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_VERSION_TEXT 12 string 13 default "$(CC_VERSION_TEXT)" 14 help 15 This is used in unclear ways: 16 17 - Re-run Kconfig when the compiler is updated 18 The 'default' property references the environment variable, 19 CC_VERSION_TEXT so it is recorded in include/config/auto.conf.cmd. 20 When the compiler is updated, Kconfig will be invoked. 21 22 - Ensure full rebuild when the compier is updated 23 include/linux/kconfig.h contains this option in the comment line so 24 fixdep adds include/config/cc/version/text.h into the auto-generated 25 dependency. When the compiler is updated, syncconfig will touch it 26 and then every file will be rebuilt. 27 28config CC_IS_GCC 29 def_bool $(success,echo "$(CC_VERSION_TEXT)" | grep -q gcc) 30 31config GCC_VERSION 32 int 33 default $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) if CC_IS_GCC 34 default 0 35 36config LD_VERSION 37 int 38 default $(shell,$(LD) --version | $(srctree)/scripts/ld-version.sh) 39 40config CC_IS_CLANG 41 def_bool $(success,echo "$(CC_VERSION_TEXT)" | grep -q clang) 42 43config CLANG_VERSION 44 int 45 default $(shell,$(srctree)/scripts/clang-version.sh $(CC)) 46 47config CC_CAN_LINK 48 bool 49 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(m64-flag)) if 64BIT 50 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(m32-flag)) 51 52config CC_CAN_LINK_STATIC 53 bool 54 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) -static $(m64-flag)) if 64BIT 55 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) -static $(m32-flag)) 56 57config CC_HAS_ASM_GOTO 58 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) 59 60config TOOLS_SUPPORT_RELR 61 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 62 63config CC_HAS_ASM_INLINE 64 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 65 66config CONSTRUCTORS 67 bool 68 depends on !UML 69 70config IRQ_WORK 71 bool 72 73config BUILDTIME_TABLE_SORT 74 bool 75 76config THREAD_INFO_IN_TASK 77 bool 78 help 79 Select this to move thread_info off the stack into task_struct. To 80 make this work, an arch will need to remove all thread_info fields 81 except flags and fix any runtime bugs. 82 83 One subtle change that will be needed is to use try_get_task_stack() 84 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 85 86menu "General setup" 87 88config BROKEN 89 bool 90 91config BROKEN_ON_SMP 92 bool 93 depends on BROKEN || !SMP 94 default y 95 96config INIT_ENV_ARG_LIMIT 97 int 98 default 32 if !UML 99 default 128 if UML 100 help 101 Maximum of each of the number of arguments and environment 102 variables passed to init from the kernel command line. 103 104config COMPILE_TEST 105 bool "Compile also drivers which will not load" 106 depends on !UML 107 default n 108 help 109 Some drivers can be compiled on a different platform than they are 110 intended to be run on. Despite they cannot be loaded there (or even 111 when they load they cannot be used due to missing HW support), 112 developers still, opposing to distributors, might want to build such 113 drivers to compile-test them. 114 115 If you are a developer and want to build everything available, say Y 116 here. If you are a user/distributor, say N here to exclude useless 117 drivers to be distributed. 118 119config UAPI_HEADER_TEST 120 bool "Compile test UAPI headers" 121 depends on HEADERS_INSTALL && CC_CAN_LINK 122 help 123 Compile test headers exported to user-space to ensure they are 124 self-contained, i.e. compilable as standalone units. 125 126 If you are a developer or tester and want to ensure the exported 127 headers are self-contained, say Y here. Otherwise, choose N. 128 129config LOCALVERSION 130 string "Local version - append to kernel release" 131 help 132 Append an extra string to the end of your kernel version. 133 This will show up when you type uname, for example. 134 The string you set here will be appended after the contents of 135 any files with a filename matching localversion* in your 136 object and source tree, in that order. Your total string can 137 be a maximum of 64 characters. 138 139config LOCALVERSION_AUTO 140 bool "Automatically append version information to the version string" 141 default y 142 depends on !COMPILE_TEST 143 help 144 This will try to automatically determine if the current tree is a 145 release tree by looking for git tags that belong to the current 146 top of tree revision. 147 148 A string of the format -gxxxxxxxx will be added to the localversion 149 if a git-based tree is found. The string generated by this will be 150 appended after any matching localversion* files, and after the value 151 set in CONFIG_LOCALVERSION. 152 153 (The actual string used here is the first eight characters produced 154 by running the command: 155 156 $ git rev-parse --verify HEAD 157 158 which is done within the script "scripts/setlocalversion".) 159 160config BUILD_SALT 161 string "Build ID Salt" 162 default "" 163 help 164 The build ID is used to link binaries and their debug info. Setting 165 this option will use the value in the calculation of the build id. 166 This is mostly useful for distributions which want to ensure the 167 build is unique between builds. It's safe to leave the default. 168 169config HAVE_KERNEL_GZIP 170 bool 171 172config HAVE_KERNEL_BZIP2 173 bool 174 175config HAVE_KERNEL_LZMA 176 bool 177 178config HAVE_KERNEL_XZ 179 bool 180 181config HAVE_KERNEL_LZO 182 bool 183 184config HAVE_KERNEL_LZ4 185 bool 186 187config HAVE_KERNEL_UNCOMPRESSED 188 bool 189 190choice 191 prompt "Kernel compression mode" 192 default KERNEL_GZIP 193 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED 194 help 195 The linux kernel is a kind of self-extracting executable. 196 Several compression algorithms are available, which differ 197 in efficiency, compression and decompression speed. 198 Compression speed is only relevant when building a kernel. 199 Decompression speed is relevant at each boot. 200 201 If you have any problems with bzip2 or lzma compressed 202 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 203 version of this functionality (bzip2 only), for 2.4, was 204 supplied by Christian Ludwig) 205 206 High compression options are mostly useful for users, who 207 are low on disk space (embedded systems), but for whom ram 208 size matters less. 209 210 If in doubt, select 'gzip' 211 212config KERNEL_GZIP 213 bool "Gzip" 214 depends on HAVE_KERNEL_GZIP 215 help 216 The old and tried gzip compression. It provides a good balance 217 between compression ratio and decompression speed. 218 219config KERNEL_BZIP2 220 bool "Bzip2" 221 depends on HAVE_KERNEL_BZIP2 222 help 223 Its compression ratio and speed is intermediate. 224 Decompression speed is slowest among the choices. The kernel 225 size is about 10% smaller with bzip2, in comparison to gzip. 226 Bzip2 uses a large amount of memory. For modern kernels you 227 will need at least 8MB RAM or more for booting. 228 229config KERNEL_LZMA 230 bool "LZMA" 231 depends on HAVE_KERNEL_LZMA 232 help 233 This compression algorithm's ratio is best. Decompression speed 234 is between gzip and bzip2. Compression is slowest. 235 The kernel size is about 33% smaller with LZMA in comparison to gzip. 236 237config KERNEL_XZ 238 bool "XZ" 239 depends on HAVE_KERNEL_XZ 240 help 241 XZ uses the LZMA2 algorithm and instruction set specific 242 BCJ filters which can improve compression ratio of executable 243 code. The size of the kernel is about 30% smaller with XZ in 244 comparison to gzip. On architectures for which there is a BCJ 245 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 246 will create a few percent smaller kernel than plain LZMA. 247 248 The speed is about the same as with LZMA: The decompression 249 speed of XZ is better than that of bzip2 but worse than gzip 250 and LZO. Compression is slow. 251 252config KERNEL_LZO 253 bool "LZO" 254 depends on HAVE_KERNEL_LZO 255 help 256 Its compression ratio is the poorest among the choices. The kernel 257 size is about 10% bigger than gzip; however its speed 258 (both compression and decompression) is the fastest. 259 260config KERNEL_LZ4 261 bool "LZ4" 262 depends on HAVE_KERNEL_LZ4 263 help 264 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 265 A preliminary version of LZ4 de/compression tool is available at 266 <https://code.google.com/p/lz4/>. 267 268 Its compression ratio is worse than LZO. The size of the kernel 269 is about 8% bigger than LZO. But the decompression speed is 270 faster than LZO. 271 272config KERNEL_UNCOMPRESSED 273 bool "None" 274 depends on HAVE_KERNEL_UNCOMPRESSED 275 help 276 Produce uncompressed kernel image. This option is usually not what 277 you want. It is useful for debugging the kernel in slow simulation 278 environments, where decompressing and moving the kernel is awfully 279 slow. This option allows early boot code to skip the decompressor 280 and jump right at uncompressed kernel image. 281 282endchoice 283 284config DEFAULT_HOSTNAME 285 string "Default hostname" 286 default "(none)" 287 help 288 This option determines the default system hostname before userspace 289 calls sethostname(2). The kernel traditionally uses "(none)" here, 290 but you may wish to use a different default here to make a minimal 291 system more usable with less configuration. 292 293# 294# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can 295# add proper SWAP support to them, in which case this can be remove. 296# 297config ARCH_NO_SWAP 298 bool 299 300config SWAP 301 bool "Support for paging of anonymous memory (swap)" 302 depends on MMU && BLOCK && !ARCH_NO_SWAP 303 default y 304 help 305 This option allows you to choose whether you want to have support 306 for so called swap devices or swap files in your kernel that are 307 used to provide more virtual memory than the actual RAM present 308 in your computer. If unsure say Y. 309 310config SYSVIPC 311 bool "System V IPC" 312 ---help--- 313 Inter Process Communication is a suite of library functions and 314 system calls which let processes (running programs) synchronize and 315 exchange information. It is generally considered to be a good thing, 316 and some programs won't run unless you say Y here. In particular, if 317 you want to run the DOS emulator dosemu under Linux (read the 318 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 319 you'll need to say Y here. 320 321 You can find documentation about IPC with "info ipc" and also in 322 section 6.4 of the Linux Programmer's Guide, available from 323 <http://www.tldp.org/guides.html>. 