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 FHANDLE 287 bool "open by fhandle syscalls" if EXPERT 288 select EXPORTFS 289 default y 290 help 291 If you say Y here, a user level program will be able to map 292 file names to handle and then later use the handle for 293 different file system operations. This is useful in implementing 294 userspace file servers, which now track files using handles instead 295 of names. The handle would remain the same even if file names 296 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 297 syscalls. 298 299config USELIB 300 bool "uselib syscall" 301 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION 302 help 303 This option enables the uselib syscall, a system call used in the 304 dynamic linker from libc5 and earlier. glibc does not use this 305 system call. If you intend to run programs built on libc5 or 306 earlier, you may need to enable this syscall. Current systems 307 running glibc can safely disable this. 308 309config AUDIT 310 bool "Auditing support" 311 depends on NET 312 help 313 Enable auditing infrastructure that can be used with another 314 kernel subsystem, such as SELinux (which requires this for 315 logging of avc messages output). System call auditing is included 316 on architectures which support it. 317 318config HAVE_ARCH_AUDITSYSCALL 319 bool 320 321config AUDITSYSCALL 322 def_bool y 323 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 324 325config AUDIT_WATCH 326 def_bool y 327 depends on AUDITSYSCALL 328 select FSNOTIFY 329 330config AUDIT_TREE 331 def_bool y 332 depends on AUDITSYSCALL 333 select FSNOTIFY 334 335source "kernel/irq/Kconfig" 336source "kernel/time/Kconfig" 337 338menu "CPU/Task time and stats accounting" 339 340config VIRT_CPU_ACCOUNTING 341 bool 342 343choice 344 prompt "Cputime accounting" 345 default TICK_CPU_ACCOUNTING if !PPC64 346 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 347 348# Kind of a stub config for the pure tick based cputime accounting 349config TICK_CPU_ACCOUNTING 350 bool "Simple tick based cputime accounting" 351 depends on !S390 && !NO_HZ_FULL 352 help 353 This is the basic tick based cputime accounting that maintains 354 statistics about user, system and idle time spent on per jiffies 355 granularity. 356 357 If unsure, say Y. 358 359config VIRT_CPU_ACCOUNTING_NATIVE 360 bool "Deterministic task and CPU time accounting" 361 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 362 select VIRT_CPU_ACCOUNTING 363 help 364 Select this option to enable more accurate task and CPU time 365 accounting. This is done by reading a CPU counter on each 366 kernel entry and exit and on transitions within the kernel 367 between system, softirq and hardirq state, so there is a 368 small performance impact. In the case of s390 or IBM POWER > 5, 369 this also enables accounting of stolen time on logically-partitioned 370 systems. 371 372config VIRT_CPU_ACCOUNTING_GEN 373 bool "Full dynticks CPU time accounting" 374 depends on HAVE_CONTEXT_TRACKING 375 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 376 select VIRT_CPU_ACCOUNTING 377 select CONTEXT_TRACKING 378 help 379 Select this option to enable task and CPU time accounting on full 380 dynticks systems. This accounting is implemented by watching every 381 kernel-user boundaries using the context tracking subsystem. 382 The accounting is thus performed at the expense of some significant 383 overhead. 384 385 For now this is only useful if you are working on the full 386 dynticks subsystem development. 387 388 If unsure, say N. 389 390endchoice 391 392config IRQ_TIME_ACCOUNTING 393 bool "Fine granularity task level IRQ time accounting" 394 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 395 help 396 Select this option to enable fine granularity task irq time 397 accounting. This is done by reading a timestamp on each 398 transitions between softirq and hardirq state, so there can be a 399 small performance impact. 400 401 If in doubt, say N here. 402 403config BSD_PROCESS_ACCT 404 bool "BSD Process Accounting" 405 depends on MULTIUSER 406 help 407 If you say Y here, a user level program will be able to instruct the 408 kernel (via a special system call) to write process accounting 409 information to a file: whenever a process exits, information about 410 that process will be appended to the file by the kernel. The 411 information includes things such as creation time, owning user, 412 command name, memory usage, controlling terminal etc. (the complete 413 list is in the struct acct in <file:include/linux/acct.h>). It is 414 up to the user level program to do useful things with this 415 information. This is generally a good idea, so say Y. 416 417config BSD_PROCESS_ACCT_V3 418 bool "BSD Process Accounting version 3 file format" 419 depends on BSD_PROCESS_ACCT 420 default n 421 help 422 If you say Y here, the process accounting information is written 423 in a new file format that also logs the process IDs of each 424 process and it's parent. Note that this file format is incompatible 425 with previous v0/v1/v2 file formats, so you will need updated tools 426 for processing it. A preliminary version of these tools is available 427 at <http://www.gnu.org/software/acct/>. 428 429config TASKSTATS 430 bool "Export task/process statistics through netlink" 431 depends on NET 432 depends on MULTIUSER 433 default n 434 help 435 Export selected statistics for tasks/processes through the 436 generic netlink interface. Unlike BSD process accounting, the 437 statistics are available during the lifetime of tasks/processes as 438 responses to commands. Like BSD accounting, they are sent to user 439 space on task exit. 440 441 Say N if unsure. 442 443config TASK_DELAY_ACCT 444 bool "Enable per-task delay accounting" 445 depends on TASKSTATS 446 select SCHED_INFO 447 help 448 Collect information on time spent by a task waiting for system 449 resources like cpu, synchronous block I/O completion and swapping 450 in pages. Such statistics can help in setting a task's priorities 451 relative to other tasks for cpu, io, rss limits etc. 452 453 Say N if unsure. 454 455config TASK_XACCT 456 bool "Enable extended accounting over taskstats" 457 depends on TASKSTATS 458 help 459 Collect extended task accounting data and send the data 460 to userland for processing over the taskstats interface. 461 462 Say N if unsure. 463 464config TASK_IO_ACCOUNTING 465 bool "Enable per-task storage I/O accounting" 466 depends on TASK_XACCT 467 help 468 Collect information on the number of bytes of storage I/O which this 469 task has caused. 470 471 Say N if unsure. 472 473endmenu # "CPU/Task time and stats accounting" 474 475config CPU_ISOLATION 476 bool "CPU isolation" 477 help 478 Make sure that CPUs running critical tasks are not disturbed by 479 any source of "noise" such as unbound workqueues, timers, kthreads... 