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 default y 525 help 526 This option selects the sleepable version of RCU. This version 527 permits arbitrary sleeping or blocking within RCU read-side critical 528 sections. 529 530config CLASSIC_SRCU 531 bool "Use v4.11 classic SRCU implementation" 532 default n 533 depends on RCU_EXPERT && SRCU 534 help 535 This option selects the traditional well-tested classic SRCU 536 implementation from v4.11, as might be desired for enterprise 537 Linux distributions. Without this option, the shiny new 538 Tiny SRCU and Tree SRCU implementations are used instead. 539 At some point, it is hoped that Tiny SRCU and Tree SRCU 540 will accumulate enough test time and confidence to allow 541 Classic SRCU to be dropped entirely. 542 543 Say Y if you need a rock-solid SRCU. 544 545 Say N if you would like help test Tree SRCU. 546 547config TINY_SRCU 548 bool 549 default y if SRCU && TINY_RCU && !CLASSIC_SRCU 550 help 551 This option selects the single-CPU non-preemptible version of SRCU. 552 553config TREE_SRCU 554 bool 555 default y if SRCU && !TINY_RCU && !CLASSIC_SRCU 556 help 557 This option selects the full-fledged version of SRCU. 558 559config TASKS_RCU 560 bool 561 default n 562 select SRCU 563 help 564 This option enables a task-based RCU implementation that uses 565 only voluntary context switch (not preemption!), idle, and 566 user-mode execution as quiescent states. 567 568config RCU_STALL_COMMON 569 def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE ) 570 help 571 This option enables RCU CPU stall code that is common between 572 the TINY and TREE variants of RCU. The purpose is to allow 573 the tiny variants to disable RCU CPU stall warnings, while 574 making these warnings mandatory for the tree variants. 575 576config RCU_NEED_SEGCBLIST 577 def_bool ( TREE_RCU || PREEMPT_RCU || TINY_SRCU || TREE_SRCU ) 578 579config CONTEXT_TRACKING 580 bool 581 582config CONTEXT_TRACKING_FORCE 583 bool "Force context tracking" 584 depends on CONTEXT_TRACKING 585 default y if !NO_HZ_FULL 586 help 587 The major pre-requirement for full dynticks to work is to 588 support the context tracking subsystem. But there are also 589 other dependencies to provide in order to make the full 590 dynticks working. 591 592 This option stands for testing when an arch implements the 593 context tracking backend but doesn't yet fullfill all the 594 requirements to make the full dynticks feature working. 595 Without the full dynticks, there is no way to test the support 596 for context tracking and the subsystems that rely on it: RCU 597 userspace extended quiescent state and tickless cputime 598 accounting. This option copes with the absence of the full 599 dynticks subsystem by forcing the context tracking on all 600 CPUs in the system. 601 602 Say Y only if you're working on the development of an 603 architecture backend for the context tracking. 604 605 Say N otherwise, this option brings an overhead that you 606 don't want in production. 607 608 609config RCU_FANOUT 610 int "Tree-based hierarchical RCU fanout value" 611 range 2 64 if 64BIT 612 range 2 32 if !64BIT 613 depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT 614 default 64 if 64BIT 615 default 32 if !64BIT 616 help 617 This option controls the fanout of hierarchical implementations 618 of RCU, allowing RCU to work efficiently on machines with 619 large numbers of CPUs. This value must be at least the fourth 620 root of NR_CPUS, which allows NR_CPUS to be insanely large. 621 The default value of RCU_FANOUT should be used for production 622 systems, but if you are stress-testing the RCU implementation 623 itself, small RCU_FANOUT values allow you to test large-system 624 code paths on small(er) systems. 625 626 Select a specific number if testing RCU itself. 627 Take the default if unsure. 628 629config RCU_FANOUT_LEAF 630 int "Tree-based hierarchical RCU leaf-level fanout value" 631 range 2 64 if 64BIT 632 range 2 32 if !64BIT 633 depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT 634 default 16 635 help 636 This option controls the leaf-level fanout of hierarchical 637 implementations of RCU, and allows trading off cache misses 638 against lock contention. Systems that synchronize their 639 scheduling-clock interrupts for energy-efficiency reasons will 640 want the default because the smaller leaf-level fanout keeps 641 lock contention levels acceptably low. Very large systems 642 (hundreds or thousands of CPUs) will instead want to set this 643 value to the maximum value possible in order to reduce the 644 number of cache misses incurred during RCU's grace-period 645 initialization. These systems tend to run CPU-bound, and thus 646 are not helped by synchronized interrupts, and thus tend to 647 skew them, which reduces lock contention enough that large 648 leaf-level fanouts work well. That said, setting leaf-level 649 fanout to a large number will likely cause problematic 650 lock contention on the leaf-level rcu_node structures unless 651 you boot with the skew_tick kernel parameter. 652 653 Select a specific number if testing RCU itself. 654 655 Select the maximum permissible value for large systems, but 656 please understand that you may also need to set the skew_tick 657 kernel boot parameter to avoid contention on the rcu_node 658 structure's locks. 659 660 Take the default if unsure. 661 662config RCU_FAST_NO_HZ 663 bool "Accelerate last non-dyntick-idle CPU's grace periods" 664 depends on NO_HZ_COMMON && SMP && RCU_EXPERT 665 default n 666 help 667 This option permits CPUs to enter dynticks-idle state even if 668 they have RCU callbacks queued, and prevents RCU from waking 669 these CPUs up more than roughly once every four jiffies (by 670 default, you can adjust this using the rcutree.rcu_idle_gp_delay 671 parameter), thus improving energy efficiency. On the other 672 hand, this option increases the duration of RCU grace periods, 673 for example, slowing down synchronize_rcu(). 674 675 Say Y if energy efficiency is critically important, and you 676 don't care about increased grace-period durations. 677 678 Say N if you are unsure. 679 680config TREE_RCU_TRACE 681 def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU ) 682 select DEBUG_FS 683 help 684 This option provides tracing for the TREE_RCU and 685 PREEMPT_RCU implementations, permitting Makefile to 686 trivially select kernel/rcutree_trace.c. 687 688config RCU_BOOST 689 bool "Enable RCU priority boosting" 690 depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT 691 default n 692 help 693 This option boosts the priority of preempted RCU readers that 694 block the current preemptible RCU grace period for too long. 695 This option also prevents heavy loads from blocking RCU 696 callback invocation for all flavors of RCU. 697 698 Say Y here if you are working with real-time apps or heavy loads 699 Say N here if you are unsure. 700 701config RCU_KTHREAD_PRIO 702 int "Real-time priority to use for RCU worker threads" 703 range 1 99 if RCU_BOOST 704 range 0 99 if !RCU_BOOST 705 default 1 if RCU_BOOST 706 default 0 if !RCU_BOOST 707 depends on RCU_EXPERT 708 help 709 This option specifies the SCHED_FIFO priority value that will be 710 assigned to the rcuc/n and rcub/n threads and is also the value 711 used for RCU_BOOST (if enabled). If you are working with a 712 real-time application that has one or more CPU-bound threads 713 running at a real-time priority level, you should set 714 RCU_KTHREAD_PRIO to a priority higher than the highest-priority 715 real-time CPU-bound application thread. The default RCU_KTHREAD_PRIO 716 value of 1 is appropriate in the common case, which is real-time 717 applications that do not have any CPU-bound threads. 