1config DEFCONFIG_LIST 2 string 3 depends on !UML 4 option defconfig_list 5 default "/lib/modules/$(shell,uname -r)/.config" 6 default "/etc/kernel-config" 7 default "/boot/config-$(shell,uname -r)" 8 default ARCH_DEFCONFIG 9 default "arch/$(ARCH)/defconfig" 10 11config CC_IS_GCC 12 def_bool $(success,$(CC) --version | head -n 1 | grep -q gcc) 13 14config GCC_VERSION 15 int 16 default $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) if CC_IS_GCC 17 default 0 18 19config CC_IS_CLANG 20 def_bool $(success,$(CC) --version | head -n 1 | grep -q clang) 21 22config CLANG_VERSION 23 int 24 default $(shell,$(srctree)/scripts/clang-version.sh $(CC)) 25 26config CC_HAS_ASM_GOTO 27 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) 28 29config CC_HAS_WARN_MAYBE_UNINITIALIZED 30 def_bool $(cc-option,-Wmaybe-uninitialized) 31 help 32 GCC >= 4.7 supports this option. 33 34config CC_DISABLE_WARN_MAYBE_UNINITIALIZED 35 bool 36 depends on CC_HAS_WARN_MAYBE_UNINITIALIZED 37 default CC_IS_GCC && GCC_VERSION < 40900 # unreliable for GCC < 4.9 38 help 39 GCC's -Wmaybe-uninitialized is not reliable by definition. 40 Lots of false positive warnings are produced in some cases. 41 42 If this option is enabled, -Wno-maybe-uninitialzed is passed 43 to the compiler to suppress maybe-uninitialized warnings. 44 45config CONSTRUCTORS 46 bool 47 depends on !UML 48 49config IRQ_WORK 50 bool 51 52config BUILDTIME_EXTABLE_SORT 53 bool 54 55config THREAD_INFO_IN_TASK 56 bool 57 help 58 Select this to move thread_info off the stack into task_struct. To 59 make this work, an arch will need to remove all thread_info fields 60 except flags and fix any runtime bugs. 61 62 One subtle change that will be needed is to use try_get_task_stack() 63 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 64 65menu "General setup" 66 67config BROKEN 68 bool 69 70config BROKEN_ON_SMP 71 bool 72 depends on BROKEN || !SMP 73 default y 74 75config INIT_ENV_ARG_LIMIT 76 int 77 default 32 if !UML 78 default 128 if UML 79 help 80 Maximum of each of the number of arguments and environment 81 variables passed to init from the kernel command line. 82 83config COMPILE_TEST 84 bool "Compile also drivers which will not load" 85 depends on !UML 86 default n 87 help 88 Some drivers can be compiled on a different platform than they are 89 intended to be run on. Despite they cannot be loaded there (or even 90 when they load they cannot be used due to missing HW support), 91 developers still, opposing to distributors, might want to build such 92 drivers to compile-test them. 93 94 If you are a developer and want to build everything available, say Y 95 here. If you are a user/distributor, say N here to exclude useless 96 drivers to be distributed. 97 98config LOCALVERSION 99 string "Local version - append to kernel release" 100 help 101 Append an extra string to the end of your kernel version. 102 This will show up when you type uname, for example. 103 The string you set here will be appended after the contents of 104 any files with a filename matching localversion* in your 105 object and source tree, in that order. Your total string can 106 be a maximum of 64 characters. 107 108config LOCALVERSION_AUTO 109 bool "Automatically append version information to the version string" 110 default y 111 depends on !COMPILE_TEST 112 help 113 This will try to automatically determine if the current tree is a 114 release tree by looking for git tags that belong to the current 115 top of tree revision. 116 117 A string of the format -gxxxxxxxx will be added to the localversion 118 if a git-based tree is found. The string generated by this will be 119 appended after any matching localversion* files, and after the value 120 set in CONFIG_LOCALVERSION. 121 122 (The actual string used here is the first eight characters produced 123 by running the command: 124 125 $ git rev-parse --verify HEAD 126 127 which is done within the script "scripts/setlocalversion".) 128 129config BUILD_SALT 130 string "Build ID Salt" 131 default "" 132 help 133 The build ID is used to link binaries and their debug info. Setting 134 this option will use the value in the calculation of the build id. 135 This is mostly useful for distributions which want to ensure the 136 build is unique between builds. It's safe to leave the default. 137 138config HAVE_KERNEL_GZIP 139 bool 140 141config HAVE_KERNEL_BZIP2 142 bool 143 144config HAVE_KERNEL_LZMA 145 bool 146 147config HAVE_KERNEL_XZ 148 bool 149 150config HAVE_KERNEL_LZO 151 bool 152 153config HAVE_KERNEL_LZ4 154 bool 155 156config HAVE_KERNEL_UNCOMPRESSED 157 bool 158 159choice 160 prompt "Kernel compression mode" 161 default KERNEL_GZIP 162 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED 163 help 164 The linux kernel is a kind of self-extracting executable. 165 Several compression algorithms are available, which differ 166 in efficiency, compression and decompression speed. 167 Compression speed is only relevant when building a kernel. 168 Decompression speed is relevant at each boot. 169 170 If you have any problems with bzip2 or lzma compressed 171 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 172 version of this functionality (bzip2 only), for 2.4, was 173 supplied by Christian Ludwig) 174 175 High compression options are mostly useful for users, who 176 are low on disk space (embedded systems), but for whom ram 177 size matters less. 178 179 If in doubt, select 'gzip' 180 181config KERNEL_GZIP 182 bool "Gzip" 183 depends on HAVE_KERNEL_GZIP 184 help 185 The old and tried gzip compression. It provides a good balance 186 between compression ratio and decompression speed. 187 188config KERNEL_BZIP2 189 bool "Bzip2" 190 depends on HAVE_KERNEL_BZIP2 191 help 192 Its compression ratio and speed is intermediate. 193 Decompression speed is slowest among the choices. The kernel 194 size is about 10% smaller with bzip2, in comparison to gzip. 195 Bzip2 uses a large amount of memory. For modern kernels you 196 will need at least 8MB RAM or more for booting. 197 198config KERNEL_LZMA 199 bool "LZMA" 200 depends on HAVE_KERNEL_LZMA 201 help 202 This compression algorithm's ratio is best. Decompression speed 203 is between gzip and bzip2. Compression is slowest. 204 The kernel size is about 33% smaller with LZMA in comparison to gzip. 205 206config KERNEL_XZ 207 bool "XZ" 208 depends on HAVE_KERNEL_XZ 209 help 210 XZ uses the LZMA2 algorithm and instruction set specific 211 BCJ filters which can improve compression ratio of executable 212 code. The size of the kernel is about 30% smaller with XZ in 213 comparison to gzip. On architectures for which there is a BCJ 214 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 215 will create a few percent smaller kernel than plain LZMA. 216 217 The speed is about the same as with LZMA: The decompression 218 speed of XZ is better than that of bzip2 but worse than gzip 219 and LZO. Compression is slow. 220 221config KERNEL_LZO 222 bool "LZO" 223 depends on HAVE_KERNEL_LZO 224 help 225 Its compression ratio is the poorest among the choices. The kernel 226 size is about 10% bigger than gzip; however its speed 227 (both compression and decompression) is the fastest. 228 229config KERNEL_LZ4 230 bool "LZ4" 231 depends on HAVE_KERNEL_LZ4 232 help 233 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 234 A preliminary version of LZ4 de/compression tool is available at 235 <https://code.google.com/p/lz4/>. 236 237 Its compression ratio is worse than LZO. The size of the kernel 238 is about 8% bigger than LZO. But the decompression speed is 239 faster than LZO. 240 241config KERNEL_UNCOMPRESSED 242 bool "None" 243 depends on HAVE_KERNEL_UNCOMPRESSED 244 help 245 Produce uncompressed kernel image. This option is usually not what 246 you want. It is useful for debugging the kernel in slow simulation 247 environments, where decompressing and moving the kernel is awfully 248 slow. This option allows early boot code to skip the decompressor 249 and jump right at uncompressed kernel image. 250 251endchoice 252 253config DEFAULT_HOSTNAME 254 string "Default hostname" 255 default "(none)" 256 help 257 This option determines the default system hostname before userspace 258 calls sethostname(2). The kernel traditionally uses "(none)" here, 259 but you may wish to use a different default here to make a minimal 260 system more usable with less configuration. 261 262# 263# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can 264# add proper SWAP support to them, in which case this can be remove. 265# 266config ARCH_NO_SWAP 267 bool 268 269config SWAP 270 bool "Support for paging of anonymous memory (swap)" 271 depends on MMU && BLOCK && !ARCH_NO_SWAP 272 default y 273 help 274 This option allows you to choose whether you want to have support 275 for so called swap devices or swap files in your kernel that are 276 used to provide more virtual memory than the actual RAM present 277 in your computer. If unsure say Y. 278 279config SYSVIPC 280 bool "System V IPC" 281 ---help--- 282 Inter Process Communication is a suite of library functions and 283 system calls which let processes (running programs) synchronize and 284 exchange information. It is generally considered to be a good thing, 285 and some programs won't run unless you say Y here. In particular, if 286 you want to run the DOS emulator dosemu under Linux (read the 287 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 288 you'll need to say Y here. 289 290 You can find documentation about IPC with "info ipc" and also in 291 section 6.4 of the Linux Programmer's Guide, available from 292 <http://www.tldp.org/guides.html>. 