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 >= 100000 && 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_KMEM 973 bool 974 depends on MEMCG 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 SCHED_MM_CID 1043 def_bool y 1044 depends on SMP && RSEQ 1045 1046config UCLAMP_TASK_GROUP 1047 bool "Utilization clamping per group of tasks" 1048 depends on CGROUP_SCHED 1049 depends on UCLAMP_TASK 1050 default n 1051 help 1052 This feature enables the scheduler to track the clamped utilization 1053 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 1054 1055 When this option is enabled, the user can specify a min and max 1056 CPU bandwidth which is allowed for each single task in a group. 1057 The max bandwidth allows to clamp the maximum frequency a task 1058 can use, while the min bandwidth allows to define a minimum 1059 frequency a task will always use. 1060 1061 When task group based utilization clamping is enabled, an eventually 1062 specified task-specific clamp value is constrained by the cgroup 1063 specified clamp value. Both minimum and maximum task clamping cannot 1064 be bigger than the corresponding clamping defined at task group level. 1065 1066 If in doubt, say N. 1067 1068config CGROUP_PIDS 1069 bool "PIDs controller" 1070 help 1071 Provides enforcement of process number limits in the scope of a 1072 cgroup. Any attempt to fork more processes than is allowed in the 1073 cgroup will fail. PIDs are fundamentally a global resource because it 1074 is fairly trivial to reach PID exhaustion before you reach even a 1075 conservative kmemcg limit. As a result, it is possible to grind a 1076 system to halt without being limited by other cgroup policies. The 1077 PIDs controller is designed to stop this from happening. 1078 1079 It should be noted that organisational operations (such as attaching 1080 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 1081 since the PIDs limit only affects a process's ability to fork, not to 1082 attach to a cgroup. 1083 1084config CGROUP_RDMA 1085 bool "RDMA controller" 1086 help 1087 Provides enforcement of RDMA resources defined by IB stack. 1088 It is fairly easy for consumers to exhaust RDMA resources, which 1089 can result into resource unavailability to other consumers. 1090 RDMA controller is designed to stop this from happening. 1091 Attaching processes with active RDMA resources to the cgroup 1092 hierarchy is allowed even if can cross the hierarchy's limit. 1093 1094config CGROUP_FREEZER 1095 bool "Freezer controller" 1096 help 1097 Provides a way to freeze and unfreeze all tasks in a 1098 cgroup. 1099 1100 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1101 controller includes important in-kernel memory consumers per default. 1102 1103 If you're using cgroup2, say N. 1104 1105config CGROUP_HUGETLB 1106 bool "HugeTLB controller" 1107 depends on HUGETLB_PAGE 1108 select PAGE_COUNTER 1109 default n 1110 help 1111 Provides a cgroup controller for HugeTLB pages. 1112 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1113 The limit is enforced during page fault. Since HugeTLB doesn't 1114 support page reclaim, enforcing the limit at page fault time implies 1115 that, the application will get SIGBUS signal if it tries to access 1116 HugeTLB pages beyond its limit. This requires the application to know 1117 beforehand how much HugeTLB pages it would require for its use. The 1118 control group is tracked in the third page lru pointer. This means 1119 that we cannot use the controller with huge page less than 3 pages. 1120 1121config CPUSETS 1122 bool "Cpuset controller" 1123 depends on SMP 1124 help 1125 This option will let you create and manage CPUSETs which 1126 allow dynamically partitioning a system into sets of CPUs and 1127 Memory Nodes and assigning tasks to run only within those sets. 1128 This is primarily useful on large SMP or NUMA systems. 1129 1130 Say N if unsure. 