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 CC_CAN_LINK 51 bool 52 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag)) if 64BIT 53 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag)) 54 55config CC_CAN_LINK_STATIC 56 bool 57 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag) -static) if 64BIT 58 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag) -static) 59 60config CC_HAS_ASM_GOTO 61 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) 62 63config CC_HAS_ASM_GOTO_OUTPUT 64 depends on CC_HAS_ASM_GOTO 65 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) 66 67config TOOLS_SUPPORT_RELR 68 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 69 70config CC_HAS_ASM_INLINE 71 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 72 73config CONSTRUCTORS 74 bool 75 depends on !UML 76 77config IRQ_WORK 78 bool 79 80config BUILDTIME_TABLE_SORT 81 bool 82 83config THREAD_INFO_IN_TASK 84 bool 85 help 86 Select this to move thread_info off the stack into task_struct. To 87 make this work, an arch will need to remove all thread_info fields 88 except flags and fix any runtime bugs. 89 90 One subtle change that will be needed is to use try_get_task_stack() 91 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 92 93menu "General setup" 94 95config BROKEN 96 bool 97 98config BROKEN_ON_SMP 99 bool 100 depends on BROKEN || !SMP 101 default y 102 103config INIT_ENV_ARG_LIMIT 104 int 105 default 32 if !UML 106 default 128 if UML 107 help 108 Maximum of each of the number of arguments and environment 109 variables passed to init from the kernel command line. 110 111config COMPILE_TEST 112 bool "Compile also drivers which will not load" 113 depends on !UML 114 default n 115 help 116 Some drivers can be compiled on a different platform than they are 117 intended to be run on. Despite they cannot be loaded there (or even 118 when they load they cannot be used due to missing HW support), 119 developers still, opposing to distributors, might want to build such 120 drivers to compile-test them. 121 122 If you are a developer and want to build everything available, say Y 123 here. If you are a user/distributor, say N here to exclude useless 124 drivers to be distributed. 125 126config UAPI_HEADER_TEST 127 bool "Compile test UAPI headers" 128 depends on HEADERS_INSTALL && CC_CAN_LINK 129 help 130 Compile test headers exported to user-space to ensure they are 131 self-contained, i.e. compilable as standalone units. 132 133 If you are a developer or tester and want to ensure the exported 134 headers are self-contained, say Y here. Otherwise, choose N. 135 136config LOCALVERSION 137 string "Local version - append to kernel release" 138 help 139 Append an extra string to the end of your kernel version. 140 This will show up when you type uname, for example. 141 The string you set here will be appended after the contents of 142 any files with a filename matching localversion* in your 143 object and source tree, in that order. Your total string can 144 be a maximum of 64 characters. 145 146config LOCALVERSION_AUTO 147 bool "Automatically append version information to the version string" 148 default y 149 depends on !COMPILE_TEST 150 help 151 This will try to automatically determine if the current tree is a 152 release tree by looking for git tags that belong to the current 153 top of tree revision. 154 155 A string of the format -gxxxxxxxx will be added to the localversion 156 if a git-based tree is found. The string generated by this will be 157 appended after any matching localversion* files, and after the value 158 set in CONFIG_LOCALVERSION. 159 160 (The actual string used here is the first eight characters produced 161 by running the command: 162 163 $ git rev-parse --verify HEAD 164 165 which is done within the script "scripts/setlocalversion".) 166 167config BUILD_SALT 168 string "Build ID Salt" 169 default "" 170 help 171 The build ID is used to link binaries and their debug info. Setting 172 this option will use the value in the calculation of the build id. 173 This is mostly useful for distributions which want to ensure the 174 build is unique between builds. It's safe to leave the default. 175 176config HAVE_KERNEL_GZIP 177 bool 178 179config HAVE_KERNEL_BZIP2 180 bool 181 182config HAVE_KERNEL_LZMA 183 bool 184 185config HAVE_KERNEL_XZ 186 bool 187 188config HAVE_KERNEL_LZO 189 bool 190 191config HAVE_KERNEL_LZ4 192 bool 193 194config HAVE_KERNEL_ZSTD 195 bool 196 197config HAVE_KERNEL_UNCOMPRESSED 198 bool 199 200choice 201 prompt "Kernel compression mode" 202 default KERNEL_GZIP 203 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 204 help 205 The linux kernel is a kind of self-extracting executable. 206 Several compression algorithms are available, which differ 207 in efficiency, compression and decompression speed. 208 Compression speed is only relevant when building a kernel. 209 Decompression speed is relevant at each boot. 210 211 If you have any problems with bzip2 or lzma compressed 212 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 213 version of this functionality (bzip2 only), for 2.4, was 214 supplied by Christian Ludwig) 215 216 High compression options are mostly useful for users, who 217 are low on disk space (embedded systems), but for whom ram 218 size matters less. 219 220 If in doubt, select 'gzip' 221 222config KERNEL_GZIP 223 bool "Gzip" 224 depends on HAVE_KERNEL_GZIP 225 help 226 The old and tried gzip compression. It provides a good balance 227 between compression ratio and decompression speed. 228 229config KERNEL_BZIP2 230 bool "Bzip2" 231 depends on HAVE_KERNEL_BZIP2 232 help 233 Its compression ratio and speed is intermediate. 234 Decompression speed is slowest among the choices. The kernel 235 size is about 10% smaller with bzip2, in comparison to gzip. 236 Bzip2 uses a large amount of memory. For modern kernels you 237 will need at least 8MB RAM or more for booting. 238 239config KERNEL_LZMA 240 bool "LZMA" 241 depends on HAVE_KERNEL_LZMA 242 help 243 This compression algorithm's ratio is best. Decompression speed 244 is between gzip and bzip2. Compression is slowest. 245 The kernel size is about 33% smaller with LZMA in comparison to gzip. 246 247config KERNEL_XZ 248 bool "XZ" 249 depends on HAVE_KERNEL_XZ 250 help 251 XZ uses the LZMA2 algorithm and instruction set specific 252 BCJ filters which can improve compression ratio of executable 253 code. The size of the kernel is about 30% smaller with XZ in 254 comparison to gzip. On architectures for which there is a BCJ 255 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 256 will create a few percent smaller kernel than plain LZMA. 257 258 The speed is about the same as with LZMA: The decompression 259 speed of XZ is better than that of bzip2 but worse than gzip 260 and LZO. Compression is slow. 261 262config KERNEL_LZO 263 bool "LZO" 264 depends on HAVE_KERNEL_LZO 265 help 266 Its compression ratio is the poorest among the choices. The kernel 267 size is about 10% bigger than gzip; however its speed 268 (both compression and decompression) is the fastest. 269 270config KERNEL_LZ4 271 bool "LZ4" 272 depends on HAVE_KERNEL_LZ4 273 help 274 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 275 A preliminary version of LZ4 de/compression tool is available at 276 <https://code.google.com/p/lz4/>. 277 278 Its compression ratio is worse than LZO. The size of the kernel 279 is about 8% bigger than LZO. But the decompression speed is 280 faster than LZO. 281 282config KERNEL_ZSTD 283 bool "ZSTD" 284 depends on HAVE_KERNEL_ZSTD 285 help 286 ZSTD is a compression algorithm targeting intermediate compression 287 with fast decompression speed. It will compress better than GZIP and 288 decompress around the same speed as LZO, but slower than LZ4. You 289 will need at least 192 KB RAM or more for booting. The zstd command 290 line tool is required for compression. 291 292config KERNEL_UNCOMPRESSED 293 bool "None" 294 depends on HAVE_KERNEL_UNCOMPRESSED 295 help 296 Produce uncompressed kernel image. This option is usually not what 297 you want. It is useful for debugging the kernel in slow simulation 298 environments, where decompressing and moving the kernel is awfully 299 slow. This option allows early boot code to skip the decompressor 300 and jump right at uncompressed kernel image. 301 302endchoice 303 304config DEFAULT_INIT 305 string "Default init path" 306 default "" 307 help 308 This option determines the default init for the system if no init= 309 option is passed on the kernel command line. If the requested path is 310 not present, we will still then move on to attempting further 311 locations (e.g. /sbin/init, etc). If this is empty, we will just use 312 the fallback list when init= is not passed. 313 314config DEFAULT_HOSTNAME 315 string "Default hostname" 316 default "(none)" 317 help 318 This option determines the default system hostname before userspace 319 calls sethostname(2). The kernel traditionally uses "(none)" here, 320 but you may wish to use a different default here to make a minimal 321 system more usable with less configuration. 322 323# 324# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can 325# add proper SWAP support to them, in which case this can be remove. 326# 327config ARCH_NO_SWAP 328 bool 329 330config SWAP 331 bool "Support for paging of anonymous memory (swap)" 332 depends on MMU && BLOCK && !ARCH_NO_SWAP 333 default y 334 help 335 This option allows you to choose whether you want to have support 336 for so called swap devices or swap files in your kernel that are 337 used to provide more virtual memory than the actual RAM present 338 in your computer. If unsure say Y. 339 340config SYSVIPC 341 bool "System V IPC" 342 help 343 Inter Process Communication is a suite of library functions and 344 system calls which let processes (running programs) synchronize and 345 exchange information. It is generally considered to be a good thing, 346 and some programs won't run unless you say Y here. In particular, if 347 you want to run the DOS emulator dosemu under Linux (read the 348 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 349 you'll need to say Y here. 350 351 You can find documentation about IPC with "info ipc" and also in 352 section 6.4 of the Linux Programmer's Guide, available from 353 <http://www.tldp.org/guides.html>. 