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 (-O2)" 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_PERFORMANCE_O3 1244 bool "Optimize more for performance (-O3)" 1245 depends on ARC 1246 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives 1247 help 1248 Choosing this option will pass "-O3" to your compiler to optimize 1249 the kernel yet more for performance. 1250 1251config CC_OPTIMIZE_FOR_SIZE 1252 bool "Optimize for size (-Os)" 1253 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives 1254 help 1255 Choosing this option will pass "-Os" to your compiler resulting 1256 in a smaller kernel. 1257 1258endchoice 1259 1260config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1261 bool 1262 help 1263 This requires that the arch annotates or otherwise protects 1264 its external entry points from being discarded. Linker scripts 1265 must also merge .text.*, .data.*, and .bss.* correctly into 1266 output sections. Care must be taken not to pull in unrelated 1267 sections (e.g., '.text.init'). Typically '.' in section names 1268 is used to distinguish them from label names / C identifiers. 1269 1270config LD_DEAD_CODE_DATA_ELIMINATION 1271 bool "Dead code and data elimination (EXPERIMENTAL)" 1272 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1273 depends on EXPERT 1274 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800) 1275 depends on $(cc-option,-ffunction-sections -fdata-sections) 1276 depends on $(ld-option,--gc-sections) 1277 help 1278 Enable this if you want to do dead code and data elimination with 1279 the linker by compiling with -ffunction-sections -fdata-sections, 1280 and linking with --gc-sections. 1281 1282 This can reduce on disk and in-memory size of the kernel 1283 code and static data, particularly for small configs and 1284 on small systems. This has the possibility of introducing 1285 silently broken kernel if the required annotations are not 1286 present. This option is not well tested yet, so use at your 1287 own risk. 1288 1289config SYSCTL 1290 bool 1291 1292config HAVE_UID16 1293 bool 1294 1295config SYSCTL_EXCEPTION_TRACE 1296 bool 1297 help 1298 Enable support for /proc/sys/debug/exception-trace. 1299 1300config SYSCTL_ARCH_UNALIGN_NO_WARN 1301 bool 1302 help 1303 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1304 Allows arch to define/use @no_unaligned_warning to possibly warn 1305 about unaligned access emulation going on under the hood. 1306 1307config SYSCTL_ARCH_UNALIGN_ALLOW 1308 bool 1309 help 1310 Enable support for /proc/sys/kernel/unaligned-trap 1311 Allows arches to define/use @unaligned_enabled to runtime toggle 1312 the unaligned access emulation. 1313 see arch/parisc/kernel/unaligned.c for reference 1314 1315config HAVE_PCSPKR_PLATFORM 1316 bool 1317 1318# interpreter that classic socket filters depend on 1319config BPF 1320 bool 1321 1322menuconfig EXPERT 1323 bool "Configure standard kernel features (expert users)" 1324 # Unhide debug options, to make the on-by-default options visible 1325 select DEBUG_KERNEL 1326 help 1327 This option allows certain base kernel options and settings 1328 to be disabled or tweaked. This is for specialized 1329 environments which can tolerate a "non-standard" kernel. 1330 Only use this if you really know what you are doing. 1331 1332config UID16 1333 bool "Enable 16-bit UID system calls" if EXPERT 1334 depends on HAVE_UID16 && MULTIUSER 1335 default y 1336 help 1337 This enables the legacy 16-bit UID syscall wrappers. 1338 1339config MULTIUSER 1340 bool "Multiple users, groups and capabilities support" if EXPERT 1341 default y 1342 help 1343 This option enables support for non-root users, groups and 1344 capabilities. 1345 1346 If you say N here, all processes will run with UID 0, GID 0, and all 1347 possible capabilities. Saying N here also compiles out support for 1348 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1349 setgid, and capset. 1350 1351 If unsure, say Y here. 1352 1353config SGETMASK_SYSCALL 1354 bool "sgetmask/ssetmask syscalls support" if EXPERT 1355 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1356 ---help--- 1357 sys_sgetmask and sys_ssetmask are obsolete system calls 1358 no longer supported in libc but still enabled by default in some 1359 architectures. 