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 help 1101 Enable this if you want to do dead code and data elimination with 1102 the linker by compiling with -ffunction-sections -fdata-sections, 1103 and linking with --gc-sections. 1104 1105 This can reduce on disk and in-memory size of the kernel 1106 code and static data, particularly for small configs and 1107 on small systems. This has the possibility of introducing 1108 silently broken kernel if the required annotations are not 1109 present. This option is not well tested yet, so use at your 1110 own risk. 1111 1112config SYSCTL 1113 bool 1114 1115config ANON_INODES 1116 bool 1117 1118config HAVE_UID16 1119 bool 1120 1121config SYSCTL_EXCEPTION_TRACE 1122 bool 1123 help 1124 Enable support for /proc/sys/debug/exception-trace. 1125 1126config SYSCTL_ARCH_UNALIGN_NO_WARN 1127 bool 1128 help 1129 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1130 Allows arch to define/use @no_unaligned_warning to possibly warn 1131 about unaligned access emulation going on under the hood. 1132 1133config SYSCTL_ARCH_UNALIGN_ALLOW 1134 bool 1135 help 1136 Enable support for /proc/sys/kernel/unaligned-trap 1137 Allows arches to define/use @unaligned_enabled to runtime toggle 1138 the unaligned access emulation. 1139 see arch/parisc/kernel/unaligned.c for reference 1140 1141config HAVE_PCSPKR_PLATFORM 1142 bool 1143 1144# interpreter that classic socket filters depend on 1145config BPF 1146 bool 1147 1148menuconfig EXPERT 1149 bool "Configure standard kernel features (expert users)" 1150 # Unhide debug options, to make the on-by-default options visible 1151 select DEBUG_KERNEL 1152 help 1153 This option allows certain base kernel options and settings 1154 to be disabled or tweaked. This is for specialized 1155 environments which can tolerate a "non-standard" kernel. 1156 Only use this if you really know what you are doing. 1157 1158config UID16 1159 bool "Enable 16-bit UID system calls" if EXPERT 1160 depends on HAVE_UID16 && MULTIUSER 1161 default y 1162 help 1163 This enables the legacy 16-bit UID syscall wrappers. 1164 1165config MULTIUSER 1166 bool "Multiple users, groups and capabilities support" if EXPERT 1167 default y 1168 help 1169 This option enables support for non-root users, groups and 1170 capabilities. 1171 1172 If you say N here, all processes will run with UID 0, GID 0, and all 1173 possible capabilities. Saying N here also compiles out support for 1174 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1175 setgid, and capset. 1176 1177 If unsure, say Y here. 1178 1179config SGETMASK_SYSCALL 1180 bool "sgetmask/ssetmask syscalls support" if EXPERT 1181 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1182 ---help--- 1183 sys_sgetmask and sys_ssetmask are obsolete system calls 1184 no longer supported in libc but still enabled by default in some 1185 architectures. 1186 1187 If unsure, leave the default option here. 1188 1189config SYSFS_SYSCALL 1190 bool "Sysfs syscall support" if EXPERT 1191 default y 1192 ---help--- 1193 sys_sysfs is an obsolete system call no longer supported in libc. 1194 Note that disabling this option is more secure but might break 1195 compatibility with some systems. 1196 1197 If unsure say Y here. 1198 1199config SYSCTL_SYSCALL 1200 bool "Sysctl syscall support" if EXPERT 1201 depends on PROC_SYSCTL 1202 default n 1203 select SYSCTL 1204 ---help--- 1205 sys_sysctl uses binary paths that have been found challenging 1206 to properly maintain and use. The interface in /proc/sys 1207 using paths with ascii names is now the primary path to this 1208 information. 1209 1210 Almost nothing using the binary sysctl interface so if you are 1211 trying to save some space it is probably safe to disable this, 1212 making your kernel marginally smaller. 