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 CLANG_VERSION 27 int 28 default $(shell,$(srctree)/scripts/clang-version.sh $(CC)) 29 30config CC_CAN_LINK 31 def_bool $(success,$(srctree)/scripts/cc-can-link.sh $(CC)) 32 33config CC_HAS_ASM_GOTO 34 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) 35 36config TOOLS_SUPPORT_RELR 37 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 38 39config CC_HAS_ASM_INLINE 40 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 41 42config CONSTRUCTORS 43 bool 44 depends on !UML 45 46config IRQ_WORK 47 bool 48 49config BUILDTIME_TABLE_SORT 50 bool 51 52config THREAD_INFO_IN_TASK 53 bool 54 help 55 Select this to move thread_info off the stack into task_struct. To 56 make this work, an arch will need to remove all thread_info fields 57 except flags and fix any runtime bugs. 58 59 One subtle change that will be needed is to use try_get_task_stack() 60 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 61 62menu "General setup" 63 64config BROKEN 65 bool 66 67config BROKEN_ON_SMP 68 bool 69 depends on BROKEN || !SMP 70 default y 71 72config INIT_ENV_ARG_LIMIT 73 int 74 default 32 if !UML 75 default 128 if UML 76 help 77 Maximum of each of the number of arguments and environment 78 variables passed to init from the kernel command line. 79 80config COMPILE_TEST 81 bool "Compile also drivers which will not load" 82 depends on !UML 83 default n 84 help 85 Some drivers can be compiled on a different platform than they are 86 intended to be run on. Despite they cannot be loaded there (or even 87 when they load they cannot be used due to missing HW support), 88 developers still, opposing to distributors, might want to build such 89 drivers to compile-test them. 90 91 If you are a developer and want to build everything available, say Y 92 here. If you are a user/distributor, say N here to exclude useless 93 drivers to be distributed. 94 95config UAPI_HEADER_TEST 96 bool "Compile test UAPI headers" 97 depends on HEADERS_INSTALL && CC_CAN_LINK 98 help 99 Compile test headers exported to user-space to ensure they are 100 self-contained, i.e. compilable as standalone units. 101 102 If you are a developer or tester and want to ensure the exported 103 headers are self-contained, say Y here. Otherwise, choose N. 104 105config LOCALVERSION 106 string "Local version - append to kernel release" 107 help 108 Append an extra string to the end of your kernel version. 109 This will show up when you type uname, for example. 110 The string you set here will be appended after the contents of 111 any files with a filename matching localversion* in your 112 object and source tree, in that order. Your total string can 113 be a maximum of 64 characters. 114 115config LOCALVERSION_AUTO 116 bool "Automatically append version information to the version string" 117 default y 118 depends on !COMPILE_TEST 119 help 120 This will try to automatically determine if the current tree is a 121 release tree by looking for git tags that belong to the current 122 top of tree revision. 123 124 A string of the format -gxxxxxxxx will be added to the localversion 125 if a git-based tree is found. The string generated by this will be 126 appended after any matching localversion* files, and after the value 127 set in CONFIG_LOCALVERSION. 128 129 (The actual string used here is the first eight characters produced 130 by running the command: 131 132 $ git rev-parse --verify HEAD 133 134 which is done within the script "scripts/setlocalversion".) 135 136config BUILD_SALT 137 string "Build ID Salt" 138 default "" 139 help 140 The build ID is used to link binaries and their debug info. Setting 141 this option will use the value in the calculation of the build id. 142 This is mostly useful for distributions which want to ensure the 143 build is unique between builds. It's safe to leave the default. 144 145config HAVE_KERNEL_GZIP 146 bool 147 148config HAVE_KERNEL_BZIP2 149 bool 150 151config HAVE_KERNEL_LZMA 152 bool 153 154config HAVE_KERNEL_XZ 155 bool 156 157config HAVE_KERNEL_LZO 158 bool 159 160config HAVE_KERNEL_LZ4 161 bool 162 163config HAVE_KERNEL_UNCOMPRESSED 164 bool 165 166choice 167 prompt "Kernel compression mode" 168 default KERNEL_GZIP 169 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED 170 help 171 The linux kernel is a kind of self-extracting executable. 172 Several compression algorithms are available, which differ 173 in efficiency, compression and decompression speed. 174 Compression speed is only relevant when building a kernel. 175 Decompression speed is relevant at each boot. 176 177 If you have any problems with bzip2 or lzma compressed 178 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 179 version of this functionality (bzip2 only), for 2.4, was 180 supplied by Christian Ludwig) 181 182 High compression options are mostly useful for users, who 183 are low on disk space (embedded systems), but for whom ram 184 size matters less. 185 186 If in doubt, select 'gzip' 187 188config KERNEL_GZIP 189 bool "Gzip" 190 depends on HAVE_KERNEL_GZIP 191 help 192 The old and tried gzip compression. It provides a good balance 193 between compression ratio and decompression speed. 194 195config KERNEL_BZIP2 196 bool "Bzip2" 197 depends on HAVE_KERNEL_BZIP2 198 help 199 Its compression ratio and speed is intermediate. 200 Decompression speed is slowest among the choices. The kernel 201 size is about 10% smaller with bzip2, in comparison to gzip. 202 Bzip2 uses a large amount of memory. For modern kernels you 203 will need at least 8MB RAM or more for booting. 204 205config KERNEL_LZMA 206 bool "LZMA" 207 depends on HAVE_KERNEL_LZMA 208 help 209 This compression algorithm's ratio is best. Decompression speed 210 is between gzip and bzip2. Compression is slowest. 211 The kernel size is about 33% smaller with LZMA in comparison to gzip. 212 213config KERNEL_XZ 214 bool "XZ" 215 depends on HAVE_KERNEL_XZ 216 help 217 XZ uses the LZMA2 algorithm and instruction set specific 218 BCJ filters which can improve compression ratio of executable 219 code. The size of the kernel is about 30% smaller with XZ in 220 comparison to gzip. On architectures for which there is a BCJ 221 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 222 will create a few percent smaller kernel than plain LZMA. 223 224 The speed is about the same as with LZMA: The decompression 225 speed of XZ is better than that of bzip2 but worse than gzip 226 and LZO. Compression is slow. 227 228config KERNEL_LZO 229 bool "LZO" 230 depends on HAVE_KERNEL_LZO 231 help 232 Its compression ratio is the poorest among the choices. The kernel 233 size is about 10% bigger than gzip; however its speed 234 (both compression and decompression) is the fastest. 