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 !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 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 TIME_NS 1084 bool "TIME namespace" 1085 depends on GENERIC_VDSO_TIME_NS 1086 default y 1087 help 1088 In this namespace boottime and monotonic clocks can be set. 1089 The time will keep going with the same pace. 1090 1091config IPC_NS 1092 bool "IPC namespace" 1093 depends on (SYSVIPC || POSIX_MQUEUE) 1094 default y 1095 help 1096 In this namespace tasks work with IPC ids which correspond to 1097 different IPC objects in different namespaces. 1098 1099config USER_NS 1100 bool "User namespace" 1101 default n 1102 help 1103 This allows containers, i.e. vservers, to use user namespaces 1104 to provide different user info for different servers. 1105 1106 When user namespaces are enabled in the kernel it is 1107 recommended that the MEMCG option also be enabled and that 1108 user-space use the memory control groups to limit the amount 1109 of memory a memory unprivileged users can use. 1110 1111 If unsure, say N. 1112 1113config PID_NS 1114 bool "PID Namespaces" 1115 default y 1116 help 1117 Support process id namespaces. This allows having multiple 1118 processes with the same pid as long as they are in different 1119 pid namespaces. This is a building block of containers. 1120 1121config NET_NS 1122 bool "Network namespace" 1123 depends on NET 1124 default y 1125 help 1126 Allow user space to create what appear to be multiple instances 1127 of the network stack. 1128 1129endif # NAMESPACES 1130 1131config CHECKPOINT_RESTORE 1132 bool "Checkpoint/restore support" 1133 select PROC_CHILDREN 1134 default n 1135 help 1136 Enables additional kernel features in a sake of checkpoint/restore. 1137 In particular it adds auxiliary prctl codes to setup process text, 1138 data and heap segment sizes, and a few additional /proc filesystem 1139 entries. 1140 1141 If unsure, say N here. 1142 1143config SCHED_AUTOGROUP 1144 bool "Automatic process group scheduling" 1145 select CGROUPS 1146 select CGROUP_SCHED 1147 select FAIR_GROUP_SCHED 1148 help 1149 This option optimizes the scheduler for common desktop workloads by 1150 automatically creating and populating task groups. This separation 1151 of workloads isolates aggressive CPU burners (like build jobs) from 1152 desktop applications. Task group autogeneration is currently based 1153 upon task session. 1154 1155config SYSFS_DEPRECATED 1156 bool "Enable deprecated sysfs features to support old userspace tools" 1157 depends on SYSFS 1158 default n 1159 help 1160 This option adds code that switches the layout of the "block" class 1161 devices, to not show up in /sys/class/block/, but only in 1162 /sys/block/. 1163 1164 This switch is only active when the sysfs.deprecated=1 boot option is 1165 passed or the SYSFS_DEPRECATED_V2 option is set. 1166 1167 This option allows new kernels to run on old distributions and tools, 1168 which might get confused by /sys/class/block/. Since 2007/2008 all 1169 major distributions and tools handle this just fine. 1170 1171 Recent distributions and userspace tools after 2009/2010 depend on 1172 the existence of /sys/class/block/, and will not work with this 1173 option enabled. 1174 1175 Only if you are using a new kernel on an old distribution, you might 1176 need to say Y here. 1177 1178config SYSFS_DEPRECATED_V2 1179 bool "Enable deprecated sysfs features by default" 1180 default n 1181 depends on SYSFS 1182 depends on SYSFS_DEPRECATED 1183 help 1184 Enable deprecated sysfs by default. 1185 1186 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1187 option. 1188 1189 Only if you are using a new kernel on an old distribution, you might 1190 need to say Y here. Even then, odds are you would not need it 1191 enabled, you can always pass the boot option if absolutely necessary. 1192 1193config RELAY 1194 bool "Kernel->user space relay support (formerly relayfs)" 1195 select IRQ_WORK 1196 help 1197 This option enables support for relay interface support in 1198 certain file systems (such as debugfs). 1199 It is designed to provide an efficient mechanism for tools and 1200 facilities to relay large amounts of data from kernel space to 1201 user space. 1202 1203 If unsure, say N. 1204 1205config BLK_DEV_INITRD 1206 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1207 help 1208 The initial RAM filesystem is a ramfs which is loaded by the 1209 boot loader (loadlin or lilo) and that is mounted as root 1210 before the normal boot procedure. It is typically used to 1211 load modules needed to mount the "real" root file system, 1212 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1213 1214 If RAM disk support (BLK_DEV_RAM) is also included, this 1215 also enables initial RAM disk (initrd) support and adds 1216 15 Kbytes (more on some other architectures) to the kernel size. 1217 1218 If unsure say Y. 1219 1220if BLK_DEV_INITRD 1221 1222source "usr/Kconfig" 1223 1224endif 1225 1226config BOOT_CONFIG 1227 bool "Boot config support" 1228 select BLK_DEV_INITRD 1229 help 1230 Extra boot config allows system admin to pass a config file as 1231 complemental extension of kernel cmdline when booting. 