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 SCHED_WALT 404 bool "Support window based load tracking" 405 depends on SMP 406 help 407 This feature will allow the scheduler to maintain a tunable window 408 based set of metrics for tasks and runqueues. These metrics can be 409 used to guide task placement as well as task frequency requirements 410 for cpufreq governors. 411 412config BSD_PROCESS_ACCT 413 bool "BSD Process Accounting" 414 depends on MULTIUSER 415 help 416 If you say Y here, a user level program will be able to instruct the 417 kernel (via a special system call) to write process accounting 418 information to a file: whenever a process exits, information about 419 that process will be appended to the file by the kernel. The 420 information includes things such as creation time, owning user, 421 command name, memory usage, controlling terminal etc. (the complete 422 list is in the struct acct in <file:include/linux/acct.h>). It is 423 up to the user level program to do useful things with this 424 information. This is generally a good idea, so say Y. 425 426config BSD_PROCESS_ACCT_V3 427 bool "BSD Process Accounting version 3 file format" 428 depends on BSD_PROCESS_ACCT 429 default n 430 help 431 If you say Y here, the process accounting information is written 432 in a new file format that also logs the process IDs of each 433 process and it's parent. Note that this file format is incompatible 434 with previous v0/v1/v2 file formats, so you will need updated tools 435 for processing it. A preliminary version of these tools is available 436 at <http://www.gnu.org/software/acct/>. 437 438config TASKSTATS 439 bool "Export task/process statistics through netlink" 440 depends on NET 441 depends on MULTIUSER 442 default n 443 help 444 Export selected statistics for tasks/processes through the 445 generic netlink interface. Unlike BSD process accounting, the 446 statistics are available during the lifetime of tasks/processes as 447 responses to commands. Like BSD accounting, they are sent to user 448 space on task exit. 449 450 Say N if unsure. 451 452config TASK_DELAY_ACCT 453 bool "Enable per-task delay accounting" 454 depends on TASKSTATS 455 select SCHED_INFO 456 help 457 Collect information on time spent by a task waiting for system 458 resources like cpu, synchronous block I/O completion and swapping 459 in pages. Such statistics can help in setting a task's priorities 460 relative to other tasks for cpu, io, rss limits etc. 461 462 Say N if unsure. 463 464config TASK_XACCT 465 bool "Enable extended accounting over taskstats" 466 depends on TASKSTATS 467 help 468 Collect extended task accounting data and send the data 469 to userland for processing over the taskstats interface. 470 471 Say N if unsure. 472 473config TASK_IO_ACCOUNTING 474 bool "Enable per-task storage I/O accounting" 475 depends on TASK_XACCT 476 help 477 Collect information on the number of bytes of storage I/O which this 478 task has caused. 479 480 Say N if unsure. 481 482endmenu # "CPU/Task time and stats accounting" 483 484menu "RCU Subsystem" 485 486config TREE_RCU 487 bool 488 default y if !PREEMPT && SMP 489 help 490 This option selects the RCU implementation that is 491 designed for very large SMP system with hundreds or 492 thousands of CPUs. It also scales down nicely to 493 smaller systems. 494 495config PREEMPT_RCU 496 bool 497 default y if PREEMPT 498 help 499 This option selects the RCU implementation that is 500 designed for very large SMP systems with hundreds or 501 thousands of CPUs, but for which real-time response 502 is also required. It also scales down nicely to 503 smaller systems. 504 505 Select this option if you are unsure. 506 507config TINY_RCU 508 bool 509 default y if !PREEMPT && !SMP 510 help 511 This option selects the RCU implementation that is 512 designed for UP systems from which real-time response 513 is not required. This option greatly reduces the 514 memory footprint of RCU. 515 516config RCU_EXPERT 517 bool "Make expert-level adjustments to RCU configuration" 518 default n 519 help 520 This option needs to be enabled if you wish to make 521 expert-level adjustments to RCU configuration. By default, 522 no such adjustments can be made, which has the often-beneficial 523 side-effect of preventing "make oldconfig" from asking you all 524 sorts of detailed questions about how you would like numerous 525 obscure RCU options to be set up. 526 527 Say Y if you need to make expert-level adjustments to RCU. 528 529 Say N if you are unsure. 530 531config SRCU 532 bool 533 help 534 This option selects the sleepable version of RCU. This version 535 permits arbitrary sleeping or blocking within RCU read-side critical 536 sections. 537 538config TASKS_RCU 539 bool 540 default n 541 depends on !UML 542 select SRCU 543 help 544 This option enables a task-based RCU implementation that uses 545 only voluntary context switch (not preemption!), idle, and 546 user-mode execution as quiescent states. 547 548config RCU_STALL_COMMON 549 def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE ) 550 help 551 This option enables RCU CPU stall code that is common between 552 the TINY and TREE variants of RCU. The purpose is to allow 553 the tiny variants to disable RCU CPU stall warnings, while 554 making these warnings mandatory for the tree variants. 555 556config CONTEXT_TRACKING 557 bool 558 559config CONTEXT_TRACKING_FORCE 560 bool "Force context tracking" 561 depends on CONTEXT_TRACKING 562 default y if !NO_HZ_FULL 563 help 564 The major pre-requirement for full dynticks to work is to 565 support the context tracking subsystem. But there are also 566 other dependencies to provide in order to make the full 567 dynticks working. 568 569 This option stands for testing when an arch implements the 570 context tracking backend but doesn't yet fullfill all the 571 requirements to make the full dynticks feature working. 572 Without the full dynticks, there is no way to test the support 573 for context tracking and the subsystems that rely on it: RCU 574 userspace extended quiescent state and tickless cputime 575 accounting. This option copes with the absence of the full 576 dynticks subsystem by forcing the context tracking on all 577 CPUs in the system. 578 579 Say Y only if you're working on the development of an 580 architecture backend for the context tracking. 581 582 Say N otherwise, this option brings an overhead that you 583 don't want in production. 584 585 586config RCU_FANOUT 587 int "Tree-based hierarchical RCU fanout value" 588 range 2 64 if 64BIT 589 range 2 32 if !64BIT 590 depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT 591 default 64 if 64BIT 592 default 32 if !64BIT 593 help 594 This option controls the fanout of hierarchical implementations 595 of RCU, allowing RCU to work efficiently on machines with 596 large numbers of CPUs. This value must be at least the fourth 597 root of NR_CPUS, which allows NR_CPUS to be insanely large. 598 The default value of RCU_FANOUT should be used for production 599 systems, but if you are stress-testing the RCU implementation 600 itself, small RCU_FANOUT values allow you to test large-system 601 code paths on small(er) systems. 602 603 Select a specific number if testing RCU itself. 604 Take the default if unsure. 605 606config RCU_FANOUT_LEAF 607 int "Tree-based hierarchical RCU leaf-level fanout value" 608 range 2 64 if 64BIT 609 range 2 32 if !64BIT 610 depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT 611 default 16 612 help 613 This option controls the leaf-level fanout of hierarchical 614 implementations of RCU, and allows trading off cache misses 615 against lock contention. Systems that synchronize their 616 scheduling-clock interrupts for energy-efficiency reasons will 617 want the default because the smaller leaf-level fanout keeps 618 lock contention levels acceptably low. Very large systems 619 (hundreds or thousands of CPUs) will instead want to set this 620 value to the maximum value possible in order to reduce the 621 number of cache misses incurred during RCU's grace-period 622 initialization. These systems tend to run CPU-bound, and thus 623 are not helped by synchronized interrupts, and thus tend to 624 skew them, which reduces lock contention enough that large 625 leaf-level fanouts work well. 626 627 Select a specific number if testing RCU itself. 