324 325config SYSVIPC_SYSCTL 326 bool 327 depends on SYSVIPC 328 depends on SYSCTL 329 default y 330 331config POSIX_MQUEUE 332 bool "POSIX Message Queues" 333 depends on NET 334 ---help--- 335 POSIX variant of message queues is a part of IPC. In POSIX message 336 queues every message has a priority which decides about succession 337 of receiving it by a process. If you want to compile and run 338 programs written e.g. for Solaris with use of its POSIX message 339 queues (functions mq_*) say Y here. 340 341 POSIX message queues are visible as a filesystem called 'mqueue' 342 and can be mounted somewhere if you want to do filesystem 343 operations on message queues. 344 345 If unsure, say Y. 346 347config POSIX_MQUEUE_SYSCTL 348 bool 349 depends on POSIX_MQUEUE 350 depends on SYSCTL 351 default y 352 353config CROSS_MEMORY_ATTACH 354 bool "Enable process_vm_readv/writev syscalls" 355 depends on MMU 356 default y 357 help 358 Enabling this option adds the system calls process_vm_readv and 359 process_vm_writev which allow a process with the correct privileges 360 to directly read from or write to another process' address space. 361 See the man page for more details. 362 363config USELIB 364 bool "uselib syscall" 365 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION 366 help 367 This option enables the uselib syscall, a system call used in the 368 dynamic linker from libc5 and earlier. glibc does not use this 369 system call. If you intend to run programs built on libc5 or 370 earlier, you may need to enable this syscall. Current systems 371 running glibc can safely disable this. 372 373config AUDIT 374 bool "Auditing support" 375 depends on NET 376 help 377 Enable auditing infrastructure that can be used with another 378 kernel subsystem, such as SELinux (which requires this for 379 logging of avc messages output). System call auditing is included 380 on architectures which support it. 381 382config HAVE_ARCH_AUDITSYSCALL 383 bool 384 385config AUDITSYSCALL 386 def_bool y 387 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 388 select FSNOTIFY 389 390source "kernel/irq/Kconfig" 391source "kernel/time/Kconfig" 392source "kernel/Kconfig.preempt" 393 394menu "CPU/Task time and stats accounting" 395 396config VIRT_CPU_ACCOUNTING 397 bool 398 399choice 400 prompt "Cputime accounting" 401 default TICK_CPU_ACCOUNTING if !PPC64 402 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 403 404# Kind of a stub config for the pure tick based cputime accounting 405config TICK_CPU_ACCOUNTING 406 bool "Simple tick based cputime accounting" 407 depends on !S390 && !NO_HZ_FULL 408 help 409 This is the basic tick based cputime accounting that maintains 410 statistics about user, system and idle time spent on per jiffies 411 granularity. 412 413 If unsure, say Y. 414 415config VIRT_CPU_ACCOUNTING_NATIVE 416 bool "Deterministic task and CPU time accounting" 417 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 418 select VIRT_CPU_ACCOUNTING 419 help 420 Select this option to enable more accurate task and CPU time 421 accounting. This is done by reading a CPU counter on each 422 kernel entry and exit and on transitions within the kernel 423 between system, softirq and hardirq state, so there is a 424 small performance impact. In the case of s390 or IBM POWER > 5, 425 this also enables accounting of stolen time on logically-partitioned 426 systems. 427 428config VIRT_CPU_ACCOUNTING_GEN 429 bool "Full dynticks CPU time accounting" 430 depends on HAVE_CONTEXT_TRACKING 431 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 432 depends on GENERIC_CLOCKEVENTS 433 select VIRT_CPU_ACCOUNTING 434 select CONTEXT_TRACKING 435 help 436 Select this option to enable task and CPU time accounting on full 437 dynticks systems. This accounting is implemented by watching every 438 kernel-user boundaries using the context tracking subsystem. 439 The accounting is thus performed at the expense of some significant 440 overhead. 441 442 For now this is only useful if you are working on the full 443 dynticks subsystem development. 444 445 If unsure, say N. 446 447endchoice 448 449config IRQ_TIME_ACCOUNTING 450 bool "Fine granularity task level IRQ time accounting" 451 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 452 help 453 Select this option to enable fine granularity task irq time 454 accounting. This is done by reading a timestamp on each 455 transitions between softirq and hardirq state, so there can be a 456 small performance impact. 457 458 If in doubt, say N here. 459 460config HAVE_SCHED_AVG_IRQ 461 def_bool y 462 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 463 depends on SMP 464 465config SCHED_THERMAL_PRESSURE 466 bool "Enable periodic averaging of thermal pressure" 467 depends on SMP 468 469config BSD_PROCESS_ACCT 470 bool "BSD Process Accounting" 471 depends on MULTIUSER 472 help 473 If you say Y here, a user level program will be able to instruct the 474 kernel (via a special system call) to write process accounting 475 information to a file: whenever a process exits, information about 476 that process will be appended to the file by the kernel. The 477 information includes things such as creation time, owning user, 478 command name, memory usage, controlling terminal etc. (the complete 479 list is in the struct acct in <file:include/linux/acct.h>). It is 480 up to the user level program to do useful things with this 481 information. This is generally a good idea, so say Y. 482 483config BSD_PROCESS_ACCT_V3 484 bool "BSD Process Accounting version 3 file format" 485 depends on BSD_PROCESS_ACCT 486 default n 487 help 488 If you say Y here, the process accounting information is written 489 in a new file format that also logs the process IDs of each 490 process and its parent. Note that this file format is incompatible 491 with previous v0/v1/v2 file formats, so you will need updated tools 492 for processing it. A preliminary version of these tools is available 493 at <http://www.gnu.org/software/acct/>. 494 495config TASKSTATS 496 bool "Export task/process statistics through netlink" 497 depends on NET 498 depends on MULTIUSER 499 default n 500 help 501 Export selected statistics for tasks/processes through the 502 generic netlink interface. Unlike BSD process accounting, the 503 statistics are available during the lifetime of tasks/processes as 504 responses to commands. Like BSD accounting, they are sent to user 505 space on task exit. 506 507 Say N if unsure. 508 509config TASK_DELAY_ACCT 510 bool "Enable per-task delay accounting" 511 depends on TASKSTATS 512 select SCHED_INFO 513 help 514 Collect information on time spent by a task waiting for system 515 resources like cpu, synchronous block I/O completion and swapping 516 in pages. Such statistics can help in setting a task's priorities 517 relative to other tasks for cpu, io, rss limits etc. 518 519 Say N if unsure. 520 521config TASK_XACCT 522 bool "Enable extended accounting over taskstats" 523 depends on TASKSTATS 524 help 525 Collect extended task accounting data and send the data 526 to userland for processing over the taskstats interface. 527 528 Say N if unsure. 529 530config TASK_IO_ACCOUNTING 531 bool "Enable per-task storage I/O accounting" 532 depends on TASK_XACCT 533 help 534 Collect information on the number of bytes of storage I/O which this 535 task has caused. 536 537 Say N if unsure. 538 539config PSI 540 bool "Pressure stall information tracking" 541 help 542 Collect metrics that indicate how overcommitted the CPU, memory, 543 and IO capacity are in the system. 544 545 If you say Y here, the kernel will create /proc/pressure/ with the 546 pressure statistics files cpu, memory, and io. These will indicate 547 the share of walltime in which some or all tasks in the system are 548 delayed due to contention of the respective resource. 549 550 In kernels with cgroup support, cgroups (cgroup2 only) will 551 have cpu.pressure, memory.pressure, and io.pressure files, 552 which aggregate pressure stalls for the grouped tasks only. 553 554 For more details see Documentation/accounting/psi.rst. 555 556 Say N if unsure. 557 558config PSI_DEFAULT_DISABLED 559 bool "Require boot parameter to enable pressure stall information tracking" 560 default n 561 depends on PSI 562 help 563 If set, pressure stall information tracking will be disabled 564 per default but can be enabled through passing psi=1 on the 565 kernel commandline during boot. 566 567 This feature adds some code to the task wakeup and sleep 568 paths of the scheduler. The overhead is too low to affect 569 common scheduling-intense workloads in practice (such as 570 webservers, memcache), but it does show up in artificial 571 scheduler stress tests, such as hackbench. 572 573 If you are paranoid and not sure what the kernel will be 574 used for, say Y. 575 576 Say N if unsure. 577 578endmenu # "CPU/Task time and stats accounting" 579 580config CPU_ISOLATION 581 bool "CPU isolation" 582 depends on SMP || COMPILE_TEST 583 default y 584 help 585 Make sure that CPUs running critical tasks are not disturbed by 586 any source of "noise" such as unbound workqueues, timers, kthreads... 587 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 588 the "isolcpus=" boot parameter. 589 590 Say Y if unsure. 