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 select BUILD_BIN2C 566 ---help--- 567 This option enables the complete Linux kernel ".config" file 568 contents to be saved in the kernel. It provides documentation 569 of which kernel options are used in a running kernel or in an 570 on-disk kernel. This information can be extracted from the kernel 571 image file with the script scripts/extract-ikconfig and used as 572 input to rebuild the current kernel or to build another kernel. 573 It can also be extracted from a running kernel by reading 574 /proc/config.gz if enabled (below). 575 576config IKCONFIG_PROC 577 bool "Enable access to .config through /proc/config.gz" 578 depends on IKCONFIG && PROC_FS 579 ---help--- 580 This option enables access to the kernel configuration file 581 through /proc/config.gz. 582 583config LOG_BUF_SHIFT 584 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 585 range 12 25 586 default 17 587 depends on PRINTK 588 help 589 Select the minimal kernel log buffer size as a power of 2. 590 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 591 parameter, see below. Any higher size also might be forced 592 by "log_buf_len" boot parameter. 593 594 Examples: 595 17 => 128 KB 596 16 => 64 KB 597 15 => 32 KB 598 14 => 16 KB 599 13 => 8 KB 600 12 => 4 KB 601 602config LOG_CPU_MAX_BUF_SHIFT 603 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 604 depends on SMP 605 range 0 21 606 default 12 if !BASE_SMALL 607 default 0 if BASE_SMALL 608 depends on PRINTK 609 help 610 This option allows to increase the default ring buffer size 611 according to the number of CPUs. The value defines the contribution 612 of each CPU as a power of 2. The used space is typically only few 613 lines however it might be much more when problems are reported, 614 e.g. backtraces. 615 616 The increased size means that a new buffer has to be allocated and 617 the original static one is unused. It makes sense only on systems 618 with more CPUs. Therefore this value is used only when the sum of 619 contributions is greater than the half of the default kernel ring 620 buffer as defined by LOG_BUF_SHIFT. The default values are set 621 so that more than 64 CPUs are needed to trigger the allocation. 622 623 Also this option is ignored when "log_buf_len" kernel parameter is 624 used as it forces an exact (power of two) size of the ring buffer. 625 626 The number of possible CPUs is used for this computation ignoring 627 hotplugging making the computation optimal for the worst case 628 scenario while allowing a simple algorithm to be used from bootup. 629 630 Examples shift values and their meaning: 631 17 => 128 KB for each CPU 632 16 => 64 KB for each CPU 633 15 => 32 KB for each CPU 634 14 => 16 KB for each CPU 635 13 => 8 KB for each CPU 636 12 => 4 KB for each CPU 637 638config PRINTK_SAFE_LOG_BUF_SHIFT 639 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 640 range 10 21 641 default 13 642 depends on PRINTK 643 help 644 Select the size of an alternate printk per-CPU buffer where messages 645 printed from usafe contexts are temporary stored. One example would 646 be NMI messages, another one - printk recursion. The messages are 647 copied to the main log buffer in a safe context to avoid a deadlock. 648 The value defines the size as a power of 2. 649 650 Those messages are rare and limited. The largest one is when 651 a backtrace is printed. It usually fits into 4KB. Select 652 8KB if you want to be on the safe side. 653 654 Examples: 655 17 => 128 KB for each CPU 656 16 => 64 KB for each CPU 657 15 => 32 KB for each CPU 658 14 => 16 KB for each CPU 659 13 => 8 KB for each CPU 660 12 => 4 KB for each CPU 661 662# 663# Architectures with an unreliable sched_clock() should select this: 664# 665config HAVE_UNSTABLE_SCHED_CLOCK 666 bool 667 668config GENERIC_SCHED_CLOCK 669 bool 670 671# 672# For architectures that want to enable the support for NUMA-affine scheduler 673# balancing logic: 674# 675config ARCH_SUPPORTS_NUMA_BALANCING 676 bool 677 678# 679# For architectures that prefer to flush all TLBs after a number of pages 680# are unmapped instead of sending one IPI per page to flush. The architecture 681# must provide guarantees on what happens if a clean TLB cache entry is 682# written after the unmap. Details are in mm/rmap.c near the check for 683# should_defer_flush. The architecture should also consider if the full flush 684# and the refill costs are offset by the savings of sending fewer IPIs. 685config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 686 bool 687 688# 689# For architectures that know their GCC __int128 support is sound 690# 691config ARCH_SUPPORTS_INT128 692 bool 693 694# For architectures that (ab)use NUMA to represent different memory regions 695# all cpu-local but of different latencies, such as SuperH. 696# 697config ARCH_WANT_NUMA_VARIABLE_LOCALITY 698 bool 699 700config NUMA_BALANCING 701 bool "Memory placement aware NUMA scheduler" 702 depends on ARCH_SUPPORTS_NUMA_BALANCING 703 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 704 depends on SMP && NUMA && MIGRATION 705 help 706 This option adds support for automatic NUMA aware memory/task placement. 707 The mechanism is quite primitive and is based on migrating memory when 708 it has references to the node the task is running on. 709 710 This system will be inactive on UMA systems. 711 712config NUMA_BALANCING_DEFAULT_ENABLED 713 bool "Automatically enable NUMA aware memory/task placement" 714 default y 715 depends on NUMA_BALANCING 716 help 717 If set, automatic NUMA balancing will be enabled if running on a NUMA 718 machine. 719 720menuconfig CGROUPS 721 bool "Control Group support" 722 select KERNFS 723 help 724 This option adds support for grouping sets of processes together, for 725 use with process control subsystems such as Cpusets, CFS, memory 726 controls or device isolation. 727 See 728 - Documentation/scheduler/sched-design-CFS.txt (CFS) 729 - Documentation/cgroup-v1/ (features for grouping, isolation 730 and resource control) 731 732 Say N if unsure. 733 734if CGROUPS 735 736config PAGE_COUNTER 737 bool 738 739config MEMCG 740 bool "Memory controller" 741 select PAGE_COUNTER 742 select EVENTFD 743 help 744 Provides control over the memory footprint of tasks in a cgroup. 