys. This then can be used for 1922 module verification, kexec image verification and firmware blob 1923 verification. 1924 1925config PROFILING 1926 bool "Profiling support" 1927 help 1928 Say Y here to enable the extended profiling support mechanisms used 1929 by profilers. 1930 1931config RUST 1932 bool "Rust support" 1933 depends on HAVE_RUST 1934 depends on RUST_IS_AVAILABLE 1935 depends on !MODVERSIONS 1936 depends on !GCC_PLUGINS 1937 depends on !RANDSTRUCT 1938 depends on !DEBUG_INFO_BTF 1939 select CONSTRUCTORS 1940 help 1941 Enables Rust support in the kernel. 1942 1943 This allows other Rust-related options, like drivers written in Rust, 1944 to be selected. 1945 1946 It is also required to be able to load external kernel modules 1947 written in Rust. 1948 1949 See Documentation/rust/ for more information. 1950 1951 If unsure, say N. 1952 1953config RUSTC_VERSION_TEXT 1954 string 1955 depends on RUST 1956 default $(shell,command -v $(RUSTC) >/dev/null 2>&1 && $(RUSTC) --version || echo n) 1957 1958config BINDGEN_VERSION_TEXT 1959 string 1960 depends on RUST 1961 default $(shell,command -v $(BINDGEN) >/dev/null 2>&1 && $(BINDGEN) --version || echo n) 1962 1963# 1964# Place an empty function call at each tracepoint site. Can be 1965# dynamically changed for a probe function. 1966# 1967config TRACEPOINTS 1968 bool 1969 1970endmenu # General setup 1971 1972source "arch/Kconfig" 1973 1974config RT_MUTEXES 1975 bool 1976 default y if PREEMPT_RT 1977 1978config BASE_SMALL 1979 int 1980 default 0 if BASE_FULL 1981 default 1 if !BASE_FULL 1982 1983config MODULE_SIG_FORMAT 1984 def_bool n 1985 select SYSTEM_DATA_VERIFICATION 1986 1987source "kernel/module/Kconfig" 1988 1989config INIT_ALL_POSSIBLE 1990 bool 1991 help 1992 Back when each arch used to define their own cpu_online_mask and 1993 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 1994 with all 1s, and others with all 0s. When they were centralised, 1995 it was better to provide this option than to break all the archs 1996 and have several arch maintainers pursuing me down dark alleys. 1997 1998source "block/Kconfig" 1999 2000config PREEMPT_NOTIFIERS 2001 bool 2002 2003config PADATA 2004 depends on SMP 2005 bool 2006 2007config ASN1 2008 tristate 2009 help 2010 Build a simple ASN.1 grammar compiler that produces a bytecode output 2011 that can be interpreted by the ASN.1 stream decoder and used to 2012 inform it as to what tags are to be expected in a stream and what 2013 functions to call on what tags. 2014 2015source "kernel/Kconfig.locks" 2016 2017config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 2018 bool 2019 2020config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2021 bool 2022 2023# It may be useful for an architecture to override the definitions of the 2024# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2025# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2026# different calling convention for syscalls. They can also override the 2027# macros for not-implemented syscalls in kernel/sys_ni.c and 2028# kernel/time/posix-stubs.c. All these overrides need to be available in 2029# <asm/syscall_wrapper.h>. 2030config ARCH_HAS_SYSCALL_WRAPPER 2031 def_bool n 2032