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 TOOLS_SUPPORT_RELR 34 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 35 36config CC_HAS_WARN_MAYBE_UNINITIALIZED 37 def_bool $(cc-option,-Wmaybe-uninitialized) 38 help 39 GCC >= 4.7 supports this option. 40 41config CC_DISABLE_WARN_MAYBE_UNINITIALIZED 42 bool 43 depends on CC_HAS_WARN_MAYBE_UNINITIALIZED 44 default CC_IS_GCC && GCC_VERSION < 40900 # unreliable for GCC < 4.9 45 help 46 GCC's -Wmaybe-uninitialized is not reliable by definition. 47 Lots of false positive warnings are produced in some cases. 48 49 If this option is enabled, -Wno-maybe-uninitialzed is passed 50 to the compiler to suppress maybe-uninitialized warnings. 51 52config CONSTRUCTORS 53 bool 54 depends on !UML 55 56config IRQ_WORK 57 bool 58 59config BUILDTIME_EXTABLE_SORT 60 bool 61 62config THREAD_INFO_IN_TASK 63 bool 64 help 65 Select this to move thread_info off the stack into task_struct. To 66 make this work, an arch will need to remove all thread_info fields 67 except flags and fix any runtime bugs. 68 69 One subtle change that will be needed is to use try_get_task_stack() 70 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 71 72menu "General setup" 73 74config BROKEN 75 bool 76 77config BROKEN_ON_SMP 78 bool 79 depends on BROKEN || !SMP 80 default y 81 82config INIT_ENV_ARG_LIMIT 83 int 84 default 32 if !UML 85 default 128 if UML 86 help 87 Maximum of each of the number of arguments and environment 88 variables passed to init from the kernel command line. 89 90config COMPILE_TEST 91 bool "Compile also drivers which will not load" 92 depends on !UML 93 default n 94 help 95 Some drivers can be compiled on a different platform than they are 96 intended to be run on. Despite they cannot be loaded there (or even 97 when they load they cannot be used due to missing HW support), 98 developers still, opposing to distributors, might want to build such 99 drivers to compile-test them. 100 101 If you are a developer and want to build everything available, say Y 102 here. If you are a user/distributor, say N here to exclude useless 103 drivers to be distributed. 104 105config HEADER_TEST 106 bool "Compile test headers that should be standalone compilable" 107 help 108 Compile test headers listed in header-test-y target to ensure they are 109 self-contained, i.e. compilable as standalone units. 110 111 If you are a developer or tester and want to ensure the requested 112 headers are self-contained, say Y here. Otherwise, choose N. 113 114config KERNEL_HEADER_TEST 115 bool "Compile test kernel headers" 116 depends on HEADER_TEST 117 help 118 Headers in include/ are used to build external moduls. 119 Compile test them to ensure they are self-contained, i.e. 120 compilable as standalone units. 121 122 If you are a developer or tester and want to ensure the headers 123 in include/ are self-contained, say Y here. Otherwise, choose N. 124 125config UAPI_HEADER_TEST 126 bool "Compile test UAPI headers" 127 depends on HEADER_TEST && HEADERS_INSTALL && CC_CAN_LINK 128 help 129 Compile test headers exported to user-space to ensure they are 130 self-contained, i.e. compilable as standalone units. 131 132 If you are a developer or tester and want to ensure the exported 133 headers are self-contained, say Y here. Otherwise, choose N. 134 135config LOCALVERSION 136 string "Local version - append to kernel release" 137 help 138 Append an extra string to the end of your kernel version. 139 This will show up when you type uname, for example. 140 The string you set here will be appended after the contents of 141 any files with a filename matching localversion* in your 142 object and source tree, in that order. Your total string can 143 be a maximum of 64 characters. 144 145config LOCALVERSION_AUTO 146 bool "Automatically append version information to the version string" 147 default y 148 depends on !COMPILE_TEST 149 help 150 This will try to automatically determine if the current tree is a 151 release tree by looking for git tags that belong to the current 152 top of tree revision. 153 154 A string of the format -gxxxxxxxx will be added to the localversion 155 if a git-based tree is found. The string generated by this will be 156 appended after any matching localversion* files, and after the value 157 set in CONFIG_LOCALVERSION. 158 159 (The actual string used here is the first eight characters produced 160 by running the command: 161 162 $ git rev-parse --verify HEAD 163 164 which is done within the script "scripts/setlocalversion".) 165 166config BUILD_SALT 167 string "Build ID Salt" 168 default "" 169 help 170 The build ID is used to link binaries and their debug info. Setting 171 this option will use the value in the calculation of the build id. 172 This is mostly useful for distributions which want to ensure the 173 build is unique between builds. It's safe to leave the default. 174 175config HAVE_KERNEL_GZIP 176 bool 177 178config HAVE_KERNEL_BZIP2 179 bool 180 181config HAVE_KERNEL_LZMA 182 bool 183 184config HAVE_KERNEL_XZ 185 bool 186 187config HAVE_KERNEL_LZO 188 bool 189 190config HAVE_KERNEL_LZ4 191 bool 192 193config HAVE_KERNEL_UNCOMPRESSED 194 bool 195 196choice 197 prompt "Kernel compression mode" 198 default KERNEL_GZIP 199 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED 200 help 201 The linux kernel is a kind of self-extracting executable. 202 Several compression algorithms are available, which differ 203 in efficiency, compression and decompression speed. 204 Compression speed is only relevant when building a kernel. 205 Decompression speed is relevant at each boot. 206 207 If you have any problems with bzip2 or lzma compressed 208 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 209 version of this functionality (bzip2 only), for 2.4, was 210 supplied by Christian Ludwig) 211 212 High compression options are mostly useful for users, who 213 are low on disk space (embedded systems), but for whom ram 214 size matters less. 215 216 If in doubt, select 'gzip' 217 218config KERNEL_GZIP 219 bool "Gzip" 220 depends on HAVE_KERNEL_GZIP 221 help 222 The old and tried gzip compression. It provides a good balance 223 between compression ratio and decompression speed. 224 225config KERNEL_BZIP2 226 bool "Bzip2" 227 depends on HAVE_KERNEL_BZIP2 228 help 229 Its compression ratio and speed is intermediate. 230 Decompression speed is slowest among the choices. The kernel 231 size is about 10% smaller with bzip2, in comparison to gzip. 232 Bzip2 uses a large amount of memory. For modern kernels you 233 will need at least 8MB RAM or more for booting. 234 235config KERNEL_LZMA 236 bool "LZMA" 237 depends on HAVE_KERNEL_LZMA 238 help 239 This compression algorithm's ratio is best. Decompression speed 240 is between gzip and bzip2. Compression is slowest. 241 The kernel size is about 33% smaller with LZMA in comparison to gzip. 242 243config KERNEL_XZ 244 bool "XZ" 245 depends on HAVE_KERNEL_XZ 246 help 247 XZ uses the LZMA2 algorithm and instruction set specific 248 BCJ filters which can improve compression ratio of executable 249 code. The size of the kernel is about 30% smaller with XZ in 250 comparison to gzip. On architectures for which there is a BCJ 251 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 252 will create a few percent smaller kernel than plain LZMA. 253 254 The speed is about the same as with LZMA: The decompression 255 speed of XZ is better than that of bzip2 but worse than gzip 256 and LZO. Compression is slow. 257 258config KERNEL_LZO 259 bool "LZO" 260 depends on HAVE_KERNEL_LZO 261 help 262 Its compression ratio is the poorest among the choices. The kernel 263 size is about 10% bigger than gzip; however its speed 264 (both compression and decompression) is the fastest. 265 266config KERNEL_LZ4 267 bool "LZ4" 268 depends on HAVE_KERNEL_LZ4 269 help 270 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 271 A preliminary version of LZ4 de/compression tool is available at 272 <https://code.google.com/p/lz4/>. 273 274 Its compression ratio is worse than LZO. The size of the kernel 275 is about 8% bigger than LZO. But the decompression speed is 276 faster than LZO. 277 278config KERNEL_UNCOMPRESSED 279 bool "None" 280 depends on HAVE_KERNEL_UNCOMPRESSED 281 help 282 Produce uncompressed kernel image. This option is usually not what 283 you want. It is useful for debugging the kernel in slow simulation 284 environments, where decompressing and moving the kernel is awfully 285 slow. This option allows early boot code to skip the decompressor 286 and jump right at uncompressed kernel image. 287 288endchoice 289 290config DEFAULT_HOSTNAME 291 string "Default hostname" 292 default "(none)" 293 help 294 This option determines the default system hostname before userspace 295 calls sethostname(2). The kernel traditionally uses "(none)" here, 296 but you may wish to use a different default here to make a minimal 297 system more usable with less configuration. 298 299# 300# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can 301# add proper SWAP support to them, in which case this can be remove. 