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 CC_HAS_NO_PROFILE_FN_ATTR 87 def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror) 88 89config CONSTRUCTORS 90 bool 91 92config IRQ_WORK 93 bool 94 95config BUILDTIME_TABLE_SORT 96 bool 97 98config THREAD_INFO_IN_TASK 99 bool 100 help 101 Select this to move thread_info off the stack into task_struct. To 102 make this work, an arch will need to remove all thread_info fields 103 except flags and fix any runtime bugs. 104 105 One subtle change that will be needed is to use try_get_task_stack() 106 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 107 108menu "General setup" 109 110config BROKEN 111 bool 112 113config BROKEN_ON_SMP 114 bool 115 depends on BROKEN || !SMP 116 default y 117 118config INIT_ENV_ARG_LIMIT 119 int 120 default 32 if !UML 121 default 128 if UML 122 help 123 Maximum of each of the number of arguments and environment 124 variables passed to init from the kernel command line. 125 126config COMPILE_TEST 127 bool "Compile also drivers which will not load" 128 depends on HAS_IOMEM 129 help 130 Some drivers can be compiled on a different platform than they are 131 intended to be run on. Despite they cannot be loaded there (or even 132 when they load they cannot be used due to missing HW support), 133 developers still, opposing to distributors, might want to build such 134 drivers to compile-test them. 135 136 If you are a developer and want to build everything available, say Y 137 here. If you are a user/distributor, say N here to exclude useless 138 drivers to be distributed. 139 140config WERROR 141 bool "Compile the kernel with warnings as errors" 142 default COMPILE_TEST 143 help 144 A kernel build should not cause any compiler warnings, and this 145 enables the '-Werror' flag to enforce that rule by default. 146 147 However, if you have a new (or very old) compiler with odd and 148 unusual warnings, or you have some architecture with problems, 149 you may need to disable this config option in order to 150 successfully build the kernel. 151 152 If in doubt, say Y. 153 154config UAPI_HEADER_TEST 155 bool "Compile test UAPI headers" 156 depends on HEADERS_INSTALL && CC_CAN_LINK 157 help 158 Compile test headers exported to user-space to ensure they are 159 self-contained, i.e. compilable as standalone units. 160 161 If you are a developer or tester and want to ensure the exported 162 headers are self-contained, say Y here. Otherwise, choose N. 163 164config LOCALVERSION 165 string "Local version - append to kernel release" 166 help 167 Append an extra string to the end of your kernel version. 168 This will show up when you type uname, for example. 169 The string you set here will be appended after the contents of 170 any files with a filename matching localversion* in your 171 object and source tree, in that order. Your total string can 172 be a maximum of 64 characters. 173 174config LOCALVERSION_AUTO 175 bool "Automatically append version information to the version string" 176 default y 177 depends on !COMPILE_TEST 178 help 179 This will try to automatically determine if the current tree is a 180 release tree by looking for git tags that belong to the current 181 top of tree revision. 182 183 A string of the format -gxxxxxxxx will be added to the localversion 184 if a git-based tree is found. The string generated by this will be 185 appended after any matching localversion* files, and after the value 186 set in CONFIG_LOCALVERSION. 187 188 (The actual string used here is the first eight characters produced 189 by running the command: 190 191 $ git rev-parse --verify HEAD 192 193 which is done within the script "scripts/setlocalversion".) 194 195config BUILD_SALT 196 string "Build ID Salt" 197 default "" 198 help 199 The build ID is used to link binaries and their debug info. Setting 200 this option will use the value in the calculation of the build id. 201 This is mostly useful for distributions which want to ensure the 202 build is unique between builds. It's safe to leave the default. 203 204config HAVE_KERNEL_GZIP 205 bool 206 207config HAVE_KERNEL_BZIP2 208 bool 209 210config HAVE_KERNEL_LZMA 211 bool 212 213config HAVE_KERNEL_XZ 214 bool 215 216config HAVE_KERNEL_LZO 217 bool 218 219config HAVE_KERNEL_LZ4 220 bool 221 222config HAVE_KERNEL_ZSTD 223 bool 224 225config HAVE_KERNEL_UNCOMPRESSED 226 bool 227 228choice 229 prompt "Kernel compression mode" 230 default KERNEL_GZIP 231 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 232 help 233 The linux kernel is a kind of self-extracting executable. 234 Several compression algorithms are available, which differ 235 in efficiency, compression and decompression speed. 236 Compression speed is only relevant when building a kernel. 237 Decompression speed is relevant at each boot. 238 239 If you have any problems with bzip2 or lzma compressed 240 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 241 version of this functionality (bzip2 only), for 2.4, was 242 supplied by Christian Ludwig) 243 244 High compression options are mostly useful for users, who 245 are low on disk space (embedded systems), but for whom ram 246 size matters less. 247 248 If in doubt, select 'gzip' 249 250config KERNEL_GZIP 251 bool "Gzip" 252 depends on HAVE_KERNEL_GZIP 253 help 254 The old and tried gzip compression. It provides a good balance 255 between compression ratio and decompression speed. 256 257config KERNEL_BZIP2 258 bool "Bzip2" 259 depends on HAVE_KERNEL_BZIP2 260 help 261 Its compression ratio and speed is intermediate. 262 Decompression speed is slowest among the choices. The kernel 263 size is about 10% smaller with bzip2, in comparison to gzip. 264 Bzip2 uses a large amount of memory. For modern kernels you 265 will need at least 8MB RAM or more for booting. 266 267config KERNEL_LZMA 268 bool "LZMA" 269 depends on HAVE_KERNEL_LZMA 270 help 271 This compression algorithm's ratio is best. Decompression speed 272 is between gzip and bzip2. Compression is slowest. 273 The kernel size is about 33% smaller with LZMA in comparison to gzip. 274 275config KERNEL_XZ 276 bool "XZ" 277 depends on HAVE_KERNEL_XZ 278 help 279 XZ uses the LZMA2 algorithm and instruction set specific 280 BCJ filters which can improve compression ratio of executable 281 code. The size of the kernel is about 30% smaller with XZ in 282 comparison to gzip. On architectures for which there is a BCJ 283 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 284 will create a few percent smaller kernel than plain LZMA. 285 286 The speed is about the same as with LZMA: The decompression 287 speed of XZ is better than that of bzip2 but worse than gzip 288 and LZO. Compression is slow. 289 290config KERNEL_LZO 291 bool "LZO" 292 depends on HAVE_KERNEL_LZO 293 help 294 Its compression ratio is the poorest among the choices. The kernel 295 size is about 10% bigger than gzip; however its speed 296 (both compression and decompression) is the fastest. 297 298config KERNEL_LZ4 299 bool "LZ4" 300 depends on HAVE_KERNEL_LZ4 301 help 302 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 303 A preliminary version of LZ4 de/compression tool is available at 304 <https://code.google.com/p/lz4/>. 305 306 Its compression ratio is worse than LZO. The size of the kernel 307 is about 8% bigger than LZO. But the decompression speed is 308 faster than LZO. 309 310config KERNEL_ZSTD 311 bool "ZSTD" 312 depends on HAVE_KERNEL_ZSTD 313 help 314 ZSTD is a compression algorithm targeting intermediate compression 315 with fast decompression speed. It will compress better than GZIP and 316 decompress around the same speed as LZO, but slower than LZ4. You 317 will need at least 192 KB RAM or more for booting. The zstd command 318 line tool is required for compression. 319 320config KERNEL_UNCOMPRESSED 321 bool "None" 322 depends on HAVE_KERNEL_UNCOMPRESSED 323 help 324 Produce uncompressed kernel image. This option is usually not what 325 you want. It is useful for debugging the kernel in slow simulation 326 environments, where decompressing and moving the kernel is awfully 327 slow. This option allows early boot code to skip the decompressor 328 and jump right at uncompressed kernel image. 329 330endchoice 331 332config DEFAULT_INIT 333 string "Default init path" 334 default "" 335 help 336 This option determines the default init for the system if no init= 337 option is passed on the kernel command line. If the requested path is 338 not present, we will still then move on to attempting further 339 locations (e.g. /sbin/init, etc). If this is empty, we will just use 340 the fallback list when init= is not passed. 341 342config DEFAULT_HOSTNAME 343 string "Default hostname" 344 default "(none)" 345 help 346 This option determines the default system hostname before userspace 347 calls sethostname(2). The kernel traditionally uses "(none)" here, 348 but you may wish to use a different default here to make a minimal 349 system more usable with less configuration. 350 351# 352# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can 353# add proper SWAP support to them, in which case this can be remove. 354# 355config ARCH_NO_SWAP 356 bool 357 358config SWAP 359 bool "Support for paging of anonymous memory (swap)" 360 depends on MMU && BLOCK && !ARCH_NO_SWAP 361 default y 362 help 363 This option allows you to choose whether you want to have support 364 for so called swap devices or swap files in your kernel that are 365 used to provide more virtual memory than the actual RAM present 366 in your computer. If unsure say Y. 367 368config SYSVIPC 369 bool "System V IPC" 370 help 371 Inter Process Communication is a suite of library functions and 372 system calls which let processes (running programs) synchronize and 373 exchange information. It is generally considered to be a good thing, 374 and some programs won't run unless you say Y here. In particular, if 375 you want to run the DOS emulator dosemu under Linux (read the 376 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 377 you'll need to say Y here. 378 379 You can find documentation about IPC with "info ipc" and also in 380 section 6.4 of the Linux Programmer's Guide, available from 381 <http://www.tldp.org/guides.html>. 