1# SPDX-License-Identifier: GPL-2.0-only 2config CC_VERSION_TEXT 3 string 4 default "$(CC_VERSION_TEXT)" 5 help 6 This is used in unclear ways: 7 8 - Re-run Kconfig when the compiler is updated 9 The 'default' property references the environment variable, 10 CC_VERSION_TEXT so it is recorded in include/config/auto.conf.cmd. 11 When the compiler is updated, Kconfig will be invoked. 12 13 - Ensure full rebuild when the compiler is updated 14 include/linux/compiler-version.h contains this option in the comment 15 line so fixdep adds include/config/CC_VERSION_TEXT into the 16 auto-generated dependency. When the compiler is updated, syncconfig 17 will touch it and then every file will be rebuilt. 18 19config CC_IS_GCC 20 def_bool $(success,test "$(cc-name)" = GCC) 21 22config GCC_VERSION 23 int 24 default $(cc-version) if CC_IS_GCC 25 default 0 26 27config CC_IS_CLANG 28 def_bool $(success,test "$(cc-name)" = Clang) 29 30config CLANG_VERSION 31 int 32 default $(cc-version) if CC_IS_CLANG 33 default 0 34 35config AS_IS_GNU 36 def_bool $(success,test "$(as-name)" = GNU) 37 38config AS_IS_LLVM 39 def_bool $(success,test "$(as-name)" = LLVM) 40 41config AS_VERSION 42 int 43 # Use clang version if this is the integrated assembler 44 default CLANG_VERSION if AS_IS_LLVM 45 default $(as-version) 46 47config LD_IS_BFD 48 def_bool $(success,test "$(ld-name)" = BFD) 49 50config LD_VERSION 51 int 52 default $(ld-version) if LD_IS_BFD 53 default 0 54 55config LD_IS_LLD 56 def_bool $(success,test "$(ld-name)" = LLD) 57 58config LLD_VERSION 59 int 60 default $(ld-version) if LD_IS_LLD 61 default 0 62 63config RUST_IS_AVAILABLE 64 def_bool $(success,$(srctree)/scripts/rust_is_available.sh) 65 help 66 This shows whether a suitable Rust toolchain is available (found). 67 68 Please see Documentation/rust/quick-start.rst for instructions on how 69 to satisfy the build requirements of Rust support. 70 71 In particular, the Makefile target 'rustavailable' is useful to check 72 why the Rust toolchain is not being detected. 73 74config CC_CAN_LINK 75 bool 76 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT 77 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag)) 78 79config CC_CAN_LINK_STATIC 80 bool 81 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag) -static) if 64BIT 82 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag) -static) 83 84config CC_HAS_ASM_GOTO_OUTPUT 85 def_bool $(success,echo 'int foo(int x) { asm goto ("": "=r"(x) ::: bar); return x; bar: return 0; }' | $(CC) -x c - -c -o /dev/null) 86 87config CC_HAS_ASM_GOTO_TIED_OUTPUT 88 depends on CC_HAS_ASM_GOTO_OUTPUT 89 # Detect buggy gcc and clang, fixed in gcc-11 clang-14. 90 def_bool $(success,echo 'int foo(int *x) { asm goto (".long (%l[bar]) - .": "+m"(*x) ::: bar); return *x; bar: return 0; }' | $CC -x c - -c -o /dev/null) 91 92config TOOLS_SUPPORT_RELR 93 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 94 95config CC_HAS_ASM_INLINE 96 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 97 98config CC_HAS_NO_PROFILE_FN_ATTR 99 def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror) 100 101config PAHOLE_VERSION 102 int 103 default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE)) 104 105config CONSTRUCTORS 106 bool 107 108config IRQ_WORK 109 bool 110 111config BUILDTIME_TABLE_SORT 112 bool 113 114config THREAD_INFO_IN_TASK 115 bool 116 help 117 Select this to move thread_info off the stack into task_struct. To 118 make this work, an arch will need to remove all thread_info fields 119 except flags and fix any runtime bugs. 120 121 One subtle change that will be needed is to use try_get_task_stack() 122 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 123 124menu "General setup" 125 126config BROKEN 127 bool 128 129config BROKEN_ON_SMP 130 bool 131 depends on BROKEN || !SMP 132 default y 133 134config INIT_ENV_ARG_LIMIT 135 int 136 default 32 if !UML 137 default 128 if UML 138 help 139 Maximum of each of the number of arguments and environment 140 variables passed to init from the kernel command line. 141 142config COMPILE_TEST 143 bool "Compile also drivers which will not load" 144 depends on HAS_IOMEM 145 help 146 Some drivers can be compiled on a different platform than they are 147 intended to be run on. Despite they cannot be loaded there (or even 148 when they load they cannot be used due to missing HW support), 149 developers still, opposing to distributors, might want to build such 150 drivers to compile-test them. 151 152 If you are a developer and want to build everything available, say Y 153 here. If you are a user/distributor, say N here to exclude useless 154 drivers to be distributed. 155 156config WERROR 157 bool "Compile the kernel with warnings as errors" 158 default COMPILE_TEST 159 help 160 A kernel build should not cause any compiler warnings, and this 161 enables the '-Werror' (for C) and '-Dwarnings' (for Rust) flags 162 to enforce that rule by default. Certain warnings from other tools 163 such as the linker may be upgraded to errors with this option as 164 well. 165 166 However, if you have a new (or very old) compiler or linker with odd 167 and unusual warnings, or you have some architecture with problems, 168 you may need to disable this config option in order to 169 successfully build the kernel. 170 171 If in doubt, say Y. 172 173config UAPI_HEADER_TEST 174 bool "Compile test UAPI headers" 175 depends on HEADERS_INSTALL && CC_CAN_LINK 176 help 177 Compile test headers exported to user-space to ensure they are 178 self-contained, i.e. compilable as standalone units. 179 180 If you are a developer or tester and want to ensure the exported 181 headers are self-contained, say Y here. Otherwise, choose N. 182 183config LOCALVERSION 184 string "Local version - append to kernel release" 185 help 186 Append an extra string to the end of your kernel version. 187 This will show up when you type uname, for example. 188 The string you set here will be appended after the contents of 189 any files with a filename matching localversion* in your 190 object and source tree, in that order. Your total string can 191 be a maximum of 64 characters. 192 193config LOCALVERSION_AUTO 194 bool "Automatically append version information to the version string" 195 default y 196 depends on !COMPILE_TEST 197 help 198 This will try to automatically determine if the current tree is a 199 release tree by looking for git tags that belong to the current 200 top of tree revision. 201 202 A string of the format -gxxxxxxxx will be added to the localversion 203 if a git-based tree is found. The string generated by this will be 204 appended after any matching localversion* files, and after the value 205 set in CONFIG_LOCALVERSION. 206 207 (The actual string used here is the first 12 characters produced 208 by running the command: 209 210 $ git rev-parse --verify HEAD 211 212 which is done within the script "scripts/setlocalversion".) 213 214config BUILD_SALT 215 string "Build ID Salt" 216 default "" 217 help 218 The build ID is used to link binaries and their debug info. Setting 219 this option will use the value in the calculation of the build id. 220 This is mostly useful for distributions which want to ensure the 221 build is unique between builds. It's safe to leave the default. 222 223config HAVE_KERNEL_GZIP 224 bool 225 226config HAVE_KERNEL_BZIP2 227 bool 228 229config HAVE_KERNEL_LZMA 230 bool 231 232config HAVE_KERNEL_XZ 233 bool 234 235config HAVE_KERNEL_LZO 236 bool 237 238config HAVE_KERNEL_LZ4 239 bool 240 241config HAVE_KERNEL_ZSTD 242 bool 243 244config HAVE_KERNEL_UNCOMPRESSED 245 bool 246 247choice 248 prompt "Kernel compression mode" 249 default KERNEL_GZIP 250 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_ZSTD || HAVE_KERNEL_UNCOMPRESSED 251 help 252 The linux kernel is a kind of self-extracting executable. 253 Several compression algorithms are available, which differ 254 in efficiency, compression and decompression speed. 255 Compression speed is only relevant when building a kernel. 256 Decompression speed is relevant at each boot. 257 258 If you have any problems with bzip2 or lzma compressed 259 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 260 version of this functionality (bzip2 only), for 2.4, was 261 supplied by Christian Ludwig) 262 263 High compression options are mostly useful for users, who 264 are low on disk space (embedded systems), but for whom ram 265 size matters less. 266 267 If in doubt, select 'gzip' 268 269config KERNEL_GZIP 270 bool "Gzip" 271 depends on HAVE_KERNEL_GZIP 272 help 273 The old and tried gzip compression. It provides a good balance 274 between compression ratio and decompression speed. 