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 select KERNFS 633 help 634 Collect metrics that indicate how overcommitted the CPU, memory, 635 and IO capacity are in the system. 636 637 If you say Y here, the kernel will create /proc/pressure/ with the 638 pressure statistics files cpu, memory, and io. These will indicate 639 the share of walltime in which some or all tasks in the system are 640 delayed due to contention of the respective resource. 641 642 In kernels with cgroup support, cgroups (cgroup2 only) will 643 have cpu.pressure, memory.pressure, and io.pressure files, 644 which aggregate pressure stalls for the grouped tasks only. 645 646 For more details see Documentation/accounting/psi.rst. 647 648 Say N if unsure. 649 650config PSI_DEFAULT_DISABLED 651 bool "Require boot parameter to enable pressure stall information tracking" 652 default n 653 depends on PSI 654 help 655 If set, pressure stall information tracking will be disabled 656 per default but can be enabled through passing psi=1 on the 657 kernel commandline during boot. 658 659 This feature adds some code to the task wakeup and sleep 660 paths of the scheduler. The overhead is too low to affect 661 common scheduling-intense workloads in practice (such as 662 webservers, memcache), but it does show up in artificial 663 scheduler stress tests, such as hackbench. 664 665 If you are paranoid and not sure what the kernel will be 666 used for, say Y. 667 668 Say N if unsure. 669 670endmenu # "CPU/Task time and stats accounting" 671 672config CPU_ISOLATION 673 bool "CPU isolation" 674 depends on SMP || COMPILE_TEST 675 default y 676 help 677 Make sure that CPUs running critical tasks are not disturbed by 678 any source of "noise" such as unbound workqueues, timers, kthreads... 679 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 680 the "isolcpus=" boot parameter. 681 682 Say Y if unsure. 683 684source "kernel/rcu/Kconfig" 685 686config IKCONFIG 687 tristate "Kernel .config support" 688 help 689 This option enables the complete Linux kernel ".config" file 690 contents to be saved in the kernel. It provides documentation 691 of which kernel options are used in a running kernel or in an 692 on-disk kernel. This information can be extracted from the kernel 693 image file with the script scripts/extract-ikconfig and used as 694 input to rebuild the current kernel or to build another kernel. 695 It can also be extracted from a running kernel by reading 696 /proc/config.gz if enabled (below). 697 698config IKCONFIG_PROC 699 bool "Enable access to .config through /proc/config.gz" 700 depends on IKCONFIG && PROC_FS 701 help 702 This option enables access to the kernel configuration file 703 through /proc/config.gz. 704 705config IKHEADERS 706 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 707 depends on SYSFS 708 help 709 This option enables access to the in-kernel headers that are generated during 710 the build process. These can be used to build eBPF tracing programs, 711 or similar programs. If you build the headers as a module, a module called 712 kheaders.ko is built which can be loaded on-demand to get access to headers. 713 714config LOG_BUF_SHIFT 715 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 716 range 12 25 717 default 17 718 depends on PRINTK 719 help 720 Select the minimal kernel log buffer size as a power of 2. 721 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 722 parameter, see below. Any higher size also might be forced 723 by "log_buf_len" boot parameter. 724 725 Examples: 726 17 => 128 KB 727 16 => 64 KB 728 15 => 32 KB 729 14 => 16 KB 730 13 => 8 KB 731 12 => 4 KB 732 733config LOG_CPU_MAX_BUF_SHIFT 734 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 735 depends on SMP 736 range 0 21 737 default 12 if !BASE_SMALL 738 default 0 if BASE_SMALL 739 depends on PRINTK 740 help 741 This option allows to increase the default ring buffer size 742 according to the number of CPUs. The value defines the contribution 743 of each CPU as a power of 2. The used space is typically only few 744 lines however it might be much more when problems are reported, 745 e.g. backtraces. 746 747 The increased size means that a new buffer has to be allocated and 748 the original static one is unused. It makes sense only on systems 749 with more CPUs. Therefore this value is used only when the sum of 750 contributions is greater than the half of the default kernel ring 751 buffer as defined by LOG_BUF_SHIFT. The default values are set 752 so that more than 16 CPUs are needed to trigger the allocation. 753 754 Also this option is ignored when "log_buf_len" kernel parameter is 755 used as it forces an exact (power of two) size of the ring buffer. 756 757 The number of possible CPUs is used for this computation ignoring 758 hotplugging making the computation optimal for the worst case 759 scenario while allowing a simple algorithm to be used from bootup. 760 761 Examples shift values and their meaning: 762 17 => 128 KB for each CPU 763 16 => 64 KB for each CPU 764 15 => 32 KB for each CPU 765 14 => 16 KB for each CPU 766 13 => 8 KB for each CPU 767 12 => 4 KB for each CPU 768 769config PRINTK_INDEX 770 bool "Printk indexing debugfs interface" 771 depends on PRINTK && DEBUG_FS 772 help 773 Add support for indexing of all printk formats known at compile time 774 at <debugfs>/printk/index/<module>. 775 776 This can be used as part of maintaining daemons which monitor 777 /dev/kmsg, as it permits auditing the printk formats present in a 778 kernel, allowing detection of cases where monitored printks are 779 changed or no longer present. 780 781 There is no additional runtime cost to printk with this enabled. 