1# SPDX-License-Identifier: GPL-2.0-only 2config DEFCONFIG_LIST 3 string 4 depends on !UML 5 option defconfig_list 6 default "/lib/modules/$(shell,uname -r)/.config" 7 default "/etc/kernel-config" 8 default "/boot/config-$(shell,uname -r)" 9 default "arch/$(SRCARCH)/configs/$(KBUILD_DEFCONFIG)" 10 11config CC_IS_GCC 12 def_bool $(success,$(CC) --version | head -n 1 | grep -q gcc) 13 14config GCC_VERSION 15 int 16 default $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) if CC_IS_GCC 17 default 0 18 19config LD_VERSION 20 int 21 default $(shell,$(LD) --version | $(srctree)/scripts/ld-version.sh) 22 23config CC_IS_CLANG 24 def_bool $(success,$(CC) --version | head -n 1 | grep -q clang) 25 26config CLANG_VERSION 27 int 28 default $(shell,$(srctree)/scripts/clang-version.sh $(CC)) 29 30config CC_CAN_LINK 31 def_bool $(success,$(srctree)/scripts/cc-can-link.sh $(CC)) 32 33config CC_HAS_ASM_GOTO 34 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) 35 36config TOOLS_SUPPORT_RELR 37 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 38 39config CC_HAS_ASM_INLINE 40 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 41 42config CC_HAS_WARN_MAYBE_UNINITIALIZED 43 def_bool $(cc-option,-Wmaybe-uninitialized) 44 help 45 GCC >= 4.7 supports this option. 46 47config CC_DISABLE_WARN_MAYBE_UNINITIALIZED 48 bool 49 depends on CC_HAS_WARN_MAYBE_UNINITIALIZED 50 default CC_IS_GCC && GCC_VERSION < 40900 # unreliable for GCC < 4.9 51 help 52 GCC's -Wmaybe-uninitialized is not reliable by definition. 53 Lots of false positive warnings are produced in some cases. 54 55 If this option is enabled, -Wno-maybe-uninitialzed is passed 56 to the compiler to suppress maybe-uninitialized warnings. 57 58config CONSTRUCTORS 59 bool 60 depends on !UML 61 62config IRQ_WORK 63 bool 64 65config BUILDTIME_TABLE_SORT 66 bool 67 68config THREAD_INFO_IN_TASK 69 bool 70 help 71 Select this to move thread_info off the stack into task_struct. To 72 make this work, an arch will need to remove all thread_info fields 73 except flags and fix any runtime bugs. 74 75 One subtle change that will be needed is to use try_get_task_stack() 76 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 77 78menu "General setup" 79 80config BROKEN 81 bool 82 83config BROKEN_ON_SMP 84 bool 85 depends on BROKEN || !SMP 86 default y 87 88config INIT_ENV_ARG_LIMIT 89 int 90 default 32 if !UML 91 default 128 if UML 92 help 93 Maximum of each of the number of arguments and environment 94 variables passed to init from the kernel command line. 95 96config COMPILE_TEST 97 bool "Compile also drivers which will not load" 98 depends on !UML 99 default n 100 help 101 Some drivers can be compiled on a different platform than they are 102 intended to be run on. Despite they cannot be loaded there (or even 103 when they load they cannot be used due to missing HW support), 104 developers still, opposing to distributors, might want to build such 105 drivers to compile-test them. 106 107 If you are a developer and want to build everything available, say Y 108 here. If you are a user/distributor, say N here to exclude useless 109 drivers to be distributed. 110 111config UAPI_HEADER_TEST 112 bool "Compile test UAPI headers" 113 depends on HEADERS_INSTALL && CC_CAN_LINK 114 help 115 Compile test headers exported to user-space to ensure they are 116 self-contained, i.e. compilable as standalone units. 117 118 If you are a developer or tester and want to ensure the exported 119 headers are self-contained, say Y here. Otherwise, choose N. 120 121config LOCALVERSION 122 string "Local version - append to kernel release" 123 help 124 Append an extra string to the end of your kernel version. 125 This will show up when you type uname, for example. 126 The string you set here will be appended after the contents of 127 any files with a filename matching localversion* in your 128 object and source tree, in that order. Your total string can 129 be a maximum of 64 characters. 130 131config LOCALVERSION_AUTO 132 bool "Automatically append version information to the version string" 133 default y 134 depends on !COMPILE_TEST 135 help 136 This will try to automatically determine if the current tree is a 137 release tree by looking for git tags that belong to the current 138 top of tree revision. 139 140 A string of the format -gxxxxxxxx will be added to the localversion 141 if a git-based tree is found. The string generated by this will be 142 appended after any matching localversion* files, and after the value 143 set in CONFIG_LOCALVERSION. 144 145 (The actual string used here is the first eight characters produced 146 by running the command: 147 148 $ git rev-parse --verify HEAD 149 150 which is done within the script "scripts/setlocalversion".) 151 152config BUILD_SALT 153 string "Build ID Salt" 154 default "" 155 help 156 The build ID is used to link binaries and their debug info. Setting 157 this option will use the value in the calculation of the build id. 158 This is mostly useful for distributions which want to ensure the 159 build is unique between builds. It's safe to leave the default. 160 161config HAVE_KERNEL_GZIP 162 bool 163 164config HAVE_KERNEL_BZIP2 165 bool 166 167config HAVE_KERNEL_LZMA 168 bool 169 170config HAVE_KERNEL_XZ 171 bool 172 173config HAVE_KERNEL_LZO 174 bool 175 176config HAVE_KERNEL_LZ4 177 bool 178 179config HAVE_KERNEL_UNCOMPRESSED 180 bool 181 182choice 183 prompt "Kernel compression mode" 184 default KERNEL_GZIP 185 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED 186 help 187 The linux kernel is a kind of self-extracting executable. 188 Several compression algorithms are available, which differ 189 in efficiency, compression and decompression speed. 190 Compression speed is only relevant when building a kernel. 191 Decompression speed is relevant at each boot. 192 193 If you have any problems with bzip2 or lzma compressed 194 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 195 version of this functionality (bzip2 only), for 2.4, was 196 supplied by Christian Ludwig) 197 198 High compression options are mostly useful for users, who 199 are low on disk space (embedded systems), but for whom ram 200 size matters less. 201 202 If in doubt, select 'gzip' 203 204config KERNEL_GZIP 205 bool "Gzip" 206 depends on HAVE_KERNEL_GZIP 207 help 208 The old and tried gzip compression. It provides a good balance 209 between compression ratio and decompression speed. 210 211config KERNEL_BZIP2 212 bool "Bzip2" 213 depends on HAVE_KERNEL_BZIP2 214 help 215 Its compression ratio and speed is intermediate. 216 Decompression speed is slowest among the choices. The kernel 217 size is about 10% smaller with bzip2, in comparison to gzip. 218 Bzip2 uses a large amount of memory. For modern kernels you 219 will need at least 8MB RAM or more for booting. 220 221config KERNEL_LZMA 222 bool "LZMA" 223 depends on HAVE_KERNEL_LZMA 224 help 225 This compression algorithm's ratio is best. Decompression speed 226 is between gzip and bzip2. Compression is slowest. 227 The kernel size is about 33% smaller with LZMA in comparison to gzip. 228 229config KERNEL_XZ 230 bool "XZ" 231 depends on HAVE_KERNEL_XZ 232 help 233 XZ uses the LZMA2 algorithm and instruction set specific 234 BCJ filters which can improve compression ratio of executable 235 code. The size of the kernel is about 30% smaller with XZ in 236 comparison to gzip. On architectures for which there is a BCJ 237 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 238 will create a few percent smaller kernel than plain LZMA. 239 240 The speed is about the same as with LZMA: The decompression 241 speed of XZ is better than that of bzip2 but worse than gzip 242 and LZO. Compression is slow. 243 244config KERNEL_LZO 245 bool "LZO" 246 depends on HAVE_KERNEL_LZO 247 help 248 Its compression ratio is the poorest among the choices. The kernel 249 size is about 10% bigger than gzip; however its speed 250 (both compression and decompression) is the fastest. 251 252config KERNEL_LZ4 253 bool "LZ4" 254 depends on HAVE_KERNEL_LZ4 255 help 256 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 257 A preliminary version of LZ4 de/compression tool is available at 258 <https://code.google.com/p/lz4/>. 259 260 Its compression ratio is worse than LZO. The size of the kernel 261 is about 8% bigger than LZO. But the decompression speed is 262 faster than LZO. 263 264config KERNEL_UNCOMPRESSED 265 bool "None" 266 depends on HAVE_KERNEL_UNCOMPRESSED 267 help 268 Produce uncompressed kernel image. This option is usually not what 269 you want. It is useful for debugging the kernel in slow simulation 270 environments, where decompressing and moving the kernel is awfully 271 slow. This option allows early boot code to skip the decompressor 272 and jump right at uncompressed kernel image. 273 274endchoice 275 276config DEFAULT_HOSTNAME 277 string "Default hostname" 278 default "(none)" 279 help 280 This option determines the default system hostname before userspace 281 calls sethostname(2). The kernel traditionally uses "(none)" here, 282 but you may wish to use a different default here to make a minimal 283 system more usable with less configuration. 284 285# 286# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can 287# add proper SWAP support to them, in which case this can be remove. 288# 289config ARCH_NO_SWAP 290 bool 291 292config SWAP 293 bool "Support for paging of anonymous memory (swap)" 294 depends on MMU && BLOCK && !ARCH_NO_SWAP 295 default y 296 help 297 This option allows you to choose whether you want to have support 298 for so called swap devices or swap files in your kernel that are 299 used to provide more virtual memory than the actual RAM present 300 in your computer. If unsure say Y. 301 302config SYSVIPC 303 bool "System V IPC" 304 ---help--- 305 Inter Process Communication is a suite of library functions and 306 system calls which let processes (running programs) synchronize and 307 exchange information. It is generally considered to be a good thing, 308 and some programs won't run unless you say Y here. In particular, if 309 you want to run the DOS emulator dosemu under Linux (read the 310 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 311 you'll need to say Y here. 312 313 You can find documentation about IPC with "info ipc" and also in 314 section 6.4 of the Linux Programmer's Guide, available from 315 <http://www.tldp.org/guides.html>. 