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 !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800) 1128 depends on $(cc-option,-ffunction-sections -fdata-sections) 1129 depends on $(ld-option,--gc-sections) 1130 help 1131 Enable this if you want to do dead code and data elimination with 1132 the linker by compiling with -ffunction-sections -fdata-sections, 1133 and linking with --gc-sections. 1134 1135 This can reduce on disk and in-memory size of the kernel 1136 code and static data, particularly for small configs and 1137 on small systems. This has the possibility of introducing 1138 silently broken kernel if the required annotations are not 1139 present. This option is not well tested yet, so use at your 1140 own risk. 1141 1142config SYSCTL 1143 bool 1144 1145config ANON_INODES 1146 bool 1147 1148config HAVE_UID16 1149 bool 1150 1151config SYSCTL_EXCEPTION_TRACE 1152 bool 1153 help 1154 Enable support for /proc/sys/debug/exception-trace. 1155 1156config SYSCTL_ARCH_UNALIGN_NO_WARN 1157 bool 1158 help 1159 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1160 Allows arch to define/use @no_unaligned_warning to possibly warn 1161 about unaligned access emulation going on under the hood. 1162 1163config SYSCTL_ARCH_UNALIGN_ALLOW 1164 bool 1165 help 1166 Enable support for /proc/sys/kernel/unaligned-trap 1167 Allows arches to define/use @unaligned_enabled to runtime toggle 1168 the unaligned access emulation. 1169 see arch/parisc/kernel/unaligned.c for reference 1170 1171config HAVE_PCSPKR_PLATFORM 1172 bool 1173 1174# interpreter that classic socket filters depend on 1175config BPF 1176 bool 1177 1178menuconfig EXPERT 1179 bool "Configure standard kernel features (expert users)" 1180 # Unhide debug options, to make the on-by-default options visible 1181 select DEBUG_KERNEL 1182 help 1183 This option allows certain base kernel options and settings 1184 to be disabled or tweaked. This is for specialized 1185 environments which can tolerate a "non-standard" kernel. 1186 Only use this if you really know what you are doing. 1187 1188config UID16 1189 bool "Enable 16-bit UID system calls" if EXPERT 1190 depends on HAVE_UID16 && MULTIUSER 1191 default y 1192 help 1193 This enables the legacy 16-bit UID syscall wrappers. 1194 1195config MULTIUSER 1196 bool "Multiple users, groups and capabilities support" if EXPERT 1197 default y 1198 help 1199 This option enables support for non-root users, groups and 1200 capabilities. 1201 1202 If you say N here, all processes will run with UID 0, GID 0, and all 1203 possible capabilities. Saying N here also compiles out support for 1204 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1205 setgid, and capset. 1206 1207 If unsure, say Y here. 1208 1209config SGETMASK_SYSCALL 1210 bool "sgetmask/ssetmask syscalls support" if EXPERT 1211 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1212 ---help--- 1213 sys_sgetmask and sys_ssetmask are obsolete system calls 1214 no longer supported in libc but still enabled by default in some 1215 architectures. 1216 1217 If unsure, leave the default option here. 1218 1219config SYSFS_SYSCALL 1220 bool "Sysfs syscall support" if EXPERT 1221 default y 1222 ---help--- 1223 sys_sysfs is an obsolete system call no longer supported in libc. 1224 Note that disabling this option is more secure but might break 1225 compatibility with some systems. 1226 1227 If unsure say Y here. 1228 1229config SYSCTL_SYSCALL 1230 bool "Sysctl syscall support" if EXPERT 1231 depends on PROC_SYSCTL 1232 default n 1233 select SYSCTL 1234 ---help--- 1235 sys_sysctl uses binary paths that have been found challenging 1236 to properly maintain and use. The interface in /proc/sys 1237 using paths with ascii names is now the primary path to this 1238 information. 1239 1240 Almost nothing using the binary sysctl interface so if you are 1241 trying to save some space it is probably safe to disable this, 1242 making your kernel marginally smaller. 