782 783# 784# Architectures with an unreliable sched_clock() should select this: 785# 786config HAVE_UNSTABLE_SCHED_CLOCK 787 bool 788 789config GENERIC_SCHED_CLOCK 790 bool 791 792menu "Scheduler features" 793 794config UCLAMP_TASK 795 bool "Enable utilization clamping for RT/FAIR tasks" 796 depends on CPU_FREQ_GOV_SCHEDUTIL 797 help 798 This feature enables the scheduler to track the clamped utilization 799 of each CPU based on RUNNABLE tasks scheduled on that CPU. 800 801 With this option, the user can specify the min and max CPU 802 utilization allowed for RUNNABLE tasks. The max utilization defines 803 the maximum frequency a task should use while the min utilization 804 defines the minimum frequency it should use. 805 806 Both min and max utilization clamp values are hints to the scheduler, 807 aiming at improving its frequency selection policy, but they do not 808 enforce or grant any specific bandwidth for tasks. 809 810 If in doubt, say N. 811 812config UCLAMP_BUCKETS_COUNT 813 int "Number of supported utilization clamp buckets" 814 range 5 20 815 default 5 816 depends on UCLAMP_TASK 817 help 818 Defines the number of clamp buckets to use. The range of each bucket 819 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 820 number of clamp buckets the finer their granularity and the higher 821 the precision of clamping aggregation and tracking at run-time. 822 823 For example, with the minimum configuration value we will have 5 824 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 825 be refcounted in the [20..39]% bucket and will set the bucket clamp 826 effective value to 25%. 827 If a second 30% boosted task should be co-scheduled on the same CPU, 828 that task will be refcounted in the same bucket of the first task and 829 it will boost the bucket clamp effective value to 30%. 830 The clamp effective value of a bucket is reset to its nominal value 831 (20% in the example above) when there are no more tasks refcounted in 832 that bucket. 833 834 An additional boost/capping margin can be added to some tasks. In the 835 example above the 25% task will be boosted to 30% until it exits the 836 CPU. If that should be considered not acceptable on certain systems, 837 it's always possible to reduce the margin by increasing the number of 838 clamp buckets to trade off used memory for run-time tracking 839 precision. 840 841 If in doubt, use the default value. 842 843endmenu 844 845# 846# For architectures that want to enable the support for NUMA-affine scheduler 847# balancing logic: 848# 849config ARCH_SUPPORTS_NUMA_BALANCING 850 bool 851 852# 853# For architectures that prefer to flush all TLBs after a number of pages 854# are unmapped instead of sending one IPI per page to flush. The architecture 855# must provide guarantees on what happens if a clean TLB cache entry is 856# written after the unmap. Details are in mm/rmap.c near the check for 857# should_defer_flush. The architecture should also consider if the full flush 858# and the refill costs are offset by the savings of sending fewer IPIs. 859config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 860 bool 861 862config CC_HAS_INT128 863 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 864 865config CC_IMPLICIT_FALLTHROUGH 866 string 867 default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5) 868 default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough) 869 870# Currently, disable gcc-11+ array-bounds globally. 871# It's still broken in gcc-13, so no upper bound yet. 872config GCC11_NO_ARRAY_BOUNDS 873 def_bool y 874 875config CC_NO_ARRAY_BOUNDS 876 bool 877 default y if CC_IS_GCC && GCC_VERSION >= 110000 && GCC11_NO_ARRAY_BOUNDS 878 879# 880# For architectures that know their GCC __int128 support is sound 881# 882config ARCH_SUPPORTS_INT128 883 bool 884 885# For architectures that (ab)use NUMA to represent different memory regions 886# all cpu-local but of different latencies, such as SuperH. 887# 888config ARCH_WANT_NUMA_VARIABLE_LOCALITY 889 bool 890 891config NUMA_BALANCING 892 bool "Memory placement aware NUMA scheduler" 893 depends on ARCH_SUPPORTS_NUMA_BALANCING 894 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 895 depends on SMP && NUMA && MIGRATION && !PREEMPT_RT 896 help 897 This option adds support for automatic NUMA aware memory/task placement. 898 The mechanism is quite primitive and is based on migrating memory when 899 it has references to the node the task is running on. 900 901 This system will be inactive on UMA systems. 902 903config NUMA_BALANCING_DEFAULT_ENABLED 904 bool "Automatically enable NUMA aware memory/task placement" 905 default y 906 depends on NUMA_BALANCING 907 help 908 If set, automatic NUMA balancing will be enabled if running on a NUMA 909 machine. 910 911menuconfig CGROUPS 912 bool "Control Group support" 913 select KERNFS 914 help 915 This option adds support for grouping sets of processes together, for 916 use with process control subsystems such as Cpusets, CFS, memory 917 controls or device isolation. 918 See 919 - Documentation/scheduler/sched-design-CFS.rst (CFS) 920 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 921 and resource control) 922 923 Say N if unsure. 924 925if CGROUPS 926 927config PAGE_COUNTER 928 bool 929 930config CGROUP_FAVOR_DYNMODS 931 bool "Favor dynamic modification latency reduction by default" 932 help 933 This option enables the "favordynmods" mount option by default 934 which reduces the latencies of dynamic cgroup modifications such 935 as task migrations and controller on/offs at the cost of making 936 hot path operations such as forks and exits more expensive. 937 938 Say N if unsure. 939 940config MEMCG 941 bool "Memory controller" 942 select PAGE_COUNTER 943 select EVENTFD 944 help 945 Provides control over the memory footprint of tasks in a cgroup. 946 947config MEMCG_KMEM 948 bool 949 depends on MEMCG 950 default y 951 952config BLK_CGROUP 953 bool "IO controller" 954 depends on BLOCK 955 default n 956 help 957 Generic block IO controller cgroup interface. This is the common 958 cgroup interface which should be used by various IO controlling 959 policies. 