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) $(m64-flag)) if 64BIT 66 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag)) 67 68config CC_CAN_LINK_STATIC 69 bool 70 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag) -static) if 64BIT 71 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(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 TOOLS_SUPPORT_RELR 81 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 82 83config CC_HAS_ASM_INLINE 84 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 85 86config CONSTRUCTORS 87 bool 88 89config IRQ_WORK 90 bool 91 92config BUILDTIME_TABLE_SORT 93 bool 94 95config THREAD_INFO_IN_TASK 96 bool 97 help 98 Select this to move thread_info off the stack into task_struct. To 99 make this work, an arch will need to remove all thread_info fields 100 except flags and fix any runtime bugs. 101 102 One subtle change that will be needed is to use try_get_task_stack() 103 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 104 105menu "General setup" 106 107config BROKEN 108 bool 109 110config BROKEN_ON_SMP 111 bool 112 depends on BROKEN || !SMP 113 default y 114 115config INIT_ENV_ARG_LIMIT 116 int 117 default 32 if !UML 118 default 128 if UML 119 help 120 Maximum of each of the number of arguments and environment 121 variables passed to init from the kernel command line. 122 123config COMPILE_TEST 124 bool "Compile also drivers which will not load" 125 depends on HAS_IOMEM 126 help 127 Some drivers can be compiled on a different platform than they are 128 intended to be run on. Despite they cannot be loaded there (or even 129 when they load they cannot be used due to missing HW support), 130 developers still, opposing to distributors, might want to build such 131 drivers to compile-test them. 132 133 If you are a developer and want to build everything available, say Y 134 here. If you are a user/distributor, say N here to exclude useless 135 drivers to be distributed. 136 137config UAPI_HEADER_TEST 138 bool "Compile test UAPI headers" 139 depends on HEADERS_INSTALL && CC_CAN_LINK 140 help 141 Compile test headers exported to user-space to ensure they are 142 self-contained, i.e. compilable as standalone units. 143 144 If you are a developer or tester and want to ensure the exported 145 headers are self-contained, say Y here. Otherwise, choose N. 146 147config LOCALVERSION 148 string "Local version - append to kernel release" 149 help 150 Append an extra string to the end of your kernel version. 151 This will show up when you type uname, for example. 152 The string you set here will be appended after the contents of 153 any files with a filename matching localversion* in your 154 object and source tree, in that order. Your total string can 155 be a maximum of 64 characters. 156 157config LOCALVERSION_AUTO 158 bool "Automatically append version information to the version string" 159 default y 160 depends on !COMPILE_TEST 161 help 162 This will try to automatically determine if the current tree is a 163 release tree by looking for git tags that belong to the current 164 top of tree revision. 165 166 A string of the format -gxxxxxxxx will be added to the localversion 167 if a git-based tree is found. The string generated by this will be 168 appended after any matching localversion* files, and after the value 169 set in CONFIG_LOCALVERSION. 170 171 (The actual string used here is the first eight characters produced 172 by running the command: 173 174 $ git rev-parse --verify HEAD 175 176 which is done within the script "scripts/setlocalversion".) 177 178config BUILD_SALT 179 string "Build ID Salt" 180 default "" 181 help 182 The build ID is used to link binaries and their debug info. Setting 183 this option will use the value in the calculation of the build id. 184 This is mostly useful for distributions which want to ensure the 185 build is unique between builds. It's safe to leave the default. 186 187config HAVE_KERNEL_GZIP 188 bool 189 190config HAVE_KERNEL_BZIP2 191 bool 192 193config HAVE_KERNEL_LZMA 194 bool 195 196config HAVE_KERNEL_XZ 197 bool 198 199config HAVE_KERNEL_LZO 200 bool 201 202config HAVE_KERNEL_LZ4 203 bool 204 205config HAVE_KERNEL_ZSTD 206 bool 207 208config HAVE_KERNEL_UNCOMPRESSED 209 bool 210 211choice 212 prompt "Kernel compression mode" 213 default KERNEL_GZIP 214 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 215 help 216 The linux kernel is a kind of self-extracting executable. 217 Several compression algorithms are available, which differ 218 in efficiency, compression and decompression speed. 219 Compression speed is only relevant when building a kernel. 220 Decompression speed is relevant at each boot. 221 222 If you have any problems with bzip2 or lzma compressed 223 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 224 version of this functionality (bzip2 only), for 2.4, was 225 supplied by Christian Ludwig) 226 227 High compression options are mostly useful for users, who 228 are low on disk space (embedded systems), but for whom ram 229 size matters less. 230 231 If in doubt, select 'gzip' 232 233config KERNEL_GZIP 234 bool "Gzip" 235 depends on HAVE_KERNEL_GZIP 236 help 237 The old and tried gzip compression. It provides a good balance 238 between compression ratio and decompression speed. 239 240config KERNEL_BZIP2 241 bool "Bzip2" 242 depends on HAVE_KERNEL_BZIP2 243 help 244 Its compression ratio and speed is intermediate. 245 Decompression speed is slowest among the choices. The kernel 246 size is about 10% smaller with bzip2, in comparison to gzip. 247 Bzip2 uses a large amount of memory. For modern kernels you 248 will need at least 8MB RAM or more for booting. 249 250config KERNEL_LZMA 251 bool "LZMA" 252 depends on HAVE_KERNEL_LZMA 253 help 254 This compression algorithm's ratio is best. Decompression speed 255 is between gzip and bzip2. Compression is slowest. 256 The kernel size is about 33% smaller with LZMA in comparison to gzip. 257 258config KERNEL_XZ 259 bool "XZ" 260 depends on HAVE_KERNEL_XZ 261 help 262 XZ uses the LZMA2 algorithm and instruction set specific 263 BCJ filters which can improve compression ratio of executable 264 code. The size of the kernel is about 30% smaller with XZ in 265 comparison to gzip. On architectures for which there is a BCJ 266 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 267 will create a few percent smaller kernel than plain LZMA. 268 269 The speed is about the same as with LZMA: The decompression 270 speed of XZ is better than that of bzip2 but worse than gzip 271 and LZO. Compression is slow. 272 273config KERNEL_LZO 274 bool "LZO" 275 depends on HAVE_KERNEL_LZO 276 help 277 Its compression ratio is the poorest among the choices. The kernel 278 size is about 10% bigger than gzip; however its speed 279 (both compression and decompression) is the fastest. 280 281config KERNEL_LZ4 282 bool "LZ4" 283 depends on HAVE_KERNEL_LZ4 284 help 285 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 286 A preliminary version of LZ4 de/compression tool is available at 287 <https://code.google.com/p/lz4/>. 288 289 Its compression ratio is worse than LZO. The size of the kernel 290 is about 8% bigger than LZO. But the decompression speed is 291 faster than LZO. 292 293config KERNEL_ZSTD 294 bool "ZSTD" 295 depends on HAVE_KERNEL_ZSTD 296 help 297 ZSTD is a compression algorithm targeting intermediate compression 298 with fast decompression speed. It will compress better than GZIP and 299 decompress around the same speed as LZO, but slower than LZ4. You 300 will need at least 192 KB RAM or more for booting. The zstd command 301 line tool is required for compression. 302 303config KERNEL_UNCOMPRESSED 304 bool "None" 305 depends on HAVE_KERNEL_UNCOMPRESSED 306 help 307 Produce uncompressed kernel image. This option is usually not what 308 you want. It is useful for debugging the kernel in slow simulation 309 environments, where decompressing and moving the kernel is awfully 310 slow. This option allows early boot code to skip the decompressor 311 and jump right at uncompressed kernel image. 312 313endchoice 314 315config DEFAULT_INIT 316 string "Default init path" 317 default "" 318 help 319 This option determines the default init for the system if no init= 320 option is passed on the kernel command line. If the requested path is 321 not present, we will still then move on to attempting further 322 locations (e.g. /sbin/init, etc). If this is empty, we will just use 323 the fallback list when init= is not passed. 324 325config DEFAULT_HOSTNAME 326 string "Default hostname" 327 default "(none)" 328 help 329 This option determines the default system hostname before userspace 330 calls sethostname(2). The kernel traditionally uses "(none)" here, 331 but you may wish to use a different default here to make a minimal 332 system more usable with less configuration. 333 334# 335# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can 336# add proper SWAP support to them, in which case this can be remove. 337# 338config ARCH_NO_SWAP 339 bool 340 341config SWAP 342 bool "Support for paging of anonymous memory (swap)" 343 depends on MMU && BLOCK && !ARCH_NO_SWAP 344 default y 345 help 346 This option allows you to choose whether you want to have support 347 for so called swap devices or swap files in your kernel that are 348 used to provide more virtual memory than the actual RAM present 349 in your computer. If unsure say Y. 350 351config SYSVIPC 352 bool "System V IPC" 353 help 354 Inter Process Communication is a suite of library functions and 355 system calls which let processes (running programs) synchronize and 356 exchange information. It is generally considered to be a good thing, 357 and some programs won't run unless you say Y here. In particular, if 358 you want to run the DOS emulator dosemu under Linux (read the 359 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 360 you'll need to say Y here. 361 362 You can find documentation about IPC with "info ipc" and also in 363 section 6.4 of the Linux Programmer's Guide, available from 364 <http://www.tldp.org/guides.html>. 