1243 1244 If unsure say N here. 1245 1246config FHANDLE 1247 bool "open by fhandle syscalls" if EXPERT 1248 select EXPORTFS 1249 default y 1250 help 1251 If you say Y here, a user level program will be able to map 1252 file names to handle and then later use the handle for 1253 different file system operations. This is useful in implementing 1254 userspace file servers, which now track files using handles instead 1255 of names. The handle would remain the same even if file names 1256 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1257 syscalls. 1258 1259config POSIX_TIMERS 1260 bool "Posix Clocks & timers" if EXPERT 1261 default y 1262 help 1263 This includes native support for POSIX timers to the kernel. 1264 Some embedded systems have no use for them and therefore they 1265 can be configured out to reduce the size of the kernel image. 1266 1267 When this option is disabled, the following syscalls won't be 1268 available: timer_create, timer_gettime: timer_getoverrun, 1269 timer_settime, timer_delete, clock_adjtime, getitimer, 1270 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1271 clock_getres and clock_nanosleep syscalls will be limited to 1272 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1273 1274 If unsure say y. 1275 1276config PRINTK 1277 default y 1278 bool "Enable support for printk" if EXPERT 1279 select IRQ_WORK 1280 help 1281 This option enables normal printk support. Removing it 1282 eliminates most of the message strings from the kernel image 1283 and makes the kernel more or less silent. As this makes it 1284 very difficult to diagnose system problems, saying N here is 1285 strongly discouraged. 1286 1287config PRINTK_NMI 1288 def_bool y 1289 depends on PRINTK 1290 depends on HAVE_NMI 1291 1292config BUG 1293 bool "BUG() support" if EXPERT 1294 default y 1295 help 1296 Disabling this option eliminates support for BUG and WARN, reducing 1297 the size of your kernel image and potentially quietly ignoring 1298 numerous fatal conditions. You should only consider disabling this 1299 option for embedded systems with no facilities for reporting errors. 1300 Just say Y. 1301 1302config ELF_CORE 1303 depends on COREDUMP 1304 default y 1305 bool "Enable ELF core dumps" if EXPERT 1306 help 1307 Enable support for generating core dumps. Disabling saves about 4k. 1308 1309 1310config PCSPKR_PLATFORM 1311 bool "Enable PC-Speaker support" if EXPERT 1312 depends on HAVE_PCSPKR_PLATFORM 1313 select I8253_LOCK 1314 default y 1315 help 1316 This option allows to disable the internal PC-Speaker 1317 support, saving some memory. 1318 1319config BASE_FULL 1320 default y 1321 bool "Enable full-sized data structures for core" if EXPERT 1322 help 1323 Disabling this option reduces the size of miscellaneous core 1324 kernel data structures. This saves memory on small machines, 1325 but may reduce performance. 1326 1327config FUTEX 1328 bool "Enable futex support" if EXPERT 1329 default y 1330 imply RT_MUTEXES 1331 help 1332 Disabling this option will cause the kernel to be built without 1333 support for "fast userspace mutexes". The resulting kernel may not 1334 run glibc-based applications correctly. 1335 1336config FUTEX_PI 1337 bool 1338 depends on FUTEX && RT_MUTEXES 1339 default y 1340 1341config HAVE_FUTEX_CMPXCHG 1342 bool 1343 depends on FUTEX 1344 help 1345 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1346 is implemented and always working. This removes a couple of runtime 1347 checks. 1348 1349config EPOLL 1350 bool "Enable eventpoll support" if EXPERT 1351 default y 1352 select ANON_INODES 1353 help 1354 Disabling this option will cause the kernel to be built without 1355 support for epoll family of system calls. 1356 1357config SIGNALFD 1358 bool "Enable signalfd() system call" if EXPERT 1359 select ANON_INODES 1360 default y 1361 help 1362 Enable the signalfd() system call that allows to receive signals 1363 on a file descriptor. 