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 TOOLS_SUPPORT_RELR 81 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 82 83config CC_HAS_ASM_INLINE 84 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 85 86config CC_HAS_NO_PROFILE_FN_ATTR 87 def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror) 88 89config PAHOLE_VERSION 90 int 91 default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE)) 92 93config CONSTRUCTORS 94 bool 95 96config IRQ_WORK 97 bool 98 99config BUILDTIME_TABLE_SORT 100 bool 101 102config THREAD_INFO_IN_TASK 103 bool 104 help 105 Select this to move thread_info off the stack into task_struct. To 106 make this work, an arch will need to remove all thread_info fields 107 except flags and fix any runtime bugs. 108 109 One subtle change that will be needed is to use try_get_task_stack() 110 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 111 112menu "General setup" 113 114config BROKEN 115 bool 116 117config BROKEN_ON_SMP 118 bool 119 depends on BROKEN || !SMP 120 default y 121 122config INIT_ENV_ARG_LIMIT 123 int 124 default 32 if !UML 125 default 128 if UML 126 help 127 Maximum of each of the number of arguments and environment 128 variables passed to init from the kernel command line. 129 130config COMPILE_TEST 131 bool "Compile also drivers which will not load" 132 depends on HAS_IOMEM 133 help 134 Some drivers can be compiled on a different platform than they are 135 intended to be run on. Despite they cannot be loaded there (or even 136 when they load they cannot be used due to missing HW support), 137 developers still, opposing to distributors, might want to build such 138 drivers to compile-test them. 139 140 If you are a developer and want to build everything available, say Y 141 here. If you are a user/distributor, say N here to exclude useless 142 drivers to be distributed. 143 144config WERROR 145 bool "Compile the kernel with warnings as errors" 146 default COMPILE_TEST 147 help 148 A kernel build should not cause any compiler warnings, and this 149 enables the '-Werror' flag to enforce that rule by default. 150 151 However, if you have a new (or very old) compiler with odd and 152 unusual warnings, or you have some architecture with problems, 153 you may need to disable this config option in order to 154 successfully build the kernel. 155 156 If in doubt, say Y. 157 158config UAPI_HEADER_TEST 159 bool "Compile test UAPI headers" 160 depends on HEADERS_INSTALL && CC_CAN_LINK 161 help 162 Compile test headers exported to user-space to ensure they are 163 self-contained, i.e. compilable as standalone units. 164 165 If you are a developer or tester and want to ensure the exported 166 headers are self-contained, say Y here. Otherwise, choose N. 167 168config LOCALVERSION 169 string "Local version - append to kernel release" 170 help 171 Append an extra string to the end of your kernel version. 172 This will show up when you type uname, for example. 173 The string you set here will be appended after the contents of 174 any files with a filename matching localversion* in your 175 object and source tree, in that order. Your total string can 176 be a maximum of 64 characters. 177 178config LOCALVERSION_AUTO 179 bool "Automatically append version information to the version string" 180 default y 181 depends on !COMPILE_TEST 182 help 183 This will try to automatically determine if the current tree is a 184 release tree by looking for git tags that belong to the current 185 top of tree revision. 186 187 A string of the format -gxxxxxxxx will be added to the localversion 188 if a git-based tree is found. The string generated by this will be 189 appended after any matching localversion* files, and after the value 190 set in CONFIG_LOCALVERSION. 191 192 (The actual string used here is the first eight characters produced 193 by running the command: 194 195 $ git rev-parse --verify HEAD 196 197 which is done within the script "scripts/setlocalversion".) 198 199config BUILD_SALT 200 string "Build ID Salt" 201 default "" 202 help 203 The build ID is used to link binaries and their debug info. Setting 204 this option will use the value in the calculation of the build id. 205 This is mostly useful for distributions which want to ensure the 206 build is unique between builds. It's safe to leave the default. 207 208config HAVE_KERNEL_GZIP 209 bool 210 211config HAVE_KERNEL_BZIP2 212 bool 213 214config HAVE_KERNEL_LZMA 215 bool 216 217config HAVE_KERNEL_XZ 218 bool 219 220config HAVE_KERNEL_LZO 221 bool 222 223config HAVE_KERNEL_LZ4 224 bool 225 226config HAVE_KERNEL_ZSTD 227 bool 228 229config HAVE_KERNEL_UNCOMPRESSED 230 bool 231 232choice 233 prompt "Kernel compression mode" 234 default KERNEL_GZIP 235 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 236 help 237 The linux kernel is a kind of self-extracting executable. 238 Several compression algorithms are available, which differ 239 in efficiency, compression and decompression speed. 240 Compression speed is only relevant when building a kernel. 241 Decompression speed is relevant at each boot. 242 243 If you have any problems with bzip2 or lzma compressed 244 kernels, mail me (Alain Knaff) <[email protected]>. (An older 245 version of this functionality (bzip2 only), for 2.4, was 246 supplied by Christian Ludwig) 247 248 High compression options are mostly useful for users, who 249 are low on disk space (embedded systems), but for whom ram 250 size matters less. 251 252 If in doubt, select 'gzip' 253 254config KERNEL_GZIP 255 bool "Gzip" 256 depends on HAVE_KERNEL_GZIP 257 help 258 The old and tried gzip compression. It provides a good balance 259 between compression ratio and decompression speed. 260 261config KERNEL_BZIP2 262 bool "Bzip2" 263 depends on HAVE_KERNEL_BZIP2 264 help 265 Its compression ratio and speed is intermediate. 266 Decompression speed is slowest among the choices. The kernel 267 size is about 10% smaller with bzip2, in comparison to gzip. 268 Bzip2 uses a large amount of memory. For modern kernels you 269 will need at least 8MB RAM or more for booting. 270 271config KERNEL_LZMA 272 bool "LZMA" 273 depends on HAVE_KERNEL_LZMA 274 help 275 This compression algorithm's ratio is best. Decompression speed 276 is between gzip and bzip2. Compression is slowest. 277 The kernel size is about 33% smaller with LZMA in comparison to gzip. 278 279config KERNEL_XZ 280 bool "XZ" 281 depends on HAVE_KERNEL_XZ 282 help 283 XZ uses the LZMA2 algorithm and instruction set specific 284 BCJ filters which can improve compression ratio of executable 285 code. The size of the kernel is about 30% smaller with XZ in 286 comparison to gzip. On architectures for which there is a BCJ 287 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 288 will create a few percent smaller kernel than plain LZMA. 289 290 The speed is about the same as with LZMA: The decompression 291 speed of XZ is better than that of bzip2 but worse than gzip 292 and LZO. Compression is slow. 293 294config KERNEL_LZO 295 bool "LZO" 296 depends on HAVE_KERNEL_LZO 297 help 298 Its compression ratio is the poorest among the choices. The kernel 299 size is about 10% bigger than gzip; however its speed 300 (both compression and decompression) is the fastest. 301 302config KERNEL_LZ4 303 bool "LZ4" 304 depends on HAVE_KERNEL_LZ4 305 help 306 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 307 A preliminary version of LZ4 de/compression tool is available at 308 <https://code.google.com/p/lz4/>. 309 310 Its compression ratio is worse than LZO. The size of the kernel 311 is about 8% bigger than LZO. But the decompression speed is 312 faster than LZO. 313 314config KERNEL_ZSTD 315 bool "ZSTD" 316 depends on HAVE_KERNEL_ZSTD 317 help 318 ZSTD is a compression algorithm targeting intermediate compression 319 with fast decompression speed. It will compress better than GZIP and 320 decompress around the same speed as LZO, but slower than LZ4. You 321 will need at least 192 KB RAM or more for booting. The zstd command 322 line tool is required for compression. 323 324config KERNEL_UNCOMPRESSED 325 bool "None" 326 depends on HAVE_KERNEL_UNCOMPRESSED 327 help 328 Produce uncompressed kernel image. This option is usually not what 329 you want. It is useful for debugging the kernel in slow simulation 330 environments, where decompressing and moving the kernel is awfully 331 slow. This option allows early boot code to skip the decompressor 332 and jump right at uncompressed kernel image. 333 334endchoice 335 336config DEFAULT_INIT 337 string "Default init path" 338 default "" 339 help 340 This option determines the default init for the system if no init= 341 option is passed on the kernel command line. If the requested path is 342 not present, we will still then move on to attempting further 343 locations (e.g. /sbin/init, etc). If this is empty, we will just use 344 the fallback list when init= is not passed. 345 346config DEFAULT_HOSTNAME 347 string "Default hostname" 348 default "(none)" 349 help 350 This option determines the default system hostname before userspace 351 calls sethostname(2). The kernel traditionally uses "(none)" here, 352 but you may wish to use a different default here to make a minimal 353 system more usable with less configuration. 354 355# 356# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can 357# add proper SWAP support to them, in which case this can be remove. 358# 359config ARCH_NO_SWAP 360 bool 361 362config SWAP 363 bool "Support for paging of anonymous memory (swap)" 364 depends on MMU && BLOCK && !ARCH_NO_SWAP 365 default y 366 help 367 This option allows you to choose whether you want to have support 368 for so called swap devices or swap files in your kernel that are 369 used to provide more virtual memory than the actual RAM present 370 in your computer. If unsure say Y. 371 372config SYSVIPC 373 bool "System V IPC" 374 help 375 Inter Process Communication is a suite of library functions and 376 system calls which let processes (running programs) synchronize and 377 exchange information. It is generally considered to be a good thing, 378 and some programs won't run unless you say Y here. In particular, if 379 you want to run the DOS emulator dosemu under Linux (read the 380 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 381 you'll need to say Y here. 382 383 You can find documentation about IPC with "info ipc" and also in 384 section 6.4 of the Linux Programmer's Guide, available from 385 <http://www.tldp.org/guides.html>. 