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 RUSTC_VERSION 64 int 65 default $(rustc-version) 66 help 67 It does not depend on `RUST` since that one may need to use the version 68 in a `depends on`. 69 70config RUST_IS_AVAILABLE 71 def_bool $(success,$(srctree)/scripts/rust_is_available.sh) 72 help 73 This shows whether a suitable Rust toolchain is available (found). 74 75 Please see Documentation/rust/quick-start.rst for instructions on how 76 to satisfy the build requirements of Rust support. 77 78 In particular, the Makefile target 'rustavailable' is useful to check 79 why the Rust toolchain is not being detected. 80 81config RUSTC_LLVM_VERSION 82 int 83 default $(rustc-llvm-version) 84 85config RUSTC_LLVM_MAJOR_VERSION 86 int 87 default $(shell,expr $(rustc-llvm-version) / 10000) 88 89config RUSTC_CLANG_LLVM_COMPATIBLE 90 bool 91 default y if CC_IS_CLANG && RUSTC_LLVM_MAJOR_VERSION = $(shell,expr $(cc-version) / 10000) 92 help 93 This indicates whether Rust and Clang use LLVM of the same major 94 version. 95 96 Operations involving handling LLVM IR or bitcode (e.g. cross-language 97 LTO) require the same LLVM major version to work properly. For best 98 compatibility it is recommended that the exact same LLVM is used. 99 100config ARCH_HAS_CC_CAN_LINK 101 bool 102 103config CC_CAN_LINK 104 bool 105 default ARCH_CC_CAN_LINK if ARCH_HAS_CC_CAN_LINK 106 default $(cc_can_link_user,$(m64-flag)) if 64BIT 107 default $(cc_can_link_user,$(m32-flag)) 108 109# Fixed in GCC 14, 13.3, 12.4 and 11.5 110# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113921 111config GCC_ASM_GOTO_OUTPUT_BROKEN 112 bool 113 depends on CC_IS_GCC 114 default y if GCC_VERSION < 110500 115 default y if GCC_VERSION >= 120000 && GCC_VERSION < 120400 116 default y if GCC_VERSION >= 130000 && GCC_VERSION < 130300 117 118config CC_HAS_ASM_GOTO_OUTPUT 119 def_bool y 120 depends on !GCC_ASM_GOTO_OUTPUT_BROKEN 121 depends on $(success,echo 'int foo(int x) { asm goto ("": "=r"(x) ::: bar); return x; bar: return 0; }' | $(CC) -x c - -c -o /dev/null) 122 123config CC_HAS_ASM_GOTO_TIED_OUTPUT 124 depends on CC_HAS_ASM_GOTO_OUTPUT 125 # Detect buggy gcc and clang, fixed in gcc-11 clang-14. 126 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) 127 128config TOOLS_SUPPORT_RELR 129 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 130 131config CC_HAS_ASM_INLINE 132 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 133 134config CC_HAS_ASSUME 135 bool 136 # clang needs to be at least 19.1.0 since the meaning of the assume 137 # attribute changed: 138 # https://github.com/llvm/llvm-project/commit/c44fa3e8a9a44c2e9a575768a3c185354b9f6c17 139 default y if CC_IS_CLANG && CLANG_VERSION >= 190100 140 # supported since gcc 13.1.0 141 # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106654 142 default y if CC_IS_GCC && GCC_VERSION >= 130100 143 144config CC_HAS_NO_PROFILE_FN_ATTR 145 def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror) 146 147config CC_HAS_COUNTED_BY 148 bool 149 # clang needs to be at least 20.1.0 to avoid potential crashes 150 # when building structures that contain __counted_by 151 # https://github.com/ClangBuiltLinux/linux/issues/2114 152 # https://github.com/llvm/llvm-project/commit/160fb1121cdf703c3ef5e61fb26c5659eb581489 153 default y if CC_IS_CLANG && CLANG_VERSION >= 200100 154 # supported since gcc 15.1.0 155 # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108896 156 default y if CC_IS_GCC && GCC_VERSION >= 150100 157 158config CC_HAS_COUNTED_BY_PTR 159 bool 160 # supported since clang 22 161 default y if CC_IS_CLANG && CLANG_VERSION >= 220100 162 # supported since gcc 16.0.0 163 default y if CC_IS_GCC && GCC_VERSION >= 160000 164 165config CC_HAS_BROKEN_COUNTED_BY_REF 166 bool 167 # https://github.com/llvm/llvm-project/issues/182575 168 default y if CC_IS_CLANG && CLANG_VERSION < 220100 169 170config CC_HAS_ALLOC_TOKEN 171 def_bool $(cc-option,-falloc-token-max=123) 172 173config CC_HAS_MULTIDIMENSIONAL_NONSTRING 174 def_bool $(success,echo 'char tag[][4] __attribute__((__nonstring__)) = { };' | $(CC) $(CLANG_FLAGS) -x c - -c -o /dev/null -Werror) 175 176config CC_OPT_INLINE_MEMSET 177 string 178 default "-finline-stringops=memset" if $(cc-option,-finline-stringops=memset) 179 default "-mllvm -max-store-memset=4294967294" if $(cc-option,-mllvm -max-store-memset=4294967294) 180 181config LD_CAN_USE_KEEP_IN_OVERLAY 182 # ld.lld prior to 21.0.0 did not support KEEP within an overlay description 183 # https://github.com/llvm/llvm-project/pull/130661 184 def_bool LD_IS_BFD || LLD_VERSION >= 210000 185 186config RUSTC_HAS_SPAN_FILE 187 def_bool RUSTC_VERSION >= 108800 188 189config RUSTC_HAS_UNNECESSARY_TRANSMUTES 190 def_bool RUSTC_VERSION >= 108800 191 192config RUSTC_HAS_FILE_WITH_NUL 193 def_bool RUSTC_VERSION >= 108900 194 195config RUSTC_HAS_FILE_AS_C_STR 196 def_bool RUSTC_VERSION >= 109100 197 198config RUSTC_HAS_SUSPICIOUS_RUNTIME_SYMBOL_DEFINITIONS 199 def_bool RUSTC_VERSION >= 109800 200 201config PAHOLE_VERSION 202 int 203 default "$(PAHOLE_VERSION)" 204 205config CONSTRUCTORS 206 bool 207 208config IRQ_WORK 209 def_bool y if SMP 210 211config BUILDTIME_TABLE_SORT 212 bool 213 214config THREAD_INFO_IN_TASK 215 bool 216 help 217 Select this to move thread_info off the stack into task_struct. To 218 make this work, an arch will need to remove all thread_info fields 219 except flags and fix any runtime bugs. 220 221 One subtle change that will be needed is to use try_get_task_stack() 222 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 223 224menu "General setup" 225 226config BROKEN 227 bool 228 help 229 This option allows you to choose whether you want to try to 230 compile (and fix) old drivers that haven't been updated to 231 new infrastructure. 232 233config BROKEN_ON_SMP 234 bool 235 depends on BROKEN || !SMP 236 default y 237 238config INIT_ENV_ARG_LIMIT 239 int 240 default 32 if !UML 241 default 128 if UML 242 help 243 Maximum of each of the number of arguments and environment 244 variables passed to init from the kernel command line. 245 246config COMPILE_TEST 247 bool "Compile also drivers which will not load" 248 depends on HAS_IOMEM 249 help 250 Some drivers can be compiled on a different platform than they are 251 intended to be run on. Despite they cannot be loaded there (or even 252 when they load they cannot be used due to missing HW support), 253 developers still, opposing to distributors, might want to build such 254 drivers to compile-test them. 255 256 If you are a developer and want to build everything available, say Y 257 here. If you are a user/distributor, say N here to exclude useless 258 drivers to be distributed. 259 260config WERROR 261 bool "Compile the kernel with warnings as errors" 262 default COMPILE_TEST 263 help 264 A kernel build should not cause any compiler warnings, and this 265 enables the '-Werror' (for C) and '-Dwarnings' (for Rust) flags 266 to enforce that rule by default. Certain warnings from other tools 267 such as the linker may be upgraded to errors with this option as 268 well. 269 270 However, if you have a new (or very old) compiler or linker with odd 271 and unusual warnings, or you have some architecture with problems, 272 you may need to disable this config option in order to 273 successfully build the kernel. 274 275 If in doubt, say Y. 276 277config UAPI_HEADER_TEST 278 bool "Compile test UAPI headers" 279 depends on HEADERS_INSTALL 280 help 281 Compile test headers exported to user-space to ensure they are 282 self-contained, i.e. compilable as standalone units. 283 284 If you are a developer or tester and want to ensure the exported 285 headers are self-contained, say Y here. Otherwise, choose N. 286 287config LOCALVERSION 288 string "Local version - append to kernel release" 289 help 290 Append an extra string to the end of your kernel version. 291 This will show up when you type uname, for example. 292 The string you set here will be appended after the contents of 293 any files with a filename matching localversion* in your 294 object and source tree, in that order. Your total string can 295 be a maximum of 64 characters. 296 297config LOCALVERSION_AUTO 298 bool "Automatically append version information to the version string" 299 default y 300 depends on !COMPILE_TEST 301 help 302 This will try to automatically determine if the current tree is a 303 release tree by looking for git tags that belong to the current 304 top of tree revision. 305 306 A string of the format -gxxxxxxxx will be added to the localversion 307 if a git-based tree is found. The string generated by this will be 308 appended after any matching localversion* files, and after the value 309 set in CONFIG_LOCALVERSION. 310 311 (The actual string used here is the first 12 characters produced 312 by running the command: 313 314 $ git rev-parse --verify HEAD 315 316 which is done within the script "scripts/setlocalversion".) 317 318config BUILD_SALT 319 string "Build ID Salt" 320 default "" 321 help 322 The build ID is used to link binaries and their debug info. Setting 323 this option will use the value in the calculation of the build id. 324 This is mostly useful for distributions which want to ensure the 325 build is unique between builds. It's safe to leave the default. 326 327config HAVE_KERNEL_GZIP 328 bool 329 330config HAVE_KERNEL_BZIP2 331 bool 332 333config HAVE_KERNEL_LZMA 334 bool 335 336config HAVE_KERNEL_XZ 337 bool 338 339config HAVE_KERNEL_LZO 340 bool 341 342config HAVE_KERNEL_LZ4 343 bool 344 345config HAVE_KERNEL_ZSTD 346 bool 347 348config HAVE_KERNEL_UNCOMPRESSED 349 bool 350 351choice 352 prompt "Kernel compression mode" 353 default KERNEL_GZIP 354 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 355 help 356 The linux kernel is a kind of self-extracting executable. 357 Several compression algorithms are available, which differ 358 in efficiency, compression and decompression speed. 359 Compression speed is only relevant when building a kernel. 