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