1config ARCH 2 string 3 option env="ARCH" 4 5config KERNELVERSION 6 string 7 option env="KERNELVERSION" 8 9config DEFCONFIG_LIST 10 string 11 depends on !UML 12 option defconfig_list 13 default "/lib/modules/$UNAME_RELEASE/.config" 14 default "/etc/kernel-config" 15 default "/boot/config-$UNAME_RELEASE" 16 default "$ARCH_DEFCONFIG" 17 default "arch/$ARCH/defconfig" 18 19config CONSTRUCTORS 20 bool 21 depends on !UML 22 23config IRQ_WORK 24 bool 25 26config BUILDTIME_EXTABLE_SORT 27 bool 28 29config THREAD_INFO_IN_TASK 30 bool 31 help 32 Select this to move thread_info off the stack into task_struct. To 33 make this work, an arch will need to remove all thread_info fields 34 except flags and fix any runtime bugs. 35 36 One subtle change that will be needed is to use try_get_task_stack() 37 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 38 39menu "General setup" 40 41config BROKEN 42 bool 43 44config BROKEN_ON_SMP 45 bool 46 depends on BROKEN || !SMP 47 default y 48 49config INIT_ENV_ARG_LIMIT 50 int 51 default 32 if !UML 52 default 128 if UML 53 help 54 Maximum of each of the number of arguments and environment 55 variables passed to init from the kernel command line. 56 57 58config CROSS_COMPILE 59 string "Cross-compiler tool prefix" 60 help 61 Same as running 'make CROSS_COMPILE=prefix-' but stored for 62 default make runs in this kernel build directory. You don't 63 need to set this unless you want the configured kernel build 64 directory to select the cross-compiler automatically. 65 66config COMPILE_TEST 67 bool "Compile also drivers which will not load" 68 depends on !UML 69 default n 70 help 71 Some drivers can be compiled on a different platform than they are 72 intended to be run on. Despite they cannot be loaded there (or even 73 when they load they cannot be used due to missing HW support), 74 developers still, opposing to distributors, might want to build such 75 drivers to compile-test them. 76 77 If you are a developer and want to build everything available, say Y 78 here. If you are a user/distributor, say N here to exclude useless 79 drivers to be distributed. 80 81config LOCALVERSION 82 string "Local version - append to kernel release" 83 help 84 Append an extra string to the end of your kernel version. 85 This will show up when you type uname, for example. 86 The string you set here will be appended after the contents of 87 any files with a filename matching localversion* in your 88 object and source tree, in that order. Your total string can 89 be a maximum of 64 characters. 90 91config LOCALVERSION_AUTO 92 bool "Automatically append version information to the version string" 93 default y 94 depends on !COMPILE_TEST 95 help 96 This will try to automatically determine if the current tree is a 97 release tree by looking for git tags that belong to the current 98 top of tree revision. 99 100 A string of the format -gxxxxxxxx will be added to the localversion 101 if a git-based tree is found. The string generated by this will be 102 appended after any matching localversion* files, and after the value 103 set in CONFIG_LOCALVERSION. 104 105 (The actual string used here is the first eight characters produced 106 by running the command: 107 108 $ git rev-parse --verify HEAD 109 110 which is done within the script "scripts/setlocalversion".) 111 112config HAVE_KERNEL_GZIP 113 bool 114 115config HAVE_KERNEL_BZIP2 116 bool 117 118config HAVE_KERNEL_LZMA 119 bool 120 121config HAVE_KERNEL_XZ 122 bool 123 124config HAVE_KERNEL_LZO 125 bool 126 127config HAVE_KERNEL_LZ4 128 bool 129 130choice 131 prompt "Kernel compression mode" 132 default KERNEL_GZIP 133 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 134 help 135 The linux kernel is a kind of self-extracting executable. 136 Several compression algorithms are available, which differ 137 in efficiency, compression and decompression speed. 138 Compression speed is only relevant when building a kernel. 139 Decompression speed is relevant at each boot. 140 141 If you have any problems with bzip2 or lzma compressed 142 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 143 version of this functionality (bzip2 only), for 2.4, was 144 supplied by Christian Ludwig) 145 146 High compression options are mostly useful for users, who 147 are low on disk space (embedded systems), but for whom ram 148 size matters less. 149 150 If in doubt, select 'gzip' 151 152config KERNEL_GZIP 153 bool "Gzip" 154 depends on HAVE_KERNEL_GZIP 155 help 156 The old and tried gzip compression. It provides a good balance 157 between compression ratio and decompression speed. 158 159config KERNEL_BZIP2 160 bool "Bzip2" 161 depends on HAVE_KERNEL_BZIP2 162 help 163 Its compression ratio and speed is intermediate. 164 Decompression speed is slowest among the choices. The kernel 165 size is about 10% smaller with bzip2, in comparison to gzip. 166 Bzip2 uses a large amount of memory. For modern kernels you 167 will need at least 8MB RAM or more for booting. 168 169config KERNEL_LZMA 170 bool "LZMA" 171 depends on HAVE_KERNEL_LZMA 172 help 173 This compression algorithm's ratio is best. Decompression speed 174 is between gzip and bzip2. Compression is slowest. 175 The kernel size is about 33% smaller with LZMA in comparison to gzip. 176 177config KERNEL_XZ 178 bool "XZ" 179 depends on HAVE_KERNEL_XZ 180 help 181 XZ uses the LZMA2 algorithm and instruction set specific 182 BCJ filters which can improve compression ratio of executable 183 code. The size of the kernel is about 30% smaller with XZ in 184 comparison to gzip. On architectures for which there is a BCJ 185 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 186 will create a few percent smaller kernel than plain LZMA. 187 188 The speed is about the same as with LZMA: The decompression 189 speed of XZ is better than that of bzip2 but worse than gzip 190 and LZO. Compression is slow. 191 192config KERNEL_LZO 193 bool "LZO" 194 depends on HAVE_KERNEL_LZO 195 help 196 Its compression ratio is the poorest among the choices. The kernel 197 size is about 10% bigger than gzip; however its speed 198 (both compression and decompression) is the fastest. 199 200config KERNEL_LZ4 201 bool "LZ4" 202 depends on HAVE_KERNEL_LZ4 203 help 204 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 205 A preliminary version of LZ4 de/compression tool is available at 206 <https://code.google.com/p/lz4/>. 207 208 Its compression ratio is worse than LZO. The size of the kernel 209 is about 8% bigger than LZO. But the decompression speed is 210 faster than LZO. 211 212endchoice 213 214config DEFAULT_HOSTNAME 215 string "Default hostname" 216 default "(none)" 217 help 218 This option determines the default system hostname before userspace 219 calls sethostname(2). The kernel traditionally uses "(none)" here, 220 but you may wish to use a different default here to make a minimal 221 system more usable with less configuration. 222 223config SWAP 224 bool "Support for paging of anonymous memory (swap)" 225 depends on MMU && BLOCK 226 default y 227 help 228 This option allows you to choose whether you want to have support 229 for so called swap devices or swap files in your kernel that are 230 used to provide more virtual memory than the actual RAM present 231 in your computer. If unsure say Y. 232 233config SYSVIPC 234 bool "System V IPC" 235 ---help--- 236 Inter Process Communication is a suite of library functions and 237 system calls which let processes (running programs) synchronize and 238 exchange information. It is generally considered to be a good thing, 239 and some programs won't run unless you say Y here. In particular, if 240 you want to run the DOS emulator dosemu under Linux (read the 241 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 242 you'll need to say Y here. 243 244 You can find documentation about IPC with "info ipc" and also in 245 section 6.4 of the Linux Programmer's Guide, available from 246 <http://www.tldp.org/guides.html>. 