293 294config SYSVIPC_SYSCTL 295 bool 296 depends on SYSVIPC 297 depends on SYSCTL 298 default y 299 300config POSIX_MQUEUE 301 bool "POSIX Message Queues" 302 depends on NET 303 ---help--- 304 POSIX variant of message queues is a part of IPC. In POSIX message 305 queues every message has a priority which decides about succession 306 of receiving it by a process. If you want to compile and run 307 programs written e.g. for Solaris with use of its POSIX message 308 queues (functions mq_*) say Y here. 309 310 POSIX message queues are visible as a filesystem called 'mqueue' 311 and can be mounted somewhere if you want to do filesystem 312 operations on message queues. 313 314 If unsure, say Y. 315 316config POSIX_MQUEUE_SYSCTL 317 bool 318 depends on POSIX_MQUEUE 319 depends on SYSCTL 320 default y 321 322config CROSS_MEMORY_ATTACH 323 bool "Enable process_vm_readv/writev syscalls" 324 depends on MMU 325 default y 326 help 327 Enabling this option adds the system calls process_vm_readv and 328 process_vm_writev which allow a process with the correct privileges 329 to directly read from or write to another process' address space. 330 See the man page for more details. 331 332config USELIB 333 bool "uselib syscall" 334 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION 335 help 336 This option enables the uselib syscall, a system call used in the 337 dynamic linker from libc5 and earlier. glibc does not use this 338 system call. If you intend to run programs built on libc5 or 339 earlier, you may need to enable this syscall. Current systems 340 running glibc can safely disable this. 341 342config AUDIT 343 bool "Auditing support" 344 depends on NET 345 help 346 Enable auditing infrastructure that can be used with another 347 kernel subsystem, such as SELinux (which requires this for 348 logging of avc messages output). System call auditing is included 349 on architectures which support it. 350 351config HAVE_ARCH_AUDITSYSCALL 352 bool 353 354config AUDITSYSCALL 355 def_bool y 356 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 357 select FSNOTIFY 358 359source "kernel/irq/Kconfig" 360source "kernel/time/Kconfig" 361source "kernel/Kconfig.preempt" 362 363menu "CPU/Task time and stats accounting" 364 365config VIRT_CPU_ACCOUNTING 366 bool 367 368choice 369 prompt "Cputime accounting" 370 default TICK_CPU_ACCOUNTING if !PPC64 371 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 372 373# Kind of a stub config for the pure tick based cputime accounting 374config TICK_CPU_ACCOUNTING 375 bool "Simple tick based cputime accounting" 376 depends on !S390 && !NO_HZ_FULL 377 help 378 This is the basic tick based cputime accounting that maintains 379 statistics about user, system and idle time spent on per jiffies 380 granularity. 381 382 If unsure, say Y. 383 384config VIRT_CPU_ACCOUNTING_NATIVE 385 bool "Deterministic task and CPU time accounting" 386 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 387 select VIRT_CPU_ACCOUNTING 388 help 389 Select this option to enable more accurate task and CPU time 390 accounting. This is done by reading a CPU counter on each 391 kernel entry and exit and on transitions within the kernel 392 between system, softirq and hardirq state, so there is a 393 small performance impact. In the case of s390 or IBM POWER > 5, 394 this also enables accounting of stolen time on logically-partitioned 395 systems. 396 397config VIRT_CPU_ACCOUNTING_GEN 398 bool "Full dynticks CPU time accounting" 399 depends on HAVE_CONTEXT_TRACKING 400 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 401 depends on GENERIC_CLOCKEVENTS 402 select VIRT_CPU_ACCOUNTING 403 select CONTEXT_TRACKING 404 help 405 Select this option to enable task and CPU time accounting on full 406 dynticks systems. This accounting is implemented by watching every 407 kernel-user boundaries using the context tracking subsystem. 408 The accounting is thus performed at the expense of some significant 409 overhead. 410 411 For now this is only useful if you are working on the full 412 dynticks subsystem development. 413 414 If unsure, say N. 415 416endchoice 417 418config IRQ_TIME_ACCOUNTING 419 bool "Fine granularity task level IRQ time accounting" 420 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 421 help 422 Select this option to enable fine granularity task irq time 423 accounting. This is done by reading a timestamp on each 424 transitions between softirq and hardirq state, so there can be a 425 small performance impact. 426 427 If in doubt, say N here. 428 429config HAVE_SCHED_AVG_IRQ 430 def_bool y 431 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 432 depends on SMP 433 434config BSD_PROCESS_ACCT 435 bool "BSD Process Accounting" 436 depends on MULTIUSER 437 help 438 If you say Y here, a user level program will be able to instruct the 439 kernel (via a special system call) to write process accounting 440 information to a file: whenever a process exits, information about 441 that process will be appended to the file by the kernel. The 442 information includes things such as creation time, owning user, 443 command name, memory usage, controlling terminal etc. (the complete 444 list is in the struct acct in <file:include/linux/acct.h>). It is 445 up to the user level program to do useful things with this 446 information. This is generally a good idea, so say Y. 447 448config BSD_PROCESS_ACCT_V3 449 bool "BSD Process Accounting version 3 file format" 450 depends on BSD_PROCESS_ACCT 451 default n 452 help 453 If you say Y here, the process accounting information is written 454 in a new file format that also logs the process IDs of each 455 process and its parent. Note that this file format is incompatible 456 with previous v0/v1/v2 file formats, so you will need updated tools 457 for processing it. A preliminary version of these tools is available 458 at <http://www.gnu.org/software/acct/>. 459 460config TASKSTATS 461 bool "Export task/process statistics through netlink" 462 depends on NET 463 depends on MULTIUSER 464 default n 465 help 466 Export selected statistics for tasks/processes through the 467 generic netlink interface. Unlike BSD process accounting, the 468 statistics are available during the lifetime of tasks/processes as 469 responses to commands. Like BSD accounting, they are sent to user 470 space on task exit. 471 472 Say N if unsure. 473 474config TASK_DELAY_ACCT 475 bool "Enable per-task delay accounting" 476 depends on TASKSTATS 477 select SCHED_INFO 478 help 479 Collect information on time spent by a task waiting for system 480 resources like cpu, synchronous block I/O completion and swapping 481 in pages. Such statistics can help in setting a task's priorities 482 relative to other tasks for cpu, io, rss limits etc. 483 484 Say N if unsure. 485 486config TASK_XACCT 487 bool "Enable extended accounting over taskstats" 488 depends on TASKSTATS 489 help 490 Collect extended task accounting data and send the data 491 to userland for processing over the taskstats interface. 492 493 Say N if unsure. 494 495config TASK_IO_ACCOUNTING 496 bool "Enable per-task storage I/O accounting" 497 depends on TASK_XACCT 498 help 499 Collect information on the number of bytes of storage I/O which this 500 task has caused. 501 502 Say N if unsure. 503 504config PSI 505 bool "Pressure stall information tracking" 506 help 507 Collect metrics that indicate how overcommitted the CPU, memory, 508 and IO capacity are in the system. 509 510 If you say Y here, the kernel will create /proc/pressure/ with the 511 pressure statistics files cpu, memory, and io. These will indicate 512 the share of walltime in which some or all tasks in the system are 513 delayed due to contention of the respective resource. 514 515 In kernels with cgroup support, cgroups (cgroup2 only) will 516 have cpu.pressure, memory.pressure, and io.pressure files, 517 which aggregate pressure stalls for the grouped tasks only. 518 519 For more details see Documentation/accounting/psi.txt. 520 521 Say N if unsure. 522 523config PSI_DEFAULT_DISABLED 524 bool "Require boot parameter to enable pressure stall information tracking" 525 default n 526 depends on PSI 527 help 528 If set, pressure stall information tracking will be disabled 529 per default but can be enabled through passing psi=1 on the 530 kernel commandline during boot. 531 532 This feature adds some code to the task wakeup and sleep 533 paths of the scheduler. The overhead is too low to affect 534 common scheduling-intense workloads in practice (such as 535 webservers, memcache), but it does show up in artificial 536 scheduler stress tests, such as hackbench. 