360 Decompression speed is relevant at each boot. 361 362 If you have any problems with bzip2 or lzma compressed 363 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 364 version of this functionality (bzip2 only), for 2.4, was 365 supplied by Christian Ludwig) 366 367 High compression options are mostly useful for users, who 368 are low on disk space (embedded systems), but for whom ram 369 size matters less. 370 371 If in doubt, select 'gzip' 372 373config KERNEL_GZIP 374 bool "Gzip" 375 depends on HAVE_KERNEL_GZIP 376 help 377 The old and tried gzip compression. It provides a good balance 378 between compression ratio and decompression speed. 379 380config KERNEL_BZIP2 381 bool "Bzip2" 382 depends on HAVE_KERNEL_BZIP2 383 help 384 Its compression ratio and speed is intermediate. 385 Decompression speed is slowest among the choices. The kernel 386 size is about 10% smaller with bzip2, in comparison to gzip. 387 Bzip2 uses a large amount of memory. For modern kernels you 388 will need at least 8MB RAM or more for booting. 389 390config KERNEL_LZMA 391 bool "LZMA" 392 depends on HAVE_KERNEL_LZMA 393 help 394 This compression algorithm's ratio is best. Decompression speed 395 is between gzip and bzip2. Compression is slowest. 396 The kernel size is about 33% smaller with LZMA in comparison to gzip. 397 398config KERNEL_XZ 399 bool "XZ" 400 depends on HAVE_KERNEL_XZ 401 help 402 XZ uses the LZMA2 algorithm and instruction set specific 403 BCJ filters which can improve compression ratio of executable 404 code. The size of the kernel is about 30% smaller with XZ in 405 comparison to gzip. On architectures for which there is a BCJ 406 filter (i386, x86_64, ARM, ARM64, RISC-V, big endian PowerPC, 407 and SPARC), XZ will create a few percent smaller kernel than 408 plain LZMA. 409 410 The speed is about the same as with LZMA: The decompression 411 speed of XZ is better than that of bzip2 but worse than gzip 412 and LZO. Compression is slow. 413 414config KERNEL_LZO 415 bool "LZO" 416 depends on HAVE_KERNEL_LZO 417 help 418 Its compression ratio is the poorest among the choices. The kernel 419 size is about 10% bigger than gzip; however its speed 420 (both compression and decompression) is the fastest. 421 422config KERNEL_LZ4 423 bool "LZ4" 424 depends on HAVE_KERNEL_LZ4 425 help 426 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 427 A preliminary version of LZ4 de/compression tool is available at 428 <https://code.google.com/p/lz4/>. 429 430 Its compression ratio is worse than LZO. The size of the kernel 431 is about 8% bigger than LZO. But the decompression speed is 432 faster than LZO. 433 434config KERNEL_ZSTD 435 bool "ZSTD" 436 depends on HAVE_KERNEL_ZSTD 437 help 438 ZSTD is a compression algorithm targeting intermediate compression 439 with fast decompression speed. It will compress better than GZIP and 440 decompress around the same speed as LZO, but slower than LZ4. You 441 will need at least 192 KB RAM or more for booting. The zstd command 442 line tool is required for compression. 443 444config KERNEL_UNCOMPRESSED 445 bool "None" 446 depends on HAVE_KERNEL_UNCOMPRESSED 447 help 448 Produce uncompressed kernel image. This option is usually not what 449 you want. It is useful for debugging the kernel in slow simulation 450 environments, where decompressing and moving the kernel is awfully 451 slow. This option allows early boot code to skip the decompressor 452 and jump right at uncompressed kernel image. 453 454endchoice 455 456config DEFAULT_INIT 457 string "Default init path" 458 default "" 459 help 460 This option determines the default init for the system if no init= 461 option is passed on the kernel command line. If the requested path is 462 not present, we will still then move on to attempting further 463 locations (e.g. /sbin/init, etc). If this is empty, we will just use 464 the fallback list when init= is not passed. 465 466config DEFAULT_HOSTNAME 467 string "Default hostname" 468 default "(none)" 469 help 470 This option determines the default system hostname before userspace 471 calls sethostname(2). The kernel traditionally uses "(none)" here, 472 but you may wish to use a different default here to make a minimal 473 system more usable with less configuration. 474 475config SYSVIPC 476 bool "System V IPC" 477 help 478 Inter Process Communication is a suite of library functions and 479 system calls which let processes (running programs) synchronize and 480 exchange information. It is generally considered to be a good thing, 481 and some programs won't run unless you say Y here. In particular, if 482 you want to run the DOS emulator dosemu under Linux (read the 483 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 484 you'll need to say Y here. 485 486 You can find documentation about IPC with "info ipc" and also in 487 section 6.4 of the Linux Programmer's Guide, available from 488 <http://www.tldp.org/guides.html>. 489 490config SYSVIPC_SYSCTL 491 bool 492 depends on SYSVIPC 493 depends on SYSCTL 494 default y 495 496config SYSVIPC_COMPAT 497 def_bool y 498 depends on COMPAT && SYSVIPC 499 500config POSIX_MQUEUE 501 bool "POSIX Message Queues" 502 depends on NET 503 help 504 POSIX variant of message queues is a part of IPC. In POSIX message 505 queues every message has a priority which decides about succession 506 of receiving it by a process. If you want to compile and run 507 programs written e.g. for Solaris with use of its POSIX message 508 queues (functions mq_*) say Y here. 509 510 POSIX message queues are visible as a filesystem called 'mqueue' 511 and can be mounted somewhere if you want to do filesystem 512 operations on message queues. 513 514 If unsure, say Y. 515 516config POSIX_MQUEUE_SYSCTL 517 bool 518 depends on POSIX_MQUEUE 519 depends on SYSCTL 520 default y 521 522config WATCH_QUEUE 523 bool "General notification queue" 524 default n 525 help 526 527 This is a general notification queue for the kernel to pass events to 528 userspace by splicing them into pipes. It can be used in conjunction 529 with watches for key/keyring change notifications and device 530 notifications. 531 532 See Documentation/core-api/watch_queue.rst 533 534config CROSS_MEMORY_ATTACH 535 bool "Enable process_vm_readv/writev syscalls" 536 depends on MMU 537 default y 538 help 539 Enabling this option adds the system calls process_vm_readv and 540 process_vm_writev which allow a process with the correct privileges 541 to directly read from or write to another process' address space. 542 See the man page for more details. 543 544config AUDIT 545 bool "Auditing support" 546 depends on NET 547 help 548 Enable auditing infrastructure that can be used with another 549 kernel subsystem, such as SELinux (which requires this for 550 logging of avc messages output). System call auditing is included 551 on architectures which support it. 552 553config HAVE_ARCH_AUDITSYSCALL 554 bool 555 556config AUDITSYSCALL 557 def_bool y 558 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 559 select FSNOTIFY 560 561source "kernel/irq/Kconfig" 562source "kernel/time/Kconfig" 563source "kernel/bpf/Kconfig" 564source "kernel/Kconfig.preempt" 565 566menu "CPU/Task time and stats accounting" 567 568config VIRT_CPU_ACCOUNTING 569 bool 570 571choice 572 prompt "Cputime accounting" 573 default VIRT_CPU_ACCOUNTING_GEN if NO_HZ_FULL 574 default TICK_CPU_ACCOUNTING 575 576# Kind of a stub config for the pure tick based cputime accounting 577config TICK_CPU_ACCOUNTING 578 bool "Simple tick based cputime accounting" 579 depends on !S390 && !NO_HZ_FULL 580 help 581 This is the basic tick based cputime accounting that maintains 582 statistics about user, system and idle time spent on per jiffies 583 granularity. 584 585 If unsure, say Y. 586 587config VIRT_CPU_ACCOUNTING_NATIVE 588 bool "Deterministic task and CPU time accounting" 589 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 590 select VIRT_CPU_ACCOUNTING 591 help 592 Select this option to enable more accurate task and CPU time 593 accounting. This is done by reading a CPU counter on each 594 kernel entry and exit and on transitions within the kernel 595 between system, softirq and hardirq state, so there is a 596 small performance impact. In the case of s390 or IBM POWER > 5, 597 this also enables accounting of stolen time on logically-partitioned 598 systems. 599 600config VIRT_CPU_ACCOUNTING_GEN 601 bool "Full dynticks CPU time accounting" 602 depends on HAVE_CONTEXT_TRACKING_USER 603 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 604 depends on GENERIC_CLOCKEVENTS 605 select VIRT_CPU_ACCOUNTING 606 select CONTEXT_TRACKING_USER 607 help 608 Select this option to enable task and CPU time accounting on full 609 dynticks systems. This accounting is implemented by watching every 610 kernel-user boundaries using the context tracking subsystem. 611 The accounting is thus performed at the expense of some significant 612 overhead. 613 614 For now this is only useful if you are working on the full 615 dynticks subsystem development. 616 617 If unsure, say N. 618 619endchoice 620 621config IRQ_TIME_ACCOUNTING 622 bool "Fine granularity task level IRQ time accounting" 623 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 624 help 625 Select this option to enable fine granularity task irq time 626 accounting. This is done by reading a timestamp on each 627 transitions between softirq and hardirq state, so there can be a 628 small performance impact. 629 630 If in doubt, say N here. 631 632config HAVE_SCHED_AVG_IRQ 633 def_bool y 634 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 635 depends on SMP 636 637config SCHED_HW_PRESSURE 638 bool 639 default y if ARM && ARM_CPU_TOPOLOGY 640 default y if ARM64 641 depends on SMP 642 depends on CPU_FREQ_THERMAL 643 help 644 Select this option to enable HW pressure accounting in the 645 scheduler. HW pressure is the value conveyed to the scheduler 646 that reflects the reduction in CPU compute capacity resulted from 647 HW throttling. HW throttling occurs when the performance of 648 a CPU is capped due to high operating temperatures as an example. 