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 compier is updated 23 include/linux/kconfig.h contains this option in the comment line so 24 fixdep adds include/config/cc/version/text.h into the auto-generated 25 dependency. When the compiler is updated, syncconfig will touch it 26 and then every file will be rebuilt. 27 28config CC_IS_GCC 29 def_bool $(success,echo "$(CC_VERSION_TEXT)" | grep -q gcc) 30 31config GCC_VERSION 32 int 33 default $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) if CC_IS_GCC 34 default 0 35 36config LD_VERSION 37 int 38 default $(shell,$(LD) --version | $(srctree)/scripts/ld-version.sh) 39 40config CC_IS_CLANG 41 def_bool $(success,echo "$(CC_VERSION_TEXT)" | grep -q clang) 42 43config LD_IS_LLD 44 def_bool $(success,$(LD) -v | head -n 1 | grep -q LLD) 45 46config CLANG_VERSION 47 int 48 default $(shell,$(srctree)/scripts/clang-version.sh $(CC)) 49 50config LLD_VERSION 51 int 52 default $(shell,$(srctree)/scripts/lld-version.sh $(LD)) 53 54config CC_CAN_LINK 55 bool 56 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag)) if 64BIT 57 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag)) 58 59config CC_CAN_LINK_STATIC 60 bool 61 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag) -static) if 64BIT 62 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag) -static) 63 64config CC_HAS_ASM_GOTO 65 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) 66 67config CC_HAS_ASM_GOTO_OUTPUT 68 depends on CC_HAS_ASM_GOTO 69 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) 70 71config TOOLS_SUPPORT_RELR 72 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 73 74config CC_HAS_ASM_INLINE 75 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 76 77config CONSTRUCTORS 78 bool 79 depends on !UML 80 81config IRQ_WORK 82 bool 83 84config BUILDTIME_TABLE_SORT 85 bool 86 87config THREAD_INFO_IN_TASK 88 bool 89 help 90 Select this to move thread_info off the stack into task_struct. To 91 make this work, an arch will need to remove all thread_info fields 92 except flags and fix any runtime bugs. 93 94 One subtle change that will be needed is to use try_get_task_stack() 95 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 96 97menu "General setup" 98 99config BROKEN 100 bool 101 102config BROKEN_ON_SMP 103 bool 104 depends on BROKEN || !SMP 105 default y 106 107config INIT_ENV_ARG_LIMIT 108 int 109 default 32 if !UML 110 default 128 if UML 111 help 112 Maximum of each of the number of arguments and environment 113 variables passed to init from the kernel command line. 114 115config COMPILE_TEST 116 bool "Compile also drivers which will not load" 117 depends on !UML 118 default n 119 help 120 Some drivers can be compiled on a different platform than they are 121 intended to be run on. Despite they cannot be loaded there (or even 122 when they load they cannot be used due to missing HW support), 123 developers still, opposing to distributors, might want to build such 124 drivers to compile-test them. 125 126 If you are a developer and want to build everything available, say Y 127 here. If you are a user/distributor, say N here to exclude useless 128 drivers to be distributed. 129 130config UAPI_HEADER_TEST 131 bool "Compile test UAPI headers" 132 depends on HEADERS_INSTALL && CC_CAN_LINK 133 help 134 Compile test headers exported to user-space to ensure they are 135 self-contained, i.e. compilable as standalone units. 136 137 If you are a developer or tester and want to ensure the exported 138 headers are self-contained, say Y here. Otherwise, choose N. 139 140config LOCALVERSION 141 string "Local version - append to kernel release" 142 help 143 Append an extra string to the end of your kernel version. 144 This will show up when you type uname, for example. 145 The string you set here will be appended after the contents of 146 any files with a filename matching localversion* in your 147 object and source tree, in that order. Your total string can 148 be a maximum of 64 characters. 149 150config LOCALVERSION_AUTO 151 bool "Automatically append version information to the version string" 152 default y 153 depends on !COMPILE_TEST 154 help 155 This will try to automatically determine if the current tree is a 156 release tree by looking for git tags that belong to the current 157 top of tree revision. 158 159 A string of the format -gxxxxxxxx will be added to the localversion 160 if a git-based tree is found. The string generated by this will be 161 appended after any matching localversion* files, and after the value 162 set in CONFIG_LOCALVERSION. 163 164 (The actual string used here is the first eight characters produced 165 by running the command: 166 167 $ git rev-parse --verify HEAD 168 169 which is done within the script "scripts/setlocalversion".) 170 171config BUILD_SALT 172 string "Build ID Salt" 173 default "" 174 help 175 The build ID is used to link binaries and their debug info. Setting 176 this option will use the value in the calculation of the build id. 177 This is mostly useful for distributions which want to ensure the 178 build is unique between builds. It's safe to leave the default. 179 180config HAVE_KERNEL_GZIP 181 bool 182 183config HAVE_KERNEL_BZIP2 184 bool 185 186config HAVE_KERNEL_LZMA 187 bool 188 189config HAVE_KERNEL_XZ 190 bool 191 192config HAVE_KERNEL_LZO 193 bool 194 195config HAVE_KERNEL_LZ4 196 bool 197 198config HAVE_KERNEL_ZSTD 199 bool 200 201config HAVE_KERNEL_UNCOMPRESSED 202 bool 203 204choice 205 prompt "Kernel compression mode" 206 default KERNEL_GZIP 207 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 208 help 209 The linux kernel is a kind of self-extracting executable. 210 Several compression algorithms are available, which differ 211 in efficiency, compression and decompression speed. 212 Compression speed is only relevant when building a kernel. 213 Decompression speed is relevant at each boot. 214 215 If you have any problems with bzip2 or lzma compressed 216 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 217 version of this functionality (bzip2 only), for 2.4, was 218 supplied by Christian Ludwig) 219 220 High compression options are mostly useful for users, who 221 are low on disk space (embedded systems), but for whom ram 222 size matters less. 223 224 If in doubt, select 'gzip' 225 226config KERNEL_GZIP 227 bool "Gzip" 228 depends on HAVE_KERNEL_GZIP 229 help 230 The old and tried gzip compression. It provides a good balance 231 between compression ratio and decompression speed. 232 233config KERNEL_BZIP2 234 bool "Bzip2" 235 depends on HAVE_KERNEL_BZIP2 236 help 237 Its compression ratio and speed is intermediate. 238 Decompression speed is slowest among the choices. The kernel 239 size is about 10% smaller with bzip2, in comparison to gzip. 240 Bzip2 uses a large amount of memory. For modern kernels you 241 will need at least 8MB RAM or more for booting. 242 243config KERNEL_LZMA 244 bool "LZMA" 245 depends on HAVE_KERNEL_LZMA 246 help 247 This compression algorithm's ratio is best. Decompression speed 248 is between gzip and bzip2. Compression is slowest. 249 The kernel size is about 33% smaller with LZMA in comparison to gzip. 250 251config KERNEL_XZ 252 bool "XZ" 253 depends on HAVE_KERNEL_XZ 254 help 255 XZ uses the LZMA2 algorithm and instruction set specific 256 BCJ filters which can improve compression ratio of executable 257 code. The size of the kernel is about 30% smaller with XZ in 258 comparison to gzip. On architectures for which there is a BCJ 259 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 260 will create a few percent smaller kernel than plain LZMA. 261 262 The speed is about the same as with LZMA: The decompression 263 speed of XZ is better than that of bzip2 but worse than gzip 264 and LZO. Compression is slow. 265 266config KERNEL_LZO 267 bool "LZO" 268 depends on HAVE_KERNEL_LZO 269 help 270 Its compression ratio is the poorest among the choices. The kernel 271 size is about 10% bigger than gzip; however its speed 272 (both compression and decompression) is the fastest. 273 274config KERNEL_LZ4 275 bool "LZ4" 276 depends on HAVE_KERNEL_LZ4 277 help 278 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 279 A preliminary version of LZ4 de/compression tool is available at 280 <https://code.google.com/p/lz4/>. 281 282 Its compression ratio is worse than LZO. The size of the kernel 283 is about 8% bigger than LZO. But the decompression speed is 284 faster than LZO. 285 286config KERNEL_ZSTD 287 bool "ZSTD" 288 depends on HAVE_KERNEL_ZSTD 289 help 290 ZSTD is a compression algorithm targeting intermediate compression 291 with fast decompression speed. It will compress better than GZIP and 292 decompress around the same speed as LZO, but slower than LZ4. You 293 will need at least 192 KB RAM or more for booting. The zstd command 294 line tool is required for compression. 295 296config KERNEL_UNCOMPRESSED 297 bool "None" 298 depends on HAVE_KERNEL_UNCOMPRESSED 299 help 300 Produce uncompressed kernel image. This option is usually not what 301 you want. It is useful for debugging the kernel in slow simulation 302 environments, where decompressing and moving the kernel is awfully 303 slow. This option allows early boot code to skip the decompressor 304 and jump right at uncompressed kernel image. 305 306endchoice 307 308config DEFAULT_INIT 309 string "Default init path" 310 default "" 311 help 312 This option determines the default init for the system if no init= 313 option is passed on the kernel command line. If the requested path is 314 not present, we will still then move on to attempting further 315 locations (e.g. /sbin/init, etc). If this is empty, we will just use 316 the fallback list when init= is not passed. 317 318config DEFAULT_HOSTNAME 319 string "Default hostname" 320 default "(none)" 321 help 322 This option determines the default system hostname before userspace 323 calls sethostname(2). The kernel traditionally uses "(none)" here, 324 but you may wish to use a different default here to make a minimal 325 system more usable with less configuration. 326 327# 328# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can 329# add proper SWAP support to them, in which case this can be remove. 