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_ASM_INLINE 37 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 38 39config CC_HAS_WARN_MAYBE_UNINITIALIZED 40 def_bool $(cc-option,-Wmaybe-uninitialized) 41 help 42 GCC >= 4.7 supports this option. 43 44config CC_DISABLE_WARN_MAYBE_UNINITIALIZED 45 bool 46 depends on CC_HAS_WARN_MAYBE_UNINITIALIZED 47 default CC_IS_GCC && GCC_VERSION < 40900 # unreliable for GCC < 4.9 48 help 49 GCC's -Wmaybe-uninitialized is not reliable by definition. 50 Lots of false positive warnings are produced in some cases. 51 52 If this option is enabled, -Wno-maybe-uninitialzed is passed 53 to the compiler to suppress maybe-uninitialized warnings. 54 55config CONSTRUCTORS 56 bool 57 58config IRQ_WORK 59 bool 60 61config BUILDTIME_EXTABLE_SORT 62 bool 63 64config THREAD_INFO_IN_TASK 65 bool 66 help 67 Select this to move thread_info off the stack into task_struct. To 68 make this work, an arch will need to remove all thread_info fields 69 except flags and fix any runtime bugs. 70 71 One subtle change that will be needed is to use try_get_task_stack() 72 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 73 74menu "General setup" 75 76config BROKEN 77 bool 78 79config BROKEN_ON_SMP 80 bool 81 depends on BROKEN || !SMP 82 default y 83 84config INIT_ENV_ARG_LIMIT 85 int 86 default 32 if !UML 87 default 128 if UML 88 help 89 Maximum of each of the number of arguments and environment 90 variables passed to init from the kernel command line. 91 92config COMPILE_TEST 93 bool "Compile also drivers which will not load" 94 depends on !UML 95 default n 96 help 97 Some drivers can be compiled on a different platform than they are 98 intended to be run on. Despite they cannot be loaded there (or even 99 when they load they cannot be used due to missing HW support), 100 developers still, opposing to distributors, might want to build such 101 drivers to compile-test them. 102 103 If you are a developer and want to build everything available, say Y 104 here. If you are a user/distributor, say N here to exclude useless 105 drivers to be distributed. 106 107config HEADER_TEST 108 bool "Compile test headers that should be standalone compilable" 109 help 110 Compile test headers listed in header-test-y target to ensure they are 111 self-contained, i.e. compilable as standalone units. 112 113 If you are a developer or tester and want to ensure the requested 114 headers are self-contained, say Y here. Otherwise, choose N. 115 116config KERNEL_HEADER_TEST 117 bool "Compile test kernel headers" 118 depends on HEADER_TEST 119 help 120 Headers in include/ are used to build external moduls. 121 Compile test them to ensure they are self-contained, i.e. 122 compilable as standalone units. 123 124 If you are a developer or tester and want to ensure the headers 125 in include/ are self-contained, say Y here. Otherwise, choose N. 126 127config UAPI_HEADER_TEST 128 bool "Compile test UAPI headers" 129 depends on HEADER_TEST && HEADERS_INSTALL && CC_CAN_LINK 130 help 131 Compile test headers exported to user-space to ensure they are 132 self-contained, i.e. compilable as standalone units. 133 134 If you are a developer or tester and want to ensure the exported 135 headers are self-contained, say Y here. Otherwise, choose N. 136 137config LOCALVERSION 138 string "Local version - append to kernel release" 139 help 140 Append an extra string to the end of your kernel version. 141 This will show up when you type uname, for example. 142 The string you set here will be appended after the contents of 143 any files with a filename matching localversion* in your 144 object and source tree, in that order. Your total string can 145 be a maximum of 64 characters. 146 147config LOCALVERSION_AUTO 148 bool "Automatically append version information to the version string" 149 default y 150 depends on !COMPILE_TEST 151 help 152 This will try to automatically determine if the current tree is a 153 release tree by looking for git tags that belong to the current 154 top of tree revision. 155 156 A string of the format -gxxxxxxxx will be added to the localversion 157 if a git-based tree is found. The string generated by this will be 158 appended after any matching localversion* files, and after the value 159 set in CONFIG_LOCALVERSION. 160 161 (The actual string used here is the first eight characters produced 162 by running the command: 163 164 $ git rev-parse --verify HEAD 165 166 which is done within the script "scripts/setlocalversion".) 167 168config BUILD_SALT 169 string "Build ID Salt" 170 default "" 171 help 172 The build ID is used to link binaries and their debug info. Setting 173 this option will use the value in the calculation of the build id. 174 This is mostly useful for distributions which want to ensure the 175 build is unique between builds. It's safe to leave the default. 176 177config HAVE_KERNEL_GZIP 178 bool 179 180config HAVE_KERNEL_BZIP2 181 bool 182 183config HAVE_KERNEL_LZMA 184 bool 185 186config HAVE_KERNEL_XZ 187 bool 188 189config HAVE_KERNEL_LZO 190 bool 191 192config HAVE_KERNEL_LZ4 193 bool 194 195config HAVE_KERNEL_UNCOMPRESSED 196 bool 197 198choice 199 prompt "Kernel compression mode" 200 default KERNEL_GZIP 201 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED 202 help 203 The linux kernel is a kind of self-extracting executable. 204 Several compression algorithms are available, which differ 205 in efficiency, compression and decompression speed. 206 Compression speed is only relevant when building a kernel. 207 Decompression speed is relevant at each boot. 208 209 If you have any problems with bzip2 or lzma compressed 210 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 211 version of this functionality (bzip2 only), for 2.4, was 212 supplied by Christian Ludwig) 213 214 High compression options are mostly useful for users, who 215 are low on disk space (embedded systems), but for whom ram 216 size matters less. 217 218 If in doubt, select 'gzip' 219 220config KERNEL_GZIP 221 bool "Gzip" 222 depends on HAVE_KERNEL_GZIP 223 help 224 The old and tried gzip compression. It provides a good balance 225 between compression ratio and decompression speed. 226 227config KERNEL_BZIP2 228 bool "Bzip2" 229 depends on HAVE_KERNEL_BZIP2 230 help 231 Its compression ratio and speed is intermediate. 232 Decompression speed is slowest among the choices. The kernel 233 size is about 10% smaller with bzip2, in comparison to gzip. 234 Bzip2 uses a large amount of memory. For modern kernels you 235 will need at least 8MB RAM or more for booting. 236 237config KERNEL_LZMA 238 bool "LZMA" 239 depends on HAVE_KERNEL_LZMA 240 help 241 This compression algorithm's ratio is best. Decompression speed 242 is between gzip and bzip2. Compression is slowest. 243 The kernel size is about 33% smaller with LZMA in comparison to gzip. 244 245config KERNEL_XZ 246 bool "XZ" 247 depends on HAVE_KERNEL_XZ 248 help 249 XZ uses the LZMA2 algorithm and instruction set specific 250 BCJ filters which can improve compression ratio of executable 251 code. The size of the kernel is about 30% smaller with XZ in 252 comparison to gzip. On architectures for which there is a BCJ 253 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 254 will create a few percent smaller kernel than plain LZMA. 255 256 The speed is about the same as with LZMA: The decompression 257 speed of XZ is better than that of bzip2 but worse than gzip 258 and LZO. Compression is slow. 259 260config KERNEL_LZO 261 bool "LZO" 262 depends on HAVE_KERNEL_LZO 263 help 264 Its compression ratio is the poorest among the choices. The kernel 265 size is about 10% bigger than gzip; however its speed 266 (both compression and decompression) is the fastest. 267 268config KERNEL_LZ4 269 bool "LZ4" 270 depends on HAVE_KERNEL_LZ4 271 help 272 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 273 A preliminary version of LZ4 de/compression tool is available at 274 <https://code.google.com/p/lz4/>. 275 276 Its compression ratio is worse than LZO. The size of the kernel 277 is about 8% bigger than LZO. But the decompression speed is 278 faster than LZO. 279 280config KERNEL_UNCOMPRESSED 281 bool "None" 282 depends on HAVE_KERNEL_UNCOMPRESSED 283 help 284 Produce uncompressed kernel image. This option is usually not what 285 you want. It is useful for debugging the kernel in slow simulation 286 environments, where decompressing and moving the kernel is awfully 287 slow. This option allows early boot code to skip the decompressor 288 and jump right at uncompressed kernel image. 289 290endchoice 291 292config DEFAULT_HOSTNAME 293 string "Default hostname" 294 default "(none)" 295 help 296 This option determines the default system hostname before userspace 297 calls sethostname(2). The kernel traditionally uses "(none)" here, 298 but you may wish to use a different default here to make a minimal 299 system more usable with less configuration. 300 301# 302# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can 303# add proper SWAP support to them, in which case this can be remove. 304# 305config ARCH_NO_SWAP 306 bool 307 308config SWAP 309 bool "Support for paging of anonymous memory (swap)" 310 depends on MMU && BLOCK && !ARCH_NO_SWAP 311 default y 312 help 313 This option allows you to choose whether you want to have support 314 for so called swap devices or swap files in your kernel that are 315 used to provide more virtual memory than the actual RAM present 316 in your computer. If unsure say Y. 317 318config SYSVIPC 319 bool "System V IPC" 320 ---help--- 321 Inter Process Communication is a suite of library functions and 322 system calls which let processes (running programs) synchronize and 323 exchange information. It is generally considered to be a good thing, 324 and some programs won't run unless you say Y here. In particular, if 325 you want to run the DOS emulator dosemu under Linux (read the 326 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 327 you'll need to say Y here. 328 329 You can find documentation about IPC with "info ipc" and also in 330 section 6.4 of the Linux Programmer's Guide, available from 331 <http://www.tldp.org/guides.html>. 