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 HAVE_IRQ_WORK 24 bool 25 26config IRQ_WORK 27 bool 28 depends on HAVE_IRQ_WORK 29 30config BUILDTIME_EXTABLE_SORT 31 bool 32 33menu "General setup" 34 35config EXPERIMENTAL 36 bool "Prompt for development and/or incomplete code/drivers" 37 ---help--- 38 Some of the various things that Linux supports (such as network 39 drivers, file systems, network protocols, etc.) can be in a state 40 of development where the functionality, stability, or the level of 41 testing is not yet high enough for general use. This is usually 42 known as the "alpha-test" phase among developers. If a feature is 43 currently in alpha-test, then the developers usually discourage 44 uninformed widespread use of this feature by the general public to 45 avoid "Why doesn't this work?" type mail messages. However, active 46 testing and use of these systems is welcomed. Just be aware that it 47 may not meet the normal level of reliability or it may fail to work 48 in some special cases. Detailed bug reports from people familiar 49 with the kernel internals are usually welcomed by the developers 50 (before submitting bug reports, please read the documents 51 <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>, 52 <file:Documentation/BUG-HUNTING>, and 53 <file:Documentation/oops-tracing.txt> in the kernel source). 54 55 This option will also make obsoleted drivers available. These are 56 drivers that have been replaced by something else, and/or are 57 scheduled to be removed in a future kernel release. 58 59 Unless you intend to help test and develop a feature or driver that 60 falls into this category, or you have a situation that requires 61 using these features, you should probably say N here, which will 62 cause the configurator to present you with fewer choices. If 63 you say Y here, you will be offered the choice of using features or 64 drivers that are currently considered to be in the alpha-test phase. 65 66config BROKEN 67 bool 68 69config BROKEN_ON_SMP 70 bool 71 depends on BROKEN || !SMP 72 default y 73 74config INIT_ENV_ARG_LIMIT 75 int 76 default 32 if !UML 77 default 128 if UML 78 help 79 Maximum of each of the number of arguments and environment 80 variables passed to init from the kernel command line. 81 82 83config CROSS_COMPILE 84 string "Cross-compiler tool prefix" 85 help 86 Same as running 'make CROSS_COMPILE=prefix-' but stored for 87 default make runs in this kernel build directory. You don't 88 need to set this unless you want the configured kernel build 89 directory to select the cross-compiler automatically. 90 91config LOCALVERSION 92 string "Local version - append to kernel release" 93 help 94 Append an extra string to the end of your kernel version. 95 This will show up when you type uname, for example. 96 The string you set here will be appended after the contents of 97 any files with a filename matching localversion* in your 98 object and source tree, in that order. Your total string can 99 be a maximum of 64 characters. 100 101config LOCALVERSION_AUTO 102 bool "Automatically append version information to the version string" 103 default y 104 help 105 This will try to automatically determine if the current tree is a 106 release tree by looking for git tags that belong to the current 107 top of tree revision. 108 109 A string of the format -gxxxxxxxx will be added to the localversion 110 if a git-based tree is found. The string generated by this will be 111 appended after any matching localversion* files, and after the value 112 set in CONFIG_LOCALVERSION. 113 114 (The actual string used here is the first eight characters produced 115 by running the command: 116 117 $ git rev-parse --verify HEAD 118 119 which is done within the script "scripts/setlocalversion".) 120 121config HAVE_KERNEL_GZIP 122 bool 123 124config HAVE_KERNEL_BZIP2 125 bool 126 127config HAVE_KERNEL_LZMA 128 bool 129 130config HAVE_KERNEL_XZ 131 bool 132 133config HAVE_KERNEL_LZO 134 bool 135 136choice 137 prompt "Kernel compression mode" 138 default KERNEL_GZIP 139 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO 140 help 141 The linux kernel is a kind of self-extracting executable. 142 Several compression algorithms are available, which differ 143 in efficiency, compression and decompression speed. 144 Compression speed is only relevant when building a kernel. 145 Decompression speed is relevant at each boot. 146 147 If you have any problems with bzip2 or lzma compressed 148 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 149 version of this functionality (bzip2 only), for 2.4, was 150 supplied by Christian Ludwig) 151 152 High compression options are mostly useful for users, who 153 are low on disk space (embedded systems), but for whom ram 154 size matters less. 155 156 If in doubt, select 'gzip' 157 158config KERNEL_GZIP 159 bool "Gzip" 160 depends on HAVE_KERNEL_GZIP 161 help 162 The old and tried gzip compression. It provides a good balance 163 between compression ratio and decompression speed. 164 165config KERNEL_BZIP2 166 bool "Bzip2" 167 depends on HAVE_KERNEL_BZIP2 168 help 169 Its compression ratio and speed is intermediate. 170 Decompression speed is slowest among the choices. The kernel 171 size is about 10% smaller with bzip2, in comparison to gzip. 172 Bzip2 uses a large amount of memory. For modern kernels you 173 will need at least 8MB RAM or more for booting. 174 175config KERNEL_LZMA 176 bool "LZMA" 177 depends on HAVE_KERNEL_LZMA 178 help 179 This compression algorithm's ratio is best. Decompression speed 180 is between gzip and bzip2. Compression is slowest. 181 The kernel size is about 33% smaller with LZMA in comparison to gzip. 182 183config KERNEL_XZ 184 bool "XZ" 185 depends on HAVE_KERNEL_XZ 186 help 187 XZ uses the LZMA2 algorithm and instruction set specific 188 BCJ filters which can improve compression ratio of executable 189 code. The size of the kernel is about 30% smaller with XZ in 190 comparison to gzip. On architectures for which there is a BCJ 191 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 192 will create a few percent smaller kernel than plain LZMA. 193 194 The speed is about the same as with LZMA: The decompression 195 speed of XZ is better than that of bzip2 but worse than gzip 196 and LZO. Compression is slow. 197 198config KERNEL_LZO 199 bool "LZO" 200 depends on HAVE_KERNEL_LZO 201 help 202 Its compression ratio is the poorest among the choices. The kernel 203 size is about 10% bigger than gzip; however its speed 204 (both compression and decompression) is the fastest. 