1 # SPDX-License-Identifier: GPL-2.0-only 2 config 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 19 config CC_IS_GCC 20 def_bool $(success,test "$(cc-name)" = GCC) 21 22 config GCC_VERSION 23 int 24 default $(cc-version) if CC_IS_GCC 25 default 0 26 27 config CC_IS_CLANG 28 def_bool $(success,test "$(cc-name)" = Clang) 29 30 config CLANG_VERSION 31 int 32 default $(cc-version) if CC_IS_CLANG 33 default 0 34 35 config AS_IS_GNU 36 def_bool $(success,test "$(as-name)" = GNU) 37 38 config AS_IS_LLVM 39 def_bool $(success,test "$(as-name)" = LLVM) 40 41 config 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 47 config LD_IS_BFD 48 def_bool $(success,test "$(ld-name)" = BFD) 49 50 config LD_VERSION 51 int 52 default $(ld-version) if LD_IS_BFD 53 default 0 54 55 config LD_IS_LLD 56 def_bool $(success,test "$(ld-name)" = LLD) 57 58 config LLD_VERSION 59 int 60 default $(ld-version) if LD_IS_LLD 61 default 0 62 63 config RUSTC_VERSION 64 int 65 default $(rustc-version) 66 help 67 It does not depend on `RUST` since that one may need to use the version 68 in a `depends on`. 69 70 config RUST_IS_AVAILABLE 71 def_bool $(success,$(srctree)/scripts/rust_is_available.sh) 72 help 73 This shows whether a suitable Rust toolchain is available (found). 74 75 Please see Documentation/rust/quick-start.rst for instructions on how 76 to satisfy the build requirements of Rust support. 77 78 In particular, the Makefile target 'rustavailable' is useful to check 79 why the Rust toolchain is not being detected. 80 81 config RUSTC_LLVM_VERSION 82 int 83 default $(rustc-llvm-version) 84 85 config CC_CAN_LINK 86 bool 87 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT 88 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag)) 89 90 config CC_CAN_LINK_STATIC 91 bool 92 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag) -static) if 64BIT 93 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag) -static) 94 95 # Fixed in GCC 14, 13.3, 12.4 and 11.5 96 # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113921 97 config GCC_ASM_GOTO_OUTPUT_BROKEN 98 bool 99 depends on CC_IS_GCC 100 default y if GCC_VERSION < 110500 101 default y if GCC_VERSION >= 120000 && GCC_VERSION < 120400 102 default y if GCC_VERSION >= 130000 && GCC_VERSION < 130300 103 104 config CC_HAS_ASM_GOTO_OUTPUT 105 def_bool y 106 depends on !GCC_ASM_GOTO_OUTPUT_BROKEN 107 depends on $(success,echo 'int foo(int x) { asm goto ("": "=r"(x) ::: bar); return x; bar: return 0; }' | $(CC) -x c - -c -o /dev/null) 108 109 config CC_HAS_ASM_GOTO_TIED_OUTPUT 110 depends on CC_HAS_ASM_GOTO_OUTPUT 111 # Detect buggy gcc and clang, fixed in gcc-11 clang-14. 112 def_bool $(success,echo 'int foo(int *x) { asm goto (".long (%l[bar]) - .": "+m"(*x) ::: bar); return *x; bar: return 0; }' | $CC -x c - -c -o /dev/null) 113 114 config TOOLS_SUPPORT_RELR 115 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 116 117 config CC_HAS_ASM_INLINE 118 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 119 120 config CC_HAS_NO_PROFILE_FN_ATTR 121 def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror) 122 123 config PAHOLE_VERSION 124 int 125 default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE)) 126 127 config CONSTRUCTORS 128 bool 129 130 config IRQ_WORK 131 def_bool y if SMP 132 133 config BUILDTIME_TABLE_SORT 134 bool 135 136 config THREAD_INFO_IN_TASK 137 bool 138 help 139 Select this to move thread_info off the stack into task_struct. To 140 make this work, an arch will need to remove all thread_info fields 141 except flags and fix any runtime bugs. 142 143 One subtle change that will be needed is to use try_get_task_stack() 144 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 145 146 menu "General setup" 147 148 config BROKEN 149 bool 150 151 config BROKEN_ON_SMP 152 bool 153 depends on BROKEN || !SMP 154 default y 155 156 config INIT_ENV_ARG_LIMIT 157 int 158 default 32 if !UML 159 default 128 if UML 160 help 161 Maximum of each of the number of arguments and environment 162 variables passed to init from the kernel command line. 163 164 config COMPILE_TEST 165 bool "Compile also drivers which will not load" 166 depends on HAS_IOMEM 167 help 168 Some drivers can be compiled on a different platform than they are 169 intended to be run on. Despite they cannot be loaded there (or even 170 when they load they cannot be used due to missing HW support), 171 developers still, opposing to distributors, might want to build such 172 drivers to compile-test them. 173 174 If you are a developer and want to build everything available, say Y 175 here. If you are a user/distributor, say N here to exclude useless 176 drivers to be distributed. 177 178 config WERROR 179 bool "Compile the kernel with warnings as errors" 180 default COMPILE_TEST 181 help 182 A kernel build should not cause any compiler warnings, and this 183 enables the '-Werror' (for C) and '-Dwarnings' (for Rust) flags 184 to enforce that rule by default. Certain warnings from other tools 185 such as the linker may be upgraded to errors with this option as 186 well. 187 188 However, if you have a new (or very old) compiler or linker with odd 189 and unusual warnings, or you have some architecture with problems, 190 you may need to disable this config option in order to 191 successfully build the kernel. 192 193 If in doubt, say Y. 194 195 config UAPI_HEADER_TEST 196 bool "Compile test UAPI headers" 197 depends on HEADERS_INSTALL && CC_CAN_LINK 198 help 199 Compile test headers exported to user-space to ensure they are 200 self-contained, i.e. compilable as standalone units. 201 202 If you are a developer or tester and want to ensure the exported 203 headers are self-contained, say Y here. Otherwise, choose N. 204 205 config LOCALVERSION 206 string "Local version - append to kernel release" 207 help 208 Append an extra string to the end of your kernel version. 209 This will show up when you type uname, for example. 210 The string you set here will be appended after the contents of 211 any files with a filename matching localversion* in your 212 object and source tree, in that order. Your total string can 213 be a maximum of 64 characters. 214 215 config LOCALVERSION_AUTO 216 bool "Automatically append version information to the version string" 217 default y 218 depends on !COMPILE_TEST 219 help 220 This will try to automatically determine if the current tree is a 221 release tree by looking for git tags that belong to the current 222 top of tree revision. 223 224 A string of the format -gxxxxxxxx will be added to the localversion 225 if a git-based tree is found. The string generated by this will be 226 appended after any matching localversion* files, and after the value 227 set in CONFIG_LOCALVERSION. 228 229 (The actual string used here is the first 12 characters produced 230 by running the command: 231 232 $ git rev-parse --verify HEAD 233 234 which is done within the script "scripts/setlocalversion".) 235 236 config BUILD_SALT 237 string "Build ID Salt" 238 default "" 239 help 240 The build ID is used to link binaries and their debug info. Setting 241 this option will use the value in the calculation of the build id. 242 This is mostly useful for distributions which want to ensure the 243 build is unique between builds. It's safe to leave the default. 244 245 config HAVE_KERNEL_GZIP 246 bool 247 248 config HAVE_KERNEL_BZIP2 249 bool 250 251 config HAVE_KERNEL_LZMA 252 bool 253 254 config HAVE_KERNEL_XZ 255 bool 256 257 config HAVE_KERNEL_LZO 258 bool 259 260 config HAVE_KERNEL_LZ4 261 bool 262 263 config HAVE_KERNEL_ZSTD 264 bool 265 266 config HAVE_KERNEL_UNCOMPRESSED 267 bool 268 269 choice 270 prompt "Kernel compression mode" 271 default KERNEL_GZIP 272 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 273 help 274 The linux kernel is a kind of self-extracting executable. 275 Several compression algorithms are available, which differ 276 in efficiency, compression and decompression speed. 277 Compression speed is only relevant when building a kernel. 278 Decompression speed is relevant at each boot. 279 280 If you have any problems with bzip2 or lzma compressed 281 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 282 version of this functionality (bzip2 only), for 2.4, was 283 supplied by Christian Ludwig) 284 285 High compression options are mostly useful for users, who 286 are low on disk space (embedded systems), but for whom ram 287 size matters less. 288 289 If in doubt, select 'gzip' 290 291 config KERNEL_GZIP 292 bool "Gzip" 293 depends on HAVE_KERNEL_GZIP 294 help 295 The old and tried gzip compression. It provides a good balance 296 between compression ratio and decompression speed. 