1# SPDX-License-Identifier: GPL-2.0-only 2config CC_VERSION_TEXT 3 string 4 default "$(CC_VERSION_TEXT)" 5 help 6 This is used in unclear ways: 7 8 - Re-run Kconfig when the compiler is updated 9 The 'default' property references the environment variable, 10 CC_VERSION_TEXT so it is recorded in include/config/auto.conf.cmd. 11 When the compiler is updated, Kconfig will be invoked. 12 13 - Ensure full rebuild when the compiler is updated 14 include/linux/compiler-version.h contains this option in the comment 15 line so fixdep adds include/config/CC_VERSION_TEXT into the 16 auto-generated dependency. When the compiler is updated, syncconfig 17 will touch it and then every file will be rebuilt. 18 19config CC_IS_GCC 20 def_bool $(success,test "$(cc-name)" = GCC) 21 22config GCC_VERSION 23 int 24 default $(cc-version) if CC_IS_GCC 25 default 0 26 27config CC_IS_CLANG 28 def_bool $(success,test "$(cc-name)" = Clang) 29 30config CLANG_VERSION 31 int 32 default $(cc-version) if CC_IS_CLANG 33 default 0 34 35config AS_IS_GNU 36 def_bool $(success,test "$(as-name)" = GNU) 37 38config AS_IS_LLVM 39 def_bool $(success,test "$(as-name)" = LLVM) 40 41config AS_VERSION 42 int 43 # Use clang version if this is the integrated assembler 44 default CLANG_VERSION if AS_IS_LLVM 45 default $(as-version) 46 47config LD_IS_BFD 48 def_bool $(success,test "$(ld-name)" = BFD) 49 50config LD_VERSION 51 int 52 default $(ld-version) if LD_IS_BFD 53 default 0 54 55config LD_IS_LLD 56 def_bool $(success,test "$(ld-name)" = LLD) 57 58config LLD_VERSION 59 int 60 default $(ld-version) if LD_IS_LLD 61 default 0 62 63config CC_CAN_LINK 64 bool 65 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT 66 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag)) 67 68config CC_CAN_LINK_STATIC 69 bool 70 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag) -static) if 64BIT 71 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag) -static) 72 73config CC_HAS_ASM_GOTO 74 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) 75 76config CC_HAS_ASM_GOTO_OUTPUT 77 depends on CC_HAS_ASM_GOTO 78 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) 79 80config CC_HAS_ASM_GOTO_TIED_OUTPUT 81 depends on CC_HAS_ASM_GOTO_OUTPUT 82 # Detect buggy gcc and clang, fixed in gcc-11 clang-14. 83 def_bool $(success,echo 'int foo(int *x) { asm goto (".long (%l[bar]) - .": "+m"(*x) ::: bar); return *x; bar: return 0; }' | $CC -x c - -c -o /dev/null) 84 85config TOOLS_SUPPORT_RELR 86 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 87 88config CC_HAS_ASM_INLINE 89 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 90 91config CC_HAS_NO_PROFILE_FN_ATTR 92 def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror) 93 94config PAHOLE_VERSION 95 int 96 default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE)) 97 98config CONSTRUCTORS 99 bool 100 101config IRQ_WORK 102 bool 103 104config BUILDTIME_TABLE_SORT 105 bool 106 107config THREAD_INFO_IN_TASK 108 bool 109 help 110 Select this to move thread_info off the stack into task_struct. To 111 make this work, an arch will need to remove all thread_info fields 112 except flags and fix any runtime bugs. 113 114 One subtle change that will be needed is to use try_get_task_stack() 115 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 116 117menu "General setup" 118 119config BROKEN 120 bool 121 122config BROKEN_ON_SMP 123 bool 124 depends on BROKEN || !SMP 125 default y 126 127config INIT_ENV_ARG_LIMIT 128 int 129 default 32 if !UML 130 default 128 if UML 131 help 132 Maximum of each of the number of arguments and environment 133 variables passed to init from the kernel command line. 134 135config COMPILE_TEST 136 bool "Compile also drivers which will not load" 137 depends on HAS_IOMEM 138 help 139 Some drivers can be compiled on a different platform than they are 140 intended to be run on. Despite they cannot be loaded there (or even 141 when they load they cannot be used due to missing HW support), 142 developers still, opposing to distributors, might want to build such 143 drivers to compile-test them. 144 145 If you are a developer and want to build everything available, say Y 146 here. If you are a user/distributor, say N here to exclude useless 147 drivers to be distributed. 148 149config WERROR 150 bool "Compile the kernel with warnings as errors" 151 default y 152 help 153 A kernel build should not cause any compiler warnings, and this 154 enables the '-Werror' flag to enforce that rule by default. 155 156 However, if you have a new (or very old) compiler with odd and 157 unusual warnings, or you have some architecture with problems, 158 you may need to disable this config option in order to 159 successfully build the kernel. 160 161 If in doubt, say Y. 162 163config UAPI_HEADER_TEST 164 bool "Compile test UAPI headers" 165 depends on HEADERS_INSTALL && CC_CAN_LINK 166 help 167 Compile test headers exported to user-space to ensure they are 168 self-contained, i.e. compilable as standalone units. 169 170 If you are a developer or tester and want to ensure the exported 171 headers are self-contained, say Y here. Otherwise, choose N. 172 173config LOCALVERSION 174 string "Local version - append to kernel release" 175 help 176 Append an extra string to the end of your kernel version. 177 This will show up when you type uname, for example. 178 The string you set here will be appended after the contents of 179 any files with a filename matching localversion* in your 180 object and source tree, in that order. Your total string can 181 be a maximum of 64 characters. 182 183config LOCALVERSION_AUTO 184 bool "Automatically append version information to the version string" 185 default y 186 depends on !COMPILE_TEST 187 help 188 This will try to automatically determine if the current tree is a 189 release tree by looking for git tags that belong to the current 190 top of tree revision. 191 192 A string of the format -gxxxxxxxx will be added to the localversion 193 if a git-based tree is found. The string generated by this will be 194 appended after any matching localversion* files, and after the value 195 set in CONFIG_LOCALVERSION. 196 197 (The actual string used here is the first eight characters produced 198 by running the command: 199 200 $ git rev-parse --verify HEAD 201 202 which is done within the script "scripts/setlocalversion".) 203 204config BUILD_SALT 205 string "Build ID Salt" 206 default "" 207 help 208 The build ID is used to link binaries and their debug info. Setting 209 this option will use the value in the calculation of the build id. 210 This is mostly useful for distributions which want to ensure the 211 build is unique between builds. It's safe to leave the default. 212 213config HAVE_KERNEL_GZIP 214 bool 215 216config HAVE_KERNEL_BZIP2 217 bool 218 219config HAVE_KERNEL_LZMA 220 bool 221 222config HAVE_KERNEL_XZ 223 bool 224 225config HAVE_KERNEL_LZO 226 bool 227 228config HAVE_KERNEL_LZ4 229 bool 230 231config HAVE_KERNEL_ZSTD 232 bool 233 234config HAVE_KERNEL_UNCOMPRESSED 235 bool 236 237choice 238 prompt "Kernel compression mode" 239 default KERNEL_GZIP 240 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 241 help 242 The linux kernel is a kind of self-extracting executable. 243 Several compression algorithms are available, which differ 244 in efficiency, compression and decompression speed. 245 Compression speed is only relevant when building a kernel. 246 Decompression speed is relevant at each boot. 247 248 If you have any problems with bzip2 or lzma compressed 249 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 250 version of this functionality (bzip2 only), for 2.4, was 251 supplied by Christian Ludwig) 252 253 High compression options are mostly useful for users, who 254 are low on disk space (embedded systems), but for whom ram 255 size matters less. 256 257 If in doubt, select 'gzip' 258 259config KERNEL_GZIP 260 bool "Gzip" 261 depends on HAVE_KERNEL_GZIP 262 help 263 The old and tried gzip compression. It provides a good balance 264 between compression ratio and decompression speed. 265 266config KERNEL_BZIP2 267 bool "Bzip2" 268 depends on HAVE_KERNEL_BZIP2 269 help 270 Its compression ratio and speed is intermediate. 271 Decompression speed is slowest among the choices. The kernel 272 size is about 10% smaller with bzip2, in comparison to gzip. 273 Bzip2 uses a large amount of memory. For modern kernels you 274 will need at least 8MB RAM or more for booting. 275 276config KERNEL_LZMA 277 bool "LZMA" 278 depends on HAVE_KERNEL_LZMA 279 help 280 This compression algorithm's ratio is best. Decompression speed 281 is between gzip and bzip2. Compression is slowest. 282 The kernel size is about 33% smaller with LZMA in comparison to gzip. 283 284config KERNEL_XZ 285 bool "XZ" 286 depends on HAVE_KERNEL_XZ 287 help 288 XZ uses the LZMA2 algorithm and instruction set specific 289 BCJ filters which can improve compression ratio of executable 290 code. The size of the kernel is about 30% smaller with XZ in 291 comparison to gzip. On architectures for which there is a BCJ 292 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 293 will create a few percent smaller kernel than plain LZMA. 294 295 The speed is about the same as with LZMA: The decompression 296 speed of XZ is better than that of bzip2 but worse than gzip 297 and LZO. Compression is slow. 298 299config KERNEL_LZO 300 bool "LZO" 301 depends on HAVE_KERNEL_LZO 302 help 303 Its compression ratio is the poorest among the choices. The kernel 304 size is about 10% bigger than gzip; however its speed 305 (both compression and decompression) is the fastest. 306 307config KERNEL_LZ4 308 bool "LZ4" 309 depends on HAVE_KERNEL_LZ4 310 help 311 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 312 A preliminary version of LZ4 de/compression tool is available at 313 <https://code.google.com/p/lz4/>. 314 315 Its compression ratio is worse than LZO. The size of the kernel 316 is about 8% bigger than LZO. But the decompression speed is 317 faster than LZO. 318 319config KERNEL_ZSTD 320 bool "ZSTD" 321 depends on HAVE_KERNEL_ZSTD 322 help 323 ZSTD is a compression algorithm targeting intermediate compression 324 with fast decompression speed. It will compress better than GZIP and 325 decompress around the same speed as LZO, but slower than LZ4. You 326 will need at least 192 KB RAM or more for booting. The zstd command 327 line tool is required for compression. 