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 LD_VERSION 20 int 21 default $(shell,$(LD) --version | $(srctree)/scripts/ld-version.sh) 22 23config CC_IS_CLANG 24 def_bool $(success,$(CC) --version | head -n 1 | grep -q clang) 25 26config LD_IS_LLD 27 def_bool $(success,$(LD) -v | head -n 1 | grep -q LLD) 28 29config CLANG_VERSION 30 int 31 default $(shell,$(srctree)/scripts/clang-version.sh $(CC)) 32 33config CC_CAN_LINK 34 def_bool $(success,$(srctree)/scripts/cc-can-link.sh $(CC)) 35 36config CC_HAS_ASM_GOTO 37 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) 38 39config TOOLS_SUPPORT_RELR 40 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 41 42config CC_HAS_ASM_INLINE 43 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 44 45config CONSTRUCTORS 46 bool 47 depends on !UML 48 49config IRQ_WORK 50 bool 51 52config BUILDTIME_TABLE_SORT 53 bool 54 55config THREAD_INFO_IN_TASK 56 bool 57 help 58 Select this to move thread_info off the stack into task_struct. To 59 make this work, an arch will need to remove all thread_info fields 60 except flags and fix any runtime bugs. 61 62 One subtle change that will be needed is to use try_get_task_stack() 63 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 64 65menu "General setup" 66 67config BROKEN 68 bool 69 70config BROKEN_ON_SMP 71 bool 72 depends on BROKEN || !SMP 73 default y 74 75config INIT_ENV_ARG_LIMIT 76 int 77 default 32 if !UML 78 default 128 if UML 79 help 80 Maximum of each of the number of arguments and environment 81 variables passed to init from the kernel command line. 82 83config COMPILE_TEST 84 bool "Compile also drivers which will not load" 85 depends on !UML 86 default n 87 help 88 Some drivers can be compiled on a different platform than they are 89 intended to be run on. Despite they cannot be loaded there (or even 90 when they load they cannot be used due to missing HW support), 91 developers still, opposing to distributors, might want to build such 92 drivers to compile-test them. 93 94 If you are a developer and want to build everything available, say Y 95 here. If you are a user/distributor, say N here to exclude useless 96 drivers to be distributed. 97 98config UAPI_HEADER_TEST 99 bool "Compile test UAPI headers" 100 depends on HEADERS_INSTALL && CC_CAN_LINK 101 help 102 Compile test headers exported to user-space to ensure they are 103 self-contained, i.e. compilable as standalone units. 104 105 If you are a developer or tester and want to ensure the exported 106 headers are self-contained, say Y here. Otherwise, choose N. 107 108config LOCALVERSION 109 string "Local version - append to kernel release" 110 help 111 Append an extra string to the end of your kernel version. 112 This will show up when you type uname, for example. 113 The string you set here will be appended after the contents of 114 any files with a filename matching localversion* in your 115 object and source tree, in that order. Your total string can 116 be a maximum of 64 characters. 117 118config LOCALVERSION_AUTO 119 bool "Automatically append version information to the version string" 120 default y 121 depends on !COMPILE_TEST 122 help 123 This will try to automatically determine if the current tree is a 124 release tree by looking for git tags that belong to the current 125 top of tree revision. 126 127 A string of the format -gxxxxxxxx will be added to the localversion 128 if a git-based tree is found. The string generated by this will be 129 appended after any matching localversion* files, and after the value 130 set in CONFIG_LOCALVERSION. 131 132 (The actual string used here is the first eight characters produced 133 by running the command: 134 135 $ git rev-parse --verify HEAD 136 137 which is done within the script "scripts/setlocalversion".) 138 139config BUILD_SALT 140 string "Build ID Salt" 141 default "" 142 help 143 The build ID is used to link binaries and their debug info. Setting 144 this option will use the value in the calculation of the build id. 145 This is mostly useful for distributions which want to ensure the 146 build is unique between builds. It's safe to leave the default. 147 148config HAVE_KERNEL_GZIP 149 bool 150 151config HAVE_KERNEL_BZIP2 152 bool 153 154config HAVE_KERNEL_LZMA 155 bool 156 157config HAVE_KERNEL_XZ 158 bool 159 160config HAVE_KERNEL_LZO 161 bool 162 163config HAVE_KERNEL_LZ4 164 bool 165 166config HAVE_KERNEL_UNCOMPRESSED 167 bool 168 169choice 170 prompt "Kernel compression mode" 171 default KERNEL_GZIP 172 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED 173 help 174 The linux kernel is a kind of self-extracting executable. 175 Several compression algorithms are available, which differ 176 in efficiency, compression and decompression speed. 177 Compression speed is only relevant when building a kernel. 178 Decompression speed is relevant at each boot. 179 180 If you have any problems with bzip2 or lzma compressed 181 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 182 version of this functionality (bzip2 only), for 2.4, was 183 supplied by Christian Ludwig) 184 185 High compression options are mostly useful for users, who 186 are low on disk space (embedded systems), but for whom ram 187 size matters less. 188 189 If in doubt, select 'gzip' 190 191config KERNEL_GZIP 192 bool "Gzip" 193 depends on HAVE_KERNEL_GZIP 194 help 195 The old and tried gzip compression. It provides a good balance 196 between compression ratio and decompression speed. 197 198config KERNEL_BZIP2 199 bool "Bzip2" 200 depends on HAVE_KERNEL_BZIP2 201 help 202 Its compression ratio and speed is intermediate. 203 Decompression speed is slowest among the choices. The kernel 204 size is about 10% smaller with bzip2, in comparison to gzip. 205 Bzip2 uses a large amount of memory. For modern kernels you 206 will need at least 8MB RAM or more for booting. 207 208config KERNEL_LZMA 209 bool "LZMA" 210 depends on HAVE_KERNEL_LZMA 211 help 212 This compression algorithm's ratio is best. Decompression speed 213 is between gzip and bzip2. Compression is slowest. 214 The kernel size is about 33% smaller with LZMA in comparison to gzip. 215 216config KERNEL_XZ 217 bool "XZ" 218 depends on HAVE_KERNEL_XZ 219 help 220 XZ uses the LZMA2 algorithm and instruction set specific 221 BCJ filters which can improve compression ratio of executable 222 code. The size of the kernel is about 30% smaller with XZ in 223 comparison to gzip. On architectures for which there is a BCJ 224 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 225 will create a few percent smaller kernel than plain LZMA. 226 227 The speed is about the same as with LZMA: The decompression 228 speed of XZ is better than that of bzip2 but worse than gzip 229 and LZO. Compression is slow. 230 231config KERNEL_LZO 232 bool "LZO" 233 depends on HAVE_KERNEL_LZO 234 help 235 Its compression ratio is the poorest among the choices. The kernel 236 size is about 10% bigger than gzip; however its speed 237 (both compression and decompression) is the fastest. 238 239config KERNEL_LZ4 240 bool "LZ4" 241 depends on HAVE_KERNEL_LZ4 242 help 243 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 244 A preliminary version of LZ4 de/compression tool is available at 245 <https://code.google.com/p/lz4/>. 246 247 Its compression ratio is worse than LZO. The size of the kernel 248 is about 8% bigger than LZO. But the decompression speed is 249 faster than LZO. 250 251config KERNEL_UNCOMPRESSED 252 bool "None" 253 depends on HAVE_KERNEL_UNCOMPRESSED 254 help 255 Produce uncompressed kernel image. This option is usually not what 256 you want. It is useful for debugging the kernel in slow simulation 257 environments, where decompressing and moving the kernel is awfully 258 slow. This option allows early boot code to skip the decompressor 259 and jump right at uncompressed kernel image. 260 261endchoice 262 263config DEFAULT_HOSTNAME 264 string "Default hostname" 265 default "(none)" 266 help 267 This option determines the default system hostname before userspace 268 calls sethostname(2). The kernel traditionally uses "(none)" here, 269 but you may wish to use a different default here to make a minimal 270 system more usable with less configuration. 271 272# 273# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can 274# add proper SWAP support to them, in which case this can be remove. 275# 276config ARCH_NO_SWAP 277 bool 278 279config SWAP 280 bool "Support for paging of anonymous memory (swap)" 281 depends on MMU && BLOCK && !ARCH_NO_SWAP 282 default y 283 help 284 This option allows you to choose whether you want to have support 285 for so called swap devices or swap files in your kernel that are 286 used to provide more virtual memory than the actual RAM present 287 in your computer. If unsure say Y. 288 289config SYSVIPC 290 bool "System V IPC" 291 ---help--- 292 Inter Process Communication is a suite of library functions and 293 system calls which let processes (running programs) synchronize and 294 exchange information. It is generally considered to be a good thing, 295 and some programs won't run unless you say Y here. In particular, if 296 you want to run the DOS emulator dosemu under Linux (read the 297 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 298 you'll need to say Y here. 299 300 You can find documentation about IPC with "info ipc" and also in 301 section 6.4 of the Linux Programmer's Guide, available from 302 <http://www.tldp.org/guides.html>. 303 304config SYSVIPC_SYSCTL 305 bool 306 depends on SYSVIPC 307 depends on SYSCTL 308 default y 309 310config POSIX_MQUEUE 311 bool "POSIX Message Queues" 312 depends on NET 313 ---help--- 314 POSIX variant of message queues is a part of IPC. In POSIX message 315 queues every message has a priority which decides about succession 316 of receiving it by a process. If you want to compile and run 317 programs written e.g. for Solaris with use of its POSIX message 318 queues (functions mq_*) say Y here. 319 320 POSIX message queues are visible as a filesystem called 'mqueue' 321 and can be mounted somewhere if you want to do filesystem 322 operations on message queues. 