1# SPDX-License-Identifier: GPL-2.0-only 2config DEFCONFIG_LIST 3 string 4 depends on !UML 5 option defconfig_list 6 default "/lib/modules/$(shell,uname -r)/.config" 7 default "/etc/kernel-config" 8 default "/boot/config-$(shell,uname -r)" 9 default "arch/$(SRCARCH)/configs/$(KBUILD_DEFCONFIG)" 10 11config CC_VERSION_TEXT 12 string 13 default "$(CC_VERSION_TEXT)" 14 help 15 This is used in unclear ways: 16 17 - Re-run Kconfig when the compiler is updated 18 The 'default' property references the environment variable, 19 CC_VERSION_TEXT so it is recorded in include/config/auto.conf.cmd. 20 When the compiler is updated, Kconfig will be invoked. 21 22 - Ensure full rebuild when the compiler is updated 23 include/linux/compiler-version.h contains this option in the comment 24 line so fixdep adds include/config/CC_VERSION_TEXT into the 25 auto-generated dependency. When the compiler is updated, syncconfig 26 will touch it and then every file will be rebuilt. 27 28config CC_IS_GCC 29 def_bool $(success,test "$(cc-name)" = GCC) 30 31config GCC_VERSION 32 int 33 default $(cc-version) if CC_IS_GCC 34 default 0 35 36config CC_IS_CLANG 37 def_bool $(success,test "$(cc-name)" = Clang) 38 39config CLANG_VERSION 40 int 41 default $(cc-version) if CC_IS_CLANG 42 default 0 43 44config AS_IS_GNU 45 def_bool $(success,test "$(as-name)" = GNU) 46 47config AS_IS_LLVM 48 def_bool $(success,test "$(as-name)" = LLVM) 49 50config AS_VERSION 51 int 52 # Use clang version if this is the integrated assembler 53 default CLANG_VERSION if AS_IS_LLVM 54 default $(as-version) 55 56config LD_IS_BFD 57 def_bool $(success,test "$(ld-name)" = BFD) 58 59config LD_VERSION 60 int 61 default $(ld-version) if LD_IS_BFD 62 default 0 63 64config LD_IS_LLD 65 def_bool $(success,test "$(ld-name)" = LLD) 66 67config LLD_VERSION 68 int 69 default $(ld-version) if LD_IS_LLD 70 default 0 71 72config CC_CAN_LINK 73 bool 74 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag)) if 64BIT 75 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag)) 76 77config CC_CAN_LINK_STATIC 78 bool 79 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag) -static) if 64BIT 80 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag) -static) 81 82config CC_HAS_ASM_GOTO 83 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) 84 85config CC_HAS_ASM_GOTO_OUTPUT 86 depends on CC_HAS_ASM_GOTO 87 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) 88 89config TOOLS_SUPPORT_RELR 90 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 91 92config CC_HAS_ASM_INLINE 93 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 94 95config CONSTRUCTORS 96 bool 97 98config IRQ_WORK 99 bool 100 101config BUILDTIME_TABLE_SORT 102 bool 103 104config THREAD_INFO_IN_TASK 105 bool 106 help 107 Select this to move thread_info off the stack into task_struct. To 108 make this work, an arch will need to remove all thread_info fields 109 except flags and fix any runtime bugs. 110 111 One subtle change that will be needed is to use try_get_task_stack() 112 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 113 114menu "General setup" 115 116config BROKEN 117 bool 118 119config BROKEN_ON_SMP 120 bool 121 depends on BROKEN || !SMP 122 default y 123 124config INIT_ENV_ARG_LIMIT 125 int 126 default 32 if !UML 127 default 128 if UML 128 help 129 Maximum of each of the number of arguments and environment 130 variables passed to init from the kernel command line. 131 132config COMPILE_TEST 133 bool "Compile also drivers which will not load" 134 depends on HAS_IOMEM 135 help 136 Some drivers can be compiled on a different platform than they are 137 intended to be run on. Despite they cannot be loaded there (or even 138 when they load they cannot be used due to missing HW support), 139 developers still, opposing to distributors, might want to build such 140 drivers to compile-test them. 141 142 If you are a developer and want to build everything available, say Y 143 here. If you are a user/distributor, say N here to exclude useless 144 drivers to be distributed. 145 146config UAPI_HEADER_TEST 147 bool "Compile test UAPI headers" 148 depends on HEADERS_INSTALL && CC_CAN_LINK 149 help 150 Compile test headers exported to user-space to ensure they are 151 self-contained, i.e. compilable as standalone units. 152 153 If you are a developer or tester and want to ensure the exported 154 headers are self-contained, say Y here. Otherwise, choose N. 155 156config LOCALVERSION 157 string "Local version - append to kernel release" 158 help 159 Append an extra string to the end of your kernel version. 160 This will show up when you type uname, for example. 161 The string you set here will be appended after the contents of 162 any files with a filename matching localversion* in your 163 object and source tree, in that order. Your total string can 164 be a maximum of 64 characters. 165 166config LOCALVERSION_AUTO 167 bool "Automatically append version information to the version string" 168 default y 169 depends on !COMPILE_TEST 170 help 171 This will try to automatically determine if the current tree is a 172 release tree by looking for git tags that belong to the current 173 top of tree revision. 174 175 A string of the format -gxxxxxxxx will be added to the localversion 176 if a git-based tree is found. The string generated by this will be 177 appended after any matching localversion* files, and after the value 178 set in CONFIG_LOCALVERSION. 179 180 (The actual string used here is the first eight characters produced 181 by running the command: 182 183 $ git rev-parse --verify HEAD 184 185 which is done within the script "scripts/setlocalversion".) 186 187config BUILD_SALT 188 string "Build ID Salt" 189 default "" 190 help 191 The build ID is used to link binaries and their debug info. Setting 192 this option will use the value in the calculation of the build id. 193 This is mostly useful for distributions which want to ensure the 194 build is unique between builds. It's safe to leave the default. 195 196config HAVE_KERNEL_GZIP 197 bool 198 199config HAVE_KERNEL_BZIP2 200 bool 201 202config HAVE_KERNEL_LZMA 203 bool 204 205config HAVE_KERNEL_XZ 206 bool 207 208config HAVE_KERNEL_LZO 209 bool 210 211config HAVE_KERNEL_LZ4 212 bool 213 214config HAVE_KERNEL_ZSTD 215 bool 216 217config HAVE_KERNEL_UNCOMPRESSED 218 bool 219 220choice 221 prompt "Kernel compression mode" 222 default KERNEL_GZIP 223 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 224 help 225 The linux kernel is a kind of self-extracting executable. 226 Several compression algorithms are available, which differ 227 in efficiency, compression and decompression speed. 228 Compression speed is only relevant when building a kernel. 229 Decompression speed is relevant at each boot. 230 231 If you have any problems with bzip2 or lzma compressed 232 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 233 version of this functionality (bzip2 only), for 2.4, was 234 supplied by Christian Ludwig) 235 236 High compression options are mostly useful for users, who 237 are low on disk space (embedded systems), but for whom ram 238 size matters less. 239 240 If in doubt, select 'gzip' 241 242config KERNEL_GZIP 243 bool "Gzip" 244 depends on HAVE_KERNEL_GZIP 245 help 246 The old and tried gzip compression. It provides a good balance 247 between compression ratio and decompression speed. 248 249config KERNEL_BZIP2 250 bool "Bzip2" 251 depends on HAVE_KERNEL_BZIP2 252 help 253 Its compression ratio and speed is intermediate. 254 Decompression speed is slowest among the choices. The kernel 255 size is about 10% smaller with bzip2, in comparison to gzip. 256 Bzip2 uses a large amount of memory. For modern kernels you 257 will need at least 8MB RAM or more for booting. 258 259config KERNEL_LZMA 260 bool "LZMA" 261 depends on HAVE_KERNEL_LZMA 262 help 263 This compression algorithm's ratio is best. Decompression speed 264 is between gzip and bzip2. Compression is slowest. 265 The kernel size is about 33% smaller with LZMA in comparison to gzip. 266 267config KERNEL_XZ 268 bool "XZ" 269 depends on HAVE_KERNEL_XZ 270 help 271 XZ uses the LZMA2 algorithm and instruction set specific 272 BCJ filters which can improve compression ratio of executable 273 code. The size of the kernel is about 30% smaller with XZ in 274 comparison to gzip. On architectures for which there is a BCJ 275 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 276 will create a few percent smaller kernel than plain LZMA. 277 278 The speed is about the same as with LZMA: The decompression 279 speed of XZ is better than that of bzip2 but worse than gzip 280 and LZO. Compression is slow. 281 282config KERNEL_LZO 283 bool "LZO" 284 depends on HAVE_KERNEL_LZO 285 help 286 Its compression ratio is the poorest among the choices. The kernel 287 size is about 10% bigger than gzip; however its speed 288 (both compression and decompression) is the fastest. 289 290config KERNEL_LZ4 291 bool "LZ4" 292 depends on HAVE_KERNEL_LZ4 293 help 294 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 295 A preliminary version of LZ4 de/compression tool is available at 296 <https://code.google.com/p/lz4/>. 297 298 Its compression ratio is worse than LZO. The size of the kernel 299 is about 8% bigger than LZO. But the decompression speed is 300 faster than LZO. 301 302config KERNEL_ZSTD 303 bool "ZSTD" 304 depends on HAVE_KERNEL_ZSTD 305 help 306 ZSTD is a compression algorithm targeting intermediate compression 307 with fast decompression speed. It will compress better than GZIP and 308 decompress around the same speed as LZO, but slower than LZ4. You 309 will need at least 192 KB RAM or more for booting. The zstd command 310 line tool is required for compression. 311 312config KERNEL_UNCOMPRESSED 313 bool "None" 314 depends on HAVE_KERNEL_UNCOMPRESSED 315 help 316 Produce uncompressed kernel image. This option is usually not what 317 you want. It is useful for debugging the kernel in slow simulation 318 environments, where decompressing and moving the kernel is awfully 319 slow. This option allows early boot code to skip the decompressor 320 and jump right at uncompressed kernel image. 