328 329config KERNEL_UNCOMPRESSED 330 bool "None" 331 depends on HAVE_KERNEL_UNCOMPRESSED 332 help 333 Produce uncompressed kernel image. This option is usually not what 334 you want. It is useful for debugging the kernel in slow simulation 335 environments, where decompressing and moving the kernel is awfully 336 slow. This option allows early boot code to skip the decompressor 337 and jump right at uncompressed kernel image. 338 339endchoice 340 341config DEFAULT_INIT 342 string "Default init path" 343 default "" 344 help 345 This option determines the default init for the system if no init= 346 option is passed on the kernel command line. If the requested path is 347 not present, we will still then move on to attempting further 348 locations (e.g. /sbin/init, etc). If this is empty, we will just use 349 the fallback list when init= is not passed. 350 351config DEFAULT_HOSTNAME 352 string "Default hostname" 353 default "(none)" 354 help 355 This option determines the default system hostname before userspace 356 calls sethostname(2). The kernel traditionally uses "(none)" here, 357 but you may wish to use a different default here to make a minimal 358 system more usable with less configuration. 359 360# 361# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can 362# add proper SWAP support to them, in which case this can be remove. 363# 364config ARCH_NO_SWAP 365 bool 366 367config SWAP 368 bool "Support for paging of anonymous memory (swap)" 369 depends on MMU && BLOCK && !ARCH_NO_SWAP 370 default y 371 help 372 This option allows you to choose whether you want to have support 373 for so called swap devices or swap files in your kernel that are 374 used to provide more virtual memory than the actual RAM present 375 in your computer. If unsure say Y. 376 377config SYSVIPC 378 bool "System V IPC" 379 help 380 Inter Process Communication is a suite of library functions and 381 system calls which let processes (running programs) synchronize and 382 exchange information. It is generally considered to be a good thing, 383 and some programs won't run unless you say Y here. In particular, if 384 you want to run the DOS emulator dosemu under Linux (read the 385 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 386 you'll need to say Y here. 387 388 You can find documentation about IPC with "info ipc" and also in 389 section 6.4 of the Linux Programmer's Guide, available from 390 <http://www.tldp.org/guides.html>. 391 392config SYSVIPC_SYSCTL 393 bool 394 depends on SYSVIPC 395 depends on SYSCTL 396 default y 397 398config POSIX_MQUEUE 399 bool "POSIX Message Queues" 400 depends on NET 401 help 402 POSIX variant of message queues is a part of IPC. In POSIX message 403 queues every message has a priority which decides about succession 404 of receiving it by a process. If you want to compile and run 405 programs written e.g. for Solaris with use of its POSIX message 406 queues (functions mq_*) say Y here. 407 408 POSIX message queues are visible as a filesystem called 'mqueue' 409 and can be mounted somewhere if you want to do filesystem 410 operations on message queues. 411 412 If unsure, say Y. 413 414config POSIX_MQUEUE_SYSCTL 415 bool 416 depends on POSIX_MQUEUE 417 depends on SYSCTL 418 default y 419 420config WATCH_QUEUE 421 bool "General notification queue" 422 default n 423 help 424 425 This is a general notification queue for the kernel to pass events to 426 userspace by splicing them into pipes. It can be used in conjunction 427 with watches for key/keyring change notifications and device 428 notifications. 429 430 See Documentation/watch_queue.rst 431 432config CROSS_MEMORY_ATTACH 433 bool "Enable process_vm_readv/writev syscalls" 434 depends on MMU 435 default y 436 help 437 Enabling this option adds the system calls process_vm_readv and 438 process_vm_writev which allow a process with the correct privileges 439 to directly read from or write to another process' address space. 440 See the man page for more details. 441 442config USELIB 443 bool "uselib syscall" 444 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION 445 help 446 This option enables the uselib syscall, a system call used in the 447 dynamic linker from libc5 and earlier. glibc does not use this 448 system call. If you intend to run programs built on libc5 or 449 earlier, you may need to enable this syscall. Current systems 450 running glibc can safely disable this. 451 452config AUDIT 453 bool "Auditing support" 454 depends on NET 455 help 456 Enable auditing infrastructure that can be used with another 457 kernel subsystem, such as SELinux (which requires this for 458 logging of avc messages output). System call auditing is included 459 on architectures which support it. 460 461config HAVE_ARCH_AUDITSYSCALL 462 bool 463 464config AUDITSYSCALL 465 def_bool y 466 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 467 select FSNOTIFY 468 469source "kernel/irq/Kconfig" 470source "kernel/time/Kconfig" 471source "kernel/bpf/Kconfig" 472source "kernel/Kconfig.preempt" 473 474menu "CPU/Task time and stats accounting" 475 476config VIRT_CPU_ACCOUNTING 477 bool 478 479choice 480 prompt "Cputime accounting" 481 default TICK_CPU_ACCOUNTING if !PPC64 482 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 483 484# Kind of a stub config for the pure tick based cputime accounting 485config TICK_CPU_ACCOUNTING 486 bool "Simple tick based cputime accounting" 487 depends on !S390 && !NO_HZ_FULL 488 help 489 This is the basic tick based cputime accounting that maintains 490 statistics about user, system and idle time spent on per jiffies 491 granularity. 492 493 If unsure, say Y. 494 495config VIRT_CPU_ACCOUNTING_NATIVE 496 bool "Deterministic task and CPU time accounting" 497 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 498 select VIRT_CPU_ACCOUNTING 499 help 500 Select this option to enable more accurate task and CPU time 501 accounting. This is done by reading a CPU counter on each 502 kernel entry and exit and on transitions within the kernel 503 between system, softirq and hardirq state, so there is a 504 small performance impact. In the case of s390 or IBM POWER > 5, 505 this also enables accounting of stolen time on logically-partitioned 506 systems. 507 508config VIRT_CPU_ACCOUNTING_GEN 509 bool "Full dynticks CPU time accounting" 510 depends on HAVE_CONTEXT_TRACKING 511 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 512 depends on GENERIC_CLOCKEVENTS 513 select VIRT_CPU_ACCOUNTING 514 select CONTEXT_TRACKING 515 help 516 Select this option to enable task and CPU time accounting on full 517 dynticks systems. This accounting is implemented by watching every 518 kernel-user boundaries using the context tracking subsystem. 519 The accounting is thus performed at the expense of some significant 520 overhead. 521 522 For now this is only useful if you are working on the full 523 dynticks subsystem development. 524 525 If unsure, say N. 526 527endchoice 528 529config IRQ_TIME_ACCOUNTING 530 bool "Fine granularity task level IRQ time accounting" 531 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 532 help 533 Select this option to enable fine granularity task irq time 534 accounting. This is done by reading a timestamp on each 535 transitions between softirq and hardirq state, so there can be a 536 small performance impact. 537 538 If in doubt, say N here. 539 540config HAVE_SCHED_AVG_IRQ 541 def_bool y 542 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 543 depends on SMP 544 545config SCHED_THERMAL_PRESSURE 546 bool 547 default y if ARM && ARM_CPU_TOPOLOGY 548 default y if ARM64 549 depends on SMP 550 depends on CPU_FREQ_THERMAL 551 help 552 Select this option to enable thermal pressure accounting in the 553 scheduler. Thermal pressure is the value conveyed to the scheduler 554 that reflects the reduction in CPU compute capacity resulted from 555 thermal throttling. Thermal throttling occurs when the performance of 556 a CPU is capped due to high operating temperatures. 557 558 If selected, the scheduler will be able to balance tasks accordingly, 559 i.e. put less load on throttled CPUs than on non/less throttled ones. 560 561 This requires the architecture to implement 562 arch_set_thermal_pressure() and arch_scale_thermal_pressure(). 563 564config BSD_PROCESS_ACCT 565 bool "BSD Process Accounting" 566 depends on MULTIUSER 567 help 568 If you say Y here, a user level program will be able to instruct the 569 kernel (via a special system call) to write process accounting 570 information to a file: whenever a process exits, information about 571 that process will be appended to the file by the kernel. The 572 information includes things such as creation time, owning user, 573 command name, memory usage, controlling terminal etc. (the complete 574 list is in the struct acct in <file:include/linux/acct.h>). It is 575 up to the user level program to do useful things with this 576 information. This is generally a good idea, so say Y. 577 578config BSD_PROCESS_ACCT_V3 579 bool "BSD Process Accounting version 3 file format" 580 depends on BSD_PROCESS_ACCT 581 default n 582 help 583 If you say Y here, the process accounting information is written 584 in a new file format that also logs the process IDs of each 585 process and its parent. Note that this file format is incompatible 586 with previous v0/v1/v2 file formats, so you will need updated tools 587 for processing it. A preliminary version of these tools is available 588 at <http://www.gnu.org/software/acct/>. 589 590config TASKSTATS 591 bool "Export task/process statistics through netlink" 592 depends on NET 593 depends on MULTIUSER 594 default n 595 help 596 Export selected statistics for tasks/processes through the 597 generic netlink interface. Unlike BSD process accounting, the 598 statistics are available during the lifetime of tasks/processes as 599 responses to commands. Like BSD accounting, they are sent to user 600 space on task exit. 601 602 Say N if unsure. 603 604config TASK_DELAY_ACCT 605 bool "Enable per-task delay accounting" 606 depends on TASKSTATS 607 select SCHED_INFO 608 help 609 Collect information on time spent by a task waiting for system 610 resources like cpu, synchronous block I/O completion and swapping 611 in pages. Such statistics can help in setting a task's priorities 612 relative to other tasks for cpu, io, rss limits etc. 613 614 Say N if unsure. 615 616config TASK_XACCT 617 bool "Enable extended accounting over taskstats" 618 depends on TASKSTATS 619 help 620 Collect extended task accounting data and send the data 621 to userland for processing over the taskstats interface. 622 623 Say N if unsure. 624 625config TASK_IO_ACCOUNTING 626 bool "Enable per-task storage I/O accounting" 627 depends on TASK_XACCT 628 help 629 Collect information on the number of bytes of storage I/O which this 630 task has caused. 