330# 331config ARCH_NO_SWAP 332 bool 333 334config SWAP 335 bool "Support for paging of anonymous memory (swap)" 336 depends on MMU && BLOCK && !ARCH_NO_SWAP 337 default y 338 help 339 This option allows you to choose whether you want to have support 340 for so called swap devices or swap files in your kernel that are 341 used to provide more virtual memory than the actual RAM present 342 in your computer. If unsure say Y. 343 344config SYSVIPC 345 bool "System V IPC" 346 help 347 Inter Process Communication is a suite of library functions and 348 system calls which let processes (running programs) synchronize and 349 exchange information. It is generally considered to be a good thing, 350 and some programs won't run unless you say Y here. In particular, if 351 you want to run the DOS emulator dosemu under Linux (read the 352 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 353 you'll need to say Y here. 354 355 You can find documentation about IPC with "info ipc" and also in 356 section 6.4 of the Linux Programmer's Guide, available from 357 <http://www.tldp.org/guides.html>. 358 359config SYSVIPC_SYSCTL 360 bool 361 depends on SYSVIPC 362 depends on SYSCTL 363 default y 364 365config POSIX_MQUEUE 366 bool "POSIX Message Queues" 367 depends on NET 368 help 369 POSIX variant of message queues is a part of IPC. In POSIX message 370 queues every message has a priority which decides about succession 371 of receiving it by a process. If you want to compile and run 372 programs written e.g. for Solaris with use of its POSIX message 373 queues (functions mq_*) say Y here. 374 375 POSIX message queues are visible as a filesystem called 'mqueue' 376 and can be mounted somewhere if you want to do filesystem 377 operations on message queues. 378 379 If unsure, say Y. 380 381config POSIX_MQUEUE_SYSCTL 382 bool 383 depends on POSIX_MQUEUE 384 depends on SYSCTL 385 default y 386 387config WATCH_QUEUE 388 bool "General notification queue" 389 default n 390 help 391 392 This is a general notification queue for the kernel to pass events to 393 userspace by splicing them into pipes. It can be used in conjunction 394 with watches for key/keyring change notifications and device 395 notifications. 396 397 See Documentation/watch_queue.rst 398 399config CROSS_MEMORY_ATTACH 400 bool "Enable process_vm_readv/writev syscalls" 401 depends on MMU 402 default y 403 help 404 Enabling this option adds the system calls process_vm_readv and 405 process_vm_writev which allow a process with the correct privileges 406 to directly read from or write to another process' address space. 407 See the man page for more details. 408 409config USELIB 410 bool "uselib syscall" 411 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION 412 help 413 This option enables the uselib syscall, a system call used in the 414 dynamic linker from libc5 and earlier. glibc does not use this 415 system call. If you intend to run programs built on libc5 or 416 earlier, you may need to enable this syscall. Current systems 417 running glibc can safely disable this. 418 419config AUDIT 420 bool "Auditing support" 421 depends on NET 422 help 423 Enable auditing infrastructure that can be used with another 424 kernel subsystem, such as SELinux (which requires this for 425 logging of avc messages output). System call auditing is included 426 on architectures which support it. 427 428config HAVE_ARCH_AUDITSYSCALL 429 bool 430 431config AUDITSYSCALL 432 def_bool y 433 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 434 select FSNOTIFY 435 436source "kernel/irq/Kconfig" 437source "kernel/time/Kconfig" 438source "kernel/Kconfig.preempt" 439 440menu "CPU/Task time and stats accounting" 441 442config VIRT_CPU_ACCOUNTING 443 bool 444 445choice 446 prompt "Cputime accounting" 447 default TICK_CPU_ACCOUNTING if !PPC64 448 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 449 450# Kind of a stub config for the pure tick based cputime accounting 451config TICK_CPU_ACCOUNTING 452 bool "Simple tick based cputime accounting" 453 depends on !S390 && !NO_HZ_FULL 454 help 455 This is the basic tick based cputime accounting that maintains 456 statistics about user, system and idle time spent on per jiffies 457 granularity. 458 459 If unsure, say Y. 460 461config VIRT_CPU_ACCOUNTING_NATIVE 462 bool "Deterministic task and CPU time accounting" 463 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 464 select VIRT_CPU_ACCOUNTING 465 help 466 Select this option to enable more accurate task and CPU time 467 accounting. This is done by reading a CPU counter on each 468 kernel entry and exit and on transitions within the kernel 469 between system, softirq and hardirq state, so there is a 470 small performance impact. In the case of s390 or IBM POWER > 5, 471 this also enables accounting of stolen time on logically-partitioned 472 systems. 473 474config VIRT_CPU_ACCOUNTING_GEN 475 bool "Full dynticks CPU time accounting" 476 depends on HAVE_CONTEXT_TRACKING 477 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 478 depends on GENERIC_CLOCKEVENTS 479 select VIRT_CPU_ACCOUNTING 480 select CONTEXT_TRACKING 481 help 482 Select this option to enable task and CPU time accounting on full 483 dynticks systems. This accounting is implemented by watching every 484 kernel-user boundaries using the context tracking subsystem. 485 The accounting is thus performed at the expense of some significant 486 overhead. 487 488 For now this is only useful if you are working on the full 489 dynticks subsystem development. 490 491 If unsure, say N. 492 493endchoice 494 495config IRQ_TIME_ACCOUNTING 496 bool "Fine granularity task level IRQ time accounting" 497 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 498 help 499 Select this option to enable fine granularity task irq time 500 accounting. This is done by reading a timestamp on each 501 transitions between softirq and hardirq state, so there can be a 502 small performance impact. 503 504 If in doubt, say N here. 505 506config HAVE_SCHED_AVG_IRQ 507 def_bool y 508 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 509 depends on SMP 510 511config SCHED_THERMAL_PRESSURE 512 bool 513 default y if ARM && ARM_CPU_TOPOLOGY 514 default y if ARM64 515 depends on SMP 516 depends on CPU_FREQ_THERMAL 517 help 518 Select this option to enable thermal pressure accounting in the 519 scheduler. Thermal pressure is the value conveyed to the scheduler 520 that reflects the reduction in CPU compute capacity resulted from 521 thermal throttling. Thermal throttling occurs when the performance of 522 a CPU is capped due to high operating temperatures. 523 524 If selected, the scheduler will be able to balance tasks accordingly, 525 i.e. put less load on throttled CPUs than on non/less throttled ones. 526 527 This requires the architecture to implement 528 arch_set_thermal_pressure() and arch_get_thermal_pressure(). 529 530config BSD_PROCESS_ACCT 531 bool "BSD Process Accounting" 532 depends on MULTIUSER 533 help 534 If you say Y here, a user level program will be able to instruct the 535 kernel (via a special system call) to write process accounting 536 information to a file: whenever a process exits, information about 537 that process will be appended to the file by the kernel. The 538 information includes things such as creation time, owning user, 539 command name, memory usage, controlling terminal etc. (the complete 540 list is in the struct acct in <file:include/linux/acct.h>). It is 541 up to the user level program to do useful things with this 542 information. This is generally a good idea, so say Y. 543 544config BSD_PROCESS_ACCT_V3 545 bool "BSD Process Accounting version 3 file format" 546 depends on BSD_PROCESS_ACCT 547 default n 548 help 549 If you say Y here, the process accounting information is written 550 in a new file format that also logs the process IDs of each 551 process and its parent. Note that this file format is incompatible 552 with previous v0/v1/v2 file formats, so you will need updated tools 553 for processing it. A preliminary version of these tools is available 554 at <http://www.gnu.org/software/acct/>. 555 556config TASKSTATS 557 bool "Export task/process statistics through netlink" 558 depends on NET 559 depends on MULTIUSER 560 default n 561 help 562 Export selected statistics for tasks/processes through the 563 generic netlink interface. Unlike BSD process accounting, the 564 statistics are available during the lifetime of tasks/processes as 565 responses to commands. Like BSD accounting, they are sent to user 566 space on task exit. 567 568 Say N if unsure. 569 570config TASK_DELAY_ACCT 571 bool "Enable per-task delay accounting" 572 depends on TASKSTATS 573 select SCHED_INFO 574 help 575 Collect information on time spent by a task waiting for system 576 resources like cpu, synchronous block I/O completion and swapping 577 in pages. Such statistics can help in setting a task's priorities 578 relative to other tasks for cpu, io, rss limits etc. 579 580 Say N if unsure. 581 582config TASK_XACCT 583 bool "Enable extended accounting over taskstats" 584 depends on TASKSTATS 585 help 586 Collect extended task accounting data and send the data 587 to userland for processing over the taskstats interface. 588 589 Say N if unsure. 590 591config TASK_IO_ACCOUNTING 592 bool "Enable per-task storage I/O accounting" 593 depends on TASK_XACCT 594 help 595 Collect information on the number of bytes of storage I/O which this 596 task has caused. 597 598 Say N if unsure. 599 600config PSI 601 bool "Pressure stall information tracking" 602 help 603 Collect metrics that indicate how overcommitted the CPU, memory, 604 and IO capacity are in the system. 605 606 If you say Y here, the kernel will create /proc/pressure/ with the 607 pressure statistics files cpu, memory, and io. These will indicate 608 the share of walltime in which some or all tasks in the system are 609 delayed due to contention of the respective resource. 610 611 In kernels with cgroup support, cgroups (cgroup2 only) will 612 have cpu.pressure, memory.pressure, and io.pressure files, 613 which aggregate pressure stalls for the grouped tasks only. 614 615 For more details see Documentation/accounting/psi.rst. 616 617 Say N if unsure. 