745 746config MEMCG_SWAP 747 bool "Swap controller" 748 depends on MEMCG && SWAP 749 help 750 Provides control over the swap space consumed by tasks in a cgroup. 751 752config MEMCG_SWAP_ENABLED 753 bool "Swap controller enabled by default" 754 depends on MEMCG_SWAP 755 default y 756 help 757 Memory Resource Controller Swap Extension comes with its price in 758 a bigger memory consumption. General purpose distribution kernels 759 which want to enable the feature but keep it disabled by default 760 and let the user enable it by swapaccount=1 boot command line 761 parameter should have this option unselected. 762 For those who want to have the feature enabled by default should 763 select this option (if, for some reason, they need to disable it 764 then swapaccount=0 does the trick). 765 766config MEMCG_KMEM 767 bool 768 depends on MEMCG && !SLOB 769 default y 770 771config BLK_CGROUP 772 bool "IO controller" 773 depends on BLOCK 774 default n 775 ---help--- 776 Generic block IO controller cgroup interface. This is the common 777 cgroup interface which should be used by various IO controlling 778 policies. 779 780 Currently, CFQ IO scheduler uses it to recognize task groups and 781 control disk bandwidth allocation (proportional time slice allocation) 782 to such task groups. It is also used by bio throttling logic in 783 block layer to implement upper limit in IO rates on a device. 784 785 This option only enables generic Block IO controller infrastructure. 786 One needs to also enable actual IO controlling logic/policy. For 787 enabling proportional weight division of disk bandwidth in CFQ, set 788 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 789 CONFIG_BLK_DEV_THROTTLING=y. 790 791 See Documentation/cgroup-v1/blkio-controller.txt for more information. 792 793config DEBUG_BLK_CGROUP 794 bool "IO controller debugging" 795 depends on BLK_CGROUP 796 default n 797 ---help--- 798 Enable some debugging help. Currently it exports additional stat 799 files in a cgroup which can be useful for debugging. 800 801config CGROUP_WRITEBACK 802 bool 803 depends on MEMCG && BLK_CGROUP 804 default y 805 806menuconfig CGROUP_SCHED 807 bool "CPU controller" 808 default n 809 help 810 This feature lets CPU scheduler recognize task groups and control CPU 811 bandwidth allocation to such task groups. It uses cgroups to group 812 tasks. 813 814if CGROUP_SCHED 815config FAIR_GROUP_SCHED 816 bool "Group scheduling for SCHED_OTHER" 817 depends on CGROUP_SCHED 818 default CGROUP_SCHED 819 820config CFS_BANDWIDTH 821 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 822 depends on FAIR_GROUP_SCHED 823 default n 824 help 825 This option allows users to define CPU bandwidth rates (limits) for 826 tasks running within the fair group scheduler. Groups with no limit 827 set are considered to be unconstrained and will run with no 828 restriction. 829 See Documentation/scheduler/sched-bwc.txt for more information. 830 831config RT_GROUP_SCHED 832 bool "Group scheduling for SCHED_RR/FIFO" 833 depends on CGROUP_SCHED 834 default n 835 help 836 This feature lets you explicitly allocate real CPU bandwidth 837 to task groups. If enabled, it will also make it impossible to 838 schedule realtime tasks for non-root users until you allocate 839 realtime bandwidth for them. 840 See Documentation/scheduler/sched-rt-group.txt for more information. 841 842endif #CGROUP_SCHED 843 844config CGROUP_PIDS 845 bool "PIDs controller" 846 help 847 Provides enforcement of process number limits in the scope of a 848 cgroup. Any attempt to fork more processes than is allowed in the 849 cgroup will fail. PIDs are fundamentally a global resource because it 850 is fairly trivial to reach PID exhaustion before you reach even a 851 conservative kmemcg limit. As a result, it is possible to grind a 852 system to halt without being limited by other cgroup policies. The 853 PIDs controller is designed to stop this from happening. 854 855 It should be noted that organisational operations (such as attaching 856 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 857 since the PIDs limit only affects a process's ability to fork, not to 858 attach to a cgroup. 859 860config CGROUP_RDMA 861 bool "RDMA controller" 862 help 863 Provides enforcement of RDMA resources defined by IB stack. 864 It is fairly easy for consumers to exhaust RDMA resources, which 865 can result into resource unavailability to other consumers. 866 RDMA controller is designed to stop this from happening. 867 Attaching processes with active RDMA resources to the cgroup 868 hierarchy is allowed even if can cross the hierarchy's limit. 869 870config CGROUP_FREEZER 871 bool "Freezer controller" 872 help 873 Provides a way to freeze and unfreeze all tasks in a 874 cgroup. 875 876 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 877 controller includes important in-kernel memory consumers per default. 878 879 If you're using cgroup2, say N. 880 881config CGROUP_HUGETLB 882 bool "HugeTLB controller" 883 depends on HUGETLB_PAGE 884 select PAGE_COUNTER 885 default n 886 help 887 Provides a cgroup controller for HugeTLB pages. 888 When you enable this, you can put a per cgroup limit on HugeTLB usage. 889 The limit is enforced during page fault. Since HugeTLB doesn't 890 support page reclaim, enforcing the limit at page fault time implies 891 that, the application will get SIGBUS signal if it tries to access 892 HugeTLB pages beyond its limit. This requires the application to know 893 beforehand how much HugeTLB pages it would require for its use. The 894 control group is tracked in the third page lru pointer. This means 895 that we cannot use the controller with huge page less than 3 pages. 896 897config CPUSETS 898 bool "Cpuset controller" 899 depends on SMP 900 help 901 This option will let you create and manage CPUSETs which 902 allow dynamically partitioning a system into sets of CPUs and 903 Memory Nodes and assigning tasks to run only within those sets. 904 This is primarily useful on large SMP or NUMA systems. 905 906 Say N if unsure. 907 908config PROC_PID_CPUSET 909 bool "Include legacy /proc/<pid>/cpuset file" 910 depends on CPUSETS 911 default y 912 913config CGROUP_DEVICE 914 bool "Device controller" 915 help 916 Provides a cgroup controller implementing whitelists for 917 devices which a process in the cgroup can mknod or open. 918 919config CGROUP_CPUACCT 920 bool "Simple CPU accounting controller" 921 help 922 Provides a simple controller for monitoring the 923 total CPU consumed by the tasks in a cgroup. 