1# SPDX-License-Identifier: GPL-2.0-only 2config DEFCONFIG_LIST 3 string 4 depends on !UML 5 option defconfig_list 6 default "/lib/modules/$(shell,uname -r)/.config" 7 default "/etc/kernel-config" 8 default "/boot/config-$(shell,uname -r)" 9 default "arch/$(SRCARCH)/configs/$(KBUILD_DEFCONFIG)" 10 11config CC_VERSION_TEXT 12 string 13 default "$(CC_VERSION_TEXT)" 14 help 15 This is used in unclear ways: 16 17 - Re-run Kconfig when the compiler is updated 18 The 'default' property references the environment variable, 19 CC_VERSION_TEXT so it is recorded in include/config/auto.conf.cmd. 20 When the compiler is updated, Kconfig will be invoked. 21 22 - Ensure full rebuild when the compier is updated 23 include/linux/kconfig.h contains this option in the comment line so 24 fixdep adds include/config/cc/version/text.h into the auto-generated 25 dependency. When the compiler is updated, syncconfig will touch it 26 and then every file will be rebuilt. 27 28config CC_IS_GCC 29 def_bool $(success,echo "$(CC_VERSION_TEXT)" | grep -q gcc) 30 31config GCC_VERSION 32 int 33 default $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) if CC_IS_GCC 34 default 0 35 36config LD_VERSION 37 int 38 default $(shell,$(LD) --version | $(srctree)/scripts/ld-version.sh) 39 40config CC_IS_CLANG 41 def_bool $(success,echo "$(CC_VERSION_TEXT)" | grep -q clang) 42 43config LD_IS_LLD 44 def_bool $(success,$(LD) -v | head -n 1 | grep -q LLD) 45 46config CLANG_VERSION 47 int 48 default $(shell,$(srctree)/scripts/clang-version.sh $(CC)) 49 50config LLD_VERSION 51 int 52 default $(shell,$(srctree)/scripts/lld-version.sh $(LD)) 53 54config CC_CAN_LINK 55 bool 56 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag)) if 64BIT 57 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag)) 58 59config CC_CAN_LINK_STATIC 60 bool 61 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag) -static) if 64BIT 62 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag) -static) 63 64config CC_HAS_ASM_GOTO 65 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) 66 67config CC_HAS_ASM_GOTO_OUTPUT 68 depends on CC_HAS_ASM_GOTO 69 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) 70 71config TOOLS_SUPPORT_RELR 72 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 73 74config CC_HAS_ASM_INLINE 75 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 76 77config CONSTRUCTORS 78 bool 79 80config IRQ_WORK 81 bool 82 83config BUILDTIME_TABLE_SORT 84 bool 85 86config THREAD_INFO_IN_TASK 87 bool 88 help 89 Select this to move thread_info off the stack into task_struct. To 90 make this work, an arch will need to remove all thread_info fields 91 except flags and fix any runtime bugs. 92 93 One subtle change that will be needed is to use try_get_task_stack() 94 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 95 96menu "General setup" 97 98config BROKEN 99 bool 100 101config BROKEN_ON_SMP 102 bool 103 depends on BROKEN || !SMP 104 default y 105 106config INIT_ENV_ARG_LIMIT 107 int 108 default 32 if !UML 109 default 128 if UML 110 help 111 Maximum of each of the number of arguments and environment 112 variables passed to init from the kernel command line. 113 114config COMPILE_TEST 115 bool "Compile also drivers which will not load" 116 depends on !UML && !S390 117 default n 118 help 119 Some drivers can be compiled on a different platform than they are 120 intended to be run on. Despite they cannot be loaded there (or even 121 when they load they cannot be used due to missing HW support), 122 developers still, opposing to distributors, might want to build such 123 drivers to compile-test them. 124 125 If you are a developer and want to build everything available, say Y 126 here. If you are a user/distributor, say N here to exclude useless 127 drivers to be distributed. 128 129config UAPI_HEADER_TEST 130 bool "Compile test UAPI headers" 131 depends on HEADERS_INSTALL && CC_CAN_LINK 132 help 133 Compile test headers exported to user-space to ensure they are 134 self-contained, i.e. compilable as standalone units. 135 136 If you are a developer or tester and want to ensure the exported 137 headers are self-contained, say Y here. Otherwise, choose N. 138 139config LOCALVERSION 140 string "Local version - append to kernel release" 141 help 142 Append an extra string to the end of your kernel version. 143 This will show up when you type uname, for example. 144 The string you set here will be appended after the contents of 145 any files with a filename matching localversion* in your 146 object and source tree, in that order. Your total string can 147 be a maximum of 64 characters. 148 149config LOCALVERSION_AUTO 150 bool "Automatically append version information to the version string" 151 default y 152 depends on !COMPILE_TEST 153 help 154 This will try to automatically determine if the current tree is a 155 release tree by looking for git tags that belong to the current 156 top of tree revision. 157 158 A string of the format -gxxxxxxxx will be added to the localversion 159 if a git-based tree is found. The string generated by this will be 160 appended after any matching localversion* files, and after the value 161 set in CONFIG_LOCALVERSION. 162 163 (The actual string used here is the first eight characters produced 164 by running the command: 165 166 $ git rev-parse --verify HEAD 167 168 which is done within the script "scripts/setlocalversion".) 169 170config BUILD_SALT 171 string "Build ID Salt" 172 default "" 173 help 174 The build ID is used to link binaries and their debug info. Setting 175 this option will use the value in the calculation of the build id. 176 This is mostly useful for distributions which want to ensure the 177 build is unique between builds. It's safe to leave the default. 178 179config HAVE_KERNEL_GZIP 180 bool 181 182config HAVE_KERNEL_BZIP2 183 bool 184 185config HAVE_KERNEL_LZMA 186 bool 187 188config HAVE_KERNEL_XZ 189 bool 190 191config HAVE_KERNEL_LZO 192 bool 193 194config HAVE_KERNEL_LZ4 195 bool 196 197config HAVE_KERNEL_ZSTD 198 bool 199 200config HAVE_KERNEL_UNCOMPRESSED 201 bool 202 203choice 204 prompt "Kernel compression mode" 205 default KERNEL_GZIP 206 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 207 help 208 The linux kernel is a kind of self-extracting executable. 209 Several compression algorithms are available, which differ 210 in efficiency, compression and decompression speed. 211 Compression speed is only relevant when building a kernel. 212 Decompression speed is relevant at each boot. 213 214 If you have any problems with bzip2 or lzma compressed 215 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 216 version of this functionality (bzip2 only), for 2.4, was 217 supplied by Christian Ludwig) 218 219 High compression options are mostly useful for users, who 220 are low on disk space (embedded systems), but for whom ram 221 size matters less. 222 223 If in doubt, select 'gzip' 224 225config KERNEL_GZIP 226 bool "Gzip" 227 depends on HAVE_KERNEL_GZIP 228 help 229 The old and tried gzip compression. It provides a good balance 230 between compression ratio and decompression speed. 231 232config KERNEL_BZIP2 233 bool "Bzip2" 234 depends on HAVE_KERNEL_BZIP2 235 help 236 Its compression ratio and speed is intermediate. 237 Decompression speed is slowest among the choices. The kernel 238 size is about 10% smaller with bzip2, in comparison to gzip. 239 Bzip2 uses a large amount of memory. For modern kernels you 240 will need at least 8MB RAM or more for booting. 241 242config KERNEL_LZMA 243 bool "LZMA" 244 depends on HAVE_KERNEL_LZMA 245 help 246 This compression algorithm's ratio is best. Decompression speed 247 is between gzip and bzip2. Compression is slowest. 248 The kernel size is about 33% smaller with LZMA in comparison to gzip. 249 250config KERNEL_XZ 251 bool "XZ" 252 depends on HAVE_KERNEL_XZ 253 help 254 XZ uses the LZMA2 algorithm and instruction set specific 255 BCJ filters which can improve compression ratio of executable 256 code. The size of the kernel is about 30% smaller with XZ in 257 comparison to gzip. On architectures for which there is a BCJ 258 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 259 will create a few percent smaller kernel than plain LZMA. 260 261 The speed is about the same as with LZMA: The decompression 262 speed of XZ is better than that of bzip2 but worse than gzip 263 and LZO. Compression is slow. 264 265config KERNEL_LZO 266 bool "LZO" 267 depends on HAVE_KERNEL_LZO 268 help 269 Its compression ratio is the poorest among the choices. The kernel 270 size is about 10% bigger than gzip; however its speed 271 (both compression and decompression) is the fastest. 272 273config KERNEL_LZ4 274 bool "LZ4" 275 depends on HAVE_KERNEL_LZ4 276 help 277 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 278 A preliminary version of LZ4 de/compression tool is available at 279 <https://code.google.com/p/lz4/>. 280 281 Its compression ratio is worse than LZO. The size of the kernel 282 is about 8% bigger than LZO. But the decompression speed is 283 faster than LZO. 284 285config KERNEL_ZSTD 286 bool "ZSTD" 287 depends on HAVE_KERNEL_ZSTD 288 help 289 ZSTD is a compression algorithm targeting intermediate compression 290 with fast decompression speed. It will compress better than GZIP and 291 decompress around the same speed as LZO, but slower than LZ4. You 292 will need at least 192 KB RAM or more for booting. The zstd command 293 line tool is required for compression. 294 295config KERNEL_UNCOMPRESSED 296 bool "None" 297 depends on HAVE_KERNEL_UNCOMPRESSED 298 help 299 Produce uncompressed kernel image. This option is usually not what 300 you want. It is useful for debugging the kernel in slow simulation 301 environments, where decompressing and moving the kernel is awfully 302 slow. This option allows early boot code to skip the decompressor 303 and jump right at uncompressed kernel image. 304 305endchoice 306 307config DEFAULT_INIT 308 string "Default init path" 309 default "" 310 help 311 This option determines the default init for the system if no init= 312 option is passed on the kernel command line. If the requested path is 313 not present, we will still then move on to attempting further 314 locations (e.g. /sbin/init, etc). If this is empty, we will just use 315 the fallback list when init= is not passed. 