618 619config PSI_DEFAULT_DISABLED 620 bool "Require boot parameter to enable pressure stall information tracking" 621 default n 622 depends on PSI 623 help 624 If set, pressure stall information tracking will be disabled 625 per default but can be enabled through passing psi=1 on the 626 kernel commandline during boot. 627 628 This feature adds some code to the task wakeup and sleep 629 paths of the scheduler. The overhead is too low to affect 630 common scheduling-intense workloads in practice (such as 631 webservers, memcache), but it does show up in artificial 632 scheduler stress tests, such as hackbench. 633 634 If you are paranoid and not sure what the kernel will be 635 used for, say Y. 636 637 Say N if unsure. 638 639endmenu # "CPU/Task time and stats accounting" 640 641config CPU_ISOLATION 642 bool "CPU isolation" 643 depends on SMP || COMPILE_TEST 644 default y 645 help 646 Make sure that CPUs running critical tasks are not disturbed by 647 any source of "noise" such as unbound workqueues, timers, kthreads... 648 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 649 the "isolcpus=" boot parameter. 650 651 Say Y if unsure. 652 653source "kernel/rcu/Kconfig" 654 655config BUILD_BIN2C 656 bool 657 default n 658 659config IKCONFIG 660 tristate "Kernel .config support" 661 help 662 This option enables the complete Linux kernel ".config" file 663 contents to be saved in the kernel. It provides documentation 664 of which kernel options are used in a running kernel or in an 665 on-disk kernel. This information can be extracted from the kernel 666 image file with the script scripts/extract-ikconfig and used as 667 input to rebuild the current kernel or to build another kernel. 668 It can also be extracted from a running kernel by reading 669 /proc/config.gz if enabled (below). 670 671config IKCONFIG_PROC 672 bool "Enable access to .config through /proc/config.gz" 673 depends on IKCONFIG && PROC_FS 674 help 675 This option enables access to the kernel configuration file 676 through /proc/config.gz. 677 678config IKHEADERS 679 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 680 depends on SYSFS 681 help 682 This option enables access to the in-kernel headers that are generated during 683 the build process. These can be used to build eBPF tracing programs, 684 or similar programs. If you build the headers as a module, a module called 685 kheaders.ko is built which can be loaded on-demand to get access to headers. 686 687config LOG_BUF_SHIFT 688 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 689 range 12 25 if !H8300 690 range 12 19 if H8300 691 default 17 692 depends on PRINTK 693 help 694 Select the minimal kernel log buffer size as a power of 2. 695 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 696 parameter, see below. Any higher size also might be forced 697 by "log_buf_len" boot parameter. 698 699 Examples: 700 17 => 128 KB 701 16 => 64 KB 702 15 => 32 KB 703 14 => 16 KB 704 13 => 8 KB 705 12 => 4 KB 706 707config LOG_CPU_MAX_BUF_SHIFT 708 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 709 depends on SMP 710 range 0 21 711 default 12 if !BASE_SMALL 712 default 0 if BASE_SMALL 713 depends on PRINTK 714 help 715 This option allows to increase the default ring buffer size 716 according to the number of CPUs. The value defines the contribution 717 of each CPU as a power of 2. The used space is typically only few 718 lines however it might be much more when problems are reported, 719 e.g. backtraces. 720 721 The increased size means that a new buffer has to be allocated and 722 the original static one is unused. It makes sense only on systems 723 with more CPUs. Therefore this value is used only when the sum of 724 contributions is greater than the half of the default kernel ring 725 buffer as defined by LOG_BUF_SHIFT. The default values are set 726 so that more than 16 CPUs are needed to trigger the allocation. 727 728 Also this option is ignored when "log_buf_len" kernel parameter is 729 used as it forces an exact (power of two) size of the ring buffer. 730 731 The number of possible CPUs is used for this computation ignoring 732 hotplugging making the computation optimal for the worst case 733 scenario while allowing a simple algorithm to be used from bootup. 734 735 Examples shift values and their meaning: 736 17 => 128 KB for each CPU 737 16 => 64 KB for each CPU 738 15 => 32 KB for each CPU 739 14 => 16 KB for each CPU 740 13 => 8 KB for each CPU 741 12 => 4 KB for each CPU 742 743config PRINTK_SAFE_LOG_BUF_SHIFT 744 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 745 range 10 21 746 default 13 747 depends on PRINTK 748 help 749 Select the size of an alternate printk per-CPU buffer where messages 750 printed from usafe contexts are temporary stored. One example would 751 be NMI messages, another one - printk recursion. The messages are 752 copied to the main log buffer in a safe context to avoid a deadlock. 753 The value defines the size as a power of 2. 754 755 Those messages are rare and limited. The largest one is when 756 a backtrace is printed. It usually fits into 4KB. Select 757 8KB if you want to be on the safe side. 758 759 Examples: 760 17 => 128 KB for each CPU 761 16 => 64 KB for each CPU 762 15 => 32 KB for each CPU 763 14 => 16 KB for each CPU 764 13 => 8 KB for each CPU 765 12 => 4 KB for each CPU 766 767# 768# Architectures with an unreliable sched_clock() should select this: 769# 770config HAVE_UNSTABLE_SCHED_CLOCK 771 bool 772 773config GENERIC_SCHED_CLOCK 774 bool 775 776menu "Scheduler features" 777 778config UCLAMP_TASK 779 bool "Enable utilization clamping for RT/FAIR tasks" 780 depends on CPU_FREQ_GOV_SCHEDUTIL 781 help 782 This feature enables the scheduler to track the clamped utilization 783 of each CPU based on RUNNABLE tasks scheduled on that CPU. 784 785 With this option, the user can specify the min and max CPU 786 utilization allowed for RUNNABLE tasks. The max utilization defines 787 the maximum frequency a task should use while the min utilization 788 defines the minimum frequency it should use. 789 790 Both min and max utilization clamp values are hints to the scheduler, 791 aiming at improving its frequency selection policy, but they do not 792 enforce or grant any specific bandwidth for tasks. 793 794 If in doubt, say N. 795 796config UCLAMP_BUCKETS_COUNT 797 int "Number of supported utilization clamp buckets" 798 range 5 20 799 default 5 800 depends on UCLAMP_TASK 801 help 802 Defines the number of clamp buckets to use. The range of each bucket 803 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 804 number of clamp buckets the finer their granularity and the higher 805 the precision of clamping aggregation and tracking at run-time. 806 807 For example, with the minimum configuration value we will have 5 808 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 809 be refcounted in the [20..39]% bucket and will set the bucket clamp 810 effective value to 25%. 811 If a second 30% boosted task should be co-scheduled on the same CPU, 812 that task will be refcounted in the same bucket of the first task and 813 it will boost the bucket clamp effective value to 30%. 814 The clamp effective value of a bucket is reset to its nominal value 815 (20% in the example above) when there are no more tasks refcounted in 816 that bucket. 817 818 An additional boost/capping margin can be added to some tasks. In the 819 example above the 25% task will be boosted to 30% until it exits the 820 CPU. If that should be considered not acceptable on certain systems, 821 it's always possible to reduce the margin by increasing the number of 822 clamp buckets to trade off used memory for run-time tracking 823 precision. 824 825 If in doubt, use the default value. 826 827endmenu 828 829# 830# For architectures that want to enable the support for NUMA-affine scheduler 831# balancing logic: 832# 833config ARCH_SUPPORTS_NUMA_BALANCING 834 bool 835 836# 837# For architectures that prefer to flush all TLBs after a number of pages 838# are unmapped instead of sending one IPI per page to flush. The architecture 839# must provide guarantees on what happens if a clean TLB cache entry is 840# written after the unmap. Details are in mm/rmap.c near the check for 841# should_defer_flush. The architecture should also consider if the full flush 842# and the refill costs are offset by the savings of sending fewer IPIs. 843config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 844 bool 845 846config CC_HAS_INT128 847 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 848 849# 850# For architectures that know their GCC __int128 support is sound 851# 852config ARCH_SUPPORTS_INT128 853 bool 854 855# For architectures that (ab)use NUMA to represent different memory regions 856# all cpu-local but of different latencies, such as SuperH. 857# 858config ARCH_WANT_NUMA_VARIABLE_LOCALITY 859 bool 860 861config NUMA_BALANCING 862 bool "Memory placement aware NUMA scheduler" 863 depends on ARCH_SUPPORTS_NUMA_BALANCING 864 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 865 depends on SMP && NUMA && MIGRATION 866 help 867 This option adds support for automatic NUMA aware memory/task placement. 868 The mechanism is quite primitive and is based on migrating memory when 869 it has references to the node the task is running on. 870 871 This system will be inactive on UMA systems. 872 873config NUMA_BALANCING_DEFAULT_ENABLED 874 bool "Automatically enable NUMA aware memory/task placement" 875 default y 876 depends on NUMA_BALANCING 877 help 878 If set, automatic NUMA balancing will be enabled if running on a NUMA 879 machine. 880 881menuconfig CGROUPS 882 bool "Control Group support" 883 select KERNFS 884 help 885 This option adds support for grouping sets of processes together, for 886 use with process control subsystems such as Cpusets, CFS, memory 887 controls or device isolation. 888 See 889 - Documentation/scheduler/sched-design-CFS.rst (CFS) 890 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 891 and resource control) 892 893 Say N if unsure. 