382 383config SYSVIPC_SYSCTL 384 bool 385 depends on SYSVIPC 386 depends on SYSCTL 387 default y 388 389config POSIX_MQUEUE 390 bool "POSIX Message Queues" 391 depends on NET 392 help 393 POSIX variant of message queues is a part of IPC. In POSIX message 394 queues every message has a priority which decides about succession 395 of receiving it by a process. If you want to compile and run 396 programs written e.g. for Solaris with use of its POSIX message 397 queues (functions mq_*) say Y here. 398 399 POSIX message queues are visible as a filesystem called 'mqueue' 400 and can be mounted somewhere if you want to do filesystem 401 operations on message queues. 402 403 If unsure, say Y. 404 405config POSIX_MQUEUE_SYSCTL 406 bool 407 depends on POSIX_MQUEUE 408 depends on SYSCTL 409 default y 410 411config WATCH_QUEUE 412 bool "General notification queue" 413 default n 414 help 415 416 This is a general notification queue for the kernel to pass events to 417 userspace by splicing them into pipes. It can be used in conjunction 418 with watches for key/keyring change notifications and device 419 notifications. 420 421 See Documentation/watch_queue.rst 422 423config CROSS_MEMORY_ATTACH 424 bool "Enable process_vm_readv/writev syscalls" 425 depends on MMU 426 default y 427 help 428 Enabling this option adds the system calls process_vm_readv and 429 process_vm_writev which allow a process with the correct privileges 430 to directly read from or write to another process' address space. 431 See the man page for more details. 432 433config USELIB 434 bool "uselib syscall" 435 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION 436 help 437 This option enables the uselib syscall, a system call used in the 438 dynamic linker from libc5 and earlier. glibc does not use this 439 system call. If you intend to run programs built on libc5 or 440 earlier, you may need to enable this syscall. Current systems 441 running glibc can safely disable this. 442 443config AUDIT 444 bool "Auditing support" 445 depends on NET 446 help 447 Enable auditing infrastructure that can be used with another 448 kernel subsystem, such as SELinux (which requires this for 449 logging of avc messages output). System call auditing is included 450 on architectures which support it. 451 452config HAVE_ARCH_AUDITSYSCALL 453 bool 454 455config AUDITSYSCALL 456 def_bool y 457 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 458 select FSNOTIFY 459 460source "kernel/irq/Kconfig" 461source "kernel/time/Kconfig" 462source "kernel/bpf/Kconfig" 463source "kernel/Kconfig.preempt" 464 465menu "CPU/Task time and stats accounting" 466 467config VIRT_CPU_ACCOUNTING 468 bool 469 470choice 471 prompt "Cputime accounting" 472 default TICK_CPU_ACCOUNTING if !PPC64 473 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 474 475# Kind of a stub config for the pure tick based cputime accounting 476config TICK_CPU_ACCOUNTING 477 bool "Simple tick based cputime accounting" 478 depends on !S390 && !NO_HZ_FULL 479 help 480 This is the basic tick based cputime accounting that maintains 481 statistics about user, system and idle time spent on per jiffies 482 granularity. 483 484 If unsure, say Y. 485 486config VIRT_CPU_ACCOUNTING_NATIVE 487 bool "Deterministic task and CPU time accounting" 488 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 489 select VIRT_CPU_ACCOUNTING 490 help 491 Select this option to enable more accurate task and CPU time 492 accounting. This is done by reading a CPU counter on each 493 kernel entry and exit and on transitions within the kernel 494 between system, softirq and hardirq state, so there is a 495 small performance impact. In the case of s390 or IBM POWER > 5, 496 this also enables accounting of stolen time on logically-partitioned 497 systems. 498 499config VIRT_CPU_ACCOUNTING_GEN 500 bool "Full dynticks CPU time accounting" 501 depends on HAVE_CONTEXT_TRACKING 502 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 503 depends on GENERIC_CLOCKEVENTS 504 select VIRT_CPU_ACCOUNTING 505 select CONTEXT_TRACKING 506 help 507 Select this option to enable task and CPU time accounting on full 508 dynticks systems. This accounting is implemented by watching every 509 kernel-user boundaries using the context tracking subsystem. 510 The accounting is thus performed at the expense of some significant 511 overhead. 512 513 For now this is only useful if you are working on the full 514 dynticks subsystem development. 515 516 If unsure, say N. 517 518endchoice 519 520config IRQ_TIME_ACCOUNTING 521 bool "Fine granularity task level IRQ time accounting" 522 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 523 help 524 Select this option to enable fine granularity task irq time 525 accounting. This is done by reading a timestamp on each 526 transitions between softirq and hardirq state, so there can be a 527 small performance impact. 528 529 If in doubt, say N here. 530 531config HAVE_SCHED_AVG_IRQ 532 def_bool y 533 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 534 depends on SMP 535 536config SCHED_THERMAL_PRESSURE 537 bool 538 default y if ARM && ARM_CPU_TOPOLOGY 539 default y if ARM64 540 depends on SMP 541 depends on CPU_FREQ_THERMAL 542 help 543 Select this option to enable thermal pressure accounting in the 544 scheduler. Thermal pressure is the value conveyed to the scheduler 545 that reflects the reduction in CPU compute capacity resulted from 546 thermal throttling. Thermal throttling occurs when the performance of 547 a CPU is capped due to high operating temperatures. 548 549 If selected, the scheduler will be able to balance tasks accordingly, 550 i.e. put less load on throttled CPUs than on non/less throttled ones. 551 552 This requires the architecture to implement 553 arch_update_thermal_pressure() and arch_scale_thermal_pressure(). 554 555config BSD_PROCESS_ACCT 556 bool "BSD Process Accounting" 557 depends on MULTIUSER 558 help 559 If you say Y here, a user level program will be able to instruct the 560 kernel (via a special system call) to write process accounting 561 information to a file: whenever a process exits, information about 562 that process will be appended to the file by the kernel. The 563 information includes things such as creation time, owning user, 564 command name, memory usage, controlling terminal etc. (the complete 565 list is in the struct acct in <file:include/linux/acct.h>). It is 566 up to the user level program to do useful things with this 567 information. This is generally a good idea, so say Y. 568 569config BSD_PROCESS_ACCT_V3 570 bool "BSD Process Accounting version 3 file format" 571 depends on BSD_PROCESS_ACCT 572 default n 573 help 574 If you say Y here, the process accounting information is written 575 in a new file format that also logs the process IDs of each 576 process and its parent. Note that this file format is incompatible 577 with previous v0/v1/v2 file formats, so you will need updated tools 578 for processing it. A preliminary version of these tools is available 579 at <http://www.gnu.org/software/acct/>. 580 581config TASKSTATS 582 bool "Export task/process statistics through netlink" 583 depends on NET 584 depends on MULTIUSER 585 default n 586 help 587 Export selected statistics for tasks/processes through the 588 generic netlink interface. Unlike BSD process accounting, the 589 statistics are available during the lifetime of tasks/processes as 590 responses to commands. Like BSD accounting, they are sent to user 591 space on task exit. 592 593 Say N if unsure. 594 595config TASK_DELAY_ACCT 596 bool "Enable per-task delay accounting" 597 depends on TASKSTATS 598 select SCHED_INFO 599 help 600 Collect information on time spent by a task waiting for system 601 resources like cpu, synchronous block I/O completion and swapping 602 in pages. Such statistics can help in setting a task's priorities 603 relative to other tasks for cpu, io, rss limits etc. 604 605 Say N if unsure. 606 607config TASK_XACCT 608 bool "Enable extended accounting over taskstats" 609 depends on TASKSTATS 610 help 611 Collect extended task accounting data and send the data 612 to userland for processing over the taskstats interface. 613 614 Say N if unsure. 615 616config TASK_IO_ACCOUNTING 617 bool "Enable per-task storage I/O accounting" 618 depends on TASK_XACCT 619 help 620 Collect information on the number of bytes of storage I/O which this 621 task has caused. 622 623 Say N if unsure. 624 625config PSI 626 bool "Pressure stall information tracking" 627 help 628 Collect metrics that indicate how overcommitted the CPU, memory, 629 and IO capacity are in the system. 630 631 If you say Y here, the kernel will create /proc/pressure/ with the 632 pressure statistics files cpu, memory, and io. These will indicate 633 the share of walltime in which some or all tasks in the system are 634 delayed due to contention of the respective resource. 635 636 In kernels with cgroup support, cgroups (cgroup2 only) will 637 have cpu.pressure, memory.pressure, and io.pressure files, 638 which aggregate pressure stalls for the grouped tasks only. 639 640 For more details see Documentation/accounting/psi.rst. 641 642 Say N if unsure. 643 644config PSI_DEFAULT_DISABLED 645 bool "Require boot parameter to enable pressure stall information tracking" 646 default n 647 depends on PSI 648 help 649 If set, pressure stall information tracking will be disabled 650 per default but can be enabled through passing psi=1 on the 651 kernel commandline during boot. 652 653 This feature adds some code to the task wakeup and sleep 654 paths of the scheduler. The overhead is too low to affect 655 common scheduling-intense workloads in practice (such as 656 webservers, memcache), but it does show up in artificial 657 scheduler stress tests, such as hackbench. 658 659 If you are paranoid and not sure what the kernel will be 660 used for, say Y. 661 662 Say N if unsure. 663 664endmenu # "CPU/Task time and stats accounting" 665 666config CPU_ISOLATION 667 bool "CPU isolation" 668 depends on SMP || COMPILE_TEST 669 default y 670 help 671 Make sure that CPUs running critical tasks are not disturbed by 672 any source of "noise" such as unbound workqueues, timers, kthreads... 