205 206endchoice 207 208config DEFAULT_HOSTNAME 209 string "Default hostname" 210 default "(none)" 211 help 212 This option determines the default system hostname before userspace 213 calls sethostname(2). The kernel traditionally uses "(none)" here, 214 but you may wish to use a different default here to make a minimal 215 system more usable with less configuration. 216 217config SWAP 218 bool "Support for paging of anonymous memory (swap)" 219 depends on MMU && BLOCK 220 default y 221 help 222 This option allows you to choose whether you want to have support 223 for so called swap devices or swap files in your kernel that are 224 used to provide more virtual memory than the actual RAM present 225 in your computer. If unsure say Y. 226 227config SYSVIPC 228 bool "System V IPC" 229 ---help--- 230 Inter Process Communication is a suite of library functions and 231 system calls which let processes (running programs) synchronize and 232 exchange information. It is generally considered to be a good thing, 233 and some programs won't run unless you say Y here. In particular, if 234 you want to run the DOS emulator dosemu under Linux (read the 235 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 236 you'll need to say Y here. 237 238 You can find documentation about IPC with "info ipc" and also in 239 section 6.4 of the Linux Programmer's Guide, available from 240 <http://www.tldp.org/guides.html>. 241 242config SYSVIPC_SYSCTL 243 bool 244 depends on SYSVIPC 245 depends on SYSCTL 246 default y 247 248config POSIX_MQUEUE 249 bool "POSIX Message Queues" 250 depends on NET && EXPERIMENTAL 251 ---help--- 252 POSIX variant of message queues is a part of IPC. In POSIX message 253 queues every message has a priority which decides about succession 254 of receiving it by a process. If you want to compile and run 255 programs written e.g. for Solaris with use of its POSIX message 256 queues (functions mq_*) say Y here. 257 258 POSIX message queues are visible as a filesystem called 'mqueue' 259 and can be mounted somewhere if you want to do filesystem 260 operations on message queues. 261 262 If unsure, say Y. 263 264config POSIX_MQUEUE_SYSCTL 265 bool 266 depends on POSIX_MQUEUE 267 depends on SYSCTL 268 default y 269 270config FHANDLE 271 bool "open by fhandle syscalls" 272 select EXPORTFS 273 help 274 If you say Y here, a user level program will be able to map 275 file names to handle and then later use the handle for 276 different file system operations. This is useful in implementing 277 userspace file servers, which now track files using handles instead 278 of names. The handle would remain the same even if file names 279 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 280 syscalls. 281 282config AUDIT 283 bool "Auditing support" 284 depends on NET 285 help 286 Enable auditing infrastructure that can be used with another 287 kernel subsystem, such as SELinux (which requires this for 288 logging of avc messages output). Does not do system-call 289 auditing without CONFIG_AUDITSYSCALL. 290 291config AUDITSYSCALL 292 bool "Enable system-call auditing support" 293 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH || (ARM && AEABI && !OABI_COMPAT)) 294 default y if SECURITY_SELINUX 295 help 296 Enable low-overhead system-call auditing infrastructure that 297 can be used independently or with another kernel subsystem, 298 such as SELinux. 299 300config AUDIT_WATCH 301 def_bool y 302 depends on AUDITSYSCALL 303 select FSNOTIFY 304 305config AUDIT_TREE 306 def_bool y 307 depends on AUDITSYSCALL 308 select FSNOTIFY 309 310config AUDIT_LOGINUID_IMMUTABLE 311 bool "Make audit loginuid immutable" 312 depends on AUDIT 313 help 314 The config option toggles if a task setting its loginuid requires 315 CAP_SYS_AUDITCONTROL or if that task should require no special permissions 316 but should instead only allow setting its loginuid if it was never 317 previously set. On systems which use systemd or a similar central 318 process to restart login services this should be set to true. On older 319 systems in which an admin would typically have to directly stop and 320 start processes this should be set to false. Setting this to true allows 321 one to drop potentially dangerous capabilites from the login tasks, 322 but may not be backwards compatible with older init systems. 323 324source "kernel/irq/Kconfig" 325source "kernel/time/Kconfig" 326 327menu "CPU/Task time and stats accounting" 328 329choice 330 prompt "Cputime accounting" 331 default TICK_CPU_ACCOUNTING if !PPC64 332 default VIRT_CPU_ACCOUNTING if PPC64 333 334# Kind of a stub config for the pure tick based cputime accounting 335config TICK_CPU_ACCOUNTING 336 bool "Simple tick based cputime accounting" 337 depends on !S390 338 help 339 This is the basic tick based cputime accounting that maintains 340 statistics about user, system and idle time spent on per jiffies 341 granularity. 342 343 If unsure, say Y. 344 345config VIRT_CPU_ACCOUNTING 346 bool "Deterministic task and CPU time accounting" 347 depends on HAVE_VIRT_CPU_ACCOUNTING 348 help 349 Select this option to enable more accurate task and CPU time 350 accounting. This is done by reading a CPU counter on each 351 kernel entry and exit and on transitions within the kernel 352 between system, softirq and hardirq state, so there is a 353 small performance impact. In the case of s390 or IBM POWER > 5, 354 this also enables accounting of stolen time on logically-partitioned 355 systems. 356 357config IRQ_TIME_ACCOUNTING 358 bool "Fine granularity task level IRQ time accounting" 359 depends on HAVE_IRQ_TIME_ACCOUNTING 360 help 361 Select this option to enable fine granularity task irq time 362 accounting. This is done by reading a timestamp on each 363 transitions between softirq and hardirq state, so there can be a 364 small performance impact. 