321 322endchoice 323 324config DEFAULT_INIT 325 string "Default init path" 326 default "" 327 help 328 This option determines the default init for the system if no init= 329 option is passed on the kernel command line. If the requested path is 330 not present, we will still then move on to attempting further 331 locations (e.g. /sbin/init, etc). If this is empty, we will just use 332 the fallback list when init= is not passed. 333 334config DEFAULT_HOSTNAME 335 string "Default hostname" 336 default "(none)" 337 help 338 This option determines the default system hostname before userspace 339 calls sethostname(2). The kernel traditionally uses "(none)" here, 340 but you may wish to use a different default here to make a minimal 341 system more usable with less configuration. 342 343# 344# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can 345# add proper SWAP support to them, in which case this can be remove. 346# 347config ARCH_NO_SWAP 348 bool 349 350config SWAP 351 bool "Support for paging of anonymous memory (swap)" 352 depends on MMU && BLOCK && !ARCH_NO_SWAP 353 default y 354 help 355 This option allows you to choose whether you want to have support 356 for so called swap devices or swap files in your kernel that are 357 used to provide more virtual memory than the actual RAM present 358 in your computer. If unsure say Y. 359 360config SYSVIPC 361 bool "System V IPC" 362 help 363 Inter Process Communication is a suite of library functions and 364 system calls which let processes (running programs) synchronize and 365 exchange information. It is generally considered to be a good thing, 366 and some programs won't run unless you say Y here. In particular, if 367 you want to run the DOS emulator dosemu under Linux (read the 368 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 369 you'll need to say Y here. 370 371 You can find documentation about IPC with "info ipc" and also in 372 section 6.4 of the Linux Programmer's Guide, available from 373 <http://www.tldp.org/guides.html>. 374 375config SYSVIPC_SYSCTL 376 bool 377 depends on SYSVIPC 378 depends on SYSCTL 379 default y 380 381config POSIX_MQUEUE 382 bool "POSIX Message Queues" 383 depends on NET 384 help 385 POSIX variant of message queues is a part of IPC. In POSIX message 386 queues every message has a priority which decides about succession 387 of receiving it by a process. If you want to compile and run 388 programs written e.g. for Solaris with use of its POSIX message 389 queues (functions mq_*) say Y here. 390 391 POSIX message queues are visible as a filesystem called 'mqueue' 392 and can be mounted somewhere if you want to do filesystem 393 operations on message queues. 394 395 If unsure, say Y. 396 397config POSIX_MQUEUE_SYSCTL 398 bool 399 depends on POSIX_MQUEUE 400 depends on SYSCTL 401 default y 402 403config WATCH_QUEUE 404 bool "General notification queue" 405 default n 406 help 407 408 This is a general notification queue for the kernel to pass events to 409 userspace by splicing them into pipes. It can be used in conjunction 410 with watches for key/keyring change notifications and device 411 notifications. 412 413 See Documentation/watch_queue.rst 414 415config CROSS_MEMORY_ATTACH 416 bool "Enable process_vm_readv/writev syscalls" 417 depends on MMU 418 default y 419 help 420 Enabling this option adds the system calls process_vm_readv and 421 process_vm_writev which allow a process with the correct privileges 422 to directly read from or write to another process' address space. 423 See the man page for more details. 424 425config USELIB 426 bool "uselib syscall" 427 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION 428 help 429 This option enables the uselib syscall, a system call used in the 430 dynamic linker from libc5 and earlier. glibc does not use this 431 system call. If you intend to run programs built on libc5 or 432 earlier, you may need to enable this syscall. Current systems 433 running glibc can safely disable this. 434 435config AUDIT 436 bool "Auditing support" 437 depends on NET 438 help 439 Enable auditing infrastructure that can be used with another 440 kernel subsystem, such as SELinux (which requires this for 441 logging of avc messages output). System call auditing is included 442 on architectures which support it. 443 444config HAVE_ARCH_AUDITSYSCALL 445 bool 446 447config AUDITSYSCALL 448 def_bool y 449 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 450 select FSNOTIFY 451 452source "kernel/irq/Kconfig" 453source "kernel/time/Kconfig" 454source "kernel/Kconfig.preempt" 455 456menu "CPU/Task time and stats accounting" 457 458config VIRT_CPU_ACCOUNTING 459 bool 460 461choice 462 prompt "Cputime accounting" 463 default TICK_CPU_ACCOUNTING if !PPC64 464 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 465 466# Kind of a stub config for the pure tick based cputime accounting 467config TICK_CPU_ACCOUNTING 468 bool "Simple tick based cputime accounting" 469 depends on !S390 && !NO_HZ_FULL 470 help 471 This is the basic tick based cputime accounting that maintains 472 statistics about user, system and idle time spent on per jiffies 473 granularity. 474 475 If unsure, say Y. 476 477config VIRT_CPU_ACCOUNTING_NATIVE 478 bool "Deterministic task and CPU time accounting" 479 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 480 select VIRT_CPU_ACCOUNTING 481 help 482 Select this option to enable more accurate task and CPU time 483 accounting. This is done by reading a CPU counter on each 484 kernel entry and exit and on transitions within the kernel 485 between system, softirq and hardirq state, so there is a 486 small performance impact. In the case of s390 or IBM POWER > 5, 487 this also enables accounting of stolen time on logically-partitioned 488 systems. 489 490config VIRT_CPU_ACCOUNTING_GEN 491 bool "Full dynticks CPU time accounting" 492 depends on HAVE_CONTEXT_TRACKING 493 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 494 depends on GENERIC_CLOCKEVENTS 495 select VIRT_CPU_ACCOUNTING 496 select CONTEXT_TRACKING 497 help 498 Select this option to enable task and CPU time accounting on full 499 dynticks systems. This accounting is implemented by watching every 500 kernel-user boundaries using the context tracking subsystem. 501 The accounting is thus performed at the expense of some significant 502 overhead. 503 504 For now this is only useful if you are working on the full 505 dynticks subsystem development. 506 507 If unsure, say N. 508 509endchoice 510 511config IRQ_TIME_ACCOUNTING 512 bool "Fine granularity task level IRQ time accounting" 513 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 514 help 515 Select this option to enable fine granularity task irq time 516 accounting. This is done by reading a timestamp on each 517 transitions between softirq and hardirq state, so there can be a 518 small performance impact. 519 520 If in doubt, say N here. 521 522config HAVE_SCHED_AVG_IRQ 523 def_bool y 524 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 525 depends on SMP 526 527config SCHED_THERMAL_PRESSURE 528 bool 529 default y if ARM && ARM_CPU_TOPOLOGY 530 default y if ARM64 531 depends on SMP 532 depends on CPU_FREQ_THERMAL 533 help 534 Select this option to enable thermal pressure accounting in the 535 scheduler. Thermal pressure is the value conveyed to the scheduler 536 that reflects the reduction in CPU compute capacity resulted from 537 thermal throttling. Thermal throttling occurs when the performance of 538 a CPU is capped due to high operating temperatures. 539 540 If selected, the scheduler will be able to balance tasks accordingly, 541 i.e. put less load on throttled CPUs than on non/less throttled ones. 542 543 This requires the architecture to implement 544 arch_set_thermal_pressure() and arch_scale_thermal_pressure(). 545 546config BSD_PROCESS_ACCT 547 bool "BSD Process Accounting" 548 depends on MULTIUSER 549 help 550 If you say Y here, a user level program will be able to instruct the 551 kernel (via a special system call) to write process accounting 552 information to a file: whenever a process exits, information about 553 that process will be appended to the file by the kernel. The 554 information includes things such as creation time, owning user, 555 command name, memory usage, controlling terminal etc. (the complete 556 list is in the struct acct in <file:include/linux/acct.h>). It is 557 up to the user level program to do useful things with this 558 information. This is generally a good idea, so say Y. 559 560config BSD_PROCESS_ACCT_V3 561 bool "BSD Process Accounting version 3 file format" 562 depends on BSD_PROCESS_ACCT 563 default n 564 help 565 If you say Y here, the process accounting information is written 566 in a new file format that also logs the process IDs of each 567 process and its parent. Note that this file format is incompatible 568 with previous v0/v1/v2 file formats, so you will need updated tools 569 for processing it. A preliminary version of these tools is available 570 at <http://www.gnu.org/software/acct/>. 571 572config TASKSTATS 573 bool "Export task/process statistics through netlink" 574 depends on NET 575 depends on MULTIUSER 576 default n 577 help 578 Export selected statistics for tasks/processes through the 579 generic netlink interface. Unlike BSD process accounting, the 580 statistics are available during the lifetime of tasks/processes as 581 responses to commands. Like BSD accounting, they are sent to user 582 space on task exit. 583 584 Say N if unsure. 585 586config TASK_DELAY_ACCT 587 bool "Enable per-task delay accounting" 588 depends on TASKSTATS 589 select SCHED_INFO 590 help 591 Collect information on time spent by a task waiting for system 592 resources like cpu, synchronous block I/O completion and swapping 593 in pages. Such statistics can help in setting a task's priorities 594 relative to other tasks for cpu, io, rss limits etc. 595 596 Say N if unsure. 597 598config TASK_XACCT 599 bool "Enable extended accounting over taskstats" 600 depends on TASKSTATS 601 help 602 Collect extended task accounting data and send the data 603 to userland for processing over the taskstats interface. 604 605 Say N if unsure. 606 607config TASK_IO_ACCOUNTING 608 bool "Enable per-task storage I/O accounting" 609 depends on TASK_XACCT 610 help 611 Collect information on the number of bytes of storage I/O which this 612 task has caused. 