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 GCC_ASM_GOTO_OUTPUT_WORKAROUND 93 bool 94 depends on CC_IS_GCC && CC_HAS_ASM_GOTO_OUTPUT 95 # Fixed in GCC 14, 13.3, 12.4 and 11.5 96 # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113921 97 default y if GCC_VERSION < 110500 98 default y if GCC_VERSION >= 120000 && GCC_VERSION < 120400 99 default y if GCC_VERSION >= 130000 && GCC_VERSION < 130300 100 101config TOOLS_SUPPORT_RELR 102 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 103 104config CC_HAS_ASM_INLINE 105 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 106 107config CC_HAS_NO_PROFILE_FN_ATTR 108 def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror) 109 110config PAHOLE_VERSION 111 int 112 default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE)) 113 114config CONSTRUCTORS 115 bool 116 117config IRQ_WORK 118 def_bool y if SMP 119 120config BUILDTIME_TABLE_SORT 121 bool 122 123config THREAD_INFO_IN_TASK 124 bool 125 help 126 Select this to move thread_info off the stack into task_struct. To 127 make this work, an arch will need to remove all thread_info fields 128 except flags and fix any runtime bugs. 129 130 One subtle change that will be needed is to use try_get_task_stack() 131 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 132 133menu "General setup" 134 135config BROKEN 136 bool 137 138config BROKEN_ON_SMP 139 bool 140 depends on BROKEN || !SMP 141 default y 142 143config INIT_ENV_ARG_LIMIT 144 int 145 default 32 if !UML 146 default 128 if UML 147 help 148 Maximum of each of the number of arguments and environment 149 variables passed to init from the kernel command line. 150 151config COMPILE_TEST 152 bool "Compile also drivers which will not load" 153 depends on HAS_IOMEM 154 help 155 Some drivers can be compiled on a different platform than they are 156 intended to be run on. Despite they cannot be loaded there (or even 157 when they load they cannot be used due to missing HW support), 158 developers still, opposing to distributors, might want to build such 159 drivers to compile-test them. 160 161 If you are a developer and want to build everything available, say Y 162 here. If you are a user/distributor, say N here to exclude useless 163 drivers to be distributed. 164 165config WERROR 166 bool "Compile the kernel with warnings as errors" 167 default COMPILE_TEST 168 help 169 A kernel build should not cause any compiler warnings, and this 170 enables the '-Werror' (for C) and '-Dwarnings' (for Rust) flags 171 to enforce that rule by default. Certain warnings from other tools 172 such as the linker may be upgraded to errors with this option as 173 well. 174 175 However, if you have a new (or very old) compiler or linker with odd 176 and unusual warnings, or you have some architecture with problems, 177 you may need to disable this config option in order to 178 successfully build the kernel. 179 180 If in doubt, say Y. 181 182config UAPI_HEADER_TEST 183 bool "Compile test UAPI headers" 184 depends on HEADERS_INSTALL && CC_CAN_LINK 185 help 186 Compile test headers exported to user-space to ensure they are 187 self-contained, i.e. compilable as standalone units. 188 189 If you are a developer or tester and want to ensure the exported 190 headers are self-contained, say Y here. Otherwise, choose N. 191 192config LOCALVERSION 193 string "Local version - append to kernel release" 194 help 195 Append an extra string to the end of your kernel version. 196 This will show up when you type uname, for example. 197 The string you set here will be appended after the contents of 198 any files with a filename matching localversion* in your 199 object and source tree, in that order. Your total string can 200 be a maximum of 64 characters. 201 202config LOCALVERSION_AUTO 203 bool "Automatically append version information to the version string" 204 default y 205 depends on !COMPILE_TEST 206 help 207 This will try to automatically determine if the current tree is a 208 release tree by looking for git tags that belong to the current 209 top of tree revision. 210 211 A string of the format -gxxxxxxxx will be added to the localversion 212 if a git-based tree is found. The string generated by this will be 213 appended after any matching localversion* files, and after the value 214 set in CONFIG_LOCALVERSION. 215 216 (The actual string used here is the first 12 characters produced 217 by running the command: 218 219 $ git rev-parse --verify HEAD 220 221 which is done within the script "scripts/setlocalversion".) 222 223config BUILD_SALT 224 string "Build ID Salt" 225 default "" 226 help 227 The build ID is used to link binaries and their debug info. Setting 228 this option will use the value in the calculation of the build id. 229 This is mostly useful for distributions which want to ensure the 230 build is unique between builds. It's safe to leave the default. 231 232config HAVE_KERNEL_GZIP 233 bool 234 235config HAVE_KERNEL_BZIP2 236 bool 237 238config HAVE_KERNEL_LZMA 239 bool 240 241config HAVE_KERNEL_XZ 242 bool 243 244config HAVE_KERNEL_LZO 245 bool 246 247config HAVE_KERNEL_LZ4 248 bool 249 250config HAVE_KERNEL_ZSTD 251 bool 252 253config HAVE_KERNEL_UNCOMPRESSED 254 bool 255 256choice 257 prompt "Kernel compression mode" 258 default KERNEL_GZIP 259 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 260 help 261 The linux kernel is a kind of self-extracting executable. 262 Several compression algorithms are available, which differ 263 in efficiency, compression and decompression speed. 264 Compression speed is only relevant when building a kernel. 265 Decompression speed is relevant at each boot. 266 267 If you have any problems with bzip2 or lzma compressed 268 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 269 version of this functionality (bzip2 only), for 2.4, was 270 supplied by Christian Ludwig) 271 272 High compression options are mostly useful for users, who 273 are low on disk space (embedded systems), but for whom ram 274 size matters less. 275 276 If in doubt, select 'gzip' 277 278config KERNEL_GZIP 279 bool "Gzip" 280 depends on HAVE_KERNEL_GZIP 281 help 282 The old and tried gzip compression. It provides a good balance 283 between compression ratio and decompression speed. 284 285config KERNEL_BZIP2 286 bool "Bzip2" 287 depends on HAVE_KERNEL_BZIP2 288 help 289 Its compression ratio and speed is intermediate. 290 Decompression speed is slowest among the choices. The kernel 291 size is about 10% smaller with bzip2, in comparison to gzip. 292 Bzip2 uses a large amount of memory. For modern kernels you 293 will need at least 8MB RAM or more for booting. 294 295config KERNEL_LZMA 296 bool "LZMA" 297 depends on HAVE_KERNEL_LZMA 298 help 299 This compression algorithm's ratio is best. Decompression speed 300 is between gzip and bzip2. Compression is slowest. 301 The kernel size is about 33% smaller with LZMA in comparison to gzip. 302 303config KERNEL_XZ 304 bool "XZ" 305 depends on HAVE_KERNEL_XZ 306 help 307 XZ uses the LZMA2 algorithm and instruction set specific 308 BCJ filters which can improve compression ratio of executable 309 code. The size of the kernel is about 30% smaller with XZ in 310 comparison to gzip. On architectures for which there is a BCJ 311 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 312 will create a few percent smaller kernel than plain LZMA. 313 314 The speed is about the same as with LZMA: The decompression 315 speed of XZ is better than that of bzip2 but worse than gzip 316 and LZO. Compression is slow. 317 318config KERNEL_LZO 319 bool "LZO" 320 depends on HAVE_KERNEL_LZO 321 help 322 Its compression ratio is the poorest among the choices. The kernel 323 size is about 10% bigger than gzip; however its speed 324 (both compression and decompression) is the fastest. 325 326config KERNEL_LZ4 327 bool "LZ4" 328 depends on HAVE_KERNEL_LZ4 329 help 330 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 331 A preliminary version of LZ4 de/compression tool is available at 332 <https://code.google.com/p/lz4/>. 333 334 Its compression ratio is worse than LZO. The size of the kernel 335 is about 8% bigger than LZO. But the decompression speed is 336 faster than LZO. 337 338config KERNEL_ZSTD 339 bool "ZSTD" 340 depends on HAVE_KERNEL_ZSTD 341 help 342 ZSTD is a compression algorithm targeting intermediate compression 343 with fast decompression speed. It will compress better than GZIP and 344 decompress around the same speed as LZO, but slower than LZ4. You 345 will need at least 192 KB RAM or more for booting. The zstd command 346 line tool is required for compression. 