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_OUTPUT 74 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) 75 76config CC_HAS_ASM_GOTO_TIED_OUTPUT 77 depends on CC_HAS_ASM_GOTO_OUTPUT 78 # Detect buggy gcc and clang, fixed in gcc-11 clang-14. 79 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) 80 81config TOOLS_SUPPORT_RELR 82 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 83 84config CC_HAS_ASM_INLINE 85 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 86 87config CC_HAS_NO_PROFILE_FN_ATTR 88 def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror) 89 90config PAHOLE_VERSION 91 int 92 default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE)) 93 94config CONSTRUCTORS 95 bool 96 97config IRQ_WORK 98 bool 99 100config BUILDTIME_TABLE_SORT 101 bool 102 103config THREAD_INFO_IN_TASK 104 bool 105 help 106 Select this to move thread_info off the stack into task_struct. To 107 make this work, an arch will need to remove all thread_info fields 108 except flags and fix any runtime bugs. 109 110 One subtle change that will be needed is to use try_get_task_stack() 111 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 112 113menu "General setup" 114 115config BROKEN 116 bool 117 118config BROKEN_ON_SMP 119 bool 120 depends on BROKEN || !SMP 121 default y 122 123config INIT_ENV_ARG_LIMIT 124 int 125 default 32 if !UML 126 default 128 if UML 127 help 128 Maximum of each of the number of arguments and environment 129 variables passed to init from the kernel command line. 130 131config COMPILE_TEST 132 bool "Compile also drivers which will not load" 133 depends on HAS_IOMEM 134 help 135 Some drivers can be compiled on a different platform than they are 136 intended to be run on. Despite they cannot be loaded there (or even 137 when they load they cannot be used due to missing HW support), 138 developers still, opposing to distributors, might want to build such 139 drivers to compile-test them. 140 141 If you are a developer and want to build everything available, say Y 142 here. If you are a user/distributor, say N here to exclude useless 143 drivers to be distributed. 144 145config WERROR 146 bool "Compile the kernel with warnings as errors" 147 default COMPILE_TEST 148 help 149 A kernel build should not cause any compiler warnings, and this 150 enables the '-Werror' flag to enforce that rule by default. 151 152 However, if you have a new (or very old) compiler with odd and 153 unusual warnings, or you have some architecture with problems, 154 you may need to disable this config option in order to 155 successfully build the kernel. 156 157 If in doubt, say Y. 158 159config UAPI_HEADER_TEST 160 bool "Compile test UAPI headers" 161 depends on HEADERS_INSTALL && CC_CAN_LINK 162 help 163 Compile test headers exported to user-space to ensure they are 164 self-contained, i.e. compilable as standalone units. 165 166 If you are a developer or tester and want to ensure the exported 167 headers are self-contained, say Y here. Otherwise, choose N. 168 169config LOCALVERSION 170 string "Local version - append to kernel release" 171 help 172 Append an extra string to the end of your kernel version. 173 This will show up when you type uname, for example. 174 The string you set here will be appended after the contents of 175 any files with a filename matching localversion* in your 176 object and source tree, in that order. Your total string can 177 be a maximum of 64 characters. 178 179config LOCALVERSION_AUTO 180 bool "Automatically append version information to the version string" 181 default y 182 depends on !COMPILE_TEST 183 help 184 This will try to automatically determine if the current tree is a 185 release tree by looking for git tags that belong to the current 186 top of tree revision. 187 188 A string of the format -gxxxxxxxx will be added to the localversion 189 if a git-based tree is found. The string generated by this will be 190 appended after any matching localversion* files, and after the value 191 set in CONFIG_LOCALVERSION. 192 193 (The actual string used here is the first eight characters produced 194 by running the command: 195 196 $ git rev-parse --verify HEAD 197 198 which is done within the script "scripts/setlocalversion".) 199 200config BUILD_SALT 201 string "Build ID Salt" 202 default "" 203 help 204 The build ID is used to link binaries and their debug info. Setting 205 this option will use the value in the calculation of the build id. 206 This is mostly useful for distributions which want to ensure the 207 build is unique between builds. It's safe to leave the default. 208 209config HAVE_KERNEL_GZIP 210 bool 211 212config HAVE_KERNEL_BZIP2 213 bool 214 215config HAVE_KERNEL_LZMA 216 bool 217 218config HAVE_KERNEL_XZ 219 bool 220 221config HAVE_KERNEL_LZO 222 bool 223 224config HAVE_KERNEL_LZ4 225 bool 226 227config HAVE_KERNEL_ZSTD 228 bool 229 230config HAVE_KERNEL_UNCOMPRESSED 231 bool 232 233choice 234 prompt "Kernel compression mode" 235 default KERNEL_GZIP 236 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 237 help 238 The linux kernel is a kind of self-extracting executable. 239 Several compression algorithms are available, which differ 240 in efficiency, compression and decompression speed. 241 Compression speed is only relevant when building a kernel. 242 Decompression speed is relevant at each boot. 243 244 If you have any problems with bzip2 or lzma compressed 245 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 246 version of this functionality (bzip2 only), for 2.4, was 247 supplied by Christian Ludwig) 248 249 High compression options are mostly useful for users, who 250 are low on disk space (embedded systems), but for whom ram 251 size matters less. 252 253 If in doubt, select 'gzip' 254 255config KERNEL_GZIP 256 bool "Gzip" 257 depends on HAVE_KERNEL_GZIP 258 help 259 The old and tried gzip compression. It provides a good balance 260 between compression ratio and decompression speed. 261 262config KERNEL_BZIP2 263 bool "Bzip2" 264 depends on HAVE_KERNEL_BZIP2 265 help 266 Its compression ratio and speed is intermediate. 267 Decompression speed is slowest among the choices. The kernel 268 size is about 10% smaller with bzip2, in comparison to gzip. 269 Bzip2 uses a large amount of memory. For modern kernels you 270 will need at least 8MB RAM or more for booting. 271 272config KERNEL_LZMA 273 bool "LZMA" 274 depends on HAVE_KERNEL_LZMA 275 help 276 This compression algorithm's ratio is best. Decompression speed 277 is between gzip and bzip2. Compression is slowest. 278 The kernel size is about 33% smaller with LZMA in comparison to gzip. 279 280config KERNEL_XZ 281 bool "XZ" 282 depends on HAVE_KERNEL_XZ 283 help 284 XZ uses the LZMA2 algorithm and instruction set specific 285 BCJ filters which can improve compression ratio of executable 286 code. The size of the kernel is about 30% smaller with XZ in 287 comparison to gzip. On architectures for which there is a BCJ 288 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 289 will create a few percent smaller kernel than plain LZMA. 290 291 The speed is about the same as with LZMA: The decompression 292 speed of XZ is better than that of bzip2 but worse than gzip 293 and LZO. Compression is slow. 294 295config KERNEL_LZO 296 bool "LZO" 297 depends on HAVE_KERNEL_LZO 298 help 299 Its compression ratio is the poorest among the choices. The kernel 300 size is about 10% bigger than gzip; however its speed 301 (both compression and decompression) is the fastest. 302 303config KERNEL_LZ4 304 bool "LZ4" 305 depends on HAVE_KERNEL_LZ4 306 help 307 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 308 A preliminary version of LZ4 de/compression tool is available at 309 <https://code.google.com/p/lz4/>. 310 311 Its compression ratio is worse than LZO. The size of the kernel 312 is about 8% bigger than LZO. But the decompression speed is 313 faster than LZO. 314 315config KERNEL_ZSTD 316 bool "ZSTD" 317 depends on HAVE_KERNEL_ZSTD 318 help 319 ZSTD is a compression algorithm targeting intermediate compression 320 with fast decompression speed. It will compress better than GZIP and 321 decompress around the same speed as LZO, but slower than LZ4. You 322 will need at least 192 KB RAM or more for booting. The zstd command 323 line tool is required for compression. 