613 614 Say N if unsure. 615 616config PSI 617 bool "Pressure stall information tracking" 618 help 619 Collect metrics that indicate how overcommitted the CPU, memory, 620 and IO capacity are in the system. 621 622 If you say Y here, the kernel will create /proc/pressure/ with the 623 pressure statistics files cpu, memory, and io. These will indicate 624 the share of walltime in which some or all tasks in the system are 625 delayed due to contention of the respective resource. 626 627 In kernels with cgroup support, cgroups (cgroup2 only) will 628 have cpu.pressure, memory.pressure, and io.pressure files, 629 which aggregate pressure stalls for the grouped tasks only. 630 631 For more details see Documentation/accounting/psi.rst. 632 633 Say N if unsure. 634 635config PSI_DEFAULT_DISABLED 636 bool "Require boot parameter to enable pressure stall information tracking" 637 default n 638 depends on PSI 639 help 640 If set, pressure stall information tracking will be disabled 641 per default but can be enabled through passing psi=1 on the 642 kernel commandline during boot. 643 644 This feature adds some code to the task wakeup and sleep 645 paths of the scheduler. The overhead is too low to affect 646 common scheduling-intense workloads in practice (such as 647 webservers, memcache), but it does show up in artificial 648 scheduler stress tests, such as hackbench. 649 650 If you are paranoid and not sure what the kernel will be 651 used for, say Y. 652 653 Say N if unsure. 654 655endmenu # "CPU/Task time and stats accounting" 656 657config CPU_ISOLATION 658 bool "CPU isolation" 659 depends on SMP || COMPILE_TEST 660 default y 661 help 662 Make sure that CPUs running critical tasks are not disturbed by 663 any source of "noise" such as unbound workqueues, timers, kthreads... 664 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 665 the "isolcpus=" boot parameter. 666 667 Say Y if unsure. 668 669source "kernel/rcu/Kconfig" 670 671config BUILD_BIN2C 672 bool 673 default n 674 675config IKCONFIG 676 tristate "Kernel .config support" 677 help 678 This option enables the complete Linux kernel ".config" file 679 contents to be saved in the kernel. It provides documentation 680 of which kernel options are used in a running kernel or in an 681 on-disk kernel. This information can be extracted from the kernel 682 image file with the script scripts/extract-ikconfig and used as 683 input to rebuild the current kernel or to build another kernel. 684 It can also be extracted from a running kernel by reading 685 /proc/config.gz if enabled (below). 686 687config IKCONFIG_PROC 688 bool "Enable access to .config through /proc/config.gz" 689 depends on IKCONFIG && PROC_FS 690 help 691 This option enables access to the kernel configuration file 692 through /proc/config.gz. 693 694config IKHEADERS 695 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 696 depends on SYSFS 697 help 698 This option enables access to the in-kernel headers that are generated during 699 the build process. These can be used to build eBPF tracing programs, 700 or similar programs. If you build the headers as a module, a module called 701 kheaders.ko is built which can be loaded on-demand to get access to headers. 702 703config LOG_BUF_SHIFT 704 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 705 range 12 25 if !H8300 706 range 12 19 if H8300 707 default 17 708 depends on PRINTK 709 help 710 Select the minimal kernel log buffer size as a power of 2. 711 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 712 parameter, see below. Any higher size also might be forced 713 by "log_buf_len" boot parameter. 714 715 Examples: 716 17 => 128 KB 717 16 => 64 KB 718 15 => 32 KB 719 14 => 16 KB 720 13 => 8 KB 721 12 => 4 KB 722 723config LOG_CPU_MAX_BUF_SHIFT 724 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 725 depends on SMP 726 range 0 21 727 default 12 if !BASE_SMALL 728 default 0 if BASE_SMALL 729 depends on PRINTK 730 help 731 This option allows to increase the default ring buffer size 732 according to the number of CPUs. The value defines the contribution 733 of each CPU as a power of 2. The used space is typically only few 734 lines however it might be much more when problems are reported, 735 e.g. backtraces. 736 737 The increased size means that a new buffer has to be allocated and 738 the original static one is unused. It makes sense only on systems 739 with more CPUs. Therefore this value is used only when the sum of 740 contributions is greater than the half of the default kernel ring 741 buffer as defined by LOG_BUF_SHIFT. The default values are set 742 so that more than 16 CPUs are needed to trigger the allocation. 743 744 Also this option is ignored when "log_buf_len" kernel parameter is 745 used as it forces an exact (power of two) size of the ring buffer. 746 747 The number of possible CPUs is used for this computation ignoring 748 hotplugging making the computation optimal for the worst case 749 scenario while allowing a simple algorithm to be used from bootup. 750 751 Examples shift values and their meaning: 752 17 => 128 KB for each CPU 753 16 => 64 KB for each CPU 754 15 => 32 KB for each CPU 755 14 => 16 KB for each CPU 756 13 => 8 KB for each CPU 757 12 => 4 KB for each CPU 758 759config PRINTK_SAFE_LOG_BUF_SHIFT 760 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 761 range 10 21 762 default 13 763 depends on PRINTK 764 help 765 Select the size of an alternate printk per-CPU buffer where messages 766 printed from usafe contexts are temporary stored. One example would 767 be NMI messages, another one - printk recursion. The messages are 768 copied to the main log buffer in a safe context to avoid a deadlock. 769 The value defines the size as a power of 2. 770 771 Those messages are rare and limited. The largest one is when 772 a backtrace is printed. It usually fits into 4KB. Select 773 8KB if you want to be on the safe side. 774 775 Examples: 776 17 => 128 KB for each CPU 777 16 => 64 KB for each CPU 778 15 => 32 KB for each CPU 779 14 => 16 KB for each CPU 780 13 => 8 KB for each CPU 781 12 => 4 KB for each CPU 782 783# 784# Architectures with an unreliable sched_clock() should select this: 785# 786config HAVE_UNSTABLE_SCHED_CLOCK 787 bool 788 789config GENERIC_SCHED_CLOCK 790 bool 791 792menu "Scheduler features" 793 794config UCLAMP_TASK 795 bool "Enable utilization clamping for RT/FAIR tasks" 796 depends on CPU_FREQ_GOV_SCHEDUTIL 797 help 798 This feature enables the scheduler to track the clamped utilization 799 of each CPU based on RUNNABLE tasks scheduled on that CPU. 800 801 With this option, the user can specify the min and max CPU 802 utilization allowed for RUNNABLE tasks. The max utilization defines 803 the maximum frequency a task should use while the min utilization 804 defines the minimum frequency it should use. 805 806 Both min and max utilization clamp values are hints to the scheduler, 807 aiming at improving its frequency selection policy, but they do not 808 enforce or grant any specific bandwidth for tasks. 809 810 If in doubt, say N. 811 812config UCLAMP_BUCKETS_COUNT 813 int "Number of supported utilization clamp buckets" 814 range 5 20 815 default 5 816 depends on UCLAMP_TASK 817 help 818 Defines the number of clamp buckets to use. The range of each bucket 819 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 820 number of clamp buckets the finer their granularity and the higher 821 the precision of clamping aggregation and tracking at run-time. 822 823 For example, with the minimum configuration value we will have 5 824 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 825 be refcounted in the [20..39]% bucket and will set the bucket clamp 826 effective value to 25%. 827 If a second 30% boosted task should be co-scheduled on the same CPU, 828 that task will be refcounted in the same bucket of the first task and 829 it will boost the bucket clamp effective value to 30%. 830 The clamp effective value of a bucket is reset to its nominal value 831 (20% in the example above) when there are no more tasks refcounted in 832 that bucket. 833 834 An additional boost/capping margin can be added to some tasks. In the 835 example above the 25% task will be boosted to 30% until it exits the 836 CPU. If that should be considered not acceptable on certain systems, 837 it's always possible to reduce the margin by increasing the number of 838 clamp buckets to trade off used memory for run-time tracking 839 precision. 840 841 If in doubt, use the default value. 842 843endmenu 844 845# 846# For architectures that want to enable the support for NUMA-affine scheduler 847# balancing logic: 848# 849config ARCH_SUPPORTS_NUMA_BALANCING 850 bool 851 852# 853# For architectures that prefer to flush all TLBs after a number of pages 854# are unmapped instead of sending one IPI per page to flush. The architecture 855# must provide guarantees on what happens if a clean TLB cache entry is 856# written after the unmap. Details are in mm/rmap.c near the check for 857# should_defer_flush. The architecture should also consider if the full flush 858# and the refill costs are offset by the savings of sending fewer IPIs. 859config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 860 bool 861 862config CC_HAS_INT128 863 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 864 865# 866# For architectures that know their GCC __int128 support is sound 867# 868config ARCH_SUPPORTS_INT128 869 bool 870 871# For architectures that (ab)use NUMA to represent different memory regions 872# all cpu-local but of different latencies, such as SuperH. 873# 874config ARCH_WANT_NUMA_VARIABLE_LOCALITY 875 bool 876 877config NUMA_BALANCING 878 bool "Memory placement aware NUMA scheduler" 879 depends on ARCH_SUPPORTS_NUMA_BALANCING 880 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 881 depends on SMP && NUMA && MIGRATION 882 help 883 This option adds support for automatic NUMA aware memory/task placement. 884 The mechanism is quite primitive and is based on migrating memory when 885 it has references to the node the task is running on. 886 887 This system will be inactive on UMA systems. 888 889config NUMA_BALANCING_DEFAULT_ENABLED 890 bool "Automatically enable NUMA aware memory/task placement" 891 default y 892 depends on NUMA_BALANCING 893 help 894 If set, automatic NUMA balancing will be enabled if running on a NUMA 895 machine. 