347 348config KERNEL_UNCOMPRESSED 349 bool "None" 350 depends on HAVE_KERNEL_UNCOMPRESSED 351 help 352 Produce uncompressed kernel image. This option is usually not what 353 you want. It is useful for debugging the kernel in slow simulation 354 environments, where decompressing and moving the kernel is awfully 355 slow. This option allows early boot code to skip the decompressor 356 and jump right at uncompressed kernel image. 357 358endchoice 359 360config DEFAULT_INIT 361 string "Default init path" 362 default "" 363 help 364 This option determines the default init for the system if no init= 365 option is passed on the kernel command line. If the requested path is 366 not present, we will still then move on to attempting further 367 locations (e.g. /sbin/init, etc). If this is empty, we will just use 368 the fallback list when init= is not passed. 369 370config DEFAULT_HOSTNAME 371 string "Default hostname" 372 default "(none)" 373 help 374 This option determines the default system hostname before userspace 375 calls sethostname(2). The kernel traditionally uses "(none)" here, 376 but you may wish to use a different default here to make a minimal 377 system more usable with less configuration. 378 379config SYSVIPC 380 bool "System V IPC" 381 help 382 Inter Process Communication is a suite of library functions and 383 system calls which let processes (running programs) synchronize and 384 exchange information. It is generally considered to be a good thing, 385 and some programs won't run unless you say Y here. In particular, if 386 you want to run the DOS emulator dosemu under Linux (read the 387 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 388 you'll need to say Y here. 389 390 You can find documentation about IPC with "info ipc" and also in 391 section 6.4 of the Linux Programmer's Guide, available from 392 <http://www.tldp.org/guides.html>. 393 394config SYSVIPC_SYSCTL 395 bool 396 depends on SYSVIPC 397 depends on SYSCTL 398 default y 399 400config SYSVIPC_COMPAT 401 def_bool y 402 depends on COMPAT && SYSVIPC 403 404config POSIX_MQUEUE 405 bool "POSIX Message Queues" 406 depends on NET 407 help 408 POSIX variant of message queues is a part of IPC. In POSIX message 409 queues every message has a priority which decides about succession 410 of receiving it by a process. If you want to compile and run 411 programs written e.g. for Solaris with use of its POSIX message 412 queues (functions mq_*) say Y here. 413 414 POSIX message queues are visible as a filesystem called 'mqueue' 415 and can be mounted somewhere if you want to do filesystem 416 operations on message queues. 417 418 If unsure, say Y. 419 420config POSIX_MQUEUE_SYSCTL 421 bool 422 depends on POSIX_MQUEUE 423 depends on SYSCTL 424 default y 425 426config WATCH_QUEUE 427 bool "General notification queue" 428 default n 429 help 430 431 This is a general notification queue for the kernel to pass events to 432 userspace by splicing them into pipes. It can be used in conjunction 433 with watches for key/keyring change notifications and device 434 notifications. 435 436 See Documentation/core-api/watch_queue.rst 437 438config CROSS_MEMORY_ATTACH 439 bool "Enable process_vm_readv/writev syscalls" 440 depends on MMU 441 default y 442 help 443 Enabling this option adds the system calls process_vm_readv and 444 process_vm_writev which allow a process with the correct privileges 445 to directly read from or write to another process' address space. 446 See the man page for more details. 447 448config USELIB 449 bool "uselib syscall (for libc5 and earlier)" 450 default ALPHA || M68K || SPARC 451 help 452 This option enables the uselib syscall, a system call used in the 453 dynamic linker from libc5 and earlier. glibc does not use this 454 system call. If you intend to run programs built on libc5 or 455 earlier, you may need to enable this syscall. Current systems 456 running glibc can safely disable this. 457 458config AUDIT 459 bool "Auditing support" 460 depends on NET 461 help 462 Enable auditing infrastructure that can be used with another 463 kernel subsystem, such as SELinux (which requires this for 464 logging of avc messages output). System call auditing is included 465 on architectures which support it. 466 467config HAVE_ARCH_AUDITSYSCALL 468 bool 469 470config AUDITSYSCALL 471 def_bool y 472 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 473 select FSNOTIFY 474 475source "kernel/irq/Kconfig" 476source "kernel/time/Kconfig" 477source "kernel/bpf/Kconfig" 478source "kernel/Kconfig.preempt" 479 480menu "CPU/Task time and stats accounting" 481 482config VIRT_CPU_ACCOUNTING 483 bool 484 485choice 486 prompt "Cputime accounting" 487 default TICK_CPU_ACCOUNTING 488 489# Kind of a stub config for the pure tick based cputime accounting 490config TICK_CPU_ACCOUNTING 491 bool "Simple tick based cputime accounting" 492 depends on !S390 && !NO_HZ_FULL 493 help 494 This is the basic tick based cputime accounting that maintains 495 statistics about user, system and idle time spent on per jiffies 496 granularity. 497 498 If unsure, say Y. 499 500config VIRT_CPU_ACCOUNTING_NATIVE 501 bool "Deterministic task and CPU time accounting" 502 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 503 select VIRT_CPU_ACCOUNTING 504 help 505 Select this option to enable more accurate task and CPU time 506 accounting. This is done by reading a CPU counter on each 507 kernel entry and exit and on transitions within the kernel 508 between system, softirq and hardirq state, so there is a 509 small performance impact. In the case of s390 or IBM POWER > 5, 510 this also enables accounting of stolen time on logically-partitioned 511 systems. 512 513config VIRT_CPU_ACCOUNTING_GEN 514 bool "Full dynticks CPU time accounting" 515 depends on HAVE_CONTEXT_TRACKING_USER 516 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 517 depends on GENERIC_CLOCKEVENTS 518 select VIRT_CPU_ACCOUNTING 519 select CONTEXT_TRACKING_USER 520 help 521 Select this option to enable task and CPU time accounting on full 522 dynticks systems. This accounting is implemented by watching every 523 kernel-user boundaries using the context tracking subsystem. 524 The accounting is thus performed at the expense of some significant 525 overhead. 526 527 For now this is only useful if you are working on the full 528 dynticks subsystem development. 529 530 If unsure, say N. 531 532endchoice 533 534config IRQ_TIME_ACCOUNTING 535 bool "Fine granularity task level IRQ time accounting" 536 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 537 help 538 Select this option to enable fine granularity task irq time 539 accounting. This is done by reading a timestamp on each 540 transitions between softirq and hardirq state, so there can be a 541 small performance impact. 542 543 If in doubt, say N here. 544 545config HAVE_SCHED_AVG_IRQ 546 def_bool y 547 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 548 depends on SMP 549 550config SCHED_HW_PRESSURE 551 bool 552 default y if ARM && ARM_CPU_TOPOLOGY 553 default y if ARM64 554 depends on SMP 555 depends on CPU_FREQ_THERMAL 556 help 557 Select this option to enable HW pressure accounting in the 558 scheduler. HW pressure is the value conveyed to the scheduler 559 that reflects the reduction in CPU compute capacity resulted from 560 HW throttling. HW throttling occurs when the performance of 561 a CPU is capped due to high operating temperatures as an example. 562 563 If selected, the scheduler will be able to balance tasks accordingly, 564 i.e. put less load on throttled CPUs than on non/less throttled ones. 565 566 This requires the architecture to implement 567 arch_update_hw_pressure() and arch_scale_thermal_pressure(). 