1# SPDX-License-Identifier: GPL-2.0-only 2config DEFCONFIG_LIST 3 string 4 depends on !UML 5 option defconfig_list 6 default "/lib/modules/$(shell,uname -r)/.config" 7 default "/etc/kernel-config" 8 default "/boot/config-$(shell,uname -r)" 9 default ARCH_DEFCONFIG 10 default "arch/$(ARCH)/defconfig" 11 12config CC_IS_GCC 13 def_bool $(success,$(CC) --version | head -n 1 | grep -q gcc) 14 15config GCC_VERSION 16 int 17 default $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) if CC_IS_GCC 18 default 0 19 20config CC_IS_CLANG 21 def_bool $(success,$(CC) --version | head -n 1 | grep -q clang) 22 23config CLANG_VERSION 24 int 25 default $(shell,$(srctree)/scripts/clang-version.sh $(CC)) 26 27config CC_CAN_LINK 28 def_bool $(success,$(srctree)/scripts/cc-can-link.sh $(CC)) 29 30config CC_HAS_ASM_GOTO 31 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) 32 33config CC_HAS_WARN_MAYBE_UNINITIALIZED 34 def_bool $(cc-option,-Wmaybe-uninitialized) 35 help 36 GCC >= 4.7 supports this option. 37 38config CC_DISABLE_WARN_MAYBE_UNINITIALIZED 39 bool 40 depends on CC_HAS_WARN_MAYBE_UNINITIALIZED 41 default CC_IS_GCC && GCC_VERSION < 40900 # unreliable for GCC < 4.9 42 help 43 GCC's -Wmaybe-uninitialized is not reliable by definition. 44 Lots of false positive warnings are produced in some cases. 45 46 If this option is enabled, -Wno-maybe-uninitialzed is passed 47 to the compiler to suppress maybe-uninitialized warnings. 48 49config CONSTRUCTORS 50 bool 51 depends on !UML 52 53config IRQ_WORK 54 bool 55 56config BUILDTIME_EXTABLE_SORT 57 bool 58 59config THREAD_INFO_IN_TASK 60 bool 61 help 62 Select this to move thread_info off the stack into task_struct. To 63 make this work, an arch will need to remove all thread_info fields 64 except flags and fix any runtime bugs. 65 66 One subtle change that will be needed is to use try_get_task_stack() 67 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 68 69menu "General setup" 70 71config BROKEN 72 bool 73 74config BROKEN_ON_SMP 75 bool 76 depends on BROKEN || !SMP 77 default y 78 79config INIT_ENV_ARG_LIMIT 80 int 81 default 32 if !UML 82 default 128 if UML 83 help 84 Maximum of each of the number of arguments and environment 85 variables passed to init from the kernel command line. 86 87config COMPILE_TEST 88 bool "Compile also drivers which will not load" 89 depends on !UML 90 default n 91 help 92 Some drivers can be compiled on a different platform than they are 93 intended to be run on. Despite they cannot be loaded there (or even 94 when they load they cannot be used due to missing HW support), 95 developers still, opposing to distributors, might want to build such 96 drivers to compile-test them. 97 98 If you are a developer and want to build everything available, say Y 99 here. If you are a user/distributor, say N here to exclude useless 100 drivers to be distributed. 101 102config HEADER_TEST 103 bool "Compile test headers that should be standalone compilable" 104 help 105 Compile test headers listed in header-test-y target to ensure they are 106 self-contained, i.e. compilable as standalone units. 107 108 If you are a developer or tester and want to ensure the requested 109 headers are self-contained, say Y here. Otherwise, choose N. 110 111config KERNEL_HEADER_TEST 112 bool "Compile test kernel headers" 113 depends on HEADER_TEST 114 help 115 Headers in include/ are used to build external moduls. 116 Compile test them to ensure they are self-contained, i.e. 117 compilable as standalone units. 118 119 If you are a developer or tester and want to ensure the headers 120 in include/ are self-contained, say Y here. Otherwise, choose N. 121 122config UAPI_HEADER_TEST 123 bool "Compile test UAPI headers" 124 depends on HEADER_TEST && HEADERS_INSTALL && CC_CAN_LINK 125 help 126 Compile test headers exported to user-space to ensure they are 127 self-contained, i.e. compilable as standalone units. 128 129 If you are a developer or tester and want to ensure the exported 130 headers are self-contained, say Y here. Otherwise, choose N. 131 132config LOCALVERSION 133 string "Local version - append to kernel release" 134 help 135 Append an extra string to the end of your kernel version. 136 This will show up when you type uname, for example. 137 The string you set here will be appended after the contents of 138 any files with a filename matching localversion* in your 139 object and source tree, in that order. Your total string can 140 be a maximum of 64 characters. 141 142config LOCALVERSION_AUTO 143 bool "Automatically append version information to the version string" 144 default y 145 depends on !COMPILE_TEST 146 help 147 This will try to automatically determine if the current tree is a 148 release tree by looking for git tags that belong to the current 149 top of tree revision. 150 151 A string of the format -gxxxxxxxx will be added to the localversion 152 if a git-based tree is found. The string generated by this will be 153 appended after any matching localversion* files, and after the value 154 set in CONFIG_LOCALVERSION. 155 156 (The actual string used here is the first eight characters produced 157 by running the command: 158 159 $ git rev-parse --verify HEAD 160 161 which is done within the script "scripts/setlocalversion".) 162 163config BUILD_SALT 164 string "Build ID Salt" 165 default "" 166 help 167 The build ID is used to link binaries and their debug info. Setting 168 this option will use the value in the calculation of the build id. 169 This is mostly useful for distributions which want to ensure the 170 build is unique between builds. It's safe to leave the default. 171 172config HAVE_KERNEL_GZIP 173 bool 174 175config HAVE_KERNEL_BZIP2 176 bool 177 178config HAVE_KERNEL_LZMA 179 bool 180 181config HAVE_KERNEL_XZ 182 bool 183 184config HAVE_KERNEL_LZO 185 bool 186 187config HAVE_KERNEL_LZ4 188 bool 189 190config HAVE_KERNEL_UNCOMPRESSED 191 bool 192 193choice 194 prompt "Kernel compression mode" 195 default KERNEL_GZIP 196 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED 197 help 198 The linux kernel is a kind of self-extracting executable. 199 Several compression algorithms are available, which differ 200 in efficiency, compression and decompression speed. 201 Compression speed is only relevant when building a kernel. 202 Decompression speed is relevant at each boot. 203 204 If you have any problems with bzip2 or lzma compressed 205 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 206 version of this functionality (bzip2 only), for 2.4, was 207 supplied by Christian Ludwig) 208 209 High compression options are mostly useful for users, who 210 are low on disk space (embedded systems), but for whom ram 211 size matters less. 212 213 If in doubt, select 'gzip' 214 215config KERNEL_GZIP 216 bool "Gzip" 217 depends on HAVE_KERNEL_GZIP 218 help 219 The old and tried gzip compression. It provides a good balance 220 between compression ratio and decompression speed. 221 222config KERNEL_BZIP2 223 bool "Bzip2" 224 depends on HAVE_KERNEL_BZIP2 225 help 226 Its compression ratio and speed is intermediate. 227 Decompression speed is slowest among the choices. The kernel 228 size is about 10% smaller with bzip2, in comparison to gzip. 229 Bzip2 uses a large amount of memory. For modern kernels you 230 will need at least 8MB RAM or more for booting. 231 232config KERNEL_LZMA 233 bool "LZMA" 234 depends on HAVE_KERNEL_LZMA 235 help 236 This compression algorithm's ratio is best. Decompression speed 237 is between gzip and bzip2. Compression is slowest. 238 The kernel size is about 33% smaller with LZMA in comparison to gzip. 239 240config KERNEL_XZ 241 bool "XZ" 242 depends on HAVE_KERNEL_XZ 243 help 244 XZ uses the LZMA2 algorithm and instruction set specific 245 BCJ filters which can improve compression ratio of executable 246 code. The size of the kernel is about 30% smaller with XZ in 247 comparison to gzip. On architectures for which there is a BCJ 248 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 249 will create a few percent smaller kernel than plain LZMA. 250 251 The speed is about the same as with LZMA: The decompression 252 speed of XZ is better than that of bzip2 but worse than gzip 253 and LZO. Compression is slow. 254 255config KERNEL_LZO 256 bool "LZO" 257 depends on HAVE_KERNEL_LZO 258 help 259 Its compression ratio is the poorest among the choices. The kernel 260 size is about 10% bigger than gzip; however its speed 261 (both compression and decompression) is the fastest. 262 263config KERNEL_LZ4 264 bool "LZ4" 265 depends on HAVE_KERNEL_LZ4 266 help 267 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 268 A preliminary version of LZ4 de/compression tool is available at 269 <https://code.google.com/p/lz4/>. 270 271 Its compression ratio is worse than LZO. The size of the kernel 272 is about 8% bigger than LZO. But the decompression speed is 273 faster than LZO. 274 275config KERNEL_UNCOMPRESSED 276 bool "None" 277 depends on HAVE_KERNEL_UNCOMPRESSED 278 help 279 Produce uncompressed kernel image. This option is usually not what 280 you want. It is useful for debugging the kernel in slow simulation 281 environments, where decompressing and moving the kernel is awfully 282 slow. This option allows early boot code to skip the decompressor 283 and jump right at uncompressed kernel image. 284 285endchoice 286 287config DEFAULT_HOSTNAME 288 string "Default hostname" 289 default "(none)" 290 help 291 This option determines the default system hostname before userspace 292 calls sethostname(2). The kernel traditionally uses "(none)" here, 293 but you may wish to use a different default here to make a minimal 294 system more usable with less configuration. 