960 961 Currently, CFQ IO scheduler uses it to recognize task groups and 962 control disk bandwidth allocation (proportional time slice allocation) 963 to such task groups. It is also used by bio throttling logic in 964 block layer to implement upper limit in IO rates on a device. 965 966 This option only enables generic Block IO controller infrastructure. 967 One needs to also enable actual IO controlling logic/policy. For 968 enabling proportional weight division of disk bandwidth in CFQ, set 969 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 970 CONFIG_BLK_DEV_THROTTLING=y. 971 972 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 973 974config CGROUP_WRITEBACK 975 bool 976 depends on MEMCG && BLK_CGROUP 977 default y 978 979menuconfig CGROUP_SCHED 980 bool "CPU controller" 981 default n 982 help 983 This feature lets CPU scheduler recognize task groups and control CPU 984 bandwidth allocation to such task groups. It uses cgroups to group 985 tasks. 986 987if CGROUP_SCHED 988config FAIR_GROUP_SCHED 989 bool "Group scheduling for SCHED_OTHER" 990 depends on CGROUP_SCHED 991 default CGROUP_SCHED 992 993config CFS_BANDWIDTH 994 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 995 depends on FAIR_GROUP_SCHED 996 default n 997 help 998 This option allows users to define CPU bandwidth rates (limits) for 999 tasks running within the fair group scheduler. Groups with no limit 1000 set are considered to be unconstrained and will run with no 1001 restriction. 1002 See Documentation/scheduler/sched-bwc.rst for more information. 1003 1004config RT_GROUP_SCHED 1005 bool "Group scheduling for SCHED_RR/FIFO" 1006 depends on CGROUP_SCHED 1007 default n 1008 help 1009 This feature lets you explicitly allocate real CPU bandwidth 1010 to task groups. If enabled, it will also make it impossible to 1011 schedule realtime tasks for non-root users until you allocate 1012 realtime bandwidth for them. 1013 See Documentation/scheduler/sched-rt-group.rst for more information. 1014 1015endif #CGROUP_SCHED 1016 1017config SCHED_MM_CID 1018 def_bool y 1019 depends on SMP && RSEQ 1020 1021config UCLAMP_TASK_GROUP 1022 bool "Utilization clamping per group of tasks" 1023 depends on CGROUP_SCHED 1024 depends on UCLAMP_TASK 1025 default n 1026 help 1027 This feature enables the scheduler to track the clamped utilization 1028 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 1029 1030 When this option is enabled, the user can specify a min and max 1031 CPU bandwidth which is allowed for each single task in a group. 1032 The max bandwidth allows to clamp the maximum frequency a task 1033 can use, while the min bandwidth allows to define a minimum 1034 frequency a task will always use. 1035 1036 When task group based utilization clamping is enabled, an eventually 1037 specified task-specific clamp value is constrained by the cgroup 1038 specified clamp value. Both minimum and maximum task clamping cannot 1039 be bigger than the corresponding clamping defined at task group level. 1040 1041 If in doubt, say N. 1042 1043config CGROUP_PIDS 1044 bool "PIDs controller" 1045 help 1046 Provides enforcement of process number limits in the scope of a 1047 cgroup. Any attempt to fork more processes than is allowed in the 1048 cgroup will fail. PIDs are fundamentally a global resource because it 1049 is fairly trivial to reach PID exhaustion before you reach even a 1050 conservative kmemcg limit. As a result, it is possible to grind a 1051 system to halt without being limited by other cgroup policies. The 1052 PIDs controller is designed to stop this from happening. 1053 1054 It should be noted that organisational operations (such as attaching 1055 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 1056 since the PIDs limit only affects a process's ability to fork, not to 1057 attach to a cgroup. 1058 1059config CGROUP_RDMA 1060 bool "RDMA controller" 1061 help 1062 Provides enforcement of RDMA resources defined by IB stack. 1063 It is fairly easy for consumers to exhaust RDMA resources, which 1064 can result into resource unavailability to other consumers. 1065 RDMA controller is designed to stop this from happening. 1066 Attaching processes with active RDMA resources to the cgroup 1067 hierarchy is allowed even if can cross the hierarchy's limit. 1068 1069config CGROUP_FREEZER 1070 bool "Freezer controller" 1071 help 1072 Provides a way to freeze and unfreeze all tasks in a 1073 cgroup. 1074 1075 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1076 controller includes important in-kernel memory consumers per default. 1077 1078 If you're using cgroup2, say N. 1079 1080config CGROUP_HUGETLB 1081 bool "HugeTLB controller" 1082 depends on HUGETLB_PAGE 1083 select PAGE_COUNTER 1084 default n 1085 help 1086 Provides a cgroup controller for HugeTLB pages. 1087 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1088 The limit is enforced during page fault. Since HugeTLB doesn't 1089 support page reclaim, enforcing the limit at page fault time implies 1090 that, the application will get SIGBUS signal if it tries to access 1091 HugeTLB pages beyond its limit. This requires the application to know 1092 beforehand how much HugeTLB pages it would require for its use. The 1093 control group is tracked in the third page lru pointer. This means 1094 that we cannot use the controller with huge page less than 3 pages. 1095 1096config CPUSETS 1097 bool "Cpuset controller" 1098 depends on SMP 1099 help 1100 This option will let you create and manage CPUSETs which 1101 allow dynamically partitioning a system into sets of CPUs and 1102 Memory Nodes and assigning tasks to run only within those sets. 1103 This is primarily useful on large SMP or NUMA systems. 1104 1105 Say N if unsure. 