1360 1361 If unsure, leave the default option here. 1362 1363config SYSFS_SYSCALL 1364 bool "Sysfs syscall support" if EXPERT 1365 default y 1366 ---help--- 1367 sys_sysfs is an obsolete system call no longer supported in libc. 1368 Note that disabling this option is more secure but might break 1369 compatibility with some systems. 1370 1371 If unsure say Y here. 1372 1373config SYSCTL_SYSCALL 1374 bool "Sysctl syscall support" if EXPERT 1375 depends on PROC_SYSCTL 1376 default n 1377 select SYSCTL 1378 ---help--- 1379 sys_sysctl uses binary paths that have been found challenging 1380 to properly maintain and use. The interface in /proc/sys 1381 using paths with ascii names is now the primary path to this 1382 information. 1383 1384 Almost nothing using the binary sysctl interface so if you are 1385 trying to save some space it is probably safe to disable this, 1386 making your kernel marginally smaller. 1387 1388 If unsure say N here. 1389 1390config FHANDLE 1391 bool "open by fhandle syscalls" if EXPERT 1392 select EXPORTFS 1393 default y 1394 help 1395 If you say Y here, a user level program will be able to map 1396 file names to handle and then later use the handle for 1397 different file system operations. This is useful in implementing 1398 userspace file servers, which now track files using handles instead 1399 of names. The handle would remain the same even if file names 1400 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1401 syscalls. 1402 1403config POSIX_TIMERS 1404 bool "Posix Clocks & timers" if EXPERT 1405 default y 1406 help 1407 This includes native support for POSIX timers to the kernel. 1408 Some embedded systems have no use for them and therefore they 1409 can be configured out to reduce the size of the kernel image. 1410 1411 When this option is disabled, the following syscalls won't be 1412 available: timer_create, timer_gettime: timer_getoverrun, 1413 timer_settime, timer_delete, clock_adjtime, getitimer, 1414 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1415 clock_getres and clock_nanosleep syscalls will be limited to 1416 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1417 1418 If unsure say y. 1419 1420config PRINTK 1421 default y 1422 bool "Enable support for printk" if EXPERT 1423 select IRQ_WORK 1424 help 1425 This option enables normal printk support. Removing it 1426 eliminates most of the message strings from the kernel image 1427 and makes the kernel more or less silent. As this makes it 1428 very difficult to diagnose system problems, saying N here is 1429 strongly discouraged. 1430 1431config PRINTK_NMI 1432 def_bool y 1433 depends on PRINTK 1434 depends on HAVE_NMI 1435 1436config BUG 1437 bool "BUG() support" if EXPERT 1438 default y 1439 help 1440 Disabling this option eliminates support for BUG and WARN, reducing 1441 the size of your kernel image and potentially quietly ignoring 1442 numerous fatal conditions. You should only consider disabling this 1443 option for embedded systems with no facilities for reporting errors. 1444 Just say Y. 1445 1446config ELF_CORE 1447 depends on COREDUMP 1448 default y 1449 bool "Enable ELF core dumps" if EXPERT 1450 help 1451 Enable support for generating core dumps. Disabling saves about 4k. 1452 1453 1454config PCSPKR_PLATFORM 1455 bool "Enable PC-Speaker support" if EXPERT 1456 depends on HAVE_PCSPKR_PLATFORM 1457 select I8253_LOCK 1458 default y 1459 help 1460 This option allows to disable the internal PC-Speaker 1461 support, saving some memory. 1462 1463config BASE_FULL 1464 default y 1465 bool "Enable full-sized data structures for core" if EXPERT 1466 help 1467 Disabling this option reduces the size of miscellaneous core 1468 kernel data structures. This saves memory on small machines, 1469 but may reduce performance. 1470 1471config FUTEX 1472 bool "Enable futex support" if EXPERT 1473 default y 1474 imply RT_MUTEXES 1475 help 1476 Disabling this option will cause the kernel to be built without 1477 support for "fast userspace mutexes". The resulting kernel may not 1478 run glibc-based applications correctly. 1479 1480config FUTEX_PI 1481 bool 1482 depends on FUTEX && RT_MUTEXES 1483 default y 1484 1485config HAVE_FUTEX_CMPXCHG 1486 bool 1487 depends on FUTEX 1488 help 1489 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1490 is implemented and always working. This removes a couple of runtime 1491 checks. 