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