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 LD_IS_LLD 27 def_bool $(success,$(LD) -v | head -n 1 | grep -q LLD) 28 29config CLANG_VERSION 30 int 31 default $(shell,$(srctree)/scripts/clang-version.sh $(CC)) 32 33config CC_CAN_LINK 34 def_bool $(success,$(srctree)/scripts/cc-can-link.sh $(CC)) 35 36config CC_HAS_ASM_GOTO 37 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) 38 39config TOOLS_SUPPORT_RELR 40 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 41 42config CC_HAS_ASM_INLINE 43 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 44 45config CC_HAS_WARN_MAYBE_UNINITIALIZED 46 def_bool $(cc-option,-Wmaybe-uninitialized) 47 help 48 GCC >= 4.7 supports this option. 49 50config CC_DISABLE_WARN_MAYBE_UNINITIALIZED 51 bool 52 depends on CC_HAS_WARN_MAYBE_UNINITIALIZED 53 default CC_IS_GCC && GCC_VERSION < 40900 # unreliable for GCC < 4.9 54 help 55 GCC's -Wmaybe-uninitialized is not reliable by definition. 56 Lots of false positive warnings are produced in some cases. 57 58 If this option is enabled, -Wno-maybe-uninitialzed is passed 59 to the compiler to suppress maybe-uninitialized warnings. 60 61config CONSTRUCTORS 62 bool 63 depends on !UML 64 65config IRQ_WORK 66 bool 67 68config BUILDTIME_TABLE_SORT 69 bool 70 71config THREAD_INFO_IN_TASK 72 bool 73 help 74 Select this to move thread_info off the stack into task_struct. To 75 make this work, an arch will need to remove all thread_info fields 76 except flags and fix any runtime bugs. 77 78 One subtle change that will be needed is to use try_get_task_stack() 79 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 80 81menu "General setup" 82 83config BROKEN 84 bool 85 86config BROKEN_ON_SMP 87 bool 88 depends on BROKEN || !SMP 89 default y 90 91config INIT_ENV_ARG_LIMIT 92 int 93 default 32 if !UML 94 default 128 if UML 95 help 96 Maximum of each of the number of arguments and environment 97 variables passed to init from the kernel command line. 98 99config COMPILE_TEST 100 bool "Compile also drivers which will not load" 101 depends on !UML 102 default n 103 help 104 Some drivers can be compiled on a different platform than they are 105 intended to be run on. Despite they cannot be loaded there (or even 106 when they load they cannot be used due to missing HW support), 107 developers still, opposing to distributors, might want to build such 108 drivers to compile-test them. 109 110 If you are a developer and want to build everything available, say Y 111 here. If you are a user/distributor, say N here to exclude useless 112 drivers to be distributed. 113 114config UAPI_HEADER_TEST 115 bool "Compile test UAPI headers" 116 depends on HEADERS_INSTALL && CC_CAN_LINK 117 help 118 Compile test headers exported to user-space to ensure they are 119 self-contained, i.e. compilable as standalone units. 120 121 If you are a developer or tester and want to ensure the exported 122 headers are self-contained, say Y here. Otherwise, choose N. 123 124config LOCALVERSION 125 string "Local version - append to kernel release" 126 help 127 Append an extra string to the end of your kernel version. 128 This will show up when you type uname, for example. 129 The string you set here will be appended after the contents of 130 any files with a filename matching localversion* in your 131 object and source tree, in that order. Your total string can 132 be a maximum of 64 characters. 133 134config LOCALVERSION_AUTO 135 bool "Automatically append version information to the version string" 136 default y 137 depends on !COMPILE_TEST 138 help 139 This will try to automatically determine if the current tree is a 140 release tree by looking for git tags that belong to the current 141 top of tree revision. 142 143 A string of the format -gxxxxxxxx will be added to the localversion 144 if a git-based tree is found. The string generated by this will be 145 appended after any matching localversion* files, and after the value 146 set in CONFIG_LOCALVERSION. 147 148 (The actual string used here is the first eight characters produced 149 by running the command: 150 151 $ git rev-parse --verify HEAD 152 153 which is done within the script "scripts/setlocalversion".) 154 155config BUILD_SALT 156 string "Build ID Salt" 157 default "" 158 help 159 The build ID is used to link binaries and their debug info. Setting 160 this option will use the value in the calculation of the build id. 161 This is mostly useful for distributions which want to ensure the 162 build is unique between builds. It's safe to leave the default. 163 164config HAVE_KERNEL_GZIP 165 bool 166 167config HAVE_KERNEL_BZIP2 168 bool 169 170config HAVE_KERNEL_LZMA 171 bool 172 173config HAVE_KERNEL_XZ 174 bool 175 176config HAVE_KERNEL_LZO 177 bool 178 179config HAVE_KERNEL_LZ4 180 bool 181 182config HAVE_KERNEL_UNCOMPRESSED 183 bool 184 185choice 186 prompt "Kernel compression mode" 187 default KERNEL_GZIP 188 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_UNCOMPRESSED 189 help 190 The linux kernel is a kind of self-extracting executable. 191 Several compression algorithms are available, which differ 192 in efficiency, compression and decompression speed. 193 Compression speed is only relevant when building a kernel. 194 Decompression speed is relevant at each boot. 195 196 If you have any problems with bzip2 or lzma compressed 197 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 198 version of this functionality (bzip2 only), for 2.4, was 199 supplied by Christian Ludwig) 200 201 High compression options are mostly useful for users, who 202 are low on disk space (embedded systems), but for whom ram 203 size matters less. 204 205 If in doubt, select 'gzip' 206 207config KERNEL_GZIP 208 bool "Gzip" 209 depends on HAVE_KERNEL_GZIP 210 help 211 The old and tried gzip compression. It provides a good balance 212 between compression ratio and decompression speed. 213 214config KERNEL_BZIP2 215 bool "Bzip2" 216 depends on HAVE_KERNEL_BZIP2 217 help 218 Its compression ratio and speed is intermediate. 219 Decompression speed is slowest among the choices. The kernel 220 size is about 10% smaller with bzip2, in comparison to gzip. 221 Bzip2 uses a large amount of memory. For modern kernels you 222 will need at least 8MB RAM or more for booting. 223 224config KERNEL_LZMA 225 bool "LZMA" 226 depends on HAVE_KERNEL_LZMA 227 help 228 This compression algorithm's ratio is best. Decompression speed 229 is between gzip and bzip2. Compression is slowest. 230 The kernel size is about 33% smaller with LZMA in comparison to gzip. 231 232config KERNEL_XZ 233 bool "XZ" 234 depends on HAVE_KERNEL_XZ 235 help 236 XZ uses the LZMA2 algorithm and instruction set specific 237 BCJ filters which can improve compression ratio of executable 238 code. The size of the kernel is about 30% smaller with XZ in 239 comparison to gzip. On architectures for which there is a BCJ 240 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 241 will create a few percent smaller kernel than plain LZMA. 242 243 The speed is about the same as with LZMA: The decompression 244 speed of XZ is better than that of bzip2 but worse than gzip 245 and LZO. Compression is slow. 246 247config KERNEL_LZO 248 bool "LZO" 249 depends on HAVE_KERNEL_LZO 250 help 251 Its compression ratio is the poorest among the choices. The kernel 252 size is about 10% bigger than gzip; however its speed 253 (both compression and decompression) is the fastest. 254 255config KERNEL_LZ4 256 bool "LZ4" 257 depends on HAVE_KERNEL_LZ4 258 help 259 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 260 A preliminary version of LZ4 de/compression tool is available at 261 <https://code.google.com/p/lz4/>. 262 263 Its compression ratio is worse than LZO. The size of the kernel 264 is about 8% bigger than LZO. But the decompression speed is 265 faster than LZO. 266 267config KERNEL_UNCOMPRESSED 268 bool "None" 269 depends on HAVE_KERNEL_UNCOMPRESSED 270 help 271 Produce uncompressed kernel image. This option is usually not what 272 you want. It is useful for debugging the kernel in slow simulation 273 environments, where decompressing and moving the kernel is awfully 274 slow. This option allows early boot code to skip the decompressor 275 and jump right at uncompressed kernel image. 276 277endchoice 278 279config DEFAULT_HOSTNAME 280 string "Default hostname" 281 default "(none)" 282 help 283 This option determines the default system hostname before userspace 284 calls sethostname(2). The kernel traditionally uses "(none)" here, 285 but you may wish to use a different default here to make a minimal 286 system more usable with less configuration. 287 288# 289# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can 290# add proper SWAP support to them, in which case this can be remove. 291# 292config ARCH_NO_SWAP 293 bool 294 295config SWAP 296 bool "Support for paging of anonymous memory (swap)" 297 depends on MMU && BLOCK && !ARCH_NO_SWAP 298 default y 299 help 300 This option allows you to choose whether you want to have support 301 for so called swap devices or swap files in your kernel that are 302 used to provide more virtual memory than the actual RAM present 303 in your computer. If unsure say Y. 304 305config SYSVIPC 306 bool "System V IPC" 307 ---help--- 308 Inter Process Communication is a suite of library functions and 309 system calls which let processes (running programs) synchronize and 310 exchange information. It is generally considered to be a good thing, 311 and some programs won't run unless you say Y here. In particular, if 312 you want to run the DOS emulator dosemu under Linux (read the 313 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 314 you'll need to say Y here. 315 316 You can find documentation about IPC with "info ipc" and also in 317 section 6.4 of the Linux Programmer's Guide, available from 318 <http://www.tldp.org/guides.html>. 