354 355config SYSVIPC_SYSCTL 356 bool 357 depends on SYSVIPC 358 depends on SYSCTL 359 default y 360 361config POSIX_MQUEUE 362 bool "POSIX Message Queues" 363 depends on NET 364 help 365 POSIX variant of message queues is a part of IPC. In POSIX message 366 queues every message has a priority which decides about succession 367 of receiving it by a process. If you want to compile and run 368 programs written e.g. for Solaris with use of its POSIX message 369 queues (functions mq_*) say Y here. 370 371 POSIX message queues are visible as a filesystem called 'mqueue' 372 and can be mounted somewhere if you want to do filesystem 373 operations on message queues. 374 375 If unsure, say Y. 376 377config POSIX_MQUEUE_SYSCTL 378 bool 379 depends on POSIX_MQUEUE 380 depends on SYSCTL 381 default y 382 383config WATCH_QUEUE 384 bool "General notification queue" 385 default n 386 help 387 388 This is a general notification queue for the kernel to pass events to 389 userspace by splicing them into pipes. It can be used in conjunction 390 with watches for key/keyring change notifications and device 391 notifications. 392 393 See Documentation/watch_queue.rst 394 395config CROSS_MEMORY_ATTACH 396 bool "Enable process_vm_readv/writev syscalls" 397 depends on MMU 398 default y 399 help 400 Enabling this option adds the system calls process_vm_readv and 401 process_vm_writev which allow a process with the correct privileges 402 to directly read from or write to another process' address space. 403 See the man page for more details. 404 405config USELIB 406 bool "uselib syscall" 407 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION 408 help 409 This option enables the uselib syscall, a system call used in the 410 dynamic linker from libc5 and earlier. glibc does not use this 411 system call. If you intend to run programs built on libc5 or 412 earlier, you may need to enable this syscall. Current systems 413 running glibc can safely disable this. 414 415config AUDIT 416 bool "Auditing support" 417 depends on NET 418 help 419 Enable auditing infrastructure that can be used with another 420 kernel subsystem, such as SELinux (which requires this for 421 logging of avc messages output). System call auditing is included 422 on architectures which support it. 423 424config HAVE_ARCH_AUDITSYSCALL 425 bool 426 427config AUDITSYSCALL 428 def_bool y 429 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 430 select FSNOTIFY 431 432source "kernel/irq/Kconfig" 433source "kernel/time/Kconfig" 434source "kernel/Kconfig.preempt" 435 436menu "CPU/Task time and stats accounting" 437 438config VIRT_CPU_ACCOUNTING 439 bool 440 441choice 442 prompt "Cputime accounting" 443 default TICK_CPU_ACCOUNTING if !PPC64 444 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 445 446# Kind of a stub config for the pure tick based cputime accounting 447config TICK_CPU_ACCOUNTING 448 bool "Simple tick based cputime accounting" 449 depends on !S390 && !NO_HZ_FULL 450 help 451 This is the basic tick based cputime accounting that maintains 452 statistics about user, system and idle time spent on per jiffies 453 granularity. 454 455 If unsure, say Y. 456 457config VIRT_CPU_ACCOUNTING_NATIVE 458 bool "Deterministic task and CPU time accounting" 459 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 460 select VIRT_CPU_ACCOUNTING 461 help 462 Select this option to enable more accurate task and CPU time 463 accounting. This is done by reading a CPU counter on each 464 kernel entry and exit and on transitions within the kernel 465 between system, softirq and hardirq state, so there is a 466 small performance impact. In the case of s390 or IBM POWER > 5, 467 this also enables accounting of stolen time on logically-partitioned 468 systems. 469 470config VIRT_CPU_ACCOUNTING_GEN 471 bool "Full dynticks CPU time accounting" 472 depends on HAVE_CONTEXT_TRACKING 473 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 474 depends on GENERIC_CLOCKEVENTS 475 select VIRT_CPU_ACCOUNTING 476 select CONTEXT_TRACKING 477 help 478 Select this option to enable task and CPU time accounting on full 479 dynticks systems. This accounting is implemented by watching every 480 kernel-user boundaries using the context tracking subsystem. 481 The accounting is thus performed at the expense of some significant 482 overhead. 483 484 For now this is only useful if you are working on the full 485 dynticks subsystem development. 486 487 If unsure, say N. 488 489endchoice 490 491config IRQ_TIME_ACCOUNTING 492 bool "Fine granularity task level IRQ time accounting" 493 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 494 help 495 Select this option to enable fine granularity task irq time 496 accounting. This is done by reading a timestamp on each 497 transitions between softirq and hardirq state, so there can be a 498 small performance impact. 499 500 If in doubt, say N here. 501 502config HAVE_SCHED_AVG_IRQ 503 def_bool y 504 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 505 depends on SMP 506 507config SCHED_THERMAL_PRESSURE 508 bool 509 default y if ARM && ARM_CPU_TOPOLOGY 510 default y if ARM64 511 depends on SMP 512 depends on CPU_FREQ_THERMAL 513 help 514 Select this option to enable thermal pressure accounting in the 515 scheduler. Thermal pressure is the value conveyed to the scheduler 516 that reflects the reduction in CPU compute capacity resulted from 517 thermal throttling. Thermal throttling occurs when the performance of 518 a CPU is capped due to high operating temperatures. 519 520 If selected, the scheduler will be able to balance tasks accordingly, 521 i.e. put less load on throttled CPUs than on non/less throttled ones. 522 523 This requires the architecture to implement 524 arch_set_thermal_pressure() and arch_get_thermal_pressure(). 525 526config BSD_PROCESS_ACCT 527 bool "BSD Process Accounting" 528 depends on MULTIUSER 529 help 530 If you say Y here, a user level program will be able to instruct the 531 kernel (via a special system call) to write process accounting 532 information to a file: whenever a process exits, information about 533 that process will be appended to the file by the kernel. The 534 information includes things such as creation time, owning user, 535 command name, memory usage, controlling terminal etc. (the complete 536 list is in the struct acct in <file:include/linux/acct.h>). It is 537 up to the user level program to do useful things with this 538 information. This is generally a good idea, so say Y. 539 540config BSD_PROCESS_ACCT_V3 541 bool "BSD Process Accounting version 3 file format" 542 depends on BSD_PROCESS_ACCT 543 default n 544 help 545 If you say Y here, the process accounting information is written 546 in a new file format that also logs the process IDs of each 547 process and its parent. Note that this file format is incompatible 548 with previous v0/v1/v2 file formats, so you will need updated tools 549 for processing it. A preliminary version of these tools is available 550 at <http://www.gnu.org/software/acct/>. 551 552config TASKSTATS 553 bool "Export task/process statistics through netlink" 554 depends on NET 555 depends on MULTIUSER 556 default n 557 help 558 Export selected statistics for tasks/processes through the 559 generic netlink interface. Unlike BSD process accounting, the 560 statistics are available during the lifetime of tasks/processes as 561 responses to commands. Like BSD accounting, they are sent to user 562 space on task exit. 563 564 Say N if unsure. 565 566config TASK_DELAY_ACCT 567 bool "Enable per-task delay accounting" 568 depends on TASKSTATS 569 select SCHED_INFO 570 help 571 Collect information on time spent by a task waiting for system 572 resources like cpu, synchronous block I/O completion and swapping 573 in pages. Such statistics can help in setting a task's priorities 574 relative to other tasks for cpu, io, rss limits etc. 575 576 Say N if unsure. 577 578config TASK_XACCT 579 bool "Enable extended accounting over taskstats" 580 depends on TASKSTATS 581 help 582 Collect extended task accounting data and send the data 583 to userland for processing over the taskstats interface. 584 585 Say N if unsure. 586 587config TASK_IO_ACCOUNTING 588 bool "Enable per-task storage I/O accounting" 589 depends on TASK_XACCT 590 help 591 Collect information on the number of bytes of storage I/O which this 592 task has caused. 593 594 Say N if unsure. 595 596config PSI 597 bool "Pressure stall information tracking" 598 help 599 Collect metrics that indicate how overcommitted the CPU, memory, 600 and IO capacity are in the system. 601 602 If you say Y here, the kernel will create /proc/pressure/ with the 603 pressure statistics files cpu, memory, and io. These will indicate 604 the share of walltime in which some or all tasks in the system are 605 delayed due to contention of the respective resource. 606 607 In kernels with cgroup support, cgroups (cgroup2 only) will 608 have cpu.pressure, memory.pressure, and io.pressure files, 609 which aggregate pressure stalls for the grouped tasks only. 610 611 For more details see Documentation/accounting/psi.rst. 612 613 Say N if unsure. 614 615config PSI_DEFAULT_DISABLED 616 bool "Require boot parameter to enable pressure stall information tracking" 617 default n 618 depends on PSI 619 help 620 If set, pressure stall information tracking will be disabled 621 per default but can be enabled through passing psi=1 on the 622 kernel commandline during boot. 623 624 This feature adds some code to the task wakeup and sleep 625 paths of the scheduler. The overhead is too low to affect 626 common scheduling-intense workloads in practice (such as 627 webservers, memcache), but it does show up in artificial 628 scheduler stress tests, such as hackbench. 629 630 If you are paranoid and not sure what the kernel will be 631 used for, say Y. 632 633 Say N if unsure. 