480 Unbound jobs get offloaded to housekeeping CPUs. 481 482source "kernel/rcu/Kconfig" 483 484config BUILD_BIN2C 485 bool 486 default n 487 488config IKCONFIG 489 tristate "Kernel .config support" 490 select BUILD_BIN2C 491 ---help--- 492 This option enables the complete Linux kernel ".config" file 493 contents to be saved in the kernel. It provides documentation 494 of which kernel options are used in a running kernel or in an 495 on-disk kernel. This information can be extracted from the kernel 496 image file with the script scripts/extract-ikconfig and used as 497 input to rebuild the current kernel or to build another kernel. 498 It can also be extracted from a running kernel by reading 499 /proc/config.gz if enabled (below). 500 501config IKCONFIG_PROC 502 bool "Enable access to .config through /proc/config.gz" 503 depends on IKCONFIG && PROC_FS 504 ---help--- 505 This option enables access to the kernel configuration file 506 through /proc/config.gz. 507 508config LOG_BUF_SHIFT 509 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 510 range 12 25 511 default 17 512 depends on PRINTK 513 help 514 Select the minimal kernel log buffer size as a power of 2. 515 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 516 parameter, see below. Any higher size also might be forced 517 by "log_buf_len" boot parameter. 518 519 Examples: 520 17 => 128 KB 521 16 => 64 KB 522 15 => 32 KB 523 14 => 16 KB 524 13 => 8 KB 525 12 => 4 KB 526 527config LOG_CPU_MAX_BUF_SHIFT 528 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 529 depends on SMP 530 range 0 21 531 default 12 if !BASE_SMALL 532 default 0 if BASE_SMALL 533 depends on PRINTK 534 help 535 This option allows to increase the default ring buffer size 536 according to the number of CPUs. The value defines the contribution 537 of each CPU as a power of 2. The used space is typically only few 538 lines however it might be much more when problems are reported, 539 e.g. backtraces. 540 541 The increased size means that a new buffer has to be allocated and 542 the original static one is unused. It makes sense only on systems 543 with more CPUs. Therefore this value is used only when the sum of 544 contributions is greater than the half of the default kernel ring 545 buffer as defined by LOG_BUF_SHIFT. The default values are set 546 so that more than 64 CPUs are needed to trigger the allocation. 547 548 Also this option is ignored when "log_buf_len" kernel parameter is 549 used as it forces an exact (power of two) size of the ring buffer. 550 551 The number of possible CPUs is used for this computation ignoring 552 hotplugging making the computation optimal for the worst case 553 scenario while allowing a simple algorithm to be used from bootup. 554 555 Examples shift values and their meaning: 556 17 => 128 KB for each CPU 557 16 => 64 KB for each CPU 558 15 => 32 KB for each CPU 559 14 => 16 KB for each CPU 560 13 => 8 KB for each CPU 561 12 => 4 KB for each CPU 562 563config PRINTK_SAFE_LOG_BUF_SHIFT 564 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 565 range 10 21 566 default 13 567 depends on PRINTK 568 help 569 Select the size of an alternate printk per-CPU buffer where messages 570 printed from usafe contexts are temporary stored. One example would 571 be NMI messages, another one - printk recursion. The messages are 572 copied to the main log buffer in a safe context to avoid a deadlock. 573 The value defines the size as a power of 2. 574 575 Those messages are rare and limited. The largest one is when 576 a backtrace is printed. It usually fits into 4KB. Select 577 8KB if you want to be on the safe side. 578 579 Examples: 580 17 => 128 KB for each CPU 581 16 => 64 KB for each CPU 582 15 => 32 KB for each CPU 583 14 => 16 KB for each CPU 584 13 => 8 KB for each CPU 585 12 => 4 KB for each CPU 586 587# 588# Architectures with an unreliable sched_clock() should select this: 589# 590config HAVE_UNSTABLE_SCHED_CLOCK 591 bool 592 593config GENERIC_SCHED_CLOCK 594 bool 595 596# 597# For architectures that want to enable the support for NUMA-affine scheduler 598# balancing logic: 599# 600config ARCH_SUPPORTS_NUMA_BALANCING 601 bool 602 603# 604# For architectures that prefer to flush all TLBs after a number of pages 605# are unmapped instead of sending one IPI per page to flush. The architecture 606# must provide guarantees on what happens if a clean TLB cache entry is 607# written after the unmap. Details are in mm/rmap.c near the check for 608# should_defer_flush. The architecture should also consider if the full flush 609# and the refill costs are offset by the savings of sending fewer IPIs. 610config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 611 bool 612 613# 614# For architectures that know their GCC __int128 support is sound 615# 616config ARCH_SUPPORTS_INT128 617 bool 618 619# For architectures that (ab)use NUMA to represent different memory regions 620# all cpu-local but of different latencies, such as SuperH. 621# 622config ARCH_WANT_NUMA_VARIABLE_LOCALITY 623 bool 624 625config NUMA_BALANCING 626 bool "Memory placement aware NUMA scheduler" 627 depends on ARCH_SUPPORTS_NUMA_BALANCING 628 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 629 depends on SMP && NUMA && MIGRATION 630 help 631 This option adds support for automatic NUMA aware memory/task placement. 632 The mechanism is quite primitive and is based on migrating memory when 633 it has references to the node the task is running on. 634 635 This system will be inactive on UMA systems. 636 637config NUMA_BALANCING_DEFAULT_ENABLED 638 bool "Automatically enable NUMA aware memory/task placement" 639 default y 640 depends on NUMA_BALANCING 641 help 642 If set, automatic NUMA balancing will be enabled if running on a NUMA 643 machine. 644 645menuconfig CGROUPS 646 bool "Control Group support" 647 select KERNFS 648 help 649 This option adds support for grouping sets of processes together, for 650 use with process control subsystems such as Cpusets, CFS, memory 651 controls or device isolation. 652 See 653 - Documentation/scheduler/sched-design-CFS.txt (CFS) 654 - Documentation/cgroup-v1/ (features for grouping, isolation 655 and resource control) 656 657 Say N if unsure. 658 659if CGROUPS 660 661config PAGE_COUNTER 662 bool 663 664config MEMCG 665 bool "Memory controller" 666 select PAGE_COUNTER 667 select EVENTFD 668 help 669 Provides control over the memory footprint of tasks in a cgroup. 670 671config MEMCG_SWAP 672 bool "Swap controller" 673 depends on MEMCG && SWAP 674 help 675 Provides control over the swap space consumed by tasks in a cgroup. 676 677config MEMCG_SWAP_ENABLED 678 bool "Swap controller enabled by default" 679 depends on MEMCG_SWAP 680 default y 681 help 682 Memory Resource Controller Swap Extension comes with its price in 683 a bigger memory consumption. General purpose distribution kernels 684 which want to enable the feature but keep it disabled by default 685 and let the user enable it by swapaccount=1 boot command line 686 parameter should have this option unselected. 