295 296# 297# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can 298# add proper SWAP support to them, in which case this can be remove. 299# 300config ARCH_NO_SWAP 301 bool 302 303config SWAP 304 bool "Support for paging of anonymous memory (swap)" 305 depends on MMU && BLOCK && !ARCH_NO_SWAP 306 default y 307 help 308 This option allows you to choose whether you want to have support 309 for so called swap devices or swap files in your kernel that are 310 used to provide more virtual memory than the actual RAM present 311 in your computer. If unsure say Y. 312 313config SYSVIPC 314 bool "System V IPC" 315 ---help--- 316 Inter Process Communication is a suite of library functions and 317 system calls which let processes (running programs) synchronize and 318 exchange information. It is generally considered to be a good thing, 319 and some programs won't run unless you say Y here. In particular, if 320 you want to run the DOS emulator dosemu under Linux (read the 321 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 322 you'll need to say Y here. 323 324 You can find documentation about IPC with "info ipc" and also in 325 section 6.4 of the Linux Programmer's Guide, available from 326 <http://www.tldp.org/guides.html>. 327 328config SYSVIPC_SYSCTL 329 bool 330 depends on SYSVIPC 331 depends on SYSCTL 332 default y 333 334config POSIX_MQUEUE 335 bool "POSIX Message Queues" 336 depends on NET 337 ---help--- 338 POSIX variant of message queues is a part of IPC. In POSIX message 339 queues every message has a priority which decides about succession 340 of receiving it by a process. If you want to compile and run 341 programs written e.g. for Solaris with use of its POSIX message 342 queues (functions mq_*) say Y here. 343 344 POSIX message queues are visible as a filesystem called 'mqueue' 345 and can be mounted somewhere if you want to do filesystem 346 operations on message queues. 347 348 If unsure, say Y. 349 350config POSIX_MQUEUE_SYSCTL 351 bool 352 depends on POSIX_MQUEUE 353 depends on SYSCTL 354 default y 355 356config CROSS_MEMORY_ATTACH 357 bool "Enable process_vm_readv/writev syscalls" 358 depends on MMU 359 default y 360 help 361 Enabling this option adds the system calls process_vm_readv and 362 process_vm_writev which allow a process with the correct privileges 363 to directly read from or write to another process' address space. 364 See the man page for more details. 365 366config USELIB 367 bool "uselib syscall" 368 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION 369 help 370 This option enables the uselib syscall, a system call used in the 371 dynamic linker from libc5 and earlier. glibc does not use this 372 system call. If you intend to run programs built on libc5 or 373 earlier, you may need to enable this syscall. Current systems 374 running glibc can safely disable this. 375 376config AUDIT 377 bool "Auditing support" 378 depends on NET 379 help 380 Enable auditing infrastructure that can be used with another 381 kernel subsystem, such as SELinux (which requires this for 382 logging of avc messages output). System call auditing is included 383 on architectures which support it. 384 385config HAVE_ARCH_AUDITSYSCALL 386 bool 387 388config AUDITSYSCALL 389 def_bool y 390 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 391 select FSNOTIFY 392 393source "kernel/irq/Kconfig" 394source "kernel/time/Kconfig" 395source "kernel/Kconfig.preempt" 396 397menu "CPU/Task time and stats accounting" 398 399config VIRT_CPU_ACCOUNTING 400 bool 401 402choice 403 prompt "Cputime accounting" 404 default TICK_CPU_ACCOUNTING if !PPC64 405 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 406 407# Kind of a stub config for the pure tick based cputime accounting 408config TICK_CPU_ACCOUNTING 409 bool "Simple tick based cputime accounting" 410 depends on !S390 && !NO_HZ_FULL 411 help 412 This is the basic tick based cputime accounting that maintains 413 statistics about user, system and idle time spent on per jiffies 414 granularity. 415 416 If unsure, say Y. 417 418config VIRT_CPU_ACCOUNTING_NATIVE 419 bool "Deterministic task and CPU time accounting" 420 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 421 select VIRT_CPU_ACCOUNTING 422 help 423 Select this option to enable more accurate task and CPU time 424 accounting. This is done by reading a CPU counter on each 425 kernel entry and exit and on transitions within the kernel 426 between system, softirq and hardirq state, so there is a 427 small performance impact. In the case of s390 or IBM POWER > 5, 428 this also enables accounting of stolen time on logically-partitioned 429 systems. 430 431config VIRT_CPU_ACCOUNTING_GEN 432 bool "Full dynticks CPU time accounting" 433 depends on HAVE_CONTEXT_TRACKING 434 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 435 depends on GENERIC_CLOCKEVENTS 436 select VIRT_CPU_ACCOUNTING 437 select CONTEXT_TRACKING 438 help 439 Select this option to enable task and CPU time accounting on full 440 dynticks systems. This accounting is implemented by watching every 441 kernel-user boundaries using the context tracking subsystem. 442 The accounting is thus performed at the expense of some significant 443 overhead. 444 445 For now this is only useful if you are working on the full 446 dynticks subsystem development. 447 448 If unsure, say N. 449 450endchoice 451 452config IRQ_TIME_ACCOUNTING 453 bool "Fine granularity task level IRQ time accounting" 454 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 455 help 456 Select this option to enable fine granularity task irq time 457 accounting. This is done by reading a timestamp on each 458 transitions between softirq and hardirq state, so there can be a 459 small performance impact. 460 461 If in doubt, say N here. 462 463config HAVE_SCHED_AVG_IRQ 464 def_bool y 465 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 466 depends on SMP 467 468config BSD_PROCESS_ACCT 469 bool "BSD Process Accounting" 470 depends on MULTIUSER 471 help 472 If you say Y here, a user level program will be able to instruct the 473 kernel (via a special system call) to write process accounting 474 information to a file: whenever a process exits, information about 475 that process will be appended to the file by the kernel. The 476 information includes things such as creation time, owning user, 477 command name, memory usage, controlling terminal etc. (the complete 478 list is in the struct acct in <file:include/linux/acct.h>). It is 479 up to the user level program to do useful things with this 480 information. This is generally a good idea, so say Y. 481 482config BSD_PROCESS_ACCT_V3 483 bool "BSD Process Accounting version 3 file format" 484 depends on BSD_PROCESS_ACCT 485 default n 486 help 487 If you say Y here, the process accounting information is written 488 in a new file format that also logs the process IDs of each 489 process and its parent. Note that this file format is incompatible 490 with previous v0/v1/v2 file formats, so you will need updated tools 491 for processing it. A preliminary version of these tools is available 492 at <http://www.gnu.org/software/acct/>. 493 494config TASKSTATS 495 bool "Export task/process statistics through netlink" 496 depends on NET 497 depends on MULTIUSER 498 default n 499 help 500 Export selected statistics for tasks/processes through the 501 generic netlink interface. Unlike BSD process accounting, the 502 statistics are available during the lifetime of tasks/processes as 503 responses to commands. Like BSD accounting, they are sent to user 504 space on task exit. 505 506 Say N if unsure. 507 508config TASK_DELAY_ACCT 509 bool "Enable per-task delay accounting" 510 depends on TASKSTATS 511 select SCHED_INFO 512 help 513 Collect information on time spent by a task waiting for system 514 resources like cpu, synchronous block I/O completion and swapping 515 in pages. Such statistics can help in setting a task's priorities 516 relative to other tasks for cpu, io, rss limits etc. 517 518 Say N if unsure. 519 520config TASK_XACCT 521 bool "Enable extended accounting over taskstats" 522 depends on TASKSTATS 523 help 524 Collect extended task accounting data and send the data 525 to userland for processing over the taskstats interface. 526 527 Say N if unsure. 528 529config TASK_IO_ACCOUNTING 530 bool "Enable per-task storage I/O accounting" 531 depends on TASK_XACCT 532 help 533 Collect information on the number of bytes of storage I/O which this 534 task has caused. 535 536 Say N if unsure. 537 538config PSI 539 bool "Pressure stall information tracking" 540 help 541 Collect metrics that indicate how overcommitted the CPU, memory, 542 and IO capacity are in the system. 543 544 If you say Y here, the kernel will create /proc/pressure/ with the 545 pressure statistics files cpu, memory, and io. These will indicate 546 the share of walltime in which some or all tasks in the system are 547 delayed due to contention of the respective resource. 548 549 In kernels with cgroup support, cgroups (cgroup2 only) will 550 have cpu.pressure, memory.pressure, and io.pressure files, 551 which aggregate pressure stalls for the grouped tasks only. 552 553 For more details see Documentation/accounting/psi.rst. 554 555 Say N if unsure. 