324 325config KERNEL_UNCOMPRESSED 326 bool "None" 327 depends on HAVE_KERNEL_UNCOMPRESSED 328 help 329 Produce uncompressed kernel image. This option is usually not what 330 you want. It is useful for debugging the kernel in slow simulation 331 environments, where decompressing and moving the kernel is awfully 332 slow. This option allows early boot code to skip the decompressor 333 and jump right at uncompressed kernel image. 334 335endchoice 336 337config DEFAULT_INIT 338 string "Default init path" 339 default "" 340 help 341 This option determines the default init for the system if no init= 342 option is passed on the kernel command line. If the requested path is 343 not present, we will still then move on to attempting further 344 locations (e.g. /sbin/init, etc). If this is empty, we will just use 345 the fallback list when init= is not passed. 346 347config DEFAULT_HOSTNAME 348 string "Default hostname" 349 default "(none)" 350 help 351 This option determines the default system hostname before userspace 352 calls sethostname(2). The kernel traditionally uses "(none)" here, 353 but you may wish to use a different default here to make a minimal 354 system more usable with less configuration. 355 356config SYSVIPC 357 bool "System V IPC" 358 help 359 Inter Process Communication is a suite of library functions and 360 system calls which let processes (running programs) synchronize and 361 exchange information. It is generally considered to be a good thing, 362 and some programs won't run unless you say Y here. In particular, if 363 you want to run the DOS emulator dosemu under Linux (read the 364 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 365 you'll need to say Y here. 366 367 You can find documentation about IPC with "info ipc" and also in 368 section 6.4 of the Linux Programmer's Guide, available from 369 <http://www.tldp.org/guides.html>. 370 371config SYSVIPC_SYSCTL 372 bool 373 depends on SYSVIPC 374 depends on SYSCTL 375 default y 376 377config SYSVIPC_COMPAT 378 def_bool y 379 depends on COMPAT && SYSVIPC 380 381config POSIX_MQUEUE 382 bool "POSIX Message Queues" 383 depends on NET 384 help 385 POSIX variant of message queues is a part of IPC. In POSIX message 386 queues every message has a priority which decides about succession 387 of receiving it by a process. If you want to compile and run 388 programs written e.g. for Solaris with use of its POSIX message 389 queues (functions mq_*) say Y here. 390 391 POSIX message queues are visible as a filesystem called 'mqueue' 392 and can be mounted somewhere if you want to do filesystem 393 operations on message queues. 394 395 If unsure, say Y. 396 397config POSIX_MQUEUE_SYSCTL 398 bool 399 depends on POSIX_MQUEUE 400 depends on SYSCTL 401 default y 402 403config WATCH_QUEUE 404 bool "General notification queue" 405 default n 406 help 407 408 This is a general notification queue for the kernel to pass events to 409 userspace by splicing them into pipes. It can be used in conjunction 410 with watches for key/keyring change notifications and device 411 notifications. 412 413 See Documentation/core-api/watch_queue.rst 414 415config CROSS_MEMORY_ATTACH 416 bool "Enable process_vm_readv/writev syscalls" 417 depends on MMU 418 default y 419 help 420 Enabling this option adds the system calls process_vm_readv and 421 process_vm_writev which allow a process with the correct privileges 422 to directly read from or write to another process' address space. 423 See the man page for more details. 424 425config USELIB 426 bool "uselib syscall (for libc5 and earlier)" 427 default ALPHA || M68K || SPARC 428 help 429 This option enables the uselib syscall, a system call used in the 430 dynamic linker from libc5 and earlier. glibc does not use this 431 system call. If you intend to run programs built on libc5 or 432 earlier, you may need to enable this syscall. Current systems 433 running glibc can safely disable this. 434 435config AUDIT 436 bool "Auditing support" 437 depends on NET 438 help 439 Enable auditing infrastructure that can be used with another 440 kernel subsystem, such as SELinux (which requires this for 441 logging of avc messages output). System call auditing is included 442 on architectures which support it. 443 444config HAVE_ARCH_AUDITSYSCALL 445 bool 446 447config AUDITSYSCALL 448 def_bool y 449 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 450 select FSNOTIFY 451 452source "kernel/irq/Kconfig" 453source "kernel/time/Kconfig" 454source "kernel/bpf/Kconfig" 455source "kernel/Kconfig.preempt" 456 457menu "CPU/Task time and stats accounting" 458 459config VIRT_CPU_ACCOUNTING 460 bool 461 462choice 463 prompt "Cputime accounting" 464 default TICK_CPU_ACCOUNTING if !PPC64 465 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 466 467# Kind of a stub config for the pure tick based cputime accounting 468config TICK_CPU_ACCOUNTING 469 bool "Simple tick based cputime accounting" 470 depends on !S390 && !NO_HZ_FULL 471 help 472 This is the basic tick based cputime accounting that maintains 473 statistics about user, system and idle time spent on per jiffies 474 granularity. 475 476 If unsure, say Y. 477 478config VIRT_CPU_ACCOUNTING_NATIVE 479 bool "Deterministic task and CPU time accounting" 480 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 481 select VIRT_CPU_ACCOUNTING 482 help 483 Select this option to enable more accurate task and CPU time 484 accounting. This is done by reading a CPU counter on each 485 kernel entry and exit and on transitions within the kernel 486 between system, softirq and hardirq state, so there is a 487 small performance impact. In the case of s390 or IBM POWER > 5, 488 this also enables accounting of stolen time on logically-partitioned 489 systems. 490 491config VIRT_CPU_ACCOUNTING_GEN 492 bool "Full dynticks CPU time accounting" 493 depends on HAVE_CONTEXT_TRACKING_USER 494 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 495 depends on GENERIC_CLOCKEVENTS 496 select VIRT_CPU_ACCOUNTING 497 select CONTEXT_TRACKING_USER 498 help 499 Select this option to enable task and CPU time accounting on full 500 dynticks systems. This accounting is implemented by watching every 501 kernel-user boundaries using the context tracking subsystem. 502 The accounting is thus performed at the expense of some significant 503 overhead. 504 505 For now this is only useful if you are working on the full 506 dynticks subsystem development. 507 508 If unsure, say N. 509 510endchoice 511 512config IRQ_TIME_ACCOUNTING 513 bool "Fine granularity task level IRQ time accounting" 514 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 515 help 516 Select this option to enable fine granularity task irq time 517 accounting. This is done by reading a timestamp on each 518 transitions between softirq and hardirq state, so there can be a 519 small performance impact. 520 521 If in doubt, say N here. 522 523config HAVE_SCHED_AVG_IRQ 524 def_bool y 525 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 526 depends on SMP 527 528config SCHED_THERMAL_PRESSURE 529 bool 530 default y if ARM && ARM_CPU_TOPOLOGY 531 default y if ARM64 532 depends on SMP 533 depends on CPU_FREQ_THERMAL 534 help 535 Select this option to enable thermal pressure accounting in the 536 scheduler. Thermal pressure is the value conveyed to the scheduler 537 that reflects the reduction in CPU compute capacity resulted from 538 thermal throttling. Thermal throttling occurs when the performance of 539 a CPU is capped due to high operating temperatures. 540 541 If selected, the scheduler will be able to balance tasks accordingly, 542 i.e. put less load on throttled CPUs than on non/less throttled ones. 543 544 This requires the architecture to implement 545 arch_update_thermal_pressure() and arch_scale_thermal_pressure(). 