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_set_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 if !H8300 715 range 12 19 if H8300 716 default 17 717 depends on PRINTK 718 help 719 Select the minimal kernel log buffer size as a power of 2. 720 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 721 parameter, see below. Any higher size also might be forced 722 by "log_buf_len" boot parameter. 723 724 Examples: 725 17 => 128 KB 726 16 => 64 KB 727 15 => 32 KB 728 14 => 16 KB 729 13 => 8 KB 730 12 => 4 KB 731 732config LOG_CPU_MAX_BUF_SHIFT 733 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 734 depends on SMP 735 range 0 21 736 default 12 if !BASE_SMALL 737 default 0 if BASE_SMALL 738 depends on PRINTK 739 help 740 This option allows to increase the default ring buffer size 741 according to the number of CPUs. The value defines the contribution 742 of each CPU as a power of 2. The used space is typically only few 743 lines however it might be much more when problems are reported, 744 e.g. backtraces. 745 746 The increased size means that a new buffer has to be allocated and 747 the original static one is unused. It makes sense only on systems 748 with more CPUs. Therefore this value is used only when the sum of 749 contributions is greater than the half of the default kernel ring 750 buffer as defined by LOG_BUF_SHIFT. The default values are set 751 so that more than 16 CPUs are needed to trigger the allocation. 752 753 Also this option is ignored when "log_buf_len" kernel parameter is 754 used as it forces an exact (power of two) size of the ring buffer. 755 756 The number of possible CPUs is used for this computation ignoring 757 hotplugging making the computation optimal for the worst case 758 scenario while allowing a simple algorithm to be used from bootup. 759 760 Examples shift values and their meaning: 761 17 => 128 KB for each CPU 762 16 => 64 KB for each CPU 763 15 => 32 KB for each CPU 764 14 => 16 KB for each CPU 765 13 => 8 KB for each CPU 766 12 => 4 KB for each CPU 767 768config PRINTK_SAFE_LOG_BUF_SHIFT 769 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 770 range 10 21 771 default 13 772 depends on PRINTK 773 help 774 Select the size of an alternate printk per-CPU buffer where messages 775 printed from usafe contexts are temporary stored. One example would 776 be NMI messages, another one - printk recursion. The messages are 777 copied to the main log buffer in a safe context to avoid a deadlock. 778 The value defines the size as a power of 2. 779 780 Those messages are rare and limited. The largest one is when 781 a backtrace is printed. It usually fits into 4KB. Select 782 8KB if you want to be on the safe side. 783 784 Examples: 785 17 => 128 KB for each CPU 786 16 => 64 KB for each CPU 787 15 => 32 KB for each CPU 788 14 => 16 KB for each CPU 789 13 => 8 KB for each CPU 790 12 => 4 KB for each CPU 791 792config PRINTK_INDEX 793 bool "Printk indexing debugfs interface" 794 depends on PRINTK && DEBUG_FS 795 help 796 Add support for indexing of all printk formats known at compile time 797 at <debugfs>/printk/index/<module>. 798 799 This can be used as part of maintaining daemons which monitor 800 /dev/kmsg, as it permits auditing the printk formats present in a 801 kernel, allowing detection of cases where monitored printks are 802 changed or no longer present. 803 804 There is no additional runtime cost to printk with this enabled. 805 806# 807# Architectures with an unreliable sched_clock() should select this: 808# 809config HAVE_UNSTABLE_SCHED_CLOCK 810 bool 811 812config GENERIC_SCHED_CLOCK 813 bool 814 815menu "Scheduler features" 816 817config UCLAMP_TASK 818 bool "Enable utilization clamping for RT/FAIR tasks" 819 depends on CPU_FREQ_GOV_SCHEDUTIL 820 help 821 This feature enables the scheduler to track the clamped utilization 822 of each CPU based on RUNNABLE tasks scheduled on that CPU. 823 824 With this option, the user can specify the min and max CPU 825 utilization allowed for RUNNABLE tasks. The max utilization defines 826 the maximum frequency a task should use while the min utilization 827 defines the minimum frequency it should use. 828 829 Both min and max utilization clamp values are hints to the scheduler, 830 aiming at improving its frequency selection policy, but they do not 831 enforce or grant any specific bandwidth for tasks. 832 833 If in doubt, say N. 834 835config UCLAMP_BUCKETS_COUNT 836 int "Number of supported utilization clamp buckets" 837 range 5 20 838 default 5 839 depends on UCLAMP_TASK 840 help 841 Defines the number of clamp buckets to use. The range of each bucket 842 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 843 number of clamp buckets the finer their granularity and the higher 844 the precision of clamping aggregation and tracking at run-time. 845 846 For example, with the minimum configuration value we will have 5 847 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 848 be refcounted in the [20..39]% bucket and will set the bucket clamp 849 effective value to 25%. 850 If a second 30% boosted task should be co-scheduled on the same CPU, 851 that task will be refcounted in the same bucket of the first task and 852 it will boost the bucket clamp effective value to 30%. 853 The clamp effective value of a bucket is reset to its nominal value 854 (20% in the example above) when there are no more tasks refcounted in 855 that bucket. 856 857 An additional boost/capping margin can be added to some tasks. In the 858 example above the 25% task will be boosted to 30% until it exits the 859 CPU. If that should be considered not acceptable on certain systems, 860 it's always possible to reduce the margin by increasing the number of 861 clamp buckets to trade off used memory for run-time tracking 862 precision. 863 864 If in doubt, use the default value. 865 866endmenu 867 868# 869# For architectures that want to enable the support for NUMA-affine scheduler 870# balancing logic: 871# 872config ARCH_SUPPORTS_NUMA_BALANCING 873 bool 874 875# 876# For architectures that prefer to flush all TLBs after a number of pages 877# are unmapped instead of sending one IPI per page to flush. The architecture 878# must provide guarantees on what happens if a clean TLB cache entry is 879# written after the unmap. Details are in mm/rmap.c near the check for 880# should_defer_flush. The architecture should also consider if the full flush 881# and the refill costs are offset by the savings of sending fewer IPIs. 882config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 883 bool 884 885config CC_HAS_INT128 886 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 887 888# 889# For architectures that know their GCC __int128 support is sound 890# 891config ARCH_SUPPORTS_INT128 892 bool 893 894# For architectures that (ab)use NUMA to represent different memory regions 895# all cpu-local but of different latencies, such as SuperH. 