316 317config SYSVIPC_SYSCTL 318 bool 319 depends on SYSVIPC 320 depends on SYSCTL 321 default y 322 323config POSIX_MQUEUE 324 bool "POSIX Message Queues" 325 depends on NET 326 ---help--- 327 POSIX variant of message queues is a part of IPC. In POSIX message 328 queues every message has a priority which decides about succession 329 of receiving it by a process. If you want to compile and run 330 programs written e.g. for Solaris with use of its POSIX message 331 queues (functions mq_*) say Y here. 332 333 POSIX message queues are visible as a filesystem called 'mqueue' 334 and can be mounted somewhere if you want to do filesystem 335 operations on message queues. 336 337 If unsure, say Y. 338 339config POSIX_MQUEUE_SYSCTL 340 bool 341 depends on POSIX_MQUEUE 342 depends on SYSCTL 343 default y 344 345config CROSS_MEMORY_ATTACH 346 bool "Enable process_vm_readv/writev syscalls" 347 depends on MMU 348 default y 349 help 350 Enabling this option adds the system calls process_vm_readv and 351 process_vm_writev which allow a process with the correct privileges 352 to directly read from or write to another process' address space. 353 See the man page for more details. 354 355config USELIB 356 bool "uselib syscall" 357 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION 358 help 359 This option enables the uselib syscall, a system call used in the 360 dynamic linker from libc5 and earlier. glibc does not use this 361 system call. If you intend to run programs built on libc5 or 362 earlier, you may need to enable this syscall. Current systems 363 running glibc can safely disable this. 364 365config AUDIT 366 bool "Auditing support" 367 depends on NET 368 help 369 Enable auditing infrastructure that can be used with another 370 kernel subsystem, such as SELinux (which requires this for 371 logging of avc messages output). System call auditing is included 372 on architectures which support it. 373 374config HAVE_ARCH_AUDITSYSCALL 375 bool 376 377config AUDITSYSCALL 378 def_bool y 379 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 380 select FSNOTIFY 381 382source "kernel/irq/Kconfig" 383source "kernel/time/Kconfig" 384source "kernel/Kconfig.preempt" 385 386menu "CPU/Task time and stats accounting" 387 388config VIRT_CPU_ACCOUNTING 389 bool 390 391choice 392 prompt "Cputime accounting" 393 default TICK_CPU_ACCOUNTING if !PPC64 394 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 395 396# Kind of a stub config for the pure tick based cputime accounting 397config TICK_CPU_ACCOUNTING 398 bool "Simple tick based cputime accounting" 399 depends on !S390 && !NO_HZ_FULL 400 help 401 This is the basic tick based cputime accounting that maintains 402 statistics about user, system and idle time spent on per jiffies 403 granularity. 404 405 If unsure, say Y. 406 407config VIRT_CPU_ACCOUNTING_NATIVE 408 bool "Deterministic task and CPU time accounting" 409 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 410 select VIRT_CPU_ACCOUNTING 411 help 412 Select this option to enable more accurate task and CPU time 413 accounting. This is done by reading a CPU counter on each 414 kernel entry and exit and on transitions within the kernel 415 between system, softirq and hardirq state, so there is a 416 small performance impact. In the case of s390 or IBM POWER > 5, 417 this also enables accounting of stolen time on logically-partitioned 418 systems. 419 420config VIRT_CPU_ACCOUNTING_GEN 421 bool "Full dynticks CPU time accounting" 422 depends on HAVE_CONTEXT_TRACKING 423 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 424 depends on GENERIC_CLOCKEVENTS 425 select VIRT_CPU_ACCOUNTING 426 select CONTEXT_TRACKING 427 help 428 Select this option to enable task and CPU time accounting on full 429 dynticks systems. This accounting is implemented by watching every 430 kernel-user boundaries using the context tracking subsystem. 431 The accounting is thus performed at the expense of some significant 432 overhead. 433 434 For now this is only useful if you are working on the full 435 dynticks subsystem development. 436 437 If unsure, say N. 438 439endchoice 440 441config IRQ_TIME_ACCOUNTING 442 bool "Fine granularity task level IRQ time accounting" 443 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 444 help 445 Select this option to enable fine granularity task irq time 446 accounting. This is done by reading a timestamp on each 447 transitions between softirq and hardirq state, so there can be a 448 small performance impact. 449 450 If in doubt, say N here. 451 452config HAVE_SCHED_AVG_IRQ 453 def_bool y 454 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 455 depends on SMP 456 457config SCHED_THERMAL_PRESSURE 458 bool "Enable periodic averaging of thermal pressure" 459 depends on SMP 460 461config BSD_PROCESS_ACCT 462 bool "BSD Process Accounting" 463 depends on MULTIUSER 464 help 465 If you say Y here, a user level program will be able to instruct the 466 kernel (via a special system call) to write process accounting 467 information to a file: whenever a process exits, information about 468 that process will be appended to the file by the kernel. The 469 information includes things such as creation time, owning user, 470 command name, memory usage, controlling terminal etc. (the complete 471 list is in the struct acct in <file:include/linux/acct.h>). It is 472 up to the user level program to do useful things with this 473 information. This is generally a good idea, so say Y. 474 475config BSD_PROCESS_ACCT_V3 476 bool "BSD Process Accounting version 3 file format" 477 depends on BSD_PROCESS_ACCT 478 default n 479 help 480 If you say Y here, the process accounting information is written 481 in a new file format that also logs the process IDs of each 482 process and its parent. Note that this file format is incompatible 483 with previous v0/v1/v2 file formats, so you will need updated tools 484 for processing it. A preliminary version of these tools is available 485 at <http://www.gnu.org/software/acct/>. 486 487config TASKSTATS 488 bool "Export task/process statistics through netlink" 489 depends on NET 490 depends on MULTIUSER 491 default n 492 help 493 Export selected statistics for tasks/processes through the 494 generic netlink interface. Unlike BSD process accounting, the 495 statistics are available during the lifetime of tasks/processes as 496 responses to commands. Like BSD accounting, they are sent to user 497 space on task exit. 498 499 Say N if unsure. 500 501config TASK_DELAY_ACCT 502 bool "Enable per-task delay accounting" 503 depends on TASKSTATS 504 select SCHED_INFO 505 help 506 Collect information on time spent by a task waiting for system 507 resources like cpu, synchronous block I/O completion and swapping 508 in pages. Such statistics can help in setting a task's priorities 509 relative to other tasks for cpu, io, rss limits etc. 510 511 Say N if unsure. 512 513config TASK_XACCT 514 bool "Enable extended accounting over taskstats" 515 depends on TASKSTATS 516 help 517 Collect extended task accounting data and send the data 518 to userland for processing over the taskstats interface. 519 520 Say N if unsure. 521 522config TASK_IO_ACCOUNTING 523 bool "Enable per-task storage I/O accounting" 524 depends on TASK_XACCT 525 help 526 Collect information on the number of bytes of storage I/O which this 527 task has caused. 528 529 Say N if unsure. 530 531config PSI 532 bool "Pressure stall information tracking" 533 help 534 Collect metrics that indicate how overcommitted the CPU, memory, 535 and IO capacity are in the system. 536 537 If you say Y here, the kernel will create /proc/pressure/ with the 538 pressure statistics files cpu, memory, and io. These will indicate 539 the share of walltime in which some or all tasks in the system are 540 delayed due to contention of the respective resource. 541 542 In kernels with cgroup support, cgroups (cgroup2 only) will 543 have cpu.pressure, memory.pressure, and io.pressure files, 544 which aggregate pressure stalls for the grouped tasks only. 545 546 For more details see Documentation/accounting/psi.rst. 547 548 Say N if unsure. 549 550config PSI_DEFAULT_DISABLED 551 bool "Require boot parameter to enable pressure stall information tracking" 552 default n 553 depends on PSI 554 help 555 If set, pressure stall information tracking will be disabled 556 per default but can be enabled through passing psi=1 on the 557 kernel commandline during boot. 558 559 This feature adds some code to the task wakeup and sleep 560 paths of the scheduler. The overhead is too low to affect 561 common scheduling-intense workloads in practice (such as 562 webservers, memcache), but it does show up in artificial 563 scheduler stress tests, such as hackbench. 564 565 If you are paranoid and not sure what the kernel will be 566 used for, say Y. 567 568 Say N if unsure. 569 570endmenu # "CPU/Task time and stats accounting" 571 572config CPU_ISOLATION 573 bool "CPU isolation" 574 depends on SMP || COMPILE_TEST 575 default y 576 help 577 Make sure that CPUs running critical tasks are not disturbed by 578 any source of "noise" such as unbound workqueues, timers, kthreads... 579 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 580 the "isolcpus=" boot parameter. 581 582 Say Y if unsure. 583 584source "kernel/rcu/Kconfig" 585 586config BUILD_BIN2C 587 bool 588 default n 589 590config IKCONFIG 591 tristate "Kernel .config support" 592 ---help--- 593 This option enables the complete Linux kernel ".config" file 594 contents to be saved in the kernel. It provides documentation 595 of which kernel options are used in a running kernel or in an 596 on-disk kernel. This information can be extracted from the kernel 597 image file with the script scripts/extract-ikconfig and used as 598 input to rebuild the current kernel or to build another kernel. 