1# SPDX-License-Identifier: GPL-2.0-only 2config CC_VERSION_TEXT 3 string 4 default "$(CC_VERSION_TEXT)" 5 help 6 This is used in unclear ways: 7 8 - Re-run Kconfig when the compiler is updated 9 The 'default' property references the environment variable, 10 CC_VERSION_TEXT so it is recorded in include/config/auto.conf.cmd. 11 When the compiler is updated, Kconfig will be invoked. 12 13 - Ensure full rebuild when the compiler is updated 14 include/linux/compiler-version.h contains this option in the comment 15 line so fixdep adds include/config/CC_VERSION_TEXT into the 16 auto-generated dependency. When the compiler is updated, syncconfig 17 will touch it and then every file will be rebuilt. 18 19config CC_IS_GCC 20 def_bool $(success,test "$(cc-name)" = GCC) 21 22config GCC_VERSION 23 int 24 default $(cc-version) if CC_IS_GCC 25 default 0 26 27config CC_IS_CLANG 28 def_bool $(success,test "$(cc-name)" = Clang) 29 30config CLANG_VERSION 31 int 32 default $(cc-version) if CC_IS_CLANG 33 default 0 34 35config AS_IS_GNU 36 def_bool $(success,test "$(as-name)" = GNU) 37 38config AS_IS_LLVM 39 def_bool $(success,test "$(as-name)" = LLVM) 40 41config AS_VERSION 42 int 43 # Use clang version if this is the integrated assembler 44 default CLANG_VERSION if AS_IS_LLVM 45 default $(as-version) 46 47config LD_IS_BFD 48 def_bool $(success,test "$(ld-name)" = BFD) 49 50config LD_VERSION 51 int 52 default $(ld-version) if LD_IS_BFD 53 default 0 54 55config LD_IS_LLD 56 def_bool $(success,test "$(ld-name)" = LLD) 57 58config LLD_VERSION 59 int 60 default $(ld-version) if LD_IS_LLD 61 default 0 62 63config RUST_IS_AVAILABLE 64 def_bool $(success,$(srctree)/scripts/rust_is_available.sh) 65 help 66 This shows whether a suitable Rust toolchain is available (found). 67 68 Please see Documentation/rust/quick-start.rst for instructions on how 69 to satisfy the build requirements of Rust support. 70 71 In particular, the Makefile target 'rustavailable' is useful to check 72 why the Rust toolchain is not being detected. 73 74config CC_CAN_LINK 75 bool 76 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT 77 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag)) 78 79config CC_CAN_LINK_STATIC 80 bool 81 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag) -static) if 64BIT 82 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag) -static) 83 84# Fixed in GCC 14, 13.3, 12.4 and 11.5 85# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113921 86config GCC_ASM_GOTO_OUTPUT_BROKEN 87 bool 88 depends on CC_IS_GCC 89 default y if GCC_VERSION < 110500 90 default y if GCC_VERSION >= 120000 && GCC_VERSION < 120400 91 default y if GCC_VERSION >= 130000 && GCC_VERSION < 130300 92 93config CC_HAS_ASM_GOTO_OUTPUT 94 def_bool y 95 depends on !GCC_ASM_GOTO_OUTPUT_BROKEN 96 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) 97 98config CC_HAS_ASM_GOTO_TIED_OUTPUT 99 depends on CC_HAS_ASM_GOTO_OUTPUT 100 # Detect buggy gcc and clang, fixed in gcc-11 clang-14. 101 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) 102 103config TOOLS_SUPPORT_RELR 104 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 105 106config CC_HAS_ASM_INLINE 107 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 108 109config CC_HAS_NO_PROFILE_FN_ATTR 110 def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror) 111 112config PAHOLE_VERSION 113 int 114 default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE)) 115 116config CONSTRUCTORS 117 bool 118 119config IRQ_WORK 120 def_bool y if SMP 121 122config BUILDTIME_TABLE_SORT 123 bool 124 125config THREAD_INFO_IN_TASK 126 bool 127 help 128 Select this to move thread_info off the stack into task_struct. To 129 make this work, an arch will need to remove all thread_info fields 130 except flags and fix any runtime bugs. 131 132 One subtle change that will be needed is to use try_get_task_stack() 133 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 134 135menu "General setup" 136 137config BROKEN 138 bool 139 140config BROKEN_ON_SMP 141 bool 142 depends on BROKEN || !SMP 143 default y 144 145config INIT_ENV_ARG_LIMIT 146 int 147 default 32 if !UML 148 default 128 if UML 149 help 150 Maximum of each of the number of arguments and environment 151 variables passed to init from the kernel command line. 152 153config COMPILE_TEST 154 bool "Compile also drivers which will not load" 155 depends on HAS_IOMEM 156 help 157 Some drivers can be compiled on a different platform than they are 158 intended to be run on. Despite they cannot be loaded there (or even 159 when they load they cannot be used due to missing HW support), 160 developers still, opposing to distributors, might want to build such 161 drivers to compile-test them. 162 163 If you are a developer and want to build everything available, say Y 164 here. If you are a user/distributor, say N here to exclude useless 165 drivers to be distributed. 166 167config WERROR 168 bool "Compile the kernel with warnings as errors" 169 default COMPILE_TEST 170 help 171 A kernel build should not cause any compiler warnings, and this 172 enables the '-Werror' (for C) and '-Dwarnings' (for Rust) flags 173 to enforce that rule by default. Certain warnings from other tools 174 such as the linker may be upgraded to errors with this option as 175 well. 176 177 However, if you have a new (or very old) compiler or linker with odd 178 and unusual warnings, or you have some architecture with problems, 179 you may need to disable this config option in order to 180 successfully build the kernel. 181 182 If in doubt, say Y. 183 184config UAPI_HEADER_TEST 185 bool "Compile test UAPI headers" 186 depends on HEADERS_INSTALL && CC_CAN_LINK 187 help 188 Compile test headers exported to user-space to ensure they are 189 self-contained, i.e. compilable as standalone units. 190 191 If you are a developer or tester and want to ensure the exported 192 headers are self-contained, say Y here. Otherwise, choose N. 193 194config LOCALVERSION 195 string "Local version - append to kernel release" 196 help 197 Append an extra string to the end of your kernel version. 198 This will show up when you type uname, for example. 199 The string you set here will be appended after the contents of 200 any files with a filename matching localversion* in your 201 object and source tree, in that order. Your total string can 202 be a maximum of 64 characters. 203 204config LOCALVERSION_AUTO 205 bool "Automatically append version information to the version string" 206 default y 207 depends on !COMPILE_TEST 208 help 209 This will try to automatically determine if the current tree is a 210 release tree by looking for git tags that belong to the current 211 top of tree revision. 212 213 A string of the format -gxxxxxxxx will be added to the localversion 214 if a git-based tree is found. The string generated by this will be 215 appended after any matching localversion* files, and after the value 216 set in CONFIG_LOCALVERSION. 217 218 (The actual string used here is the first 12 characters produced 219 by running the command: 220 221 $ git rev-parse --verify HEAD 222 223 which is done within the script "scripts/setlocalversion".) 224 225config BUILD_SALT 226 string "Build ID Salt" 227 default "" 228 help 229 The build ID is used to link binaries and their debug info. Setting 230 this option will use the value in the calculation of the build id. 231 This is mostly useful for distributions which want to ensure the 232 build is unique between builds. It's safe to leave the default. 233 234config HAVE_KERNEL_GZIP 235 bool 236 237config HAVE_KERNEL_BZIP2 238 bool 239 240config HAVE_KERNEL_LZMA 241 bool 242 243config HAVE_KERNEL_XZ 244 bool 245 246config HAVE_KERNEL_LZO 247 bool 248 249config HAVE_KERNEL_LZ4 250 bool 251 252config HAVE_KERNEL_ZSTD 253 bool 254 255config HAVE_KERNEL_UNCOMPRESSED 256 bool 257 258choice 259 prompt "Kernel compression mode" 260 default KERNEL_GZIP 261 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 262 help 263 The linux kernel is a kind of self-extracting executable. 264 Several compression algorithms are available, which differ 265 in efficiency, compression and decompression speed. 266 Compression speed is only relevant when building a kernel. 267 Decompression speed is relevant at each boot. 268 269 If you have any problems with bzip2 or lzma compressed 270 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 271 version of this functionality (bzip2 only), for 2.4, was 272 supplied by Christian Ludwig) 273 274 High compression options are mostly useful for users, who 275 are low on disk space (embedded systems), but for whom ram 276 size matters less. 277 278 If in doubt, select 'gzip' 279 280config KERNEL_GZIP 281 bool "Gzip" 282 depends on HAVE_KERNEL_GZIP 283 help 284 The old and tried gzip compression. It provides a good balance 285 between compression ratio and decompression speed. 