896# 897config ARCH_WANT_NUMA_VARIABLE_LOCALITY 898 bool 899 900config NUMA_BALANCING 901 bool "Memory placement aware NUMA scheduler" 902 depends on ARCH_SUPPORTS_NUMA_BALANCING 903 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 904 depends on SMP && NUMA && MIGRATION 905 help 906 This option adds support for automatic NUMA aware memory/task placement. 907 The mechanism is quite primitive and is based on migrating memory when 908 it has references to the node the task is running on. 909 910 This system will be inactive on UMA systems. 911 912config NUMA_BALANCING_DEFAULT_ENABLED 913 bool "Automatically enable NUMA aware memory/task placement" 914 default y 915 depends on NUMA_BALANCING 916 help 917 If set, automatic NUMA balancing will be enabled if running on a NUMA 918 machine. 919 920menuconfig CGROUPS 921 bool "Control Group support" 922 select KERNFS 923 help 924 This option adds support for grouping sets of processes together, for 925 use with process control subsystems such as Cpusets, CFS, memory 926 controls or device isolation. 927 See 928 - Documentation/scheduler/sched-design-CFS.rst (CFS) 929 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 930 and resource control) 931 932 Say N if unsure. 933 934if CGROUPS 935 936config PAGE_COUNTER 937 bool 938 939config MEMCG 940 bool "Memory controller" 941 select PAGE_COUNTER 942 select EVENTFD 943 help 944 Provides control over the memory footprint of tasks in a cgroup. 945 946config MEMCG_SWAP 947 bool 948 depends on MEMCG && SWAP 949 default y 950 951config MEMCG_KMEM 952 bool 953 depends on MEMCG && !SLOB 954 default y 955 956config BLK_CGROUP 957 bool "IO controller" 958 depends on BLOCK 959 default n 960 help 961 Generic block IO controller cgroup interface. This is the common 962 cgroup interface which should be used by various IO controlling 963 policies. 964 965 Currently, CFQ IO scheduler uses it to recognize task groups and 966 control disk bandwidth allocation (proportional time slice allocation) 967 to such task groups. It is also used by bio throttling logic in 968 block layer to implement upper limit in IO rates on a device. 969 970 This option only enables generic Block IO controller infrastructure. 971 One needs to also enable actual IO controlling logic/policy. For 972 enabling proportional weight division of disk bandwidth in CFQ, set 973 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 974 CONFIG_BLK_DEV_THROTTLING=y. 975 976 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 977 978config CGROUP_WRITEBACK 979 bool 980 depends on MEMCG && BLK_CGROUP 981 default y 982 983menuconfig CGROUP_SCHED 984 bool "CPU controller" 985 default n 986 help 987 This feature lets CPU scheduler recognize task groups and control CPU 988 bandwidth allocation to such task groups. It uses cgroups to group 989 tasks. 990 991if CGROUP_SCHED 992config FAIR_GROUP_SCHED 993 bool "Group scheduling for SCHED_OTHER" 994 depends on CGROUP_SCHED 995 default CGROUP_SCHED 996 997config CFS_BANDWIDTH 998 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 999 depends on FAIR_GROUP_SCHED 1000 default n 1001 help 1002 This option allows users to define CPU bandwidth rates (limits) for 1003 tasks running within the fair group scheduler. Groups with no limit 1004 set are considered to be unconstrained and will run with no 1005 restriction. 1006 See Documentation/scheduler/sched-bwc.rst for more information. 1007 1008config RT_GROUP_SCHED 1009 bool "Group scheduling for SCHED_RR/FIFO" 1010 depends on CGROUP_SCHED 1011 default n 1012 help 1013 This feature lets you explicitly allocate real CPU bandwidth 1014 to task groups. If enabled, it will also make it impossible to 1015 schedule realtime tasks for non-root users until you allocate 1016 realtime bandwidth for them. 1017 See Documentation/scheduler/sched-rt-group.rst for more information. 1018 1019endif #CGROUP_SCHED 1020 1021config UCLAMP_TASK_GROUP 1022 bool "Utilization clamping per group of tasks" 1023 depends on CGROUP_SCHED 1024 depends on UCLAMP_TASK 1025 default n 1026 help 1027 This feature enables the scheduler to track the clamped utilization 1028 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 1029 1030 When this option is enabled, the user can specify a min and max 1031 CPU bandwidth which is allowed for each single task in a group. 1032 The max bandwidth allows to clamp the maximum frequency a task 1033 can use, while the min bandwidth allows to define a minimum 1034 frequency a task will always use. 1035 1036 When task group based utilization clamping is enabled, an eventually 1037 specified task-specific clamp value is constrained by the cgroup 1038 specified clamp value. Both minimum and maximum task clamping cannot 1039 be bigger than the corresponding clamping defined at task group level. 1040 1041 If in doubt, say N. 1042 1043config CGROUP_PIDS 1044 bool "PIDs controller" 1045 help 1046 Provides enforcement of process number limits in the scope of a 1047 cgroup. Any attempt to fork more processes than is allowed in the 1048 cgroup will fail. PIDs are fundamentally a global resource because it 1049 is fairly trivial to reach PID exhaustion before you reach even a 1050 conservative kmemcg limit. As a result, it is possible to grind a 1051 system to halt without being limited by other cgroup policies. The 1052 PIDs controller is designed to stop this from happening. 1053 1054 It should be noted that organisational operations (such as attaching 1055 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 1056 since the PIDs limit only affects a process's ability to fork, not to 1057 attach to a cgroup. 1058 1059config CGROUP_RDMA 1060 bool "RDMA controller" 1061 help 1062 Provides enforcement of RDMA resources defined by IB stack. 1063 It is fairly easy for consumers to exhaust RDMA resources, which 1064 can result into resource unavailability to other consumers. 1065 RDMA controller is designed to stop this from happening. 1066 Attaching processes with active RDMA resources to the cgroup 1067 hierarchy is allowed even if can cross the hierarchy's limit. 1068 1069config CGROUP_FREEZER 1070 bool "Freezer controller" 1071 help 1072 Provides a way to freeze and unfreeze all tasks in a 1073 cgroup. 1074 1075 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1076 controller includes important in-kernel memory consumers per default. 1077 1078 If you're using cgroup2, say N. 1079 1080config CGROUP_HUGETLB 1081 bool "HugeTLB controller" 1082 depends on HUGETLB_PAGE 1083 select PAGE_COUNTER 1084 default n 1085 help 1086 Provides a cgroup controller for HugeTLB pages. 1087 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1088 The limit is enforced during page fault. Since HugeTLB doesn't 1089 support page reclaim, enforcing the limit at page fault time implies 1090 that, the application will get SIGBUS signal if it tries to access 1091 HugeTLB pages beyond its limit. This requires the application to know 1092 beforehand how much HugeTLB pages it would require for its use. The 1093 control group is tracked in the third page lru pointer. This means 1094 that we cannot use the controller with huge page less than 3 pages. 