687 For those who want to have the feature enabled by default should 688 select this option (if, for some reason, they need to disable it 689 then swapaccount=0 does the trick). 690 691config BLK_CGROUP 692 bool "IO controller" 693 depends on BLOCK 694 default n 695 ---help--- 696 Generic block IO controller cgroup interface. This is the common 697 cgroup interface which should be used by various IO controlling 698 policies. 699 700 Currently, CFQ IO scheduler uses it to recognize task groups and 701 control disk bandwidth allocation (proportional time slice allocation) 702 to such task groups. It is also used by bio throttling logic in 703 block layer to implement upper limit in IO rates on a device. 704 705 This option only enables generic Block IO controller infrastructure. 706 One needs to also enable actual IO controlling logic/policy. For 707 enabling proportional weight division of disk bandwidth in CFQ, set 708 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 709 CONFIG_BLK_DEV_THROTTLING=y. 710 711 See Documentation/cgroup-v1/blkio-controller.txt for more information. 712 713config DEBUG_BLK_CGROUP 714 bool "IO controller debugging" 715 depends on BLK_CGROUP 716 default n 717 ---help--- 718 Enable some debugging help. Currently it exports additional stat 719 files in a cgroup which can be useful for debugging. 720 721config CGROUP_WRITEBACK 722 bool 723 depends on MEMCG && BLK_CGROUP 724 default y 725 726menuconfig CGROUP_SCHED 727 bool "CPU controller" 728 default n 729 help 730 This feature lets CPU scheduler recognize task groups and control CPU 731 bandwidth allocation to such task groups. It uses cgroups to group 732 tasks. 733 734if CGROUP_SCHED 735config FAIR_GROUP_SCHED 736 bool "Group scheduling for SCHED_OTHER" 737 depends on CGROUP_SCHED 738 default CGROUP_SCHED 739 740config CFS_BANDWIDTH 741 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 742 depends on FAIR_GROUP_SCHED 743 default n 744 help 745 This option allows users to define CPU bandwidth rates (limits) for 746 tasks running within the fair group scheduler. Groups with no limit 747 set are considered to be unconstrained and will run with no 748 restriction. 749 See tip/Documentation/scheduler/sched-bwc.txt for more information. 750 751config RT_GROUP_SCHED 752 bool "Group scheduling for SCHED_RR/FIFO" 753 depends on CGROUP_SCHED 754 default n 755 help 756 This feature lets you explicitly allocate real CPU bandwidth 757 to task groups. If enabled, it will also make it impossible to 758 schedule realtime tasks for non-root users until you allocate 759 realtime bandwidth for them. 760 See Documentation/scheduler/sched-rt-group.txt for more information. 761 762endif #CGROUP_SCHED 763 764config CGROUP_PIDS 765 bool "PIDs controller" 766 help 767 Provides enforcement of process number limits in the scope of a 768 cgroup. Any attempt to fork more processes than is allowed in the 769 cgroup will fail. PIDs are fundamentally a global resource because it 770 is fairly trivial to reach PID exhaustion before you reach even a 771 conservative kmemcg limit. As a result, it is possible to grind a 772 system to halt without being limited by other cgroup policies. The 773 PIDs controller is designed to stop this from happening. 774 775 It should be noted that organisational operations (such as attaching 776 to a cgroup hierarchy will *not* be blocked by the PIDs controller), 777 since the PIDs limit only affects a process's ability to fork, not to 778 attach to a cgroup. 779 780config CGROUP_RDMA 781 bool "RDMA controller" 782 help 783 Provides enforcement of RDMA resources defined by IB stack. 784 It is fairly easy for consumers to exhaust RDMA resources, which 785 can result into resource unavailability to other consumers. 786 RDMA controller is designed to stop this from happening. 787 Attaching processes with active RDMA resources to the cgroup 788 hierarchy is allowed even if can cross the hierarchy's limit. 789 790config CGROUP_FREEZER 791 bool "Freezer controller" 792 help 793 Provides a way to freeze and unfreeze all tasks in a 794 cgroup. 795 796 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 797 controller includes important in-kernel memory consumers per default. 798 799 If you're using cgroup2, say N. 800 801config CGROUP_HUGETLB 802 bool "HugeTLB controller" 803 depends on HUGETLB_PAGE 804 select PAGE_COUNTER 805 default n 806 help 807 Provides a cgroup controller for HugeTLB pages. 808 When you enable this, you can put a per cgroup limit on HugeTLB usage. 809 The limit is enforced during page fault. Since HugeTLB doesn't 810 support page reclaim, enforcing the limit at page fault time implies 811 that, the application will get SIGBUS signal if it tries to access 812 HugeTLB pages beyond its limit. This requires the application to know 813 beforehand how much HugeTLB pages it would require for its use. The 814 control group is tracked in the third page lru pointer. This means 815 that we cannot use the controller with huge page less than 3 pages. 816 817config CPUSETS 818 bool "Cpuset controller" 819 depends on SMP 820 help 821 This option will let you create and manage CPUSETs which 822 allow dynamically partitioning a system into sets of CPUs and 823 Memory Nodes and assigning tasks to run only within those sets. 824 This is primarily useful on large SMP or NUMA systems. 825 826 Say N if unsure. 827 828config PROC_PID_CPUSET 829 bool "Include legacy /proc/<pid>/cpuset file" 830 depends on CPUSETS 831 default y 832 833config CGROUP_DEVICE 834 bool "Device controller" 835 help 836 Provides a cgroup controller implementing whitelists for 837 devices which a process in the cgroup can mknod or open. 838 839config CGROUP_CPUACCT 840 bool "Simple CPU accounting controller" 841 help 842 Provides a simple controller for monitoring the 843 total CPU consumed by the tasks in a cgroup. 844 845config CGROUP_PERF 846 bool "Perf controller" 847 depends on PERF_EVENTS 848 help 849 This option extends the perf per-cpu mode to restrict monitoring 850 to threads which belong to the cgroup specified and run on the 851 designated cpu. 852 853 Say N if unsure. 854 855config CGROUP_BPF 856 bool "Support for eBPF programs attached to cgroups" 857 depends on BPF_SYSCALL 858 select SOCK_CGROUP_DATA 859 help 860 Allow attaching eBPF programs to a cgroup using the bpf(2) 861 syscall command BPF_PROG_ATTACH. 862 863 In which context these programs are accessed depends on the type 864 of attachment. For instance, programs that are attached using 865 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 866 inet sockets. 867 868config CGROUP_DEBUG 869 bool "Debug controller" 870 default n 871 depends on DEBUG_KERNEL 872 help 873 This option enables a simple controller that exports 874 debugging information about the cgroups framework. This 875 controller is for control cgroup debugging only. Its 876 interfaces are not stable. 