365 366config SYSVIPC_SYSCTL 367 bool 368 depends on SYSVIPC 369 depends on SYSCTL 370 default y 371 372config POSIX_MQUEUE 373 bool "POSIX Message Queues" 374 depends on NET 375 help 376 POSIX variant of message queues is a part of IPC. In POSIX message 377 queues every message has a priority which decides about succession 378 of receiving it by a process. If you want to compile and run 379 programs written e.g. for Solaris with use of its POSIX message 380 queues (functions mq_*) say Y here. 381 382 POSIX message queues are visible as a filesystem called 'mqueue' 383 and can be mounted somewhere if you want to do filesystem 384 operations on message queues. 385 386 If unsure, say Y. 387 388config POSIX_MQUEUE_SYSCTL 389 bool 390 depends on POSIX_MQUEUE 391 depends on SYSCTL 392 default y 393 394config WATCH_QUEUE 395 bool "General notification queue" 396 default n 397 help 398 399 This is a general notification queue for the kernel to pass events to 400 userspace by splicing them into pipes. It can be used in conjunction 401 with watches for key/keyring change notifications and device 402 notifications. 403 404 See Documentation/watch_queue.rst 405 406config CROSS_MEMORY_ATTACH 407 bool "Enable process_vm_readv/writev syscalls" 408 depends on MMU 409 default y 410 help 411 Enabling this option adds the system calls process_vm_readv and 412 process_vm_writev which allow a process with the correct privileges 413 to directly read from or write to another process' address space. 414 See the man page for more details. 415 416config USELIB 417 bool "uselib syscall" 418 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION 419 help 420 This option enables the uselib syscall, a system call used in the 421 dynamic linker from libc5 and earlier. glibc does not use this 422 system call. If you intend to run programs built on libc5 or 423 earlier, you may need to enable this syscall. Current systems 424 running glibc can safely disable this. 425 426config AUDIT 427 bool "Auditing support" 428 depends on NET 429 help 430 Enable auditing infrastructure that can be used with another 431 kernel subsystem, such as SELinux (which requires this for 432 logging of avc messages output). System call auditing is included 433 on architectures which support it. 434 435config HAVE_ARCH_AUDITSYSCALL 436 bool 437 438config AUDITSYSCALL 439 def_bool y 440 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 441 select FSNOTIFY 442 443source "kernel/irq/Kconfig" 444source "kernel/time/Kconfig" 445source "kernel/Kconfig.preempt" 446 447menu "CPU/Task time and stats accounting" 448 449config VIRT_CPU_ACCOUNTING 450 bool 451 452choice 453 prompt "Cputime accounting" 454 default TICK_CPU_ACCOUNTING if !PPC64 455 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 456 457# Kind of a stub config for the pure tick based cputime accounting 458config TICK_CPU_ACCOUNTING 459 bool "Simple tick based cputime accounting" 460 depends on !S390 && !NO_HZ_FULL 461 help 462 This is the basic tick based cputime accounting that maintains 463 statistics about user, system and idle time spent on per jiffies 464 granularity. 465 466 If unsure, say Y. 467 468config VIRT_CPU_ACCOUNTING_NATIVE 469 bool "Deterministic task and CPU time accounting" 470 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 471 select VIRT_CPU_ACCOUNTING 472 help 473 Select this option to enable more accurate task and CPU time 474 accounting. This is done by reading a CPU counter on each 475 kernel entry and exit and on transitions within the kernel 476 between system, softirq and hardirq state, so there is a 477 small performance impact. In the case of s390 or IBM POWER > 5, 478 this also enables accounting of stolen time on logically-partitioned 479 systems. 480 481config VIRT_CPU_ACCOUNTING_GEN 482 bool "Full dynticks CPU time accounting" 483 depends on HAVE_CONTEXT_TRACKING 484 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 485 depends on GENERIC_CLOCKEVENTS 486 select VIRT_CPU_ACCOUNTING 487 select CONTEXT_TRACKING 488 help 489 Select this option to enable task and CPU time accounting on full 490 dynticks systems. This accounting is implemented by watching every 491 kernel-user boundaries using the context tracking subsystem. 492 The accounting is thus performed at the expense of some significant 493 overhead. 494 495 For now this is only useful if you are working on the full 496 dynticks subsystem development. 497 498 If unsure, say N. 499 500endchoice 501 502config IRQ_TIME_ACCOUNTING 503 bool "Fine granularity task level IRQ time accounting" 504 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 505 help 506 Select this option to enable fine granularity task irq time 507 accounting. This is done by reading a timestamp on each 508 transitions between softirq and hardirq state, so there can be a 509 small performance impact. 510 511 If in doubt, say N here. 512 513config HAVE_SCHED_AVG_IRQ 514 def_bool y 515 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 516 depends on SMP 517 518config SCHED_THERMAL_PRESSURE 519 bool 520 default y if ARM && ARM_CPU_TOPOLOGY 521 default y if ARM64 522 depends on SMP 523 depends on CPU_FREQ_THERMAL 524 help 525 Select this option to enable thermal pressure accounting in the 526 scheduler. Thermal pressure is the value conveyed to the scheduler 527 that reflects the reduction in CPU compute capacity resulted from 528 thermal throttling. Thermal throttling occurs when the performance of 529 a CPU is capped due to high operating temperatures. 530 531 If selected, the scheduler will be able to balance tasks accordingly, 532 i.e. put less load on throttled CPUs than on non/less throttled ones. 533 534 This requires the architecture to implement 535 arch_set_thermal_pressure() and arch_scale_thermal_pressure(). 536 537config BSD_PROCESS_ACCT 538 bool "BSD Process Accounting" 539 depends on MULTIUSER 540 help 541 If you say Y here, a user level program will be able to instruct the 542 kernel (via a special system call) to write process accounting 543 information to a file: whenever a process exits, information about 544 that process will be appended to the file by the kernel. The 545 information includes things such as creation time, owning user, 546 command name, memory usage, controlling terminal etc. (the complete 547 list is in the struct acct in <file:include/linux/acct.h>). It is 548 up to the user level program to do useful things with this 549 information. This is generally a good idea, so say Y. 550 551config BSD_PROCESS_ACCT_V3 552 bool "BSD Process Accounting version 3 file format" 553 depends on BSD_PROCESS_ACCT 554 default n 555 help 556 If you say Y here, the process accounting information is written 557 in a new file format that also logs the process IDs of each 558 process and its parent. Note that this file format is incompatible 559 with previous v0/v1/v2 file formats, so you will need updated tools 560 for processing it. A preliminary version of these tools is available 561 at <http://www.gnu.org/software/acct/>. 562 563config TASKSTATS 564 bool "Export task/process statistics through netlink" 565 depends on NET 566 depends on MULTIUSER 567 default n 568 help 569 Export selected statistics for tasks/processes through the 570 generic netlink interface. Unlike BSD process accounting, the 571 statistics are available during the lifetime of tasks/processes as 572 responses to commands. Like BSD accounting, they are sent to user 573 space on task exit. 574 575 Say N if unsure. 576 577config TASK_DELAY_ACCT 578 bool "Enable per-task delay accounting" 579 depends on TASKSTATS 580 select SCHED_INFO 581 help 582 Collect information on time spent by a task waiting for system 583 resources like cpu, synchronous block I/O completion and swapping 584 in pages. Such statistics can help in setting a task's priorities 585 relative to other tasks for cpu, io, rss limits etc. 586 587 Say N if unsure. 588 589config TASK_XACCT 590 bool "Enable extended accounting over taskstats" 591 depends on TASKSTATS 592 help 593 Collect extended task accounting data and send the data 594 to userland for processing over the taskstats interface. 595 596 Say N if unsure. 597 598config TASK_IO_ACCOUNTING 599 bool "Enable per-task storage I/O accounting" 600 depends on TASK_XACCT 601 help 602 Collect information on the number of bytes of storage I/O which this 603 task has caused. 604 605 Say N if unsure. 606 607config PSI 608 bool "Pressure stall information tracking" 609 help 610 Collect metrics that indicate how overcommitted the CPU, memory, 611 and IO capacity are in the system. 612 613 If you say Y here, the kernel will create /proc/pressure/ with the 614 pressure statistics files cpu, memory, and io. These will indicate 615 the share of walltime in which some or all tasks in the system are 616 delayed due to contention of the respective resource. 617 618 In kernels with cgroup support, cgroups (cgroup2 only) will 619 have cpu.pressure, memory.pressure, and io.pressure files, 620 which aggregate pressure stalls for the grouped tasks only. 621 622 For more details see Documentation/accounting/psi.rst. 623 624 Say N if unsure. 625 626config PSI_DEFAULT_DISABLED 627 bool "Require boot parameter to enable pressure stall information tracking" 628 default n 629 depends on PSI 630 help 631 If set, pressure stall information tracking will be disabled 632 per default but can be enabled through passing psi=1 on the 633 kernel commandline during boot. 634 635 This feature adds some code to the task wakeup and sleep 636 paths of the scheduler. The overhead is too low to affect 637 common scheduling-intense workloads in practice (such as 638 webservers, memcache), but it does show up in artificial 639 scheduler stress tests, such as hackbench. 640 641 If you are paranoid and not sure what the kernel will be 642 used for, say Y. 643 644 Say N if unsure. 645 646endmenu # "CPU/Task time and stats accounting" 647 648config CPU_ISOLATION 649 bool "CPU isolation" 650 depends on SMP || COMPILE_TEST 651 default y 652 help 653 Make sure that CPUs running critical tasks are not disturbed by 654 any source of "noise" such as unbound workqueues, timers, kthreads... 655 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 656 the "isolcpus=" boot parameter. 