556 557config PSI_DEFAULT_DISABLED 558 bool "Require boot parameter to enable pressure stall information tracking" 559 default n 560 depends on PSI 561 help 562 If set, pressure stall information tracking will be disabled 563 per default but can be enabled through passing psi=1 on the 564 kernel commandline during boot. 565 566 This feature adds some code to the task wakeup and sleep 567 paths of the scheduler. The overhead is too low to affect 568 common scheduling-intense workloads in practice (such as 569 webservers, memcache), but it does show up in artificial 570 scheduler stress tests, such as hackbench. 571 572 If you are paranoid and not sure what the kernel will be 573 used for, say Y. 574 575 Say N if unsure. 576 577endmenu # "CPU/Task time and stats accounting" 578 579config CPU_ISOLATION 580 bool "CPU isolation" 581 depends on SMP || COMPILE_TEST 582 default y 583 help 584 Make sure that CPUs running critical tasks are not disturbed by 585 any source of "noise" such as unbound workqueues, timers, kthreads... 586 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 587 the "isolcpus=" boot parameter. 588 589 Say Y if unsure. 590 591source "kernel/rcu/Kconfig" 592 593config BUILD_BIN2C 594 bool 595 default n 596 597config IKCONFIG 598 tristate "Kernel .config support" 599 ---help--- 600 This option enables the complete Linux kernel ".config" file 601 contents to be saved in the kernel. It provides documentation 602 of which kernel options are used in a running kernel or in an 603 on-disk kernel. This information can be extracted from the kernel 604 image file with the script scripts/extract-ikconfig and used as 605 input to rebuild the current kernel or to build another kernel. 606 It can also be extracted from a running kernel by reading 607 /proc/config.gz if enabled (below). 608 609config IKCONFIG_PROC 610 bool "Enable access to .config through /proc/config.gz" 611 depends on IKCONFIG && PROC_FS 612 ---help--- 613 This option enables access to the kernel configuration file 614 through /proc/config.gz. 615 616config IKHEADERS 617 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 618 depends on SYSFS 619 help 620 This option enables access to the in-kernel headers that are generated during 621 the build process. These can be used to build eBPF tracing programs, 622 or similar programs. If you build the headers as a module, a module called 623 kheaders.ko is built which can be loaded on-demand to get access to headers. 624 625config LOG_BUF_SHIFT 626 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 627 range 12 25 628 default 17 629 depends on PRINTK 630 help 631 Select the minimal kernel log buffer size as a power of 2. 632 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 633 parameter, see below. Any higher size also might be forced 634 by "log_buf_len" boot parameter. 635 636 Examples: 637 17 => 128 KB 638 16 => 64 KB 639 15 => 32 KB 640 14 => 16 KB 641 13 => 8 KB 642 12 => 4 KB 643 644config LOG_CPU_MAX_BUF_SHIFT 645 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 646 depends on SMP 647 range 0 21 648 default 12 if !BASE_SMALL 649 default 0 if BASE_SMALL 650 depends on PRINTK 651 help 652 This option allows to increase the default ring buffer size 653 according to the number of CPUs. The value defines the contribution 654 of each CPU as a power of 2. The used space is typically only few 655 lines however it might be much more when problems are reported, 656 e.g. backtraces. 657 658 The increased size means that a new buffer has to be allocated and 659 the original static one is unused. It makes sense only on systems 660 with more CPUs. Therefore this value is used only when the sum of 661 contributions is greater than the half of the default kernel ring 662 buffer as defined by LOG_BUF_SHIFT. The default values are set 663 so that more than 64 CPUs are needed to trigger the allocation. 664 665 Also this option is ignored when "log_buf_len" kernel parameter is 666 used as it forces an exact (power of two) size of the ring buffer. 667 668 The number of possible CPUs is used for this computation ignoring 669 hotplugging making the computation optimal for the worst case 670 scenario while allowing a simple algorithm to be used from bootup. 671 672 Examples shift values and their meaning: 673 17 => 128 KB for each CPU 674 16 => 64 KB for each CPU 675 15 => 32 KB for each CPU 676 14 => 16 KB for each CPU 677 13 => 8 KB for each CPU 678 12 => 4 KB for each CPU 679 680config PRINTK_SAFE_LOG_BUF_SHIFT 681 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 682 range 10 21 683 default 13 684 depends on PRINTK 685 help 686 Select the size of an alternate printk per-CPU buffer where messages 687 printed from usafe contexts are temporary stored. One example would 688 be NMI messages, another one - printk recursion. The messages are 689 copied to the main log buffer in a safe context to avoid a deadlock. 690 The value defines the size as a power of 2. 691 692 Those messages are rare and limited. The largest one is when 693 a backtrace is printed. It usually fits into 4KB. Select 694 8KB if you want to be on the safe side. 695 696 Examples: 697 17 => 128 KB for each CPU 698 16 => 64 KB for each CPU 699 15 => 32 KB for each CPU 700 14 => 16 KB for each CPU 701 13 => 8 KB for each CPU 702 12 => 4 KB for each CPU 703 704# 705# Architectures with an unreliable sched_clock() should select this: 706# 707config HAVE_UNSTABLE_SCHED_CLOCK 708 bool 709 710config GENERIC_SCHED_CLOCK 711 bool 712 713menu "Scheduler features" 714 715config UCLAMP_TASK 716 bool "Enable utilization clamping for RT/FAIR tasks" 717 depends on CPU_FREQ_GOV_SCHEDUTIL 718 help 719 This feature enables the scheduler to track the clamped utilization 720 of each CPU based on RUNNABLE tasks scheduled on that CPU. 721 722 With this option, the user can specify the min and max CPU 723 utilization allowed for RUNNABLE tasks. The max utilization defines 724 the maximum frequency a task should use while the min utilization 725 defines the minimum frequency it should use. 726 727 Both min and max utilization clamp values are hints to the scheduler, 728 aiming at improving its frequency selection policy, but they do not 729 enforce or grant any specific bandwidth for tasks. 730 731 If in doubt, say N. 732 733config UCLAMP_BUCKETS_COUNT 734 int "Number of supported utilization clamp buckets" 735 range 5 20 736 default 5 737 depends on UCLAMP_TASK 738 help 739 Defines the number of clamp buckets to use. The range of each bucket 740 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 741 number of clamp buckets the finer their granularity and the higher 742 the precision of clamping aggregation and tracking at run-time. 743 744 For example, with the minimum configuration value we will have 5 745 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 746 be refcounted in the [20..39]% bucket and will set the bucket clamp 747 effective value to 25%. 748 If a second 30% boosted task should be co-scheduled on the same CPU, 749 that task will be refcounted in the same bucket of the first task and 750 it will boost the bucket clamp effective value to 30%. 751 The clamp effective value of a bucket is reset to its nominal value 752 (20% in the example above) when there are no more tasks refcounted in 753 that bucket. 754 755 An additional boost/capping margin can be added to some tasks. In the 756 example above the 25% task will be boosted to 30% until it exits the 757 CPU. If that should be considered not acceptable on certain systems, 758 it's always possible to reduce the margin by increasing the number of 759 clamp buckets to trade off used memory for run-time tracking 760 precision. 761 762 If in doubt, use the default value. 763 764endmenu 765 766# 767# For architectures that want to enable the support for NUMA-affine scheduler 768# balancing logic: 769# 770config ARCH_SUPPORTS_NUMA_BALANCING 771 bool 772 773# 774# For architectures that prefer to flush all TLBs after a number of pages 775# are unmapped instead of sending one IPI per page to flush. The architecture 776# must provide guarantees on what happens if a clean TLB cache entry is 777# written after the unmap. Details are in mm/rmap.c near the check for 778# should_defer_flush. The architecture should also consider if the full flush 779# and the refill costs are offset by the savings of sending fewer IPIs. 780config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 781 bool 782 783# 784# For architectures that know their GCC __int128 support is sound 785# 786config ARCH_SUPPORTS_INT128 787 bool 788 789# For architectures that (ab)use NUMA to represent different memory regions 790# all cpu-local but of different latencies, such as SuperH. 791# 792config ARCH_WANT_NUMA_VARIABLE_LOCALITY 793 bool 794 795config NUMA_BALANCING 796 bool "Memory placement aware NUMA scheduler" 797 depends on ARCH_SUPPORTS_NUMA_BALANCING 798 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 799 depends on SMP && NUMA && MIGRATION 800 help 801 This option adds support for automatic NUMA aware memory/task placement. 802 The mechanism is quite primitive and is based on migrating memory when 803 it has references to the node the task is running on. 804 805 This system will be inactive on UMA systems. 806 807config NUMA_BALANCING_DEFAULT_ENABLED 808 bool "Automatically enable NUMA aware memory/task placement" 809 default y 810 depends on NUMA_BALANCING 811 help 812 If set, automatic NUMA balancing will be enabled if running on a NUMA 813 machine. 814 815menuconfig CGROUPS 816 bool "Control Group support" 817 select KERNFS 818 help 819 This option adds support for grouping sets of processes together, for 820 use with process control subsystems such as Cpusets, CFS, memory 821 controls or device isolation. 