599 It can also be extracted from a running kernel by reading 600 /proc/config.gz if enabled (below). 601 602config IKCONFIG_PROC 603 bool "Enable access to .config through /proc/config.gz" 604 depends on IKCONFIG && PROC_FS 605 ---help--- 606 This option enables access to the kernel configuration file 607 through /proc/config.gz. 608 609config IKHEADERS 610 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 611 depends on SYSFS 612 help 613 This option enables access to the in-kernel headers that are generated during 614 the build process. These can be used to build eBPF tracing programs, 615 or similar programs. If you build the headers as a module, a module called 616 kheaders.ko is built which can be loaded on-demand to get access to headers. 617 618config LOG_BUF_SHIFT 619 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 620 range 12 25 621 default 17 622 depends on PRINTK 623 help 624 Select the minimal kernel log buffer size as a power of 2. 625 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 626 parameter, see below. Any higher size also might be forced 627 by "log_buf_len" boot parameter. 628 629 Examples: 630 17 => 128 KB 631 16 => 64 KB 632 15 => 32 KB 633 14 => 16 KB 634 13 => 8 KB 635 12 => 4 KB 636 637config LOG_CPU_MAX_BUF_SHIFT 638 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 639 depends on SMP 640 range 0 21 641 default 12 if !BASE_SMALL 642 default 0 if BASE_SMALL 643 depends on PRINTK 644 help 645 This option allows to increase the default ring buffer size 646 according to the number of CPUs. The value defines the contribution 647 of each CPU as a power of 2. The used space is typically only few 648 lines however it might be much more when problems are reported, 649 e.g. backtraces. 650 651 The increased size means that a new buffer has to be allocated and 652 the original static one is unused. It makes sense only on systems 653 with more CPUs. Therefore this value is used only when the sum of 654 contributions is greater than the half of the default kernel ring 655 buffer as defined by LOG_BUF_SHIFT. The default values are set 656 so that more than 64 CPUs are needed to trigger the allocation. 657 658 Also this option is ignored when "log_buf_len" kernel parameter is 659 used as it forces an exact (power of two) size of the ring buffer. 660 661 The number of possible CPUs is used for this computation ignoring 662 hotplugging making the computation optimal for the worst case 663 scenario while allowing a simple algorithm to be used from bootup. 664 665 Examples shift values and their meaning: 666 17 => 128 KB for each CPU 667 16 => 64 KB for each CPU 668 15 => 32 KB for each CPU 669 14 => 16 KB for each CPU 670 13 => 8 KB for each CPU 671 12 => 4 KB for each CPU 672 673config PRINTK_SAFE_LOG_BUF_SHIFT 674 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 675 range 10 21 676 default 13 677 depends on PRINTK 678 help 679 Select the size of an alternate printk per-CPU buffer where messages 680 printed from usafe contexts are temporary stored. One example would 681 be NMI messages, another one - printk recursion. The messages are 682 copied to the main log buffer in a safe context to avoid a deadlock. 683 The value defines the size as a power of 2. 684 685 Those messages are rare and limited. The largest one is when 686 a backtrace is printed. It usually fits into 4KB. Select 687 8KB if you want to be on the safe side. 688 689 Examples: 690 17 => 128 KB for each CPU 691 16 => 64 KB for each CPU 692 15 => 32 KB for each CPU 693 14 => 16 KB for each CPU 694 13 => 8 KB for each CPU 695 12 => 4 KB for each CPU 696 697# 698# Architectures with an unreliable sched_clock() should select this: 699# 700config HAVE_UNSTABLE_SCHED_CLOCK 701 bool 702 703config GENERIC_SCHED_CLOCK 704 bool 705 706menu "Scheduler features" 707 708config UCLAMP_TASK 709 bool "Enable utilization clamping for RT/FAIR tasks" 710 depends on CPU_FREQ_GOV_SCHEDUTIL 711 help 712 This feature enables the scheduler to track the clamped utilization 713 of each CPU based on RUNNABLE tasks scheduled on that CPU. 714 715 With this option, the user can specify the min and max CPU 716 utilization allowed for RUNNABLE tasks. The max utilization defines 717 the maximum frequency a task should use while the min utilization 718 defines the minimum frequency it should use. 719 720 Both min and max utilization clamp values are hints to the scheduler, 721 aiming at improving its frequency selection policy, but they do not 722 enforce or grant any specific bandwidth for tasks. 723 724 If in doubt, say N. 725 726config UCLAMP_BUCKETS_COUNT 727 int "Number of supported utilization clamp buckets" 728 range 5 20 729 default 5 730 depends on UCLAMP_TASK 731 help 732 Defines the number of clamp buckets to use. The range of each bucket 733 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 734 number of clamp buckets the finer their granularity and the higher 735 the precision of clamping aggregation and tracking at run-time. 736 737 For example, with the minimum configuration value we will have 5 738 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 739 be refcounted in the [20..39]% bucket and will set the bucket clamp 740 effective value to 25%. 741 If a second 30% boosted task should be co-scheduled on the same CPU, 742 that task will be refcounted in the same bucket of the first task and 743 it will boost the bucket clamp effective value to 30%. 744 The clamp effective value of a bucket is reset to its nominal value 745 (20% in the example above) when there are no more tasks refcounted in 746 that bucket. 747 748 An additional boost/capping margin can be added to some tasks. In the 749 example above the 25% task will be boosted to 30% until it exits the 750 CPU. If that should be considered not acceptable on certain systems, 751 it's always possible to reduce the margin by increasing the number of 752 clamp buckets to trade off used memory for run-time tracking 753 precision. 754 755 If in doubt, use the default value. 756 757endmenu 758 759# 760# For architectures that want to enable the support for NUMA-affine scheduler 761# balancing logic: 762# 763config ARCH_SUPPORTS_NUMA_BALANCING 764 bool 765 766# 767# For architectures that prefer to flush all TLBs after a number of pages 768# are unmapped instead of sending one IPI per page to flush. The architecture 769# must provide guarantees on what happens if a clean TLB cache entry is 770# written after the unmap. Details are in mm/rmap.c near the check for 771# should_defer_flush. The architecture should also consider if the full flush 772# and the refill costs are offset by the savings of sending fewer IPIs. 773config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 774 bool 775 776config CC_HAS_INT128 777 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 778 779# 780# For architectures that know their GCC __int128 support is sound 781# 782config ARCH_SUPPORTS_INT128 783 bool 784 785# For architectures that (ab)use NUMA to represent different memory regions 786# all cpu-local but of different latencies, such as SuperH. 787# 788config ARCH_WANT_NUMA_VARIABLE_LOCALITY 789 bool 790 791config NUMA_BALANCING 792 bool "Memory placement aware NUMA scheduler" 793 depends on ARCH_SUPPORTS_NUMA_BALANCING 794 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 795 depends on SMP && NUMA && MIGRATION 796 help 797 This option adds support for automatic NUMA aware memory/task placement. 798 The mechanism is quite primitive and is based on migrating memory when 799 it has references to the node the task is running on. 800 801 This system will be inactive on UMA systems. 802 803config NUMA_BALANCING_DEFAULT_ENABLED 804 bool "Automatically enable NUMA aware memory/task placement" 805 default y 806 depends on NUMA_BALANCING 807 help 808 If set, automatic NUMA balancing will be enabled if running on a NUMA 809 machine. 810 811menuconfig CGROUPS 812 bool "Control Group support" 813 select KERNFS 814 help 815 This option adds support for grouping sets of processes together, for 816 use with process control subsystems such as Cpusets, CFS, memory 817 controls or device isolation. 818 See 819 - Documentation/scheduler/sched-design-CFS.rst (CFS) 820 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 821 and resource control) 822 823 Say N if unsure. 824 825if CGROUPS 826 827config PAGE_COUNTER 828 bool 829 830config MEMCG 831 bool "Memory controller" 832 select PAGE_COUNTER 833 select EVENTFD 834 help 835 Provides control over the memory footprint of tasks in a cgroup. 836 837config MEMCG_SWAP 838 bool "Swap controller" 839 depends on MEMCG && SWAP 840 help 841 Provides control over the swap space consumed by tasks in a cgroup. 842 843config MEMCG_SWAP_ENABLED 844 bool "Swap controller enabled by default" 845 depends on MEMCG_SWAP 846 default y 847 help 848 Memory Resource Controller Swap Extension comes with its price in 849 a bigger memory consumption. General purpose distribution kernels 850 which want to enable the feature but keep it disabled by default 851 and let the user enable it by swapaccount=1 boot command line 852 parameter should have this option unselected. 853 For those who want to have the feature enabled by default should 854 select this option (if, for some reason, they need to disable it 855 then swapaccount=0 does the trick). 856 857config MEMCG_KMEM 858 bool 859 depends on MEMCG && !SLOB 860 default y 861 862config BLK_CGROUP 863 bool "IO controller" 864 depends on BLOCK 865 default n 866 ---help--- 867 Generic block IO controller cgroup interface. This is the common 868 cgroup interface which should be used by various IO controlling 869 policies. 870 871 Currently, CFQ IO scheduler uses it to recognize task groups and 872 control disk bandwidth allocation (proportional time slice allocation) 873 to such task groups. It is also used by bio throttling logic in 874 block layer to implement upper limit in IO rates on a device. 