631 632 Say N if unsure. 633 634config PSI 635 bool "Pressure stall information tracking" 636 help 637 Collect metrics that indicate how overcommitted the CPU, memory, 638 and IO capacity are in the system. 639 640 If you say Y here, the kernel will create /proc/pressure/ with the 641 pressure statistics files cpu, memory, and io. These will indicate 642 the share of walltime in which some or all tasks in the system are 643 delayed due to contention of the respective resource. 644 645 In kernels with cgroup support, cgroups (cgroup2 only) will 646 have cpu.pressure, memory.pressure, and io.pressure files, 647 which aggregate pressure stalls for the grouped tasks only. 648 649 For more details see Documentation/accounting/psi.rst. 650 651 Say N if unsure. 652 653config PSI_DEFAULT_DISABLED 654 bool "Require boot parameter to enable pressure stall information tracking" 655 default n 656 depends on PSI 657 help 658 If set, pressure stall information tracking will be disabled 659 per default but can be enabled through passing psi=1 on the 660 kernel commandline during boot. 661 662 This feature adds some code to the task wakeup and sleep 663 paths of the scheduler. The overhead is too low to affect 664 common scheduling-intense workloads in practice (such as 665 webservers, memcache), but it does show up in artificial 666 scheduler stress tests, such as hackbench. 667 668 If you are paranoid and not sure what the kernel will be 669 used for, say Y. 670 671 Say N if unsure. 672 673endmenu # "CPU/Task time and stats accounting" 674 675config CPU_ISOLATION 676 bool "CPU isolation" 677 depends on SMP || COMPILE_TEST 678 default y 679 help 680 Make sure that CPUs running critical tasks are not disturbed by 681 any source of "noise" such as unbound workqueues, timers, kthreads... 682 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 683 the "isolcpus=" boot parameter. 684 685 Say Y if unsure. 686 687source "kernel/rcu/Kconfig" 688 689config BUILD_BIN2C 690 bool 691 default n 692 693config IKCONFIG 694 tristate "Kernel .config support" 695 help 696 This option enables the complete Linux kernel ".config" file 697 contents to be saved in the kernel. It provides documentation 698 of which kernel options are used in a running kernel or in an 699 on-disk kernel. This information can be extracted from the kernel 700 image file with the script scripts/extract-ikconfig and used as 701 input to rebuild the current kernel or to build another kernel. 702 It can also be extracted from a running kernel by reading 703 /proc/config.gz if enabled (below). 704 705config IKCONFIG_PROC 706 bool "Enable access to .config through /proc/config.gz" 707 depends on IKCONFIG && PROC_FS 708 help 709 This option enables access to the kernel configuration file 710 through /proc/config.gz. 711 712config IKHEADERS 713 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 714 depends on SYSFS 715 help 716 This option enables access to the in-kernel headers that are generated during 717 the build process. These can be used to build eBPF tracing programs, 718 or similar programs. If you build the headers as a module, a module called 719 kheaders.ko is built which can be loaded on-demand to get access to headers. 720 721config LOG_BUF_SHIFT 722 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 723 range 12 25 if !H8300 724 range 12 19 if H8300 725 default 17 726 depends on PRINTK 727 help 728 Select the minimal kernel log buffer size as a power of 2. 729 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 730 parameter, see below. Any higher size also might be forced 731 by "log_buf_len" boot parameter. 732 733 Examples: 734 17 => 128 KB 735 16 => 64 KB 736 15 => 32 KB 737 14 => 16 KB 738 13 => 8 KB 739 12 => 4 KB 740 741config LOG_CPU_MAX_BUF_SHIFT 742 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 743 depends on SMP 744 range 0 21 745 default 12 if !BASE_SMALL 746 default 0 if BASE_SMALL 747 depends on PRINTK 748 help 749 This option allows to increase the default ring buffer size 750 according to the number of CPUs. The value defines the contribution 751 of each CPU as a power of 2. The used space is typically only few 752 lines however it might be much more when problems are reported, 753 e.g. backtraces. 754 755 The increased size means that a new buffer has to be allocated and 756 the original static one is unused. It makes sense only on systems 757 with more CPUs. Therefore this value is used only when the sum of 758 contributions is greater than the half of the default kernel ring 759 buffer as defined by LOG_BUF_SHIFT. The default values are set 760 so that more than 16 CPUs are needed to trigger the allocation. 761 762 Also this option is ignored when "log_buf_len" kernel parameter is 763 used as it forces an exact (power of two) size of the ring buffer. 764 765 The number of possible CPUs is used for this computation ignoring 766 hotplugging making the computation optimal for the worst case 767 scenario while allowing a simple algorithm to be used from bootup. 768 769 Examples shift values and their meaning: 770 17 => 128 KB for each CPU 771 16 => 64 KB for each CPU 772 15 => 32 KB for each CPU 773 14 => 16 KB for each CPU 774 13 => 8 KB for each CPU 775 12 => 4 KB for each CPU 776 777config PRINTK_SAFE_LOG_BUF_SHIFT 778 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 779 range 10 21 780 default 13 781 depends on PRINTK 782 help 783 Select the size of an alternate printk per-CPU buffer where messages 784 printed from usafe contexts are temporary stored. One example would 785 be NMI messages, another one - printk recursion. The messages are 786 copied to the main log buffer in a safe context to avoid a deadlock. 787 The value defines the size as a power of 2. 788 789 Those messages are rare and limited. The largest one is when 790 a backtrace is printed. It usually fits into 4KB. Select 791 8KB if you want to be on the safe side. 792 793 Examples: 794 17 => 128 KB for each CPU 795 16 => 64 KB for each CPU 796 15 => 32 KB for each CPU 797 14 => 16 KB for each CPU 798 13 => 8 KB for each CPU 799 12 => 4 KB for each CPU 800 801config PRINTK_INDEX 802 bool "Printk indexing debugfs interface" 803 depends on PRINTK && DEBUG_FS 804 help 805 Add support for indexing of all printk formats known at compile time 806 at <debugfs>/printk/index/<module>. 807 808 This can be used as part of maintaining daemons which monitor 809 /dev/kmsg, as it permits auditing the printk formats present in a 810 kernel, allowing detection of cases where monitored printks are 811 changed or no longer present. 812 813 There is no additional runtime cost to printk with this enabled. 814 815# 816# Architectures with an unreliable sched_clock() should select this: 817# 818config HAVE_UNSTABLE_SCHED_CLOCK 819 bool 820 821config GENERIC_SCHED_CLOCK 822 bool 823 824menu "Scheduler features" 825 826config UCLAMP_TASK 827 bool "Enable utilization clamping for RT/FAIR tasks" 828 depends on CPU_FREQ_GOV_SCHEDUTIL 829 help 830 This feature enables the scheduler to track the clamped utilization 831 of each CPU based on RUNNABLE tasks scheduled on that CPU. 832 833 With this option, the user can specify the min and max CPU 834 utilization allowed for RUNNABLE tasks. The max utilization defines 835 the maximum frequency a task should use while the min utilization 836 defines the minimum frequency it should use. 837 838 Both min and max utilization clamp values are hints to the scheduler, 839 aiming at improving its frequency selection policy, but they do not 840 enforce or grant any specific bandwidth for tasks. 841 842 If in doubt, say N. 843 844config UCLAMP_BUCKETS_COUNT 845 int "Number of supported utilization clamp buckets" 846 range 5 20 847 default 5 848 depends on UCLAMP_TASK 849 help 850 Defines the number of clamp buckets to use. The range of each bucket 851 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 852 number of clamp buckets the finer their granularity and the higher 853 the precision of clamping aggregation and tracking at run-time. 854 855 For example, with the minimum configuration value we will have 5 856 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 857 be refcounted in the [20..39]% bucket and will set the bucket clamp 858 effective value to 25%. 859 If a second 30% boosted task should be co-scheduled on the same CPU, 860 that task will be refcounted in the same bucket of the first task and 861 it will boost the bucket clamp effective value to 30%. 862 The clamp effective value of a bucket is reset to its nominal value 863 (20% in the example above) when there are no more tasks refcounted in 864 that bucket. 865 866 An additional boost/capping margin can be added to some tasks. In the 867 example above the 25% task will be boosted to 30% until it exits the 868 CPU. If that should be considered not acceptable on certain systems, 869 it's always possible to reduce the margin by increasing the number of 870 clamp buckets to trade off used memory for run-time tracking 871 precision. 872 873 If in doubt, use the default value. 874 875endmenu 876 877# 878# For architectures that want to enable the support for NUMA-affine scheduler 879# balancing logic: 880# 881config ARCH_SUPPORTS_NUMA_BALANCING 882 bool 883 884# 885# For architectures that prefer to flush all TLBs after a number of pages 886# are unmapped instead of sending one IPI per page to flush. The architecture 887# must provide guarantees on what happens if a clean TLB cache entry is 888# written after the unmap. Details are in mm/rmap.c near the check for 889# should_defer_flush. The architecture should also consider if the full flush 890# and the refill costs are offset by the savings of sending fewer IPIs. 891config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 892 bool 893 894config CC_HAS_INT128 895 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 896 897# 898# For architectures that know their GCC __int128 support is sound 899# 900config ARCH_SUPPORTS_INT128 901 bool 902 903# For architectures that (ab)use NUMA to represent different memory regions 904# all cpu-local but of different latencies, such as SuperH. 905# 906config ARCH_WANT_NUMA_VARIABLE_LOCALITY 907 bool 908 909config NUMA_BALANCING 910 bool "Memory placement aware NUMA scheduler" 911 depends on ARCH_SUPPORTS_NUMA_BALANCING 912 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 913 depends on SMP && NUMA && MIGRATION 914 help 915 This option adds support for automatic NUMA aware memory/task placement. 916 The mechanism is quite primitive and is based on migrating memory when 917 it has references to the node the task is running on. 918 919 This system will be inactive on UMA systems. 