896 897menuconfig CGROUPS 898 bool "Control Group support" 899 select KERNFS 900 help 901 This option adds support for grouping sets of processes together, for 902 use with process control subsystems such as Cpusets, CFS, memory 903 controls or device isolation. 904 See 905 - Documentation/scheduler/sched-design-CFS.rst (CFS) 906 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 907 and resource control) 908 909 Say N if unsure. 910 911if CGROUPS 912 913config PAGE_COUNTER 914 bool 915 916config MEMCG 917 bool "Memory controller" 918 select PAGE_COUNTER 919 select EVENTFD 920 help 921 Provides control over the memory footprint of tasks in a cgroup. 922 923config MEMCG_SWAP 924 bool 925 depends on MEMCG && SWAP 926 default y 927 928config MEMCG_KMEM 929 bool 930 depends on MEMCG && !SLOB 931 default y 932 933config BLK_CGROUP 934 bool "IO controller" 935 depends on BLOCK 936 default n 937 help 938 Generic block IO controller cgroup interface. This is the common 939 cgroup interface which should be used by various IO controlling 940 policies. 941 942 Currently, CFQ IO scheduler uses it to recognize task groups and 943 control disk bandwidth allocation (proportional time slice allocation) 944 to such task groups. It is also used by bio throttling logic in 945 block layer to implement upper limit in IO rates on a device. 946 947 This option only enables generic Block IO controller infrastructure. 948 One needs to also enable actual IO controlling logic/policy. For 949 enabling proportional weight division of disk bandwidth in CFQ, set 950 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 951 CONFIG_BLK_DEV_THROTTLING=y. 952 953 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 954 955config CGROUP_WRITEBACK 956 bool 957 depends on MEMCG && BLK_CGROUP 958 default y 959 960menuconfig CGROUP_SCHED 961 bool "CPU controller" 962 default n 963 help 964 This feature lets CPU scheduler recognize task groups and control CPU 965 bandwidth allocation to such task groups. It uses cgroups to group 966 tasks. 967 968if CGROUP_SCHED 969config FAIR_GROUP_SCHED 970 bool "Group scheduling for SCHED_OTHER" 971 depends on CGROUP_SCHED 972 default CGROUP_SCHED 973 974config CFS_BANDWIDTH 975 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 976 depends on FAIR_GROUP_SCHED 977 default n 978 help 979 This option allows users to define CPU bandwidth rates (limits) for 980 tasks running within the fair group scheduler. Groups with no limit 981 set are considered to be unconstrained and will run with no 982 restriction. 983 See Documentation/scheduler/sched-bwc.rst for more information. 984 985config RT_GROUP_SCHED 986 bool "Group scheduling for SCHED_RR/FIFO" 987 depends on CGROUP_SCHED 988 default n 989 help 990 This feature lets you explicitly allocate real CPU bandwidth 991 to task groups. If enabled, it will also make it impossible to 992 schedule realtime tasks for non-root users until you allocate 993 realtime bandwidth for them. 994 See Documentation/scheduler/sched-rt-group.rst for more information. 995 996endif #CGROUP_SCHED 997 998config UCLAMP_TASK_GROUP 999 bool "Utilization clamping per group of tasks" 1000 depends on CGROUP_SCHED 1001 depends on UCLAMP_TASK 1002 default n 1003 help 1004 This feature enables the scheduler to track the clamped utilization 1005 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 1006 1007 When this option is enabled, the user can specify a min and max 1008 CPU bandwidth which is allowed for each single task in a group. 1009 The max bandwidth allows to clamp the maximum frequency a task 1010 can use, while the min bandwidth allows to define a minimum 1011 frequency a task will always use. 1012 1013 When task group based utilization clamping is enabled, an eventually 1014 specified task-specific clamp value is constrained by the cgroup 1015 specified clamp value. Both minimum and maximum task clamping cannot 1016 be bigger than the corresponding clamping defined at task group level. 1017 1018 If in doubt, say N. 1019 1020config CGROUP_PIDS 1021 bool "PIDs controller" 1022 help 1023 Provides enforcement of process number limits in the scope of a 1024 cgroup. Any attempt to fork more processes than is allowed in the 1025 cgroup will fail. PIDs are fundamentally a global resource because it 1026 is fairly trivial to reach PID exhaustion before you reach even a 1027 conservative kmemcg limit. As a result, it is possible to grind a 1028 system to halt without being limited by other cgroup policies. The 1029 PIDs controller is designed to stop this from happening. 1030 1031 It should be noted that organisational operations (such as attaching 1032 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 1033 since the PIDs limit only affects a process's ability to fork, not to 1034 attach to a cgroup. 1035 1036config CGROUP_RDMA 1037 bool "RDMA controller" 1038 help 1039 Provides enforcement of RDMA resources defined by IB stack. 1040 It is fairly easy for consumers to exhaust RDMA resources, which 1041 can result into resource unavailability to other consumers. 1042 RDMA controller is designed to stop this from happening. 1043 Attaching processes with active RDMA resources to the cgroup 1044 hierarchy is allowed even if can cross the hierarchy's limit. 1045 1046config CGROUP_FREEZER 1047 bool "Freezer controller" 1048 help 1049 Provides a way to freeze and unfreeze all tasks in a 1050 cgroup. 1051 1052 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1053 controller includes important in-kernel memory consumers per default. 1054 1055 If you're using cgroup2, say N. 1056 1057config CGROUP_HUGETLB 1058 bool "HugeTLB controller" 1059 depends on HUGETLB_PAGE 1060 select PAGE_COUNTER 1061 default n 1062 help 1063 Provides a cgroup controller for HugeTLB pages. 1064 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1065 The limit is enforced during page fault. Since HugeTLB doesn't 1066 support page reclaim, enforcing the limit at page fault time implies 1067 that, the application will get SIGBUS signal if it tries to access 1068 HugeTLB pages beyond its limit. This requires the application to know 1069 beforehand how much HugeTLB pages it would require for its use. The 1070 control group is tracked in the third page lru pointer. This means 1071 that we cannot use the controller with huge page less than 3 pages. 1072 1073config CPUSETS 1074 bool "Cpuset controller" 1075 depends on SMP 1076 help 1077 This option will let you create and manage CPUSETs which 1078 allow dynamically partitioning a system into sets of CPUs and 1079 Memory Nodes and assigning tasks to run only within those sets. 1080 This is primarily useful on large SMP or NUMA systems. 1081 1082 Say N if unsure. 1083 1084config PROC_PID_CPUSET 1085 bool "Include legacy /proc/<pid>/cpuset file" 1086 depends on CPUSETS 1087 default y 1088 1089config CGROUP_DEVICE 1090 bool "Device controller" 1091 help 1092 Provides a cgroup controller implementing whitelists for 1093 devices which a process in the cgroup can mknod or open. 1094 1095config CGROUP_CPUACCT 1096 bool "Simple CPU accounting controller" 1097 help 1098 Provides a simple controller for monitoring the 1099 total CPU consumed by the tasks in a cgroup. 1100 1101config CGROUP_PERF 1102 bool "Perf controller" 1103 depends on PERF_EVENTS 1104 help 1105 This option extends the perf per-cpu mode to restrict monitoring 1106 to threads which belong to the cgroup specified and run on the 1107 designated cpu. Or this can be used to have cgroup ID in samples 1108 so that it can monitor performance events among cgroups. 1109 1110 Say N if unsure. 1111 1112config CGROUP_BPF 1113 bool "Support for eBPF programs attached to cgroups" 1114 depends on BPF_SYSCALL 1115 select SOCK_CGROUP_DATA 1116 help 1117 Allow attaching eBPF programs to a cgroup using the bpf(2) 1118 syscall command BPF_PROG_ATTACH. 1119 1120 In which context these programs are accessed depends on the type 1121 of attachment. For instance, programs that are attached using 1122 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1123 inet sockets. 1124 1125config CGROUP_DEBUG 1126 bool "Debug controller" 1127 default n 1128 depends on DEBUG_KERNEL 1129 help 1130 This option enables a simple controller that exports 1131 debugging information about the cgroups framework. This 1132 controller is for control cgroup debugging only. Its 1133 interfaces are not stable. 1134 1135 Say N. 1136 1137config SOCK_CGROUP_DATA 1138 bool 1139 default n 1140 1141endif # CGROUPS 1142 1143menuconfig NAMESPACES 1144 bool "Namespaces support" if EXPERT 1145 depends on MULTIUSER 1146 default !EXPERT 1147 help 1148 Provides the way to make tasks work with different objects using 1149 the same id. For example same IPC id may refer to different objects 1150 or same user id or pid may refer to different tasks when used in 1151 different namespaces. 1152 1153if NAMESPACES 1154 1155config UTS_NS 1156 bool "UTS namespace" 1157 default y 1158 help 1159 In this namespace tasks see different info provided with the 1160 uname() system call 1161 1162config TIME_NS 1163 bool "TIME namespace" 1164 depends on GENERIC_VDSO_TIME_NS 1165 default y 1166 help 1167 In this namespace boottime and monotonic clocks can be set. 1168 The time will keep going with the same pace. 1169 1170config IPC_NS 1171 bool "IPC namespace" 1172 depends on (SYSVIPC || POSIX_MQUEUE) 1173 default y 1174 help 1175 In this namespace tasks work with IPC ids which correspond to 1176 different IPC objects in different namespaces. 1177 1178config USER_NS 1179 bool "User namespace" 1180 default n 1181 help 1182 This allows containers, i.e. vservers, to use user namespaces 1183 to provide different user info for different servers. 1184 1185 When user namespaces are enabled in the kernel it is 1186 recommended that the MEMCG option also be enabled and that 1187 user-space use the memory control groups to limit the amount 1188 of memory a memory unprivileged users can use. 1189 1190 If unsure, say N. 1191 1192config PID_NS 1193 bool "PID Namespaces" 1194 default y 1195 help 1196 Support process id namespaces. This allows having multiple 1197 processes with the same pid as long as they are in different 1198 pid namespaces. This is a building block of containers. 