718 719 Some real-time applications might not have a single real-time 720 thread that saturates a given CPU, but instead might have 721 multiple real-time threads that, taken together, fully utilize 722 that CPU. In this case, you should set RCU_KTHREAD_PRIO to 723 a priority higher than the lowest-priority thread that is 724 conspiring to prevent the CPU from running any non-real-time 725 tasks. For example, if one thread at priority 10 and another 726 thread at priority 5 are between themselves fully consuming 727 the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be 728 set to priority 6 or higher. 729 730 Specify the real-time priority, or take the default if unsure. 731 732config RCU_BOOST_DELAY 733 int "Milliseconds to delay boosting after RCU grace-period start" 734 range 0 3000 735 depends on RCU_BOOST 736 default 500 737 help 738 This option specifies the time to wait after the beginning of 739 a given grace period before priority-boosting preempted RCU 740 readers blocking that grace period. Note that any RCU reader 741 blocking an expedited RCU grace period is boosted immediately. 742 743 Accept the default if unsure. 744 745config RCU_NOCB_CPU 746 bool "Offload RCU callback processing from boot-selected CPUs" 747 depends on TREE_RCU || PREEMPT_RCU 748 depends on RCU_EXPERT || NO_HZ_FULL 749 default n 750 help 751 Use this option to reduce OS jitter for aggressive HPC or 752 real-time workloads. It can also be used to offload RCU 753 callback invocation to energy-efficient CPUs in battery-powered 754 asymmetric multiprocessors. 755 756 This option offloads callback invocation from the set of 757 CPUs specified at boot time by the rcu_nocbs parameter. 758 For each such CPU, a kthread ("rcuox/N") will be created to 759 invoke callbacks, where the "N" is the CPU being offloaded, 760 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and 761 "s" for RCU-sched. Nothing prevents this kthread from running 762 on the specified CPUs, but (1) the kthreads may be preempted 763 between each callback, and (2) affinity or cgroups can be used 764 to force the kthreads to run on whatever set of CPUs is desired. 765 766 Say Y here if you want to help to debug reduced OS jitter. 767 Say N here if you are unsure. 768 769choice 770 prompt "Build-forced no-CBs CPUs" 771 default RCU_NOCB_CPU_NONE 772 depends on RCU_NOCB_CPU 773 help 774 This option allows no-CBs CPUs (whose RCU callbacks are invoked 775 from kthreads rather than from softirq context) to be specified 776 at build time. Additional no-CBs CPUs may be specified by 777 the rcu_nocbs= boot parameter. 778 779config RCU_NOCB_CPU_NONE 780 bool "No build_forced no-CBs CPUs" 781 help 782 This option does not force any of the CPUs to be no-CBs CPUs. 783 Only CPUs designated by the rcu_nocbs= boot parameter will be 784 no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU 785 kthreads whose names begin with "rcuo". All other CPUs will 786 invoke their own RCU callbacks in softirq context. 787 788 Select this option if you want to choose no-CBs CPUs at 789 boot time, for example, to allow testing of different no-CBs 790 configurations without having to rebuild the kernel each time. 791 792config RCU_NOCB_CPU_ZERO 793 bool "CPU 0 is a build_forced no-CBs CPU" 794 help 795 This option forces CPU 0 to be a no-CBs CPU, so that its RCU 796 callbacks are invoked by a per-CPU kthread whose name begins 797 with "rcuo". Additional CPUs may be designated as no-CBs 798 CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs. 799 All other CPUs will invoke their own RCU callbacks in softirq 800 context. 801 802 Select this if CPU 0 needs to be a no-CBs CPU for real-time 803 or energy-efficiency reasons, but the real reason it exists 804 is to ensure that randconfig testing covers mixed systems. 805 806config RCU_NOCB_CPU_ALL 807 bool "All CPUs are build_forced no-CBs CPUs" 808 help 809 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs= 810 boot parameter will be ignored. All CPUs' RCU callbacks will 811 be executed in the context of per-CPU rcuo kthreads created for 812 this purpose. Assuming that the kthreads whose names start with 813 "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter 814 on the remaining CPUs, but might decrease memory locality during 815 RCU-callback invocation, thus potentially degrading throughput. 816 817 Select this if all CPUs need to be no-CBs CPUs for real-time 818 or energy-efficiency reasons. 819 820endchoice 821 822endmenu # "RCU Subsystem" 823 824config BUILD_BIN2C 825 bool 826 default n 827 828config IKCONFIG 829 tristate "Kernel .config support" 830 select BUILD_BIN2C 831 ---help--- 832 This option enables the complete Linux kernel ".config" file 833 contents to be saved in the kernel. It provides documentation 834 of which kernel options are used in a running kernel or in an 835 on-disk kernel. This information can be extracted from the kernel 836 image file with the script scripts/extract-ikconfig and used as 837 input to rebuild the current kernel or to build another kernel. 838 It can also be extracted from a running kernel by reading 839 /proc/config.gz if enabled (below). 840 841config IKCONFIG_PROC 842 bool "Enable access to .config through /proc/config.gz" 843 depends on IKCONFIG && PROC_FS 844 ---help--- 845 This option enables access to the kernel configuration file 846 through /proc/config.gz. 847 848config LOG_BUF_SHIFT 849 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 850 range 12 25 851 default 17 852 depends on PRINTK 853 help 854 Select the minimal kernel log buffer size as a power of 2. 855 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 856 parameter, see below. Any higher size also might be forced 857 by "log_buf_len" boot parameter. 858 859 Examples: 860 17 => 128 KB 861 16 => 64 KB 862 15 => 32 KB 863 14 => 16 KB 864 13 => 8 KB 865 12 => 4 KB 866 867config LOG_CPU_MAX_BUF_SHIFT 868 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 869 depends on SMP 870 range 0 21 871 default 12 if !BASE_SMALL 872 default 0 if BASE_SMALL 873 depends on PRINTK 874 help 875 This option allows to increase the default ring buffer size 876 according to the number of CPUs. The value defines the contribution 877 of each CPU as a power of 2. The used space is typically only few 878 lines however it might be much more when problems are reported, 879 e.g. backtraces. 880 881 The increased size means that a new buffer has to be allocated and 882 the original static one is unused. It makes sense only on systems 883 with more CPUs. Therefore this value is used only when the sum of 884 contributions is greater than the half of the default kernel ring 885 buffer as defined by LOG_BUF_SHIFT. The default values are set 886 so that more than 64 CPUs are needed to trigger the allocation. 887 888 Also this option is ignored when "log_buf_len" kernel parameter is 889 used as it forces an exact (power of two) size of the ring buffer. 890 891 The number of possible CPUs is used for this computation ignoring 892 hotplugging making the computation optimal for the worst case 893 scenario while allowing a simple algorithm to be used from bootup. 