235 236config KERNEL_LZ4 237 bool "LZ4" 238 depends on HAVE_KERNEL_LZ4 239 help 240 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 241 A preliminary version of LZ4 de/compression tool is available at 242 <https://code.google.com/p/lz4/>. 243 244 Its compression ratio is worse than LZO. The size of the kernel 245 is about 8% bigger than LZO. But the decompression speed is 246 faster than LZO. 247 248config KERNEL_UNCOMPRESSED 249 bool "None" 250 depends on HAVE_KERNEL_UNCOMPRESSED 251 help 252 Produce uncompressed kernel image. This option is usually not what 253 you want. It is useful for debugging the kernel in slow simulation 254 environments, where decompressing and moving the kernel is awfully 255 slow. This option allows early boot code to skip the decompressor 256 and jump right at uncompressed kernel image. 257 258endchoice 259 260config DEFAULT_HOSTNAME 261 string "Default hostname" 262 default "(none)" 263 help 264 This option determines the default system hostname before userspace 265 calls sethostname(2). The kernel traditionally uses "(none)" here, 266 but you may wish to use a different default here to make a minimal 267 system more usable with less configuration. 268 269# 270# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can 271# add proper SWAP support to them, in which case this can be remove. 272# 273config ARCH_NO_SWAP 274 bool 275 276config SWAP 277 bool "Support for paging of anonymous memory (swap)" 278 depends on MMU && BLOCK && !ARCH_NO_SWAP 279 default y 280 help 281 This option allows you to choose whether you want to have support 282 for so called swap devices or swap files in your kernel that are 283 used to provide more virtual memory than the actual RAM present 284 in your computer. If unsure say Y. 285 286config SYSVIPC 287 bool "System V IPC" 288 ---help--- 289 Inter Process Communication is a suite of library functions and 290 system calls which let processes (running programs) synchronize and 291 exchange information. It is generally considered to be a good thing, 292 and some programs won't run unless you say Y here. In particular, if 293 you want to run the DOS emulator dosemu under Linux (read the 294 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 295 you'll need to say Y here. 296 297 You can find documentation about IPC with "info ipc" and also in 298 section 6.4 of the Linux Programmer's Guide, available from 299 <http://www.tldp.org/guides.html>. 300 301config SYSVIPC_SYSCTL 302 bool 303 depends on SYSVIPC 304 depends on SYSCTL 305 default y 306 307config POSIX_MQUEUE 308 bool "POSIX Message Queues" 309 depends on NET 310 ---help--- 311 POSIX variant of message queues is a part of IPC. In POSIX message 312 queues every message has a priority which decides about succession 313 of receiving it by a process. If you want to compile and run 314 programs written e.g. for Solaris with use of its POSIX message 315 queues (functions mq_*) say Y here. 316 317 POSIX message queues are visible as a filesystem called 'mqueue' 318 and can be mounted somewhere if you want to do filesystem 319 operations on message queues. 320 321 If unsure, say Y. 322 323config POSIX_MQUEUE_SYSCTL 324 bool 325 depends on POSIX_MQUEUE 326 depends on SYSCTL 327 default y 328 329config WATCH_QUEUE 330 bool "General notification queue" 331 default n 332 help 333 334 This is a general notification queue for the kernel to pass events to 335 userspace by splicing them into pipes. It can be used in conjunction 336 with watches for key/keyring change notifications and device 337 notifications. 338 339 See Documentation/watch_queue.rst 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_BFQ_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. Or this can be used to have cgroup ID in samples 1033 so that it can monitor performance events among cgroups. 1034 1035 Say N if unsure. 1036 1037config CGROUP_BPF 1038 bool "Support for eBPF programs attached to cgroups" 1039 depends on BPF_SYSCALL 1040 select SOCK_CGROUP_DATA 1041 help 1042 Allow attaching eBPF programs to a cgroup using the bpf(2) 1043 syscall command BPF_PROG_ATTACH. 1044 1045 In which context these programs are accessed depends on the type 1046 of attachment. For instance, programs that are attached using 1047 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1048 inet sockets. 1049 1050config CGROUP_DEBUG 1051 bool "Debug controller" 1052 default n 1053 depends on DEBUG_KERNEL 1054 help 1055 This option enables a simple controller that exports 1056 debugging information about the cgroups framework. This 1057 controller is for control cgroup debugging only. Its 1058 interfaces are not stable. 1059 1060 Say N. 1061 1062config SOCK_CGROUP_DATA 1063 bool 1064 default n 1065 1066endif # CGROUPS 1067 1068menuconfig NAMESPACES 1069 bool "Namespaces support" if EXPERT 1070 depends on MULTIUSER 1071 default !EXPERT 1072 help 1073 Provides the way to make tasks work with different objects using 1074 the same id. For example same IPC id may refer to different objects 1075 or same user id or pid may refer to different tasks when used in 1076 different namespaces. 1077 1078if NAMESPACES 1079 1080config UTS_NS 1081 bool "UTS namespace" 1082 default y 1083 help 1084 In this namespace tasks see different info provided with the 1085 uname() system call 1086 1087config TIME_NS 1088 bool "TIME namespace" 1089 depends on GENERIC_VDSO_TIME_NS 1090 default y 1091 help 1092 In this namespace boottime and monotonic clocks can be set. 1093 The time will keep going with the same pace. 1094 1095config IPC_NS 1096 bool "IPC namespace" 1097 depends on (SYSVIPC || POSIX_MQUEUE) 1098 default y 1099 help 1100 In this namespace tasks work with IPC ids which correspond to 1101 different IPC objects in different namespaces. 1102 1103config USER_NS 1104 bool "User namespace" 1105 default n 1106 help 1107 This allows containers, i.e. vservers, to use user namespaces 1108 to provide different user info for different servers. 1109 1110 When user namespaces are enabled in the kernel it is 1111 recommended that the MEMCG option also be enabled and that 1112 user-space use the memory control groups to limit the amount 1113 of memory a memory unprivileged users can use. 1114 1115 If unsure, say N. 1116 1117config PID_NS 1118 bool "PID Namespaces" 1119 default y 1120 help 1121 Support process id namespaces. This allows having multiple 1122 processes with the same pid as long as they are in different 1123 pid namespaces. This is a building block of containers. 1124 1125config NET_NS 1126 bool "Network namespace" 1127 depends on NET 1128 default y 1129 help 1130 Allow user space to create what appear to be multiple instances 1131 of the network stack. 1132 1133endif # NAMESPACES 1134 1135config CHECKPOINT_RESTORE 1136 bool "Checkpoint/restore support" 1137 select PROC_CHILDREN 1138 default n 1139 help 1140 Enables additional kernel features in a sake of checkpoint/restore. 