1199 1200config NET_NS 1201 bool "Network namespace" 1202 depends on NET 1203 default y 1204 help 1205 Allow user space to create what appear to be multiple instances 1206 of the network stack. 1207 1208endif # NAMESPACES 1209 1210config CHECKPOINT_RESTORE 1211 bool "Checkpoint/restore support" 1212 select PROC_CHILDREN 1213 select KCMP 1214 default n 1215 help 1216 Enables additional kernel features in a sake of checkpoint/restore. 1217 In particular it adds auxiliary prctl codes to setup process text, 1218 data and heap segment sizes, and a few additional /proc filesystem 1219 entries. 1220 1221 If unsure, say N here. 1222 1223config SCHED_AUTOGROUP 1224 bool "Automatic process group scheduling" 1225 select CGROUPS 1226 select CGROUP_SCHED 1227 select FAIR_GROUP_SCHED 1228 help 1229 This option optimizes the scheduler for common desktop workloads by 1230 automatically creating and populating task groups. This separation 1231 of workloads isolates aggressive CPU burners (like build jobs) from 1232 desktop applications. Task group autogeneration is currently based 1233 upon task session. 1234 1235config SYSFS_DEPRECATED 1236 bool "Enable deprecated sysfs features to support old userspace tools" 1237 depends on SYSFS 1238 default n 1239 help 1240 This option adds code that switches the layout of the "block" class 1241 devices, to not show up in /sys/class/block/, but only in 1242 /sys/block/. 1243 1244 This switch is only active when the sysfs.deprecated=1 boot option is 1245 passed or the SYSFS_DEPRECATED_V2 option is set. 1246 1247 This option allows new kernels to run on old distributions and tools, 1248 which might get confused by /sys/class/block/. Since 2007/2008 all 1249 major distributions and tools handle this just fine. 1250 1251 Recent distributions and userspace tools after 2009/2010 depend on 1252 the existence of /sys/class/block/, and will not work with this 1253 option enabled. 1254 1255 Only if you are using a new kernel on an old distribution, you might 1256 need to say Y here. 1257 1258config SYSFS_DEPRECATED_V2 1259 bool "Enable deprecated sysfs features by default" 1260 default n 1261 depends on SYSFS 1262 depends on SYSFS_DEPRECATED 1263 help 1264 Enable deprecated sysfs by default. 1265 1266 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1267 option. 1268 1269 Only if you are using a new kernel on an old distribution, you might 1270 need to say Y here. Even then, odds are you would not need it 1271 enabled, you can always pass the boot option if absolutely necessary. 1272 1273config RELAY 1274 bool "Kernel->user space relay support (formerly relayfs)" 1275 select IRQ_WORK 1276 help 1277 This option enables support for relay interface support in 1278 certain file systems (such as debugfs). 1279 It is designed to provide an efficient mechanism for tools and 1280 facilities to relay large amounts of data from kernel space to 1281 user space. 1282 1283 If unsure, say N. 1284 1285config BLK_DEV_INITRD 1286 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1287 help 1288 The initial RAM filesystem is a ramfs which is loaded by the 1289 boot loader (loadlin or lilo) and that is mounted as root 1290 before the normal boot procedure. It is typically used to 1291 load modules needed to mount the "real" root file system, 1292 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1293 1294 If RAM disk support (BLK_DEV_RAM) is also included, this 1295 also enables initial RAM disk (initrd) support and adds 1296 15 Kbytes (more on some other architectures) to the kernel size. 1297 1298 If unsure say Y. 1299 1300if BLK_DEV_INITRD 1301 1302source "usr/Kconfig" 1303 1304endif 1305 1306config BOOT_CONFIG 1307 bool "Boot config support" 1308 select BLK_DEV_INITRD 1309 help 1310 Extra boot config allows system admin to pass a config file as 1311 complemental extension of kernel cmdline when booting. 1312 The boot config file must be attached at the end of initramfs 1313 with checksum, size and magic word. 1314 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1315 1316 If unsure, say Y. 1317 1318choice 1319 prompt "Compiler optimization level" 1320 default CC_OPTIMIZE_FOR_PERFORMANCE 1321 1322config CC_OPTIMIZE_FOR_PERFORMANCE 1323 bool "Optimize for performance (-O2)" 1324 help 1325 This is the default optimization level for the kernel, building 1326 with the "-O2" compiler flag for best performance and most 1327 helpful compile-time warnings. 1328 1329config CC_OPTIMIZE_FOR_PERFORMANCE_O3 1330 bool "Optimize more for performance (-O3)" 1331 depends on ARC 1332 help 1333 Choosing this option will pass "-O3" to your compiler to optimize 1334 the kernel yet more for performance. 1335 1336config CC_OPTIMIZE_FOR_SIZE 1337 bool "Optimize for size (-Os)" 1338 help 1339 Choosing this option will pass "-Os" to your compiler resulting 1340 in a smaller kernel. 1341 1342endchoice 1343 1344config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1345 bool 1346 help 1347 This requires that the arch annotates or otherwise protects 1348 its external entry points from being discarded. Linker scripts 1349 must also merge .text.*, .data.*, and .bss.* correctly into 1350 output sections. Care must be taken not to pull in unrelated 1351 sections (e.g., '.text.init'). Typically '.' in section names 1352 is used to distinguish them from label names / C identifiers. 1353 1354config LD_DEAD_CODE_DATA_ELIMINATION 1355 bool "Dead code and data elimination (EXPERIMENTAL)" 1356 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1357 depends on EXPERT 1358 depends on $(cc-option,-ffunction-sections -fdata-sections) 1359 depends on $(ld-option,--gc-sections) 1360 help 1361 Enable this if you want to do dead code and data elimination with 1362 the linker by compiling with -ffunction-sections -fdata-sections, 1363 and linking with --gc-sections. 1364 1365 This can reduce on disk and in-memory size of the kernel 1366 code and static data, particularly for small configs and 1367 on small systems. This has the possibility of introducing 1368 silently broken kernel if the required annotations are not 1369 present. This option is not well tested yet, so use at your 1370 own risk. 1371 1372config LD_ORPHAN_WARN 1373 def_bool y 1374 depends on ARCH_WANT_LD_ORPHAN_WARN 1375 depends on !LD_IS_LLD || LLD_VERSION >= 110000 1376 depends on $(ld-option,--orphan-handling=warn) 1377 1378config SYSCTL 1379 bool 1380 1381config HAVE_UID16 1382 bool 1383 1384config SYSCTL_EXCEPTION_TRACE 1385 bool 1386 help 1387 Enable support for /proc/sys/debug/exception-trace. 1388 1389config SYSCTL_ARCH_UNALIGN_NO_WARN 1390 bool 1391 help 1392 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1393 Allows arch to define/use @no_unaligned_warning to possibly warn 1394 about unaligned access emulation going on under the hood. 1395 1396config SYSCTL_ARCH_UNALIGN_ALLOW 1397 bool 1398 help 1399 Enable support for /proc/sys/kernel/unaligned-trap 1400 Allows arches to define/use @unaligned_enabled to runtime toggle 1401 the unaligned access emulation. 1402 see arch/parisc/kernel/unaligned.c for reference 1403 1404config HAVE_PCSPKR_PLATFORM 1405 bool 1406 1407# interpreter that classic socket filters depend on 1408config BPF 1409 bool 1410 1411menuconfig EXPERT 1412 bool "Configure standard kernel features (expert users)" 1413 # Unhide debug options, to make the on-by-default options visible 1414 select DEBUG_KERNEL 1415 help 1416 This option allows certain base kernel options and settings 1417 to be disabled or tweaked. This is for specialized 1418 environments which can tolerate a "non-standard" kernel. 1419 Only use this if you really know what you are doing. 1420 1421config UID16 1422 bool "Enable 16-bit UID system calls" if EXPERT 1423 depends on HAVE_UID16 && MULTIUSER 1424 default y 1425 help 1426 This enables the legacy 16-bit UID syscall wrappers. 1427 1428config MULTIUSER 1429 bool "Multiple users, groups and capabilities support" if EXPERT 1430 default y 1431 help 1432 This option enables support for non-root users, groups and 1433 capabilities. 1434 1435 If you say N here, all processes will run with UID 0, GID 0, and all 1436 possible capabilities. Saying N here also compiles out support for 1437 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1438 setgid, and capset. 1439 1440 If unsure, say Y here. 1441 1442config SGETMASK_SYSCALL 1443 bool "sgetmask/ssetmask syscalls support" if EXPERT 1444 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1445 help 1446 sys_sgetmask and sys_ssetmask are obsolete system calls 1447 no longer supported in libc but still enabled by default in some 1448 architectures. 1449 1450 If unsure, leave the default option here. 1451 1452config SYSFS_SYSCALL 1453 bool "Sysfs syscall support" if EXPERT 1454 default y 1455 help 1456 sys_sysfs is an obsolete system call no longer supported in libc. 1457 Note that disabling this option is more secure but might break 1458 compatibility with some systems. 1459 1460 If unsure say Y here. 1461 1462config FHANDLE 1463 bool "open by fhandle syscalls" if EXPERT 1464 select EXPORTFS 1465 default y 1466 help 1467 If you say Y here, a user level program will be able to map 1468 file names to handle and then later use the handle for 1469 different file system operations. This is useful in implementing 1470 userspace file servers, which now track files using handles instead 1471 of names. The handle would remain the same even if file names 1472 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1473 syscalls. 1474 1475config POSIX_TIMERS 1476 bool "Posix Clocks & timers" if EXPERT 1477 default y 1478 help 1479 This includes native support for POSIX timers to the kernel. 1480 Some embedded systems have no use for them and therefore they 1481 can be configured out to reduce the size of the kernel image. 