319 320config SYSVIPC_SYSCTL 321 bool 322 depends on SYSVIPC 323 depends on SYSCTL 324 default y 325 326config POSIX_MQUEUE 327 bool "POSIX Message Queues" 328 depends on NET 329 ---help--- 330 POSIX variant of message queues is a part of IPC. In POSIX message 331 queues every message has a priority which decides about succession 332 of receiving it by a process. If you want to compile and run 333 programs written e.g. for Solaris with use of its POSIX message 334 queues (functions mq_*) say Y here. 335 336 POSIX message queues are visible as a filesystem called 'mqueue' 337 and can be mounted somewhere if you want to do filesystem 338 operations on message queues. 339 340 If unsure, say Y. 341 342config POSIX_MQUEUE_SYSCTL 343 bool 344 depends on POSIX_MQUEUE 345 depends on SYSCTL 346 default y 347 348config CROSS_MEMORY_ATTACH 349 bool "Enable process_vm_readv/writev syscalls" 350 depends on MMU 351 default y 352 help 353 Enabling this option adds the system calls process_vm_readv and 354 process_vm_writev which allow a process with the correct privileges 355 to directly read from or write to another process' address space. 356 See the man page for more details. 357 358config USELIB 359 bool "uselib syscall" 360 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION 361 help 362 This option enables the uselib syscall, a system call used in the 363 dynamic linker from libc5 and earlier. glibc does not use this 364 system call. If you intend to run programs built on libc5 or 365 earlier, you may need to enable this syscall. Current systems 366 running glibc can safely disable this. 367 368config AUDIT 369 bool "Auditing support" 370 depends on NET 371 help 372 Enable auditing infrastructure that can be used with another 373 kernel subsystem, such as SELinux (which requires this for 374 logging of avc messages output). System call auditing is included 375 on architectures which support it. 376 377config HAVE_ARCH_AUDITSYSCALL 378 bool 379 380config AUDITSYSCALL 381 def_bool y 382 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 383 select FSNOTIFY 384 385source "kernel/irq/Kconfig" 386source "kernel/time/Kconfig" 387source "kernel/Kconfig.preempt" 388 389menu "CPU/Task time and stats accounting" 390 391config VIRT_CPU_ACCOUNTING 392 bool 393 394choice 395 prompt "Cputime accounting" 396 default TICK_CPU_ACCOUNTING if !PPC64 397 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 398 399# Kind of a stub config for the pure tick based cputime accounting 400config TICK_CPU_ACCOUNTING 401 bool "Simple tick based cputime accounting" 402 depends on !S390 && !NO_HZ_FULL 403 help 404 This is the basic tick based cputime accounting that maintains 405 statistics about user, system and idle time spent on per jiffies 406 granularity. 407 408 If unsure, say Y. 409 410config VIRT_CPU_ACCOUNTING_NATIVE 411 bool "Deterministic task and CPU time accounting" 412 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 413 select VIRT_CPU_ACCOUNTING 414 help 415 Select this option to enable more accurate task and CPU time 416 accounting. This is done by reading a CPU counter on each 417 kernel entry and exit and on transitions within the kernel 418 between system, softirq and hardirq state, so there is a 419 small performance impact. In the case of s390 or IBM POWER > 5, 420 this also enables accounting of stolen time on logically-partitioned 421 systems. 422 423config VIRT_CPU_ACCOUNTING_GEN 424 bool "Full dynticks CPU time accounting" 425 depends on HAVE_CONTEXT_TRACKING 426 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 427 depends on GENERIC_CLOCKEVENTS 428 select VIRT_CPU_ACCOUNTING 429 select CONTEXT_TRACKING 430 help 431 Select this option to enable task and CPU time accounting on full 432 dynticks systems. This accounting is implemented by watching every 433 kernel-user boundaries using the context tracking subsystem. 434 The accounting is thus performed at the expense of some significant 435 overhead. 436 437 For now this is only useful if you are working on the full 438 dynticks subsystem development. 439 440 If unsure, say N. 441 442endchoice 443 444config IRQ_TIME_ACCOUNTING 445 bool "Fine granularity task level IRQ time accounting" 446 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 447 help 448 Select this option to enable fine granularity task irq time 449 accounting. This is done by reading a timestamp on each 450 transitions between softirq and hardirq state, so there can be a 451 small performance impact. 452 453 If in doubt, say N here. 454 455config HAVE_SCHED_AVG_IRQ 456 def_bool y 457 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 458 depends on SMP 459 460config SCHED_THERMAL_PRESSURE 461 bool "Enable periodic averaging of thermal pressure" 462 depends on SMP 463 464config BSD_PROCESS_ACCT 465 bool "BSD Process Accounting" 466 depends on MULTIUSER 467 help 468 If you say Y here, a user level program will be able to instruct the 469 kernel (via a special system call) to write process accounting 470 information to a file: whenever a process exits, information about 471 that process will be appended to the file by the kernel. The 472 information includes things such as creation time, owning user, 473 command name, memory usage, controlling terminal etc. (the complete 474 list is in the struct acct in <file:include/linux/acct.h>). It is 475 up to the user level program to do useful things with this 476 information. This is generally a good idea, so say Y. 477 478config BSD_PROCESS_ACCT_V3 479 bool "BSD Process Accounting version 3 file format" 480 depends on BSD_PROCESS_ACCT 481 default n 482 help 483 If you say Y here, the process accounting information is written 484 in a new file format that also logs the process IDs of each 485 process and its parent. Note that this file format is incompatible 486 with previous v0/v1/v2 file formats, so you will need updated tools 487 for processing it. A preliminary version of these tools is available 488 at <http://www.gnu.org/software/acct/>. 489 490config TASKSTATS 491 bool "Export task/process statistics through netlink" 492 depends on NET 493 depends on MULTIUSER 494 default n 495 help 496 Export selected statistics for tasks/processes through the 497 generic netlink interface. Unlike BSD process accounting, the 498 statistics are available during the lifetime of tasks/processes as 499 responses to commands. Like BSD accounting, they are sent to user 500 space on task exit. 501 502 Say N if unsure. 503 504config TASK_DELAY_ACCT 505 bool "Enable per-task delay accounting" 506 depends on TASKSTATS 507 select SCHED_INFO 508 help 509 Collect information on time spent by a task waiting for system 510 resources like cpu, synchronous block I/O completion and swapping 511 in pages. Such statistics can help in setting a task's priorities 512 relative to other tasks for cpu, io, rss limits etc. 513 514 Say N if unsure. 515 516config TASK_XACCT 517 bool "Enable extended accounting over taskstats" 518 depends on TASKSTATS 519 help 520 Collect extended task accounting data and send the data 521 to userland for processing over the taskstats interface. 522 523 Say N if unsure. 524 525config TASK_IO_ACCOUNTING 526 bool "Enable per-task storage I/O accounting" 527 depends on TASK_XACCT 528 help 529 Collect information on the number of bytes of storage I/O which this 530 task has caused. 531 532 Say N if unsure. 533 534config PSI 535 bool "Pressure stall information tracking" 536 help 537 Collect metrics that indicate how overcommitted the CPU, memory, 538 and IO capacity are in the system. 539 540 If you say Y here, the kernel will create /proc/pressure/ with the 541 pressure statistics files cpu, memory, and io. These will indicate 542 the share of walltime in which some or all tasks in the system are 543 delayed due to contention of the respective resource. 544 545 In kernels with cgroup support, cgroups (cgroup2 only) will 546 have cpu.pressure, memory.pressure, and io.pressure files, 547 which aggregate pressure stalls for the grouped tasks only. 548 549 For more details see Documentation/accounting/psi.rst. 550 551 Say N if unsure. 552 553config PSI_DEFAULT_DISABLED 554 bool "Require boot parameter to enable pressure stall information tracking" 555 default n 556 depends on PSI 557 help 558 If set, pressure stall information tracking will be disabled 559 per default but can be enabled through passing psi=1 on the 560 kernel commandline during boot. 561 562 This feature adds some code to the task wakeup and sleep 563 paths of the scheduler. The overhead is too low to affect 564 common scheduling-intense workloads in practice (such as 565 webservers, memcache), but it does show up in artificial 566 scheduler stress tests, such as hackbench. 567 568 If you are paranoid and not sure what the kernel will be 569 used for, say Y. 570 571 Say N if unsure. 572 573endmenu # "CPU/Task time and stats accounting" 574 575config CPU_ISOLATION 576 bool "CPU isolation" 577 depends on SMP || COMPILE_TEST 578 default y 579 help 580 Make sure that CPUs running critical tasks are not disturbed by 581 any source of "noise" such as unbound workqueues, timers, kthreads... 582 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 583 the "isolcpus=" boot parameter. 584 585 Say Y if unsure. 586 587source "kernel/rcu/Kconfig" 588 589config BUILD_BIN2C 590 bool 591 default n 592 593config IKCONFIG 594 tristate "Kernel .config support" 595 ---help--- 596 This option enables the complete Linux kernel ".config" file 597 contents to be saved in the kernel. It provides documentation 598 of which kernel options are used in a running kernel or in an 599 on-disk kernel. This information can be extracted from the kernel 600 image file with the script scripts/extract-ikconfig and used as 601 input to rebuild the current kernel or to build another kernel. 602 It can also be extracted from a running kernel by reading 603 /proc/config.gz if enabled (below). 