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 LD_IS_LLD 44 def_bool $(success,$(LD) -v | head -n 1 | grep -q LLD) 45 46config CLANG_VERSION 47 int 48 default $(shell,$(srctree)/scripts/clang-version.sh $(CC)) 49 50config CC_CAN_LINK 51 bool 52 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(m64-flag)) if 64BIT 53 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(m32-flag)) 54 55config CC_CAN_LINK_STATIC 56 bool 57 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) -static $(m64-flag)) if 64BIT 58 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) -static $(m32-flag)) 59 60config CC_HAS_ASM_GOTO 61 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) 62 63config CC_HAS_ASM_GOTO_OUTPUT 64 depends on CC_HAS_ASM_GOTO 65 def_bool $(success,echo 'int foo(int x) { asm goto ("": "=r"(x) ::: bar); return x; bar: return 0; }' | $(CC) -x c - -c -o /dev/null) 66 67config TOOLS_SUPPORT_RELR 68 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 69 70config CC_HAS_ASM_INLINE 71 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 72 73config CONSTRUCTORS 74 bool 75 depends on !UML 76 77config IRQ_WORK 78 bool 79 80config BUILDTIME_TABLE_SORT 81 bool 82 83config THREAD_INFO_IN_TASK 84 bool 85 help 86 Select this to move thread_info off the stack into task_struct. To 87 make this work, an arch will need to remove all thread_info fields 88 except flags and fix any runtime bugs. 89 90 One subtle change that will be needed is to use try_get_task_stack() 91 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 92 93menu "General setup" 94 95config BROKEN 96 bool 97 98config BROKEN_ON_SMP 99 bool 100 depends on BROKEN || !SMP 101 default y 102 103config INIT_ENV_ARG_LIMIT 104 int 105 default 32 if !UML 106 default 128 if UML 107 help 108 Maximum of each of the number of arguments and environment 109 variables passed to init from the kernel command line. 110 111config COMPILE_TEST 112 bool "Compile also drivers which will not load" 113 depends on !UML 114 default n 115 help 116 Some drivers can be compiled on a different platform than they are 117 intended to be run on. Despite they cannot be loaded there (or even 118 when they load they cannot be used due to missing HW support), 119 developers still, opposing to distributors, might want to build such 120 drivers to compile-test them. 121 122 If you are a developer and want to build everything available, say Y 123 here. If you are a user/distributor, say N here to exclude useless 124 drivers to be distributed. 125 126config UAPI_HEADER_TEST 127 bool "Compile test UAPI headers" 128 depends on HEADERS_INSTALL && CC_CAN_LINK 129 help 130 Compile test headers exported to user-space to ensure they are 131 self-contained, i.e. compilable as standalone units. 132 133 If you are a developer or tester and want to ensure the exported 134 headers are self-contained, say Y here. Otherwise, choose N. 135 136config LOCALVERSION 137 string "Local version - append to kernel release" 138 help 139 Append an extra string to the end of your kernel version. 140 This will show up when you type uname, for example. 141 The string you set here will be appended after the contents of 142 any files with a filename matching localversion* in your 143 object and source tree, in that order. Your total string can 144 be a maximum of 64 characters. 145 146config LOCALVERSION_AUTO 147 bool "Automatically append version information to the version string" 148 default y 149 depends on !COMPILE_TEST 150 help 151 This will try to automatically determine if the current tree is a 152 release tree by looking for git tags that belong to the current 153 top of tree revision. 154 155 A string of the format -gxxxxxxxx will be added to the localversion 156 if a git-based tree is found. The string generated by this will be 157 appended after any matching localversion* files, and after the value 158 set in CONFIG_LOCALVERSION. 159 160 (The actual string used here is the first eight characters produced 161 by running the command: 162 163 $ git rev-parse --verify HEAD 164 165 which is done within the script "scripts/setlocalversion".) 166 167config BUILD_SALT 168 string "Build ID Salt" 169 default "" 170 help 171 The build ID is used to link binaries and their debug info. Setting 172 this option will use the value in the calculation of the build id. 173 This is mostly useful for distributions which want to ensure the 174 build is unique between builds. It's safe to leave the default. 175 176config HAVE_KERNEL_GZIP 177 bool 178 179config HAVE_KERNEL_BZIP2 180 bool 181 182config HAVE_KERNEL_LZMA 183 bool 184 185config HAVE_KERNEL_XZ 186 bool 187 188config HAVE_KERNEL_LZO 189 bool 190 191config HAVE_KERNEL_LZ4 192 bool 193 194config HAVE_KERNEL_UNCOMPRESSED 195 bool 196 197choice 198 prompt "Kernel compression mode" 199 default KERNEL_GZIP 200 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED 201 help 202 The linux kernel is a kind of self-extracting executable. 203 Several compression algorithms are available, which differ 204 in efficiency, compression and decompression speed. 205 Compression speed is only relevant when building a kernel. 206 Decompression speed is relevant at each boot. 207 208 If you have any problems with bzip2 or lzma compressed 209 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 210 version of this functionality (bzip2 only), for 2.4, was 211 supplied by Christian Ludwig) 212 213 High compression options are mostly useful for users, who 214 are low on disk space (embedded systems), but for whom ram 215 size matters less. 216 217 If in doubt, select 'gzip' 218 219config KERNEL_GZIP 220 bool "Gzip" 221 depends on HAVE_KERNEL_GZIP 222 help 223 The old and tried gzip compression. It provides a good balance 224 between compression ratio and decompression speed. 225 226config KERNEL_BZIP2 227 bool "Bzip2" 228 depends on HAVE_KERNEL_BZIP2 229 help 230 Its compression ratio and speed is intermediate. 231 Decompression speed is slowest among the choices. The kernel 232 size is about 10% smaller with bzip2, in comparison to gzip. 233 Bzip2 uses a large amount of memory. For modern kernels you 234 will need at least 8MB RAM or more for booting. 235 236config KERNEL_LZMA 237 bool "LZMA" 238 depends on HAVE_KERNEL_LZMA 239 help 240 This compression algorithm's ratio is best. Decompression speed 241 is between gzip and bzip2. Compression is slowest. 242 The kernel size is about 33% smaller with LZMA in comparison to gzip. 243 244config KERNEL_XZ 245 bool "XZ" 246 depends on HAVE_KERNEL_XZ 247 help 248 XZ uses the LZMA2 algorithm and instruction set specific 249 BCJ filters which can improve compression ratio of executable 250 code. The size of the kernel is about 30% smaller with XZ in 251 comparison to gzip. On architectures for which there is a BCJ 252 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 253 will create a few percent smaller kernel than plain LZMA. 254 255 The speed is about the same as with LZMA: The decompression 256 speed of XZ is better than that of bzip2 but worse than gzip 257 and LZO. Compression is slow. 258 259config KERNEL_LZO 260 bool "LZO" 261 depends on HAVE_KERNEL_LZO 262 help 263 Its compression ratio is the poorest among the choices. The kernel 264 size is about 10% bigger than gzip; however its speed 265 (both compression and decompression) is the fastest. 266 267config KERNEL_LZ4 268 bool "LZ4" 269 depends on HAVE_KERNEL_LZ4 270 help 271 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 272 A preliminary version of LZ4 de/compression tool is available at 273 <https://code.google.com/p/lz4/>. 274 275 Its compression ratio is worse than LZO. The size of the kernel 276 is about 8% bigger than LZO. But the decompression speed is 277 faster than LZO. 278 279config KERNEL_UNCOMPRESSED 280 bool "None" 281 depends on HAVE_KERNEL_UNCOMPRESSED 282 help 283 Produce uncompressed kernel image. This option is usually not what 284 you want. It is useful for debugging the kernel in slow simulation 285 environments, where decompressing and moving the kernel is awfully 286 slow. This option allows early boot code to skip the decompressor 287 and jump right at uncompressed kernel image. 288 289endchoice 290 291config DEFAULT_INIT 292 string "Default init path" 293 default "" 294 help 295 This option determines the default init for the system if no init= 296 option is passed on the kernel command line. If the requested path is 297 not present, we will still then move on to attempting further 298 locations (e.g. /sbin/init, etc). If this is empty, we will just use 299 the fallback list when init= is not passed. 300 301config DEFAULT_HOSTNAME 302 string "Default hostname" 303 default "(none)" 304 help 305 This option determines the default system hostname before userspace 306 calls sethostname(2). The kernel traditionally uses "(none)" here, 307 but you may wish to use a different default here to make a minimal 308 system more usable with less configuration. 309 310# 311# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can 312# add proper SWAP support to them, in which case this can be remove. 313# 314config ARCH_NO_SWAP 315 bool 316 317config SWAP 318 bool "Support for paging of anonymous memory (swap)" 319 depends on MMU && BLOCK && !ARCH_NO_SWAP 320 default y 321 help 322 This option allows you to choose whether you want to have support 323 for so called swap devices or swap files in your kernel that are 324 used to provide more virtual memory than the actual RAM present 325 in your computer. If unsure say Y. 326 327config SYSVIPC 328 bool "System V IPC" 329 ---help--- 330 Inter Process Communication is a suite of library functions and 331 system calls which let processes (running programs) synchronize and 332 exchange information. It is generally considered to be a good thing, 333 and some programs won't run unless you say Y here. In particular, if 334 you want to run the DOS emulator dosemu under Linux (read the 335 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 336 you'll need to say Y here. 337 338 You can find documentation about IPC with "info ipc" and also in 339 section 6.4 of the Linux Programmer's Guide, available from 340 <http://www.tldp.org/guides.html>. 