546 547config BSD_PROCESS_ACCT 548 bool "BSD Process Accounting" 549 depends on MULTIUSER 550 help 551 If you say Y here, a user level program will be able to instruct the 552 kernel (via a special system call) to write process accounting 553 information to a file: whenever a process exits, information about 554 that process will be appended to the file by the kernel. The 555 information includes things such as creation time, owning user, 556 command name, memory usage, controlling terminal etc. (the complete 557 list is in the struct acct in <file:include/linux/acct.h>). It is 558 up to the user level program to do useful things with this 559 information. This is generally a good idea, so say Y. 560 561config BSD_PROCESS_ACCT_V3 562 bool "BSD Process Accounting version 3 file format" 563 depends on BSD_PROCESS_ACCT 564 default n 565 help 566 If you say Y here, the process accounting information is written 567 in a new file format that also logs the process IDs of each 568 process and its parent. Note that this file format is incompatible 569 with previous v0/v1/v2 file formats, so you will need updated tools 570 for processing it. A preliminary version of these tools is available 571 at <http://www.gnu.org/software/acct/>. 572 573config TASKSTATS 574 bool "Export task/process statistics through netlink" 575 depends on NET 576 depends on MULTIUSER 577 default n 578 help 579 Export selected statistics for tasks/processes through the 580 generic netlink interface. Unlike BSD process accounting, the 581 statistics are available during the lifetime of tasks/processes as 582 responses to commands. Like BSD accounting, they are sent to user 583 space on task exit. 584 585 Say N if unsure. 586 587config TASK_DELAY_ACCT 588 bool "Enable per-task delay accounting" 589 depends on TASKSTATS 590 select SCHED_INFO 591 help 592 Collect information on time spent by a task waiting for system 593 resources like cpu, synchronous block I/O completion and swapping 594 in pages. Such statistics can help in setting a task's priorities 595 relative to other tasks for cpu, io, rss limits etc. 596 597 Say N if unsure. 598 599config TASK_XACCT 600 bool "Enable extended accounting over taskstats" 601 depends on TASKSTATS 602 help 603 Collect extended task accounting data and send the data 604 to userland for processing over the taskstats interface. 605 606 Say N if unsure. 607 608config TASK_IO_ACCOUNTING 609 bool "Enable per-task storage I/O accounting" 610 depends on TASK_XACCT 611 help 612 Collect information on the number of bytes of storage I/O which this 613 task has caused. 614 615 Say N if unsure. 616 617config PSI 618 bool "Pressure stall information tracking" 619 help 620 Collect metrics that indicate how overcommitted the CPU, memory, 621 and IO capacity are in the system. 622 623 If you say Y here, the kernel will create /proc/pressure/ with the 624 pressure statistics files cpu, memory, and io. These will indicate 625 the share of walltime in which some or all tasks in the system are 626 delayed due to contention of the respective resource. 627 628 In kernels with cgroup support, cgroups (cgroup2 only) will 629 have cpu.pressure, memory.pressure, and io.pressure files, 630 which aggregate pressure stalls for the grouped tasks only. 631 632 For more details see Documentation/accounting/psi.rst. 633 634 Say N if unsure. 635 636config PSI_DEFAULT_DISABLED 637 bool "Require boot parameter to enable pressure stall information tracking" 638 default n 639 depends on PSI 640 help 641 If set, pressure stall information tracking will be disabled 642 per default but can be enabled through passing psi=1 on the 643 kernel commandline during boot. 644 645 This feature adds some code to the task wakeup and sleep 646 paths of the scheduler. The overhead is too low to affect 647 common scheduling-intense workloads in practice (such as 648 webservers, memcache), but it does show up in artificial 649 scheduler stress tests, such as hackbench. 650 651 If you are paranoid and not sure what the kernel will be 652 used for, say Y. 653 654 Say N if unsure. 655 656endmenu # "CPU/Task time and stats accounting" 657 658config CPU_ISOLATION 659 bool "CPU isolation" 660 depends on SMP || COMPILE_TEST 661 default y 662 help 663 Make sure that CPUs running critical tasks are not disturbed by 664 any source of "noise" such as unbound workqueues, timers, kthreads... 665 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 666 the "isolcpus=" boot parameter. 667 668 Say Y if unsure. 669 670source "kernel/rcu/Kconfig" 671 672config BUILD_BIN2C 673 bool 674 default n 675 676config IKCONFIG 677 tristate "Kernel .config support" 678 help 679 This option enables the complete Linux kernel ".config" file 680 contents to be saved in the kernel. It provides documentation 681 of which kernel options are used in a running kernel or in an 682 on-disk kernel. This information can be extracted from the kernel 683 image file with the script scripts/extract-ikconfig and used as 684 input to rebuild the current kernel or to build another kernel. 685 It can also be extracted from a running kernel by reading 686 /proc/config.gz if enabled (below). 687 688config IKCONFIG_PROC 689 bool "Enable access to .config through /proc/config.gz" 690 depends on IKCONFIG && PROC_FS 691 help 692 This option enables access to the kernel configuration file 693 through /proc/config.gz. 694 695config IKHEADERS 696 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 697 depends on SYSFS 698 help 699 This option enables access to the in-kernel headers that are generated during 700 the build process. These can be used to build eBPF tracing programs, 701 or similar programs. If you build the headers as a module, a module called 702 kheaders.ko is built which can be loaded on-demand to get access to headers. 703 704config LOG_BUF_SHIFT 705 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 706 range 12 25 707 default 17 708 depends on PRINTK 709 help 710 Select the minimal kernel log buffer size as a power of 2. 711 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 712 parameter, see below. Any higher size also might be forced 713 by "log_buf_len" boot parameter. 714 715 Examples: 716 17 => 128 KB 717 16 => 64 KB 718 15 => 32 KB 719 14 => 16 KB 720 13 => 8 KB 721 12 => 4 KB 722 723config LOG_CPU_MAX_BUF_SHIFT 724 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 725 depends on SMP 726 range 0 21 727 default 12 if !BASE_SMALL 728 default 0 if BASE_SMALL 729 depends on PRINTK 730 help 731 This option allows to increase the default ring buffer size 732 according to the number of CPUs. The value defines the contribution 733 of each CPU as a power of 2. The used space is typically only few 734 lines however it might be much more when problems are reported, 735 e.g. backtraces. 736 737 The increased size means that a new buffer has to be allocated and 738 the original static one is unused. It makes sense only on systems 739 with more CPUs. Therefore this value is used only when the sum of 740 contributions is greater than the half of the default kernel ring 741 buffer as defined by LOG_BUF_SHIFT. The default values are set 742 so that more than 16 CPUs are needed to trigger the allocation. 743 744 Also this option is ignored when "log_buf_len" kernel parameter is 745 used as it forces an exact (power of two) size of the ring buffer. 746 747 The number of possible CPUs is used for this computation ignoring 748 hotplugging making the computation optimal for the worst case 749 scenario while allowing a simple algorithm to be used from bootup. 750 751 Examples shift values and their meaning: 752 17 => 128 KB for each CPU 753 16 => 64 KB for each CPU 754 15 => 32 KB for each CPU 755 14 => 16 KB for each CPU 756 13 => 8 KB for each CPU 757 12 => 4 KB for each CPU 758 759config PRINTK_SAFE_LOG_BUF_SHIFT 760 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 761 range 10 21 762 default 13 763 depends on PRINTK 764 help 765 Select the size of an alternate printk per-CPU buffer where messages 766 printed from usafe contexts are temporary stored. One example would 767 be NMI messages, another one - printk recursion. The messages are 768 copied to the main log buffer in a safe context to avoid a deadlock. 769 The value defines the size as a power of 2. 