628 629 Select the maximum permissible value for large systems. 630 631 Take the default if unsure. 632 633config RCU_FAST_NO_HZ 634 bool "Accelerate last non-dyntick-idle CPU's grace periods" 635 depends on NO_HZ_COMMON && SMP && RCU_EXPERT 636 default n 637 help 638 This option permits CPUs to enter dynticks-idle state even if 639 they have RCU callbacks queued, and prevents RCU from waking 640 these CPUs up more than roughly once every four jiffies (by 641 default, you can adjust this using the rcutree.rcu_idle_gp_delay 642 parameter), thus improving energy efficiency. On the other 643 hand, this option increases the duration of RCU grace periods, 644 for example, slowing down synchronize_rcu(). 645 646 Say Y if energy efficiency is critically important, and you 647 don't care about increased grace-period durations. 648 649 Say N if you are unsure. 650 651config TREE_RCU_TRACE 652 def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU ) 653 select DEBUG_FS 654 help 655 This option provides tracing for the TREE_RCU and 656 PREEMPT_RCU implementations, permitting Makefile to 657 trivially select kernel/rcutree_trace.c. 658 659config RCU_BOOST 660 bool "Enable RCU priority boosting" 661 depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT 662 default n 663 help 664 This option boosts the priority of preempted RCU readers that 665 block the current preemptible RCU grace period for too long. 666 This option also prevents heavy loads from blocking RCU 667 callback invocation for all flavors of RCU. 668 669 Say Y here if you are working with real-time apps or heavy loads 670 Say N here if you are unsure. 671 672config RCU_KTHREAD_PRIO 673 int "Real-time priority to use for RCU worker threads" 674 range 1 99 if RCU_BOOST 675 range 0 99 if !RCU_BOOST 676 default 1 if RCU_BOOST 677 default 0 if !RCU_BOOST 678 depends on RCU_EXPERT 679 help 680 This option specifies the SCHED_FIFO priority value that will be 681 assigned to the rcuc/n and rcub/n threads and is also the value 682 used for RCU_BOOST (if enabled). If you are working with a 683 real-time application that has one or more CPU-bound threads 684 running at a real-time priority level, you should set 685 RCU_KTHREAD_PRIO to a priority higher than the highest-priority 686 real-time CPU-bound application thread. The default RCU_KTHREAD_PRIO 687 value of 1 is appropriate in the common case, which is real-time 688 applications that do not have any CPU-bound threads. 689 690 Some real-time applications might not have a single real-time 691 thread that saturates a given CPU, but instead might have 692 multiple real-time threads that, taken together, fully utilize 693 that CPU. In this case, you should set RCU_KTHREAD_PRIO to 694 a priority higher than the lowest-priority thread that is 695 conspiring to prevent the CPU from running any non-real-time 696 tasks. For example, if one thread at priority 10 and another 697 thread at priority 5 are between themselves fully consuming 698 the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be 699 set to priority 6 or higher. 700 701 Specify the real-time priority, or take the default if unsure. 702 703config RCU_BOOST_DELAY 704 int "Milliseconds to delay boosting after RCU grace-period start" 705 range 0 3000 706 depends on RCU_BOOST 707 default 500 708 help 709 This option specifies the time to wait after the beginning of 710 a given grace period before priority-boosting preempted RCU 711 readers blocking that grace period. Note that any RCU reader 712 blocking an expedited RCU grace period is boosted immediately. 713 714 Accept the default if unsure. 715 716config RCU_NOCB_CPU 717 bool "Offload RCU callback processing from boot-selected CPUs" 718 depends on TREE_RCU || PREEMPT_RCU 719 depends on RCU_EXPERT || NO_HZ_FULL 720 default n 721 help 722 Use this option to reduce OS jitter for aggressive HPC or 723 real-time workloads. It can also be used to offload RCU 724 callback invocation to energy-efficient CPUs in battery-powered 725 asymmetric multiprocessors. 726 727 This option offloads callback invocation from the set of 728 CPUs specified at boot time by the rcu_nocbs parameter. 729 For each such CPU, a kthread ("rcuox/N") will be created to 730 invoke callbacks, where the "N" is the CPU being offloaded, 731 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and 732 "s" for RCU-sched. Nothing prevents this kthread from running 733 on the specified CPUs, but (1) the kthreads may be preempted 734 between each callback, and (2) affinity or cgroups can be used 735 to force the kthreads to run on whatever set of CPUs is desired. 736 737 Say Y here if you want to help to debug reduced OS jitter. 738 Say N here if you are unsure. 739 740choice 741 prompt "Build-forced no-CBs CPUs" 742 default RCU_NOCB_CPU_NONE 743 depends on RCU_NOCB_CPU 744 help 745 This option allows no-CBs CPUs (whose RCU callbacks are invoked 746 from kthreads rather than from softirq context) to be specified 747 at build time. Additional no-CBs CPUs may be specified by 748 the rcu_nocbs= boot parameter. 749 750config RCU_NOCB_CPU_NONE 751 bool "No build_forced no-CBs CPUs" 752 help 753 This option does not force any of the CPUs to be no-CBs CPUs. 754 Only CPUs designated by the rcu_nocbs= boot parameter will be 755 no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU 756 kthreads whose names begin with "rcuo". All other CPUs will 757 invoke their own RCU callbacks in softirq context. 758 759 Select this option if you want to choose no-CBs CPUs at 760 boot time, for example, to allow testing of different no-CBs 761 configurations without having to rebuild the kernel each time. 762 763config RCU_NOCB_CPU_ZERO 764 bool "CPU 0 is a build_forced no-CBs CPU" 765 help 766 This option forces CPU 0 to be a no-CBs CPU, so that its RCU 767 callbacks are invoked by a per-CPU kthread whose name begins 768 with "rcuo". Additional CPUs may be designated as no-CBs 769 CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs. 770 All other CPUs will invoke their own RCU callbacks in softirq 771 context. 772 773 Select this if CPU 0 needs to be a no-CBs CPU for real-time 774 or energy-efficiency reasons, but the real reason it exists 775 is to ensure that randconfig testing covers mixed systems. 776 777config RCU_NOCB_CPU_ALL 778 bool "All CPUs are build_forced no-CBs CPUs" 779 help 780 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs= 781 boot parameter will be ignored. All CPUs' RCU callbacks will 782 be executed in the context of per-CPU rcuo kthreads created for 783 this purpose. Assuming that the kthreads whose names start with 784 "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter 785 on the remaining CPUs, but might decrease memory locality during 786 RCU-callback invocation, thus potentially degrading throughput. 787 788 Select this if all CPUs need to be no-CBs CPUs for real-time 789 or energy-efficiency reasons. 790 791endchoice 792 793config RCU_EXPEDITE_BOOT 794 bool 795 default n 796 help 797 This option enables expedited grace periods at boot time, 798 as if rcu_expedite_gp() had been invoked early in boot. 799 The corresponding rcu_unexpedite_gp() is invoked from 800 rcu_end_inkernel_boot(), which is intended to be invoked 801 at the end of the kernel-only boot sequence, just before 802 init is exec'ed. 803 804 Accept the default if unsure. 805 806endmenu # "RCU Subsystem" 807 808config BUILD_BIN2C 809 bool 810 default n 811 812config IKCONFIG 813 tristate "Kernel .config support" 814 select BUILD_BIN2C 815 ---help--- 816 This option enables the complete Linux kernel ".config" file 817 contents to be saved in the kernel. It provides documentation 818 of which kernel options are used in a running kernel or in an 819 on-disk kernel. This information can be extracted from the kernel 820 image file with the script scripts/extract-ikconfig and used as 821 input to rebuild the current kernel or to build another kernel. 822 It can also be extracted from a running kernel by reading 823 /proc/config.gz if enabled (below). 