894 895 Examples shift values and their meaning: 896 17 => 128 KB for each CPU 897 16 => 64 KB for each CPU 898 15 => 32 KB for each CPU 899 14 => 16 KB for each CPU 900 13 => 8 KB for each CPU 901 12 => 4 KB for each CPU 902 903config PRINTK_SAFE_LOG_BUF_SHIFT 904 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)" 905 range 10 21 906 default 13 907 depends on PRINTK 908 help 909 Select the size of an alternate printk per-CPU buffer where messages 910 printed from usafe contexts are temporary stored. One example would 911 be NMI messages, another one - printk recursion. The messages are 912 copied to the main log buffer in a safe context to avoid a deadlock. 913 The value defines the size as a power of 2. 914 915 Those messages are rare and limited. The largest one is when 916 a backtrace is printed. It usually fits into 4KB. Select 917 8KB if you want to be on the safe side. 918 919 Examples: 920 17 => 128 KB for each CPU 921 16 => 64 KB for each CPU 922 15 => 32 KB for each CPU 923 14 => 16 KB for each CPU 924 13 => 8 KB for each CPU 925 12 => 4 KB for each CPU 926 927# 928# Architectures with an unreliable sched_clock() should select this: 929# 930config HAVE_UNSTABLE_SCHED_CLOCK 931 bool 932 933config GENERIC_SCHED_CLOCK 934 bool 935 936# 937# For architectures that want to enable the support for NUMA-affine scheduler 938# balancing logic: 939# 940config ARCH_SUPPORTS_NUMA_BALANCING 941 bool 942 943# 944# For architectures that prefer to flush all TLBs after a number of pages 945# are unmapped instead of sending one IPI per page to flush. The architecture 946# must provide guarantees on what happens if a clean TLB cache entry is 947# written after the unmap. Details are in mm/rmap.c near the check for 948# should_defer_flush. The architecture should also consider if the full flush 949# and the refill costs are offset by the savings of sending fewer IPIs. 950config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH 951 bool 952 953# 954# For architectures that know their GCC __int128 support is sound 955# 956config ARCH_SUPPORTS_INT128 957 bool 958 959# For architectures that (ab)use NUMA to represent different memory regions 960# all cpu-local but of different latencies, such as SuperH. 961# 962config ARCH_WANT_NUMA_VARIABLE_LOCALITY 963 bool 964 965config NUMA_BALANCING 966 bool "Memory placement aware NUMA scheduler" 967 depends on ARCH_SUPPORTS_NUMA_BALANCING 968 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 969 depends on SMP && NUMA && MIGRATION 970 help 971 This option adds support for automatic NUMA aware memory/task placement. 972 The mechanism is quite primitive and is based on migrating memory when 973 it has references to the node the task is running on. 974 975 This system will be inactive on UMA systems. 976 977config NUMA_BALANCING_DEFAULT_ENABLED 978 bool "Automatically enable NUMA aware memory/task placement" 979 default y 980 depends on NUMA_BALANCING 981 help 982 If set, automatic NUMA balancing will be enabled if running on a NUMA 983 machine. 984 985menuconfig CGROUPS 986 bool "Control Group support" 987 select KERNFS 988 help 989 This option adds support for grouping sets of processes together, for 990 use with process control subsystems such as Cpusets, CFS, memory 991 controls or device isolation. 992 See 993 - Documentation/scheduler/sched-design-CFS.txt (CFS) 994 - Documentation/cgroup-v1/ (features for grouping, isolation 995 and resource control) 996 997 Say N if unsure. 998 999if CGROUPS 1000 1001config PAGE_COUNTER 1002 bool 1003 1004config MEMCG 1005 bool "Memory controller" 1006 select PAGE_COUNTER 1007 select EVENTFD 1008 help 1009 Provides control over the memory footprint of tasks in a cgroup. 1010 1011config MEMCG_SWAP 1012 bool "Swap controller" 1013 depends on MEMCG && SWAP 1014 help 1015 Provides control over the swap space consumed by tasks in a cgroup. 1016 1017config MEMCG_SWAP_ENABLED 1018 bool "Swap controller enabled by default" 1019 depends on MEMCG_SWAP 1020 default y 1021 help 1022 Memory Resource Controller Swap Extension comes with its price in 1023 a bigger memory consumption. General purpose distribution kernels 1024 which want to enable the feature but keep it disabled by default 1025 and let the user enable it by swapaccount=1 boot command line 1026 parameter should have this option unselected. 1027 For those who want to have the feature enabled by default should 1028 select this option (if, for some reason, they need to disable it 1029 then swapaccount=0 does the trick). 1030 1031config BLK_CGROUP 1032 bool "IO controller" 1033 depends on BLOCK 1034 default n 1035 ---help--- 1036 Generic block IO controller cgroup interface. This is the common 1037 cgroup interface which should be used by various IO controlling 1038 policies. 1039 1040 Currently, CFQ IO scheduler uses it to recognize task groups and 1041 control disk bandwidth allocation (proportional time slice allocation) 1042 to such task groups. It is also used by bio throttling logic in 1043 block layer to implement upper limit in IO rates on a device. 1044 1045 This option only enables generic Block IO controller infrastructure. 1046 One needs to also enable actual IO controlling logic/policy. For 1047 enabling proportional weight division of disk bandwidth in CFQ, set 1048 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 1049 CONFIG_BLK_DEV_THROTTLING=y. 1050 1051 See Documentation/cgroup-v1/blkio-controller.txt for more information. 1052 1053config DEBUG_BLK_CGROUP 1054 bool "IO controller debugging" 1055 depends on BLK_CGROUP 1056 default n 1057 ---help--- 1058 Enable some debugging help. Currently it exports additional stat 1059 files in a cgroup which can be useful for debugging. 1060 1061config CGROUP_WRITEBACK 1062 bool 1063 depends on MEMCG && BLK_CGROUP 1064 default y 1065 1066menuconfig CGROUP_SCHED 1067 bool "CPU controller" 1068 default n 1069 help 1070 This feature lets CPU scheduler recognize task groups and control CPU 1071 bandwidth allocation to such task groups. It uses cgroups to group 1072 tasks. 1073 1074if CGROUP_SCHED 1075config FAIR_GROUP_SCHED 1076 bool "Group scheduling for SCHED_OTHER" 1077 depends on CGROUP_SCHED 1078 default CGROUP_SCHED 1079 1080config CFS_BANDWIDTH 1081 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 1082 depends on FAIR_GROUP_SCHED 1083 default n 1084 help 1085 This option allows users to define CPU bandwidth rates (limits) for 1086 tasks running within the fair group scheduler. Groups with no limit 1087 set are considered to be unconstrained and will run with no 1088 restriction. 1089 See tip/Documentation/scheduler/sched-bwc.txt for more information. 1090 1091config RT_GROUP_SCHED 1092 bool "Group scheduling for SCHED_RR/FIFO" 1093 depends on CGROUP_SCHED 1094 default n 1095 help 1096 This feature lets you explicitly allocate real CPU bandwidth 1097 to task groups. If enabled, it will also make it impossible to 1098 schedule realtime tasks for non-root users until you allocate 1099 realtime bandwidth for them. 1100 See Documentation/scheduler/sched-rt-group.txt for more information. 1101 1102endif #CGROUP_SCHED 1103 1104config CGROUP_PIDS 1105 bool "PIDs controller" 1106 help 1107 Provides enforcement of process number limits in the scope of a 1108 cgroup. Any attempt to fork more processes than is allowed in the 1109 cgroup will fail. PIDs are fundamentally a global resource because it 1110 is fairly trivial to reach PID exhaustion before you reach even a 1111 conservative kmemcg limit. As a result, it is possible to grind a 1112 system to halt without being limited by other cgroup policies. The 1113 PIDs controller is designed to stop this from happening. 