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_scale_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 select KCMP 1197 default n 1198 help 1199 Enables additional kernel features in a sake of checkpoint/restore. 1200 In particular it adds auxiliary prctl codes to setup process text, 1201 data and heap segment sizes, and a few additional /proc filesystem 1202 entries. 1203 1204 If unsure, say N here. 1205 1206config SCHED_AUTOGROUP 1207 bool "Automatic process group scheduling" 1208 select CGROUPS 1209 select CGROUP_SCHED 1210 select FAIR_GROUP_SCHED 1211 help 1212 This option optimizes the scheduler for common desktop workloads by 1213 automatically creating and populating task groups. This separation 1214 of workloads isolates aggressive CPU burners (like build jobs) from 1215 desktop applications. Task group autogeneration is currently based 1216 upon task session. 1217 1218config SYSFS_DEPRECATED 1219 bool "Enable deprecated sysfs features to support old userspace tools" 1220 depends on SYSFS 1221 default n 1222 help 1223 This option adds code that switches the layout of the "block" class 1224 devices, to not show up in /sys/class/block/, but only in 1225 /sys/block/. 1226 1227 This switch is only active when the sysfs.deprecated=1 boot option is 1228 passed or the SYSFS_DEPRECATED_V2 option is set. 1229 1230 This option allows new kernels to run on old distributions and tools, 1231 which might get confused by /sys/class/block/. Since 2007/2008 all 1232 major distributions and tools handle this just fine. 1233 1234 Recent distributions and userspace tools after 2009/2010 depend on 1235 the existence of /sys/class/block/, and will not work with this 1236 option enabled. 1237 1238 Only if you are using a new kernel on an old distribution, you might 1239 need to say Y here. 1240 1241config SYSFS_DEPRECATED_V2 1242 bool "Enable deprecated sysfs features by default" 1243 default n 1244 depends on SYSFS 1245 depends on SYSFS_DEPRECATED 1246 help 1247 Enable deprecated sysfs by default. 1248 1249 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1250 option. 1251 1252 Only if you are using a new kernel on an old distribution, you might 1253 need to say Y here. Even then, odds are you would not need it 1254 enabled, you can always pass the boot option if absolutely necessary. 1255 1256config RELAY 1257 bool "Kernel->user space relay support (formerly relayfs)" 1258 select IRQ_WORK 1259 help 1260 This option enables support for relay interface support in 1261 certain file systems (such as debugfs). 1262 It is designed to provide an efficient mechanism for tools and 1263 facilities to relay large amounts of data from kernel space to 1264 user space. 1265 1266 If unsure, say N. 1267 1268config BLK_DEV_INITRD 1269 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1270 help 1271 The initial RAM filesystem is a ramfs which is loaded by the 1272 boot loader (loadlin or lilo) and that is mounted as root 1273 before the normal boot procedure. It is typically used to 1274 load modules needed to mount the "real" root file system, 1275 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1276 1277 If RAM disk support (BLK_DEV_RAM) is also included, this 1278 also enables initial RAM disk (initrd) support and adds 1279 15 Kbytes (more on some other architectures) to the kernel size. 1280 1281 If unsure say Y. 1282 1283if BLK_DEV_INITRD 1284 1285source "usr/Kconfig" 1286 1287endif 1288 1289config BOOT_CONFIG 1290 bool "Boot config support" 1291 select BLK_DEV_INITRD 1292 help 1293 Extra boot config allows system admin to pass a config file as 1294 complemental extension of kernel cmdline when booting. 1295 The boot config file must be attached at the end of initramfs 1296 with checksum, size and magic word. 1297 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1298 1299 If unsure, say Y. 1300 1301choice 1302 prompt "Compiler optimization level" 1303 default CC_OPTIMIZE_FOR_PERFORMANCE 1304 1305config CC_OPTIMIZE_FOR_PERFORMANCE 1306 bool "Optimize for performance (-O2)" 1307 help 1308 This is the default optimization level for the kernel, building 1309 with the "-O2" compiler flag for best performance and most 1310 helpful compile-time warnings. 1311 1312config CC_OPTIMIZE_FOR_PERFORMANCE_O3 1313 bool "Optimize more for performance (-O3)" 1314 depends on ARC 1315 help 1316 Choosing this option will pass "-O3" to your compiler to optimize 1317 the kernel yet more for performance. 1318 1319config CC_OPTIMIZE_FOR_SIZE 1320 bool "Optimize for size (-Os)" 1321 help 1322 Choosing this option will pass "-Os" to your compiler resulting 1323 in a smaller kernel. 1324 1325endchoice 1326 1327config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1328 bool 1329 help 1330 This requires that the arch annotates or otherwise protects 1331 its external entry points from being discarded. Linker scripts 1332 must also merge .text.*, .data.*, and .bss.* correctly into 1333 output sections. Care must be taken not to pull in unrelated 1334 sections (e.g., '.text.init'). Typically '.' in section names 1335 is used to distinguish them from label names / C identifiers. 