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