286 287config KERNEL_BZIP2 288 bool "Bzip2" 289 depends on HAVE_KERNEL_BZIP2 290 help 291 Its compression ratio and speed is intermediate. 292 Decompression speed is slowest among the choices. The kernel 293 size is about 10% smaller with bzip2, in comparison to gzip. 294 Bzip2 uses a large amount of memory. For modern kernels you 295 will need at least 8MB RAM or more for booting. 296 297config KERNEL_LZMA 298 bool "LZMA" 299 depends on HAVE_KERNEL_LZMA 300 help 301 This compression algorithm's ratio is best. Decompression speed 302 is between gzip and bzip2. Compression is slowest. 303 The kernel size is about 33% smaller with LZMA in comparison to gzip. 304 305config KERNEL_XZ 306 bool "XZ" 307 depends on HAVE_KERNEL_XZ 308 help 309 XZ uses the LZMA2 algorithm and instruction set specific 310 BCJ filters which can improve compression ratio of executable 311 code. The size of the kernel is about 30% smaller with XZ in 312 comparison to gzip. On architectures for which there is a BCJ 313 filter (i386, x86_64, ARM, ARM64, RISC-V, big endian PowerPC, 314 and SPARC), XZ will create a few percent smaller kernel than 315 plain LZMA. 316 317 The speed is about the same as with LZMA: The decompression 318 speed of XZ is better than that of bzip2 but worse than gzip 319 and LZO. Compression is slow. 320 321config KERNEL_LZO 322 bool "LZO" 323 depends on HAVE_KERNEL_LZO 324 help 325 Its compression ratio is the poorest among the choices. The kernel 326 size is about 10% bigger than gzip; however its speed 327 (both compression and decompression) is the fastest. 328 329config KERNEL_LZ4 330 bool "LZ4" 331 depends on HAVE_KERNEL_LZ4 332 help 333 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 334 A preliminary version of LZ4 de/compression tool is available at 335 <https://code.google.com/p/lz4/>. 336 337 Its compression ratio is worse than LZO. The size of the kernel 338 is about 8% bigger than LZO. But the decompression speed is 339 faster than LZO. 340 341config KERNEL_ZSTD 342 bool "ZSTD" 343 depends on HAVE_KERNEL_ZSTD 344 help 345 ZSTD is a compression algorithm targeting intermediate compression 346 with fast decompression speed. It will compress better than GZIP and 347 decompress around the same speed as LZO, but slower than LZ4. You 348 will need at least 192 KB RAM or more for booting. The zstd command 349 line tool is required for compression. 350 351config KERNEL_UNCOMPRESSED 352 bool "None" 353 depends on HAVE_KERNEL_UNCOMPRESSED 354 help 355 Produce uncompressed kernel image. This option is usually not what 356 you want. It is useful for debugging the kernel in slow simulation 357 environments, where decompressing and moving the kernel is awfully 358 slow. This option allows early boot code to skip the decompressor 359 and jump right at uncompressed kernel image. 360 361endchoice 362 363config DEFAULT_INIT 364 string "Default init path" 365 default "" 366 help 367 This option determines the default init for the system if no init= 368 option is passed on the kernel command line. If the requested path is 369 not present, we will still then move on to attempting further 370 locations (e.g. /sbin/init, etc). If this is empty, we will just use 371 the fallback list when init= is not passed. 372 373config DEFAULT_HOSTNAME 374 string "Default hostname" 375 default "(none)" 376 help 377 This option determines the default system hostname before userspace 378 calls sethostname(2). The kernel traditionally uses "(none)" here, 379 but you may wish to use a different default here to make a minimal 380 system more usable with less configuration. 381 382config SYSVIPC 383 bool "System V IPC" 384 help 385 Inter Process Communication is a suite of library functions and 386 system calls which let processes (running programs) synchronize and 387 exchange information. It is generally considered to be a good thing, 388 and some programs won't run unless you say Y here. In particular, if 389 you want to run the DOS emulator dosemu under Linux (read the 390 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 391 you'll need to say Y here. 392 393 You can find documentation about IPC with "info ipc" and also in 394 section 6.4 of the Linux Programmer's Guide, available from 395 <http://www.tldp.org/guides.html>. 396 397config SYSVIPC_SYSCTL 398 bool 399 depends on SYSVIPC 400 depends on SYSCTL 401 default y 402 403config SYSVIPC_COMPAT 404 def_bool y 405 depends on COMPAT && SYSVIPC 406 407config POSIX_MQUEUE 408 bool "POSIX Message Queues" 409 depends on NET 410 help 411 POSIX variant of message queues is a part of IPC. In POSIX message 412 queues every message has a priority which decides about succession 413 of receiving it by a process. If you want to compile and run 414 programs written e.g. for Solaris with use of its POSIX message 415 queues (functions mq_*) say Y here. 416 417 POSIX message queues are visible as a filesystem called 'mqueue' 418 and can be mounted somewhere if you want to do filesystem 419 operations on message queues. 420 421 If unsure, say Y. 422 423config POSIX_MQUEUE_SYSCTL 424 bool 425 depends on POSIX_MQUEUE 426 depends on SYSCTL 427 default y 428 429config WATCH_QUEUE 430 bool "General notification queue" 431 default n 432 help 433 434 This is a general notification queue for the kernel to pass events to 435 userspace by splicing them into pipes. It can be used in conjunction 436 with watches for key/keyring change notifications and device 437 notifications. 438 439 See Documentation/core-api/watch_queue.rst 440 441config CROSS_MEMORY_ATTACH 442 bool "Enable process_vm_readv/writev syscalls" 443 depends on MMU 444 default y 445 help 446 Enabling this option adds the system calls process_vm_readv and 447 process_vm_writev which allow a process with the correct privileges 448 to directly read from or write to another process' address space. 449 See the man page for more details. 450 451config USELIB 452 bool "uselib syscall (for libc5 and earlier)" 453 default ALPHA || M68K || SPARC 454 help 455 This option enables the uselib syscall, a system call used in the 456 dynamic linker from libc5 and earlier. glibc does not use this 457 system call. If you intend to run programs built on libc5 or 458 earlier, you may need to enable this syscall. Current systems 459 running glibc can safely disable this. 460 461config AUDIT 462 bool "Auditing support" 463 depends on NET 464 help 465 Enable auditing infrastructure that can be used with another 466 kernel subsystem, such as SELinux (which requires this for 467 logging of avc messages output). System call auditing is included 468 on architectures which support it. 469 470config HAVE_ARCH_AUDITSYSCALL 471 bool 472 473config AUDITSYSCALL 474 def_bool y 475 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 476 select FSNOTIFY 477 478source "kernel/irq/Kconfig" 479source "kernel/time/Kconfig" 480source "kernel/bpf/Kconfig" 481source "kernel/Kconfig.preempt" 482 483menu "CPU/Task time and stats accounting" 484 485config VIRT_CPU_ACCOUNTING 486 bool 487 488choice 489 prompt "Cputime accounting" 490 default TICK_CPU_ACCOUNTING 491 492# Kind of a stub config for the pure tick based cputime accounting 493config TICK_CPU_ACCOUNTING 494 bool "Simple tick based cputime accounting" 495 depends on !S390 && !NO_HZ_FULL 496 help 497 This is the basic tick based cputime accounting that maintains 498 statistics about user, system and idle time spent on per jiffies 499 granularity. 500 501 If unsure, say Y. 502 503config VIRT_CPU_ACCOUNTING_NATIVE 504 bool "Deterministic task and CPU time accounting" 505 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 506 select VIRT_CPU_ACCOUNTING 507 help 508 Select this option to enable more accurate task and CPU time 509 accounting. This is done by reading a CPU counter on each 510 kernel entry and exit and on transitions within the kernel 511 between system, softirq and hardirq state, so there is a 512 small performance impact. In the case of s390 or IBM POWER > 5, 513 this also enables accounting of stolen time on logically-partitioned 514 systems. 