341 342config SYSVIPC_SYSCTL 343 bool 344 depends on SYSVIPC 345 depends on SYSCTL 346 default y 347 348config POSIX_MQUEUE 349 bool "POSIX Message Queues" 350 depends on NET 351 ---help--- 352 POSIX variant of message queues is a part of IPC. In POSIX message 353 queues every message has a priority which decides about succession 354 of receiving it by a process. If you want to compile and run 355 programs written e.g. for Solaris with use of its POSIX message 356 queues (functions mq_*) say Y here. 357 358 POSIX message queues are visible as a filesystem called 'mqueue' 359 and can be mounted somewhere if you want to do filesystem 360 operations on message queues. 361 362 If unsure, say Y. 363 364config POSIX_MQUEUE_SYSCTL 365 bool 366 depends on POSIX_MQUEUE 367 depends on SYSCTL 368 default y 369 370config CROSS_MEMORY_ATTACH 371 bool "Enable process_vm_readv/writev syscalls" 372 depends on MMU 373 default y 374 help 375 Enabling this option adds the system calls process_vm_readv and 376 process_vm_writev which allow a process with the correct privileges 377 to directly read from or write to another process' address space. 378 See the man page for more details. 379 380config USELIB 381 bool "uselib syscall" 382 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION 383 help 384 This option enables the uselib syscall, a system call used in the 385 dynamic linker from libc5 and earlier. glibc does not use this 386 system call. If you intend to run programs built on libc5 or 387 earlier, you may need to enable this syscall. Current systems 388 running glibc can safely disable this. 389 390config AUDIT 391 bool "Auditing support" 392 depends on NET 393 help 394 Enable auditing infrastructure that can be used with another 395 kernel subsystem, such as SELinux (which requires this for 396 logging of avc messages output). System call auditing is included 397 on architectures which support it. 398 399config HAVE_ARCH_AUDITSYSCALL 400 bool 401 402config AUDITSYSCALL 403 def_bool y 404 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 405 select FSNOTIFY 406 407source "kernel/irq/Kconfig" 408source "kernel/time/Kconfig" 409source "kernel/Kconfig.preempt" 410 411menu "CPU/Task time and stats accounting" 412 413config VIRT_CPU_ACCOUNTING 414 bool 415 416choice 417 prompt "Cputime accounting" 418 default TICK_CPU_ACCOUNTING if !PPC64 419 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 420 421# Kind of a stub config for the pure tick based cputime accounting 422config TICK_CPU_ACCOUNTING 423 bool "Simple tick based cputime accounting" 424 depends on !S390 && !NO_HZ_FULL 425 help 426 This is the basic tick based cputime accounting that maintains 427 statistics about user, system and idle time spent on per jiffies 428 granularity. 429 430 If unsure, say Y. 431 432config VIRT_CPU_ACCOUNTING_NATIVE 433 bool "Deterministic task and CPU time accounting" 434 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 435 select VIRT_CPU_ACCOUNTING 436 help 437 Select this option to enable more accurate task and CPU time 438 accounting. This is done by reading a CPU counter on each 439 kernel entry and exit and on transitions within the kernel 440 between system, softirq and hardirq state, so there is a 441 small performance impact. In the case of s390 or IBM POWER > 5, 442 this also enables accounting of stolen time on logically-partitioned 443 systems. 444 445config VIRT_CPU_ACCOUNTING_GEN 446 bool "Full dynticks CPU time accounting" 447 depends on HAVE_CONTEXT_TRACKING 448 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 449 depends on GENERIC_CLOCKEVENTS 450 select VIRT_CPU_ACCOUNTING 451 select CONTEXT_TRACKING 452 help 453 Select this option to enable task and CPU time accounting on full 454 dynticks systems. This accounting is implemented by watching every 455 kernel-user boundaries using the context tracking subsystem. 456 The accounting is thus performed at the expense of some significant 457 overhead. 458 459 For now this is only useful if you are working on the full 460 dynticks subsystem development. 461 462 If unsure, say N. 463 464endchoice 465 466config IRQ_TIME_ACCOUNTING 467 bool "Fine granularity task level IRQ time accounting" 468 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 469 help 470 Select this option to enable fine granularity task irq time 471 accounting. This is done by reading a timestamp on each 472 transitions between softirq and hardirq state, so there can be a 473 small performance impact. 474 475 If in doubt, say N here. 476 477config HAVE_SCHED_AVG_IRQ 478 def_bool y 479 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 480 depends on SMP 481 482config SCHED_THERMAL_PRESSURE 483 bool "Enable periodic averaging of thermal pressure" 484 depends on SMP 485 486config BSD_PROCESS_ACCT 487 bool "BSD Process Accounting" 488 depends on MULTIUSER 489 help 490 If you say Y here, a user level program will be able to instruct the 491 kernel (via a special system call) to write process accounting 492 information to a file: whenever a process exits, information about 493 that process will be appended to the file by the kernel. The 494 information includes things such as creation time, owning user, 495 command name, memory usage, controlling terminal etc. (the complete 496 list is in the struct acct in <file:include/linux/acct.h>). It is 497 up to the user level program to do useful things with this 498 information. This is generally a good idea, so say Y. 499 500config BSD_PROCESS_ACCT_V3 501 bool "BSD Process Accounting version 3 file format" 502 depends on BSD_PROCESS_ACCT 503 default n 504 help 505 If you say Y here, the process accounting information is written 506 in a new file format that also logs the process IDs of each 507 process and its parent. Note that this file format is incompatible 508 with previous v0/v1/v2 file formats, so you will need updated tools 509 for processing it. A preliminary version of these tools is available 510 at <http://www.gnu.org/software/acct/>. 511 512config TASKSTATS 513 bool "Export task/process statistics through netlink" 514 depends on NET 515 depends on MULTIUSER 516 default n 517 help 518 Export selected statistics for tasks/processes through the 519 generic netlink interface. Unlike BSD process accounting, the 520 statistics are available during the lifetime of tasks/processes as 521 responses to commands. Like BSD accounting, they are sent to user 522 space on task exit. 523 524 Say N if unsure. 525 526config TASK_DELAY_ACCT 527 bool "Enable per-task delay accounting" 528 depends on TASKSTATS 529 select SCHED_INFO 530 help 531 Collect information on time spent by a task waiting for system 532 resources like cpu, synchronous block I/O completion and swapping 533 in pages. Such statistics can help in setting a task's priorities 534 relative to other tasks for cpu, io, rss limits etc. 535 536 Say N if unsure. 537 538config TASK_XACCT 539 bool "Enable extended accounting over taskstats" 540 depends on TASKSTATS 541 help 542 Collect extended task accounting data and send the data 543 to userland for processing over the taskstats interface. 544 545 Say N if unsure. 546 547config TASK_IO_ACCOUNTING 548 bool "Enable per-task storage I/O accounting" 549 depends on TASK_XACCT 550 help 551 Collect information on the number of bytes of storage I/O which this 552 task has caused. 553 554 Say N if unsure. 555 556config PSI 557 bool "Pressure stall information tracking" 558 help 559 Collect metrics that indicate how overcommitted the CPU, memory, 560 and IO capacity are in the system. 561 562 If you say Y here, the kernel will create /proc/pressure/ with the 563 pressure statistics files cpu, memory, and io. These will indicate 564 the share of walltime in which some or all tasks in the system are 565 delayed due to contention of the respective resource. 566 567 In kernels with cgroup support, cgroups (cgroup2 only) will 568 have cpu.pressure, memory.pressure, and io.pressure files, 569 which aggregate pressure stalls for the grouped tasks only. 570 571 For more details see Documentation/accounting/psi.rst. 572 573 Say N if unsure. 574 575config PSI_DEFAULT_DISABLED 576 bool "Require boot parameter to enable pressure stall information tracking" 577 default n 578 depends on PSI 579 help 580 If set, pressure stall information tracking will be disabled 581 per default but can be enabled through passing psi=1 on the 582 kernel commandline during boot. 583 584 This feature adds some code to the task wakeup and sleep 585 paths of the scheduler. The overhead is too low to affect 586 common scheduling-intense workloads in practice (such as 587 webservers, memcache), but it does show up in artificial 588 scheduler stress tests, such as hackbench. 589 590 If you are paranoid and not sure what the kernel will be 591 used for, say Y. 592 593 Say N if unsure. 594 595endmenu # "CPU/Task time and stats accounting" 596 597config CPU_ISOLATION 598 bool "CPU isolation" 599 depends on SMP || COMPILE_TEST 600 default y 601 help 602 Make sure that CPUs running critical tasks are not disturbed by 603 any source of "noise" such as unbound workqueues, timers, kthreads... 604 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 605 the "isolcpus=" boot parameter. 606 607 Say Y if unsure. 608 609source "kernel/rcu/Kconfig" 610 611config BUILD_BIN2C 612 bool 613 default n 614 615config IKCONFIG 616 tristate "Kernel .config support" 617 ---help--- 618 This option enables the complete Linux kernel ".config" file 619 contents to be saved in the kernel. It provides documentation 620 of which kernel options are used in a running kernel or in an 621 on-disk kernel. This information can be extracted from the kernel 622 image file with the script scripts/extract-ikconfig and used as 623 input to rebuild the current kernel or to build another kernel. 