1# SPDX-License-Identifier: GPL-2.0-only 2config CC_VERSION_TEXT 3 string 4 default "$(CC_VERSION_TEXT)" 5 help 6 This is used in unclear ways: 7 8 - Re-run Kconfig when the compiler is updated 9 The 'default' property references the environment variable, 10 CC_VERSION_TEXT so it is recorded in include/config/auto.conf.cmd. 11 When the compiler is updated, Kconfig will be invoked. 12 13 - Ensure full rebuild when the compiler is updated 14 include/linux/compiler-version.h contains this option in the comment 15 line so fixdep adds include/config/CC_VERSION_TEXT into the 16 auto-generated dependency. When the compiler is updated, syncconfig 17 will touch it and then every file will be rebuilt. 18 19config CC_IS_GCC 20 def_bool $(success,test "$(cc-name)" = GCC) 21 22config GCC_VERSION 23 int 24 default $(cc-version) if CC_IS_GCC 25 default 0 26 27config CC_IS_CLANG 28 def_bool $(success,test "$(cc-name)" = Clang) 29 30config CLANG_VERSION 31 int 32 default $(cc-version) if CC_IS_CLANG 33 default 0 34 35config AS_IS_GNU 36 def_bool $(success,test "$(as-name)" = GNU) 37 38config AS_IS_LLVM 39 def_bool $(success,test "$(as-name)" = LLVM) 40 41config AS_VERSION 42 int 43 # Use clang version if this is the integrated assembler 44 default CLANG_VERSION if AS_IS_LLVM 45 default $(as-version) 46 47config LD_IS_BFD 48 def_bool $(success,test "$(ld-name)" = BFD) 49 50config LD_VERSION 51 int 52 default $(ld-version) if LD_IS_BFD 53 default 0 54 55config LD_IS_LLD 56 def_bool $(success,test "$(ld-name)" = LLD) 57 58config LLD_VERSION 59 int 60 default $(ld-version) if LD_IS_LLD 61 default 0 62 63config RUST_IS_AVAILABLE 64 def_bool $(success,$(srctree)/scripts/rust_is_available.sh) 65 help 66 This shows whether a suitable Rust toolchain is available (found). 67 68 Please see Documentation/rust/quick-start.rst for instructions on how 69 to satisfy the build requirements of Rust support. 70 71 In particular, the Makefile target 'rustavailable' is useful to check 72 why the Rust toolchain is not being detected. 73 74config CC_CAN_LINK 75 bool 76 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT 77 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag)) 78 79config CC_CAN_LINK_STATIC 80 bool 81 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag) -static) if 64BIT 82 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag) -static) 83 84config CC_HAS_ASM_GOTO_OUTPUT 85 def_bool $(success,echo 'int foo(int x) { asm goto ("": "=r"(x) ::: bar); return x; bar: return 0; }' | $(CC) -x c - -c -o /dev/null) 86 87config CC_HAS_ASM_GOTO_TIED_OUTPUT 88 depends on CC_HAS_ASM_GOTO_OUTPUT 89 # Detect buggy gcc and clang, fixed in gcc-11 clang-14. 90 def_bool $(success,echo 'int foo(int *x) { asm goto (".long (%l[bar]) - .": "+m"(*x) ::: bar); return *x; bar: return 0; }' | $CC -x c - -c -o /dev/null) 91 92config TOOLS_SUPPORT_RELR 93 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 94 95config CC_HAS_ASM_INLINE 96 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 97 98config CC_HAS_NO_PROFILE_FN_ATTR 99 def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror) 100 101config PAHOLE_VERSION 102 int 103 default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE)) 104 105config CONSTRUCTORS 106 bool 107 108config IRQ_WORK 109 bool 110 111config BUILDTIME_TABLE_SORT 112 bool 113 114config THREAD_INFO_IN_TASK 115 bool 116 help 117 Select this to move thread_info off the stack into task_struct. To 118 make this work, an arch will need to remove all thread_info fields 119 except flags and fix any runtime bugs. 120 121 One subtle change that will be needed is to use try_get_task_stack() 122 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 123 124menu "General setup" 125 126config BROKEN 127 bool 128 129config BROKEN_ON_SMP 130 bool 131 depends on BROKEN || !SMP 132 default y 133 134config INIT_ENV_ARG_LIMIT 135 int 136 default 32 if !UML 137 default 128 if UML 138 help 139 Maximum of each of the number of arguments and environment 140 variables passed to init from the kernel command line. 141 142config COMPILE_TEST 143 bool "Compile also drivers which will not load" 144 depends on HAS_IOMEM 145 help 146 Some drivers can be compiled on a different platform than they are 147 intended to be run on. Despite they cannot be loaded there (or even 148 when they load they cannot be used due to missing HW support), 149 developers still, opposing to distributors, might want to build such 150 drivers to compile-test them. 151 152 If you are a developer and want to build everything available, say Y 153 here. If you are a user/distributor, say N here to exclude useless 154 drivers to be distributed. 155 156config WERROR 157 bool "Compile the kernel with warnings as errors" 158 default COMPILE_TEST 159 help 160 A kernel build should not cause any compiler warnings, and this 161 enables the '-Werror' (for C) and '-Dwarnings' (for Rust) flags 162 to enforce that rule by default. Certain warnings from other tools 163 such as the linker may be upgraded to errors with this option as 164 well. 165 166 However, if you have a new (or very old) compiler or linker with odd 167 and unusual warnings, or you have some architecture with problems, 168 you may need to disable this config option in order to 169 successfully build the kernel. 170 171 If in doubt, say Y. 172 173config UAPI_HEADER_TEST 174 bool "Compile test UAPI headers" 175 depends on HEADERS_INSTALL && CC_CAN_LINK 176 help 177 Compile test headers exported to user-space to ensure they are 178 self-contained, i.e. compilable as standalone units. 179 180 If you are a developer or tester and want to ensure the exported 181 headers are self-contained, say Y here. Otherwise, choose N. 182 183config LOCALVERSION 184 string "Local version - append to kernel release" 185 help 186 Append an extra string to the end of your kernel version. 187 This will show up when you type uname, for example. 188 The string you set here will be appended after the contents of 189 any files with a filename matching localversion* in your 190 object and source tree, in that order. Your total string can 191 be a maximum of 64 characters. 192 193config LOCALVERSION_AUTO 194 bool "Automatically append version information to the version string" 195 default y 196 depends on !COMPILE_TEST 197 help 198 This will try to automatically determine if the current tree is a 199 release tree by looking for git tags that belong to the current 200 top of tree revision. 201 202 A string of the format -gxxxxxxxx will be added to the localversion 203 if a git-based tree is found. The string generated by this will be 204 appended after any matching localversion* files, and after the value 205 set in CONFIG_LOCALVERSION. 206 207 (The actual string used here is the first 12 characters produced 208 by running the command: 209 210 $ git rev-parse --verify HEAD 211 212 which is done within the script "scripts/setlocalversion".) 213 214config BUILD_SALT 215 string "Build ID Salt" 216 default "" 217 help 218 The build ID is used to link binaries and their debug info. Setting 219 this option will use the value in the calculation of the build id. 220 This is mostly useful for distributions which want to ensure the 221 build is unique between builds. It's safe to leave the default. 222 223config HAVE_KERNEL_GZIP 224 bool 225 226config HAVE_KERNEL_BZIP2 227 bool 228 229config HAVE_KERNEL_LZMA 230 bool 231 232config HAVE_KERNEL_XZ 233 bool 234 235config HAVE_KERNEL_LZO 236 bool 237 238config HAVE_KERNEL_LZ4 239 bool 240 241config HAVE_KERNEL_ZSTD 242 bool 243 244config HAVE_KERNEL_UNCOMPRESSED 245 bool 246 247choice 248 prompt "Kernel compression mode" 249 default KERNEL_GZIP 250 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_ZSTD || HAVE_KERNEL_UNCOMPRESSED 251 help 252 The linux kernel is a kind of self-extracting executable. 253 Several compression algorithms are available, which differ 254 in efficiency, compression and decompression speed. 255 Compression speed is only relevant when building a kernel. 256 Decompression speed is relevant at each boot. 257 258 If you have any problems with bzip2 or lzma compressed 259 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 260 version of this functionality (bzip2 only), for 2.4, was 261 supplied by Christian Ludwig) 262 263 High compression options are mostly useful for users, who 264 are low on disk space (embedded systems), but for whom ram 265 size matters less. 266 267 If in doubt, select 'gzip' 268 269config KERNEL_GZIP 270 bool "Gzip" 271 depends on HAVE_KERNEL_GZIP 272 help 273 The old and tried gzip compression. It provides a good balance 274 between compression ratio and decompression speed. 