332 333config SYSVIPC_SYSCTL 334 bool 335 depends on SYSVIPC 336 depends on SYSCTL 337 default y 338 339config POSIX_MQUEUE 340 bool "POSIX Message Queues" 341 depends on NET 342 ---help--- 343 POSIX variant of message queues is a part of IPC. In POSIX message 344 queues every message has a priority which decides about succession 345 of receiving it by a process. If you want to compile and run 346 programs written e.g. for Solaris with use of its POSIX message 347 queues (functions mq_*) say Y here. 348 349 POSIX message queues are visible as a filesystem called 'mqueue' 350 and can be mounted somewhere if you want to do filesystem 351 operations on message queues. 352 353 If unsure, say Y. 354 355config POSIX_MQUEUE_SYSCTL 356 bool 357 depends on POSIX_MQUEUE 358 depends on SYSCTL 359 default y 360 361config CROSS_MEMORY_ATTACH 362 bool "Enable process_vm_readv/writev syscalls" 363 depends on MMU 364 default y 365 help 366 Enabling this option adds the system calls process_vm_readv and 367 process_vm_writev which allow a process with the correct privileges 368 to directly read from or write to another process' address space. 369 See the man page for more details. 370 371config USELIB 372 bool "uselib syscall" 373 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION 374 help 375 This option enables the uselib syscall, a system call used in the 376 dynamic linker from libc5 and earlier. glibc does not use this 377 system call. If you intend to run programs built on libc5 or 378 earlier, you may need to enable this syscall. Current systems 379 running glibc can safely disable this. 380 381config AUDIT 382 bool "Auditing support" 383 depends on NET 384 help 385 Enable auditing infrastructure that can be used with another 386 kernel subsystem, such as SELinux (which requires this for 387 logging of avc messages output). System call auditing is included 388 on architectures which support it. 389 390config HAVE_ARCH_AUDITSYSCALL 391 bool 392 393config AUDITSYSCALL 394 def_bool y 395 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 396 select FSNOTIFY 397 398source "kernel/irq/Kconfig" 399source "kernel/time/Kconfig" 400source "kernel/Kconfig.preempt" 401 402menu "CPU/Task time and stats accounting" 403 404config VIRT_CPU_ACCOUNTING 405 bool 406 407choice 408 prompt "Cputime accounting" 409 default TICK_CPU_ACCOUNTING if !PPC64 410 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 411 412# Kind of a stub config for the pure tick based cputime accounting 413config TICK_CPU_ACCOUNTING 414 bool "Simple tick based cputime accounting" 415 depends on !S390 && !NO_HZ_FULL 416 help 417 This is the basic tick based cputime accounting that maintains 418 statistics about user, system and idle time spent on per jiffies 419 granularity. 420 421 If unsure, say Y. 422 423config VIRT_CPU_ACCOUNTING_NATIVE 424 bool "Deterministic task and CPU time accounting" 425 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 426 select VIRT_CPU_ACCOUNTING 427 help 428 Select this option to enable more accurate task and CPU time 429 accounting. This is done by reading a CPU counter on each 430 kernel entry and exit and on transitions within the kernel 431 between system, softirq and hardirq state, so there is a 432 small performance impact. In the case of s390 or IBM POWER > 5, 433 this also enables accounting of stolen time on logically-partitioned 434 systems. 435 436config VIRT_CPU_ACCOUNTING_GEN 437 bool "Full dynticks CPU time accounting" 438 depends on HAVE_CONTEXT_TRACKING 439 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 440 depends on GENERIC_CLOCKEVENTS 441 select VIRT_CPU_ACCOUNTING 442 select CONTEXT_TRACKING 443 help 444 Select this option to enable task and CPU time accounting on full 445 dynticks systems. This accounting is implemented by watching every 446 kernel-user boundaries using the context tracking subsystem. 447 The accounting is thus performed at the expense of some significant 448 overhead. 449 450 For now this is only useful if you are working on the full 451 dynticks subsystem development. 452 453 If unsure, say N. 454 455endchoice 456 457config IRQ_TIME_ACCOUNTING 458 bool "Fine granularity task level IRQ time accounting" 459 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 460 help 461 Select this option to enable fine granularity task irq time 462 accounting. This is done by reading a timestamp on each 463 transitions between softirq and hardirq state, so there can be a 464 small performance impact. 465 466 If in doubt, say N here. 467 468config HAVE_SCHED_AVG_IRQ 469 def_bool y 470 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 471 depends on SMP 472 473config BSD_PROCESS_ACCT 474 bool "BSD Process Accounting" 475 depends on MULTIUSER 476 help 477 If you say Y here, a user level program will be able to instruct the 478 kernel (via a special system call) to write process accounting 479 information to a file: whenever a process exits, information about 480 that process will be appended to the file by the kernel. The 481 information includes things such as creation time, owning user, 482 command name, memory usage, controlling terminal etc. (the complete 483 list is in the struct acct in <file:include/linux/acct.h>). It is 484 up to the user level program to do useful things with this 485 information. This is generally a good idea, so say Y. 486 487config BSD_PROCESS_ACCT_V3 488 bool "BSD Process Accounting version 3 file format" 489 depends on BSD_PROCESS_ACCT 490 default n 491 help 492 If you say Y here, the process accounting information is written 493 in a new file format that also logs the process IDs of each 494 process and its parent. Note that this file format is incompatible 495 with previous v0/v1/v2 file formats, so you will need updated tools 496 for processing it. A preliminary version of these tools is available 497 at <http://www.gnu.org/software/acct/>. 498 499config TASKSTATS 500 bool "Export task/process statistics through netlink" 501 depends on NET 502 depends on MULTIUSER 503 default n 504 help 505 Export selected statistics for tasks/processes through the 506 generic netlink interface. Unlike BSD process accounting, the 507 statistics are available during the lifetime of tasks/processes as 508 responses to commands. Like BSD accounting, they are sent to user 509 space on task exit. 510 511 Say N if unsure. 512 513config TASK_DELAY_ACCT 514 bool "Enable per-task delay accounting" 515 depends on TASKSTATS 516 select SCHED_INFO 517 help 518 Collect information on time spent by a task waiting for system 519 resources like cpu, synchronous block I/O completion and swapping 520 in pages. Such statistics can help in setting a task's priorities 521 relative to other tasks for cpu, io, rss limits etc. 522 523 Say N if unsure. 524 525config TASK_XACCT 526 bool "Enable extended accounting over taskstats" 527 depends on TASKSTATS 528 help 529 Collect extended task accounting data and send the data 530 to userland for processing over the taskstats interface. 531 532 Say N if unsure. 533 534config TASK_IO_ACCOUNTING 535 bool "Enable per-task storage I/O accounting" 536 depends on TASK_XACCT 537 help 538 Collect information on the number of bytes of storage I/O which this 539 task has caused. 540 541 Say N if unsure. 542 543config PSI 544 bool "Pressure stall information tracking" 545 help 546 Collect metrics that indicate how overcommitted the CPU, memory, 547 and IO capacity are in the system. 548 549 If you say Y here, the kernel will create /proc/pressure/ with the 550 pressure statistics files cpu, memory, and io. These will indicate 551 the share of walltime in which some or all tasks in the system are 552 delayed due to contention of the respective resource. 553 554 In kernels with cgroup support, cgroups (cgroup2 only) will 555 have cpu.pressure, memory.pressure, and io.pressure files, 556 which aggregate pressure stalls for the grouped tasks only. 557 558 For more details see Documentation/accounting/psi.rst. 559 560 Say N if unsure. 561 562config PSI_DEFAULT_DISABLED 563 bool "Require boot parameter to enable pressure stall information tracking" 564 default n 565 depends on PSI 566 help 567 If set, pressure stall information tracking will be disabled 568 per default but can be enabled through passing psi=1 on the 569 kernel commandline during boot. 570 571 This feature adds some code to the task wakeup and sleep 572 paths of the scheduler. The overhead is too low to affect 573 common scheduling-intense workloads in practice (such as 574 webservers, memcache), but it does show up in artificial 575 scheduler stress tests, such as hackbench. 576 577 If you are paranoid and not sure what the kernel will be 578 used for, say Y. 579 580 Say N if unsure. 581 582endmenu # "CPU/Task time and stats accounting" 583 584config CPU_ISOLATION 585 bool "CPU isolation" 586 depends on SMP || COMPILE_TEST 587 default y 588 help 589 Make sure that CPUs running critical tasks are not disturbed by 590 any source of "noise" such as unbound workqueues, timers, kthreads... 591 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 592 the "isolcpus=" boot parameter. 593 594 Say Y if unsure. 595 596source "kernel/rcu/Kconfig" 597 598config BUILD_BIN2C 599 bool 600 default n 601 602config IKCONFIG 603 tristate "Kernel .config support" 604 ---help--- 605 This option enables the complete Linux kernel ".config" file 606 contents to be saved in the kernel. It provides documentation 607 of which kernel options are used in a running kernel or in an 608 on-disk kernel. This information can be extracted from the kernel 609 image file with the script scripts/extract-ikconfig and used as 610 input to rebuild the current kernel or to build another kernel. 