515 516config VIRT_CPU_ACCOUNTING_GEN 517 bool "Full dynticks CPU time accounting" 518 depends on HAVE_CONTEXT_TRACKING_USER 519 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 520 depends on GENERIC_CLOCKEVENTS 521 select VIRT_CPU_ACCOUNTING 522 select CONTEXT_TRACKING_USER 523 help 524 Select this option to enable task and CPU time accounting on full 525 dynticks systems. This accounting is implemented by watching every 526 kernel-user boundaries using the context tracking subsystem. 527 The accounting is thus performed at the expense of some significant 528 overhead. 529 530 For now this is only useful if you are working on the full 531 dynticks subsystem development. 532 533 If unsure, say N. 534 535endchoice 536 537config IRQ_TIME_ACCOUNTING 538 bool "Fine granularity task level IRQ time accounting" 539 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 540 help 541 Select this option to enable fine granularity task irq time 542 accounting. This is done by reading a timestamp on each 543 transitions between softirq and hardirq state, so there can be a 544 small performance impact. 545 546 If in doubt, say N here. 547 548config HAVE_SCHED_AVG_IRQ 549 def_bool y 550 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 551 depends on SMP 552 553config SCHED_HW_PRESSURE 554 bool 555 default y if ARM && ARM_CPU_TOPOLOGY 556 default y if ARM64 557 depends on SMP 558 depends on CPU_FREQ_THERMAL 559 help 560 Select this option to enable HW pressure accounting in the 561 scheduler. HW pressure is the value conveyed to the scheduler 562 that reflects the reduction in CPU compute capacity resulted from 563 HW throttling. HW throttling occurs when the performance of 564 a CPU is capped due to high operating temperatures as an example. 565 566 If selected, the scheduler will be able to balance tasks accordingly, 567 i.e. put less load on throttled CPUs than on non/less throttled ones. 568 569 This requires the architecture to implement 570 arch_update_hw_pressure() and arch_scale_thermal_pressure(). 571 572config BSD_PROCESS_ACCT 573 bool "BSD Process Accounting" 574 depends on MULTIUSER 575 help 576 If you say Y here, a user level program will be able to instruct the 577 kernel (via a special system call) to write process accounting 578 information to a file: whenever a process exits, information about 579 that process will be appended to the file by the kernel. The 580 information includes things such as creation time, owning user, 581 command name, memory usage, controlling terminal etc. (the complete 582 list is in the struct acct in <file:include/linux/acct.h>). It is 583 up to the user level program to do useful things with this 584 information. This is generally a good idea, so say Y. 585 586config BSD_PROCESS_ACCT_V3 587 bool "BSD Process Accounting version 3 file format" 588 depends on BSD_PROCESS_ACCT 589 default n 590 help 591 If you say Y here, the process accounting information is written 592 in a new file format that also logs the process IDs of each 593 process and its parent. Note that this file format is incompatible 594 with previous v0/v1/v2 file formats, so you will need updated tools 595 for processing it. A preliminary version of these tools is available 596 at <http://www.gnu.org/software/acct/>. 597 598config TASKSTATS 599 bool "Export task/process statistics through netlink" 600 depends on NET 601 depends on MULTIUSER 602 default n 603 help 604 Export selected statistics for tasks/processes through the 605 generic netlink interface. Unlike BSD process accounting, the 606 statistics are available during the lifetime of tasks/processes as 607 responses to commands. Like BSD accounting, they are sent to user 608 space on task exit. 609 610 Say N if unsure. 611 612config TASK_DELAY_ACCT 613 bool "Enable per-task delay accounting" 614 depends on TASKSTATS 615 select SCHED_INFO 616 help 617 Collect information on time spent by a task waiting for system 618 resources like cpu, synchronous block I/O completion and swapping 619 in pages. Such statistics can help in setting a task's priorities 620 relative to other tasks for cpu, io, rss limits etc. 621 622 Say N if unsure. 623 624config TASK_XACCT 625 bool "Enable extended accounting over taskstats" 626 depends on TASKSTATS 627 help 628 Collect extended task accounting data and send the data 629 to userland for processing over the taskstats interface. 630 631 Say N if unsure. 632 633config TASK_IO_ACCOUNTING 634 bool "Enable per-task storage I/O accounting" 635 depends on TASK_XACCT 636 help 637 Collect information on the number of bytes of storage I/O which this 638 task has caused. 639 640 Say N if unsure. 641 642config PSI 643 bool "Pressure stall information tracking" 644 select KERNFS 645 help 646 Collect metrics that indicate how overcommitted the CPU, memory, 647 and IO capacity are in the system. 648 649 If you say Y here, the kernel will create /proc/pressure/ with the 650 pressure statistics files cpu, memory, and io. These will indicate 651 the share of walltime in which some or all tasks in the system are 652 delayed due to contention of the respective resource. 653 654 In kernels with cgroup support, cgroups (cgroup2 only) will 655 have cpu.pressure, memory.pressure, and io.pressure files, 656 which aggregate pressure stalls for the grouped tasks only. 657 658 For more details see Documentation/accounting/psi.rst. 659 660 Say N if unsure. 661 662config PSI_DEFAULT_DISABLED 663 bool "Require boot parameter to enable pressure stall information tracking" 664 default n 665 depends on PSI 666 help 667 If set, pressure stall information tracking will be disabled 668 per default but can be enabled through passing psi=1 on the 669 kernel commandline during boot. 670 671 This feature adds some code to the task wakeup and sleep 672 paths of the scheduler. The overhead is too low to affect 673 common scheduling-intense workloads in practice (such as 674 webservers, memcache), but it does show up in artificial 675 scheduler stress tests, such as hackbench. 676 677 If you are paranoid and not sure what the kernel will be 678 used for, say Y. 679 680 Say N if unsure. 681 682endmenu # "CPU/Task time and stats accounting" 683 684config CPU_ISOLATION 685 bool "CPU isolation" 686 depends on SMP || COMPILE_TEST 687 default y 688 help 689 Make sure that CPUs running critical tasks are not disturbed by 690 any source of "noise" such as unbound workqueues, timers, kthreads... 691 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 692 the "isolcpus=" boot parameter. 693 694 Say Y if unsure. 695 696source "kernel/rcu/Kconfig" 697 698config IKCONFIG 699 tristate "Kernel .config support" 700 help 701 This option enables the complete Linux kernel ".config" file 702 contents to be saved in the kernel. It provides documentation 703 of which kernel options are used in a running kernel or in an 704 on-disk kernel. This information can be extracted from the kernel 705 image file with the script scripts/extract-ikconfig and used as 706 input to rebuild the current kernel or to build another kernel. 707 It can also be extracted from a running kernel by reading 708 /proc/config.gz if enabled (below). 709 710config IKCONFIG_PROC 711 bool "Enable access to .config through /proc/config.gz" 712 depends on IKCONFIG && PROC_FS 713 help 714 This option enables access to the kernel configuration file 715 through /proc/config.gz. 716 717config IKHEADERS 718 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 719 depends on SYSFS 720 help 721 This option enables access to the in-kernel headers that are generated during 722 the build process. These can be used to build eBPF tracing programs, 723 or similar programs. If you build the headers as a module, a module called 724 kheaders.ko is built which can be loaded on-demand to get access to headers. 725 726config LOG_BUF_SHIFT 727 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 728 range 12 25 729 default 17 730 depends on PRINTK 731 help 732 Select the minimal kernel log buffer size as a power of 2. 733 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 734 parameter, see below. Any higher size also might be forced 735 by "log_buf_len" boot parameter. 736 737 Examples: 738 17 => 128 KB 739 16 => 64 KB 740 15 => 32 KB 741 14 => 16 KB 742 13 => 8 KB 743 12 => 4 KB 744 745config LOG_CPU_MAX_BUF_SHIFT 746 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 747 depends on SMP 748 range 0 21 749 default 0 if BASE_SMALL 750 default 12 751 depends on PRINTK 752 help 753 This option allows to increase the default ring buffer size 754 according to the number of CPUs. The value defines the contribution 755 of each CPU as a power of 2. The used space is typically only few 756 lines however it might be much more when problems are reported, 757 e.g. backtraces. 