894 895if CGROUPS 896 897config PAGE_COUNTER 898 bool 899 900config MEMCG 901 bool "Memory controller" 902 select PAGE_COUNTER 903 select EVENTFD 904 help 905 Provides control over the memory footprint of tasks in a cgroup. 906 907config MEMCG_SWAP 908 bool 909 depends on MEMCG && SWAP 910 default y 911 912config MEMCG_KMEM 913 bool 914 depends on MEMCG && !SLOB 915 default y 916 917config BLK_CGROUP 918 bool "IO controller" 919 depends on BLOCK 920 default n 921 help 922 Generic block IO controller cgroup interface. This is the common 923 cgroup interface which should be used by various IO controlling 924 policies. 925 926 Currently, CFQ IO scheduler uses it to recognize task groups and 927 control disk bandwidth allocation (proportional time slice allocation) 928 to such task groups. It is also used by bio throttling logic in 929 block layer to implement upper limit in IO rates on a device. 930 931 This option only enables generic Block IO controller infrastructure. 932 One needs to also enable actual IO controlling logic/policy. For 933 enabling proportional weight division of disk bandwidth in CFQ, set 934 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 935 CONFIG_BLK_DEV_THROTTLING=y. 936 937 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 938 939config CGROUP_WRITEBACK 940 bool 941 depends on MEMCG && BLK_CGROUP 942 default y 943 944menuconfig CGROUP_SCHED 945 bool "CPU controller" 946 default n 947 help 948 This feature lets CPU scheduler recognize task groups and control CPU 949 bandwidth allocation to such task groups. It uses cgroups to group 950 tasks. 951 952if CGROUP_SCHED 953config FAIR_GROUP_SCHED 954 bool "Group scheduling for SCHED_OTHER" 955 depends on CGROUP_SCHED 956 default CGROUP_SCHED 957 958config CFS_BANDWIDTH 959 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 960 depends on FAIR_GROUP_SCHED 961 default n 962 help 963 This option allows users to define CPU bandwidth rates (limits) for 964 tasks running within the fair group scheduler. Groups with no limit 965 set are considered to be unconstrained and will run with no 966 restriction. 967 See Documentation/scheduler/sched-bwc.rst for more information. 968 969config RT_GROUP_SCHED 970 bool "Group scheduling for SCHED_RR/FIFO" 971 depends on CGROUP_SCHED 972 default n 973 help 974 This feature lets you explicitly allocate real CPU bandwidth 975 to task groups. If enabled, it will also make it impossible to 976 schedule realtime tasks for non-root users until you allocate 977 realtime bandwidth for them. 978 See Documentation/scheduler/sched-rt-group.rst for more information. 979 980endif #CGROUP_SCHED 981 982config UCLAMP_TASK_GROUP 983 bool "Utilization clamping per group of tasks" 984 depends on CGROUP_SCHED 985 depends on UCLAMP_TASK 986 default n 987 help 988 This feature enables the scheduler to track the clamped utilization 989 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 990 991 When this option is enabled, the user can specify a min and max 992 CPU bandwidth which is allowed for each single task in a group. 993 The max bandwidth allows to clamp the maximum frequency a task 994 can use, while the min bandwidth allows to define a minimum 995 frequency a task will always use. 996 997 When task group based utilization clamping is enabled, an eventually 998 specified task-specific clamp value is constrained by the cgroup 999 specified clamp value. Both minimum and maximum task clamping cannot 1000 be bigger than the corresponding clamping defined at task group level. 1001 1002 If in doubt, say N. 1003 1004config CGROUP_PIDS 1005 bool "PIDs controller" 1006 help 1007 Provides enforcement of process number limits in the scope of a 1008 cgroup. Any attempt to fork more processes than is allowed in the 1009 cgroup will fail. PIDs are fundamentally a global resource because it 1010 is fairly trivial to reach PID exhaustion before you reach even a 1011 conservative kmemcg limit. As a result, it is possible to grind a 1012 system to halt without being limited by other cgroup policies. The 1013 PIDs controller is designed to stop this from happening. 1014 1015 It should be noted that organisational operations (such as attaching 1016 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 1017 since the PIDs limit only affects a process's ability to fork, not to 1018 attach to a cgroup. 1019 1020config CGROUP_RDMA 1021 bool "RDMA controller" 1022 help 1023 Provides enforcement of RDMA resources defined by IB stack. 1024 It is fairly easy for consumers to exhaust RDMA resources, which 1025 can result into resource unavailability to other consumers. 1026 RDMA controller is designed to stop this from happening. 1027 Attaching processes with active RDMA resources to the cgroup 1028 hierarchy is allowed even if can cross the hierarchy's limit. 1029 1030config CGROUP_FREEZER 1031 bool "Freezer controller" 1032 help 1033 Provides a way to freeze and unfreeze all tasks in a 1034 cgroup. 1035 1036 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1037 controller includes important in-kernel memory consumers per default. 1038 1039 If you're using cgroup2, say N. 1040 1041config CGROUP_HUGETLB 1042 bool "HugeTLB controller" 1043 depends on HUGETLB_PAGE 1044 select PAGE_COUNTER 1045 default n 1046 help 1047 Provides a cgroup controller for HugeTLB pages. 1048 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1049 The limit is enforced during page fault. Since HugeTLB doesn't 1050 support page reclaim, enforcing the limit at page fault time implies 1051 that, the application will get SIGBUS signal if it tries to access 1052 HugeTLB pages beyond its limit. This requires the application to know 1053 beforehand how much HugeTLB pages it would require for its use. The 1054 control group is tracked in the third page lru pointer. This means 1055 that we cannot use the controller with huge page less than 3 pages. 1056 1057config CPUSETS 1058 bool "Cpuset controller" 1059 depends on SMP 1060 help 1061 This option will let you create and manage CPUSETs which 1062 allow dynamically partitioning a system into sets of CPUs and 1063 Memory Nodes and assigning tasks to run only within those sets. 1064 This is primarily useful on large SMP or NUMA systems. 1065 1066 Say N if unsure. 1067 1068config PROC_PID_CPUSET 1069 bool "Include legacy /proc/<pid>/cpuset file" 1070 depends on CPUSETS 1071 default y 1072 1073config CGROUP_DEVICE 1074 bool "Device controller" 1075 help 1076 Provides a cgroup controller implementing whitelists for 1077 devices which a process in the cgroup can mknod or open. 1078 1079config CGROUP_CPUACCT 1080 bool "Simple CPU accounting controller" 1081 help 1082 Provides a simple controller for monitoring the 1083 total CPU consumed by the tasks in a cgroup. 1084 1085config CGROUP_PERF 1086 bool "Perf controller" 1087 depends on PERF_EVENTS 1088 help 1089 This option extends the perf per-cpu mode to restrict monitoring 1090 to threads which belong to the cgroup specified and run on the 1091 designated cpu. Or this can be used to have cgroup ID in samples 1092 so that it can monitor performance events among cgroups. 1093 1094 Say N if unsure. 1095 1096config CGROUP_BPF 1097 bool "Support for eBPF programs attached to cgroups" 1098 depends on BPF_SYSCALL 1099 select SOCK_CGROUP_DATA 1100 help 1101 Allow attaching eBPF programs to a cgroup using the bpf(2) 1102 syscall command BPF_PROG_ATTACH. 1103 1104 In which context these programs are accessed depends on the type 1105 of attachment. For instance, programs that are attached using 1106 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1107 inet sockets. 1108 1109config CGROUP_DEBUG 1110 bool "Debug controller" 1111 default n 1112 depends on DEBUG_KERNEL 1113 help 1114 This option enables a simple controller that exports 1115 debugging information about the cgroups framework. This 1116 controller is for control cgroup debugging only. Its 1117 interfaces are not stable. 1118 1119 Say N. 1120 1121config SOCK_CGROUP_DATA 1122 bool 1123 default n 1124 1125endif # CGROUPS 1126 1127menuconfig NAMESPACES 1128 bool "Namespaces support" if EXPERT 1129 depends on MULTIUSER 1130 default !EXPERT 1131 help 1132 Provides the way to make tasks work with different objects using 1133 the same id. For example same IPC id may refer to different objects 1134 or same user id or pid may refer to different tasks when used in 1135 different namespaces. 1136 1137if NAMESPACES 1138 1139config UTS_NS 1140 bool "UTS namespace" 1141 default y 1142 help 1143 In this namespace tasks see different info provided with the 1144 uname() system call 1145 1146config TIME_NS 1147 bool "TIME namespace" 1148 depends on GENERIC_VDSO_TIME_NS 1149 default y 1150 help 1151 In this namespace boottime and monotonic clocks can be set. 1152 The time will keep going with the same pace. 1153 1154config IPC_NS 1155 bool "IPC namespace" 1156 depends on (SYSVIPC || POSIX_MQUEUE) 1157 default y 1158 help 1159 In this namespace tasks work with IPC ids which correspond to 1160 different IPC objects in different namespaces. 1161 1162config USER_NS 1163 bool "User namespace" 1164 default n 1165 help 1166 This allows containers, i.e. vservers, to use user namespaces 1167 to provide different user info for different servers. 1168 1169 When user namespaces are enabled in the kernel it is 1170 recommended that the MEMCG option also be enabled and that 1171 user-space use the memory control groups to limit the amount 1172 of memory a memory unprivileged users can use. 1173 1174 If unsure, say N. 1175 1176config PID_NS 1177 bool "PID Namespaces" 1178 default y 1179 help 1180 Support process id namespaces. This allows having multiple 1181 processes with the same pid as long as they are in different 1182 pid namespaces. This is a building block of containers. 1183 1184config NET_NS 1185 bool "Network namespace" 1186 depends on NET 1187 default y 1188 help 1189 Allow user space to create what appear to be multiple instances 1190 of the network stack. 1191 1192endif # NAMESPACES 1193 1194config CHECKPOINT_RESTORE 1195 bool "Checkpoint/restore support" 1196 select PROC_CHILDREN 1197 default n 1198 help 1199 Enables additional kernel features in a sake of checkpoint/restore. 