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 CC_CAN_LINK 64 bool 65 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT 66 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag)) 67 68config CC_CAN_LINK_STATIC 69 bool 70 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag) -static) if 64BIT 71 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag) -static) 72 73config CC_HAS_ASM_GOTO 74 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) 75 76config CC_HAS_ASM_GOTO_OUTPUT 77 depends on CC_HAS_ASM_GOTO 78 def_bool $(success,echo 'int foo(int x) { asm goto ("": "=r"(x) ::: bar); return x; bar: return 0; }' | $(CC) -x c - -c -o /dev/null) 79 80config CC_HAS_ASM_GOTO_TIED_OUTPUT 81 depends on CC_HAS_ASM_GOTO_OUTPUT 82 # Detect buggy gcc and clang, fixed in gcc-11 clang-14. 83 def_bool $(success,echo 'int foo(int *x) { asm goto (".long (%l[bar]) - .\n": "+m"(*x) ::: bar); return *x; bar: return 0; }' | $CC -x c - -c -o /dev/null) 84 85config TOOLS_SUPPORT_RELR 86 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 87 88config CC_HAS_ASM_INLINE 89 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 90 91config CC_HAS_NO_PROFILE_FN_ATTR 92 def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror) 93 94config PAHOLE_VERSION 95 int 96 default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE)) 97 98config CONSTRUCTORS 99 bool 100 101config IRQ_WORK 102 bool 103 104config BUILDTIME_TABLE_SORT 105 bool 106 107config THREAD_INFO_IN_TASK 108 bool 109 help 110 Select this to move thread_info off the stack into task_struct. To 111 make this work, an arch will need to remove all thread_info fields 112 except flags and fix any runtime bugs. 113 114 One subtle change that will be needed is to use try_get_task_stack() 115 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 116 117menu "General setup" 118 119config BROKEN 120 bool 121 122config BROKEN_ON_SMP 123 bool 124 depends on BROKEN || !SMP 125 default y 126 127config INIT_ENV_ARG_LIMIT 128 int 129 default 32 if !UML 130 default 128 if UML 131 help 132 Maximum of each of the number of arguments and environment 133 variables passed to init from the kernel command line. 134 135config COMPILE_TEST 136 bool "Compile also drivers which will not load" 137 depends on HAS_IOMEM 138 help 139 Some drivers can be compiled on a different platform than they are 140 intended to be run on. Despite they cannot be loaded there (or even 141 when they load they cannot be used due to missing HW support), 142 developers still, opposing to distributors, might want to build such 143 drivers to compile-test them. 144 145 If you are a developer and want to build everything available, say Y 146 here. If you are a user/distributor, say N here to exclude useless 147 drivers to be distributed. 148 149config WERROR 150 bool "Compile the kernel with warnings as errors" 151 default COMPILE_TEST 152 help 153 A kernel build should not cause any compiler warnings, and this 154 enables the '-Werror' flag to enforce that rule by default. 155 156 However, if you have a new (or very old) compiler with odd and 157 unusual warnings, or you have some architecture with problems, 158 you may need to disable this config option in order to 159 successfully build the kernel. 160 161 If in doubt, say Y. 162 163config UAPI_HEADER_TEST 164 bool "Compile test UAPI headers" 165 depends on HEADERS_INSTALL && CC_CAN_LINK 166 help 167 Compile test headers exported to user-space to ensure they are 168 self-contained, i.e. compilable as standalone units. 169 170 If you are a developer or tester and want to ensure the exported 171 headers are self-contained, say Y here. Otherwise, choose N. 172 173config LOCALVERSION 174 string "Local version - append to kernel release" 175 help 176 Append an extra string to the end of your kernel version. 177 This will show up when you type uname, for example. 178 The string you set here will be appended after the contents of 179 any files with a filename matching localversion* in your 180 object and source tree, in that order. Your total string can 181 be a maximum of 64 characters. 182 183config LOCALVERSION_AUTO 184 bool "Automatically append version information to the version string" 185 default y 186 depends on !COMPILE_TEST 187 help 188 This will try to automatically determine if the current tree is a 189 release tree by looking for git tags that belong to the current 190 top of tree revision. 191 192 A string of the format -gxxxxxxxx will be added to the localversion 193 if a git-based tree is found. The string generated by this will be 194 appended after any matching localversion* files, and after the value 195 set in CONFIG_LOCALVERSION. 196 197 (The actual string used here is the first eight characters produced 198 by running the command: 199 200 $ git rev-parse --verify HEAD 201 202 which is done within the script "scripts/setlocalversion".) 203 204config BUILD_SALT 205 string "Build ID Salt" 206 default "" 207 help 208 The build ID is used to link binaries and their debug info. Setting 209 this option will use the value in the calculation of the build id. 210 This is mostly useful for distributions which want to ensure the 211 build is unique between builds. It's safe to leave the default. 212 213config HAVE_KERNEL_GZIP 214 bool 215 216config HAVE_KERNEL_BZIP2 217 bool 218 219config HAVE_KERNEL_LZMA 220 bool 221 222config HAVE_KERNEL_XZ 223 bool 224 225config HAVE_KERNEL_LZO 226 bool 227 228config HAVE_KERNEL_LZ4 229 bool 230 231config HAVE_KERNEL_ZSTD 232 bool 233 234config HAVE_KERNEL_UNCOMPRESSED 235 bool 236 237choice 238 prompt "Kernel compression mode" 239 default KERNEL_GZIP 240 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 241 help 242 The linux kernel is a kind of self-extracting executable. 243 Several compression algorithms are available, which differ 244 in efficiency, compression and decompression speed. 245 Compression speed is only relevant when building a kernel. 246 Decompression speed is relevant at each boot. 247 248 If you have any problems with bzip2 or lzma compressed 249 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 250 version of this functionality (bzip2 only), for 2.4, was 251 supplied by Christian Ludwig) 252 253 High compression options are mostly useful for users, who 254 are low on disk space (embedded systems), but for whom ram 255 size matters less. 256 257 If in doubt, select 'gzip' 258 259config KERNEL_GZIP 260 bool "Gzip" 261 depends on HAVE_KERNEL_GZIP 262 help 263 The old and tried gzip compression. It provides a good balance 264 between compression ratio and decompression speed. 265 266config KERNEL_BZIP2 267 bool "Bzip2" 268 depends on HAVE_KERNEL_BZIP2 269 help 270 Its compression ratio and speed is intermediate. 271 Decompression speed is slowest among the choices. The kernel 272 size is about 10% smaller with bzip2, in comparison to gzip. 273 Bzip2 uses a large amount of memory. For modern kernels you 274 will need at least 8MB RAM or more for booting. 275 276config KERNEL_LZMA 277 bool "LZMA" 278 depends on HAVE_KERNEL_LZMA 279 help 280 This compression algorithm's ratio is best. Decompression speed 281 is between gzip and bzip2. Compression is slowest. 282 The kernel size is about 33% smaller with LZMA in comparison to gzip. 283 284config KERNEL_XZ 285 bool "XZ" 286 depends on HAVE_KERNEL_XZ 287 help 288 XZ uses the LZMA2 algorithm and instruction set specific 289 BCJ filters which can improve compression ratio of executable 290 code. The size of the kernel is about 30% smaller with XZ in 291 comparison to gzip. On architectures for which there is a BCJ 292 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 293 will create a few percent smaller kernel than plain LZMA. 294 295 The speed is about the same as with LZMA: The decompression 296 speed of XZ is better than that of bzip2 but worse than gzip 297 and LZO. Compression is slow. 298 299config KERNEL_LZO 300 bool "LZO" 301 depends on HAVE_KERNEL_LZO 302 help 303 Its compression ratio is the poorest among the choices. The kernel 304 size is about 10% bigger than gzip; however its speed 305 (both compression and decompression) is the fastest. 