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_RDMA 1082 bool "RDMA controller" 1083 help 1084 Provides enforcement of RDMA resources defined by IB stack. 1085 It is fairly easy for consumers to exhaust RDMA resources, which 1086 can result into resource unavailability to other consumers. 1087 RDMA controller is designed to stop this from happening. 1088 Attaching processes with active RDMA resources to the cgroup 1089 hierarchy is allowed even if can cross the hierarchy's limit. 1090 1091config CGROUP_FREEZER 1092 bool "Freezer controller" 1093 help 1094 Provides a way to freeze and unfreeze all tasks in a 1095 cgroup. 1096 1097 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1098 controller includes important in-kernel memory consumers per default. 1099 1100 If you're using cgroup2, say N. 1101 1102config CGROUP_HUGETLB 1103 bool "HugeTLB controller" 1104 depends on HUGETLB_PAGE 1105 select PAGE_COUNTER 1106 default n 1107 help 1108 Provides a cgroup controller for HugeTLB pages. 1109 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1110 The limit is enforced during page fault. Since HugeTLB doesn't 1111 support page reclaim, enforcing the limit at page fault time implies 1112 that, the application will get SIGBUS signal if it tries to access 1113 HugeTLB pages beyond its limit. This requires the application to know 1114 beforehand how much HugeTLB pages it would require for its use. The 1115 control group is tracked in the third page lru pointer. This means 1116 that we cannot use the controller with huge page less than 3 pages. 1117 1118config CPUSETS 1119 bool "Cpuset controller" 1120 help 1121 This option will let you create and manage CPUSETs which 1122 allow dynamically partitioning a system into sets of CPUs and 1123 Memory Nodes and assigning tasks to run only within those sets. 1124 This is primarily useful on large SMP or NUMA systems. 1125 1126 Say N if unsure. 1127 1128config PROC_PID_CPUSET 1129 bool "Include legacy /proc/<pid>/cpuset file" 1130 depends on CPUSETS 1131 default y 1132 1133config CGROUP_DEVICE 1134 bool "Device controller" 1135 help 1136 Provides a cgroup controller implementing whitelists for 1137 devices which a process in the cgroup can mknod or open. 1138 1139config CGROUP_CPUACCT 1140 bool "Simple CPU accounting controller" 1141 help 1142 Provides a simple controller for monitoring the 1143 total CPU consumed by the tasks in a cgroup. 1144 1145config CGROUP_PERF 1146 bool "Perf controller" 1147 depends on PERF_EVENTS 1148 help 1149 This option extends the perf per-cpu mode to restrict monitoring 1150 to threads which belong to the cgroup specified and run on the 1151 designated cpu. 1152 1153 Say N if unsure. 1154 1155config CGROUP_BPF 1156 bool "Support for eBPF programs attached to cgroups" 1157 depends on BPF_SYSCALL 1158 select SOCK_CGROUP_DATA 1159 help 1160 Allow attaching eBPF programs to a cgroup using the bpf(2) 1161 syscall command BPF_PROG_ATTACH. 1162 1163 In which context these programs are accessed depends on the type 1164 of attachment. For instance, programs that are attached using 1165 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1166 inet sockets. 1167 1168config CGROUP_DEBUG 1169 bool "Example controller" 1170 default n 1171 help 1172 This option enables a simple controller that exports 1173 debugging information about the cgroups framework. 1174 1175 Say N. 1176 1177config SOCK_CGROUP_DATA 1178 bool 1179 default n 1180 1181endif # CGROUPS 1182 1183config CHECKPOINT_RESTORE 1184 bool "Checkpoint/restore support" if EXPERT 1185 select PROC_CHILDREN 1186 default n 1187 help 1188 Enables additional kernel features in a sake of checkpoint/restore. 1189 In particular it adds auxiliary prctl codes to setup process text, 1190 data and heap segment sizes, and a few additional /proc filesystem 1191 entries. 1192 1193 If unsure, say N here. 1194 1195menuconfig NAMESPACES 1196 bool "Namespaces support" if EXPERT 1197 depends on MULTIUSER 1198 default !EXPERT 1199 help 1200 Provides the way to make tasks work with different objects using 1201 the same id. For example same IPC id may refer to different objects 1202 or same user id or pid may refer to different tasks when used in 1203 different namespaces. 1204 1205if NAMESPACES 1206 1207config UTS_NS 1208 bool "UTS namespace" 1209 default y 1210 help 1211 In this namespace tasks see different info provided with the 1212 uname() system call 1213 1214config IPC_NS 1215 bool "IPC namespace" 1216 depends on (SYSVIPC || POSIX_MQUEUE) 1217 default y 1218 help 1219 In this namespace tasks work with IPC ids which correspond to 1220 different IPC objects in different namespaces. 