591 592source "kernel/rcu/Kconfig" 593 594config BUILD_BIN2C 595 bool 596 default n 597 598config IKCONFIG 599 tristate "Kernel .config support" 600 ---help--- 601 This option enables the complete Linux kernel ".config" file 602 contents to be saved in the kernel. It provides documentation 603 of which kernel options are used in a running kernel or in an 604 on-disk kernel. This information can be extracted from the kernel 605 image file with the script scripts/extract-ikconfig and used as 606 input to rebuild the current kernel or to build another kernel. 607 It can also be extracted from a running kernel by reading 608 /proc/config.gz if enabled (below). 609 610config IKCONFIG_PROC 611 bool "Enable access to .config through /proc/config.gz" 612 depends on IKCONFIG && PROC_FS 613 ---help--- 614 This option enables access to the kernel configuration file 615 through /proc/config.gz. 616 617config IKHEADERS 618 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 619 depends on SYSFS 620 help 621 This option enables access to the in-kernel headers that are generated during 622 the build process. These can be used to build eBPF tracing programs, 623 or similar programs. If you build the headers as a module, a module called 624 kheaders.ko is built which can be loaded on-demand to get access to headers. 625 626config LOG_BUF_SHIFT 627 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 628 range 12 25 629 default 17 630 depends on PRINTK 631 help 632 Select the minimal kernel log buffer size as a power of 2. 633 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 634 parameter, see below. Any higher size also might be forced 635 by "log_buf_len" boot parameter. 636 637 Examples: 638 17 => 128 KB 639 16 => 64 KB 640 15 => 32 KB 641 14 => 16 KB 642 13 => 8 KB 643 12 => 4 KB 644 645config LOG_CPU_MAX_BUF_SHIFT 646 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 647 depends on SMP 648 range 0 21 649 default 12 if !BASE_SMALL 650 default 0 if BASE_SMALL 651 depends on PRINTK 652 help 653 This option allows to increase the default ring buffer size 654 according to the number of CPUs. The value defines the contribution 655 of each CPU as a power of 2. The used space is typically only few 656 lines however it might be much more when problems are reported, 657 e.g. backtraces. 658 659 The increased size means that a new buffer has to be allocated and 660 the original static one is unused. It makes sense only on systems 661 with more CPUs. Therefore this value is used only when the sum of 662 contributions is greater than the half of the default kernel ring 663 buffer as defined by LOG_BUF_SHIFT. The default values are set 664 so that more than 64 CPUs are needed to trigger the allocation. 665 666 Also this option is ignored when "log_buf_len" kernel parameter is 667 used as it forces an exact (power of two) size of the ring buffer. 668 669 The number of possible CPUs is used for this computation ignoring 670 hotplugging making the computation optimal for the worst case 671 scenario while allowing a simple algorithm to be used from bootup. 672 673 Examples shift values and their meaning: 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 681config PRINTK_SAFE_LOG_BUF_SHIFT 682 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 683 range 10 21 684 default 13 685 depends on PRINTK 686 help 687 Select the size of an alternate printk per-CPU buffer where messages 688 printed from usafe contexts are temporary stored. One example would 689 be NMI messages, another one - printk recursion. The messages are 690 copied to the main log buffer in a safe context to avoid a deadlock. 691 The value defines the size as a power of 2. 692 693 Those messages are rare and limited. The largest one is when 694 a backtrace is printed. It usually fits into 4KB. Select 695 8KB if you want to be on the safe side. 696 697 Examples: 698 17 => 128 KB for each CPU 699 16 => 64 KB for each CPU 700 15 => 32 KB for each CPU 701 14 => 16 KB for each CPU 702 13 => 8 KB for each CPU 703 12 => 4 KB for each CPU 704 705# 706# Architectures with an unreliable sched_clock() should select this: 707# 708config HAVE_UNSTABLE_SCHED_CLOCK 709 bool 710 711config GENERIC_SCHED_CLOCK 712 bool 713 714menu "Scheduler features" 715 716config UCLAMP_TASK 717 bool "Enable utilization clamping for RT/FAIR tasks" 718 depends on CPU_FREQ_GOV_SCHEDUTIL 719 help 720 This feature enables the scheduler to track the clamped utilization 721 of each CPU based on RUNNABLE tasks scheduled on that CPU. 722 723 With this option, the user can specify the min and max CPU 724 utilization allowed for RUNNABLE tasks. The max utilization defines 725 the maximum frequency a task should use while the min utilization 726 defines the minimum frequency it should use. 727 728 Both min and max utilization clamp values are hints to the scheduler, 729 aiming at improving its frequency selection policy, but they do not 730 enforce or grant any specific bandwidth for tasks. 731 732 If in doubt, say N. 733 734config UCLAMP_BUCKETS_COUNT 735 int "Number of supported utilization clamp buckets" 736 range 5 20 737 default 5 738 depends on UCLAMP_TASK 739 help 740 Defines the number of clamp buckets to use. The range of each bucket 741 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 742 number of clamp buckets the finer their granularity and the higher 743 the precision of clamping aggregation and tracking at run-time. 744 745 For example, with the minimum configuration value we will have 5 746 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 747 be refcounted in the [20..39]% bucket and will set the bucket clamp 748 effective value to 25%. 749 If a second 30% boosted task should be co-scheduled on the same CPU, 750 that task will be refcounted in the same bucket of the first task and 751 it will boost the bucket clamp effective value to 30%. 752 The clamp effective value of a bucket is reset to its nominal value 753 (20% in the example above) when there are no more tasks refcounted in 754 that bucket. 755 756 An additional boost/capping margin can be added to some tasks. In the 757 example above the 25% task will be boosted to 30% until it exits the 758 CPU. If that should be considered not acceptable on certain systems, 759 it's always possible to reduce the margin by increasing the number of 760 clamp buckets to trade off used memory for run-time tracking 761 precision. 762 763 If in doubt, use the default value. 764 765endmenu 766 767# 768# For architectures that want to enable the support for NUMA-affine scheduler 769# balancing logic: 770# 771config ARCH_SUPPORTS_NUMA_BALANCING 772 bool 773 774# 775# For architectures that prefer to flush all TLBs after a number of pages 776# are unmapped instead of sending one IPI per page to flush. The architecture 777# must provide guarantees on what happens if a clean TLB cache entry is 778# written after the unmap. Details are in mm/rmap.c near the check for 779# should_defer_flush. The architecture should also consider if the full flush 780# and the refill costs are offset by the savings of sending fewer IPIs. 781config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 782 bool 783 784config CC_HAS_INT128 785 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 786 787# 788# For architectures that know their GCC __int128 support is sound 789# 790config ARCH_SUPPORTS_INT128 791 bool 792 793# For architectures that (ab)use NUMA to represent different memory regions 794# all cpu-local but of different latencies, such as SuperH. 795# 796config ARCH_WANT_NUMA_VARIABLE_LOCALITY 797 bool 798 799config NUMA_BALANCING 800 bool "Memory placement aware NUMA scheduler" 801 depends on ARCH_SUPPORTS_NUMA_BALANCING 802 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 803 depends on SMP && NUMA && MIGRATION 804 help 805 This option adds support for automatic NUMA aware memory/task placement. 806 The mechanism is quite primitive and is based on migrating memory when 807 it has references to the node the task is running on. 808 809 This system will be inactive on UMA systems. 810 811config NUMA_BALANCING_DEFAULT_ENABLED 812 bool "Automatically enable NUMA aware memory/task placement" 813 default y 814 depends on NUMA_BALANCING 815 help 816 If set, automatic NUMA balancing will be enabled if running on a NUMA 817 machine. 818 819menuconfig CGROUPS 820 bool "Control Group support" 821 select KERNFS 822 help 823 This option adds support for grouping sets of processes together, for 824 use with process control subsystems such as Cpusets, CFS, memory 825 controls or device isolation. 826 See 827 - Documentation/scheduler/sched-design-CFS.rst (CFS) 828 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 829 and resource control) 830 831 Say N if unsure. 832 833if CGROUPS 834 835config PAGE_COUNTER 836 bool 837 838config MEMCG 839 bool "Memory controller" 840 select PAGE_COUNTER 841 select EVENTFD 842 help 843 Provides control over the memory footprint of tasks in a cgroup. 844 845config MEMCG_SWAP 846 bool "Swap controller" 847 depends on MEMCG && SWAP 848 help 849 Provides control over the swap space consumed by tasks in a cgroup. 850 851config MEMCG_SWAP_ENABLED 852 bool "Swap controller enabled by default" 853 depends on MEMCG_SWAP 854 default y 855 help 856 Memory Resource Controller Swap Extension comes with its price in 857 a bigger memory consumption. General purpose distribution kernels 858 which want to enable the feature but keep it disabled by default 859 and let the user enable it by swapaccount=1 boot command line 860 parameter should have this option unselected. 861 For those who want to have the feature enabled by default should 862 select this option (if, for some reason, they need to disable it 863 then swapaccount=0 does the trick). 864 865config MEMCG_KMEM 866 bool 867 depends on MEMCG && !SLOB 868 default y 869 870config BLK_CGROUP 871 bool "IO controller" 872 depends on BLOCK 873 default n 874 ---help--- 875 Generic block IO controller cgroup interface. This is the common 876 cgroup interface which should be used by various IO controlling 877 policies. 878 879 Currently, CFQ IO scheduler uses it to recognize task groups and 880 control disk bandwidth allocation (proportional time slice allocation) 881 to such task groups. It is also used by bio throttling logic in 882 block layer to implement upper limit in IO rates on a device. 