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 $(shell,$(srctree)/scripts/rustc-version.sh $(RUSTC)) 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 CC_CAN_LINK 82 bool 83 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT 84 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag)) 85 86config CC_CAN_LINK_STATIC 87 bool 88 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag) -static) if 64BIT 89 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag) -static) 90 91# Fixed in GCC 14, 13.3, 12.4 and 11.5 92# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113921 93config GCC_ASM_GOTO_OUTPUT_BROKEN 94 bool 95 depends on CC_IS_GCC 96 default y if GCC_VERSION < 110500 97 default y if GCC_VERSION >= 120000 && GCC_VERSION < 120400 98 default y if GCC_VERSION >= 130000 && GCC_VERSION < 130300 99 100config CC_HAS_ASM_GOTO_OUTPUT 101 def_bool y 102 depends on !GCC_ASM_GOTO_OUTPUT_BROKEN 103 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) 104 105config CC_HAS_ASM_GOTO_TIED_OUTPUT 106 depends on CC_HAS_ASM_GOTO_OUTPUT 107 # Detect buggy gcc and clang, fixed in gcc-11 clang-14. 108 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) 109 110config TOOLS_SUPPORT_RELR 111 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 112 113config CC_HAS_ASM_INLINE 114 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 115 116config CC_HAS_NO_PROFILE_FN_ATTR 117 def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror) 118 119config PAHOLE_VERSION 120 int 121 default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE)) 122 123config CONSTRUCTORS 124 bool 125 126config IRQ_WORK 127 def_bool y if SMP 128 129config BUILDTIME_TABLE_SORT 130 bool 131 132config THREAD_INFO_IN_TASK 133 bool 134 help 135 Select this to move thread_info off the stack into task_struct. To 136 make this work, an arch will need to remove all thread_info fields 137 except flags and fix any runtime bugs. 138 139 One subtle change that will be needed is to use try_get_task_stack() 140 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 141 142menu "General setup" 143 144config BROKEN 145 bool 146 147config BROKEN_ON_SMP 148 bool 149 depends on BROKEN || !SMP 150 default y 151 152config INIT_ENV_ARG_LIMIT 153 int 154 default 32 if !UML 155 default 128 if UML 156 help 157 Maximum of each of the number of arguments and environment 158 variables passed to init from the kernel command line. 159 160config COMPILE_TEST 161 bool "Compile also drivers which will not load" 162 depends on HAS_IOMEM 163 help 164 Some drivers can be compiled on a different platform than they are 165 intended to be run on. Despite they cannot be loaded there (or even 166 when they load they cannot be used due to missing HW support), 167 developers still, opposing to distributors, might want to build such 168 drivers to compile-test them. 169 170 If you are a developer and want to build everything available, say Y 171 here. If you are a user/distributor, say N here to exclude useless 172 drivers to be distributed. 173 174config WERROR 175 bool "Compile the kernel with warnings as errors" 176 default COMPILE_TEST 177 help 178 A kernel build should not cause any compiler warnings, and this 179 enables the '-Werror' (for C) and '-Dwarnings' (for Rust) flags 180 to enforce that rule by default. Certain warnings from other tools 181 such as the linker may be upgraded to errors with this option as 182 well. 183 184 However, if you have a new (or very old) compiler or linker with odd 185 and unusual warnings, or you have some architecture with problems, 186 you may need to disable this config option in order to 187 successfully build the kernel. 188 189 If in doubt, say Y. 190 191config UAPI_HEADER_TEST 192 bool "Compile test UAPI headers" 193 depends on HEADERS_INSTALL && CC_CAN_LINK 194 help 195 Compile test headers exported to user-space to ensure they are 196 self-contained, i.e. compilable as standalone units. 197 198 If you are a developer or tester and want to ensure the exported 199 headers are self-contained, say Y here. Otherwise, choose N. 200 201config LOCALVERSION 202 string "Local version - append to kernel release" 203 help 204 Append an extra string to the end of your kernel version. 205 This will show up when you type uname, for example. 206 The string you set here will be appended after the contents of 207 any files with a filename matching localversion* in your 208 object and source tree, in that order. Your total string can 209 be a maximum of 64 characters. 210 211config LOCALVERSION_AUTO 212 bool "Automatically append version information to the version string" 213 default y 214 depends on !COMPILE_TEST 215 help 216 This will try to automatically determine if the current tree is a 217 release tree by looking for git tags that belong to the current 218 top of tree revision. 219 220 A string of the format -gxxxxxxxx will be added to the localversion 221 if a git-based tree is found. The string generated by this will be 222 appended after any matching localversion* files, and after the value 223 set in CONFIG_LOCALVERSION. 224 225 (The actual string used here is the first 12 characters produced 226 by running the command: 227 228 $ git rev-parse --verify HEAD 229 230 which is done within the script "scripts/setlocalversion".) 231 232config BUILD_SALT 233 string "Build ID Salt" 234 default "" 235 help 236 The build ID is used to link binaries and their debug info. Setting 237 this option will use the value in the calculation of the build id. 238 This is mostly useful for distributions which want to ensure the 239 build is unique between builds. It's safe to leave the default. 240 241config HAVE_KERNEL_GZIP 242 bool 243 244config HAVE_KERNEL_BZIP2 245 bool 246 247config HAVE_KERNEL_LZMA 248 bool 249 250config HAVE_KERNEL_XZ 251 bool 252 253config HAVE_KERNEL_LZO 254 bool 255 256config HAVE_KERNEL_LZ4 257 bool 258 259config HAVE_KERNEL_ZSTD 260 bool 261 262config HAVE_KERNEL_UNCOMPRESSED 263 bool 264 265choice 266 prompt "Kernel compression mode" 267 default KERNEL_GZIP 268 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 269 help 270 The linux kernel is a kind of self-extracting executable. 271 Several compression algorithms are available, which differ 272 in efficiency, compression and decompression speed. 273 Compression speed is only relevant when building a kernel. 274 Decompression speed is relevant at each boot. 275 276 If you have any problems with bzip2 or lzma compressed 277 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 278 version of this functionality (bzip2 only), for 2.4, was 279 supplied by Christian Ludwig) 280 281 High compression options are mostly useful for users, who 282 are low on disk space (embedded systems), but for whom ram 283 size matters less. 284 285 If in doubt, select 'gzip' 286 287config KERNEL_GZIP 288 bool "Gzip" 289 depends on HAVE_KERNEL_GZIP 290 help 291 The old and tried gzip compression. It provides a good balance 292 between compression ratio and decompression speed. 293 294config KERNEL_BZIP2 295 bool "Bzip2" 296 depends on HAVE_KERNEL_BZIP2 297 help 298 Its compression ratio and speed is intermediate. 299 Decompression speed is slowest among the choices. The kernel 300 size is about 10% smaller with bzip2, in comparison to gzip. 301 Bzip2 uses a large amount of memory. For modern kernels you 302 will need at least 8MB RAM or more for booting. 303 304config KERNEL_LZMA 305 bool "LZMA" 306 depends on HAVE_KERNEL_LZMA 307 help 308 This compression algorithm's ratio is best. Decompression speed 309 is between gzip and bzip2. Compression is slowest. 310 The kernel size is about 33% smaller with LZMA in comparison to gzip. 311 312config KERNEL_XZ 313 bool "XZ" 314 depends on HAVE_KERNEL_XZ 315 help 316 XZ uses the LZMA2 algorithm and instruction set specific 317 BCJ filters which can improve compression ratio of executable 318 code. The size of the kernel is about 30% smaller with XZ in 319 comparison to gzip. On architectures for which there is a BCJ 320 filter (i386, x86_64, ARM, ARM64, RISC-V, big endian PowerPC, 321 and SPARC), XZ will create a few percent smaller kernel than 322 plain LZMA. 323 324 The speed is about the same as with LZMA: The decompression 325 speed of XZ is better than that of bzip2 but worse than gzip 326 and LZO. Compression is slow. 327 328config KERNEL_LZO 329 bool "LZO" 330 depends on HAVE_KERNEL_LZO 331 help 332 Its compression ratio is the poorest among the choices. The kernel 333 size is about 10% bigger than gzip; however its speed 334 (both compression and decompression) is the fastest. 