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