247 248config SYSVIPC_SYSCTL 249 bool 250 depends on SYSVIPC 251 depends on SYSCTL 252 default y 253 254config POSIX_MQUEUE 255 bool "POSIX Message Queues" 256 depends on NET 257 ---help--- 258 POSIX variant of message queues is a part of IPC. In POSIX message 259 queues every message has a priority which decides about succession 260 of receiving it by a process. If you want to compile and run 261 programs written e.g. for Solaris with use of its POSIX message 262 queues (functions mq_*) say Y here. 263 264 POSIX message queues are visible as a filesystem called 'mqueue' 265 and can be mounted somewhere if you want to do filesystem 266 operations on message queues. 267 268 If unsure, say Y. 269 270config POSIX_MQUEUE_SYSCTL 271 bool 272 depends on POSIX_MQUEUE 273 depends on SYSCTL 274 default y 275 276config CROSS_MEMORY_ATTACH 277 bool "Enable process_vm_readv/writev syscalls" 278 depends on MMU 279 default y 280 help 281 Enabling this option adds the system calls process_vm_readv and 282 process_vm_writev which allow a process with the correct privileges 283 to directly read from or write to another process' address space. 284 See the man page for more details. 285 286config USELIB 287 bool "uselib syscall" 288 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION 289 help 290 This option enables the uselib syscall, a system call used in the 291 dynamic linker from libc5 and earlier. glibc does not use this 292 system call. If you intend to run programs built on libc5 or 293 earlier, you may need to enable this syscall. Current systems 294 running glibc can safely disable this. 295 296config AUDIT 297 bool "Auditing support" 298 depends on NET 299 help 300 Enable auditing infrastructure that can be used with another 301 kernel subsystem, such as SELinux (which requires this for 302 logging of avc messages output). System call auditing is included 303 on architectures which support it. 304 305config HAVE_ARCH_AUDITSYSCALL 306 bool 307 308config AUDITSYSCALL 309 def_bool y 310 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 311 312config AUDIT_WATCH 313 def_bool y 314 depends on AUDITSYSCALL 315 select FSNOTIFY 316 317config AUDIT_TREE 318 def_bool y 319 depends on AUDITSYSCALL 320 select FSNOTIFY 321 322source "kernel/irq/Kconfig" 323source "kernel/time/Kconfig" 324 325menu "CPU/Task time and stats accounting" 326 327config VIRT_CPU_ACCOUNTING 328 bool 329 330choice 331 prompt "Cputime accounting" 332 default TICK_CPU_ACCOUNTING if !PPC64 333 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 334 335# Kind of a stub config for the pure tick based cputime accounting 336config TICK_CPU_ACCOUNTING 337 bool "Simple tick based cputime accounting" 338 depends on !S390 && !NO_HZ_FULL 339 help 340 This is the basic tick based cputime accounting that maintains 341 statistics about user, system and idle time spent on per jiffies 342 granularity. 343 344 If unsure, say Y. 345 346config VIRT_CPU_ACCOUNTING_NATIVE 347 bool "Deterministic task and CPU time accounting" 348 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 349 select VIRT_CPU_ACCOUNTING 350 help 351 Select this option to enable more accurate task and CPU time 352 accounting. This is done by reading a CPU counter on each 353 kernel entry and exit and on transitions within the kernel 354 between system, softirq and hardirq state, so there is a 355 small performance impact. In the case of s390 or IBM POWER > 5, 356 this also enables accounting of stolen time on logically-partitioned 357 systems. 358 359config VIRT_CPU_ACCOUNTING_GEN 360 bool "Full dynticks CPU time accounting" 361 depends on HAVE_CONTEXT_TRACKING 362 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 363 select VIRT_CPU_ACCOUNTING 364 select CONTEXT_TRACKING 365 help 366 Select this option to enable task and CPU time accounting on full 367 dynticks systems. This accounting is implemented by watching every 368 kernel-user boundaries using the context tracking subsystem. 369 The accounting is thus performed at the expense of some significant 370 overhead. 371 372 For now this is only useful if you are working on the full 373 dynticks subsystem development. 374 375 If unsure, say N. 376 377endchoice 378 379config IRQ_TIME_ACCOUNTING 380 bool "Fine granularity task level IRQ time accounting" 381 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 382 help 383 Select this option to enable fine granularity task irq time 384 accounting. This is done by reading a timestamp on each 385 transitions between softirq and hardirq state, so there can be a 386 small performance impact. 387 388 If in doubt, say N here. 389 390config BSD_PROCESS_ACCT 391 bool "BSD Process Accounting" 392 depends on MULTIUSER 393 help 394 If you say Y here, a user level program will be able to instruct the 395 kernel (via a special system call) to write process accounting 396 information to a file: whenever a process exits, information about 397 that process will be appended to the file by the kernel. The 398 information includes things such as creation time, owning user, 399 command name, memory usage, controlling terminal etc. (the complete 400 list is in the struct acct in <file:include/linux/acct.h>). It is 401 up to the user level program to do useful things with this 402 information. This is generally a good idea, so say Y. 403 404config BSD_PROCESS_ACCT_V3 405 bool "BSD Process Accounting version 3 file format" 406 depends on BSD_PROCESS_ACCT 407 default n 408 help 409 If you say Y here, the process accounting information is written 410 in a new file format that also logs the process IDs of each 411 process and it's parent. Note that this file format is incompatible 412 with previous v0/v1/v2 file formats, so you will need updated tools 413 for processing it. A preliminary version of these tools is available 414 at <http://www.gnu.org/software/acct/>. 415 416config TASKSTATS 417 bool "Export task/process statistics through netlink" 418 depends on NET 419 depends on MULTIUSER 420 default n 421 help 422 Export selected statistics for tasks/processes through the 423 generic netlink interface. Unlike BSD process accounting, the 424 statistics are available during the lifetime of tasks/processes as 425 responses to commands. Like BSD accounting, they are sent to user 426 space on task exit. 427 428 Say N if unsure. 429 430config TASK_DELAY_ACCT 431 bool "Enable per-task delay accounting" 432 depends on TASKSTATS 433 select SCHED_INFO 434 help 435 Collect information on time spent by a task waiting for system 436 resources like cpu, synchronous block I/O completion and swapping 437 in pages. Such statistics can help in setting a task's priorities 438 relative to other tasks for cpu, io, rss limits etc. 439 440 Say N if unsure. 441 442config TASK_XACCT 443 bool "Enable extended accounting over taskstats" 444 depends on TASKSTATS 445 help 446 Collect extended task accounting data and send the data 447 to userland for processing over the taskstats interface. 448 449 Say N if unsure. 450 451config TASK_IO_ACCOUNTING 452 bool "Enable per-task storage I/O accounting" 453 depends on TASK_XACCT 454 help 455 Collect information on the number of bytes of storage I/O which this 456 task has caused. 457 458 Say N if unsure. 459 460endmenu # "CPU/Task time and stats accounting" 461 462config CPU_ISOLATION 463 bool "CPU isolation" 464 help 465 Make sure that CPUs running critical tasks are not disturbed by 466 any source of "noise" such as unbound workqueues, timers, kthreads... 467 Unbound jobs get offloaded to housekeeping CPUs. 468 469source "kernel/rcu/Kconfig" 470 471config BUILD_BIN2C 472 bool 473 default n 474 475config IKCONFIG 476 tristate "Kernel .config support" 477 select BUILD_BIN2C 478 ---help--- 479 This option enables the complete Linux kernel ".config" file 480 contents to be saved in the kernel. It provides documentation 481 of which kernel options are used in a running kernel or in an 482 on-disk kernel. This information can be extracted from the kernel 483 image file with the script scripts/extract-ikconfig and used as 484 input to rebuild the current kernel or to build another kernel. 485 It can also be extracted from a running kernel by reading 486 /proc/config.gz if enabled (below). 