275 276config KERNEL_BZIP2 277 bool "Bzip2" 278 depends on HAVE_KERNEL_BZIP2 279 help 280 Its compression ratio and speed is intermediate. 281 Decompression speed is slowest among the choices. The kernel 282 size is about 10% smaller with bzip2, in comparison to gzip. 283 Bzip2 uses a large amount of memory. For modern kernels you 284 will need at least 8MB RAM or more for booting. 285 286config KERNEL_LZMA 287 bool "LZMA" 288 depends on HAVE_KERNEL_LZMA 289 help 290 This compression algorithm's ratio is best. Decompression speed 291 is between gzip and bzip2. Compression is slowest. 292 The kernel size is about 33% smaller with LZMA in comparison to gzip. 293 294config KERNEL_XZ 295 bool "XZ" 296 depends on HAVE_KERNEL_XZ 297 help 298 XZ uses the LZMA2 algorithm and instruction set specific 299 BCJ filters which can improve compression ratio of executable 300 code. The size of the kernel is about 30% smaller with XZ in 301 comparison to gzip. On architectures for which there is a BCJ 302 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 303 will create a few percent smaller kernel than plain LZMA. 304 305 The speed is about the same as with LZMA: The decompression 306 speed of XZ is better than that of bzip2 but worse than gzip 307 and LZO. Compression is slow. 308 309config KERNEL_LZO 310 bool "LZO" 311 depends on HAVE_KERNEL_LZO 312 help 313 Its compression ratio is the poorest among the choices. The kernel 314 size is about 10% bigger than gzip; however its speed 315 (both compression and decompression) is the fastest. 316 317config KERNEL_LZ4 318 bool "LZ4" 319 depends on HAVE_KERNEL_LZ4 320 help 321 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 322 A preliminary version of LZ4 de/compression tool is available at 323 <https://code.google.com/p/lz4/>. 324 325 Its compression ratio is worse than LZO. The size of the kernel 326 is about 8% bigger than LZO. But the decompression speed is 327 faster than LZO. 328 329config KERNEL_ZSTD 330 bool "ZSTD" 331 depends on HAVE_KERNEL_ZSTD 332 help 333 ZSTD is a compression algorithm targeting intermediate compression 334 with fast decompression speed. It will compress better than GZIP and 335 decompress around the same speed as LZO, but slower than LZ4. You 336 will need at least 192 KB RAM or more for booting. The zstd command 337 line tool is required for compression. 338 339config KERNEL_UNCOMPRESSED 340 bool "None" 341 depends on HAVE_KERNEL_UNCOMPRESSED 342 help 343 Produce uncompressed kernel image. This option is usually not what 344 you want. It is useful for debugging the kernel in slow simulation 345 environments, where decompressing and moving the kernel is awfully 346 slow. This option allows early boot code to skip the decompressor 347 and jump right at uncompressed kernel image. 348 349endchoice 350 351config DEFAULT_INIT 352 string "Default init path" 353 default "" 354 help 355 This option determines the default init for the system if no init= 356 option is passed on the kernel command line. If the requested path is 357 not present, we will still then move on to attempting further 358 locations (e.g. /sbin/init, etc). If this is empty, we will just use 359 the fallback list when init= is not passed. 360 361config DEFAULT_HOSTNAME 362 string "Default hostname" 363 default "(none)" 364 help 365 This option determines the default system hostname before userspace 366 calls sethostname(2). The kernel traditionally uses "(none)" here, 367 but you may wish to use a different default here to make a minimal 368 system more usable with less configuration. 369 370config SYSVIPC 371 bool "System V IPC" 372 help 373 Inter Process Communication is a suite of library functions and 374 system calls which let processes (running programs) synchronize and 375 exchange information. It is generally considered to be a good thing, 376 and some programs won't run unless you say Y here. In particular, if 377 you want to run the DOS emulator dosemu under Linux (read the 378 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 379 you'll need to say Y here. 380 381 You can find documentation about IPC with "info ipc" and also in 382 section 6.4 of the Linux Programmer's Guide, available from 383 <http://www.tldp.org/guides.html>. 384 385config SYSVIPC_SYSCTL 386 bool 387 depends on SYSVIPC 388 depends on SYSCTL 389 default y 390 391config SYSVIPC_COMPAT 392 def_bool y 393 depends on COMPAT && SYSVIPC 394 395config POSIX_MQUEUE 396 bool "POSIX Message Queues" 397 depends on NET 398 help 399 POSIX variant of message queues is a part of IPC. In POSIX message 400 queues every message has a priority which decides about succession 401 of receiving it by a process. If you want to compile and run 402 programs written e.g. for Solaris with use of its POSIX message 403 queues (functions mq_*) say Y here. 404 405 POSIX message queues are visible as a filesystem called 'mqueue' 406 and can be mounted somewhere if you want to do filesystem 407 operations on message queues. 408 409 If unsure, say Y. 410 411config POSIX_MQUEUE_SYSCTL 412 bool 413 depends on POSIX_MQUEUE 414 depends on SYSCTL 415 default y 416 417config WATCH_QUEUE 418 bool "General notification queue" 419 default n 420 help 421 422 This is a general notification queue for the kernel to pass events to 423 userspace by splicing them into pipes. It can be used in conjunction 424 with watches for key/keyring change notifications and device 425 notifications. 426 427 See Documentation/core-api/watch_queue.rst 428 429config CROSS_MEMORY_ATTACH 430 bool "Enable process_vm_readv/writev syscalls" 431 depends on MMU 432 default y 433 help 434 Enabling this option adds the system calls process_vm_readv and 435 process_vm_writev which allow a process with the correct privileges 436 to directly read from or write to another process' address space. 437 See the man page for more details. 438 439config USELIB 440 bool "uselib syscall (for libc5 and earlier)" 441 default ALPHA || M68K || SPARC 442 help 443 This option enables the uselib syscall, a system call used in the 444 dynamic linker from libc5 and earlier. glibc does not use this 445 system call. If you intend to run programs built on libc5 or 446 earlier, you may need to enable this syscall. Current systems 447 running glibc can safely disable this. 448 449config AUDIT 450 bool "Auditing support" 451 depends on NET 452 help 453 Enable auditing infrastructure that can be used with another 454 kernel subsystem, such as SELinux (which requires this for 455 logging of avc messages output). System call auditing is included 456 on architectures which support it. 457 458config HAVE_ARCH_AUDITSYSCALL 459 bool 460 461config AUDITSYSCALL 462 def_bool y 463 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 464 select FSNOTIFY 465 466source "kernel/irq/Kconfig" 467source "kernel/time/Kconfig" 468source "kernel/bpf/Kconfig" 469source "kernel/Kconfig.preempt" 470 471menu "CPU/Task time and stats accounting" 472 473config VIRT_CPU_ACCOUNTING 474 bool 475 476choice 477 prompt "Cputime accounting" 478 default TICK_CPU_ACCOUNTING 479 480# Kind of a stub config for the pure tick based cputime accounting 481config TICK_CPU_ACCOUNTING 482 bool "Simple tick based cputime accounting" 483 depends on !S390 && !NO_HZ_FULL 484 help 485 This is the basic tick based cputime accounting that maintains 486 statistics about user, system and idle time spent on per jiffies 487 granularity. 488 489 If unsure, say Y. 490 491config VIRT_CPU_ACCOUNTING_NATIVE 492 bool "Deterministic task and CPU time accounting" 493 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 494 select VIRT_CPU_ACCOUNTING 495 help 496 Select this option to enable more accurate task and CPU time 497 accounting. This is done by reading a CPU counter on each 498 kernel entry and exit and on transitions within the kernel 499 between system, softirq and hardirq state, so there is a 500 small performance impact. In the case of s390 or IBM POWER > 5, 501 this also enables accounting of stolen time on logically-partitioned 502 systems. 503 504config VIRT_CPU_ACCOUNTING_GEN 505 bool "Full dynticks CPU time accounting" 506 depends on HAVE_CONTEXT_TRACKING_USER 507 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 508 depends on GENERIC_CLOCKEVENTS 509 select VIRT_CPU_ACCOUNTING 510 select CONTEXT_TRACKING_USER 511 help 512 Select this option to enable task and CPU time accounting on full 513 dynticks systems. This accounting is implemented by watching every 514 kernel-user boundaries using the context tracking subsystem. 