1213 1214 If unsure say N here. 1215 1216config FHANDLE 1217 bool "open by fhandle syscalls" if EXPERT 1218 select EXPORTFS 1219 default y 1220 help 1221 If you say Y here, a user level program will be able to map 1222 file names to handle and then later use the handle for 1223 different file system operations. This is useful in implementing 1224 userspace file servers, which now track files using handles instead 1225 of names. The handle would remain the same even if file names 1226 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1227 syscalls. 1228 1229config POSIX_TIMERS 1230 bool "Posix Clocks & timers" if EXPERT 1231 default y 1232 help 1233 This includes native support for POSIX timers to the kernel. 1234 Some embedded systems have no use for them and therefore they 1235 can be configured out to reduce the size of the kernel image. 1236 1237 When this option is disabled, the following syscalls won't be 1238 available: timer_create, timer_gettime: timer_getoverrun, 1239 timer_settime, timer_delete, clock_adjtime, getitimer, 1240 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1241 clock_getres and clock_nanosleep syscalls will be limited to 1242 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1243 1244 If unsure say y. 1245 1246config PRINTK 1247 default y 1248 bool "Enable support for printk" if EXPERT 1249 select IRQ_WORK 1250 help 1251 This option enables normal printk support. Removing it 1252 eliminates most of the message strings from the kernel image 1253 and makes the kernel more or less silent. As this makes it 1254 very difficult to diagnose system problems, saying N here is 1255 strongly discouraged. 1256 1257config PRINTK_NMI 1258 def_bool y 1259 depends on PRINTK 1260 depends on HAVE_NMI 1261 1262config BUG 1263 bool "BUG() support" if EXPERT 1264 default y 1265 help 1266 Disabling this option eliminates support for BUG and WARN, reducing 1267 the size of your kernel image and potentially quietly ignoring 1268 numerous fatal conditions. You should only consider disabling this 1269 option for embedded systems with no facilities for reporting errors. 1270 Just say Y. 1271 1272config ELF_CORE 1273 depends on COREDUMP 1274 default y 1275 bool "Enable ELF core dumps" if EXPERT 1276 help 1277 Enable support for generating core dumps. Disabling saves about 4k. 1278 1279 1280config PCSPKR_PLATFORM 1281 bool "Enable PC-Speaker support" if EXPERT 1282 depends on HAVE_PCSPKR_PLATFORM 1283 select I8253_LOCK 1284 default y 1285 help 1286 This option allows to disable the internal PC-Speaker 1287 support, saving some memory. 1288 1289config BASE_FULL 1290 default y 1291 bool "Enable full-sized data structures for core" if EXPERT 1292 help 1293 Disabling this option reduces the size of miscellaneous core 1294 kernel data structures. This saves memory on small machines, 1295 but may reduce performance. 1296 1297config FUTEX 1298 bool "Enable futex support" if EXPERT 1299 default y 1300 imply RT_MUTEXES 1301 help 1302 Disabling this option will cause the kernel to be built without 1303 support for "fast userspace mutexes". The resulting kernel may not 1304 run glibc-based applications correctly. 1305 1306config FUTEX_PI 1307 bool 1308 depends on FUTEX && RT_MUTEXES 1309 default y 1310 1311config HAVE_FUTEX_CMPXCHG 1312 bool 1313 depends on FUTEX 1314 help 1315 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1316 is implemented and always working. This removes a couple of runtime 1317 checks. 1318 1319config EPOLL 1320 bool "Enable eventpoll support" if EXPERT 1321 default y 1322 select ANON_INODES 1323 help 1324 Disabling this option will cause the kernel to be built without 1325 support for epoll family of system calls. 1326 1327config SIGNALFD 1328 bool "Enable signalfd() system call" if EXPERT 1329 select ANON_INODES 1330 default y 1331 help 1332 Enable the signalfd() system call that allows to receive signals 1333 on a file descriptor. 1334 1335 If unsure, say Y. 1336 1337config TIMERFD 1338 bool "Enable timerfd() system call" if EXPERT 1339 select ANON_INODES 1340 default y 1341 help 1342 Enable the timerfd() system call that allows to receive timer 1343 events on a file descriptor. 