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/$(SRCARCH)/configs/$(KBUILD_DEFCONFIG)" 10 11config CC_IS_GCC 12 def_bool $(success,$(CC) --version | head -n 1 | grep -q gcc) 13 14config GCC_VERSION 15 int 16 default $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) if CC_IS_GCC 17 default 0 18 19config CC_IS_CLANG 20 def_bool $(success,$(CC) --version | head -n 1 | grep -q clang) 21 22config CLANG_VERSION 23 int 24 default $(shell,$(srctree)/scripts/clang-version.sh $(CC)) 25 26config CC_CAN_LINK 27 def_bool $(success,$(srctree)/scripts/cc-can-link.sh $(CC)) 28 29config CC_HAS_ASM_GOTO 30 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) 31 32config TOOLS_SUPPORT_RELR 33 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 34 35config CC_HAS_ASM_INLINE 36 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 37 38config CC_HAS_WARN_MAYBE_UNINITIALIZED 39 def_bool $(cc-option,-Wmaybe-uninitialized) 40 help 41 GCC >= 4.7 supports this option. 42 43config CC_DISABLE_WARN_MAYBE_UNINITIALIZED 44 bool 45 depends on CC_HAS_WARN_MAYBE_UNINITIALIZED 46 default CC_IS_GCC && GCC_VERSION < 40900 # unreliable for GCC < 4.9 47 help 48 GCC's -Wmaybe-uninitialized is not reliable by definition. 49 Lots of false positive warnings are produced in some cases. 50 51 If this option is enabled, -Wno-maybe-uninitialzed is passed 52 to the compiler to suppress maybe-uninitialized warnings. 53 54config CONSTRUCTORS 55 bool 56 depends on !UML 57 58config IRQ_WORK 59 bool 60 61config BUILDTIME_TABLE_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 UAPI_HEADER_TEST 108 bool "Compile test UAPI headers" 109 depends on HEADERS_INSTALL && CC_CAN_LINK 110 help 111 Compile test headers exported to user-space to ensure they are 112 self-contained, i.e. compilable as standalone units. 113 114 If you are a developer or tester and want to ensure the exported 115 headers are self-contained, say Y here. Otherwise, choose N. 116 117config LOCALVERSION 118 string "Local version - append to kernel release" 119 help 120 Append an extra string to the end of your kernel version. 121 This will show up when you type uname, for example. 122 The string you set here will be appended after the contents of 123 any files with a filename matching localversion* in your 124 object and source tree, in that order. Your total string can 125 be a maximum of 64 characters. 126 127config LOCALVERSION_AUTO 128 bool "Automatically append version information to the version string" 129 default y 130 depends on !COMPILE_TEST 131 help 132 This will try to automatically determine if the current tree is a 133 release tree by looking for git tags that belong to the current 134 top of tree revision. 135 136 A string of the format -gxxxxxxxx will be added to the localversion 137 if a git-based tree is found. The string generated by this will be 138 appended after any matching localversion* files, and after the value 139 set in CONFIG_LOCALVERSION. 140 141 (The actual string used here is the first eight characters produced 142 by running the command: 143 144 $ git rev-parse --verify HEAD 145 146 which is done within the script "scripts/setlocalversion".) 147 148config BUILD_SALT 149 string "Build ID Salt" 150 default "" 151 help 152 The build ID is used to link binaries and their debug info. Setting 153 this option will use the value in the calculation of the build id. 154 This is mostly useful for distributions which want to ensure the 155 build is unique between builds. It's safe to leave the default. 156 157config HAVE_KERNEL_GZIP 158 bool 159 160config HAVE_KERNEL_BZIP2 161 bool 162 163config HAVE_KERNEL_LZMA 164 bool 165 166config HAVE_KERNEL_XZ 167 bool 168 169config HAVE_KERNEL_LZO 170 bool 171 172config HAVE_KERNEL_LZ4 173 bool 174 175config HAVE_KERNEL_UNCOMPRESSED 176 bool 177 178choice 179 prompt "Kernel compression mode" 180 default KERNEL_GZIP 181 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED 182 help 183 The linux kernel is a kind of self-extracting executable. 184 Several compression algorithms are available, which differ 185 in efficiency, compression and decompression speed. 186 Compression speed is only relevant when building a kernel. 187 Decompression speed is relevant at each boot. 188 189 If you have any problems with bzip2 or lzma compressed 190 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 191 version of this functionality (bzip2 only), for 2.4, was 192 supplied by Christian Ludwig) 193 194 High compression options are mostly useful for users, who 195 are low on disk space (embedded systems), but for whom ram 196 size matters less. 197 198 If in doubt, select 'gzip' 199 200config KERNEL_GZIP 201 bool "Gzip" 202 depends on HAVE_KERNEL_GZIP 203 help 204 The old and tried gzip compression. It provides a good balance 205 between compression ratio and decompression speed. 206 207config KERNEL_BZIP2 208 bool "Bzip2" 209 depends on HAVE_KERNEL_BZIP2 210 help 211 Its compression ratio and speed is intermediate. 212 Decompression speed is slowest among the choices. The kernel 213 size is about 10% smaller with bzip2, in comparison to gzip. 214 Bzip2 uses a large amount of memory. For modern kernels you 215 will need at least 8MB RAM or more for booting. 216 217config KERNEL_LZMA 218 bool "LZMA" 219 depends on HAVE_KERNEL_LZMA 220 help 221 This compression algorithm's ratio is best. Decompression speed 222 is between gzip and bzip2. Compression is slowest. 223 The kernel size is about 33% smaller with LZMA in comparison to gzip. 224 225config KERNEL_XZ 226 bool "XZ" 227 depends on HAVE_KERNEL_XZ 228 help 229 XZ uses the LZMA2 algorithm and instruction set specific 230 BCJ filters which can improve compression ratio of executable 231 code. The size of the kernel is about 30% smaller with XZ in 232 comparison to gzip. On architectures for which there is a BCJ 233 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 234 will create a few percent smaller kernel than plain LZMA. 235 236 The speed is about the same as with LZMA: The decompression 237 speed of XZ is better than that of bzip2 but worse than gzip 238 and LZO. Compression is slow. 239 240config KERNEL_LZO 241 bool "LZO" 242 depends on HAVE_KERNEL_LZO 243 help 244 Its compression ratio is the poorest among the choices. The kernel 245 size is about 10% bigger than gzip; however its speed 246 (both compression and decompression) is the fastest. 247 248config KERNEL_LZ4 249 bool "LZ4" 250 depends on HAVE_KERNEL_LZ4 251 help 252 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 253 A preliminary version of LZ4 de/compression tool is available at 254 <https://code.google.com/p/lz4/>. 255 256 Its compression ratio is worse than LZO. The size of the kernel 257 is about 8% bigger than LZO. But the decompression speed is 258 faster than LZO. 259 260config KERNEL_UNCOMPRESSED 261 bool "None" 262 depends on HAVE_KERNEL_UNCOMPRESSED 263 help 264 Produce uncompressed kernel image. This option is usually not what 265 you want. It is useful for debugging the kernel in slow simulation 266 environments, where decompressing and moving the kernel is awfully 267 slow. This option allows early boot code to skip the decompressor 268 and jump right at uncompressed kernel image. 269 270endchoice 271 272config DEFAULT_HOSTNAME 273 string "Default hostname" 274 default "(none)" 275 help 276 This option determines the default system hostname before userspace 277 calls sethostname(2). The kernel traditionally uses "(none)" here, 278 but you may wish to use a different default here to make a minimal 279 system more usable with less configuration. 280 281# 282# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can 283# add proper SWAP support to them, in which case this can be remove. 284# 285config ARCH_NO_SWAP 286 bool 287 288config SWAP 289 bool "Support for paging of anonymous memory (swap)" 290 depends on MMU && BLOCK && !ARCH_NO_SWAP 291 default y 292 help 293 This option allows you to choose whether you want to have support 294 for so called swap devices or swap files in your kernel that are 295 used to provide more virtual memory than the actual RAM present 296 in your computer. If unsure say Y. 297 298config SYSVIPC 299 bool "System V IPC" 300 ---help--- 301 Inter Process Communication is a suite of library functions and 302 system calls which let processes (running programs) synchronize and 303 exchange information. It is generally considered to be a good thing, 304 and some programs won't run unless you say Y here. In particular, if 305 you want to run the DOS emulator dosemu under Linux (read the 306 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 307 you'll need to say Y here. 308 309 You can find documentation about IPC with "info ipc" and also in 310 section 6.4 of the Linux Programmer's Guide, available from 311 <http://www.tldp.org/guides.html>. 312 313config SYSVIPC_SYSCTL 314 bool 315 depends on SYSVIPC 316 depends on SYSCTL 317 default y 318 319config POSIX_MQUEUE 320 bool "POSIX Message Queues" 321 depends on NET 322 ---help--- 323 POSIX variant of message queues is a part of IPC. In POSIX message 324 queues every message has a priority which decides about succession 325 of receiving it by a process. If you want to compile and run 326 programs written e.g. for Solaris with use of its POSIX message 327 queues (functions mq_*) say Y here. 328 329 POSIX message queues are visible as a filesystem called 'mqueue' 330 and can be mounted somewhere if you want to do filesystem 331 operations on message queues. 332 333 If unsure, say Y. 334 335config POSIX_MQUEUE_SYSCTL 336 bool 337 depends on POSIX_MQUEUE 338 depends on SYSCTL 339 default y 340 341config CROSS_MEMORY_ATTACH 342 bool "Enable process_vm_readv/writev syscalls" 343 depends on MMU 344 default y 345 help 346 Enabling this option adds the system calls process_vm_readv and 347 process_vm_writev which allow a process with the correct privileges 348 to directly read from or write to another process' address space. 