302# 303config ARCH_NO_SWAP 304 bool 305 306config SWAP 307 bool "Support for paging of anonymous memory (swap)" 308 depends on MMU && BLOCK && !ARCH_NO_SWAP 309 default y 310 help 311 This option allows you to choose whether you want to have support 312 for so called swap devices or swap files in your kernel that are 313 used to provide more virtual memory than the actual RAM present 314 in your computer. If unsure say Y. 315 316config SYSVIPC 317 bool "System V IPC" 318 ---help--- 319 Inter Process Communication is a suite of library functions and 320 system calls which let processes (running programs) synchronize and 321 exchange information. It is generally considered to be a good thing, 322 and some programs won't run unless you say Y here. In particular, if 323 you want to run the DOS emulator dosemu under Linux (read the 324 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 325 you'll need to say Y here. 326 327 You can find documentation about IPC with "info ipc" and also in 328 section 6.4 of the Linux Programmer's Guide, available from 329 <http://www.tldp.org/guides.html>. 330 331config SYSVIPC_SYSCTL 332 bool 333 depends on SYSVIPC 334 depends on SYSCTL 335 default y 336 337config POSIX_MQUEUE 338 bool "POSIX Message Queues" 339 depends on NET 340 ---help--- 341 POSIX variant of message queues is a part of IPC. In POSIX message 342 queues every message has a priority which decides about succession 343 of receiving it by a process. If you want to compile and run 344 programs written e.g. for Solaris with use of its POSIX message 345 queues (functions mq_*) say Y here. 346 347 POSIX message queues are visible as a filesystem called 'mqueue' 348 and can be mounted somewhere if you want to do filesystem 349 operations on message queues. 350 351 If unsure, say Y. 352 353config POSIX_MQUEUE_SYSCTL 354 bool 355 depends on POSIX_MQUEUE 356 depends on SYSCTL 357 default y 358 359config CROSS_MEMORY_ATTACH 360 bool "Enable process_vm_readv/writev syscalls" 361 depends on MMU 362 default y 363 help 364 Enabling this option adds the system calls process_vm_readv and 365 process_vm_writev which allow a process with the correct privileges 366 to directly read from or write to another process' address space. 367 See the man page for more details. 368 369config USELIB 370 bool "uselib syscall" 371 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION 372 help 373 This option enables the uselib syscall, a system call used in the 374 dynamic linker from libc5 and earlier. glibc does not use this 375 system call. If you intend to run programs built on libc5 or 376 earlier, you may need to enable this syscall. Current systems 377 running glibc can safely disable this. 378 379config AUDIT 380 bool "Auditing support" 381 depends on NET 382 help 383 Enable auditing infrastructure that can be used with another 384 kernel subsystem, such as SELinux (which requires this for 385 logging of avc messages output). System call auditing is included 386 on architectures which support it. 387 388config HAVE_ARCH_AUDITSYSCALL 389 bool 390 391config AUDITSYSCALL 392 def_bool y 393 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 394 select FSNOTIFY 395 396source "kernel/irq/Kconfig" 397source "kernel/time/Kconfig" 398source "kernel/Kconfig.preempt" 399 400menu "CPU/Task time and stats accounting" 401 402config VIRT_CPU_ACCOUNTING 403 bool 404 405choice 406 prompt "Cputime accounting" 407 default TICK_CPU_ACCOUNTING if !PPC64 408 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 409 410# Kind of a stub config for the pure tick based cputime accounting 411config TICK_CPU_ACCOUNTING 412 bool "Simple tick based cputime accounting" 413 depends on !S390 && !NO_HZ_FULL 414 help 415 This is the basic tick based cputime accounting that maintains 416 statistics about user, system and idle time spent on per jiffies 417 granularity. 418 419 If unsure, say Y. 420 421config VIRT_CPU_ACCOUNTING_NATIVE 422 bool "Deterministic task and CPU time accounting" 423 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 424 select VIRT_CPU_ACCOUNTING 425 help 426 Select this option to enable more accurate task and CPU time 427 accounting. This is done by reading a CPU counter on each 428 kernel entry and exit and on transitions within the kernel 429 between system, softirq and hardirq state, so there is a 430 small performance impact. In the case of s390 or IBM POWER > 5, 431 this also enables accounting of stolen time on logically-partitioned 432 systems. 433 434config VIRT_CPU_ACCOUNTING_GEN 435 bool "Full dynticks CPU time accounting" 436 depends on HAVE_CONTEXT_TRACKING 437 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 438 depends on GENERIC_CLOCKEVENTS 439 select VIRT_CPU_ACCOUNTING 440 select CONTEXT_TRACKING 441 help 442 Select this option to enable task and CPU time accounting on full 443 dynticks systems. This accounting is implemented by watching every 444 kernel-user boundaries using the context tracking subsystem. 445 The accounting is thus performed at the expense of some significant 446 overhead. 447 448 For now this is only useful if you are working on the full 449 dynticks subsystem development. 450 451 If unsure, say N. 452 453endchoice 454 455config IRQ_TIME_ACCOUNTING 456 bool "Fine granularity task level IRQ time accounting" 457 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 458 help 459 Select this option to enable fine granularity task irq time 460 accounting. This is done by reading a timestamp on each 461 transitions between softirq and hardirq state, so there can be a 462 small performance impact. 463 464 If in doubt, say N here. 465 466config HAVE_SCHED_AVG_IRQ 467 def_bool y 468 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 469 depends on SMP 470 471config BSD_PROCESS_ACCT 472 bool "BSD Process Accounting" 473 depends on MULTIUSER 474 help 475 If you say Y here, a user level program will be able to instruct the 476 kernel (via a special system call) to write process accounting 477 information to a file: whenever a process exits, information about 478 that process will be appended to the file by the kernel. The 479 information includes things such as creation time, owning user, 480 command name, memory usage, controlling terminal etc. (the complete 481 list is in the struct acct in <file:include/linux/acct.h>). It is 482 up to the user level program to do useful things with this 483 information. This is generally a good idea, so say Y. 484 485config BSD_PROCESS_ACCT_V3 486 bool "BSD Process Accounting version 3 file format" 487 depends on BSD_PROCESS_ACCT 488 default n 489 help 490 If you say Y here, the process accounting information is written 491 in a new file format that also logs the process IDs of each 492 process and its parent. Note that this file format is incompatible 493 with previous v0/v1/v2 file formats, so you will need updated tools 494 for processing it. A preliminary version of these tools is available 495 at <http://www.gnu.org/software/acct/>. 496 497config TASKSTATS 498 bool "Export task/process statistics through netlink" 499 depends on NET 500 depends on MULTIUSER 501 default n 502 help 503 Export selected statistics for tasks/processes through the 504 generic netlink interface. Unlike BSD process accounting, the 505 statistics are available during the lifetime of tasks/processes as 506 responses to commands. Like BSD accounting, they are sent to user 507 space on task exit. 508 509 Say N if unsure. 510 511config TASK_DELAY_ACCT 512 bool "Enable per-task delay accounting" 513 depends on TASKSTATS 514 select SCHED_INFO 515 help 516 Collect information on time spent by a task waiting for system 517 resources like cpu, synchronous block I/O completion and swapping 518 in pages. Such statistics can help in setting a task's priorities 519 relative to other tasks for cpu, io, rss limits etc. 520 521 Say N if unsure. 522 523config TASK_XACCT 524 bool "Enable extended accounting over taskstats" 525 depends on TASKSTATS 526 help 527 Collect extended task accounting data and send the data 528 to userland for processing over the taskstats interface. 529 530 Say N if unsure. 531 532config TASK_IO_ACCOUNTING 533 bool "Enable per-task storage I/O accounting" 534 depends on TASK_XACCT 535 help 536 Collect information on the number of bytes of storage I/O which this 537 task has caused. 538 539 Say N if unsure. 540 541config PSI 542 bool "Pressure stall information tracking" 543 help 544 Collect metrics that indicate how overcommitted the CPU, memory, 545 and IO capacity are in the system. 546 547 If you say Y here, the kernel will create /proc/pressure/ with the 548 pressure statistics files cpu, memory, and io. These will indicate 549 the share of walltime in which some or all tasks in the system are 550 delayed due to contention of the respective resource. 551 552 In kernels with cgroup support, cgroups (cgroup2 only) will 553 have cpu.pressure, memory.pressure, and io.pressure files, 554 which aggregate pressure stalls for the grouped tasks only. 555 556 For more details see Documentation/accounting/psi.rst. 557 558 Say N if unsure. 559 560config PSI_DEFAULT_DISABLED 561 bool "Require boot parameter to enable pressure stall information tracking" 562 default n 563 depends on PSI 564 help 565 If set, pressure stall information tracking will be disabled 566 per default but can be enabled through passing psi=1 on the 567 kernel commandline during boot. 568 569 This feature adds some code to the task wakeup and sleep 570 paths of the scheduler. The overhead is too low to affect 571 common scheduling-intense workloads in practice (such as 572 webservers, memcache), but it does show up in artificial 573 scheduler stress tests, such as hackbench. 574 575 If you are paranoid and not sure what the kernel will be 576 used for, say Y. 577 578 Say N if unsure. 