1492 1493config EPOLL 1494 bool "Enable eventpoll support" if EXPERT 1495 default y 1496 help 1497 Disabling this option will cause the kernel to be built without 1498 support for epoll family of system calls. 1499 1500config SIGNALFD 1501 bool "Enable signalfd() system call" if EXPERT 1502 default y 1503 help 1504 Enable the signalfd() system call that allows to receive signals 1505 on a file descriptor. 1506 1507 If unsure, say Y. 1508 1509config TIMERFD 1510 bool "Enable timerfd() system call" if EXPERT 1511 default y 1512 help 1513 Enable the timerfd() system call that allows to receive timer 1514 events on a file descriptor. 1515 1516 If unsure, say Y. 1517 1518config EVENTFD 1519 bool "Enable eventfd() system call" if EXPERT 1520 default y 1521 help 1522 Enable the eventfd() system call that allows to receive both 1523 kernel notification (ie. KAIO) or userspace notifications. 1524 1525 If unsure, say Y. 1526 1527config SHMEM 1528 bool "Use full shmem filesystem" if EXPERT 1529 default y 1530 depends on MMU 1531 help 1532 The shmem is an internal filesystem used to manage shared memory. 1533 It is backed by swap and manages resource limits. It is also exported 1534 to userspace as tmpfs if TMPFS is enabled. Disabling this 1535 option replaces shmem and tmpfs with the much simpler ramfs code, 1536 which may be appropriate on small systems without swap. 1537 1538config AIO 1539 bool "Enable AIO support" if EXPERT 1540 default y 1541 help 1542 This option enables POSIX asynchronous I/O which may by used 1543 by some high performance threaded applications. Disabling 1544 this option saves about 7k. 1545 1546config IO_URING 1547 bool "Enable IO uring support" if EXPERT 1548 select ANON_INODES 1549 default y 1550 help 1551 This option enables support for the io_uring interface, enabling 1552 applications to submit and complete IO through submission and 1553 completion rings that are shared between the kernel and application. 1554 1555config ADVISE_SYSCALLS 1556 bool "Enable madvise/fadvise syscalls" if EXPERT 1557 default y 1558 help 1559 This option enables the madvise and fadvise syscalls, used by 1560 applications to advise the kernel about their future memory or file 1561 usage, improving performance. If building an embedded system where no 1562 applications use these syscalls, you can disable this option to save 1563 space. 1564 1565config MEMBARRIER 1566 bool "Enable membarrier() system call" if EXPERT 1567 default y 1568 help 1569 Enable the membarrier() system call that allows issuing memory 1570 barriers across all running threads, which can be used to distribute 1571 the cost of user-space memory barriers asymmetrically by transforming 1572 pairs of memory barriers into pairs consisting of membarrier() and a 1573 compiler barrier. 1574 1575 If unsure, say Y. 1576 1577config KALLSYMS 1578 bool "Load all symbols for debugging/ksymoops" if EXPERT 1579 default y 1580 help 1581 Say Y here to let the kernel print out symbolic crash information and 1582 symbolic stack backtraces. This increases the size of the kernel 1583 somewhat, as all symbols have to be loaded into the kernel image. 1584 1585config KALLSYMS_ALL 1586 bool "Include all symbols in kallsyms" 1587 depends on DEBUG_KERNEL && KALLSYMS 1588 help 1589 Normally kallsyms only contains the symbols of functions for nicer 1590 OOPS messages and backtraces (i.e., symbols from the text and inittext 1591 sections). This is sufficient for most cases. And only in very rare 1592 cases (e.g., when a debugger is used) all symbols are required (e.g., 1593 names of variables from the data sections, etc). 1594 1595 This option makes sure that all symbols are loaded into the kernel 1596 image (i.e., symbols from all sections) in cost of increased kernel 1597 size (depending on the kernel configuration, it may be 300KiB or 1598 something like this). 1599 1600 Say N unless you really need all symbols. 1601 1602config KALLSYMS_ABSOLUTE_PERCPU 1603 bool 1604 depends on KALLSYMS 1605 default X86_64 && SMP 1606 1607config KALLSYMS_BASE_RELATIVE 1608 bool 1609 depends on KALLSYMS 1610 default !IA64 1611 help 1612 Instead of emitting them as absolute values in the native word size, 1613 emit the symbol references in the kallsyms table as 32-bit entries, 1614 each containing a relative value in the range [base, base + U32_MAX] 1615 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1616 an absolute value in the range [0, S32_MAX] or a relative value in the 1617 range [base, base + S32_MAX], where base is the lowest relative symbol 1618 address encountered in the image. 