306 307config KERNEL_LZ4 308 bool "LZ4" 309 depends on HAVE_KERNEL_LZ4 310 help 311 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 312 A preliminary version of LZ4 de/compression tool is available at 313 <https://code.google.com/p/lz4/>. 314 315 Its compression ratio is worse than LZO. The size of the kernel 316 is about 8% bigger than LZO. But the decompression speed is 317 faster than LZO. 318 319config KERNEL_ZSTD 320 bool "ZSTD" 321 depends on HAVE_KERNEL_ZSTD 322 help 323 ZSTD is a compression algorithm targeting intermediate compression 324 with fast decompression speed. It will compress better than GZIP and 325 decompress around the same speed as LZO, but slower than LZ4. You 326 will need at least 192 KB RAM or more for booting. The zstd command 327 line tool is required for compression. 328 329config KERNEL_UNCOMPRESSED 330 bool "None" 331 depends on HAVE_KERNEL_UNCOMPRESSED 332 help 333 Produce uncompressed kernel image. This option is usually not what 334 you want. It is useful for debugging the kernel in slow simulation 335 environments, where decompressing and moving the kernel is awfully 336 slow. This option allows early boot code to skip the decompressor 337 and jump right at uncompressed kernel image. 338 339endchoice 340 341config DEFAULT_INIT 342 string "Default init path" 343 default "" 344 help 345 This option determines the default init for the system if no init= 346 option is passed on the kernel command line. If the requested path is 347 not present, we will still then move on to attempting further 348 locations (e.g. /sbin/init, etc). If this is empty, we will just use 349 the fallback list when init= is not passed. 350 351config DEFAULT_HOSTNAME 352 string "Default hostname" 353 default "(none)" 354 help 355 This option determines the default system hostname before userspace 356 calls sethostname(2). The kernel traditionally uses "(none)" here, 357 but you may wish to use a different default here to make a minimal 358 system more usable with less configuration. 359 360config SYSVIPC 361 bool "System V IPC" 362 help 363 Inter Process Communication is a suite of library functions and 364 system calls which let processes (running programs) synchronize and 365 exchange information. It is generally considered to be a good thing, 366 and some programs won't run unless you say Y here. In particular, if 367 you want to run the DOS emulator dosemu under Linux (read the 368 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 369 you'll need to say Y here. 370 371 You can find documentation about IPC with "info ipc" and also in 372 section 6.4 of the Linux Programmer's Guide, available from 373 <http://www.tldp.org/guides.html>. 374 375config SYSVIPC_SYSCTL 376 bool 377 depends on SYSVIPC 378 depends on SYSCTL 379 default y 380 381config SYSVIPC_COMPAT 382 def_bool y 383 depends on COMPAT && SYSVIPC 384 385config POSIX_MQUEUE 386 bool "POSIX Message Queues" 387 depends on NET 388 help 389 POSIX variant of message queues is a part of IPC. In POSIX message 390 queues every message has a priority which decides about succession 391 of receiving it by a process. If you want to compile and run 392 programs written e.g. for Solaris with use of its POSIX message 393 queues (functions mq_*) say Y here. 394 395 POSIX message queues are visible as a filesystem called 'mqueue' 396 and can be mounted somewhere if you want to do filesystem 397 operations on message queues. 398 399 If unsure, say Y. 400 401config POSIX_MQUEUE_SYSCTL 402 bool 403 depends on POSIX_MQUEUE 404 depends on SYSCTL 405 default y 406 407config WATCH_QUEUE 408 bool "General notification queue" 409 default n 410 help 411 412 This is a general notification queue for the kernel to pass events to 413 userspace by splicing them into pipes. It can be used in conjunction 414 with watches for key/keyring change notifications and device 415 notifications. 416 417 See Documentation/core-api/watch_queue.rst 418 419config CROSS_MEMORY_ATTACH 420 bool "Enable process_vm_readv/writev syscalls" 421 depends on MMU 422 default y 423 help 424 Enabling this option adds the system calls process_vm_readv and 425 process_vm_writev which allow a process with the correct privileges 426 to directly read from or write to another process' address space. 427 See the man page for more details. 428 429config USELIB 430 bool "uselib syscall (for libc5 and earlier)" 431 default ALPHA || M68K || SPARC 432 help 433 This option enables the uselib syscall, a system call used in the 434 dynamic linker from libc5 and earlier. glibc does not use this 435 system call. If you intend to run programs built on libc5 or 436 earlier, you may need to enable this syscall. Current systems 437 running glibc can safely disable this. 438 439config AUDIT 440 bool "Auditing support" 441 depends on NET 442 help 443 Enable auditing infrastructure that can be used with another 444 kernel subsystem, such as SELinux (which requires this for 445 logging of avc messages output). System call auditing is included 446 on architectures which support it. 447 448config HAVE_ARCH_AUDITSYSCALL 449 bool 450 451config AUDITSYSCALL 452 def_bool y 453 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 454 select FSNOTIFY 455 456source "kernel/irq/Kconfig" 457source "kernel/time/Kconfig" 458source "kernel/bpf/Kconfig" 459source "kernel/Kconfig.preempt" 460 461menu "CPU/Task time and stats accounting" 462 463config VIRT_CPU_ACCOUNTING 464 bool 465 466choice 467 prompt "Cputime accounting" 468 default TICK_CPU_ACCOUNTING if !PPC64 469 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 470 471# Kind of a stub config for the pure tick based cputime accounting 472config TICK_CPU_ACCOUNTING 473 bool "Simple tick based cputime accounting" 474 depends on !S390 && !NO_HZ_FULL 475 help 476 This is the basic tick based cputime accounting that maintains 477 statistics about user, system and idle time spent on per jiffies 478 granularity. 479 480 If unsure, say Y. 481 482config VIRT_CPU_ACCOUNTING_NATIVE 483 bool "Deterministic task and CPU time accounting" 484 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 485 select VIRT_CPU_ACCOUNTING 486 help 487 Select this option to enable more accurate task and CPU time 488 accounting. This is done by reading a CPU counter on each 489 kernel entry and exit and on transitions within the kernel 490 between system, softirq and hardirq state, so there is a 491 small performance impact. In the case of s390 or IBM POWER > 5, 492 this also enables accounting of stolen time on logically-partitioned 493 systems. 494 495config VIRT_CPU_ACCOUNTING_GEN 496 bool "Full dynticks CPU time accounting" 497 depends on HAVE_CONTEXT_TRACKING_USER 498 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 499 depends on GENERIC_CLOCKEVENTS 500 select VIRT_CPU_ACCOUNTING 501 select CONTEXT_TRACKING_USER 502 help 503 Select this option to enable task and CPU time accounting on full 504 dynticks systems. This accounting is implemented by watching every 505 kernel-user boundaries using the context tracking subsystem. 506 The accounting is thus performed at the expense of some significant 507 overhead. 508 509 For now this is only useful if you are working on the full 510 dynticks subsystem development. 511 512 If unsure, say N. 513 514endchoice 515 516config IRQ_TIME_ACCOUNTING 517 bool "Fine granularity task level IRQ time accounting" 518 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 519 help 520 Select this option to enable fine granularity task irq time 521 accounting. This is done by reading a timestamp on each 522 transitions between softirq and hardirq state, so there can be a 523 small performance impact. 524 525 If in doubt, say N here. 526 527config HAVE_SCHED_AVG_IRQ 528 def_bool y 529 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 530 depends on SMP 531 532config SCHED_THERMAL_PRESSURE 533 bool 534 default y if ARM && ARM_CPU_TOPOLOGY 535 default y if ARM64 536 depends on SMP 537 depends on CPU_FREQ_THERMAL 538 help 539 Select this option to enable thermal pressure accounting in the 540 scheduler. Thermal pressure is the value conveyed to the scheduler 541 that reflects the reduction in CPU compute capacity resulted from 542 thermal throttling. Thermal throttling occurs when the performance of 543 a CPU is capped due to high operating temperatures. 