386 387config SYSVIPC_SYSCTL 388 bool 389 depends on SYSVIPC 390 depends on SYSCTL 391 default y 392 393config POSIX_MQUEUE 394 bool "POSIX Message Queues" 395 depends on NET 396 help 397 POSIX variant of message queues is a part of IPC. In POSIX message 398 queues every message has a priority which decides about succession 399 of receiving it by a process. If you want to compile and run 400 programs written e.g. for Solaris with use of its POSIX message 401 queues (functions mq_*) say Y here. 402 403 POSIX message queues are visible as a filesystem called 'mqueue' 404 and can be mounted somewhere if you want to do filesystem 405 operations on message queues. 406 407 If unsure, say Y. 408 409config POSIX_MQUEUE_SYSCTL 410 bool 411 depends on POSIX_MQUEUE 412 depends on SYSCTL 413 default y 414 415config WATCH_QUEUE 416 bool "General notification queue" 417 default n 418 help 419 420 This is a general notification queue for the kernel to pass events to 421 userspace by splicing them into pipes. It can be used in conjunction 422 with watches for key/keyring change notifications and device 423 notifications. 424 425 See Documentation/watch_queue.rst 426 427config CROSS_MEMORY_ATTACH 428 bool "Enable process_vm_readv/writev syscalls" 429 depends on MMU 430 default y 431 help 432 Enabling this option adds the system calls process_vm_readv and 433 process_vm_writev which allow a process with the correct privileges 434 to directly read from or write to another process' address space. 435 See the man page for more details. 436 437config USELIB 438 bool "uselib syscall" 439 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION 440 help 441 This option enables the uselib syscall, a system call used in the 442 dynamic linker from libc5 and earlier. glibc does not use this 443 system call. If you intend to run programs built on libc5 or 444 earlier, you may need to enable this syscall. Current systems 445 running glibc can safely disable this. 446 447config AUDIT 448 bool "Auditing support" 449 depends on NET 450 help 451 Enable auditing infrastructure that can be used with another 452 kernel subsystem, such as SELinux (which requires this for 453 logging of avc messages output). System call auditing is included 454 on architectures which support it. 455 456config HAVE_ARCH_AUDITSYSCALL 457 bool 458 459config AUDITSYSCALL 460 def_bool y 461 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 462 select FSNOTIFY 463 464source "kernel/irq/Kconfig" 465source "kernel/time/Kconfig" 466source "kernel/bpf/Kconfig" 467source "kernel/Kconfig.preempt" 468 469menu "CPU/Task time and stats accounting" 470 471config VIRT_CPU_ACCOUNTING 472 bool 473 474choice 475 prompt "Cputime accounting" 476 default TICK_CPU_ACCOUNTING if !PPC64 477 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 478 479# Kind of a stub config for the pure tick based cputime accounting 480config TICK_CPU_ACCOUNTING 481 bool "Simple tick based cputime accounting" 482 depends on !S390 && !NO_HZ_FULL 483 help 484 This is the basic tick based cputime accounting that maintains 485 statistics about user, system and idle time spent on per jiffies 486 granularity. 487 488 If unsure, say Y. 489 490config VIRT_CPU_ACCOUNTING_NATIVE 491 bool "Deterministic task and CPU time accounting" 492 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 493 select VIRT_CPU_ACCOUNTING 494 help 495 Select this option to enable more accurate task and CPU time 496 accounting. This is done by reading a CPU counter on each 497 kernel entry and exit and on transitions within the kernel 498 between system, softirq and hardirq state, so there is a 499 small performance impact. In the case of s390 or IBM POWER > 5, 500 this also enables accounting of stolen time on logically-partitioned 501 systems. 502 503config VIRT_CPU_ACCOUNTING_GEN 504 bool "Full dynticks CPU time accounting" 505 depends on HAVE_CONTEXT_TRACKING 506 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 507 depends on GENERIC_CLOCKEVENTS 508 select VIRT_CPU_ACCOUNTING 509 select CONTEXT_TRACKING 510 help 511 Select this option to enable task and CPU time accounting on full 512 dynticks systems. This accounting is implemented by watching every 513 kernel-user boundaries using the context tracking subsystem. 514 The accounting is thus performed at the expense of some significant 515 overhead. 516 517 For now this is only useful if you are working on the full 518 dynticks subsystem development. 519 520 If unsure, say N. 521 522endchoice 523 524config IRQ_TIME_ACCOUNTING 525 bool "Fine granularity task level IRQ time accounting" 526 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 527 help 528 Select this option to enable fine granularity task irq time 529 accounting. This is done by reading a timestamp on each 530 transitions between softirq and hardirq state, so there can be a 531 small performance impact. 532 533 If in doubt, say N here. 534 535config HAVE_SCHED_AVG_IRQ 536 def_bool y 537 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 538 depends on SMP 539 540config SCHED_THERMAL_PRESSURE 541 bool 542 default y if ARM && ARM_CPU_TOPOLOGY 543 default y if ARM64 544 depends on SMP 545 depends on CPU_FREQ_THERMAL 546 help 547 Select this option to enable thermal pressure accounting in the 548 scheduler. Thermal pressure is the value conveyed to the scheduler 549 that reflects the reduction in CPU compute capacity resulted from 550 thermal throttling. Thermal throttling occurs when the performance of 551 a CPU is capped due to high operating temperatures. 552 553 If selected, the scheduler will be able to balance tasks accordingly, 554 i.e. put less load on throttled CPUs than on non/less throttled ones. 555 556 This requires the architecture to implement 557 arch_update_thermal_pressure() and arch_scale_thermal_pressure(). 558 559config BSD_PROCESS_ACCT 560 bool "BSD Process Accounting" 561 depends on MULTIUSER 562 help 563 If you say Y here, a user level program will be able to instruct the 564 kernel (via a special system call) to write process accounting 565 information to a file: whenever a process exits, information about 566 that process will be appended to the file by the kernel. The 567 information includes things such as creation time, owning user, 568 command name, memory usage, controlling terminal etc. (the complete 569 list is in the struct acct in <file:include/linux/acct.h>). It is 570 up to the user level program to do useful things with this 571 information. This is generally a good idea, so say Y. 572 573config BSD_PROCESS_ACCT_V3 574 bool "BSD Process Accounting version 3 file format" 575 depends on BSD_PROCESS_ACCT 576 default n 577 help 578 If you say Y here, the process accounting information is written 579 in a new file format that also logs the process IDs of each 580 process and its parent. Note that this file format is incompatible 581 with previous v0/v1/v2 file formats, so you will need updated tools 582 for processing it. A preliminary version of these tools is available 583 at <http://www.gnu.org/software/acct/>. 584 585config TASKSTATS 586 bool "Export task/process statistics through netlink" 587 depends on NET 588 depends on MULTIUSER 589 default n 590 help 591 Export selected statistics for tasks/processes through the 592 generic netlink interface. Unlike BSD process accounting, the 593 statistics are available during the lifetime of tasks/processes as 594 responses to commands. Like BSD accounting, they are sent to user 595 space on task exit. 596 597 Say N if unsure. 598 599config TASK_DELAY_ACCT 600 bool "Enable per-task delay accounting" 601 depends on TASKSTATS 602 select SCHED_INFO 603 help 604 Collect information on time spent by a task waiting for system 605 resources like cpu, synchronous block I/O completion and swapping 606 in pages. Such statistics can help in setting a task's priorities 607 relative to other tasks for cpu, io, rss limits etc. 608 609 Say N if unsure. 610 611config TASK_XACCT 612 bool "Enable extended accounting over taskstats" 613 depends on TASKSTATS 614 help 615 Collect extended task accounting data and send the data 616 to userland for processing over the taskstats interface. 617 618 Say N if unsure. 619 620config TASK_IO_ACCOUNTING 621 bool "Enable per-task storage I/O accounting" 622 depends on TASK_XACCT 623 help 624 Collect information on the number of bytes of storage I/O which this 625 task has caused. 626 627 Say N if unsure. 628 629config PSI 630 bool "Pressure stall information tracking" 631 help 632 Collect metrics that indicate how overcommitted the CPU, memory, 633 and IO capacity are in the system. 634 635 If you say Y here, the kernel will create /proc/pressure/ with the 636 pressure statistics files cpu, memory, and io. These will indicate 637 the share of walltime in which some or all tasks in the system are 638 delayed due to contention of the respective resource. 639 640 In kernels with cgroup support, cgroups (cgroup2 only) will 641 have cpu.pressure, memory.pressure, and io.pressure files, 642 which aggregate pressure stalls for the grouped tasks only. 643 644 For more details see Documentation/accounting/psi.rst. 645 646 Say N if unsure. 647 648config PSI_DEFAULT_DISABLED 649 bool "Require boot parameter to enable pressure stall information tracking" 650 default n 651 depends on PSI 652 help 653 If set, pressure stall information tracking will be disabled 654 per default but can be enabled through passing psi=1 on the 655 kernel commandline during boot. 656 657 This feature adds some code to the task wakeup and sleep 658 paths of the scheduler. The overhead is too low to affect 659 common scheduling-intense workloads in practice (such as 660 webservers, memcache), but it does show up in artificial 661 scheduler stress tests, such as hackbench. 662 663 If you are paranoid and not sure what the kernel will be 664 used for, say Y. 665 666 Say N if unsure. 