316 317config DEFAULT_HOSTNAME 318 string "Default hostname" 319 default "(none)" 320 help 321 This option determines the default system hostname before userspace 322 calls sethostname(2). The kernel traditionally uses "(none)" here, 323 but you may wish to use a different default here to make a minimal 324 system more usable with less configuration. 325 326# 327# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can 328# add proper SWAP support to them, in which case this can be remove. 329# 330config ARCH_NO_SWAP 331 bool 332 333config SWAP 334 bool "Support for paging of anonymous memory (swap)" 335 depends on MMU && BLOCK && !ARCH_NO_SWAP 336 default y 337 help 338 This option allows you to choose whether you want to have support 339 for so called swap devices or swap files in your kernel that are 340 used to provide more virtual memory than the actual RAM present 341 in your computer. If unsure say Y. 342 343config SYSVIPC 344 bool "System V IPC" 345 help 346 Inter Process Communication is a suite of library functions and 347 system calls which let processes (running programs) synchronize and 348 exchange information. It is generally considered to be a good thing, 349 and some programs won't run unless you say Y here. In particular, if 350 you want to run the DOS emulator dosemu under Linux (read the 351 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 352 you'll need to say Y here. 353 354 You can find documentation about IPC with "info ipc" and also in 355 section 6.4 of the Linux Programmer's Guide, available from 356 <http://www.tldp.org/guides.html>. 357 358config SYSVIPC_SYSCTL 359 bool 360 depends on SYSVIPC 361 depends on SYSCTL 362 default y 363 364config POSIX_MQUEUE 365 bool "POSIX Message Queues" 366 depends on NET 367 help 368 POSIX variant of message queues is a part of IPC. In POSIX message 369 queues every message has a priority which decides about succession 370 of receiving it by a process. If you want to compile and run 371 programs written e.g. for Solaris with use of its POSIX message 372 queues (functions mq_*) say Y here. 373 374 POSIX message queues are visible as a filesystem called 'mqueue' 375 and can be mounted somewhere if you want to do filesystem 376 operations on message queues. 377 378 If unsure, say Y. 379 380config POSIX_MQUEUE_SYSCTL 381 bool 382 depends on POSIX_MQUEUE 383 depends on SYSCTL 384 default y 385 386config WATCH_QUEUE 387 bool "General notification queue" 388 default n 389 help 390 391 This is a general notification queue for the kernel to pass events to 392 userspace by splicing them into pipes. It can be used in conjunction 393 with watches for key/keyring change notifications and device 394 notifications. 395 396 See Documentation/watch_queue.rst 397 398config CROSS_MEMORY_ATTACH 399 bool "Enable process_vm_readv/writev syscalls" 400 depends on MMU 401 default y 402 help 403 Enabling this option adds the system calls process_vm_readv and 404 process_vm_writev which allow a process with the correct privileges 405 to directly read from or write to another process' address space. 406 See the man page for more details. 407 408config USELIB 409 bool "uselib syscall" 410 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION 411 help 412 This option enables the uselib syscall, a system call used in the 413 dynamic linker from libc5 and earlier. glibc does not use this 414 system call. If you intend to run programs built on libc5 or 415 earlier, you may need to enable this syscall. Current systems 416 running glibc can safely disable this. 417 418config AUDIT 419 bool "Auditing support" 420 depends on NET 421 help 422 Enable auditing infrastructure that can be used with another 423 kernel subsystem, such as SELinux (which requires this for 424 logging of avc messages output). System call auditing is included 425 on architectures which support it. 426 427config HAVE_ARCH_AUDITSYSCALL 428 bool 429 430config AUDITSYSCALL 431 def_bool y 432 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 433 select FSNOTIFY 434 435source "kernel/irq/Kconfig" 436source "kernel/time/Kconfig" 437source "kernel/Kconfig.preempt" 438 439menu "CPU/Task time and stats accounting" 440 441config VIRT_CPU_ACCOUNTING 442 bool 443 444choice 445 prompt "Cputime accounting" 446 default TICK_CPU_ACCOUNTING if !PPC64 447 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 448 449# Kind of a stub config for the pure tick based cputime accounting 450config TICK_CPU_ACCOUNTING 451 bool "Simple tick based cputime accounting" 452 depends on !S390 && !NO_HZ_FULL 453 help 454 This is the basic tick based cputime accounting that maintains 455 statistics about user, system and idle time spent on per jiffies 456 granularity. 457 458 If unsure, say Y. 459 460config VIRT_CPU_ACCOUNTING_NATIVE 461 bool "Deterministic task and CPU time accounting" 462 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 463 select VIRT_CPU_ACCOUNTING 464 help 465 Select this option to enable more accurate task and CPU time 466 accounting. This is done by reading a CPU counter on each 467 kernel entry and exit and on transitions within the kernel 468 between system, softirq and hardirq state, so there is a 469 small performance impact. In the case of s390 or IBM POWER > 5, 470 this also enables accounting of stolen time on logically-partitioned 471 systems. 472 473config VIRT_CPU_ACCOUNTING_GEN 474 bool "Full dynticks CPU time accounting" 475 depends on HAVE_CONTEXT_TRACKING 476 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 477 depends on GENERIC_CLOCKEVENTS 478 select VIRT_CPU_ACCOUNTING 479 select CONTEXT_TRACKING 480 help 481 Select this option to enable task and CPU time accounting on full 482 dynticks systems. This accounting is implemented by watching every 483 kernel-user boundaries using the context tracking subsystem. 484 The accounting is thus performed at the expense of some significant 485 overhead. 486 487 For now this is only useful if you are working on the full 488 dynticks subsystem development. 489 490 If unsure, say N. 491 492endchoice 493 494config IRQ_TIME_ACCOUNTING 495 bool "Fine granularity task level IRQ time accounting" 496 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 497 help 498 Select this option to enable fine granularity task irq time 499 accounting. This is done by reading a timestamp on each 500 transitions between softirq and hardirq state, so there can be a 501 small performance impact. 502 503 If in doubt, say N here. 504 505config HAVE_SCHED_AVG_IRQ 506 def_bool y 507 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 508 depends on SMP 509 510config SCHED_THERMAL_PRESSURE 511 bool 512 default y if ARM && ARM_CPU_TOPOLOGY 513 default y if ARM64 514 depends on SMP 515 depends on CPU_FREQ_THERMAL 516 help 517 Select this option to enable thermal pressure accounting in the 518 scheduler. Thermal pressure is the value conveyed to the scheduler 519 that reflects the reduction in CPU compute capacity resulted from 520 thermal throttling. Thermal throttling occurs when the performance of 521 a CPU is capped due to high operating temperatures. 522 523 If selected, the scheduler will be able to balance tasks accordingly, 524 i.e. put less load on throttled CPUs than on non/less throttled ones. 525 526 This requires the architecture to implement 527 arch_set_thermal_pressure() and arch_get_thermal_pressure(). 528 529config BSD_PROCESS_ACCT 530 bool "BSD Process Accounting" 531 depends on MULTIUSER 532 help 533 If you say Y here, a user level program will be able to instruct the 534 kernel (via a special system call) to write process accounting 535 information to a file: whenever a process exits, information about 536 that process will be appended to the file by the kernel. The 537 information includes things such as creation time, owning user, 538 command name, memory usage, controlling terminal etc. (the complete 539 list is in the struct acct in <file:include/linux/acct.h>). It is 540 up to the user level program to do useful things with this 541 information. This is generally a good idea, so say Y. 542 543config BSD_PROCESS_ACCT_V3 544 bool "BSD Process Accounting version 3 file format" 545 depends on BSD_PROCESS_ACCT 546 default n 547 help 548 If you say Y here, the process accounting information is written 549 in a new file format that also logs the process IDs of each 550 process and its parent. Note that this file format is incompatible 551 with previous v0/v1/v2 file formats, so you will need updated tools 552 for processing it. A preliminary version of these tools is available 553 at <http://www.gnu.org/software/acct/>. 554 555config TASKSTATS 556 bool "Export task/process statistics through netlink" 557 depends on NET 558 depends on MULTIUSER 559 default n 560 help 561 Export selected statistics for tasks/processes through the 562 generic netlink interface. Unlike BSD process accounting, the 563 statistics are available during the lifetime of tasks/processes as 564 responses to commands. Like BSD accounting, they are sent to user 565 space on task exit. 566 567 Say N if unsure. 568 569config TASK_DELAY_ACCT 570 bool "Enable per-task delay accounting" 571 depends on TASKSTATS 572 select SCHED_INFO 573 help 574 Collect information on time spent by a task waiting for system 575 resources like cpu, synchronous block I/O completion and swapping 576 in pages. Such statistics can help in setting a task's priorities 577 relative to other tasks for cpu, io, rss limits etc. 578 579 Say N if unsure. 580 581config TASK_XACCT 582 bool "Enable extended accounting over taskstats" 583 depends on TASKSTATS 584 help 585 Collect extended task accounting data and send the data 586 to userland for processing over the taskstats interface. 587 588 Say N if unsure. 589 590config TASK_IO_ACCOUNTING 591 bool "Enable per-task storage I/O accounting" 592 depends on TASK_XACCT 593 help 594 Collect information on the number of bytes of storage I/O which this 595 task has caused. 596 597 Say N if unsure. 598 599config PSI 600 bool "Pressure stall information tracking" 601 help 602 Collect metrics that indicate how overcommitted the CPU, memory, 603 and IO capacity are in the system. 604 605 If you say Y here, the kernel will create /proc/pressure/ with the 606 pressure statistics files cpu, memory, and io. These will indicate 607 the share of walltime in which some or all tasks in the system are 608 delayed due to contention of the respective resource. 