1095 1096config CPUSETS 1097 bool "Cpuset controller" 1098 depends on SMP 1099 help 1100 This option will let you create and manage CPUSETs which 1101 allow dynamically partitioning a system into sets of CPUs and 1102 Memory Nodes and assigning tasks to run only within those sets. 1103 This is primarily useful on large SMP or NUMA systems. 1104 1105 Say N if unsure. 1106 1107config PROC_PID_CPUSET 1108 bool "Include legacy /proc/<pid>/cpuset file" 1109 depends on CPUSETS 1110 default y 1111 1112config CGROUP_DEVICE 1113 bool "Device controller" 1114 help 1115 Provides a cgroup controller implementing whitelists for 1116 devices which a process in the cgroup can mknod or open. 1117 1118config CGROUP_CPUACCT 1119 bool "Simple CPU accounting controller" 1120 help 1121 Provides a simple controller for monitoring the 1122 total CPU consumed by the tasks in a cgroup. 1123 1124config CGROUP_PERF 1125 bool "Perf controller" 1126 depends on PERF_EVENTS 1127 help 1128 This option extends the perf per-cpu mode to restrict monitoring 1129 to threads which belong to the cgroup specified and run on the 1130 designated cpu. Or this can be used to have cgroup ID in samples 1131 so that it can monitor performance events among cgroups. 1132 1133 Say N if unsure. 1134 1135config CGROUP_BPF 1136 bool "Support for eBPF programs attached to cgroups" 1137 depends on BPF_SYSCALL 1138 select SOCK_CGROUP_DATA 1139 help 1140 Allow attaching eBPF programs to a cgroup using the bpf(2) 1141 syscall command BPF_PROG_ATTACH. 1142 1143 In which context these programs are accessed depends on the type 1144 of attachment. For instance, programs that are attached using 1145 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1146 inet sockets. 1147 1148config CGROUP_MISC 1149 bool "Misc resource controller" 1150 default n 1151 help 1152 Provides a controller for miscellaneous resources on a host. 1153 1154 Miscellaneous scalar resources are the resources on the host system 1155 which cannot be abstracted like the other cgroups. This controller 1156 tracks and limits the miscellaneous resources used by a process 1157 attached to a cgroup hierarchy. 1158 1159 For more information, please check misc cgroup section in 1160 /Documentation/admin-guide/cgroup-v2.rst. 1161 1162config CGROUP_DEBUG 1163 bool "Debug controller" 1164 default n 1165 depends on DEBUG_KERNEL 1166 help 1167 This option enables a simple controller that exports 1168 debugging information about the cgroups framework. This 1169 controller is for control cgroup debugging only. Its 1170 interfaces are not stable. 1171 1172 Say N. 1173 1174config SOCK_CGROUP_DATA 1175 bool 1176 default n 1177 1178endif # CGROUPS 1179 1180menuconfig NAMESPACES 1181 bool "Namespaces support" if EXPERT 1182 depends on MULTIUSER 1183 default !EXPERT 1184 help 1185 Provides the way to make tasks work with different objects using 1186 the same id. For example same IPC id may refer to different objects 1187 or same user id or pid may refer to different tasks when used in 1188 different namespaces. 1189 1190if NAMESPACES 1191 1192config UTS_NS 1193 bool "UTS namespace" 1194 default y 1195 help 1196 In this namespace tasks see different info provided with the 1197 uname() system call 1198 1199config TIME_NS 1200 bool "TIME namespace" 1201 depends on GENERIC_VDSO_TIME_NS 1202 default y 1203 help 1204 In this namespace boottime and monotonic clocks can be set. 1205 The time will keep going with the same pace. 1206 1207config IPC_NS 1208 bool "IPC namespace" 1209 depends on (SYSVIPC || POSIX_MQUEUE) 1210 default y 1211 help 1212 In this namespace tasks work with IPC ids which correspond to 1213 different IPC objects in different namespaces. 1214 1215config USER_NS 1216 bool "User namespace" 1217 default n 1218 help 1219 This allows containers, i.e. vservers, to use user namespaces 1220 to provide different user info for different servers. 1221 1222 When user namespaces are enabled in the kernel it is 1223 recommended that the MEMCG option also be enabled and that 1224 user-space use the memory control groups to limit the amount 1225 of memory a memory unprivileged users can use. 1226 1227 If unsure, say N. 1228 1229config PID_NS 1230 bool "PID Namespaces" 1231 default y 1232 help 1233 Support process id namespaces. This allows having multiple 1234 processes with the same pid as long as they are in different 1235 pid namespaces. This is a building block of containers. 1236 1237config NET_NS 1238 bool "Network namespace" 1239 depends on NET 1240 default y 1241 help 1242 Allow user space to create what appear to be multiple instances 1243 of the network stack. 1244 1245endif # NAMESPACES 1246 1247config CHECKPOINT_RESTORE 1248 bool "Checkpoint/restore support" 1249 select PROC_CHILDREN 1250 select KCMP 1251 default n 1252 help 1253 Enables additional kernel features in a sake of checkpoint/restore. 1254 In particular it adds auxiliary prctl codes to setup process text, 1255 data and heap segment sizes, and a few additional /proc filesystem 1256 entries. 1257 1258 If unsure, say N here. 1259 1260config SCHED_AUTOGROUP 1261 bool "Automatic process group scheduling" 1262 select CGROUPS 1263 select CGROUP_SCHED 1264 select FAIR_GROUP_SCHED 1265 help 1266 This option optimizes the scheduler for common desktop workloads by 1267 automatically creating and populating task groups. This separation 1268 of workloads isolates aggressive CPU burners (like build jobs) from 1269 desktop applications. Task group autogeneration is currently based 1270 upon task session. 1271 1272config SYSFS_DEPRECATED 1273 bool "Enable deprecated sysfs features to support old userspace tools" 1274 depends on SYSFS 1275 default n 1276 help 1277 This option adds code that switches the layout of the "block" class 1278 devices, to not show up in /sys/class/block/, but only in 1279 /sys/block/. 1280 1281 This switch is only active when the sysfs.deprecated=1 boot option is 1282 passed or the SYSFS_DEPRECATED_V2 option is set. 1283 1284 This option allows new kernels to run on old distributions and tools, 1285 which might get confused by /sys/class/block/. Since 2007/2008 all 1286 major distributions and tools handle this just fine. 1287 1288 Recent distributions and userspace tools after 2009/2010 depend on 1289 the existence of /sys/class/block/, and will not work with this 1290 option enabled. 1291 1292 Only if you are using a new kernel on an old distribution, you might 1293 need to say Y here. 1294 1295config SYSFS_DEPRECATED_V2 1296 bool "Enable deprecated sysfs features by default" 1297 default n 1298 depends on SYSFS 1299 depends on SYSFS_DEPRECATED 1300 help 1301 Enable deprecated sysfs by default. 1302 1303 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1304 option. 