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_VERSION_TEXT 12 string 13 default "$(CC_VERSION_TEXT)" 14 help 15 This is used in unclear ways: 16 17 - Re-run Kconfig when the compiler is updated 18 The 'default' property references the environment variable, 19 CC_VERSION_TEXT so it is recorded in include/config/auto.conf.cmd. 20 When the compiler is updated, Kconfig will be invoked. 21 22 - Ensure full rebuild when the compier is updated 23 include/linux/kconfig.h contains this option in the comment line so 24 fixdep adds include/config/cc/version/text.h into the auto-generated 25 dependency. When the compiler is updated, syncconfig will touch it 26 and then every file will be rebuilt. 27 28config CC_IS_GCC 29 def_bool $(success,echo "$(CC_VERSION_TEXT)" | grep -q gcc) 30 31config GCC_VERSION 32 int 33 default $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) if CC_IS_GCC 34 default 0 35 36config LD_VERSION 37 int 38 default $(shell,$(LD) --version | $(srctree)/scripts/ld-version.sh) 39 40config CC_IS_CLANG 41 def_bool $(success,echo "$(CC_VERSION_TEXT)" | grep -q clang) 42 43config LD_IS_LLD 44 def_bool $(success,$(LD) -v | head -n 1 | grep -q LLD) 45 46config CLANG_VERSION 47 int 48 default $(shell,$(srctree)/scripts/clang-version.sh $(CC)) 49 50config LLD_VERSION 51 int 52 default $(shell,$(srctree)/scripts/lld-version.sh $(LD)) 53 54config CC_CAN_LINK 55 bool 56 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT 57 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag)) 58 59config CC_CAN_LINK_STATIC 60 bool 61 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag) -static) if 64BIT 62 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag) -static) 63 64config CC_HAS_ASM_GOTO 65 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) 66 67config CC_HAS_ASM_GOTO_OUTPUT 68 depends on CC_HAS_ASM_GOTO 69 def_bool $(success,echo 'int foo(int x) { asm goto ("": "=r"(x) ::: bar); return x; bar: return 0; }' | $(CC) -x c - -c -o /dev/null) 70 71config CC_HAS_ASM_GOTO_TIED_OUTPUT 72 depends on CC_HAS_ASM_GOTO_OUTPUT 73 # Detect buggy gcc and clang, fixed in gcc-11 clang-14. 74 def_bool $(success,echo 'int foo(int *x) { asm goto (".long (%l[bar]) - .": "+m"(*x) ::: bar); return *x; bar: return 0; }' | $CC -x c - -c -o /dev/null) 75 76config TOOLS_SUPPORT_RELR 77 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) 78 79config CC_HAS_ASM_INLINE 80 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) 81 82config CONSTRUCTORS 83 bool 84 depends on !UML 85 86config IRQ_WORK 87 bool 88 89config BUILDTIME_TABLE_SORT 90 bool 91 92config THREAD_INFO_IN_TASK 93 bool 94 help 95 Select this to move thread_info off the stack into task_struct. To 96 make this work, an arch will need to remove all thread_info fields 97 except flags and fix any runtime bugs. 98 99 One subtle change that will be needed is to use try_get_task_stack() 100 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 101 102menu "General setup" 103 104config BROKEN 105 bool 106 107config BROKEN_ON_SMP 108 bool 109 depends on BROKEN || !SMP 110 default y 111 112config INIT_ENV_ARG_LIMIT 113 int 114 default 32 if !UML 115 default 128 if UML 116 help 117 Maximum of each of the number of arguments and environment 118 variables passed to init from the kernel command line. 119 120config COMPILE_TEST 121 bool "Compile also drivers which will not load" 122 depends on HAS_IOMEM 123 help 124 Some drivers can be compiled on a different platform than they are 125 intended to be run on. Despite they cannot be loaded there (or even 126 when they load they cannot be used due to missing HW support), 127 developers still, opposing to distributors, might want to build such 128 drivers to compile-test them. 129 130 If you are a developer and want to build everything available, say Y 131 here. If you are a user/distributor, say N here to exclude useless 132 drivers to be distributed. 133 134config WERROR 135 bool "Compile the kernel with warnings as errors" 136 default y 137 help 138 A kernel build should not cause any compiler warnings, and this 139 enables the '-Werror' flag to enforce that rule by default. 140 141 However, if you have a new (or very old) compiler with odd and 142 unusual warnings, or you have some architecture with problems, 143 you may need to disable this config option in order to 144 successfully build the kernel. 145 146 If in doubt, say Y. 147 148config UAPI_HEADER_TEST 149 bool "Compile test UAPI headers" 150 depends on HEADERS_INSTALL && CC_CAN_LINK 151 help 152 Compile test headers exported to user-space to ensure they are 153 self-contained, i.e. compilable as standalone units. 154 155 If you are a developer or tester and want to ensure the exported 156 headers are self-contained, say Y here. Otherwise, choose N. 157 158config LOCALVERSION 159 string "Local version - append to kernel release" 160 help 161 Append an extra string to the end of your kernel version. 162 This will show up when you type uname, for example. 163 The string you set here will be appended after the contents of 164 any files with a filename matching localversion* in your 165 object and source tree, in that order. Your total string can 166 be a maximum of 64 characters. 167 168config LOCALVERSION_AUTO 169 bool "Automatically append version information to the version string" 170 default y 171 depends on !COMPILE_TEST 172 help 173 This will try to automatically determine if the current tree is a 174 release tree by looking for git tags that belong to the current 175 top of tree revision. 176 177 A string of the format -gxxxxxxxx will be added to the localversion 178 if a git-based tree is found. The string generated by this will be 179 appended after any matching localversion* files, and after the value 180 set in CONFIG_LOCALVERSION. 181 182 (The actual string used here is the first eight characters produced 183 by running the command: 184 185 $ git rev-parse --verify HEAD 186 187 which is done within the script "scripts/setlocalversion".) 188 189config BUILD_SALT 190 string "Build ID Salt" 191 default "" 192 help 193 The build ID is used to link binaries and their debug info. Setting 194 this option will use the value in the calculation of the build id. 195 This is mostly useful for distributions which want to ensure the 196 build is unique between builds. It's safe to leave the default. 197 198config HAVE_KERNEL_GZIP 199 bool 200 201config HAVE_KERNEL_BZIP2 202 bool 203 204config HAVE_KERNEL_LZMA 205 bool 206 207config HAVE_KERNEL_XZ 208 bool 209 210config HAVE_KERNEL_LZO 211 bool 212 213config HAVE_KERNEL_LZ4 214 bool 215 216config HAVE_KERNEL_ZSTD 217 bool 218 219config HAVE_KERNEL_UNCOMPRESSED 220 bool 221 222choice 223 prompt "Kernel compression mode" 224 default KERNEL_GZIP 225 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_ZSTD || HAVE_KERNEL_UNCOMPRESSED 226 help 227 The linux kernel is a kind of self-extracting executable. 228 Several compression algorithms are available, which differ 229 in efficiency, compression and decompression speed. 230 Compression speed is only relevant when building a kernel. 231 Decompression speed is relevant at each boot. 232 233 If you have any problems with bzip2 or lzma compressed 234 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 235 version of this functionality (bzip2 only), for 2.4, was 236 supplied by Christian Ludwig) 237 238 High compression options are mostly useful for users, who 239 are low on disk space (embedded systems), but for whom ram 240 size matters less. 241 242 If in doubt, select 'gzip' 243 244config KERNEL_GZIP 245 bool "Gzip" 246 depends on HAVE_KERNEL_GZIP 247 help 248 The old and tried gzip compression. It provides a good balance 249 between compression ratio and decompression speed. 250 251config KERNEL_BZIP2 252 bool "Bzip2" 253 depends on HAVE_KERNEL_BZIP2 254 help 255 Its compression ratio and speed is intermediate. 256 Decompression speed is slowest among the choices. The kernel 257 size is about 10% smaller with bzip2, in comparison to gzip. 258 Bzip2 uses a large amount of memory. For modern kernels you 259 will need at least 8MB RAM or more for booting. 260 261config KERNEL_LZMA 262 bool "LZMA" 263 depends on HAVE_KERNEL_LZMA 264 help 265 This compression algorithm's ratio is best. Decompression speed 266 is between gzip and bzip2. Compression is slowest. 267 The kernel size is about 33% smaller with LZMA in comparison to gzip. 268 269config KERNEL_XZ 270 bool "XZ" 271 depends on HAVE_KERNEL_XZ 272 help 273 XZ uses the LZMA2 algorithm and instruction set specific 274 BCJ filters which can improve compression ratio of executable 275 code. The size of the kernel is about 30% smaller with XZ in 276 comparison to gzip. On architectures for which there is a BCJ 277 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 278 will create a few percent smaller kernel than plain LZMA. 279 280 The speed is about the same as with LZMA: The decompression 281 speed of XZ is better than that of bzip2 but worse than gzip 282 and LZO. Compression is slow. 283 284config KERNEL_LZO 285 bool "LZO" 286 depends on HAVE_KERNEL_LZO 287 help 288 Its compression ratio is the poorest among the choices. The kernel 289 size is about 10% bigger than gzip; however its speed 290 (both compression and decompression) is the fastest. 291 292config KERNEL_LZ4 293 bool "LZ4" 294 depends on HAVE_KERNEL_LZ4 295 help 296 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 297 A preliminary version of LZ4 de/compression tool is available at 298 <https://code.google.com/p/lz4/>. 299 300 Its compression ratio is worse than LZO. The size of the kernel 301 is about 8% bigger than LZO. But the decompression speed is 302 faster than LZO. 303 304config KERNEL_ZSTD 305 bool "ZSTD" 306 depends on HAVE_KERNEL_ZSTD 307 help 308 ZSTD is a compression algorithm targeting intermediate compression 309 with fast decompression speed. It will compress better than GZIP and 310 decompress around the same speed as LZO, but slower than LZ4. You 311 will need at least 192 KB RAM or more for booting. The zstd command 312 line tool is required for compression. 313 314config KERNEL_UNCOMPRESSED 315 bool "None" 316 depends on HAVE_KERNEL_UNCOMPRESSED 317 help 318 Produce uncompressed kernel image. This option is usually not what 319 you want. It is useful for debugging the kernel in slow simulation 320 environments, where decompressing and moving the kernel is awfully 321 slow. This option allows early boot code to skip the decompressor 322 and jump right at uncompressed kernel image. 