667 668endmenu # "CPU/Task time and stats accounting" 669 670config CPU_ISOLATION 671 bool "CPU isolation" 672 depends on SMP || COMPILE_TEST 673 default y 674 help 675 Make sure that CPUs running critical tasks are not disturbed by 676 any source of "noise" such as unbound workqueues, timers, kthreads... 677 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 678 the "isolcpus=" boot parameter. 679 680 Say Y if unsure. 681 682source "kernel/rcu/Kconfig" 683 684config BUILD_BIN2C 685 bool 686 default n 687 688config IKCONFIG 689 tristate "Kernel .config support" 690 help 691 This option enables the complete Linux kernel ".config" file 692 contents to be saved in the kernel. It provides documentation 693 of which kernel options are used in a running kernel or in an 694 on-disk kernel. This information can be extracted from the kernel 695 image file with the script scripts/extract-ikconfig and used as 696 input to rebuild the current kernel or to build another kernel. 697 It can also be extracted from a running kernel by reading 698 /proc/config.gz if enabled (below). 699 700config IKCONFIG_PROC 701 bool "Enable access to .config through /proc/config.gz" 702 depends on IKCONFIG && PROC_FS 703 help 704 This option enables access to the kernel configuration file 705 through /proc/config.gz. 706 707config IKHEADERS 708 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 709 depends on SYSFS 710 help 711 This option enables access to the in-kernel headers that are generated during 712 the build process. These can be used to build eBPF tracing programs, 713 or similar programs. If you build the headers as a module, a module called 714 kheaders.ko is built which can be loaded on-demand to get access to headers. 715 716config LOG_BUF_SHIFT 717 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 718 range 12 25 719 default 17 720 depends on PRINTK 721 help 722 Select the minimal kernel log buffer size as a power of 2. 723 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 724 parameter, see below. Any higher size also might be forced 725 by "log_buf_len" boot parameter. 726 727 Examples: 728 17 => 128 KB 729 16 => 64 KB 730 15 => 32 KB 731 14 => 16 KB 732 13 => 8 KB 733 12 => 4 KB 734 735config LOG_CPU_MAX_BUF_SHIFT 736 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 737 depends on SMP 738 range 0 21 739 default 12 if !BASE_SMALL 740 default 0 if BASE_SMALL 741 depends on PRINTK 742 help 743 This option allows to increase the default ring buffer size 744 according to the number of CPUs. The value defines the contribution 745 of each CPU as a power of 2. The used space is typically only few 746 lines however it might be much more when problems are reported, 747 e.g. backtraces. 748 749 The increased size means that a new buffer has to be allocated and 750 the original static one is unused. It makes sense only on systems 751 with more CPUs. Therefore this value is used only when the sum of 752 contributions is greater than the half of the default kernel ring 753 buffer as defined by LOG_BUF_SHIFT. The default values are set 754 so that more than 16 CPUs are needed to trigger the allocation. 755 756 Also this option is ignored when "log_buf_len" kernel parameter is 757 used as it forces an exact (power of two) size of the ring buffer. 758 759 The number of possible CPUs is used for this computation ignoring 760 hotplugging making the computation optimal for the worst case 761 scenario while allowing a simple algorithm to be used from bootup. 762 763 Examples shift values and their meaning: 764 17 => 128 KB for each CPU 765 16 => 64 KB for each CPU 766 15 => 32 KB for each CPU 767 14 => 16 KB for each CPU 768 13 => 8 KB for each CPU 769 12 => 4 KB for each CPU 770 771config PRINTK_SAFE_LOG_BUF_SHIFT 772 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 773 range 10 21 774 default 13 775 depends on PRINTK 776 help 777 Select the size of an alternate printk per-CPU buffer where messages 778 printed from usafe contexts are temporary stored. One example would 779 be NMI messages, another one - printk recursion. The messages are 780 copied to the main log buffer in a safe context to avoid a deadlock. 781 The value defines the size as a power of 2. 782 783 Those messages are rare and limited. The largest one is when 784 a backtrace is printed. It usually fits into 4KB. Select 785 8KB if you want to be on the safe side. 786 787 Examples: 788 17 => 128 KB for each CPU 789 16 => 64 KB for each CPU 790 15 => 32 KB for each CPU 791 14 => 16 KB for each CPU 792 13 => 8 KB for each CPU 793 12 => 4 KB for each CPU 794 795config PRINTK_INDEX 796 bool "Printk indexing debugfs interface" 797 depends on PRINTK && DEBUG_FS 798 help 799 Add support for indexing of all printk formats known at compile time 800 at <debugfs>/printk/index/<module>. 801 802 This can be used as part of maintaining daemons which monitor 803 /dev/kmsg, as it permits auditing the printk formats present in a 804 kernel, allowing detection of cases where monitored printks are 805 changed or no longer present. 806 807 There is no additional runtime cost to printk with this enabled. 808 809# 810# Architectures with an unreliable sched_clock() should select this: 811# 812config HAVE_UNSTABLE_SCHED_CLOCK 813 bool 814 815config GENERIC_SCHED_CLOCK 816 bool 817 818menu "Scheduler features" 819 820config UCLAMP_TASK 821 bool "Enable utilization clamping for RT/FAIR tasks" 822 depends on CPU_FREQ_GOV_SCHEDUTIL 823 help 824 This feature enables the scheduler to track the clamped utilization 825 of each CPU based on RUNNABLE tasks scheduled on that CPU. 826 827 With this option, the user can specify the min and max CPU 828 utilization allowed for RUNNABLE tasks. The max utilization defines 829 the maximum frequency a task should use while the min utilization 830 defines the minimum frequency it should use. 831 832 Both min and max utilization clamp values are hints to the scheduler, 833 aiming at improving its frequency selection policy, but they do not 834 enforce or grant any specific bandwidth for tasks. 835 836 If in doubt, say N. 837 838config UCLAMP_BUCKETS_COUNT 839 int "Number of supported utilization clamp buckets" 840 range 5 20 841 default 5 842 depends on UCLAMP_TASK 843 help 844 Defines the number of clamp buckets to use. The range of each bucket 845 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 846 number of clamp buckets the finer their granularity and the higher 847 the precision of clamping aggregation and tracking at run-time. 848 849 For example, with the minimum configuration value we will have 5 850 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 851 be refcounted in the [20..39]% bucket and will set the bucket clamp 852 effective value to 25%. 853 If a second 30% boosted task should be co-scheduled on the same CPU, 854 that task will be refcounted in the same bucket of the first task and 855 it will boost the bucket clamp effective value to 30%. 856 The clamp effective value of a bucket is reset to its nominal value 857 (20% in the example above) when there are no more tasks refcounted in 858 that bucket. 859 860 An additional boost/capping margin can be added to some tasks. In the 861 example above the 25% task will be boosted to 30% until it exits the 862 CPU. If that should be considered not acceptable on certain systems, 863 it's always possible to reduce the margin by increasing the number of 864 clamp buckets to trade off used memory for run-time tracking 865 precision. 866 867 If in doubt, use the default value. 868 869endmenu 870 871# 872# For architectures that want to enable the support for NUMA-affine scheduler 873# balancing logic: 874# 875config ARCH_SUPPORTS_NUMA_BALANCING 876 bool 877 878# 879# For architectures that prefer to flush all TLBs after a number of pages 880# are unmapped instead of sending one IPI per page to flush. The architecture 881# must provide guarantees on what happens if a clean TLB cache entry is 882# written after the unmap. Details are in mm/rmap.c near the check for 883# should_defer_flush. The architecture should also consider if the full flush 884# and the refill costs are offset by the savings of sending fewer IPIs. 885config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 886 bool 887 888config CC_HAS_INT128 889 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 890 891config CC_IMPLICIT_FALLTHROUGH 892 string 893 default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5) 894 default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough) 895 896# 897# For architectures that know their GCC __int128 support is sound 898# 899config ARCH_SUPPORTS_INT128 900 bool 901 902# For architectures that (ab)use NUMA to represent different memory regions 903# all cpu-local but of different latencies, such as SuperH. 904# 905config ARCH_WANT_NUMA_VARIABLE_LOCALITY 906 bool 907 908config NUMA_BALANCING 909 bool "Memory placement aware NUMA scheduler" 910 depends on ARCH_SUPPORTS_NUMA_BALANCING 911 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 912 depends on SMP && NUMA && MIGRATION && !PREEMPT_RT 913 help 914 This option adds support for automatic NUMA aware memory/task placement. 915 The mechanism is quite primitive and is based on migrating memory when 916 it has references to the node the task is running on. 917 918 This system will be inactive on UMA systems. 919 920config NUMA_BALANCING_DEFAULT_ENABLED 921 bool "Automatically enable NUMA aware memory/task placement" 922 default y 923 depends on NUMA_BALANCING 924 help 925 If set, automatic NUMA balancing will be enabled if running on a NUMA 926 machine. 927 928menuconfig CGROUPS 929 bool "Control Group support" 930 select KERNFS 931 help 932 This option adds support for grouping sets of processes together, for 933 use with process control subsystems such as Cpusets, CFS, memory 934 controls or device isolation. 935 See 936 - Documentation/scheduler/sched-design-CFS.rst (CFS) 937 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 938 and resource control) 939 940 Say N if unsure. 941 942if CGROUPS 943 944config PAGE_COUNTER 945 bool 946 947config MEMCG 948 bool "Memory controller" 949 select PAGE_COUNTER 950 select EVENTFD 951 help 952 Provides control over the memory footprint of tasks in a cgroup. 