624 It can also be extracted from a running kernel by reading 625 /proc/config.gz if enabled (below). 626 627config IKCONFIG_PROC 628 bool "Enable access to .config through /proc/config.gz" 629 depends on IKCONFIG && PROC_FS 630 ---help--- 631 This option enables access to the kernel configuration file 632 through /proc/config.gz. 633 634config IKHEADERS 635 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 636 depends on SYSFS 637 help 638 This option enables access to the in-kernel headers that are generated during 639 the build process. These can be used to build eBPF tracing programs, 640 or similar programs. If you build the headers as a module, a module called 641 kheaders.ko is built which can be loaded on-demand to get access to headers. 642 643config LOG_BUF_SHIFT 644 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 645 range 12 25 646 default 17 647 depends on PRINTK 648 help 649 Select the minimal kernel log buffer size as a power of 2. 650 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 651 parameter, see below. Any higher size also might be forced 652 by "log_buf_len" boot parameter. 653 654 Examples: 655 17 => 128 KB 656 16 => 64 KB 657 15 => 32 KB 658 14 => 16 KB 659 13 => 8 KB 660 12 => 4 KB 661 662config LOG_CPU_MAX_BUF_SHIFT 663 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 664 depends on SMP 665 range 0 21 666 default 12 if !BASE_SMALL 667 default 0 if BASE_SMALL 668 depends on PRINTK 669 help 670 This option allows to increase the default ring buffer size 671 according to the number of CPUs. The value defines the contribution 672 of each CPU as a power of 2. The used space is typically only few 673 lines however it might be much more when problems are reported, 674 e.g. backtraces. 675 676 The increased size means that a new buffer has to be allocated and 677 the original static one is unused. It makes sense only on systems 678 with more CPUs. Therefore this value is used only when the sum of 679 contributions is greater than the half of the default kernel ring 680 buffer as defined by LOG_BUF_SHIFT. The default values are set 681 so that more than 64 CPUs are needed to trigger the allocation. 682 683 Also this option is ignored when "log_buf_len" kernel parameter is 684 used as it forces an exact (power of two) size of the ring buffer. 685 686 The number of possible CPUs is used for this computation ignoring 687 hotplugging making the computation optimal for the worst case 688 scenario while allowing a simple algorithm to be used from bootup. 689 690 Examples shift values and their meaning: 691 17 => 128 KB for each CPU 692 16 => 64 KB for each CPU 693 15 => 32 KB for each CPU 694 14 => 16 KB for each CPU 695 13 => 8 KB for each CPU 696 12 => 4 KB for each CPU 697 698config PRINTK_SAFE_LOG_BUF_SHIFT 699 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 700 range 10 21 701 default 13 702 depends on PRINTK 703 help 704 Select the size of an alternate printk per-CPU buffer where messages 705 printed from usafe contexts are temporary stored. One example would 706 be NMI messages, another one - printk recursion. The messages are 707 copied to the main log buffer in a safe context to avoid a deadlock. 708 The value defines the size as a power of 2. 709 710 Those messages are rare and limited. The largest one is when 711 a backtrace is printed. It usually fits into 4KB. Select 712 8KB if you want to be on the safe side. 713 714 Examples: 715 17 => 128 KB for each CPU 716 16 => 64 KB for each CPU 717 15 => 32 KB for each CPU 718 14 => 16 KB for each CPU 719 13 => 8 KB for each CPU 720 12 => 4 KB for each CPU 721 722# 723# Architectures with an unreliable sched_clock() should select this: 724# 725config HAVE_UNSTABLE_SCHED_CLOCK 726 bool 727 728config GENERIC_SCHED_CLOCK 729 bool 730 731menu "Scheduler features" 732 733config UCLAMP_TASK 734 bool "Enable utilization clamping for RT/FAIR tasks" 735 depends on CPU_FREQ_GOV_SCHEDUTIL 736 help 737 This feature enables the scheduler to track the clamped utilization 738 of each CPU based on RUNNABLE tasks scheduled on that CPU. 739 740 With this option, the user can specify the min and max CPU 741 utilization allowed for RUNNABLE tasks. The max utilization defines 742 the maximum frequency a task should use while the min utilization 743 defines the minimum frequency it should use. 744 745 Both min and max utilization clamp values are hints to the scheduler, 746 aiming at improving its frequency selection policy, but they do not 747 enforce or grant any specific bandwidth for tasks. 748 749 If in doubt, say N. 750 751config UCLAMP_BUCKETS_COUNT 752 int "Number of supported utilization clamp buckets" 753 range 5 20 754 default 5 755 depends on UCLAMP_TASK 756 help 757 Defines the number of clamp buckets to use. The range of each bucket 758 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 759 number of clamp buckets the finer their granularity and the higher 760 the precision of clamping aggregation and tracking at run-time. 761 762 For example, with the minimum configuration value we will have 5 763 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 764 be refcounted in the [20..39]% bucket and will set the bucket clamp 765 effective value to 25%. 766 If a second 30% boosted task should be co-scheduled on the same CPU, 767 that task will be refcounted in the same bucket of the first task and 768 it will boost the bucket clamp effective value to 30%. 769 The clamp effective value of a bucket is reset to its nominal value 770 (20% in the example above) when there are no more tasks refcounted in 771 that bucket. 772 773 An additional boost/capping margin can be added to some tasks. In the 774 example above the 25% task will be boosted to 30% until it exits the 775 CPU. If that should be considered not acceptable on certain systems, 776 it's always possible to reduce the margin by increasing the number of 777 clamp buckets to trade off used memory for run-time tracking 778 precision. 779 780 If in doubt, use the default value. 781 782endmenu 783 784# 785# For architectures that want to enable the support for NUMA-affine scheduler 786# balancing logic: 787# 788config ARCH_SUPPORTS_NUMA_BALANCING 789 bool 790 791# 792# For architectures that prefer to flush all TLBs after a number of pages 793# are unmapped instead of sending one IPI per page to flush. The architecture 794# must provide guarantees on what happens if a clean TLB cache entry is 795# written after the unmap. Details are in mm/rmap.c near the check for 796# should_defer_flush. The architecture should also consider if the full flush 797# and the refill costs are offset by the savings of sending fewer IPIs. 798config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 799 bool 800 801config CC_HAS_INT128 802 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 803 804# 805# For architectures that know their GCC __int128 support is sound 806# 807config ARCH_SUPPORTS_INT128 808 bool 809 810# For architectures that (ab)use NUMA to represent different memory regions 811# all cpu-local but of different latencies, such as SuperH. 812# 813config ARCH_WANT_NUMA_VARIABLE_LOCALITY 814 bool 815 816config NUMA_BALANCING 817 bool "Memory placement aware NUMA scheduler" 818 depends on ARCH_SUPPORTS_NUMA_BALANCING 819 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 820 depends on SMP && NUMA && MIGRATION 821 help 822 This option adds support for automatic NUMA aware memory/task placement. 823 The mechanism is quite primitive and is based on migrating memory when 824 it has references to the node the task is running on. 825 826 This system will be inactive on UMA systems. 827 828config NUMA_BALANCING_DEFAULT_ENABLED 829 bool "Automatically enable NUMA aware memory/task placement" 830 default y 831 depends on NUMA_BALANCING 832 help 833 If set, automatic NUMA balancing will be enabled if running on a NUMA 834 machine. 835 836menuconfig CGROUPS 837 bool "Control Group support" 838 select KERNFS 839 help 840 This option adds support for grouping sets of processes together, for 841 use with process control subsystems such as Cpusets, CFS, memory 842 controls or device isolation. 843 See 844 - Documentation/scheduler/sched-design-CFS.rst (CFS) 845 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 846 and resource control) 847 848 Say N if unsure. 849 850if CGROUPS 851 852config PAGE_COUNTER 853 bool 854 855config MEMCG 856 bool "Memory controller" 857 select PAGE_COUNTER 858 select EVENTFD 859 help 860 Provides control over the memory footprint of tasks in a cgroup. 861 862config MEMCG_SWAP 863 bool 864 depends on MEMCG && SWAP 865 default y 866 867config MEMCG_KMEM 868 bool 869 depends on MEMCG && !SLOB 870 default y 871 872config BLK_CGROUP 873 bool "IO controller" 874 depends on BLOCK 875 default n 876 ---help--- 877 Generic block IO controller cgroup interface. This is the common 878 cgroup interface which should be used by various IO controlling 879 policies. 880 881 Currently, CFQ IO scheduler uses it to recognize task groups and 882 control disk bandwidth allocation (proportional time slice allocation) 883 to such task groups. It is also used by bio throttling logic in 884 block layer to implement upper limit in IO rates on a device. 885 886 This option only enables generic Block IO controller infrastructure. 887 One needs to also enable actual IO controlling logic/policy. For 888 enabling proportional weight division of disk bandwidth in CFQ, set 889 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 890 CONFIG_BLK_DEV_THROTTLING=y. 891 892 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 893 894config CGROUP_WRITEBACK 895 bool 896 depends on MEMCG && BLK_CGROUP 897 default y 898 899menuconfig CGROUP_SCHED 900 bool "CPU controller" 901 default n 902 help 903 This feature lets CPU scheduler recognize task groups and control CPU 904 bandwidth allocation to such task groups. It uses cgroups to group 905 tasks. 