349 See the man page for more details. 350 351config USELIB 352 bool "uselib syscall" 353 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION 354 help 355 This option enables the uselib syscall, a system call used in the 356 dynamic linker from libc5 and earlier. glibc does not use this 357 system call. If you intend to run programs built on libc5 or 358 earlier, you may need to enable this syscall. Current systems 359 running glibc can safely disable this. 360 361config AUDIT 362 bool "Auditing support" 363 depends on NET 364 help 365 Enable auditing infrastructure that can be used with another 366 kernel subsystem, such as SELinux (which requires this for 367 logging of avc messages output). System call auditing is included 368 on architectures which support it. 369 370config HAVE_ARCH_AUDITSYSCALL 371 bool 372 373config AUDITSYSCALL 374 def_bool y 375 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 376 select FSNOTIFY 377 378source "kernel/irq/Kconfig" 379source "kernel/time/Kconfig" 380source "kernel/Kconfig.preempt" 381 382menu "CPU/Task time and stats accounting" 383 384config VIRT_CPU_ACCOUNTING 385 bool 386 387choice 388 prompt "Cputime accounting" 389 default TICK_CPU_ACCOUNTING if !PPC64 390 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 391 392# Kind of a stub config for the pure tick based cputime accounting 393config TICK_CPU_ACCOUNTING 394 bool "Simple tick based cputime accounting" 395 depends on !S390 && !NO_HZ_FULL 396 help 397 This is the basic tick based cputime accounting that maintains 398 statistics about user, system and idle time spent on per jiffies 399 granularity. 400 401 If unsure, say Y. 402 403config VIRT_CPU_ACCOUNTING_NATIVE 404 bool "Deterministic task and CPU time accounting" 405 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 406 select VIRT_CPU_ACCOUNTING 407 help 408 Select this option to enable more accurate task and CPU time 409 accounting. This is done by reading a CPU counter on each 410 kernel entry and exit and on transitions within the kernel 411 between system, softirq and hardirq state, so there is a 412 small performance impact. In the case of s390 or IBM POWER > 5, 413 this also enables accounting of stolen time on logically-partitioned 414 systems. 415 416config VIRT_CPU_ACCOUNTING_GEN 417 bool "Full dynticks CPU time accounting" 418 depends on HAVE_CONTEXT_TRACKING 419 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 420 depends on GENERIC_CLOCKEVENTS 421 select VIRT_CPU_ACCOUNTING 422 select CONTEXT_TRACKING 423 help 424 Select this option to enable task and CPU time accounting on full 425 dynticks systems. This accounting is implemented by watching every 426 kernel-user boundaries using the context tracking subsystem. 427 The accounting is thus performed at the expense of some significant 428 overhead. 429 430 For now this is only useful if you are working on the full 431 dynticks subsystem development. 432 433 If unsure, say N. 434 435endchoice 436 437config IRQ_TIME_ACCOUNTING 438 bool "Fine granularity task level IRQ time accounting" 439 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 440 help 441 Select this option to enable fine granularity task irq time 442 accounting. This is done by reading a timestamp on each 443 transitions between softirq and hardirq state, so there can be a 444 small performance impact. 445 446 If in doubt, say N here. 447 448config HAVE_SCHED_AVG_IRQ 449 def_bool y 450 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 451 depends on SMP 452 453config SCHED_THERMAL_PRESSURE 454 bool "Enable periodic averaging of thermal pressure" 455 depends on SMP 456 457config BSD_PROCESS_ACCT 458 bool "BSD Process Accounting" 459 depends on MULTIUSER 460 help 461 If you say Y here, a user level program will be able to instruct the 462 kernel (via a special system call) to write process accounting 463 information to a file: whenever a process exits, information about 464 that process will be appended to the file by the kernel. The 465 information includes things such as creation time, owning user, 466 command name, memory usage, controlling terminal etc. (the complete 467 list is in the struct acct in <file:include/linux/acct.h>). It is 468 up to the user level program to do useful things with this 469 information. This is generally a good idea, so say Y. 470 471config BSD_PROCESS_ACCT_V3 472 bool "BSD Process Accounting version 3 file format" 473 depends on BSD_PROCESS_ACCT 474 default n 475 help 476 If you say Y here, the process accounting information is written 477 in a new file format that also logs the process IDs of each 478 process and its parent. Note that this file format is incompatible 479 with previous v0/v1/v2 file formats, so you will need updated tools 480 for processing it. A preliminary version of these tools is available 481 at <http://www.gnu.org/software/acct/>. 482 483config TASKSTATS 484 bool "Export task/process statistics through netlink" 485 depends on NET 486 depends on MULTIUSER 487 default n 488 help 489 Export selected statistics for tasks/processes through the 490 generic netlink interface. Unlike BSD process accounting, the 491 statistics are available during the lifetime of tasks/processes as 492 responses to commands. Like BSD accounting, they are sent to user 493 space on task exit. 494 495 Say N if unsure. 496 497config TASK_DELAY_ACCT 498 bool "Enable per-task delay accounting" 499 depends on TASKSTATS 500 select SCHED_INFO 501 help 502 Collect information on time spent by a task waiting for system 503 resources like cpu, synchronous block I/O completion and swapping 504 in pages. Such statistics can help in setting a task's priorities 505 relative to other tasks for cpu, io, rss limits etc. 506 507 Say N if unsure. 508 509config TASK_XACCT 510 bool "Enable extended accounting over taskstats" 511 depends on TASKSTATS 512 help 513 Collect extended task accounting data and send the data 514 to userland for processing over the taskstats interface. 515 516 Say N if unsure. 517 518config TASK_IO_ACCOUNTING 519 bool "Enable per-task storage I/O accounting" 520 depends on TASK_XACCT 521 help 522 Collect information on the number of bytes of storage I/O which this 523 task has caused. 524 525 Say N if unsure. 526 527config PSI 528 bool "Pressure stall information tracking" 529 help 530 Collect metrics that indicate how overcommitted the CPU, memory, 531 and IO capacity are in the system. 532 533 If you say Y here, the kernel will create /proc/pressure/ with the 534 pressure statistics files cpu, memory, and io. These will indicate 535 the share of walltime in which some or all tasks in the system are 536 delayed due to contention of the respective resource. 537 538 In kernels with cgroup support, cgroups (cgroup2 only) will 539 have cpu.pressure, memory.pressure, and io.pressure files, 540 which aggregate pressure stalls for the grouped tasks only. 541 542 For more details see Documentation/accounting/psi.rst. 543 544 Say N if unsure. 545 546config PSI_DEFAULT_DISABLED 547 bool "Require boot parameter to enable pressure stall information tracking" 548 default n 549 depends on PSI 550 help 551 If set, pressure stall information tracking will be disabled 552 per default but can be enabled through passing psi=1 on the 553 kernel commandline during boot. 554 555 This feature adds some code to the task wakeup and sleep 556 paths of the scheduler. The overhead is too low to affect 557 common scheduling-intense workloads in practice (such as 558 webservers, memcache), but it does show up in artificial 559 scheduler stress tests, such as hackbench. 560 561 If you are paranoid and not sure what the kernel will be 562 used for, say Y. 563 564 Say N if unsure. 565 566endmenu # "CPU/Task time and stats accounting" 567 568config CPU_ISOLATION 569 bool "CPU isolation" 570 depends on SMP || COMPILE_TEST 571 default y 572 help 573 Make sure that CPUs running critical tasks are not disturbed by 574 any source of "noise" such as unbound workqueues, timers, kthreads... 575 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 576 the "isolcpus=" boot parameter. 577 578 Say Y if unsure. 579 580source "kernel/rcu/Kconfig" 581 582config BUILD_BIN2C 583 bool 584 default n 585 586config IKCONFIG 587 tristate "Kernel .config support" 588 ---help--- 589 This option enables the complete Linux kernel ".config" file 590 contents to be saved in the kernel. It provides documentation 591 of which kernel options are used in a running kernel or in an 592 on-disk kernel. This information can be extracted from the kernel 593 image file with the script scripts/extract-ikconfig and used as 594 input to rebuild the current kernel or to build another kernel. 595 It can also be extracted from a running kernel by reading 596 /proc/config.gz if enabled (below). 597 598config IKCONFIG_PROC 599 bool "Enable access to .config through /proc/config.gz" 600 depends on IKCONFIG && PROC_FS 601 ---help--- 602 This option enables access to the kernel configuration file 603 through /proc/config.gz. 604 605config IKHEADERS 606 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 607 depends on SYSFS 608 help 609 This option enables access to the in-kernel headers that are generated during 610 the build process. These can be used to build eBPF tracing programs, 611 or similar programs. If you build the headers as a module, a module called 612 kheaders.ko is built which can be loaded on-demand to get access to headers. 613 614config LOG_BUF_SHIFT 615 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 616 range 12 25 617 default 17 618 depends on PRINTK 619 help 620 Select the minimal kernel log buffer size as a power of 2. 