1114 1115 It should be noted that organisational operations (such as attaching 1116 to a cgroup hierarchy will *not* be blocked by the PIDs controller), 1117 since the PIDs limit only affects a process's ability to fork, not to 1118 attach to a cgroup. 1119 1120config CGROUP_RDMA 1121 bool "RDMA controller" 1122 help 1123 Provides enforcement of RDMA resources defined by IB stack. 1124 It is fairly easy for consumers to exhaust RDMA resources, which 1125 can result into resource unavailability to other consumers. 1126 RDMA controller is designed to stop this from happening. 1127 Attaching processes with active RDMA resources to the cgroup 1128 hierarchy is allowed even if can cross the hierarchy's limit. 1129 1130config CGROUP_FREEZER 1131 bool "Freezer controller" 1132 help 1133 Provides a way to freeze and unfreeze all tasks in a 1134 cgroup. 1135 1136 This option affects the ORIGINAL cgroup interface. The cgroup2 memory 1137 controller includes important in-kernel memory consumers per default. 1138 1139 If you're using cgroup2, say N. 1140 1141config CGROUP_HUGETLB 1142 bool "HugeTLB controller" 1143 depends on HUGETLB_PAGE 1144 select PAGE_COUNTER 1145 default n 1146 help 1147 Provides a cgroup controller for HugeTLB pages. 1148 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1149 The limit is enforced during page fault. Since HugeTLB doesn't 1150 support page reclaim, enforcing the limit at page fault time implies 1151 that, the application will get SIGBUS signal if it tries to access 1152 HugeTLB pages beyond its limit. This requires the application to know 1153 beforehand how much HugeTLB pages it would require for its use. The 1154 control group is tracked in the third page lru pointer. This means 1155 that we cannot use the controller with huge page less than 3 pages. 1156 1157config CPUSETS 1158 bool "Cpuset controller" 1159 help 1160 This option will let you create and manage CPUSETs which 1161 allow dynamically partitioning a system into sets of CPUs and 1162 Memory Nodes and assigning tasks to run only within those sets. 1163 This is primarily useful on large SMP or NUMA systems. 1164 1165 Say N if unsure. 1166 1167config PROC_PID_CPUSET 1168 bool "Include legacy /proc/<pid>/cpuset file" 1169 depends on CPUSETS 1170 default y 1171 1172config CGROUP_DEVICE 1173 bool "Device controller" 1174 help 1175 Provides a cgroup controller implementing whitelists for 1176 devices which a process in the cgroup can mknod or open. 1177 1178config CGROUP_CPUACCT 1179 bool "Simple CPU accounting controller" 1180 help 1181 Provides a simple controller for monitoring the 1182 total CPU consumed by the tasks in a cgroup. 1183 1184config CGROUP_PERF 1185 bool "Perf controller" 1186 depends on PERF_EVENTS 1187 help 1188 This option extends the perf per-cpu mode to restrict monitoring 1189 to threads which belong to the cgroup specified and run on the 1190 designated cpu. 1191 1192 Say N if unsure. 1193 1194config CGROUP_BPF 1195 bool "Support for eBPF programs attached to cgroups" 1196 depends on BPF_SYSCALL 1197 select SOCK_CGROUP_DATA 1198 help 1199 Allow attaching eBPF programs to a cgroup using the bpf(2) 1200 syscall command BPF_PROG_ATTACH. 1201 1202 In which context these programs are accessed depends on the type 1203 of attachment. For instance, programs that are attached using 1204 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of 1205 inet sockets. 1206 1207config CGROUP_DEBUG 1208 bool "Example controller" 1209 default n 1210 help 1211 This option enables a simple controller that exports 1212 debugging information about the cgroups framework. 1213 1214 Say N. 1215 1216config SOCK_CGROUP_DATA 1217 bool 1218 default n 1219 1220endif # CGROUPS 1221 1222config CHECKPOINT_RESTORE 1223 bool "Checkpoint/restore support" if EXPERT 1224 select PROC_CHILDREN 1225 default n 1226 help 1227 Enables additional kernel features in a sake of checkpoint/restore. 1228 In particular it adds auxiliary prctl codes to setup process text, 1229 data and heap segment sizes, and a few additional /proc filesystem 1230 entries. 1231 1232 If unsure, say N here. 1233 1234menuconfig NAMESPACES 1235 bool "Namespaces support" if EXPERT 1236 depends on MULTIUSER 1237 default !EXPERT 1238 help 1239 Provides the way to make tasks work with different objects using 1240 the same id. For example same IPC id may refer to different objects 1241 or same user id or pid may refer to different tasks when used in 1242 different namespaces. 1243 1244if NAMESPACES 1245 1246config UTS_NS 1247 bool "UTS namespace" 1248 default y 1249 help 1250 In this namespace tasks see different info provided with the 1251 uname() system call 1252 1253config IPC_NS 1254 bool "IPC namespace" 1255 depends on (SYSVIPC || POSIX_MQUEUE) 1256 default y 1257 help 1258 In this namespace tasks work with IPC ids which correspond to 1259 different IPC objects in different namespaces. 1260 1261config USER_NS 1262 bool "User namespace" 1263 default n 1264 help 1265 This allows containers, i.e. vservers, to use user namespaces 1266 to provide different user info for different servers. 1267 1268 When user namespaces are enabled in the kernel it is 1269 recommended that the MEMCG option also be enabled and that 1270 user-space use the memory control groups to limit the amount 1271 of memory a memory unprivileged users can use. 1272 1273 If unsure, say N. 1274 1275config PID_NS 1276 bool "PID Namespaces" 1277 default y 1278 help 1279 Support process id namespaces. This allows having multiple 1280 processes with the same pid as long as they are in different 1281 pid namespaces. This is a building block of containers. 1282 1283config NET_NS 1284 bool "Network namespace" 1285 depends on NET 1286 default y 1287 help 1288 Allow user space to create what appear to be multiple instances 1289 of the network stack. 1290 1291endif # NAMESPACES 1292 1293config SCHED_AUTOGROUP 1294 bool "Automatic process group scheduling" 1295 select CGROUPS 1296 select CGROUP_SCHED 1297 select FAIR_GROUP_SCHED 1298 help 1299 This option optimizes the scheduler for common desktop workloads by 1300 automatically creating and populating task groups. This separation 1301 of workloads isolates aggressive CPU burners (like build jobs) from 1302 desktop applications. Task group autogeneration is currently based 1303 upon task session. 1304 1305config SYSFS_DEPRECATED 1306 bool "Enable deprecated sysfs features to support old userspace tools" 1307 depends on SYSFS 1308 default n 1309 help 1310 This option adds code that switches the layout of the "block" class 1311 devices, to not show up in /sys/class/block/, but only in 1312 /sys/block/. 1313 1314 This switch is only active when the sysfs.deprecated=1 boot option is 1315 passed or the SYSFS_DEPRECATED_V2 option is set. 1316 1317 This option allows new kernels to run on old distributions and tools, 1318 which might get confused by /sys/class/block/. Since 2007/2008 all 1319 major distributions and tools handle this just fine. 1320 1321 Recent distributions and userspace tools after 2009/2010 depend on 1322 the existence of /sys/class/block/, and will not work with this 1323 option enabled. 1324 1325 Only if you are using a new kernel on an old distribution, you might 1326 need to say Y here. 1327 1328config SYSFS_DEPRECATED_V2 1329 bool "Enable deprecated sysfs features by default" 1330 default n 1331 depends on SYSFS 1332 depends on SYSFS_DEPRECATED 1333 help 1334 Enable deprecated sysfs by default. 1335 1336 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1337 option. 