323 324endchoice 325 326config DEFAULT_INIT 327 string "Default init path" 328 default "" 329 help 330 This option determines the default init for the system if no init= 331 option is passed on the kernel command line. If the requested path is 332 not present, we will still then move on to attempting further 333 locations (e.g. /sbin/init, etc). If this is empty, we will just use 334 the fallback list when init= is not passed. 335 336config DEFAULT_HOSTNAME 337 string "Default hostname" 338 default "(none)" 339 help 340 This option determines the default system hostname before userspace 341 calls sethostname(2). The kernel traditionally uses "(none)" here, 342 but you may wish to use a different default here to make a minimal 343 system more usable with less configuration. 344 345# 346# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can 347# add proper SWAP support to them, in which case this can be remove. 348# 349config ARCH_NO_SWAP 350 bool 351 352config SWAP 353 bool "Support for paging of anonymous memory (swap)" 354 depends on MMU && BLOCK && !ARCH_NO_SWAP 355 default y 356 help 357 This option allows you to choose whether you want to have support 358 for so called swap devices or swap files in your kernel that are 359 used to provide more virtual memory than the actual RAM present 360 in your computer. If unsure say Y. 361 362config SYSVIPC 363 bool "System V IPC" 364 help 365 Inter Process Communication is a suite of library functions and 366 system calls which let processes (running programs) synchronize and 367 exchange information. It is generally considered to be a good thing, 368 and some programs won't run unless you say Y here. In particular, if 369 you want to run the DOS emulator dosemu under Linux (read the 370 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 371 you'll need to say Y here. 372 373 You can find documentation about IPC with "info ipc" and also in 374 section 6.4 of the Linux Programmer's Guide, available from 375 <http://www.tldp.org/guides.html>. 376 377config SYSVIPC_SYSCTL 378 bool 379 depends on SYSVIPC 380 depends on SYSCTL 381 default y 382 383config POSIX_MQUEUE 384 bool "POSIX Message Queues" 385 depends on NET 386 help 387 POSIX variant of message queues is a part of IPC. In POSIX message 388 queues every message has a priority which decides about succession 389 of receiving it by a process. If you want to compile and run 390 programs written e.g. for Solaris with use of its POSIX message 391 queues (functions mq_*) say Y here. 392 393 POSIX message queues are visible as a filesystem called 'mqueue' 394 and can be mounted somewhere if you want to do filesystem 395 operations on message queues. 396 397 If unsure, say Y. 398 399config POSIX_MQUEUE_SYSCTL 400 bool 401 depends on POSIX_MQUEUE 402 depends on SYSCTL 403 default y 404 405config WATCH_QUEUE 406 bool "General notification queue" 407 default n 408 help 409 410 This is a general notification queue for the kernel to pass events to 411 userspace by splicing them into pipes. It can be used in conjunction 412 with watches for key/keyring change notifications and device 413 notifications. 414 415 See Documentation/watch_queue.rst 416 417config CROSS_MEMORY_ATTACH 418 bool "Enable process_vm_readv/writev syscalls" 419 depends on MMU 420 default y 421 help 422 Enabling this option adds the system calls process_vm_readv and 423 process_vm_writev which allow a process with the correct privileges 424 to directly read from or write to another process' address space. 425 See the man page for more details. 426 427config USELIB 428 bool "uselib syscall" 429 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION 430 help 431 This option enables the uselib syscall, a system call used in the 432 dynamic linker from libc5 and earlier. glibc does not use this 433 system call. If you intend to run programs built on libc5 or 434 earlier, you may need to enable this syscall. Current systems 435 running glibc can safely disable this. 436 437config AUDIT 438 bool "Auditing support" 439 depends on NET 440 help 441 Enable auditing infrastructure that can be used with another 442 kernel subsystem, such as SELinux (which requires this for 443 logging of avc messages output). System call auditing is included 444 on architectures which support it. 445 446config HAVE_ARCH_AUDITSYSCALL 447 bool 448 449config AUDITSYSCALL 450 def_bool y 451 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 452 select FSNOTIFY 453 454source "kernel/irq/Kconfig" 455source "kernel/time/Kconfig" 456source "kernel/Kconfig.preempt" 457 458menu "CPU/Task time and stats accounting" 459 460config VIRT_CPU_ACCOUNTING 461 bool 462 463choice 464 prompt "Cputime accounting" 465 default TICK_CPU_ACCOUNTING if !PPC64 466 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 467 468# Kind of a stub config for the pure tick based cputime accounting 469config TICK_CPU_ACCOUNTING 470 bool "Simple tick based cputime accounting" 471 depends on !S390 && !NO_HZ_FULL 472 help 473 This is the basic tick based cputime accounting that maintains 474 statistics about user, system and idle time spent on per jiffies 475 granularity. 476 477 If unsure, say Y. 478 479config VIRT_CPU_ACCOUNTING_NATIVE 480 bool "Deterministic task and CPU time accounting" 481 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 482 select VIRT_CPU_ACCOUNTING 483 help 484 Select this option to enable more accurate task and CPU time 485 accounting. This is done by reading a CPU counter on each 486 kernel entry and exit and on transitions within the kernel 487 between system, softirq and hardirq state, so there is a 488 small performance impact. In the case of s390 or IBM POWER > 5, 489 this also enables accounting of stolen time on logically-partitioned 490 systems. 491 492config VIRT_CPU_ACCOUNTING_GEN 493 bool "Full dynticks CPU time accounting" 494 depends on HAVE_CONTEXT_TRACKING 495 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 496 depends on GENERIC_CLOCKEVENTS 497 select VIRT_CPU_ACCOUNTING 498 select CONTEXT_TRACKING 499 help 500 Select this option to enable task and CPU time accounting on full 501 dynticks systems. This accounting is implemented by watching every 502 kernel-user boundaries using the context tracking subsystem. 503 The accounting is thus performed at the expense of some significant 504 overhead. 505 506 For now this is only useful if you are working on the full 507 dynticks subsystem development. 508 509 If unsure, say N. 510 511endchoice 512 513config IRQ_TIME_ACCOUNTING 514 bool "Fine granularity task level IRQ time accounting" 515 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 516 help 517 Select this option to enable fine granularity task irq time 518 accounting. This is done by reading a timestamp on each 519 transitions between softirq and hardirq state, so there can be a 520 small performance impact. 521 522 If in doubt, say N here. 523 524config HAVE_SCHED_AVG_IRQ 525 def_bool y 526 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING 527 depends on SMP 528 529config SCHED_THERMAL_PRESSURE 530 bool 531 default y if ARM && ARM_CPU_TOPOLOGY 532 default y if ARM64 533 depends on SMP 534 depends on CPU_FREQ_THERMAL 535 help 536 Select this option to enable thermal pressure accounting in the 537 scheduler. Thermal pressure is the value conveyed to the scheduler 538 that reflects the reduction in CPU compute capacity resulted from 539 thermal throttling. Thermal throttling occurs when the performance of 540 a CPU is capped due to high operating temperatures. 541 542 If selected, the scheduler will be able to balance tasks accordingly, 543 i.e. put less load on throttled CPUs than on non/less throttled ones. 544 545 This requires the architecture to implement 546 arch_set_thermal_pressure() and arch_get_thermal_pressure(). 547 548config BSD_PROCESS_ACCT 549 bool "BSD Process Accounting" 550 depends on MULTIUSER 551 help 552 If you say Y here, a user level program will be able to instruct the 553 kernel (via a special system call) to write process accounting 554 information to a file: whenever a process exits, information about 555 that process will be appended to the file by the kernel. The 556 information includes things such as creation time, owning user, 557 command name, memory usage, controlling terminal etc. (the complete 558 list is in the struct acct in <file:include/linux/acct.h>). It is 559 up to the user level program to do useful things with this 560 information. This is generally a good idea, so say Y. 561 562config BSD_PROCESS_ACCT_V3 563 bool "BSD Process Accounting version 3 file format" 564 depends on BSD_PROCESS_ACCT 565 default n 566 help 567 If you say Y here, the process accounting information is written 568 in a new file format that also logs the process IDs of each 569 process and its parent. Note that this file format is incompatible 570 with previous v0/v1/v2 file formats, so you will need updated tools 571 for processing it. A preliminary version of these tools is available 572 at <http://www.gnu.org/software/acct/>. 573 574config TASKSTATS 575 bool "Export task/process statistics through netlink" 576 depends on NET 577 depends on MULTIUSER 578 default n 579 help 580 Export selected statistics for tasks/processes through the 581 generic netlink interface. Unlike BSD process accounting, the 582 statistics are available during the lifetime of tasks/processes as 583 responses to commands. Like BSD accounting, they are sent to user 584 space on task exit. 585 586 Say N if unsure. 587 588config TASK_DELAY_ACCT 589 bool "Enable per-task delay accounting" 590 depends on TASKSTATS 591 select SCHED_INFO 592 help 593 Collect information on time spent by a task waiting for system 594 resources like cpu, synchronous block I/O completion and swapping 595 in pages. Such statistics can help in setting a task's priorities 596 relative to other tasks for cpu, io, rss limits etc. 597 598 Say N if unsure. 599 600config TASK_XACCT 601 bool "Enable extended accounting over taskstats" 602 depends on TASKSTATS 603 help 604 Collect extended task accounting data and send the data 605 to userland for processing over the taskstats interface. 606 607 Say N if unsure. 608 609config TASK_IO_ACCOUNTING 610 bool "Enable per-task storage I/O accounting" 611 depends on TASK_XACCT 612 help 613 Collect information on the number of bytes of storage I/O which this 614 task has caused. 615 616 Say N if unsure. 617 618config PSI 619 bool "Pressure stall information tracking" 620 help 621 Collect metrics that indicate how overcommitted the CPU, memory, 622 and IO capacity are in the system. 623 624 If you say Y here, the kernel will create /proc/pressure/ with the 625 pressure statistics files cpu, memory, and io. These will indicate 626 the share of walltime in which some or all tasks in the system are 627 delayed due to contention of the respective resource. 