883 884 This option only enables generic Block IO controller infrastructure. 885 One needs to also enable actual IO controlling logic/policy. For 886 enabling proportional weight division of disk bandwidth in CFQ, set 887 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 888 CONFIG_BLK_DEV_THROTTLING=y. 889 890 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 891 892config CGROUP_WRITEBACK 893 bool 894 depends on MEMCG && BLK_CGROUP 895 default y 896 897menuconfig CGROUP_SCHED 898 bool "CPU controller" 899 default n 900 help 901 This feature lets CPU scheduler recognize task groups and control CPU 902 bandwidth allocation to such task groups. It uses cgroups to group 903 tasks. 904 905if CGROUP_SCHED 906config FAIR_GROUP_SCHED 907 bool "Group scheduling for SCHED_OTHER" 908 depends on CGROUP_SCHED 909 default CGROUP_SCHED 910 911config CFS_BANDWIDTH 912 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 913 depends on FAIR_GROUP_SCHED 914 default n 915 help 916 This option allows users to define CPU bandwidth rates (limits) for 917 tasks running within the fair group scheduler. Groups with no limit 918 set are considered to be unconstrained and will run with no 919 restriction. 920 See Documentation/scheduler/sched-bwc.rst for more information. 921 922config RT_GROUP_SCHED 923 bool "Group scheduling for SCHED_RR/FIFO" 924 depends on CGROUP_SCHED 925 default n 926 help 927 This feature lets you explicitly allocate real CPU bandwidth 928 to task groups. If enabled, it will also make it impossible to 929 schedule realtime tasks for non-root users until you allocate 930 realtime bandwidth for them. 931 See Documentation/scheduler/sched-rt-group.rst for more information. 932 933endif #CGROUP_SCHED 934 935config UCLAMP_TASK_GROUP 936 bool "Utilization clamping per group of tasks" 937 depends on CGROUP_SCHED 938 depends on UCLAMP_TASK 939 default n 940 help 941 This feature enables the scheduler to track the clamped utilization 942 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 943 944 When this option is enabled, the user can specify a min and max 945 CPU bandwidth which is allowed for each single task in a group. 946 The max bandwidth allows to clamp the maximum frequency a task 947 can use, while the min bandwidth allows to define a minimum 948 frequency a task will always use. 949 950 When task group based utilization clamping is enabled, an eventually 951 specified task-specific clamp value is constrained by the cgroup 952 specified clamp value. Both minimum and maximum task clamping cannot 953 be bigger than the corresponding clamping defined at task group level. 954 955 If in doubt, say N. 956 957config CGROUP_PIDS 958 bool "PIDs controller" 959 help 960 Provides enforcement of process number limits in the scope of a 961 cgroup. Any attempt to fork more processes than is allowed in the 962 cgroup will fail. PIDs are fundamentally a global resource because it 963 is fairly trivial to reach PID exhaustion before you reach even a 964 conservative kmemcg limit. As a result, it is possible to grind a 965 system to halt without being limited by other cgroup policies. The 966 PIDs controller is designed to stop this from happening. 967 968 It should be noted that organisational operations (such as attaching 969 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 970 since the PIDs limit only affects a process's ability to fork, not to 971 attach to a cgroup. 972 973config CGROUP_RDMA 974 bool "RDMA controller" 975 help 976 Provides enforcement of RDMA resources defined by IB stack. 977 It is fairly easy for consumers to exhaust RDMA resources, which 978 can result into resource unavailability to other consumers. 979 RDMA controller is designed to stop this from happening. 980 Attaching processes with active RDMA resources to the cgroup 981 hierarchy is allowed even if can cross the hierarchy's limit. 982 983config CGROUP_FREEZER 984 bool "Freezer controller" 985 help 986 Provides a way to freeze and unfreeze all tasks in a 987 cgroup. 988 989 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 990 controller includes important in-kernel memory consumers per default. 991 992 If you're using cgroup2, say N. 993 994config CGROUP_HUGETLB 995 bool "HugeTLB controller" 996 depends on HUGETLB_PAGE 997 select PAGE_COUNTER 998 default n 999 help 1000 Provides a cgroup controller for HugeTLB pages. 1001 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1002 The limit is enforced during page fault. Since HugeTLB doesn't 1003 support page reclaim, enforcing the limit at page fault time implies 1004 that, the application will get SIGBUS signal if it tries to access 1005 HugeTLB pages beyond its limit. This requires the application to know 1006 beforehand how much HugeTLB pages it would require for its use. The 1007 control group is tracked in the third page lru pointer. This means 1008 that we cannot use the controller with huge page less than 3 pages. 1009 1010config CPUSETS 1011 bool "Cpuset controller" 1012 depends on SMP 1013 help 1014 This option will let you create and manage CPUSETs which 1015 allow dynamically partitioning a system into sets of CPUs and 1016 Memory Nodes and assigning tasks to run only within those sets. 1017 This is primarily useful on large SMP or NUMA systems. 1018 1019 Say N if unsure. 1020 1021config PROC_PID_CPUSET 1022 bool "Include legacy /proc/<pid>/cpuset file" 1023 depends on CPUSETS 1024 default y 1025 1026config CGROUP_DEVICE 1027 bool "Device controller" 1028 help 1029 Provides a cgroup controller implementing whitelists for 1030 devices which a process in the cgroup can mknod or open. 1031 1032config CGROUP_CPUACCT 1033 bool "Simple CPU accounting controller" 1034 help 1035 Provides a simple controller for monitoring the 1036 total CPU consumed by the tasks in a cgroup. 1037 1038config CGROUP_PERF 1039 bool "Perf controller" 1040 depends on PERF_EVENTS 1041 help 1042 This option extends the perf per-cpu mode to restrict monitoring 1043 to threads which belong to the cgroup specified and run on the 1044 designated cpu. Or this can be used to have cgroup ID in samples 1045 so that it can monitor performance events among cgroups. 1046 1047 Say N if unsure. 1048 1049config CGROUP_BPF 1050 bool "Support for eBPF programs attached to cgroups" 1051 depends on BPF_SYSCALL 1052 select SOCK_CGROUP_DATA 1053 help 1054 Allow attaching eBPF programs to a cgroup using the bpf(2) 1055 syscall command BPF_PROG_ATTACH. 1056 1057 In which context these programs are accessed depends on the type 1058 of attachment. For instance, programs that are attached using 1059 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1060 inet sockets. 1061 1062config CGROUP_DEBUG 1063 bool "Debug controller" 1064 default n 1065 depends on DEBUG_KERNEL 1066 help 1067 This option enables a simple controller that exports 1068 debugging information about the cgroups framework. This 1069 controller is for control cgroup debugging only. Its 1070 interfaces are not stable. 1071 1072 Say N. 1073 1074config SOCK_CGROUP_DATA 1075 bool 1076 default n 1077 1078endif # CGROUPS 1079 1080menuconfig NAMESPACES 1081 bool "Namespaces support" if EXPERT 1082 depends on MULTIUSER 1083 default !EXPERT 1084 help 1085 Provides the way to make tasks work with different objects using 1086 the same id. For example same IPC id may refer to different objects 1087 or same user id or pid may refer to different tasks when used in 1088 different namespaces. 1089 1090if NAMESPACES 1091 1092config UTS_NS 1093 bool "UTS namespace" 1094 default y 1095 help 1096 In this namespace tasks see different info provided with the 1097 uname() system call 1098 1099config TIME_NS 1100 bool "TIME namespace" 1101 depends on GENERIC_VDSO_TIME_NS 1102 default y 1103 help 1104 In this namespace boottime and monotonic clocks can be set. 1105 The time will keep going with the same pace. 1106 1107config IPC_NS 1108 bool "IPC namespace" 1109 depends on (SYSVIPC || POSIX_MQUEUE) 1110 default y 1111 help 1112 In this namespace tasks work with IPC ids which correspond to 1113 different IPC objects in different namespaces. 1114 1115config USER_NS 1116 bool "User namespace" 1117 default n 1118 help 1119 This allows containers, i.e. vservers, to use user namespaces 1120 to provide different user info for different servers. 1121 1122 When user namespaces are enabled in the kernel it is 1123 recommended that the MEMCG option also be enabled and that 1124 user-space use the memory control groups to limit the amount 1125 of memory a memory unprivileged users can use. 1126 1127 If unsure, say N. 1128 1129config PID_NS 1130 bool "PID Namespaces" 1131 default y 1132 help 1133 Support process id namespaces. This allows having multiple 1134 processes with the same pid as long as they are in different 1135 pid namespaces. This is a building block of containers. 1136 1137config NET_NS 1138 bool "Network namespace" 1139 depends on NET 1140 default y 1141 help 1142 Allow user space to create what appear to be multiple instances 1143 of the network stack. 1144 1145endif # NAMESPACES 1146 1147config CHECKPOINT_RESTORE 1148 bool "Checkpoint/restore support" 1149 select PROC_CHILDREN 1150 default n 1151 help 1152 Enables additional kernel features in a sake of checkpoint/restore. 1153 In particular it adds auxiliary prctl codes to setup process text, 1154 data and heap segment sizes, and a few additional /proc filesystem 1155 entries. 1156 1157 If unsure, say N here. 1158 1159config SCHED_AUTOGROUP 1160 bool "Automatic process group scheduling" 1161 select CGROUPS 1162 select CGROUP_SCHED 1163 select FAIR_GROUP_SCHED 1164 help 1165 This option optimizes the scheduler for common desktop workloads by 1166 automatically creating and populating task groups. This separation 1167 of workloads isolates aggressive CPU burners (like build jobs) from 1168 desktop applications. Task group autogeneration is currently based 1169 upon task session. 