621 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 622 parameter, see below. Any higher size also might be forced 623 by "log_buf_len" boot parameter. 624 625 Examples: 626 17 => 128 KB 627 16 => 64 KB 628 15 => 32 KB 629 14 => 16 KB 630 13 => 8 KB 631 12 => 4 KB 632 633config LOG_CPU_MAX_BUF_SHIFT 634 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 635 depends on SMP 636 range 0 21 637 default 12 if !BASE_SMALL 638 default 0 if BASE_SMALL 639 depends on PRINTK 640 help 641 This option allows to increase the default ring buffer size 642 according to the number of CPUs. The value defines the contribution 643 of each CPU as a power of 2. The used space is typically only few 644 lines however it might be much more when problems are reported, 645 e.g. backtraces. 646 647 The increased size means that a new buffer has to be allocated and 648 the original static one is unused. It makes sense only on systems 649 with more CPUs. Therefore this value is used only when the sum of 650 contributions is greater than the half of the default kernel ring 651 buffer as defined by LOG_BUF_SHIFT. The default values are set 652 so that more than 64 CPUs are needed to trigger the allocation. 653 654 Also this option is ignored when "log_buf_len" kernel parameter is 655 used as it forces an exact (power of two) size of the ring buffer. 656 657 The number of possible CPUs is used for this computation ignoring 658 hotplugging making the computation optimal for the worst case 659 scenario while allowing a simple algorithm to be used from bootup. 660 661 Examples shift values and their meaning: 662 17 => 128 KB for each CPU 663 16 => 64 KB for each CPU 664 15 => 32 KB for each CPU 665 14 => 16 KB for each CPU 666 13 => 8 KB for each CPU 667 12 => 4 KB for each CPU 668 669config PRINTK_SAFE_LOG_BUF_SHIFT 670 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 671 range 10 21 672 default 13 673 depends on PRINTK 674 help 675 Select the size of an alternate printk per-CPU buffer where messages 676 printed from usafe contexts are temporary stored. One example would 677 be NMI messages, another one - printk recursion. The messages are 678 copied to the main log buffer in a safe context to avoid a deadlock. 679 The value defines the size as a power of 2. 680 681 Those messages are rare and limited. The largest one is when 682 a backtrace is printed. It usually fits into 4KB. Select 683 8KB if you want to be on the safe side. 684 685 Examples: 686 17 => 128 KB for each CPU 687 16 => 64 KB for each CPU 688 15 => 32 KB for each CPU 689 14 => 16 KB for each CPU 690 13 => 8 KB for each CPU 691 12 => 4 KB for each CPU 692 693# 694# Architectures with an unreliable sched_clock() should select this: 695# 696config HAVE_UNSTABLE_SCHED_CLOCK 697 bool 698 699config GENERIC_SCHED_CLOCK 700 bool 701 702menu "Scheduler features" 703 704config UCLAMP_TASK 705 bool "Enable utilization clamping for RT/FAIR tasks" 706 depends on CPU_FREQ_GOV_SCHEDUTIL 707 help 708 This feature enables the scheduler to track the clamped utilization 709 of each CPU based on RUNNABLE tasks scheduled on that CPU. 710 711 With this option, the user can specify the min and max CPU 712 utilization allowed for RUNNABLE tasks. The max utilization defines 713 the maximum frequency a task should use while the min utilization 714 defines the minimum frequency it should use. 715 716 Both min and max utilization clamp values are hints to the scheduler, 717 aiming at improving its frequency selection policy, but they do not 718 enforce or grant any specific bandwidth for tasks. 719 720 If in doubt, say N. 721 722config UCLAMP_BUCKETS_COUNT 723 int "Number of supported utilization clamp buckets" 724 range 5 20 725 default 5 726 depends on UCLAMP_TASK 727 help 728 Defines the number of clamp buckets to use. The range of each bucket 729 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 730 number of clamp buckets the finer their granularity and the higher 731 the precision of clamping aggregation and tracking at run-time. 732 733 For example, with the minimum configuration value we will have 5 734 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 735 be refcounted in the [20..39]% bucket and will set the bucket clamp 736 effective value to 25%. 737 If a second 30% boosted task should be co-scheduled on the same CPU, 738 that task will be refcounted in the same bucket of the first task and 739 it will boost the bucket clamp effective value to 30%. 740 The clamp effective value of a bucket is reset to its nominal value 741 (20% in the example above) when there are no more tasks refcounted in 742 that bucket. 743 744 An additional boost/capping margin can be added to some tasks. In the 745 example above the 25% task will be boosted to 30% until it exits the 746 CPU. If that should be considered not acceptable on certain systems, 747 it's always possible to reduce the margin by increasing the number of 748 clamp buckets to trade off used memory for run-time tracking 749 precision. 750 751 If in doubt, use the default value. 752 753endmenu 754 755# 756# For architectures that want to enable the support for NUMA-affine scheduler 757# balancing logic: 758# 759config ARCH_SUPPORTS_NUMA_BALANCING 760 bool 761 762# 763# For architectures that prefer to flush all TLBs after a number of pages 764# are unmapped instead of sending one IPI per page to flush. The architecture 765# must provide guarantees on what happens if a clean TLB cache entry is 766# written after the unmap. Details are in mm/rmap.c near the check for 767# should_defer_flush. The architecture should also consider if the full flush 768# and the refill costs are offset by the savings of sending fewer IPIs. 769config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 770 bool 771 772config CC_HAS_INT128 773 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 774 775# 776# For architectures that know their GCC __int128 support is sound 777# 778config ARCH_SUPPORTS_INT128 779 bool 780 781# For architectures that (ab)use NUMA to represent different memory regions 782# all cpu-local but of different latencies, such as SuperH. 783# 784config ARCH_WANT_NUMA_VARIABLE_LOCALITY 785 bool 786 787config NUMA_BALANCING 788 bool "Memory placement aware NUMA scheduler" 789 depends on ARCH_SUPPORTS_NUMA_BALANCING 790 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 791 depends on SMP && NUMA && MIGRATION 792 help 793 This option adds support for automatic NUMA aware memory/task placement. 794 The mechanism is quite primitive and is based on migrating memory when 795 it has references to the node the task is running on. 796 797 This system will be inactive on UMA systems. 798 799config NUMA_BALANCING_DEFAULT_ENABLED 800 bool "Automatically enable NUMA aware memory/task placement" 801 default y 802 depends on NUMA_BALANCING 803 help 804 If set, automatic NUMA balancing will be enabled if running on a NUMA 805 machine. 806 807menuconfig CGROUPS 808 bool "Control Group support" 809 select KERNFS 810 help 811 This option adds support for grouping sets of processes together, for 812 use with process control subsystems such as Cpusets, CFS, memory 813 controls or device isolation. 814 See 815 - Documentation/scheduler/sched-design-CFS.rst (CFS) 816 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 817 and resource control) 818 819 Say N if unsure. 820 821if CGROUPS 822 823config PAGE_COUNTER 824 bool 825 826config MEMCG 827 bool "Memory controller" 828 select PAGE_COUNTER 829 select EVENTFD 830 help 831 Provides control over the memory footprint of tasks in a cgroup. 832 833config MEMCG_SWAP 834 bool "Swap controller" 835 depends on MEMCG && SWAP 836 help 837 Provides control over the swap space consumed by tasks in a cgroup. 838 839config MEMCG_SWAP_ENABLED 840 bool "Swap controller enabled by default" 841 depends on MEMCG_SWAP 842 default y 843 help 844 Memory Resource Controller Swap Extension comes with its price in 845 a bigger memory consumption. General purpose distribution kernels 846 which want to enable the feature but keep it disabled by default 847 and let the user enable it by swapaccount=1 boot command line 848 parameter should have this option unselected. 849 For those who want to have the feature enabled by default should 850 select this option (if, for some reason, they need to disable it 851 then swapaccount=0 does the trick). 852 853config MEMCG_KMEM 854 bool 855 depends on MEMCG && !SLOB 856 default y 857 858config BLK_CGROUP 859 bool "IO controller" 860 depends on BLOCK 861 default n 862 ---help--- 863 Generic block IO controller cgroup interface. This is the common 864 cgroup interface which should be used by various IO controlling 865 policies. 866 867 Currently, CFQ IO scheduler uses it to recognize task groups and 868 control disk bandwidth allocation (proportional time slice allocation) 869 to such task groups. It is also used by bio throttling logic in 870 block layer to implement upper limit in IO rates on a device. 871 872 This option only enables generic Block IO controller infrastructure. 873 One needs to also enable actual IO controlling logic/policy. For 874 enabling proportional weight division of disk bandwidth in CFQ, set 875 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 876 CONFIG_BLK_DEV_THROTTLING=y. 877 878 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 879 880config CGROUP_WRITEBACK 881 bool 882 depends on MEMCG && BLK_CGROUP 883 default y 884 885menuconfig CGROUP_SCHED 886 bool "CPU controller" 887 default n 888 help 889 This feature lets CPU scheduler recognize task groups and control CPU 890 bandwidth allocation to such task groups. It uses cgroups to group 891 tasks. 