1232 The boot config file must be attached at the end of initramfs 1233 with checksum, size and magic word. 1234 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1235 1236 If unsure, say Y. 1237 1238choice 1239 prompt "Compiler optimization level" 1240 default CC_OPTIMIZE_FOR_PERFORMANCE 1241 1242config CC_OPTIMIZE_FOR_PERFORMANCE 1243 bool "Optimize for performance (-O2)" 1244 help 1245 This is the default optimization level for the kernel, building 1246 with the "-O2" compiler flag for best performance and most 1247 helpful compile-time warnings. 1248 1249config CC_OPTIMIZE_FOR_PERFORMANCE_O3 1250 bool "Optimize more for performance (-O3)" 1251 depends on ARC 1252 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives 1253 help 1254 Choosing this option will pass "-O3" to your compiler to optimize 1255 the kernel yet more for performance. 1256 1257config CC_OPTIMIZE_FOR_SIZE 1258 bool "Optimize for size (-Os)" 1259 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives 1260 help 1261 Choosing this option will pass "-Os" to your compiler resulting 1262 in a smaller kernel. 1263 1264endchoice 1265 1266config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1267 bool 1268 help 1269 This requires that the arch annotates or otherwise protects 1270 its external entry points from being discarded. Linker scripts 1271 must also merge .text.*, .data.*, and .bss.* correctly into 1272 output sections. Care must be taken not to pull in unrelated 1273 sections (e.g., '.text.init'). Typically '.' in section names 1274 is used to distinguish them from label names / C identifiers. 1275 1276config LD_DEAD_CODE_DATA_ELIMINATION 1277 bool "Dead code and data elimination (EXPERIMENTAL)" 1278 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1279 depends on EXPERT 1280 depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800) 1281 depends on $(cc-option,-ffunction-sections -fdata-sections) 1282 depends on $(ld-option,--gc-sections) 1283 help 1284 Enable this if you want to do dead code and data elimination with 1285 the linker by compiling with -ffunction-sections -fdata-sections, 1286 and linking with --gc-sections. 1287 1288 This can reduce on disk and in-memory size of the kernel 1289 code and static data, particularly for small configs and 1290 on small systems. This has the possibility of introducing 1291 silently broken kernel if the required annotations are not 1292 present. This option is not well tested yet, so use at your 1293 own risk. 1294 1295config SYSCTL 1296 bool 1297 1298config HAVE_UID16 1299 bool 1300 1301config SYSCTL_EXCEPTION_TRACE 1302 bool 1303 help 1304 Enable support for /proc/sys/debug/exception-trace. 1305 1306config SYSCTL_ARCH_UNALIGN_NO_WARN 1307 bool 1308 help 1309 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1310 Allows arch to define/use @no_unaligned_warning to possibly warn 1311 about unaligned access emulation going on under the hood. 1312 1313config SYSCTL_ARCH_UNALIGN_ALLOW 1314 bool 1315 help 1316 Enable support for /proc/sys/kernel/unaligned-trap 1317 Allows arches to define/use @unaligned_enabled to runtime toggle 1318 the unaligned access emulation. 1319 see arch/parisc/kernel/unaligned.c for reference 1320 1321config HAVE_PCSPKR_PLATFORM 1322 bool 1323 1324# interpreter that classic socket filters depend on 1325config BPF 1326 bool 1327 1328menuconfig EXPERT 1329 bool "Configure standard kernel features (expert users)" 1330 # Unhide debug options, to make the on-by-default options visible 1331 select DEBUG_KERNEL 1332 help 1333 This option allows certain base kernel options and settings 1334 to be disabled or tweaked. This is for specialized 1335 environments which can tolerate a "non-standard" kernel. 1336 Only use this if you really know what you are doing. 1337 1338config UID16 1339 bool "Enable 16-bit UID system calls" if EXPERT 1340 depends on HAVE_UID16 && MULTIUSER 1341 default y 1342 help 1343 This enables the legacy 16-bit UID syscall wrappers. 1344 1345config MULTIUSER 1346 bool "Multiple users, groups and capabilities support" if EXPERT 1347 default y 1348 help 1349 This option enables support for non-root users, groups and 1350 capabilities. 1351 1352 If you say N here, all processes will run with UID 0, GID 0, and all 1353 possible capabilities. Saying N here also compiles out support for 1354 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1355 setgid, and capset. 1356 1357 If unsure, say Y here. 1358 1359config SGETMASK_SYSCALL 1360 bool "sgetmask/ssetmask syscalls support" if EXPERT 1361 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1362 ---help--- 1363 sys_sgetmask and sys_ssetmask are obsolete system calls 1364 no longer supported in libc but still enabled by default in some 1365 architectures. 1366 1367 If unsure, leave the default option here. 1368 1369config SYSFS_SYSCALL 1370 bool "Sysfs syscall support" if EXPERT 1371 default y 1372 ---help--- 1373 sys_sysfs is an obsolete system call no longer supported in libc. 1374 Note that disabling this option is more secure but might break 1375 compatibility with some systems. 