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 Enabling this option will pass "-Os" instead of "-O2" to 1223 your compiler resulting in a smaller kernel. 1224 1225 If unsure, say N. 1226 1227endchoice 1228 1229config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1230 bool 1231 help 1232 This requires that the arch annotates or otherwise protects 1233 its external entry points from being discarded. Linker scripts 1234 must also merge .text.*, .data.*, and .bss.* correctly into 1235 output sections. Care must be taken not to pull in unrelated 1236 sections (e.g., '.text.init'). Typically '.' in section names 1237 is used to distinguish them from label names / C identifiers. 1238 1239config LD_DEAD_CODE_DATA_ELIMINATION 1240 bool "Dead code and data elimination (EXPERIMENTAL)" 1241 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1242 depends on EXPERT 1243 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800) 1244 depends on $(cc-option,-ffunction-sections -fdata-sections) 1245 depends on $(ld-option,--gc-sections) 1246 help 1247 Enable this if you want to do dead code and data elimination with 1248 the linker by compiling with -ffunction-sections -fdata-sections, 1249 and linking with --gc-sections. 1250 1251 This can reduce on disk and in-memory size of the kernel 1252 code and static data, particularly for small configs and 1253 on small systems. This has the possibility of introducing 1254 silently broken kernel if the required annotations are not 1255 present. This option is not well tested yet, so use at your 1256 own risk. 1257 1258config SYSCTL 1259 bool 1260 1261config HAVE_UID16 1262 bool 1263 1264config SYSCTL_EXCEPTION_TRACE 1265 bool 1266 help 1267 Enable support for /proc/sys/debug/exception-trace. 1268 1269config SYSCTL_ARCH_UNALIGN_NO_WARN 1270 bool 1271 help 1272 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1273 Allows arch to define/use @no_unaligned_warning to possibly warn 1274 about unaligned access emulation going on under the hood. 1275 1276config SYSCTL_ARCH_UNALIGN_ALLOW 1277 bool 1278 help 1279 Enable support for /proc/sys/kernel/unaligned-trap 1280 Allows arches to define/use @unaligned_enabled to runtime toggle 1281 the unaligned access emulation. 1282 see arch/parisc/kernel/unaligned.c for reference 1283 1284config HAVE_PCSPKR_PLATFORM 1285 bool 1286 1287# interpreter that classic socket filters depend on 1288config BPF 1289 bool 1290 1291menuconfig EXPERT 1292 bool "Configure standard kernel features (expert users)" 1293 # Unhide debug options, to make the on-by-default options visible 1294 select DEBUG_KERNEL 1295 help 1296 This option allows certain base kernel options and settings 1297 to be disabled or tweaked. This is for specialized 1298 environments which can tolerate a "non-standard" kernel. 1299 Only use this if you really know what you are doing. 1300 1301config UID16 1302 bool "Enable 16-bit UID system calls" if EXPERT 1303 depends on HAVE_UID16 && MULTIUSER 1304 default y 1305 help 1306 This enables the legacy 16-bit UID syscall wrappers. 1307 1308config MULTIUSER 1309 bool "Multiple users, groups and capabilities support" if EXPERT 1310 default y 1311 help 1312 This option enables support for non-root users, groups and 1313 capabilities. 1314 1315 If you say N here, all processes will run with UID 0, GID 0, and all 1316 possible capabilities. Saying N here also compiles out support for 1317 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1318 setgid, and capset. 1319 1320 If unsure, say Y here. 1321 1322config SGETMASK_SYSCALL 1323 bool "sgetmask/ssetmask syscalls support" if EXPERT 1324 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1325 ---help--- 1326 sys_sgetmask and sys_ssetmask are obsolete system calls 1327 no longer supported in libc but still enabled by default in some 1328 architectures. 1329 1330 If unsure, leave the default option here. 1331 1332config SYSFS_SYSCALL 1333 bool "Sysfs syscall support" if EXPERT 1334 default y 1335 ---help--- 1336 sys_sysfs is an obsolete system call no longer supported in libc. 1337 Note that disabling this option is more secure but might break 1338 compatibility with some systems. 