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