275 276config KERNEL_BZIP2 277 bool "Bzip2" 278 depends on HAVE_KERNEL_BZIP2 279 help 280 Its compression ratio and speed is intermediate. 281 Decompression speed is slowest among the choices. The kernel 282 size is about 10% smaller with bzip2, in comparison to gzip. 283 Bzip2 uses a large amount of memory. For modern kernels you 284 will need at least 8MB RAM or more for booting. 285 286config KERNEL_LZMA 287 bool "LZMA" 288 depends on HAVE_KERNEL_LZMA 289 help 290 This compression algorithm's ratio is best. Decompression speed 291 is between gzip and bzip2. Compression is slowest. 292 The kernel size is about 33% smaller with LZMA in comparison to gzip. 293 294config KERNEL_XZ 295 bool "XZ" 296 depends on HAVE_KERNEL_XZ 297 help 298 XZ uses the LZMA2 algorithm and instruction set specific 299 BCJ filters which can improve compression ratio of executable 300 code. The size of the kernel is about 30% smaller with XZ in 301 comparison to gzip. On architectures for which there is a BCJ 302 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 303 will create a few percent smaller kernel than plain LZMA. 304 305 The speed is about the same as with LZMA: The decompression 306 speed of XZ is better than that of bzip2 but worse than gzip 307 and LZO. Compression is slow. 308 309config KERNEL_LZO 310 bool "LZO" 311 depends on HAVE_KERNEL_LZO 312 help 313 Its compression ratio is the poorest among the choices. The kernel 314 size is about 10% bigger than gzip; however its speed 315 (both compression and decompression) is the fastest. 316 317config KERNEL_LZ4 318 bool "LZ4" 319 depends on HAVE_KERNEL_LZ4 320 help 321 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 322 A preliminary version of LZ4 de/compression tool is available at 323 <https://code.google.com/p/lz4/>. 324 325 Its compression ratio is worse than LZO. The size of the kernel 326 is about 8% bigger than LZO. But the decompression speed is 327 faster than LZO. 328 329config KERNEL_ZSTD 330 bool "ZSTD" 331 depends on HAVE_KERNEL_ZSTD 332 help 333 ZSTD is a compression algorithm targeting intermediate compression 334 with fast decompression speed. It will compress better than GZIP and 335 decompress around the same speed as LZO, but slower than LZ4. You 336 will need at least 192 KB RAM or more for booting. The zstd command 337 line tool is required for compression. 338 339config KERNEL_UNCOMPRESSED 340 bool "None" 341 depends on HAVE_KERNEL_UNCOMPRESSED 342 help 343 Produce uncompressed kernel image. This option is usually not what 344 you want. It is useful for debugging the kernel in slow simulation 345 environments, where decompressing and moving the kernel is awfully 346 slow. This option allows early boot code to skip the decompressor 347 and jump right at uncompressed kernel image. 348 349endchoice 350 351config DEFAULT_INIT 352 string "Default init path" 353 default "" 354 help 355 This option determines the default init for the system if no init= 356 option is passed on the kernel command line. If the requested path is 357 not present, we will still then move on to attempting further 358 locations (e.g. /sbin/init, etc). If this is empty, we will just use 359 the fallback list when init= is not passed. 360 361config DEFAULT_HOSTNAME 362 string "Default hostname" 363 default "(none)" 364 help 365 This option determines the default system hostname before userspace 366 calls sethostname(2). The kernel traditionally uses "(none)" here, 367 but you may wish to use a different default here to make a minimal 368 system more usable with less configuration. 369 370config SYSVIPC 371 bool "System V IPC" 372 help 373 Inter Process Communication is a suite of library functions and 374 system calls which let processes (running programs) synchronize and 375 exchange information. It is generally considered to be a good thing, 376 and some programs won't run unless you say Y here. In particular, if 377 you want to run the DOS emulator dosemu under Linux (read the 378 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 379 you'll need to say Y here. 380 381 You can find documentation about IPC with "info ipc" and also in 382 section 6.4 of the Linux Programmer's Guide, available from 383 <http://www.tldp.org/guides.html>. 384 385config SYSVIPC_SYSCTL 386 bool 387 depends on SYSVIPC 388 depends on SYSCTL 389 default y 390 391config SYSVIPC_COMPAT 392 def_bool y 393 depends on COMPAT && SYSVIPC 394 395config POSIX_MQUEUE 396 bool "POSIX Message Queues" 397 depends on NET 398 help 399 POSIX variant of message queues is a part of IPC. In POSIX message 400 queues every message has a priority which decides about succession 401 of receiving it by a process. If you want to compile and run 402 programs written e.g. for Solaris with use of its POSIX message 403 queues (functions mq_*) say Y here. 404 405 POSIX message queues are visible as a filesystem called 'mqueue' 406 and can be mounted somewhere if you want to do filesystem 407 operations on message queues. 408 409 If unsure, say Y. 410 411config POSIX_MQUEUE_SYSCTL 412 bool 413 depends on POSIX_MQUEUE 414 depends on SYSCTL 415 default y 416 417config WATCH_QUEUE 418 bool "General notification queue" 419 default n 420 help 421 422 This is a general notification queue for the kernel to pass events to 423 userspace by splicing them into pipes. It can be used in conjunction 424 with watches for key/keyring change notifications and device 425 notifications. 426 427 See Documentation/core-api/watch_queue.rst 428 429config CROSS_MEMORY_ATTACH 430 bool "Enable process_vm_readv/writev syscalls" 431 depends on MMU 432 default y 433 help 434 Enabling this option adds the system calls process_vm_readv and 435 process_vm_writev which allow a process with the correct privileges 436 to directly read from or write to another process' address space. 437 See the man page for more details. 438 439config USELIB 440 bool "uselib syscall (for libc5 and earlier)" 441 default ALPHA || M68K || SPARC 442 help 443 This option enables the uselib syscall, a system call used in the 444 dynamic linker from libc5 and earlier. glibc does not use this 445 system call. If you intend to run programs built on libc5 or 446 earlier, you may need to enable this syscall. Current systems 447 running glibc can safely disable this. 448 449config AUDIT 450 bool "Auditing support" 451 depends on NET 452 help 453 Enable auditing infrastructure that can be used with another 454 kernel subsystem, such as SELinux (which requires this for 455 logging of avc messages output). System call auditing is included 456 on architectures which support it. 457 458config HAVE_ARCH_AUDITSYSCALL 459 bool 460 461config AUDITSYSCALL 462 def_bool y 463 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 464 select FSNOTIFY 465 466source "kernel/irq/Kconfig" 467source "kernel/time/Kconfig" 468source "kernel/bpf/Kconfig" 469source "kernel/Kconfig.preempt" 470 471menu "CPU/Task time and stats accounting" 472 473config VIRT_CPU_ACCOUNTING 474 bool 475 476choice 477 prompt "Cputime accounting" 478 default TICK_CPU_ACCOUNTING 479 480# Kind of a stub config for the pure tick based cputime accounting 481config TICK_CPU_ACCOUNTING 482 bool "Simple tick based cputime accounting" 483 depends on !S390 && !NO_HZ_FULL 484 help 485 This is the basic tick based cputime accounting that maintains 486 statistics about user, system and idle time spent on per jiffies 487 granularity. 488 489 If unsure, say Y. 490 491config VIRT_CPU_ACCOUNTING_NATIVE 492 bool "Deterministic task and CPU time accounting" 493 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 494 select VIRT_CPU_ACCOUNTING 495 help 496 Select this option to enable more accurate task and CPU time 497 accounting. This is done by reading a CPU counter on each 498 kernel entry and exit and on transitions within the kernel 499 between system, softirq and hardirq state, so there is a 500 small performance impact. In the case of s390 or IBM POWER > 5, 501 this also enables accounting of stolen time on logically-partitioned 502 systems. 503 504config VIRT_CPU_ACCOUNTING_GEN 505 bool "Full dynticks CPU time accounting" 506 depends on HAVE_CONTEXT_TRACKING_USER 507 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 508 depends on GENERIC_CLOCKEVENTS 509 select VIRT_CPU_ACCOUNTING 510 select CONTEXT_TRACKING_USER 511 help 512 Select this option to enable task and CPU time accounting on full 513 dynticks systems. This accounting is implemented by watching every 514 kernel-user boundaries using the context tracking subsystem. 