924 925config CGROUP_PERF 926 bool "Perf controller" 927 depends on PERF_EVENTS 928 help 929 This option extends the perf per-cpu mode to restrict monitoring 930 to threads which belong to the cgroup specified and run on the 931 designated cpu. 932 933 Say N if unsure. 934 935config CGROUP_BPF 936 bool "Support for eBPF programs attached to cgroups" 937 depends on BPF_SYSCALL 938 select SOCK_CGROUP_DATA 939 help 940 Allow attaching eBPF programs to a cgroup using the bpf(2) 941 syscall command BPF_PROG_ATTACH. 942 943 In which context these programs are accessed depends on the type 944 of attachment. For instance, programs that are attached using 945 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 946 inet sockets. 947 948config CGROUP_DEBUG 949 bool "Debug controller" 950 default n 951 depends on DEBUG_KERNEL 952 help 953 This option enables a simple controller that exports 954 debugging information about the cgroups framework. This 955 controller is for control cgroup debugging only. Its 956 interfaces are not stable. 957 958 Say N. 959 960config SOCK_CGROUP_DATA 961 bool 962 default n 963 964endif # CGROUPS 965 966menuconfig NAMESPACES 967 bool "Namespaces support" if EXPERT 968 depends on MULTIUSER 969 default !EXPERT 970 help 971 Provides the way to make tasks work with different objects using 972 the same id. For example same IPC id may refer to different objects 973 or same user id or pid may refer to different tasks when used in 974 different namespaces. 975 976if NAMESPACES 977 978config UTS_NS 979 bool "UTS namespace" 980 default y 981 help 982 In this namespace tasks see different info provided with the 983 uname() system call 984 985config IPC_NS 986 bool "IPC namespace" 987 depends on (SYSVIPC || POSIX_MQUEUE) 988 default y 989 help 990 In this namespace tasks work with IPC ids which correspond to 991 different IPC objects in different namespaces. 992 993config USER_NS 994 bool "User namespace" 995 default n 996 help 997 This allows containers, i.e. vservers, to use user namespaces 998 to provide different user info for different servers. 999 1000 When user namespaces are enabled in the kernel it is 1001 recommended that the MEMCG option also be enabled and that 1002 user-space use the memory control groups to limit the amount 1003 of memory a memory unprivileged users can use. 1004 1005 If unsure, say N. 1006 1007config PID_NS 1008 bool "PID Namespaces" 1009 default y 1010 help 1011 Support process id namespaces. This allows having multiple 1012 processes with the same pid as long as they are in different 1013 pid namespaces. This is a building block of containers. 1014 1015config NET_NS 1016 bool "Network namespace" 1017 depends on NET 1018 default y 1019 help 1020 Allow user space to create what appear to be multiple instances 1021 of the network stack. 1022 1023endif # NAMESPACES 1024 1025config CHECKPOINT_RESTORE 1026 bool "Checkpoint/restore support" 1027 select PROC_CHILDREN 1028 default n 1029 help 1030 Enables additional kernel features in a sake of checkpoint/restore. 1031 In particular it adds auxiliary prctl codes to setup process text, 1032 data and heap segment sizes, and a few additional /proc filesystem 1033 entries. 1034 1035 If unsure, say N here. 1036 1037config SCHED_AUTOGROUP 1038 bool "Automatic process group scheduling" 1039 select CGROUPS 1040 select CGROUP_SCHED 1041 select FAIR_GROUP_SCHED 1042 help 1043 This option optimizes the scheduler for common desktop workloads by 1044 automatically creating and populating task groups. This separation 1045 of workloads isolates aggressive CPU burners (like build jobs) from 1046 desktop applications. Task group autogeneration is currently based 1047 upon task session. 1048 1049config SYSFS_DEPRECATED 1050 bool "Enable deprecated sysfs features to support old userspace tools" 1051 depends on SYSFS 1052 default n 1053 help 1054 This option adds code that switches the layout of the "block" class 1055 devices, to not show up in /sys/class/block/, but only in 1056 /sys/block/. 1057 1058 This switch is only active when the sysfs.deprecated=1 boot option is 1059 passed or the SYSFS_DEPRECATED_V2 option is set. 1060 1061 This option allows new kernels to run on old distributions and tools, 1062 which might get confused by /sys/class/block/. Since 2007/2008 all 1063 major distributions and tools handle this just fine. 1064 1065 Recent distributions and userspace tools after 2009/2010 depend on 1066 the existence of /sys/class/block/, and will not work with this 1067 option enabled. 1068 1069 Only if you are using a new kernel on an old distribution, you might 1070 need to say Y here. 1071 1072config SYSFS_DEPRECATED_V2 1073 bool "Enable deprecated sysfs features by default" 1074 default n 1075 depends on SYSFS 1076 depends on SYSFS_DEPRECATED 1077 help 1078 Enable deprecated sysfs by default. 1079 1080 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1081 option. 1082 1083 Only if you are using a new kernel on an old distribution, you might 1084 need to say Y here. Even then, odds are you would not need it 1085 enabled, you can always pass the boot option if absolutely necessary. 1086 1087config RELAY 1088 bool "Kernel->user space relay support (formerly relayfs)" 1089 select IRQ_WORK 1090 help 1091 This option enables support for relay interface support in 1092 certain file systems (such as debugfs). 1093 It is designed to provide an efficient mechanism for tools and 1094 facilities to relay large amounts of data from kernel space to 1095 user space. 1096 1097 If unsure, say N. 1098 1099config BLK_DEV_INITRD 1100 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1101 help 1102 The initial RAM filesystem is a ramfs which is loaded by the 1103 boot loader (loadlin or lilo) and that is mounted as root 1104 before the normal boot procedure. It is typically used to 1105 load modules needed to mount the "real" root file system, 1106 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1107 1108 If RAM disk support (BLK_DEV_RAM) is also included, this 1109 also enables initial RAM disk (initrd) support and adds 1110 15 Kbytes (more on some other architectures) to the kernel size. 1111 1112 If unsure say Y. 1113 1114if BLK_DEV_INITRD 1115 1116source "usr/Kconfig" 1117 1118endif 1119 1120choice 1121 prompt "Compiler optimization level" 1122 default CC_OPTIMIZE_FOR_PERFORMANCE 1123 1124config CC_OPTIMIZE_FOR_PERFORMANCE 1125 bool "Optimize for performance" 1126 help 1127 This is the default optimization level for the kernel, building 1128 with the "-O2" compiler flag for best performance and most 1129 helpful compile-time warnings. 