1339 1340 If unsure say Y here. 1341 1342config SYSCTL_SYSCALL 1343 bool "Sysctl syscall support" if EXPERT 1344 depends on PROC_SYSCTL 1345 default n 1346 select SYSCTL 1347 ---help--- 1348 sys_sysctl uses binary paths that have been found challenging 1349 to properly maintain and use. The interface in /proc/sys 1350 using paths with ascii names is now the primary path to this 1351 information. 1352 1353 Almost nothing using the binary sysctl interface so if you are 1354 trying to save some space it is probably safe to disable this, 1355 making your kernel marginally smaller. 1356 1357 If unsure say N here. 1358 1359config FHANDLE 1360 bool "open by fhandle syscalls" if EXPERT 1361 select EXPORTFS 1362 default y 1363 help 1364 If you say Y here, a user level program will be able to map 1365 file names to handle and then later use the handle for 1366 different file system operations. This is useful in implementing 1367 userspace file servers, which now track files using handles instead 1368 of names. The handle would remain the same even if file names 1369 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1370 syscalls. 1371 1372config POSIX_TIMERS 1373 bool "Posix Clocks & timers" if EXPERT 1374 default y 1375 help 1376 This includes native support for POSIX timers to the kernel. 1377 Some embedded systems have no use for them and therefore they 1378 can be configured out to reduce the size of the kernel image. 1379 1380 When this option is disabled, the following syscalls won't be 1381 available: timer_create, timer_gettime: timer_getoverrun, 1382 timer_settime, timer_delete, clock_adjtime, getitimer, 1383 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1384 clock_getres and clock_nanosleep syscalls will be limited to 1385 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1386 1387 If unsure say y. 1388 1389config PRINTK 1390 default y 1391 bool "Enable support for printk" if EXPERT 1392 select IRQ_WORK 1393 help 1394 This option enables normal printk support. Removing it 1395 eliminates most of the message strings from the kernel image 1396 and makes the kernel more or less silent. As this makes it 1397 very difficult to diagnose system problems, saying N here is 1398 strongly discouraged. 1399 1400config PRINTK_NMI 1401 def_bool y 1402 depends on PRINTK 1403 depends on HAVE_NMI 1404 1405config BUG 1406 bool "BUG() support" if EXPERT 1407 default y 1408 help 1409 Disabling this option eliminates support for BUG and WARN, reducing 1410 the size of your kernel image and potentially quietly ignoring 1411 numerous fatal conditions. You should only consider disabling this 1412 option for embedded systems with no facilities for reporting errors. 1413 Just say Y. 1414 1415config ELF_CORE 1416 depends on COREDUMP 1417 default y 1418 bool "Enable ELF core dumps" if EXPERT 1419 help 1420 Enable support for generating core dumps. Disabling saves about 4k. 1421 1422 1423config PCSPKR_PLATFORM 1424 bool "Enable PC-Speaker support" if EXPERT 1425 depends on HAVE_PCSPKR_PLATFORM 1426 select I8253_LOCK 1427 default y 1428 help 1429 This option allows to disable the internal PC-Speaker 1430 support, saving some memory. 1431 1432config BASE_FULL 1433 default y 1434 bool "Enable full-sized data structures for core" if EXPERT 1435 help 1436 Disabling this option reduces the size of miscellaneous core 1437 kernel data structures. This saves memory on small machines, 1438 but may reduce performance. 1439 1440config FUTEX 1441 bool "Enable futex support" if EXPERT 1442 default y 1443 imply RT_MUTEXES 1444 help 1445 Disabling this option will cause the kernel to be built without 1446 support for "fast userspace mutexes". The resulting kernel may not 1447 run glibc-based applications correctly. 1448 1449config FUTEX_PI 1450 bool 1451 depends on FUTEX && RT_MUTEXES 1452 default y 1453 1454config HAVE_FUTEX_CMPXCHG 1455 bool 1456 depends on FUTEX 1457 help 1458 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1459 is implemented and always working. This removes a couple of runtime 1460 checks. 1461 1462config EPOLL 1463 bool "Enable eventpoll support" if EXPERT 1464 default y 1465 help 1466 Disabling this option will cause the kernel to be built without 1467 support for epoll family of system calls. 