920 921config NUMA_BALANCING_DEFAULT_ENABLED 922 bool "Automatically enable NUMA aware memory/task placement" 923 default y 924 depends on NUMA_BALANCING 925 help 926 If set, automatic NUMA balancing will be enabled if running on a NUMA 927 machine. 928 929menuconfig CGROUPS 930 bool "Control Group support" 931 select KERNFS 932 help 933 This option adds support for grouping sets of processes together, for 934 use with process control subsystems such as Cpusets, CFS, memory 935 controls or device isolation. 936 See 937 - Documentation/scheduler/sched-design-CFS.rst (CFS) 938 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 939 and resource control) 940 941 Say N if unsure. 942 943if CGROUPS 944 945config PAGE_COUNTER 946 bool 947 948config MEMCG 949 bool "Memory controller" 950 select PAGE_COUNTER 951 select EVENTFD 952 help 953 Provides control over the memory footprint of tasks in a cgroup. 954 955config MEMCG_SWAP 956 bool 957 depends on MEMCG && SWAP 958 default y 959 960config MEMCG_KMEM 961 bool 962 depends on MEMCG && !SLOB 963 default y 964 965config BLK_CGROUP 966 bool "IO controller" 967 depends on BLOCK 968 default n 969 help 970 Generic block IO controller cgroup interface. This is the common 971 cgroup interface which should be used by various IO controlling 972 policies. 973 974 Currently, CFQ IO scheduler uses it to recognize task groups and 975 control disk bandwidth allocation (proportional time slice allocation) 976 to such task groups. It is also used by bio throttling logic in 977 block layer to implement upper limit in IO rates on a device. 978 979 This option only enables generic Block IO controller infrastructure. 980 One needs to also enable actual IO controlling logic/policy. For 981 enabling proportional weight division of disk bandwidth in CFQ, set 982 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 983 CONFIG_BLK_DEV_THROTTLING=y. 984 985 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 986 987config CGROUP_WRITEBACK 988 bool 989 depends on MEMCG && BLK_CGROUP 990 default y 991 992menuconfig CGROUP_SCHED 993 bool "CPU controller" 994 default n 995 help 996 This feature lets CPU scheduler recognize task groups and control CPU 997 bandwidth allocation to such task groups. It uses cgroups to group 998 tasks. 999 1000if CGROUP_SCHED 1001config FAIR_GROUP_SCHED 1002 bool "Group scheduling for SCHED_OTHER" 1003 depends on CGROUP_SCHED 1004 default CGROUP_SCHED 1005 1006config CFS_BANDWIDTH 1007 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 1008 depends on FAIR_GROUP_SCHED 1009 default n 1010 help 1011 This option allows users to define CPU bandwidth rates (limits) for 1012 tasks running within the fair group scheduler. Groups with no limit 1013 set are considered to be unconstrained and will run with no 1014 restriction. 1015 See Documentation/scheduler/sched-bwc.rst for more information. 1016 1017config RT_GROUP_SCHED 1018 bool "Group scheduling for SCHED_RR/FIFO" 1019 depends on CGROUP_SCHED 1020 default n 1021 help 1022 This feature lets you explicitly allocate real CPU bandwidth 1023 to task groups. If enabled, it will also make it impossible to 1024 schedule realtime tasks for non-root users until you allocate 1025 realtime bandwidth for them. 1026 See Documentation/scheduler/sched-rt-group.rst for more information. 1027 1028endif #CGROUP_SCHED 1029 1030config UCLAMP_TASK_GROUP 1031 bool "Utilization clamping per group of tasks" 1032 depends on CGROUP_SCHED 1033 depends on UCLAMP_TASK 1034 default n 1035 help 1036 This feature enables the scheduler to track the clamped utilization 1037 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 1038 1039 When this option is enabled, the user can specify a min and max 1040 CPU bandwidth which is allowed for each single task in a group. 1041 The max bandwidth allows to clamp the maximum frequency a task 1042 can use, while the min bandwidth allows to define a minimum 1043 frequency a task will always use. 1044 1045 When task group based utilization clamping is enabled, an eventually 1046 specified task-specific clamp value is constrained by the cgroup 1047 specified clamp value. Both minimum and maximum task clamping cannot 1048 be bigger than the corresponding clamping defined at task group level. 1049 1050 If in doubt, say N. 1051 1052config CGROUP_PIDS 1053 bool "PIDs controller" 1054 help 1055 Provides enforcement of process number limits in the scope of a 1056 cgroup. Any attempt to fork more processes than is allowed in the 1057 cgroup will fail. PIDs are fundamentally a global resource because it 1058 is fairly trivial to reach PID exhaustion before you reach even a 1059 conservative kmemcg limit. As a result, it is possible to grind a 1060 system to halt without being limited by other cgroup policies. The 1061 PIDs controller is designed to stop this from happening. 1062 1063 It should be noted that organisational operations (such as attaching 1064 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 1065 since the PIDs limit only affects a process's ability to fork, not to 1066 attach to a cgroup. 1067 1068config CGROUP_RDMA 1069 bool "RDMA controller" 1070 help 1071 Provides enforcement of RDMA resources defined by IB stack. 1072 It is fairly easy for consumers to exhaust RDMA resources, which 1073 can result into resource unavailability to other consumers. 1074 RDMA controller is designed to stop this from happening. 1075 Attaching processes with active RDMA resources to the cgroup 1076 hierarchy is allowed even if can cross the hierarchy's limit. 1077 1078config CGROUP_FREEZER 1079 bool "Freezer controller" 1080 help 1081 Provides a way to freeze and unfreeze all tasks in a 1082 cgroup. 1083 1084 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1085 controller includes important in-kernel memory consumers per default. 1086 1087 If you're using cgroup2, say N. 1088 1089config CGROUP_HUGETLB 1090 bool "HugeTLB controller" 1091 depends on HUGETLB_PAGE 1092 select PAGE_COUNTER 1093 default n 1094 help 1095 Provides a cgroup controller for HugeTLB pages. 1096 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1097 The limit is enforced during page fault. Since HugeTLB doesn't 1098 support page reclaim, enforcing the limit at page fault time implies 1099 that, the application will get SIGBUS signal if it tries to access 1100 HugeTLB pages beyond its limit. This requires the application to know 1101 beforehand how much HugeTLB pages it would require for its use. The 1102 control group is tracked in the third page lru pointer. This means 1103 that we cannot use the controller with huge page less than 3 pages. 1104 1105config CPUSETS 1106 bool "Cpuset controller" 1107 depends on SMP 1108 help 1109 This option will let you create and manage CPUSETs which 1110 allow dynamically partitioning a system into sets of CPUs and 1111 Memory Nodes and assigning tasks to run only within those sets. 1112 This is primarily useful on large SMP or NUMA systems. 1113 1114 Say N if unsure. 1115 1116config PROC_PID_CPUSET 1117 bool "Include legacy /proc/<pid>/cpuset file" 1118 depends on CPUSETS 1119 default y 1120 1121config CGROUP_DEVICE 1122 bool "Device controller" 1123 help 1124 Provides a cgroup controller implementing whitelists for 1125 devices which a process in the cgroup can mknod or open. 1126 1127config CGROUP_CPUACCT 1128 bool "Simple CPU accounting controller" 1129 help 1130 Provides a simple controller for monitoring the 1131 total CPU consumed by the tasks in a cgroup. 1132 1133config CGROUP_PERF 1134 bool "Perf controller" 1135 depends on PERF_EVENTS 1136 help 1137 This option extends the perf per-cpu mode to restrict monitoring 1138 to threads which belong to the cgroup specified and run on the 1139 designated cpu. Or this can be used to have cgroup ID in samples 1140 so that it can monitor performance events among cgroups. 1141 1142 Say N if unsure. 1143 1144config CGROUP_BPF 1145 bool "Support for eBPF programs attached to cgroups" 1146 depends on BPF_SYSCALL 1147 select SOCK_CGROUP_DATA 1148 help 1149 Allow attaching eBPF programs to a cgroup using the bpf(2) 1150 syscall command BPF_PROG_ATTACH. 1151 1152 In which context these programs are accessed depends on the type 1153 of attachment. For instance, programs that are attached using 1154 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1155 inet sockets. 1156 1157config CGROUP_MISC 1158 bool "Misc resource controller" 1159 default n 1160 help 1161 Provides a controller for miscellaneous resources on a host. 1162 1163 Miscellaneous scalar resources are the resources on the host system 1164 which cannot be abstracted like the other cgroups. This controller 1165 tracks and limits the miscellaneous resources used by a process 1166 attached to a cgroup hierarchy. 1167 1168 For more information, please check misc cgroup section in 1169 /Documentation/admin-guide/cgroup-v2.rst. 1170 1171config CGROUP_DEBUG 1172 bool "Debug controller" 1173 default n 1174 depends on DEBUG_KERNEL 1175 help 1176 This option enables a simple controller that exports 1177 debugging information about the cgroups framework. This 1178 controller is for control cgroup debugging only. Its 1179 interfaces are not stable. 1180 1181 Say N. 1182 1183config SOCK_CGROUP_DATA 1184 bool 1185 default n 1186 1187endif # CGROUPS 1188 1189menuconfig NAMESPACES 1190 bool "Namespaces support" if EXPERT 1191 depends on MULTIUSER 1192 default !EXPERT 1193 help 1194 Provides the way to make tasks work with different objects using 1195 the same id. For example same IPC id may refer to different objects 1196 or same user id or pid may refer to different tasks when used in 1197 different namespaces. 1198 1199if NAMESPACES 1200 1201config UTS_NS 1202 bool "UTS namespace" 1203 default y 1204 help 1205 In this namespace tasks see different info provided with the 1206 uname() system call 1207 1208config TIME_NS 1209 bool "TIME namespace" 1210 depends on GENERIC_VDSO_TIME_NS 1211 default y 1212 help 1213 In this namespace boottime and monotonic clocks can be set. 1214 The time will keep going with the same pace. 1215 1216config IPC_NS 1217 bool "IPC namespace" 1218 depends on (SYSVIPC || POSIX_MQUEUE) 1219 default y 1220 help 1221 In this namespace tasks work with IPC ids which correspond to 1222 different IPC objects in different namespaces. 1223 1224config USER_NS 1225 bool "User namespace" 1226 default n 1227 help 1228 This allows containers, i.e. vservers, to use user namespaces 1229 to provide different user info for different servers. 