1130 1131config CC_OPTIMIZE_FOR_SIZE 1132 bool "Optimize for size" 1133 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives 1134 help 1135 Enabling this option will pass "-Os" instead of "-O2" to 1136 your compiler resulting in a smaller kernel. 1137 1138 If unsure, say N. 1139 1140endchoice 1141 1142config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1143 bool 1144 help 1145 This requires that the arch annotates or otherwise protects 1146 its external entry points from being discarded. Linker scripts 1147 must also merge .text.*, .data.*, and .bss.* correctly into 1148 output sections. Care must be taken not to pull in unrelated 1149 sections (e.g., '.text.init'). Typically '.' in section names 1150 is used to distinguish them from label names / C identifiers. 1151 1152config LD_DEAD_CODE_DATA_ELIMINATION 1153 bool "Dead code and data elimination (EXPERIMENTAL)" 1154 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1155 depends on EXPERT 1156 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800) 1157 depends on $(cc-option,-ffunction-sections -fdata-sections) 1158 depends on $(ld-option,--gc-sections) 1159 help 1160 Enable this if you want to do dead code and data elimination with 1161 the linker by compiling with -ffunction-sections -fdata-sections, 1162 and linking with --gc-sections. 1163 1164 This can reduce on disk and in-memory size of the kernel 1165 code and static data, particularly for small configs and 1166 on small systems. This has the possibility of introducing 1167 silently broken kernel if the required annotations are not 1168 present. This option is not well tested yet, so use at your 1169 own risk. 1170 1171config SYSCTL 1172 bool 1173 1174config ANON_INODES 1175 bool 1176 1177config HAVE_UID16 1178 bool 1179 1180config SYSCTL_EXCEPTION_TRACE 1181 bool 1182 help 1183 Enable support for /proc/sys/debug/exception-trace. 1184 1185config SYSCTL_ARCH_UNALIGN_NO_WARN 1186 bool 1187 help 1188 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1189 Allows arch to define/use @no_unaligned_warning to possibly warn 1190 about unaligned access emulation going on under the hood. 1191 1192config SYSCTL_ARCH_UNALIGN_ALLOW 1193 bool 1194 help 1195 Enable support for /proc/sys/kernel/unaligned-trap 1196 Allows arches to define/use @unaligned_enabled to runtime toggle 1197 the unaligned access emulation. 1198 see arch/parisc/kernel/unaligned.c for reference 1199 1200config HAVE_PCSPKR_PLATFORM 1201 bool 1202 1203# interpreter that classic socket filters depend on 1204config BPF 1205 bool 1206 1207menuconfig EXPERT 1208 bool "Configure standard kernel features (expert users)" 1209 # Unhide debug options, to make the on-by-default options visible 1210 select DEBUG_KERNEL 1211 help 1212 This option allows certain base kernel options and settings 1213 to be disabled or tweaked. This is for specialized 1214 environments which can tolerate a "non-standard" kernel. 1215 Only use this if you really know what you are doing. 1216 1217config UID16 1218 bool "Enable 16-bit UID system calls" if EXPERT 1219 depends on HAVE_UID16 && MULTIUSER 1220 default y 1221 help 1222 This enables the legacy 16-bit UID syscall wrappers. 1223 1224config MULTIUSER 1225 bool "Multiple users, groups and capabilities support" if EXPERT 1226 default y 1227 help 1228 This option enables support for non-root users, groups and 1229 capabilities. 1230 1231 If you say N here, all processes will run with UID 0, GID 0, and all 1232 possible capabilities. Saying N here also compiles out support for 1233 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1234 setgid, and capset. 1235 1236 If unsure, say Y here. 1237 1238config SGETMASK_SYSCALL 1239 bool "sgetmask/ssetmask syscalls support" if EXPERT 1240 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1241 ---help--- 1242 sys_sgetmask and sys_ssetmask are obsolete system calls 1243 no longer supported in libc but still enabled by default in some 1244 architectures. 1245 1246 If unsure, leave the default option here. 1247 1248config SYSFS_SYSCALL 1249 bool "Sysfs syscall support" if EXPERT 1250 default y 1251 ---help--- 1252 sys_sysfs is an obsolete system call no longer supported in libc. 1253 Note that disabling this option is more secure but might break 1254 compatibility with some systems. 1255 1256 If unsure say Y here. 1257 1258config SYSCTL_SYSCALL 1259 bool "Sysctl syscall support" if EXPERT 1260 depends on PROC_SYSCTL 1261 default n 1262 select SYSCTL 1263 ---help--- 1264 sys_sysctl uses binary paths that have been found challenging 1265 to properly maintain and use. The interface in /proc/sys 1266 using paths with ascii names is now the primary path to this 1267 information. 1268 1269 Almost nothing using the binary sysctl interface so if you are 1270 trying to save some space it is probably safe to disable this, 1271 making your kernel marginally smaller. 1272 1273 If unsure say N here. 1274 1275config FHANDLE 1276 bool "open by fhandle syscalls" if EXPERT 1277 select EXPORTFS 1278 default y 1279 help 1280 If you say Y here, a user level program will be able to map 1281 file names to handle and then later use the handle for 1282 different file system operations. This is useful in implementing 1283 userspace file servers, which now track files using handles instead 1284 of names. The handle would remain the same even if file names 1285 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1286 syscalls. 1287 1288config POSIX_TIMERS 1289 bool "Posix Clocks & timers" if EXPERT 1290 default y 1291 help 1292 This includes native support for POSIX timers to the kernel. 1293 Some embedded systems have no use for them and therefore they 1294 can be configured out to reduce the size of the kernel image. 