1344 1345 If unsure, say Y. 1346 1347config EVENTFD 1348 bool "Enable eventfd() system call" if EXPERT 1349 select ANON_INODES 1350 default y 1351 help 1352 Enable the eventfd() system call that allows to receive both 1353 kernel notification (ie. KAIO) or userspace notifications. 1354 1355 If unsure, say Y. 1356 1357config SHMEM 1358 bool "Use full shmem filesystem" if EXPERT 1359 default y 1360 depends on MMU 1361 help 1362 The shmem is an internal filesystem used to manage shared memory. 1363 It is backed by swap and manages resource limits. It is also exported 1364 to userspace as tmpfs if TMPFS is enabled. Disabling this 1365 option replaces shmem and tmpfs with the much simpler ramfs code, 1366 which may be appropriate on small systems without swap. 1367 1368config AIO 1369 bool "Enable AIO support" if EXPERT 1370 default y 1371 help 1372 This option enables POSIX asynchronous I/O which may by used 1373 by some high performance threaded applications. Disabling 1374 this option saves about 7k. 1375 1376config ADVISE_SYSCALLS 1377 bool "Enable madvise/fadvise syscalls" if EXPERT 1378 default y 1379 help 1380 This option enables the madvise and fadvise syscalls, used by 1381 applications to advise the kernel about their future memory or file 1382 usage, improving performance. If building an embedded system where no 1383 applications use these syscalls, you can disable this option to save 1384 space. 1385 1386config MEMBARRIER 1387 bool "Enable membarrier() system call" if EXPERT 1388 default y 1389 help 1390 Enable the membarrier() system call that allows issuing memory 1391 barriers across all running threads, which can be used to distribute 1392 the cost of user-space memory barriers asymmetrically by transforming 1393 pairs of memory barriers into pairs consisting of membarrier() and a 1394 compiler barrier. 1395 1396 If unsure, say Y. 1397 1398config KALLSYMS 1399 bool "Load all symbols for debugging/ksymoops" if EXPERT 1400 default y 1401 help 1402 Say Y here to let the kernel print out symbolic crash information and 1403 symbolic stack backtraces. This increases the size of the kernel 1404 somewhat, as all symbols have to be loaded into the kernel image. 1405 1406config KALLSYMS_ALL 1407 bool "Include all symbols in kallsyms" 1408 depends on DEBUG_KERNEL && KALLSYMS 1409 help 1410 Normally kallsyms only contains the symbols of functions for nicer 1411 OOPS messages and backtraces (i.e., symbols from the text and inittext 1412 sections). This is sufficient for most cases. And only in very rare 1413 cases (e.g., when a debugger is used) all symbols are required (e.g., 1414 names of variables from the data sections, etc). 1415 1416 This option makes sure that all symbols are loaded into the kernel 1417 image (i.e., symbols from all sections) in cost of increased kernel 1418 size (depending on the kernel configuration, it may be 300KiB or 1419 something like this). 1420 1421 Say N unless you really need all symbols. 1422 1423config KALLSYMS_ABSOLUTE_PERCPU 1424 bool 1425 depends on KALLSYMS 1426 default X86_64 && SMP 1427 1428config KALLSYMS_BASE_RELATIVE 1429 bool 1430 depends on KALLSYMS 1431 default !IA64 1432 help 1433 Instead of emitting them as absolute values in the native word size, 1434 emit the symbol references in the kallsyms table as 32-bit entries, 1435 each containing a relative value in the range [base, base + U32_MAX] 1436 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1437 an absolute value in the range [0, S32_MAX] or a relative value in the 1438 range [base, base + S32_MAX], where base is the lowest relative symbol 1439 address encountered in the image. 1440 1441 On 64-bit builds, this reduces the size of the address table by 50%, 1442 but more importantly, it results in entries whose values are build 1443 time constants, and no relocation pass is required at runtime to fix 1444 up the entries based on the runtime load address of the kernel. 