1200 In particular it adds auxiliary prctl codes to setup process text, 1201 data and heap segment sizes, and a few additional /proc filesystem 1202 entries. 1203 1204 If unsure, say N here. 1205 1206config SCHED_AUTOGROUP 1207 bool "Automatic process group scheduling" 1208 select CGROUPS 1209 select CGROUP_SCHED 1210 select FAIR_GROUP_SCHED 1211 help 1212 This option optimizes the scheduler for common desktop workloads by 1213 automatically creating and populating task groups. This separation 1214 of workloads isolates aggressive CPU burners (like build jobs) from 1215 desktop applications. Task group autogeneration is currently based 1216 upon task session. 1217 1218config SYSFS_DEPRECATED 1219 bool "Enable deprecated sysfs features to support old userspace tools" 1220 depends on SYSFS 1221 default n 1222 help 1223 This option adds code that switches the layout of the "block" class 1224 devices, to not show up in /sys/class/block/, but only in 1225 /sys/block/. 1226 1227 This switch is only active when the sysfs.deprecated=1 boot option is 1228 passed or the SYSFS_DEPRECATED_V2 option is set. 1229 1230 This option allows new kernels to run on old distributions and tools, 1231 which might get confused by /sys/class/block/. Since 2007/2008 all 1232 major distributions and tools handle this just fine. 1233 1234 Recent distributions and userspace tools after 2009/2010 depend on 1235 the existence of /sys/class/block/, and will not work with this 1236 option enabled. 1237 1238 Only if you are using a new kernel on an old distribution, you might 1239 need to say Y here. 1240 1241config SYSFS_DEPRECATED_V2 1242 bool "Enable deprecated sysfs features by default" 1243 default n 1244 depends on SYSFS 1245 depends on SYSFS_DEPRECATED 1246 help 1247 Enable deprecated sysfs by default. 1248 1249 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1250 option. 1251 1252 Only if you are using a new kernel on an old distribution, you might 1253 need to say Y here. Even then, odds are you would not need it 1254 enabled, you can always pass the boot option if absolutely necessary. 1255 1256config RELAY 1257 bool "Kernel->user space relay support (formerly relayfs)" 1258 select IRQ_WORK 1259 help 1260 This option enables support for relay interface support in 1261 certain file systems (such as debugfs). 1262 It is designed to provide an efficient mechanism for tools and 1263 facilities to relay large amounts of data from kernel space to 1264 user space. 1265 1266 If unsure, say N. 1267 1268config BLK_DEV_INITRD 1269 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1270 help 1271 The initial RAM filesystem is a ramfs which is loaded by the 1272 boot loader (loadlin or lilo) and that is mounted as root 1273 before the normal boot procedure. It is typically used to 1274 load modules needed to mount the "real" root file system, 1275 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1276 1277 If RAM disk support (BLK_DEV_RAM) is also included, this 1278 also enables initial RAM disk (initrd) support and adds 1279 15 Kbytes (more on some other architectures) to the kernel size. 1280 1281 If unsure say Y. 1282 1283if BLK_DEV_INITRD 1284 1285source "usr/Kconfig" 1286 1287endif 1288 1289config BOOT_CONFIG 1290 bool "Boot config support" 1291 select BLK_DEV_INITRD 1292 help 1293 Extra boot config allows system admin to pass a config file as 1294 complemental extension of kernel cmdline when booting. 1295 The boot config file must be attached at the end of initramfs 1296 with checksum, size and magic word. 1297 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1298 1299 If unsure, say Y. 1300 1301choice 1302 prompt "Compiler optimization level" 1303 default CC_OPTIMIZE_FOR_PERFORMANCE 1304 1305config CC_OPTIMIZE_FOR_PERFORMANCE 1306 bool "Optimize for performance (-O2)" 1307 help 1308 This is the default optimization level for the kernel, building 1309 with the "-O2" compiler flag for best performance and most 1310 helpful compile-time warnings. 1311 1312config CC_OPTIMIZE_FOR_PERFORMANCE_O3 1313 bool "Optimize more for performance (-O3)" 1314 depends on ARC 1315 help 1316 Choosing this option will pass "-O3" to your compiler to optimize 1317 the kernel yet more for performance. 1318 1319config CC_OPTIMIZE_FOR_SIZE 1320 bool "Optimize for size (-Os)" 1321 help 1322 Choosing this option will pass "-Os" to your compiler resulting 1323 in a smaller kernel. 1324 1325endchoice 1326 1327config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1328 bool 1329 help 1330 This requires that the arch annotates or otherwise protects 1331 its external entry points from being discarded. Linker scripts 1332 must also merge .text.*, .data.*, and .bss.* correctly into 1333 output sections. Care must be taken not to pull in unrelated 1334 sections (e.g., '.text.init'). Typically '.' in section names 1335 is used to distinguish them from label names / C identifiers. 1336 1337config LD_DEAD_CODE_DATA_ELIMINATION 1338 bool "Dead code and data elimination (EXPERIMENTAL)" 1339 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1340 depends on EXPERT 1341 depends on $(cc-option,-ffunction-sections -fdata-sections) 1342 depends on $(ld-option,--gc-sections) 1343 help 1344 Enable this if you want to do dead code and data elimination with 1345 the linker by compiling with -ffunction-sections -fdata-sections, 1346 and linking with --gc-sections. 1347 1348 This can reduce on disk and in-memory size of the kernel 1349 code and static data, particularly for small configs and 1350 on small systems. This has the possibility of introducing 1351 silently broken kernel if the required annotations are not 1352 present. This option is not well tested yet, so use at your 1353 own risk. 1354 1355config LD_ORPHAN_WARN 1356 def_bool y 1357 depends on ARCH_WANT_LD_ORPHAN_WARN 1358 depends on !LD_IS_LLD || LLD_VERSION >= 110000 1359 depends on $(ld-option,--orphan-handling=warn) 1360 1361config SYSCTL 1362 bool 1363 1364config HAVE_UID16 1365 bool 1366 1367config SYSCTL_EXCEPTION_TRACE 1368 bool 1369 help 1370 Enable support for /proc/sys/debug/exception-trace. 1371 1372config SYSCTL_ARCH_UNALIGN_NO_WARN 1373 bool 1374 help 1375 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1376 Allows arch to define/use @no_unaligned_warning to possibly warn 1377 about unaligned access emulation going on under the hood. 1378 1379config SYSCTL_ARCH_UNALIGN_ALLOW 1380 bool 1381 help 1382 Enable support for /proc/sys/kernel/unaligned-trap 1383 Allows arches to define/use @unaligned_enabled to runtime toggle 1384 the unaligned access emulation. 1385 see arch/parisc/kernel/unaligned.c for reference 1386 1387config HAVE_PCSPKR_PLATFORM 1388 bool 1389 1390# interpreter that classic socket filters depend on 1391config BPF 1392 bool 1393 1394menuconfig EXPERT 1395 bool "Configure standard kernel features (expert users)" 1396 # Unhide debug options, to make the on-by-default options visible 1397 select DEBUG_KERNEL 1398 help 1399 This option allows certain base kernel options and settings 1400 to be disabled or tweaked. This is for specialized 1401 environments which can tolerate a "non-standard" kernel. 1402 Only use this if you really know what you are doing. 1403 1404config UID16 1405 bool "Enable 16-bit UID system calls" if EXPERT 1406 depends on HAVE_UID16 && MULTIUSER 1407 default y 1408 help 1409 This enables the legacy 16-bit UID syscall wrappers. 1410 1411config MULTIUSER 1412 bool "Multiple users, groups and capabilities support" if EXPERT 1413 default y 1414 help 1415 This option enables support for non-root users, groups and 1416 capabilities. 1417 1418 If you say N here, all processes will run with UID 0, GID 0, and all 1419 possible capabilities. Saying N here also compiles out support for 1420 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1421 setgid, and capset. 1422 1423 If unsure, say Y here. 1424 1425config SGETMASK_SYSCALL 1426 bool "sgetmask/ssetmask syscalls support" if EXPERT 1427 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1428 help 1429 sys_sgetmask and sys_ssetmask are obsolete system calls 1430 no longer supported in libc but still enabled by default in some 1431 architectures. 1432 1433 If unsure, leave the default option here. 1434 1435config SYSFS_SYSCALL 1436 bool "Sysfs syscall support" if EXPERT 1437 default y 1438 help 1439 sys_sysfs is an obsolete system call no longer supported in libc. 1440 Note that disabling this option is more secure but might break 1441 compatibility with some systems. 1442 1443 If unsure say Y here. 1444 1445config FHANDLE 1446 bool "open by fhandle syscalls" if EXPERT 1447 select EXPORTFS 1448 default y 1449 help 1450 If you say Y here, a user level program will be able to map 1451 file names to handle and then later use the handle for 1452 different file system operations. This is useful in implementing 1453 userspace file servers, which now track files using handles instead 1454 of names. The handle would remain the same even if file names 1455 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1456 syscalls. 1457 1458config POSIX_TIMERS 1459 bool "Posix Clocks & timers" if EXPERT 1460 default y 1461 help 1462 This includes native support for POSIX timers to the kernel. 1463 Some embedded systems have no use for them and therefore they 1464 can be configured out to reduce the size of the kernel image. 1465 1466 When this option is disabled, the following syscalls won't be 1467 available: timer_create, timer_gettime: timer_getoverrun, 1468 timer_settime, timer_delete, clock_adjtime, getitimer, 1469 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1470 clock_getres and clock_nanosleep syscalls will be limited to 1471 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1472 1473 If unsure say y. 1474 1475config PRINTK 1476 default y 1477 bool "Enable support for printk" if EXPERT 1478 select IRQ_WORK 1479 help 1480 This option enables normal printk support. Removing it 1481 eliminates most of the message strings from the kernel image 1482 and makes the kernel more or less silent. As this makes it 1483 very difficult to diagnose system problems, saying N here is 1484 strongly discouraged. 