515 The accounting is thus performed at the expense of some significant 516 overhead. 517 518 For now this is only useful if you are working on the full 519 dynticks subsystem development. 520 521 If unsure, say N. 522 523endchoice 524 525config IRQ_TIME_ACCOUNTING 526 bool "Fine granularity task level IRQ time accounting" 527 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 528 help 529 Select this option to enable fine granularity task irq time 530 accounting. This is done by reading a timestamp on each 531 transitions between softirq and hardirq state, so there can be a 532 small performance impact. 533 534 If in doubt, say N here. 535 536config HAVE_SCHED_AVG_IRQ 537 def_bool y 538 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 539 depends on SMP 540 541config SCHED_THERMAL_PRESSURE 542 bool 543 default y if ARM && ARM_CPU_TOPOLOGY 544 default y if ARM64 545 depends on SMP 546 depends on CPU_FREQ_THERMAL 547 help 548 Select this option to enable thermal pressure accounting in the 549 scheduler. Thermal pressure is the value conveyed to the scheduler 550 that reflects the reduction in CPU compute capacity resulted from 551 thermal throttling. Thermal throttling occurs when the performance of 552 a CPU is capped due to high operating temperatures. 553 554 If selected, the scheduler will be able to balance tasks accordingly, 555 i.e. put less load on throttled CPUs than on non/less throttled ones. 556 557 This requires the architecture to implement 558 arch_update_thermal_pressure() and arch_scale_thermal_pressure(). 559 560config BSD_PROCESS_ACCT 561 bool "BSD Process Accounting" 562 depends on MULTIUSER 563 help 564 If you say Y here, a user level program will be able to instruct the 565 kernel (via a special system call) to write process accounting 566 information to a file: whenever a process exits, information about 567 that process will be appended to the file by the kernel. The 568 information includes things such as creation time, owning user, 569 command name, memory usage, controlling terminal etc. (the complete 570 list is in the struct acct in <file:include/linux/acct.h>). It is 571 up to the user level program to do useful things with this 572 information. This is generally a good idea, so say Y. 573 574config BSD_PROCESS_ACCT_V3 575 bool "BSD Process Accounting version 3 file format" 576 depends on BSD_PROCESS_ACCT 577 default n 578 help 579 If you say Y here, the process accounting information is written 580 in a new file format that also logs the process IDs of each 581 process and its parent. Note that this file format is incompatible 582 with previous v0/v1/v2 file formats, so you will need updated tools 583 for processing it. A preliminary version of these tools is available 584 at <http://www.gnu.org/software/acct/>. 585 586config TASKSTATS 587 bool "Export task/process statistics through netlink" 588 depends on NET 589 depends on MULTIUSER 590 default n 591 help 592 Export selected statistics for tasks/processes through the 593 generic netlink interface. Unlike BSD process accounting, the 594 statistics are available during the lifetime of tasks/processes as 595 responses to commands. Like BSD accounting, they are sent to user 596 space on task exit. 597 598 Say N if unsure. 599 600config TASK_DELAY_ACCT 601 bool "Enable per-task delay accounting" 602 depends on TASKSTATS 603 select SCHED_INFO 604 help 605 Collect information on time spent by a task waiting for system 606 resources like cpu, synchronous block I/O completion and swapping 607 in pages. Such statistics can help in setting a task's priorities 608 relative to other tasks for cpu, io, rss limits etc. 609 610 Say N if unsure. 611 612config TASK_XACCT 613 bool "Enable extended accounting over taskstats" 614 depends on TASKSTATS 615 help 616 Collect extended task accounting data and send the data 617 to userland for processing over the taskstats interface. 618 619 Say N if unsure. 620 621config TASK_IO_ACCOUNTING 622 bool "Enable per-task storage I/O accounting" 623 depends on TASK_XACCT 624 help 625 Collect information on the number of bytes of storage I/O which this 626 task has caused. 627 628 Say N if unsure. 629 630config PSI 631 bool "Pressure stall information tracking" 632 select KERNFS 633 help 634 Collect metrics that indicate how overcommitted the CPU, memory, 635 and IO capacity are in the system. 636 637 If you say Y here, the kernel will create /proc/pressure/ with the 638 pressure statistics files cpu, memory, and io. These will indicate 639 the share of walltime in which some or all tasks in the system are 640 delayed due to contention of the respective resource. 641 642 In kernels with cgroup support, cgroups (cgroup2 only) will 643 have cpu.pressure, memory.pressure, and io.pressure files, 644 which aggregate pressure stalls for the grouped tasks only. 645 646 For more details see Documentation/accounting/psi.rst. 647 648 Say N if unsure. 649 650config PSI_DEFAULT_DISABLED 651 bool "Require boot parameter to enable pressure stall information tracking" 652 default n 653 depends on PSI 654 help 655 If set, pressure stall information tracking will be disabled 656 per default but can be enabled through passing psi=1 on the 657 kernel commandline during boot. 658 659 This feature adds some code to the task wakeup and sleep 660 paths of the scheduler. The overhead is too low to affect 661 common scheduling-intense workloads in practice (such as 662 webservers, memcache), but it does show up in artificial 663 scheduler stress tests, such as hackbench. 664 665 If you are paranoid and not sure what the kernel will be 666 used for, say Y. 667 668 Say N if unsure. 669 670endmenu # "CPU/Task time and stats accounting" 671 672config CPU_ISOLATION 673 bool "CPU isolation" 674 depends on SMP || COMPILE_TEST 675 default y 676 help 677 Make sure that CPUs running critical tasks are not disturbed by 678 any source of "noise" such as unbound workqueues, timers, kthreads... 679 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 680 the "isolcpus=" boot parameter. 681 682 Say Y if unsure. 683 684source "kernel/rcu/Kconfig" 685 686config IKCONFIG 687 tristate "Kernel .config support" 688 help 689 This option enables the complete Linux kernel ".config" file 690 contents to be saved in the kernel. It provides documentation 691 of which kernel options are used in a running kernel or in an 692 on-disk kernel. This information can be extracted from the kernel 693 image file with the script scripts/extract-ikconfig and used as 694 input to rebuild the current kernel or to build another kernel. 695 It can also be extracted from a running kernel by reading 696 /proc/config.gz if enabled (below). 697 698config IKCONFIG_PROC 699 bool "Enable access to .config through /proc/config.gz" 700 depends on IKCONFIG && PROC_FS 701 help 702 This option enables access to the kernel configuration file 703 through /proc/config.gz. 704 705config IKHEADERS 706 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 707 depends on SYSFS 708 help 709 This option enables access to the in-kernel headers that are generated during 710 the build process. These can be used to build eBPF tracing programs, 711 or similar programs. If you build the headers as a module, a module called 712 kheaders.ko is built which can be loaded on-demand to get access to headers. 713 714config LOG_BUF_SHIFT 715 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 716 range 12 25 717 default 17 718 depends on PRINTK 719 help 720 Select the minimal kernel log buffer size as a power of 2. 721 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 722 parameter, see below. Any higher size also might be forced 723 by "log_buf_len" boot parameter. 724 725 Examples: 726 17 => 128 KB 727 16 => 64 KB 728 15 => 32 KB 729 14 => 16 KB 730 13 => 8 KB 731 12 => 4 KB 732 733config LOG_CPU_MAX_BUF_SHIFT 734 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 735 depends on SMP 736 range 0 21 737 default 12 if !BASE_SMALL 738 default 0 if BASE_SMALL 739 depends on PRINTK 740 help 741 This option allows to increase the default ring buffer size 742 according to the number of CPUs. The value defines the contribution 743 of each CPU as a power of 2. The used space is typically only few 744 lines however it might be much more when problems are reported, 745 e.g. backtraces. 