824 825config IKCONFIG_PROC 826 bool "Enable access to .config through /proc/config.gz" 827 depends on IKCONFIG && PROC_FS 828 ---help--- 829 This option enables access to the kernel configuration file 830 through /proc/config.gz. 831 832config LOG_BUF_SHIFT 833 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 834 range 12 25 835 default 17 836 depends on PRINTK 837 help 838 Select the minimal kernel log buffer size as a power of 2. 839 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 840 parameter, see below. Any higher size also might be forced 841 by "log_buf_len" boot parameter. 842 843 Examples: 844 17 => 128 KB 845 16 => 64 KB 846 15 => 32 KB 847 14 => 16 KB 848 13 => 8 KB 849 12 => 4 KB 850 851config LOG_CPU_MAX_BUF_SHIFT 852 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 853 depends on SMP 854 range 0 21 855 default 12 if !BASE_SMALL 856 default 0 if BASE_SMALL 857 depends on PRINTK 858 help 859 This option allows to increase the default ring buffer size 860 according to the number of CPUs. The value defines the contribution 861 of each CPU as a power of 2. The used space is typically only few 862 lines however it might be much more when problems are reported, 863 e.g. backtraces. 864 865 The increased size means that a new buffer has to be allocated and 866 the original static one is unused. It makes sense only on systems 867 with more CPUs. Therefore this value is used only when the sum of 868 contributions is greater than the half of the default kernel ring 869 buffer as defined by LOG_BUF_SHIFT. The default values are set 870 so that more than 64 CPUs are needed to trigger the allocation. 871 872 Also this option is ignored when "log_buf_len" kernel parameter is 873 used as it forces an exact (power of two) size of the ring buffer. 874 875 The number of possible CPUs is used for this computation ignoring 876 hotplugging making the computation optimal for the worst case 877 scenario while allowing a simple algorithm to be used from bootup. 878 879 Examples shift values and their meaning: 880 17 => 128 KB for each CPU 881 16 => 64 KB for each CPU 882 15 => 32 KB for each CPU 883 14 => 16 KB for each CPU 884 13 => 8 KB for each CPU 885 12 => 4 KB for each CPU 886 887config NMI_LOG_BUF_SHIFT 888 int "Temporary per-CPU NMI log buffer size (12 => 4KB, 13 => 8KB)" 889 range 10 21 890 default 13 891 depends on PRINTK_NMI 892 help 893 Select the size of a per-CPU buffer where NMI messages are temporary 894 stored. They are copied to the main log buffer in a safe context 895 to avoid a deadlock. The value defines the size as a power of 2. 896 897 NMI messages are rare and limited. The largest one is when 898 a backtrace is printed. It usually fits into 4KB. Select 899 8KB if you want to be on the safe side. 900 901 Examples: 902 17 => 128 KB for each CPU 903 16 => 64 KB for each CPU 904 15 => 32 KB for each CPU 905 14 => 16 KB for each CPU 906 13 => 8 KB for each CPU 907 12 => 4 KB for each CPU 908 909# 910# Architectures with an unreliable sched_clock() should select this: 911# 912config HAVE_UNSTABLE_SCHED_CLOCK 913 bool 914 915config GENERIC_SCHED_CLOCK 916 bool 917 918# 919# For architectures that want to enable the support for NUMA-affine scheduler 920# balancing logic: 921# 922config ARCH_SUPPORTS_NUMA_BALANCING 923 bool 924 925# 926# For architectures that prefer to flush all TLBs after a number of pages 927# are unmapped instead of sending one IPI per page to flush. The architecture 928# must provide guarantees on what happens if a clean TLB cache entry is 929# written after the unmap. Details are in mm/rmap.c near the check for 930# should_defer_flush. The architecture should also consider if the full flush 931# and the refill costs are offset by the savings of sending fewer IPIs. 932config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 933 bool 934 935# 936# For architectures that know their GCC __int128 support is sound 937# 938config ARCH_SUPPORTS_INT128 939 bool 940 941# For architectures that (ab)use NUMA to represent different memory regions 942# all cpu-local but of different latencies, such as SuperH. 943# 944config ARCH_WANT_NUMA_VARIABLE_LOCALITY 945 bool 946 947config NUMA_BALANCING 948 bool "Memory placement aware NUMA scheduler" 949 depends on ARCH_SUPPORTS_NUMA_BALANCING 950 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 951 depends on SMP && NUMA && MIGRATION 952 help 953 This option adds support for automatic NUMA aware memory/task placement. 954 The mechanism is quite primitive and is based on migrating memory when 955 it has references to the node the task is running on. 956 957 This system will be inactive on UMA systems. 958 959config NUMA_BALANCING_DEFAULT_ENABLED 960 bool "Automatically enable NUMA aware memory/task placement" 961 default y 962 depends on NUMA_BALANCING 963 help 964 If set, automatic NUMA balancing will be enabled if running on a NUMA 965 machine. 966 967menuconfig CGROUPS 968 bool "Control Group support" 969 select KERNFS 970 help 971 This option adds support for grouping sets of processes together, for 972 use with process control subsystems such as Cpusets, CFS, memory 973 controls or device isolation. 974 See 975 - Documentation/scheduler/sched-design-CFS.txt (CFS) 976 - Documentation/cgroup-v1/ (features for grouping, isolation 977 and resource control) 978 979 Say N if unsure. 980 981if CGROUPS 982 983config CGROUP_DEBUG 984 bool "Example debug cgroup subsystem" 985 default n 986 help 987 This option enables a simple cgroup subsystem that 988 exports useful debugging information about the cgroups 989 framework. 990 991 Say N if unsure. 992 993config CGROUP_FREEZER 994 bool "Freezer cgroup subsystem" 995 help 996 Provides a way to freeze and unfreeze all tasks in a 997 cgroup. 998 999config CGROUP_PIDS 1000 bool "PIDs cgroup subsystem" 1001 help 1002 Provides enforcement of process number limits in the scope of a 1003 cgroup. Any attempt to fork more processes than is allowed in the 1004 cgroup will fail. PIDs are fundamentally a global resource because it 1005 is fairly trivial to reach PID exhaustion before you reach even a 1006 conservative kmemcg limit. As a result, it is possible to grind a 1007 system to halt without being limited by other cgroup policies. The 1008 PIDs cgroup subsystem is designed to stop this from happening. 1009 1010 It should be noted that organisational operations (such as attaching 1011 to a cgroup hierarchy will *not* be blocked by the PIDs subsystem), 1012 since the PIDs limit only affects a process's ability to fork, not to 1013 attach to a cgroup. 1014 1015config CGROUP_DEVICE 1016 bool "Device controller for cgroups" 1017 help 1018 Provides a cgroup implementing whitelists for devices which 1019 a process in the cgroup can mknod or open. 1020 1021config CPUSETS 1022 bool "Cpuset support" 1023 help 1024 This option will let you create and manage CPUSETs which 1025 allow dynamically partitioning a system into sets of CPUs and 1026 Memory Nodes and assigning tasks to run only within those sets. 1027 This is primarily useful on large SMP or NUMA systems. 1028 1029 Say N if unsure. 1030 1031config PROC_PID_CPUSET 1032 bool "Include legacy /proc/<pid>/cpuset file" 1033 depends on CPUSETS 1034 default y 1035 1036config CGROUP_CPUACCT 1037 bool "Simple CPU accounting cgroup subsystem" 1038 help 1039 Provides a simple Resource Controller for monitoring the 1040 total CPU consumed by the tasks in a cgroup. 1041 1042config CGROUP_SCHEDTUNE 1043 bool "CFS tasks boosting cgroup subsystem (EXPERIMENTAL)" 1044 depends on SCHED_TUNE 1045 help 1046 This option provides the "schedtune" controller which improves the 1047 flexibility of the task boosting mechanism by introducing the support 1048 to define "per task" boost values. 1049 1050 This new controller: 1051 1. allows only a two layers hierarchy, where the root defines the 1052 system-wide boost value and its direct childrens define each one a 1053 different "class of tasks" to be boosted with a different value 1054 2. supports up to 16 different task classes, each one which could be 1055 configured with a different boost value 1056 1057 Say N if unsure. 1058 1059config PAGE_COUNTER 1060 bool 1061 1062config MEMCG 1063 bool "Memory controller" 1064 select PAGE_COUNTER 1065 select EVENTFD 1066 help 1067 Provides control over the memory footprint of tasks in a cgroup. 