365 366 If in doubt, say N here. 367 368endchoice 369 370config BSD_PROCESS_ACCT 371 bool "BSD Process Accounting" 372 help 373 If you say Y here, a user level program will be able to instruct the 374 kernel (via a special system call) to write process accounting 375 information to a file: whenever a process exits, information about 376 that process will be appended to the file by the kernel. The 377 information includes things such as creation time, owning user, 378 command name, memory usage, controlling terminal etc. (the complete 379 list is in the struct acct in <file:include/linux/acct.h>). It is 380 up to the user level program to do useful things with this 381 information. This is generally a good idea, so say Y. 382 383config BSD_PROCESS_ACCT_V3 384 bool "BSD Process Accounting version 3 file format" 385 depends on BSD_PROCESS_ACCT 386 default n 387 help 388 If you say Y here, the process accounting information is written 389 in a new file format that also logs the process IDs of each 390 process and it's parent. Note that this file format is incompatible 391 with previous v0/v1/v2 file formats, so you will need updated tools 392 for processing it. A preliminary version of these tools is available 393 at <http://www.gnu.org/software/acct/>. 394 395config TASKSTATS 396 bool "Export task/process statistics through netlink (EXPERIMENTAL)" 397 depends on NET 398 default n 399 help 400 Export selected statistics for tasks/processes through the 401 generic netlink interface. Unlike BSD process accounting, the 402 statistics are available during the lifetime of tasks/processes as 403 responses to commands. Like BSD accounting, they are sent to user 404 space on task exit. 405 406 Say N if unsure. 407 408config TASK_DELAY_ACCT 409 bool "Enable per-task delay accounting (EXPERIMENTAL)" 410 depends on TASKSTATS 411 help 412 Collect information on time spent by a task waiting for system 413 resources like cpu, synchronous block I/O completion and swapping 414 in pages. Such statistics can help in setting a task's priorities 415 relative to other tasks for cpu, io, rss limits etc. 416 417 Say N if unsure. 418 419config TASK_XACCT 420 bool "Enable extended accounting over taskstats (EXPERIMENTAL)" 421 depends on TASKSTATS 422 help 423 Collect extended task accounting data and send the data 424 to userland for processing over the taskstats interface. 425 426 Say N if unsure. 427 428config TASK_IO_ACCOUNTING 429 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)" 430 depends on TASK_XACCT 431 help 432 Collect information on the number of bytes of storage I/O which this 433 task has caused. 434 435 Say N if unsure. 436 437endmenu # "CPU/Task time and stats accounting" 438 439menu "RCU Subsystem" 440 441choice 442 prompt "RCU Implementation" 443 default TREE_RCU 444 445config TREE_RCU 446 bool "Tree-based hierarchical RCU" 447 depends on !PREEMPT && SMP 448 help 449 This option selects the RCU implementation that is 450 designed for very large SMP system with hundreds or 451 thousands of CPUs. It also scales down nicely to 452 smaller systems. 453 454config TREE_PREEMPT_RCU 455 bool "Preemptible tree-based hierarchical RCU" 456 depends on PREEMPT && SMP 457 help 458 This option selects the RCU implementation that is 459 designed for very large SMP systems with hundreds or 460 thousands of CPUs, but for which real-time response 461 is also required. It also scales down nicely to 462 smaller systems. 463 464config TINY_RCU 465 bool "UP-only small-memory-footprint RCU" 466 depends on !PREEMPT && !SMP 467 help 468 This option selects the RCU implementation that is 469 designed for UP systems from which real-time response 470 is not required. This option greatly reduces the 471 memory footprint of RCU. 472 473config TINY_PREEMPT_RCU 474 bool "Preemptible UP-only small-memory-footprint RCU" 475 depends on PREEMPT && !SMP 476 help 477 This option selects the RCU implementation that is designed 478 for real-time UP systems. This option greatly reduces the 479 memory footprint of RCU. 480 481endchoice 482 483config PREEMPT_RCU 484 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU ) 485 help 486 This option enables preemptible-RCU code that is common between 487 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations. 488 489config CONTEXT_TRACKING 490 bool 491 492config RCU_USER_QS 493 bool "Consider userspace as in RCU extended quiescent state" 494 depends on HAVE_CONTEXT_TRACKING && SMP 495 select CONTEXT_TRACKING 496 help 497 This option sets hooks on kernel / userspace boundaries and 498 puts RCU in extended quiescent state when the CPU runs in 499 userspace. It means that when a CPU runs in userspace, it is 500 excluded from the global RCU state machine and thus doesn't 501 try to keep the timer tick on for RCU. 502 503 Unless you want to hack and help the development of the full 504 dynticks mode, you shouldn't enable this option. It also 505 adds unnecessary overhead. 506 507 If unsure say N 508 509config CONTEXT_TRACKING_FORCE 510 bool "Force context tracking" 511 depends on CONTEXT_TRACKING 512 help 513 Probe on user/kernel boundaries by default in order to 514 test the features that rely on it such as userspace RCU extended 515 quiescent states. 516 This test is there for debugging until we have a real user like the 517 full dynticks mode. 518 519config RCU_FANOUT 520 int "Tree-based hierarchical RCU fanout value" 521 range 2 64 if 64BIT 522 range 2 32 if !64BIT 523 depends on TREE_RCU || TREE_PREEMPT_RCU 524 default 64 if 64BIT 525 default 32 if !64BIT 526 help 527 This option controls the fanout of hierarchical implementations 528 of RCU, allowing RCU to work efficiently on machines with 529 large numbers of CPUs. This value must be at least the fourth 530 root of NR_CPUS, which allows NR_CPUS to be insanely large. 531 The default value of RCU_FANOUT should be used for production 532 systems, but if you are stress-testing the RCU implementation 533 itself, small RCU_FANOUT values allow you to test large-system 534 code paths on small(er) systems. 535 536 Select a specific number if testing RCU itself. 537 Take the default if unsure. 538 539config RCU_FANOUT_LEAF 540 int "Tree-based hierarchical RCU leaf-level fanout value" 541 range 2 RCU_FANOUT if 64BIT 542 range 2 RCU_FANOUT if !64BIT 543 depends on TREE_RCU || TREE_PREEMPT_RCU 544 default 16 545 help 546 This option controls the leaf-level fanout of hierarchical 547 implementations of RCU, and allows trading off cache misses 548 against lock contention. Systems that synchronize their 549 scheduling-clock interrupts for energy-efficiency reasons will 550 want the default because the smaller leaf-level fanout keeps 551 lock contention levels acceptably low. Very large systems 552 (hundreds or thousands of CPUs) will instead want to set this 553 value to the maximum value possible in order to reduce the 554 number of cache misses incurred during RCU's grace-period 555 initialization. These systems tend to run CPU-bound, and thus 556 are not helped by synchronized interrupts, and thus tend to 557 skew them, which reduces lock contention enough that large 558 leaf-level fanouts work well. 559 560 Select a specific number if testing RCU itself. 