1338 1339 Only if you are using a new kernel on an old distribution, you might 1340 need to say Y here. Even then, odds are you would not need it 1341 enabled, you can always pass the boot option if absolutely necessary. 1342 1343config RELAY 1344 bool "Kernel->user space relay support (formerly relayfs)" 1345 select IRQ_WORK 1346 help 1347 This option enables support for relay interface support in 1348 certain file systems (such as debugfs). 1349 It is designed to provide an efficient mechanism for tools and 1350 facilities to relay large amounts of data from kernel space to 1351 user space. 1352 1353 If unsure, say N. 1354 1355config BLK_DEV_INITRD 1356 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1357 depends on BROKEN || !FRV 1358 help 1359 The initial RAM filesystem is a ramfs which is loaded by the 1360 boot loader (loadlin or lilo) and that is mounted as root 1361 before the normal boot procedure. It is typically used to 1362 load modules needed to mount the "real" root file system, 1363 etc. See <file:Documentation/admin-guide/initrd.rst> for details. 1364 1365 If RAM disk support (BLK_DEV_RAM) is also included, this 1366 also enables initial RAM disk (initrd) support and adds 1367 15 Kbytes (more on some other architectures) to the kernel size. 1368 1369 If unsure say Y. 1370 1371if BLK_DEV_INITRD 1372 1373source "usr/Kconfig" 1374 1375endif 1376 1377choice 1378 prompt "Compiler optimization level" 1379 default CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE 1380 1381config CC_OPTIMIZE_FOR_PERFORMANCE 1382 bool "Optimize for performance" 1383 help 1384 This is the default optimization level for the kernel, building 1385 with the "-O2" compiler flag for best performance and most 1386 helpful compile-time warnings. 1387 1388config CC_OPTIMIZE_FOR_SIZE 1389 bool "Optimize for size" 1390 help 1391 Enabling this option will pass "-Os" instead of "-O2" to 1392 your compiler resulting in a smaller kernel. 1393 1394 If unsure, say N. 1395 1396endchoice 1397 1398config SYSCTL 1399 bool 1400 1401config ANON_INODES 1402 bool 1403 1404config HAVE_UID16 1405 bool 1406 1407config SYSCTL_EXCEPTION_TRACE 1408 bool 1409 help 1410 Enable support for /proc/sys/debug/exception-trace. 1411 1412config SYSCTL_ARCH_UNALIGN_NO_WARN 1413 bool 1414 help 1415 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1416 Allows arch to define/use @no_unaligned_warning to possibly warn 1417 about unaligned access emulation going on under the hood. 1418 1419config SYSCTL_ARCH_UNALIGN_ALLOW 1420 bool 1421 help 1422 Enable support for /proc/sys/kernel/unaligned-trap 1423 Allows arches to define/use @unaligned_enabled to runtime toggle 1424 the unaligned access emulation. 1425 see arch/parisc/kernel/unaligned.c for reference 1426 1427config HAVE_PCSPKR_PLATFORM 1428 bool 1429 1430# interpreter that classic socket filters depend on 1431config BPF 1432 bool 1433 1434menuconfig EXPERT 1435 bool "Configure standard kernel features (expert users)" 1436 # Unhide debug options, to make the on-by-default options visible 1437 select DEBUG_KERNEL 1438 help 1439 This option allows certain base kernel options and settings 1440 to be disabled or tweaked. This is for specialized 1441 environments which can tolerate a "non-standard" kernel. 1442 Only use this if you really know what you are doing. 1443 1444config UID16 1445 bool "Enable 16-bit UID system calls" if EXPERT 1446 depends on HAVE_UID16 && MULTIUSER 1447 default y 1448 help 1449 This enables the legacy 16-bit UID syscall wrappers. 1450 1451config MULTIUSER 1452 bool "Multiple users, groups and capabilities support" if EXPERT 1453 default y 1454 help 1455 This option enables support for non-root users, groups and 1456 capabilities. 1457 1458 If you say N here, all processes will run with UID 0, GID 0, and all 1459 possible capabilities. Saying N here also compiles out support for 1460 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1461 setgid, and capset. 1462 1463 If unsure, say Y here. 1464 1465config SGETMASK_SYSCALL 1466 bool "sgetmask/ssetmask syscalls support" if EXPERT 1467 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH 1468 ---help--- 1469 sys_sgetmask and sys_ssetmask are obsolete system calls 1470 no longer supported in libc but still enabled by default in some 1471 architectures. 1472 1473 If unsure, leave the default option here. 1474 1475config SYSFS_SYSCALL 1476 bool "Sysfs syscall support" if EXPERT 1477 default y 1478 ---help--- 1479 sys_sysfs is an obsolete system call no longer supported in libc. 1480 Note that disabling this option is more secure but might break 1481 compatibility with some systems. 1482 1483 If unsure say Y here. 1484 1485config SYSCTL_SYSCALL 1486 bool "Sysctl syscall support" if EXPERT 1487 depends on PROC_SYSCTL 1488 default n 1489 select SYSCTL 1490 ---help--- 1491 sys_sysctl uses binary paths that have been found challenging 1492 to properly maintain and use. The interface in /proc/sys 1493 using paths with ascii names is now the primary path to this 1494 information. 1495 1496 Almost nothing using the binary sysctl interface so if you are 1497 trying to save some space it is probably safe to disable this, 1498 making your kernel marginally smaller. 1499 1500 If unsure say N here. 1501 1502config POSIX_TIMERS 1503 bool "Posix Clocks & timers" if EXPERT 1504 default y 1505 help 1506 This includes native support for POSIX timers to the kernel. 1507 Some embedded systems have no use for them and therefore they 1508 can be configured out to reduce the size of the kernel image. 1509 1510 When this option is disabled, the following syscalls won't be 1511 available: timer_create, timer_gettime: timer_getoverrun, 1512 timer_settime, timer_delete, clock_adjtime, getitimer, 1513 setitimer, alarm. Furthermore, the clock_settime, clock_gettime, 1514 clock_getres and clock_nanosleep syscalls will be limited to 1515 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. 1516 1517 If unsure say y. 1518 1519config KALLSYMS 1520 bool "Load all symbols for debugging/ksymoops" if EXPERT 1521 default y 1522 help 1523 Say Y here to let the kernel print out symbolic crash information and 1524 symbolic stack backtraces. This increases the size of the kernel 1525 somewhat, as all symbols have to be loaded into the kernel image. 1526 1527config KALLSYMS_ALL 1528 bool "Include all symbols in kallsyms" 1529 depends on DEBUG_KERNEL && KALLSYMS 1530 help 1531 Normally kallsyms only contains the symbols of functions for nicer 1532 OOPS messages and backtraces (i.e., symbols from the text and inittext 1533 sections). This is sufficient for most cases. And only in very rare 1534 cases (e.g., when a debugger is used) all symbols are required (e.g., 1535 names of variables from the data sections, etc). 1536 1537 This option makes sure that all symbols are loaded into the kernel 1538 image (i.e., symbols from all sections) in cost of increased kernel 1539 size (depending on the kernel configuration, it may be 300KiB or 1540 something like this). 1541 1542 Say N unless you really need all symbols. 1543 1544config KALLSYMS_ABSOLUTE_PERCPU 1545 bool 1546 depends on KALLSYMS 1547 default X86_64 && SMP 1548 1549config KALLSYMS_BASE_RELATIVE 1550 bool 1551 depends on KALLSYMS 1552 default !IA64 && !(TILE && 64BIT) 1553 help 1554 Instead of emitting them as absolute values in the native word size, 1555 emit the symbol references in the kallsyms table as 32-bit entries, 1556 each containing a relative value in the range [base, base + U32_MAX] 1557 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either 1558 an absolute value in the range [0, S32_MAX] or a relative value in the 1559 range [base, base + S32_MAX], where base is the lowest relative symbol 1560 address encountered in the image. 