1445 1446# end of the "standard kernel features (expert users)" menu 1447 1448# syscall, maps, verifier 1449config BPF_SYSCALL 1450 bool "Enable bpf() system call" 1451 select ANON_INODES 1452 select BPF 1453 select IRQ_WORK 1454 default n 1455 help 1456 Enable the bpf() system call that allows to manipulate eBPF 1457 programs and maps via file descriptors. 1458 1459config BPF_JIT_ALWAYS_ON 1460 bool "Permanently enable BPF JIT and remove BPF interpreter" 1461 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1462 help 1463 Enables BPF JIT and removes BPF interpreter to avoid 1464 speculative execution of BPF instructions by the interpreter 1465 1466config USERFAULTFD 1467 bool "Enable userfaultfd() system call" 1468 select ANON_INODES 1469 depends on MMU 1470 help 1471 Enable the userfaultfd() system call that allows to intercept and 1472 handle page faults in userland. 1473 1474config ARCH_HAS_MEMBARRIER_CALLBACKS 1475 bool 1476 1477config ARCH_HAS_MEMBARRIER_SYNC_CORE 1478 bool 1479 1480config RSEQ 1481 bool "Enable rseq() system call" if EXPERT 1482 default y 1483 depends on HAVE_RSEQ 1484 select MEMBARRIER 1485 help 1486 Enable the restartable sequences system call. It provides a 1487 user-space cache for the current CPU number value, which 1488 speeds up getting the current CPU number from user-space, 1489 as well as an ABI to speed up user-space operations on 1490 per-CPU data. 1491 1492 If unsure, say Y. 1493 1494config DEBUG_RSEQ 1495 default n 1496 bool "Enabled debugging of rseq() system call" if EXPERT 1497 depends on RSEQ && DEBUG_KERNEL 1498 help 1499 Enable extra debugging checks for the rseq system call. 1500 1501 If unsure, say N. 1502 1503config EMBEDDED 1504 bool "Embedded system" 1505 option allnoconfig_y 1506 select EXPERT 1507 help 1508 This option should be enabled if compiling the kernel for 1509 an embedded system so certain expert options are available 1510 for configuration. 1511 1512config HAVE_PERF_EVENTS 1513 bool 1514 help 1515 See tools/perf/design.txt for details. 1516 1517config PERF_USE_VMALLOC 1518 bool 1519 help 1520 See tools/perf/design.txt for details 1521 1522config PC104 1523 bool "PC/104 support" if EXPERT 1524 help 1525 Expose PC/104 form factor device drivers and options available for 1526 selection and configuration. Enable this option if your target 1527 machine has a PC/104 bus. 1528 1529menu "Kernel Performance Events And Counters" 1530 1531config PERF_EVENTS 1532 bool "Kernel performance events and counters" 1533 default y if PROFILING 1534 depends on HAVE_PERF_EVENTS 1535 select ANON_INODES 1536 select IRQ_WORK 1537 select SRCU 1538 help 1539 Enable kernel support for various performance events provided 1540 by software and hardware. 1541 1542 Software events are supported either built-in or via the 1543 use of generic tracepoints. 1544 1545 Most modern CPUs support performance events via performance 1546 counter registers. These registers count the number of certain 1547 types of hw events: such as instructions executed, cachemisses 1548 suffered, or branches mis-predicted - without slowing down the 1549 kernel or applications. These registers can also trigger interrupts 1550 when a threshold number of events have passed - and can thus be 1551 used to profile the code that runs on that CPU. 1552 1553 The Linux Performance Event subsystem provides an abstraction of 1554 these software and hardware event capabilities, available via a 1555 system call and used by the "perf" utility in tools/perf/. It 1556 provides per task and per CPU counters, and it provides event 1557 capabilities on top of those. 1558 1559 Say Y if unsure. 1560 1561config DEBUG_PERF_USE_VMALLOC 1562 default n 1563 bool "Debug: use vmalloc to back perf mmap() buffers" 1564 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1565 select PERF_USE_VMALLOC 1566 help 1567 Use vmalloc memory to back perf mmap() buffers. 