323 324 If unsure, say Y. 325 326config POSIX_MQUEUE_SYSCTL 327 bool 328 depends on POSIX_MQUEUE 329 depends on SYSCTL 330 default y 331 332config CROSS_MEMORY_ATTACH 333 bool "Enable process_vm_readv/writev syscalls" 334 depends on MMU 335 default y 336 help 337 Enabling this option adds the system calls process_vm_readv and 338 process_vm_writev which allow a process with the correct privileges 339 to directly read from or write to another process' address space. 340 See the man page for more details. 341 342config USELIB 343 bool "uselib syscall" 344 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION 345 help 346 This option enables the uselib syscall, a system call used in the 347 dynamic linker from libc5 and earlier. glibc does not use this 348 system call. If you intend to run programs built on libc5 or 349 earlier, you may need to enable this syscall. Current systems 350 running glibc can safely disable this. 351 352config AUDIT 353 bool "Auditing support" 354 depends on NET 355 help 356 Enable auditing infrastructure that can be used with another 357 kernel subsystem, such as SELinux (which requires this for 358 logging of avc messages output). System call auditing is included 359 on architectures which support it. 360 361config HAVE_ARCH_AUDITSYSCALL 362 bool 363 364config AUDITSYSCALL 365 def_bool y 366 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 367 select FSNOTIFY 368 369source "kernel/irq/Kconfig" 370source "kernel/time/Kconfig" 371source "kernel/Kconfig.preempt" 372 373menu "CPU/Task time and stats accounting" 374 375config VIRT_CPU_ACCOUNTING 376 bool 377 378choice 379 prompt "Cputime accounting" 380 default TICK_CPU_ACCOUNTING if !PPC64 381 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 382 383# Kind of a stub config for the pure tick based cputime accounting 384config TICK_CPU_ACCOUNTING 385 bool "Simple tick based cputime accounting" 386 depends on !S390 && !NO_HZ_FULL 387 help 388 This is the basic tick based cputime accounting that maintains 389 statistics about user, system and idle time spent on per jiffies 390 granularity. 391 392 If unsure, say Y. 393 394config VIRT_CPU_ACCOUNTING_NATIVE 395 bool "Deterministic task and CPU time accounting" 396 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 397 select VIRT_CPU_ACCOUNTING 398 help 399 Select this option to enable more accurate task and CPU time 400 accounting. This is done by reading a CPU counter on each 401 kernel entry and exit and on transitions within the kernel 402 between system, softirq and hardirq state, so there is a 403 small performance impact. In the case of s390 or IBM POWER > 5, 404 this also enables accounting of stolen time on logically-partitioned 405 systems. 406 407config VIRT_CPU_ACCOUNTING_GEN 408 bool "Full dynticks CPU time accounting" 409 depends on HAVE_CONTEXT_TRACKING 410 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 411 depends on GENERIC_CLOCKEVENTS 412 select VIRT_CPU_ACCOUNTING 413 select CONTEXT_TRACKING 414 help 415 Select this option to enable task and CPU time accounting on full 416 dynticks systems. This accounting is implemented by watching every 417 kernel-user boundaries using the context tracking subsystem. 418 The accounting is thus performed at the expense of some significant 419 overhead. 420 421 For now this is only useful if you are working on the full 422 dynticks subsystem development. 423 424 If unsure, say N. 425 426endchoice 427 428config IRQ_TIME_ACCOUNTING 429 bool "Fine granularity task level IRQ time accounting" 430 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 431 help 432 Select this option to enable fine granularity task irq time 433 accounting. This is done by reading a timestamp on each 434 transitions between softirq and hardirq state, so there can be a 435 small performance impact. 436 437 If in doubt, say N here. 438 439config HAVE_SCHED_AVG_IRQ 440 def_bool y 441 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 442 depends on SMP 443 444config SCHED_THERMAL_PRESSURE 445 bool "Enable periodic averaging of thermal pressure" 446 depends on SMP 447 448config BSD_PROCESS_ACCT 449 bool "BSD Process Accounting" 450 depends on MULTIUSER 451 help 452 If you say Y here, a user level program will be able to instruct the 453 kernel (via a special system call) to write process accounting 454 information to a file: whenever a process exits, information about 455 that process will be appended to the file by the kernel. The 456 information includes things such as creation time, owning user, 457 command name, memory usage, controlling terminal etc. (the complete 458 list is in the struct acct in <file:include/linux/acct.h>). It is 459 up to the user level program to do useful things with this 460 information. This is generally a good idea, so say Y. 461 462config BSD_PROCESS_ACCT_V3 463 bool "BSD Process Accounting version 3 file format" 464 depends on BSD_PROCESS_ACCT 465 default n 466 help 467 If you say Y here, the process accounting information is written 468 in a new file format that also logs the process IDs of each 469 process and its parent. Note that this file format is incompatible 470 with previous v0/v1/v2 file formats, so you will need updated tools 471 for processing it. A preliminary version of these tools is available 472 at <http://www.gnu.org/software/acct/>. 473 474config TASKSTATS 475 bool "Export task/process statistics through netlink" 476 depends on NET 477 depends on MULTIUSER 478 default n 479 help 480 Export selected statistics for tasks/processes through the 481 generic netlink interface. Unlike BSD process accounting, the 482 statistics are available during the lifetime of tasks/processes as 483 responses to commands. Like BSD accounting, they are sent to user 484 space on task exit. 485 486 Say N if unsure. 487 488config TASK_DELAY_ACCT 489 bool "Enable per-task delay accounting" 490 depends on TASKSTATS 491 select SCHED_INFO 492 help 493 Collect information on time spent by a task waiting for system 494 resources like cpu, synchronous block I/O completion and swapping 495 in pages. Such statistics can help in setting a task's priorities 496 relative to other tasks for cpu, io, rss limits etc. 497 498 Say N if unsure. 499 500config TASK_XACCT 501 bool "Enable extended accounting over taskstats" 502 depends on TASKSTATS 503 help 504 Collect extended task accounting data and send the data 505 to userland for processing over the taskstats interface. 506 507 Say N if unsure. 508 509config TASK_IO_ACCOUNTING 510 bool "Enable per-task storage I/O accounting" 511 depends on TASK_XACCT 512 help 513 Collect information on the number of bytes of storage I/O which this 514 task has caused. 515 516 Say N if unsure. 517 518config PSI 519 bool "Pressure stall information tracking" 520 help 521 Collect metrics that indicate how overcommitted the CPU, memory, 522 and IO capacity are in the system. 523 524 If you say Y here, the kernel will create /proc/pressure/ with the 525 pressure statistics files cpu, memory, and io. These will indicate 526 the share of walltime in which some or all tasks in the system are 527 delayed due to contention of the respective resource. 528 529 In kernels with cgroup support, cgroups (cgroup2 only) will 530 have cpu.pressure, memory.pressure, and io.pressure files, 531 which aggregate pressure stalls for the grouped tasks only. 532 533 For more details see Documentation/accounting/psi.rst. 534 535 Say N if unsure. 536 537config PSI_DEFAULT_DISABLED 538 bool "Require boot parameter to enable pressure stall information tracking" 539 default n 540 depends on PSI 541 help 542 If set, pressure stall information tracking will be disabled 543 per default but can be enabled through passing psi=1 on the 544 kernel commandline during boot. 545 546 This feature adds some code to the task wakeup and sleep 547 paths of the scheduler. The overhead is too low to affect 548 common scheduling-intense workloads in practice (such as 549 webservers, memcache), but it does show up in artificial 550 scheduler stress tests, such as hackbench. 551 552 If you are paranoid and not sure what the kernel will be 553 used for, say Y. 554 555 Say N if unsure. 556 557endmenu # "CPU/Task time and stats accounting" 558 559config CPU_ISOLATION 560 bool "CPU isolation" 561 depends on SMP || COMPILE_TEST 562 default y 563 help 564 Make sure that CPUs running critical tasks are not disturbed by 565 any source of "noise" such as unbound workqueues, timers, kthreads... 566 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 567 the "isolcpus=" boot parameter. 568 569 Say Y if unsure. 570 571source "kernel/rcu/Kconfig" 572 573config BUILD_BIN2C 574 bool 575 default n 576 577config IKCONFIG 578 tristate "Kernel .config support" 579 ---help--- 580 This option enables the complete Linux kernel ".config" file 581 contents to be saved in the kernel. It provides documentation 582 of which kernel options are used in a running kernel or in an 583 on-disk kernel. This information can be extracted from the kernel 584 image file with the script scripts/extract-ikconfig and used as 585 input to rebuild the current kernel or to build another kernel. 586 It can also be extracted from a running kernel by reading 587 /proc/config.gz if enabled (below). 