1295 1296 When this option is disabled, the following syscalls won't be 1297 available: timer_create, timer_gettime: timer_getoverrun, 1298 timer_settime, timer_delete, clock_adjtime, getitimer, 1299 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1300 clock_getres and clock_nanosleep syscalls will be limited to 1301 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1302 1303 If unsure say y. 1304 1305config PRINTK 1306 default y 1307 bool "Enable support for printk" if EXPERT 1308 select IRQ_WORK 1309 help 1310 This option enables normal printk support. Removing it 1311 eliminates most of the message strings from the kernel image 1312 and makes the kernel more or less silent. As this makes it 1313 very difficult to diagnose system problems, saying N here is 1314 strongly discouraged. 1315 1316config PRINTK_NMI 1317 def_bool y 1318 depends on PRINTK 1319 depends on HAVE_NMI 1320 1321config BUG 1322 bool "BUG() support" if EXPERT 1323 default y 1324 help 1325 Disabling this option eliminates support for BUG and WARN, reducing 1326 the size of your kernel image and potentially quietly ignoring 1327 numerous fatal conditions. You should only consider disabling this 1328 option for embedded systems with no facilities for reporting errors. 1329 Just say Y. 1330 1331config ELF_CORE 1332 depends on COREDUMP 1333 default y 1334 bool "Enable ELF core dumps" if EXPERT 1335 help 1336 Enable support for generating core dumps. Disabling saves about 4k. 1337 1338 1339config PCSPKR_PLATFORM 1340 bool "Enable PC-Speaker support" if EXPERT 1341 depends on HAVE_PCSPKR_PLATFORM 1342 select I8253_LOCK 1343 default y 1344 help 1345 This option allows to disable the internal PC-Speaker 1346 support, saving some memory. 1347 1348config BASE_FULL 1349 default y 1350 bool "Enable full-sized data structures for core" if EXPERT 1351 help 1352 Disabling this option reduces the size of miscellaneous core 1353 kernel data structures. This saves memory on small machines, 1354 but may reduce performance. 1355 1356config FUTEX 1357 bool "Enable futex support" if EXPERT 1358 default y 1359 imply RT_MUTEXES 1360 help 1361 Disabling this option will cause the kernel to be built without 1362 support for "fast userspace mutexes". The resulting kernel may not 1363 run glibc-based applications correctly. 1364 1365config FUTEX_PI 1366 bool 1367 depends on FUTEX && RT_MUTEXES 1368 default y 1369 1370config HAVE_FUTEX_CMPXCHG 1371 bool 1372 depends on FUTEX 1373 help 1374 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1375 is implemented and always working. This removes a couple of runtime 1376 checks. 1377 1378config EPOLL 1379 bool "Enable eventpoll support" if EXPERT 1380 default y 1381 select ANON_INODES 1382 help 1383 Disabling this option will cause the kernel to be built without 1384 support for epoll family of system calls. 1385 1386config SIGNALFD 1387 bool "Enable signalfd() system call" if EXPERT 1388 select ANON_INODES 1389 default y 1390 help 1391 Enable the signalfd() system call that allows to receive signals 1392 on a file descriptor. 1393 1394 If unsure, say Y. 1395 1396config TIMERFD 1397 bool "Enable timerfd() system call" if EXPERT 1398 select ANON_INODES 1399 default y 1400 help 1401 Enable the timerfd() system call that allows to receive timer 1402 events on a file descriptor. 1403 1404 If unsure, say Y. 1405 1406config EVENTFD 1407 bool "Enable eventfd() system call" if EXPERT 1408 select ANON_INODES 1409 default y 1410 help 1411 Enable the eventfd() system call that allows to receive both 1412 kernel notification (ie. KAIO) or userspace notifications. 1413 1414 If unsure, say Y. 1415 1416config SHMEM 1417 bool "Use full shmem filesystem" if EXPERT 1418 default y 1419 depends on MMU 1420 help 1421 The shmem is an internal filesystem used to manage shared memory. 1422 It is backed by swap and manages resource limits. It is also exported 1423 to userspace as tmpfs if TMPFS is enabled. Disabling this 1424 option replaces shmem and tmpfs with the much simpler ramfs code, 1425 which may be appropriate on small systems without swap. 1426 1427config AIO 1428 bool "Enable AIO support" if EXPERT 1429 default y 1430 help 1431 This option enables POSIX asynchronous I/O which may by used 1432 by some high performance threaded applications. Disabling 1433 this option saves about 7k. 1434 1435config IO_URING 1436 bool "Enable IO uring support" if EXPERT 1437 select ANON_INODES 1438 default y 1439 help 1440 This option enables support for the io_uring interface, enabling 1441 applications to submit and complete IO through submission and 1442 completion rings that are shared between the kernel and application. 1443 1444config ADVISE_SYSCALLS 1445 bool "Enable madvise/fadvise syscalls" if EXPERT 1446 default y 1447 help 1448 This option enables the madvise and fadvise syscalls, used by 1449 applications to advise the kernel about their future memory or file 1450 usage, improving performance. If building an embedded system where no 1451 applications use these syscalls, you can disable this option to save 1452 space. 1453 1454config MEMBARRIER 1455 bool "Enable membarrier() system call" if EXPERT 1456 default y 1457 help 1458 Enable the membarrier() system call that allows issuing memory 1459 barriers across all running threads, which can be used to distribute 1460 the cost of user-space memory barriers asymmetrically by transforming 1461 pairs of memory barriers into pairs consisting of membarrier() and a 1462 compiler barrier. 1463 1464 If unsure, say Y. 1465 1466config KALLSYMS 1467 bool "Load all symbols for debugging/ksymoops" if EXPERT 1468 default y 1469 help 1470 Say Y here to let the kernel print out symbolic crash information and 1471 symbolic stack backtraces. This increases the size of the kernel 1472 somewhat, as all symbols have to be loaded into the kernel image. 1473 1474config KALLSYMS_ALL 1475 bool "Include all symbols in kallsyms" 1476 depends on DEBUG_KERNEL && KALLSYMS 1477 help 1478 Normally kallsyms only contains the symbols of functions for nicer 1479 OOPS messages and backtraces (i.e., symbols from the text and inittext 1480 sections). This is sufficient for most cases. And only in very rare 1481 cases (e.g., when a debugger is used) all symbols are required (e.g., 1482 names of variables from the data sections, etc). 1483 1484 This option makes sure that all symbols are loaded into the kernel 1485 image (i.e., symbols from all sections) in cost of increased kernel 1486 size (depending on the kernel configuration, it may be 300KiB or 1487 something like this). 