1568 1569 Mostly useful for debugging the vmalloc code on platforms 1570 that don't require it. 1571 1572 Say N if unsure. 1573 1574endmenu 1575 1576config VM_EVENT_COUNTERS 1577 default y 1578 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1579 help 1580 VM event counters are needed for event counts to be shown. 1581 This option allows the disabling of the VM event counters 1582 on EXPERT systems. /proc/vmstat will only show page counts 1583 if VM event counters are disabled. 1584 1585config SLUB_DEBUG 1586 default y 1587 bool "Enable SLUB debugging support" if EXPERT 1588 depends on SLUB && SYSFS 1589 help 1590 SLUB has extensive debug support features. Disabling these can 1591 result in significant savings in code size. This also disables 1592 SLUB sysfs support. /sys/slab will not exist and there will be 1593 no support for cache validation etc. 1594 1595config SLUB_MEMCG_SYSFS_ON 1596 default n 1597 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1598 depends on SLUB && SYSFS && MEMCG 1599 help 1600 SLUB creates a directory under /sys/kernel/slab for each 1601 allocation cache to host info and debug files. If memory 1602 cgroup is enabled, each cache can have per memory cgroup 1603 caches. SLUB can create the same sysfs directories for these 1604 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1605 to a very high number of debug files being created. This is 1606 controlled by slub_memcg_sysfs boot parameter and this 1607 config option determines the parameter's default value. 1608 1609config COMPAT_BRK 1610 bool "Disable heap randomization" 1611 default y 1612 help 1613 Randomizing heap placement makes heap exploits harder, but it 1614 also breaks ancient binaries (including anything libc5 based). 1615 This option changes the bootup default to heap randomization 1616 disabled, and can be overridden at runtime by setting 1617 /proc/sys/kernel/randomize_va_space to 2. 1618 1619 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1620 1621choice 1622 prompt "Choose SLAB allocator" 1623 default SLUB 1624 help 1625 This option allows to select a slab allocator. 1626 1627config SLAB 1628 bool "SLAB" 1629 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1630 help 1631 The regular slab allocator that is established and known to work 1632 well in all environments. It organizes cache hot objects in 1633 per cpu and per node queues. 1634 1635config SLUB 1636 bool "SLUB (Unqueued Allocator)" 1637 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1638 help 1639 SLUB is a slab allocator that minimizes cache line usage 1640 instead of managing queues of cached objects (SLAB approach). 1641 Per cpu caching is realized using slabs of objects instead 1642 of queues of objects. SLUB can use memory efficiently 1643 and has enhanced diagnostics. SLUB is the default choice for 1644 a slab allocator. 1645 1646config SLOB 1647 depends on EXPERT 1648 bool "SLOB (Simple Allocator)" 1649 help 1650 SLOB replaces the stock allocator with a drastically simpler 1651 allocator. SLOB is generally more space efficient but 1652 does not perform as well on large systems. 1653 1654endchoice 1655 1656config SLAB_MERGE_DEFAULT 1657 bool "Allow slab caches to be merged" 1658 default y 1659 help 1660 For reduced kernel memory fragmentation, slab caches can be 1661 merged when they share the same size and other characteristics. 1662 This carries a risk of kernel heap overflows being able to 1663 overwrite objects from merged caches (and more easily control 1664 cache layout), which makes such heap attacks easier to exploit 1665 by attackers. By keeping caches unmerged, these kinds of exploits 1666 can usually only damage objects in the same cache. To disable 1667 merging at runtime, "slab_nomerge" can be passed on the kernel 1668 command line. 1669 1670config SLAB_FREELIST_RANDOM 1671 default n 1672 depends on SLAB || SLUB 1673 bool "SLAB freelist randomization" 1674 help 1675 Randomizes the freelist order used on creating new pages. This 1676 security feature reduces the predictability of the kernel slab 1677 allocator against heap overflows. 