1305 1306 Only if you are using a new kernel on an old distribution, you might 1307 need to say Y here. Even then, odds are you would not need it 1308 enabled, you can always pass the boot option if absolutely necessary. 1309 1310config RELAY 1311 bool "Kernel->user space relay support (formerly relayfs)" 1312 select IRQ_WORK 1313 help 1314 This option enables support for relay interface support in 1315 certain file systems (such as debugfs). 1316 It is designed to provide an efficient mechanism for tools and 1317 facilities to relay large amounts of data from kernel space to 1318 user space. 1319 1320 If unsure, say N. 1321 1322config BLK_DEV_INITRD 1323 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1324 help 1325 The initial RAM filesystem is a ramfs which is loaded by the 1326 boot loader (loadlin or lilo) and that is mounted as root 1327 before the normal boot procedure. It is typically used to 1328 load modules needed to mount the "real" root file system, 1329 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1330 1331 If RAM disk support (BLK_DEV_RAM) is also included, this 1332 also enables initial RAM disk (initrd) support and adds 1333 15 Kbytes (more on some other architectures) to the kernel size. 1334 1335 If unsure say Y. 1336 1337if BLK_DEV_INITRD 1338 1339source "usr/Kconfig" 1340 1341endif 1342 1343config BOOT_CONFIG 1344 bool "Boot config support" 1345 select BLK_DEV_INITRD 1346 help 1347 Extra boot config allows system admin to pass a config file as 1348 complemental extension of kernel cmdline when booting. 1349 The boot config file must be attached at the end of initramfs 1350 with checksum, size and magic word. 1351 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1352 1353 If unsure, say Y. 1354 1355choice 1356 prompt "Compiler optimization level" 1357 default CC_OPTIMIZE_FOR_PERFORMANCE 1358 1359config CC_OPTIMIZE_FOR_PERFORMANCE 1360 bool "Optimize for performance (-O2)" 1361 help 1362 This is the default optimization level for the kernel, building 1363 with the "-O2" compiler flag for best performance and most 1364 helpful compile-time warnings. 1365 1366config CC_OPTIMIZE_FOR_PERFORMANCE_O3 1367 bool "Optimize more for performance (-O3)" 1368 depends on ARC 1369 help 1370 Choosing this option will pass "-O3" to your compiler to optimize 1371 the kernel yet more for performance. 1372 1373config CC_OPTIMIZE_FOR_SIZE 1374 bool "Optimize for size (-Os)" 1375 help 1376 Choosing this option will pass "-Os" to your compiler resulting 1377 in a smaller kernel. 1378 1379endchoice 1380 1381config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1382 bool 1383 help 1384 This requires that the arch annotates or otherwise protects 1385 its external entry points from being discarded. Linker scripts 1386 must also merge .text.*, .data.*, and .bss.* correctly into 1387 output sections. Care must be taken not to pull in unrelated 1388 sections (e.g., '.text.init'). Typically '.' in section names 1389 is used to distinguish them from label names / C identifiers. 1390 1391config LD_DEAD_CODE_DATA_ELIMINATION 1392 bool "Dead code and data elimination (EXPERIMENTAL)" 1393 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1394 depends on EXPERT 1395 depends on $(cc-option,-ffunction-sections -fdata-sections) 1396 depends on $(ld-option,--gc-sections) 1397 help 1398 Enable this if you want to do dead code and data elimination with 1399 the linker by compiling with -ffunction-sections -fdata-sections, 1400 and linking with --gc-sections. 1401 1402 This can reduce on disk and in-memory size of the kernel 1403 code and static data, particularly for small configs and 1404 on small systems. This has the possibility of introducing 1405 silently broken kernel if the required annotations are not 1406 present. This option is not well tested yet, so use at your 1407 own risk. 1408 1409config LD_ORPHAN_WARN 1410 def_bool y 1411 depends on ARCH_WANT_LD_ORPHAN_WARN 1412 depends on !LD_IS_LLD || LLD_VERSION >= 110000 1413 depends on $(ld-option,--orphan-handling=warn) 1414 1415config SYSCTL 1416 bool 1417 1418config HAVE_UID16 1419 bool 1420 1421config SYSCTL_EXCEPTION_TRACE 1422 bool 1423 help 1424 Enable support for /proc/sys/debug/exception-trace. 1425 1426config SYSCTL_ARCH_UNALIGN_NO_WARN 1427 bool 1428 help 1429 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1430 Allows arch to define/use @no_unaligned_warning to possibly warn 1431 about unaligned access emulation going on under the hood. 1432 1433config SYSCTL_ARCH_UNALIGN_ALLOW 1434 bool 1435 help 1436 Enable support for /proc/sys/kernel/unaligned-trap 1437 Allows arches to define/use @unaligned_enabled to runtime toggle 1438 the unaligned access emulation. 1439 see arch/parisc/kernel/unaligned.c for reference 1440 1441config HAVE_PCSPKR_PLATFORM 1442 bool 1443 1444# interpreter that classic socket filters depend on 1445config BPF 1446 bool 1447 1448menuconfig EXPERT 1449 bool "Configure standard kernel features (expert users)" 1450 # Unhide debug options, to make the on-by-default options visible 1451 select DEBUG_KERNEL 1452 help 1453 This option allows certain base kernel options and settings 1454 to be disabled or tweaked. This is for specialized 1455 environments which can tolerate a "non-standard" kernel. 1456 Only use this if you really know what you are doing. 1457 1458config UID16 1459 bool "Enable 16-bit UID system calls" if EXPERT 1460 depends on HAVE_UID16 && MULTIUSER 1461 default y 1462 help 1463 This enables the legacy 16-bit UID syscall wrappers. 1464 1465config MULTIUSER 1466 bool "Multiple users, groups and capabilities support" if EXPERT 1467 default y 1468 help 1469 This option enables support for non-root users, groups and 1470 capabilities. 1471 1472 If you say N here, all processes will run with UID 0, GID 0, and all 1473 possible capabilities. Saying N here also compiles out support for 1474 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1475 setgid, and capset. 1476 1477 If unsure, say Y here. 1478 1479config SGETMASK_SYSCALL 1480 bool "sgetmask/ssetmask syscalls support" if EXPERT 1481 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1482 help 1483 sys_sgetmask and sys_ssetmask are obsolete system calls 1484 no longer supported in libc but still enabled by default in some 1485 architectures. 1486 1487 If unsure, leave the default option here. 1488 1489config SYSFS_SYSCALL 1490 bool "Sysfs syscall support" if EXPERT 1491 default y 1492 help 1493 sys_sysfs is an obsolete system call no longer supported in libc. 1494 Note that disabling this option is more secure but might break 1495 compatibility with some systems. 1496 1497 If unsure say Y here. 1498 1499config FHANDLE 1500 bool "open by fhandle syscalls" if EXPERT 1501 select EXPORTFS 1502 default y 1503 help 1504 If you say Y here, a user level program will be able to map 1505 file names to handle and then later use the handle for 1506 different file system operations. This is useful in implementing 1507 userspace file servers, which now track files using handles instead 1508 of names. The handle would remain the same even if file names 1509 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1510 syscalls. 