1221 1222config USER_NS 1223 bool "User namespace" 1224 default n 1225 help 1226 This allows containers, i.e. vservers, to use user namespaces 1227 to provide different user info for different servers. 1228 1229 When user namespaces are enabled in the kernel it is 1230 recommended that the MEMCG option also be enabled and that 1231 user-space use the memory control groups to limit the amount 1232 of memory a memory unprivileged users can use. 1233 1234 If unsure, say N. 1235 1236config PID_NS 1237 bool "PID Namespaces" 1238 default y 1239 help 1240 Support process id namespaces. This allows having multiple 1241 processes with the same pid as long as they are in different 1242 pid namespaces. This is a building block of containers. 1243 1244config NET_NS 1245 bool "Network namespace" 1246 depends on NET 1247 default y 1248 help 1249 Allow user space to create what appear to be multiple instances 1250 of the network stack. 1251 1252endif # NAMESPACES 1253 1254config SCHED_AUTOGROUP 1255 bool "Automatic process group scheduling" 1256 select CGROUPS 1257 select CGROUP_SCHED 1258 select FAIR_GROUP_SCHED 1259 help 1260 This option optimizes the scheduler for common desktop workloads by 1261 automatically creating and populating task groups. This separation 1262 of workloads isolates aggressive CPU burners (like build jobs) from 1263 desktop applications. Task group autogeneration is currently based 1264 upon task session. 1265 1266config SYSFS_DEPRECATED 1267 bool "Enable deprecated sysfs features to support old userspace tools" 1268 depends on SYSFS 1269 default n 1270 help 1271 This option adds code that switches the layout of the "block" class 1272 devices, to not show up in /sys/class/block/, but only in 1273 /sys/block/. 1274 1275 This switch is only active when the sysfs.deprecated=1 boot option is 1276 passed or the SYSFS_DEPRECATED_V2 option is set. 1277 1278 This option allows new kernels to run on old distributions and tools, 1279 which might get confused by /sys/class/block/. Since 2007/2008 all 1280 major distributions and tools handle this just fine. 1281 1282 Recent distributions and userspace tools after 2009/2010 depend on 1283 the existence of /sys/class/block/, and will not work with this 1284 option enabled. 1285 1286 Only if you are using a new kernel on an old distribution, you might 1287 need to say Y here. 1288 1289config SYSFS_DEPRECATED_V2 1290 bool "Enable deprecated sysfs features by default" 1291 default n 1292 depends on SYSFS 1293 depends on SYSFS_DEPRECATED 1294 help 1295 Enable deprecated sysfs by default. 1296 1297 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1298 option. 1299 1300 Only if you are using a new kernel on an old distribution, you might 1301 need to say Y here. Even then, odds are you would not need it 1302 enabled, you can always pass the boot option if absolutely necessary. 1303 1304config RELAY 1305 bool "Kernel->user space relay support (formerly relayfs)" 1306 select IRQ_WORK 1307 help 1308 This option enables support for relay interface support in 1309 certain file systems (such as debugfs). 1310 It is designed to provide an efficient mechanism for tools and 1311 facilities to relay large amounts of data from kernel space to 1312 user space. 1313 1314 If unsure, say N. 1315 1316config BLK_DEV_INITRD 1317 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1318 depends on BROKEN || !FRV 1319 help 1320 The initial RAM filesystem is a ramfs which is loaded by the 1321 boot loader (loadlin or lilo) and that is mounted as root 1322 before the normal boot procedure. It is typically used to 1323 load modules needed to mount the "real" root file system, 1324 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1325 1326 If RAM disk support (BLK_DEV_RAM) is also included, this 1327 also enables initial RAM disk (initrd) support and adds 1328 15 Kbytes (more on some other architectures) to the kernel size. 1329 1330 If unsure say Y. 1331 1332if BLK_DEV_INITRD 1333 1334source "usr/Kconfig" 1335 1336endif 1337 1338choice 1339 prompt "Compiler optimization level" 1340 default CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE 1341 1342config CC_OPTIMIZE_FOR_PERFORMANCE 1343 bool "Optimize for performance" 1344 help 1345 This is the default optimization level for the kernel, building 1346 with the "-O2" compiler flag for best performance and most 1347 helpful compile-time warnings. 1348 1349config CC_OPTIMIZE_FOR_SIZE 1350 bool "Optimize for size" 1351 help 1352 Enabling this option will pass "-Os" instead of "-O2" to 1353 your compiler resulting in a smaller kernel. 