561 562 Select the maximum permissible value for large systems. 563 564 Take the default if unsure. 565 566config RCU_FANOUT_EXACT 567 bool "Disable tree-based hierarchical RCU auto-balancing" 568 depends on TREE_RCU || TREE_PREEMPT_RCU 569 default n 570 help 571 This option forces use of the exact RCU_FANOUT value specified, 572 regardless of imbalances in the hierarchy. This is useful for 573 testing RCU itself, and might one day be useful on systems with 574 strong NUMA behavior. 575 576 Without RCU_FANOUT_EXACT, the code will balance the hierarchy. 577 578 Say N if unsure. 579 580config RCU_FAST_NO_HZ 581 bool "Accelerate last non-dyntick-idle CPU's grace periods" 582 depends on NO_HZ && SMP 583 default n 584 help 585 This option causes RCU to attempt to accelerate grace periods in 586 order to allow CPUs to enter dynticks-idle state more quickly. 587 On the other hand, this option increases the overhead of the 588 dynticks-idle checking, thus degrading scheduling latency. 589 590 Say Y if energy efficiency is critically important, and you don't 591 care about real-time response. 592 593 Say N if you are unsure. 594 595config TREE_RCU_TRACE 596 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU ) 597 select DEBUG_FS 598 help 599 This option provides tracing for the TREE_RCU and 600 TREE_PREEMPT_RCU implementations, permitting Makefile to 601 trivially select kernel/rcutree_trace.c. 602 603config RCU_BOOST 604 bool "Enable RCU priority boosting" 605 depends on RT_MUTEXES && PREEMPT_RCU 606 default n 607 help 608 This option boosts the priority of preempted RCU readers that 609 block the current preemptible RCU grace period for too long. 610 This option also prevents heavy loads from blocking RCU 611 callback invocation for all flavors of RCU. 612 613 Say Y here if you are working with real-time apps or heavy loads 614 Say N here if you are unsure. 615 616config RCU_BOOST_PRIO 617 int "Real-time priority to boost RCU readers to" 618 range 1 99 619 depends on RCU_BOOST 620 default 1 621 help 622 This option specifies the real-time priority to which long-term 623 preempted RCU readers are to be boosted. If you are working 624 with a real-time application that has one or more CPU-bound 625 threads running at a real-time priority level, you should set 626 RCU_BOOST_PRIO to a priority higher then the highest-priority 627 real-time CPU-bound thread. The default RCU_BOOST_PRIO value 628 of 1 is appropriate in the common case, which is real-time 629 applications that do not have any CPU-bound threads. 630 631 Some real-time applications might not have a single real-time 632 thread that saturates a given CPU, but instead might have 633 multiple real-time threads that, taken together, fully utilize 634 that CPU. In this case, you should set RCU_BOOST_PRIO to 635 a priority higher than the lowest-priority thread that is 636 conspiring to prevent the CPU from running any non-real-time 637 tasks. For example, if one thread at priority 10 and another 638 thread at priority 5 are between themselves fully consuming 639 the CPU time on a given CPU, then RCU_BOOST_PRIO should be 640 set to priority 6 or higher. 641 642 Specify the real-time priority, or take the default if unsure. 643 644config RCU_BOOST_DELAY 645 int "Milliseconds to delay boosting after RCU grace-period start" 646 range 0 3000 647 depends on RCU_BOOST 648 default 500 649 help 650 This option specifies the time to wait after the beginning of 651 a given grace period before priority-boosting preempted RCU 652 readers blocking that grace period. Note that any RCU reader 653 blocking an expedited RCU grace period is boosted immediately. 654 655 Accept the default if unsure. 656 657config RCU_NOCB_CPU 658 bool "Offload RCU callback processing from boot-selected CPUs" 659 depends on TREE_RCU || TREE_PREEMPT_RCU 660 default n 661 help 662 Use this option to reduce OS jitter for aggressive HPC or 663 real-time workloads. It can also be used to offload RCU 664 callback invocation to energy-efficient CPUs in battery-powered 665 asymmetric multiprocessors. 666 667 This option offloads callback invocation from the set of 668 CPUs specified at boot time by the rcu_nocbs parameter. 669 For each such CPU, a kthread ("rcuoN") will be created to 670 invoke callbacks, where the "N" is the CPU being offloaded. 671 Nothing prevents this kthread from running on the specified 672 CPUs, but (1) the kthreads may be preempted between each 673 callback, and (2) affinity or cgroups can be used to force 674 the kthreads to run on whatever set of CPUs is desired. 675 676 Say Y here if you want reduced OS jitter on selected CPUs. 677 Say N here if you are unsure. 678 679endmenu # "RCU Subsystem" 680 681config IKCONFIG 682 tristate "Kernel .config support" 683 ---help--- 684 This option enables the complete Linux kernel ".config" file 685 contents to be saved in the kernel. It provides documentation 686 of which kernel options are used in a running kernel or in an 687 on-disk kernel. This information can be extracted from the kernel 688 image file with the script scripts/extract-ikconfig and used as 689 input to rebuild the current kernel or to build another kernel. 690 It can also be extracted from a running kernel by reading 691 /proc/config.gz if enabled (below). 692 693config IKCONFIG_PROC 694 bool "Enable access to .config through /proc/config.gz" 695 depends on IKCONFIG && PROC_FS 696 ---help--- 697 This option enables access to the kernel configuration file 698 through /proc/config.gz. 699 700config LOG_BUF_SHIFT 701 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 702 range 12 21 703 default 17 704 help 705 Select kernel log buffer size as a power of 2. 706 Examples: 707 17 => 128 KB 708 16 => 64 KB 709 15 => 32 KB 710 14 => 16 KB 711 13 => 8 KB 712 12 => 4 KB 713 714# 715# Architectures with an unreliable sched_clock() should select this: 716# 717config HAVE_UNSTABLE_SCHED_CLOCK 718 bool 719 720menuconfig CGROUPS 721 boolean "Control Group support" 722 depends on EVENTFD 723 help 724 This option adds support for grouping sets of processes together, for 725 use with process control subsystems such as Cpusets, CFS, memory 726 controls or device isolation. 727 See 728 - Documentation/scheduler/sched-design-CFS.txt (CFS) 729 - Documentation/cgroups/ (features for grouping, isolation 730 and resource control) 731 732 Say N if unsure. 