604 605config IKCONFIG_PROC 606 bool "Enable access to .config through /proc/config.gz" 607 depends on IKCONFIG && PROC_FS 608 ---help--- 609 This option enables access to the kernel configuration file 610 through /proc/config.gz. 611 612config IKHEADERS 613 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 614 depends on SYSFS 615 help 616 This option enables access to the in-kernel headers that are generated during 617 the build process. These can be used to build eBPF tracing programs, 618 or similar programs. If you build the headers as a module, a module called 619 kheaders.ko is built which can be loaded on-demand to get access to headers. 620 621config LOG_BUF_SHIFT 622 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 623 range 12 25 624 default 17 625 depends on PRINTK 626 help 627 Select the minimal kernel log buffer size as a power of 2. 628 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 629 parameter, see below. Any higher size also might be forced 630 by "log_buf_len" boot parameter. 631 632 Examples: 633 17 => 128 KB 634 16 => 64 KB 635 15 => 32 KB 636 14 => 16 KB 637 13 => 8 KB 638 12 => 4 KB 639 640config LOG_CPU_MAX_BUF_SHIFT 641 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 642 depends on SMP 643 range 0 21 644 default 12 if !BASE_SMALL 645 default 0 if BASE_SMALL 646 depends on PRINTK 647 help 648 This option allows to increase the default ring buffer size 649 according to the number of CPUs. The value defines the contribution 650 of each CPU as a power of 2. The used space is typically only few 651 lines however it might be much more when problems are reported, 652 e.g. backtraces. 653 654 The increased size means that a new buffer has to be allocated and 655 the original static one is unused. It makes sense only on systems 656 with more CPUs. Therefore this value is used only when the sum of 657 contributions is greater than the half of the default kernel ring 658 buffer as defined by LOG_BUF_SHIFT. The default values are set 659 so that more than 64 CPUs are needed to trigger the allocation. 660 661 Also this option is ignored when "log_buf_len" kernel parameter is 662 used as it forces an exact (power of two) size of the ring buffer. 663 664 The number of possible CPUs is used for this computation ignoring 665 hotplugging making the computation optimal for the worst case 666 scenario while allowing a simple algorithm to be used from bootup. 667 668 Examples shift values and their meaning: 669 17 => 128 KB for each CPU 670 16 => 64 KB for each CPU 671 15 => 32 KB for each CPU 672 14 => 16 KB for each CPU 673 13 => 8 KB for each CPU 674 12 => 4 KB for each CPU 675 676config PRINTK_SAFE_LOG_BUF_SHIFT 677 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 678 range 10 21 679 default 13 680 depends on PRINTK 681 help 682 Select the size of an alternate printk per-CPU buffer where messages 683 printed from usafe contexts are temporary stored. One example would 684 be NMI messages, another one - printk recursion. The messages are 685 copied to the main log buffer in a safe context to avoid a deadlock. 686 The value defines the size as a power of 2. 687 688 Those messages are rare and limited. The largest one is when 689 a backtrace is printed. It usually fits into 4KB. Select 690 8KB if you want to be on the safe side. 691 692 Examples: 693 17 => 128 KB for each CPU 694 16 => 64 KB for each CPU 695 15 => 32 KB for each CPU 696 14 => 16 KB for each CPU 697 13 => 8 KB for each CPU 698 12 => 4 KB for each CPU 699 700# 701# Architectures with an unreliable sched_clock() should select this: 702# 703config HAVE_UNSTABLE_SCHED_CLOCK 704 bool 705 706config GENERIC_SCHED_CLOCK 707 bool 708 709menu "Scheduler features" 710 711config UCLAMP_TASK 712 bool "Enable utilization clamping for RT/FAIR tasks" 713 depends on CPU_FREQ_GOV_SCHEDUTIL 714 help 715 This feature enables the scheduler to track the clamped utilization 716 of each CPU based on RUNNABLE tasks scheduled on that CPU. 717 718 With this option, the user can specify the min and max CPU 719 utilization allowed for RUNNABLE tasks. The max utilization defines 720 the maximum frequency a task should use while the min utilization 721 defines the minimum frequency it should use. 722 723 Both min and max utilization clamp values are hints to the scheduler, 724 aiming at improving its frequency selection policy, but they do not 725 enforce or grant any specific bandwidth for tasks. 726 727 If in doubt, say N. 728 729config UCLAMP_BUCKETS_COUNT 730 int "Number of supported utilization clamp buckets" 731 range 5 20 732 default 5 733 depends on UCLAMP_TASK 734 help 735 Defines the number of clamp buckets to use. The range of each bucket 736 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 737 number of clamp buckets the finer their granularity and the higher 738 the precision of clamping aggregation and tracking at run-time. 739 740 For example, with the minimum configuration value we will have 5 741 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 742 be refcounted in the [20..39]% bucket and will set the bucket clamp 743 effective value to 25%. 744 If a second 30% boosted task should be co-scheduled on the same CPU, 745 that task will be refcounted in the same bucket of the first task and 746 it will boost the bucket clamp effective value to 30%. 747 The clamp effective value of a bucket is reset to its nominal value 748 (20% in the example above) when there are no more tasks refcounted in 749 that bucket. 750 751 An additional boost/capping margin can be added to some tasks. In the 752 example above the 25% task will be boosted to 30% until it exits the 753 CPU. If that should be considered not acceptable on certain systems, 754 it's always possible to reduce the margin by increasing the number of 755 clamp buckets to trade off used memory for run-time tracking 756 precision. 757 758 If in doubt, use the default value. 759 760endmenu 761 762# 763# For architectures that want to enable the support for NUMA-affine scheduler 764# balancing logic: 765# 766config ARCH_SUPPORTS_NUMA_BALANCING 767 bool 768 769# 770# For architectures that prefer to flush all TLBs after a number of pages 771# are unmapped instead of sending one IPI per page to flush. The architecture 772# must provide guarantees on what happens if a clean TLB cache entry is 773# written after the unmap. Details are in mm/rmap.c near the check for 774# should_defer_flush. The architecture should also consider if the full flush 775# and the refill costs are offset by the savings of sending fewer IPIs. 776config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 777 bool 778 779config CC_HAS_INT128 780 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 781 782# 783# For architectures that know their GCC __int128 support is sound 784# 785config ARCH_SUPPORTS_INT128 786 bool 787 788# For architectures that (ab)use NUMA to represent different memory regions 789# all cpu-local but of different latencies, such as SuperH. 790# 791config ARCH_WANT_NUMA_VARIABLE_LOCALITY 792 bool 793 794config NUMA_BALANCING 795 bool "Memory placement aware NUMA scheduler" 796 depends on ARCH_SUPPORTS_NUMA_BALANCING 797 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 798 depends on SMP && NUMA && MIGRATION 799 help 800 This option adds support for automatic NUMA aware memory/task placement. 801 The mechanism is quite primitive and is based on migrating memory when 802 it has references to the node the task is running on. 803 804 This system will be inactive on UMA systems. 805 806config NUMA_BALANCING_DEFAULT_ENABLED 807 bool "Automatically enable NUMA aware memory/task placement" 808 default y 809 depends on NUMA_BALANCING 810 help 811 If set, automatic NUMA balancing will be enabled if running on a NUMA 812 machine. 813 814menuconfig CGROUPS 815 bool "Control Group support" 816 select KERNFS 817 help 818 This option adds support for grouping sets of processes together, for 819 use with process control subsystems such as Cpusets, CFS, memory 820 controls or device isolation. 821 See 822 - Documentation/scheduler/sched-design-CFS.rst (CFS) 823 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 824 and resource control) 825 826 Say N if unsure. 827 828if CGROUPS 829 830config PAGE_COUNTER 831 bool 832 833config MEMCG 834 bool "Memory controller" 835 select PAGE_COUNTER 836 select EVENTFD 837 help 838 Provides control over the memory footprint of tasks in a cgroup. 839 840config MEMCG_SWAP 841 bool "Swap controller" 842 depends on MEMCG && SWAP 843 help 844 Provides control over the swap space consumed by tasks in a cgroup. 845 846config MEMCG_SWAP_ENABLED 847 bool "Swap controller enabled by default" 848 depends on MEMCG_SWAP 849 default y 850 help 851 Memory Resource Controller Swap Extension comes with its price in 852 a bigger memory consumption. General purpose distribution kernels 853 which want to enable the feature but keep it disabled by default 854 and let the user enable it by swapaccount=1 boot command line 855 parameter should have this option unselected. 856 For those who want to have the feature enabled by default should 857 select this option (if, for some reason, they need to disable it 858 then swapaccount=0 does the trick). 859 860config MEMCG_KMEM 861 bool 862 depends on MEMCG && !SLOB 863 default y 864 865config BLK_CGROUP 866 bool "IO controller" 867 depends on BLOCK 868 default n 869 ---help--- 870 Generic block IO controller cgroup interface. This is the common 871 cgroup interface which should be used by various IO controlling 872 policies. 873 874 Currently, CFQ IO scheduler uses it to recognize task groups and 875 control disk bandwidth allocation (proportional time slice allocation) 876 to such task groups. It is also used by bio throttling logic in 877 block layer to implement upper limit in IO rates on a device. 878 879 This option only enables generic Block IO controller infrastructure. 