1106 1107config PROC_PID_CPUSET 1108 bool "Include legacy /proc/<pid>/cpuset file" 1109 depends on CPUSETS 1110 default y 1111 1112config CGROUP_DEVICE 1113 bool "Device controller" 1114 help 1115 Provides a cgroup controller implementing whitelists for 1116 devices which a process in the cgroup can mknod or open. 1117 1118config CGROUP_CPUACCT 1119 bool "Simple CPU accounting controller" 1120 help 1121 Provides a simple controller for monitoring the 1122 total CPU consumed by the tasks in a cgroup. 1123 1124config CGROUP_PERF 1125 bool "Perf controller" 1126 depends on PERF_EVENTS 1127 help 1128 This option extends the perf per-cpu mode to restrict monitoring 1129 to threads which belong to the cgroup specified and run on the 1130 designated cpu. Or this can be used to have cgroup ID in samples 1131 so that it can monitor performance events among cgroups. 1132 1133 Say N if unsure. 1134 1135config CGROUP_BPF 1136 bool "Support for eBPF programs attached to cgroups" 1137 depends on BPF_SYSCALL 1138 select SOCK_CGROUP_DATA 1139 help 1140 Allow attaching eBPF programs to a cgroup using the bpf(2) 1141 syscall command BPF_PROG_ATTACH. 1142 1143 In which context these programs are accessed depends on the type 1144 of attachment. For instance, programs that are attached using 1145 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1146 inet sockets. 1147 1148config CGROUP_MISC 1149 bool "Misc resource controller" 1150 default n 1151 help 1152 Provides a controller for miscellaneous resources on a host. 1153 1154 Miscellaneous scalar resources are the resources on the host system 1155 which cannot be abstracted like the other cgroups. This controller 1156 tracks and limits the miscellaneous resources used by a process 1157 attached to a cgroup hierarchy. 1158 1159 For more information, please check misc cgroup section in 1160 /Documentation/admin-guide/cgroup-v2.rst. 1161 1162config CGROUP_DEBUG 1163 bool "Debug controller" 1164 default n 1165 depends on DEBUG_KERNEL 1166 help 1167 This option enables a simple controller that exports 1168 debugging information about the cgroups framework. This 1169 controller is for control cgroup debugging only. Its 1170 interfaces are not stable. 1171 1172 Say N. 1173 1174config SOCK_CGROUP_DATA 1175 bool 1176 default n 1177 1178endif # CGROUPS 1179 1180menuconfig NAMESPACES 1181 bool "Namespaces support" if EXPERT 1182 depends on MULTIUSER 1183 default !EXPERT 1184 help 1185 Provides the way to make tasks work with different objects using 1186 the same id. For example same IPC id may refer to different objects 1187 or same user id or pid may refer to different tasks when used in 1188 different namespaces. 1189 1190if NAMESPACES 1191 1192config UTS_NS 1193 bool "UTS namespace" 1194 default y 1195 help 1196 In this namespace tasks see different info provided with the 1197 uname() system call 1198 1199config TIME_NS 1200 bool "TIME namespace" 1201 depends on GENERIC_VDSO_TIME_NS 1202 default y 1203 help 1204 In this namespace boottime and monotonic clocks can be set. 1205 The time will keep going with the same pace. 1206 1207config IPC_NS 1208 bool "IPC namespace" 1209 depends on (SYSVIPC || POSIX_MQUEUE) 1210 default y 1211 help 1212 In this namespace tasks work with IPC ids which correspond to 1213 different IPC objects in different namespaces. 1214 1215config USER_NS 1216 bool "User namespace" 1217 default n 1218 help 1219 This allows containers, i.e. vservers, to use user namespaces 1220 to provide different user info for different servers. 1221 1222 When user namespaces are enabled in the kernel it is 1223 recommended that the MEMCG option also be enabled and that 1224 user-space use the memory control groups to limit the amount 1225 of memory a memory unprivileged users can use. 1226 1227 If unsure, say N. 1228 1229config PID_NS 1230 bool "PID Namespaces" 1231 default y 1232 help 1233 Support process id namespaces. This allows having multiple 1234 processes with the same pid as long as they are in different 1235 pid namespaces. This is a building block of containers. 1236 1237config NET_NS 1238 bool "Network namespace" 1239 depends on NET 1240 default y 1241 help 1242 Allow user space to create what appear to be multiple instances 1243 of the network stack. 1244 1245endif # NAMESPACES 1246 1247config CHECKPOINT_RESTORE 1248 bool "Checkpoint/restore support" 1249 depends on PROC_FS 1250 select PROC_CHILDREN 1251 select KCMP 1252 default n 1253 help 1254 Enables additional kernel features in a sake of checkpoint/restore. 1255 In particular it adds auxiliary prctl codes to setup process text, 1256 data and heap segment sizes, and a few additional /proc filesystem 1257 entries. 1258 1259 If unsure, say N here. 1260 1261config SCHED_AUTOGROUP 1262 bool "Automatic process group scheduling" 1263 select CGROUPS 1264 select CGROUP_SCHED 1265 select FAIR_GROUP_SCHED 1266 help 1267 This option optimizes the scheduler for common desktop workloads by 1268 automatically creating and populating task groups. This separation 1269 of workloads isolates aggressive CPU burners (like build jobs) from 1270 desktop applications. Task group autogeneration is currently based 1271 upon task session. 1272 1273config RELAY 1274 bool "Kernel->user space relay support (formerly relayfs)" 1275 select IRQ_WORK 1276 help 1277 This option enables support for relay interface support in 1278 certain file systems (such as debugfs). 1279 It is designed to provide an efficient mechanism for tools and 1280 facilities to relay large amounts of data from kernel space to 1281 user space. 