634 635endmenu # "CPU/Task time and stats accounting" 636 637config CPU_ISOLATION 638 bool "CPU isolation" 639 depends on SMP || COMPILE_TEST 640 default y 641 help 642 Make sure that CPUs running critical tasks are not disturbed by 643 any source of "noise" such as unbound workqueues, timers, kthreads... 644 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 645 the "isolcpus=" boot parameter. 646 647 Say Y if unsure. 648 649source "kernel/rcu/Kconfig" 650 651config BUILD_BIN2C 652 bool 653 default n 654 655config IKCONFIG 656 tristate "Kernel .config support" 657 help 658 This option enables the complete Linux kernel ".config" file 659 contents to be saved in the kernel. It provides documentation 660 of which kernel options are used in a running kernel or in an 661 on-disk kernel. This information can be extracted from the kernel 662 image file with the script scripts/extract-ikconfig and used as 663 input to rebuild the current kernel or to build another kernel. 664 It can also be extracted from a running kernel by reading 665 /proc/config.gz if enabled (below). 666 667config IKCONFIG_PROC 668 bool "Enable access to .config through /proc/config.gz" 669 depends on IKCONFIG && PROC_FS 670 help 671 This option enables access to the kernel configuration file 672 through /proc/config.gz. 673 674config IKHEADERS 675 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 676 depends on SYSFS 677 help 678 This option enables access to the in-kernel headers that are generated during 679 the build process. These can be used to build eBPF tracing programs, 680 or similar programs. If you build the headers as a module, a module called 681 kheaders.ko is built which can be loaded on-demand to get access to headers. 682 683config LOG_BUF_SHIFT 684 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 685 range 12 25 686 default 17 687 depends on PRINTK 688 help 689 Select the minimal kernel log buffer size as a power of 2. 690 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 691 parameter, see below. Any higher size also might be forced 692 by "log_buf_len" boot parameter. 693 694 Examples: 695 17 => 128 KB 696 16 => 64 KB 697 15 => 32 KB 698 14 => 16 KB 699 13 => 8 KB 700 12 => 4 KB 701 702config LOG_CPU_MAX_BUF_SHIFT 703 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 704 depends on SMP 705 range 0 21 706 default 12 if !BASE_SMALL 707 default 0 if BASE_SMALL 708 depends on PRINTK 709 help 710 This option allows to increase the default ring buffer size 711 according to the number of CPUs. The value defines the contribution 712 of each CPU as a power of 2. The used space is typically only few 713 lines however it might be much more when problems are reported, 714 e.g. backtraces. 715 716 The increased size means that a new buffer has to be allocated and 717 the original static one is unused. It makes sense only on systems 718 with more CPUs. Therefore this value is used only when the sum of 719 contributions is greater than the half of the default kernel ring 720 buffer as defined by LOG_BUF_SHIFT. The default values are set 721 so that more than 64 CPUs are needed to trigger the allocation. 722 723 Also this option is ignored when "log_buf_len" kernel parameter is 724 used as it forces an exact (power of two) size of the ring buffer. 725 726 The number of possible CPUs is used for this computation ignoring 727 hotplugging making the computation optimal for the worst case 728 scenario while allowing a simple algorithm to be used from bootup. 729 730 Examples shift values and their meaning: 731 17 => 128 KB for each CPU 732 16 => 64 KB for each CPU 733 15 => 32 KB for each CPU 734 14 => 16 KB for each CPU 735 13 => 8 KB for each CPU 736 12 => 4 KB for each CPU 737 738config PRINTK_SAFE_LOG_BUF_SHIFT 739 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 740 range 10 21 741 default 13 742 depends on PRINTK 743 help 744 Select the size of an alternate printk per-CPU buffer where messages 745 printed from usafe contexts are temporary stored. One example would 746 be NMI messages, another one - printk recursion. The messages are 747 copied to the main log buffer in a safe context to avoid a deadlock. 748 The value defines the size as a power of 2. 749 750 Those messages are rare and limited. The largest one is when 751 a backtrace is printed. It usually fits into 4KB. Select 752 8KB if you want to be on the safe side. 753 754 Examples: 755 17 => 128 KB for each CPU 756 16 => 64 KB for each CPU 757 15 => 32 KB for each CPU 758 14 => 16 KB for each CPU 759 13 => 8 KB for each CPU 760 12 => 4 KB for each CPU 761 762# 763# Architectures with an unreliable sched_clock() should select this: 764# 765config HAVE_UNSTABLE_SCHED_CLOCK 766 bool 767 768config GENERIC_SCHED_CLOCK 769 bool 770 771menu "Scheduler features" 772 773config UCLAMP_TASK 774 bool "Enable utilization clamping for RT/FAIR tasks" 775 depends on CPU_FREQ_GOV_SCHEDUTIL 776 help 777 This feature enables the scheduler to track the clamped utilization 778 of each CPU based on RUNNABLE tasks scheduled on that CPU. 779 780 With this option, the user can specify the min and max CPU 781 utilization allowed for RUNNABLE tasks. The max utilization defines 782 the maximum frequency a task should use while the min utilization 783 defines the minimum frequency it should use. 784 785 Both min and max utilization clamp values are hints to the scheduler, 786 aiming at improving its frequency selection policy, but they do not 787 enforce or grant any specific bandwidth for tasks. 788 789 If in doubt, say N. 790 791config UCLAMP_BUCKETS_COUNT 792 int "Number of supported utilization clamp buckets" 793 range 5 20 794 default 5 795 depends on UCLAMP_TASK 796 help 797 Defines the number of clamp buckets to use. The range of each bucket 798 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 799 number of clamp buckets the finer their granularity and the higher 800 the precision of clamping aggregation and tracking at run-time. 801 802 For example, with the minimum configuration value we will have 5 803 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 804 be refcounted in the [20..39]% bucket and will set the bucket clamp 805 effective value to 25%. 806 If a second 30% boosted task should be co-scheduled on the same CPU, 807 that task will be refcounted in the same bucket of the first task and 808 it will boost the bucket clamp effective value to 30%. 809 The clamp effective value of a bucket is reset to its nominal value 810 (20% in the example above) when there are no more tasks refcounted in 811 that bucket. 812 813 An additional boost/capping margin can be added to some tasks. In the 814 example above the 25% task will be boosted to 30% until it exits the 815 CPU. If that should be considered not acceptable on certain systems, 816 it's always possible to reduce the margin by increasing the number of 817 clamp buckets to trade off used memory for run-time tracking 818 precision. 819 820 If in doubt, use the default value. 821 822endmenu 823 824# 825# For architectures that want to enable the support for NUMA-affine scheduler 826# balancing logic: 827# 828config ARCH_SUPPORTS_NUMA_BALANCING 829 bool 830 831# 832# For architectures that prefer to flush all TLBs after a number of pages 833# are unmapped instead of sending one IPI per page to flush. The architecture 834# must provide guarantees on what happens if a clean TLB cache entry is 835# written after the unmap. Details are in mm/rmap.c near the check for 836# should_defer_flush. The architecture should also consider if the full flush 837# and the refill costs are offset by the savings of sending fewer IPIs. 838config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 839 bool 840 841config CC_HAS_INT128 842 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 843 844# 845# For architectures that know their GCC __int128 support is sound 846# 847config ARCH_SUPPORTS_INT128 848 bool 849 850# For architectures that (ab)use NUMA to represent different memory regions 851# all cpu-local but of different latencies, such as SuperH. 852# 853config ARCH_WANT_NUMA_VARIABLE_LOCALITY 854 bool 855 856config NUMA_BALANCING 857 bool "Memory placement aware NUMA scheduler" 858 depends on ARCH_SUPPORTS_NUMA_BALANCING 859 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 860 depends on SMP && NUMA && MIGRATION 861 help 862 This option adds support for automatic NUMA aware memory/task placement. 863 The mechanism is quite primitive and is based on migrating memory when 864 it has references to the node the task is running on. 865 866 This system will be inactive on UMA systems. 867 868config NUMA_BALANCING_DEFAULT_ENABLED 869 bool "Automatically enable NUMA aware memory/task placement" 870 default y 871 depends on NUMA_BALANCING 872 help 873 If set, automatic NUMA balancing will be enabled if running on a NUMA 874 machine. 875 876menuconfig CGROUPS 877 bool "Control Group support" 878 select KERNFS 879 help 880 This option adds support for grouping sets of processes together, for 881 use with process control subsystems such as Cpusets, CFS, memory 882 controls or device isolation. 883 See 884 - Documentation/scheduler/sched-design-CFS.rst (CFS) 885 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 886 and resource control) 887 888 Say N if unsure. 889 890if CGROUPS 891 892config PAGE_COUNTER 893 bool 894 895config MEMCG 896 bool "Memory controller" 897 select PAGE_COUNTER 898 select EVENTFD 899 help 900 Provides control over the memory footprint of tasks in a cgroup. 901 902config MEMCG_SWAP 903 bool 904 depends on MEMCG && SWAP 905 default y 906 907config MEMCG_KMEM 908 bool 909 depends on MEMCG && !SLOB 910 default y 911 912config BLK_CGROUP 913 bool "IO controller" 914 depends on BLOCK 915 default n 916 help 917 Generic block IO controller cgroup interface. This is the common 918 cgroup interface which should be used by various IO controlling 919 policies. 