877 878 Say N. 879 880config SOCK_CGROUP_DATA 881 bool 882 default n 883 884endif # CGROUPS 885 886config CHECKPOINT_RESTORE 887 bool "Checkpoint/restore support" if EXPERT 888 select PROC_CHILDREN 889 default n 890 help 891 Enables additional kernel features in a sake of checkpoint/restore. 892 In particular it adds auxiliary prctl codes to setup process text, 893 data and heap segment sizes, and a few additional /proc filesystem 894 entries. 895 896 If unsure, say N here. 897 898menuconfig NAMESPACES 899 bool "Namespaces support" if EXPERT 900 depends on MULTIUSER 901 default !EXPERT 902 help 903 Provides the way to make tasks work with different objects using 904 the same id. For example same IPC id may refer to different objects 905 or same user id or pid may refer to different tasks when used in 906 different namespaces. 907 908if NAMESPACES 909 910config UTS_NS 911 bool "UTS namespace" 912 default y 913 help 914 In this namespace tasks see different info provided with the 915 uname() system call 916 917config IPC_NS 918 bool "IPC namespace" 919 depends on (SYSVIPC || POSIX_MQUEUE) 920 default y 921 help 922 In this namespace tasks work with IPC ids which correspond to 923 different IPC objects in different namespaces. 924 925config USER_NS 926 bool "User namespace" 927 default n 928 help 929 This allows containers, i.e. vservers, to use user namespaces 930 to provide different user info for different servers. 931 932 When user namespaces are enabled in the kernel it is 933 recommended that the MEMCG option also be enabled and that 934 user-space use the memory control groups to limit the amount 935 of memory a memory unprivileged users can use. 936 937 If unsure, say N. 938 939config PID_NS 940 bool "PID Namespaces" 941 default y 942 help 943 Support process id namespaces. This allows having multiple 944 processes with the same pid as long as they are in different 945 pid namespaces. This is a building block of containers. 946 947config NET_NS 948 bool "Network namespace" 949 depends on NET 950 default y 951 help 952 Allow user space to create what appear to be multiple instances 953 of the network stack. 954 955endif # NAMESPACES 956 957config SCHED_AUTOGROUP 958 bool "Automatic process group scheduling" 959 select CGROUPS 960 select CGROUP_SCHED 961 select FAIR_GROUP_SCHED 962 help 963 This option optimizes the scheduler for common desktop workloads by 964 automatically creating and populating task groups. This separation 965 of workloads isolates aggressive CPU burners (like build jobs) from 966 desktop applications. Task group autogeneration is currently based 967 upon task session. 968 969config SYSFS_DEPRECATED 970 bool "Enable deprecated sysfs features to support old userspace tools" 971 depends on SYSFS 972 default n 973 help 974 This option adds code that switches the layout of the "block" class 975 devices, to not show up in /sys/class/block/, but only in 976 /sys/block/. 977 978 This switch is only active when the sysfs.deprecated=1 boot option is 979 passed or the SYSFS_DEPRECATED_V2 option is set. 980 981 This option allows new kernels to run on old distributions and tools, 982 which might get confused by /sys/class/block/. Since 2007/2008 all 983 major distributions and tools handle this just fine. 984 985 Recent distributions and userspace tools after 2009/2010 depend on 986 the existence of /sys/class/block/, and will not work with this 987 option enabled. 988 989 Only if you are using a new kernel on an old distribution, you might 990 need to say Y here. 991 992config SYSFS_DEPRECATED_V2 993 bool "Enable deprecated sysfs features by default" 994 default n 995 depends on SYSFS 996 depends on SYSFS_DEPRECATED 997 help 998 Enable deprecated sysfs by default. 999 1000 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1001 option. 1002 1003 Only if you are using a new kernel on an old distribution, you might 1004 need to say Y here. Even then, odds are you would not need it 1005 enabled, you can always pass the boot option if absolutely necessary. 1006 1007config RELAY 1008 bool "Kernel->user space relay support (formerly relayfs)" 1009 select IRQ_WORK 1010 help 1011 This option enables support for relay interface support in 1012 certain file systems (such as debugfs). 1013 It is designed to provide an efficient mechanism for tools and 1014 facilities to relay large amounts of data from kernel space to 1015 user space. 1016 1017 If unsure, say N. 1018 1019config BLK_DEV_INITRD 1020 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1021 depends on BROKEN || !FRV 1022 help 1023 The initial RAM filesystem is a ramfs which is loaded by the 1024 boot loader (loadlin or lilo) and that is mounted as root 1025 before the normal boot procedure. It is typically used to 1026 load modules needed to mount the "real" root file system, 1027 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1028 1029 If RAM disk support (BLK_DEV_RAM) is also included, this 1030 also enables initial RAM disk (initrd) support and adds 1031 15 Kbytes (more on some other architectures) to the kernel size. 1032 1033 If unsure say Y. 1034 1035if BLK_DEV_INITRD 1036 1037source "usr/Kconfig" 1038 1039endif 1040 1041choice 1042 prompt "Compiler optimization level" 1043 default CC_OPTIMIZE_FOR_PERFORMANCE 1044 1045config CC_OPTIMIZE_FOR_PERFORMANCE 1046 bool "Optimize for performance" 1047 help 1048 This is the default optimization level for the kernel, building 1049 with the "-O2" compiler flag for best performance and most 1050 helpful compile-time warnings. 1051 1052config CC_OPTIMIZE_FOR_SIZE 1053 bool "Optimize for size" 1054 help 1055 Enabling this option will pass "-Os" instead of "-O2" to 1056 your compiler resulting in a smaller kernel. 1057 1058 If unsure, say N. 1059 1060endchoice 1061 1062config SYSCTL 1063 bool 1064 1065config ANON_INODES 1066 bool 1067 1068config HAVE_UID16 1069 bool 1070 1071config SYSCTL_EXCEPTION_TRACE 1072 bool 1073 help 1074 Enable support for /proc/sys/debug/exception-trace. 1075 1076config SYSCTL_ARCH_UNALIGN_NO_WARN 1077 bool 1078 help 1079 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1080 Allows arch to define/use @no_unaligned_warning to possibly warn 1081 about unaligned access emulation going on under the hood. 1082 1083config SYSCTL_ARCH_UNALIGN_ALLOW 1084 bool 1085 help 1086 Enable support for /proc/sys/kernel/unaligned-trap 1087 Allows arches to define/use @unaligned_enabled to runtime toggle 1088 the unaligned access emulation. 1089 see arch/parisc/kernel/unaligned.c for reference 1090 1091config HAVE_PCSPKR_PLATFORM 1092 bool 1093 1094# interpreter that classic socket filters depend on 1095config BPF 1096 bool 1097 1098menuconfig EXPERT 1099 bool "Configure standard kernel features (expert users)" 1100 # Unhide debug options, to make the on-by-default options visible 1101 select DEBUG_KERNEL 1102 help 1103 This option allows certain base kernel options and settings 1104 to be disabled or tweaked. This is for specialized 1105 environments which can tolerate a "non-standard" kernel. 1106 Only use this if you really know what you are doing. 