1364 1365 If unsure, say Y. 1366 1367config TIMERFD 1368 bool "Enable timerfd() system call" if EXPERT 1369 select ANON_INODES 1370 default y 1371 help 1372 Enable the timerfd() system call that allows to receive timer 1373 events on a file descriptor. 1374 1375 If unsure, say Y. 1376 1377config EVENTFD 1378 bool "Enable eventfd() system call" if EXPERT 1379 select ANON_INODES 1380 default y 1381 help 1382 Enable the eventfd() system call that allows to receive both 1383 kernel notification (ie. KAIO) or userspace notifications. 1384 1385 If unsure, say Y. 1386 1387config SHMEM 1388 bool "Use full shmem filesystem" if EXPERT 1389 default y 1390 depends on MMU 1391 help 1392 The shmem is an internal filesystem used to manage shared memory. 1393 It is backed by swap and manages resource limits. It is also exported 1394 to userspace as tmpfs if TMPFS is enabled. Disabling this 1395 option replaces shmem and tmpfs with the much simpler ramfs code, 1396 which may be appropriate on small systems without swap. 1397 1398config AIO 1399 bool "Enable AIO support" if EXPERT 1400 default y 1401 help 1402 This option enables POSIX asynchronous I/O which may by used 1403 by some high performance threaded applications. Disabling 1404 this option saves about 7k. 1405 1406config ADVISE_SYSCALLS 1407 bool "Enable madvise/fadvise syscalls" if EXPERT 1408 default y 1409 help 1410 This option enables the madvise and fadvise syscalls, used by 1411 applications to advise the kernel about their future memory or file 1412 usage, improving performance. If building an embedded system where no 1413 applications use these syscalls, you can disable this option to save 1414 space. 1415 1416config MEMBARRIER 1417 bool "Enable membarrier() system call" if EXPERT 1418 default y 1419 help 1420 Enable the membarrier() system call that allows issuing memory 1421 barriers across all running threads, which can be used to distribute 1422 the cost of user-space memory barriers asymmetrically by transforming 1423 pairs of memory barriers into pairs consisting of membarrier() and a 1424 compiler barrier. 1425 1426 If unsure, say Y. 1427 1428config KALLSYMS 1429 bool "Load all symbols for debugging/ksymoops" if EXPERT 1430 default y 1431 help 1432 Say Y here to let the kernel print out symbolic crash information and 1433 symbolic stack backtraces. This increases the size of the kernel 1434 somewhat, as all symbols have to be loaded into the kernel image. 1435 1436config KALLSYMS_ALL 1437 bool "Include all symbols in kallsyms" 1438 depends on DEBUG_KERNEL && KALLSYMS 1439 help 1440 Normally kallsyms only contains the symbols of functions for nicer 1441 OOPS messages and backtraces (i.e., symbols from the text and inittext 1442 sections). This is sufficient for most cases. And only in very rare 1443 cases (e.g., when a debugger is used) all symbols are required (e.g., 1444 names of variables from the data sections, etc). 1445 1446 This option makes sure that all symbols are loaded into the kernel 1447 image (i.e., symbols from all sections) in cost of increased kernel 1448 size (depending on the kernel configuration, it may be 300KiB or 1449 something like this). 1450 1451 Say N unless you really need all symbols. 1452 1453config KALLSYMS_ABSOLUTE_PERCPU 1454 bool 1455 depends on KALLSYMS 1456 default X86_64 && SMP 1457 1458config KALLSYMS_BASE_RELATIVE 1459 bool 1460 depends on KALLSYMS 1461 default !IA64 1462 help 1463 Instead of emitting them as absolute values in the native word size, 1464 emit the symbol references in the kallsyms table as 32-bit entries, 1465 each containing a relative value in the range [base, base + U32_MAX] 1466 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1467 an absolute value in the range [0, S32_MAX] or a relative value in the 1468 range [base, base + S32_MAX], where base is the lowest relative symbol 1469 address encountered in the image. 1470 1471 On 64-bit builds, this reduces the size of the address table by 50%, 1472 but more importantly, it results in entries whose values are build 1473 time constants, and no relocation pass is required at runtime to fix 1474 up the entries based on the runtime load address of the kernel. 