1282 1283 If unsure, say N. 1284 1285config BLK_DEV_INITRD 1286 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1287 help 1288 The initial RAM filesystem is a ramfs which is loaded by the 1289 boot loader (loadlin or lilo) and that is mounted as root 1290 before the normal boot procedure. It is typically used to 1291 load modules needed to mount the "real" root file system, 1292 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1293 1294 If RAM disk support (BLK_DEV_RAM) is also included, this 1295 also enables initial RAM disk (initrd) support and adds 1296 15 Kbytes (more on some other architectures) to the kernel size. 1297 1298 If unsure say Y. 1299 1300if BLK_DEV_INITRD 1301 1302source "usr/Kconfig" 1303 1304endif 1305 1306config BOOT_CONFIG 1307 bool "Boot config support" 1308 select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED 1309 help 1310 Extra boot config allows system admin to pass a config file as 1311 complemental extension of kernel cmdline when booting. 1312 The boot config file must be attached at the end of initramfs 1313 with checksum, size and magic word. 1314 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1315 1316 If unsure, say Y. 1317 1318config BOOT_CONFIG_FORCE 1319 bool "Force unconditional bootconfig processing" 1320 depends on BOOT_CONFIG 1321 default y if BOOT_CONFIG_EMBED 1322 help 1323 With this Kconfig option set, BOOT_CONFIG processing is carried 1324 out even when the "bootconfig" kernel-boot parameter is omitted. 1325 In fact, with this Kconfig option set, there is no way to 1326 make the kernel ignore the BOOT_CONFIG-supplied kernel-boot 1327 parameters. 1328 1329 If unsure, say N. 1330 1331config BOOT_CONFIG_EMBED 1332 bool "Embed bootconfig file in the kernel" 1333 depends on BOOT_CONFIG 1334 help 1335 Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the 1336 kernel. Usually, the bootconfig file is loaded with the initrd 1337 image. But if the system doesn't support initrd, this option will 1338 help you by embedding a bootconfig file while building the kernel. 1339 1340 If unsure, say N. 1341 1342config BOOT_CONFIG_EMBED_FILE 1343 string "Embedded bootconfig file path" 1344 depends on BOOT_CONFIG_EMBED 1345 help 1346 Specify a bootconfig file which will be embedded to the kernel. 1347 This bootconfig will be used if there is no initrd or no other 1348 bootconfig in the initrd. 1349 1350config INITRAMFS_PRESERVE_MTIME 1351 bool "Preserve cpio archive mtimes in initramfs" 1352 default y 1353 help 1354 Each entry in an initramfs cpio archive carries an mtime value. When 1355 enabled, extracted cpio items take this mtime, with directory mtime 1356 setting deferred until after creation of any child entries. 1357 1358 If unsure, say Y. 1359 1360choice 1361 prompt "Compiler optimization level" 1362 default CC_OPTIMIZE_FOR_PERFORMANCE 1363 1364config CC_OPTIMIZE_FOR_PERFORMANCE 1365 bool "Optimize for performance (-O2)" 1366 help 1367 This is the default optimization level for the kernel, building 1368 with the "-O2" compiler flag for best performance and most 1369 helpful compile-time warnings. 1370 1371config CC_OPTIMIZE_FOR_SIZE 1372 bool "Optimize for size (-Os)" 1373 help 1374 Choosing this option will pass "-Os" to your compiler resulting 1375 in a smaller kernel. 1376 1377endchoice 1378 1379config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1380 bool 1381 help 1382 This requires that the arch annotates or otherwise protects 1383 its external entry points from being discarded. Linker scripts 1384 must also merge .text.*, .data.*, and .bss.* correctly into 1385 output sections. Care must be taken not to pull in unrelated 1386 sections (e.g., '.text.init'). Typically '.' in section names 1387 is used to distinguish them from label names / C identifiers. 1388 1389config LD_DEAD_CODE_DATA_ELIMINATION 1390 bool "Dead code and data elimination (EXPERIMENTAL)" 1391 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1392 depends on EXPERT 1393 depends on $(cc-option,-ffunction-sections -fdata-sections) 1394 depends on $(ld-option,--gc-sections) 1395 help 1396 Enable this if you want to do dead code and data elimination with 1397 the linker by compiling with -ffunction-sections -fdata-sections, 1398 and linking with --gc-sections. 1399 1400 This can reduce on disk and in-memory size of the kernel 1401 code and static data, particularly for small configs and 1402 on small systems. This has the possibility of introducing 1403 silently broken kernel if the required annotations are not 1404 present. This option is not well tested yet, so use at your 1405 own risk. 1406 1407config LD_ORPHAN_WARN 1408 def_bool y 1409 depends on ARCH_WANT_LD_ORPHAN_WARN 1410 depends on $(ld-option,--orphan-handling=warn) 1411 depends on $(ld-option,--orphan-handling=error) 1412 1413config LD_ORPHAN_WARN_LEVEL 1414 string 1415 depends on LD_ORPHAN_WARN 1416 default "error" if WERROR 1417 default "warn" 1418 1419config SYSCTL 1420 bool 1421 1422config HAVE_UID16 1423 bool 1424 1425config SYSCTL_EXCEPTION_TRACE 1426 bool 1427 help 1428 Enable support for /proc/sys/debug/exception-trace. 1429 1430config SYSCTL_ARCH_UNALIGN_NO_WARN 1431 bool 1432 help 1433 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1434 Allows arch to define/use @no_unaligned_warning to possibly warn 1435 about unaligned access emulation going on under the hood. 1436 1437config SYSCTL_ARCH_UNALIGN_ALLOW 1438 bool 1439 help 1440 Enable support for /proc/sys/kernel/unaligned-trap 1441 Allows arches to define/use @unaligned_enabled to runtime toggle 1442 the unaligned access emulation. 1443 see arch/parisc/kernel/unaligned.c for reference 1444 1445config HAVE_PCSPKR_PLATFORM 1446 bool 1447 1448# interpreter that classic socket filters depend on 1449config BPF 1450 bool 1451 select CRYPTO_LIB_SHA1 1452 1453menuconfig EXPERT 1454 bool "Configure standard kernel features (expert users)" 1455 # Unhide debug options, to make the on-by-default options visible 1456 select DEBUG_KERNEL 1457 help 1458 This option allows certain base kernel options and settings 1459 to be disabled or tweaked. This is for specialized 1460 environments which can tolerate a "non-standard" kernel. 