920 921 Currently, CFQ IO scheduler uses it to recognize task groups and 922 control disk bandwidth allocation (proportional time slice allocation) 923 to such task groups. It is also used by bio throttling logic in 924 block layer to implement upper limit in IO rates on a device. 925 926 This option only enables generic Block IO controller infrastructure. 927 One needs to also enable actual IO controlling logic/policy. For 928 enabling proportional weight division of disk bandwidth in CFQ, set 929 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 930 CONFIG_BLK_DEV_THROTTLING=y. 931 932 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 933 934config CGROUP_WRITEBACK 935 bool 936 depends on MEMCG && BLK_CGROUP 937 default y 938 939menuconfig CGROUP_SCHED 940 bool "CPU controller" 941 default n 942 help 943 This feature lets CPU scheduler recognize task groups and control CPU 944 bandwidth allocation to such task groups. It uses cgroups to group 945 tasks. 946 947if CGROUP_SCHED 948config FAIR_GROUP_SCHED 949 bool "Group scheduling for SCHED_OTHER" 950 depends on CGROUP_SCHED 951 default CGROUP_SCHED 952 953config CFS_BANDWIDTH 954 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 955 depends on FAIR_GROUP_SCHED 956 default n 957 help 958 This option allows users to define CPU bandwidth rates (limits) for 959 tasks running within the fair group scheduler. Groups with no limit 960 set are considered to be unconstrained and will run with no 961 restriction. 962 See Documentation/scheduler/sched-bwc.rst for more information. 963 964config RT_GROUP_SCHED 965 bool "Group scheduling for SCHED_RR/FIFO" 966 depends on CGROUP_SCHED 967 default n 968 help 969 This feature lets you explicitly allocate real CPU bandwidth 970 to task groups. If enabled, it will also make it impossible to 971 schedule realtime tasks for non-root users until you allocate 972 realtime bandwidth for them. 973 See Documentation/scheduler/sched-rt-group.rst for more information. 974 975endif #CGROUP_SCHED 976 977config UCLAMP_TASK_GROUP 978 bool "Utilization clamping per group of tasks" 979 depends on CGROUP_SCHED 980 depends on UCLAMP_TASK 981 default n 982 help 983 This feature enables the scheduler to track the clamped utilization 984 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 985 986 When this option is enabled, the user can specify a min and max 987 CPU bandwidth which is allowed for each single task in a group. 988 The max bandwidth allows to clamp the maximum frequency a task 989 can use, while the min bandwidth allows to define a minimum 990 frequency a task will always use. 991 992 When task group based utilization clamping is enabled, an eventually 993 specified task-specific clamp value is constrained by the cgroup 994 specified clamp value. Both minimum and maximum task clamping cannot 995 be bigger than the corresponding clamping defined at task group level. 996 997 If in doubt, say N. 998 999config CGROUP_PIDS 1000 bool "PIDs controller" 1001 help 1002 Provides enforcement of process number limits in the scope of a 1003 cgroup. Any attempt to fork more processes than is allowed in the 1004 cgroup will fail. PIDs are fundamentally a global resource because it 1005 is fairly trivial to reach PID exhaustion before you reach even a 1006 conservative kmemcg limit. As a result, it is possible to grind a 1007 system to halt without being limited by other cgroup policies. The 1008 PIDs controller is designed to stop this from happening. 1009 1010 It should be noted that organisational operations (such as attaching 1011 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 1012 since the PIDs limit only affects a process's ability to fork, not to 1013 attach to a cgroup. 1014 1015config CGROUP_RDMA 1016 bool "RDMA controller" 1017 help 1018 Provides enforcement of RDMA resources defined by IB stack. 1019 It is fairly easy for consumers to exhaust RDMA resources, which 1020 can result into resource unavailability to other consumers. 1021 RDMA controller is designed to stop this from happening. 1022 Attaching processes with active RDMA resources to the cgroup 1023 hierarchy is allowed even if can cross the hierarchy's limit. 1024 1025config CGROUP_FREEZER 1026 bool "Freezer controller" 1027 help 1028 Provides a way to freeze and unfreeze all tasks in a 1029 cgroup. 1030 1031 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1032 controller includes important in-kernel memory consumers per default. 1033 1034 If you're using cgroup2, say N. 1035 1036config CGROUP_HUGETLB 1037 bool "HugeTLB controller" 1038 depends on HUGETLB_PAGE 1039 select PAGE_COUNTER 1040 default n 1041 help 1042 Provides a cgroup controller for HugeTLB pages. 1043 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1044 The limit is enforced during page fault. Since HugeTLB doesn't 1045 support page reclaim, enforcing the limit at page fault time implies 1046 that, the application will get SIGBUS signal if it tries to access 1047 HugeTLB pages beyond its limit. This requires the application to know 1048 beforehand how much HugeTLB pages it would require for its use. The 1049 control group is tracked in the third page lru pointer. This means 1050 that we cannot use the controller with huge page less than 3 pages. 1051 1052config CPUSETS 1053 bool "Cpuset controller" 1054 depends on SMP 1055 help 1056 This option will let you create and manage CPUSETs which 1057 allow dynamically partitioning a system into sets of CPUs and 1058 Memory Nodes and assigning tasks to run only within those sets. 1059 This is primarily useful on large SMP or NUMA systems. 1060 1061 Say N if unsure. 1062 1063config PROC_PID_CPUSET 1064 bool "Include legacy /proc/<pid>/cpuset file" 1065 depends on CPUSETS 1066 default y 1067 1068config CGROUP_DEVICE 1069 bool "Device controller" 1070 help 1071 Provides a cgroup controller implementing whitelists for 1072 devices which a process in the cgroup can mknod or open. 1073 1074config CGROUP_CPUACCT 1075 bool "Simple CPU accounting controller" 1076 help 1077 Provides a simple controller for monitoring the 1078 total CPU consumed by the tasks in a cgroup. 1079 1080config CGROUP_PERF 1081 bool "Perf controller" 1082 depends on PERF_EVENTS 1083 help 1084 This option extends the perf per-cpu mode to restrict monitoring 1085 to threads which belong to the cgroup specified and run on the 1086 designated cpu. Or this can be used to have cgroup ID in samples 1087 so that it can monitor performance events among cgroups. 1088 1089 Say N if unsure. 1090 1091config CGROUP_BPF 1092 bool "Support for eBPF programs attached to cgroups" 1093 depends on BPF_SYSCALL 1094 select SOCK_CGROUP_DATA 1095 help 1096 Allow attaching eBPF programs to a cgroup using the bpf(2) 1097 syscall command BPF_PROG_ATTACH. 1098 1099 In which context these programs are accessed depends on the type 1100 of attachment. For instance, programs that are attached using 1101 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1102 inet sockets. 1103 1104config CGROUP_DEBUG 1105 bool "Debug controller" 1106 default n 1107 depends on DEBUG_KERNEL 1108 help 1109 This option enables a simple controller that exports 1110 debugging information about the cgroups framework. This 1111 controller is for control cgroup debugging only. Its 1112 interfaces are not stable. 1113 1114 Say N. 1115 1116config SOCK_CGROUP_DATA 1117 bool 1118 default n 1119 1120endif # CGROUPS 1121 1122menuconfig NAMESPACES 1123 bool "Namespaces support" if EXPERT 1124 depends on MULTIUSER 1125 default !EXPERT 1126 help 1127 Provides the way to make tasks work with different objects using 1128 the same id. For example same IPC id may refer to different objects 1129 or same user id or pid may refer to different tasks when used in 1130 different namespaces. 1131 1132if NAMESPACES 1133 1134config UTS_NS 1135 bool "UTS namespace" 1136 default y 1137 help 1138 In this namespace tasks see different info provided with the 1139 uname() system call 1140 1141config TIME_NS 1142 bool "TIME namespace" 1143 depends on GENERIC_VDSO_TIME_NS 1144 default y 1145 help 1146 In this namespace boottime and monotonic clocks can be set. 1147 The time will keep going with the same pace. 1148 1149config IPC_NS 1150 bool "IPC namespace" 1151 depends on (SYSVIPC || POSIX_MQUEUE) 1152 default y 1153 help 1154 In this namespace tasks work with IPC ids which correspond to 1155 different IPC objects in different namespaces. 1156 1157config USER_NS 1158 bool "User namespace" 1159 default n 1160 help 1161 This allows containers, i.e. vservers, to use user namespaces 1162 to provide different user info for different servers. 1163 1164 When user namespaces are enabled in the kernel it is 1165 recommended that the MEMCG option also be enabled and that 1166 user-space use the memory control groups to limit the amount 1167 of memory a memory unprivileged users can use. 1168 1169 If unsure, say N. 1170 1171config PID_NS 1172 bool "PID Namespaces" 1173 default y 1174 help 1175 Support process id namespaces. This allows having multiple 1176 processes with the same pid as long as they are in different 1177 pid namespaces. This is a building block of containers. 1178 1179config NET_NS 1180 bool "Network namespace" 1181 depends on NET 1182 default y 1183 help 1184 Allow user space to create what appear to be multiple instances 1185 of the network stack. 1186 1187endif # NAMESPACES 1188 1189config CHECKPOINT_RESTORE 1190 bool "Checkpoint/restore support" 1191 select PROC_CHILDREN 1192 default n 1193 help 1194 Enables additional kernel features in a sake of checkpoint/restore. 1195 In particular it adds auxiliary prctl codes to setup process text, 1196 data and heap segment sizes, and a few additional /proc filesystem 1197 entries. 1198 1199 If unsure, say N here. 1200 1201config SCHED_AUTOGROUP 1202 bool "Automatic process group scheduling" 1203 select CGROUPS 1204 select CGROUP_SCHED 1205 select FAIR_GROUP_SCHED 1206 help 1207 This option optimizes the scheduler for common desktop workloads by 1208 automatically creating and populating task groups. This separation 1209 of workloads isolates aggressive CPU burners (like build jobs) from 1210 desktop applications. Task group autogeneration is currently based 1211 upon task session. 