1354 1355 If unsure, say N. 1356 1357endchoice 1358 1359config SYSCTL 1360 bool 1361 1362config ANON_INODES 1363 bool 1364 1365config HAVE_UID16 1366 bool 1367 1368config SYSCTL_EXCEPTION_TRACE 1369 bool 1370 help 1371 Enable support for /proc/sys/debug/exception-trace. 1372 1373config SYSCTL_ARCH_UNALIGN_NO_WARN 1374 bool 1375 help 1376 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1377 Allows arch to define/use @no_unaligned_warning to possibly warn 1378 about unaligned access emulation going on under the hood. 1379 1380config SYSCTL_ARCH_UNALIGN_ALLOW 1381 bool 1382 help 1383 Enable support for /proc/sys/kernel/unaligned-trap 1384 Allows arches to define/use @unaligned_enabled to runtime toggle 1385 the unaligned access emulation. 1386 see arch/parisc/kernel/unaligned.c for reference 1387 1388config HAVE_PCSPKR_PLATFORM 1389 bool 1390 1391# interpreter that classic socket filters depend on 1392config BPF 1393 bool 1394 1395menuconfig EXPERT 1396 bool "Configure standard kernel features (expert users)" 1397 # Unhide debug options, to make the on-by-default options visible 1398 select DEBUG_KERNEL 1399 help 1400 This option allows certain base kernel options and settings 1401 to be disabled or tweaked. This is for specialized 1402 environments which can tolerate a "non-standard" kernel. 1403 Only use this if you really know what you are doing. 1404 1405config UID16 1406 bool "Enable 16-bit UID system calls" if EXPERT 1407 depends on HAVE_UID16 && MULTIUSER 1408 default y 1409 help 1410 This enables the legacy 16-bit UID syscall wrappers. 1411 1412config MULTIUSER 1413 bool "Multiple users, groups and capabilities support" if EXPERT 1414 default y 1415 help 1416 This option enables support for non-root users, groups and 1417 capabilities. 1418 1419 If you say N here, all processes will run with UID 0, GID 0, and all 1420 possible capabilities. Saying N here also compiles out support for 1421 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1422 setgid, and capset. 1423 1424 If unsure, say Y here. 1425 1426config SGETMASK_SYSCALL 1427 bool "sgetmask/ssetmask syscalls support" if EXPERT 1428 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH 1429 ---help--- 1430 sys_sgetmask and sys_ssetmask are obsolete system calls 1431 no longer supported in libc but still enabled by default in some 1432 architectures. 1433 1434 If unsure, leave the default option here. 1435 1436config SYSFS_SYSCALL 1437 bool "Sysfs syscall support" if EXPERT 1438 default y 1439 ---help--- 1440 sys_sysfs is an obsolete system call no longer supported in libc. 1441 Note that disabling this option is more secure but might break 1442 compatibility with some systems. 1443 1444 If unsure say Y here. 1445 1446config SYSCTL_SYSCALL 1447 bool "Sysctl syscall support" if EXPERT 1448 depends on PROC_SYSCTL 1449 default n 1450 select SYSCTL 1451 ---help--- 1452 sys_sysctl uses binary paths that have been found challenging 1453 to properly maintain and use. The interface in /proc/sys 1454 using paths with ascii names is now the primary path to this 1455 information. 1456 1457 Almost nothing using the binary sysctl interface so if you are 1458 trying to save some space it is probably safe to disable this, 1459 making your kernel marginally smaller. 1460 1461 If unsure say N here. 1462 1463config POSIX_TIMERS 1464 bool "Posix Clocks & timers" if EXPERT 1465 default y 1466 help 1467 This includes native support for POSIX timers to the kernel. 1468 Some embedded systems have no use for them and therefore they 1469 can be configured out to reduce the size of the kernel image. 1470 1471 When this option is disabled, the following syscalls won't be 1472 available: timer_create, timer_gettime: timer_getoverrun, 1473 timer_settime, timer_delete, clock_adjtime, getitimer, 1474 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1475 clock_getres and clock_nanosleep syscalls will be limited to 1476 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1477 1478 If unsure say y. 1479 1480config KALLSYMS 1481 bool "Load all symbols for debugging/ksymoops" if EXPERT 1482 default y 1483 help 1484 Say Y here to let the kernel print out symbolic crash information and 1485 symbolic stack backtraces. This increases the size of the kernel 1486 somewhat, as all symbols have to be loaded into the kernel image. 1487 1488config KALLSYMS_ALL 1489 bool "Include all symbols in kallsyms" 1490 depends on DEBUG_KERNEL && KALLSYMS 1491 help 1492 Normally kallsyms only contains the symbols of functions for nicer 1493 OOPS messages and backtraces (i.e., symbols from the text and inittext 1494 sections). This is sufficient for most cases. And only in very rare 1495 cases (e.g., when a debugger is used) all symbols are required (e.g., 1496 names of variables from the data sections, etc). 