579 580endmenu # "CPU/Task time and stats accounting" 581 582config CPU_ISOLATION 583 bool "CPU isolation" 584 depends on SMP || COMPILE_TEST 585 default y 586 help 587 Make sure that CPUs running critical tasks are not disturbed by 588 any source of "noise" such as unbound workqueues, timers, kthreads... 589 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 590 the "isolcpus=" boot parameter. 591 592 Say Y if unsure. 593 594source "kernel/rcu/Kconfig" 595 596config BUILD_BIN2C 597 bool 598 default n 599 600config IKCONFIG 601 tristate "Kernel .config support" 602 ---help--- 603 This option enables the complete Linux kernel ".config" file 604 contents to be saved in the kernel. It provides documentation 605 of which kernel options are used in a running kernel or in an 606 on-disk kernel. This information can be extracted from the kernel 607 image file with the script scripts/extract-ikconfig and used as 608 input to rebuild the current kernel or to build another kernel. 609 It can also be extracted from a running kernel by reading 610 /proc/config.gz if enabled (below). 611 612config IKCONFIG_PROC 613 bool "Enable access to .config through /proc/config.gz" 614 depends on IKCONFIG && PROC_FS 615 ---help--- 616 This option enables access to the kernel configuration file 617 through /proc/config.gz. 618 619config IKHEADERS 620 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 621 depends on SYSFS 622 help 623 This option enables access to the in-kernel headers that are generated during 624 the build process. These can be used to build eBPF tracing programs, 625 or similar programs. If you build the headers as a module, a module called 626 kheaders.ko is built which can be loaded on-demand to get access to headers. 627 628config LOG_BUF_SHIFT 629 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 630 range 12 25 631 default 17 632 depends on PRINTK 633 help 634 Select the minimal kernel log buffer size as a power of 2. 635 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 636 parameter, see below. Any higher size also might be forced 637 by "log_buf_len" boot parameter. 638 639 Examples: 640 17 => 128 KB 641 16 => 64 KB 642 15 => 32 KB 643 14 => 16 KB 644 13 => 8 KB 645 12 => 4 KB 646 647config LOG_CPU_MAX_BUF_SHIFT 648 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 649 depends on SMP 650 range 0 21 651 default 12 if !BASE_SMALL 652 default 0 if BASE_SMALL 653 depends on PRINTK 654 help 655 This option allows to increase the default ring buffer size 656 according to the number of CPUs. The value defines the contribution 657 of each CPU as a power of 2. The used space is typically only few 658 lines however it might be much more when problems are reported, 659 e.g. backtraces. 660 661 The increased size means that a new buffer has to be allocated and 662 the original static one is unused. It makes sense only on systems 663 with more CPUs. Therefore this value is used only when the sum of 664 contributions is greater than the half of the default kernel ring 665 buffer as defined by LOG_BUF_SHIFT. The default values are set 666 so that more than 64 CPUs are needed to trigger the allocation. 667 668 Also this option is ignored when "log_buf_len" kernel parameter is 669 used as it forces an exact (power of two) size of the ring buffer. 670 671 The number of possible CPUs is used for this computation ignoring 672 hotplugging making the computation optimal for the worst case 673 scenario while allowing a simple algorithm to be used from bootup. 674 675 Examples shift values and their meaning: 676 17 => 128 KB for each CPU 677 16 => 64 KB for each CPU 678 15 => 32 KB for each CPU 679 14 => 16 KB for each CPU 680 13 => 8 KB for each CPU 681 12 => 4 KB for each CPU 682 683config PRINTK_SAFE_LOG_BUF_SHIFT 684 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 685 range 10 21 686 default 13 687 depends on PRINTK 688 help 689 Select the size of an alternate printk per-CPU buffer where messages 690 printed from usafe contexts are temporary stored. One example would 691 be NMI messages, another one - printk recursion. The messages are 692 copied to the main log buffer in a safe context to avoid a deadlock. 693 The value defines the size as a power of 2. 694 695 Those messages are rare and limited. The largest one is when 696 a backtrace is printed. It usually fits into 4KB. Select 697 8KB if you want to be on the safe side. 698 699 Examples: 700 17 => 128 KB for each CPU 701 16 => 64 KB for each CPU 702 15 => 32 KB for each CPU 703 14 => 16 KB for each CPU 704 13 => 8 KB for each CPU 705 12 => 4 KB for each CPU 706 707# 708# Architectures with an unreliable sched_clock() should select this: 709# 710config HAVE_UNSTABLE_SCHED_CLOCK 711 bool 712 713config GENERIC_SCHED_CLOCK 714 bool 715 716menu "Scheduler features" 717 718config UCLAMP_TASK 719 bool "Enable utilization clamping for RT/FAIR tasks" 720 depends on CPU_FREQ_GOV_SCHEDUTIL 721 help 722 This feature enables the scheduler to track the clamped utilization 723 of each CPU based on RUNNABLE tasks scheduled on that CPU. 724 725 With this option, the user can specify the min and max CPU 726 utilization allowed for RUNNABLE tasks. The max utilization defines 727 the maximum frequency a task should use while the min utilization 728 defines the minimum frequency it should use. 729 730 Both min and max utilization clamp values are hints to the scheduler, 731 aiming at improving its frequency selection policy, but they do not 732 enforce or grant any specific bandwidth for tasks. 733 734 If in doubt, say N. 735 736config UCLAMP_BUCKETS_COUNT 737 int "Number of supported utilization clamp buckets" 738 range 5 20 739 default 5 740 depends on UCLAMP_TASK 741 help 742 Defines the number of clamp buckets to use. The range of each bucket 743 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 744 number of clamp buckets the finer their granularity and the higher 745 the precision of clamping aggregation and tracking at run-time. 746 747 For example, with the minimum configuration value we will have 5 748 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 749 be refcounted in the [20..39]% bucket and will set the bucket clamp 750 effective value to 25%. 751 If a second 30% boosted task should be co-scheduled on the same CPU, 752 that task will be refcounted in the same bucket of the first task and 753 it will boost the bucket clamp effective value to 30%. 754 The clamp effective value of a bucket is reset to its nominal value 755 (20% in the example above) when there are no more tasks refcounted in 756 that bucket. 757 758 An additional boost/capping margin can be added to some tasks. In the 759 example above the 25% task will be boosted to 30% until it exits the 760 CPU. If that should be considered not acceptable on certain systems, 761 it's always possible to reduce the margin by increasing the number of 762 clamp buckets to trade off used memory for run-time tracking 763 precision. 764 765 If in doubt, use the default value. 766 767endmenu 768 769# 770# For architectures that want to enable the support for NUMA-affine scheduler 771# balancing logic: 772# 773config ARCH_SUPPORTS_NUMA_BALANCING 774 bool 775 776# 777# For architectures that prefer to flush all TLBs after a number of pages 778# are unmapped instead of sending one IPI per page to flush. The architecture 779# must provide guarantees on what happens if a clean TLB cache entry is 780# written after the unmap. Details are in mm/rmap.c near the check for 781# should_defer_flush. The architecture should also consider if the full flush 782# and the refill costs are offset by the savings of sending fewer IPIs. 783config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 784 bool 785 786# 787# For architectures that know their GCC __int128 support is sound 788# 789config ARCH_SUPPORTS_INT128 790 bool 791 792# For architectures that (ab)use NUMA to represent different memory regions 793# all cpu-local but of different latencies, such as SuperH. 794# 795config ARCH_WANT_NUMA_VARIABLE_LOCALITY 796 bool 797 798config NUMA_BALANCING 799 bool "Memory placement aware NUMA scheduler" 800 depends on ARCH_SUPPORTS_NUMA_BALANCING 801 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 802 depends on SMP && NUMA && MIGRATION 803 help 804 This option adds support for automatic NUMA aware memory/task placement. 805 The mechanism is quite primitive and is based on migrating memory when 806 it has references to the node the task is running on. 807 808 This system will be inactive on UMA systems. 809 810config NUMA_BALANCING_DEFAULT_ENABLED 811 bool "Automatically enable NUMA aware memory/task placement" 812 default y 813 depends on NUMA_BALANCING 814 help 815 If set, automatic NUMA balancing will be enabled if running on a NUMA 816 machine. 817 818menuconfig CGROUPS 819 bool "Control Group support" 820 select KERNFS 821 help 822 This option adds support for grouping sets of processes together, for 823 use with process control subsystems such as Cpusets, CFS, memory 824 controls or device isolation. 825 See 826 - Documentation/scheduler/sched-design-CFS.rst (CFS) 827 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 828 and resource control) 829 830 Say N if unsure. 831 832if CGROUPS 833 834config PAGE_COUNTER 835 bool 836 837config MEMCG 838 bool "Memory controller" 839 select PAGE_COUNTER 840 select EVENTFD 841 help 842 Provides control over the memory footprint of tasks in a cgroup. 843 844config MEMCG_SWAP 845 bool "Swap controller" 846 depends on MEMCG && SWAP 847 help 848 Provides control over the swap space consumed by tasks in a cgroup. 