1068 1069config MEMCG_SWAP 1070 bool "Swap controller" 1071 depends on MEMCG && SWAP 1072 help 1073 Provides control over the swap space consumed by tasks in a cgroup. 1074 1075config MEMCG_SWAP_ENABLED 1076 bool "Swap controller enabled by default" 1077 depends on MEMCG_SWAP 1078 default y 1079 help 1080 Memory Resource Controller Swap Extension comes with its price in 1081 a bigger memory consumption. General purpose distribution kernels 1082 which want to enable the feature but keep it disabled by default 1083 and let the user enable it by swapaccount=1 boot command line 1084 parameter should have this option unselected. 1085 For those who want to have the feature enabled by default should 1086 select this option (if, for some reason, they need to disable it 1087 then swapaccount=0 does the trick). 1088 1089config BLK_CGROUP 1090 bool "IO controller" 1091 depends on BLOCK 1092 default n 1093 ---help--- 1094 Generic block IO controller cgroup interface. This is the common 1095 cgroup interface which should be used by various IO controlling 1096 policies. 1097 1098 Currently, CFQ IO scheduler uses it to recognize task groups and 1099 control disk bandwidth allocation (proportional time slice allocation) 1100 to such task groups. It is also used by bio throttling logic in 1101 block layer to implement upper limit in IO rates on a device. 1102 1103 This option only enables generic Block IO controller infrastructure. 1104 One needs to also enable actual IO controlling logic/policy. For 1105 enabling proportional weight division of disk bandwidth in CFQ, set 1106 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 1107 CONFIG_BLK_DEV_THROTTLING=y. 1108 1109 See Documentation/cgroup-v1/blkio-controller.txt for more information. 1110 1111config DEBUG_BLK_CGROUP 1112 bool "IO controller debugging" 1113 depends on BLK_CGROUP 1114 default n 1115 ---help--- 1116 Enable some debugging help. Currently it exports additional stat 1117 files in a cgroup which can be useful for debugging. 1118 1119config CGROUP_WRITEBACK 1120 bool 1121 depends on MEMCG && BLK_CGROUP 1122 default y 1123 1124menuconfig CGROUP_SCHED 1125 bool "CPU controller" 1126 default n 1127 help 1128 This feature lets CPU scheduler recognize task groups and control CPU 1129 bandwidth allocation to such task groups. It uses cgroups to group 1130 tasks. 1131 1132if CGROUP_SCHED 1133config FAIR_GROUP_SCHED 1134 bool "Group scheduling for SCHED_OTHER" 1135 depends on CGROUP_SCHED 1136 default CGROUP_SCHED 1137 1138config CFS_BANDWIDTH 1139 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 1140 depends on FAIR_GROUP_SCHED 1141 default n 1142 help 1143 This option allows users to define CPU bandwidth rates (limits) for 1144 tasks running within the fair group scheduler. Groups with no limit 1145 set are considered to be unconstrained and will run with no 1146 restriction. 1147 See tip/Documentation/scheduler/sched-bwc.txt for more information. 1148 1149config RT_GROUP_SCHED 1150 bool "Group scheduling for SCHED_RR/FIFO" 1151 depends on CGROUP_SCHED 1152 default n 1153 help 1154 This feature lets you explicitly allocate real CPU bandwidth 1155 to task groups. If enabled, it will also make it impossible to 1156 schedule realtime tasks for non-root users until you allocate 1157 realtime bandwidth for them. 1158 See Documentation/scheduler/sched-rt-group.txt for more information. 1159 1160endif #CGROUP_SCHED 1161 1162config CGROUP_PIDS 1163 bool "PIDs controller" 1164 help 1165 Provides enforcement of process number limits in the scope of a 1166 cgroup. Any attempt to fork more processes than is allowed in the 1167 cgroup will fail. PIDs are fundamentally a global resource because it 1168 is fairly trivial to reach PID exhaustion before you reach even a 1169 conservative kmemcg limit. As a result, it is possible to grind a 1170 system to halt without being limited by other cgroup policies. The 1171 PIDs controller is designed to stop this from happening. 1172 1173 It should be noted that organisational operations (such as attaching 1174 to a cgroup hierarchy will *not* be blocked by the PIDs controller), 1175 since the PIDs limit only affects a process's ability to fork, not to 1176 attach to a cgroup. 1177 1178config CGROUP_FREEZER 1179 bool "Freezer controller" 1180 help 1181 Provides a way to freeze and unfreeze all tasks in a 1182 cgroup. 1183 1184 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1185 controller includes important in-kernel memory consumers per default. 1186 1187 If you're using cgroup2, say N. 1188 1189config CGROUP_HUGETLB 1190 bool "HugeTLB controller" 1191 depends on HUGETLB_PAGE 1192 select PAGE_COUNTER 1193 default n 1194 help 1195 Provides a cgroup controller for HugeTLB pages. 1196 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1197 The limit is enforced during page fault. Since HugeTLB doesn't 1198 support page reclaim, enforcing the limit at page fault time implies 1199 that, the application will get SIGBUS signal if it tries to access 1200 HugeTLB pages beyond its limit. This requires the application to know 1201 beforehand how much HugeTLB pages it would require for its use. The 1202 control group is tracked in the third page lru pointer. This means 1203 that we cannot use the controller with huge page less than 3 pages. 1204 1205config CPUSETS 1206 bool "Cpuset controller" 1207 help 1208 This option will let you create and manage CPUSETs which 1209 allow dynamically partitioning a system into sets of CPUs and 1210 Memory Nodes and assigning tasks to run only within those sets. 1211 This is primarily useful on large SMP or NUMA systems. 1212 1213 Say N if unsure. 1214 1215config PROC_PID_CPUSET 1216 bool "Include legacy /proc/<pid>/cpuset file" 1217 depends on CPUSETS 1218 default y 1219 1220config CGROUP_DEVICE 1221 bool "Device controller" 1222 help 1223 Provides a cgroup controller implementing whitelists for 1224 devices which a process in the cgroup can mknod or open. 1225 1226config CGROUP_CPUACCT 1227 bool "Simple CPU accounting controller" 1228 help 1229 Provides a simple controller for monitoring the 1230 total CPU consumed by the tasks in a cgroup. 1231 1232config CGROUP_PERF 1233 bool "Perf controller" 1234 depends on PERF_EVENTS 1235 help 1236 This option extends the perf per-cpu mode to restrict monitoring 1237 to threads which belong to the cgroup specified and run on the 1238 designated cpu. 1239 1240 Say N if unsure. 1241 1242config CGROUP_BPF 1243 bool "Support for eBPF programs attached to cgroups" 1244 depends on BPF_SYSCALL 1245 select SOCK_CGROUP_DATA 1246 help 1247 Allow attaching eBPF programs to a cgroup using the bpf(2) 1248 syscall command BPF_PROG_ATTACH. 1249 1250 In which context these programs are accessed depends on the type 1251 of attachment. For instance, programs that are attached using 1252 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1253 inet sockets. 1254 1255config CGROUP_DEBUG 1256 bool "Example controller" 1257 default n 1258 help 1259 This option enables a simple controller that exports 1260 debugging information about the cgroups framework. 1261 1262 Say N. 1263 1264config SOCK_CGROUP_DATA 1265 bool 1266 default n 1267 1268endif # CGROUPS 1269 1270config CHECKPOINT_RESTORE 1271 bool "Checkpoint/restore support" if EXPERT 1272 select PROC_CHILDREN 1273 default n 1274 help 1275 Enables additional kernel features in a sake of checkpoint/restore. 1276 In particular it adds auxiliary prctl codes to setup process text, 1277 data and heap segment sizes, and a few additional /proc filesystem 1278 entries. 1279 1280 If unsure, say N here. 1281 1282menuconfig NAMESPACES 1283 bool "Namespaces support" if EXPERT 1284 depends on MULTIUSER 1285 default !EXPERT 1286 help 1287 Provides the way to make tasks work with different objects using 1288 the same id. For example same IPC id may refer to different objects 1289 or same user id or pid may refer to different tasks when used in 1290 different namespaces. 1291 1292if NAMESPACES 1293 1294config UTS_NS 1295 bool "UTS namespace" 1296 default y 1297 help 1298 In this namespace tasks see different info provided with the 1299 uname() system call 1300 1301config IPC_NS 1302 bool "IPC namespace" 1303 depends on (SYSVIPC || POSIX_MQUEUE) 1304 default y 1305 help 1306 In this namespace tasks work with IPC ids which correspond to 1307 different IPC objects in different namespaces. 