1336 1337config LD_DEAD_CODE_DATA_ELIMINATION 1338 bool "Dead code and data elimination (EXPERIMENTAL)" 1339 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1340 depends on EXPERT 1341 depends on $(cc-option,-ffunction-sections -fdata-sections) 1342 depends on $(ld-option,--gc-sections) 1343 help 1344 Enable this if you want to do dead code and data elimination with 1345 the linker by compiling with -ffunction-sections -fdata-sections, 1346 and linking with --gc-sections. 1347 1348 This can reduce on disk and in-memory size of the kernel 1349 code and static data, particularly for small configs and 1350 on small systems. This has the possibility of introducing 1351 silently broken kernel if the required annotations are not 1352 present. This option is not well tested yet, so use at your 1353 own risk. 1354 1355config LD_ORPHAN_WARN 1356 def_bool y 1357 depends on ARCH_WANT_LD_ORPHAN_WARN 1358 depends on !LD_IS_LLD || LLD_VERSION >= 110000 1359 depends on $(ld-option,--orphan-handling=warn) 1360 1361config SYSCTL 1362 bool 1363 1364config HAVE_UID16 1365 bool 1366 1367config SYSCTL_EXCEPTION_TRACE 1368 bool 1369 help 1370 Enable support for /proc/sys/debug/exception-trace. 1371 1372config SYSCTL_ARCH_UNALIGN_NO_WARN 1373 bool 1374 help 1375 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1376 Allows arch to define/use @no_unaligned_warning to possibly warn 1377 about unaligned access emulation going on under the hood. 1378 1379config SYSCTL_ARCH_UNALIGN_ALLOW 1380 bool 1381 help 1382 Enable support for /proc/sys/kernel/unaligned-trap 1383 Allows arches to define/use @unaligned_enabled to runtime toggle 1384 the unaligned access emulation. 1385 see arch/parisc/kernel/unaligned.c for reference 1386 1387config HAVE_PCSPKR_PLATFORM 1388 bool 1389 1390# interpreter that classic socket filters depend on 1391config BPF 1392 bool 1393 1394menuconfig EXPERT 1395 bool "Configure standard kernel features (expert users)" 1396 # Unhide debug options, to make the on-by-default options visible 1397 select DEBUG_KERNEL 1398 help 1399 This option allows certain base kernel options and settings 1400 to be disabled or tweaked. This is for specialized 1401 environments which can tolerate a "non-standard" kernel. 1402 Only use this if you really know what you are doing. 1403 1404config UID16 1405 bool "Enable 16-bit UID system calls" if EXPERT 1406 depends on HAVE_UID16 && MULTIUSER 1407 default y 1408 help 1409 This enables the legacy 16-bit UID syscall wrappers. 1410 1411config MULTIUSER 1412 bool "Multiple users, groups and capabilities support" if EXPERT 1413 default y 1414 help 1415 This option enables support for non-root users, groups and 1416 capabilities. 1417 1418 If you say N here, all processes will run with UID 0, GID 0, and all 1419 possible capabilities. Saying N here also compiles out support for 1420 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1421 setgid, and capset. 1422 1423 If unsure, say Y here. 1424 1425config SGETMASK_SYSCALL 1426 bool "sgetmask/ssetmask syscalls support" if EXPERT 1427 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1428 help 1429 sys_sgetmask and sys_ssetmask are obsolete system calls 1430 no longer supported in libc but still enabled by default in some 1431 architectures. 1432 1433 If unsure, leave the default option here. 1434 1435config SYSFS_SYSCALL 1436 bool "Sysfs syscall support" if EXPERT 1437 default y 1438 help 1439 sys_sysfs is an obsolete system call no longer supported in libc. 1440 Note that disabling this option is more secure but might break 1441 compatibility with some systems. 1442 1443 If unsure say Y here. 1444 1445config FHANDLE 1446 bool "open by fhandle syscalls" if EXPERT 1447 select EXPORTFS 1448 default y 1449 help 1450 If you say Y here, a user level program will be able to map 1451 file names to handle and then later use the handle for 1452 different file system operations. This is useful in implementing 1453 userspace file servers, which now track files using handles instead 1454 of names. The handle would remain the same even if file names 1455 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1456 syscalls. 1457 1458config POSIX_TIMERS 1459 bool "Posix Clocks & timers" if EXPERT 1460 default y 1461 help 1462 This includes native support for POSIX timers to the kernel. 1463 Some embedded systems have no use for them and therefore they 1464 can be configured out to reduce the size of the kernel image. 1465 1466 When this option is disabled, the following syscalls won't be 1467 available: timer_create, timer_gettime: timer_getoverrun, 1468 timer_settime, timer_delete, clock_adjtime, getitimer, 1469 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1470 clock_getres and clock_nanosleep syscalls will be limited to 1471 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1472 1473 If unsure say y. 1474 1475config PRINTK 1476 default y 1477 bool "Enable support for printk" if EXPERT 1478 select IRQ_WORK 1479 help 1480 This option enables normal printk support. Removing it 1481 eliminates most of the message strings from the kernel image 1482 and makes the kernel more or less silent. As this makes it 1483 very difficult to diagnose system problems, saying N here is 1484 strongly discouraged. 