906 907if CGROUP_SCHED 908config FAIR_GROUP_SCHED 909 bool "Group scheduling for SCHED_OTHER" 910 depends on CGROUP_SCHED 911 default CGROUP_SCHED 912 913config CFS_BANDWIDTH 914 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 915 depends on FAIR_GROUP_SCHED 916 default n 917 help 918 This option allows users to define CPU bandwidth rates (limits) for 919 tasks running within the fair group scheduler. Groups with no limit 920 set are considered to be unconstrained and will run with no 921 restriction. 922 See Documentation/scheduler/sched-bwc.rst for more information. 923 924config RT_GROUP_SCHED 925 bool "Group scheduling for SCHED_RR/FIFO" 926 depends on CGROUP_SCHED 927 default n 928 help 929 This feature lets you explicitly allocate real CPU bandwidth 930 to task groups. If enabled, it will also make it impossible to 931 schedule realtime tasks for non-root users until you allocate 932 realtime bandwidth for them. 933 See Documentation/scheduler/sched-rt-group.rst for more information. 934 935endif #CGROUP_SCHED 936 937config UCLAMP_TASK_GROUP 938 bool "Utilization clamping per group of tasks" 939 depends on CGROUP_SCHED 940 depends on UCLAMP_TASK 941 default n 942 help 943 This feature enables the scheduler to track the clamped utilization 944 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 945 946 When this option is enabled, the user can specify a min and max 947 CPU bandwidth which is allowed for each single task in a group. 948 The max bandwidth allows to clamp the maximum frequency a task 949 can use, while the min bandwidth allows to define a minimum 950 frequency a task will always use. 951 952 When task group based utilization clamping is enabled, an eventually 953 specified task-specific clamp value is constrained by the cgroup 954 specified clamp value. Both minimum and maximum task clamping cannot 955 be bigger than the corresponding clamping defined at task group level. 956 957 If in doubt, say N. 958 959config CGROUP_PIDS 960 bool "PIDs controller" 961 help 962 Provides enforcement of process number limits in the scope of a 963 cgroup. Any attempt to fork more processes than is allowed in the 964 cgroup will fail. PIDs are fundamentally a global resource because it 965 is fairly trivial to reach PID exhaustion before you reach even a 966 conservative kmemcg limit. As a result, it is possible to grind a 967 system to halt without being limited by other cgroup policies. The 968 PIDs controller is designed to stop this from happening. 969 970 It should be noted that organisational operations (such as attaching 971 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 972 since the PIDs limit only affects a process's ability to fork, not to 973 attach to a cgroup. 974 975config CGROUP_RDMA 976 bool "RDMA controller" 977 help 978 Provides enforcement of RDMA resources defined by IB stack. 979 It is fairly easy for consumers to exhaust RDMA resources, which 980 can result into resource unavailability to other consumers. 981 RDMA controller is designed to stop this from happening. 982 Attaching processes with active RDMA resources to the cgroup 983 hierarchy is allowed even if can cross the hierarchy's limit. 984 985config CGROUP_FREEZER 986 bool "Freezer controller" 987 help 988 Provides a way to freeze and unfreeze all tasks in a 989 cgroup. 990 991 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 992 controller includes important in-kernel memory consumers per default. 993 994 If you're using cgroup2, say N. 995 996config CGROUP_HUGETLB 997 bool "HugeTLB controller" 998 depends on HUGETLB_PAGE 999 select PAGE_COUNTER 1000 default n 1001 help 1002 Provides a cgroup controller for HugeTLB pages. 1003 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1004 The limit is enforced during page fault. Since HugeTLB doesn't 1005 support page reclaim, enforcing the limit at page fault time implies 1006 that, the application will get SIGBUS signal if it tries to access 1007 HugeTLB pages beyond its limit. This requires the application to know 1008 beforehand how much HugeTLB pages it would require for its use. The 1009 control group is tracked in the third page lru pointer. This means 1010 that we cannot use the controller with huge page less than 3 pages. 1011 1012config CPUSETS 1013 bool "Cpuset controller" 1014 depends on SMP 1015 help 1016 This option will let you create and manage CPUSETs which 1017 allow dynamically partitioning a system into sets of CPUs and 1018 Memory Nodes and assigning tasks to run only within those sets. 1019 This is primarily useful on large SMP or NUMA systems. 1020 1021 Say N if unsure. 1022 1023config PROC_PID_CPUSET 1024 bool "Include legacy /proc/<pid>/cpuset file" 1025 depends on CPUSETS 1026 default y 1027 1028config CGROUP_DEVICE 1029 bool "Device controller" 1030 help 1031 Provides a cgroup controller implementing whitelists for 1032 devices which a process in the cgroup can mknod or open. 1033 1034config CGROUP_CPUACCT 1035 bool "Simple CPU accounting controller" 1036 help 1037 Provides a simple controller for monitoring the 1038 total CPU consumed by the tasks in a cgroup. 1039 1040config CGROUP_PERF 1041 bool "Perf controller" 1042 depends on PERF_EVENTS 1043 help 1044 This option extends the perf per-cpu mode to restrict monitoring 1045 to threads which belong to the cgroup specified and run on the 1046 designated cpu. Or this can be used to have cgroup ID in samples 1047 so that it can monitor performance events among cgroups. 1048 1049 Say N if unsure. 1050 1051config CGROUP_BPF 1052 bool "Support for eBPF programs attached to cgroups" 1053 depends on BPF_SYSCALL 1054 select SOCK_CGROUP_DATA 1055 help 1056 Allow attaching eBPF programs to a cgroup using the bpf(2) 1057 syscall command BPF_PROG_ATTACH. 1058 1059 In which context these programs are accessed depends on the type 1060 of attachment. For instance, programs that are attached using 1061 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1062 inet sockets. 1063 1064config CGROUP_DEBUG 1065 bool "Debug controller" 1066 default n 1067 depends on DEBUG_KERNEL 1068 help 1069 This option enables a simple controller that exports 1070 debugging information about the cgroups framework. This 1071 controller is for control cgroup debugging only. Its 1072 interfaces are not stable. 1073 1074 Say N. 1075 1076config SOCK_CGROUP_DATA 1077 bool 1078 default n 1079 1080endif # CGROUPS 1081 1082menuconfig NAMESPACES 1083 bool "Namespaces support" if EXPERT 1084 depends on MULTIUSER 1085 default !EXPERT 1086 help 1087 Provides the way to make tasks work with different objects using 1088 the same id. For example same IPC id may refer to different objects 1089 or same user id or pid may refer to different tasks when used in 1090 different namespaces. 1091 1092if NAMESPACES 1093 1094config UTS_NS 1095 bool "UTS namespace" 1096 default y 1097 help 1098 In this namespace tasks see different info provided with the 1099 uname() system call 1100 1101config TIME_NS 1102 bool "TIME namespace" 1103 depends on GENERIC_VDSO_TIME_NS 1104 default y 1105 help 1106 In this namespace boottime and monotonic clocks can be set. 1107 The time will keep going with the same pace. 1108 1109config IPC_NS 1110 bool "IPC namespace" 1111 depends on (SYSVIPC || POSIX_MQUEUE) 1112 default y 1113 help 1114 In this namespace tasks work with IPC ids which correspond to 1115 different IPC objects in different namespaces. 1116 1117config USER_NS 1118 bool "User namespace" 1119 default n 1120 help 1121 This allows containers, i.e. vservers, to use user namespaces 1122 to provide different user info for different servers. 1123 1124 When user namespaces are enabled in the kernel it is 1125 recommended that the MEMCG option also be enabled and that 1126 user-space use the memory control groups to limit the amount 1127 of memory a memory unprivileged users can use. 1128 1129 If unsure, say N. 1130 1131config PID_NS 1132 bool "PID Namespaces" 1133 default y 1134 help 1135 Support process id namespaces. This allows having multiple 1136 processes with the same pid as long as they are in different 1137 pid namespaces. This is a building block of containers. 1138 1139config NET_NS 1140 bool "Network namespace" 1141 depends on NET 1142 default y 1143 help 1144 Allow user space to create what appear to be multiple instances 1145 of the network stack. 1146 1147endif # NAMESPACES 1148 1149config CHECKPOINT_RESTORE 1150 bool "Checkpoint/restore support" 1151 select PROC_CHILDREN 1152 default n 1153 help 1154 Enables additional kernel features in a sake of checkpoint/restore. 1155 In particular it adds auxiliary prctl codes to setup process text, 1156 data and heap segment sizes, and a few additional /proc filesystem 1157 entries. 1158 1159 If unsure, say N here. 1160 1161config SCHED_AUTOGROUP 1162 bool "Automatic process group scheduling" 1163 select CGROUPS 1164 select CGROUP_SCHED 1165 select FAIR_GROUP_SCHED 1166 help 1167 This option optimizes the scheduler for common desktop workloads by 1168 automatically creating and populating task groups. This separation 1169 of workloads isolates aggressive CPU burners (like build jobs) from 1170 desktop applications. Task group autogeneration is currently based 1171 upon task session. 1172 1173config SYSFS_DEPRECATED 1174 bool "Enable deprecated sysfs features to support old userspace tools" 1175 depends on SYSFS 1176 default n 1177 help 1178 This option adds code that switches the layout of the "block" class 1179 devices, to not show up in /sys/class/block/, but only in 1180 /sys/block/. 