1308 1309config USER_NS 1310 bool "User namespace" 1311 default n 1312 help 1313 This allows containers, i.e. vservers, to use user namespaces 1314 to provide different user info for different servers. 1315 1316 When user namespaces are enabled in the kernel it is 1317 recommended that the MEMCG option also be enabled and that 1318 user-space use the memory control groups to limit the amount 1319 of memory a memory unprivileged users can use. 1320 1321 If unsure, say N. 1322 1323config PID_NS 1324 bool "PID Namespaces" 1325 default y 1326 help 1327 Support process id namespaces. This allows having multiple 1328 processes with the same pid as long as they are in different 1329 pid namespaces. This is a building block of containers. 1330 1331config NET_NS 1332 bool "Network namespace" 1333 depends on NET 1334 default y 1335 help 1336 Allow user space to create what appear to be multiple instances 1337 of the network stack. 1338 1339endif # NAMESPACES 1340 1341config SCHED_AUTOGROUP 1342 bool "Automatic process group scheduling" 1343 select CGROUPS 1344 select CGROUP_SCHED 1345 select FAIR_GROUP_SCHED 1346 help 1347 This option optimizes the scheduler for common desktop workloads by 1348 automatically creating and populating task groups. This separation 1349 of workloads isolates aggressive CPU burners (like build jobs) from 1350 desktop applications. Task group autogeneration is currently based 1351 upon task session. 1352 1353config SCHED_TUNE 1354 bool "Boosting for CFS tasks (EXPERIMENTAL)" 1355 depends on SMP 1356 help 1357 This option enables the system-wide support for task boosting. 1358 When this support is enabled a new sysctl interface is exposed to 1359 userspace via: 1360 /proc/sys/kernel/sched_cfs_boost 1361 which allows to set a system-wide boost value in range [0..100]. 1362 1363 The currently boosting strategy is implemented in such a way that: 1364 - a 0% boost value requires to operate in "standard" mode by 1365 scheduling all tasks at the minimum capacities required by their 1366 workload demand 1367 - a 100% boost value requires to push at maximum the task 1368 performances, "regardless" of the incurred energy consumption 1369 1370 A boost value in between these two boundaries is used to bias the 1371 power/performance trade-off, the higher the boost value the more the 1372 scheduler is biased toward performance boosting instead of energy 1373 efficiency. 1374 1375 Since this support exposes a single system-wide knob, the specified 1376 boost value is applied to all (CFS) tasks in the system. 1377 1378 If unsure, say N. 1379 1380config DEFAULT_USE_ENERGY_AWARE 1381 bool "Default to enabling the Energy Aware Scheduler feature" 1382 default n 1383 help 1384 This option defaults the ENERGY_AWARE scheduling feature to true, 1385 as without SCHED_DEBUG set this feature can't be enabled or disabled 1386 via sysctl. 1387 1388 Say N if unsure. 1389 1390config SYSFS_DEPRECATED 1391 bool "Enable deprecated sysfs features to support old userspace tools" 1392 depends on SYSFS 1393 default n 1394 help 1395 This option adds code that switches the layout of the "block" class 1396 devices, to not show up in /sys/class/block/, but only in 1397 /sys/block/. 1398 1399 This switch is only active when the sysfs.deprecated=1 boot option is 1400 passed or the SYSFS_DEPRECATED_V2 option is set. 1401 1402 This option allows new kernels to run on old distributions and tools, 1403 which might get confused by /sys/class/block/. Since 2007/2008 all 1404 major distributions and tools handle this just fine. 1405 1406 Recent distributions and userspace tools after 2009/2010 depend on 1407 the existence of /sys/class/block/, and will not work with this 1408 option enabled. 1409 1410 Only if you are using a new kernel on an old distribution, you might 1411 need to say Y here. 1412 1413config SYSFS_DEPRECATED_V2 1414 bool "Enable deprecated sysfs features by default" 1415 default n 1416 depends on SYSFS 1417 depends on SYSFS_DEPRECATED 1418 help 1419 Enable deprecated sysfs by default. 1420 1421 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1422 option. 1423 1424 Only if you are using a new kernel on an old distribution, you might 1425 need to say Y here. Even then, odds are you would not need it 1426 enabled, you can always pass the boot option if absolutely necessary. 1427 1428config RELAY 1429 bool "Kernel->user space relay support (formerly relayfs)" 1430 select IRQ_WORK 1431 help 1432 This option enables support for relay interface support in 1433 certain file systems (such as debugfs). 1434 It is designed to provide an efficient mechanism for tools and 1435 facilities to relay large amounts of data from kernel space to 1436 user space. 1437 1438 If unsure, say N. 1439 1440config BLK_DEV_INITRD 1441 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1442 depends on BROKEN || !FRV 1443 help 1444 The initial RAM filesystem is a ramfs which is loaded by the 1445 boot loader (loadlin or lilo) and that is mounted as root 1446 before the normal boot procedure. It is typically used to 1447 load modules needed to mount the "real" root file system, 1448 etc. See <file:Documentation/initrd.txt> for details. 1449 1450 If RAM disk support (BLK_DEV_RAM) is also included, this 1451 also enables initial RAM disk (initrd) support and adds 1452 15 Kbytes (more on some other architectures) to the kernel size. 1453 1454 If unsure say Y. 1455 1456if BLK_DEV_INITRD 1457 1458source "usr/Kconfig" 1459 1460endif 1461 1462choice 1463 prompt "Compiler optimization level" 1464 default CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE 1465 1466config CC_OPTIMIZE_FOR_PERFORMANCE 1467 bool "Optimize for performance" 1468 help 1469 This is the default optimization level for the kernel, building 1470 with the "-O2" compiler flag for best performance and most 1471 helpful compile-time warnings. 1472 1473config CC_OPTIMIZE_FOR_SIZE 1474 bool "Optimize for size" 1475 help 1476 Enabling this option will pass "-Os" instead of "-O2" to 1477 your compiler resulting in a smaller kernel. 1478 1479 If unsure, say N. 1480 1481endchoice 1482 1483config SYSCTL 1484 bool 1485 1486config ANON_INODES 1487 bool 1488 1489config HAVE_UID16 1490 bool 1491 1492config SYSCTL_EXCEPTION_TRACE 1493 bool 1494 help 1495 Enable support for /proc/sys/debug/exception-trace. 1496 1497config SYSCTL_ARCH_UNALIGN_NO_WARN 1498 bool 1499 help 1500 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1501 Allows arch to define/use @no_unaligned_warning to possibly warn 1502 about unaligned access emulation going on under the hood. 1503 1504config SYSCTL_ARCH_UNALIGN_ALLOW 1505 bool 1506 help 1507 Enable support for /proc/sys/kernel/unaligned-trap 1508 Allows arches to define/use @unaligned_enabled to runtime toggle 1509 the unaligned access emulation. 1510 see arch/parisc/kernel/unaligned.c for reference 1511 1512config HAVE_PCSPKR_PLATFORM 1513 bool 1514 1515# interpreter that classic socket filters depend on 1516config BPF 1517 bool 1518 1519menuconfig EXPERT 1520 bool "Configure standard kernel features (expert users)" 1521 # Unhide debug options, to make the on-by-default options visible 1522 select DEBUG_KERNEL 1523 help 1524 This option allows certain base kernel options and settings 1525 to be disabled or tweaked. This is for specialized 1526 environments which can tolerate a "non-standard" kernel. 1527 Only use this if you really know what you are doing. 1528 1529config UID16 1530 bool "Enable 16-bit UID system calls" if EXPERT 1531 depends on HAVE_UID16 && MULTIUSER 1532 default y 1533 help 1534 This enables the legacy 16-bit UID syscall wrappers. 1535 1536config MULTIUSER 1537 bool "Multiple users, groups and capabilities support" if EXPERT 1538 default y 1539 help 1540 This option enables support for non-root users, groups and 1541 capabilities. 1542 1543 If you say N here, all processes will run with UID 0, GID 0, and all 1544 possible capabilities. Saying N here also compiles out support for 1545 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1546 setgid, and capset. 