1107 1108config UID16 1109 bool "Enable 16-bit UID system calls" if EXPERT 1110 depends on HAVE_UID16 && MULTIUSER 1111 default y 1112 help 1113 This enables the legacy 16-bit UID syscall wrappers. 1114 1115config MULTIUSER 1116 bool "Multiple users, groups and capabilities support" if EXPERT 1117 default y 1118 help 1119 This option enables support for non-root users, groups and 1120 capabilities. 1121 1122 If you say N here, all processes will run with UID 0, GID 0, and all 1123 possible capabilities. Saying N here also compiles out support for 1124 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1125 setgid, and capset. 1126 1127 If unsure, say Y here. 1128 1129config SGETMASK_SYSCALL 1130 bool "sgetmask/ssetmask syscalls support" if EXPERT 1131 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH 1132 ---help--- 1133 sys_sgetmask and sys_ssetmask are obsolete system calls 1134 no longer supported in libc but still enabled by default in some 1135 architectures. 1136 1137 If unsure, leave the default option here. 1138 1139config SYSFS_SYSCALL 1140 bool "Sysfs syscall support" if EXPERT 1141 default y 1142 ---help--- 1143 sys_sysfs is an obsolete system call no longer supported in libc. 1144 Note that disabling this option is more secure but might break 1145 compatibility with some systems. 1146 1147 If unsure say Y here. 1148 1149config SYSCTL_SYSCALL 1150 bool "Sysctl syscall support" if EXPERT 1151 depends on PROC_SYSCTL 1152 default n 1153 select SYSCTL 1154 ---help--- 1155 sys_sysctl uses binary paths that have been found challenging 1156 to properly maintain and use. The interface in /proc/sys 1157 using paths with ascii names is now the primary path to this 1158 information. 1159 1160 Almost nothing using the binary sysctl interface so if you are 1161 trying to save some space it is probably safe to disable this, 1162 making your kernel marginally smaller. 1163 1164 If unsure say N here. 1165 1166config POSIX_TIMERS 1167 bool "Posix Clocks & timers" if EXPERT 1168 default y 1169 help 1170 This includes native support for POSIX timers to the kernel. 1171 Some embedded systems have no use for them and therefore they 1172 can be configured out to reduce the size of the kernel image. 1173 1174 When this option is disabled, the following syscalls won't be 1175 available: timer_create, timer_gettime: timer_getoverrun, 1176 timer_settime, timer_delete, clock_adjtime, getitimer, 1177 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1178 clock_getres and clock_nanosleep syscalls will be limited to 1179 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1180 1181 If unsure say y. 1182 1183config KALLSYMS 1184 bool "Load all symbols for debugging/ksymoops" if EXPERT 1185 default y 1186 help 1187 Say Y here to let the kernel print out symbolic crash information and 1188 symbolic stack backtraces. This increases the size of the kernel 1189 somewhat, as all symbols have to be loaded into the kernel image. 1190 1191config KALLSYMS_ALL 1192 bool "Include all symbols in kallsyms" 1193 depends on DEBUG_KERNEL && KALLSYMS 1194 help 1195 Normally kallsyms only contains the symbols of functions for nicer 1196 OOPS messages and backtraces (i.e., symbols from the text and inittext 1197 sections). This is sufficient for most cases. And only in very rare 1198 cases (e.g., when a debugger is used) all symbols are required (e.g., 1199 names of variables from the data sections, etc). 1200 1201 This option makes sure that all symbols are loaded into the kernel 1202 image (i.e., symbols from all sections) in cost of increased kernel 1203 size (depending on the kernel configuration, it may be 300KiB or 1204 something like this). 1205 1206 Say N unless you really need all symbols. 1207 1208config KALLSYMS_ABSOLUTE_PERCPU 1209 bool 1210 depends on KALLSYMS 1211 default X86_64 && SMP 1212 1213config KALLSYMS_BASE_RELATIVE 1214 bool 1215 depends on KALLSYMS 1216 default !IA64 && !(TILE && 64BIT) 1217 help 1218 Instead of emitting them as absolute values in the native word size, 1219 emit the symbol references in the kallsyms table as 32-bit entries, 1220 each containing a relative value in the range [base, base + U32_MAX] 1221 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1222 an absolute value in the range [0, S32_MAX] or a relative value in the 1223 range [base, base + S32_MAX], where base is the lowest relative symbol 1224 address encountered in the image. 1225 1226 On 64-bit builds, this reduces the size of the address table by 50%, 1227 but more importantly, it results in entries whose values are build 1228 time constants, and no relocation pass is required at runtime to fix 1229 up the entries based on the runtime load address of the kernel. 1230 1231config PRINTK 1232 default y 1233 bool "Enable support for printk" if EXPERT 1234 select IRQ_WORK 1235 help 1236 This option enables normal printk support. Removing it 1237 eliminates most of the message strings from the kernel image 1238 and makes the kernel more or less silent. As this makes it 1239 very difficult to diagnose system problems, saying N here is 1240 strongly discouraged. 1241 1242config PRINTK_NMI 1243 def_bool y 1244 depends on PRINTK 1245 depends on HAVE_NMI 1246 1247config BUG 1248 bool "BUG() support" if EXPERT 1249 default y 1250 help 1251 Disabling this option eliminates support for BUG and WARN, reducing 1252 the size of your kernel image and potentially quietly ignoring 1253 numerous fatal conditions. You should only consider disabling this 1254 option for embedded systems with no facilities for reporting errors. 1255 Just say Y. 1256 1257config ELF_CORE 1258 depends on COREDUMP 1259 default y 1260 bool "Enable ELF core dumps" if EXPERT 1261 help 1262 Enable support for generating core dumps. Disabling saves about 4k. 1263 1264 1265config PCSPKR_PLATFORM 1266 bool "Enable PC-Speaker support" if EXPERT 1267 depends on HAVE_PCSPKR_PLATFORM 1268 select I8253_LOCK 1269 default y 1270 help 1271 This option allows to disable the internal PC-Speaker 1272 support, saving some memory. 1273 1274config BASE_FULL 1275 default y 1276 bool "Enable full-sized data structures for core" if EXPERT 1277 help 1278 Disabling this option reduces the size of miscellaneous core 1279 kernel data structures. This saves memory on small machines, 1280 but may reduce performance. 1281 1282config FUTEX 1283 bool "Enable futex support" if EXPERT 1284 default y 1285 imply RT_MUTEXES 1286 help 1287 Disabling this option will cause the kernel to be built without 1288 support for "fast userspace mutexes". The resulting kernel may not 1289 run glibc-based applications correctly. 1290 1291config FUTEX_PI 1292 bool 1293 depends on FUTEX && RT_MUTEXES 1294 default y 1295 1296config HAVE_FUTEX_CMPXCHG 1297 bool 1298 depends on FUTEX 1299 help 1300 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1301 is implemented and always working. This removes a couple of runtime 1302 checks. 