335 336config KERNEL_LZ4 337 bool "LZ4" 338 depends on HAVE_KERNEL_LZ4 339 help 340 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 341 A preliminary version of LZ4 de/compression tool is available at 342 <https://code.google.com/p/lz4/>. 343 344 Its compression ratio is worse than LZO. The size of the kernel 345 is about 8% bigger than LZO. But the decompression speed is 346 faster than LZO. 347 348config KERNEL_ZSTD 349 bool "ZSTD" 350 depends on HAVE_KERNEL_ZSTD 351 help 352 ZSTD is a compression algorithm targeting intermediate compression 353 with fast decompression speed. It will compress better than GZIP and 354 decompress around the same speed as LZO, but slower than LZ4. You 355 will need at least 192 KB RAM or more for booting. The zstd command 356 line tool is required for compression. 357 358config KERNEL_UNCOMPRESSED 359 bool "None" 360 depends on HAVE_KERNEL_UNCOMPRESSED 361 help 362 Produce uncompressed kernel image. This option is usually not what 363 you want. It is useful for debugging the kernel in slow simulation 364 environments, where decompressing and moving the kernel is awfully 365 slow. This option allows early boot code to skip the decompressor 366 and jump right at uncompressed kernel image. 367 368endchoice 369 370config DEFAULT_INIT 371 string "Default init path" 372 default "" 373 help 374 This option determines the default init for the system if no init= 375 option is passed on the kernel command line. If the requested path is 376 not present, we will still then move on to attempting further 377 locations (e.g. /sbin/init, etc). If this is empty, we will just use 378 the fallback list when init= is not passed. 379 380config DEFAULT_HOSTNAME 381 string "Default hostname" 382 default "(none)" 383 help 384 This option determines the default system hostname before userspace 385 calls sethostname(2). The kernel traditionally uses "(none)" here, 386 but you may wish to use a different default here to make a minimal 387 system more usable with less configuration. 388 389config SYSVIPC 390 bool "System V IPC" 391 help 392 Inter Process Communication is a suite of library functions and 393 system calls which let processes (running programs) synchronize and 394 exchange information. It is generally considered to be a good thing, 395 and some programs won't run unless you say Y here. In particular, if 396 you want to run the DOS emulator dosemu under Linux (read the 397 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 398 you'll need to say Y here. 399 400 You can find documentation about IPC with "info ipc" and also in 401 section 6.4 of the Linux Programmer's Guide, available from 402 <http://www.tldp.org/guides.html>. 403 404config SYSVIPC_SYSCTL 405 bool 406 depends on SYSVIPC 407 depends on SYSCTL 408 default y 409 410config SYSVIPC_COMPAT 411 def_bool y 412 depends on COMPAT && SYSVIPC 413 414config POSIX_MQUEUE 415 bool "POSIX Message Queues" 416 depends on NET 417 help 418 POSIX variant of message queues is a part of IPC. In POSIX message 419 queues every message has a priority which decides about succession 420 of receiving it by a process. If you want to compile and run 421 programs written e.g. for Solaris with use of its POSIX message 422 queues (functions mq_*) say Y here. 423 424 POSIX message queues are visible as a filesystem called 'mqueue' 425 and can be mounted somewhere if you want to do filesystem 426 operations on message queues. 427 428 If unsure, say Y. 429 430config POSIX_MQUEUE_SYSCTL 431 bool 432 depends on POSIX_MQUEUE 433 depends on SYSCTL 434 default y 435 436config WATCH_QUEUE 437 bool "General notification queue" 438 default n 439 help 440 441 This is a general notification queue for the kernel to pass events to 442 userspace by splicing them into pipes. It can be used in conjunction 443 with watches for key/keyring change notifications and device 444 notifications. 445 446 See Documentation/core-api/watch_queue.rst 447 448config CROSS_MEMORY_ATTACH 449 bool "Enable process_vm_readv/writev syscalls" 450 depends on MMU 451 default y 452 help 453 Enabling this option adds the system calls process_vm_readv and 454 process_vm_writev which allow a process with the correct privileges 455 to directly read from or write to another process' address space. 456 See the man page for more details. 457 458config USELIB 459 bool "uselib syscall (for libc5 and earlier)" 460 default ALPHA || M68K || SPARC 461 help 462 This option enables the uselib syscall, a system call used in the 463 dynamic linker from libc5 and earlier. glibc does not use this 464 system call. If you intend to run programs built on libc5 or 465 earlier, you may need to enable this syscall. Current systems 466 running glibc can safely disable this. 467 468config AUDIT 469 bool "Auditing support" 470 depends on NET 471 help 472 Enable auditing infrastructure that can be used with another 473 kernel subsystem, such as SELinux (which requires this for 474 logging of avc messages output). System call auditing is included 475 on architectures which support it. 476 477config HAVE_ARCH_AUDITSYSCALL 478 bool 479 480config AUDITSYSCALL 481 def_bool y 482 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 483 select FSNOTIFY 484 485source "kernel/irq/Kconfig" 486source "kernel/time/Kconfig" 487source "kernel/bpf/Kconfig" 488source "kernel/Kconfig.preempt" 489 490menu "CPU/Task time and stats accounting" 491 492config VIRT_CPU_ACCOUNTING 493 bool 494 495choice 496 prompt "Cputime accounting" 497 default TICK_CPU_ACCOUNTING 498 499# Kind of a stub config for the pure tick based cputime accounting 500config TICK_CPU_ACCOUNTING 501 bool "Simple tick based cputime accounting" 502 depends on !S390 && !NO_HZ_FULL 503 help 504 This is the basic tick based cputime accounting that maintains 505 statistics about user, system and idle time spent on per jiffies 506 granularity. 507 508 If unsure, say Y. 509 510config VIRT_CPU_ACCOUNTING_NATIVE 511 bool "Deterministic task and CPU time accounting" 512 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 513 select VIRT_CPU_ACCOUNTING 514 help 515 Select this option to enable more accurate task and CPU time 516 accounting. This is done by reading a CPU counter on each 517 kernel entry and exit and on transitions within the kernel 518 between system, softirq and hardirq state, so there is a 519 small performance impact. In the case of s390 or IBM POWER > 5, 520 this also enables accounting of stolen time on logically-partitioned 521 systems. 522 523config VIRT_CPU_ACCOUNTING_GEN 524 bool "Full dynticks CPU time accounting" 525 depends on HAVE_CONTEXT_TRACKING_USER 526 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 527 depends on GENERIC_CLOCKEVENTS 528 select VIRT_CPU_ACCOUNTING 529 select CONTEXT_TRACKING_USER 530 help 531 Select this option to enable task and CPU time accounting on full 532 dynticks systems. This accounting is implemented by watching every 533 kernel-user boundaries using the context tracking subsystem. 534 The accounting is thus performed at the expense of some significant 535 overhead. 536 537 For now this is only useful if you are working on the full 538 dynticks subsystem development. 539 540 If unsure, say N. 541 542endchoice 543 544config IRQ_TIME_ACCOUNTING 545 bool "Fine granularity task level IRQ time accounting" 546 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 547 help 548 Select this option to enable fine granularity task irq time 549 accounting. This is done by reading a timestamp on each 550 transitions between softirq and hardirq state, so there can be a 551 small performance impact. 552 553 If in doubt, say N here. 554 555config HAVE_SCHED_AVG_IRQ 556 def_bool y 557 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 558 depends on SMP 559 560config SCHED_HW_PRESSURE 561 bool 562 default y if ARM && ARM_CPU_TOPOLOGY 563 default y if ARM64 564 depends on SMP 565 depends on CPU_FREQ_THERMAL 566 help 567 Select this option to enable HW pressure accounting in the 568 scheduler. HW pressure is the value conveyed to the scheduler 569 that reflects the reduction in CPU compute capacity resulted from 570 HW throttling. HW throttling occurs when the performance of 571 a CPU is capped due to high operating temperatures as an example. 572 573 If selected, the scheduler will be able to balance tasks accordingly, 574 i.e. put less load on throttled CPUs than on non/less throttled ones. 575 576 This requires the architecture to implement 577 arch_update_hw_pressure() and arch_scale_thermal_pressure(). 