1141 In particular it adds auxiliary prctl codes to setup process text, 1142 data and heap segment sizes, and a few additional /proc filesystem 1143 entries. 1144 1145 If unsure, say N here. 1146 1147config SCHED_AUTOGROUP 1148 bool "Automatic process group scheduling" 1149 select CGROUPS 1150 select CGROUP_SCHED 1151 select FAIR_GROUP_SCHED 1152 help 1153 This option optimizes the scheduler for common desktop workloads by 1154 automatically creating and populating task groups. This separation 1155 of workloads isolates aggressive CPU burners (like build jobs) from 1156 desktop applications. Task group autogeneration is currently based 1157 upon task session. 1158 1159config SYSFS_DEPRECATED 1160 bool "Enable deprecated sysfs features to support old userspace tools" 1161 depends on SYSFS 1162 default n 1163 help 1164 This option adds code that switches the layout of the "block" class 1165 devices, to not show up in /sys/class/block/, but only in 1166 /sys/block/. 1167 1168 This switch is only active when the sysfs.deprecated=1 boot option is 1169 passed or the SYSFS_DEPRECATED_V2 option is set. 1170 1171 This option allows new kernels to run on old distributions and tools, 1172 which might get confused by /sys/class/block/. Since 2007/2008 all 1173 major distributions and tools handle this just fine. 1174 1175 Recent distributions and userspace tools after 2009/2010 depend on 1176 the existence of /sys/class/block/, and will not work with this 1177 option enabled. 1178 1179 Only if you are using a new kernel on an old distribution, you might 1180 need to say Y here. 1181 1182config SYSFS_DEPRECATED_V2 1183 bool "Enable deprecated sysfs features by default" 1184 default n 1185 depends on SYSFS 1186 depends on SYSFS_DEPRECATED 1187 help 1188 Enable deprecated sysfs by default. 1189 1190 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1191 option. 1192 1193 Only if you are using a new kernel on an old distribution, you might 1194 need to say Y here. Even then, odds are you would not need it 1195 enabled, you can always pass the boot option if absolutely necessary. 1196 1197config RELAY 1198 bool "Kernel->user space relay support (formerly relayfs)" 1199 select IRQ_WORK 1200 help 1201 This option enables support for relay interface support in 1202 certain file systems (such as debugfs). 1203 It is designed to provide an efficient mechanism for tools and 1204 facilities to relay large amounts of data from kernel space to 1205 user space. 1206 1207 If unsure, say N. 1208 1209config BLK_DEV_INITRD 1210 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1211 help 1212 The initial RAM filesystem is a ramfs which is loaded by the 1213 boot loader (loadlin or lilo) and that is mounted as root 1214 before the normal boot procedure. It is typically used to 1215 load modules needed to mount the "real" root file system, 1216 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1217 1218 If RAM disk support (BLK_DEV_RAM) is also included, this 1219 also enables initial RAM disk (initrd) support and adds 1220 15 Kbytes (more on some other architectures) to the kernel size. 1221 1222 If unsure say Y. 1223 1224if BLK_DEV_INITRD 1225 1226source "usr/Kconfig" 1227 1228endif 1229 1230config BOOT_CONFIG 1231 bool "Boot config support" 1232 select BLK_DEV_INITRD 1233 help 1234 Extra boot config allows system admin to pass a config file as 1235 complemental extension of kernel cmdline when booting. 1236 The boot config file must be attached at the end of initramfs 1237 with checksum, size and magic word. 1238 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1239 1240 If unsure, say Y. 1241 1242choice 1243 prompt "Compiler optimization level" 1244 default CC_OPTIMIZE_FOR_PERFORMANCE 1245 1246config CC_OPTIMIZE_FOR_PERFORMANCE 1247 bool "Optimize for performance (-O2)" 1248 help 1249 This is the default optimization level for the kernel, building 1250 with the "-O2" compiler flag for best performance and most 1251 helpful compile-time warnings. 1252 1253config CC_OPTIMIZE_FOR_PERFORMANCE_O3 1254 bool "Optimize more for performance (-O3)" 1255 depends on ARC 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 help 1263 Choosing this option will pass "-Os" to your compiler resulting 1264 in a smaller kernel. 1265 1266endchoice 1267 1268config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1269 bool 1270 help 1271 This requires that the arch annotates or otherwise protects 1272 its external entry points from being discarded. Linker scripts 1273 must also merge .text.*, .data.*, and .bss.* correctly into 1274 output sections. Care must be taken not to pull in unrelated 1275 sections (e.g., '.text.init'). Typically '.' in section names 1276 is used to distinguish them from label names / C identifiers. 1277 1278config LD_DEAD_CODE_DATA_ELIMINATION 1279 bool "Dead code and data elimination (EXPERIMENTAL)" 1280 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1281 depends on EXPERT 1282 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800) 1283 depends on $(cc-option,-ffunction-sections -fdata-sections) 1284 depends on $(ld-option,--gc-sections) 1285 help 1286 Enable this if you want to do dead code and data elimination with 1287 the linker by compiling with -ffunction-sections -fdata-sections, 1288 and linking with --gc-sections. 1289 1290 This can reduce on disk and in-memory size of the kernel 1291 code and static data, particularly for small configs and 1292 on small systems. This has the possibility of introducing 1293 silently broken kernel if the required annotations are not 1294 present. This option is not well tested yet, so use at your 1295 own risk. 1296 1297config SYSCTL 1298 bool 1299 1300config HAVE_UID16 1301 bool 1302 1303config SYSCTL_EXCEPTION_TRACE 1304 bool 1305 help 1306 Enable support for /proc/sys/debug/exception-trace. 1307 1308config SYSCTL_ARCH_UNALIGN_NO_WARN 1309 bool 1310 help 1311 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1312 Allows arch to define/use @no_unaligned_warning to possibly warn 1313 about unaligned access emulation going on under the hood. 1314 1315config SYSCTL_ARCH_UNALIGN_ALLOW 1316 bool 1317 help 1318 Enable support for /proc/sys/kernel/unaligned-trap 1319 Allows arches to define/use @unaligned_enabled to runtime toggle 1320 the unaligned access emulation. 1321 see arch/parisc/kernel/unaligned.c for reference 1322 1323config HAVE_PCSPKR_PLATFORM 1324 bool 1325 1326# interpreter that classic socket filters depend on 1327config BPF 1328 bool 1329 1330menuconfig EXPERT 1331 bool "Configure standard kernel features (expert users)" 1332 # Unhide debug options, to make the on-by-default options visible 1333 select DEBUG_KERNEL 1334 help 1335 This option allows certain base kernel options and settings 1336 to be disabled or tweaked. This is for specialized 1337 environments which can tolerate a "non-standard" kernel. 