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