1461 Only use this if you really know what you are doing. 1462 1463config UID16 1464 bool "Enable 16-bit UID system calls" if EXPERT 1465 depends on HAVE_UID16 && MULTIUSER 1466 default y 1467 help 1468 This enables the legacy 16-bit UID syscall wrappers. 1469 1470config MULTIUSER 1471 bool "Multiple users, groups and capabilities support" if EXPERT 1472 default y 1473 help 1474 This option enables support for non-root users, groups and 1475 capabilities. 1476 1477 If you say N here, all processes will run with UID 0, GID 0, and all 1478 possible capabilities. Saying N here also compiles out support for 1479 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1480 setgid, and capset. 1481 1482 If unsure, say Y here. 1483 1484config SGETMASK_SYSCALL 1485 bool "sgetmask/ssetmask syscalls support" if EXPERT 1486 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1487 help 1488 sys_sgetmask and sys_ssetmask are obsolete system calls 1489 no longer supported in libc but still enabled by default in some 1490 architectures. 1491 1492 If unsure, leave the default option here. 1493 1494config SYSFS_SYSCALL 1495 bool "Sysfs syscall support" if EXPERT 1496 default y 1497 help 1498 sys_sysfs is an obsolete system call no longer supported in libc. 1499 Note that disabling this option is more secure but might break 1500 compatibility with some systems. 1501 1502 If unsure say Y here. 1503 1504config FHANDLE 1505 bool "open by fhandle syscalls" if EXPERT 1506 select EXPORTFS 1507 default y 1508 help 1509 If you say Y here, a user level program will be able to map 1510 file names to handle and then later use the handle for 1511 different file system operations. This is useful in implementing 1512 userspace file servers, which now track files using handles instead 1513 of names. The handle would remain the same even if file names 1514 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1515 syscalls. 1516 1517config POSIX_TIMERS 1518 bool "Posix Clocks & timers" if EXPERT 1519 default y 1520 help 1521 This includes native support for POSIX timers to the kernel. 1522 Some embedded systems have no use for them and therefore they 1523 can be configured out to reduce the size of the kernel image. 1524 1525 When this option is disabled, the following syscalls won't be 1526 available: timer_create, timer_gettime: timer_getoverrun, 1527 timer_settime, timer_delete, clock_adjtime, getitimer, 1528 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1529 clock_getres and clock_nanosleep syscalls will be limited to 1530 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1531 1532 If unsure say y. 1533 1534config PRINTK 1535 default y 1536 bool "Enable support for printk" if EXPERT 1537 select IRQ_WORK 1538 help 1539 This option enables normal printk support. Removing it 1540 eliminates most of the message strings from the kernel image 1541 and makes the kernel more or less silent. As this makes it 1542 very difficult to diagnose system problems, saying N here is 1543 strongly discouraged. 1544 1545config BUG 1546 bool "BUG() support" if EXPERT 1547 default y 1548 help 1549 Disabling this option eliminates support for BUG and WARN, reducing 1550 the size of your kernel image and potentially quietly ignoring 1551 numerous fatal conditions. You should only consider disabling this 1552 option for embedded systems with no facilities for reporting errors. 1553 Just say Y. 1554 1555config ELF_CORE 1556 depends on COREDUMP 1557 default y 1558 bool "Enable ELF core dumps" if EXPERT 1559 help 1560 Enable support for generating core dumps. Disabling saves about 4k. 1561 1562 1563config PCSPKR_PLATFORM 1564 bool "Enable PC-Speaker support" if EXPERT 1565 depends on HAVE_PCSPKR_PLATFORM 1566 select I8253_LOCK 1567 default y 1568 help 1569 This option allows to disable the internal PC-Speaker 1570 support, saving some memory. 1571 1572config BASE_FULL 1573 default y 1574 bool "Enable full-sized data structures for core" if EXPERT 1575 help 1576 Disabling this option reduces the size of miscellaneous core 1577 kernel data structures. This saves memory on small machines, 1578 but may reduce performance. 1579 1580config FUTEX 1581 bool "Enable futex support" if EXPERT 1582 depends on !(SPARC32 && SMP) 1583 default y 1584 imply RT_MUTEXES 1585 help 1586 Disabling this option will cause the kernel to be built without 1587 support for "fast userspace mutexes". The resulting kernel may not 1588 run glibc-based applications correctly. 1589 1590config FUTEX_PI 1591 bool 1592 depends on FUTEX && RT_MUTEXES 1593 default y 1594 1595config EPOLL 1596 bool "Enable eventpoll support" if EXPERT 1597 default y 1598 help 1599 Disabling this option will cause the kernel to be built without 1600 support for epoll family of system calls. 1601 1602config SIGNALFD 1603 bool "Enable signalfd() system call" if EXPERT 1604 default y 1605 help 1606 Enable the signalfd() system call that allows to receive signals 1607 on a file descriptor. 1608 1609 If unsure, say Y. 1610 1611config TIMERFD 1612 bool "Enable timerfd() system call" if EXPERT 1613 default y 1614 help 1615 Enable the timerfd() system call that allows to receive timer 1616 events on a file descriptor. 1617 1618 If unsure, say Y. 1619 1620config EVENTFD 1621 bool "Enable eventfd() system call" if EXPERT 1622 default y 1623 help 1624 Enable the eventfd() system call that allows to receive both 1625 kernel notification (ie. KAIO) or userspace notifications. 1626 1627 If unsure, say Y. 1628 1629config SHMEM 1630 bool "Use full shmem filesystem" if EXPERT 1631 default y 1632 depends on MMU 1633 help 1634 The shmem is an internal filesystem used to manage shared memory. 