880 One needs to also enable actual IO controlling logic/policy. For 881 enabling proportional weight division of disk bandwidth in CFQ, set 882 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 883 CONFIG_BLK_DEV_THROTTLING=y. 884 885 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 886 887config CGROUP_WRITEBACK 888 bool 889 depends on MEMCG && BLK_CGROUP 890 default y 891 892menuconfig CGROUP_SCHED 893 bool "CPU controller" 894 default n 895 help 896 This feature lets CPU scheduler recognize task groups and control CPU 897 bandwidth allocation to such task groups. It uses cgroups to group 898 tasks. 899 900if CGROUP_SCHED 901config FAIR_GROUP_SCHED 902 bool "Group scheduling for SCHED_OTHER" 903 depends on CGROUP_SCHED 904 default CGROUP_SCHED 905 906config CFS_BANDWIDTH 907 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 908 depends on FAIR_GROUP_SCHED 909 default n 910 help 911 This option allows users to define CPU bandwidth rates (limits) for 912 tasks running within the fair group scheduler. Groups with no limit 913 set are considered to be unconstrained and will run with no 914 restriction. 915 See Documentation/scheduler/sched-bwc.rst for more information. 916 917config RT_GROUP_SCHED 918 bool "Group scheduling for SCHED_RR/FIFO" 919 depends on CGROUP_SCHED 920 default n 921 help 922 This feature lets you explicitly allocate real CPU bandwidth 923 to task groups. If enabled, it will also make it impossible to 924 schedule realtime tasks for non-root users until you allocate 925 realtime bandwidth for them. 926 See Documentation/scheduler/sched-rt-group.rst for more information. 927 928endif #CGROUP_SCHED 929 930config UCLAMP_TASK_GROUP 931 bool "Utilization clamping per group of tasks" 932 depends on CGROUP_SCHED 933 depends on UCLAMP_TASK 934 default n 935 help 936 This feature enables the scheduler to track the clamped utilization 937 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 938 939 When this option is enabled, the user can specify a min and max 940 CPU bandwidth which is allowed for each single task in a group. 941 The max bandwidth allows to clamp the maximum frequency a task 942 can use, while the min bandwidth allows to define a minimum 943 frequency a task will always use. 944 945 When task group based utilization clamping is enabled, an eventually 946 specified task-specific clamp value is constrained by the cgroup 947 specified clamp value. Both minimum and maximum task clamping cannot 948 be bigger than the corresponding clamping defined at task group level. 949 950 If in doubt, say N. 951 952config CGROUP_PIDS 953 bool "PIDs controller" 954 help 955 Provides enforcement of process number limits in the scope of a 956 cgroup. Any attempt to fork more processes than is allowed in the 957 cgroup will fail. PIDs are fundamentally a global resource because it 958 is fairly trivial to reach PID exhaustion before you reach even a 959 conservative kmemcg limit. As a result, it is possible to grind a 960 system to halt without being limited by other cgroup policies. The 961 PIDs controller is designed to stop this from happening. 962 963 It should be noted that organisational operations (such as attaching 964 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 965 since the PIDs limit only affects a process's ability to fork, not to 966 attach to a cgroup. 967 968config CGROUP_RDMA 969 bool "RDMA controller" 970 help 971 Provides enforcement of RDMA resources defined by IB stack. 972 It is fairly easy for consumers to exhaust RDMA resources, which 973 can result into resource unavailability to other consumers. 974 RDMA controller is designed to stop this from happening. 975 Attaching processes with active RDMA resources to the cgroup 976 hierarchy is allowed even if can cross the hierarchy's limit. 977 978config CGROUP_FREEZER 979 bool "Freezer controller" 980 help 981 Provides a way to freeze and unfreeze all tasks in a 982 cgroup. 983 984 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 985 controller includes important in-kernel memory consumers per default. 986 987 If you're using cgroup2, say N. 988 989config CGROUP_HUGETLB 990 bool "HugeTLB controller" 991 depends on HUGETLB_PAGE 992 select PAGE_COUNTER 993 default n 994 help 995 Provides a cgroup controller for HugeTLB pages. 996 When you enable this, you can put a per cgroup limit on HugeTLB usage. 997 The limit is enforced during page fault. Since HugeTLB doesn't 998 support page reclaim, enforcing the limit at page fault time implies 999 that, the application will get SIGBUS signal if it tries to access 1000 HugeTLB pages beyond its limit. This requires the application to know 1001 beforehand how much HugeTLB pages it would require for its use. The 1002 control group is tracked in the third page lru pointer. This means 1003 that we cannot use the controller with huge page less than 3 pages. 1004 1005config CPUSETS 1006 bool "Cpuset controller" 1007 depends on SMP 1008 help 1009 This option will let you create and manage CPUSETs which 1010 allow dynamically partitioning a system into sets of CPUs and 1011 Memory Nodes and assigning tasks to run only within those sets. 1012 This is primarily useful on large SMP or NUMA systems. 1013 1014 Say N if unsure. 1015 1016config PROC_PID_CPUSET 1017 bool "Include legacy /proc/<pid>/cpuset file" 1018 depends on CPUSETS 1019 default y 1020 1021config CGROUP_DEVICE 1022 bool "Device controller" 1023 help 1024 Provides a cgroup controller implementing whitelists for 1025 devices which a process in the cgroup can mknod or open. 1026 1027config CGROUP_CPUACCT 1028 bool "Simple CPU accounting controller" 1029 help 1030 Provides a simple controller for monitoring the 1031 total CPU consumed by the tasks in a cgroup. 1032 1033config CGROUP_PERF 1034 bool "Perf controller" 1035 depends on PERF_EVENTS 1036 help 1037 This option extends the perf per-cpu mode to restrict monitoring 1038 to threads which belong to the cgroup specified and run on the 1039 designated cpu. Or this can be used to have cgroup ID in samples 1040 so that it can monitor performance events among cgroups. 1041 1042 Say N if unsure. 1043 1044config CGROUP_BPF 1045 bool "Support for eBPF programs attached to cgroups" 1046 depends on BPF_SYSCALL 1047 select SOCK_CGROUP_DATA 1048 help 1049 Allow attaching eBPF programs to a cgroup using the bpf(2) 1050 syscall command BPF_PROG_ATTACH. 1051 1052 In which context these programs are accessed depends on the type 1053 of attachment. For instance, programs that are attached using 1054 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1055 inet sockets. 1056 1057config CGROUP_DEBUG 1058 bool "Debug controller" 1059 default n 1060 depends on DEBUG_KERNEL 1061 help 1062 This option enables a simple controller that exports 1063 debugging information about the cgroups framework. This 1064 controller is for control cgroup debugging only. Its 1065 interfaces are not stable. 1066 1067 Say N. 1068 1069config SOCK_CGROUP_DATA 1070 bool 1071 default n 1072 1073endif # CGROUPS 1074 1075menuconfig NAMESPACES 1076 bool "Namespaces support" if EXPERT 1077 depends on MULTIUSER 1078 default !EXPERT 1079 help 1080 Provides the way to make tasks work with different objects using 1081 the same id. For example same IPC id may refer to different objects 1082 or same user id or pid may refer to different tasks when used in 1083 different namespaces. 1084 1085if NAMESPACES 1086 1087config UTS_NS 1088 bool "UTS namespace" 1089 default y 1090 help 1091 In this namespace tasks see different info provided with the 1092 uname() system call 1093 1094config TIME_NS 1095 bool "TIME namespace" 1096 depends on GENERIC_VDSO_TIME_NS 1097 default y 1098 help 1099 In this namespace boottime and monotonic clocks can be set. 1100 The time will keep going with the same pace. 1101 1102config IPC_NS 1103 bool "IPC namespace" 1104 depends on (SYSVIPC || POSIX_MQUEUE) 1105 default y 1106 help 1107 In this namespace tasks work with IPC ids which correspond to 1108 different IPC objects in different namespaces. 1109 1110config USER_NS 1111 bool "User namespace" 1112 default n 1113 help 1114 This allows containers, i.e. vservers, to use user namespaces 1115 to provide different user info for different servers. 1116 1117 When user namespaces are enabled in the kernel it is 1118 recommended that the MEMCG option also be enabled and that 1119 user-space use the memory control groups to limit the amount 1120 of memory a memory unprivileged users can use. 1121 1122 If unsure, say N. 1123 1124config PID_NS 1125 bool "PID Namespaces" 1126 default y 1127 help 1128 Support process id namespaces. This allows having multiple 1129 processes with the same pid as long as they are in different 1130 pid namespaces. This is a building block of containers. 1131 1132config NET_NS 1133 bool "Network namespace" 1134 depends on NET 1135 default y 1136 help 1137 Allow user space to create what appear to be multiple instances 1138 of the network stack. 1139 1140endif # NAMESPACES 1141 1142config CHECKPOINT_RESTORE 1143 bool "Checkpoint/restore support" 1144 select PROC_CHILDREN 1145 default n 1146 help 1147 Enables additional kernel features in a sake of checkpoint/restore. 1148 In particular it adds auxiliary prctl codes to setup process text, 1149 data and heap segment sizes, and a few additional /proc filesystem 1150 entries. 1151 1152 If unsure, say N here. 1153 1154config SCHED_AUTOGROUP 1155 bool "Automatic process group scheduling" 1156 select CGROUPS 1157 select CGROUP_SCHED 1158 select FAIR_GROUP_SCHED 1159 help 1160 This option optimizes the scheduler for common desktop workloads by 1161 automatically creating and populating task groups. This separation 1162 of workloads isolates aggressive CPU burners (like build jobs) from 1163 desktop applications. Task group autogeneration is currently based 1164 upon task session. 1165 1166config SYSFS_DEPRECATED 1167 bool "Enable deprecated sysfs features to support old userspace tools" 1168 depends on SYSFS 1169 default n 1170 help 1171 This option adds code that switches the layout of the "block" class 1172 devices, to not show up in /sys/class/block/, but only in 1173 /sys/block/. 