1511 1512config POSIX_TIMERS 1513 bool "Posix Clocks & timers" if EXPERT 1514 default y 1515 help 1516 This includes native support for POSIX timers to the kernel. 1517 Some embedded systems have no use for them and therefore they 1518 can be configured out to reduce the size of the kernel image. 1519 1520 When this option is disabled, the following syscalls won't be 1521 available: timer_create, timer_gettime: timer_getoverrun, 1522 timer_settime, timer_delete, clock_adjtime, getitimer, 1523 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1524 clock_getres and clock_nanosleep syscalls will be limited to 1525 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1526 1527 If unsure say y. 1528 1529config PRINTK 1530 default y 1531 bool "Enable support for printk" if EXPERT 1532 select IRQ_WORK 1533 help 1534 This option enables normal printk support. Removing it 1535 eliminates most of the message strings from the kernel image 1536 and makes the kernel more or less silent. As this makes it 1537 very difficult to diagnose system problems, saying N here is 1538 strongly discouraged. 1539 1540config BUG 1541 bool "BUG() support" if EXPERT 1542 default y 1543 help 1544 Disabling this option eliminates support for BUG and WARN, reducing 1545 the size of your kernel image and potentially quietly ignoring 1546 numerous fatal conditions. You should only consider disabling this 1547 option for embedded systems with no facilities for reporting errors. 1548 Just say Y. 1549 1550config ELF_CORE 1551 depends on COREDUMP 1552 default y 1553 bool "Enable ELF core dumps" if EXPERT 1554 help 1555 Enable support for generating core dumps. Disabling saves about 4k. 1556 1557 1558config PCSPKR_PLATFORM 1559 bool "Enable PC-Speaker support" if EXPERT 1560 depends on HAVE_PCSPKR_PLATFORM 1561 select I8253_LOCK 1562 default y 1563 help 1564 This option allows to disable the internal PC-Speaker 1565 support, saving some memory. 1566 1567config BASE_FULL 1568 default y 1569 bool "Enable full-sized data structures for core" if EXPERT 1570 help 1571 Disabling this option reduces the size of miscellaneous core 1572 kernel data structures. This saves memory on small machines, 1573 but may reduce performance. 1574 1575config FUTEX 1576 bool "Enable futex support" if EXPERT 1577 default y 1578 imply RT_MUTEXES 1579 help 1580 Disabling this option will cause the kernel to be built without 1581 support for "fast userspace mutexes". The resulting kernel may not 1582 run glibc-based applications correctly. 1583 1584config FUTEX_PI 1585 bool 1586 depends on FUTEX && RT_MUTEXES 1587 default y 1588 1589config HAVE_FUTEX_CMPXCHG 1590 bool 1591 depends on FUTEX 1592 help 1593 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1594 is implemented and always working. This removes a couple of runtime 1595 checks. 1596 1597config EPOLL 1598 bool "Enable eventpoll support" if EXPERT 1599 default y 1600 help 1601 Disabling this option will cause the kernel to be built without 1602 support for epoll family of system calls. 1603 1604config SIGNALFD 1605 bool "Enable signalfd() system call" if EXPERT 1606 default y 1607 help 1608 Enable the signalfd() system call that allows to receive signals 1609 on a file descriptor. 1610 1611 If unsure, say Y. 1612 1613config TIMERFD 1614 bool "Enable timerfd() system call" if EXPERT 1615 default y 1616 help 1617 Enable the timerfd() system call that allows to receive timer 1618 events on a file descriptor. 1619 1620 If unsure, say Y. 1621 1622config EVENTFD 1623 bool "Enable eventfd() system call" if EXPERT 1624 default y 1625 help 1626 Enable the eventfd() system call that allows to receive both 1627 kernel notification (ie. KAIO) or userspace notifications. 1628 1629 If unsure, say Y. 1630 1631config SHMEM 1632 bool "Use full shmem filesystem" if EXPERT 1633 default y 1634 depends on MMU 1635 help 1636 The shmem is an internal filesystem used to manage shared memory. 1637 It is backed by swap and manages resource limits. It is also exported 1638 to userspace as tmpfs if TMPFS is enabled. Disabling this 1639 option replaces shmem and tmpfs with the much simpler ramfs code, 1640 which may be appropriate on small systems without swap. 1641 1642config AIO 1643 bool "Enable AIO support" if EXPERT 1644 default y 1645 help 1646 This option enables POSIX asynchronous I/O which may by used 1647 by some high performance threaded applications. Disabling 1648 this option saves about 7k. 1649 1650config IO_URING 1651 bool "Enable IO uring support" if EXPERT 1652 select IO_WQ 1653 default y 1654 help 1655 This option enables support for the io_uring interface, enabling 1656 applications to submit and complete IO through submission and 1657 completion rings that are shared between the kernel and application. 1658 1659config ADVISE_SYSCALLS 1660 bool "Enable madvise/fadvise syscalls" if EXPERT 1661 default y 1662 help 1663 This option enables the madvise and fadvise syscalls, used by 1664 applications to advise the kernel about their future memory or file 1665 usage, improving performance. If building an embedded system where no 1666 applications use these syscalls, you can disable this option to save 1667 space. 1668 1669config HAVE_ARCH_USERFAULTFD_WP 1670 bool 1671 help 1672 Arch has userfaultfd write protection support 1673 1674config HAVE_ARCH_USERFAULTFD_MINOR 1675 bool 1676 help 1677 Arch has userfaultfd minor fault support 1678 1679config MEMBARRIER 1680 bool "Enable membarrier() system call" if EXPERT 1681 default y 1682 help 1683 Enable the membarrier() system call that allows issuing memory 1684 barriers across all running threads, which can be used to distribute 1685 the cost of user-space memory barriers asymmetrically by transforming 1686 pairs of memory barriers into pairs consisting of membarrier() and a 1687 compiler barrier. 1688 1689 If unsure, say Y. 1690 1691config KALLSYMS 1692 bool "Load all symbols for debugging/ksymoops" if EXPERT 1693 default y 1694 help 1695 Say Y here to let the kernel print out symbolic crash information and 1696 symbolic stack backtraces. This increases the size of the kernel 1697 somewhat, as all symbols have to be loaded into the kernel image. 1698 1699config KALLSYMS_ALL 1700 bool "Include all symbols in kallsyms" 1701 depends on DEBUG_KERNEL && KALLSYMS 1702 help 1703 Normally kallsyms only contains the symbols of functions for nicer 1704 OOPS messages and backtraces (i.e., symbols from the text and inittext 1705 sections). This is sufficient for most cases. And only in very rare 1706 cases (e.g., when a debugger is used) all symbols are required (e.g., 1707 names of variables from the data sections, etc). 