657 658 Say Y if unsure. 659 660source "kernel/rcu/Kconfig" 661 662config BUILD_BIN2C 663 bool 664 default n 665 666config IKCONFIG 667 tristate "Kernel .config support" 668 help 669 This option enables the complete Linux kernel ".config" file 670 contents to be saved in the kernel. It provides documentation 671 of which kernel options are used in a running kernel or in an 672 on-disk kernel. This information can be extracted from the kernel 673 image file with the script scripts/extract-ikconfig and used as 674 input to rebuild the current kernel or to build another kernel. 675 It can also be extracted from a running kernel by reading 676 /proc/config.gz if enabled (below). 677 678config IKCONFIG_PROC 679 bool "Enable access to .config through /proc/config.gz" 680 depends on IKCONFIG && PROC_FS 681 help 682 This option enables access to the kernel configuration file 683 through /proc/config.gz. 684 685config IKHEADERS 686 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 687 depends on SYSFS 688 help 689 This option enables access to the in-kernel headers that are generated during 690 the build process. These can be used to build eBPF tracing programs, 691 or similar programs. If you build the headers as a module, a module called 692 kheaders.ko is built which can be loaded on-demand to get access to headers. 693 694config LOG_BUF_SHIFT 695 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 696 range 12 25 if !H8300 697 range 12 19 if H8300 698 default 17 699 depends on PRINTK 700 help 701 Select the minimal kernel log buffer size as a power of 2. 702 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 703 parameter, see below. Any higher size also might be forced 704 by "log_buf_len" boot parameter. 705 706 Examples: 707 17 => 128 KB 708 16 => 64 KB 709 15 => 32 KB 710 14 => 16 KB 711 13 => 8 KB 712 12 => 4 KB 713 714config LOG_CPU_MAX_BUF_SHIFT 715 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 716 depends on SMP 717 range 0 21 718 default 12 if !BASE_SMALL 719 default 0 if BASE_SMALL 720 depends on PRINTK 721 help 722 This option allows to increase the default ring buffer size 723 according to the number of CPUs. The value defines the contribution 724 of each CPU as a power of 2. The used space is typically only few 725 lines however it might be much more when problems are reported, 726 e.g. backtraces. 727 728 The increased size means that a new buffer has to be allocated and 729 the original static one is unused. It makes sense only on systems 730 with more CPUs. Therefore this value is used only when the sum of 731 contributions is greater than the half of the default kernel ring 732 buffer as defined by LOG_BUF_SHIFT. The default values are set 733 so that more than 16 CPUs are needed to trigger the allocation. 734 735 Also this option is ignored when "log_buf_len" kernel parameter is 736 used as it forces an exact (power of two) size of the ring buffer. 737 738 The number of possible CPUs is used for this computation ignoring 739 hotplugging making the computation optimal for the worst case 740 scenario while allowing a simple algorithm to be used from bootup. 741 742 Examples shift values and their meaning: 743 17 => 128 KB for each CPU 744 16 => 64 KB for each CPU 745 15 => 32 KB for each CPU 746 14 => 16 KB for each CPU 747 13 => 8 KB for each CPU 748 12 => 4 KB for each CPU 749 750config PRINTK_SAFE_LOG_BUF_SHIFT 751 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 752 range 10 21 753 default 13 754 depends on PRINTK 755 help 756 Select the size of an alternate printk per-CPU buffer where messages 757 printed from usafe contexts are temporary stored. One example would 758 be NMI messages, another one - printk recursion. The messages are 759 copied to the main log buffer in a safe context to avoid a deadlock. 760 The value defines the size as a power of 2. 761 762 Those messages are rare and limited. The largest one is when 763 a backtrace is printed. It usually fits into 4KB. Select 764 8KB if you want to be on the safe side. 765 766 Examples: 767 17 => 128 KB for each CPU 768 16 => 64 KB for each CPU 769 15 => 32 KB for each CPU 770 14 => 16 KB for each CPU 771 13 => 8 KB for each CPU 772 12 => 4 KB for each CPU 773 774# 775# Architectures with an unreliable sched_clock() should select this: 776# 777config HAVE_UNSTABLE_SCHED_CLOCK 778 bool 779 780config GENERIC_SCHED_CLOCK 781 bool 782 783menu "Scheduler features" 784 785config UCLAMP_TASK 786 bool "Enable utilization clamping for RT/FAIR tasks" 787 depends on CPU_FREQ_GOV_SCHEDUTIL 788 help 789 This feature enables the scheduler to track the clamped utilization 790 of each CPU based on RUNNABLE tasks scheduled on that CPU. 791 792 With this option, the user can specify the min and max CPU 793 utilization allowed for RUNNABLE tasks. The max utilization defines 794 the maximum frequency a task should use while the min utilization 795 defines the minimum frequency it should use. 796 797 Both min and max utilization clamp values are hints to the scheduler, 798 aiming at improving its frequency selection policy, but they do not 799 enforce or grant any specific bandwidth for tasks. 800 801 If in doubt, say N. 802 803config UCLAMP_BUCKETS_COUNT 804 int "Number of supported utilization clamp buckets" 805 range 5 20 806 default 5 807 depends on UCLAMP_TASK 808 help 809 Defines the number of clamp buckets to use. The range of each bucket 810 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 811 number of clamp buckets the finer their granularity and the higher 812 the precision of clamping aggregation and tracking at run-time. 813 814 For example, with the minimum configuration value we will have 5 815 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 816 be refcounted in the [20..39]% bucket and will set the bucket clamp 817 effective value to 25%. 818 If a second 30% boosted task should be co-scheduled on the same CPU, 819 that task will be refcounted in the same bucket of the first task and 820 it will boost the bucket clamp effective value to 30%. 821 The clamp effective value of a bucket is reset to its nominal value 822 (20% in the example above) when there are no more tasks refcounted in 823 that bucket. 824 825 An additional boost/capping margin can be added to some tasks. In the 826 example above the 25% task will be boosted to 30% until it exits the 827 CPU. If that should be considered not acceptable on certain systems, 828 it's always possible to reduce the margin by increasing the number of 829 clamp buckets to trade off used memory for run-time tracking 830 precision. 831 832 If in doubt, use the default value. 833 834endmenu 835 836# 837# For architectures that want to enable the support for NUMA-affine scheduler 838# balancing logic: 839# 840config ARCH_SUPPORTS_NUMA_BALANCING 841 bool 842 843# 844# For architectures that prefer to flush all TLBs after a number of pages 845# are unmapped instead of sending one IPI per page to flush. The architecture 846# must provide guarantees on what happens if a clean TLB cache entry is 847# written after the unmap. Details are in mm/rmap.c near the check for 848# should_defer_flush. The architecture should also consider if the full flush 849# and the refill costs are offset by the savings of sending fewer IPIs. 850config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 851 bool 852 853config CC_HAS_INT128 854 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 855 856# 857# For architectures that know their GCC __int128 support is sound 858# 859config ARCH_SUPPORTS_INT128 860 bool 861 862# For architectures that (ab)use NUMA to represent different memory regions 863# all cpu-local but of different latencies, such as SuperH. 864# 865config ARCH_WANT_NUMA_VARIABLE_LOCALITY 866 bool 867 868config NUMA_BALANCING 869 bool "Memory placement aware NUMA scheduler" 870 depends on ARCH_SUPPORTS_NUMA_BALANCING 871 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 872 depends on SMP && NUMA && MIGRATION 873 help 874 This option adds support for automatic NUMA aware memory/task placement. 875 The mechanism is quite primitive and is based on migrating memory when 876 it has references to the node the task is running on. 877 878 This system will be inactive on UMA systems. 879 880config NUMA_BALANCING_DEFAULT_ENABLED 881 bool "Automatically enable NUMA aware memory/task placement" 882 default y 883 depends on NUMA_BALANCING 884 help 885 If set, automatic NUMA balancing will be enabled if running on a NUMA 886 machine. 887 888menuconfig CGROUPS 889 bool "Control Group support" 890 select KERNFS 891 help 892 This option adds support for grouping sets of processes together, for 893 use with process control subsystems such as Cpusets, CFS, memory 894 controls or device isolation. 895 See 896 - Documentation/scheduler/sched-design-CFS.rst (CFS) 897 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 898 and resource control) 899 900 Say N if unsure. 901 902if CGROUPS 903 904config PAGE_COUNTER 905 bool 906 907config MEMCG 908 bool "Memory controller" 909 select PAGE_COUNTER 910 select EVENTFD 911 help 912 Provides control over the memory footprint of tasks in a cgroup. 913 914config MEMCG_SWAP 915 bool 916 depends on MEMCG && SWAP 917 default y 918 919config MEMCG_KMEM 920 bool 921 depends on MEMCG && !SLOB 922 default y 923 924config BLK_CGROUP 925 bool "IO controller" 926 depends on BLOCK 927 default n 928 help 929 Generic block IO controller cgroup interface. This is the common 930 cgroup interface which should be used by various IO controlling 931 policies. 932 933 Currently, CFQ IO scheduler uses it to recognize task groups and 934 control disk bandwidth allocation (proportional time slice allocation) 935 to such task groups. It is also used by bio throttling logic in 936 block layer to implement upper limit in IO rates on a device. 937 938 This option only enables generic Block IO controller infrastructure. 