1338 Only use this if you really know what you are doing. 1339 1340config UID16 1341 bool "Enable 16-bit UID system calls" if EXPERT 1342 depends on HAVE_UID16 && MULTIUSER 1343 default y 1344 help 1345 This enables the legacy 16-bit UID syscall wrappers. 1346 1347config MULTIUSER 1348 bool "Multiple users, groups and capabilities support" if EXPERT 1349 default y 1350 help 1351 This option enables support for non-root users, groups and 1352 capabilities. 1353 1354 If you say N here, all processes will run with UID 0, GID 0, and all 1355 possible capabilities. Saying N here also compiles out support for 1356 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1357 setgid, and capset. 1358 1359 If unsure, say Y here. 1360 1361config SGETMASK_SYSCALL 1362 bool "sgetmask/ssetmask syscalls support" if EXPERT 1363 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1364 ---help--- 1365 sys_sgetmask and sys_ssetmask are obsolete system calls 1366 no longer supported in libc but still enabled by default in some 1367 architectures. 1368 1369 If unsure, leave the default option here. 1370 1371config SYSFS_SYSCALL 1372 bool "Sysfs syscall support" if EXPERT 1373 default y 1374 ---help--- 1375 sys_sysfs is an obsolete system call no longer supported in libc. 1376 Note that disabling this option is more secure but might break 1377 compatibility with some systems. 1378 1379 If unsure say Y here. 1380 1381config FHANDLE 1382 bool "open by fhandle syscalls" if EXPERT 1383 select EXPORTFS 1384 default y 1385 help 1386 If you say Y here, a user level program will be able to map 1387 file names to handle and then later use the handle for 1388 different file system operations. This is useful in implementing 1389 userspace file servers, which now track files using handles instead 1390 of names. The handle would remain the same even if file names 1391 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1392 syscalls. 1393 1394config POSIX_TIMERS 1395 bool "Posix Clocks & timers" if EXPERT 1396 default y 1397 help 1398 This includes native support for POSIX timers to the kernel. 1399 Some embedded systems have no use for them and therefore they 1400 can be configured out to reduce the size of the kernel image. 1401 1402 When this option is disabled, the following syscalls won't be 1403 available: timer_create, timer_gettime: timer_getoverrun, 1404 timer_settime, timer_delete, clock_adjtime, getitimer, 1405 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1406 clock_getres and clock_nanosleep syscalls will be limited to 1407 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1408 1409 If unsure say y. 1410 1411config PRINTK 1412 default y 1413 bool "Enable support for printk" if EXPERT 1414 select IRQ_WORK 1415 help 1416 This option enables normal printk support. Removing it 1417 eliminates most of the message strings from the kernel image 1418 and makes the kernel more or less silent. As this makes it 1419 very difficult to diagnose system problems, saying N here is 1420 strongly discouraged. 1421 1422config PRINTK_NMI 1423 def_bool y 1424 depends on PRINTK 1425 depends on HAVE_NMI 1426 1427config BUG 1428 bool "BUG() support" if EXPERT 1429 default y 1430 help 1431 Disabling this option eliminates support for BUG and WARN, reducing 1432 the size of your kernel image and potentially quietly ignoring 1433 numerous fatal conditions. You should only consider disabling this 1434 option for embedded systems with no facilities for reporting errors. 1435 Just say Y. 1436 1437config ELF_CORE 1438 depends on COREDUMP 1439 default y 1440 bool "Enable ELF core dumps" if EXPERT 1441 help 1442 Enable support for generating core dumps. Disabling saves about 4k. 1443 1444 1445config PCSPKR_PLATFORM 1446 bool "Enable PC-Speaker support" if EXPERT 1447 depends on HAVE_PCSPKR_PLATFORM 1448 select I8253_LOCK 1449 default y 1450 help 1451 This option allows to disable the internal PC-Speaker 1452 support, saving some memory. 1453 1454config BASE_FULL 1455 default y 1456 bool "Enable full-sized data structures for core" if EXPERT 1457 help 1458 Disabling this option reduces the size of miscellaneous core 1459 kernel data structures. This saves memory on small machines, 1460 but may reduce performance. 1461 1462config FUTEX 1463 bool "Enable futex support" if EXPERT 1464 default y 1465 imply RT_MUTEXES 1466 help 1467 Disabling this option will cause the kernel to be built without 1468 support for "fast userspace mutexes". The resulting kernel may not 1469 run glibc-based applications correctly. 1470 1471config FUTEX_PI 1472 bool 1473 depends on FUTEX && RT_MUTEXES 1474 default y 1475 1476config HAVE_FUTEX_CMPXCHG 1477 bool 1478 depends on FUTEX 1479 help 1480 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1481 is implemented and always working. This removes a couple of runtime 1482 checks. 1483 1484config EPOLL 1485 bool "Enable eventpoll support" if EXPERT 1486 default y 1487 help 1488 Disabling this option will cause the kernel to be built without 1489 support for epoll family of system calls. 1490 1491config SIGNALFD 1492 bool "Enable signalfd() system call" if EXPERT 1493 default y 1494 help 1495 Enable the signalfd() system call that allows to receive signals 1496 on a file descriptor. 1497 1498 If unsure, say Y. 1499 1500config TIMERFD 1501 bool "Enable timerfd() system call" if EXPERT 1502 default y 1503 help 1504 Enable the timerfd() system call that allows to receive timer 1505 events on a file descriptor. 1506 1507 If unsure, say Y. 1508 1509config EVENTFD 1510 bool "Enable eventfd() system call" if EXPERT 1511 default y 1512 help 1513 Enable the eventfd() system call that allows to receive both 1514 kernel notification (ie. KAIO) or userspace notifications. 1515 1516 If unsure, say Y. 1517 1518config SHMEM 1519 bool "Use full shmem filesystem" if EXPERT 1520 default y 1521 depends on MMU 1522 help 1523 The shmem is an internal filesystem used to manage shared memory. 1524 It is backed by swap and manages resource limits. It is also exported 1525 to userspace as tmpfs if TMPFS is enabled. Disabling this 1526 option replaces shmem and tmpfs with the much simpler ramfs code, 1527 which may be appropriate on small systems without swap. 1528 1529config AIO 1530 bool "Enable AIO support" if EXPERT 1531 default y 1532 help 1533 This option enables POSIX asynchronous I/O which may by used 1534 by some high performance threaded applications. Disabling 1535 this option saves about 7k. 1536 1537config IO_URING 1538 bool "Enable IO uring support" if EXPERT 1539 select IO_WQ 1540 default y 1541 help 1542 This option enables support for the io_uring interface, enabling 1543 applications to submit and complete IO through submission and 1544 completion rings that are shared between the kernel and application. 