1475 1476# end of the "standard kernel features (expert users)" menu 1477 1478# syscall, maps, verifier 1479config BPF_SYSCALL 1480 bool "Enable bpf() system call" 1481 select ANON_INODES 1482 select BPF 1483 select IRQ_WORK 1484 default n 1485 help 1486 Enable the bpf() system call that allows to manipulate eBPF 1487 programs and maps via file descriptors. 1488 1489config BPF_JIT_ALWAYS_ON 1490 bool "Permanently enable BPF JIT and remove BPF interpreter" 1491 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1492 help 1493 Enables BPF JIT and removes BPF interpreter to avoid 1494 speculative execution of BPF instructions by the interpreter 1495 1496config USERFAULTFD 1497 bool "Enable userfaultfd() system call" 1498 select ANON_INODES 1499 depends on MMU 1500 help 1501 Enable the userfaultfd() system call that allows to intercept and 1502 handle page faults in userland. 1503 1504config ARCH_HAS_MEMBARRIER_CALLBACKS 1505 bool 1506 1507config ARCH_HAS_MEMBARRIER_SYNC_CORE 1508 bool 1509 1510config RSEQ 1511 bool "Enable rseq() system call" if EXPERT 1512 default y 1513 depends on HAVE_RSEQ 1514 select MEMBARRIER 1515 help 1516 Enable the restartable sequences system call. It provides a 1517 user-space cache for the current CPU number value, which 1518 speeds up getting the current CPU number from user-space, 1519 as well as an ABI to speed up user-space operations on 1520 per-CPU data. 1521 1522 If unsure, say Y. 1523 1524config DEBUG_RSEQ 1525 default n 1526 bool "Enabled debugging of rseq() system call" if EXPERT 1527 depends on RSEQ && DEBUG_KERNEL 1528 help 1529 Enable extra debugging checks for the rseq system call. 1530 1531 If unsure, say N. 1532 1533config EMBEDDED 1534 bool "Embedded system" 1535 option allnoconfig_y 1536 select EXPERT 1537 help 1538 This option should be enabled if compiling the kernel for 1539 an embedded system so certain expert options are available 1540 for configuration. 1541 1542config HAVE_PERF_EVENTS 1543 bool 1544 help 1545 See tools/perf/design.txt for details. 1546 1547config PERF_USE_VMALLOC 1548 bool 1549 help 1550 See tools/perf/design.txt for details 1551 1552config PC104 1553 bool "PC/104 support" if EXPERT 1554 help 1555 Expose PC/104 form factor device drivers and options available for 1556 selection and configuration. Enable this option if your target 1557 machine has a PC/104 bus. 1558 1559menu "Kernel Performance Events And Counters" 1560 1561config PERF_EVENTS 1562 bool "Kernel performance events and counters" 1563 default y if PROFILING 1564 depends on HAVE_PERF_EVENTS 1565 select ANON_INODES 1566 select IRQ_WORK 1567 select SRCU 1568 help 1569 Enable kernel support for various performance events provided 1570 by software and hardware. 1571 1572 Software events are supported either built-in or via the 1573 use of generic tracepoints. 1574 1575 Most modern CPUs support performance events via performance 1576 counter registers. These registers count the number of certain 1577 types of hw events: such as instructions executed, cachemisses 1578 suffered, or branches mis-predicted - without slowing down the 1579 kernel or applications. These registers can also trigger interrupts 1580 when a threshold number of events have passed - and can thus be 1581 used to profile the code that runs on that CPU. 1582 1583 The Linux Performance Event subsystem provides an abstraction of 1584 these software and hardware event capabilities, available via a 1585 system call and used by the "perf" utility in tools/perf/. It 1586 provides per task and per CPU counters, and it provides event 1587 capabilities on top of those. 1588 1589 Say Y if unsure. 1590 1591config DEBUG_PERF_USE_VMALLOC 1592 default n 1593 bool "Debug: use vmalloc to back perf mmap() buffers" 1594 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1595 select PERF_USE_VMALLOC 1596 help 1597 Use vmalloc memory to back perf mmap() buffers. 