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