673 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 674 the "isolcpus=" boot parameter. 675 676 Say Y if unsure. 677 678source "kernel/rcu/Kconfig" 679 680config BUILD_BIN2C 681 bool 682 default n 683 684config IKCONFIG 685 tristate "Kernel .config support" 686 help 687 This option enables the complete Linux kernel ".config" file 688 contents to be saved in the kernel. It provides documentation 689 of which kernel options are used in a running kernel or in an 690 on-disk kernel. This information can be extracted from the kernel 691 image file with the script scripts/extract-ikconfig and used as 692 input to rebuild the current kernel or to build another kernel. 693 It can also be extracted from a running kernel by reading 694 /proc/config.gz if enabled (below). 695 696config IKCONFIG_PROC 697 bool "Enable access to .config through /proc/config.gz" 698 depends on IKCONFIG && PROC_FS 699 help 700 This option enables access to the kernel configuration file 701 through /proc/config.gz. 702 703config IKHEADERS 704 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 705 depends on SYSFS 706 help 707 This option enables access to the in-kernel headers that are generated during 708 the build process. These can be used to build eBPF tracing programs, 709 or similar programs. If you build the headers as a module, a module called 710 kheaders.ko is built which can be loaded on-demand to get access to headers. 711 712config LOG_BUF_SHIFT 713 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 714 range 12 25 715 default 17 716 depends on PRINTK 717 help 718 Select the minimal kernel log buffer size as a power of 2. 719 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 720 parameter, see below. Any higher size also might be forced 721 by "log_buf_len" boot parameter. 722 723 Examples: 724 17 => 128 KB 725 16 => 64 KB 726 15 => 32 KB 727 14 => 16 KB 728 13 => 8 KB 729 12 => 4 KB 730 731config LOG_CPU_MAX_BUF_SHIFT 732 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 733 depends on SMP 734 range 0 21 735 default 12 if !BASE_SMALL 736 default 0 if BASE_SMALL 737 depends on PRINTK 738 help 739 This option allows to increase the default ring buffer size 740 according to the number of CPUs. The value defines the contribution 741 of each CPU as a power of 2. The used space is typically only few 742 lines however it might be much more when problems are reported, 743 e.g. backtraces. 744 745 The increased size means that a new buffer has to be allocated and 746 the original static one is unused. It makes sense only on systems 747 with more CPUs. Therefore this value is used only when the sum of 748 contributions is greater than the half of the default kernel ring 749 buffer as defined by LOG_BUF_SHIFT. The default values are set 750 so that more than 16 CPUs are needed to trigger the allocation. 751 752 Also this option is ignored when "log_buf_len" kernel parameter is 753 used as it forces an exact (power of two) size of the ring buffer. 754 755 The number of possible CPUs is used for this computation ignoring 756 hotplugging making the computation optimal for the worst case 757 scenario while allowing a simple algorithm to be used from bootup. 758 759 Examples shift values and their meaning: 760 17 => 128 KB for each CPU 761 16 => 64 KB for each CPU 762 15 => 32 KB for each CPU 763 14 => 16 KB for each CPU 764 13 => 8 KB for each CPU 765 12 => 4 KB for each CPU 766 767config PRINTK_SAFE_LOG_BUF_SHIFT 768 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 769 range 10 21 770 default 13 771 depends on PRINTK 772 help 773 Select the size of an alternate printk per-CPU buffer where messages 774 printed from usafe contexts are temporary stored. One example would 775 be NMI messages, another one - printk recursion. The messages are 776 copied to the main log buffer in a safe context to avoid a deadlock. 777 The value defines the size as a power of 2. 778 779 Those messages are rare and limited. The largest one is when 780 a backtrace is printed. It usually fits into 4KB. Select 781 8KB if you want to be on the safe side. 782 783 Examples: 784 17 => 128 KB for each CPU 785 16 => 64 KB for each CPU 786 15 => 32 KB for each CPU 787 14 => 16 KB for each CPU 788 13 => 8 KB for each CPU 789 12 => 4 KB for each CPU 790 791config PRINTK_INDEX 792 bool "Printk indexing debugfs interface" 793 depends on PRINTK && DEBUG_FS 794 help 795 Add support for indexing of all printk formats known at compile time 796 at <debugfs>/printk/index/<module>. 797 798 This can be used as part of maintaining daemons which monitor 799 /dev/kmsg, as it permits auditing the printk formats present in a 800 kernel, allowing detection of cases where monitored printks are 801 changed or no longer present. 802 803 There is no additional runtime cost to printk with this enabled. 804 805# 806# Architectures with an unreliable sched_clock() should select this: 807# 808config HAVE_UNSTABLE_SCHED_CLOCK 809 bool 810 811config GENERIC_SCHED_CLOCK 812 bool 813 814menu "Scheduler features" 815 816config UCLAMP_TASK 817 bool "Enable utilization clamping for RT/FAIR tasks" 818 depends on CPU_FREQ_GOV_SCHEDUTIL 819 help 820 This feature enables the scheduler to track the clamped utilization 821 of each CPU based on RUNNABLE tasks scheduled on that CPU. 822 823 With this option, the user can specify the min and max CPU 824 utilization allowed for RUNNABLE tasks. The max utilization defines 825 the maximum frequency a task should use while the min utilization 826 defines the minimum frequency it should use. 827 828 Both min and max utilization clamp values are hints to the scheduler, 829 aiming at improving its frequency selection policy, but they do not 830 enforce or grant any specific bandwidth for tasks. 831 832 If in doubt, say N. 833 834config UCLAMP_BUCKETS_COUNT 835 int "Number of supported utilization clamp buckets" 836 range 5 20 837 default 5 838 depends on UCLAMP_TASK 839 help 840 Defines the number of clamp buckets to use. The range of each bucket 841 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 842 number of clamp buckets the finer their granularity and the higher 843 the precision of clamping aggregation and tracking at run-time. 844 845 For example, with the minimum configuration value we will have 5 846 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 847 be refcounted in the [20..39]% bucket and will set the bucket clamp 848 effective value to 25%. 849 If a second 30% boosted task should be co-scheduled on the same CPU, 850 that task will be refcounted in the same bucket of the first task and 851 it will boost the bucket clamp effective value to 30%. 852 The clamp effective value of a bucket is reset to its nominal value 853 (20% in the example above) when there are no more tasks refcounted in 854 that bucket. 855 856 An additional boost/capping margin can be added to some tasks. In the 857 example above the 25% task will be boosted to 30% until it exits the 858 CPU. If that should be considered not acceptable on certain systems, 859 it's always possible to reduce the margin by increasing the number of 860 clamp buckets to trade off used memory for run-time tracking 861 precision. 862 863 If in doubt, use the default value. 864 865endmenu 866 867# 868# For architectures that want to enable the support for NUMA-affine scheduler 869# balancing logic: 870# 871config ARCH_SUPPORTS_NUMA_BALANCING 872 bool 873 874# 875# For architectures that prefer to flush all TLBs after a number of pages 876# are unmapped instead of sending one IPI per page to flush. The architecture 877# must provide guarantees on what happens if a clean TLB cache entry is 878# written after the unmap. Details are in mm/rmap.c near the check for 879# should_defer_flush. The architecture should also consider if the full flush 880# and the refill costs are offset by the savings of sending fewer IPIs. 881config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 882 bool 883 884config CC_HAS_INT128 885 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 886 887config CC_IMPLICIT_FALLTHROUGH 888 string 889 default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5) 890 default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough) 891 892# 893# For architectures that know their GCC __int128 support is sound 894# 895config ARCH_SUPPORTS_INT128 896 bool 897 898# For architectures that (ab)use NUMA to represent different memory regions 899# all cpu-local but of different latencies, such as SuperH. 900# 901config ARCH_WANT_NUMA_VARIABLE_LOCALITY 902 bool 903 904config NUMA_BALANCING 905 bool "Memory placement aware NUMA scheduler" 906 depends on ARCH_SUPPORTS_NUMA_BALANCING 907 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 908 depends on SMP && NUMA && MIGRATION && !PREEMPT_RT 909 help 910 This option adds support for automatic NUMA aware memory/task placement. 911 The mechanism is quite primitive and is based on migrating memory when 912 it has references to the node the task is running on. 913 914 This system will be inactive on UMA systems. 915 916config NUMA_BALANCING_DEFAULT_ENABLED 917 bool "Automatically enable NUMA aware memory/task placement" 918 default y 919 depends on NUMA_BALANCING 920 help 921 If set, automatic NUMA balancing will be enabled if running on a NUMA 922 machine. 923 924menuconfig CGROUPS 925 bool "Control Group support" 926 select KERNFS 927 help 928 This option adds support for grouping sets of processes together, for 929 use with process control subsystems such as Cpusets, CFS, memory 930 controls or device isolation. 931 See 932 - Documentation/scheduler/sched-design-CFS.rst (CFS) 933 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 934 and resource control) 935 936 Say N if unsure. 937 938if CGROUPS 939 940config PAGE_COUNTER 941 bool 942 943config MEMCG 944 bool "Memory controller" 945 select PAGE_COUNTER 946 select EVENTFD 947 help 948 Provides control over the memory footprint of tasks in a cgroup. 