649 650 If selected, the scheduler will be able to balance tasks accordingly, 651 i.e. put less load on throttled CPUs than on non/less throttled ones. 652 653 This requires the architecture to implement 654 arch_update_hw_pressure() and arch_scale_thermal_pressure(). 655 656config BSD_PROCESS_ACCT 657 bool "BSD Process Accounting (DEPRECATED)" 658 depends on MULTIUSER 659 default n 660 help 661 If you say Y here, a user level program will be able to instruct the 662 kernel (via a special system call) to write process accounting 663 information to a file: whenever a process exits, information about 664 that process will be appended to the file by the kernel. The 665 information includes things such as creation time, owning user, 666 command name, memory usage, controlling terminal etc. (the complete 667 list is in the struct acct in <file:include/linux/acct.h>). It is 668 up to the user level program to do useful things with this 669 information. This mechanism is antiquated and has significant 670 scalability issues. You probably want to use eBPF instead. Say 671 N unless you really need this. 672 673config BSD_PROCESS_ACCT_V3 674 bool "BSD Process Accounting version 3 file format" 675 depends on BSD_PROCESS_ACCT 676 default n 677 help 678 If you say Y here, the process accounting information is written 679 in a new file format that also logs the process IDs of each 680 process and its parent. Note that this file format is incompatible 681 with previous v0/v1/v2 file formats, so you will need updated tools 682 for processing it. A preliminary version of these tools is available 683 at <http://www.gnu.org/software/acct/>. 684 685config TASKSTATS 686 bool "Export task/process statistics through netlink" 687 depends on NET 688 depends on MULTIUSER 689 default n 690 help 691 Export selected statistics for tasks/processes through the 692 generic netlink interface. Unlike BSD process accounting, the 693 statistics are available during the lifetime of tasks/processes as 694 responses to commands. Like BSD accounting, they are sent to user 695 space on task exit. 696 697 Say N if unsure. 698 699config TASK_DELAY_ACCT 700 bool "Enable per-task delay accounting" 701 depends on TASKSTATS 702 select SCHED_INFO 703 help 704 Collect information on time spent by a task waiting for system 705 resources like cpu, synchronous block I/O completion and swapping 706 in pages. Such statistics can help in setting a task's priorities 707 relative to other tasks for cpu, io, rss limits etc. 708 709 Say N if unsure. 710 711config TASK_XACCT 712 bool "Enable extended accounting over taskstats" 713 depends on TASKSTATS 714 help 715 Collect extended task accounting data and send the data 716 to userland for processing over the taskstats interface. 717 718 Say N if unsure. 719 720config TASK_IO_ACCOUNTING 721 bool "Enable per-task storage I/O accounting" 722 depends on TASK_XACCT 723 help 724 Collect information on the number of bytes of storage I/O which this 725 task has caused. 726 727 Say N if unsure. 728 729config PSI 730 bool "Pressure stall information tracking" 731 select KERNFS 732 help 733 Collect metrics that indicate how overcommitted the CPU, memory, 734 and IO capacity are in the system. 735 736 If you say Y here, the kernel will create /proc/pressure/ with the 737 pressure statistics files cpu, memory, and io. These will indicate 738 the share of walltime in which some or all tasks in the system are 739 delayed due to contention of the respective resource. 740 741 In kernels with cgroup support, cgroups (cgroup2 only) will 742 have cpu.pressure, memory.pressure, and io.pressure files, 743 which aggregate pressure stalls for the grouped tasks only. 744 745 For more details see Documentation/accounting/psi.rst. 746 747 Say N if unsure. 748 749config PSI_DEFAULT_DISABLED 750 bool "Require boot parameter to enable pressure stall information tracking" 751 default n 752 depends on PSI 753 help 754 If set, pressure stall information tracking will be disabled 755 per default but can be enabled through passing psi=1 on the 756 kernel commandline during boot. 757 758 This feature adds some code to the task wakeup and sleep 759 paths of the scheduler. The overhead is too low to affect 760 common scheduling-intense workloads in practice (such as 761 webservers, memcache), but it does show up in artificial 762 scheduler stress tests, such as hackbench. 763 764 If you are paranoid and not sure what the kernel will be 765 used for, say Y. 766 767 Say N if unsure. 768 769endmenu # "CPU/Task time and stats accounting" 770 771config CPU_ISOLATION 772 bool "CPU isolation" 773 depends on SMP 774 default y 775 help 776 Make sure that CPUs running critical tasks are not disturbed by 777 any source of "noise" such as unbound workqueues, timers, kthreads... 778 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 779 the "isolcpus=" boot parameter. 780 781 Say Y if unsure. 782 783source "kernel/rcu/Kconfig" 784 785config IKCONFIG 786 tristate "Kernel .config support" 787 help 788 This option enables the complete Linux kernel ".config" file 789 contents to be saved in the kernel. It provides documentation 790 of which kernel options are used in a running kernel or in an 791 on-disk kernel. This information can be extracted from the kernel 792 image file with the script scripts/extract-ikconfig and used as 793 input to rebuild the current kernel or to build another kernel. 794 It can also be extracted from a running kernel by reading 795 /proc/config.gz if enabled (below). 796 797config IKCONFIG_PROC 798 bool "Enable access to .config through /proc/config.gz" 799 depends on IKCONFIG && PROC_FS 800 help 801 This option enables access to the kernel configuration file 802 through /proc/config.gz. 803 804config IKHEADERS 805 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 806 depends on SYSFS 807 help 808 This option enables access to the in-kernel headers that are generated during 809 the build process. These can be used to build eBPF tracing programs, 810 or similar programs. If you build the headers as a module, a module called 811 kheaders.ko is built which can be loaded on-demand to get access to headers. 812 813config LOG_BUF_SHIFT 814 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 815 range 12 25 816 default 17 817 depends on PRINTK 818 help 819 Select the minimal kernel log buffer size as a power of 2. 820 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 821 parameter, see below. Any higher size also might be forced 822 by "log_buf_len" boot parameter. 823 824 Examples: 825 17 => 128 KB 826 16 => 64 KB 827 15 => 32 KB 828 14 => 16 KB 829 13 => 8 KB 830 12 => 4 KB 831 832config LOG_CPU_MAX_BUF_SHIFT 833 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 834 depends on SMP 835 range 0 21 836 default 0 if BASE_SMALL 837 default 12 838 depends on PRINTK 839 help 840 This option allows to increase the default ring buffer size 841 according to the number of CPUs. The value defines the contribution 842 of each CPU as a power of 2. The used space is typically only few 843 lines however it might be much more when problems are reported, 844 e.g. backtraces. 845 846 The increased size means that a new buffer has to be allocated and 847 the original static one is unused. It makes sense only on systems 848 with more CPUs. Therefore this value is used only when the sum of 849 contributions is greater than the half of the default kernel ring 850 buffer as defined by LOG_BUF_SHIFT. The default values are set 851 so that more than 16 CPUs are needed to trigger the allocation. 852 853 Also this option is ignored when "log_buf_len" kernel parameter is 854 used as it forces an exact (power of two) size of the ring buffer. 855 856 The number of possible CPUs is used for this computation ignoring 857 hotplugging making the computation optimal for the worst case 858 scenario while allowing a simple algorithm to be used from bootup. 859 860 Examples shift values and their meaning: 861 17 => 128 KB for each CPU 862 16 => 64 KB for each CPU 863 15 => 32 KB for each CPU 864 14 => 16 KB for each CPU 865 13 => 8 KB for each CPU 866 12 => 4 KB for each CPU 867 868config PRINTK_INDEX 869 bool "Printk indexing debugfs interface" 870 depends on PRINTK && DEBUG_FS 871 help 872 Add support for indexing of all printk formats known at compile time 873 at <debugfs>/printk/index/<module>. 874 875 This can be used as part of maintaining daemons which monitor 876 /dev/kmsg, as it permits auditing the printk formats present in a 877 kernel, allowing detection of cases where monitored printks are 878 changed or no longer present. 879 880 There is no additional runtime cost to printk with this enabled. 881 882# 883# Architectures with an unreliable sched_clock() should select this: 884# 885config HAVE_UNSTABLE_SCHED_CLOCK 886 bool 887 888config GENERIC_SCHED_CLOCK 889 bool 890 891menu "Scheduler features" 892 893config UCLAMP_TASK 894 bool "Enable utilization clamping for RT/FAIR tasks" 895 depends on CPU_FREQ_GOV_SCHEDUTIL 896 help 897 This feature enables the scheduler to track the clamped utilization 898 of each CPU based on RUNNABLE tasks scheduled on that CPU. 899 900 With this option, the user can specify the min and max CPU 901 utilization allowed for RUNNABLE tasks. The max utilization defines 902 the maximum frequency a task should use while the min utilization 903 defines the minimum frequency it should use. 904 905 Both min and max utilization clamp values are hints to the scheduler, 906 aiming at improving its frequency selection policy, but they do not 907 enforce or grant any specific bandwidth for tasks. 