515 The accounting is thus performed at the expense of some significant 516 overhead. 517 518 For now this is only useful if you are working on the full 519 dynticks subsystem development. 520 521 If unsure, say N. 522 523endchoice 524 525config IRQ_TIME_ACCOUNTING 526 bool "Fine granularity task level IRQ time accounting" 527 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 528 help 529 Select this option to enable fine granularity task irq time 530 accounting. This is done by reading a timestamp on each 531 transitions between softirq and hardirq state, so there can be a 532 small performance impact. 533 534 If in doubt, say N here. 535 536config HAVE_SCHED_AVG_IRQ 537 def_bool y 538 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 539 depends on SMP 540 541config SCHED_THERMAL_PRESSURE 542 bool 543 default y if ARM && ARM_CPU_TOPOLOGY 544 default y if ARM64 545 depends on SMP 546 depends on CPU_FREQ_THERMAL 547 help 548 Select this option to enable thermal pressure accounting in the 549 scheduler. Thermal pressure is the value conveyed to the scheduler 550 that reflects the reduction in CPU compute capacity resulted from 551 thermal throttling. Thermal throttling occurs when the performance of 552 a CPU is capped due to high operating temperatures. 553 554 If selected, the scheduler will be able to balance tasks accordingly, 555 i.e. put less load on throttled CPUs than on non/less throttled ones. 556 557 This requires the architecture to implement 558 arch_update_thermal_pressure() and arch_scale_thermal_pressure(). 559 560config BSD_PROCESS_ACCT 561 bool "BSD Process Accounting" 562 depends on MULTIUSER 563 help 564 If you say Y here, a user level program will be able to instruct the 565 kernel (via a special system call) to write process accounting 566 information to a file: whenever a process exits, information about 567 that process will be appended to the file by the kernel. The 568 information includes things such as creation time, owning user, 569 command name, memory usage, controlling terminal etc. (the complete 570 list is in the struct acct in <file:include/linux/acct.h>). It is 571 up to the user level program to do useful things with this 572 information. This is generally a good idea, so say Y. 573 574config BSD_PROCESS_ACCT_V3 575 bool "BSD Process Accounting version 3 file format" 576 depends on BSD_PROCESS_ACCT 577 default n 578 help 579 If you say Y here, the process accounting information is written 580 in a new file format that also logs the process IDs of each 581 process and its parent. Note that this file format is incompatible 582 with previous v0/v1/v2 file formats, so you will need updated tools 583 for processing it. A preliminary version of these tools is available 584 at <http://www.gnu.org/software/acct/>. 585 586config TASKSTATS 587 bool "Export task/process statistics through netlink" 588 depends on NET 589 depends on MULTIUSER 590 default n 591 help 592 Export selected statistics for tasks/processes through the 593 generic netlink interface. Unlike BSD process accounting, the 594 statistics are available during the lifetime of tasks/processes as 595 responses to commands. Like BSD accounting, they are sent to user 596 space on task exit. 597 598 Say N if unsure. 599 600config TASK_DELAY_ACCT 601 bool "Enable per-task delay accounting" 602 depends on TASKSTATS 603 select SCHED_INFO 604 help 605 Collect information on time spent by a task waiting for system 606 resources like cpu, synchronous block I/O completion and swapping 607 in pages. Such statistics can help in setting a task's priorities 608 relative to other tasks for cpu, io, rss limits etc. 609 610 Say N if unsure. 611 612config TASK_XACCT 613 bool "Enable extended accounting over taskstats" 614 depends on TASKSTATS 615 help 616 Collect extended task accounting data and send the data 617 to userland for processing over the taskstats interface. 618 619 Say N if unsure. 620 621config TASK_IO_ACCOUNTING 622 bool "Enable per-task storage I/O accounting" 623 depends on TASK_XACCT 624 help 625 Collect information on the number of bytes of storage I/O which this 626 task has caused. 627 628 Say N if unsure. 629 630config PSI 631 bool "Pressure stall information tracking" 632 help 633 Collect metrics that indicate how overcommitted the CPU, memory, 634 and IO capacity are in the system. 635 636 If you say Y here, the kernel will create /proc/pressure/ with the 637 pressure statistics files cpu, memory, and io. These will indicate 638 the share of walltime in which some or all tasks in the system are 639 delayed due to contention of the respective resource. 640 641 In kernels with cgroup support, cgroups (cgroup2 only) will 642 have cpu.pressure, memory.pressure, and io.pressure files, 643 which aggregate pressure stalls for the grouped tasks only. 644 645 For more details see Documentation/accounting/psi.rst. 646 647 Say N if unsure. 648 649config PSI_DEFAULT_DISABLED 650 bool "Require boot parameter to enable pressure stall information tracking" 651 default n 652 depends on PSI 653 help 654 If set, pressure stall information tracking will be disabled 655 per default but can be enabled through passing psi=1 on the 656 kernel commandline during boot. 657 658 This feature adds some code to the task wakeup and sleep 659 paths of the scheduler. The overhead is too low to affect 660 common scheduling-intense workloads in practice (such as 661 webservers, memcache), but it does show up in artificial 662 scheduler stress tests, such as hackbench. 663 664 If you are paranoid and not sure what the kernel will be 665 used for, say Y. 666 667 Say N if unsure. 668 669endmenu # "CPU/Task time and stats accounting" 670 671config CPU_ISOLATION 672 bool "CPU isolation" 673 depends on SMP || COMPILE_TEST 674 default y 675 help 676 Make sure that CPUs running critical tasks are not disturbed by 677 any source of "noise" such as unbound workqueues, timers, kthreads... 678 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 679 the "isolcpus=" boot parameter. 680 681 Say Y if unsure. 682 683source "kernel/rcu/Kconfig" 684 685config IKCONFIG 686 tristate "Kernel .config support" 687 help 688 This option enables the complete Linux kernel ".config" file 689 contents to be saved in the kernel. It provides documentation 690 of which kernel options are used in a running kernel or in an 691 on-disk kernel. This information can be extracted from the kernel 692 image file with the script scripts/extract-ikconfig and used as 693 input to rebuild the current kernel or to build another kernel. 694 It can also be extracted from a running kernel by reading 695 /proc/config.gz if enabled (below). 696 697config IKCONFIG_PROC 698 bool "Enable access to .config through /proc/config.gz" 699 depends on IKCONFIG && PROC_FS 700 help 701 This option enables access to the kernel configuration file 702 through /proc/config.gz. 703 704config IKHEADERS 705 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 706 depends on SYSFS 707 help 708 This option enables access to the in-kernel headers that are generated during 709 the build process. These can be used to build eBPF tracing programs, 710 or similar programs. If you build the headers as a module, a module called 711 kheaders.ko is built which can be loaded on-demand to get access to headers. 712 713config LOG_BUF_SHIFT 714 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 715 range 12 25 716 default 17 717 depends on PRINTK 718 help 719 Select the minimal kernel log buffer size as a power of 2. 720 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 721 parameter, see below. Any higher size also might be forced 722 by "log_buf_len" boot parameter. 723 724 Examples: 725 17 => 128 KB 726 16 => 64 KB 727 15 => 32 KB 728 14 => 16 KB 729 13 => 8 KB 730 12 => 4 KB 731 732config LOG_CPU_MAX_BUF_SHIFT 733 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 734 depends on SMP 735 range 0 21 736 default 12 if !BASE_SMALL 737 default 0 if BASE_SMALL 738 depends on PRINTK 739 help 740 This option allows to increase the default ring buffer size 741 according to the number of CPUs. The value defines the contribution 742 of each CPU as a power of 2. The used space is typically only few 743 lines however it might be much more when problems are reported, 744 e.g. backtraces. 