588 589config IKCONFIG_PROC 590 bool "Enable access to .config through /proc/config.gz" 591 depends on IKCONFIG && PROC_FS 592 ---help--- 593 This option enables access to the kernel configuration file 594 through /proc/config.gz. 595 596config IKHEADERS 597 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 598 depends on SYSFS 599 help 600 This option enables access to the in-kernel headers that are generated during 601 the build process. These can be used to build eBPF tracing programs, 602 or similar programs. If you build the headers as a module, a module called 603 kheaders.ko is built which can be loaded on-demand to get access to headers. 604 605config LOG_BUF_SHIFT 606 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 607 range 12 25 608 default 17 609 depends on PRINTK 610 help 611 Select the minimal kernel log buffer size as a power of 2. 612 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 613 parameter, see below. Any higher size also might be forced 614 by "log_buf_len" boot parameter. 615 616 Examples: 617 17 => 128 KB 618 16 => 64 KB 619 15 => 32 KB 620 14 => 16 KB 621 13 => 8 KB 622 12 => 4 KB 623 624config LOG_CPU_MAX_BUF_SHIFT 625 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 626 depends on SMP 627 range 0 21 628 default 12 if !BASE_SMALL 629 default 0 if BASE_SMALL 630 depends on PRINTK 631 help 632 This option allows to increase the default ring buffer size 633 according to the number of CPUs. The value defines the contribution 634 of each CPU as a power of 2. The used space is typically only few 635 lines however it might be much more when problems are reported, 636 e.g. backtraces. 637 638 The increased size means that a new buffer has to be allocated and 639 the original static one is unused. It makes sense only on systems 640 with more CPUs. Therefore this value is used only when the sum of 641 contributions is greater than the half of the default kernel ring 642 buffer as defined by LOG_BUF_SHIFT. The default values are set 643 so that more than 64 CPUs are needed to trigger the allocation. 644 645 Also this option is ignored when "log_buf_len" kernel parameter is 646 used as it forces an exact (power of two) size of the ring buffer. 647 648 The number of possible CPUs is used for this computation ignoring 649 hotplugging making the computation optimal for the worst case 650 scenario while allowing a simple algorithm to be used from bootup. 651 652 Examples shift values and their meaning: 653 17 => 128 KB for each CPU 654 16 => 64 KB for each CPU 655 15 => 32 KB for each CPU 656 14 => 16 KB for each CPU 657 13 => 8 KB for each CPU 658 12 => 4 KB for each CPU 659 660config PRINTK_SAFE_LOG_BUF_SHIFT 661 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 662 range 10 21 663 default 13 664 depends on PRINTK 665 help 666 Select the size of an alternate printk per-CPU buffer where messages 667 printed from usafe contexts are temporary stored. One example would 668 be NMI messages, another one - printk recursion. The messages are 669 copied to the main log buffer in a safe context to avoid a deadlock. 670 The value defines the size as a power of 2. 671 672 Those messages are rare and limited. The largest one is when 673 a backtrace is printed. It usually fits into 4KB. Select 674 8KB if you want to be on the safe side. 675 676 Examples: 677 17 => 128 KB for each CPU 678 16 => 64 KB for each CPU 679 15 => 32 KB for each CPU 680 14 => 16 KB for each CPU 681 13 => 8 KB for each CPU 682 12 => 4 KB for each CPU 683 684# 685# Architectures with an unreliable sched_clock() should select this: 686# 687config HAVE_UNSTABLE_SCHED_CLOCK 688 bool 689 690config GENERIC_SCHED_CLOCK 691 bool 692 693menu "Scheduler features" 694 695config UCLAMP_TASK 696 bool "Enable utilization clamping for RT/FAIR tasks" 697 depends on CPU_FREQ_GOV_SCHEDUTIL 698 help 699 This feature enables the scheduler to track the clamped utilization 700 of each CPU based on RUNNABLE tasks scheduled on that CPU. 701 702 With this option, the user can specify the min and max CPU 703 utilization allowed for RUNNABLE tasks. The max utilization defines 704 the maximum frequency a task should use while the min utilization 705 defines the minimum frequency it should use. 706 707 Both min and max utilization clamp values are hints to the scheduler, 708 aiming at improving its frequency selection policy, but they do not 709 enforce or grant any specific bandwidth for tasks. 710 711 If in doubt, say N. 712 713config UCLAMP_BUCKETS_COUNT 714 int "Number of supported utilization clamp buckets" 715 range 5 20 716 default 5 717 depends on UCLAMP_TASK 718 help 719 Defines the number of clamp buckets to use. The range of each bucket 720 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 721 number of clamp buckets the finer their granularity and the higher 722 the precision of clamping aggregation and tracking at run-time. 723 724 For example, with the minimum configuration value we will have 5 725 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 726 be refcounted in the [20..39]% bucket and will set the bucket clamp 727 effective value to 25%. 728 If a second 30% boosted task should be co-scheduled on the same CPU, 729 that task will be refcounted in the same bucket of the first task and 730 it will boost the bucket clamp effective value to 30%. 731 The clamp effective value of a bucket is reset to its nominal value 732 (20% in the example above) when there are no more tasks refcounted in 733 that bucket. 734 735 An additional boost/capping margin can be added to some tasks. In the 736 example above the 25% task will be boosted to 30% until it exits the 737 CPU. If that should be considered not acceptable on certain systems, 738 it's always possible to reduce the margin by increasing the number of 739 clamp buckets to trade off used memory for run-time tracking 740 precision. 741 742 If in doubt, use the default value. 743 744endmenu 745 746# 747# For architectures that want to enable the support for NUMA-affine scheduler 748# balancing logic: 749# 750config ARCH_SUPPORTS_NUMA_BALANCING 751 bool 752 753# 754# For architectures that prefer to flush all TLBs after a number of pages 755# are unmapped instead of sending one IPI per page to flush. The architecture 756# must provide guarantees on what happens if a clean TLB cache entry is 757# written after the unmap. Details are in mm/rmap.c near the check for 758# should_defer_flush. The architecture should also consider if the full flush 759# and the refill costs are offset by the savings of sending fewer IPIs. 760config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 761 bool 762 763config CC_HAS_INT128 764 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 765 766# 767# For architectures that know their GCC __int128 support is sound 768# 769config ARCH_SUPPORTS_INT128 770 bool 771 772# For architectures that (ab)use NUMA to represent different memory regions 773# all cpu-local but of different latencies, such as SuperH. 774# 775config ARCH_WANT_NUMA_VARIABLE_LOCALITY 776 bool 777 778config NUMA_BALANCING 779 bool "Memory placement aware NUMA scheduler" 780 depends on ARCH_SUPPORTS_NUMA_BALANCING 781 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 782 depends on SMP && NUMA && MIGRATION 783 help 784 This option adds support for automatic NUMA aware memory/task placement. 785 The mechanism is quite primitive and is based on migrating memory when 786 it has references to the node the task is running on. 787 788 This system will be inactive on UMA systems. 789 790config NUMA_BALANCING_DEFAULT_ENABLED 791 bool "Automatically enable NUMA aware memory/task placement" 792 default y 793 depends on NUMA_BALANCING 794 help 795 If set, automatic NUMA balancing will be enabled if running on a NUMA 796 machine. 797 798menuconfig CGROUPS 799 bool "Control Group support" 800 select KERNFS 801 help 802 This option adds support for grouping sets of processes together, for 803 use with process control subsystems such as Cpusets, CFS, memory 804 controls or device isolation. 805 See 806 - Documentation/scheduler/sched-design-CFS.rst (CFS) 807 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 808 and resource control) 809 810 Say N if unsure. 811 812if CGROUPS 813 814config PAGE_COUNTER 815 bool 816 817config MEMCG 818 bool "Memory controller" 819 select PAGE_COUNTER 820 select EVENTFD 821 help 822 Provides control over the memory footprint of tasks in a cgroup. 823 824config MEMCG_SWAP 825 bool 826 depends on MEMCG && SWAP 827 default y 828 829config MEMCG_KMEM 830 bool 831 depends on MEMCG && !SLOB 832 default y 833 834config BLK_CGROUP 835 bool "IO controller" 836 depends on BLOCK 837 default n 838 ---help--- 839 Generic block IO controller cgroup interface. This is the common 840 cgroup interface which should be used by various IO controlling 841 policies. 842 843 Currently, CFQ IO scheduler uses it to recognize task groups and 844 control disk bandwidth allocation (proportional time slice allocation) 845 to such task groups. It is also used by bio throttling logic in 846 block layer to implement upper limit in IO rates on a device. 847 848 This option only enables generic Block IO controller infrastructure. 849 One needs to also enable actual IO controlling logic/policy. For 850 enabling proportional weight division of disk bandwidth in CFQ, set 851 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 852 CONFIG_BLK_DEV_THROTTLING=y. 853 854 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 855 856config CGROUP_WRITEBACK 857 bool 858 depends on MEMCG && BLK_CGROUP 859 default y 860 861menuconfig CGROUP_SCHED 862 bool "CPU controller" 863 default n 864 help 865 This feature lets CPU scheduler recognize task groups and control CPU 866 bandwidth allocation to such task groups. It uses cgroups to group 867 tasks. 868 869if CGROUP_SCHED 870config FAIR_GROUP_SCHED 871 bool "Group scheduling for SCHED_OTHER" 872 depends on CGROUP_SCHED 873 default CGROUP_SCHED 874 875config CFS_BANDWIDTH 876 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 877 depends on FAIR_GROUP_SCHED 878 default n 879 help 880 This option allows users to define CPU bandwidth rates (limits) for 881 tasks running within the fair group scheduler. Groups with no limit 882 set are considered to be unconstrained and will run with no 883 restriction. 