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