1174 1175 This switch is only active when the sysfs.deprecated=1 boot option is 1176 passed or the SYSFS_DEPRECATED_V2 option is set. 1177 1178 This option allows new kernels to run on old distributions and tools, 1179 which might get confused by /sys/class/block/. Since 2007/2008 all 1180 major distributions and tools handle this just fine. 1181 1182 Recent distributions and userspace tools after 2009/2010 depend on 1183 the existence of /sys/class/block/, and will not work with this 1184 option enabled. 1185 1186 Only if you are using a new kernel on an old distribution, you might 1187 need to say Y here. 1188 1189config SYSFS_DEPRECATED_V2 1190 bool "Enable deprecated sysfs features by default" 1191 default n 1192 depends on SYSFS 1193 depends on SYSFS_DEPRECATED 1194 help 1195 Enable deprecated sysfs by default. 1196 1197 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1198 option. 1199 1200 Only if you are using a new kernel on an old distribution, you might 1201 need to say Y here. Even then, odds are you would not need it 1202 enabled, you can always pass the boot option if absolutely necessary. 1203 1204config RELAY 1205 bool "Kernel->user space relay support (formerly relayfs)" 1206 select IRQ_WORK 1207 help 1208 This option enables support for relay interface support in 1209 certain file systems (such as debugfs). 1210 It is designed to provide an efficient mechanism for tools and 1211 facilities to relay large amounts of data from kernel space to 1212 user space. 1213 1214 If unsure, say N. 1215 1216config BLK_DEV_INITRD 1217 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1218 help 1219 The initial RAM filesystem is a ramfs which is loaded by the 1220 boot loader (loadlin or lilo) and that is mounted as root 1221 before the normal boot procedure. It is typically used to 1222 load modules needed to mount the "real" root file system, 1223 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1224 1225 If RAM disk support (BLK_DEV_RAM) is also included, this 1226 also enables initial RAM disk (initrd) support and adds 1227 15 Kbytes (more on some other architectures) to the kernel size. 1228 1229 If unsure say Y. 1230 1231if BLK_DEV_INITRD 1232 1233source "usr/Kconfig" 1234 1235endif 1236 1237config BOOT_CONFIG 1238 bool "Boot config support" 1239 select BLK_DEV_INITRD 1240 help 1241 Extra boot config allows system admin to pass a config file as 1242 complemental extension of kernel cmdline when booting. 1243 The boot config file must be attached at the end of initramfs 1244 with checksum, size and magic word. 1245 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1246 1247 If unsure, say Y. 1248 1249choice 1250 prompt "Compiler optimization level" 1251 default CC_OPTIMIZE_FOR_PERFORMANCE 1252 1253config CC_OPTIMIZE_FOR_PERFORMANCE 1254 bool "Optimize for performance (-O2)" 1255 help 1256 This is the default optimization level for the kernel, building 1257 with the "-O2" compiler flag for best performance and most 1258 helpful compile-time warnings. 1259 1260config CC_OPTIMIZE_FOR_PERFORMANCE_O3 1261 bool "Optimize more for performance (-O3)" 1262 depends on ARC 1263 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives 1264 help 1265 Choosing this option will pass "-O3" to your compiler to optimize 1266 the kernel yet more for performance. 1267 1268config CC_OPTIMIZE_FOR_SIZE 1269 bool "Optimize for size (-Os)" 1270 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives 1271 help 1272 Choosing this option will pass "-Os" to your compiler resulting 1273 in a smaller kernel. 1274 1275endchoice 1276 1277config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1278 bool 1279 help 1280 This requires that the arch annotates or otherwise protects 1281 its external entry points from being discarded. Linker scripts 1282 must also merge .text.*, .data.*, and .bss.* correctly into 1283 output sections. Care must be taken not to pull in unrelated 1284 sections (e.g., '.text.init'). Typically '.' in section names 1285 is used to distinguish them from label names / C identifiers. 1286 1287config LD_DEAD_CODE_DATA_ELIMINATION 1288 bool "Dead code and data elimination (EXPERIMENTAL)" 1289 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1290 depends on EXPERT 1291 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800) 1292 depends on $(cc-option,-ffunction-sections -fdata-sections) 1293 depends on $(ld-option,--gc-sections) 1294 help 1295 Enable this if you want to do dead code and data elimination with 1296 the linker by compiling with -ffunction-sections -fdata-sections, 1297 and linking with --gc-sections. 1298 1299 This can reduce on disk and in-memory size of the kernel 1300 code and static data, particularly for small configs and 1301 on small systems. This has the possibility of introducing 1302 silently broken kernel if the required annotations are not 1303 present. This option is not well tested yet, so use at your 1304 own risk. 1305 1306config SYSCTL 1307 bool 1308 1309config HAVE_UID16 1310 bool 1311 1312config SYSCTL_EXCEPTION_TRACE 1313 bool 1314 help 1315 Enable support for /proc/sys/debug/exception-trace. 1316 1317config SYSCTL_ARCH_UNALIGN_NO_WARN 1318 bool 1319 help 1320 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1321 Allows arch to define/use @no_unaligned_warning to possibly warn 1322 about unaligned access emulation going on under the hood. 1323 1324config SYSCTL_ARCH_UNALIGN_ALLOW 1325 bool 1326 help 1327 Enable support for /proc/sys/kernel/unaligned-trap 1328 Allows arches to define/use @unaligned_enabled to runtime toggle 1329 the unaligned access emulation. 1330 see arch/parisc/kernel/unaligned.c for reference 1331 1332config HAVE_PCSPKR_PLATFORM 1333 bool 1334 1335# interpreter that classic socket filters depend on 1336config BPF 1337 bool 1338 1339menuconfig EXPERT 1340 bool "Configure standard kernel features (expert users)" 1341 # Unhide debug options, to make the on-by-default options visible 1342 select DEBUG_KERNEL 1343 help 1344 This option allows certain base kernel options and settings 1345 to be disabled or tweaked. This is for specialized 1346 environments which can tolerate a "non-standard" kernel. 1347 Only use this if you really know what you are doing. 1348 1349config UID16 1350 bool "Enable 16-bit UID system calls" if EXPERT 1351 depends on HAVE_UID16 && MULTIUSER 1352 default y 1353 help 1354 This enables the legacy 16-bit UID syscall wrappers. 1355 1356config MULTIUSER 1357 bool "Multiple users, groups and capabilities support" if EXPERT 1358 default y 1359 help 1360 This option enables support for non-root users, groups and 1361 capabilities. 1362 1363 If you say N here, all processes will run with UID 0, GID 0, and all 1364 possible capabilities. Saying N here also compiles out support for 1365 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1366 setgid, and capset. 1367 1368 If unsure, say Y here. 1369 1370config SGETMASK_SYSCALL 1371 bool "sgetmask/ssetmask syscalls support" if EXPERT 1372 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1373 ---help--- 1374 sys_sgetmask and sys_ssetmask are obsolete system calls 1375 no longer supported in libc but still enabled by default in some 1376 architectures. 1377 1378 If unsure, leave the default option here. 1379 1380config SYSFS_SYSCALL 1381 bool "Sysfs syscall support" if EXPERT 1382 default y 1383 ---help--- 1384 sys_sysfs is an obsolete system call no longer supported in libc. 1385 Note that disabling this option is more secure but might break 1386 compatibility with some systems. 1387 1388 If unsure say Y here. 1389 1390config FHANDLE 1391 bool "open by fhandle syscalls" if EXPERT 1392 select EXPORTFS 1393 default y 1394 help 1395 If you say Y here, a user level program will be able to map 1396 file names to handle and then later use the handle for 1397 different file system operations. This is useful in implementing 1398 userspace file servers, which now track files using handles instead 1399 of names. The handle would remain the same even if file names 1400 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1401 syscalls. 1402 1403config POSIX_TIMERS 1404 bool "Posix Clocks & timers" if EXPERT 1405 default y 1406 help 1407 This includes native support for POSIX timers to the kernel. 1408 Some embedded systems have no use for them and therefore they 1409 can be configured out to reduce the size of the kernel image. 1410 1411 When this option is disabled, the following syscalls won't be 1412 available: timer_create, timer_gettime: timer_getoverrun, 1413 timer_settime, timer_delete, clock_adjtime, getitimer, 1414 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1415 clock_getres and clock_nanosleep syscalls will be limited to 1416 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1417 1418 If unsure say y. 1419 1420config PRINTK 1421 default y 1422 bool "Enable support for printk" if EXPERT 1423 select IRQ_WORK 1424 help 1425 This option enables normal printk support. Removing it 1426 eliminates most of the message strings from the kernel image 1427 and makes the kernel more or less silent. As this makes it 1428 very difficult to diagnose system problems, saying N here is 1429 strongly discouraged. 1430 1431config PRINTK_NMI 1432 def_bool y 1433 depends on PRINTK 1434 depends on HAVE_NMI 1435 1436config BUG 1437 bool "BUG() support" if EXPERT 1438 default y 1439 help 1440 Disabling this option eliminates support for BUG and WARN, reducing 1441 the size of your kernel image and potentially quietly ignoring 1442 numerous fatal conditions. You should only consider disabling this 1443 option for embedded systems with no facilities for reporting errors. 1444 Just say Y. 1445 1446config ELF_CORE 1447 depends on COREDUMP 1448 default y 1449 bool "Enable ELF core dumps" if EXPERT 1450 help 1451 Enable support for generating core dumps. Disabling saves about 4k. 1452 1453 1454config PCSPKR_PLATFORM 1455 bool "Enable PC-Speaker support" if EXPERT 1456 depends on HAVE_PCSPKR_PLATFORM 1457 select I8253_LOCK 1458 default y 1459 help 1460 This option allows to disable the internal PC-Speaker 1461 support, saving some memory. 