609 610 In kernels with cgroup support, cgroups (cgroup2 only) will 611 have cpu.pressure, memory.pressure, and io.pressure files, 612 which aggregate pressure stalls for the grouped tasks only. 613 614 For more details see Documentation/accounting/psi.rst. 615 616 Say N if unsure. 617 618config PSI_DEFAULT_DISABLED 619 bool "Require boot parameter to enable pressure stall information tracking" 620 default n 621 depends on PSI 622 help 623 If set, pressure stall information tracking will be disabled 624 per default but can be enabled through passing psi=1 on the 625 kernel commandline during boot. 626 627 This feature adds some code to the task wakeup and sleep 628 paths of the scheduler. The overhead is too low to affect 629 common scheduling-intense workloads in practice (such as 630 webservers, memcache), but it does show up in artificial 631 scheduler stress tests, such as hackbench. 632 633 If you are paranoid and not sure what the kernel will be 634 used for, say Y. 635 636 Say N if unsure. 637 638endmenu # "CPU/Task time and stats accounting" 639 640config CPU_ISOLATION 641 bool "CPU isolation" 642 depends on SMP || COMPILE_TEST 643 default y 644 help 645 Make sure that CPUs running critical tasks are not disturbed by 646 any source of "noise" such as unbound workqueues, timers, kthreads... 647 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 648 the "isolcpus=" boot parameter. 649 650 Say Y if unsure. 651 652source "kernel/rcu/Kconfig" 653 654config BUILD_BIN2C 655 bool 656 default n 657 658config IKCONFIG 659 tristate "Kernel .config support" 660 help 661 This option enables the complete Linux kernel ".config" file 662 contents to be saved in the kernel. It provides documentation 663 of which kernel options are used in a running kernel or in an 664 on-disk kernel. This information can be extracted from the kernel 665 image file with the script scripts/extract-ikconfig and used as 666 input to rebuild the current kernel or to build another kernel. 667 It can also be extracted from a running kernel by reading 668 /proc/config.gz if enabled (below). 669 670config IKCONFIG_PROC 671 bool "Enable access to .config through /proc/config.gz" 672 depends on IKCONFIG && PROC_FS 673 help 674 This option enables access to the kernel configuration file 675 through /proc/config.gz. 676 677config IKHEADERS 678 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 679 depends on SYSFS 680 help 681 This option enables access to the in-kernel headers that are generated during 682 the build process. These can be used to build eBPF tracing programs, 683 or similar programs. If you build the headers as a module, a module called 684 kheaders.ko is built which can be loaded on-demand to get access to headers. 685 686config LOG_BUF_SHIFT 687 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 688 range 12 25 if !H8300 689 range 12 19 if H8300 690 default 17 691 depends on PRINTK 692 help 693 Select the minimal kernel log buffer size as a power of 2. 694 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 695 parameter, see below. Any higher size also might be forced 696 by "log_buf_len" boot parameter. 697 698 Examples: 699 17 => 128 KB 700 16 => 64 KB 701 15 => 32 KB 702 14 => 16 KB 703 13 => 8 KB 704 12 => 4 KB 705 706config LOG_CPU_MAX_BUF_SHIFT 707 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 708 depends on SMP 709 range 0 21 710 default 12 if !BASE_SMALL 711 default 0 if BASE_SMALL 712 depends on PRINTK 713 help 714 This option allows to increase the default ring buffer size 715 according to the number of CPUs. The value defines the contribution 716 of each CPU as a power of 2. The used space is typically only few 717 lines however it might be much more when problems are reported, 718 e.g. backtraces. 719 720 The increased size means that a new buffer has to be allocated and 721 the original static one is unused. It makes sense only on systems 722 with more CPUs. Therefore this value is used only when the sum of 723 contributions is greater than the half of the default kernel ring 724 buffer as defined by LOG_BUF_SHIFT. The default values are set 725 so that more than 16 CPUs are needed to trigger the allocation. 726 727 Also this option is ignored when "log_buf_len" kernel parameter is 728 used as it forces an exact (power of two) size of the ring buffer. 729 730 The number of possible CPUs is used for this computation ignoring 731 hotplugging making the computation optimal for the worst case 732 scenario while allowing a simple algorithm to be used from bootup. 733 734 Examples shift values and their meaning: 735 17 => 128 KB for each CPU 736 16 => 64 KB for each CPU 737 15 => 32 KB for each CPU 738 14 => 16 KB for each CPU 739 13 => 8 KB for each CPU 740 12 => 4 KB for each CPU 741 742config PRINTK_SAFE_LOG_BUF_SHIFT 743 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 744 range 10 21 745 default 13 746 depends on PRINTK 747 help 748 Select the size of an alternate printk per-CPU buffer where messages 749 printed from usafe contexts are temporary stored. One example would 750 be NMI messages, another one - printk recursion. The messages are 751 copied to the main log buffer in a safe context to avoid a deadlock. 752 The value defines the size as a power of 2. 753 754 Those messages are rare and limited. The largest one is when 755 a backtrace is printed. It usually fits into 4KB. Select 756 8KB if you want to be on the safe side. 757 758 Examples: 759 17 => 128 KB for each CPU 760 16 => 64 KB for each CPU 761 15 => 32 KB for each CPU 762 14 => 16 KB for each CPU 763 13 => 8 KB for each CPU 764 12 => 4 KB for each CPU 765 766# 767# Architectures with an unreliable sched_clock() should select this: 768# 769config HAVE_UNSTABLE_SCHED_CLOCK 770 bool 771 772config GENERIC_SCHED_CLOCK 773 bool 774 775menu "Scheduler features" 776 777config UCLAMP_TASK 778 bool "Enable utilization clamping for RT/FAIR tasks" 779 depends on CPU_FREQ_GOV_SCHEDUTIL 780 help 781 This feature enables the scheduler to track the clamped utilization 782 of each CPU based on RUNNABLE tasks scheduled on that CPU. 783 784 With this option, the user can specify the min and max CPU 785 utilization allowed for RUNNABLE tasks. The max utilization defines 786 the maximum frequency a task should use while the min utilization 787 defines the minimum frequency it should use. 788 789 Both min and max utilization clamp values are hints to the scheduler, 790 aiming at improving its frequency selection policy, but they do not 791 enforce or grant any specific bandwidth for tasks. 792 793 If in doubt, say N. 794 795config UCLAMP_BUCKETS_COUNT 796 int "Number of supported utilization clamp buckets" 797 range 5 20 798 default 5 799 depends on UCLAMP_TASK 800 help 801 Defines the number of clamp buckets to use. The range of each bucket 802 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 803 number of clamp buckets the finer their granularity and the higher 804 the precision of clamping aggregation and tracking at run-time. 805 806 For example, with the minimum configuration value we will have 5 807 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 808 be refcounted in the [20..39]% bucket and will set the bucket clamp 809 effective value to 25%. 810 If a second 30% boosted task should be co-scheduled on the same CPU, 811 that task will be refcounted in the same bucket of the first task and 812 it will boost the bucket clamp effective value to 30%. 813 The clamp effective value of a bucket is reset to its nominal value 814 (20% in the example above) when there are no more tasks refcounted in 815 that bucket. 816 817 An additional boost/capping margin can be added to some tasks. In the 818 example above the 25% task will be boosted to 30% until it exits the 819 CPU. If that should be considered not acceptable on certain systems, 820 it's always possible to reduce the margin by increasing the number of 821 clamp buckets to trade off used memory for run-time tracking 822 precision. 823 824 If in doubt, use the default value. 825 826endmenu 827 828# 829# For architectures that want to enable the support for NUMA-affine scheduler 830# balancing logic: 831# 832config ARCH_SUPPORTS_NUMA_BALANCING 833 bool 834 835# 836# For architectures that prefer to flush all TLBs after a number of pages 837# are unmapped instead of sending one IPI per page to flush. The architecture 838# must provide guarantees on what happens if a clean TLB cache entry is 839# written after the unmap. Details are in mm/rmap.c near the check for 840# should_defer_flush. The architecture should also consider if the full flush 841# and the refill costs are offset by the savings of sending fewer IPIs. 842config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 843 bool 844 845config CC_HAS_INT128 846 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 847 848# 849# For architectures that know their GCC __int128 support is sound 850# 851config ARCH_SUPPORTS_INT128 852 bool 853 854# For architectures that (ab)use NUMA to represent different memory regions 855# all cpu-local but of different latencies, such as SuperH. 856# 857config ARCH_WANT_NUMA_VARIABLE_LOCALITY 858 bool 859 860config NUMA_BALANCING 861 bool "Memory placement aware NUMA scheduler" 862 depends on ARCH_SUPPORTS_NUMA_BALANCING 863 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 864 depends on SMP && NUMA && MIGRATION 865 help 866 This option adds support for automatic NUMA aware memory/task placement. 867 The mechanism is quite primitive and is based on migrating memory when 868 it has references to the node the task is running on. 869 870 This system will be inactive on UMA systems. 871 872config NUMA_BALANCING_DEFAULT_ENABLED 873 bool "Automatically enable NUMA aware memory/task placement" 874 default y 875 depends on NUMA_BALANCING 876 help 877 If set, automatic NUMA balancing will be enabled if running on a NUMA 878 machine. 879 880menuconfig CGROUPS 881 bool "Control Group support" 882 select KERNFS 883 help 884 This option adds support for grouping sets of processes together, for 885 use with process control subsystems such as Cpusets, CFS, memory 886 controls or device isolation. 