1497 1498 This option makes sure that all symbols are loaded into the kernel 1499 image (i.e., symbols from all sections) in cost of increased kernel 1500 size (depending on the kernel configuration, it may be 300KiB or 1501 something like this). 1502 1503 Say N unless you really need all symbols. 1504 1505config KALLSYMS_ABSOLUTE_PERCPU 1506 bool 1507 depends on KALLSYMS 1508 default X86_64 && SMP 1509 1510config KALLSYMS_BASE_RELATIVE 1511 bool 1512 depends on KALLSYMS 1513 default !IA64 && !(TILE && 64BIT) 1514 help 1515 Instead of emitting them as absolute values in the native word size, 1516 emit the symbol references in the kallsyms table as 32-bit entries, 1517 each containing a relative value in the range [base, base + U32_MAX] 1518 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1519 an absolute value in the range [0, S32_MAX] or a relative value in the 1520 range [base, base + S32_MAX], where base is the lowest relative symbol 1521 address encountered in the image. 1522 1523 On 64-bit builds, this reduces the size of the address table by 50%, 1524 but more importantly, it results in entries whose values are build 1525 time constants, and no relocation pass is required at runtime to fix 1526 up the entries based on the runtime load address of the kernel. 1527 1528config PRINTK 1529 default y 1530 bool "Enable support for printk" if EXPERT 1531 select IRQ_WORK 1532 help 1533 This option enables normal printk support. Removing it 1534 eliminates most of the message strings from the kernel image 1535 and makes the kernel more or less silent. As this makes it 1536 very difficult to diagnose system problems, saying N here is 1537 strongly discouraged. 1538 1539config PRINTK_NMI 1540 def_bool y 1541 depends on PRINTK 1542 depends on HAVE_NMI 1543 1544config BUG 1545 bool "BUG() support" if EXPERT 1546 default y 1547 help 1548 Disabling this option eliminates support for BUG and WARN, reducing 1549 the size of your kernel image and potentially quietly ignoring 1550 numerous fatal conditions. You should only consider disabling this 1551 option for embedded systems with no facilities for reporting errors. 1552 Just say Y. 1553 1554config ELF_CORE 1555 depends on COREDUMP 1556 default y 1557 bool "Enable ELF core dumps" if EXPERT 1558 help 1559 Enable support for generating core dumps. Disabling saves about 4k. 1560 1561 1562config PCSPKR_PLATFORM 1563 bool "Enable PC-Speaker support" if EXPERT 1564 depends on HAVE_PCSPKR_PLATFORM 1565 select I8253_LOCK 1566 default y 1567 help 1568 This option allows to disable the internal PC-Speaker 1569 support, saving some memory. 1570 1571config BASE_FULL 1572 default y 1573 bool "Enable full-sized data structures for core" if EXPERT 1574 help 1575 Disabling this option reduces the size of miscellaneous core 1576 kernel data structures. This saves memory on small machines, 1577 but may reduce performance. 1578 1579config FUTEX 1580 bool "Enable futex support" if EXPERT 1581 default y 1582 select RT_MUTEXES 1583 help 1584 Disabling this option will cause the kernel to be built without 1585 support for "fast userspace mutexes". The resulting kernel may not 1586 run glibc-based applications correctly. 1587 1588config HAVE_FUTEX_CMPXCHG 1589 bool 1590 depends on FUTEX 1591 help 1592 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1593 is implemented and always working. This removes a couple of runtime 1594 checks. 1595 1596config EPOLL 1597 bool "Enable eventpoll support" if EXPERT 1598 default y 1599 select ANON_INODES 1600 help 1601 Disabling this option will cause the kernel to be built without 1602 support for epoll family of system calls. 1603 1604config SIGNALFD 1605 bool "Enable signalfd() system call" if EXPERT 1606 select ANON_INODES 1607 default y 1608 help 1609 Enable the signalfd() system call that allows to receive signals 1610 on a file descriptor. 1611 1612 If unsure, say Y. 1613 1614config TIMERFD 1615 bool "Enable timerfd() system call" if EXPERT 1616 select ANON_INODES 1617 default y 1618 help 1619 Enable the timerfd() system call that allows to receive timer 1620 events on a file descriptor. 1621 1622 If unsure, say Y. 1623 1624config EVENTFD 1625 bool "Enable eventfd() system call" if EXPERT 1626 select ANON_INODES 1627 default y 1628 help 1629 Enable the eventfd() system call that allows to receive both 1630 kernel notification (ie. KAIO) or userspace notifications. 1631 1632 If unsure, say Y. 1633 1634# syscall, maps, verifier 1635config BPF_SYSCALL 1636 bool "Enable bpf() system call" 1637 select ANON_INODES 1638 select BPF 1639 default n 1640 help 1641 Enable the bpf() system call that allows to manipulate eBPF 1642 programs and maps via file descriptors. 