297 298 config KERNEL_BZIP2 299 bool "Bzip2" 300 depends on HAVE_KERNEL_BZIP2 301 help 302 Its compression ratio and speed is intermediate. 303 Decompression speed is slowest among the choices. The kernel 304 size is about 10% smaller with bzip2, in comparison to gzip. 305 Bzip2 uses a large amount of memory. For modern kernels you 306 will need at least 8MB RAM or more for booting. 307 308 config KERNEL_LZMA 309 bool "LZMA" 310 depends on HAVE_KERNEL_LZMA 311 help 312 This compression algorithm's ratio is best. Decompression speed 313 is between gzip and bzip2. Compression is slowest. 314 The kernel size is about 33% smaller with LZMA in comparison to gzip. 315 316 config KERNEL_XZ 317 bool "XZ" 318 depends on HAVE_KERNEL_XZ 319 help 320 XZ uses the LZMA2 algorithm and instruction set specific 321 BCJ filters which can improve compression ratio of executable 322 code. The size of the kernel is about 30% smaller with XZ in 323 comparison to gzip. On architectures for which there is a BCJ 324 filter (i386, x86_64, ARM, ARM64, RISC-V, big endian PowerPC, 325 and SPARC), XZ will create a few percent smaller kernel than 326 plain LZMA. 327 328 The speed is about the same as with LZMA: The decompression 329 speed of XZ is better than that of bzip2 but worse than gzip 330 and LZO. Compression is slow. 331 332 config KERNEL_LZO 333 bool "LZO" 334 depends on HAVE_KERNEL_LZO 335 help 336 Its compression ratio is the poorest among the choices. The kernel 337 size is about 10% bigger than gzip; however its speed 338 (both compression and decompression) is the fastest. 339 340 config KERNEL_LZ4 341 bool "LZ4" 342 depends on HAVE_KERNEL_LZ4 343 help 344 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 345 A preliminary version of LZ4 de/compression tool is available at 346 <https://code.google.com/p/lz4/>. 347 348 Its compression ratio is worse than LZO. The size of the kernel 349 is about 8% bigger than LZO. But the decompression speed is 350 faster than LZO. 351 352 config KERNEL_ZSTD 353 bool "ZSTD" 354 depends on HAVE_KERNEL_ZSTD 355 help 356 ZSTD is a compression algorithm targeting intermediate compression 357 with fast decompression speed. It will compress better than GZIP and 358 decompress around the same speed as LZO, but slower than LZ4. You 359 will need at least 192 KB RAM or more for booting. The zstd command 360 line tool is required for compression. 361 362 config KERNEL_UNCOMPRESSED 363 bool "None" 364 depends on HAVE_KERNEL_UNCOMPRESSED 365 help 366 Produce uncompressed kernel image. This option is usually not what 367 you want. It is useful for debugging the kernel in slow simulation 368 environments, where decompressing and moving the kernel is awfully 369 slow. This option allows early boot code to skip the decompressor 370 and jump right at uncompressed kernel image. 371 372 endchoice 373 374 config DEFAULT_INIT 375 string "Default init path" 376 default "" 377 help 378 This option determines the default init for the system if no init= 379 option is passed on the kernel command line. If the requested path is 380 not present, we will still then move on to attempting further 381 locations (e.g. /sbin/init, etc). If this is empty, we will just use 382 the fallback list when init= is not passed. 383 384 config DEFAULT_HOSTNAME 385 string "Default hostname" 386 default "(none)" 387 help 388 This option determines the default system hostname before userspace 389 calls sethostname(2). The kernel traditionally uses "(none)" here, 390 but you may wish to use a different default here to make a minimal 391 system more usable with less configuration. 392 393 config SYSVIPC 394 bool "System V IPC" 395 help 396 Inter Process Communication is a suite of library functions and 397 system calls which let processes (running programs) synchronize and 398 exchange information. It is generally considered to be a good thing, 399 and some programs won't run unless you say Y here. In particular, if 400 you want to run the DOS emulator dosemu under Linux (read the 401 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 402 you'll need to say Y here. 403 404 You can find documentation about IPC with "info ipc" and also in 405 section 6.4 of the Linux Programmer's Guide, available from 406 <http://www.tldp.org/guides.html>. 407 408 config SYSVIPC_SYSCTL 409 bool 410 depends on SYSVIPC 411 depends on SYSCTL 412 default y 413 414 config SYSVIPC_COMPAT 415 def_bool y 416 depends on COMPAT && SYSVIPC 417 418 config POSIX_MQUEUE 419 bool "POSIX Message Queues" 420 depends on NET 421 help 422 POSIX variant of message queues is a part of IPC. In POSIX message 423 queues every message has a priority which decides about succession 424 of receiving it by a process. If you want to compile and run 425 programs written e.g. for Solaris with use of its POSIX message 426 queues (functions mq_*) say Y here. 427 428 POSIX message queues are visible as a filesystem called 'mqueue' 429 and can be mounted somewhere if you want to do filesystem 430 operations on message queues. 431 432 If unsure, say Y. 433 434 config POSIX_MQUEUE_SYSCTL 435 bool 436 depends on POSIX_MQUEUE 437 depends on SYSCTL 438 default y 439 440 config WATCH_QUEUE 441 bool "General notification queue" 442 default n 443 help 444 445 This is a general notification queue for the kernel to pass events to 446 userspace by splicing them into pipes. It can be used in conjunction 447 with watches for key/keyring change notifications and device 448 notifications. 449 450 See Documentation/core-api/watch_queue.rst 451 452 config CROSS_MEMORY_ATTACH 453 bool "Enable process_vm_readv/writev syscalls" 454 depends on MMU 455 default y 456 help 457 Enabling this option adds the system calls process_vm_readv and 458 process_vm_writev which allow a process with the correct privileges 459 to directly read from or write to another process' address space. 460 See the man page for more details. 461 462 config USELIB 463 bool "uselib syscall (for libc5 and earlier)" 464 default ALPHA || M68K || SPARC 465 help 466 This option enables the uselib syscall, a system call used in the 467 dynamic linker from libc5 and earlier. glibc does not use this 468 system call. If you intend to run programs built on libc5 or 469 earlier, you may need to enable this syscall. Current systems 470 running glibc can safely disable this. 471 472 config AUDIT 473 bool "Auditing support" 474 depends on NET 475 help 476 Enable auditing infrastructure that can be used with another 477 kernel subsystem, such as SELinux (which requires this for 478 logging of avc messages output). System call auditing is included 479 on architectures which support it. 480 481 config HAVE_ARCH_AUDITSYSCALL 482 bool 483 484 config AUDITSYSCALL 485 def_bool y 486 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 487 select FSNOTIFY 488 489 source "kernel/irq/Kconfig" 490 source "kernel/time/Kconfig" 491 source "kernel/bpf/Kconfig" 492 source "kernel/Kconfig.preempt" 493 494 menu "CPU/Task time and stats accounting" 495 496 config VIRT_CPU_ACCOUNTING 497 bool 498 499 choice 500 prompt "Cputime accounting" 501 default TICK_CPU_ACCOUNTING 502 503 # Kind of a stub config for the pure tick based cputime accounting 504 config TICK_CPU_ACCOUNTING 505 bool "Simple tick based cputime accounting" 506 depends on !S390 && !NO_HZ_FULL 507 help 508 This is the basic tick based cputime accounting that maintains 509 statistics about user, system and idle time spent on per jiffies 510 granularity. 511 512 If unsure, say Y. 513 514 config VIRT_CPU_ACCOUNTING_NATIVE 515 bool "Deterministic task and CPU time accounting" 516 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 517 select VIRT_CPU_ACCOUNTING 518 help 519 Select this option to enable more accurate task and CPU time 520 accounting. This is done by reading a CPU counter on each 521 kernel entry and exit and on transitions within the kernel 522 between system, softirq and hardirq state, so there is a 523 small performance impact. In the case of s390 or IBM POWER > 5, 524 this also enables accounting of stolen time on logically-partitioned 525 systems. 526 527 config VIRT_CPU_ACCOUNTING_GEN 528 bool "Full dynticks CPU time accounting" 529 depends on HAVE_CONTEXT_TRACKING_USER 530 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 531 depends on GENERIC_CLOCKEVENTS 532 select VIRT_CPU_ACCOUNTING 533 select CONTEXT_TRACKING_USER 534 help 535 Select this option to enable task and CPU time accounting on full 536 dynticks systems. This accounting is implemented by watching every 537 kernel-user boundaries using the context tracking subsystem. 538 The accounting is thus performed at the expense of some significant 539 overhead. 