939 One needs to also enable actual IO controlling logic/policy. For 940 enabling proportional weight division of disk bandwidth in CFQ, set 941 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 942 CONFIG_BLK_DEV_THROTTLING=y. 943 944 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 945 946config CGROUP_WRITEBACK 947 bool 948 depends on MEMCG && BLK_CGROUP 949 default y 950 951menuconfig CGROUP_SCHED 952 bool "CPU controller" 953 default n 954 help 955 This feature lets CPU scheduler recognize task groups and control CPU 956 bandwidth allocation to such task groups. It uses cgroups to group 957 tasks. 958 959if CGROUP_SCHED 960config FAIR_GROUP_SCHED 961 bool "Group scheduling for SCHED_OTHER" 962 depends on CGROUP_SCHED 963 default CGROUP_SCHED 964 965config CFS_BANDWIDTH 966 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 967 depends on FAIR_GROUP_SCHED 968 default n 969 help 970 This option allows users to define CPU bandwidth rates (limits) for 971 tasks running within the fair group scheduler. Groups with no limit 972 set are considered to be unconstrained and will run with no 973 restriction. 974 See Documentation/scheduler/sched-bwc.rst for more information. 975 976config RT_GROUP_SCHED 977 bool "Group scheduling for SCHED_RR/FIFO" 978 depends on CGROUP_SCHED 979 default n 980 help 981 This feature lets you explicitly allocate real CPU bandwidth 982 to task groups. If enabled, it will also make it impossible to 983 schedule realtime tasks for non-root users until you allocate 984 realtime bandwidth for them. 985 See Documentation/scheduler/sched-rt-group.rst for more information. 986 987endif #CGROUP_SCHED 988 989config UCLAMP_TASK_GROUP 990 bool "Utilization clamping per group of tasks" 991 depends on CGROUP_SCHED 992 depends on UCLAMP_TASK 993 default n 994 help 995 This feature enables the scheduler to track the clamped utilization 996 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 997 998 When this option is enabled, the user can specify a min and max 999 CPU bandwidth which is allowed for each single task in a group. 1000 The max bandwidth allows to clamp the maximum frequency a task 1001 can use, while the min bandwidth allows to define a minimum 1002 frequency a task will always use. 1003 1004 When task group based utilization clamping is enabled, an eventually 1005 specified task-specific clamp value is constrained by the cgroup 1006 specified clamp value. Both minimum and maximum task clamping cannot 1007 be bigger than the corresponding clamping defined at task group level. 1008 1009 If in doubt, say N. 1010 1011config CGROUP_PIDS 1012 bool "PIDs controller" 1013 help 1014 Provides enforcement of process number limits in the scope of a 1015 cgroup. Any attempt to fork more processes than is allowed in the 1016 cgroup will fail. PIDs are fundamentally a global resource because it 1017 is fairly trivial to reach PID exhaustion before you reach even a 1018 conservative kmemcg limit. As a result, it is possible to grind a 1019 system to halt without being limited by other cgroup policies. The 1020 PIDs controller is designed to stop this from happening. 1021 1022 It should be noted that organisational operations (such as attaching 1023 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 1024 since the PIDs limit only affects a process's ability to fork, not to 1025 attach to a cgroup. 1026 1027config CGROUP_RDMA 1028 bool "RDMA controller" 1029 help 1030 Provides enforcement of RDMA resources defined by IB stack. 1031 It is fairly easy for consumers to exhaust RDMA resources, which 1032 can result into resource unavailability to other consumers. 1033 RDMA controller is designed to stop this from happening. 1034 Attaching processes with active RDMA resources to the cgroup 1035 hierarchy is allowed even if can cross the hierarchy's limit. 1036 1037config CGROUP_FREEZER 1038 bool "Freezer controller" 1039 help 1040 Provides a way to freeze and unfreeze all tasks in a 1041 cgroup. 1042 1043 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1044 controller includes important in-kernel memory consumers per default. 1045 1046 If you're using cgroup2, say N. 1047 1048config CGROUP_HUGETLB 1049 bool "HugeTLB controller" 1050 depends on HUGETLB_PAGE 1051 select PAGE_COUNTER 1052 default n 1053 help 1054 Provides a cgroup controller for HugeTLB pages. 1055 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1056 The limit is enforced during page fault. Since HugeTLB doesn't 1057 support page reclaim, enforcing the limit at page fault time implies 1058 that, the application will get SIGBUS signal if it tries to access 1059 HugeTLB pages beyond its limit. This requires the application to know 1060 beforehand how much HugeTLB pages it would require for its use. The 1061 control group is tracked in the third page lru pointer. This means 1062 that we cannot use the controller with huge page less than 3 pages. 1063 1064config CPUSETS 1065 bool "Cpuset controller" 1066 depends on SMP 1067 help 1068 This option will let you create and manage CPUSETs which 1069 allow dynamically partitioning a system into sets of CPUs and 1070 Memory Nodes and assigning tasks to run only within those sets. 1071 This is primarily useful on large SMP or NUMA systems. 1072 1073 Say N if unsure. 1074 1075config PROC_PID_CPUSET 1076 bool "Include legacy /proc/<pid>/cpuset file" 1077 depends on CPUSETS 1078 default y 1079 1080config CGROUP_DEVICE 1081 bool "Device controller" 1082 help 1083 Provides a cgroup controller implementing whitelists for 1084 devices which a process in the cgroup can mknod or open. 1085 1086config CGROUP_CPUACCT 1087 bool "Simple CPU accounting controller" 1088 help 1089 Provides a simple controller for monitoring the 1090 total CPU consumed by the tasks in a cgroup. 1091 1092config CGROUP_PERF 1093 bool "Perf controller" 1094 depends on PERF_EVENTS 1095 help 1096 This option extends the perf per-cpu mode to restrict monitoring 1097 to threads which belong to the cgroup specified and run on the 1098 designated cpu. Or this can be used to have cgroup ID in samples 1099 so that it can monitor performance events among cgroups. 1100 1101 Say N if unsure. 1102 1103config CGROUP_BPF 1104 bool "Support for eBPF programs attached to cgroups" 1105 depends on BPF_SYSCALL 1106 select SOCK_CGROUP_DATA 1107 help 1108 Allow attaching eBPF programs to a cgroup using the bpf(2) 1109 syscall command BPF_PROG_ATTACH. 1110 1111 In which context these programs are accessed depends on the type 1112 of attachment. For instance, programs that are attached using 1113 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1114 inet sockets. 1115 1116config CGROUP_MISC 1117 bool "Misc resource controller" 1118 default n 1119 help 1120 Provides a controller for miscellaneous resources on a host. 1121 1122 Miscellaneous scalar resources are the resources on the host system 1123 which cannot be abstracted like the other cgroups. This controller 1124 tracks and limits the miscellaneous resources used by a process 1125 attached to a cgroup hierarchy. 1126 1127 For more information, please check misc cgroup section in 1128 /Documentation/admin-guide/cgroup-v2.rst. 1129 1130config CGROUP_DEBUG 1131 bool "Debug controller" 1132 default n 1133 depends on DEBUG_KERNEL 1134 help 1135 This option enables a simple controller that exports 1136 debugging information about the cgroups framework. This 1137 controller is for control cgroup debugging only. Its 1138 interfaces are not stable. 1139 1140 Say N. 1141 1142config SOCK_CGROUP_DATA 1143 bool 1144 default n 1145 1146endif # CGROUPS 1147 1148menuconfig NAMESPACES 1149 bool "Namespaces support" if EXPERT 1150 depends on MULTIUSER 1151 default !EXPERT 1152 help 1153 Provides the way to make tasks work with different objects using 1154 the same id. For example same IPC id may refer to different objects 1155 or same user id or pid may refer to different tasks when used in 1156 different namespaces. 1157 1158if NAMESPACES 1159 1160config UTS_NS 1161 bool "UTS namespace" 1162 default y 1163 help 1164 In this namespace tasks see different info provided with the 1165 uname() system call 1166 1167config TIME_NS 1168 bool "TIME namespace" 1169 depends on GENERIC_VDSO_TIME_NS 1170 default y 1171 help 1172 In this namespace boottime and monotonic clocks can be set. 1173 The time will keep going with the same pace. 1174 1175config IPC_NS 1176 bool "IPC namespace" 1177 depends on (SYSVIPC || POSIX_MQUEUE) 1178 default y 1179 help 1180 In this namespace tasks work with IPC ids which correspond to 1181 different IPC objects in different namespaces. 1182 1183config USER_NS 1184 bool "User namespace" 1185 default n 1186 help 1187 This allows containers, i.e. vservers, to use user namespaces 1188 to provide different user info for different servers. 1189 1190 When user namespaces are enabled in the kernel it is 1191 recommended that the MEMCG option also be enabled and that 1192 user-space use the memory control groups to limit the amount 1193 of memory a memory unprivileged users can use. 1194 1195 If unsure, say N. 1196 1197config PID_NS 1198 bool "PID Namespaces" 1199 default y 1200 help 1201 Support process id namespaces. This allows having multiple 1202 processes with the same pid as long as they are in different 1203 pid namespaces. This is a building block of containers. 1204 1205config NET_NS 1206 bool "Network namespace" 1207 depends on NET 1208 default y 1209 help 1210 Allow user space to create what appear to be multiple instances 1211 of the network stack. 1212 1213endif # NAMESPACES 1214 1215config CHECKPOINT_RESTORE 1216 bool "Checkpoint/restore support" 1217 select PROC_CHILDREN 1218 select KCMP 1219 default n 1220 help 1221 Enables additional kernel features in a sake of checkpoint/restore. 1222 In particular it adds auxiliary prctl codes to setup process text, 1223 data and heap segment sizes, and a few additional /proc filesystem 1224 entries. 1225 1226 If unsure, say N here. 1227 1228config SCHED_AUTOGROUP 1229 bool "Automatic process group scheduling" 1230 select CGROUPS 1231 select CGROUP_SCHED 1232 select FAIR_GROUP_SCHED 1233 help 1234 This option optimizes the scheduler for common desktop workloads by 1235 automatically creating and populating task groups. This separation 1236 of workloads isolates aggressive CPU burners (like build jobs) from 1237 desktop applications. Task group autogeneration is currently based 1238 upon task session. 