746 747 The increased size means that a new buffer has to be allocated and 748 the original static one is unused. It makes sense only on systems 749 with more CPUs. Therefore this value is used only when the sum of 750 contributions is greater than the half of the default kernel ring 751 buffer as defined by LOG_BUF_SHIFT. The default values are set 752 so that more than 16 CPUs are needed to trigger the allocation. 753 754 Also this option is ignored when "log_buf_len" kernel parameter is 755 used as it forces an exact (power of two) size of the ring buffer. 756 757 The number of possible CPUs is used for this computation ignoring 758 hotplugging making the computation optimal for the worst case 759 scenario while allowing a simple algorithm to be used from bootup. 760 761 Examples shift values and their meaning: 762 17 => 128 KB for each CPU 763 16 => 64 KB for each CPU 764 15 => 32 KB for each CPU 765 14 => 16 KB for each CPU 766 13 => 8 KB for each CPU 767 12 => 4 KB for each CPU 768 769config PRINTK_INDEX 770 bool "Printk indexing debugfs interface" 771 depends on PRINTK && DEBUG_FS 772 help 773 Add support for indexing of all printk formats known at compile time 774 at <debugfs>/printk/index/<module>. 775 776 This can be used as part of maintaining daemons which monitor 777 /dev/kmsg, as it permits auditing the printk formats present in a 778 kernel, allowing detection of cases where monitored printks are 779 changed or no longer present. 780 781 There is no additional runtime cost to printk with this enabled. 782 783# 784# Architectures with an unreliable sched_clock() should select this: 785# 786config HAVE_UNSTABLE_SCHED_CLOCK 787 bool 788 789config GENERIC_SCHED_CLOCK 790 bool 791 792menu "Scheduler features" 793 794config UCLAMP_TASK 795 bool "Enable utilization clamping for RT/FAIR tasks" 796 depends on CPU_FREQ_GOV_SCHEDUTIL 797 help 798 This feature enables the scheduler to track the clamped utilization 799 of each CPU based on RUNNABLE tasks scheduled on that CPU. 800 801 With this option, the user can specify the min and max CPU 802 utilization allowed for RUNNABLE tasks. The max utilization defines 803 the maximum frequency a task should use while the min utilization 804 defines the minimum frequency it should use. 805 806 Both min and max utilization clamp values are hints to the scheduler, 807 aiming at improving its frequency selection policy, but they do not 808 enforce or grant any specific bandwidth for tasks. 809 810 If in doubt, say N. 811 812config UCLAMP_BUCKETS_COUNT 813 int "Number of supported utilization clamp buckets" 814 range 5 20 815 default 5 816 depends on UCLAMP_TASK 817 help 818 Defines the number of clamp buckets to use. The range of each bucket 819 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 820 number of clamp buckets the finer their granularity and the higher 821 the precision of clamping aggregation and tracking at run-time. 822 823 For example, with the minimum configuration value we will have 5 824 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 825 be refcounted in the [20..39]% bucket and will set the bucket clamp 826 effective value to 25%. 827 If a second 30% boosted task should be co-scheduled on the same CPU, 828 that task will be refcounted in the same bucket of the first task and 829 it will boost the bucket clamp effective value to 30%. 830 The clamp effective value of a bucket is reset to its nominal value 831 (20% in the example above) when there are no more tasks refcounted in 832 that bucket. 833 834 An additional boost/capping margin can be added to some tasks. In the 835 example above the 25% task will be boosted to 30% until it exits the 836 CPU. If that should be considered not acceptable on certain systems, 837 it's always possible to reduce the margin by increasing the number of 838 clamp buckets to trade off used memory for run-time tracking 839 precision. 840 841 If in doubt, use the default value. 842 843endmenu 844 845# 846# For architectures that want to enable the support for NUMA-affine scheduler 847# balancing logic: 848# 849config ARCH_SUPPORTS_NUMA_BALANCING 850 bool 851 852# 853# For architectures that prefer to flush all TLBs after a number of pages 854# are unmapped instead of sending one IPI per page to flush. The architecture 855# must provide guarantees on what happens if a clean TLB cache entry is 856# written after the unmap. Details are in mm/rmap.c near the check for 857# should_defer_flush. The architecture should also consider if the full flush 858# and the refill costs are offset by the savings of sending fewer IPIs. 859config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 860 bool 861 862config CC_HAS_INT128 863 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 864 865config CC_IMPLICIT_FALLTHROUGH 866 string 867 default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5) 868 default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough) 869 870# Currently, disable gcc-11+ array-bounds globally. 871# It's still broken in gcc-13, so no upper bound yet. 872config GCC11_NO_ARRAY_BOUNDS 873 def_bool y 874 875config CC_NO_ARRAY_BOUNDS 876 bool 877 default y if CC_IS_GCC && GCC_VERSION >= 110000 && GCC11_NO_ARRAY_BOUNDS 878 879# Currently, disable -Wstringop-overflow for GCC globally. 880config GCC_NO_STRINGOP_OVERFLOW 881 def_bool y 882 883config CC_NO_STRINGOP_OVERFLOW 884 bool 885 default y if CC_IS_GCC && GCC_NO_STRINGOP_OVERFLOW 886 887config CC_STRINGOP_OVERFLOW 888 bool 889 default y if CC_IS_GCC && !CC_NO_STRINGOP_OVERFLOW 890 891# 892# For architectures that know their GCC __int128 support is sound 893# 894config ARCH_SUPPORTS_INT128 895 bool 896 897# For architectures that (ab)use NUMA to represent different memory regions 898# all cpu-local but of different latencies, such as SuperH. 899# 900config ARCH_WANT_NUMA_VARIABLE_LOCALITY 901 bool 902 903config NUMA_BALANCING 904 bool "Memory placement aware NUMA scheduler" 905 depends on ARCH_SUPPORTS_NUMA_BALANCING 906 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 907 depends on SMP && NUMA && MIGRATION && !PREEMPT_RT 908 help 909 This option adds support for automatic NUMA aware memory/task placement. 910 The mechanism is quite primitive and is based on migrating memory when 911 it has references to the node the task is running on. 912 913 This system will be inactive on UMA systems. 914 915config NUMA_BALANCING_DEFAULT_ENABLED 916 bool "Automatically enable NUMA aware memory/task placement" 917 default y 918 depends on NUMA_BALANCING 919 help 920 If set, automatic NUMA balancing will be enabled if running on a NUMA 921 machine. 922 923menuconfig CGROUPS 924 bool "Control Group support" 925 select KERNFS 926 help 927 This option adds support for grouping sets of processes together, for 928 use with process control subsystems such as Cpusets, CFS, memory 929 controls or device isolation. 930 See 931 - Documentation/scheduler/sched-design-CFS.rst (CFS) 932 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 933 and resource control) 934 935 Say N if unsure. 936 937if CGROUPS 938 939config PAGE_COUNTER 940 bool 941 942config CGROUP_FAVOR_DYNMODS 943 bool "Favor dynamic modification latency reduction by default" 944 help 945 This option enables the "favordynmods" mount option by default 946 which reduces the latencies of dynamic cgroup modifications such 947 as task migrations and controller on/offs at the cost of making 948 hot path operations such as forks and exits more expensive. 949 950 Say N if unsure. 951 952config MEMCG 953 bool "Memory controller" 954 select PAGE_COUNTER 955 select EVENTFD 956 help 957 Provides control over the memory footprint of tasks in a cgroup. 958 959config MEMCG_KMEM 960 bool 961 depends on MEMCG 962 default y 963 964config BLK_CGROUP 965 bool "IO controller" 966 depends on BLOCK 967 default n 968 help 969 Generic block IO controller cgroup interface. This is the common 970 cgroup interface which should be used by various IO controlling 971 policies. 972 973 Currently, CFQ IO scheduler uses it to recognize task groups and 974 control disk bandwidth allocation (proportional time slice allocation) 975 to such task groups. It is also used by bio throttling logic in 976 block layer to implement upper limit in IO rates on a device. 977 978 This option only enables generic Block IO controller infrastructure. 979 One needs to also enable actual IO controlling logic/policy. For 980 enabling proportional weight division of disk bandwidth in CFQ, set 981 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 982 CONFIG_BLK_DEV_THROTTLING=y. 983 984 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 985 986config CGROUP_WRITEBACK 987 bool 988 depends on MEMCG && BLK_CGROUP 989 default y 990 991menuconfig CGROUP_SCHED 992 bool "CPU controller" 993 default n 994 help 995 This feature lets CPU scheduler recognize task groups and control CPU 996 bandwidth allocation to such task groups. It uses cgroups to group 997 tasks. 