1181 1182 This switch is only active when the sysfs.deprecated=1 boot option is 1183 passed or the SYSFS_DEPRECATED_V2 option is set. 1184 1185 This option allows new kernels to run on old distributions and tools, 1186 which might get confused by /sys/class/block/. Since 2007/2008 all 1187 major distributions and tools handle this just fine. 1188 1189 Recent distributions and userspace tools after 2009/2010 depend on 1190 the existence of /sys/class/block/, and will not work with this 1191 option enabled. 1192 1193 Only if you are using a new kernel on an old distribution, you might 1194 need to say Y here. 1195 1196config SYSFS_DEPRECATED_V2 1197 bool "Enable deprecated sysfs features by default" 1198 default n 1199 depends on SYSFS 1200 depends on SYSFS_DEPRECATED 1201 help 1202 Enable deprecated sysfs by default. 1203 1204 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1205 option. 1206 1207 Only if you are using a new kernel on an old distribution, you might 1208 need to say Y here. Even then, odds are you would not need it 1209 enabled, you can always pass the boot option if absolutely necessary. 1210 1211config RELAY 1212 bool "Kernel->user space relay support (formerly relayfs)" 1213 select IRQ_WORK 1214 help 1215 This option enables support for relay interface support in 1216 certain file systems (such as debugfs). 1217 It is designed to provide an efficient mechanism for tools and 1218 facilities to relay large amounts of data from kernel space to 1219 user space. 1220 1221 If unsure, say N. 1222 1223config BLK_DEV_INITRD 1224 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1225 help 1226 The initial RAM filesystem is a ramfs which is loaded by the 1227 boot loader (loadlin or lilo) and that is mounted as root 1228 before the normal boot procedure. It is typically used to 1229 load modules needed to mount the "real" root file system, 1230 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1231 1232 If RAM disk support (BLK_DEV_RAM) is also included, this 1233 also enables initial RAM disk (initrd) support and adds 1234 15 Kbytes (more on some other architectures) to the kernel size. 1235 1236 If unsure say Y. 1237 1238if BLK_DEV_INITRD 1239 1240source "usr/Kconfig" 1241 1242endif 1243 1244config BOOT_CONFIG 1245 bool "Boot config support" 1246 select BLK_DEV_INITRD 1247 help 1248 Extra boot config allows system admin to pass a config file as 1249 complemental extension of kernel cmdline when booting. 1250 The boot config file must be attached at the end of initramfs 1251 with checksum, size and magic word. 1252 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1253 1254 If unsure, say Y. 1255 1256choice 1257 prompt "Compiler optimization level" 1258 default CC_OPTIMIZE_FOR_PERFORMANCE 1259 1260config CC_OPTIMIZE_FOR_PERFORMANCE 1261 bool "Optimize for performance (-O2)" 1262 help 1263 This is the default optimization level for the kernel, building 1264 with the "-O2" compiler flag for best performance and most 1265 helpful compile-time warnings. 1266 1267config CC_OPTIMIZE_FOR_PERFORMANCE_O3 1268 bool "Optimize more for performance (-O3)" 1269 depends on ARC 1270 help 1271 Choosing this option will pass "-O3" to your compiler to optimize 1272 the kernel yet more for performance. 1273 1274config CC_OPTIMIZE_FOR_SIZE 1275 bool "Optimize for size (-Os)" 1276 help 1277 Choosing this option will pass "-Os" to your compiler resulting 1278 in a smaller kernel. 1279 1280endchoice 1281 1282config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1283 bool 1284 help 1285 This requires that the arch annotates or otherwise protects 1286 its external entry points from being discarded. Linker scripts 1287 must also merge .text.*, .data.*, and .bss.* correctly into 1288 output sections. Care must be taken not to pull in unrelated 1289 sections (e.g., '.text.init'). Typically '.' in section names 1290 is used to distinguish them from label names / C identifiers. 1291 1292config LD_DEAD_CODE_DATA_ELIMINATION 1293 bool "Dead code and data elimination (EXPERIMENTAL)" 1294 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1295 depends on EXPERT 1296 depends on $(cc-option,-ffunction-sections -fdata-sections) 1297 depends on $(ld-option,--gc-sections) 1298 help 1299 Enable this if you want to do dead code and data elimination with 1300 the linker by compiling with -ffunction-sections -fdata-sections, 1301 and linking with --gc-sections. 1302 1303 This can reduce on disk and in-memory size of the kernel 1304 code and static data, particularly for small configs and 1305 on small systems. This has the possibility of introducing 1306 silently broken kernel if the required annotations are not 1307 present. This option is not well tested yet, so use at your 1308 own risk. 1309 1310config SYSCTL 1311 bool 1312 1313config HAVE_UID16 1314 bool 1315 1316config SYSCTL_EXCEPTION_TRACE 1317 bool 1318 help 1319 Enable support for /proc/sys/debug/exception-trace. 1320 1321config SYSCTL_ARCH_UNALIGN_NO_WARN 1322 bool 1323 help 1324 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1325 Allows arch to define/use @no_unaligned_warning to possibly warn 1326 about unaligned access emulation going on under the hood. 1327 1328config SYSCTL_ARCH_UNALIGN_ALLOW 1329 bool 1330 help 1331 Enable support for /proc/sys/kernel/unaligned-trap 1332 Allows arches to define/use @unaligned_enabled to runtime toggle 1333 the unaligned access emulation. 1334 see arch/parisc/kernel/unaligned.c for reference 1335 1336config HAVE_PCSPKR_PLATFORM 1337 bool 1338 1339# interpreter that classic socket filters depend on 1340config BPF 1341 bool 1342 1343menuconfig EXPERT 1344 bool "Configure standard kernel features (expert users)" 1345 # Unhide debug options, to make the on-by-default options visible 1346 select DEBUG_KERNEL 1347 help 1348 This option allows certain base kernel options and settings 1349 to be disabled or tweaked. This is for specialized 1350 environments which can tolerate a "non-standard" kernel. 1351 Only use this if you really know what you are doing. 1352 1353config UID16 1354 bool "Enable 16-bit UID system calls" if EXPERT 1355 depends on HAVE_UID16 && MULTIUSER 1356 default y 1357 help 1358 This enables the legacy 16-bit UID syscall wrappers. 1359 1360config MULTIUSER 1361 bool "Multiple users, groups and capabilities support" if EXPERT 1362 default y 1363 help 1364 This option enables support for non-root users, groups and 1365 capabilities. 1366 1367 If you say N here, all processes will run with UID 0, GID 0, and all 1368 possible capabilities. Saying N here also compiles out support for 1369 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1370 setgid, and capset. 1371 1372 If unsure, say Y here. 1373 1374config SGETMASK_SYSCALL 1375 bool "sgetmask/ssetmask syscalls support" if EXPERT 1376 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1377 ---help--- 1378 sys_sgetmask and sys_ssetmask are obsolete system calls 1379 no longer supported in libc but still enabled by default in some 1380 architectures. 1381 1382 If unsure, leave the default option here. 1383 1384config SYSFS_SYSCALL 1385 bool "Sysfs syscall support" if EXPERT 1386 default y 1387 ---help--- 1388 sys_sysfs is an obsolete system call no longer supported in libc. 1389 Note that disabling this option is more secure but might break 1390 compatibility with some systems. 1391 1392 If unsure say Y here. 1393 1394config FHANDLE 1395 bool "open by fhandle syscalls" if EXPERT 1396 select EXPORTFS 1397 default y 1398 help 1399 If you say Y here, a user level program will be able to map 1400 file names to handle and then later use the handle for 1401 different file system operations. This is useful in implementing 1402 userspace file servers, which now track files using handles instead 1403 of names. The handle would remain the same even if file names 1404 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1405 syscalls. 1406 1407config POSIX_TIMERS 1408 bool "Posix Clocks & timers" if EXPERT 1409 default y 1410 help 1411 This includes native support for POSIX timers to the kernel. 1412 Some embedded systems have no use for them and therefore they 1413 can be configured out to reduce the size of the kernel image. 1414 1415 When this option is disabled, the following syscalls won't be 1416 available: timer_create, timer_gettime: timer_getoverrun, 1417 timer_settime, timer_delete, clock_adjtime, getitimer, 1418 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1419 clock_getres and clock_nanosleep syscalls will be limited to 1420 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1421 1422 If unsure say y. 1423 1424config PRINTK 1425 default y 1426 bool "Enable support for printk" if EXPERT 1427 select IRQ_WORK 1428 help 1429 This option enables normal printk support. Removing it 1430 eliminates most of the message strings from the kernel image 1431 and makes the kernel more or less silent. As this makes it 1432 very difficult to diagnose system problems, saying N here is 1433 strongly discouraged. 1434 1435config PRINTK_NMI 1436 def_bool y 1437 depends on PRINTK 1438 depends on HAVE_NMI 1439 1440config BUG 1441 bool "BUG() support" if EXPERT 1442 default y 1443 help 1444 Disabling this option eliminates support for BUG and WARN, reducing 1445 the size of your kernel image and potentially quietly ignoring 1446 numerous fatal conditions. You should only consider disabling this 1447 option for embedded systems with no facilities for reporting errors. 1448 Just say Y. 1449 1450config ELF_CORE 1451 depends on COREDUMP 1452 default y 1453 bool "Enable ELF core dumps" if EXPERT 1454 help 1455 Enable support for generating core dumps. Disabling saves about 4k. 1456 1457 1458config PCSPKR_PLATFORM 1459 bool "Enable PC-Speaker support" if EXPERT 1460 depends on HAVE_PCSPKR_PLATFORM 1461 select I8253_LOCK 1462 default y 1463 help 1464 This option allows to disable the internal PC-Speaker 1465 support, saving some memory. 1466 1467config BASE_FULL 1468 default y 1469 bool "Enable full-sized data structures for core" if EXPERT 1470 help 1471 Disabling this option reduces the size of miscellaneous core 1472 kernel data structures. This saves memory on small machines, 1473 but may reduce performance. 