611 It can also be extracted from a running kernel by reading 612 /proc/config.gz if enabled (below). 613 614config IKCONFIG_PROC 615 bool "Enable access to .config through /proc/config.gz" 616 depends on IKCONFIG && PROC_FS 617 ---help--- 618 This option enables access to the kernel configuration file 619 through /proc/config.gz. 620 621config IKHEADERS 622 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 623 depends on SYSFS 624 help 625 This option enables access to the in-kernel headers that are generated during 626 the build process. These can be used to build eBPF tracing programs, 627 or similar programs. If you build the headers as a module, a module called 628 kheaders.ko is built which can be loaded on-demand to get access to headers. 629 630config LOG_BUF_SHIFT 631 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 632 range 12 25 633 default 17 634 depends on PRINTK 635 help 636 Select the minimal kernel log buffer size as a power of 2. 637 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 638 parameter, see below. Any higher size also might be forced 639 by "log_buf_len" boot parameter. 640 641 Examples: 642 17 => 128 KB 643 16 => 64 KB 644 15 => 32 KB 645 14 => 16 KB 646 13 => 8 KB 647 12 => 4 KB 648 649config LOG_CPU_MAX_BUF_SHIFT 650 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 651 depends on SMP 652 range 0 21 653 default 12 if !BASE_SMALL 654 default 0 if BASE_SMALL 655 depends on PRINTK 656 help 657 This option allows to increase the default ring buffer size 658 according to the number of CPUs. The value defines the contribution 659 of each CPU as a power of 2. The used space is typically only few 660 lines however it might be much more when problems are reported, 661 e.g. backtraces. 662 663 The increased size means that a new buffer has to be allocated and 664 the original static one is unused. It makes sense only on systems 665 with more CPUs. Therefore this value is used only when the sum of 666 contributions is greater than the half of the default kernel ring 667 buffer as defined by LOG_BUF_SHIFT. The default values are set 668 so that more than 64 CPUs are needed to trigger the allocation. 669 670 Also this option is ignored when "log_buf_len" kernel parameter is 671 used as it forces an exact (power of two) size of the ring buffer. 672 673 The number of possible CPUs is used for this computation ignoring 674 hotplugging making the computation optimal for the worst case 675 scenario while allowing a simple algorithm to be used from bootup. 676 677 Examples shift values and their meaning: 678 17 => 128 KB for each CPU 679 16 => 64 KB for each CPU 680 15 => 32 KB for each CPU 681 14 => 16 KB for each CPU 682 13 => 8 KB for each CPU 683 12 => 4 KB for each CPU 684 685config PRINTK_SAFE_LOG_BUF_SHIFT 686 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 687 range 10 21 688 default 13 689 depends on PRINTK 690 help 691 Select the size of an alternate printk per-CPU buffer where messages 692 printed from usafe contexts are temporary stored. One example would 693 be NMI messages, another one - printk recursion. The messages are 694 copied to the main log buffer in a safe context to avoid a deadlock. 695 The value defines the size as a power of 2. 696 697 Those messages are rare and limited. The largest one is when 698 a backtrace is printed. It usually fits into 4KB. Select 699 8KB if you want to be on the safe side. 700 701 Examples: 702 17 => 128 KB for each CPU 703 16 => 64 KB for each CPU 704 15 => 32 KB for each CPU 705 14 => 16 KB for each CPU 706 13 => 8 KB for each CPU 707 12 => 4 KB for each CPU 708 709# 710# Architectures with an unreliable sched_clock() should select this: 711# 712config HAVE_UNSTABLE_SCHED_CLOCK 713 bool 714 715config GENERIC_SCHED_CLOCK 716 bool 717 718menu "Scheduler features" 719 720config UCLAMP_TASK 721 bool "Enable utilization clamping for RT/FAIR tasks" 722 depends on CPU_FREQ_GOV_SCHEDUTIL 723 help 724 This feature enables the scheduler to track the clamped utilization 725 of each CPU based on RUNNABLE tasks scheduled on that CPU. 726 727 With this option, the user can specify the min and max CPU 728 utilization allowed for RUNNABLE tasks. The max utilization defines 729 the maximum frequency a task should use while the min utilization 730 defines the minimum frequency it should use. 731 732 Both min and max utilization clamp values are hints to the scheduler, 733 aiming at improving its frequency selection policy, but they do not 734 enforce or grant any specific bandwidth for tasks. 735 736 If in doubt, say N. 737 738config UCLAMP_BUCKETS_COUNT 739 int "Number of supported utilization clamp buckets" 740 range 5 20 741 default 5 742 depends on UCLAMP_TASK 743 help 744 Defines the number of clamp buckets to use. The range of each bucket 745 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 746 number of clamp buckets the finer their granularity and the higher 747 the precision of clamping aggregation and tracking at run-time. 748 749 For example, with the minimum configuration value we will have 5 750 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 751 be refcounted in the [20..39]% bucket and will set the bucket clamp 752 effective value to 25%. 753 If a second 30% boosted task should be co-scheduled on the same CPU, 754 that task will be refcounted in the same bucket of the first task and 755 it will boost the bucket clamp effective value to 30%. 756 The clamp effective value of a bucket is reset to its nominal value 757 (20% in the example above) when there are no more tasks refcounted in 758 that bucket. 759 760 An additional boost/capping margin can be added to some tasks. In the 761 example above the 25% task will be boosted to 30% until it exits the 762 CPU. If that should be considered not acceptable on certain systems, 763 it's always possible to reduce the margin by increasing the number of 764 clamp buckets to trade off used memory for run-time tracking 765 precision. 766 767 If in doubt, use the default value. 768 769endmenu 770 771# 772# For architectures that want to enable the support for NUMA-affine scheduler 773# balancing logic: 774# 775config ARCH_SUPPORTS_NUMA_BALANCING 776 bool 777 778# 779# For architectures that prefer to flush all TLBs after a number of pages 780# are unmapped instead of sending one IPI per page to flush. The architecture 781# must provide guarantees on what happens if a clean TLB cache entry is 782# written after the unmap. Details are in mm/rmap.c near the check for 783# should_defer_flush. The architecture should also consider if the full flush 784# and the refill costs are offset by the savings of sending fewer IPIs. 785config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 786 bool 787 788# 789# For architectures that know their GCC __int128 support is sound 790# 791config ARCH_SUPPORTS_INT128 792 bool 793 794# For architectures that (ab)use NUMA to represent different memory regions 795# all cpu-local but of different latencies, such as SuperH. 796# 797config ARCH_WANT_NUMA_VARIABLE_LOCALITY 798 bool 799 800config NUMA_BALANCING 801 bool "Memory placement aware NUMA scheduler" 802 depends on ARCH_SUPPORTS_NUMA_BALANCING 803 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 804 depends on SMP && NUMA && MIGRATION 805 help 806 This option adds support for automatic NUMA aware memory/task placement. 807 The mechanism is quite primitive and is based on migrating memory when 808 it has references to the node the task is running on. 809 810 This system will be inactive on UMA systems. 811 812config NUMA_BALANCING_DEFAULT_ENABLED 813 bool "Automatically enable NUMA aware memory/task placement" 814 default y 815 depends on NUMA_BALANCING 816 help 817 If set, automatic NUMA balancing will be enabled if running on a NUMA 818 machine. 819 820menuconfig CGROUPS 821 bool "Control Group support" 822 select KERNFS 823 help 824 This option adds support for grouping sets of processes together, for 825 use with process control subsystems such as Cpusets, CFS, memory 826 controls or device isolation. 827 See 828 - Documentation/scheduler/sched-design-CFS.rst (CFS) 829 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 830 and resource control) 831 832 Say N if unsure. 833 834if CGROUPS 835 836config PAGE_COUNTER 837 bool 838 839config MEMCG 840 bool "Memory controller" 841 select PAGE_COUNTER 842 select EVENTFD 843 help 844 Provides control over the memory footprint of tasks in a cgroup. 845 846config MEMCG_SWAP 847 bool "Swap controller" 848 depends on MEMCG && SWAP 849 help 850 Provides control over the swap space consumed by tasks in a cgroup. 851 852config MEMCG_SWAP_ENABLED 853 bool "Swap controller enabled by default" 854 depends on MEMCG_SWAP 855 default y 856 help 857 Memory Resource Controller Swap Extension comes with its price in 858 a bigger memory consumption. General purpose distribution kernels 859 which want to enable the feature but keep it disabled by default 860 and let the user enable it by swapaccount=1 boot command line 861 parameter should have this option unselected. 862 For those who want to have the feature enabled by default should 863 select this option (if, for some reason, they need to disable it 864 then swapaccount=0 does the trick). 865 866config MEMCG_KMEM 867 bool 868 depends on MEMCG && !SLOB 869 default y 870 871config BLK_CGROUP 872 bool "IO controller" 873 depends on BLOCK 874 default n 875 ---help--- 876 Generic block IO controller cgroup interface. This is the common 877 cgroup interface which should be used by various IO controlling 878 policies. 