537 538 If you are paranoid and not sure what the kernel will be 539 used for, say Y. 540 541 Say N if unsure. 542 543endmenu # "CPU/Task time and stats accounting" 544 545config CPU_ISOLATION 546 bool "CPU isolation" 547 depends on SMP || COMPILE_TEST 548 default y 549 help 550 Make sure that CPUs running critical tasks are not disturbed by 551 any source of "noise" such as unbound workqueues, timers, kthreads... 552 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 553 the "isolcpus=" boot parameter. 554 555 Say Y if unsure. 556 557source "kernel/rcu/Kconfig" 558 559config BUILD_BIN2C 560 bool 561 default n 562 563config IKCONFIG 564 tristate "Kernel .config support" 565 ---help--- 566 This option enables the complete Linux kernel ".config" file 567 contents to be saved in the kernel. It provides documentation 568 of which kernel options are used in a running kernel or in an 569 on-disk kernel. This information can be extracted from the kernel 570 image file with the script scripts/extract-ikconfig and used as 571 input to rebuild the current kernel or to build another kernel. 572 It can also be extracted from a running kernel by reading 573 /proc/config.gz if enabled (below). 574 575config IKCONFIG_PROC 576 bool "Enable access to .config through /proc/config.gz" 577 depends on IKCONFIG && PROC_FS 578 ---help--- 579 This option enables access to the kernel configuration file 580 through /proc/config.gz. 581 582config IKHEADERS_PROC 583 tristate "Enable kernel header artifacts through /proc/kheaders.tar.xz" 584 depends on PROC_FS 585 help 586 This option enables access to the kernel header and other artifacts that 587 are generated during the build process. These can be used to build eBPF 588 tracing programs, or similar programs. If you build the headers as a 589 module, a module called kheaders.ko is built which can be loaded on-demand 590 to get access to the headers. 591 592config LOG_BUF_SHIFT 593 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 594 range 12 25 595 default 17 596 depends on PRINTK 597 help 598 Select the minimal kernel log buffer size as a power of 2. 599 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 600 parameter, see below. Any higher size also might be forced 601 by "log_buf_len" boot parameter. 602 603 Examples: 604 17 => 128 KB 605 16 => 64 KB 606 15 => 32 KB 607 14 => 16 KB 608 13 => 8 KB 609 12 => 4 KB 610 611config LOG_CPU_MAX_BUF_SHIFT 612 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 613 depends on SMP 614 range 0 21 615 default 12 if !BASE_SMALL 616 default 0 if BASE_SMALL 617 depends on PRINTK 618 help 619 This option allows to increase the default ring buffer size 620 according to the number of CPUs. The value defines the contribution 621 of each CPU as a power of 2. The used space is typically only few 622 lines however it might be much more when problems are reported, 623 e.g. backtraces. 624 625 The increased size means that a new buffer has to be allocated and 626 the original static one is unused. It makes sense only on systems 627 with more CPUs. Therefore this value is used only when the sum of 628 contributions is greater than the half of the default kernel ring 629 buffer as defined by LOG_BUF_SHIFT. The default values are set 630 so that more than 64 CPUs are needed to trigger the allocation. 631 632 Also this option is ignored when "log_buf_len" kernel parameter is 633 used as it forces an exact (power of two) size of the ring buffer. 634 635 The number of possible CPUs is used for this computation ignoring 636 hotplugging making the computation optimal for the worst case 637 scenario while allowing a simple algorithm to be used from bootup. 638 639 Examples shift values and their meaning: 640 17 => 128 KB for each CPU 641 16 => 64 KB for each CPU 642 15 => 32 KB for each CPU 643 14 => 16 KB for each CPU 644 13 => 8 KB for each CPU 645 12 => 4 KB for each CPU 646 647config PRINTK_SAFE_LOG_BUF_SHIFT 648 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 649 range 10 21 650 default 13 651 depends on PRINTK 652 help 653 Select the size of an alternate printk per-CPU buffer where messages 654 printed from usafe contexts are temporary stored. One example would 655 be NMI messages, another one - printk recursion. The messages are 656 copied to the main log buffer in a safe context to avoid a deadlock. 657 The value defines the size as a power of 2. 658 659 Those messages are rare and limited. The largest one is when 660 a backtrace is printed. It usually fits into 4KB. Select 661 8KB if you want to be on the safe side. 662 663 Examples: 664 17 => 128 KB for each CPU 665 16 => 64 KB for each CPU 666 15 => 32 KB for each CPU 667 14 => 16 KB for each CPU 668 13 => 8 KB for each CPU 669 12 => 4 KB for each CPU 670 671# 672# Architectures with an unreliable sched_clock() should select this: 673# 674config HAVE_UNSTABLE_SCHED_CLOCK 675 bool 676 677config GENERIC_SCHED_CLOCK 678 bool 679 680# 681# For architectures that want to enable the support for NUMA-affine scheduler 682# balancing logic: 683# 684config ARCH_SUPPORTS_NUMA_BALANCING 685 bool 686 687# 688# For architectures that prefer to flush all TLBs after a number of pages 689# are unmapped instead of sending one IPI per page to flush. The architecture 690# must provide guarantees on what happens if a clean TLB cache entry is 691# written after the unmap. Details are in mm/rmap.c near the check for 692# should_defer_flush. The architecture should also consider if the full flush 693# and the refill costs are offset by the savings of sending fewer IPIs. 694config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 695 bool 696 697# 698# For architectures that know their GCC __int128 support is sound 699# 700config ARCH_SUPPORTS_INT128 701 bool 702 703# For architectures that (ab)use NUMA to represent different memory regions 704# all cpu-local but of different latencies, such as SuperH. 705# 706config ARCH_WANT_NUMA_VARIABLE_LOCALITY 707 bool 708 709config NUMA_BALANCING 710 bool "Memory placement aware NUMA scheduler" 711 depends on ARCH_SUPPORTS_NUMA_BALANCING 712 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 713 depends on SMP && NUMA && MIGRATION 714 help 715 This option adds support for automatic NUMA aware memory/task placement. 716 The mechanism is quite primitive and is based on migrating memory when 717 it has references to the node the task is running on. 718 719 This system will be inactive on UMA systems. 720 721config NUMA_BALANCING_DEFAULT_ENABLED 722 bool "Automatically enable NUMA aware memory/task placement" 723 default y 724 depends on NUMA_BALANCING 725 help 726 If set, automatic NUMA balancing will be enabled if running on a NUMA 727 machine. 728 729menuconfig CGROUPS 730 bool "Control Group support" 731 select KERNFS 732 help 733 This option adds support for grouping sets of processes together, for 734 use with process control subsystems such as Cpusets, CFS, memory 735 controls or device isolation. 736 See 737 - Documentation/scheduler/sched-design-CFS.txt (CFS) 738 - Documentation/cgroup-v1/ (features for grouping, isolation 739 and resource control) 740 741 Say N if unsure. 742 743if CGROUPS 744 745config PAGE_COUNTER 746 bool 747 748config MEMCG 749 bool "Memory controller" 750 select PAGE_COUNTER 751 select EVENTFD 752 help 753 Provides control over the memory footprint of tasks in a cgroup. 754 755config MEMCG_SWAP 756 bool "Swap controller" 757 depends on MEMCG && SWAP 758 help 759 Provides control over the swap space consumed by tasks in a cgroup. 760 761config MEMCG_SWAP_ENABLED 762 bool "Swap controller enabled by default" 763 depends on MEMCG_SWAP 764 default y 765 help 766 Memory Resource Controller Swap Extension comes with its price in 767 a bigger memory consumption. General purpose distribution kernels 768 which want to enable the feature but keep it disabled by default 769 and let the user enable it by swapaccount=1 boot command line 770 parameter should have this option unselected. 771 For those who want to have the feature enabled by default should 772 select this option (if, for some reason, they need to disable it 773 then swapaccount=0 does the trick). 774 775config MEMCG_KMEM 776 bool 777 depends on MEMCG && !SLOB 778 default y 779 780config BLK_CGROUP 781 bool "IO controller" 782 depends on BLOCK 783 default n 784 ---help--- 785 Generic block IO controller cgroup interface. This is the common 786 cgroup interface which should be used by various IO controlling 787 policies. 788 789 Currently, CFQ IO scheduler uses it to recognize task groups and 790 control disk bandwidth allocation (proportional time slice allocation) 791 to such task groups. It is also used by bio throttling logic in 792 block layer to implement upper limit in IO rates on a device. 793 794 This option only enables generic Block IO controller infrastructure. 795 One needs to also enable actual IO controlling logic/policy. For 796 enabling proportional weight division of disk bandwidth in CFQ, set 797 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 798 CONFIG_BLK_DEV_THROTTLING=y. 799 800 See Documentation/cgroup-v1/blkio-controller.txt for more information. 