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