1474 1475config FUTEX 1476 bool "Enable futex support" if EXPERT 1477 default y 1478 imply RT_MUTEXES 1479 help 1480 Disabling this option will cause the kernel to be built without 1481 support for "fast userspace mutexes". The resulting kernel may not 1482 run glibc-based applications correctly. 1483 1484config FUTEX_PI 1485 bool 1486 depends on FUTEX && RT_MUTEXES 1487 default y 1488 1489config HAVE_FUTEX_CMPXCHG 1490 bool 1491 depends on FUTEX 1492 help 1493 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1494 is implemented and always working. This removes a couple of runtime 1495 checks. 1496 1497config EPOLL 1498 bool "Enable eventpoll support" if EXPERT 1499 default y 1500 help 1501 Disabling this option will cause the kernel to be built without 1502 support for epoll family of system calls. 1503 1504config SIGNALFD 1505 bool "Enable signalfd() system call" if EXPERT 1506 default y 1507 help 1508 Enable the signalfd() system call that allows to receive signals 1509 on a file descriptor. 1510 1511 If unsure, say Y. 1512 1513config TIMERFD 1514 bool "Enable timerfd() system call" if EXPERT 1515 default y 1516 help 1517 Enable the timerfd() system call that allows to receive timer 1518 events on a file descriptor. 1519 1520 If unsure, say Y. 1521 1522config EVENTFD 1523 bool "Enable eventfd() system call" if EXPERT 1524 default y 1525 help 1526 Enable the eventfd() system call that allows to receive both 1527 kernel notification (ie. KAIO) or userspace notifications. 1528 1529 If unsure, say Y. 1530 1531config SHMEM 1532 bool "Use full shmem filesystem" if EXPERT 1533 default y 1534 depends on MMU 1535 help 1536 The shmem is an internal filesystem used to manage shared memory. 1537 It is backed by swap and manages resource limits. It is also exported 1538 to userspace as tmpfs if TMPFS is enabled. Disabling this 1539 option replaces shmem and tmpfs with the much simpler ramfs code, 1540 which may be appropriate on small systems without swap. 1541 1542config AIO 1543 bool "Enable AIO support" if EXPERT 1544 default y 1545 help 1546 This option enables POSIX asynchronous I/O which may by used 1547 by some high performance threaded applications. Disabling 1548 this option saves about 7k. 1549 1550config IO_URING 1551 bool "Enable IO uring support" if EXPERT 1552 select IO_WQ 1553 default y 1554 help 1555 This option enables support for the io_uring interface, enabling 1556 applications to submit and complete IO through submission and 1557 completion rings that are shared between the kernel and application. 1558 1559config ADVISE_SYSCALLS 1560 bool "Enable madvise/fadvise syscalls" if EXPERT 1561 default y 1562 help 1563 This option enables the madvise and fadvise syscalls, used by 1564 applications to advise the kernel about their future memory or file 1565 usage, improving performance. If building an embedded system where no 1566 applications use these syscalls, you can disable this option to save 1567 space. 1568 1569config HAVE_ARCH_USERFAULTFD_WP 1570 bool 1571 help 1572 Arch has userfaultfd write protection support 1573 1574config MEMBARRIER 1575 bool "Enable membarrier() system call" if EXPERT 1576 default y 1577 help 1578 Enable the membarrier() system call that allows issuing memory 1579 barriers across all running threads, which can be used to distribute 1580 the cost of user-space memory barriers asymmetrically by transforming 1581 pairs of memory barriers into pairs consisting of membarrier() and a 1582 compiler barrier. 1583 1584 If unsure, say Y. 1585 1586config KALLSYMS 1587 bool "Load all symbols for debugging/ksymoops" if EXPERT 1588 default y 1589 help 1590 Say Y here to let the kernel print out symbolic crash information and 1591 symbolic stack backtraces. This increases the size of the kernel 1592 somewhat, as all symbols have to be loaded into the kernel image. 1593 1594config KALLSYMS_ALL 1595 bool "Include all symbols in kallsyms" 1596 depends on DEBUG_KERNEL && KALLSYMS 1597 help 1598 Normally kallsyms only contains the symbols of functions for nicer 1599 OOPS messages and backtraces (i.e., symbols from the text and inittext 1600 sections). This is sufficient for most cases. And only in very rare 1601 cases (e.g., when a debugger is used) all symbols are required (e.g., 1602 names of variables from the data sections, etc). 1603 1604 This option makes sure that all symbols are loaded into the kernel 1605 image (i.e., symbols from all sections) in cost of increased kernel 1606 size (depending on the kernel configuration, it may be 300KiB or 1607 something like this). 1608 1609 Say N unless you really need all symbols. 1610 1611config KALLSYMS_ABSOLUTE_PERCPU 1612 bool 1613 depends on KALLSYMS 1614 default X86_64 && SMP 1615 1616config KALLSYMS_BASE_RELATIVE 1617 bool 1618 depends on KALLSYMS 1619 default !IA64 1620 help 1621 Instead of emitting them as absolute values in the native word size, 1622 emit the symbol references in the kallsyms table as 32-bit entries, 1623 each containing a relative value in the range [base, base + U32_MAX] 1624 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1625 an absolute value in the range [0, S32_MAX] or a relative value in the 1626 range [base, base + S32_MAX], where base is the lowest relative symbol 1627 address encountered in the image. 1628 1629 On 64-bit builds, this reduces the size of the address table by 50%, 1630 but more importantly, it results in entries whose values are build 1631 time constants, and no relocation pass is required at runtime to fix 1632 up the entries based on the runtime load address of the kernel. 1633 1634# end of the "standard kernel features (expert users)" menu 1635 1636# syscall, maps, verifier 1637 1638config BPF_LSM 1639 bool "LSM Instrumentation with BPF" 1640 depends on BPF_EVENTS 1641 depends on BPF_SYSCALL 1642 depends on SECURITY 1643 depends on BPF_JIT 1644 help 1645 Enables instrumentation of the security hooks with eBPF programs for 1646 implementing dynamic MAC and Audit Policies. 1647 1648 If you are unsure how to answer this question, answer N. 1649 1650config BPF_SYSCALL 1651 bool "Enable bpf() system call" 1652 select BPF 1653 select IRQ_WORK 1654 default n 1655 help 1656 Enable the bpf() system call that allows to manipulate eBPF 1657 programs and maps via file descriptors. 1658 1659config ARCH_WANT_DEFAULT_BPF_JIT 1660 bool 1661 1662config BPF_JIT_ALWAYS_ON 1663 bool "Permanently enable BPF JIT and remove BPF interpreter" 1664 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1665 help 1666 Enables BPF JIT and removes BPF interpreter to avoid 1667 speculative execution of BPF instructions by the interpreter 1668 1669config BPF_JIT_DEFAULT_ON 1670 def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON 1671 depends on HAVE_EBPF_JIT && BPF_JIT 1672 1673config USERFAULTFD 1674 bool "Enable userfaultfd() system call" 1675 depends on MMU 1676 help 1677 Enable the userfaultfd() system call that allows to intercept and 1678 handle page faults in userland. 1679 1680config ARCH_HAS_MEMBARRIER_CALLBACKS 1681 bool 1682 1683config ARCH_HAS_MEMBARRIER_SYNC_CORE 1684 bool 1685 1686config RSEQ 1687 bool "Enable rseq() system call" if EXPERT 1688 default y 1689 depends on HAVE_RSEQ 1690 select MEMBARRIER 1691 help 1692 Enable the restartable sequences system call. It provides a 1693 user-space cache for the current CPU number value, which 1694 speeds up getting the current CPU number from user-space, 1695 as well as an ABI to speed up user-space operations on 1696 per-CPU data. 1697 1698 If unsure, say Y. 1699 1700config DEBUG_RSEQ 1701 default n 1702 bool "Enabled debugging of rseq() system call" if EXPERT 1703 depends on RSEQ && DEBUG_KERNEL 1704 help 1705 Enable extra debugging checks for the rseq system call. 1706 1707 If unsure, say N. 1708 1709config EMBEDDED 1710 bool "Embedded system" 1711 option allnoconfig_y 1712 select EXPERT 1713 help 1714 This option should be enabled if compiling the kernel for 1715 an embedded system so certain expert options are available 1716 for configuration. 1717 1718config HAVE_PERF_EVENTS 1719 bool 1720 help 1721 See tools/perf/design.txt for details. 1722 1723config PERF_USE_VMALLOC 1724 bool 1725 help 1726 See tools/perf/design.txt for details 1727 1728config PC104 1729 bool "PC/104 support" if EXPERT 1730 help 1731 Expose PC/104 form factor device drivers and options available for 1732 selection and configuration. Enable this option if your target 1733 machine has a PC/104 bus. 1734 1735menu "Kernel Performance Events And Counters" 1736 1737config PERF_EVENTS 1738 bool "Kernel performance events and counters" 1739 default y if PROFILING 1740 depends on HAVE_PERF_EVENTS 1741 select IRQ_WORK 1742 select SRCU 1743 help 1744 Enable kernel support for various performance events provided 1745 by software and hardware. 1746 1747 Software events are supported either built-in or via the 1748 use of generic tracepoints. 1749 1750 Most modern CPUs support performance events via performance 1751 counter registers. These registers count the number of certain 1752 types of hw events: such as instructions executed, cachemisses 1753 suffered, or branches mis-predicted - without slowing down the 1754 kernel or applications. These registers can also trigger interrupts 1755 when a threshold number of events have passed - and can thus be 1756 used to profile the code that runs on that CPU. 1757 1758 The Linux Performance Event subsystem provides an abstraction of 1759 these software and hardware event capabilities, available via a 1760 system call and used by the "perf" utility in tools/perf/. It 1761 provides per task and per CPU counters, and it provides event 1762 capabilities on top of those. 1763 1764 Say Y if unsure. 