1239 1240config SYSFS_DEPRECATED 1241 bool "Enable deprecated sysfs features to support old userspace tools" 1242 depends on SYSFS 1243 default n 1244 help 1245 This option adds code that switches the layout of the "block" class 1246 devices, to not show up in /sys/class/block/, but only in 1247 /sys/block/. 1248 1249 This switch is only active when the sysfs.deprecated=1 boot option is 1250 passed or the SYSFS_DEPRECATED_V2 option is set. 1251 1252 This option allows new kernels to run on old distributions and tools, 1253 which might get confused by /sys/class/block/. Since 2007/2008 all 1254 major distributions and tools handle this just fine. 1255 1256 Recent distributions and userspace tools after 2009/2010 depend on 1257 the existence of /sys/class/block/, and will not work with this 1258 option enabled. 1259 1260 Only if you are using a new kernel on an old distribution, you might 1261 need to say Y here. 1262 1263config SYSFS_DEPRECATED_V2 1264 bool "Enable deprecated sysfs features by default" 1265 default n 1266 depends on SYSFS 1267 depends on SYSFS_DEPRECATED 1268 help 1269 Enable deprecated sysfs by default. 1270 1271 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1272 option. 1273 1274 Only if you are using a new kernel on an old distribution, you might 1275 need to say Y here. Even then, odds are you would not need it 1276 enabled, you can always pass the boot option if absolutely necessary. 1277 1278config RELAY 1279 bool "Kernel->user space relay support (formerly relayfs)" 1280 select IRQ_WORK 1281 help 1282 This option enables support for relay interface support in 1283 certain file systems (such as debugfs). 1284 It is designed to provide an efficient mechanism for tools and 1285 facilities to relay large amounts of data from kernel space to 1286 user space. 1287 1288 If unsure, say N. 1289 1290config BLK_DEV_INITRD 1291 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1292 help 1293 The initial RAM filesystem is a ramfs which is loaded by the 1294 boot loader (loadlin or lilo) and that is mounted as root 1295 before the normal boot procedure. It is typically used to 1296 load modules needed to mount the "real" root file system, 1297 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1298 1299 If RAM disk support (BLK_DEV_RAM) is also included, this 1300 also enables initial RAM disk (initrd) support and adds 1301 15 Kbytes (more on some other architectures) to the kernel size. 1302 1303 If unsure say Y. 1304 1305if BLK_DEV_INITRD 1306 1307source "usr/Kconfig" 1308 1309endif 1310 1311config BOOT_CONFIG 1312 bool "Boot config support" 1313 select BLK_DEV_INITRD 1314 help 1315 Extra boot config allows system admin to pass a config file as 1316 complemental extension of kernel cmdline when booting. 1317 The boot config file must be attached at the end of initramfs 1318 with checksum, size and magic word. 1319 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1320 1321 If unsure, say Y. 1322 1323choice 1324 prompt "Compiler optimization level" 1325 default CC_OPTIMIZE_FOR_PERFORMANCE 1326 1327config CC_OPTIMIZE_FOR_PERFORMANCE 1328 bool "Optimize for performance (-O2)" 1329 help 1330 This is the default optimization level for the kernel, building 1331 with the "-O2" compiler flag for best performance and most 1332 helpful compile-time warnings. 1333 1334config CC_OPTIMIZE_FOR_PERFORMANCE_O3 1335 bool "Optimize more for performance (-O3)" 1336 depends on ARC 1337 help 1338 Choosing this option will pass "-O3" to your compiler to optimize 1339 the kernel yet more for performance. 1340 1341config CC_OPTIMIZE_FOR_SIZE 1342 bool "Optimize for size (-Os)" 1343 help 1344 Choosing this option will pass "-Os" to your compiler resulting 1345 in a smaller kernel. 1346 1347endchoice 1348 1349config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1350 bool 1351 help 1352 This requires that the arch annotates or otherwise protects 1353 its external entry points from being discarded. Linker scripts 1354 must also merge .text.*, .data.*, and .bss.* correctly into 1355 output sections. Care must be taken not to pull in unrelated 1356 sections (e.g., '.text.init'). Typically '.' in section names 1357 is used to distinguish them from label names / C identifiers. 1358 1359config LD_DEAD_CODE_DATA_ELIMINATION 1360 bool "Dead code and data elimination (EXPERIMENTAL)" 1361 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1362 depends on EXPERT 1363 depends on $(cc-option,-ffunction-sections -fdata-sections) 1364 depends on $(ld-option,--gc-sections) 1365 help 1366 Enable this if you want to do dead code and data elimination with 1367 the linker by compiling with -ffunction-sections -fdata-sections, 1368 and linking with --gc-sections. 1369 1370 This can reduce on disk and in-memory size of the kernel 1371 code and static data, particularly for small configs and 1372 on small systems. This has the possibility of introducing 1373 silently broken kernel if the required annotations are not 1374 present. This option is not well tested yet, so use at your 1375 own risk. 1376 1377config LD_ORPHAN_WARN 1378 def_bool y 1379 depends on ARCH_WANT_LD_ORPHAN_WARN 1380 depends on !LD_IS_LLD || LLD_VERSION >= 110000 1381 depends on $(ld-option,--orphan-handling=warn) 1382 1383config SYSCTL 1384 bool 1385 1386config HAVE_UID16 1387 bool 1388 1389config SYSCTL_EXCEPTION_TRACE 1390 bool 1391 help 1392 Enable support for /proc/sys/debug/exception-trace. 1393 1394config SYSCTL_ARCH_UNALIGN_NO_WARN 1395 bool 1396 help 1397 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1398 Allows arch to define/use @no_unaligned_warning to possibly warn 1399 about unaligned access emulation going on under the hood. 1400 1401config SYSCTL_ARCH_UNALIGN_ALLOW 1402 bool 1403 help 1404 Enable support for /proc/sys/kernel/unaligned-trap 1405 Allows arches to define/use @unaligned_enabled to runtime toggle 1406 the unaligned access emulation. 1407 see arch/parisc/kernel/unaligned.c for reference 1408 1409config HAVE_PCSPKR_PLATFORM 1410 bool 1411 1412# interpreter that classic socket filters depend on 1413config BPF 1414 bool 1415 1416menuconfig EXPERT 1417 bool "Configure standard kernel features (expert users)" 1418 # Unhide debug options, to make the on-by-default options visible 1419 select DEBUG_KERNEL 1420 help 1421 This option allows certain base kernel options and settings 1422 to be disabled or tweaked. This is for specialized 1423 environments which can tolerate a "non-standard" kernel. 1424 Only use this if you really know what you are doing. 1425 1426config UID16 1427 bool "Enable 16-bit UID system calls" if EXPERT 1428 depends on HAVE_UID16 && MULTIUSER 1429 default y 1430 help 1431 This enables the legacy 16-bit UID syscall wrappers. 1432 1433config MULTIUSER 1434 bool "Multiple users, groups and capabilities support" if EXPERT 1435 default y 1436 help 1437 This option enables support for non-root users, groups and 1438 capabilities. 1439 1440 If you say N here, all processes will run with UID 0, GID 0, and all 1441 possible capabilities. Saying N here also compiles out support for 1442 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1443 setgid, and capset. 1444 1445 If unsure, say Y here. 1446 1447config SGETMASK_SYSCALL 1448 bool "sgetmask/ssetmask syscalls support" if EXPERT 1449 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1450 help 1451 sys_sgetmask and sys_ssetmask are obsolete system calls 1452 no longer supported in libc but still enabled by default in some 1453 architectures. 1454 1455 If unsure, leave the default option here. 1456 1457config SYSFS_SYSCALL 1458 bool "Sysfs syscall support" if EXPERT 1459 default y 1460 help 1461 sys_sysfs is an obsolete system call no longer supported in libc. 1462 Note that disabling this option is more secure but might break 1463 compatibility with some systems. 1464 1465 If unsure say Y here. 1466 1467config FHANDLE 1468 bool "open by fhandle syscalls" if EXPERT 1469 select EXPORTFS 1470 default y 1471 help 1472 If you say Y here, a user level program will be able to map 1473 file names to handle and then later use the handle for 1474 different file system operations. This is useful in implementing 1475 userspace file servers, which now track files using handles instead 1476 of names. The handle would remain the same even if file names 1477 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1478 syscalls. 1479 1480config POSIX_TIMERS 1481 bool "Posix Clocks & timers" if EXPERT 1482 default y 1483 help 1484 This includes native support for POSIX timers to the kernel. 1485 Some embedded systems have no use for them and therefore they 1486 can be configured out to reduce the size of the kernel image. 1487 1488 When this option is disabled, the following syscalls won't be 1489 available: timer_create, timer_gettime: timer_getoverrun, 1490 timer_settime, timer_delete, clock_adjtime, getitimer, 1491 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1492 clock_getres and clock_nanosleep syscalls will be limited to 1493 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1494 1495 If unsure say y. 1496 1497config PRINTK 1498 default y 1499 bool "Enable support for printk" if EXPERT 1500 select IRQ_WORK 1501 help 1502 This option enables normal printk support. Removing it 1503 eliminates most of the message strings from the kernel image 1504 and makes the kernel more or less silent. As this makes it 1505 very difficult to diagnose system problems, saying N here is 1506 strongly discouraged. 1507 1508config PRINTK_NMI 1509 def_bool y 1510 depends on PRINTK 1511 depends on HAVE_NMI 1512 1513config BUG 1514 bool "BUG() support" if EXPERT 1515 default y 1516 help 1517 Disabling this option eliminates support for BUG and WARN, reducing 1518 the size of your kernel image and potentially quietly ignoring 1519 numerous fatal conditions. You should only consider disabling this 1520 option for embedded systems with no facilities for reporting errors. 