540 541 For now this is only useful if you are working on the full 542 dynticks subsystem development. 543 544 If unsure, say N. 545 546 endchoice 547 548 config IRQ_TIME_ACCOUNTING 549 bool "Fine granularity task level IRQ time accounting" 550 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 551 help 552 Select this option to enable fine granularity task irq time 553 accounting. This is done by reading a timestamp on each 554 transitions between softirq and hardirq state, so there can be a 555 small performance impact. 556 557 If in doubt, say N here. 558 559 config HAVE_SCHED_AVG_IRQ 560 def_bool y 561 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 562 depends on SMP 563 564 config SCHED_HW_PRESSURE 565 bool 566 default y if ARM && ARM_CPU_TOPOLOGY 567 default y if ARM64 568 depends on SMP 569 depends on CPU_FREQ_THERMAL 570 help 571 Select this option to enable HW pressure accounting in the 572 scheduler. HW pressure is the value conveyed to the scheduler 573 that reflects the reduction in CPU compute capacity resulted from 574 HW throttling. HW throttling occurs when the performance of 575 a CPU is capped due to high operating temperatures as an example. 576 577 If selected, the scheduler will be able to balance tasks accordingly, 578 i.e. put less load on throttled CPUs than on non/less throttled ones. 579 580 This requires the architecture to implement 581 arch_update_hw_pressure() and arch_scale_thermal_pressure(). 582 583 config BSD_PROCESS_ACCT 584 bool "BSD Process Accounting" 585 depends on MULTIUSER 586 help 587 If you say Y here, a user level program will be able to instruct the 588 kernel (via a special system call) to write process accounting 589 information to a file: whenever a process exits, information about 590 that process will be appended to the file by the kernel. The 591 information includes things such as creation time, owning user, 592 command name, memory usage, controlling terminal etc. (the complete 593 list is in the struct acct in <file:include/linux/acct.h>). It is 594 up to the user level program to do useful things with this 595 information. This is generally a good idea, so say Y. 596 597 config BSD_PROCESS_ACCT_V3 598 bool "BSD Process Accounting version 3 file format" 599 depends on BSD_PROCESS_ACCT 600 default n 601 help 602 If you say Y here, the process accounting information is written 603 in a new file format that also logs the process IDs of each 604 process and its parent. Note that this file format is incompatible 605 with previous v0/v1/v2 file formats, so you will need updated tools 606 for processing it. A preliminary version of these tools is available 607 at <http://www.gnu.org/software/acct/>. 608 609 config TASKSTATS 610 bool "Export task/process statistics through netlink" 611 depends on NET 612 depends on MULTIUSER 613 default n 614 help 615 Export selected statistics for tasks/processes through the 616 generic netlink interface. Unlike BSD process accounting, the 617 statistics are available during the lifetime of tasks/processes as 618 responses to commands. Like BSD accounting, they are sent to user 619 space on task exit. 620 621 Say N if unsure. 622 623 config TASK_DELAY_ACCT 624 bool "Enable per-task delay accounting" 625 depends on TASKSTATS 626 select SCHED_INFO 627 help 628 Collect information on time spent by a task waiting for system 629 resources like cpu, synchronous block I/O completion and swapping 630 in pages. Such statistics can help in setting a task's priorities 631 relative to other tasks for cpu, io, rss limits etc. 632 633 Say N if unsure. 634 635 config TASK_XACCT 636 bool "Enable extended accounting over taskstats" 637 depends on TASKSTATS 638 help 639 Collect extended task accounting data and send the data 640 to userland for processing over the taskstats interface. 641 642 Say N if unsure. 643 644 config TASK_IO_ACCOUNTING 645 bool "Enable per-task storage I/O accounting" 646 depends on TASK_XACCT 647 help 648 Collect information on the number of bytes of storage I/O which this 649 task has caused. 650 651 Say N if unsure. 652 653 config PSI 654 bool "Pressure stall information tracking" 655 select KERNFS 656 help 657 Collect metrics that indicate how overcommitted the CPU, memory, 658 and IO capacity are in the system. 659 660 If you say Y here, the kernel will create /proc/pressure/ with the 661 pressure statistics files cpu, memory, and io. These will indicate 662 the share of walltime in which some or all tasks in the system are 663 delayed due to contention of the respective resource. 664 665 In kernels with cgroup support, cgroups (cgroup2 only) will 666 have cpu.pressure, memory.pressure, and io.pressure files, 667 which aggregate pressure stalls for the grouped tasks only. 668 669 For more details see Documentation/accounting/psi.rst. 670 671 Say N if unsure. 672 673 config PSI_DEFAULT_DISABLED 674 bool "Require boot parameter to enable pressure stall information tracking" 675 default n 676 depends on PSI 677 help 678 If set, pressure stall information tracking will be disabled 679 per default but can be enabled through passing psi=1 on the 680 kernel commandline during boot. 681 682 This feature adds some code to the task wakeup and sleep 683 paths of the scheduler. The overhead is too low to affect 684 common scheduling-intense workloads in practice (such as 685 webservers, memcache), but it does show up in artificial 686 scheduler stress tests, such as hackbench. 687 688 If you are paranoid and not sure what the kernel will be 689 used for, say Y. 690 691 Say N if unsure. 692 693 endmenu # "CPU/Task time and stats accounting" 694 695 config CPU_ISOLATION 696 bool "CPU isolation" 697 depends on SMP || COMPILE_TEST 698 default y 699 help 700 Make sure that CPUs running critical tasks are not disturbed by 701 any source of "noise" such as unbound workqueues, timers, kthreads... 702 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 703 the "isolcpus=" boot parameter. 704 705 Say Y if unsure. 706 707 source "kernel/rcu/Kconfig" 708 709 config IKCONFIG 710 tristate "Kernel .config support" 711 help 712 This option enables the complete Linux kernel ".config" file 713 contents to be saved in the kernel. It provides documentation 714 of which kernel options are used in a running kernel or in an 715 on-disk kernel. This information can be extracted from the kernel 716 image file with the script scripts/extract-ikconfig and used as 717 input to rebuild the current kernel or to build another kernel. 718 It can also be extracted from a running kernel by reading 719 /proc/config.gz if enabled (below). 720 721 config IKCONFIG_PROC 722 bool "Enable access to .config through /proc/config.gz" 723 depends on IKCONFIG && PROC_FS 724 help 725 This option enables access to the kernel configuration file 726 through /proc/config.gz. 727 728 config IKHEADERS 729 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 730 depends on SYSFS 731 help 732 This option enables access to the in-kernel headers that are generated during 733 the build process. These can be used to build eBPF tracing programs, 734 or similar programs. If you build the headers as a module, a module called 735 kheaders.ko is built which can be loaded on-demand to get access to headers. 736 737 config LOG_BUF_SHIFT 738 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 739 range 12 25 740 default 17 741 depends on PRINTK 742 help 743 Select the minimal kernel log buffer size as a power of 2. 744 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 745 parameter, see below. Any higher size also might be forced 746 by "log_buf_len" boot parameter. 747 748 Examples: 749 17 => 128 KB 750 16 => 64 KB 751 15 => 32 KB 752 14 => 16 KB 753 13 => 8 KB 754 12 => 4 KB 755 756 config LOG_CPU_MAX_BUF_SHIFT 757 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 758 depends on SMP 759 range 0 21 760 default 0 if BASE_SMALL 761 default 12 762 depends on PRINTK 763 help 764 This option allows to increase the default ring buffer size 765 according to the number of CPUs. The value defines the contribution 766 of each CPU as a power of 2. The used space is typically only few 767 lines however it might be much more when problems are reported, 768 e.g. backtraces. 769 770 The increased size means that a new buffer has to be allocated and 771 the original static one is unused. It makes sense only on systems 772 with more CPUs. Therefore this value is used only when the sum of 773 contributions is greater than the half of the default kernel ring 774 buffer as defined by LOG_BUF_SHIFT. The default values are set 775 so that more than 16 CPUs are needed to trigger the allocation. 