884 See Documentation/scheduler/sched-bwc.rst for more information. 885 886config RT_GROUP_SCHED 887 bool "Group scheduling for SCHED_RR/FIFO" 888 depends on CGROUP_SCHED 889 default n 890 help 891 This feature lets you explicitly allocate real CPU bandwidth 892 to task groups. If enabled, it will also make it impossible to 893 schedule realtime tasks for non-root users until you allocate 894 realtime bandwidth for them. 895 See Documentation/scheduler/sched-rt-group.rst for more information. 896 897endif #CGROUP_SCHED 898 899config UCLAMP_TASK_GROUP 900 bool "Utilization clamping per group of tasks" 901 depends on CGROUP_SCHED 902 depends on UCLAMP_TASK 903 default n 904 help 905 This feature enables the scheduler to track the clamped utilization 906 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 907 908 When this option is enabled, the user can specify a min and max 909 CPU bandwidth which is allowed for each single task in a group. 910 The max bandwidth allows to clamp the maximum frequency a task 911 can use, while the min bandwidth allows to define a minimum 912 frequency a task will always use. 913 914 When task group based utilization clamping is enabled, an eventually 915 specified task-specific clamp value is constrained by the cgroup 916 specified clamp value. Both minimum and maximum task clamping cannot 917 be bigger than the corresponding clamping defined at task group level. 918 919 If in doubt, say N. 920 921config CGROUP_PIDS 922 bool "PIDs controller" 923 help 924 Provides enforcement of process number limits in the scope of a 925 cgroup. Any attempt to fork more processes than is allowed in the 926 cgroup will fail. PIDs are fundamentally a global resource because it 927 is fairly trivial to reach PID exhaustion before you reach even a 928 conservative kmemcg limit. As a result, it is possible to grind a 929 system to halt without being limited by other cgroup policies. The 930 PIDs controller is designed to stop this from happening. 931 932 It should be noted that organisational operations (such as attaching 933 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 934 since the PIDs limit only affects a process's ability to fork, not to 935 attach to a cgroup. 936 937config CGROUP_RDMA 938 bool "RDMA controller" 939 help 940 Provides enforcement of RDMA resources defined by IB stack. 941 It is fairly easy for consumers to exhaust RDMA resources, which 942 can result into resource unavailability to other consumers. 943 RDMA controller is designed to stop this from happening. 944 Attaching processes with active RDMA resources to the cgroup 945 hierarchy is allowed even if can cross the hierarchy's limit. 946 947config CGROUP_FREEZER 948 bool "Freezer controller" 949 help 950 Provides a way to freeze and unfreeze all tasks in a 951 cgroup. 952 953 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 954 controller includes important in-kernel memory consumers per default. 955 956 If you're using cgroup2, say N. 957 958config CGROUP_HUGETLB 959 bool "HugeTLB controller" 960 depends on HUGETLB_PAGE 961 select PAGE_COUNTER 962 default n 963 help 964 Provides a cgroup controller for HugeTLB pages. 965 When you enable this, you can put a per cgroup limit on HugeTLB usage. 966 The limit is enforced during page fault. Since HugeTLB doesn't 967 support page reclaim, enforcing the limit at page fault time implies 968 that, the application will get SIGBUS signal if it tries to access 969 HugeTLB pages beyond its limit. This requires the application to know 970 beforehand how much HugeTLB pages it would require for its use. The 971 control group is tracked in the third page lru pointer. This means 972 that we cannot use the controller with huge page less than 3 pages. 973 974config CPUSETS 975 bool "Cpuset controller" 976 depends on SMP 977 help 978 This option will let you create and manage CPUSETs which 979 allow dynamically partitioning a system into sets of CPUs and 980 Memory Nodes and assigning tasks to run only within those sets. 981 This is primarily useful on large SMP or NUMA systems. 982 983 Say N if unsure. 984 985config PROC_PID_CPUSET 986 bool "Include legacy /proc/<pid>/cpuset file" 987 depends on CPUSETS 988 default y 989 990config CGROUP_DEVICE 991 bool "Device controller" 992 help 993 Provides a cgroup controller implementing whitelists for 994 devices which a process in the cgroup can mknod or open. 995 996config CGROUP_CPUACCT 997 bool "Simple CPU accounting controller" 998 help 999 Provides a simple controller for monitoring the 1000 total CPU consumed by the tasks in a cgroup. 1001 1002config CGROUP_PERF 1003 bool "Perf controller" 1004 depends on PERF_EVENTS 1005 help 1006 This option extends the perf per-cpu mode to restrict monitoring 1007 to threads which belong to the cgroup specified and run on the 1008 designated cpu. Or this can be used to have cgroup ID in samples 1009 so that it can monitor performance events among cgroups. 1010 1011 Say N if unsure. 1012 1013config CGROUP_BPF 1014 bool "Support for eBPF programs attached to cgroups" 1015 depends on BPF_SYSCALL 1016 select SOCK_CGROUP_DATA 1017 help 1018 Allow attaching eBPF programs to a cgroup using the bpf(2) 1019 syscall command BPF_PROG_ATTACH. 1020 1021 In which context these programs are accessed depends on the type 1022 of attachment. For instance, programs that are attached using 1023 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1024 inet sockets. 1025 1026config CGROUP_DEBUG 1027 bool "Debug controller" 1028 default n 1029 depends on DEBUG_KERNEL 1030 help 1031 This option enables a simple controller that exports 1032 debugging information about the cgroups framework. This 1033 controller is for control cgroup debugging only. Its 1034 interfaces are not stable. 1035 1036 Say N. 1037 1038config SOCK_CGROUP_DATA 1039 bool 1040 default n 1041 1042endif # CGROUPS 1043 1044menuconfig NAMESPACES 1045 bool "Namespaces support" if EXPERT 1046 depends on MULTIUSER 1047 default !EXPERT 1048 help 1049 Provides the way to make tasks work with different objects using 1050 the same id. For example same IPC id may refer to different objects 1051 or same user id or pid may refer to different tasks when used in 1052 different namespaces. 1053 1054if NAMESPACES 1055 1056config UTS_NS 1057 bool "UTS namespace" 1058 default y 1059 help 1060 In this namespace tasks see different info provided with the 1061 uname() system call 1062 1063config TIME_NS 1064 bool "TIME namespace" 1065 depends on GENERIC_VDSO_TIME_NS 1066 default y 1067 help 1068 In this namespace boottime and monotonic clocks can be set. 1069 The time will keep going with the same pace. 1070 1071config IPC_NS 1072 bool "IPC namespace" 1073 depends on (SYSVIPC || POSIX_MQUEUE) 1074 default y 1075 help 1076 In this namespace tasks work with IPC ids which correspond to 1077 different IPC objects in different namespaces. 1078 1079config USER_NS 1080 bool "User namespace" 1081 default n 1082 help 1083 This allows containers, i.e. vservers, to use user namespaces 1084 to provide different user info for different servers. 1085 1086 When user namespaces are enabled in the kernel it is 1087 recommended that the MEMCG option also be enabled and that 1088 user-space use the memory control groups to limit the amount 1089 of memory a memory unprivileged users can use. 1090 1091 If unsure, say N. 1092 1093config PID_NS 1094 bool "PID Namespaces" 1095 default y 1096 help 1097 Support process id namespaces. This allows having multiple 1098 processes with the same pid as long as they are in different 1099 pid namespaces. This is a building block of containers. 1100 1101config NET_NS 1102 bool "Network namespace" 1103 depends on NET 1104 default y 1105 help 1106 Allow user space to create what appear to be multiple instances 1107 of the network stack. 1108 1109endif # NAMESPACES 1110 1111config CHECKPOINT_RESTORE 1112 bool "Checkpoint/restore support" 1113 select PROC_CHILDREN 1114 default n 1115 help 1116 Enables additional kernel features in a sake of checkpoint/restore. 1117 In particular it adds auxiliary prctl codes to setup process text, 1118 data and heap segment sizes, and a few additional /proc filesystem 1119 entries. 1120 1121 If unsure, say N here. 1122 1123config SCHED_AUTOGROUP 1124 bool "Automatic process group scheduling" 1125 select CGROUPS 1126 select CGROUP_SCHED 1127 select FAIR_GROUP_SCHED 1128 help 1129 This option optimizes the scheduler for common desktop workloads by 1130 automatically creating and populating task groups. This separation 1131 of workloads isolates aggressive CPU burners (like build jobs) from 1132 desktop applications. Task group autogeneration is currently based 1133 upon task session. 1134 1135config SYSFS_DEPRECATED 1136 bool "Enable deprecated sysfs features to support old userspace tools" 1137 depends on SYSFS 1138 default n 1139 help 1140 This option adds code that switches the layout of the "block" class 1141 devices, to not show up in /sys/class/block/, but only in 1142 /sys/block/. 1143 1144 This switch is only active when the sysfs.deprecated=1 boot option is 1145 passed or the SYSFS_DEPRECATED_V2 option is set. 1146 1147 This option allows new kernels to run on old distributions and tools, 1148 which might get confused by /sys/class/block/. Since 2007/2008 all 1149 major distributions and tools handle this just fine. 1150 1151 Recent distributions and userspace tools after 2009/2010 depend on 1152 the existence of /sys/class/block/, and will not work with this 1153 option enabled. 