949 950config MEMCG_SWAP 951 bool 952 depends on MEMCG && SWAP 953 default y 954 955config MEMCG_KMEM 956 bool 957 depends on MEMCG && !SLOB 958 default y 959 960config BLK_CGROUP 961 bool "IO controller" 962 depends on BLOCK 963 default n 964 help 965 Generic block IO controller cgroup interface. This is the common 966 cgroup interface which should be used by various IO controlling 967 policies. 968 969 Currently, CFQ IO scheduler uses it to recognize task groups and 970 control disk bandwidth allocation (proportional time slice allocation) 971 to such task groups. It is also used by bio throttling logic in 972 block layer to implement upper limit in IO rates on a device. 973 974 This option only enables generic Block IO controller infrastructure. 975 One needs to also enable actual IO controlling logic/policy. For 976 enabling proportional weight division of disk bandwidth in CFQ, set 977 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 978 CONFIG_BLK_DEV_THROTTLING=y. 979 980 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 981 982config CGROUP_WRITEBACK 983 bool 984 depends on MEMCG && BLK_CGROUP 985 default y 986 987menuconfig CGROUP_SCHED 988 bool "CPU controller" 989 default n 990 help 991 This feature lets CPU scheduler recognize task groups and control CPU 992 bandwidth allocation to such task groups. It uses cgroups to group 993 tasks. 994 995if CGROUP_SCHED 996config FAIR_GROUP_SCHED 997 bool "Group scheduling for SCHED_OTHER" 998 depends on CGROUP_SCHED 999 default CGROUP_SCHED 1000 1001config CFS_BANDWIDTH 1002 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 1003 depends on FAIR_GROUP_SCHED 1004 default n 1005 help 1006 This option allows users to define CPU bandwidth rates (limits) for 1007 tasks running within the fair group scheduler. Groups with no limit 1008 set are considered to be unconstrained and will run with no 1009 restriction. 1010 See Documentation/scheduler/sched-bwc.rst for more information. 1011 1012config RT_GROUP_SCHED 1013 bool "Group scheduling for SCHED_RR/FIFO" 1014 depends on CGROUP_SCHED 1015 default n 1016 help 1017 This feature lets you explicitly allocate real CPU bandwidth 1018 to task groups. If enabled, it will also make it impossible to 1019 schedule realtime tasks for non-root users until you allocate 1020 realtime bandwidth for them. 1021 See Documentation/scheduler/sched-rt-group.rst for more information. 1022 1023endif #CGROUP_SCHED 1024 1025config UCLAMP_TASK_GROUP 1026 bool "Utilization clamping per group of tasks" 1027 depends on CGROUP_SCHED 1028 depends on UCLAMP_TASK 1029 default n 1030 help 1031 This feature enables the scheduler to track the clamped utilization 1032 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 1033 1034 When this option is enabled, the user can specify a min and max 1035 CPU bandwidth which is allowed for each single task in a group. 1036 The max bandwidth allows to clamp the maximum frequency a task 1037 can use, while the min bandwidth allows to define a minimum 1038 frequency a task will always use. 1039 1040 When task group based utilization clamping is enabled, an eventually 1041 specified task-specific clamp value is constrained by the cgroup 1042 specified clamp value. Both minimum and maximum task clamping cannot 1043 be bigger than the corresponding clamping defined at task group level. 1044 1045 If in doubt, say N. 1046 1047config CGROUP_PIDS 1048 bool "PIDs controller" 1049 help 1050 Provides enforcement of process number limits in the scope of a 1051 cgroup. Any attempt to fork more processes than is allowed in the 1052 cgroup will fail. PIDs are fundamentally a global resource because it 1053 is fairly trivial to reach PID exhaustion before you reach even a 1054 conservative kmemcg limit. As a result, it is possible to grind a 1055 system to halt without being limited by other cgroup policies. The 1056 PIDs controller is designed to stop this from happening. 1057 1058 It should be noted that organisational operations (such as attaching 1059 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 1060 since the PIDs limit only affects a process's ability to fork, not to 1061 attach to a cgroup. 1062 1063config CGROUP_RDMA 1064 bool "RDMA controller" 1065 help 1066 Provides enforcement of RDMA resources defined by IB stack. 1067 It is fairly easy for consumers to exhaust RDMA resources, which 1068 can result into resource unavailability to other consumers. 1069 RDMA controller is designed to stop this from happening. 1070 Attaching processes with active RDMA resources to the cgroup 1071 hierarchy is allowed even if can cross the hierarchy's limit. 1072 1073config CGROUP_FREEZER 1074 bool "Freezer controller" 1075 help 1076 Provides a way to freeze and unfreeze all tasks in a 1077 cgroup. 1078 1079 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1080 controller includes important in-kernel memory consumers per default. 1081 1082 If you're using cgroup2, say N. 1083 1084config CGROUP_HUGETLB 1085 bool "HugeTLB controller" 1086 depends on HUGETLB_PAGE 1087 select PAGE_COUNTER 1088 default n 1089 help 1090 Provides a cgroup controller for HugeTLB pages. 1091 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1092 The limit is enforced during page fault. Since HugeTLB doesn't 1093 support page reclaim, enforcing the limit at page fault time implies 1094 that, the application will get SIGBUS signal if it tries to access 1095 HugeTLB pages beyond its limit. This requires the application to know 1096 beforehand how much HugeTLB pages it would require for its use. The 1097 control group is tracked in the third page lru pointer. This means 1098 that we cannot use the controller with huge page less than 3 pages. 1099 1100config CPUSETS 1101 bool "Cpuset controller" 1102 depends on SMP 1103 help 1104 This option will let you create and manage CPUSETs which 1105 allow dynamically partitioning a system into sets of CPUs and 1106 Memory Nodes and assigning tasks to run only within those sets. 1107 This is primarily useful on large SMP or NUMA systems. 1108 1109 Say N if unsure. 1110 1111config PROC_PID_CPUSET 1112 bool "Include legacy /proc/<pid>/cpuset file" 1113 depends on CPUSETS 1114 default y 1115 1116config CGROUP_DEVICE 1117 bool "Device controller" 1118 help 1119 Provides a cgroup controller implementing whitelists for 1120 devices which a process in the cgroup can mknod or open. 1121 1122config CGROUP_CPUACCT 1123 bool "Simple CPU accounting controller" 1124 help 1125 Provides a simple controller for monitoring the 1126 total CPU consumed by the tasks in a cgroup. 1127 1128config CGROUP_PERF 1129 bool "Perf controller" 1130 depends on PERF_EVENTS 1131 help 1132 This option extends the perf per-cpu mode to restrict monitoring 1133 to threads which belong to the cgroup specified and run on the 1134 designated cpu. Or this can be used to have cgroup ID in samples 1135 so that it can monitor performance events among cgroups. 1136 1137 Say N if unsure. 1138 1139config CGROUP_BPF 1140 bool "Support for eBPF programs attached to cgroups" 1141 depends on BPF_SYSCALL 1142 select SOCK_CGROUP_DATA 1143 help 1144 Allow attaching eBPF programs to a cgroup using the bpf(2) 1145 syscall command BPF_PROG_ATTACH. 1146 1147 In which context these programs are accessed depends on the type 1148 of attachment. For instance, programs that are attached using 1149 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1150 inet sockets. 1151 1152config CGROUP_MISC 1153 bool "Misc resource controller" 1154 default n 1155 help 1156 Provides a controller for miscellaneous resources on a host. 1157 1158 Miscellaneous scalar resources are the resources on the host system 1159 which cannot be abstracted like the other cgroups. This controller 1160 tracks and limits the miscellaneous resources used by a process 1161 attached to a cgroup hierarchy. 1162 1163 For more information, please check misc cgroup section in 1164 /Documentation/admin-guide/cgroup-v2.rst. 1165 1166config CGROUP_DEBUG 1167 bool "Debug controller" 1168 default n 1169 depends on DEBUG_KERNEL 1170 help 1171 This option enables a simple controller that exports 1172 debugging information about the cgroups framework. This 1173 controller is for control cgroup debugging only. Its 1174 interfaces are not stable. 1175 1176 Say N. 1177 1178config SOCK_CGROUP_DATA 1179 bool 1180 default n 1181 1182endif # CGROUPS 1183 1184menuconfig NAMESPACES 1185 bool "Namespaces support" if EXPERT 1186 depends on MULTIUSER 1187 default !EXPERT 1188 help 1189 Provides the way to make tasks work with different objects using 1190 the same id. For example same IPC id may refer to different objects 1191 or same user id or pid may refer to different tasks when used in 1192 different namespaces. 1193 1194if NAMESPACES 1195 1196config UTS_NS 1197 bool "UTS namespace" 1198 default y 1199 help 1200 In this namespace tasks see different info provided with the 1201 uname() system call 1202 1203config TIME_NS 1204 bool "TIME namespace" 1205 depends on GENERIC_VDSO_TIME_NS 1206 default y 1207 help 1208 In this namespace boottime and monotonic clocks can be set. 1209 The time will keep going with the same pace. 1210 1211config IPC_NS 1212 bool "IPC namespace" 1213 depends on (SYSVIPC || POSIX_MQUEUE) 1214 default y 1215 help 1216 In this namespace tasks work with IPC ids which correspond to 1217 different IPC objects in different namespaces. 1218 1219config USER_NS 1220 bool "User namespace" 1221 default n 1222 help 1223 This allows containers, i.e. vservers, to use user namespaces 1224 to provide different user info for different servers. 1225 1226 When user namespaces are enabled in the kernel it is 1227 recommended that the MEMCG option also be enabled and that 1228 user-space use the memory control groups to limit the amount 1229 of memory a memory unprivileged users can use. 1230 1231 If unsure, say N. 1232 1233config PID_NS 1234 bool "PID Namespaces" 1235 default y 1236 help 1237 Support process id namespaces. This allows having multiple 1238 processes with the same pid as long as they are in different 1239 pid namespaces. This is a building block of containers. 1240 1241config NET_NS 1242 bool "Network namespace" 1243 depends on NET 1244 default y 1245 help 1246 Allow user space to create what appear to be multiple instances 1247 of the network stack. 