1708 1709 This option makes sure that all symbols are loaded into the kernel 1710 image (i.e., symbols from all sections) in cost of increased kernel 1711 size (depending on the kernel configuration, it may be 300KiB or 1712 something like this). 1713 1714 Say N unless you really need all symbols. 1715 1716config KALLSYMS_ABSOLUTE_PERCPU 1717 bool 1718 depends on KALLSYMS 1719 default X86_64 && SMP 1720 1721config KALLSYMS_BASE_RELATIVE 1722 bool 1723 depends on KALLSYMS 1724 default !IA64 1725 help 1726 Instead of emitting them as absolute values in the native word size, 1727 emit the symbol references in the kallsyms table as 32-bit entries, 1728 each containing a relative value in the range [base, base + U32_MAX] 1729 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1730 an absolute value in the range [0, S32_MAX] or a relative value in the 1731 range [base, base + S32_MAX], where base is the lowest relative symbol 1732 address encountered in the image. 1733 1734 On 64-bit builds, this reduces the size of the address table by 50%, 1735 but more importantly, it results in entries whose values are build 1736 time constants, and no relocation pass is required at runtime to fix 1737 up the entries based on the runtime load address of the kernel. 1738 1739# end of the "standard kernel features (expert users)" menu 1740 1741# syscall, maps, verifier 1742 1743config USERFAULTFD 1744 bool "Enable userfaultfd() system call" 1745 depends on MMU 1746 help 1747 Enable the userfaultfd() system call that allows to intercept and 1748 handle page faults in userland. 1749 1750config ARCH_HAS_MEMBARRIER_CALLBACKS 1751 bool 1752 1753config ARCH_HAS_MEMBARRIER_SYNC_CORE 1754 bool 1755 1756config KCMP 1757 bool "Enable kcmp() system call" if EXPERT 1758 help 1759 Enable the kernel resource comparison system call. It provides 1760 user-space with the ability to compare two processes to see if they 1761 share a common resource, such as a file descriptor or even virtual 1762 memory space. 1763 1764 If unsure, say N. 1765 1766config RSEQ 1767 bool "Enable rseq() system call" if EXPERT 1768 default y 1769 depends on HAVE_RSEQ 1770 select MEMBARRIER 1771 help 1772 Enable the restartable sequences system call. It provides a 1773 user-space cache for the current CPU number value, which 1774 speeds up getting the current CPU number from user-space, 1775 as well as an ABI to speed up user-space operations on 1776 per-CPU data. 1777 1778 If unsure, say Y. 1779 1780config DEBUG_RSEQ 1781 default n 1782 bool "Enabled debugging of rseq() system call" if EXPERT 1783 depends on RSEQ && DEBUG_KERNEL 1784 help 1785 Enable extra debugging checks for the rseq system call. 1786 1787 If unsure, say N. 1788 1789config EMBEDDED 1790 bool "Embedded system" 1791 select EXPERT 1792 help 1793 This option should be enabled if compiling the kernel for 1794 an embedded system so certain expert options are available 1795 for configuration. 1796 1797config HAVE_PERF_EVENTS 1798 bool 1799 help 1800 See tools/perf/design.txt for details. 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 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1900 help 1901 The regular slab allocator that is established and known to work 1902 well in all environments. It organizes cache hot objects in 1903 per cpu and per node queues. 1904 1905config SLUB 1906 bool "SLUB (Unqueued Allocator)" 1907 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1908 help 1909 SLUB is a slab allocator that minimizes cache line usage 1910 instead of managing queues of cached objects (SLAB approach). 1911 Per cpu caching is realized using slabs of objects instead 1912 of queues of objects. SLUB can use memory efficiently 1913 and has enhanced diagnostics. SLUB is the default choice for 1914 a slab allocator. 1915 1916config SLOB 1917 depends on EXPERT 1918 bool "SLOB (Simple Allocator)" 1919 help 1920 SLOB replaces the stock allocator with a drastically simpler 1921 allocator. SLOB is generally more space efficient but 1922 does not perform as well on large systems. 1923 1924endchoice 1925 1926config SLAB_MERGE_DEFAULT 1927 bool "Allow slab caches to be merged" 1928 default y 1929 help 1930 For reduced kernel memory fragmentation, slab caches can be 1931 merged when they share the same size and other characteristics. 1932 This carries a risk of kernel heap overflows being able to 1933 overwrite objects from merged caches (and more easily control 1934 cache layout), which makes such heap attacks easier to exploit 1935 by attackers. By keeping caches unmerged, these kinds of exploits 1936 can usually only damage objects in the same cache. To disable 1937 merging at runtime, "slab_nomerge" can be passed on the kernel 1938 command line. 1939 1940config SLAB_FREELIST_RANDOM 1941 bool "Randomize slab freelist" 1942 depends on SLAB || SLUB 1943 help 1944 Randomizes the freelist order used on creating new pages. This 1945 security feature reduces the predictability of the kernel slab 1946 allocator against heap overflows. 1947 1948config SLAB_FREELIST_HARDENED 1949 bool "Harden slab freelist metadata" 1950 depends on SLAB || SLUB 1951 help 1952 Many kernel heap attacks try to target slab cache metadata and 1953 other infrastructure. This options makes minor performance 1954 sacrifices to harden the kernel slab allocator against common 1955 freelist exploit methods. Some slab implementations have more 1956 sanity-checking than others. This option is most effective with 1957 CONFIG_SLUB. 1958 1959config SHUFFLE_PAGE_ALLOCATOR 1960 bool "Page allocator randomization" 1961 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1962 help 1963 Randomization of the page allocator improves the average 1964 utilization of a direct-mapped memory-side-cache. See section 1965 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1966 6.2a specification for an example of how a platform advertises 1967 the presence of a memory-side-cache. There are also incidental 1968 security benefits as it reduces the predictability of page 1969 allocations to compliment SLAB_FREELIST_RANDOM, but the 1970 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1971 10th order of pages is selected based on cache utilization 1972 benefits on x86. 1973 1974 While the randomization improves cache utilization it may 1975 negatively impact workloads on platforms without a cache. For 1976 this reason, by default, the randomization is enabled only 1977 after runtime detection of a direct-mapped memory-side-cache. 1978 Otherwise, the randomization may be force enabled with the 1979 'page_alloc.shuffle' kernel command line parameter. 1980 1981 Say Y if unsure. 1982 1983config SLUB_CPU_PARTIAL 1984 default y 1985 depends on SLUB && SMP 1986 bool "SLUB per cpu partial cache" 1987 help 1988 Per cpu partial caches accelerate objects allocation and freeing 1989 that is local to a processor at the price of more indeterminism 1990 in the latency of the free. On overflow these caches will be cleared 1991 which requires the taking of locks that may cause latency spikes. 1992 Typically one would choose no for a realtime system. 