1619 1620 On 64-bit builds, this reduces the size of the address table by 50%, 1621 but more importantly, it results in entries whose values are build 1622 time constants, and no relocation pass is required at runtime to fix 1623 up the entries based on the runtime load address of the kernel. 1624 1625# end of the "standard kernel features (expert users)" menu 1626 1627# syscall, maps, verifier 1628config BPF_SYSCALL 1629 bool "Enable bpf() system call" 1630 select BPF 1631 select IRQ_WORK 1632 default n 1633 help 1634 Enable the bpf() system call that allows to manipulate eBPF 1635 programs and maps via file descriptors. 1636 1637config BPF_JIT_ALWAYS_ON 1638 bool "Permanently enable BPF JIT and remove BPF interpreter" 1639 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1640 help 1641 Enables BPF JIT and removes BPF interpreter to avoid 1642 speculative execution of BPF instructions by the interpreter 1643 1644config USERFAULTFD 1645 bool "Enable userfaultfd() system call" 1646 depends on MMU 1647 help 1648 Enable the userfaultfd() system call that allows to intercept and 1649 handle page faults in userland. 1650 1651config ARCH_HAS_MEMBARRIER_CALLBACKS 1652 bool 1653 1654config ARCH_HAS_MEMBARRIER_SYNC_CORE 1655 bool 1656 1657config RSEQ 1658 bool "Enable rseq() system call" if EXPERT 1659 default y 1660 depends on HAVE_RSEQ 1661 select MEMBARRIER 1662 help 1663 Enable the restartable sequences system call. It provides a 1664 user-space cache for the current CPU number value, which 1665 speeds up getting the current CPU number from user-space, 1666 as well as an ABI to speed up user-space operations on 1667 per-CPU data. 1668 1669 If unsure, say Y. 1670 1671config DEBUG_RSEQ 1672 default n 1673 bool "Enabled debugging of rseq() system call" if EXPERT 1674 depends on RSEQ && DEBUG_KERNEL 1675 help 1676 Enable extra debugging checks for the rseq system call. 1677 1678 If unsure, say N. 1679 1680config EMBEDDED 1681 bool "Embedded system" 1682 option allnoconfig_y 1683 select EXPERT 1684 help 1685 This option should be enabled if compiling the kernel for 1686 an embedded system so certain expert options are available 1687 for configuration. 1688 1689config HAVE_PERF_EVENTS 1690 bool 1691 help 1692 See tools/perf/design.txt for details. 1693 1694config PERF_USE_VMALLOC 1695 bool 1696 help 1697 See tools/perf/design.txt for details 1698 1699config PC104 1700 bool "PC/104 support" if EXPERT 1701 help 1702 Expose PC/104 form factor device drivers and options available for 1703 selection and configuration. Enable this option if your target 1704 machine has a PC/104 bus. 1705 1706menu "Kernel Performance Events And Counters" 1707 1708config PERF_EVENTS 1709 bool "Kernel performance events and counters" 1710 default y if PROFILING 1711 depends on HAVE_PERF_EVENTS 1712 select IRQ_WORK 1713 select SRCU 1714 help 1715 Enable kernel support for various performance events provided 1716 by software and hardware. 1717 1718 Software events are supported either built-in or via the 1719 use of generic tracepoints. 1720 1721 Most modern CPUs support performance events via performance 1722 counter registers. These registers count the number of certain 1723 types of hw events: such as instructions executed, cachemisses 1724 suffered, or branches mis-predicted - without slowing down the 1725 kernel or applications. These registers can also trigger interrupts 1726 when a threshold number of events have passed - and can thus be 1727 used to profile the code that runs on that CPU. 1728 1729 The Linux Performance Event subsystem provides an abstraction of 1730 these software and hardware event capabilities, available via a 1731 system call and used by the "perf" utility in tools/perf/. It 1732 provides per task and per CPU counters, and it provides event 1733 capabilities on top of those. 1734 1735 Say Y if unsure. 1736 1737config DEBUG_PERF_USE_VMALLOC 1738 default n 1739 bool "Debug: use vmalloc to back perf mmap() buffers" 1740 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1741 select PERF_USE_VMALLOC 1742 help 1743 Use vmalloc memory to back perf mmap() buffers. 