801 802config DEBUG_BLK_CGROUP 803 bool "IO controller debugging" 804 depends on BLK_CGROUP 805 default n 806 ---help--- 807 Enable some debugging help. Currently it exports additional stat 808 files in a cgroup which can be useful for debugging. 809 810config CGROUP_WRITEBACK 811 bool 812 depends on MEMCG && BLK_CGROUP 813 default y 814 815menuconfig CGROUP_SCHED 816 bool "CPU controller" 817 default n 818 help 819 This feature lets CPU scheduler recognize task groups and control CPU 820 bandwidth allocation to such task groups. It uses cgroups to group 821 tasks. 822 823if CGROUP_SCHED 824config FAIR_GROUP_SCHED 825 bool "Group scheduling for SCHED_OTHER" 826 depends on CGROUP_SCHED 827 default CGROUP_SCHED 828 829config CFS_BANDWIDTH 830 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 831 depends on FAIR_GROUP_SCHED 832 default n 833 help 834 This option allows users to define CPU bandwidth rates (limits) for 835 tasks running within the fair group scheduler. Groups with no limit 836 set are considered to be unconstrained and will run with no 837 restriction. 838 See Documentation/scheduler/sched-bwc.txt for more information. 839 840config RT_GROUP_SCHED 841 bool "Group scheduling for SCHED_RR/FIFO" 842 depends on CGROUP_SCHED 843 default n 844 help 845 This feature lets you explicitly allocate real CPU bandwidth 846 to task groups. If enabled, it will also make it impossible to 847 schedule realtime tasks for non-root users until you allocate 848 realtime bandwidth for them. 849 See Documentation/scheduler/sched-rt-group.txt for more information. 850 851endif #CGROUP_SCHED 852 853config CGROUP_PIDS 854 bool "PIDs controller" 855 help 856 Provides enforcement of process number limits in the scope of a 857 cgroup. Any attempt to fork more processes than is allowed in the 858 cgroup will fail. PIDs are fundamentally a global resource because it 859 is fairly trivial to reach PID exhaustion before you reach even a 860 conservative kmemcg limit. As a result, it is possible to grind a 861 system to halt without being limited by other cgroup policies. The 862 PIDs controller is designed to stop this from happening. 863 864 It should be noted that organisational operations (such as attaching 865 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 866 since the PIDs limit only affects a process's ability to fork, not to 867 attach to a cgroup. 868 869config CGROUP_RDMA 870 bool "RDMA controller" 871 help 872 Provides enforcement of RDMA resources defined by IB stack. 873 It is fairly easy for consumers to exhaust RDMA resources, which 874 can result into resource unavailability to other consumers. 875 RDMA controller is designed to stop this from happening. 876 Attaching processes with active RDMA resources to the cgroup 877 hierarchy is allowed even if can cross the hierarchy's limit. 878 879config CGROUP_FREEZER 880 bool "Freezer controller" 881 help 882 Provides a way to freeze and unfreeze all tasks in a 883 cgroup. 884 885 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 886 controller includes important in-kernel memory consumers per default. 887 888 If you're using cgroup2, say N. 889 890config CGROUP_HUGETLB 891 bool "HugeTLB controller" 892 depends on HUGETLB_PAGE 893 select PAGE_COUNTER 894 default n 895 help 896 Provides a cgroup controller for HugeTLB pages. 897 When you enable this, you can put a per cgroup limit on HugeTLB usage. 898 The limit is enforced during page fault. Since HugeTLB doesn't 899 support page reclaim, enforcing the limit at page fault time implies 900 that, the application will get SIGBUS signal if it tries to access 901 HugeTLB pages beyond its limit. This requires the application to know 902 beforehand how much HugeTLB pages it would require for its use. The 903 control group is tracked in the third page lru pointer. This means 904 that we cannot use the controller with huge page less than 3 pages. 905 906config CPUSETS 907 bool "Cpuset controller" 908 depends on SMP 909 help 910 This option will let you create and manage CPUSETs which 911 allow dynamically partitioning a system into sets of CPUs and 912 Memory Nodes and assigning tasks to run only within those sets. 913 This is primarily useful on large SMP or NUMA systems. 914 915 Say N if unsure. 916 917config PROC_PID_CPUSET 918 bool "Include legacy /proc/<pid>/cpuset file" 919 depends on CPUSETS 920 default y 921 922config CGROUP_DEVICE 923 bool "Device controller" 924 help 925 Provides a cgroup controller implementing whitelists for 926 devices which a process in the cgroup can mknod or open. 927 928config CGROUP_CPUACCT 929 bool "Simple CPU accounting controller" 930 help 931 Provides a simple controller for monitoring the 932 total CPU consumed by the tasks in a cgroup. 933 934config CGROUP_PERF 935 bool "Perf controller" 936 depends on PERF_EVENTS 937 help 938 This option extends the perf per-cpu mode to restrict monitoring 939 to threads which belong to the cgroup specified and run on the 940 designated cpu. 941 942 Say N if unsure. 943 944config CGROUP_BPF 945 bool "Support for eBPF programs attached to cgroups" 946 depends on BPF_SYSCALL 947 select SOCK_CGROUP_DATA 948 help 949 Allow attaching eBPF programs to a cgroup using the bpf(2) 950 syscall command BPF_PROG_ATTACH. 951 952 In which context these programs are accessed depends on the type 953 of attachment. For instance, programs that are attached using 954 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 955 inet sockets. 956 957config CGROUP_DEBUG 958 bool "Debug controller" 959 default n 960 depends on DEBUG_KERNEL 961 help 962 This option enables a simple controller that exports 963 debugging information about the cgroups framework. This 964 controller is for control cgroup debugging only. Its 965 interfaces are not stable. 966 967 Say N. 968 969config SOCK_CGROUP_DATA 970 bool 971 default n 972 973endif # CGROUPS 974 975menuconfig NAMESPACES 976 bool "Namespaces support" if EXPERT 977 depends on MULTIUSER 978 default !EXPERT 979 help 980 Provides the way to make tasks work with different objects using 981 the same id. For example same IPC id may refer to different objects 982 or same user id or pid may refer to different tasks when used in 983 different namespaces. 984 985if NAMESPACES 986 987config UTS_NS 988 bool "UTS namespace" 989 default y 990 help 991 In this namespace tasks see different info provided with the 992 uname() system call 993 994config IPC_NS 995 bool "IPC namespace" 996 depends on (SYSVIPC || POSIX_MQUEUE) 997 default y 998 help 999 In this namespace tasks work with IPC ids which correspond to 1000 different IPC objects in different namespaces. 1001 1002config USER_NS 1003 bool "User namespace" 1004 default n 1005 help 1006 This allows containers, i.e. vservers, to use user namespaces 1007 to provide different user info for different servers. 1008 1009 When user namespaces are enabled in the kernel it is 1010 recommended that the MEMCG option also be enabled and that 1011 user-space use the memory control groups to limit the amount 1012 of memory a memory unprivileged users can use. 1013 1014 If unsure, say N. 1015 1016config PID_NS 1017 bool "PID Namespaces" 1018 default y 1019 help 1020 Support process id namespaces. This allows having multiple 1021 processes with the same pid as long as they are in different 1022 pid namespaces. This is a building block of containers. 1023 1024config NET_NS 1025 bool "Network namespace" 1026 depends on NET 1027 default y 1028 help 1029 Allow user space to create what appear to be multiple instances 1030 of the network stack. 1031 1032endif # NAMESPACES 1033 1034config CHECKPOINT_RESTORE 1035 bool "Checkpoint/restore support" 1036 select PROC_CHILDREN 1037 default n 1038 help 1039 Enables additional kernel features in a sake of checkpoint/restore. 1040 In particular it adds auxiliary prctl codes to setup process text, 1041 data and heap segment sizes, and a few additional /proc filesystem 1042 entries. 1043 1044 If unsure, say N here. 1045 1046config SCHED_AUTOGROUP 1047 bool "Automatic process group scheduling" 1048 select CGROUPS 1049 select CGROUP_SCHED 1050 select FAIR_GROUP_SCHED 1051 help 1052 This option optimizes the scheduler for common desktop workloads by 1053 automatically creating and populating task groups. This separation 1054 of workloads isolates aggressive CPU burners (like build jobs) from 1055 desktop applications. Task group autogeneration is currently based 1056 upon task session. 1057 1058config SYSFS_DEPRECATED 1059 bool "Enable deprecated sysfs features to support old userspace tools" 1060 depends on SYSFS 1061 default n 1062 help 1063 This option adds code that switches the layout of the "block" class 1064 devices, to not show up in /sys/class/block/, but only in 1065 /sys/block/. 