770 771 Those messages are rare and limited. The largest one is when 772 a backtrace is printed. It usually fits into 4KB. Select 773 8KB if you want to be on the safe side. 774 775 Examples: 776 17 => 128 KB for each CPU 777 16 => 64 KB for each CPU 778 15 => 32 KB for each CPU 779 14 => 16 KB for each CPU 780 13 => 8 KB for each CPU 781 12 => 4 KB for each CPU 782 783config PRINTK_INDEX 784 bool "Printk indexing debugfs interface" 785 depends on PRINTK && DEBUG_FS 786 help 787 Add support for indexing of all printk formats known at compile time 788 at <debugfs>/printk/index/<module>. 789 790 This can be used as part of maintaining daemons which monitor 791 /dev/kmsg, as it permits auditing the printk formats present in a 792 kernel, allowing detection of cases where monitored printks are 793 changed or no longer present. 794 795 There is no additional runtime cost to printk with this enabled. 796 797# 798# Architectures with an unreliable sched_clock() should select this: 799# 800config HAVE_UNSTABLE_SCHED_CLOCK 801 bool 802 803config GENERIC_SCHED_CLOCK 804 bool 805 806menu "Scheduler features" 807 808config UCLAMP_TASK 809 bool "Enable utilization clamping for RT/FAIR tasks" 810 depends on CPU_FREQ_GOV_SCHEDUTIL 811 help 812 This feature enables the scheduler to track the clamped utilization 813 of each CPU based on RUNNABLE tasks scheduled on that CPU. 814 815 With this option, the user can specify the min and max CPU 816 utilization allowed for RUNNABLE tasks. The max utilization defines 817 the maximum frequency a task should use while the min utilization 818 defines the minimum frequency it should use. 819 820 Both min and max utilization clamp values are hints to the scheduler, 821 aiming at improving its frequency selection policy, but they do not 822 enforce or grant any specific bandwidth for tasks. 823 824 If in doubt, say N. 825 826config UCLAMP_BUCKETS_COUNT 827 int "Number of supported utilization clamp buckets" 828 range 5 20 829 default 5 830 depends on UCLAMP_TASK 831 help 832 Defines the number of clamp buckets to use. The range of each bucket 833 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 834 number of clamp buckets the finer their granularity and the higher 835 the precision of clamping aggregation and tracking at run-time. 836 837 For example, with the minimum configuration value we will have 5 838 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 839 be refcounted in the [20..39]% bucket and will set the bucket clamp 840 effective value to 25%. 841 If a second 30% boosted task should be co-scheduled on the same CPU, 842 that task will be refcounted in the same bucket of the first task and 843 it will boost the bucket clamp effective value to 30%. 844 The clamp effective value of a bucket is reset to its nominal value 845 (20% in the example above) when there are no more tasks refcounted in 846 that bucket. 847 848 An additional boost/capping margin can be added to some tasks. In the 849 example above the 25% task will be boosted to 30% until it exits the 850 CPU. If that should be considered not acceptable on certain systems, 851 it's always possible to reduce the margin by increasing the number of 852 clamp buckets to trade off used memory for run-time tracking 853 precision. 854 855 If in doubt, use the default value. 856 857endmenu 858 859# 860# For architectures that want to enable the support for NUMA-affine scheduler 861# balancing logic: 862# 863config ARCH_SUPPORTS_NUMA_BALANCING 864 bool 865 866# 867# For architectures that prefer to flush all TLBs after a number of pages 868# are unmapped instead of sending one IPI per page to flush. The architecture 869# must provide guarantees on what happens if a clean TLB cache entry is 870# written after the unmap. Details are in mm/rmap.c near the check for 871# should_defer_flush. The architecture should also consider if the full flush 872# and the refill costs are offset by the savings of sending fewer IPIs. 873config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 874 bool 875 876config CC_HAS_INT128 877 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 878 879config CC_IMPLICIT_FALLTHROUGH 880 string 881 default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5) 882 default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough) 883 884# Currently, disable gcc-12 array-bounds globally. 885# We may want to target only particular configurations some day. 886config GCC12_NO_ARRAY_BOUNDS 887 def_bool y 888 889config CC_NO_ARRAY_BOUNDS 890 bool 891 default y if CC_IS_GCC && GCC_VERSION >= 120000 && GCC_VERSION < 130000 && GCC12_NO_ARRAY_BOUNDS 892 893# 894# For architectures that know their GCC __int128 support is sound 895# 896config ARCH_SUPPORTS_INT128 897 bool 898 899# For architectures that (ab)use NUMA to represent different memory regions 900# all cpu-local but of different latencies, such as SuperH. 901# 902config ARCH_WANT_NUMA_VARIABLE_LOCALITY 903 bool 904 905config NUMA_BALANCING 906 bool "Memory placement aware NUMA scheduler" 907 depends on ARCH_SUPPORTS_NUMA_BALANCING 908 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 909 depends on SMP && NUMA && MIGRATION && !PREEMPT_RT 910 help 911 This option adds support for automatic NUMA aware memory/task placement. 912 The mechanism is quite primitive and is based on migrating memory when 913 it has references to the node the task is running on. 914 915 This system will be inactive on UMA systems. 916 917config NUMA_BALANCING_DEFAULT_ENABLED 918 bool "Automatically enable NUMA aware memory/task placement" 919 default y 920 depends on NUMA_BALANCING 921 help 922 If set, automatic NUMA balancing will be enabled if running on a NUMA 923 machine. 924 925menuconfig CGROUPS 926 bool "Control Group support" 927 select KERNFS 928 help 929 This option adds support for grouping sets of processes together, for 930 use with process control subsystems such as Cpusets, CFS, memory 931 controls or device isolation. 932 See 933 - Documentation/scheduler/sched-design-CFS.rst (CFS) 934 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 935 and resource control) 936 937 Say N if unsure. 938 939if CGROUPS 940 941config PAGE_COUNTER 942 bool 943 944config CGROUP_FAVOR_DYNMODS 945 bool "Favor dynamic modification latency reduction by default" 946 help 947 This option enables the "favordynmods" mount option by default 948 which reduces the latencies of dynamic cgroup modifications such 949 as task migrations and controller on/offs at the cost of making 950 hot path operations such as forks and exits more expensive. 951 952 Say N if unsure. 953 954config MEMCG 955 bool "Memory controller" 956 select PAGE_COUNTER 957 select EVENTFD 958 help 959 Provides control over the memory footprint of tasks in a cgroup. 960 961config MEMCG_SWAP 962 bool 963 depends on MEMCG && SWAP 964 default y 965 966config MEMCG_KMEM 967 bool 968 depends on MEMCG && !SLOB 969 default y 970 971config BLK_CGROUP 972 bool "IO controller" 973 depends on BLOCK 974 default n 975 help 976 Generic block IO controller cgroup interface. This is the common 977 cgroup interface which should be used by various IO controlling 978 policies. 979 980 Currently, CFQ IO scheduler uses it to recognize task groups and 981 control disk bandwidth allocation (proportional time slice allocation) 982 to such task groups. It is also used by bio throttling logic in 983 block layer to implement upper limit in IO rates on a device. 984 985 This option only enables generic Block IO controller infrastructure. 986 One needs to also enable actual IO controlling logic/policy. For 987 enabling proportional weight division of disk bandwidth in CFQ, set 988 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 989 CONFIG_BLK_DEV_THROTTLING=y. 990 991 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 992 993config CGROUP_WRITEBACK 994 bool 995 depends on MEMCG && BLK_CGROUP 996 default y 997 998menuconfig CGROUP_SCHED 999 bool "CPU controller" 1000 default n 1001 help 1002 This feature lets CPU scheduler recognize task groups and control CPU 1003 bandwidth allocation to such task groups. It uses cgroups to group 1004 tasks. 1005 1006if CGROUP_SCHED 1007config FAIR_GROUP_SCHED 1008 bool "Group scheduling for SCHED_OTHER" 1009 depends on CGROUP_SCHED 1010 default CGROUP_SCHED 1011 1012config CFS_BANDWIDTH 1013 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 1014 depends on FAIR_GROUP_SCHED 1015 default n 1016 help 1017 This option allows users to define CPU bandwidth rates (limits) for 1018 tasks running within the fair group scheduler. Groups with no limit 1019 set are considered to be unconstrained and will run with no 1020 restriction. 