875 876 This option only enables generic Block IO controller infrastructure. 877 One needs to also enable actual IO controlling logic/policy. For 878 enabling proportional weight division of disk bandwidth in CFQ, set 879 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 880 CONFIG_BLK_DEV_THROTTLING=y. 881 882 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 883 884config CGROUP_WRITEBACK 885 bool 886 depends on MEMCG && BLK_CGROUP 887 default y 888 889menuconfig CGROUP_SCHED 890 bool "CPU controller" 891 default n 892 help 893 This feature lets CPU scheduler recognize task groups and control CPU 894 bandwidth allocation to such task groups. It uses cgroups to group 895 tasks. 896 897if CGROUP_SCHED 898config FAIR_GROUP_SCHED 899 bool "Group scheduling for SCHED_OTHER" 900 depends on CGROUP_SCHED 901 default CGROUP_SCHED 902 903config CFS_BANDWIDTH 904 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 905 depends on FAIR_GROUP_SCHED 906 default n 907 help 908 This option allows users to define CPU bandwidth rates (limits) for 909 tasks running within the fair group scheduler. Groups with no limit 910 set are considered to be unconstrained and will run with no 911 restriction. 912 See Documentation/scheduler/sched-bwc.rst for more information. 913 914config RT_GROUP_SCHED 915 bool "Group scheduling for SCHED_RR/FIFO" 916 depends on CGROUP_SCHED 917 default n 918 help 919 This feature lets you explicitly allocate real CPU bandwidth 920 to task groups. If enabled, it will also make it impossible to 921 schedule realtime tasks for non-root users until you allocate 922 realtime bandwidth for them. 923 See Documentation/scheduler/sched-rt-group.rst for more information. 924 925endif #CGROUP_SCHED 926 927config UCLAMP_TASK_GROUP 928 bool "Utilization clamping per group of tasks" 929 depends on CGROUP_SCHED 930 depends on UCLAMP_TASK 931 default n 932 help 933 This feature enables the scheduler to track the clamped utilization 934 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 935 936 When this option is enabled, the user can specify a min and max 937 CPU bandwidth which is allowed for each single task in a group. 938 The max bandwidth allows to clamp the maximum frequency a task 939 can use, while the min bandwidth allows to define a minimum 940 frequency a task will always use. 941 942 When task group based utilization clamping is enabled, an eventually 943 specified task-specific clamp value is constrained by the cgroup 944 specified clamp value. Both minimum and maximum task clamping cannot 945 be bigger than the corresponding clamping defined at task group level. 946 947 If in doubt, say N. 948 949config CGROUP_PIDS 950 bool "PIDs controller" 951 help 952 Provides enforcement of process number limits in the scope of a 953 cgroup. Any attempt to fork more processes than is allowed in the 954 cgroup will fail. PIDs are fundamentally a global resource because it 955 is fairly trivial to reach PID exhaustion before you reach even a 956 conservative kmemcg limit. As a result, it is possible to grind a 957 system to halt without being limited by other cgroup policies. The 958 PIDs controller is designed to stop this from happening. 959 960 It should be noted that organisational operations (such as attaching 961 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 962 since the PIDs limit only affects a process's ability to fork, not to 963 attach to a cgroup. 964 965config CGROUP_RDMA 966 bool "RDMA controller" 967 help 968 Provides enforcement of RDMA resources defined by IB stack. 969 It is fairly easy for consumers to exhaust RDMA resources, which 970 can result into resource unavailability to other consumers. 971 RDMA controller is designed to stop this from happening. 972 Attaching processes with active RDMA resources to the cgroup 973 hierarchy is allowed even if can cross the hierarchy's limit. 974 975config CGROUP_FREEZER 976 bool "Freezer controller" 977 help 978 Provides a way to freeze and unfreeze all tasks in a 979 cgroup. 980 981 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 982 controller includes important in-kernel memory consumers per default. 983 984 If you're using cgroup2, say N. 985 986config CGROUP_HUGETLB 987 bool "HugeTLB controller" 988 depends on HUGETLB_PAGE 989 select PAGE_COUNTER 990 default n 991 help 992 Provides a cgroup controller for HugeTLB pages. 993 When you enable this, you can put a per cgroup limit on HugeTLB usage. 994 The limit is enforced during page fault. Since HugeTLB doesn't 995 support page reclaim, enforcing the limit at page fault time implies 996 that, the application will get SIGBUS signal if it tries to access 997 HugeTLB pages beyond its limit. This requires the application to know 998 beforehand how much HugeTLB pages it would require for its use. The 999 control group is tracked in the third page lru pointer. This means 1000 that we cannot use the controller with huge page less than 3 pages. 1001 1002config CPUSETS 1003 bool "Cpuset controller" 1004 depends on SMP 1005 help 1006 This option will let you create and manage CPUSETs which 1007 allow dynamically partitioning a system into sets of CPUs and 1008 Memory Nodes and assigning tasks to run only within those sets. 1009 This is primarily useful on large SMP or NUMA systems. 1010 1011 Say N if unsure. 1012 1013config PROC_PID_CPUSET 1014 bool "Include legacy /proc/<pid>/cpuset file" 1015 depends on CPUSETS 1016 default y 1017 1018config CGROUP_DEVICE 1019 bool "Device controller" 1020 help 1021 Provides a cgroup controller implementing whitelists for 1022 devices which a process in the cgroup can mknod or open. 1023 1024config CGROUP_CPUACCT 1025 bool "Simple CPU accounting controller" 1026 help 1027 Provides a simple controller for monitoring the 1028 total CPU consumed by the tasks in a cgroup. 1029 1030config CGROUP_PERF 1031 bool "Perf controller" 1032 depends on PERF_EVENTS 1033 help 1034 This option extends the perf per-cpu mode to restrict monitoring 1035 to threads which belong to the cgroup specified and run on the 1036 designated cpu. Or this can be used to have cgroup ID in samples 1037 so that it can monitor performance events among cgroups. 1038 1039 Say N if unsure. 1040 1041config CGROUP_BPF 1042 bool "Support for eBPF programs attached to cgroups" 1043 depends on BPF_SYSCALL 1044 select SOCK_CGROUP_DATA 1045 help 1046 Allow attaching eBPF programs to a cgroup using the bpf(2) 1047 syscall command BPF_PROG_ATTACH. 1048 1049 In which context these programs are accessed depends on the type 1050 of attachment. For instance, programs that are attached using 1051 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1052 inet sockets. 1053 1054config CGROUP_DEBUG 1055 bool "Debug controller" 1056 default n 1057 depends on DEBUG_KERNEL 1058 help 1059 This option enables a simple controller that exports 1060 debugging information about the cgroups framework. This 1061 controller is for control cgroup debugging only. Its 1062 interfaces are not stable. 1063 1064 Say N. 1065 1066config SOCK_CGROUP_DATA 1067 bool 1068 default n 1069 1070endif # CGROUPS 1071 1072menuconfig NAMESPACES 1073 bool "Namespaces support" if EXPERT 1074 depends on MULTIUSER 1075 default !EXPERT 1076 help 1077 Provides the way to make tasks work with different objects using 1078 the same id. For example same IPC id may refer to different objects 1079 or same user id or pid may refer to different tasks when used in 1080 different namespaces. 1081 1082if NAMESPACES 1083 1084config UTS_NS 1085 bool "UTS namespace" 1086 default y 1087 help 1088 In this namespace tasks see different info provided with the 1089 uname() system call 1090 1091config TIME_NS 1092 bool "TIME namespace" 1093 depends on GENERIC_VDSO_TIME_NS 1094 default y 1095 help 1096 In this namespace boottime and monotonic clocks can be set. 1097 The time will keep going with the same pace. 1098 1099config IPC_NS 1100 bool "IPC namespace" 1101 depends on (SYSVIPC || POSIX_MQUEUE) 1102 default y 1103 help 1104 In this namespace tasks work with IPC ids which correspond to 1105 different IPC objects in different namespaces. 1106 1107config USER_NS 1108 bool "User namespace" 1109 default n 1110 help 1111 This allows containers, i.e. vservers, to use user namespaces 1112 to provide different user info for different servers. 1113 1114 When user namespaces are enabled in the kernel it is 1115 recommended that the MEMCG option also be enabled and that 1116 user-space use the memory control groups to limit the amount 1117 of memory a memory unprivileged users can use. 1118 1119 If unsure, say N. 1120 1121config PID_NS 1122 bool "PID Namespaces" 1123 default y 1124 help 1125 Support process id namespaces. This allows having multiple 1126 processes with the same pid as long as they are in different 1127 pid namespaces. This is a building block of containers. 1128 1129config NET_NS 1130 bool "Network namespace" 1131 depends on NET 1132 default y 1133 help 1134 Allow user space to create what appear to be multiple instances 1135 of the network stack. 1136 1137endif # NAMESPACES 1138 1139config CHECKPOINT_RESTORE 1140 bool "Checkpoint/restore support" 1141 select PROC_CHILDREN 1142 default n 1143 help 1144 Enables additional kernel features in a sake of checkpoint/restore. 1145 In particular it adds auxiliary prctl codes to setup process text, 1146 data and heap segment sizes, and a few additional /proc filesystem 1147 entries. 1148 1149 If unsure, say N here. 1150 1151config SCHED_AUTOGROUP 1152 bool "Automatic process group scheduling" 1153 select CGROUPS 1154 select CGROUP_SCHED 1155 select FAIR_GROUP_SCHED 1156 help 1157 This option optimizes the scheduler for common desktop workloads by 1158 automatically creating and populating task groups. This separation 1159 of workloads isolates aggressive CPU burners (like build jobs) from 1160 desktop applications. Task group autogeneration is currently based 1161 upon task session. 