953 954config MEMCG_SWAP 955 bool 956 depends on MEMCG && SWAP 957 default y 958 959config MEMCG_KMEM 960 bool 961 depends on MEMCG && !SLOB 962 default y 963 964config BLK_CGROUP 965 bool "IO controller" 966 depends on BLOCK 967 default n 968 help 969 Generic block IO controller cgroup interface. This is the common 970 cgroup interface which should be used by various IO controlling 971 policies. 972 973 Currently, CFQ IO scheduler uses it to recognize task groups and 974 control disk bandwidth allocation (proportional time slice allocation) 975 to such task groups. It is also used by bio throttling logic in 976 block layer to implement upper limit in IO rates on a device. 977 978 This option only enables generic Block IO controller infrastructure. 979 One needs to also enable actual IO controlling logic/policy. For 980 enabling proportional weight division of disk bandwidth in CFQ, set 981 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 982 CONFIG_BLK_DEV_THROTTLING=y. 983 984 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 985 986config CGROUP_WRITEBACK 987 bool 988 depends on MEMCG && BLK_CGROUP 989 default y 990 991menuconfig CGROUP_SCHED 992 bool "CPU controller" 993 default n 994 help 995 This feature lets CPU scheduler recognize task groups and control CPU 996 bandwidth allocation to such task groups. It uses cgroups to group 997 tasks. 998 999if CGROUP_SCHED 1000config FAIR_GROUP_SCHED 1001 bool "Group scheduling for SCHED_OTHER" 1002 depends on CGROUP_SCHED 1003 default CGROUP_SCHED 1004 1005config CFS_BANDWIDTH 1006 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 1007 depends on FAIR_GROUP_SCHED 1008 default n 1009 help 1010 This option allows users to define CPU bandwidth rates (limits) for 1011 tasks running within the fair group scheduler. Groups with no limit 1012 set are considered to be unconstrained and will run with no 1013 restriction. 1014 See Documentation/scheduler/sched-bwc.rst for more information. 1015 1016config RT_GROUP_SCHED 1017 bool "Group scheduling for SCHED_RR/FIFO" 1018 depends on CGROUP_SCHED 1019 default n 1020 help 1021 This feature lets you explicitly allocate real CPU bandwidth 1022 to task groups. If enabled, it will also make it impossible to 1023 schedule realtime tasks for non-root users until you allocate 1024 realtime bandwidth for them. 1025 See Documentation/scheduler/sched-rt-group.rst for more information. 1026 1027endif #CGROUP_SCHED 1028 1029config UCLAMP_TASK_GROUP 1030 bool "Utilization clamping per group of tasks" 1031 depends on CGROUP_SCHED 1032 depends on UCLAMP_TASK 1033 default n 1034 help 1035 This feature enables the scheduler to track the clamped utilization 1036 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 1037 1038 When this option is enabled, the user can specify a min and max 1039 CPU bandwidth which is allowed for each single task in a group. 1040 The max bandwidth allows to clamp the maximum frequency a task 1041 can use, while the min bandwidth allows to define a minimum 1042 frequency a task will always use. 1043 1044 When task group based utilization clamping is enabled, an eventually 1045 specified task-specific clamp value is constrained by the cgroup 1046 specified clamp value. Both minimum and maximum task clamping cannot 1047 be bigger than the corresponding clamping defined at task group level. 1048 1049 If in doubt, say N. 1050 1051config CGROUP_PIDS 1052 bool "PIDs controller" 1053 help 1054 Provides enforcement of process number limits in the scope of a 1055 cgroup. Any attempt to fork more processes than is allowed in the 1056 cgroup will fail. PIDs are fundamentally a global resource because it 1057 is fairly trivial to reach PID exhaustion before you reach even a 1058 conservative kmemcg limit. As a result, it is possible to grind a 1059 system to halt without being limited by other cgroup policies. The 1060 PIDs controller is designed to stop this from happening. 1061 1062 It should be noted that organisational operations (such as attaching 1063 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 1064 since the PIDs limit only affects a process's ability to fork, not to 1065 attach to a cgroup. 1066 1067config CGROUP_RDMA 1068 bool "RDMA controller" 1069 help 1070 Provides enforcement of RDMA resources defined by IB stack. 1071 It is fairly easy for consumers to exhaust RDMA resources, which 1072 can result into resource unavailability to other consumers. 1073 RDMA controller is designed to stop this from happening. 1074 Attaching processes with active RDMA resources to the cgroup 1075 hierarchy is allowed even if can cross the hierarchy's limit. 1076 1077config CGROUP_FREEZER 1078 bool "Freezer controller" 1079 help 1080 Provides a way to freeze and unfreeze all tasks in a 1081 cgroup. 1082 1083 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1084 controller includes important in-kernel memory consumers per default. 1085 1086 If you're using cgroup2, say N. 1087 1088config CGROUP_HUGETLB 1089 bool "HugeTLB controller" 1090 depends on HUGETLB_PAGE 1091 select PAGE_COUNTER 1092 default n 1093 help 1094 Provides a cgroup controller for HugeTLB pages. 1095 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1096 The limit is enforced during page fault. Since HugeTLB doesn't 1097 support page reclaim, enforcing the limit at page fault time implies 1098 that, the application will get SIGBUS signal if it tries to access 1099 HugeTLB pages beyond its limit. This requires the application to know 1100 beforehand how much HugeTLB pages it would require for its use. The 1101 control group is tracked in the third page lru pointer. This means 1102 that we cannot use the controller with huge page less than 3 pages. 1103 1104config CPUSETS 1105 bool "Cpuset controller" 1106 depends on SMP 1107 help 1108 This option will let you create and manage CPUSETs which 1109 allow dynamically partitioning a system into sets of CPUs and 1110 Memory Nodes and assigning tasks to run only within those sets. 1111 This is primarily useful on large SMP or NUMA systems. 1112 1113 Say N if unsure. 1114 1115config PROC_PID_CPUSET 1116 bool "Include legacy /proc/<pid>/cpuset file" 1117 depends on CPUSETS 1118 default y 1119 1120config CGROUP_DEVICE 1121 bool "Device controller" 1122 help 1123 Provides a cgroup controller implementing whitelists for 1124 devices which a process in the cgroup can mknod or open. 1125 1126config CGROUP_CPUACCT 1127 bool "Simple CPU accounting controller" 1128 help 1129 Provides a simple controller for monitoring the 1130 total CPU consumed by the tasks in a cgroup. 1131 1132config CGROUP_PERF 1133 bool "Perf controller" 1134 depends on PERF_EVENTS 1135 help 1136 This option extends the perf per-cpu mode to restrict monitoring 1137 to threads which belong to the cgroup specified and run on the 1138 designated cpu. Or this can be used to have cgroup ID in samples 1139 so that it can monitor performance events among cgroups. 1140 1141 Say N if unsure. 1142 1143config CGROUP_BPF 1144 bool "Support for eBPF programs attached to cgroups" 1145 depends on BPF_SYSCALL 1146 select SOCK_CGROUP_DATA 1147 help 1148 Allow attaching eBPF programs to a cgroup using the bpf(2) 1149 syscall command BPF_PROG_ATTACH. 1150 1151 In which context these programs are accessed depends on the type 1152 of attachment. For instance, programs that are attached using 1153 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1154 inet sockets. 1155 1156config CGROUP_MISC 1157 bool "Misc resource controller" 1158 default n 1159 help 1160 Provides a controller for miscellaneous resources on a host. 1161 1162 Miscellaneous scalar resources are the resources on the host system 1163 which cannot be abstracted like the other cgroups. This controller 1164 tracks and limits the miscellaneous resources used by a process 1165 attached to a cgroup hierarchy. 1166 1167 For more information, please check misc cgroup section in 1168 /Documentation/admin-guide/cgroup-v2.rst. 1169 1170config CGROUP_DEBUG 1171 bool "Debug controller" 1172 default n 1173 depends on DEBUG_KERNEL 1174 help 1175 This option enables a simple controller that exports 1176 debugging information about the cgroups framework. This 1177 controller is for control cgroup debugging only. Its 1178 interfaces are not stable. 1179 1180 Say N. 1181 1182config SOCK_CGROUP_DATA 1183 bool 1184 default n 1185 1186endif # CGROUPS 1187 1188menuconfig NAMESPACES 1189 bool "Namespaces support" if EXPERT 1190 depends on MULTIUSER 1191 default !EXPERT 1192 help 1193 Provides the way to make tasks work with different objects using 1194 the same id. For example same IPC id may refer to different objects 1195 or same user id or pid may refer to different tasks when used in 1196 different namespaces. 1197 1198if NAMESPACES 1199 1200config UTS_NS 1201 bool "UTS namespace" 1202 default y 1203 help 1204 In this namespace tasks see different info provided with the 1205 uname() system call 1206 1207config TIME_NS 1208 bool "TIME namespace" 1209 depends on GENERIC_VDSO_TIME_NS 1210 default y 1211 help 1212 In this namespace boottime and monotonic clocks can be set. 1213 The time will keep going with the same pace. 1214 1215config IPC_NS 1216 bool "IPC namespace" 1217 depends on (SYSVIPC || POSIX_MQUEUE) 1218 default y 1219 help 1220 In this namespace tasks work with IPC ids which correspond to 1221 different IPC objects in different namespaces. 1222 1223config USER_NS 1224 bool "User namespace" 1225 default n 1226 help 1227 This allows containers, i.e. vservers, to use user namespaces 1228 to provide different user info for different servers. 1229 1230 When user namespaces are enabled in the kernel it is 1231 recommended that the MEMCG option also be enabled and that 1232 user-space use the memory control groups to limit the amount 1233 of memory a memory unprivileged users can use. 1234 1235 If unsure, say N. 1236 1237config PID_NS 1238 bool "PID Namespaces" 1239 default y 1240 help 1241 Support process id namespaces. This allows having multiple 1242 processes with the same pid as long as they are in different 1243 pid namespaces. This is a building block of containers. 