568 569config BSD_PROCESS_ACCT 570 bool "BSD Process Accounting" 571 depends on MULTIUSER 572 help 573 If you say Y here, a user level program will be able to instruct the 574 kernel (via a special system call) to write process accounting 575 information to a file: whenever a process exits, information about 576 that process will be appended to the file by the kernel. The 577 information includes things such as creation time, owning user, 578 command name, memory usage, controlling terminal etc. (the complete 579 list is in the struct acct in <file:include/linux/acct.h>). It is 580 up to the user level program to do useful things with this 581 information. This is generally a good idea, so say Y. 582 583config BSD_PROCESS_ACCT_V3 584 bool "BSD Process Accounting version 3 file format" 585 depends on BSD_PROCESS_ACCT 586 default n 587 help 588 If you say Y here, the process accounting information is written 589 in a new file format that also logs the process IDs of each 590 process and its parent. Note that this file format is incompatible 591 with previous v0/v1/v2 file formats, so you will need updated tools 592 for processing it. A preliminary version of these tools is available 593 at <http://www.gnu.org/software/acct/>. 594 595config TASKSTATS 596 bool "Export task/process statistics through netlink" 597 depends on NET 598 depends on MULTIUSER 599 default n 600 help 601 Export selected statistics for tasks/processes through the 602 generic netlink interface. Unlike BSD process accounting, the 603 statistics are available during the lifetime of tasks/processes as 604 responses to commands. Like BSD accounting, they are sent to user 605 space on task exit. 606 607 Say N if unsure. 608 609config TASK_DELAY_ACCT 610 bool "Enable per-task delay accounting" 611 depends on TASKSTATS 612 select SCHED_INFO 613 help 614 Collect information on time spent by a task waiting for system 615 resources like cpu, synchronous block I/O completion and swapping 616 in pages. Such statistics can help in setting a task's priorities 617 relative to other tasks for cpu, io, rss limits etc. 618 619 Say N if unsure. 620 621config TASK_XACCT 622 bool "Enable extended accounting over taskstats" 623 depends on TASKSTATS 624 help 625 Collect extended task accounting data and send the data 626 to userland for processing over the taskstats interface. 627 628 Say N if unsure. 629 630config TASK_IO_ACCOUNTING 631 bool "Enable per-task storage I/O accounting" 632 depends on TASK_XACCT 633 help 634 Collect information on the number of bytes of storage I/O which this 635 task has caused. 636 637 Say N if unsure. 638 639config PSI 640 bool "Pressure stall information tracking" 641 select KERNFS 642 help 643 Collect metrics that indicate how overcommitted the CPU, memory, 644 and IO capacity are in the system. 645 646 If you say Y here, the kernel will create /proc/pressure/ with the 647 pressure statistics files cpu, memory, and io. These will indicate 648 the share of walltime in which some or all tasks in the system are 649 delayed due to contention of the respective resource. 650 651 In kernels with cgroup support, cgroups (cgroup2 only) will 652 have cpu.pressure, memory.pressure, and io.pressure files, 653 which aggregate pressure stalls for the grouped tasks only. 654 655 For more details see Documentation/accounting/psi.rst. 656 657 Say N if unsure. 658 659config PSI_DEFAULT_DISABLED 660 bool "Require boot parameter to enable pressure stall information tracking" 661 default n 662 depends on PSI 663 help 664 If set, pressure stall information tracking will be disabled 665 per default but can be enabled through passing psi=1 on the 666 kernel commandline during boot. 667 668 This feature adds some code to the task wakeup and sleep 669 paths of the scheduler. The overhead is too low to affect 670 common scheduling-intense workloads in practice (such as 671 webservers, memcache), but it does show up in artificial 672 scheduler stress tests, such as hackbench. 673 674 If you are paranoid and not sure what the kernel will be 675 used for, say Y. 676 677 Say N if unsure. 678 679endmenu # "CPU/Task time and stats accounting" 680 681config CPU_ISOLATION 682 bool "CPU isolation" 683 depends on SMP || COMPILE_TEST 684 default y 685 help 686 Make sure that CPUs running critical tasks are not disturbed by 687 any source of "noise" such as unbound workqueues, timers, kthreads... 688 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 689 the "isolcpus=" boot parameter. 690 691 Say Y if unsure. 692 693source "kernel/rcu/Kconfig" 694 695config IKCONFIG 696 tristate "Kernel .config support" 697 help 698 This option enables the complete Linux kernel ".config" file 699 contents to be saved in the kernel. It provides documentation 700 of which kernel options are used in a running kernel or in an 701 on-disk kernel. This information can be extracted from the kernel 702 image file with the script scripts/extract-ikconfig and used as 703 input to rebuild the current kernel or to build another kernel. 704 It can also be extracted from a running kernel by reading 705 /proc/config.gz if enabled (below). 706 707config IKCONFIG_PROC 708 bool "Enable access to .config through /proc/config.gz" 709 depends on IKCONFIG && PROC_FS 710 help 711 This option enables access to the kernel configuration file 712 through /proc/config.gz. 713 714config IKHEADERS 715 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 716 depends on SYSFS 717 help 718 This option enables access to the in-kernel headers that are generated during 719 the build process. These can be used to build eBPF tracing programs, 720 or similar programs. If you build the headers as a module, a module called 721 kheaders.ko is built which can be loaded on-demand to get access to headers. 722 723config LOG_BUF_SHIFT 724 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 725 range 12 25 726 default 17 727 depends on PRINTK 728 help 729 Select the minimal kernel log buffer size as a power of 2. 730 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 731 parameter, see below. Any higher size also might be forced 732 by "log_buf_len" boot parameter. 733 734 Examples: 735 17 => 128 KB 736 16 => 64 KB 737 15 => 32 KB 738 14 => 16 KB 739 13 => 8 KB 740 12 => 4 KB 741 742config LOG_CPU_MAX_BUF_SHIFT 743 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 744 depends on SMP 745 range 0 21 746 default 0 if BASE_SMALL 747 default 12 748 depends on PRINTK 749 help 750 This option allows to increase the default ring buffer size 751 according to the number of CPUs. The value defines the contribution 752 of each CPU as a power of 2. The used space is typically only few 753 lines however it might be much more when problems are reported, 754 e.g. backtraces. 755 756 The increased size means that a new buffer has to be allocated and 757 the original static one is unused. It makes sense only on systems 758 with more CPUs. Therefore this value is used only when the sum of 759 contributions is greater than the half of the default kernel ring 760 buffer as defined by LOG_BUF_SHIFT. The default values are set 761 so that more than 16 CPUs are needed to trigger the allocation. 762 763 Also this option is ignored when "log_buf_len" kernel parameter is 764 used as it forces an exact (power of two) size of the ring buffer. 765 766 The number of possible CPUs is used for this computation ignoring 767 hotplugging making the computation optimal for the worst case 768 scenario while allowing a simple algorithm to be used from bootup. 769 770 Examples shift values and their meaning: 771 17 => 128 KB for each CPU 772 16 => 64 KB for each CPU 773 15 => 32 KB for each CPU 774 14 => 16 KB for each CPU 775 13 => 8 KB for each CPU 776 12 => 4 KB for each CPU 777 778config PRINTK_INDEX 779 bool "Printk indexing debugfs interface" 780 depends on PRINTK && DEBUG_FS 781 help 782 Add support for indexing of all printk formats known at compile time 783 at <debugfs>/printk/index/<module>. 784 785 This can be used as part of maintaining daemons which monitor 786 /dev/kmsg, as it permits auditing the printk formats present in a 787 kernel, allowing detection of cases where monitored printks are 788 changed or no longer present. 789 790 There is no additional runtime cost to printk with this enabled. 