1162 1163config SYSFS_DEPRECATED 1164 bool "Enable deprecated sysfs features to support old userspace tools" 1165 depends on SYSFS 1166 default n 1167 help 1168 This option adds code that switches the layout of the "block" class 1169 devices, to not show up in /sys/class/block/, but only in 1170 /sys/block/. 1171 1172 This switch is only active when the sysfs.deprecated=1 boot option is 1173 passed or the SYSFS_DEPRECATED_V2 option is set. 1174 1175 This option allows new kernels to run on old distributions and tools, 1176 which might get confused by /sys/class/block/. Since 2007/2008 all 1177 major distributions and tools handle this just fine. 1178 1179 Recent distributions and userspace tools after 2009/2010 depend on 1180 the existence of /sys/class/block/, and will not work with this 1181 option enabled. 1182 1183 Only if you are using a new kernel on an old distribution, you might 1184 need to say Y here. 1185 1186config SYSFS_DEPRECATED_V2 1187 bool "Enable deprecated sysfs features by default" 1188 default n 1189 depends on SYSFS 1190 depends on SYSFS_DEPRECATED 1191 help 1192 Enable deprecated sysfs by default. 1193 1194 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1195 option. 1196 1197 Only if you are using a new kernel on an old distribution, you might 1198 need to say Y here. Even then, odds are you would not need it 1199 enabled, you can always pass the boot option if absolutely necessary. 1200 1201config RELAY 1202 bool "Kernel->user space relay support (formerly relayfs)" 1203 select IRQ_WORK 1204 help 1205 This option enables support for relay interface support in 1206 certain file systems (such as debugfs). 1207 It is designed to provide an efficient mechanism for tools and 1208 facilities to relay large amounts of data from kernel space to 1209 user space. 1210 1211 If unsure, say N. 1212 1213config BLK_DEV_INITRD 1214 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1215 help 1216 The initial RAM filesystem is a ramfs which is loaded by the 1217 boot loader (loadlin or lilo) and that is mounted as root 1218 before the normal boot procedure. It is typically used to 1219 load modules needed to mount the "real" root file system, 1220 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1221 1222 If RAM disk support (BLK_DEV_RAM) is also included, this 1223 also enables initial RAM disk (initrd) support and adds 1224 15 Kbytes (more on some other architectures) to the kernel size. 1225 1226 If unsure say Y. 1227 1228if BLK_DEV_INITRD 1229 1230source "usr/Kconfig" 1231 1232endif 1233 1234config BOOT_CONFIG 1235 bool "Boot config support" 1236 select BLK_DEV_INITRD 1237 help 1238 Extra boot config allows system admin to pass a config file as 1239 complemental extension of kernel cmdline when booting. 1240 The boot config file must be attached at the end of initramfs 1241 with checksum, size and magic word. 1242 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1243 1244 If unsure, say Y. 1245 1246choice 1247 prompt "Compiler optimization level" 1248 default CC_OPTIMIZE_FOR_PERFORMANCE 1249 1250config CC_OPTIMIZE_FOR_PERFORMANCE 1251 bool "Optimize for performance (-O2)" 1252 help 1253 This is the default optimization level for the kernel, building 1254 with the "-O2" compiler flag for best performance and most 1255 helpful compile-time warnings. 1256 1257config CC_OPTIMIZE_FOR_PERFORMANCE_O3 1258 bool "Optimize more for performance (-O3)" 1259 depends on ARC 1260 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives 1261 help 1262 Choosing this option will pass "-O3" to your compiler to optimize 1263 the kernel yet more for performance. 1264 1265config CC_OPTIMIZE_FOR_SIZE 1266 bool "Optimize for size (-Os)" 1267 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives 1268 help 1269 Choosing this option will pass "-Os" to your compiler resulting 1270 in a smaller kernel. 1271 1272endchoice 1273 1274config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1275 bool 1276 help 1277 This requires that the arch annotates or otherwise protects 1278 its external entry points from being discarded. Linker scripts 1279 must also merge .text.*, .data.*, and .bss.* correctly into 1280 output sections. Care must be taken not to pull in unrelated 1281 sections (e.g., '.text.init'). Typically '.' in section names 1282 is used to distinguish them from label names / C identifiers. 1283 1284config LD_DEAD_CODE_DATA_ELIMINATION 1285 bool "Dead code and data elimination (EXPERIMENTAL)" 1286 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1287 depends on EXPERT 1288 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800) 1289 depends on $(cc-option,-ffunction-sections -fdata-sections) 1290 depends on $(ld-option,--gc-sections) 1291 help 1292 Enable this if you want to do dead code and data elimination with 1293 the linker by compiling with -ffunction-sections -fdata-sections, 1294 and linking with --gc-sections. 1295 1296 This can reduce on disk and in-memory size of the kernel 1297 code and static data, particularly for small configs and 1298 on small systems. This has the possibility of introducing 1299 silently broken kernel if the required annotations are not 1300 present. This option is not well tested yet, so use at your 1301 own risk. 1302 1303config SYSCTL 1304 bool 1305 1306config HAVE_UID16 1307 bool 1308 1309config SYSCTL_EXCEPTION_TRACE 1310 bool 1311 help 1312 Enable support for /proc/sys/debug/exception-trace. 1313 1314config SYSCTL_ARCH_UNALIGN_NO_WARN 1315 bool 1316 help 1317 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1318 Allows arch to define/use @no_unaligned_warning to possibly warn 1319 about unaligned access emulation going on under the hood. 1320 1321config SYSCTL_ARCH_UNALIGN_ALLOW 1322 bool 1323 help 1324 Enable support for /proc/sys/kernel/unaligned-trap 1325 Allows arches to define/use @unaligned_enabled to runtime toggle 1326 the unaligned access emulation. 1327 see arch/parisc/kernel/unaligned.c for reference 1328 1329config HAVE_PCSPKR_PLATFORM 1330 bool 1331 1332# interpreter that classic socket filters depend on 1333config BPF 1334 bool 1335 1336menuconfig EXPERT 1337 bool "Configure standard kernel features (expert users)" 1338 # Unhide debug options, to make the on-by-default options visible 1339 select DEBUG_KERNEL 1340 help 1341 This option allows certain base kernel options and settings 1342 to be disabled or tweaked. This is for specialized 1343 environments which can tolerate a "non-standard" kernel. 1344 Only use this if you really know what you are doing. 1345 1346config UID16 1347 bool "Enable 16-bit UID system calls" if EXPERT 1348 depends on HAVE_UID16 && MULTIUSER 1349 default y 1350 help 1351 This enables the legacy 16-bit UID syscall wrappers. 1352 1353config MULTIUSER 1354 bool "Multiple users, groups and capabilities support" if EXPERT 1355 default y 1356 help 1357 This option enables support for non-root users, groups and 1358 capabilities. 1359 1360 If you say N here, all processes will run with UID 0, GID 0, and all 1361 possible capabilities. Saying N here also compiles out support for 1362 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1363 setgid, and capset. 1364 1365 If unsure, say Y here. 1366 1367config SGETMASK_SYSCALL 1368 bool "sgetmask/ssetmask syscalls support" if EXPERT 1369 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1370 ---help--- 1371 sys_sgetmask and sys_ssetmask are obsolete system calls 1372 no longer supported in libc but still enabled by default in some 1373 architectures. 1374 1375 If unsure, leave the default option here. 1376 1377config SYSFS_SYSCALL 1378 bool "Sysfs syscall support" if EXPERT 1379 default y 1380 ---help--- 1381 sys_sysfs is an obsolete system call no longer supported in libc. 1382 Note that disabling this option is more secure but might break 1383 compatibility with some systems. 1384 1385 If unsure say Y here. 1386 1387config FHANDLE 1388 bool "open by fhandle syscalls" if EXPERT 1389 select EXPORTFS 1390 default y 1391 help 1392 If you say Y here, a user level program will be able to map 1393 file names to handle and then later use the handle for 1394 different file system operations. This is useful in implementing 1395 userspace file servers, which now track files using handles instead 1396 of names. The handle would remain the same even if file names 1397 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1398 syscalls. 1399 1400config POSIX_TIMERS 1401 bool "Posix Clocks & timers" if EXPERT 1402 default y 1403 help 1404 This includes native support for POSIX timers to the kernel. 1405 Some embedded systems have no use for them and therefore they 1406 can be configured out to reduce the size of the kernel image. 1407 1408 When this option is disabled, the following syscalls won't be 1409 available: timer_create, timer_gettime: timer_getoverrun, 1410 timer_settime, timer_delete, clock_adjtime, getitimer, 1411 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1412 clock_getres and clock_nanosleep syscalls will be limited to 1413 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1414 1415 If unsure say y. 1416 1417config PRINTK 1418 default y 1419 bool "Enable support for printk" if EXPERT 1420 select IRQ_WORK 1421 help 1422 This option enables normal printk support. Removing it 1423 eliminates most of the message strings from the kernel image 1424 and makes the kernel more or less silent. As this makes it 1425 very difficult to diagnose system problems, saying N here is 1426 strongly discouraged. 1427 1428config PRINTK_NMI 1429 def_bool y 1430 depends on PRINTK 1431 depends on HAVE_NMI 1432 1433config BUG 1434 bool "BUG() support" if EXPERT 1435 default y 1436 help 1437 Disabling this option eliminates support for BUG and WARN, reducing 1438 the size of your kernel image and potentially quietly ignoring 1439 numerous fatal conditions. You should only consider disabling this 1440 option for embedded systems with no facilities for reporting errors. 