628 629 In kernels with cgroup support, cgroups (cgroup2 only) will 630 have cpu.pressure, memory.pressure, and io.pressure files, 631 which aggregate pressure stalls for the grouped tasks only. 632 633 For more details see Documentation/accounting/psi.rst. 634 635 Say N if unsure. 636 637config PSI_DEFAULT_DISABLED 638 bool "Require boot parameter to enable pressure stall information tracking" 639 default n 640 depends on PSI 641 help 642 If set, pressure stall information tracking will be disabled 643 per default but can be enabled through passing psi=1 on the 644 kernel commandline during boot. 645 646 This feature adds some code to the task wakeup and sleep 647 paths of the scheduler. The overhead is too low to affect 648 common scheduling-intense workloads in practice (such as 649 webservers, memcache), but it does show up in artificial 650 scheduler stress tests, such as hackbench. 651 652 If you are paranoid and not sure what the kernel will be 653 used for, say Y. 654 655 Say N if unsure. 656 657endmenu # "CPU/Task time and stats accounting" 658 659config CPU_ISOLATION 660 bool "CPU isolation" 661 depends on SMP || COMPILE_TEST 662 default y 663 help 664 Make sure that CPUs running critical tasks are not disturbed by 665 any source of "noise" such as unbound workqueues, timers, kthreads... 666 Unbound jobs get offloaded to housekeeping CPUs. This is driven by 667 the "isolcpus=" boot parameter. 668 669 Say Y if unsure. 670 671source "kernel/rcu/Kconfig" 672 673config BUILD_BIN2C 674 bool 675 default n 676 677config IKCONFIG 678 tristate "Kernel .config support" 679 help 680 This option enables the complete Linux kernel ".config" file 681 contents to be saved in the kernel. It provides documentation 682 of which kernel options are used in a running kernel or in an 683 on-disk kernel. This information can be extracted from the kernel 684 image file with the script scripts/extract-ikconfig and used as 685 input to rebuild the current kernel or to build another kernel. 686 It can also be extracted from a running kernel by reading 687 /proc/config.gz if enabled (below). 688 689config IKCONFIG_PROC 690 bool "Enable access to .config through /proc/config.gz" 691 depends on IKCONFIG && PROC_FS 692 help 693 This option enables access to the kernel configuration file 694 through /proc/config.gz. 695 696config IKHEADERS 697 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz" 698 depends on SYSFS 699 help 700 This option enables access to the in-kernel headers that are generated during 701 the build process. These can be used to build eBPF tracing programs, 702 or similar programs. If you build the headers as a module, a module called 703 kheaders.ko is built which can be loaded on-demand to get access to headers. 704 705config LOG_BUF_SHIFT 706 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 707 range 12 25 if !H8300 708 range 12 19 if H8300 709 default 17 710 depends on PRINTK 711 help 712 Select the minimal kernel log buffer size as a power of 2. 713 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 714 parameter, see below. Any higher size also might be forced 715 by "log_buf_len" boot parameter. 716 717 Examples: 718 17 => 128 KB 719 16 => 64 KB 720 15 => 32 KB 721 14 => 16 KB 722 13 => 8 KB 723 12 => 4 KB 724 725config LOG_CPU_MAX_BUF_SHIFT 726 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 727 depends on SMP 728 range 0 21 729 default 12 if !BASE_SMALL 730 default 0 if BASE_SMALL 731 depends on PRINTK 732 help 733 This option allows to increase the default ring buffer size 734 according to the number of CPUs. The value defines the contribution 735 of each CPU as a power of 2. The used space is typically only few 736 lines however it might be much more when problems are reported, 737 e.g. backtraces. 738 739 The increased size means that a new buffer has to be allocated and 740 the original static one is unused. It makes sense only on systems 741 with more CPUs. Therefore this value is used only when the sum of 742 contributions is greater than the half of the default kernel ring 743 buffer as defined by LOG_BUF_SHIFT. The default values are set 744 so that more than 16 CPUs are needed to trigger the allocation. 745 746 Also this option is ignored when "log_buf_len" kernel parameter is 747 used as it forces an exact (power of two) size of the ring buffer. 748 749 The number of possible CPUs is used for this computation ignoring 750 hotplugging making the computation optimal for the worst case 751 scenario while allowing a simple algorithm to be used from bootup. 752 753 Examples shift values and their meaning: 754 17 => 128 KB for each CPU 755 16 => 64 KB for each CPU 756 15 => 32 KB for each CPU 757 14 => 16 KB for each CPU 758 13 => 8 KB for each CPU 759 12 => 4 KB for each CPU 760 761config PRINTK_SAFE_LOG_BUF_SHIFT 762 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 763 range 10 21 764 default 13 765 depends on PRINTK 766 help 767 Select the size of an alternate printk per-CPU buffer where messages 768 printed from usafe contexts are temporary stored. One example would 769 be NMI messages, another one - printk recursion. The messages are 770 copied to the main log buffer in a safe context to avoid a deadlock. 771 The value defines the size as a power of 2. 772 773 Those messages are rare and limited. The largest one is when 774 a backtrace is printed. It usually fits into 4KB. Select 775 8KB if you want to be on the safe side. 776 777 Examples: 778 17 => 128 KB for each CPU 779 16 => 64 KB for each CPU 780 15 => 32 KB for each CPU 781 14 => 16 KB for each CPU 782 13 => 8 KB for each CPU 783 12 => 4 KB for each CPU 784 785# 786# Architectures with an unreliable sched_clock() should select this: 787# 788config HAVE_UNSTABLE_SCHED_CLOCK 789 bool 790 791config GENERIC_SCHED_CLOCK 792 bool 793 794menu "Scheduler features" 795 796config UCLAMP_TASK 797 bool "Enable utilization clamping for RT/FAIR tasks" 798 depends on CPU_FREQ_GOV_SCHEDUTIL 799 help 800 This feature enables the scheduler to track the clamped utilization 801 of each CPU based on RUNNABLE tasks scheduled on that CPU. 802 803 With this option, the user can specify the min and max CPU 804 utilization allowed for RUNNABLE tasks. The max utilization defines 805 the maximum frequency a task should use while the min utilization 806 defines the minimum frequency it should use. 807 808 Both min and max utilization clamp values are hints to the scheduler, 809 aiming at improving its frequency selection policy, but they do not 810 enforce or grant any specific bandwidth for tasks. 811 812 If in doubt, say N. 813 814config UCLAMP_BUCKETS_COUNT 815 int "Number of supported utilization clamp buckets" 816 range 5 20 817 default 5 818 depends on UCLAMP_TASK 819 help 820 Defines the number of clamp buckets to use. The range of each bucket 821 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the 822 number of clamp buckets the finer their granularity and the higher 823 the precision of clamping aggregation and tracking at run-time. 824 825 For example, with the minimum configuration value we will have 5 826 clamp buckets tracking 20% utilization each. A 25% boosted tasks will 827 be refcounted in the [20..39]% bucket and will set the bucket clamp 828 effective value to 25%. 829 If a second 30% boosted task should be co-scheduled on the same CPU, 830 that task will be refcounted in the same bucket of the first task and 831 it will boost the bucket clamp effective value to 30%. 832 The clamp effective value of a bucket is reset to its nominal value 833 (20% in the example above) when there are no more tasks refcounted in 834 that bucket. 835 836 An additional boost/capping margin can be added to some tasks. In the 837 example above the 25% task will be boosted to 30% until it exits the 838 CPU. If that should be considered not acceptable on certain systems, 839 it's always possible to reduce the margin by increasing the number of 840 clamp buckets to trade off used memory for run-time tracking 841 precision. 842 843 If in doubt, use the default value. 844 845endmenu 846 847# 848# For architectures that want to enable the support for NUMA-affine scheduler 849# balancing logic: 850# 851config ARCH_SUPPORTS_NUMA_BALANCING 852 bool 853 854# 855# For architectures that prefer to flush all TLBs after a number of pages 856# are unmapped instead of sending one IPI per page to flush. The architecture 857# must provide guarantees on what happens if a clean TLB cache entry is 858# written after the unmap. Details are in mm/rmap.c near the check for 859# should_defer_flush. The architecture should also consider if the full flush 860# and the refill costs are offset by the savings of sending fewer IPIs. 861config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 862 bool 863 864config CC_HAS_INT128 865 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT 866 867# 868# For architectures that know their GCC __int128 support is sound 869# 870config ARCH_SUPPORTS_INT128 871 bool 872 873# For architectures that (ab)use NUMA to represent different memory regions 874# all cpu-local but of different latencies, such as SuperH. 875# 876config ARCH_WANT_NUMA_VARIABLE_LOCALITY 877 bool 878 879config NUMA_BALANCING 880 bool "Memory placement aware NUMA scheduler" 881 depends on ARCH_SUPPORTS_NUMA_BALANCING 882 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 883 depends on SMP && NUMA && MIGRATION 884 help 885 This option adds support for automatic NUMA aware memory/task placement. 886 The mechanism is quite primitive and is based on migrating memory when 887 it has references to the node the task is running on. 888 889 This system will be inactive on UMA systems. 890 891config NUMA_BALANCING_DEFAULT_ENABLED 892 bool "Automatically enable NUMA aware memory/task placement" 893 default y 894 depends on NUMA_BALANCING 895 help 896 If set, automatic NUMA balancing will be enabled if running on a NUMA 897 machine. 898 899menuconfig CGROUPS 900 bool "Control Group support" 901 select KERNFS 902 help 903 This option adds support for grouping sets of processes together, for 904 use with process control subsystems such as Cpusets, CFS, memory 905 controls or device isolation. 906 See 907 - Documentation/scheduler/sched-design-CFS.rst (CFS) 908 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation 909 and resource control) 910 911 Say N if unsure. 912 913if CGROUPS 914 915config PAGE_COUNTER 916 bool 917 918config MEMCG 919 bool "Memory controller" 920 select PAGE_COUNTER 921 select EVENTFD 922 help 923 Provides control over the memory footprint of tasks in a cgroup. 924 925config MEMCG_SWAP 926 bool 927 depends on MEMCG && SWAP 928 default y 929 930config MEMCG_KMEM 931 bool 932 depends on MEMCG && !SLOB 933 default y 934 935config BLK_CGROUP 936 bool "IO controller" 937 depends on BLOCK 938 default n 939 help 940 Generic block IO controller cgroup interface. This is the common 941 cgroup interface which should be used by various IO controlling 942 policies. 