822 See 823 - Documentation/scheduler/sched-design-CFS.rst (CFS) 824 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 825 and resource control) 826 827 Say N if unsure. 828 829if CGROUPS 830 831config PAGE_COUNTER 832 bool 833 834config MEMCG 835 bool "Memory controller" 836 select PAGE_COUNTER 837 select EVENTFD 838 help 839 Provides control over the memory footprint of tasks in a cgroup. 840 841config MEMCG_SWAP 842 bool "Swap controller" 843 depends on MEMCG && SWAP 844 help 845 Provides control over the swap space consumed by tasks in a cgroup. 846 847config MEMCG_SWAP_ENABLED 848 bool "Swap controller enabled by default" 849 depends on MEMCG_SWAP 850 default y 851 help 852 Memory Resource Controller Swap Extension comes with its price in 853 a bigger memory consumption. General purpose distribution kernels 854 which want to enable the feature but keep it disabled by default 855 and let the user enable it by swapaccount=1 boot command line 856 parameter should have this option unselected. 857 For those who want to have the feature enabled by default should 858 select this option (if, for some reason, they need to disable it 859 then swapaccount=0 does the trick). 860 861config MEMCG_KMEM 862 bool 863 depends on MEMCG && !SLOB 864 default y 865 866config BLK_CGROUP 867 bool "IO controller" 868 depends on BLOCK 869 default n 870 ---help--- 871 Generic block IO controller cgroup interface. This is the common 872 cgroup interface which should be used by various IO controlling 873 policies. 874 875 Currently, CFQ IO scheduler uses it to recognize task groups and 876 control disk bandwidth allocation (proportional time slice allocation) 877 to such task groups. It is also used by bio throttling logic in 878 block layer to implement upper limit in IO rates on a device. 879 880 This option only enables generic Block IO controller infrastructure. 881 One needs to also enable actual IO controlling logic/policy. For 882 enabling proportional weight division of disk bandwidth in CFQ, set 883 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 884 CONFIG_BLK_DEV_THROTTLING=y. 885 886 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 887 888config CGROUP_WRITEBACK 889 bool 890 depends on MEMCG && BLK_CGROUP 891 default y 892 893menuconfig CGROUP_SCHED 894 bool "CPU controller" 895 default n 896 help 897 This feature lets CPU scheduler recognize task groups and control CPU 898 bandwidth allocation to such task groups. It uses cgroups to group 899 tasks. 900 901if CGROUP_SCHED 902config FAIR_GROUP_SCHED 903 bool "Group scheduling for SCHED_OTHER" 904 depends on CGROUP_SCHED 905 default CGROUP_SCHED 906 907config CFS_BANDWIDTH 908 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 909 depends on FAIR_GROUP_SCHED 910 default n 911 help 912 This option allows users to define CPU bandwidth rates (limits) for 913 tasks running within the fair group scheduler. Groups with no limit 914 set are considered to be unconstrained and will run with no 915 restriction. 916 See Documentation/scheduler/sched-bwc.rst for more information. 917 918config RT_GROUP_SCHED 919 bool "Group scheduling for SCHED_RR/FIFO" 920 depends on CGROUP_SCHED 921 default n 922 help 923 This feature lets you explicitly allocate real CPU bandwidth 924 to task groups. If enabled, it will also make it impossible to 925 schedule realtime tasks for non-root users until you allocate 926 realtime bandwidth for them. 927 See Documentation/scheduler/sched-rt-group.rst for more information. 928 929endif #CGROUP_SCHED 930 931config CGROUP_PIDS 932 bool "PIDs controller" 933 help 934 Provides enforcement of process number limits in the scope of a 935 cgroup. Any attempt to fork more processes than is allowed in the 936 cgroup will fail. PIDs are fundamentally a global resource because it 937 is fairly trivial to reach PID exhaustion before you reach even a 938 conservative kmemcg limit. As a result, it is possible to grind a 939 system to halt without being limited by other cgroup policies. The 940 PIDs controller is designed to stop this from happening. 941 942 It should be noted that organisational operations (such as attaching 943 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 944 since the PIDs limit only affects a process's ability to fork, not to 945 attach to a cgroup. 946 947config CGROUP_RDMA 948 bool "RDMA controller" 949 help 950 Provides enforcement of RDMA resources defined by IB stack. 951 It is fairly easy for consumers to exhaust RDMA resources, which 952 can result into resource unavailability to other consumers. 953 RDMA controller is designed to stop this from happening. 954 Attaching processes with active RDMA resources to the cgroup 955 hierarchy is allowed even if can cross the hierarchy's limit. 956 957config CGROUP_FREEZER 958 bool "Freezer controller" 959 help 960 Provides a way to freeze and unfreeze all tasks in a 961 cgroup. 962 963 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 964 controller includes important in-kernel memory consumers per default. 965 966 If you're using cgroup2, say N. 967 968config CGROUP_HUGETLB 969 bool "HugeTLB controller" 970 depends on HUGETLB_PAGE 971 select PAGE_COUNTER 972 default n 973 help 974 Provides a cgroup controller for HugeTLB pages. 975 When you enable this, you can put a per cgroup limit on HugeTLB usage. 976 The limit is enforced during page fault. Since HugeTLB doesn't 977 support page reclaim, enforcing the limit at page fault time implies 978 that, the application will get SIGBUS signal if it tries to access 979 HugeTLB pages beyond its limit. This requires the application to know 980 beforehand how much HugeTLB pages it would require for its use. The 981 control group is tracked in the third page lru pointer. This means 982 that we cannot use the controller with huge page less than 3 pages. 983 984config CPUSETS 985 bool "Cpuset controller" 986 depends on SMP 987 help 988 This option will let you create and manage CPUSETs which 989 allow dynamically partitioning a system into sets of CPUs and 990 Memory Nodes and assigning tasks to run only within those sets. 991 This is primarily useful on large SMP or NUMA systems. 992 993 Say N if unsure. 994 995config PROC_PID_CPUSET 996 bool "Include legacy /proc/<pid>/cpuset file" 997 depends on CPUSETS 998 default y 999 1000config CGROUP_DEVICE 1001 bool "Device controller" 1002 help 1003 Provides a cgroup controller implementing whitelists for 1004 devices which a process in the cgroup can mknod or open. 1005 1006config CGROUP_CPUACCT 1007 bool "Simple CPU accounting controller" 1008 help 1009 Provides a simple controller for monitoring the 1010 total CPU consumed by the tasks in a cgroup. 1011 1012config CGROUP_PERF 1013 bool "Perf controller" 1014 depends on PERF_EVENTS 1015 help 1016 This option extends the perf per-cpu mode to restrict monitoring 1017 to threads which belong to the cgroup specified and run on the 1018 designated cpu. 1019 1020 Say N if unsure. 1021 1022config CGROUP_BPF 1023 bool "Support for eBPF programs attached to cgroups" 1024 depends on BPF_SYSCALL 1025 select SOCK_CGROUP_DATA 1026 help 1027 Allow attaching eBPF programs to a cgroup using the bpf(2) 1028 syscall command BPF_PROG_ATTACH. 1029 1030 In which context these programs are accessed depends on the type 1031 of attachment. For instance, programs that are attached using 1032 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1033 inet sockets. 1034 1035config CGROUP_DEBUG 1036 bool "Debug controller" 1037 default n 1038 depends on DEBUG_KERNEL 1039 help 1040 This option enables a simple controller that exports 1041 debugging information about the cgroups framework. This 1042 controller is for control cgroup debugging only. Its 1043 interfaces are not stable. 1044 1045 Say N. 1046 1047config SOCK_CGROUP_DATA 1048 bool 1049 default n 1050 1051endif # CGROUPS 1052 1053menuconfig NAMESPACES 1054 bool "Namespaces support" if EXPERT 1055 depends on MULTIUSER 1056 default !EXPERT 1057 help 1058 Provides the way to make tasks work with different objects using 1059 the same id. For example same IPC id may refer to different objects 1060 or same user id or pid may refer to different tasks when used in 1061 different namespaces. 1062 1063if NAMESPACES 1064 1065config UTS_NS 1066 bool "UTS namespace" 1067 default y 1068 help 1069 In this namespace tasks see different info provided with the 1070 uname() system call 1071 1072config IPC_NS 1073 bool "IPC namespace" 1074 depends on (SYSVIPC || POSIX_MQUEUE) 1075 default y 1076 help 1077 In this namespace tasks work with IPC ids which correspond to 1078 different IPC objects in different namespaces. 1079 1080config USER_NS 1081 bool "User namespace" 1082 default n 1083 help 1084 This allows containers, i.e. vservers, to use user namespaces 1085 to provide different user info for different servers. 1086 1087 When user namespaces are enabled in the kernel it is 1088 recommended that the MEMCG option also be enabled and that 1089 user-space use the memory control groups to limit the amount 1090 of memory a memory unprivileged users can use. 1091 1092 If unsure, say N. 1093 1094config PID_NS 1095 bool "PID Namespaces" 1096 default y 1097 help 1098 Support process id namespaces. This allows having multiple 1099 processes with the same pid as long as they are in different 1100 pid namespaces. This is a building block of containers. 