1482 1483 When this option is disabled, the following syscalls won't be 1484 available: timer_create, timer_gettime: timer_getoverrun, 1485 timer_settime, timer_delete, clock_adjtime, getitimer, 1486 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1487 clock_getres and clock_nanosleep syscalls will be limited to 1488 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1489 1490 If unsure say y. 1491 1492config PRINTK 1493 default y 1494 bool "Enable support for printk" if EXPERT 1495 select IRQ_WORK 1496 help 1497 This option enables normal printk support. Removing it 1498 eliminates most of the message strings from the kernel image 1499 and makes the kernel more or less silent. As this makes it 1500 very difficult to diagnose system problems, saying N here is 1501 strongly discouraged. 1502 1503config PRINTK_NMI 1504 def_bool y 1505 depends on PRINTK 1506 depends on HAVE_NMI 1507 1508config BUG 1509 bool "BUG() support" if EXPERT 1510 default y 1511 help 1512 Disabling this option eliminates support for BUG and WARN, reducing 1513 the size of your kernel image and potentially quietly ignoring 1514 numerous fatal conditions. You should only consider disabling this 1515 option for embedded systems with no facilities for reporting errors. 1516 Just say Y. 1517 1518config ELF_CORE 1519 depends on COREDUMP 1520 default y 1521 bool "Enable ELF core dumps" if EXPERT 1522 help 1523 Enable support for generating core dumps. Disabling saves about 4k. 1524 1525 1526config PCSPKR_PLATFORM 1527 bool "Enable PC-Speaker support" if EXPERT 1528 depends on HAVE_PCSPKR_PLATFORM 1529 select I8253_LOCK 1530 default y 1531 help 1532 This option allows to disable the internal PC-Speaker 1533 support, saving some memory. 1534 1535config BASE_FULL 1536 default y 1537 bool "Enable full-sized data structures for core" if EXPERT 1538 help 1539 Disabling this option reduces the size of miscellaneous core 1540 kernel data structures. This saves memory on small machines, 1541 but may reduce performance. 1542 1543config FUTEX 1544 bool "Enable futex support" if EXPERT 1545 default y 1546 imply RT_MUTEXES 1547 help 1548 Disabling this option will cause the kernel to be built without 1549 support for "fast userspace mutexes". The resulting kernel may not 1550 run glibc-based applications correctly. 1551 1552config FUTEX_PI 1553 bool 1554 depends on FUTEX && RT_MUTEXES 1555 default y 1556 1557config HAVE_FUTEX_CMPXCHG 1558 bool 1559 depends on FUTEX 1560 help 1561 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1562 is implemented and always working. This removes a couple of runtime 1563 checks. 1564 1565config EPOLL 1566 bool "Enable eventpoll support" if EXPERT 1567 default y 1568 help 1569 Disabling this option will cause the kernel to be built without 1570 support for epoll family of system calls. 1571 1572config SIGNALFD 1573 bool "Enable signalfd() system call" if EXPERT 1574 default y 1575 help 1576 Enable the signalfd() system call that allows to receive signals 1577 on a file descriptor. 1578 1579 If unsure, say Y. 1580 1581config TIMERFD 1582 bool "Enable timerfd() system call" if EXPERT 1583 default y 1584 help 1585 Enable the timerfd() system call that allows to receive timer 1586 events on a file descriptor. 1587 1588 If unsure, say Y. 1589 1590config EVENTFD 1591 bool "Enable eventfd() system call" if EXPERT 1592 default y 1593 help 1594 Enable the eventfd() system call that allows to receive both 1595 kernel notification (ie. KAIO) or userspace notifications. 1596 1597 If unsure, say Y. 1598 1599config SHMEM 1600 bool "Use full shmem filesystem" if EXPERT 1601 default y 1602 depends on MMU 1603 help 1604 The shmem is an internal filesystem used to manage shared memory. 1605 It is backed by swap and manages resource limits. It is also exported 1606 to userspace as tmpfs if TMPFS is enabled. Disabling this 1607 option replaces shmem and tmpfs with the much simpler ramfs code, 1608 which may be appropriate on small systems without swap. 1609 1610config AIO 1611 bool "Enable AIO support" if EXPERT 1612 default y 1613 help 1614 This option enables POSIX asynchronous I/O which may by used 1615 by some high performance threaded applications. Disabling 1616 this option saves about 7k. 1617 1618config IO_URING 1619 bool "Enable IO uring support" if EXPERT 1620 select IO_WQ 1621 default y 1622 help 1623 This option enables support for the io_uring interface, enabling 1624 applications to submit and complete IO through submission and 1625 completion rings that are shared between the kernel and application. 1626 1627config ADVISE_SYSCALLS 1628 bool "Enable madvise/fadvise syscalls" if EXPERT 1629 default y 1630 help 1631 This option enables the madvise and fadvise syscalls, used by 1632 applications to advise the kernel about their future memory or file 1633 usage, improving performance. If building an embedded system where no 1634 applications use these syscalls, you can disable this option to save 1635 space. 1636 1637config HAVE_ARCH_USERFAULTFD_WP 1638 bool 1639 help 1640 Arch has userfaultfd write protection support 1641 1642config MEMBARRIER 1643 bool "Enable membarrier() system call" if EXPERT 1644 default y 1645 help 1646 Enable the membarrier() system call that allows issuing memory 1647 barriers across all running threads, which can be used to distribute 1648 the cost of user-space memory barriers asymmetrically by transforming 1649 pairs of memory barriers into pairs consisting of membarrier() and a 1650 compiler barrier. 1651 1652 If unsure, say Y. 1653 1654config KALLSYMS 1655 bool "Load all symbols for debugging/ksymoops" if EXPERT 1656 default y 1657 help 1658 Say Y here to let the kernel print out symbolic crash information and 1659 symbolic stack backtraces. This increases the size of the kernel 1660 somewhat, as all symbols have to be loaded into the kernel image. 1661 1662config KALLSYMS_ALL 1663 bool "Include all symbols in kallsyms" 1664 depends on DEBUG_KERNEL && KALLSYMS 1665 help 1666 Normally kallsyms only contains the symbols of functions for nicer 1667 OOPS messages and backtraces (i.e., symbols from the text and inittext 1668 sections). This is sufficient for most cases. And only in very rare 1669 cases (e.g., when a debugger is used) all symbols are required (e.g., 1670 names of variables from the data sections, etc). 1671 1672 This option makes sure that all symbols are loaded into the kernel 1673 image (i.e., symbols from all sections) in cost of increased kernel 1674 size (depending on the kernel configuration, it may be 300KiB or 1675 something like this). 1676 1677 Say N unless you really need all symbols. 1678 1679config KALLSYMS_ABSOLUTE_PERCPU 1680 bool 1681 depends on KALLSYMS 1682 default X86_64 && SMP 1683 1684config KALLSYMS_BASE_RELATIVE 1685 bool 1686 depends on KALLSYMS 1687 default !IA64 1688 help 1689 Instead of emitting them as absolute values in the native word size, 1690 emit the symbol references in the kallsyms table as 32-bit entries, 1691 each containing a relative value in the range [base, base + U32_MAX] 1692 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1693 an absolute value in the range [0, S32_MAX] or a relative value in the 1694 range [base, base + S32_MAX], where base is the lowest relative symbol 1695 address encountered in the image. 1696 1697 On 64-bit builds, this reduces the size of the address table by 50%, 1698 but more importantly, it results in entries whose values are build 1699 time constants, and no relocation pass is required at runtime to fix 1700 up the entries based on the runtime load address of the kernel. 1701 1702# end of the "standard kernel features (expert users)" menu 1703 1704# syscall, maps, verifier 1705 1706config BPF_LSM 1707 bool "LSM Instrumentation with BPF" 1708 depends on BPF_EVENTS 1709 depends on BPF_SYSCALL 1710 depends on SECURITY 1711 depends on BPF_JIT 1712 help 1713 Enables instrumentation of the security hooks with eBPF programs for 1714 implementing dynamic MAC and Audit Policies. 1715 1716 If you are unsure how to answer this question, answer N. 1717 1718config BPF_SYSCALL 1719 bool "Enable bpf() system call" 1720 select BPF 1721 select IRQ_WORK 1722 select TASKS_TRACE_RCU 1723 default n 1724 help 1725 Enable the bpf() system call that allows to manipulate eBPF 1726 programs and maps via file descriptors. 1727 1728config ARCH_WANT_DEFAULT_BPF_JIT 1729 bool 1730 1731config BPF_JIT_ALWAYS_ON 1732 bool "Permanently enable BPF JIT and remove BPF interpreter" 1733 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1734 help 1735 Enables BPF JIT and removes BPF interpreter to avoid 1736 speculative execution of BPF instructions by the interpreter 1737 1738config BPF_JIT_DEFAULT_ON 1739 def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON 1740 depends on HAVE_EBPF_JIT && BPF_JIT 1741 1742source "kernel/bpf/preload/Kconfig" 1743 1744config USERFAULTFD 1745 bool "Enable userfaultfd() system call" 1746 depends on MMU 1747 help 1748 Enable the userfaultfd() system call that allows to intercept and 1749 handle page faults in userland. 1750 1751config ARCH_HAS_MEMBARRIER_CALLBACKS 1752 bool 1753 1754config ARCH_HAS_MEMBARRIER_SYNC_CORE 1755 bool 1756 1757config KCMP 1758 bool "Enable kcmp() system call" if EXPERT 1759 help 1760 Enable the kernel resource comparison system call. It provides 1761 user-space with the ability to compare two processes to see if they 1762 share a common resource, such as a file descriptor or even virtual 1763 memory space. 1764 1765 If unsure, say N. 1766 1767config RSEQ 1768 bool "Enable rseq() system call" if EXPERT 1769 default y 1770 depends on HAVE_RSEQ 1771 select MEMBARRIER 1772 help 1773 Enable the restartable sequences system call. It provides a 1774 user-space cache for the current CPU number value, which 1775 speeds up getting the current CPU number from user-space, 1776 as well as an ABI to speed up user-space operations on 1777 per-CPU data. 1778 1779 If unsure, say Y. 1780 1781config DEBUG_RSEQ 1782 default n 1783 bool "Enabled debugging of rseq() system call" if EXPERT 1784 depends on RSEQ && DEBUG_KERNEL 1785 help 1786 Enable extra debugging checks for the rseq system call. 1787 1788 If unsure, say N. 1789 1790config EMBEDDED 1791 bool "Embedded system" 1792 option allnoconfig_y 1793 select EXPERT 1794 help 1795 This option should be enabled if compiling the kernel for 1796 an embedded system so certain expert options are available 1797 for configuration. 1798 1799config HAVE_PERF_EVENTS 1800 bool 1801 help 1802 See tools/perf/design.txt for details. 