578 579config BSD_PROCESS_ACCT 580 bool "BSD Process Accounting" 581 depends on MULTIUSER 582 help 583 If you say Y here, a user level program will be able to instruct the 584 kernel (via a special system call) to write process accounting 585 information to a file: whenever a process exits, information about 586 that process will be appended to the file by the kernel. The 587 information includes things such as creation time, owning user, 588 command name, memory usage, controlling terminal etc. (the complete 589 list is in the struct acct in <file:include/linux/acct.h>). It is 590 up to the user level program to do useful things with this 591 information. This is generally a good idea, so say Y. 592 593config BSD_PROCESS_ACCT_V3 594 bool "BSD Process Accounting version 3 file format" 595 depends on BSD_PROCESS_ACCT 596 default n 597 help 598 If you say Y here, the process accounting information is written 599 in a new file format that also logs the process IDs of each 600 process and its parent. Note that this file format is incompatible 601 with previous v0/v1/v2 file formats, so you will need updated tools 602 for processing it. A preliminary version of these tools is available 603 at <http://www.gnu.org/software/acct/>. 604 605config TASKSTATS 606 bool "Export task/process statistics through netlink" 607 depends on NET 608 depends on MULTIUSER 609 default n 610 help 611 Export selected statistics for tasks/processes through the 612 generic netlink interface. Unlike BSD process accounting, the 613 statistics are available during the lifetime of tasks/processes as 614 responses to commands. Like BSD accounting, they are sent to user 615 space on task exit. 616 617 Say N if unsure. 618 619config TASK_DELAY_ACCT 620 bool "Enable per-task delay accounting" 621 depends on TASKSTATS 622 select SCHED_INFO 623 help 624 Collect information on time spent by a task waiting for system 625 resources like cpu, synchronous block I/O completion and swapping 626 in pages. Such statistics can help in setting a task's priorities 627 relative to other tasks for cpu, io, rss limits etc. 628 629 Say N if unsure. 630 631config TASK_XACCT 632 bool "Enable extended accounting over taskstats" 633 depends on TASKSTATS 634 help 635 Collect extended task accounting data and send the data 636 to userland for processing over the taskstats interface. 637 638 Say N if unsure. 639 640config TASK_IO_ACCOUNTING 641 bool "Enable per-task storage I/O accounting" 642 depends on TASK_XACCT 643 help 644 Collect information on the number of bytes of storage I/O which this 645 task has caused. 646 647 Say N if unsure. 648 649config PSI 650 bool "Pressure stall information tracking" 651 select KERNFS 652 help 653 Collect metrics that indicate how overcommitted the CPU, memory, 654 and IO capacity are in the system. 655 656 If you say Y here, the kernel will create /proc/pressure/ with the 657 pressure statistics files cpu, memory, and io. These will indicate 658 the share of walltime in which some or all tasks in the system are 659 delayed due to contention of the respective resource. 660 661 In kernels with cgroup support, cgroups (cgroup2 only) will 662 have cpu.pressure, memory.pressure, and io.pressure files, 663 which aggregate pressure stalls for the grouped tasks only. 664 665 For more details see Documentation/accounting/psi.rst. 666 667 Say N if unsure. 668 669config PSI_DEFAULT_DISABLED 670 bool "Require boot parameter to enable pressure stall information tracking" 671 default n 672 depends on PSI 673 help 674 If set, pressure stall information tracking will be disabled 675 per default but can be enabled through passing psi=1 on the 676 kernel commandline during boot. 677 678 This feature adds some code to the task wakeup and sleep 679 paths of the scheduler. The overhead is too low to affect 680 common scheduling-intense workloads in practice (such as 681 webservers, memcache), but it does show up in artificial 682 scheduler stress tests, such as hackbench. 683 684 If you are paranoid and not sure what the kernel will be 685 used for, say Y. 686 687 Say N if unsure. 688 689endmenu # "CPU/Task time and stats accounting" 690 691config CPU_ISOLATION 692 bool "CPU isolation" 693 depends on SMP || COMPILE_TEST 694 default y 695 help 696 Make sure that CPUs running critical tasks are not disturbed by 697 any source of "noise" such as unbound workqueues, timers, kthreads... 698 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 699 the "isolcpus=" boot parameter. 700 701 Say Y if unsure. 702 703source "kernel/rcu/Kconfig" 704 705config IKCONFIG 706 tristate "Kernel .config support" 707 help 708 This option enables the complete Linux kernel ".config" file 709 contents to be saved in the kernel. It provides documentation 710 of which kernel options are used in a running kernel or in an 711 on-disk kernel. This information can be extracted from the kernel 712 image file with the script scripts/extract-ikconfig and used as 713 input to rebuild the current kernel or to build another kernel. 714 It can also be extracted from a running kernel by reading 715 /proc/config.gz if enabled (below). 716 717config IKCONFIG_PROC 718 bool "Enable access to .config through /proc/config.gz" 719 depends on IKCONFIG && PROC_FS 720 help 721 This option enables access to the kernel configuration file 722 through /proc/config.gz. 723 724config IKHEADERS 725 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 726 depends on SYSFS 727 help 728 This option enables access to the in-kernel headers that are generated during 729 the build process. These can be used to build eBPF tracing programs, 730 or similar programs. If you build the headers as a module, a module called 731 kheaders.ko is built which can be loaded on-demand to get access to headers. 732 733config LOG_BUF_SHIFT 734 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 735 range 12 25 736 default 17 737 depends on PRINTK 738 help 739 Select the minimal kernel log buffer size as a power of 2. 740 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 741 parameter, see below. Any higher size also might be forced 742 by "log_buf_len" boot parameter. 743 744 Examples: 745 17 => 128 KB 746 16 => 64 KB 747 15 => 32 KB 748 14 => 16 KB 749 13 => 8 KB 750 12 => 4 KB 751 752config LOG_CPU_MAX_BUF_SHIFT 753 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 754 depends on SMP 755 range 0 21 756 default 0 if BASE_SMALL 757 default 12 758 depends on PRINTK 759 help 760 This option allows to increase the default ring buffer size 761 according to the number of CPUs. The value defines the contribution 762 of each CPU as a power of 2. The used space is typically only few 763 lines however it might be much more when problems are reported, 764 e.g. backtraces. 765 766 The increased size means that a new buffer has to be allocated and 767 the original static one is unused. It makes sense only on systems 768 with more CPUs. Therefore this value is used only when the sum of 769 contributions is greater than the half of the default kernel ring 770 buffer as defined by LOG_BUF_SHIFT. The default values are set 771 so that more than 16 CPUs are needed to trigger the allocation. 772 773 Also this option is ignored when "log_buf_len" kernel parameter is 774 used as it forces an exact (power of two) size of the ring buffer. 775 776 The number of possible CPUs is used for this computation ignoring 777 hotplugging making the computation optimal for the worst case 778 scenario while allowing a simple algorithm to be used from bootup. 779 780 Examples shift values and their meaning: 781 17 => 128 KB for each CPU 782 16 => 64 KB for each CPU 783 15 => 32 KB for each CPU 784 14 => 16 KB for each CPU 785 13 => 8 KB for each CPU 786 12 => 4 KB for each CPU 787 788config PRINTK_INDEX 789 bool "Printk indexing debugfs interface" 790 depends on PRINTK && DEBUG_FS 791 help 792 Add support for indexing of all printk formats known at compile time 793 at <debugfs>/printk/index/<module>. 794 795 This can be used as part of maintaining daemons which monitor 796 /dev/kmsg, as it permits auditing the printk formats present in a 797 kernel, allowing detection of cases where monitored printks are 798 changed or no longer present. 799 800 There is no additional runtime cost to printk with this enabled. 