1131 1132config PROC_PID_CPUSET 1133 bool "Include legacy /proc/<pid>/cpuset file" 1134 depends on CPUSETS 1135 default y 1136 1137config CGROUP_DEVICE 1138 bool "Device controller" 1139 help 1140 Provides a cgroup controller implementing whitelists for 1141 devices which a process in the cgroup can mknod or open. 1142 1143config CGROUP_CPUACCT 1144 bool "Simple CPU accounting controller" 1145 help 1146 Provides a simple controller for monitoring the 1147 total CPU consumed by the tasks in a cgroup. 1148 1149config CGROUP_PERF 1150 bool "Perf controller" 1151 depends on PERF_EVENTS 1152 help 1153 This option extends the perf per-cpu mode to restrict monitoring 1154 to threads which belong to the cgroup specified and run on the 1155 designated cpu. Or this can be used to have cgroup ID in samples 1156 so that it can monitor performance events among cgroups. 1157 1158 Say N if unsure. 1159 1160config CGROUP_BPF 1161 bool "Support for eBPF programs attached to cgroups" 1162 depends on BPF_SYSCALL 1163 select SOCK_CGROUP_DATA 1164 help 1165 Allow attaching eBPF programs to a cgroup using the bpf(2) 1166 syscall command BPF_PROG_ATTACH. 1167 1168 In which context these programs are accessed depends on the type 1169 of attachment. For instance, programs that are attached using 1170 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1171 inet sockets. 1172 1173config CGROUP_MISC 1174 bool "Misc resource controller" 1175 default n 1176 help 1177 Provides a controller for miscellaneous resources on a host. 1178 1179 Miscellaneous scalar resources are the resources on the host system 1180 which cannot be abstracted like the other cgroups. This controller 1181 tracks and limits the miscellaneous resources used by a process 1182 attached to a cgroup hierarchy. 1183 1184 For more information, please check misc cgroup section in 1185 /Documentation/admin-guide/cgroup-v2.rst. 1186 1187config CGROUP_DEBUG 1188 bool "Debug controller" 1189 default n 1190 depends on DEBUG_KERNEL 1191 help 1192 This option enables a simple controller that exports 1193 debugging information about the cgroups framework. This 1194 controller is for control cgroup debugging only. Its 1195 interfaces are not stable. 1196 1197 Say N. 1198 1199config SOCK_CGROUP_DATA 1200 bool 1201 default n 1202 1203endif # CGROUPS 1204 1205menuconfig NAMESPACES 1206 bool "Namespaces support" if EXPERT 1207 depends on MULTIUSER 1208 default !EXPERT 1209 help 1210 Provides the way to make tasks work with different objects using 1211 the same id. For example same IPC id may refer to different objects 1212 or same user id or pid may refer to different tasks when used in 1213 different namespaces. 1214 1215if NAMESPACES 1216 1217config UTS_NS 1218 bool "UTS namespace" 1219 default y 1220 help 1221 In this namespace tasks see different info provided with the 1222 uname() system call 1223 1224config TIME_NS 1225 bool "TIME namespace" 1226 depends on GENERIC_VDSO_TIME_NS 1227 default y 1228 help 1229 In this namespace boottime and monotonic clocks can be set. 1230 The time will keep going with the same pace. 1231 1232config IPC_NS 1233 bool "IPC namespace" 1234 depends on (SYSVIPC || POSIX_MQUEUE) 1235 default y 1236 help 1237 In this namespace tasks work with IPC ids which correspond to 1238 different IPC objects in different namespaces. 1239 1240config USER_NS 1241 bool "User namespace" 1242 default n 1243 help 1244 This allows containers, i.e. vservers, to use user namespaces 1245 to provide different user info for different servers. 1246 1247 When user namespaces are enabled in the kernel it is 1248 recommended that the MEMCG option also be enabled and that 1249 user-space use the memory control groups to limit the amount 1250 of memory a memory unprivileged users can use. 1251 1252 If unsure, say N. 1253 1254config PID_NS 1255 bool "PID Namespaces" 1256 default y 1257 help 1258 Support process id namespaces. This allows having multiple 1259 processes with the same pid as long as they are in different 1260 pid namespaces. This is a building block of containers. 1261 1262config NET_NS 1263 bool "Network namespace" 1264 depends on NET 1265 default y 1266 help 1267 Allow user space to create what appear to be multiple instances 1268 of the network stack. 