1config ARCH 2 string 3 option env="ARCH" 4 5config KERNELVERSION 6 string 7 option env="KERNELVERSION" 8 9config DEFCONFIG_LIST 10 string 11 depends on !UML 12 option defconfig_list 13 default "/lib/modules/$UNAME_RELEASE/.config" 14 default "/etc/kernel-config" 15 default "/boot/config-$UNAME_RELEASE" 16 default "$ARCH_DEFCONFIG" 17 default "arch/$ARCH/defconfig" 18 19config CONSTRUCTORS 20 bool 21 depends on !UML 22 23config IRQ_WORK 24 bool 25 26config BUILDTIME_EXTABLE_SORT 27 bool 28 29config THREAD_INFO_IN_TASK 30 bool 31 help 32 Select this to move thread_info off the stack into task_struct. To 33 make this work, an arch will need to remove all thread_info fields 34 except flags and fix any runtime bugs. 35 36 One subtle change that will be needed is to use try_get_task_stack() 37 and put_task_stack() in save_thread_stack_tsk() and get_wchan(). 38 39menu "General setup" 40 41config BROKEN 42 bool 43 44config BROKEN_ON_SMP 45 bool 46 depends on BROKEN || !SMP 47 default y 48 49config INIT_ENV_ARG_LIMIT 50 int 51 default 32 if !UML 52 default 128 if UML 53 help 54 Maximum of each of the number of arguments and environment 55 variables passed to init from the kernel command line. 56 57 58config CROSS_COMPILE 59 string "Cross-compiler tool prefix" 60 help 61 Same as running 'make CROSS_COMPILE=prefix-' but stored for 62 default make runs in this kernel build directory. You don't 63 need to set this unless you want the configured kernel build 64 directory to select the cross-compiler automatically. 65 66config COMPILE_TEST 67 bool "Compile also drivers which will not load" 68 depends on !UML 69 default n 70 help 71 Some drivers can be compiled on a different platform than they are 72 intended to be run on. Despite they cannot be loaded there (or even 73 when they load they cannot be used due to missing HW support), 74 developers still, opposing to distributors, might want to build such 75 drivers to compile-test them. 76 77 If you are a developer and want to build everything available, say Y 78 here. If you are a user/distributor, say N here to exclude useless 79 drivers to be distributed. 80 81config LOCALVERSION 82 string "Local version - append to kernel release" 83 help 84 Append an extra string to the end of your kernel version. 85 This will show up when you type uname, for example. 86 The string you set here will be appended after the contents of 87 any files with a filename matching localversion* in your 88 object and source tree, in that order. Your total string can 89 be a maximum of 64 characters. 90 91config LOCALVERSION_AUTO 92 bool "Automatically append version information to the version string" 93 default y 94 depends on !COMPILE_TEST 95 help 96 This will try to automatically determine if the current tree is a 97 release tree by looking for git tags that belong to the current 98 top of tree revision. 99 100 A string of the format -gxxxxxxxx will be added to the localversion 101 if a git-based tree is found. The string generated by this will be 102 appended after any matching localversion* files, and after the value 103 set in CONFIG_LOCALVERSION. 104 105 (The actual string used here is the first eight characters produced 106 by running the command: 107 108 $ git rev-parse --verify HEAD 109 110 which is done within the script "scripts/setlocalversion".) 111 112config HAVE_KERNEL_GZIP 113 bool 114 115config HAVE_KERNEL_BZIP2 116 bool 117 118config HAVE_KERNEL_LZMA 119 bool 120 121config HAVE_KERNEL_XZ 122 bool 123 124config HAVE_KERNEL_LZO 125 bool 126 127config HAVE_KERNEL_LZ4 128 bool 129 130choice 131 prompt "Kernel compression mode" 132 default KERNEL_GZIP 133 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 134 help 135 The linux kernel is a kind of self-extracting executable. 136 Several compression algorithms are available, which differ 137 in efficiency, compression and decompression speed. 138 Compression speed is only relevant when building a kernel. 139 Decompression speed is relevant at each boot. 140 141 If you have any problems with bzip2 or lzma compressed 142 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 143 version of this functionality (bzip2 only), for 2.4, was 144 supplied by Christian Ludwig) 145 146 High compression options are mostly useful for users, who 147 are low on disk space (embedded systems), but for whom ram 148 size matters less. 149 150 If in doubt, select 'gzip' 151 152config KERNEL_GZIP 153 bool "Gzip" 154 depends on HAVE_KERNEL_GZIP 155 help 156 The old and tried gzip compression. It provides a good balance 157 between compression ratio and decompression speed. 158 159config KERNEL_BZIP2 160 bool "Bzip2" 161 depends on HAVE_KERNEL_BZIP2 162 help 163 Its compression ratio and speed is intermediate. 164 Decompression speed is slowest among the choices. The kernel 165 size is about 10% smaller with bzip2, in comparison to gzip. 166 Bzip2 uses a large amount of memory. For modern kernels you 167 will need at least 8MB RAM or more for booting. 168 169config KERNEL_LZMA 170 bool "LZMA" 171 depends on HAVE_KERNEL_LZMA 172 help 173 This compression algorithm's ratio is best. Decompression speed 174 is between gzip and bzip2. Compression is slowest. 175 The kernel size is about 33% smaller with LZMA in comparison to gzip. 176 177config KERNEL_XZ 178 bool "XZ" 179 depends on HAVE_KERNEL_XZ 180 help 181 XZ uses the LZMA2 algorithm and instruction set specific 182 BCJ filters which can improve compression ratio of executable 183 code. The size of the kernel is about 30% smaller with XZ in 184 comparison to gzip. On architectures for which there is a BCJ 185 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 186 will create a few percent smaller kernel than plain LZMA. 187 188 The speed is about the same as with LZMA: The decompression 189 speed of XZ is better than that of bzip2 but worse than gzip 190 and LZO. Compression is slow. 191 192config KERNEL_LZO 193 bool "LZO" 194 depends on HAVE_KERNEL_LZO 195 help 196 Its compression ratio is the poorest among the choices. The kernel 197 size is about 10% bigger than gzip; however its speed 198 (both compression and decompression) is the fastest. 199 200config KERNEL_LZ4 201 bool "LZ4" 202 depends on HAVE_KERNEL_LZ4 203 help 204 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 205 A preliminary version of LZ4 de/compression tool is available at 206 <https://code.google.com/p/lz4/>. 207 208 Its compression ratio is worse than LZO. The size of the kernel 209 is about 8% bigger than LZO. But the decompression speed is 210 faster than LZO. 211 212endchoice 213 214config DEFAULT_HOSTNAME 215 string "Default hostname" 216 default "(none)" 217 help 218 This option determines the default system hostname before userspace 219 calls sethostname(2). The kernel traditionally uses "(none)" here, 220 but you may wish to use a different default here to make a minimal 221 system more usable with less configuration. 222 223config SWAP 224 bool "Support for paging of anonymous memory (swap)" 225 depends on MMU && BLOCK 226 default y 227 help 228 This option allows you to choose whether you want to have support 229 for so called swap devices or swap files in your kernel that are 230 used to provide more virtual memory than the actual RAM present 231 in your computer. If unsure say Y. 232 233config SYSVIPC 234 bool "System V IPC" 235 ---help--- 236 Inter Process Communication is a suite of library functions and 237 system calls which let processes (running programs) synchronize and 238 exchange information. It is generally considered to be a good thing, 239 and some programs won't run unless you say Y here. In particular, if 240 you want to run the DOS emulator dosemu under Linux (read the 241 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 242 you'll need to say Y here. 243 244 You can find documentation about IPC with "info ipc" and also in 245 section 6.4 of the Linux Programmer's Guide, available from 246 <http://www.tldp.org/guides.html>. 247 248config SYSVIPC_SYSCTL 249 bool 250 depends on SYSVIPC 251 depends on SYSCTL 252 default y 253 254config POSIX_MQUEUE 255 bool "POSIX Message Queues" 256 depends on NET 257 ---help--- 258 POSIX variant of message queues is a part of IPC. In POSIX message 259 queues every message has a priority which decides about succession 260 of receiving it by a process. If you want to compile and run 261 programs written e.g. for Solaris with use of its POSIX message 262 queues (functions mq_*) say Y here. 263 264 POSIX message queues are visible as a filesystem called 'mqueue' 265 and can be mounted somewhere if you want to do filesystem 266 operations on message queues. 267 268 If unsure, say Y. 269 270config POSIX_MQUEUE_SYSCTL 271 bool 272 depends on POSIX_MQUEUE 273 depends on SYSCTL 274 default y 275 276config CROSS_MEMORY_ATTACH 277 bool "Enable process_vm_readv/writev syscalls" 278 depends on MMU 279 default y 280 help 281 Enabling this option adds the system calls process_vm_readv and 282 process_vm_writev which allow a process with the correct privileges 283 to directly read from or write to another process' address space. 284 See the man page for more details. 285 286config FHANDLE 287 bool "open by fhandle syscalls" if EXPERT 288 select EXPORTFS 289 default y 290 help 291 If you say Y here, a user level program will be able to map 292 file names to handle and then later use the handle for 293 different file system operations. This is useful in implementing 294 userspace file servers, which now track files using handles instead 295 of names. The handle would remain the same even if file names 296 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 297 syscalls. 