544 545 If selected, the scheduler will be able to balance tasks accordingly, 546 i.e. put less load on throttled CPUs than on non/less throttled ones. 547 548 This requires the architecture to implement 549 arch_update_thermal_pressure() and arch_scale_thermal_pressure(). 550 551config BSD_PROCESS_ACCT 552 bool "BSD Process Accounting" 553 depends on MULTIUSER 554 help 555 If you say Y here, a user level program will be able to instruct the 556 kernel (via a special system call) to write process accounting 557 information to a file: whenever a process exits, information about 558 that process will be appended to the file by the kernel. The 559 information includes things such as creation time, owning user, 560 command name, memory usage, controlling terminal etc. (the complete 561 list is in the struct acct in <file:include/linux/acct.h>). It is 562 up to the user level program to do useful things with this 563 information. This is generally a good idea, so say Y. 564 565config BSD_PROCESS_ACCT_V3 566 bool "BSD Process Accounting version 3 file format" 567 depends on BSD_PROCESS_ACCT 568 default n 569 help 570 If you say Y here, the process accounting information is written 571 in a new file format that also logs the process IDs of each 572 process and its parent. Note that this file format is incompatible 573 with previous v0/v1/v2 file formats, so you will need updated tools 574 for processing it. A preliminary version of these tools is available 575 at <http://www.gnu.org/software/acct/>. 576 577config TASKSTATS 578 bool "Export task/process statistics through netlink" 579 depends on NET 580 depends on MULTIUSER 581 default n 582 help 583 Export selected statistics for tasks/processes through the 584 generic netlink interface. Unlike BSD process accounting, the 585 statistics are available during the lifetime of tasks/processes as 586 responses to commands. Like BSD accounting, they are sent to user 587 space on task exit. 588 589 Say N if unsure. 590 591config TASK_DELAY_ACCT 592 bool "Enable per-task delay accounting" 593 depends on TASKSTATS 594 select SCHED_INFO 595 help 596 Collect information on time spent by a task waiting for system 597 resources like cpu, synchronous block I/O completion and swapping 598 in pages. Such statistics can help in setting a task's priorities 599 relative to other tasks for cpu, io, rss limits etc. 600 601 Say N if unsure. 602 603config TASK_XACCT 604 bool "Enable extended accounting over taskstats" 605 depends on TASKSTATS 606 help 607 Collect extended task accounting data and send the data 608 to userland for processing over the taskstats interface. 609 610 Say N if unsure. 611 612config TASK_IO_ACCOUNTING 613 bool "Enable per-task storage I/O accounting" 614 depends on TASK_XACCT 615 help 616 Collect information on the number of bytes of storage I/O which this 617 task has caused. 618 619 Say N if unsure. 620 621config PSI 622 bool "Pressure stall information tracking" 623 help 624 Collect metrics that indicate how overcommitted the CPU, memory, 625 and IO capacity are in the system. 626 627 If you say Y here, the kernel will create /proc/pressure/ with the 628 pressure statistics files cpu, memory, and io. These will indicate 629 the share of walltime in which some or all tasks in the system are 630 delayed due to contention of the respective resource. 631 632 In kernels with cgroup support, cgroups (cgroup2 only) will 633 have cpu.pressure, memory.pressure, and io.pressure files, 634 which aggregate pressure stalls for the grouped tasks only. 635 636 For more details see Documentation/accounting/psi.rst. 637 638 Say N if unsure. 639 640config PSI_DEFAULT_DISABLED 641 bool "Require boot parameter to enable pressure stall information tracking" 642 default n 643 depends on PSI 644 help 645 If set, pressure stall information tracking will be disabled 646 per default but can be enabled through passing psi=1 on the 647 kernel commandline during boot. 648 649 This feature adds some code to the task wakeup and sleep 650 paths of the scheduler. The overhead is too low to affect 651 common scheduling-intense workloads in practice (such as 652 webservers, memcache), but it does show up in artificial 653 scheduler stress tests, such as hackbench. 654 655 If you are paranoid and not sure what the kernel will be 656 used for, say Y. 657 658 Say N if unsure. 659 660endmenu # "CPU/Task time and stats accounting" 661 662config CPU_ISOLATION 663 bool "CPU isolation" 664 depends on SMP || COMPILE_TEST 665 default y 666 help 667 Make sure that CPUs running critical tasks are not disturbed by 668 any source of "noise" such as unbound workqueues, timers, kthreads... 669 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 670 the "isolcpus=" boot parameter. 671 672 Say Y if unsure. 673 674source "kernel/rcu/Kconfig" 675 676config BUILD_BIN2C 677 bool 678 default n 679 680config IKCONFIG 681 tristate "Kernel .config support" 682 help 683 This option enables the complete Linux kernel ".config" file 684 contents to be saved in the kernel. It provides documentation 685 of which kernel options are used in a running kernel or in an 686 on-disk kernel. This information can be extracted from the kernel 687 image file with the script scripts/extract-ikconfig and used as 688 input to rebuild the current kernel or to build another kernel. 689 It can also be extracted from a running kernel by reading 690 /proc/config.gz if enabled (below). 691 692config IKCONFIG_PROC 693 bool "Enable access to .config through /proc/config.gz" 694 depends on IKCONFIG && PROC_FS 695 help 696 This option enables access to the kernel configuration file 697 through /proc/config.gz. 698 699config IKHEADERS 700 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 701 depends on SYSFS 702 help 703 This option enables access to the in-kernel headers that are generated during 704 the build process. These can be used to build eBPF tracing programs, 705 or similar programs. If you build the headers as a module, a module called 706 kheaders.ko is built which can be loaded on-demand to get access to headers. 707 708config LOG_BUF_SHIFT 709 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 710 range 12 25 711 default 17 712 depends on PRINTK 713 help 714 Select the minimal kernel log buffer size as a power of 2. 715 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 716 parameter, see below. Any higher size also might be forced 717 by "log_buf_len" boot parameter. 718 719 Examples: 720 17 => 128 KB 721 16 => 64 KB 722 15 => 32 KB 723 14 => 16 KB 724 13 => 8 KB 725 12 => 4 KB 726 727config LOG_CPU_MAX_BUF_SHIFT 728 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 729 depends on SMP 730 range 0 21 731 default 12 if !BASE_SMALL 732 default 0 if BASE_SMALL 733 depends on PRINTK 734 help 735 This option allows to increase the default ring buffer size 736 according to the number of CPUs. The value defines the contribution 737 of each CPU as a power of 2. The used space is typically only few 738 lines however it might be much more when problems are reported, 739 e.g. backtraces. 740 741 The increased size means that a new buffer has to be allocated and 742 the original static one is unused. It makes sense only on systems 743 with more CPUs. Therefore this value is used only when the sum of 744 contributions is greater than the half of the default kernel ring 745 buffer as defined by LOG_BUF_SHIFT. The default values are set 746 so that more than 16 CPUs are needed to trigger the allocation. 747 748 Also this option is ignored when "log_buf_len" kernel parameter is 749 used as it forces an exact (power of two) size of the ring buffer. 750 751 The number of possible CPUs is used for this computation ignoring 752 hotplugging making the computation optimal for the worst case 753 scenario while allowing a simple algorithm to be used from bootup. 754 755 Examples shift values and their meaning: 756 17 => 128 KB for each CPU 757 16 => 64 KB for each CPU 758 15 => 32 KB for each CPU 759 14 => 16 KB for each CPU 760 13 => 8 KB for each CPU 761 12 => 4 KB for each CPU 762 763config PRINTK_SAFE_LOG_BUF_SHIFT 764 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 765 range 10 21 766 default 13 767 depends on PRINTK 768 help 769 Select the size of an alternate printk per-CPU buffer where messages 770 printed from usafe contexts are temporary stored. One example would 771 be NMI messages, another one - printk recursion. The messages are 772 copied to the main log buffer in a safe context to avoid a deadlock. 