791 792# 793# Architectures with an unreliable sched_clock() should select this: 794# 795config HAVE_UNSTABLE_SCHED_CLOCK 796 bool 797 798config GENERIC_SCHED_CLOCK 799 bool 800 801menu "Scheduler features" 802 803config UCLAMP_TASK 804 bool "Enable utilization clamping for RT/FAIR tasks" 805 depends on CPU_FREQ_GOV_SCHEDUTIL 806 help 807 This feature enables the scheduler to track the clamped utilization 808 of each CPU based on RUNNABLE tasks scheduled on that CPU. 809 810 With this option, the user can specify the min and max CPU 811 utilization allowed for RUNNABLE tasks. The max utilization defines 812 the maximum frequency a task should use while the min utilization 813 defines the minimum frequency it should use. 814 815 Both min and max utilization clamp values are hints to the scheduler, 816 aiming at improving its frequency selection policy, but they do not 817 enforce or grant any specific bandwidth for tasks. 818 819 If in doubt, say N. 820 821config UCLAMP_BUCKETS_COUNT 822 int "Number of supported utilization clamp buckets" 823 range 5 20 824 default 5 825 depends on UCLAMP_TASK 826 help 827 Defines the number of clamp buckets to use. The range of each bucket 828 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 829 number of clamp buckets the finer their granularity and the higher 830 the precision of clamping aggregation and tracking at run-time. 831 832 For example, with the minimum configuration value we will have 5 833 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 834 be refcounted in the [20..39]% bucket and will set the bucket clamp 835 effective value to 25%. 836 If a second 30% boosted task should be co-scheduled on the same CPU, 837 that task will be refcounted in the same bucket of the first task and 838 it will boost the bucket clamp effective value to 30%. 839 The clamp effective value of a bucket is reset to its nominal value 840 (20% in the example above) when there are no more tasks refcounted in 841 that bucket. 842 843 An additional boost/capping margin can be added to some tasks. In the 844 example above the 25% task will be boosted to 30% until it exits the 845 CPU. If that should be considered not acceptable on certain systems, 846 it's always possible to reduce the margin by increasing the number of 847 clamp buckets to trade off used memory for run-time tracking 848 precision. 849 850 If in doubt, use the default value. 851 852endmenu 853 854# 855# For architectures that want to enable the support for NUMA-affine scheduler 856# balancing logic: 857# 858config ARCH_SUPPORTS_NUMA_BALANCING 859 bool 860 861# 862# For architectures that prefer to flush all TLBs after a number of pages 863# are unmapped instead of sending one IPI per page to flush. The architecture 864# must provide guarantees on what happens if a clean TLB cache entry is 865# written after the unmap. Details are in mm/rmap.c near the check for 866# should_defer_flush. The architecture should also consider if the full flush 867# and the refill costs are offset by the savings of sending fewer IPIs. 868config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 869 bool 870 871config CC_HAS_INT128 872 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 873 874config CC_IMPLICIT_FALLTHROUGH 875 string 876 default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5) 877 default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough) 878 879# Currently, disable gcc-10+ array-bounds globally. 880# It's still broken in gcc-13, so no upper bound yet. 881config GCC10_NO_ARRAY_BOUNDS 882 def_bool y 883 884config CC_NO_ARRAY_BOUNDS 885 bool 886 default y if CC_IS_GCC && GCC_VERSION >= 90000 && GCC10_NO_ARRAY_BOUNDS 887 888# Currently, disable -Wstringop-overflow for GCC globally. 889config GCC_NO_STRINGOP_OVERFLOW 890 def_bool y 891 892config CC_NO_STRINGOP_OVERFLOW 893 bool 894 default y if CC_IS_GCC && GCC_NO_STRINGOP_OVERFLOW 895 896config CC_STRINGOP_OVERFLOW 897 bool 898 default y if CC_IS_GCC && !CC_NO_STRINGOP_OVERFLOW 899 900# 901# For architectures that know their GCC __int128 support is sound 902# 903config ARCH_SUPPORTS_INT128 904 bool 905 906# For architectures that (ab)use NUMA to represent different memory regions 907# all cpu-local but of different latencies, such as SuperH. 908# 909config ARCH_WANT_NUMA_VARIABLE_LOCALITY 910 bool 911 912config NUMA_BALANCING 913 bool "Memory placement aware NUMA scheduler" 914 depends on ARCH_SUPPORTS_NUMA_BALANCING 915 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 916 depends on SMP && NUMA && MIGRATION && !PREEMPT_RT 917 help 918 This option adds support for automatic NUMA aware memory/task placement. 919 The mechanism is quite primitive and is based on migrating memory when 920 it has references to the node the task is running on. 921 922 This system will be inactive on UMA systems. 923 924config NUMA_BALANCING_DEFAULT_ENABLED 925 bool "Automatically enable NUMA aware memory/task placement" 926 default y 927 depends on NUMA_BALANCING 928 help 929 If set, automatic NUMA balancing will be enabled if running on a NUMA 930 machine. 931 932config SLAB_OBJ_EXT 933 bool 934 935menuconfig CGROUPS 936 bool "Control Group support" 937 select KERNFS 938 help 939 This option adds support for grouping sets of processes together, for 940 use with process control subsystems such as Cpusets, CFS, memory 941 controls or device isolation. 942 See 943 - Documentation/scheduler/sched-design-CFS.rst (CFS) 944 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 945 and resource control) 946 947 Say N if unsure. 948 949if CGROUPS 950 951config PAGE_COUNTER 952 bool 953 954config CGROUP_FAVOR_DYNMODS 955 bool "Favor dynamic modification latency reduction by default" 956 help 957 This option enables the "favordynmods" mount option by default 958 which reduces the latencies of dynamic cgroup modifications such 959 as task migrations and controller on/offs at the cost of making 960 hot path operations such as forks and exits more expensive. 961 962 Say N if unsure. 963 964config MEMCG 965 bool "Memory controller" 966 select PAGE_COUNTER 967 select EVENTFD 968 select SLAB_OBJ_EXT 969 help 970 Provides control over the memory footprint of tasks in a cgroup. 971 972config MEMCG_V1 973 bool "Legacy cgroup v1 memory controller" 974 depends on MEMCG 975 default n 976 help 977 Legacy cgroup v1 memory controller which has been deprecated by 978 cgroup v2 implementation. The v1 is there for legacy applications 979 which haven't migrated to the new cgroup v2 interface yet. If you 980 do not have any such application then you are completely fine leaving 981 this option disabled. 982 983 Please note that feature set of the legacy memory controller is likely 984 going to shrink due to deprecation process. New deployments with v1 985 controller are highly discouraged. 986 987 San N is unsure. 988 989config BLK_CGROUP 990 bool "IO controller" 991 depends on BLOCK 992 default n 993 help 994 Generic block IO controller cgroup interface. This is the common 995 cgroup interface which should be used by various IO controlling 996 policies. 997 998 Currently, CFQ IO scheduler uses it to recognize task groups and 999 control disk bandwidth allocation (proportional time slice allocation) 1000 to such task groups. It is also used by bio throttling logic in 1001 block layer to implement upper limit in IO rates on a device. 1002 1003 This option only enables generic Block IO controller infrastructure. 1004 One needs to also enable actual IO controlling logic/policy. For 1005 enabling proportional weight division of disk bandwidth in CFQ, set 1006 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 1007 CONFIG_BLK_DEV_THROTTLING=y. 1008 1009 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 1010 1011config CGROUP_WRITEBACK 1012 bool 1013 depends on MEMCG && BLK_CGROUP 1014 default y 1015 1016menuconfig CGROUP_SCHED 1017 bool "CPU controller" 1018 default n 1019 help 1020 This feature lets CPU scheduler recognize task groups and control CPU 1021 bandwidth allocation to such task groups. It uses cgroups to group 1022 tasks. 1023 1024if CGROUP_SCHED 1025config FAIR_GROUP_SCHED 1026 bool "Group scheduling for SCHED_OTHER" 1027 depends on CGROUP_SCHED 1028 default CGROUP_SCHED 1029 1030config CFS_BANDWIDTH 1031 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 1032 depends on FAIR_GROUP_SCHED 1033 default n 1034 help 1035 This option allows users to define CPU bandwidth rates (limits) for 1036 tasks running within the fair group scheduler. Groups with no limit 1037 set are considered to be unconstrained and will run with no 1038 restriction. 1039 See Documentation/scheduler/sched-bwc.rst for more information. 