1230 1231 When user namespaces are enabled in the kernel it is 1232 recommended that the MEMCG option also be enabled and that 1233 user-space use the memory control groups to limit the amount 1234 of memory a memory unprivileged users can use. 1235 1236 If unsure, say N. 1237 1238config PID_NS 1239 bool "PID Namespaces" 1240 default y 1241 help 1242 Support process id namespaces. This allows having multiple 1243 processes with the same pid as long as they are in different 1244 pid namespaces. This is a building block of containers. 1245 1246config NET_NS 1247 bool "Network namespace" 1248 depends on NET 1249 default y 1250 help 1251 Allow user space to create what appear to be multiple instances 1252 of the network stack. 1253 1254endif # NAMESPACES 1255 1256config CHECKPOINT_RESTORE 1257 bool "Checkpoint/restore support" 1258 select PROC_CHILDREN 1259 select KCMP 1260 default n 1261 help 1262 Enables additional kernel features in a sake of checkpoint/restore. 1263 In particular it adds auxiliary prctl codes to setup process text, 1264 data and heap segment sizes, and a few additional /proc filesystem 1265 entries. 1266 1267 If unsure, say N here. 1268 1269config SCHED_AUTOGROUP 1270 bool "Automatic process group scheduling" 1271 select CGROUPS 1272 select CGROUP_SCHED 1273 select FAIR_GROUP_SCHED 1274 help 1275 This option optimizes the scheduler for common desktop workloads by 1276 automatically creating and populating task groups. This separation 1277 of workloads isolates aggressive CPU burners (like build jobs) from 1278 desktop applications. Task group autogeneration is currently based 1279 upon task session. 1280 1281config RT_SOFTINT_OPTIMIZATION 1282 bool "Improve RT scheduling during long softint execution" 1283 depends on ARM64 1284 depends on SMP 1285 default n 1286 help 1287 Enable an optimization which tries to avoid placing RT tasks on CPUs 1288 occupied by nonpreemptible tasks, such as a long softint, or CPUs 1289 which may soon block preemptions, such as a CPU running a ksoftirq 1290 thread which handles slow softints. 1291 1292config SYSFS_DEPRECATED 1293 bool "Enable deprecated sysfs features to support old userspace tools" 1294 depends on SYSFS 1295 default n 1296 help 1297 This option adds code that switches the layout of the "block" class 1298 devices, to not show up in /sys/class/block/, but only in 1299 /sys/block/. 1300 1301 This switch is only active when the sysfs.deprecated=1 boot option is 1302 passed or the SYSFS_DEPRECATED_V2 option is set. 1303 1304 This option allows new kernels to run on old distributions and tools, 1305 which might get confused by /sys/class/block/. Since 2007/2008 all 1306 major distributions and tools handle this just fine. 1307 1308 Recent distributions and userspace tools after 2009/2010 depend on 1309 the existence of /sys/class/block/, and will not work with this 1310 option enabled. 1311 1312 Only if you are using a new kernel on an old distribution, you might 1313 need to say Y here. 1314 1315config SYSFS_DEPRECATED_V2 1316 bool "Enable deprecated sysfs features by default" 1317 default n 1318 depends on SYSFS 1319 depends on SYSFS_DEPRECATED 1320 help 1321 Enable deprecated sysfs by default. 1322 1323 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1324 option. 1325 1326 Only if you are using a new kernel on an old distribution, you might 1327 need to say Y here. Even then, odds are you would not need it 1328 enabled, you can always pass the boot option if absolutely necessary. 1329 1330config RELAY 1331 bool "Kernel->user space relay support (formerly relayfs)" 1332 select IRQ_WORK 1333 help 1334 This option enables support for relay interface support in 1335 certain file systems (such as debugfs). 1336 It is designed to provide an efficient mechanism for tools and 1337 facilities to relay large amounts of data from kernel space to 1338 user space. 1339 1340 If unsure, say N. 1341 1342config BLK_DEV_INITRD 1343 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1344 help 1345 The initial RAM filesystem is a ramfs which is loaded by the 1346 boot loader (loadlin or lilo) and that is mounted as root 1347 before the normal boot procedure. It is typically used to 1348 load modules needed to mount the "real" root file system, 1349 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1350 1351 If RAM disk support (BLK_DEV_RAM) is also included, this 1352 also enables initial RAM disk (initrd) support and adds 1353 15 Kbytes (more on some other architectures) to the kernel size. 1354 1355 If unsure say Y. 1356 1357if BLK_DEV_INITRD 1358 1359source "usr/Kconfig" 1360 1361endif 1362 1363config BOOT_CONFIG 1364 bool "Boot config support" 1365 select BLK_DEV_INITRD 1366 help 1367 Extra boot config allows system admin to pass a config file as 1368 complemental extension of kernel cmdline when booting. 1369 The boot config file must be attached at the end of initramfs 1370 with checksum, size and magic word. 1371 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1372 1373 If unsure, say Y. 1374 1375choice 1376 prompt "Compiler optimization level" 1377 default CC_OPTIMIZE_FOR_PERFORMANCE 1378 1379config CC_OPTIMIZE_FOR_PERFORMANCE 1380 bool "Optimize for performance (-O2)" 1381 help 1382 This is the default optimization level for the kernel, building 1383 with the "-O2" compiler flag for best performance and most 1384 helpful compile-time warnings. 1385 1386config CC_OPTIMIZE_FOR_PERFORMANCE_O3 1387 bool "Optimize more for performance (-O3)" 1388 depends on ARC 1389 help 1390 Choosing this option will pass "-O3" to your compiler to optimize 1391 the kernel yet more for performance. 1392 1393config CC_OPTIMIZE_FOR_SIZE 1394 bool "Optimize for size (-Os)" 1395 help 1396 Choosing this option will pass "-Os" to your compiler resulting 1397 in a smaller kernel. 1398 1399endchoice 1400 1401config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1402 bool 1403 help 1404 This requires that the arch annotates or otherwise protects 1405 its external entry points from being discarded. Linker scripts 1406 must also merge .text.*, .data.*, and .bss.* correctly into 1407 output sections. Care must be taken not to pull in unrelated 1408 sections (e.g., '.text.init'). Typically '.' in section names 1409 is used to distinguish them from label names / C identifiers. 1410 1411config LD_DEAD_CODE_DATA_ELIMINATION 1412 bool "Dead code and data elimination (EXPERIMENTAL)" 1413 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1414 depends on EXPERT 1415 depends on $(cc-option,-ffunction-sections -fdata-sections) 1416 depends on $(ld-option,--gc-sections) 1417 help 1418 Enable this if you want to do dead code and data elimination with 1419 the linker by compiling with -ffunction-sections -fdata-sections, 1420 and linking with --gc-sections. 1421 1422 This can reduce on disk and in-memory size of the kernel 1423 code and static data, particularly for small configs and 1424 on small systems. This has the possibility of introducing 1425 silently broken kernel if the required annotations are not 1426 present. This option is not well tested yet, so use at your 1427 own risk. 1428 1429config LD_ORPHAN_WARN 1430 def_bool y 1431 depends on ARCH_WANT_LD_ORPHAN_WARN 1432 depends on !LD_IS_LLD || LLD_VERSION >= 110000 1433 depends on $(ld-option,--orphan-handling=warn) 1434 1435config SYSCTL 1436 bool 1437 1438config HAVE_UID16 1439 bool 1440 1441config SYSCTL_EXCEPTION_TRACE 1442 bool 1443 help 1444 Enable support for /proc/sys/debug/exception-trace. 1445 1446config SYSCTL_ARCH_UNALIGN_NO_WARN 1447 bool 1448 help 1449 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1450 Allows arch to define/use @no_unaligned_warning to possibly warn 1451 about unaligned access emulation going on under the hood. 1452 1453config SYSCTL_ARCH_UNALIGN_ALLOW 1454 bool 1455 help 1456 Enable support for /proc/sys/kernel/unaligned-trap 1457 Allows arches to define/use @unaligned_enabled to runtime toggle 1458 the unaligned access emulation. 1459 see arch/parisc/kernel/unaligned.c for reference 1460 1461config HAVE_PCSPKR_PLATFORM 1462 bool 1463 1464# interpreter that classic socket filters depend on 1465config BPF 1466 bool 1467 1468menuconfig EXPERT 1469 bool "Configure standard kernel features (expert users)" 1470 # Unhide debug options, to make the on-by-default options visible 1471 select DEBUG_KERNEL 1472 help 1473 This option allows certain base kernel options and settings 1474 to be disabled or tweaked. This is for specialized 1475 environments which can tolerate a "non-standard" kernel. 1476 Only use this if you really know what you are doing. 1477 1478config UID16 1479 bool "Enable 16-bit UID system calls" if EXPERT 1480 depends on HAVE_UID16 && MULTIUSER 1481 default y 1482 help 1483 This enables the legacy 16-bit UID syscall wrappers. 1484 1485config MULTIUSER 1486 bool "Multiple users, groups and capabilities support" if EXPERT 1487 default y 1488 help 1489 This option enables support for non-root users, groups and 1490 capabilities. 1491 1492 If you say N here, all processes will run with UID 0, GID 0, and all 1493 possible capabilities. Saying N here also compiles out support for 1494 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1495 setgid, and capset. 1496 1497 If unsure, say Y here. 1498 1499config SGETMASK_SYSCALL 1500 bool "sgetmask/ssetmask syscalls support" if EXPERT 1501 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1502 help 1503 sys_sgetmask and sys_ssetmask are obsolete system calls 1504 no longer supported in libc but still enabled by default in some 1505 architectures. 1506 1507 If unsure, leave the default option here. 1508 1509config SYSFS_SYSCALL 1510 bool "Sysfs syscall support" if EXPERT 1511 default y 1512 help 1513 sys_sysfs is an obsolete system call no longer supported in libc. 1514 Note that disabling this option is more secure but might break 1515 compatibility with some systems. 1516 1517 If unsure say Y here. 1518 1519config FHANDLE 1520 bool "open by fhandle syscalls" if EXPERT 1521 select EXPORTFS 1522 default y 1523 help 1524 If you say Y here, a user level program will be able to map 1525 file names to handle and then later use the handle for 1526 different file system operations. This is useful in implementing 1527 userspace file servers, which now track files using handles instead 1528 of names. The handle would remain the same even if file names 1529 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1530 syscalls. 1531 1532config POSIX_TIMERS 1533 bool "Posix Clocks & timers" if EXPERT 1534 default y 1535 help 1536 This includes native support for POSIX timers to the kernel. 1537 Some embedded systems have no use for them and therefore they 1538 can be configured out to reduce the size of the kernel image. 