1021 See Documentation/scheduler/sched-bwc.rst for more information. 1022 1023config RT_GROUP_SCHED 1024 bool "Group scheduling for SCHED_RR/FIFO" 1025 depends on CGROUP_SCHED 1026 default n 1027 help 1028 This feature lets you explicitly allocate real CPU bandwidth 1029 to task groups. If enabled, it will also make it impossible to 1030 schedule realtime tasks for non-root users until you allocate 1031 realtime bandwidth for them. 1032 See Documentation/scheduler/sched-rt-group.rst for more information. 1033 1034endif #CGROUP_SCHED 1035 1036config UCLAMP_TASK_GROUP 1037 bool "Utilization clamping per group of tasks" 1038 depends on CGROUP_SCHED 1039 depends on UCLAMP_TASK 1040 default n 1041 help 1042 This feature enables the scheduler to track the clamped utilization 1043 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 1044 1045 When this option is enabled, the user can specify a min and max 1046 CPU bandwidth which is allowed for each single task in a group. 1047 The max bandwidth allows to clamp the maximum frequency a task 1048 can use, while the min bandwidth allows to define a minimum 1049 frequency a task will always use. 1050 1051 When task group based utilization clamping is enabled, an eventually 1052 specified task-specific clamp value is constrained by the cgroup 1053 specified clamp value. Both minimum and maximum task clamping cannot 1054 be bigger than the corresponding clamping defined at task group level. 1055 1056 If in doubt, say N. 1057 1058config CGROUP_PIDS 1059 bool "PIDs controller" 1060 help 1061 Provides enforcement of process number limits in the scope of a 1062 cgroup. Any attempt to fork more processes than is allowed in the 1063 cgroup will fail. PIDs are fundamentally a global resource because it 1064 is fairly trivial to reach PID exhaustion before you reach even a 1065 conservative kmemcg limit. As a result, it is possible to grind a 1066 system to halt without being limited by other cgroup policies. The 1067 PIDs controller is designed to stop this from happening. 1068 1069 It should be noted that organisational operations (such as attaching 1070 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 1071 since the PIDs limit only affects a process's ability to fork, not to 1072 attach to a cgroup. 1073 1074config CGROUP_RDMA 1075 bool "RDMA controller" 1076 help 1077 Provides enforcement of RDMA resources defined by IB stack. 1078 It is fairly easy for consumers to exhaust RDMA resources, which 1079 can result into resource unavailability to other consumers. 1080 RDMA controller is designed to stop this from happening. 1081 Attaching processes with active RDMA resources to the cgroup 1082 hierarchy is allowed even if can cross the hierarchy's limit. 1083 1084config CGROUP_FREEZER 1085 bool "Freezer controller" 1086 help 1087 Provides a way to freeze and unfreeze all tasks in a 1088 cgroup. 1089 1090 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1091 controller includes important in-kernel memory consumers per default. 1092 1093 If you're using cgroup2, say N. 1094 1095config CGROUP_HUGETLB 1096 bool "HugeTLB controller" 1097 depends on HUGETLB_PAGE 1098 select PAGE_COUNTER 1099 default n 1100 help 1101 Provides a cgroup controller for HugeTLB pages. 1102 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1103 The limit is enforced during page fault. Since HugeTLB doesn't 1104 support page reclaim, enforcing the limit at page fault time implies 1105 that, the application will get SIGBUS signal if it tries to access 1106 HugeTLB pages beyond its limit. This requires the application to know 1107 beforehand how much HugeTLB pages it would require for its use. The 1108 control group is tracked in the third page lru pointer. This means 1109 that we cannot use the controller with huge page less than 3 pages. 1110 1111config CPUSETS 1112 bool "Cpuset controller" 1113 depends on SMP 1114 help 1115 This option will let you create and manage CPUSETs which 1116 allow dynamically partitioning a system into sets of CPUs and 1117 Memory Nodes and assigning tasks to run only within those sets. 1118 This is primarily useful on large SMP or NUMA systems. 1119 1120 Say N if unsure. 1121 1122config PROC_PID_CPUSET 1123 bool "Include legacy /proc/<pid>/cpuset file" 1124 depends on CPUSETS 1125 default y 1126 1127config CGROUP_DEVICE 1128 bool "Device controller" 1129 help 1130 Provides a cgroup controller implementing whitelists for 1131 devices which a process in the cgroup can mknod or open. 1132 1133config CGROUP_CPUACCT 1134 bool "Simple CPU accounting controller" 1135 help 1136 Provides a simple controller for monitoring the 1137 total CPU consumed by the tasks in a cgroup. 1138 1139config CGROUP_PERF 1140 bool "Perf controller" 1141 depends on PERF_EVENTS 1142 help 1143 This option extends the perf per-cpu mode to restrict monitoring 1144 to threads which belong to the cgroup specified and run on the 1145 designated cpu. Or this can be used to have cgroup ID in samples 1146 so that it can monitor performance events among cgroups. 1147 1148 Say N if unsure. 1149 1150config CGROUP_BPF 1151 bool "Support for eBPF programs attached to cgroups" 1152 depends on BPF_SYSCALL 1153 select SOCK_CGROUP_DATA 1154 help 1155 Allow attaching eBPF programs to a cgroup using the bpf(2) 1156 syscall command BPF_PROG_ATTACH. 1157 1158 In which context these programs are accessed depends on the type 1159 of attachment. For instance, programs that are attached using 1160 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1161 inet sockets. 1162 1163config CGROUP_MISC 1164 bool "Misc resource controller" 1165 default n 1166 help 1167 Provides a controller for miscellaneous resources on a host. 1168 1169 Miscellaneous scalar resources are the resources on the host system 1170 which cannot be abstracted like the other cgroups. This controller 1171 tracks and limits the miscellaneous resources used by a process 1172 attached to a cgroup hierarchy. 1173 1174 For more information, please check misc cgroup section in 1175 /Documentation/admin-guide/cgroup-v2.rst. 1176 1177config CGROUP_DEBUG 1178 bool "Debug controller" 1179 default n 1180 depends on DEBUG_KERNEL 1181 help 1182 This option enables a simple controller that exports 1183 debugging information about the cgroups framework. This 1184 controller is for control cgroup debugging only. Its 1185 interfaces are not stable. 1186 1187 Say N. 1188 1189config SOCK_CGROUP_DATA 1190 bool 1191 default n 1192 1193endif # CGROUPS 1194 1195menuconfig NAMESPACES 1196 bool "Namespaces support" if EXPERT 1197 depends on MULTIUSER 1198 default !EXPERT 1199 help 1200 Provides the way to make tasks work with different objects using 1201 the same id. For example same IPC id may refer to different objects 1202 or same user id or pid may refer to different tasks when used in 1203 different namespaces. 1204 1205if NAMESPACES 1206 1207config UTS_NS 1208 bool "UTS namespace" 1209 default y 1210 help 1211 In this namespace tasks see different info provided with the 1212 uname() system call 1213 1214config TIME_NS 1215 bool "TIME namespace" 1216 depends on GENERIC_VDSO_TIME_NS 1217 default y 1218 help 1219 In this namespace boottime and monotonic clocks can be set. 1220 The time will keep going with the same pace. 1221 1222config IPC_NS 1223 bool "IPC namespace" 1224 depends on (SYSVIPC || POSIX_MQUEUE) 1225 default y 1226 help 1227 In this namespace tasks work with IPC ids which correspond to 1228 different IPC objects in different namespaces. 1229 1230config USER_NS 1231 bool "User namespace" 1232 default n 1233 help 1234 This allows containers, i.e. vservers, to use user namespaces 1235 to provide different user info for different servers. 