1561 1562 On 64-bit builds, this reduces the size of the address table by 50%, 1563 but more importantly, it results in entries whose values are build 1564 time constants, and no relocation pass is required at runtime to fix 1565 up the entries based on the runtime load address of the kernel. 1566 1567config PRINTK 1568 default y 1569 bool "Enable support for printk" if EXPERT 1570 select IRQ_WORK 1571 help 1572 This option enables normal printk support. Removing it 1573 eliminates most of the message strings from the kernel image 1574 and makes the kernel more or less silent. As this makes it 1575 very difficult to diagnose system problems, saying N here is 1576 strongly discouraged. 1577 1578config PRINTK_NMI 1579 def_bool y 1580 depends on PRINTK 1581 depends on HAVE_NMI 1582 1583config BUG 1584 bool "BUG() support" if EXPERT 1585 default y 1586 help 1587 Disabling this option eliminates support for BUG and WARN, reducing 1588 the size of your kernel image and potentially quietly ignoring 1589 numerous fatal conditions. You should only consider disabling this 1590 option for embedded systems with no facilities for reporting errors. 1591 Just say Y. 1592 1593config ELF_CORE 1594 depends on COREDUMP 1595 default y 1596 bool "Enable ELF core dumps" if EXPERT 1597 help 1598 Enable support for generating core dumps. Disabling saves about 4k. 1599 1600 1601config PCSPKR_PLATFORM 1602 bool "Enable PC-Speaker support" if EXPERT 1603 depends on HAVE_PCSPKR_PLATFORM 1604 select I8253_LOCK 1605 default y 1606 help 1607 This option allows to disable the internal PC-Speaker 1608 support, saving some memory. 1609 1610config BASE_FULL 1611 default y 1612 bool "Enable full-sized data structures for core" if EXPERT 1613 help 1614 Disabling this option reduces the size of miscellaneous core 1615 kernel data structures. This saves memory on small machines, 1616 but may reduce performance. 1617 1618config FUTEX 1619 bool "Enable futex support" if EXPERT 1620 default y 1621 select RT_MUTEXES 1622 help 1623 Disabling this option will cause the kernel to be built without 1624 support for "fast userspace mutexes". The resulting kernel may not 1625 run glibc-based applications correctly. 1626 1627config HAVE_FUTEX_CMPXCHG 1628 bool 1629 depends on FUTEX 1630 help 1631 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1632 is implemented and always working. This removes a couple of runtime 1633 checks. 1634 1635config EPOLL 1636 bool "Enable eventpoll support" if EXPERT 1637 default y 1638 select ANON_INODES 1639 help 1640 Disabling this option will cause the kernel to be built without 1641 support for epoll family of system calls. 1642 1643config SIGNALFD 1644 bool "Enable signalfd() system call" if EXPERT 1645 select ANON_INODES 1646 default y 1647 help 1648 Enable the signalfd() system call that allows to receive signals 1649 on a file descriptor. 1650 1651 If unsure, say Y. 1652 1653config TIMERFD 1654 bool "Enable timerfd() system call" if EXPERT 1655 select ANON_INODES 1656 default y 1657 help 1658 Enable the timerfd() system call that allows to receive timer 1659 events on a file descriptor. 1660 1661 If unsure, say Y. 1662 1663config EVENTFD 1664 bool "Enable eventfd() system call" if EXPERT 1665 select ANON_INODES 1666 default y 1667 help 1668 Enable the eventfd() system call that allows to receive both 1669 kernel notification (ie. KAIO) or userspace notifications. 1670 1671 If unsure, say Y. 1672 1673# syscall, maps, verifier 1674config BPF_SYSCALL 1675 bool "Enable bpf() system call" 1676 select ANON_INODES 1677 select BPF 1678 default n 1679 help 1680 Enable the bpf() system call that allows to manipulate eBPF 1681 programs and maps via file descriptors. 1682 1683config SHMEM 1684 bool "Use full shmem filesystem" if EXPERT 1685 default y 1686 depends on MMU 1687 help 1688 The shmem is an internal filesystem used to manage shared memory. 1689 It is backed by swap and manages resource limits. It is also exported 1690 to userspace as tmpfs if TMPFS is enabled. Disabling this 1691 option replaces shmem and tmpfs with the much simpler ramfs code, 1692 which may be appropriate on small systems without swap. 1693 1694config AIO 1695 bool "Enable AIO support" if EXPERT 1696 default y 1697 help 1698 This option enables POSIX asynchronous I/O which may by used 1699 by some high performance threaded applications. Disabling 1700 this option saves about 7k. 1701 1702config ADVISE_SYSCALLS 1703 bool "Enable madvise/fadvise syscalls" if EXPERT 1704 default y 1705 help 1706 This option enables the madvise and fadvise syscalls, used by 1707 applications to advise the kernel about their future memory or file 1708 usage, improving performance. If building an embedded system where no 1709 applications use these syscalls, you can disable this option to save 1710 space. 1711 1712config USERFAULTFD 1713 bool "Enable userfaultfd() system call" 1714 select ANON_INODES 1715 depends on MMU 1716 help 1717 Enable the userfaultfd() system call that allows to intercept and 1718 handle page faults in userland. 1719 1720config PCI_QUIRKS 1721 default y 1722 bool "Enable PCI quirk workarounds" if EXPERT 1723 depends on PCI 1724 help 1725 This enables workarounds for various PCI chipset 1726 bugs/quirks. Disable this only if your target machine is 1727 unaffected by PCI quirks. 1728 1729config MEMBARRIER 1730 bool "Enable membarrier() system call" if EXPERT 1731 default y 1732 help 1733 Enable the membarrier() system call that allows issuing memory 1734 barriers across all running threads, which can be used to distribute 1735 the cost of user-space memory barriers asymmetrically by transforming 1736 pairs of memory barriers into pairs consisting of membarrier() and a 1737 compiler barrier. 1738 1739 If unsure, say Y. 1740 1741config EMBEDDED 1742 bool "Embedded system" 1743 option allnoconfig_y 1744 select EXPERT 1745 help 1746 This option should be enabled if compiling the kernel for 1747 an embedded system so certain expert options are available 1748 for configuration. 1749 1750config HAVE_PERF_EVENTS 1751 bool 1752 help 1753 See tools/perf/design.txt for details. 1754 1755config PERF_USE_VMALLOC 1756 bool 1757 help 1758 See tools/perf/design.txt for details 1759 1760config PC104 1761 bool "PC/104 support" 1762 help 1763 Expose PC/104 form factor device drivers and options available for 1764 selection and configuration. Enable this option if your target 1765 machine has a PC/104 bus. 1766 1767menu "Kernel Performance Events And Counters" 1768 1769config PERF_EVENTS 1770 bool "Kernel performance events and counters" 1771 default y if PROFILING 1772 depends on HAVE_PERF_EVENTS 1773 select ANON_INODES 1774 select IRQ_WORK 1775 select SRCU 1776 help 1777 Enable kernel support for various performance events provided 1778 by software and hardware. 1779 1780 Software events are supported either built-in or via the 1781 use of generic tracepoints. 1782 1783 Most modern CPUs support performance events via performance 1784 counter registers. These registers count the number of certain 1785 types of hw events: such as instructions executed, cachemisses 1786 suffered, or branches mis-predicted - without slowing down the 1787 kernel or applications. These registers can also trigger interrupts 1788 when a threshold number of events have passed - and can thus be 1789 used to profile the code that runs on that CPU. 1790 1791 The Linux Performance Event subsystem provides an abstraction of 1792 these software and hardware event capabilities, available via a 1793 system call and used by the "perf" utility in tools/perf/. It 1794 provides per task and per CPU counters, and it provides event 1795 capabilities on top of those. 