1539 1540 When this option is disabled, the following syscalls won't be 1541 available: timer_create, timer_gettime: timer_getoverrun, 1542 timer_settime, timer_delete, clock_adjtime, getitimer, 1543 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1544 clock_getres and clock_nanosleep syscalls will be limited to 1545 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1546 1547 If unsure say y. 1548 1549config PRINTK 1550 default y 1551 bool "Enable support for printk" if EXPERT 1552 select IRQ_WORK 1553 help 1554 This option enables normal printk support. Removing it 1555 eliminates most of the message strings from the kernel image 1556 and makes the kernel more or less silent. As this makes it 1557 very difficult to diagnose system problems, saying N here is 1558 strongly discouraged. 1559 1560config BUG 1561 bool "BUG() support" if EXPERT 1562 default y 1563 help 1564 Disabling this option eliminates support for BUG and WARN, reducing 1565 the size of your kernel image and potentially quietly ignoring 1566 numerous fatal conditions. You should only consider disabling this 1567 option for embedded systems with no facilities for reporting errors. 1568 Just say Y. 1569 1570config ELF_CORE 1571 depends on COREDUMP 1572 default y 1573 bool "Enable ELF core dumps" if EXPERT 1574 help 1575 Enable support for generating core dumps. Disabling saves about 4k. 1576 1577 1578config PCSPKR_PLATFORM 1579 bool "Enable PC-Speaker support" if EXPERT 1580 depends on HAVE_PCSPKR_PLATFORM 1581 select I8253_LOCK 1582 default y 1583 help 1584 This option allows to disable the internal PC-Speaker 1585 support, saving some memory. 1586 1587config BASE_FULL 1588 default y 1589 bool "Enable full-sized data structures for core" if EXPERT 1590 help 1591 Disabling this option reduces the size of miscellaneous core 1592 kernel data structures. This saves memory on small machines, 1593 but may reduce performance. 1594 1595config FUTEX 1596 bool "Enable futex support" if EXPERT 1597 default y 1598 imply RT_MUTEXES 1599 help 1600 Disabling this option will cause the kernel to be built without 1601 support for "fast userspace mutexes". The resulting kernel may not 1602 run glibc-based applications correctly. 1603 1604config FUTEX_PI 1605 bool 1606 depends on FUTEX && RT_MUTEXES 1607 default y 1608 1609config HAVE_FUTEX_CMPXCHG 1610 bool 1611 depends on FUTEX 1612 help 1613 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1614 is implemented and always working. This removes a couple of runtime 1615 checks. 1616 1617config EPOLL 1618 bool "Enable eventpoll support" if EXPERT 1619 default y 1620 help 1621 Disabling this option will cause the kernel to be built without 1622 support for epoll family of system calls. 1623 1624config SIGNALFD 1625 bool "Enable signalfd() system call" if EXPERT 1626 default y 1627 help 1628 Enable the signalfd() system call that allows to receive signals 1629 on a file descriptor. 1630 1631 If unsure, say Y. 1632 1633config TIMERFD 1634 bool "Enable timerfd() system call" if EXPERT 1635 default y 1636 help 1637 Enable the timerfd() system call that allows to receive timer 1638 events on a file descriptor. 1639 1640 If unsure, say Y. 1641 1642config EVENTFD 1643 bool "Enable eventfd() system call" if EXPERT 1644 default y 1645 help 1646 Enable the eventfd() system call that allows to receive both 1647 kernel notification (ie. KAIO) or userspace notifications. 1648 1649 If unsure, say Y. 1650 1651config SHMEM 1652 bool "Use full shmem filesystem" if EXPERT 1653 default y 1654 depends on MMU 1655 help 1656 The shmem is an internal filesystem used to manage shared memory. 1657 It is backed by swap and manages resource limits. It is also exported 1658 to userspace as tmpfs if TMPFS is enabled. Disabling this 1659 option replaces shmem and tmpfs with the much simpler ramfs code, 1660 which may be appropriate on small systems without swap. 1661 1662config AIO 1663 bool "Enable AIO support" if EXPERT 1664 default y 1665 help 1666 This option enables POSIX asynchronous I/O which may by used 1667 by some high performance threaded applications. Disabling 1668 this option saves about 7k. 1669 1670config IO_URING 1671 bool "Enable IO uring support" if EXPERT 1672 select IO_WQ 1673 default y 1674 help 1675 This option enables support for the io_uring interface, enabling 1676 applications to submit and complete IO through submission and 1677 completion rings that are shared between the kernel and application. 1678 1679config ADVISE_SYSCALLS 1680 bool "Enable madvise/fadvise syscalls" if EXPERT 1681 default y 1682 help 1683 This option enables the madvise and fadvise syscalls, used by 1684 applications to advise the kernel about their future memory or file 1685 usage, improving performance. If building an embedded system where no 1686 applications use these syscalls, you can disable this option to save 1687 space. 1688 1689config HAVE_ARCH_USERFAULTFD_WP 1690 bool 1691 help 1692 Arch has userfaultfd write protection support 1693 1694config HAVE_ARCH_USERFAULTFD_MINOR 1695 bool 1696 help 1697 Arch has userfaultfd minor fault support 1698 1699config MEMBARRIER 1700 bool "Enable membarrier() system call" if EXPERT 1701 default y 1702 help 1703 Enable the membarrier() system call that allows issuing memory 1704 barriers across all running threads, which can be used to distribute 1705 the cost of user-space memory barriers asymmetrically by transforming 1706 pairs of memory barriers into pairs consisting of membarrier() and a 1707 compiler barrier. 1708 1709 If unsure, say Y. 1710 1711config KALLSYMS 1712 bool "Load all symbols for debugging/ksymoops" if EXPERT 1713 default y 1714 help 1715 Say Y here to let the kernel print out symbolic crash information and 1716 symbolic stack backtraces. This increases the size of the kernel 1717 somewhat, as all symbols have to be loaded into the kernel image. 1718 1719config KALLSYMS_ALL 1720 bool "Include all symbols in kallsyms" 1721 depends on DEBUG_KERNEL && KALLSYMS 1722 help 1723 Normally kallsyms only contains the symbols of functions for nicer 1724 OOPS messages and backtraces (i.e., symbols from the text and inittext 1725 sections). This is sufficient for most cases. And only in very rare 1726 cases (e.g., when a debugger is used) all symbols are required (e.g., 1727 names of variables from the data sections, etc). 1728 1729 This option makes sure that all symbols are loaded into the kernel 1730 image (i.e., symbols from all sections) in cost of increased kernel 1731 size (depending on the kernel configuration, it may be 300KiB or 1732 something like this). 1733 1734 Say N unless you really need all symbols. 1735 1736config KALLSYMS_ABSOLUTE_PERCPU 1737 bool 1738 depends on KALLSYMS 1739 default X86_64 && SMP 1740 1741config KALLSYMS_BASE_RELATIVE 1742 bool 1743 depends on KALLSYMS 1744 default !IA64 1745 help 1746 Instead of emitting them as absolute values in the native word size, 1747 emit the symbol references in the kallsyms table as 32-bit entries, 1748 each containing a relative value in the range [base, base + U32_MAX] 1749 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1750 an absolute value in the range [0, S32_MAX] or a relative value in the 1751 range [base, base + S32_MAX], where base is the lowest relative symbol 1752 address encountered in the image. 1753 1754 On 64-bit builds, this reduces the size of the address table by 50%, 1755 but more importantly, it results in entries whose values are build 1756 time constants, and no relocation pass is required at runtime to fix 1757 up the entries based on the runtime load address of the kernel. 1758 1759# end of the "standard kernel features (expert users)" menu 1760 1761# syscall, maps, verifier 1762 1763config USERFAULTFD 1764 bool "Enable userfaultfd() system call" 1765 depends on MMU 1766 help 1767 Enable the userfaultfd() system call that allows to intercept and 1768 handle page faults in userland. 1769 1770config ARCH_HAS_MEMBARRIER_CALLBACKS 1771 bool 1772 1773config ARCH_HAS_MEMBARRIER_SYNC_CORE 1774 bool 1775 1776config KCMP 1777 bool "Enable kcmp() system call" if EXPERT 1778 help 1779 Enable the kernel resource comparison system call. It provides 1780 user-space with the ability to compare two processes to see if they 1781 share a common resource, such as a file descriptor or even virtual 1782 memory space. 1783 1784 If unsure, say N. 1785 1786config RSEQ 1787 bool "Enable rseq() system call" if EXPERT 1788 default y 1789 depends on HAVE_RSEQ 1790 select MEMBARRIER 1791 help 1792 Enable the restartable sequences system call. It provides a 1793 user-space cache for the current CPU number value, which 1794 speeds up getting the current CPU number from user-space, 1795 as well as an ABI to speed up user-space operations on 1796 per-CPU data. 1797 1798 If unsure, say Y. 1799 1800config DEBUG_RSEQ 1801 default n 1802 bool "Enabled debugging of rseq() system call" if EXPERT 1803 depends on RSEQ && DEBUG_KERNEL 1804 help 1805 Enable extra debugging checks for the rseq system call. 1806 1807 If unsure, say N. 1808 1809config EMBEDDED 1810 bool "Embedded system" 1811 select EXPERT 1812 help 1813 This option should be enabled if compiling the kernel for 1814 an embedded system so certain expert options are available 1815 for configuration. 1816 1817config HAVE_PERF_EVENTS 1818 bool 1819 help 1820 See tools/perf/design.txt for details. 1821 1822config GUEST_PERF_EVENTS 1823 bool 1824 depends on HAVE_PERF_EVENTS 1825 1826config PERF_USE_VMALLOC 1827 bool 1828 help 1829 See tools/perf/design.txt for details 1830 1831config PC104 1832 bool "PC/104 support" if EXPERT 1833 help 1834 Expose PC/104 form factor device drivers and options available for 1835 selection and configuration. Enable this option if your target 1836 machine has a PC/104 bus. 1837 1838menu "Kernel Performance Events And Counters" 1839 1840config PERF_EVENTS 1841 bool "Kernel performance events and counters" 1842 default y if PROFILING 1843 depends on HAVE_PERF_EVENTS 1844 select IRQ_WORK 1845 select SRCU 1846 help 1847 Enable kernel support for various performance events provided 1848 by software and hardware. 1849 1850 Software events are supported either built-in or via the 1851 use of generic tracepoints. 