1244 1245config NET_NS 1246 bool "Network namespace" 1247 depends on NET 1248 default y 1249 help 1250 Allow user space to create what appear to be multiple instances 1251 of the network stack. 1252 1253endif # NAMESPACES 1254 1255config CHECKPOINT_RESTORE 1256 bool "Checkpoint/restore support" 1257 select PROC_CHILDREN 1258 select KCMP 1259 default n 1260 help 1261 Enables additional kernel features in a sake of checkpoint/restore. 1262 In particular it adds auxiliary prctl codes to setup process text, 1263 data and heap segment sizes, and a few additional /proc filesystem 1264 entries. 1265 1266 If unsure, say N here. 1267 1268config SCHED_AUTOGROUP 1269 bool "Automatic process group scheduling" 1270 select CGROUPS 1271 select CGROUP_SCHED 1272 select FAIR_GROUP_SCHED 1273 help 1274 This option optimizes the scheduler for common desktop workloads by 1275 automatically creating and populating task groups. This separation 1276 of workloads isolates aggressive CPU burners (like build jobs) from 1277 desktop applications. Task group autogeneration is currently based 1278 upon task session. 1279 1280config SYSFS_DEPRECATED 1281 bool "Enable deprecated sysfs features to support old userspace tools" 1282 depends on SYSFS 1283 default n 1284 help 1285 This option adds code that switches the layout of the "block" class 1286 devices, to not show up in /sys/class/block/, but only in 1287 /sys/block/. 1288 1289 This switch is only active when the sysfs.deprecated=1 boot option is 1290 passed or the SYSFS_DEPRECATED_V2 option is set. 1291 1292 This option allows new kernels to run on old distributions and tools, 1293 which might get confused by /sys/class/block/. Since 2007/2008 all 1294 major distributions and tools handle this just fine. 1295 1296 Recent distributions and userspace tools after 2009/2010 depend on 1297 the existence of /sys/class/block/, and will not work with this 1298 option enabled. 1299 1300 Only if you are using a new kernel on an old distribution, you might 1301 need to say Y here. 1302 1303config SYSFS_DEPRECATED_V2 1304 bool "Enable deprecated sysfs features by default" 1305 default n 1306 depends on SYSFS 1307 depends on SYSFS_DEPRECATED 1308 help 1309 Enable deprecated sysfs by default. 1310 1311 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1312 option. 1313 1314 Only if you are using a new kernel on an old distribution, you might 1315 need to say Y here. Even then, odds are you would not need it 1316 enabled, you can always pass the boot option if absolutely necessary. 1317 1318config RELAY 1319 bool "Kernel->user space relay support (formerly relayfs)" 1320 select IRQ_WORK 1321 help 1322 This option enables support for relay interface support in 1323 certain file systems (such as debugfs). 1324 It is designed to provide an efficient mechanism for tools and 1325 facilities to relay large amounts of data from kernel space to 1326 user space. 1327 1328 If unsure, say N. 1329 1330config BLK_DEV_INITRD 1331 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1332 help 1333 The initial RAM filesystem is a ramfs which is loaded by the 1334 boot loader (loadlin or lilo) and that is mounted as root 1335 before the normal boot procedure. It is typically used to 1336 load modules needed to mount the "real" root file system, 1337 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1338 1339 If RAM disk support (BLK_DEV_RAM) is also included, this 1340 also enables initial RAM disk (initrd) support and adds 1341 15 Kbytes (more on some other architectures) to the kernel size. 1342 1343 If unsure say Y. 1344 1345if BLK_DEV_INITRD 1346 1347source "usr/Kconfig" 1348 1349endif 1350 1351config BOOT_CONFIG 1352 bool "Boot config support" 1353 select BLK_DEV_INITRD 1354 help 1355 Extra boot config allows system admin to pass a config file as 1356 complemental extension of kernel cmdline when booting. 1357 The boot config file must be attached at the end of initramfs 1358 with checksum, size and magic word. 1359 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1360 1361 If unsure, say Y. 1362 1363choice 1364 prompt "Compiler optimization level" 1365 default CC_OPTIMIZE_FOR_PERFORMANCE 1366 1367config CC_OPTIMIZE_FOR_PERFORMANCE 1368 bool "Optimize for performance (-O2)" 1369 help 1370 This is the default optimization level for the kernel, building 1371 with the "-O2" compiler flag for best performance and most 1372 helpful compile-time warnings. 1373 1374config CC_OPTIMIZE_FOR_PERFORMANCE_O3 1375 bool "Optimize more for performance (-O3)" 1376 depends on ARC 1377 help 1378 Choosing this option will pass "-O3" to your compiler to optimize 1379 the kernel yet more for performance. 1380 1381config CC_OPTIMIZE_FOR_SIZE 1382 bool "Optimize for size (-Os)" 1383 help 1384 Choosing this option will pass "-Os" to your compiler resulting 1385 in a smaller kernel. 1386 1387endchoice 1388 1389config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1390 bool 1391 help 1392 This requires that the arch annotates or otherwise protects 1393 its external entry points from being discarded. Linker scripts 1394 must also merge .text.*, .data.*, and .bss.* correctly into 1395 output sections. Care must be taken not to pull in unrelated 1396 sections (e.g., '.text.init'). Typically '.' in section names 1397 is used to distinguish them from label names / C identifiers. 1398 1399config LD_DEAD_CODE_DATA_ELIMINATION 1400 bool "Dead code and data elimination (EXPERIMENTAL)" 1401 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1402 depends on EXPERT 1403 depends on $(cc-option,-ffunction-sections -fdata-sections) 1404 depends on $(ld-option,--gc-sections) 1405 help 1406 Enable this if you want to do dead code and data elimination with 1407 the linker by compiling with -ffunction-sections -fdata-sections, 1408 and linking with --gc-sections. 1409 1410 This can reduce on disk and in-memory size of the kernel 1411 code and static data, particularly for small configs and 1412 on small systems. This has the possibility of introducing 1413 silently broken kernel if the required annotations are not 1414 present. This option is not well tested yet, so use at your 1415 own risk. 1416 1417config LD_ORPHAN_WARN 1418 def_bool y 1419 depends on ARCH_WANT_LD_ORPHAN_WARN 1420 depends on $(ld-option,--orphan-handling=warn) 1421 1422config SYSCTL 1423 bool 1424 1425config HAVE_UID16 1426 bool 1427 1428config SYSCTL_EXCEPTION_TRACE 1429 bool 1430 help 1431 Enable support for /proc/sys/debug/exception-trace. 1432 1433config SYSCTL_ARCH_UNALIGN_NO_WARN 1434 bool 1435 help 1436 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1437 Allows arch to define/use @no_unaligned_warning to possibly warn 1438 about unaligned access emulation going on under the hood. 1439 1440config SYSCTL_ARCH_UNALIGN_ALLOW 1441 bool 1442 help 1443 Enable support for /proc/sys/kernel/unaligned-trap 1444 Allows arches to define/use @unaligned_enabled to runtime toggle 1445 the unaligned access emulation. 1446 see arch/parisc/kernel/unaligned.c for reference 1447 1448config HAVE_PCSPKR_PLATFORM 1449 bool 1450 1451# interpreter that classic socket filters depend on 1452config BPF 1453 bool 1454 1455menuconfig EXPERT 1456 bool "Configure standard kernel features (expert users)" 1457 # Unhide debug options, to make the on-by-default options visible 1458 select DEBUG_KERNEL 1459 help 1460 This option allows certain base kernel options and settings 1461 to be disabled or tweaked. This is for specialized 1462 environments which can tolerate a "non-standard" kernel. 1463 Only use this if you really know what you are doing. 1464 1465config UID16 1466 bool "Enable 16-bit UID system calls" if EXPERT 1467 depends on HAVE_UID16 && MULTIUSER 1468 default y 1469 help 1470 This enables the legacy 16-bit UID syscall wrappers. 1471 1472config MULTIUSER 1473 bool "Multiple users, groups and capabilities support" if EXPERT 1474 default y 1475 help 1476 This option enables support for non-root users, groups and 1477 capabilities. 1478 1479 If you say N here, all processes will run with UID 0, GID 0, and all 1480 possible capabilities. Saying N here also compiles out support for 1481 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1482 setgid, and capset. 1483 1484 If unsure, say Y here. 1485 1486config SGETMASK_SYSCALL 1487 bool "sgetmask/ssetmask syscalls support" if EXPERT 1488 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1489 help 1490 sys_sgetmask and sys_ssetmask are obsolete system calls 1491 no longer supported in libc but still enabled by default in some 1492 architectures. 1493 1494 If unsure, leave the default option here. 1495 1496config SYSFS_SYSCALL 1497 bool "Sysfs syscall support" if EXPERT 1498 default y 1499 help 1500 sys_sysfs is an obsolete system call no longer supported in libc. 1501 Note that disabling this option is more secure but might break 1502 compatibility with some systems. 1503 1504 If unsure say Y here. 1505 1506config FHANDLE 1507 bool "open by fhandle syscalls" if EXPERT 1508 select EXPORTFS 1509 default y 1510 help 1511 If you say Y here, a user level program will be able to map 1512 file names to handle and then later use the handle for 1513 different file system operations. This is useful in implementing 1514 userspace file servers, which now track files using handles instead 1515 of names. The handle would remain the same even if file names 1516 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1517 syscalls. 1518 1519config POSIX_TIMERS 1520 bool "Posix Clocks & timers" if EXPERT 1521 default y 1522 help 1523 This includes native support for POSIX timers to the kernel. 1524 Some embedded systems have no use for them and therefore they 1525 can be configured out to reduce the size of the kernel image. 1526 1527 When this option is disabled, the following syscalls won't be 1528 available: timer_create, timer_gettime: timer_getoverrun, 1529 timer_settime, timer_delete, clock_adjtime, getitimer, 1530 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1531 clock_getres and clock_nanosleep syscalls will be limited to 1532 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1533 1534 If unsure say y. 1535 1536config PRINTK 1537 default y 1538 bool "Enable support for printk" if EXPERT 1539 select IRQ_WORK 1540 help 1541 This option enables normal printk support. Removing it 1542 eliminates most of the message strings from the kernel image 1543 and makes the kernel more or less silent. As this makes it 1544 very difficult to diagnose system problems, saying N here is 1545 strongly discouraged. 