1993 1994config MMAP_ALLOW_UNINITIALIZED 1995 bool "Allow mmapped anonymous memory to be uninitialized" 1996 depends on EXPERT && !MMU 1997 default n 1998 help 1999 Normally, and according to the Linux spec, anonymous memory obtained 2000 from mmap() has its contents cleared before it is passed to 2001 userspace. Enabling this config option allows you to request that 2002 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 2003 providing a huge performance boost. If this option is not enabled, 2004 then the flag will be ignored. 2005 2006 This is taken advantage of by uClibc's malloc(), and also by 2007 ELF-FDPIC binfmt's brk and stack allocator. 2008 2009 Because of the obvious security issues, this option should only be 2010 enabled on embedded devices where you control what is run in 2011 userspace. Since that isn't generally a problem on no-MMU systems, 2012 it is normally safe to say Y here. 2013 2014 See Documentation/admin-guide/mm/nommu-mmap.rst for more information. 2015 2016config SYSTEM_DATA_VERIFICATION 2017 def_bool n 2018 select SYSTEM_TRUSTED_KEYRING 2019 select KEYS 2020 select CRYPTO 2021 select CRYPTO_RSA 2022 select ASYMMETRIC_KEY_TYPE 2023 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 2024 select ASN1 2025 select OID_REGISTRY 2026 select X509_CERTIFICATE_PARSER 2027 select PKCS7_MESSAGE_PARSER 2028 help 2029 Provide PKCS#7 message verification using the contents of the system 2030 trusted keyring to provide public keys. This then can be used for 2031 module verification, kexec image verification and firmware blob 2032 verification. 2033 2034config PROFILING 2035 bool "Profiling support" 2036 help 2037 Say Y here to enable the extended profiling support mechanisms used 2038 by profilers. 2039 2040# 2041# Place an empty function call at each tracepoint site. Can be 2042# dynamically changed for a probe function. 2043# 2044config TRACEPOINTS 2045 bool 2046 2047endmenu # General setup 2048 2049source "arch/Kconfig" 2050 2051config RT_MUTEXES 2052 bool 2053 2054config BASE_SMALL 2055 int 2056 default 0 if BASE_FULL 2057 default 1 if !BASE_FULL 2058 2059config MODULE_SIG_FORMAT 2060 def_bool n 2061 select SYSTEM_DATA_VERIFICATION 2062 2063menuconfig MODULES 2064 bool "Enable loadable module support" 2065 modules 2066 help 2067 Kernel modules are small pieces of compiled code which can 2068 be inserted in the running kernel, rather than being 2069 permanently built into the kernel. You use the "modprobe" 2070 tool to add (and sometimes remove) them. If you say Y here, 2071 many parts of the kernel can be built as modules (by 2072 answering M instead of Y where indicated): this is most 2073 useful for infrequently used options which are not required 2074 for booting. For more information, see the man pages for 2075 modprobe, lsmod, modinfo, insmod and rmmod. 2076 2077 If you say Y here, you will need to run "make 2078 modules_install" to put the modules under /lib/modules/ 2079 where modprobe can find them (you may need to be root to do 2080 this). 2081 2082 If unsure, say Y. 2083 2084if MODULES 2085 2086config MODULE_FORCE_LOAD 2087 bool "Forced module loading" 2088 default n 2089 help 2090 Allow loading of modules without version information (ie. modprobe 2091 --force). Forced module loading sets the 'F' (forced) taint flag and 2092 is usually a really bad idea. 2093 2094config MODULE_UNLOAD 2095 bool "Module unloading" 2096 help 2097 Without this option you will not be able to unload any 2098 modules (note that some modules may not be unloadable 2099 anyway), which makes your kernel smaller, faster 2100 and simpler. If unsure, say Y. 2101 2102config MODULE_FORCE_UNLOAD 2103 bool "Forced module unloading" 2104 depends on MODULE_UNLOAD 2105 help 2106 This option allows you to force a module to unload, even if the 2107 kernel believes it is unsafe: the kernel will remove the module 2108 without waiting for anyone to stop using it (using the -f option to 2109 rmmod). This is mainly for kernel developers and desperate users. 2110 If unsure, say N. 2111 2112config MODVERSIONS 2113 bool "Module versioning support" 2114 help 2115 Usually, you have to use modules compiled with your kernel. 2116 Saying Y here makes it sometimes possible to use modules 2117 compiled for different kernels, by adding enough information 2118 to the modules to (hopefully) spot any changes which would 2119 make them incompatible with the kernel you are running. If 2120 unsure, say N. 2121 2122config ASM_MODVERSIONS 2123 bool 2124 default HAVE_ASM_MODVERSIONS && MODVERSIONS 2125 help 2126 This enables module versioning for exported symbols also from 2127 assembly. This can be enabled only when the target architecture 2128 supports it. 2129 2130config MODULE_REL_CRCS 2131 bool 2132 depends on MODVERSIONS 2133 2134config MODULE_SRCVERSION_ALL 2135 bool "Source checksum for all modules" 2136 help 2137 Modules which contain a MODULE_VERSION get an extra "srcversion" 2138 field inserted into their modinfo section, which contains a 2139 sum of the source files which made it. This helps maintainers 2140 see exactly which source was used to build a module (since 2141 others sometimes change the module source without updating 2142 the version). With this option, such a "srcversion" field 2143 will be created for all modules. If unsure, say N. 2144 2145config MODULE_SIG 2146 bool "Module signature verification" 2147 select MODULE_SIG_FORMAT 2148 help 2149 Check modules for valid signatures upon load: the signature 2150 is simply appended to the module. For more information see 2151 <file:Documentation/admin-guide/module-signing.rst>. 2152 2153 Note that this option adds the OpenSSL development packages as a 2154 kernel build dependency so that the signing tool can use its crypto 2155 library. 2156 2157 You should enable this option if you wish to use either 2158 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via 2159 another LSM - otherwise unsigned modules will be loadable regardless 2160 of the lockdown policy. 2161 2162 !!!WARNING!!! If you enable this option, you MUST make sure that the 2163 module DOES NOT get stripped after being signed. This includes the 2164 debuginfo strip done by some packagers (such as rpmbuild) and 2165 inclusion into an initramfs that wants the module size reduced. 2166 2167config MODULE_SIG_FORCE 2168 bool "Require modules to be validly signed" 2169 depends on MODULE_SIG 2170 help 2171 Reject unsigned modules or signed modules for which we don't have a 2172 key. Without this, such modules will simply taint the kernel. 