773 The value defines the size as a power of 2. 774 775 Those messages are rare and limited. The largest one is when 776 a backtrace is printed. It usually fits into 4KB. Select 777 8KB if you want to be on the safe side. 778 779 Examples: 780 17 => 128 KB for each CPU 781 16 => 64 KB for each CPU 782 15 => 32 KB for each CPU 783 14 => 16 KB for each CPU 784 13 => 8 KB for each CPU 785 12 => 4 KB for each CPU 786 787config PRINTK_INDEX 788 bool "Printk indexing debugfs interface" 789 depends on PRINTK && DEBUG_FS 790 help 791 Add support for indexing of all printk formats known at compile time 792 at <debugfs>/printk/index/<module>. 793 794 This can be used as part of maintaining daemons which monitor 795 /dev/kmsg, as it permits auditing the printk formats present in a 796 kernel, allowing detection of cases where monitored printks are 797 changed or no longer present. 798 799 There is no additional runtime cost to printk with this enabled. 800 801# 802# Architectures with an unreliable sched_clock() should select this: 803# 804config HAVE_UNSTABLE_SCHED_CLOCK 805 bool 806 807config GENERIC_SCHED_CLOCK 808 bool 809 810menu "Scheduler features" 811 812config UCLAMP_TASK 813 bool "Enable utilization clamping for RT/FAIR tasks" 814 depends on CPU_FREQ_GOV_SCHEDUTIL 815 help 816 This feature enables the scheduler to track the clamped utilization 817 of each CPU based on RUNNABLE tasks scheduled on that CPU. 818 819 With this option, the user can specify the min and max CPU 820 utilization allowed for RUNNABLE tasks. The max utilization defines 821 the maximum frequency a task should use while the min utilization 822 defines the minimum frequency it should use. 823 824 Both min and max utilization clamp values are hints to the scheduler, 825 aiming at improving its frequency selection policy, but they do not 826 enforce or grant any specific bandwidth for tasks. 827 828 If in doubt, say N. 829 830config UCLAMP_BUCKETS_COUNT 831 int "Number of supported utilization clamp buckets" 832 range 5 20 833 default 5 834 depends on UCLAMP_TASK 835 help 836 Defines the number of clamp buckets to use. The range of each bucket 837 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 838 number of clamp buckets the finer their granularity and the higher 839 the precision of clamping aggregation and tracking at run-time. 840 841 For example, with the minimum configuration value we will have 5 842 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 843 be refcounted in the [20..39]% bucket and will set the bucket clamp 844 effective value to 25%. 845 If a second 30% boosted task should be co-scheduled on the same CPU, 846 that task will be refcounted in the same bucket of the first task and 847 it will boost the bucket clamp effective value to 30%. 848 The clamp effective value of a bucket is reset to its nominal value 849 (20% in the example above) when there are no more tasks refcounted in 850 that bucket. 851 852 An additional boost/capping margin can be added to some tasks. In the 853 example above the 25% task will be boosted to 30% until it exits the 854 CPU. If that should be considered not acceptable on certain systems, 855 it's always possible to reduce the margin by increasing the number of 856 clamp buckets to trade off used memory for run-time tracking 857 precision. 858 859 If in doubt, use the default value. 860 861endmenu 862 863# 864# For architectures that want to enable the support for NUMA-affine scheduler 865# balancing logic: 866# 867config ARCH_SUPPORTS_NUMA_BALANCING 868 bool 869 870# 871# For architectures that prefer to flush all TLBs after a number of pages 872# are unmapped instead of sending one IPI per page to flush. The architecture 873# must provide guarantees on what happens if a clean TLB cache entry is 874# written after the unmap. Details are in mm/rmap.c near the check for 875# should_defer_flush. The architecture should also consider if the full flush 876# and the refill costs are offset by the savings of sending fewer IPIs. 877config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 878 bool 879 880config CC_HAS_INT128 881 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 882 883config CC_IMPLICIT_FALLTHROUGH 884 string 885 default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5) 886 default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough) 887 888# Currently, disable gcc-12 array-bounds globally. 889# We may want to target only particular configurations some day. 890config GCC12_NO_ARRAY_BOUNDS 891 def_bool y 892 893config CC_NO_ARRAY_BOUNDS 894 bool 895 default y if CC_IS_GCC && GCC_VERSION >= 120000 && GCC_VERSION < 130000 && GCC12_NO_ARRAY_BOUNDS 896 897# 898# For architectures that know their GCC __int128 support is sound 899# 900config ARCH_SUPPORTS_INT128 901 bool 902 903# For architectures that (ab)use NUMA to represent different memory regions 904# all cpu-local but of different latencies, such as SuperH. 905# 906config ARCH_WANT_NUMA_VARIABLE_LOCALITY 907 bool 908 909config NUMA_BALANCING 910 bool "Memory placement aware NUMA scheduler" 911 depends on ARCH_SUPPORTS_NUMA_BALANCING 912 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 913 depends on SMP && NUMA && MIGRATION && !PREEMPT_RT 914 help 915 This option adds support for automatic NUMA aware memory/task placement. 916 The mechanism is quite primitive and is based on migrating memory when 917 it has references to the node the task is running on. 918 919 This system will be inactive on UMA systems. 920 921config NUMA_BALANCING_DEFAULT_ENABLED 922 bool "Automatically enable NUMA aware memory/task placement" 923 default y 924 depends on NUMA_BALANCING 925 help 926 If set, automatic NUMA balancing will be enabled if running on a NUMA 927 machine. 928 929menuconfig CGROUPS 930 bool "Control Group support" 931 select KERNFS 932 help 933 This option adds support for grouping sets of processes together, for 934 use with process control subsystems such as Cpusets, CFS, memory 935 controls or device isolation. 936 See 937 - Documentation/scheduler/sched-design-CFS.rst (CFS) 938 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 939 and resource control) 940 941 Say N if unsure. 942 943if CGROUPS 944 945config PAGE_COUNTER 946 bool 947 948config CGROUP_FAVOR_DYNMODS 949 bool "Favor dynamic modification latency reduction by default" 950 help 951 This option enables the "favordynmods" mount option by default 952 which reduces the latencies of dynamic cgroup modifications such 953 as task migrations and controller on/offs at the cost of making 954 hot path operations such as forks and exits more expensive. 955 956 Say N if unsure. 957 958config MEMCG 959 bool "Memory controller" 960 select PAGE_COUNTER 961 select EVENTFD 962 help 963 Provides control over the memory footprint of tasks in a cgroup. 964 965config MEMCG_SWAP 966 bool 967 depends on MEMCG && SWAP 968 default y 969 970config MEMCG_KMEM 971 bool 972 depends on MEMCG && !SLOB 973 default y 974 975config BLK_CGROUP 976 bool "IO controller" 977 depends on BLOCK 978 default n 979 help 980 Generic block IO controller cgroup interface. This is the common 981 cgroup interface which should be used by various IO controlling 982 policies. 983 984 Currently, CFQ IO scheduler uses it to recognize task groups and 985 control disk bandwidth allocation (proportional time slice allocation) 986 to such task groups. It is also used by bio throttling logic in 987 block layer to implement upper limit in IO rates on a device. 988 989 This option only enables generic Block IO controller infrastructure. 990 One needs to also enable actual IO controlling logic/policy. For 991 enabling proportional weight division of disk bandwidth in CFQ, set 992 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 993 CONFIG_BLK_DEV_THROTTLING=y. 994 995 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 996 997config CGROUP_WRITEBACK 998 bool 999 depends on MEMCG && BLK_CGROUP 1000 default y 1001 1002menuconfig CGROUP_SCHED 1003 bool "CPU controller" 1004 default n 1005 help 1006 This feature lets CPU scheduler recognize task groups and control CPU 1007 bandwidth allocation to such task groups. It uses cgroups to group 1008 tasks. 