1547 1548 If unsure, say Y here. 1549 1550config SGETMASK_SYSCALL 1551 bool "sgetmask/ssetmask syscalls support" if EXPERT 1552 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH 1553 ---help--- 1554 sys_sgetmask and sys_ssetmask are obsolete system calls 1555 no longer supported in libc but still enabled by default in some 1556 architectures. 1557 1558 If unsure, leave the default option here. 1559 1560config SYSFS_SYSCALL 1561 bool "Sysfs syscall support" if EXPERT 1562 default y 1563 ---help--- 1564 sys_sysfs is an obsolete system call no longer supported in libc. 1565 Note that disabling this option is more secure but might break 1566 compatibility with some systems. 1567 1568 If unsure say Y here. 1569 1570config SYSCTL_SYSCALL 1571 bool "Sysctl syscall support" if EXPERT 1572 depends on PROC_SYSCTL 1573 default n 1574 select SYSCTL 1575 ---help--- 1576 sys_sysctl uses binary paths that have been found challenging 1577 to properly maintain and use. The interface in /proc/sys 1578 using paths with ascii names is now the primary path to this 1579 information. 1580 1581 Almost nothing using the binary sysctl interface so if you are 1582 trying to save some space it is probably safe to disable this, 1583 making your kernel marginally smaller. 1584 1585 If unsure say N here. 1586 1587config KALLSYMS 1588 bool "Load all symbols for debugging/ksymoops" if EXPERT 1589 default y 1590 help 1591 Say Y here to let the kernel print out symbolic crash information and 1592 symbolic stack backtraces. This increases the size of the kernel 1593 somewhat, as all symbols have to be loaded into the kernel image. 1594 1595config KALLSYMS_ALL 1596 bool "Include all symbols in kallsyms" 1597 depends on DEBUG_KERNEL && KALLSYMS 1598 help 1599 Normally kallsyms only contains the symbols of functions for nicer 1600 OOPS messages and backtraces (i.e., symbols from the text and inittext 1601 sections). This is sufficient for most cases. And only in very rare 1602 cases (e.g., when a debugger is used) all symbols are required (e.g., 1603 names of variables from the data sections, etc). 1604 1605 This option makes sure that all symbols are loaded into the kernel 1606 image (i.e., symbols from all sections) in cost of increased kernel 1607 size (depending on the kernel configuration, it may be 300KiB or 1608 something like this). 1609 1610 Say N unless you really need all symbols. 1611 1612config KALLSYMS_ABSOLUTE_PERCPU 1613 bool 1614 depends on KALLSYMS 1615 default X86_64 && SMP 1616 1617config KALLSYMS_BASE_RELATIVE 1618 bool 1619 depends on KALLSYMS 1620 default !IA64 && !(TILE && 64BIT) 1621 help 1622 Instead of emitting them as absolute values in the native word size, 1623 emit the symbol references in the kallsyms table as 32-bit entries, 1624 each containing a relative value in the range [base, base + U32_MAX] 1625 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1626 an absolute value in the range [0, S32_MAX] or a relative value in the 1627 range [base, base + S32_MAX], where base is the lowest relative symbol 1628 address encountered in the image. 1629 1630 On 64-bit builds, this reduces the size of the address table by 50%, 1631 but more importantly, it results in entries whose values are build 1632 time constants, and no relocation pass is required at runtime to fix 1633 up the entries based on the runtime load address of the kernel. 1634 1635config PRINTK 1636 default y 1637 bool "Enable support for printk" if EXPERT 1638 select IRQ_WORK 1639 help 1640 This option enables normal printk support. Removing it 1641 eliminates most of the message strings from the kernel image 1642 and makes the kernel more or less silent. As this makes it 1643 very difficult to diagnose system problems, saying N here is 1644 strongly discouraged. 1645 1646config PRINTK_NMI 1647 def_bool y 1648 depends on PRINTK 1649 depends on HAVE_NMI 1650 1651config BUG 1652 bool "BUG() support" if EXPERT 1653 default y 1654 help 1655 Disabling this option eliminates support for BUG and WARN, reducing 1656 the size of your kernel image and potentially quietly ignoring 1657 numerous fatal conditions. You should only consider disabling this 1658 option for embedded systems with no facilities for reporting errors. 1659 Just say Y. 1660 1661config ELF_CORE 1662 depends on COREDUMP 1663 default y 1664 bool "Enable ELF core dumps" if EXPERT 1665 help 1666 Enable support for generating core dumps. Disabling saves about 4k. 1667 1668 1669config PCSPKR_PLATFORM 1670 bool "Enable PC-Speaker support" if EXPERT 1671 depends on HAVE_PCSPKR_PLATFORM 1672 select I8253_LOCK 1673 default y 1674 help 1675 This option allows to disable the internal PC-Speaker 1676 support, saving some memory. 1677 1678config BASE_FULL 1679 default y 1680 bool "Enable full-sized data structures for core" if EXPERT 1681 help 1682 Disabling this option reduces the size of miscellaneous core 1683 kernel data structures. This saves memory on small machines, 1684 but may reduce performance. 1685 1686config FUTEX 1687 bool "Enable futex support" if EXPERT 1688 default y 1689 select RT_MUTEXES 1690 help 1691 Disabling this option will cause the kernel to be built without 1692 support for "fast userspace mutexes". The resulting kernel may not 1693 run glibc-based applications correctly. 1694 1695config HAVE_FUTEX_CMPXCHG 1696 bool 1697 depends on FUTEX 1698 help 1699 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1700 is implemented and always working. This removes a couple of runtime 1701 checks. 1702 1703config EPOLL 1704 bool "Enable eventpoll support" if EXPERT 1705 default y 1706 select ANON_INODES 1707 help 1708 Disabling this option will cause the kernel to be built without 1709 support for epoll family of system calls. 1710 1711config SIGNALFD 1712 bool "Enable signalfd() system call" if EXPERT 1713 select ANON_INODES 1714 default y 1715 help 1716 Enable the signalfd() system call that allows to receive signals 1717 on a file descriptor. 1718 1719 If unsure, say Y. 1720 1721config TIMERFD 1722 bool "Enable timerfd() system call" if EXPERT 1723 select ANON_INODES 1724 default y 1725 help 1726 Enable the timerfd() system call that allows to receive timer 1727 events on a file descriptor. 1728 1729 If unsure, say Y. 1730 1731config EVENTFD 1732 bool "Enable eventfd() system call" if EXPERT 1733 select ANON_INODES 1734 default y 1735 help 1736 Enable the eventfd() system call that allows to receive both 1737 kernel notification (ie. KAIO) or userspace notifications. 1738 1739 If unsure, say Y. 1740 1741# syscall, maps, verifier 1742config BPF_SYSCALL 1743 bool "Enable bpf() system call" 1744 select ANON_INODES 1745 select BPF 1746 default n 1747 help 1748 Enable the bpf() system call that allows to manipulate eBPF 1749 programs and maps via file descriptors. 1750 1751config BPF_JIT_ALWAYS_ON 1752 bool "Permanently enable BPF JIT and remove BPF interpreter" 1753 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT 1754 help 1755 Enables BPF JIT and removes BPF interpreter to avoid 1756 speculative execution of BPF instructions by the interpreter 1757 1758config SHMEM 1759 bool "Use full shmem filesystem" if EXPERT 1760 default y 1761 depends on MMU 1762 help 1763 The shmem is an internal filesystem used to manage shared memory. 1764 It is backed by swap and manages resource limits. It is also exported 1765 to userspace as tmpfs if TMPFS is enabled. Disabling this 1766 option replaces shmem and tmpfs with the much simpler ramfs code, 1767 which may be appropriate on small systems without swap. 1768 1769config AIO 1770 bool "Enable AIO support" if EXPERT 1771 default y 1772 help 1773 This option enables POSIX asynchronous I/O which may by used 1774 by some high performance threaded applications. Disabling 1775 this option saves about 7k. 1776 1777config ADVISE_SYSCALLS 1778 bool "Enable madvise/fadvise syscalls" if EXPERT 1779 default y 1780 help 1781 This option enables the madvise and fadvise syscalls, used by 1782 applications to advise the kernel about their future memory or file 1783 usage, improving performance. If building an embedded system where no 1784 applications use these syscalls, you can disable this option to save 1785 space. 1786 1787config USERFAULTFD 1788 bool "Enable userfaultfd() system call" 1789 select ANON_INODES 1790 depends on MMU 1791 help 1792 Enable the userfaultfd() system call that allows to intercept and 1793 handle page faults in userland. 