801 802# 803# Architectures with an unreliable sched_clock() should select this: 804# 805config HAVE_UNSTABLE_SCHED_CLOCK 806 bool 807 808config GENERIC_SCHED_CLOCK 809 bool 810 811menu "Scheduler features" 812 813config UCLAMP_TASK 814 bool "Enable utilization clamping for RT/FAIR tasks" 815 depends on CPU_FREQ_GOV_SCHEDUTIL 816 help 817 This feature enables the scheduler to track the clamped utilization 818 of each CPU based on RUNNABLE tasks scheduled on that CPU. 819 820 With this option, the user can specify the min and max CPU 821 utilization allowed for RUNNABLE tasks. The max utilization defines 822 the maximum frequency a task should use while the min utilization 823 defines the minimum frequency it should use. 824 825 Both min and max utilization clamp values are hints to the scheduler, 826 aiming at improving its frequency selection policy, but they do not 827 enforce or grant any specific bandwidth for tasks. 828 829 If in doubt, say N. 830 831config UCLAMP_BUCKETS_COUNT 832 int "Number of supported utilization clamp buckets" 833 range 5 20 834 default 5 835 depends on UCLAMP_TASK 836 help 837 Defines the number of clamp buckets to use. The range of each bucket 838 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 839 number of clamp buckets the finer their granularity and the higher 840 the precision of clamping aggregation and tracking at run-time. 841 842 For example, with the minimum configuration value we will have 5 843 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 844 be refcounted in the [20..39]% bucket and will set the bucket clamp 845 effective value to 25%. 846 If a second 30% boosted task should be co-scheduled on the same CPU, 847 that task will be refcounted in the same bucket of the first task and 848 it will boost the bucket clamp effective value to 30%. 849 The clamp effective value of a bucket is reset to its nominal value 850 (20% in the example above) when there are no more tasks refcounted in 851 that bucket. 852 853 An additional boost/capping margin can be added to some tasks. In the 854 example above the 25% task will be boosted to 30% until it exits the 855 CPU. If that should be considered not acceptable on certain systems, 856 it's always possible to reduce the margin by increasing the number of 857 clamp buckets to trade off used memory for run-time tracking 858 precision. 859 860 If in doubt, use the default value. 861 862endmenu 863 864# 865# For architectures that want to enable the support for NUMA-affine scheduler 866# balancing logic: 867# 868config ARCH_SUPPORTS_NUMA_BALANCING 869 bool 870 871# 872# For architectures that prefer to flush all TLBs after a number of pages 873# are unmapped instead of sending one IPI per page to flush. The architecture 874# must provide guarantees on what happens if a clean TLB cache entry is 875# written after the unmap. Details are in mm/rmap.c near the check for 876# should_defer_flush. The architecture should also consider if the full flush 877# and the refill costs are offset by the savings of sending fewer IPIs. 878config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 879 bool 880 881config CC_HAS_INT128 882 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 883 884config CC_IMPLICIT_FALLTHROUGH 885 string 886 default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5) 887 default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough) 888 889# Currently, disable gcc-10+ array-bounds globally. 890# It's still broken in gcc-13, so no upper bound yet. 891config GCC10_NO_ARRAY_BOUNDS 892 def_bool y 893 894config CC_NO_ARRAY_BOUNDS 895 bool 896 default y if CC_IS_GCC && GCC_VERSION >= 90000 && GCC10_NO_ARRAY_BOUNDS 897 898# Currently, disable -Wstringop-overflow for GCC globally. 899config GCC_NO_STRINGOP_OVERFLOW 900 def_bool y 901 902config CC_NO_STRINGOP_OVERFLOW 903 bool 904 default y if CC_IS_GCC && GCC_NO_STRINGOP_OVERFLOW 905 906config CC_STRINGOP_OVERFLOW 907 bool 908 default y if CC_IS_GCC && !CC_NO_STRINGOP_OVERFLOW 909 910# 911# For architectures that know their GCC __int128 support is sound 912# 913config ARCH_SUPPORTS_INT128 914 bool 915 916# For architectures that (ab)use NUMA to represent different memory regions 917# all cpu-local but of different latencies, such as SuperH. 918# 919config ARCH_WANT_NUMA_VARIABLE_LOCALITY 920 bool 921 922config NUMA_BALANCING 923 bool "Memory placement aware NUMA scheduler" 924 depends on ARCH_SUPPORTS_NUMA_BALANCING 925 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 926 depends on SMP && NUMA && MIGRATION && !PREEMPT_RT 927 help 928 This option adds support for automatic NUMA aware memory/task placement. 929 The mechanism is quite primitive and is based on migrating memory when 930 it has references to the node the task is running on. 931 932 This system will be inactive on UMA systems. 933 934config NUMA_BALANCING_DEFAULT_ENABLED 935 bool "Automatically enable NUMA aware memory/task placement" 936 default y 937 depends on NUMA_BALANCING 938 help 939 If set, automatic NUMA balancing will be enabled if running on a NUMA 940 machine. 941 942config SLAB_OBJ_EXT 943 bool 944 945menuconfig CGROUPS 946 bool "Control Group support" 947 select KERNFS 948 help 949 This option adds support for grouping sets of processes together, for 950 use with process control subsystems such as Cpusets, CFS, memory 951 controls or device isolation. 952 See 953 - Documentation/scheduler/sched-design-CFS.rst (CFS) 954 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 955 and resource control) 956 957 Say N if unsure. 958 959if CGROUPS 960 961config PAGE_COUNTER 962 bool 963 964config CGROUP_FAVOR_DYNMODS 965 bool "Favor dynamic modification latency reduction by default" 966 help 967 This option enables the "favordynmods" mount option by default 968 which reduces the latencies of dynamic cgroup modifications such 969 as task migrations and controller on/offs at the cost of making 970 hot path operations such as forks and exits more expensive. 971 972 Say N if unsure. 973 974config MEMCG 975 bool "Memory controller" 976 select PAGE_COUNTER 977 select EVENTFD 978 select SLAB_OBJ_EXT 979 help 980 Provides control over the memory footprint of tasks in a cgroup. 981 982config MEMCG_V1 983 bool "Legacy cgroup v1 memory controller" 984 depends on MEMCG 985 default n 986 help 987 Legacy cgroup v1 memory controller which has been deprecated by 988 cgroup v2 implementation. The v1 is there for legacy applications 989 which haven't migrated to the new cgroup v2 interface yet. If you 990 do not have any such application then you are completely fine leaving 991 this option disabled. 992 993 Please note that feature set of the legacy memory controller is likely 994 going to shrink due to deprecation process. New deployments with v1 995 controller are highly discouraged. 996 997 Say N if unsure. 998 999config BLK_CGROUP 1000 bool "IO controller" 1001 depends on BLOCK 1002 default n 1003 help 1004 Generic block IO controller cgroup interface. This is the common 1005 cgroup interface which should be used by various IO controlling 1006 policies. 1007 1008 Currently, CFQ IO scheduler uses it to recognize task groups and 1009 control disk bandwidth allocation (proportional time slice allocation) 1010 to such task groups. It is also used by bio throttling logic in 1011 block layer to implement upper limit in IO rates on a device. 1012 1013 This option only enables generic Block IO controller infrastructure. 1014 One needs to also enable actual IO controlling logic/policy. For 1015 enabling proportional weight division of disk bandwidth in CFQ, set 1016 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 1017 CONFIG_BLK_DEV_THROTTLING=y. 1018 1019 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 1020 1021config CGROUP_WRITEBACK 1022 bool 1023 depends on MEMCG && BLK_CGROUP 1024 default y 1025 1026menuconfig CGROUP_SCHED 1027 bool "CPU controller" 1028 default n 1029 help 1030 This feature lets CPU scheduler recognize task groups and control CPU 1031 bandwidth allocation to such task groups. It uses cgroups to group 1032 tasks. 1033 1034if CGROUP_SCHED 1035config GROUP_SCHED_WEIGHT 1036 def_bool n 1037 1038config FAIR_GROUP_SCHED 1039 bool "Group scheduling for SCHED_OTHER" 1040 depends on CGROUP_SCHED 1041 select GROUP_SCHED_WEIGHT 1042 default CGROUP_SCHED 1043 1044config CFS_BANDWIDTH 1045 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 1046 depends on FAIR_GROUP_SCHED 1047 default n 1048 help 1049 This option allows users to define CPU bandwidth rates (limits) for 1050 tasks running within the fair group scheduler. Groups with no limit 1051 set are considered to be unconstrained and will run with no 1052 restriction. 