1154 1155 Only if you are using a new kernel on an old distribution, you might 1156 need to say Y here. 1157 1158config SYSFS_DEPRECATED_V2 1159 bool "Enable deprecated sysfs features by default" 1160 default n 1161 depends on SYSFS 1162 depends on SYSFS_DEPRECATED 1163 help 1164 Enable deprecated sysfs by default. 1165 1166 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1167 option. 1168 1169 Only if you are using a new kernel on an old distribution, you might 1170 need to say Y here. Even then, odds are you would not need it 1171 enabled, you can always pass the boot option if absolutely necessary. 1172 1173config RELAY 1174 bool "Kernel->user space relay support (formerly relayfs)" 1175 select IRQ_WORK 1176 help 1177 This option enables support for relay interface support in 1178 certain file systems (such as debugfs). 1179 It is designed to provide an efficient mechanism for tools and 1180 facilities to relay large amounts of data from kernel space to 1181 user space. 1182 1183 If unsure, say N. 1184 1185config BLK_DEV_INITRD 1186 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1187 help 1188 The initial RAM filesystem is a ramfs which is loaded by the 1189 boot loader (loadlin or lilo) and that is mounted as root 1190 before the normal boot procedure. It is typically used to 1191 load modules needed to mount the "real" root file system, 1192 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1193 1194 If RAM disk support (BLK_DEV_RAM) is also included, this 1195 also enables initial RAM disk (initrd) support and adds 1196 15 Kbytes (more on some other architectures) to the kernel size. 1197 1198 If unsure say Y. 1199 1200if BLK_DEV_INITRD 1201 1202source "usr/Kconfig" 1203 1204endif 1205 1206config BOOT_CONFIG 1207 bool "Boot config support" 1208 select BLK_DEV_INITRD 1209 help 1210 Extra boot config allows system admin to pass a config file as 1211 complemental extension of kernel cmdline when booting. 1212 The boot config file must be attached at the end of initramfs 1213 with checksum, size and magic word. 1214 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1215 1216 If unsure, say Y. 1217 1218choice 1219 prompt "Compiler optimization level" 1220 default CC_OPTIMIZE_FOR_PERFORMANCE 1221 1222config CC_OPTIMIZE_FOR_PERFORMANCE 1223 bool "Optimize for performance (-O2)" 1224 help 1225 This is the default optimization level for the kernel, building 1226 with the "-O2" compiler flag for best performance and most 1227 helpful compile-time warnings. 1228 1229config CC_OPTIMIZE_FOR_PERFORMANCE_O3 1230 bool "Optimize more for performance (-O3)" 1231 depends on ARC 1232 help 1233 Choosing this option will pass "-O3" to your compiler to optimize 1234 the kernel yet more for performance. 1235 1236config CC_OPTIMIZE_FOR_SIZE 1237 bool "Optimize for size (-Os)" 1238 help 1239 Choosing this option will pass "-Os" to your compiler resulting 1240 in a smaller kernel. 1241 1242endchoice 1243 1244config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1245 bool 1246 help 1247 This requires that the arch annotates or otherwise protects 1248 its external entry points from being discarded. Linker scripts 1249 must also merge .text.*, .data.*, and .bss.* correctly into 1250 output sections. Care must be taken not to pull in unrelated 1251 sections (e.g., '.text.init'). Typically '.' in section names 1252 is used to distinguish them from label names / C identifiers. 1253 1254config LD_DEAD_CODE_DATA_ELIMINATION 1255 bool "Dead code and data elimination (EXPERIMENTAL)" 1256 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1257 depends on EXPERT 1258 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800) 1259 depends on $(cc-option,-ffunction-sections -fdata-sections) 1260 depends on $(ld-option,--gc-sections) 1261 help 1262 Enable this if you want to do dead code and data elimination with 1263 the linker by compiling with -ffunction-sections -fdata-sections, 1264 and linking with --gc-sections. 1265 1266 This can reduce on disk and in-memory size of the kernel 1267 code and static data, particularly for small configs and 1268 on small systems. This has the possibility of introducing 1269 silently broken kernel if the required annotations are not 1270 present. This option is not well tested yet, so use at your 1271 own risk. 1272 1273config SYSCTL 1274 bool 1275 1276config HAVE_UID16 1277 bool 1278 1279config SYSCTL_EXCEPTION_TRACE 1280 bool 1281 help 1282 Enable support for /proc/sys/debug/exception-trace. 1283 1284config SYSCTL_ARCH_UNALIGN_NO_WARN 1285 bool 1286 help 1287 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1288 Allows arch to define/use @no_unaligned_warning to possibly warn 1289 about unaligned access emulation going on under the hood. 1290 1291config SYSCTL_ARCH_UNALIGN_ALLOW 1292 bool 1293 help 1294 Enable support for /proc/sys/kernel/unaligned-trap 1295 Allows arches to define/use @unaligned_enabled to runtime toggle 1296 the unaligned access emulation. 1297 see arch/parisc/kernel/unaligned.c for reference 1298 1299config HAVE_PCSPKR_PLATFORM 1300 bool 1301 1302# interpreter that classic socket filters depend on 1303config BPF 1304 bool 1305 1306menuconfig EXPERT 1307 bool "Configure standard kernel features (expert users)" 1308 # Unhide debug options, to make the on-by-default options visible 1309 select DEBUG_KERNEL 1310 help 1311 This option allows certain base kernel options and settings 1312 to be disabled or tweaked. This is for specialized 1313 environments which can tolerate a "non-standard" kernel. 1314 Only use this if you really know what you are doing. 1315 1316config UID16 1317 bool "Enable 16-bit UID system calls" if EXPERT 1318 depends on HAVE_UID16 && MULTIUSER 1319 default y 1320 help 1321 This enables the legacy 16-bit UID syscall wrappers. 1322 1323config MULTIUSER 1324 bool "Multiple users, groups and capabilities support" if EXPERT 1325 default y 1326 help 1327 This option enables support for non-root users, groups and 1328 capabilities. 1329 1330 If you say N here, all processes will run with UID 0, GID 0, and all 1331 possible capabilities. Saying N here also compiles out support for 1332 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1333 setgid, and capset. 1334 1335 If unsure, say Y here. 1336 1337config SGETMASK_SYSCALL 1338 bool "sgetmask/ssetmask syscalls support" if EXPERT 1339 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1340 ---help--- 1341 sys_sgetmask and sys_ssetmask are obsolete system calls 1342 no longer supported in libc but still enabled by default in some 1343 architectures. 1344 1345 If unsure, leave the default option here. 1346 1347config SYSFS_SYSCALL 1348 bool "Sysfs syscall support" if EXPERT 1349 default y 1350 ---help--- 1351 sys_sysfs is an obsolete system call no longer supported in libc. 1352 Note that disabling this option is more secure but might break 1353 compatibility with some systems. 1354 1355 If unsure say Y here. 1356 1357config FHANDLE 1358 bool "open by fhandle syscalls" if EXPERT 1359 select EXPORTFS 1360 default y 1361 help 1362 If you say Y here, a user level program will be able to map 1363 file names to handle and then later use the handle for 1364 different file system operations. This is useful in implementing 1365 userspace file servers, which now track files using handles instead 1366 of names. The handle would remain the same even if file names 1367 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1368 syscalls. 1369 1370config POSIX_TIMERS 1371 bool "Posix Clocks & timers" if EXPERT 1372 default y 1373 help 1374 This includes native support for POSIX timers to the kernel. 1375 Some embedded systems have no use for them and therefore they 1376 can be configured out to reduce the size of the kernel image. 1377 1378 When this option is disabled, the following syscalls won't be 1379 available: timer_create, timer_gettime: timer_getoverrun, 1380 timer_settime, timer_delete, clock_adjtime, getitimer, 1381 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1382 clock_getres and clock_nanosleep syscalls will be limited to 1383 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1384 1385 If unsure say y. 1386 1387config PRINTK 1388 default y 1389 bool "Enable support for printk" if EXPERT 1390 select IRQ_WORK 1391 help 1392 This option enables normal printk support. Removing it 1393 eliminates most of the message strings from the kernel image 1394 and makes the kernel more or less silent. As this makes it 1395 very difficult to diagnose system problems, saying N here is 1396 strongly discouraged. 1397 1398config PRINTK_NMI 1399 def_bool y 1400 depends on PRINTK 1401 depends on HAVE_NMI 1402 1403config BUG 1404 bool "BUG() support" if EXPERT 1405 default y 1406 help 1407 Disabling this option eliminates support for BUG and WARN, reducing 1408 the size of your kernel image and potentially quietly ignoring 1409 numerous fatal conditions. You should only consider disabling this 1410 option for embedded systems with no facilities for reporting errors. 1411 Just say Y. 1412 1413config ELF_CORE 1414 depends on COREDUMP 1415 default y 1416 bool "Enable ELF core dumps" if EXPERT 1417 help 1418 Enable support for generating core dumps. Disabling saves about 4k. 1419 1420 1421config PCSPKR_PLATFORM 1422 bool "Enable PC-Speaker support" if EXPERT 1423 depends on HAVE_PCSPKR_PLATFORM 1424 select I8253_LOCK 1425 default y 1426 help 1427 This option allows to disable the internal PC-Speaker 1428 support, saving some memory. 1429 1430config BASE_FULL 1431 default y 1432 bool "Enable full-sized data structures for core" if EXPERT 1433 help 1434 Disabling this option reduces the size of miscellaneous core 1435 kernel data structures. This saves memory on small machines, 1436 but may reduce performance. 1437 1438config FUTEX 1439 bool "Enable futex support" if EXPERT 1440 default y 1441 imply RT_MUTEXES 1442 help 1443 Disabling this option will cause the kernel to be built without 1444 support for "fast userspace mutexes". The resulting kernel may not 1445 run glibc-based applications correctly. 