2173 2174config MODULE_SIG_ALL 2175 bool "Automatically sign all modules" 2176 default y 2177 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 2178 help 2179 Sign all modules during make modules_install. Without this option, 2180 modules must be signed manually, using the scripts/sign-file tool. 2181 2182comment "Do not forget to sign required modules with scripts/sign-file" 2183 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2184 2185choice 2186 prompt "Which hash algorithm should modules be signed with?" 2187 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 2188 help 2189 This determines which sort of hashing algorithm will be used during 2190 signature generation. This algorithm _must_ be built into the kernel 2191 directly so that signature verification can take place. It is not 2192 possible to load a signed module containing the algorithm to check 2193 the signature on that module. 2194 2195config MODULE_SIG_SHA1 2196 bool "Sign modules with SHA-1" 2197 select CRYPTO_SHA1 2198 2199config MODULE_SIG_SHA224 2200 bool "Sign modules with SHA-224" 2201 select CRYPTO_SHA256 2202 2203config MODULE_SIG_SHA256 2204 bool "Sign modules with SHA-256" 2205 select CRYPTO_SHA256 2206 2207config MODULE_SIG_SHA384 2208 bool "Sign modules with SHA-384" 2209 select CRYPTO_SHA512 2210 2211config MODULE_SIG_SHA512 2212 bool "Sign modules with SHA-512" 2213 select CRYPTO_SHA512 2214 2215endchoice 2216 2217config MODULE_SIG_HASH 2218 string 2219 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 2220 default "sha1" if MODULE_SIG_SHA1 2221 default "sha224" if MODULE_SIG_SHA224 2222 default "sha256" if MODULE_SIG_SHA256 2223 default "sha384" if MODULE_SIG_SHA384 2224 default "sha512" if MODULE_SIG_SHA512 2225 2226choice 2227 prompt "Module compression mode" 2228 help 2229 This option allows you to choose the algorithm which will be used to 2230 compress modules when 'make modules_install' is run. (or, you can 2231 choose to not compress modules at all.) 2232 2233 External modules will also be compressed in the same way during the 2234 installation. 2235 2236 For modules inside an initrd or initramfs, it's more efficient to 2237 compress the whole initrd or initramfs instead. 2238 2239 This is fully compatible with signed modules. 2240 2241 Please note that the tool used to load modules needs to support the 2242 corresponding algorithm. module-init-tools MAY support gzip, and kmod 2243 MAY support gzip, xz and zstd. 2244 2245 Your build system needs to provide the appropriate compression tool 2246 to compress the modules. 2247 2248 If in doubt, select 'None'. 2249 2250config MODULE_COMPRESS_NONE 2251 bool "None" 2252 help 2253 Do not compress modules. The installed modules are suffixed 2254 with .ko. 2255 2256config MODULE_COMPRESS_GZIP 2257 bool "GZIP" 2258 help 2259 Compress modules with GZIP. The installed modules are suffixed 2260 with .ko.gz. 2261 2262config MODULE_COMPRESS_XZ 2263 bool "XZ" 2264 help 2265 Compress modules with XZ. The installed modules are suffixed 2266 with .ko.xz. 2267 2268config MODULE_COMPRESS_ZSTD 2269 bool "ZSTD" 2270 help 2271 Compress modules with ZSTD. The installed modules are suffixed 2272 with .ko.zst. 2273 2274endchoice 2275 2276config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS 2277 bool "Allow loading of modules with missing namespace imports" 2278 help 2279 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in 2280 a namespace. A module that makes use of a symbol exported with such a 2281 namespace is required to import the namespace via MODULE_IMPORT_NS(). 2282 There is no technical reason to enforce correct namespace imports, 2283 but it creates consistency between symbols defining namespaces and 2284 users importing namespaces they make use of. This option relaxes this 2285 requirement and lifts the enforcement when loading a module. 2286 2287 If unsure, say N. 2288 2289config MODPROBE_PATH 2290 string "Path to modprobe binary" 2291 default "/sbin/modprobe" 2292 help 2293 When kernel code requests a module, it does so by calling 2294 the "modprobe" userspace utility. This option allows you to 2295 set the path where that binary is found. This can be changed 2296 at runtime via the sysctl file 2297 /proc/sys/kernel/modprobe. Setting this to the empty string 2298 removes the kernel's ability to request modules (but 2299 userspace can still load modules explicitly). 2300 2301config TRIM_UNUSED_KSYMS 2302 bool "Trim unused exported kernel symbols" if EXPERT 2303 depends on !COMPILE_TEST 2304 help 2305 The kernel and some modules make many symbols available for 2306 other modules to use via EXPORT_SYMBOL() and variants. Depending 2307 on the set of modules being selected in your kernel configuration, 2308 many of those exported symbols might never be used. 2309 2310 This option allows for unused exported symbols to be dropped from 2311 the build. In turn, this provides the compiler more opportunities 2312 (especially when using LTO) for optimizing the code and reducing 2313 binary size. This might have some security advantages as well. 2314 2315 If unsure, or if you need to build out-of-tree modules, say N. 2316 2317config UNUSED_KSYMS_WHITELIST 2318 string "Whitelist of symbols to keep in ksymtab" 2319 depends on TRIM_UNUSED_KSYMS 2320 help 2321 By default, all unused exported symbols will be un-exported from the 2322 build when TRIM_UNUSED_KSYMS is selected. 2323 2324 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept 2325 exported at all times, even in absence of in-tree users. The value to 2326 set here is the path to a text file containing the list of symbols, 2327 one per line. The path can be absolute, or relative to the kernel 2328 source tree. 2329 2330endif # MODULES 2331 2332config MODULES_TREE_LOOKUP 2333 def_bool y 2334 depends on PERF_EVENTS || TRACING || CFI_CLANG 2335 2336config INIT_ALL_POSSIBLE 2337 bool 2338 help 2339 Back when each arch used to define their own cpu_online_mask and 2340 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2341 with all 1s, and others with all 0s. When they were centralised, 2342 it was better to provide this option than to break all the archs 2343 and have several arch maintainers pursuing me down dark alleys. 2344 2345source "block/Kconfig" 2346 2347config PREEMPT_NOTIFIERS 2348 bool 2349 2350config PADATA 2351 depends on SMP 2352 bool 2353 2354config ASN1 2355 tristate 2356 help 2357 Build a simple ASN.1 grammar compiler that produces a bytecode output 2358 that can be interpreted by the ASN.1 stream decoder and used to 2359 inform it as to what tags are to be expected in a stream and what 2360 functions to call on what tags. 2361 2362source "kernel/Kconfig.locks" 2363 2364config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 2365 bool 2366 2367config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2368 bool 2369 2370# It may be useful for an architecture to override the definitions of the 2371# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2372# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2373# different calling convention for syscalls. They can also override the 2374# macros for not-implemented syscalls in kernel/sys_ni.c and 2375# kernel/time/posix-stubs.c. All these overrides need to be available in 2376# <asm/syscall_wrapper.h>. 2377config ARCH_HAS_SYSCALL_WRAPPER 2378 def_bool n 2379