745 746 The increased size means that a new buffer has to be allocated and 747 the original static one is unused. It makes sense only on systems 748 with more CPUs. Therefore this value is used only when the sum of 749 contributions is greater than the half of the default kernel ring 750 buffer as defined by LOG_BUF_SHIFT. The default values are set 751 so that more than 16 CPUs are needed to trigger the allocation. 752 753 Also this option is ignored when "log_buf_len" kernel parameter is 754 used as it forces an exact (power of two) size of the ring buffer. 755 756 The number of possible CPUs is used for this computation ignoring 757 hotplugging making the computation optimal for the worst case 758 scenario while allowing a simple algorithm to be used from bootup. 759 760 Examples shift values and their meaning: 761 17 => 128 KB for each CPU 762 16 => 64 KB for each CPU 763 15 => 32 KB for each CPU 764 14 => 16 KB for each CPU 765 13 => 8 KB for each CPU 766 12 => 4 KB for each CPU 767 768config PRINTK_INDEX 769 bool "Printk indexing debugfs interface" 770 depends on PRINTK && DEBUG_FS 771 help 772 Add support for indexing of all printk formats known at compile time 773 at <debugfs>/printk/index/<module>. 774 775 This can be used as part of maintaining daemons which monitor 776 /dev/kmsg, as it permits auditing the printk formats present in a 777 kernel, allowing detection of cases where monitored printks are 778 changed or no longer present. 779 780 There is no additional runtime cost to printk with this enabled. 781 782# 783# Architectures with an unreliable sched_clock() should select this: 784# 785config HAVE_UNSTABLE_SCHED_CLOCK 786 bool 787 788config GENERIC_SCHED_CLOCK 789 bool 790 791menu "Scheduler features" 792 793config UCLAMP_TASK 794 bool "Enable utilization clamping for RT/FAIR tasks" 795 depends on CPU_FREQ_GOV_SCHEDUTIL 796 help 797 This feature enables the scheduler to track the clamped utilization 798 of each CPU based on RUNNABLE tasks scheduled on that CPU. 799 800 With this option, the user can specify the min and max CPU 801 utilization allowed for RUNNABLE tasks. The max utilization defines 802 the maximum frequency a task should use while the min utilization 803 defines the minimum frequency it should use. 804 805 Both min and max utilization clamp values are hints to the scheduler, 806 aiming at improving its frequency selection policy, but they do not 807 enforce or grant any specific bandwidth for tasks. 808 809 If in doubt, say N. 810 811config UCLAMP_BUCKETS_COUNT 812 int "Number of supported utilization clamp buckets" 813 range 5 20 814 default 5 815 depends on UCLAMP_TASK 816 help 817 Defines the number of clamp buckets to use. The range of each bucket 818 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 819 number of clamp buckets the finer their granularity and the higher 820 the precision of clamping aggregation and tracking at run-time. 821 822 For example, with the minimum configuration value we will have 5 823 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 824 be refcounted in the [20..39]% bucket and will set the bucket clamp 825 effective value to 25%. 826 If a second 30% boosted task should be co-scheduled on the same CPU, 827 that task will be refcounted in the same bucket of the first task and 828 it will boost the bucket clamp effective value to 30%. 829 The clamp effective value of a bucket is reset to its nominal value 830 (20% in the example above) when there are no more tasks refcounted in 831 that bucket. 832 833 An additional boost/capping margin can be added to some tasks. In the 834 example above the 25% task will be boosted to 30% until it exits the 835 CPU. If that should be considered not acceptable on certain systems, 836 it's always possible to reduce the margin by increasing the number of 837 clamp buckets to trade off used memory for run-time tracking 838 precision. 839 840 If in doubt, use the default value. 841 842endmenu 843 844# 845# For architectures that want to enable the support for NUMA-affine scheduler 846# balancing logic: 847# 848config ARCH_SUPPORTS_NUMA_BALANCING 849 bool 850 851# 852# For architectures that prefer to flush all TLBs after a number of pages 853# are unmapped instead of sending one IPI per page to flush. The architecture 854# must provide guarantees on what happens if a clean TLB cache entry is 855# written after the unmap. Details are in mm/rmap.c near the check for 856# should_defer_flush. The architecture should also consider if the full flush 857# and the refill costs are offset by the savings of sending fewer IPIs. 858config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 859 bool 860 861config CC_HAS_INT128 862 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 863 864config CC_IMPLICIT_FALLTHROUGH 865 string 866 default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5) 867 default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough) 868 869# Currently, disable gcc-11+ array-bounds globally. 870# It's still broken in gcc-13, so no upper bound yet. 871config GCC11_NO_ARRAY_BOUNDS 872 def_bool y 873 874config CC_NO_ARRAY_BOUNDS 875 bool 876 default y if CC_IS_GCC && GCC_VERSION >= 110000 && GCC11_NO_ARRAY_BOUNDS 877 878# 879# For architectures that know their GCC __int128 support is sound 880# 881config ARCH_SUPPORTS_INT128 882 bool 883 884# For architectures that (ab)use NUMA to represent different memory regions 885# all cpu-local but of different latencies, such as SuperH. 886# 887config ARCH_WANT_NUMA_VARIABLE_LOCALITY 888 bool 889 890config NUMA_BALANCING 891 bool "Memory placement aware NUMA scheduler" 892 depends on ARCH_SUPPORTS_NUMA_BALANCING 893 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 894 depends on SMP && NUMA && MIGRATION && !PREEMPT_RT 895 help 896 This option adds support for automatic NUMA aware memory/task placement. 897 The mechanism is quite primitive and is based on migrating memory when 898 it has references to the node the task is running on. 899 900 This system will be inactive on UMA systems. 901 902config NUMA_BALANCING_DEFAULT_ENABLED 903 bool "Automatically enable NUMA aware memory/task placement" 904 default y 905 depends on NUMA_BALANCING 906 help 907 If set, automatic NUMA balancing will be enabled if running on a NUMA 908 machine. 909 910menuconfig CGROUPS 911 bool "Control Group support" 912 select KERNFS 913 help 914 This option adds support for grouping sets of processes together, for 915 use with process control subsystems such as Cpusets, CFS, memory 916 controls or device isolation. 917 See 918 - Documentation/scheduler/sched-design-CFS.rst (CFS) 919 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 920 and resource control) 921 922 Say N if unsure. 923 924if CGROUPS 925 926config PAGE_COUNTER 927 bool 928 929config CGROUP_FAVOR_DYNMODS 930 bool "Favor dynamic modification latency reduction by default" 931 help 932 This option enables the "favordynmods" mount option by default 933 which reduces the latencies of dynamic cgroup modifications such 934 as task migrations and controller on/offs at the cost of making 935 hot path operations such as forks and exits more expensive. 936 937 Say N if unsure. 938 939config MEMCG 940 bool "Memory controller" 941 select PAGE_COUNTER 942 select EVENTFD 943 help 944 Provides control over the memory footprint of tasks in a cgroup. 945 946config MEMCG_KMEM 947 bool 948 depends on MEMCG 949 default y 950 951config BLK_CGROUP 952 bool "IO controller" 953 depends on BLOCK 954 default n 955 help 956 Generic block IO controller cgroup interface. This is the common 957 cgroup interface which should be used by various IO controlling 958 policies. 959 960 Currently, CFQ IO scheduler uses it to recognize task groups and 961 control disk bandwidth allocation (proportional time slice allocation) 962 to such task groups. It is also used by bio throttling logic in 963 block layer to implement upper limit in IO rates on a device. 964 965 This option only enables generic Block IO controller infrastructure. 966 One needs to also enable actual IO controlling logic/policy. For 967 enabling proportional weight division of disk bandwidth in CFQ, set 968 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 969 CONFIG_BLK_DEV_THROTTLING=y. 970 971 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 972 973config CGROUP_WRITEBACK 974 bool 975 depends on MEMCG && BLK_CGROUP 976 default y 977 978menuconfig CGROUP_SCHED 979 bool "CPU controller" 980 default n 981 help 982 This feature lets CPU scheduler recognize task groups and control CPU 983 bandwidth allocation to such task groups. It uses cgroups to group 984 tasks. 