1485 1486config PRINTK_NMI 1487 def_bool y 1488 depends on PRINTK 1489 depends on HAVE_NMI 1490 1491config BUG 1492 bool "BUG() support" if EXPERT 1493 default y 1494 help 1495 Disabling this option eliminates support for BUG and WARN, reducing 1496 the size of your kernel image and potentially quietly ignoring 1497 numerous fatal conditions. You should only consider disabling this 1498 option for embedded systems with no facilities for reporting errors. 1499 Just say Y. 1500 1501config ELF_CORE 1502 depends on COREDUMP 1503 default y 1504 bool "Enable ELF core dumps" if EXPERT 1505 help 1506 Enable support for generating core dumps. Disabling saves about 4k. 1507 1508 1509config PCSPKR_PLATFORM 1510 bool "Enable PC-Speaker support" if EXPERT 1511 depends on HAVE_PCSPKR_PLATFORM 1512 select I8253_LOCK 1513 default y 1514 help 1515 This option allows to disable the internal PC-Speaker 1516 support, saving some memory. 1517 1518config BASE_FULL 1519 default y 1520 bool "Enable full-sized data structures for core" if EXPERT 1521 help 1522 Disabling this option reduces the size of miscellaneous core 1523 kernel data structures. This saves memory on small machines, 1524 but may reduce performance. 1525 1526config FUTEX 1527 bool "Enable futex support" if EXPERT 1528 default y 1529 imply RT_MUTEXES 1530 help 1531 Disabling this option will cause the kernel to be built without 1532 support for "fast userspace mutexes". The resulting kernel may not 1533 run glibc-based applications correctly. 1534 1535config FUTEX_PI 1536 bool 1537 depends on FUTEX && RT_MUTEXES 1538 default y 1539 1540config HAVE_FUTEX_CMPXCHG 1541 bool 1542 depends on FUTEX 1543 help 1544 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1545 is implemented and always working. This removes a couple of runtime 1546 checks. 1547 1548config EPOLL 1549 bool "Enable eventpoll support" if EXPERT 1550 default y 1551 help 1552 Disabling this option will cause the kernel to be built without 1553 support for epoll family of system calls. 1554 1555config SIGNALFD 1556 bool "Enable signalfd() system call" if EXPERT 1557 default y 1558 help 1559 Enable the signalfd() system call that allows to receive signals 1560 on a file descriptor. 1561 1562 If unsure, say Y. 1563 1564config TIMERFD 1565 bool "Enable timerfd() system call" if EXPERT 1566 default y 1567 help 1568 Enable the timerfd() system call that allows to receive timer 1569 events on a file descriptor. 1570 1571 If unsure, say Y. 1572 1573config EVENTFD 1574 bool "Enable eventfd() system call" if EXPERT 1575 default y 1576 help 1577 Enable the eventfd() system call that allows to receive both 1578 kernel notification (ie. KAIO) or userspace notifications. 1579 1580 If unsure, say Y. 1581 1582config SHMEM 1583 bool "Use full shmem filesystem" if EXPERT 1584 default y 1585 depends on MMU 1586 help 1587 The shmem is an internal filesystem used to manage shared memory. 1588 It is backed by swap and manages resource limits. It is also exported 1589 to userspace as tmpfs if TMPFS is enabled. Disabling this 1590 option replaces shmem and tmpfs with the much simpler ramfs code, 1591 which may be appropriate on small systems without swap. 1592 1593config AIO 1594 bool "Enable AIO support" if EXPERT 1595 default y 1596 help 1597 This option enables POSIX asynchronous I/O which may by used 1598 by some high performance threaded applications. Disabling 1599 this option saves about 7k. 1600 1601config IO_URING 1602 bool "Enable IO uring support" if EXPERT 1603 select IO_WQ 1604 default y 1605 help 1606 This option enables support for the io_uring interface, enabling 1607 applications to submit and complete IO through submission and 1608 completion rings that are shared between the kernel and application. 1609 1610config ADVISE_SYSCALLS 1611 bool "Enable madvise/fadvise syscalls" if EXPERT 1612 default y 1613 help 1614 This option enables the madvise and fadvise syscalls, used by 1615 applications to advise the kernel about their future memory or file 1616 usage, improving performance. If building an embedded system where no 1617 applications use these syscalls, you can disable this option to save 1618 space. 1619 1620config HAVE_ARCH_USERFAULTFD_WP 1621 bool 1622 help 1623 Arch has userfaultfd write protection support 1624 1625config MEMBARRIER 1626 bool "Enable membarrier() system call" if EXPERT 1627 default y 1628 help 1629 Enable the membarrier() system call that allows issuing memory 1630 barriers across all running threads, which can be used to distribute 1631 the cost of user-space memory barriers asymmetrically by transforming 1632 pairs of memory barriers into pairs consisting of membarrier() and a 1633 compiler barrier. 1634 1635 If unsure, say Y. 1636 1637config KALLSYMS 1638 bool "Load all symbols for debugging/ksymoops" if EXPERT 1639 default y 1640 help 1641 Say Y here to let the kernel print out symbolic crash information and 1642 symbolic stack backtraces. This increases the size of the kernel 1643 somewhat, as all symbols have to be loaded into the kernel image. 1644 1645config KALLSYMS_ALL 1646 bool "Include all symbols in kallsyms" 1647 depends on DEBUG_KERNEL && KALLSYMS 1648 help 1649 Normally kallsyms only contains the symbols of functions for nicer 1650 OOPS messages and backtraces (i.e., symbols from the text and inittext 1651 sections). This is sufficient for most cases. And only in very rare 1652 cases (e.g., when a debugger is used) all symbols are required (e.g., 1653 names of variables from the data sections, etc). 