1053 See Documentation/scheduler/sched-bwc.rst for more information. 1054 1055config RT_GROUP_SCHED 1056 bool "Group scheduling for SCHED_RR/FIFO" 1057 depends on CGROUP_SCHED 1058 default n 1059 help 1060 This feature lets you explicitly allocate real CPU bandwidth 1061 to task groups. If enabled, it will also make it impossible to 1062 schedule realtime tasks for non-root users until you allocate 1063 realtime bandwidth for them. 1064 See Documentation/scheduler/sched-rt-group.rst for more information. 1065 1066config EXT_GROUP_SCHED 1067 bool 1068 depends on SCHED_CLASS_EXT && CGROUP_SCHED 1069 select GROUP_SCHED_WEIGHT 1070 default y 1071 1072endif #CGROUP_SCHED 1073 1074config SCHED_MM_CID 1075 def_bool y 1076 depends on SMP && RSEQ 1077 1078config UCLAMP_TASK_GROUP 1079 bool "Utilization clamping per group of tasks" 1080 depends on CGROUP_SCHED 1081 depends on UCLAMP_TASK 1082 default n 1083 help 1084 This feature enables the scheduler to track the clamped utilization 1085 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 1086 1087 When this option is enabled, the user can specify a min and max 1088 CPU bandwidth which is allowed for each single task in a group. 1089 The max bandwidth allows to clamp the maximum frequency a task 1090 can use, while the min bandwidth allows to define a minimum 1091 frequency a task will always use. 1092 1093 When task group based utilization clamping is enabled, an eventually 1094 specified task-specific clamp value is constrained by the cgroup 1095 specified clamp value. Both minimum and maximum task clamping cannot 1096 be bigger than the corresponding clamping defined at task group level. 1097 1098 If in doubt, say N. 1099 1100config CGROUP_PIDS 1101 bool "PIDs controller" 1102 help 1103 Provides enforcement of process number limits in the scope of a 1104 cgroup. Any attempt to fork more processes than is allowed in the 1105 cgroup will fail. PIDs are fundamentally a global resource because it 1106 is fairly trivial to reach PID exhaustion before you reach even a 1107 conservative kmemcg limit. As a result, it is possible to grind a 1108 system to halt without being limited by other cgroup policies. The 1109 PIDs controller is designed to stop this from happening. 1110 1111 It should be noted that organisational operations (such as attaching 1112 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 1113 since the PIDs limit only affects a process's ability to fork, not to 1114 attach to a cgroup. 1115 1116config CGROUP_RDMA 1117 bool "RDMA controller" 1118 help 1119 Provides enforcement of RDMA resources defined by IB stack. 1120 It is fairly easy for consumers to exhaust RDMA resources, which 1121 can result into resource unavailability to other consumers. 1122 RDMA controller is designed to stop this from happening. 1123 Attaching processes with active RDMA resources to the cgroup 1124 hierarchy is allowed even if can cross the hierarchy's limit. 1125 1126config CGROUP_FREEZER 1127 bool "Freezer controller" 1128 help 1129 Provides a way to freeze and unfreeze all tasks in a 1130 cgroup. 1131 1132 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1133 controller includes important in-kernel memory consumers per default. 1134 1135 If you're using cgroup2, say N. 1136 1137config CGROUP_HUGETLB 1138 bool "HugeTLB controller" 1139 depends on HUGETLB_PAGE 1140 select PAGE_COUNTER 1141 default n 1142 help 1143 Provides a cgroup controller for HugeTLB pages. 1144 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1145 The limit is enforced during page fault. Since HugeTLB doesn't 1146 support page reclaim, enforcing the limit at page fault time implies 1147 that, the application will get SIGBUS signal if it tries to access 1148 HugeTLB pages beyond its limit. This requires the application to know 1149 beforehand how much HugeTLB pages it would require for its use. The 1150 control group is tracked in the third page lru pointer. This means 1151 that we cannot use the controller with huge page less than 3 pages. 1152 1153config CPUSETS 1154 bool "Cpuset controller" 1155 depends on SMP 1156 help 1157 This option will let you create and manage CPUSETs which 1158 allow dynamically partitioning a system into sets of CPUs and 1159 Memory Nodes and assigning tasks to run only within those sets. 1160 This is primarily useful on large SMP or NUMA systems. 1161 1162 Say N if unsure. 1163 1164config CPUSETS_V1 1165 bool "Legacy cgroup v1 cpusets controller" 1166 depends on CPUSETS 1167 default n 1168 help 1169 Legacy cgroup v1 cpusets controller which has been deprecated by 1170 cgroup v2 implementation. The v1 is there for legacy applications 1171 which haven't migrated to the new cgroup v2 interface yet. If you 1172 do not have any such application then you are completely fine leaving 1173 this option disabled. 1174 1175 Say N if unsure. 1176 1177config PROC_PID_CPUSET 1178 bool "Include legacy /proc/<pid>/cpuset file" 1179 depends on CPUSETS 1180 default y 1181 1182config CGROUP_DEVICE 1183 bool "Device controller" 1184 help 1185 Provides a cgroup controller implementing whitelists for 1186 devices which a process in the cgroup can mknod or open. 1187 1188config CGROUP_CPUACCT 1189 bool "Simple CPU accounting controller" 1190 help 1191 Provides a simple controller for monitoring the 1192 total CPU consumed by the tasks in a cgroup. 1193 1194config CGROUP_PERF 1195 bool "Perf controller" 1196 depends on PERF_EVENTS 1197 help 1198 This option extends the perf per-cpu mode to restrict monitoring 1199 to threads which belong to the cgroup specified and run on the 1200 designated cpu. Or this can be used to have cgroup ID in samples 1201 so that it can monitor performance events among cgroups. 1202 1203 Say N if unsure. 1204 1205config CGROUP_BPF 1206 bool "Support for eBPF programs attached to cgroups" 1207 depends on BPF_SYSCALL 1208 select SOCK_CGROUP_DATA 1209 help 1210 Allow attaching eBPF programs to a cgroup using the bpf(2) 1211 syscall command BPF_PROG_ATTACH. 1212 1213 In which context these programs are accessed depends on the type 1214 of attachment. For instance, programs that are attached using 1215 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1216 inet sockets. 1217 1218config CGROUP_MISC 1219 bool "Misc resource controller" 1220 default n 1221 help 1222 Provides a controller for miscellaneous resources on a host. 1223 1224 Miscellaneous scalar resources are the resources on the host system 1225 which cannot be abstracted like the other cgroups. This controller 1226 tracks and limits the miscellaneous resources used by a process 1227 attached to a cgroup hierarchy. 1228 1229 For more information, please check misc cgroup section in 1230 /Documentation/admin-guide/cgroup-v2.rst. 1231 1232config CGROUP_DEBUG 1233 bool "Debug controller" 1234 default n 1235 depends on DEBUG_KERNEL 1236 help 1237 This option enables a simple controller that exports 1238 debugging information about the cgroups framework. This 1239 controller is for control cgroup debugging only. Its 1240 interfaces are not stable. 1241 1242 Say N. 1243 1244config SOCK_CGROUP_DATA 1245 bool 1246 default n 1247 1248endif # CGROUPS 1249 1250menuconfig NAMESPACES 1251 bool "Namespaces support" if EXPERT 1252 depends on MULTIUSER 1253 default !EXPERT 1254 help 1255 Provides the way to make tasks work with different objects using 1256 the same id. For example same IPC id may refer to different objects 1257 or same user id or pid may refer to different tasks when used in 1258 different namespaces. 1259 1260if NAMESPACES 1261 1262config UTS_NS 1263 bool "UTS namespace" 1264 default y 1265 help 1266 In this namespace tasks see different info provided with the 1267 uname() system call 1268 1269config TIME_NS 1270 bool "TIME namespace" 1271 depends on GENERIC_VDSO_TIME_NS 1272 default y 1273 help 1274 In this namespace boottime and monotonic clocks can be set. 1275 The time will keep going with the same pace. 1276 1277config IPC_NS 1278 bool "IPC namespace" 1279 depends on (SYSVIPC || POSIX_MQUEUE) 1280 default y 1281 help 1282 In this namespace tasks work with IPC ids which correspond to 1283 different IPC objects in different namespaces. 1284 1285config USER_NS 1286 bool "User namespace" 1287 default n 1288 help 1289 This allows containers, i.e. vservers, to use user namespaces 1290 to provide different user info for different servers. 