1468 1469config SIGNALFD 1470 bool "Enable signalfd() system call" if EXPERT 1471 default y 1472 help 1473 Enable the signalfd() system call that allows to receive signals 1474 on a file descriptor. 1475 1476 If unsure, say Y. 1477 1478config TIMERFD 1479 bool "Enable timerfd() system call" if EXPERT 1480 default y 1481 help 1482 Enable the timerfd() system call that allows to receive timer 1483 events on a file descriptor. 1484 1485 If unsure, say Y. 1486 1487config EVENTFD 1488 bool "Enable eventfd() system call" if EXPERT 1489 default y 1490 help 1491 Enable the eventfd() system call that allows to receive both 1492 kernel notification (ie. KAIO) or userspace notifications. 1493 1494 If unsure, say Y. 1495 1496config SHMEM 1497 bool "Use full shmem filesystem" if EXPERT 1498 default y 1499 depends on MMU 1500 help 1501 The shmem is an internal filesystem used to manage shared memory. 1502 It is backed by swap and manages resource limits. It is also exported 1503 to userspace as tmpfs if TMPFS is enabled. Disabling this 1504 option replaces shmem and tmpfs with the much simpler ramfs code, 1505 which may be appropriate on small systems without swap. 1506 1507config AIO 1508 bool "Enable AIO support" if EXPERT 1509 default y 1510 help 1511 This option enables POSIX asynchronous I/O which may by used 1512 by some high performance threaded applications. Disabling 1513 this option saves about 7k. 1514 1515config IO_URING 1516 bool "Enable IO uring support" if EXPERT 1517 select ANON_INODES 1518 default y 1519 help 1520 This option enables support for the io_uring interface, enabling 1521 applications to submit and complete IO through submission and 1522 completion rings that are shared between the kernel and application. 1523 1524config ADVISE_SYSCALLS 1525 bool "Enable madvise/fadvise syscalls" if EXPERT 1526 default y 1527 help 1528 This option enables the madvise and fadvise syscalls, used by 1529 applications to advise the kernel about their future memory or file 1530 usage, improving performance. If building an embedded system where no 1531 applications use these syscalls, you can disable this option to save 1532 space. 1533 1534config MEMBARRIER 1535 bool "Enable membarrier() system call" if EXPERT 1536 default y 1537 help 1538 Enable the membarrier() system call that allows issuing memory 1539 barriers across all running threads, which can be used to distribute 1540 the cost of user-space memory barriers asymmetrically by transforming 1541 pairs of memory barriers into pairs consisting of membarrier() and a 1542 compiler barrier. 1543 1544 If unsure, say Y. 1545 1546config KALLSYMS 1547 bool "Load all symbols for debugging/ksymoops" if EXPERT 1548 default y 1549 help 1550 Say Y here to let the kernel print out symbolic crash information and 1551 symbolic stack backtraces. This increases the size of the kernel 1552 somewhat, as all symbols have to be loaded into the kernel image. 1553 1554config KALLSYMS_ALL 1555 bool "Include all symbols in kallsyms" 1556 depends on DEBUG_KERNEL && KALLSYMS 1557 help 1558 Normally kallsyms only contains the symbols of functions for nicer 1559 OOPS messages and backtraces (i.e., symbols from the text and inittext 1560 sections). This is sufficient for most cases. And only in very rare 1561 cases (e.g., when a debugger is used) all symbols are required (e.g., 1562 names of variables from the data sections, etc). 1563 1564 This option makes sure that all symbols are loaded into the kernel 1565 image (i.e., symbols from all sections) in cost of increased kernel 1566 size (depending on the kernel configuration, it may be 300KiB or 1567 something like this). 1568 1569 Say N unless you really need all symbols. 1570 1571config KALLSYMS_ABSOLUTE_PERCPU 1572 bool 1573 depends on KALLSYMS 1574 default X86_64 && SMP 1575 1576config KALLSYMS_BASE_RELATIVE 1577 bool 1578 depends on KALLSYMS 1579 default !IA64 1580 help 1581 Instead of emitting them as absolute values in the native word size, 1582 emit the symbol references in the kallsyms table as 32-bit entries, 1583 each containing a relative value in the range [base, base + U32_MAX] 1584 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1585 an absolute value in the range [0, S32_MAX] or a relative value in the 1586 range [base, base + S32_MAX], where base is the lowest relative symbol 1587 address encountered in the image. 