1598 1599 Mostly useful for debugging the vmalloc code on platforms 1600 that don't require it. 1601 1602 Say N if unsure. 1603 1604endmenu 1605 1606config VM_EVENT_COUNTERS 1607 default y 1608 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1609 help 1610 VM event counters are needed for event counts to be shown. 1611 This option allows the disabling of the VM event counters 1612 on EXPERT systems. /proc/vmstat will only show page counts 1613 if VM event counters are disabled. 1614 1615config SLUB_DEBUG 1616 default y 1617 bool "Enable SLUB debugging support" if EXPERT 1618 depends on SLUB && SYSFS 1619 help 1620 SLUB has extensive debug support features. Disabling these can 1621 result in significant savings in code size. This also disables 1622 SLUB sysfs support. /sys/slab will not exist and there will be 1623 no support for cache validation etc. 1624 1625config SLUB_MEMCG_SYSFS_ON 1626 default n 1627 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1628 depends on SLUB && SYSFS && MEMCG 1629 help 1630 SLUB creates a directory under /sys/kernel/slab for each 1631 allocation cache to host info and debug files. If memory 1632 cgroup is enabled, each cache can have per memory cgroup 1633 caches. SLUB can create the same sysfs directories for these 1634 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1635 to a very high number of debug files being created. This is 1636 controlled by slub_memcg_sysfs boot parameter and this 1637 config option determines the parameter's default value. 1638 1639config COMPAT_BRK 1640 bool "Disable heap randomization" 1641 default y 1642 help 1643 Randomizing heap placement makes heap exploits harder, but it 1644 also breaks ancient binaries (including anything libc5 based). 1645 This option changes the bootup default to heap randomization 1646 disabled, and can be overridden at runtime by setting 1647 /proc/sys/kernel/randomize_va_space to 2. 1648 1649 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1650 1651choice 1652 prompt "Choose SLAB allocator" 1653 default SLUB 1654 help 1655 This option allows to select a slab allocator. 1656 1657config SLAB 1658 bool "SLAB" 1659 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1660 help 1661 The regular slab allocator that is established and known to work 1662 well in all environments. It organizes cache hot objects in 1663 per cpu and per node queues. 1664 1665config SLUB 1666 bool "SLUB (Unqueued Allocator)" 1667 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1668 help 1669 SLUB is a slab allocator that minimizes cache line usage 1670 instead of managing queues of cached objects (SLAB approach). 1671 Per cpu caching is realized using slabs of objects instead 1672 of queues of objects. SLUB can use memory efficiently 1673 and has enhanced diagnostics. SLUB is the default choice for 1674 a slab allocator. 1675 1676config SLOB 1677 depends on EXPERT 1678 bool "SLOB (Simple Allocator)" 1679 help 1680 SLOB replaces the stock allocator with a drastically simpler 1681 allocator. SLOB is generally more space efficient but 1682 does not perform as well on large systems. 1683 1684endchoice 1685 1686config SLAB_MERGE_DEFAULT 1687 bool "Allow slab caches to be merged" 1688 default y 1689 help 1690 For reduced kernel memory fragmentation, slab caches can be 1691 merged when they share the same size and other characteristics. 1692 This carries a risk of kernel heap overflows being able to 1693 overwrite objects from merged caches (and more easily control 1694 cache layout), which makes such heap attacks easier to exploit 1695 by attackers. By keeping caches unmerged, these kinds of exploits 1696 can usually only damage objects in the same cache. To disable 1697 merging at runtime, "slab_nomerge" can be passed on the kernel 1698 command line. 1699 1700config SLAB_FREELIST_RANDOM 1701 default n 1702 depends on SLAB || SLUB 1703 bool "SLAB freelist randomization" 1704 help 1705 Randomizes the freelist order used on creating new pages. This 1706 security feature reduces the predictability of the kernel slab 1707 allocator against heap overflows. 