1170 1171config SYSFS_DEPRECATED 1172 bool "Enable deprecated sysfs features to support old userspace tools" 1173 depends on SYSFS 1174 default n 1175 help 1176 This option adds code that switches the layout of the "block" class 1177 devices, to not show up in /sys/class/block/, but only in 1178 /sys/block/. 1179 1180 This switch is only active when the sysfs.deprecated=1 boot option is 1181 passed or the SYSFS_DEPRECATED_V2 option is set. 1182 1183 This option allows new kernels to run on old distributions and tools, 1184 which might get confused by /sys/class/block/. Since 2007/2008 all 1185 major distributions and tools handle this just fine. 1186 1187 Recent distributions and userspace tools after 2009/2010 depend on 1188 the existence of /sys/class/block/, and will not work with this 1189 option enabled. 1190 1191 Only if you are using a new kernel on an old distribution, you might 1192 need to say Y here. 1193 1194config SYSFS_DEPRECATED_V2 1195 bool "Enable deprecated sysfs features by default" 1196 default n 1197 depends on SYSFS 1198 depends on SYSFS_DEPRECATED 1199 help 1200 Enable deprecated sysfs by default. 1201 1202 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1203 option. 1204 1205 Only if you are using a new kernel on an old distribution, you might 1206 need to say Y here. Even then, odds are you would not need it 1207 enabled, you can always pass the boot option if absolutely necessary. 1208 1209config RELAY 1210 bool "Kernel->user space relay support (formerly relayfs)" 1211 select IRQ_WORK 1212 help 1213 This option enables support for relay interface support in 1214 certain file systems (such as debugfs). 1215 It is designed to provide an efficient mechanism for tools and 1216 facilities to relay large amounts of data from kernel space to 1217 user space. 1218 1219 If unsure, say N. 1220 1221config BLK_DEV_INITRD 1222 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1223 help 1224 The initial RAM filesystem is a ramfs which is loaded by the 1225 boot loader (loadlin or lilo) and that is mounted as root 1226 before the normal boot procedure. It is typically used to 1227 load modules needed to mount the "real" root file system, 1228 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1229 1230 If RAM disk support (BLK_DEV_RAM) is also included, this 1231 also enables initial RAM disk (initrd) support and adds 1232 15 Kbytes (more on some other architectures) to the kernel size. 1233 1234 If unsure say Y. 1235 1236if BLK_DEV_INITRD 1237 1238source "usr/Kconfig" 1239 1240endif 1241 1242config BOOT_CONFIG 1243 bool "Boot config support" 1244 select BLK_DEV_INITRD 1245 help 1246 Extra boot config allows system admin to pass a config file as 1247 complemental extension of kernel cmdline when booting. 1248 The boot config file must be attached at the end of initramfs 1249 with checksum, size and magic word. 1250 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1251 1252 If unsure, say Y. 1253 1254choice 1255 prompt "Compiler optimization level" 1256 default CC_OPTIMIZE_FOR_PERFORMANCE 1257 1258config CC_OPTIMIZE_FOR_PERFORMANCE 1259 bool "Optimize for performance (-O2)" 1260 help 1261 This is the default optimization level for the kernel, building 1262 with the "-O2" compiler flag for best performance and most 1263 helpful compile-time warnings. 1264 1265config CC_OPTIMIZE_FOR_PERFORMANCE_O3 1266 bool "Optimize more for performance (-O3)" 1267 depends on ARC 1268 help 1269 Choosing this option will pass "-O3" to your compiler to optimize 1270 the kernel yet more for performance. 1271 1272config CC_OPTIMIZE_FOR_SIZE 1273 bool "Optimize for size (-Os)" 1274 help 1275 Choosing this option will pass "-Os" to your compiler resulting 1276 in a smaller kernel. 1277 1278endchoice 1279 1280config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1281 bool 1282 help 1283 This requires that the arch annotates or otherwise protects 1284 its external entry points from being discarded. Linker scripts 1285 must also merge .text.*, .data.*, and .bss.* correctly into 1286 output sections. Care must be taken not to pull in unrelated 1287 sections (e.g., '.text.init'). Typically '.' in section names 1288 is used to distinguish them from label names / C identifiers. 1289 1290config LD_DEAD_CODE_DATA_ELIMINATION 1291 bool "Dead code and data elimination (EXPERIMENTAL)" 1292 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1293 depends on EXPERT 1294 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800) 1295 depends on $(cc-option,-ffunction-sections -fdata-sections) 1296 depends on $(ld-option,--gc-sections) 1297 help 1298 Enable this if you want to do dead code and data elimination with 1299 the linker by compiling with -ffunction-sections -fdata-sections, 1300 and linking with --gc-sections. 1301 1302 This can reduce on disk and in-memory size of the kernel 1303 code and static data, particularly for small configs and 1304 on small systems. This has the possibility of introducing 1305 silently broken kernel if the required annotations are not 1306 present. This option is not well tested yet, so use at your 1307 own risk. 1308 1309config SYSCTL 1310 bool 1311 1312config HAVE_UID16 1313 bool 1314 1315config SYSCTL_EXCEPTION_TRACE 1316 bool 1317 help 1318 Enable support for /proc/sys/debug/exception-trace. 1319 1320config SYSCTL_ARCH_UNALIGN_NO_WARN 1321 bool 1322 help 1323 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1324 Allows arch to define/use @no_unaligned_warning to possibly warn 1325 about unaligned access emulation going on under the hood. 1326 1327config SYSCTL_ARCH_UNALIGN_ALLOW 1328 bool 1329 help 1330 Enable support for /proc/sys/kernel/unaligned-trap 1331 Allows arches to define/use @unaligned_enabled to runtime toggle 1332 the unaligned access emulation. 1333 see arch/parisc/kernel/unaligned.c for reference 1334 1335config HAVE_PCSPKR_PLATFORM 1336 bool 1337 1338# interpreter that classic socket filters depend on 1339config BPF 1340 bool 1341 1342menuconfig EXPERT 1343 bool "Configure standard kernel features (expert users)" 1344 # Unhide debug options, to make the on-by-default options visible 1345 select DEBUG_KERNEL 1346 help 1347 This option allows certain base kernel options and settings 1348 to be disabled or tweaked. This is for specialized 1349 environments which can tolerate a "non-standard" kernel. 1350 Only use this if you really know what you are doing. 1351 1352config UID16 1353 bool "Enable 16-bit UID system calls" if EXPERT 1354 depends on HAVE_UID16 && MULTIUSER 1355 default y 1356 help 1357 This enables the legacy 16-bit UID syscall wrappers. 1358 1359config MULTIUSER 1360 bool "Multiple users, groups and capabilities support" if EXPERT 1361 default y 1362 help 1363 This option enables support for non-root users, groups and 1364 capabilities. 1365 1366 If you say N here, all processes will run with UID 0, GID 0, and all 1367 possible capabilities. Saying N here also compiles out support for 1368 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1369 setgid, and capset. 1370 1371 If unsure, say Y here. 1372 1373config SGETMASK_SYSCALL 1374 bool "sgetmask/ssetmask syscalls support" if EXPERT 1375 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1376 ---help--- 1377 sys_sgetmask and sys_ssetmask are obsolete system calls 1378 no longer supported in libc but still enabled by default in some 1379 architectures. 1380 1381 If unsure, leave the default option here. 1382 1383config SYSFS_SYSCALL 1384 bool "Sysfs syscall support" if EXPERT 1385 default y 1386 ---help--- 1387 sys_sysfs is an obsolete system call no longer supported in libc. 1388 Note that disabling this option is more secure but might break 1389 compatibility with some systems. 1390 1391 If unsure say Y here. 1392 1393config FHANDLE 1394 bool "open by fhandle syscalls" if EXPERT 1395 select EXPORTFS 1396 default y 1397 help 1398 If you say Y here, a user level program will be able to map 1399 file names to handle and then later use the handle for 1400 different file system operations. This is useful in implementing 1401 userspace file servers, which now track files using handles instead 1402 of names. The handle would remain the same even if file names 1403 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1404 syscalls. 1405 1406config POSIX_TIMERS 1407 bool "Posix Clocks & timers" if EXPERT 1408 default y 1409 help 1410 This includes native support for POSIX timers to the kernel. 1411 Some embedded systems have no use for them and therefore they 1412 can be configured out to reduce the size of the kernel image. 1413 1414 When this option is disabled, the following syscalls won't be 1415 available: timer_create, timer_gettime: timer_getoverrun, 1416 timer_settime, timer_delete, clock_adjtime, getitimer, 1417 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1418 clock_getres and clock_nanosleep syscalls will be limited to 1419 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1420 1421 If unsure say y. 1422 1423config PRINTK 1424 default y 1425 bool "Enable support for printk" if EXPERT 1426 select IRQ_WORK 1427 help 1428 This option enables normal printk support. Removing it 1429 eliminates most of the message strings from the kernel image 1430 and makes the kernel more or less silent. As this makes it 1431 very difficult to diagnose system problems, saying N here is 1432 strongly discouraged. 1433 1434config PRINTK_NMI 1435 def_bool y 1436 depends on PRINTK 1437 depends on HAVE_NMI 1438 1439config BUG 1440 bool "BUG() support" if EXPERT 1441 default y 1442 help 1443 Disabling this option eliminates support for BUG and WARN, reducing 1444 the size of your kernel image and potentially quietly ignoring 1445 numerous fatal conditions. You should only consider disabling this 1446 option for embedded systems with no facilities for reporting errors. 1447 Just say Y. 1448 1449config ELF_CORE 1450 depends on COREDUMP 1451 default y 1452 bool "Enable ELF core dumps" if EXPERT 1453 help 1454 Enable support for generating core dumps. Disabling saves about 4k. 1455 1456 1457config PCSPKR_PLATFORM 1458 bool "Enable PC-Speaker support" if EXPERT 1459 depends on HAVE_PCSPKR_PLATFORM 1460 select I8253_LOCK 1461 default y 1462 help 1463 This option allows to disable the internal PC-Speaker 1464 support, saving some memory. 