998 999if CGROUP_SCHED 1000config FAIR_GROUP_SCHED 1001 bool "Group scheduling for SCHED_OTHER" 1002 depends on CGROUP_SCHED 1003 default CGROUP_SCHED 1004 1005config CFS_BANDWIDTH 1006 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 1007 depends on FAIR_GROUP_SCHED 1008 default n 1009 help 1010 This option allows users to define CPU bandwidth rates (limits) for 1011 tasks running within the fair group scheduler. Groups with no limit 1012 set are considered to be unconstrained and will run with no 1013 restriction. 1014 See Documentation/scheduler/sched-bwc.rst for more information. 1015 1016config RT_GROUP_SCHED 1017 bool "Group scheduling for SCHED_RR/FIFO" 1018 depends on CGROUP_SCHED 1019 default n 1020 help 1021 This feature lets you explicitly allocate real CPU bandwidth 1022 to task groups. If enabled, it will also make it impossible to 1023 schedule realtime tasks for non-root users until you allocate 1024 realtime bandwidth for them. 1025 See Documentation/scheduler/sched-rt-group.rst for more information. 1026 1027endif #CGROUP_SCHED 1028 1029config SCHED_MM_CID 1030 def_bool y 1031 depends on SMP && RSEQ 1032 1033config UCLAMP_TASK_GROUP 1034 bool "Utilization clamping per group of tasks" 1035 depends on CGROUP_SCHED 1036 depends on UCLAMP_TASK 1037 default n 1038 help 1039 This feature enables the scheduler to track the clamped utilization 1040 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 1041 1042 When this option is enabled, the user can specify a min and max 1043 CPU bandwidth which is allowed for each single task in a group. 1044 The max bandwidth allows to clamp the maximum frequency a task 1045 can use, while the min bandwidth allows to define a minimum 1046 frequency a task will always use. 1047 1048 When task group based utilization clamping is enabled, an eventually 1049 specified task-specific clamp value is constrained by the cgroup 1050 specified clamp value. Both minimum and maximum task clamping cannot 1051 be bigger than the corresponding clamping defined at task group level. 1052 1053 If in doubt, say N. 1054 1055config CGROUP_PIDS 1056 bool "PIDs controller" 1057 help 1058 Provides enforcement of process number limits in the scope of a 1059 cgroup. Any attempt to fork more processes than is allowed in the 1060 cgroup will fail. PIDs are fundamentally a global resource because it 1061 is fairly trivial to reach PID exhaustion before you reach even a 1062 conservative kmemcg limit. As a result, it is possible to grind a 1063 system to halt without being limited by other cgroup policies. The 1064 PIDs controller is designed to stop this from happening. 1065 1066 It should be noted that organisational operations (such as attaching 1067 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 1068 since the PIDs limit only affects a process's ability to fork, not to 1069 attach to a cgroup. 1070 1071config CGROUP_RDMA 1072 bool "RDMA controller" 1073 help 1074 Provides enforcement of RDMA resources defined by IB stack. 1075 It is fairly easy for consumers to exhaust RDMA resources, which 1076 can result into resource unavailability to other consumers. 1077 RDMA controller is designed to stop this from happening. 1078 Attaching processes with active RDMA resources to the cgroup 1079 hierarchy is allowed even if can cross the hierarchy's limit. 1080 1081config CGROUP_FREEZER 1082 bool "Freezer controller" 1083 help 1084 Provides a way to freeze and unfreeze all tasks in a 1085 cgroup. 1086 1087 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1088 controller includes important in-kernel memory consumers per default. 1089 1090 If you're using cgroup2, say N. 1091 1092config CGROUP_HUGETLB 1093 bool "HugeTLB controller" 1094 depends on HUGETLB_PAGE 1095 select PAGE_COUNTER 1096 default n 1097 help 1098 Provides a cgroup controller for HugeTLB pages. 1099 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1100 The limit is enforced during page fault. Since HugeTLB doesn't 1101 support page reclaim, enforcing the limit at page fault time implies 1102 that, the application will get SIGBUS signal if it tries to access 1103 HugeTLB pages beyond its limit. This requires the application to know 1104 beforehand how much HugeTLB pages it would require for its use. The 1105 control group is tracked in the third page lru pointer. This means 1106 that we cannot use the controller with huge page less than 3 pages. 1107 1108config CPUSETS 1109 bool "Cpuset controller" 1110 depends on SMP 1111 help 1112 This option will let you create and manage CPUSETs which 1113 allow dynamically partitioning a system into sets of CPUs and 1114 Memory Nodes and assigning tasks to run only within those sets. 1115 This is primarily useful on large SMP or NUMA systems. 1116 1117 Say N if unsure. 1118 1119config PROC_PID_CPUSET 1120 bool "Include legacy /proc/<pid>/cpuset file" 1121 depends on CPUSETS 1122 default y 1123 1124config CGROUP_DEVICE 1125 bool "Device controller" 1126 help 1127 Provides a cgroup controller implementing whitelists for 1128 devices which a process in the cgroup can mknod or open. 1129 1130config CGROUP_CPUACCT 1131 bool "Simple CPU accounting controller" 1132 help 1133 Provides a simple controller for monitoring the 1134 total CPU consumed by the tasks in a cgroup. 1135 1136config CGROUP_PERF 1137 bool "Perf controller" 1138 depends on PERF_EVENTS 1139 help 1140 This option extends the perf per-cpu mode to restrict monitoring 1141 to threads which belong to the cgroup specified and run on the 1142 designated cpu. Or this can be used to have cgroup ID in samples 1143 so that it can monitor performance events among cgroups. 1144 1145 Say N if unsure. 1146 1147config CGROUP_BPF 1148 bool "Support for eBPF programs attached to cgroups" 1149 depends on BPF_SYSCALL 1150 select SOCK_CGROUP_DATA 1151 help 1152 Allow attaching eBPF programs to a cgroup using the bpf(2) 1153 syscall command BPF_PROG_ATTACH. 1154 1155 In which context these programs are accessed depends on the type 1156 of attachment. For instance, programs that are attached using 1157 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1158 inet sockets. 1159 1160config CGROUP_MISC 1161 bool "Misc resource controller" 1162 default n 1163 help 1164 Provides a controller for miscellaneous resources on a host. 1165 1166 Miscellaneous scalar resources are the resources on the host system 1167 which cannot be abstracted like the other cgroups. This controller 1168 tracks and limits the miscellaneous resources used by a process 1169 attached to a cgroup hierarchy. 1170 1171 For more information, please check misc cgroup section in 1172 /Documentation/admin-guide/cgroup-v2.rst. 1173 1174config CGROUP_DEBUG 1175 bool "Debug controller" 1176 default n 1177 depends on DEBUG_KERNEL 1178 help 1179 This option enables a simple controller that exports 1180 debugging information about the cgroups framework. This 1181 controller is for control cgroup debugging only. Its 1182 interfaces are not stable. 1183 1184 Say N. 1185 1186config SOCK_CGROUP_DATA 1187 bool 1188 default n 1189 1190endif # CGROUPS 1191 1192menuconfig NAMESPACES 1193 bool "Namespaces support" if EXPERT 1194 depends on MULTIUSER 1195 default !EXPERT 1196 help 1197 Provides the way to make tasks work with different objects using 1198 the same id. For example same IPC id may refer to different objects 1199 or same user id or pid may refer to different tasks when used in 1200 different namespaces. 1201 1202if NAMESPACES 1203 1204config UTS_NS 1205 bool "UTS namespace" 1206 default y 1207 help 1208 In this namespace tasks see different info provided with the 1209 uname() system call 1210 1211config TIME_NS 1212 bool "TIME namespace" 1213 depends on GENERIC_VDSO_TIME_NS 1214 default y 1215 help 1216 In this namespace boottime and monotonic clocks can be set. 1217 The time will keep going with the same pace. 1218 1219config IPC_NS 1220 bool "IPC namespace" 1221 depends on (SYSVIPC || POSIX_MQUEUE) 1222 default y 1223 help 1224 In this namespace tasks work with IPC ids which correspond to 1225 different IPC objects in different namespaces. 1226 1227config USER_NS 1228 bool "User namespace" 1229 default n 1230 help 1231 This allows containers, i.e. vservers, to use user namespaces 1232 to provide different user info for different servers. 