1654 1655 This option makes sure that all symbols are loaded into the kernel 1656 image (i.e., symbols from all sections) in cost of increased kernel 1657 size (depending on the kernel configuration, it may be 300KiB or 1658 something like this). 1659 1660 Say N unless you really need all symbols. 1661 1662config KALLSYMS_ABSOLUTE_PERCPU 1663 bool 1664 depends on KALLSYMS 1665 default X86_64 && SMP 1666 1667config KALLSYMS_BASE_RELATIVE 1668 bool 1669 depends on KALLSYMS 1670 default !IA64 1671 help 1672 Instead of emitting them as absolute values in the native word size, 1673 emit the symbol references in the kallsyms table as 32-bit entries, 1674 each containing a relative value in the range [base, base + U32_MAX] 1675 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1676 an absolute value in the range [0, S32_MAX] or a relative value in the 1677 range [base, base + S32_MAX], where base is the lowest relative symbol 1678 address encountered in the image. 1679 1680 On 64-bit builds, this reduces the size of the address table by 50%, 1681 but more importantly, it results in entries whose values are build 1682 time constants, and no relocation pass is required at runtime to fix 1683 up the entries based on the runtime load address of the kernel. 1684 1685# end of the "standard kernel features (expert users)" menu 1686 1687# syscall, maps, verifier 1688 1689config BPF_LSM 1690 bool "LSM Instrumentation with BPF" 1691 depends on BPF_EVENTS 1692 depends on BPF_SYSCALL 1693 depends on SECURITY 1694 depends on BPF_JIT 1695 help 1696 Enables instrumentation of the security hooks with eBPF programs for 1697 implementing dynamic MAC and Audit Policies. 1698 1699 If you are unsure how to answer this question, answer N. 1700 1701config BPF_SYSCALL 1702 bool "Enable bpf() system call" 1703 select BPF 1704 select IRQ_WORK 1705 select TASKS_TRACE_RCU 1706 default n 1707 help 1708 Enable the bpf() system call that allows to manipulate eBPF 1709 programs and maps via file descriptors. 1710 1711config ARCH_WANT_DEFAULT_BPF_JIT 1712 bool 1713 1714config BPF_JIT_ALWAYS_ON 1715 bool "Permanently enable BPF JIT and remove BPF interpreter" 1716 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1717 help 1718 Enables BPF JIT and removes BPF interpreter to avoid 1719 speculative execution of BPF instructions by the interpreter 1720 1721config BPF_JIT_DEFAULT_ON 1722 def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON 1723 depends on HAVE_EBPF_JIT && BPF_JIT 1724 1725source "kernel/bpf/preload/Kconfig" 1726 1727config USERFAULTFD 1728 bool "Enable userfaultfd() system call" 1729 depends on MMU 1730 help 1731 Enable the userfaultfd() system call that allows to intercept and 1732 handle page faults in userland. 1733 1734config ARCH_HAS_MEMBARRIER_CALLBACKS 1735 bool 1736 1737config ARCH_HAS_MEMBARRIER_SYNC_CORE 1738 bool 1739 1740config KCMP 1741 bool "Enable kcmp() system call" if EXPERT 1742 help 1743 Enable the kernel resource comparison system call. It provides 1744 user-space with the ability to compare two processes to see if they 1745 share a common resource, such as a file descriptor or even virtual 1746 memory space. 1747 1748 If unsure, say N. 1749 1750config RSEQ 1751 bool "Enable rseq() system call" if EXPERT 1752 default y 1753 depends on HAVE_RSEQ 1754 select MEMBARRIER 1755 help 1756 Enable the restartable sequences system call. It provides a 1757 user-space cache for the current CPU number value, which 1758 speeds up getting the current CPU number from user-space, 1759 as well as an ABI to speed up user-space operations on 1760 per-CPU data. 1761 1762 If unsure, say Y. 1763 1764config DEBUG_RSEQ 1765 default n 1766 bool "Enabled debugging of rseq() system call" if EXPERT 1767 depends on RSEQ && DEBUG_KERNEL 1768 help 1769 Enable extra debugging checks for the rseq system call. 1770 1771 If unsure, say N. 1772 1773config EMBEDDED 1774 bool "Embedded system" 1775 option allnoconfig_y 1776 select EXPERT 1777 help 1778 This option should be enabled if compiling the kernel for 1779 an embedded system so certain expert options are available 1780 for configuration. 1781 1782config HAVE_PERF_EVENTS 1783 bool 1784 help 1785 See tools/perf/design.txt for details. 1786 1787config PERF_USE_VMALLOC 1788 bool 1789 help 1790 See tools/perf/design.txt for details 1791 1792config PC104 1793 bool "PC/104 support" if EXPERT 1794 help 1795 Expose PC/104 form factor device drivers and options available for 1796 selection and configuration. Enable this option if your target 1797 machine has a PC/104 bus. 1798 1799menu "Kernel Performance Events And Counters" 1800 1801config PERF_EVENTS 1802 bool "Kernel performance events and counters" 1803 default y if PROFILING 1804 depends on HAVE_PERF_EVENTS 1805 select IRQ_WORK 1806 select SRCU 1807 help 1808 Enable kernel support for various performance events provided 1809 by software and hardware. 1810 1811 Software events are supported either built-in or via the 1812 use of generic tracepoints. 