487 488config IKCONFIG_PROC 489 bool "Enable access to .config through /proc/config.gz" 490 depends on IKCONFIG && PROC_FS 491 ---help--- 492 This option enables access to the kernel configuration file 493 through /proc/config.gz. 494 495config LOG_BUF_SHIFT 496 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 497 range 12 25 498 default 17 499 depends on PRINTK 500 help 501 Select the minimal kernel log buffer size as a power of 2. 502 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 503 parameter, see below. Any higher size also might be forced 504 by "log_buf_len" boot parameter. 505 506 Examples: 507 17 => 128 KB 508 16 => 64 KB 509 15 => 32 KB 510 14 => 16 KB 511 13 => 8 KB 512 12 => 4 KB 513 514config LOG_CPU_MAX_BUF_SHIFT 515 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 516 depends on SMP 517 range 0 21 518 default 12 if !BASE_SMALL 519 default 0 if BASE_SMALL 520 depends on PRINTK 521 help 522 This option allows to increase the default ring buffer size 523 according to the number of CPUs. The value defines the contribution 524 of each CPU as a power of 2. The used space is typically only few 525 lines however it might be much more when problems are reported, 526 e.g. backtraces. 527 528 The increased size means that a new buffer has to be allocated and 529 the original static one is unused. It makes sense only on systems 530 with more CPUs. Therefore this value is used only when the sum of 531 contributions is greater than the half of the default kernel ring 532 buffer as defined by LOG_BUF_SHIFT. The default values are set 533 so that more than 64 CPUs are needed to trigger the allocation. 534 535 Also this option is ignored when "log_buf_len" kernel parameter is 536 used as it forces an exact (power of two) size of the ring buffer. 537 538 The number of possible CPUs is used for this computation ignoring 539 hotplugging making the computation optimal for the worst case 540 scenario while allowing a simple algorithm to be used from bootup. 541 542 Examples shift values and their meaning: 543 17 => 128 KB for each CPU 544 16 => 64 KB for each CPU 545 15 => 32 KB for each CPU 546 14 => 16 KB for each CPU 547 13 => 8 KB for each CPU 548 12 => 4 KB for each CPU 549 550config PRINTK_SAFE_LOG_BUF_SHIFT 551 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 552 range 10 21 553 default 13 554 depends on PRINTK 555 help 556 Select the size of an alternate printk per-CPU buffer where messages 557 printed from usafe contexts are temporary stored. One example would 558 be NMI messages, another one - printk recursion. The messages are 559 copied to the main log buffer in a safe context to avoid a deadlock. 560 The value defines the size as a power of 2. 561 562 Those messages are rare and limited. The largest one is when 563 a backtrace is printed. It usually fits into 4KB. Select 564 8KB if you want to be on the safe side. 565 566 Examples: 567 17 => 128 KB for each CPU 568 16 => 64 KB for each CPU 569 15 => 32 KB for each CPU 570 14 => 16 KB for each CPU 571 13 => 8 KB for each CPU 572 12 => 4 KB for each CPU 573 574# 575# Architectures with an unreliable sched_clock() should select this: 576# 577config HAVE_UNSTABLE_SCHED_CLOCK 578 bool 579 580config GENERIC_SCHED_CLOCK 581 bool 582 583# 584# For architectures that want to enable the support for NUMA-affine scheduler 585# balancing logic: 586# 587config ARCH_SUPPORTS_NUMA_BALANCING 588 bool 589 590# 591# For architectures that prefer to flush all TLBs after a number of pages 592# are unmapped instead of sending one IPI per page to flush. The architecture 593# must provide guarantees on what happens if a clean TLB cache entry is 594# written after the unmap. Details are in mm/rmap.c near the check for 595# should_defer_flush. The architecture should also consider if the full flush 596# and the refill costs are offset by the savings of sending fewer IPIs. 597config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 598 bool 599 600# 601# For architectures that know their GCC __int128 support is sound 602# 603config ARCH_SUPPORTS_INT128 604 bool 605 606# For architectures that (ab)use NUMA to represent different memory regions 607# all cpu-local but of different latencies, such as SuperH. 608# 609config ARCH_WANT_NUMA_VARIABLE_LOCALITY 610 bool 611 612config NUMA_BALANCING 613 bool "Memory placement aware NUMA scheduler" 614 depends on ARCH_SUPPORTS_NUMA_BALANCING 615 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 616 depends on SMP && NUMA && MIGRATION 617 help 618 This option adds support for automatic NUMA aware memory/task placement. 619 The mechanism is quite primitive and is based on migrating memory when 620 it has references to the node the task is running on. 621 622 This system will be inactive on UMA systems. 623 624config NUMA_BALANCING_DEFAULT_ENABLED 625 bool "Automatically enable NUMA aware memory/task placement" 626 default y 627 depends on NUMA_BALANCING 628 help 629 If set, automatic NUMA balancing will be enabled if running on a NUMA 630 machine. 631 632menuconfig CGROUPS 633 bool "Control Group support" 634 select KERNFS 635 help 636 This option adds support for grouping sets of processes together, for 637 use with process control subsystems such as Cpusets, CFS, memory 638 controls or device isolation. 639 See 640 - Documentation/scheduler/sched-design-CFS.txt (CFS) 641 - Documentation/cgroup-v1/ (features for grouping, isolation 642 and resource control) 643 644 Say N if unsure. 645 646if CGROUPS 647 648config PAGE_COUNTER 649 bool 650 651config MEMCG 652 bool "Memory controller" 653 select PAGE_COUNTER 654 select EVENTFD 655 help 656 Provides control over the memory footprint of tasks in a cgroup. 657 658config MEMCG_SWAP 659 bool "Swap controller" 660 depends on MEMCG && SWAP 661 help 662 Provides control over the swap space consumed by tasks in a cgroup. 663 664config MEMCG_SWAP_ENABLED 665 bool "Swap controller enabled by default" 666 depends on MEMCG_SWAP 667 default y 668 help 669 Memory Resource Controller Swap Extension comes with its price in 670 a bigger memory consumption. General purpose distribution kernels 671 which want to enable the feature but keep it disabled by default 672 and let the user enable it by swapaccount=1 boot command line 673 parameter should have this option unselected. 674 For those who want to have the feature enabled by default should 675 select this option (if, for some reason, they need to disable it 676 then swapaccount=0 does the trick). 677 678config BLK_CGROUP 679 bool "IO controller" 680 depends on BLOCK 681 default n 682 ---help--- 683 Generic block IO controller cgroup interface. This is the common 684 cgroup interface which should be used by various IO controlling 685 policies. 686 687 Currently, CFQ IO scheduler uses it to recognize task groups and 688 control disk bandwidth allocation (proportional time slice allocation) 689 to such task groups. It is also used by bio throttling logic in 690 block layer to implement upper limit in IO rates on a device. 691 692 This option only enables generic Block IO controller infrastructure. 693 One needs to also enable actual IO controlling logic/policy. For 694 enabling proportional weight division of disk bandwidth in CFQ, set 695 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 696 CONFIG_BLK_DEV_THROTTLING=y. 697 698 See Documentation/cgroup-v1/blkio-controller.txt for more information. 699 700config DEBUG_BLK_CGROUP 701 bool "IO controller debugging" 702 depends on BLK_CGROUP 703 default n 704 ---help--- 705 Enable some debugging help. Currently it exports additional stat 706 files in a cgroup which can be useful for debugging. 707 708config CGROUP_WRITEBACK 709 bool 710 depends on MEMCG && BLK_CGROUP 711 default y 712 713menuconfig CGROUP_SCHED 714 bool "CPU controller" 715 default n 716 help 717 This feature lets CPU scheduler recognize task groups and control CPU 718 bandwidth allocation to such task groups. It uses cgroups to group 719 tasks. 