298 299config USELIB 300 bool "uselib syscall" 301 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION 302 help 303 This option enables the uselib syscall, a system call used in the 304 dynamic linker from libc5 and earlier. glibc does not use this 305 system call. If you intend to run programs built on libc5 or 306 earlier, you may need to enable this syscall. Current systems 307 running glibc can safely disable this. 308 309config AUDIT 310 bool "Auditing support" 311 depends on NET 312 help 313 Enable auditing infrastructure that can be used with another 314 kernel subsystem, such as SELinux (which requires this for 315 logging of avc messages output). System call auditing is included 316 on architectures which support it. 317 318config HAVE_ARCH_AUDITSYSCALL 319 bool 320 321config AUDITSYSCALL 322 def_bool y 323 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 324 325config AUDIT_WATCH 326 def_bool y 327 depends on AUDITSYSCALL 328 select FSNOTIFY 329 330config AUDIT_TREE 331 def_bool y 332 depends on AUDITSYSCALL 333 select FSNOTIFY 334 335source "kernel/irq/Kconfig" 336source "kernel/time/Kconfig" 337 338menu "CPU/Task time and stats accounting" 339 340config VIRT_CPU_ACCOUNTING 341 bool 342 343choice 344 prompt "Cputime accounting" 345 default TICK_CPU_ACCOUNTING if !PPC64 346 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 347 348# Kind of a stub config for the pure tick based cputime accounting 349config TICK_CPU_ACCOUNTING 350 bool "Simple tick based cputime accounting" 351 depends on !S390 && !NO_HZ_FULL 352 help 353 This is the basic tick based cputime accounting that maintains 354 statistics about user, system and idle time spent on per jiffies 355 granularity. 356 357 If unsure, say Y. 358 359config VIRT_CPU_ACCOUNTING_NATIVE 360 bool "Deterministic task and CPU time accounting" 361 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 362 select VIRT_CPU_ACCOUNTING 363 help 364 Select this option to enable more accurate task and CPU time 365 accounting. This is done by reading a CPU counter on each 366 kernel entry and exit and on transitions within the kernel 367 between system, softirq and hardirq state, so there is a 368 small performance impact. In the case of s390 or IBM POWER > 5, 369 this also enables accounting of stolen time on logically-partitioned 370 systems. 371 372config VIRT_CPU_ACCOUNTING_GEN 373 bool "Full dynticks CPU time accounting" 374 depends on HAVE_CONTEXT_TRACKING 375 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 376 select VIRT_CPU_ACCOUNTING 377 select CONTEXT_TRACKING 378 help 379 Select this option to enable task and CPU time accounting on full 380 dynticks systems. This accounting is implemented by watching every 381 kernel-user boundaries using the context tracking subsystem. 382 The accounting is thus performed at the expense of some significant 383 overhead. 384 385 For now this is only useful if you are working on the full 386 dynticks subsystem development. 387 388 If unsure, say N. 389 390endchoice 391 392config IRQ_TIME_ACCOUNTING 393 bool "Fine granularity task level IRQ time accounting" 394 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE 395 help 396 Select this option to enable fine granularity task irq time 397 accounting. This is done by reading a timestamp on each 398 transitions between softirq and hardirq state, so there can be a 399 small performance impact. 400 401 If in doubt, say N here. 402 403config BSD_PROCESS_ACCT 404 bool "BSD Process Accounting" 405 depends on MULTIUSER 406 help 407 If you say Y here, a user level program will be able to instruct the 408 kernel (via a special system call) to write process accounting 409 information to a file: whenever a process exits, information about 410 that process will be appended to the file by the kernel. The 411 information includes things such as creation time, owning user, 412 command name, memory usage, controlling terminal etc. (the complete 413 list is in the struct acct in <file:include/linux/acct.h>). It is 414 up to the user level program to do useful things with this 415 information. This is generally a good idea, so say Y. 416 417config BSD_PROCESS_ACCT_V3 418 bool "BSD Process Accounting version 3 file format" 419 depends on BSD_PROCESS_ACCT 420 default n 421 help 422 If you say Y here, the process accounting information is written 423 in a new file format that also logs the process IDs of each 424 process and it's parent. Note that this file format is incompatible 425 with previous v0/v1/v2 file formats, so you will need updated tools 426 for processing it. A preliminary version of these tools is available 427 at <http://www.gnu.org/software/acct/>. 428 429config TASKSTATS 430 bool "Export task/process statistics through netlink" 431 depends on NET 432 depends on MULTIUSER 433 default n 434 help 435 Export selected statistics for tasks/processes through the 436 generic netlink interface. Unlike BSD process accounting, the 437 statistics are available during the lifetime of tasks/processes as 438 responses to commands. Like BSD accounting, they are sent to user 439 space on task exit. 440 441 Say N if unsure. 442 443config TASK_DELAY_ACCT 444 bool "Enable per-task delay accounting" 445 depends on TASKSTATS 446 select SCHED_INFO 447 help 448 Collect information on time spent by a task waiting for system 449 resources like cpu, synchronous block I/O completion and swapping 450 in pages. Such statistics can help in setting a task's priorities 451 relative to other tasks for cpu, io, rss limits etc. 452 453 Say N if unsure. 454 455config TASK_XACCT 456 bool "Enable extended accounting over taskstats" 457 depends on TASKSTATS 458 help 459 Collect extended task accounting data and send the data 460 to userland for processing over the taskstats interface. 461 462 Say N if unsure. 463 464config TASK_IO_ACCOUNTING 465 bool "Enable per-task storage I/O accounting" 466 depends on TASK_XACCT 467 help 468 Collect information on the number of bytes of storage I/O which this 469 task has caused. 470 471 Say N if unsure. 472 473endmenu # "CPU/Task time and stats accounting" 474 475menu "RCU Subsystem" 476 477config TREE_RCU 478 bool 479 default y if !PREEMPT && SMP 480 help 481 This option selects the RCU implementation that is 482 designed for very large SMP system with hundreds or 483 thousands of CPUs. It also scales down nicely to 484 smaller systems. 485 486config PREEMPT_RCU 487 bool 488 default y if PREEMPT 489 help 490 This option selects the RCU implementation that is 491 designed for very large SMP systems with hundreds or 492 thousands of CPUs, but for which real-time response 493 is also required. It also scales down nicely to 494 smaller systems. 495 496 Select this option if you are unsure. 497 498config TINY_RCU 499 bool 500 default y if !PREEMPT && !SMP 501 help 502 This option selects the RCU implementation that is 503 designed for UP systems from which real-time response 504 is not required. This option greatly reduces the 505 memory footprint of RCU. 506 507config RCU_EXPERT 508 bool "Make expert-level adjustments to RCU configuration" 509 default n 510 help 511 This option needs to be enabled if you wish to make 512 expert-level adjustments to RCU configuration. By default, 513 no such adjustments can be made, which has the often-beneficial 514 side-effect of preventing "make oldconfig" from asking you all 515 sorts of detailed questions about how you would like numerous 516 obscure RCU options to be set up. 517 518 Say Y if you need to make expert-level adjustments to RCU. 519 520 Say N if you are unsure. 521 522config SRCU 523 bool 524 help 525 This option selects the sleepable version of RCU. This version 526 permits arbitrary sleeping or blocking within RCU read-side critical 527 sections. 528 529config TASKS_RCU 530 bool 531 default n 532 select SRCU 533 help 534 This option enables a task-based RCU implementation that uses 535 only voluntary context switch (not preemption!), idle, and 536 user-mode execution as quiescent states. 537 538config RCU_STALL_COMMON 539 def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE ) 540 help 541 This option enables RCU CPU stall code that is common between 542 the TINY and TREE variants of RCU. The purpose is to allow 543 the tiny variants to disable RCU CPU stall warnings, while 544 making these warnings mandatory for the tree variants. 545 546config CONTEXT_TRACKING 547 bool 548 549config CONTEXT_TRACKING_FORCE 550 bool "Force context tracking" 551 depends on CONTEXT_TRACKING 552 default y if !NO_HZ_FULL 553 help 554 The major pre-requirement for full dynticks to work is to 555 support the context tracking subsystem. But there are also 556 other dependencies to provide in order to make the full 557 dynticks working. 558 559 This option stands for testing when an arch implements the 560 context tracking backend but doesn't yet fullfill all the 561 requirements to make the full dynticks feature working. 562 Without the full dynticks, there is no way to test the support 563 for context tracking and the subsystems that rely on it: RCU 564 userspace extended quiescent state and tickless cputime 565 accounting. This option copes with the absence of the full 566 dynticks subsystem by forcing the context tracking on all 567 CPUs in the system. 