1813 1814 Most modern CPUs support performance events via performance 1815 counter registers. These registers count the number of certain 1816 types of hw events: such as instructions executed, cachemisses 1817 suffered, or branches mis-predicted - without slowing down the 1818 kernel or applications. These registers can also trigger interrupts 1819 when a threshold number of events have passed - and can thus be 1820 used to profile the code that runs on that CPU. 1821 1822 The Linux Performance Event subsystem provides an abstraction of 1823 these software and hardware event capabilities, available via a 1824 system call and used by the "perf" utility in tools/perf/. It 1825 provides per task and per CPU counters, and it provides event 1826 capabilities on top of those. 1827 1828 Say Y if unsure. 1829 1830config DEBUG_PERF_USE_VMALLOC 1831 default n 1832 bool "Debug: use vmalloc to back perf mmap() buffers" 1833 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1834 select PERF_USE_VMALLOC 1835 help 1836 Use vmalloc memory to back perf mmap() buffers. 1837 1838 Mostly useful for debugging the vmalloc code on platforms 1839 that don't require it. 1840 1841 Say N if unsure. 1842 1843endmenu 1844 1845config VM_EVENT_COUNTERS 1846 default y 1847 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1848 help 1849 VM event counters are needed for event counts to be shown. 1850 This option allows the disabling of the VM event counters 1851 on EXPERT systems. /proc/vmstat will only show page counts 1852 if VM event counters are disabled. 1853 1854config SLUB_DEBUG 1855 default y 1856 bool "Enable SLUB debugging support" if EXPERT 1857 depends on SLUB && SYSFS 1858 help 1859 SLUB has extensive debug support features. Disabling these can 1860 result in significant savings in code size. This also disables 1861 SLUB sysfs support. /sys/slab will not exist and there will be 1862 no support for cache validation etc. 1863 1864config SLUB_MEMCG_SYSFS_ON 1865 default n 1866 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1867 depends on SLUB && SYSFS && MEMCG 1868 help 1869 SLUB creates a directory under /sys/kernel/slab for each 1870 allocation cache to host info and debug files. If memory 1871 cgroup is enabled, each cache can have per memory cgroup 1872 caches. SLUB can create the same sysfs directories for these 1873 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1874 to a very high number of debug files being created. This is 1875 controlled by slub_memcg_sysfs boot parameter and this 1876 config option determines the parameter's default value. 1877 1878config COMPAT_BRK 1879 bool "Disable heap randomization" 1880 default y 1881 help 1882 Randomizing heap placement makes heap exploits harder, but it 1883 also breaks ancient binaries (including anything libc5 based). 1884 This option changes the bootup default to heap randomization 1885 disabled, and can be overridden at runtime by setting 1886 /proc/sys/kernel/randomize_va_space to 2. 1887 1888 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1889 1890choice 1891 prompt "Choose SLAB allocator" 1892 default SLUB 1893 help 1894 This option allows to select a slab allocator. 1895 1896config SLAB 1897 bool "SLAB" 1898 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1899 help 1900 The regular slab allocator that is established and known to work 1901 well in all environments. It organizes cache hot objects in 1902 per cpu and per node queues. 1903 1904config SLUB 1905 bool "SLUB (Unqueued Allocator)" 1906 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1907 help 1908 SLUB is a slab allocator that minimizes cache line usage 1909 instead of managing queues of cached objects (SLAB approach). 1910 Per cpu caching is realized using slabs of objects instead 1911 of queues of objects. SLUB can use memory efficiently 1912 and has enhanced diagnostics. SLUB is the default choice for 1913 a slab allocator. 1914 1915config SLOB 1916 depends on EXPERT 1917 bool "SLOB (Simple Allocator)" 1918 help 1919 SLOB replaces the stock allocator with a drastically simpler 1920 allocator. SLOB is generally more space efficient but 1921 does not perform as well on large systems. 1922 1923endchoice 1924 1925config SLAB_MERGE_DEFAULT 1926 bool "Allow slab caches to be merged" 1927 default y 1928 help 1929 For reduced kernel memory fragmentation, slab caches can be 1930 merged when they share the same size and other characteristics. 1931 This carries a risk of kernel heap overflows being able to 1932 overwrite objects from merged caches (and more easily control 1933 cache layout), which makes such heap attacks easier to exploit 1934 by attackers. By keeping caches unmerged, these kinds of exploits 1935 can usually only damage objects in the same cache. To disable 1936 merging at runtime, "slab_nomerge" can be passed on the kernel 1937 command line. 1938 1939config SLAB_FREELIST_RANDOM 1940 bool "Randomize slab freelist" 1941 depends on SLAB || SLUB 1942 help 1943 Randomizes the freelist order used on creating new pages. This 1944 security feature reduces the predictability of the kernel slab 1945 allocator against heap overflows. 