1233 1234 When user namespaces are enabled in the kernel it is 1235 recommended that the MEMCG option also be enabled and that 1236 user-space use the memory control groups to limit the amount 1237 of memory a memory unprivileged users can use. 1238 1239 If unsure, say N. 1240 1241config PID_NS 1242 bool "PID Namespaces" 1243 default y 1244 help 1245 Support process id namespaces. This allows having multiple 1246 processes with the same pid as long as they are in different 1247 pid namespaces. This is a building block of containers. 1248 1249config NET_NS 1250 bool "Network namespace" 1251 depends on NET 1252 default y 1253 help 1254 Allow user space to create what appear to be multiple instances 1255 of the network stack. 1256 1257endif # NAMESPACES 1258 1259config CHECKPOINT_RESTORE 1260 bool "Checkpoint/restore support" 1261 depends on PROC_FS 1262 select PROC_CHILDREN 1263 select KCMP 1264 default n 1265 help 1266 Enables additional kernel features in a sake of checkpoint/restore. 1267 In particular it adds auxiliary prctl codes to setup process text, 1268 data and heap segment sizes, and a few additional /proc filesystem 1269 entries. 1270 1271 If unsure, say N here. 1272 1273config SCHED_AUTOGROUP 1274 bool "Automatic process group scheduling" 1275 select CGROUPS 1276 select CGROUP_SCHED 1277 select FAIR_GROUP_SCHED 1278 help 1279 This option optimizes the scheduler for common desktop workloads by 1280 automatically creating and populating task groups. This separation 1281 of workloads isolates aggressive CPU burners (like build jobs) from 1282 desktop applications. Task group autogeneration is currently based 1283 upon task session. 1284 1285config RELAY 1286 bool "Kernel->user space relay support (formerly relayfs)" 1287 select IRQ_WORK 1288 help 1289 This option enables support for relay interface support in 1290 certain file systems (such as debugfs). 1291 It is designed to provide an efficient mechanism for tools and 1292 facilities to relay large amounts of data from kernel space to 1293 user space. 1294 1295 If unsure, say N. 1296 1297config BLK_DEV_INITRD 1298 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1299 help 1300 The initial RAM filesystem is a ramfs which is loaded by the 1301 boot loader (loadlin or lilo) and that is mounted as root 1302 before the normal boot procedure. It is typically used to 1303 load modules needed to mount the "real" root file system, 1304 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1305 1306 If RAM disk support (BLK_DEV_RAM) is also included, this 1307 also enables initial RAM disk (initrd) support and adds 1308 15 Kbytes (more on some other architectures) to the kernel size. 1309 1310 If unsure say Y. 1311 1312if BLK_DEV_INITRD 1313 1314source "usr/Kconfig" 1315 1316endif 1317 1318config BOOT_CONFIG 1319 bool "Boot config support" 1320 select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED 1321 help 1322 Extra boot config allows system admin to pass a config file as 1323 complemental extension of kernel cmdline when booting. 1324 The boot config file must be attached at the end of initramfs 1325 with checksum, size and magic word. 1326 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1327 1328 If unsure, say Y. 1329 1330config BOOT_CONFIG_FORCE 1331 bool "Force unconditional bootconfig processing" 1332 depends on BOOT_CONFIG 1333 default y if BOOT_CONFIG_EMBED 1334 help 1335 With this Kconfig option set, BOOT_CONFIG processing is carried 1336 out even when the "bootconfig" kernel-boot parameter is omitted. 1337 In fact, with this Kconfig option set, there is no way to 1338 make the kernel ignore the BOOT_CONFIG-supplied kernel-boot 1339 parameters. 1340 1341 If unsure, say N. 1342 1343config BOOT_CONFIG_EMBED 1344 bool "Embed bootconfig file in the kernel" 1345 depends on BOOT_CONFIG 1346 help 1347 Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the 1348 kernel. Usually, the bootconfig file is loaded with the initrd 1349 image. But if the system doesn't support initrd, this option will 1350 help you by embedding a bootconfig file while building the kernel. 1351 1352 If unsure, say N. 1353 1354config BOOT_CONFIG_EMBED_FILE 1355 string "Embedded bootconfig file path" 1356 depends on BOOT_CONFIG_EMBED 1357 help 1358 Specify a bootconfig file which will be embedded to the kernel. 1359 This bootconfig will be used if there is no initrd or no other 1360 bootconfig in the initrd. 1361 1362config INITRAMFS_PRESERVE_MTIME 1363 bool "Preserve cpio archive mtimes in initramfs" 1364 default y 1365 help 1366 Each entry in an initramfs cpio archive carries an mtime value. When 1367 enabled, extracted cpio items take this mtime, with directory mtime 1368 setting deferred until after creation of any child entries. 1369 1370 If unsure, say Y. 1371 1372choice 1373 prompt "Compiler optimization level" 1374 default CC_OPTIMIZE_FOR_PERFORMANCE 1375 1376config CC_OPTIMIZE_FOR_PERFORMANCE 1377 bool "Optimize for performance (-O2)" 1378 help 1379 This is the default optimization level for the kernel, building 1380 with the "-O2" compiler flag for best performance and most 1381 helpful compile-time warnings. 1382 1383config CC_OPTIMIZE_FOR_SIZE 1384 bool "Optimize for size (-Os)" 1385 help 1386 Choosing this option will pass "-Os" to your compiler resulting 1387 in a smaller kernel. 1388 1389endchoice 1390 1391config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1392 bool 1393 help 1394 This requires that the arch annotates or otherwise protects 1395 its external entry points from being discarded. Linker scripts 1396 must also merge .text.*, .data.*, and .bss.* correctly into 1397 output sections. Care must be taken not to pull in unrelated 1398 sections (e.g., '.text.init'). Typically '.' in section names 1399 is used to distinguish them from label names / C identifiers. 1400 1401config LD_DEAD_CODE_DATA_ELIMINATION 1402 bool "Dead code and data elimination (EXPERIMENTAL)" 1403 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1404 depends on EXPERT 1405 depends on $(cc-option,-ffunction-sections -fdata-sections) 1406 depends on $(ld-option,--gc-sections) 1407 help 1408 Enable this if you want to do dead code and data elimination with 1409 the linker by compiling with -ffunction-sections -fdata-sections, 1410 and linking with --gc-sections. 1411 1412 This can reduce on disk and in-memory size of the kernel 1413 code and static data, particularly for small configs and 1414 on small systems. This has the possibility of introducing 1415 silently broken kernel if the required annotations are not 1416 present. This option is not well tested yet, so use at your 1417 own risk. 1418 1419config LD_ORPHAN_WARN 1420 def_bool y 1421 depends on ARCH_WANT_LD_ORPHAN_WARN 1422 depends on $(ld-option,--orphan-handling=warn) 1423 depends on $(ld-option,--orphan-handling=error) 1424 1425config LD_ORPHAN_WARN_LEVEL 1426 string 1427 depends on LD_ORPHAN_WARN 1428 default "error" if WERROR 1429 default "warn" 1430 1431config SYSCTL 1432 bool 1433 1434config HAVE_UID16 1435 bool 1436 1437config SYSCTL_EXCEPTION_TRACE 1438 bool 1439 help 1440 Enable support for /proc/sys/debug/exception-trace. 1441 1442config SYSCTL_ARCH_UNALIGN_NO_WARN 1443 bool 1444 help 1445 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1446 Allows arch to define/use @no_unaligned_warning to possibly warn 1447 about unaligned access emulation going on under the hood. 1448 1449config SYSCTL_ARCH_UNALIGN_ALLOW 1450 bool 1451 help 1452 Enable support for /proc/sys/kernel/unaligned-trap 1453 Allows arches to define/use @unaligned_enabled to runtime toggle 1454 the unaligned access emulation. 1455 see arch/parisc/kernel/unaligned.c for reference 1456 1457config HAVE_PCSPKR_PLATFORM 1458 bool 1459 1460# interpreter that classic socket filters depend on 1461config BPF 1462 bool 1463 select CRYPTO_LIB_SHA1 1464 1465menuconfig EXPERT 1466 bool "Configure standard kernel features (expert users)" 1467 # Unhide debug options, to make the on-by-default options visible 1468 select DEBUG_KERNEL 1469 help 1470 This option allows certain base kernel options and settings 1471 to be disabled or tweaked. This is for specialized 1472 environments which can tolerate a "non-standard" kernel. 1473 Only use this if you really know what you are doing. 1474 1475config UID16 1476 bool "Enable 16-bit UID system calls" if EXPERT 1477 depends on HAVE_UID16 && MULTIUSER 1478 default y 1479 help 1480 This enables the legacy 16-bit UID syscall wrappers. 1481 1482config MULTIUSER 1483 bool "Multiple users, groups and capabilities support" if EXPERT 1484 default y 1485 help 1486 This option enables support for non-root users, groups and 1487 capabilities. 