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