1101 1102config NET_NS 1103 bool "Network namespace" 1104 depends on NET 1105 default y 1106 help 1107 Allow user space to create what appear to be multiple instances 1108 of the network stack. 1109 1110endif # NAMESPACES 1111 1112config CHECKPOINT_RESTORE 1113 bool "Checkpoint/restore support" 1114 select PROC_CHILDREN 1115 default n 1116 help 1117 Enables additional kernel features in a sake of checkpoint/restore. 1118 In particular it adds auxiliary prctl codes to setup process text, 1119 data and heap segment sizes, and a few additional /proc filesystem 1120 entries. 1121 1122 If unsure, say N here. 1123 1124config SCHED_AUTOGROUP 1125 bool "Automatic process group scheduling" 1126 select CGROUPS 1127 select CGROUP_SCHED 1128 select FAIR_GROUP_SCHED 1129 help 1130 This option optimizes the scheduler for common desktop workloads by 1131 automatically creating and populating task groups. This separation 1132 of workloads isolates aggressive CPU burners (like build jobs) from 1133 desktop applications. Task group autogeneration is currently based 1134 upon task session. 1135 1136config SYSFS_DEPRECATED 1137 bool "Enable deprecated sysfs features to support old userspace tools" 1138 depends on SYSFS 1139 default n 1140 help 1141 This option adds code that switches the layout of the "block" class 1142 devices, to not show up in /sys/class/block/, but only in 1143 /sys/block/. 1144 1145 This switch is only active when the sysfs.deprecated=1 boot option is 1146 passed or the SYSFS_DEPRECATED_V2 option is set. 1147 1148 This option allows new kernels to run on old distributions and tools, 1149 which might get confused by /sys/class/block/. Since 2007/2008 all 1150 major distributions and tools handle this just fine. 1151 1152 Recent distributions and userspace tools after 2009/2010 depend on 1153 the existence of /sys/class/block/, and will not work with this 1154 option enabled. 1155 1156 Only if you are using a new kernel on an old distribution, you might 1157 need to say Y here. 1158 1159config SYSFS_DEPRECATED_V2 1160 bool "Enable deprecated sysfs features by default" 1161 default n 1162 depends on SYSFS 1163 depends on SYSFS_DEPRECATED 1164 help 1165 Enable deprecated sysfs by default. 1166 1167 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1168 option. 1169 1170 Only if you are using a new kernel on an old distribution, you might 1171 need to say Y here. Even then, odds are you would not need it 1172 enabled, you can always pass the boot option if absolutely necessary. 1173 1174config RELAY 1175 bool "Kernel->user space relay support (formerly relayfs)" 1176 select IRQ_WORK 1177 help 1178 This option enables support for relay interface support in 1179 certain file systems (such as debugfs). 1180 It is designed to provide an efficient mechanism for tools and 1181 facilities to relay large amounts of data from kernel space to 1182 user space. 1183 1184 If unsure, say N. 1185 1186config BLK_DEV_INITRD 1187 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1188 help 1189 The initial RAM filesystem is a ramfs which is loaded by the 1190 boot loader (loadlin or lilo) and that is mounted as root 1191 before the normal boot procedure. It is typically used to 1192 load modules needed to mount the "real" root file system, 1193 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1194 1195 If RAM disk support (BLK_DEV_RAM) is also included, this 1196 also enables initial RAM disk (initrd) support and adds 1197 15 Kbytes (more on some other architectures) to the kernel size. 1198 1199 If unsure say Y. 1200 1201if BLK_DEV_INITRD 1202 1203source "usr/Kconfig" 1204 1205endif 1206 1207choice 1208 prompt "Compiler optimization level" 1209 default CC_OPTIMIZE_FOR_PERFORMANCE 1210 1211config CC_OPTIMIZE_FOR_PERFORMANCE 1212 bool "Optimize for performance" 1213 help 1214 This is the default optimization level for the kernel, building 1215 with the "-O2" compiler flag for best performance and most 1216 helpful compile-time warnings. 1217 1218config CC_OPTIMIZE_FOR_SIZE 1219 bool "Optimize for size" 1220 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives 1221 help 1222 Choosing this option will pass "-Os" to your compiler resulting 1223 in a smaller kernel. 1224 1225endchoice 1226 1227config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1228 bool 1229 help 1230 This requires that the arch annotates or otherwise protects 1231 its external entry points from being discarded. Linker scripts 1232 must also merge .text.*, .data.*, and .bss.* correctly into 1233 output sections. Care must be taken not to pull in unrelated 1234 sections (e.g., '.text.init'). Typically '.' in section names 1235 is used to distinguish them from label names / C identifiers. 1236 1237config LD_DEAD_CODE_DATA_ELIMINATION 1238 bool "Dead code and data elimination (EXPERIMENTAL)" 1239 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1240 depends on EXPERT 1241 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800) 1242 depends on $(cc-option,-ffunction-sections -fdata-sections) 1243 depends on $(ld-option,--gc-sections) 1244 help 1245 Enable this if you want to do dead code and data elimination with 1246 the linker by compiling with -ffunction-sections -fdata-sections, 1247 and linking with --gc-sections. 1248 1249 This can reduce on disk and in-memory size of the kernel 1250 code and static data, particularly for small configs and 1251 on small systems. This has the possibility of introducing 1252 silently broken kernel if the required annotations are not 1253 present. This option is not well tested yet, so use at your 1254 own risk. 1255 1256config SYSCTL 1257 bool 1258 1259config HAVE_UID16 1260 bool 1261 1262config SYSCTL_EXCEPTION_TRACE 1263 bool 1264 help 1265 Enable support for /proc/sys/debug/exception-trace. 1266 1267config SYSCTL_ARCH_UNALIGN_NO_WARN 1268 bool 1269 help 1270 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1271 Allows arch to define/use @no_unaligned_warning to possibly warn 1272 about unaligned access emulation going on under the hood. 1273 1274config SYSCTL_ARCH_UNALIGN_ALLOW 1275 bool 1276 help 1277 Enable support for /proc/sys/kernel/unaligned-trap 1278 Allows arches to define/use @unaligned_enabled to runtime toggle 1279 the unaligned access emulation. 1280 see arch/parisc/kernel/unaligned.c for reference 1281 1282config HAVE_PCSPKR_PLATFORM 1283 bool 1284 1285# interpreter that classic socket filters depend on 1286config BPF 1287 bool 1288 1289menuconfig EXPERT 1290 bool "Configure standard kernel features (expert users)" 1291 # Unhide debug options, to make the on-by-default options visible 1292 select DEBUG_KERNEL 1293 help 1294 This option allows certain base kernel options and settings 1295 to be disabled or tweaked. This is for specialized 1296 environments which can tolerate a "non-standard" kernel. 1297 Only use this if you really know what you are doing. 1298 1299config UID16 1300 bool "Enable 16-bit UID system calls" if EXPERT 1301 depends on HAVE_UID16 && MULTIUSER 1302 default y 1303 help 1304 This enables the legacy 16-bit UID syscall wrappers. 1305 1306config MULTIUSER 1307 bool "Multiple users, groups and capabilities support" if EXPERT 1308 default y 1309 help 1310 This option enables support for non-root users, groups and 1311 capabilities. 1312 1313 If you say N here, all processes will run with UID 0, GID 0, and all 1314 possible capabilities. Saying N here also compiles out support for 1315 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1316 setgid, and capset. 1317 1318 If unsure, say Y here. 1319 1320config SGETMASK_SYSCALL 1321 bool "sgetmask/ssetmask syscalls support" if EXPERT 1322 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1323 ---help--- 1324 sys_sgetmask and sys_ssetmask are obsolete system calls 1325 no longer supported in libc but still enabled by default in some 1326 architectures. 1327 1328 If unsure, leave the default option here. 1329 1330config SYSFS_SYSCALL 1331 bool "Sysfs syscall support" if EXPERT 1332 default y 1333 ---help--- 1334 sys_sysfs is an obsolete system call no longer supported in libc. 1335 Note that disabling this option is more secure but might break 1336 compatibility with some systems. 1337 1338 If unsure say Y here. 1339 1340config SYSCTL_SYSCALL 1341 bool "Sysctl syscall support" if EXPERT 1342 depends on PROC_SYSCTL 1343 default n 1344 select SYSCTL 1345 ---help--- 1346 sys_sysctl uses binary paths that have been found challenging 1347 to properly maintain and use. The interface in /proc/sys 1348 using paths with ascii names is now the primary path to this 1349 information. 1350 1351 Almost nothing using the binary sysctl interface so if you are 1352 trying to save some space it is probably safe to disable this, 1353 making your kernel marginally smaller. 1354 1355 If unsure say N here. 1356 1357config FHANDLE 1358 bool "open by fhandle syscalls" if EXPERT 1359 select EXPORTFS 1360 default y 1361 help 1362 If you say Y here, a user level program will be able to map 1363 file names to handle and then later use the handle for 1364 different file system operations. This is useful in implementing 1365 userspace file servers, which now track files using handles instead 1366 of names. The handle would remain the same even if file names 1367 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1368 syscalls. 1369 1370config POSIX_TIMERS 1371 bool "Posix Clocks & timers" if EXPERT 1372 default y 1373 help 1374 This includes native support for POSIX timers to the kernel. 1375 Some embedded systems have no use for them and therefore they 1376 can be configured out to reduce the size of the kernel image. 