758 759 The increased size means that a new buffer has to be allocated and 760 the original static one is unused. It makes sense only on systems 761 with more CPUs. Therefore this value is used only when the sum of 762 contributions is greater than the half of the default kernel ring 763 buffer as defined by LOG_BUF_SHIFT. The default values are set 764 so that more than 16 CPUs are needed to trigger the allocation. 765 766 Also this option is ignored when "log_buf_len" kernel parameter is 767 used as it forces an exact (power of two) size of the ring buffer. 768 769 The number of possible CPUs is used for this computation ignoring 770 hotplugging making the computation optimal for the worst case 771 scenario while allowing a simple algorithm to be used from bootup. 772 773 Examples shift values and their meaning: 774 17 => 128 KB for each CPU 775 16 => 64 KB for each CPU 776 15 => 32 KB for each CPU 777 14 => 16 KB for each CPU 778 13 => 8 KB for each CPU 779 12 => 4 KB for each CPU 780 781config PRINTK_INDEX 782 bool "Printk indexing debugfs interface" 783 depends on PRINTK && DEBUG_FS 784 help 785 Add support for indexing of all printk formats known at compile time 786 at <debugfs>/printk/index/<module>. 787 788 This can be used as part of maintaining daemons which monitor 789 /dev/kmsg, as it permits auditing the printk formats present in a 790 kernel, allowing detection of cases where monitored printks are 791 changed or no longer present. 792 793 There is no additional runtime cost to printk with this enabled. 794 795# 796# Architectures with an unreliable sched_clock() should select this: 797# 798config HAVE_UNSTABLE_SCHED_CLOCK 799 bool 800 801config GENERIC_SCHED_CLOCK 802 bool 803 804menu "Scheduler features" 805 806config UCLAMP_TASK 807 bool "Enable utilization clamping for RT/FAIR tasks" 808 depends on CPU_FREQ_GOV_SCHEDUTIL 809 help 810 This feature enables the scheduler to track the clamped utilization 811 of each CPU based on RUNNABLE tasks scheduled on that CPU. 812 813 With this option, the user can specify the min and max CPU 814 utilization allowed for RUNNABLE tasks. The max utilization defines 815 the maximum frequency a task should use while the min utilization 816 defines the minimum frequency it should use. 817 818 Both min and max utilization clamp values are hints to the scheduler, 819 aiming at improving its frequency selection policy, but they do not 820 enforce or grant any specific bandwidth for tasks. 821 822 If in doubt, say N. 823 824config UCLAMP_BUCKETS_COUNT 825 int "Number of supported utilization clamp buckets" 826 range 5 20 827 default 5 828 depends on UCLAMP_TASK 829 help 830 Defines the number of clamp buckets to use. The range of each bucket 831 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 832 number of clamp buckets the finer their granularity and the higher 833 the precision of clamping aggregation and tracking at run-time. 834 835 For example, with the minimum configuration value we will have 5 836 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 837 be refcounted in the [20..39]% bucket and will set the bucket clamp 838 effective value to 25%. 839 If a second 30% boosted task should be co-scheduled on the same CPU, 840 that task will be refcounted in the same bucket of the first task and 841 it will boost the bucket clamp effective value to 30%. 842 The clamp effective value of a bucket is reset to its nominal value 843 (20% in the example above) when there are no more tasks refcounted in 844 that bucket. 845 846 An additional boost/capping margin can be added to some tasks. In the 847 example above the 25% task will be boosted to 30% until it exits the 848 CPU. If that should be considered not acceptable on certain systems, 849 it's always possible to reduce the margin by increasing the number of 850 clamp buckets to trade off used memory for run-time tracking 851 precision. 852 853 If in doubt, use the default value. 854 855endmenu 856 857# 858# For architectures that want to enable the support for NUMA-affine scheduler 859# balancing logic: 860# 861config ARCH_SUPPORTS_NUMA_BALANCING 862 bool 863 864# 865# For architectures that prefer to flush all TLBs after a number of pages 866# are unmapped instead of sending one IPI per page to flush. The architecture 867# must provide guarantees on what happens if a clean TLB cache entry is 868# written after the unmap. Details are in mm/rmap.c near the check for 869# should_defer_flush. The architecture should also consider if the full flush 870# and the refill costs are offset by the savings of sending fewer IPIs. 871config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 872 bool 873 874config CC_HAS_INT128 875 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 876 877config CC_IMPLICIT_FALLTHROUGH 878 string 879 default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5) 880 default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough) 881 882# Currently, disable gcc-10+ array-bounds globally. 883# It's still broken in gcc-13, so no upper bound yet. 884config GCC10_NO_ARRAY_BOUNDS 885 def_bool y 886 887config CC_NO_ARRAY_BOUNDS 888 bool 889 default y if CC_IS_GCC && GCC_VERSION >= 90000 && GCC10_NO_ARRAY_BOUNDS 890 891# Currently, disable -Wstringop-overflow for GCC globally. 892config GCC_NO_STRINGOP_OVERFLOW 893 def_bool y 894 895config CC_NO_STRINGOP_OVERFLOW 896 bool 897 default y if CC_IS_GCC && GCC_NO_STRINGOP_OVERFLOW 898 899config CC_STRINGOP_OVERFLOW 900 bool 901 default y if CC_IS_GCC && !CC_NO_STRINGOP_OVERFLOW 902 903# 904# For architectures that know their GCC __int128 support is sound 905# 906config ARCH_SUPPORTS_INT128 907 bool 908 909# For architectures that (ab)use NUMA to represent different memory regions 910# all cpu-local but of different latencies, such as SuperH. 911# 912config ARCH_WANT_NUMA_VARIABLE_LOCALITY 913 bool 914 915config NUMA_BALANCING 916 bool "Memory placement aware NUMA scheduler" 917 depends on ARCH_SUPPORTS_NUMA_BALANCING 918 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 919 depends on SMP && NUMA && MIGRATION && !PREEMPT_RT 920 help 921 This option adds support for automatic NUMA aware memory/task placement. 922 The mechanism is quite primitive and is based on migrating memory when 923 it has references to the node the task is running on. 924 925 This system will be inactive on UMA systems. 926 927config NUMA_BALANCING_DEFAULT_ENABLED 928 bool "Automatically enable NUMA aware memory/task placement" 929 default y 930 depends on NUMA_BALANCING 931 help 932 If set, automatic NUMA balancing will be enabled if running on a NUMA 933 machine. 934 935config SLAB_OBJ_EXT 936 bool 937 938menuconfig CGROUPS 939 bool "Control Group support" 940 select KERNFS 941 help 942 This option adds support for grouping sets of processes together, for 943 use with process control subsystems such as Cpusets, CFS, memory 944 controls or device isolation. 945 See 946 - Documentation/scheduler/sched-design-CFS.rst (CFS) 947 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 948 and resource control) 949 950 Say N if unsure. 951 952if CGROUPS 953 954config PAGE_COUNTER 955 bool 956 957config CGROUP_FAVOR_DYNMODS 958 bool "Favor dynamic modification latency reduction by default" 959 help 960 This option enables the "favordynmods" mount option by default 961 which reduces the latencies of dynamic cgroup modifications such 962 as task migrations and controller on/offs at the cost of making 963 hot path operations such as forks and exits more expensive. 964 965 Say N if unsure. 966 967config MEMCG 968 bool "Memory controller" 969 select PAGE_COUNTER 970 select EVENTFD 971 select SLAB_OBJ_EXT 972 help 973 Provides control over the memory footprint of tasks in a cgroup. 974 975config MEMCG_V1 976 bool "Legacy cgroup v1 memory controller" 977 depends on MEMCG 978 default n 979 help 980 Legacy cgroup v1 memory controller which has been deprecated by 981 cgroup v2 implementation. The v1 is there for legacy applications 982 which haven't migrated to the new cgroup v2 interface yet. If you 983 do not have any such application then you are completely fine leaving 984 this option disabled. 985 986 Please note that feature set of the legacy memory controller is likely 987 going to shrink due to deprecation process. New deployments with v1 988 controller are highly discouraged. 989 990 San N is unsure. 991 992config BLK_CGROUP 993 bool "IO controller" 994 depends on BLOCK 995 default n 996 help 997 Generic block IO controller cgroup interface. This is the common 998 cgroup interface which should be used by various IO controlling 999 policies. 