1708 1709config SLAB_FREELIST_HARDENED 1710 bool "Harden slab freelist metadata" 1711 depends on SLUB 1712 help 1713 Many kernel heap attacks try to target slab cache metadata and 1714 other infrastructure. This options makes minor performance 1715 sacrifies to harden the kernel slab allocator against common 1716 freelist exploit methods. 1717 1718config SLUB_CPU_PARTIAL 1719 default y 1720 depends on SLUB && SMP 1721 bool "SLUB per cpu partial cache" 1722 help 1723 Per cpu partial caches accellerate objects allocation and freeing 1724 that is local to a processor at the price of more indeterminism 1725 in the latency of the free. On overflow these caches will be cleared 1726 which requires the taking of locks that may cause latency spikes. 1727 Typically one would choose no for a realtime system. 1728 1729config MMAP_ALLOW_UNINITIALIZED 1730 bool "Allow mmapped anonymous memory to be uninitialized" 1731 depends on EXPERT && !MMU 1732 default n 1733 help 1734 Normally, and according to the Linux spec, anonymous memory obtained 1735 from mmap() has its contents cleared before it is passed to 1736 userspace. Enabling this config option allows you to request that 1737 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1738 providing a huge performance boost. If this option is not enabled, 1739 then the flag will be ignored. 1740 1741 This is taken advantage of by uClibc's malloc(), and also by 1742 ELF-FDPIC binfmt's brk and stack allocator. 1743 1744 Because of the obvious security issues, this option should only be 1745 enabled on embedded devices where you control what is run in 1746 userspace. Since that isn't generally a problem on no-MMU systems, 1747 it is normally safe to say Y here. 1748 1749 See Documentation/nommu-mmap.txt for more information. 1750 1751config SYSTEM_DATA_VERIFICATION 1752 def_bool n 1753 select SYSTEM_TRUSTED_KEYRING 1754 select KEYS 1755 select CRYPTO 1756 select CRYPTO_RSA 1757 select ASYMMETRIC_KEY_TYPE 1758 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1759 select ASN1 1760 select OID_REGISTRY 1761 select X509_CERTIFICATE_PARSER 1762 select PKCS7_MESSAGE_PARSER 1763 help 1764 Provide PKCS#7 message verification using the contents of the system 1765 trusted keyring to provide public keys. This then can be used for 1766 module verification, kexec image verification and firmware blob 1767 verification. 1768 1769config PROFILING 1770 bool "Profiling support" 1771 help 1772 Say Y here to enable the extended profiling support mechanisms used 1773 by profilers such as OProfile. 1774 1775# 1776# Place an empty function call at each tracepoint site. Can be 1777# dynamically changed for a probe function. 1778# 1779config TRACEPOINTS 1780 bool 1781 1782endmenu # General setup 1783 1784source "arch/Kconfig" 1785 1786config RT_MUTEXES 1787 bool 1788 1789config BASE_SMALL 1790 int 1791 default 0 if BASE_FULL 1792 default 1 if !BASE_FULL 1793 1794menuconfig MODULES 1795 bool "Enable loadable module support" 1796 option modules 1797 help 1798 Kernel modules are small pieces of compiled code which can 1799 be inserted in the running kernel, rather than being 1800 permanently built into the kernel. You use the "modprobe" 1801 tool to add (and sometimes remove) them. If you say Y here, 1802 many parts of the kernel can be built as modules (by 1803 answering M instead of Y where indicated): this is most 1804 useful for infrequently used options which are not required 1805 for booting. For more information, see the man pages for 1806 modprobe, lsmod, modinfo, insmod and rmmod. 1807 1808 If you say Y here, you will need to run "make 1809 modules_install" to put the modules under /lib/modules/ 1810 where modprobe can find them (you may need to be root to do 1811 this). 