892 893if CGROUP_SCHED 894config FAIR_GROUP_SCHED 895 bool "Group scheduling for SCHED_OTHER" 896 depends on CGROUP_SCHED 897 default CGROUP_SCHED 898 899config CFS_BANDWIDTH 900 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 901 depends on FAIR_GROUP_SCHED 902 default n 903 help 904 This option allows users to define CPU bandwidth rates (limits) for 905 tasks running within the fair group scheduler. Groups with no limit 906 set are considered to be unconstrained and will run with no 907 restriction. 908 See Documentation/scheduler/sched-bwc.rst for more information. 909 910config RT_GROUP_SCHED 911 bool "Group scheduling for SCHED_RR/FIFO" 912 depends on CGROUP_SCHED 913 default n 914 help 915 This feature lets you explicitly allocate real CPU bandwidth 916 to task groups. If enabled, it will also make it impossible to 917 schedule realtime tasks for non-root users until you allocate 918 realtime bandwidth for them. 919 See Documentation/scheduler/sched-rt-group.rst for more information. 920 921endif #CGROUP_SCHED 922 923config UCLAMP_TASK_GROUP 924 bool "Utilization clamping per group of tasks" 925 depends on CGROUP_SCHED 926 depends on UCLAMP_TASK 927 default n 928 help 929 This feature enables the scheduler to track the clamped utilization 930 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 931 932 When this option is enabled, the user can specify a min and max 933 CPU bandwidth which is allowed for each single task in a group. 934 The max bandwidth allows to clamp the maximum frequency a task 935 can use, while the min bandwidth allows to define a minimum 936 frequency a task will always use. 937 938 When task group based utilization clamping is enabled, an eventually 939 specified task-specific clamp value is constrained by the cgroup 940 specified clamp value. Both minimum and maximum task clamping cannot 941 be bigger than the corresponding clamping defined at task group level. 942 943 If in doubt, say N. 944 945config CGROUP_PIDS 946 bool "PIDs controller" 947 help 948 Provides enforcement of process number limits in the scope of a 949 cgroup. Any attempt to fork more processes than is allowed in the 950 cgroup will fail. PIDs are fundamentally a global resource because it 951 is fairly trivial to reach PID exhaustion before you reach even a 952 conservative kmemcg limit. As a result, it is possible to grind a 953 system to halt without being limited by other cgroup policies. The 954 PIDs controller is designed to stop this from happening. 955 956 It should be noted that organisational operations (such as attaching 957 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 958 since the PIDs limit only affects a process's ability to fork, not to 959 attach to a cgroup. 960 961config CGROUP_RDMA 962 bool "RDMA controller" 963 help 964 Provides enforcement of RDMA resources defined by IB stack. 965 It is fairly easy for consumers to exhaust RDMA resources, which 966 can result into resource unavailability to other consumers. 967 RDMA controller is designed to stop this from happening. 968 Attaching processes with active RDMA resources to the cgroup 969 hierarchy is allowed even if can cross the hierarchy's limit. 970 971config CGROUP_FREEZER 972 bool "Freezer controller" 973 help 974 Provides a way to freeze and unfreeze all tasks in a 975 cgroup. 976 977 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 978 controller includes important in-kernel memory consumers per default. 979 980 If you're using cgroup2, say N. 981 982config CGROUP_HUGETLB 983 bool "HugeTLB controller" 984 depends on HUGETLB_PAGE 985 select PAGE_COUNTER 986 default n 987 help 988 Provides a cgroup controller for HugeTLB pages. 989 When you enable this, you can put a per cgroup limit on HugeTLB usage. 990 The limit is enforced during page fault. Since HugeTLB doesn't 991 support page reclaim, enforcing the limit at page fault time implies 992 that, the application will get SIGBUS signal if it tries to access 993 HugeTLB pages beyond its limit. This requires the application to know 994 beforehand how much HugeTLB pages it would require for its use. The 995 control group is tracked in the third page lru pointer. This means 996 that we cannot use the controller with huge page less than 3 pages. 997 998config CPUSETS 999 bool "Cpuset controller" 1000 depends on SMP 1001 help 1002 This option will let you create and manage CPUSETs which 1003 allow dynamically partitioning a system into sets of CPUs and 1004 Memory Nodes and assigning tasks to run only within those sets. 1005 This is primarily useful on large SMP or NUMA systems. 1006 1007 Say N if unsure. 1008 1009config PROC_PID_CPUSET 1010 bool "Include legacy /proc/<pid>/cpuset file" 1011 depends on CPUSETS 1012 default y 1013 1014config CGROUP_DEVICE 1015 bool "Device controller" 1016 help 1017 Provides a cgroup controller implementing whitelists for 1018 devices which a process in the cgroup can mknod or open. 1019 1020config CGROUP_CPUACCT 1021 bool "Simple CPU accounting controller" 1022 help 1023 Provides a simple controller for monitoring the 1024 total CPU consumed by the tasks in a cgroup. 1025 1026config CGROUP_PERF 1027 bool "Perf controller" 1028 depends on PERF_EVENTS 1029 help 1030 This option extends the perf per-cpu mode to restrict monitoring 1031 to threads which belong to the cgroup specified and run on the 1032 designated cpu. 1033 1034 Say N if unsure. 1035 1036config CGROUP_BPF 1037 bool "Support for eBPF programs attached to cgroups" 1038 depends on BPF_SYSCALL 1039 select SOCK_CGROUP_DATA 1040 help 1041 Allow attaching eBPF programs to a cgroup using the bpf(2) 1042 syscall command BPF_PROG_ATTACH. 1043 1044 In which context these programs are accessed depends on the type 1045 of attachment. For instance, programs that are attached using 1046 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1047 inet sockets. 1048 1049config CGROUP_DEBUG 1050 bool "Debug controller" 1051 default n 1052 depends on DEBUG_KERNEL 1053 help 1054 This option enables a simple controller that exports 1055 debugging information about the cgroups framework. This 1056 controller is for control cgroup debugging only. Its 1057 interfaces are not stable. 1058 1059 Say N. 1060 1061config SOCK_CGROUP_DATA 1062 bool 1063 default n 1064 1065endif # CGROUPS 1066 1067menuconfig NAMESPACES 1068 bool "Namespaces support" if EXPERT 1069 depends on MULTIUSER 1070 default !EXPERT 1071 help 1072 Provides the way to make tasks work with different objects using 1073 the same id. For example same IPC id may refer to different objects 1074 or same user id or pid may refer to different tasks when used in 1075 different namespaces. 1076 1077if NAMESPACES 1078 1079config UTS_NS 1080 bool "UTS namespace" 1081 default y 1082 help 1083 In this namespace tasks see different info provided with the 1084 uname() system call 1085 1086config TIME_NS 1087 bool "TIME namespace" 1088 depends on GENERIC_VDSO_TIME_NS 1089 default y 1090 help 1091 In this namespace boottime and monotonic clocks can be set. 1092 The time will keep going with the same pace. 1093 1094config IPC_NS 1095 bool "IPC namespace" 1096 depends on (SYSVIPC || POSIX_MQUEUE) 1097 default y 1098 help 1099 In this namespace tasks work with IPC ids which correspond to 1100 different IPC objects in different namespaces. 1101 1102config USER_NS 1103 bool "User namespace" 1104 default n 1105 help 1106 This allows containers, i.e. vservers, to use user namespaces 1107 to provide different user info for different servers. 1108 1109 When user namespaces are enabled in the kernel it is 1110 recommended that the MEMCG option also be enabled and that 1111 user-space use the memory control groups to limit the amount 1112 of memory a memory unprivileged users can use. 1113 1114 If unsure, say N. 1115 1116config PID_NS 1117 bool "PID Namespaces" 1118 default y 1119 help 1120 Support process id namespaces. This allows having multiple 1121 processes with the same pid as long as they are in different 1122 pid namespaces. This is a building block of containers. 1123 1124config NET_NS 1125 bool "Network namespace" 1126 depends on NET 1127 default y 1128 help 1129 Allow user space to create what appear to be multiple instances 1130 of the network stack. 1131 1132endif # NAMESPACES 1133 1134config CHECKPOINT_RESTORE 1135 bool "Checkpoint/restore support" 1136 select PROC_CHILDREN 1137 default n 1138 help 1139 Enables additional kernel features in a sake of checkpoint/restore. 1140 In particular it adds auxiliary prctl codes to setup process text, 1141 data and heap segment sizes, and a few additional /proc filesystem 1142 entries. 1143 1144 If unsure, say N here. 1145 1146config SCHED_AUTOGROUP 1147 bool "Automatic process group scheduling" 1148 select CGROUPS 1149 select CGROUP_SCHED 1150 select FAIR_GROUP_SCHED 1151 help 1152 This option optimizes the scheduler for common desktop workloads by 1153 automatically creating and populating task groups. This separation 1154 of workloads isolates aggressive CPU burners (like build jobs) from 1155 desktop applications. Task group autogeneration is currently based 1156 upon task session. 1157 1158config SYSFS_DEPRECATED 1159 bool "Enable deprecated sysfs features to support old userspace tools" 1160 depends on SYSFS 1161 default n 1162 help 1163 This option adds code that switches the layout of the "block" class 1164 devices, to not show up in /sys/class/block/, but only in 1165 /sys/block/. 1166 1167 This switch is only active when the sysfs.deprecated=1 boot option is 1168 passed or the SYSFS_DEPRECATED_V2 option is set. 1169 1170 This option allows new kernels to run on old distributions and tools, 1171 which might get confused by /sys/class/block/. Since 2007/2008 all 1172 major distributions and tools handle this just fine. 1173 1174 Recent distributions and userspace tools after 2009/2010 depend on 1175 the existence of /sys/class/block/, and will not work with this 1176 option enabled. 