1000 1001 Currently, CFQ IO scheduler uses it to recognize task groups and 1002 control disk bandwidth allocation (proportional time slice allocation) 1003 to such task groups. It is also used by bio throttling logic in 1004 block layer to implement upper limit in IO rates on a device. 1005 1006 This option only enables generic Block IO controller infrastructure. 1007 One needs to also enable actual IO controlling logic/policy. For 1008 enabling proportional weight division of disk bandwidth in CFQ, set 1009 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 1010 CONFIG_BLK_DEV_THROTTLING=y. 1011 1012 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 1013 1014config CGROUP_WRITEBACK 1015 bool 1016 depends on MEMCG && BLK_CGROUP 1017 default y 1018 1019menuconfig CGROUP_SCHED 1020 bool "CPU controller" 1021 default n 1022 help 1023 This feature lets CPU scheduler recognize task groups and control CPU 1024 bandwidth allocation to such task groups. It uses cgroups to group 1025 tasks. 1026 1027if CGROUP_SCHED 1028config FAIR_GROUP_SCHED 1029 bool "Group scheduling for SCHED_OTHER" 1030 depends on CGROUP_SCHED 1031 default CGROUP_SCHED 1032 1033config CFS_BANDWIDTH 1034 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 1035 depends on FAIR_GROUP_SCHED 1036 default n 1037 help 1038 This option allows users to define CPU bandwidth rates (limits) for 1039 tasks running within the fair group scheduler. Groups with no limit 1040 set are considered to be unconstrained and will run with no 1041 restriction. 1042 See Documentation/scheduler/sched-bwc.rst for more information. 1043 1044config RT_GROUP_SCHED 1045 bool "Group scheduling for SCHED_RR/FIFO" 1046 depends on CGROUP_SCHED 1047 default n 1048 help 1049 This feature lets you explicitly allocate real CPU bandwidth 1050 to task groups. If enabled, it will also make it impossible to 1051 schedule realtime tasks for non-root users until you allocate 1052 realtime bandwidth for them. 1053 See Documentation/scheduler/sched-rt-group.rst for more information. 1054 1055endif #CGROUP_SCHED 1056 1057config SCHED_MM_CID 1058 def_bool y 1059 depends on SMP && RSEQ 1060 1061config UCLAMP_TASK_GROUP 1062 bool "Utilization clamping per group of tasks" 1063 depends on CGROUP_SCHED 1064 depends on UCLAMP_TASK 1065 default n 1066 help 1067 This feature enables the scheduler to track the clamped utilization 1068 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 1069 1070 When this option is enabled, the user can specify a min and max 1071 CPU bandwidth which is allowed for each single task in a group. 1072 The max bandwidth allows to clamp the maximum frequency a task 1073 can use, while the min bandwidth allows to define a minimum 1074 frequency a task will always use. 1075 1076 When task group based utilization clamping is enabled, an eventually 1077 specified task-specific clamp value is constrained by the cgroup 1078 specified clamp value. Both minimum and maximum task clamping cannot 1079 be bigger than the corresponding clamping defined at task group level. 1080 1081 If in doubt, say N. 1082 1083config CGROUP_PIDS 1084 bool "PIDs controller" 1085 help 1086 Provides enforcement of process number limits in the scope of a 1087 cgroup. Any attempt to fork more processes than is allowed in the 1088 cgroup will fail. PIDs are fundamentally a global resource because it 1089 is fairly trivial to reach PID exhaustion before you reach even a 1090 conservative kmemcg limit. As a result, it is possible to grind a 1091 system to halt without being limited by other cgroup policies. The 1092 PIDs controller is designed to stop this from happening. 1093 1094 It should be noted that organisational operations (such as attaching 1095 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 1096 since the PIDs limit only affects a process's ability to fork, not to 1097 attach to a cgroup. 1098 1099config CGROUP_RDMA 1100 bool "RDMA controller" 1101 help 1102 Provides enforcement of RDMA resources defined by IB stack. 1103 It is fairly easy for consumers to exhaust RDMA resources, which 1104 can result into resource unavailability to other consumers. 1105 RDMA controller is designed to stop this from happening. 1106 Attaching processes with active RDMA resources to the cgroup 1107 hierarchy is allowed even if can cross the hierarchy's limit. 1108 1109config CGROUP_FREEZER 1110 bool "Freezer controller" 1111 help 1112 Provides a way to freeze and unfreeze all tasks in a 1113 cgroup. 1114 1115 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1116 controller includes important in-kernel memory consumers per default. 1117 1118 If you're using cgroup2, say N. 1119 1120config CGROUP_HUGETLB 1121 bool "HugeTLB controller" 1122 depends on HUGETLB_PAGE 1123 select PAGE_COUNTER 1124 default n 1125 help 1126 Provides a cgroup controller for HugeTLB pages. 1127 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1128 The limit is enforced during page fault. Since HugeTLB doesn't 1129 support page reclaim, enforcing the limit at page fault time implies 1130 that, the application will get SIGBUS signal if it tries to access 1131 HugeTLB pages beyond its limit. This requires the application to know 1132 beforehand how much HugeTLB pages it would require for its use. The 1133 control group is tracked in the third page lru pointer. This means 1134 that we cannot use the controller with huge page less than 3 pages. 1135 1136config CPUSETS 1137 bool "Cpuset controller" 1138 depends on SMP 1139 help 1140 This option will let you create and manage CPUSETs which 1141 allow dynamically partitioning a system into sets of CPUs and 1142 Memory Nodes and assigning tasks to run only within those sets. 1143 This is primarily useful on large SMP or NUMA systems. 1144 1145 Say N if unsure. 1146 1147config PROC_PID_CPUSET 1148 bool "Include legacy /proc/<pid>/cpuset file" 1149 depends on CPUSETS 1150 default y 1151 1152config CGROUP_DEVICE 1153 bool "Device controller" 1154 help 1155 Provides a cgroup controller implementing whitelists for 1156 devices which a process in the cgroup can mknod or open. 1157 1158config CGROUP_CPUACCT 1159 bool "Simple CPU accounting controller" 1160 help 1161 Provides a simple controller for monitoring the 1162 total CPU consumed by the tasks in a cgroup. 1163 1164config CGROUP_PERF 1165 bool "Perf controller" 1166 depends on PERF_EVENTS 1167 help 1168 This option extends the perf per-cpu mode to restrict monitoring 1169 to threads which belong to the cgroup specified and run on the 1170 designated cpu. Or this can be used to have cgroup ID in samples 1171 so that it can monitor performance events among cgroups. 1172 1173 Say N if unsure. 1174 1175config CGROUP_BPF 1176 bool "Support for eBPF programs attached to cgroups" 1177 depends on BPF_SYSCALL 1178 select SOCK_CGROUP_DATA 1179 help 1180 Allow attaching eBPF programs to a cgroup using the bpf(2) 1181 syscall command BPF_PROG_ATTACH. 1182 1183 In which context these programs are accessed depends on the type 1184 of attachment. For instance, programs that are attached using 1185 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1186 inet sockets. 1187 1188config CGROUP_MISC 1189 bool "Misc resource controller" 1190 default n 1191 help 1192 Provides a controller for miscellaneous resources on a host. 1193 1194 Miscellaneous scalar resources are the resources on the host system 1195 which cannot be abstracted like the other cgroups. This controller 1196 tracks and limits the miscellaneous resources used by a process 1197 attached to a cgroup hierarchy. 1198 1199 For more information, please check misc cgroup section in 1200 /Documentation/admin-guide/cgroup-v2.rst. 1201 1202config CGROUP_DEBUG 1203 bool "Debug controller" 1204 default n 1205 depends on DEBUG_KERNEL 1206 help 1207 This option enables a simple controller that exports 1208 debugging information about the cgroups framework. This 1209 controller is for control cgroup debugging only. Its 1210 interfaces are not stable. 1211 1212 Say N. 1213 1214config SOCK_CGROUP_DATA 1215 bool 1216 default n 1217 1218endif # CGROUPS 1219 1220menuconfig NAMESPACES 1221 bool "Namespaces support" if EXPERT 1222 depends on MULTIUSER 1223 default !EXPERT 1224 help 1225 Provides the way to make tasks work with different objects using 1226 the same id. For example same IPC id may refer to different objects 1227 or same user id or pid may refer to different tasks when used in 1228 different namespaces. 