1744 1745 Mostly useful for debugging the vmalloc code on platforms 1746 that don't require it. 1747 1748 Say N if unsure. 1749 1750endmenu 1751 1752config VM_EVENT_COUNTERS 1753 default y 1754 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1755 help 1756 VM event counters are needed for event counts to be shown. 1757 This option allows the disabling of the VM event counters 1758 on EXPERT systems. /proc/vmstat will only show page counts 1759 if VM event counters are disabled. 1760 1761config SLUB_DEBUG 1762 default y 1763 bool "Enable SLUB debugging support" if EXPERT 1764 depends on SLUB && SYSFS 1765 help 1766 SLUB has extensive debug support features. Disabling these can 1767 result in significant savings in code size. This also disables 1768 SLUB sysfs support. /sys/slab will not exist and there will be 1769 no support for cache validation etc. 1770 1771config SLUB_MEMCG_SYSFS_ON 1772 default n 1773 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1774 depends on SLUB && SYSFS && MEMCG 1775 help 1776 SLUB creates a directory under /sys/kernel/slab for each 1777 allocation cache to host info and debug files. If memory 1778 cgroup is enabled, each cache can have per memory cgroup 1779 caches. SLUB can create the same sysfs directories for these 1780 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1781 to a very high number of debug files being created. This is 1782 controlled by slub_memcg_sysfs boot parameter and this 1783 config option determines the parameter's default value. 1784 1785config COMPAT_BRK 1786 bool "Disable heap randomization" 1787 default y 1788 help 1789 Randomizing heap placement makes heap exploits harder, but it 1790 also breaks ancient binaries (including anything libc5 based). 1791 This option changes the bootup default to heap randomization 1792 disabled, and can be overridden at runtime by setting 1793 /proc/sys/kernel/randomize_va_space to 2. 1794 1795 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1796 1797choice 1798 prompt "Choose SLAB allocator" 1799 default SLUB 1800 help 1801 This option allows to select a slab allocator. 1802 1803config SLAB 1804 bool "SLAB" 1805 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1806 help 1807 The regular slab allocator that is established and known to work 1808 well in all environments. It organizes cache hot objects in 1809 per cpu and per node queues. 1810 1811config SLUB 1812 bool "SLUB (Unqueued Allocator)" 1813 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1814 help 1815 SLUB is a slab allocator that minimizes cache line usage 1816 instead of managing queues of cached objects (SLAB approach). 1817 Per cpu caching is realized using slabs of objects instead 1818 of queues of objects. SLUB can use memory efficiently 1819 and has enhanced diagnostics. SLUB is the default choice for 1820 a slab allocator. 1821 1822config SLOB 1823 depends on EXPERT 1824 bool "SLOB (Simple Allocator)" 1825 help 1826 SLOB replaces the stock allocator with a drastically simpler 1827 allocator. SLOB is generally more space efficient but 1828 does not perform as well on large systems. 1829 1830endchoice 1831 1832config SLAB_MERGE_DEFAULT 1833 bool "Allow slab caches to be merged" 1834 default y 1835 help 1836 For reduced kernel memory fragmentation, slab caches can be 1837 merged when they share the same size and other characteristics. 1838 This carries a risk of kernel heap overflows being able to 1839 overwrite objects from merged caches (and more easily control 1840 cache layout), which makes such heap attacks easier to exploit 1841 by attackers. By keeping caches unmerged, these kinds of exploits 1842 can usually only damage objects in the same cache. To disable 1843 merging at runtime, "slab_nomerge" can be passed on the kernel 1844 command line. 1845 1846config SLAB_FREELIST_RANDOM 1847 default n 1848 depends on SLAB || SLUB 1849 bool "SLAB freelist randomization" 1850 help 1851 Randomizes the freelist order used on creating new pages. This 1852 security feature reduces the predictability of the kernel slab 1853 allocator against heap overflows. 1854 1855config SLAB_FREELIST_HARDENED 1856 bool "Harden slab freelist metadata" 1857 depends on SLUB 1858 help 1859 Many kernel heap attacks try to target slab cache metadata and 1860 other infrastructure. This options makes minor performance 1861 sacrifices to harden the kernel slab allocator against common 1862 freelist exploit methods. 