887 See 888 - Documentation/scheduler/sched-design-CFS.rst (CFS) 889 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 890 and resource control) 891 892 Say N if unsure. 893 894if CGROUPS 895 896config PAGE_COUNTER 897 bool 898 899config MEMCG 900 bool "Memory controller" 901 select PAGE_COUNTER 902 select EVENTFD 903 help 904 Provides control over the memory footprint of tasks in a cgroup. 905 906config MEMCG_SWAP 907 bool 908 depends on MEMCG && SWAP 909 default y 910 911config MEMCG_KMEM 912 bool 913 depends on MEMCG && !SLOB 914 default y 915 916config BLK_CGROUP 917 bool "IO controller" 918 depends on BLOCK 919 default n 920 help 921 Generic block IO controller cgroup interface. This is the common 922 cgroup interface which should be used by various IO controlling 923 policies. 924 925 Currently, CFQ IO scheduler uses it to recognize task groups and 926 control disk bandwidth allocation (proportional time slice allocation) 927 to such task groups. It is also used by bio throttling logic in 928 block layer to implement upper limit in IO rates on a device. 929 930 This option only enables generic Block IO controller infrastructure. 931 One needs to also enable actual IO controlling logic/policy. For 932 enabling proportional weight division of disk bandwidth in CFQ, set 933 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 934 CONFIG_BLK_DEV_THROTTLING=y. 935 936 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 937 938config CGROUP_WRITEBACK 939 bool 940 depends on MEMCG && BLK_CGROUP 941 default y 942 943menuconfig CGROUP_SCHED 944 bool "CPU controller" 945 default n 946 help 947 This feature lets CPU scheduler recognize task groups and control CPU 948 bandwidth allocation to such task groups. It uses cgroups to group 949 tasks. 950 951if CGROUP_SCHED 952config FAIR_GROUP_SCHED 953 bool "Group scheduling for SCHED_OTHER" 954 depends on CGROUP_SCHED 955 default CGROUP_SCHED 956 957config CFS_BANDWIDTH 958 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 959 depends on FAIR_GROUP_SCHED 960 default n 961 help 962 This option allows users to define CPU bandwidth rates (limits) for 963 tasks running within the fair group scheduler. Groups with no limit 964 set are considered to be unconstrained and will run with no 965 restriction. 966 See Documentation/scheduler/sched-bwc.rst for more information. 967 968config RT_GROUP_SCHED 969 bool "Group scheduling for SCHED_RR/FIFO" 970 depends on CGROUP_SCHED 971 default n 972 help 973 This feature lets you explicitly allocate real CPU bandwidth 974 to task groups. If enabled, it will also make it impossible to 975 schedule realtime tasks for non-root users until you allocate 976 realtime bandwidth for them. 977 See Documentation/scheduler/sched-rt-group.rst for more information. 978 979endif #CGROUP_SCHED 980 981config UCLAMP_TASK_GROUP 982 bool "Utilization clamping per group of tasks" 983 depends on CGROUP_SCHED 984 depends on UCLAMP_TASK 985 default n 986 help 987 This feature enables the scheduler to track the clamped utilization 988 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 989 990 When this option is enabled, the user can specify a min and max 991 CPU bandwidth which is allowed for each single task in a group. 992 The max bandwidth allows to clamp the maximum frequency a task 993 can use, while the min bandwidth allows to define a minimum 994 frequency a task will always use. 995 996 When task group based utilization clamping is enabled, an eventually 997 specified task-specific clamp value is constrained by the cgroup 998 specified clamp value. Both minimum and maximum task clamping cannot 999 be bigger than the corresponding clamping defined at task group level. 1000 1001 If in doubt, say N. 1002 1003config CGROUP_PIDS 1004 bool "PIDs controller" 1005 help 1006 Provides enforcement of process number limits in the scope of a 1007 cgroup. Any attempt to fork more processes than is allowed in the 1008 cgroup will fail. PIDs are fundamentally a global resource because it 1009 is fairly trivial to reach PID exhaustion before you reach even a 1010 conservative kmemcg limit. As a result, it is possible to grind a 1011 system to halt without being limited by other cgroup policies. The 1012 PIDs controller is designed to stop this from happening. 1013 1014 It should be noted that organisational operations (such as attaching 1015 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 1016 since the PIDs limit only affects a process's ability to fork, not to 1017 attach to a cgroup. 1018 1019config CGROUP_RDMA 1020 bool "RDMA controller" 1021 help 1022 Provides enforcement of RDMA resources defined by IB stack. 1023 It is fairly easy for consumers to exhaust RDMA resources, which 1024 can result into resource unavailability to other consumers. 1025 RDMA controller is designed to stop this from happening. 1026 Attaching processes with active RDMA resources to the cgroup 1027 hierarchy is allowed even if can cross the hierarchy's limit. 1028 1029config CGROUP_FREEZER 1030 bool "Freezer controller" 1031 help 1032 Provides a way to freeze and unfreeze all tasks in a 1033 cgroup. 1034 1035 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1036 controller includes important in-kernel memory consumers per default. 1037 1038 If you're using cgroup2, say N. 1039 1040config CGROUP_HUGETLB 1041 bool "HugeTLB controller" 1042 depends on HUGETLB_PAGE 1043 select PAGE_COUNTER 1044 default n 1045 help 1046 Provides a cgroup controller for HugeTLB pages. 1047 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1048 The limit is enforced during page fault. Since HugeTLB doesn't 1049 support page reclaim, enforcing the limit at page fault time implies 1050 that, the application will get SIGBUS signal if it tries to access 1051 HugeTLB pages beyond its limit. This requires the application to know 1052 beforehand how much HugeTLB pages it would require for its use. The 1053 control group is tracked in the third page lru pointer. This means 1054 that we cannot use the controller with huge page less than 3 pages. 1055 1056config CPUSETS 1057 bool "Cpuset controller" 1058 depends on SMP 1059 help 1060 This option will let you create and manage CPUSETs which 1061 allow dynamically partitioning a system into sets of CPUs and 1062 Memory Nodes and assigning tasks to run only within those sets. 1063 This is primarily useful on large SMP or NUMA systems. 1064 1065 Say N if unsure. 1066 1067config PROC_PID_CPUSET 1068 bool "Include legacy /proc/<pid>/cpuset file" 1069 depends on CPUSETS 1070 default y 1071 1072config CGROUP_DEVICE 1073 bool "Device controller" 1074 help 1075 Provides a cgroup controller implementing whitelists for 1076 devices which a process in the cgroup can mknod or open. 1077 1078config CGROUP_CPUACCT 1079 bool "Simple CPU accounting controller" 1080 help 1081 Provides a simple controller for monitoring the 1082 total CPU consumed by the tasks in a cgroup. 1083 1084config CGROUP_PERF 1085 bool "Perf controller" 1086 depends on PERF_EVENTS 1087 help 1088 This option extends the perf per-cpu mode to restrict monitoring 1089 to threads which belong to the cgroup specified and run on the 1090 designated cpu. Or this can be used to have cgroup ID in samples 1091 so that it can monitor performance events among cgroups. 1092 1093 Say N if unsure. 1094 1095config CGROUP_BPF 1096 bool "Support for eBPF programs attached to cgroups" 1097 depends on BPF_SYSCALL 1098 select SOCK_CGROUP_DATA 1099 help 1100 Allow attaching eBPF programs to a cgroup using the bpf(2) 1101 syscall command BPF_PROG_ATTACH. 1102 1103 In which context these programs are accessed depends on the type 1104 of attachment. For instance, programs that are attached using 1105 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1106 inet sockets. 1107 1108config CGROUP_DEBUG 1109 bool "Debug controller" 1110 default n 1111 depends on DEBUG_KERNEL 1112 help 1113 This option enables a simple controller that exports 1114 debugging information about the cgroups framework. This 1115 controller is for control cgroup debugging only. Its 1116 interfaces are not stable. 1117 1118 Say N. 1119 1120config SOCK_CGROUP_DATA 1121 bool 1122 default n 1123 1124endif # CGROUPS 1125 1126menuconfig NAMESPACES 1127 bool "Namespaces support" if EXPERT 1128 depends on MULTIUSER 1129 default !EXPERT 1130 help 1131 Provides the way to make tasks work with different objects using 1132 the same id. For example same IPC id may refer to different objects 1133 or same user id or pid may refer to different tasks when used in 1134 different namespaces. 1135 1136if NAMESPACES 1137 1138config UTS_NS 1139 bool "UTS namespace" 1140 default y 1141 help 1142 In this namespace tasks see different info provided with the 1143 uname() system call 1144 1145config TIME_NS 1146 bool "TIME namespace" 1147 depends on GENERIC_VDSO_TIME_NS 1148 default y 1149 help 1150 In this namespace boottime and monotonic clocks can be set. 1151 The time will keep going with the same pace. 1152 1153config IPC_NS 1154 bool "IPC namespace" 1155 depends on (SYSVIPC || POSIX_MQUEUE) 1156 default y 1157 help 1158 In this namespace tasks work with IPC ids which correspond to 1159 different IPC objects in different namespaces. 1160 1161config USER_NS 1162 bool "User namespace" 1163 default n 1164 help 1165 This allows containers, i.e. vservers, to use user namespaces 1166 to provide different user info for different servers. 1167 1168 When user namespaces are enabled in the kernel it is 1169 recommended that the MEMCG option also be enabled and that 1170 user-space use the memory control groups to limit the amount 1171 of memory a memory unprivileged users can use. 1172 1173 If unsure, say N. 1174 1175config PID_NS 1176 bool "PID Namespaces" 1177 default y 1178 help 1179 Support process id namespaces. This allows having multiple 1180 processes with the same pid as long as they are in different 1181 pid namespaces. This is a building block of containers. 1182 1183config NET_NS 1184 bool "Network namespace" 1185 depends on NET 1186 default y 1187 help 1188 Allow user space to create what appear to be multiple instances 1189 of the network stack. 1190 1191endif # NAMESPACES 1192 1193config CHECKPOINT_RESTORE 1194 bool "Checkpoint/restore support" 1195 select PROC_CHILDREN 1196 default n 1197 help 1198 Enables additional kernel features in a sake of checkpoint/restore. 