1545 1546config ADVISE_SYSCALLS 1547 bool "Enable madvise/fadvise syscalls" if EXPERT 1548 default y 1549 help 1550 This option enables the madvise and fadvise syscalls, used by 1551 applications to advise the kernel about their future memory or file 1552 usage, improving performance. If building an embedded system where no 1553 applications use these syscalls, you can disable this option to save 1554 space. 1555 1556config HAVE_ARCH_USERFAULTFD_WP 1557 bool 1558 help 1559 Arch has userfaultfd write protection support 1560 1561config MEMBARRIER 1562 bool "Enable membarrier() system call" if EXPERT 1563 default y 1564 help 1565 Enable the membarrier() system call that allows issuing memory 1566 barriers across all running threads, which can be used to distribute 1567 the cost of user-space memory barriers asymmetrically by transforming 1568 pairs of memory barriers into pairs consisting of membarrier() and a 1569 compiler barrier. 1570 1571 If unsure, say Y. 1572 1573config KALLSYMS 1574 bool "Load all symbols for debugging/ksymoops" if EXPERT 1575 default y 1576 help 1577 Say Y here to let the kernel print out symbolic crash information and 1578 symbolic stack backtraces. This increases the size of the kernel 1579 somewhat, as all symbols have to be loaded into the kernel image. 1580 1581config KALLSYMS_ALL 1582 bool "Include all symbols in kallsyms" 1583 depends on DEBUG_KERNEL && KALLSYMS 1584 help 1585 Normally kallsyms only contains the symbols of functions for nicer 1586 OOPS messages and backtraces (i.e., symbols from the text and inittext 1587 sections). This is sufficient for most cases. And only in very rare 1588 cases (e.g., when a debugger is used) all symbols are required (e.g., 1589 names of variables from the data sections, etc). 1590 1591 This option makes sure that all symbols are loaded into the kernel 1592 image (i.e., symbols from all sections) in cost of increased kernel 1593 size (depending on the kernel configuration, it may be 300KiB or 1594 something like this). 1595 1596 Say N unless you really need all symbols. 1597 1598config KALLSYMS_ABSOLUTE_PERCPU 1599 bool 1600 depends on KALLSYMS 1601 default X86_64 && SMP 1602 1603config KALLSYMS_BASE_RELATIVE 1604 bool 1605 depends on KALLSYMS 1606 default !IA64 1607 help 1608 Instead of emitting them as absolute values in the native word size, 1609 emit the symbol references in the kallsyms table as 32-bit entries, 1610 each containing a relative value in the range [base, base + U32_MAX] 1611 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1612 an absolute value in the range [0, S32_MAX] or a relative value in the 1613 range [base, base + S32_MAX], where base is the lowest relative symbol 1614 address encountered in the image. 1615 1616 On 64-bit builds, this reduces the size of the address table by 50%, 1617 but more importantly, it results in entries whose values are build 1618 time constants, and no relocation pass is required at runtime to fix 1619 up the entries based on the runtime load address of the kernel. 1620 1621# end of the "standard kernel features (expert users)" menu 1622 1623# syscall, maps, verifier 1624 1625config BPF_LSM 1626 bool "LSM Instrumentation with BPF" 1627 depends on BPF_EVENTS 1628 depends on BPF_SYSCALL 1629 depends on SECURITY 1630 depends on BPF_JIT 1631 help 1632 Enables instrumentation of the security hooks with eBPF programs for 1633 implementing dynamic MAC and Audit Policies. 1634 1635 If you are unsure how to answer this question, answer N. 1636 1637config BPF_SYSCALL 1638 bool "Enable bpf() system call" 1639 select BPF 1640 select IRQ_WORK 1641 default n 1642 help 1643 Enable the bpf() system call that allows to manipulate eBPF 1644 programs and maps via file descriptors. 1645 1646config ARCH_WANT_DEFAULT_BPF_JIT 1647 bool 1648 1649config BPF_JIT_ALWAYS_ON 1650 bool "Permanently enable BPF JIT and remove BPF interpreter" 1651 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1652 help 1653 Enables BPF JIT and removes BPF interpreter to avoid 1654 speculative execution of BPF instructions by the interpreter 1655 1656config BPF_JIT_DEFAULT_ON 1657 def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON 1658 depends on HAVE_EBPF_JIT && BPF_JIT 1659 1660config USERFAULTFD 1661 bool "Enable userfaultfd() system call" 1662 depends on MMU 1663 help 1664 Enable the userfaultfd() system call that allows to intercept and 1665 handle page faults in userland. 1666 1667config ARCH_HAS_MEMBARRIER_CALLBACKS 1668 bool 1669 1670config ARCH_HAS_MEMBARRIER_SYNC_CORE 1671 bool 1672 1673config RSEQ 1674 bool "Enable rseq() system call" if EXPERT 1675 default y 1676 depends on HAVE_RSEQ 1677 select MEMBARRIER 1678 help 1679 Enable the restartable sequences system call. It provides a 1680 user-space cache for the current CPU number value, which 1681 speeds up getting the current CPU number from user-space, 1682 as well as an ABI to speed up user-space operations on 1683 per-CPU data. 1684 1685 If unsure, say Y. 1686 1687config DEBUG_RSEQ 1688 default n 1689 bool "Enabled debugging of rseq() system call" if EXPERT 1690 depends on RSEQ && DEBUG_KERNEL 1691 help 1692 Enable extra debugging checks for the rseq system call. 1693 1694 If unsure, say N. 1695 1696config EMBEDDED 1697 bool "Embedded system" 1698 option allnoconfig_y 1699 select EXPERT 1700 help 1701 This option should be enabled if compiling the kernel for 1702 an embedded system so certain expert options are available 1703 for configuration. 1704 1705config HAVE_PERF_EVENTS 1706 bool 1707 help 1708 See tools/perf/design.txt for details. 1709 1710config PERF_USE_VMALLOC 1711 bool 1712 help 1713 See tools/perf/design.txt for details 1714 1715config PC104 1716 bool "PC/104 support" if EXPERT 1717 help 1718 Expose PC/104 form factor device drivers and options available for 1719 selection and configuration. Enable this option if your target 1720 machine has a PC/104 bus. 1721 1722menu "Kernel Performance Events And Counters" 1723 1724config PERF_EVENTS 1725 bool "Kernel performance events and counters" 1726 default y if PROFILING 1727 depends on HAVE_PERF_EVENTS 1728 select IRQ_WORK 1729 select SRCU 1730 help 1731 Enable kernel support for various performance events provided 1732 by software and hardware. 1733 1734 Software events are supported either built-in or via the 1735 use of generic tracepoints. 