985 986if CGROUP_SCHED 987config FAIR_GROUP_SCHED 988 bool "Group scheduling for SCHED_OTHER" 989 depends on CGROUP_SCHED 990 default CGROUP_SCHED 991 992config CFS_BANDWIDTH 993 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 994 depends on FAIR_GROUP_SCHED 995 default n 996 help 997 This option allows users to define CPU bandwidth rates (limits) for 998 tasks running within the fair group scheduler. Groups with no limit 999 set are considered to be unconstrained and will run with no 1000 restriction. 1001 See Documentation/scheduler/sched-bwc.rst for more information. 1002 1003config RT_GROUP_SCHED 1004 bool "Group scheduling for SCHED_RR/FIFO" 1005 depends on CGROUP_SCHED 1006 default n 1007 help 1008 This feature lets you explicitly allocate real CPU bandwidth 1009 to task groups. If enabled, it will also make it impossible to 1010 schedule realtime tasks for non-root users until you allocate 1011 realtime bandwidth for them. 1012 See Documentation/scheduler/sched-rt-group.rst for more information. 1013 1014endif #CGROUP_SCHED 1015 1016config SCHED_MM_CID 1017 def_bool y 1018 depends on SMP && RSEQ 1019 1020config UCLAMP_TASK_GROUP 1021 bool "Utilization clamping per group of tasks" 1022 depends on CGROUP_SCHED 1023 depends on UCLAMP_TASK 1024 default n 1025 help 1026 This feature enables the scheduler to track the clamped utilization 1027 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 1028 1029 When this option is enabled, the user can specify a min and max 1030 CPU bandwidth which is allowed for each single task in a group. 1031 The max bandwidth allows to clamp the maximum frequency a task 1032 can use, while the min bandwidth allows to define a minimum 1033 frequency a task will always use. 1034 1035 When task group based utilization clamping is enabled, an eventually 1036 specified task-specific clamp value is constrained by the cgroup 1037 specified clamp value. Both minimum and maximum task clamping cannot 1038 be bigger than the corresponding clamping defined at task group level. 1039 1040 If in doubt, say N. 1041 1042config CGROUP_PIDS 1043 bool "PIDs controller" 1044 help 1045 Provides enforcement of process number limits in the scope of a 1046 cgroup. Any attempt to fork more processes than is allowed in the 1047 cgroup will fail. PIDs are fundamentally a global resource because it 1048 is fairly trivial to reach PID exhaustion before you reach even a 1049 conservative kmemcg limit. As a result, it is possible to grind a 1050 system to halt without being limited by other cgroup policies. The 1051 PIDs controller is designed to stop this from happening. 1052 1053 It should be noted that organisational operations (such as attaching 1054 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 1055 since the PIDs limit only affects a process's ability to fork, not to 1056 attach to a cgroup. 1057 1058config CGROUP_RDMA 1059 bool "RDMA controller" 1060 help 1061 Provides enforcement of RDMA resources defined by IB stack. 1062 It is fairly easy for consumers to exhaust RDMA resources, which 1063 can result into resource unavailability to other consumers. 1064 RDMA controller is designed to stop this from happening. 1065 Attaching processes with active RDMA resources to the cgroup 1066 hierarchy is allowed even if can cross the hierarchy's limit. 1067 1068config CGROUP_FREEZER 1069 bool "Freezer controller" 1070 help 1071 Provides a way to freeze and unfreeze all tasks in a 1072 cgroup. 1073 1074 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1075 controller includes important in-kernel memory consumers per default. 1076 1077 If you're using cgroup2, say N. 1078 1079config CGROUP_HUGETLB 1080 bool "HugeTLB controller" 1081 depends on HUGETLB_PAGE 1082 select PAGE_COUNTER 1083 default n 1084 help 1085 Provides a cgroup controller for HugeTLB pages. 1086 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1087 The limit is enforced during page fault. Since HugeTLB doesn't 1088 support page reclaim, enforcing the limit at page fault time implies 1089 that, the application will get SIGBUS signal if it tries to access 1090 HugeTLB pages beyond its limit. This requires the application to know 1091 beforehand how much HugeTLB pages it would require for its use. The 1092 control group is tracked in the third page lru pointer. This means 1093 that we cannot use the controller with huge page less than 3 pages. 1094 1095config CPUSETS 1096 bool "Cpuset controller" 1097 depends on SMP 1098 help 1099 This option will let you create and manage CPUSETs which 1100 allow dynamically partitioning a system into sets of CPUs and 1101 Memory Nodes and assigning tasks to run only within those sets. 1102 This is primarily useful on large SMP or NUMA systems. 1103 1104 Say N if unsure. 1105 1106config PROC_PID_CPUSET 1107 bool "Include legacy /proc/<pid>/cpuset file" 1108 depends on CPUSETS 1109 default y 1110 1111config CGROUP_DEVICE 1112 bool "Device controller" 1113 help 1114 Provides a cgroup controller implementing whitelists for 1115 devices which a process in the cgroup can mknod or open. 1116 1117config CGROUP_CPUACCT 1118 bool "Simple CPU accounting controller" 1119 help 1120 Provides a simple controller for monitoring the 1121 total CPU consumed by the tasks in a cgroup. 1122 1123config CGROUP_PERF 1124 bool "Perf controller" 1125 depends on PERF_EVENTS 1126 help 1127 This option extends the perf per-cpu mode to restrict monitoring 1128 to threads which belong to the cgroup specified and run on the 1129 designated cpu. Or this can be used to have cgroup ID in samples 1130 so that it can monitor performance events among cgroups. 1131 1132 Say N if unsure. 1133 1134config CGROUP_BPF 1135 bool "Support for eBPF programs attached to cgroups" 1136 depends on BPF_SYSCALL 1137 select SOCK_CGROUP_DATA 1138 help 1139 Allow attaching eBPF programs to a cgroup using the bpf(2) 1140 syscall command BPF_PROG_ATTACH. 1141 1142 In which context these programs are accessed depends on the type 1143 of attachment. For instance, programs that are attached using 1144 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1145 inet sockets. 1146 1147config CGROUP_MISC 1148 bool "Misc resource controller" 1149 default n 1150 help 1151 Provides a controller for miscellaneous resources on a host. 1152 1153 Miscellaneous scalar resources are the resources on the host system 1154 which cannot be abstracted like the other cgroups. This controller 1155 tracks and limits the miscellaneous resources used by a process 1156 attached to a cgroup hierarchy. 1157 1158 For more information, please check misc cgroup section in 1159 /Documentation/admin-guide/cgroup-v2.rst. 1160 1161config CGROUP_DEBUG 1162 bool "Debug controller" 1163 default n 1164 depends on DEBUG_KERNEL 1165 help 1166 This option enables a simple controller that exports 1167 debugging information about the cgroups framework. This 1168 controller is for control cgroup debugging only. Its 1169 interfaces are not stable. 1170 1171 Say N. 1172 1173config SOCK_CGROUP_DATA 1174 bool 1175 default n 1176 1177endif # CGROUPS 1178 1179menuconfig NAMESPACES 1180 bool "Namespaces support" if EXPERT 1181 depends on MULTIUSER 1182 default !EXPERT 1183 help 1184 Provides the way to make tasks work with different objects using 1185 the same id. For example same IPC id may refer to different objects 1186 or same user id or pid may refer to different tasks when used in 1187 different namespaces. 1188 1189if NAMESPACES 1190 1191config UTS_NS 1192 bool "UTS namespace" 1193 default y 1194 help 1195 In this namespace tasks see different info provided with the 1196 uname() system call 1197 1198config TIME_NS 1199 bool "TIME namespace" 1200 depends on GENERIC_VDSO_TIME_NS 1201 default y 1202 help 1203 In this namespace boottime and monotonic clocks can be set. 1204 The time will keep going with the same pace. 1205 1206config IPC_NS 1207 bool "IPC namespace" 1208 depends on (SYSVIPC || POSIX_MQUEUE) 1209 default y 1210 help 1211 In this namespace tasks work with IPC ids which correspond to 1212 different IPC objects in different namespaces. 1213 1214config USER_NS 1215 bool "User namespace" 1216 default n 1217 help 1218 This allows containers, i.e. vservers, to use user namespaces 1219 to provide different user info for different servers. 