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