1488 1489 Say N unless you really need all symbols. 1490 1491config KALLSYMS_ABSOLUTE_PERCPU 1492 bool 1493 depends on KALLSYMS 1494 default X86_64 && SMP 1495 1496config KALLSYMS_BASE_RELATIVE 1497 bool 1498 depends on KALLSYMS 1499 default !IA64 1500 help 1501 Instead of emitting them as absolute values in the native word size, 1502 emit the symbol references in the kallsyms table as 32-bit entries, 1503 each containing a relative value in the range [base, base + U32_MAX] 1504 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1505 an absolute value in the range [0, S32_MAX] or a relative value in the 1506 range [base, base + S32_MAX], where base is the lowest relative symbol 1507 address encountered in the image. 1508 1509 On 64-bit builds, this reduces the size of the address table by 50%, 1510 but more importantly, it results in entries whose values are build 1511 time constants, and no relocation pass is required at runtime to fix 1512 up the entries based on the runtime load address of the kernel. 1513 1514# end of the "standard kernel features (expert users)" menu 1515 1516# syscall, maps, verifier 1517config BPF_SYSCALL 1518 bool "Enable bpf() system call" 1519 select ANON_INODES 1520 select BPF 1521 select IRQ_WORK 1522 default n 1523 help 1524 Enable the bpf() system call that allows to manipulate eBPF 1525 programs and maps via file descriptors. 1526 1527config BPF_JIT_ALWAYS_ON 1528 bool "Permanently enable BPF JIT and remove BPF interpreter" 1529 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1530 help 1531 Enables BPF JIT and removes BPF interpreter to avoid 1532 speculative execution of BPF instructions by the interpreter 1533 1534config USERFAULTFD 1535 bool "Enable userfaultfd() system call" 1536 select ANON_INODES 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 ANON_INODES 1604 select IRQ_WORK 1605 select SRCU 1606 help 1607 Enable kernel support for various performance events provided 1608 by software and hardware. 1609 1610 Software events are supported either built-in or via the 1611 use of generic tracepoints. 1612 1613 Most modern CPUs support performance events via performance 1614 counter registers. These registers count the number of certain 1615 types of hw events: such as instructions executed, cachemisses 1616 suffered, or branches mis-predicted - without slowing down the 1617 kernel or applications. These registers can also trigger interrupts 1618 when a threshold number of events have passed - and can thus be 1619 used to profile the code that runs on that CPU. 1620 1621 The Linux Performance Event subsystem provides an abstraction of 1622 these software and hardware event capabilities, available via a 1623 system call and used by the "perf" utility in tools/perf/. It 1624 provides per task and per CPU counters, and it provides event 1625 capabilities on top of those. 1626 1627 Say Y if unsure. 1628 1629config DEBUG_PERF_USE_VMALLOC 1630 default n 1631 bool "Debug: use vmalloc to back perf mmap() buffers" 1632 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1633 select PERF_USE_VMALLOC 1634 help 1635 Use vmalloc memory to back perf mmap() buffers. 1636 1637 Mostly useful for debugging the vmalloc code on platforms 1638 that don't require it. 1639 1640 Say N if unsure. 1641 1642endmenu 1643 1644config VM_EVENT_COUNTERS 1645 default y 1646 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1647 help 1648 VM event counters are needed for event counts to be shown. 1649 This option allows the disabling of the VM event counters 1650 on EXPERT systems. /proc/vmstat will only show page counts 1651 if VM event counters are disabled. 1652 1653config SLUB_DEBUG 1654 default y 1655 bool "Enable SLUB debugging support" if EXPERT 1656 depends on SLUB && SYSFS 1657 help 1658 SLUB has extensive debug support features. Disabling these can 1659 result in significant savings in code size. This also disables 1660 SLUB sysfs support. /sys/slab will not exist and there will be 1661 no support for cache validation etc. 1662 1663config SLUB_MEMCG_SYSFS_ON 1664 default n 1665 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1666 depends on SLUB && SYSFS && MEMCG 1667 help 1668 SLUB creates a directory under /sys/kernel/slab for each 1669 allocation cache to host info and debug files. If memory 1670 cgroup is enabled, each cache can have per memory cgroup 1671 caches. SLUB can create the same sysfs directories for these 1672 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1673 to a very high number of debug files being created. This is 1674 controlled by slub_memcg_sysfs boot parameter and this 1675 config option determines the parameter's default value. 1676 1677config COMPAT_BRK 1678 bool "Disable heap randomization" 1679 default y 1680 help 1681 Randomizing heap placement makes heap exploits harder, but it 1682 also breaks ancient binaries (including anything libc5 based). 1683 This option changes the bootup default to heap randomization 1684 disabled, and can be overridden at runtime by setting 1685 /proc/sys/kernel/randomize_va_space to 2. 1686 1687 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1688 1689choice 1690 prompt "Choose SLAB allocator" 1691 default SLUB 1692 help 1693 This option allows to select a slab allocator. 1694 1695config SLAB 1696 bool "SLAB" 1697 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1698 help 1699 The regular slab allocator that is established and known to work 1700 well in all environments. It organizes cache hot objects in 1701 per cpu and per node queues. 1702 1703config SLUB 1704 bool "SLUB (Unqueued Allocator)" 1705 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1706 help 1707 SLUB is a slab allocator that minimizes cache line usage 1708 instead of managing queues of cached objects (SLAB approach). 1709 Per cpu caching is realized using slabs of objects instead 1710 of queues of objects. SLUB can use memory efficiently 1711 and has enhanced diagnostics. SLUB is the default choice for 1712 a slab allocator. 1713 1714config SLOB 1715 depends on EXPERT 1716 bool "SLOB (Simple Allocator)" 1717 help 1718 SLOB replaces the stock allocator with a drastically simpler 1719 allocator. SLOB is generally more space efficient but 1720 does not perform as well on large systems. 