568 569 Say Y only if you're working on the development of an 570 architecture backend for the context tracking. 571 572 Say N otherwise, this option brings an overhead that you 573 don't want in production. 574 575 576config RCU_FANOUT 577 int "Tree-based hierarchical RCU fanout value" 578 range 2 64 if 64BIT 579 range 2 32 if !64BIT 580 depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT 581 default 64 if 64BIT 582 default 32 if !64BIT 583 help 584 This option controls the fanout of hierarchical implementations 585 of RCU, allowing RCU to work efficiently on machines with 586 large numbers of CPUs. This value must be at least the fourth 587 root of NR_CPUS, which allows NR_CPUS to be insanely large. 588 The default value of RCU_FANOUT should be used for production 589 systems, but if you are stress-testing the RCU implementation 590 itself, small RCU_FANOUT values allow you to test large-system 591 code paths on small(er) systems. 592 593 Select a specific number if testing RCU itself. 594 Take the default if unsure. 595 596config RCU_FANOUT_LEAF 597 int "Tree-based hierarchical RCU leaf-level fanout value" 598 range 2 64 if 64BIT 599 range 2 32 if !64BIT 600 depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT 601 default 16 602 help 603 This option controls the leaf-level fanout of hierarchical 604 implementations of RCU, and allows trading off cache misses 605 against lock contention. Systems that synchronize their 606 scheduling-clock interrupts for energy-efficiency reasons will 607 want the default because the smaller leaf-level fanout keeps 608 lock contention levels acceptably low. Very large systems 609 (hundreds or thousands of CPUs) will instead want to set this 610 value to the maximum value possible in order to reduce the 611 number of cache misses incurred during RCU's grace-period 612 initialization. These systems tend to run CPU-bound, and thus 613 are not helped by synchronized interrupts, and thus tend to 614 skew them, which reduces lock contention enough that large 615 leaf-level fanouts work well. 616 617 Select a specific number if testing RCU itself. 618 619 Select the maximum permissible value for large systems. 620 621 Take the default if unsure. 622 623config RCU_FAST_NO_HZ 624 bool "Accelerate last non-dyntick-idle CPU's grace periods" 625 depends on NO_HZ_COMMON && SMP && RCU_EXPERT 626 default n 627 help 628 This option permits CPUs to enter dynticks-idle state even if 629 they have RCU callbacks queued, and prevents RCU from waking 630 these CPUs up more than roughly once every four jiffies (by 631 default, you can adjust this using the rcutree.rcu_idle_gp_delay 632 parameter), thus improving energy efficiency. On the other 633 hand, this option increases the duration of RCU grace periods, 634 for example, slowing down synchronize_rcu(). 635 636 Say Y if energy efficiency is critically important, and you 637 don't care about increased grace-period durations. 638 639 Say N if you are unsure. 640 641config TREE_RCU_TRACE 642 def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU ) 643 select DEBUG_FS 644 help 645 This option provides tracing for the TREE_RCU and 646 PREEMPT_RCU implementations, permitting Makefile to 647 trivially select kernel/rcutree_trace.c. 648 649config RCU_BOOST 650 bool "Enable RCU priority boosting" 651 depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT 652 default n 653 help 654 This option boosts the priority of preempted RCU readers that 655 block the current preemptible RCU grace period for too long. 656 This option also prevents heavy loads from blocking RCU 657 callback invocation for all flavors of RCU. 658 659 Say Y here if you are working with real-time apps or heavy loads 660 Say N here if you are unsure. 661 662config RCU_KTHREAD_PRIO 663 int "Real-time priority to use for RCU worker threads" 664 range 1 99 if RCU_BOOST 665 range 0 99 if !RCU_BOOST 666 default 1 if RCU_BOOST 667 default 0 if !RCU_BOOST 668 depends on RCU_EXPERT 669 help 670 This option specifies the SCHED_FIFO priority value that will be 671 assigned to the rcuc/n and rcub/n threads and is also the value 672 used for RCU_BOOST (if enabled). If you are working with a 673 real-time application that has one or more CPU-bound threads 674 running at a real-time priority level, you should set 675 RCU_KTHREAD_PRIO to a priority higher than the highest-priority 676 real-time CPU-bound application thread. The default RCU_KTHREAD_PRIO 677 value of 1 is appropriate in the common case, which is real-time 678 applications that do not have any CPU-bound threads. 679 680 Some real-time applications might not have a single real-time 681 thread that saturates a given CPU, but instead might have 682 multiple real-time threads that, taken together, fully utilize 683 that CPU. In this case, you should set RCU_KTHREAD_PRIO to 684 a priority higher than the lowest-priority thread that is 685 conspiring to prevent the CPU from running any non-real-time 686 tasks. For example, if one thread at priority 10 and another 687 thread at priority 5 are between themselves fully consuming 688 the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be 689 set to priority 6 or higher. 690 691 Specify the real-time priority, or take the default if unsure. 692 693config RCU_BOOST_DELAY 694 int "Milliseconds to delay boosting after RCU grace-period start" 695 range 0 3000 696 depends on RCU_BOOST 697 default 500 698 help 699 This option specifies the time to wait after the beginning of 700 a given grace period before priority-boosting preempted RCU 701 readers blocking that grace period. Note that any RCU reader 702 blocking an expedited RCU grace period is boosted immediately. 703 704 Accept the default if unsure. 705 706config RCU_NOCB_CPU 707 bool "Offload RCU callback processing from boot-selected CPUs" 708 depends on TREE_RCU || PREEMPT_RCU 709 depends on RCU_EXPERT || NO_HZ_FULL 710 default n 711 help 712 Use this option to reduce OS jitter for aggressive HPC or 713 real-time workloads. It can also be used to offload RCU 714 callback invocation to energy-efficient CPUs in battery-powered 715 asymmetric multiprocessors. 716 717 This option offloads callback invocation from the set of 718 CPUs specified at boot time by the rcu_nocbs parameter. 719 For each such CPU, a kthread ("rcuox/N") will be created to 720 invoke callbacks, where the "N" is the CPU being offloaded, 721 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and 722 "s" for RCU-sched. Nothing prevents this kthread from running 723 on the specified CPUs, but (1) the kthreads may be preempted 724 between each callback, and (2) affinity or cgroups can be used 725 to force the kthreads to run on whatever set of CPUs is desired. 726 727 Say Y here if you want to help to debug reduced OS jitter. 728 Say N here if you are unsure. 729 730choice 731 prompt "Build-forced no-CBs CPUs" 732 default RCU_NOCB_CPU_NONE 733 depends on RCU_NOCB_CPU 734 help 735 This option allows no-CBs CPUs (whose RCU callbacks are invoked 736 from kthreads rather than from softirq context) to be specified 737 at build time. Additional no-CBs CPUs may be specified by 738 the rcu_nocbs= boot parameter. 739 740config RCU_NOCB_CPU_NONE 741 bool "No build_forced no-CBs CPUs" 742 help 743 This option does not force any of the CPUs to be no-CBs CPUs. 744 Only CPUs designated by the rcu_nocbs= boot parameter will be 745 no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU 746 kthreads whose names begin with "rcuo". All other CPUs will 747 invoke their own RCU callbacks in softirq context. 748 749 Select this option if you want to choose no-CBs CPUs at 750 boot time, for example, to allow testing of different no-CBs 751 configurations without having to rebuild the kernel each time. 752 753config RCU_NOCB_CPU_ZERO 754 bool "CPU 0 is a build_forced no-CBs CPU" 755 help 756 This option forces CPU 0 to be a no-CBs CPU, so that its RCU 757 callbacks are invoked by a per-CPU kthread whose name begins 758 with "rcuo". Additional CPUs may be designated as no-CBs 759 CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs. 760 All other CPUs will invoke their own RCU callbacks in softirq 761 context. 762 763 Select this if CPU 0 needs to be a no-CBs CPU for real-time 764 or energy-efficiency reasons, but the real reason it exists 765 is to ensure that randconfig testing covers mixed systems. 766 767config RCU_NOCB_CPU_ALL 768 bool "All CPUs are build_forced no-CBs CPUs" 769 help 770 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs= 771 boot parameter will be ignored. All CPUs' RCU callbacks will 772 be executed in the context of per-CPU rcuo kthreads created for 773 this purpose. Assuming that the kthreads whose names start with 774 "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter 775 on the remaining CPUs, but might decrease memory locality during 776 RCU-callback invocation, thus potentially degrading throughput. 777 778 Select this if all CPUs need to be no-CBs CPUs for real-time 779 or energy-efficiency reasons. 780 781endchoice 782 783endmenu # "RCU Subsystem" 784 785config BUILD_BIN2C 786 bool 787 default n 788 789config IKCONFIG 790 tristate "Kernel .config support" 791 select BUILD_BIN2C 792 ---help--- 793 This option enables the complete Linux kernel ".config" file 794 contents to be saved in the kernel. It provides documentation 795 of which kernel options are used in a running kernel or in an 796 on-disk kernel. This information can be extracted from the kernel 797 image file with the script scripts/extract-ikconfig and used as 798 input to rebuild the current kernel or to build another kernel. 