1765 1766config DEBUG_PERF_USE_VMALLOC 1767 default n 1768 bool "Debug: use vmalloc to back perf mmap() buffers" 1769 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1770 select PERF_USE_VMALLOC 1771 help 1772 Use vmalloc memory to back perf mmap() buffers. 1773 1774 Mostly useful for debugging the vmalloc code on platforms 1775 that don't require it. 1776 1777 Say N if unsure. 1778 1779endmenu 1780 1781config VM_EVENT_COUNTERS 1782 default y 1783 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1784 help 1785 VM event counters are needed for event counts to be shown. 1786 This option allows the disabling of the VM event counters 1787 on EXPERT systems. /proc/vmstat will only show page counts 1788 if VM event counters are disabled. 1789 1790config SLUB_DEBUG 1791 default y 1792 bool "Enable SLUB debugging support" if EXPERT 1793 depends on SLUB && SYSFS 1794 help 1795 SLUB has extensive debug support features. Disabling these can 1796 result in significant savings in code size. This also disables 1797 SLUB sysfs support. /sys/slab will not exist and there will be 1798 no support for cache validation etc. 1799 1800config SLUB_MEMCG_SYSFS_ON 1801 default n 1802 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1803 depends on SLUB && SYSFS && MEMCG 1804 help 1805 SLUB creates a directory under /sys/kernel/slab for each 1806 allocation cache to host info and debug files. If memory 1807 cgroup is enabled, each cache can have per memory cgroup 1808 caches. SLUB can create the same sysfs directories for these 1809 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1810 to a very high number of debug files being created. This is 1811 controlled by slub_memcg_sysfs boot parameter and this 1812 config option determines the parameter's default value. 1813 1814config COMPAT_BRK 1815 bool "Disable heap randomization" 1816 default y 1817 help 1818 Randomizing heap placement makes heap exploits harder, but it 1819 also breaks ancient binaries (including anything libc5 based). 1820 This option changes the bootup default to heap randomization 1821 disabled, and can be overridden at runtime by setting 1822 /proc/sys/kernel/randomize_va_space to 2. 1823 1824 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1825 1826choice 1827 prompt "Choose SLAB allocator" 1828 default SLUB 1829 help 1830 This option allows to select a slab allocator. 1831 1832config SLAB 1833 bool "SLAB" 1834 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1835 help 1836 The regular slab allocator that is established and known to work 1837 well in all environments. It organizes cache hot objects in 1838 per cpu and per node queues. 1839 1840config SLUB 1841 bool "SLUB (Unqueued Allocator)" 1842 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1843 help 1844 SLUB is a slab allocator that minimizes cache line usage 1845 instead of managing queues of cached objects (SLAB approach). 1846 Per cpu caching is realized using slabs of objects instead 1847 of queues of objects. SLUB can use memory efficiently 1848 and has enhanced diagnostics. SLUB is the default choice for 1849 a slab allocator. 1850 1851config SLOB 1852 depends on EXPERT 1853 bool "SLOB (Simple Allocator)" 1854 help 1855 SLOB replaces the stock allocator with a drastically simpler 1856 allocator. SLOB is generally more space efficient but 1857 does not perform as well on large systems. 1858 1859endchoice 1860 1861config SLAB_MERGE_DEFAULT 1862 bool "Allow slab caches to be merged" 1863 default y 1864 help 1865 For reduced kernel memory fragmentation, slab caches can be 1866 merged when they share the same size and other characteristics. 1867 This carries a risk of kernel heap overflows being able to 1868 overwrite objects from merged caches (and more easily control 1869 cache layout), which makes such heap attacks easier to exploit 1870 by attackers. By keeping caches unmerged, these kinds of exploits 1871 can usually only damage objects in the same cache. To disable 1872 merging at runtime, "slab_nomerge" can be passed on the kernel 1873 command line. 1874 1875config SLAB_FREELIST_RANDOM 1876 default n 1877 depends on SLAB || SLUB 1878 bool "SLAB freelist randomization" 1879 help 1880 Randomizes the freelist order used on creating new pages. This 1881 security feature reduces the predictability of the kernel slab 1882 allocator against heap overflows. 1883 1884config SLAB_FREELIST_HARDENED 1885 bool "Harden slab freelist metadata" 1886 depends on SLUB 1887 help 1888 Many kernel heap attacks try to target slab cache metadata and 1889 other infrastructure. This options makes minor performance 1890 sacrifices to harden the kernel slab allocator against common 1891 freelist exploit methods. 1892 1893config SHUFFLE_PAGE_ALLOCATOR 1894 bool "Page allocator randomization" 1895 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1896 help 1897 Randomization of the page allocator improves the average 1898 utilization of a direct-mapped memory-side-cache. See section 1899 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1900 6.2a specification for an example of how a platform advertises 1901 the presence of a memory-side-cache. There are also incidental 1902 security benefits as it reduces the predictability of page 1903 allocations to compliment SLAB_FREELIST_RANDOM, but the 1904 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1905 10th order of pages is selected based on cache utilization 1906 benefits on x86. 1907 1908 While the randomization improves cache utilization it may 1909 negatively impact workloads on platforms without a cache. For 1910 this reason, by default, the randomization is enabled only 1911 after runtime detection of a direct-mapped memory-side-cache. 1912 Otherwise, the randomization may be force enabled with the 1913 'page_alloc.shuffle' kernel command line parameter. 1914 1915 Say Y if unsure. 1916 1917config SLUB_CPU_PARTIAL 1918 default y 1919 depends on SLUB && SMP 1920 bool "SLUB per cpu partial cache" 1921 help 1922 Per cpu partial caches accelerate objects allocation and freeing 1923 that is local to a processor at the price of more indeterminism 1924 in the latency of the free. On overflow these caches will be cleared 1925 which requires the taking of locks that may cause latency spikes. 1926 Typically one would choose no for a realtime system. 1927 1928config MMAP_ALLOW_UNINITIALIZED 1929 bool "Allow mmapped anonymous memory to be uninitialized" 1930 depends on EXPERT && !MMU 1931 default n 1932 help 1933 Normally, and according to the Linux spec, anonymous memory obtained 1934 from mmap() has its contents cleared before it is passed to 1935 userspace. Enabling this config option allows you to request that 1936 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1937 providing a huge performance boost. If this option is not enabled, 1938 then the flag will be ignored. 1939 1940 This is taken advantage of by uClibc's malloc(), and also by 1941 ELF-FDPIC binfmt's brk and stack allocator. 1942 1943 Because of the obvious security issues, this option should only be 1944 enabled on embedded devices where you control what is run in 1945 userspace. Since that isn't generally a problem on no-MMU systems, 1946 it is normally safe to say Y here. 1947 1948 See Documentation/nommu-mmap.txt for more information. 1949 1950config SYSTEM_DATA_VERIFICATION 1951 def_bool n 1952 select SYSTEM_TRUSTED_KEYRING 1953 select KEYS 1954 select CRYPTO 1955 select CRYPTO_RSA 1956 select ASYMMETRIC_KEY_TYPE 1957 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1958 select ASN1 1959 select OID_REGISTRY 1960 select X509_CERTIFICATE_PARSER 1961 select PKCS7_MESSAGE_PARSER 1962 help 1963 Provide PKCS#7 message verification using the contents of the system 1964 trusted keyring to provide public keys. This then can be used for 1965 module verification, kexec image verification and firmware blob 1966 verification. 1967 1968config PROFILING 1969 bool "Profiling support" 1970 help 1971 Say Y here to enable the extended profiling support mechanisms used 1972 by profilers such as OProfile. 1973 1974# 1975# Place an empty function call at each tracepoint site. Can be 1976# dynamically changed for a probe function. 1977# 1978config TRACEPOINTS 1979 bool 1980 1981endmenu # General setup 1982 1983source "arch/Kconfig" 1984 1985config RT_MUTEXES 1986 bool 1987 1988config BASE_SMALL 1989 int 1990 default 0 if BASE_FULL 1991 default 1 if !BASE_FULL 1992 1993config MODULE_SIG_FORMAT 1994 def_bool n 1995 select SYSTEM_DATA_VERIFICATION 1996 1997menuconfig MODULES 1998 bool "Enable loadable module support" 1999 option modules 2000 help 2001 Kernel modules are small pieces of compiled code which can 2002 be inserted in the running kernel, rather than being 2003 permanently built into the kernel. You use the "modprobe" 2004 tool to add (and sometimes remove) them. If you say Y here, 2005 many parts of the kernel can be built as modules (by 2006 answering M instead of Y where indicated): this is most 2007 useful for infrequently used options which are not required 2008 for booting. For more information, see the man pages for 2009 modprobe, lsmod, modinfo, insmod and rmmod. 2010 2011 If you say Y here, you will need to run "make 2012 modules_install" to put the modules under /lib/modules/ 2013 where modprobe can find them (you may need to be root to do 2014 this). 2015 2016 If unsure, say Y. 2017 2018if MODULES 2019 2020config MODULE_FORCE_LOAD 2021 bool "Forced module loading" 2022 default n 2023 help 2024 Allow loading of modules without version information (ie. modprobe 2025 --force). Forced module loading sets the 'F' (forced) taint flag and 2026 is usually a really bad idea. 2027 2028config MODULE_UNLOAD 2029 bool "Module unloading" 2030 help 2031 Without this option you will not be able to unload any 2032 modules (note that some modules may not be unloadable 2033 anyway), which makes your kernel smaller, faster 2034 and simpler. If unsure, say Y. 2035 2036config MODULE_FORCE_UNLOAD 2037 bool "Forced module unloading" 2038 depends on MODULE_UNLOAD 2039 help 2040 This option allows you to force a module to unload, even if the 2041 kernel believes it is unsafe: the kernel will remove the module 2042 without waiting for anyone to stop using it (using the -f option to 2043 rmmod). This is mainly for kernel developers and desperate users. 