1212 1213config SYSFS_DEPRECATED 1214 bool "Enable deprecated sysfs features to support old userspace tools" 1215 depends on SYSFS 1216 default n 1217 help 1218 This option adds code that switches the layout of the "block" class 1219 devices, to not show up in /sys/class/block/, but only in 1220 /sys/block/. 1221 1222 This switch is only active when the sysfs.deprecated=1 boot option is 1223 passed or the SYSFS_DEPRECATED_V2 option is set. 1224 1225 This option allows new kernels to run on old distributions and tools, 1226 which might get confused by /sys/class/block/. Since 2007/2008 all 1227 major distributions and tools handle this just fine. 1228 1229 Recent distributions and userspace tools after 2009/2010 depend on 1230 the existence of /sys/class/block/, and will not work with this 1231 option enabled. 1232 1233 Only if you are using a new kernel on an old distribution, you might 1234 need to say Y here. 1235 1236config SYSFS_DEPRECATED_V2 1237 bool "Enable deprecated sysfs features by default" 1238 default n 1239 depends on SYSFS 1240 depends on SYSFS_DEPRECATED 1241 help 1242 Enable deprecated sysfs by default. 1243 1244 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1245 option. 1246 1247 Only if you are using a new kernel on an old distribution, you might 1248 need to say Y here. Even then, odds are you would not need it 1249 enabled, you can always pass the boot option if absolutely necessary. 1250 1251config RELAY 1252 bool "Kernel->user space relay support (formerly relayfs)" 1253 select IRQ_WORK 1254 help 1255 This option enables support for relay interface support in 1256 certain file systems (such as debugfs). 1257 It is designed to provide an efficient mechanism for tools and 1258 facilities to relay large amounts of data from kernel space to 1259 user space. 1260 1261 If unsure, say N. 1262 1263config BLK_DEV_INITRD 1264 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1265 help 1266 The initial RAM filesystem is a ramfs which is loaded by the 1267 boot loader (loadlin or lilo) and that is mounted as root 1268 before the normal boot procedure. It is typically used to 1269 load modules needed to mount the "real" root file system, 1270 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1271 1272 If RAM disk support (BLK_DEV_RAM) is also included, this 1273 also enables initial RAM disk (initrd) support and adds 1274 15 Kbytes (more on some other architectures) to the kernel size. 1275 1276 If unsure say Y. 1277 1278if BLK_DEV_INITRD 1279 1280source "usr/Kconfig" 1281 1282endif 1283 1284config BOOT_CONFIG 1285 bool "Boot config support" 1286 select BLK_DEV_INITRD 1287 help 1288 Extra boot config allows system admin to pass a config file as 1289 complemental extension of kernel cmdline when booting. 1290 The boot config file must be attached at the end of initramfs 1291 with checksum, size and magic word. 1292 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1293 1294 If unsure, say Y. 1295 1296choice 1297 prompt "Compiler optimization level" 1298 default CC_OPTIMIZE_FOR_PERFORMANCE 1299 1300config CC_OPTIMIZE_FOR_PERFORMANCE 1301 bool "Optimize for performance (-O2)" 1302 help 1303 This is the default optimization level for the kernel, building 1304 with the "-O2" compiler flag for best performance and most 1305 helpful compile-time warnings. 1306 1307config CC_OPTIMIZE_FOR_PERFORMANCE_O3 1308 bool "Optimize more for performance (-O3)" 1309 depends on ARC 1310 help 1311 Choosing this option will pass "-O3" to your compiler to optimize 1312 the kernel yet more for performance. 1313 1314config CC_OPTIMIZE_FOR_SIZE 1315 bool "Optimize for size (-Os)" 1316 help 1317 Choosing this option will pass "-Os" to your compiler resulting 1318 in a smaller kernel. 1319 1320endchoice 1321 1322config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1323 bool 1324 help 1325 This requires that the arch annotates or otherwise protects 1326 its external entry points from being discarded. Linker scripts 1327 must also merge .text.*, .data.*, and .bss.* correctly into 1328 output sections. Care must be taken not to pull in unrelated 1329 sections (e.g., '.text.init'). Typically '.' in section names 1330 is used to distinguish them from label names / C identifiers. 1331 1332config LD_DEAD_CODE_DATA_ELIMINATION 1333 bool "Dead code and data elimination (EXPERIMENTAL)" 1334 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1335 depends on EXPERT 1336 depends on $(cc-option,-ffunction-sections -fdata-sections) 1337 depends on $(ld-option,--gc-sections) 1338 help 1339 Enable this if you want to do dead code and data elimination with 1340 the linker by compiling with -ffunction-sections -fdata-sections, 1341 and linking with --gc-sections. 1342 1343 This can reduce on disk and in-memory size of the kernel 1344 code and static data, particularly for small configs and 1345 on small systems. This has the possibility of introducing 1346 silently broken kernel if the required annotations are not 1347 present. This option is not well tested yet, so use at your 1348 own risk. 1349 1350config SYSCTL 1351 bool 1352 1353config HAVE_UID16 1354 bool 1355 1356config SYSCTL_EXCEPTION_TRACE 1357 bool 1358 help 1359 Enable support for /proc/sys/debug/exception-trace. 1360 1361config SYSCTL_ARCH_UNALIGN_NO_WARN 1362 bool 1363 help 1364 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1365 Allows arch to define/use @no_unaligned_warning to possibly warn 1366 about unaligned access emulation going on under the hood. 1367 1368config SYSCTL_ARCH_UNALIGN_ALLOW 1369 bool 1370 help 1371 Enable support for /proc/sys/kernel/unaligned-trap 1372 Allows arches to define/use @unaligned_enabled to runtime toggle 1373 the unaligned access emulation. 1374 see arch/parisc/kernel/unaligned.c for reference 1375 1376config HAVE_PCSPKR_PLATFORM 1377 bool 1378 1379# interpreter that classic socket filters depend on 1380config BPF 1381 bool 1382 1383menuconfig EXPERT 1384 bool "Configure standard kernel features (expert users)" 1385 # Unhide debug options, to make the on-by-default options visible 1386 select DEBUG_KERNEL 1387 help 1388 This option allows certain base kernel options and settings 1389 to be disabled or tweaked. This is for specialized 1390 environments which can tolerate a "non-standard" kernel. 1391 Only use this if you really know what you are doing. 1392 1393config UID16 1394 bool "Enable 16-bit UID system calls" if EXPERT 1395 depends on HAVE_UID16 && MULTIUSER 1396 default y 1397 help 1398 This enables the legacy 16-bit UID syscall wrappers. 1399 1400config MULTIUSER 1401 bool "Multiple users, groups and capabilities support" if EXPERT 1402 default y 1403 help 1404 This option enables support for non-root users, groups and 1405 capabilities. 1406 1407 If you say N here, all processes will run with UID 0, GID 0, and all 1408 possible capabilities. Saying N here also compiles out support for 1409 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1410 setgid, and capset. 1411 1412 If unsure, say Y here. 1413 1414config SGETMASK_SYSCALL 1415 bool "sgetmask/ssetmask syscalls support" if EXPERT 1416 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1417 help 1418 sys_sgetmask and sys_ssetmask are obsolete system calls 1419 no longer supported in libc but still enabled by default in some 1420 architectures. 1421 1422 If unsure, leave the default option here. 1423 1424config SYSFS_SYSCALL 1425 bool "Sysfs syscall support" if EXPERT 1426 default y 1427 help 1428 sys_sysfs is an obsolete system call no longer supported in libc. 1429 Note that disabling this option is more secure but might break 1430 compatibility with some systems. 1431 1432 If unsure say Y here. 1433 1434config FHANDLE 1435 bool "open by fhandle syscalls" if EXPERT 1436 select EXPORTFS 1437 default y 1438 help 1439 If you say Y here, a user level program will be able to map 1440 file names to handle and then later use the handle for 1441 different file system operations. This is useful in implementing 1442 userspace file servers, which now track files using handles instead 1443 of names. The handle would remain the same even if file names 1444 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1445 syscalls. 1446 1447config POSIX_TIMERS 1448 bool "Posix Clocks & timers" if EXPERT 1449 default y 1450 help 1451 This includes native support for POSIX timers to the kernel. 1452 Some embedded systems have no use for them and therefore they 1453 can be configured out to reduce the size of the kernel image. 1454 1455 When this option is disabled, the following syscalls won't be 1456 available: timer_create, timer_gettime: timer_getoverrun, 1457 timer_settime, timer_delete, clock_adjtime, getitimer, 1458 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1459 clock_getres and clock_nanosleep syscalls will be limited to 1460 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1461 1462 If unsure say y. 1463 1464config PRINTK 1465 default y 1466 bool "Enable support for printk" if EXPERT 1467 select IRQ_WORK 1468 help 1469 This option enables normal printk support. Removing it 1470 eliminates most of the message strings from the kernel image 1471 and makes the kernel more or less silent. As this makes it 1472 very difficult to diagnose system problems, saying N here is 1473 strongly discouraged. 1474 1475config PRINTK_NMI 1476 def_bool y 1477 depends on PRINTK 1478 depends on HAVE_NMI 1479 1480config BUG 1481 bool "BUG() support" if EXPERT 1482 default y 1483 help 1484 Disabling this option eliminates support for BUG and WARN, reducing 1485 the size of your kernel image and potentially quietly ignoring 1486 numerous fatal conditions. You should only consider disabling this 1487 option for embedded systems with no facilities for reporting errors. 1488 Just say Y. 1489 1490config ELF_CORE 1491 depends on COREDUMP 1492 default y 1493 bool "Enable ELF core dumps" if EXPERT 1494 help 1495 Enable support for generating core dumps. Disabling saves about 4k. 1496 1497 1498config PCSPKR_PLATFORM 1499 bool "Enable PC-Speaker support" if EXPERT 1500 depends on HAVE_PCSPKR_PLATFORM 1501 select I8253_LOCK 1502 default y 1503 help 1504 This option allows to disable the internal PC-Speaker 1505 support, saving some memory. 