908 909 If in doubt, say N. 910 911config UCLAMP_BUCKETS_COUNT 912 int "Number of supported utilization clamp buckets" 913 range 5 20 914 default 5 915 depends on UCLAMP_TASK 916 help 917 Defines the number of clamp buckets to use. The range of each bucket 918 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 919 number of clamp buckets the finer their granularity and the higher 920 the precision of clamping aggregation and tracking at run-time. 921 922 For example, with the minimum configuration value we will have 5 923 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 924 be refcounted in the [20..39]% bucket and will set the bucket clamp 925 effective value to 25%. 926 If a second 30% boosted task should be co-scheduled on the same CPU, 927 that task will be refcounted in the same bucket of the first task and 928 it will boost the bucket clamp effective value to 30%. 929 The clamp effective value of a bucket is reset to its nominal value 930 (20% in the example above) when there are no more tasks refcounted in 931 that bucket. 932 933 An additional boost/capping margin can be added to some tasks. In the 934 example above the 25% task will be boosted to 30% until it exits the 935 CPU. If that should be considered not acceptable on certain systems, 936 it's always possible to reduce the margin by increasing the number of 937 clamp buckets to trade off used memory for run-time tracking 938 precision. 939 940 If in doubt, use the default value. 941 942config SCHED_PROXY_EXEC 943 bool "Proxy Execution" 944 # Avoid some build failures w/ PREEMPT_RT until it can be fixed 945 depends on !PREEMPT_RT 946 # Need to investigate how to inform sched_ext of split contexts 947 depends on !SCHED_CLASS_EXT 948 # Not particularly useful until we get to multi-rq proxying 949 depends on EXPERT 950 help 951 This option enables proxy execution, a mechanism for mutex-owning 952 tasks to inherit the scheduling context of higher priority waiters. 953 954endmenu 955 956# 957# For architectures that support present-but-inaccessible (PROT_NONE) page 958# table entries detectable via pte_protnone() / pmd_protnone(): 959# 960config ARCH_HAS_PTE_PROTNONE 961 bool 962 963# 964# For architectures that want to enable the support for NUMA-affine scheduler 965# balancing logic: 966# 967config ARCH_SUPPORTS_NUMA_BALANCING 968 bool 969 970# 971# For architectures that prefer to flush all TLBs after a number of pages 972# are unmapped instead of sending one IPI per page to flush. The architecture 973# must provide guarantees on what happens if a clean TLB cache entry is 974# written after the unmap. Details are in mm/rmap.c near the check for 975# should_defer_flush. The architecture should also consider if the full flush 976# and the refill costs are offset by the savings of sending fewer IPIs. 977config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 978 bool 979 980config CC_HAS_INT128 981 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 982 983config CC_IMPLICIT_FALLTHROUGH 984 string 985 default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5) 986 default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough) 987 988config CC_MS_EXTENSIONS 989 string 990 default "-fms-anonymous-structs" if $(cc-option,-fms-anonymous-structs) 991 default "-fms-extensions" 992 993# Currently, disable gcc-10+ array-bounds globally. 994# It's still broken in gcc-13, so no upper bound yet. 995config GCC10_NO_ARRAY_BOUNDS 996 def_bool y 997 998config CC_NO_ARRAY_BOUNDS 999 bool 1000 default y if CC_IS_GCC && GCC_VERSION >= 90000 && GCC10_NO_ARRAY_BOUNDS 1001 1002# Currently, disable -Wstringop-overflow for GCC globally. 1003config GCC_NO_STRINGOP_OVERFLOW 1004 def_bool y 1005 1006config CC_NO_STRINGOP_OVERFLOW 1007 bool 1008 default y if CC_IS_GCC && GCC_NO_STRINGOP_OVERFLOW 1009 1010config CC_STRINGOP_OVERFLOW 1011 bool 1012 default y if CC_IS_GCC && !CC_NO_STRINGOP_OVERFLOW 1013 1014# 1015# For architectures that know their GCC __int128 support is sound 1016# 1017config ARCH_SUPPORTS_INT128 1018 bool 1019 1020# For architectures that (ab)use NUMA to represent different memory regions 1021# all cpu-local but of different latencies, such as SuperH. 1022# 1023config ARCH_WANT_NUMA_VARIABLE_LOCALITY 1024 bool 1025 1026config NUMA_BALANCING 1027 bool "Memory placement aware NUMA scheduler" 1028 depends on ARCH_SUPPORTS_NUMA_BALANCING 1029 depends on ARCH_HAS_PTE_PROTNONE 1030 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 1031 depends on SMP && NUMA_MIGRATION && !PREEMPT_RT 1032 help 1033 This option adds support for automatic NUMA aware memory/task placement. 1034 The mechanism is quite primitive and is based on migrating memory when 1035 it has references to the node the task is running on. 1036 1037 This system will be inactive on UMA systems. 1038 1039config SCHED_CACHE 1040 bool "Cache aware load balance" 1041 default y 1042 depends on SMP 1043 help 1044 When enabled, the scheduler will attempt to aggregate tasks from 1045 the same process onto a single Last Level Cache (LLC) domain when 1046 possible. This improves cache locality by keeping tasks that share 1047 resources within the same cache domain, reducing cache misses and 1048 lowering data access latency. 1049 1050config NUMA_BALANCING_DEFAULT_ENABLED 1051 bool "Automatically enable NUMA aware memory/task placement" 1052 default y 1053 depends on NUMA_BALANCING 1054 help 1055 If set, automatic NUMA balancing will be enabled if running on a NUMA 1056 machine. 1057 1058config SLAB_OBJ_EXT 1059 bool 1060 1061menuconfig CGROUPS 1062 bool "Control Group support" 1063 select KERNFS 1064 help 1065 This option adds support for grouping sets of processes together, for 1066 use with process control subsystems such as Cpusets, CFS, memory 1067 controls or device isolation. 1068 See 1069 - Documentation/scheduler/sched-design-CFS.rst (CFS) 1070 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 1071 and resource control) 1072 1073 Say N if unsure. 1074 1075if CGROUPS 1076 1077config PAGE_COUNTER 1078 bool 1079 1080config CGROUP_FAVOR_DYNMODS 1081 bool "Favor dynamic modification latency reduction by default" 1082 help 1083 This option enables the "favordynmods" mount option by default 1084 which reduces the latencies of dynamic cgroup modifications such 1085 as task migrations and controller on/offs at the cost of making 1086 hot path operations such as forks and exits more expensive. 1087 1088 Say N if unsure. 1089 1090config MEMCG 1091 bool "Memory controller" 1092 select PAGE_COUNTER 1093 select EVENTFD 1094 select SLAB_OBJ_EXT 1095 select VM_EVENT_COUNTERS 1096 help 1097 Provides control over the memory footprint of tasks in a cgroup. 1098 1099config MEMCG_NMI_UNSAFE 1100 bool 1101 depends on MEMCG 1102 depends on HAVE_NMI 1103 depends on !ARCH_HAS_NMI_SAFE_THIS_CPU_OPS && !ARCH_HAVE_NMI_SAFE_CMPXCHG 1104 default y 1105 1106config MEMCG_NMI_SAFETY_REQUIRES_ATOMIC 1107 bool 1108 depends on MEMCG 1109 depends on HAVE_NMI 1110 depends on !ARCH_HAS_NMI_SAFE_THIS_CPU_OPS && ARCH_HAVE_NMI_SAFE_CMPXCHG 1111 default y 1112 1113config MEMCG_V1 1114 bool "Legacy cgroup v1 memory controller" 1115 depends on MEMCG 1116 default n 1117 help 1118 Legacy cgroup v1 memory controller which has been deprecated by 1119 cgroup v2 implementation. The v1 is there for legacy applications 1120 which haven't migrated to the new cgroup v2 interface yet. If you 1121 do not have any such application then you are completely fine leaving 1122 this option disabled. 1123 1124 Please note that feature set of the legacy memory controller is likely 1125 going to shrink due to deprecation process. New deployments with v1 1126 controller are highly discouraged. 1127 1128 Say N if unsure. 1129 1130config BLK_CGROUP 1131 bool "IO controller" 1132 depends on BLOCK 1133 default n 1134 help 1135 Generic block IO controller cgroup interface. This is the common 1136 cgroup interface which should be used by various IO controlling 1137 policies. 1138 1139 Currently, CFQ IO scheduler uses it to recognize task groups and 1140 control disk bandwidth allocation (proportional time slice allocation) 1141 to such task groups. It is also used by bio throttling logic in 1142 block layer to implement upper limit in IO rates on a device. 1143 1144 This option only enables generic Block IO controller infrastructure. 1145 One needs to also enable actual IO controlling logic/policy. For 1146 enabling proportional weight division of disk bandwidth in CFQ, set 1147 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 1148 CONFIG_BLK_DEV_THROTTLING=y. 1149 1150 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 1151 1152config CGROUP_WRITEBACK 1153 bool 1154 depends on MEMCG && BLK_CGROUP 1155 default y 1156 1157menuconfig CGROUP_SCHED 1158 bool "CPU controller" 1159 default n 1160 help 1161 This feature lets CPU scheduler recognize task groups and control CPU 1162 bandwidth allocation to such task groups. It uses cgroups to group 1163 tasks. 1164 1165if CGROUP_SCHED 1166config GROUP_SCHED_WEIGHT 1167 def_bool n 1168 1169config GROUP_SCHED_BANDWIDTH 1170 def_bool n 1171 1172config FAIR_GROUP_SCHED 1173 bool "Group scheduling for SCHED_OTHER" 1174 depends on CGROUP_SCHED 1175 select GROUP_SCHED_WEIGHT 1176 default CGROUP_SCHED 1177 1178config CFS_BANDWIDTH 1179 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 1180 depends on FAIR_GROUP_SCHED 1181 select GROUP_SCHED_BANDWIDTH 1182 default n 1183 help 1184 This option allows users to define CPU bandwidth rates (limits) for 1185 tasks running within the fair group scheduler. Groups with no limit 1186 set are considered to be unconstrained and will run with no 1187 restriction. 1188 See Documentation/scheduler/sched-bwc.rst for more information. 1189 1190config RT_GROUP_SCHED 1191 bool "Group scheduling for SCHED_RR/FIFO" 1192 depends on CGROUP_SCHED 1193 default n 1194 help 1195 This feature lets you explicitly allocate real CPU bandwidth 1196 to task groups. If enabled, it will also make it impossible to 1197 schedule realtime tasks for non-root users until you allocate 1198 realtime bandwidth for them. 1199 See Documentation/scheduler/sched-rt-group.rst for more information. 1200 1201config RT_GROUP_SCHED_DEFAULT_DISABLED 1202 bool "Require boot parameter to enable group scheduling for SCHED_RR/FIFO" 1203 depends on RT_GROUP_SCHED 1204 default n 1205 help 1206 When set, the RT group scheduling is disabled by default. The option 1207 is in inverted form so that mere RT_GROUP_SCHED enables the group 1208 scheduling. 