1291 1292 When user namespaces are enabled in the kernel it is 1293 recommended that the MEMCG option also be enabled and that 1294 user-space use the memory control groups to limit the amount 1295 of memory a memory unprivileged users can use. 1296 1297 If unsure, say N. 1298 1299config PID_NS 1300 bool "PID Namespaces" 1301 default y 1302 help 1303 Support process id namespaces. This allows having multiple 1304 processes with the same pid as long as they are in different 1305 pid namespaces. This is a building block of containers. 1306 1307config NET_NS 1308 bool "Network namespace" 1309 depends on NET 1310 default y 1311 help 1312 Allow user space to create what appear to be multiple instances 1313 of the network stack. 1314 1315endif # NAMESPACES 1316 1317config CHECKPOINT_RESTORE 1318 bool "Checkpoint/restore support" 1319 depends on PROC_FS 1320 select PROC_CHILDREN 1321 select KCMP 1322 default n 1323 help 1324 Enables additional kernel features in a sake of checkpoint/restore. 1325 In particular it adds auxiliary prctl codes to setup process text, 1326 data and heap segment sizes, and a few additional /proc filesystem 1327 entries. 1328 1329 If unsure, say N here. 1330 1331config SCHED_AUTOGROUP 1332 bool "Automatic process group scheduling" 1333 select CGROUPS 1334 select CGROUP_SCHED 1335 select FAIR_GROUP_SCHED 1336 help 1337 This option optimizes the scheduler for common desktop workloads by 1338 automatically creating and populating task groups. This separation 1339 of workloads isolates aggressive CPU burners (like build jobs) from 1340 desktop applications. Task group autogeneration is currently based 1341 upon task session. 1342 1343config RELAY 1344 bool "Kernel->user space relay support (formerly relayfs)" 1345 select IRQ_WORK 1346 help 1347 This option enables support for relay interface support in 1348 certain file systems (such as debugfs). 1349 It is designed to provide an efficient mechanism for tools and 1350 facilities to relay large amounts of data from kernel space to 1351 user space. 1352 1353 If unsure, say N. 1354 1355config BLK_DEV_INITRD 1356 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1357 help 1358 The initial RAM filesystem is a ramfs which is loaded by the 1359 boot loader (loadlin or lilo) and that is mounted as root 1360 before the normal boot procedure. It is typically used to 1361 load modules needed to mount the "real" root file system, 1362 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1363 1364 If RAM disk support (BLK_DEV_RAM) is also included, this 1365 also enables initial RAM disk (initrd) support and adds 1366 15 Kbytes (more on some other architectures) to the kernel size. 1367 1368 If unsure say Y. 1369 1370if BLK_DEV_INITRD 1371 1372source "usr/Kconfig" 1373 1374endif 1375 1376config BOOT_CONFIG 1377 bool "Boot config support" 1378 select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED 1379 help 1380 Extra boot config allows system admin to pass a config file as 1381 complemental extension of kernel cmdline when booting. 1382 The boot config file must be attached at the end of initramfs 1383 with checksum, size and magic word. 1384 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1385 1386 If unsure, say Y. 1387 1388config BOOT_CONFIG_FORCE 1389 bool "Force unconditional bootconfig processing" 1390 depends on BOOT_CONFIG 1391 default y if BOOT_CONFIG_EMBED 1392 help 1393 With this Kconfig option set, BOOT_CONFIG processing is carried 1394 out even when the "bootconfig" kernel-boot parameter is omitted. 1395 In fact, with this Kconfig option set, there is no way to 1396 make the kernel ignore the BOOT_CONFIG-supplied kernel-boot 1397 parameters. 1398 1399 If unsure, say N. 1400 1401config BOOT_CONFIG_EMBED 1402 bool "Embed bootconfig file in the kernel" 1403 depends on BOOT_CONFIG 1404 help 1405 Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the 1406 kernel. Usually, the bootconfig file is loaded with the initrd 1407 image. But if the system doesn't support initrd, this option will 1408 help you by embedding a bootconfig file while building the kernel. 1409 1410 If unsure, say N. 1411 1412config BOOT_CONFIG_EMBED_FILE 1413 string "Embedded bootconfig file path" 1414 depends on BOOT_CONFIG_EMBED 1415 help 1416 Specify a bootconfig file which will be embedded to the kernel. 1417 This bootconfig will be used if there is no initrd or no other 1418 bootconfig in the initrd. 1419 1420config INITRAMFS_PRESERVE_MTIME 1421 bool "Preserve cpio archive mtimes in initramfs" 1422 default y 1423 help 1424 Each entry in an initramfs cpio archive carries an mtime value. When 1425 enabled, extracted cpio items take this mtime, with directory mtime 1426 setting deferred until after creation of any child entries. 1427 1428 If unsure, say Y. 1429 1430choice 1431 prompt "Compiler optimization level" 1432 default CC_OPTIMIZE_FOR_PERFORMANCE 1433 1434config CC_OPTIMIZE_FOR_PERFORMANCE 1435 bool "Optimize for performance (-O2)" 1436 help 1437 This is the default optimization level for the kernel, building 1438 with the "-O2" compiler flag for best performance and most 1439 helpful compile-time warnings. 1440 1441config CC_OPTIMIZE_FOR_SIZE 1442 bool "Optimize for size (-Os)" 1443 help 1444 Choosing this option will pass "-Os" to your compiler resulting 1445 in a smaller kernel. 1446 1447endchoice 1448 1449config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1450 bool 1451 help 1452 This requires that the arch annotates or otherwise protects 1453 its external entry points from being discarded. Linker scripts 1454 must also merge .text.*, .data.*, and .bss.* correctly into 1455 output sections. Care must be taken not to pull in unrelated 1456 sections (e.g., '.text.init'). Typically '.' in section names 1457 is used to distinguish them from label names / C identifiers. 1458 1459config LD_DEAD_CODE_DATA_ELIMINATION 1460 bool "Dead code and data elimination (EXPERIMENTAL)" 1461 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1462 depends on EXPERT 1463 depends on $(cc-option,-ffunction-sections -fdata-sections) 1464 depends on $(ld-option,--gc-sections) 1465 help 1466 Enable this if you want to do dead code and data elimination with 1467 the linker by compiling with -ffunction-sections -fdata-sections, 1468 and linking with --gc-sections. 1469 1470 This can reduce on disk and in-memory size of the kernel 1471 code and static data, particularly for small configs and 1472 on small systems. This has the possibility of introducing 1473 silently broken kernel if the required annotations are not 1474 present. This option is not well tested yet, so use at your 1475 own risk. 1476 1477config LD_ORPHAN_WARN 1478 def_bool y 1479 depends on ARCH_WANT_LD_ORPHAN_WARN 1480 depends on $(ld-option,--orphan-handling=warn) 1481 depends on $(ld-option,--orphan-handling=error) 1482 1483config LD_ORPHAN_WARN_LEVEL 1484 string 1485 depends on LD_ORPHAN_WARN 1486 default "error" if WERROR 1487 default "warn" 1488 1489config SYSCTL 1490 bool 1491 1492config HAVE_UID16 1493 bool 1494 1495config SYSCTL_EXCEPTION_TRACE 1496 bool 1497 help 1498 Enable support for /proc/sys/debug/exception-trace. 1499 1500config SYSCTL_ARCH_UNALIGN_NO_WARN 1501 bool 1502 help 1503 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1504 Allows arch to define/use @no_unaligned_warning to possibly warn 1505 about unaligned access emulation going on under the hood. 1506 1507config SYSCTL_ARCH_UNALIGN_ALLOW 1508 bool 1509 help 1510 Enable support for /proc/sys/kernel/unaligned-trap 1511 Allows arches to define/use @unaligned_enabled to runtime toggle 1512 the unaligned access emulation. 1513 see arch/parisc/kernel/unaligned.c for reference 1514 1515config HAVE_PCSPKR_PLATFORM 1516 bool 1517 1518menuconfig EXPERT 1519 bool "Configure standard kernel features (expert users)" 1520 # Unhide debug options, to make the on-by-default options visible 1521 select DEBUG_KERNEL 1522 help 1523 This option allows certain base kernel options and settings 1524 to be disabled or tweaked. This is for specialized 1525 environments which can tolerate a "non-standard" kernel. 1526 Only use this if you really know what you are doing. 1527 1528config UID16 1529 bool "Enable 16-bit UID system calls" if EXPERT 1530 depends on HAVE_UID16 && MULTIUSER 1531 default y 1532 help 1533 This enables the legacy 16-bit UID syscall wrappers. 1534 1535config MULTIUSER 1536 bool "Multiple users, groups and capabilities support" if EXPERT 1537 default y 1538 help 1539 This option enables support for non-root users, groups and 1540 capabilities. 