1446 1447config FUTEX_PI 1448 bool 1449 depends on FUTEX && RT_MUTEXES 1450 default y 1451 1452config HAVE_FUTEX_CMPXCHG 1453 bool 1454 depends on FUTEX 1455 help 1456 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1457 is implemented and always working. This removes a couple of runtime 1458 checks. 1459 1460config EPOLL 1461 bool "Enable eventpoll support" if EXPERT 1462 default y 1463 help 1464 Disabling this option will cause the kernel to be built without 1465 support for epoll family of system calls. 1466 1467config SIGNALFD 1468 bool "Enable signalfd() system call" if EXPERT 1469 default y 1470 help 1471 Enable the signalfd() system call that allows to receive signals 1472 on a file descriptor. 1473 1474 If unsure, say Y. 1475 1476config TIMERFD 1477 bool "Enable timerfd() system call" if EXPERT 1478 default y 1479 help 1480 Enable the timerfd() system call that allows to receive timer 1481 events on a file descriptor. 1482 1483 If unsure, say Y. 1484 1485config EVENTFD 1486 bool "Enable eventfd() system call" if EXPERT 1487 default y 1488 help 1489 Enable the eventfd() system call that allows to receive both 1490 kernel notification (ie. KAIO) or userspace notifications. 1491 1492 If unsure, say Y. 1493 1494config SHMEM 1495 bool "Use full shmem filesystem" if EXPERT 1496 default y 1497 depends on MMU 1498 help 1499 The shmem is an internal filesystem used to manage shared memory. 1500 It is backed by swap and manages resource limits. It is also exported 1501 to userspace as tmpfs if TMPFS is enabled. Disabling this 1502 option replaces shmem and tmpfs with the much simpler ramfs code, 1503 which may be appropriate on small systems without swap. 1504 1505config AIO 1506 bool "Enable AIO support" if EXPERT 1507 default y 1508 help 1509 This option enables POSIX asynchronous I/O which may by used 1510 by some high performance threaded applications. Disabling 1511 this option saves about 7k. 1512 1513config IO_URING 1514 bool "Enable IO uring support" if EXPERT 1515 select IO_WQ 1516 default y 1517 help 1518 This option enables support for the io_uring interface, enabling 1519 applications to submit and complete IO through submission and 1520 completion rings that are shared between the kernel and application. 1521 1522config ADVISE_SYSCALLS 1523 bool "Enable madvise/fadvise syscalls" if EXPERT 1524 default y 1525 help 1526 This option enables the madvise and fadvise syscalls, used by 1527 applications to advise the kernel about their future memory or file 1528 usage, improving performance. If building an embedded system where no 1529 applications use these syscalls, you can disable this option to save 1530 space. 1531 1532config HAVE_ARCH_USERFAULTFD_WP 1533 bool 1534 help 1535 Arch has userfaultfd write protection support 1536 1537config MEMBARRIER 1538 bool "Enable membarrier() system call" if EXPERT 1539 default y 1540 help 1541 Enable the membarrier() system call that allows issuing memory 1542 barriers across all running threads, which can be used to distribute 1543 the cost of user-space memory barriers asymmetrically by transforming 1544 pairs of memory barriers into pairs consisting of membarrier() and a 1545 compiler barrier. 1546 1547 If unsure, say Y. 1548 1549config KALLSYMS 1550 bool "Load all symbols for debugging/ksymoops" if EXPERT 1551 default y 1552 help 1553 Say Y here to let the kernel print out symbolic crash information and 1554 symbolic stack backtraces. This increases the size of the kernel 1555 somewhat, as all symbols have to be loaded into the kernel image. 1556 1557config KALLSYMS_ALL 1558 bool "Include all symbols in kallsyms" 1559 depends on DEBUG_KERNEL && KALLSYMS 1560 help 1561 Normally kallsyms only contains the symbols of functions for nicer 1562 OOPS messages and backtraces (i.e., symbols from the text and inittext 1563 sections). This is sufficient for most cases. And only in very rare 1564 cases (e.g., when a debugger is used) all symbols are required (e.g., 1565 names of variables from the data sections, etc). 1566 1567 This option makes sure that all symbols are loaded into the kernel 1568 image (i.e., symbols from all sections) in cost of increased kernel 1569 size (depending on the kernel configuration, it may be 300KiB or 1570 something like this). 1571 1572 Say N unless you really need all symbols. 1573 1574config KALLSYMS_ABSOLUTE_PERCPU 1575 bool 1576 depends on KALLSYMS 1577 default X86_64 && SMP 1578 1579config KALLSYMS_BASE_RELATIVE 1580 bool 1581 depends on KALLSYMS 1582 default !IA64 1583 help 1584 Instead of emitting them as absolute values in the native word size, 1585 emit the symbol references in the kallsyms table as 32-bit entries, 1586 each containing a relative value in the range [base, base + U32_MAX] 1587 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1588 an absolute value in the range [0, S32_MAX] or a relative value in the 1589 range [base, base + S32_MAX], where base is the lowest relative symbol 1590 address encountered in the image. 1591 1592 On 64-bit builds, this reduces the size of the address table by 50%, 1593 but more importantly, it results in entries whose values are build 1594 time constants, and no relocation pass is required at runtime to fix 1595 up the entries based on the runtime load address of the kernel. 1596 1597# end of the "standard kernel features (expert users)" menu 1598 1599# syscall, maps, verifier 1600 1601config BPF_LSM 1602 bool "LSM Instrumentation with BPF" 1603 depends on BPF_EVENTS 1604 depends on BPF_SYSCALL 1605 depends on SECURITY 1606 depends on BPF_JIT 1607 help 1608 Enables instrumentation of the security hooks with eBPF programs for 1609 implementing dynamic MAC and Audit Policies. 1610 1611 If you are unsure how to answer this question, answer N. 1612 1613config BPF_SYSCALL 1614 bool "Enable bpf() system call" 1615 select BPF 1616 select IRQ_WORK 1617 default n 1618 help 1619 Enable the bpf() system call that allows to manipulate eBPF 1620 programs and maps via file descriptors. 1621 1622config ARCH_WANT_DEFAULT_BPF_JIT 1623 bool 1624 1625config BPF_JIT_ALWAYS_ON 1626 bool "Permanently enable BPF JIT and remove BPF interpreter" 1627 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1628 help 1629 Enables BPF JIT and removes BPF interpreter to avoid 1630 speculative execution of BPF instructions by the interpreter 1631 1632config BPF_JIT_DEFAULT_ON 1633 def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON 1634 depends on HAVE_EBPF_JIT && BPF_JIT 1635 1636config USERFAULTFD 1637 bool "Enable userfaultfd() system call" 1638 depends on MMU 1639 help 1640 Enable the userfaultfd() system call that allows to intercept and 1641 handle page faults in userland. 1642 1643config ARCH_HAS_MEMBARRIER_CALLBACKS 1644 bool 1645 1646config ARCH_HAS_MEMBARRIER_SYNC_CORE 1647 bool 1648 1649config RSEQ 1650 bool "Enable rseq() system call" if EXPERT 1651 default y 1652 depends on HAVE_RSEQ 1653 select MEMBARRIER 1654 help 1655 Enable the restartable sequences system call. It provides a 1656 user-space cache for the current CPU number value, which 1657 speeds up getting the current CPU number from user-space, 1658 as well as an ABI to speed up user-space operations on 1659 per-CPU data. 1660 1661 If unsure, say Y. 1662 1663config DEBUG_RSEQ 1664 default n 1665 bool "Enabled debugging of rseq() system call" if EXPERT 1666 depends on RSEQ && DEBUG_KERNEL 1667 help 1668 Enable extra debugging checks for the rseq system call. 1669 1670 If unsure, say N. 1671 1672config EMBEDDED 1673 bool "Embedded system" 1674 option allnoconfig_y 1675 select EXPERT 1676 help 1677 This option should be enabled if compiling the kernel for 1678 an embedded system so certain expert options are available 1679 for configuration. 1680 1681config HAVE_PERF_EVENTS 1682 bool 1683 help 1684 See tools/perf/design.txt for details. 1685 1686config PERF_USE_VMALLOC 1687 bool 1688 help 1689 See tools/perf/design.txt for details 1690 1691config PC104 1692 bool "PC/104 support" if EXPERT 1693 help 1694 Expose PC/104 form factor device drivers and options available for 1695 selection and configuration. Enable this option if your target 1696 machine has a PC/104 bus. 1697 1698menu "Kernel Performance Events And Counters" 1699 1700config PERF_EVENTS 1701 bool "Kernel performance events and counters" 1702 default y if PROFILING 1703 depends on HAVE_PERF_EVENTS 1704 select IRQ_WORK 1705 select SRCU 1706 help 1707 Enable kernel support for various performance events provided 1708 by software and hardware. 1709 1710 Software events are supported either built-in or via the 1711 use of generic tracepoints. 1712 1713 Most modern CPUs support performance events via performance 1714 counter registers. These registers count the number of certain 1715 types of hw events: such as instructions executed, cachemisses 1716 suffered, or branches mis-predicted - without slowing down the 1717 kernel or applications. These registers can also trigger interrupts 1718 when a threshold number of events have passed - and can thus be 1719 used to profile the code that runs on that CPU. 1720 1721 The Linux Performance Event subsystem provides an abstraction of 1722 these software and hardware event capabilities, available via a 1723 system call and used by the "perf" utility in tools/perf/. It 1724 provides per task and per CPU counters, and it provides event 1725 capabilities on top of those. 1726 1727 Say Y if unsure. 1728 1729config DEBUG_PERF_USE_VMALLOC 1730 default n 1731 bool "Debug: use vmalloc to back perf mmap() buffers" 1732 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1733 select PERF_USE_VMALLOC 1734 help 1735 Use vmalloc memory to back perf mmap() buffers. 