1066 1067 This switch is only active when the sysfs.deprecated=1 boot option is 1068 passed or the SYSFS_DEPRECATED_V2 option is set. 1069 1070 This option allows new kernels to run on old distributions and tools, 1071 which might get confused by /sys/class/block/. Since 2007/2008 all 1072 major distributions and tools handle this just fine. 1073 1074 Recent distributions and userspace tools after 2009/2010 depend on 1075 the existence of /sys/class/block/, and will not work with this 1076 option enabled. 1077 1078 Only if you are using a new kernel on an old distribution, you might 1079 need to say Y here. 1080 1081config SYSFS_DEPRECATED_V2 1082 bool "Enable deprecated sysfs features by default" 1083 default n 1084 depends on SYSFS 1085 depends on SYSFS_DEPRECATED 1086 help 1087 Enable deprecated sysfs by default. 1088 1089 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1090 option. 1091 1092 Only if you are using a new kernel on an old distribution, you might 1093 need to say Y here. Even then, odds are you would not need it 1094 enabled, you can always pass the boot option if absolutely necessary. 1095 1096config RELAY 1097 bool "Kernel->user space relay support (formerly relayfs)" 1098 select IRQ_WORK 1099 help 1100 This option enables support for relay interface support in 1101 certain file systems (such as debugfs). 1102 It is designed to provide an efficient mechanism for tools and 1103 facilities to relay large amounts of data from kernel space to 1104 user space. 1105 1106 If unsure, say N. 1107 1108config BLK_DEV_INITRD 1109 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1110 help 1111 The initial RAM filesystem is a ramfs which is loaded by the 1112 boot loader (loadlin or lilo) and that is mounted as root 1113 before the normal boot procedure. It is typically used to 1114 load modules needed to mount the "real" root file system, 1115 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1116 1117 If RAM disk support (BLK_DEV_RAM) is also included, this 1118 also enables initial RAM disk (initrd) support and adds 1119 15 Kbytes (more on some other architectures) to the kernel size. 1120 1121 If unsure say Y. 1122 1123if BLK_DEV_INITRD 1124 1125source "usr/Kconfig" 1126 1127endif 1128 1129choice 1130 prompt "Compiler optimization level" 1131 default CC_OPTIMIZE_FOR_PERFORMANCE 1132 1133config CC_OPTIMIZE_FOR_PERFORMANCE 1134 bool "Optimize for performance" 1135 help 1136 This is the default optimization level for the kernel, building 1137 with the "-O2" compiler flag for best performance and most 1138 helpful compile-time warnings. 1139 1140config CC_OPTIMIZE_FOR_SIZE 1141 bool "Optimize for size" 1142 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives 1143 help 1144 Enabling this option will pass "-Os" instead of "-O2" to 1145 your compiler resulting in a smaller kernel. 1146 1147 If unsure, say N. 1148 1149endchoice 1150 1151config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1152 bool 1153 help 1154 This requires that the arch annotates or otherwise protects 1155 its external entry points from being discarded. Linker scripts 1156 must also merge .text.*, .data.*, and .bss.* correctly into 1157 output sections. Care must be taken not to pull in unrelated 1158 sections (e.g., '.text.init'). Typically '.' in section names 1159 is used to distinguish them from label names / C identifiers. 1160 1161config LD_DEAD_CODE_DATA_ELIMINATION 1162 bool "Dead code and data elimination (EXPERIMENTAL)" 1163 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1164 depends on EXPERT 1165 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800) 1166 depends on $(cc-option,-ffunction-sections -fdata-sections) 1167 depends on $(ld-option,--gc-sections) 1168 help 1169 Enable this if you want to do dead code and data elimination with 1170 the linker by compiling with -ffunction-sections -fdata-sections, 1171 and linking with --gc-sections. 1172 1173 This can reduce on disk and in-memory size of the kernel 1174 code and static data, particularly for small configs and 1175 on small systems. This has the possibility of introducing 1176 silently broken kernel if the required annotations are not 1177 present. This option is not well tested yet, so use at your 1178 own risk. 1179 1180config SYSCTL 1181 bool 1182 1183config HAVE_UID16 1184 bool 1185 1186config SYSCTL_EXCEPTION_TRACE 1187 bool 1188 help 1189 Enable support for /proc/sys/debug/exception-trace. 1190 1191config SYSCTL_ARCH_UNALIGN_NO_WARN 1192 bool 1193 help 1194 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1195 Allows arch to define/use @no_unaligned_warning to possibly warn 1196 about unaligned access emulation going on under the hood. 1197 1198config SYSCTL_ARCH_UNALIGN_ALLOW 1199 bool 1200 help 1201 Enable support for /proc/sys/kernel/unaligned-trap 1202 Allows arches to define/use @unaligned_enabled to runtime toggle 1203 the unaligned access emulation. 1204 see arch/parisc/kernel/unaligned.c for reference 1205 1206config HAVE_PCSPKR_PLATFORM 1207 bool 1208 1209# interpreter that classic socket filters depend on 1210config BPF 1211 bool 1212 1213menuconfig EXPERT 1214 bool "Configure standard kernel features (expert users)" 1215 # Unhide debug options, to make the on-by-default options visible 1216 select DEBUG_KERNEL 1217 help 1218 This option allows certain base kernel options and settings 1219 to be disabled or tweaked. This is for specialized 1220 environments which can tolerate a "non-standard" kernel. 1221 Only use this if you really know what you are doing. 1222 1223config UID16 1224 bool "Enable 16-bit UID system calls" if EXPERT 1225 depends on HAVE_UID16 && MULTIUSER 1226 default y 1227 help 1228 This enables the legacy 16-bit UID syscall wrappers. 1229 1230config MULTIUSER 1231 bool "Multiple users, groups and capabilities support" if EXPERT 1232 default y 1233 help 1234 This option enables support for non-root users, groups and 1235 capabilities. 1236 1237 If you say N here, all processes will run with UID 0, GID 0, and all 1238 possible capabilities. Saying N here also compiles out support for 1239 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1240 setgid, and capset. 1241 1242 If unsure, say Y here. 1243 1244config SGETMASK_SYSCALL 1245 bool "sgetmask/ssetmask syscalls support" if EXPERT 1246 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1247 ---help--- 1248 sys_sgetmask and sys_ssetmask are obsolete system calls 1249 no longer supported in libc but still enabled by default in some 1250 architectures. 1251 1252 If unsure, leave the default option here. 1253 1254config SYSFS_SYSCALL 1255 bool "Sysfs syscall support" if EXPERT 1256 default y 1257 ---help--- 1258 sys_sysfs is an obsolete system call no longer supported in libc. 1259 Note that disabling this option is more secure but might break 1260 compatibility with some systems. 1261 1262 If unsure say Y here. 1263 1264config SYSCTL_SYSCALL 1265 bool "Sysctl syscall support" if EXPERT 1266 depends on PROC_SYSCTL 1267 default n 1268 select SYSCTL 1269 ---help--- 1270 sys_sysctl uses binary paths that have been found challenging 1271 to properly maintain and use. The interface in /proc/sys 1272 using paths with ascii names is now the primary path to this 1273 information. 1274 1275 Almost nothing using the binary sysctl interface so if you are 1276 trying to save some space it is probably safe to disable this, 1277 making your kernel marginally smaller. 1278 1279 If unsure say N here. 1280 1281config FHANDLE 1282 bool "open by fhandle syscalls" if EXPERT 1283 select EXPORTFS 1284 default y 1285 help 1286 If you say Y here, a user level program will be able to map 1287 file names to handle and then later use the handle for 1288 different file system operations. This is useful in implementing 1289 userspace file servers, which now track files using handles instead 1290 of names. The handle would remain the same even if file names 1291 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1292 syscalls. 1293 1294config POSIX_TIMERS 1295 bool "Posix Clocks & timers" if EXPERT 1296 default y 1297 help 1298 This includes native support for POSIX timers to the kernel. 1299 Some embedded systems have no use for them and therefore they 1300 can be configured out to reduce the size of the kernel image. 1301 1302 When this option is disabled, the following syscalls won't be 1303 available: timer_create, timer_gettime: timer_getoverrun, 1304 timer_settime, timer_delete, clock_adjtime, getitimer, 1305 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1306 clock_getres and clock_nanosleep syscalls will be limited to 1307 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1308 1309 If unsure say y. 1310 1311config PRINTK 1312 default y 1313 bool "Enable support for printk" if EXPERT 1314 select IRQ_WORK 1315 help 1316 This option enables normal printk support. Removing it 1317 eliminates most of the message strings from the kernel image 1318 and makes the kernel more or less silent. As this makes it 1319 very difficult to diagnose system problems, saying N here is 1320 strongly discouraged. 1321 1322config PRINTK_NMI 1323 def_bool y 1324 depends on PRINTK 1325 depends on HAVE_NMI 1326 1327config BUG 1328 bool "BUG() support" if EXPERT 1329 default y 1330 help 1331 Disabling this option eliminates support for BUG and WARN, reducing 1332 the size of your kernel image and potentially quietly ignoring 1333 numerous fatal conditions. You should only consider disabling this 1334 option for embedded systems with no facilities for reporting errors. 