943 944 Currently, CFQ IO scheduler uses it to recognize task groups and 945 control disk bandwidth allocation (proportional time slice allocation) 946 to such task groups. It is also used by bio throttling logic in 947 block layer to implement upper limit in IO rates on a device. 948 949 This option only enables generic Block IO controller infrastructure. 950 One needs to also enable actual IO controlling logic/policy. For 951 enabling proportional weight division of disk bandwidth in CFQ, set 952 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 953 CONFIG_BLK_DEV_THROTTLING=y. 954 955 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information. 956 957config CGROUP_WRITEBACK 958 bool 959 depends on MEMCG && BLK_CGROUP 960 default y 961 962menuconfig CGROUP_SCHED 963 bool "CPU controller" 964 default n 965 help 966 This feature lets CPU scheduler recognize task groups and control CPU 967 bandwidth allocation to such task groups. It uses cgroups to group 968 tasks. 969 970if CGROUP_SCHED 971config FAIR_GROUP_SCHED 972 bool "Group scheduling for SCHED_OTHER" 973 depends on CGROUP_SCHED 974 default CGROUP_SCHED 975 976config CFS_BANDWIDTH 977 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 978 depends on FAIR_GROUP_SCHED 979 default n 980 help 981 This option allows users to define CPU bandwidth rates (limits) for 982 tasks running within the fair group scheduler. Groups with no limit 983 set are considered to be unconstrained and will run with no 984 restriction. 985 See Documentation/scheduler/sched-bwc.rst for more information. 986 987config RT_GROUP_SCHED 988 bool "Group scheduling for SCHED_RR/FIFO" 989 depends on CGROUP_SCHED 990 default n 991 help 992 This feature lets you explicitly allocate real CPU bandwidth 993 to task groups. If enabled, it will also make it impossible to 994 schedule realtime tasks for non-root users until you allocate 995 realtime bandwidth for them. 996 See Documentation/scheduler/sched-rt-group.rst for more information. 997 998endif #CGROUP_SCHED 999 1000config UCLAMP_TASK_GROUP 1001 bool "Utilization clamping per group of tasks" 1002 depends on CGROUP_SCHED 1003 depends on UCLAMP_TASK 1004 default n 1005 help 1006 This feature enables the scheduler to track the clamped utilization 1007 of each CPU based on RUNNABLE tasks currently scheduled on that CPU. 1008 1009 When this option is enabled, the user can specify a min and max 1010 CPU bandwidth which is allowed for each single task in a group. 1011 The max bandwidth allows to clamp the maximum frequency a task 1012 can use, while the min bandwidth allows to define a minimum 1013 frequency a task will always use. 1014 1015 When task group based utilization clamping is enabled, an eventually 1016 specified task-specific clamp value is constrained by the cgroup 1017 specified clamp value. Both minimum and maximum task clamping cannot 1018 be bigger than the corresponding clamping defined at task group level. 1019 1020 If in doubt, say N. 1021 1022config CGROUP_PIDS 1023 bool "PIDs controller" 1024 help 1025 Provides enforcement of process number limits in the scope of a 1026 cgroup. Any attempt to fork more processes than is allowed in the 1027 cgroup will fail. PIDs are fundamentally a global resource because it 1028 is fairly trivial to reach PID exhaustion before you reach even a 1029 conservative kmemcg limit. As a result, it is possible to grind a 1030 system to halt without being limited by other cgroup policies. The 1031 PIDs controller is designed to stop this from happening. 1032 1033 It should be noted that organisational operations (such as attaching 1034 to a cgroup hierarchy) will *not* be blocked by the PIDs controller, 1035 since the PIDs limit only affects a process's ability to fork, not to 1036 attach to a cgroup. 1037 1038config CGROUP_RDMA 1039 bool "RDMA controller" 1040 help 1041 Provides enforcement of RDMA resources defined by IB stack. 1042 It is fairly easy for consumers to exhaust RDMA resources, which 1043 can result into resource unavailability to other consumers. 1044 RDMA controller is designed to stop this from happening. 1045 Attaching processes with active RDMA resources to the cgroup 1046 hierarchy is allowed even if can cross the hierarchy's limit. 1047 1048config CGROUP_FREEZER 1049 bool "Freezer controller" 1050 help 1051 Provides a way to freeze and unfreeze all tasks in a 1052 cgroup. 1053 1054 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1055 controller includes important in-kernel memory consumers per default. 1056 1057 If you're using cgroup2, say N. 1058 1059config CGROUP_HUGETLB 1060 bool "HugeTLB controller" 1061 depends on HUGETLB_PAGE 1062 select PAGE_COUNTER 1063 default n 1064 help 1065 Provides a cgroup controller for HugeTLB pages. 1066 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1067 The limit is enforced during page fault. Since HugeTLB doesn't 1068 support page reclaim, enforcing the limit at page fault time implies 1069 that, the application will get SIGBUS signal if it tries to access 1070 HugeTLB pages beyond its limit. This requires the application to know 1071 beforehand how much HugeTLB pages it would require for its use. The 1072 control group is tracked in the third page lru pointer. This means 1073 that we cannot use the controller with huge page less than 3 pages. 1074 1075config CPUSETS 1076 bool "Cpuset controller" 1077 depends on SMP 1078 help 1079 This option will let you create and manage CPUSETs which 1080 allow dynamically partitioning a system into sets of CPUs and 1081 Memory Nodes and assigning tasks to run only within those sets. 1082 This is primarily useful on large SMP or NUMA systems. 1083 1084 Say N if unsure. 1085 1086config PROC_PID_CPUSET 1087 bool "Include legacy /proc/<pid>/cpuset file" 1088 depends on CPUSETS 1089 default y 1090 1091config CGROUP_DEVICE 1092 bool "Device controller" 1093 help 1094 Provides a cgroup controller implementing whitelists for 1095 devices which a process in the cgroup can mknod or open. 1096 1097config CGROUP_CPUACCT 1098 bool "Simple CPU accounting controller" 1099 help 1100 Provides a simple controller for monitoring the 1101 total CPU consumed by the tasks in a cgroup. 1102 1103config CGROUP_PERF 1104 bool "Perf controller" 1105 depends on PERF_EVENTS 1106 help 1107 This option extends the perf per-cpu mode to restrict monitoring 1108 to threads which belong to the cgroup specified and run on the 1109 designated cpu. Or this can be used to have cgroup ID in samples 1110 so that it can monitor performance events among cgroups. 1111 1112 Say N if unsure. 1113 1114config CGROUP_BPF 1115 bool "Support for eBPF programs attached to cgroups" 1116 depends on BPF_SYSCALL 1117 select SOCK_CGROUP_DATA 1118 help 1119 Allow attaching eBPF programs to a cgroup using the bpf(2) 1120 syscall command BPF_PROG_ATTACH. 1121 1122 In which context these programs are accessed depends on the type 1123 of attachment. For instance, programs that are attached using 1124 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1125 inet sockets. 1126 1127config CGROUP_DEBUG 1128 bool "Debug controller" 1129 default n 1130 depends on DEBUG_KERNEL 1131 help 1132 This option enables a simple controller that exports 1133 debugging information about the cgroups framework. This 1134 controller is for control cgroup debugging only. Its 1135 interfaces are not stable. 1136 1137 Say N. 1138 1139config SOCK_CGROUP_DATA 1140 bool 1141 default n 1142 1143endif # CGROUPS 1144 1145menuconfig NAMESPACES 1146 bool "Namespaces support" if EXPERT 1147 depends on MULTIUSER 1148 default !EXPERT 1149 help 1150 Provides the way to make tasks work with different objects using 1151 the same id. For example same IPC id may refer to different objects 1152 or same user id or pid may refer to different tasks when used in 1153 different namespaces. 1154 1155if NAMESPACES 1156 1157config UTS_NS 1158 bool "UTS namespace" 1159 default y 1160 help 1161 In this namespace tasks see different info provided with the 1162 uname() system call 1163 1164config TIME_NS 1165 bool "TIME namespace" 1166 depends on GENERIC_VDSO_TIME_NS 1167 default y 1168 help 1169 In this namespace boottime and monotonic clocks can be set. 1170 The time will keep going with the same pace. 1171 1172config IPC_NS 1173 bool "IPC namespace" 1174 depends on (SYSVIPC || POSIX_MQUEUE) 1175 default y 1176 help 1177 In this namespace tasks work with IPC ids which correspond to 1178 different IPC objects in different namespaces. 1179 1180config USER_NS 1181 bool "User namespace" 1182 default n 1183 help 1184 This allows containers, i.e. vservers, to use user namespaces 1185 to provide different user info for different servers. 1186 1187 When user namespaces are enabled in the kernel it is 1188 recommended that the MEMCG option also be enabled and that 1189 user-space use the memory control groups to limit the amount 1190 of memory a memory unprivileged users can use. 1191 1192 If unsure, say N. 1193 1194config PID_NS 1195 bool "PID Namespaces" 1196 default y 1197 help 1198 Support process id namespaces. This allows having multiple 1199 processes with the same pid as long as they are in different 1200 pid namespaces. This is a building block of containers. 1201 1202config NET_NS 1203 bool "Network namespace" 1204 depends on NET 1205 default y 1206 help 1207 Allow user space to create what appear to be multiple instances 1208 of the network stack. 1209 1210endif # NAMESPACES 1211 1212config CHECKPOINT_RESTORE 1213 bool "Checkpoint/restore support" 1214 select PROC_CHILDREN 1215 select KCMP 1216 default n 1217 help 1218 Enables additional kernel features in a sake of checkpoint/restore. 1219 In particular it adds auxiliary prctl codes to setup process text, 1220 data and heap segment sizes, and a few additional /proc filesystem 1221 entries. 1222 1223 If unsure, say N here. 1224 1225config SCHED_AUTOGROUP 1226 bool "Automatic process group scheduling" 1227 select CGROUPS 1228 select CGROUP_SCHED 1229 select FAIR_GROUP_SCHED 1230 help 1231 This option optimizes the scheduler for common desktop workloads by 1232 automatically creating and populating task groups. This separation 1233 of workloads isolates aggressive CPU burners (like build jobs) from 1234 desktop applications. Task group autogeneration is currently based 1235 upon task session. 1236 1237config RT_SOFTINT_OPTIMIZATION 1238 bool "Improve RT scheduling during long softint execution" 1239 depends on ARM64 1240 depends on SMP 1241 default n 1242 help 1243 Enable an optimization which tries to avoid placing RT tasks on CPUs 1244 occupied by nonpreemptible tasks, such as a long softint, or CPUs 1245 which may soon block preemptions, such as a CPU running a ksoftirq 1246 thread which handles slow softints. 