1220 1221 When user namespaces are enabled in the kernel it is 1222 recommended that the MEMCG option also be enabled and that 1223 user-space use the memory control groups to limit the amount 1224 of memory a memory unprivileged users can use. 1225 1226 If unsure, say N. 1227 1228config PID_NS 1229 bool "PID Namespaces" 1230 default y 1231 help 1232 Support process id namespaces. This allows having multiple 1233 processes with the same pid as long as they are in different 1234 pid namespaces. This is a building block of containers. 1235 1236config NET_NS 1237 bool "Network namespace" 1238 depends on NET 1239 default y 1240 help 1241 Allow user space to create what appear to be multiple instances 1242 of the network stack. 1243 1244endif # NAMESPACES 1245 1246config CHECKPOINT_RESTORE 1247 bool "Checkpoint/restore support" 1248 depends on PROC_FS 1249 select PROC_CHILDREN 1250 select KCMP 1251 default n 1252 help 1253 Enables additional kernel features in a sake of checkpoint/restore. 1254 In particular it adds auxiliary prctl codes to setup process text, 1255 data and heap segment sizes, and a few additional /proc filesystem 1256 entries. 1257 1258 If unsure, say N here. 1259 1260config SCHED_AUTOGROUP 1261 bool "Automatic process group scheduling" 1262 select CGROUPS 1263 select CGROUP_SCHED 1264 select FAIR_GROUP_SCHED 1265 help 1266 This option optimizes the scheduler for common desktop workloads by 1267 automatically creating and populating task groups. This separation 1268 of workloads isolates aggressive CPU burners (like build jobs) from 1269 desktop applications. Task group autogeneration is currently based 1270 upon task session. 1271 1272config RELAY 1273 bool "Kernel->user space relay support (formerly relayfs)" 1274 select IRQ_WORK 1275 help 1276 This option enables support for relay interface support in 1277 certain file systems (such as debugfs). 1278 It is designed to provide an efficient mechanism for tools and 1279 facilities to relay large amounts of data from kernel space to 1280 user space. 1281 1282 If unsure, say N. 1283 1284config BLK_DEV_INITRD 1285 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1286 help 1287 The initial RAM filesystem is a ramfs which is loaded by the 1288 boot loader (loadlin or lilo) and that is mounted as root 1289 before the normal boot procedure. It is typically used to 1290 load modules needed to mount the "real" root file system, 1291 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1292 1293 If RAM disk support (BLK_DEV_RAM) is also included, this 1294 also enables initial RAM disk (initrd) support and adds 1295 15 Kbytes (more on some other architectures) to the kernel size. 1296 1297 If unsure say Y. 1298 1299if BLK_DEV_INITRD 1300 1301source "usr/Kconfig" 1302 1303endif 1304 1305config BOOT_CONFIG 1306 bool "Boot config support" 1307 select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED 1308 help 1309 Extra boot config allows system admin to pass a config file as 1310 complemental extension of kernel cmdline when booting. 1311 The boot config file must be attached at the end of initramfs 1312 with checksum, size and magic word. 1313 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1314 1315 If unsure, say Y. 1316 1317config BOOT_CONFIG_FORCE 1318 bool "Force unconditional bootconfig processing" 1319 depends on BOOT_CONFIG 1320 default y if BOOT_CONFIG_EMBED 1321 help 1322 With this Kconfig option set, BOOT_CONFIG processing is carried 1323 out even when the "bootconfig" kernel-boot parameter is omitted. 1324 In fact, with this Kconfig option set, there is no way to 1325 make the kernel ignore the BOOT_CONFIG-supplied kernel-boot 1326 parameters. 1327 1328 If unsure, say N. 1329 1330config BOOT_CONFIG_EMBED 1331 bool "Embed bootconfig file in the kernel" 1332 depends on BOOT_CONFIG 1333 help 1334 Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the 1335 kernel. Usually, the bootconfig file is loaded with the initrd 1336 image. But if the system doesn't support initrd, this option will 1337 help you by embedding a bootconfig file while building the kernel. 1338 1339 If unsure, say N. 1340 1341config BOOT_CONFIG_EMBED_FILE 1342 string "Embedded bootconfig file path" 1343 depends on BOOT_CONFIG_EMBED 1344 help 1345 Specify a bootconfig file which will be embedded to the kernel. 1346 This bootconfig will be used if there is no initrd or no other 1347 bootconfig in the initrd. 1348 1349config INITRAMFS_PRESERVE_MTIME 1350 bool "Preserve cpio archive mtimes in initramfs" 1351 default y 1352 help 1353 Each entry in an initramfs cpio archive carries an mtime value. When 1354 enabled, extracted cpio items take this mtime, with directory mtime 1355 setting deferred until after creation of any child entries. 1356 1357 If unsure, say Y. 1358 1359choice 1360 prompt "Compiler optimization level" 1361 default CC_OPTIMIZE_FOR_PERFORMANCE 1362 1363config CC_OPTIMIZE_FOR_PERFORMANCE 1364 bool "Optimize for performance (-O2)" 1365 help 1366 This is the default optimization level for the kernel, building 1367 with the "-O2" compiler flag for best performance and most 1368 helpful compile-time warnings. 1369 1370config CC_OPTIMIZE_FOR_SIZE 1371 bool "Optimize for size (-Os)" 1372 help 1373 Choosing this option will pass "-Os" to your compiler resulting 1374 in a smaller kernel. 1375 1376endchoice 1377 1378config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1379 bool 1380 help 1381 This requires that the arch annotates or otherwise protects 1382 its external entry points from being discarded. Linker scripts 1383 must also merge .text.*, .data.*, and .bss.* correctly into 1384 output sections. Care must be taken not to pull in unrelated 1385 sections (e.g., '.text.init'). Typically '.' in section names 1386 is used to distinguish them from label names / C identifiers. 1387 1388config LD_DEAD_CODE_DATA_ELIMINATION 1389 bool "Dead code and data elimination (EXPERIMENTAL)" 1390 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1391 depends on EXPERT 1392 depends on $(cc-option,-ffunction-sections -fdata-sections) 1393 depends on $(ld-option,--gc-sections) 1394 help 1395 Enable this if you want to do dead code and data elimination with 1396 the linker by compiling with -ffunction-sections -fdata-sections, 1397 and linking with --gc-sections. 1398 1399 This can reduce on disk and in-memory size of the kernel 1400 code and static data, particularly for small configs and 1401 on small systems. This has the possibility of introducing 1402 silently broken kernel if the required annotations are not 1403 present. This option is not well tested yet, so use at your 1404 own risk. 1405 1406config LD_ORPHAN_WARN 1407 def_bool y 1408 depends on ARCH_WANT_LD_ORPHAN_WARN 1409 depends on $(ld-option,--orphan-handling=warn) 1410 depends on $(ld-option,--orphan-handling=error) 1411 1412config LD_ORPHAN_WARN_LEVEL 1413 string 1414 depends on LD_ORPHAN_WARN 1415 default "error" if WERROR 1416 default "warn" 1417 1418config SYSCTL 1419 bool 1420 1421config HAVE_UID16 1422 bool 1423 1424config SYSCTL_EXCEPTION_TRACE 1425 bool 1426 help 1427 Enable support for /proc/sys/debug/exception-trace. 1428 1429config SYSCTL_ARCH_UNALIGN_NO_WARN 1430 bool 1431 help 1432 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1433 Allows arch to define/use @no_unaligned_warning to possibly warn 1434 about unaligned access emulation going on under the hood. 1435 1436config SYSCTL_ARCH_UNALIGN_ALLOW 1437 bool 1438 help 1439 Enable support for /proc/sys/kernel/unaligned-trap 1440 Allows arches to define/use @unaligned_enabled to runtime toggle 1441 the unaligned access emulation. 1442 see arch/parisc/kernel/unaligned.c for reference 1443 1444config HAVE_PCSPKR_PLATFORM 1445 bool 1446 1447# interpreter that classic socket filters depend on 1448config BPF 1449 bool 1450 select CRYPTO_LIB_SHA1 1451 1452menuconfig EXPERT 1453 bool "Configure standard kernel features (expert users)" 1454 # Unhide debug options, to make the on-by-default options visible 1455 select DEBUG_KERNEL 1456 help 1457 This option allows certain base kernel options and settings 1458 to be disabled or tweaked. This is for specialized 1459 environments which can tolerate a "non-standard" kernel. 1460 Only use this if you really know what you are doing. 1461 1462config UID16 1463 bool "Enable 16-bit UID system calls" if EXPERT 1464 depends on HAVE_UID16 && MULTIUSER 1465 default y 1466 help 1467 This enables the legacy 16-bit UID syscall wrappers. 1468 1469config MULTIUSER 1470 bool "Multiple users, groups and capabilities support" if EXPERT 1471 default y 1472 help 1473 This option enables support for non-root users, groups and 1474 capabilities. 