720 721if CGROUP_SCHED 722config FAIR_GROUP_SCHED 723 bool "Group scheduling for SCHED_OTHER" 724 depends on CGROUP_SCHED 725 default CGROUP_SCHED 726 727config CFS_BANDWIDTH 728 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 729 depends on FAIR_GROUP_SCHED 730 default n 731 help 732 This option allows users to define CPU bandwidth rates (limits) for 733 tasks running within the fair group scheduler. Groups with no limit 734 set are considered to be unconstrained and will run with no 735 restriction. 736 See tip/Documentation/scheduler/sched-bwc.txt for more information. 737 738config RT_GROUP_SCHED 739 bool "Group scheduling for SCHED_RR/FIFO" 740 depends on CGROUP_SCHED 741 default n 742 help 743 This feature lets you explicitly allocate real CPU bandwidth 744 to task groups. If enabled, it will also make it impossible to 745 schedule realtime tasks for non-root users until you allocate 746 realtime bandwidth for them. 747 See Documentation/scheduler/sched-rt-group.txt for more information. 748 749endif #CGROUP_SCHED 750 751config CGROUP_PIDS 752 bool "PIDs controller" 753 help 754 Provides enforcement of process number limits in the scope of a 755 cgroup. Any attempt to fork more processes than is allowed in the 756 cgroup will fail. PIDs are fundamentally a global resource because it 757 is fairly trivial to reach PID exhaustion before you reach even a 758 conservative kmemcg limit. As a result, it is possible to grind a 759 system to halt without being limited by other cgroup policies. The 760 PIDs controller is designed to stop this from happening. 761 762 It should be noted that organisational operations (such as attaching 763 to a cgroup hierarchy will *not* be blocked by the PIDs controller), 764 since the PIDs limit only affects a process's ability to fork, not to 765 attach to a cgroup. 766 767config CGROUP_RDMA 768 bool "RDMA controller" 769 help 770 Provides enforcement of RDMA resources defined by IB stack. 771 It is fairly easy for consumers to exhaust RDMA resources, which 772 can result into resource unavailability to other consumers. 773 RDMA controller is designed to stop this from happening. 774 Attaching processes with active RDMA resources to the cgroup 775 hierarchy is allowed even if can cross the hierarchy's limit. 776 777config CGROUP_FREEZER 778 bool "Freezer controller" 779 help 780 Provides a way to freeze and unfreeze all tasks in a 781 cgroup. 782 783 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 784 controller includes important in-kernel memory consumers per default. 785 786 If you're using cgroup2, say N. 787 788config CGROUP_HUGETLB 789 bool "HugeTLB controller" 790 depends on HUGETLB_PAGE 791 select PAGE_COUNTER 792 default n 793 help 794 Provides a cgroup controller for HugeTLB pages. 795 When you enable this, you can put a per cgroup limit on HugeTLB usage. 796 The limit is enforced during page fault. Since HugeTLB doesn't 797 support page reclaim, enforcing the limit at page fault time implies 798 that, the application will get SIGBUS signal if it tries to access 799 HugeTLB pages beyond its limit. This requires the application to know 800 beforehand how much HugeTLB pages it would require for its use. The 801 control group is tracked in the third page lru pointer. This means 802 that we cannot use the controller with huge page less than 3 pages. 803 804config CPUSETS 805 bool "Cpuset controller" 806 depends on SMP 807 help 808 This option will let you create and manage CPUSETs which 809 allow dynamically partitioning a system into sets of CPUs and 810 Memory Nodes and assigning tasks to run only within those sets. 811 This is primarily useful on large SMP or NUMA systems. 812 813 Say N if unsure. 814 815config PROC_PID_CPUSET 816 bool "Include legacy /proc/<pid>/cpuset file" 817 depends on CPUSETS 818 default y 819 820config CGROUP_DEVICE 821 bool "Device controller" 822 help 823 Provides a cgroup controller implementing whitelists for 824 devices which a process in the cgroup can mknod or open. 825 826config CGROUP_CPUACCT 827 bool "Simple CPU accounting controller" 828 help 829 Provides a simple controller for monitoring the 830 total CPU consumed by the tasks in a cgroup. 831 832config CGROUP_PERF 833 bool "Perf controller" 834 depends on PERF_EVENTS 835 help 836 This option extends the perf per-cpu mode to restrict monitoring 837 to threads which belong to the cgroup specified and run on the 838 designated cpu. 839 840 Say N if unsure. 841 842config CGROUP_BPF 843 bool "Support for eBPF programs attached to cgroups" 844 depends on BPF_SYSCALL 845 select SOCK_CGROUP_DATA 846 help 847 Allow attaching eBPF programs to a cgroup using the bpf(2) 848 syscall command BPF_PROG_ATTACH. 849 850 In which context these programs are accessed depends on the type 851 of attachment. For instance, programs that are attached using 852 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 853 inet sockets. 854 855config CGROUP_DEBUG 856 bool "Debug controller" 857 default n 858 depends on DEBUG_KERNEL 859 help 860 This option enables a simple controller that exports 861 debugging information about the cgroups framework. This 862 controller is for control cgroup debugging only. Its 863 interfaces are not stable. 864 865 Say N. 866 867config SOCK_CGROUP_DATA 868 bool 869 default n 870 871endif # CGROUPS 872 873menuconfig NAMESPACES 874 bool "Namespaces support" if EXPERT 875 depends on MULTIUSER 876 default !EXPERT 877 help 878 Provides the way to make tasks work with different objects using 879 the same id. For example same IPC id may refer to different objects 880 or same user id or pid may refer to different tasks when used in 881 different namespaces. 882 883if NAMESPACES 884 885config UTS_NS 886 bool "UTS namespace" 887 default y 888 help 889 In this namespace tasks see different info provided with the 890 uname() system call 891 892config IPC_NS 893 bool "IPC namespace" 894 depends on (SYSVIPC || POSIX_MQUEUE) 895 default y 896 help 897 In this namespace tasks work with IPC ids which correspond to 898 different IPC objects in different namespaces. 899 900config USER_NS 901 bool "User namespace" 902 default n 903 help 904 This allows containers, i.e. vservers, to use user namespaces 905 to provide different user info for different servers. 906 907 When user namespaces are enabled in the kernel it is 908 recommended that the MEMCG option also be enabled and that 909 user-space use the memory control groups to limit the amount 910 of memory a memory unprivileged users can use. 911 912 If unsure, say N. 913 914config PID_NS 915 bool "PID Namespaces" 916 default y 917 help 918 Support process id namespaces. This allows having multiple 919 processes with the same pid as long as they are in different 920 pid namespaces. This is a building block of containers. 921 922config NET_NS 923 bool "Network namespace" 924 depends on NET 925 default y 926 help 927 Allow user space to create what appear to be multiple instances 928 of the network stack. 929 930endif # NAMESPACES 931 932config SCHED_AUTOGROUP 933 bool "Automatic process group scheduling" 934 select CGROUPS 935 select CGROUP_SCHED 936 select FAIR_GROUP_SCHED 937 help 938 This option optimizes the scheduler for common desktop workloads by 939 automatically creating and populating task groups. This separation 940 of workloads isolates aggressive CPU burners (like build jobs) from 941 desktop applications. Task group autogeneration is currently based 942 upon task session. 943 944config SYSFS_DEPRECATED 945 bool "Enable deprecated sysfs features to support old userspace tools" 946 depends on SYSFS 947 default n 948 help 949 This option adds code that switches the layout of the "block" class 950 devices, to not show up in /sys/class/block/, but only in 951 /sys/block/. 952 953 This switch is only active when the sysfs.deprecated=1 boot option is 954 passed or the SYSFS_DEPRECATED_V2 option is set. 955 956 This option allows new kernels to run on old distributions and tools, 957 which might get confused by /sys/class/block/. Since 2007/2008 all 958 major distributions and tools handle this just fine. 959 960 Recent distributions and userspace tools after 2009/2010 depend on 961 the existence of /sys/class/block/, and will not work with this 962 option enabled. 