1009 1010if CGROUP_SCHED 1011config FAIR_GROUP_SCHED 1012 bool "Group scheduling for SCHED_OTHER" 1013 depends on CGROUP_SCHED 1014 default CGROUP_SCHED 1015 1016config CFS_BANDWIDTH 1017 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 1018 depends on FAIR_GROUP_SCHED 1019 default n 1020 help 1021 This option allows users to define CPU bandwidth rates (limits) for 1022 tasks running within the fair group scheduler. Groups with no limit 1023 set are considered to be unconstrained and will run with no 1024 restriction. 1025 See Documentation/scheduler/sched-bwc.rst for more information. 1026 1027config RT_GROUP_SCHED 1028 bool "Group scheduling for SCHED_RR/FIFO" 1029 depends on CGROUP_SCHED 1030 default n 1031 help 1032 This feature lets you explicitly allocate real CPU bandwidth 1033 to task groups. If enabled, it will also make it impossible to 1034 schedule realtime tasks for non-root users until you allocate 1035 realtime bandwidth for them. 1036 See Documentation/scheduler/sched-rt-group.rst for more information. 1037 1038endif #CGROUP_SCHED 1039 1040config UCLAMP_TASK_GROUP 1041 bool "Utilization clamping per group of tasks" 1042 depends on CGROUP_SCHED 1043 depends on UCLAMP_TASK 1044 default n 1045 help 1046 This feature enables the scheduler to track the clamped utilization 1047 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 1048 1049 When this option is enabled, the user can specify a min and max 1050 CPU bandwidth which is allowed for each single task in a group. 1051 The max bandwidth allows to clamp the maximum frequency a task 1052 can use, while the min bandwidth allows to define a minimum 1053 frequency a task will always use. 1054 1055 When task group based utilization clamping is enabled, an eventually 1056 specified task-specific clamp value is constrained by the cgroup 1057 specified clamp value. Both minimum and maximum task clamping cannot 1058 be bigger than the corresponding clamping defined at task group level. 1059 1060 If in doubt, say N. 1061 1062config CGROUP_PIDS 1063 bool "PIDs controller" 1064 help 1065 Provides enforcement of process number limits in the scope of a 1066 cgroup. Any attempt to fork more processes than is allowed in the 1067 cgroup will fail. PIDs are fundamentally a global resource because it 1068 is fairly trivial to reach PID exhaustion before you reach even a 1069 conservative kmemcg limit. As a result, it is possible to grind a 1070 system to halt without being limited by other cgroup policies. The 1071 PIDs controller is designed to stop this from happening. 1072 1073 It should be noted that organisational operations (such as attaching 1074 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 1075 since the PIDs limit only affects a process's ability to fork, not to 1076 attach to a cgroup. 1077 1078config CGROUP_RDMA 1079 bool "RDMA controller" 1080 help 1081 Provides enforcement of RDMA resources defined by IB stack. 1082 It is fairly easy for consumers to exhaust RDMA resources, which 1083 can result into resource unavailability to other consumers. 1084 RDMA controller is designed to stop this from happening. 1085 Attaching processes with active RDMA resources to the cgroup 1086 hierarchy is allowed even if can cross the hierarchy's limit. 1087 1088config CGROUP_FREEZER 1089 bool "Freezer controller" 1090 help 1091 Provides a way to freeze and unfreeze all tasks in a 1092 cgroup. 1093 1094 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1095 controller includes important in-kernel memory consumers per default. 1096 1097 If you're using cgroup2, say N. 1098 1099config CGROUP_HUGETLB 1100 bool "HugeTLB controller" 1101 depends on HUGETLB_PAGE 1102 select PAGE_COUNTER 1103 default n 1104 help 1105 Provides a cgroup controller for HugeTLB pages. 1106 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1107 The limit is enforced during page fault. Since HugeTLB doesn't 1108 support page reclaim, enforcing the limit at page fault time implies 1109 that, the application will get SIGBUS signal if it tries to access 1110 HugeTLB pages beyond its limit. This requires the application to know 1111 beforehand how much HugeTLB pages it would require for its use. The 1112 control group is tracked in the third page lru pointer. This means 1113 that we cannot use the controller with huge page less than 3 pages. 1114 1115config CPUSETS 1116 bool "Cpuset controller" 1117 depends on SMP 1118 help 1119 This option will let you create and manage CPUSETs which 1120 allow dynamically partitioning a system into sets of CPUs and 1121 Memory Nodes and assigning tasks to run only within those sets. 1122 This is primarily useful on large SMP or NUMA systems. 1123 1124 Say N if unsure. 1125 1126config PROC_PID_CPUSET 1127 bool "Include legacy /proc/<pid>/cpuset file" 1128 depends on CPUSETS 1129 default y 1130 1131config CGROUP_DEVICE 1132 bool "Device controller" 1133 help 1134 Provides a cgroup controller implementing whitelists for 1135 devices which a process in the cgroup can mknod or open. 1136 1137config CGROUP_CPUACCT 1138 bool "Simple CPU accounting controller" 1139 help 1140 Provides a simple controller for monitoring the 1141 total CPU consumed by the tasks in a cgroup. 1142 1143config CGROUP_PERF 1144 bool "Perf controller" 1145 depends on PERF_EVENTS 1146 help 1147 This option extends the perf per-cpu mode to restrict monitoring 1148 to threads which belong to the cgroup specified and run on the 1149 designated cpu. Or this can be used to have cgroup ID in samples 1150 so that it can monitor performance events among cgroups. 1151 1152 Say N if unsure. 1153 1154config CGROUP_BPF 1155 bool "Support for eBPF programs attached to cgroups" 1156 depends on BPF_SYSCALL 1157 select SOCK_CGROUP_DATA 1158 help 1159 Allow attaching eBPF programs to a cgroup using the bpf(2) 1160 syscall command BPF_PROG_ATTACH. 1161 1162 In which context these programs are accessed depends on the type 1163 of attachment. For instance, programs that are attached using 1164 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1165 inet sockets. 1166 1167config CGROUP_MISC 1168 bool "Misc resource controller" 1169 default n 1170 help 1171 Provides a controller for miscellaneous resources on a host. 1172 1173 Miscellaneous scalar resources are the resources on the host system 1174 which cannot be abstracted like the other cgroups. This controller 1175 tracks and limits the miscellaneous resources used by a process 1176 attached to a cgroup hierarchy. 1177 1178 For more information, please check misc cgroup section in 1179 /Documentation/admin-guide/cgroup-v2.rst. 1180 1181config CGROUP_DEBUG 1182 bool "Debug controller" 1183 default n 1184 depends on DEBUG_KERNEL 1185 help 1186 This option enables a simple controller that exports 1187 debugging information about the cgroups framework. This 1188 controller is for control cgroup debugging only. Its 1189 interfaces are not stable. 1190 1191 Say N. 1192 1193config SOCK_CGROUP_DATA 1194 bool 1195 default n 1196 1197endif # CGROUPS 1198 1199menuconfig NAMESPACES 1200 bool "Namespaces support" if EXPERT 1201 depends on MULTIUSER 1202 default !EXPERT 1203 help 1204 Provides the way to make tasks work with different objects using 1205 the same id. For example same IPC id may refer to different objects 1206 or same user id or pid may refer to different tasks when used in 1207 different namespaces. 1208 1209if NAMESPACES 1210 1211config UTS_NS 1212 bool "UTS namespace" 1213 default y 1214 help 1215 In this namespace tasks see different info provided with the 1216 uname() system call 1217 1218config TIME_NS 1219 bool "TIME namespace" 1220 depends on GENERIC_VDSO_TIME_NS 1221 default y 1222 help 1223 In this namespace boottime and monotonic clocks can be set. 1224 The time will keep going with the same pace. 1225 1226config IPC_NS 1227 bool "IPC namespace" 1228 depends on (SYSVIPC || POSIX_MQUEUE) 1229 default y 1230 help 1231 In this namespace tasks work with IPC ids which correspond to 1232 different IPC objects in different namespaces. 