1376 1377 If unsure say Y here. 1378 1379config FHANDLE 1380 bool "open by fhandle syscalls" if EXPERT 1381 select EXPORTFS 1382 default y 1383 help 1384 If you say Y here, a user level program will be able to map 1385 file names to handle and then later use the handle for 1386 different file system operations. This is useful in implementing 1387 userspace file servers, which now track files using handles instead 1388 of names. The handle would remain the same even if file names 1389 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1390 syscalls. 1391 1392config POSIX_TIMERS 1393 bool "Posix Clocks & timers" if EXPERT 1394 default y 1395 help 1396 This includes native support for POSIX timers to the kernel. 1397 Some embedded systems have no use for them and therefore they 1398 can be configured out to reduce the size of the kernel image. 1399 1400 When this option is disabled, the following syscalls won't be 1401 available: timer_create, timer_gettime: timer_getoverrun, 1402 timer_settime, timer_delete, clock_adjtime, getitimer, 1403 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1404 clock_getres and clock_nanosleep syscalls will be limited to 1405 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1406 1407 If unsure say y. 1408 1409config PRINTK 1410 default y 1411 bool "Enable support for printk" if EXPERT 1412 select IRQ_WORK 1413 help 1414 This option enables normal printk support. Removing it 1415 eliminates most of the message strings from the kernel image 1416 and makes the kernel more or less silent. As this makes it 1417 very difficult to diagnose system problems, saying N here is 1418 strongly discouraged. 1419 1420config PRINTK_NMI 1421 def_bool y 1422 depends on PRINTK 1423 depends on HAVE_NMI 1424 1425config BUG 1426 bool "BUG() support" if EXPERT 1427 default y 1428 help 1429 Disabling this option eliminates support for BUG and WARN, reducing 1430 the size of your kernel image and potentially quietly ignoring 1431 numerous fatal conditions. You should only consider disabling this 1432 option for embedded systems with no facilities for reporting errors. 1433 Just say Y. 1434 1435config ELF_CORE 1436 depends on COREDUMP 1437 default y 1438 bool "Enable ELF core dumps" if EXPERT 1439 help 1440 Enable support for generating core dumps. Disabling saves about 4k. 1441 1442 1443config PCSPKR_PLATFORM 1444 bool "Enable PC-Speaker support" if EXPERT 1445 depends on HAVE_PCSPKR_PLATFORM 1446 select I8253_LOCK 1447 default y 1448 help 1449 This option allows to disable the internal PC-Speaker 1450 support, saving some memory. 1451 1452config BASE_FULL 1453 default y 1454 bool "Enable full-sized data structures for core" if EXPERT 1455 help 1456 Disabling this option reduces the size of miscellaneous core 1457 kernel data structures. This saves memory on small machines, 1458 but may reduce performance. 1459 1460config FUTEX 1461 bool "Enable futex support" if EXPERT 1462 default y 1463 imply RT_MUTEXES 1464 help 1465 Disabling this option will cause the kernel to be built without 1466 support for "fast userspace mutexes". The resulting kernel may not 1467 run glibc-based applications correctly. 1468 1469config FUTEX_PI 1470 bool 1471 depends on FUTEX && RT_MUTEXES 1472 default y 1473 1474config HAVE_FUTEX_CMPXCHG 1475 bool 1476 depends on FUTEX 1477 help 1478 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1479 is implemented and always working. This removes a couple of runtime 1480 checks. 1481 1482config EPOLL 1483 bool "Enable eventpoll support" if EXPERT 1484 default y 1485 help 1486 Disabling this option will cause the kernel to be built without 1487 support for epoll family of system calls. 1488 1489config SIGNALFD 1490 bool "Enable signalfd() system call" if EXPERT 1491 default y 1492 help 1493 Enable the signalfd() system call that allows to receive signals 1494 on a file descriptor. 1495 1496 If unsure, say Y. 1497 1498config TIMERFD 1499 bool "Enable timerfd() system call" if EXPERT 1500 default y 1501 help 1502 Enable the timerfd() system call that allows to receive timer 1503 events on a file descriptor. 1504 1505 If unsure, say Y. 1506 1507config EVENTFD 1508 bool "Enable eventfd() system call" if EXPERT 1509 default y 1510 help 1511 Enable the eventfd() system call that allows to receive both 1512 kernel notification (ie. KAIO) or userspace notifications. 1513 1514 If unsure, say Y. 1515 1516config SHMEM 1517 bool "Use full shmem filesystem" if EXPERT 1518 default y 1519 depends on MMU 1520 help 1521 The shmem is an internal filesystem used to manage shared memory. 1522 It is backed by swap and manages resource limits. It is also exported 1523 to userspace as tmpfs if TMPFS is enabled. Disabling this 1524 option replaces shmem and tmpfs with the much simpler ramfs code, 1525 which may be appropriate on small systems without swap. 1526 1527config AIO 1528 bool "Enable AIO support" if EXPERT 1529 default y 1530 help 1531 This option enables POSIX asynchronous I/O which may by used 1532 by some high performance threaded applications. Disabling 1533 this option saves about 7k. 1534 1535config IO_URING 1536 bool "Enable IO uring support" if EXPERT 1537 select ANON_INODES 1538 select IO_WQ 1539 default y 1540 help 1541 This option enables support for the io_uring interface, enabling 1542 applications to submit and complete IO through submission and 1543 completion rings that are shared between the kernel and application. 