963 964 Only if you are using a new kernel on an old distribution, you might 965 need to say Y here. 966 967config SYSFS_DEPRECATED_V2 968 bool "Enable deprecated sysfs features by default" 969 default n 970 depends on SYSFS 971 depends on SYSFS_DEPRECATED 972 help 973 Enable deprecated sysfs by default. 974 975 See the CONFIG_SYSFS_DEPRECATED option for more details about this 976 option. 977 978 Only if you are using a new kernel on an old distribution, you might 979 need to say Y here. Even then, odds are you would not need it 980 enabled, you can always pass the boot option if absolutely necessary. 981 982config RELAY 983 bool "Kernel->user space relay support (formerly relayfs)" 984 select IRQ_WORK 985 help 986 This option enables support for relay interface support in 987 certain file systems (such as debugfs). 988 It is designed to provide an efficient mechanism for tools and 989 facilities to relay large amounts of data from kernel space to 990 user space. 991 992 If unsure, say N. 993 994config BLK_DEV_INITRD 995 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 996 depends on BROKEN || !FRV 997 help 998 The initial RAM filesystem is a ramfs which is loaded by the 999 boot loader (loadlin or lilo) and that is mounted as root 1000 before the normal boot procedure. It is typically used to 1001 load modules needed to mount the "real" root file system, 1002 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1003 1004 If RAM disk support (BLK_DEV_RAM) is also included, this 1005 also enables initial RAM disk (initrd) support and adds 1006 15 Kbytes (more on some other architectures) to the kernel size. 1007 1008 If unsure say Y. 1009 1010if BLK_DEV_INITRD 1011 1012source "usr/Kconfig" 1013 1014endif 1015 1016choice 1017 prompt "Compiler optimization level" 1018 default CC_OPTIMIZE_FOR_PERFORMANCE 1019 1020config CC_OPTIMIZE_FOR_PERFORMANCE 1021 bool "Optimize for performance" 1022 help 1023 This is the default optimization level for the kernel, building 1024 with the "-O2" compiler flag for best performance and most 1025 helpful compile-time warnings. 1026 1027config CC_OPTIMIZE_FOR_SIZE 1028 bool "Optimize for size" 1029 help 1030 Enabling this option will pass "-Os" instead of "-O2" to 1031 your compiler resulting in a smaller kernel. 1032 1033 If unsure, say N. 1034 1035endchoice 1036 1037config SYSCTL 1038 bool 1039 1040config ANON_INODES 1041 bool 1042 1043config HAVE_UID16 1044 bool 1045 1046config SYSCTL_EXCEPTION_TRACE 1047 bool 1048 help 1049 Enable support for /proc/sys/debug/exception-trace. 1050 1051config SYSCTL_ARCH_UNALIGN_NO_WARN 1052 bool 1053 help 1054 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1055 Allows arch to define/use @no_unaligned_warning to possibly warn 1056 about unaligned access emulation going on under the hood. 1057 1058config SYSCTL_ARCH_UNALIGN_ALLOW 1059 bool 1060 help 1061 Enable support for /proc/sys/kernel/unaligned-trap 1062 Allows arches to define/use @unaligned_enabled to runtime toggle 1063 the unaligned access emulation. 1064 see arch/parisc/kernel/unaligned.c for reference 1065 1066config HAVE_PCSPKR_PLATFORM 1067 bool 1068 1069# interpreter that classic socket filters depend on 1070config BPF 1071 bool 1072 1073menuconfig EXPERT 1074 bool "Configure standard kernel features (expert users)" 1075 # Unhide debug options, to make the on-by-default options visible 1076 select DEBUG_KERNEL 1077 help 1078 This option allows certain base kernel options and settings 1079 to be disabled or tweaked. This is for specialized 1080 environments which can tolerate a "non-standard" kernel. 1081 Only use this if you really know what you are doing. 1082 1083config UID16 1084 bool "Enable 16-bit UID system calls" if EXPERT 1085 depends on HAVE_UID16 && MULTIUSER 1086 default y 1087 help 1088 This enables the legacy 16-bit UID syscall wrappers. 1089 1090config MULTIUSER 1091 bool "Multiple users, groups and capabilities support" if EXPERT 1092 default y 1093 help 1094 This option enables support for non-root users, groups and 1095 capabilities. 1096 1097 If you say N here, all processes will run with UID 0, GID 0, and all 1098 possible capabilities. Saying N here also compiles out support for 1099 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1100 setgid, and capset. 1101 1102 If unsure, say Y here. 1103 1104config SGETMASK_SYSCALL 1105 bool "sgetmask/ssetmask syscalls support" if EXPERT 1106 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH 1107 ---help--- 1108 sys_sgetmask and sys_ssetmask are obsolete system calls 1109 no longer supported in libc but still enabled by default in some 1110 architectures. 1111 1112 If unsure, leave the default option here. 1113 1114config SYSFS_SYSCALL 1115 bool "Sysfs syscall support" if EXPERT 1116 default y 1117 ---help--- 1118 sys_sysfs is an obsolete system call no longer supported in libc. 1119 Note that disabling this option is more secure but might break 1120 compatibility with some systems. 1121 1122 If unsure say Y here. 1123 1124config SYSCTL_SYSCALL 1125 bool "Sysctl syscall support" if EXPERT 1126 depends on PROC_SYSCTL 1127 default n 1128 select SYSCTL 1129 ---help--- 1130 sys_sysctl uses binary paths that have been found challenging 1131 to properly maintain and use. The interface in /proc/sys 1132 using paths with ascii names is now the primary path to this 1133 information. 1134 1135 Almost nothing using the binary sysctl interface so if you are 1136 trying to save some space it is probably safe to disable this, 1137 making your kernel marginally smaller. 1138 1139 If unsure say N here. 1140 1141config FHANDLE 1142 bool "open by fhandle syscalls" if EXPERT 1143 select EXPORTFS 1144 default y 1145 help 1146 If you say Y here, a user level program will be able to map 1147 file names to handle and then later use the handle for 1148 different file system operations. This is useful in implementing 1149 userspace file servers, which now track files using handles instead 1150 of names. The handle would remain the same even if file names 1151 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1152 syscalls. 1153 1154config POSIX_TIMERS 1155 bool "Posix Clocks & timers" if EXPERT 1156 default y 1157 help 1158 This includes native support for POSIX timers to the kernel. 1159 Some embedded systems have no use for them and therefore they 1160 can be configured out to reduce the size of the kernel image. 1161 1162 When this option is disabled, the following syscalls won't be 1163 available: timer_create, timer_gettime: timer_getoverrun, 1164 timer_settime, timer_delete, clock_adjtime, getitimer, 1165 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1166 clock_getres and clock_nanosleep syscalls will be limited to 1167 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1168 1169 If unsure say y. 1170 1171config PRINTK 1172 default y 1173 bool "Enable support for printk" if EXPERT 1174 select IRQ_WORK 1175 help 1176 This option enables normal printk support. Removing it 1177 eliminates most of the message strings from the kernel image 1178 and makes the kernel more or less silent. As this makes it 1179 very difficult to diagnose system problems, saying N here is 1180 strongly discouraged. 1181 1182config PRINTK_NMI 1183 def_bool y 1184 depends on PRINTK 1185 depends on HAVE_NMI 1186 1187config BUG 1188 bool "BUG() support" if EXPERT 1189 default y 1190 help 1191 Disabling this option eliminates support for BUG and WARN, reducing 1192 the size of your kernel image and potentially quietly ignoring 1193 numerous fatal conditions. You should only consider disabling this 1194 option for embedded systems with no facilities for reporting errors. 1195 Just say Y. 1196 1197config ELF_CORE 1198 depends on COREDUMP 1199 default y 1200 bool "Enable ELF core dumps" if EXPERT 1201 help 1202 Enable support for generating core dumps. Disabling saves about 4k. 1203 1204 1205config PCSPKR_PLATFORM 1206 bool "Enable PC-Speaker support" if EXPERT 1207 depends on HAVE_PCSPKR_PLATFORM 1208 select I8253_LOCK 1209 default y 1210 help 1211 This option allows to disable the internal PC-Speaker 1212 support, saving some memory. 