1465 1466config BASE_FULL 1467 default y 1468 bool "Enable full-sized data structures for core" if EXPERT 1469 help 1470 Disabling this option reduces the size of miscellaneous core 1471 kernel data structures. This saves memory on small machines, 1472 but may reduce performance. 1473 1474config FUTEX 1475 bool "Enable futex support" if EXPERT 1476 default y 1477 imply RT_MUTEXES 1478 help 1479 Disabling this option will cause the kernel to be built without 1480 support for "fast userspace mutexes". The resulting kernel may not 1481 run glibc-based applications correctly. 1482 1483config FUTEX_PI 1484 bool 1485 depends on FUTEX && RT_MUTEXES 1486 default y 1487 1488config HAVE_FUTEX_CMPXCHG 1489 bool 1490 depends on FUTEX 1491 help 1492 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1493 is implemented and always working. This removes a couple of runtime 1494 checks. 1495 1496config EPOLL 1497 bool "Enable eventpoll support" if EXPERT 1498 default y 1499 help 1500 Disabling this option will cause the kernel to be built without 1501 support for epoll family of system calls. 1502 1503config SIGNALFD 1504 bool "Enable signalfd() system call" if EXPERT 1505 default y 1506 help 1507 Enable the signalfd() system call that allows to receive signals 1508 on a file descriptor. 1509 1510 If unsure, say Y. 1511 1512config TIMERFD 1513 bool "Enable timerfd() system call" if EXPERT 1514 default y 1515 help 1516 Enable the timerfd() system call that allows to receive timer 1517 events on a file descriptor. 1518 1519 If unsure, say Y. 1520 1521config EVENTFD 1522 bool "Enable eventfd() system call" if EXPERT 1523 default y 1524 help 1525 Enable the eventfd() system call that allows to receive both 1526 kernel notification (ie. KAIO) or userspace notifications. 1527 1528 If unsure, say Y. 1529 1530config SHMEM 1531 bool "Use full shmem filesystem" if EXPERT 1532 default y 1533 depends on MMU 1534 help 1535 The shmem is an internal filesystem used to manage shared memory. 1536 It is backed by swap and manages resource limits. It is also exported 1537 to userspace as tmpfs if TMPFS is enabled. Disabling this 1538 option replaces shmem and tmpfs with the much simpler ramfs code, 1539 which may be appropriate on small systems without swap. 1540 1541config AIO 1542 bool "Enable AIO support" if EXPERT 1543 default y 1544 help 1545 This option enables POSIX asynchronous I/O which may by used 1546 by some high performance threaded applications. Disabling 1547 this option saves about 7k. 1548 1549config IO_URING 1550 bool "Enable IO uring support" if EXPERT 1551 select IO_WQ 1552 default y 1553 help 1554 This option enables support for the io_uring interface, enabling 1555 applications to submit and complete IO through submission and 1556 completion rings that are shared between the kernel and application. 1557 1558config ADVISE_SYSCALLS 1559 bool "Enable madvise/fadvise syscalls" if EXPERT 1560 default y 1561 help 1562 This option enables the madvise and fadvise syscalls, used by 1563 applications to advise the kernel about their future memory or file 1564 usage, improving performance. If building an embedded system where no 1565 applications use these syscalls, you can disable this option to save 1566 space. 1567 1568config HAVE_ARCH_USERFAULTFD_WP 1569 bool 1570 help 1571 Arch has userfaultfd write protection support 1572 1573config MEMBARRIER 1574 bool "Enable membarrier() system call" if EXPERT 1575 default y 1576 help 1577 Enable the membarrier() system call that allows issuing memory 1578 barriers across all running threads, which can be used to distribute 1579 the cost of user-space memory barriers asymmetrically by transforming 1580 pairs of memory barriers into pairs consisting of membarrier() and a 1581 compiler barrier. 1582 1583 If unsure, say Y. 1584 1585config KALLSYMS 1586 bool "Load all symbols for debugging/ksymoops" if EXPERT 1587 default y 1588 help 1589 Say Y here to let the kernel print out symbolic crash information and 1590 symbolic stack backtraces. This increases the size of the kernel 1591 somewhat, as all symbols have to be loaded into the kernel image. 1592 1593config KALLSYMS_ALL 1594 bool "Include all symbols in kallsyms" 1595 depends on DEBUG_KERNEL && KALLSYMS 1596 help 1597 Normally kallsyms only contains the symbols of functions for nicer 1598 OOPS messages and backtraces (i.e., symbols from the text and inittext 1599 sections). This is sufficient for most cases. And only in very rare 1600 cases (e.g., when a debugger is used) all symbols are required (e.g., 1601 names of variables from the data sections, etc). 1602 1603 This option makes sure that all symbols are loaded into the kernel 1604 image (i.e., symbols from all sections) in cost of increased kernel 1605 size (depending on the kernel configuration, it may be 300KiB or 1606 something like this). 1607 1608 Say N unless you really need all symbols. 1609 1610config KALLSYMS_ABSOLUTE_PERCPU 1611 bool 1612 depends on KALLSYMS 1613 default X86_64 && SMP 1614 1615config KALLSYMS_BASE_RELATIVE 1616 bool 1617 depends on KALLSYMS 1618 default !IA64 1619 help 1620 Instead of emitting them as absolute values in the native word size, 1621 emit the symbol references in the kallsyms table as 32-bit entries, 1622 each containing a relative value in the range [base, base + U32_MAX] 1623 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1624 an absolute value in the range [0, S32_MAX] or a relative value in the 1625 range [base, base + S32_MAX], where base is the lowest relative symbol 1626 address encountered in the image. 1627 1628 On 64-bit builds, this reduces the size of the address table by 50%, 1629 but more importantly, it results in entries whose values are build 1630 time constants, and no relocation pass is required at runtime to fix 1631 up the entries based on the runtime load address of the kernel. 1632 1633# end of the "standard kernel features (expert users)" menu 1634 1635# syscall, maps, verifier 1636 1637config BPF_LSM 1638 bool "LSM Instrumentation with BPF" 1639 depends on BPF_EVENTS 1640 depends on BPF_SYSCALL 1641 depends on SECURITY 1642 depends on BPF_JIT 1643 help 1644 Enables instrumentation of the security hooks with eBPF programs for 1645 implementing dynamic MAC and Audit Policies. 1646 1647 If you are unsure how to answer this question, answer N. 1648 1649config BPF_SYSCALL 1650 bool "Enable bpf() system call" 1651 select BPF 1652 select IRQ_WORK 1653 default n 1654 help 1655 Enable the bpf() system call that allows to manipulate eBPF 1656 programs and maps via file descriptors. 1657 1658config ARCH_WANT_DEFAULT_BPF_JIT 1659 bool 1660 1661config BPF_JIT_ALWAYS_ON 1662 bool "Permanently enable BPF JIT and remove BPF interpreter" 1663 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1664 help 1665 Enables BPF JIT and removes BPF interpreter to avoid 1666 speculative execution of BPF instructions by the interpreter 1667 1668config BPF_JIT_DEFAULT_ON 1669 def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON 1670 depends on HAVE_EBPF_JIT && BPF_JIT 1671 1672config USERFAULTFD 1673 bool "Enable userfaultfd() system call" 1674 depends on MMU 1675 help 1676 Enable the userfaultfd() system call that allows to intercept and 1677 handle page faults in userland. 1678 1679config ARCH_HAS_MEMBARRIER_CALLBACKS 1680 bool 1681 1682config ARCH_HAS_MEMBARRIER_SYNC_CORE 1683 bool 1684 1685config RSEQ 1686 bool "Enable rseq() system call" if EXPERT 1687 default y 1688 depends on HAVE_RSEQ 1689 select MEMBARRIER 1690 help 1691 Enable the restartable sequences system call. It provides a 1692 user-space cache for the current CPU number value, which 1693 speeds up getting the current CPU number from user-space, 1694 as well as an ABI to speed up user-space operations on 1695 per-CPU data. 1696 1697 If unsure, say Y. 1698 1699config DEBUG_RSEQ 1700 default n 1701 bool "Enabled debugging of rseq() system call" if EXPERT 1702 depends on RSEQ && DEBUG_KERNEL 1703 help 1704 Enable extra debugging checks for the rseq system call. 1705 1706 If unsure, say N. 1707 1708config EMBEDDED 1709 bool "Embedded system" 1710 option allnoconfig_y 1711 select EXPERT 1712 help 1713 This option should be enabled if compiling the kernel for 1714 an embedded system so certain expert options are available 1715 for configuration. 1716 1717config HAVE_PERF_EVENTS 1718 bool 1719 help 1720 See tools/perf/design.txt for details. 1721 1722config PERF_USE_VMALLOC 1723 bool 1724 help 1725 See tools/perf/design.txt for details 1726 1727config PC104 1728 bool "PC/104 support" if EXPERT 1729 help 1730 Expose PC/104 form factor device drivers and options available for 1731 selection and configuration. Enable this option if your target 1732 machine has a PC/104 bus. 1733 1734menu "Kernel Performance Events And Counters" 1735 1736config PERF_EVENTS 1737 bool "Kernel performance events and counters" 1738 default y if PROFILING 1739 depends on HAVE_PERF_EVENTS 1740 select IRQ_WORK 1741 select SRCU 1742 help 1743 Enable kernel support for various performance events provided 1744 by software and hardware. 1745 1746 Software events are supported either built-in or via the 1747 use of generic tracepoints. 1748 1749 Most modern CPUs support performance events via performance 1750 counter registers. These registers count the number of certain 1751 types of hw events: such as instructions executed, cachemisses 1752 suffered, or branches mis-predicted - without slowing down the 1753 kernel or applications. These registers can also trigger interrupts 1754 when a threshold number of events have passed - and can thus be 1755 used to profile the code that runs on that CPU. 1756 1757 The Linux Performance Event subsystem provides an abstraction of 1758 these software and hardware event capabilities, available via a 1759 system call and used by the "perf" utility in tools/perf/. It 1760 provides per task and per CPU counters, and it provides event 1761 capabilities on top of those. 