1488 1489 If you say N here, all processes will run with UID 0, GID 0, and all 1490 possible capabilities. Saying N here also compiles out support for 1491 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1492 setgid, and capset. 1493 1494 If unsure, say Y here. 1495 1496config SGETMASK_SYSCALL 1497 bool "sgetmask/ssetmask syscalls support" if EXPERT 1498 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1499 help 1500 sys_sgetmask and sys_ssetmask are obsolete system calls 1501 no longer supported in libc but still enabled by default in some 1502 architectures. 1503 1504 If unsure, leave the default option here. 1505 1506config SYSFS_SYSCALL 1507 bool "Sysfs syscall support" if EXPERT 1508 default y 1509 help 1510 sys_sysfs is an obsolete system call no longer supported in libc. 1511 Note that disabling this option is more secure but might break 1512 compatibility with some systems. 1513 1514 If unsure say Y here. 1515 1516config FHANDLE 1517 bool "open by fhandle syscalls" if EXPERT 1518 select EXPORTFS 1519 default y 1520 help 1521 If you say Y here, a user level program will be able to map 1522 file names to handle and then later use the handle for 1523 different file system operations. This is useful in implementing 1524 userspace file servers, which now track files using handles instead 1525 of names. The handle would remain the same even if file names 1526 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1527 syscalls. 1528 1529config POSIX_TIMERS 1530 bool "Posix Clocks & timers" if EXPERT 1531 default y 1532 help 1533 This includes native support for POSIX timers to the kernel. 1534 Some embedded systems have no use for them and therefore they 1535 can be configured out to reduce the size of the kernel image. 1536 1537 When this option is disabled, the following syscalls won't be 1538 available: timer_create, timer_gettime: timer_getoverrun, 1539 timer_settime, timer_delete, clock_adjtime, getitimer, 1540 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1541 clock_getres and clock_nanosleep syscalls will be limited to 1542 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1543 1544 If unsure say y. 1545 1546config PRINTK 1547 default y 1548 bool "Enable support for printk" if EXPERT 1549 select IRQ_WORK 1550 help 1551 This option enables normal printk support. Removing it 1552 eliminates most of the message strings from the kernel image 1553 and makes the kernel more or less silent. As this makes it 1554 very difficult to diagnose system problems, saying N here is 1555 strongly discouraged. 1556 1557config BUG 1558 bool "BUG() support" if EXPERT 1559 default y 1560 help 1561 Disabling this option eliminates support for BUG and WARN, reducing 1562 the size of your kernel image and potentially quietly ignoring 1563 numerous fatal conditions. You should only consider disabling this 1564 option for embedded systems with no facilities for reporting errors. 1565 Just say Y. 1566 1567config ELF_CORE 1568 depends on COREDUMP 1569 default y 1570 bool "Enable ELF core dumps" if EXPERT 1571 help 1572 Enable support for generating core dumps. Disabling saves about 4k. 1573 1574 1575config PCSPKR_PLATFORM 1576 bool "Enable PC-Speaker support" if EXPERT 1577 depends on HAVE_PCSPKR_PLATFORM 1578 select I8253_LOCK 1579 default y 1580 help 1581 This option allows to disable the internal PC-Speaker 1582 support, saving some memory. 1583 1584config BASE_FULL 1585 default y 1586 bool "Enable full-sized data structures for core" if EXPERT 1587 help 1588 Disabling this option reduces the size of miscellaneous core 1589 kernel data structures. This saves memory on small machines, 1590 but may reduce performance. 1591 1592config FUTEX 1593 bool "Enable futex support" if EXPERT 1594 depends on !(SPARC32 && SMP) 1595 default y 1596 imply RT_MUTEXES 1597 help 1598 Disabling this option will cause the kernel to be built without 1599 support for "fast userspace mutexes". The resulting kernel may not 1600 run glibc-based applications correctly. 1601 1602config FUTEX_PI 1603 bool 1604 depends on FUTEX && RT_MUTEXES 1605 default y 1606 1607config EPOLL 1608 bool "Enable eventpoll support" if EXPERT 1609 default y 1610 help 1611 Disabling this option will cause the kernel to be built without 1612 support for epoll family of system calls. 1613 1614config SIGNALFD 1615 bool "Enable signalfd() system call" if EXPERT 1616 default y 1617 help 1618 Enable the signalfd() system call that allows to receive signals 1619 on a file descriptor. 1620 1621 If unsure, say Y. 1622 1623config TIMERFD 1624 bool "Enable timerfd() system call" if EXPERT 1625 default y 1626 help 1627 Enable the timerfd() system call that allows to receive timer 1628 events on a file descriptor. 1629 1630 If unsure, say Y. 1631 1632config EVENTFD 1633 bool "Enable eventfd() system call" if EXPERT 1634 default y 1635 help 1636 Enable the eventfd() system call that allows to receive both 1637 kernel notification (ie. KAIO) or userspace notifications. 1638 1639 If unsure, say Y. 1640 1641config SHMEM 1642 bool "Use full shmem filesystem" if EXPERT 1643 default y 1644 depends on MMU 1645 help 1646 The shmem is an internal filesystem used to manage shared memory. 1647 It is backed by swap and manages resource limits. It is also exported 1648 to userspace as tmpfs if TMPFS is enabled. Disabling this 1649 option replaces shmem and tmpfs with the much simpler ramfs code, 1650 which may be appropriate on small systems without swap. 1651 1652config AIO 1653 bool "Enable AIO support" if EXPERT 1654 default y 1655 help 1656 This option enables POSIX asynchronous I/O which may by used 1657 by some high performance threaded applications. Disabling 1658 this option saves about 7k. 1659 1660config IO_URING 1661 bool "Enable IO uring support" if EXPERT 1662 select IO_WQ 1663 default y 1664 help 1665 This option enables support for the io_uring interface, enabling 1666 applications to submit and complete IO through submission and 1667 completion rings that are shared between the kernel and application. 1668 1669config ADVISE_SYSCALLS 1670 bool "Enable madvise/fadvise syscalls" if EXPERT 1671 default y 1672 help 1673 This option enables the madvise and fadvise syscalls, used by 1674 applications to advise the kernel about their future memory or file 1675 usage, improving performance. If building an embedded system where no 1676 applications use these syscalls, you can disable this option to save 1677 space. 1678 1679config MEMBARRIER 1680 bool "Enable membarrier() system call" if EXPERT 1681 default y 1682 help 1683 Enable the membarrier() system call that allows issuing memory 1684 barriers across all running threads, which can be used to distribute 1685 the cost of user-space memory barriers asymmetrically by transforming 1686 pairs of memory barriers into pairs consisting of membarrier() and a 1687 compiler barrier. 1688 1689 If unsure, say Y. 1690 1691config KCMP 1692 bool "Enable kcmp() system call" if EXPERT 1693 help 1694 Enable the kernel resource comparison system call. It provides 1695 user-space with the ability to compare two processes to see if they 1696 share a common resource, such as a file descriptor or even virtual 1697 memory space. 1698 1699 If unsure, say N. 1700 1701config RSEQ 1702 bool "Enable rseq() system call" if EXPERT 1703 default y 1704 depends on HAVE_RSEQ 1705 select MEMBARRIER 1706 help 1707 Enable the restartable sequences system call. It provides a 1708 user-space cache for the current CPU number value, which 1709 speeds up getting the current CPU number from user-space, 1710 as well as an ABI to speed up user-space operations on 1711 per-CPU data. 1712 1713 If unsure, say Y. 1714 1715config DEBUG_RSEQ 1716 default n 1717 bool "Enable debugging of rseq() system call" if EXPERT 1718 depends on RSEQ && DEBUG_KERNEL 1719 help 1720 Enable extra debugging checks for the rseq system call. 1721 1722 If unsure, say N. 1723 1724config CACHESTAT_SYSCALL 1725 bool "Enable cachestat() system call" if EXPERT 1726 default y 1727 help 1728 Enable the cachestat system call, which queries the page cache 1729 statistics of a file (number of cached pages, dirty pages, 1730 pages marked for writeback, (recently) evicted pages). 