849 850config MEMCG_SWAP_ENABLED 851 bool "Swap controller enabled by default" 852 depends on MEMCG_SWAP 853 default y 854 help 855 Memory Resource Controller Swap Extension comes with its price in 856 a bigger memory consumption. General purpose distribution kernels 857 which want to enable the feature but keep it disabled by default 858 and let the user enable it by swapaccount=1 boot command line 859 parameter should have this option unselected. 860 For those who want to have the feature enabled by default should 861 select this option (if, for some reason, they need to disable it 862 then swapaccount=0 does the trick). 863 864config MEMCG_KMEM 865 bool 866 depends on MEMCG && !SLOB 867 default y 868 869config BLK_CGROUP 870 bool "IO controller" 871 depends on BLOCK 872 default n 873 ---help--- 874 Generic block IO controller cgroup interface. This is the common 875 cgroup interface which should be used by various IO controlling 876 policies. 877 878 Currently, CFQ IO scheduler uses it to recognize task groups and 879 control disk bandwidth allocation (proportional time slice allocation) 880 to such task groups. It is also used by bio throttling logic in 881 block layer to implement upper limit in IO rates on a device. 882 883 This option only enables generic Block IO controller infrastructure. 884 One needs to also enable actual IO controlling logic/policy. For 885 enabling proportional weight division of disk bandwidth in CFQ, set 886 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 887 CONFIG_BLK_DEV_THROTTLING=y. 888 889 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 890 891config CGROUP_WRITEBACK 892 bool 893 depends on MEMCG && BLK_CGROUP 894 default y 895 896menuconfig CGROUP_SCHED 897 bool "CPU controller" 898 default n 899 help 900 This feature lets CPU scheduler recognize task groups and control CPU 901 bandwidth allocation to such task groups. It uses cgroups to group 902 tasks. 903 904if CGROUP_SCHED 905config FAIR_GROUP_SCHED 906 bool "Group scheduling for SCHED_OTHER" 907 depends on CGROUP_SCHED 908 default CGROUP_SCHED 909 910config CFS_BANDWIDTH 911 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 912 depends on FAIR_GROUP_SCHED 913 default n 914 help 915 This option allows users to define CPU bandwidth rates (limits) for 916 tasks running within the fair group scheduler. Groups with no limit 917 set are considered to be unconstrained and will run with no 918 restriction. 919 See Documentation/scheduler/sched-bwc.rst for more information. 920 921config RT_GROUP_SCHED 922 bool "Group scheduling for SCHED_RR/FIFO" 923 depends on CGROUP_SCHED 924 default n 925 help 926 This feature lets you explicitly allocate real CPU bandwidth 927 to task groups. If enabled, it will also make it impossible to 928 schedule realtime tasks for non-root users until you allocate 929 realtime bandwidth for them. 930 See Documentation/scheduler/sched-rt-group.rst for more information. 931 932endif #CGROUP_SCHED 933 934config UCLAMP_TASK_GROUP 935 bool "Utilization clamping per group of tasks" 936 depends on CGROUP_SCHED 937 depends on UCLAMP_TASK 938 default n 939 help 940 This feature enables the scheduler to track the clamped utilization 941 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 942 943 When this option is enabled, the user can specify a min and max 944 CPU bandwidth which is allowed for each single task in a group. 945 The max bandwidth allows to clamp the maximum frequency a task 946 can use, while the min bandwidth allows to define a minimum 947 frequency a task will always use. 948 949 When task group based utilization clamping is enabled, an eventually 950 specified task-specific clamp value is constrained by the cgroup 951 specified clamp value. Both minimum and maximum task clamping cannot 952 be bigger than the corresponding clamping defined at task group level. 953 954 If in doubt, say N. 955 956config CGROUP_PIDS 957 bool "PIDs controller" 958 help 959 Provides enforcement of process number limits in the scope of a 960 cgroup. Any attempt to fork more processes than is allowed in the 961 cgroup will fail. PIDs are fundamentally a global resource because it 962 is fairly trivial to reach PID exhaustion before you reach even a 963 conservative kmemcg limit. As a result, it is possible to grind a 964 system to halt without being limited by other cgroup policies. The 965 PIDs controller is designed to stop this from happening. 966 967 It should be noted that organisational operations (such as attaching 968 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 969 since the PIDs limit only affects a process's ability to fork, not to 970 attach to a cgroup. 971 972config CGROUP_RDMA 973 bool "RDMA controller" 974 help 975 Provides enforcement of RDMA resources defined by IB stack. 976 It is fairly easy for consumers to exhaust RDMA resources, which 977 can result into resource unavailability to other consumers. 978 RDMA controller is designed to stop this from happening. 979 Attaching processes with active RDMA resources to the cgroup 980 hierarchy is allowed even if can cross the hierarchy's limit. 981 982config CGROUP_FREEZER 983 bool "Freezer controller" 984 help 985 Provides a way to freeze and unfreeze all tasks in a 986 cgroup. 987 988 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 989 controller includes important in-kernel memory consumers per default. 990 991 If you're using cgroup2, say N. 992 993config CGROUP_HUGETLB 994 bool "HugeTLB controller" 995 depends on HUGETLB_PAGE 996 select PAGE_COUNTER 997 default n 998 help 999 Provides a cgroup controller for HugeTLB pages. 1000 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1001 The limit is enforced during page fault. Since HugeTLB doesn't 1002 support page reclaim, enforcing the limit at page fault time implies 1003 that, the application will get SIGBUS signal if it tries to access 1004 HugeTLB pages beyond its limit. This requires the application to know 1005 beforehand how much HugeTLB pages it would require for its use. The 1006 control group is tracked in the third page lru pointer. This means 1007 that we cannot use the controller with huge page less than 3 pages. 1008 1009config CPUSETS 1010 bool "Cpuset controller" 1011 depends on SMP 1012 help 1013 This option will let you create and manage CPUSETs which 1014 allow dynamically partitioning a system into sets of CPUs and 1015 Memory Nodes and assigning tasks to run only within those sets. 1016 This is primarily useful on large SMP or NUMA systems. 1017 1018 Say N if unsure. 1019 1020config PROC_PID_CPUSET 1021 bool "Include legacy /proc/<pid>/cpuset file" 1022 depends on CPUSETS 1023 default y 1024 1025config CGROUP_DEVICE 1026 bool "Device controller" 1027 help 1028 Provides a cgroup controller implementing whitelists for 1029 devices which a process in the cgroup can mknod or open. 1030 1031config CGROUP_CPUACCT 1032 bool "Simple CPU accounting controller" 1033 help 1034 Provides a simple controller for monitoring the 1035 total CPU consumed by the tasks in a cgroup. 1036 1037config CGROUP_PERF 1038 bool "Perf controller" 1039 depends on PERF_EVENTS 1040 help 1041 This option extends the perf per-cpu mode to restrict monitoring 1042 to threads which belong to the cgroup specified and run on the 1043 designated cpu. 1044 1045 Say N if unsure. 1046 1047config CGROUP_BPF 1048 bool "Support for eBPF programs attached to cgroups" 1049 depends on BPF_SYSCALL 1050 select SOCK_CGROUP_DATA 1051 help 1052 Allow attaching eBPF programs to a cgroup using the bpf(2) 1053 syscall command BPF_PROG_ATTACH. 1054 1055 In which context these programs are accessed depends on the type 1056 of attachment. For instance, programs that are attached using 1057 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1058 inet sockets. 1059 1060config CGROUP_DEBUG 1061 bool "Debug controller" 1062 default n 1063 depends on DEBUG_KERNEL 1064 help 1065 This option enables a simple controller that exports 1066 debugging information about the cgroups framework. This 1067 controller is for control cgroup debugging only. Its 1068 interfaces are not stable. 1069 1070 Say N. 1071 1072config SOCK_CGROUP_DATA 1073 bool 1074 default n 1075 1076endif # CGROUPS 1077 1078menuconfig NAMESPACES 1079 bool "Namespaces support" if EXPERT 1080 depends on MULTIUSER 1081 default !EXPERT 1082 help 1083 Provides the way to make tasks work with different objects using 1084 the same id. For example same IPC id may refer to different objects 1085 or same user id or pid may refer to different tasks when used in 1086 different namespaces. 1087 1088if NAMESPACES 1089 1090config UTS_NS 1091 bool "UTS namespace" 1092 default y 1093 help 1094 In this namespace tasks see different info provided with the 1095 uname() system call 1096 1097config IPC_NS 1098 bool "IPC namespace" 1099 depends on (SYSVIPC || POSIX_MQUEUE) 1100 default y 1101 help 1102 In this namespace tasks work with IPC ids which correspond to 1103 different IPC objects in different namespaces. 1104 1105config USER_NS 1106 bool "User namespace" 1107 default n 1108 help 1109 This allows containers, i.e. vservers, to use user namespaces 1110 to provide different user info for different servers. 1111 1112 When user namespaces are enabled in the kernel it is 1113 recommended that the MEMCG option also be enabled and that 1114 user-space use the memory control groups to limit the amount 1115 of memory a memory unprivileged users can use. 1116 1117 If unsure, say N. 1118 1119config PID_NS 1120 bool "PID Namespaces" 1121 default y 1122 help 1123 Support process id namespaces. This allows having multiple 1124 processes with the same pid as long as they are in different 1125 pid namespaces. This is a building block of containers. 