1588 1589 On 64-bit builds, this reduces the size of the address table by 50%, 1590 but more importantly, it results in entries whose values are build 1591 time constants, and no relocation pass is required at runtime to fix 1592 up the entries based on the runtime load address of the kernel. 1593 1594# end of the "standard kernel features (expert users)" menu 1595 1596# syscall, maps, verifier 1597config BPF_SYSCALL 1598 bool "Enable bpf() system call" 1599 select BPF 1600 select IRQ_WORK 1601 default n 1602 help 1603 Enable the bpf() system call that allows to manipulate eBPF 1604 programs and maps via file descriptors. 1605 1606config BPF_JIT_ALWAYS_ON 1607 bool "Permanently enable BPF JIT and remove BPF interpreter" 1608 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1609 help 1610 Enables BPF JIT and removes BPF interpreter to avoid 1611 speculative execution of BPF instructions by the interpreter 1612 1613config USERFAULTFD 1614 bool "Enable userfaultfd() system call" 1615 depends on MMU 1616 help 1617 Enable the userfaultfd() system call that allows to intercept and 1618 handle page faults in userland. 1619 1620config ARCH_HAS_MEMBARRIER_CALLBACKS 1621 bool 1622 1623config ARCH_HAS_MEMBARRIER_SYNC_CORE 1624 bool 1625 1626config RSEQ 1627 bool "Enable rseq() system call" if EXPERT 1628 default y 1629 depends on HAVE_RSEQ 1630 select MEMBARRIER 1631 help 1632 Enable the restartable sequences system call. It provides a 1633 user-space cache for the current CPU number value, which 1634 speeds up getting the current CPU number from user-space, 1635 as well as an ABI to speed up user-space operations on 1636 per-CPU data. 1637 1638 If unsure, say Y. 1639 1640config DEBUG_RSEQ 1641 default n 1642 bool "Enabled debugging of rseq() system call" if EXPERT 1643 depends on RSEQ && DEBUG_KERNEL 1644 help 1645 Enable extra debugging checks for the rseq system call. 1646 1647 If unsure, say N. 1648 1649config EMBEDDED 1650 bool "Embedded system" 1651 option allnoconfig_y 1652 select EXPERT 1653 help 1654 This option should be enabled if compiling the kernel for 1655 an embedded system so certain expert options are available 1656 for configuration. 1657 1658config HAVE_PERF_EVENTS 1659 bool 1660 help 1661 See tools/perf/design.txt for details. 1662 1663config PERF_USE_VMALLOC 1664 bool 1665 help 1666 See tools/perf/design.txt for details 1667 1668config PC104 1669 bool "PC/104 support" if EXPERT 1670 help 1671 Expose PC/104 form factor device drivers and options available for 1672 selection and configuration. Enable this option if your target 1673 machine has a PC/104 bus. 1674 1675menu "Kernel Performance Events And Counters" 1676 1677config PERF_EVENTS 1678 bool "Kernel performance events and counters" 1679 default y if PROFILING 1680 depends on HAVE_PERF_EVENTS 1681 select IRQ_WORK 1682 select SRCU 1683 help 1684 Enable kernel support for various performance events provided 1685 by software and hardware. 1686 1687 Software events are supported either built-in or via the 1688 use of generic tracepoints. 1689 1690 Most modern CPUs support performance events via performance 1691 counter registers. These registers count the number of certain 1692 types of hw events: such as instructions executed, cachemisses 1693 suffered, or branches mis-predicted - without slowing down the 1694 kernel or applications. These registers can also trigger interrupts 1695 when a threshold number of events have passed - and can thus be 1696 used to profile the code that runs on that CPU. 1697 1698 The Linux Performance Event subsystem provides an abstraction of 1699 these software and hardware event capabilities, available via a 1700 system call and used by the "perf" utility in tools/perf/. It 1701 provides per task and per CPU counters, and it provides event 1702 capabilities on top of those. 1703 1704 Say Y if unsure. 1705 1706config DEBUG_PERF_USE_VMALLOC 1707 default n 1708 bool "Debug: use vmalloc to back perf mmap() buffers" 1709 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1710 select PERF_USE_VMALLOC 1711 help 1712 Use vmalloc memory to back perf mmap() buffers. 