1736 1737 Mostly useful for debugging the vmalloc code on platforms 1738 that don't require it. 1739 1740 Say N if unsure. 1741 1742endmenu 1743 1744config VM_EVENT_COUNTERS 1745 default y 1746 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1747 help 1748 VM event counters are needed for event counts to be shown. 1749 This option allows the disabling of the VM event counters 1750 on EXPERT systems. /proc/vmstat will only show page counts 1751 if VM event counters are disabled. 1752 1753config SLUB_DEBUG 1754 default y 1755 bool "Enable SLUB debugging support" if EXPERT 1756 depends on SLUB && SYSFS 1757 help 1758 SLUB has extensive debug support features. Disabling these can 1759 result in significant savings in code size. This also disables 1760 SLUB sysfs support. /sys/slab will not exist and there will be 1761 no support for cache validation etc. 1762 1763config SLUB_MEMCG_SYSFS_ON 1764 default n 1765 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1766 depends on SLUB && SYSFS && MEMCG 1767 help 1768 SLUB creates a directory under /sys/kernel/slab for each 1769 allocation cache to host info and debug files. If memory 1770 cgroup is enabled, each cache can have per memory cgroup 1771 caches. SLUB can create the same sysfs directories for these 1772 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1773 to a very high number of debug files being created. This is 1774 controlled by slub_memcg_sysfs boot parameter and this 1775 config option determines the parameter's default value. 1776 1777config COMPAT_BRK 1778 bool "Disable heap randomization" 1779 default y 1780 help 1781 Randomizing heap placement makes heap exploits harder, but it 1782 also breaks ancient binaries (including anything libc5 based). 1783 This option changes the bootup default to heap randomization 1784 disabled, and can be overridden at runtime by setting 1785 /proc/sys/kernel/randomize_va_space to 2. 1786 1787 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1788 1789choice 1790 prompt "Choose SLAB allocator" 1791 default SLUB 1792 help 1793 This option allows to select a slab allocator. 1794 1795config SLAB 1796 bool "SLAB" 1797 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1798 help 1799 The regular slab allocator that is established and known to work 1800 well in all environments. It organizes cache hot objects in 1801 per cpu and per node queues. 1802 1803config SLUB 1804 bool "SLUB (Unqueued Allocator)" 1805 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1806 help 1807 SLUB is a slab allocator that minimizes cache line usage 1808 instead of managing queues of cached objects (SLAB approach). 1809 Per cpu caching is realized using slabs of objects instead 1810 of queues of objects. SLUB can use memory efficiently 1811 and has enhanced diagnostics. SLUB is the default choice for 1812 a slab allocator. 1813 1814config SLOB 1815 depends on EXPERT 1816 bool "SLOB (Simple Allocator)" 1817 help 1818 SLOB replaces the stock allocator with a drastically simpler 1819 allocator. SLOB is generally more space efficient but 1820 does not perform as well on large systems. 1821 1822endchoice 1823 1824config SLAB_MERGE_DEFAULT 1825 bool "Allow slab caches to be merged" 1826 default y 1827 help 1828 For reduced kernel memory fragmentation, slab caches can be 1829 merged when they share the same size and other characteristics. 1830 This carries a risk of kernel heap overflows being able to 1831 overwrite objects from merged caches (and more easily control 1832 cache layout), which makes such heap attacks easier to exploit 1833 by attackers. By keeping caches unmerged, these kinds of exploits 1834 can usually only damage objects in the same cache. To disable 1835 merging at runtime, "slab_nomerge" can be passed on the kernel 1836 command line. 1837 1838config SLAB_FREELIST_RANDOM 1839 default n 1840 depends on SLAB || SLUB 1841 bool "SLAB freelist randomization" 1842 help 1843 Randomizes the freelist order used on creating new pages. This 1844 security feature reduces the predictability of the kernel slab 1845 allocator against heap overflows. 1846 1847config SLAB_FREELIST_HARDENED 1848 bool "Harden slab freelist metadata" 1849 depends on SLUB 1850 help 1851 Many kernel heap attacks try to target slab cache metadata and 1852 other infrastructure. This options makes minor performance 1853 sacrifices to harden the kernel slab allocator against common 1854 freelist exploit methods. 1855 1856config SHUFFLE_PAGE_ALLOCATOR 1857 bool "Page allocator randomization" 1858 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1859 help 1860 Randomization of the page allocator improves the average 1861 utilization of a direct-mapped memory-side-cache. See section 1862 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1863 6.2a specification for an example of how a platform advertises 1864 the presence of a memory-side-cache. There are also incidental 1865 security benefits as it reduces the predictability of page 1866 allocations to compliment SLAB_FREELIST_RANDOM, but the 1867 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1868 10th order of pages is selected based on cache utilization 1869 benefits on x86. 1870 1871 While the randomization improves cache utilization it may 1872 negatively impact workloads on platforms without a cache. For 1873 this reason, by default, the randomization is enabled only 1874 after runtime detection of a direct-mapped memory-side-cache. 1875 Otherwise, the randomization may be force enabled with the 1876 'page_alloc.shuffle' kernel command line parameter. 1877 1878 Say Y if unsure. 1879 1880config SLUB_CPU_PARTIAL 1881 default y 1882 depends on SLUB && SMP 1883 bool "SLUB per cpu partial cache" 1884 help 1885 Per cpu partial caches accelerate objects allocation and freeing 1886 that is local to a processor at the price of more indeterminism 1887 in the latency of the free. On overflow these caches will be cleared 1888 which requires the taking of locks that may cause latency spikes. 1889 Typically one would choose no for a realtime system. 1890 1891config MMAP_ALLOW_UNINITIALIZED 1892 bool "Allow mmapped anonymous memory to be uninitialized" 1893 depends on EXPERT && !MMU 1894 default n 1895 help 1896 Normally, and according to the Linux spec, anonymous memory obtained 1897 from mmap() has its contents cleared before it is passed to 1898 userspace. Enabling this config option allows you to request that 1899 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1900 providing a huge performance boost. If this option is not enabled, 1901 then the flag will be ignored. 1902 1903 This is taken advantage of by uClibc's malloc(), and also by 1904 ELF-FDPIC binfmt's brk and stack allocator. 1905 1906 Because of the obvious security issues, this option should only be 1907 enabled on embedded devices where you control what is run in 1908 userspace. Since that isn't generally a problem on no-MMU systems, 1909 it is normally safe to say Y here. 1910 1911 See Documentation/nommu-mmap.txt for more information. 1912 1913config SYSTEM_DATA_VERIFICATION 1914 def_bool n 1915 select SYSTEM_TRUSTED_KEYRING 1916 select KEYS 1917 select CRYPTO 1918 select CRYPTO_RSA 1919 select ASYMMETRIC_KEY_TYPE 1920 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1921 select ASN1 1922 select OID_REGISTRY 1923 select X509_CERTIFICATE_PARSER 1924 select PKCS7_MESSAGE_PARSER 1925 help 1926 Provide PKCS#7 message verification using the contents of the system 1927 trusted keyring to provide public keys. This then can be used for 1928 module verification, kexec image verification and firmware blob 1929 verification. 1930 1931config PROFILING 1932 bool "Profiling support" 1933 help 1934 Say Y here to enable the extended profiling support mechanisms used 1935 by profilers such as OProfile. 1936 1937# 1938# Place an empty function call at each tracepoint site. Can be 1939# dynamically changed for a probe function. 1940# 1941config TRACEPOINTS 1942 bool 1943 1944endmenu # General setup 1945 1946source "arch/Kconfig" 1947 1948config RT_MUTEXES 1949 bool 1950 1951config BASE_SMALL 1952 int 1953 default 0 if BASE_FULL 1954 default 1 if !BASE_FULL 1955 1956config MODULE_SIG_FORMAT 1957 def_bool n 1958 select SYSTEM_DATA_VERIFICATION 1959 1960menuconfig MODULES 1961 bool "Enable loadable module support" 1962 option modules 1963 help 1964 Kernel modules are small pieces of compiled code which can 1965 be inserted in the running kernel, rather than being 1966 permanently built into the kernel. You use the "modprobe" 1967 tool to add (and sometimes remove) them. If you say Y here, 1968 many parts of the kernel can be built as modules (by 1969 answering M instead of Y where indicated): this is most 1970 useful for infrequently used options which are not required 1971 for booting. For more information, see the man pages for 1972 modprobe, lsmod, modinfo, insmod and rmmod. 1973 1974 If you say Y here, you will need to run "make 1975 modules_install" to put the modules under /lib/modules/ 1976 where modprobe can find them (you may need to be root to do 1977 this). 1978 1979 If unsure, say Y. 1980 1981if MODULES 1982 1983config MODULE_FORCE_LOAD 1984 bool "Forced module loading" 1985 default n 1986 help 1987 Allow loading of modules without version information (ie. modprobe 1988 --force). Forced module loading sets the 'F' (forced) taint flag and 1989 is usually a really bad idea. 1990 1991config MODULE_UNLOAD 1992 bool "Module unloading" 1993 help 1994 Without this option you will not be able to unload any 1995 modules (note that some modules may not be unloadable 1996 anyway), which makes your kernel smaller, faster 1997 and simpler. If unsure, say Y. 1998 1999config MODULE_FORCE_UNLOAD 2000 bool "Forced module unloading" 2001 depends on MODULE_UNLOAD 2002 help 2003 This option allows you to force a module to unload, even if the 2004 kernel believes it is unsafe: the kernel will remove the module 2005 without waiting for anyone to stop using it (using the -f option to 2006 rmmod). This is mainly for kernel developers and desperate users. 