1946 1947config SLAB_FREELIST_HARDENED 1948 bool "Harden slab freelist metadata" 1949 depends on SLAB || SLUB 1950 help 1951 Many kernel heap attacks try to target slab cache metadata and 1952 other infrastructure. This options makes minor performance 1953 sacrifices to harden the kernel slab allocator against common 1954 freelist exploit methods. Some slab implementations have more 1955 sanity-checking than others. This option is most effective with 1956 CONFIG_SLUB. 1957 1958config SHUFFLE_PAGE_ALLOCATOR 1959 bool "Page allocator randomization" 1960 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1961 help 1962 Randomization of the page allocator improves the average 1963 utilization of a direct-mapped memory-side-cache. See section 1964 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1965 6.2a specification for an example of how a platform advertises 1966 the presence of a memory-side-cache. There are also incidental 1967 security benefits as it reduces the predictability of page 1968 allocations to compliment SLAB_FREELIST_RANDOM, but the 1969 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1970 10th order of pages is selected based on cache utilization 1971 benefits on x86. 1972 1973 While the randomization improves cache utilization it may 1974 negatively impact workloads on platforms without a cache. For 1975 this reason, by default, the randomization is enabled only 1976 after runtime detection of a direct-mapped memory-side-cache. 1977 Otherwise, the randomization may be force enabled with the 1978 'page_alloc.shuffle' kernel command line parameter. 1979 1980 Say Y if unsure. 1981 1982config SLUB_CPU_PARTIAL 1983 default y 1984 depends on SLUB && SMP 1985 bool "SLUB per cpu partial cache" 1986 help 1987 Per cpu partial caches accelerate objects allocation and freeing 1988 that is local to a processor at the price of more indeterminism 1989 in the latency of the free. On overflow these caches will be cleared 1990 which requires the taking of locks that may cause latency spikes. 1991 Typically one would choose no for a realtime system. 1992 1993config MMAP_ALLOW_UNINITIALIZED 1994 bool "Allow mmapped anonymous memory to be uninitialized" 1995 depends on EXPERT && !MMU 1996 default n 1997 help 1998 Normally, and according to the Linux spec, anonymous memory obtained 1999 from mmap() has its contents cleared before it is passed to 2000 userspace. Enabling this config option allows you to request that 2001 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 2002 providing a huge performance boost. If this option is not enabled, 2003 then the flag will be ignored. 2004 2005 This is taken advantage of by uClibc's malloc(), and also by 2006 ELF-FDPIC binfmt's brk and stack allocator. 2007 2008 Because of the obvious security issues, this option should only be 2009 enabled on embedded devices where you control what is run in 2010 userspace. Since that isn't generally a problem on no-MMU systems, 2011 it is normally safe to say Y here. 2012 2013 See Documentation/admin-guide/mm/nommu-mmap.rst for more information. 2014 2015config SYSTEM_DATA_VERIFICATION 2016 def_bool n 2017 select SYSTEM_TRUSTED_KEYRING 2018 select KEYS 2019 select CRYPTO 2020 select CRYPTO_RSA 2021 select ASYMMETRIC_KEY_TYPE 2022 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 2023 select ASN1 2024 select OID_REGISTRY 2025 select X509_CERTIFICATE_PARSER 2026 select PKCS7_MESSAGE_PARSER 2027 help 2028 Provide PKCS#7 message verification using the contents of the system 2029 trusted keyring to provide public keys. This then can be used for 2030 module verification, kexec image verification and firmware blob 2031 verification. 2032 2033config PROFILING 2034 bool "Profiling support" 2035 help 2036 Say Y here to enable the extended profiling support mechanisms used 2037 by profilers. 2038 2039# 2040# Place an empty function call at each tracepoint site. Can be 2041# dynamically changed for a probe function. 2042# 2043config TRACEPOINTS 2044 bool 2045 2046endmenu # General setup 2047 2048source "arch/Kconfig" 2049 2050config RT_MUTEXES 2051 bool 2052 2053config BASE_SMALL 2054 int 2055 default 0 if BASE_FULL 2056 default 1 if !BASE_FULL 2057 2058config MODULE_SIG_FORMAT 2059 def_bool n 2060 select SYSTEM_DATA_VERIFICATION 2061 2062menuconfig MODULES 2063 bool "Enable loadable module support" 2064 option modules 2065 help 2066 Kernel modules are small pieces of compiled code which can 2067 be inserted in the running kernel, rather than being 2068 permanently built into the kernel. You use the "modprobe" 2069 tool to add (and sometimes remove) them. If you say Y here, 2070 many parts of the kernel can be built as modules (by 2071 answering M instead of Y where indicated): this is most 2072 useful for infrequently used options which are not required 2073 for booting. For more information, see the man pages for 2074 modprobe, lsmod, modinfo, insmod and rmmod. 2075 2076 If you say Y here, you will need to run "make 2077 modules_install" to put the modules under /lib/modules/ 2078 where modprobe can find them (you may need to be root to do 2079 this). 