1643 1644config SHMEM 1645 bool "Use full shmem filesystem" if EXPERT 1646 default y 1647 depends on MMU 1648 help 1649 The shmem is an internal filesystem used to manage shared memory. 1650 It is backed by swap and manages resource limits. It is also exported 1651 to userspace as tmpfs if TMPFS is enabled. Disabling this 1652 option replaces shmem and tmpfs with the much simpler ramfs code, 1653 which may be appropriate on small systems without swap. 1654 1655config AIO 1656 bool "Enable AIO support" if EXPERT 1657 default y 1658 help 1659 This option enables POSIX asynchronous I/O which may by used 1660 by some high performance threaded applications. Disabling 1661 this option saves about 7k. 1662 1663config ADVISE_SYSCALLS 1664 bool "Enable madvise/fadvise syscalls" if EXPERT 1665 default y 1666 help 1667 This option enables the madvise and fadvise syscalls, used by 1668 applications to advise the kernel about their future memory or file 1669 usage, improving performance. If building an embedded system where no 1670 applications use these syscalls, you can disable this option to save 1671 space. 1672 1673config USERFAULTFD 1674 bool "Enable userfaultfd() system call" 1675 select ANON_INODES 1676 depends on MMU 1677 help 1678 Enable the userfaultfd() system call that allows to intercept and 1679 handle page faults in userland. 1680 1681config PCI_QUIRKS 1682 default y 1683 bool "Enable PCI quirk workarounds" if EXPERT 1684 depends on PCI 1685 help 1686 This enables workarounds for various PCI chipset 1687 bugs/quirks. Disable this only if your target machine is 1688 unaffected by PCI quirks. 1689 1690config MEMBARRIER 1691 bool "Enable membarrier() system call" if EXPERT 1692 default y 1693 help 1694 Enable the membarrier() system call that allows issuing memory 1695 barriers across all running threads, which can be used to distribute 1696 the cost of user-space memory barriers asymmetrically by transforming 1697 pairs of memory barriers into pairs consisting of membarrier() and a 1698 compiler barrier. 1699 1700 If unsure, say Y. 1701 1702config EMBEDDED 1703 bool "Embedded system" 1704 option allnoconfig_y 1705 select EXPERT 1706 help 1707 This option should be enabled if compiling the kernel for 1708 an embedded system so certain expert options are available 1709 for configuration. 1710 1711config HAVE_PERF_EVENTS 1712 bool 1713 help 1714 See tools/perf/design.txt for details. 1715 1716config PERF_USE_VMALLOC 1717 bool 1718 help 1719 See tools/perf/design.txt for details 1720 1721config PC104 1722 bool "PC/104 support" 1723 help 1724 Expose PC/104 form factor device drivers and options available for 1725 selection and configuration. Enable this option if your target 1726 machine has a PC/104 bus. 1727 1728menu "Kernel Performance Events And Counters" 1729 1730config PERF_EVENTS 1731 bool "Kernel performance events and counters" 1732 default y if PROFILING 1733 depends on HAVE_PERF_EVENTS 1734 select ANON_INODES 1735 select IRQ_WORK 1736 select SRCU 1737 help 1738 Enable kernel support for various performance events provided 1739 by software and hardware. 1740 1741 Software events are supported either built-in or via the 1742 use of generic tracepoints. 1743 1744 Most modern CPUs support performance events via performance 1745 counter registers. These registers count the number of certain 1746 types of hw events: such as instructions executed, cachemisses 1747 suffered, or branches mis-predicted - without slowing down the 1748 kernel or applications. These registers can also trigger interrupts 1749 when a threshold number of events have passed - and can thus be 1750 used to profile the code that runs on that CPU. 1751 1752 The Linux Performance Event subsystem provides an abstraction of 1753 these software and hardware event capabilities, available via a 1754 system call and used by the "perf" utility in tools/perf/. It 1755 provides per task and per CPU counters, and it provides event 1756 capabilities on top of those. 1757 1758 Say Y if unsure. 1759 1760config DEBUG_PERF_USE_VMALLOC 1761 default n 1762 bool "Debug: use vmalloc to back perf mmap() buffers" 1763 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1764 select PERF_USE_VMALLOC 1765 help 1766 Use vmalloc memory to back perf mmap() buffers. 1767 1768 Mostly useful for debugging the vmalloc code on platforms 1769 that don't require it. 1770 1771 Say N if unsure. 1772 1773endmenu 1774 1775config VM_EVENT_COUNTERS 1776 default y 1777 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1778 help 1779 VM event counters are needed for event counts to be shown. 1780 This option allows the disabling of the VM event counters 1781 on EXPERT systems. /proc/vmstat will only show page counts 1782 if VM event counters are disabled. 