733 734if CGROUPS 735 736config CGROUP_DEBUG 737 bool "Example debug cgroup subsystem" 738 default n 739 help 740 This option enables a simple cgroup subsystem that 741 exports useful debugging information about the cgroups 742 framework. 743 744 Say N if unsure. 745 746config CGROUP_FREEZER 747 bool "Freezer cgroup subsystem" 748 help 749 Provides a way to freeze and unfreeze all tasks in a 750 cgroup. 751 752config CGROUP_DEVICE 753 bool "Device controller for cgroups" 754 help 755 Provides a cgroup implementing whitelists for devices which 756 a process in the cgroup can mknod or open. 757 758config CPUSETS 759 bool "Cpuset support" 760 help 761 This option will let you create and manage CPUSETs which 762 allow dynamically partitioning a system into sets of CPUs and 763 Memory Nodes and assigning tasks to run only within those sets. 764 This is primarily useful on large SMP or NUMA systems. 765 766 Say N if unsure. 767 768config PROC_PID_CPUSET 769 bool "Include legacy /proc/<pid>/cpuset file" 770 depends on CPUSETS 771 default y 772 773config CGROUP_CPUACCT 774 bool "Simple CPU accounting cgroup subsystem" 775 help 776 Provides a simple Resource Controller for monitoring the 777 total CPU consumed by the tasks in a cgroup. 778 779config RESOURCE_COUNTERS 780 bool "Resource counters" 781 help 782 This option enables controller independent resource accounting 783 infrastructure that works with cgroups. 784 785config MEMCG 786 bool "Memory Resource Controller for Control Groups" 787 depends on RESOURCE_COUNTERS 788 select MM_OWNER 789 help 790 Provides a memory resource controller that manages both anonymous 791 memory and page cache. (See Documentation/cgroups/memory.txt) 792 793 Note that setting this option increases fixed memory overhead 794 associated with each page of memory in the system. By this, 795 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory 796 usage tracking struct at boot. Total amount of this is printed out 797 at boot. 798 799 Only enable when you're ok with these trade offs and really 800 sure you need the memory resource controller. Even when you enable 801 this, you can set "cgroup_disable=memory" at your boot option to 802 disable memory resource controller and you can avoid overheads. 803 (and lose benefits of memory resource controller) 804 805 This config option also selects MM_OWNER config option, which 806 could in turn add some fork/exit overhead. 807 808config MEMCG_SWAP 809 bool "Memory Resource Controller Swap Extension" 810 depends on MEMCG && SWAP 811 help 812 Add swap management feature to memory resource controller. When you 813 enable this, you can limit mem+swap usage per cgroup. In other words, 814 when you disable this, memory resource controller has no cares to 815 usage of swap...a process can exhaust all of the swap. This extension 816 is useful when you want to avoid exhaustion swap but this itself 817 adds more overheads and consumes memory for remembering information. 818 Especially if you use 32bit system or small memory system, please 819 be careful about enabling this. When memory resource controller 820 is disabled by boot option, this will be automatically disabled and 821 there will be no overhead from this. Even when you set this config=y, 822 if boot option "swapaccount=0" is set, swap will not be accounted. 823 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page 824 size is 4096bytes, 512k per 1Gbytes of swap. 825config MEMCG_SWAP_ENABLED 826 bool "Memory Resource Controller Swap Extension enabled by default" 827 depends on MEMCG_SWAP 828 default y 829 help 830 Memory Resource Controller Swap Extension comes with its price in 831 a bigger memory consumption. General purpose distribution kernels 832 which want to enable the feature but keep it disabled by default 833 and let the user enable it by swapaccount boot command line 834 parameter should have this option unselected. 835 For those who want to have the feature enabled by default should 836 select this option (if, for some reason, they need to disable it 837 then swapaccount=0 does the trick). 838config MEMCG_KMEM 839 bool "Memory Resource Controller Kernel Memory accounting (EXPERIMENTAL)" 840 depends on MEMCG && EXPERIMENTAL 841 default n 842 help 843 The Kernel Memory extension for Memory Resource Controller can limit 844 the amount of memory used by kernel objects in the system. Those are 845 fundamentally different from the entities handled by the standard 846 Memory Controller, which are page-based, and can be swapped. Users of 847 the kmem extension can use it to guarantee that no group of processes 848 will ever exhaust kernel resources alone. 849 850config CGROUP_HUGETLB 851 bool "HugeTLB Resource Controller for Control Groups" 852 depends on RESOURCE_COUNTERS && HUGETLB_PAGE && EXPERIMENTAL 853 default n 854 help 855 Provides a cgroup Resource Controller for HugeTLB pages. 856 When you enable this, you can put a per cgroup limit on HugeTLB usage. 857 The limit is enforced during page fault. Since HugeTLB doesn't 858 support page reclaim, enforcing the limit at page fault time implies 859 that, the application will get SIGBUS signal if it tries to access 860 HugeTLB pages beyond its limit. This requires the application to know 861 beforehand how much HugeTLB pages it would require for its use. The 862 control group is tracked in the third page lru pointer. This means 863 that we cannot use the controller with huge page less than 3 pages. 864 865config CGROUP_PERF 866 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring" 867 depends on PERF_EVENTS && CGROUPS 868 help 869 This option extends the per-cpu mode to restrict monitoring to 870 threads which belong to the cgroup specified and run on the 871 designated cpu. 872 873 Say N if unsure. 874 875menuconfig CGROUP_SCHED 876 bool "Group CPU scheduler" 877 default n 878 help 879 This feature lets CPU scheduler recognize task groups and control CPU 880 bandwidth allocation to such task groups. It uses cgroups to group 881 tasks. 882 883if CGROUP_SCHED 884config FAIR_GROUP_SCHED 885 bool "Group scheduling for SCHED_OTHER" 886 depends on CGROUP_SCHED 887 default CGROUP_SCHED 888 889config CFS_BANDWIDTH 890 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 891 depends on EXPERIMENTAL 892 depends on FAIR_GROUP_SCHED 893 default n 894 help 895 This option allows users to define CPU bandwidth rates (limits) for 896 tasks running within the fair group scheduler. Groups with no limit 897 set are considered to be unconstrained and will run with no 898 restriction. 