1713 1714 Mostly useful for debugging the vmalloc code on platforms 1715 that don't require it. 1716 1717 Say N if unsure. 1718 1719endmenu 1720 1721config VM_EVENT_COUNTERS 1722 default y 1723 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1724 help 1725 VM event counters are needed for event counts to be shown. 1726 This option allows the disabling of the VM event counters 1727 on EXPERT systems. /proc/vmstat will only show page counts 1728 if VM event counters are disabled. 1729 1730config SLUB_DEBUG 1731 default y 1732 bool "Enable SLUB debugging support" if EXPERT 1733 depends on SLUB && SYSFS 1734 help 1735 SLUB has extensive debug support features. Disabling these can 1736 result in significant savings in code size. This also disables 1737 SLUB sysfs support. /sys/slab will not exist and there will be 1738 no support for cache validation etc. 1739 1740config SLUB_MEMCG_SYSFS_ON 1741 default n 1742 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1743 depends on SLUB && SYSFS && MEMCG 1744 help 1745 SLUB creates a directory under /sys/kernel/slab for each 1746 allocation cache to host info and debug files. If memory 1747 cgroup is enabled, each cache can have per memory cgroup 1748 caches. SLUB can create the same sysfs directories for these 1749 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1750 to a very high number of debug files being created. This is 1751 controlled by slub_memcg_sysfs boot parameter and this 1752 config option determines the parameter's default value. 1753 1754config COMPAT_BRK 1755 bool "Disable heap randomization" 1756 default y 1757 help 1758 Randomizing heap placement makes heap exploits harder, but it 1759 also breaks ancient binaries (including anything libc5 based). 1760 This option changes the bootup default to heap randomization 1761 disabled, and can be overridden at runtime by setting 1762 /proc/sys/kernel/randomize_va_space to 2. 1763 1764 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1765 1766choice 1767 prompt "Choose SLAB allocator" 1768 default SLUB 1769 help 1770 This option allows to select a slab allocator. 1771 1772config SLAB 1773 bool "SLAB" 1774 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1775 help 1776 The regular slab allocator that is established and known to work 1777 well in all environments. It organizes cache hot objects in 1778 per cpu and per node queues. 1779 1780config SLUB 1781 bool "SLUB (Unqueued Allocator)" 1782 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1783 help 1784 SLUB is a slab allocator that minimizes cache line usage 1785 instead of managing queues of cached objects (SLAB approach). 1786 Per cpu caching is realized using slabs of objects instead 1787 of queues of objects. SLUB can use memory efficiently 1788 and has enhanced diagnostics. SLUB is the default choice for 1789 a slab allocator. 1790 1791config SLOB 1792 depends on EXPERT 1793 bool "SLOB (Simple Allocator)" 1794 help 1795 SLOB replaces the stock allocator with a drastically simpler 1796 allocator. SLOB is generally more space efficient but 1797 does not perform as well on large systems. 1798 1799endchoice 1800 1801config SLAB_MERGE_DEFAULT 1802 bool "Allow slab caches to be merged" 1803 default y 1804 help 1805 For reduced kernel memory fragmentation, slab caches can be 1806 merged when they share the same size and other characteristics. 1807 This carries a risk of kernel heap overflows being able to 1808 overwrite objects from merged caches (and more easily control 1809 cache layout), which makes such heap attacks easier to exploit 1810 by attackers. By keeping caches unmerged, these kinds of exploits 1811 can usually only damage objects in the same cache. To disable 1812 merging at runtime, "slab_nomerge" can be passed on the kernel 1813 command line. 1814 1815config SLAB_FREELIST_RANDOM 1816 default n 1817 depends on SLAB || SLUB 1818 bool "SLAB freelist randomization" 1819 help 1820 Randomizes the freelist order used on creating new pages. This 1821 security feature reduces the predictability of the kernel slab 1822 allocator against heap overflows. 1823 1824config SLAB_FREELIST_HARDENED 1825 bool "Harden slab freelist metadata" 1826 depends on SLUB 1827 help 1828 Many kernel heap attacks try to target slab cache metadata and 1829 other infrastructure. This options makes minor performance 1830 sacrifices to harden the kernel slab allocator against common 1831 freelist exploit methods. 