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