1377 1378 When this option is disabled, the following syscalls won't be 1379 available: timer_create, timer_gettime: timer_getoverrun, 1380 timer_settime, timer_delete, clock_adjtime, getitimer, 1381 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1382 clock_getres and clock_nanosleep syscalls will be limited to 1383 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1384 1385 If unsure say y. 1386 1387config PRINTK 1388 default y 1389 bool "Enable support for printk" if EXPERT 1390 select IRQ_WORK 1391 help 1392 This option enables normal printk support. Removing it 1393 eliminates most of the message strings from the kernel image 1394 and makes the kernel more or less silent. As this makes it 1395 very difficult to diagnose system problems, saying N here is 1396 strongly discouraged. 1397 1398config PRINTK_NMI 1399 def_bool y 1400 depends on PRINTK 1401 depends on HAVE_NMI 1402 1403config BUG 1404 bool "BUG() support" if EXPERT 1405 default y 1406 help 1407 Disabling this option eliminates support for BUG and WARN, reducing 1408 the size of your kernel image and potentially quietly ignoring 1409 numerous fatal conditions. You should only consider disabling this 1410 option for embedded systems with no facilities for reporting errors. 1411 Just say Y. 1412 1413config ELF_CORE 1414 depends on COREDUMP 1415 default y 1416 bool "Enable ELF core dumps" if EXPERT 1417 help 1418 Enable support for generating core dumps. Disabling saves about 4k. 1419 1420 1421config PCSPKR_PLATFORM 1422 bool "Enable PC-Speaker support" if EXPERT 1423 depends on HAVE_PCSPKR_PLATFORM 1424 select I8253_LOCK 1425 default y 1426 help 1427 This option allows to disable the internal PC-Speaker 1428 support, saving some memory. 1429 1430config BASE_FULL 1431 default y 1432 bool "Enable full-sized data structures for core" if EXPERT 1433 help 1434 Disabling this option reduces the size of miscellaneous core 1435 kernel data structures. This saves memory on small machines, 1436 but may reduce performance. 1437 1438config FUTEX 1439 bool "Enable futex support" if EXPERT 1440 default y 1441 imply RT_MUTEXES 1442 help 1443 Disabling this option will cause the kernel to be built without 1444 support for "fast userspace mutexes". The resulting kernel may not 1445 run glibc-based applications correctly. 1446 1447config FUTEX_PI 1448 bool 1449 depends on FUTEX && RT_MUTEXES 1450 default y 1451 1452config HAVE_FUTEX_CMPXCHG 1453 bool 1454 depends on FUTEX 1455 help 1456 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1457 is implemented and always working. This removes a couple of runtime 1458 checks. 1459 1460config EPOLL 1461 bool "Enable eventpoll support" if EXPERT 1462 default y 1463 help 1464 Disabling this option will cause the kernel to be built without 1465 support for epoll family of system calls. 1466 1467config SIGNALFD 1468 bool "Enable signalfd() system call" if EXPERT 1469 default y 1470 help 1471 Enable the signalfd() system call that allows to receive signals 1472 on a file descriptor. 1473 1474 If unsure, say Y. 1475 1476config TIMERFD 1477 bool "Enable timerfd() system call" if EXPERT 1478 default y 1479 help 1480 Enable the timerfd() system call that allows to receive timer 1481 events on a file descriptor. 1482 1483 If unsure, say Y. 1484 1485config EVENTFD 1486 bool "Enable eventfd() system call" if EXPERT 1487 default y 1488 help 1489 Enable the eventfd() system call that allows to receive both 1490 kernel notification (ie. KAIO) or userspace notifications. 1491 1492 If unsure, say Y. 1493 1494config SHMEM 1495 bool "Use full shmem filesystem" if EXPERT 1496 default y 1497 depends on MMU 1498 help 1499 The shmem is an internal filesystem used to manage shared memory. 1500 It is backed by swap and manages resource limits. It is also exported 1501 to userspace as tmpfs if TMPFS is enabled. Disabling this 1502 option replaces shmem and tmpfs with the much simpler ramfs code, 1503 which may be appropriate on small systems without swap. 1504 1505config AIO 1506 bool "Enable AIO support" if EXPERT 1507 default y 1508 help 1509 This option enables POSIX asynchronous I/O which may by used 1510 by some high performance threaded applications. Disabling 1511 this option saves about 7k. 1512 1513config IO_URING 1514 bool "Enable IO uring support" if EXPERT 1515 select ANON_INODES 1516 default y 1517 help 1518 This option enables support for the io_uring interface, enabling 1519 applications to submit and complete IO through submission and 1520 completion rings that are shared between the kernel and application. 1521 1522config ADVISE_SYSCALLS 1523 bool "Enable madvise/fadvise syscalls" if EXPERT 1524 default y 1525 help 1526 This option enables the madvise and fadvise syscalls, used by 1527 applications to advise the kernel about their future memory or file 1528 usage, improving performance. If building an embedded system where no 1529 applications use these syscalls, you can disable this option to save 1530 space. 1531 1532config MEMBARRIER 1533 bool "Enable membarrier() system call" if EXPERT 1534 default y 1535 help 1536 Enable the membarrier() system call that allows issuing memory 1537 barriers across all running threads, which can be used to distribute 1538 the cost of user-space memory barriers asymmetrically by transforming 1539 pairs of memory barriers into pairs consisting of membarrier() and a 1540 compiler barrier. 1541 1542 If unsure, say Y. 1543 1544config KALLSYMS 1545 bool "Load all symbols for debugging/ksymoops" if EXPERT 1546 default y 1547 help 1548 Say Y here to let the kernel print out symbolic crash information and 1549 symbolic stack backtraces. This increases the size of the kernel 1550 somewhat, as all symbols have to be loaded into the kernel image. 1551 1552config KALLSYMS_ALL 1553 bool "Include all symbols in kallsyms" 1554 depends on DEBUG_KERNEL && KALLSYMS 1555 help 1556 Normally kallsyms only contains the symbols of functions for nicer 1557 OOPS messages and backtraces (i.e., symbols from the text and inittext 1558 sections). This is sufficient for most cases. And only in very rare 1559 cases (e.g., when a debugger is used) all symbols are required (e.g., 1560 names of variables from the data sections, etc). 1561 1562 This option makes sure that all symbols are loaded into the kernel 1563 image (i.e., symbols from all sections) in cost of increased kernel 1564 size (depending on the kernel configuration, it may be 300KiB or 1565 something like this). 1566 1567 Say N unless you really need all symbols. 1568 1569config KALLSYMS_ABSOLUTE_PERCPU 1570 bool 1571 depends on KALLSYMS 1572 default X86_64 && SMP 1573 1574config KALLSYMS_BASE_RELATIVE 1575 bool 1576 depends on KALLSYMS 1577 default !IA64 1578 help 1579 Instead of emitting them as absolute values in the native word size, 1580 emit the symbol references in the kallsyms table as 32-bit entries, 1581 each containing a relative value in the range [base, base + U32_MAX] 1582 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1583 an absolute value in the range [0, S32_MAX] or a relative value in the 1584 range [base, base + S32_MAX], where base is the lowest relative symbol 1585 address encountered in the image. 1586 1587 On 64-bit builds, this reduces the size of the address table by 50%, 1588 but more importantly, it results in entries whose values are build 1589 time constants, and no relocation pass is required at runtime to fix 1590 up the entries based on the runtime load address of the kernel. 1591 1592# end of the "standard kernel features (expert users)" menu 1593 1594# syscall, maps, verifier 1595config BPF_SYSCALL 1596 bool "Enable bpf() system call" 1597 select BPF 1598 select IRQ_WORK 1599 default n 1600 help 1601 Enable the bpf() system call that allows to manipulate eBPF 1602 programs and maps via file descriptors. 1603 1604config BPF_JIT_ALWAYS_ON 1605 bool "Permanently enable BPF JIT and remove BPF interpreter" 1606 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1607 help 1608 Enables BPF JIT and removes BPF interpreter to avoid 1609 speculative execution of BPF instructions by the interpreter 1610 1611config USERFAULTFD 1612 bool "Enable userfaultfd() system call" 1613 depends on MMU 1614 help 1615 Enable the userfaultfd() system call that allows to intercept and 1616 handle page faults in userland. 1617 1618config ARCH_HAS_MEMBARRIER_CALLBACKS 1619 bool 1620 1621config ARCH_HAS_MEMBARRIER_SYNC_CORE 1622 bool 1623 1624config RSEQ 1625 bool "Enable rseq() system call" if EXPERT 1626 default y 1627 depends on HAVE_RSEQ 1628 select MEMBARRIER 1629 help 1630 Enable the restartable sequences system call. It provides a 1631 user-space cache for the current CPU number value, which 1632 speeds up getting the current CPU number from user-space, 1633 as well as an ABI to speed up user-space operations on 1634 per-CPU data. 1635 1636 If unsure, say Y. 1637 1638config DEBUG_RSEQ 1639 default n 1640 bool "Enabled debugging of rseq() system call" if EXPERT 1641 depends on RSEQ && DEBUG_KERNEL 1642 help 1643 Enable extra debugging checks for the rseq system call. 1644 1645 If unsure, say N. 1646 1647config EMBEDDED 1648 bool "Embedded system" 1649 option allnoconfig_y 1650 select EXPERT 1651 help 1652 This option should be enabled if compiling the kernel for 1653 an embedded system so certain expert options are available 1654 for configuration. 1655 1656config HAVE_PERF_EVENTS 1657 bool 1658 help 1659 See tools/perf/design.txt for details. 