1544 1545config ADVISE_SYSCALLS 1546 bool "Enable madvise/fadvise syscalls" if EXPERT 1547 default y 1548 help 1549 This option enables the madvise and fadvise syscalls, used by 1550 applications to advise the kernel about their future memory or file 1551 usage, improving performance. If building an embedded system where no 1552 applications use these syscalls, you can disable this option to save 1553 space. 1554 1555config MEMBARRIER 1556 bool "Enable membarrier() system call" if EXPERT 1557 default y 1558 help 1559 Enable the membarrier() system call that allows issuing memory 1560 barriers across all running threads, which can be used to distribute 1561 the cost of user-space memory barriers asymmetrically by transforming 1562 pairs of memory barriers into pairs consisting of membarrier() and a 1563 compiler barrier. 1564 1565 If unsure, say Y. 1566 1567config KALLSYMS 1568 bool "Load all symbols for debugging/ksymoops" if EXPERT 1569 default y 1570 help 1571 Say Y here to let the kernel print out symbolic crash information and 1572 symbolic stack backtraces. This increases the size of the kernel 1573 somewhat, as all symbols have to be loaded into the kernel image. 1574 1575config KALLSYMS_ALL 1576 bool "Include all symbols in kallsyms" 1577 depends on DEBUG_KERNEL && KALLSYMS 1578 help 1579 Normally kallsyms only contains the symbols of functions for nicer 1580 OOPS messages and backtraces (i.e., symbols from the text and inittext 1581 sections). This is sufficient for most cases. And only in very rare 1582 cases (e.g., when a debugger is used) all symbols are required (e.g., 1583 names of variables from the data sections, etc). 1584 1585 This option makes sure that all symbols are loaded into the kernel 1586 image (i.e., symbols from all sections) in cost of increased kernel 1587 size (depending on the kernel configuration, it may be 300KiB or 1588 something like this). 1589 1590 Say N unless you really need all symbols. 1591 1592config KALLSYMS_ABSOLUTE_PERCPU 1593 bool 1594 depends on KALLSYMS 1595 default X86_64 && SMP 1596 1597config KALLSYMS_BASE_RELATIVE 1598 bool 1599 depends on KALLSYMS 1600 default !IA64 1601 help 1602 Instead of emitting them as absolute values in the native word size, 1603 emit the symbol references in the kallsyms table as 32-bit entries, 1604 each containing a relative value in the range [base, base + U32_MAX] 1605 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1606 an absolute value in the range [0, S32_MAX] or a relative value in the 1607 range [base, base + S32_MAX], where base is the lowest relative symbol 1608 address encountered in the image. 1609 1610 On 64-bit builds, this reduces the size of the address table by 50%, 1611 but more importantly, it results in entries whose values are build 1612 time constants, and no relocation pass is required at runtime to fix 1613 up the entries based on the runtime load address of the kernel. 1614 1615# end of the "standard kernel features (expert users)" menu 1616 1617# syscall, maps, verifier 1618config BPF_SYSCALL 1619 bool "Enable bpf() system call" 1620 select BPF 1621 select IRQ_WORK 1622 default n 1623 help 1624 Enable the bpf() system call that allows to manipulate eBPF 1625 programs and maps via file descriptors. 1626 1627config ARCH_WANT_DEFAULT_BPF_JIT 1628 bool 1629 1630config BPF_JIT_ALWAYS_ON 1631 bool "Permanently enable BPF JIT and remove BPF interpreter" 1632 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1633 help 1634 Enables BPF JIT and removes BPF interpreter to avoid 1635 speculative execution of BPF instructions by the interpreter 1636 1637config BPF_JIT_DEFAULT_ON 1638 def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON 1639 depends on HAVE_EBPF_JIT && BPF_JIT 1640 1641config USERFAULTFD 1642 bool "Enable userfaultfd() system call" 1643 depends on MMU 1644 help 1645 Enable the userfaultfd() system call that allows to intercept and 1646 handle page faults in userland. 1647 1648config ARCH_HAS_MEMBARRIER_CALLBACKS 1649 bool 1650 1651config ARCH_HAS_MEMBARRIER_SYNC_CORE 1652 bool 1653 1654config RSEQ 1655 bool "Enable rseq() system call" if EXPERT 1656 default y 1657 depends on HAVE_RSEQ 1658 select MEMBARRIER 1659 help 1660 Enable the restartable sequences system call. It provides a 1661 user-space cache for the current CPU number value, which 1662 speeds up getting the current CPU number from user-space, 1663 as well as an ABI to speed up user-space operations on 1664 per-CPU data. 1665 1666 If unsure, say Y. 1667 1668config DEBUG_RSEQ 1669 default n 1670 bool "Enabled debugging of rseq() system call" if EXPERT 1671 depends on RSEQ && DEBUG_KERNEL 1672 help 1673 Enable extra debugging checks for the rseq system call. 1674 1675 If unsure, say N. 1676 1677config EMBEDDED 1678 bool "Embedded system" 1679 option allnoconfig_y 1680 select EXPERT 1681 help 1682 This option should be enabled if compiling the kernel for 1683 an embedded system so certain expert options are available 1684 for configuration. 1685 1686config HAVE_PERF_EVENTS 1687 bool 1688 help 1689 See tools/perf/design.txt for details. 