1441 Just say Y. 1442 1443config ELF_CORE 1444 depends on COREDUMP 1445 default y 1446 bool "Enable ELF core dumps" if EXPERT 1447 help 1448 Enable support for generating core dumps. Disabling saves about 4k. 1449 1450 1451config PCSPKR_PLATFORM 1452 bool "Enable PC-Speaker support" if EXPERT 1453 depends on HAVE_PCSPKR_PLATFORM 1454 select I8253_LOCK 1455 default y 1456 help 1457 This option allows to disable the internal PC-Speaker 1458 support, saving some memory. 1459 1460config BASE_FULL 1461 default y 1462 bool "Enable full-sized data structures for core" if EXPERT 1463 help 1464 Disabling this option reduces the size of miscellaneous core 1465 kernel data structures. This saves memory on small machines, 1466 but may reduce performance. 1467 1468config FUTEX 1469 bool "Enable futex support" if EXPERT 1470 default y 1471 imply RT_MUTEXES 1472 help 1473 Disabling this option will cause the kernel to be built without 1474 support for "fast userspace mutexes". The resulting kernel may not 1475 run glibc-based applications correctly. 1476 1477config FUTEX_PI 1478 bool 1479 depends on FUTEX && RT_MUTEXES 1480 default y 1481 1482config HAVE_FUTEX_CMPXCHG 1483 bool 1484 depends on FUTEX 1485 help 1486 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1487 is implemented and always working. This removes a couple of runtime 1488 checks. 1489 1490config EPOLL 1491 bool "Enable eventpoll support" if EXPERT 1492 default y 1493 help 1494 Disabling this option will cause the kernel to be built without 1495 support for epoll family of system calls. 1496 1497config SIGNALFD 1498 bool "Enable signalfd() system call" if EXPERT 1499 default y 1500 help 1501 Enable the signalfd() system call that allows to receive signals 1502 on a file descriptor. 1503 1504 If unsure, say Y. 1505 1506config TIMERFD 1507 bool "Enable timerfd() system call" if EXPERT 1508 default y 1509 help 1510 Enable the timerfd() system call that allows to receive timer 1511 events on a file descriptor. 1512 1513 If unsure, say Y. 1514 1515config EVENTFD 1516 bool "Enable eventfd() system call" if EXPERT 1517 default y 1518 help 1519 Enable the eventfd() system call that allows to receive both 1520 kernel notification (ie. KAIO) or userspace notifications. 1521 1522 If unsure, say Y. 1523 1524config SHMEM 1525 bool "Use full shmem filesystem" if EXPERT 1526 default y 1527 depends on MMU 1528 help 1529 The shmem is an internal filesystem used to manage shared memory. 1530 It is backed by swap and manages resource limits. It is also exported 1531 to userspace as tmpfs if TMPFS is enabled. Disabling this 1532 option replaces shmem and tmpfs with the much simpler ramfs code, 1533 which may be appropriate on small systems without swap. 1534 1535config AIO 1536 bool "Enable AIO support" if EXPERT 1537 default y 1538 help 1539 This option enables POSIX asynchronous I/O which may by used 1540 by some high performance threaded applications. Disabling 1541 this option saves about 7k. 1542 1543config IO_URING 1544 bool "Enable IO uring support" if EXPERT 1545 select IO_WQ 1546 default y 1547 help 1548 This option enables support for the io_uring interface, enabling 1549 applications to submit and complete IO through submission and 1550 completion rings that are shared between the kernel and application. 1551 1552config ADVISE_SYSCALLS 1553 bool "Enable madvise/fadvise syscalls" if EXPERT 1554 default y 1555 help 1556 This option enables the madvise and fadvise syscalls, used by 1557 applications to advise the kernel about their future memory or file 1558 usage, improving performance. If building an embedded system where no 1559 applications use these syscalls, you can disable this option to save 1560 space. 1561 1562config HAVE_ARCH_USERFAULTFD_WP 1563 bool 1564 help 1565 Arch has userfaultfd write protection support 1566 1567config MEMBARRIER 1568 bool "Enable membarrier() system call" if EXPERT 1569 default y 1570 help 1571 Enable the membarrier() system call that allows issuing memory 1572 barriers across all running threads, which can be used to distribute 1573 the cost of user-space memory barriers asymmetrically by transforming 1574 pairs of memory barriers into pairs consisting of membarrier() and a 1575 compiler barrier. 1576 1577 If unsure, say Y. 1578 1579config KALLSYMS 1580 bool "Load all symbols for debugging/ksymoops" if EXPERT 1581 default y 1582 help 1583 Say Y here to let the kernel print out symbolic crash information and 1584 symbolic stack backtraces. This increases the size of the kernel 1585 somewhat, as all symbols have to be loaded into the kernel image. 1586 1587config KALLSYMS_ALL 1588 bool "Include all symbols in kallsyms" 1589 depends on DEBUG_KERNEL && KALLSYMS 1590 help 1591 Normally kallsyms only contains the symbols of functions for nicer 1592 OOPS messages and backtraces (i.e., symbols from the text and inittext 1593 sections). This is sufficient for most cases. And only in very rare 1594 cases (e.g., when a debugger is used) all symbols are required (e.g., 1595 names of variables from the data sections, etc). 1596 1597 This option makes sure that all symbols are loaded into the kernel 1598 image (i.e., symbols from all sections) in cost of increased kernel 1599 size (depending on the kernel configuration, it may be 300KiB or 1600 something like this). 1601 1602 Say N unless you really need all symbols. 1603 1604config KALLSYMS_ABSOLUTE_PERCPU 1605 bool 1606 depends on KALLSYMS 1607 default X86_64 && SMP 1608 1609config KALLSYMS_BASE_RELATIVE 1610 bool 1611 depends on KALLSYMS 1612 default !IA64 1613 help 1614 Instead of emitting them as absolute values in the native word size, 1615 emit the symbol references in the kallsyms table as 32-bit entries, 1616 each containing a relative value in the range [base, base + U32_MAX] 1617 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1618 an absolute value in the range [0, S32_MAX] or a relative value in the 1619 range [base, base + S32_MAX], where base is the lowest relative symbol 1620 address encountered in the image. 1621 1622 On 64-bit builds, this reduces the size of the address table by 50%, 1623 but more importantly, it results in entries whose values are build 1624 time constants, and no relocation pass is required at runtime to fix 1625 up the entries based on the runtime load address of the kernel. 1626 1627# end of the "standard kernel features (expert users)" menu 1628 1629# syscall, maps, verifier 1630 1631config BPF_LSM 1632 bool "LSM Instrumentation with BPF" 1633 depends on BPF_EVENTS 1634 depends on BPF_SYSCALL 1635 depends on SECURITY 1636 depends on BPF_JIT 1637 help 1638 Enables instrumentation of the security hooks with eBPF programs for 1639 implementing dynamic MAC and Audit Policies. 1640 1641 If you are unsure how to answer this question, answer N. 1642 1643config BPF_SYSCALL 1644 bool "Enable bpf() system call" 1645 select BPF 1646 select IRQ_WORK 1647 default n 1648 help 1649 Enable the bpf() system call that allows to manipulate eBPF 1650 programs and maps via file descriptors. 1651 1652config ARCH_WANT_DEFAULT_BPF_JIT 1653 bool 1654 1655config BPF_JIT_ALWAYS_ON 1656 bool "Permanently enable BPF JIT and remove BPF interpreter" 1657 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1658 help 1659 Enables BPF JIT and removes BPF interpreter to avoid 1660 speculative execution of BPF instructions by the interpreter 1661 1662config BPF_JIT_DEFAULT_ON 1663 def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON 1664 depends on HAVE_EBPF_JIT && BPF_JIT 1665 1666config USERFAULTFD 1667 bool "Enable userfaultfd() system call" 1668 depends on MMU 1669 help 1670 Enable the userfaultfd() system call that allows to intercept and 1671 handle page faults in userland. 1672 1673config ARCH_HAS_MEMBARRIER_CALLBACKS 1674 bool 1675 1676config ARCH_HAS_MEMBARRIER_SYNC_CORE 1677 bool 1678 1679config RSEQ 1680 bool "Enable rseq() system call" if EXPERT 1681 default y 1682 depends on HAVE_RSEQ 1683 select MEMBARRIER 1684 help 1685 Enable the restartable sequences system call. It provides a 1686 user-space cache for the current CPU number value, which 1687 speeds up getting the current CPU number from user-space, 1688 as well as an ABI to speed up user-space operations on 1689 per-CPU data. 1690 1691 If unsure, say Y. 1692 1693config DEBUG_RSEQ 1694 default n 1695 bool "Enabled debugging of rseq() system call" if EXPERT 1696 depends on RSEQ && DEBUG_KERNEL 1697 help 1698 Enable extra debugging checks for the rseq system call. 1699 1700 If unsure, say N. 1701 1702config EMBEDDED 1703 bool "Embedded system" 1704 option allnoconfig_y 1705 select EXPERT 1706 help 1707 This option should be enabled if compiling the kernel for 1708 an embedded system so certain expert options are available 1709 for configuration. 1710 1711config HAVE_PERF_EVENTS 1712 bool 1713 help 1714 See tools/perf/design.txt for details. 1715 1716config PERF_USE_VMALLOC 1717 bool 1718 help 1719 See tools/perf/design.txt for details 1720 1721config PC104 1722 bool "PC/104 support" if EXPERT 1723 help 1724 Expose PC/104 form factor device drivers and options available for 1725 selection and configuration. Enable this option if your target 1726 machine has a PC/104 bus. 1727 1728menu "Kernel Performance Events And Counters" 1729 1730config PERF_EVENTS 1731 bool "Kernel performance events and counters" 1732 default y if PROFILING 1733 depends on HAVE_PERF_EVENTS 1734 select IRQ_WORK 1735 select SRCU 1736 help 1737 Enable kernel support for various performance events provided 1738 by software and hardware. 1739 1740 Software events are supported either built-in or via the 1741 use of generic tracepoints. 1742 1743 Most modern CPUs support performance events via performance 1744 counter registers. These registers count the number of certain 1745 types of hw events: such as instructions executed, cachemisses 1746 suffered, or branches mis-predicted - without slowing down the 1747 kernel or applications. These registers can also trigger interrupts 1748 when a threshold number of events have passed - and can thus be 1749 used to profile the code that runs on that CPU. 1750 1751 The Linux Performance Event subsystem provides an abstraction of 1752 these software and hardware event capabilities, available via a 1753 system call and used by the "perf" utility in tools/perf/. It 1754 provides per task and per CPU counters, and it provides event 1755 capabilities on top of those. 