1229 1230if NAMESPACES 1231 1232config UTS_NS 1233 bool "UTS namespace" 1234 default y 1235 help 1236 In this namespace tasks see different info provided with the 1237 uname() system call 1238 1239config TIME_NS 1240 bool "TIME namespace" 1241 depends on GENERIC_VDSO_TIME_NS 1242 default y 1243 help 1244 In this namespace boottime and monotonic clocks can be set. 1245 The time will keep going with the same pace. 1246 1247config IPC_NS 1248 bool "IPC namespace" 1249 depends on (SYSVIPC || POSIX_MQUEUE) 1250 default y 1251 help 1252 In this namespace tasks work with IPC ids which correspond to 1253 different IPC objects in different namespaces. 1254 1255config USER_NS 1256 bool "User namespace" 1257 default n 1258 help 1259 This allows containers, i.e. vservers, to use user namespaces 1260 to provide different user info for different servers. 1261 1262 When user namespaces are enabled in the kernel it is 1263 recommended that the MEMCG option also be enabled and that 1264 user-space use the memory control groups to limit the amount 1265 of memory a memory unprivileged users can use. 1266 1267 If unsure, say N. 1268 1269config PID_NS 1270 bool "PID Namespaces" 1271 default y 1272 help 1273 Support process id namespaces. This allows having multiple 1274 processes with the same pid as long as they are in different 1275 pid namespaces. This is a building block of containers. 1276 1277config NET_NS 1278 bool "Network namespace" 1279 depends on NET 1280 default y 1281 help 1282 Allow user space to create what appear to be multiple instances 1283 of the network stack. 1284 1285endif # NAMESPACES 1286 1287config CHECKPOINT_RESTORE 1288 bool "Checkpoint/restore support" 1289 depends on PROC_FS 1290 select PROC_CHILDREN 1291 select KCMP 1292 default n 1293 help 1294 Enables additional kernel features in a sake of checkpoint/restore. 1295 In particular it adds auxiliary prctl codes to setup process text, 1296 data and heap segment sizes, and a few additional /proc filesystem 1297 entries. 1298 1299 If unsure, say N here. 1300 1301config SCHED_AUTOGROUP 1302 bool "Automatic process group scheduling" 1303 select CGROUPS 1304 select CGROUP_SCHED 1305 select FAIR_GROUP_SCHED 1306 help 1307 This option optimizes the scheduler for common desktop workloads by 1308 automatically creating and populating task groups. This separation 1309 of workloads isolates aggressive CPU burners (like build jobs) from 1310 desktop applications. Task group autogeneration is currently based 1311 upon task session. 1312 1313config RELAY 1314 bool "Kernel->user space relay support (formerly relayfs)" 1315 select IRQ_WORK 1316 help 1317 This option enables support for relay interface support in 1318 certain file systems (such as debugfs). 1319 It is designed to provide an efficient mechanism for tools and 1320 facilities to relay large amounts of data from kernel space to 1321 user space. 1322 1323 If unsure, say N. 1324 1325config BLK_DEV_INITRD 1326 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1327 help 1328 The initial RAM filesystem is a ramfs which is loaded by the 1329 boot loader (loadlin or lilo) and that is mounted as root 1330 before the normal boot procedure. It is typically used to 1331 load modules needed to mount the "real" root file system, 1332 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1333 1334 If RAM disk support (BLK_DEV_RAM) is also included, this 1335 also enables initial RAM disk (initrd) support and adds 1336 15 Kbytes (more on some other architectures) to the kernel size. 1337 1338 If unsure say Y. 1339 1340if BLK_DEV_INITRD 1341 1342source "usr/Kconfig" 1343 1344endif 1345 1346config BOOT_CONFIG 1347 bool "Boot config support" 1348 select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED 1349 help 1350 Extra boot config allows system admin to pass a config file as 1351 complemental extension of kernel cmdline when booting. 1352 The boot config file must be attached at the end of initramfs 1353 with checksum, size and magic word. 1354 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1355 1356 If unsure, say Y. 1357 1358config BOOT_CONFIG_FORCE 1359 bool "Force unconditional bootconfig processing" 1360 depends on BOOT_CONFIG 1361 default y if BOOT_CONFIG_EMBED 1362 help 1363 With this Kconfig option set, BOOT_CONFIG processing is carried 1364 out even when the "bootconfig" kernel-boot parameter is omitted. 1365 In fact, with this Kconfig option set, there is no way to 1366 make the kernel ignore the BOOT_CONFIG-supplied kernel-boot 1367 parameters. 1368 1369 If unsure, say N. 1370 1371config BOOT_CONFIG_EMBED 1372 bool "Embed bootconfig file in the kernel" 1373 depends on BOOT_CONFIG 1374 help 1375 Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the 1376 kernel. Usually, the bootconfig file is loaded with the initrd 1377 image. But if the system doesn't support initrd, this option will 1378 help you by embedding a bootconfig file while building the kernel. 1379 1380 If unsure, say N. 1381 1382config BOOT_CONFIG_EMBED_FILE 1383 string "Embedded bootconfig file path" 1384 depends on BOOT_CONFIG_EMBED 1385 help 1386 Specify a bootconfig file which will be embedded to the kernel. 1387 This bootconfig will be used if there is no initrd or no other 1388 bootconfig in the initrd. 1389 1390config INITRAMFS_PRESERVE_MTIME 1391 bool "Preserve cpio archive mtimes in initramfs" 1392 default y 1393 help 1394 Each entry in an initramfs cpio archive carries an mtime value. When 1395 enabled, extracted cpio items take this mtime, with directory mtime 1396 setting deferred until after creation of any child entries. 1397 1398 If unsure, say Y. 1399 1400choice 1401 prompt "Compiler optimization level" 1402 default CC_OPTIMIZE_FOR_PERFORMANCE 1403 1404config CC_OPTIMIZE_FOR_PERFORMANCE 1405 bool "Optimize for performance (-O2)" 1406 help 1407 This is the default optimization level for the kernel, building 1408 with the "-O2" compiler flag for best performance and most 1409 helpful compile-time warnings. 1410 1411config CC_OPTIMIZE_FOR_SIZE 1412 bool "Optimize for size (-Os)" 1413 help 1414 Choosing this option will pass "-Os" to your compiler resulting 1415 in a smaller kernel. 1416 1417endchoice 1418 1419config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1420 bool 1421 help 1422 This requires that the arch annotates or otherwise protects 1423 its external entry points from being discarded. Linker scripts 1424 must also merge .text.*, .data.*, and .bss.* correctly into 1425 output sections. Care must be taken not to pull in unrelated 1426 sections (e.g., '.text.init'). Typically '.' in section names 1427 is used to distinguish them from label names / C identifiers. 1428 1429config LD_DEAD_CODE_DATA_ELIMINATION 1430 bool "Dead code and data elimination (EXPERIMENTAL)" 1431 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1432 depends on EXPERT 1433 depends on $(cc-option,-ffunction-sections -fdata-sections) 1434 depends on $(ld-option,--gc-sections) 1435 help 1436 Enable this if you want to do dead code and data elimination with 1437 the linker by compiling with -ffunction-sections -fdata-sections, 1438 and linking with --gc-sections. 1439 1440 This can reduce on disk and in-memory size of the kernel 1441 code and static data, particularly for small configs and 1442 on small systems. This has the possibility of introducing 1443 silently broken kernel if the required annotations are not 1444 present. This option is not well tested yet, so use at your 1445 own risk. 1446 1447config LD_ORPHAN_WARN 1448 def_bool y 1449 depends on ARCH_WANT_LD_ORPHAN_WARN 1450 depends on $(ld-option,--orphan-handling=warn) 1451 depends on $(ld-option,--orphan-handling=error) 1452 1453config LD_ORPHAN_WARN_LEVEL 1454 string 1455 depends on LD_ORPHAN_WARN 1456 default "error" if WERROR 1457 default "warn" 1458 1459config SYSCTL 1460 bool 1461 1462config HAVE_UID16 1463 bool 1464 1465config SYSCTL_EXCEPTION_TRACE 1466 bool 1467 help 1468 Enable support for /proc/sys/debug/exception-trace. 1469 1470config SYSCTL_ARCH_UNALIGN_NO_WARN 1471 bool 1472 help 1473 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1474 Allows arch to define/use @no_unaligned_warning to possibly warn 1475 about unaligned access emulation going on under the hood. 1476 1477config SYSCTL_ARCH_UNALIGN_ALLOW 1478 bool 1479 help 1480 Enable support for /proc/sys/kernel/unaligned-trap 1481 Allows arches to define/use @unaligned_enabled to runtime toggle 1482 the unaligned access emulation. 