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