1678 1679config SLAB_FREELIST_HARDENED 1680 bool "Harden slab freelist metadata" 1681 depends on SLUB 1682 help 1683 Many kernel heap attacks try to target slab cache metadata and 1684 other infrastructure. This options makes minor performance 1685 sacrifies to harden the kernel slab allocator against common 1686 freelist exploit methods. 1687 1688config SLUB_CPU_PARTIAL 1689 default y 1690 depends on SLUB && SMP 1691 bool "SLUB per cpu partial cache" 1692 help 1693 Per cpu partial caches accellerate objects allocation and freeing 1694 that is local to a processor at the price of more indeterminism 1695 in the latency of the free. On overflow these caches will be cleared 1696 which requires the taking of locks that may cause latency spikes. 1697 Typically one would choose no for a realtime system. 1698 1699config MMAP_ALLOW_UNINITIALIZED 1700 bool "Allow mmapped anonymous memory to be uninitialized" 1701 depends on EXPERT && !MMU 1702 default n 1703 help 1704 Normally, and according to the Linux spec, anonymous memory obtained 1705 from mmap() has its contents cleared before it is passed to 1706 userspace. Enabling this config option allows you to request that 1707 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1708 providing a huge performance boost. If this option is not enabled, 1709 then the flag will be ignored. 1710 1711 This is taken advantage of by uClibc's malloc(), and also by 1712 ELF-FDPIC binfmt's brk and stack allocator. 1713 1714 Because of the obvious security issues, this option should only be 1715 enabled on embedded devices where you control what is run in 1716 userspace. Since that isn't generally a problem on no-MMU systems, 1717 it is normally safe to say Y here. 1718 1719 See Documentation/nommu-mmap.txt for more information. 1720 1721config SYSTEM_DATA_VERIFICATION 1722 def_bool n 1723 select SYSTEM_TRUSTED_KEYRING 1724 select KEYS 1725 select CRYPTO 1726 select CRYPTO_RSA 1727 select ASYMMETRIC_KEY_TYPE 1728 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1729 select ASN1 1730 select OID_REGISTRY 1731 select X509_CERTIFICATE_PARSER 1732 select PKCS7_MESSAGE_PARSER 1733 help 1734 Provide PKCS#7 message verification using the contents of the system 1735 trusted keyring to provide public keys. This then can be used for 1736 module verification, kexec image verification and firmware blob 1737 verification. 1738 1739config PROFILING 1740 bool "Profiling support" 1741 help 1742 Say Y here to enable the extended profiling support mechanisms used 1743 by profilers such as OProfile. 1744 1745# 1746# Place an empty function call at each tracepoint site. Can be 1747# dynamically changed for a probe function. 1748# 1749config TRACEPOINTS 1750 bool 1751 1752endmenu # General setup 1753 1754source "arch/Kconfig" 1755 1756config RT_MUTEXES 1757 bool 1758 1759config BASE_SMALL 1760 int 1761 default 0 if BASE_FULL 1762 default 1 if !BASE_FULL 1763 1764menuconfig MODULES 1765 bool "Enable loadable module support" 1766 option modules 1767 help 1768 Kernel modules are small pieces of compiled code which can 1769 be inserted in the running kernel, rather than being 1770 permanently built into the kernel. You use the "modprobe" 1771 tool to add (and sometimes remove) them. If you say Y here, 1772 many parts of the kernel can be built as modules (by 1773 answering M instead of Y where indicated): this is most 1774 useful for infrequently used options which are not required 1775 for booting. For more information, see the man pages for 1776 modprobe, lsmod, modinfo, insmod and rmmod. 1777 1778 If you say Y here, you will need to run "make 1779 modules_install" to put the modules under /lib/modules/ 1780 where modprobe can find them (you may need to be root to do 1781 this). 