1248 1249endif # NAMESPACES 1250 1251config CHECKPOINT_RESTORE 1252 bool "Checkpoint/restore support" 1253 select PROC_CHILDREN 1254 select KCMP 1255 default n 1256 help 1257 Enables additional kernel features in a sake of checkpoint/restore. 1258 In particular it adds auxiliary prctl codes to setup process text, 1259 data and heap segment sizes, and a few additional /proc filesystem 1260 entries. 1261 1262 If unsure, say N here. 1263 1264config SCHED_AUTOGROUP 1265 bool "Automatic process group scheduling" 1266 select CGROUPS 1267 select CGROUP_SCHED 1268 select FAIR_GROUP_SCHED 1269 help 1270 This option optimizes the scheduler for common desktop workloads by 1271 automatically creating and populating task groups. This separation 1272 of workloads isolates aggressive CPU burners (like build jobs) from 1273 desktop applications. Task group autogeneration is currently based 1274 upon task session. 1275 1276config SYSFS_DEPRECATED 1277 bool "Enable deprecated sysfs features to support old userspace tools" 1278 depends on SYSFS 1279 default n 1280 help 1281 This option adds code that switches the layout of the "block" class 1282 devices, to not show up in /sys/class/block/, but only in 1283 /sys/block/. 1284 1285 This switch is only active when the sysfs.deprecated=1 boot option is 1286 passed or the SYSFS_DEPRECATED_V2 option is set. 1287 1288 This option allows new kernels to run on old distributions and tools, 1289 which might get confused by /sys/class/block/. Since 2007/2008 all 1290 major distributions and tools handle this just fine. 1291 1292 Recent distributions and userspace tools after 2009/2010 depend on 1293 the existence of /sys/class/block/, and will not work with this 1294 option enabled. 1295 1296 Only if you are using a new kernel on an old distribution, you might 1297 need to say Y here. 1298 1299config SYSFS_DEPRECATED_V2 1300 bool "Enable deprecated sysfs features by default" 1301 default n 1302 depends on SYSFS 1303 depends on SYSFS_DEPRECATED 1304 help 1305 Enable deprecated sysfs by default. 1306 1307 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1308 option. 1309 1310 Only if you are using a new kernel on an old distribution, you might 1311 need to say Y here. Even then, odds are you would not need it 1312 enabled, you can always pass the boot option if absolutely necessary. 1313 1314config RELAY 1315 bool "Kernel->user space relay support (formerly relayfs)" 1316 select IRQ_WORK 1317 help 1318 This option enables support for relay interface support in 1319 certain file systems (such as debugfs). 1320 It is designed to provide an efficient mechanism for tools and 1321 facilities to relay large amounts of data from kernel space to 1322 user space. 1323 1324 If unsure, say N. 1325 1326config BLK_DEV_INITRD 1327 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1328 help 1329 The initial RAM filesystem is a ramfs which is loaded by the 1330 boot loader (loadlin or lilo) and that is mounted as root 1331 before the normal boot procedure. It is typically used to 1332 load modules needed to mount the "real" root file system, 1333 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1334 1335 If RAM disk support (BLK_DEV_RAM) is also included, this 1336 also enables initial RAM disk (initrd) support and adds 1337 15 Kbytes (more on some other architectures) to the kernel size. 1338 1339 If unsure say Y. 1340 1341if BLK_DEV_INITRD 1342 1343source "usr/Kconfig" 1344 1345endif 1346 1347config BOOT_CONFIG 1348 bool "Boot config support" 1349 select BLK_DEV_INITRD 1350 help 1351 Extra boot config allows system admin to pass a config file as 1352 complemental extension of kernel cmdline when booting. 1353 The boot config file must be attached at the end of initramfs 1354 with checksum, size and magic word. 1355 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1356 1357 If unsure, say Y. 1358 1359choice 1360 prompt "Compiler optimization level" 1361 default CC_OPTIMIZE_FOR_PERFORMANCE 1362 1363config CC_OPTIMIZE_FOR_PERFORMANCE 1364 bool "Optimize for performance (-O2)" 1365 help 1366 This is the default optimization level for the kernel, building 1367 with the "-O2" compiler flag for best performance and most 1368 helpful compile-time warnings. 1369 1370config CC_OPTIMIZE_FOR_PERFORMANCE_O3 1371 bool "Optimize more for performance (-O3)" 1372 depends on ARC 1373 help 1374 Choosing this option will pass "-O3" to your compiler to optimize 1375 the kernel yet more for performance. 1376 1377config CC_OPTIMIZE_FOR_SIZE 1378 bool "Optimize for size (-Os)" 1379 help 1380 Choosing this option will pass "-Os" to your compiler resulting 1381 in a smaller kernel. 1382 1383endchoice 1384 1385config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1386 bool 1387 help 1388 This requires that the arch annotates or otherwise protects 1389 its external entry points from being discarded. Linker scripts 1390 must also merge .text.*, .data.*, and .bss.* correctly into 1391 output sections. Care must be taken not to pull in unrelated 1392 sections (e.g., '.text.init'). Typically '.' in section names 1393 is used to distinguish them from label names / C identifiers. 1394 1395config LD_DEAD_CODE_DATA_ELIMINATION 1396 bool "Dead code and data elimination (EXPERIMENTAL)" 1397 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1398 depends on EXPERT 1399 depends on $(cc-option,-ffunction-sections -fdata-sections) 1400 depends on $(ld-option,--gc-sections) 1401 help 1402 Enable this if you want to do dead code and data elimination with 1403 the linker by compiling with -ffunction-sections -fdata-sections, 1404 and linking with --gc-sections. 1405 1406 This can reduce on disk and in-memory size of the kernel 1407 code and static data, particularly for small configs and 1408 on small systems. This has the possibility of introducing 1409 silently broken kernel if the required annotations are not 1410 present. This option is not well tested yet, so use at your 1411 own risk. 1412 1413config LD_ORPHAN_WARN 1414 def_bool y 1415 depends on ARCH_WANT_LD_ORPHAN_WARN 1416 depends on $(ld-option,--orphan-handling=warn) 1417 1418config SYSCTL 1419 bool 1420 1421config HAVE_UID16 1422 bool 1423 1424config SYSCTL_EXCEPTION_TRACE 1425 bool 1426 help 1427 Enable support for /proc/sys/debug/exception-trace. 1428 1429config SYSCTL_ARCH_UNALIGN_NO_WARN 1430 bool 1431 help 1432 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1433 Allows arch to define/use @no_unaligned_warning to possibly warn 1434 about unaligned access emulation going on under the hood. 1435 1436config SYSCTL_ARCH_UNALIGN_ALLOW 1437 bool 1438 help 1439 Enable support for /proc/sys/kernel/unaligned-trap 1440 Allows arches to define/use @unaligned_enabled to runtime toggle 1441 the unaligned access emulation. 1442 see arch/parisc/kernel/unaligned.c for reference 1443 1444config HAVE_PCSPKR_PLATFORM 1445 bool 1446 1447# interpreter that classic socket filters depend on 1448config BPF 1449 bool 1450 1451menuconfig EXPERT 1452 bool "Configure standard kernel features (expert users)" 1453 # Unhide debug options, to make the on-by-default options visible 1454 select DEBUG_KERNEL 1455 help 1456 This option allows certain base kernel options and settings 1457 to be disabled or tweaked. This is for specialized 1458 environments which can tolerate a "non-standard" kernel. 1459 Only use this if you really know what you are doing. 1460 1461config UID16 1462 bool "Enable 16-bit UID system calls" if EXPERT 1463 depends on HAVE_UID16 && MULTIUSER 1464 default y 1465 help 1466 This enables the legacy 16-bit UID syscall wrappers. 1467 1468config MULTIUSER 1469 bool "Multiple users, groups and capabilities support" if EXPERT 1470 default y 1471 help 1472 This option enables support for non-root users, groups and 1473 capabilities. 1474 1475 If you say N here, all processes will run with UID 0, GID 0, and all 1476 possible capabilities. Saying N here also compiles out support for 1477 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1478 setgid, and capset. 1479 1480 If unsure, say Y here. 1481 1482config SGETMASK_SYSCALL 1483 bool "sgetmask/ssetmask syscalls support" if EXPERT 1484 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1485 help 1486 sys_sgetmask and sys_ssetmask are obsolete system calls 1487 no longer supported in libc but still enabled by default in some 1488 architectures. 1489 1490 If unsure, leave the default option here. 1491 1492config SYSFS_SYSCALL 1493 bool "Sysfs syscall support" if EXPERT 1494 default y 1495 help 1496 sys_sysfs is an obsolete system call no longer supported in libc. 1497 Note that disabling this option is more secure but might break 1498 compatibility with some systems. 1499 1500 If unsure say Y here. 1501 1502config FHANDLE 1503 bool "open by fhandle syscalls" if EXPERT 1504 select EXPORTFS 1505 default y 1506 help 1507 If you say Y here, a user level program will be able to map 1508 file names to handle and then later use the handle for 1509 different file system operations. This is useful in implementing 1510 userspace file servers, which now track files using handles instead 1511 of names. The handle would remain the same even if file names 1512 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1513 syscalls. 1514 1515config POSIX_TIMERS 1516 bool "Posix Clocks & timers" if EXPERT 1517 default y 1518 help 1519 This includes native support for POSIX timers to the kernel. 1520 Some embedded systems have no use for them and therefore they 1521 can be configured out to reduce the size of the kernel image. 1522 1523 When this option is disabled, the following syscalls won't be 1524 available: timer_create, timer_gettime: timer_getoverrun, 1525 timer_settime, timer_delete, clock_adjtime, getitimer, 1526 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1527 clock_getres and clock_nanosleep syscalls will be limited to 1528 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1529 1530 If unsure say y. 1531 1532config PRINTK 1533 default y 1534 bool "Enable support for printk" if EXPERT 1535 select IRQ_WORK 1536 help 1537 This option enables normal printk support. Removing it 1538 eliminates most of the message strings from the kernel image 1539 and makes the kernel more or less silent. As this makes it 1540 very difficult to diagnose system problems, saying N here is 1541 strongly discouraged. 