776 777 Also this option is ignored when "log_buf_len" kernel parameter is 778 used as it forces an exact (power of two) size of the ring buffer. 779 780 The number of possible CPUs is used for this computation ignoring 781 hotplugging making the computation optimal for the worst case 782 scenario while allowing a simple algorithm to be used from bootup. 783 784 Examples shift values and their meaning: 785 17 => 128 KB for each CPU 786 16 => 64 KB for each CPU 787 15 => 32 KB for each CPU 788 14 => 16 KB for each CPU 789 13 => 8 KB for each CPU 790 12 => 4 KB for each CPU 791 792 config PRINTK_INDEX 793 bool "Printk indexing debugfs interface" 794 depends on PRINTK && DEBUG_FS 795 help 796 Add support for indexing of all printk formats known at compile time 797 at <debugfs>/printk/index/<module>. 798 799 This can be used as part of maintaining daemons which monitor 800 /dev/kmsg, as it permits auditing the printk formats present in a 801 kernel, allowing detection of cases where monitored printks are 802 changed or no longer present. 803 804 There is no additional runtime cost to printk with this enabled. 805 806 # 807 # Architectures with an unreliable sched_clock() should select this: 808 # 809 config HAVE_UNSTABLE_SCHED_CLOCK 810 bool 811 812 config GENERIC_SCHED_CLOCK 813 bool 814 815 menu "Scheduler features" 816 817 config UCLAMP_TASK 818 bool "Enable utilization clamping for RT/FAIR tasks" 819 depends on CPU_FREQ_GOV_SCHEDUTIL 820 help 821 This feature enables the scheduler to track the clamped utilization 822 of each CPU based on RUNNABLE tasks scheduled on that CPU. 823 824 With this option, the user can specify the min and max CPU 825 utilization allowed for RUNNABLE tasks. The max utilization defines 826 the maximum frequency a task should use while the min utilization 827 defines the minimum frequency it should use. 828 829 Both min and max utilization clamp values are hints to the scheduler, 830 aiming at improving its frequency selection policy, but they do not 831 enforce or grant any specific bandwidth for tasks. 832 833 If in doubt, say N. 834 835 config UCLAMP_BUCKETS_COUNT 836 int "Number of supported utilization clamp buckets" 837 range 5 20 838 default 5 839 depends on UCLAMP_TASK 840 help 841 Defines the number of clamp buckets to use. The range of each bucket 842 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 843 number of clamp buckets the finer their granularity and the higher 844 the precision of clamping aggregation and tracking at run-time. 845 846 For example, with the minimum configuration value we will have 5 847 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 848 be refcounted in the [20..39]% bucket and will set the bucket clamp 849 effective value to 25%. 850 If a second 30% boosted task should be co-scheduled on the same CPU, 851 that task will be refcounted in the same bucket of the first task and 852 it will boost the bucket clamp effective value to 30%. 853 The clamp effective value of a bucket is reset to its nominal value 854 (20% in the example above) when there are no more tasks refcounted in 855 that bucket. 856 857 An additional boost/capping margin can be added to some tasks. In the 858 example above the 25% task will be boosted to 30% until it exits the 859 CPU. If that should be considered not acceptable on certain systems, 860 it's always possible to reduce the margin by increasing the number of 861 clamp buckets to trade off used memory for run-time tracking 862 precision. 863 864 If in doubt, use the default value. 865 866 endmenu 867 868 # 869 # For architectures that want to enable the support for NUMA-affine scheduler 870 # balancing logic: 871 # 872 config ARCH_SUPPORTS_NUMA_BALANCING 873 bool 874 875 # 876 # For architectures that prefer to flush all TLBs after a number of pages 877 # are unmapped instead of sending one IPI per page to flush. The architecture 878 # must provide guarantees on what happens if a clean TLB cache entry is 879 # written after the unmap. Details are in mm/rmap.c near the check for 880 # should_defer_flush. The architecture should also consider if the full flush 881 # and the refill costs are offset by the savings of sending fewer IPIs. 882 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 883 bool 884 885 config CC_HAS_INT128 886 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 887 888 config CC_IMPLICIT_FALLTHROUGH 889 string 890 default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5) 891 default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough) 892 893 # Currently, disable gcc-10+ array-bounds globally. 894 # It's still broken in gcc-13, so no upper bound yet. 895 config GCC10_NO_ARRAY_BOUNDS 896 def_bool y 897 898 config CC_NO_ARRAY_BOUNDS 899 bool 900 default y if CC_IS_GCC && GCC_VERSION >= 90000 && GCC10_NO_ARRAY_BOUNDS 901 902 # Currently, disable -Wstringop-overflow for GCC globally. 903 config GCC_NO_STRINGOP_OVERFLOW 904 def_bool y 905 906 config CC_NO_STRINGOP_OVERFLOW 907 bool 908 default y if CC_IS_GCC && GCC_NO_STRINGOP_OVERFLOW 909 910 config CC_STRINGOP_OVERFLOW 911 bool 912 default y if CC_IS_GCC && !CC_NO_STRINGOP_OVERFLOW 913 914 # 915 # For architectures that know their GCC __int128 support is sound 916 # 917 config ARCH_SUPPORTS_INT128 918 bool 919 920 # For architectures that (ab)use NUMA to represent different memory regions 921 # all cpu-local but of different latencies, such as SuperH. 922 # 923 config ARCH_WANT_NUMA_VARIABLE_LOCALITY 924 bool 925 926 config NUMA_BALANCING 927 bool "Memory placement aware NUMA scheduler" 928 depends on ARCH_SUPPORTS_NUMA_BALANCING 929 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 930 depends on SMP && NUMA && MIGRATION && !PREEMPT_RT 931 help 932 This option adds support for automatic NUMA aware memory/task placement. 933 The mechanism is quite primitive and is based on migrating memory when 934 it has references to the node the task is running on. 935 936 This system will be inactive on UMA systems. 937 938 config NUMA_BALANCING_DEFAULT_ENABLED 939 bool "Automatically enable NUMA aware memory/task placement" 940 default y 941 depends on NUMA_BALANCING 942 help 943 If set, automatic NUMA balancing will be enabled if running on a NUMA 944 machine. 945 946 config SLAB_OBJ_EXT 947 bool 948 949 menuconfig CGROUPS 950 bool "Control Group support" 951 select KERNFS 952 help 953 This option adds support for grouping sets of processes together, for 954 use with process control subsystems such as Cpusets, CFS, memory 955 controls or device isolation. 956 See 957 - Documentation/scheduler/sched-design-CFS.rst (CFS) 958 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 959 and resource control) 960 961 Say N if unsure. 962 963 if CGROUPS 964 965 config PAGE_COUNTER 966 bool 967 968 config CGROUP_FAVOR_DYNMODS 969 bool "Favor dynamic modification latency reduction by default" 970 help 971 This option enables the "favordynmods" mount option by default 972 which reduces the latencies of dynamic cgroup modifications such 973 as task migrations and controller on/offs at the cost of making 974 hot path operations such as forks and exits more expensive. 975 976 Say N if unsure. 977 978 config MEMCG 979 bool "Memory controller" 980 select PAGE_COUNTER 981 select EVENTFD 982 select SLAB_OBJ_EXT 983 help 984 Provides control over the memory footprint of tasks in a cgroup. 985 986 config MEMCG_V1 987 bool "Legacy cgroup v1 memory controller" 988 depends on MEMCG 989 default n 990 help 991 Legacy cgroup v1 memory controller which has been deprecated by 992 cgroup v2 implementation. The v1 is there for legacy applications 993 which haven't migrated to the new cgroup v2 interface yet. If you 994 do not have any such application then you are completely fine leaving 995 this option disabled. 996 997 Please note that feature set of the legacy memory controller is likely 998 going to shrink due to deprecation process. New deployments with v1 999 controller are highly discouraged. 1000 1001 Say N if unsure. 1002 1003 config BLK_CGROUP 1004 bool "IO controller" 1005 depends on BLOCK 1006 default n 1007 help 1008 Generic block IO controller cgroup interface. This is the common 1009 cgroup interface which should be used by various IO controlling 1010 policies. 1011 1012 Currently, CFQ IO scheduler uses it to recognize task groups and 1013 control disk bandwidth allocation (proportional time slice allocation) 1014 to such task groups. It is also used by bio throttling logic in 1015 block layer to implement upper limit in IO rates on a device. 1016 1017 This option only enables generic Block IO controller infrastructure. 