1736 1737 Most modern CPUs support performance events via performance 1738 counter registers. These registers count the number of certain 1739 types of hw events: such as instructions executed, cachemisses 1740 suffered, or branches mis-predicted - without slowing down the 1741 kernel or applications. These registers can also trigger interrupts 1742 when a threshold number of events have passed - and can thus be 1743 used to profile the code that runs on that CPU. 1744 1745 The Linux Performance Event subsystem provides an abstraction of 1746 these software and hardware event capabilities, available via a 1747 system call and used by the "perf" utility in tools/perf/. It 1748 provides per task and per CPU counters, and it provides event 1749 capabilities on top of those. 1750 1751 Say Y if unsure. 1752 1753config DEBUG_PERF_USE_VMALLOC 1754 default n 1755 bool "Debug: use vmalloc to back perf mmap() buffers" 1756 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1757 select PERF_USE_VMALLOC 1758 help 1759 Use vmalloc memory to back perf mmap() buffers. 1760 1761 Mostly useful for debugging the vmalloc code on platforms 1762 that don't require it. 1763 1764 Say N if unsure. 1765 1766endmenu 1767 1768config VM_EVENT_COUNTERS 1769 default y 1770 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1771 help 1772 VM event counters are needed for event counts to be shown. 1773 This option allows the disabling of the VM event counters 1774 on EXPERT systems. /proc/vmstat will only show page counts 1775 if VM event counters are disabled. 1776 1777config SLUB_DEBUG 1778 default y 1779 bool "Enable SLUB debugging support" if EXPERT 1780 depends on SLUB && SYSFS 1781 help 1782 SLUB has extensive debug support features. Disabling these can 1783 result in significant savings in code size. This also disables 1784 SLUB sysfs support. /sys/slab will not exist and there will be 1785 no support for cache validation etc. 1786 1787config SLUB_MEMCG_SYSFS_ON 1788 default n 1789 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1790 depends on SLUB && SYSFS && MEMCG 1791 help 1792 SLUB creates a directory under /sys/kernel/slab for each 1793 allocation cache to host info and debug files. If memory 1794 cgroup is enabled, each cache can have per memory cgroup 1795 caches. SLUB can create the same sysfs directories for these 1796 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1797 to a very high number of debug files being created. This is 1798 controlled by slub_memcg_sysfs boot parameter and this 1799 config option determines the parameter's default value. 1800 1801config COMPAT_BRK 1802 bool "Disable heap randomization" 1803 default y 1804 help 1805 Randomizing heap placement makes heap exploits harder, but it 1806 also breaks ancient binaries (including anything libc5 based). 1807 This option changes the bootup default to heap randomization 1808 disabled, and can be overridden at runtime by setting 1809 /proc/sys/kernel/randomize_va_space to 2. 1810 1811 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1812 1813choice 1814 prompt "Choose SLAB allocator" 1815 default SLUB 1816 help 1817 This option allows to select a slab allocator. 1818 1819config SLAB 1820 bool "SLAB" 1821 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1822 help 1823 The regular slab allocator that is established and known to work 1824 well in all environments. It organizes cache hot objects in 1825 per cpu and per node queues. 1826 1827config SLUB 1828 bool "SLUB (Unqueued Allocator)" 1829 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1830 help 1831 SLUB is a slab allocator that minimizes cache line usage 1832 instead of managing queues of cached objects (SLAB approach). 1833 Per cpu caching is realized using slabs of objects instead 1834 of queues of objects. SLUB can use memory efficiently 1835 and has enhanced diagnostics. SLUB is the default choice for 1836 a slab allocator. 1837 1838config SLOB 1839 depends on EXPERT 1840 bool "SLOB (Simple Allocator)" 1841 help 1842 SLOB replaces the stock allocator with a drastically simpler 1843 allocator. SLOB is generally more space efficient but 1844 does not perform as well on large systems. 1845 1846endchoice 1847 1848config SLAB_MERGE_DEFAULT 1849 bool "Allow slab caches to be merged" 1850 default y 1851 help 1852 For reduced kernel memory fragmentation, slab caches can be 1853 merged when they share the same size and other characteristics. 1854 This carries a risk of kernel heap overflows being able to 1855 overwrite objects from merged caches (and more easily control 1856 cache layout), which makes such heap attacks easier to exploit 1857 by attackers. By keeping caches unmerged, these kinds of exploits 1858 can usually only damage objects in the same cache. To disable 1859 merging at runtime, "slab_nomerge" can be passed on the kernel 1860 command line. 1861 1862config SLAB_FREELIST_RANDOM 1863 default n 1864 depends on SLAB || SLUB 1865 bool "SLAB freelist randomization" 1866 help 1867 Randomizes the freelist order used on creating new pages. This 1868 security feature reduces the predictability of the kernel slab 1869 allocator against heap overflows. 1870 1871config SLAB_FREELIST_HARDENED 1872 bool "Harden slab freelist metadata" 1873 depends on SLUB 1874 help 1875 Many kernel heap attacks try to target slab cache metadata and 1876 other infrastructure. This options makes minor performance 1877 sacrifices to harden the kernel slab allocator against common 1878 freelist exploit methods. 1879 1880config SHUFFLE_PAGE_ALLOCATOR 1881 bool "Page allocator randomization" 1882 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1883 help 1884 Randomization of the page allocator improves the average 1885 utilization of a direct-mapped memory-side-cache. See section 1886 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1887 6.2a specification for an example of how a platform advertises 1888 the presence of a memory-side-cache. There are also incidental 1889 security benefits as it reduces the predictability of page 1890 allocations to compliment SLAB_FREELIST_RANDOM, but the 1891 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1892 10th order of pages is selected based on cache utilization 1893 benefits on x86. 1894 1895 While the randomization improves cache utilization it may 1896 negatively impact workloads on platforms without a cache. For 1897 this reason, by default, the randomization is enabled only 1898 after runtime detection of a direct-mapped memory-side-cache. 1899 Otherwise, the randomization may be force enabled with the 1900 'page_alloc.shuffle' kernel command line parameter. 1901 1902 Say Y if unsure. 1903 1904config SLUB_CPU_PARTIAL 1905 default y 1906 depends on SLUB && SMP 1907 bool "SLUB per cpu partial cache" 1908 help 1909 Per cpu partial caches accelerate objects allocation and freeing 1910 that is local to a processor at the price of more indeterminism 1911 in the latency of the free. On overflow these caches will be cleared 1912 which requires the taking of locks that may cause latency spikes. 1913 Typically one would choose no for a realtime system. 