1236 1237 When user namespaces are enabled in the kernel it is 1238 recommended that the MEMCG option also be enabled and that 1239 user-space use the memory control groups to limit the amount 1240 of memory a memory unprivileged users can use. 1241 1242 If unsure, say N. 1243 1244config PID_NS 1245 bool "PID Namespaces" 1246 default y 1247 help 1248 Support process id namespaces. This allows having multiple 1249 processes with the same pid as long as they are in different 1250 pid namespaces. This is a building block of containers. 1251 1252config NET_NS 1253 bool "Network namespace" 1254 depends on NET 1255 default y 1256 help 1257 Allow user space to create what appear to be multiple instances 1258 of the network stack. 1259 1260endif # NAMESPACES 1261 1262config CHECKPOINT_RESTORE 1263 bool "Checkpoint/restore support" 1264 select PROC_CHILDREN 1265 select KCMP 1266 default n 1267 help 1268 Enables additional kernel features in a sake of checkpoint/restore. 1269 In particular it adds auxiliary prctl codes to setup process text, 1270 data and heap segment sizes, and a few additional /proc filesystem 1271 entries. 1272 1273 If unsure, say N here. 1274 1275config SCHED_AUTOGROUP 1276 bool "Automatic process group scheduling" 1277 select CGROUPS 1278 select CGROUP_SCHED 1279 select FAIR_GROUP_SCHED 1280 help 1281 This option optimizes the scheduler for common desktop workloads by 1282 automatically creating and populating task groups. This separation 1283 of workloads isolates aggressive CPU burners (like build jobs) from 1284 desktop applications. Task group autogeneration is currently based 1285 upon task session. 1286 1287config SYSFS_DEPRECATED 1288 bool "Enable deprecated sysfs features to support old userspace tools" 1289 depends on SYSFS 1290 default n 1291 help 1292 This option adds code that switches the layout of the "block" class 1293 devices, to not show up in /sys/class/block/, but only in 1294 /sys/block/. 1295 1296 This switch is only active when the sysfs.deprecated=1 boot option is 1297 passed or the SYSFS_DEPRECATED_V2 option is set. 1298 1299 This option allows new kernels to run on old distributions and tools, 1300 which might get confused by /sys/class/block/. Since 2007/2008 all 1301 major distributions and tools handle this just fine. 1302 1303 Recent distributions and userspace tools after 2009/2010 depend on 1304 the existence of /sys/class/block/, and will not work with this 1305 option enabled. 1306 1307 Only if you are using a new kernel on an old distribution, you might 1308 need to say Y here. 1309 1310config SYSFS_DEPRECATED_V2 1311 bool "Enable deprecated sysfs features by default" 1312 default n 1313 depends on SYSFS 1314 depends on SYSFS_DEPRECATED 1315 help 1316 Enable deprecated sysfs by default. 1317 1318 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1319 option. 1320 1321 Only if you are using a new kernel on an old distribution, you might 1322 need to say Y here. Even then, odds are you would not need it 1323 enabled, you can always pass the boot option if absolutely necessary. 1324 1325config RELAY 1326 bool "Kernel->user space relay support (formerly relayfs)" 1327 select IRQ_WORK 1328 help 1329 This option enables support for relay interface support in 1330 certain file systems (such as debugfs). 1331 It is designed to provide an efficient mechanism for tools and 1332 facilities to relay large amounts of data from kernel space to 1333 user space. 1334 1335 If unsure, say N. 1336 1337config BLK_DEV_INITRD 1338 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1339 help 1340 The initial RAM filesystem is a ramfs which is loaded by the 1341 boot loader (loadlin or lilo) and that is mounted as root 1342 before the normal boot procedure. It is typically used to 1343 load modules needed to mount the "real" root file system, 1344 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1345 1346 If RAM disk support (BLK_DEV_RAM) is also included, this 1347 also enables initial RAM disk (initrd) support and adds 1348 15 Kbytes (more on some other architectures) to the kernel size. 1349 1350 If unsure say Y. 1351 1352if BLK_DEV_INITRD 1353 1354source "usr/Kconfig" 1355 1356endif 1357 1358config BOOT_CONFIG 1359 bool "Boot config support" 1360 select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED 1361 help 1362 Extra boot config allows system admin to pass a config file as 1363 complemental extension of kernel cmdline when booting. 1364 The boot config file must be attached at the end of initramfs 1365 with checksum, size and magic word. 1366 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1367 1368 If unsure, say Y. 1369 1370config BOOT_CONFIG_EMBED 1371 bool "Embed bootconfig file in the kernel" 1372 depends on BOOT_CONFIG 1373 help 1374 Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the 1375 kernel. Usually, the bootconfig file is loaded with the initrd 1376 image. But if the system doesn't support initrd, this option will 1377 help you by embedding a bootconfig file while building the kernel. 1378 1379 If unsure, say N. 1380 1381config BOOT_CONFIG_EMBED_FILE 1382 string "Embedded bootconfig file path" 1383 depends on BOOT_CONFIG_EMBED 1384 help 1385 Specify a bootconfig file which will be embedded to the kernel. 1386 This bootconfig will be used if there is no initrd or no other 1387 bootconfig in the initrd. 1388 1389config INITRAMFS_PRESERVE_MTIME 1390 bool "Preserve cpio archive mtimes in initramfs" 1391 default y 1392 help 1393 Each entry in an initramfs cpio archive carries an mtime value. When 1394 enabled, extracted cpio items take this mtime, with directory mtime 1395 setting deferred until after creation of any child entries. 1396 1397 If unsure, say Y. 1398 1399choice 1400 prompt "Compiler optimization level" 1401 default CC_OPTIMIZE_FOR_PERFORMANCE 1402 1403config CC_OPTIMIZE_FOR_PERFORMANCE 1404 bool "Optimize for performance (-O2)" 1405 help 1406 This is the default optimization level for the kernel, building 1407 with the "-O2" compiler flag for best performance and most 1408 helpful compile-time warnings. 1409 1410config CC_OPTIMIZE_FOR_SIZE 1411 bool "Optimize for size (-Os)" 1412 help 1413 Choosing this option will pass "-Os" to your compiler resulting 1414 in a smaller kernel. 1415 1416endchoice 1417 1418config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1419 bool 1420 help 1421 This requires that the arch annotates or otherwise protects 1422 its external entry points from being discarded. Linker scripts 1423 must also merge .text.*, .data.*, and .bss.* correctly into 1424 output sections. Care must be taken not to pull in unrelated 1425 sections (e.g., '.text.init'). Typically '.' in section names 1426 is used to distinguish them from label names / C identifiers. 1427 1428config LD_DEAD_CODE_DATA_ELIMINATION 1429 bool "Dead code and data elimination (EXPERIMENTAL)" 1430 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1431 depends on EXPERT 1432 depends on $(cc-option,-ffunction-sections -fdata-sections) 1433 depends on $(ld-option,--gc-sections) 1434 help 1435 Enable this if you want to do dead code and data elimination with 1436 the linker by compiling with -ffunction-sections -fdata-sections, 1437 and linking with --gc-sections. 1438 1439 This can reduce on disk and in-memory size of the kernel 1440 code and static data, particularly for small configs and 1441 on small systems. This has the possibility of introducing 1442 silently broken kernel if the required annotations are not 1443 present. This option is not well tested yet, so use at your 1444 own risk. 1445 1446config LD_ORPHAN_WARN 1447 def_bool y 1448 depends on ARCH_WANT_LD_ORPHAN_WARN 1449 depends on $(ld-option,--orphan-handling=warn) 1450 1451config SYSCTL 1452 bool 1453 1454config HAVE_UID16 1455 bool 1456 1457config SYSCTL_EXCEPTION_TRACE 1458 bool 1459 help 1460 Enable support for /proc/sys/debug/exception-trace. 1461 1462config SYSCTL_ARCH_UNALIGN_NO_WARN 1463 bool 1464 help 1465 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1466 Allows arch to define/use @no_unaligned_warning to possibly warn 1467 about unaligned access emulation going on under the hood. 1468 1469config SYSCTL_ARCH_UNALIGN_ALLOW 1470 bool 1471 help 1472 Enable support for /proc/sys/kernel/unaligned-trap 1473 Allows arches to define/use @unaligned_enabled to runtime toggle 1474 the unaligned access emulation. 