1832 1833config SHUFFLE_PAGE_ALLOCATOR 1834 bool "Page allocator randomization" 1835 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1836 help 1837 Randomization of the page allocator improves the average 1838 utilization of a direct-mapped memory-side-cache. See section 1839 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1840 6.2a specification for an example of how a platform advertises 1841 the presence of a memory-side-cache. There are also incidental 1842 security benefits as it reduces the predictability of page 1843 allocations to compliment SLAB_FREELIST_RANDOM, but the 1844 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1845 10th order of pages is selected based on cache utilization 1846 benefits on x86. 1847 1848 While the randomization improves cache utilization it may 1849 negatively impact workloads on platforms without a cache. For 1850 this reason, by default, the randomization is enabled only 1851 after runtime detection of a direct-mapped memory-side-cache. 1852 Otherwise, the randomization may be force enabled with the 1853 'page_alloc.shuffle' kernel command line parameter. 1854 1855 Say Y if unsure. 1856 1857config SLUB_CPU_PARTIAL 1858 default y 1859 depends on SLUB && SMP 1860 bool "SLUB per cpu partial cache" 1861 help 1862 Per cpu partial caches accelerate objects allocation and freeing 1863 that is local to a processor at the price of more indeterminism 1864 in the latency of the free. On overflow these caches will be cleared 1865 which requires the taking of locks that may cause latency spikes. 1866 Typically one would choose no for a realtime system. 1867 1868config MMAP_ALLOW_UNINITIALIZED 1869 bool "Allow mmapped anonymous memory to be uninitialized" 1870 depends on EXPERT && !MMU 1871 default n 1872 help 1873 Normally, and according to the Linux spec, anonymous memory obtained 1874 from mmap() has its contents cleared before it is passed to 1875 userspace. Enabling this config option allows you to request that 1876 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1877 providing a huge performance boost. If this option is not enabled, 1878 then the flag will be ignored. 1879 1880 This is taken advantage of by uClibc's malloc(), and also by 1881 ELF-FDPIC binfmt's brk and stack allocator. 1882 1883 Because of the obvious security issues, this option should only be 1884 enabled on embedded devices where you control what is run in 1885 userspace. Since that isn't generally a problem on no-MMU systems, 1886 it is normally safe to say Y here. 1887 1888 See Documentation/nommu-mmap.txt for more information. 1889 1890config SYSTEM_DATA_VERIFICATION 1891 def_bool n 1892 select SYSTEM_TRUSTED_KEYRING 1893 select KEYS 1894 select CRYPTO 1895 select CRYPTO_RSA 1896 select ASYMMETRIC_KEY_TYPE 1897 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1898 select ASN1 1899 select OID_REGISTRY 1900 select X509_CERTIFICATE_PARSER 1901 select PKCS7_MESSAGE_PARSER 1902 help 1903 Provide PKCS#7 message verification using the contents of the system 1904 trusted keyring to provide public keys. This then can be used for 1905 module verification, kexec image verification and firmware blob 1906 verification. 1907 1908config PROFILING 1909 bool "Profiling support" 1910 help 1911 Say Y here to enable the extended profiling support mechanisms used 1912 by profilers such as OProfile. 1913 1914# 1915# Place an empty function call at each tracepoint site. Can be 1916# dynamically changed for a probe function. 1917# 1918config TRACEPOINTS 1919 bool 1920 1921endmenu # General setup 1922 1923source "arch/Kconfig" 1924 1925config RT_MUTEXES 1926 bool 1927 1928config BASE_SMALL 1929 int 1930 default 0 if BASE_FULL 1931 default 1 if !BASE_FULL 1932 1933menuconfig MODULES 1934 bool "Enable loadable module support" 1935 option modules 1936 help 1937 Kernel modules are small pieces of compiled code which can 1938 be inserted in the running kernel, rather than being 1939 permanently built into the kernel. You use the "modprobe" 1940 tool to add (and sometimes remove) them. If you say Y here, 1941 many parts of the kernel can be built as modules (by 1942 answering M instead of Y where indicated): this is most 1943 useful for infrequently used options which are not required 1944 for booting. For more information, see the man pages for 1945 modprobe, lsmod, modinfo, insmod and rmmod. 