1914 1915config MMAP_ALLOW_UNINITIALIZED 1916 bool "Allow mmapped anonymous memory to be uninitialized" 1917 depends on EXPERT && !MMU 1918 default n 1919 help 1920 Normally, and according to the Linux spec, anonymous memory obtained 1921 from mmap() has its contents cleared before it is passed to 1922 userspace. Enabling this config option allows you to request that 1923 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1924 providing a huge performance boost. If this option is not enabled, 1925 then the flag will be ignored. 1926 1927 This is taken advantage of by uClibc's malloc(), and also by 1928 ELF-FDPIC binfmt's brk and stack allocator. 1929 1930 Because of the obvious security issues, this option should only be 1931 enabled on embedded devices where you control what is run in 1932 userspace. Since that isn't generally a problem on no-MMU systems, 1933 it is normally safe to say Y here. 1934 1935 See Documentation/nommu-mmap.txt for more information. 1936 1937config SYSTEM_DATA_VERIFICATION 1938 def_bool n 1939 select SYSTEM_TRUSTED_KEYRING 1940 select KEYS 1941 select CRYPTO 1942 select CRYPTO_RSA 1943 select ASYMMETRIC_KEY_TYPE 1944 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1945 select ASN1 1946 select OID_REGISTRY 1947 select X509_CERTIFICATE_PARSER 1948 select PKCS7_MESSAGE_PARSER 1949 help 1950 Provide PKCS#7 message verification using the contents of the system 1951 trusted keyring to provide public keys. This then can be used for 1952 module verification, kexec image verification and firmware blob 1953 verification. 1954 1955config PROFILING 1956 bool "Profiling support" 1957 help 1958 Say Y here to enable the extended profiling support mechanisms used 1959 by profilers such as OProfile. 1960 1961# 1962# Place an empty function call at each tracepoint site. Can be 1963# dynamically changed for a probe function. 1964# 1965config TRACEPOINTS 1966 bool 1967 1968endmenu # General setup 1969 1970source "arch/Kconfig" 1971 1972config RT_MUTEXES 1973 bool 1974 1975config BASE_SMALL 1976 int 1977 default 0 if BASE_FULL 1978 default 1 if !BASE_FULL 1979 1980config MODULE_SIG_FORMAT 1981 def_bool n 1982 select SYSTEM_DATA_VERIFICATION 1983 1984menuconfig MODULES 1985 bool "Enable loadable module support" 1986 option modules 1987 help 1988 Kernel modules are small pieces of compiled code which can 1989 be inserted in the running kernel, rather than being 1990 permanently built into the kernel. You use the "modprobe" 1991 tool to add (and sometimes remove) them. If you say Y here, 1992 many parts of the kernel can be built as modules (by 1993 answering M instead of Y where indicated): this is most 1994 useful for infrequently used options which are not required 1995 for booting. For more information, see the man pages for 1996 modprobe, lsmod, modinfo, insmod and rmmod. 1997 1998 If you say Y here, you will need to run "make 1999 modules_install" to put the modules under /lib/modules/ 2000 where modprobe can find them (you may need to be root to do 2001 this). 2002 2003 If unsure, say Y. 2004 2005if MODULES 2006 2007config MODULE_FORCE_LOAD 2008 bool "Forced module loading" 2009 default n 2010 help 2011 Allow loading of modules without version information (ie. modprobe 2012 --force). Forced module loading sets the 'F' (forced) taint flag and 2013 is usually a really bad idea. 2014 2015config MODULE_UNLOAD 2016 bool "Module unloading" 2017 help 2018 Without this option you will not be able to unload any 2019 modules (note that some modules may not be unloadable 2020 anyway), which makes your kernel smaller, faster 2021 and simpler. If unsure, say Y. 2022 2023config MODULE_FORCE_UNLOAD 2024 bool "Forced module unloading" 2025 depends on MODULE_UNLOAD 2026 help 2027 This option allows you to force a module to unload, even if the 2028 kernel believes it is unsafe: the kernel will remove the module 2029 without waiting for anyone to stop using it (using the -f option to 2030 rmmod). This is mainly for kernel developers and desperate users. 2031 If unsure, say N. 2032 2033config MODVERSIONS 2034 bool "Module versioning support" 2035 help 2036 Usually, you have to use modules compiled with your kernel. 2037 Saying Y here makes it sometimes possible to use modules 2038 compiled for different kernels, by adding enough information 2039 to the modules to (hopefully) spot any changes which would 2040 make them incompatible with the kernel you are running. If 2041 unsure, say N. 2042 2043config ASM_MODVERSIONS 2044 bool 2045 default HAVE_ASM_MODVERSIONS && MODVERSIONS 2046 help 2047 This enables module versioning for exported symbols also from 2048 assembly. This can be enabled only when the target architecture 2049 supports it. 2050 2051config MODULE_REL_CRCS 2052 bool 2053 depends on MODVERSIONS 2054 2055config MODULE_SRCVERSION_ALL 2056 bool "Source checksum for all modules" 2057 help 2058 Modules which contain a MODULE_VERSION get an extra "srcversion" 2059 field inserted into their modinfo section, which contains a 2060 sum of the source files which made it. This helps maintainers 2061 see exactly which source was used to build a module (since 2062 others sometimes change the module source without updating 2063 the version). With this option, such a "srcversion" field 2064 will be created for all modules. If unsure, say N. 2065 2066config MODULE_SIG 2067 bool "Module signature verification" 2068 select MODULE_SIG_FORMAT 2069 help 2070 Check modules for valid signatures upon load: the signature 2071 is simply appended to the module. For more information see 2072 <file:Documentation/admin-guide/module-signing.rst>. 2073 2074 Note that this option adds the OpenSSL development packages as a 2075 kernel build dependency so that the signing tool can use its crypto 2076 library. 2077 2078 You should enable this option if you wish to use either 2079 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via 2080 another LSM - otherwise unsigned modules will be loadable regardless 2081 of the lockdown policy. 2082 2083 !!!WARNING!!! If you enable this option, you MUST make sure that the 2084 module DOES NOT get stripped after being signed. This includes the 2085 debuginfo strip done by some packagers (such as rpmbuild) and 2086 inclusion into an initramfs that wants the module size reduced. 2087 2088config MODULE_SIG_FORCE 2089 bool "Require modules to be validly signed" 2090 depends on MODULE_SIG 2091 help 2092 Reject unsigned modules or signed modules for which we don't have a 2093 key. Without this, such modules will simply taint the kernel. 