1756 1757 Say Y if unsure. 1758 1759config DEBUG_PERF_USE_VMALLOC 1760 default n 1761 bool "Debug: use vmalloc to back perf mmap() buffers" 1762 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1763 select PERF_USE_VMALLOC 1764 help 1765 Use vmalloc memory to back perf mmap() buffers. 1766 1767 Mostly useful for debugging the vmalloc code on platforms 1768 that don't require it. 1769 1770 Say N if unsure. 1771 1772endmenu 1773 1774config VM_EVENT_COUNTERS 1775 default y 1776 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1777 help 1778 VM event counters are needed for event counts to be shown. 1779 This option allows the disabling of the VM event counters 1780 on EXPERT systems. /proc/vmstat will only show page counts 1781 if VM event counters are disabled. 1782 1783config SLUB_DEBUG 1784 default y 1785 bool "Enable SLUB debugging support" if EXPERT 1786 depends on SLUB && SYSFS 1787 help 1788 SLUB has extensive debug support features. Disabling these can 1789 result in significant savings in code size. This also disables 1790 SLUB sysfs support. /sys/slab will not exist and there will be 1791 no support for cache validation etc. 1792 1793config SLUB_MEMCG_SYSFS_ON 1794 default n 1795 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1796 depends on SLUB && SYSFS && MEMCG 1797 help 1798 SLUB creates a directory under /sys/kernel/slab for each 1799 allocation cache to host info and debug files. If memory 1800 cgroup is enabled, each cache can have per memory cgroup 1801 caches. SLUB can create the same sysfs directories for these 1802 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1803 to a very high number of debug files being created. This is 1804 controlled by slub_memcg_sysfs boot parameter and this 1805 config option determines the parameter's default value. 1806 1807config COMPAT_BRK 1808 bool "Disable heap randomization" 1809 default y 1810 help 1811 Randomizing heap placement makes heap exploits harder, but it 1812 also breaks ancient binaries (including anything libc5 based). 1813 This option changes the bootup default to heap randomization 1814 disabled, and can be overridden at runtime by setting 1815 /proc/sys/kernel/randomize_va_space to 2. 1816 1817 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1818 1819choice 1820 prompt "Choose SLAB allocator" 1821 default SLUB 1822 help 1823 This option allows to select a slab allocator. 1824 1825config SLAB 1826 bool "SLAB" 1827 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1828 help 1829 The regular slab allocator that is established and known to work 1830 well in all environments. It organizes cache hot objects in 1831 per cpu and per node queues. 1832 1833config SLUB 1834 bool "SLUB (Unqueued Allocator)" 1835 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1836 help 1837 SLUB is a slab allocator that minimizes cache line usage 1838 instead of managing queues of cached objects (SLAB approach). 1839 Per cpu caching is realized using slabs of objects instead 1840 of queues of objects. SLUB can use memory efficiently 1841 and has enhanced diagnostics. SLUB is the default choice for 1842 a slab allocator. 1843 1844config SLOB 1845 depends on EXPERT 1846 bool "SLOB (Simple Allocator)" 1847 help 1848 SLOB replaces the stock allocator with a drastically simpler 1849 allocator. SLOB is generally more space efficient but 1850 does not perform as well on large systems. 1851 1852endchoice 1853 1854config SLAB_MERGE_DEFAULT 1855 bool "Allow slab caches to be merged" 1856 default y 1857 help 1858 For reduced kernel memory fragmentation, slab caches can be 1859 merged when they share the same size and other characteristics. 1860 This carries a risk of kernel heap overflows being able to 1861 overwrite objects from merged caches (and more easily control 1862 cache layout), which makes such heap attacks easier to exploit 1863 by attackers. By keeping caches unmerged, these kinds of exploits 1864 can usually only damage objects in the same cache. To disable 1865 merging at runtime, "slab_nomerge" can be passed on the kernel 1866 command line. 1867 1868config SLAB_FREELIST_RANDOM 1869 default n 1870 depends on SLAB || SLUB 1871 bool "SLAB freelist randomization" 1872 help 1873 Randomizes the freelist order used on creating new pages. This 1874 security feature reduces the predictability of the kernel slab 1875 allocator against heap overflows. 1876 1877config SLAB_FREELIST_HARDENED 1878 bool "Harden slab freelist metadata" 1879 depends on SLUB 1880 help 1881 Many kernel heap attacks try to target slab cache metadata and 1882 other infrastructure. This options makes minor performance 1883 sacrifices to harden the kernel slab allocator against common 1884 freelist exploit methods. 1885 1886config SHUFFLE_PAGE_ALLOCATOR 1887 bool "Page allocator randomization" 1888 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1889 help 1890 Randomization of the page allocator improves the average 1891 utilization of a direct-mapped memory-side-cache. See section 1892 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1893 6.2a specification for an example of how a platform advertises 1894 the presence of a memory-side-cache. There are also incidental 1895 security benefits as it reduces the predictability of page 1896 allocations to compliment SLAB_FREELIST_RANDOM, but the 1897 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1898 10th order of pages is selected based on cache utilization 1899 benefits on x86. 1900 1901 While the randomization improves cache utilization it may 1902 negatively impact workloads on platforms without a cache. For 1903 this reason, by default, the randomization is enabled only 1904 after runtime detection of a direct-mapped memory-side-cache. 1905 Otherwise, the randomization may be force enabled with the 1906 'page_alloc.shuffle' kernel command line parameter. 1907 1908 Say Y if unsure. 1909 1910config SLUB_CPU_PARTIAL 1911 default y 1912 depends on SLUB && SMP 1913 bool "SLUB per cpu partial cache" 1914 help 1915 Per cpu partial caches accelerate objects allocation and freeing 1916 that is local to a processor at the price of more indeterminism 1917 in the latency of the free. On overflow these caches will be cleared 1918 which requires the taking of locks that may cause latency spikes. 1919 Typically one would choose no for a realtime system. 1920 1921config MMAP_ALLOW_UNINITIALIZED 1922 bool "Allow mmapped anonymous memory to be uninitialized" 1923 depends on EXPERT && !MMU 1924 default n 1925 help 1926 Normally, and according to the Linux spec, anonymous memory obtained 1927 from mmap() has its contents cleared before it is passed to 1928 userspace. Enabling this config option allows you to request that 1929 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1930 providing a huge performance boost. If this option is not enabled, 1931 then the flag will be ignored. 1932 1933 This is taken advantage of by uClibc's malloc(), and also by 1934 ELF-FDPIC binfmt's brk and stack allocator. 1935 1936 Because of the obvious security issues, this option should only be 1937 enabled on embedded devices where you control what is run in 1938 userspace. Since that isn't generally a problem on no-MMU systems, 1939 it is normally safe to say Y here. 1940 1941 See Documentation/nommu-mmap.txt for more information. 1942 1943config SYSTEM_DATA_VERIFICATION 1944 def_bool n 1945 select SYSTEM_TRUSTED_KEYRING 1946 select KEYS 1947 select CRYPTO 1948 select CRYPTO_RSA 1949 select ASYMMETRIC_KEY_TYPE 1950 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1951 select ASN1 1952 select OID_REGISTRY 1953 select X509_CERTIFICATE_PARSER 1954 select PKCS7_MESSAGE_PARSER 1955 help 1956 Provide PKCS#7 message verification using the contents of the system 1957 trusted keyring to provide public keys. This then can be used for 1958 module verification, kexec image verification and firmware blob 1959 verification. 1960 1961config PROFILING 1962 bool "Profiling support" 1963 help 1964 Say Y here to enable the extended profiling support mechanisms used 1965 by profilers such as OProfile. 1966 1967# 1968# Place an empty function call at each tracepoint site. Can be 1969# dynamically changed for a probe function. 1970# 1971config TRACEPOINTS 1972 bool 1973 1974endmenu # General setup 1975 1976source "arch/Kconfig" 1977 1978config RT_MUTEXES 1979 bool 1980 1981config BASE_SMALL 1982 int 1983 default 0 if BASE_FULL 1984 default 1 if !BASE_FULL 1985 1986config MODULE_SIG_FORMAT 1987 def_bool n 1988 select SYSTEM_DATA_VERIFICATION 1989 1990menuconfig MODULES 1991 bool "Enable loadable module support" 1992 option modules 1993 help 1994 Kernel modules are small pieces of compiled code which can 1995 be inserted in the running kernel, rather than being 1996 permanently built into the kernel. You use the "modprobe" 1997 tool to add (and sometimes remove) them. If you say Y here, 1998 many parts of the kernel can be built as modules (by 1999 answering M instead of Y where indicated): this is most 2000 useful for infrequently used options which are not required 2001 for booting. For more information, see the man pages for 2002 modprobe, lsmod, modinfo, insmod and rmmod. 2003 2004 If you say Y here, you will need to run "make 2005 modules_install" to put the modules under /lib/modules/ 2006 where modprobe can find them (you may need to be root to do 2007 this). 2008 2009 If unsure, say Y. 2010 2011if MODULES 2012 2013config MODULE_FORCE_LOAD 2014 bool "Forced module loading" 2015 default n 2016 help 2017 Allow loading of modules without version information (ie. modprobe 2018 --force). Forced module loading sets the 'F' (forced) taint flag and 2019 is usually a really bad idea. 2020 2021config MODULE_UNLOAD 2022 bool "Module unloading" 2023 help 2024 Without this option you will not be able to unload any 2025 modules (note that some modules may not be unloadable 2026 anyway), which makes your kernel smaller, faster 2027 and simpler. If unsure, say Y. 2028 2029config MODULE_FORCE_UNLOAD 2030 bool "Forced module unloading" 2031 depends on MODULE_UNLOAD 2032 help 2033 This option allows you to force a module to unload, even if the 2034 kernel believes it is unsafe: the kernel will remove the module 2035 without waiting for anyone to stop using it (using the -f option to 2036 rmmod). This is mainly for kernel developers and desperate users. 