1475 see arch/parisc/kernel/unaligned.c for reference 1476 1477config HAVE_PCSPKR_PLATFORM 1478 bool 1479 1480# interpreter that classic socket filters depend on 1481config BPF 1482 bool 1483 select CRYPTO_LIB_SHA1 1484 1485menuconfig EXPERT 1486 bool "Configure standard kernel features (expert users)" 1487 # Unhide debug options, to make the on-by-default options visible 1488 select DEBUG_KERNEL 1489 help 1490 This option allows certain base kernel options and settings 1491 to be disabled or tweaked. This is for specialized 1492 environments which can tolerate a "non-standard" kernel. 1493 Only use this if you really know what you are doing. 1494 1495config UID16 1496 bool "Enable 16-bit UID system calls" if EXPERT 1497 depends on HAVE_UID16 && MULTIUSER 1498 default y 1499 help 1500 This enables the legacy 16-bit UID syscall wrappers. 1501 1502config MULTIUSER 1503 bool "Multiple users, groups and capabilities support" if EXPERT 1504 default y 1505 help 1506 This option enables support for non-root users, groups and 1507 capabilities. 1508 1509 If you say N here, all processes will run with UID 0, GID 0, and all 1510 possible capabilities. Saying N here also compiles out support for 1511 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1512 setgid, and capset. 1513 1514 If unsure, say Y here. 1515 1516config SGETMASK_SYSCALL 1517 bool "sgetmask/ssetmask syscalls support" if EXPERT 1518 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1519 help 1520 sys_sgetmask and sys_ssetmask are obsolete system calls 1521 no longer supported in libc but still enabled by default in some 1522 architectures. 1523 1524 If unsure, leave the default option here. 1525 1526config SYSFS_SYSCALL 1527 bool "Sysfs syscall support" if EXPERT 1528 default y 1529 help 1530 sys_sysfs is an obsolete system call no longer supported in libc. 1531 Note that disabling this option is more secure but might break 1532 compatibility with some systems. 1533 1534 If unsure say Y here. 1535 1536config FHANDLE 1537 bool "open by fhandle syscalls" if EXPERT 1538 select EXPORTFS 1539 default y 1540 help 1541 If you say Y here, a user level program will be able to map 1542 file names to handle and then later use the handle for 1543 different file system operations. This is useful in implementing 1544 userspace file servers, which now track files using handles instead 1545 of names. The handle would remain the same even if file names 1546 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1547 syscalls. 1548 1549config POSIX_TIMERS 1550 bool "Posix Clocks & timers" if EXPERT 1551 default y 1552 help 1553 This includes native support for POSIX timers to the kernel. 1554 Some embedded systems have no use for them and therefore they 1555 can be configured out to reduce the size of the kernel image. 1556 1557 When this option is disabled, the following syscalls won't be 1558 available: timer_create, timer_gettime: timer_getoverrun, 1559 timer_settime, timer_delete, clock_adjtime, getitimer, 1560 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1561 clock_getres and clock_nanosleep syscalls will be limited to 1562 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1563 1564 If unsure say y. 1565 1566config PRINTK 1567 default y 1568 bool "Enable support for printk" if EXPERT 1569 select IRQ_WORK 1570 help 1571 This option enables normal printk support. Removing it 1572 eliminates most of the message strings from the kernel image 1573 and makes the kernel more or less silent. As this makes it 1574 very difficult to diagnose system problems, saying N here is 1575 strongly discouraged. 1576 1577config BUG 1578 bool "BUG() support" if EXPERT 1579 default y 1580 help 1581 Disabling this option eliminates support for BUG and WARN, reducing 1582 the size of your kernel image and potentially quietly ignoring 1583 numerous fatal conditions. You should only consider disabling this 1584 option for embedded systems with no facilities for reporting errors. 1585 Just say Y. 1586 1587config ELF_CORE 1588 depends on COREDUMP 1589 default y 1590 bool "Enable ELF core dumps" if EXPERT 1591 help 1592 Enable support for generating core dumps. Disabling saves about 4k. 1593 1594 1595config PCSPKR_PLATFORM 1596 bool "Enable PC-Speaker support" if EXPERT 1597 depends on HAVE_PCSPKR_PLATFORM 1598 select I8253_LOCK 1599 default y 1600 help 1601 This option allows to disable the internal PC-Speaker 1602 support, saving some memory. 1603 1604config BASE_FULL 1605 default y 1606 bool "Enable full-sized data structures for core" if EXPERT 1607 help 1608 Disabling this option reduces the size of miscellaneous core 1609 kernel data structures. This saves memory on small machines, 1610 but may reduce performance. 1611 1612config FUTEX 1613 bool "Enable futex support" if EXPERT 1614 depends on !(SPARC32 && SMP) 1615 default y 1616 imply RT_MUTEXES 1617 help 1618 Disabling this option will cause the kernel to be built without 1619 support for "fast userspace mutexes". The resulting kernel may not 1620 run glibc-based applications correctly. 1621 1622config FUTEX_PI 1623 bool 1624 depends on FUTEX && RT_MUTEXES 1625 default y 1626 1627config EPOLL 1628 bool "Enable eventpoll support" if EXPERT 1629 default y 1630 help 1631 Disabling this option will cause the kernel to be built without 1632 support for epoll family of system calls. 1633 1634config SIGNALFD 1635 bool "Enable signalfd() system call" if EXPERT 1636 default y 1637 help 1638 Enable the signalfd() system call that allows to receive signals 1639 on a file descriptor. 1640 1641 If unsure, say Y. 1642 1643config TIMERFD 1644 bool "Enable timerfd() system call" if EXPERT 1645 default y 1646 help 1647 Enable the timerfd() system call that allows to receive timer 1648 events on a file descriptor. 1649 1650 If unsure, say Y. 1651 1652config EVENTFD 1653 bool "Enable eventfd() system call" if EXPERT 1654 default y 1655 help 1656 Enable the eventfd() system call that allows to receive both 1657 kernel notification (ie. KAIO) or userspace notifications. 1658 1659 If unsure, say Y. 1660 1661config SHMEM 1662 bool "Use full shmem filesystem" if EXPERT 1663 default y 1664 depends on MMU 1665 help 1666 The shmem is an internal filesystem used to manage shared memory. 1667 It is backed by swap and manages resource limits. It is also exported 1668 to userspace as tmpfs if TMPFS is enabled. Disabling this 1669 option replaces shmem and tmpfs with the much simpler ramfs code, 1670 which may be appropriate on small systems without swap. 1671 1672config AIO 1673 bool "Enable AIO support" if EXPERT 1674 default y 1675 help 1676 This option enables POSIX asynchronous I/O which may by used 1677 by some high performance threaded applications. Disabling 1678 this option saves about 7k. 1679 1680config IO_URING 1681 bool "Enable IO uring support" if EXPERT 1682 select IO_WQ 1683 default y 1684 help 1685 This option enables support for the io_uring interface, enabling 1686 applications to submit and complete IO through submission and 1687 completion rings that are shared between the kernel and application. 1688 1689config ADVISE_SYSCALLS 1690 bool "Enable madvise/fadvise syscalls" if EXPERT 1691 default y 1692 help 1693 This option enables the madvise and fadvise syscalls, used by 1694 applications to advise the kernel about their future memory or file 1695 usage, improving performance. If building an embedded system where no 1696 applications use these syscalls, you can disable this option to save 1697 space. 1698 1699config MEMBARRIER 1700 bool "Enable membarrier() system call" if EXPERT 1701 default y 1702 help 1703 Enable the membarrier() system call that allows issuing memory 1704 barriers across all running threads, which can be used to distribute 1705 the cost of user-space memory barriers asymmetrically by transforming 1706 pairs of memory barriers into pairs consisting of membarrier() and a 1707 compiler barrier. 1708 1709 If unsure, say Y. 1710 1711config KALLSYMS 1712 bool "Load all symbols for debugging/ksymoops" if EXPERT 1713 default y 1714 help 1715 Say Y here to let the kernel print out symbolic crash information and 1716 symbolic stack backtraces. This increases the size of the kernel 1717 somewhat, as all symbols have to be loaded into the kernel image. 