2094 2095config MODULE_SIG_ALL 2096 bool "Automatically sign all modules" 2097 default y 2098 depends on MODULE_SIG 2099 help 2100 Sign all modules during make modules_install. Without this option, 2101 modules must be signed manually, using the scripts/sign-file tool. 2102 2103comment "Do not forget to sign required modules with scripts/sign-file" 2104 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2105 2106choice 2107 prompt "Which hash algorithm should modules be signed with?" 2108 depends on MODULE_SIG 2109 help 2110 This determines which sort of hashing algorithm will be used during 2111 signature generation. This algorithm _must_ be built into the kernel 2112 directly so that signature verification can take place. It is not 2113 possible to load a signed module containing the algorithm to check 2114 the signature on that module. 2115 2116config MODULE_SIG_SHA1 2117 bool "Sign modules with SHA-1" 2118 select CRYPTO_SHA1 2119 2120config MODULE_SIG_SHA224 2121 bool "Sign modules with SHA-224" 2122 select CRYPTO_SHA256 2123 2124config MODULE_SIG_SHA256 2125 bool "Sign modules with SHA-256" 2126 select CRYPTO_SHA256 2127 2128config MODULE_SIG_SHA384 2129 bool "Sign modules with SHA-384" 2130 select CRYPTO_SHA512 2131 2132config MODULE_SIG_SHA512 2133 bool "Sign modules with SHA-512" 2134 select CRYPTO_SHA512 2135 2136endchoice 2137 2138config MODULE_SIG_HASH 2139 string 2140 depends on MODULE_SIG 2141 default "sha1" if MODULE_SIG_SHA1 2142 default "sha224" if MODULE_SIG_SHA224 2143 default "sha256" if MODULE_SIG_SHA256 2144 default "sha384" if MODULE_SIG_SHA384 2145 default "sha512" if MODULE_SIG_SHA512 2146 2147config MODULE_COMPRESS 2148 bool "Compress modules on installation" 2149 help 2150 2151 Compresses kernel modules when 'make modules_install' is run; gzip or 2152 xz depending on "Compression algorithm" below. 2153 2154 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 2155 2156 Out-of-tree kernel modules installed using Kbuild will also be 2157 compressed upon installation. 2158 2159 Note: for modules inside an initrd or initramfs, it's more efficient 2160 to compress the whole initrd or initramfs instead. 2161 2162 Note: This is fully compatible with signed modules. 2163 2164 If in doubt, say N. 2165 2166choice 2167 prompt "Compression algorithm" 2168 depends on MODULE_COMPRESS 2169 default MODULE_COMPRESS_GZIP 2170 help 2171 This determines which sort of compression will be used during 2172 'make modules_install'. 2173 2174 GZIP (default) and XZ are supported. 2175 2176config MODULE_COMPRESS_GZIP 2177 bool "GZIP" 2178 2179config MODULE_COMPRESS_XZ 2180 bool "XZ" 2181 2182endchoice 2183 2184config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS 2185 bool "Allow loading of modules with missing namespace imports" 2186 help 2187 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in 2188 a namespace. A module that makes use of a symbol exported with such a 2189 namespace is required to import the namespace via MODULE_IMPORT_NS(). 2190 There is no technical reason to enforce correct namespace imports, 2191 but it creates consistency between symbols defining namespaces and 2192 users importing namespaces they make use of. This option relaxes this 2193 requirement and lifts the enforcement when loading a module. 2194 2195 If unsure, say N. 2196 2197config UNUSED_SYMBOLS 2198 bool "Enable unused/obsolete exported symbols" 2199 default y if X86 2200 help 2201 Unused but exported symbols make the kernel needlessly bigger. For 2202 that reason most of these unused exports will soon be removed. This 2203 option is provided temporarily to provide a transition period in case 2204 some external kernel module needs one of these symbols anyway. If you 2205 encounter such a case in your module, consider if you are actually 2206 using the right API. (rationale: since nobody in the kernel is using 2207 this in a module, there is a pretty good chance it's actually the 2208 wrong interface to use). If you really need the symbol, please send a 2209 mail to the linux kernel mailing list mentioning the symbol and why 2210 you really need it, and what the merge plan to the mainline kernel for 2211 your module is. 2212 2213config TRIM_UNUSED_KSYMS 2214 bool "Trim unused exported kernel symbols" 2215 depends on !UNUSED_SYMBOLS 2216 help 2217 The kernel and some modules make many symbols available for 2218 other modules to use via EXPORT_SYMBOL() and variants. Depending 2219 on the set of modules being selected in your kernel configuration, 2220 many of those exported symbols might never be used. 2221 2222 This option allows for unused exported symbols to be dropped from 2223 the build. In turn, this provides the compiler more opportunities 2224 (especially when using LTO) for optimizing the code and reducing 2225 binary size. This might have some security advantages as well. 2226 2227 If unsure, or if you need to build out-of-tree modules, say N. 2228 2229config UNUSED_KSYMS_WHITELIST 2230 string "Whitelist of symbols to keep in ksymtab" 2231 depends on TRIM_UNUSED_KSYMS 2232 help 2233 By default, all unused exported symbols will be un-exported from the 2234 build when TRIM_UNUSED_KSYMS is selected. 2235 2236 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept 2237 exported at all times, even in absence of in-tree users. The value to 2238 set here is the path to a text file containing the list of symbols, 2239 one per line. The path can be absolute, or relative to the kernel 2240 source tree. 2241 2242endif # MODULES 2243 2244config MODULES_TREE_LOOKUP 2245 def_bool y 2246 depends on PERF_EVENTS || TRACING 2247 2248config INIT_ALL_POSSIBLE 2249 bool 2250 help 2251 Back when each arch used to define their own cpu_online_mask and 2252 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2253 with all 1s, and others with all 0s. When they were centralised, 2254 it was better to provide this option than to break all the archs 2255 and have several arch maintainers pursuing me down dark alleys. 2256 2257source "block/Kconfig" 2258 2259config PREEMPT_NOTIFIERS 2260 bool 2261 2262config PADATA 2263 depends on SMP 2264 bool 2265 2266config ASN1 2267 tristate 2268 help 2269 Build a simple ASN.1 grammar compiler that produces a bytecode output 2270 that can be interpreted by the ASN.1 stream decoder and used to 2271 inform it as to what tags are to be expected in a stream and what 2272 functions to call on what tags. 2273 2274source "kernel/Kconfig.locks" 2275 2276config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 2277 bool 2278 2279config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2280 bool 2281 2282# It may be useful for an architecture to override the definitions of the 2283# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2284# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2285# different calling convention for syscalls. They can also override the 2286# macros for not-implemented syscalls in kernel/sys_ni.c and 2287# kernel/time/posix-stubs.c. All these overrides need to be available in 2288# <asm/syscall_wrapper.h>. 2289config ARCH_HAS_SYSCALL_WRAPPER 2290 def_bool n 2291