1690 1691config PERF_USE_VMALLOC 1692 bool 1693 help 1694 See tools/perf/design.txt for details 1695 1696config PC104 1697 bool "PC/104 support" if EXPERT 1698 help 1699 Expose PC/104 form factor device drivers and options available for 1700 selection and configuration. Enable this option if your target 1701 machine has a PC/104 bus. 1702 1703menu "Kernel Performance Events And Counters" 1704 1705config PERF_EVENTS 1706 bool "Kernel performance events and counters" 1707 default y if PROFILING 1708 depends on HAVE_PERF_EVENTS 1709 select IRQ_WORK 1710 select SRCU 1711 help 1712 Enable kernel support for various performance events provided 1713 by software and hardware. 1714 1715 Software events are supported either built-in or via the 1716 use of generic tracepoints. 1717 1718 Most modern CPUs support performance events via performance 1719 counter registers. These registers count the number of certain 1720 types of hw events: such as instructions executed, cachemisses 1721 suffered, or branches mis-predicted - without slowing down the 1722 kernel or applications. These registers can also trigger interrupts 1723 when a threshold number of events have passed - and can thus be 1724 used to profile the code that runs on that CPU. 1725 1726 The Linux Performance Event subsystem provides an abstraction of 1727 these software and hardware event capabilities, available via a 1728 system call and used by the "perf" utility in tools/perf/. It 1729 provides per task and per CPU counters, and it provides event 1730 capabilities on top of those. 1731 1732 Say Y if unsure. 1733 1734config DEBUG_PERF_USE_VMALLOC 1735 default n 1736 bool "Debug: use vmalloc to back perf mmap() buffers" 1737 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1738 select PERF_USE_VMALLOC 1739 help 1740 Use vmalloc memory to back perf mmap() buffers. 1741 1742 Mostly useful for debugging the vmalloc code on platforms 1743 that don't require it. 1744 1745 Say N if unsure. 1746 1747endmenu 1748 1749config VM_EVENT_COUNTERS 1750 default y 1751 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1752 help 1753 VM event counters are needed for event counts to be shown. 1754 This option allows the disabling of the VM event counters 1755 on EXPERT systems. /proc/vmstat will only show page counts 1756 if VM event counters are disabled. 1757 1758config SLUB_DEBUG 1759 default y 1760 bool "Enable SLUB debugging support" if EXPERT 1761 depends on SLUB && SYSFS 1762 help 1763 SLUB has extensive debug support features. Disabling these can 1764 result in significant savings in code size. This also disables 1765 SLUB sysfs support. /sys/slab will not exist and there will be 1766 no support for cache validation etc. 1767 1768config SLUB_MEMCG_SYSFS_ON 1769 default n 1770 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1771 depends on SLUB && SYSFS && MEMCG 1772 help 1773 SLUB creates a directory under /sys/kernel/slab for each 1774 allocation cache to host info and debug files. If memory 1775 cgroup is enabled, each cache can have per memory cgroup 1776 caches. SLUB can create the same sysfs directories for these 1777 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1778 to a very high number of debug files being created. This is 1779 controlled by slub_memcg_sysfs boot parameter and this 1780 config option determines the parameter's default value. 1781 1782config COMPAT_BRK 1783 bool "Disable heap randomization" 1784 default y 1785 help 1786 Randomizing heap placement makes heap exploits harder, but it 1787 also breaks ancient binaries (including anything libc5 based). 1788 This option changes the bootup default to heap randomization 1789 disabled, and can be overridden at runtime by setting 1790 /proc/sys/kernel/randomize_va_space to 2. 1791 1792 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1793 1794choice 1795 prompt "Choose SLAB allocator" 1796 default SLUB 1797 help 1798 This option allows to select a slab allocator. 1799 1800config SLAB 1801 bool "SLAB" 1802 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1803 help 1804 The regular slab allocator that is established and known to work 1805 well in all environments. It organizes cache hot objects in 1806 per cpu and per node queues. 1807 1808config SLUB 1809 bool "SLUB (Unqueued Allocator)" 1810 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1811 help 1812 SLUB is a slab allocator that minimizes cache line usage 1813 instead of managing queues of cached objects (SLAB approach). 1814 Per cpu caching is realized using slabs of objects instead 1815 of queues of objects. SLUB can use memory efficiently 1816 and has enhanced diagnostics. SLUB is the default choice for 1817 a slab allocator. 1818 1819config SLOB 1820 depends on EXPERT 1821 bool "SLOB (Simple Allocator)" 1822 help 1823 SLOB replaces the stock allocator with a drastically simpler 1824 allocator. SLOB is generally more space efficient but 1825 does not perform as well on large systems. 1826 1827endchoice 1828 1829config SLAB_MERGE_DEFAULT 1830 bool "Allow slab caches to be merged" 1831 default y 1832 help 1833 For reduced kernel memory fragmentation, slab caches can be 1834 merged when they share the same size and other characteristics. 