2080 2081 If unsure, say Y. 2082 2083if MODULES 2084 2085config MODULE_FORCE_LOAD 2086 bool "Forced module loading" 2087 default n 2088 help 2089 Allow loading of modules without version information (ie. modprobe 2090 --force). Forced module loading sets the 'F' (forced) taint flag and 2091 is usually a really bad idea. 2092 2093config MODULE_UNLOAD 2094 bool "Module unloading" 2095 help 2096 Without this option you will not be able to unload any 2097 modules (note that some modules may not be unloadable 2098 anyway), which makes your kernel smaller, faster 2099 and simpler. If unsure, say Y. 2100 2101config MODULE_FORCE_UNLOAD 2102 bool "Forced module unloading" 2103 depends on MODULE_UNLOAD 2104 help 2105 This option allows you to force a module to unload, even if the 2106 kernel believes it is unsafe: the kernel will remove the module 2107 without waiting for anyone to stop using it (using the -f option to 2108 rmmod). This is mainly for kernel developers and desperate users. 2109 If unsure, say N. 2110 2111config MODVERSIONS 2112 bool "Module versioning support" 2113 help 2114 Usually, you have to use modules compiled with your kernel. 2115 Saying Y here makes it sometimes possible to use modules 2116 compiled for different kernels, by adding enough information 2117 to the modules to (hopefully) spot any changes which would 2118 make them incompatible with the kernel you are running. If 2119 unsure, say N. 2120 2121config ASM_MODVERSIONS 2122 bool 2123 default HAVE_ASM_MODVERSIONS && MODVERSIONS 2124 help 2125 This enables module versioning for exported symbols also from 2126 assembly. This can be enabled only when the target architecture 2127 supports it. 2128 2129config MODULE_REL_CRCS 2130 bool 2131 depends on MODVERSIONS 2132 2133config MODULE_SRCVERSION_ALL 2134 bool "Source checksum for all modules" 2135 help 2136 Modules which contain a MODULE_VERSION get an extra "srcversion" 2137 field inserted into their modinfo section, which contains a 2138 sum of the source files which made it. This helps maintainers 2139 see exactly which source was used to build a module (since 2140 others sometimes change the module source without updating 2141 the version). With this option, such a "srcversion" field 2142 will be created for all modules. If unsure, say N. 2143 2144config MODULE_SIG 2145 bool "Module signature verification" 2146 select MODULE_SIG_FORMAT 2147 help 2148 Check modules for valid signatures upon load: the signature 2149 is simply appended to the module. For more information see 2150 <file:Documentation/admin-guide/module-signing.rst>. 2151 2152 Note that this option adds the OpenSSL development packages as a 2153 kernel build dependency so that the signing tool can use its crypto 2154 library. 2155 2156 You should enable this option if you wish to use either 2157 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via 2158 another LSM - otherwise unsigned modules will be loadable regardless 2159 of the lockdown policy. 2160 2161 !!!WARNING!!! If you enable this option, you MUST make sure that the 2162 module DOES NOT get stripped after being signed. This includes the 2163 debuginfo strip done by some packagers (such as rpmbuild) and 2164 inclusion into an initramfs that wants the module size reduced. 2165 2166config MODULE_SIG_FORCE 2167 bool "Require modules to be validly signed" 2168 depends on MODULE_SIG 2169 help 2170 Reject unsigned modules or signed modules for which we don't have a 2171 key. Without this, such modules will simply taint the kernel. 2172 2173config MODULE_SIG_ALL 2174 bool "Automatically sign all modules" 2175 default y 2176 depends on MODULE_SIG 2177 help 2178 Sign all modules during make modules_install. Without this option, 2179 modules must be signed manually, using the scripts/sign-file tool. 2180 2181comment "Do not forget to sign required modules with scripts/sign-file" 2182 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2183 2184choice 2185 prompt "Which hash algorithm should modules be signed with?" 2186 depends on MODULE_SIG 2187 help 2188 This determines which sort of hashing algorithm will be used during 2189 signature generation. This algorithm _must_ be built into the kernel 2190 directly so that signature verification can take place. It is not 2191 possible to load a signed module containing the algorithm to check 2192 the signature on that module. 2193 2194config MODULE_SIG_SHA1 2195 bool "Sign modules with SHA-1" 2196 select CRYPTO_SHA1 2197 2198config MODULE_SIG_SHA224 2199 bool "Sign modules with SHA-224" 2200 select CRYPTO_SHA256 2201 2202config MODULE_SIG_SHA256 2203 bool "Sign modules with SHA-256" 2204 select CRYPTO_SHA256 2205 2206config MODULE_SIG_SHA384 2207 bool "Sign modules with SHA-384" 2208 select CRYPTO_SHA512 2209 2210config MODULE_SIG_SHA512 2211 bool "Sign modules with SHA-512" 2212 select CRYPTO_SHA512 2213 2214endchoice 2215 2216config MODULE_SIG_HASH 2217 string 2218 depends on MODULE_SIG 2219 default "sha1" if MODULE_SIG_SHA1 2220 default "sha224" if MODULE_SIG_SHA224 2221 default "sha256" if MODULE_SIG_SHA256 2222 default "sha384" if MODULE_SIG_SHA384 2223 default "sha512" if MODULE_SIG_SHA512 2224 2225config MODULE_COMPRESS 2226 bool "Compress modules on installation" 2227 help 2228 2229 Compresses kernel modules when 'make modules_install' is run; gzip or 2230 xz depending on "Compression algorithm" below. 