1199 In particular it adds auxiliary prctl codes to setup process text, 1200 data and heap segment sizes, and a few additional /proc filesystem 1201 entries. 1202 1203 If unsure, say N here. 1204 1205config SCHED_AUTOGROUP 1206 bool "Automatic process group scheduling" 1207 select CGROUPS 1208 select CGROUP_SCHED 1209 select FAIR_GROUP_SCHED 1210 help 1211 This option optimizes the scheduler for common desktop workloads by 1212 automatically creating and populating task groups. This separation 1213 of workloads isolates aggressive CPU burners (like build jobs) from 1214 desktop applications. Task group autogeneration is currently based 1215 upon task session. 1216 1217config SYSFS_DEPRECATED 1218 bool "Enable deprecated sysfs features to support old userspace tools" 1219 depends on SYSFS 1220 default n 1221 help 1222 This option adds code that switches the layout of the "block" class 1223 devices, to not show up in /sys/class/block/, but only in 1224 /sys/block/. 1225 1226 This switch is only active when the sysfs.deprecated=1 boot option is 1227 passed or the SYSFS_DEPRECATED_V2 option is set. 1228 1229 This option allows new kernels to run on old distributions and tools, 1230 which might get confused by /sys/class/block/. Since 2007/2008 all 1231 major distributions and tools handle this just fine. 1232 1233 Recent distributions and userspace tools after 2009/2010 depend on 1234 the existence of /sys/class/block/, and will not work with this 1235 option enabled. 1236 1237 Only if you are using a new kernel on an old distribution, you might 1238 need to say Y here. 1239 1240config SYSFS_DEPRECATED_V2 1241 bool "Enable deprecated sysfs features by default" 1242 default n 1243 depends on SYSFS 1244 depends on SYSFS_DEPRECATED 1245 help 1246 Enable deprecated sysfs by default. 1247 1248 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1249 option. 1250 1251 Only if you are using a new kernel on an old distribution, you might 1252 need to say Y here. Even then, odds are you would not need it 1253 enabled, you can always pass the boot option if absolutely necessary. 1254 1255config RELAY 1256 bool "Kernel->user space relay support (formerly relayfs)" 1257 select IRQ_WORK 1258 help 1259 This option enables support for relay interface support in 1260 certain file systems (such as debugfs). 1261 It is designed to provide an efficient mechanism for tools and 1262 facilities to relay large amounts of data from kernel space to 1263 user space. 1264 1265 If unsure, say N. 1266 1267config BLK_DEV_INITRD 1268 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1269 help 1270 The initial RAM filesystem is a ramfs which is loaded by the 1271 boot loader (loadlin or lilo) and that is mounted as root 1272 before the normal boot procedure. It is typically used to 1273 load modules needed to mount the "real" root file system, 1274 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1275 1276 If RAM disk support (BLK_DEV_RAM) is also included, this 1277 also enables initial RAM disk (initrd) support and adds 1278 15 Kbytes (more on some other architectures) to the kernel size. 1279 1280 If unsure say Y. 1281 1282if BLK_DEV_INITRD 1283 1284source "usr/Kconfig" 1285 1286endif 1287 1288config BOOT_CONFIG 1289 bool "Boot config support" 1290 select BLK_DEV_INITRD 1291 help 1292 Extra boot config allows system admin to pass a config file as 1293 complemental extension of kernel cmdline when booting. 1294 The boot config file must be attached at the end of initramfs 1295 with checksum, size and magic word. 1296 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1297 1298 If unsure, say Y. 1299 1300choice 1301 prompt "Compiler optimization level" 1302 default CC_OPTIMIZE_FOR_PERFORMANCE 1303 1304config CC_OPTIMIZE_FOR_PERFORMANCE 1305 bool "Optimize for performance (-O2)" 1306 help 1307 This is the default optimization level for the kernel, building 1308 with the "-O2" compiler flag for best performance and most 1309 helpful compile-time warnings. 1310 1311config CC_OPTIMIZE_FOR_PERFORMANCE_O3 1312 bool "Optimize more for performance (-O3)" 1313 depends on ARC 1314 help 1315 Choosing this option will pass "-O3" to your compiler to optimize 1316 the kernel yet more for performance. 1317 1318config CC_OPTIMIZE_FOR_SIZE 1319 bool "Optimize for size (-Os)" 1320 help 1321 Choosing this option will pass "-Os" to your compiler resulting 1322 in a smaller kernel. 1323 1324endchoice 1325 1326config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1327 bool 1328 help 1329 This requires that the arch annotates or otherwise protects 1330 its external entry points from being discarded. Linker scripts 1331 must also merge .text.*, .data.*, and .bss.* correctly into 1332 output sections. Care must be taken not to pull in unrelated 1333 sections (e.g., '.text.init'). Typically '.' in section names 1334 is used to distinguish them from label names / C identifiers. 1335 1336config LD_DEAD_CODE_DATA_ELIMINATION 1337 bool "Dead code and data elimination (EXPERIMENTAL)" 1338 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1339 depends on EXPERT 1340 depends on $(cc-option,-ffunction-sections -fdata-sections) 1341 depends on $(ld-option,--gc-sections) 1342 help 1343 Enable this if you want to do dead code and data elimination with 1344 the linker by compiling with -ffunction-sections -fdata-sections, 1345 and linking with --gc-sections. 1346 1347 This can reduce on disk and in-memory size of the kernel 1348 code and static data, particularly for small configs and 1349 on small systems. This has the possibility of introducing 1350 silently broken kernel if the required annotations are not 1351 present. This option is not well tested yet, so use at your 1352 own risk. 1353 1354config LD_ORPHAN_WARN 1355 def_bool y 1356 depends on ARCH_WANT_LD_ORPHAN_WARN 1357 depends on !LD_IS_LLD || LLD_VERSION >= 110000 1358 depends on $(ld-option,--orphan-handling=warn) 1359 1360config SYSCTL 1361 bool 1362 1363config HAVE_UID16 1364 bool 1365 1366config SYSCTL_EXCEPTION_TRACE 1367 bool 1368 help 1369 Enable support for /proc/sys/debug/exception-trace. 1370 1371config SYSCTL_ARCH_UNALIGN_NO_WARN 1372 bool 1373 help 1374 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1375 Allows arch to define/use @no_unaligned_warning to possibly warn 1376 about unaligned access emulation going on under the hood. 1377 1378config SYSCTL_ARCH_UNALIGN_ALLOW 1379 bool 1380 help 1381 Enable support for /proc/sys/kernel/unaligned-trap 1382 Allows arches to define/use @unaligned_enabled to runtime toggle 1383 the unaligned access emulation. 1384 see arch/parisc/kernel/unaligned.c for reference 1385 1386config HAVE_PCSPKR_PLATFORM 1387 bool 1388 1389# interpreter that classic socket filters depend on 1390config BPF 1391 bool 1392 1393menuconfig EXPERT 1394 bool "Configure standard kernel features (expert users)" 1395 # Unhide debug options, to make the on-by-default options visible 1396 select DEBUG_KERNEL 1397 help 1398 This option allows certain base kernel options and settings 1399 to be disabled or tweaked. This is for specialized 1400 environments which can tolerate a "non-standard" kernel. 1401 Only use this if you really know what you are doing. 1402 1403config UID16 1404 bool "Enable 16-bit UID system calls" if EXPERT 1405 depends on HAVE_UID16 && MULTIUSER 1406 default y 1407 help 1408 This enables the legacy 16-bit UID syscall wrappers. 1409 1410config MULTIUSER 1411 bool "Multiple users, groups and capabilities support" if EXPERT 1412 default y 1413 help 1414 This option enables support for non-root users, groups and 1415 capabilities. 1416 1417 If you say N here, all processes will run with UID 0, GID 0, and all 1418 possible capabilities. Saying N here also compiles out support for 1419 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1420 setgid, and capset. 1421 1422 If unsure, say Y here. 1423 1424config SGETMASK_SYSCALL 1425 bool "sgetmask/ssetmask syscalls support" if EXPERT 1426 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1427 help 1428 sys_sgetmask and sys_ssetmask are obsolete system calls 1429 no longer supported in libc but still enabled by default in some 1430 architectures. 1431 1432 If unsure, leave the default option here. 1433 1434config SYSFS_SYSCALL 1435 bool "Sysfs syscall support" if EXPERT 1436 default y 1437 help 1438 sys_sysfs is an obsolete system call no longer supported in libc. 1439 Note that disabling this option is more secure but might break 1440 compatibility with some systems. 1441 1442 If unsure say Y here. 1443 1444config FHANDLE 1445 bool "open by fhandle syscalls" if EXPERT 1446 select EXPORTFS 1447 default y 1448 help 1449 If you say Y here, a user level program will be able to map 1450 file names to handle and then later use the handle for 1451 different file system operations. This is useful in implementing 1452 userspace file servers, which now track files using handles instead 1453 of names. The handle would remain the same even if file names 1454 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1455 syscalls. 1456 1457config POSIX_TIMERS 1458 bool "Posix Clocks & timers" if EXPERT 1459 default y 1460 help 1461 This includes native support for POSIX timers to the kernel. 1462 Some embedded systems have no use for them and therefore they 1463 can be configured out to reduce the size of the kernel image. 1464 1465 When this option is disabled, the following syscalls won't be 1466 available: timer_create, timer_gettime: timer_getoverrun, 1467 timer_settime, timer_delete, clock_adjtime, getitimer, 1468 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1469 clock_getres and clock_nanosleep syscalls will be limited to 1470 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1471 1472 If unsure say y. 1473 1474config PRINTK 1475 default y 1476 bool "Enable support for printk" if EXPERT 1477 select IRQ_WORK 1478 help 1479 This option enables normal printk support. Removing it 1480 eliminates most of the message strings from the kernel image 1481 and makes the kernel more or less silent. As this makes it 1482 very difficult to diagnose system problems, saying N here is 1483 strongly discouraged. 