1462 1463config BASE_FULL 1464 default y 1465 bool "Enable full-sized data structures for core" if EXPERT 1466 help 1467 Disabling this option reduces the size of miscellaneous core 1468 kernel data structures. This saves memory on small machines, 1469 but may reduce performance. 1470 1471config FUTEX 1472 bool "Enable futex support" if EXPERT 1473 default y 1474 imply RT_MUTEXES 1475 help 1476 Disabling this option will cause the kernel to be built without 1477 support for "fast userspace mutexes". The resulting kernel may not 1478 run glibc-based applications correctly. 1479 1480config FUTEX_PI 1481 bool 1482 depends on FUTEX && RT_MUTEXES 1483 default y 1484 1485config HAVE_FUTEX_CMPXCHG 1486 bool 1487 depends on FUTEX 1488 help 1489 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1490 is implemented and always working. This removes a couple of runtime 1491 checks. 1492 1493config EPOLL 1494 bool "Enable eventpoll support" if EXPERT 1495 default y 1496 help 1497 Disabling this option will cause the kernel to be built without 1498 support for epoll family of system calls. 1499 1500config SIGNALFD 1501 bool "Enable signalfd() system call" if EXPERT 1502 default y 1503 help 1504 Enable the signalfd() system call that allows to receive signals 1505 on a file descriptor. 1506 1507 If unsure, say Y. 1508 1509config TIMERFD 1510 bool "Enable timerfd() system call" if EXPERT 1511 default y 1512 help 1513 Enable the timerfd() system call that allows to receive timer 1514 events on a file descriptor. 1515 1516 If unsure, say Y. 1517 1518config EVENTFD 1519 bool "Enable eventfd() system call" if EXPERT 1520 default y 1521 help 1522 Enable the eventfd() system call that allows to receive both 1523 kernel notification (ie. KAIO) or userspace notifications. 1524 1525 If unsure, say Y. 1526 1527config SHMEM 1528 bool "Use full shmem filesystem" if EXPERT 1529 default y 1530 depends on MMU 1531 help 1532 The shmem is an internal filesystem used to manage shared memory. 1533 It is backed by swap and manages resource limits. It is also exported 1534 to userspace as tmpfs if TMPFS is enabled. Disabling this 1535 option replaces shmem and tmpfs with the much simpler ramfs code, 1536 which may be appropriate on small systems without swap. 1537 1538config AIO 1539 bool "Enable AIO support" if EXPERT 1540 default y 1541 help 1542 This option enables POSIX asynchronous I/O which may by used 1543 by some high performance threaded applications. Disabling 1544 this option saves about 7k. 1545 1546config IO_URING 1547 bool "Enable IO uring support" if EXPERT 1548 select IO_WQ 1549 default y 1550 help 1551 This option enables support for the io_uring interface, enabling 1552 applications to submit and complete IO through submission and 1553 completion rings that are shared between the kernel and application. 1554 1555config ADVISE_SYSCALLS 1556 bool "Enable madvise/fadvise syscalls" if EXPERT 1557 default y 1558 help 1559 This option enables the madvise and fadvise syscalls, used by 1560 applications to advise the kernel about their future memory or file 1561 usage, improving performance. If building an embedded system where no 1562 applications use these syscalls, you can disable this option to save 1563 space. 1564 1565config HAVE_ARCH_USERFAULTFD_WP 1566 bool 1567 help 1568 Arch has userfaultfd write protection support 1569 1570config MEMBARRIER 1571 bool "Enable membarrier() system call" if EXPERT 1572 default y 1573 help 1574 Enable the membarrier() system call that allows issuing memory 1575 barriers across all running threads, which can be used to distribute 1576 the cost of user-space memory barriers asymmetrically by transforming 1577 pairs of memory barriers into pairs consisting of membarrier() and a 1578 compiler barrier. 1579 1580 If unsure, say Y. 1581 1582config KALLSYMS 1583 bool "Load all symbols for debugging/ksymoops" if EXPERT 1584 default y 1585 help 1586 Say Y here to let the kernel print out symbolic crash information and 1587 symbolic stack backtraces. This increases the size of the kernel 1588 somewhat, as all symbols have to be loaded into the kernel image. 1589 1590config KALLSYMS_ALL 1591 bool "Include all symbols in kallsyms" 1592 depends on DEBUG_KERNEL && KALLSYMS 1593 help 1594 Normally kallsyms only contains the symbols of functions for nicer 1595 OOPS messages and backtraces (i.e., symbols from the text and inittext 1596 sections). This is sufficient for most cases. And only in very rare 1597 cases (e.g., when a debugger is used) all symbols are required (e.g., 1598 names of variables from the data sections, etc). 1599 1600 This option makes sure that all symbols are loaded into the kernel 1601 image (i.e., symbols from all sections) in cost of increased kernel 1602 size (depending on the kernel configuration, it may be 300KiB or 1603 something like this). 1604 1605 Say N unless you really need all symbols. 1606 1607config KALLSYMS_ABSOLUTE_PERCPU 1608 bool 1609 depends on KALLSYMS 1610 default X86_64 && SMP 1611 1612config KALLSYMS_BASE_RELATIVE 1613 bool 1614 depends on KALLSYMS 1615 default !IA64 1616 help 1617 Instead of emitting them as absolute values in the native word size, 1618 emit the symbol references in the kallsyms table as 32-bit entries, 1619 each containing a relative value in the range [base, base + U32_MAX] 1620 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1621 an absolute value in the range [0, S32_MAX] or a relative value in the 1622 range [base, base + S32_MAX], where base is the lowest relative symbol 1623 address encountered in the image. 1624 1625 On 64-bit builds, this reduces the size of the address table by 50%, 1626 but more importantly, it results in entries whose values are build 1627 time constants, and no relocation pass is required at runtime to fix 1628 up the entries based on the runtime load address of the kernel. 1629 1630# end of the "standard kernel features (expert users)" menu 1631 1632# syscall, maps, verifier 1633 1634config BPF_LSM 1635 bool "LSM Instrumentation with BPF" 1636 depends on BPF_EVENTS 1637 depends on BPF_SYSCALL 1638 depends on SECURITY 1639 depends on BPF_JIT 1640 help 1641 Enables instrumentation of the security hooks with eBPF programs for 1642 implementing dynamic MAC and Audit Policies. 1643 1644 If you are unsure how to answer this question, answer N. 1645 1646config BPF_SYSCALL 1647 bool "Enable bpf() system call" 1648 select BPF 1649 select IRQ_WORK 1650 default n 1651 help 1652 Enable the bpf() system call that allows to manipulate eBPF 1653 programs and maps via file descriptors. 1654 1655config ARCH_WANT_DEFAULT_BPF_JIT 1656 bool 1657 1658config BPF_JIT_ALWAYS_ON 1659 bool "Permanently enable BPF JIT and remove BPF interpreter" 1660 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1661 help 1662 Enables BPF JIT and removes BPF interpreter to avoid 1663 speculative execution of BPF instructions by the interpreter 1664 1665config BPF_JIT_DEFAULT_ON 1666 def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON 1667 depends on HAVE_EBPF_JIT && BPF_JIT 1668 1669config USERFAULTFD 1670 bool "Enable userfaultfd() system call" 1671 depends on MMU 1672 help 1673 Enable the userfaultfd() system call that allows to intercept and 1674 handle page faults in userland. 1675 1676config ARCH_HAS_MEMBARRIER_CALLBACKS 1677 bool 1678 1679config ARCH_HAS_MEMBARRIER_SYNC_CORE 1680 bool 1681 1682config RSEQ 1683 bool "Enable rseq() system call" if EXPERT 1684 default y 1685 depends on HAVE_RSEQ 1686 select MEMBARRIER 1687 help 1688 Enable the restartable sequences system call. It provides a 1689 user-space cache for the current CPU number value, which 1690 speeds up getting the current CPU number from user-space, 1691 as well as an ABI to speed up user-space operations on 1692 per-CPU data. 1693 1694 If unsure, say Y. 1695 1696config DEBUG_RSEQ 1697 default n 1698 bool "Enabled debugging of rseq() system call" if EXPERT 1699 depends on RSEQ && DEBUG_KERNEL 1700 help 1701 Enable extra debugging checks for the rseq system call. 1702 1703 If unsure, say N. 1704 1705config EMBEDDED 1706 bool "Embedded system" 1707 option allnoconfig_y 1708 select EXPERT 1709 help 1710 This option should be enabled if compiling the kernel for 1711 an embedded system so certain expert options are available 1712 for configuration. 1713 1714config HAVE_PERF_EVENTS 1715 bool 1716 help 1717 See tools/perf/design.txt for details. 1718 1719config PERF_USE_VMALLOC 1720 bool 1721 help 1722 See tools/perf/design.txt for details 1723 1724config PC104 1725 bool "PC/104 support" if EXPERT 1726 help 1727 Expose PC/104 form factor device drivers and options available for 1728 selection and configuration. Enable this option if your target 1729 machine has a PC/104 bus. 1730 1731menu "Kernel Performance Events And Counters" 1732 1733config PERF_EVENTS 1734 bool "Kernel performance events and counters" 1735 default y if PROFILING 1736 depends on HAVE_PERF_EVENTS 1737 select IRQ_WORK 1738 select SRCU 1739 help 1740 Enable kernel support for various performance events provided 1741 by software and hardware. 1742 1743 Software events are supported either built-in or via the 1744 use of generic tracepoints. 1745 1746 Most modern CPUs support performance events via performance 1747 counter registers. These registers count the number of certain 1748 types of hw events: such as instructions executed, cachemisses 1749 suffered, or branches mis-predicted - without slowing down the 1750 kernel or applications. These registers can also trigger interrupts 1751 when a threshold number of events have passed - and can thus be 1752 used to profile the code that runs on that CPU. 1753 1754 The Linux Performance Event subsystem provides an abstraction of 1755 these software and hardware event capabilities, available via a 1756 system call and used by the "perf" utility in tools/perf/. It 1757 provides per task and per CPU counters, and it provides event 1758 capabilities on top of those. 