1863 1864config SHUFFLE_PAGE_ALLOCATOR 1865 bool "Page allocator randomization" 1866 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1867 help 1868 Randomization of the page allocator improves the average 1869 utilization of a direct-mapped memory-side-cache. See section 1870 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1871 6.2a specification for an example of how a platform advertises 1872 the presence of a memory-side-cache. There are also incidental 1873 security benefits as it reduces the predictability of page 1874 allocations to compliment SLAB_FREELIST_RANDOM, but the 1875 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1876 10th order of pages is selected based on cache utilization 1877 benefits on x86. 1878 1879 While the randomization improves cache utilization it may 1880 negatively impact workloads on platforms without a cache. For 1881 this reason, by default, the randomization is enabled only 1882 after runtime detection of a direct-mapped memory-side-cache. 1883 Otherwise, the randomization may be force enabled with the 1884 'page_alloc.shuffle' kernel command line parameter. 1885 1886 Say Y if unsure. 1887 1888config SLUB_CPU_PARTIAL 1889 default y 1890 depends on SLUB && SMP 1891 bool "SLUB per cpu partial cache" 1892 help 1893 Per cpu partial caches accelerate objects allocation and freeing 1894 that is local to a processor at the price of more indeterminism 1895 in the latency of the free. On overflow these caches will be cleared 1896 which requires the taking of locks that may cause latency spikes. 1897 Typically one would choose no for a realtime system. 1898 1899config MMAP_ALLOW_UNINITIALIZED 1900 bool "Allow mmapped anonymous memory to be uninitialized" 1901 depends on EXPERT && !MMU 1902 default n 1903 help 1904 Normally, and according to the Linux spec, anonymous memory obtained 1905 from mmap() has its contents cleared before it is passed to 1906 userspace. Enabling this config option allows you to request that 1907 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1908 providing a huge performance boost. If this option is not enabled, 1909 then the flag will be ignored. 1910 1911 This is taken advantage of by uClibc's malloc(), and also by 1912 ELF-FDPIC binfmt's brk and stack allocator. 1913 1914 Because of the obvious security issues, this option should only be 1915 enabled on embedded devices where you control what is run in 1916 userspace. Since that isn't generally a problem on no-MMU systems, 1917 it is normally safe to say Y here. 1918 1919 See Documentation/nommu-mmap.txt for more information. 1920 1921config SYSTEM_DATA_VERIFICATION 1922 def_bool n 1923 select SYSTEM_TRUSTED_KEYRING 1924 select KEYS 1925 select CRYPTO 1926 select CRYPTO_RSA 1927 select ASYMMETRIC_KEY_TYPE 1928 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1929 select ASN1 1930 select OID_REGISTRY 1931 select X509_CERTIFICATE_PARSER 1932 select PKCS7_MESSAGE_PARSER 1933 help 1934 Provide PKCS#7 message verification using the contents of the system 1935 trusted keyring to provide public keys. This then can be used for 1936 module verification, kexec image verification and firmware blob 1937 verification. 1938 1939config PROFILING 1940 bool "Profiling support" 1941 help 1942 Say Y here to enable the extended profiling support mechanisms used 1943 by profilers such as OProfile. 1944 1945# 1946# Place an empty function call at each tracepoint site. Can be 1947# dynamically changed for a probe function. 1948# 1949config TRACEPOINTS 1950 bool 1951 1952endmenu # General setup 1953 1954source "arch/Kconfig" 1955 1956config RT_MUTEXES 1957 bool 1958 1959config BASE_SMALL 1960 int 1961 default 0 if BASE_FULL 1962 default 1 if !BASE_FULL 1963 1964menuconfig MODULES 1965 bool "Enable loadable module support" 1966 option modules 1967 help 1968 Kernel modules are small pieces of compiled code which can 1969 be inserted in the running kernel, rather than being 1970 permanently built into the kernel. You use the "modprobe" 1971 tool to add (and sometimes remove) them. If you say Y here, 1972 many parts of the kernel can be built as modules (by 1973 answering M instead of Y where indicated): this is most 1974 useful for infrequently used options which are not required 1975 for booting. For more information, see the man pages for 1976 modprobe, lsmod, modinfo, insmod and rmmod. 