2044 If unsure, say N. 2045 2046config MODVERSIONS 2047 bool "Module versioning support" 2048 help 2049 Usually, you have to use modules compiled with your kernel. 2050 Saying Y here makes it sometimes possible to use modules 2051 compiled for different kernels, by adding enough information 2052 to the modules to (hopefully) spot any changes which would 2053 make them incompatible with the kernel you are running. If 2054 unsure, say N. 2055 2056config ASM_MODVERSIONS 2057 bool 2058 default HAVE_ASM_MODVERSIONS && MODVERSIONS 2059 help 2060 This enables module versioning for exported symbols also from 2061 assembly. This can be enabled only when the target architecture 2062 supports it. 2063 2064config MODULE_REL_CRCS 2065 bool 2066 depends on MODVERSIONS 2067 2068config MODULE_SRCVERSION_ALL 2069 bool "Source checksum for all modules" 2070 help 2071 Modules which contain a MODULE_VERSION get an extra "srcversion" 2072 field inserted into their modinfo section, which contains a 2073 sum of the source files which made it. This helps maintainers 2074 see exactly which source was used to build a module (since 2075 others sometimes change the module source without updating 2076 the version). With this option, such a "srcversion" field 2077 will be created for all modules. If unsure, say N. 2078 2079config MODULE_SIG 2080 bool "Module signature verification" 2081 select MODULE_SIG_FORMAT 2082 help 2083 Check modules for valid signatures upon load: the signature 2084 is simply appended to the module. For more information see 2085 <file:Documentation/admin-guide/module-signing.rst>. 2086 2087 Note that this option adds the OpenSSL development packages as a 2088 kernel build dependency so that the signing tool can use its crypto 2089 library. 2090 2091 You should enable this option if you wish to use either 2092 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via 2093 another LSM - otherwise unsigned modules will be loadable regardless 2094 of the lockdown policy. 2095 2096 !!!WARNING!!! If you enable this option, you MUST make sure that the 2097 module DOES NOT get stripped after being signed. This includes the 2098 debuginfo strip done by some packagers (such as rpmbuild) and 2099 inclusion into an initramfs that wants the module size reduced. 2100 2101config MODULE_SIG_FORCE 2102 bool "Require modules to be validly signed" 2103 depends on MODULE_SIG 2104 help 2105 Reject unsigned modules or signed modules for which we don't have a 2106 key. Without this, such modules will simply taint the kernel. 2107 2108config MODULE_SIG_ALL 2109 bool "Automatically sign all modules" 2110 default y 2111 depends on MODULE_SIG 2112 help 2113 Sign all modules during make modules_install. Without this option, 2114 modules must be signed manually, using the scripts/sign-file tool. 2115 2116comment "Do not forget to sign required modules with scripts/sign-file" 2117 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2118 2119choice 2120 prompt "Which hash algorithm should modules be signed with?" 2121 depends on MODULE_SIG 2122 help 2123 This determines which sort of hashing algorithm will be used during 2124 signature generation. This algorithm _must_ be built into the kernel 2125 directly so that signature verification can take place. It is not 2126 possible to load a signed module containing the algorithm to check 2127 the signature on that module. 2128 2129config MODULE_SIG_SHA1 2130 bool "Sign modules with SHA-1" 2131 select CRYPTO_SHA1 2132 2133config MODULE_SIG_SHA224 2134 bool "Sign modules with SHA-224" 2135 select CRYPTO_SHA256 2136 2137config MODULE_SIG_SHA256 2138 bool "Sign modules with SHA-256" 2139 select CRYPTO_SHA256 2140 2141config MODULE_SIG_SHA384 2142 bool "Sign modules with SHA-384" 2143 select CRYPTO_SHA512 2144 2145config MODULE_SIG_SHA512 2146 bool "Sign modules with SHA-512" 2147 select CRYPTO_SHA512 2148 2149endchoice 2150 2151config MODULE_SIG_HASH 2152 string 2153 depends on MODULE_SIG 2154 default "sha1" if MODULE_SIG_SHA1 2155 default "sha224" if MODULE_SIG_SHA224 2156 default "sha256" if MODULE_SIG_SHA256 2157 default "sha384" if MODULE_SIG_SHA384 2158 default "sha512" if MODULE_SIG_SHA512 2159 2160config MODULE_COMPRESS 2161 bool "Compress modules on installation" 2162 help 2163 2164 Compresses kernel modules when 'make modules_install' is run; gzip or 2165 xz depending on "Compression algorithm" below. 2166 2167 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 2168 2169 Out-of-tree kernel modules installed using Kbuild will also be 2170 compressed upon installation. 2171 2172 Note: for modules inside an initrd or initramfs, it's more efficient 2173 to compress the whole initrd or initramfs instead. 2174 2175 Note: This is fully compatible with signed modules. 2176 2177 If in doubt, say N. 2178 2179choice 2180 prompt "Compression algorithm" 2181 depends on MODULE_COMPRESS 2182 default MODULE_COMPRESS_GZIP 2183 help 2184 This determines which sort of compression will be used during 2185 'make modules_install'. 2186 2187 GZIP (default) and XZ are supported. 2188 2189config MODULE_COMPRESS_GZIP 2190 bool "GZIP" 2191 2192config MODULE_COMPRESS_XZ 2193 bool "XZ" 2194 2195endchoice 2196 2197config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS 2198 bool "Allow loading of modules with missing namespace imports" 2199 help 2200 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in 2201 a namespace. A module that makes use of a symbol exported with such a 2202 namespace is required to import the namespace via MODULE_IMPORT_NS(). 2203 There is no technical reason to enforce correct namespace imports, 2204 but it creates consistency between symbols defining namespaces and 2205 users importing namespaces they make use of. This option relaxes this 2206 requirement and lifts the enforcement when loading a module. 2207 2208 If unsure, say N. 2209 2210config UNUSED_SYMBOLS 2211 bool "Enable unused/obsolete exported symbols" 2212 default y if X86 2213 help 2214 Unused but exported symbols make the kernel needlessly bigger. For 2215 that reason most of these unused exports will soon be removed. This 2216 option is provided temporarily to provide a transition period in case 2217 some external kernel module needs one of these symbols anyway. If you 2218 encounter such a case in your module, consider if you are actually 2219 using the right API. (rationale: since nobody in the kernel is using 2220 this in a module, there is a pretty good chance it's actually the 2221 wrong interface to use). If you really need the symbol, please send a 2222 mail to the linux kernel mailing list mentioning the symbol and why 2223 you really need it, and what the merge plan to the mainline kernel for 2224 your module is. 2225 2226config TRIM_UNUSED_KSYMS 2227 bool "Trim unused exported kernel symbols" 2228 depends on !UNUSED_SYMBOLS 2229 help 2230 The kernel and some modules make many symbols available for 2231 other modules to use via EXPORT_SYMBOL() and variants. Depending 2232 on the set of modules being selected in your kernel configuration, 2233 many of those exported symbols might never be used. 2234 2235 This option allows for unused exported symbols to be dropped from 2236 the build. In turn, this provides the compiler more opportunities 2237 (especially when using LTO) for optimizing the code and reducing 2238 binary size. This might have some security advantages as well. 2239 2240 If unsure, or if you need to build out-of-tree modules, say N. 2241 2242config UNUSED_KSYMS_WHITELIST 2243 string "Whitelist of symbols to keep in ksymtab" 2244 depends on TRIM_UNUSED_KSYMS 2245 help 2246 By default, all unused exported symbols will be un-exported from the 2247 build when TRIM_UNUSED_KSYMS is selected. 2248 2249 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept 2250 exported at all times, even in absence of in-tree users. The value to 2251 set here is the path to a text file containing the list of symbols, 2252 one per line. The path can be absolute, or relative to the kernel 2253 source tree. 2254 2255endif # MODULES 2256 2257config MODULES_TREE_LOOKUP 2258 def_bool y 2259 depends on PERF_EVENTS || TRACING 2260 2261config INIT_ALL_POSSIBLE 2262 bool 2263 help 2264 Back when each arch used to define their own cpu_online_mask and 2265 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2266 with all 1s, and others with all 0s. When they were centralised, 2267 it was better to provide this option than to break all the archs 2268 and have several arch maintainers pursuing me down dark alleys. 2269 2270source "block/Kconfig" 2271 2272config PREEMPT_NOTIFIERS 2273 bool 2274 2275config PADATA 2276 depends on SMP 2277 bool 2278 2279config ASN1 2280 tristate 2281 help 2282 Build a simple ASN.1 grammar compiler that produces a bytecode output 2283 that can be interpreted by the ASN.1 stream decoder and used to 2284 inform it as to what tags are to be expected in a stream and what 2285 functions to call on what tags. 2286 2287source "kernel/Kconfig.locks" 2288 2289config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 2290 bool 2291 2292config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2293 bool 2294 2295# It may be useful for an architecture to override the definitions of the 2296# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2297# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2298# different calling convention for syscalls. They can also override the 2299# macros for not-implemented syscalls in kernel/sys_ni.c and 2300# kernel/time/posix-stubs.c. All these overrides need to be available in 2301# <asm/syscall_wrapper.h>. 2302config ARCH_HAS_SYSCALL_WRAPPER 2303 def_bool n 2304