1506 1507config BASE_FULL 1508 default y 1509 bool "Enable full-sized data structures for core" if EXPERT 1510 help 1511 Disabling this option reduces the size of miscellaneous core 1512 kernel data structures. This saves memory on small machines, 1513 but may reduce performance. 1514 1515config FUTEX 1516 bool "Enable futex support" if EXPERT 1517 default y 1518 imply RT_MUTEXES 1519 help 1520 Disabling this option will cause the kernel to be built without 1521 support for "fast userspace mutexes". The resulting kernel may not 1522 run glibc-based applications correctly. 1523 1524config FUTEX_PI 1525 bool 1526 depends on FUTEX && RT_MUTEXES 1527 default y 1528 1529config HAVE_FUTEX_CMPXCHG 1530 bool 1531 depends on FUTEX 1532 help 1533 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1534 is implemented and always working. This removes a couple of runtime 1535 checks. 1536 1537config EPOLL 1538 bool "Enable eventpoll support" if EXPERT 1539 default y 1540 help 1541 Disabling this option will cause the kernel to be built without 1542 support for epoll family of system calls. 1543 1544config SIGNALFD 1545 bool "Enable signalfd() system call" if EXPERT 1546 default y 1547 help 1548 Enable the signalfd() system call that allows to receive signals 1549 on a file descriptor. 1550 1551 If unsure, say Y. 1552 1553config TIMERFD 1554 bool "Enable timerfd() system call" if EXPERT 1555 default y 1556 help 1557 Enable the timerfd() system call that allows to receive timer 1558 events on a file descriptor. 1559 1560 If unsure, say Y. 1561 1562config EVENTFD 1563 bool "Enable eventfd() system call" if EXPERT 1564 default y 1565 help 1566 Enable the eventfd() system call that allows to receive both 1567 kernel notification (ie. KAIO) or userspace notifications. 1568 1569 If unsure, say Y. 1570 1571config SHMEM 1572 bool "Use full shmem filesystem" if EXPERT 1573 default y 1574 depends on MMU 1575 help 1576 The shmem is an internal filesystem used to manage shared memory. 1577 It is backed by swap and manages resource limits. It is also exported 1578 to userspace as tmpfs if TMPFS is enabled. Disabling this 1579 option replaces shmem and tmpfs with the much simpler ramfs code, 1580 which may be appropriate on small systems without swap. 1581 1582config AIO 1583 bool "Enable AIO support" if EXPERT 1584 default y 1585 help 1586 This option enables POSIX asynchronous I/O which may by used 1587 by some high performance threaded applications. Disabling 1588 this option saves about 7k. 1589 1590config IO_URING 1591 bool "Enable IO uring support" if EXPERT 1592 select IO_WQ 1593 default y 1594 help 1595 This option enables support for the io_uring interface, enabling 1596 applications to submit and complete IO through submission and 1597 completion rings that are shared between the kernel and application. 1598 1599config ADVISE_SYSCALLS 1600 bool "Enable madvise/fadvise syscalls" if EXPERT 1601 default y 1602 help 1603 This option enables the madvise and fadvise syscalls, used by 1604 applications to advise the kernel about their future memory or file 1605 usage, improving performance. If building an embedded system where no 1606 applications use these syscalls, you can disable this option to save 1607 space. 1608 1609config HAVE_ARCH_USERFAULTFD_WP 1610 bool 1611 help 1612 Arch has userfaultfd write protection support 1613 1614config MEMBARRIER 1615 bool "Enable membarrier() system call" if EXPERT 1616 default y 1617 help 1618 Enable the membarrier() system call that allows issuing memory 1619 barriers across all running threads, which can be used to distribute 1620 the cost of user-space memory barriers asymmetrically by transforming 1621 pairs of memory barriers into pairs consisting of membarrier() and a 1622 compiler barrier. 1623 1624 If unsure, say Y. 1625 1626config KALLSYMS 1627 bool "Load all symbols for debugging/ksymoops" if EXPERT 1628 default y 1629 help 1630 Say Y here to let the kernel print out symbolic crash information and 1631 symbolic stack backtraces. This increases the size of the kernel 1632 somewhat, as all symbols have to be loaded into the kernel image. 1633 1634config KALLSYMS_ALL 1635 bool "Include all symbols in kallsyms" 1636 depends on DEBUG_KERNEL && KALLSYMS 1637 help 1638 Normally kallsyms only contains the symbols of functions for nicer 1639 OOPS messages and backtraces (i.e., symbols from the text and inittext 1640 sections). This is sufficient for most cases. And only in very rare 1641 cases (e.g., when a debugger is used) all symbols are required (e.g., 1642 names of variables from the data sections, etc). 1643 1644 This option makes sure that all symbols are loaded into the kernel 1645 image (i.e., symbols from all sections) in cost of increased kernel 1646 size (depending on the kernel configuration, it may be 300KiB or 1647 something like this). 1648 1649 Say N unless you really need all symbols. 1650 1651config KALLSYMS_ABSOLUTE_PERCPU 1652 bool 1653 depends on KALLSYMS 1654 default X86_64 && SMP 1655 1656config KALLSYMS_BASE_RELATIVE 1657 bool 1658 depends on KALLSYMS 1659 default !IA64 1660 help 1661 Instead of emitting them as absolute values in the native word size, 1662 emit the symbol references in the kallsyms table as 32-bit entries, 1663 each containing a relative value in the range [base, base + U32_MAX] 1664 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1665 an absolute value in the range [0, S32_MAX] or a relative value in the 1666 range [base, base + S32_MAX], where base is the lowest relative symbol 1667 address encountered in the image. 1668 1669 On 64-bit builds, this reduces the size of the address table by 50%, 1670 but more importantly, it results in entries whose values are build 1671 time constants, and no relocation pass is required at runtime to fix 1672 up the entries based on the runtime load address of the kernel. 1673 1674# end of the "standard kernel features (expert users)" menu 1675 1676# syscall, maps, verifier 1677 1678config BPF_LSM 1679 bool "LSM Instrumentation with BPF" 1680 depends on BPF_EVENTS 1681 depends on BPF_SYSCALL 1682 depends on SECURITY 1683 depends on BPF_JIT 1684 help 1685 Enables instrumentation of the security hooks with eBPF programs for 1686 implementing dynamic MAC and Audit Policies. 1687 1688 If you are unsure how to answer this question, answer N. 1689 1690config BPF_SYSCALL 1691 bool "Enable bpf() system call" 1692 select BPF 1693 select IRQ_WORK 1694 default n 1695 help 1696 Enable the bpf() system call that allows to manipulate eBPF 1697 programs and maps via file descriptors. 1698 1699config ARCH_WANT_DEFAULT_BPF_JIT 1700 bool 1701 1702config BPF_JIT_ALWAYS_ON 1703 bool "Permanently enable BPF JIT and remove BPF interpreter" 1704 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1705 help 1706 Enables BPF JIT and removes BPF interpreter to avoid 1707 speculative execution of BPF instructions by the interpreter 1708 1709config BPF_JIT_DEFAULT_ON 1710 def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON 1711 depends on HAVE_EBPF_JIT && BPF_JIT 1712 1713config USERFAULTFD 1714 bool "Enable userfaultfd() system call" 1715 depends on MMU 1716 help 1717 Enable the userfaultfd() system call that allows to intercept and 1718 handle page faults in userland. 1719 1720config ARCH_HAS_MEMBARRIER_CALLBACKS 1721 bool 1722 1723config ARCH_HAS_MEMBARRIER_SYNC_CORE 1724 bool 1725 1726config RSEQ 1727 bool "Enable rseq() system call" if EXPERT 1728 default y 1729 depends on HAVE_RSEQ 1730 select MEMBARRIER 1731 help 1732 Enable the restartable sequences system call. It provides a 1733 user-space cache for the current CPU number value, which 1734 speeds up getting the current CPU number from user-space, 1735 as well as an ABI to speed up user-space operations on 1736 per-CPU data. 1737 1738 If unsure, say Y. 1739 1740config DEBUG_RSEQ 1741 default n 1742 bool "Enabled debugging of rseq() system call" if EXPERT 1743 depends on RSEQ && DEBUG_KERNEL 1744 help 1745 Enable extra debugging checks for the rseq system call. 1746 1747 If unsure, say N. 1748 1749config EMBEDDED 1750 bool "Embedded system" 1751 option allnoconfig_y 1752 select EXPERT 1753 help 1754 This option should be enabled if compiling the kernel for 1755 an embedded system so certain expert options are available 1756 for configuration. 1757 1758config HAVE_PERF_EVENTS 1759 bool 1760 help 1761 See tools/perf/design.txt for details. 1762 1763config PERF_USE_VMALLOC 1764 bool 1765 help 1766 See tools/perf/design.txt for details 1767 1768config PC104 1769 bool "PC/104 support" if EXPERT 1770 help 1771 Expose PC/104 form factor device drivers and options available for 1772 selection and configuration. Enable this option if your target 1773 machine has a PC/104 bus. 1774 1775menu "Kernel Performance Events And Counters" 1776 1777config PERF_EVENTS 1778 bool "Kernel performance events and counters" 1779 default y if PROFILING 1780 depends on HAVE_PERF_EVENTS 1781 select IRQ_WORK 1782 select SRCU 1783 help 1784 Enable kernel support for various performance events provided 1785 by software and hardware. 1786 1787 Software events are supported either built-in or via the 1788 use of generic tracepoints. 1789 1790 Most modern CPUs support performance events via performance 1791 counter registers. These registers count the number of certain 1792 types of hw events: such as instructions executed, cachemisses 1793 suffered, or branches mis-predicted - without slowing down the 1794 kernel or applications. These registers can also trigger interrupts 1795 when a threshold number of events have passed - and can thus be 1796 used to profile the code that runs on that CPU. 1797 1798 The Linux Performance Event subsystem provides an abstraction of 1799 these software and hardware event capabilities, available via a 1800 system call and used by the "perf" utility in tools/perf/. It 1801 provides per task and per CPU counters, and it provides event 1802 capabilities on top of those. 