1977 1978 If you say Y here, you will need to run "make 1979 modules_install" to put the modules under /lib/modules/ 1980 where modprobe can find them (you may need to be root to do 1981 this). 1982 1983 If unsure, say Y. 1984 1985if MODULES 1986 1987config MODULE_FORCE_LOAD 1988 bool "Forced module loading" 1989 default n 1990 help 1991 Allow loading of modules without version information (ie. modprobe 1992 --force). Forced module loading sets the 'F' (forced) taint flag and 1993 is usually a really bad idea. 1994 1995config MODULE_UNLOAD 1996 bool "Module unloading" 1997 help 1998 Without this option you will not be able to unload any 1999 modules (note that some modules may not be unloadable 2000 anyway), which makes your kernel smaller, faster 2001 and simpler. If unsure, say Y. 2002 2003config MODULE_FORCE_UNLOAD 2004 bool "Forced module unloading" 2005 depends on MODULE_UNLOAD 2006 help 2007 This option allows you to force a module to unload, even if the 2008 kernel believes it is unsafe: the kernel will remove the module 2009 without waiting for anyone to stop using it (using the -f option to 2010 rmmod). This is mainly for kernel developers and desperate users. 2011 If unsure, say N. 2012 2013config MODVERSIONS 2014 bool "Module versioning support" 2015 help 2016 Usually, you have to use modules compiled with your kernel. 2017 Saying Y here makes it sometimes possible to use modules 2018 compiled for different kernels, by adding enough information 2019 to the modules to (hopefully) spot any changes which would 2020 make them incompatible with the kernel you are running. If 2021 unsure, say N. 2022 2023config ASM_MODVERSIONS 2024 bool 2025 default HAVE_ASM_MODVERSIONS && MODVERSIONS 2026 help 2027 This enables module versioning for exported symbols also from 2028 assembly. This can be enabled only when the target architecture 2029 supports it. 2030 2031config MODULE_REL_CRCS 2032 bool 2033 depends on MODVERSIONS 2034 2035config MODULE_SRCVERSION_ALL 2036 bool "Source checksum for all modules" 2037 help 2038 Modules which contain a MODULE_VERSION get an extra "srcversion" 2039 field inserted into their modinfo section, which contains a 2040 sum of the source files which made it. This helps maintainers 2041 see exactly which source was used to build a module (since 2042 others sometimes change the module source without updating 2043 the version). With this option, such a "srcversion" field 2044 will be created for all modules. If unsure, say N. 2045 2046config MODULE_SIG 2047 bool "Module signature verification" 2048 depends on MODULES 2049 select SYSTEM_DATA_VERIFICATION 2050 help 2051 Check modules for valid signatures upon load: the signature 2052 is simply appended to the module. For more information see 2053 <file:Documentation/admin-guide/module-signing.rst>. 2054 2055 Note that this option adds the OpenSSL development packages as a 2056 kernel build dependency so that the signing tool can use its crypto 2057 library. 2058 2059 !!!WARNING!!! If you enable this option, you MUST make sure that the 2060 module DOES NOT get stripped after being signed. This includes the 2061 debuginfo strip done by some packagers (such as rpmbuild) and 2062 inclusion into an initramfs that wants the module size reduced. 2063 2064config MODULE_SIG_FORCE 2065 bool "Require modules to be validly signed" 2066 depends on MODULE_SIG 2067 help 2068 Reject unsigned modules or signed modules for which we don't have a 2069 key. Without this, such modules will simply taint the kernel. 2070 2071config MODULE_SIG_ALL 2072 bool "Automatically sign all modules" 2073 default y 2074 depends on MODULE_SIG 2075 help 2076 Sign all modules during make modules_install. Without this option, 2077 modules must be signed manually, using the scripts/sign-file tool. 2078 2079comment "Do not forget to sign required modules with scripts/sign-file" 2080 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2081 2082choice 2083 prompt "Which hash algorithm should modules be signed with?" 2084 depends on MODULE_SIG 2085 help 2086 This determines which sort of hashing algorithm will be used during 2087 signature generation. This algorithm _must_ be built into the kernel 2088 directly so that signature verification can take place. It is not 2089 possible to load a signed module containing the algorithm to check 2090 the signature on that module. 