1521 Just say Y. 1522 1523config ELF_CORE 1524 depends on COREDUMP 1525 default y 1526 bool "Enable ELF core dumps" if EXPERT 1527 help 1528 Enable support for generating core dumps. Disabling saves about 4k. 1529 1530 1531config PCSPKR_PLATFORM 1532 bool "Enable PC-Speaker support" if EXPERT 1533 depends on HAVE_PCSPKR_PLATFORM 1534 select I8253_LOCK 1535 default y 1536 help 1537 This option allows to disable the internal PC-Speaker 1538 support, saving some memory. 1539 1540config BASE_FULL 1541 default y 1542 bool "Enable full-sized data structures for core" if EXPERT 1543 help 1544 Disabling this option reduces the size of miscellaneous core 1545 kernel data structures. This saves memory on small machines, 1546 but may reduce performance. 1547 1548config FUTEX 1549 bool "Enable futex support" if EXPERT 1550 default y 1551 imply RT_MUTEXES 1552 help 1553 Disabling this option will cause the kernel to be built without 1554 support for "fast userspace mutexes". The resulting kernel may not 1555 run glibc-based applications correctly. 1556 1557config FUTEX_PI 1558 bool 1559 depends on FUTEX && RT_MUTEXES 1560 default y 1561 1562config HAVE_FUTEX_CMPXCHG 1563 bool 1564 depends on FUTEX 1565 help 1566 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1567 is implemented and always working. This removes a couple of runtime 1568 checks. 1569 1570config EPOLL 1571 bool "Enable eventpoll support" if EXPERT 1572 default y 1573 help 1574 Disabling this option will cause the kernel to be built without 1575 support for epoll family of system calls. 1576 1577config SIGNALFD 1578 bool "Enable signalfd() system call" if EXPERT 1579 default y 1580 help 1581 Enable the signalfd() system call that allows to receive signals 1582 on a file descriptor. 1583 1584 If unsure, say Y. 1585 1586config TIMERFD 1587 bool "Enable timerfd() system call" if EXPERT 1588 default y 1589 help 1590 Enable the timerfd() system call that allows to receive timer 1591 events on a file descriptor. 1592 1593 If unsure, say Y. 1594 1595config EVENTFD 1596 bool "Enable eventfd() system call" if EXPERT 1597 default y 1598 help 1599 Enable the eventfd() system call that allows to receive both 1600 kernel notification (ie. KAIO) or userspace notifications. 1601 1602 If unsure, say Y. 1603 1604config SHMEM 1605 bool "Use full shmem filesystem" if EXPERT 1606 default y 1607 depends on MMU 1608 help 1609 The shmem is an internal filesystem used to manage shared memory. 1610 It is backed by swap and manages resource limits. It is also exported 1611 to userspace as tmpfs if TMPFS is enabled. Disabling this 1612 option replaces shmem and tmpfs with the much simpler ramfs code, 1613 which may be appropriate on small systems without swap. 1614 1615config AIO 1616 bool "Enable AIO support" if EXPERT 1617 default y 1618 help 1619 This option enables POSIX asynchronous I/O which may by used 1620 by some high performance threaded applications. Disabling 1621 this option saves about 7k. 1622 1623config IO_URING 1624 bool "Enable IO uring support" if EXPERT 1625 select IO_WQ 1626 default y 1627 help 1628 This option enables support for the io_uring interface, enabling 1629 applications to submit and complete IO through submission and 1630 completion rings that are shared between the kernel and application. 1631 1632config ADVISE_SYSCALLS 1633 bool "Enable madvise/fadvise syscalls" if EXPERT 1634 default y 1635 help 1636 This option enables the madvise and fadvise syscalls, used by 1637 applications to advise the kernel about their future memory or file 1638 usage, improving performance. If building an embedded system where no 1639 applications use these syscalls, you can disable this option to save 1640 space. 1641 1642config HAVE_ARCH_USERFAULTFD_WP 1643 bool 1644 help 1645 Arch has userfaultfd write protection support 1646 1647config HAVE_ARCH_USERFAULTFD_MINOR 1648 bool 1649 help 1650 Arch has userfaultfd minor fault support 1651 1652config MEMBARRIER 1653 bool "Enable membarrier() system call" if EXPERT 1654 default y 1655 help 1656 Enable the membarrier() system call that allows issuing memory 1657 barriers across all running threads, which can be used to distribute 1658 the cost of user-space memory barriers asymmetrically by transforming 1659 pairs of memory barriers into pairs consisting of membarrier() and a 1660 compiler barrier. 1661 1662 If unsure, say Y. 1663 1664config KALLSYMS 1665 bool "Load all symbols for debugging/ksymoops" if EXPERT 1666 default y 1667 help 1668 Say Y here to let the kernel print out symbolic crash information and 1669 symbolic stack backtraces. This increases the size of the kernel 1670 somewhat, as all symbols have to be loaded into the kernel image. 1671 1672config KALLSYMS_ALL 1673 bool "Include all symbols in kallsyms" 1674 depends on DEBUG_KERNEL && KALLSYMS 1675 help 1676 Normally kallsyms only contains the symbols of functions for nicer 1677 OOPS messages and backtraces (i.e., symbols from the text and inittext 1678 sections). This is sufficient for most cases. And only in very rare 1679 cases (e.g., when a debugger is used) all symbols are required (e.g., 1680 names of variables from the data sections, etc). 1681 1682 This option makes sure that all symbols are loaded into the kernel 1683 image (i.e., symbols from all sections) in cost of increased kernel 1684 size (depending on the kernel configuration, it may be 300KiB or 1685 something like this). 1686 1687 Say N unless you really need all symbols. 1688 1689config KALLSYMS_ABSOLUTE_PERCPU 1690 bool 1691 depends on KALLSYMS 1692 default X86_64 && SMP 1693 1694config KALLSYMS_BASE_RELATIVE 1695 bool 1696 depends on KALLSYMS 1697 default !IA64 1698 help 1699 Instead of emitting them as absolute values in the native word size, 1700 emit the symbol references in the kallsyms table as 32-bit entries, 1701 each containing a relative value in the range [base, base + U32_MAX] 1702 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1703 an absolute value in the range [0, S32_MAX] or a relative value in the 1704 range [base, base + S32_MAX], where base is the lowest relative symbol 1705 address encountered in the image. 1706 1707 On 64-bit builds, this reduces the size of the address table by 50%, 1708 but more importantly, it results in entries whose values are build 1709 time constants, and no relocation pass is required at runtime to fix 1710 up the entries based on the runtime load address of the kernel. 1711 1712# end of the "standard kernel features (expert users)" menu 1713 1714# syscall, maps, verifier 1715 1716config BPF_LSM 1717 bool "LSM Instrumentation with BPF" 1718 depends on BPF_EVENTS 1719 depends on BPF_SYSCALL 1720 depends on SECURITY 1721 depends on BPF_JIT 1722 help 1723 Enables instrumentation of the security hooks with eBPF programs for 1724 implementing dynamic MAC and Audit Policies. 1725 1726 If you are unsure how to answer this question, answer N. 1727 1728config BPF_SYSCALL 1729 bool "Enable bpf() system call" 1730 select BPF 1731 select IRQ_WORK 1732 select TASKS_TRACE_RCU 1733 select BINARY_PRINTF 1734 select NET_SOCK_MSG if INET 1735 default n 1736 help 1737 Enable the bpf() system call that allows to manipulate eBPF 1738 programs and maps via file descriptors. 1739 1740config ARCH_WANT_DEFAULT_BPF_JIT 1741 bool 1742 1743config BPF_JIT_ALWAYS_ON 1744 bool "Permanently enable BPF JIT and remove BPF interpreter" 1745 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1746 help 1747 Enables BPF JIT and removes BPF interpreter to avoid 1748 speculative execution of BPF instructions by the interpreter 1749 1750config BPF_JIT_DEFAULT_ON 1751 def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON 1752 depends on HAVE_EBPF_JIT && BPF_JIT 1753 1754source "kernel/bpf/preload/Kconfig" 1755 1756config USERFAULTFD 1757 bool "Enable userfaultfd() system call" 1758 depends on MMU 1759 help 1760 Enable the userfaultfd() system call that allows to intercept and 1761 handle page faults in userland. 1762 1763config ARCH_HAS_MEMBARRIER_CALLBACKS 1764 bool 1765 1766config ARCH_HAS_MEMBARRIER_SYNC_CORE 1767 bool 1768 1769config KCMP 1770 bool "Enable kcmp() system call" if EXPERT 1771 help 1772 Enable the kernel resource comparison system call. It provides 1773 user-space with the ability to compare two processes to see if they 1774 share a common resource, such as a file descriptor or even virtual 1775 memory space. 1776 1777 If unsure, say N. 1778 1779config RSEQ 1780 bool "Enable rseq() system call" if EXPERT 1781 default y 1782 depends on HAVE_RSEQ 1783 select MEMBARRIER 1784 help 1785 Enable the restartable sequences system call. It provides a 1786 user-space cache for the current CPU number value, which 1787 speeds up getting the current CPU number from user-space, 1788 as well as an ABI to speed up user-space operations on 1789 per-CPU data. 1790 1791 If unsure, say Y. 1792 1793config DEBUG_RSEQ 1794 default n 1795 bool "Enabled debugging of rseq() system call" if EXPERT 1796 depends on RSEQ && DEBUG_KERNEL 1797 help 1798 Enable extra debugging checks for the rseq system call. 1799 1800 If unsure, say N. 1801 1802config EMBEDDED 1803 bool "Embedded system" 1804 select EXPERT 1805 help 1806 This option should be enabled if compiling the kernel for 1807 an embedded system so certain expert options are available 1808 for configuration. 1809 1810config HAVE_PERF_EVENTS 1811 bool 1812 help 1813 See tools/perf/design.txt for details. 1814 1815config PERF_USE_VMALLOC 1816 bool 1817 help 1818 See tools/perf/design.txt for details 1819 1820config PC104 1821 bool "PC/104 support" if EXPERT 1822 help 1823 Expose PC/104 form factor device drivers and options available for 1824 selection and configuration. Enable this option if your target 1825 machine has a PC/104 bus. 1826 1827menu "Kernel Performance Events And Counters" 1828 1829config PERF_EVENTS 1830 bool "Kernel performance events and counters" 1831 default y if PROFILING 1832 depends on HAVE_PERF_EVENTS 1833 select IRQ_WORK 1834 select SRCU 1835 help 1836 Enable kernel support for various performance events provided 1837 by software and hardware. 1838 1839 Software events are supported either built-in or via the 1840 use of generic tracepoints. 