1269 1270endif # NAMESPACES 1271 1272config CHECKPOINT_RESTORE 1273 bool "Checkpoint/restore support" 1274 depends on PROC_FS 1275 select PROC_CHILDREN 1276 select KCMP 1277 default n 1278 help 1279 Enables additional kernel features in a sake of checkpoint/restore. 1280 In particular it adds auxiliary prctl codes to setup process text, 1281 data and heap segment sizes, and a few additional /proc filesystem 1282 entries. 1283 1284 If unsure, say N here. 1285 1286config SCHED_AUTOGROUP 1287 bool "Automatic process group scheduling" 1288 select CGROUPS 1289 select CGROUP_SCHED 1290 select FAIR_GROUP_SCHED 1291 help 1292 This option optimizes the scheduler for common desktop workloads by 1293 automatically creating and populating task groups. This separation 1294 of workloads isolates aggressive CPU burners (like build jobs) from 1295 desktop applications. Task group autogeneration is currently based 1296 upon task session. 1297 1298config RELAY 1299 bool "Kernel->user space relay support (formerly relayfs)" 1300 select IRQ_WORK 1301 help 1302 This option enables support for relay interface support in 1303 certain file systems (such as debugfs). 1304 It is designed to provide an efficient mechanism for tools and 1305 facilities to relay large amounts of data from kernel space to 1306 user space. 1307 1308 If unsure, say N. 1309 1310config BLK_DEV_INITRD 1311 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1312 help 1313 The initial RAM filesystem is a ramfs which is loaded by the 1314 boot loader (loadlin or lilo) and that is mounted as root 1315 before the normal boot procedure. It is typically used to 1316 load modules needed to mount the "real" root file system, 1317 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1318 1319 If RAM disk support (BLK_DEV_RAM) is also included, this 1320 also enables initial RAM disk (initrd) support and adds 1321 15 Kbytes (more on some other architectures) to the kernel size. 1322 1323 If unsure say Y. 1324 1325if BLK_DEV_INITRD 1326 1327source "usr/Kconfig" 1328 1329endif 1330 1331config BOOT_CONFIG 1332 bool "Boot config support" 1333 select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED 1334 help 1335 Extra boot config allows system admin to pass a config file as 1336 complemental extension of kernel cmdline when booting. 1337 The boot config file must be attached at the end of initramfs 1338 with checksum, size and magic word. 1339 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1340 1341 If unsure, say Y. 1342 1343config BOOT_CONFIG_FORCE 1344 bool "Force unconditional bootconfig processing" 1345 depends on BOOT_CONFIG 1346 default y if BOOT_CONFIG_EMBED 1347 help 1348 With this Kconfig option set, BOOT_CONFIG processing is carried 1349 out even when the "bootconfig" kernel-boot parameter is omitted. 1350 In fact, with this Kconfig option set, there is no way to 1351 make the kernel ignore the BOOT_CONFIG-supplied kernel-boot 1352 parameters. 1353 1354 If unsure, say N. 1355 1356config BOOT_CONFIG_EMBED 1357 bool "Embed bootconfig file in the kernel" 1358 depends on BOOT_CONFIG 1359 help 1360 Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the 1361 kernel. Usually, the bootconfig file is loaded with the initrd 1362 image. But if the system doesn't support initrd, this option will 1363 help you by embedding a bootconfig file while building the kernel. 1364 1365 If unsure, say N. 1366 1367config BOOT_CONFIG_EMBED_FILE 1368 string "Embedded bootconfig file path" 1369 depends on BOOT_CONFIG_EMBED 1370 help 1371 Specify a bootconfig file which will be embedded to the kernel. 1372 This bootconfig will be used if there is no initrd or no other 1373 bootconfig in the initrd. 1374 1375config INITRAMFS_PRESERVE_MTIME 1376 bool "Preserve cpio archive mtimes in initramfs" 1377 default y 1378 help 1379 Each entry in an initramfs cpio archive carries an mtime value. When 1380 enabled, extracted cpio items take this mtime, with directory mtime 1381 setting deferred until after creation of any child entries. 