1835 This carries a risk of kernel heap overflows being able to 1836 overwrite objects from merged caches (and more easily control 1837 cache layout), which makes such heap attacks easier to exploit 1838 by attackers. By keeping caches unmerged, these kinds of exploits 1839 can usually only damage objects in the same cache. To disable 1840 merging at runtime, "slab_nomerge" can be passed on the kernel 1841 command line. 1842 1843config SLAB_FREELIST_RANDOM 1844 default n 1845 depends on SLAB || SLUB 1846 bool "SLAB freelist randomization" 1847 help 1848 Randomizes the freelist order used on creating new pages. This 1849 security feature reduces the predictability of the kernel slab 1850 allocator against heap overflows. 1851 1852config SLAB_FREELIST_HARDENED 1853 bool "Harden slab freelist metadata" 1854 depends on SLUB 1855 help 1856 Many kernel heap attacks try to target slab cache metadata and 1857 other infrastructure. This options makes minor performance 1858 sacrifices to harden the kernel slab allocator against common 1859 freelist exploit methods. 1860 1861config SHUFFLE_PAGE_ALLOCATOR 1862 bool "Page allocator randomization" 1863 default SLAB_FREELIST_RANDOM && ACPI_NUMA 1864 help 1865 Randomization of the page allocator improves the average 1866 utilization of a direct-mapped memory-side-cache. See section 1867 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 1868 6.2a specification for an example of how a platform advertises 1869 the presence of a memory-side-cache. There are also incidental 1870 security benefits as it reduces the predictability of page 1871 allocations to compliment SLAB_FREELIST_RANDOM, but the 1872 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 1873 10th order of pages is selected based on cache utilization 1874 benefits on x86. 1875 1876 While the randomization improves cache utilization it may 1877 negatively impact workloads on platforms without a cache. For 1878 this reason, by default, the randomization is enabled only 1879 after runtime detection of a direct-mapped memory-side-cache. 1880 Otherwise, the randomization may be force enabled with the 1881 'page_alloc.shuffle' kernel command line parameter. 1882 1883 Say Y if unsure. 1884 1885config SLUB_CPU_PARTIAL 1886 default y 1887 depends on SLUB && SMP 1888 bool "SLUB per cpu partial cache" 1889 help 1890 Per cpu partial caches accelerate objects allocation and freeing 1891 that is local to a processor at the price of more indeterminism 1892 in the latency of the free. On overflow these caches will be cleared 1893 which requires the taking of locks that may cause latency spikes. 1894 Typically one would choose no for a realtime system. 1895 1896config MMAP_ALLOW_UNINITIALIZED 1897 bool "Allow mmapped anonymous memory to be uninitialized" 1898 depends on EXPERT && !MMU 1899 default n 1900 help 1901 Normally, and according to the Linux spec, anonymous memory obtained 1902 from mmap() has its contents cleared before it is passed to 1903 userspace. Enabling this config option allows you to request that 1904 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1905 providing a huge performance boost. If this option is not enabled, 1906 then the flag will be ignored. 1907 1908 This is taken advantage of by uClibc's malloc(), and also by 1909 ELF-FDPIC binfmt's brk and stack allocator. 1910 1911 Because of the obvious security issues, this option should only be 1912 enabled on embedded devices where you control what is run in 1913 userspace. Since that isn't generally a problem on no-MMU systems, 1914 it is normally safe to say Y here. 1915 1916 See Documentation/nommu-mmap.txt for more information. 1917 1918config SYSTEM_DATA_VERIFICATION 1919 def_bool n 1920 select SYSTEM_TRUSTED_KEYRING 1921 select KEYS 1922 select CRYPTO 1923 select CRYPTO_RSA 1924 select ASYMMETRIC_KEY_TYPE 1925 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1926 select ASN1 1927 select OID_REGISTRY 1928 select X509_CERTIFICATE_PARSER 1929 select PKCS7_MESSAGE_PARSER 1930 help 1931 Provide PKCS#7 message verification using the contents of the system 1932 trusted keyring to provide public keys. This then can be used for 1933 module verification, kexec image verification and firmware blob 1934 verification. 1935 1936config PROFILING 1937 bool "Profiling support" 1938 help 1939 Say Y here to enable the extended profiling support mechanisms used 1940 by profilers such as OProfile. 1941 1942# 1943# Place an empty function call at each tracepoint site. Can be 1944# dynamically changed for a probe function. 1945# 1946config TRACEPOINTS 1947 bool 1948 1949endmenu # General setup 1950 1951source "arch/Kconfig" 1952 1953config RT_MUTEXES 1954 bool 1955 1956config BASE_SMALL 1957 int 1958 default 0 if BASE_FULL 1959 default 1 if !BASE_FULL 1960 1961config MODULE_SIG_FORMAT 1962 def_bool n 1963 select SYSTEM_DATA_VERIFICATION 1964 1965menuconfig MODULES 1966 bool "Enable loadable module support" 1967 option modules 1968 help 1969 Kernel modules are small pieces of compiled code which can 1970 be inserted in the running kernel, rather than being 1971 permanently built into the kernel. You use the "modprobe" 1972 tool to add (and sometimes remove) them. If you say Y here, 1973 many parts of the kernel can be built as modules (by 1974 answering M instead of Y where indicated): this is most 1975 useful for infrequently used options which are not required 1976 for booting. For more information, see the man pages for 1977 modprobe, lsmod, modinfo, insmod and rmmod. 