1812 1813 If unsure, say Y. 1814 1815if MODULES 1816 1817config MODULE_FORCE_LOAD 1818 bool "Forced module loading" 1819 default n 1820 help 1821 Allow loading of modules without version information (ie. modprobe 1822 --force). Forced module loading sets the 'F' (forced) taint flag and 1823 is usually a really bad idea. 1824 1825config MODULE_UNLOAD 1826 bool "Module unloading" 1827 help 1828 Without this option you will not be able to unload any 1829 modules (note that some modules may not be unloadable 1830 anyway), which makes your kernel smaller, faster 1831 and simpler. If unsure, say Y. 1832 1833config MODULE_FORCE_UNLOAD 1834 bool "Forced module unloading" 1835 depends on MODULE_UNLOAD 1836 help 1837 This option allows you to force a module to unload, even if the 1838 kernel believes it is unsafe: the kernel will remove the module 1839 without waiting for anyone to stop using it (using the -f option to 1840 rmmod). This is mainly for kernel developers and desperate users. 1841 If unsure, say N. 1842 1843config MODVERSIONS 1844 bool "Module versioning support" 1845 help 1846 Usually, you have to use modules compiled with your kernel. 1847 Saying Y here makes it sometimes possible to use modules 1848 compiled for different kernels, by adding enough information 1849 to the modules to (hopefully) spot any changes which would 1850 make them incompatible with the kernel you are running. If 1851 unsure, say N. 1852 1853config MODULE_REL_CRCS 1854 bool 1855 depends on MODVERSIONS 1856 1857config MODULE_SRCVERSION_ALL 1858 bool "Source checksum for all modules" 1859 help 1860 Modules which contain a MODULE_VERSION get an extra "srcversion" 1861 field inserted into their modinfo section, which contains a 1862 sum of the source files which made it. This helps maintainers 1863 see exactly which source was used to build a module (since 1864 others sometimes change the module source without updating 1865 the version). With this option, such a "srcversion" field 1866 will be created for all modules. If unsure, say N. 1867 1868config MODULE_SIG 1869 bool "Module signature verification" 1870 depends on MODULES 1871 select SYSTEM_DATA_VERIFICATION 1872 help 1873 Check modules for valid signatures upon load: the signature 1874 is simply appended to the module. For more information see 1875 <file:Documentation/admin-guide/module-signing.rst>. 1876 1877 Note that this option adds the OpenSSL development packages as a 1878 kernel build dependency so that the signing tool can use its crypto 1879 library. 1880 1881 !!!WARNING!!! If you enable this option, you MUST make sure that the 1882 module DOES NOT get stripped after being signed. This includes the 1883 debuginfo strip done by some packagers (such as rpmbuild) and 1884 inclusion into an initramfs that wants the module size reduced. 1885 1886config MODULE_SIG_FORCE 1887 bool "Require modules to be validly signed" 1888 depends on MODULE_SIG 1889 help 1890 Reject unsigned modules or signed modules for which we don't have a 1891 key. Without this, such modules will simply taint the kernel. 1892 1893config MODULE_SIG_ALL 1894 bool "Automatically sign all modules" 1895 default y 1896 depends on MODULE_SIG 1897 help 1898 Sign all modules during make modules_install. Without this option, 1899 modules must be signed manually, using the scripts/sign-file tool. 1900 1901comment "Do not forget to sign required modules with scripts/sign-file" 1902 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 1903 1904choice 1905 prompt "Which hash algorithm should modules be signed with?" 1906 depends on MODULE_SIG 1907 help 1908 This determines which sort of hashing algorithm will be used during 1909 signature generation. This algorithm _must_ be built into the kernel 1910 directly so that signature verification can take place. It is not 1911 possible to load a signed module containing the algorithm to check 1912 the signature on that module. 