1382 1383 If unsure, say Y. 1384 1385choice 1386 prompt "Compiler optimization level" 1387 default CC_OPTIMIZE_FOR_PERFORMANCE 1388 1389config CC_OPTIMIZE_FOR_PERFORMANCE 1390 bool "Optimize for performance (-O2)" 1391 help 1392 This is the default optimization level for the kernel, building 1393 with the "-O2" compiler flag for best performance and most 1394 helpful compile-time warnings. 1395 1396config CC_OPTIMIZE_FOR_SIZE 1397 bool "Optimize for size (-Os)" 1398 help 1399 Choosing this option will pass "-Os" to your compiler resulting 1400 in a smaller kernel. 1401 1402endchoice 1403 1404config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1405 bool 1406 help 1407 This requires that the arch annotates or otherwise protects 1408 its external entry points from being discarded. Linker scripts 1409 must also merge .text.*, .data.*, and .bss.* correctly into 1410 output sections. Care must be taken not to pull in unrelated 1411 sections (e.g., '.text.init'). Typically '.' in section names 1412 is used to distinguish them from label names / C identifiers. 1413 1414config LD_DEAD_CODE_DATA_ELIMINATION 1415 bool "Dead code and data elimination (EXPERIMENTAL)" 1416 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1417 depends on EXPERT 1418 depends on $(cc-option,-ffunction-sections -fdata-sections) 1419 depends on $(ld-option,--gc-sections) 1420 help 1421 Enable this if you want to do dead code and data elimination with 1422 the linker by compiling with -ffunction-sections -fdata-sections, 1423 and linking with --gc-sections. 1424 1425 This can reduce on disk and in-memory size of the kernel 1426 code and static data, particularly for small configs and 1427 on small systems. This has the possibility of introducing 1428 silently broken kernel if the required annotations are not 1429 present. This option is not well tested yet, so use at your 1430 own risk. 1431 1432config LD_ORPHAN_WARN 1433 def_bool y 1434 depends on ARCH_WANT_LD_ORPHAN_WARN 1435 depends on $(ld-option,--orphan-handling=warn) 1436 depends on $(ld-option,--orphan-handling=error) 1437 1438config LD_ORPHAN_WARN_LEVEL 1439 string 1440 depends on LD_ORPHAN_WARN 1441 default "error" if WERROR 1442 default "warn" 1443 1444config SYSCTL 1445 bool 1446 1447config HAVE_UID16 1448 bool 1449 1450config SYSCTL_EXCEPTION_TRACE 1451 bool 1452 help 1453 Enable support for /proc/sys/debug/exception-trace. 1454 1455config SYSCTL_ARCH_UNALIGN_NO_WARN 1456 bool 1457 help 1458 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1459 Allows arch to define/use @no_unaligned_warning to possibly warn 1460 about unaligned access emulation going on under the hood. 1461 1462config SYSCTL_ARCH_UNALIGN_ALLOW 1463 bool 1464 help 1465 Enable support for /proc/sys/kernel/unaligned-trap 1466 Allows arches to define/use @unaligned_enabled to runtime toggle 1467 the unaligned access emulation. 1468 see arch/parisc/kernel/unaligned.c for reference 1469 1470config HAVE_PCSPKR_PLATFORM 1471 bool 1472 1473menuconfig EXPERT 1474 bool "Configure standard kernel features (expert users)" 1475 # Unhide debug options, to make the on-by-default options visible 1476 select DEBUG_KERNEL 1477 help 1478 This option allows certain base kernel options and settings 1479 to be disabled or tweaked. This is for specialized 1480 environments which can tolerate a "non-standard" kernel. 1481 Only use this if you really know what you are doing. 1482 1483config UID16 1484 bool "Enable 16-bit UID system calls" if EXPERT 1485 depends on HAVE_UID16 && MULTIUSER 1486 default y 1487 help 1488 This enables the legacy 16-bit UID syscall wrappers. 1489 1490config MULTIUSER 1491 bool "Multiple users, groups and capabilities support" if EXPERT 1492 default y 1493 help 1494 This option enables support for non-root users, groups and 1495 capabilities. 1496 1497 If you say N here, all processes will run with UID 0, GID 0, and all 1498 possible capabilities. Saying N here also compiles out support for 1499 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1500 setgid, and capset. 