1718 1719config KALLSYMS_ALL 1720 bool "Include all symbols in kallsyms" 1721 depends on DEBUG_KERNEL && KALLSYMS 1722 help 1723 Normally kallsyms only contains the symbols of functions for nicer 1724 OOPS messages and backtraces (i.e., symbols from the text and inittext 1725 sections). This is sufficient for most cases. And only if you want to 1726 enable kernel live patching, or other less common use cases (e.g., 1727 when a debugger is used) all symbols are required (i.e., names of 1728 variables from the data sections, etc). 1729 1730 This option makes sure that all symbols are loaded into the kernel 1731 image (i.e., symbols from all sections) in cost of increased kernel 1732 size (depending on the kernel configuration, it may be 300KiB or 1733 something like this). 1734 1735 Say N unless you really need all symbols, or kernel live patching. 1736 1737config KALLSYMS_ABSOLUTE_PERCPU 1738 bool 1739 depends on KALLSYMS 1740 default X86_64 && SMP 1741 1742config KALLSYMS_BASE_RELATIVE 1743 bool 1744 depends on KALLSYMS 1745 default !IA64 1746 help 1747 Instead of emitting them as absolute values in the native word size, 1748 emit the symbol references in the kallsyms table as 32-bit entries, 1749 each containing a relative value in the range [base, base + U32_MAX] 1750 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1751 an absolute value in the range [0, S32_MAX] or a relative value in the 1752 range [base, base + S32_MAX], where base is the lowest relative symbol 1753 address encountered in the image. 1754 1755 On 64-bit builds, this reduces the size of the address table by 50%, 1756 but more importantly, it results in entries whose values are build 1757 time constants, and no relocation pass is required at runtime to fix 1758 up the entries based on the runtime load address of the kernel. 1759 1760# end of the "standard kernel features (expert users)" menu 1761 1762# syscall, maps, verifier 1763 1764config ARCH_HAS_MEMBARRIER_CALLBACKS 1765 bool 1766 1767config ARCH_HAS_MEMBARRIER_SYNC_CORE 1768 bool 1769 1770config KCMP 1771 bool "Enable kcmp() system call" if EXPERT 1772 help 1773 Enable the kernel resource comparison system call. It provides 1774 user-space with the ability to compare two processes to see if they 1775 share a common resource, such as a file descriptor or even virtual 1776 memory space. 1777 1778 If unsure, say N. 1779 1780config RSEQ 1781 bool "Enable rseq() system call" if EXPERT 1782 default y 1783 depends on HAVE_RSEQ 1784 select MEMBARRIER 1785 help 1786 Enable the restartable sequences system call. It provides a 1787 user-space cache for the current CPU number value, which 1788 speeds up getting the current CPU number from user-space, 1789 as well as an ABI to speed up user-space operations on 1790 per-CPU data. 1791 1792 If unsure, say Y. 1793 1794config DEBUG_RSEQ 1795 default n 1796 bool "Enabled debugging of rseq() system call" if EXPERT 1797 depends on RSEQ && DEBUG_KERNEL 1798 help 1799 Enable extra debugging checks for the rseq system call. 1800 1801 If unsure, say N. 1802 1803config EMBEDDED 1804 bool "Embedded system" 1805 select EXPERT 1806 help 1807 This option should be enabled if compiling the kernel for 1808 an embedded system so certain expert options are available 1809 for configuration. 1810 1811config HAVE_PERF_EVENTS 1812 bool 1813 help 1814 See tools/perf/design.txt for details. 1815 1816config GUEST_PERF_EVENTS 1817 bool 1818 depends on HAVE_PERF_EVENTS 1819 1820config PERF_USE_VMALLOC 1821 bool 1822 help 1823 See tools/perf/design.txt for details 1824 1825config PC104 1826 bool "PC/104 support" if EXPERT 1827 help 1828 Expose PC/104 form factor device drivers and options available for 1829 selection and configuration. Enable this option if your target 1830 machine has a PC/104 bus. 1831 1832menu "Kernel Performance Events And Counters" 1833 1834config PERF_EVENTS 1835 bool "Kernel performance events and counters" 1836 default y if PROFILING 1837 depends on HAVE_PERF_EVENTS 1838 select IRQ_WORK 1839 select SRCU 1840 help 1841 Enable kernel support for various performance events provided 1842 by software and hardware. 1843 1844 Software events are supported either built-in or via the 1845 use of generic tracepoints. 1846 1847 Most modern CPUs support performance events via performance 1848 counter registers. These registers count the number of certain 1849 types of hw events: such as instructions executed, cachemisses 1850 suffered, or branches mis-predicted - without slowing down the 1851 kernel or applications. These registers can also trigger interrupts 1852 when a threshold number of events have passed - and can thus be 1853 used to profile the code that runs on that CPU. 1854 1855 The Linux Performance Event subsystem provides an abstraction of 1856 these software and hardware event capabilities, available via a 1857 system call and used by the "perf" utility in tools/perf/. It 1858 provides per task and per CPU counters, and it provides event 1859 capabilities on top of those. 1860 1861 Say Y if unsure. 1862 1863config DEBUG_PERF_USE_VMALLOC 1864 default n 1865 bool "Debug: use vmalloc to back perf mmap() buffers" 1866 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1867 select PERF_USE_VMALLOC 1868 help 1869 Use vmalloc memory to back perf mmap() buffers. 1870 1871 Mostly useful for debugging the vmalloc code on platforms 1872 that don't require it. 1873 1874 Say N if unsure. 1875 1876endmenu 1877 1878config SYSTEM_DATA_VERIFICATION 1879 def_bool n 1880 select SYSTEM_TRUSTED_KEYRING 1881 select KEYS 1882 select CRYPTO 1883 select CRYPTO_RSA 1884 select ASYMMETRIC_KEY_TYPE 1885 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1886 select ASN1 1887 select OID_REGISTRY 1888 select X509_CERTIFICATE_PARSER 1889 select PKCS7_MESSAGE_PARSER 1890 help 1891 Provide PKCS#7 message verification using the contents of the system 1892 trusted keyring to provide public keys. This then can be used for 1893 module verification, kexec image verification and firmware blob 1894 verification. 1895 1896config PROFILING 1897 bool "Profiling support" 1898 help 1899 Say Y here to enable the extended profiling support mechanisms used 1900 by profilers. 1901 1902# 1903# Place an empty function call at each tracepoint site. Can be 1904# dynamically changed for a probe function. 1905# 1906config TRACEPOINTS 1907 bool 1908 1909endmenu # General setup 1910 1911source "arch/Kconfig" 1912 1913config RT_MUTEXES 1914 bool 1915 default y if PREEMPT_RT 1916 1917config BASE_SMALL 1918 int 1919 default 0 if BASE_FULL 1920 default 1 if !BASE_FULL 1921 1922config MODULE_SIG_FORMAT 1923 def_bool n 1924 select SYSTEM_DATA_VERIFICATION 1925 1926source "kernel/module/Kconfig" 1927 1928config INIT_ALL_POSSIBLE 1929 bool 1930 help 1931 Back when each arch used to define their own cpu_online_mask and 1932 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 1933 with all 1s, and others with all 0s. When they were centralised, 1934 it was better to provide this option than to break all the archs 1935 and have several arch maintainers pursuing me down dark alleys. 1936 1937source "block/Kconfig" 1938 1939config PREEMPT_NOTIFIERS 1940 bool 1941 1942config PADATA 1943 depends on SMP 1944 bool 1945 1946config ASN1 1947 tristate 1948 help 1949 Build a simple ASN.1 grammar compiler that produces a bytecode output 1950 that can be interpreted by the ASN.1 stream decoder and used to 1951 inform it as to what tags are to be expected in a stream and what 1952 functions to call on what tags. 1953 1954source "kernel/Kconfig.locks" 1955 1956config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 1957 bool 1958 1959config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 1960 bool 1961 1962# It may be useful for an architecture to override the definitions of the 1963# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 1964# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 1965# different calling convention for syscalls. They can also override the 1966# macros for not-implemented syscalls in kernel/sys_ni.c and 1967# kernel/time/posix-stubs.c. All these overrides need to be available in 1968# <asm/syscall_wrapper.h>. 1969config ARCH_HAS_SYSCALL_WRAPPER 1970 def_bool n 1971