1635 It is backed by swap and manages resource limits. It is also exported 1636 to userspace as tmpfs if TMPFS is enabled. Disabling this 1637 option replaces shmem and tmpfs with the much simpler ramfs code, 1638 which may be appropriate on small systems without swap. 1639 1640config AIO 1641 bool "Enable AIO support" if EXPERT 1642 default y 1643 help 1644 This option enables POSIX asynchronous I/O which may by used 1645 by some high performance threaded applications. Disabling 1646 this option saves about 7k. 1647 1648config IO_URING 1649 bool "Enable IO uring support" if EXPERT 1650 select IO_WQ 1651 default y 1652 help 1653 This option enables support for the io_uring interface, enabling 1654 applications to submit and complete IO through submission and 1655 completion rings that are shared between the kernel and application. 1656 1657config ADVISE_SYSCALLS 1658 bool "Enable madvise/fadvise syscalls" if EXPERT 1659 default y 1660 help 1661 This option enables the madvise and fadvise syscalls, used by 1662 applications to advise the kernel about their future memory or file 1663 usage, improving performance. If building an embedded system where no 1664 applications use these syscalls, you can disable this option to save 1665 space. 1666 1667config MEMBARRIER 1668 bool "Enable membarrier() system call" if EXPERT 1669 default y 1670 help 1671 Enable the membarrier() system call that allows issuing memory 1672 barriers across all running threads, which can be used to distribute 1673 the cost of user-space memory barriers asymmetrically by transforming 1674 pairs of memory barriers into pairs consisting of membarrier() and a 1675 compiler barrier. 1676 1677 If unsure, say Y. 1678 1679config KALLSYMS 1680 bool "Load all symbols for debugging/ksymoops" if EXPERT 1681 default y 1682 help 1683 Say Y here to let the kernel print out symbolic crash information and 1684 symbolic stack backtraces. This increases the size of the kernel 1685 somewhat, as all symbols have to be loaded into the kernel image. 1686 1687config KALLSYMS_SELFTEST 1688 bool "Test the basic functions and performance of kallsyms" 1689 depends on KALLSYMS 1690 default n 1691 help 1692 Test the basic functions and performance of some interfaces, such as 1693 kallsyms_lookup_name. It also calculates the compression rate of the 1694 kallsyms compression algorithm for the current symbol set. 1695 1696 Start self-test automatically after system startup. Suggest executing 1697 "dmesg | grep kallsyms_selftest" to collect test results. "finish" is 1698 displayed in the last line, indicating that the test is complete. 1699 1700config KALLSYMS_ALL 1701 bool "Include all symbols in kallsyms" 1702 depends on DEBUG_KERNEL && KALLSYMS 1703 help 1704 Normally kallsyms only contains the symbols of functions for nicer 1705 OOPS messages and backtraces (i.e., symbols from the text and inittext 1706 sections). This is sufficient for most cases. And only if you want to 1707 enable kernel live patching, or other less common use cases (e.g., 1708 when a debugger is used) all symbols are required (i.e., names of 1709 variables from the data sections, etc). 1710 1711 This option makes sure that all symbols are loaded into the kernel 1712 image (i.e., symbols from all sections) in cost of increased kernel 1713 size (depending on the kernel configuration, it may be 300KiB or 1714 something like this). 1715 1716 Say N unless you really need all symbols, or kernel live patching. 1717 1718config KALLSYMS_ABSOLUTE_PERCPU 1719 bool 1720 depends on KALLSYMS 1721 default X86_64 && SMP 1722 1723config KALLSYMS_BASE_RELATIVE 1724 bool 1725 depends on KALLSYMS 1726 default y 1727 help 1728 Instead of emitting them as absolute values in the native word size, 1729 emit the symbol references in the kallsyms table as 32-bit entries, 1730 each containing a relative value in the range [base, base + U32_MAX] 1731 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1732 an absolute value in the range [0, S32_MAX] or a relative value in the 1733 range [base, base + S32_MAX], where base is the lowest relative symbol 1734 address encountered in the image. 1735 1736 On 64-bit builds, this reduces the size of the address table by 50%, 1737 but more importantly, it results in entries whose values are build 1738 time constants, and no relocation pass is required at runtime to fix 1739 up the entries based on the runtime load address of the kernel. 1740 1741# end of the "standard kernel features (expert users)" menu 1742 1743# syscall, maps, verifier 1744 1745config ARCH_HAS_MEMBARRIER_CALLBACKS 1746 bool 1747 1748config ARCH_HAS_MEMBARRIER_SYNC_CORE 1749 bool 1750 1751config KCMP 1752 bool "Enable kcmp() system call" if EXPERT 1753 help 1754 Enable the kernel resource comparison system call. It provides 1755 user-space with the ability to compare two processes to see if they 1756 share a common resource, such as a file descriptor or even virtual 1757 memory space. 1758 1759 If unsure, say N. 1760 1761config RSEQ 1762 bool "Enable rseq() system call" if EXPERT 1763 default y 1764 depends on HAVE_RSEQ 1765 select MEMBARRIER 1766 help 1767 Enable the restartable sequences system call. It provides a 1768 user-space cache for the current CPU number value, which 1769 speeds up getting the current CPU number from user-space, 1770 as well as an ABI to speed up user-space operations on 1771 per-CPU data. 1772 1773 If unsure, say Y. 1774 1775config CACHESTAT_SYSCALL 1776 bool "Enable cachestat() system call" if EXPERT 1777 default y 1778 help 1779 Enable the cachestat system call, which queries the page cache 1780 statistics of a file (number of cached pages, dirty pages, 1781 pages marked for writeback, (recently) evicted pages). 1782 1783 If unsure say Y here. 1784 1785config DEBUG_RSEQ 1786 default n 1787 bool "Enabled debugging of rseq() system call" if EXPERT 1788 depends on RSEQ && DEBUG_KERNEL 1789 help 1790 Enable extra debugging checks for the rseq system call. 1791 1792 If unsure, say N. 1793 1794config HAVE_PERF_EVENTS 1795 bool 1796 help 1797 See tools/perf/design.txt for details. 