1501 1502 If unsure, say Y here. 1503 1504config SGETMASK_SYSCALL 1505 bool "sgetmask/ssetmask syscalls support" if EXPERT 1506 default PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1507 help 1508 sys_sgetmask and sys_ssetmask are obsolete system calls 1509 no longer supported in libc but still enabled by default in some 1510 architectures. 1511 1512 If unsure, leave the default option here. 1513 1514config SYSFS_SYSCALL 1515 bool "Sysfs syscall support" if EXPERT 1516 default y 1517 help 1518 sys_sysfs is an obsolete system call no longer supported in libc. 1519 Note that disabling this option is more secure but might break 1520 compatibility with some systems. 1521 1522 If unsure say Y here. 1523 1524config FHANDLE 1525 bool "open by fhandle syscalls" if EXPERT 1526 select EXPORTFS 1527 default y 1528 help 1529 If you say Y here, a user level program will be able to map 1530 file names to handle and then later use the handle for 1531 different file system operations. This is useful in implementing 1532 userspace file servers, which now track files using handles instead 1533 of names. The handle would remain the same even if file names 1534 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1535 syscalls. 1536 1537config POSIX_TIMERS 1538 bool "Posix Clocks & timers" if EXPERT 1539 default y 1540 help 1541 This includes native support for POSIX timers to the kernel. 1542 Some embedded systems have no use for them and therefore they 1543 can be configured out to reduce the size of the kernel image. 1544 1545 When this option is disabled, the following syscalls won't be 1546 available: timer_create, timer_gettime: timer_getoverrun, 1547 timer_settime, timer_delete, clock_adjtime, getitimer, 1548 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1549 clock_getres and clock_nanosleep syscalls will be limited to 1550 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1551 1552 If unsure say y. 1553 1554config PRINTK 1555 default y 1556 bool "Enable support for printk" if EXPERT 1557 select IRQ_WORK 1558 help 1559 This option enables normal printk support. Removing it 1560 eliminates most of the message strings from the kernel image 1561 and makes the kernel more or less silent. As this makes it 1562 very difficult to diagnose system problems, saying N here is 1563 strongly discouraged. 1564 1565config BUG 1566 bool "BUG() support" if EXPERT 1567 default y 1568 help 1569 Disabling this option eliminates support for BUG and WARN, reducing 1570 the size of your kernel image and potentially quietly ignoring 1571 numerous fatal conditions. You should only consider disabling this 1572 option for embedded systems with no facilities for reporting errors. 1573 Just say Y. 1574 1575config ELF_CORE 1576 depends on COREDUMP 1577 default y 1578 bool "Enable ELF core dumps" if EXPERT 1579 help 1580 Enable support for generating core dumps. Disabling saves about 4k. 1581 1582 1583config PCSPKR_PLATFORM 1584 bool "Enable PC-Speaker support" if EXPERT 1585 depends on HAVE_PCSPKR_PLATFORM 1586 select I8253_LOCK 1587 default y 1588 help 1589 This option allows to disable the internal PC-Speaker 1590 support, saving some memory. 1591 1592config BASE_SMALL 1593 bool "Enable smaller-sized data structures for core" if EXPERT 1594 help 1595 Enabling this option reduces the size of miscellaneous core 1596 kernel data structures. This saves memory on small machines, 1597 but may reduce performance. 1598 1599config FUTEX 1600 bool "Enable futex support" if EXPERT 1601 depends on !(SPARC32 && SMP) 1602 default y 1603 imply RT_MUTEXES 1604 help 1605 Disabling this option will cause the kernel to be built without 1606 support for "fast userspace mutexes". The resulting kernel may not 1607 run glibc-based applications correctly. 1608 1609config FUTEX_PI 1610 bool 1611 depends on FUTEX && RT_MUTEXES 1612 default y 1613 1614config EPOLL 1615 bool "Enable eventpoll support" if EXPERT 1616 default y 1617 help 1618 Disabling this option will cause the kernel to be built without 1619 support for epoll family of system calls. 1620 1621config SIGNALFD 1622 bool "Enable signalfd() system call" if EXPERT 1623 default y 1624 help 1625 Enable the signalfd() system call that allows to receive signals 1626 on a file descriptor. 