1484 1485config PRINTK_NMI 1486 def_bool y 1487 depends on PRINTK 1488 depends on HAVE_NMI 1489 1490config BUG 1491 bool "BUG() support" if EXPERT 1492 default y 1493 help 1494 Disabling this option eliminates support for BUG and WARN, reducing 1495 the size of your kernel image and potentially quietly ignoring 1496 numerous fatal conditions. You should only consider disabling this 1497 option for embedded systems with no facilities for reporting errors. 1498 Just say Y. 1499 1500config ELF_CORE 1501 depends on COREDUMP 1502 default y 1503 bool "Enable ELF core dumps" if EXPERT 1504 help 1505 Enable support for generating core dumps. Disabling saves about 4k. 1506 1507 1508config PCSPKR_PLATFORM 1509 bool "Enable PC-Speaker support" if EXPERT 1510 depends on HAVE_PCSPKR_PLATFORM 1511 select I8253_LOCK 1512 default y 1513 help 1514 This option allows to disable the internal PC-Speaker 1515 support, saving some memory. 1516 1517config BASE_FULL 1518 default y 1519 bool "Enable full-sized data structures for core" if EXPERT 1520 help 1521 Disabling this option reduces the size of miscellaneous core 1522 kernel data structures. This saves memory on small machines, 1523 but may reduce performance. 1524 1525config FUTEX 1526 bool "Enable futex support" if EXPERT 1527 default y 1528 imply RT_MUTEXES 1529 help 1530 Disabling this option will cause the kernel to be built without 1531 support for "fast userspace mutexes". The resulting kernel may not 1532 run glibc-based applications correctly. 1533 1534config FUTEX_PI 1535 bool 1536 depends on FUTEX && RT_MUTEXES 1537 default y 1538 1539config HAVE_FUTEX_CMPXCHG 1540 bool 1541 depends on FUTEX 1542 help 1543 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1544 is implemented and always working. This removes a couple of runtime 1545 checks. 1546 1547config EPOLL 1548 bool "Enable eventpoll support" if EXPERT 1549 default y 1550 help 1551 Disabling this option will cause the kernel to be built without 1552 support for epoll family of system calls. 1553 1554config SIGNALFD 1555 bool "Enable signalfd() system call" if EXPERT 1556 default y 1557 help 1558 Enable the signalfd() system call that allows to receive signals 1559 on a file descriptor. 1560 1561 If unsure, say Y. 1562 1563config TIMERFD 1564 bool "Enable timerfd() system call" if EXPERT 1565 default y 1566 help 1567 Enable the timerfd() system call that allows to receive timer 1568 events on a file descriptor. 1569 1570 If unsure, say Y. 1571 1572config EVENTFD 1573 bool "Enable eventfd() system call" if EXPERT 1574 default y 1575 help 1576 Enable the eventfd() system call that allows to receive both 1577 kernel notification (ie. KAIO) or userspace notifications. 1578 1579 If unsure, say Y. 1580 1581config SHMEM 1582 bool "Use full shmem filesystem" if EXPERT 1583 default y 1584 depends on MMU 1585 help 1586 The shmem is an internal filesystem used to manage shared memory. 1587 It is backed by swap and manages resource limits. It is also exported 1588 to userspace as tmpfs if TMPFS is enabled. Disabling this 1589 option replaces shmem and tmpfs with the much simpler ramfs code, 1590 which may be appropriate on small systems without swap. 1591 1592config AIO 1593 bool "Enable AIO support" if EXPERT 1594 default y 1595 help 1596 This option enables POSIX asynchronous I/O which may by used 1597 by some high performance threaded applications. Disabling 1598 this option saves about 7k. 1599 1600config IO_URING 1601 bool "Enable IO uring support" if EXPERT 1602 select IO_WQ 1603 default y 1604 help 1605 This option enables support for the io_uring interface, enabling 1606 applications to submit and complete IO through submission and 1607 completion rings that are shared between the kernel and application. 1608 1609config ADVISE_SYSCALLS 1610 bool "Enable madvise/fadvise syscalls" if EXPERT 1611 default y 1612 help 1613 This option enables the madvise and fadvise syscalls, used by 1614 applications to advise the kernel about their future memory or file 1615 usage, improving performance. If building an embedded system where no 1616 applications use these syscalls, you can disable this option to save 1617 space. 1618 1619config HAVE_ARCH_USERFAULTFD_WP 1620 bool 1621 help 1622 Arch has userfaultfd write protection support 1623 1624config MEMBARRIER 1625 bool "Enable membarrier() system call" if EXPERT 1626 default y 1627 help 1628 Enable the membarrier() system call that allows issuing memory 1629 barriers across all running threads, which can be used to distribute 1630 the cost of user-space memory barriers asymmetrically by transforming 1631 pairs of memory barriers into pairs consisting of membarrier() and a 1632 compiler barrier. 1633 1634 If unsure, say Y. 1635 1636config KALLSYMS 1637 bool "Load all symbols for debugging/ksymoops" if EXPERT 1638 default y 1639 help 1640 Say Y here to let the kernel print out symbolic crash information and 1641 symbolic stack backtraces. This increases the size of the kernel 1642 somewhat, as all symbols have to be loaded into the kernel image. 1643 1644config KALLSYMS_ALL 1645 bool "Include all symbols in kallsyms" 1646 depends on DEBUG_KERNEL && KALLSYMS 1647 help 1648 Normally kallsyms only contains the symbols of functions for nicer 1649 OOPS messages and backtraces (i.e., symbols from the text and inittext 1650 sections). This is sufficient for most cases. And only in very rare 1651 cases (e.g., when a debugger is used) all symbols are required (e.g., 1652 names of variables from the data sections, etc). 1653 1654 This option makes sure that all symbols are loaded into the kernel 1655 image (i.e., symbols from all sections) in cost of increased kernel 1656 size (depending on the kernel configuration, it may be 300KiB or 1657 something like this). 1658 1659 Say N unless you really need all symbols. 1660 1661config KALLSYMS_ABSOLUTE_PERCPU 1662 bool 1663 depends on KALLSYMS 1664 default X86_64 && SMP 1665 1666config KALLSYMS_BASE_RELATIVE 1667 bool 1668 depends on KALLSYMS 1669 default !IA64 1670 help 1671 Instead of emitting them as absolute values in the native word size, 1672 emit the symbol references in the kallsyms table as 32-bit entries, 1673 each containing a relative value in the range [base, base + U32_MAX] 1674 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1675 an absolute value in the range [0, S32_MAX] or a relative value in the 1676 range [base, base + S32_MAX], where base is the lowest relative symbol 1677 address encountered in the image. 1678 1679 On 64-bit builds, this reduces the size of the address table by 50%, 1680 but more importantly, it results in entries whose values are build 1681 time constants, and no relocation pass is required at runtime to fix 1682 up the entries based on the runtime load address of the kernel. 1683 1684# end of the "standard kernel features (expert users)" menu 1685 1686# syscall, maps, verifier 1687 1688config BPF_LSM 1689 bool "LSM Instrumentation with BPF" 1690 depends on BPF_EVENTS 1691 depends on BPF_SYSCALL 1692 depends on SECURITY 1693 depends on BPF_JIT 1694 help 1695 Enables instrumentation of the security hooks with eBPF programs for 1696 implementing dynamic MAC and Audit Policies. 1697 1698 If you are unsure how to answer this question, answer N. 1699 1700config BPF_SYSCALL 1701 bool "Enable bpf() system call" 1702 select BPF 1703 select IRQ_WORK 1704 select TASKS_TRACE_RCU 1705 default n 1706 help 1707 Enable the bpf() system call that allows to manipulate eBPF 1708 programs and maps via file descriptors. 1709 1710config ARCH_WANT_DEFAULT_BPF_JIT 1711 bool 1712 1713config BPF_JIT_ALWAYS_ON 1714 bool "Permanently enable BPF JIT and remove BPF interpreter" 1715 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1716 help 1717 Enables BPF JIT and removes BPF interpreter to avoid 1718 speculative execution of BPF instructions by the interpreter 1719 1720config BPF_JIT_DEFAULT_ON 1721 def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON 1722 depends on HAVE_EBPF_JIT && BPF_JIT 1723 1724source "kernel/bpf/preload/Kconfig" 1725 1726config USERFAULTFD 1727 bool "Enable userfaultfd() system call" 1728 depends on MMU 1729 help 1730 Enable the userfaultfd() system call that allows to intercept and 1731 handle page faults in userland. 1732 1733config ARCH_HAS_MEMBARRIER_CALLBACKS 1734 bool 1735 1736config ARCH_HAS_MEMBARRIER_SYNC_CORE 1737 bool 1738 1739config RSEQ 1740 bool "Enable rseq() system call" if EXPERT 1741 default y 1742 depends on HAVE_RSEQ 1743 select MEMBARRIER 1744 help 1745 Enable the restartable sequences system call. It provides a 1746 user-space cache for the current CPU number value, which 1747 speeds up getting the current CPU number from user-space, 1748 as well as an ABI to speed up user-space operations on 1749 per-CPU data. 1750 1751 If unsure, say Y. 1752 1753config DEBUG_RSEQ 1754 default n 1755 bool "Enabled debugging of rseq() system call" if EXPERT 1756 depends on RSEQ && DEBUG_KERNEL 1757 help 1758 Enable extra debugging checks for the rseq system call. 1759 1760 If unsure, say N. 1761 1762config EMBEDDED 1763 bool "Embedded system" 1764 option allnoconfig_y 1765 select EXPERT 1766 help 1767 This option should be enabled if compiling the kernel for 1768 an embedded system so certain expert options are available 1769 for configuration. 1770 1771config HAVE_PERF_EVENTS 1772 bool 1773 help 1774 See tools/perf/design.txt for details. 1775 1776config PERF_USE_VMALLOC 1777 bool 1778 help 1779 See tools/perf/design.txt for details 1780 1781config PC104 1782 bool "PC/104 support" if EXPERT 1783 help 1784 Expose PC/104 form factor device drivers and options available for 1785 selection and configuration. Enable this option if your target 1786 machine has a PC/104 bus. 1787 1788menu "Kernel Performance Events And Counters" 1789 1790config PERF_EVENTS 1791 bool "Kernel performance events and counters" 1792 default y if PROFILING 1793 depends on HAVE_PERF_EVENTS 1794 select IRQ_WORK 1795 select SRCU 1796 help 1797 Enable kernel support for various performance events provided 1798 by software and hardware. 1799 1800 Software events are supported either built-in or via the 1801 use of generic tracepoints. 