1783 1784config SLUB_DEBUG 1785 default y 1786 bool "Enable SLUB debugging support" if EXPERT 1787 depends on SLUB && SYSFS 1788 help 1789 SLUB has extensive debug support features. Disabling these can 1790 result in significant savings in code size. This also disables 1791 SLUB sysfs support. /sys/slab will not exist and there will be 1792 no support for cache validation etc. 1793 1794config SLUB_MEMCG_SYSFS_ON 1795 default n 1796 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1797 depends on SLUB && SYSFS && MEMCG 1798 help 1799 SLUB creates a directory under /sys/kernel/slab for each 1800 allocation cache to host info and debug files. If memory 1801 cgroup is enabled, each cache can have per memory cgroup 1802 caches. SLUB can create the same sysfs directories for these 1803 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1804 to a very high number of debug files being created. This is 1805 controlled by slub_memcg_sysfs boot parameter and this 1806 config option determines the parameter's default value. 1807 1808config COMPAT_BRK 1809 bool "Disable heap randomization" 1810 default y 1811 help 1812 Randomizing heap placement makes heap exploits harder, but it 1813 also breaks ancient binaries (including anything libc5 based). 1814 This option changes the bootup default to heap randomization 1815 disabled, and can be overridden at runtime by setting 1816 /proc/sys/kernel/randomize_va_space to 2. 1817 1818 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1819 1820choice 1821 prompt "Choose SLAB allocator" 1822 default SLUB 1823 help 1824 This option allows to select a slab allocator. 1825 1826config SLAB 1827 bool "SLAB" 1828 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1829 help 1830 The regular slab allocator that is established and known to work 1831 well in all environments. It organizes cache hot objects in 1832 per cpu and per node queues. 1833 1834config SLUB 1835 bool "SLUB (Unqueued Allocator)" 1836 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1837 help 1838 SLUB is a slab allocator that minimizes cache line usage 1839 instead of managing queues of cached objects (SLAB approach). 1840 Per cpu caching is realized using slabs of objects instead 1841 of queues of objects. SLUB can use memory efficiently 1842 and has enhanced diagnostics. SLUB is the default choice for 1843 a slab allocator. 1844 1845config SLOB 1846 depends on EXPERT 1847 bool "SLOB (Simple Allocator)" 1848 help 1849 SLOB replaces the stock allocator with a drastically simpler 1850 allocator. SLOB is generally more space efficient but 1851 does not perform as well on large systems. 1852 1853endchoice 1854 1855config SLAB_FREELIST_RANDOM 1856 default n 1857 depends on SLAB || SLUB 1858 bool "SLAB freelist randomization" 1859 help 1860 Randomizes the freelist order used on creating new pages. This 1861 security feature reduces the predictability of the kernel slab 1862 allocator against heap overflows. 1863 1864config SLUB_CPU_PARTIAL 1865 default y 1866 depends on SLUB && SMP 1867 bool "SLUB per cpu partial cache" 1868 help 1869 Per cpu partial caches accellerate objects allocation and freeing 1870 that is local to a processor at the price of more indeterminism 1871 in the latency of the free. On overflow these caches will be cleared 1872 which requires the taking of locks that may cause latency spikes. 1873 Typically one would choose no for a realtime system. 1874 1875config MMAP_ALLOW_UNINITIALIZED 1876 bool "Allow mmapped anonymous memory to be uninitialized" 1877 depends on EXPERT && !MMU 1878 default n 1879 help 1880 Normally, and according to the Linux spec, anonymous memory obtained 1881 from mmap() has it's contents cleared before it is passed to 1882 userspace. Enabling this config option allows you to request that 1883 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1884 providing a huge performance boost. If this option is not enabled, 1885 then the flag will be ignored. 1886 1887 This is taken advantage of by uClibc's malloc(), and also by 1888 ELF-FDPIC binfmt's brk and stack allocator. 1889 1890 Because of the obvious security issues, this option should only be 1891 enabled on embedded devices where you control what is run in 1892 userspace. Since that isn't generally a problem on no-MMU systems, 1893 it is normally safe to say Y here. 1894 1895 See Documentation/nommu-mmap.txt for more information. 