1209 1210 Say N if unsure. 1211 1212config EXT_GROUP_SCHED 1213 bool 1214 depends on SCHED_CLASS_EXT && CGROUP_SCHED 1215 select GROUP_SCHED_WEIGHT 1216 select GROUP_SCHED_BANDWIDTH 1217 default y 1218 1219endif #CGROUP_SCHED 1220 1221config EXT_SUB_SCHED 1222 def_bool y 1223 depends on SCHED_CLASS_EXT && CGROUPS 1224 1225config SCHED_MM_CID 1226 def_bool y 1227 depends on SMP && RSEQ 1228 1229config UCLAMP_TASK_GROUP 1230 bool "Utilization clamping per group of tasks" 1231 depends on CGROUP_SCHED 1232 depends on UCLAMP_TASK 1233 default n 1234 help 1235 This feature enables the scheduler to track the clamped utilization 1236 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 1237 1238 When this option is enabled, the user can specify a min and max 1239 CPU bandwidth which is allowed for each single task in a group. 1240 The max bandwidth allows to clamp the maximum frequency a task 1241 can use, while the min bandwidth allows to define a minimum 1242 frequency a task will always use. 1243 1244 When task group based utilization clamping is enabled, an eventually 1245 specified task-specific clamp value is constrained by the cgroup 1246 specified clamp value. Both minimum and maximum task clamping cannot 1247 be bigger than the corresponding clamping defined at task group level. 1248 1249 If in doubt, say N. 1250 1251config CGROUP_PIDS 1252 bool "PIDs controller" 1253 help 1254 Provides enforcement of process number limits in the scope of a 1255 cgroup. Any attempt to fork more processes than is allowed in the 1256 cgroup will fail. PIDs are fundamentally a global resource because it 1257 is fairly trivial to reach PID exhaustion before you reach even a 1258 conservative kmemcg limit. As a result, it is possible to grind a 1259 system to halt without being limited by other cgroup policies. The 1260 PIDs controller is designed to stop this from happening. 1261 1262 It should be noted that organisational operations (such as attaching 1263 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 1264 since the PIDs limit only affects a process's ability to fork, not to 1265 attach to a cgroup. 1266 1267config CGROUP_RDMA 1268 bool "RDMA controller" 1269 help 1270 Provides enforcement of RDMA resources defined by IB stack. 1271 It is fairly easy for consumers to exhaust RDMA resources, which 1272 can result into resource unavailability to other consumers. 1273 RDMA controller is designed to stop this from happening. 1274 Attaching processes with active RDMA resources to the cgroup 1275 hierarchy is allowed even if can cross the hierarchy's limit. 1276 1277config CGROUP_DMEM 1278 bool "Device memory controller (DMEM)" 1279 select PAGE_COUNTER 1280 help 1281 The DMEM controller allows compatible devices to restrict device 1282 memory usage based on the cgroup hierarchy. 1283 1284 As an example, it allows you to restrict VRAM usage for applications 1285 in the DRM subsystem. 1286 1287config CGROUP_FREEZER 1288 bool "Freezer controller" 1289 help 1290 Provides a way to freeze and unfreeze all tasks in a 1291 cgroup. 1292 1293 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1294 controller includes important in-kernel memory consumers per default. 1295 1296 If you're using cgroup2, say N. 1297 1298config CGROUP_HUGETLB 1299 bool "HugeTLB controller" 1300 depends on HUGETLB_PAGE 1301 select PAGE_COUNTER 1302 default n 1303 help 1304 Provides a cgroup controller for HugeTLB pages. 1305 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1306 The limit is enforced during page fault. Since HugeTLB doesn't 1307 support page reclaim, enforcing the limit at page fault time implies 1308 that, the application will get SIGBUS signal if it tries to access 1309 HugeTLB pages beyond its limit. This requires the application to know 1310 beforehand how much HugeTLB pages it would require for its use. The 1311 control group is tracked in the third page lru pointer. This means 1312 that we cannot use the controller with huge page less than 3 pages. 1313 1314config CPUSETS 1315 bool "Cpuset controller" 1316 depends on SMP 1317 select UNION_FIND 1318 select CPU_ISOLATION 1319 help 1320 This option will let you create and manage CPUSETs which 1321 allow dynamically partitioning a system into sets of CPUs and 1322 Memory Nodes and assigning tasks to run only within those sets. 1323 This is primarily useful on large SMP or NUMA systems. 1324 1325 Say N if unsure. 1326 1327config CPUSETS_V1 1328 bool "Legacy cgroup v1 cpusets controller" 1329 depends on CPUSETS 1330 default n 1331 help 1332 Legacy cgroup v1 cpusets controller which has been deprecated by 1333 cgroup v2 implementation. The v1 is there for legacy applications 1334 which haven't migrated to the new cgroup v2 interface yet. Legacy 1335 interface includes cpuset filesystem and /proc/<pid>/cpuset. If you 1336 do not have any such application then you are completely fine leaving 1337 this option disabled. 1338 1339 Say N if unsure. 1340 1341config PROC_PID_CPUSET 1342 bool "Include legacy /proc/<pid>/cpuset file" 1343 depends on CPUSETS_V1 1344 default y 1345 1346config CGROUP_DEVICE 1347 bool "Device controller" 1348 help 1349 Provides a cgroup controller implementing whitelists for 1350 devices which a process in the cgroup can mknod or open. 1351 1352config CGROUP_CPUACCT 1353 bool "Simple CPU accounting controller" 1354 help 1355 Provides a simple controller for monitoring the 1356 total CPU consumed by the tasks in a cgroup. 1357 1358config CGROUP_PERF 1359 bool "Perf controller" 1360 depends on PERF_EVENTS 1361 help 1362 This option extends the perf per-cpu mode to restrict monitoring 1363 to threads which belong to the cgroup specified and run on the 1364 designated cpu. Or this can be used to have cgroup ID in samples 1365 so that it can monitor performance events among cgroups. 1366 1367 Say N if unsure. 1368 1369config CGROUP_BPF 1370 bool "Support for eBPF programs attached to cgroups" 1371 depends on BPF_SYSCALL 1372 select SOCK_CGROUP_DATA 1373 help 1374 Allow attaching eBPF programs to a cgroup using the bpf(2) 1375 syscall command BPF_PROG_ATTACH. 1376 1377 In which context these programs are accessed depends on the type 1378 of attachment. For instance, programs that are attached using 1379 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1380 inet sockets. 1381 1382config CGROUP_MISC 1383 bool "Misc resource controller" 1384 default n 1385 help 1386 Provides a controller for miscellaneous resources on a host. 1387 1388 Miscellaneous scalar resources are the resources on the host system 1389 which cannot be abstracted like the other cgroups. This controller 1390 tracks and limits the miscellaneous resources used by a process 1391 attached to a cgroup hierarchy. 1392 1393 For more information, please check misc cgroup section in 1394 /Documentation/admin-guide/cgroup-v2.rst. 1395 1396config CGROUP_DEBUG 1397 bool "Debug controller" 1398 default n 1399 depends on DEBUG_KERNEL 1400 help 1401 This option enables a simple controller that exports 1402 debugging information about the cgroups framework. This 1403 controller is for control cgroup debugging only. Its 1404 interfaces are not stable. 1405 1406 Say N. 1407 1408config SOCK_CGROUP_DATA 1409 bool 1410 default n 1411 1412endif # CGROUPS 1413 1414menuconfig NAMESPACES 1415 bool "Namespaces support" if EXPERT 1416 depends on MULTIUSER 1417 default !EXPERT 1418 help 1419 Provides the way to make tasks work with different objects using 1420 the same id. For example same IPC id may refer to different objects 1421 or same user id or pid may refer to different tasks when used in 1422 different namespaces. 1423 1424if NAMESPACES 1425 1426config UTS_NS 1427 bool "UTS namespace" 1428 default y 1429 help 1430 In this namespace tasks see different info provided with the 1431 uname() system call 1432 1433config TIME_NS 1434 bool "TIME namespace" 1435 default y 1436 help 1437 In this namespace boottime and monotonic clocks can be set. 1438 The time will keep going with the same pace. 1439 1440config TIME_NS_VDSO 1441 def_bool TIME_NS && GENERIC_GETTIMEOFDAY 1442 1443config IPC_NS 1444 bool "IPC namespace" 1445 depends on (SYSVIPC || POSIX_MQUEUE) 1446 default y 1447 help 1448 In this namespace tasks work with IPC ids which correspond to 1449 different IPC objects in different namespaces. 1450 1451config USER_NS 1452 bool "User namespace" 1453 default n 1454 help 1455 This allows containers, i.e. vservers, to use user namespaces 1456 to provide different user info for different servers. 1457 1458 When user namespaces are enabled in the kernel it is 1459 recommended that the MEMCG option also be enabled and that 1460 user-space use the memory control groups to limit the amount 1461 of memory a memory unprivileged users can use. 1462 1463 If unsure, say N. 1464 1465config PID_NS 1466 bool "PID Namespaces" 1467 default y 1468 help 1469 Support process id namespaces. This allows having multiple 1470 processes with the same pid as long as they are in different 1471 pid namespaces. This is a building block of containers. 1472 1473config NET_NS 1474 bool "Network namespace" 1475 depends on NET 1476 default y 1477 help 1478 Allow user space to create what appear to be multiple instances 1479 of the network stack. 1480 1481endif # NAMESPACES 1482 1483config CHECKPOINT_RESTORE 1484 bool "Checkpoint/restore support" 1485 depends on PROC_FS 1486 select PROC_CHILDREN 1487 select KCMP 1488 default n 1489 help 1490 Enables additional kernel features in a sake of checkpoint/restore. 1491 In particular it adds auxiliary prctl codes to setup process text, 1492 data and heap segment sizes, and a few additional /proc filesystem 1493 entries. 