1794 1795config PCI_QUIRKS 1796 default y 1797 bool "Enable PCI quirk workarounds" if EXPERT 1798 depends on PCI 1799 help 1800 This enables workarounds for various PCI chipset 1801 bugs/quirks. Disable this only if your target machine is 1802 unaffected by PCI quirks. 1803 1804config MEMBARRIER 1805 bool "Enable membarrier() system call" if EXPERT 1806 default y 1807 help 1808 Enable the membarrier() system call that allows issuing memory 1809 barriers across all running threads, which can be used to distribute 1810 the cost of user-space memory barriers asymmetrically by transforming 1811 pairs of memory barriers into pairs consisting of membarrier() and a 1812 compiler barrier. 1813 1814 If unsure, say Y. 1815 1816config EMBEDDED 1817 bool "Embedded system" 1818 option allnoconfig_y 1819 select EXPERT 1820 help 1821 This option should be enabled if compiling the kernel for 1822 an embedded system so certain expert options are available 1823 for configuration. 1824 1825config HAVE_PERF_EVENTS 1826 bool 1827 help 1828 See tools/perf/design.txt for details. 1829 1830config PERF_USE_VMALLOC 1831 bool 1832 help 1833 See tools/perf/design.txt for details 1834 1835menu "Kernel Performance Events And Counters" 1836 1837config PERF_EVENTS 1838 bool "Kernel performance events and counters" 1839 default y if PROFILING 1840 depends on HAVE_PERF_EVENTS 1841 select ANON_INODES 1842 select IRQ_WORK 1843 select SRCU 1844 help 1845 Enable kernel support for various performance events provided 1846 by software and hardware. 1847 1848 Software events are supported either built-in or via the 1849 use of generic tracepoints. 1850 1851 Most modern CPUs support performance events via performance 1852 counter registers. These registers count the number of certain 1853 types of hw events: such as instructions executed, cachemisses 1854 suffered, or branches mis-predicted - without slowing down the 1855 kernel or applications. These registers can also trigger interrupts 1856 when a threshold number of events have passed - and can thus be 1857 used to profile the code that runs on that CPU. 1858 1859 The Linux Performance Event subsystem provides an abstraction of 1860 these software and hardware event capabilities, available via a 1861 system call and used by the "perf" utility in tools/perf/. It 1862 provides per task and per CPU counters, and it provides event 1863 capabilities on top of those. 1864 1865 Say Y if unsure. 1866 1867config DEBUG_PERF_USE_VMALLOC 1868 default n 1869 bool "Debug: use vmalloc to back perf mmap() buffers" 1870 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1871 select PERF_USE_VMALLOC 1872 help 1873 Use vmalloc memory to back perf mmap() buffers. 1874 1875 Mostly useful for debugging the vmalloc code on platforms 1876 that don't require it. 1877 1878 Say N if unsure. 1879 1880endmenu 1881 1882config VM_EVENT_COUNTERS 1883 default y 1884 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1885 help 1886 VM event counters are needed for event counts to be shown. 1887 This option allows the disabling of the VM event counters 1888 on EXPERT systems. /proc/vmstat will only show page counts 1889 if VM event counters are disabled. 1890 1891config SLUB_DEBUG 1892 default y 1893 bool "Enable SLUB debugging support" if EXPERT 1894 depends on SLUB && SYSFS 1895 help 1896 SLUB has extensive debug support features. Disabling these can 1897 result in significant savings in code size. This also disables 1898 SLUB sysfs support. /sys/slab will not exist and there will be 1899 no support for cache validation etc. 1900 1901config COMPAT_BRK 1902 bool "Disable heap randomization" 1903 default y 1904 help 1905 Randomizing heap placement makes heap exploits harder, but it 1906 also breaks ancient binaries (including anything libc5 based). 1907 This option changes the bootup default to heap randomization 1908 disabled, and can be overridden at runtime by setting 1909 /proc/sys/kernel/randomize_va_space to 2. 1910 1911 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1912 1913choice 1914 prompt "Choose SLAB allocator" 1915 default SLUB 1916 help 1917 This option allows to select a slab allocator. 1918 1919config SLAB 1920 bool "SLAB" 1921 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1922 help 1923 The regular slab allocator that is established and known to work 1924 well in all environments. It organizes cache hot objects in 1925 per cpu and per node queues. 1926 1927config SLUB 1928 bool "SLUB (Unqueued Allocator)" 1929 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1930 help 1931 SLUB is a slab allocator that minimizes cache line usage 1932 instead of managing queues of cached objects (SLAB approach). 1933 Per cpu caching is realized using slabs of objects instead 1934 of queues of objects. SLUB can use memory efficiently 1935 and has enhanced diagnostics. SLUB is the default choice for 1936 a slab allocator. 1937 1938config SLOB 1939 depends on EXPERT 1940 bool "SLOB (Simple Allocator)" 1941 help 1942 SLOB replaces the stock allocator with a drastically simpler 1943 allocator. SLOB is generally more space efficient but 1944 does not perform as well on large systems. 1945 1946endchoice 1947 1948config SLAB_FREELIST_RANDOM 1949 default n 1950 depends on SLAB || SLUB 1951 bool "SLAB freelist randomization" 1952 help 1953 Randomizes the freelist order used on creating new pages. This 1954 security feature reduces the predictability of the kernel slab 1955 allocator against heap overflows. 1956 1957config SLUB_CPU_PARTIAL 1958 default y 1959 depends on SLUB && SMP 1960 bool "SLUB per cpu partial cache" 1961 help 1962 Per cpu partial caches accellerate objects allocation and freeing 1963 that is local to a processor at the price of more indeterminism 1964 in the latency of the free. On overflow these caches will be cleared 1965 which requires the taking of locks that may cause latency spikes. 1966 Typically one would choose no for a realtime system. 1967 1968config MMAP_ALLOW_UNINITIALIZED 1969 bool "Allow mmapped anonymous memory to be uninitialized" 1970 depends on EXPERT && !MMU 1971 default n 1972 help 1973 Normally, and according to the Linux spec, anonymous memory obtained 1974 from mmap() has it's contents cleared before it is passed to 1975 userspace. Enabling this config option allows you to request that 1976 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1977 providing a huge performance boost. If this option is not enabled, 1978 then the flag will be ignored. 1979 1980 This is taken advantage of by uClibc's malloc(), and also by 1981 ELF-FDPIC binfmt's brk and stack allocator. 1982 1983 Because of the obvious security issues, this option should only be 1984 enabled on embedded devices where you control what is run in 1985 userspace. Since that isn't generally a problem on no-MMU systems, 1986 it is normally safe to say Y here. 1987 1988 See Documentation/nommu-mmap.txt for more information. 1989 1990config SYSTEM_DATA_VERIFICATION 1991 def_bool n 1992 select SYSTEM_TRUSTED_KEYRING 1993 select KEYS 1994 select CRYPTO 1995 select CRYPTO_RSA 1996 select ASYMMETRIC_KEY_TYPE 1997 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1998 select ASN1 1999 select OID_REGISTRY 2000 select X509_CERTIFICATE_PARSER 2001 select PKCS7_MESSAGE_PARSER 2002 help 2003 Provide PKCS#7 message verification using the contents of the system 2004 trusted keyring to provide public keys. This then can be used for 2005 module verification, kexec image verification and firmware blob 2006 verification. 2007 2008config PROFILING 2009 bool "Profiling support" 2010 help 2011 Say Y here to enable the extended profiling support mechanisms used 2012 by profilers such as OProfile. 2013 2014# 2015# Place an empty function call at each tracepoint site. Can be 2016# dynamically changed for a probe function. 