1018 One needs to also enable actual IO controlling logic/policy. For 1019 enabling proportional weight division of disk bandwidth in CFQ, set 1020 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 1021 CONFIG_BLK_DEV_THROTTLING=y. 1022 1023 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 1024 1025 config CGROUP_WRITEBACK 1026 bool 1027 depends on MEMCG && BLK_CGROUP 1028 default y 1029 1030 menuconfig CGROUP_SCHED 1031 bool "CPU controller" 1032 default n 1033 help 1034 This feature lets CPU scheduler recognize task groups and control CPU 1035 bandwidth allocation to such task groups. It uses cgroups to group 1036 tasks. 1037 1038 if CGROUP_SCHED 1039 config GROUP_SCHED_WEIGHT 1040 def_bool n 1041 1042 config FAIR_GROUP_SCHED 1043 bool "Group scheduling for SCHED_OTHER" 1044 depends on CGROUP_SCHED 1045 select GROUP_SCHED_WEIGHT 1046 default CGROUP_SCHED 1047 1048 config CFS_BANDWIDTH 1049 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 1050 depends on FAIR_GROUP_SCHED 1051 default n 1052 help 1053 This option allows users to define CPU bandwidth rates (limits) for 1054 tasks running within the fair group scheduler. Groups with no limit 1055 set are considered to be unconstrained and will run with no 1056 restriction. 1057 See Documentation/scheduler/sched-bwc.rst for more information. 1058 1059 config RT_GROUP_SCHED 1060 bool "Group scheduling for SCHED_RR/FIFO" 1061 depends on CGROUP_SCHED 1062 default n 1063 help 1064 This feature lets you explicitly allocate real CPU bandwidth 1065 to task groups. If enabled, it will also make it impossible to 1066 schedule realtime tasks for non-root users until you allocate 1067 realtime bandwidth for them. 1068 See Documentation/scheduler/sched-rt-group.rst for more information. 1069 1070 config EXT_GROUP_SCHED 1071 bool 1072 depends on SCHED_CLASS_EXT && CGROUP_SCHED 1073 select GROUP_SCHED_WEIGHT 1074 default y 1075 1076 endif #CGROUP_SCHED 1077 1078 config SCHED_MM_CID 1079 def_bool y 1080 depends on SMP && RSEQ 1081 1082 config UCLAMP_TASK_GROUP 1083 bool "Utilization clamping per group of tasks" 1084 depends on CGROUP_SCHED 1085 depends on UCLAMP_TASK 1086 default n 1087 help 1088 This feature enables the scheduler to track the clamped utilization 1089 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 1090 1091 When this option is enabled, the user can specify a min and max 1092 CPU bandwidth which is allowed for each single task in a group. 1093 The max bandwidth allows to clamp the maximum frequency a task 1094 can use, while the min bandwidth allows to define a minimum 1095 frequency a task will always use. 1096 1097 When task group based utilization clamping is enabled, an eventually 1098 specified task-specific clamp value is constrained by the cgroup 1099 specified clamp value. Both minimum and maximum task clamping cannot 1100 be bigger than the corresponding clamping defined at task group level. 1101 1102 If in doubt, say N. 1103 1104 config CGROUP_PIDS 1105 bool "PIDs controller" 1106 help 1107 Provides enforcement of process number limits in the scope of a 1108 cgroup. Any attempt to fork more processes than is allowed in the 1109 cgroup will fail. PIDs are fundamentally a global resource because it 1110 is fairly trivial to reach PID exhaustion before you reach even a 1111 conservative kmemcg limit. As a result, it is possible to grind a 1112 system to halt without being limited by other cgroup policies. The 1113 PIDs controller is designed to stop this from happening. 1114 1115 It should be noted that organisational operations (such as attaching 1116 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 1117 since the PIDs limit only affects a process's ability to fork, not to 1118 attach to a cgroup. 1119 1120 config CGROUP_RDMA 1121 bool "RDMA controller" 1122 help 1123 Provides enforcement of RDMA resources defined by IB stack. 1124 It is fairly easy for consumers to exhaust RDMA resources, which 1125 can result into resource unavailability to other consumers. 1126 RDMA controller is designed to stop this from happening. 1127 Attaching processes with active RDMA resources to the cgroup 1128 hierarchy is allowed even if can cross the hierarchy's limit. 1129 1130 config CGROUP_FREEZER 1131 bool "Freezer controller" 1132 help 1133 Provides a way to freeze and unfreeze all tasks in a 1134 cgroup. 1135 1136 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1137 controller includes important in-kernel memory consumers per default. 1138 1139 If you're using cgroup2, say N. 1140 1141 config CGROUP_HUGETLB 1142 bool "HugeTLB controller" 1143 depends on HUGETLB_PAGE 1144 select PAGE_COUNTER 1145 default n 1146 help 1147 Provides a cgroup controller for HugeTLB pages. 1148 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1149 The limit is enforced during page fault. Since HugeTLB doesn't 1150 support page reclaim, enforcing the limit at page fault time implies 1151 that, the application will get SIGBUS signal if it tries to access 1152 HugeTLB pages beyond its limit. This requires the application to know 1153 beforehand how much HugeTLB pages it would require for its use. The 1154 control group is tracked in the third page lru pointer. This means 1155 that we cannot use the controller with huge page less than 3 pages. 1156 1157 config CPUSETS 1158 bool "Cpuset controller" 1159 depends on SMP 1160 help 1161 This option will let you create and manage CPUSETs which 1162 allow dynamically partitioning a system into sets of CPUs and 1163 Memory Nodes and assigning tasks to run only within those sets. 1164 This is primarily useful on large SMP or NUMA systems. 1165 1166 Say N if unsure. 1167 1168 config CPUSETS_V1 1169 bool "Legacy cgroup v1 cpusets controller" 1170 depends on CPUSETS 1171 default n 1172 help 1173 Legacy cgroup v1 cpusets controller which has been deprecated by 1174 cgroup v2 implementation. The v1 is there for legacy applications 1175 which haven't migrated to the new cgroup v2 interface yet. If you 1176 do not have any such application then you are completely fine leaving 1177 this option disabled. 1178 1179 Say N if unsure. 1180 1181 config PROC_PID_CPUSET 1182 bool "Include legacy /proc/<pid>/cpuset file" 1183 depends on CPUSETS 1184 default y 1185 1186 config CGROUP_DEVICE 1187 bool "Device controller" 1188 help 1189 Provides a cgroup controller implementing whitelists for 1190 devices which a process in the cgroup can mknod or open. 1191 1192 config CGROUP_CPUACCT 1193 bool "Simple CPU accounting controller" 1194 help 1195 Provides a simple controller for monitoring the 1196 total CPU consumed by the tasks in a cgroup. 1197 1198 config CGROUP_PERF 1199 bool "Perf controller" 1200 depends on PERF_EVENTS 1201 help 1202 This option extends the perf per-cpu mode to restrict monitoring 1203 to threads which belong to the cgroup specified and run on the 1204 designated cpu. Or this can be used to have cgroup ID in samples 1205 so that it can monitor performance events among cgroups. 1206 1207 Say N if unsure. 1208 1209 config CGROUP_BPF 1210 bool "Support for eBPF programs attached to cgroups" 1211 depends on BPF_SYSCALL 1212 select SOCK_CGROUP_DATA 1213 help 1214 Allow attaching eBPF programs to a cgroup using the bpf(2) 1215 syscall command BPF_PROG_ATTACH. 1216 1217 In which context these programs are accessed depends on the type 1218 of attachment. For instance, programs that are attached using 1219 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1220 inet sockets. 1221 1222 config CGROUP_MISC 1223 bool "Misc resource controller" 1224 default n 1225 help 1226 Provides a controller for miscellaneous resources on a host. 1227 1228 Miscellaneous scalar resources are the resources on the host system 1229 which cannot be abstracted like the other cgroups. This controller 1230 tracks and limits the miscellaneous resources used by a process 1231 attached to a cgroup hierarchy. 1232 1233 For more information, please check misc cgroup section in 1234 /Documentation/admin-guide/cgroup-v2.rst. 1235 1236 config CGROUP_DEBUG 1237 bool "Debug controller" 1238 default n 1239 depends on DEBUG_KERNEL 1240 help 1241 This option enables a simple controller that exports 1242 debugging information about the cgroups framework. This 1243 controller is for control cgroup debugging only. Its 1244 interfaces are not stable. 1245 1246 Say N. 1247 1248 config SOCK_CGROUP_DATA 1249 bool 1250 default n 1251 1252 endif # CGROUPS 1253 1254 menuconfig NAMESPACES 1255 bool "Namespaces support" if EXPERT 1256 depends on MULTIUSER 1257 default !EXPERT 1258 help 1259 Provides the way to make tasks work with different objects using 1260 the same id. For example same IPC id may refer to different objects 1261 or same user id or pid may refer to different tasks when used in 1262 different namespaces. 