879 880 Currently, CFQ IO scheduler uses it to recognize task groups and 881 control disk bandwidth allocation (proportional time slice allocation) 882 to such task groups. It is also used by bio throttling logic in 883 block layer to implement upper limit in IO rates on a device. 884 885 This option only enables generic Block IO controller infrastructure. 886 One needs to also enable actual IO controlling logic/policy. For 887 enabling proportional weight division of disk bandwidth in CFQ, set 888 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 889 CONFIG_BLK_DEV_THROTTLING=y. 890 891 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 892 893config CGROUP_WRITEBACK 894 bool 895 depends on MEMCG && BLK_CGROUP 896 default y 897 898menuconfig CGROUP_SCHED 899 bool "CPU controller" 900 default n 901 help 902 This feature lets CPU scheduler recognize task groups and control CPU 903 bandwidth allocation to such task groups. It uses cgroups to group 904 tasks. 905 906if CGROUP_SCHED 907config FAIR_GROUP_SCHED 908 bool "Group scheduling for SCHED_OTHER" 909 depends on CGROUP_SCHED 910 default CGROUP_SCHED 911 912config CFS_BANDWIDTH 913 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 914 depends on FAIR_GROUP_SCHED 915 default n 916 help 917 This option allows users to define CPU bandwidth rates (limits) for 918 tasks running within the fair group scheduler. Groups with no limit 919 set are considered to be unconstrained and will run with no 920 restriction. 921 See Documentation/scheduler/sched-bwc.rst for more information. 922 923config RT_GROUP_SCHED 924 bool "Group scheduling for SCHED_RR/FIFO" 925 depends on CGROUP_SCHED 926 default n 927 help 928 This feature lets you explicitly allocate real CPU bandwidth 929 to task groups. If enabled, it will also make it impossible to 930 schedule realtime tasks for non-root users until you allocate 931 realtime bandwidth for them. 932 See Documentation/scheduler/sched-rt-group.rst for more information. 933 934endif #CGROUP_SCHED 935 936config UCLAMP_TASK_GROUP 937 bool "Utilization clamping per group of tasks" 938 depends on CGROUP_SCHED 939 depends on UCLAMP_TASK 940 default n 941 help 942 This feature enables the scheduler to track the clamped utilization 943 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 944 945 When this option is enabled, the user can specify a min and max 946 CPU bandwidth which is allowed for each single task in a group. 947 The max bandwidth allows to clamp the maximum frequency a task 948 can use, while the min bandwidth allows to define a minimum 949 frequency a task will always use. 950 951 When task group based utilization clamping is enabled, an eventually 952 specified task-specific clamp value is constrained by the cgroup 953 specified clamp value. Both minimum and maximum task clamping cannot 954 be bigger than the corresponding clamping defined at task group level. 955 956 If in doubt, say N. 957 958config CGROUP_PIDS 959 bool "PIDs controller" 960 help 961 Provides enforcement of process number limits in the scope of a 962 cgroup. Any attempt to fork more processes than is allowed in the 963 cgroup will fail. PIDs are fundamentally a global resource because it 964 is fairly trivial to reach PID exhaustion before you reach even a 965 conservative kmemcg limit. As a result, it is possible to grind a 966 system to halt without being limited by other cgroup policies. The 967 PIDs controller is designed to stop this from happening. 968 969 It should be noted that organisational operations (such as attaching 970 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 971 since the PIDs limit only affects a process's ability to fork, not to 972 attach to a cgroup. 973 974config CGROUP_RDMA 975 bool "RDMA controller" 976 help 977 Provides enforcement of RDMA resources defined by IB stack. 978 It is fairly easy for consumers to exhaust RDMA resources, which 979 can result into resource unavailability to other consumers. 980 RDMA controller is designed to stop this from happening. 981 Attaching processes with active RDMA resources to the cgroup 982 hierarchy is allowed even if can cross the hierarchy's limit. 983 984config CGROUP_FREEZER 985 bool "Freezer controller" 986 help 987 Provides a way to freeze and unfreeze all tasks in a 988 cgroup. 989 990 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 991 controller includes important in-kernel memory consumers per default. 992 993 If you're using cgroup2, say N. 994 995config CGROUP_HUGETLB 996 bool "HugeTLB controller" 997 depends on HUGETLB_PAGE 998 select PAGE_COUNTER 999 default n 1000 help 1001 Provides a cgroup controller for HugeTLB pages. 1002 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1003 The limit is enforced during page fault. Since HugeTLB doesn't 1004 support page reclaim, enforcing the limit at page fault time implies 1005 that, the application will get SIGBUS signal if it tries to access 1006 HugeTLB pages beyond its limit. This requires the application to know 1007 beforehand how much HugeTLB pages it would require for its use. The 1008 control group is tracked in the third page lru pointer. This means 1009 that we cannot use the controller with huge page less than 3 pages. 1010 1011config CPUSETS 1012 bool "Cpuset controller" 1013 depends on SMP 1014 help 1015 This option will let you create and manage CPUSETs which 1016 allow dynamically partitioning a system into sets of CPUs and 1017 Memory Nodes and assigning tasks to run only within those sets. 1018 This is primarily useful on large SMP or NUMA systems. 1019 1020 Say N if unsure. 1021 1022config PROC_PID_CPUSET 1023 bool "Include legacy /proc/<pid>/cpuset file" 1024 depends on CPUSETS 1025 default y 1026 1027config CGROUP_DEVICE 1028 bool "Device controller" 1029 help 1030 Provides a cgroup controller implementing whitelists for 1031 devices which a process in the cgroup can mknod or open. 1032 1033config CGROUP_CPUACCT 1034 bool "Simple CPU accounting controller" 1035 help 1036 Provides a simple controller for monitoring the 1037 total CPU consumed by the tasks in a cgroup. 1038 1039config CGROUP_PERF 1040 bool "Perf controller" 1041 depends on PERF_EVENTS 1042 help 1043 This option extends the perf per-cpu mode to restrict monitoring 1044 to threads which belong to the cgroup specified and run on the 1045 designated cpu. 1046 1047 Say N if unsure. 1048 1049config CGROUP_BPF 1050 bool "Support for eBPF programs attached to cgroups" 1051 depends on BPF_SYSCALL 1052 select SOCK_CGROUP_DATA 1053 help 1054 Allow attaching eBPF programs to a cgroup using the bpf(2) 1055 syscall command BPF_PROG_ATTACH. 1056 1057 In which context these programs are accessed depends on the type 1058 of attachment. For instance, programs that are attached using 1059 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1060 inet sockets. 1061 1062config CGROUP_DEBUG 1063 bool "Debug controller" 1064 default n 1065 depends on DEBUG_KERNEL 1066 help 1067 This option enables a simple controller that exports 1068 debugging information about the cgroups framework. This 1069 controller is for control cgroup debugging only. Its 1070 interfaces are not stable. 1071 1072 Say N. 1073 1074config SOCK_CGROUP_DATA 1075 bool 1076 default n 1077 1078endif # CGROUPS 1079 1080menuconfig NAMESPACES 1081 bool "Namespaces support" if EXPERT 1082 depends on MULTIUSER 1083 default !EXPERT 1084 help 1085 Provides the way to make tasks work with different objects using 1086 the same id. For example same IPC id may refer to different objects 1087 or same user id or pid may refer to different tasks when used in 1088 different namespaces. 1089 1090if NAMESPACES 1091 1092config UTS_NS 1093 bool "UTS namespace" 1094 default y 1095 help 1096 In this namespace tasks see different info provided with the 1097 uname() system call 1098 1099config IPC_NS 1100 bool "IPC namespace" 1101 depends on (SYSVIPC || POSIX_MQUEUE) 1102 default y 1103 help 1104 In this namespace tasks work with IPC ids which correspond to 1105 different IPC objects in different namespaces. 1106 1107config USER_NS 1108 bool "User namespace" 1109 default n 1110 help 1111 This allows containers, i.e. vservers, to use user namespaces 1112 to provide different user info for different servers. 1113 1114 When user namespaces are enabled in the kernel it is 1115 recommended that the MEMCG option also be enabled and that 1116 user-space use the memory control groups to limit the amount 1117 of memory a memory unprivileged users can use. 1118 1119 If unsure, say N. 1120 1121config PID_NS 1122 bool "PID Namespaces" 1123 default y 1124 help 1125 Support process id namespaces. This allows having multiple 1126 processes with the same pid as long as they are in different 1127 pid namespaces. This is a building block of containers. 1128 1129config NET_NS 1130 bool "Network namespace" 1131 depends on NET 1132 default y 1133 help 1134 Allow user space to create what appear to be multiple instances 1135 of the network stack. 1136 1137endif # NAMESPACES 1138 1139config CHECKPOINT_RESTORE 1140 bool "Checkpoint/restore support" 1141 select PROC_CHILDREN 1142 default n 1143 help 1144 Enables additional kernel features in a sake of checkpoint/restore. 1145 In particular it adds auxiliary prctl codes to setup process text, 1146 data and heap segment sizes, and a few additional /proc filesystem 1147 entries. 1148 1149 If unsure, say N here. 1150 1151config SCHED_AUTOGROUP 1152 bool "Automatic process group scheduling" 1153 select CGROUPS 1154 select CGROUP_SCHED 1155 select FAIR_GROUP_SCHED 1156 help 1157 This option optimizes the scheduler for common desktop workloads by 1158 automatically creating and populating task groups. This separation 1159 of workloads isolates aggressive CPU burners (like build jobs) from 1160 desktop applications. Task group autogeneration is currently based 1161 upon task session. 