1759 1760 Say Y if unsure. 1761 1762config DEBUG_PERF_USE_VMALLOC 1763 default n 1764 bool "Debug: use vmalloc to back perf mmap() buffers" 1765 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1766 select PERF_USE_VMALLOC 1767 help 1768 Use vmalloc memory to back perf mmap() buffers. 1769 1770 Mostly useful for debugging the vmalloc code on platforms 1771 that don't require it. 1772 1773 Say N if unsure. 1774 1775endmenu 1776 1777config VM_EVENT_COUNTERS 1778 default y 1779 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1780 help 1781 VM event counters are needed for event counts to be shown. 1782 This option allows the disabling of the VM event counters 1783 on EXPERT systems. /proc/vmstat will only show page counts 1784 if VM event counters are disabled. 1785 1786config SLUB_DEBUG 1787 default y 1788 bool "Enable SLUB debugging support" if EXPERT 1789 depends on SLUB && SYSFS 1790 help 1791 SLUB has extensive debug support features. Disabling these can 1792 result in significant savings in code size. This also disables 1793 SLUB sysfs support. /sys/slab will not exist and there will be 1794 no support for cache validation etc. 1795 1796config SLUB_MEMCG_SYSFS_ON 1797 default n 1798 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1799 depends on SLUB && SYSFS && MEMCG 1800 help 1801 SLUB creates a directory under /sys/kernel/slab for each 1802 allocation cache to host info and debug files. If memory 1803 cgroup is enabled, each cache can have per memory cgroup 1804 caches. SLUB can create the same sysfs directories for these 1805 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1806 to a very high number of debug files being created. This is 1807 controlled by slub_memcg_sysfs boot parameter and this 1808 config option determines the parameter's default value. 1809 1810config COMPAT_BRK 1811 bool "Disable heap randomization" 1812 default y 1813 help 1814 Randomizing heap placement makes heap exploits harder, but it 1815 also breaks ancient binaries (including anything libc5 based). 1816 This option changes the bootup default to heap randomization 1817 disabled, and can be overridden at runtime by setting 1818 /proc/sys/kernel/randomize_va_space to 2. 1819 1820 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1821 1822choice 1823 prompt "Choose SLAB allocator" 1824 default SLUB 1825 help 1826 This option allows to select a slab allocator. 1827 1828config SLAB 1829 bool "SLAB" 1830 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1831 help 1832 The regular slab allocator that is established and known to work 1833 well in all environments. It organizes cache hot objects in 1834 per cpu and per node queues. 1835 1836config SLUB 1837 bool "SLUB (Unqueued Allocator)" 1838 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1839 help 1840 SLUB is a slab allocator that minimizes cache line usage 1841 instead of managing queues of cached objects (SLAB approach). 1842 Per cpu caching is realized using slabs of objects instead 1843 of queues of objects. SLUB can use memory efficiently 1844 and has enhanced diagnostics. SLUB is the default choice for 1845 a slab allocator. 1846 1847config SLOB 1848 depends on EXPERT 1849 bool "SLOB (Simple Allocator)" 1850 help 1851 SLOB replaces the stock allocator with a drastically simpler 1852 allocator. SLOB is generally more space efficient but 1853 does not perform as well on large systems. 1854 1855endchoice 1856 1857config SLAB_MERGE_DEFAULT 1858 bool "Allow slab caches to be merged" 1859 default y 1860 help 1861 For reduced kernel memory fragmentation, slab caches can be 1862 merged when they share the same size and other characteristics. 1863 This carries a risk of kernel heap overflows being able to 1864 overwrite objects from merged caches (and more easily control 1865 cache layout), which makes such heap attacks easier to exploit 1866 by attackers. By keeping caches unmerged, these kinds of exploits 1867 can usually only damage objects in the same cache. To disable 1868 merging at runtime, "slab_nomerge" can be passed on the kernel 1869 command line. 1870 1871config SLAB_FREELIST_RANDOM 1872 default n 1873 depends on SLAB || SLUB 1874 bool "SLAB freelist randomization" 1875 help 1876 Randomizes the freelist order used on creating new pages. This 1877 security feature reduces the predictability of the kernel slab 1878 allocator against heap overflows. 1879 1880config SLAB_FREELIST_HARDENED 1881 bool "Harden slab freelist metadata" 1882 depends on SLUB 1883 help 1884 Many kernel heap attacks try to target slab cache metadata and 1885 other infrastructure. This options makes minor performance 1886 sacrifices to harden the kernel slab allocator against common 1887 freelist exploit methods. 1888 1889config SHUFFLE_PAGE_ALLOCATOR 1890 bool "Page allocator randomization" 1891 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1892 help 1893 Randomization of the page allocator improves the average 1894 utilization of a direct-mapped memory-side-cache. See section 1895 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1896 6.2a specification for an example of how a platform advertises 1897 the presence of a memory-side-cache. There are also incidental 1898 security benefits as it reduces the predictability of page 1899 allocations to compliment SLAB_FREELIST_RANDOM, but the 1900 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1901 10th order of pages is selected based on cache utilization 1902 benefits on x86. 1903 1904 While the randomization improves cache utilization it may 1905 negatively impact workloads on platforms without a cache. For 1906 this reason, by default, the randomization is enabled only 1907 after runtime detection of a direct-mapped memory-side-cache. 1908 Otherwise, the randomization may be force enabled with the 1909 'page_alloc.shuffle' kernel command line parameter. 1910 1911 Say Y if unsure. 1912 1913config SLUB_CPU_PARTIAL 1914 default y 1915 depends on SLUB && SMP 1916 bool "SLUB per cpu partial cache" 1917 help 1918 Per cpu partial caches accelerate objects allocation and freeing 1919 that is local to a processor at the price of more indeterminism 1920 in the latency of the free. On overflow these caches will be cleared 1921 which requires the taking of locks that may cause latency spikes. 1922 Typically one would choose no for a realtime system. 1923 1924config MMAP_ALLOW_UNINITIALIZED 1925 bool "Allow mmapped anonymous memory to be uninitialized" 1926 depends on EXPERT && !MMU 1927 default n 1928 help 1929 Normally, and according to the Linux spec, anonymous memory obtained 1930 from mmap() has its contents cleared before it is passed to 1931 userspace. Enabling this config option allows you to request that 1932 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1933 providing a huge performance boost. If this option is not enabled, 1934 then the flag will be ignored. 1935 1936 This is taken advantage of by uClibc's malloc(), and also by 1937 ELF-FDPIC binfmt's brk and stack allocator. 1938 1939 Because of the obvious security issues, this option should only be 1940 enabled on embedded devices where you control what is run in 1941 userspace. Since that isn't generally a problem on no-MMU systems, 1942 it is normally safe to say Y here. 1943 1944 See Documentation/nommu-mmap.txt for more information. 1945 1946config SYSTEM_DATA_VERIFICATION 1947 def_bool n 1948 select SYSTEM_TRUSTED_KEYRING 1949 select KEYS 1950 select CRYPTO 1951 select CRYPTO_RSA 1952 select ASYMMETRIC_KEY_TYPE 1953 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1954 select ASN1 1955 select OID_REGISTRY 1956 select X509_CERTIFICATE_PARSER 1957 select PKCS7_MESSAGE_PARSER 1958 help 1959 Provide PKCS#7 message verification using the contents of the system 1960 trusted keyring to provide public keys. This then can be used for 1961 module verification, kexec image verification and firmware blob 1962 verification. 1963 1964config PROFILING 1965 bool "Profiling support" 1966 help 1967 Say Y here to enable the extended profiling support mechanisms used 1968 by profilers such as OProfile. 1969 1970# 1971# Place an empty function call at each tracepoint site. Can be 1972# dynamically changed for a probe function. 1973# 1974config TRACEPOINTS 1975 bool 1976 1977endmenu # General setup 1978 1979source "arch/Kconfig" 1980 1981config RT_MUTEXES 1982 bool 1983 1984config BASE_SMALL 1985 int 1986 default 0 if BASE_FULL 1987 default 1 if !BASE_FULL 1988 1989config MODULE_SIG_FORMAT 1990 def_bool n 1991 select SYSTEM_DATA_VERIFICATION 1992 1993menuconfig MODULES 1994 bool "Enable loadable module support" 1995 option modules 1996 help 1997 Kernel modules are small pieces of compiled code which can 1998 be inserted in the running kernel, rather than being 1999 permanently built into the kernel. You use the "modprobe" 2000 tool to add (and sometimes remove) them. If you say Y here, 2001 many parts of the kernel can be built as modules (by 2002 answering M instead of Y where indicated): this is most 2003 useful for infrequently used options which are not required 2004 for booting. For more information, see the man pages for 2005 modprobe, lsmod, modinfo, insmod and rmmod. 2006 2007 If you say Y here, you will need to run "make 2008 modules_install" to put the modules under /lib/modules/ 2009 where modprobe can find them (you may need to be root to do 2010 this). 2011 2012 If unsure, say Y. 2013 2014if MODULES 2015 2016config MODULE_FORCE_LOAD 2017 bool "Forced module loading" 2018 default n 2019 help 2020 Allow loading of modules without version information (ie. modprobe 2021 --force). Forced module loading sets the 'F' (forced) taint flag and 2022 is usually a really bad idea. 2023 2024config MODULE_UNLOAD 2025 bool "Module unloading" 2026 help 2027 Without this option you will not be able to unload any 2028 modules (note that some modules may not be unloadable 2029 anyway), which makes your kernel smaller, faster 2030 and simpler. If unsure, say Y. 2031 2032config MODULE_FORCE_UNLOAD 2033 bool "Forced module unloading" 2034 depends on MODULE_UNLOAD 2035 help 2036 This option allows you to force a module to unload, even if the 2037 kernel believes it is unsafe: the kernel will remove the module 2038 without waiting for anyone to stop using it (using the -f option to 2039 rmmod). This is mainly for kernel developers and desperate users. 