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