1177 1178 Only if you are using a new kernel on an old distribution, you might 1179 need to say Y here. 1180 1181config SYSFS_DEPRECATED_V2 1182 bool "Enable deprecated sysfs features by default" 1183 default n 1184 depends on SYSFS 1185 depends on SYSFS_DEPRECATED 1186 help 1187 Enable deprecated sysfs by default. 1188 1189 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1190 option. 1191 1192 Only if you are using a new kernel on an old distribution, you might 1193 need to say Y here. Even then, odds are you would not need it 1194 enabled, you can always pass the boot option if absolutely necessary. 1195 1196config RELAY 1197 bool "Kernel->user space relay support (formerly relayfs)" 1198 select IRQ_WORK 1199 help 1200 This option enables support for relay interface support in 1201 certain file systems (such as debugfs). 1202 It is designed to provide an efficient mechanism for tools and 1203 facilities to relay large amounts of data from kernel space to 1204 user space. 1205 1206 If unsure, say N. 1207 1208config BLK_DEV_INITRD 1209 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1210 help 1211 The initial RAM filesystem is a ramfs which is loaded by the 1212 boot loader (loadlin or lilo) and that is mounted as root 1213 before the normal boot procedure. It is typically used to 1214 load modules needed to mount the "real" root file system, 1215 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1216 1217 If RAM disk support (BLK_DEV_RAM) is also included, this 1218 also enables initial RAM disk (initrd) support and adds 1219 15 Kbytes (more on some other architectures) to the kernel size. 1220 1221 If unsure say Y. 1222 1223if BLK_DEV_INITRD 1224 1225source "usr/Kconfig" 1226 1227endif 1228 1229config BOOT_CONFIG 1230 bool "Boot config support" 1231 select BLK_DEV_INITRD 1232 help 1233 Extra boot config allows system admin to pass a config file as 1234 complemental extension of kernel cmdline when booting. 1235 The boot config file must be attached at the end of initramfs 1236 with checksum, size and magic word. 1237 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1238 1239 If unsure, say Y. 1240 1241choice 1242 prompt "Compiler optimization level" 1243 default CC_OPTIMIZE_FOR_PERFORMANCE 1244 1245config CC_OPTIMIZE_FOR_PERFORMANCE 1246 bool "Optimize for performance (-O2)" 1247 help 1248 This is the default optimization level for the kernel, building 1249 with the "-O2" compiler flag for best performance and most 1250 helpful compile-time warnings. 1251 1252config CC_OPTIMIZE_FOR_PERFORMANCE_O3 1253 bool "Optimize more for performance (-O3)" 1254 depends on ARC 1255 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives 1256 help 1257 Choosing this option will pass "-O3" to your compiler to optimize 1258 the kernel yet more for performance. 1259 1260config CC_OPTIMIZE_FOR_SIZE 1261 bool "Optimize for size (-Os)" 1262 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives 1263 help 1264 Choosing this option will pass "-Os" to your compiler resulting 1265 in a smaller kernel. 1266 1267endchoice 1268 1269config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1270 bool 1271 help 1272 This requires that the arch annotates or otherwise protects 1273 its external entry points from being discarded. Linker scripts 1274 must also merge .text.*, .data.*, and .bss.* correctly into 1275 output sections. Care must be taken not to pull in unrelated 1276 sections (e.g., '.text.init'). Typically '.' in section names 1277 is used to distinguish them from label names / C identifiers. 1278 1279config LD_DEAD_CODE_DATA_ELIMINATION 1280 bool "Dead code and data elimination (EXPERIMENTAL)" 1281 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1282 depends on EXPERT 1283 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800) 1284 depends on $(cc-option,-ffunction-sections -fdata-sections) 1285 depends on $(ld-option,--gc-sections) 1286 help 1287 Enable this if you want to do dead code and data elimination with 1288 the linker by compiling with -ffunction-sections -fdata-sections, 1289 and linking with --gc-sections. 1290 1291 This can reduce on disk and in-memory size of the kernel 1292 code and static data, particularly for small configs and 1293 on small systems. This has the possibility of introducing 1294 silently broken kernel if the required annotations are not 1295 present. This option is not well tested yet, so use at your 1296 own risk. 1297 1298config SYSCTL 1299 bool 1300 1301config HAVE_UID16 1302 bool 1303 1304config SYSCTL_EXCEPTION_TRACE 1305 bool 1306 help 1307 Enable support for /proc/sys/debug/exception-trace. 1308 1309config SYSCTL_ARCH_UNALIGN_NO_WARN 1310 bool 1311 help 1312 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1313 Allows arch to define/use @no_unaligned_warning to possibly warn 1314 about unaligned access emulation going on under the hood. 1315 1316config SYSCTL_ARCH_UNALIGN_ALLOW 1317 bool 1318 help 1319 Enable support for /proc/sys/kernel/unaligned-trap 1320 Allows arches to define/use @unaligned_enabled to runtime toggle 1321 the unaligned access emulation. 1322 see arch/parisc/kernel/unaligned.c for reference 1323 1324config HAVE_PCSPKR_PLATFORM 1325 bool 1326 1327# interpreter that classic socket filters depend on 1328config BPF 1329 bool 1330 1331menuconfig EXPERT 1332 bool "Configure standard kernel features (expert users)" 1333 # Unhide debug options, to make the on-by-default options visible 1334 select DEBUG_KERNEL 1335 help 1336 This option allows certain base kernel options and settings 1337 to be disabled or tweaked. This is for specialized 1338 environments which can tolerate a "non-standard" kernel. 1339 Only use this if you really know what you are doing. 1340 1341config UID16 1342 bool "Enable 16-bit UID system calls" if EXPERT 1343 depends on HAVE_UID16 && MULTIUSER 1344 default y 1345 help 1346 This enables the legacy 16-bit UID syscall wrappers. 1347 1348config MULTIUSER 1349 bool "Multiple users, groups and capabilities support" if EXPERT 1350 default y 1351 help 1352 This option enables support for non-root users, groups and 1353 capabilities. 1354 1355 If you say N here, all processes will run with UID 0, GID 0, and all 1356 possible capabilities. Saying N here also compiles out support for 1357 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1358 setgid, and capset. 1359 1360 If unsure, say Y here. 1361 1362config SGETMASK_SYSCALL 1363 bool "sgetmask/ssetmask syscalls support" if EXPERT 1364 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1365 ---help--- 1366 sys_sgetmask and sys_ssetmask are obsolete system calls 1367 no longer supported in libc but still enabled by default in some 1368 architectures. 1369 1370 If unsure, leave the default option here. 1371 1372config SYSFS_SYSCALL 1373 bool "Sysfs syscall support" if EXPERT 1374 default y 1375 ---help--- 1376 sys_sysfs is an obsolete system call no longer supported in libc. 1377 Note that disabling this option is more secure but might break 1378 compatibility with some systems. 1379 1380 If unsure say Y here. 1381 1382config FHANDLE 1383 bool "open by fhandle syscalls" if EXPERT 1384 select EXPORTFS 1385 default y 1386 help 1387 If you say Y here, a user level program will be able to map 1388 file names to handle and then later use the handle for 1389 different file system operations. This is useful in implementing 1390 userspace file servers, which now track files using handles instead 1391 of names. The handle would remain the same even if file names 1392 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1393 syscalls. 1394 1395config POSIX_TIMERS 1396 bool "Posix Clocks & timers" if EXPERT 1397 default y 1398 help 1399 This includes native support for POSIX timers to the kernel. 1400 Some embedded systems have no use for them and therefore they 1401 can be configured out to reduce the size of the kernel image. 1402 1403 When this option is disabled, the following syscalls won't be 1404 available: timer_create, timer_gettime: timer_getoverrun, 1405 timer_settime, timer_delete, clock_adjtime, getitimer, 1406 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1407 clock_getres and clock_nanosleep syscalls will be limited to 1408 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1409 1410 If unsure say y. 1411 1412config PRINTK 1413 default y 1414 bool "Enable support for printk" if EXPERT 1415 select IRQ_WORK 1416 help 1417 This option enables normal printk support. Removing it 1418 eliminates most of the message strings from the kernel image 1419 and makes the kernel more or less silent. As this makes it 1420 very difficult to diagnose system problems, saying N here is 1421 strongly discouraged. 1422 1423config PRINTK_NMI 1424 def_bool y 1425 depends on PRINTK 1426 depends on HAVE_NMI 1427 1428config BUG 1429 bool "BUG() support" if EXPERT 1430 default y 1431 help 1432 Disabling this option eliminates support for BUG and WARN, reducing 1433 the size of your kernel image and potentially quietly ignoring 1434 numerous fatal conditions. You should only consider disabling this 1435 option for embedded systems with no facilities for reporting errors. 1436 Just say Y. 1437 1438config ELF_CORE 1439 depends on COREDUMP 1440 default y 1441 bool "Enable ELF core dumps" if EXPERT 1442 help 1443 Enable support for generating core dumps. Disabling saves about 4k. 1444 1445 1446config PCSPKR_PLATFORM 1447 bool "Enable PC-Speaker support" if EXPERT 1448 depends on HAVE_PCSPKR_PLATFORM 1449 select I8253_LOCK 1450 default y 1451 help 1452 This option allows to disable the internal PC-Speaker 1453 support, saving some memory. 1454 1455config BASE_FULL 1456 default y 1457 bool "Enable full-sized data structures for core" if EXPERT 1458 help 1459 Disabling this option reduces the size of miscellaneous core 1460 kernel data structures. This saves memory on small machines, 1461 but may reduce performance. 