1335 Just say Y. 1336 1337config ELF_CORE 1338 depends on COREDUMP 1339 default y 1340 bool "Enable ELF core dumps" if EXPERT 1341 help 1342 Enable support for generating core dumps. Disabling saves about 4k. 1343 1344 1345config PCSPKR_PLATFORM 1346 bool "Enable PC-Speaker support" if EXPERT 1347 depends on HAVE_PCSPKR_PLATFORM 1348 select I8253_LOCK 1349 default y 1350 help 1351 This option allows to disable the internal PC-Speaker 1352 support, saving some memory. 1353 1354config BASE_FULL 1355 default y 1356 bool "Enable full-sized data structures for core" if EXPERT 1357 help 1358 Disabling this option reduces the size of miscellaneous core 1359 kernel data structures. This saves memory on small machines, 1360 but may reduce performance. 1361 1362config FUTEX 1363 bool "Enable futex support" if EXPERT 1364 default y 1365 imply RT_MUTEXES 1366 help 1367 Disabling this option will cause the kernel to be built without 1368 support for "fast userspace mutexes". The resulting kernel may not 1369 run glibc-based applications correctly. 1370 1371config FUTEX_PI 1372 bool 1373 depends on FUTEX && RT_MUTEXES 1374 default y 1375 1376config HAVE_FUTEX_CMPXCHG 1377 bool 1378 depends on FUTEX 1379 help 1380 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1381 is implemented and always working. This removes a couple of runtime 1382 checks. 1383 1384config EPOLL 1385 bool "Enable eventpoll support" if EXPERT 1386 default y 1387 help 1388 Disabling this option will cause the kernel to be built without 1389 support for epoll family of system calls. 1390 1391config SIGNALFD 1392 bool "Enable signalfd() system call" if EXPERT 1393 default y 1394 help 1395 Enable the signalfd() system call that allows to receive signals 1396 on a file descriptor. 1397 1398 If unsure, say Y. 1399 1400config TIMERFD 1401 bool "Enable timerfd() system call" if EXPERT 1402 default y 1403 help 1404 Enable the timerfd() system call that allows to receive timer 1405 events on a file descriptor. 1406 1407 If unsure, say Y. 1408 1409config EVENTFD 1410 bool "Enable eventfd() system call" if EXPERT 1411 default y 1412 help 1413 Enable the eventfd() system call that allows to receive both 1414 kernel notification (ie. KAIO) or userspace notifications. 1415 1416 If unsure, say Y. 1417 1418config SHMEM 1419 bool "Use full shmem filesystem" if EXPERT 1420 default y 1421 depends on MMU 1422 help 1423 The shmem is an internal filesystem used to manage shared memory. 1424 It is backed by swap and manages resource limits. It is also exported 1425 to userspace as tmpfs if TMPFS is enabled. Disabling this 1426 option replaces shmem and tmpfs with the much simpler ramfs code, 1427 which may be appropriate on small systems without swap. 1428 1429config AIO 1430 bool "Enable AIO support" if EXPERT 1431 default y 1432 help 1433 This option enables POSIX asynchronous I/O which may by used 1434 by some high performance threaded applications. Disabling 1435 this option saves about 7k. 1436 1437config IO_URING 1438 bool "Enable IO uring support" if EXPERT 1439 select ANON_INODES 1440 default y 1441 help 1442 This option enables support for the io_uring interface, enabling 1443 applications to submit and complete IO through submission and 1444 completion rings that are shared between the kernel and application. 1445 1446config ADVISE_SYSCALLS 1447 bool "Enable madvise/fadvise syscalls" if EXPERT 1448 default y 1449 help 1450 This option enables the madvise and fadvise syscalls, used by 1451 applications to advise the kernel about their future memory or file 1452 usage, improving performance. If building an embedded system where no 1453 applications use these syscalls, you can disable this option to save 1454 space. 1455 1456config MEMBARRIER 1457 bool "Enable membarrier() system call" if EXPERT 1458 default y 1459 help 1460 Enable the membarrier() system call that allows issuing memory 1461 barriers across all running threads, which can be used to distribute 1462 the cost of user-space memory barriers asymmetrically by transforming 1463 pairs of memory barriers into pairs consisting of membarrier() and a 1464 compiler barrier. 1465 1466 If unsure, say Y. 1467 1468config KALLSYMS 1469 bool "Load all symbols for debugging/ksymoops" if EXPERT 1470 default y 1471 help 1472 Say Y here to let the kernel print out symbolic crash information and 1473 symbolic stack backtraces. This increases the size of the kernel 1474 somewhat, as all symbols have to be loaded into the kernel image. 1475 1476config KALLSYMS_ALL 1477 bool "Include all symbols in kallsyms" 1478 depends on DEBUG_KERNEL && KALLSYMS 1479 help 1480 Normally kallsyms only contains the symbols of functions for nicer 1481 OOPS messages and backtraces (i.e., symbols from the text and inittext 1482 sections). This is sufficient for most cases. And only in very rare 1483 cases (e.g., when a debugger is used) all symbols are required (e.g., 1484 names of variables from the data sections, etc). 1485 1486 This option makes sure that all symbols are loaded into the kernel 1487 image (i.e., symbols from all sections) in cost of increased kernel 1488 size (depending on the kernel configuration, it may be 300KiB or 1489 something like this). 1490 1491 Say N unless you really need all symbols. 1492 1493config KALLSYMS_ABSOLUTE_PERCPU 1494 bool 1495 depends on KALLSYMS 1496 default X86_64 && SMP 1497 1498config KALLSYMS_BASE_RELATIVE 1499 bool 1500 depends on KALLSYMS 1501 default !IA64 1502 help 1503 Instead of emitting them as absolute values in the native word size, 1504 emit the symbol references in the kallsyms table as 32-bit entries, 1505 each containing a relative value in the range [base, base + U32_MAX] 1506 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1507 an absolute value in the range [0, S32_MAX] or a relative value in the 1508 range [base, base + S32_MAX], where base is the lowest relative symbol 1509 address encountered in the image. 1510 1511 On 64-bit builds, this reduces the size of the address table by 50%, 1512 but more importantly, it results in entries whose values are build 1513 time constants, and no relocation pass is required at runtime to fix 1514 up the entries based on the runtime load address of the kernel. 1515 1516# end of the "standard kernel features (expert users)" menu 1517 1518# syscall, maps, verifier 1519config BPF_SYSCALL 1520 bool "Enable bpf() system call" 1521 select BPF 1522 select IRQ_WORK 1523 default n 1524 help 1525 Enable the bpf() system call that allows to manipulate eBPF 1526 programs and maps via file descriptors. 1527 1528config BPF_JIT_ALWAYS_ON 1529 bool "Permanently enable BPF JIT and remove BPF interpreter" 1530 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1531 help 1532 Enables BPF JIT and removes BPF interpreter to avoid 1533 speculative execution of BPF instructions by the interpreter 1534 1535config USERFAULTFD 1536 bool "Enable userfaultfd() system call" 1537 depends on MMU 1538 help 1539 Enable the userfaultfd() system call that allows to intercept and 1540 handle page faults in userland. 1541 1542config ARCH_HAS_MEMBARRIER_CALLBACKS 1543 bool 1544 1545config ARCH_HAS_MEMBARRIER_SYNC_CORE 1546 bool 1547 1548config RSEQ 1549 bool "Enable rseq() system call" if EXPERT 1550 default y 1551 depends on HAVE_RSEQ 1552 select MEMBARRIER 1553 help 1554 Enable the restartable sequences system call. It provides a 1555 user-space cache for the current CPU number value, which 1556 speeds up getting the current CPU number from user-space, 1557 as well as an ABI to speed up user-space operations on 1558 per-CPU data. 1559 1560 If unsure, say Y. 1561 1562config DEBUG_RSEQ 1563 default n 1564 bool "Enabled debugging of rseq() system call" if EXPERT 1565 depends on RSEQ && DEBUG_KERNEL 1566 help 1567 Enable extra debugging checks for the rseq system call. 1568 1569 If unsure, say N. 1570 1571config EMBEDDED 1572 bool "Embedded system" 1573 option allnoconfig_y 1574 select EXPERT 1575 help 1576 This option should be enabled if compiling the kernel for 1577 an embedded system so certain expert options are available 1578 for configuration. 1579 1580config HAVE_PERF_EVENTS 1581 bool 1582 help 1583 See tools/perf/design.txt for details. 1584 1585config PERF_USE_VMALLOC 1586 bool 1587 help 1588 See tools/perf/design.txt for details 1589 1590config PC104 1591 bool "PC/104 support" if EXPERT 1592 help 1593 Expose PC/104 form factor device drivers and options available for 1594 selection and configuration. Enable this option if your target 1595 machine has a PC/104 bus. 1596 1597menu "Kernel Performance Events And Counters" 1598 1599config PERF_EVENTS 1600 bool "Kernel performance events and counters" 1601 default y if PROFILING 1602 depends on HAVE_PERF_EVENTS 1603 select IRQ_WORK 1604 select SRCU 1605 help 1606 Enable kernel support for various performance events provided 1607 by software and hardware. 