1841 1842 Most modern CPUs support performance events via performance 1843 counter registers. These registers count the number of certain 1844 types of hw events: such as instructions executed, cachemisses 1845 suffered, or branches mis-predicted - without slowing down the 1846 kernel or applications. These registers can also trigger interrupts 1847 when a threshold number of events have passed - and can thus be 1848 used to profile the code that runs on that CPU. 1849 1850 The Linux Performance Event subsystem provides an abstraction of 1851 these software and hardware event capabilities, available via a 1852 system call and used by the "perf" utility in tools/perf/. It 1853 provides per task and per CPU counters, and it provides event 1854 capabilities on top of those. 1855 1856 Say Y if unsure. 1857 1858config DEBUG_PERF_USE_VMALLOC 1859 default n 1860 bool "Debug: use vmalloc to back perf mmap() buffers" 1861 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1862 select PERF_USE_VMALLOC 1863 help 1864 Use vmalloc memory to back perf mmap() buffers. 1865 1866 Mostly useful for debugging the vmalloc code on platforms 1867 that don't require it. 1868 1869 Say N if unsure. 1870 1871endmenu 1872 1873config VM_EVENT_COUNTERS 1874 default y 1875 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1876 help 1877 VM event counters are needed for event counts to be shown. 1878 This option allows the disabling of the VM event counters 1879 on EXPERT systems. /proc/vmstat will only show page counts 1880 if VM event counters are disabled. 1881 1882config SLUB_DEBUG 1883 default y 1884 bool "Enable SLUB debugging support" if EXPERT 1885 depends on SLUB && SYSFS 1886 help 1887 SLUB has extensive debug support features. Disabling these can 1888 result in significant savings in code size. This also disables 1889 SLUB sysfs support. /sys/slab will not exist and there will be 1890 no support for cache validation etc. 1891 1892config COMPAT_BRK 1893 bool "Disable heap randomization" 1894 default y 1895 help 1896 Randomizing heap placement makes heap exploits harder, but it 1897 also breaks ancient binaries (including anything libc5 based). 1898 This option changes the bootup default to heap randomization 1899 disabled, and can be overridden at runtime by setting 1900 /proc/sys/kernel/randomize_va_space to 2. 1901 1902 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1903 1904choice 1905 prompt "Choose SLAB allocator" 1906 default SLUB 1907 help 1908 This option allows to select a slab allocator. 1909 1910config SLAB 1911 bool "SLAB" 1912 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1913 help 1914 The regular slab allocator that is established and known to work 1915 well in all environments. It organizes cache hot objects in 1916 per cpu and per node queues. 1917 1918config SLUB 1919 bool "SLUB (Unqueued Allocator)" 1920 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1921 help 1922 SLUB is a slab allocator that minimizes cache line usage 1923 instead of managing queues of cached objects (SLAB approach). 1924 Per cpu caching is realized using slabs of objects instead 1925 of queues of objects. SLUB can use memory efficiently 1926 and has enhanced diagnostics. SLUB is the default choice for 1927 a slab allocator. 1928 1929config SLOB 1930 depends on EXPERT 1931 bool "SLOB (Simple Allocator)" 1932 help 1933 SLOB replaces the stock allocator with a drastically simpler 1934 allocator. SLOB is generally more space efficient but 1935 does not perform as well on large systems. 1936 1937endchoice 1938 1939config SLAB_MERGE_DEFAULT 1940 bool "Allow slab caches to be merged" 1941 default y 1942 help 1943 For reduced kernel memory fragmentation, slab caches can be 1944 merged when they share the same size and other characteristics. 1945 This carries a risk of kernel heap overflows being able to 1946 overwrite objects from merged caches (and more easily control 1947 cache layout), which makes such heap attacks easier to exploit 1948 by attackers. By keeping caches unmerged, these kinds of exploits 1949 can usually only damage objects in the same cache. To disable 1950 merging at runtime, "slab_nomerge" can be passed on the kernel 1951 command line. 1952 1953config SLAB_FREELIST_RANDOM 1954 bool "Randomize slab freelist" 1955 depends on SLAB || SLUB 1956 help 1957 Randomizes the freelist order used on creating new pages. This 1958 security feature reduces the predictability of the kernel slab 1959 allocator against heap overflows. 1960 1961config SLAB_FREELIST_HARDENED 1962 bool "Harden slab freelist metadata" 1963 depends on SLAB || SLUB 1964 help 1965 Many kernel heap attacks try to target slab cache metadata and 1966 other infrastructure. This options makes minor performance 1967 sacrifices to harden the kernel slab allocator against common 1968 freelist exploit methods. Some slab implementations have more 1969 sanity-checking than others. This option is most effective with 1970 CONFIG_SLUB. 1971 1972config SHUFFLE_PAGE_ALLOCATOR 1973 bool "Page allocator randomization" 1974 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1975 help 1976 Randomization of the page allocator improves the average 1977 utilization of a direct-mapped memory-side-cache. See section 1978 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1979 6.2a specification for an example of how a platform advertises 1980 the presence of a memory-side-cache. There are also incidental 1981 security benefits as it reduces the predictability of page 1982 allocations to compliment SLAB_FREELIST_RANDOM, but the 1983 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1984 10th order of pages is selected based on cache utilization 1985 benefits on x86. 1986 1987 While the randomization improves cache utilization it may 1988 negatively impact workloads on platforms without a cache. For 1989 this reason, by default, the randomization is enabled only 1990 after runtime detection of a direct-mapped memory-side-cache. 1991 Otherwise, the randomization may be force enabled with the 1992 'page_alloc.shuffle' kernel command line parameter. 1993 1994 Say Y if unsure. 1995 1996config SLUB_CPU_PARTIAL 1997 default y 1998 depends on SLUB && SMP 1999 bool "SLUB per cpu partial cache" 2000 help 2001 Per cpu partial caches accelerate objects allocation and freeing 2002 that is local to a processor at the price of more indeterminism 2003 in the latency of the free. On overflow these caches will be cleared 2004 which requires the taking of locks that may cause latency spikes. 2005 Typically one would choose no for a realtime system. 2006 2007config MMAP_ALLOW_UNINITIALIZED 2008 bool "Allow mmapped anonymous memory to be uninitialized" 2009 depends on EXPERT && !MMU 2010 default n 2011 help 2012 Normally, and according to the Linux spec, anonymous memory obtained 2013 from mmap() has its contents cleared before it is passed to 2014 userspace. Enabling this config option allows you to request that 2015 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 2016 providing a huge performance boost. If this option is not enabled, 2017 then the flag will be ignored. 2018 2019 This is taken advantage of by uClibc's malloc(), and also by 2020 ELF-FDPIC binfmt's brk and stack allocator. 2021 2022 Because of the obvious security issues, this option should only be 2023 enabled on embedded devices where you control what is run in 2024 userspace. Since that isn't generally a problem on no-MMU systems, 2025 it is normally safe to say Y here. 2026 2027 See Documentation/admin-guide/mm/nommu-mmap.rst for more information. 2028 2029config SYSTEM_DATA_VERIFICATION 2030 def_bool n 2031 select SYSTEM_TRUSTED_KEYRING 2032 select KEYS 2033 select CRYPTO 2034 select CRYPTO_RSA 2035 select ASYMMETRIC_KEY_TYPE 2036 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 2037 select ASN1 2038 select OID_REGISTRY 2039 select X509_CERTIFICATE_PARSER 2040 select PKCS7_MESSAGE_PARSER 2041 help 2042 Provide PKCS#7 message verification using the contents of the system 2043 trusted keyring to provide public keys. This then can be used for 2044 module verification, kexec image verification and firmware blob 2045 verification. 2046 2047config PROFILING 2048 bool "Profiling support" 2049 help 2050 Say Y here to enable the extended profiling support mechanisms used 2051 by profilers. 2052 2053# 2054# Place an empty function call at each tracepoint site. Can be 2055# dynamically changed for a probe function. 2056# 2057config TRACEPOINTS 2058 bool 2059 2060endmenu # General setup 2061 2062source "arch/Kconfig" 2063 2064config RT_MUTEXES 2065 bool 2066 2067config BASE_SMALL 2068 int 2069 default 0 if BASE_FULL 2070 default 1 if !BASE_FULL 2071 2072config MODULE_SIG_FORMAT 2073 def_bool n 2074 select SYSTEM_DATA_VERIFICATION 2075 2076menuconfig MODULES 2077 bool "Enable loadable module support" 2078 modules 2079 help 2080 Kernel modules are small pieces of compiled code which can 2081 be inserted in the running kernel, rather than being 2082 permanently built into the kernel. You use the "modprobe" 2083 tool to add (and sometimes remove) them. If you say Y here, 2084 many parts of the kernel can be built as modules (by 2085 answering M instead of Y where indicated): this is most 2086 useful for infrequently used options which are not required 2087 for booting. For more information, see the man pages for 2088 modprobe, lsmod, modinfo, insmod and rmmod. 2089 2090 If you say Y here, you will need to run "make 2091 modules_install" to put the modules under /lib/modules/ 2092 where modprobe can find them (you may need to be root to do 2093 this). 2094 2095 If unsure, say Y. 2096 2097if MODULES 2098 2099config MODULE_FORCE_LOAD 2100 bool "Forced module loading" 2101 default n 2102 help 2103 Allow loading of modules without version information (ie. modprobe 2104 --force). Forced module loading sets the 'F' (forced) taint flag and 2105 is usually a really bad idea. 2106 2107config MODULE_UNLOAD 2108 bool "Module unloading" 2109 help 2110 Without this option you will not be able to unload any 2111 modules (note that some modules may not be unloadable 2112 anyway), which makes your kernel smaller, faster 2113 and simpler. If unsure, say Y. 2114 2115config MODULE_FORCE_UNLOAD 2116 bool "Forced module unloading" 2117 depends on MODULE_UNLOAD 2118 help 2119 This option allows you to force a module to unload, even if the 2120 kernel believes it is unsafe: the kernel will remove the module 2121 without waiting for anyone to stop using it (using the -f option to 2122 rmmod). This is mainly for kernel developers and desperate users. 