1802 1803 Most modern CPUs support performance events via performance 1804 counter registers. These registers count the number of certain 1805 types of hw events: such as instructions executed, cachemisses 1806 suffered, or branches mis-predicted - without slowing down the 1807 kernel or applications. These registers can also trigger interrupts 1808 when a threshold number of events have passed - and can thus be 1809 used to profile the code that runs on that CPU. 1810 1811 The Linux Performance Event subsystem provides an abstraction of 1812 these software and hardware event capabilities, available via a 1813 system call and used by the "perf" utility in tools/perf/. It 1814 provides per task and per CPU counters, and it provides event 1815 capabilities on top of those. 1816 1817 Say Y if unsure. 1818 1819config DEBUG_PERF_USE_VMALLOC 1820 default n 1821 bool "Debug: use vmalloc to back perf mmap() buffers" 1822 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1823 select PERF_USE_VMALLOC 1824 help 1825 Use vmalloc memory to back perf mmap() buffers. 1826 1827 Mostly useful for debugging the vmalloc code on platforms 1828 that don't require it. 1829 1830 Say N if unsure. 1831 1832endmenu 1833 1834config VM_EVENT_COUNTERS 1835 default y 1836 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1837 help 1838 VM event counters are needed for event counts to be shown. 1839 This option allows the disabling of the VM event counters 1840 on EXPERT systems. /proc/vmstat will only show page counts 1841 if VM event counters are disabled. 1842 1843config SLUB_DEBUG 1844 default y 1845 bool "Enable SLUB debugging support" if EXPERT 1846 depends on SLUB && SYSFS 1847 help 1848 SLUB has extensive debug support features. Disabling these can 1849 result in significant savings in code size. This also disables 1850 SLUB sysfs support. /sys/slab will not exist and there will be 1851 no support for cache validation etc. 1852 1853config SLUB_MEMCG_SYSFS_ON 1854 default n 1855 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1856 depends on SLUB && SYSFS && MEMCG 1857 help 1858 SLUB creates a directory under /sys/kernel/slab for each 1859 allocation cache to host info and debug files. If memory 1860 cgroup is enabled, each cache can have per memory cgroup 1861 caches. SLUB can create the same sysfs directories for these 1862 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1863 to a very high number of debug files being created. This is 1864 controlled by slub_memcg_sysfs boot parameter and this 1865 config option determines the parameter's default value. 1866 1867config COMPAT_BRK 1868 bool "Disable heap randomization" 1869 default y 1870 help 1871 Randomizing heap placement makes heap exploits harder, but it 1872 also breaks ancient binaries (including anything libc5 based). 1873 This option changes the bootup default to heap randomization 1874 disabled, and can be overridden at runtime by setting 1875 /proc/sys/kernel/randomize_va_space to 2. 1876 1877 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1878 1879choice 1880 prompt "Choose SLAB allocator" 1881 default SLUB 1882 help 1883 This option allows to select a slab allocator. 1884 1885config SLAB 1886 bool "SLAB" 1887 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1888 help 1889 The regular slab allocator that is established and known to work 1890 well in all environments. It organizes cache hot objects in 1891 per cpu and per node queues. 1892 1893config SLUB 1894 bool "SLUB (Unqueued Allocator)" 1895 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1896 help 1897 SLUB is a slab allocator that minimizes cache line usage 1898 instead of managing queues of cached objects (SLAB approach). 1899 Per cpu caching is realized using slabs of objects instead 1900 of queues of objects. SLUB can use memory efficiently 1901 and has enhanced diagnostics. SLUB is the default choice for 1902 a slab allocator. 1903 1904config SLOB 1905 depends on EXPERT 1906 bool "SLOB (Simple Allocator)" 1907 help 1908 SLOB replaces the stock allocator with a drastically simpler 1909 allocator. SLOB is generally more space efficient but 1910 does not perform as well on large systems. 1911 1912endchoice 1913 1914config SLAB_MERGE_DEFAULT 1915 bool "Allow slab caches to be merged" 1916 default y 1917 help 1918 For reduced kernel memory fragmentation, slab caches can be 1919 merged when they share the same size and other characteristics. 1920 This carries a risk of kernel heap overflows being able to 1921 overwrite objects from merged caches (and more easily control 1922 cache layout), which makes such heap attacks easier to exploit 1923 by attackers. By keeping caches unmerged, these kinds of exploits 1924 can usually only damage objects in the same cache. To disable 1925 merging at runtime, "slab_nomerge" can be passed on the kernel 1926 command line. 1927 1928config SLAB_FREELIST_RANDOM 1929 bool "Randomize slab freelist" 1930 depends on SLAB || SLUB 1931 help 1932 Randomizes the freelist order used on creating new pages. This 1933 security feature reduces the predictability of the kernel slab 1934 allocator against heap overflows. 1935 1936config SLAB_FREELIST_HARDENED 1937 bool "Harden slab freelist metadata" 1938 depends on SLAB || SLUB 1939 help 1940 Many kernel heap attacks try to target slab cache metadata and 1941 other infrastructure. This options makes minor performance 1942 sacrifices to harden the kernel slab allocator against common 1943 freelist exploit methods. Some slab implementations have more 1944 sanity-checking than others. This option is most effective with 1945 CONFIG_SLUB. 1946 1947config SHUFFLE_PAGE_ALLOCATOR 1948 bool "Page allocator randomization" 1949 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1950 help 1951 Randomization of the page allocator improves the average 1952 utilization of a direct-mapped memory-side-cache. See section 1953 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1954 6.2a specification for an example of how a platform advertises 1955 the presence of a memory-side-cache. There are also incidental 1956 security benefits as it reduces the predictability of page 1957 allocations to compliment SLAB_FREELIST_RANDOM, but the 1958 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1959 10th order of pages is selected based on cache utilization 1960 benefits on x86. 1961 1962 While the randomization improves cache utilization it may 1963 negatively impact workloads on platforms without a cache. For 1964 this reason, by default, the randomization is enabled only 1965 after runtime detection of a direct-mapped memory-side-cache. 1966 Otherwise, the randomization may be force enabled with the 1967 'page_alloc.shuffle' kernel command line parameter. 1968 1969 Say Y if unsure. 1970 1971config SLUB_CPU_PARTIAL 1972 default y 1973 depends on SLUB && SMP 1974 bool "SLUB per cpu partial cache" 1975 help 1976 Per cpu partial caches accelerate objects allocation and freeing 1977 that is local to a processor at the price of more indeterminism 1978 in the latency of the free. On overflow these caches will be cleared 1979 which requires the taking of locks that may cause latency spikes. 1980 Typically one would choose no for a realtime system. 1981 1982config MMAP_ALLOW_UNINITIALIZED 1983 bool "Allow mmapped anonymous memory to be uninitialized" 1984 depends on EXPERT && !MMU 1985 default n 1986 help 1987 Normally, and according to the Linux spec, anonymous memory obtained 1988 from mmap() has its contents cleared before it is passed to 1989 userspace. Enabling this config option allows you to request that 1990 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1991 providing a huge performance boost. If this option is not enabled, 1992 then the flag will be ignored. 1993 1994 This is taken advantage of by uClibc's malloc(), and also by 1995 ELF-FDPIC binfmt's brk and stack allocator. 1996 1997 Because of the obvious security issues, this option should only be 1998 enabled on embedded devices where you control what is run in 1999 userspace. Since that isn't generally a problem on no-MMU systems, 2000 it is normally safe to say Y here. 2001 2002 See Documentation/admin-guide/mm/nommu-mmap.rst for more information. 2003 2004config SYSTEM_DATA_VERIFICATION 2005 def_bool n 2006 select SYSTEM_TRUSTED_KEYRING 2007 select KEYS 2008 select CRYPTO 2009 select CRYPTO_RSA 2010 select ASYMMETRIC_KEY_TYPE 2011 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 2012 select ASN1 2013 select OID_REGISTRY 2014 select X509_CERTIFICATE_PARSER 2015 select PKCS7_MESSAGE_PARSER 2016 help 2017 Provide PKCS#7 message verification using the contents of the system 2018 trusted keyring to provide public keys. This then can be used for 2019 module verification, kexec image verification and firmware blob 2020 verification. 2021 2022config PROFILING 2023 bool "Profiling support" 2024 help 2025 Say Y here to enable the extended profiling support mechanisms used 2026 by profilers such as OProfile. 2027 2028# 2029# Place an empty function call at each tracepoint site. Can be 2030# dynamically changed for a probe function. 2031# 2032config TRACEPOINTS 2033 bool 2034 2035endmenu # General setup 2036 2037source "arch/Kconfig" 2038 2039config RT_MUTEXES 2040 bool 2041 2042config BASE_SMALL 2043 int 2044 default 0 if BASE_FULL 2045 default 1 if !BASE_FULL 2046 2047config MODULE_SIG_FORMAT 2048 def_bool n 2049 select SYSTEM_DATA_VERIFICATION 2050 2051menuconfig MODULES 2052 bool "Enable loadable module support" 2053 option modules 2054 help 2055 Kernel modules are small pieces of compiled code which can 2056 be inserted in the running kernel, rather than being 2057 permanently built into the kernel. You use the "modprobe" 2058 tool to add (and sometimes remove) them. If you say Y here, 2059 many parts of the kernel can be built as modules (by 2060 answering M instead of Y where indicated): this is most 2061 useful for infrequently used options which are not required 2062 for booting. For more information, see the man pages for 2063 modprobe, lsmod, modinfo, insmod and rmmod. 2064 2065 If you say Y here, you will need to run "make 2066 modules_install" to put the modules under /lib/modules/ 2067 where modprobe can find them (you may need to be root to do 2068 this). 