1263 1264 if NAMESPACES 1265 1266 config UTS_NS 1267 bool "UTS namespace" 1268 default y 1269 help 1270 In this namespace tasks see different info provided with the 1271 uname() system call 1272 1273 config TIME_NS 1274 bool "TIME namespace" 1275 depends on GENERIC_VDSO_TIME_NS 1276 default y 1277 help 1278 In this namespace boottime and monotonic clocks can be set. 1279 The time will keep going with the same pace. 1280 1281 config IPC_NS 1282 bool "IPC namespace" 1283 depends on (SYSVIPC || POSIX_MQUEUE) 1284 default y 1285 help 1286 In this namespace tasks work with IPC ids which correspond to 1287 different IPC objects in different namespaces. 1288 1289 config USER_NS 1290 bool "User namespace" 1291 default n 1292 help 1293 This allows containers, i.e. vservers, to use user namespaces 1294 to provide different user info for different servers. 1295 1296 When user namespaces are enabled in the kernel it is 1297 recommended that the MEMCG option also be enabled and that 1298 user-space use the memory control groups to limit the amount 1299 of memory a memory unprivileged users can use. 1300 1301 If unsure, say N. 1302 1303 config PID_NS 1304 bool "PID Namespaces" 1305 default y 1306 help 1307 Support process id namespaces. This allows having multiple 1308 processes with the same pid as long as they are in different 1309 pid namespaces. This is a building block of containers. 1310 1311 config NET_NS 1312 bool "Network namespace" 1313 depends on NET 1314 default y 1315 help 1316 Allow user space to create what appear to be multiple instances 1317 of the network stack. 1318 1319 endif # NAMESPACES 1320 1321 config CHECKPOINT_RESTORE 1322 bool "Checkpoint/restore support" 1323 depends on PROC_FS 1324 select PROC_CHILDREN 1325 select KCMP 1326 default n 1327 help 1328 Enables additional kernel features in a sake of checkpoint/restore. 1329 In particular it adds auxiliary prctl codes to setup process text, 1330 data and heap segment sizes, and a few additional /proc filesystem 1331 entries. 1332 1333 If unsure, say N here. 1334 1335 config SCHED_AUTOGROUP 1336 bool "Automatic process group scheduling" 1337 select CGROUPS 1338 select CGROUP_SCHED 1339 select FAIR_GROUP_SCHED 1340 help 1341 This option optimizes the scheduler for common desktop workloads by 1342 automatically creating and populating task groups. This separation 1343 of workloads isolates aggressive CPU burners (like build jobs) from 1344 desktop applications. Task group autogeneration is currently based 1345 upon task session. 1346 1347 config RELAY 1348 bool "Kernel->user space relay support (formerly relayfs)" 1349 select IRQ_WORK 1350 help 1351 This option enables support for relay interface support in 1352 certain file systems (such as debugfs). 1353 It is designed to provide an efficient mechanism for tools and 1354 facilities to relay large amounts of data from kernel space to 1355 user space. 1356 1357 If unsure, say N. 1358 1359 config BLK_DEV_INITRD 1360 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1361 help 1362 The initial RAM filesystem is a ramfs which is loaded by the 1363 boot loader (loadlin or lilo) and that is mounted as root 1364 before the normal boot procedure. It is typically used to 1365 load modules needed to mount the "real" root file system, 1366 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1367 1368 If RAM disk support (BLK_DEV_RAM) is also included, this 1369 also enables initial RAM disk (initrd) support and adds 1370 15 Kbytes (more on some other architectures) to the kernel size. 1371 1372 If unsure say Y. 1373 1374 if BLK_DEV_INITRD 1375 1376 source "usr/Kconfig" 1377 1378 endif 1379 1380 config BOOT_CONFIG 1381 bool "Boot config support" 1382 select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED 1383 help 1384 Extra boot config allows system admin to pass a config file as 1385 complemental extension of kernel cmdline when booting. 1386 The boot config file must be attached at the end of initramfs 1387 with checksum, size and magic word. 1388 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1389 1390 If unsure, say Y. 1391 1392 config BOOT_CONFIG_FORCE 1393 bool "Force unconditional bootconfig processing" 1394 depends on BOOT_CONFIG 1395 default y if BOOT_CONFIG_EMBED 1396 help 1397 With this Kconfig option set, BOOT_CONFIG processing is carried 1398 out even when the "bootconfig" kernel-boot parameter is omitted. 1399 In fact, with this Kconfig option set, there is no way to 1400 make the kernel ignore the BOOT_CONFIG-supplied kernel-boot 1401 parameters. 1402 1403 If unsure, say N. 1404 1405 config BOOT_CONFIG_EMBED 1406 bool "Embed bootconfig file in the kernel" 1407 depends on BOOT_CONFIG 1408 help 1409 Embed a bootconfig file given by BOOT_CONFIG_EMBED_FILE in the 1410 kernel. Usually, the bootconfig file is loaded with the initrd 1411 image. But if the system doesn't support initrd, this option will 1412 help you by embedding a bootconfig file while building the kernel. 1413 1414 If unsure, say N. 1415 1416 config BOOT_CONFIG_EMBED_FILE 1417 string "Embedded bootconfig file path" 1418 depends on BOOT_CONFIG_EMBED 1419 help 1420 Specify a bootconfig file which will be embedded to the kernel. 1421 This bootconfig will be used if there is no initrd or no other 1422 bootconfig in the initrd. 1423 1424 config INITRAMFS_PRESERVE_MTIME 1425 bool "Preserve cpio archive mtimes in initramfs" 1426 default y 1427 help 1428 Each entry in an initramfs cpio archive carries an mtime value. When 1429 enabled, extracted cpio items take this mtime, with directory mtime 1430 setting deferred until after creation of any child entries. 1431 1432 If unsure, say Y. 1433 1434 choice 1435 prompt "Compiler optimization level" 1436 default CC_OPTIMIZE_FOR_PERFORMANCE 1437 1438 config CC_OPTIMIZE_FOR_PERFORMANCE 1439 bool "Optimize for performance (-O2)" 1440 help 1441 This is the default optimization level for the kernel, building 1442 with the "-O2" compiler flag for best performance and most 1443 helpful compile-time warnings. 1444 1445 config CC_OPTIMIZE_FOR_SIZE 1446 bool "Optimize for size (-Os)" 1447 help 1448 Choosing this option will pass "-Os" to your compiler resulting 1449 in a smaller kernel. 1450 1451 endchoice 1452 1453 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1454 bool 1455 help 1456 This requires that the arch annotates or otherwise protects 1457 its external entry points from being discarded. Linker scripts 1458 must also merge .text.*, .data.*, and .bss.* correctly into 1459 output sections. Care must be taken not to pull in unrelated 1460 sections (e.g., '.text.init'). Typically '.' in section names 1461 is used to distinguish them from label names / C identifiers. 1462 1463 config LD_DEAD_CODE_DATA_ELIMINATION 1464 bool "Dead code and data elimination (EXPERIMENTAL)" 1465 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1466 depends on EXPERT 1467 depends on $(cc-option,-ffunction-sections -fdata-sections) 1468 depends on $(ld-option,--gc-sections) 1469 help 1470 Enable this if you want to do dead code and data elimination with 1471 the linker by compiling with -ffunction-sections -fdata-sections, 1472 and linking with --gc-sections. 1473 1474 This can reduce on disk and in-memory size of the kernel 1475 code and static data, particularly for small configs and 1476 on small systems. This has the possibility of introducing 1477 silently broken kernel if the required annotations are not 1478 present. This option is not well tested yet, so use at your 1479 own risk. 1480 1481 config LD_ORPHAN_WARN 1482 def_bool y 1483 depends on ARCH_WANT_LD_ORPHAN_WARN 1484 depends on $(ld-option,--orphan-handling=warn) 1485 depends on $(ld-option,--orphan-handling=error) 1486 1487 config LD_ORPHAN_WARN_LEVEL 1488 string 1489 depends on LD_ORPHAN_WARN 1490 default "error" if WERROR 1491 default "warn" 1492 1493 config SYSCTL 1494 bool 1495 1496 config HAVE_UID16 1497 bool 1498 1499 config SYSCTL_EXCEPTION_TRACE 1500 bool 1501 help 1502 Enable support for /proc/sys/debug/exception-trace. 1503 1504 config SYSCTL_ARCH_UNALIGN_NO_WARN 1505 bool 1506 help 1507 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1508 Allows arch to define/use @no_unaligned_warning to possibly warn 1509 about unaligned access emulation going on under the hood. 1510 1511 config SYSCTL_ARCH_UNALIGN_ALLOW 1512 bool 1513 help 1514 Enable support for /proc/sys/kernel/unaligned-trap 1515 Allows arches to define/use @unaligned_enabled to runtime toggle 1516 the unaligned access emulation. 