1542 1543config BUG 1544 bool "BUG() support" if EXPERT 1545 default y 1546 help 1547 Disabling this option eliminates support for BUG and WARN, reducing 1548 the size of your kernel image and potentially quietly ignoring 1549 numerous fatal conditions. You should only consider disabling this 1550 option for embedded systems with no facilities for reporting errors. 1551 Just say Y. 1552 1553config ELF_CORE 1554 depends on COREDUMP 1555 default y 1556 bool "Enable ELF core dumps" if EXPERT 1557 help 1558 Enable support for generating core dumps. Disabling saves about 4k. 1559 1560 1561config PCSPKR_PLATFORM 1562 bool "Enable PC-Speaker support" if EXPERT 1563 depends on HAVE_PCSPKR_PLATFORM 1564 select I8253_LOCK 1565 default y 1566 help 1567 This option allows to disable the internal PC-Speaker 1568 support, saving some memory. 1569 1570config BASE_FULL 1571 default y 1572 bool "Enable full-sized data structures for core" if EXPERT 1573 help 1574 Disabling this option reduces the size of miscellaneous core 1575 kernel data structures. This saves memory on small machines, 1576 but may reduce performance. 1577 1578config FUTEX 1579 bool "Enable futex support" if EXPERT 1580 depends on !(SPARC32 && SMP) 1581 default y 1582 imply RT_MUTEXES 1583 help 1584 Disabling this option will cause the kernel to be built without 1585 support for "fast userspace mutexes". The resulting kernel may not 1586 run glibc-based applications correctly. 1587 1588config FUTEX_PI 1589 bool 1590 depends on FUTEX && RT_MUTEXES 1591 default y 1592 1593config EPOLL 1594 bool "Enable eventpoll support" if EXPERT 1595 default y 1596 help 1597 Disabling this option will cause the kernel to be built without 1598 support for epoll family of system calls. 1599 1600config SIGNALFD 1601 bool "Enable signalfd() system call" if EXPERT 1602 default y 1603 help 1604 Enable the signalfd() system call that allows to receive signals 1605 on a file descriptor. 1606 1607 If unsure, say Y. 1608 1609config TIMERFD 1610 bool "Enable timerfd() system call" if EXPERT 1611 default y 1612 help 1613 Enable the timerfd() system call that allows to receive timer 1614 events on a file descriptor. 1615 1616 If unsure, say Y. 1617 1618config EVENTFD 1619 bool "Enable eventfd() system call" if EXPERT 1620 default y 1621 help 1622 Enable the eventfd() system call that allows to receive both 1623 kernel notification (ie. KAIO) or userspace notifications. 1624 1625 If unsure, say Y. 1626 1627config SHMEM 1628 bool "Use full shmem filesystem" if EXPERT 1629 default y 1630 depends on MMU 1631 help 1632 The shmem is an internal filesystem used to manage shared memory. 1633 It is backed by swap and manages resource limits. It is also exported 1634 to userspace as tmpfs if TMPFS is enabled. Disabling this 1635 option replaces shmem and tmpfs with the much simpler ramfs code, 1636 which may be appropriate on small systems without swap. 1637 1638config AIO 1639 bool "Enable AIO support" if EXPERT 1640 default y 1641 help 1642 This option enables POSIX asynchronous I/O which may by used 1643 by some high performance threaded applications. Disabling 1644 this option saves about 7k. 1645 1646config IO_URING 1647 bool "Enable IO uring support" if EXPERT 1648 select IO_WQ 1649 default y 1650 help 1651 This option enables support for the io_uring interface, enabling 1652 applications to submit and complete IO through submission and 1653 completion rings that are shared between the kernel and application. 1654 1655config ADVISE_SYSCALLS 1656 bool "Enable madvise/fadvise syscalls" if EXPERT 1657 default y 1658 help 1659 This option enables the madvise and fadvise syscalls, used by 1660 applications to advise the kernel about their future memory or file 1661 usage, improving performance. If building an embedded system where no 1662 applications use these syscalls, you can disable this option to save 1663 space. 1664 1665config HAVE_ARCH_USERFAULTFD_WP 1666 bool 1667 help 1668 Arch has userfaultfd write protection support 1669 1670config HAVE_ARCH_USERFAULTFD_MINOR 1671 bool 1672 help 1673 Arch has userfaultfd minor fault support 1674 1675config MEMBARRIER 1676 bool "Enable membarrier() system call" if EXPERT 1677 default y 1678 help 1679 Enable the membarrier() system call that allows issuing memory 1680 barriers across all running threads, which can be used to distribute 1681 the cost of user-space memory barriers asymmetrically by transforming 1682 pairs of memory barriers into pairs consisting of membarrier() and a 1683 compiler barrier. 1684 1685 If unsure, say Y. 1686 1687config KALLSYMS 1688 bool "Load all symbols for debugging/ksymoops" if EXPERT 1689 default y 1690 help 1691 Say Y here to let the kernel print out symbolic crash information and 1692 symbolic stack backtraces. This increases the size of the kernel 1693 somewhat, as all symbols have to be loaded into the kernel image. 1694 1695config KALLSYMS_ALL 1696 bool "Include all symbols in kallsyms" 1697 depends on DEBUG_KERNEL && KALLSYMS 1698 help 1699 Normally kallsyms only contains the symbols of functions for nicer 1700 OOPS messages and backtraces (i.e., symbols from the text and inittext 1701 sections). This is sufficient for most cases. And only in very rare 1702 cases (e.g., when a debugger is used) all symbols are required (e.g., 1703 names of variables from the data sections, etc). 1704 1705 This option makes sure that all symbols are loaded into the kernel 1706 image (i.e., symbols from all sections) in cost of increased kernel 1707 size (depending on the kernel configuration, it may be 300KiB or 1708 something like this). 1709 1710 Say N unless you really need all symbols. 1711 1712config KALLSYMS_ABSOLUTE_PERCPU 1713 bool 1714 depends on KALLSYMS 1715 default X86_64 && SMP 1716 1717config KALLSYMS_BASE_RELATIVE 1718 bool 1719 depends on KALLSYMS 1720 default !IA64 1721 help 1722 Instead of emitting them as absolute values in the native word size, 1723 emit the symbol references in the kallsyms table as 32-bit entries, 1724 each containing a relative value in the range [base, base + U32_MAX] 1725 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1726 an absolute value in the range [0, S32_MAX] or a relative value in the 1727 range [base, base + S32_MAX], where base is the lowest relative symbol 1728 address encountered in the image. 1729 1730 On 64-bit builds, this reduces the size of the address table by 50%, 1731 but more importantly, it results in entries whose values are build 1732 time constants, and no relocation pass is required at runtime to fix 1733 up the entries based on the runtime load address of the kernel. 1734 1735# end of the "standard kernel features (expert users)" menu 1736 1737# syscall, maps, verifier 1738 1739config USERFAULTFD 1740 bool "Enable userfaultfd() system call" 1741 depends on MMU 1742 help 1743 Enable the userfaultfd() system call that allows to intercept and 1744 handle page faults in userland. 1745 1746config ARCH_HAS_MEMBARRIER_CALLBACKS 1747 bool 1748 1749config ARCH_HAS_MEMBARRIER_SYNC_CORE 1750 bool 1751 1752config KCMP 1753 bool "Enable kcmp() system call" if EXPERT 1754 help 1755 Enable the kernel resource comparison system call. It provides 1756 user-space with the ability to compare two processes to see if they 1757 share a common resource, such as a file descriptor or even virtual 1758 memory space. 1759 1760 If unsure, say N. 1761 1762config RSEQ 1763 bool "Enable rseq() system call" if EXPERT 1764 default y 1765 depends on HAVE_RSEQ 1766 select MEMBARRIER 1767 help 1768 Enable the restartable sequences system call. It provides a 1769 user-space cache for the current CPU number value, which 1770 speeds up getting the current CPU number from user-space, 1771 as well as an ABI to speed up user-space operations on 1772 per-CPU data. 1773 1774 If unsure, say Y. 1775 1776config DEBUG_RSEQ 1777 default n 1778 bool "Enabled debugging of rseq() system call" if EXPERT 1779 depends on RSEQ && DEBUG_KERNEL 1780 help 1781 Enable extra debugging checks for the rseq system call. 1782 1783 If unsure, say N. 1784 1785config EMBEDDED 1786 bool "Embedded system" 1787 select EXPERT 1788 help 1789 This option should be enabled if compiling the kernel for 1790 an embedded system so certain expert options are available 1791 for configuration. 1792 1793config HAVE_PERF_EVENTS 1794 bool 1795 help 1796 See tools/perf/design.txt for details. 1797 1798config GUEST_PERF_EVENTS 1799 bool 1800 depends on HAVE_PERF_EVENTS 1801 1802config PERF_USE_VMALLOC 1803 bool 1804 help 1805 See tools/perf/design.txt for details 1806 1807config PC104 1808 bool "PC/104 support" if EXPERT 1809 help 1810 Expose PC/104 form factor device drivers and options available for 1811 selection and configuration. Enable this option if your target 1812 machine has a PC/104 bus. 1813 1814menu "Kernel Performance Events And Counters" 1815 1816config PERF_EVENTS 1817 bool "Kernel performance events and counters" 1818 default y if PROFILING 1819 depends on HAVE_PERF_EVENTS 1820 select IRQ_WORK 1821 select SRCU 1822 help 1823 Enable kernel support for various performance events provided 1824 by software and hardware. 1825 1826 Software events are supported either built-in or via the 1827 use of generic tracepoints. 1828 1829 Most modern CPUs support performance events via performance 1830 counter registers. These registers count the number of certain 1831 types of hw events: such as instructions executed, cachemisses 1832 suffered, or branches mis-predicted - without slowing down the 1833 kernel or applications. These registers can also trigger interrupts 1834 when a threshold number of events have passed - and can thus be 1835 used to profile the code that runs on that CPU. 1836 1837 The Linux Performance Event subsystem provides an abstraction of 1838 these software and hardware event capabilities, available via a 1839 system call and used by the "perf" utility in tools/perf/. It 1840 provides per task and per CPU counters, and it provides event 1841 capabilities on top of those. 