1782 1783 If unsure, say Y. 1784 1785if MODULES 1786 1787config MODULE_FORCE_LOAD 1788 bool "Forced module loading" 1789 default n 1790 help 1791 Allow loading of modules without version information (ie. modprobe 1792 --force). Forced module loading sets the 'F' (forced) taint flag and 1793 is usually a really bad idea. 1794 1795config MODULE_UNLOAD 1796 bool "Module unloading" 1797 help 1798 Without this option you will not be able to unload any 1799 modules (note that some modules may not be unloadable 1800 anyway), which makes your kernel smaller, faster 1801 and simpler. If unsure, say Y. 1802 1803config MODULE_FORCE_UNLOAD 1804 bool "Forced module unloading" 1805 depends on MODULE_UNLOAD 1806 help 1807 This option allows you to force a module to unload, even if the 1808 kernel believes it is unsafe: the kernel will remove the module 1809 without waiting for anyone to stop using it (using the -f option to 1810 rmmod). This is mainly for kernel developers and desperate users. 1811 If unsure, say N. 1812 1813config MODVERSIONS 1814 bool "Module versioning support" 1815 help 1816 Usually, you have to use modules compiled with your kernel. 1817 Saying Y here makes it sometimes possible to use modules 1818 compiled for different kernels, by adding enough information 1819 to the modules to (hopefully) spot any changes which would 1820 make them incompatible with the kernel you are running. If 1821 unsure, say N. 1822 1823config MODULE_REL_CRCS 1824 bool 1825 depends on MODVERSIONS 1826 1827config MODULE_SRCVERSION_ALL 1828 bool "Source checksum for all modules" 1829 help 1830 Modules which contain a MODULE_VERSION get an extra "srcversion" 1831 field inserted into their modinfo section, which contains a 1832 sum of the source files which made it. This helps maintainers 1833 see exactly which source was used to build a module (since 1834 others sometimes change the module source without updating 1835 the version). With this option, such a "srcversion" field 1836 will be created for all modules. If unsure, say N. 1837 1838config MODULE_SIG 1839 bool "Module signature verification" 1840 depends on MODULES 1841 select SYSTEM_DATA_VERIFICATION 1842 help 1843 Check modules for valid signatures upon load: the signature 1844 is simply appended to the module. For more information see 1845 <file:Documentation/admin-guide/module-signing.rst>. 1846 1847 Note that this option adds the OpenSSL development packages as a 1848 kernel build dependency so that the signing tool can use its crypto 1849 library. 1850 1851 !!!WARNING!!! If you enable this option, you MUST make sure that the 1852 module DOES NOT get stripped after being signed. This includes the 1853 debuginfo strip done by some packagers (such as rpmbuild) and 1854 inclusion into an initramfs that wants the module size reduced. 1855 1856config MODULE_SIG_FORCE 1857 bool "Require modules to be validly signed" 1858 depends on MODULE_SIG 1859 help 1860 Reject unsigned modules or signed modules for which we don't have a 1861 key. Without this, such modules will simply taint the kernel. 1862 1863config MODULE_SIG_ALL 1864 bool "Automatically sign all modules" 1865 default y 1866 depends on MODULE_SIG 1867 help 1868 Sign all modules during make modules_install. Without this option, 1869 modules must be signed manually, using the scripts/sign-file tool. 1870 1871comment "Do not forget to sign required modules with scripts/sign-file" 1872 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 1873 1874choice 1875 prompt "Which hash algorithm should modules be signed with?" 1876 depends on MODULE_SIG 1877 help 1878 This determines which sort of hashing algorithm will be used during 1879 signature generation. This algorithm _must_ be built into the kernel 1880 directly so that signature verification can take place. It is not 1881 possible to load a signed module containing the algorithm to check 1882 the signature on that module. 