1517 see arch/parisc/kernel/unaligned.c for reference 1518 1519 config HAVE_PCSPKR_PLATFORM 1520 bool 1521 1522 menuconfig EXPERT 1523 bool "Configure standard kernel features (expert users)" 1524 # Unhide debug options, to make the on-by-default options visible 1525 select DEBUG_KERNEL 1526 help 1527 This option allows certain base kernel options and settings 1528 to be disabled or tweaked. This is for specialized 1529 environments which can tolerate a "non-standard" kernel. 1530 Only use this if you really know what you are doing. 1531 1532 config UID16 1533 bool "Enable 16-bit UID system calls" if EXPERT 1534 depends on HAVE_UID16 && MULTIUSER 1535 default y 1536 help 1537 This enables the legacy 16-bit UID syscall wrappers. 1538 1539 config MULTIUSER 1540 bool "Multiple users, groups and capabilities support" if EXPERT 1541 default y 1542 help 1543 This option enables support for non-root users, groups and 1544 capabilities. 1545 1546 If you say N here, all processes will run with UID 0, GID 0, and all 1547 possible capabilities. Saying N here also compiles out support for 1548 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1549 setgid, and capset. 1550 1551 If unsure, say Y here. 1552 1553 config SGETMASK_SYSCALL 1554 bool "sgetmask/ssetmask syscalls support" if EXPERT 1555 default PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1556 help 1557 sys_sgetmask and sys_ssetmask are obsolete system calls 1558 no longer supported in libc but still enabled by default in some 1559 architectures. 1560 1561 If unsure, leave the default option here. 1562 1563 config SYSFS_SYSCALL 1564 bool "Sysfs syscall support" if EXPERT 1565 default y 1566 help 1567 sys_sysfs is an obsolete system call no longer supported in libc. 1568 Note that disabling this option is more secure but might break 1569 compatibility with some systems. 1570 1571 If unsure say Y here. 1572 1573 config FHANDLE 1574 bool "open by fhandle syscalls" if EXPERT 1575 select EXPORTFS 1576 default y 1577 help 1578 If you say Y here, a user level program will be able to map 1579 file names to handle and then later use the handle for 1580 different file system operations. This is useful in implementing 1581 userspace file servers, which now track files using handles instead 1582 of names. The handle would remain the same even if file names 1583 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1584 syscalls. 1585 1586 config POSIX_TIMERS 1587 bool "Posix Clocks & timers" if EXPERT 1588 default y 1589 help 1590 This includes native support for POSIX timers to the kernel. 1591 Some embedded systems have no use for them and therefore they 1592 can be configured out to reduce the size of the kernel image. 1593 1594 When this option is disabled, the following syscalls won't be 1595 available: timer_create, timer_gettime: timer_getoverrun, 1596 timer_settime, timer_delete, clock_adjtime, getitimer, 1597 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1598 clock_getres and clock_nanosleep syscalls will be limited to 1599 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1600 1601 If unsure say y. 1602 1603 config PRINTK 1604 default y 1605 bool "Enable support for printk" if EXPERT 1606 select IRQ_WORK 1607 help 1608 This option enables normal printk support. Removing it 1609 eliminates most of the message strings from the kernel image 1610 and makes the kernel more or less silent. As this makes it 1611 very difficult to diagnose system problems, saying N here is 1612 strongly discouraged. 1613 1614 config BUG 1615 bool "BUG() support" if EXPERT 1616 default y 1617 help 1618 Disabling this option eliminates support for BUG and WARN, reducing 1619 the size of your kernel image and potentially quietly ignoring 1620 numerous fatal conditions. You should only consider disabling this 1621 option for embedded systems with no facilities for reporting errors. 1622 Just say Y. 1623 1624 config ELF_CORE 1625 depends on COREDUMP 1626 default y 1627 bool "Enable ELF core dumps" if EXPERT 1628 help 1629 Enable support for generating core dumps. Disabling saves about 4k. 1630 1631 1632 config PCSPKR_PLATFORM 1633 bool "Enable PC-Speaker support" if EXPERT 1634 depends on HAVE_PCSPKR_PLATFORM 1635 select I8253_LOCK 1636 default y 1637 help 1638 This option allows to disable the internal PC-Speaker 1639 support, saving some memory. 1640 1641 config BASE_SMALL 1642 bool "Enable smaller-sized data structures for core" if EXPERT 1643 help 1644 Enabling this option reduces the size of miscellaneous core 1645 kernel data structures. This saves memory on small machines, 1646 but may reduce performance. 1647 1648 config FUTEX 1649 bool "Enable futex support" if EXPERT 1650 depends on !(SPARC32 && SMP) 1651 default y 1652 imply RT_MUTEXES 1653 help 1654 Disabling this option will cause the kernel to be built without 1655 support for "fast userspace mutexes". The resulting kernel may not 1656 run glibc-based applications correctly. 1657 1658 config FUTEX_PI 1659 bool 1660 depends on FUTEX && RT_MUTEXES 1661 default y 1662 1663 config EPOLL 1664 bool "Enable eventpoll support" if EXPERT 1665 default y 1666 help 1667 Disabling this option will cause the kernel to be built without 1668 support for epoll family of system calls. 1669 1670 config SIGNALFD 1671 bool "Enable signalfd() system call" if EXPERT 1672 default y 1673 help 1674 Enable the signalfd() system call that allows to receive signals 1675 on a file descriptor. 1676 1677 If unsure, say Y. 1678 1679 config TIMERFD 1680 bool "Enable timerfd() system call" if EXPERT 1681 default y 1682 help 1683 Enable the timerfd() system call that allows to receive timer 1684 events on a file descriptor. 1685 1686 If unsure, say Y. 1687 1688 config EVENTFD 1689 bool "Enable eventfd() system call" if EXPERT 1690 default y 1691 help 1692 Enable the eventfd() system call that allows to receive both 1693 kernel notification (ie. KAIO) or userspace notifications. 1694 1695 If unsure, say Y. 1696 1697 config SHMEM 1698 bool "Use full shmem filesystem" if EXPERT 1699 default y 1700 depends on MMU 1701 help 1702 The shmem is an internal filesystem used to manage shared memory. 1703 It is backed by swap and manages resource limits. It is also exported 1704 to userspace as tmpfs if TMPFS is enabled. Disabling this 1705 option replaces shmem and tmpfs with the much simpler ramfs code, 1706 which may be appropriate on small systems without swap. 1707 1708 config AIO 1709 bool "Enable AIO support" if EXPERT 1710 default y 1711 help 1712 This option enables POSIX asynchronous I/O which may by used 1713 by some high performance threaded applications. Disabling 1714 this option saves about 7k. 1715 1716 config IO_URING 1717 bool "Enable IO uring support" if EXPERT 1718 select IO_WQ 1719 default y 1720 help 1721 This option enables support for the io_uring interface, enabling 1722 applications to submit and complete IO through submission and 1723 completion rings that are shared between the kernel and application. 1724 1725 config GCOV_PROFILE_URING 1726 bool "Enable GCOV profiling on the io_uring subsystem" 1727 depends on GCOV_KERNEL 1728 help 1729 Enable GCOV profiling on the io_uring subsystem, to facilitate 1730 code coverage testing. 1731 1732 If unsure, say N. 1733 1734 Note that this will have a negative impact on the performance of 1735 the io_uring subsystem, hence this should only be enabled for 1736 specific test purposes. 1737 1738 config ADVISE_SYSCALLS 1739 bool "Enable madvise/fadvise syscalls" if EXPERT 1740 default y 1741 help 1742 This option enables the madvise and fadvise syscalls, used by 1743 applications to advise the kernel about their future memory or file 1744 usage, improving performance. If building an embedded system where no 1745 applications use these syscalls, you can disable this option to save 1746 space. 1747 1748 config MEMBARRIER 1749 bool "Enable membarrier() system call" if EXPERT 1750 default y 1751 help 1752 Enable the membarrier() system call that allows issuing memory 1753 barriers across all running threads, which can be used to distribute 1754 the cost of user-space memory barriers asymmetrically by transforming 1755 pairs of memory barriers into pairs consisting of membarrier() and a 1756 compiler barrier. 1757 1758 If unsure, say Y. 1759 1760 config 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 1770 config 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 1784 config DEBUG_RSEQ 1785 default n 1786 bool "Enable 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 1793 config CACHESTAT_SYSCALL 1794 bool "Enable cachestat() system call" if EXPERT 1795 default y 1796 help 1797 Enable the cachestat system call, which queries the page cache 1798 statistics of a file (number of cached pages, dirty pages, 1799 pages marked for writeback, (recently) evicted pages). 