1842 1843 Say Y if unsure. 1844 1845config DEBUG_PERF_USE_VMALLOC 1846 default n 1847 bool "Debug: use vmalloc to back perf mmap() buffers" 1848 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1849 select PERF_USE_VMALLOC 1850 help 1851 Use vmalloc memory to back perf mmap() buffers. 1852 1853 Mostly useful for debugging the vmalloc code on platforms 1854 that don't require it. 1855 1856 Say N if unsure. 1857 1858endmenu 1859 1860config VM_EVENT_COUNTERS 1861 default y 1862 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1863 help 1864 VM event counters are needed for event counts to be shown. 1865 This option allows the disabling of the VM event counters 1866 on EXPERT systems. /proc/vmstat will only show page counts 1867 if VM event counters are disabled. 1868 1869config SLUB_DEBUG 1870 default y 1871 bool "Enable SLUB debugging support" if EXPERT 1872 depends on SLUB && SYSFS 1873 help 1874 SLUB has extensive debug support features. Disabling these can 1875 result in significant savings in code size. This also disables 1876 SLUB sysfs support. /sys/slab will not exist and there will be 1877 no support for cache validation etc. 1878 1879config COMPAT_BRK 1880 bool "Disable heap randomization" 1881 default y 1882 help 1883 Randomizing heap placement makes heap exploits harder, but it 1884 also breaks ancient binaries (including anything libc5 based). 1885 This option changes the bootup default to heap randomization 1886 disabled, and can be overridden at runtime by setting 1887 /proc/sys/kernel/randomize_va_space to 2. 1888 1889 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1890 1891choice 1892 prompt "Choose SLAB allocator" 1893 default SLUB 1894 help 1895 This option allows to select a slab allocator. 1896 1897config SLAB 1898 bool "SLAB" 1899 depends on !PREEMPT_RT 1900 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1901 help 1902 The regular slab allocator that is established and known to work 1903 well in all environments. It organizes cache hot objects in 1904 per cpu and per node queues. 1905 1906config SLUB 1907 bool "SLUB (Unqueued Allocator)" 1908 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1909 help 1910 SLUB is a slab allocator that minimizes cache line usage 1911 instead of managing queues of cached objects (SLAB approach). 1912 Per cpu caching is realized using slabs of objects instead 1913 of queues of objects. SLUB can use memory efficiently 1914 and has enhanced diagnostics. SLUB is the default choice for 1915 a slab allocator. 1916 1917config SLOB 1918 depends on EXPERT 1919 bool "SLOB (Simple Allocator)" 1920 depends on !PREEMPT_RT 1921 help 1922 SLOB replaces the stock allocator with a drastically simpler 1923 allocator. SLOB is generally more space efficient but 1924 does not perform as well on large systems. 1925 1926endchoice 1927 1928config SLAB_MERGE_DEFAULT 1929 bool "Allow slab caches to be merged" 1930 default y 1931 depends on SLAB || SLUB 1932 help 1933 For reduced kernel memory fragmentation, slab caches can be 1934 merged when they share the same size and other characteristics. 1935 This carries a risk of kernel heap overflows being able to 1936 overwrite objects from merged caches (and more easily control 1937 cache layout), which makes such heap attacks easier to exploit 1938 by attackers. By keeping caches unmerged, these kinds of exploits 1939 can usually only damage objects in the same cache. To disable 1940 merging at runtime, "slab_nomerge" can be passed on the kernel 1941 command line. 1942 1943config SLAB_FREELIST_RANDOM 1944 bool "Randomize slab freelist" 1945 depends on SLAB || SLUB 1946 help 1947 Randomizes the freelist order used on creating new pages. This 1948 security feature reduces the predictability of the kernel slab 1949 allocator against heap overflows. 1950 1951config SLAB_FREELIST_HARDENED 1952 bool "Harden slab freelist metadata" 1953 depends on SLAB || SLUB 1954 help 1955 Many kernel heap attacks try to target slab cache metadata and 1956 other infrastructure. This options makes minor performance 1957 sacrifices to harden the kernel slab allocator against common 1958 freelist exploit methods. Some slab implementations have more 1959 sanity-checking than others. This option is most effective with 1960 CONFIG_SLUB. 1961 1962config SHUFFLE_PAGE_ALLOCATOR 1963 bool "Page allocator randomization" 1964 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1965 help 1966 Randomization of the page allocator improves the average 1967 utilization of a direct-mapped memory-side-cache. See section 1968 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1969 6.2a specification for an example of how a platform advertises 1970 the presence of a memory-side-cache. There are also incidental 1971 security benefits as it reduces the predictability of page 1972 allocations to compliment SLAB_FREELIST_RANDOM, but the 1973 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1974 10th order of pages is selected based on cache utilization 1975 benefits on x86. 1976 1977 While the randomization improves cache utilization it may 1978 negatively impact workloads on platforms without a cache. For 1979 this reason, by default, the randomization is enabled only 1980 after runtime detection of a direct-mapped memory-side-cache. 1981 Otherwise, the randomization may be force enabled with the 1982 'page_alloc.shuffle' kernel command line parameter. 1983 1984 Say Y if unsure. 1985 1986config SLUB_CPU_PARTIAL 1987 default y 1988 depends on SLUB && SMP 1989 bool "SLUB per cpu partial cache" 1990 help 1991 Per cpu partial caches accelerate objects allocation and freeing 1992 that is local to a processor at the price of more indeterminism 1993 in the latency of the free. On overflow these caches will be cleared 1994 which requires the taking of locks that may cause latency spikes. 1995 Typically one would choose no for a realtime system. 1996 1997config MMAP_ALLOW_UNINITIALIZED 1998 bool "Allow mmapped anonymous memory to be uninitialized" 1999 depends on EXPERT && !MMU 2000 default n 2001 help 2002 Normally, and according to the Linux spec, anonymous memory obtained 2003 from mmap() has its contents cleared before it is passed to 2004 userspace. Enabling this config option allows you to request that 2005 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 2006 providing a huge performance boost. If this option is not enabled, 2007 then the flag will be ignored. 2008 2009 This is taken advantage of by uClibc's malloc(), and also by 2010 ELF-FDPIC binfmt's brk and stack allocator. 2011 2012 Because of the obvious security issues, this option should only be 2013 enabled on embedded devices where you control what is run in 2014 userspace. Since that isn't generally a problem on no-MMU systems, 2015 it is normally safe to say Y here. 2016 2017 See Documentation/admin-guide/mm/nommu-mmap.rst for more information. 2018 2019config SYSTEM_DATA_VERIFICATION 2020 def_bool n 2021 select SYSTEM_TRUSTED_KEYRING 2022 select KEYS 2023 select CRYPTO 2024 select CRYPTO_RSA 2025 select ASYMMETRIC_KEY_TYPE 2026 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 2027 select ASN1 2028 select OID_REGISTRY 2029 select X509_CERTIFICATE_PARSER 2030 select PKCS7_MESSAGE_PARSER 2031 help 2032 Provide PKCS#7 message verification using the contents of the system 2033 trusted keyring to provide public keys. This then can be used for 2034 module verification, kexec image verification and firmware blob 2035 verification. 2036 2037config PROFILING 2038 bool "Profiling support" 2039 help 2040 Say Y here to enable the extended profiling support mechanisms used 2041 by profilers. 2042 2043# 2044# Place an empty function call at each tracepoint site. Can be 2045# dynamically changed for a probe function. 2046# 2047config TRACEPOINTS 2048 bool 2049 2050endmenu # General setup 2051 2052source "arch/Kconfig" 2053 2054config RT_MUTEXES 2055 bool 2056 2057config BASE_SMALL 2058 int 2059 default 0 if BASE_FULL 2060 default 1 if !BASE_FULL 2061 2062config MODULE_SIG_FORMAT 2063 def_bool n 2064 select SYSTEM_DATA_VERIFICATION 2065 2066menuconfig MODULES 2067 bool "Enable loadable module support" 2068 modules 2069 help 2070 Kernel modules are small pieces of compiled code which can 2071 be inserted in the running kernel, rather than being 2072 permanently built into the kernel. You use the "modprobe" 2073 tool to add (and sometimes remove) them. If you say Y here, 2074 many parts of the kernel can be built as modules (by 2075 answering M instead of Y where indicated): this is most 2076 useful for infrequently used options which are not required 2077 for booting. For more information, see the man pages for 2078 modprobe, lsmod, modinfo, insmod and rmmod. 2079 2080 If you say Y here, you will need to run "make 2081 modules_install" to put the modules under /lib/modules/ 2082 where modprobe can find them (you may need to be root to do 2083 this). 2084 2085 If unsure, say Y. 2086 2087if MODULES 2088 2089config MODULE_FORCE_LOAD 2090 bool "Forced module loading" 2091 default n 2092 help 2093 Allow loading of modules without version information (ie. modprobe 2094 --force). Forced module loading sets the 'F' (forced) taint flag and 2095 is usually a really bad idea. 2096 2097config MODULE_UNLOAD 2098 bool "Module unloading" 2099 help 2100 Without this option you will not be able to unload any 2101 modules (note that some modules may not be unloadable 2102 anyway), which makes your kernel smaller, faster 2103 and simpler. If unsure, say Y. 2104 2105config MODULE_FORCE_UNLOAD 2106 bool "Forced module unloading" 2107 depends on MODULE_UNLOAD 2108 help 2109 This option allows you to force a module to unload, even if the 2110 kernel believes it is unsafe: the kernel will remove the module 2111 without waiting for anyone to stop using it (using the -f option to 2112 rmmod). This is mainly for kernel developers and desperate users. 2113 If unsure, say N. 2114 2115config MODVERSIONS 2116 bool "Module versioning support" 2117 help 2118 Usually, you have to use modules compiled with your kernel. 