1803 1804 Say Y if unsure. 1805 1806config DEBUG_PERF_USE_VMALLOC 1807 default n 1808 bool "Debug: use vmalloc to back perf mmap() buffers" 1809 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1810 select PERF_USE_VMALLOC 1811 help 1812 Use vmalloc memory to back perf mmap() buffers. 1813 1814 Mostly useful for debugging the vmalloc code on platforms 1815 that don't require it. 1816 1817 Say N if unsure. 1818 1819endmenu 1820 1821config VM_EVENT_COUNTERS 1822 default y 1823 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1824 help 1825 VM event counters are needed for event counts to be shown. 1826 This option allows the disabling of the VM event counters 1827 on EXPERT systems. /proc/vmstat will only show page counts 1828 if VM event counters are disabled. 1829 1830config SLUB_DEBUG 1831 default y 1832 bool "Enable SLUB debugging support" if EXPERT 1833 depends on SLUB && SYSFS 1834 help 1835 SLUB has extensive debug support features. Disabling these can 1836 result in significant savings in code size. This also disables 1837 SLUB sysfs support. /sys/slab will not exist and there will be 1838 no support for cache validation etc. 1839 1840config SLUB_MEMCG_SYSFS_ON 1841 default n 1842 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1843 depends on SLUB && SYSFS && MEMCG 1844 help 1845 SLUB creates a directory under /sys/kernel/slab for each 1846 allocation cache to host info and debug files. If memory 1847 cgroup is enabled, each cache can have per memory cgroup 1848 caches. SLUB can create the same sysfs directories for these 1849 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1850 to a very high number of debug files being created. This is 1851 controlled by slub_memcg_sysfs boot parameter and this 1852 config option determines the parameter's default value. 1853 1854config COMPAT_BRK 1855 bool "Disable heap randomization" 1856 default y 1857 help 1858 Randomizing heap placement makes heap exploits harder, but it 1859 also breaks ancient binaries (including anything libc5 based). 1860 This option changes the bootup default to heap randomization 1861 disabled, and can be overridden at runtime by setting 1862 /proc/sys/kernel/randomize_va_space to 2. 1863 1864 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1865 1866choice 1867 prompt "Choose SLAB allocator" 1868 default SLUB 1869 help 1870 This option allows to select a slab allocator. 1871 1872config SLAB 1873 bool "SLAB" 1874 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1875 help 1876 The regular slab allocator that is established and known to work 1877 well in all environments. It organizes cache hot objects in 1878 per cpu and per node queues. 1879 1880config SLUB 1881 bool "SLUB (Unqueued Allocator)" 1882 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1883 help 1884 SLUB is a slab allocator that minimizes cache line usage 1885 instead of managing queues of cached objects (SLAB approach). 1886 Per cpu caching is realized using slabs of objects instead 1887 of queues of objects. SLUB can use memory efficiently 1888 and has enhanced diagnostics. SLUB is the default choice for 1889 a slab allocator. 1890 1891config SLOB 1892 depends on EXPERT 1893 bool "SLOB (Simple Allocator)" 1894 help 1895 SLOB replaces the stock allocator with a drastically simpler 1896 allocator. SLOB is generally more space efficient but 1897 does not perform as well on large systems. 1898 1899endchoice 1900 1901config SLAB_MERGE_DEFAULT 1902 bool "Allow slab caches to be merged" 1903 default y 1904 help 1905 For reduced kernel memory fragmentation, slab caches can be 1906 merged when they share the same size and other characteristics. 1907 This carries a risk of kernel heap overflows being able to 1908 overwrite objects from merged caches (and more easily control 1909 cache layout), which makes such heap attacks easier to exploit 1910 by attackers. By keeping caches unmerged, these kinds of exploits 1911 can usually only damage objects in the same cache. To disable 1912 merging at runtime, "slab_nomerge" can be passed on the kernel 1913 command line. 1914 1915config SLAB_FREELIST_RANDOM 1916 bool "Randomize slab freelist" 1917 depends on SLAB || SLUB 1918 help 1919 Randomizes the freelist order used on creating new pages. This 1920 security feature reduces the predictability of the kernel slab 1921 allocator against heap overflows. 1922 1923config SLAB_FREELIST_HARDENED 1924 bool "Harden slab freelist metadata" 1925 depends on SLAB || SLUB 1926 help 1927 Many kernel heap attacks try to target slab cache metadata and 1928 other infrastructure. This options makes minor performance 1929 sacrifices to harden the kernel slab allocator against common 1930 freelist exploit methods. Some slab implementations have more 1931 sanity-checking than others. This option is most effective with 1932 CONFIG_SLUB. 1933 1934config SHUFFLE_PAGE_ALLOCATOR 1935 bool "Page allocator randomization" 1936 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1937 help 1938 Randomization of the page allocator improves the average 1939 utilization of a direct-mapped memory-side-cache. See section 1940 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1941 6.2a specification for an example of how a platform advertises 1942 the presence of a memory-side-cache. There are also incidental 1943 security benefits as it reduces the predictability of page 1944 allocations to compliment SLAB_FREELIST_RANDOM, but the 1945 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1946 10th order of pages is selected based on cache utilization 1947 benefits on x86. 1948 1949 While the randomization improves cache utilization it may 1950 negatively impact workloads on platforms without a cache. For 1951 this reason, by default, the randomization is enabled only 1952 after runtime detection of a direct-mapped memory-side-cache. 1953 Otherwise, the randomization may be force enabled with the 1954 'page_alloc.shuffle' kernel command line parameter. 1955 1956 Say Y if unsure. 1957 1958config SLUB_CPU_PARTIAL 1959 default y 1960 depends on SLUB && SMP 1961 bool "SLUB per cpu partial cache" 1962 help 1963 Per cpu partial caches accelerate objects allocation and freeing 1964 that is local to a processor at the price of more indeterminism 1965 in the latency of the free. On overflow these caches will be cleared 1966 which requires the taking of locks that may cause latency spikes. 1967 Typically one would choose no for a realtime system. 1968 1969config MMAP_ALLOW_UNINITIALIZED 1970 bool "Allow mmapped anonymous memory to be uninitialized" 1971 depends on EXPERT && !MMU 1972 default n 1973 help 1974 Normally, and according to the Linux spec, anonymous memory obtained 1975 from mmap() has its contents cleared before it is passed to 1976 userspace. Enabling this config option allows you to request that 1977 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1978 providing a huge performance boost. If this option is not enabled, 1979 then the flag will be ignored. 1980 1981 This is taken advantage of by uClibc's malloc(), and also by 1982 ELF-FDPIC binfmt's brk and stack allocator. 1983 1984 Because of the obvious security issues, this option should only be 1985 enabled on embedded devices where you control what is run in 1986 userspace. Since that isn't generally a problem on no-MMU systems, 1987 it is normally safe to say Y here. 1988 1989 See Documentation/mm/nommu-mmap.rst for more information. 1990 1991config SYSTEM_DATA_VERIFICATION 1992 def_bool n 1993 select SYSTEM_TRUSTED_KEYRING 1994 select KEYS 1995 select CRYPTO 1996 select CRYPTO_RSA 1997 select ASYMMETRIC_KEY_TYPE 1998 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1999 select ASN1 2000 select OID_REGISTRY 2001 select X509_CERTIFICATE_PARSER 2002 select PKCS7_MESSAGE_PARSER 2003 help 2004 Provide PKCS#7 message verification using the contents of the system 2005 trusted keyring to provide public keys. This then can be used for 2006 module verification, kexec image verification and firmware blob 2007 verification. 2008 2009config PROFILING 2010 bool "Profiling support" 2011 help 2012 Say Y here to enable the extended profiling support mechanisms used 2013 by profilers such as OProfile. 2014 2015# 2016# Place an empty function call at each tracepoint site. Can be 2017# dynamically changed for a probe function. 2018# 2019config TRACEPOINTS 2020 bool 2021 2022endmenu # General setup 2023 2024source "arch/Kconfig" 2025 2026config RT_MUTEXES 2027 bool 2028 2029config BASE_SMALL 2030 int 2031 default 0 if BASE_FULL 2032 default 1 if !BASE_FULL 2033 2034config MODULE_SIG_FORMAT 2035 def_bool n 2036 select SYSTEM_DATA_VERIFICATION 2037 2038menuconfig MODULES 2039 bool "Enable loadable module support" 2040 option modules 2041 help 2042 Kernel modules are small pieces of compiled code which can 2043 be inserted in the running kernel, rather than being 2044 permanently built into the kernel. You use the "modprobe" 2045 tool to add (and sometimes remove) them. If you say Y here, 2046 many parts of the kernel can be built as modules (by 2047 answering M instead of Y where indicated): this is most 2048 useful for infrequently used options which are not required 2049 for booting. For more information, see the man pages for 2050 modprobe, lsmod, modinfo, insmod and rmmod. 2051 2052 If you say Y here, you will need to run "make 2053 modules_install" to put the modules under /lib/modules/ 2054 where modprobe can find them (you may need to be root to do 2055 this). 2056 2057 If unsure, say Y. 2058 2059if MODULES 2060 2061config MODULE_FORCE_LOAD 2062 bool "Forced module loading" 2063 default n 2064 help 2065 Allow loading of modules without version information (ie. modprobe 2066 --force). Forced module loading sets the 'F' (forced) taint flag and 2067 is usually a really bad idea. 2068 2069config MODULE_UNLOAD 2070 bool "Module unloading" 2071 help 2072 Without this option you will not be able to unload any 2073 modules (note that some modules may not be unloadable 2074 anyway), which makes your kernel smaller, faster 2075 and simpler. If unsure, say Y. 2076 2077config MODULE_FORCE_UNLOAD 2078 bool "Forced module unloading" 2079 depends on MODULE_UNLOAD 2080 help 2081 This option allows you to force a module to unload, even if the 2082 kernel believes it is unsafe: the kernel will remove the module 2083 without waiting for anyone to stop using it (using the -f option to 2084 rmmod). This is mainly for kernel developers and desperate users. 