2007 If unsure, say N. 2008 2009config MODVERSIONS 2010 bool "Module versioning support" 2011 help 2012 Usually, you have to use modules compiled with your kernel. 2013 Saying Y here makes it sometimes possible to use modules 2014 compiled for different kernels, by adding enough information 2015 to the modules to (hopefully) spot any changes which would 2016 make them incompatible with the kernel you are running. If 2017 unsure, say N. 2018 2019config ASM_MODVERSIONS 2020 bool 2021 default HAVE_ASM_MODVERSIONS && MODVERSIONS 2022 help 2023 This enables module versioning for exported symbols also from 2024 assembly. This can be enabled only when the target architecture 2025 supports it. 2026 2027config MODULE_REL_CRCS 2028 bool 2029 depends on MODVERSIONS 2030 2031config MODULE_SRCVERSION_ALL 2032 bool "Source checksum for all modules" 2033 help 2034 Modules which contain a MODULE_VERSION get an extra "srcversion" 2035 field inserted into their modinfo section, which contains a 2036 sum of the source files which made it. This helps maintainers 2037 see exactly which source was used to build a module (since 2038 others sometimes change the module source without updating 2039 the version). With this option, such a "srcversion" field 2040 will be created for all modules. If unsure, say N. 2041 2042config MODULE_SIG 2043 bool "Module signature verification" 2044 select MODULE_SIG_FORMAT 2045 help 2046 Check modules for valid signatures upon load: the signature 2047 is simply appended to the module. For more information see 2048 <file:Documentation/admin-guide/module-signing.rst>. 2049 2050 Note that this option adds the OpenSSL development packages as a 2051 kernel build dependency so that the signing tool can use its crypto 2052 library. 2053 2054 You should enable this option if you wish to use either 2055 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via 2056 another LSM - otherwise unsigned modules will be loadable regardless 2057 of the lockdown policy. 2058 2059 !!!WARNING!!! If you enable this option, you MUST make sure that the 2060 module DOES NOT get stripped after being signed. This includes the 2061 debuginfo strip done by some packagers (such as rpmbuild) and 2062 inclusion into an initramfs that wants the module size reduced. 2063 2064config MODULE_SIG_FORCE 2065 bool "Require modules to be validly signed" 2066 depends on MODULE_SIG 2067 help 2068 Reject unsigned modules or signed modules for which we don't have a 2069 key. Without this, such modules will simply taint the kernel. 2070 2071config MODULE_SIG_ALL 2072 bool "Automatically sign all modules" 2073 default y 2074 depends on MODULE_SIG 2075 help 2076 Sign all modules during make modules_install. Without this option, 2077 modules must be signed manually, using the scripts/sign-file tool. 2078 2079comment "Do not forget to sign required modules with scripts/sign-file" 2080 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2081 2082choice 2083 prompt "Which hash algorithm should modules be signed with?" 2084 depends on MODULE_SIG 2085 help 2086 This determines which sort of hashing algorithm will be used during 2087 signature generation. This algorithm _must_ be built into the kernel 2088 directly so that signature verification can take place. It is not 2089 possible to load a signed module containing the algorithm to check 2090 the signature on that module. 2091 2092config MODULE_SIG_SHA1 2093 bool "Sign modules with SHA-1" 2094 select CRYPTO_SHA1 2095 2096config MODULE_SIG_SHA224 2097 bool "Sign modules with SHA-224" 2098 select CRYPTO_SHA256 2099 2100config MODULE_SIG_SHA256 2101 bool "Sign modules with SHA-256" 2102 select CRYPTO_SHA256 2103 2104config MODULE_SIG_SHA384 2105 bool "Sign modules with SHA-384" 2106 select CRYPTO_SHA512 2107 2108config MODULE_SIG_SHA512 2109 bool "Sign modules with SHA-512" 2110 select CRYPTO_SHA512 2111 2112endchoice 2113 2114config MODULE_SIG_HASH 2115 string 2116 depends on MODULE_SIG 2117 default "sha1" if MODULE_SIG_SHA1 2118 default "sha224" if MODULE_SIG_SHA224 2119 default "sha256" if MODULE_SIG_SHA256 2120 default "sha384" if MODULE_SIG_SHA384 2121 default "sha512" if MODULE_SIG_SHA512 2122 2123config MODULE_COMPRESS 2124 bool "Compress modules on installation" 2125 help 2126 2127 Compresses kernel modules when 'make modules_install' is run; gzip or 2128 xz depending on "Compression algorithm" below. 2129 2130 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 2131 2132 Out-of-tree kernel modules installed using Kbuild will also be 2133 compressed upon installation. 2134 2135 Note: for modules inside an initrd or initramfs, it's more efficient 2136 to compress the whole initrd or initramfs instead. 2137 2138 Note: This is fully compatible with signed modules. 2139 2140 If in doubt, say N. 2141 2142choice 2143 prompt "Compression algorithm" 2144 depends on MODULE_COMPRESS 2145 default MODULE_COMPRESS_GZIP 2146 help 2147 This determines which sort of compression will be used during 2148 'make modules_install'. 2149 2150 GZIP (default) and XZ are supported. 2151 2152config MODULE_COMPRESS_GZIP 2153 bool "GZIP" 2154 2155config MODULE_COMPRESS_XZ 2156 bool "XZ" 2157 2158endchoice 2159 2160config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS 2161 bool "Allow loading of modules with missing namespace imports" 2162 help 2163 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in 2164 a namespace. A module that makes use of a symbol exported with such a 2165 namespace is required to import the namespace via MODULE_IMPORT_NS(). 2166 There is no technical reason to enforce correct namespace imports, 2167 but it creates consistency between symbols defining namespaces and 2168 users importing namespaces they make use of. This option relaxes this 2169 requirement and lifts the enforcement when loading a module. 2170 2171 If unsure, say N. 2172 2173config UNUSED_SYMBOLS 2174 bool "Enable unused/obsolete exported symbols" 2175 default y if X86 2176 help 2177 Unused but exported symbols make the kernel needlessly bigger. For 2178 that reason most of these unused exports will soon be removed. This 2179 option is provided temporarily to provide a transition period in case 2180 some external kernel module needs one of these symbols anyway. If you 2181 encounter such a case in your module, consider if you are actually 2182 using the right API. (rationale: since nobody in the kernel is using 2183 this in a module, there is a pretty good chance it's actually the 2184 wrong interface to use). If you really need the symbol, please send a 2185 mail to the linux kernel mailing list mentioning the symbol and why 2186 you really need it, and what the merge plan to the mainline kernel for 2187 your module is. 2188 2189config TRIM_UNUSED_KSYMS 2190 bool "Trim unused exported kernel symbols" 2191 depends on !UNUSED_SYMBOLS 2192 help 2193 The kernel and some modules make many symbols available for 2194 other modules to use via EXPORT_SYMBOL() and variants. Depending 2195 on the set of modules being selected in your kernel configuration, 2196 many of those exported symbols might never be used. 2197 2198 This option allows for unused exported symbols to be dropped from 2199 the build. In turn, this provides the compiler more opportunities 2200 (especially when using LTO) for optimizing the code and reducing 2201 binary size. This might have some security advantages as well. 2202 2203 If unsure, or if you need to build out-of-tree modules, say N. 2204 2205config UNUSED_KSYMS_WHITELIST 2206 string "Whitelist of symbols to keep in ksymtab" 2207 depends on TRIM_UNUSED_KSYMS 2208 help 2209 By default, all unused exported symbols will be un-exported from the 2210 build when TRIM_UNUSED_KSYMS is selected. 2211 2212 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept 2213 exported at all times, even in absence of in-tree users. The value to 2214 set here is the path to a text file containing the list of symbols, 2215 one per line. The path can be absolute, or relative to the kernel 2216 source tree. 2217 2218endif # MODULES 2219 2220config MODULES_TREE_LOOKUP 2221 def_bool y 2222 depends on PERF_EVENTS || TRACING 2223 2224config INIT_ALL_POSSIBLE 2225 bool 2226 help 2227 Back when each arch used to define their own cpu_online_mask and 2228 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2229 with all 1s, and others with all 0s. When they were centralised, 2230 it was better to provide this option than to break all the archs 2231 and have several arch maintainers pursuing me down dark alleys. 2232 2233source "block/Kconfig" 2234 2235config PREEMPT_NOTIFIERS 2236 bool 2237 2238config PADATA 2239 depends on SMP 2240 bool 2241 2242config ASN1 2243 tristate 2244 help 2245 Build a simple ASN.1 grammar compiler that produces a bytecode output 2246 that can be interpreted by the ASN.1 stream decoder and used to 2247 inform it as to what tags are to be expected in a stream and what 2248 functions to call on what tags. 2249 2250source "kernel/Kconfig.locks" 2251 2252config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 2253 bool 2254 2255config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2256 bool 2257 2258# It may be useful for an architecture to override the definitions of the 2259# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2260# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2261# different calling convention for syscalls. They can also override the 2262# macros for not-implemented syscalls in kernel/sys_ni.c and 2263# kernel/time/posix-stubs.c. All these overrides need to be available in 2264# <asm/syscall_wrapper.h>. 2265config ARCH_HAS_SYSCALL_WRAPPER 2266 def_bool n 2267