1233 1234config USER_NS 1235 bool "User namespace" 1236 default n 1237 help 1238 This allows containers, i.e. vservers, to use user namespaces 1239 to provide different user info for different servers. 1240 1241 When user namespaces are enabled in the kernel it is 1242 recommended that the MEMCG option also be enabled and that 1243 user-space use the memory control groups to limit the amount 1244 of memory a memory unprivileged users can use. 1245 1246 If unsure, say N. 1247 1248config PID_NS 1249 bool "PID Namespaces" 1250 default y 1251 help 1252 Support process id namespaces. This allows having multiple 1253 processes with the same pid as long as they are in different 1254 pid namespaces. This is a building block of containers. 1255 1256config NET_NS 1257 bool "Network namespace" 1258 depends on NET 1259 default y 1260 help 1261 Allow user space to create what appear to be multiple instances 1262 of the network stack. 1263 1264endif # NAMESPACES 1265 1266config CHECKPOINT_RESTORE 1267 bool "Checkpoint/restore support" 1268 select PROC_CHILDREN 1269 select KCMP 1270 default n 1271 help 1272 Enables additional kernel features in a sake of checkpoint/restore. 1273 In particular it adds auxiliary prctl codes to setup process text, 1274 data and heap segment sizes, and a few additional /proc filesystem 1275 entries. 1276 1277 If unsure, say N here. 1278 1279config SCHED_AUTOGROUP 1280 bool "Automatic process group scheduling" 1281 select CGROUPS 1282 select CGROUP_SCHED 1283 select FAIR_GROUP_SCHED 1284 help 1285 This option optimizes the scheduler for common desktop workloads by 1286 automatically creating and populating task groups. This separation 1287 of workloads isolates aggressive CPU burners (like build jobs) from 1288 desktop applications. Task group autogeneration is currently based 1289 upon task session. 1290 1291config SYSFS_DEPRECATED 1292 bool "Enable deprecated sysfs features to support old userspace tools" 1293 depends on SYSFS 1294 default n 1295 help 1296 This option adds code that switches the layout of the "block" class 1297 devices, to not show up in /sys/class/block/, but only in 1298 /sys/block/. 1299 1300 This switch is only active when the sysfs.deprecated=1 boot option is 1301 passed or the SYSFS_DEPRECATED_V2 option is set. 1302 1303 This option allows new kernels to run on old distributions and tools, 1304 which might get confused by /sys/class/block/. Since 2007/2008 all 1305 major distributions and tools handle this just fine. 1306 1307 Recent distributions and userspace tools after 2009/2010 depend on 1308 the existence of /sys/class/block/, and will not work with this 1309 option enabled. 1310 1311 Only if you are using a new kernel on an old distribution, you might 1312 need to say Y here. 1313 1314config SYSFS_DEPRECATED_V2 1315 bool "Enable deprecated sysfs features by default" 1316 default n 1317 depends on SYSFS 1318 depends on SYSFS_DEPRECATED 1319 help 1320 Enable deprecated sysfs by default. 1321 1322 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1323 option. 1324 1325 Only if you are using a new kernel on an old distribution, you might 1326 need to say Y here. Even then, odds are you would not need it 1327 enabled, you can always pass the boot option if absolutely necessary. 1328 1329config RELAY 1330 bool "Kernel->user space relay support (formerly relayfs)" 1331 select IRQ_WORK 1332 help 1333 This option enables support for relay interface support in 1334 certain file systems (such as debugfs). 1335 It is designed to provide an efficient mechanism for tools and 1336 facilities to relay large amounts of data from kernel space to 1337 user space. 1338 1339 If unsure, say N. 1340 1341config BLK_DEV_INITRD 1342 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1343 help 1344 The initial RAM filesystem is a ramfs which is loaded by the 1345 boot loader (loadlin or lilo) and that is mounted as root 1346 before the normal boot procedure. It is typically used to 1347 load modules needed to mount the "real" root file system, 1348 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1349 1350 If RAM disk support (BLK_DEV_RAM) is also included, this 1351 also enables initial RAM disk (initrd) support and adds 1352 15 Kbytes (more on some other architectures) to the kernel size. 1353 1354 If unsure say Y. 1355 1356if BLK_DEV_INITRD 1357 1358source "usr/Kconfig" 1359 1360endif 1361 1362config BOOT_CONFIG 1363 bool "Boot config support" 1364 select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED 1365 help 1366 Extra boot config allows system admin to pass a config file as 1367 complemental extension of kernel cmdline when booting. 1368 The boot config file must be attached at the end of initramfs 1369 with checksum, size and magic word. 1370 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1371 1372 If unsure, say Y. 1373 1374config BOOT_CONFIG_EMBED 1375 bool "Embed bootconfig file in the kernel" 1376 depends on BOOT_CONFIG 1377 help 1378 Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the 1379 kernel. Usually, the bootconfig file is loaded with the initrd 1380 image. But if the system doesn't support initrd, this option will 1381 help you by embedding a bootconfig file while building the kernel. 1382 1383 If unsure, say N. 1384 1385config BOOT_CONFIG_EMBED_FILE 1386 string "Embedded bootconfig file path" 1387 depends on BOOT_CONFIG_EMBED 1388 help 1389 Specify a bootconfig file which will be embedded to the kernel. 1390 This bootconfig will be used if there is no initrd or no other 1391 bootconfig in the initrd. 1392 1393config INITRAMFS_PRESERVE_MTIME 1394 bool "Preserve cpio archive mtimes in initramfs" 1395 default y 1396 help 1397 Each entry in an initramfs cpio archive carries an mtime value. When 1398 enabled, extracted cpio items take this mtime, with directory mtime 1399 setting deferred until after creation of any child entries. 1400 1401 If unsure, say Y. 1402 1403choice 1404 prompt "Compiler optimization level" 1405 default CC_OPTIMIZE_FOR_PERFORMANCE 1406 1407config CC_OPTIMIZE_FOR_PERFORMANCE 1408 bool "Optimize for performance (-O2)" 1409 help 1410 This is the default optimization level for the kernel, building 1411 with the "-O2" compiler flag for best performance and most 1412 helpful compile-time warnings. 1413 1414config CC_OPTIMIZE_FOR_SIZE 1415 bool "Optimize for size (-Os)" 1416 help 1417 Choosing this option will pass "-Os" to your compiler resulting 1418 in a smaller kernel. 1419 1420endchoice 1421 1422config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1423 bool 1424 help 1425 This requires that the arch annotates or otherwise protects 1426 its external entry points from being discarded. Linker scripts 1427 must also merge .text.*, .data.*, and .bss.* correctly into 1428 output sections. Care must be taken not to pull in unrelated 1429 sections (e.g., '.text.init'). Typically '.' in section names 1430 is used to distinguish them from label names / C identifiers. 1431 1432config LD_DEAD_CODE_DATA_ELIMINATION 1433 bool "Dead code and data elimination (EXPERIMENTAL)" 1434 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1435 depends on EXPERT 1436 depends on $(cc-option,-ffunction-sections -fdata-sections) 1437 depends on $(ld-option,--gc-sections) 1438 help 1439 Enable this if you want to do dead code and data elimination with 1440 the linker by compiling with -ffunction-sections -fdata-sections, 1441 and linking with --gc-sections. 1442 1443 This can reduce on disk and in-memory size of the kernel 1444 code and static data, particularly for small configs and 1445 on small systems. This has the possibility of introducing 1446 silently broken kernel if the required annotations are not 1447 present. This option is not well tested yet, so use at your 1448 own risk. 1449 1450config LD_ORPHAN_WARN 1451 def_bool y 1452 depends on ARCH_WANT_LD_ORPHAN_WARN 1453 depends on $(ld-option,--orphan-handling=warn) 1454 1455config SYSCTL 1456 bool 1457 1458config HAVE_UID16 1459 bool 1460 1461config SYSCTL_EXCEPTION_TRACE 1462 bool 1463 help 1464 Enable support for /proc/sys/debug/exception-trace. 