1627 1628 If unsure, say Y. 1629 1630config TIMERFD 1631 bool "Enable timerfd() system call" if EXPERT 1632 default y 1633 help 1634 Enable the timerfd() system call that allows to receive timer 1635 events on a file descriptor. 1636 1637 If unsure, say Y. 1638 1639config EVENTFD 1640 bool "Enable eventfd() system call" if EXPERT 1641 default y 1642 help 1643 Enable the eventfd() system call that allows to receive both 1644 kernel notification (ie. KAIO) or userspace notifications. 1645 1646 If unsure, say Y. 1647 1648config SHMEM 1649 bool "Use full shmem filesystem" if EXPERT 1650 default y 1651 depends on MMU 1652 help 1653 The shmem is an internal filesystem used to manage shared memory. 1654 It is backed by swap and manages resource limits. It is also exported 1655 to userspace as tmpfs if TMPFS is enabled. Disabling this 1656 option replaces shmem and tmpfs with the much simpler ramfs code, 1657 which may be appropriate on small systems without swap. 1658 1659config AIO 1660 bool "Enable AIO support" if EXPERT 1661 default y 1662 help 1663 This option enables POSIX asynchronous I/O which may by used 1664 by some high performance threaded applications. Disabling 1665 this option saves about 7k. 1666 1667config IO_URING 1668 bool "Enable IO uring support" if EXPERT 1669 select IO_WQ 1670 default y 1671 help 1672 This option enables support for the io_uring interface, enabling 1673 applications to submit and complete IO through submission and 1674 completion rings that are shared between the kernel and application. 1675 1676config ADVISE_SYSCALLS 1677 bool "Enable madvise/fadvise syscalls" if EXPERT 1678 default y 1679 help 1680 This option enables the madvise and fadvise syscalls, used by 1681 applications to advise the kernel about their future memory or file 1682 usage, improving performance. If building an embedded system where no 1683 applications use these syscalls, you can disable this option to save 1684 space. 1685 1686config MEMBARRIER 1687 bool "Enable membarrier() system call" if EXPERT 1688 default y 1689 help 1690 Enable the membarrier() system call that allows issuing memory 1691 barriers across all running threads, which can be used to distribute 1692 the cost of user-space memory barriers asymmetrically by transforming 1693 pairs of memory barriers into pairs consisting of membarrier() and a 1694 compiler barrier. 1695 1696 If unsure, say Y. 1697 1698config KCMP 1699 bool "Enable kcmp() system call" if EXPERT 1700 help 1701 Enable the kernel resource comparison system call. It provides 1702 user-space with the ability to compare two processes to see if they 1703 share a common resource, such as a file descriptor or even virtual 1704 memory space. 1705 1706 If unsure, say N. 1707 1708config RSEQ 1709 bool "Enable rseq() system call" if EXPERT 1710 default y 1711 depends on HAVE_RSEQ 1712 select MEMBARRIER 1713 help 1714 Enable the restartable sequences system call. It provides a 1715 user-space cache for the current CPU number value, which 1716 speeds up getting the current CPU number from user-space, 1717 as well as an ABI to speed up user-space operations on 1718 per-CPU data. 1719 1720 If unsure, say Y. 1721 1722config DEBUG_RSEQ 1723 default n 1724 bool "Enable debugging of rseq() system call" if EXPERT 1725 depends on RSEQ && DEBUG_KERNEL 1726 help 1727 Enable extra debugging checks for the rseq system call. 1728 1729 If unsure, say N. 1730 1731config CACHESTAT_SYSCALL 1732 bool "Enable cachestat() system call" if EXPERT 1733 default y 1734 help 1735 Enable the cachestat system call, which queries the page cache 1736 statistics of a file (number of cached pages, dirty pages, 1737 pages marked for writeback, (recently) evicted pages). 1738 1739 If unsure say Y here. 1740 1741config PC104 1742 bool "PC/104 support" if EXPERT 1743 help 1744 Expose PC/104 form factor device drivers and options available for 1745 selection and configuration. Enable this option if your target 1746 machine has a PC/104 bus. 1747 1748config KALLSYMS 1749 bool "Load all symbols for debugging/ksymoops" if EXPERT 1750 default y 1751 help 1752 Say Y here to let the kernel print out symbolic crash information and 1753 symbolic stack backtraces. This increases the size of the kernel 1754 somewhat, as all symbols have to be loaded into the kernel image. 