2231 2232 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 2233 2234 Out-of-tree kernel modules installed using Kbuild will also be 2235 compressed upon installation. 2236 2237 Note: for modules inside an initrd or initramfs, it's more efficient 2238 to compress the whole initrd or initramfs instead. 2239 2240 Note: This is fully compatible with signed modules. 2241 2242 If in doubt, say N. 2243 2244choice 2245 prompt "Compression algorithm" 2246 depends on MODULE_COMPRESS 2247 default MODULE_COMPRESS_GZIP 2248 help 2249 This determines which sort of compression will be used during 2250 'make modules_install'. 2251 2252 GZIP (default) and XZ are supported. 2253 2254config MODULE_COMPRESS_GZIP 2255 bool "GZIP" 2256 2257config MODULE_COMPRESS_XZ 2258 bool "XZ" 2259 2260endchoice 2261 2262config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS 2263 bool "Allow loading of modules with missing namespace imports" 2264 help 2265 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in 2266 a namespace. A module that makes use of a symbol exported with such a 2267 namespace is required to import the namespace via MODULE_IMPORT_NS(). 2268 There is no technical reason to enforce correct namespace imports, 2269 but it creates consistency between symbols defining namespaces and 2270 users importing namespaces they make use of. This option relaxes this 2271 requirement and lifts the enforcement when loading a module. 2272 2273 If unsure, say N. 2274 2275config UNUSED_SYMBOLS 2276 bool "Enable unused/obsolete exported symbols" 2277 default y if X86 2278 help 2279 Unused but exported symbols make the kernel needlessly bigger. For 2280 that reason most of these unused exports will soon be removed. This 2281 option is provided temporarily to provide a transition period in case 2282 some external kernel module needs one of these symbols anyway. If you 2283 encounter such a case in your module, consider if you are actually 2284 using the right API. (rationale: since nobody in the kernel is using 2285 this in a module, there is a pretty good chance it's actually the 2286 wrong interface to use). If you really need the symbol, please send a 2287 mail to the linux kernel mailing list mentioning the symbol and why 2288 you really need it, and what the merge plan to the mainline kernel for 2289 your module is. 2290 2291config TRIM_UNUSED_KSYMS 2292 bool "Trim unused exported kernel symbols" 2293 depends on !UNUSED_SYMBOLS 2294 help 2295 The kernel and some modules make many symbols available for 2296 other modules to use via EXPORT_SYMBOL() and variants. Depending 2297 on the set of modules being selected in your kernel configuration, 2298 many of those exported symbols might never be used. 2299 2300 This option allows for unused exported symbols to be dropped from 2301 the build. In turn, this provides the compiler more opportunities 2302 (especially when using LTO) for optimizing the code and reducing 2303 binary size. This might have some security advantages as well. 2304 2305 If unsure, or if you need to build out-of-tree modules, say N. 2306 2307config UNUSED_KSYMS_WHITELIST 2308 string "Whitelist of symbols to keep in ksymtab" 2309 depends on TRIM_UNUSED_KSYMS 2310 help 2311 By default, all unused exported symbols will be un-exported from the 2312 build when TRIM_UNUSED_KSYMS is selected. 2313 2314 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept 2315 exported at all times, even in absence of in-tree users. The value to 2316 set here is the path to a text file containing the list of symbols, 2317 one per line. The path can be absolute, or relative to the kernel 2318 source tree. 2319 2320endif # MODULES 2321 2322config MODULES_TREE_LOOKUP 2323 def_bool y 2324 depends on PERF_EVENTS || TRACING 2325 2326config INIT_ALL_POSSIBLE 2327 bool 2328 help 2329 Back when each arch used to define their own cpu_online_mask and 2330 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2331 with all 1s, and others with all 0s. When they were centralised, 2332 it was better to provide this option than to break all the archs 2333 and have several arch maintainers pursuing me down dark alleys. 2334 2335source "block/Kconfig" 2336 2337config PREEMPT_NOTIFIERS 2338 bool 2339 2340config PADATA 2341 depends on SMP 2342 bool 2343 2344config ASN1 2345 tristate 2346 help 2347 Build a simple ASN.1 grammar compiler that produces a bytecode output 2348 that can be interpreted by the ASN.1 stream decoder and used to 2349 inform it as to what tags are to be expected in a stream and what 2350 functions to call on what tags. 2351 2352source "kernel/Kconfig.locks" 2353 2354config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 2355 bool 2356 2357config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2358 bool 2359 2360# It may be useful for an architecture to override the definitions of the 2361# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2362# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2363# different calling convention for syscalls. They can also override the 2364# macros for not-implemented syscalls in kernel/sys_ni.c and 2365# kernel/time/posix-stubs.c. All these overrides need to be available in 2366# <asm/syscall_wrapper.h>. 2367config ARCH_HAS_SYSCALL_WRAPPER 2368 def_bool n 2369