1465 1466config SYSCTL_ARCH_UNALIGN_NO_WARN 1467 bool 1468 help 1469 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1470 Allows arch to define/use @no_unaligned_warning to possibly warn 1471 about unaligned access emulation going on under the hood. 1472 1473config SYSCTL_ARCH_UNALIGN_ALLOW 1474 bool 1475 help 1476 Enable support for /proc/sys/kernel/unaligned-trap 1477 Allows arches to define/use @unaligned_enabled to runtime toggle 1478 the unaligned access emulation. 1479 see arch/parisc/kernel/unaligned.c for reference 1480 1481config HAVE_PCSPKR_PLATFORM 1482 bool 1483 1484# interpreter that classic socket filters depend on 1485config BPF 1486 bool 1487 select CRYPTO_LIB_SHA1 1488 1489menuconfig EXPERT 1490 bool "Configure standard kernel features (expert users)" 1491 # Unhide debug options, to make the on-by-default options visible 1492 select DEBUG_KERNEL 1493 help 1494 This option allows certain base kernel options and settings 1495 to be disabled or tweaked. This is for specialized 1496 environments which can tolerate a "non-standard" kernel. 1497 Only use this if you really know what you are doing. 1498 1499config UID16 1500 bool "Enable 16-bit UID system calls" if EXPERT 1501 depends on HAVE_UID16 && MULTIUSER 1502 default y 1503 help 1504 This enables the legacy 16-bit UID syscall wrappers. 1505 1506config MULTIUSER 1507 bool "Multiple users, groups and capabilities support" if EXPERT 1508 default y 1509 help 1510 This option enables support for non-root users, groups and 1511 capabilities. 1512 1513 If you say N here, all processes will run with UID 0, GID 0, and all 1514 possible capabilities. Saying N here also compiles out support for 1515 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1516 setgid, and capset. 1517 1518 If unsure, say Y here. 1519 1520config SGETMASK_SYSCALL 1521 bool "sgetmask/ssetmask syscalls support" if EXPERT 1522 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1523 help 1524 sys_sgetmask and sys_ssetmask are obsolete system calls 1525 no longer supported in libc but still enabled by default in some 1526 architectures. 1527 1528 If unsure, leave the default option here. 1529 1530config SYSFS_SYSCALL 1531 bool "Sysfs syscall support" if EXPERT 1532 default y 1533 help 1534 sys_sysfs is an obsolete system call no longer supported in libc. 1535 Note that disabling this option is more secure but might break 1536 compatibility with some systems. 1537 1538 If unsure say Y here. 1539 1540config FHANDLE 1541 bool "open by fhandle syscalls" if EXPERT 1542 select EXPORTFS 1543 default y 1544 help 1545 If you say Y here, a user level program will be able to map 1546 file names to handle and then later use the handle for 1547 different file system operations. This is useful in implementing 1548 userspace file servers, which now track files using handles instead 1549 of names. The handle would remain the same even if file names 1550 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1551 syscalls. 1552 1553config POSIX_TIMERS 1554 bool "Posix Clocks & timers" if EXPERT 1555 default y 1556 help 1557 This includes native support for POSIX timers to the kernel. 1558 Some embedded systems have no use for them and therefore they 1559 can be configured out to reduce the size of the kernel image. 1560 1561 When this option is disabled, the following syscalls won't be 1562 available: timer_create, timer_gettime: timer_getoverrun, 1563 timer_settime, timer_delete, clock_adjtime, getitimer, 1564 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1565 clock_getres and clock_nanosleep syscalls will be limited to 1566 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1567 1568 If unsure say y. 1569 1570config PRINTK 1571 default y 1572 bool "Enable support for printk" if EXPERT 1573 select IRQ_WORK 1574 help 1575 This option enables normal printk support. Removing it 1576 eliminates most of the message strings from the kernel image 1577 and makes the kernel more or less silent. As this makes it 1578 very difficult to diagnose system problems, saying N here is 1579 strongly discouraged. 1580 1581config BUG 1582 bool "BUG() support" if EXPERT 1583 default y 1584 help 1585 Disabling this option eliminates support for BUG and WARN, reducing 1586 the size of your kernel image and potentially quietly ignoring 1587 numerous fatal conditions. You should only consider disabling this 1588 option for embedded systems with no facilities for reporting errors. 1589 Just say Y. 1590 1591config ELF_CORE 1592 depends on COREDUMP 1593 default y 1594 bool "Enable ELF core dumps" if EXPERT 1595 help 1596 Enable support for generating core dumps. Disabling saves about 4k. 1597 1598 1599config PCSPKR_PLATFORM 1600 bool "Enable PC-Speaker support" if EXPERT 1601 depends on HAVE_PCSPKR_PLATFORM 1602 select I8253_LOCK 1603 default y 1604 help 1605 This option allows to disable the internal PC-Speaker 1606 support, saving some memory. 1607 1608config BASE_FULL 1609 default y 1610 bool "Enable full-sized data structures for core" if EXPERT 1611 help 1612 Disabling this option reduces the size of miscellaneous core 1613 kernel data structures. This saves memory on small machines, 1614 but may reduce performance. 1615 1616config FUTEX 1617 bool "Enable futex support" if EXPERT 1618 depends on !(SPARC32 && SMP) 1619 default y 1620 imply RT_MUTEXES 1621 help 1622 Disabling this option will cause the kernel to be built without 1623 support for "fast userspace mutexes". The resulting kernel may not 1624 run glibc-based applications correctly. 1625 1626config FUTEX_PI 1627 bool 1628 depends on FUTEX && RT_MUTEXES 1629 default y 1630 1631config EPOLL 1632 bool "Enable eventpoll support" if EXPERT 1633 default y 1634 help 1635 Disabling this option will cause the kernel to be built without 1636 support for epoll family of system calls. 1637 1638config SIGNALFD 1639 bool "Enable signalfd() system call" if EXPERT 1640 default y 1641 help 1642 Enable the signalfd() system call that allows to receive signals 1643 on a file descriptor. 1644 1645 If unsure, say Y. 1646 1647config TIMERFD 1648 bool "Enable timerfd() system call" if EXPERT 1649 default y 1650 help 1651 Enable the timerfd() system call that allows to receive timer 1652 events on a file descriptor. 1653 1654 If unsure, say Y. 1655 1656config EVENTFD 1657 bool "Enable eventfd() system call" if EXPERT 1658 default y 1659 help 1660 Enable the eventfd() system call that allows to receive both 1661 kernel notification (ie. KAIO) or userspace notifications. 1662 1663 If unsure, say Y. 1664 1665config SHMEM 1666 bool "Use full shmem filesystem" if EXPERT 1667 default y 1668 depends on MMU 1669 help 1670 The shmem is an internal filesystem used to manage shared memory. 1671 It is backed by swap and manages resource limits. It is also exported 1672 to userspace as tmpfs if TMPFS is enabled. Disabling this 1673 option replaces shmem and tmpfs with the much simpler ramfs code, 1674 which may be appropriate on small systems without swap. 1675 1676config AIO 1677 bool "Enable AIO support" if EXPERT 1678 default y 1679 help 1680 This option enables POSIX asynchronous I/O which may by used 1681 by some high performance threaded applications. Disabling 1682 this option saves about 7k. 1683 1684config IO_URING 1685 bool "Enable IO uring support" if EXPERT 1686 select IO_WQ 1687 default y 1688 help 1689 This option enables support for the io_uring interface, enabling 1690 applications to submit and complete IO through submission and 1691 completion rings that are shared between the kernel and application. 1692 1693config ADVISE_SYSCALLS 1694 bool "Enable madvise/fadvise syscalls" if EXPERT 1695 default y 1696 help 1697 This option enables the madvise and fadvise syscalls, used by 1698 applications to advise the kernel about their future memory or file 1699 usage, improving performance. If building an embedded system where no 1700 applications use these syscalls, you can disable this option to save 1701 space. 1702 1703config MEMBARRIER 1704 bool "Enable membarrier() system call" if EXPERT 1705 default y 1706 help 1707 Enable the membarrier() system call that allows issuing memory 1708 barriers across all running threads, which can be used to distribute 1709 the cost of user-space memory barriers asymmetrically by transforming 1710 pairs of memory barriers into pairs consisting of membarrier() and a 1711 compiler barrier. 