1755 1756config KALLSYMS_SELFTEST 1757 bool "Test the basic functions and performance of kallsyms" 1758 depends on KALLSYMS 1759 default n 1760 help 1761 Test the basic functions and performance of some interfaces, such as 1762 kallsyms_lookup_name. It also calculates the compression rate of the 1763 kallsyms compression algorithm for the current symbol set. 1764 1765 Start self-test automatically after system startup. Suggest executing 1766 "dmesg | grep kallsyms_selftest" to collect test results. "finish" is 1767 displayed in the last line, indicating that the test is complete. 1768 1769config KALLSYMS_ALL 1770 bool "Include all symbols in kallsyms" 1771 depends on DEBUG_KERNEL && KALLSYMS 1772 help 1773 Normally kallsyms only contains the symbols of functions for nicer 1774 OOPS messages and backtraces (i.e., symbols from the text and inittext 1775 sections). This is sufficient for most cases. And only if you want to 1776 enable kernel live patching, or other less common use cases (e.g., 1777 when a debugger is used) all symbols are required (i.e., names of 1778 variables from the data sections, etc). 1779 1780 This option makes sure that all symbols are loaded into the kernel 1781 image (i.e., symbols from all sections) in cost of increased kernel 1782 size (depending on the kernel configuration, it may be 300KiB or 1783 something like this). 1784 1785 Say N unless you really need all symbols, or kernel live patching. 1786 1787config KALLSYMS_ABSOLUTE_PERCPU 1788 bool 1789 depends on KALLSYMS 1790 default X86_64 && SMP 1791 1792config KALLSYMS_BASE_RELATIVE 1793 bool 1794 depends on KALLSYMS 1795 default y 1796 help 1797 Instead of emitting them as absolute values in the native word size, 1798 emit the symbol references in the kallsyms table as 32-bit entries, 1799 each containing a relative value in the range [base, base + U32_MAX] 1800 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1801 an absolute value in the range [0, S32_MAX] or a relative value in the 1802 range [base, base + S32_MAX], where base is the lowest relative symbol 1803 address encountered in the image. 1804 1805 On 64-bit builds, this reduces the size of the address table by 50%, 1806 but more importantly, it results in entries whose values are build 1807 time constants, and no relocation pass is required at runtime to fix 1808 up the entries based on the runtime load address of the kernel. 1809 1810# end of the "standard kernel features (expert users)" menu 1811 1812config ARCH_HAS_MEMBARRIER_CALLBACKS 1813 bool 1814 1815config ARCH_HAS_MEMBARRIER_SYNC_CORE 1816 bool 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 1832menu "Kernel Performance Events And Counters" 1833 1834config PERF_EVENTS 1835 bool "Kernel performance events and counters" 1836 default y if PROFILING 1837 depends on HAVE_PERF_EVENTS 1838 select IRQ_WORK 1839 help 1840 Enable kernel support for various performance events provided 1841 by software and hardware. 1842 1843 Software events are supported either built-in or via the 1844 use of generic tracepoints. 1845 1846 Most modern CPUs support performance events via performance 1847 counter registers. These registers count the number of certain 1848 types of hw events: such as instructions executed, cachemisses 1849 suffered, or branches mis-predicted - without slowing down the 1850 kernel or applications. These registers can also trigger interrupts 1851 when a threshold number of events have passed - and can thus be 1852 used to profile the code that runs on that CPU. 1853 1854 The Linux Performance Event subsystem provides an abstraction of 1855 these software and hardware event capabilities, available via a 1856 system call and used by the "perf" utility in tools/perf/. It 1857 provides per task and per CPU counters, and it provides event 1858 capabilities on top of those. 1859 1860 Say Y if unsure. 