1660 1661config PERF_USE_VMALLOC 1662 bool 1663 help 1664 See tools/perf/design.txt for details 1665 1666config PC104 1667 bool "PC/104 support" if EXPERT 1668 help 1669 Expose PC/104 form factor device drivers and options available for 1670 selection and configuration. Enable this option if your target 1671 machine has a PC/104 bus. 1672 1673menu "Kernel Performance Events And Counters" 1674 1675config PERF_EVENTS 1676 bool "Kernel performance events and counters" 1677 default y if PROFILING 1678 depends on HAVE_PERF_EVENTS 1679 select IRQ_WORK 1680 select SRCU 1681 help 1682 Enable kernel support for various performance events provided 1683 by software and hardware. 1684 1685 Software events are supported either built-in or via the 1686 use of generic tracepoints. 1687 1688 Most modern CPUs support performance events via performance 1689 counter registers. These registers count the number of certain 1690 types of hw events: such as instructions executed, cachemisses 1691 suffered, or branches mis-predicted - without slowing down the 1692 kernel or applications. These registers can also trigger interrupts 1693 when a threshold number of events have passed - and can thus be 1694 used to profile the code that runs on that CPU. 1695 1696 The Linux Performance Event subsystem provides an abstraction of 1697 these software and hardware event capabilities, available via a 1698 system call and used by the "perf" utility in tools/perf/. It 1699 provides per task and per CPU counters, and it provides event 1700 capabilities on top of those. 1701 1702 Say Y if unsure. 1703 1704config DEBUG_PERF_USE_VMALLOC 1705 default n 1706 bool "Debug: use vmalloc to back perf mmap() buffers" 1707 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1708 select PERF_USE_VMALLOC 1709 help 1710 Use vmalloc memory to back perf mmap() buffers. 1711 1712 Mostly useful for debugging the vmalloc code on platforms 1713 that don't require it. 1714 1715 Say N if unsure. 1716 1717endmenu 1718 1719config VM_EVENT_COUNTERS 1720 default y 1721 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1722 help 1723 VM event counters are needed for event counts to be shown. 1724 This option allows the disabling of the VM event counters 1725 on EXPERT systems. /proc/vmstat will only show page counts 1726 if VM event counters are disabled. 1727 1728config SLUB_DEBUG 1729 default y 1730 bool "Enable SLUB debugging support" if EXPERT 1731 depends on SLUB && SYSFS 1732 help 1733 SLUB has extensive debug support features. Disabling these can 1734 result in significant savings in code size. This also disables 1735 SLUB sysfs support. /sys/slab will not exist and there will be 1736 no support for cache validation etc. 1737 1738config SLUB_MEMCG_SYSFS_ON 1739 default n 1740 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1741 depends on SLUB && SYSFS && MEMCG 1742 help 1743 SLUB creates a directory under /sys/kernel/slab for each 1744 allocation cache to host info and debug files. If memory 1745 cgroup is enabled, each cache can have per memory cgroup 1746 caches. SLUB can create the same sysfs directories for these 1747 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1748 to a very high number of debug files being created. This is 1749 controlled by slub_memcg_sysfs boot parameter and this 1750 config option determines the parameter's default value. 1751 1752config COMPAT_BRK 1753 bool "Disable heap randomization" 1754 default y 1755 help 1756 Randomizing heap placement makes heap exploits harder, but it 1757 also breaks ancient binaries (including anything libc5 based). 1758 This option changes the bootup default to heap randomization 1759 disabled, and can be overridden at runtime by setting 1760 /proc/sys/kernel/randomize_va_space to 2. 1761 1762 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1763 1764choice 1765 prompt "Choose SLAB allocator" 1766 default SLUB 1767 help 1768 This option allows to select a slab allocator. 1769 1770config SLAB 1771 bool "SLAB" 1772 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1773 help 1774 The regular slab allocator that is established and known to work 1775 well in all environments. It organizes cache hot objects in 1776 per cpu and per node queues. 1777 1778config SLUB 1779 bool "SLUB (Unqueued Allocator)" 1780 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1781 help 1782 SLUB is a slab allocator that minimizes cache line usage 1783 instead of managing queues of cached objects (SLAB approach). 1784 Per cpu caching is realized using slabs of objects instead 1785 of queues of objects. SLUB can use memory efficiently 1786 and has enhanced diagnostics. SLUB is the default choice for 1787 a slab allocator. 1788 1789config SLOB 1790 depends on EXPERT 1791 bool "SLOB (Simple Allocator)" 1792 help 1793 SLOB replaces the stock allocator with a drastically simpler 1794 allocator. SLOB is generally more space efficient but 1795 does not perform as well on large systems. 1796 1797endchoice 1798 1799config SLAB_MERGE_DEFAULT 1800 bool "Allow slab caches to be merged" 1801 default y 1802 help 1803 For reduced kernel memory fragmentation, slab caches can be 1804 merged when they share the same size and other characteristics. 1805 This carries a risk of kernel heap overflows being able to 1806 overwrite objects from merged caches (and more easily control 1807 cache layout), which makes such heap attacks easier to exploit 1808 by attackers. By keeping caches unmerged, these kinds of exploits 1809 can usually only damage objects in the same cache. To disable 1810 merging at runtime, "slab_nomerge" can be passed on the kernel 1811 command line. 1812 1813config SLAB_FREELIST_RANDOM 1814 default n 1815 depends on SLAB || SLUB 1816 bool "SLAB freelist randomization" 1817 help 1818 Randomizes the freelist order used on creating new pages. This 1819 security feature reduces the predictability of the kernel slab 1820 allocator against heap overflows. 1821 1822config SLAB_FREELIST_HARDENED 1823 bool "Harden slab freelist metadata" 1824 depends on SLUB 1825 help 1826 Many kernel heap attacks try to target slab cache metadata and 1827 other infrastructure. This options makes minor performance 1828 sacrifices to harden the kernel slab allocator against common 1829 freelist exploit methods. 1830 1831config SHUFFLE_PAGE_ALLOCATOR 1832 bool "Page allocator randomization" 1833 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1834 help 1835 Randomization of the page allocator improves the average 1836 utilization of a direct-mapped memory-side-cache. See section 1837 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1838 6.2a specification for an example of how a platform advertises 1839 the presence of a memory-side-cache. There are also incidental 1840 security benefits as it reduces the predictability of page 1841 allocations to compliment SLAB_FREELIST_RANDOM, but the 1842 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1843 10th order of pages is selected based on cache utilization 1844 benefits on x86. 1845 1846 While the randomization improves cache utilization it may 1847 negatively impact workloads on platforms without a cache. For 1848 this reason, by default, the randomization is enabled only 1849 after runtime detection of a direct-mapped memory-side-cache. 1850 Otherwise, the randomization may be force enabled with the 1851 'page_alloc.shuffle' kernel command line parameter. 1852 1853 Say Y if unsure. 1854 1855config SLUB_CPU_PARTIAL 1856 default y 1857 depends on SLUB && SMP 1858 bool "SLUB per cpu partial cache" 1859 help 1860 Per cpu partial caches accelerate objects allocation and freeing 1861 that is local to a processor at the price of more indeterminism 1862 in the latency of the free. On overflow these caches will be cleared 1863 which requires the taking of locks that may cause latency spikes. 1864 Typically one would choose no for a realtime system. 1865 1866config MMAP_ALLOW_UNINITIALIZED 1867 bool "Allow mmapped anonymous memory to be uninitialized" 1868 depends on EXPERT && !MMU 1869 default n 1870 help 1871 Normally, and according to the Linux spec, anonymous memory obtained 1872 from mmap() has its contents cleared before it is passed to 1873 userspace. Enabling this config option allows you to request that 1874 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1875 providing a huge performance boost. If this option is not enabled, 1876 then the flag will be ignored. 1877 1878 This is taken advantage of by uClibc's malloc(), and also by 1879 ELF-FDPIC binfmt's brk and stack allocator. 1880 1881 Because of the obvious security issues, this option should only be 1882 enabled on embedded devices where you control what is run in 1883 userspace. Since that isn't generally a problem on no-MMU systems, 1884 it is normally safe to say Y here. 1885 1886 See Documentation/nommu-mmap.txt for more information. 1887 1888config SYSTEM_DATA_VERIFICATION 1889 def_bool n 1890 select SYSTEM_TRUSTED_KEYRING 1891 select KEYS 1892 select CRYPTO 1893 select CRYPTO_RSA 1894 select ASYMMETRIC_KEY_TYPE 1895 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1896 select ASN1 1897 select OID_REGISTRY 1898 select X509_CERTIFICATE_PARSER 1899 select PKCS7_MESSAGE_PARSER 1900 help 1901 Provide PKCS#7 message verification using the contents of the system 1902 trusted keyring to provide public keys. This then can be used for 1903 module verification, kexec image verification and firmware blob 1904 verification. 1905 1906config PROFILING 1907 bool "Profiling support" 1908 help 1909 Say Y here to enable the extended profiling support mechanisms used 1910 by profilers such as OProfile. 