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