1803 1804config PERF_USE_VMALLOC 1805 bool 1806 help 1807 See tools/perf/design.txt for details 1808 1809config PC104 1810 bool "PC/104 support" if EXPERT 1811 help 1812 Expose PC/104 form factor device drivers and options available for 1813 selection and configuration. Enable this option if your target 1814 machine has a PC/104 bus. 1815 1816menu "Kernel Performance Events And Counters" 1817 1818config PERF_EVENTS 1819 bool "Kernel performance events and counters" 1820 default y if PROFILING 1821 depends on HAVE_PERF_EVENTS 1822 select IRQ_WORK 1823 select SRCU 1824 help 1825 Enable kernel support for various performance events provided 1826 by software and hardware. 1827 1828 Software events are supported either built-in or via the 1829 use of generic tracepoints. 1830 1831 Most modern CPUs support performance events via performance 1832 counter registers. These registers count the number of certain 1833 types of hw events: such as instructions executed, cachemisses 1834 suffered, or branches mis-predicted - without slowing down the 1835 kernel or applications. These registers can also trigger interrupts 1836 when a threshold number of events have passed - and can thus be 1837 used to profile the code that runs on that CPU. 1838 1839 The Linux Performance Event subsystem provides an abstraction of 1840 these software and hardware event capabilities, available via a 1841 system call and used by the "perf" utility in tools/perf/. It 1842 provides per task and per CPU counters, and it provides event 1843 capabilities on top of those. 1844 1845 Say Y if unsure. 1846 1847config DEBUG_PERF_USE_VMALLOC 1848 default n 1849 bool "Debug: use vmalloc to back perf mmap() buffers" 1850 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1851 select PERF_USE_VMALLOC 1852 help 1853 Use vmalloc memory to back perf mmap() buffers. 1854 1855 Mostly useful for debugging the vmalloc code on platforms 1856 that don't require it. 1857 1858 Say N if unsure. 1859 1860endmenu 1861 1862config VM_EVENT_COUNTERS 1863 default y 1864 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1865 help 1866 VM event counters are needed for event counts to be shown. 1867 This option allows the disabling of the VM event counters 1868 on EXPERT systems. /proc/vmstat will only show page counts 1869 if VM event counters are disabled. 1870 1871config SLUB_DEBUG 1872 default y 1873 bool "Enable SLUB debugging support" if EXPERT 1874 depends on SLUB && SYSFS 1875 help 1876 SLUB has extensive debug support features. Disabling these can 1877 result in significant savings in code size. This also disables 1878 SLUB sysfs support. /sys/slab will not exist and there will be 1879 no support for cache validation etc. 1880 1881config COMPAT_BRK 1882 bool "Disable heap randomization" 1883 default y 1884 help 1885 Randomizing heap placement makes heap exploits harder, but it 1886 also breaks ancient binaries (including anything libc5 based). 1887 This option changes the bootup default to heap randomization 1888 disabled, and can be overridden at runtime by setting 1889 /proc/sys/kernel/randomize_va_space to 2. 1890 1891 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1892 1893choice 1894 prompt "Choose SLAB allocator" 1895 default SLUB 1896 help 1897 This option allows to select a slab allocator. 1898 1899config SLAB 1900 bool "SLAB" 1901 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1902 help 1903 The regular slab allocator that is established and known to work 1904 well in all environments. It organizes cache hot objects in 1905 per cpu and per node queues. 1906 1907config SLUB 1908 bool "SLUB (Unqueued Allocator)" 1909 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1910 help 1911 SLUB is a slab allocator that minimizes cache line usage 1912 instead of managing queues of cached objects (SLAB approach). 1913 Per cpu caching is realized using slabs of objects instead 1914 of queues of objects. SLUB can use memory efficiently 1915 and has enhanced diagnostics. SLUB is the default choice for 1916 a slab allocator. 1917 1918config SLOB 1919 depends on EXPERT 1920 bool "SLOB (Simple Allocator)" 1921 help 1922 SLOB replaces the stock allocator with a drastically simpler 1923 allocator. SLOB is generally more space efficient but 1924 does not perform as well on large systems. 1925 1926endchoice 1927 1928config SLAB_MERGE_DEFAULT 1929 bool "Allow slab caches to be merged" 1930 default y 1931 help 1932 For reduced kernel memory fragmentation, slab caches can be 1933 merged when they share the same size and other characteristics. 1934 This carries a risk of kernel heap overflows being able to 1935 overwrite objects from merged caches (and more easily control 1936 cache layout), which makes such heap attacks easier to exploit 1937 by attackers. By keeping caches unmerged, these kinds of exploits 1938 can usually only damage objects in the same cache. To disable 1939 merging at runtime, "slab_nomerge" can be passed on the kernel 1940 command line. 1941 1942config SLAB_FREELIST_RANDOM 1943 bool "Randomize slab freelist" 1944 depends on SLAB || SLUB 1945 help 1946 Randomizes the freelist order used on creating new pages. This 1947 security feature reduces the predictability of the kernel slab 1948 allocator against heap overflows. 1949 1950config SLAB_FREELIST_HARDENED 1951 bool "Harden slab freelist metadata" 1952 depends on SLAB || SLUB 1953 help 1954 Many kernel heap attacks try to target slab cache metadata and 1955 other infrastructure. This options makes minor performance 1956 sacrifices to harden the kernel slab allocator against common 1957 freelist exploit methods. Some slab implementations have more 1958 sanity-checking than others. This option is most effective with 1959 CONFIG_SLUB. 1960 1961config SHUFFLE_PAGE_ALLOCATOR 1962 bool "Page allocator randomization" 1963 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1964 help 1965 Randomization of the page allocator improves the average 1966 utilization of a direct-mapped memory-side-cache. See section 1967 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1968 6.2a specification for an example of how a platform advertises 1969 the presence of a memory-side-cache. There are also incidental 1970 security benefits as it reduces the predictability of page 1971 allocations to compliment SLAB_FREELIST_RANDOM, but the 1972 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1973 10th order of pages is selected based on cache utilization 1974 benefits on x86. 1975 1976 While the randomization improves cache utilization it may 1977 negatively impact workloads on platforms without a cache. For 1978 this reason, by default, the randomization is enabled only 1979 after runtime detection of a direct-mapped memory-side-cache. 1980 Otherwise, the randomization may be force enabled with the 1981 'page_alloc.shuffle' kernel command line parameter. 1982 1983 Say Y if unsure. 1984 1985config SLUB_CPU_PARTIAL 1986 default y 1987 depends on SLUB && SMP 1988 bool "SLUB per cpu partial cache" 1989 help 1990 Per cpu partial caches accelerate objects allocation and freeing 1991 that is local to a processor at the price of more indeterminism 1992 in the latency of the free. On overflow these caches will be cleared 1993 which requires the taking of locks that may cause latency spikes. 1994 Typically one would choose no for a realtime system. 1995 1996config MMAP_ALLOW_UNINITIALIZED 1997 bool "Allow mmapped anonymous memory to be uninitialized" 1998 depends on EXPERT && !MMU 1999 default n 2000 help 2001 Normally, and according to the Linux spec, anonymous memory obtained 2002 from mmap() has its contents cleared before it is passed to 2003 userspace. Enabling this config option allows you to request that 2004 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 2005 providing a huge performance boost. If this option is not enabled, 2006 then the flag will be ignored. 2007 2008 This is taken advantage of by uClibc's malloc(), and also by 2009 ELF-FDPIC binfmt's brk and stack allocator. 2010 2011 Because of the obvious security issues, this option should only be 2012 enabled on embedded devices where you control what is run in 2013 userspace. Since that isn't generally a problem on no-MMU systems, 2014 it is normally safe to say Y here. 2015 2016 See Documentation/admin-guide/mm/nommu-mmap.rst for more information. 2017 2018config SYSTEM_DATA_VERIFICATION 2019 def_bool n 2020 select SYSTEM_TRUSTED_KEYRING 2021 select KEYS 2022 select CRYPTO 2023 select CRYPTO_RSA 2024 select ASYMMETRIC_KEY_TYPE 2025 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 2026 select ASN1 2027 select OID_REGISTRY 2028 select X509_CERTIFICATE_PARSER 2029 select PKCS7_MESSAGE_PARSER 2030 help 2031 Provide PKCS#7 message verification using the contents of the system 2032 trusted keyring to provide public keys. This then can be used for 2033 module verification, kexec image verification and firmware blob 2034 verification. 2035 2036config PROFILING 2037 bool "Profiling support" 2038 help 2039 Say Y here to enable the extended profiling support mechanisms used 2040 by profilers. 2041 2042# 2043# Place an empty function call at each tracepoint site. Can be 2044# dynamically changed for a probe function. 2045# 2046config TRACEPOINTS 2047 bool 2048 2049endmenu # General setup 2050 2051source "arch/Kconfig" 2052 2053config RT_MUTEXES 2054 bool 2055 2056config BASE_SMALL 2057 int 2058 default 0 if BASE_FULL 2059 default 1 if !BASE_FULL 2060 2061config MODULE_SIG_FORMAT 2062 def_bool n 2063 select SYSTEM_DATA_VERIFICATION 2064 2065menuconfig MODULES 2066 bool "Enable loadable module support" 2067 option modules 2068 help 2069 Kernel modules are small pieces of compiled code which can 2070 be inserted in the running kernel, rather than being 2071 permanently built into the kernel. You use the "modprobe" 2072 tool to add (and sometimes remove) them. If you say Y here, 2073 many parts of the kernel can be built as modules (by 2074 answering M instead of Y where indicated): this is most 2075 useful for infrequently used options which are not required 2076 for booting. For more information, see the man pages for 2077 modprobe, lsmod, modinfo, insmod and rmmod. 2078 2079 If you say Y here, you will need to run "make 2080 modules_install" to put the modules under /lib/modules/ 2081 where modprobe can find them (you may need to be root to do 2082 this). 