899 See tip/Documentation/scheduler/sched-bwc.txt for more information. 900 901config RT_GROUP_SCHED 902 bool "Group scheduling for SCHED_RR/FIFO" 903 depends on EXPERIMENTAL 904 depends on CGROUP_SCHED 905 default n 906 help 907 This feature lets you explicitly allocate real CPU bandwidth 908 to task groups. If enabled, it will also make it impossible to 909 schedule realtime tasks for non-root users until you allocate 910 realtime bandwidth for them. 911 See Documentation/scheduler/sched-rt-group.txt for more information. 912 913endif #CGROUP_SCHED 914 915config BLK_CGROUP 916 bool "Block IO controller" 917 depends on BLOCK 918 default n 919 ---help--- 920 Generic block IO controller cgroup interface. This is the common 921 cgroup interface which should be used by various IO controlling 922 policies. 923 924 Currently, CFQ IO scheduler uses it to recognize task groups and 925 control disk bandwidth allocation (proportional time slice allocation) 926 to such task groups. It is also used by bio throttling logic in 927 block layer to implement upper limit in IO rates on a device. 928 929 This option only enables generic Block IO controller infrastructure. 930 One needs to also enable actual IO controlling logic/policy. For 931 enabling proportional weight division of disk bandwidth in CFQ, set 932 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 933 CONFIG_BLK_DEV_THROTTLING=y. 934 935 See Documentation/cgroups/blkio-controller.txt for more information. 936 937config DEBUG_BLK_CGROUP 938 bool "Enable Block IO controller debugging" 939 depends on BLK_CGROUP 940 default n 941 ---help--- 942 Enable some debugging help. Currently it exports additional stat 943 files in a cgroup which can be useful for debugging. 944 945endif # CGROUPS 946 947config CHECKPOINT_RESTORE 948 bool "Checkpoint/restore support" if EXPERT 949 default n 950 help 951 Enables additional kernel features in a sake of checkpoint/restore. 952 In particular it adds auxiliary prctl codes to setup process text, 953 data and heap segment sizes, and a few additional /proc filesystem 954 entries. 955 956 If unsure, say N here. 957 958menuconfig NAMESPACES 959 bool "Namespaces support" if EXPERT 960 default !EXPERT 961 help 962 Provides the way to make tasks work with different objects using 963 the same id. For example same IPC id may refer to different objects 964 or same user id or pid may refer to different tasks when used in 965 different namespaces. 966 967if NAMESPACES 968 969config UTS_NS 970 bool "UTS namespace" 971 default y 972 help 973 In this namespace tasks see different info provided with the 974 uname() system call 975 976config IPC_NS 977 bool "IPC namespace" 978 depends on (SYSVIPC || POSIX_MQUEUE) 979 default y 980 help 981 In this namespace tasks work with IPC ids which correspond to 982 different IPC objects in different namespaces. 983 984config USER_NS 985 bool "User namespace (EXPERIMENTAL)" 986 depends on EXPERIMENTAL 987 depends on UIDGID_CONVERTED 988 select UIDGID_STRICT_TYPE_CHECKS 989 990 default n 991 help 992 This allows containers, i.e. vservers, to use user namespaces 993 to provide different user info for different servers. 994 If unsure, say N. 995 996config PID_NS 997 bool "PID Namespaces" 998 default y 999 help 1000 Support process id namespaces. This allows having multiple 1001 processes with the same pid as long as they are in different 1002 pid namespaces. This is a building block of containers. 1003 1004config NET_NS 1005 bool "Network namespace" 1006 depends on NET 1007 default y 1008 help 1009 Allow user space to create what appear to be multiple instances 1010 of the network stack. 1011 1012endif # NAMESPACES 1013 1014config UIDGID_CONVERTED 1015 # True if all of the selected software conmponents are known 1016 # to have uid_t and gid_t converted to kuid_t and kgid_t 1017 # where appropriate and are otherwise safe to use with 1018 # the user namespace. 1019 bool 1020 default y 1021 1022 # Networking 1023 depends on NET_9P = n 1024 1025 # Filesystems 1026 depends on 9P_FS = n 1027 depends on AFS_FS = n 1028 depends on AUTOFS4_FS = n 1029 depends on CEPH_FS = n 1030 depends on CIFS = n 1031 depends on CODA_FS = n 1032 depends on FUSE_FS = n 1033 depends on GFS2_FS = n 1034 depends on NCP_FS = n 1035 depends on NFSD = n 1036 depends on NFS_FS = n 1037 depends on OCFS2_FS = n 1038 depends on XFS_FS = n 1039 1040config UIDGID_STRICT_TYPE_CHECKS 1041 bool "Require conversions between uid/gids and their internal representation" 1042 depends on UIDGID_CONVERTED 1043 default n 1044 help 1045 While the nececessary conversions are being added to all subsystems this option allows 1046 the code to continue to build for unconverted subsystems. 1047 1048 Say Y here if you want the strict type checking enabled 1049 1050config SCHED_AUTOGROUP 1051 bool "Automatic process group scheduling" 1052 select EVENTFD 1053 select CGROUPS 1054 select CGROUP_SCHED 1055 select FAIR_GROUP_SCHED 1056 help 1057 This option optimizes the scheduler for common desktop workloads by 1058 automatically creating and populating task groups. This separation 1059 of workloads isolates aggressive CPU burners (like build jobs) from 1060 desktop applications. Task group autogeneration is currently based 1061 upon task session. 1062 1063config MM_OWNER 1064 bool 1065 1066config SYSFS_DEPRECATED 1067 bool "Enable deprecated sysfs features to support old userspace tools" 1068 depends on SYSFS 1069 default n 1070 help 1071 This option adds code that switches the layout of the "block" class 1072 devices, to not show up in /sys/class/block/, but only in 1073 /sys/block/. 1074 1075 This switch is only active when the sysfs.deprecated=1 boot option is 1076 passed or the SYSFS_DEPRECATED_V2 option is set. 1077 1078 This option allows new kernels to run on old distributions and tools, 1079 which might get confused by /sys/class/block/. Since 2007/2008 all 1080 major distributions and tools handle this just fine. 1081 1082 Recent distributions and userspace tools after 2009/2010 depend on 1083 the existence of /sys/class/block/, and will not work with this 1084 option enabled. 1085 1086 Only if you are using a new kernel on an old distribution, you might 1087 need to say Y here. 1088 1089config SYSFS_DEPRECATED_V2 1090 bool "Enable deprecated sysfs features by default" 1091 default n 1092 depends on SYSFS 1093 depends on SYSFS_DEPRECATED 1094 help 1095 Enable deprecated sysfs by default. 