1040 1041config RT_GROUP_SCHED 1042 bool "Group scheduling for SCHED_RR/FIFO" 1043 depends on CGROUP_SCHED 1044 default n 1045 help 1046 This feature lets you explicitly allocate real CPU bandwidth 1047 to task groups. If enabled, it will also make it impossible to 1048 schedule realtime tasks for non-root users until you allocate 1049 realtime bandwidth for them. 1050 See Documentation/scheduler/sched-rt-group.rst for more information. 1051 1052endif #CGROUP_SCHED 1053 1054config SCHED_MM_CID 1055 def_bool y 1056 depends on SMP && RSEQ 1057 1058config UCLAMP_TASK_GROUP 1059 bool "Utilization clamping per group of tasks" 1060 depends on CGROUP_SCHED 1061 depends on UCLAMP_TASK 1062 default n 1063 help 1064 This feature enables the scheduler to track the clamped utilization 1065 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 1066 1067 When this option is enabled, the user can specify a min and max 1068 CPU bandwidth which is allowed for each single task in a group. 1069 The max bandwidth allows to clamp the maximum frequency a task 1070 can use, while the min bandwidth allows to define a minimum 1071 frequency a task will always use. 1072 1073 When task group based utilization clamping is enabled, an eventually 1074 specified task-specific clamp value is constrained by the cgroup 1075 specified clamp value. Both minimum and maximum task clamping cannot 1076 be bigger than the corresponding clamping defined at task group level. 1077 1078 If in doubt, say N. 1079 1080config CGROUP_PIDS 1081 bool "PIDs controller" 1082 help 1083 Provides enforcement of process number limits in the scope of a 1084 cgroup. Any attempt to fork more processes than is allowed in the 1085 cgroup will fail. PIDs are fundamentally a global resource because it 1086 is fairly trivial to reach PID exhaustion before you reach even a 1087 conservative kmemcg limit. As a result, it is possible to grind a 1088 system to halt without being limited by other cgroup policies. The 1089 PIDs controller is designed to stop this from happening. 1090 1091 It should be noted that organisational operations (such as attaching 1092 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 1093 since the PIDs limit only affects a process's ability to fork, not to 1094 attach to a cgroup. 1095 1096config CGROUP_RDMA 1097 bool "RDMA controller" 1098 help 1099 Provides enforcement of RDMA resources defined by IB stack. 1100 It is fairly easy for consumers to exhaust RDMA resources, which 1101 can result into resource unavailability to other consumers. 1102 RDMA controller is designed to stop this from happening. 1103 Attaching processes with active RDMA resources to the cgroup 1104 hierarchy is allowed even if can cross the hierarchy's limit. 1105 1106config CGROUP_FREEZER 1107 bool "Freezer controller" 1108 help 1109 Provides a way to freeze and unfreeze all tasks in a 1110 cgroup. 1111 1112 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1113 controller includes important in-kernel memory consumers per default. 1114 1115 If you're using cgroup2, say N. 1116 1117config CGROUP_HUGETLB 1118 bool "HugeTLB controller" 1119 depends on HUGETLB_PAGE 1120 select PAGE_COUNTER 1121 default n 1122 help 1123 Provides a cgroup controller for HugeTLB pages. 1124 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1125 The limit is enforced during page fault. Since HugeTLB doesn't 1126 support page reclaim, enforcing the limit at page fault time implies 1127 that, the application will get SIGBUS signal if it tries to access 1128 HugeTLB pages beyond its limit. This requires the application to know 1129 beforehand how much HugeTLB pages it would require for its use. The 1130 control group is tracked in the third page lru pointer. This means 1131 that we cannot use the controller with huge page less than 3 pages. 1132 1133config CPUSETS 1134 bool "Cpuset controller" 1135 depends on SMP 1136 help 1137 This option will let you create and manage CPUSETs which 1138 allow dynamically partitioning a system into sets of CPUs and 1139 Memory Nodes and assigning tasks to run only within those sets. 1140 This is primarily useful on large SMP or NUMA systems. 1141 1142 Say N if unsure. 1143 1144config PROC_PID_CPUSET 1145 bool "Include legacy /proc/<pid>/cpuset file" 1146 depends on CPUSETS 1147 default y 1148 1149config CGROUP_DEVICE 1150 bool "Device controller" 1151 help 1152 Provides a cgroup controller implementing whitelists for 1153 devices which a process in the cgroup can mknod or open. 1154 1155config CGROUP_CPUACCT 1156 bool "Simple CPU accounting controller" 1157 help 1158 Provides a simple controller for monitoring the 1159 total CPU consumed by the tasks in a cgroup. 1160 1161config CGROUP_PERF 1162 bool "Perf controller" 1163 depends on PERF_EVENTS 1164 help 1165 This option extends the perf per-cpu mode to restrict monitoring 1166 to threads which belong to the cgroup specified and run on the 1167 designated cpu. Or this can be used to have cgroup ID in samples 1168 so that it can monitor performance events among cgroups. 1169 1170 Say N if unsure. 1171 1172config CGROUP_BPF 1173 bool "Support for eBPF programs attached to cgroups" 1174 depends on BPF_SYSCALL 1175 select SOCK_CGROUP_DATA 1176 help 1177 Allow attaching eBPF programs to a cgroup using the bpf(2) 1178 syscall command BPF_PROG_ATTACH. 1179 1180 In which context these programs are accessed depends on the type 1181 of attachment. For instance, programs that are attached using 1182 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1183 inet sockets. 1184 1185config CGROUP_MISC 1186 bool "Misc resource controller" 1187 default n 1188 help 1189 Provides a controller for miscellaneous resources on a host. 1190 1191 Miscellaneous scalar resources are the resources on the host system 1192 which cannot be abstracted like the other cgroups. This controller 1193 tracks and limits the miscellaneous resources used by a process 1194 attached to a cgroup hierarchy. 1195 1196 For more information, please check misc cgroup section in 1197 /Documentation/admin-guide/cgroup-v2.rst. 1198 1199config CGROUP_DEBUG 1200 bool "Debug controller" 1201 default n 1202 depends on DEBUG_KERNEL 1203 help 1204 This option enables a simple controller that exports 1205 debugging information about the cgroups framework. This 1206 controller is for control cgroup debugging only. Its 1207 interfaces are not stable. 1208 1209 Say N. 1210 1211config SOCK_CGROUP_DATA 1212 bool 1213 default n 1214 1215endif # CGROUPS 1216 1217menuconfig NAMESPACES 1218 bool "Namespaces support" if EXPERT 1219 depends on MULTIUSER 1220 default !EXPERT 1221 help 1222 Provides the way to make tasks work with different objects using 1223 the same id. For example same IPC id may refer to different objects 1224 or same user id or pid may refer to different tasks when used in 1225 different namespaces. 1226 1227if NAMESPACES 1228 1229config UTS_NS 1230 bool "UTS namespace" 1231 default y 1232 help 1233 In this namespace tasks see different info provided with the 1234 uname() system call 1235 1236config TIME_NS 1237 bool "TIME namespace" 1238 depends on GENERIC_VDSO_TIME_NS 1239 default y 1240 help 1241 In this namespace boottime and monotonic clocks can be set. 1242 The time will keep going with the same pace. 1243 1244config IPC_NS 1245 bool "IPC namespace" 1246 depends on (SYSVIPC || POSIX_MQUEUE) 1247 default y 1248 help 1249 In this namespace tasks work with IPC ids which correspond to 1250 different IPC objects in different namespaces. 1251 1252config USER_NS 1253 bool "User namespace" 1254 default n 1255 help 1256 This allows containers, i.e. vservers, to use user namespaces 1257 to provide different user info for different servers. 1258 1259 When user namespaces are enabled in the kernel it is 1260 recommended that the MEMCG option also be enabled and that 1261 user-space use the memory control groups to limit the amount 1262 of memory a memory unprivileged users can use. 1263 1264 If unsure, say N. 1265 1266config PID_NS 1267 bool "PID Namespaces" 1268 default y 1269 help 1270 Support process id namespaces. This allows having multiple 1271 processes with the same pid as long as they are in different 1272 pid namespaces. This is a building block of containers. 