2085 If unsure, say N. 2086 2087config MODVERSIONS 2088 bool "Module versioning support" 2089 help 2090 Usually, you have to use modules compiled with your kernel. 2091 Saying Y here makes it sometimes possible to use modules 2092 compiled for different kernels, by adding enough information 2093 to the modules to (hopefully) spot any changes which would 2094 make them incompatible with the kernel you are running. If 2095 unsure, say N. 2096 2097config ASM_MODVERSIONS 2098 bool 2099 default HAVE_ASM_MODVERSIONS && MODVERSIONS 2100 help 2101 This enables module versioning for exported symbols also from 2102 assembly. This can be enabled only when the target architecture 2103 supports it. 2104 2105config MODULE_REL_CRCS 2106 bool 2107 depends on MODVERSIONS 2108 2109config MODULE_SRCVERSION_ALL 2110 bool "Source checksum for all modules" 2111 help 2112 Modules which contain a MODULE_VERSION get an extra "srcversion" 2113 field inserted into their modinfo section, which contains a 2114 sum of the source files which made it. This helps maintainers 2115 see exactly which source was used to build a module (since 2116 others sometimes change the module source without updating 2117 the version). With this option, such a "srcversion" field 2118 will be created for all modules. If unsure, say N. 2119 2120config MODULE_SIG 2121 bool "Module signature verification" 2122 select MODULE_SIG_FORMAT 2123 help 2124 Check modules for valid signatures upon load: the signature 2125 is simply appended to the module. For more information see 2126 <file:Documentation/admin-guide/module-signing.rst>. 2127 2128 Note that this option adds the OpenSSL development packages as a 2129 kernel build dependency so that the signing tool can use its crypto 2130 library. 2131 2132 You should enable this option if you wish to use either 2133 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via 2134 another LSM - otherwise unsigned modules will be loadable regardless 2135 of the lockdown policy. 2136 2137 !!!WARNING!!! If you enable this option, you MUST make sure that the 2138 module DOES NOT get stripped after being signed. This includes the 2139 debuginfo strip done by some packagers (such as rpmbuild) and 2140 inclusion into an initramfs that wants the module size reduced. 2141 2142config MODULE_SIG_FORCE 2143 bool "Require modules to be validly signed" 2144 depends on MODULE_SIG 2145 help 2146 Reject unsigned modules or signed modules for which we don't have a 2147 key. Without this, such modules will simply taint the kernel. 2148 2149config MODULE_SIG_ALL 2150 bool "Automatically sign all modules" 2151 default y 2152 depends on MODULE_SIG 2153 help 2154 Sign all modules during make modules_install. Without this option, 2155 modules must be signed manually, using the scripts/sign-file tool. 2156 2157comment "Do not forget to sign required modules with scripts/sign-file" 2158 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2159 2160choice 2161 prompt "Which hash algorithm should modules be signed with?" 2162 depends on MODULE_SIG 2163 help 2164 This determines which sort of hashing algorithm will be used during 2165 signature generation. This algorithm _must_ be built into the kernel 2166 directly so that signature verification can take place. It is not 2167 possible to load a signed module containing the algorithm to check 2168 the signature on that module. 2169 2170config MODULE_SIG_SHA1 2171 bool "Sign modules with SHA-1" 2172 select CRYPTO_SHA1 2173 2174config MODULE_SIG_SHA224 2175 bool "Sign modules with SHA-224" 2176 select CRYPTO_SHA256 2177 2178config MODULE_SIG_SHA256 2179 bool "Sign modules with SHA-256" 2180 select CRYPTO_SHA256 2181 2182config MODULE_SIG_SHA384 2183 bool "Sign modules with SHA-384" 2184 select CRYPTO_SHA512 2185 2186config MODULE_SIG_SHA512 2187 bool "Sign modules with SHA-512" 2188 select CRYPTO_SHA512 2189 2190endchoice 2191 2192config MODULE_SIG_HASH 2193 string 2194 depends on MODULE_SIG 2195 default "sha1" if MODULE_SIG_SHA1 2196 default "sha224" if MODULE_SIG_SHA224 2197 default "sha256" if MODULE_SIG_SHA256 2198 default "sha384" if MODULE_SIG_SHA384 2199 default "sha512" if MODULE_SIG_SHA512 2200 2201config MODULE_COMPRESS 2202 bool "Compress modules on installation" 2203 help 2204 2205 Compresses kernel modules when 'make modules_install' is run; gzip or 2206 xz depending on "Compression algorithm" below. 2207 2208 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 2209 2210 Out-of-tree kernel modules installed using Kbuild will also be 2211 compressed upon installation. 2212 2213 Note: for modules inside an initrd or initramfs, it's more efficient 2214 to compress the whole initrd or initramfs instead. 2215 2216 Note: This is fully compatible with signed modules. 2217 2218 If in doubt, say N. 2219 2220choice 2221 prompt "Compression algorithm" 2222 depends on MODULE_COMPRESS 2223 default MODULE_COMPRESS_GZIP 2224 help 2225 This determines which sort of compression will be used during 2226 'make modules_install'. 2227 2228 GZIP (default) and XZ are supported. 2229 2230config MODULE_COMPRESS_GZIP 2231 bool "GZIP" 2232 2233config MODULE_COMPRESS_XZ 2234 bool "XZ" 2235 2236endchoice 2237 2238config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS 2239 bool "Allow loading of modules with missing namespace imports" 2240 help 2241 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in 2242 a namespace. A module that makes use of a symbol exported with such a 2243 namespace is required to import the namespace via MODULE_IMPORT_NS(). 2244 There is no technical reason to enforce correct namespace imports, 2245 but it creates consistency between symbols defining namespaces and 2246 users importing namespaces they make use of. This option relaxes this 2247 requirement and lifts the enforcement when loading a module. 2248 2249 If unsure, say N. 2250 2251config UNUSED_SYMBOLS 2252 bool "Enable unused/obsolete exported symbols" 2253 default y if X86 2254 help 2255 Unused but exported symbols make the kernel needlessly bigger. For 2256 that reason most of these unused exports will soon be removed. This 2257 option is provided temporarily to provide a transition period in case 2258 some external kernel module needs one of these symbols anyway. If you 2259 encounter such a case in your module, consider if you are actually 2260 using the right API. (rationale: since nobody in the kernel is using 2261 this in a module, there is a pretty good chance it's actually the 2262 wrong interface to use). If you really need the symbol, please send a 2263 mail to the linux kernel mailing list mentioning the symbol and why 2264 you really need it, and what the merge plan to the mainline kernel for 2265 your module is. 2266 2267config TRIM_UNUSED_KSYMS 2268 bool "Trim unused exported kernel symbols" 2269 depends on !UNUSED_SYMBOLS 2270 help 2271 The kernel and some modules make many symbols available for 2272 other modules to use via EXPORT_SYMBOL() and variants. Depending 2273 on the set of modules being selected in your kernel configuration, 2274 many of those exported symbols might never be used. 2275 2276 This option allows for unused exported symbols to be dropped from 2277 the build. In turn, this provides the compiler more opportunities 2278 (especially when using LTO) for optimizing the code and reducing 2279 binary size. This might have some security advantages as well. 2280 2281 If unsure, or if you need to build out-of-tree modules, say N. 2282 2283config UNUSED_KSYMS_WHITELIST 2284 string "Whitelist of symbols to keep in ksymtab" 2285 depends on TRIM_UNUSED_KSYMS 2286 help 2287 By default, all unused exported symbols will be un-exported from the 2288 build when TRIM_UNUSED_KSYMS is selected. 2289 2290 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept 2291 exported at all times, even in absence of in-tree users. The value to 2292 set here is the path to a text file containing the list of symbols, 2293 one per line. The path can be absolute, or relative to the kernel 2294 source tree. 2295 2296endif # MODULES 2297 2298config MODULES_TREE_LOOKUP 2299 def_bool y 2300 depends on PERF_EVENTS || TRACING 2301 2302config INIT_ALL_POSSIBLE 2303 bool 2304 help 2305 Back when each arch used to define their own cpu_online_mask and 2306 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2307 with all 1s, and others with all 0s. When they were centralised, 2308 it was better to provide this option than to break all the archs 2309 and have several arch maintainers pursuing me down dark alleys. 2310 2311source "block/Kconfig" 2312 2313config PREEMPT_NOTIFIERS 2314 bool 2315 2316config PADATA 2317 depends on SMP 2318 bool 2319 2320config ASN1 2321 tristate 2322 help 2323 Build a simple ASN.1 grammar compiler that produces a bytecode output 2324 that can be interpreted by the ASN.1 stream decoder and used to 2325 inform it as to what tags are to be expected in a stream and what 2326 functions to call on what tags. 2327 2328source "kernel/Kconfig.locks" 2329 2330config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 2331 bool 2332 2333config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2334 bool 2335 2336# It may be useful for an architecture to override the definitions of the 2337# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2338# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2339# different calling convention for syscalls. They can also override the 2340# macros for not-implemented syscalls in kernel/sys_ni.c and 2341# kernel/time/posix-stubs.c. All these overrides need to be available in 2342# <asm/syscall_wrapper.h>. 2343config ARCH_HAS_SYSCALL_WRAPPER 2344 def_bool n 2345