2119 Saying Y here makes it sometimes possible to use modules 2120 compiled for different kernels, by adding enough information 2121 to the modules to (hopefully) spot any changes which would 2122 make them incompatible with the kernel you are running. If 2123 unsure, say N. 2124 2125config ASM_MODVERSIONS 2126 bool 2127 default HAVE_ASM_MODVERSIONS && MODVERSIONS 2128 help 2129 This enables module versioning for exported symbols also from 2130 assembly. This can be enabled only when the target architecture 2131 supports it. 2132 2133config MODULE_REL_CRCS 2134 bool 2135 depends on MODVERSIONS 2136 2137config MODULE_SRCVERSION_ALL 2138 bool "Source checksum for all modules" 2139 help 2140 Modules which contain a MODULE_VERSION get an extra "srcversion" 2141 field inserted into their modinfo section, which contains a 2142 sum of the source files which made it. This helps maintainers 2143 see exactly which source was used to build a module (since 2144 others sometimes change the module source without updating 2145 the version). With this option, such a "srcversion" field 2146 will be created for all modules. If unsure, say N. 2147 2148config MODULE_SIG 2149 bool "Module signature verification" 2150 select MODULE_SIG_FORMAT 2151 help 2152 Check modules for valid signatures upon load: the signature 2153 is simply appended to the module. For more information see 2154 <file:Documentation/admin-guide/module-signing.rst>. 2155 2156 Note that this option adds the OpenSSL development packages as a 2157 kernel build dependency so that the signing tool can use its crypto 2158 library. 2159 2160 You should enable this option if you wish to use either 2161 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via 2162 another LSM - otherwise unsigned modules will be loadable regardless 2163 of the lockdown policy. 2164 2165 !!!WARNING!!! If you enable this option, you MUST make sure that the 2166 module DOES NOT get stripped after being signed. This includes the 2167 debuginfo strip done by some packagers (such as rpmbuild) and 2168 inclusion into an initramfs that wants the module size reduced. 2169 2170config MODULE_SIG_FORCE 2171 bool "Require modules to be validly signed" 2172 depends on MODULE_SIG 2173 help 2174 Reject unsigned modules or signed modules for which we don't have a 2175 key. Without this, such modules will simply taint the kernel. 2176 2177config MODULE_SIG_ALL 2178 bool "Automatically sign all modules" 2179 default y 2180 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 2181 help 2182 Sign all modules during make modules_install. Without this option, 2183 modules must be signed manually, using the scripts/sign-file tool. 2184 2185comment "Do not forget to sign required modules with scripts/sign-file" 2186 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2187 2188choice 2189 prompt "Which hash algorithm should modules be signed with?" 2190 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 2191 help 2192 This determines which sort of hashing algorithm will be used during 2193 signature generation. This algorithm _must_ be built into the kernel 2194 directly so that signature verification can take place. It is not 2195 possible to load a signed module containing the algorithm to check 2196 the signature on that module. 2197 2198config MODULE_SIG_SHA1 2199 bool "Sign modules with SHA-1" 2200 select CRYPTO_SHA1 2201 2202config MODULE_SIG_SHA224 2203 bool "Sign modules with SHA-224" 2204 select CRYPTO_SHA256 2205 2206config MODULE_SIG_SHA256 2207 bool "Sign modules with SHA-256" 2208 select CRYPTO_SHA256 2209 2210config MODULE_SIG_SHA384 2211 bool "Sign modules with SHA-384" 2212 select CRYPTO_SHA512 2213 2214config MODULE_SIG_SHA512 2215 bool "Sign modules with SHA-512" 2216 select CRYPTO_SHA512 2217 2218endchoice 2219 2220config MODULE_SIG_HASH 2221 string 2222 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 2223 default "sha1" if MODULE_SIG_SHA1 2224 default "sha224" if MODULE_SIG_SHA224 2225 default "sha256" if MODULE_SIG_SHA256 2226 default "sha384" if MODULE_SIG_SHA384 2227 default "sha512" if MODULE_SIG_SHA512 2228 2229choice 2230 prompt "Module compression mode" 2231 help 2232 This option allows you to choose the algorithm which will be used to 2233 compress modules when 'make modules_install' is run. (or, you can 2234 choose to not compress modules at all.) 2235 2236 External modules will also be compressed in the same way during the 2237 installation. 2238 2239 For modules inside an initrd or initramfs, it's more efficient to 2240 compress the whole initrd or initramfs instead. 2241 2242 This is fully compatible with signed modules. 2243 2244 Please note that the tool used to load modules needs to support the 2245 corresponding algorithm. module-init-tools MAY support gzip, and kmod 2246 MAY support gzip, xz and zstd. 2247 2248 Your build system needs to provide the appropriate compression tool 2249 to compress the modules. 2250 2251 If in doubt, select 'None'. 2252 2253config MODULE_COMPRESS_NONE 2254 bool "None" 2255 help 2256 Do not compress modules. The installed modules are suffixed 2257 with .ko. 2258 2259config MODULE_COMPRESS_GZIP 2260 bool "GZIP" 2261 help 2262 Compress modules with GZIP. The installed modules are suffixed 2263 with .ko.gz. 2264 2265config MODULE_COMPRESS_XZ 2266 bool "XZ" 2267 help 2268 Compress modules with XZ. The installed modules are suffixed 2269 with .ko.xz. 2270 2271config MODULE_COMPRESS_ZSTD 2272 bool "ZSTD" 2273 help 2274 Compress modules with ZSTD. The installed modules are suffixed 2275 with .ko.zst. 2276 2277endchoice 2278 2279config MODULE_DECOMPRESS 2280 bool "Support in-kernel module decompression" 2281 depends on MODULE_COMPRESS_GZIP || MODULE_COMPRESS_XZ 2282 select ZLIB_INFLATE if MODULE_COMPRESS_GZIP 2283 select XZ_DEC if MODULE_COMPRESS_XZ 2284 help 2285 2286 Support for decompressing kernel modules by the kernel itself 2287 instead of relying on userspace to perform this task. Useful when 2288 load pinning security policy is enabled. 2289 2290 If unsure, say N. 2291 2292config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS 2293 bool "Allow loading of modules with missing namespace imports" 2294 help 2295 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in 2296 a namespace. A module that makes use of a symbol exported with such a 2297 namespace is required to import the namespace via MODULE_IMPORT_NS(). 2298 There is no technical reason to enforce correct namespace imports, 2299 but it creates consistency between symbols defining namespaces and 2300 users importing namespaces they make use of. This option relaxes this 2301 requirement and lifts the enforcement when loading a module. 2302 2303 If unsure, say N. 2304 2305config MODPROBE_PATH 2306 string "Path to modprobe binary" 2307 default "/sbin/modprobe" 2308 help 2309 When kernel code requests a module, it does so by calling 2310 the "modprobe" userspace utility. This option allows you to 2311 set the path where that binary is found. This can be changed 2312 at runtime via the sysctl file 2313 /proc/sys/kernel/modprobe. Setting this to the empty string 2314 removes the kernel's ability to request modules (but 2315 userspace can still load modules explicitly). 2316 2317config TRIM_UNUSED_KSYMS 2318 bool "Trim unused exported kernel symbols" if EXPERT 2319 depends on !COMPILE_TEST 2320 help 2321 The kernel and some modules make many symbols available for 2322 other modules to use via EXPORT_SYMBOL() and variants. Depending 2323 on the set of modules being selected in your kernel configuration, 2324 many of those exported symbols might never be used. 2325 2326 This option allows for unused exported symbols to be dropped from 2327 the build. In turn, this provides the compiler more opportunities 2328 (especially when using LTO) for optimizing the code and reducing 2329 binary size. This might have some security advantages as well. 2330 2331 If unsure, or if you need to build out-of-tree modules, say N. 2332 2333config UNUSED_KSYMS_WHITELIST 2334 string "Whitelist of symbols to keep in ksymtab" 2335 depends on TRIM_UNUSED_KSYMS 2336 help 2337 By default, all unused exported symbols will be un-exported from the 2338 build when TRIM_UNUSED_KSYMS is selected. 2339 2340 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept 2341 exported at all times, even in absence of in-tree users. The value to 2342 set here is the path to a text file containing the list of symbols, 2343 one per line. The path can be absolute, or relative to the kernel 2344 source tree. 2345 2346endif # MODULES 2347 2348config MODULES_TREE_LOOKUP 2349 def_bool y 2350 depends on PERF_EVENTS || TRACING || CFI_CLANG 2351 2352config INIT_ALL_POSSIBLE 2353 bool 2354 help 2355 Back when each arch used to define their own cpu_online_mask and 2356 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2357 with all 1s, and others with all 0s. When they were centralised, 2358 it was better to provide this option than to break all the archs 2359 and have several arch maintainers pursuing me down dark alleys. 2360 2361source "block/Kconfig" 2362 2363config PREEMPT_NOTIFIERS 2364 bool 2365 2366config PADATA 2367 depends on SMP 2368 bool 2369 2370config ASN1 2371 tristate 2372 help 2373 Build a simple ASN.1 grammar compiler that produces a bytecode output 2374 that can be interpreted by the ASN.1 stream decoder and used to 2375 inform it as to what tags are to be expected in a stream and what 2376 functions to call on what tags. 2377 2378source "kernel/Kconfig.locks" 2379 2380config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 2381 bool 2382 2383config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2384 bool 2385 2386# It may be useful for an architecture to override the definitions of the 2387# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2388# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2389# different calling convention for syscalls. They can also override the 2390# macros for not-implemented syscalls in kernel/sys_ni.c and 2391# kernel/time/posix-stubs.c. All these overrides need to be available in 2392# <asm/syscall_wrapper.h>. 2393config ARCH_HAS_SYSCALL_WRAPPER 2394 def_bool n 2395