1162 1163config SYSFS_DEPRECATED 1164 bool "Enable deprecated sysfs features to support old userspace tools" 1165 depends on SYSFS 1166 default n 1167 help 1168 This option adds code that switches the layout of the "block" class 1169 devices, to not show up in /sys/class/block/, but only in 1170 /sys/block/. 1171 1172 This switch is only active when the sysfs.deprecated=1 boot option is 1173 passed or the SYSFS_DEPRECATED_V2 option is set. 1174 1175 This option allows new kernels to run on old distributions and tools, 1176 which might get confused by /sys/class/block/. Since 2007/2008 all 1177 major distributions and tools handle this just fine. 1178 1179 Recent distributions and userspace tools after 2009/2010 depend on 1180 the existence of /sys/class/block/, and will not work with this 1181 option enabled. 1182 1183 Only if you are using a new kernel on an old distribution, you might 1184 need to say Y here. 1185 1186config SYSFS_DEPRECATED_V2 1187 bool "Enable deprecated sysfs features by default" 1188 default n 1189 depends on SYSFS 1190 depends on SYSFS_DEPRECATED 1191 help 1192 Enable deprecated sysfs by default. 1193 1194 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1195 option. 1196 1197 Only if you are using a new kernel on an old distribution, you might 1198 need to say Y here. Even then, odds are you would not need it 1199 enabled, you can always pass the boot option if absolutely necessary. 1200 1201config RELAY 1202 bool "Kernel->user space relay support (formerly relayfs)" 1203 select IRQ_WORK 1204 help 1205 This option enables support for relay interface support in 1206 certain file systems (such as debugfs). 1207 It is designed to provide an efficient mechanism for tools and 1208 facilities to relay large amounts of data from kernel space to 1209 user space. 1210 1211 If unsure, say N. 1212 1213config BLK_DEV_INITRD 1214 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1215 help 1216 The initial RAM filesystem is a ramfs which is loaded by the 1217 boot loader (loadlin or lilo) and that is mounted as root 1218 before the normal boot procedure. It is typically used to 1219 load modules needed to mount the "real" root file system, 1220 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1221 1222 If RAM disk support (BLK_DEV_RAM) is also included, this 1223 also enables initial RAM disk (initrd) support and adds 1224 15 Kbytes (more on some other architectures) to the kernel size. 1225 1226 If unsure say Y. 1227 1228if BLK_DEV_INITRD 1229 1230source "usr/Kconfig" 1231 1232endif 1233 1234choice 1235 prompt "Compiler optimization level" 1236 default CC_OPTIMIZE_FOR_PERFORMANCE 1237 1238config CC_OPTIMIZE_FOR_PERFORMANCE 1239 bool "Optimize for performance (-O2)" 1240 help 1241 This is the default optimization level for the kernel, building 1242 with the "-O2" compiler flag for best performance and most 1243 helpful compile-time warnings. 1244 1245config CC_OPTIMIZE_FOR_PERFORMANCE_O3 1246 bool "Optimize more for performance (-O3)" 1247 depends on ARC 1248 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives 1249 help 1250 Choosing this option will pass "-O3" to your compiler to optimize 1251 the kernel yet more for performance. 1252 1253config CC_OPTIMIZE_FOR_SIZE 1254 bool "Optimize for size (-Os)" 1255 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives 1256 help 1257 Choosing this option will pass "-Os" to your compiler resulting 1258 in a smaller kernel. 1259 1260endchoice 1261 1262config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1263 bool 1264 help 1265 This requires that the arch annotates or otherwise protects 1266 its external entry points from being discarded. Linker scripts 1267 must also merge .text.*, .data.*, and .bss.* correctly into 1268 output sections. Care must be taken not to pull in unrelated 1269 sections (e.g., '.text.init'). Typically '.' in section names 1270 is used to distinguish them from label names / C identifiers. 1271 1272config LD_DEAD_CODE_DATA_ELIMINATION 1273 bool "Dead code and data elimination (EXPERIMENTAL)" 1274 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1275 depends on EXPERT 1276 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800) 1277 depends on $(cc-option,-ffunction-sections -fdata-sections) 1278 depends on $(ld-option,--gc-sections) 1279 help 1280 Enable this if you want to do dead code and data elimination with 1281 the linker by compiling with -ffunction-sections -fdata-sections, 1282 and linking with --gc-sections. 1283 1284 This can reduce on disk and in-memory size of the kernel 1285 code and static data, particularly for small configs and 1286 on small systems. This has the possibility of introducing 1287 silently broken kernel if the required annotations are not 1288 present. This option is not well tested yet, so use at your 1289 own risk. 1290 1291config SYSCTL 1292 bool 1293 1294config HAVE_UID16 1295 bool 1296 1297config SYSCTL_EXCEPTION_TRACE 1298 bool 1299 help 1300 Enable support for /proc/sys/debug/exception-trace. 1301 1302config SYSCTL_ARCH_UNALIGN_NO_WARN 1303 bool 1304 help 1305 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1306 Allows arch to define/use @no_unaligned_warning to possibly warn 1307 about unaligned access emulation going on under the hood. 1308 1309config SYSCTL_ARCH_UNALIGN_ALLOW 1310 bool 1311 help 1312 Enable support for /proc/sys/kernel/unaligned-trap 1313 Allows arches to define/use @unaligned_enabled to runtime toggle 1314 the unaligned access emulation. 1315 see arch/parisc/kernel/unaligned.c for reference 1316 1317config HAVE_PCSPKR_PLATFORM 1318 bool 1319 1320# interpreter that classic socket filters depend on 1321config BPF 1322 bool 1323 1324menuconfig EXPERT 1325 bool "Configure standard kernel features (expert users)" 1326 # Unhide debug options, to make the on-by-default options visible 1327 select DEBUG_KERNEL 1328 help 1329 This option allows certain base kernel options and settings 1330 to be disabled or tweaked. This is for specialized 1331 environments which can tolerate a "non-standard" kernel. 1332 Only use this if you really know what you are doing. 1333 1334config UID16 1335 bool "Enable 16-bit UID system calls" if EXPERT 1336 depends on HAVE_UID16 && MULTIUSER 1337 default y 1338 help 1339 This enables the legacy 16-bit UID syscall wrappers. 1340 1341config MULTIUSER 1342 bool "Multiple users, groups and capabilities support" if EXPERT 1343 default y 1344 help 1345 This option enables support for non-root users, groups and 1346 capabilities. 1347 1348 If you say N here, all processes will run with UID 0, GID 0, and all 1349 possible capabilities. Saying N here also compiles out support for 1350 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1351 setgid, and capset. 1352 1353 If unsure, say Y here. 1354 1355config SGETMASK_SYSCALL 1356 bool "sgetmask/ssetmask syscalls support" if EXPERT 1357 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1358 ---help--- 1359 sys_sgetmask and sys_ssetmask are obsolete system calls 1360 no longer supported in libc but still enabled by default in some 1361 architectures. 1362 1363 If unsure, leave the default option here. 1364 1365config SYSFS_SYSCALL 1366 bool "Sysfs syscall support" if EXPERT 1367 default y 1368 ---help--- 1369 sys_sysfs is an obsolete system call no longer supported in libc. 1370 Note that disabling this option is more secure but might break 1371 compatibility with some systems. 1372 1373 If unsure say Y here. 1374 1375config SYSCTL_SYSCALL 1376 bool "Sysctl syscall support" if EXPERT 1377 depends on PROC_SYSCTL 1378 default n 1379 select SYSCTL 1380 ---help--- 1381 sys_sysctl uses binary paths that have been found challenging 1382 to properly maintain and use. The interface in /proc/sys 1383 using paths with ascii names is now the primary path to this 1384 information. 1385 1386 Almost nothing using the binary sysctl interface so if you are 1387 trying to save some space it is probably safe to disable this, 1388 making your kernel marginally smaller. 1389 1390 If unsure say N here. 1391 1392config FHANDLE 1393 bool "open by fhandle syscalls" if EXPERT 1394 select EXPORTFS 1395 default y 1396 help 1397 If you say Y here, a user level program will be able to map 1398 file names to handle and then later use the handle for 1399 different file system operations. This is useful in implementing 1400 userspace file servers, which now track files using handles instead 1401 of names. The handle would remain the same even if file names 1402 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1403 syscalls. 1404 1405config POSIX_TIMERS 1406 bool "Posix Clocks & timers" if EXPERT 1407 default y 1408 help 1409 This includes native support for POSIX timers to the kernel. 1410 Some embedded systems have no use for them and therefore they 1411 can be configured out to reduce the size of the kernel image. 1412 1413 When this option is disabled, the following syscalls won't be 1414 available: timer_create, timer_gettime: timer_getoverrun, 1415 timer_settime, timer_delete, clock_adjtime, getitimer, 1416 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1417 clock_getres and clock_nanosleep syscalls will be limited to 1418 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1419 1420 If unsure say y. 1421 1422config PRINTK 1423 default y 1424 bool "Enable support for printk" if EXPERT 1425 select IRQ_WORK 1426 help 1427 This option enables normal printk support. Removing it 1428 eliminates most of the message strings from the kernel image 1429 and makes the kernel more or less silent. As this makes it 1430 very difficult to diagnose system problems, saying N here is 1431 strongly discouraged. 