799 It can also be extracted from a running kernel by reading 800 /proc/config.gz if enabled (below). 801 802config IKCONFIG_PROC 803 bool "Enable access to .config through /proc/config.gz" 804 depends on IKCONFIG && PROC_FS 805 ---help--- 806 This option enables access to the kernel configuration file 807 through /proc/config.gz. 808 809config LOG_BUF_SHIFT 810 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 811 range 12 25 812 default 17 813 depends on PRINTK 814 help 815 Select the minimal kernel log buffer size as a power of 2. 816 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 817 parameter, see below. Any higher size also might be forced 818 by "log_buf_len" boot parameter. 819 820 Examples: 821 17 => 128 KB 822 16 => 64 KB 823 15 => 32 KB 824 14 => 16 KB 825 13 => 8 KB 826 12 => 4 KB 827 828config LOG_CPU_MAX_BUF_SHIFT 829 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 830 depends on SMP 831 range 0 21 832 default 12 if !BASE_SMALL 833 default 0 if BASE_SMALL 834 depends on PRINTK 835 help 836 This option allows to increase the default ring buffer size 837 according to the number of CPUs. The value defines the contribution 838 of each CPU as a power of 2. The used space is typically only few 839 lines however it might be much more when problems are reported, 840 e.g. backtraces. 841 842 The increased size means that a new buffer has to be allocated and 843 the original static one is unused. It makes sense only on systems 844 with more CPUs. Therefore this value is used only when the sum of 845 contributions is greater than the half of the default kernel ring 846 buffer as defined by LOG_BUF_SHIFT. The default values are set 847 so that more than 64 CPUs are needed to trigger the allocation. 848 849 Also this option is ignored when "log_buf_len" kernel parameter is 850 used as it forces an exact (power of two) size of the ring buffer. 851 852 The number of possible CPUs is used for this computation ignoring 853 hotplugging making the computation optimal for the worst case 854 scenario while allowing a simple algorithm to be used from bootup. 855 856 Examples shift values and their meaning: 857 17 => 128 KB for each CPU 858 16 => 64 KB for each CPU 859 15 => 32 KB for each CPU 860 14 => 16 KB for each CPU 861 13 => 8 KB for each CPU 862 12 => 4 KB for each CPU 863 864config PRINTK_SAFE_LOG_BUF_SHIFT 865 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 866 range 10 21 867 default 13 868 depends on PRINTK 869 help 870 Select the size of an alternate printk per-CPU buffer where messages 871 printed from usafe contexts are temporary stored. One example would 872 be NMI messages, another one - printk recursion. The messages are 873 copied to the main log buffer in a safe context to avoid a deadlock. 874 The value defines the size as a power of 2. 875 876 Those messages are rare and limited. The largest one is when 877 a backtrace is printed. It usually fits into 4KB. Select 878 8KB if you want to be on the safe side. 879 880 Examples: 881 17 => 128 KB for each CPU 882 16 => 64 KB for each CPU 883 15 => 32 KB for each CPU 884 14 => 16 KB for each CPU 885 13 => 8 KB for each CPU 886 12 => 4 KB for each CPU 887 888# 889# Architectures with an unreliable sched_clock() should select this: 890# 891config HAVE_UNSTABLE_SCHED_CLOCK 892 bool 893 894config GENERIC_SCHED_CLOCK 895 bool 896 897# 898# For architectures that want to enable the support for NUMA-affine scheduler 899# balancing logic: 900# 901config ARCH_SUPPORTS_NUMA_BALANCING 902 bool 903 904# 905# For architectures that prefer to flush all TLBs after a number of pages 906# are unmapped instead of sending one IPI per page to flush. The architecture 907# must provide guarantees on what happens if a clean TLB cache entry is 908# written after the unmap. Details are in mm/rmap.c near the check for 909# should_defer_flush. The architecture should also consider if the full flush 910# and the refill costs are offset by the savings of sending fewer IPIs. 911config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 912 bool 913 914# 915# For architectures that know their GCC __int128 support is sound 916# 917config ARCH_SUPPORTS_INT128 918 bool 919 920# For architectures that (ab)use NUMA to represent different memory regions 921# all cpu-local but of different latencies, such as SuperH. 922# 923config ARCH_WANT_NUMA_VARIABLE_LOCALITY 924 bool 925 926config NUMA_BALANCING 927 bool "Memory placement aware NUMA scheduler" 928 depends on ARCH_SUPPORTS_NUMA_BALANCING 929 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 930 depends on SMP && NUMA && MIGRATION 931 help 932 This option adds support for automatic NUMA aware memory/task placement. 933 The mechanism is quite primitive and is based on migrating memory when 934 it has references to the node the task is running on. 935 936 This system will be inactive on UMA systems. 937 938config NUMA_BALANCING_DEFAULT_ENABLED 939 bool "Automatically enable NUMA aware memory/task placement" 940 default y 941 depends on NUMA_BALANCING 942 help 943 If set, automatic NUMA balancing will be enabled if running on a NUMA 944 machine. 945 946menuconfig CGROUPS 947 bool "Control Group support" 948 select KERNFS 949 help 950 This option adds support for grouping sets of processes together, for 951 use with process control subsystems such as Cpusets, CFS, memory 952 controls or device isolation. 953 See 954 - Documentation/scheduler/sched-design-CFS.txt (CFS) 955 - Documentation/cgroup-v1/ (features for grouping, isolation 956 and resource control) 957 958 Say N if unsure. 959 960if CGROUPS 961 962config PAGE_COUNTER 963 bool 964 965config MEMCG 966 bool "Memory controller" 967 select PAGE_COUNTER 968 select EVENTFD 969 help 970 Provides control over the memory footprint of tasks in a cgroup. 971 972config MEMCG_SWAP 973 bool "Swap controller" 974 depends on MEMCG && SWAP 975 help 976 Provides control over the swap space consumed by tasks in a cgroup. 977 978config MEMCG_SWAP_ENABLED 979 bool "Swap controller enabled by default" 980 depends on MEMCG_SWAP 981 default y 982 help 983 Memory Resource Controller Swap Extension comes with its price in 984 a bigger memory consumption. General purpose distribution kernels 985 which want to enable the feature but keep it disabled by default 986 and let the user enable it by swapaccount=1 boot command line 987 parameter should have this option unselected. 988 For those who want to have the feature enabled by default should 989 select this option (if, for some reason, they need to disable it 990 then swapaccount=0 does the trick). 991 992config BLK_CGROUP 993 bool "IO controller" 994 depends on BLOCK 995 default n 996 ---help--- 997 Generic block IO controller cgroup interface. This is the common 998 cgroup interface which should be used by various IO controlling 999 policies. 1000 1001 Currently, CFQ IO scheduler uses it to recognize task groups and 1002 control disk bandwidth allocation (proportional time slice allocation) 1003 to such task groups. It is also used by bio throttling logic in 1004 block layer to implement upper limit in IO rates on a device. 1005 1006 This option only enables generic Block IO controller infrastructure. 1007 One needs to also enable actual IO controlling logic/policy. For 1008 enabling proportional weight division of disk bandwidth in CFQ, set 1009 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 1010 CONFIG_BLK_DEV_THROTTLING=y. 1011 1012 See Documentation/cgroup-v1/blkio-controller.txt for more information. 1013 1014config DEBUG_BLK_CGROUP 1015 bool "IO controller debugging" 1016 depends on BLK_CGROUP 1017 default n 1018 ---help--- 1019 Enable some debugging help. Currently it exports additional stat 1020 files in a cgroup which can be useful for debugging. 1021 1022config CGROUP_WRITEBACK 1023 bool 1024 depends on MEMCG && BLK_CGROUP 1025 default y 1026 1027menuconfig CGROUP_SCHED 1028 bool "CPU controller" 1029 default n 1030 help 1031 This feature lets CPU scheduler recognize task groups and control CPU 1032 bandwidth allocation to such task groups. It uses cgroups to group 1033 tasks. 1034 1035if CGROUP_SCHED 1036config FAIR_GROUP_SCHED 1037 bool "Group scheduling for SCHED_OTHER" 1038 depends on CGROUP_SCHED 1039 default CGROUP_SCHED 1040 1041config CFS_BANDWIDTH 1042 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 1043 depends on FAIR_GROUP_SCHED 1044 default n 1045 help 1046 This option allows users to define CPU bandwidth rates (limits) for 1047 tasks running within the fair group scheduler. Groups with no limit 1048 set are considered to be unconstrained and will run with no 1049 restriction. 1050 See tip/Documentation/scheduler/sched-bwc.txt for more information. 1051 1052config RT_GROUP_SCHED 1053 bool "Group scheduling for SCHED_RR/FIFO" 1054 depends on CGROUP_SCHED 1055 default n 1056 help 1057 This feature lets you explicitly allocate real CPU bandwidth 1058 to task groups. If enabled, it will also make it impossible to 1059 schedule realtime tasks for non-root users until you allocate 1060 realtime bandwidth for them. 1061 See Documentation/scheduler/sched-rt-group.txt for more information. 