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