1861 1862config DEBUG_PERF_USE_VMALLOC 1863 default n 1864 bool "Debug: use vmalloc to back perf mmap() buffers" 1865 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1866 select PERF_USE_VMALLOC 1867 help 1868 Use vmalloc memory to back perf mmap() buffers. 1869 1870 Mostly useful for debugging the vmalloc code on platforms 1871 that don't require it. 1872 1873 Say N if unsure. 1874 1875endmenu 1876 1877config SYSTEM_DATA_VERIFICATION 1878 def_bool n 1879 select SYSTEM_TRUSTED_KEYRING 1880 select KEYS 1881 select CRYPTO 1882 select CRYPTO_RSA 1883 select ASYMMETRIC_KEY_TYPE 1884 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1885 select ASN1 1886 select OID_REGISTRY 1887 select X509_CERTIFICATE_PARSER 1888 select PKCS7_MESSAGE_PARSER 1889 help 1890 Provide PKCS#7 message verification using the contents of the system 1891 trusted keyring to provide public keys. This then can be used for 1892 module verification, kexec image verification and firmware blob 1893 verification. 1894 1895config PROFILING 1896 bool "Profiling support" 1897 help 1898 Say Y here to enable the extended profiling support mechanisms used 1899 by profilers. 1900 1901config RUST 1902 bool "Rust support" 1903 depends on HAVE_RUST 1904 depends on RUST_IS_AVAILABLE 1905 depends on !CFI_CLANG 1906 depends on !MODVERSIONS 1907 depends on !GCC_PLUGINS 1908 depends on !RANDSTRUCT 1909 depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE 1910 help 1911 Enables Rust support in the kernel. 1912 1913 This allows other Rust-related options, like drivers written in Rust, 1914 to be selected. 1915 1916 It is also required to be able to load external kernel modules 1917 written in Rust. 1918 1919 See Documentation/rust/ for more information. 1920 1921 If unsure, say N. 1922 1923config RUSTC_VERSION_TEXT 1924 string 1925 depends on RUST 1926 default $(shell,command -v $(RUSTC) >/dev/null 2>&1 && $(RUSTC) --version || echo n) 1927 1928config BINDGEN_VERSION_TEXT 1929 string 1930 depends on RUST 1931 default $(shell,command -v $(BINDGEN) >/dev/null 2>&1 && $(BINDGEN) --version || echo n) 1932 1933# 1934# Place an empty function call at each tracepoint site. Can be 1935# dynamically changed for a probe function. 1936# 1937config TRACEPOINTS 1938 bool 1939 1940source "kernel/Kconfig.kexec" 1941 1942endmenu # General setup 1943 1944source "arch/Kconfig" 1945 1946config RT_MUTEXES 1947 bool 1948 default y if PREEMPT_RT 1949 1950config MODULE_SIG_FORMAT 1951 def_bool n 1952 select SYSTEM_DATA_VERIFICATION 1953 1954source "kernel/module/Kconfig" 1955 1956config INIT_ALL_POSSIBLE 1957 bool 1958 help 1959 Back when each arch used to define their own cpu_online_mask and 1960 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 1961 with all 1s, and others with all 0s. When they were centralised, 1962 it was better to provide this option than to break all the archs 1963 and have several arch maintainers pursuing me down dark alleys. 1964 1965source "block/Kconfig" 1966 1967config PREEMPT_NOTIFIERS 1968 bool 1969 1970config PADATA 1971 depends on SMP 1972 bool 1973 1974config ASN1 1975 tristate 1976 help 1977 Build a simple ASN.1 grammar compiler that produces a bytecode output 1978 that can be interpreted by the ASN.1 stream decoder and used to 1979 inform it as to what tags are to be expected in a stream and what 1980 functions to call on what tags. 1981 1982source "kernel/Kconfig.locks" 1983 1984config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 1985 bool 1986 1987config ARCH_HAS_PREPARE_SYNC_CORE_CMD 1988 bool 1989 1990config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 1991 bool 1992 1993# It may be useful for an architecture to override the definitions of the 1994# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 1995# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 1996# different calling convention for syscalls. They can also override the 1997# macros for not-implemented syscalls in kernel/sys_ni.c and 1998# kernel/time/posix-stubs.c. All these overrides need to be available in 1999# <asm/syscall_wrapper.h>. 2000config ARCH_HAS_SYSCALL_WRAPPER 2001 def_bool n 2002