1062 1063endif #CGROUP_SCHED 1064 1065config CGROUP_PIDS 1066 bool "PIDs controller" 1067 help 1068 Provides enforcement of process number limits in the scope of a 1069 cgroup. Any attempt to fork more processes than is allowed in the 1070 cgroup will fail. PIDs are fundamentally a global resource because it 1071 is fairly trivial to reach PID exhaustion before you reach even a 1072 conservative kmemcg limit. As a result, it is possible to grind a 1073 system to halt without being limited by other cgroup policies. The 1074 PIDs controller is designed to stop this from happening. 1075 1076 It should be noted that organisational operations (such as attaching 1077 to a cgroup hierarchy will *not* be blocked by the PIDs controller), 1078 since the PIDs limit only affects a process's ability to fork, not to 1079 attach to a cgroup. 1080 1081config CGROUP_FREEZER 1082 bool "Freezer controller" 1083 help 1084 Provides a way to freeze and unfreeze all tasks in a 1085 cgroup. 1086 1087 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1088 controller includes important in-kernel memory consumers per default. 1089 1090 If you're using cgroup2, say N. 1091 1092config CGROUP_HUGETLB 1093 bool "HugeTLB controller" 1094 depends on HUGETLB_PAGE 1095 select PAGE_COUNTER 1096 default n 1097 help 1098 Provides a cgroup controller for HugeTLB pages. 1099 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1100 The limit is enforced during page fault. Since HugeTLB doesn't 1101 support page reclaim, enforcing the limit at page fault time implies 1102 that, the application will get SIGBUS signal if it tries to access 1103 HugeTLB pages beyond its limit. This requires the application to know 1104 beforehand how much HugeTLB pages it would require for its use. The 1105 control group is tracked in the third page lru pointer. This means 1106 that we cannot use the controller with huge page less than 3 pages. 1107 1108config CPUSETS 1109 bool "Cpuset controller" 1110 help 1111 This option will let you create and manage CPUSETs which 1112 allow dynamically partitioning a system into sets of CPUs and 1113 Memory Nodes and assigning tasks to run only within those sets. 1114 This is primarily useful on large SMP or NUMA systems. 1115 1116 Say N if unsure. 1117 1118config PROC_PID_CPUSET 1119 bool "Include legacy /proc/<pid>/cpuset file" 1120 depends on CPUSETS 1121 default y 1122 1123config CGROUP_DEVICE 1124 bool "Device controller" 1125 help 1126 Provides a cgroup controller implementing whitelists for 1127 devices which a process in the cgroup can mknod or open. 1128 1129config CGROUP_CPUACCT 1130 bool "Simple CPU accounting controller" 1131 help 1132 Provides a simple controller for monitoring the 1133 total CPU consumed by the tasks in a cgroup. 1134 1135config CGROUP_PERF 1136 bool "Perf controller" 1137 depends on PERF_EVENTS 1138 help 1139 This option extends the perf per-cpu mode to restrict monitoring 1140 to threads which belong to the cgroup specified and run on the 1141 designated cpu. 1142 1143 Say N if unsure. 1144 1145config CGROUP_BPF 1146 bool "Support for eBPF programs attached to cgroups" 1147 depends on BPF_SYSCALL 1148 select SOCK_CGROUP_DATA 1149 help 1150 Allow attaching eBPF programs to a cgroup using the bpf(2) 1151 syscall command BPF_PROG_ATTACH. 1152 1153 In which context these programs are accessed depends on the type 1154 of attachment. For instance, programs that are attached using 1155 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1156 inet sockets. 1157 1158config CGROUP_DEBUG 1159 bool "Example controller" 1160 default n 1161 help 1162 This option enables a simple controller that exports 1163 debugging information about the cgroups framework. 1164 1165 Say N. 1166 1167config SOCK_CGROUP_DATA 1168 bool 1169 default n 1170 1171endif # CGROUPS 1172 1173config CHECKPOINT_RESTORE 1174 bool "Checkpoint/restore support" if EXPERT 1175 select PROC_CHILDREN 1176 default n 1177 help 1178 Enables additional kernel features in a sake of checkpoint/restore. 1179 In particular it adds auxiliary prctl codes to setup process text, 1180 data and heap segment sizes, and a few additional /proc filesystem 1181 entries. 1182 1183 If unsure, say N here. 1184 1185menuconfig NAMESPACES 1186 bool "Namespaces support" if EXPERT 1187 depends on MULTIUSER 1188 default !EXPERT 1189 help 1190 Provides the way to make tasks work with different objects using 1191 the same id. For example same IPC id may refer to different objects 1192 or same user id or pid may refer to different tasks when used in 1193 different namespaces. 1194 1195if NAMESPACES 1196 1197config UTS_NS 1198 bool "UTS namespace" 1199 default y 1200 help 1201 In this namespace tasks see different info provided with the 1202 uname() system call 1203 1204config IPC_NS 1205 bool "IPC namespace" 1206 depends on (SYSVIPC || POSIX_MQUEUE) 1207 default y 1208 help 1209 In this namespace tasks work with IPC ids which correspond to 1210 different IPC objects in different namespaces. 1211 1212config USER_NS 1213 bool "User namespace" 1214 default n 1215 help 1216 This allows containers, i.e. vservers, to use user namespaces 1217 to provide different user info for different servers. 1218 1219 When user namespaces are enabled in the kernel it is 1220 recommended that the MEMCG option also be enabled and that 1221 user-space use the memory control groups to limit the amount 1222 of memory a memory unprivileged users can use. 1223 1224 If unsure, say N. 1225 1226config PID_NS 1227 bool "PID Namespaces" 1228 default y 1229 help 1230 Support process id namespaces. This allows having multiple 1231 processes with the same pid as long as they are in different 1232 pid namespaces. This is a building block of containers. 1233 1234config NET_NS 1235 bool "Network namespace" 1236 depends on NET 1237 default y 1238 help 1239 Allow user space to create what appear to be multiple instances 1240 of the network stack. 1241 1242endif # NAMESPACES 1243 1244config SCHED_AUTOGROUP 1245 bool "Automatic process group scheduling" 1246 select CGROUPS 1247 select CGROUP_SCHED 1248 select FAIR_GROUP_SCHED 1249 help 1250 This option optimizes the scheduler for common desktop workloads by 1251 automatically creating and populating task groups. This separation 1252 of workloads isolates aggressive CPU burners (like build jobs) from 1253 desktop applications. Task group autogeneration is currently based 1254 upon task session. 1255 1256config SYSFS_DEPRECATED 1257 bool "Enable deprecated sysfs features to support old userspace tools" 1258 depends on SYSFS 1259 default n 1260 help 1261 This option adds code that switches the layout of the "block" class 1262 devices, to not show up in /sys/class/block/, but only in 1263 /sys/block/. 1264 1265 This switch is only active when the sysfs.deprecated=1 boot option is 1266 passed or the SYSFS_DEPRECATED_V2 option is set. 1267 1268 This option allows new kernels to run on old distributions and tools, 1269 which might get confused by /sys/class/block/. Since 2007/2008 all 1270 major distributions and tools handle this just fine. 1271 1272 Recent distributions and userspace tools after 2009/2010 depend on 1273 the existence of /sys/class/block/, and will not work with this 1274 option enabled. 1275 1276 Only if you are using a new kernel on an old distribution, you might 1277 need to say Y here. 1278 1279config SYSFS_DEPRECATED_V2 1280 bool "Enable deprecated sysfs features by default" 1281 default n 1282 depends on SYSFS 1283 depends on SYSFS_DEPRECATED 1284 help 1285 Enable deprecated sysfs by default. 1286 1287 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1288 option. 1289 1290 Only if you are using a new kernel on an old distribution, you might 1291 need to say Y here. Even then, odds are you would not need it 1292 enabled, you can always pass the boot option if absolutely necessary. 1293 1294config RELAY 1295 bool "Kernel->user space relay support (formerly relayfs)" 1296 select IRQ_WORK 1297 help 1298 This option enables support for relay interface support in 1299 certain file systems (such as debugfs). 1300 It is designed to provide an efficient mechanism for tools and 1301 facilities to relay large amounts of data from kernel space to 1302 user space. 1303 1304 If unsure, say N. 1305 1306config BLK_DEV_INITRD 1307 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1308 depends on BROKEN || !FRV 1309 help 1310 The initial RAM filesystem is a ramfs which is loaded by the 1311 boot loader (loadlin or lilo) and that is mounted as root 1312 before the normal boot procedure. It is typically used to 1313 load modules needed to mount the "real" root file system, 1314 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1315 1316 If RAM disk support (BLK_DEV_RAM) is also included, this 1317 also enables initial RAM disk (initrd) support and adds 1318 15 Kbytes (more on some other architectures) to the kernel size. 1319 1320 If unsure say Y. 1321 1322if BLK_DEV_INITRD 1323 1324source "usr/Kconfig" 1325 1326endif 1327 1328choice 1329 prompt "Compiler optimization level" 1330 default CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE 1331 1332config CC_OPTIMIZE_FOR_PERFORMANCE 1333 bool "Optimize for performance" 1334 help 1335 This is the default optimization level for the kernel, building 1336 with the "-O2" compiler flag for best performance and most 1337 helpful compile-time warnings. 1338 1339config CC_OPTIMIZE_FOR_SIZE 1340 bool "Optimize for size" 1341 help 1342 Enabling this option will pass "-Os" instead of "-O2" to 1343 your compiler resulting in a smaller kernel. 