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