1096 1097 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1098 option. 1099 1100 Only if you are using a new kernel on an old distribution, you might 1101 need to say Y here. Even then, odds are you would not need it 1102 enabled, you can always pass the boot option if absolutely necessary. 1103 1104config RELAY 1105 bool "Kernel->user space relay support (formerly relayfs)" 1106 help 1107 This option enables support for relay interface support in 1108 certain file systems (such as debugfs). 1109 It is designed to provide an efficient mechanism for tools and 1110 facilities to relay large amounts of data from kernel space to 1111 user space. 1112 1113 If unsure, say N. 1114 1115config BLK_DEV_INITRD 1116 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1117 depends on BROKEN || !FRV 1118 help 1119 The initial RAM filesystem is a ramfs which is loaded by the 1120 boot loader (loadlin or lilo) and that is mounted as root 1121 before the normal boot procedure. It is typically used to 1122 load modules needed to mount the "real" root file system, 1123 etc. See <file:Documentation/initrd.txt> for details. 1124 1125 If RAM disk support (BLK_DEV_RAM) is also included, this 1126 also enables initial RAM disk (initrd) support and adds 1127 15 Kbytes (more on some other architectures) to the kernel size. 1128 1129 If unsure say Y. 1130 1131if BLK_DEV_INITRD 1132 1133source "usr/Kconfig" 1134 1135endif 1136 1137config CC_OPTIMIZE_FOR_SIZE 1138 bool "Optimize for size" 1139 help 1140 Enabling this option will pass "-Os" instead of "-O2" to gcc 1141 resulting in a smaller kernel. 1142 1143 If unsure, say Y. 1144 1145config SYSCTL 1146 bool 1147 1148config ANON_INODES 1149 bool 1150 1151menuconfig EXPERT 1152 bool "Configure standard kernel features (expert users)" 1153 # Unhide debug options, to make the on-by-default options visible 1154 select DEBUG_KERNEL 1155 help 1156 This option allows certain base kernel options and settings 1157 to be disabled or tweaked. This is for specialized 1158 environments which can tolerate a "non-standard" kernel. 1159 Only use this if you really know what you are doing. 1160 1161config HAVE_UID16 1162 bool 1163 1164config UID16 1165 bool "Enable 16-bit UID system calls" if EXPERT 1166 depends on HAVE_UID16 1167 default y 1168 help 1169 This enables the legacy 16-bit UID syscall wrappers. 1170 1171config SYSCTL_SYSCALL 1172 bool "Sysctl syscall support" if EXPERT 1173 depends on PROC_SYSCTL 1174 default n 1175 select SYSCTL 1176 ---help--- 1177 sys_sysctl uses binary paths that have been found challenging 1178 to properly maintain and use. The interface in /proc/sys 1179 using paths with ascii names is now the primary path to this 1180 information. 1181 1182 Almost nothing using the binary sysctl interface so if you are 1183 trying to save some space it is probably safe to disable this, 1184 making your kernel marginally smaller. 1185 1186 If unsure say N here. 1187 1188config SYSCTL_EXCEPTION_TRACE 1189 bool 1190 help 1191 Enable support for /proc/sys/debug/exception-trace. 1192 1193config KALLSYMS 1194 bool "Load all symbols for debugging/ksymoops" if EXPERT 1195 default y 1196 help 1197 Say Y here to let the kernel print out symbolic crash information and 1198 symbolic stack backtraces. This increases the size of the kernel 1199 somewhat, as all symbols have to be loaded into the kernel image. 1200 1201config KALLSYMS_ALL 1202 bool "Include all symbols in kallsyms" 1203 depends on DEBUG_KERNEL && KALLSYMS 1204 help 1205 Normally kallsyms only contains the symbols of functions for nicer 1206 OOPS messages and backtraces (i.e., symbols from the text and inittext 1207 sections). This is sufficient for most cases. And only in very rare 1208 cases (e.g., when a debugger is used) all symbols are required (e.g., 1209 names of variables from the data sections, etc). 1210 1211 This option makes sure that all symbols are loaded into the kernel 1212 image (i.e., symbols from all sections) in cost of increased kernel 1213 size (depending on the kernel configuration, it may be 300KiB or 1214 something like this). 1215 1216 Say N unless you really need all symbols. 1217 1218config HOTPLUG 1219 def_bool y 1220 1221config PRINTK 1222 default y 1223 bool "Enable support for printk" if EXPERT 1224 help 1225 This option enables normal printk support. Removing it 1226 eliminates most of the message strings from the kernel image 1227 and makes the kernel more or less silent. As this makes it 1228 very difficult to diagnose system problems, saying N here is 1229 strongly discouraged. 1230 1231config BUG 1232 bool "BUG() support" if EXPERT 1233 default y 1234 help 1235 Disabling this option eliminates support for BUG and WARN, reducing 1236 the size of your kernel image and potentially quietly ignoring 1237 numerous fatal conditions. You should only consider disabling this 1238 option for embedded systems with no facilities for reporting errors. 1239 Just say Y. 1240 1241config ELF_CORE 1242 depends on COREDUMP 1243 default y 1244 bool "Enable ELF core dumps" if EXPERT 1245 help 1246 Enable support for generating core dumps. Disabling saves about 4k. 1247 1248 1249config PCSPKR_PLATFORM 1250 bool "Enable PC-Speaker support" if EXPERT 1251 depends on HAVE_PCSPKR_PLATFORM 1252 select I8253_LOCK 1253 default y 1254 help 1255 This option allows to disable the internal PC-Speaker 1256 support, saving some memory. 1257 1258config HAVE_PCSPKR_PLATFORM 1259 bool 1260 1261config BASE_FULL 1262 default y 1263 bool "Enable full-sized data structures for core" if EXPERT 1264 help 1265 Disabling this option reduces the size of miscellaneous core 1266 kernel data structures. This saves memory on small machines, 1267 but may reduce performance. 1268 1269config FUTEX 1270 bool "Enable futex support" if EXPERT 1271 default y 1272 select RT_MUTEXES 1273 help 1274 Disabling this option will cause the kernel to be built without 1275 support for "fast userspace mutexes". The resulting kernel may not 1276 run glibc-based applications correctly. 1277 1278config EPOLL 1279 bool "Enable eventpoll support" if EXPERT 1280 default y 1281 select ANON_INODES 1282 help 1283 Disabling this option will cause the kernel to be built without 1284 support for epoll family of system calls. 1285 1286config SIGNALFD 1287 bool "Enable signalfd() system call" if EXPERT 1288 select ANON_INODES 1289 default y 1290 help 1291 Enable the signalfd() system call that allows to receive signals 1292 on a file descriptor. 