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