1344 1345 If unsure, say N. 1346 1347endchoice 1348 1349config SYSCTL 1350 bool 1351 1352config ANON_INODES 1353 bool 1354 1355config HAVE_UID16 1356 bool 1357 1358config SYSCTL_EXCEPTION_TRACE 1359 bool 1360 help 1361 Enable support for /proc/sys/debug/exception-trace. 1362 1363config SYSCTL_ARCH_UNALIGN_NO_WARN 1364 bool 1365 help 1366 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1367 Allows arch to define/use @no_unaligned_warning to possibly warn 1368 about unaligned access emulation going on under the hood. 1369 1370config SYSCTL_ARCH_UNALIGN_ALLOW 1371 bool 1372 help 1373 Enable support for /proc/sys/kernel/unaligned-trap 1374 Allows arches to define/use @unaligned_enabled to runtime toggle 1375 the unaligned access emulation. 1376 see arch/parisc/kernel/unaligned.c for reference 1377 1378config HAVE_PCSPKR_PLATFORM 1379 bool 1380 1381# interpreter that classic socket filters depend on 1382config BPF 1383 bool 1384 1385menuconfig EXPERT 1386 bool "Configure standard kernel features (expert users)" 1387 # Unhide debug options, to make the on-by-default options visible 1388 select DEBUG_KERNEL 1389 help 1390 This option allows certain base kernel options and settings 1391 to be disabled or tweaked. This is for specialized 1392 environments which can tolerate a "non-standard" kernel. 1393 Only use this if you really know what you are doing. 1394 1395config UID16 1396 bool "Enable 16-bit UID system calls" if EXPERT 1397 depends on HAVE_UID16 && MULTIUSER 1398 default y 1399 help 1400 This enables the legacy 16-bit UID syscall wrappers. 1401 1402config MULTIUSER 1403 bool "Multiple users, groups and capabilities support" if EXPERT 1404 default y 1405 help 1406 This option enables support for non-root users, groups and 1407 capabilities. 1408 1409 If you say N here, all processes will run with UID 0, GID 0, and all 1410 possible capabilities. Saying N here also compiles out support for 1411 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1412 setgid, and capset. 1413 1414 If unsure, say Y here. 1415 1416config SGETMASK_SYSCALL 1417 bool "sgetmask/ssetmask syscalls support" if EXPERT 1418 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH 1419 ---help--- 1420 sys_sgetmask and sys_ssetmask are obsolete system calls 1421 no longer supported in libc but still enabled by default in some 1422 architectures. 1423 1424 If unsure, leave the default option here. 1425 1426config SYSFS_SYSCALL 1427 bool "Sysfs syscall support" if EXPERT 1428 default y 1429 ---help--- 1430 sys_sysfs is an obsolete system call no longer supported in libc. 1431 Note that disabling this option is more secure but might break 1432 compatibility with some systems. 1433 1434 If unsure say Y here. 1435 1436config SYSCTL_SYSCALL 1437 bool "Sysctl syscall support" if EXPERT 1438 depends on PROC_SYSCTL 1439 default n 1440 select SYSCTL 1441 ---help--- 1442 sys_sysctl uses binary paths that have been found challenging 1443 to properly maintain and use. The interface in /proc/sys 1444 using paths with ascii names is now the primary path to this 1445 information. 1446 1447 Almost nothing using the binary sysctl interface so if you are 1448 trying to save some space it is probably safe to disable this, 1449 making your kernel marginally smaller. 1450 1451 If unsure say N here. 1452 1453config POSIX_TIMERS 1454 bool "Posix Clocks & timers" if EXPERT 1455 default y 1456 help 1457 This includes native support for POSIX timers to the kernel. 1458 Some embedded systems have no use for them and therefore they 1459 can be configured out to reduce the size of the kernel image. 1460 1461 When this option is disabled, the following syscalls won't be 1462 available: timer_create, timer_gettime: timer_getoverrun, 1463 timer_settime, timer_delete, clock_adjtime, getitimer, 1464 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1465 clock_getres and clock_nanosleep syscalls will be limited to 1466 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1467 1468 If unsure say y. 1469 1470config KALLSYMS 1471 bool "Load all symbols for debugging/ksymoops" if EXPERT 1472 default y 1473 help 1474 Say Y here to let the kernel print out symbolic crash information and 1475 symbolic stack backtraces. This increases the size of the kernel 1476 somewhat, as all symbols have to be loaded into the kernel image. 1477 1478config KALLSYMS_ALL 1479 bool "Include all symbols in kallsyms" 1480 depends on DEBUG_KERNEL && KALLSYMS 1481 help 1482 Normally kallsyms only contains the symbols of functions for nicer 1483 OOPS messages and backtraces (i.e., symbols from the text and inittext 1484 sections). This is sufficient for most cases. And only in very rare 1485 cases (e.g., when a debugger is used) all symbols are required (e.g., 1486 names of variables from the data sections, etc). 1487 1488 This option makes sure that all symbols are loaded into the kernel 1489 image (i.e., symbols from all sections) in cost of increased kernel 1490 size (depending on the kernel configuration, it may be 300KiB or 1491 something like this). 1492 1493 Say N unless you really need all symbols. 1494 1495config KALLSYMS_ABSOLUTE_PERCPU 1496 bool 1497 depends on KALLSYMS 1498 default X86_64 && SMP 1499 1500config KALLSYMS_BASE_RELATIVE 1501 bool 1502 depends on KALLSYMS 1503 default !IA64 && !(TILE && 64BIT) 1504 help 1505 Instead of emitting them as absolute values in the native word size, 1506 emit the symbol references in the kallsyms table as 32-bit entries, 1507 each containing a relative value in the range [base, base + U32_MAX] 1508 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1509 an absolute value in the range [0, S32_MAX] or a relative value in the 1510 range [base, base + S32_MAX], where base is the lowest relative symbol 1511 address encountered in the image. 1512 1513 On 64-bit builds, this reduces the size of the address table by 50%, 1514 but more importantly, it results in entries whose values are build 1515 time constants, and no relocation pass is required at runtime to fix 1516 up the entries based on the runtime load address of the kernel. 1517 1518config PRINTK 1519 default y 1520 bool "Enable support for printk" if EXPERT 1521 select IRQ_WORK 1522 help 1523 This option enables normal printk support. Removing it 1524 eliminates most of the message strings from the kernel image 1525 and makes the kernel more or less silent. As this makes it 1526 very difficult to diagnose system problems, saying N here is 1527 strongly discouraged. 1528 1529config PRINTK_NMI 1530 def_bool y 1531 depends on PRINTK 1532 depends on HAVE_NMI 1533 1534config BUG 1535 bool "BUG() support" if EXPERT 1536 default y 1537 help 1538 Disabling this option eliminates support for BUG and WARN, reducing 1539 the size of your kernel image and potentially quietly ignoring 1540 numerous fatal conditions. You should only consider disabling this 1541 option for embedded systems with no facilities for reporting errors. 1542 Just say Y. 1543 1544config ELF_CORE 1545 depends on COREDUMP 1546 default y 1547 bool "Enable ELF core dumps" if EXPERT 1548 help 1549 Enable support for generating core dumps. Disabling saves about 4k. 1550 1551 1552config PCSPKR_PLATFORM 1553 bool "Enable PC-Speaker support" if EXPERT 1554 depends on HAVE_PCSPKR_PLATFORM 1555 select I8253_LOCK 1556 default y 1557 help 1558 This option allows to disable the internal PC-Speaker 1559 support, saving some memory. 1560 1561config BASE_FULL 1562 default y 1563 bool "Enable full-sized data structures for core" if EXPERT 1564 help 1565 Disabling this option reduces the size of miscellaneous core 1566 kernel data structures. This saves memory on small machines, 1567 but may reduce performance. 1568 1569config FUTEX 1570 bool "Enable futex support" if EXPERT 1571 default y 1572 select RT_MUTEXES 1573 help 1574 Disabling this option will cause the kernel to be built without 1575 support for "fast userspace mutexes". The resulting kernel may not 1576 run glibc-based applications correctly. 1577 1578config HAVE_FUTEX_CMPXCHG 1579 bool 1580 depends on FUTEX 1581 help 1582 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1583 is implemented and always working. This removes a couple of runtime 1584 checks. 1585 1586config EPOLL 1587 bool "Enable eventpoll support" if EXPERT 1588 default y 1589 select ANON_INODES 1590 help 1591 Disabling this option will cause the kernel to be built without 1592 support for epoll family of system calls. 1593 1594config SIGNALFD 1595 bool "Enable signalfd() system call" if EXPERT 1596 select ANON_INODES 1597 default y 1598 help 1599 Enable the signalfd() system call that allows to receive signals 1600 on a file descriptor. 1601 1602 If unsure, say Y. 1603 1604config TIMERFD 1605 bool "Enable timerfd() system call" if EXPERT 1606 select ANON_INODES 1607 default y 1608 help 1609 Enable the timerfd() system call that allows to receive timer 1610 events on a file descriptor. 1611 1612 If unsure, say Y. 1613 1614config EVENTFD 1615 bool "Enable eventfd() system call" if EXPERT 1616 select ANON_INODES 1617 default y 1618 help 1619 Enable the eventfd() system call that allows to receive both 1620 kernel notification (ie. KAIO) or userspace notifications. 1621 1622 If unsure, say Y. 1623 1624# syscall, maps, verifier 1625config BPF_SYSCALL 1626 bool "Enable bpf() system call" 1627 select ANON_INODES 1628 select BPF 1629 default n 1630 help 1631 Enable the bpf() system call that allows to manipulate eBPF 1632 programs and maps via file descriptors. 