1762 1763 Say Y if unsure. 1764 1765config DEBUG_PERF_USE_VMALLOC 1766 default n 1767 bool "Debug: use vmalloc to back perf mmap() buffers" 1768 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1769 select PERF_USE_VMALLOC 1770 help 1771 Use vmalloc memory to back perf mmap() buffers. 1772 1773 Mostly useful for debugging the vmalloc code on platforms 1774 that don't require it. 1775 1776 Say N if unsure. 1777 1778endmenu 1779 1780config VM_EVENT_COUNTERS 1781 default y 1782 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1783 help 1784 VM event counters are needed for event counts to be shown. 1785 This option allows the disabling of the VM event counters 1786 on EXPERT systems. /proc/vmstat will only show page counts 1787 if VM event counters are disabled. 1788 1789config SLUB_DEBUG 1790 default y 1791 bool "Enable SLUB debugging support" if EXPERT 1792 depends on SLUB && SYSFS 1793 help 1794 SLUB has extensive debug support features. Disabling these can 1795 result in significant savings in code size. This also disables 1796 SLUB sysfs support. /sys/slab will not exist and there will be 1797 no support for cache validation etc. 1798 1799config SLUB_MEMCG_SYSFS_ON 1800 default n 1801 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1802 depends on SLUB && SYSFS && MEMCG 1803 help 1804 SLUB creates a directory under /sys/kernel/slab for each 1805 allocation cache to host info and debug files. If memory 1806 cgroup is enabled, each cache can have per memory cgroup 1807 caches. SLUB can create the same sysfs directories for these 1808 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1809 to a very high number of debug files being created. This is 1810 controlled by slub_memcg_sysfs boot parameter and this 1811 config option determines the parameter's default value. 1812 1813config COMPAT_BRK 1814 bool "Disable heap randomization" 1815 default y 1816 help 1817 Randomizing heap placement makes heap exploits harder, but it 1818 also breaks ancient binaries (including anything libc5 based). 1819 This option changes the bootup default to heap randomization 1820 disabled, and can be overridden at runtime by setting 1821 /proc/sys/kernel/randomize_va_space to 2. 1822 1823 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1824 1825choice 1826 prompt "Choose SLAB allocator" 1827 default SLUB 1828 help 1829 This option allows to select a slab allocator. 1830 1831config SLAB 1832 bool "SLAB" 1833 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1834 help 1835 The regular slab allocator that is established and known to work 1836 well in all environments. It organizes cache hot objects in 1837 per cpu and per node queues. 1838 1839config SLUB 1840 bool "SLUB (Unqueued Allocator)" 1841 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1842 help 1843 SLUB is a slab allocator that minimizes cache line usage 1844 instead of managing queues of cached objects (SLAB approach). 1845 Per cpu caching is realized using slabs of objects instead 1846 of queues of objects. SLUB can use memory efficiently 1847 and has enhanced diagnostics. SLUB is the default choice for 1848 a slab allocator. 1849 1850config SLOB 1851 depends on EXPERT 1852 bool "SLOB (Simple Allocator)" 1853 help 1854 SLOB replaces the stock allocator with a drastically simpler 1855 allocator. SLOB is generally more space efficient but 1856 does not perform as well on large systems. 1857 1858endchoice 1859 1860config SLAB_MERGE_DEFAULT 1861 bool "Allow slab caches to be merged" 1862 default y 1863 help 1864 For reduced kernel memory fragmentation, slab caches can be 1865 merged when they share the same size and other characteristics. 1866 This carries a risk of kernel heap overflows being able to 1867 overwrite objects from merged caches (and more easily control 1868 cache layout), which makes such heap attacks easier to exploit 1869 by attackers. By keeping caches unmerged, these kinds of exploits 1870 can usually only damage objects in the same cache. To disable 1871 merging at runtime, "slab_nomerge" can be passed on the kernel 1872 command line. 1873 1874config SLAB_FREELIST_RANDOM 1875 default n 1876 depends on SLAB || SLUB 1877 bool "SLAB freelist randomization" 1878 help 1879 Randomizes the freelist order used on creating new pages. This 1880 security feature reduces the predictability of the kernel slab 1881 allocator against heap overflows. 1882 1883config SLAB_FREELIST_HARDENED 1884 bool "Harden slab freelist metadata" 1885 depends on SLUB 1886 help 1887 Many kernel heap attacks try to target slab cache metadata and 1888 other infrastructure. This options makes minor performance 1889 sacrifices to harden the kernel slab allocator against common 1890 freelist exploit methods. 1891 1892config SHUFFLE_PAGE_ALLOCATOR 1893 bool "Page allocator randomization" 1894 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1895 help 1896 Randomization of the page allocator improves the average 1897 utilization of a direct-mapped memory-side-cache. See section 1898 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1899 6.2a specification for an example of how a platform advertises 1900 the presence of a memory-side-cache. There are also incidental 1901 security benefits as it reduces the predictability of page 1902 allocations to compliment SLAB_FREELIST_RANDOM, but the 1903 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1904 10th order of pages is selected based on cache utilization 1905 benefits on x86. 1906 1907 While the randomization improves cache utilization it may 1908 negatively impact workloads on platforms without a cache. For 1909 this reason, by default, the randomization is enabled only 1910 after runtime detection of a direct-mapped memory-side-cache. 1911 Otherwise, the randomization may be force enabled with the 1912 'page_alloc.shuffle' kernel command line parameter. 1913 1914 Say Y if unsure. 1915 1916config SLUB_CPU_PARTIAL 1917 default y 1918 depends on SLUB && SMP 1919 bool "SLUB per cpu partial cache" 1920 help 1921 Per cpu partial caches accelerate objects allocation and freeing 1922 that is local to a processor at the price of more indeterminism 1923 in the latency of the free. On overflow these caches will be cleared 1924 which requires the taking of locks that may cause latency spikes. 1925 Typically one would choose no for a realtime system. 1926 1927config MMAP_ALLOW_UNINITIALIZED 1928 bool "Allow mmapped anonymous memory to be uninitialized" 1929 depends on EXPERT && !MMU 1930 default n 1931 help 1932 Normally, and according to the Linux spec, anonymous memory obtained 1933 from mmap() has its contents cleared before it is passed to 1934 userspace. Enabling this config option allows you to request that 1935 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1936 providing a huge performance boost. If this option is not enabled, 1937 then the flag will be ignored. 1938 1939 This is taken advantage of by uClibc's malloc(), and also by 1940 ELF-FDPIC binfmt's brk and stack allocator. 1941 1942 Because of the obvious security issues, this option should only be 1943 enabled on embedded devices where you control what is run in 1944 userspace. Since that isn't generally a problem on no-MMU systems, 1945 it is normally safe to say Y here. 1946 1947 See Documentation/nommu-mmap.txt for more information. 1948 1949config SYSTEM_DATA_VERIFICATION 1950 def_bool n 1951 select SYSTEM_TRUSTED_KEYRING 1952 select KEYS 1953 select CRYPTO 1954 select CRYPTO_RSA 1955 select ASYMMETRIC_KEY_TYPE 1956 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1957 select ASN1 1958 select OID_REGISTRY 1959 select X509_CERTIFICATE_PARSER 1960 select PKCS7_MESSAGE_PARSER 1961 help 1962 Provide PKCS#7 message verification using the contents of the system 1963 trusted keyring to provide public keys. This then can be used for 1964 module verification, kexec image verification and firmware blob 1965 verification. 1966 1967config PROFILING 1968 bool "Profiling support" 1969 help 1970 Say Y here to enable the extended profiling support mechanisms used 1971 by profilers such as OProfile. 1972 1973# 1974# Place an empty function call at each tracepoint site. Can be 1975# dynamically changed for a probe function. 1976# 1977config TRACEPOINTS 1978 bool 1979 1980endmenu # General setup 1981 1982source "arch/Kconfig" 1983 1984config RT_MUTEXES 1985 bool 1986 1987config BASE_SMALL 1988 int 1989 default 0 if BASE_FULL 1990 default 1 if !BASE_FULL 1991 1992config MODULE_SIG_FORMAT 1993 def_bool n 1994 select SYSTEM_DATA_VERIFICATION 1995 1996menuconfig MODULES 1997 bool "Enable loadable module support" 1998 option modules 1999 help 2000 Kernel modules are small pieces of compiled code which can 2001 be inserted in the running kernel, rather than being 2002 permanently built into the kernel. You use the "modprobe" 2003 tool to add (and sometimes remove) them. If you say Y here, 2004 many parts of the kernel can be built as modules (by 2005 answering M instead of Y where indicated): this is most 2006 useful for infrequently used options which are not required 2007 for booting. For more information, see the man pages for 2008 modprobe, lsmod, modinfo, insmod and rmmod. 2009 2010 If you say Y here, you will need to run "make 2011 modules_install" to put the modules under /lib/modules/ 2012 where modprobe can find them (you may need to be root to do 2013 this). 2014 2015 If unsure, say Y. 2016 2017if MODULES 2018 2019config MODULE_FORCE_LOAD 2020 bool "Forced module loading" 2021 default n 2022 help 2023 Allow loading of modules without version information (ie. modprobe 2024 --force). Forced module loading sets the 'F' (forced) taint flag and 2025 is usually a really bad idea. 2026 2027config MODULE_UNLOAD 2028 bool "Module unloading" 2029 help 2030 Without this option you will not be able to unload any 2031 modules (note that some modules may not be unloadable 2032 anyway), which makes your kernel smaller, faster 2033 and simpler. If unsure, say Y. 2034 2035config MODULE_FORCE_UNLOAD 2036 bool "Forced module unloading" 2037 depends on MODULE_UNLOAD 2038 help 2039 This option allows you to force a module to unload, even if the 2040 kernel believes it is unsafe: the kernel will remove the module 2041 without waiting for anyone to stop using it (using the -f option to 2042 rmmod). This is mainly for kernel developers and desperate users. 