1800 1801 If unsure say Y here. 1802 1803 config PC104 1804 bool "PC/104 support" if EXPERT 1805 help 1806 Expose PC/104 form factor device drivers and options available for 1807 selection and configuration. Enable this option if your target 1808 machine has a PC/104 bus. 1809 1810 config KALLSYMS 1811 bool "Load all symbols for debugging/ksymoops" if EXPERT 1812 default y 1813 help 1814 Say Y here to let the kernel print out symbolic crash information and 1815 symbolic stack backtraces. This increases the size of the kernel 1816 somewhat, as all symbols have to be loaded into the kernel image. 1817 1818 config KALLSYMS_SELFTEST 1819 bool "Test the basic functions and performance of kallsyms" 1820 depends on KALLSYMS 1821 default n 1822 help 1823 Test the basic functions and performance of some interfaces, such as 1824 kallsyms_lookup_name. It also calculates the compression rate of the 1825 kallsyms compression algorithm for the current symbol set. 1826 1827 Start self-test automatically after system startup. Suggest executing 1828 "dmesg | grep kallsyms_selftest" to collect test results. "finish" is 1829 displayed in the last line, indicating that the test is complete. 1830 1831 config KALLSYMS_ALL 1832 bool "Include all symbols in kallsyms" 1833 depends on DEBUG_KERNEL && KALLSYMS 1834 help 1835 Normally kallsyms only contains the symbols of functions for nicer 1836 OOPS messages and backtraces (i.e., symbols from the text and inittext 1837 sections). This is sufficient for most cases. And only if you want to 1838 enable kernel live patching, or other less common use cases (e.g., 1839 when a debugger is used) all symbols are required (i.e., names of 1840 variables from the data sections, etc). 1841 1842 This option makes sure that all symbols are loaded into the kernel 1843 image (i.e., symbols from all sections) in cost of increased kernel 1844 size (depending on the kernel configuration, it may be 300KiB or 1845 something like this). 1846 1847 Say N unless you really need all symbols, or kernel live patching. 1848 1849 config KALLSYMS_ABSOLUTE_PERCPU 1850 bool 1851 depends on KALLSYMS 1852 default X86_64 && SMP 1853 1854 # end of the "standard kernel features (expert users)" menu 1855 1856 config ARCH_HAS_MEMBARRIER_CALLBACKS 1857 bool 1858 1859 config ARCH_HAS_MEMBARRIER_SYNC_CORE 1860 bool 1861 1862 config HAVE_PERF_EVENTS 1863 bool 1864 help 1865 See tools/perf/design.txt for details. 1866 1867 config GUEST_PERF_EVENTS 1868 bool 1869 depends on HAVE_PERF_EVENTS 1870 1871 config PERF_USE_VMALLOC 1872 bool 1873 help 1874 See tools/perf/design.txt for details 1875 1876 menu "Kernel Performance Events And Counters" 1877 1878 config PERF_EVENTS 1879 bool "Kernel performance events and counters" 1880 default y if PROFILING 1881 depends on HAVE_PERF_EVENTS 1882 select IRQ_WORK 1883 help 1884 Enable kernel support for various performance events provided 1885 by software and hardware. 1886 1887 Software events are supported either built-in or via the 1888 use of generic tracepoints. 1889 1890 Most modern CPUs support performance events via performance 1891 counter registers. These registers count the number of certain 1892 types of hw events: such as instructions executed, cachemisses 1893 suffered, or branches mis-predicted - without slowing down the 1894 kernel or applications. These registers can also trigger interrupts 1895 when a threshold number of events have passed - and can thus be 1896 used to profile the code that runs on that CPU. 1897 1898 The Linux Performance Event subsystem provides an abstraction of 1899 these software and hardware event capabilities, available via a 1900 system call and used by the "perf" utility in tools/perf/. It 1901 provides per task and per CPU counters, and it provides event 1902 capabilities on top of those. 1903 1904 Say Y if unsure. 1905 1906 config DEBUG_PERF_USE_VMALLOC 1907 default n 1908 bool "Debug: use vmalloc to back perf mmap() buffers" 1909 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1910 select PERF_USE_VMALLOC 1911 help 1912 Use vmalloc memory to back perf mmap() buffers. 1913 1914 Mostly useful for debugging the vmalloc code on platforms 1915 that don't require it. 1916 1917 Say N if unsure. 1918 1919 endmenu 1920 1921 config SYSTEM_DATA_VERIFICATION 1922 def_bool n 1923 select SYSTEM_TRUSTED_KEYRING 1924 select KEYS 1925 select CRYPTO 1926 select CRYPTO_RSA 1927 select ASYMMETRIC_KEY_TYPE 1928 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1929 select ASN1 1930 select OID_REGISTRY 1931 select X509_CERTIFICATE_PARSER 1932 select PKCS7_MESSAGE_PARSER 1933 help 1934 Provide PKCS#7 message verification using the contents of the system 1935 trusted keyring to provide public keys. This then can be used for 1936 module verification, kexec image verification and firmware blob 1937 verification. 1938 1939 config PROFILING 1940 bool "Profiling support" 1941 help 1942 Say Y here to enable the extended profiling support mechanisms used 1943 by profilers. 1944 1945 config RUST 1946 bool "Rust support" 1947 depends on HAVE_RUST 1948 depends on RUST_IS_AVAILABLE 1949 depends on !MODVERSIONS 1950 depends on !GCC_PLUGIN_RANDSTRUCT 1951 depends on !RANDSTRUCT 1952 depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE 1953 depends on !CFI_CLANG || HAVE_CFI_ICALL_NORMALIZE_INTEGERS_RUSTC 1954 select CFI_ICALL_NORMALIZE_INTEGERS if CFI_CLANG 1955 depends on !CALL_PADDING || RUSTC_VERSION >= 108100 1956 depends on !KASAN_SW_TAGS 1957 depends on !(MITIGATION_RETHUNK && KASAN) || RUSTC_VERSION >= 108300 1958 help 1959 Enables Rust support in the kernel. 1960 1961 This allows other Rust-related options, like drivers written in Rust, 1962 to be selected. 1963 1964 It is also required to be able to load external kernel modules 1965 written in Rust. 1966 1967 See Documentation/rust/ for more information. 1968 1969 If unsure, say N. 1970 1971 config RUSTC_VERSION_TEXT 1972 string 1973 depends on RUST 1974 default "$(RUSTC_VERSION_TEXT)" 1975 help 1976 See `CC_VERSION_TEXT`. 1977 1978 config BINDGEN_VERSION_TEXT 1979 string 1980 depends on RUST 1981 # The dummy parameter `workaround-for-0.69.0` is required to support 0.69.0 1982 # (https://github.com/rust-lang/rust-bindgen/pull/2678). It can be removed when 1983 # the minimum version is upgraded past that (0.69.1 already fixed the issue). 1984 default "$(shell,$(BINDGEN) --version workaround-for-0.69.0 2>/dev/null)" 1985 1986 # 1987 # Place an empty function call at each tracepoint site. Can be 1988 # dynamically changed for a probe function. 1989 # 1990 config TRACEPOINTS 1991 bool 1992 1993 source "kernel/Kconfig.kexec" 1994 1995 endmenu # General setup 1996 1997 source "arch/Kconfig" 1998 1999 config RT_MUTEXES 2000 bool 2001 default y if PREEMPT_RT 2002 2003 config MODULE_SIG_FORMAT 2004 def_bool n 2005 select SYSTEM_DATA_VERIFICATION 2006 2007 source "kernel/module/Kconfig" 2008 2009 config INIT_ALL_POSSIBLE 2010 bool 2011 help 2012 Back when each arch used to define their own cpu_online_mask and 2013 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2014 with all 1s, and others with all 0s. When they were centralised, 2015 it was better to provide this option than to break all the archs 2016 and have several arch maintainers pursuing me down dark alleys. 2017 2018 source "block/Kconfig" 2019 2020 config PREEMPT_NOTIFIERS 2021 bool 2022 2023 config PADATA 2024 depends on SMP 2025 bool 2026 2027 config ASN1 2028 tristate 2029 help 2030 Build a simple ASN.1 grammar compiler that produces a bytecode output 2031 that can be interpreted by the ASN.1 stream decoder and used to 2032 inform it as to what tags are to be expected in a stream and what 2033 functions to call on what tags. 2034 2035 source "kernel/Kconfig.locks" 2036 2037 config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 2038 bool 2039 2040 config ARCH_HAS_PREPARE_SYNC_CORE_CMD 2041 bool 2042 2043 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2044 bool 2045 2046 # It may be useful for an architecture to override the definitions of the 2047 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2048 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2049 # different calling convention for syscalls. They can also override the 2050 # macros for not-implemented syscalls in kernel/sys_ni.c and 2051 # kernel/time/posix-stubs.c. All these overrides need to be available in 2052 # <asm/syscall_wrapper.h>. 2053 config ARCH_HAS_SYSCALL_WRAPPER 2054 def_bool n 2055