1303 1304config EPOLL 1305 bool "Enable eventpoll support" if EXPERT 1306 default y 1307 select ANON_INODES 1308 help 1309 Disabling this option will cause the kernel to be built without 1310 support for epoll family of system calls. 1311 1312config SIGNALFD 1313 bool "Enable signalfd() system call" if EXPERT 1314 select ANON_INODES 1315 default y 1316 help 1317 Enable the signalfd() system call that allows to receive signals 1318 on a file descriptor. 1319 1320 If unsure, say Y. 1321 1322config TIMERFD 1323 bool "Enable timerfd() system call" if EXPERT 1324 select ANON_INODES 1325 default y 1326 help 1327 Enable the timerfd() system call that allows to receive timer 1328 events on a file descriptor. 1329 1330 If unsure, say Y. 1331 1332config EVENTFD 1333 bool "Enable eventfd() system call" if EXPERT 1334 select ANON_INODES 1335 default y 1336 help 1337 Enable the eventfd() system call that allows to receive both 1338 kernel notification (ie. KAIO) or userspace notifications. 1339 1340 If unsure, say Y. 1341 1342# syscall, maps, verifier 1343config BPF_SYSCALL 1344 bool "Enable bpf() system call" 1345 select ANON_INODES 1346 select BPF 1347 default n 1348 help 1349 Enable the bpf() system call that allows to manipulate eBPF 1350 programs and maps via file descriptors. 1351 1352config SHMEM 1353 bool "Use full shmem filesystem" if EXPERT 1354 default y 1355 depends on MMU 1356 help 1357 The shmem is an internal filesystem used to manage shared memory. 1358 It is backed by swap and manages resource limits. It is also exported 1359 to userspace as tmpfs if TMPFS is enabled. Disabling this 1360 option replaces shmem and tmpfs with the much simpler ramfs code, 1361 which may be appropriate on small systems without swap. 1362 1363config AIO 1364 bool "Enable AIO support" if EXPERT 1365 default y 1366 help 1367 This option enables POSIX asynchronous I/O which may by used 1368 by some high performance threaded applications. Disabling 1369 this option saves about 7k. 1370 1371config ADVISE_SYSCALLS 1372 bool "Enable madvise/fadvise syscalls" if EXPERT 1373 default y 1374 help 1375 This option enables the madvise and fadvise syscalls, used by 1376 applications to advise the kernel about their future memory or file 1377 usage, improving performance. If building an embedded system where no 1378 applications use these syscalls, you can disable this option to save 1379 space. 1380 1381config USERFAULTFD 1382 bool "Enable userfaultfd() system call" 1383 select ANON_INODES 1384 depends on MMU 1385 help 1386 Enable the userfaultfd() system call that allows to intercept and 1387 handle page faults in userland. 1388 1389config PCI_QUIRKS 1390 default y 1391 bool "Enable PCI quirk workarounds" if EXPERT 1392 depends on PCI 1393 help 1394 This enables workarounds for various PCI chipset 1395 bugs/quirks. Disable this only if your target machine is 1396 unaffected by PCI quirks. 1397 1398config MEMBARRIER 1399 bool "Enable membarrier() system call" if EXPERT 1400 default y 1401 help 1402 Enable the membarrier() system call that allows issuing memory 1403 barriers across all running threads, which can be used to distribute 1404 the cost of user-space memory barriers asymmetrically by transforming 1405 pairs of memory barriers into pairs consisting of membarrier() and a 1406 compiler barrier. 1407 1408 If unsure, say Y. 1409 1410config EMBEDDED 1411 bool "Embedded system" 1412 option allnoconfig_y 1413 select EXPERT 1414 help 1415 This option should be enabled if compiling the kernel for 1416 an embedded system so certain expert options are available 1417 for configuration. 1418 1419config HAVE_PERF_EVENTS 1420 bool 1421 help 1422 See tools/perf/design.txt for details. 1423 1424config PERF_USE_VMALLOC 1425 bool 1426 help 1427 See tools/perf/design.txt for details 1428 1429config PC104 1430 bool "PC/104 support" 1431 help 1432 Expose PC/104 form factor device drivers and options available for 1433 selection and configuration. Enable this option if your target 1434 machine has a PC/104 bus. 1435 1436menu "Kernel Performance Events And Counters" 1437 1438config PERF_EVENTS 1439 bool "Kernel performance events and counters" 1440 default y if PROFILING 1441 depends on HAVE_PERF_EVENTS 1442 select ANON_INODES 1443 select IRQ_WORK 1444 select SRCU 1445 help 1446 Enable kernel support for various performance events provided 1447 by software and hardware. 1448 1449 Software events are supported either built-in or via the 1450 use of generic tracepoints. 1451 1452 Most modern CPUs support performance events via performance 1453 counter registers. These registers count the number of certain 1454 types of hw events: such as instructions executed, cachemisses 1455 suffered, or branches mis-predicted - without slowing down the 1456 kernel or applications. These registers can also trigger interrupts 1457 when a threshold number of events have passed - and can thus be 1458 used to profile the code that runs on that CPU. 1459 1460 The Linux Performance Event subsystem provides an abstraction of 1461 these software and hardware event capabilities, available via a 1462 system call and used by the "perf" utility in tools/perf/. It 1463 provides per task and per CPU counters, and it provides event 1464 capabilities on top of those. 1465 1466 Say Y if unsure. 1467 1468config DEBUG_PERF_USE_VMALLOC 1469 default n 1470 bool "Debug: use vmalloc to back perf mmap() buffers" 1471 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1472 select PERF_USE_VMALLOC 1473 help 1474 Use vmalloc memory to back perf mmap() buffers. 1475 1476 Mostly useful for debugging the vmalloc code on platforms 1477 that don't require it. 1478 1479 Say N if unsure. 1480 1481endmenu 1482 1483config VM_EVENT_COUNTERS 1484 default y 1485 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1486 help 1487 VM event counters are needed for event counts to be shown. 1488 This option allows the disabling of the VM event counters 1489 on EXPERT systems. /proc/vmstat will only show page counts 1490 if VM event counters are disabled. 1491 1492config SLUB_DEBUG 1493 default y 1494 bool "Enable SLUB debugging support" if EXPERT 1495 depends on SLUB && SYSFS 1496 help 1497 SLUB has extensive debug support features. Disabling these can 1498 result in significant savings in code size. This also disables 1499 SLUB sysfs support. /sys/slab will not exist and there will be 1500 no support for cache validation etc. 1501 1502config SLUB_MEMCG_SYSFS_ON 1503 default n 1504 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1505 depends on SLUB && SYSFS && MEMCG 1506 help 1507 SLUB creates a directory under /sys/kernel/slab for each 1508 allocation cache to host info and debug files. If memory 1509 cgroup is enabled, each cache can have per memory cgroup 1510 caches. SLUB can create the same sysfs directories for these 1511 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1512 to a very high number of debug files being created. This is 1513 controlled by slub_memcg_sysfs boot parameter and this 1514 config option determines the parameter's default value. 