1946 1947 If you say Y here, you will need to run "make 1948 modules_install" to put the modules under /lib/modules/ 1949 where modprobe can find them (you may need to be root to do 1950 this). 1951 1952 If unsure, say Y. 1953 1954if MODULES 1955 1956config MODULE_FORCE_LOAD 1957 bool "Forced module loading" 1958 default n 1959 help 1960 Allow loading of modules without version information (ie. modprobe 1961 --force). Forced module loading sets the 'F' (forced) taint flag and 1962 is usually a really bad idea. 1963 1964config MODULE_UNLOAD 1965 bool "Module unloading" 1966 help 1967 Without this option you will not be able to unload any 1968 modules (note that some modules may not be unloadable 1969 anyway), which makes your kernel smaller, faster 1970 and simpler. If unsure, say Y. 1971 1972config MODULE_FORCE_UNLOAD 1973 bool "Forced module unloading" 1974 depends on MODULE_UNLOAD 1975 help 1976 This option allows you to force a module to unload, even if the 1977 kernel believes it is unsafe: the kernel will remove the module 1978 without waiting for anyone to stop using it (using the -f option to 1979 rmmod). This is mainly for kernel developers and desperate users. 1980 If unsure, say N. 1981 1982config MODVERSIONS 1983 bool "Module versioning support" 1984 help 1985 Usually, you have to use modules compiled with your kernel. 1986 Saying Y here makes it sometimes possible to use modules 1987 compiled for different kernels, by adding enough information 1988 to the modules to (hopefully) spot any changes which would 1989 make them incompatible with the kernel you are running. If 1990 unsure, say N. 1991 1992config MODULE_REL_CRCS 1993 bool 1994 depends on MODVERSIONS 1995 1996config MODULE_SRCVERSION_ALL 1997 bool "Source checksum for all modules" 1998 help 1999 Modules which contain a MODULE_VERSION get an extra "srcversion" 2000 field inserted into their modinfo section, which contains a 2001 sum of the source files which made it. This helps maintainers 2002 see exactly which source was used to build a module (since 2003 others sometimes change the module source without updating 2004 the version). With this option, such a "srcversion" field 2005 will be created for all modules. If unsure, say N. 2006 2007config MODULE_SIG 2008 bool "Module signature verification" 2009 depends on MODULES 2010 select SYSTEM_DATA_VERIFICATION 2011 help 2012 Check modules for valid signatures upon load: the signature 2013 is simply appended to the module. For more information see 2014 <file:Documentation/admin-guide/module-signing.rst>. 2015 2016 Note that this option adds the OpenSSL development packages as a 2017 kernel build dependency so that the signing tool can use its crypto 2018 library. 2019 2020 !!!WARNING!!! If you enable this option, you MUST make sure that the 2021 module DOES NOT get stripped after being signed. This includes the 2022 debuginfo strip done by some packagers (such as rpmbuild) and 2023 inclusion into an initramfs that wants the module size reduced. 2024 2025config MODULE_SIG_FORCE 2026 bool "Require modules to be validly signed" 2027 depends on MODULE_SIG 2028 help 2029 Reject unsigned modules or signed modules for which we don't have a 2030 key. Without this, such modules will simply taint the kernel. 2031 2032config MODULE_SIG_ALL 2033 bool "Automatically sign all modules" 2034 default y 2035 depends on MODULE_SIG 2036 help 2037 Sign all modules during make modules_install. Without this option, 2038 modules must be signed manually, using the scripts/sign-file tool. 2039 2040comment "Do not forget to sign required modules with scripts/sign-file" 2041 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2042 2043choice 2044 prompt "Which hash algorithm should modules be signed with?" 2045 depends on MODULE_SIG 2046 help 2047 This determines which sort of hashing algorithm will be used during 2048 signature generation. This algorithm _must_ be built into the kernel 2049 directly so that signature verification can take place. It is not 2050 possible to load a signed module containing the algorithm to check 2051 the signature on that module. 