1247 1248config SYSFS_DEPRECATED 1249 bool "Enable deprecated sysfs features to support old userspace tools" 1250 depends on SYSFS 1251 default n 1252 help 1253 This option adds code that switches the layout of the "block" class 1254 devices, to not show up in /sys/class/block/, but only in 1255 /sys/block/. 1256 1257 This switch is only active when the sysfs.deprecated=1 boot option is 1258 passed or the SYSFS_DEPRECATED_V2 option is set. 1259 1260 This option allows new kernels to run on old distributions and tools, 1261 which might get confused by /sys/class/block/. Since 2007/2008 all 1262 major distributions and tools handle this just fine. 1263 1264 Recent distributions and userspace tools after 2009/2010 depend on 1265 the existence of /sys/class/block/, and will not work with this 1266 option enabled. 1267 1268 Only if you are using a new kernel on an old distribution, you might 1269 need to say Y here. 1270 1271config SYSFS_DEPRECATED_V2 1272 bool "Enable deprecated sysfs features by default" 1273 default n 1274 depends on SYSFS 1275 depends on SYSFS_DEPRECATED 1276 help 1277 Enable deprecated sysfs by default. 1278 1279 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1280 option. 1281 1282 Only if you are using a new kernel on an old distribution, you might 1283 need to say Y here. Even then, odds are you would not need it 1284 enabled, you can always pass the boot option if absolutely necessary. 1285 1286config RELAY 1287 bool "Kernel->user space relay support (formerly relayfs)" 1288 select IRQ_WORK 1289 help 1290 This option enables support for relay interface support in 1291 certain file systems (such as debugfs). 1292 It is designed to provide an efficient mechanism for tools and 1293 facilities to relay large amounts of data from kernel space to 1294 user space. 1295 1296 If unsure, say N. 1297 1298config BLK_DEV_INITRD 1299 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1300 help 1301 The initial RAM filesystem is a ramfs which is loaded by the 1302 boot loader (loadlin or lilo) and that is mounted as root 1303 before the normal boot procedure. It is typically used to 1304 load modules needed to mount the "real" root file system, 1305 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1306 1307 If RAM disk support (BLK_DEV_RAM) is also included, this 1308 also enables initial RAM disk (initrd) support and adds 1309 15 Kbytes (more on some other architectures) to the kernel size. 1310 1311 If unsure say Y. 1312 1313if BLK_DEV_INITRD 1314 1315source "usr/Kconfig" 1316 1317config INITRD_ASYNC 1318 bool "Initrd async" 1319 depends on NO_GKI 1320 help 1321 Init ramdisk async, can reduce kernel init time. 1322 1323endif 1324 1325config INITCALL_ASYNC 1326 bool "Call initcall async" 1327 depends on ROCKCHIP_THUNDER_BOOT 1328 help 1329 Call same level initcall async in kthread. 1330 Kernel parameter "initcall_nr_threads" control how many threads. 1331 initcall_nr_threads default is 0, which disable intcall async. 1332 initcall_nr_threads=-1, auto selected the number of threads. 1333 1334config BOOT_CONFIG 1335 bool "Boot config support" 1336 select BLK_DEV_INITRD 1337 help 1338 Extra boot config allows system admin to pass a config file as 1339 complemental extension of kernel cmdline when booting. 1340 The boot config file must be attached at the end of initramfs 1341 with checksum, size and magic word. 1342 See <file:Documentation/admin-guide/bootconfig.rst> for details. 1343 1344 If unsure, say Y. 1345 1346choice 1347 prompt "Compiler optimization level" 1348 default CC_OPTIMIZE_FOR_PERFORMANCE 1349 1350config CC_OPTIMIZE_FOR_PERFORMANCE 1351 bool "Optimize for performance (-O2)" 1352 help 1353 This is the default optimization level for the kernel, building 1354 with the "-O2" compiler flag for best performance and most 1355 helpful compile-time warnings. 1356 1357config CC_OPTIMIZE_FOR_PERFORMANCE_O3 1358 bool "Optimize more for performance (-O3)" 1359 depends on ARC 1360 help 1361 Choosing this option will pass "-O3" to your compiler to optimize 1362 the kernel yet more for performance. 1363 1364config CC_OPTIMIZE_FOR_SIZE 1365 bool "Optimize for size (-Os)" 1366 help 1367 Choosing this option will pass "-Os" to your compiler resulting 1368 in a smaller kernel. 1369 1370endchoice 1371 1372config HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1373 bool 1374 help 1375 This requires that the arch annotates or otherwise protects 1376 its external entry points from being discarded. Linker scripts 1377 must also merge .text.*, .data.*, and .bss.* correctly into 1378 output sections. Care must be taken not to pull in unrelated 1379 sections (e.g., '.text.init'). Typically '.' in section names 1380 is used to distinguish them from label names / C identifiers. 1381 1382config LD_DEAD_CODE_DATA_ELIMINATION 1383 bool "Dead code and data elimination (EXPERIMENTAL)" 1384 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION 1385 depends on EXPERT 1386 depends on $(cc-option,-ffunction-sections -fdata-sections) 1387 depends on $(ld-option,--gc-sections) 1388 help 1389 Enable this if you want to do dead code and data elimination with 1390 the linker by compiling with -ffunction-sections -fdata-sections, 1391 and linking with --gc-sections. 1392 1393 This can reduce on disk and in-memory size of the kernel 1394 code and static data, particularly for small configs and 1395 on small systems. This has the possibility of introducing 1396 silently broken kernel if the required annotations are not 1397 present. This option is not well tested yet, so use at your 1398 own risk. 1399 1400config LD_ORPHAN_WARN 1401 def_bool y 1402 depends on ARCH_WANT_LD_ORPHAN_WARN 1403 depends on !LD_IS_LLD || LLD_VERSION >= 110000 1404 depends on $(ld-option,--orphan-handling=warn) 1405 1406config SYSCTL 1407 bool 1408 1409config HAVE_UID16 1410 bool 1411 1412config SYSCTL_EXCEPTION_TRACE 1413 bool 1414 help 1415 Enable support for /proc/sys/debug/exception-trace. 1416 1417config SYSCTL_ARCH_UNALIGN_NO_WARN 1418 bool 1419 help 1420 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1421 Allows arch to define/use @no_unaligned_warning to possibly warn 1422 about unaligned access emulation going on under the hood. 1423 1424config SYSCTL_ARCH_UNALIGN_ALLOW 1425 bool 1426 help 1427 Enable support for /proc/sys/kernel/unaligned-trap 1428 Allows arches to define/use @unaligned_enabled to runtime toggle 1429 the unaligned access emulation. 1430 see arch/parisc/kernel/unaligned.c for reference 1431 1432config HAVE_PCSPKR_PLATFORM 1433 bool 1434 1435# interpreter that classic socket filters depend on 1436config BPF 1437 bool 1438 1439menuconfig EXPERT 1440 bool "Configure standard kernel features (expert users)" 1441 # Unhide debug options, to make the on-by-default options visible 1442 select DEBUG_KERNEL 1443 help 1444 This option allows certain base kernel options and settings 1445 to be disabled or tweaked. This is for specialized 1446 environments which can tolerate a "non-standard" kernel. 1447 Only use this if you really know what you are doing. 1448 1449config UID16 1450 bool "Enable 16-bit UID system calls" if EXPERT 1451 depends on HAVE_UID16 && MULTIUSER 1452 default y 1453 help 1454 This enables the legacy 16-bit UID syscall wrappers. 1455 1456config MULTIUSER 1457 bool "Multiple users, groups and capabilities support" if EXPERT 1458 default y 1459 help 1460 This option enables support for non-root users, groups and 1461 capabilities. 1462 1463 If you say N here, all processes will run with UID 0, GID 0, and all 1464 possible capabilities. Saying N here also compiles out support for 1465 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1466 setgid, and capset. 1467 1468 If unsure, say Y here. 1469 1470config SGETMASK_SYSCALL 1471 bool "sgetmask/ssetmask syscalls support" if EXPERT 1472 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH 1473 help 1474 sys_sgetmask and sys_ssetmask are obsolete system calls 1475 no longer supported in libc but still enabled by default in some 1476 architectures. 1477 1478 If unsure, leave the default option here. 1479 1480config SYSFS_SYSCALL 1481 bool "Sysfs syscall support" if EXPERT 1482 default y 1483 help 1484 sys_sysfs is an obsolete system call no longer supported in libc. 1485 Note that disabling this option is more secure but might break 1486 compatibility with some systems. 1487 1488 If unsure say Y here. 1489 1490config FHANDLE 1491 bool "open by fhandle syscalls" if EXPERT 1492 select EXPORTFS 1493 default y 1494 help 1495 If you say Y here, a user level program will be able to map 1496 file names to handle and then later use the handle for 1497 different file system operations. This is useful in implementing 1498 userspace file servers, which now track files using handles instead 1499 of names. The handle would remain the same even if file names 1500 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 1501 syscalls. 1502 1503config POSIX_TIMERS 1504 bool "Posix Clocks & timers" if EXPERT 1505 default y 1506 help 1507 This includes native support for POSIX timers to the kernel. 1508 Some embedded systems have no use for them and therefore they 1509 can be configured out to reduce the size of the kernel image. 1510 1511 When this option is disabled, the following syscalls won't be 1512 available: timer_create, timer_gettime: timer_getoverrun, 1513 timer_settime, timer_delete, clock_adjtime, getitimer, 1514 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1515 clock_getres and clock_nanosleep syscalls will be limited to 1516 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1517 1518 If unsure say y. 1519 1520config PRINTK 1521 default y 1522 bool "Enable support for printk" if EXPERT 1523 select IRQ_WORK 1524 help 1525 This option enables normal printk support. Removing it 1526 eliminates most of the message strings from the kernel image 1527 and makes the kernel more or less silent. As this makes it 1528 very difficult to diagnose system problems, saying N here is 1529 strongly discouraged. 1530 1531config PRINTK_NMI 1532 def_bool y 1533 depends on PRINTK 1534 depends on HAVE_NMI 1535 1536config BUG 1537 bool "BUG() support" if EXPERT 1538 default y 1539 help 1540 Disabling this option eliminates support for BUG and WARN, reducing 1541 the size of your kernel image and potentially quietly ignoring 1542 numerous fatal conditions. You should only consider disabling this 1543 option for embedded systems with no facilities for reporting errors. 