2037 If unsure, say N. 2038 2039config MODVERSIONS 2040 bool "Module versioning support" 2041 help 2042 Usually, you have to use modules compiled with your kernel. 2043 Saying Y here makes it sometimes possible to use modules 2044 compiled for different kernels, by adding enough information 2045 to the modules to (hopefully) spot any changes which would 2046 make them incompatible with the kernel you are running. If 2047 unsure, say N. 2048 2049config ASM_MODVERSIONS 2050 bool 2051 default HAVE_ASM_MODVERSIONS && MODVERSIONS 2052 help 2053 This enables module versioning for exported symbols also from 2054 assembly. This can be enabled only when the target architecture 2055 supports it. 2056 2057config MODULE_REL_CRCS 2058 bool 2059 depends on MODVERSIONS 2060 2061config MODULE_SRCVERSION_ALL 2062 bool "Source checksum for all modules" 2063 help 2064 Modules which contain a MODULE_VERSION get an extra "srcversion" 2065 field inserted into their modinfo section, which contains a 2066 sum of the source files which made it. This helps maintainers 2067 see exactly which source was used to build a module (since 2068 others sometimes change the module source without updating 2069 the version). With this option, such a "srcversion" field 2070 will be created for all modules. If unsure, say N. 2071 2072config MODULE_SIG 2073 bool "Module signature verification" 2074 select MODULE_SIG_FORMAT 2075 help 2076 Check modules for valid signatures upon load: the signature 2077 is simply appended to the module. For more information see 2078 <file:Documentation/admin-guide/module-signing.rst>. 2079 2080 Note that this option adds the OpenSSL development packages as a 2081 kernel build dependency so that the signing tool can use its crypto 2082 library. 2083 2084 You should enable this option if you wish to use either 2085 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via 2086 another LSM - otherwise unsigned modules will be loadable regardless 2087 of the lockdown policy. 2088 2089 !!!WARNING!!! If you enable this option, you MUST make sure that the 2090 module DOES NOT get stripped after being signed. This includes the 2091 debuginfo strip done by some packagers (such as rpmbuild) and 2092 inclusion into an initramfs that wants the module size reduced. 2093 2094config MODULE_SIG_FORCE 2095 bool "Require modules to be validly signed" 2096 depends on MODULE_SIG 2097 help 2098 Reject unsigned modules or signed modules for which we don't have a 2099 key. Without this, such modules will simply taint the kernel. 2100 2101config MODULE_SIG_ALL 2102 bool "Automatically sign all modules" 2103 default y 2104 depends on MODULE_SIG 2105 help 2106 Sign all modules during make modules_install. Without this option, 2107 modules must be signed manually, using the scripts/sign-file tool. 2108 2109comment "Do not forget to sign required modules with scripts/sign-file" 2110 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2111 2112choice 2113 prompt "Which hash algorithm should modules be signed with?" 2114 depends on MODULE_SIG 2115 help 2116 This determines which sort of hashing algorithm will be used during 2117 signature generation. This algorithm _must_ be built into the kernel 2118 directly so that signature verification can take place. It is not 2119 possible to load a signed module containing the algorithm to check 2120 the signature on that module. 2121 2122config MODULE_SIG_SHA1 2123 bool "Sign modules with SHA-1" 2124 select CRYPTO_SHA1 2125 2126config MODULE_SIG_SHA224 2127 bool "Sign modules with SHA-224" 2128 select CRYPTO_SHA256 2129 2130config MODULE_SIG_SHA256 2131 bool "Sign modules with SHA-256" 2132 select CRYPTO_SHA256 2133 2134config MODULE_SIG_SHA384 2135 bool "Sign modules with SHA-384" 2136 select CRYPTO_SHA512 2137 2138config MODULE_SIG_SHA512 2139 bool "Sign modules with SHA-512" 2140 select CRYPTO_SHA512 2141 2142endchoice 2143 2144config MODULE_SIG_HASH 2145 string 2146 depends on MODULE_SIG 2147 default "sha1" if MODULE_SIG_SHA1 2148 default "sha224" if MODULE_SIG_SHA224 2149 default "sha256" if MODULE_SIG_SHA256 2150 default "sha384" if MODULE_SIG_SHA384 2151 default "sha512" if MODULE_SIG_SHA512 2152 2153config MODULE_COMPRESS 2154 bool "Compress modules on installation" 2155 help 2156 2157 Compresses kernel modules when 'make modules_install' is run; gzip or 2158 xz depending on "Compression algorithm" below. 2159 2160 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 2161 2162 Out-of-tree kernel modules installed using Kbuild will also be 2163 compressed upon installation. 2164 2165 Note: for modules inside an initrd or initramfs, it's more efficient 2166 to compress the whole initrd or initramfs instead. 2167 2168 Note: This is fully compatible with signed modules. 2169 2170 If in doubt, say N. 2171 2172choice 2173 prompt "Compression algorithm" 2174 depends on MODULE_COMPRESS 2175 default MODULE_COMPRESS_GZIP 2176 help 2177 This determines which sort of compression will be used during 2178 'make modules_install'. 2179 2180 GZIP (default) and XZ are supported. 2181 2182config MODULE_COMPRESS_GZIP 2183 bool "GZIP" 2184 2185config MODULE_COMPRESS_XZ 2186 bool "XZ" 2187 2188endchoice 2189 2190config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS 2191 bool "Allow loading of modules with missing namespace imports" 2192 help 2193 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in 2194 a namespace. A module that makes use of a symbol exported with such a 2195 namespace is required to import the namespace via MODULE_IMPORT_NS(). 2196 There is no technical reason to enforce correct namespace imports, 2197 but it creates consistency between symbols defining namespaces and 2198 users importing namespaces they make use of. This option relaxes this 2199 requirement and lifts the enforcement when loading a module. 2200 2201 If unsure, say N. 2202 2203config UNUSED_SYMBOLS 2204 bool "Enable unused/obsolete exported symbols" 2205 default y if X86 2206 help 2207 Unused but exported symbols make the kernel needlessly bigger. For 2208 that reason most of these unused exports will soon be removed. This 2209 option is provided temporarily to provide a transition period in case 2210 some external kernel module needs one of these symbols anyway. If you 2211 encounter such a case in your module, consider if you are actually 2212 using the right API. (rationale: since nobody in the kernel is using 2213 this in a module, there is a pretty good chance it's actually the 2214 wrong interface to use). If you really need the symbol, please send a 2215 mail to the linux kernel mailing list mentioning the symbol and why 2216 you really need it, and what the merge plan to the mainline kernel for 2217 your module is. 2218 2219config TRIM_UNUSED_KSYMS 2220 bool "Trim unused exported kernel symbols" 2221 depends on !UNUSED_SYMBOLS 2222 help 2223 The kernel and some modules make many symbols available for 2224 other modules to use via EXPORT_SYMBOL() and variants. Depending 2225 on the set of modules being selected in your kernel configuration, 2226 many of those exported symbols might never be used. 2227 2228 This option allows for unused exported symbols to be dropped from 2229 the build. In turn, this provides the compiler more opportunities 2230 (especially when using LTO) for optimizing the code and reducing 2231 binary size. This might have some security advantages as well. 2232 2233 If unsure, or if you need to build out-of-tree modules, say N. 2234 2235config UNUSED_KSYMS_WHITELIST 2236 string "Whitelist of symbols to keep in ksymtab" 2237 depends on TRIM_UNUSED_KSYMS 2238 help 2239 By default, all unused exported symbols will be un-exported from the 2240 build when TRIM_UNUSED_KSYMS is selected. 2241 2242 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept 2243 exported at all times, even in absence of in-tree users. The value to 2244 set here is the path to a text file containing the list of symbols, 2245 one per line. The path can be absolute, or relative to the kernel 2246 source tree. 2247 2248endif # MODULES 2249 2250config MODULES_TREE_LOOKUP 2251 def_bool y 2252 depends on PERF_EVENTS || TRACING 2253 2254config INIT_ALL_POSSIBLE 2255 bool 2256 help 2257 Back when each arch used to define their own cpu_online_mask and 2258 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2259 with all 1s, and others with all 0s. When they were centralised, 2260 it was better to provide this option than to break all the archs 2261 and have several arch maintainers pursuing me down dark alleys. 2262 2263source "block/Kconfig" 2264 2265config PREEMPT_NOTIFIERS 2266 bool 2267 2268config PADATA 2269 depends on SMP 2270 bool 2271 2272config ASN1 2273 tristate 2274 help 2275 Build a simple ASN.1 grammar compiler that produces a bytecode output 2276 that can be interpreted by the ASN.1 stream decoder and used to 2277 inform it as to what tags are to be expected in a stream and what 2278 functions to call on what tags. 2279 2280source "kernel/Kconfig.locks" 2281 2282config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2283 bool 2284 2285# It may be useful for an architecture to override the definitions of the 2286# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2287# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2288# different calling convention for syscalls. They can also override the 2289# macros for not-implemented syscalls in kernel/sys_ni.c and 2290# kernel/time/posix-stubs.c. All these overrides need to be available in 2291# <asm/syscall_wrapper.h>. 2292config ARCH_HAS_SYSCALL_WRAPPER 2293 def_bool n 2294