1913 1914config MODULE_SIG_SHA1 1915 bool "Sign modules with SHA-1" 1916 select CRYPTO_SHA1 1917 1918config MODULE_SIG_SHA224 1919 bool "Sign modules with SHA-224" 1920 select CRYPTO_SHA256 1921 1922config MODULE_SIG_SHA256 1923 bool "Sign modules with SHA-256" 1924 select CRYPTO_SHA256 1925 1926config MODULE_SIG_SHA384 1927 bool "Sign modules with SHA-384" 1928 select CRYPTO_SHA512 1929 1930config MODULE_SIG_SHA512 1931 bool "Sign modules with SHA-512" 1932 select CRYPTO_SHA512 1933 1934endchoice 1935 1936config MODULE_SIG_HASH 1937 string 1938 depends on MODULE_SIG 1939 default "sha1" if MODULE_SIG_SHA1 1940 default "sha224" if MODULE_SIG_SHA224 1941 default "sha256" if MODULE_SIG_SHA256 1942 default "sha384" if MODULE_SIG_SHA384 1943 default "sha512" if MODULE_SIG_SHA512 1944 1945config MODULE_COMPRESS 1946 bool "Compress modules on installation" 1947 depends on MODULES 1948 help 1949 1950 Compresses kernel modules when 'make modules_install' is run; gzip or 1951 xz depending on "Compression algorithm" below. 1952 1953 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 1954 1955 Out-of-tree kernel modules installed using Kbuild will also be 1956 compressed upon installation. 1957 1958 Note: for modules inside an initrd or initramfs, it's more efficient 1959 to compress the whole initrd or initramfs instead. 1960 1961 Note: This is fully compatible with signed modules. 1962 1963 If in doubt, say N. 1964 1965choice 1966 prompt "Compression algorithm" 1967 depends on MODULE_COMPRESS 1968 default MODULE_COMPRESS_GZIP 1969 help 1970 This determines which sort of compression will be used during 1971 'make modules_install'. 1972 1973 GZIP (default) and XZ are supported. 1974 1975config MODULE_COMPRESS_GZIP 1976 bool "GZIP" 1977 1978config MODULE_COMPRESS_XZ 1979 bool "XZ" 1980 1981endchoice 1982 1983config TRIM_UNUSED_KSYMS 1984 bool "Trim unused exported kernel symbols" 1985 depends on MODULES && !UNUSED_SYMBOLS 1986 help 1987 The kernel and some modules make many symbols available for 1988 other modules to use via EXPORT_SYMBOL() and variants. Depending 1989 on the set of modules being selected in your kernel configuration, 1990 many of those exported symbols might never be used. 1991 1992 This option allows for unused exported symbols to be dropped from 1993 the build. In turn, this provides the compiler more opportunities 1994 (especially when using LTO) for optimizing the code and reducing 1995 binary size. This might have some security advantages as well. 1996 1997 If unsure, or if you need to build out-of-tree modules, say N. 1998 1999endif # MODULES 2000 2001config MODULES_TREE_LOOKUP 2002 def_bool y 2003 depends on PERF_EVENTS || TRACING 2004 2005config INIT_ALL_POSSIBLE 2006 bool 2007 help 2008 Back when each arch used to define their own cpu_online_mask and 2009 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2010 with all 1s, and others with all 0s. When they were centralised, 2011 it was better to provide this option than to break all the archs 2012 and have several arch maintainers pursuing me down dark alleys. 2013 2014source "block/Kconfig" 2015 2016config PREEMPT_NOTIFIERS 2017 bool 2018 2019config PADATA 2020 depends on SMP 2021 bool 2022 2023config ASN1 2024 tristate 2025 help 2026 Build a simple ASN.1 grammar compiler that produces a bytecode output 2027 that can be interpreted by the ASN.1 stream decoder and used to 2028 inform it as to what tags are to be expected in a stream and what 2029 functions to call on what tags. 2030 2031source "kernel/Kconfig.locks" 2032 2033config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2034 bool 2035 2036# It may be useful for an architecture to override the definitions of the 2037# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2038# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2039# different calling convention for syscalls. They can also override the 2040# macros for not-implemented syscalls in kernel/sys_ni.c and 2041# kernel/time/posix-stubs.c. All these overrides need to be available in 2042# <asm/syscall_wrapper.h>. 2043config ARCH_HAS_SYSCALL_WRAPPER 2044 def_bool n 2045