1544 Just say Y. 1545 1546config ELF_CORE 1547 depends on COREDUMP 1548 default y 1549 bool "Enable ELF core dumps" if EXPERT 1550 help 1551 Enable support for generating core dumps. Disabling saves about 4k. 1552 1553 1554config PCSPKR_PLATFORM 1555 bool "Enable PC-Speaker support" if EXPERT 1556 depends on HAVE_PCSPKR_PLATFORM 1557 select I8253_LOCK 1558 default y 1559 help 1560 This option allows to disable the internal PC-Speaker 1561 support, saving some memory. 1562 1563config BASE_FULL 1564 default y 1565 bool "Enable full-sized data structures for core" if EXPERT 1566 help 1567 Disabling this option reduces the size of miscellaneous core 1568 kernel data structures. This saves memory on small machines, 1569 but may reduce performance. 1570 1571config FUTEX 1572 bool "Enable futex support" if EXPERT 1573 default y 1574 imply RT_MUTEXES 1575 help 1576 Disabling this option will cause the kernel to be built without 1577 support for "fast userspace mutexes". The resulting kernel may not 1578 run glibc-based applications correctly. 1579 1580config FUTEX_PI 1581 bool 1582 depends on FUTEX && RT_MUTEXES 1583 default y 1584 1585config HAVE_FUTEX_CMPXCHG 1586 bool 1587 depends on FUTEX 1588 help 1589 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1590 is implemented and always working. This removes a couple of runtime 1591 checks. 1592 1593config EPOLL 1594 bool "Enable eventpoll support" if EXPERT 1595 default y 1596 help 1597 Disabling this option will cause the kernel to be built without 1598 support for epoll family of system calls. 1599 1600config SIGNALFD 1601 bool "Enable signalfd() system call" if EXPERT 1602 default y 1603 help 1604 Enable the signalfd() system call that allows to receive signals 1605 on a file descriptor. 1606 1607 If unsure, say Y. 1608 1609config TIMERFD 1610 bool "Enable timerfd() system call" if EXPERT 1611 default y 1612 help 1613 Enable the timerfd() system call that allows to receive timer 1614 events on a file descriptor. 1615 1616 If unsure, say Y. 1617 1618config EVENTFD 1619 bool "Enable eventfd() system call" if EXPERT 1620 default y 1621 help 1622 Enable the eventfd() system call that allows to receive both 1623 kernel notification (ie. KAIO) or userspace notifications. 1624 1625 If unsure, say Y. 1626 1627config SHMEM 1628 bool "Use full shmem filesystem" if EXPERT 1629 default y 1630 depends on MMU 1631 help 1632 The shmem is an internal filesystem used to manage shared memory. 1633 It is backed by swap and manages resource limits. It is also exported 1634 to userspace as tmpfs if TMPFS is enabled. Disabling this 1635 option replaces shmem and tmpfs with the much simpler ramfs code, 1636 which may be appropriate on small systems without swap. 1637 1638config AIO 1639 bool "Enable AIO support" if EXPERT 1640 default y 1641 help 1642 This option enables POSIX asynchronous I/O which may by used 1643 by some high performance threaded applications. Disabling 1644 this option saves about 7k. 1645 1646config IO_URING 1647 bool "Enable IO uring support" if EXPERT 1648 select IO_WQ 1649 default y 1650 help 1651 This option enables support for the io_uring interface, enabling 1652 applications to submit and complete IO through submission and 1653 completion rings that are shared between the kernel and application. 1654 1655config ADVISE_SYSCALLS 1656 bool "Enable madvise/fadvise syscalls" if EXPERT 1657 default y 1658 help 1659 This option enables the madvise and fadvise syscalls, used by 1660 applications to advise the kernel about their future memory or file 1661 usage, improving performance. If building an embedded system where no 1662 applications use these syscalls, you can disable this option to save 1663 space. 1664 1665config HAVE_ARCH_USERFAULTFD_WP 1666 bool 1667 help 1668 Arch has userfaultfd write protection support 1669 1670config HAVE_ARCH_USERFAULTFD_MINOR 1671 bool 1672 help 1673 Arch has userfaultfd minor fault support 1674 1675config MEMBARRIER 1676 bool "Enable membarrier() system call" if EXPERT 1677 default y 1678 help 1679 Enable the membarrier() system call that allows issuing memory 1680 barriers across all running threads, which can be used to distribute 1681 the cost of user-space memory barriers asymmetrically by transforming 1682 pairs of memory barriers into pairs consisting of membarrier() and a 1683 compiler barrier. 1684 1685 If unsure, say Y. 1686 1687config KALLSYMS 1688 bool "Load all symbols for debugging/ksymoops" if EXPERT 1689 default y 1690 help 1691 Say Y here to let the kernel print out symbolic crash information and 1692 symbolic stack backtraces. This increases the size of the kernel 1693 somewhat, as all symbols have to be loaded into the kernel image. 1694 1695config KALLSYMS_ALL 1696 bool "Include all symbols in kallsyms" 1697 depends on DEBUG_KERNEL && KALLSYMS 1698 help 1699 Normally kallsyms only contains the symbols of functions for nicer 1700 OOPS messages and backtraces (i.e., symbols from the text and inittext 1701 sections). This is sufficient for most cases. And only in very rare 1702 cases (e.g., when a debugger is used) all symbols are required (e.g., 1703 names of variables from the data sections, etc). 1704 1705 This option makes sure that all symbols are loaded into the kernel 1706 image (i.e., symbols from all sections) in cost of increased kernel 1707 size (depending on the kernel configuration, it may be 300KiB or 1708 something like this). 1709 1710 Say N unless you really need all symbols. 1711 1712config KALLSYMS_ABSOLUTE_PERCPU 1713 bool 1714 depends on KALLSYMS 1715 default X86_64 && SMP 1716 1717config KALLSYMS_BASE_RELATIVE 1718 bool 1719 depends on KALLSYMS 1720 default !IA64 1721 help 1722 Instead of emitting them as absolute values in the native word size, 1723 emit the symbol references in the kallsyms table as 32-bit entries, 1724 each containing a relative value in the range [base, base + U32_MAX] 1725 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1726 an absolute value in the range [0, S32_MAX] or a relative value in the 1727 range [base, base + S32_MAX], where base is the lowest relative symbol 1728 address encountered in the image. 1729 1730 On 64-bit builds, this reduces the size of the address table by 50%, 1731 but more importantly, it results in entries whose values are build 1732 time constants, and no relocation pass is required at runtime to fix 1733 up the entries based on the runtime load address of the kernel. 1734 1735# end of the "standard kernel features (expert users)" menu 1736 1737# syscall, maps, verifier 1738 1739config BPF_LSM 1740 bool "LSM Instrumentation with BPF" 1741 depends on BPF_EVENTS 1742 depends on BPF_SYSCALL 1743 depends on SECURITY 1744 depends on BPF_JIT 1745 help 1746 Enables instrumentation of the security hooks with eBPF programs for 1747 implementing dynamic MAC and Audit Policies. 1748 1749 If you are unsure how to answer this question, answer N. 1750 1751config BPF_SYSCALL 1752 bool "Enable bpf() system call" 1753 select BPF 1754 select IRQ_WORK 1755 select TASKS_TRACE_RCU 1756 default n 1757 help 1758 Enable the bpf() system call that allows to manipulate eBPF 1759 programs and maps via file descriptors. 1760 1761config ARCH_WANT_DEFAULT_BPF_JIT 1762 bool 1763 1764config BPF_JIT_ALWAYS_ON 1765 bool "Permanently enable BPF JIT and remove BPF interpreter" 1766 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1767 help 1768 Enables BPF JIT and removes BPF interpreter to avoid 1769 speculative execution of BPF instructions by the interpreter 1770 1771config BPF_JIT_DEFAULT_ON 1772 def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON 1773 depends on HAVE_EBPF_JIT && BPF_JIT 1774 1775config BPF_UNPRIV_DEFAULT_OFF 1776 bool "Disable unprivileged BPF by default" 1777 depends on BPF_SYSCALL 1778 help 1779 Disables unprivileged BPF by default by setting the corresponding 1780 /proc/sys/kernel/unprivileged_bpf_disabled knob to 2. An admin can 1781 still reenable it by setting it to 0 later on, or permanently 1782 disable it by setting it to 1 (from which no other transition to 1783 0 is possible anymore). 1784 1785source "kernel/bpf/preload/Kconfig" 1786 1787config USERFAULTFD 1788 bool "Enable userfaultfd() system call" 1789 depends on MMU 1790 help 1791 Enable the userfaultfd() system call that allows to intercept and 1792 handle page faults in userland. 1793 1794config ARCH_HAS_MEMBARRIER_CALLBACKS 1795 bool 1796 1797config ARCH_HAS_MEMBARRIER_SYNC_CORE 1798 bool 1799 1800config KCMP 1801 bool "Enable kcmp() system call" if EXPERT 1802 help 1803 Enable the kernel resource comparison system call. It provides 1804 user-space with the ability to compare two processes to see if they 1805 share a common resource, such as a file descriptor or even virtual 1806 memory space. 1807 1808 If unsure, say N. 1809 1810config RSEQ 1811 bool "Enable rseq() system call" if EXPERT 1812 default y 1813 depends on HAVE_RSEQ 1814 select MEMBARRIER 1815 help 1816 Enable the restartable sequences system call. It provides a 1817 user-space cache for the current CPU number value, which 1818 speeds up getting the current CPU number from user-space, 1819 as well as an ABI to speed up user-space operations on 1820 per-CPU data. 1821 1822 If unsure, say Y. 1823 1824config DEBUG_RSEQ 1825 default n 1826 bool "Enabled debugging of rseq() system call" if EXPERT 1827 depends on RSEQ && DEBUG_KERNEL 1828 help 1829 Enable extra debugging checks for the rseq system call. 1830 1831 If unsure, say N. 1832 1833config EMBEDDED 1834 bool "Embedded system" 1835 option allnoconfig_y 1836 select EXPERT 1837 help 1838 This option should be enabled if compiling the kernel for 1839 an embedded system so certain expert options are available 1840 for configuration. 1841 1842config HAVE_PERF_EVENTS 1843 bool 1844 help 1845 See tools/perf/design.txt for details. 1846 1847config PERF_USE_VMALLOC 1848 bool 1849 help 1850 See tools/perf/design.txt for details 1851 1852config PC104 1853 bool "PC/104 support" if EXPERT 1854 help 1855 Expose PC/104 form factor device drivers and options available for 1856 selection and configuration. Enable this option if your target 1857 machine has a PC/104 bus. 1858 1859menu "Kernel Performance Events And Counters" 1860 1861config PERF_EVENTS 1862 bool "Kernel performance events and counters" 1863 default y if PROFILING 1864 depends on HAVE_PERF_EVENTS 1865 select IRQ_WORK 1866 select SRCU 1867 help 1868 Enable kernel support for various performance events provided 1869 by software and hardware. 1870 1871 Software events are supported either built-in or via the 1872 use of generic tracepoints. 