1462 1463config FUTEX 1464 bool "Enable futex support" if EXPERT 1465 default y 1466 imply RT_MUTEXES 1467 help 1468 Disabling this option will cause the kernel to be built without 1469 support for "fast userspace mutexes". The resulting kernel may not 1470 run glibc-based applications correctly. 1471 1472config FUTEX_PI 1473 bool 1474 depends on FUTEX && RT_MUTEXES 1475 default y 1476 1477config HAVE_FUTEX_CMPXCHG 1478 bool 1479 depends on FUTEX 1480 help 1481 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1482 is implemented and always working. This removes a couple of runtime 1483 checks. 1484 1485config EPOLL 1486 bool "Enable eventpoll support" if EXPERT 1487 default y 1488 help 1489 Disabling this option will cause the kernel to be built without 1490 support for epoll family of system calls. 1491 1492config SIGNALFD 1493 bool "Enable signalfd() system call" if EXPERT 1494 default y 1495 help 1496 Enable the signalfd() system call that allows to receive signals 1497 on a file descriptor. 1498 1499 If unsure, say Y. 1500 1501config TIMERFD 1502 bool "Enable timerfd() system call" if EXPERT 1503 default y 1504 help 1505 Enable the timerfd() system call that allows to receive timer 1506 events on a file descriptor. 1507 1508 If unsure, say Y. 1509 1510config EVENTFD 1511 bool "Enable eventfd() system call" if EXPERT 1512 default y 1513 help 1514 Enable the eventfd() system call that allows to receive both 1515 kernel notification (ie. KAIO) or userspace notifications. 1516 1517 If unsure, say Y. 1518 1519config SHMEM 1520 bool "Use full shmem filesystem" if EXPERT 1521 default y 1522 depends on MMU 1523 help 1524 The shmem is an internal filesystem used to manage shared memory. 1525 It is backed by swap and manages resource limits. It is also exported 1526 to userspace as tmpfs if TMPFS is enabled. Disabling this 1527 option replaces shmem and tmpfs with the much simpler ramfs code, 1528 which may be appropriate on small systems without swap. 1529 1530config AIO 1531 bool "Enable AIO support" if EXPERT 1532 default y 1533 help 1534 This option enables POSIX asynchronous I/O which may by used 1535 by some high performance threaded applications. Disabling 1536 this option saves about 7k. 1537 1538config IO_URING 1539 bool "Enable IO uring support" if EXPERT 1540 select ANON_INODES 1541 select IO_WQ 1542 default y 1543 help 1544 This option enables support for the io_uring interface, enabling 1545 applications to submit and complete IO through submission and 1546 completion rings that are shared between the kernel and application. 1547 1548config ADVISE_SYSCALLS 1549 bool "Enable madvise/fadvise syscalls" if EXPERT 1550 default y 1551 help 1552 This option enables the madvise and fadvise syscalls, used by 1553 applications to advise the kernel about their future memory or file 1554 usage, improving performance. If building an embedded system where no 1555 applications use these syscalls, you can disable this option to save 1556 space. 1557 1558config MEMBARRIER 1559 bool "Enable membarrier() system call" if EXPERT 1560 default y 1561 help 1562 Enable the membarrier() system call that allows issuing memory 1563 barriers across all running threads, which can be used to distribute 1564 the cost of user-space memory barriers asymmetrically by transforming 1565 pairs of memory barriers into pairs consisting of membarrier() and a 1566 compiler barrier. 1567 1568 If unsure, say Y. 1569 1570config KALLSYMS 1571 bool "Load all symbols for debugging/ksymoops" if EXPERT 1572 default y 1573 help 1574 Say Y here to let the kernel print out symbolic crash information and 1575 symbolic stack backtraces. This increases the size of the kernel 1576 somewhat, as all symbols have to be loaded into the kernel image. 1577 1578config KALLSYMS_ALL 1579 bool "Include all symbols in kallsyms" 1580 depends on DEBUG_KERNEL && KALLSYMS 1581 help 1582 Normally kallsyms only contains the symbols of functions for nicer 1583 OOPS messages and backtraces (i.e., symbols from the text and inittext 1584 sections). This is sufficient for most cases. And only in very rare 1585 cases (e.g., when a debugger is used) all symbols are required (e.g., 1586 names of variables from the data sections, etc). 1587 1588 This option makes sure that all symbols are loaded into the kernel 1589 image (i.e., symbols from all sections) in cost of increased kernel 1590 size (depending on the kernel configuration, it may be 300KiB or 1591 something like this). 1592 1593 Say N unless you really need all symbols. 1594 1595config KALLSYMS_ABSOLUTE_PERCPU 1596 bool 1597 depends on KALLSYMS 1598 default X86_64 && SMP 1599 1600config KALLSYMS_BASE_RELATIVE 1601 bool 1602 depends on KALLSYMS 1603 default !IA64 1604 help 1605 Instead of emitting them as absolute values in the native word size, 1606 emit the symbol references in the kallsyms table as 32-bit entries, 1607 each containing a relative value in the range [base, base + U32_MAX] 1608 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1609 an absolute value in the range [0, S32_MAX] or a relative value in the 1610 range [base, base + S32_MAX], where base is the lowest relative symbol 1611 address encountered in the image. 1612 1613 On 64-bit builds, this reduces the size of the address table by 50%, 1614 but more importantly, it results in entries whose values are build 1615 time constants, and no relocation pass is required at runtime to fix 1616 up the entries based on the runtime load address of the kernel. 1617 1618# end of the "standard kernel features (expert users)" menu 1619 1620# syscall, maps, verifier 1621 1622config BPF_LSM 1623 bool "LSM Instrumentation with BPF" 1624 depends on BPF_EVENTS 1625 depends on BPF_SYSCALL 1626 depends on SECURITY 1627 depends on BPF_JIT 1628 help 1629 Enables instrumentation of the security hooks with eBPF programs for 1630 implementing dynamic MAC and Audit Policies. 1631 1632 If you are unsure how to answer this question, answer N. 1633 1634config BPF_SYSCALL 1635 bool "Enable bpf() system call" 1636 select BPF 1637 select IRQ_WORK 1638 default n 1639 help 1640 Enable the bpf() system call that allows to manipulate eBPF 1641 programs and maps via file descriptors. 1642 1643config ARCH_WANT_DEFAULT_BPF_JIT 1644 bool 1645 1646config BPF_JIT_ALWAYS_ON 1647 bool "Permanently enable BPF JIT and remove BPF interpreter" 1648 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1649 help 1650 Enables BPF JIT and removes BPF interpreter to avoid 1651 speculative execution of BPF instructions by the interpreter 1652 1653config BPF_JIT_DEFAULT_ON 1654 def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON 1655 depends on HAVE_EBPF_JIT && BPF_JIT 1656 1657config USERFAULTFD 1658 bool "Enable userfaultfd() system call" 1659 depends on MMU 1660 help 1661 Enable the userfaultfd() system call that allows to intercept and 1662 handle page faults in userland. 1663 1664config ARCH_HAS_MEMBARRIER_CALLBACKS 1665 bool 1666 1667config ARCH_HAS_MEMBARRIER_SYNC_CORE 1668 bool 1669 1670config RSEQ 1671 bool "Enable rseq() system call" if EXPERT 1672 default y 1673 depends on HAVE_RSEQ 1674 select MEMBARRIER 1675 help 1676 Enable the restartable sequences system call. It provides a 1677 user-space cache for the current CPU number value, which 1678 speeds up getting the current CPU number from user-space, 1679 as well as an ABI to speed up user-space operations on 1680 per-CPU data. 1681 1682 If unsure, say Y. 1683 1684config DEBUG_RSEQ 1685 default n 1686 bool "Enabled debugging of rseq() system call" if EXPERT 1687 depends on RSEQ && DEBUG_KERNEL 1688 help 1689 Enable extra debugging checks for the rseq system call. 1690 1691 If unsure, say N. 1692 1693config EMBEDDED 1694 bool "Embedded system" 1695 option allnoconfig_y 1696 select EXPERT 1697 help 1698 This option should be enabled if compiling the kernel for 1699 an embedded system so certain expert options are available 1700 for configuration. 1701 1702config HAVE_PERF_EVENTS 1703 bool 1704 help 1705 See tools/perf/design.txt for details. 1706 1707config PERF_USE_VMALLOC 1708 bool 1709 help 1710 See tools/perf/design.txt for details 1711 1712config PC104 1713 bool "PC/104 support" if EXPERT 1714 help 1715 Expose PC/104 form factor device drivers and options available for 1716 selection and configuration. Enable this option if your target 1717 machine has a PC/104 bus. 1718 1719menu "Kernel Performance Events And Counters" 1720 1721config PERF_EVENTS 1722 bool "Kernel performance events and counters" 1723 default y if PROFILING 1724 depends on HAVE_PERF_EVENTS 1725 select IRQ_WORK 1726 select SRCU 1727 help 1728 Enable kernel support for various performance events provided 1729 by software and hardware. 1730 1731 Software events are supported either built-in or via the 1732 use of generic tracepoints. 1733 1734 Most modern CPUs support performance events via performance 1735 counter registers. These registers count the number of certain 1736 types of hw events: such as instructions executed, cachemisses 1737 suffered, or branches mis-predicted - without slowing down the 1738 kernel or applications. These registers can also trigger interrupts 1739 when a threshold number of events have passed - and can thus be 1740 used to profile the code that runs on that CPU. 1741 1742 The Linux Performance Event subsystem provides an abstraction of 1743 these software and hardware event capabilities, available via a 1744 system call and used by the "perf" utility in tools/perf/. It 1745 provides per task and per CPU counters, and it provides event 1746 capabilities on top of those. 1747 1748 Say Y if unsure. 1749 1750config DEBUG_PERF_USE_VMALLOC 1751 default n 1752 bool "Debug: use vmalloc to back perf mmap() buffers" 1753 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1754 select PERF_USE_VMALLOC 1755 help 1756 Use vmalloc memory to back perf mmap() buffers. 