1721 1722endchoice 1723 1724config SLAB_MERGE_DEFAULT 1725 bool "Allow slab caches to be merged" 1726 default y 1727 help 1728 For reduced kernel memory fragmentation, slab caches can be 1729 merged when they share the same size and other characteristics. 1730 This carries a risk of kernel heap overflows being able to 1731 overwrite objects from merged caches (and more easily control 1732 cache layout), which makes such heap attacks easier to exploit 1733 by attackers. By keeping caches unmerged, these kinds of exploits 1734 can usually only damage objects in the same cache. To disable 1735 merging at runtime, "slab_nomerge" can be passed on the kernel 1736 command line. 1737 1738config SLAB_FREELIST_RANDOM 1739 default n 1740 depends on SLAB || SLUB 1741 bool "SLAB freelist randomization" 1742 help 1743 Randomizes the freelist order used on creating new pages. This 1744 security feature reduces the predictability of the kernel slab 1745 allocator against heap overflows. 1746 1747config SLAB_FREELIST_HARDENED 1748 bool "Harden slab freelist metadata" 1749 depends on SLUB 1750 help 1751 Many kernel heap attacks try to target slab cache metadata and 1752 other infrastructure. This options makes minor performance 1753 sacrifies to harden the kernel slab allocator against common 1754 freelist exploit methods. 1755 1756config SLUB_CPU_PARTIAL 1757 default y 1758 depends on SLUB && SMP 1759 bool "SLUB per cpu partial cache" 1760 help 1761 Per cpu partial caches accellerate objects allocation and freeing 1762 that is local to a processor at the price of more indeterminism 1763 in the latency of the free. On overflow these caches will be cleared 1764 which requires the taking of locks that may cause latency spikes. 1765 Typically one would choose no for a realtime system. 1766 1767config MMAP_ALLOW_UNINITIALIZED 1768 bool "Allow mmapped anonymous memory to be uninitialized" 1769 depends on EXPERT && !MMU 1770 default n 1771 help 1772 Normally, and according to the Linux spec, anonymous memory obtained 1773 from mmap() has its contents cleared before it is passed to 1774 userspace. Enabling this config option allows you to request that 1775 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1776 providing a huge performance boost. If this option is not enabled, 1777 then the flag will be ignored. 1778 1779 This is taken advantage of by uClibc's malloc(), and also by 1780 ELF-FDPIC binfmt's brk and stack allocator. 1781 1782 Because of the obvious security issues, this option should only be 1783 enabled on embedded devices where you control what is run in 1784 userspace. Since that isn't generally a problem on no-MMU systems, 1785 it is normally safe to say Y here. 1786 1787 See Documentation/nommu-mmap.txt for more information. 1788 1789config SYSTEM_DATA_VERIFICATION 1790 def_bool n 1791 select SYSTEM_TRUSTED_KEYRING 1792 select KEYS 1793 select CRYPTO 1794 select CRYPTO_RSA 1795 select ASYMMETRIC_KEY_TYPE 1796 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1797 select ASN1 1798 select OID_REGISTRY 1799 select X509_CERTIFICATE_PARSER 1800 select PKCS7_MESSAGE_PARSER 1801 help 1802 Provide PKCS#7 message verification using the contents of the system 1803 trusted keyring to provide public keys. This then can be used for 1804 module verification, kexec image verification and firmware blob 1805 verification. 1806 1807config PROFILING 1808 bool "Profiling support" 1809 help 1810 Say Y here to enable the extended profiling support mechanisms used 1811 by profilers such as OProfile. 1812 1813# 1814# Place an empty function call at each tracepoint site. Can be 1815# dynamically changed for a probe function. 1816# 1817config TRACEPOINTS 1818 bool 1819 1820endmenu # General setup 1821 1822source "arch/Kconfig" 1823 1824config RT_MUTEXES 1825 bool 1826 1827config BASE_SMALL 1828 int 1829 default 0 if BASE_FULL 1830 default 1 if !BASE_FULL 1831 1832menuconfig MODULES 1833 bool "Enable loadable module support" 1834 option modules 1835 help 1836 Kernel modules are small pieces of compiled code which can 1837 be inserted in the running kernel, rather than being 1838 permanently built into the kernel. You use the "modprobe" 1839 tool to add (and sometimes remove) them. If you say Y here, 1840 many parts of the kernel can be built as modules (by 1841 answering M instead of Y where indicated): this is most 1842 useful for infrequently used options which are not required 1843 for booting. For more information, see the man pages for 1844 modprobe, lsmod, modinfo, insmod and rmmod. 1845 1846 If you say Y here, you will need to run "make 1847 modules_install" to put the modules under /lib/modules/ 1848 where modprobe can find them (you may need to be root to do 1849 this). 1850 1851 If unsure, say Y. 1852 1853if MODULES 1854 1855config MODULE_FORCE_LOAD 1856 bool "Forced module loading" 1857 default n 1858 help 1859 Allow loading of modules without version information (ie. modprobe 1860 --force). Forced module loading sets the 'F' (forced) taint flag and 1861 is usually a really bad idea. 1862 1863config MODULE_UNLOAD 1864 bool "Module unloading" 1865 help 1866 Without this option you will not be able to unload any 1867 modules (note that some modules may not be unloadable 1868 anyway), which makes your kernel smaller, faster 1869 and simpler. If unsure, say Y. 1870 1871config MODULE_FORCE_UNLOAD 1872 bool "Forced module unloading" 1873 depends on MODULE_UNLOAD 1874 help 1875 This option allows you to force a module to unload, even if the 1876 kernel believes it is unsafe: the kernel will remove the module 1877 without waiting for anyone to stop using it (using the -f option to 1878 rmmod). This is mainly for kernel developers and desperate users. 1879 If unsure, say N. 1880 1881config MODVERSIONS 1882 bool "Module versioning support" 1883 help 1884 Usually, you have to use modules compiled with your kernel. 