1633 1634config SHMEM 1635 bool "Use full shmem filesystem" if EXPERT 1636 default y 1637 depends on MMU 1638 help 1639 The shmem is an internal filesystem used to manage shared memory. 1640 It is backed by swap and manages resource limits. It is also exported 1641 to userspace as tmpfs if TMPFS is enabled. Disabling this 1642 option replaces shmem and tmpfs with the much simpler ramfs code, 1643 which may be appropriate on small systems without swap. 1644 1645config AIO 1646 bool "Enable AIO support" if EXPERT 1647 default y 1648 help 1649 This option enables POSIX asynchronous I/O which may by used 1650 by some high performance threaded applications. Disabling 1651 this option saves about 7k. 1652 1653config ADVISE_SYSCALLS 1654 bool "Enable madvise/fadvise syscalls" if EXPERT 1655 default y 1656 help 1657 This option enables the madvise and fadvise syscalls, used by 1658 applications to advise the kernel about their future memory or file 1659 usage, improving performance. If building an embedded system where no 1660 applications use these syscalls, you can disable this option to save 1661 space. 1662 1663config USERFAULTFD 1664 bool "Enable userfaultfd() system call" 1665 select ANON_INODES 1666 depends on MMU 1667 help 1668 Enable the userfaultfd() system call that allows to intercept and 1669 handle page faults in userland. 1670 1671config PCI_QUIRKS 1672 default y 1673 bool "Enable PCI quirk workarounds" if EXPERT 1674 depends on PCI 1675 help 1676 This enables workarounds for various PCI chipset 1677 bugs/quirks. Disable this only if your target machine is 1678 unaffected by PCI quirks. 1679 1680config MEMBARRIER 1681 bool "Enable membarrier() system call" if EXPERT 1682 default y 1683 help 1684 Enable the membarrier() system call that allows issuing memory 1685 barriers across all running threads, which can be used to distribute 1686 the cost of user-space memory barriers asymmetrically by transforming 1687 pairs of memory barriers into pairs consisting of membarrier() and a 1688 compiler barrier. 1689 1690 If unsure, say Y. 1691 1692config EMBEDDED 1693 bool "Embedded system" 1694 option allnoconfig_y 1695 select EXPERT 1696 help 1697 This option should be enabled if compiling the kernel for 1698 an embedded system so certain expert options are available 1699 for configuration. 1700 1701config HAVE_PERF_EVENTS 1702 bool 1703 help 1704 See tools/perf/design.txt for details. 1705 1706config PERF_USE_VMALLOC 1707 bool 1708 help 1709 See tools/perf/design.txt for details 1710 1711config PC104 1712 bool "PC/104 support" 1713 help 1714 Expose PC/104 form factor device drivers and options available for 1715 selection and configuration. Enable this option if your target 1716 machine has a PC/104 bus. 1717 1718menu "Kernel Performance Events And Counters" 1719 1720config PERF_EVENTS 1721 bool "Kernel performance events and counters" 1722 default y if PROFILING 1723 depends on HAVE_PERF_EVENTS 1724 select ANON_INODES 1725 select IRQ_WORK 1726 select SRCU 1727 help 1728 Enable kernel support for various performance events provided 1729 by software and hardware. 1730 1731 Software events are supported either built-in or via the 1732 use of generic tracepoints. 1733 1734 Most modern CPUs support performance events via performance 1735 counter registers. These registers count the number of certain 1736 types of hw events: such as instructions executed, cachemisses 1737 suffered, or branches mis-predicted - without slowing down the 1738 kernel or applications. These registers can also trigger interrupts 1739 when a threshold number of events have passed - and can thus be 1740 used to profile the code that runs on that CPU. 1741 1742 The Linux Performance Event subsystem provides an abstraction of 1743 these software and hardware event capabilities, available via a 1744 system call and used by the "perf" utility in tools/perf/. It 1745 provides per task and per CPU counters, and it provides event 1746 capabilities on top of those. 1747 1748 Say Y if unsure. 1749 1750config DEBUG_PERF_USE_VMALLOC 1751 default n 1752 bool "Debug: use vmalloc to back perf mmap() buffers" 1753 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1754 select PERF_USE_VMALLOC 1755 help 1756 Use vmalloc memory to back perf mmap() buffers. 1757 1758 Mostly useful for debugging the vmalloc code on platforms 1759 that don't require it. 1760 1761 Say N if unsure. 1762 1763endmenu 1764 1765config VM_EVENT_COUNTERS 1766 default y 1767 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1768 help 1769 VM event counters are needed for event counts to be shown. 1770 This option allows the disabling of the VM event counters 1771 on EXPERT systems. /proc/vmstat will only show page counts 1772 if VM event counters are disabled. 1773 1774config SLUB_DEBUG 1775 default y 1776 bool "Enable SLUB debugging support" if EXPERT 1777 depends on SLUB && SYSFS 1778 help 1779 SLUB has extensive debug support features. Disabling these can 1780 result in significant savings in code size. This also disables 1781 SLUB sysfs support. /sys/slab will not exist and there will be 1782 no support for cache validation etc. 1783 1784config SLUB_MEMCG_SYSFS_ON 1785 default n 1786 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1787 depends on SLUB && SYSFS && MEMCG 1788 help 1789 SLUB creates a directory under /sys/kernel/slab for each 1790 allocation cache to host info and debug files. If memory 1791 cgroup is enabled, each cache can have per memory cgroup 1792 caches. SLUB can create the same sysfs directories for these 1793 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1794 to a very high number of debug files being created. This is 1795 controlled by slub_memcg_sysfs boot parameter and this 1796 config option determines the parameter's default value. 1797 1798config COMPAT_BRK 1799 bool "Disable heap randomization" 1800 default y 1801 help 1802 Randomizing heap placement makes heap exploits harder, but it 1803 also breaks ancient binaries (including anything libc5 based). 1804 This option changes the bootup default to heap randomization 1805 disabled, and can be overridden at runtime by setting 1806 /proc/sys/kernel/randomize_va_space to 2. 1807 1808 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1809 1810choice 1811 prompt "Choose SLAB allocator" 1812 default SLUB 1813 help 1814 This option allows to select a slab allocator. 1815 1816config SLAB 1817 bool "SLAB" 1818 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1819 help 1820 The regular slab allocator that is established and known to work 1821 well in all environments. It organizes cache hot objects in 1822 per cpu and per node queues. 1823 1824config SLUB 1825 bool "SLUB (Unqueued Allocator)" 1826 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1827 help 1828 SLUB is a slab allocator that minimizes cache line usage 1829 instead of managing queues of cached objects (SLAB approach). 1830 Per cpu caching is realized using slabs of objects instead 1831 of queues of objects. SLUB can use memory efficiently 1832 and has enhanced diagnostics. SLUB is the default choice for 1833 a slab allocator. 1834 1835config SLOB 1836 depends on EXPERT 1837 bool "SLOB (Simple Allocator)" 1838 help 1839 SLOB replaces the stock allocator with a drastically simpler 1840 allocator. SLOB is generally more space efficient but 1841 does not perform as well on large systems. 1842 1843endchoice 1844 1845config SLAB_FREELIST_RANDOM 1846 default n 1847 depends on SLAB || SLUB 1848 bool "SLAB freelist randomization" 1849 help 1850 Randomizes the freelist order used on creating new pages. This 1851 security feature reduces the predictability of the kernel slab 1852 allocator against heap overflows. 1853 1854config SLUB_CPU_PARTIAL 1855 default y 1856 depends on SLUB && SMP 1857 bool "SLUB per cpu partial cache" 1858 help 1859 Per cpu partial caches accellerate objects allocation and freeing 1860 that is local to a processor at the price of more indeterminism 1861 in the latency of the free. On overflow these caches will be cleared 1862 which requires the taking of locks that may cause latency spikes. 1863 Typically one would choose no for a realtime system. 1864 1865config MMAP_ALLOW_UNINITIALIZED 1866 bool "Allow mmapped anonymous memory to be uninitialized" 1867 depends on EXPERT && !MMU 1868 default n 1869 help 1870 Normally, and according to the Linux spec, anonymous memory obtained 1871 from mmap() has it's contents cleared before it is passed to 1872 userspace. Enabling this config option allows you to request that 1873 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1874 providing a huge performance boost. If this option is not enabled, 1875 then the flag will be ignored. 1876 1877 This is taken advantage of by uClibc's malloc(), and also by 1878 ELF-FDPIC binfmt's brk and stack allocator. 1879 1880 Because of the obvious security issues, this option should only be 1881 enabled on embedded devices where you control what is run in 1882 userspace. Since that isn't generally a problem on no-MMU systems, 1883 it is normally safe to say Y here. 1884 1885 See Documentation/nommu-mmap.txt for more information. 