2069 2070 If unsure, say Y. 2071 2072if MODULES 2073 2074config MODULE_FORCE_LOAD 2075 bool "Forced module loading" 2076 default n 2077 help 2078 Allow loading of modules without version information (ie. modprobe 2079 --force). Forced module loading sets the 'F' (forced) taint flag and 2080 is usually a really bad idea. 2081 2082config MODULE_UNLOAD 2083 bool "Module unloading" 2084 help 2085 Without this option you will not be able to unload any 2086 modules (note that some modules may not be unloadable 2087 anyway), which makes your kernel smaller, faster 2088 and simpler. If unsure, say Y. 2089 2090config MODULE_FORCE_UNLOAD 2091 bool "Forced module unloading" 2092 depends on MODULE_UNLOAD 2093 help 2094 This option allows you to force a module to unload, even if the 2095 kernel believes it is unsafe: the kernel will remove the module 2096 without waiting for anyone to stop using it (using the -f option to 2097 rmmod). This is mainly for kernel developers and desperate users. 2098 If unsure, say N. 2099 2100config MODVERSIONS 2101 bool "Module versioning support" 2102 help 2103 Usually, you have to use modules compiled with your kernel. 2104 Saying Y here makes it sometimes possible to use modules 2105 compiled for different kernels, by adding enough information 2106 to the modules to (hopefully) spot any changes which would 2107 make them incompatible with the kernel you are running. If 2108 unsure, say N. 2109 2110config ASM_MODVERSIONS 2111 bool 2112 default HAVE_ASM_MODVERSIONS && MODVERSIONS 2113 help 2114 This enables module versioning for exported symbols also from 2115 assembly. This can be enabled only when the target architecture 2116 supports it. 2117 2118config MODULE_REL_CRCS 2119 bool 2120 depends on MODVERSIONS 2121 2122config MODULE_SRCVERSION_ALL 2123 bool "Source checksum for all modules" 2124 help 2125 Modules which contain a MODULE_VERSION get an extra "srcversion" 2126 field inserted into their modinfo section, which contains a 2127 sum of the source files which made it. This helps maintainers 2128 see exactly which source was used to build a module (since 2129 others sometimes change the module source without updating 2130 the version). With this option, such a "srcversion" field 2131 will be created for all modules. If unsure, say N. 2132 2133config MODULE_SIG 2134 bool "Module signature verification" 2135 select MODULE_SIG_FORMAT 2136 help 2137 Check modules for valid signatures upon load: the signature 2138 is simply appended to the module. For more information see 2139 <file:Documentation/admin-guide/module-signing.rst>. 2140 2141 Note that this option adds the OpenSSL development packages as a 2142 kernel build dependency so that the signing tool can use its crypto 2143 library. 2144 2145 You should enable this option if you wish to use either 2146 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via 2147 another LSM - otherwise unsigned modules will be loadable regardless 2148 of the lockdown policy. 2149 2150 !!!WARNING!!! If you enable this option, you MUST make sure that the 2151 module DOES NOT get stripped after being signed. This includes the 2152 debuginfo strip done by some packagers (such as rpmbuild) and 2153 inclusion into an initramfs that wants the module size reduced. 2154 2155config MODULE_SIG_FORCE 2156 bool "Require modules to be validly signed" 2157 depends on MODULE_SIG 2158 help 2159 Reject unsigned modules or signed modules for which we don't have a 2160 key. Without this, such modules will simply taint the kernel. 2161 2162config MODULE_SIG_ALL 2163 bool "Automatically sign all modules" 2164 default y 2165 depends on MODULE_SIG 2166 help 2167 Sign all modules during make modules_install. Without this option, 2168 modules must be signed manually, using the scripts/sign-file tool. 2169 2170comment "Do not forget to sign required modules with scripts/sign-file" 2171 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2172 2173choice 2174 prompt "Which hash algorithm should modules be signed with?" 2175 depends on MODULE_SIG 2176 help 2177 This determines which sort of hashing algorithm will be used during 2178 signature generation. This algorithm _must_ be built into the kernel 2179 directly so that signature verification can take place. It is not 2180 possible to load a signed module containing the algorithm to check 2181 the signature on that module. 2182 2183config MODULE_SIG_SHA1 2184 bool "Sign modules with SHA-1" 2185 select CRYPTO_SHA1 2186 2187config MODULE_SIG_SHA224 2188 bool "Sign modules with SHA-224" 2189 select CRYPTO_SHA256 2190 2191config MODULE_SIG_SHA256 2192 bool "Sign modules with SHA-256" 2193 select CRYPTO_SHA256 2194 2195config MODULE_SIG_SHA384 2196 bool "Sign modules with SHA-384" 2197 select CRYPTO_SHA512 2198 2199config MODULE_SIG_SHA512 2200 bool "Sign modules with SHA-512" 2201 select CRYPTO_SHA512 2202 2203endchoice 2204 2205config MODULE_SIG_HASH 2206 string 2207 depends on MODULE_SIG 2208 default "sha1" if MODULE_SIG_SHA1 2209 default "sha224" if MODULE_SIG_SHA224 2210 default "sha256" if MODULE_SIG_SHA256 2211 default "sha384" if MODULE_SIG_SHA384 2212 default "sha512" if MODULE_SIG_SHA512 2213 2214config MODULE_COMPRESS 2215 bool "Compress modules on installation" 2216 help 2217 2218 Compresses kernel modules when 'make modules_install' is run; gzip or 2219 xz depending on "Compression algorithm" below. 2220 2221 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 2222 2223 Out-of-tree kernel modules installed using Kbuild will also be 2224 compressed upon installation. 2225 2226 Note: for modules inside an initrd or initramfs, it's more efficient 2227 to compress the whole initrd or initramfs instead. 2228 2229 Note: This is fully compatible with signed modules. 2230 2231 If in doubt, say N. 2232 2233choice 2234 prompt "Compression algorithm" 2235 depends on MODULE_COMPRESS 2236 default MODULE_COMPRESS_GZIP 2237 help 2238 This determines which sort of compression will be used during 2239 'make modules_install'. 2240 2241 GZIP (default) and XZ are supported. 2242 2243config MODULE_COMPRESS_GZIP 2244 bool "GZIP" 2245 2246config MODULE_COMPRESS_XZ 2247 bool "XZ" 2248 2249endchoice 2250 2251config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS 2252 bool "Allow loading of modules with missing namespace imports" 2253 help 2254 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in 2255 a namespace. A module that makes use of a symbol exported with such a 2256 namespace is required to import the namespace via MODULE_IMPORT_NS(). 2257 There is no technical reason to enforce correct namespace imports, 2258 but it creates consistency between symbols defining namespaces and 2259 users importing namespaces they make use of. This option relaxes this 2260 requirement and lifts the enforcement when loading a module. 2261 2262 If unsure, say N. 2263 2264config UNUSED_SYMBOLS 2265 bool "Enable unused/obsolete exported symbols" 2266 default y if X86 2267 help 2268 Unused but exported symbols make the kernel needlessly bigger. For 2269 that reason most of these unused exports will soon be removed. This 2270 option is provided temporarily to provide a transition period in case 2271 some external kernel module needs one of these symbols anyway. If you 2272 encounter such a case in your module, consider if you are actually 2273 using the right API. (rationale: since nobody in the kernel is using 2274 this in a module, there is a pretty good chance it's actually the 2275 wrong interface to use). If you really need the symbol, please send a 2276 mail to the linux kernel mailing list mentioning the symbol and why 2277 you really need it, and what the merge plan to the mainline kernel for 2278 your module is. 2279 2280config TRIM_UNUSED_KSYMS 2281 bool "Trim unused exported kernel symbols" 2282 depends on !UNUSED_SYMBOLS 2283 help 2284 The kernel and some modules make many symbols available for 2285 other modules to use via EXPORT_SYMBOL() and variants. Depending 2286 on the set of modules being selected in your kernel configuration, 2287 many of those exported symbols might never be used. 2288 2289 This option allows for unused exported symbols to be dropped from 2290 the build. In turn, this provides the compiler more opportunities 2291 (especially when using LTO) for optimizing the code and reducing 2292 binary size. This might have some security advantages as well. 2293 2294 If unsure, or if you need to build out-of-tree modules, say N. 2295 2296config UNUSED_KSYMS_WHITELIST 2297 string "Whitelist of symbols to keep in ksymtab" 2298 depends on TRIM_UNUSED_KSYMS 2299 help 2300 By default, all unused exported symbols will be un-exported from the 2301 build when TRIM_UNUSED_KSYMS is selected. 2302 2303 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept 2304 exported at all times, even in absence of in-tree users. The value to 2305 set here is the path to a text file containing the list of symbols, 2306 one per line. The path can be absolute, or relative to the kernel 2307 source tree. 2308 2309endif # MODULES 2310 2311config MODULES_TREE_LOOKUP 2312 def_bool y 2313 depends on PERF_EVENTS || TRACING 2314 2315config INIT_ALL_POSSIBLE 2316 bool 2317 help 2318 Back when each arch used to define their own cpu_online_mask and 2319 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2320 with all 1s, and others with all 0s. When they were centralised, 2321 it was better to provide this option than to break all the archs 2322 and have several arch maintainers pursuing me down dark alleys. 2323 2324source "block/Kconfig" 2325 2326config PREEMPT_NOTIFIERS 2327 bool 2328 2329config PADATA 2330 depends on SMP 2331 bool 2332 2333config ASN1 2334 tristate 2335 help 2336 Build a simple ASN.1 grammar compiler that produces a bytecode output 2337 that can be interpreted by the ASN.1 stream decoder and used to 2338 inform it as to what tags are to be expected in a stream and what 2339 functions to call on what tags. 2340 2341source "kernel/Kconfig.locks" 2342 2343config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 2344 bool 2345 2346config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2347 bool 2348 2349# It may be useful for an architecture to override the definitions of the 2350# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2351# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2352# different calling convention for syscalls. They can also override the 2353# macros for not-implemented syscalls in kernel/sys_ni.c and 2354# kernel/time/posix-stubs.c. All these overrides need to be available in 2355# <asm/syscall_wrapper.h>. 2356config ARCH_HAS_SYSCALL_WRAPPER 2357 def_bool n 2358