1485 1486config PRINTK_NMI 1487 def_bool y 1488 depends on PRINTK 1489 depends on HAVE_NMI 1490 1491config BUG 1492 bool "BUG() support" if EXPERT 1493 default y 1494 help 1495 Disabling this option eliminates support for BUG and WARN, reducing 1496 the size of your kernel image and potentially quietly ignoring 1497 numerous fatal conditions. You should only consider disabling this 1498 option for embedded systems with no facilities for reporting errors. 1499 Just say Y. 1500 1501config ELF_CORE 1502 depends on COREDUMP 1503 default y 1504 bool "Enable ELF core dumps" if EXPERT 1505 help 1506 Enable support for generating core dumps. Disabling saves about 4k. 1507 1508 1509config PCSPKR_PLATFORM 1510 bool "Enable PC-Speaker support" if EXPERT 1511 depends on HAVE_PCSPKR_PLATFORM 1512 select I8253_LOCK 1513 default y 1514 help 1515 This option allows to disable the internal PC-Speaker 1516 support, saving some memory. 1517 1518config BASE_FULL 1519 default y 1520 bool "Enable full-sized data structures for core" if EXPERT 1521 help 1522 Disabling this option reduces the size of miscellaneous core 1523 kernel data structures. This saves memory on small machines, 1524 but may reduce performance. 1525 1526config FUTEX 1527 bool "Enable futex support" if EXPERT 1528 default y 1529 imply RT_MUTEXES 1530 help 1531 Disabling this option will cause the kernel to be built without 1532 support for "fast userspace mutexes". The resulting kernel may not 1533 run glibc-based applications correctly. 1534 1535config FUTEX_PI 1536 bool 1537 depends on FUTEX && RT_MUTEXES 1538 default y 1539 1540config HAVE_FUTEX_CMPXCHG 1541 bool 1542 depends on FUTEX 1543 help 1544 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1545 is implemented and always working. This removes a couple of runtime 1546 checks. 1547 1548config EPOLL 1549 bool "Enable eventpoll support" if EXPERT 1550 default y 1551 help 1552 Disabling this option will cause the kernel to be built without 1553 support for epoll family of system calls. 1554 1555config SIGNALFD 1556 bool "Enable signalfd() system call" if EXPERT 1557 default y 1558 help 1559 Enable the signalfd() system call that allows to receive signals 1560 on a file descriptor. 1561 1562 If unsure, say Y. 1563 1564config TIMERFD 1565 bool "Enable timerfd() system call" if EXPERT 1566 default y 1567 help 1568 Enable the timerfd() system call that allows to receive timer 1569 events on a file descriptor. 1570 1571 If unsure, say Y. 1572 1573config EVENTFD 1574 bool "Enable eventfd() system call" if EXPERT 1575 default y 1576 help 1577 Enable the eventfd() system call that allows to receive both 1578 kernel notification (ie. KAIO) or userspace notifications. 1579 1580 If unsure, say Y. 1581 1582config SHMEM 1583 bool "Use full shmem filesystem" if EXPERT 1584 default y 1585 depends on MMU 1586 help 1587 The shmem is an internal filesystem used to manage shared memory. 1588 It is backed by swap and manages resource limits. It is also exported 1589 to userspace as tmpfs if TMPFS is enabled. Disabling this 1590 option replaces shmem and tmpfs with the much simpler ramfs code, 1591 which may be appropriate on small systems without swap. 1592 1593config AIO 1594 bool "Enable AIO support" if EXPERT 1595 default y 1596 help 1597 This option enables POSIX asynchronous I/O which may by used 1598 by some high performance threaded applications. Disabling 1599 this option saves about 7k. 1600 1601config IO_URING 1602 bool "Enable IO uring support" if EXPERT 1603 select IO_WQ 1604 default y 1605 help 1606 This option enables support for the io_uring interface, enabling 1607 applications to submit and complete IO through submission and 1608 completion rings that are shared between the kernel and application. 1609 1610config ADVISE_SYSCALLS 1611 bool "Enable madvise/fadvise syscalls" if EXPERT 1612 default y 1613 help 1614 This option enables the madvise and fadvise syscalls, used by 1615 applications to advise the kernel about their future memory or file 1616 usage, improving performance. If building an embedded system where no 1617 applications use these syscalls, you can disable this option to save 1618 space. 1619 1620config HAVE_ARCH_USERFAULTFD_WP 1621 bool 1622 help 1623 Arch has userfaultfd write protection support 1624 1625config MEMBARRIER 1626 bool "Enable membarrier() system call" if EXPERT 1627 default y 1628 help 1629 Enable the membarrier() system call that allows issuing memory 1630 barriers across all running threads, which can be used to distribute 1631 the cost of user-space memory barriers asymmetrically by transforming 1632 pairs of memory barriers into pairs consisting of membarrier() and a 1633 compiler barrier. 1634 1635 If unsure, say Y. 1636 1637config KALLSYMS 1638 bool "Load all symbols for debugging/ksymoops" if EXPERT 1639 default y 1640 help 1641 Say Y here to let the kernel print out symbolic crash information and 1642 symbolic stack backtraces. This increases the size of the kernel 1643 somewhat, as all symbols have to be loaded into the kernel image. 1644 1645config KALLSYMS_ALL 1646 bool "Include all symbols in kallsyms" 1647 depends on DEBUG_KERNEL && KALLSYMS 1648 help 1649 Normally kallsyms only contains the symbols of functions for nicer 1650 OOPS messages and backtraces (i.e., symbols from the text and inittext 1651 sections). This is sufficient for most cases. And only in very rare 1652 cases (e.g., when a debugger is used) all symbols are required (e.g., 1653 names of variables from the data sections, etc). 1654 1655 This option makes sure that all symbols are loaded into the kernel 1656 image (i.e., symbols from all sections) in cost of increased kernel 1657 size (depending on the kernel configuration, it may be 300KiB or 1658 something like this). 1659 1660 Say N unless you really need all symbols. 1661 1662config KALLSYMS_ABSOLUTE_PERCPU 1663 bool 1664 depends on KALLSYMS 1665 default X86_64 && SMP 1666 1667config KALLSYMS_BASE_RELATIVE 1668 bool 1669 depends on KALLSYMS 1670 default !IA64 1671 help 1672 Instead of emitting them as absolute values in the native word size, 1673 emit the symbol references in the kallsyms table as 32-bit entries, 1674 each containing a relative value in the range [base, base + U32_MAX] 1675 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1676 an absolute value in the range [0, S32_MAX] or a relative value in the 1677 range [base, base + S32_MAX], where base is the lowest relative symbol 1678 address encountered in the image. 1679 1680 On 64-bit builds, this reduces the size of the address table by 50%, 1681 but more importantly, it results in entries whose values are build 1682 time constants, and no relocation pass is required at runtime to fix 1683 up the entries based on the runtime load address of the kernel. 1684 1685# end of the "standard kernel features (expert users)" menu 1686 1687# syscall, maps, verifier 1688 1689config BPF_LSM 1690 bool "LSM Instrumentation with BPF" 1691 depends on BPF_EVENTS 1692 depends on BPF_SYSCALL 1693 depends on SECURITY 1694 depends on BPF_JIT 1695 help 1696 Enables instrumentation of the security hooks with eBPF programs for 1697 implementing dynamic MAC and Audit Policies. 1698 1699 If you are unsure how to answer this question, answer N. 1700 1701config BPF_SYSCALL 1702 bool "Enable bpf() system call" 1703 select BPF 1704 select IRQ_WORK 1705 select TASKS_TRACE_RCU 1706 default n 1707 help 1708 Enable the bpf() system call that allows to manipulate eBPF 1709 programs and maps via file descriptors. 1710 1711config ARCH_WANT_DEFAULT_BPF_JIT 1712 bool 1713 1714config BPF_JIT_ALWAYS_ON 1715 bool "Permanently enable BPF JIT and remove BPF interpreter" 1716 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1717 help 1718 Enables BPF JIT and removes BPF interpreter to avoid 1719 speculative execution of BPF instructions by the interpreter 1720 1721config BPF_JIT_DEFAULT_ON 1722 def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON 1723 depends on HAVE_EBPF_JIT && BPF_JIT 1724 1725source "kernel/bpf/preload/Kconfig" 1726 1727config USERFAULTFD 1728 bool "Enable userfaultfd() system call" 1729 depends on MMU 1730 help 1731 Enable the userfaultfd() system call that allows to intercept and 1732 handle page faults in userland. 1733 1734config ARCH_HAS_MEMBARRIER_CALLBACKS 1735 bool 1736 1737config ARCH_HAS_MEMBARRIER_SYNC_CORE 1738 bool 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 option allnoconfig_y 1766 select EXPERT 1767 help 1768 This option should be enabled if compiling the kernel for 1769 an embedded system so certain expert options are available 1770 for configuration. 1771 1772config HAVE_PERF_EVENTS 1773 bool 1774 help 1775 See tools/perf/design.txt for details. 1776 1777config PERF_USE_VMALLOC 1778 bool 1779 help 1780 See tools/perf/design.txt for details 1781 1782config PC104 1783 bool "PC/104 support" if EXPERT 1784 help 1785 Expose PC/104 form factor device drivers and options available for 1786 selection and configuration. Enable this option if your target 1787 machine has a PC/104 bus. 1788 1789menu "Kernel Performance Events And Counters" 1790 1791config PERF_EVENTS 1792 bool "Kernel performance events and counters" 1793 default y if PROFILING 1794 depends on HAVE_PERF_EVENTS 1795 select IRQ_WORK 1796 select SRCU 1797 help 1798 Enable kernel support for various performance events provided 1799 by software and hardware. 1800 1801 Software events are supported either built-in or via the 1802 use of generic tracepoints. 1803 1804 Most modern CPUs support performance events via performance 1805 counter registers. These registers count the number of certain 1806 types of hw events: such as instructions executed, cachemisses 1807 suffered, or branches mis-predicted - without slowing down the 1808 kernel or applications. These registers can also trigger interrupts 1809 when a threshold number of events have passed - and can thus be 1810 used to profile the code that runs on that CPU. 1811 1812 The Linux Performance Event subsystem provides an abstraction of 1813 these software and hardware event capabilities, available via a 1814 system call and used by the "perf" utility in tools/perf/. It 1815 provides per task and per CPU counters, and it provides event 1816 capabilities on top of those. 