1126 1127config NET_NS 1128 bool "Network namespace" 1129 depends on NET 1130 default y 1131 help 1132 Allow user space to create what appear to be multiple instances 1133 of the network stack. 1134 1135endif # NAMESPACES 1136 1137config CHECKPOINT_RESTORE 1138 bool "Checkpoint/restore support" 1139 select PROC_CHILDREN 1140 default n 1141 help 1142 Enables additional kernel features in a sake of checkpoint/restore. 1143 In particular it adds auxiliary prctl codes to setup process text, 1144 data and heap segment sizes, and a few additional /proc filesystem 1145 entries. 1146 1147 If unsure, say N here. 1148 1149config SCHED_AUTOGROUP 1150 bool "Automatic process group scheduling" 1151 select CGROUPS 1152 select CGROUP_SCHED 1153 select FAIR_GROUP_SCHED 1154 help 1155 This option optimizes the scheduler for common desktop workloads by 1156 automatically creating and populating task groups. This separation 1157 of workloads isolates aggressive CPU burners (like build jobs) from 1158 desktop applications. Task group autogeneration is currently based 1159 upon task session. 1160 1161config SYSFS_DEPRECATED 1162 bool "Enable deprecated sysfs features to support old userspace tools" 1163 depends on SYSFS 1164 default n 1165 help 1166 This option adds code that switches the layout of the "block" class 1167 devices, to not show up in /sys/class/block/, but only in 1168 /sys/block/. 1169 1170 This switch is only active when the sysfs.deprecated=1 boot option is 1171 passed or the SYSFS_DEPRECATED_V2 option is set. 1172 1173 This option allows new kernels to run on old distributions and tools, 1174 which might get confused by /sys/class/block/. Since 2007/2008 all 1175 major distributions and tools handle this just fine. 1176 1177 Recent distributions and userspace tools after 2009/2010 depend on 1178 the existence of /sys/class/block/, and will not work with this 1179 option enabled. 1180 1181 Only if you are using a new kernel on an old distribution, you might 1182 need to say Y here. 1183 1184config SYSFS_DEPRECATED_V2 1185 bool "Enable deprecated sysfs features by default" 1186 default n 1187 depends on SYSFS 1188 depends on SYSFS_DEPRECATED 1189 help 1190 Enable deprecated sysfs by default. 1191 1192 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1193 option. 1194 1195 Only if you are using a new kernel on an old distribution, you might 1196 need to say Y here. Even then, odds are you would not need it 1197 enabled, you can always pass the boot option if absolutely necessary. 1198 1199config RELAY 1200 bool "Kernel->user space relay support (formerly relayfs)" 1201 select IRQ_WORK 1202 help 1203 This option enables support for relay interface support in 1204 certain file systems (such as debugfs). 1205 It is designed to provide an efficient mechanism for tools and 1206 facilities to relay large amounts of data from kernel space to 1207 user space. 1208 1209 If unsure, say N. 1210 1211config BLK_DEV_INITRD 1212 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1213 help 1214 The initial RAM filesystem is a ramfs which is loaded by the 1215 boot loader (loadlin or lilo) and that is mounted as root 1216 before the normal boot procedure. It is typically used to 1217 load modules needed to mount the "real" root file system, 1218 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1219 1220 If RAM disk support (BLK_DEV_RAM) is also included, this 1221 also enables initial RAM disk (initrd) support and adds 1222 15 Kbytes (more on some other architectures) to the kernel size. 1223 1224 If unsure say Y. 1225 1226if BLK_DEV_INITRD 1227 1228source "usr/Kconfig" 1229 1230endif 1231 1232choice 1233 prompt "Compiler optimization level" 1234 default CC_OPTIMIZE_FOR_PERFORMANCE 1235 1236config CC_OPTIMIZE_FOR_PERFORMANCE 1237 bool "Optimize for performance" 1238 help 1239 This is the default optimization level for the kernel, building 1240 with the "-O2" compiler flag for best performance and most 1241 helpful compile-time warnings. 1242 1243config CC_OPTIMIZE_FOR_SIZE 1244 bool "Optimize for size" 1245 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives 1246 help 1247 Enabling this option will pass "-Os" instead of "-O2" to 1248 your compiler resulting in a smaller kernel. 1249 1250 If unsure, say N. 1251 1252endchoice 1253 1254config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1255 bool 1256 help 1257 This requires that the arch annotates or otherwise protects 1258 its external entry points from being discarded. Linker scripts 1259 must also merge .text.*, .data.*, and .bss.* correctly into 1260 output sections. Care must be taken not to pull in unrelated 1261 sections (e.g., '.text.init'). Typically '.' in section names 1262 is used to distinguish them from label names / C identifiers. 1263 1264config LD_DEAD_CODE_DATA_ELIMINATION 1265 bool "Dead code and data elimination (EXPERIMENTAL)" 1266 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1267 depends on EXPERT 1268 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800) 1269 depends on $(cc-option,-ffunction-sections -fdata-sections) 1270 depends on $(ld-option,--gc-sections) 1271 help 1272 Enable this if you want to do dead code and data elimination with 1273 the linker by compiling with -ffunction-sections -fdata-sections, 1274 and linking with --gc-sections. 1275 1276 This can reduce on disk and in-memory size of the kernel 1277 code and static data, particularly for small configs and 1278 on small systems. This has the possibility of introducing 1279 silently broken kernel if the required annotations are not 1280 present. This option is not well tested yet, so use at your 1281 own risk. 1282 1283config SYSCTL 1284 bool 1285 1286config HAVE_UID16 1287 bool 1288 1289config SYSCTL_EXCEPTION_TRACE 1290 bool 1291 help 1292 Enable support for /proc/sys/debug/exception-trace. 1293 1294config SYSCTL_ARCH_UNALIGN_NO_WARN 1295 bool 1296 help 1297 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1298 Allows arch to define/use @no_unaligned_warning to possibly warn 1299 about unaligned access emulation going on under the hood. 1300 1301config SYSCTL_ARCH_UNALIGN_ALLOW 1302 bool 1303 help 1304 Enable support for /proc/sys/kernel/unaligned-trap 1305 Allows arches to define/use @unaligned_enabled to runtime toggle 1306 the unaligned access emulation. 1307 see arch/parisc/kernel/unaligned.c for reference 1308 1309config HAVE_PCSPKR_PLATFORM 1310 bool 1311 1312# interpreter that classic socket filters depend on 1313config BPF 1314 bool 1315 1316menuconfig EXPERT 1317 bool "Configure standard kernel features (expert users)" 1318 # Unhide debug options, to make the on-by-default options visible 1319 select DEBUG_KERNEL 1320 help 1321 This option allows certain base kernel options and settings 1322 to be disabled or tweaked. This is for specialized 1323 environments which can tolerate a "non-standard" kernel. 1324 Only use this if you really know what you are doing. 1325 1326config UID16 1327 bool "Enable 16-bit UID system calls" if EXPERT 1328 depends on HAVE_UID16 && MULTIUSER 1329 default y 1330 help 1331 This enables the legacy 16-bit UID syscall wrappers. 1332 1333config MULTIUSER 1334 bool "Multiple users, groups and capabilities support" if EXPERT 1335 default y 1336 help 1337 This option enables support for non-root users, groups and 1338 capabilities. 1339 1340 If you say N here, all processes will run with UID 0, GID 0, and all 1341 possible capabilities. Saying N here also compiles out support for 1342 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1343 setgid, and capset. 1344 1345 If unsure, say Y here. 1346 1347config SGETMASK_SYSCALL 1348 bool "sgetmask/ssetmask syscalls support" if EXPERT 1349 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1350 ---help--- 1351 sys_sgetmask and sys_ssetmask are obsolete system calls 1352 no longer supported in libc but still enabled by default in some 1353 architectures. 1354 1355 If unsure, leave the default option here. 1356 1357config SYSFS_SYSCALL 1358 bool "Sysfs syscall support" if EXPERT 1359 default y 1360 ---help--- 1361 sys_sysfs is an obsolete system call no longer supported in libc. 1362 Note that disabling this option is more secure but might break 1363 compatibility with some systems. 1364 1365 If unsure say Y here. 1366 1367config SYSCTL_SYSCALL 1368 bool "Sysctl syscall support" if EXPERT 1369 depends on PROC_SYSCTL 1370 default n 1371 select SYSCTL 1372 ---help--- 1373 sys_sysctl uses binary paths that have been found challenging 1374 to properly maintain and use. The interface in /proc/sys 1375 using paths with ascii names is now the primary path to this 1376 information. 1377 1378 Almost nothing using the binary sysctl interface so if you are 1379 trying to save some space it is probably safe to disable this, 1380 making your kernel marginally smaller. 1381 1382 If unsure say N here. 1383 1384config FHANDLE 1385 bool "open by fhandle syscalls" if EXPERT 1386 select EXPORTFS 1387 default y 1388 help 1389 If you say Y here, a user level program will be able to map 1390 file names to handle and then later use the handle for 1391 different file system operations. This is useful in implementing 1392 userspace file servers, which now track files using handles instead 1393 of names. The handle would remain the same even if file names 1394 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1395 syscalls. 