1798 1799config GUEST_PERF_EVENTS 1800 bool 1801 depends on HAVE_PERF_EVENTS 1802 1803config PERF_USE_VMALLOC 1804 bool 1805 help 1806 See tools/perf/design.txt for details 1807 1808config PC104 1809 bool "PC/104 support" if EXPERT 1810 help 1811 Expose PC/104 form factor device drivers and options available for 1812 selection and configuration. Enable this option if your target 1813 machine has a PC/104 bus. 1814 1815menu "Kernel Performance Events And Counters" 1816 1817config PERF_EVENTS 1818 bool "Kernel performance events and counters" 1819 default y if PROFILING 1820 depends on HAVE_PERF_EVENTS 1821 select IRQ_WORK 1822 help 1823 Enable kernel support for various performance events provided 1824 by software and hardware. 1825 1826 Software events are supported either built-in or via the 1827 use of generic tracepoints. 1828 1829 Most modern CPUs support performance events via performance 1830 counter registers. These registers count the number of certain 1831 types of hw events: such as instructions executed, cachemisses 1832 suffered, or branches mis-predicted - without slowing down the 1833 kernel or applications. These registers can also trigger interrupts 1834 when a threshold number of events have passed - and can thus be 1835 used to profile the code that runs on that CPU. 1836 1837 The Linux Performance Event subsystem provides an abstraction of 1838 these software and hardware event capabilities, available via a 1839 system call and used by the "perf" utility in tools/perf/. It 1840 provides per task and per CPU counters, and it provides event 1841 capabilities on top of those. 1842 1843 Say Y if unsure. 1844 1845config DEBUG_PERF_USE_VMALLOC 1846 default n 1847 bool "Debug: use vmalloc to back perf mmap() buffers" 1848 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1849 select PERF_USE_VMALLOC 1850 help 1851 Use vmalloc memory to back perf mmap() buffers. 1852 1853 Mostly useful for debugging the vmalloc code on platforms 1854 that don't require it. 1855 1856 Say N if unsure. 1857 1858endmenu 1859 1860config SYSTEM_DATA_VERIFICATION 1861 def_bool n 1862 select SYSTEM_TRUSTED_KEYRING 1863 select KEYS 1864 select CRYPTO 1865 select CRYPTO_RSA 1866 select ASYMMETRIC_KEY_TYPE 1867 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1868 select ASN1 1869 select OID_REGISTRY 1870 select X509_CERTIFICATE_PARSER 1871 select PKCS7_MESSAGE_PARSER 1872 help 1873 Provide PKCS#7 message verification using the contents of the system 1874 trusted keyring to provide public keys. This then can be used for 1875 module verification, kexec image verification and firmware blob 1876 verification. 1877 1878config PROFILING 1879 bool "Profiling support" 1880 help 1881 Say Y here to enable the extended profiling support mechanisms used 1882 by profilers. 1883 1884config RUST 1885 bool "Rust support" 1886 depends on HAVE_RUST 1887 depends on RUST_IS_AVAILABLE 1888 depends on !MODVERSIONS 1889 depends on !GCC_PLUGINS 1890 depends on !RANDSTRUCT 1891 depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE 1892 select CONSTRUCTORS 1893 help 1894 Enables Rust support in the kernel. 1895 1896 This allows other Rust-related options, like drivers written in Rust, 1897 to be selected. 1898 1899 It is also required to be able to load external kernel modules 1900 written in Rust. 1901 1902 See Documentation/rust/ for more information. 1903 1904 If unsure, say N. 1905 1906config RUSTC_VERSION_TEXT 1907 string 1908 depends on RUST 1909 default $(shell,command -v $(RUSTC) >/dev/null 2>&1 && $(RUSTC) --version || echo n) 1910 1911config BINDGEN_VERSION_TEXT 1912 string 1913 depends on RUST 1914 default $(shell,command -v $(BINDGEN) >/dev/null 2>&1 && $(BINDGEN) --version || echo n) 1915 1916# 1917# Place an empty function call at each tracepoint site. Can be 1918# dynamically changed for a probe function. 1919# 1920config TRACEPOINTS 1921 bool 1922 1923source "kernel/Kconfig.kexec" 1924 1925endmenu # General setup 1926 1927source "arch/Kconfig" 1928 1929config RT_MUTEXES 1930 bool 1931 default y if PREEMPT_RT 1932 1933config BASE_SMALL 1934 int 1935 default 0 if BASE_FULL 1936 default 1 if !BASE_FULL 1937 1938config MODULE_SIG_FORMAT 1939 def_bool n 1940 select SYSTEM_DATA_VERIFICATION 1941 1942source "kernel/module/Kconfig" 1943 1944config INIT_ALL_POSSIBLE 1945 bool 1946 help 1947 Back when each arch used to define their own cpu_online_mask and 1948 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 1949 with all 1s, and others with all 0s. When they were centralised, 1950 it was better to provide this option than to break all the archs 1951 and have several arch maintainers pursuing me down dark alleys. 1952 1953source "block/Kconfig" 1954 1955config PREEMPT_NOTIFIERS 1956 bool 1957 1958config PADATA 1959 depends on SMP 1960 bool 1961 1962config ASN1 1963 tristate 1964 help 1965 Build a simple ASN.1 grammar compiler that produces a bytecode output 1966 that can be interpreted by the ASN.1 stream decoder and used to 1967 inform it as to what tags are to be expected in a stream and what 1968 functions to call on what tags. 1969 1970source "kernel/Kconfig.locks" 1971 1972config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 1973 bool 1974 1975config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 1976 bool 1977 1978# It may be useful for an architecture to override the definitions of the 1979# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 1980# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 1981# different calling convention for syscalls. They can also override the 1982# macros for not-implemented syscalls in kernel/sys_ni.c and 1983# kernel/time/posix-stubs.c. All these overrides need to be available in 1984# <asm/syscall_wrapper.h>. 1985config ARCH_HAS_SYSCALL_WRAPPER 1986 def_bool n 1987