1817 1818 Say Y if unsure. 1819 1820config DEBUG_PERF_USE_VMALLOC 1821 default n 1822 bool "Debug: use vmalloc to back perf mmap() buffers" 1823 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1824 select PERF_USE_VMALLOC 1825 help 1826 Use vmalloc memory to back perf mmap() buffers. 1827 1828 Mostly useful for debugging the vmalloc code on platforms 1829 that don't require it. 1830 1831 Say N if unsure. 1832 1833endmenu 1834 1835config VM_EVENT_COUNTERS 1836 default y 1837 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1838 help 1839 VM event counters are needed for event counts to be shown. 1840 This option allows the disabling of the VM event counters 1841 on EXPERT systems. /proc/vmstat will only show page counts 1842 if VM event counters are disabled. 1843 1844config SLUB_DEBUG 1845 default y 1846 bool "Enable SLUB debugging support" if EXPERT 1847 depends on SLUB && SYSFS 1848 help 1849 SLUB has extensive debug support features. Disabling these can 1850 result in significant savings in code size. This also disables 1851 SLUB sysfs support. /sys/slab will not exist and there will be 1852 no support for cache validation etc. 1853 1854config SLUB_MEMCG_SYSFS_ON 1855 default n 1856 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1857 depends on SLUB && SYSFS && MEMCG 1858 help 1859 SLUB creates a directory under /sys/kernel/slab for each 1860 allocation cache to host info and debug files. If memory 1861 cgroup is enabled, each cache can have per memory cgroup 1862 caches. SLUB can create the same sysfs directories for these 1863 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1864 to a very high number of debug files being created. This is 1865 controlled by slub_memcg_sysfs boot parameter and this 1866 config option determines the parameter's default value. 1867 1868config COMPAT_BRK 1869 bool "Disable heap randomization" 1870 default y 1871 help 1872 Randomizing heap placement makes heap exploits harder, but it 1873 also breaks ancient binaries (including anything libc5 based). 1874 This option changes the bootup default to heap randomization 1875 disabled, and can be overridden at runtime by setting 1876 /proc/sys/kernel/randomize_va_space to 2. 1877 1878 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1879 1880choice 1881 prompt "Choose SLAB allocator" 1882 default SLUB 1883 help 1884 This option allows to select a slab allocator. 1885 1886config SLAB 1887 bool "SLAB" 1888 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1889 help 1890 The regular slab allocator that is established and known to work 1891 well in all environments. It organizes cache hot objects in 1892 per cpu and per node queues. 1893 1894config SLUB 1895 bool "SLUB (Unqueued Allocator)" 1896 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1897 help 1898 SLUB is a slab allocator that minimizes cache line usage 1899 instead of managing queues of cached objects (SLAB approach). 1900 Per cpu caching is realized using slabs of objects instead 1901 of queues of objects. SLUB can use memory efficiently 1902 and has enhanced diagnostics. SLUB is the default choice for 1903 a slab allocator. 1904 1905config SLOB 1906 depends on EXPERT 1907 bool "SLOB (Simple Allocator)" 1908 help 1909 SLOB replaces the stock allocator with a drastically simpler 1910 allocator. SLOB is generally more space efficient but 1911 does not perform as well on large systems. 1912 1913endchoice 1914 1915config SLAB_MERGE_DEFAULT 1916 bool "Allow slab caches to be merged" 1917 default y 1918 help 1919 For reduced kernel memory fragmentation, slab caches can be 1920 merged when they share the same size and other characteristics. 1921 This carries a risk of kernel heap overflows being able to 1922 overwrite objects from merged caches (and more easily control 1923 cache layout), which makes such heap attacks easier to exploit 1924 by attackers. By keeping caches unmerged, these kinds of exploits 1925 can usually only damage objects in the same cache. To disable 1926 merging at runtime, "slab_nomerge" can be passed on the kernel 1927 command line. 1928 1929config SLAB_FREELIST_RANDOM 1930 bool "Randomize slab freelist" 1931 depends on SLAB || SLUB 1932 help 1933 Randomizes the freelist order used on creating new pages. This 1934 security feature reduces the predictability of the kernel slab 1935 allocator against heap overflows. 1936 1937config SLAB_FREELIST_HARDENED 1938 bool "Harden slab freelist metadata" 1939 depends on SLAB || SLUB 1940 help 1941 Many kernel heap attacks try to target slab cache metadata and 1942 other infrastructure. This options makes minor performance 1943 sacrifices to harden the kernel slab allocator against common 1944 freelist exploit methods. Some slab implementations have more 1945 sanity-checking than others. This option is most effective with 1946 CONFIG_SLUB. 1947 1948config SHUFFLE_PAGE_ALLOCATOR 1949 bool "Page allocator randomization" 1950 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1951 help 1952 Randomization of the page allocator improves the average 1953 utilization of a direct-mapped memory-side-cache. See section 1954 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1955 6.2a specification for an example of how a platform advertises 1956 the presence of a memory-side-cache. There are also incidental 1957 security benefits as it reduces the predictability of page 1958 allocations to compliment SLAB_FREELIST_RANDOM, but the 1959 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1960 10th order of pages is selected based on cache utilization 1961 benefits on x86. 1962 1963 While the randomization improves cache utilization it may 1964 negatively impact workloads on platforms without a cache. For 1965 this reason, by default, the randomization is enabled only 1966 after runtime detection of a direct-mapped memory-side-cache. 1967 Otherwise, the randomization may be force enabled with the 1968 'page_alloc.shuffle' kernel command line parameter. 1969 1970 Say Y if unsure. 1971 1972config SLUB_CPU_PARTIAL 1973 default y 1974 depends on SLUB && SMP 1975 bool "SLUB per cpu partial cache" 1976 help 1977 Per cpu partial caches accelerate objects allocation and freeing 1978 that is local to a processor at the price of more indeterminism 1979 in the latency of the free. On overflow these caches will be cleared 1980 which requires the taking of locks that may cause latency spikes. 1981 Typically one would choose no for a realtime system. 1982 1983config MMAP_ALLOW_UNINITIALIZED 1984 bool "Allow mmapped anonymous memory to be uninitialized" 1985 depends on EXPERT && !MMU 1986 default n 1987 help 1988 Normally, and according to the Linux spec, anonymous memory obtained 1989 from mmap() has its contents cleared before it is passed to 1990 userspace. Enabling this config option allows you to request that 1991 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1992 providing a huge performance boost. If this option is not enabled, 1993 then the flag will be ignored. 1994 1995 This is taken advantage of by uClibc's malloc(), and also by 1996 ELF-FDPIC binfmt's brk and stack allocator. 1997 1998 Because of the obvious security issues, this option should only be 1999 enabled on embedded devices where you control what is run in 2000 userspace. Since that isn't generally a problem on no-MMU systems, 2001 it is normally safe to say Y here. 2002 2003 See Documentation/admin-guide/mm/nommu-mmap.rst for more information. 2004 2005config SYSTEM_DATA_VERIFICATION 2006 def_bool n 2007 select SYSTEM_TRUSTED_KEYRING 2008 select KEYS 2009 select CRYPTO 2010 select CRYPTO_RSA 2011 select ASYMMETRIC_KEY_TYPE 2012 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 2013 select ASN1 2014 select OID_REGISTRY 2015 select X509_CERTIFICATE_PARSER 2016 select PKCS7_MESSAGE_PARSER 2017 help 2018 Provide PKCS#7 message verification using the contents of the system 2019 trusted keyring to provide public keys. This then can be used for 2020 module verification, kexec image verification and firmware blob 2021 verification. 2022 2023config PROFILING 2024 bool "Profiling support" 2025 help 2026 Say Y here to enable the extended profiling support mechanisms used 2027 by profilers such as OProfile. 2028 2029# 2030# Place an empty function call at each tracepoint site. Can be 2031# dynamically changed for a probe function. 2032# 2033config TRACEPOINTS 2034 bool 2035 2036endmenu # General setup 2037 2038source "arch/Kconfig" 2039 2040config RT_MUTEXES 2041 bool 2042 2043config BASE_SMALL 2044 int 2045 default 0 if BASE_FULL 2046 default 1 if !BASE_FULL 2047 2048config MODULE_SIG_FORMAT 2049 def_bool n 2050 select SYSTEM_DATA_VERIFICATION 2051 2052menuconfig MODULES 2053 bool "Enable loadable module support" 2054 option modules 2055 help 2056 Kernel modules are small pieces of compiled code which can 2057 be inserted in the running kernel, rather than being 2058 permanently built into the kernel. You use the "modprobe" 2059 tool to add (and sometimes remove) them. If you say Y here, 2060 many parts of the kernel can be built as modules (by 2061 answering M instead of Y where indicated): this is most 2062 useful for infrequently used options which are not required 2063 for booting. For more information, see the man pages for 2064 modprobe, lsmod, modinfo, insmod and rmmod. 2065 2066 If you say Y here, you will need to run "make 2067 modules_install" to put the modules under /lib/modules/ 2068 where modprobe can find them (you may need to be root to do 2069 this). 