1885 Saying Y here makes it sometimes possible to use modules 1886 compiled for different kernels, by adding enough information 1887 to the modules to (hopefully) spot any changes which would 1888 make them incompatible with the kernel you are running. If 1889 unsure, say N. 1890 1891config MODULE_REL_CRCS 1892 bool 1893 depends on MODVERSIONS 1894 1895config MODULE_SRCVERSION_ALL 1896 bool "Source checksum for all modules" 1897 help 1898 Modules which contain a MODULE_VERSION get an extra "srcversion" 1899 field inserted into their modinfo section, which contains a 1900 sum of the source files which made it. This helps maintainers 1901 see exactly which source was used to build a module (since 1902 others sometimes change the module source without updating 1903 the version). With this option, such a "srcversion" field 1904 will be created for all modules. If unsure, say N. 1905 1906config MODULE_SIG 1907 bool "Module signature verification" 1908 depends on MODULES 1909 select SYSTEM_DATA_VERIFICATION 1910 help 1911 Check modules for valid signatures upon load: the signature 1912 is simply appended to the module. For more information see 1913 <file:Documentation/admin-guide/module-signing.rst>. 1914 1915 Note that this option adds the OpenSSL development packages as a 1916 kernel build dependency so that the signing tool can use its crypto 1917 library. 1918 1919 !!!WARNING!!! If you enable this option, you MUST make sure that the 1920 module DOES NOT get stripped after being signed. This includes the 1921 debuginfo strip done by some packagers (such as rpmbuild) and 1922 inclusion into an initramfs that wants the module size reduced. 1923 1924config MODULE_SIG_FORCE 1925 bool "Require modules to be validly signed" 1926 depends on MODULE_SIG 1927 help 1928 Reject unsigned modules or signed modules for which we don't have a 1929 key. Without this, such modules will simply taint the kernel. 1930 1931config MODULE_SIG_ALL 1932 bool "Automatically sign all modules" 1933 default y 1934 depends on MODULE_SIG 1935 help 1936 Sign all modules during make modules_install. Without this option, 1937 modules must be signed manually, using the scripts/sign-file tool. 1938 1939comment "Do not forget to sign required modules with scripts/sign-file" 1940 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 1941 1942choice 1943 prompt "Which hash algorithm should modules be signed with?" 1944 depends on MODULE_SIG 1945 help 1946 This determines which sort of hashing algorithm will be used during 1947 signature generation. This algorithm _must_ be built into the kernel 1948 directly so that signature verification can take place. It is not 1949 possible to load a signed module containing the algorithm to check 1950 the signature on that module. 1951 1952config MODULE_SIG_SHA1 1953 bool "Sign modules with SHA-1" 1954 select CRYPTO_SHA1 1955 1956config MODULE_SIG_SHA224 1957 bool "Sign modules with SHA-224" 1958 select CRYPTO_SHA256 1959 1960config MODULE_SIG_SHA256 1961 bool "Sign modules with SHA-256" 1962 select CRYPTO_SHA256 1963 1964config MODULE_SIG_SHA384 1965 bool "Sign modules with SHA-384" 1966 select CRYPTO_SHA512 1967 1968config MODULE_SIG_SHA512 1969 bool "Sign modules with SHA-512" 1970 select CRYPTO_SHA512 1971 1972endchoice 1973 1974config MODULE_SIG_HASH 1975 string 1976 depends on MODULE_SIG 1977 default "sha1" if MODULE_SIG_SHA1 1978 default "sha224" if MODULE_SIG_SHA224 1979 default "sha256" if MODULE_SIG_SHA256 1980 default "sha384" if MODULE_SIG_SHA384 1981 default "sha512" if MODULE_SIG_SHA512 1982 1983config MODULE_COMPRESS 1984 bool "Compress modules on installation" 1985 depends on MODULES 1986 help 1987 1988 Compresses kernel modules when 'make modules_install' is run; gzip or 1989 xz depending on "Compression algorithm" below. 1990 1991 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 1992 1993 Out-of-tree kernel modules installed using Kbuild will also be 1994 compressed upon installation. 1995 1996 Note: for modules inside an initrd or initramfs, it's more efficient 1997 to compress the whole initrd or initramfs instead. 1998 1999 Note: This is fully compatible with signed modules. 2000 2001 If in doubt, say N. 2002 2003choice 2004 prompt "Compression algorithm" 2005 depends on MODULE_COMPRESS 2006 default MODULE_COMPRESS_GZIP 2007 help 2008 This determines which sort of compression will be used during 2009 'make modules_install'. 2010 2011 GZIP (default) and XZ are supported. 2012 2013config MODULE_COMPRESS_GZIP 2014 bool "GZIP" 2015 2016config MODULE_COMPRESS_XZ 2017 bool "XZ" 2018 2019endchoice 2020 2021config TRIM_UNUSED_KSYMS 2022 bool "Trim unused exported kernel symbols" 2023 depends on MODULES && !UNUSED_SYMBOLS 2024 help 2025 The kernel and some modules make many symbols available for 2026 other modules to use via EXPORT_SYMBOL() and variants. Depending 2027 on the set of modules being selected in your kernel configuration, 2028 many of those exported symbols might never be used. 2029 2030 This option allows for unused exported symbols to be dropped from 2031 the build. In turn, this provides the compiler more opportunities 2032 (especially when using LTO) for optimizing the code and reducing 2033 binary size. This might have some security advantages as well. 2034 2035 If unsure, or if you need to build out-of-tree modules, say N. 2036 2037endif # MODULES 2038 2039config MODULES_TREE_LOOKUP 2040 def_bool y 2041 depends on PERF_EVENTS || TRACING 2042 2043config INIT_ALL_POSSIBLE 2044 bool 2045 help 2046 Back when each arch used to define their own cpu_online_mask and 2047 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2048 with all 1s, and others with all 0s. When they were centralised, 2049 it was better to provide this option than to break all the archs 2050 and have several arch maintainers pursuing me down dark alleys. 2051 2052source "block/Kconfig" 2053 2054config PREEMPT_NOTIFIERS 2055 bool 2056 2057config PADATA 2058 depends on SMP 2059 bool 2060 2061config ASN1 2062 tristate 2063 help 2064 Build a simple ASN.1 grammar compiler that produces a bytecode output 2065 that can be interpreted by the ASN.1 stream decoder and used to 2066 inform it as to what tags are to be expected in a stream and what 2067 functions to call on what tags. 2068 2069source "kernel/Kconfig.locks" 2070 2071config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2072 bool 2073 2074# It may be useful for an architecture to override the definitions of the 2075# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2076# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2077# different calling convention for syscalls. They can also override the 2078# macros for not-implemented syscalls in kernel/sys_ni.c and 2079# kernel/time/posix-stubs.c. All these overrides need to be available in 2080# <asm/syscall_wrapper.h>. 2081config ARCH_HAS_SYSCALL_WRAPPER 2082 def_bool n 2083