1546 1547config BUG 1548 bool "BUG() support" if EXPERT 1549 default y 1550 help 1551 Disabling this option eliminates support for BUG and WARN, reducing 1552 the size of your kernel image and potentially quietly ignoring 1553 numerous fatal conditions. You should only consider disabling this 1554 option for embedded systems with no facilities for reporting errors. 1555 Just say Y. 1556 1557config ELF_CORE 1558 depends on COREDUMP 1559 default y 1560 bool "Enable ELF core dumps" if EXPERT 1561 help 1562 Enable support for generating core dumps. Disabling saves about 4k. 1563 1564 1565config PCSPKR_PLATFORM 1566 bool "Enable PC-Speaker support" if EXPERT 1567 depends on HAVE_PCSPKR_PLATFORM 1568 select I8253_LOCK 1569 default y 1570 help 1571 This option allows to disable the internal PC-Speaker 1572 support, saving some memory. 1573 1574config BASE_FULL 1575 default y 1576 bool "Enable full-sized data structures for core" if EXPERT 1577 help 1578 Disabling this option reduces the size of miscellaneous core 1579 kernel data structures. This saves memory on small machines, 1580 but may reduce performance. 1581 1582config FUTEX 1583 bool "Enable futex support" if EXPERT 1584 depends on !(SPARC32 && SMP) 1585 default y 1586 imply RT_MUTEXES 1587 help 1588 Disabling this option will cause the kernel to be built without 1589 support for "fast userspace mutexes". The resulting kernel may not 1590 run glibc-based applications correctly. 1591 1592config FUTEX_PI 1593 bool 1594 depends on FUTEX && RT_MUTEXES 1595 default y 1596 1597config EPOLL 1598 bool "Enable eventpoll support" if EXPERT 1599 default y 1600 help 1601 Disabling this option will cause the kernel to be built without 1602 support for epoll family of system calls. 1603 1604config SIGNALFD 1605 bool "Enable signalfd() system call" if EXPERT 1606 default y 1607 help 1608 Enable the signalfd() system call that allows to receive signals 1609 on a file descriptor. 1610 1611 If unsure, say Y. 1612 1613config TIMERFD 1614 bool "Enable timerfd() system call" if EXPERT 1615 default y 1616 help 1617 Enable the timerfd() system call that allows to receive timer 1618 events on a file descriptor. 1619 1620 If unsure, say Y. 1621 1622config EVENTFD 1623 bool "Enable eventfd() system call" if EXPERT 1624 default y 1625 help 1626 Enable the eventfd() system call that allows to receive both 1627 kernel notification (ie. KAIO) or userspace notifications. 1628 1629 If unsure, say Y. 1630 1631config SHMEM 1632 bool "Use full shmem filesystem" if EXPERT 1633 default y 1634 depends on MMU 1635 help 1636 The shmem is an internal filesystem used to manage shared memory. 1637 It is backed by swap and manages resource limits. It is also exported 1638 to userspace as tmpfs if TMPFS is enabled. Disabling this 1639 option replaces shmem and tmpfs with the much simpler ramfs code, 1640 which may be appropriate on small systems without swap. 1641 1642config AIO 1643 bool "Enable AIO support" if EXPERT 1644 default y 1645 help 1646 This option enables POSIX asynchronous I/O which may by used 1647 by some high performance threaded applications. Disabling 1648 this option saves about 7k. 1649 1650config IO_URING 1651 bool "Enable IO uring support" if EXPERT 1652 select IO_WQ 1653 default y 1654 help 1655 This option enables support for the io_uring interface, enabling 1656 applications to submit and complete IO through submission and 1657 completion rings that are shared between the kernel and application. 1658 1659config ADVISE_SYSCALLS 1660 bool "Enable madvise/fadvise syscalls" if EXPERT 1661 default y 1662 help 1663 This option enables the madvise and fadvise syscalls, used by 1664 applications to advise the kernel about their future memory or file 1665 usage, improving performance. If building an embedded system where no 1666 applications use these syscalls, you can disable this option to save 1667 space. 1668 1669config HAVE_ARCH_USERFAULTFD_WP 1670 bool 1671 help 1672 Arch has userfaultfd write protection support 1673 1674config HAVE_ARCH_USERFAULTFD_MINOR 1675 bool 1676 help 1677 Arch has userfaultfd minor fault support 1678 1679config MEMBARRIER 1680 bool "Enable membarrier() system call" if EXPERT 1681 default y 1682 help 1683 Enable the membarrier() system call that allows issuing memory 1684 barriers across all running threads, which can be used to distribute 1685 the cost of user-space memory barriers asymmetrically by transforming 1686 pairs of memory barriers into pairs consisting of membarrier() and a 1687 compiler barrier. 1688 1689 If unsure, say Y. 1690 1691config KALLSYMS 1692 bool "Load all symbols for debugging/ksymoops" if EXPERT 1693 default y 1694 help 1695 Say Y here to let the kernel print out symbolic crash information and 1696 symbolic stack backtraces. This increases the size of the kernel 1697 somewhat, as all symbols have to be loaded into the kernel image. 1698 1699config KALLSYMS_ALL 1700 bool "Include all symbols in kallsyms" 1701 depends on DEBUG_KERNEL && KALLSYMS 1702 help 1703 Normally kallsyms only contains the symbols of functions for nicer 1704 OOPS messages and backtraces (i.e., symbols from the text and inittext 1705 sections). This is sufficient for most cases. And only in very rare 1706 cases (e.g., when a debugger is used) all symbols are required (e.g., 1707 names of variables from the data sections, etc). 1708 1709 This option makes sure that all symbols are loaded into the kernel 1710 image (i.e., symbols from all sections) in cost of increased kernel 1711 size (depending on the kernel configuration, it may be 300KiB or 1712 something like this). 1713 1714 Say N unless you really need all symbols. 1715 1716config KALLSYMS_ABSOLUTE_PERCPU 1717 bool 1718 depends on KALLSYMS 1719 default X86_64 && SMP 1720 1721config KALLSYMS_BASE_RELATIVE 1722 bool 1723 depends on KALLSYMS 1724 default !IA64 1725 help 1726 Instead of emitting them as absolute values in the native word size, 1727 emit the symbol references in the kallsyms table as 32-bit entries, 1728 each containing a relative value in the range [base, base + U32_MAX] 1729 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1730 an absolute value in the range [0, S32_MAX] or a relative value in the 1731 range [base, base + S32_MAX], where base is the lowest relative symbol 1732 address encountered in the image. 1733 1734 On 64-bit builds, this reduces the size of the address table by 50%, 1735 but more importantly, it results in entries whose values are build 1736 time constants, and no relocation pass is required at runtime to fix 1737 up the entries based on the runtime load address of the kernel. 1738 1739# end of the "standard kernel features (expert users)" menu 1740 1741# syscall, maps, verifier 1742 1743config USERFAULTFD 1744 bool "Enable userfaultfd() system call" 1745 depends on MMU 1746 help 1747 Enable the userfaultfd() system call that allows to intercept and 1748 handle page faults in userland. 1749 1750config ARCH_HAS_MEMBARRIER_CALLBACKS 1751 bool 1752 1753config ARCH_HAS_MEMBARRIER_SYNC_CORE 1754 bool 1755 1756config KCMP 1757 bool "Enable kcmp() system call" if EXPERT 1758 help 1759 Enable the kernel resource comparison system call. It provides 1760 user-space with the ability to compare two processes to see if they 1761 share a common resource, such as a file descriptor or even virtual 1762 memory space. 1763 1764 If unsure, say N. 1765 1766config RSEQ 1767 bool "Enable rseq() system call" if EXPERT 1768 default y 1769 depends on HAVE_RSEQ 1770 select MEMBARRIER 1771 help 1772 Enable the restartable sequences system call. It provides a 1773 user-space cache for the current CPU number value, which 1774 speeds up getting the current CPU number from user-space, 1775 as well as an ABI to speed up user-space operations on 1776 per-CPU data. 1777 1778 If unsure, say Y. 1779 1780config DEBUG_RSEQ 1781 default n 1782 bool "Enabled debugging of rseq() system call" if EXPERT 1783 depends on RSEQ && DEBUG_KERNEL 1784 help 1785 Enable extra debugging checks for the rseq system call. 1786 1787 If unsure, say N. 1788 1789config EMBEDDED 1790 bool "Embedded system" 1791 select EXPERT 1792 help 1793 This option should be enabled if compiling the kernel for 1794 an embedded system so certain expert options are available 1795 for configuration. 1796 1797config HAVE_PERF_EVENTS 1798 bool 1799 help 1800 See tools/perf/design.txt for details. 1801 1802config GUEST_PERF_EVENTS 1803 bool 1804 depends on HAVE_PERF_EVENTS 1805 1806config PERF_USE_VMALLOC 1807 bool 1808 help 1809 See tools/perf/design.txt for details 1810 1811config PC104 1812 bool "PC/104 support" if EXPERT 1813 help 1814 Expose PC/104 form factor device drivers and options available for 1815 selection and configuration. Enable this option if your target 1816 machine has a PC/104 bus. 1817 1818menu "Kernel Performance Events And Counters" 1819 1820config PERF_EVENTS 1821 bool "Kernel performance events and counters" 1822 default y if PROFILING 1823 depends on HAVE_PERF_EVENTS 1824 select IRQ_WORK 1825 select SRCU 1826 help 1827 Enable kernel support for various performance events provided 1828 by software and hardware. 1829 1830 Software events are supported either built-in or via the 1831 use of generic tracepoints. 1832 1833 Most modern CPUs support performance events via performance 1834 counter registers. These registers count the number of certain 1835 types of hw events: such as instructions executed, cachemisses 1836 suffered, or branches mis-predicted - without slowing down the 1837 kernel or applications. These registers can also trigger interrupts 1838 when a threshold number of events have passed - and can thus be 1839 used to profile the code that runs on that CPU. 1840 1841 The Linux Performance Event subsystem provides an abstraction of 1842 these software and hardware event capabilities, available via a 1843 system call and used by the "perf" utility in tools/perf/. It 1844 provides per task and per CPU counters, and it provides event 1845 capabilities on top of those. 