1273 1274config NET_NS 1275 bool "Network namespace" 1276 depends on NET 1277 default y 1278 help 1279 Allow user space to create what appear to be multiple instances 1280 of the network stack. 1281 1282endif # NAMESPACES 1283 1284config CHECKPOINT_RESTORE 1285 bool "Checkpoint/restore support" 1286 depends on PROC_FS 1287 select PROC_CHILDREN 1288 select KCMP 1289 default n 1290 help 1291 Enables additional kernel features in a sake of checkpoint/restore. 1292 In particular it adds auxiliary prctl codes to setup process text, 1293 data and heap segment sizes, and a few additional /proc filesystem 1294 entries. 1295 1296 If unsure, say N here. 1297 1298config SCHED_AUTOGROUP 1299 bool "Automatic process group scheduling" 1300 select CGROUPS 1301 select CGROUP_SCHED 1302 select FAIR_GROUP_SCHED 1303 help 1304 This option optimizes the scheduler for common desktop workloads by 1305 automatically creating and populating task groups. This separation 1306 of workloads isolates aggressive CPU burners (like build jobs) from 1307 desktop applications. Task group autogeneration is currently based 1308 upon task session. 1309 1310config RELAY 1311 bool "Kernel->user space relay support (formerly relayfs)" 1312 select IRQ_WORK 1313 help 1314 This option enables support for relay interface support in 1315 certain file systems (such as debugfs). 1316 It is designed to provide an efficient mechanism for tools and 1317 facilities to relay large amounts of data from kernel space to 1318 user space. 1319 1320 If unsure, say N. 1321 1322config BLK_DEV_INITRD 1323 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1324 help 1325 The initial RAM filesystem is a ramfs which is loaded by the 1326 boot loader (loadlin or lilo) and that is mounted as root 1327 before the normal boot procedure. It is typically used to 1328 load modules needed to mount the "real" root file system, 1329 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1330 1331 If RAM disk support (BLK_DEV_RAM) is also included, this 1332 also enables initial RAM disk (initrd) support and adds 1333 15 Kbytes (more on some other architectures) to the kernel size. 1334 1335 If unsure say Y. 1336 1337if BLK_DEV_INITRD 1338 1339source "usr/Kconfig" 1340 1341endif 1342 1343config BOOT_CONFIG 1344 bool "Boot config support" 1345 select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED 1346 help 1347 Extra boot config allows system admin to pass a config file as 1348 complemental extension of kernel cmdline when booting. 1349 The boot config file must be attached at the end of initramfs 1350 with checksum, size and magic word. 1351 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1352 1353 If unsure, say Y. 1354 1355config BOOT_CONFIG_FORCE 1356 bool "Force unconditional bootconfig processing" 1357 depends on BOOT_CONFIG 1358 default y if BOOT_CONFIG_EMBED 1359 help 1360 With this Kconfig option set, BOOT_CONFIG processing is carried 1361 out even when the "bootconfig" kernel-boot parameter is omitted. 1362 In fact, with this Kconfig option set, there is no way to 1363 make the kernel ignore the BOOT_CONFIG-supplied kernel-boot 1364 parameters. 1365 1366 If unsure, say N. 1367 1368config BOOT_CONFIG_EMBED 1369 bool "Embed bootconfig file in the kernel" 1370 depends on BOOT_CONFIG 1371 help 1372 Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the 1373 kernel. Usually, the bootconfig file is loaded with the initrd 1374 image. But if the system doesn't support initrd, this option will 1375 help you by embedding a bootconfig file while building the kernel. 1376 1377 If unsure, say N. 1378 1379config BOOT_CONFIG_EMBED_FILE 1380 string "Embedded bootconfig file path" 1381 depends on BOOT_CONFIG_EMBED 1382 help 1383 Specify a bootconfig file which will be embedded to the kernel. 1384 This bootconfig will be used if there is no initrd or no other 1385 bootconfig in the initrd. 1386 1387config INITRAMFS_PRESERVE_MTIME 1388 bool "Preserve cpio archive mtimes in initramfs" 1389 default y 1390 help 1391 Each entry in an initramfs cpio archive carries an mtime value. When 1392 enabled, extracted cpio items take this mtime, with directory mtime 1393 setting deferred until after creation of any child entries. 1394 1395 If unsure, say Y. 1396 1397choice 1398 prompt "Compiler optimization level" 1399 default CC_OPTIMIZE_FOR_PERFORMANCE 1400 1401config CC_OPTIMIZE_FOR_PERFORMANCE 1402 bool "Optimize for performance (-O2)" 1403 help 1404 This is the default optimization level for the kernel, building 1405 with the "-O2" compiler flag for best performance and most 1406 helpful compile-time warnings. 1407 1408config CC_OPTIMIZE_FOR_SIZE 1409 bool "Optimize for size (-Os)" 1410 help 1411 Choosing this option will pass "-Os" to your compiler resulting 1412 in a smaller kernel. 1413 1414endchoice 1415 1416config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1417 bool 1418 help 1419 This requires that the arch annotates or otherwise protects 1420 its external entry points from being discarded. Linker scripts 1421 must also merge .text.*, .data.*, and .bss.* correctly into 1422 output sections. Care must be taken not to pull in unrelated 1423 sections (e.g., '.text.init'). Typically '.' in section names 1424 is used to distinguish them from label names / C identifiers. 1425 1426config LD_DEAD_CODE_DATA_ELIMINATION 1427 bool "Dead code and data elimination (EXPERIMENTAL)" 1428 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1429 depends on EXPERT 1430 depends on $(cc-option,-ffunction-sections -fdata-sections) 1431 depends on $(ld-option,--gc-sections) 1432 help 1433 Enable this if you want to do dead code and data elimination with 1434 the linker by compiling with -ffunction-sections -fdata-sections, 1435 and linking with --gc-sections. 1436 1437 This can reduce on disk and in-memory size of the kernel 1438 code and static data, particularly for small configs and 1439 on small systems. This has the possibility of introducing 1440 silently broken kernel if the required annotations are not 1441 present. This option is not well tested yet, so use at your 1442 own risk. 1443 1444config LD_ORPHAN_WARN 1445 def_bool y 1446 depends on ARCH_WANT_LD_ORPHAN_WARN 1447 depends on $(ld-option,--orphan-handling=warn) 1448 depends on $(ld-option,--orphan-handling=error) 1449 1450config LD_ORPHAN_WARN_LEVEL 1451 string 1452 depends on LD_ORPHAN_WARN 1453 default "error" if WERROR 1454 default "warn" 1455 1456config SYSCTL 1457 bool 1458 1459config HAVE_UID16 1460 bool 1461 1462config SYSCTL_EXCEPTION_TRACE 1463 bool 1464 help 1465 Enable support for /proc/sys/debug/exception-trace. 1466 1467config SYSCTL_ARCH_UNALIGN_NO_WARN 1468 bool 1469 help 1470 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1471 Allows arch to define/use @no_unaligned_warning to possibly warn 1472 about unaligned access emulation going on under the hood. 1473 1474config SYSCTL_ARCH_UNALIGN_ALLOW 1475 bool 1476 help 1477 Enable support for /proc/sys/kernel/unaligned-trap 1478 Allows arches to define/use @unaligned_enabled to runtime toggle 1479 the unaligned access emulation. 1480 see arch/parisc/kernel/unaligned.c for reference 1481 1482config HAVE_PCSPKR_PLATFORM 1483 bool 1484 1485menuconfig EXPERT 1486 bool "Configure standard kernel features (expert users)" 1487 # Unhide debug options, to make the on-by-default options visible 1488 select DEBUG_KERNEL 1489 help 1490 This option allows certain base kernel options and settings 1491 to be disabled or tweaked. This is for specialized 1492 environments which can tolerate a "non-standard" kernel. 1493 Only use this if you really know what you are doing. 1494 1495config UID16 1496 bool "Enable 16-bit UID system calls" if EXPERT 1497 depends on HAVE_UID16 && MULTIUSER 1498 default y 1499 help 1500 This enables the legacy 16-bit UID syscall wrappers. 1501 1502config MULTIUSER 1503 bool "Multiple users, groups and capabilities support" if EXPERT 1504 default y 1505 help 1506 This option enables support for non-root users, groups and 1507 capabilities. 1508 1509 If you say N here, all processes will run with UID 0, GID 0, and all 1510 possible capabilities. Saying N here also compiles out support for 1511 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1512 setgid, and capset. 