1852 1853 Most modern CPUs support performance events via performance 1854 counter registers. These registers count the number of certain 1855 types of hw events: such as instructions executed, cachemisses 1856 suffered, or branches mis-predicted - without slowing down the 1857 kernel or applications. These registers can also trigger interrupts 1858 when a threshold number of events have passed - and can thus be 1859 used to profile the code that runs on that CPU. 1860 1861 The Linux Performance Event subsystem provides an abstraction of 1862 these software and hardware event capabilities, available via a 1863 system call and used by the "perf" utility in tools/perf/. It 1864 provides per task and per CPU counters, and it provides event 1865 capabilities on top of those. 1866 1867 Say Y if unsure. 1868 1869config DEBUG_PERF_USE_VMALLOC 1870 default n 1871 bool "Debug: use vmalloc to back perf mmap() buffers" 1872 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1873 select PERF_USE_VMALLOC 1874 help 1875 Use vmalloc memory to back perf mmap() buffers. 1876 1877 Mostly useful for debugging the vmalloc code on platforms 1878 that don't require it. 1879 1880 Say N if unsure. 1881 1882endmenu 1883 1884config VM_EVENT_COUNTERS 1885 default y 1886 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1887 help 1888 VM event counters are needed for event counts to be shown. 1889 This option allows the disabling of the VM event counters 1890 on EXPERT systems. /proc/vmstat will only show page counts 1891 if VM event counters are disabled. 1892 1893config SLUB_DEBUG 1894 default y 1895 bool "Enable SLUB debugging support" if EXPERT 1896 depends on SLUB && SYSFS 1897 help 1898 SLUB has extensive debug support features. Disabling these can 1899 result in significant savings in code size. This also disables 1900 SLUB sysfs support. /sys/slab will not exist and there will be 1901 no support for cache validation etc. 1902 1903config COMPAT_BRK 1904 bool "Disable heap randomization" 1905 default y 1906 help 1907 Randomizing heap placement makes heap exploits harder, but it 1908 also breaks ancient binaries (including anything libc5 based). 1909 This option changes the bootup default to heap randomization 1910 disabled, and can be overridden at runtime by setting 1911 /proc/sys/kernel/randomize_va_space to 2. 1912 1913 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1914 1915choice 1916 prompt "Choose SLAB allocator" 1917 default SLUB 1918 help 1919 This option allows to select a slab allocator. 1920 1921config SLAB 1922 bool "SLAB" 1923 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1924 help 1925 The regular slab allocator that is established and known to work 1926 well in all environments. It organizes cache hot objects in 1927 per cpu and per node queues. 1928 1929config SLUB 1930 bool "SLUB (Unqueued Allocator)" 1931 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1932 help 1933 SLUB is a slab allocator that minimizes cache line usage 1934 instead of managing queues of cached objects (SLAB approach). 1935 Per cpu caching is realized using slabs of objects instead 1936 of queues of objects. SLUB can use memory efficiently 1937 and has enhanced diagnostics. SLUB is the default choice for 1938 a slab allocator. 1939 1940config SLOB 1941 depends on EXPERT 1942 bool "SLOB (Simple Allocator)" 1943 help 1944 SLOB replaces the stock allocator with a drastically simpler 1945 allocator. SLOB is generally more space efficient but 1946 does not perform as well on large systems. 1947 1948endchoice 1949 1950config SLAB_MERGE_DEFAULT 1951 bool "Allow slab caches to be merged" 1952 default y 1953 help 1954 For reduced kernel memory fragmentation, slab caches can be 1955 merged when they share the same size and other characteristics. 1956 This carries a risk of kernel heap overflows being able to 1957 overwrite objects from merged caches (and more easily control 1958 cache layout), which makes such heap attacks easier to exploit 1959 by attackers. By keeping caches unmerged, these kinds of exploits 1960 can usually only damage objects in the same cache. To disable 1961 merging at runtime, "slab_nomerge" can be passed on the kernel 1962 command line. 1963 1964config SLAB_FREELIST_RANDOM 1965 bool "Randomize slab freelist" 1966 depends on SLAB || SLUB 1967 help 1968 Randomizes the freelist order used on creating new pages. This 1969 security feature reduces the predictability of the kernel slab 1970 allocator against heap overflows. 1971 1972config SLAB_FREELIST_HARDENED 1973 bool "Harden slab freelist metadata" 1974 depends on SLAB || SLUB 1975 help 1976 Many kernel heap attacks try to target slab cache metadata and 1977 other infrastructure. This options makes minor performance 1978 sacrifices to harden the kernel slab allocator against common 1979 freelist exploit methods. Some slab implementations have more 1980 sanity-checking than others. This option is most effective with 1981 CONFIG_SLUB. 1982 1983config SHUFFLE_PAGE_ALLOCATOR 1984 bool "Page allocator randomization" 1985 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1986 help 1987 Randomization of the page allocator improves the average 1988 utilization of a direct-mapped memory-side-cache. See section 1989 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1990 6.2a specification for an example of how a platform advertises 1991 the presence of a memory-side-cache. There are also incidental 1992 security benefits as it reduces the predictability of page 1993 allocations to compliment SLAB_FREELIST_RANDOM, but the 1994 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1995 10th order of pages is selected based on cache utilization 1996 benefits on x86. 1997 1998 While the randomization improves cache utilization it may 1999 negatively impact workloads on platforms without a cache. For 2000 this reason, by default, the randomization is enabled only 2001 after runtime detection of a direct-mapped memory-side-cache. 2002 Otherwise, the randomization may be force enabled with the 2003 'page_alloc.shuffle' kernel command line parameter. 2004 2005 Say Y if unsure. 2006 2007config SLUB_CPU_PARTIAL 2008 default y 2009 depends on SLUB && SMP 2010 bool "SLUB per cpu partial cache" 2011 help 2012 Per cpu partial caches accelerate objects allocation and freeing 2013 that is local to a processor at the price of more indeterminism 2014 in the latency of the free. On overflow these caches will be cleared 2015 which requires the taking of locks that may cause latency spikes. 2016 Typically one would choose no for a realtime system. 2017 2018config MMAP_ALLOW_UNINITIALIZED 2019 bool "Allow mmapped anonymous memory to be uninitialized" 2020 depends on EXPERT && !MMU 2021 default n 2022 help 2023 Normally, and according to the Linux spec, anonymous memory obtained 2024 from mmap() has its contents cleared before it is passed to 2025 userspace. Enabling this config option allows you to request that 2026 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 2027 providing a huge performance boost. If this option is not enabled, 2028 then the flag will be ignored. 2029 2030 This is taken advantage of by uClibc's malloc(), and also by 2031 ELF-FDPIC binfmt's brk and stack allocator. 2032 2033 Because of the obvious security issues, this option should only be 2034 enabled on embedded devices where you control what is run in 2035 userspace. Since that isn't generally a problem on no-MMU systems, 2036 it is normally safe to say Y here. 2037 2038 See Documentation/admin-guide/mm/nommu-mmap.rst for more information. 2039 2040config SYSTEM_DATA_VERIFICATION 2041 def_bool n 2042 select SYSTEM_TRUSTED_KEYRING 2043 select KEYS 2044 select CRYPTO 2045 select CRYPTO_RSA 2046 select ASYMMETRIC_KEY_TYPE 2047 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 2048 select ASN1 2049 select OID_REGISTRY 2050 select X509_CERTIFICATE_PARSER 2051 select PKCS7_MESSAGE_PARSER 2052 help 2053 Provide PKCS#7 message verification using the contents of the system 2054 trusted keyring to provide public keys. This then can be used for 2055 module verification, kexec image verification and firmware blob 2056 verification. 2057 2058config PROFILING 2059 bool "Profiling support" 2060 help 2061 Say Y here to enable the extended profiling support mechanisms used 2062 by profilers. 2063 2064# 2065# Place an empty function call at each tracepoint site. Can be 2066# dynamically changed for a probe function. 2067# 2068config TRACEPOINTS 2069 bool 2070 2071endmenu # General setup 2072 2073source "arch/Kconfig" 2074 2075config RT_MUTEXES 2076 bool 2077 2078config BASE_SMALL 2079 int 2080 default 0 if BASE_FULL 2081 default 1 if !BASE_FULL 2082 2083config MODULE_SIG_FORMAT 2084 def_bool n 2085 select SYSTEM_DATA_VERIFICATION 2086 2087menuconfig MODULES 2088 bool "Enable loadable module support" 2089 modules 2090 help 2091 Kernel modules are small pieces of compiled code which can 2092 be inserted in the running kernel, rather than being 2093 permanently built into the kernel. You use the "modprobe" 2094 tool to add (and sometimes remove) them. If you say Y here, 2095 many parts of the kernel can be built as modules (by 2096 answering M instead of Y where indicated): this is most 2097 useful for infrequently used options which are not required 2098 for booting. For more information, see the man pages for 2099 modprobe, lsmod, modinfo, insmod and rmmod. 2100 2101 If you say Y here, you will need to run "make 2102 modules_install" to put the modules under /lib/modules/ 2103 where modprobe can find them (you may need to be root to do 2104 this). 2105 2106 If unsure, say Y. 2107 2108if MODULES 2109 2110config MODULE_FORCE_LOAD 2111 bool "Forced module loading" 2112 default n 2113 help 2114 Allow loading of modules without version information (ie. modprobe 2115 --force). Forced module loading sets the 'F' (forced) taint flag and 2116 is usually a really bad idea. 2117 2118config MODULE_UNLOAD 2119 bool "Module unloading" 2120 help 2121 Without this option you will not be able to unload any 2122 modules (note that some modules may not be unloadable 2123 anyway), which makes your kernel smaller, faster 2124 and simpler. If unsure, say Y. 2125 2126config MODULE_FORCE_UNLOAD 2127 bool "Forced module unloading" 2128 depends on MODULE_UNLOAD 2129 help 2130 This option allows you to force a module to unload, even if the 2131 kernel believes it is unsafe: the kernel will remove the module 2132 without waiting for anyone to stop using it (using the -f option to 2133 rmmod). This is mainly for kernel developers and desperate users. 2134 If unsure, say N. 2135 2136config MODVERSIONS 2137 bool "Module versioning support" 2138 help 2139 Usually, you have to use modules compiled with your kernel. 