1475 1476 If you say N here, all processes will run with UID 0, GID 0, and all 1477 possible capabilities. Saying N here also compiles out support for 1478 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1479 setgid, and capset. 1480 1481 If unsure, say Y here. 1482 1483config SGETMASK_SYSCALL 1484 bool "sgetmask/ssetmask syscalls support" if EXPERT 1485 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1486 help 1487 sys_sgetmask and sys_ssetmask are obsolete system calls 1488 no longer supported in libc but still enabled by default in some 1489 architectures. 1490 1491 If unsure, leave the default option here. 1492 1493config SYSFS_SYSCALL 1494 bool "Sysfs syscall support" if EXPERT 1495 default y 1496 help 1497 sys_sysfs is an obsolete system call no longer supported in libc. 1498 Note that disabling this option is more secure but might break 1499 compatibility with some systems. 1500 1501 If unsure say Y here. 1502 1503config FHANDLE 1504 bool "open by fhandle syscalls" if EXPERT 1505 select EXPORTFS 1506 default y 1507 help 1508 If you say Y here, a user level program will be able to map 1509 file names to handle and then later use the handle for 1510 different file system operations. This is useful in implementing 1511 userspace file servers, which now track files using handles instead 1512 of names. The handle would remain the same even if file names 1513 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1514 syscalls. 1515 1516config POSIX_TIMERS 1517 bool "Posix Clocks & timers" if EXPERT 1518 default y 1519 help 1520 This includes native support for POSIX timers to the kernel. 1521 Some embedded systems have no use for them and therefore they 1522 can be configured out to reduce the size of the kernel image. 1523 1524 When this option is disabled, the following syscalls won't be 1525 available: timer_create, timer_gettime: timer_getoverrun, 1526 timer_settime, timer_delete, clock_adjtime, getitimer, 1527 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1528 clock_getres and clock_nanosleep syscalls will be limited to 1529 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1530 1531 If unsure say y. 1532 1533config PRINTK 1534 default y 1535 bool "Enable support for printk" if EXPERT 1536 select IRQ_WORK 1537 help 1538 This option enables normal printk support. Removing it 1539 eliminates most of the message strings from the kernel image 1540 and makes the kernel more or less silent. As this makes it 1541 very difficult to diagnose system problems, saying N here is 1542 strongly discouraged. 1543 1544config BUG 1545 bool "BUG() support" if EXPERT 1546 default y 1547 help 1548 Disabling this option eliminates support for BUG and WARN, reducing 1549 the size of your kernel image and potentially quietly ignoring 1550 numerous fatal conditions. You should only consider disabling this 1551 option for embedded systems with no facilities for reporting errors. 1552 Just say Y. 1553 1554config ELF_CORE 1555 depends on COREDUMP 1556 default y 1557 bool "Enable ELF core dumps" if EXPERT 1558 help 1559 Enable support for generating core dumps. Disabling saves about 4k. 1560 1561 1562config PCSPKR_PLATFORM 1563 bool "Enable PC-Speaker support" if EXPERT 1564 depends on HAVE_PCSPKR_PLATFORM 1565 select I8253_LOCK 1566 default y 1567 help 1568 This option allows to disable the internal PC-Speaker 1569 support, saving some memory. 1570 1571config BASE_FULL 1572 default y 1573 bool "Enable full-sized data structures for core" if EXPERT 1574 help 1575 Disabling this option reduces the size of miscellaneous core 1576 kernel data structures. This saves memory on small machines, 1577 but may reduce performance. 1578 1579config FUTEX 1580 bool "Enable futex support" if EXPERT 1581 depends on !(SPARC32 && SMP) 1582 default y 1583 imply RT_MUTEXES 1584 help 1585 Disabling this option will cause the kernel to be built without 1586 support for "fast userspace mutexes". The resulting kernel may not 1587 run glibc-based applications correctly. 1588 1589config FUTEX_PI 1590 bool 1591 depends on FUTEX && RT_MUTEXES 1592 default y 1593 1594config EPOLL 1595 bool "Enable eventpoll support" if EXPERT 1596 default y 1597 help 1598 Disabling this option will cause the kernel to be built without 1599 support for epoll family of system calls. 1600 1601config SIGNALFD 1602 bool "Enable signalfd() system call" if EXPERT 1603 default y 1604 help 1605 Enable the signalfd() system call that allows to receive signals 1606 on a file descriptor. 1607 1608 If unsure, say Y. 1609 1610config TIMERFD 1611 bool "Enable timerfd() system call" if EXPERT 1612 default y 1613 help 1614 Enable the timerfd() system call that allows to receive timer 1615 events on a file descriptor. 1616 1617 If unsure, say Y. 1618 1619config EVENTFD 1620 bool "Enable eventfd() system call" if EXPERT 1621 default y 1622 help 1623 Enable the eventfd() system call that allows to receive both 1624 kernel notification (ie. KAIO) or userspace notifications. 1625 1626 If unsure, say Y. 1627 1628config SHMEM 1629 bool "Use full shmem filesystem" if EXPERT 1630 default y 1631 depends on MMU 1632 help 1633 The shmem is an internal filesystem used to manage shared memory. 1634 It is backed by swap and manages resource limits. It is also exported 1635 to userspace as tmpfs if TMPFS is enabled. Disabling this 1636 option replaces shmem and tmpfs with the much simpler ramfs code, 1637 which may be appropriate on small systems without swap. 1638 1639config AIO 1640 bool "Enable AIO support" if EXPERT 1641 default y 1642 help 1643 This option enables POSIX asynchronous I/O which may by used 1644 by some high performance threaded applications. Disabling 1645 this option saves about 7k. 1646 1647config IO_URING 1648 bool "Enable IO uring support" if EXPERT 1649 select IO_WQ 1650 default y 1651 help 1652 This option enables support for the io_uring interface, enabling 1653 applications to submit and complete IO through submission and 1654 completion rings that are shared between the kernel and application. 1655 1656config ADVISE_SYSCALLS 1657 bool "Enable madvise/fadvise syscalls" if EXPERT 1658 default y 1659 help 1660 This option enables the madvise and fadvise syscalls, used by 1661 applications to advise the kernel about their future memory or file 1662 usage, improving performance. If building an embedded system where no 1663 applications use these syscalls, you can disable this option to save 1664 space. 1665 1666config MEMBARRIER 1667 bool "Enable membarrier() system call" if EXPERT 1668 default y 1669 help 1670 Enable the membarrier() system call that allows issuing memory 1671 barriers across all running threads, which can be used to distribute 1672 the cost of user-space memory barriers asymmetrically by transforming 1673 pairs of memory barriers into pairs consisting of membarrier() and a 1674 compiler barrier. 1675 1676 If unsure, say Y. 1677 1678config KALLSYMS 1679 bool "Load all symbols for debugging/ksymoops" if EXPERT 1680 default y 1681 help 1682 Say Y here to let the kernel print out symbolic crash information and 1683 symbolic stack backtraces. This increases the size of the kernel 1684 somewhat, as all symbols have to be loaded into the kernel image. 1685 1686config KALLSYMS_SELFTEST 1687 bool "Test the basic functions and performance of kallsyms" 1688 depends on KALLSYMS 1689 default n 1690 help 1691 Test the basic functions and performance of some interfaces, such as 1692 kallsyms_lookup_name. It also calculates the compression rate of the 1693 kallsyms compression algorithm for the current symbol set. 1694 1695 Start self-test automatically after system startup. Suggest executing 1696 "dmesg | grep kallsyms_selftest" to collect test results. "finish" is 1697 displayed in the last line, indicating that the test is complete. 1698 1699config KALLSYMS_ALL 1700 bool "Include all symbols in kallsyms" 1701 depends on DEBUG_KERNEL && KALLSYMS 1702 help 1703 Normally kallsyms only contains the symbols of functions for nicer 1704 OOPS messages and backtraces (i.e., symbols from the text and inittext 1705 sections). This is sufficient for most cases. And only if you want to 1706 enable kernel live patching, or other less common use cases (e.g., 1707 when a debugger is used) all symbols are required (i.e., names of 1708 variables from the data sections, etc). 