1432 1433config PRINTK_NMI 1434 def_bool y 1435 depends on PRINTK 1436 depends on HAVE_NMI 1437 1438config BUG 1439 bool "BUG() support" if EXPERT 1440 default y 1441 help 1442 Disabling this option eliminates support for BUG and WARN, reducing 1443 the size of your kernel image and potentially quietly ignoring 1444 numerous fatal conditions. You should only consider disabling this 1445 option for embedded systems with no facilities for reporting errors. 1446 Just say Y. 1447 1448config ELF_CORE 1449 depends on COREDUMP 1450 default y 1451 bool "Enable ELF core dumps" if EXPERT 1452 help 1453 Enable support for generating core dumps. Disabling saves about 4k. 1454 1455 1456config PCSPKR_PLATFORM 1457 bool "Enable PC-Speaker support" if EXPERT 1458 depends on HAVE_PCSPKR_PLATFORM 1459 select I8253_LOCK 1460 default y 1461 help 1462 This option allows to disable the internal PC-Speaker 1463 support, saving some memory. 1464 1465config BASE_FULL 1466 default y 1467 bool "Enable full-sized data structures for core" if EXPERT 1468 help 1469 Disabling this option reduces the size of miscellaneous core 1470 kernel data structures. This saves memory on small machines, 1471 but may reduce performance. 1472 1473config FUTEX 1474 bool "Enable futex support" if EXPERT 1475 default y 1476 imply RT_MUTEXES 1477 help 1478 Disabling this option will cause the kernel to be built without 1479 support for "fast userspace mutexes". The resulting kernel may not 1480 run glibc-based applications correctly. 1481 1482config FUTEX_PI 1483 bool 1484 depends on FUTEX && RT_MUTEXES 1485 default y 1486 1487config HAVE_FUTEX_CMPXCHG 1488 bool 1489 depends on FUTEX 1490 help 1491 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1492 is implemented and always working. This removes a couple of runtime 1493 checks. 1494 1495config EPOLL 1496 bool "Enable eventpoll support" if EXPERT 1497 default y 1498 help 1499 Disabling this option will cause the kernel to be built without 1500 support for epoll family of system calls. 1501 1502config SIGNALFD 1503 bool "Enable signalfd() system call" if EXPERT 1504 default y 1505 help 1506 Enable the signalfd() system call that allows to receive signals 1507 on a file descriptor. 1508 1509 If unsure, say Y. 1510 1511config TIMERFD 1512 bool "Enable timerfd() system call" if EXPERT 1513 default y 1514 help 1515 Enable the timerfd() system call that allows to receive timer 1516 events on a file descriptor. 1517 1518 If unsure, say Y. 1519 1520config EVENTFD 1521 bool "Enable eventfd() system call" if EXPERT 1522 default y 1523 help 1524 Enable the eventfd() system call that allows to receive both 1525 kernel notification (ie. KAIO) or userspace notifications. 1526 1527 If unsure, say Y. 1528 1529config SHMEM 1530 bool "Use full shmem filesystem" if EXPERT 1531 default y 1532 depends on MMU 1533 help 1534 The shmem is an internal filesystem used to manage shared memory. 1535 It is backed by swap and manages resource limits. It is also exported 1536 to userspace as tmpfs if TMPFS is enabled. Disabling this 1537 option replaces shmem and tmpfs with the much simpler ramfs code, 1538 which may be appropriate on small systems without swap. 1539 1540config AIO 1541 bool "Enable AIO support" if EXPERT 1542 default y 1543 help 1544 This option enables POSIX asynchronous I/O which may by used 1545 by some high performance threaded applications. Disabling 1546 this option saves about 7k. 1547 1548config IO_URING 1549 bool "Enable IO uring support" if EXPERT 1550 select ANON_INODES 1551 default y 1552 help 1553 This option enables support for the io_uring interface, enabling 1554 applications to submit and complete IO through submission and 1555 completion rings that are shared between the kernel and application. 1556 1557config ADVISE_SYSCALLS 1558 bool "Enable madvise/fadvise syscalls" if EXPERT 1559 default y 1560 help 1561 This option enables the madvise and fadvise syscalls, used by 1562 applications to advise the kernel about their future memory or file 1563 usage, improving performance. If building an embedded system where no 1564 applications use these syscalls, you can disable this option to save 1565 space. 1566 1567config MEMBARRIER 1568 bool "Enable membarrier() system call" if EXPERT 1569 default y 1570 help 1571 Enable the membarrier() system call that allows issuing memory 1572 barriers across all running threads, which can be used to distribute 1573 the cost of user-space memory barriers asymmetrically by transforming 1574 pairs of memory barriers into pairs consisting of membarrier() and a 1575 compiler barrier. 1576 1577 If unsure, say Y. 1578 1579config KALLSYMS 1580 bool "Load all symbols for debugging/ksymoops" if EXPERT 1581 default y 1582 help 1583 Say Y here to let the kernel print out symbolic crash information and 1584 symbolic stack backtraces. This increases the size of the kernel 1585 somewhat, as all symbols have to be loaded into the kernel image. 1586 1587config KALLSYMS_ALL 1588 bool "Include all symbols in kallsyms" 1589 depends on DEBUG_KERNEL && KALLSYMS 1590 help 1591 Normally kallsyms only contains the symbols of functions for nicer 1592 OOPS messages and backtraces (i.e., symbols from the text and inittext 1593 sections). This is sufficient for most cases. And only in very rare 1594 cases (e.g., when a debugger is used) all symbols are required (e.g., 1595 names of variables from the data sections, etc). 1596 1597 This option makes sure that all symbols are loaded into the kernel 1598 image (i.e., symbols from all sections) in cost of increased kernel 1599 size (depending on the kernel configuration, it may be 300KiB or 1600 something like this). 1601 1602 Say N unless you really need all symbols. 1603 1604config KALLSYMS_ABSOLUTE_PERCPU 1605 bool 1606 depends on KALLSYMS 1607 default X86_64 && SMP 1608 1609config KALLSYMS_BASE_RELATIVE 1610 bool 1611 depends on KALLSYMS 1612 default !IA64 1613 help 1614 Instead of emitting them as absolute values in the native word size, 1615 emit the symbol references in the kallsyms table as 32-bit entries, 1616 each containing a relative value in the range [base, base + U32_MAX] 1617 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1618 an absolute value in the range [0, S32_MAX] or a relative value in the 1619 range [base, base + S32_MAX], where base is the lowest relative symbol 1620 address encountered in the image. 1621 1622 On 64-bit builds, this reduces the size of the address table by 50%, 1623 but more importantly, it results in entries whose values are build 1624 time constants, and no relocation pass is required at runtime to fix 1625 up the entries based on the runtime load address of the kernel. 1626 1627# end of the "standard kernel features (expert users)" menu 1628 1629# syscall, maps, verifier 1630config BPF_SYSCALL 1631 bool "Enable bpf() system call" 1632 select BPF 1633 select IRQ_WORK 1634 default n 1635 help 1636 Enable the bpf() system call that allows to manipulate eBPF 1637 programs and maps via file descriptors. 1638 1639config BPF_JIT_ALWAYS_ON 1640 bool "Permanently enable BPF JIT and remove BPF interpreter" 1641 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1642 help 1643 Enables BPF JIT and removes BPF interpreter to avoid 1644 speculative execution of BPF instructions by the interpreter 1645 1646config USERFAULTFD 1647 bool "Enable userfaultfd() system call" 1648 depends on MMU 1649 help 1650 Enable the userfaultfd() system call that allows to intercept and 1651 handle page faults in userland. 1652 1653config ARCH_HAS_MEMBARRIER_CALLBACKS 1654 bool 1655 1656config ARCH_HAS_MEMBARRIER_SYNC_CORE 1657 bool 1658 1659config RSEQ 1660 bool "Enable rseq() system call" if EXPERT 1661 default y 1662 depends on HAVE_RSEQ 1663 select MEMBARRIER 1664 help 1665 Enable the restartable sequences system call. It provides a 1666 user-space cache for the current CPU number value, which 1667 speeds up getting the current CPU number from user-space, 1668 as well as an ABI to speed up user-space operations on 1669 per-CPU data. 1670 1671 If unsure, say Y. 1672 1673config DEBUG_RSEQ 1674 default n 1675 bool "Enabled debugging of rseq() system call" if EXPERT 1676 depends on RSEQ && DEBUG_KERNEL 1677 help 1678 Enable extra debugging checks for the rseq system call. 1679 1680 If unsure, say N. 1681 1682config EMBEDDED 1683 bool "Embedded system" 1684 option allnoconfig_y 1685 select EXPERT 1686 help 1687 This option should be enabled if compiling the kernel for 1688 an embedded system so certain expert options are available 1689 for configuration. 1690 1691config HAVE_PERF_EVENTS 1692 bool 1693 help 1694 See tools/perf/design.txt for details. 1695 1696config PERF_USE_VMALLOC 1697 bool 1698 help 1699 See tools/perf/design.txt for details 1700 1701config PC104 1702 bool "PC/104 support" if EXPERT 1703 help 1704 Expose PC/104 form factor device drivers and options available for 1705 selection and configuration. Enable this option if your target 1706 machine has a PC/104 bus. 1707 1708menu "Kernel Performance Events And Counters" 1709 1710config PERF_EVENTS 1711 bool "Kernel performance events and counters" 1712 default y if PROFILING 1713 depends on HAVE_PERF_EVENTS 1714 select IRQ_WORK 1715 select SRCU 1716 help 1717 Enable kernel support for various performance events provided 1718 by software and hardware. 1719 1720 Software events are supported either built-in or via the 1721 use of generic tracepoints. 1722 1723 Most modern CPUs support performance events via performance 1724 counter registers. These registers count the number of certain 1725 types of hw events: such as instructions executed, cachemisses 1726 suffered, or branches mis-predicted - without slowing down the 1727 kernel or applications. These registers can also trigger interrupts 1728 when a threshold number of events have passed - and can thus be 1729 used to profile the code that runs on that CPU. 1730 1731 The Linux Performance Event subsystem provides an abstraction of 1732 these software and hardware event capabilities, available via a 1733 system call and used by the "perf" utility in tools/perf/. It 1734 provides per task and per CPU counters, and it provides event 1735 capabilities on top of those. 