1886 1887config SYSTEM_DATA_VERIFICATION 1888 def_bool n 1889 select SYSTEM_TRUSTED_KEYRING 1890 select KEYS 1891 select CRYPTO 1892 select CRYPTO_RSA 1893 select ASYMMETRIC_KEY_TYPE 1894 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1895 select ASN1 1896 select OID_REGISTRY 1897 select X509_CERTIFICATE_PARSER 1898 select PKCS7_MESSAGE_PARSER 1899 help 1900 Provide PKCS#7 message verification using the contents of the system 1901 trusted keyring to provide public keys. This then can be used for 1902 module verification, kexec image verification and firmware blob 1903 verification. 1904 1905config PROFILING 1906 bool "Profiling support" 1907 help 1908 Say Y here to enable the extended profiling support mechanisms used 1909 by profilers such as OProfile. 1910 1911# 1912# Place an empty function call at each tracepoint site. Can be 1913# dynamically changed for a probe function. 1914# 1915config TRACEPOINTS 1916 bool 1917 1918source "arch/Kconfig" 1919 1920endmenu # General setup 1921 1922config HAVE_GENERIC_DMA_COHERENT 1923 bool 1924 default n 1925 1926config SLABINFO 1927 bool 1928 depends on PROC_FS 1929 depends on SLAB || SLUB_DEBUG 1930 default y 1931 1932config RT_MUTEXES 1933 bool 1934 1935config BASE_SMALL 1936 int 1937 default 0 if BASE_FULL 1938 default 1 if !BASE_FULL 1939 1940menuconfig MODULES 1941 bool "Enable loadable module support" 1942 option modules 1943 help 1944 Kernel modules are small pieces of compiled code which can 1945 be inserted in the running kernel, rather than being 1946 permanently built into the kernel. You use the "modprobe" 1947 tool to add (and sometimes remove) them. If you say Y here, 1948 many parts of the kernel can be built as modules (by 1949 answering M instead of Y where indicated): this is most 1950 useful for infrequently used options which are not required 1951 for booting. For more information, see the man pages for 1952 modprobe, lsmod, modinfo, insmod and rmmod. 1953 1954 If you say Y here, you will need to run "make 1955 modules_install" to put the modules under /lib/modules/ 1956 where modprobe can find them (you may need to be root to do 1957 this). 1958 1959 If unsure, say Y. 1960 1961if MODULES 1962 1963config MODULE_FORCE_LOAD 1964 bool "Forced module loading" 1965 default n 1966 help 1967 Allow loading of modules without version information (ie. modprobe 1968 --force). Forced module loading sets the 'F' (forced) taint flag and 1969 is usually a really bad idea. 1970 1971config MODULE_UNLOAD 1972 bool "Module unloading" 1973 help 1974 Without this option you will not be able to unload any 1975 modules (note that some modules may not be unloadable 1976 anyway), which makes your kernel smaller, faster 1977 and simpler. If unsure, say Y. 1978 1979config MODULE_FORCE_UNLOAD 1980 bool "Forced module unloading" 1981 depends on MODULE_UNLOAD 1982 help 1983 This option allows you to force a module to unload, even if the 1984 kernel believes it is unsafe: the kernel will remove the module 1985 without waiting for anyone to stop using it (using the -f option to 1986 rmmod). This is mainly for kernel developers and desperate users. 1987 If unsure, say N. 1988 1989config MODVERSIONS 1990 bool "Module versioning support" 1991 help 1992 Usually, you have to use modules compiled with your kernel. 1993 Saying Y here makes it sometimes possible to use modules 1994 compiled for different kernels, by adding enough information 1995 to the modules to (hopefully) spot any changes which would 1996 make them incompatible with the kernel you are running. If 1997 unsure, say N. 1998 1999config MODULE_REL_CRCS 2000 bool 2001 depends on MODVERSIONS 2002 2003config MODULE_SRCVERSION_ALL 2004 bool "Source checksum for all modules" 2005 help 2006 Modules which contain a MODULE_VERSION get an extra "srcversion" 2007 field inserted into their modinfo section, which contains a 2008 sum of the source files which made it. This helps maintainers 2009 see exactly which source was used to build a module (since 2010 others sometimes change the module source without updating 2011 the version). With this option, such a "srcversion" field 2012 will be created for all modules. If unsure, say N. 2013 2014config MODULE_SIG 2015 bool "Module signature verification" 2016 depends on MODULES 2017 select SYSTEM_DATA_VERIFICATION 2018 help 2019 Check modules for valid signatures upon load: the signature 2020 is simply appended to the module. For more information see 2021 Documentation/module-signing.txt. 2022 2023 Note that this option adds the OpenSSL development packages as a 2024 kernel build dependency so that the signing tool can use its crypto 2025 library. 2026 2027 !!!WARNING!!! If you enable this option, you MUST make sure that the 2028 module DOES NOT get stripped after being signed. This includes the 2029 debuginfo strip done by some packagers (such as rpmbuild) and 2030 inclusion into an initramfs that wants the module size reduced. 2031 2032config MODULE_SIG_FORCE 2033 bool "Require modules to be validly signed" 2034 depends on MODULE_SIG 2035 help 2036 Reject unsigned modules or signed modules for which we don't have a 2037 key. Without this, such modules will simply taint the kernel. 2038 2039config MODULE_SIG_ALL 2040 bool "Automatically sign all modules" 2041 default y 2042 depends on MODULE_SIG 2043 help 2044 Sign all modules during make modules_install. Without this option, 2045 modules must be signed manually, using the scripts/sign-file tool. 2046 2047comment "Do not forget to sign required modules with scripts/sign-file" 2048 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2049 2050choice 2051 prompt "Which hash algorithm should modules be signed with?" 2052 depends on MODULE_SIG 2053 help 2054 This determines which sort of hashing algorithm will be used during 2055 signature generation. This algorithm _must_ be built into the kernel 2056 directly so that signature verification can take place. It is not 2057 possible to load a signed module containing the algorithm to check 2058 the signature on that module. 2059 2060config MODULE_SIG_SHA1 2061 bool "Sign modules with SHA-1" 2062 select CRYPTO_SHA1 2063 2064config MODULE_SIG_SHA224 2065 bool "Sign modules with SHA-224" 2066 select CRYPTO_SHA256 2067 2068config MODULE_SIG_SHA256 2069 bool "Sign modules with SHA-256" 2070 select CRYPTO_SHA256 2071 2072config MODULE_SIG_SHA384 2073 bool "Sign modules with SHA-384" 2074 select CRYPTO_SHA512 2075 2076config MODULE_SIG_SHA512 2077 bool "Sign modules with SHA-512" 2078 select CRYPTO_SHA512 2079 2080endchoice 2081 2082config MODULE_SIG_HASH 2083 string 2084 depends on MODULE_SIG 2085 default "sha1" if MODULE_SIG_SHA1 2086 default "sha224" if MODULE_SIG_SHA224 2087 default "sha256" if MODULE_SIG_SHA256 2088 default "sha384" if MODULE_SIG_SHA384 2089 default "sha512" if MODULE_SIG_SHA512 2090 2091config MODULE_COMPRESS 2092 bool "Compress modules on installation" 2093 depends on MODULES 2094 help 2095 2096 Compresses kernel modules when 'make modules_install' is run; gzip or 2097 xz depending on "Compression algorithm" below. 2098 2099 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 2100 2101 Out-of-tree kernel modules installed using Kbuild will also be 2102 compressed upon installation. 2103 2104 Note: for modules inside an initrd or initramfs, it's more efficient 2105 to compress the whole initrd or initramfs instead. 2106 2107 Note: This is fully compatible with signed modules. 2108 2109 If in doubt, say N. 2110 2111choice 2112 prompt "Compression algorithm" 2113 depends on MODULE_COMPRESS 2114 default MODULE_COMPRESS_GZIP 2115 help 2116 This determines which sort of compression will be used during 2117 'make modules_install'. 2118 2119 GZIP (default) and XZ are supported. 2120 2121config MODULE_COMPRESS_GZIP 2122 bool "GZIP" 2123 2124config MODULE_COMPRESS_XZ 2125 bool "XZ" 2126 2127endchoice 2128 2129config TRIM_UNUSED_KSYMS 2130 bool "Trim unused exported kernel symbols" 2131 depends on MODULES && !UNUSED_SYMBOLS 2132 help 2133 The kernel and some modules make many symbols available for 2134 other modules to use via EXPORT_SYMBOL() and variants. Depending 2135 on the set of modules being selected in your kernel configuration, 2136 many of those exported symbols might never be used. 2137 2138 This option allows for unused exported symbols to be dropped from 2139 the build. In turn, this provides the compiler more opportunities 2140 (especially when using LTO) for optimizing the code and reducing 2141 binary size. This might have some security advantages as well. 2142 2143 If unsure, or if you need to build out-of-tree modules, say N. 2144 2145endif # MODULES 2146 2147config MODULES_TREE_LOOKUP 2148 def_bool y 2149 depends on PERF_EVENTS || TRACING 2150 2151config INIT_ALL_POSSIBLE 2152 bool 2153 help 2154 Back when each arch used to define their own cpu_online_mask and 2155 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2156 with all 1s, and others with all 0s. When they were centralised, 2157 it was better to provide this option than to break all the archs 2158 and have several arch maintainers pursuing me down dark alleys. 2159 2160source "block/Kconfig" 2161 2162config PREEMPT_NOTIFIERS 2163 bool 2164 2165config PADATA 2166 depends on SMP 2167 bool 2168 2169config ASN1 2170 tristate 2171 help 2172 Build a simple ASN.1 grammar compiler that produces a bytecode output 2173 that can be interpreted by the ASN.1 stream decoder and used to 2174 inform it as to what tags are to be expected in a stream and what 2175 functions to call on what tags. 2176 2177source "kernel/Kconfig.locks" 2178