2043 If unsure, say N. 2044 2045config MODVERSIONS 2046 bool "Module versioning support" 2047 help 2048 Usually, you have to use modules compiled with your kernel. 2049 Saying Y here makes it sometimes possible to use modules 2050 compiled for different kernels, by adding enough information 2051 to the modules to (hopefully) spot any changes which would 2052 make them incompatible with the kernel you are running. If 2053 unsure, say N. 2054 2055config ASM_MODVERSIONS 2056 bool 2057 default HAVE_ASM_MODVERSIONS && MODVERSIONS 2058 help 2059 This enables module versioning for exported symbols also from 2060 assembly. This can be enabled only when the target architecture 2061 supports it. 2062 2063config MODULE_REL_CRCS 2064 bool 2065 depends on MODVERSIONS 2066 2067config MODULE_SRCVERSION_ALL 2068 bool "Source checksum for all modules" 2069 help 2070 Modules which contain a MODULE_VERSION get an extra "srcversion" 2071 field inserted into their modinfo section, which contains a 2072 sum of the source files which made it. This helps maintainers 2073 see exactly which source was used to build a module (since 2074 others sometimes change the module source without updating 2075 the version). With this option, such a "srcversion" field 2076 will be created for all modules. If unsure, say N. 2077 2078config MODULE_SIG 2079 bool "Module signature verification" 2080 select MODULE_SIG_FORMAT 2081 help 2082 Check modules for valid signatures upon load: the signature 2083 is simply appended to the module. For more information see 2084 <file:Documentation/admin-guide/module-signing.rst>. 2085 2086 Note that this option adds the OpenSSL development packages as a 2087 kernel build dependency so that the signing tool can use its crypto 2088 library. 2089 2090 You should enable this option if you wish to use either 2091 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via 2092 another LSM - otherwise unsigned modules will be loadable regardless 2093 of the lockdown policy. 2094 2095 !!!WARNING!!! If you enable this option, you MUST make sure that the 2096 module DOES NOT get stripped after being signed. This includes the 2097 debuginfo strip done by some packagers (such as rpmbuild) and 2098 inclusion into an initramfs that wants the module size reduced. 2099 2100config MODULE_SIG_FORCE 2101 bool "Require modules to be validly signed" 2102 depends on MODULE_SIG 2103 help 2104 Reject unsigned modules or signed modules for which we don't have a 2105 key. Without this, such modules will simply taint the kernel. 2106 2107config MODULE_SIG_ALL 2108 bool "Automatically sign all modules" 2109 default y 2110 depends on MODULE_SIG 2111 help 2112 Sign all modules during make modules_install. Without this option, 2113 modules must be signed manually, using the scripts/sign-file tool. 2114 2115comment "Do not forget to sign required modules with scripts/sign-file" 2116 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2117 2118choice 2119 prompt "Which hash algorithm should modules be signed with?" 2120 depends on MODULE_SIG 2121 help 2122 This determines which sort of hashing algorithm will be used during 2123 signature generation. This algorithm _must_ be built into the kernel 2124 directly so that signature verification can take place. It is not 2125 possible to load a signed module containing the algorithm to check 2126 the signature on that module. 2127 2128config MODULE_SIG_SHA1 2129 bool "Sign modules with SHA-1" 2130 select CRYPTO_SHA1 2131 2132config MODULE_SIG_SHA224 2133 bool "Sign modules with SHA-224" 2134 select CRYPTO_SHA256 2135 2136config MODULE_SIG_SHA256 2137 bool "Sign modules with SHA-256" 2138 select CRYPTO_SHA256 2139 2140config MODULE_SIG_SHA384 2141 bool "Sign modules with SHA-384" 2142 select CRYPTO_SHA512 2143 2144config MODULE_SIG_SHA512 2145 bool "Sign modules with SHA-512" 2146 select CRYPTO_SHA512 2147 2148endchoice 2149 2150config MODULE_SIG_HASH 2151 string 2152 depends on MODULE_SIG 2153 default "sha1" if MODULE_SIG_SHA1 2154 default "sha224" if MODULE_SIG_SHA224 2155 default "sha256" if MODULE_SIG_SHA256 2156 default "sha384" if MODULE_SIG_SHA384 2157 default "sha512" if MODULE_SIG_SHA512 2158 2159config MODULE_COMPRESS 2160 bool "Compress modules on installation" 2161 help 2162 2163 Compresses kernel modules when 'make modules_install' is run; gzip or 2164 xz depending on "Compression algorithm" below. 2165 2166 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 2167 2168 Out-of-tree kernel modules installed using Kbuild will also be 2169 compressed upon installation. 2170 2171 Note: for modules inside an initrd or initramfs, it's more efficient 2172 to compress the whole initrd or initramfs instead. 2173 2174 Note: This is fully compatible with signed modules. 2175 2176 If in doubt, say N. 2177 2178choice 2179 prompt "Compression algorithm" 2180 depends on MODULE_COMPRESS 2181 default MODULE_COMPRESS_GZIP 2182 help 2183 This determines which sort of compression will be used during 2184 'make modules_install'. 2185 2186 GZIP (default) and XZ are supported. 2187 2188config MODULE_COMPRESS_GZIP 2189 bool "GZIP" 2190 2191config MODULE_COMPRESS_XZ 2192 bool "XZ" 2193 2194endchoice 2195 2196config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS 2197 bool "Allow loading of modules with missing namespace imports" 2198 help 2199 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in 2200 a namespace. A module that makes use of a symbol exported with such a 2201 namespace is required to import the namespace via MODULE_IMPORT_NS(). 2202 There is no technical reason to enforce correct namespace imports, 2203 but it creates consistency between symbols defining namespaces and 2204 users importing namespaces they make use of. This option relaxes this 2205 requirement and lifts the enforcement when loading a module. 2206 2207 If unsure, say N. 2208 2209config UNUSED_SYMBOLS 2210 bool "Enable unused/obsolete exported symbols" 2211 default y if X86 2212 help 2213 Unused but exported symbols make the kernel needlessly bigger. For 2214 that reason most of these unused exports will soon be removed. This 2215 option is provided temporarily to provide a transition period in case 2216 some external kernel module needs one of these symbols anyway. If you 2217 encounter such a case in your module, consider if you are actually 2218 using the right API. (rationale: since nobody in the kernel is using 2219 this in a module, there is a pretty good chance it's actually the 2220 wrong interface to use). If you really need the symbol, please send a 2221 mail to the linux kernel mailing list mentioning the symbol and why 2222 you really need it, and what the merge plan to the mainline kernel for 2223 your module is. 2224 2225config TRIM_UNUSED_KSYMS 2226 bool "Trim unused exported kernel symbols" 2227 depends on !UNUSED_SYMBOLS 2228 help 2229 The kernel and some modules make many symbols available for 2230 other modules to use via EXPORT_SYMBOL() and variants. Depending 2231 on the set of modules being selected in your kernel configuration, 2232 many of those exported symbols might never be used. 2233 2234 This option allows for unused exported symbols to be dropped from 2235 the build. In turn, this provides the compiler more opportunities 2236 (especially when using LTO) for optimizing the code and reducing 2237 binary size. This might have some security advantages as well. 2238 2239 If unsure, or if you need to build out-of-tree modules, say N. 2240 2241config UNUSED_KSYMS_WHITELIST 2242 string "Whitelist of symbols to keep in ksymtab" 2243 depends on TRIM_UNUSED_KSYMS 2244 help 2245 By default, all unused exported symbols will be un-exported from the 2246 build when TRIM_UNUSED_KSYMS is selected. 2247 2248 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept 2249 exported at all times, even in absence of in-tree users. The value to 2250 set here is the path to a text file containing the list of symbols, 2251 one per line. The path can be absolute, or relative to the kernel 2252 source tree. 2253 2254endif # MODULES 2255 2256config MODULES_TREE_LOOKUP 2257 def_bool y 2258 depends on PERF_EVENTS || TRACING 2259 2260config INIT_ALL_POSSIBLE 2261 bool 2262 help 2263 Back when each arch used to define their own cpu_online_mask and 2264 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2265 with all 1s, and others with all 0s. When they were centralised, 2266 it was better to provide this option than to break all the archs 2267 and have several arch maintainers pursuing me down dark alleys. 2268 2269source "block/Kconfig" 2270 2271config PREEMPT_NOTIFIERS 2272 bool 2273 2274config PADATA 2275 depends on SMP 2276 bool 2277 2278config ASN1 2279 tristate 2280 help 2281 Build a simple ASN.1 grammar compiler that produces a bytecode output 2282 that can be interpreted by the ASN.1 stream decoder and used to 2283 inform it as to what tags are to be expected in a stream and what 2284 functions to call on what tags. 2285 2286source "kernel/Kconfig.locks" 2287 2288config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2289 bool 2290 2291# It may be useful for an architecture to override the definitions of the 2292# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2293# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2294# different calling convention for syscalls. They can also override the 2295# macros for not-implemented syscalls in kernel/sys_ni.c and 2296# kernel/time/posix-stubs.c. All these overrides need to be available in 2297# <asm/syscall_wrapper.h>. 2298config ARCH_HAS_SYSCALL_WRAPPER 2299 def_bool n 2300