1608 1609 Software events are supported either built-in or via the 1610 use of generic tracepoints. 1611 1612 Most modern CPUs support performance events via performance 1613 counter registers. These registers count the number of certain 1614 types of hw events: such as instructions executed, cachemisses 1615 suffered, or branches mis-predicted - without slowing down the 1616 kernel or applications. These registers can also trigger interrupts 1617 when a threshold number of events have passed - and can thus be 1618 used to profile the code that runs on that CPU. 1619 1620 The Linux Performance Event subsystem provides an abstraction of 1621 these software and hardware event capabilities, available via a 1622 system call and used by the "perf" utility in tools/perf/. It 1623 provides per task and per CPU counters, and it provides event 1624 capabilities on top of those. 1625 1626 Say Y if unsure. 1627 1628config DEBUG_PERF_USE_VMALLOC 1629 default n 1630 bool "Debug: use vmalloc to back perf mmap() buffers" 1631 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1632 select PERF_USE_VMALLOC 1633 help 1634 Use vmalloc memory to back perf mmap() buffers. 1635 1636 Mostly useful for debugging the vmalloc code on platforms 1637 that don't require it. 1638 1639 Say N if unsure. 1640 1641endmenu 1642 1643config VM_EVENT_COUNTERS 1644 default y 1645 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1646 help 1647 VM event counters are needed for event counts to be shown. 1648 This option allows the disabling of the VM event counters 1649 on EXPERT systems. /proc/vmstat will only show page counts 1650 if VM event counters are disabled. 1651 1652config SLUB_DEBUG 1653 default y 1654 bool "Enable SLUB debugging support" if EXPERT 1655 depends on SLUB && SYSFS 1656 help 1657 SLUB has extensive debug support features. Disabling these can 1658 result in significant savings in code size. This also disables 1659 SLUB sysfs support. /sys/slab will not exist and there will be 1660 no support for cache validation etc. 1661 1662config SLUB_MEMCG_SYSFS_ON 1663 default n 1664 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1665 depends on SLUB && SYSFS && MEMCG 1666 help 1667 SLUB creates a directory under /sys/kernel/slab for each 1668 allocation cache to host info and debug files. If memory 1669 cgroup is enabled, each cache can have per memory cgroup 1670 caches. SLUB can create the same sysfs directories for these 1671 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1672 to a very high number of debug files being created. This is 1673 controlled by slub_memcg_sysfs boot parameter and this 1674 config option determines the parameter's default value. 1675 1676config COMPAT_BRK 1677 bool "Disable heap randomization" 1678 default y 1679 help 1680 Randomizing heap placement makes heap exploits harder, but it 1681 also breaks ancient binaries (including anything libc5 based). 1682 This option changes the bootup default to heap randomization 1683 disabled, and can be overridden at runtime by setting 1684 /proc/sys/kernel/randomize_va_space to 2. 1685 1686 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1687 1688choice 1689 prompt "Choose SLAB allocator" 1690 default SLUB 1691 help 1692 This option allows to select a slab allocator. 1693 1694config SLAB 1695 bool "SLAB" 1696 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1697 help 1698 The regular slab allocator that is established and known to work 1699 well in all environments. It organizes cache hot objects in 1700 per cpu and per node queues. 1701 1702config SLUB 1703 bool "SLUB (Unqueued Allocator)" 1704 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1705 help 1706 SLUB is a slab allocator that minimizes cache line usage 1707 instead of managing queues of cached objects (SLAB approach). 1708 Per cpu caching is realized using slabs of objects instead 1709 of queues of objects. SLUB can use memory efficiently 1710 and has enhanced diagnostics. SLUB is the default choice for 1711 a slab allocator. 1712 1713config SLOB 1714 depends on EXPERT 1715 bool "SLOB (Simple Allocator)" 1716 help 1717 SLOB replaces the stock allocator with a drastically simpler 1718 allocator. SLOB is generally more space efficient but 1719 does not perform as well on large systems. 1720 1721endchoice 1722 1723config SLAB_MERGE_DEFAULT 1724 bool "Allow slab caches to be merged" 1725 default y 1726 help 1727 For reduced kernel memory fragmentation, slab caches can be 1728 merged when they share the same size and other characteristics. 1729 This carries a risk of kernel heap overflows being able to 1730 overwrite objects from merged caches (and more easily control 1731 cache layout), which makes such heap attacks easier to exploit 1732 by attackers. By keeping caches unmerged, these kinds of exploits 1733 can usually only damage objects in the same cache. To disable 1734 merging at runtime, "slab_nomerge" can be passed on the kernel 1735 command line. 1736 1737config SLAB_FREELIST_RANDOM 1738 default n 1739 depends on SLAB || SLUB 1740 bool "SLAB freelist randomization" 1741 help 1742 Randomizes the freelist order used on creating new pages. This 1743 security feature reduces the predictability of the kernel slab 1744 allocator against heap overflows. 1745 1746config SLAB_FREELIST_HARDENED 1747 bool "Harden slab freelist metadata" 1748 depends on SLUB 1749 help 1750 Many kernel heap attacks try to target slab cache metadata and 1751 other infrastructure. This options makes minor performance 1752 sacrifies to harden the kernel slab allocator against common 1753 freelist exploit methods. 1754 1755config SHUFFLE_PAGE_ALLOCATOR 1756 bool "Page allocator randomization" 1757 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1758 help 1759 Randomization of the page allocator improves the average 1760 utilization of a direct-mapped memory-side-cache. See section 1761 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1762 6.2a specification for an example of how a platform advertises 1763 the presence of a memory-side-cache. There are also incidental 1764 security benefits as it reduces the predictability of page 1765 allocations to compliment SLAB_FREELIST_RANDOM, but the 1766 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1767 10th order of pages is selected based on cache utilization 1768 benefits on x86. 1769 1770 While the randomization improves cache utilization it may 1771 negatively impact workloads on platforms without a cache. For 1772 this reason, by default, the randomization is enabled only 1773 after runtime detection of a direct-mapped memory-side-cache. 1774 Otherwise, the randomization may be force enabled with the 1775 'page_alloc.shuffle' kernel command line parameter. 1776 1777 Say Y if unsure. 1778 1779config SLUB_CPU_PARTIAL 1780 default y 1781 depends on SLUB && SMP 1782 bool "SLUB per cpu partial cache" 1783 help 1784 Per cpu partial caches accellerate objects allocation and freeing 1785 that is local to a processor at the price of more indeterminism 1786 in the latency of the free. On overflow these caches will be cleared 1787 which requires the taking of locks that may cause latency spikes. 1788 Typically one would choose no for a realtime system. 1789 1790config MMAP_ALLOW_UNINITIALIZED 1791 bool "Allow mmapped anonymous memory to be uninitialized" 1792 depends on EXPERT && !MMU 1793 default n 1794 help 1795 Normally, and according to the Linux spec, anonymous memory obtained 1796 from mmap() has its contents cleared before it is passed to 1797 userspace. Enabling this config option allows you to request that 1798 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1799 providing a huge performance boost. If this option is not enabled, 1800 then the flag will be ignored. 1801 1802 This is taken advantage of by uClibc's malloc(), and also by 1803 ELF-FDPIC binfmt's brk and stack allocator. 1804 1805 Because of the obvious security issues, this option should only be 1806 enabled on embedded devices where you control what is run in 1807 userspace. Since that isn't generally a problem on no-MMU systems, 1808 it is normally safe to say Y here. 1809 1810 See Documentation/nommu-mmap.txt for more information. 1811 1812config SYSTEM_DATA_VERIFICATION 1813 def_bool n 1814 select SYSTEM_TRUSTED_KEYRING 1815 select KEYS 1816 select CRYPTO 1817 select CRYPTO_RSA 1818 select ASYMMETRIC_KEY_TYPE 1819 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1820 select ASN1 1821 select OID_REGISTRY 1822 select X509_CERTIFICATE_PARSER 1823 select PKCS7_MESSAGE_PARSER 1824 help 1825 Provide PKCS#7 message verification using the contents of the system 1826 trusted keyring to provide public keys. This then can be used for 1827 module verification, kexec image verification and firmware blob 1828 verification. 1829 1830config PROFILING 1831 bool "Profiling support" 1832 help 1833 Say Y here to enable the extended profiling support mechanisms used 1834 by profilers such as OProfile. 1835 1836# 1837# Place an empty function call at each tracepoint site. Can be 1838# dynamically changed for a probe function. 