2123 If unsure, say N. 2124 2125config MODVERSIONS 2126 bool "Module versioning support" 2127 help 2128 Usually, you have to use modules compiled with your kernel. 2129 Saying Y here makes it sometimes possible to use modules 2130 compiled for different kernels, by adding enough information 2131 to the modules to (hopefully) spot any changes which would 2132 make them incompatible with the kernel you are running. If 2133 unsure, say N. 2134 2135config ASM_MODVERSIONS 2136 bool 2137 default HAVE_ASM_MODVERSIONS && MODVERSIONS 2138 help 2139 This enables module versioning for exported symbols also from 2140 assembly. This can be enabled only when the target architecture 2141 supports it. 2142 2143config MODULE_REL_CRCS 2144 bool 2145 depends on MODVERSIONS 2146 2147config MODULE_SRCVERSION_ALL 2148 bool "Source checksum for all modules" 2149 help 2150 Modules which contain a MODULE_VERSION get an extra "srcversion" 2151 field inserted into their modinfo section, which contains a 2152 sum of the source files which made it. This helps maintainers 2153 see exactly which source was used to build a module (since 2154 others sometimes change the module source without updating 2155 the version). With this option, such a "srcversion" field 2156 will be created for all modules. If unsure, say N. 2157 2158config MODULE_SIG 2159 bool "Module signature verification" 2160 select MODULE_SIG_FORMAT 2161 help 2162 Check modules for valid signatures upon load: the signature 2163 is simply appended to the module. For more information see 2164 <file:Documentation/admin-guide/module-signing.rst>. 2165 2166 Note that this option adds the OpenSSL development packages as a 2167 kernel build dependency so that the signing tool can use its crypto 2168 library. 2169 2170 You should enable this option if you wish to use either 2171 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via 2172 another LSM - otherwise unsigned modules will be loadable regardless 2173 of the lockdown policy. 2174 2175 !!!WARNING!!! If you enable this option, you MUST make sure that the 2176 module DOES NOT get stripped after being signed. This includes the 2177 debuginfo strip done by some packagers (such as rpmbuild) and 2178 inclusion into an initramfs that wants the module size reduced. 2179 2180config MODULE_SIG_FORCE 2181 bool "Require modules to be validly signed" 2182 depends on MODULE_SIG 2183 help 2184 Reject unsigned modules or signed modules for which we don't have a 2185 key. Without this, such modules will simply taint the kernel. 2186 2187config MODULE_SIG_ALL 2188 bool "Automatically sign all modules" 2189 default y 2190 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 2191 help 2192 Sign all modules during make modules_install. Without this option, 2193 modules must be signed manually, using the scripts/sign-file tool. 2194 2195comment "Do not forget to sign required modules with scripts/sign-file" 2196 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2197 2198choice 2199 prompt "Which hash algorithm should modules be signed with?" 2200 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 2201 help 2202 This determines which sort of hashing algorithm will be used during 2203 signature generation. This algorithm _must_ be built into the kernel 2204 directly so that signature verification can take place. It is not 2205 possible to load a signed module containing the algorithm to check 2206 the signature on that module. 2207 2208config MODULE_SIG_SHA1 2209 bool "Sign modules with SHA-1" 2210 select CRYPTO_SHA1 2211 2212config MODULE_SIG_SHA224 2213 bool "Sign modules with SHA-224" 2214 select CRYPTO_SHA256 2215 2216config MODULE_SIG_SHA256 2217 bool "Sign modules with SHA-256" 2218 select CRYPTO_SHA256 2219 2220config MODULE_SIG_SHA384 2221 bool "Sign modules with SHA-384" 2222 select CRYPTO_SHA512 2223 2224config MODULE_SIG_SHA512 2225 bool "Sign modules with SHA-512" 2226 select CRYPTO_SHA512 2227 2228endchoice 2229 2230config MODULE_SIG_HASH 2231 string 2232 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 2233 default "sha1" if MODULE_SIG_SHA1 2234 default "sha224" if MODULE_SIG_SHA224 2235 default "sha256" if MODULE_SIG_SHA256 2236 default "sha384" if MODULE_SIG_SHA384 2237 default "sha512" if MODULE_SIG_SHA512 2238 2239choice 2240 prompt "Module compression mode" 2241 help 2242 This option allows you to choose the algorithm which will be used to 2243 compress modules when 'make modules_install' is run. (or, you can 2244 choose to not compress modules at all.) 2245 2246 External modules will also be compressed in the same way during the 2247 installation. 2248 2249 For modules inside an initrd or initramfs, it's more efficient to 2250 compress the whole initrd or initramfs instead. 2251 2252 This is fully compatible with signed modules. 2253 2254 Please note that the tool used to load modules needs to support the 2255 corresponding algorithm. module-init-tools MAY support gzip, and kmod 2256 MAY support gzip, xz and zstd. 2257 2258 Your build system needs to provide the appropriate compression tool 2259 to compress the modules. 2260 2261 If in doubt, select 'None'. 2262 2263config MODULE_COMPRESS_NONE 2264 bool "None" 2265 help 2266 Do not compress modules. The installed modules are suffixed 2267 with .ko. 2268 2269config MODULE_COMPRESS_GZIP 2270 bool "GZIP" 2271 help 2272 Compress modules with GZIP. The installed modules are suffixed 2273 with .ko.gz. 2274 2275config MODULE_COMPRESS_XZ 2276 bool "XZ" 2277 help 2278 Compress modules with XZ. The installed modules are suffixed 2279 with .ko.xz. 2280 2281config MODULE_COMPRESS_ZSTD 2282 bool "ZSTD" 2283 help 2284 Compress modules with ZSTD. The installed modules are suffixed 2285 with .ko.zst. 2286 2287endchoice 2288 2289config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS 2290 bool "Allow loading of modules with missing namespace imports" 2291 help 2292 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in 2293 a namespace. A module that makes use of a symbol exported with such a 2294 namespace is required to import the namespace via MODULE_IMPORT_NS(). 2295 There is no technical reason to enforce correct namespace imports, 2296 but it creates consistency between symbols defining namespaces and 2297 users importing namespaces they make use of. This option relaxes this 2298 requirement and lifts the enforcement when loading a module. 2299 2300 If unsure, say N. 2301 2302config MODPROBE_PATH 2303 string "Path to modprobe binary" 2304 default "/sbin/modprobe" 2305 help 2306 When kernel code requests a module, it does so by calling 2307 the "modprobe" userspace utility. This option allows you to 2308 set the path where that binary is found. This can be changed 2309 at runtime via the sysctl file 2310 /proc/sys/kernel/modprobe. Setting this to the empty string 2311 removes the kernel's ability to request modules (but 2312 userspace can still load modules explicitly). 2313 2314config TRIM_UNUSED_KSYMS 2315 bool "Trim unused exported kernel symbols" if EXPERT 2316 depends on !COMPILE_TEST 2317 help 2318 The kernel and some modules make many symbols available for 2319 other modules to use via EXPORT_SYMBOL() and variants. Depending 2320 on the set of modules being selected in your kernel configuration, 2321 many of those exported symbols might never be used. 2322 2323 This option allows for unused exported symbols to be dropped from 2324 the build. In turn, this provides the compiler more opportunities 2325 (especially when using LTO) for optimizing the code and reducing 2326 binary size. This might have some security advantages as well. 2327 2328 If unsure, or if you need to build out-of-tree modules, say N. 2329 2330config UNUSED_KSYMS_WHITELIST 2331 string "Whitelist of symbols to keep in ksymtab" 2332 depends on TRIM_UNUSED_KSYMS 2333 help 2334 By default, all unused exported symbols will be un-exported from the 2335 build when TRIM_UNUSED_KSYMS is selected. 2336 2337 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept 2338 exported at all times, even in absence of in-tree users. The value to 2339 set here is the path to a text file containing the list of symbols, 2340 one per line. The path can be absolute, or relative to the kernel 2341 source tree. 2342 2343endif # MODULES 2344 2345config MODULES_TREE_LOOKUP 2346 def_bool y 2347 depends on PERF_EVENTS || TRACING || CFI_CLANG 2348 2349config INIT_ALL_POSSIBLE 2350 bool 2351 help 2352 Back when each arch used to define their own cpu_online_mask and 2353 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2354 with all 1s, and others with all 0s. When they were centralised, 2355 it was better to provide this option than to break all the archs 2356 and have several arch maintainers pursuing me down dark alleys. 2357 2358source "block/Kconfig" 2359 2360config PREEMPT_NOTIFIERS 2361 bool 2362 2363config PADATA 2364 depends on SMP 2365 bool 2366 2367config ASN1 2368 tristate 2369 help 2370 Build a simple ASN.1 grammar compiler that produces a bytecode output 2371 that can be interpreted by the ASN.1 stream decoder and used to 2372 inform it as to what tags are to be expected in a stream and what 2373 functions to call on what tags. 2374 2375source "kernel/Kconfig.locks" 2376 2377config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 2378 bool 2379 2380config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2381 bool 2382 2383# It may be useful for an architecture to override the definitions of the 2384# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2385# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2386# different calling convention for syscalls. They can also override the 2387# macros for not-implemented syscalls in kernel/sys_ni.c and 2388# kernel/time/posix-stubs.c. All these overrides need to be available in 2389# <asm/syscall_wrapper.h>. 2390config ARCH_HAS_SYSCALL_WRAPPER 2391 def_bool n 2392