1513 1514 If unsure, say Y here. 1515 1516config SGETMASK_SYSCALL 1517 bool "sgetmask/ssetmask syscalls support" if EXPERT 1518 default PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1519 help 1520 sys_sgetmask and sys_ssetmask are obsolete system calls 1521 no longer supported in libc but still enabled by default in some 1522 architectures. 1523 1524 If unsure, leave the default option here. 1525 1526config SYSFS_SYSCALL 1527 bool "Sysfs syscall support" if EXPERT 1528 default y 1529 help 1530 sys_sysfs is an obsolete system call no longer supported in libc. 1531 Note that disabling this option is more secure but might break 1532 compatibility with some systems. 1533 1534 If unsure say Y here. 1535 1536config FHANDLE 1537 bool "open by fhandle syscalls" if EXPERT 1538 select EXPORTFS 1539 default y 1540 help 1541 If you say Y here, a user level program will be able to map 1542 file names to handle and then later use the handle for 1543 different file system operations. This is useful in implementing 1544 userspace file servers, which now track files using handles instead 1545 of names. The handle would remain the same even if file names 1546 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1547 syscalls. 1548 1549config POSIX_TIMERS 1550 bool "Posix Clocks & timers" if EXPERT 1551 default y 1552 help 1553 This includes native support for POSIX timers to the kernel. 1554 Some embedded systems have no use for them and therefore they 1555 can be configured out to reduce the size of the kernel image. 1556 1557 When this option is disabled, the following syscalls won't be 1558 available: timer_create, timer_gettime: timer_getoverrun, 1559 timer_settime, timer_delete, clock_adjtime, getitimer, 1560 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1561 clock_getres and clock_nanosleep syscalls will be limited to 1562 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1563 1564 If unsure say y. 1565 1566config PRINTK 1567 default y 1568 bool "Enable support for printk" if EXPERT 1569 select IRQ_WORK 1570 help 1571 This option enables normal printk support. Removing it 1572 eliminates most of the message strings from the kernel image 1573 and makes the kernel more or less silent. As this makes it 1574 very difficult to diagnose system problems, saying N here is 1575 strongly discouraged. 1576 1577config BUG 1578 bool "BUG() support" if EXPERT 1579 default y 1580 help 1581 Disabling this option eliminates support for BUG and WARN, reducing 1582 the size of your kernel image and potentially quietly ignoring 1583 numerous fatal conditions. You should only consider disabling this 1584 option for embedded systems with no facilities for reporting errors. 1585 Just say Y. 1586 1587config ELF_CORE 1588 depends on COREDUMP 1589 default y 1590 bool "Enable ELF core dumps" if EXPERT 1591 help 1592 Enable support for generating core dumps. Disabling saves about 4k. 1593 1594 1595config PCSPKR_PLATFORM 1596 bool "Enable PC-Speaker support" if EXPERT 1597 depends on HAVE_PCSPKR_PLATFORM 1598 select I8253_LOCK 1599 default y 1600 help 1601 This option allows to disable the internal PC-Speaker 1602 support, saving some memory. 1603 1604config BASE_SMALL 1605 bool "Enable smaller-sized data structures for core" if EXPERT 1606 help 1607 Enabling this option reduces the size of miscellaneous core 1608 kernel data structures. This saves memory on small machines, 1609 but may reduce performance. 1610 1611config FUTEX 1612 bool "Enable futex support" if EXPERT 1613 depends on !(SPARC32 && SMP) 1614 default y 1615 imply RT_MUTEXES 1616 help 1617 Disabling this option will cause the kernel to be built without 1618 support for "fast userspace mutexes". The resulting kernel may not 1619 run glibc-based applications correctly. 1620 1621config FUTEX_PI 1622 bool 1623 depends on FUTEX && RT_MUTEXES 1624 default y 1625 1626config EPOLL 1627 bool "Enable eventpoll support" if EXPERT 1628 default y 1629 help 1630 Disabling this option will cause the kernel to be built without 1631 support for epoll family of system calls. 1632 1633config SIGNALFD 1634 bool "Enable signalfd() system call" if EXPERT 1635 default y 1636 help 1637 Enable the signalfd() system call that allows to receive signals 1638 on a file descriptor. 1639 1640 If unsure, say Y. 1641 1642config TIMERFD 1643 bool "Enable timerfd() system call" if EXPERT 1644 default y 1645 help 1646 Enable the timerfd() system call that allows to receive timer 1647 events on a file descriptor. 1648 1649 If unsure, say Y. 1650 1651config EVENTFD 1652 bool "Enable eventfd() system call" if EXPERT 1653 default y 1654 help 1655 Enable the eventfd() system call that allows to receive both 1656 kernel notification (ie. KAIO) or userspace notifications. 1657 1658 If unsure, say Y. 1659 1660config SHMEM 1661 bool "Use full shmem filesystem" if EXPERT 1662 default y 1663 depends on MMU 1664 help 1665 The shmem is an internal filesystem used to manage shared memory. 1666 It is backed by swap and manages resource limits. It is also exported 1667 to userspace as tmpfs if TMPFS is enabled. Disabling this 1668 option replaces shmem and tmpfs with the much simpler ramfs code, 1669 which may be appropriate on small systems without swap. 1670 1671config AIO 1672 bool "Enable AIO support" if EXPERT 1673 default y 1674 help 1675 This option enables POSIX asynchronous I/O which may by used 1676 by some high performance threaded applications. Disabling 1677 this option saves about 7k. 1678 1679config IO_URING 1680 bool "Enable IO uring support" if EXPERT 1681 select IO_WQ 1682 default y 1683 help 1684 This option enables support for the io_uring interface, enabling 1685 applications to submit and complete IO through submission and 1686 completion rings that are shared between the kernel and application. 1687 1688config ADVISE_SYSCALLS 1689 bool "Enable madvise/fadvise syscalls" if EXPERT 1690 default y 1691 help 1692 This option enables the madvise and fadvise syscalls, used by 1693 applications to advise the kernel about their future memory or file 1694 usage, improving performance. If building an embedded system where no 1695 applications use these syscalls, you can disable this option to save 1696 space. 1697 1698config MEMBARRIER 1699 bool "Enable membarrier() system call" if EXPERT 1700 default y 1701 help 1702 Enable the membarrier() system call that allows issuing memory 1703 barriers across all running threads, which can be used to distribute 1704 the cost of user-space memory barriers asymmetrically by transforming 1705 pairs of memory barriers into pairs consisting of membarrier() and a 1706 compiler barrier. 1707 1708 If unsure, say Y. 1709 1710config KCMP 1711 bool "Enable kcmp() system call" if EXPERT 1712 help 1713 Enable the kernel resource comparison system call. It provides 1714 user-space with the ability to compare two processes to see if they 1715 share a common resource, such as a file descriptor or even virtual 1716 memory space. 1717 1718 If unsure, say N. 1719 1720config RSEQ 1721 bool "Enable rseq() system call" if EXPERT 1722 default y 1723 depends on HAVE_RSEQ 1724 select MEMBARRIER 1725 help 1726 Enable the restartable sequences system call. It provides a 1727 user-space cache for the current CPU number value, which 1728 speeds up getting the current CPU number from user-space, 1729 as well as an ABI to speed up user-space operations on 1730 per-CPU data. 1731 1732 If unsure, say Y. 1733 1734config DEBUG_RSEQ 1735 default n 1736 bool "Enable debugging of rseq() system call" if EXPERT 1737 depends on RSEQ && DEBUG_KERNEL 1738 help 1739 Enable extra debugging checks for the rseq system call. 1740 1741 If unsure, say N. 1742 1743config CACHESTAT_SYSCALL 1744 bool "Enable cachestat() system call" if EXPERT 1745 default y 1746 help 1747 Enable the cachestat system call, which queries the page cache 1748 statistics of a file (number of cached pages, dirty pages, 1749 pages marked for writeback, (recently) evicted pages). 1750 1751 If unsure say Y here. 1752 1753config PC104 1754 bool "PC/104 support" if EXPERT 1755 help 1756 Expose PC/104 form factor device drivers and options available for 1757 selection and configuration. Enable this option if your target 1758 machine has a PC/104 bus. 1759 1760config KALLSYMS 1761 bool "Load all symbols for debugging/ksymoops" if EXPERT 1762 default y 1763 help 1764 Say Y here to let the kernel print out symbolic crash information and 1765 symbolic stack backtraces. This increases the size of the kernel 1766 somewhat, as all symbols have to be loaded into the kernel image. 