2052 2053config MODULE_SIG_SHA1 2054 bool "Sign modules with SHA-1" 2055 select CRYPTO_SHA1 2056 2057config MODULE_SIG_SHA224 2058 bool "Sign modules with SHA-224" 2059 select CRYPTO_SHA256 2060 2061config MODULE_SIG_SHA256 2062 bool "Sign modules with SHA-256" 2063 select CRYPTO_SHA256 2064 2065config MODULE_SIG_SHA384 2066 bool "Sign modules with SHA-384" 2067 select CRYPTO_SHA512 2068 2069config MODULE_SIG_SHA512 2070 bool "Sign modules with SHA-512" 2071 select CRYPTO_SHA512 2072 2073endchoice 2074 2075config MODULE_SIG_HASH 2076 string 2077 depends on MODULE_SIG 2078 default "sha1" if MODULE_SIG_SHA1 2079 default "sha224" if MODULE_SIG_SHA224 2080 default "sha256" if MODULE_SIG_SHA256 2081 default "sha384" if MODULE_SIG_SHA384 2082 default "sha512" if MODULE_SIG_SHA512 2083 2084config MODULE_COMPRESS 2085 bool "Compress modules on installation" 2086 depends on MODULES 2087 help 2088 2089 Compresses kernel modules when 'make modules_install' is run; gzip or 2090 xz depending on "Compression algorithm" below. 2091 2092 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 2093 2094 Out-of-tree kernel modules installed using Kbuild will also be 2095 compressed upon installation. 2096 2097 Note: for modules inside an initrd or initramfs, it's more efficient 2098 to compress the whole initrd or initramfs instead. 2099 2100 Note: This is fully compatible with signed modules. 2101 2102 If in doubt, say N. 2103 2104choice 2105 prompt "Compression algorithm" 2106 depends on MODULE_COMPRESS 2107 default MODULE_COMPRESS_GZIP 2108 help 2109 This determines which sort of compression will be used during 2110 'make modules_install'. 2111 2112 GZIP (default) and XZ are supported. 2113 2114config MODULE_COMPRESS_GZIP 2115 bool "GZIP" 2116 2117config MODULE_COMPRESS_XZ 2118 bool "XZ" 2119 2120endchoice 2121 2122config TRIM_UNUSED_KSYMS 2123 bool "Trim unused exported kernel symbols" 2124 depends on MODULES && !UNUSED_SYMBOLS 2125 help 2126 The kernel and some modules make many symbols available for 2127 other modules to use via EXPORT_SYMBOL() and variants. Depending 2128 on the set of modules being selected in your kernel configuration, 2129 many of those exported symbols might never be used. 2130 2131 This option allows for unused exported symbols to be dropped from 2132 the build. In turn, this provides the compiler more opportunities 2133 (especially when using LTO) for optimizing the code and reducing 2134 binary size. This might have some security advantages as well. 2135 2136 If unsure, or if you need to build out-of-tree modules, say N. 2137 2138endif # MODULES 2139 2140config MODULES_TREE_LOOKUP 2141 def_bool y 2142 depends on PERF_EVENTS || TRACING 2143 2144config INIT_ALL_POSSIBLE 2145 bool 2146 help 2147 Back when each arch used to define their own cpu_online_mask and 2148 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2149 with all 1s, and others with all 0s. When they were centralised, 2150 it was better to provide this option than to break all the archs 2151 and have several arch maintainers pursuing me down dark alleys. 2152 2153source "block/Kconfig" 2154 2155config PREEMPT_NOTIFIERS 2156 bool 2157 2158config PADATA 2159 depends on SMP 2160 bool 2161 2162config ASN1 2163 tristate 2164 help 2165 Build a simple ASN.1 grammar compiler that produces a bytecode output 2166 that can be interpreted by the ASN.1 stream decoder and used to 2167 inform it as to what tags are to be expected in a stream and what 2168 functions to call on what tags. 2169 2170source "kernel/Kconfig.locks" 2171 2172config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2173 bool 2174 2175# It may be useful for an architecture to override the definitions of the 2176# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2177# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2178# different calling convention for syscalls. They can also override the 2179# macros for not-implemented syscalls in kernel/sys_ni.c and 2180# kernel/time/posix-stubs.c. All these overrides need to be available in 2181# <asm/syscall_wrapper.h>. 2182config ARCH_HAS_SYSCALL_WRAPPER 2183 def_bool n 2184