1757 1758 Mostly useful for debugging the vmalloc code on platforms 1759 that don't require it. 1760 1761 Say N if unsure. 1762 1763endmenu 1764 1765config VM_EVENT_COUNTERS 1766 default y 1767 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1768 help 1769 VM event counters are needed for event counts to be shown. 1770 This option allows the disabling of the VM event counters 1771 on EXPERT systems. /proc/vmstat will only show page counts 1772 if VM event counters are disabled. 1773 1774config SLUB_DEBUG 1775 default y 1776 bool "Enable SLUB debugging support" if EXPERT 1777 depends on SLUB && SYSFS 1778 help 1779 SLUB has extensive debug support features. Disabling these can 1780 result in significant savings in code size. This also disables 1781 SLUB sysfs support. /sys/slab will not exist and there will be 1782 no support for cache validation etc. 1783 1784config SLUB_MEMCG_SYSFS_ON 1785 default n 1786 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1787 depends on SLUB && SYSFS && MEMCG 1788 help 1789 SLUB creates a directory under /sys/kernel/slab for each 1790 allocation cache to host info and debug files. If memory 1791 cgroup is enabled, each cache can have per memory cgroup 1792 caches. SLUB can create the same sysfs directories for these 1793 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1794 to a very high number of debug files being created. This is 1795 controlled by slub_memcg_sysfs boot parameter and this 1796 config option determines the parameter's default value. 1797 1798config COMPAT_BRK 1799 bool "Disable heap randomization" 1800 default y 1801 help 1802 Randomizing heap placement makes heap exploits harder, but it 1803 also breaks ancient binaries (including anything libc5 based). 1804 This option changes the bootup default to heap randomization 1805 disabled, and can be overridden at runtime by setting 1806 /proc/sys/kernel/randomize_va_space to 2. 1807 1808 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1809 1810choice 1811 prompt "Choose SLAB allocator" 1812 default SLUB 1813 help 1814 This option allows to select a slab allocator. 1815 1816config SLAB 1817 bool "SLAB" 1818 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1819 help 1820 The regular slab allocator that is established and known to work 1821 well in all environments. It organizes cache hot objects in 1822 per cpu and per node queues. 1823 1824config SLUB 1825 bool "SLUB (Unqueued Allocator)" 1826 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1827 help 1828 SLUB is a slab allocator that minimizes cache line usage 1829 instead of managing queues of cached objects (SLAB approach). 1830 Per cpu caching is realized using slabs of objects instead 1831 of queues of objects. SLUB can use memory efficiently 1832 and has enhanced diagnostics. SLUB is the default choice for 1833 a slab allocator. 1834 1835config SLOB 1836 depends on EXPERT 1837 bool "SLOB (Simple Allocator)" 1838 help 1839 SLOB replaces the stock allocator with a drastically simpler 1840 allocator. SLOB is generally more space efficient but 1841 does not perform as well on large systems. 1842 1843endchoice 1844 1845config SLAB_MERGE_DEFAULT 1846 bool "Allow slab caches to be merged" 1847 default y 1848 help 1849 For reduced kernel memory fragmentation, slab caches can be 1850 merged when they share the same size and other characteristics. 1851 This carries a risk of kernel heap overflows being able to 1852 overwrite objects from merged caches (and more easily control 1853 cache layout), which makes such heap attacks easier to exploit 1854 by attackers. By keeping caches unmerged, these kinds of exploits 1855 can usually only damage objects in the same cache. To disable 1856 merging at runtime, "slab_nomerge" can be passed on the kernel 1857 command line. 1858 1859config SLAB_FREELIST_RANDOM 1860 default n 1861 depends on SLAB || SLUB 1862 bool "SLAB freelist randomization" 1863 help 1864 Randomizes the freelist order used on creating new pages. This 1865 security feature reduces the predictability of the kernel slab 1866 allocator against heap overflows. 1867 1868config SLAB_FREELIST_HARDENED 1869 bool "Harden slab freelist metadata" 1870 depends on SLUB 1871 help 1872 Many kernel heap attacks try to target slab cache metadata and 1873 other infrastructure. This options makes minor performance 1874 sacrifices to harden the kernel slab allocator against common 1875 freelist exploit methods. 1876 1877config SHUFFLE_PAGE_ALLOCATOR 1878 bool "Page allocator randomization" 1879 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1880 help 1881 Randomization of the page allocator improves the average 1882 utilization of a direct-mapped memory-side-cache. See section 1883 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1884 6.2a specification for an example of how a platform advertises 1885 the presence of a memory-side-cache. There are also incidental 1886 security benefits as it reduces the predictability of page 1887 allocations to compliment SLAB_FREELIST_RANDOM, but the 1888 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1889 10th order of pages is selected based on cache utilization 1890 benefits on x86. 1891 1892 While the randomization improves cache utilization it may 1893 negatively impact workloads on platforms without a cache. For 1894 this reason, by default, the randomization is enabled only 1895 after runtime detection of a direct-mapped memory-side-cache. 1896 Otherwise, the randomization may be force enabled with the 1897 'page_alloc.shuffle' kernel command line parameter. 1898 1899 Say Y if unsure. 1900 1901config SLUB_CPU_PARTIAL 1902 default y 1903 depends on SLUB && SMP 1904 bool "SLUB per cpu partial cache" 1905 help 1906 Per cpu partial caches accelerate objects allocation and freeing 1907 that is local to a processor at the price of more indeterminism 1908 in the latency of the free. On overflow these caches will be cleared 1909 which requires the taking of locks that may cause latency spikes. 1910 Typically one would choose no for a realtime system. 1911 1912config MMAP_ALLOW_UNINITIALIZED 1913 bool "Allow mmapped anonymous memory to be uninitialized" 1914 depends on EXPERT && !MMU 1915 default n 1916 help 1917 Normally, and according to the Linux spec, anonymous memory obtained 1918 from mmap() has its contents cleared before it is passed to 1919 userspace. Enabling this config option allows you to request that 1920 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1921 providing a huge performance boost. If this option is not enabled, 1922 then the flag will be ignored. 1923 1924 This is taken advantage of by uClibc's malloc(), and also by 1925 ELF-FDPIC binfmt's brk and stack allocator. 1926 1927 Because of the obvious security issues, this option should only be 1928 enabled on embedded devices where you control what is run in 1929 userspace. Since that isn't generally a problem on no-MMU systems, 1930 it is normally safe to say Y here. 1931 1932 See Documentation/nommu-mmap.txt for more information. 1933 1934config SYSTEM_DATA_VERIFICATION 1935 def_bool n 1936 select SYSTEM_TRUSTED_KEYRING 1937 select KEYS 1938 select CRYPTO 1939 select CRYPTO_RSA 1940 select ASYMMETRIC_KEY_TYPE 1941 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1942 select ASN1 1943 select OID_REGISTRY 1944 select X509_CERTIFICATE_PARSER 1945 select PKCS7_MESSAGE_PARSER 1946 help 1947 Provide PKCS#7 message verification using the contents of the system 1948 trusted keyring to provide public keys. This then can be used for 1949 module verification, kexec image verification and firmware blob 1950 verification. 1951 1952config PROFILING 1953 bool "Profiling support" 1954 help 1955 Say Y here to enable the extended profiling support mechanisms used 1956 by profilers such as OProfile. 1957 1958# 1959# Place an empty function call at each tracepoint site. Can be 1960# dynamically changed for a probe function. 1961# 1962config TRACEPOINTS 1963 bool 1964 1965endmenu # General setup 1966 1967source "arch/Kconfig" 1968 1969config RT_MUTEXES 1970 bool 1971 1972config BASE_SMALL 1973 int 1974 default 0 if BASE_FULL 1975 default 1 if !BASE_FULL 1976 1977config MODULE_SIG_FORMAT 1978 def_bool n 1979 select SYSTEM_DATA_VERIFICATION 1980 1981menuconfig MODULES 1982 bool "Enable loadable module support" 1983 option modules 1984 help 1985 Kernel modules are small pieces of compiled code which can 1986 be inserted in the running kernel, rather than being 1987 permanently built into the kernel. You use the "modprobe" 1988 tool to add (and sometimes remove) them. If you say Y here, 1989 many parts of the kernel can be built as modules (by 1990 answering M instead of Y where indicated): this is most 1991 useful for infrequently used options which are not required 1992 for booting. For more information, see the man pages for 1993 modprobe, lsmod, modinfo, insmod and rmmod. 1994 1995 If you say Y here, you will need to run "make 1996 modules_install" to put the modules under /lib/modules/ 1997 where modprobe can find them (you may need to be root to do 1998 this). 1999 2000 If unsure, say Y. 2001 2002if MODULES 2003 2004config MODULE_FORCE_LOAD 2005 bool "Forced module loading" 2006 default n 2007 help 2008 Allow loading of modules without version information (ie. modprobe 2009 --force). Forced module loading sets the 'F' (forced) taint flag and 2010 is usually a really bad idea. 2011 2012config MODULE_UNLOAD 2013 bool "Module unloading" 2014 help 2015 Without this option you will not be able to unload any 2016 modules (note that some modules may not be unloadable 2017 anyway), which makes your kernel smaller, faster 2018 and simpler. If unsure, say Y. 2019 2020config MODULE_FORCE_UNLOAD 2021 bool "Forced module unloading" 2022 depends on MODULE_UNLOAD 2023 help 2024 This option allows you to force a module to unload, even if the 2025 kernel believes it is unsafe: the kernel will remove the module 2026 without waiting for anyone to stop using it (using the -f option to 2027 rmmod). This is mainly for kernel developers and desperate users. 