1839# 1840config TRACEPOINTS 1841 bool 1842 1843endmenu # General setup 1844 1845source "arch/Kconfig" 1846 1847config RT_MUTEXES 1848 bool 1849 1850config BASE_SMALL 1851 int 1852 default 0 if BASE_FULL 1853 default 1 if !BASE_FULL 1854 1855menuconfig MODULES 1856 bool "Enable loadable module support" 1857 option modules 1858 help 1859 Kernel modules are small pieces of compiled code which can 1860 be inserted in the running kernel, rather than being 1861 permanently built into the kernel. You use the "modprobe" 1862 tool to add (and sometimes remove) them. If you say Y here, 1863 many parts of the kernel can be built as modules (by 1864 answering M instead of Y where indicated): this is most 1865 useful for infrequently used options which are not required 1866 for booting. For more information, see the man pages for 1867 modprobe, lsmod, modinfo, insmod and rmmod. 1868 1869 If you say Y here, you will need to run "make 1870 modules_install" to put the modules under /lib/modules/ 1871 where modprobe can find them (you may need to be root to do 1872 this). 1873 1874 If unsure, say Y. 1875 1876if MODULES 1877 1878config MODULE_FORCE_LOAD 1879 bool "Forced module loading" 1880 default n 1881 help 1882 Allow loading of modules without version information (ie. modprobe 1883 --force). Forced module loading sets the 'F' (forced) taint flag and 1884 is usually a really bad idea. 1885 1886config MODULE_UNLOAD 1887 bool "Module unloading" 1888 help 1889 Without this option you will not be able to unload any 1890 modules (note that some modules may not be unloadable 1891 anyway), which makes your kernel smaller, faster 1892 and simpler. If unsure, say Y. 1893 1894config MODULE_FORCE_UNLOAD 1895 bool "Forced module unloading" 1896 depends on MODULE_UNLOAD 1897 help 1898 This option allows you to force a module to unload, even if the 1899 kernel believes it is unsafe: the kernel will remove the module 1900 without waiting for anyone to stop using it (using the -f option to 1901 rmmod). This is mainly for kernel developers and desperate users. 1902 If unsure, say N. 1903 1904config MODVERSIONS 1905 bool "Module versioning support" 1906 help 1907 Usually, you have to use modules compiled with your kernel. 1908 Saying Y here makes it sometimes possible to use modules 1909 compiled for different kernels, by adding enough information 1910 to the modules to (hopefully) spot any changes which would 1911 make them incompatible with the kernel you are running. If 1912 unsure, say N. 1913 1914config MODULE_REL_CRCS 1915 bool 1916 depends on MODVERSIONS 1917 1918config MODULE_SRCVERSION_ALL 1919 bool "Source checksum for all modules" 1920 help 1921 Modules which contain a MODULE_VERSION get an extra "srcversion" 1922 field inserted into their modinfo section, which contains a 1923 sum of the source files which made it. This helps maintainers 1924 see exactly which source was used to build a module (since 1925 others sometimes change the module source without updating 1926 the version). With this option, such a "srcversion" field 1927 will be created for all modules. If unsure, say N. 1928 1929config MODULE_SIG 1930 bool "Module signature verification" 1931 depends on MODULES 1932 select SYSTEM_DATA_VERIFICATION 1933 help 1934 Check modules for valid signatures upon load: the signature 1935 is simply appended to the module. For more information see 1936 <file:Documentation/admin-guide/module-signing.rst>. 1937 1938 Note that this option adds the OpenSSL development packages as a 1939 kernel build dependency so that the signing tool can use its crypto 1940 library. 1941 1942 !!!WARNING!!! If you enable this option, you MUST make sure that the 1943 module DOES NOT get stripped after being signed. This includes the 1944 debuginfo strip done by some packagers (such as rpmbuild) and 1945 inclusion into an initramfs that wants the module size reduced. 1946 1947config MODULE_SIG_FORCE 1948 bool "Require modules to be validly signed" 1949 depends on MODULE_SIG 1950 help 1951 Reject unsigned modules or signed modules for which we don't have a 1952 key. Without this, such modules will simply taint the kernel. 1953 1954config MODULE_SIG_ALL 1955 bool "Automatically sign all modules" 1956 default y 1957 depends on MODULE_SIG 1958 help 1959 Sign all modules during make modules_install. Without this option, 1960 modules must be signed manually, using the scripts/sign-file tool. 1961 1962comment "Do not forget to sign required modules with scripts/sign-file" 1963 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 1964 1965choice 1966 prompt "Which hash algorithm should modules be signed with?" 1967 depends on MODULE_SIG 1968 help 1969 This determines which sort of hashing algorithm will be used during 1970 signature generation. This algorithm _must_ be built into the kernel 1971 directly so that signature verification can take place. It is not 1972 possible to load a signed module containing the algorithm to check 1973 the signature on that module. 1974 1975config MODULE_SIG_SHA1 1976 bool "Sign modules with SHA-1" 1977 select CRYPTO_SHA1 1978 1979config MODULE_SIG_SHA224 1980 bool "Sign modules with SHA-224" 1981 select CRYPTO_SHA256 1982 1983config MODULE_SIG_SHA256 1984 bool "Sign modules with SHA-256" 1985 select CRYPTO_SHA256 1986 1987config MODULE_SIG_SHA384 1988 bool "Sign modules with SHA-384" 1989 select CRYPTO_SHA512 1990 1991config MODULE_SIG_SHA512 1992 bool "Sign modules with SHA-512" 1993 select CRYPTO_SHA512 1994 1995endchoice 1996 1997config MODULE_SIG_HASH 1998 string 1999 depends on MODULE_SIG 2000 default "sha1" if MODULE_SIG_SHA1 2001 default "sha224" if MODULE_SIG_SHA224 2002 default "sha256" if MODULE_SIG_SHA256 2003 default "sha384" if MODULE_SIG_SHA384 2004 default "sha512" if MODULE_SIG_SHA512 2005 2006config MODULE_COMPRESS 2007 bool "Compress modules on installation" 2008 depends on MODULES 2009 help 2010 2011 Compresses kernel modules when 'make modules_install' is run; gzip or 2012 xz depending on "Compression algorithm" below. 2013 2014 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 2015 2016 Out-of-tree kernel modules installed using Kbuild will also be 2017 compressed upon installation. 2018 2019 Note: for modules inside an initrd or initramfs, it's more efficient 2020 to compress the whole initrd or initramfs instead. 2021 2022 Note: This is fully compatible with signed modules. 2023 2024 If in doubt, say N. 2025 2026choice 2027 prompt "Compression algorithm" 2028 depends on MODULE_COMPRESS 2029 default MODULE_COMPRESS_GZIP 2030 help 2031 This determines which sort of compression will be used during 2032 'make modules_install'. 2033 2034 GZIP (default) and XZ are supported. 2035 2036config MODULE_COMPRESS_GZIP 2037 bool "GZIP" 2038 2039config MODULE_COMPRESS_XZ 2040 bool "XZ" 2041 2042endchoice 2043 2044config TRIM_UNUSED_KSYMS 2045 bool "Trim unused exported kernel symbols" 2046 depends on MODULES && !UNUSED_SYMBOLS 2047 help 2048 The kernel and some modules make many symbols available for 2049 other modules to use via EXPORT_SYMBOL() and variants. Depending 2050 on the set of modules being selected in your kernel configuration, 2051 many of those exported symbols might never be used. 2052 2053 This option allows for unused exported symbols to be dropped from 2054 the build. In turn, this provides the compiler more opportunities 2055 (especially when using LTO) for optimizing the code and reducing 2056 binary size. This might have some security advantages as well. 2057 2058 If unsure, or if you need to build out-of-tree modules, say N. 2059 2060endif # MODULES 2061 2062config MODULES_TREE_LOOKUP 2063 def_bool y 2064 depends on PERF_EVENTS || TRACING 2065 2066config INIT_ALL_POSSIBLE 2067 bool 2068 help 2069 Back when each arch used to define their own cpu_online_mask and 2070 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2071 with all 1s, and others with all 0s. When they were centralised, 2072 it was better to provide this option than to break all the archs 2073 and have several arch maintainers pursuing me down dark alleys. 2074 2075source "block/Kconfig" 2076 2077config PREEMPT_NOTIFIERS 2078 bool 2079 2080config PADATA 2081 depends on SMP 2082 bool 2083 2084config ASN1 2085 tristate 2086 help 2087 Build a simple ASN.1 grammar compiler that produces a bytecode output 2088 that can be interpreted by the ASN.1 stream decoder and used to 2089 inform it as to what tags are to be expected in a stream and what 2090 functions to call on what tags. 2091 2092source "kernel/Kconfig.locks" 2093 2094config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2095 bool 2096 2097# It may be useful for an architecture to override the definitions of the 2098# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2099# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2100# different calling convention for syscalls. They can also override the 2101# macros for not-implemented syscalls in kernel/sys_ni.c and 2102# kernel/time/posix-stubs.c. All these overrides need to be available in 2103# <asm/syscall_wrapper.h>. 2104config ARCH_HAS_SYSCALL_WRAPPER 2105 def_bool n 2106