1883 1884config MODULE_SIG_SHA1 1885 bool "Sign modules with SHA-1" 1886 select CRYPTO_SHA1 1887 1888config MODULE_SIG_SHA224 1889 bool "Sign modules with SHA-224" 1890 select CRYPTO_SHA256 1891 1892config MODULE_SIG_SHA256 1893 bool "Sign modules with SHA-256" 1894 select CRYPTO_SHA256 1895 1896config MODULE_SIG_SHA384 1897 bool "Sign modules with SHA-384" 1898 select CRYPTO_SHA512 1899 1900config MODULE_SIG_SHA512 1901 bool "Sign modules with SHA-512" 1902 select CRYPTO_SHA512 1903 1904endchoice 1905 1906config MODULE_SIG_HASH 1907 string 1908 depends on MODULE_SIG 1909 default "sha1" if MODULE_SIG_SHA1 1910 default "sha224" if MODULE_SIG_SHA224 1911 default "sha256" if MODULE_SIG_SHA256 1912 default "sha384" if MODULE_SIG_SHA384 1913 default "sha512" if MODULE_SIG_SHA512 1914 1915config MODULE_COMPRESS 1916 bool "Compress modules on installation" 1917 depends on MODULES 1918 help 1919 1920 Compresses kernel modules when 'make modules_install' is run; gzip or 1921 xz depending on "Compression algorithm" below. 1922 1923 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 1924 1925 Out-of-tree kernel modules installed using Kbuild will also be 1926 compressed upon installation. 1927 1928 Note: for modules inside an initrd or initramfs, it's more efficient 1929 to compress the whole initrd or initramfs instead. 1930 1931 Note: This is fully compatible with signed modules. 1932 1933 If in doubt, say N. 1934 1935choice 1936 prompt "Compression algorithm" 1937 depends on MODULE_COMPRESS 1938 default MODULE_COMPRESS_GZIP 1939 help 1940 This determines which sort of compression will be used during 1941 'make modules_install'. 1942 1943 GZIP (default) and XZ are supported. 1944 1945config MODULE_COMPRESS_GZIP 1946 bool "GZIP" 1947 1948config MODULE_COMPRESS_XZ 1949 bool "XZ" 1950 1951endchoice 1952 1953config TRIM_UNUSED_KSYMS 1954 bool "Trim unused exported kernel symbols" 1955 depends on MODULES && !UNUSED_SYMBOLS 1956 help 1957 The kernel and some modules make many symbols available for 1958 other modules to use via EXPORT_SYMBOL() and variants. Depending 1959 on the set of modules being selected in your kernel configuration, 1960 many of those exported symbols might never be used. 1961 1962 This option allows for unused exported symbols to be dropped from 1963 the build. In turn, this provides the compiler more opportunities 1964 (especially when using LTO) for optimizing the code and reducing 1965 binary size. This might have some security advantages as well. 1966 1967 If unsure, or if you need to build out-of-tree modules, say N. 1968 1969endif # MODULES 1970 1971config MODULES_TREE_LOOKUP 1972 def_bool y 1973 depends on PERF_EVENTS || TRACING 1974 1975config INIT_ALL_POSSIBLE 1976 bool 1977 help 1978 Back when each arch used to define their own cpu_online_mask and 1979 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 1980 with all 1s, and others with all 0s. When they were centralised, 1981 it was better to provide this option than to break all the archs 1982 and have several arch maintainers pursuing me down dark alleys. 1983 1984source "block/Kconfig" 1985 1986config PREEMPT_NOTIFIERS 1987 bool 1988 1989config PADATA 1990 depends on SMP 1991 bool 1992 1993config ASN1 1994 tristate 1995 help 1996 Build a simple ASN.1 grammar compiler that produces a bytecode output 1997 that can be interpreted by the ASN.1 stream decoder and used to 1998 inform it as to what tags are to be expected in a stream and what 1999 functions to call on what tags. 2000 2001source "kernel/Kconfig.locks" 2002 2003config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2004 bool 2005 2006# It may be useful for an architecture to override the definitions of the 2007# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2008# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2009# different calling convention for syscalls. They can also override the 2010# macros for not-implemented syscalls in kernel/sys_ni.c and 2011# kernel/time/posix-stubs.c. All these overrides need to be available in 2012# <asm/syscall_wrapper.h>. 2013config ARCH_HAS_SYSCALL_WRAPPER 2014 def_bool n 2015