1396 1397config POSIX_TIMERS 1398 bool "Posix Clocks & timers" if EXPERT 1399 default y 1400 help 1401 This includes native support for POSIX timers to the kernel. 1402 Some embedded systems have no use for them and therefore they 1403 can be configured out to reduce the size of the kernel image. 1404 1405 When this option is disabled, the following syscalls won't be 1406 available: timer_create, timer_gettime: timer_getoverrun, 1407 timer_settime, timer_delete, clock_adjtime, getitimer, 1408 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1409 clock_getres and clock_nanosleep syscalls will be limited to 1410 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1411 1412 If unsure say y. 1413 1414config PRINTK 1415 default y 1416 bool "Enable support for printk" if EXPERT 1417 select IRQ_WORK 1418 help 1419 This option enables normal printk support. Removing it 1420 eliminates most of the message strings from the kernel image 1421 and makes the kernel more or less silent. As this makes it 1422 very difficult to diagnose system problems, saying N here is 1423 strongly discouraged. 1424 1425config PRINTK_NMI 1426 def_bool y 1427 depends on PRINTK 1428 depends on HAVE_NMI 1429 1430config BUG 1431 bool "BUG() support" if EXPERT 1432 default y 1433 help 1434 Disabling this option eliminates support for BUG and WARN, reducing 1435 the size of your kernel image and potentially quietly ignoring 1436 numerous fatal conditions. You should only consider disabling this 1437 option for embedded systems with no facilities for reporting errors. 1438 Just say Y. 1439 1440config ELF_CORE 1441 depends on COREDUMP 1442 default y 1443 bool "Enable ELF core dumps" if EXPERT 1444 help 1445 Enable support for generating core dumps. Disabling saves about 4k. 1446 1447 1448config PCSPKR_PLATFORM 1449 bool "Enable PC-Speaker support" if EXPERT 1450 depends on HAVE_PCSPKR_PLATFORM 1451 select I8253_LOCK 1452 default y 1453 help 1454 This option allows to disable the internal PC-Speaker 1455 support, saving some memory. 1456 1457config BASE_FULL 1458 default y 1459 bool "Enable full-sized data structures for core" if EXPERT 1460 help 1461 Disabling this option reduces the size of miscellaneous core 1462 kernel data structures. This saves memory on small machines, 1463 but may reduce performance. 1464 1465config FUTEX 1466 bool "Enable futex support" if EXPERT 1467 default y 1468 imply RT_MUTEXES 1469 help 1470 Disabling this option will cause the kernel to be built without 1471 support for "fast userspace mutexes". The resulting kernel may not 1472 run glibc-based applications correctly. 1473 1474config FUTEX_PI 1475 bool 1476 depends on FUTEX && RT_MUTEXES 1477 default y 1478 1479config HAVE_FUTEX_CMPXCHG 1480 bool 1481 depends on FUTEX 1482 help 1483 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1484 is implemented and always working. This removes a couple of runtime 1485 checks. 1486 1487config EPOLL 1488 bool "Enable eventpoll support" if EXPERT 1489 default y 1490 help 1491 Disabling this option will cause the kernel to be built without 1492 support for epoll family of system calls. 1493 1494config SIGNALFD 1495 bool "Enable signalfd() system call" if EXPERT 1496 default y 1497 help 1498 Enable the signalfd() system call that allows to receive signals 1499 on a file descriptor. 1500 1501 If unsure, say Y. 1502 1503config TIMERFD 1504 bool "Enable timerfd() system call" if EXPERT 1505 default y 1506 help 1507 Enable the timerfd() system call that allows to receive timer 1508 events on a file descriptor. 1509 1510 If unsure, say Y. 1511 1512config EVENTFD 1513 bool "Enable eventfd() system call" if EXPERT 1514 default y 1515 help 1516 Enable the eventfd() system call that allows to receive both 1517 kernel notification (ie. KAIO) or userspace notifications. 1518 1519 If unsure, say Y. 1520 1521config SHMEM 1522 bool "Use full shmem filesystem" if EXPERT 1523 default y 1524 depends on MMU 1525 help 1526 The shmem is an internal filesystem used to manage shared memory. 1527 It is backed by swap and manages resource limits. It is also exported 1528 to userspace as tmpfs if TMPFS is enabled. Disabling this 1529 option replaces shmem and tmpfs with the much simpler ramfs code, 1530 which may be appropriate on small systems without swap. 1531 1532config AIO 1533 bool "Enable AIO support" if EXPERT 1534 default y 1535 help 1536 This option enables POSIX asynchronous I/O which may by used 1537 by some high performance threaded applications. Disabling 1538 this option saves about 7k. 1539 1540config IO_URING 1541 bool "Enable IO uring support" if EXPERT 1542 select ANON_INODES 1543 default y 1544 help 1545 This option enables support for the io_uring interface, enabling 1546 applications to submit and complete IO through submission and 1547 completion rings that are shared between the kernel and application. 1548 1549config ADVISE_SYSCALLS 1550 bool "Enable madvise/fadvise syscalls" if EXPERT 1551 default y 1552 help 1553 This option enables the madvise and fadvise syscalls, used by 1554 applications to advise the kernel about their future memory or file 1555 usage, improving performance. If building an embedded system where no 1556 applications use these syscalls, you can disable this option to save 1557 space. 1558 1559config MEMBARRIER 1560 bool "Enable membarrier() system call" if EXPERT 1561 default y 1562 help 1563 Enable the membarrier() system call that allows issuing memory 1564 barriers across all running threads, which can be used to distribute 1565 the cost of user-space memory barriers asymmetrically by transforming 1566 pairs of memory barriers into pairs consisting of membarrier() and a 1567 compiler barrier. 1568 1569 If unsure, say Y. 1570 1571config KALLSYMS 1572 bool "Load all symbols for debugging/ksymoops" if EXPERT 1573 default y 1574 help 1575 Say Y here to let the kernel print out symbolic crash information and 1576 symbolic stack backtraces. This increases the size of the kernel 1577 somewhat, as all symbols have to be loaded into the kernel image. 1578 1579config KALLSYMS_ALL 1580 bool "Include all symbols in kallsyms" 1581 depends on DEBUG_KERNEL && KALLSYMS 1582 help 1583 Normally kallsyms only contains the symbols of functions for nicer 1584 OOPS messages and backtraces (i.e., symbols from the text and inittext 1585 sections). This is sufficient for most cases. And only in very rare 1586 cases (e.g., when a debugger is used) all symbols are required (e.g., 1587 names of variables from the data sections, etc). 1588 1589 This option makes sure that all symbols are loaded into the kernel 1590 image (i.e., symbols from all sections) in cost of increased kernel 1591 size (depending on the kernel configuration, it may be 300KiB or 1592 something like this). 1593 1594 Say N unless you really need all symbols. 1595 1596config KALLSYMS_ABSOLUTE_PERCPU 1597 bool 1598 depends on KALLSYMS 1599 default X86_64 && SMP 1600 1601config KALLSYMS_BASE_RELATIVE 1602 bool 1603 depends on KALLSYMS 1604 default !IA64 1605 help 1606 Instead of emitting them as absolute values in the native word size, 1607 emit the symbol references in the kallsyms table as 32-bit entries, 1608 each containing a relative value in the range [base, base + U32_MAX] 1609 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1610 an absolute value in the range [0, S32_MAX] or a relative value in the 1611 range [base, base + S32_MAX], where base is the lowest relative symbol 1612 address encountered in the image. 1613 1614 On 64-bit builds, this reduces the size of the address table by 50%, 1615 but more importantly, it results in entries whose values are build 1616 time constants, and no relocation pass is required at runtime to fix 1617 up the entries based on the runtime load address of the kernel. 1618 1619# end of the "standard kernel features (expert users)" menu 1620 1621# syscall, maps, verifier 1622config BPF_SYSCALL 1623 bool "Enable bpf() system call" 1624 select BPF 1625 select IRQ_WORK 1626 default n 1627 help 1628 Enable the bpf() system call that allows to manipulate eBPF 1629 programs and maps via file descriptors. 1630 1631config BPF_JIT_ALWAYS_ON 1632 bool "Permanently enable BPF JIT and remove BPF interpreter" 1633 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1634 help 1635 Enables BPF JIT and removes BPF interpreter to avoid 1636 speculative execution of BPF instructions by the interpreter 1637 1638config USERFAULTFD 1639 bool "Enable userfaultfd() system call" 1640 depends on MMU 1641 help 1642 Enable the userfaultfd() system call that allows to intercept and 1643 handle page faults in userland. 1644 1645config ARCH_HAS_MEMBARRIER_CALLBACKS 1646 bool 1647 1648config ARCH_HAS_MEMBARRIER_SYNC_CORE 1649 bool 1650 1651config RSEQ 1652 bool "Enable rseq() system call" if EXPERT 1653 default y 1654 depends on HAVE_RSEQ 1655 select MEMBARRIER 1656 help 1657 Enable the restartable sequences system call. It provides a 1658 user-space cache for the current CPU number value, which 1659 speeds up getting the current CPU number from user-space, 1660 as well as an ABI to speed up user-space operations on 1661 per-CPU data. 1662 1663 If unsure, say Y. 1664 1665config DEBUG_RSEQ 1666 default n 1667 bool "Enabled debugging of rseq() system call" if EXPERT 1668 depends on RSEQ && DEBUG_KERNEL 1669 help 1670 Enable extra debugging checks for the rseq system call. 1671 1672 If unsure, say N. 1673 1674config EMBEDDED 1675 bool "Embedded system" 1676 option allnoconfig_y 1677 select EXPERT 1678 help 1679 This option should be enabled if compiling the kernel for 1680 an embedded system so certain expert options are available 1681 for configuration. 