1731 1732 If unsure say Y here. 1733 1734config PC104 1735 bool "PC/104 support" if EXPERT 1736 help 1737 Expose PC/104 form factor device drivers and options available for 1738 selection and configuration. Enable this option if your target 1739 machine has a PC/104 bus. 1740 1741config KALLSYMS 1742 bool "Load all symbols for debugging/ksymoops" if EXPERT 1743 default y 1744 help 1745 Say Y here to let the kernel print out symbolic crash information and 1746 symbolic stack backtraces. This increases the size of the kernel 1747 somewhat, as all symbols have to be loaded into the kernel image. 1748 1749config KALLSYMS_SELFTEST 1750 bool "Test the basic functions and performance of kallsyms" 1751 depends on KALLSYMS 1752 default n 1753 help 1754 Test the basic functions and performance of some interfaces, such as 1755 kallsyms_lookup_name. It also calculates the compression rate of the 1756 kallsyms compression algorithm for the current symbol set. 1757 1758 Start self-test automatically after system startup. Suggest executing 1759 "dmesg | grep kallsyms_selftest" to collect test results. "finish" is 1760 displayed in the last line, indicating that the test is complete. 1761 1762config KALLSYMS_ALL 1763 bool "Include all symbols in kallsyms" 1764 depends on DEBUG_KERNEL && KALLSYMS 1765 help 1766 Normally kallsyms only contains the symbols of functions for nicer 1767 OOPS messages and backtraces (i.e., symbols from the text and inittext 1768 sections). This is sufficient for most cases. And only if you want to 1769 enable kernel live patching, or other less common use cases (e.g., 1770 when a debugger is used) all symbols are required (i.e., names of 1771 variables from the data sections, etc). 1772 1773 This option makes sure that all symbols are loaded into the kernel 1774 image (i.e., symbols from all sections) in cost of increased kernel 1775 size (depending on the kernel configuration, it may be 300KiB or 1776 something like this). 1777 1778 Say N unless you really need all symbols, or kernel live patching. 1779 1780config KALLSYMS_ABSOLUTE_PERCPU 1781 bool 1782 depends on KALLSYMS 1783 default X86_64 && SMP 1784 1785config KALLSYMS_BASE_RELATIVE 1786 bool 1787 depends on KALLSYMS 1788 default y 1789 help 1790 Instead of emitting them as absolute values in the native word size, 1791 emit the symbol references in the kallsyms table as 32-bit entries, 1792 each containing a relative value in the range [base, base + U32_MAX] 1793 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1794 an absolute value in the range [0, S32_MAX] or a relative value in the 1795 range [base, base + S32_MAX], where base is the lowest relative symbol 1796 address encountered in the image. 1797 1798 On 64-bit builds, this reduces the size of the address table by 50%, 1799 but more importantly, it results in entries whose values are build 1800 time constants, and no relocation pass is required at runtime to fix 1801 up the entries based on the runtime load address of the kernel. 1802 1803# end of the "standard kernel features (expert users)" menu 1804 1805config ARCH_HAS_MEMBARRIER_CALLBACKS 1806 bool 1807 1808config ARCH_HAS_MEMBARRIER_SYNC_CORE 1809 bool 1810 1811config HAVE_PERF_EVENTS 1812 bool 1813 help 1814 See tools/perf/design.txt for details. 1815 1816config GUEST_PERF_EVENTS 1817 bool 1818 depends on HAVE_PERF_EVENTS 1819 1820config PERF_USE_VMALLOC 1821 bool 1822 help 1823 See tools/perf/design.txt for details 1824 1825menu "Kernel Performance Events And Counters" 1826 1827config PERF_EVENTS 1828 bool "Kernel performance events and counters" 1829 default y if PROFILING 1830 depends on HAVE_PERF_EVENTS 1831 select IRQ_WORK 1832 help 1833 Enable kernel support for various performance events provided 1834 by software and hardware. 1835 1836 Software events are supported either built-in or via the 1837 use of generic tracepoints. 1838 1839 Most modern CPUs support performance events via performance 1840 counter registers. These registers count the number of certain 1841 types of hw events: such as instructions executed, cachemisses 1842 suffered, or branches mis-predicted - without slowing down the 1843 kernel or applications. These registers can also trigger interrupts 1844 when a threshold number of events have passed - and can thus be 1845 used to profile the code that runs on that CPU. 1846 1847 The Linux Performance Event subsystem provides an abstraction of 1848 these software and hardware event capabilities, available via a 1849 system call and used by the "perf" utility in tools/perf/. It 1850 provides per task and per CPU counters, and it provides event 1851 capabilities on top of those. 1852 1853 Say Y if unsure. 1854 1855config DEBUG_PERF_USE_VMALLOC 1856 default n 1857 bool "Debug: use vmalloc to back perf mmap() buffers" 1858 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1859 select PERF_USE_VMALLOC 1860 help 1861 Use vmalloc memory to back perf mmap() buffers. 1862 1863 Mostly useful for debugging the vmalloc code on platforms 1864 that don't require it. 1865 1866 Say N if unsure. 1867 1868endmenu 1869 1870config SYSTEM_DATA_VERIFICATION 1871 def_bool n 1872 select SYSTEM_TRUSTED_KEYRING 1873 select KEYS 1874 select CRYPTO 1875 select CRYPTO_RSA 1876 select ASYMMETRIC_KEY_TYPE 1877 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1878 select ASN1 1879 select OID_REGISTRY 1880 select X509_CERTIFICATE_PARSER 1881 select PKCS7_MESSAGE_PARSER 1882 help 1883 Provide PKCS#7 message verification using the contents of the system 1884 trusted keyring to provide public keys. This then can be used for 1885 module verification, kexec image verification and firmware blob 1886 verification. 1887 1888config PROFILING 1889 bool "Profiling support" 1890 help 1891 Say Y here to enable the extended profiling support mechanisms used 1892 by profilers. 1893 1894config RUST 1895 bool "Rust support" 1896 depends on HAVE_RUST 1897 depends on RUST_IS_AVAILABLE 1898 depends on !MODVERSIONS 1899 depends on !GCC_PLUGINS 1900 depends on !RANDSTRUCT 1901 depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE 1902 select CONSTRUCTORS 1903 help 1904 Enables Rust support in the kernel. 1905 1906 This allows other Rust-related options, like drivers written in Rust, 1907 to be selected. 1908 1909 It is also required to be able to load external kernel modules 1910 written in Rust. 1911 1912 See Documentation/rust/ for more information. 1913 1914 If unsure, say N. 1915 1916config RUSTC_VERSION_TEXT 1917 string 1918 depends on RUST 1919 default $(shell,command -v $(RUSTC) >/dev/null 2>&1 && $(RUSTC) --version || echo n) 1920 1921config BINDGEN_VERSION_TEXT 1922 string 1923 depends on RUST 1924 default $(shell,command -v $(BINDGEN) >/dev/null 2>&1 && $(BINDGEN) --version || echo n) 1925 1926# 1927# Place an empty function call at each tracepoint site. Can be 1928# dynamically changed for a probe function. 1929# 1930config TRACEPOINTS 1931 bool 1932 1933source "kernel/Kconfig.kexec" 1934 1935endmenu # General setup 1936 1937source "arch/Kconfig" 1938 1939config RT_MUTEXES 1940 bool 1941 default y if PREEMPT_RT 1942 1943config BASE_SMALL 1944 int 1945 default 0 if BASE_FULL 1946 default 1 if !BASE_FULL 1947 1948config MODULE_SIG_FORMAT 1949 def_bool n 1950 select SYSTEM_DATA_VERIFICATION 1951 1952source "kernel/module/Kconfig" 1953 1954config INIT_ALL_POSSIBLE 1955 bool 1956 help 1957 Back when each arch used to define their own cpu_online_mask and 1958 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 1959 with all 1s, and others with all 0s. When they were centralised, 1960 it was better to provide this option than to break all the archs 1961 and have several arch maintainers pursuing me down dark alleys. 1962 1963source "block/Kconfig" 1964 1965config PREEMPT_NOTIFIERS 1966 bool 1967 1968config PADATA 1969 depends on SMP 1970 bool 1971 1972config ASN1 1973 tristate 1974 help 1975 Build a simple ASN.1 grammar compiler that produces a bytecode output 1976 that can be interpreted by the ASN.1 stream decoder and used to 1977 inform it as to what tags are to be expected in a stream and what 1978 functions to call on what tags. 1979 1980source "kernel/Kconfig.locks" 1981 1982config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 1983 bool 1984 1985config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 1986 bool 1987 1988# It may be useful for an architecture to override the definitions of the 1989# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 1990# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 1991# different calling convention for syscalls. They can also override the 1992# macros for not-implemented syscalls in kernel/sys_ni.c and 1993# kernel/time/posix-stubs.c. All these overrides need to be available in 1994# <asm/syscall_wrapper.h>. 1995config ARCH_HAS_SYSCALL_WRAPPER 1996 def_bool n 1997