1515 1516config COMPAT_BRK 1517 bool "Disable heap randomization" 1518 default y 1519 help 1520 Randomizing heap placement makes heap exploits harder, but it 1521 also breaks ancient binaries (including anything libc5 based). 1522 This option changes the bootup default to heap randomization 1523 disabled, and can be overridden at runtime by setting 1524 /proc/sys/kernel/randomize_va_space to 2. 1525 1526 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1527 1528choice 1529 prompt "Choose SLAB allocator" 1530 default SLUB 1531 help 1532 This option allows to select a slab allocator. 1533 1534config SLAB 1535 bool "SLAB" 1536 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1537 help 1538 The regular slab allocator that is established and known to work 1539 well in all environments. It organizes cache hot objects in 1540 per cpu and per node queues. 1541 1542config SLUB 1543 bool "SLUB (Unqueued Allocator)" 1544 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1545 help 1546 SLUB is a slab allocator that minimizes cache line usage 1547 instead of managing queues of cached objects (SLAB approach). 1548 Per cpu caching is realized using slabs of objects instead 1549 of queues of objects. SLUB can use memory efficiently 1550 and has enhanced diagnostics. SLUB is the default choice for 1551 a slab allocator. 1552 1553config SLOB 1554 depends on EXPERT 1555 bool "SLOB (Simple Allocator)" 1556 help 1557 SLOB replaces the stock allocator with a drastically simpler 1558 allocator. SLOB is generally more space efficient but 1559 does not perform as well on large systems. 1560 1561endchoice 1562 1563config SLAB_MERGE_DEFAULT 1564 bool "Allow slab caches to be merged" 1565 default y 1566 help 1567 For reduced kernel memory fragmentation, slab caches can be 1568 merged when they share the same size and other characteristics. 1569 This carries a risk of kernel heap overflows being able to 1570 overwrite objects from merged caches (and more easily control 1571 cache layout), which makes such heap attacks easier to exploit 1572 by attackers. By keeping caches unmerged, these kinds of exploits 1573 can usually only damage objects in the same cache. To disable 1574 merging at runtime, "slab_nomerge" can be passed on the kernel 1575 command line. 1576 1577config SLAB_FREELIST_RANDOM 1578 default n 1579 depends on SLAB || SLUB 1580 bool "SLAB freelist randomization" 1581 help 1582 Randomizes the freelist order used on creating new pages. This 1583 security feature reduces the predictability of the kernel slab 1584 allocator against heap overflows. 1585 1586config SLAB_FREELIST_HARDENED 1587 bool "Harden slab freelist metadata" 1588 depends on SLUB 1589 help 1590 Many kernel heap attacks try to target slab cache metadata and 1591 other infrastructure. This options makes minor performance 1592 sacrifies to harden the kernel slab allocator against common 1593 freelist exploit methods. 1594 1595config SLUB_CPU_PARTIAL 1596 default y 1597 depends on SLUB && SMP 1598 bool "SLUB per cpu partial cache" 1599 help 1600 Per cpu partial caches accellerate objects allocation and freeing 1601 that is local to a processor at the price of more indeterminism 1602 in the latency of the free. On overflow these caches will be cleared 1603 which requires the taking of locks that may cause latency spikes. 1604 Typically one would choose no for a realtime system. 1605 1606config MMAP_ALLOW_UNINITIALIZED 1607 bool "Allow mmapped anonymous memory to be uninitialized" 1608 depends on EXPERT && !MMU 1609 default n 1610 help 1611 Normally, and according to the Linux spec, anonymous memory obtained 1612 from mmap() has it's contents cleared before it is passed to 1613 userspace. Enabling this config option allows you to request that 1614 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1615 providing a huge performance boost. If this option is not enabled, 1616 then the flag will be ignored. 1617 1618 This is taken advantage of by uClibc's malloc(), and also by 1619 ELF-FDPIC binfmt's brk and stack allocator. 1620 1621 Because of the obvious security issues, this option should only be 1622 enabled on embedded devices where you control what is run in 1623 userspace. Since that isn't generally a problem on no-MMU systems, 1624 it is normally safe to say Y here. 1625 1626 See Documentation/nommu-mmap.txt for more information. 1627 1628config SYSTEM_DATA_VERIFICATION 1629 def_bool n 1630 select SYSTEM_TRUSTED_KEYRING 1631 select KEYS 1632 select CRYPTO 1633 select CRYPTO_RSA 1634 select ASYMMETRIC_KEY_TYPE 1635 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1636 select ASN1 1637 select OID_REGISTRY 1638 select X509_CERTIFICATE_PARSER 1639 select PKCS7_MESSAGE_PARSER 1640 help 1641 Provide PKCS#7 message verification using the contents of the system 1642 trusted keyring to provide public keys. This then can be used for 1643 module verification, kexec image verification and firmware blob 1644 verification. 1645 1646config PROFILING 1647 bool "Profiling support" 1648 help 1649 Say Y here to enable the extended profiling support mechanisms used 1650 by profilers such as OProfile. 1651 1652# 1653# Place an empty function call at each tracepoint site. Can be 1654# dynamically changed for a probe function. 1655# 1656config TRACEPOINTS 1657 bool 1658 1659source "arch/Kconfig" 1660 1661endmenu # General setup 1662 1663config HAVE_GENERIC_DMA_COHERENT 1664 bool 1665 default n 1666 1667config SLABINFO 1668 bool 1669 depends on PROC_FS 1670 depends on SLAB || SLUB_DEBUG 1671 default y 1672 1673config RT_MUTEXES 1674 bool 1675 1676config BASE_SMALL 1677 int 1678 default 0 if BASE_FULL 1679 default 1 if !BASE_FULL 1680 1681menuconfig MODULES 1682 bool "Enable loadable module support" 1683 option modules 1684 help 1685 Kernel modules are small pieces of compiled code which can 1686 be inserted in the running kernel, rather than being 1687 permanently built into the kernel. You use the "modprobe" 1688 tool to add (and sometimes remove) them. If you say Y here, 1689 many parts of the kernel can be built as modules (by 1690 answering M instead of Y where indicated): this is most 1691 useful for infrequently used options which are not required 1692 for booting. For more information, see the man pages for 1693 modprobe, lsmod, modinfo, insmod and rmmod. 1694 1695 If you say Y here, you will need to run "make 1696 modules_install" to put the modules under /lib/modules/ 1697 where modprobe can find them (you may need to be root to do 1698 this). 