1873 1874 Most modern CPUs support performance events via performance 1875 counter registers. These registers count the number of certain 1876 types of hw events: such as instructions executed, cachemisses 1877 suffered, or branches mis-predicted - without slowing down the 1878 kernel or applications. These registers can also trigger interrupts 1879 when a threshold number of events have passed - and can thus be 1880 used to profile the code that runs on that CPU. 1881 1882 The Linux Performance Event subsystem provides an abstraction of 1883 these software and hardware event capabilities, available via a 1884 system call and used by the "perf" utility in tools/perf/. It 1885 provides per task and per CPU counters, and it provides event 1886 capabilities on top of those. 1887 1888 Say Y if unsure. 1889 1890config DEBUG_PERF_USE_VMALLOC 1891 default n 1892 bool "Debug: use vmalloc to back perf mmap() buffers" 1893 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1894 select PERF_USE_VMALLOC 1895 help 1896 Use vmalloc memory to back perf mmap() buffers. 1897 1898 Mostly useful for debugging the vmalloc code on platforms 1899 that don't require it. 1900 1901 Say N if unsure. 1902 1903endmenu 1904 1905config VM_EVENT_COUNTERS 1906 default y 1907 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1908 help 1909 VM event counters are needed for event counts to be shown. 1910 This option allows the disabling of the VM event counters 1911 on EXPERT systems. /proc/vmstat will only show page counts 1912 if VM event counters are disabled. 1913 1914config SLUB_SYSFS 1915 bool "Enable SLUB sysfs interface" 1916 depends on SLUB && SYSFS 1917 default y 1918 1919config SLUB_DEBUG 1920 default y 1921 bool "Enable SLUB debugging support" if EXPERT 1922 depends on SLUB && SYSFS 1923 help 1924 SLUB has extensive debug support features. Disabling these can 1925 result in significant savings in code size. This also disables 1926 SLUB sysfs support. /sys/slab will not exist and there will be 1927 no support for cache validation etc. 1928 1929config SLUB_MEMCG_SYSFS_ON 1930 default n 1931 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1932 depends on SLUB && SYSFS && MEMCG 1933 help 1934 SLUB creates a directory under /sys/kernel/slab for each 1935 allocation cache to host info and debug files. If memory 1936 cgroup is enabled, each cache can have per memory cgroup 1937 caches. SLUB can create the same sysfs directories for these 1938 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1939 to a very high number of debug files being created. This is 1940 controlled by slub_memcg_sysfs boot parameter and this 1941 config option determines the parameter's default value. 1942 1943config COMPAT_BRK 1944 bool "Disable heap randomization" 1945 default y 1946 help 1947 Randomizing heap placement makes heap exploits harder, but it 1948 also breaks ancient binaries (including anything libc5 based). 1949 This option changes the bootup default to heap randomization 1950 disabled, and can be overridden at runtime by setting 1951 /proc/sys/kernel/randomize_va_space to 2. 1952 1953 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1954 1955choice 1956 prompt "Choose SLAB allocator" 1957 default SLUB 1958 help 1959 This option allows to select a slab allocator. 1960 1961config SLAB 1962 bool "SLAB" 1963 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1964 help 1965 The regular slab allocator that is established and known to work 1966 well in all environments. It organizes cache hot objects in 1967 per cpu and per node queues. 1968 1969config SLUB 1970 bool "SLUB (Unqueued Allocator)" 1971 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1972 help 1973 SLUB is a slab allocator that minimizes cache line usage 1974 instead of managing queues of cached objects (SLAB approach). 1975 Per cpu caching is realized using slabs of objects instead 1976 of queues of objects. SLUB can use memory efficiently 1977 and has enhanced diagnostics. SLUB is the default choice for 1978 a slab allocator. 1979 1980config SLOB 1981 depends on EXPERT 1982 bool "SLOB (Simple Allocator)" 1983 help 1984 SLOB replaces the stock allocator with a drastically simpler 1985 allocator. SLOB is generally more space efficient but 1986 does not perform as well on large systems. 1987 1988endchoice 1989 1990config SLAB_MERGE_DEFAULT 1991 bool "Allow slab caches to be merged" 1992 default y 1993 help 1994 For reduced kernel memory fragmentation, slab caches can be 1995 merged when they share the same size and other characteristics. 1996 This carries a risk of kernel heap overflows being able to 1997 overwrite objects from merged caches (and more easily control 1998 cache layout), which makes such heap attacks easier to exploit 1999 by attackers. By keeping caches unmerged, these kinds of exploits 2000 can usually only damage objects in the same cache. To disable 2001 merging at runtime, "slab_nomerge" can be passed on the kernel 2002 command line. 2003 2004config SLAB_FREELIST_RANDOM 2005 bool "Randomize slab freelist" 2006 depends on SLAB || SLUB 2007 help 2008 Randomizes the freelist order used on creating new pages. This 2009 security feature reduces the predictability of the kernel slab 2010 allocator against heap overflows. 2011 2012config SLAB_FREELIST_HARDENED 2013 bool "Harden slab freelist metadata" 2014 depends on SLAB || SLUB 2015 help 2016 Many kernel heap attacks try to target slab cache metadata and 2017 other infrastructure. This options makes minor performance 2018 sacrifices to harden the kernel slab allocator against common 2019 freelist exploit methods. Some slab implementations have more 2020 sanity-checking than others. This option is most effective with 2021 CONFIG_SLUB. 2022 2023config SHUFFLE_PAGE_ALLOCATOR 2024 bool "Page allocator randomization" 2025 default SLAB_FREELIST_RANDOM && ACPI_NUMA 2026 help 2027 Randomization of the page allocator improves the average 2028 utilization of a direct-mapped memory-side-cache. See section 2029 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 2030 6.2a specification for an example of how a platform advertises 2031 the presence of a memory-side-cache. There are also incidental 2032 security benefits as it reduces the predictability of page 2033 allocations to compliment SLAB_FREELIST_RANDOM, but the 2034 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 2035 10th order of pages is selected based on cache utilization 2036 benefits on x86. 2037 2038 While the randomization improves cache utilization it may 2039 negatively impact workloads on platforms without a cache. For 2040 this reason, by default, the randomization is enabled only 2041 after runtime detection of a direct-mapped memory-side-cache. 2042 Otherwise, the randomization may be force enabled with the 2043 'page_alloc.shuffle' kernel command line parameter. 2044 2045 Say Y if unsure. 2046 2047config SLUB_CPU_PARTIAL 2048 default y 2049 depends on SLUB && SMP 2050 bool "SLUB per cpu partial cache" 2051 help 2052 Per cpu partial caches accelerate objects allocation and freeing 2053 that is local to a processor at the price of more indeterminism 2054 in the latency of the free. On overflow these caches will be cleared 2055 which requires the taking of locks that may cause latency spikes. 2056 Typically one would choose no for a realtime system. 2057 2058config MMAP_ALLOW_UNINITIALIZED 2059 bool "Allow mmapped anonymous memory to be uninitialized" 2060 depends on EXPERT && !MMU 2061 default n 2062 help 2063 Normally, and according to the Linux spec, anonymous memory obtained 2064 from mmap() has its contents cleared before it is passed to 2065 userspace. Enabling this config option allows you to request that 2066 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 2067 providing a huge performance boost. If this option is not enabled, 2068 then the flag will be ignored. 2069 2070 This is taken advantage of by uClibc's malloc(), and also by 2071 ELF-FDPIC binfmt's brk and stack allocator. 2072 2073 Because of the obvious security issues, this option should only be 2074 enabled on embedded devices where you control what is run in 2075 userspace. Since that isn't generally a problem on no-MMU systems, 2076 it is normally safe to say Y here. 2077 2078 See Documentation/admin-guide/mm/nommu-mmap.rst for more information. 2079 2080config SYSTEM_DATA_VERIFICATION 2081 def_bool n 2082 select SYSTEM_TRUSTED_KEYRING 2083 select KEYS 2084 select CRYPTO 2085 select CRYPTO_RSA 2086 select ASYMMETRIC_KEY_TYPE 2087 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 2088 select ASN1 2089 select OID_REGISTRY 2090 select X509_CERTIFICATE_PARSER 2091 select PKCS7_MESSAGE_PARSER 2092 help 2093 Provide PKCS#7 message verification using the contents of the system 2094 trusted keyring to provide public keys. This then can be used for 2095 module verification, kexec image verification and firmware blob 2096 verification. 2097 2098config PROFILING 2099 bool "Profiling support" 2100 help 2101 Say Y here to enable the extended profiling support mechanisms used 2102 by profilers such as OProfile. 2103 2104# 2105# Place an empty function call at each tracepoint site. Can be 2106# dynamically changed for a probe function. 2107# 2108config TRACEPOINTS 2109 bool 2110 2111endmenu # General setup 2112 2113source "arch/Kconfig" 2114 2115config RT_MUTEXES 2116 bool 2117 2118config BASE_SMALL 2119 int 2120 default 0 if BASE_FULL 2121 default 1 if !BASE_FULL 2122 2123config MODULE_SIG_FORMAT 2124 def_bool n 2125 select SYSTEM_DATA_VERIFICATION 2126 2127menuconfig MODULES 2128 bool "Enable loadable module support" 2129 option modules 2130 help 2131 Kernel modules are small pieces of compiled code which can 2132 be inserted in the running kernel, rather than being 2133 permanently built into the kernel. You use the "modprobe" 2134 tool to add (and sometimes remove) them. If you say Y here, 2135 many parts of the kernel can be built as modules (by 2136 answering M instead of Y where indicated): this is most 2137 useful for infrequently used options which are not required 2138 for booting. For more information, see the man pages for 2139 modprobe, lsmod, modinfo, insmod and rmmod. 2140 2141 If you say Y here, you will need to run "make 2142 modules_install" to put the modules under /lib/modules/ 2143 where modprobe can find them (you may need to be root to do 2144 this). 2145 2146 If unsure, say Y. 2147 2148if MODULES 2149 2150config MODULE_FORCE_LOAD 2151 bool "Forced module loading" 2152 default n 2153 help 2154 Allow loading of modules without version information (ie. modprobe 2155 --force). Forced module loading sets the 'F' (forced) taint flag and 2156 is usually a really bad idea. 2157 2158config MODULE_UNLOAD 2159 bool "Module unloading" 2160 help 2161 Without this option you will not be able to unload any 2162 modules (note that some modules may not be unloadable 2163 anyway), which makes your kernel smaller, faster 2164 and simpler. If unsure, say Y. 2165 2166config MODULE_FORCE_UNLOAD 2167 bool "Forced module unloading" 2168 depends on MODULE_UNLOAD 2169 help 2170 This option allows you to force a module to unload, even if the 2171 kernel believes it is unsafe: the kernel will remove the module 2172 without waiting for anyone to stop using it (using the -f option to 2173 rmmod). This is mainly for kernel developers and desperate users. 