1846 1847 Say Y if unsure. 1848 1849config DEBUG_PERF_USE_VMALLOC 1850 default n 1851 bool "Debug: use vmalloc to back perf mmap() buffers" 1852 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1853 select PERF_USE_VMALLOC 1854 help 1855 Use vmalloc memory to back perf mmap() buffers. 1856 1857 Mostly useful for debugging the vmalloc code on platforms 1858 that don't require it. 1859 1860 Say N if unsure. 1861 1862endmenu 1863 1864config VM_EVENT_COUNTERS 1865 default y 1866 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1867 help 1868 VM event counters are needed for event counts to be shown. 1869 This option allows the disabling of the VM event counters 1870 on EXPERT systems. /proc/vmstat will only show page counts 1871 if VM event counters are disabled. 1872 1873config SLUB_DEBUG 1874 default y 1875 bool "Enable SLUB debugging support" if EXPERT 1876 depends on SLUB && SYSFS 1877 help 1878 SLUB has extensive debug support features. Disabling these can 1879 result in significant savings in code size. This also disables 1880 SLUB sysfs support. /sys/slab will not exist and there will be 1881 no support for cache validation etc. 1882 1883config COMPAT_BRK 1884 bool "Disable heap randomization" 1885 default y 1886 help 1887 Randomizing heap placement makes heap exploits harder, but it 1888 also breaks ancient binaries (including anything libc5 based). 1889 This option changes the bootup default to heap randomization 1890 disabled, and can be overridden at runtime by setting 1891 /proc/sys/kernel/randomize_va_space to 2. 1892 1893 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1894 1895choice 1896 prompt "Choose SLAB allocator" 1897 default SLUB 1898 help 1899 This option allows to select a slab allocator. 1900 1901config SLAB 1902 bool "SLAB" 1903 depends on !PREEMPT_RT 1904 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1905 help 1906 The regular slab allocator that is established and known to work 1907 well in all environments. It organizes cache hot objects in 1908 per cpu and per node queues. 1909 1910config SLUB 1911 bool "SLUB (Unqueued Allocator)" 1912 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1913 help 1914 SLUB is a slab allocator that minimizes cache line usage 1915 instead of managing queues of cached objects (SLAB approach). 1916 Per cpu caching is realized using slabs of objects instead 1917 of queues of objects. SLUB can use memory efficiently 1918 and has enhanced diagnostics. SLUB is the default choice for 1919 a slab allocator. 1920 1921config SLOB 1922 depends on EXPERT 1923 bool "SLOB (Simple Allocator)" 1924 depends on !PREEMPT_RT 1925 help 1926 SLOB replaces the stock allocator with a drastically simpler 1927 allocator. SLOB is generally more space efficient but 1928 does not perform as well on large systems. 1929 1930endchoice 1931 1932config SLAB_MERGE_DEFAULT 1933 bool "Allow slab caches to be merged" 1934 default y 1935 depends on SLAB || SLUB 1936 help 1937 For reduced kernel memory fragmentation, slab caches can be 1938 merged when they share the same size and other characteristics. 1939 This carries a risk of kernel heap overflows being able to 1940 overwrite objects from merged caches (and more easily control 1941 cache layout), which makes such heap attacks easier to exploit 1942 by attackers. By keeping caches unmerged, these kinds of exploits 1943 can usually only damage objects in the same cache. To disable 1944 merging at runtime, "slab_nomerge" can be passed on the kernel 1945 command line. 1946 1947config SLAB_FREELIST_RANDOM 1948 bool "Randomize slab freelist" 1949 depends on SLAB || SLUB 1950 help 1951 Randomizes the freelist order used on creating new pages. This 1952 security feature reduces the predictability of the kernel slab 1953 allocator against heap overflows. 1954 1955config SLAB_FREELIST_HARDENED 1956 bool "Harden slab freelist metadata" 1957 depends on SLAB || SLUB 1958 help 1959 Many kernel heap attacks try to target slab cache metadata and 1960 other infrastructure. This options makes minor performance 1961 sacrifices to harden the kernel slab allocator against common 1962 freelist exploit methods. Some slab implementations have more 1963 sanity-checking than others. This option is most effective with 1964 CONFIG_SLUB. 1965 1966config SHUFFLE_PAGE_ALLOCATOR 1967 bool "Page allocator randomization" 1968 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1969 help 1970 Randomization of the page allocator improves the average 1971 utilization of a direct-mapped memory-side-cache. See section 1972 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1973 6.2a specification for an example of how a platform advertises 1974 the presence of a memory-side-cache. There are also incidental 1975 security benefits as it reduces the predictability of page 1976 allocations to compliment SLAB_FREELIST_RANDOM, but the 1977 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1978 10th order of pages is selected based on cache utilization 1979 benefits on x86. 1980 1981 While the randomization improves cache utilization it may 1982 negatively impact workloads on platforms without a cache. For 1983 this reason, by default, the randomization is enabled only 1984 after runtime detection of a direct-mapped memory-side-cache. 1985 Otherwise, the randomization may be force enabled with the 1986 'page_alloc.shuffle' kernel command line parameter. 1987 1988 Say Y if unsure. 1989 1990config SLUB_CPU_PARTIAL 1991 default y 1992 depends on SLUB && SMP 1993 bool "SLUB per cpu partial cache" 1994 help 1995 Per cpu partial caches accelerate objects allocation and freeing 1996 that is local to a processor at the price of more indeterminism 1997 in the latency of the free. On overflow these caches will be cleared 1998 which requires the taking of locks that may cause latency spikes. 1999 Typically one would choose no for a realtime system. 2000 2001config MMAP_ALLOW_UNINITIALIZED 2002 bool "Allow mmapped anonymous memory to be uninitialized" 2003 depends on EXPERT && !MMU 2004 default n 2005 help 2006 Normally, and according to the Linux spec, anonymous memory obtained 2007 from mmap() has its contents cleared before it is passed to 2008 userspace. Enabling this config option allows you to request that 2009 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 2010 providing a huge performance boost. If this option is not enabled, 2011 then the flag will be ignored. 2012 2013 This is taken advantage of by uClibc's malloc(), and also by 2014 ELF-FDPIC binfmt's brk and stack allocator. 2015 2016 Because of the obvious security issues, this option should only be 2017 enabled on embedded devices where you control what is run in 2018 userspace. Since that isn't generally a problem on no-MMU systems, 2019 it is normally safe to say Y here. 2020 2021 See Documentation/admin-guide/mm/nommu-mmap.rst for more information. 2022 2023config SYSTEM_DATA_VERIFICATION 2024 def_bool n 2025 select SYSTEM_TRUSTED_KEYRING 2026 select KEYS 2027 select CRYPTO 2028 select CRYPTO_RSA 2029 select ASYMMETRIC_KEY_TYPE 2030 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 2031 select ASN1 2032 select OID_REGISTRY 2033 select X509_CERTIFICATE_PARSER 2034 select PKCS7_MESSAGE_PARSER 2035 help 2036 Provide PKCS#7 message verification using the contents of the system 2037 trusted keyring to provide public keys. This then can be used for 2038 module verification, kexec image verification and firmware blob 2039 verification. 2040 2041config PROFILING 2042 bool "Profiling support" 2043 help 2044 Say Y here to enable the extended profiling support mechanisms used 2045 by profilers. 2046 2047# 2048# Place an empty function call at each tracepoint site. Can be 2049# dynamically changed for a probe function. 2050# 2051config TRACEPOINTS 2052 bool 2053 2054endmenu # General setup 2055 2056source "arch/Kconfig" 2057 2058config RT_MUTEXES 2059 bool 2060 default y if PREEMPT_RT 2061 2062config BASE_SMALL 2063 int 2064 default 0 if BASE_FULL 2065 default 1 if !BASE_FULL 2066 2067config MODULE_SIG_FORMAT 2068 def_bool n 2069 select SYSTEM_DATA_VERIFICATION 2070 2071menuconfig MODULES 2072 bool "Enable loadable module support" 2073 modules 2074 help 2075 Kernel modules are small pieces of compiled code which can 2076 be inserted in the running kernel, rather than being 2077 permanently built into the kernel. You use the "modprobe" 2078 tool to add (and sometimes remove) them. If you say Y here, 2079 many parts of the kernel can be built as modules (by 2080 answering M instead of Y where indicated): this is most 2081 useful for infrequently used options which are not required 2082 for booting. For more information, see the man pages for 2083 modprobe, lsmod, modinfo, insmod and rmmod. 2084 2085 If you say Y here, you will need to run "make 2086 modules_install" to put the modules under /lib/modules/ 2087 where modprobe can find them (you may need to be root to do 2088 this). 2089 2090 If unsure, say Y. 2091 2092if MODULES 2093 2094config MODULE_FORCE_LOAD 2095 bool "Forced module loading" 2096 default n 2097 help 2098 Allow loading of modules without version information (ie. modprobe 2099 --force). Forced module loading sets the 'F' (forced) taint flag and 2100 is usually a really bad idea. 2101 2102config MODULE_UNLOAD 2103 bool "Module unloading" 2104 help 2105 Without this option you will not be able to unload any 2106 modules (note that some modules may not be unloadable 2107 anyway), which makes your kernel smaller, faster 2108 and simpler. If unsure, say Y. 2109 2110config MODULE_FORCE_UNLOAD 2111 bool "Forced module unloading" 2112 depends on MODULE_UNLOAD 2113 help 2114 This option allows you to force a module to unload, even if the 2115 kernel believes it is unsafe: the kernel will remove the module 2116 without waiting for anyone to stop using it (using the -f option to 2117 rmmod). This is mainly for kernel developers and desperate users. 2118 If unsure, say N. 2119 2120config MODVERSIONS 2121 bool "Module versioning support" 2122 help 2123 Usually, you have to use modules compiled with your kernel. 