1213 1214config BASE_FULL 1215 default y 1216 bool "Enable full-sized data structures for core" if EXPERT 1217 help 1218 Disabling this option reduces the size of miscellaneous core 1219 kernel data structures. This saves memory on small machines, 1220 but may reduce performance. 1221 1222config FUTEX 1223 bool "Enable futex support" if EXPERT 1224 default y 1225 imply RT_MUTEXES 1226 help 1227 Disabling this option will cause the kernel to be built without 1228 support for "fast userspace mutexes". The resulting kernel may not 1229 run glibc-based applications correctly. 1230 1231config FUTEX_PI 1232 bool 1233 depends on FUTEX && RT_MUTEXES 1234 default y 1235 1236config HAVE_FUTEX_CMPXCHG 1237 bool 1238 depends on FUTEX 1239 help 1240 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1241 is implemented and always working. This removes a couple of runtime 1242 checks. 1243 1244config EPOLL 1245 bool "Enable eventpoll support" if EXPERT 1246 default y 1247 select ANON_INODES 1248 help 1249 Disabling this option will cause the kernel to be built without 1250 support for epoll family of system calls. 1251 1252config SIGNALFD 1253 bool "Enable signalfd() system call" if EXPERT 1254 select ANON_INODES 1255 default y 1256 help 1257 Enable the signalfd() system call that allows to receive signals 1258 on a file descriptor. 1259 1260 If unsure, say Y. 1261 1262config TIMERFD 1263 bool "Enable timerfd() system call" if EXPERT 1264 select ANON_INODES 1265 default y 1266 help 1267 Enable the timerfd() system call that allows to receive timer 1268 events on a file descriptor. 1269 1270 If unsure, say Y. 1271 1272config EVENTFD 1273 bool "Enable eventfd() system call" if EXPERT 1274 select ANON_INODES 1275 default y 1276 help 1277 Enable the eventfd() system call that allows to receive both 1278 kernel notification (ie. KAIO) or userspace notifications. 1279 1280 If unsure, say Y. 1281 1282config SHMEM 1283 bool "Use full shmem filesystem" if EXPERT 1284 default y 1285 depends on MMU 1286 help 1287 The shmem is an internal filesystem used to manage shared memory. 1288 It is backed by swap and manages resource limits. It is also exported 1289 to userspace as tmpfs if TMPFS is enabled. Disabling this 1290 option replaces shmem and tmpfs with the much simpler ramfs code, 1291 which may be appropriate on small systems without swap. 1292 1293config AIO 1294 bool "Enable AIO support" if EXPERT 1295 default y 1296 help 1297 This option enables POSIX asynchronous I/O which may by used 1298 by some high performance threaded applications. Disabling 1299 this option saves about 7k. 1300 1301config ADVISE_SYSCALLS 1302 bool "Enable madvise/fadvise syscalls" if EXPERT 1303 default y 1304 help 1305 This option enables the madvise and fadvise syscalls, used by 1306 applications to advise the kernel about their future memory or file 1307 usage, improving performance. If building an embedded system where no 1308 applications use these syscalls, you can disable this option to save 1309 space. 1310 1311config MEMBARRIER 1312 bool "Enable membarrier() system call" if EXPERT 1313 default y 1314 help 1315 Enable the membarrier() system call that allows issuing memory 1316 barriers across all running threads, which can be used to distribute 1317 the cost of user-space memory barriers asymmetrically by transforming 1318 pairs of memory barriers into pairs consisting of membarrier() and a 1319 compiler barrier. 1320 1321 If unsure, say Y. 1322 1323config CHECKPOINT_RESTORE 1324 bool "Checkpoint/restore support" if EXPERT 1325 select PROC_CHILDREN 1326 default n 1327 help 1328 Enables additional kernel features in a sake of checkpoint/restore. 1329 In particular it adds auxiliary prctl codes to setup process text, 1330 data and heap segment sizes, and a few additional /proc filesystem 1331 entries. 1332 1333 If unsure, say N here. 1334 1335config KALLSYMS 1336 bool "Load all symbols for debugging/ksymoops" if EXPERT 1337 default y 1338 help 1339 Say Y here to let the kernel print out symbolic crash information and 1340 symbolic stack backtraces. This increases the size of the kernel 1341 somewhat, as all symbols have to be loaded into the kernel image. 1342 1343config KALLSYMS_ALL 1344 bool "Include all symbols in kallsyms" 1345 depends on DEBUG_KERNEL && KALLSYMS 1346 help 1347 Normally kallsyms only contains the symbols of functions for nicer 1348 OOPS messages and backtraces (i.e., symbols from the text and inittext 1349 sections). This is sufficient for most cases. And only in very rare 1350 cases (e.g., when a debugger is used) all symbols are required (e.g., 1351 names of variables from the data sections, etc). 1352 1353 This option makes sure that all symbols are loaded into the kernel 1354 image (i.e., symbols from all sections) in cost of increased kernel 1355 size (depending on the kernel configuration, it may be 300KiB or 1356 something like this). 1357 1358 Say N unless you really need all symbols. 1359 1360config KALLSYMS_ABSOLUTE_PERCPU 1361 bool 1362 depends on KALLSYMS 1363 default X86_64 && SMP 1364 1365config KALLSYMS_BASE_RELATIVE 1366 bool 1367 depends on KALLSYMS 1368 default !IA64 && !(TILE && 64BIT) 1369 help 1370 Instead of emitting them as absolute values in the native word size, 1371 emit the symbol references in the kallsyms table as 32-bit entries, 1372 each containing a relative value in the range [base, base + U32_MAX] 1373 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1374 an absolute value in the range [0, S32_MAX] or a relative value in the 1375 range [base, base + S32_MAX], where base is the lowest relative symbol 1376 address encountered in the image. 1377 1378 On 64-bit builds, this reduces the size of the address table by 50%, 1379 but more importantly, it results in entries whose values are build 1380 time constants, and no relocation pass is required at runtime to fix 1381 up the entries based on the runtime load address of the kernel. 1382 1383# end of the "standard kernel features (expert users)" menu 1384 1385# syscall, maps, verifier 1386config BPF_SYSCALL 1387 bool "Enable bpf() system call" 1388 select ANON_INODES 1389 select BPF 1390 default n 1391 help 1392 Enable the bpf() system call that allows to manipulate eBPF 1393 programs and maps via file descriptors. 1394 1395config USERFAULTFD 1396 bool "Enable userfaultfd() system call" 1397 select ANON_INODES 1398 depends on MMU 1399 help 1400 Enable the userfaultfd() system call that allows to intercept and 1401 handle page faults in userland. 1402 1403config EMBEDDED 1404 bool "Embedded system" 1405 option allnoconfig_y 1406 select EXPERT 1407 help 1408 This option should be enabled if compiling the kernel for 1409 an embedded system so certain expert options are available 1410 for configuration. 1411 1412config HAVE_PERF_EVENTS 1413 bool 1414 help 1415 See tools/perf/design.txt for details. 1416 1417config PERF_USE_VMALLOC 1418 bool 1419 help 1420 See tools/perf/design.txt for details 1421 1422config PC104 1423 bool "PC/104 support" 1424 help 1425 Expose PC/104 form factor device drivers and options available for 1426 selection and configuration. Enable this option if your target 1427 machine has a PC/104 bus. 1428 1429menu "Kernel Performance Events And Counters" 1430 1431config PERF_EVENTS 1432 bool "Kernel performance events and counters" 1433 default y if PROFILING 1434 depends on HAVE_PERF_EVENTS 1435 select ANON_INODES 1436 select IRQ_WORK 1437 select SRCU 1438 help 1439 Enable kernel support for various performance events provided 1440 by software and hardware. 1441 1442 Software events are supported either built-in or via the 1443 use of generic tracepoints. 