2017# 2018config TRACEPOINTS 2019 bool 2020 2021source "arch/Kconfig" 2022 2023endmenu # General setup 2024 2025config HAVE_GENERIC_DMA_COHERENT 2026 bool 2027 default n 2028 2029config SLABINFO 2030 bool 2031 depends on PROC_FS 2032 depends on SLAB || SLUB_DEBUG 2033 default y 2034 2035config RT_MUTEXES 2036 bool 2037 2038config BASE_SMALL 2039 int 2040 default 0 if BASE_FULL 2041 default 1 if !BASE_FULL 2042 2043menuconfig MODULES 2044 bool "Enable loadable module support" 2045 option modules 2046 help 2047 Kernel modules are small pieces of compiled code which can 2048 be inserted in the running kernel, rather than being 2049 permanently built into the kernel. You use the "modprobe" 2050 tool to add (and sometimes remove) them. If you say Y here, 2051 many parts of the kernel can be built as modules (by 2052 answering M instead of Y where indicated): this is most 2053 useful for infrequently used options which are not required 2054 for booting. For more information, see the man pages for 2055 modprobe, lsmod, modinfo, insmod and rmmod. 2056 2057 If you say Y here, you will need to run "make 2058 modules_install" to put the modules under /lib/modules/ 2059 where modprobe can find them (you may need to be root to do 2060 this). 2061 2062 If unsure, say Y. 2063 2064if MODULES 2065 2066config MODULE_FORCE_LOAD 2067 bool "Forced module loading" 2068 default n 2069 help 2070 Allow loading of modules without version information (ie. modprobe 2071 --force). Forced module loading sets the 'F' (forced) taint flag and 2072 is usually a really bad idea. 2073 2074config MODULE_UNLOAD 2075 bool "Module unloading" 2076 help 2077 Without this option you will not be able to unload any 2078 modules (note that some modules may not be unloadable 2079 anyway), which makes your kernel smaller, faster 2080 and simpler. If unsure, say Y. 2081 2082config MODULE_FORCE_UNLOAD 2083 bool "Forced module unloading" 2084 depends on MODULE_UNLOAD 2085 help 2086 This option allows you to force a module to unload, even if the 2087 kernel believes it is unsafe: the kernel will remove the module 2088 without waiting for anyone to stop using it (using the -f option to 2089 rmmod). This is mainly for kernel developers and desperate users. 2090 If unsure, say N. 2091 2092config MODVERSIONS 2093 bool "Module versioning support" 2094 help 2095 Usually, you have to use modules compiled with your kernel. 2096 Saying Y here makes it sometimes possible to use modules 2097 compiled for different kernels, by adding enough information 2098 to the modules to (hopefully) spot any changes which would 2099 make them incompatible with the kernel you are running. If 2100 unsure, say N. 2101 2102config MODULE_SRCVERSION_ALL 2103 bool "Source checksum for all modules" 2104 help 2105 Modules which contain a MODULE_VERSION get an extra "srcversion" 2106 field inserted into their modinfo section, which contains a 2107 sum of the source files which made it. This helps maintainers 2108 see exactly which source was used to build a module (since 2109 others sometimes change the module source without updating 2110 the version). With this option, such a "srcversion" field 2111 will be created for all modules. If unsure, say N. 2112 2113config MODULE_SIG 2114 bool "Module signature verification" 2115 depends on MODULES 2116 select SYSTEM_DATA_VERIFICATION 2117 help 2118 Check modules for valid signatures upon load: the signature 2119 is simply appended to the module. For more information see 2120 Documentation/module-signing.txt. 2121 2122 Note that this option adds the OpenSSL development packages as a 2123 kernel build dependency so that the signing tool can use its crypto 2124 library. 2125 2126 !!!WARNING!!! If you enable this option, you MUST make sure that the 2127 module DOES NOT get stripped after being signed. This includes the 2128 debuginfo strip done by some packagers (such as rpmbuild) and 2129 inclusion into an initramfs that wants the module size reduced. 2130 2131config MODULE_SIG_FORCE 2132 bool "Require modules to be validly signed" 2133 depends on MODULE_SIG 2134 help 2135 Reject unsigned modules or signed modules for which we don't have a 2136 key. Without this, such modules will simply taint the kernel. 2137 2138config MODULE_SIG_ALL 2139 bool "Automatically sign all modules" 2140 default y 2141 depends on MODULE_SIG 2142 help 2143 Sign all modules during make modules_install. Without this option, 2144 modules must be signed manually, using the scripts/sign-file tool. 2145 2146comment "Do not forget to sign required modules with scripts/sign-file" 2147 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2148 2149choice 2150 prompt "Which hash algorithm should modules be signed with?" 2151 depends on MODULE_SIG 2152 help 2153 This determines which sort of hashing algorithm will be used during 2154 signature generation. This algorithm _must_ be built into the kernel 2155 directly so that signature verification can take place. It is not 2156 possible to load a signed module containing the algorithm to check 2157 the signature on that module. 2158 2159config MODULE_SIG_SHA1 2160 bool "Sign modules with SHA-1" 2161 select CRYPTO_SHA1 2162 2163config MODULE_SIG_SHA224 2164 bool "Sign modules with SHA-224" 2165 select CRYPTO_SHA256 2166 2167config MODULE_SIG_SHA256 2168 bool "Sign modules with SHA-256" 2169 select CRYPTO_SHA256 2170 2171config MODULE_SIG_SHA384 2172 bool "Sign modules with SHA-384" 2173 select CRYPTO_SHA512 2174 2175config MODULE_SIG_SHA512 2176 bool "Sign modules with SHA-512" 2177 select CRYPTO_SHA512 2178 2179endchoice 2180 2181config MODULE_SIG_HASH 2182 string 2183 depends on MODULE_SIG 2184 default "sha1" if MODULE_SIG_SHA1 2185 default "sha224" if MODULE_SIG_SHA224 2186 default "sha256" if MODULE_SIG_SHA256 2187 default "sha384" if MODULE_SIG_SHA384 2188 default "sha512" if MODULE_SIG_SHA512 2189 2190config MODULE_COMPRESS 2191 bool "Compress modules on installation" 2192 depends on MODULES 2193 help 2194 2195 Compresses kernel modules when 'make modules_install' is run; gzip or 2196 xz depending on "Compression algorithm" below. 2197 2198 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 2199 2200 Out-of-tree kernel modules installed using Kbuild will also be 2201 compressed upon installation. 2202 2203 Note: for modules inside an initrd or initramfs, it's more efficient 2204 to compress the whole initrd or initramfs instead. 2205 2206 Note: This is fully compatible with signed modules. 2207 2208 If in doubt, say N. 2209 2210choice 2211 prompt "Compression algorithm" 2212 depends on MODULE_COMPRESS 2213 default MODULE_COMPRESS_GZIP 2214 help 2215 This determines which sort of compression will be used during 2216 'make modules_install'. 2217 2218 GZIP (default) and XZ are supported. 2219 2220config MODULE_COMPRESS_GZIP 2221 bool "GZIP" 2222 2223config MODULE_COMPRESS_XZ 2224 bool "XZ" 2225 2226endchoice 2227 2228config TRIM_UNUSED_KSYMS 2229 bool "Trim unused exported kernel symbols" 2230 depends on MODULES && !UNUSED_SYMBOLS 2231 help 2232 The kernel and some modules make many symbols available for 2233 other modules to use via EXPORT_SYMBOL() and variants. Depending 2234 on the set of modules being selected in your kernel configuration, 2235 many of those exported symbols might never be used. 2236 2237 This option allows for unused exported symbols to be dropped from 2238 the build. In turn, this provides the compiler more opportunities 2239 (especially when using LTO) for optimizing the code and reducing 2240 binary size. This might have some security advantages as well. 2241 2242 If unsure, or if you need to build out-of-tree modules, say N. 2243 2244endif # MODULES 2245 2246config MODULES_TREE_LOOKUP 2247 def_bool y 2248 depends on PERF_EVENTS || TRACING || CFI_CLANG 2249 2250config INIT_ALL_POSSIBLE 2251 bool 2252 help 2253 Back when each arch used to define their own cpu_online_mask and 2254 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2255 with all 1s, and others with all 0s. When they were centralised, 2256 it was better to provide this option than to break all the archs 2257 and have several arch maintainers pursuing me down dark alleys. 2258 2259source "block/Kconfig" 2260 2261config PREEMPT_NOTIFIERS 2262 bool 2263 2264config PADATA 2265 depends on SMP 2266 bool 2267 2268config ASN1 2269 tristate 2270 help 2271 Build a simple ASN.1 grammar compiler that produces a bytecode output 2272 that can be interpreted by the ASN.1 stream decoder and used to 2273 inform it as to what tags are to be expected in a stream and what 2274 functions to call on what tags. 2275 2276source "kernel/Kconfig.locks" 2277