2040 If unsure, say N. 2041 2042config MODVERSIONS 2043 bool "Module versioning support" 2044 help 2045 Usually, you have to use modules compiled with your kernel. 2046 Saying Y here makes it sometimes possible to use modules 2047 compiled for different kernels, by adding enough information 2048 to the modules to (hopefully) spot any changes which would 2049 make them incompatible with the kernel you are running. If 2050 unsure, say N. 2051 2052config ASM_MODVERSIONS 2053 bool 2054 default HAVE_ASM_MODVERSIONS && MODVERSIONS 2055 help 2056 This enables module versioning for exported symbols also from 2057 assembly. This can be enabled only when the target architecture 2058 supports it. 2059 2060config MODULE_REL_CRCS 2061 bool 2062 depends on MODVERSIONS 2063 2064config MODULE_SRCVERSION_ALL 2065 bool "Source checksum for all modules" 2066 help 2067 Modules which contain a MODULE_VERSION get an extra "srcversion" 2068 field inserted into their modinfo section, which contains a 2069 sum of the source files which made it. This helps maintainers 2070 see exactly which source was used to build a module (since 2071 others sometimes change the module source without updating 2072 the version). With this option, such a "srcversion" field 2073 will be created for all modules. If unsure, say N. 2074 2075config MODULE_SIG 2076 bool "Module signature verification" 2077 select MODULE_SIG_FORMAT 2078 help 2079 Check modules for valid signatures upon load: the signature 2080 is simply appended to the module. For more information see 2081 <file:Documentation/admin-guide/module-signing.rst>. 2082 2083 Note that this option adds the OpenSSL development packages as a 2084 kernel build dependency so that the signing tool can use its crypto 2085 library. 2086 2087 You should enable this option if you wish to use either 2088 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via 2089 another LSM - otherwise unsigned modules will be loadable regardless 2090 of the lockdown policy. 2091 2092 !!!WARNING!!! If you enable this option, you MUST make sure that the 2093 module DOES NOT get stripped after being signed. This includes the 2094 debuginfo strip done by some packagers (such as rpmbuild) and 2095 inclusion into an initramfs that wants the module size reduced. 2096 2097config MODULE_SIG_FORCE 2098 bool "Require modules to be validly signed" 2099 depends on MODULE_SIG 2100 help 2101 Reject unsigned modules or signed modules for which we don't have a 2102 key. Without this, such modules will simply taint the kernel. 2103 2104config MODULE_SIG_ALL 2105 bool "Automatically sign all modules" 2106 default y 2107 depends on MODULE_SIG 2108 help 2109 Sign all modules during make modules_install. Without this option, 2110 modules must be signed manually, using the scripts/sign-file tool. 2111 2112comment "Do not forget to sign required modules with scripts/sign-file" 2113 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2114 2115choice 2116 prompt "Which hash algorithm should modules be signed with?" 2117 depends on MODULE_SIG 2118 help 2119 This determines which sort of hashing algorithm will be used during 2120 signature generation. This algorithm _must_ be built into the kernel 2121 directly so that signature verification can take place. It is not 2122 possible to load a signed module containing the algorithm to check 2123 the signature on that module. 2124 2125config MODULE_SIG_SHA1 2126 bool "Sign modules with SHA-1" 2127 select CRYPTO_SHA1 2128 2129config MODULE_SIG_SHA224 2130 bool "Sign modules with SHA-224" 2131 select CRYPTO_SHA256 2132 2133config MODULE_SIG_SHA256 2134 bool "Sign modules with SHA-256" 2135 select CRYPTO_SHA256 2136 2137config MODULE_SIG_SHA384 2138 bool "Sign modules with SHA-384" 2139 select CRYPTO_SHA512 2140 2141config MODULE_SIG_SHA512 2142 bool "Sign modules with SHA-512" 2143 select CRYPTO_SHA512 2144 2145endchoice 2146 2147config MODULE_SIG_HASH 2148 string 2149 depends on MODULE_SIG 2150 default "sha1" if MODULE_SIG_SHA1 2151 default "sha224" if MODULE_SIG_SHA224 2152 default "sha256" if MODULE_SIG_SHA256 2153 default "sha384" if MODULE_SIG_SHA384 2154 default "sha512" if MODULE_SIG_SHA512 2155 2156config MODULE_COMPRESS 2157 bool "Compress modules on installation" 2158 help 2159 2160 Compresses kernel modules when 'make modules_install' is run; gzip or 2161 xz depending on "Compression algorithm" below. 2162 2163 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 2164 2165 Out-of-tree kernel modules installed using Kbuild will also be 2166 compressed upon installation. 2167 2168 Note: for modules inside an initrd or initramfs, it's more efficient 2169 to compress the whole initrd or initramfs instead. 2170 2171 Note: This is fully compatible with signed modules. 2172 2173 If in doubt, say N. 2174 2175choice 2176 prompt "Compression algorithm" 2177 depends on MODULE_COMPRESS 2178 default MODULE_COMPRESS_GZIP 2179 help 2180 This determines which sort of compression will be used during 2181 'make modules_install'. 2182 2183 GZIP (default) and XZ are supported. 2184 2185config MODULE_COMPRESS_GZIP 2186 bool "GZIP" 2187 2188config MODULE_COMPRESS_XZ 2189 bool "XZ" 2190 2191endchoice 2192 2193config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS 2194 bool "Allow loading of modules with missing namespace imports" 2195 help 2196 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in 2197 a namespace. A module that makes use of a symbol exported with such a 2198 namespace is required to import the namespace via MODULE_IMPORT_NS(). 2199 There is no technical reason to enforce correct namespace imports, 2200 but it creates consistency between symbols defining namespaces and 2201 users importing namespaces they make use of. This option relaxes this 2202 requirement and lifts the enforcement when loading a module. 2203 2204 If unsure, say N. 2205 2206config UNUSED_SYMBOLS 2207 bool "Enable unused/obsolete exported symbols" 2208 default y if X86 2209 help 2210 Unused but exported symbols make the kernel needlessly bigger. For 2211 that reason most of these unused exports will soon be removed. This 2212 option is provided temporarily to provide a transition period in case 2213 some external kernel module needs one of these symbols anyway. If you 2214 encounter such a case in your module, consider if you are actually 2215 using the right API. (rationale: since nobody in the kernel is using 2216 this in a module, there is a pretty good chance it's actually the 2217 wrong interface to use). If you really need the symbol, please send a 2218 mail to the linux kernel mailing list mentioning the symbol and why 2219 you really need it, and what the merge plan to the mainline kernel for 2220 your module is. 2221 2222config TRIM_UNUSED_KSYMS 2223 bool "Trim unused exported kernel symbols" 2224 depends on !UNUSED_SYMBOLS 2225 help 2226 The kernel and some modules make many symbols available for 2227 other modules to use via EXPORT_SYMBOL() and variants. Depending 2228 on the set of modules being selected in your kernel configuration, 2229 many of those exported symbols might never be used. 2230 2231 This option allows for unused exported symbols to be dropped from 2232 the build. In turn, this provides the compiler more opportunities 2233 (especially when using LTO) for optimizing the code and reducing 2234 binary size. This might have some security advantages as well. 2235 2236 If unsure, or if you need to build out-of-tree modules, say N. 2237 2238config UNUSED_KSYMS_WHITELIST 2239 string "Whitelist of symbols to keep in ksymtab" 2240 depends on TRIM_UNUSED_KSYMS 2241 help 2242 By default, all unused exported symbols will be un-exported from the 2243 build when TRIM_UNUSED_KSYMS is selected. 2244 2245 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept 2246 exported at all times, even in absence of in-tree users. The value to 2247 set here is the path to a text file containing the list of symbols, 2248 one per line. The path can be absolute, or relative to the kernel 2249 source tree. 2250 2251endif # MODULES 2252 2253config MODULES_TREE_LOOKUP 2254 def_bool y 2255 depends on PERF_EVENTS || TRACING 2256 2257config INIT_ALL_POSSIBLE 2258 bool 2259 help 2260 Back when each arch used to define their own cpu_online_mask and 2261 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2262 with all 1s, and others with all 0s. When they were centralised, 2263 it was better to provide this option than to break all the archs 2264 and have several arch maintainers pursuing me down dark alleys. 2265 2266source "block/Kconfig" 2267 2268config PREEMPT_NOTIFIERS 2269 bool 2270 2271config PADATA 2272 depends on SMP 2273 bool 2274 2275config ASN1 2276 tristate 2277 help 2278 Build a simple ASN.1 grammar compiler that produces a bytecode output 2279 that can be interpreted by the ASN.1 stream decoder and used to 2280 inform it as to what tags are to be expected in a stream and what 2281 functions to call on what tags. 2282 2283source "kernel/Kconfig.locks" 2284 2285config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2286 bool 2287 2288# It may be useful for an architecture to override the definitions of the 2289# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2290# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2291# different calling convention for syscalls. They can also override the 2292# macros for not-implemented syscalls in kernel/sys_ni.c and 2293# kernel/time/posix-stubs.c. All these overrides need to be available in 2294# <asm/syscall_wrapper.h>. 2295config ARCH_HAS_SYSCALL_WRAPPER 2296 def_bool n 2297