1796 1797 Say Y if unsure. 1798 1799config DEBUG_PERF_USE_VMALLOC 1800 default n 1801 bool "Debug: use vmalloc to back perf mmap() buffers" 1802 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC 1803 select PERF_USE_VMALLOC 1804 help 1805 Use vmalloc memory to back perf mmap() buffers. 1806 1807 Mostly useful for debugging the vmalloc code on platforms 1808 that don't require it. 1809 1810 Say N if unsure. 1811 1812endmenu 1813 1814config VM_EVENT_COUNTERS 1815 default y 1816 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1817 help 1818 VM event counters are needed for event counts to be shown. 1819 This option allows the disabling of the VM event counters 1820 on EXPERT systems. /proc/vmstat will only show page counts 1821 if VM event counters are disabled. 1822 1823config SLUB_DEBUG 1824 default y 1825 bool "Enable SLUB debugging support" if EXPERT 1826 depends on SLUB && SYSFS 1827 help 1828 SLUB has extensive debug support features. Disabling these can 1829 result in significant savings in code size. This also disables 1830 SLUB sysfs support. /sys/slab will not exist and there will be 1831 no support for cache validation etc. 1832 1833config SLUB_MEMCG_SYSFS_ON 1834 default n 1835 bool "Enable memcg SLUB sysfs support by default" if EXPERT 1836 depends on SLUB && SYSFS && MEMCG 1837 help 1838 SLUB creates a directory under /sys/kernel/slab for each 1839 allocation cache to host info and debug files. If memory 1840 cgroup is enabled, each cache can have per memory cgroup 1841 caches. SLUB can create the same sysfs directories for these 1842 caches under /sys/kernel/slab/CACHE/cgroup but it can lead 1843 to a very high number of debug files being created. This is 1844 controlled by slub_memcg_sysfs boot parameter and this 1845 config option determines the parameter's default value. 1846 1847config COMPAT_BRK 1848 bool "Disable heap randomization" 1849 default y 1850 help 1851 Randomizing heap placement makes heap exploits harder, but it 1852 also breaks ancient binaries (including anything libc5 based). 1853 This option changes the bootup default to heap randomization 1854 disabled, and can be overridden at runtime by setting 1855 /proc/sys/kernel/randomize_va_space to 2. 1856 1857 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1858 1859choice 1860 prompt "Choose SLAB allocator" 1861 default SLUB 1862 help 1863 This option allows to select a slab allocator. 1864 1865config SLAB 1866 bool "SLAB" 1867 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1868 help 1869 The regular slab allocator that is established and known to work 1870 well in all environments. It organizes cache hot objects in 1871 per cpu and per node queues. 1872 1873config SLUB 1874 bool "SLUB (Unqueued Allocator)" 1875 select HAVE_HARDENED_USERCOPY_ALLOCATOR 1876 help 1877 SLUB is a slab allocator that minimizes cache line usage 1878 instead of managing queues of cached objects (SLAB approach). 1879 Per cpu caching is realized using slabs of objects instead 1880 of queues of objects. SLUB can use memory efficiently 1881 and has enhanced diagnostics. SLUB is the default choice for 1882 a slab allocator. 1883 1884config SLOB 1885 depends on EXPERT 1886 bool "SLOB (Simple Allocator)" 1887 help 1888 SLOB replaces the stock allocator with a drastically simpler 1889 allocator. SLOB is generally more space efficient but 1890 does not perform as well on large systems. 1891 1892endchoice 1893 1894config SLAB_FREELIST_RANDOM 1895 default n 1896 depends on SLAB || SLUB 1897 bool "SLAB freelist randomization" 1898 help 1899 Randomizes the freelist order used on creating new pages. This 1900 security feature reduces the predictability of the kernel slab 1901 allocator against heap overflows. 1902 1903config SLUB_CPU_PARTIAL 1904 default y 1905 depends on SLUB && SMP 1906 bool "SLUB per cpu partial cache" 1907 help 1908 Per cpu partial caches accellerate objects allocation and freeing 1909 that is local to a processor at the price of more indeterminism 1910 in the latency of the free. On overflow these caches will be cleared 1911 which requires the taking of locks that may cause latency spikes. 1912 Typically one would choose no for a realtime system. 1913 1914config MMAP_ALLOW_UNINITIALIZED 1915 bool "Allow mmapped anonymous memory to be uninitialized" 1916 depends on EXPERT && !MMU 1917 default n 1918 help 1919 Normally, and according to the Linux spec, anonymous memory obtained 1920 from mmap() has it's contents cleared before it is passed to 1921 userspace. Enabling this config option allows you to request that 1922 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1923 providing a huge performance boost. If this option is not enabled, 1924 then the flag will be ignored. 1925 1926 This is taken advantage of by uClibc's malloc(), and also by 1927 ELF-FDPIC binfmt's brk and stack allocator. 1928 1929 Because of the obvious security issues, this option should only be 1930 enabled on embedded devices where you control what is run in 1931 userspace. Since that isn't generally a problem on no-MMU systems, 1932 it is normally safe to say Y here. 1933 1934 See Documentation/nommu-mmap.txt for more information. 1935 1936config SYSTEM_DATA_VERIFICATION 1937 def_bool n 1938 select SYSTEM_TRUSTED_KEYRING 1939 select KEYS 1940 select CRYPTO 1941 select CRYPTO_RSA 1942 select ASYMMETRIC_KEY_TYPE 1943 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1944 select ASN1 1945 select OID_REGISTRY 1946 select X509_CERTIFICATE_PARSER 1947 select PKCS7_MESSAGE_PARSER 1948 help 1949 Provide PKCS#7 message verification using the contents of the system 1950 trusted keyring to provide public keys. This then can be used for 1951 module verification, kexec image verification and firmware blob 1952 verification. 1953 1954config PROFILING 1955 bool "Profiling support" 1956 help 1957 Say Y here to enable the extended profiling support mechanisms used 1958 by profilers such as OProfile. 1959 1960# 1961# Place an empty function call at each tracepoint site. Can be 1962# dynamically changed for a probe function. 1963# 1964config TRACEPOINTS 1965 bool 1966 1967source "arch/Kconfig" 1968 1969endmenu # General setup 1970 1971config HAVE_GENERIC_DMA_COHERENT 1972 bool 1973 default n 1974 1975config SLABINFO 1976 bool 1977 depends on PROC_FS 1978 depends on SLAB || SLUB_DEBUG 1979 default y 1980 1981config RT_MUTEXES 1982 bool 1983 1984config BASE_SMALL 1985 int 1986 default 0 if BASE_FULL 1987 default 1 if !BASE_FULL 1988 1989menuconfig MODULES 1990 bool "Enable loadable module support" 1991 option modules 1992 help 1993 Kernel modules are small pieces of compiled code which can 1994 be inserted in the running kernel, rather than being 1995 permanently built into the kernel. You use the "modprobe" 1996 tool to add (and sometimes remove) them. If you say Y here, 1997 many parts of the kernel can be built as modules (by 1998 answering M instead of Y where indicated): this is most 1999 useful for infrequently used options which are not required 2000 for booting. For more information, see the man pages for 2001 modprobe, lsmod, modinfo, insmod and rmmod. 2002 2003 If you say Y here, you will need to run "make 2004 modules_install" to put the modules under /lib/modules/ 2005 where modprobe can find them (you may need to be root to do 2006 this). 