2174 If unsure, say N. 2175 2176config MODVERSIONS 2177 bool "Module versioning support" 2178 help 2179 Usually, you have to use modules compiled with your kernel. 2180 Saying Y here makes it sometimes possible to use modules 2181 compiled for different kernels, by adding enough information 2182 to the modules to (hopefully) spot any changes which would 2183 make them incompatible with the kernel you are running. If 2184 unsure, say N. 2185 2186config ASM_MODVERSIONS 2187 bool 2188 default HAVE_ASM_MODVERSIONS && MODVERSIONS 2189 help 2190 This enables module versioning for exported symbols also from 2191 assembly. This can be enabled only when the target architecture 2192 supports it. 2193 2194config MODULE_REL_CRCS 2195 bool 2196 depends on MODVERSIONS 2197 2198config MODULE_SRCVERSION_ALL 2199 bool "Source checksum for all modules" 2200 help 2201 Modules which contain a MODULE_VERSION get an extra "srcversion" 2202 field inserted into their modinfo section, which contains a 2203 sum of the source files which made it. This helps maintainers 2204 see exactly which source was used to build a module (since 2205 others sometimes change the module source without updating 2206 the version). With this option, such a "srcversion" field 2207 will be created for all modules. If unsure, say N. 2208 2209config MODULE_SCMVERSION 2210 bool "SCM version for modules" 2211 depends on LOCALVERSION_AUTO 2212 help 2213 This enables the module attribute "scmversion" which can be used 2214 by developers to identify the SCM version of a given module, e.g. 2215 git sha1 or hg sha1. The SCM version can be queried by modinfo or 2216 via the sysfs node: /sys/modules/MODULENAME/scmversion. This is 2217 useful when the kernel or kernel modules are updated separately 2218 since that causes the vermagic of the kernel and the module to 2219 differ. 2220 2221 If unsure, say N. 2222 2223config MODULE_SIG 2224 bool "Module signature verification" 2225 select MODULE_SIG_FORMAT 2226 help 2227 Check modules for valid signatures upon load: the signature 2228 is simply appended to the module. For more information see 2229 <file:Documentation/admin-guide/module-signing.rst>. 2230 2231 Note that this option adds the OpenSSL development packages as a 2232 kernel build dependency so that the signing tool can use its crypto 2233 library. 2234 2235 You should enable this option if you wish to use either 2236 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via 2237 another LSM - otherwise unsigned modules will be loadable regardless 2238 of the lockdown policy. 2239 2240 !!!WARNING!!! If you enable this option, you MUST make sure that the 2241 module DOES NOT get stripped after being signed. This includes the 2242 debuginfo strip done by some packagers (such as rpmbuild) and 2243 inclusion into an initramfs that wants the module size reduced. 2244 2245config MODULE_SIG_FORCE 2246 bool "Require modules to be validly signed" 2247 depends on MODULE_SIG 2248 help 2249 Reject unsigned modules or signed modules for which we don't have a 2250 key. Without this, such modules will simply taint the kernel. 2251 2252config MODULE_SIG_ALL 2253 bool "Automatically sign all modules" 2254 default y 2255 depends on MODULE_SIG 2256 help 2257 Sign all modules during make modules_install. Without this option, 2258 modules must be signed manually, using the scripts/sign-file tool. 2259 2260comment "Do not forget to sign required modules with scripts/sign-file" 2261 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2262 2263choice 2264 prompt "Which hash algorithm should modules be signed with?" 2265 depends on MODULE_SIG 2266 help 2267 This determines which sort of hashing algorithm will be used during 2268 signature generation. This algorithm _must_ be built into the kernel 2269 directly so that signature verification can take place. It is not 2270 possible to load a signed module containing the algorithm to check 2271 the signature on that module. 2272 2273config MODULE_SIG_SHA1 2274 bool "Sign modules with SHA-1" 2275 select CRYPTO_SHA1 2276 2277config MODULE_SIG_SHA224 2278 bool "Sign modules with SHA-224" 2279 select CRYPTO_SHA256 2280 2281config MODULE_SIG_SHA256 2282 bool "Sign modules with SHA-256" 2283 select CRYPTO_SHA256 2284 2285config MODULE_SIG_SHA384 2286 bool "Sign modules with SHA-384" 2287 select CRYPTO_SHA512 2288 2289config MODULE_SIG_SHA512 2290 bool "Sign modules with SHA-512" 2291 select CRYPTO_SHA512 2292 2293endchoice 2294 2295config MODULE_SIG_HASH 2296 string 2297 depends on MODULE_SIG 2298 default "sha1" if MODULE_SIG_SHA1 2299 default "sha224" if MODULE_SIG_SHA224 2300 default "sha256" if MODULE_SIG_SHA256 2301 default "sha384" if MODULE_SIG_SHA384 2302 default "sha512" if MODULE_SIG_SHA512 2303 2304config MODULE_COMPRESS 2305 bool "Compress modules on installation" 2306 help 2307 2308 Compresses kernel modules when 'make modules_install' is run; gzip or 2309 xz depending on "Compression algorithm" below. 2310 2311 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 2312 2313 Out-of-tree kernel modules installed using Kbuild will also be 2314 compressed upon installation. 2315 2316 Note: for modules inside an initrd or initramfs, it's more efficient 2317 to compress the whole initrd or initramfs instead. 2318 2319 Note: This is fully compatible with signed modules. 2320 2321 If in doubt, say N. 2322 2323choice 2324 prompt "Compression algorithm" 2325 depends on MODULE_COMPRESS 2326 default MODULE_COMPRESS_GZIP 2327 help 2328 This determines which sort of compression will be used during 2329 'make modules_install'. 2330 2331 GZIP (default) and XZ are supported. 2332 2333config MODULE_COMPRESS_GZIP 2334 bool "GZIP" 2335 2336config MODULE_COMPRESS_XZ 2337 bool "XZ" 2338 2339endchoice 2340 2341config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS 2342 bool "Allow loading of modules with missing namespace imports" 2343 help 2344 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in 2345 a namespace. A module that makes use of a symbol exported with such a 2346 namespace is required to import the namespace via MODULE_IMPORT_NS(). 2347 There is no technical reason to enforce correct namespace imports, 2348 but it creates consistency between symbols defining namespaces and 2349 users importing namespaces they make use of. This option relaxes this 2350 requirement and lifts the enforcement when loading a module. 2351 2352 If unsure, say N. 2353 2354config UNUSED_SYMBOLS 2355 bool "Enable unused/obsolete exported symbols" 2356 default y if X86 2357 help 2358 Unused but exported symbols make the kernel needlessly bigger. For 2359 that reason most of these unused exports will soon be removed. This 2360 option is provided temporarily to provide a transition period in case 2361 some external kernel module needs one of these symbols anyway. If you 2362 encounter such a case in your module, consider if you are actually 2363 using the right API. (rationale: since nobody in the kernel is using 2364 this in a module, there is a pretty good chance it's actually the 2365 wrong interface to use). If you really need the symbol, please send a 2366 mail to the linux kernel mailing list mentioning the symbol and why 2367 you really need it, and what the merge plan to the mainline kernel for 2368 your module is. 2369 2370config TRIM_UNUSED_KSYMS 2371 bool "Trim unused exported kernel symbols" 2372 depends on !UNUSED_SYMBOLS 2373 help 2374 The kernel and some modules make many symbols available for 2375 other modules to use via EXPORT_SYMBOL() and variants. Depending 2376 on the set of modules being selected in your kernel configuration, 2377 many of those exported symbols might never be used. 2378 2379 This option allows for unused exported symbols to be dropped from 2380 the build. In turn, this provides the compiler more opportunities 2381 (especially when using LTO) for optimizing the code and reducing 2382 binary size. This might have some security advantages as well. 2383 2384 If unsure, or if you need to build out-of-tree modules, say N. 2385 2386config UNUSED_KSYMS_WHITELIST 2387 string "Whitelist of symbols to keep in ksymtab" 2388 depends on TRIM_UNUSED_KSYMS 2389 help 2390 By default, all unused exported symbols will be un-exported from the 2391 build when TRIM_UNUSED_KSYMS is selected. 2392 2393 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept 2394 exported at all times, even in absence of in-tree users. The value to 2395 set here is the path to a text file containing the list of symbols, 2396 one per line. The path can be absolute, or relative to the kernel 2397 source tree. 2398 2399endif # MODULES 2400 2401config MODULES_TREE_LOOKUP 2402 def_bool y 2403 depends on PERF_EVENTS || TRACING || CFI_CLANG 2404 2405config INIT_ALL_POSSIBLE 2406 bool 2407 help 2408 Back when each arch used to define their own cpu_online_mask and 2409 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2410 with all 1s, and others with all 0s. When they were centralised, 2411 it was better to provide this option than to break all the archs 2412 and have several arch maintainers pursuing me down dark alleys. 2413 2414source "block/Kconfig" 2415 2416config PREEMPT_NOTIFIERS 2417 bool 2418 2419config PADATA 2420 depends on SMP 2421 bool 2422 2423config ASN1 2424 tristate 2425 help 2426 Build a simple ASN.1 grammar compiler that produces a bytecode output 2427 that can be interpreted by the ASN.1 stream decoder and used to 2428 inform it as to what tags are to be expected in a stream and what 2429 functions to call on what tags. 2430 2431source "kernel/Kconfig.locks" 2432 2433config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE 2434 bool 2435 2436config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 2437 bool 2438 2439# It may be useful for an architecture to override the definitions of the 2440# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h> 2441# and the COMPAT_ variants in <linux/compat.h>, in particular to use a 2442# different calling convention for syscalls. They can also override the 2443# macros for not-implemented syscalls in kernel/sys_ni.c and 2444# kernel/time/posix-stubs.c. All these overrides need to be available in 2445# <asm/syscall_wrapper.h>. 2446config ARCH_HAS_SYSCALL_WRAPPER 2447 def_bool n 2448 2449if !ROCKCHIP_MINI_KERNEL 2450source "init/Kconfig.gki" 2451endif 2452