2083 2084 If unsure, say Y. 2085 2086if MODULES 2087 2088config MODULE_FORCE_LOAD 2089 bool "Forced module loading" 2090 default n 2091 help 2092 Allow loading of modules without version information (ie. modprobe 2093 --force). Forced module loading sets the 'F' (forced) taint flag and 2094 is usually a really bad idea. 2095 2096config MODULE_UNLOAD 2097 bool "Module unloading" 2098 help 2099 Without this option you will not be able to unload any 2100 modules (note that some modules may not be unloadable 2101 anyway), which makes your kernel smaller, faster 2102 and simpler. If unsure, say Y. 2103 2104config MODULE_FORCE_UNLOAD 2105 bool "Forced module unloading" 2106 depends on MODULE_UNLOAD 2107 help 2108 This option allows you to force a module to unload, even if the 2109 kernel believes it is unsafe: the kernel will remove the module 2110 without waiting for anyone to stop using it (using the -f option to 2111 rmmod). This is mainly for kernel developers and desperate users. 2112 If unsure, say N. 2113 2114config MODVERSIONS 2115 bool "Module versioning support" 2116 help 2117 Usually, you have to use modules compiled with your kernel. 2118 Saying Y here makes it sometimes possible to use modules 2119 compiled for different kernels, by adding enough information 2120 to the modules to (hopefully) spot any changes which would 2121 make them incompatible with the kernel you are running. If 2122 unsure, say N. 2123 2124config ASM_MODVERSIONS 2125 bool 2126 default HAVE_ASM_MODVERSIONS && MODVERSIONS 2127 help 2128 This enables module versioning for exported symbols also from 2129 assembly. This can be enabled only when the target architecture 2130 supports it. 2131 2132config MODULE_REL_CRCS 2133 bool 2134 depends on MODVERSIONS 2135 2136config MODULE_SRCVERSION_ALL 2137 bool "Source checksum for all modules" 2138 help 2139 Modules which contain a MODULE_VERSION get an extra "srcversion" 2140 field inserted into their modinfo section, which contains a 2141 sum of the source files which made it. This helps maintainers 2142 see exactly which source was used to build a module (since 2143 others sometimes change the module source without updating 2144 the version). With this option, such a "srcversion" field 2145 will be created for all modules. If unsure, say N. 2146 2147config MODULE_SIG 2148 bool "Module signature verification" 2149 select MODULE_SIG_FORMAT 2150 help 2151 Check modules for valid signatures upon load: the signature 2152 is simply appended to the module. For more information see 2153 <file:Documentation/admin-guide/module-signing.rst>. 2154 2155 Note that this option adds the OpenSSL development packages as a 2156 kernel build dependency so that the signing tool can use its crypto 2157 library. 2158 2159 You should enable this option if you wish to use either 2160 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via 2161 another LSM - otherwise unsigned modules will be loadable regardless 2162 of the lockdown policy. 2163 2164 !!!WARNING!!! If you enable this option, you MUST make sure that the 2165 module DOES NOT get stripped after being signed. This includes the 2166 debuginfo strip done by some packagers (such as rpmbuild) and 2167 inclusion into an initramfs that wants the module size reduced. 2168 2169config MODULE_SIG_FORCE 2170 bool "Require modules to be validly signed" 2171 depends on MODULE_SIG 2172 help 2173 Reject unsigned modules or signed modules for which we don't have a 2174 key. Without this, such modules will simply taint the kernel. 2175 2176config MODULE_SIG_ALL 2177 bool "Automatically sign all modules" 2178 default y 2179 depends on MODULE_SIG 2180 help 2181 Sign all modules during make modules_install. Without this option, 2182 modules must be signed manually, using the scripts/sign-file tool. 2183 2184comment "Do not forget to sign required modules with scripts/sign-file" 2185 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2186 2187choice 2188 prompt "Which hash algorithm should modules be signed with?" 2189 depends on MODULE_SIG 2190 help 2191 This determines which sort of hashing algorithm will be used during 2192 signature generation. This algorithm _must_ be built into the kernel 2193 directly so that signature verification can take place. It is not 2194 possible to load a signed module containing the algorithm to check 2195 the signature on that module. 2196 2197config MODULE_SIG_SHA1 2198 bool "Sign modules with SHA-1" 2199 select CRYPTO_SHA1 2200 2201config MODULE_SIG_SHA224 2202 bool "Sign modules with SHA-224" 2203 select CRYPTO_SHA256 2204 2205config MODULE_SIG_SHA256 2206 bool "Sign modules with SHA-256" 2207 select CRYPTO_SHA256 2208 2209config MODULE_SIG_SHA384 2210 bool "Sign modules with SHA-384" 2211 select CRYPTO_SHA512 2212 2213config MODULE_SIG_SHA512 2214 bool "Sign modules with SHA-512" 2215 select CRYPTO_SHA512 2216 2217endchoice 2218 2219config MODULE_SIG_HASH 2220 string 2221 depends on MODULE_SIG 2222 default "sha1" if MODULE_SIG_SHA1 2223 default "sha224" if MODULE_SIG_SHA224 2224 default "sha256" if MODULE_SIG_SHA256 2225 default "sha384" if MODULE_SIG_SHA384 2226 default "sha512" if MODULE_SIG_SHA512 2227 2228choice 2229 prompt "Module compression mode" 2230 help 2231 This option allows you to choose the algorithm which will be used to 2232 compress modules when 'make modules_install' is run. (or, you can 2233 choose to not compress modules at all.) 2234 2235 External modules will also be compressed in the same way during the 2236 installation. 2237 2238 For modules inside an initrd or initramfs, it's more efficient to 2239 compress the whole initrd or initramfs instead. 2240 2241 This is fully compatible with signed modules. 2242 2243 Please note that the tool used to load modules needs to support the 2244 corresponding algorithm. module-init-tools MAY support gzip, and kmod 2245 MAY support gzip, xz and zstd. 2246 2247 Your build system needs to provide the appropriate compression tool 2248 to compress the modules. 2249 2250 If in doubt, select 'None'. 2251 2252config MODULE_COMPRESS_NONE 2253 bool "None" 2254 help 2255 Do not compress modules. The installed modules are suffixed 2256 with .ko. 2257 2258config MODULE_COMPRESS_GZIP 2259 bool "GZIP" 2260 help 2261 Compress modules with GZIP. The installed modules are suffixed 2262 with .ko.gz. 2263 2264config MODULE_COMPRESS_XZ 2265 bool "XZ" 2266 help 2267 Compress modules with XZ. The installed modules are suffixed 2268 with .ko.xz. 2269 2270config MODULE_COMPRESS_ZSTD 2271 bool "ZSTD" 2272 help 2273 Compress modules with ZSTD. The installed modules are suffixed 2274 with .ko.zst. 2275 2276endchoice 2277 2278config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS 2279 bool "Allow loading of modules with missing namespace imports" 2280 help 2281 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in 2282 a namespace. A module that makes use of a symbol exported with such a 2283 namespace is required to import the namespace via MODULE_IMPORT_NS(). 2284 There is no technical reason to enforce correct namespace imports, 2285 but it creates consistency between symbols defining namespaces and 2286 users importing namespaces they make use of. This option relaxes this 2287 requirement and lifts the enforcement when loading a module. 2288 2289 If unsure, say N. 2290 2291config TRIM_UNUSED_KSYMS 2292 bool "Trim unused exported kernel symbols" if EXPERT 2293 depends on !COMPILE_TEST 2294 help 2295 The kernel and some modules make many symbols available for 2296 other modules to use via EXPORT_SYMBOL() and variants. Depending 2297 on the set of modules being selected in your kernel configuration, 2298 many of those exported symbols might never be used. 2299 2300 This option allows for unused exported symbols to be dropped from 2301 the build. In turn, this provides the compiler more opportunities 2302 (especially when using LTO) for optimizing the code and reducing 2303 binary size. This might have some security advantages as well. 2304 2305 If unsure, or if you need to build out-of-tree modules, say N. 2306 2307config UNUSED_KSYMS_WHITELIST 2308 string "Whitelist of symbols to keep in ksymtab" 2309 depends on TRIM_UNUSED_KSYMS 2310 help 2311 By default, all unused exported symbols will be un-exported from the 2312 build when TRIM_UNUSED_KSYMS is selected. 2313 2314 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept 2315 exported at all times, even in absence of in-tree users. The value to 2316 set here is the path to a text file containing the list of symbols, 2317 one per line. The path can be absolute, or relative to the kernel 2318 source tree. 2319 2320endif # MODULES 2321 2322config MODULES_TREE_LOOKUP 2323 def_bool y 2324 depends on PERF_EVENTS || TRACING 2325 2326config INIT_ALL_POSSIBLE 2327 bool 2328 help 2329 Back when each arch used to define their own cpu_online_mask and 2330 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2331 with all 1s, and others with all 0s. When they were centralised, 2332 it was better to provide this option than to break all the archs 2333 and have several arch maintainers pursuing me down dark alleys. 2334 2335source "block/Kconfig" 2336 2337config PREEMPT_NOTIFIERS 2338 bool 2339 2340config PADATA 2341 depends on SMP 2342 bool 2343 2344config ASN1 2345 tristate 2346 help 2347 Build a simple ASN.1 grammar compiler that produces a bytecode output 2348 that can be interpreted by the ASN.1 stream decoder and used to 2349 inform it as to what tags are to be expected in a stream and what 2350 functions to call on what tags. 2351 2352source "kernel/Kconfig.locks" 2353 2354config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 2355 bool 2356 2357config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2358 bool 2359 2360# It may be useful for an architecture to override the definitions of the 2361# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2362# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2363# different calling convention for syscalls. They can also override the 2364# macros for not-implemented syscalls in kernel/sys_ni.c and 2365# kernel/time/posix-stubs.c. All these overrides need to be available in 2366# <asm/syscall_wrapper.h>. 2367config ARCH_HAS_SYSCALL_WRAPPER 2368 def_bool n 2369