1896 1897config SYSTEM_DATA_VERIFICATION 1898 def_bool n 1899 select SYSTEM_TRUSTED_KEYRING 1900 select KEYS 1901 select CRYPTO 1902 select CRYPTO_RSA 1903 select ASYMMETRIC_KEY_TYPE 1904 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1905 select ASN1 1906 select OID_REGISTRY 1907 select X509_CERTIFICATE_PARSER 1908 select PKCS7_MESSAGE_PARSER 1909 help 1910 Provide PKCS#7 message verification using the contents of the system 1911 trusted keyring to provide public keys. This then can be used for 1912 module verification, kexec image verification and firmware blob 1913 verification. 1914 1915config PROFILING 1916 bool "Profiling support" 1917 help 1918 Say Y here to enable the extended profiling support mechanisms used 1919 by profilers such as OProfile. 1920 1921# 1922# Place an empty function call at each tracepoint site. Can be 1923# dynamically changed for a probe function. 1924# 1925config TRACEPOINTS 1926 bool 1927 1928source "arch/Kconfig" 1929 1930endmenu # General setup 1931 1932config HAVE_GENERIC_DMA_COHERENT 1933 bool 1934 default n 1935 1936config SLABINFO 1937 bool 1938 depends on PROC_FS 1939 depends on SLAB || SLUB_DEBUG 1940 default y 1941 1942config RT_MUTEXES 1943 bool 1944 1945config BASE_SMALL 1946 int 1947 default 0 if BASE_FULL 1948 default 1 if !BASE_FULL 1949 1950menuconfig MODULES 1951 bool "Enable loadable module support" 1952 option modules 1953 help 1954 Kernel modules are small pieces of compiled code which can 1955 be inserted in the running kernel, rather than being 1956 permanently built into the kernel. You use the "modprobe" 1957 tool to add (and sometimes remove) them. If you say Y here, 1958 many parts of the kernel can be built as modules (by 1959 answering M instead of Y where indicated): this is most 1960 useful for infrequently used options which are not required 1961 for booting. For more information, see the man pages for 1962 modprobe, lsmod, modinfo, insmod and rmmod. 1963 1964 If you say Y here, you will need to run "make 1965 modules_install" to put the modules under /lib/modules/ 1966 where modprobe can find them (you may need to be root to do 1967 this). 1968 1969 If unsure, say Y. 1970 1971if MODULES 1972 1973config MODULE_FORCE_LOAD 1974 bool "Forced module loading" 1975 default n 1976 help 1977 Allow loading of modules without version information (ie. modprobe 1978 --force). Forced module loading sets the 'F' (forced) taint flag and 1979 is usually a really bad idea. 1980 1981config MODULE_UNLOAD 1982 bool "Module unloading" 1983 help 1984 Without this option you will not be able to unload any 1985 modules (note that some modules may not be unloadable 1986 anyway), which makes your kernel smaller, faster 1987 and simpler. If unsure, say Y. 1988 1989config MODULE_FORCE_UNLOAD 1990 bool "Forced module unloading" 1991 depends on MODULE_UNLOAD 1992 help 1993 This option allows you to force a module to unload, even if the 1994 kernel believes it is unsafe: the kernel will remove the module 1995 without waiting for anyone to stop using it (using the -f option to 1996 rmmod). This is mainly for kernel developers and desperate users. 1997 If unsure, say N. 1998 1999config MODVERSIONS 2000 bool "Module versioning support" 2001 help 2002 Usually, you have to use modules compiled with your kernel. 2003 Saying Y here makes it sometimes possible to use modules 2004 compiled for different kernels, by adding enough information 2005 to the modules to (hopefully) spot any changes which would 2006 make them incompatible with the kernel you are running. If 2007 unsure, say N. 2008 2009config MODULE_REL_CRCS 2010 bool 2011 depends on MODVERSIONS 2012 2013config MODULE_SRCVERSION_ALL 2014 bool "Source checksum for all modules" 2015 help 2016 Modules which contain a MODULE_VERSION get an extra "srcversion" 2017 field inserted into their modinfo section, which contains a 2018 sum of the source files which made it. This helps maintainers 2019 see exactly which source was used to build a module (since 2020 others sometimes change the module source without updating 2021 the version). With this option, such a "srcversion" field 2022 will be created for all modules. If unsure, say N. 2023 2024config MODULE_SIG 2025 bool "Module signature verification" 2026 depends on MODULES 2027 select SYSTEM_DATA_VERIFICATION 2028 help 2029 Check modules for valid signatures upon load: the signature 2030 is simply appended to the module. For more information see 2031 Documentation/module-signing.txt. 2032 2033 Note that this option adds the OpenSSL development packages as a 2034 kernel build dependency so that the signing tool can use its crypto 2035 library. 2036 2037 !!!WARNING!!! If you enable this option, you MUST make sure that the 2038 module DOES NOT get stripped after being signed. This includes the 2039 debuginfo strip done by some packagers (such as rpmbuild) and 2040 inclusion into an initramfs that wants the module size reduced. 