1483 see arch/parisc/kernel/unaligned.c for reference 1484 1485config HAVE_PCSPKR_PLATFORM 1486 bool 1487 1488menuconfig EXPERT 1489 bool "Configure standard kernel features (expert users)" 1490 # Unhide debug options, to make the on-by-default options visible 1491 select DEBUG_KERNEL 1492 help 1493 This option allows certain base kernel options and settings 1494 to be disabled or tweaked. This is for specialized 1495 environments which can tolerate a "non-standard" kernel. 1496 Only use this if you really know what you are doing. 1497 1498config UID16 1499 bool "Enable 16-bit UID system calls" if EXPERT 1500 depends on HAVE_UID16 && MULTIUSER 1501 default y 1502 help 1503 This enables the legacy 16-bit UID syscall wrappers. 1504 1505config MULTIUSER 1506 bool "Multiple users, groups and capabilities support" if EXPERT 1507 default y 1508 help 1509 This option enables support for non-root users, groups and 1510 capabilities. 1511 1512 If you say N here, all processes will run with UID 0, GID 0, and all 1513 possible capabilities. Saying N here also compiles out support for 1514 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1515 setgid, and capset. 1516 1517 If unsure, say Y here. 1518 1519config SGETMASK_SYSCALL 1520 bool "sgetmask/ssetmask syscalls support" if EXPERT 1521 default PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1522 help 1523 sys_sgetmask and sys_ssetmask are obsolete system calls 1524 no longer supported in libc but still enabled by default in some 1525 architectures. 1526 1527 If unsure, leave the default option here. 1528 1529config SYSFS_SYSCALL 1530 bool "Sysfs syscall support" if EXPERT 1531 default y 1532 help 1533 sys_sysfs is an obsolete system call no longer supported in libc. 1534 Note that disabling this option is more secure but might break 1535 compatibility with some systems. 1536 1537 If unsure say Y here. 1538 1539config FHANDLE 1540 bool "open by fhandle syscalls" if EXPERT 1541 select EXPORTFS 1542 default y 1543 help 1544 If you say Y here, a user level program will be able to map 1545 file names to handle and then later use the handle for 1546 different file system operations. This is useful in implementing 1547 userspace file servers, which now track files using handles instead 1548 of names. The handle would remain the same even if file names 1549 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1550 syscalls. 1551 1552config POSIX_TIMERS 1553 bool "Posix Clocks & timers" if EXPERT 1554 default y 1555 help 1556 This includes native support for POSIX timers to the kernel. 1557 Some embedded systems have no use for them and therefore they 1558 can be configured out to reduce the size of the kernel image. 1559 1560 When this option is disabled, the following syscalls won't be 1561 available: timer_create, timer_gettime: timer_getoverrun, 1562 timer_settime, timer_delete, clock_adjtime, getitimer, 1563 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1564 clock_getres and clock_nanosleep syscalls will be limited to 1565 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1566 1567 If unsure say y. 1568 1569config PRINTK 1570 default y 1571 bool "Enable support for printk" if EXPERT 1572 select IRQ_WORK 1573 help 1574 This option enables normal printk support. Removing it 1575 eliminates most of the message strings from the kernel image 1576 and makes the kernel more or less silent. As this makes it 1577 very difficult to diagnose system problems, saying N here is 1578 strongly discouraged. 1579 1580config BUG 1581 bool "BUG() support" if EXPERT 1582 default y 1583 help 1584 Disabling this option eliminates support for BUG and WARN, reducing 1585 the size of your kernel image and potentially quietly ignoring 1586 numerous fatal conditions. You should only consider disabling this 1587 option for embedded systems with no facilities for reporting errors. 1588 Just say Y. 1589 1590config ELF_CORE 1591 depends on COREDUMP 1592 default y 1593 bool "Enable ELF core dumps" if EXPERT 1594 help 1595 Enable support for generating core dumps. Disabling saves about 4k. 1596 1597 1598config PCSPKR_PLATFORM 1599 bool "Enable PC-Speaker support" if EXPERT 1600 depends on HAVE_PCSPKR_PLATFORM 1601 select I8253_LOCK 1602 default y 1603 help 1604 This option allows to disable the internal PC-Speaker 1605 support, saving some memory. 1606 1607config BASE_SMALL 1608 bool "Enable smaller-sized data structures for core" if EXPERT 1609 help 1610 Enabling this option reduces the size of miscellaneous core 1611 kernel data structures. This saves memory on small machines, 1612 but may reduce performance. 1613 1614config FUTEX 1615 bool "Enable futex support" if EXPERT 1616 depends on !(SPARC32 && SMP) 1617 default y 1618 imply RT_MUTEXES 1619 help 1620 Disabling this option will cause the kernel to be built without 1621 support for "fast userspace mutexes". The resulting kernel may not 1622 run glibc-based applications correctly. 1623 1624config FUTEX_PI 1625 bool 1626 depends on FUTEX && RT_MUTEXES 1627 default y 1628 1629config EPOLL 1630 bool "Enable eventpoll support" if EXPERT 1631 default y 1632 help 1633 Disabling this option will cause the kernel to be built without 1634 support for epoll family of system calls. 1635 1636config SIGNALFD 1637 bool "Enable signalfd() system call" if EXPERT 1638 default y 1639 help 1640 Enable the signalfd() system call that allows to receive signals 1641 on a file descriptor. 1642 1643 If unsure, say Y. 1644 1645config TIMERFD 1646 bool "Enable timerfd() system call" if EXPERT 1647 default y 1648 help 1649 Enable the timerfd() system call that allows to receive timer 1650 events on a file descriptor. 1651 1652 If unsure, say Y. 1653 1654config EVENTFD 1655 bool "Enable eventfd() system call" if EXPERT 1656 default y 1657 help 1658 Enable the eventfd() system call that allows to receive both 1659 kernel notification (ie. KAIO) or userspace notifications. 1660 1661 If unsure, say Y. 1662 1663config SHMEM 1664 bool "Use full shmem filesystem" if EXPERT 1665 default y 1666 depends on MMU 1667 help 1668 The shmem is an internal filesystem used to manage shared memory. 1669 It is backed by swap and manages resource limits. It is also exported 1670 to userspace as tmpfs if TMPFS is enabled. Disabling this 1671 option replaces shmem and tmpfs with the much simpler ramfs code, 1672 which may be appropriate on small systems without swap. 1673 1674config AIO 1675 bool "Enable AIO support" if EXPERT 1676 default y 1677 help 1678 This option enables POSIX asynchronous I/O which may by used 1679 by some high performance threaded applications. Disabling 1680 this option saves about 7k. 1681 1682config IO_URING 1683 bool "Enable IO uring support" if EXPERT 1684 select IO_WQ 1685 default y 1686 help 1687 This option enables support for the io_uring interface, enabling 1688 applications to submit and complete IO through submission and 1689 completion rings that are shared between the kernel and application. 1690 1691config ADVISE_SYSCALLS 1692 bool "Enable madvise/fadvise syscalls" if EXPERT 1693 default y 1694 help 1695 This option enables the madvise and fadvise syscalls, used by 1696 applications to advise the kernel about their future memory or file 1697 usage, improving performance. If building an embedded system where no 1698 applications use these syscalls, you can disable this option to save 1699 space. 1700 1701config MEMBARRIER 1702 bool "Enable membarrier() system call" if EXPERT 1703 default y 1704 help 1705 Enable the membarrier() system call that allows issuing memory 1706 barriers across all running threads, which can be used to distribute 1707 the cost of user-space memory barriers asymmetrically by transforming 1708 pairs of memory barriers into pairs consisting of membarrier() and a 1709 compiler barrier. 1710 1711 If unsure, say Y. 1712 1713config KCMP 1714 bool "Enable kcmp() system call" if EXPERT 1715 help 1716 Enable the kernel resource comparison system call. It provides 1717 user-space with the ability to compare two processes to see if they 1718 share a common resource, such as a file descriptor or even virtual 1719 memory space. 1720 1721 If unsure, say N. 1722 1723config RSEQ 1724 bool "Enable rseq() system call" if EXPERT 1725 default y 1726 depends on HAVE_RSEQ 1727 select MEMBARRIER 1728 help 1729 Enable the restartable sequences system call. It provides a 1730 user-space cache for the current CPU number value, which 1731 speeds up getting the current CPU number from user-space, 1732 as well as an ABI to speed up user-space operations on 1733 per-CPU data. 1734 1735 If unsure, say Y. 1736 1737config DEBUG_RSEQ 1738 default n 1739 bool "Enable debugging of rseq() system call" if EXPERT 1740 depends on RSEQ && DEBUG_KERNEL 1741 help 1742 Enable extra debugging checks for the rseq system call. 1743 1744 If unsure, say N. 1745 1746config CACHESTAT_SYSCALL 1747 bool "Enable cachestat() system call" if EXPERT 1748 default y 1749 help 1750 Enable the cachestat system call, which queries the page cache 1751 statistics of a file (number of cached pages, dirty pages, 1752 pages marked for writeback, (recently) evicted pages). 