1699 1700 If unsure, say Y. 1701 1702if MODULES 1703 1704config MODULE_FORCE_LOAD 1705 bool "Forced module loading" 1706 default n 1707 help 1708 Allow loading of modules without version information (ie. modprobe 1709 --force). Forced module loading sets the 'F' (forced) taint flag and 1710 is usually a really bad idea. 1711 1712config MODULE_UNLOAD 1713 bool "Module unloading" 1714 help 1715 Without this option you will not be able to unload any 1716 modules (note that some modules may not be unloadable 1717 anyway), which makes your kernel smaller, faster 1718 and simpler. If unsure, say Y. 1719 1720config MODULE_FORCE_UNLOAD 1721 bool "Forced module unloading" 1722 depends on MODULE_UNLOAD 1723 help 1724 This option allows you to force a module to unload, even if the 1725 kernel believes it is unsafe: the kernel will remove the module 1726 without waiting for anyone to stop using it (using the -f option to 1727 rmmod). This is mainly for kernel developers and desperate users. 1728 If unsure, say N. 1729 1730config MODVERSIONS 1731 bool "Module versioning support" 1732 help 1733 Usually, you have to use modules compiled with your kernel. 1734 Saying Y here makes it sometimes possible to use modules 1735 compiled for different kernels, by adding enough information 1736 to the modules to (hopefully) spot any changes which would 1737 make them incompatible with the kernel you are running. If 1738 unsure, say N. 1739 1740config MODULE_REL_CRCS 1741 bool 1742 depends on MODVERSIONS 1743 1744config MODULE_SRCVERSION_ALL 1745 bool "Source checksum for all modules" 1746 help 1747 Modules which contain a MODULE_VERSION get an extra "srcversion" 1748 field inserted into their modinfo section, which contains a 1749 sum of the source files which made it. This helps maintainers 1750 see exactly which source was used to build a module (since 1751 others sometimes change the module source without updating 1752 the version). With this option, such a "srcversion" field 1753 will be created for all modules. If unsure, say N. 1754 1755config MODULE_SIG 1756 bool "Module signature verification" 1757 depends on MODULES 1758 select SYSTEM_DATA_VERIFICATION 1759 help 1760 Check modules for valid signatures upon load: the signature 1761 is simply appended to the module. For more information see 1762 Documentation/module-signing.txt. 1763 1764 Note that this option adds the OpenSSL development packages as a 1765 kernel build dependency so that the signing tool can use its crypto 1766 library. 1767 1768 !!!WARNING!!! If you enable this option, you MUST make sure that the 1769 module DOES NOT get stripped after being signed. This includes the 1770 debuginfo strip done by some packagers (such as rpmbuild) and 1771 inclusion into an initramfs that wants the module size reduced. 1772 1773config MODULE_SIG_FORCE 1774 bool "Require modules to be validly signed" 1775 depends on MODULE_SIG 1776 help 1777 Reject unsigned modules or signed modules for which we don't have a 1778 key. Without this, such modules will simply taint the kernel. 1779 1780config MODULE_SIG_ALL 1781 bool "Automatically sign all modules" 1782 default y 1783 depends on MODULE_SIG 1784 help 1785 Sign all modules during make modules_install. Without this option, 1786 modules must be signed manually, using the scripts/sign-file tool. 1787 1788comment "Do not forget to sign required modules with scripts/sign-file" 1789 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 1790 1791choice 1792 prompt "Which hash algorithm should modules be signed with?" 1793 depends on MODULE_SIG 1794 help 1795 This determines which sort of hashing algorithm will be used during 1796 signature generation. This algorithm _must_ be built into the kernel 1797 directly so that signature verification can take place. It is not 1798 possible to load a signed module containing the algorithm to check 1799 the signature on that module. 1800 1801config MODULE_SIG_SHA1 1802 bool "Sign modules with SHA-1" 1803 select CRYPTO_SHA1 1804 1805config MODULE_SIG_SHA224 1806 bool "Sign modules with SHA-224" 1807 select CRYPTO_SHA256 1808 1809config MODULE_SIG_SHA256 1810 bool "Sign modules with SHA-256" 1811 select CRYPTO_SHA256 1812 1813config MODULE_SIG_SHA384 1814 bool "Sign modules with SHA-384" 1815 select CRYPTO_SHA512 1816 1817config MODULE_SIG_SHA512 1818 bool "Sign modules with SHA-512" 1819 select CRYPTO_SHA512 1820 1821endchoice 1822 1823config MODULE_SIG_HASH 1824 string 1825 depends on MODULE_SIG 1826 default "sha1" if MODULE_SIG_SHA1 1827 default "sha224" if MODULE_SIG_SHA224 1828 default "sha256" if MODULE_SIG_SHA256 1829 default "sha384" if MODULE_SIG_SHA384 1830 default "sha512" if MODULE_SIG_SHA512 1831 1832config MODULE_COMPRESS 1833 bool "Compress modules on installation" 1834 depends on MODULES 1835 help 1836 1837 Compresses kernel modules when 'make modules_install' is run; gzip or 1838 xz depending on "Compression algorithm" below. 1839 1840 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 1841 1842 Out-of-tree kernel modules installed using Kbuild will also be 1843 compressed upon installation. 1844 1845 Note: for modules inside an initrd or initramfs, it's more efficient 1846 to compress the whole initrd or initramfs instead. 1847 1848 Note: This is fully compatible with signed modules. 1849 1850 If in doubt, say N. 1851 1852choice 1853 prompt "Compression algorithm" 1854 depends on MODULE_COMPRESS 1855 default MODULE_COMPRESS_GZIP 1856 help 1857 This determines which sort of compression will be used during 1858 'make modules_install'. 1859 1860 GZIP (default) and XZ are supported. 1861 1862config MODULE_COMPRESS_GZIP 1863 bool "GZIP" 1864 1865config MODULE_COMPRESS_XZ 1866 bool "XZ" 1867 1868endchoice 1869 1870config TRIM_UNUSED_KSYMS 1871 bool "Trim unused exported kernel symbols" 1872 depends on MODULES && !UNUSED_SYMBOLS 1873 help 1874 The kernel and some modules make many symbols available for 1875 other modules to use via EXPORT_SYMBOL() and variants. Depending 1876 on the set of modules being selected in your kernel configuration, 1877 many of those exported symbols might never be used. 1878 1879 This option allows for unused exported symbols to be dropped from 1880 the build. In turn, this provides the compiler more opportunities 1881 (especially when using LTO) for optimizing the code and reducing 1882 binary size. This might have some security advantages as well. 1883 1884 If unsure, or if you need to build out-of-tree modules, say N. 1885 1886endif # MODULES 1887 1888config MODULES_TREE_LOOKUP 1889 def_bool y 1890 depends on PERF_EVENTS || TRACING 1891 1892config INIT_ALL_POSSIBLE 1893 bool 1894 help 1895 Back when each arch used to define their own cpu_online_mask and 1896 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 1897 with all 1s, and others with all 0s. When they were centralised, 1898 it was better to provide this option than to break all the archs 1899 and have several arch maintainers pursuing me down dark alleys. 1900 1901source "block/Kconfig" 1902 1903config PREEMPT_NOTIFIERS 1904 bool 1905 1906config PADATA 1907 depends on SMP 1908 bool 1909 1910config ASN1 1911 tristate 1912 help 1913 Build a simple ASN.1 grammar compiler that produces a bytecode output 1914 that can be interpreted by the ASN.1 stream decoder and used to 1915 inform it as to what tags are to be expected in a stream and what 1916 functions to call on what tags. 1917 1918source "kernel/Kconfig.locks" 1919