1444 1445 Most modern CPUs support performance events via performance 1446 counter registers. These registers count the number of certain 1447 types of hw events: such as instructions executed, cachemisses 1448 suffered, or branches mis-predicted - without slowing down the 1449 kernel or applications. These registers can also trigger interrupts 1450 when a threshold number of events have passed - and can thus be 1451 used to profile the code that runs on that CPU. 1452 1453 The Linux Performance Event subsystem provides an abstraction of 1454 these software and hardware event capabilities, available via a 1455 system call and used by the "perf" utility in tools/perf/. It 1456 provides per task and per CPU counters, and it provides event 1457 capabilities on top of those. 1458 1459 Say Y if unsure. 1460 1461config DEBUG_PERF_USE_VMALLOC 1462 default n 1463 bool "Debug: use vmalloc to back perf mmap() buffers" 1464 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1465 select PERF_USE_VMALLOC 1466 help 1467 Use vmalloc memory to back perf mmap() buffers. 1468 1469 Mostly useful for debugging the vmalloc code on platforms 1470 that don't require it. 1471 1472 Say N if unsure. 1473 1474endmenu 1475 1476config VM_EVENT_COUNTERS 1477 default y 1478 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1479 help 1480 VM event counters are needed for event counts to be shown. 1481 This option allows the disabling of the VM event counters 1482 on EXPERT systems. /proc/vmstat will only show page counts 1483 if VM event counters are disabled. 1484 1485config SLUB_DEBUG 1486 default y 1487 bool "Enable SLUB debugging support" if EXPERT 1488 depends on SLUB && SYSFS 1489 help 1490 SLUB has extensive debug support features. Disabling these can 1491 result in significant savings in code size. This also disables 1492 SLUB sysfs support. /sys/slab will not exist and there will be 1493 no support for cache validation etc. 1494 1495config SLUB_MEMCG_SYSFS_ON 1496 default n 1497 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1498 depends on SLUB && SYSFS && MEMCG 1499 help 1500 SLUB creates a directory under /sys/kernel/slab for each 1501 allocation cache to host info and debug files. If memory 1502 cgroup is enabled, each cache can have per memory cgroup 1503 caches. SLUB can create the same sysfs directories for these 1504 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1505 to a very high number of debug files being created. This is 1506 controlled by slub_memcg_sysfs boot parameter and this 1507 config option determines the parameter's default value. 1508 1509config COMPAT_BRK 1510 bool "Disable heap randomization" 1511 default y 1512 help 1513 Randomizing heap placement makes heap exploits harder, but it 1514 also breaks ancient binaries (including anything libc5 based). 1515 This option changes the bootup default to heap randomization 1516 disabled, and can be overridden at runtime by setting 1517 /proc/sys/kernel/randomize_va_space to 2. 1518 1519 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1520 1521choice 1522 prompt "Choose SLAB allocator" 1523 default SLUB 1524 help 1525 This option allows to select a slab allocator. 1526 1527config SLAB 1528 bool "SLAB" 1529 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1530 help 1531 The regular slab allocator that is established and known to work 1532 well in all environments. It organizes cache hot objects in 1533 per cpu and per node queues. 1534 1535config SLUB 1536 bool "SLUB (Unqueued Allocator)" 1537 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1538 help 1539 SLUB is a slab allocator that minimizes cache line usage 1540 instead of managing queues of cached objects (SLAB approach). 1541 Per cpu caching is realized using slabs of objects instead 1542 of queues of objects. SLUB can use memory efficiently 1543 and has enhanced diagnostics. SLUB is the default choice for 1544 a slab allocator. 1545 1546config SLOB 1547 depends on EXPERT 1548 bool "SLOB (Simple Allocator)" 1549 help 1550 SLOB replaces the stock allocator with a drastically simpler 1551 allocator. SLOB is generally more space efficient but 1552 does not perform as well on large systems. 1553 1554endchoice 1555 1556config SLAB_MERGE_DEFAULT 1557 bool "Allow slab caches to be merged" 1558 default y 1559 help 1560 For reduced kernel memory fragmentation, slab caches can be 1561 merged when they share the same size and other characteristics. 1562 This carries a risk of kernel heap overflows being able to 1563 overwrite objects from merged caches (and more easily control 1564 cache layout), which makes such heap attacks easier to exploit 1565 by attackers. By keeping caches unmerged, these kinds of exploits 1566 can usually only damage objects in the same cache. To disable 1567 merging at runtime, "slab_nomerge" can be passed on the kernel 1568 command line. 1569 1570config SLAB_FREELIST_RANDOM 1571 default n 1572 depends on SLAB || SLUB 1573 bool "SLAB freelist randomization" 1574 help 1575 Randomizes the freelist order used on creating new pages. This 1576 security feature reduces the predictability of the kernel slab 1577 allocator against heap overflows. 1578 1579config SLAB_FREELIST_HARDENED 1580 bool "Harden slab freelist metadata" 1581 depends on SLUB 1582 help 1583 Many kernel heap attacks try to target slab cache metadata and 1584 other infrastructure. This options makes minor performance 1585 sacrifies to harden the kernel slab allocator against common 1586 freelist exploit methods. 1587 1588config SLUB_CPU_PARTIAL 1589 default y 1590 depends on SLUB && SMP 1591 bool "SLUB per cpu partial cache" 1592 help 1593 Per cpu partial caches accellerate objects allocation and freeing 1594 that is local to a processor at the price of more indeterminism 1595 in the latency of the free. On overflow these caches will be cleared 1596 which requires the taking of locks that may cause latency spikes. 1597 Typically one would choose no for a realtime system. 1598 1599config MMAP_ALLOW_UNINITIALIZED 1600 bool "Allow mmapped anonymous memory to be uninitialized" 1601 depends on EXPERT && !MMU 1602 default n 1603 help 1604 Normally, and according to the Linux spec, anonymous memory obtained 1605 from mmap() has it's contents cleared before it is passed to 1606 userspace. Enabling this config option allows you to request that 1607 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1608 providing a huge performance boost. If this option is not enabled, 1609 then the flag will be ignored. 1610 1611 This is taken advantage of by uClibc's malloc(), and also by 1612 ELF-FDPIC binfmt's brk and stack allocator. 1613 1614 Because of the obvious security issues, this option should only be 1615 enabled on embedded devices where you control what is run in 1616 userspace. Since that isn't generally a problem on no-MMU systems, 1617 it is normally safe to say Y here. 1618 1619 See Documentation/nommu-mmap.txt for more information. 1620 1621config SYSTEM_DATA_VERIFICATION 1622 def_bool n 1623 select SYSTEM_TRUSTED_KEYRING 1624 select KEYS 1625 select CRYPTO 1626 select CRYPTO_RSA 1627 select ASYMMETRIC_KEY_TYPE 1628 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1629 select ASN1 1630 select OID_REGISTRY 1631 select X509_CERTIFICATE_PARSER 1632 select PKCS7_MESSAGE_PARSER 1633 help 1634 Provide PKCS#7 message verification using the contents of the system 1635 trusted keyring to provide public keys. This then can be used for 1636 module verification, kexec image verification and firmware blob 1637 verification. 1638 1639config PROFILING 1640 bool "Profiling support" 1641 help 1642 Say Y here to enable the extended profiling support mechanisms used 1643 by profilers such as OProfile. 1644 1645# 1646# Place an empty function call at each tracepoint site. Can be 1647# dynamically changed for a probe function. 1648# 1649config TRACEPOINTS 1650 bool 1651 1652source "arch/Kconfig" 1653 1654endmenu # General setup 1655 1656config HAVE_GENERIC_DMA_COHERENT 1657 bool 1658 default n 1659 1660config RT_MUTEXES 1661 bool 1662 1663config BASE_SMALL 1664 int 1665 default 0 if BASE_FULL 1666 default 1 if !BASE_FULL 1667 1668menuconfig MODULES 1669 bool "Enable loadable module support" 1670 option modules 1671 help 1672 Kernel modules are small pieces of compiled code which can 1673 be inserted in the running kernel, rather than being 1674 permanently built into the kernel. You use the "modprobe" 1675 tool to add (and sometimes remove) them. If you say Y here, 1676 many parts of the kernel can be built as modules (by 1677 answering M instead of Y where indicated): this is most 1678 useful for infrequently used options which are not required 1679 for booting. For more information, see the man pages for 1680 modprobe, lsmod, modinfo, insmod and rmmod. 