1682 1683config HAVE_PERF_EVENTS 1684 bool 1685 help 1686 See tools/perf/design.txt for details. 1687 1688config PERF_USE_VMALLOC 1689 bool 1690 help 1691 See tools/perf/design.txt for details 1692 1693config PC104 1694 bool "PC/104 support" if EXPERT 1695 help 1696 Expose PC/104 form factor device drivers and options available for 1697 selection and configuration. Enable this option if your target 1698 machine has a PC/104 bus. 1699 1700menu "Kernel Performance Events And Counters" 1701 1702config PERF_EVENTS 1703 bool "Kernel performance events and counters" 1704 default y if PROFILING 1705 depends on HAVE_PERF_EVENTS 1706 select IRQ_WORK 1707 select SRCU 1708 help 1709 Enable kernel support for various performance events provided 1710 by software and hardware. 1711 1712 Software events are supported either built-in or via the 1713 use of generic tracepoints. 1714 1715 Most modern CPUs support performance events via performance 1716 counter registers. These registers count the number of certain 1717 types of hw events: such as instructions executed, cachemisses 1718 suffered, or branches mis-predicted - without slowing down the 1719 kernel or applications. These registers can also trigger interrupts 1720 when a threshold number of events have passed - and can thus be 1721 used to profile the code that runs on that CPU. 1722 1723 The Linux Performance Event subsystem provides an abstraction of 1724 these software and hardware event capabilities, available via a 1725 system call and used by the "perf" utility in tools/perf/. It 1726 provides per task and per CPU counters, and it provides event 1727 capabilities on top of those. 1728 1729 Say Y if unsure. 1730 1731config DEBUG_PERF_USE_VMALLOC 1732 default n 1733 bool "Debug: use vmalloc to back perf mmap() buffers" 1734 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1735 select PERF_USE_VMALLOC 1736 help 1737 Use vmalloc memory to back perf mmap() buffers. 1738 1739 Mostly useful for debugging the vmalloc code on platforms 1740 that don't require it. 1741 1742 Say N if unsure. 1743 1744endmenu 1745 1746config VM_EVENT_COUNTERS 1747 default y 1748 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1749 help 1750 VM event counters are needed for event counts to be shown. 1751 This option allows the disabling of the VM event counters 1752 on EXPERT systems. /proc/vmstat will only show page counts 1753 if VM event counters are disabled. 1754 1755config SLUB_DEBUG 1756 default y 1757 bool "Enable SLUB debugging support" if EXPERT 1758 depends on SLUB && SYSFS 1759 help 1760 SLUB has extensive debug support features. Disabling these can 1761 result in significant savings in code size. This also disables 1762 SLUB sysfs support. /sys/slab will not exist and there will be 1763 no support for cache validation etc. 1764 1765config SLUB_MEMCG_SYSFS_ON 1766 default n 1767 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1768 depends on SLUB && SYSFS && MEMCG 1769 help 1770 SLUB creates a directory under /sys/kernel/slab for each 1771 allocation cache to host info and debug files. If memory 1772 cgroup is enabled, each cache can have per memory cgroup 1773 caches. SLUB can create the same sysfs directories for these 1774 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1775 to a very high number of debug files being created. This is 1776 controlled by slub_memcg_sysfs boot parameter and this 1777 config option determines the parameter's default value. 1778 1779config COMPAT_BRK 1780 bool "Disable heap randomization" 1781 default y 1782 help 1783 Randomizing heap placement makes heap exploits harder, but it 1784 also breaks ancient binaries (including anything libc5 based). 1785 This option changes the bootup default to heap randomization 1786 disabled, and can be overridden at runtime by setting 1787 /proc/sys/kernel/randomize_va_space to 2. 1788 1789 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1790 1791choice 1792 prompt "Choose SLAB allocator" 1793 default SLUB 1794 help 1795 This option allows to select a slab allocator. 1796 1797config SLAB 1798 bool "SLAB" 1799 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1800 help 1801 The regular slab allocator that is established and known to work 1802 well in all environments. It organizes cache hot objects in 1803 per cpu and per node queues. 1804 1805config SLUB 1806 bool "SLUB (Unqueued Allocator)" 1807 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1808 help 1809 SLUB is a slab allocator that minimizes cache line usage 1810 instead of managing queues of cached objects (SLAB approach). 1811 Per cpu caching is realized using slabs of objects instead 1812 of queues of objects. SLUB can use memory efficiently 1813 and has enhanced diagnostics. SLUB is the default choice for 1814 a slab allocator. 1815 1816config SLOB 1817 depends on EXPERT 1818 bool "SLOB (Simple Allocator)" 1819 help 1820 SLOB replaces the stock allocator with a drastically simpler 1821 allocator. SLOB is generally more space efficient but 1822 does not perform as well on large systems. 1823 1824endchoice 1825 1826config SLAB_MERGE_DEFAULT 1827 bool "Allow slab caches to be merged" 1828 default y 1829 help 1830 For reduced kernel memory fragmentation, slab caches can be 1831 merged when they share the same size and other characteristics. 1832 This carries a risk of kernel heap overflows being able to 1833 overwrite objects from merged caches (and more easily control 1834 cache layout), which makes such heap attacks easier to exploit 1835 by attackers. By keeping caches unmerged, these kinds of exploits 1836 can usually only damage objects in the same cache. To disable 1837 merging at runtime, "slab_nomerge" can be passed on the kernel 1838 command line. 1839 1840config SLAB_FREELIST_RANDOM 1841 default n 1842 depends on SLAB || SLUB 1843 bool "SLAB freelist randomization" 1844 help 1845 Randomizes the freelist order used on creating new pages. This 1846 security feature reduces the predictability of the kernel slab 1847 allocator against heap overflows. 1848 1849config SLAB_FREELIST_HARDENED 1850 bool "Harden slab freelist metadata" 1851 depends on SLUB 1852 help 1853 Many kernel heap attacks try to target slab cache metadata and 1854 other infrastructure. This options makes minor performance 1855 sacrifices to harden the kernel slab allocator against common 1856 freelist exploit methods. 1857 1858config SHUFFLE_PAGE_ALLOCATOR 1859 bool "Page allocator randomization" 1860 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1861 help 1862 Randomization of the page allocator improves the average 1863 utilization of a direct-mapped memory-side-cache. See section 1864 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1865 6.2a specification for an example of how a platform advertises 1866 the presence of a memory-side-cache. There are also incidental 1867 security benefits as it reduces the predictability of page 1868 allocations to compliment SLAB_FREELIST_RANDOM, but the 1869 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1870 10th order of pages is selected based on cache utilization 1871 benefits on x86. 1872 1873 While the randomization improves cache utilization it may 1874 negatively impact workloads on platforms without a cache. For 1875 this reason, by default, the randomization is enabled only 1876 after runtime detection of a direct-mapped memory-side-cache. 1877 Otherwise, the randomization may be force enabled with the 1878 'page_alloc.shuffle' kernel command line parameter. 1879 1880 Say Y if unsure. 1881 1882config SLUB_CPU_PARTIAL 1883 default y 1884 depends on SLUB && SMP 1885 bool "SLUB per cpu partial cache" 1886 help 1887 Per cpu partial caches accelerate objects allocation and freeing 1888 that is local to a processor at the price of more indeterminism 1889 in the latency of the free. On overflow these caches will be cleared 1890 which requires the taking of locks that may cause latency spikes. 1891 Typically one would choose no for a realtime system. 1892 1893config MMAP_ALLOW_UNINITIALIZED 1894 bool "Allow mmapped anonymous memory to be uninitialized" 1895 depends on EXPERT && !MMU 1896 default n 1897 help 1898 Normally, and according to the Linux spec, anonymous memory obtained 1899 from mmap() has its contents cleared before it is passed to 1900 userspace. Enabling this config option allows you to request that 1901 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1902 providing a huge performance boost. If this option is not enabled, 1903 then the flag will be ignored. 1904 1905 This is taken advantage of by uClibc's malloc(), and also by 1906 ELF-FDPIC binfmt's brk and stack allocator. 1907 1908 Because of the obvious security issues, this option should only be 1909 enabled on embedded devices where you control what is run in 1910 userspace. Since that isn't generally a problem on no-MMU systems, 1911 it is normally safe to say Y here. 1912 1913 See Documentation/nommu-mmap.txt for more information. 1914 1915config SYSTEM_DATA_VERIFICATION 1916 def_bool n 1917 select SYSTEM_TRUSTED_KEYRING 1918 select KEYS 1919 select CRYPTO 1920 select CRYPTO_RSA 1921 select ASYMMETRIC_KEY_TYPE 1922 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1923 select ASN1 1924 select OID_REGISTRY 1925 select X509_CERTIFICATE_PARSER 1926 select PKCS7_MESSAGE_PARSER 1927 help 1928 Provide PKCS#7 message verification using the contents of the system 1929 trusted keyring to provide public keys. This then can be used for 1930 module verification, kexec image verification and firmware blob 1931 verification. 