1541 1542 If you say N here, all processes will run with UID 0, GID 0, and all 1543 possible capabilities. Saying N here also compiles out support for 1544 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1545 setgid, and capset. 1546 1547 If unsure, say Y here. 1548 1549config SGETMASK_SYSCALL 1550 bool "sgetmask/ssetmask syscalls support" if EXPERT 1551 default PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1552 help 1553 sys_sgetmask and sys_ssetmask are obsolete system calls 1554 no longer supported in libc but still enabled by default in some 1555 architectures. 1556 1557 If unsure, leave the default option here. 1558 1559config SYSFS_SYSCALL 1560 bool "Sysfs syscall support" if EXPERT 1561 default y 1562 help 1563 sys_sysfs is an obsolete system call no longer supported in libc. 1564 Note that disabling this option is more secure but might break 1565 compatibility with some systems. 1566 1567 If unsure say Y here. 1568 1569config FHANDLE 1570 bool "open by fhandle syscalls" if EXPERT 1571 select EXPORTFS 1572 default y 1573 help 1574 If you say Y here, a user level program will be able to map 1575 file names to handle and then later use the handle for 1576 different file system operations. This is useful in implementing 1577 userspace file servers, which now track files using handles instead 1578 of names. The handle would remain the same even if file names 1579 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1580 syscalls. 1581 1582config POSIX_TIMERS 1583 bool "Posix Clocks & timers" if EXPERT 1584 default y 1585 help 1586 This includes native support for POSIX timers to the kernel. 1587 Some embedded systems have no use for them and therefore they 1588 can be configured out to reduce the size of the kernel image. 1589 1590 When this option is disabled, the following syscalls won't be 1591 available: timer_create, timer_gettime: timer_getoverrun, 1592 timer_settime, timer_delete, clock_adjtime, getitimer, 1593 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1594 clock_getres and clock_nanosleep syscalls will be limited to 1595 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1596 1597 If unsure say y. 1598 1599config PRINTK 1600 default y 1601 bool "Enable support for printk" if EXPERT 1602 select IRQ_WORK 1603 help 1604 This option enables normal printk support. Removing it 1605 eliminates most of the message strings from the kernel image 1606 and makes the kernel more or less silent. As this makes it 1607 very difficult to diagnose system problems, saying N here is 1608 strongly discouraged. 1609 1610config BUG 1611 bool "BUG() support" if EXPERT 1612 default y 1613 help 1614 Disabling this option eliminates support for BUG and WARN, reducing 1615 the size of your kernel image and potentially quietly ignoring 1616 numerous fatal conditions. You should only consider disabling this 1617 option for embedded systems with no facilities for reporting errors. 1618 Just say Y. 1619 1620config ELF_CORE 1621 depends on COREDUMP 1622 default y 1623 bool "Enable ELF core dumps" if EXPERT 1624 help 1625 Enable support for generating core dumps. Disabling saves about 4k. 1626 1627 1628config PCSPKR_PLATFORM 1629 bool "Enable PC-Speaker support" if EXPERT 1630 depends on HAVE_PCSPKR_PLATFORM 1631 select I8253_LOCK 1632 default y 1633 help 1634 This option allows to disable the internal PC-Speaker 1635 support, saving some memory. 1636 1637config BASE_SMALL 1638 bool "Enable smaller-sized data structures for core" if EXPERT 1639 help 1640 Enabling this option reduces the size of miscellaneous core 1641 kernel data structures. This saves memory on small machines, 1642 but may reduce performance. 1643 1644config FUTEX 1645 bool "Enable futex support" if EXPERT 1646 depends on !(SPARC32 && SMP) 1647 default y 1648 imply RT_MUTEXES 1649 help 1650 Disabling this option will cause the kernel to be built without 1651 support for "fast userspace mutexes". The resulting kernel may not 1652 run glibc-based applications correctly. 1653 1654config FUTEX_PI 1655 bool 1656 depends on FUTEX && RT_MUTEXES 1657 default y 1658 1659config EPOLL 1660 bool "Enable eventpoll support" if EXPERT 1661 default y 1662 help 1663 Disabling this option will cause the kernel to be built without 1664 support for epoll family of system calls. 1665 1666config SIGNALFD 1667 bool "Enable signalfd() system call" if EXPERT 1668 default y 1669 help 1670 Enable the signalfd() system call that allows to receive signals 1671 on a file descriptor. 1672 1673 If unsure, say Y. 1674 1675config TIMERFD 1676 bool "Enable timerfd() system call" if EXPERT 1677 default y 1678 help 1679 Enable the timerfd() system call that allows to receive timer 1680 events on a file descriptor. 1681 1682 If unsure, say Y. 1683 1684config EVENTFD 1685 bool "Enable eventfd() system call" if EXPERT 1686 default y 1687 help 1688 Enable the eventfd() system call that allows to receive both 1689 kernel notification (ie. KAIO) or userspace notifications. 1690 1691 If unsure, say Y. 1692 1693config SHMEM 1694 bool "Use full shmem filesystem" if EXPERT 1695 default y 1696 depends on MMU 1697 help 1698 The shmem is an internal filesystem used to manage shared memory. 1699 It is backed by swap and manages resource limits. It is also exported 1700 to userspace as tmpfs if TMPFS is enabled. Disabling this 1701 option replaces shmem and tmpfs with the much simpler ramfs code, 1702 which may be appropriate on small systems without swap. 1703 1704config AIO 1705 bool "Enable AIO support" if EXPERT 1706 default y 1707 help 1708 This option enables POSIX asynchronous I/O which may by used 1709 by some high performance threaded applications. Disabling 1710 this option saves about 7k. 1711 1712config IO_URING 1713 bool "Enable IO uring support" if EXPERT 1714 select IO_WQ 1715 default y 1716 help 1717 This option enables support for the io_uring interface, enabling 1718 applications to submit and complete IO through submission and 1719 completion rings that are shared between the kernel and application. 1720 1721config GCOV_PROFILE_URING 1722 bool "Enable GCOV profiling on the io_uring subsystem" 1723 depends on GCOV_KERNEL 1724 help 1725 Enable GCOV profiling on the io_uring subsystem, to facilitate 1726 code coverage testing. 1727 1728 If unsure, say N. 1729 1730 Note that this will have a negative impact on the performance of 1731 the io_uring subsystem, hence this should only be enabled for 1732 specific test purposes. 1733 1734config ADVISE_SYSCALLS 1735 bool "Enable madvise/fadvise syscalls" if EXPERT 1736 default y 1737 help 1738 This option enables the madvise and fadvise syscalls, used by 1739 applications to advise the kernel about their future memory or file 1740 usage, improving performance. If building an embedded system where no 1741 applications use these syscalls, you can disable this option to save 1742 space. 1743 1744config MEMBARRIER 1745 bool "Enable membarrier() system call" if EXPERT 1746 default y 1747 help 1748 Enable the membarrier() system call that allows issuing memory 1749 barriers across all running threads, which can be used to distribute 1750 the cost of user-space memory barriers asymmetrically by transforming 1751 pairs of memory barriers into pairs consisting of membarrier() and a 1752 compiler barrier. 1753 1754 If unsure, say Y. 1755 1756config KCMP 1757 bool "Enable kcmp() system call" if EXPERT 1758 help 1759 Enable the kernel resource comparison system call. It provides 1760 user-space with the ability to compare two processes to see if they 1761 share a common resource, such as a file descriptor or even virtual 1762 memory space. 1763 1764 If unsure, say N. 1765 1766config RSEQ 1767 bool "Enable rseq() system call" if EXPERT 1768 default y 1769 depends on HAVE_RSEQ 1770 select MEMBARRIER 1771 help 1772 Enable the restartable sequences system call. It provides a 1773 user-space cache for the current CPU number value, which 1774 speeds up getting the current CPU number from user-space, 1775 as well as an ABI to speed up user-space operations on 1776 per-CPU data. 1777 1778 If unsure, say Y. 1779 1780config DEBUG_RSEQ 1781 default n 1782 bool "Enable debugging of rseq() system call" if EXPERT 1783 depends on RSEQ && DEBUG_KERNEL 1784 help 1785 Enable extra debugging checks for the rseq system call. 1786 1787 If unsure, say N. 1788 1789config CACHESTAT_SYSCALL 1790 bool "Enable cachestat() system call" if EXPERT 1791 default y 1792 help 1793 Enable the cachestat system call, which queries the page cache 1794 statistics of a file (number of cached pages, dirty pages, 1795 pages marked for writeback, (recently) evicted pages). 