2091 2092config MODULE_SIG_SHA1 2093 bool "Sign modules with SHA-1" 2094 select CRYPTO_SHA1 2095 2096config MODULE_SIG_SHA224 2097 bool "Sign modules with SHA-224" 2098 select CRYPTO_SHA256 2099 2100config MODULE_SIG_SHA256 2101 bool "Sign modules with SHA-256" 2102 select CRYPTO_SHA256 2103 2104config MODULE_SIG_SHA384 2105 bool "Sign modules with SHA-384" 2106 select CRYPTO_SHA512 2107 2108config MODULE_SIG_SHA512 2109 bool "Sign modules with SHA-512" 2110 select CRYPTO_SHA512 2111 2112endchoice 2113 2114config MODULE_SIG_HASH 2115 string 2116 depends on MODULE_SIG 2117 default "sha1" if MODULE_SIG_SHA1 2118 default "sha224" if MODULE_SIG_SHA224 2119 default "sha256" if MODULE_SIG_SHA256 2120 default "sha384" if MODULE_SIG_SHA384 2121 default "sha512" if MODULE_SIG_SHA512 2122 2123config MODULE_COMPRESS 2124 bool "Compress modules on installation" 2125 depends on MODULES 2126 help 2127 2128 Compresses kernel modules when 'make modules_install' is run; gzip or 2129 xz depending on "Compression algorithm" below. 2130 2131 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 2132 2133 Out-of-tree kernel modules installed using Kbuild will also be 2134 compressed upon installation. 2135 2136 Note: for modules inside an initrd or initramfs, it's more efficient 2137 to compress the whole initrd or initramfs instead. 2138 2139 Note: This is fully compatible with signed modules. 2140 2141 If in doubt, say N. 2142 2143choice 2144 prompt "Compression algorithm" 2145 depends on MODULE_COMPRESS 2146 default MODULE_COMPRESS_GZIP 2147 help 2148 This determines which sort of compression will be used during 2149 'make modules_install'. 2150 2151 GZIP (default) and XZ are supported. 2152 2153config MODULE_COMPRESS_GZIP 2154 bool "GZIP" 2155 2156config MODULE_COMPRESS_XZ 2157 bool "XZ" 2158 2159endchoice 2160 2161config TRIM_UNUSED_KSYMS 2162 bool "Trim unused exported kernel symbols" 2163 depends on MODULES && !UNUSED_SYMBOLS 2164 help 2165 The kernel and some modules make many symbols available for 2166 other modules to use via EXPORT_SYMBOL() and variants. Depending 2167 on the set of modules being selected in your kernel configuration, 2168 many of those exported symbols might never be used. 2169 2170 This option allows for unused exported symbols to be dropped from 2171 the build. In turn, this provides the compiler more opportunities 2172 (especially when using LTO) for optimizing the code and reducing 2173 binary size. This might have some security advantages as well. 2174 2175 If unsure, or if you need to build out-of-tree modules, say N. 2176 2177endif # MODULES 2178 2179config MODULES_TREE_LOOKUP 2180 def_bool y 2181 depends on PERF_EVENTS || TRACING 2182 2183config INIT_ALL_POSSIBLE 2184 bool 2185 help 2186 Back when each arch used to define their own cpu_online_mask and 2187 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2188 with all 1s, and others with all 0s. When they were centralised, 2189 it was better to provide this option than to break all the archs 2190 and have several arch maintainers pursuing me down dark alleys. 2191 2192source "block/Kconfig" 2193 2194config PREEMPT_NOTIFIERS 2195 bool 2196 2197config PADATA 2198 depends on SMP 2199 bool 2200 2201config ASN1 2202 tristate 2203 help 2204 Build a simple ASN.1 grammar compiler that produces a bytecode output 2205 that can be interpreted by the ASN.1 stream decoder and used to 2206 inform it as to what tags are to be expected in a stream and what 2207 functions to call on what tags. 2208 2209source "kernel/Kconfig.locks" 2210 2211config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2212 bool 2213 2214# It may be useful for an architecture to override the definitions of the 2215# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2216# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2217# different calling convention for syscalls. They can also override the 2218# macros for not-implemented syscalls in kernel/sys_ni.c and 2219# kernel/time/posix-stubs.c. All these overrides need to be available in 2220# <asm/syscall_wrapper.h>. 2221config ARCH_HAS_SYSCALL_WRAPPER 2222 def_bool n 2223