1736 1737 Say Y if unsure. 1738 1739config DEBUG_PERF_USE_VMALLOC 1740 default n 1741 bool "Debug: use vmalloc to back perf mmap() buffers" 1742 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1743 select PERF_USE_VMALLOC 1744 help 1745 Use vmalloc memory to back perf mmap() buffers. 1746 1747 Mostly useful for debugging the vmalloc code on platforms 1748 that don't require it. 1749 1750 Say N if unsure. 1751 1752endmenu 1753 1754config VM_EVENT_COUNTERS 1755 default y 1756 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1757 help 1758 VM event counters are needed for event counts to be shown. 1759 This option allows the disabling of the VM event counters 1760 on EXPERT systems. /proc/vmstat will only show page counts 1761 if VM event counters are disabled. 1762 1763config SLUB_DEBUG 1764 default y 1765 bool "Enable SLUB debugging support" if EXPERT 1766 depends on SLUB && SYSFS 1767 help 1768 SLUB has extensive debug support features. Disabling these can 1769 result in significant savings in code size. This also disables 1770 SLUB sysfs support. /sys/slab will not exist and there will be 1771 no support for cache validation etc. 1772 1773config SLUB_MEMCG_SYSFS_ON 1774 default n 1775 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1776 depends on SLUB && SYSFS && MEMCG 1777 help 1778 SLUB creates a directory under /sys/kernel/slab for each 1779 allocation cache to host info and debug files. If memory 1780 cgroup is enabled, each cache can have per memory cgroup 1781 caches. SLUB can create the same sysfs directories for these 1782 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1783 to a very high number of debug files being created. This is 1784 controlled by slub_memcg_sysfs boot parameter and this 1785 config option determines the parameter's default value. 1786 1787config COMPAT_BRK 1788 bool "Disable heap randomization" 1789 default y 1790 help 1791 Randomizing heap placement makes heap exploits harder, but it 1792 also breaks ancient binaries (including anything libc5 based). 1793 This option changes the bootup default to heap randomization 1794 disabled, and can be overridden at runtime by setting 1795 /proc/sys/kernel/randomize_va_space to 2. 1796 1797 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1798 1799choice 1800 prompt "Choose SLAB allocator" 1801 default SLUB 1802 help 1803 This option allows to select a slab allocator. 1804 1805config SLAB 1806 bool "SLAB" 1807 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1808 help 1809 The regular slab allocator that is established and known to work 1810 well in all environments. It organizes cache hot objects in 1811 per cpu and per node queues. 1812 1813config SLUB 1814 bool "SLUB (Unqueued Allocator)" 1815 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1816 help 1817 SLUB is a slab allocator that minimizes cache line usage 1818 instead of managing queues of cached objects (SLAB approach). 1819 Per cpu caching is realized using slabs of objects instead 1820 of queues of objects. SLUB can use memory efficiently 1821 and has enhanced diagnostics. SLUB is the default choice for 1822 a slab allocator. 1823 1824config SLOB 1825 depends on EXPERT 1826 bool "SLOB (Simple Allocator)" 1827 help 1828 SLOB replaces the stock allocator with a drastically simpler 1829 allocator. SLOB is generally more space efficient but 1830 does not perform as well on large systems. 1831 1832endchoice 1833 1834config SLAB_MERGE_DEFAULT 1835 bool "Allow slab caches to be merged" 1836 default y 1837 help 1838 For reduced kernel memory fragmentation, slab caches can be 1839 merged when they share the same size and other characteristics. 1840 This carries a risk of kernel heap overflows being able to 1841 overwrite objects from merged caches (and more easily control 1842 cache layout), which makes such heap attacks easier to exploit 1843 by attackers. By keeping caches unmerged, these kinds of exploits 1844 can usually only damage objects in the same cache. To disable 1845 merging at runtime, "slab_nomerge" can be passed on the kernel 1846 command line. 1847 1848config SLAB_FREELIST_RANDOM 1849 default n 1850 depends on SLAB || SLUB 1851 bool "SLAB freelist randomization" 1852 help 1853 Randomizes the freelist order used on creating new pages. This 1854 security feature reduces the predictability of the kernel slab 1855 allocator against heap overflows. 1856 1857config SLAB_FREELIST_HARDENED 1858 bool "Harden slab freelist metadata" 1859 depends on SLUB 1860 help 1861 Many kernel heap attacks try to target slab cache metadata and 1862 other infrastructure. This options makes minor performance 1863 sacrifices to harden the kernel slab allocator against common 1864 freelist exploit methods. 1865 1866config SHUFFLE_PAGE_ALLOCATOR 1867 bool "Page allocator randomization" 1868 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1869 help 1870 Randomization of the page allocator improves the average 1871 utilization of a direct-mapped memory-side-cache. See section 1872 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1873 6.2a specification for an example of how a platform advertises 1874 the presence of a memory-side-cache. There are also incidental 1875 security benefits as it reduces the predictability of page 1876 allocations to compliment SLAB_FREELIST_RANDOM, but the 1877 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1878 10th order of pages is selected based on cache utilization 1879 benefits on x86. 1880 1881 While the randomization improves cache utilization it may 1882 negatively impact workloads on platforms without a cache. For 1883 this reason, by default, the randomization is enabled only 1884 after runtime detection of a direct-mapped memory-side-cache. 1885 Otherwise, the randomization may be force enabled with the 1886 'page_alloc.shuffle' kernel command line parameter. 1887 1888 Say Y if unsure. 1889 1890config SLUB_CPU_PARTIAL 1891 default y 1892 depends on SLUB && SMP 1893 bool "SLUB per cpu partial cache" 1894 help 1895 Per cpu partial caches accelerate objects allocation and freeing 1896 that is local to a processor at the price of more indeterminism 1897 in the latency of the free. On overflow these caches will be cleared 1898 which requires the taking of locks that may cause latency spikes. 1899 Typically one would choose no for a realtime system. 1900 1901config MMAP_ALLOW_UNINITIALIZED 1902 bool "Allow mmapped anonymous memory to be uninitialized" 1903 depends on EXPERT && !MMU 1904 default n 1905 help 1906 Normally, and according to the Linux spec, anonymous memory obtained 1907 from mmap() has its contents cleared before it is passed to 1908 userspace. Enabling this config option allows you to request that 1909 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1910 providing a huge performance boost. If this option is not enabled, 1911 then the flag will be ignored. 1912 1913 This is taken advantage of by uClibc's malloc(), and also by 1914 ELF-FDPIC binfmt's brk and stack allocator. 1915 1916 Because of the obvious security issues, this option should only be 1917 enabled on embedded devices where you control what is run in 1918 userspace. Since that isn't generally a problem on no-MMU systems, 1919 it is normally safe to say Y here. 1920 1921 See Documentation/nommu-mmap.txt for more information. 1922 1923config SYSTEM_DATA_VERIFICATION 1924 def_bool n 1925 select SYSTEM_TRUSTED_KEYRING 1926 select KEYS 1927 select CRYPTO 1928 select CRYPTO_RSA 1929 select ASYMMETRIC_KEY_TYPE 1930 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1931 select ASN1 1932 select OID_REGISTRY 1933 select X509_CERTIFICATE_PARSER 1934 select PKCS7_MESSAGE_PARSER 1935 help 1936 Provide PKCS#7 message verification using the contents of the system 1937 trusted keyring to provide public keys. This then can be used for 1938 module verification, kexec image verification and firmware blob 1939 verification. 1940 1941config PROFILING 1942 bool "Profiling support" 1943 help 1944 Say Y here to enable the extended profiling support mechanisms used 1945 by profilers such as OProfile. 1946 1947# 1948# Place an empty function call at each tracepoint site. Can be 1949# dynamically changed for a probe function. 1950# 1951config TRACEPOINTS 1952 bool 1953 1954endmenu # General setup 1955 1956source "arch/Kconfig" 1957 1958config RT_MUTEXES 1959 bool 1960 1961config BASE_SMALL 1962 int 1963 default 0 if BASE_FULL 1964 default 1 if !BASE_FULL 1965 1966config MODULE_SIG_FORMAT 1967 def_bool n 1968 select SYSTEM_DATA_VERIFICATION 1969 1970menuconfig MODULES 1971 bool "Enable loadable module support" 1972 option modules 1973 help 1974 Kernel modules are small pieces of compiled code which can 1975 be inserted in the running kernel, rather than being 1976 permanently built into the kernel. You use the "modprobe" 1977 tool to add (and sometimes remove) them. If you say Y here, 1978 many parts of the kernel can be built as modules (by 1979 answering M instead of Y where indicated): this is most 1980 useful for infrequently used options which are not required 1981 for booting. For more information, see the man pages for 1982 modprobe, lsmod, modinfo, insmod and rmmod. 1983 1984 If you say Y here, you will need to run "make 1985 modules_install" to put the modules under /lib/modules/ 1986 where modprobe can find them (you may need to be root to do 1987 this). 