1796 1797 If unsure say Y here. 1798 1799config PC104 1800 bool "PC/104 support" if EXPERT 1801 help 1802 Expose PC/104 form factor device drivers and options available for 1803 selection and configuration. Enable this option if your target 1804 machine has a PC/104 bus. 1805 1806config KALLSYMS 1807 bool "Load all symbols for debugging/ksymoops" if EXPERT 1808 default y 1809 help 1810 Say Y here to let the kernel print out symbolic crash information and 1811 symbolic stack backtraces. This increases the size of the kernel 1812 somewhat, as all symbols have to be loaded into the kernel image. 1813 1814config KALLSYMS_SELFTEST 1815 bool "Test the basic functions and performance of kallsyms" 1816 depends on KALLSYMS 1817 default n 1818 help 1819 Test the basic functions and performance of some interfaces, such as 1820 kallsyms_lookup_name. It also calculates the compression rate of the 1821 kallsyms compression algorithm for the current symbol set. 1822 1823 Start self-test automatically after system startup. Suggest executing 1824 "dmesg | grep kallsyms_selftest" to collect test results. "finish" is 1825 displayed in the last line, indicating that the test is complete. 1826 1827config KALLSYMS_ALL 1828 bool "Include all symbols in kallsyms" 1829 depends on DEBUG_KERNEL && KALLSYMS 1830 help 1831 Normally kallsyms only contains the symbols of functions for nicer 1832 OOPS messages and backtraces (i.e., symbols from the text and inittext 1833 sections). This is sufficient for most cases. And only if you want to 1834 enable kernel live patching, or other less common use cases (e.g., 1835 when a debugger is used) all symbols are required (i.e., names of 1836 variables from the data sections, etc). 1837 1838 This option makes sure that all symbols are loaded into the kernel 1839 image (i.e., symbols from all sections) in cost of increased kernel 1840 size (depending on the kernel configuration, it may be 300KiB or 1841 something like this). 1842 1843 Say N unless you really need all symbols, or kernel live patching. 1844 1845config KALLSYMS_ABSOLUTE_PERCPU 1846 bool 1847 depends on KALLSYMS 1848 default X86_64 && SMP 1849 1850# end of the "standard kernel features (expert users)" menu 1851 1852config ARCH_HAS_MEMBARRIER_CALLBACKS 1853 bool 1854 1855config ARCH_HAS_MEMBARRIER_SYNC_CORE 1856 bool 1857 1858config HAVE_PERF_EVENTS 1859 bool 1860 help 1861 See tools/perf/design.txt for details. 1862 1863config GUEST_PERF_EVENTS 1864 bool 1865 depends on HAVE_PERF_EVENTS 1866 1867config PERF_USE_VMALLOC 1868 bool 1869 help 1870 See tools/perf/design.txt for details 1871 1872menu "Kernel Performance Events And Counters" 1873 1874config PERF_EVENTS 1875 bool "Kernel performance events and counters" 1876 default y if PROFILING 1877 depends on HAVE_PERF_EVENTS 1878 select IRQ_WORK 1879 help 1880 Enable kernel support for various performance events provided 1881 by software and hardware. 1882 1883 Software events are supported either built-in or via the 1884 use of generic tracepoints. 1885 1886 Most modern CPUs support performance events via performance 1887 counter registers. These registers count the number of certain 1888 types of hw events: such as instructions executed, cachemisses 1889 suffered, or branches mis-predicted - without slowing down the 1890 kernel or applications. These registers can also trigger interrupts 1891 when a threshold number of events have passed - and can thus be 1892 used to profile the code that runs on that CPU. 1893 1894 The Linux Performance Event subsystem provides an abstraction of 1895 these software and hardware event capabilities, available via a 1896 system call and used by the "perf" utility in tools/perf/. It 1897 provides per task and per CPU counters, and it provides event 1898 capabilities on top of those. 1899 1900 Say Y if unsure. 1901 1902config DEBUG_PERF_USE_VMALLOC 1903 default n 1904 bool "Debug: use vmalloc to back perf mmap() buffers" 1905 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1906 select PERF_USE_VMALLOC 1907 help 1908 Use vmalloc memory to back perf mmap() buffers. 1909 1910 Mostly useful for debugging the vmalloc code on platforms 1911 that don't require it. 1912 1913 Say N if unsure. 1914 1915endmenu 1916 1917config SYSTEM_DATA_VERIFICATION 1918 def_bool n 1919 select SYSTEM_TRUSTED_KEYRING 1920 select KEYS 1921 select CRYPTO 1922 select CRYPTO_RSA 1923 select ASYMMETRIC_KEY_TYPE 1924 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1925 select ASN1 1926 select OID_REGISTRY 1927 select X509_CERTIFICATE_PARSER 1928 select PKCS7_MESSAGE_PARSER 1929 help 1930 Provide PKCS#7 message verification using the contents of the system 1931 trusted keyring to provide public keys. This then can be used for 1932 module verification, kexec image verification and firmware blob 1933 verification. 1934 1935config PROFILING 1936 bool "Profiling support" 1937 help 1938 Say Y here to enable the extended profiling support mechanisms used 1939 by profilers. 1940 1941config RUST 1942 bool "Rust support" 1943 depends on HAVE_RUST 1944 depends on RUST_IS_AVAILABLE 1945 depends on !MODVERSIONS 1946 depends on !GCC_PLUGIN_RANDSTRUCT 1947 depends on !RANDSTRUCT 1948 depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE 1949 depends on !CFI_CLANG || RUSTC_VERSION >= 107900 && $(cc-option,-fsanitize=kcfi -fsanitize-cfi-icall-experimental-normalize-integers) 1950 select CFI_ICALL_NORMALIZE_INTEGERS if CFI_CLANG 1951 depends on !CALL_PADDING || RUSTC_VERSION >= 108000 1952 depends on !KASAN_SW_TAGS 1953 help 1954 Enables Rust support in the kernel. 1955 1956 This allows other Rust-related options, like drivers written in Rust, 1957 to be selected. 1958 1959 It is also required to be able to load external kernel modules 1960 written in Rust. 1961 1962 See Documentation/rust/ for more information. 1963 1964 If unsure, say N. 1965 1966config RUSTC_VERSION_TEXT 1967 string 1968 depends on RUST 1969 default "$(RUSTC_VERSION_TEXT)" 1970 help 1971 See `CC_VERSION_TEXT`. 1972 1973config BINDGEN_VERSION_TEXT 1974 string 1975 depends on RUST 1976 # The dummy parameter `workaround-for-0.69.0` is required to support 0.69.0 1977 # (https://github.com/rust-lang/rust-bindgen/pull/2678). It can be removed when 1978 # the minimum version is upgraded past that (0.69.1 already fixed the issue). 1979 default "$(shell,$(BINDGEN) --version workaround-for-0.69.0 2>/dev/null)" 1980 1981# 1982# Place an empty function call at each tracepoint site. Can be 1983# dynamically changed for a probe function. 1984# 1985config TRACEPOINTS 1986 bool 1987 1988source "kernel/Kconfig.kexec" 1989 1990endmenu # General setup 1991 1992source "arch/Kconfig" 1993 1994config RT_MUTEXES 1995 bool 1996 default y if PREEMPT_RT 1997 1998config MODULE_SIG_FORMAT 1999 def_bool n 2000 select SYSTEM_DATA_VERIFICATION 2001 2002source "kernel/module/Kconfig" 2003 2004config INIT_ALL_POSSIBLE 2005 bool 2006 help 2007 Back when each arch used to define their own cpu_online_mask and 2008 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2009 with all 1s, and others with all 0s. When they were centralised, 2010 it was better to provide this option than to break all the archs 2011 and have several arch maintainers pursuing me down dark alleys. 2012 2013source "block/Kconfig" 2014 2015config PREEMPT_NOTIFIERS 2016 bool 2017 2018config PADATA 2019 depends on SMP 2020 bool 2021 2022config ASN1 2023 tristate 2024 help 2025 Build a simple ASN.1 grammar compiler that produces a bytecode output 2026 that can be interpreted by the ASN.1 stream decoder and used to 2027 inform it as to what tags are to be expected in a stream and what 2028 functions to call on what tags. 2029 2030source "kernel/Kconfig.locks" 2031 2032config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 2033 bool 2034 2035config ARCH_HAS_PREPARE_SYNC_CORE_CMD 2036 bool 2037 2038config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2039 bool 2040 2041# It may be useful for an architecture to override the definitions of the 2042# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2043# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2044# different calling convention for syscalls. They can also override the 2045# macros for not-implemented syscalls in kernel/sys_ni.c and 2046# kernel/time/posix-stubs.c. All these overrides need to be available in 2047# <asm/syscall_wrapper.h>. 2048config ARCH_HAS_SYSCALL_WRAPPER 2049 def_bool n 2050