1753 1754 If unsure say Y here. 1755 1756config PC104 1757 bool "PC/104 support" if EXPERT 1758 help 1759 Expose PC/104 form factor device drivers and options available for 1760 selection and configuration. Enable this option if your target 1761 machine has a PC/104 bus. 1762 1763config KALLSYMS 1764 bool "Load all symbols for debugging/ksymoops" if EXPERT 1765 default y 1766 help 1767 Say Y here to let the kernel print out symbolic crash information and 1768 symbolic stack backtraces. This increases the size of the kernel 1769 somewhat, as all symbols have to be loaded into the kernel image. 1770 1771config KALLSYMS_SELFTEST 1772 bool "Test the basic functions and performance of kallsyms" 1773 depends on KALLSYMS 1774 default n 1775 help 1776 Test the basic functions and performance of some interfaces, such as 1777 kallsyms_lookup_name. It also calculates the compression rate of the 1778 kallsyms compression algorithm for the current symbol set. 1779 1780 Start self-test automatically after system startup. Suggest executing 1781 "dmesg | grep kallsyms_selftest" to collect test results. "finish" is 1782 displayed in the last line, indicating that the test is complete. 1783 1784config KALLSYMS_ALL 1785 bool "Include all symbols in kallsyms" 1786 depends on DEBUG_KERNEL && KALLSYMS 1787 help 1788 Normally kallsyms only contains the symbols of functions for nicer 1789 OOPS messages and backtraces (i.e., symbols from the text and inittext 1790 sections). This is sufficient for most cases. And only if you want to 1791 enable kernel live patching, or other less common use cases (e.g., 1792 when a debugger is used) all symbols are required (i.e., names of 1793 variables from the data sections, etc). 1794 1795 This option makes sure that all symbols are loaded into the kernel 1796 image (i.e., symbols from all sections) in cost of increased kernel 1797 size (depending on the kernel configuration, it may be 300KiB or 1798 something like this). 1799 1800 Say N unless you really need all symbols, or kernel live patching. 1801 1802config KALLSYMS_ABSOLUTE_PERCPU 1803 bool 1804 depends on KALLSYMS 1805 default X86_64 && SMP 1806 1807# end of the "standard kernel features (expert users)" menu 1808 1809config ARCH_HAS_MEMBARRIER_CALLBACKS 1810 bool 1811 1812config ARCH_HAS_MEMBARRIER_SYNC_CORE 1813 bool 1814 1815config HAVE_PERF_EVENTS 1816 bool 1817 help 1818 See tools/perf/design.txt for details. 1819 1820config GUEST_PERF_EVENTS 1821 bool 1822 depends on HAVE_PERF_EVENTS 1823 1824config PERF_USE_VMALLOC 1825 bool 1826 help 1827 See tools/perf/design.txt for details 1828 1829menu "Kernel Performance Events And Counters" 1830 1831config PERF_EVENTS 1832 bool "Kernel performance events and counters" 1833 default y if PROFILING 1834 depends on HAVE_PERF_EVENTS 1835 select IRQ_WORK 1836 help 1837 Enable kernel support for various performance events provided 1838 by software and hardware. 1839 1840 Software events are supported either built-in or via the 1841 use of generic tracepoints. 1842 1843 Most modern CPUs support performance events via performance 1844 counter registers. These registers count the number of certain 1845 types of hw events: such as instructions executed, cachemisses 1846 suffered, or branches mis-predicted - without slowing down the 1847 kernel or applications. These registers can also trigger interrupts 1848 when a threshold number of events have passed - and can thus be 1849 used to profile the code that runs on that CPU. 1850 1851 The Linux Performance Event subsystem provides an abstraction of 1852 these software and hardware event capabilities, available via a 1853 system call and used by the "perf" utility in tools/perf/. It 1854 provides per task and per CPU counters, and it provides event 1855 capabilities on top of those. 1856 1857 Say Y if unsure. 1858 1859config DEBUG_PERF_USE_VMALLOC 1860 default n 1861 bool "Debug: use vmalloc to back perf mmap() buffers" 1862 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1863 select PERF_USE_VMALLOC 1864 help 1865 Use vmalloc memory to back perf mmap() buffers. 1866 1867 Mostly useful for debugging the vmalloc code on platforms 1868 that don't require it. 1869 1870 Say N if unsure. 1871 1872endmenu 1873 1874config SYSTEM_DATA_VERIFICATION 1875 def_bool n 1876 select SYSTEM_TRUSTED_KEYRING 1877 select KEYS 1878 select CRYPTO 1879 select CRYPTO_RSA 1880 select ASYMMETRIC_KEY_TYPE 1881 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1882 select ASN1 1883 select OID_REGISTRY 1884 select X509_CERTIFICATE_PARSER 1885 select PKCS7_MESSAGE_PARSER 1886 help 1887 Provide PKCS#7 message verification using the contents of the system 1888 trusted keyring to provide public keys. This then can be used for 1889 module verification, kexec image verification and firmware blob 1890 verification. 1891 1892config PROFILING 1893 bool "Profiling support" 1894 help 1895 Say Y here to enable the extended profiling support mechanisms used 1896 by profilers. 1897 1898config RUST 1899 bool "Rust support" 1900 depends on HAVE_RUST 1901 depends on RUST_IS_AVAILABLE 1902 depends on !CFI_CLANG 1903 depends on !MODVERSIONS 1904 depends on !GCC_PLUGINS 1905 depends on !RANDSTRUCT 1906 depends on !SHADOW_CALL_STACK 1907 depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE 1908 help 1909 Enables Rust support in the kernel. 1910 1911 This allows other Rust-related options, like drivers written in Rust, 1912 to be selected. 1913 1914 It is also required to be able to load external kernel modules 1915 written in Rust. 1916 1917 See Documentation/rust/ for more information. 1918 1919 If unsure, say N. 1920 1921config RUSTC_VERSION_TEXT 1922 string 1923 depends on RUST 1924 default "$(shell,$(RUSTC) --version 2>/dev/null)" 1925 1926config BINDGEN_VERSION_TEXT 1927 string 1928 depends on RUST 1929 # The dummy parameter `workaround-for-0.69.0` is required to support 0.69.0 1930 # (https://github.com/rust-lang/rust-bindgen/pull/2678). It can be removed when 1931 # the minimum version is upgraded past that (0.69.1 already fixed the issue). 1932 default "$(shell,$(BINDGEN) --version workaround-for-0.69.0 2>/dev/null)" 1933 1934# 1935# Place an empty function call at each tracepoint site. Can be 1936# dynamically changed for a probe function. 1937# 1938config TRACEPOINTS 1939 bool 1940 1941source "kernel/Kconfig.kexec" 1942 1943endmenu # General setup 1944 1945source "arch/Kconfig" 1946 1947config RT_MUTEXES 1948 bool 1949 default y if PREEMPT_RT 1950 1951config MODULE_SIG_FORMAT 1952 def_bool n 1953 select SYSTEM_DATA_VERIFICATION 1954 1955source "kernel/module/Kconfig" 1956 1957config INIT_ALL_POSSIBLE 1958 bool 1959 help 1960 Back when each arch used to define their own cpu_online_mask and 1961 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 1962 with all 1s, and others with all 0s. When they were centralised, 1963 it was better to provide this option than to break all the archs 1964 and have several arch maintainers pursuing me down dark alleys. 1965 1966source "block/Kconfig" 1967 1968config PREEMPT_NOTIFIERS 1969 bool 1970 1971config PADATA 1972 depends on SMP 1973 bool 1974 1975config ASN1 1976 tristate 1977 help 1978 Build a simple ASN.1 grammar compiler that produces a bytecode output 1979 that can be interpreted by the ASN.1 stream decoder and used to 1980 inform it as to what tags are to be expected in a stream and what 1981 functions to call on what tags. 1982 1983source "kernel/Kconfig.locks" 1984 1985config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 1986 bool 1987 1988config ARCH_HAS_PREPARE_SYNC_CORE_CMD 1989 bool 1990 1991config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 1992 bool 1993 1994# It may be useful for an architecture to override the definitions of the 1995# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 1996# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 1997# different calling convention for syscalls. They can also override the 1998# macros for not-implemented syscalls in kernel/sys_ni.c and 1999# kernel/time/posix-stubs.c. All these overrides need to be available in 2000# <asm/syscall_wrapper.h>. 2001config ARCH_HAS_SYSCALL_WRAPPER 2002 def_bool n 2003