1712 1713 If unsure, say Y. 1714 1715config KALLSYMS 1716 bool "Load all symbols for debugging/ksymoops" if EXPERT 1717 default y 1718 help 1719 Say Y here to let the kernel print out symbolic crash information and 1720 symbolic stack backtraces. This increases the size of the kernel 1721 somewhat, as all symbols have to be loaded into the kernel image. 1722 1723config KALLSYMS_ALL 1724 bool "Include all symbols in kallsyms" 1725 depends on DEBUG_KERNEL && KALLSYMS 1726 help 1727 Normally kallsyms only contains the symbols of functions for nicer 1728 OOPS messages and backtraces (i.e., symbols from the text and inittext 1729 sections). This is sufficient for most cases. And only if you want to 1730 enable kernel live patching, or other less common use cases (e.g., 1731 when a debugger is used) all symbols are required (i.e., names of 1732 variables from the data sections, etc). 1733 1734 This option makes sure that all symbols are loaded into the kernel 1735 image (i.e., symbols from all sections) in cost of increased kernel 1736 size (depending on the kernel configuration, it may be 300KiB or 1737 something like this). 1738 1739 Say N unless you really need all symbols, or kernel live patching. 1740 1741config KALLSYMS_ABSOLUTE_PERCPU 1742 bool 1743 depends on KALLSYMS 1744 default X86_64 && SMP 1745 1746config KALLSYMS_BASE_RELATIVE 1747 bool 1748 depends on KALLSYMS 1749 default !IA64 1750 help 1751 Instead of emitting them as absolute values in the native word size, 1752 emit the symbol references in the kallsyms table as 32-bit entries, 1753 each containing a relative value in the range [base, base + U32_MAX] 1754 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1755 an absolute value in the range [0, S32_MAX] or a relative value in the 1756 range [base, base + S32_MAX], where base is the lowest relative symbol 1757 address encountered in the image. 1758 1759 On 64-bit builds, this reduces the size of the address table by 50%, 1760 but more importantly, it results in entries whose values are build 1761 time constants, and no relocation pass is required at runtime to fix 1762 up the entries based on the runtime load address of the kernel. 1763 1764# end of the "standard kernel features (expert users)" menu 1765 1766# syscall, maps, verifier 1767 1768config ARCH_HAS_MEMBARRIER_CALLBACKS 1769 bool 1770 1771config ARCH_HAS_MEMBARRIER_SYNC_CORE 1772 bool 1773 1774config KCMP 1775 bool "Enable kcmp() system call" if EXPERT 1776 help 1777 Enable the kernel resource comparison system call. It provides 1778 user-space with the ability to compare two processes to see if they 1779 share a common resource, such as a file descriptor or even virtual 1780 memory space. 1781 1782 If unsure, say N. 1783 1784config RSEQ 1785 bool "Enable rseq() system call" if EXPERT 1786 default y 1787 depends on HAVE_RSEQ 1788 select MEMBARRIER 1789 help 1790 Enable the restartable sequences system call. It provides a 1791 user-space cache for the current CPU number value, which 1792 speeds up getting the current CPU number from user-space, 1793 as well as an ABI to speed up user-space operations on 1794 per-CPU data. 1795 1796 If unsure, say Y. 1797 1798config DEBUG_RSEQ 1799 default n 1800 bool "Enabled debugging of rseq() system call" if EXPERT 1801 depends on RSEQ && DEBUG_KERNEL 1802 help 1803 Enable extra debugging checks for the rseq system call. 1804 1805 If unsure, say N. 1806 1807config EMBEDDED 1808 bool "Embedded system" 1809 select EXPERT 1810 help 1811 This option should be enabled if compiling the kernel for 1812 an embedded system so certain expert options are available 1813 for configuration. 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 1829config PC104 1830 bool "PC/104 support" if EXPERT 1831 help 1832 Expose PC/104 form factor device drivers and options available for 1833 selection and configuration. Enable this option if your target 1834 machine has a PC/104 bus. 1835 1836menu "Kernel Performance Events And Counters" 1837 1838config PERF_EVENTS 1839 bool "Kernel performance events and counters" 1840 default y if PROFILING 1841 depends on HAVE_PERF_EVENTS 1842 select IRQ_WORK 1843 select SRCU 1844 help 1845 Enable kernel support for various performance events provided 1846 by software and hardware. 1847 1848 Software events are supported either built-in or via the 1849 use of generic tracepoints. 1850 1851 Most modern CPUs support performance events via performance 1852 counter registers. These registers count the number of certain 1853 types of hw events: such as instructions executed, cachemisses 1854 suffered, or branches mis-predicted - without slowing down the 1855 kernel or applications. These registers can also trigger interrupts 1856 when a threshold number of events have passed - and can thus be 1857 used to profile the code that runs on that CPU. 1858 1859 The Linux Performance Event subsystem provides an abstraction of 1860 these software and hardware event capabilities, available via a 1861 system call and used by the "perf" utility in tools/perf/. It 1862 provides per task and per CPU counters, and it provides event 1863 capabilities on top of those. 1864 1865 Say Y if unsure. 1866 1867config DEBUG_PERF_USE_VMALLOC 1868 default n 1869 bool "Debug: use vmalloc to back perf mmap() buffers" 1870 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1871 select PERF_USE_VMALLOC 1872 help 1873 Use vmalloc memory to back perf mmap() buffers. 1874 1875 Mostly useful for debugging the vmalloc code on platforms 1876 that don't require it. 1877 1878 Say N if unsure. 1879 1880endmenu 1881 1882config SYSTEM_DATA_VERIFICATION 1883 def_bool n 1884 select SYSTEM_TRUSTED_KEYRING 1885 select KEYS 1886 select CRYPTO 1887 select CRYPTO_RSA 1888 select ASYMMETRIC_KEY_TYPE 1889 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1890 select ASN1 1891 select OID_REGISTRY 1892 select X509_CERTIFICATE_PARSER 1893 select PKCS7_MESSAGE_PARSER 1894 help 1895 Provide PKCS#7 message verification using the contents of the system 1896 trusted keyring to provide public keys. This then can be used for 1897 module verification, kexec image verification and firmware blob 1898 verification. 1899 1900config PROFILING 1901 bool "Profiling support" 1902 help 1903 Say Y here to enable the extended profiling support mechanisms used 1904 by profilers. 1905 1906# 1907# Place an empty function call at each tracepoint site. Can be 1908# dynamically changed for a probe function. 1909# 1910config TRACEPOINTS 1911 bool 1912 1913endmenu # General setup 1914 1915source "arch/Kconfig" 1916 1917config RT_MUTEXES 1918 bool 1919 default y if PREEMPT_RT 1920 1921config BASE_SMALL 1922 int 1923 default 0 if BASE_FULL 1924 default 1 if !BASE_FULL 1925 1926config MODULE_SIG_FORMAT 1927 def_bool n 1928 select SYSTEM_DATA_VERIFICATION 1929 1930source "kernel/module/Kconfig" 1931 1932config INIT_ALL_POSSIBLE 1933 bool 1934 help 1935 Back when each arch used to define their own cpu_online_mask and 1936 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 1937 with all 1s, and others with all 0s. When they were centralised, 1938 it was better to provide this option than to break all the archs 1939 and have several arch maintainers pursuing me down dark alleys. 1940 1941source "block/Kconfig" 1942 1943config PREEMPT_NOTIFIERS 1944 bool 1945 1946config PADATA 1947 depends on SMP 1948 bool 1949 1950config ASN1 1951 tristate 1952 help 1953 Build a simple ASN.1 grammar compiler that produces a bytecode output 1954 that can be interpreted by the ASN.1 stream decoder and used to 1955 inform it as to what tags are to be expected in a stream and what 1956 functions to call on what tags. 1957 1958source "kernel/Kconfig.locks" 1959 1960config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 1961 bool 1962 1963config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 1964 bool 1965 1966# It may be useful for an architecture to override the definitions of the 1967# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 1968# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 1969# different calling convention for syscalls. They can also override the 1970# macros for not-implemented syscalls in kernel/sys_ni.c and 1971# kernel/time/posix-stubs.c. All these overrides need to be available in 1972# <asm/syscall_wrapper.h>. 1973config ARCH_HAS_SYSCALL_WRAPPER 1974 def_bool n 1975