1494 1495 If unsure, say N here. 1496 1497config SCHED_AUTOGROUP 1498 bool "Automatic process group scheduling" 1499 select CGROUPS 1500 select CGROUP_SCHED 1501 select FAIR_GROUP_SCHED 1502 help 1503 This option optimizes the scheduler for common desktop workloads by 1504 automatically creating and populating task groups. This separation 1505 of workloads isolates aggressive CPU burners (like build jobs) from 1506 desktop applications. Task group autogeneration is currently based 1507 upon task session. 1508 1509config RELAY 1510 bool "Kernel->user space relay support (formerly relayfs)" 1511 select IRQ_WORK 1512 help 1513 This option enables support for relay interface support in 1514 certain file systems (such as debugfs). 1515 It is designed to provide an efficient mechanism for tools and 1516 facilities to relay large amounts of data from kernel space to 1517 user space. 1518 1519 If unsure, say N. 1520 1521config BLK_DEV_INITRD 1522 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1523 help 1524 The initial RAM filesystem is a ramfs which is loaded by the 1525 boot loader (loadlin or lilo) and that is mounted as root 1526 before the normal boot procedure. It is typically used to 1527 load modules needed to mount the "real" root file system, 1528 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1529 1530 If RAM disk support (BLK_DEV_RAM) is also included, this 1531 also enables initial RAM disk (initrd) support and adds 1532 15 Kbytes (more on some other architectures) to the kernel size. 1533 1534 If unsure say Y. 1535 1536if BLK_DEV_INITRD 1537 1538source "usr/Kconfig" 1539 1540endif 1541 1542config BOOT_CONFIG 1543 bool "Boot config support" 1544 select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED 1545 help 1546 Extra boot config allows system admin to pass a config file as 1547 complemental extension of kernel cmdline when booting. 1548 The boot config file must be attached at the end of initramfs 1549 with checksum, size and magic word. 1550 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1551 1552 If unsure, say Y. 1553 1554config BOOT_CONFIG_FORCE 1555 bool "Force unconditional bootconfig processing" 1556 depends on BOOT_CONFIG 1557 default y if BOOT_CONFIG_EMBED 1558 help 1559 With this Kconfig option set, BOOT_CONFIG processing is carried 1560 out even when the "bootconfig" kernel-boot parameter is omitted. 1561 In fact, with this Kconfig option set, there is no way to 1562 make the kernel ignore the BOOT_CONFIG-supplied kernel-boot 1563 parameters. 1564 1565 If unsure, say N. 1566 1567config BOOT_CONFIG_EMBED 1568 bool "Embed bootconfig file in the kernel" 1569 depends on BOOT_CONFIG 1570 help 1571 Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the 1572 kernel. Usually, the bootconfig file is loaded with the initrd 1573 image. But if the system doesn't support initrd, this option will 1574 help you by embedding a bootconfig file while building the kernel. 1575 1576 If unsure, say N. 1577 1578config BOOT_CONFIG_EMBED_FILE 1579 string "Embedded bootconfig file path" 1580 depends on BOOT_CONFIG_EMBED 1581 help 1582 Specify a bootconfig file which will be embedded to the kernel. 1583 This bootconfig will be used if there is no initrd or no other 1584 bootconfig in the initrd. 1585 1586config ARCH_SUPPORTS_CMDLINE_FROM_BOOTCONFIG 1587 bool 1588 help 1589 Silent symbol; no C code reads it directly. Architectures 1590 select it once their setup_arch() calls 1591 xbc_prepend_embedded_cmdline() before parse_early_param(). 1592 Its only role is to gate the user-visible 1593 CMDLINE_FROM_BOOTCONFIG option per-arch, the same 1594 ARCH_SUPPORTS_* idiom used by ARCH_SUPPORTS_CFI, etc. 1595 1596config CMDLINE_FROM_BOOTCONFIG 1597 bool "Render embedded bootconfig as kernel cmdline at build time" 1598 depends on BOOT_CONFIG_EMBED_FILE != "" 1599 depends on ARCH_SUPPORTS_CMDLINE_FROM_BOOTCONFIG 1600 depends on CMDLINE = "" 1601 default n 1602 help 1603 Render the "kernel" subtree of the embedded bootconfig file into a 1604 flat cmdline string at kernel build time and prepend it to 1605 boot_command_line during early architecture setup. This makes 1606 early_param() handlers (e.g. mem=, earlycon=, loglevel=) see the 1607 values supplied via the embedded bootconfig. 1608 1609 The runtime bootconfig parser is unaffected, so tree-structured 1610 consumers such as ftrace boot-time tracing keep working. 1611 1612 Note: when an initrd also carries a bootconfig, its "kernel" 1613 subtree is still parsed at runtime, but the embedded "kernel" 1614 keys remain in boot_command_line for parse_early_param() and 1615 end up later than the initrd keys in saved_command_line, so 1616 parse_args() last-wins favors the embedded values. If you need 1617 initrd to override embedded kernel.* keys, leave this option 1618 off. 1619 1620 If unsure, say N. 1621 1622config CMDLINE_LOG_WRAP_IDEAL_LEN 1623 int "Length to try to wrap the cmdline when logged at boot" 1624 default 1021 1625 range 0 1021 1626 help 1627 At boot time, the kernel command line is logged to the console. 1628 The log message will start with the prefix "Kernel command line: ". 1629 The log message will attempt to be wrapped (split into multiple log 1630 messages) at spaces based on CMDLINE_LOG_WRAP_IDEAL_LEN characters. 1631 If wrapping happens, each log message will start with the prefix and 1632 all but the last message will end with " \". Messages may exceed the 1633 ideal length if a place to wrap isn't found before the specified 1634 number of characters. 1635 1636 A value of 0 disables wrapping, though be warned that the maximum 1637 length of a log message (1021 characters) may cause the cmdline to 1638 be truncated. 1639 1640config INITRAMFS_PRESERVE_MTIME 1641 bool "Preserve cpio archive mtimes in initramfs" 1642 depends on BLK_DEV_INITRD 1643 default y 1644 help 1645 Each entry in an initramfs cpio archive carries an mtime value. When 1646 enabled, extracted cpio items take this mtime, with directory mtime 1647 setting deferred until after creation of any child entries. 1648 1649 If unsure, say Y. 1650 1651config INITRAMFS_TEST 1652 bool "Test initramfs cpio archive extraction" if !KUNIT_ALL_TESTS 1653 depends on BLK_DEV_INITRD && KUNIT=y 1654 default KUNIT_ALL_TESTS 1655 help 1656 Build KUnit tests for initramfs. See Documentation/dev-tools/kunit 1657 1658choice 1659 prompt "Compiler optimization level" 1660 default CC_OPTIMIZE_FOR_PERFORMANCE 1661 1662config CC_OPTIMIZE_FOR_PERFORMANCE 1663 bool "Optimize for performance (-O2)" 1664 help 1665 This is the default optimization level for the kernel, building 1666 with the "-O2" compiler flag for best performance and most 1667 helpful compile-time warnings. 1668 1669config CC_OPTIMIZE_FOR_SIZE 1670 bool "Optimize for size (-Os)" 1671 help 1672 Choosing this option will pass "-Os" to your compiler resulting 1673 in a smaller kernel. 1674 1675endchoice 1676 1677config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1678 bool 1679 help 1680 This requires that the arch annotates or otherwise protects 1681 its external entry points from being discarded. Linker scripts 1682 must also merge .text.*, .data.*, and .bss.* correctly into 1683 output sections. Care must be taken not to pull in unrelated 1684 sections (e.g., '.text.init'). Typically '.' in section names 1685 is used to distinguish them from label names / C identifiers. 1686 1687config LD_DEAD_CODE_DATA_ELIMINATION 1688 bool "Dead code and data elimination (EXPERIMENTAL)" 1689 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1690 depends on EXPERT 1691 depends on $(cc-option,-ffunction-sections -fdata-sections) 1692 depends on $(ld-option,--gc-sections) 1693 help 1694 Enable this if you want to do dead code and data elimination with 1695 the linker by compiling with -ffunction-sections -fdata-sections, 1696 and linking with --gc-sections. 1697 1698 This can reduce on disk and in-memory size of the kernel 1699 code and static data, particularly for small configs and 1700 on small systems. This has the possibility of introducing 1701 silently broken kernel if the required annotations are not 1702 present. This option is not well tested yet, so use at your 1703 own risk. 1704 1705config LD_ORPHAN_WARN 1706 def_bool y 1707 depends on ARCH_WANT_LD_ORPHAN_WARN 1708 depends on $(ld-option,--orphan-handling=warn) 1709 depends on $(ld-option,--orphan-handling=error) 1710 1711config LD_ORPHAN_WARN_LEVEL 1712 string 1713 depends on LD_ORPHAN_WARN 1714 default "error" if WERROR 1715 default "warn" 1716 1717config HAVE_UID16 1718 bool 1719 1720config SYSCTL_EXCEPTION_TRACE 1721 bool 1722 help 1723 Enable support for /proc/sys/debug/exception-trace. 1724 1725config SYSCTL_ARCH_UNALIGN_NO_WARN 1726 bool 1727 help 1728 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1729 Allows arch to define/use @no_unaligned_warning to possibly warn 1730 about unaligned access emulation going on under the hood. 1731 1732config SYSCTL_ARCH_UNALIGN_ALLOW 1733 bool 1734 help 1735 Enable support for /proc/sys/kernel/unaligned-trap 1736 Allows arches to define/use @unaligned_enabled to runtime toggle 1737 the unaligned access emulation. 1738 see arch/parisc/kernel/unaligned.c for reference 1739 1740config SYSFS_SYSCALL 1741 bool "Sysfs syscall support" 1742 default n 1743 help 1744 sys_sysfs is an obsolete system call no longer supported in libc. 1745 Note that disabling this option is more secure but might break 1746 compatibility with some systems. 1747 1748 If unsure say N here. 1749 1750config HAVE_PCSPKR_PLATFORM 1751 bool 1752 1753menuconfig EXPERT 1754 bool "Configure standard kernel features (expert users)" 1755 # Unhide debug options, to make the on-by-default options visible 1756 select DEBUG_KERNEL 1757 help 1758 This option allows certain base kernel options and settings 1759 to be disabled or tweaked. This is for specialized 1760 environments which can tolerate a "non-standard" kernel. 1761 Only use this if you really know what you are doing. 1762 1763config UID16 1764 bool "Enable 16-bit UID system calls" if EXPERT 1765 depends on HAVE_UID16 && MULTIUSER 1766 default y 1767 help 1768 This enables the legacy 16-bit UID syscall wrappers. 