2070 2071 If unsure, say Y. 2072 2073if MODULES 2074 2075config MODULE_FORCE_LOAD 2076 bool "Forced module loading" 2077 default n 2078 help 2079 Allow loading of modules without version information (ie. modprobe 2080 --force). Forced module loading sets the 'F' (forced) taint flag and 2081 is usually a really bad idea. 2082 2083config MODULE_UNLOAD 2084 bool "Module unloading" 2085 help 2086 Without this option you will not be able to unload any 2087 modules (note that some modules may not be unloadable 2088 anyway), which makes your kernel smaller, faster 2089 and simpler. If unsure, say Y. 2090 2091config MODULE_FORCE_UNLOAD 2092 bool "Forced module unloading" 2093 depends on MODULE_UNLOAD 2094 help 2095 This option allows you to force a module to unload, even if the 2096 kernel believes it is unsafe: the kernel will remove the module 2097 without waiting for anyone to stop using it (using the -f option to 2098 rmmod). This is mainly for kernel developers and desperate users. 2099 If unsure, say N. 2100 2101config MODVERSIONS 2102 bool "Module versioning support" 2103 help 2104 Usually, you have to use modules compiled with your kernel. 2105 Saying Y here makes it sometimes possible to use modules 2106 compiled for different kernels, by adding enough information 2107 to the modules to (hopefully) spot any changes which would 2108 make them incompatible with the kernel you are running. If 2109 unsure, say N. 2110 2111config ASM_MODVERSIONS 2112 bool 2113 default HAVE_ASM_MODVERSIONS && MODVERSIONS 2114 help 2115 This enables module versioning for exported symbols also from 2116 assembly. This can be enabled only when the target architecture 2117 supports it. 2118 2119config MODULE_REL_CRCS 2120 bool 2121 depends on MODVERSIONS 2122 2123config MODULE_SRCVERSION_ALL 2124 bool "Source checksum for all modules" 2125 help 2126 Modules which contain a MODULE_VERSION get an extra "srcversion" 2127 field inserted into their modinfo section, which contains a 2128 sum of the source files which made it. This helps maintainers 2129 see exactly which source was used to build a module (since 2130 others sometimes change the module source without updating 2131 the version). With this option, such a "srcversion" field 2132 will be created for all modules. If unsure, say N. 2133 2134config MODULE_SIG 2135 bool "Module signature verification" 2136 select MODULE_SIG_FORMAT 2137 help 2138 Check modules for valid signatures upon load: the signature 2139 is simply appended to the module. For more information see 2140 <file:Documentation/admin-guide/module-signing.rst>. 2141 2142 Note that this option adds the OpenSSL development packages as a 2143 kernel build dependency so that the signing tool can use its crypto 2144 library. 2145 2146 You should enable this option if you wish to use either 2147 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via 2148 another LSM - otherwise unsigned modules will be loadable regardless 2149 of the lockdown policy. 2150 2151 !!!WARNING!!! If you enable this option, you MUST make sure that the 2152 module DOES NOT get stripped after being signed. This includes the 2153 debuginfo strip done by some packagers (such as rpmbuild) and 2154 inclusion into an initramfs that wants the module size reduced. 2155 2156config MODULE_SIG_FORCE 2157 bool "Require modules to be validly signed" 2158 depends on MODULE_SIG 2159 help 2160 Reject unsigned modules or signed modules for which we don't have a 2161 key. Without this, such modules will simply taint the kernel. 2162 2163config MODULE_SIG_ALL 2164 bool "Automatically sign all modules" 2165 default y 2166 depends on MODULE_SIG 2167 help 2168 Sign all modules during make modules_install. Without this option, 2169 modules must be signed manually, using the scripts/sign-file tool. 2170 2171comment "Do not forget to sign required modules with scripts/sign-file" 2172 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2173 2174choice 2175 prompt "Which hash algorithm should modules be signed with?" 2176 depends on MODULE_SIG 2177 help 2178 This determines which sort of hashing algorithm will be used during 2179 signature generation. This algorithm _must_ be built into the kernel 2180 directly so that signature verification can take place. It is not 2181 possible to load a signed module containing the algorithm to check 2182 the signature on that module. 2183 2184config MODULE_SIG_SHA1 2185 bool "Sign modules with SHA-1" 2186 select CRYPTO_SHA1 2187 2188config MODULE_SIG_SHA224 2189 bool "Sign modules with SHA-224" 2190 select CRYPTO_SHA256 2191 2192config MODULE_SIG_SHA256 2193 bool "Sign modules with SHA-256" 2194 select CRYPTO_SHA256 2195 2196config MODULE_SIG_SHA384 2197 bool "Sign modules with SHA-384" 2198 select CRYPTO_SHA512 2199 2200config MODULE_SIG_SHA512 2201 bool "Sign modules with SHA-512" 2202 select CRYPTO_SHA512 2203 2204endchoice 2205 2206config MODULE_SIG_HASH 2207 string 2208 depends on MODULE_SIG 2209 default "sha1" if MODULE_SIG_SHA1 2210 default "sha224" if MODULE_SIG_SHA224 2211 default "sha256" if MODULE_SIG_SHA256 2212 default "sha384" if MODULE_SIG_SHA384 2213 default "sha512" if MODULE_SIG_SHA512 2214 2215config MODULE_COMPRESS 2216 bool "Compress modules on installation" 2217 help 2218 2219 Compresses kernel modules when 'make modules_install' is run; gzip or 2220 xz depending on "Compression algorithm" below. 2221 2222 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 2223 2224 Out-of-tree kernel modules installed using Kbuild will also be 2225 compressed upon installation. 2226 2227 Note: for modules inside an initrd or initramfs, it's more efficient 2228 to compress the whole initrd or initramfs instead. 2229 2230 Note: This is fully compatible with signed modules. 2231 2232 If in doubt, say N. 2233 2234choice 2235 prompt "Compression algorithm" 2236 depends on MODULE_COMPRESS 2237 default MODULE_COMPRESS_GZIP 2238 help 2239 This determines which sort of compression will be used during 2240 'make modules_install'. 2241 2242 GZIP (default) and XZ are supported. 2243 2244config MODULE_COMPRESS_GZIP 2245 bool "GZIP" 2246 2247config MODULE_COMPRESS_XZ 2248 bool "XZ" 2249 2250endchoice 2251 2252config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS 2253 bool "Allow loading of modules with missing namespace imports" 2254 help 2255 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in 2256 a namespace. A module that makes use of a symbol exported with such a 2257 namespace is required to import the namespace via MODULE_IMPORT_NS(). 2258 There is no technical reason to enforce correct namespace imports, 2259 but it creates consistency between symbols defining namespaces and 2260 users importing namespaces they make use of. This option relaxes this 2261 requirement and lifts the enforcement when loading a module. 2262 2263 If unsure, say N. 2264 2265config UNUSED_SYMBOLS 2266 bool "Enable unused/obsolete exported symbols" 2267 default y if X86 2268 help 2269 Unused but exported symbols make the kernel needlessly bigger. For 2270 that reason most of these unused exports will soon be removed. This 2271 option is provided temporarily to provide a transition period in case 2272 some external kernel module needs one of these symbols anyway. If you 2273 encounter such a case in your module, consider if you are actually 2274 using the right API. (rationale: since nobody in the kernel is using 2275 this in a module, there is a pretty good chance it's actually the 2276 wrong interface to use). If you really need the symbol, please send a 2277 mail to the linux kernel mailing list mentioning the symbol and why 2278 you really need it, and what the merge plan to the mainline kernel for 2279 your module is. 2280 2281config TRIM_UNUSED_KSYMS 2282 bool "Trim unused exported kernel symbols" 2283 depends on !UNUSED_SYMBOLS 2284 help 2285 The kernel and some modules make many symbols available for 2286 other modules to use via EXPORT_SYMBOL() and variants. Depending 2287 on the set of modules being selected in your kernel configuration, 2288 many of those exported symbols might never be used. 2289 2290 This option allows for unused exported symbols to be dropped from 2291 the build. In turn, this provides the compiler more opportunities 2292 (especially when using LTO) for optimizing the code and reducing 2293 binary size. This might have some security advantages as well. 2294 2295 If unsure, or if you need to build out-of-tree modules, say N. 2296 2297config UNUSED_KSYMS_WHITELIST 2298 string "Whitelist of symbols to keep in ksymtab" 2299 depends on TRIM_UNUSED_KSYMS 2300 help 2301 By default, all unused exported symbols will be un-exported from the 2302 build when TRIM_UNUSED_KSYMS is selected. 2303 2304 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept 2305 exported at all times, even in absence of in-tree users. The value to 2306 set here is the path to a text file containing the list of symbols, 2307 one per line. The path can be absolute, or relative to the kernel 2308 source tree. 2309 2310endif # MODULES 2311 2312config MODULES_TREE_LOOKUP 2313 def_bool y 2314 depends on PERF_EVENTS || TRACING 2315 2316config INIT_ALL_POSSIBLE 2317 bool 2318 help 2319 Back when each arch used to define their own cpu_online_mask and 2320 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2321 with all 1s, and others with all 0s. When they were centralised, 2322 it was better to provide this option than to break all the archs 2323 and have several arch maintainers pursuing me down dark alleys. 2324 2325source "block/Kconfig" 2326 2327config PREEMPT_NOTIFIERS 2328 bool 2329 2330config PADATA 2331 depends on SMP 2332 bool 2333 2334config ASN1 2335 tristate 2336 help 2337 Build a simple ASN.1 grammar compiler that produces a bytecode output 2338 that can be interpreted by the ASN.1 stream decoder and used to 2339 inform it as to what tags are to be expected in a stream and what 2340 functions to call on what tags. 2341 2342source "kernel/Kconfig.locks" 2343 2344config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 2345 bool 2346 2347config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2348 bool 2349 2350# It may be useful for an architecture to override the definitions of the 2351# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2352# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2353# different calling convention for syscalls. They can also override the 2354# macros for not-implemented syscalls in kernel/sys_ni.c and 2355# kernel/time/posix-stubs.c. All these overrides need to be available in 2356# <asm/syscall_wrapper.h>. 2357config ARCH_HAS_SYSCALL_WRAPPER 2358 def_bool n 2359