1767 1768config KALLSYMS_SELFTEST 1769 bool "Test the basic functions and performance of kallsyms" 1770 depends on KALLSYMS 1771 default n 1772 help 1773 Test the basic functions and performance of some interfaces, such as 1774 kallsyms_lookup_name. It also calculates the compression rate of the 1775 kallsyms compression algorithm for the current symbol set. 1776 1777 Start self-test automatically after system startup. Suggest executing 1778 "dmesg | grep kallsyms_selftest" to collect test results. "finish" is 1779 displayed in the last line, indicating that the test is complete. 1780 1781config KALLSYMS_ALL 1782 bool "Include all symbols in kallsyms" 1783 depends on DEBUG_KERNEL && KALLSYMS 1784 help 1785 Normally kallsyms only contains the symbols of functions for nicer 1786 OOPS messages and backtraces (i.e., symbols from the text and inittext 1787 sections). This is sufficient for most cases. And only if you want to 1788 enable kernel live patching, or other less common use cases (e.g., 1789 when a debugger is used) all symbols are required (i.e., names of 1790 variables from the data sections, etc). 1791 1792 This option makes sure that all symbols are loaded into the kernel 1793 image (i.e., symbols from all sections) in cost of increased kernel 1794 size (depending on the kernel configuration, it may be 300KiB or 1795 something like this). 1796 1797 Say N unless you really need all symbols, or kernel live patching. 1798 1799config KALLSYMS_ABSOLUTE_PERCPU 1800 bool 1801 depends on KALLSYMS 1802 default X86_64 && SMP 1803 1804config KALLSYMS_BASE_RELATIVE 1805 bool 1806 depends on KALLSYMS 1807 default y 1808 help 1809 Instead of emitting them as absolute values in the native word size, 1810 emit the symbol references in the kallsyms table as 32-bit entries, 1811 each containing a relative value in the range [base, base + U32_MAX] 1812 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1813 an absolute value in the range [0, S32_MAX] or a relative value in the 1814 range [base, base + S32_MAX], where base is the lowest relative symbol 1815 address encountered in the image. 1816 1817 On 64-bit builds, this reduces the size of the address table by 50%, 1818 but more importantly, it results in entries whose values are build 1819 time constants, and no relocation pass is required at runtime to fix 1820 up the entries based on the runtime load address of the kernel. 1821 1822# end of the "standard kernel features (expert users)" menu 1823 1824config ARCH_HAS_MEMBARRIER_CALLBACKS 1825 bool 1826 1827config ARCH_HAS_MEMBARRIER_SYNC_CORE 1828 bool 1829 1830config HAVE_PERF_EVENTS 1831 bool 1832 help 1833 See tools/perf/design.txt for details. 1834 1835config GUEST_PERF_EVENTS 1836 bool 1837 depends on HAVE_PERF_EVENTS 1838 1839config PERF_USE_VMALLOC 1840 bool 1841 help 1842 See tools/perf/design.txt for details 1843 1844menu "Kernel Performance Events And Counters" 1845 1846config PERF_EVENTS 1847 bool "Kernel performance events and counters" 1848 default y if PROFILING 1849 depends on HAVE_PERF_EVENTS 1850 select IRQ_WORK 1851 help 1852 Enable kernel support for various performance events provided 1853 by software and hardware. 1854 1855 Software events are supported either built-in or via the 1856 use of generic tracepoints. 1857 1858 Most modern CPUs support performance events via performance 1859 counter registers. These registers count the number of certain 1860 types of hw events: such as instructions executed, cachemisses 1861 suffered, or branches mis-predicted - without slowing down the 1862 kernel or applications. These registers can also trigger interrupts 1863 when a threshold number of events have passed - and can thus be 1864 used to profile the code that runs on that CPU. 1865 1866 The Linux Performance Event subsystem provides an abstraction of 1867 these software and hardware event capabilities, available via a 1868 system call and used by the "perf" utility in tools/perf/. It 1869 provides per task and per CPU counters, and it provides event 1870 capabilities on top of those. 1871 1872 Say Y if unsure. 1873 1874config DEBUG_PERF_USE_VMALLOC 1875 default n 1876 bool "Debug: use vmalloc to back perf mmap() buffers" 1877 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1878 select PERF_USE_VMALLOC 1879 help 1880 Use vmalloc memory to back perf mmap() buffers. 1881 1882 Mostly useful for debugging the vmalloc code on platforms 1883 that don't require it. 1884 1885 Say N if unsure. 1886 1887endmenu 1888 1889config SYSTEM_DATA_VERIFICATION 1890 def_bool n 1891 select SYSTEM_TRUSTED_KEYRING 1892 select KEYS 1893 select CRYPTO 1894 select CRYPTO_RSA 1895 select ASYMMETRIC_KEY_TYPE 1896 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1897 select ASN1 1898 select OID_REGISTRY 1899 select X509_CERTIFICATE_PARSER 1900 select PKCS7_MESSAGE_PARSER 1901 help 1902 Provide PKCS#7 message verification using the contents of the system 1903 trusted keyring to provide public keys. This then can be used for 1904 module verification, kexec image verification and firmware blob 1905 verification. 1906 1907config PROFILING 1908 bool "Profiling support" 1909 help 1910 Say Y here to enable the extended profiling support mechanisms used 1911 by profilers. 1912 1913config RUST 1914 bool "Rust support" 1915 depends on HAVE_RUST 1916 depends on RUST_IS_AVAILABLE 1917 depends on !CFI_CLANG 1918 depends on !MODVERSIONS 1919 depends on !GCC_PLUGINS 1920 depends on !RANDSTRUCT 1921 depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE 1922 help 1923 Enables Rust support in the kernel. 1924 1925 This allows other Rust-related options, like drivers written in Rust, 1926 to be selected. 1927 1928 It is also required to be able to load external kernel modules 1929 written in Rust. 1930 1931 See Documentation/rust/ for more information. 1932 1933 If unsure, say N. 1934 1935config RUSTC_VERSION_TEXT 1936 string 1937 depends on RUST 1938 default $(shell,command -v $(RUSTC) >/dev/null 2>&1 && $(RUSTC) --version || echo n) 1939 1940config BINDGEN_VERSION_TEXT 1941 string 1942 depends on RUST 1943 default $(shell,command -v $(BINDGEN) >/dev/null 2>&1 && $(BINDGEN) --version || echo n) 1944 1945# 1946# Place an empty function call at each tracepoint site. Can be 1947# dynamically changed for a probe function. 1948# 1949config TRACEPOINTS 1950 bool 1951 1952source "kernel/Kconfig.kexec" 1953 1954endmenu # General setup 1955 1956source "arch/Kconfig" 1957 1958config RT_MUTEXES 1959 bool 1960 default y if PREEMPT_RT 1961 1962config MODULE_SIG_FORMAT 1963 def_bool n 1964 select SYSTEM_DATA_VERIFICATION 1965 1966source "kernel/module/Kconfig" 1967 1968config INIT_ALL_POSSIBLE 1969 bool 1970 help 1971 Back when each arch used to define their own cpu_online_mask and 1972 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 1973 with all 1s, and others with all 0s. When they were centralised, 1974 it was better to provide this option than to break all the archs 1975 and have several arch maintainers pursuing me down dark alleys. 1976 1977source "block/Kconfig" 1978 1979config PREEMPT_NOTIFIERS 1980 bool 1981 1982config PADATA 1983 depends on SMP 1984 bool 1985 1986config ASN1 1987 tristate 1988 help 1989 Build a simple ASN.1 grammar compiler that produces a bytecode output 1990 that can be interpreted by the ASN.1 stream decoder and used to 1991 inform it as to what tags are to be expected in a stream and what 1992 functions to call on what tags. 1993 1994source "kernel/Kconfig.locks" 1995 1996config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 1997 bool 1998 1999config ARCH_HAS_PREPARE_SYNC_CORE_CMD 2000 bool 2001 2002config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2003 bool 2004 2005# It may be useful for an architecture to override the definitions of the 2006# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2007# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2008# different calling convention for syscalls. They can also override the 2009# macros for not-implemented syscalls in kernel/sys_ni.c and 2010# kernel/time/posix-stubs.c. All these overrides need to be available in 2011# <asm/syscall_wrapper.h>. 2012config ARCH_HAS_SYSCALL_WRAPPER 2013 def_bool n 2014