2140 Saying Y here makes it sometimes possible to use modules 2141 compiled for different kernels, by adding enough information 2142 to the modules to (hopefully) spot any changes which would 2143 make them incompatible with the kernel you are running. If 2144 unsure, say N. 2145 2146config ASM_MODVERSIONS 2147 bool 2148 default HAVE_ASM_MODVERSIONS && MODVERSIONS 2149 help 2150 This enables module versioning for exported symbols also from 2151 assembly. This can be enabled only when the target architecture 2152 supports it. 2153 2154config MODULE_REL_CRCS 2155 bool 2156 depends on MODVERSIONS 2157 2158config MODULE_SRCVERSION_ALL 2159 bool "Source checksum for all modules" 2160 help 2161 Modules which contain a MODULE_VERSION get an extra "srcversion" 2162 field inserted into their modinfo section, which contains a 2163 sum of the source files which made it. This helps maintainers 2164 see exactly which source was used to build a module (since 2165 others sometimes change the module source without updating 2166 the version). With this option, such a "srcversion" field 2167 will be created for all modules. If unsure, say N. 2168 2169config MODULE_SCMVERSION 2170 bool "SCM version for modules" 2171 depends on LOCALVERSION_AUTO 2172 help 2173 This enables the module attribute "scmversion" which can be used 2174 by developers to identify the SCM version of a given module, e.g. 2175 git sha1 or hg sha1. The SCM version can be queried by modinfo or 2176 via the sysfs node: /sys/modules/MODULENAME/scmversion. This is 2177 useful when the kernel or kernel modules are updated separately 2178 since that causes the vermagic of the kernel and the module to 2179 differ. 2180 2181 If unsure, say N. 2182 2183config MODULE_SIG 2184 bool "Module signature verification" 2185 select MODULE_SIG_FORMAT 2186 help 2187 Check modules for valid signatures upon load: the signature 2188 is simply appended to the module. For more information see 2189 <file:Documentation/admin-guide/module-signing.rst>. 2190 2191 Note that this option adds the OpenSSL development packages as a 2192 kernel build dependency so that the signing tool can use its crypto 2193 library. 2194 2195 You should enable this option if you wish to use either 2196 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via 2197 another LSM - otherwise unsigned modules will be loadable regardless 2198 of the lockdown policy. 2199 2200 !!!WARNING!!! If you enable this option, you MUST make sure that the 2201 module DOES NOT get stripped after being signed. This includes the 2202 debuginfo strip done by some packagers (such as rpmbuild) and 2203 inclusion into an initramfs that wants the module size reduced. 2204 2205config MODULE_SIG_FORCE 2206 bool "Require modules to be validly signed" 2207 depends on MODULE_SIG 2208 help 2209 Reject unsigned modules or signed modules for which we don't have a 2210 key. Without this, such modules will simply taint the kernel. 2211 2212config MODULE_SIG_PROTECT 2213 bool "Android GKI module protection" 2214 depends on MODULE_SIG && !MODULE_SIG_FORCE 2215 help 2216 Enables Android GKI symbol protection support. 2217 2218 This modifies the behavior of the MODULE_SIG_FORCE as follows: 2219 - Allows Android GKI Modules signed using MODULE_SIG_ALL during build. 2220 - Allows other modules to load if they don't violate the access to 2221 Android GKI protected symbols. Loading will fail and return 2222 -EACCES (Permission denied) if symbol access contidions are not met. 2223 2224config MODULE_SIG_ALL 2225 bool "Automatically sign all modules" 2226 default y 2227 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 2228 help 2229 Sign all modules during make modules_install. Without this option, 2230 modules must be signed manually, using the scripts/sign-file tool. 2231 2232comment "Do not forget to sign required modules with scripts/sign-file" 2233 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2234 2235choice 2236 prompt "Which hash algorithm should modules be signed with?" 2237 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 2238 help 2239 This determines which sort of hashing algorithm will be used during 2240 signature generation. This algorithm _must_ be built into the kernel 2241 directly so that signature verification can take place. It is not 2242 possible to load a signed module containing the algorithm to check 2243 the signature on that module. 2244 2245config MODULE_SIG_SHA1 2246 bool "Sign modules with SHA-1" 2247 select CRYPTO_SHA1 2248 2249config MODULE_SIG_SHA224 2250 bool "Sign modules with SHA-224" 2251 select CRYPTO_SHA256 2252 2253config MODULE_SIG_SHA256 2254 bool "Sign modules with SHA-256" 2255 select CRYPTO_SHA256 2256 2257config MODULE_SIG_SHA384 2258 bool "Sign modules with SHA-384" 2259 select CRYPTO_SHA512 2260 2261config MODULE_SIG_SHA512 2262 bool "Sign modules with SHA-512" 2263 select CRYPTO_SHA512 2264 2265endchoice 2266 2267config MODULE_SIG_HASH 2268 string 2269 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 2270 default "sha1" if MODULE_SIG_SHA1 2271 default "sha224" if MODULE_SIG_SHA224 2272 default "sha256" if MODULE_SIG_SHA256 2273 default "sha384" if MODULE_SIG_SHA384 2274 default "sha512" if MODULE_SIG_SHA512 2275 2276choice 2277 prompt "Module compression mode" 2278 help 2279 This option allows you to choose the algorithm which will be used to 2280 compress modules when 'make modules_install' is run. (or, you can 2281 choose to not compress modules at all.) 2282 2283 External modules will also be compressed in the same way during the 2284 installation. 2285 2286 For modules inside an initrd or initramfs, it's more efficient to 2287 compress the whole initrd or initramfs instead. 2288 2289 This is fully compatible with signed modules. 2290 2291 Please note that the tool used to load modules needs to support the 2292 corresponding algorithm. module-init-tools MAY support gzip, and kmod 2293 MAY support gzip, xz and zstd. 2294 2295 Your build system needs to provide the appropriate compression tool 2296 to compress the modules. 2297 2298 If in doubt, select 'None'. 2299 2300config MODULE_COMPRESS_NONE 2301 bool "None" 2302 help 2303 Do not compress modules. The installed modules are suffixed 2304 with .ko. 2305 2306config MODULE_COMPRESS_GZIP 2307 bool "GZIP" 2308 help 2309 Compress modules with GZIP. The installed modules are suffixed 2310 with .ko.gz. 2311 2312config MODULE_COMPRESS_XZ 2313 bool "XZ" 2314 help 2315 Compress modules with XZ. The installed modules are suffixed 2316 with .ko.xz. 2317 2318config MODULE_COMPRESS_ZSTD 2319 bool "ZSTD" 2320 help 2321 Compress modules with ZSTD. The installed modules are suffixed 2322 with .ko.zst. 2323 2324endchoice 2325 2326config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS 2327 bool "Allow loading of modules with missing namespace imports" 2328 help 2329 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in 2330 a namespace. A module that makes use of a symbol exported with such a 2331 namespace is required to import the namespace via MODULE_IMPORT_NS(). 2332 There is no technical reason to enforce correct namespace imports, 2333 but it creates consistency between symbols defining namespaces and 2334 users importing namespaces they make use of. This option relaxes this 2335 requirement and lifts the enforcement when loading a module. 2336 2337 If unsure, say N. 2338 2339config MODPROBE_PATH 2340 string "Path to modprobe binary" 2341 default "/sbin/modprobe" 2342 help 2343 When kernel code requests a module, it does so by calling 2344 the "modprobe" userspace utility. This option allows you to 2345 set the path where that binary is found. This can be changed 2346 at runtime via the sysctl file 2347 /proc/sys/kernel/modprobe. Setting this to the empty string 2348 removes the kernel's ability to request modules (but 2349 userspace can still load modules explicitly). 2350 2351config TRIM_UNUSED_KSYMS 2352 bool "Trim unused exported kernel symbols" if EXPERT 2353 depends on !COMPILE_TEST 2354 help 2355 The kernel and some modules make many symbols available for 2356 other modules to use via EXPORT_SYMBOL() and variants. Depending 2357 on the set of modules being selected in your kernel configuration, 2358 many of those exported symbols might never be used. 2359 2360 This option allows for unused exported symbols to be dropped from 2361 the build. In turn, this provides the compiler more opportunities 2362 (especially when using LTO) for optimizing the code and reducing 2363 binary size. This might have some security advantages as well. 2364 2365 If unsure, or if you need to build out-of-tree modules, say N. 2366 2367config UNUSED_KSYMS_WHITELIST 2368 string "Whitelist of symbols to keep in ksymtab" 2369 depends on TRIM_UNUSED_KSYMS 2370 help 2371 By default, all unused exported symbols will be un-exported from the 2372 build when TRIM_UNUSED_KSYMS is selected. 2373 2374 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept 2375 exported at all times, even in absence of in-tree users. The value to 2376 set here is the path to a text file containing the list of symbols, 2377 one per line. The path can be absolute, or relative to the kernel 2378 source tree. 2379 2380endif # MODULES 2381 2382config MODULES_TREE_LOOKUP 2383 def_bool y 2384 depends on PERF_EVENTS || TRACING || CFI_CLANG 2385 2386config INIT_ALL_POSSIBLE 2387 bool 2388 help 2389 Back when each arch used to define their own cpu_online_mask and 2390 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2391 with all 1s, and others with all 0s. When they were centralised, 2392 it was better to provide this option than to break all the archs 2393 and have several arch maintainers pursuing me down dark alleys. 2394 2395source "block/Kconfig" 2396 2397config PREEMPT_NOTIFIERS 2398 bool 2399 2400config PADATA 2401 depends on SMP 2402 bool 2403 2404config ASN1 2405 tristate 2406 help 2407 Build a simple ASN.1 grammar compiler that produces a bytecode output 2408 that can be interpreted by the ASN.1 stream decoder and used to 2409 inform it as to what tags are to be expected in a stream and what 2410 functions to call on what tags. 2411 2412source "kernel/Kconfig.locks" 2413 2414config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 2415 bool 2416 2417config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2418 bool 2419 2420# It may be useful for an architecture to override the definitions of the 2421# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2422# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2423# different calling convention for syscalls. They can also override the 2424# macros for not-implemented syscalls in kernel/sys_ni.c and 2425# kernel/time/posix-stubs.c. All these overrides need to be available in 2426# <asm/syscall_wrapper.h>. 2427config ARCH_HAS_SYSCALL_WRAPPER 2428 def_bool n 2429 2430source "init/Kconfig.gki" 2431