2028 If unsure, say N. 2029 2030config MODVERSIONS 2031 bool "Module versioning support" 2032 help 2033 Usually, you have to use modules compiled with your kernel. 2034 Saying Y here makes it sometimes possible to use modules 2035 compiled for different kernels, by adding enough information 2036 to the modules to (hopefully) spot any changes which would 2037 make them incompatible with the kernel you are running. If 2038 unsure, say N. 2039 2040config ASM_MODVERSIONS 2041 bool 2042 default HAVE_ASM_MODVERSIONS && MODVERSIONS 2043 help 2044 This enables module versioning for exported symbols also from 2045 assembly. This can be enabled only when the target architecture 2046 supports it. 2047 2048config MODULE_REL_CRCS 2049 bool 2050 depends on MODVERSIONS 2051 2052config MODULE_SRCVERSION_ALL 2053 bool "Source checksum for all modules" 2054 help 2055 Modules which contain a MODULE_VERSION get an extra "srcversion" 2056 field inserted into their modinfo section, which contains a 2057 sum of the source files which made it. This helps maintainers 2058 see exactly which source was used to build a module (since 2059 others sometimes change the module source without updating 2060 the version). With this option, such a "srcversion" field 2061 will be created for all modules. If unsure, say N. 2062 2063config MODULE_SIG 2064 bool "Module signature verification" 2065 select MODULE_SIG_FORMAT 2066 help 2067 Check modules for valid signatures upon load: the signature 2068 is simply appended to the module. For more information see 2069 <file:Documentation/admin-guide/module-signing.rst>. 2070 2071 Note that this option adds the OpenSSL development packages as a 2072 kernel build dependency so that the signing tool can use its crypto 2073 library. 2074 2075 You should enable this option if you wish to use either 2076 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via 2077 another LSM - otherwise unsigned modules will be loadable regardless 2078 of the lockdown policy. 2079 2080 !!!WARNING!!! If you enable this option, you MUST make sure that the 2081 module DOES NOT get stripped after being signed. This includes the 2082 debuginfo strip done by some packagers (such as rpmbuild) and 2083 inclusion into an initramfs that wants the module size reduced. 2084 2085config MODULE_SIG_FORCE 2086 bool "Require modules to be validly signed" 2087 depends on MODULE_SIG 2088 help 2089 Reject unsigned modules or signed modules for which we don't have a 2090 key. Without this, such modules will simply taint the kernel. 2091 2092config MODULE_SIG_ALL 2093 bool "Automatically sign all modules" 2094 default y 2095 depends on MODULE_SIG 2096 help 2097 Sign all modules during make modules_install. Without this option, 2098 modules must be signed manually, using the scripts/sign-file tool. 2099 2100comment "Do not forget to sign required modules with scripts/sign-file" 2101 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2102 2103choice 2104 prompt "Which hash algorithm should modules be signed with?" 2105 depends on MODULE_SIG 2106 help 2107 This determines which sort of hashing algorithm will be used during 2108 signature generation. This algorithm _must_ be built into the kernel 2109 directly so that signature verification can take place. It is not 2110 possible to load a signed module containing the algorithm to check 2111 the signature on that module. 2112 2113config MODULE_SIG_SHA1 2114 bool "Sign modules with SHA-1" 2115 select CRYPTO_SHA1 2116 2117config MODULE_SIG_SHA224 2118 bool "Sign modules with SHA-224" 2119 select CRYPTO_SHA256 2120 2121config MODULE_SIG_SHA256 2122 bool "Sign modules with SHA-256" 2123 select CRYPTO_SHA256 2124 2125config MODULE_SIG_SHA384 2126 bool "Sign modules with SHA-384" 2127 select CRYPTO_SHA512 2128 2129config MODULE_SIG_SHA512 2130 bool "Sign modules with SHA-512" 2131 select CRYPTO_SHA512 2132 2133endchoice 2134 2135config MODULE_SIG_HASH 2136 string 2137 depends on MODULE_SIG 2138 default "sha1" if MODULE_SIG_SHA1 2139 default "sha224" if MODULE_SIG_SHA224 2140 default "sha256" if MODULE_SIG_SHA256 2141 default "sha384" if MODULE_SIG_SHA384 2142 default "sha512" if MODULE_SIG_SHA512 2143 2144config MODULE_COMPRESS 2145 bool "Compress modules on installation" 2146 help 2147 2148 Compresses kernel modules when 'make modules_install' is run; gzip or 2149 xz depending on "Compression algorithm" below. 2150 2151 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 2152 2153 Out-of-tree kernel modules installed using Kbuild will also be 2154 compressed upon installation. 2155 2156 Note: for modules inside an initrd or initramfs, it's more efficient 2157 to compress the whole initrd or initramfs instead. 2158 2159 Note: This is fully compatible with signed modules. 2160 2161 If in doubt, say N. 2162 2163choice 2164 prompt "Compression algorithm" 2165 depends on MODULE_COMPRESS 2166 default MODULE_COMPRESS_GZIP 2167 help 2168 This determines which sort of compression will be used during 2169 'make modules_install'. 2170 2171 GZIP (default) and XZ are supported. 2172 2173config MODULE_COMPRESS_GZIP 2174 bool "GZIP" 2175 2176config MODULE_COMPRESS_XZ 2177 bool "XZ" 2178 2179endchoice 2180 2181config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS 2182 bool "Allow loading of modules with missing namespace imports" 2183 help 2184 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in 2185 a namespace. A module that makes use of a symbol exported with such a 2186 namespace is required to import the namespace via MODULE_IMPORT_NS(). 2187 There is no technical reason to enforce correct namespace imports, 2188 but it creates consistency between symbols defining namespaces and 2189 users importing namespaces they make use of. This option relaxes this 2190 requirement and lifts the enforcement when loading a module. 2191 2192 If unsure, say N. 2193 2194config UNUSED_SYMBOLS 2195 bool "Enable unused/obsolete exported symbols" 2196 default y if X86 2197 help 2198 Unused but exported symbols make the kernel needlessly bigger. For 2199 that reason most of these unused exports will soon be removed. This 2200 option is provided temporarily to provide a transition period in case 2201 some external kernel module needs one of these symbols anyway. If you 2202 encounter such a case in your module, consider if you are actually 2203 using the right API. (rationale: since nobody in the kernel is using 2204 this in a module, there is a pretty good chance it's actually the 2205 wrong interface to use). If you really need the symbol, please send a 2206 mail to the linux kernel mailing list mentioning the symbol and why 2207 you really need it, and what the merge plan to the mainline kernel for 2208 your module is. 2209 2210config TRIM_UNUSED_KSYMS 2211 bool "Trim unused exported kernel symbols" 2212 depends on !UNUSED_SYMBOLS 2213 help 2214 The kernel and some modules make many symbols available for 2215 other modules to use via EXPORT_SYMBOL() and variants. Depending 2216 on the set of modules being selected in your kernel configuration, 2217 many of those exported symbols might never be used. 2218 2219 This option allows for unused exported symbols to be dropped from 2220 the build. In turn, this provides the compiler more opportunities 2221 (especially when using LTO) for optimizing the code and reducing 2222 binary size. This might have some security advantages as well. 2223 2224 If unsure, or if you need to build out-of-tree modules, say N. 2225 2226config UNUSED_KSYMS_WHITELIST 2227 string "Whitelist of symbols to keep in ksymtab" 2228 depends on TRIM_UNUSED_KSYMS 2229 help 2230 By default, all unused exported symbols will be un-exported from the 2231 build when TRIM_UNUSED_KSYMS is selected. 2232 2233 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept 2234 exported at all times, even in absence of in-tree users. The value to 2235 set here is the path to a text file containing the list of symbols, 2236 one per line. The path can be absolute, or relative to the kernel 2237 source tree. 2238 2239endif # MODULES 2240 2241config MODULES_TREE_LOOKUP 2242 def_bool y 2243 depends on PERF_EVENTS || TRACING 2244 2245config INIT_ALL_POSSIBLE 2246 bool 2247 help 2248 Back when each arch used to define their own cpu_online_mask and 2249 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2250 with all 1s, and others with all 0s. When they were centralised, 2251 it was better to provide this option than to break all the archs 2252 and have several arch maintainers pursuing me down dark alleys. 2253 2254source "block/Kconfig" 2255 2256config PREEMPT_NOTIFIERS 2257 bool 2258 2259config PADATA 2260 depends on SMP 2261 bool 2262 2263config ASN1 2264 tristate 2265 help 2266 Build a simple ASN.1 grammar compiler that produces a bytecode output 2267 that can be interpreted by the ASN.1 stream decoder and used to 2268 inform it as to what tags are to be expected in a stream and what 2269 functions to call on what tags. 2270 2271source "kernel/Kconfig.locks" 2272 2273config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2274 bool 2275 2276# It may be useful for an architecture to override the definitions of the 2277# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2278# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2279# different calling convention for syscalls. They can also override the 2280# macros for not-implemented syscalls in kernel/sys_ni.c and 2281# kernel/time/posix-stubs.c. All these overrides need to be available in 2282# <asm/syscall_wrapper.h>. 2283config ARCH_HAS_SYSCALL_WRAPPER 2284 def_bool n 2285