1681 1682 If you say Y here, you will need to run "make 1683 modules_install" to put the modules under /lib/modules/ 1684 where modprobe can find them (you may need to be root to do 1685 this). 1686 1687 If unsure, say Y. 1688 1689if MODULES 1690 1691config MODULE_FORCE_LOAD 1692 bool "Forced module loading" 1693 default n 1694 help 1695 Allow loading of modules without version information (ie. modprobe 1696 --force). Forced module loading sets the 'F' (forced) taint flag and 1697 is usually a really bad idea. 1698 1699config MODULE_UNLOAD 1700 bool "Module unloading" 1701 help 1702 Without this option you will not be able to unload any 1703 modules (note that some modules may not be unloadable 1704 anyway), which makes your kernel smaller, faster 1705 and simpler. If unsure, say Y. 1706 1707config MODULE_FORCE_UNLOAD 1708 bool "Forced module unloading" 1709 depends on MODULE_UNLOAD 1710 help 1711 This option allows you to force a module to unload, even if the 1712 kernel believes it is unsafe: the kernel will remove the module 1713 without waiting for anyone to stop using it (using the -f option to 1714 rmmod). This is mainly for kernel developers and desperate users. 1715 If unsure, say N. 1716 1717config MODVERSIONS 1718 bool "Module versioning support" 1719 help 1720 Usually, you have to use modules compiled with your kernel. 1721 Saying Y here makes it sometimes possible to use modules 1722 compiled for different kernels, by adding enough information 1723 to the modules to (hopefully) spot any changes which would 1724 make them incompatible with the kernel you are running. If 1725 unsure, say N. 1726 1727config MODULE_REL_CRCS 1728 bool 1729 depends on MODVERSIONS 1730 1731config MODULE_SRCVERSION_ALL 1732 bool "Source checksum for all modules" 1733 help 1734 Modules which contain a MODULE_VERSION get an extra "srcversion" 1735 field inserted into their modinfo section, which contains a 1736 sum of the source files which made it. This helps maintainers 1737 see exactly which source was used to build a module (since 1738 others sometimes change the module source without updating 1739 the version). With this option, such a "srcversion" field 1740 will be created for all modules. If unsure, say N. 1741 1742config MODULE_SIG 1743 bool "Module signature verification" 1744 depends on MODULES 1745 select SYSTEM_DATA_VERIFICATION 1746 help 1747 Check modules for valid signatures upon load: the signature 1748 is simply appended to the module. For more information see 1749 <file:Documentation/admin-guide/module-signing.rst>. 1750 1751 Note that this option adds the OpenSSL development packages as a 1752 kernel build dependency so that the signing tool can use its crypto 1753 library. 1754 1755 !!!WARNING!!! If you enable this option, you MUST make sure that the 1756 module DOES NOT get stripped after being signed. This includes the 1757 debuginfo strip done by some packagers (such as rpmbuild) and 1758 inclusion into an initramfs that wants the module size reduced. 1759 1760config MODULE_SIG_FORCE 1761 bool "Require modules to be validly signed" 1762 depends on MODULE_SIG 1763 help 1764 Reject unsigned modules or signed modules for which we don't have a 1765 key. Without this, such modules will simply taint the kernel. 1766 1767config MODULE_SIG_ALL 1768 bool "Automatically sign all modules" 1769 default y 1770 depends on MODULE_SIG 1771 help 1772 Sign all modules during make modules_install. Without this option, 1773 modules must be signed manually, using the scripts/sign-file tool. 1774 1775comment "Do not forget to sign required modules with scripts/sign-file" 1776 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 1777 1778choice 1779 prompt "Which hash algorithm should modules be signed with?" 1780 depends on MODULE_SIG 1781 help 1782 This determines which sort of hashing algorithm will be used during 1783 signature generation. This algorithm _must_ be built into the kernel 1784 directly so that signature verification can take place. It is not 1785 possible to load a signed module containing the algorithm to check 1786 the signature on that module. 1787 1788config MODULE_SIG_SHA1 1789 bool "Sign modules with SHA-1" 1790 select CRYPTO_SHA1 1791 1792config MODULE_SIG_SHA224 1793 bool "Sign modules with SHA-224" 1794 select CRYPTO_SHA256 1795 1796config MODULE_SIG_SHA256 1797 bool "Sign modules with SHA-256" 1798 select CRYPTO_SHA256 1799 1800config MODULE_SIG_SHA384 1801 bool "Sign modules with SHA-384" 1802 select CRYPTO_SHA512 1803 1804config MODULE_SIG_SHA512 1805 bool "Sign modules with SHA-512" 1806 select CRYPTO_SHA512 1807 1808endchoice 1809 1810config MODULE_SIG_HASH 1811 string 1812 depends on MODULE_SIG 1813 default "sha1" if MODULE_SIG_SHA1 1814 default "sha224" if MODULE_SIG_SHA224 1815 default "sha256" if MODULE_SIG_SHA256 1816 default "sha384" if MODULE_SIG_SHA384 1817 default "sha512" if MODULE_SIG_SHA512 1818 1819config MODULE_COMPRESS 1820 bool "Compress modules on installation" 1821 depends on MODULES 1822 help 1823 1824 Compresses kernel modules when 'make modules_install' is run; gzip or 1825 xz depending on "Compression algorithm" below. 1826 1827 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 1828 1829 Out-of-tree kernel modules installed using Kbuild will also be 1830 compressed upon installation. 1831 1832 Note: for modules inside an initrd or initramfs, it's more efficient 1833 to compress the whole initrd or initramfs instead. 1834 1835 Note: This is fully compatible with signed modules. 1836 1837 If in doubt, say N. 1838 1839choice 1840 prompt "Compression algorithm" 1841 depends on MODULE_COMPRESS 1842 default MODULE_COMPRESS_GZIP 1843 help 1844 This determines which sort of compression will be used during 1845 'make modules_install'. 1846 1847 GZIP (default) and XZ are supported. 1848 1849config MODULE_COMPRESS_GZIP 1850 bool "GZIP" 1851 1852config MODULE_COMPRESS_XZ 1853 bool "XZ" 1854 1855endchoice 1856 1857config TRIM_UNUSED_KSYMS 1858 bool "Trim unused exported kernel symbols" 1859 depends on MODULES && !UNUSED_SYMBOLS 1860 help 1861 The kernel and some modules make many symbols available for 1862 other modules to use via EXPORT_SYMBOL() and variants. Depending 1863 on the set of modules being selected in your kernel configuration, 1864 many of those exported symbols might never be used. 1865 1866 This option allows for unused exported symbols to be dropped from 1867 the build. In turn, this provides the compiler more opportunities 1868 (especially when using LTO) for optimizing the code and reducing 1869 binary size. This might have some security advantages as well. 1870 1871 If unsure, or if you need to build out-of-tree modules, say N. 1872 1873endif # MODULES 1874 1875config MODULES_TREE_LOOKUP 1876 def_bool y 1877 depends on PERF_EVENTS || TRACING 1878 1879config INIT_ALL_POSSIBLE 1880 bool 1881 help 1882 Back when each arch used to define their own cpu_online_mask and 1883 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 1884 with all 1s, and others with all 0s. When they were centralised, 1885 it was better to provide this option than to break all the archs 1886 and have several arch maintainers pursuing me down dark alleys. 1887 1888source "block/Kconfig" 1889 1890config PREEMPT_NOTIFIERS 1891 bool 1892 1893config PADATA 1894 depends on SMP 1895 bool 1896 1897config ASN1 1898 tristate 1899 help 1900 Build a simple ASN.1 grammar compiler that produces a bytecode output 1901 that can be interpreted by the ASN.1 stream decoder and used to 1902 inform it as to what tags are to be expected in a stream and what 1903 functions to call on what tags. 1904 1905source "kernel/Kconfig.locks" 1906