1978 1979 If you say Y here, you will need to run "make 1980 modules_install" to put the modules under /lib/modules/ 1981 where modprobe can find them (you may need to be root to do 1982 this). 1983 1984 If unsure, say Y. 1985 1986if MODULES 1987 1988config MODULE_FORCE_LOAD 1989 bool "Forced module loading" 1990 default n 1991 help 1992 Allow loading of modules without version information (ie. modprobe 1993 --force). Forced module loading sets the 'F' (forced) taint flag and 1994 is usually a really bad idea. 1995 1996config MODULE_UNLOAD 1997 bool "Module unloading" 1998 help 1999 Without this option you will not be able to unload any 2000 modules (note that some modules may not be unloadable 2001 anyway), which makes your kernel smaller, faster 2002 and simpler. If unsure, say Y. 2003 2004config MODULE_FORCE_UNLOAD 2005 bool "Forced module unloading" 2006 depends on MODULE_UNLOAD 2007 help 2008 This option allows you to force a module to unload, even if the 2009 kernel believes it is unsafe: the kernel will remove the module 2010 without waiting for anyone to stop using it (using the -f option to 2011 rmmod). This is mainly for kernel developers and desperate users. 2012 If unsure, say N. 2013 2014config MODVERSIONS 2015 bool "Module versioning support" 2016 help 2017 Usually, you have to use modules compiled with your kernel. 2018 Saying Y here makes it sometimes possible to use modules 2019 compiled for different kernels, by adding enough information 2020 to the modules to (hopefully) spot any changes which would 2021 make them incompatible with the kernel you are running. If 2022 unsure, say N. 2023 2024config ASM_MODVERSIONS 2025 bool 2026 default HAVE_ASM_MODVERSIONS && MODVERSIONS 2027 help 2028 This enables module versioning for exported symbols also from 2029 assembly. This can be enabled only when the target architecture 2030 supports it. 2031 2032config MODULE_REL_CRCS 2033 bool 2034 depends on MODVERSIONS 2035 2036config MODULE_SRCVERSION_ALL 2037 bool "Source checksum for all modules" 2038 help 2039 Modules which contain a MODULE_VERSION get an extra "srcversion" 2040 field inserted into their modinfo section, which contains a 2041 sum of the source files which made it. This helps maintainers 2042 see exactly which source was used to build a module (since 2043 others sometimes change the module source without updating 2044 the version). With this option, such a "srcversion" field 2045 will be created for all modules. If unsure, say N. 2046 2047config MODULE_SIG 2048 bool "Module signature verification" 2049 select MODULE_SIG_FORMAT 2050 help 2051 Check modules for valid signatures upon load: the signature 2052 is simply appended to the module. For more information see 2053 <file:Documentation/admin-guide/module-signing.rst>. 2054 2055 Note that this option adds the OpenSSL development packages as a 2056 kernel build dependency so that the signing tool can use its crypto 2057 library. 2058 2059 You should enable this option if you wish to use either 2060 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via 2061 another LSM - otherwise unsigned modules will be loadable regardless 2062 of the lockdown policy. 2063 2064 !!!WARNING!!! If you enable this option, you MUST make sure that the 2065 module DOES NOT get stripped after being signed. This includes the 2066 debuginfo strip done by some packagers (such as rpmbuild) and 2067 inclusion into an initramfs that wants the module size reduced. 2068 2069config MODULE_SIG_FORCE 2070 bool "Require modules to be validly signed" 2071 depends on MODULE_SIG 2072 help 2073 Reject unsigned modules or signed modules for which we don't have a 2074 key. Without this, such modules will simply taint the kernel. 2075 2076config MODULE_SIG_ALL 2077 bool "Automatically sign all modules" 2078 default y 2079 depends on MODULE_SIG 2080 help 2081 Sign all modules during make modules_install. Without this option, 2082 modules must be signed manually, using the scripts/sign-file tool. 2083 2084comment "Do not forget to sign required modules with scripts/sign-file" 2085 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2086 2087choice 2088 prompt "Which hash algorithm should modules be signed with?" 2089 depends on MODULE_SIG 2090 help 2091 This determines which sort of hashing algorithm will be used during 2092 signature generation. This algorithm _must_ be built into the kernel 2093 directly so that signature verification can take place. It is not 2094 possible to load a signed module containing the algorithm to check 2095 the signature on that module. 