2124 Saying Y here makes it sometimes possible to use modules 2125 compiled for different kernels, by adding enough information 2126 to the modules to (hopefully) spot any changes which would 2127 make them incompatible with the kernel you are running. If 2128 unsure, say N. 2129 2130config ASM_MODVERSIONS 2131 bool 2132 default HAVE_ASM_MODVERSIONS && MODVERSIONS 2133 help 2134 This enables module versioning for exported symbols also from 2135 assembly. This can be enabled only when the target architecture 2136 supports it. 2137 2138config MODULE_REL_CRCS 2139 bool 2140 depends on MODVERSIONS 2141 2142config MODULE_SRCVERSION_ALL 2143 bool "Source checksum for all modules" 2144 help 2145 Modules which contain a MODULE_VERSION get an extra "srcversion" 2146 field inserted into their modinfo section, which contains a 2147 sum of the source files which made it. This helps maintainers 2148 see exactly which source was used to build a module (since 2149 others sometimes change the module source without updating 2150 the version). With this option, such a "srcversion" field 2151 will be created for all modules. If unsure, say N. 2152 2153config MODULE_SIG 2154 bool "Module signature verification" 2155 select MODULE_SIG_FORMAT 2156 help 2157 Check modules for valid signatures upon load: the signature 2158 is simply appended to the module. For more information see 2159 <file:Documentation/admin-guide/module-signing.rst>. 2160 2161 Note that this option adds the OpenSSL development packages as a 2162 kernel build dependency so that the signing tool can use its crypto 2163 library. 2164 2165 You should enable this option if you wish to use either 2166 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via 2167 another LSM - otherwise unsigned modules will be loadable regardless 2168 of the lockdown policy. 2169 2170 !!!WARNING!!! If you enable this option, you MUST make sure that the 2171 module DOES NOT get stripped after being signed. This includes the 2172 debuginfo strip done by some packagers (such as rpmbuild) and 2173 inclusion into an initramfs that wants the module size reduced. 2174 2175config MODULE_SIG_FORCE 2176 bool "Require modules to be validly signed" 2177 depends on MODULE_SIG 2178 help 2179 Reject unsigned modules or signed modules for which we don't have a 2180 key. Without this, such modules will simply taint the kernel. 2181 2182config MODULE_SIG_ALL 2183 bool "Automatically sign all modules" 2184 default y 2185 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 2186 help 2187 Sign all modules during make modules_install. Without this option, 2188 modules must be signed manually, using the scripts/sign-file tool. 2189 2190comment "Do not forget to sign required modules with scripts/sign-file" 2191 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2192 2193choice 2194 prompt "Which hash algorithm should modules be signed with?" 2195 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 2196 help 2197 This determines which sort of hashing algorithm will be used during 2198 signature generation. This algorithm _must_ be built into the kernel 2199 directly so that signature verification can take place. It is not 2200 possible to load a signed module containing the algorithm to check 2201 the signature on that module. 2202 2203config MODULE_SIG_SHA1 2204 bool "Sign modules with SHA-1" 2205 select CRYPTO_SHA1 2206 2207config MODULE_SIG_SHA224 2208 bool "Sign modules with SHA-224" 2209 select CRYPTO_SHA256 2210 2211config MODULE_SIG_SHA256 2212 bool "Sign modules with SHA-256" 2213 select CRYPTO_SHA256 2214 2215config MODULE_SIG_SHA384 2216 bool "Sign modules with SHA-384" 2217 select CRYPTO_SHA512 2218 2219config MODULE_SIG_SHA512 2220 bool "Sign modules with SHA-512" 2221 select CRYPTO_SHA512 2222 2223endchoice 2224 2225config MODULE_SIG_HASH 2226 string 2227 depends on MODULE_SIG || IMA_APPRAISE_MODSIG 2228 default "sha1" if MODULE_SIG_SHA1 2229 default "sha224" if MODULE_SIG_SHA224 2230 default "sha256" if MODULE_SIG_SHA256 2231 default "sha384" if MODULE_SIG_SHA384 2232 default "sha512" if MODULE_SIG_SHA512 2233 2234choice 2235 prompt "Module compression mode" 2236 help 2237 This option allows you to choose the algorithm which will be used to 2238 compress modules when 'make modules_install' is run. (or, you can 2239 choose to not compress modules at all.) 2240 2241 External modules will also be compressed in the same way during the 2242 installation. 2243 2244 For modules inside an initrd or initramfs, it's more efficient to 2245 compress the whole initrd or initramfs instead. 2246 2247 This is fully compatible with signed modules. 2248 2249 Please note that the tool used to load modules needs to support the 2250 corresponding algorithm. module-init-tools MAY support gzip, and kmod 2251 MAY support gzip, xz and zstd. 2252 2253 Your build system needs to provide the appropriate compression tool 2254 to compress the modules. 2255 2256 If in doubt, select 'None'. 2257 2258config MODULE_COMPRESS_NONE 2259 bool "None" 2260 help 2261 Do not compress modules. The installed modules are suffixed 2262 with .ko. 2263 2264config MODULE_COMPRESS_GZIP 2265 bool "GZIP" 2266 help 2267 Compress modules with GZIP. The installed modules are suffixed 2268 with .ko.gz. 2269 2270config MODULE_COMPRESS_XZ 2271 bool "XZ" 2272 help 2273 Compress modules with XZ. The installed modules are suffixed 2274 with .ko.xz. 2275 2276config MODULE_COMPRESS_ZSTD 2277 bool "ZSTD" 2278 help 2279 Compress modules with ZSTD. The installed modules are suffixed 2280 with .ko.zst. 2281 2282endchoice 2283 2284config MODULE_DECOMPRESS 2285 bool "Support in-kernel module decompression" 2286 depends on MODULE_COMPRESS_GZIP || MODULE_COMPRESS_XZ 2287 select ZLIB_INFLATE if MODULE_COMPRESS_GZIP 2288 select XZ_DEC if MODULE_COMPRESS_XZ 2289 help 2290 2291 Support for decompressing kernel modules by the kernel itself 2292 instead of relying on userspace to perform this task. Useful when 2293 load pinning security policy is enabled. 2294 2295 If unsure, say N. 2296 2297config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS 2298 bool "Allow loading of modules with missing namespace imports" 2299 help 2300 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in 2301 a namespace. A module that makes use of a symbol exported with such a 2302 namespace is required to import the namespace via MODULE_IMPORT_NS(). 2303 There is no technical reason to enforce correct namespace imports, 2304 but it creates consistency between symbols defining namespaces and 2305 users importing namespaces they make use of. This option relaxes this 2306 requirement and lifts the enforcement when loading a module. 2307 2308 If unsure, say N. 2309 2310config MODPROBE_PATH 2311 string "Path to modprobe binary" 2312 default "/sbin/modprobe" 2313 help 2314 When kernel code requests a module, it does so by calling 2315 the "modprobe" userspace utility. This option allows you to 2316 set the path where that binary is found. This can be changed 2317 at runtime via the sysctl file 2318 /proc/sys/kernel/modprobe. Setting this to the empty string 2319 removes the kernel's ability to request modules (but 2320 userspace can still load modules explicitly). 2321 2322config TRIM_UNUSED_KSYMS 2323 bool "Trim unused exported kernel symbols" if EXPERT 2324 depends on !COMPILE_TEST 2325 help 2326 The kernel and some modules make many symbols available for 2327 other modules to use via EXPORT_SYMBOL() and variants. Depending 2328 on the set of modules being selected in your kernel configuration, 2329 many of those exported symbols might never be used. 2330 2331 This option allows for unused exported symbols to be dropped from 2332 the build. In turn, this provides the compiler more opportunities 2333 (especially when using LTO) for optimizing the code and reducing 2334 binary size. This might have some security advantages as well. 2335 2336 If unsure, or if you need to build out-of-tree modules, say N. 2337 2338config UNUSED_KSYMS_WHITELIST 2339 string "Whitelist of symbols to keep in ksymtab" 2340 depends on TRIM_UNUSED_KSYMS 2341 help 2342 By default, all unused exported symbols will be un-exported from the 2343 build when TRIM_UNUSED_KSYMS is selected. 2344 2345 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept 2346 exported at all times, even in absence of in-tree users. The value to 2347 set here is the path to a text file containing the list of symbols, 2348 one per line. The path can be absolute, or relative to the kernel 2349 source tree. 2350 2351endif # MODULES 2352 2353config MODULES_TREE_LOOKUP 2354 def_bool y 2355 depends on PERF_EVENTS || TRACING || CFI_CLANG 2356 2357config INIT_ALL_POSSIBLE 2358 bool 2359 help 2360 Back when each arch used to define their own cpu_online_mask and 2361 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2362 with all 1s, and others with all 0s. When they were centralised, 2363 it was better to provide this option than to break all the archs 2364 and have several arch maintainers pursuing me down dark alleys. 2365 2366source "block/Kconfig" 2367 2368config PREEMPT_NOTIFIERS 2369 bool 2370 2371config PADATA 2372 depends on SMP 2373 bool 2374 2375config ASN1 2376 tristate 2377 help 2378 Build a simple ASN.1 grammar compiler that produces a bytecode output 2379 that can be interpreted by the ASN.1 stream decoder and used to 2380 inform it as to what tags are to be expected in a stream and what 2381 functions to call on what tags. 2382 2383source "kernel/Kconfig.locks" 2384 2385config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 2386 bool 2387 2388config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2389 bool 2390 2391# It may be useful for an architecture to override the definitions of the 2392# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2393# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2394# different calling convention for syscalls. They can also override the 2395# macros for not-implemented syscalls in kernel/sys_ni.c and 2396# kernel/time/posix-stubs.c. All these overrides need to be available in 2397# <asm/syscall_wrapper.h>. 2398config ARCH_HAS_SYSCALL_WRAPPER 2399 def_bool n 2400