2007 2008 If unsure, say Y. 2009 2010if MODULES 2011 2012config MODULE_FORCE_LOAD 2013 bool "Forced module loading" 2014 default n 2015 help 2016 Allow loading of modules without version information (ie. modprobe 2017 --force). Forced module loading sets the 'F' (forced) taint flag and 2018 is usually a really bad idea. 2019 2020config MODULE_UNLOAD 2021 bool "Module unloading" 2022 help 2023 Without this option you will not be able to unload any 2024 modules (note that some modules may not be unloadable 2025 anyway), which makes your kernel smaller, faster 2026 and simpler. If unsure, say Y. 2027 2028config MODULE_FORCE_UNLOAD 2029 bool "Forced module unloading" 2030 depends on MODULE_UNLOAD 2031 help 2032 This option allows you to force a module to unload, even if the 2033 kernel believes it is unsafe: the kernel will remove the module 2034 without waiting for anyone to stop using it (using the -f option to 2035 rmmod). This is mainly for kernel developers and desperate users. 2036 If unsure, say N. 2037 2038config MODVERSIONS 2039 bool "Module versioning support" 2040 help 2041 Usually, you have to use modules compiled with your kernel. 2042 Saying Y here makes it sometimes possible to use modules 2043 compiled for different kernels, by adding enough information 2044 to the modules to (hopefully) spot any changes which would 2045 make them incompatible with the kernel you are running. If 2046 unsure, say N. 2047 2048config MODULE_REL_CRCS 2049 bool 2050 depends on MODVERSIONS 2051 2052config MODULE_SRCVERSION_ALL 2053 bool "Source checksum for all modules" 2054 help 2055 Modules which contain a MODULE_VERSION get an extra "srcversion" 2056 field inserted into their modinfo section, which contains a 2057 sum of the source files which made it. This helps maintainers 2058 see exactly which source was used to build a module (since 2059 others sometimes change the module source without updating 2060 the version). With this option, such a "srcversion" field 2061 will be created for all modules. If unsure, say N. 2062 2063config MODULE_SIG 2064 bool "Module signature verification" 2065 depends on MODULES 2066 select SYSTEM_DATA_VERIFICATION 2067 help 2068 Check modules for valid signatures upon load: the signature 2069 is simply appended to the module. For more information see 2070 Documentation/module-signing.txt. 2071 2072 Note that this option adds the OpenSSL development packages as a 2073 kernel build dependency so that the signing tool can use its crypto 2074 library. 2075 2076 !!!WARNING!!! If you enable this option, you MUST make sure that the 2077 module DOES NOT get stripped after being signed. This includes the 2078 debuginfo strip done by some packagers (such as rpmbuild) and 2079 inclusion into an initramfs that wants the module size reduced. 2080 2081config MODULE_SIG_FORCE 2082 bool "Require modules to be validly signed" 2083 depends on MODULE_SIG 2084 help 2085 Reject unsigned modules or signed modules for which we don't have a 2086 key. Without this, such modules will simply taint the kernel. 2087 2088config MODULE_SIG_ALL 2089 bool "Automatically sign all modules" 2090 default y 2091 depends on MODULE_SIG 2092 help 2093 Sign all modules during make modules_install. Without this option, 2094 modules must be signed manually, using the scripts/sign-file tool. 2095 2096comment "Do not forget to sign required modules with scripts/sign-file" 2097 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 2098 2099choice 2100 prompt "Which hash algorithm should modules be signed with?" 2101 depends on MODULE_SIG 2102 help 2103 This determines which sort of hashing algorithm will be used during 2104 signature generation. This algorithm _must_ be built into the kernel 2105 directly so that signature verification can take place. It is not 2106 possible to load a signed module containing the algorithm to check 2107 the signature on that module. 2108 2109config MODULE_SIG_SHA1 2110 bool "Sign modules with SHA-1" 2111 select CRYPTO_SHA1 2112 2113config MODULE_SIG_SHA224 2114 bool "Sign modules with SHA-224" 2115 select CRYPTO_SHA256 2116 2117config MODULE_SIG_SHA256 2118 bool "Sign modules with SHA-256" 2119 select CRYPTO_SHA256 2120 2121config MODULE_SIG_SHA384 2122 bool "Sign modules with SHA-384" 2123 select CRYPTO_SHA512 2124 2125config MODULE_SIG_SHA512 2126 bool "Sign modules with SHA-512" 2127 select CRYPTO_SHA512 2128 2129endchoice 2130 2131config MODULE_SIG_HASH 2132 string 2133 depends on MODULE_SIG 2134 default "sha1" if MODULE_SIG_SHA1 2135 default "sha224" if MODULE_SIG_SHA224 2136 default "sha256" if MODULE_SIG_SHA256 2137 default "sha384" if MODULE_SIG_SHA384 2138 default "sha512" if MODULE_SIG_SHA512 2139 2140config MODULE_COMPRESS 2141 bool "Compress modules on installation" 2142 depends on MODULES 2143 help 2144 2145 Compresses kernel modules when 'make modules_install' is run; gzip or 2146 xz depending on "Compression algorithm" below. 2147 2148 module-init-tools MAY support gzip, and kmod MAY support gzip and xz. 2149 2150 Out-of-tree kernel modules installed using Kbuild will also be 2151 compressed upon installation. 2152 2153 Note: for modules inside an initrd or initramfs, it's more efficient 2154 to compress the whole initrd or initramfs instead. 2155 2156 Note: This is fully compatible with signed modules. 2157 2158 If in doubt, say N. 2159 2160choice 2161 prompt "Compression algorithm" 2162 depends on MODULE_COMPRESS 2163 default MODULE_COMPRESS_GZIP 2164 help 2165 This determines which sort of compression will be used during 2166 'make modules_install'. 2167 2168 GZIP (default) and XZ are supported. 2169 2170config MODULE_COMPRESS_GZIP 2171 bool "GZIP" 2172 2173config MODULE_COMPRESS_XZ 2174 bool "XZ" 2175 2176endchoice 2177 2178config TRIM_UNUSED_KSYMS 2179 bool "Trim unused exported kernel symbols" 2180 depends on MODULES && !UNUSED_SYMBOLS 2181 help 2182 The kernel and some modules make many symbols available for 2183 other modules to use via EXPORT_SYMBOL() and variants. Depending 2184 on the set of modules being selected in your kernel configuration, 2185 many of those exported symbols might never be used. 2186 2187 This option allows for unused exported symbols to be dropped from 2188 the build. In turn, this provides the compiler more opportunities 2189 (especially when using LTO) for optimizing the code and reducing 2190 binary size. This might have some security advantages as well. 2191 2192 If unsure, or if you need to build out-of-tree modules, say N. 2193 2194endif # MODULES 2195 2196config MODULES_TREE_LOOKUP 2197 def_bool y 2198 depends on PERF_EVENTS || TRACING 2199 2200config INIT_ALL_POSSIBLE 2201 bool 2202 help 2203 Back when each arch used to define their own cpu_online_mask and 2204 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 2205 with all 1s, and others with all 0s. When they were centralised, 2206 it was better to provide this option than to break all the archs 2207 and have several arch maintainers pursuing me down dark alleys. 2208 2209source "block/Kconfig" 2210 2211config PREEMPT_NOTIFIERS 2212 bool 2213 2214config PADATA 2215 depends on SMP 2216 bool 2217 2218config ASN1 2219 tristate 2220 help 2221 Build a simple ASN.1 grammar compiler that produces a bytecode output 2222 that can be interpreted by the ASN.1 stream decoder and used to 2223 inform it as to what tags are to be expected in a stream and what 2224 functions to call on what tags. 2225 2226source "kernel/Kconfig.locks" 2227