2096 2097config MODULE_SIG_SHA1 2098 bool "Sign modules with SHA-1" 2099 select CRYPTO_SHA1 2100 2101config MODULE_SIG_SHA224 2102 bool "Sign modules with SHA-224" 2103 select CRYPTO_SHA256 2104 2105config MODULE_SIG_SHA256 2106 bool "Sign modules with SHA-256" 2107 select CRYPTO_SHA256 2108 2109config MODULE_SIG_SHA384 2110 bool "Sign modules with SHA-384" 2111 select CRYPTO_SHA512 2112 2113config MODULE_SIG_SHA512 2114 bool "Sign modules with SHA-512" 2115 select CRYPTO_SHA512 2116 2117endchoice 2118 2119config MODULE_SIG_HASH 2120 string 2121 depends on MODULE_SIG 2122 default "sha1" if MODULE_SIG_SHA1 2123 default "sha224" if MODULE_SIG_SHA224 2124 default "sha256" if MODULE_SIG_SHA256 2125 default "sha384" if MODULE_SIG_SHA384 2126 default "sha512" if MODULE_SIG_SHA512 2127 2128config MODULE_COMPRESS 2129 bool "Compress modules on installation" 2130 help 2131 2132 Compresses kernel modules when 'make modules_install' is run; gzip or 2133 xz depending on "Compression algorithm" below. 2134 2135 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 2136 2137 Out-of-tree kernel modules installed using Kbuild will also be 2138 compressed upon installation. 2139 2140 Note: for modules inside an initrd or initramfs, it's more efficient 2141 to compress the whole initrd or initramfs instead. 2142 2143 Note: This is fully compatible with signed modules. 2144 2145 If in doubt, say N. 2146 2147choice 2148 prompt "Compression algorithm" 2149 depends on MODULE_COMPRESS 2150 default MODULE_COMPRESS_GZIP 2151 help 2152 This determines which sort of compression will be used during 2153 'make modules_install'. 2154 2155 GZIP (default) and XZ are supported. 2156 2157config MODULE_COMPRESS_GZIP 2158 bool "GZIP" 2159 2160config MODULE_COMPRESS_XZ 2161 bool "XZ" 2162 2163endchoice 2164 2165config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS 2166 bool "Allow loading of modules with missing namespace imports" 2167 help 2168 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in 2169 a namespace. A module that makes use of a symbol exported with such a 2170 namespace is required to import the namespace via MODULE_IMPORT_NS(). 2171 There is no technical reason to enforce correct namespace imports, 2172 but it creates consistency between symbols defining namespaces and 2173 users importing namespaces they make use of. This option relaxes this 2174 requirement and lifts the enforcement when loading a module. 2175 2176 If unsure, say N. 2177 2178config UNUSED_SYMBOLS 2179 bool "Enable unused/obsolete exported symbols" 2180 default y if X86 2181 help 2182 Unused but exported symbols make the kernel needlessly bigger. For 2183 that reason most of these unused exports will soon be removed. This 2184 option is provided temporarily to provide a transition period in case 2185 some external kernel module needs one of these symbols anyway. If you 2186 encounter such a case in your module, consider if you are actually 2187 using the right API. (rationale: since nobody in the kernel is using 2188 this in a module, there is a pretty good chance it's actually the 2189 wrong interface to use). If you really need the symbol, please send a 2190 mail to the linux kernel mailing list mentioning the symbol and why 2191 you really need it, and what the merge plan to the mainline kernel for 2192 your module is. 2193 2194config TRIM_UNUSED_KSYMS 2195 bool "Trim unused exported kernel symbols" 2196 depends on !UNUSED_SYMBOLS 2197 help 2198 The kernel and some modules make many symbols available for 2199 other modules to use via EXPORT_SYMBOL() and variants. Depending 2200 on the set of modules being selected in your kernel configuration, 2201 many of those exported symbols might never be used. 2202 2203 This option allows for unused exported symbols to be dropped from 2204 the build. In turn, this provides the compiler more opportunities 2205 (especially when using LTO) for optimizing the code and reducing 2206 binary size. This might have some security advantages as well. 2207 2208 If unsure, or if you need to build out-of-tree modules, say N. 2209 2210endif # MODULES 2211 2212config MODULES_TREE_LOOKUP 2213 def_bool y 2214 depends on PERF_EVENTS || TRACING 2215 2216config INIT_ALL_POSSIBLE 2217 bool 2218 help 2219 Back when each arch used to define their own cpu_online_mask and 2220 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2221 with all 1s, and others with all 0s. When they were centralised, 2222 it was better to provide this option than to break all the archs 2223 and have several arch maintainers pursuing me down dark alleys. 2224 2225source "block/Kconfig" 2226 2227config PREEMPT_NOTIFIERS 2228 bool 2229 2230config PADATA 2231 depends on SMP 2232 bool 2233 2234config ASN1 2235 tristate 2236 help 2237 Build a simple ASN.1 grammar compiler that produces a bytecode output 2238 that can be interpreted by the ASN.1 stream decoder and used to 2239 inform it as to what tags are to be expected in a stream and what 2240 functions to call on what tags. 2241 2242source "kernel/Kconfig.locks" 2243 2244config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2245 bool 2246 2247# It may be useful for an architecture to override the definitions of the 2248# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2249# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2250# different calling convention for syscalls. They can also override the 2251# macros for not-implemented syscalls in kernel/sys_ni.c and 2252# kernel/time/posix-stubs.c. All these overrides need to be available in 2253# <asm/syscall_wrapper.h>. 2254config ARCH_HAS_SYSCALL_WRAPPER 2255 def_bool n 2256