1769 1770config MULTIUSER 1771 bool "Multiple users, groups and capabilities support" if EXPERT 1772 default y 1773 help 1774 This option enables support for non-root users, groups and 1775 capabilities. 1776 1777 If you say N here, all processes will run with UID 0, GID 0, and all 1778 possible capabilities. Saying N here also compiles out support for 1779 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1780 setgid, and capset. 1781 1782 If unsure, say Y here. 1783 1784config SGETMASK_SYSCALL 1785 bool "sgetmask/ssetmask syscalls support" if EXPERT 1786 default PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1787 help 1788 sys_sgetmask and sys_ssetmask are obsolete system calls 1789 no longer supported in libc but still enabled by default in some 1790 architectures. 1791 1792 If unsure, leave the default option here. 1793 1794config FHANDLE 1795 bool "open by fhandle syscalls" if EXPERT 1796 select EXPORTFS 1797 default y 1798 help 1799 If you say Y here, a user level program will be able to map 1800 file names to handle and then later use the handle for 1801 different file system operations. This is useful in implementing 1802 userspace file servers, which now track files using handles instead 1803 of names. The handle would remain the same even if file names 1804 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1805 syscalls. 1806 1807config POSIX_TIMERS 1808 bool "Posix Clocks & timers" if EXPERT 1809 default y 1810 help 1811 This includes native support for POSIX timers to the kernel. 1812 Some embedded systems have no use for them and therefore they 1813 can be configured out to reduce the size of the kernel image. 1814 1815 When this option is disabled, the following syscalls won't be 1816 available: timer_create, timer_gettime: timer_getoverrun, 1817 timer_settime, timer_delete, clock_adjtime, getitimer, 1818 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1819 clock_getres and clock_nanosleep syscalls will be limited to 1820 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1821 1822 If unsure say y. 1823 1824config PRINTK 1825 default y 1826 bool "Enable support for printk" if EXPERT 1827 select IRQ_WORK 1828 help 1829 This option enables normal printk support. Removing it 1830 eliminates most of the message strings from the kernel image 1831 and makes the kernel more or less silent. As this makes it 1832 very difficult to diagnose system problems, saying N here is 1833 strongly discouraged. 1834 1835config PRINTK_RINGBUFFER_KUNIT_TEST 1836 tristate "KUnit Test for the printk ringbuffer" if !KUNIT_ALL_TESTS 1837 depends on PRINTK && KUNIT 1838 default KUNIT_ALL_TESTS 1839 help 1840 This builds the printk ringbuffer KUnit test suite. 1841 1842 For more information on KUnit and unit tests in general, please refer 1843 to the KUnit documentation. 1844 1845 If unsure, say N. 1846 1847config BUG 1848 bool "BUG() support" if EXPERT 1849 default y 1850 help 1851 Disabling this option eliminates support for BUG and WARN, reducing 1852 the size of your kernel image and potentially quietly ignoring 1853 numerous fatal conditions. You should only consider disabling this 1854 option for embedded systems with no facilities for reporting errors. 1855 Just say Y. 1856 1857config ELF_CORE 1858 depends on COREDUMP 1859 default y 1860 bool "Enable ELF core dumps" if EXPERT 1861 help 1862 Enable support for generating core dumps. Disabling saves about 4k. 1863 1864 1865config PCSPKR_PLATFORM 1866 bool "Enable PC-Speaker support" if EXPERT 1867 depends on HAVE_PCSPKR_PLATFORM 1868 select I8253_LOCK 1869 default y 1870 help 1871 This option allows to disable the internal PC-Speaker 1872 support, saving some memory. 1873 1874config BASE_SMALL 1875 bool "Enable smaller-sized data structures for core" if EXPERT 1876 help 1877 Enabling this option reduces the size of miscellaneous core 1878 kernel data structures. This saves memory on small machines, 1879 but may reduce performance. 1880 1881config FUTEX 1882 bool "Enable futex support" if EXPERT 1883 depends on !(SPARC32 && SMP) 1884 default y 1885 imply RT_MUTEXES 1886 help 1887 Disabling this option will cause the kernel to be built without 1888 support for "fast userspace mutexes". The resulting kernel may not 1889 run glibc-based applications correctly. 1890 1891config FUTEX_PI 1892 bool 1893 depends on FUTEX && RT_MUTEXES 1894 default y 1895 1896config FUTEX_PRIVATE_HASH 1897 bool 1898 depends on FUTEX && !BASE_SMALL && MMU 1899 default y 1900 1901config FUTEX_MPOL 1902 bool 1903 depends on FUTEX && NUMA 1904 default y 1905 1906config HAVE_FUTEX_ROBUST_UNLOCK 1907 bool 1908 1909config FUTEX_ROBUST_UNLOCK 1910 def_bool FUTEX && GENERIC_IRQ_ENTRY && RSEQ && HAVE_FUTEX_ROBUST_UNLOCK 1911 1912config EPOLL 1913 bool "Enable eventpoll support" if EXPERT 1914 default y 1915 help 1916 Disabling this option will cause the kernel to be built without 1917 support for epoll family of system calls. 1918 1919config SIGNALFD 1920 bool "Enable signalfd() system call" if EXPERT 1921 default y 1922 help 1923 Enable the signalfd() system call that allows to receive signals 1924 on a file descriptor. 1925 1926 If unsure, say Y. 1927 1928config TIMERFD 1929 bool "Enable timerfd() system call" if EXPERT 1930 default y 1931 help 1932 Enable the timerfd() system call that allows to receive timer 1933 events on a file descriptor. 1934 1935 If unsure, say Y. 1936 1937config EVENTFD 1938 bool "Enable eventfd() system call" if EXPERT 1939 default y 1940 help 1941 Enable the eventfd() system call that allows to receive both 1942 kernel notification (ie. KAIO) or userspace notifications. 1943 1944 If unsure, say Y. 1945 1946config SHMEM 1947 bool "Use full shmem filesystem" if EXPERT 1948 default y 1949 depends on MMU 1950 help 1951 The shmem is an internal filesystem used to manage shared memory. 1952 It is backed by swap and manages resource limits. It is also exported 1953 to userspace as tmpfs if TMPFS is enabled. Disabling this 1954 option replaces shmem and tmpfs with the much simpler ramfs code, 1955 which may be appropriate on small systems without swap. 1956 1957config AIO 1958 bool "Enable AIO support" if EXPERT 1959 default y 1960 help 1961 This option enables POSIX asynchronous I/O which may by used 1962 by some high performance threaded applications. Disabling 1963 this option saves about 7k. 1964 1965config IO_URING 1966 bool "Enable IO uring support" if EXPERT 1967 select IO_WQ 1968 default y 1969 help 1970 This option enables support for the io_uring interface, enabling 1971 applications to submit and complete IO through submission and 1972 completion rings that are shared between the kernel and application. 1973 1974config GCOV_PROFILE_URING 1975 bool "Enable GCOV profiling on the io_uring subsystem" 1976 depends on IO_URING && GCOV_KERNEL 1977 help 1978 Enable GCOV profiling on the io_uring subsystem, to facilitate 1979 code coverage testing. 1980 1981 If unsure, say N. 1982 1983 Note that this will have a negative impact on the performance of 1984 the io_uring subsystem, hence this should only be enabled for 1985 specific test purposes. 1986 1987config IO_URING_MOCK_FILE 1988 tristate "Enable io_uring mock files (Experimental)" if EXPERT 1989 default n 1990 depends on IO_URING 1991 help 1992 Enable mock files for io_uring subsystem testing. The ABI might 1993 still change, so it's still experimental and should only be enabled 1994 for specific test purposes. 1995 1996 If unsure, say N. 1997 1998config ADVISE_SYSCALLS 1999 bool "Enable madvise/fadvise syscalls" if EXPERT 2000 default y 2001 help 2002 This option enables the madvise and fadvise syscalls, used by 2003 applications to advise the kernel about their future memory or file 2004 usage, improving performance. If building an embedded system where no 2005 applications use these syscalls, you can disable this option to save 2006 space. 2007 2008config MEMBARRIER 2009 bool "Enable membarrier() system call" if EXPERT 2010 default y 2011 help 2012 Enable the membarrier() system call that allows issuing memory 2013 barriers across all running threads, which can be used to distribute 2014 the cost of user-space memory barriers asymmetrically by transforming 2015 pairs of memory barriers into pairs consisting of membarrier() and a 2016 compiler barrier. 2017 2018 If unsure, say Y. 2019 2020config KCMP 2021 bool "Enable kcmp() system call" if EXPERT 2022 help 2023 Enable the kernel resource comparison system call. It provides 2024 user-space with the ability to compare two processes to see if they 2025 share a common resource, such as a file descriptor or even virtual 2026 memory space. 2027 2028 If unsure, say N. 2029 2030config RSEQ 2031 bool "Enable rseq() system call" if EXPERT 2032 default y 2033 depends on HAVE_RSEQ 2034 select MEMBARRIER 2035 help 2036 Enable the restartable sequences system call. It provides a 2037 user-space cache for the current CPU number value, which 2038 speeds up getting the current CPU number from user-space, 2039 as well as an ABI to speed up user-space operations on 2040 per-CPU data. 2041 2042 If unsure, say Y. 2043 2044config RSEQ_SLICE_EXTENSION 2045 bool "Enable rseq-based time slice extension mechanism" 2046 depends on RSEQ && HIGH_RES_TIMERS && GENERIC_ENTRY && HAVE_GENERIC_TIF_BITS 2047 help 2048 Allows userspace to request a limited time slice extension when 2049 returning from an interrupt to user space via the RSEQ shared 2050 data ABI. If granted, that allows to complete a critical section, 2051 so that other threads are not stuck on a conflicted resource, 2052 while the task is scheduled out. 2053 2054 If unsure, say N. 2055 2056config RSEQ_STATS 2057 default n 2058 bool "Enable lightweight statistics of restartable sequences" if EXPERT 2059 depends on RSEQ && DEBUG_FS 2060 help 2061 Enable lightweight counters which expose information about the 2062 frequency of RSEQ operations via debugfs. Mostly interesting for 2063 kernel debugging or performance analysis. While lightweight it's 2064 still adding code into the user/kernel mode transitions. 