1911 1912# 1913# Place an empty function call at each tracepoint site. Can be 1914# dynamically changed for a probe function. 1915# 1916config TRACEPOINTS 1917 bool 1918 1919endmenu # General setup 1920 1921source "arch/Kconfig" 1922 1923config RT_MUTEXES 1924 bool 1925 1926config BASE_SMALL 1927 int 1928 default 0 if BASE_FULL 1929 default 1 if !BASE_FULL 1930 1931menuconfig MODULES 1932 bool "Enable loadable module support" 1933 option modules 1934 help 1935 Kernel modules are small pieces of compiled code which can 1936 be inserted in the running kernel, rather than being 1937 permanently built into the kernel. You use the "modprobe" 1938 tool to add (and sometimes remove) them. If you say Y here, 1939 many parts of the kernel can be built as modules (by 1940 answering M instead of Y where indicated): this is most 1941 useful for infrequently used options which are not required 1942 for booting. For more information, see the man pages for 1943 modprobe, lsmod, modinfo, insmod and rmmod. 1944 1945 If you say Y here, you will need to run "make 1946 modules_install" to put the modules under /lib/modules/ 1947 where modprobe can find them (you may need to be root to do 1948 this). 1949 1950 If unsure, say Y. 1951 1952if MODULES 1953 1954config MODULE_FORCE_LOAD 1955 bool "Forced module loading" 1956 default n 1957 help 1958 Allow loading of modules without version information (ie. modprobe 1959 --force). Forced module loading sets the 'F' (forced) taint flag and 1960 is usually a really bad idea. 1961 1962config MODULE_UNLOAD 1963 bool "Module unloading" 1964 help 1965 Without this option you will not be able to unload any 1966 modules (note that some modules may not be unloadable 1967 anyway), which makes your kernel smaller, faster 1968 and simpler. If unsure, say Y. 1969 1970config MODULE_FORCE_UNLOAD 1971 bool "Forced module unloading" 1972 depends on MODULE_UNLOAD 1973 help 1974 This option allows you to force a module to unload, even if the 1975 kernel believes it is unsafe: the kernel will remove the module 1976 without waiting for anyone to stop using it (using the -f option to 1977 rmmod). This is mainly for kernel developers and desperate users. 1978 If unsure, say N. 1979 1980config MODVERSIONS 1981 bool "Module versioning support" 1982 help 1983 Usually, you have to use modules compiled with your kernel. 1984 Saying Y here makes it sometimes possible to use modules 1985 compiled for different kernels, by adding enough information 1986 to the modules to (hopefully) spot any changes which would 1987 make them incompatible with the kernel you are running. If 1988 unsure, say N. 1989 1990config ASM_MODVERSIONS 1991 bool 1992 default HAVE_ASM_MODVERSIONS && MODVERSIONS 1993 help 1994 This enables module versioning for exported symbols also from 1995 assembly. This can be enabled only when the target architecture 1996 supports it. 1997 1998config MODULE_REL_CRCS 1999 bool 2000 depends on MODVERSIONS 2001 2002config MODULE_SRCVERSION_ALL 2003 bool "Source checksum for all modules" 2004 help 2005 Modules which contain a MODULE_VERSION get an extra "srcversion" 2006 field inserted into their modinfo section, which contains a 2007 sum of the source files which made it. This helps maintainers 2008 see exactly which source was used to build a module (since 2009 others sometimes change the module source without updating 2010 the version). With this option, such a "srcversion" field 2011 will be created for all modules. If unsure, say N. 2012 2013config MODULE_SIG 2014 bool "Module signature verification" 2015 depends on MODULES 2016 select SYSTEM_DATA_VERIFICATION 2017 help 2018 Check modules for valid signatures upon load: the signature 2019 is simply appended to the module. For more information see 2020 <file:Documentation/admin-guide/module-signing.rst>. 2021 2022 Note that this option adds the OpenSSL development packages as a 2023 kernel build dependency so that the signing tool can use its crypto 2024 library. 2025 2026 !!!WARNING!!! If you enable this option, you MUST make sure that the 2027 module DOES NOT get stripped after being signed. This includes the 2028 debuginfo strip done by some packagers (such as rpmbuild) and 2029 inclusion into an initramfs that wants the module size reduced. 2030 2031config MODULE_SIG_FORCE 2032 bool "Require modules to be validly signed" 2033 depends on MODULE_SIG 2034 help 2035 Reject unsigned modules or signed modules for which we don't have a 2036 key. Without this, such modules will simply taint the kernel. 2037 2038config MODULE_SIG_ALL 2039 bool "Automatically sign all modules" 2040 default y 2041 depends on MODULE_SIG 2042 help 2043 Sign all modules during make modules_install. Without this option, 2044 modules must be signed manually, using the scripts/sign-file tool. 2045 2046comment "Do not forget to sign required modules with scripts/sign-file" 2047 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2048 2049choice 2050 prompt "Which hash algorithm should modules be signed with?" 2051 depends on MODULE_SIG 2052 help 2053 This determines which sort of hashing algorithm will be used during 2054 signature generation. This algorithm _must_ be built into the kernel 2055 directly so that signature verification can take place. It is not 2056 possible to load a signed module containing the algorithm to check 2057 the signature on that module. 2058 2059config MODULE_SIG_SHA1 2060 bool "Sign modules with SHA-1" 2061 select CRYPTO_SHA1 2062 2063config MODULE_SIG_SHA224 2064 bool "Sign modules with SHA-224" 2065 select CRYPTO_SHA256 2066 2067config MODULE_SIG_SHA256 2068 bool "Sign modules with SHA-256" 2069 select CRYPTO_SHA256 2070 2071config MODULE_SIG_SHA384 2072 bool "Sign modules with SHA-384" 2073 select CRYPTO_SHA512 2074 2075config MODULE_SIG_SHA512 2076 bool "Sign modules with SHA-512" 2077 select CRYPTO_SHA512 2078 2079endchoice 2080 2081config MODULE_SIG_HASH 2082 string 2083 depends on MODULE_SIG 2084 default "sha1" if MODULE_SIG_SHA1 2085 default "sha224" if MODULE_SIG_SHA224 2086 default "sha256" if MODULE_SIG_SHA256 2087 default "sha384" if MODULE_SIG_SHA384 2088 default "sha512" if MODULE_SIG_SHA512 2089 2090config MODULE_COMPRESS 2091 bool "Compress modules on installation" 2092 depends on MODULES 2093 help 2094 2095 Compresses kernel modules when 'make modules_install' is run; gzip or 2096 xz depending on "Compression algorithm" below. 2097 2098 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 2099 2100 Out-of-tree kernel modules installed using Kbuild will also be 2101 compressed upon installation. 2102 2103 Note: for modules inside an initrd or initramfs, it's more efficient 2104 to compress the whole initrd or initramfs instead. 2105 2106 Note: This is fully compatible with signed modules. 2107 2108 If in doubt, say N. 2109 2110choice 2111 prompt "Compression algorithm" 2112 depends on MODULE_COMPRESS 2113 default MODULE_COMPRESS_GZIP 2114 help 2115 This determines which sort of compression will be used during 2116 'make modules_install'. 2117 2118 GZIP (default) and XZ are supported. 2119 2120config MODULE_COMPRESS_GZIP 2121 bool "GZIP" 2122 2123config MODULE_COMPRESS_XZ 2124 bool "XZ" 2125 2126endchoice 2127 2128config TRIM_UNUSED_KSYMS 2129 bool "Trim unused exported kernel symbols" 2130 depends on MODULES && !UNUSED_SYMBOLS 2131 help 2132 The kernel and some modules make many symbols available for 2133 other modules to use via EXPORT_SYMBOL() and variants. Depending 2134 on the set of modules being selected in your kernel configuration, 2135 many of those exported symbols might never be used. 2136 2137 This option allows for unused exported symbols to be dropped from 2138 the build. In turn, this provides the compiler more opportunities 2139 (especially when using LTO) for optimizing the code and reducing 2140 binary size. This might have some security advantages as well. 2141 2142 If unsure, or if you need to build out-of-tree modules, say N. 2143 2144endif # MODULES 2145 2146config MODULES_TREE_LOOKUP 2147 def_bool y 2148 depends on PERF_EVENTS || TRACING 2149 2150config INIT_ALL_POSSIBLE 2151 bool 2152 help 2153 Back when each arch used to define their own cpu_online_mask and 2154 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2155 with all 1s, and others with all 0s. When they were centralised, 2156 it was better to provide this option than to break all the archs 2157 and have several arch maintainers pursuing me down dark alleys. 2158 2159source "block/Kconfig" 2160 2161config PREEMPT_NOTIFIERS 2162 bool 2163 2164config PADATA 2165 depends on SMP 2166 bool 2167 2168config ASN1 2169 tristate 2170 help 2171 Build a simple ASN.1 grammar compiler that produces a bytecode output 2172 that can be interpreted by the ASN.1 stream decoder and used to 2173 inform it as to what tags are to be expected in a stream and what 2174 functions to call on what tags. 2175 2176source "kernel/Kconfig.locks" 2177 2178config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2179 bool 2180 2181# It may be useful for an architecture to override the definitions of the 2182# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2183# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2184# different calling convention for syscalls. They can also override the 2185# macros for not-implemented syscalls in kernel/sys_ni.c and 2186# kernel/time/posix-stubs.c. All these overrides need to be available in 2187# <asm/syscall_wrapper.h>. 2188config ARCH_HAS_SYSCALL_WRAPPER 2189 def_bool n 2190