1988 1989 If unsure, say Y. 1990 1991if MODULES 1992 1993config MODULE_FORCE_LOAD 1994 bool "Forced module loading" 1995 default n 1996 help 1997 Allow loading of modules without version information (ie. modprobe 1998 --force). Forced module loading sets the 'F' (forced) taint flag and 1999 is usually a really bad idea. 2000 2001config MODULE_UNLOAD 2002 bool "Module unloading" 2003 help 2004 Without this option you will not be able to unload any 2005 modules (note that some modules may not be unloadable 2006 anyway), which makes your kernel smaller, faster 2007 and simpler. If unsure, say Y. 2008 2009config MODULE_FORCE_UNLOAD 2010 bool "Forced module unloading" 2011 depends on MODULE_UNLOAD 2012 help 2013 This option allows you to force a module to unload, even if the 2014 kernel believes it is unsafe: the kernel will remove the module 2015 without waiting for anyone to stop using it (using the -f option to 2016 rmmod). This is mainly for kernel developers and desperate users. 2017 If unsure, say N. 2018 2019config MODVERSIONS 2020 bool "Module versioning support" 2021 help 2022 Usually, you have to use modules compiled with your kernel. 2023 Saying Y here makes it sometimes possible to use modules 2024 compiled for different kernels, by adding enough information 2025 to the modules to (hopefully) spot any changes which would 2026 make them incompatible with the kernel you are running. If 2027 unsure, say N. 2028 2029config ASM_MODVERSIONS 2030 bool 2031 default HAVE_ASM_MODVERSIONS && MODVERSIONS 2032 help 2033 This enables module versioning for exported symbols also from 2034 assembly. This can be enabled only when the target architecture 2035 supports it. 2036 2037config MODULE_REL_CRCS 2038 bool 2039 depends on MODVERSIONS 2040 2041config MODULE_SRCVERSION_ALL 2042 bool "Source checksum for all modules" 2043 help 2044 Modules which contain a MODULE_VERSION get an extra "srcversion" 2045 field inserted into their modinfo section, which contains a 2046 sum of the source files which made it. This helps maintainers 2047 see exactly which source was used to build a module (since 2048 others sometimes change the module source without updating 2049 the version). With this option, such a "srcversion" field 2050 will be created for all modules. If unsure, say N. 2051 2052config MODULE_SIG 2053 bool "Module signature verification" 2054 select MODULE_SIG_FORMAT 2055 help 2056 Check modules for valid signatures upon load: the signature 2057 is simply appended to the module. For more information see 2058 <file:Documentation/admin-guide/module-signing.rst>. 2059 2060 Note that this option adds the OpenSSL development packages as a 2061 kernel build dependency so that the signing tool can use its crypto 2062 library. 2063 2064 You should enable this option if you wish to use either 2065 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via 2066 another LSM - otherwise unsigned modules will be loadable regardless 2067 of the lockdown policy. 2068 2069 !!!WARNING!!! If you enable this option, you MUST make sure that the 2070 module DOES NOT get stripped after being signed. This includes the 2071 debuginfo strip done by some packagers (such as rpmbuild) and 2072 inclusion into an initramfs that wants the module size reduced. 2073 2074config MODULE_SIG_FORCE 2075 bool "Require modules to be validly signed" 2076 depends on MODULE_SIG 2077 help 2078 Reject unsigned modules or signed modules for which we don't have a 2079 key. Without this, such modules will simply taint the kernel. 2080 2081config MODULE_SIG_ALL 2082 bool "Automatically sign all modules" 2083 default y 2084 depends on MODULE_SIG 2085 help 2086 Sign all modules during make modules_install. Without this option, 2087 modules must be signed manually, using the scripts/sign-file tool. 2088 2089comment "Do not forget to sign required modules with scripts/sign-file" 2090 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2091 2092choice 2093 prompt "Which hash algorithm should modules be signed with?" 2094 depends on MODULE_SIG 2095 help 2096 This determines which sort of hashing algorithm will be used during 2097 signature generation. This algorithm _must_ be built into the kernel 2098 directly so that signature verification can take place. It is not 2099 possible to load a signed module containing the algorithm to check 2100 the signature on that module. 2101 2102config MODULE_SIG_SHA1 2103 bool "Sign modules with SHA-1" 2104 select CRYPTO_SHA1 2105 2106config MODULE_SIG_SHA224 2107 bool "Sign modules with SHA-224" 2108 select CRYPTO_SHA256 2109 2110config MODULE_SIG_SHA256 2111 bool "Sign modules with SHA-256" 2112 select CRYPTO_SHA256 2113 2114config MODULE_SIG_SHA384 2115 bool "Sign modules with SHA-384" 2116 select CRYPTO_SHA512 2117 2118config MODULE_SIG_SHA512 2119 bool "Sign modules with SHA-512" 2120 select CRYPTO_SHA512 2121 2122endchoice 2123 2124config MODULE_SIG_HASH 2125 string 2126 depends on MODULE_SIG 2127 default "sha1" if MODULE_SIG_SHA1 2128 default "sha224" if MODULE_SIG_SHA224 2129 default "sha256" if MODULE_SIG_SHA256 2130 default "sha384" if MODULE_SIG_SHA384 2131 default "sha512" if MODULE_SIG_SHA512 2132 2133config MODULE_COMPRESS 2134 bool "Compress modules on installation" 2135 help 2136 2137 Compresses kernel modules when 'make modules_install' is run; gzip or 2138 xz depending on "Compression algorithm" below. 2139 2140 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 2141 2142 Out-of-tree kernel modules installed using Kbuild will also be 2143 compressed upon installation. 2144 2145 Note: for modules inside an initrd or initramfs, it's more efficient 2146 to compress the whole initrd or initramfs instead. 2147 2148 Note: This is fully compatible with signed modules. 2149 2150 If in doubt, say N. 2151 2152choice 2153 prompt "Compression algorithm" 2154 depends on MODULE_COMPRESS 2155 default MODULE_COMPRESS_GZIP 2156 help 2157 This determines which sort of compression will be used during 2158 'make modules_install'. 2159 2160 GZIP (default) and XZ are supported. 2161 2162config MODULE_COMPRESS_GZIP 2163 bool "GZIP" 2164 2165config MODULE_COMPRESS_XZ 2166 bool "XZ" 2167 2168endchoice 2169 2170config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS 2171 bool "Allow loading of modules with missing namespace imports" 2172 help 2173 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in 2174 a namespace. A module that makes use of a symbol exported with such a 2175 namespace is required to import the namespace via MODULE_IMPORT_NS(). 2176 There is no technical reason to enforce correct namespace imports, 2177 but it creates consistency between symbols defining namespaces and 2178 users importing namespaces they make use of. This option relaxes this 2179 requirement and lifts the enforcement when loading a module. 2180 2181 If unsure, say N. 2182 2183config UNUSED_SYMBOLS 2184 bool "Enable unused/obsolete exported symbols" 2185 default y if X86 2186 help 2187 Unused but exported symbols make the kernel needlessly bigger. For 2188 that reason most of these unused exports will soon be removed. This 2189 option is provided temporarily to provide a transition period in case 2190 some external kernel module needs one of these symbols anyway. If you 2191 encounter such a case in your module, consider if you are actually 2192 using the right API. (rationale: since nobody in the kernel is using 2193 this in a module, there is a pretty good chance it's actually the 2194 wrong interface to use). If you really need the symbol, please send a 2195 mail to the linux kernel mailing list mentioning the symbol and why 2196 you really need it, and what the merge plan to the mainline kernel for 2197 your module is. 2198 2199config TRIM_UNUSED_KSYMS 2200 bool "Trim unused exported kernel symbols" 2201 depends on !UNUSED_SYMBOLS 2202 help 2203 The kernel and some modules make many symbols available for 2204 other modules to use via EXPORT_SYMBOL() and variants. Depending 2205 on the set of modules being selected in your kernel configuration, 2206 many of those exported symbols might never be used. 2207 2208 This option allows for unused exported symbols to be dropped from 2209 the build. In turn, this provides the compiler more opportunities 2210 (especially when using LTO) for optimizing the code and reducing 2211 binary size. This might have some security advantages as well. 2212 2213 If unsure, or if you need to build out-of-tree modules, say N. 2214 2215endif # MODULES 2216 2217config MODULES_TREE_LOOKUP 2218 def_bool y 2219 depends on PERF_EVENTS || TRACING 2220 2221config INIT_ALL_POSSIBLE 2222 bool 2223 help 2224 Back when each arch used to define their own cpu_online_mask and 2225 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2226 with all 1s, and others with all 0s. When they were centralised, 2227 it was better to provide this option than to break all the archs 2228 and have several arch maintainers pursuing me down dark alleys. 2229 2230source "block/Kconfig" 2231 2232config PREEMPT_NOTIFIERS 2233 bool 2234 2235config PADATA 2236 depends on SMP 2237 bool 2238 2239config ASN1 2240 tristate 2241 help 2242 Build a simple ASN.1 grammar compiler that produces a bytecode output 2243 that can be interpreted by the ASN.1 stream decoder and used to 2244 inform it as to what tags are to be expected in a stream and what 2245 functions to call on what tags. 2246 2247source "kernel/Kconfig.locks" 2248 2249config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2250 bool 2251 2252# It may be useful for an architecture to override the definitions of the 2253# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2254# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2255# different calling convention for syscalls. They can also override the 2256# macros for not-implemented syscalls in kernel/sys_ni.c and 2257# kernel/time/posix-stubs.c. All these overrides need to be available in 2258# <asm/syscall_wrapper.h>. 2259config ARCH_HAS_SYSCALL_WRAPPER 2260 def_bool n 2261