2065 2066 If unsure, say N. 2067 2068config RSEQ_DEBUG_DEFAULT_ENABLE 2069 default n 2070 bool "Enable restartable sequences debug mode by default" if EXPERT 2071 depends on RSEQ 2072 help 2073 This enables the static branch for debug mode of restartable 2074 sequences. 2075 2076 This also can be controlled on the kernel command line via the 2077 command line parameter "rseq_debug=0/1" and through debugfs. 2078 2079 If unsure, say N. 2080 2081config DEBUG_RSEQ 2082 default n 2083 bool "Enable debugging of rseq() system call" if EXPERT 2084 depends on RSEQ && DEBUG_KERNEL && !GENERIC_ENTRY 2085 select RSEQ_DEBUG_DEFAULT_ENABLE 2086 help 2087 Enable extra debugging checks for the rseq system call. 2088 2089 If unsure, say N. 2090 2091config CACHESTAT_SYSCALL 2092 bool "Enable cachestat() system call" if EXPERT 2093 default y 2094 help 2095 Enable the cachestat system call, which queries the page cache 2096 statistics of a file (number of cached pages, dirty pages, 2097 pages marked for writeback, (recently) evicted pages). 2098 2099 If unsure say Y here. 2100 2101config KALLSYMS 2102 bool "Load all symbols for debugging/ksymoops" if EXPERT 2103 default y 2104 help 2105 Say Y here to let the kernel print out symbolic crash information and 2106 symbolic stack backtraces. This increases the size of the kernel 2107 somewhat, as all symbols have to be loaded into the kernel image. 2108 2109config KALLSYMS_SELFTEST 2110 bool "Test the basic functions and performance of kallsyms" 2111 depends on KALLSYMS 2112 default n 2113 help 2114 Test the basic functions and performance of some interfaces, such as 2115 kallsyms_lookup_name. It also calculates the compression rate of the 2116 kallsyms compression algorithm for the current symbol set. 2117 2118 Start self-test automatically after system startup. Suggest executing 2119 "dmesg | grep kallsyms_selftest" to collect test results. "finish" is 2120 displayed in the last line, indicating that the test is complete. 2121 2122config KALLSYMS_ALL 2123 bool "Include all symbols in kallsyms" 2124 depends on DEBUG_KERNEL && KALLSYMS 2125 help 2126 Normally kallsyms only contains the symbols of functions for nicer 2127 OOPS messages and backtraces (i.e., symbols from the text and inittext 2128 sections). This is sufficient for most cases. And only if you want to 2129 enable kernel live patching, or other less common use cases (e.g., 2130 when a debugger is used) all symbols are required (i.e., names of 2131 variables from the data sections, etc). 2132 2133 This option makes sure that all symbols are loaded into the kernel 2134 image (i.e., symbols from all sections) in cost of increased kernel 2135 size (depending on the kernel configuration, it may be 300KiB or 2136 something like this). 2137 2138 Say N unless you really need all symbols, or kernel live patching. 2139 2140# end of the "standard kernel features (expert users)" menu 2141 2142config ARCH_HAS_MEMBARRIER_CALLBACKS 2143 bool 2144 2145config ARCH_HAS_MEMBARRIER_SYNC_CORE 2146 bool 2147 2148config ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS 2149 bool 2150 help 2151 Control MSEAL_SYSTEM_MAPPINGS access based on architecture. 2152 2153 A 64-bit kernel is required for the memory sealing feature. 2154 No specific hardware features from the CPU are needed. 2155 2156 To enable this feature, the architecture needs to update their 2157 special mappings calls to include the sealing flag and confirm 2158 that it doesn't unmap/remap system mappings during the life 2159 time of the process. The existence of this flag for an architecture 2160 implies that it does not require the remapping of the system 2161 mappings during process lifetime, so sealing these mappings is safe 2162 from a kernel perspective. 2163 2164 After the architecture enables this, a distribution can set 2165 CONFIG_MSEAL_SYSTEM_MAPPINGS to manage access to the feature. 2166 2167 For complete descriptions of memory sealing, please see 2168 Documentation/userspace-api/mseal.rst 2169 2170config HAVE_PERF_EVENTS 2171 bool 2172 help 2173 See tools/perf/design.txt for details. 2174 2175config GUEST_PERF_EVENTS 2176 bool 2177 depends on HAVE_PERF_EVENTS 2178 2179config PERF_GUEST_MEDIATED_PMU 2180 bool 2181 depends on GUEST_PERF_EVENTS 2182 2183config PERF_USE_VMALLOC 2184 bool 2185 help 2186 See tools/perf/design.txt for details 2187 2188menu "Kernel Performance Events And Counters" 2189 2190config PERF_EVENTS 2191 bool "Kernel performance events and counters" 2192 default y if PROFILING 2193 depends on HAVE_PERF_EVENTS 2194 select IRQ_WORK 2195 help 2196 Enable kernel support for various performance events provided 2197 by software and hardware. 2198 2199 Software events are supported either built-in or via the 2200 use of generic tracepoints. 2201 2202 Most modern CPUs support performance events via performance 2203 counter registers. These registers count the number of certain 2204 types of hw events: such as instructions executed, cachemisses 2205 suffered, or branches mis-predicted - without slowing down the 2206 kernel or applications. These registers can also trigger interrupts 2207 when a threshold number of events have passed - and can thus be 2208 used to profile the code that runs on that CPU. 2209 2210 The Linux Performance Event subsystem provides an abstraction of 2211 these software and hardware event capabilities, available via a 2212 system call and used by the "perf" utility in tools/perf/. It 2213 provides per task and per CPU counters, and it provides event 2214 capabilities on top of those. 2215 2216 Say Y if unsure. 2217 2218config DEBUG_PERF_USE_VMALLOC 2219 default n 2220 bool "Debug: use vmalloc to back perf mmap() buffers" 2221 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 2222 select PERF_USE_VMALLOC 2223 help 2224 Use vmalloc memory to back perf mmap() buffers. 2225 2226 Mostly useful for debugging the vmalloc code on platforms 2227 that don't require it. 2228 2229 Say N if unsure. 2230 2231endmenu 2232 2233config SYSTEM_DATA_VERIFICATION 2234 def_bool n 2235 select SYSTEM_TRUSTED_KEYRING 2236 select KEYS 2237 select CRYPTO 2238 select CRYPTO_RSA 2239 select ASYMMETRIC_KEY_TYPE 2240 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 2241 select ASN1 2242 select OID_REGISTRY 2243 select X509_CERTIFICATE_PARSER 2244 select PKCS7_MESSAGE_PARSER 2245 help 2246 Provide PKCS#7 message verification using the contents of the system 2247 trusted keyring to provide public keys. This then can be used for 2248 module verification, kexec image verification and firmware blob 2249 verification. 2250 2251config PROFILING 2252 bool "Profiling support" 2253 help 2254 Say Y here to enable the extended profiling support mechanisms used 2255 by profilers. 2256 2257config RUST 2258 bool "Rust support" 2259 depends on HAVE_RUST 2260 depends on RUST_IS_AVAILABLE 2261 select EXTENDED_MODVERSIONS if MODVERSIONS 2262 depends on !MODVERSIONS || GENDWARFKSYMS 2263 depends on !GCC_PLUGIN_RANDSTRUCT 2264 depends on !RANDSTRUCT 2265 depends on !DEBUG_INFO_BTF || (PAHOLE_HAS_LANG_EXCLUDE && !LTO) 2266 depends on !CFI || HAVE_CFI_ICALL_NORMALIZE_INTEGERS_RUSTC 2267 select CFI_ICALL_NORMALIZE_INTEGERS if CFI 2268 depends on !KASAN || CC_IS_CLANG 2269 depends on !KASAN_SW_TAGS || RUSTC_VERSION >= 109600 2270 help 2271 Enables Rust support in the kernel. 2272 2273 This allows other Rust-related options, like drivers written in Rust, 2274 to be selected. 2275 2276 It is also required to be able to load external kernel modules 2277 written in Rust. 2278 2279 See Documentation/rust/ for more information. 2280 2281 If unsure, say N. 2282 2283source "rust/kernel/Kconfig.test" 2284 2285config RUSTC_VERSION_TEXT 2286 string 2287 depends on RUST 2288 default "$(RUSTC_VERSION_TEXT)" 2289 help 2290 See `CC_VERSION_TEXT`. 2291 2292config BINDGEN_VERSION_TEXT 2293 string 2294 depends on RUST 2295 default "$(shell,$(BINDGEN) --version 2>/dev/null)" 2296 2297# 2298# Place an empty function call at each tracepoint site. Can be 2299# dynamically changed for a probe function. 2300# 2301config TRACEPOINTS 2302 bool 2303 select TASKS_TRACE_RCU 2304 2305source "kernel/Kconfig.kexec" 2306 2307source "kernel/liveupdate/Kconfig" 2308 2309endmenu # General setup 2310 2311source "arch/Kconfig" 2312 2313config RT_MUTEXES 2314 bool 2315 default y if PREEMPT_RT 2316 2317config MODULE_SIG_FORMAT 2318 def_bool n 2319 select SYSTEM_DATA_VERIFICATION 2320 2321source "kernel/module/Kconfig" 2322 2323config INIT_ALL_POSSIBLE 2324 bool 2325 help 2326 Back when each arch used to define their own cpu_online_mask and 2327 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2328 with all 1s, and others with all 0s. When they were centralised, 2329 it was better to provide this option than to break all the archs 2330 and have several arch maintainers pursuing me down dark alleys. 2331 2332source "block/Kconfig" 2333 2334config PREEMPT_NOTIFIERS 2335 bool 2336 2337config PADATA 2338 depends on SMP 2339 bool 2340 2341config ASN1 2342 tristate 2343 help 2344 Build a simple ASN.1 grammar compiler that produces a bytecode output 2345 that can be interpreted by the ASN.1 stream decoder and used to 2346 inform it as to what tags are to be expected in a stream and what 2347 functions to call on what tags. 2348 2349source "kernel/Kconfig.locks" 2350 2351config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 2352 bool 2353 2354config ARCH_HAS_PREPARE_SYNC_CORE_CMD 2355 bool 2356 2357config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2358 bool 2359 2360# It may be useful for an architecture to override the definitions of the 2361# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2362# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2363# different calling convention for syscalls. They can also override the 2364# macros for not-implemented syscalls in kernel/sys_ni.c and 2365# kernel/time/posix-stubs.c. All these overrides need to be available in 2366# <asm/syscall_wrapper.h>. 2367config ARCH_HAS_SYSCALL_WRAPPER 2368 def_bool n 2369