1932 1933config PROFILING 1934 bool "Profiling support" 1935 help 1936 Say Y here to enable the extended profiling support mechanisms used 1937 by profilers such as OProfile. 1938 1939# 1940# Place an empty function call at each tracepoint site. Can be 1941# dynamically changed for a probe function. 1942# 1943config TRACEPOINTS 1944 bool 1945 1946endmenu # General setup 1947 1948source "arch/Kconfig" 1949 1950config RT_MUTEXES 1951 bool 1952 1953config BASE_SMALL 1954 int 1955 default 0 if BASE_FULL 1956 default 1 if !BASE_FULL 1957 1958menuconfig MODULES 1959 bool "Enable loadable module support" 1960 option modules 1961 help 1962 Kernel modules are small pieces of compiled code which can 1963 be inserted in the running kernel, rather than being 1964 permanently built into the kernel. You use the "modprobe" 1965 tool to add (and sometimes remove) them. If you say Y here, 1966 many parts of the kernel can be built as modules (by 1967 answering M instead of Y where indicated): this is most 1968 useful for infrequently used options which are not required 1969 for booting. For more information, see the man pages for 1970 modprobe, lsmod, modinfo, insmod and rmmod. 1971 1972 If you say Y here, you will need to run "make 1973 modules_install" to put the modules under /lib/modules/ 1974 where modprobe can find them (you may need to be root to do 1975 this). 1976 1977 If unsure, say Y. 1978 1979if MODULES 1980 1981config MODULE_FORCE_LOAD 1982 bool "Forced module loading" 1983 default n 1984 help 1985 Allow loading of modules without version information (ie. modprobe 1986 --force). Forced module loading sets the 'F' (forced) taint flag and 1987 is usually a really bad idea. 1988 1989config MODULE_UNLOAD 1990 bool "Module unloading" 1991 help 1992 Without this option you will not be able to unload any 1993 modules (note that some modules may not be unloadable 1994 anyway), which makes your kernel smaller, faster 1995 and simpler. If unsure, say Y. 1996 1997config MODULE_FORCE_UNLOAD 1998 bool "Forced module unloading" 1999 depends on MODULE_UNLOAD 2000 help 2001 This option allows you to force a module to unload, even if the 2002 kernel believes it is unsafe: the kernel will remove the module 2003 without waiting for anyone to stop using it (using the -f option to 2004 rmmod). This is mainly for kernel developers and desperate users. 2005 If unsure, say N. 2006 2007config MODVERSIONS 2008 bool "Module versioning support" 2009 help 2010 Usually, you have to use modules compiled with your kernel. 2011 Saying Y here makes it sometimes possible to use modules 2012 compiled for different kernels, by adding enough information 2013 to the modules to (hopefully) spot any changes which would 2014 make them incompatible with the kernel you are running. If 2015 unsure, say N. 2016 2017config MODULE_REL_CRCS 2018 bool 2019 depends on MODVERSIONS 2020 2021config MODULE_SRCVERSION_ALL 2022 bool "Source checksum for all modules" 2023 help 2024 Modules which contain a MODULE_VERSION get an extra "srcversion" 2025 field inserted into their modinfo section, which contains a 2026 sum of the source files which made it. This helps maintainers 2027 see exactly which source was used to build a module (since 2028 others sometimes change the module source without updating 2029 the version). With this option, such a "srcversion" field 2030 will be created for all modules. If unsure, say N. 2031 2032config MODULE_SIG 2033 bool "Module signature verification" 2034 depends on MODULES 2035 select SYSTEM_DATA_VERIFICATION 2036 help 2037 Check modules for valid signatures upon load: the signature 2038 is simply appended to the module. For more information see 2039 <file:Documentation/admin-guide/module-signing.rst>. 2040 2041 Note that this option adds the OpenSSL development packages as a 2042 kernel build dependency so that the signing tool can use its crypto 2043 library. 2044 2045 !!!WARNING!!! If you enable this option, you MUST make sure that the 2046 module DOES NOT get stripped after being signed. This includes the 2047 debuginfo strip done by some packagers (such as rpmbuild) and 2048 inclusion into an initramfs that wants the module size reduced. 2049 2050config MODULE_SIG_FORCE 2051 bool "Require modules to be validly signed" 2052 depends on MODULE_SIG 2053 help 2054 Reject unsigned modules or signed modules for which we don't have a 2055 key. Without this, such modules will simply taint the kernel. 2056 2057config MODULE_SIG_ALL 2058 bool "Automatically sign all modules" 2059 default y 2060 depends on MODULE_SIG 2061 help 2062 Sign all modules during make modules_install. Without this option, 2063 modules must be signed manually, using the scripts/sign-file tool. 2064 2065comment "Do not forget to sign required modules with scripts/sign-file" 2066 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2067 2068choice 2069 prompt "Which hash algorithm should modules be signed with?" 2070 depends on MODULE_SIG 2071 help 2072 This determines which sort of hashing algorithm will be used during 2073 signature generation. This algorithm _must_ be built into the kernel 2074 directly so that signature verification can take place. It is not 2075 possible to load a signed module containing the algorithm to check 2076 the signature on that module. 2077 2078config MODULE_SIG_SHA1 2079 bool "Sign modules with SHA-1" 2080 select CRYPTO_SHA1 2081 2082config MODULE_SIG_SHA224 2083 bool "Sign modules with SHA-224" 2084 select CRYPTO_SHA256 2085 2086config MODULE_SIG_SHA256 2087 bool "Sign modules with SHA-256" 2088 select CRYPTO_SHA256 2089 2090config MODULE_SIG_SHA384 2091 bool "Sign modules with SHA-384" 2092 select CRYPTO_SHA512 2093 2094config MODULE_SIG_SHA512 2095 bool "Sign modules with SHA-512" 2096 select CRYPTO_SHA512 2097 2098endchoice 2099 2100config MODULE_SIG_HASH 2101 string 2102 depends on MODULE_SIG 2103 default "sha1" if MODULE_SIG_SHA1 2104 default "sha224" if MODULE_SIG_SHA224 2105 default "sha256" if MODULE_SIG_SHA256 2106 default "sha384" if MODULE_SIG_SHA384 2107 default "sha512" if MODULE_SIG_SHA512 2108 2109config MODULE_COMPRESS 2110 bool "Compress modules on installation" 2111 depends on MODULES 2112 help 2113 2114 Compresses kernel modules when 'make modules_install' is run; gzip or 2115 xz depending on "Compression algorithm" below. 2116 2117 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 2118 2119 Out-of-tree kernel modules installed using Kbuild will also be 2120 compressed upon installation. 2121 2122 Note: for modules inside an initrd or initramfs, it's more efficient 2123 to compress the whole initrd or initramfs instead. 2124 2125 Note: This is fully compatible with signed modules. 2126 2127 If in doubt, say N. 2128 2129choice 2130 prompt "Compression algorithm" 2131 depends on MODULE_COMPRESS 2132 default MODULE_COMPRESS_GZIP 2133 help 2134 This determines which sort of compression will be used during 2135 'make modules_install'. 2136 2137 GZIP (default) and XZ are supported. 2138 2139config MODULE_COMPRESS_GZIP 2140 bool "GZIP" 2141 2142config MODULE_COMPRESS_XZ 2143 bool "XZ" 2144 2145endchoice 2146 2147config TRIM_UNUSED_KSYMS 2148 bool "Trim unused exported kernel symbols" 2149 depends on MODULES && !UNUSED_SYMBOLS 2150 help 2151 The kernel and some modules make many symbols available for 2152 other modules to use via EXPORT_SYMBOL() and variants. Depending 2153 on the set of modules being selected in your kernel configuration, 2154 many of those exported symbols might never be used. 2155 2156 This option allows for unused exported symbols to be dropped from 2157 the build. In turn, this provides the compiler more opportunities 2158 (especially when using LTO) for optimizing the code and reducing 2159 binary size. This might have some security advantages as well. 2160 2161 If unsure, or if you need to build out-of-tree modules, say N. 2162 2163endif # MODULES 2164 2165config MODULES_TREE_LOOKUP 2166 def_bool y 2167 depends on PERF_EVENTS || TRACING 2168 2169config INIT_ALL_POSSIBLE 2170 bool 2171 help 2172 Back when each arch used to define their own cpu_online_mask and 2173 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2174 with all 1s, and others with all 0s. When they were centralised, 2175 it was better to provide this option than to break all the archs 2176 and have several arch maintainers pursuing me down dark alleys. 2177 2178source "block/Kconfig" 2179 2180config PREEMPT_NOTIFIERS 2181 bool 2182 2183config PADATA 2184 depends on SMP 2185 bool 2186 2187config ASN1 2188 tristate 2189 help 2190 Build a simple ASN.1 grammar compiler that produces a bytecode output 2191 that can be interpreted by the ASN.1 stream decoder and used to 2192 inform it as to what tags are to be expected in a stream and what 2193 functions to call on what tags. 2194 2195source "kernel/Kconfig.locks" 2196 2197config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2198 bool 2199 2200# It may be useful for an architecture to override the definitions of the 2201# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2202# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2203# different calling convention for syscalls. They can also override the 2204# macros for not-implemented syscalls in kernel/sys_ni.c and 2205# kernel/time/posix-stubs.c. All these overrides need to be available in 2206# <asm/syscall_wrapper.h>. 2207config ARCH_HAS_SYSCALL_WRAPPER 2208 def_bool n 2209