2041 2042config MODULE_SIG_FORCE 2043 bool "Require modules to be validly signed" 2044 depends on MODULE_SIG 2045 help 2046 Reject unsigned modules or signed modules for which we don't have a 2047 key. Without this, such modules will simply taint the kernel. 2048 2049config MODULE_SIG_ALL 2050 bool "Automatically sign all modules" 2051 default y 2052 depends on MODULE_SIG 2053 help 2054 Sign all modules during make modules_install. Without this option, 2055 modules must be signed manually, using the scripts/sign-file tool. 2056 2057comment "Do not forget to sign required modules with scripts/sign-file" 2058 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2059 2060choice 2061 prompt "Which hash algorithm should modules be signed with?" 2062 depends on MODULE_SIG 2063 help 2064 This determines which sort of hashing algorithm will be used during 2065 signature generation. This algorithm _must_ be built into the kernel 2066 directly so that signature verification can take place. It is not 2067 possible to load a signed module containing the algorithm to check 2068 the signature on that module. 2069 2070config MODULE_SIG_SHA1 2071 bool "Sign modules with SHA-1" 2072 select CRYPTO_SHA1 2073 2074config MODULE_SIG_SHA224 2075 bool "Sign modules with SHA-224" 2076 select CRYPTO_SHA256 2077 2078config MODULE_SIG_SHA256 2079 bool "Sign modules with SHA-256" 2080 select CRYPTO_SHA256 2081 2082config MODULE_SIG_SHA384 2083 bool "Sign modules with SHA-384" 2084 select CRYPTO_SHA512 2085 2086config MODULE_SIG_SHA512 2087 bool "Sign modules with SHA-512" 2088 select CRYPTO_SHA512 2089 2090endchoice 2091 2092config MODULE_SIG_HASH 2093 string 2094 depends on MODULE_SIG 2095 default "sha1" if MODULE_SIG_SHA1 2096 default "sha224" if MODULE_SIG_SHA224 2097 default "sha256" if MODULE_SIG_SHA256 2098 default "sha384" if MODULE_SIG_SHA384 2099 default "sha512" if MODULE_SIG_SHA512 2100 2101config MODULE_COMPRESS 2102 bool "Compress modules on installation" 2103 depends on MODULES 2104 help 2105 2106 Compresses kernel modules when 'make modules_install' is run; gzip or 2107 xz depending on "Compression algorithm" below. 2108 2109 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 2110 2111 Out-of-tree kernel modules installed using Kbuild will also be 2112 compressed upon installation. 2113 2114 Note: for modules inside an initrd or initramfs, it's more efficient 2115 to compress the whole initrd or initramfs instead. 2116 2117 Note: This is fully compatible with signed modules. 2118 2119 If in doubt, say N. 2120 2121choice 2122 prompt "Compression algorithm" 2123 depends on MODULE_COMPRESS 2124 default MODULE_COMPRESS_GZIP 2125 help 2126 This determines which sort of compression will be used during 2127 'make modules_install'. 2128 2129 GZIP (default) and XZ are supported. 2130 2131config MODULE_COMPRESS_GZIP 2132 bool "GZIP" 2133 2134config MODULE_COMPRESS_XZ 2135 bool "XZ" 2136 2137endchoice 2138 2139config TRIM_UNUSED_KSYMS 2140 bool "Trim unused exported kernel symbols" 2141 depends on MODULES && !UNUSED_SYMBOLS 2142 help 2143 The kernel and some modules make many symbols available for 2144 other modules to use via EXPORT_SYMBOL() and variants. Depending 2145 on the set of modules being selected in your kernel configuration, 2146 many of those exported symbols might never be used. 2147 2148 This option allows for unused exported symbols to be dropped from 2149 the build. In turn, this provides the compiler more opportunities 2150 (especially when using LTO) for optimizing the code and reducing 2151 binary size. This might have some security advantages as well. 2152 2153 If unsure, or if you need to build out-of-tree modules, say N. 2154 2155endif # MODULES 2156 2157config MODULES_TREE_LOOKUP 2158 def_bool y 2159 depends on PERF_EVENTS || TRACING 2160 2161config INIT_ALL_POSSIBLE 2162 bool 2163 help 2164 Back when each arch used to define their own cpu_online_mask and 2165 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2166 with all 1s, and others with all 0s. When they were centralised, 2167 it was better to provide this option than to break all the archs 2168 and have several arch maintainers pursuing me down dark alleys. 2169 2170source "block/Kconfig" 2171 2172config PREEMPT_NOTIFIERS 2173 bool 2174 2175config PADATA 2176 depends on SMP 2177 bool 2178 2179config ASN1 2180 tristate 2181 help 2182 Build a simple ASN.1 grammar compiler that produces a bytecode output 2183 that can be interpreted by the ASN.1 stream decoder and used to 2184 inform it as to what tags are to be expected in a stream and what 2185 functions to call on what tags. 2186 2187source "kernel/Kconfig.locks" 2188