1709 1710 This option makes sure that all symbols are loaded into the kernel 1711 image (i.e., symbols from all sections) in cost of increased kernel 1712 size (depending on the kernel configuration, it may be 300KiB or 1713 something like this). 1714 1715 Say N unless you really need all symbols, or kernel live patching. 1716 1717config KALLSYMS_ABSOLUTE_PERCPU 1718 bool 1719 depends on KALLSYMS 1720 default X86_64 && SMP 1721 1722config KALLSYMS_BASE_RELATIVE 1723 bool 1724 depends on KALLSYMS 1725 default !IA64 1726 help 1727 Instead of emitting them as absolute values in the native word size, 1728 emit the symbol references in the kallsyms table as 32-bit entries, 1729 each containing a relative value in the range [base, base + U32_MAX] 1730 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1731 an absolute value in the range [0, S32_MAX] or a relative value in the 1732 range [base, base + S32_MAX], where base is the lowest relative symbol 1733 address encountered in the image. 1734 1735 On 64-bit builds, this reduces the size of the address table by 50%, 1736 but more importantly, it results in entries whose values are build 1737 time constants, and no relocation pass is required at runtime to fix 1738 up the entries based on the runtime load address of the kernel. 1739 1740# end of the "standard kernel features (expert users)" menu 1741 1742# syscall, maps, verifier 1743 1744config ARCH_HAS_MEMBARRIER_CALLBACKS 1745 bool 1746 1747config ARCH_HAS_MEMBARRIER_SYNC_CORE 1748 bool 1749 1750config KCMP 1751 bool "Enable kcmp() system call" if EXPERT 1752 help 1753 Enable the kernel resource comparison system call. It provides 1754 user-space with the ability to compare two processes to see if they 1755 share a common resource, such as a file descriptor or even virtual 1756 memory space. 1757 1758 If unsure, say N. 1759 1760config RSEQ 1761 bool "Enable rseq() system call" if EXPERT 1762 default y 1763 depends on HAVE_RSEQ 1764 select MEMBARRIER 1765 help 1766 Enable the restartable sequences system call. It provides a 1767 user-space cache for the current CPU number value, which 1768 speeds up getting the current CPU number from user-space, 1769 as well as an ABI to speed up user-space operations on 1770 per-CPU data. 1771 1772 If unsure, say Y. 1773 1774config DEBUG_RSEQ 1775 default n 1776 bool "Enabled debugging of rseq() system call" if EXPERT 1777 depends on RSEQ && DEBUG_KERNEL 1778 help 1779 Enable extra debugging checks for the rseq system call. 1780 1781 If unsure, say N. 1782 1783config EMBEDDED 1784 bool "Embedded system" 1785 select EXPERT 1786 help 1787 This option should be enabled if compiling the kernel for 1788 an embedded system so certain expert options are available 1789 for configuration. 1790 1791config HAVE_PERF_EVENTS 1792 bool 1793 help 1794 See tools/perf/design.txt for details. 1795 1796config GUEST_PERF_EVENTS 1797 bool 1798 depends on HAVE_PERF_EVENTS 1799 1800config PERF_USE_VMALLOC 1801 bool 1802 help 1803 See tools/perf/design.txt for details 1804 1805config PC104 1806 bool "PC/104 support" if EXPERT 1807 help 1808 Expose PC/104 form factor device drivers and options available for 1809 selection and configuration. Enable this option if your target 1810 machine has a PC/104 bus. 1811 1812menu "Kernel Performance Events And Counters" 1813 1814config PERF_EVENTS 1815 bool "Kernel performance events and counters" 1816 default y if PROFILING 1817 depends on HAVE_PERF_EVENTS 1818 select IRQ_WORK 1819 help 1820 Enable kernel support for various performance events provided 1821 by software and hardware. 1822 1823 Software events are supported either built-in or via the 1824 use of generic tracepoints. 1825 1826 Most modern CPUs support performance events via performance 1827 counter registers. These registers count the number of certain 1828 types of hw events: such as instructions executed, cachemisses 1829 suffered, or branches mis-predicted - without slowing down the 1830 kernel or applications. These registers can also trigger interrupts 1831 when a threshold number of events have passed - and can thus be 1832 used to profile the code that runs on that CPU. 1833 1834 The Linux Performance Event subsystem provides an abstraction of 1835 these software and hardware event capabilities, available via a 1836 system call and used by the "perf" utility in tools/perf/. It 1837 provides per task and per CPU counters, and it provides event 1838 capabilities on top of those. 1839 1840 Say Y if unsure. 1841 1842config DEBUG_PERF_USE_VMALLOC 1843 default n 1844 bool "Debug: use vmalloc to back perf mmap() buffers" 1845 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1846 select PERF_USE_VMALLOC 1847 help 1848 Use vmalloc memory to back perf mmap() buffers. 1849 1850 Mostly useful for debugging the vmalloc code on platforms 1851 that don't require it. 1852 1853 Say N if unsure. 1854 1855endmenu 1856 1857config SYSTEM_DATA_VERIFICATION 1858 def_bool n 1859 select SYSTEM_TRUSTED_KEYRING 1860 select KEYS 1861 select CRYPTO 1862 select CRYPTO_RSA 1863 select ASYMMETRIC_KEY_TYPE 1864 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1865 select ASN1 1866 select OID_REGISTRY 1867 select X509_CERTIFICATE_PARSER 1868 select PKCS7_MESSAGE_PARSER 1869 help 1870 Provide PKCS#7 message verification using the contents of the system 1871 trusted keyring to provide public keys. This then can be used for 1872 module verification, kexec image verification and firmware blob 1873 verification. 1874 1875config PROFILING 1876 bool "Profiling support" 1877 help 1878 Say Y here to enable the extended profiling support mechanisms used 1879 by profilers. 1880 1881config RUST 1882 bool "Rust support" 1883 depends on HAVE_RUST 1884 depends on RUST_IS_AVAILABLE 1885 depends on !MODVERSIONS 1886 depends on !GCC_PLUGINS 1887 depends on !RANDSTRUCT 1888 depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE 1889 select CONSTRUCTORS 1890 help 1891 Enables Rust support in the kernel. 1892 1893 This allows other Rust-related options, like drivers written in Rust, 1894 to be selected. 1895 1896 It is also required to be able to load external kernel modules 1897 written in Rust. 1898 1899 See Documentation/rust/ for more information. 1900 1901 If unsure, say N. 1902 1903config RUSTC_VERSION_TEXT 1904 string 1905 depends on RUST 1906 default $(shell,command -v $(RUSTC) >/dev/null 2>&1 && $(RUSTC) --version || echo n) 1907 1908config BINDGEN_VERSION_TEXT 1909 string 1910 depends on RUST 1911 default $(shell,command -v $(BINDGEN) >/dev/null 2>&1 && $(BINDGEN) --version || echo n) 1912 1913# 1914# Place an empty function call at each tracepoint site. Can be 1915# dynamically changed for a probe function. 1916# 1917config TRACEPOINTS 1918 bool 1919 1920endmenu # General setup 1921 1922source "arch/Kconfig" 1923 1924config RT_MUTEXES 1925 bool 1926 default y if PREEMPT_RT 1927 1928config BASE_SMALL 1929 int 1930 default 0 if BASE_FULL 1931 default 1 if !BASE_FULL 1932 1933config MODULE_SIG_FORMAT 1934 def_bool n 1935 select SYSTEM_DATA_VERIFICATION 1936 1937source "kernel/module/Kconfig" 1938 1939config INIT_ALL_POSSIBLE 1940 bool 1941 help 1942 Back when each arch used to define their own cpu_online_mask and 1943 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 1944 with all 1s, and others with all 0s. When they were centralised, 1945 it was better to provide this option than to break all the archs 1946 and have several arch maintainers pursuing me down dark alleys. 1947 1948source "block/Kconfig" 1949 1950config PREEMPT_NOTIFIERS 1951 bool 1952 1953config PADATA 1954 depends on SMP 1955 bool 1956 1957config ASN1 1958 tristate 1959 help 1960 Build a simple ASN.1 grammar compiler that produces a bytecode output 1961 that can be interpreted by the ASN.1 stream decoder and used to 1962 inform it as to what tags are to be expected in a stream and what 1963 functions to call on what tags. 1964 1965source "kernel/Kconfig.locks" 1966 1967config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 1968 bool 1969 1970config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 1971 bool 1972 1973# It may be useful for an architecture to override the definitions of the 1974# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 1975# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 1976# different calling convention for syscalls. They can also override the 1977# macros for not-implemented syscalls in kernel/sys_ni.c and 1978# kernel/time/posix-stubs.c. All these overrides need to be available in 1979# <asm/syscall_wrapper.h>. 1980config ARCH_HAS_SYSCALL_WRAPPER 1981 def_bool n 1982