1293 1294 If unsure, say Y. 1295 1296config TIMERFD 1297 bool "Enable timerfd() system call" if EXPERT 1298 select ANON_INODES 1299 default y 1300 help 1301 Enable the timerfd() system call that allows to receive timer 1302 events on a file descriptor. 1303 1304 If unsure, say Y. 1305 1306config EVENTFD 1307 bool "Enable eventfd() system call" if EXPERT 1308 select ANON_INODES 1309 default y 1310 help 1311 Enable the eventfd() system call that allows to receive both 1312 kernel notification (ie. KAIO) or userspace notifications. 1313 1314 If unsure, say Y. 1315 1316config SHMEM 1317 bool "Use full shmem filesystem" if EXPERT 1318 default y 1319 depends on MMU 1320 help 1321 The shmem is an internal filesystem used to manage shared memory. 1322 It is backed by swap and manages resource limits. It is also exported 1323 to userspace as tmpfs if TMPFS is enabled. Disabling this 1324 option replaces shmem and tmpfs with the much simpler ramfs code, 1325 which may be appropriate on small systems without swap. 1326 1327config AIO 1328 bool "Enable AIO support" if EXPERT 1329 default y 1330 help 1331 This option enables POSIX asynchronous I/O which may by used 1332 by some high performance threaded applications. Disabling 1333 this option saves about 7k. 1334 1335config EMBEDDED 1336 bool "Embedded system" 1337 select EXPERT 1338 help 1339 This option should be enabled if compiling the kernel for 1340 an embedded system so certain expert options are available 1341 for configuration. 1342 1343config HAVE_PERF_EVENTS 1344 bool 1345 help 1346 See tools/perf/design.txt for details. 1347 1348config PERF_USE_VMALLOC 1349 bool 1350 help 1351 See tools/perf/design.txt for details 1352 1353menu "Kernel Performance Events And Counters" 1354 1355config PERF_EVENTS 1356 bool "Kernel performance events and counters" 1357 default y if PROFILING 1358 depends on HAVE_PERF_EVENTS 1359 select ANON_INODES 1360 select IRQ_WORK 1361 help 1362 Enable kernel support for various performance events provided 1363 by software and hardware. 1364 1365 Software events are supported either built-in or via the 1366 use of generic tracepoints. 1367 1368 Most modern CPUs support performance events via performance 1369 counter registers. These registers count the number of certain 1370 types of hw events: such as instructions executed, cachemisses 1371 suffered, or branches mis-predicted - without slowing down the 1372 kernel or applications. These registers can also trigger interrupts 1373 when a threshold number of events have passed - and can thus be 1374 used to profile the code that runs on that CPU. 1375 1376 The Linux Performance Event subsystem provides an abstraction of 1377 these software and hardware event capabilities, available via a 1378 system call and used by the "perf" utility in tools/perf/. It 1379 provides per task and per CPU counters, and it provides event 1380 capabilities on top of those. 1381 1382 Say Y if unsure. 1383 1384config DEBUG_PERF_USE_VMALLOC 1385 default n 1386 bool "Debug: use vmalloc to back perf mmap() buffers" 1387 depends on PERF_EVENTS && DEBUG_KERNEL 1388 select PERF_USE_VMALLOC 1389 help 1390 Use vmalloc memory to back perf mmap() buffers. 1391 1392 Mostly useful for debugging the vmalloc code on platforms 1393 that don't require it. 1394 1395 Say N if unsure. 1396 1397endmenu 1398 1399config VM_EVENT_COUNTERS 1400 default y 1401 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1402 help 1403 VM event counters are needed for event counts to be shown. 1404 This option allows the disabling of the VM event counters 1405 on EXPERT systems. /proc/vmstat will only show page counts 1406 if VM event counters are disabled. 1407 1408config PCI_QUIRKS 1409 default y 1410 bool "Enable PCI quirk workarounds" if EXPERT 1411 depends on PCI 1412 help 1413 This enables workarounds for various PCI chipset 1414 bugs/quirks. Disable this only if your target machine is 1415 unaffected by PCI quirks. 1416 1417config SLUB_DEBUG 1418 default y 1419 bool "Enable SLUB debugging support" if EXPERT 1420 depends on SLUB && SYSFS 1421 help 1422 SLUB has extensive debug support features. Disabling these can 1423 result in significant savings in code size. This also disables 1424 SLUB sysfs support. /sys/slab will not exist and there will be 1425 no support for cache validation etc. 1426 1427config COMPAT_BRK 1428 bool "Disable heap randomization" 1429 default y 1430 help 1431 Randomizing heap placement makes heap exploits harder, but it 1432 also breaks ancient binaries (including anything libc5 based). 1433 This option changes the bootup default to heap randomization 1434 disabled, and can be overridden at runtime by setting 1435 /proc/sys/kernel/randomize_va_space to 2. 1436 1437 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1438 1439choice 1440 prompt "Choose SLAB allocator" 1441 default SLUB 1442 help 1443 This option allows to select a slab allocator. 1444 1445config SLAB 1446 bool "SLAB" 1447 help 1448 The regular slab allocator that is established and known to work 1449 well in all environments. It organizes cache hot objects in 1450 per cpu and per node queues. 1451 1452config SLUB 1453 bool "SLUB (Unqueued Allocator)" 1454 help 1455 SLUB is a slab allocator that minimizes cache line usage 1456 instead of managing queues of cached objects (SLAB approach). 1457 Per cpu caching is realized using slabs of objects instead 1458 of queues of objects. SLUB can use memory efficiently 1459 and has enhanced diagnostics. SLUB is the default choice for 1460 a slab allocator. 1461 1462config SLOB 1463 depends on EXPERT 1464 bool "SLOB (Simple Allocator)" 1465 help 1466 SLOB replaces the stock allocator with a drastically simpler 1467 allocator. SLOB is generally more space efficient but 1468 does not perform as well on large systems. 1469 1470endchoice 1471 1472config MMAP_ALLOW_UNINITIALIZED 1473 bool "Allow mmapped anonymous memory to be uninitialized" 1474 depends on EXPERT && !MMU 1475 default n 1476 help 1477 Normally, and according to the Linux spec, anonymous memory obtained 1478 from mmap() has it's contents cleared before it is passed to 1479 userspace. Enabling this config option allows you to request that 1480 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1481 providing a huge performance boost. If this option is not enabled, 1482 then the flag will be ignored. 1483 1484 This is taken advantage of by uClibc's malloc(), and also by 1485 ELF-FDPIC binfmt's brk and stack allocator. 1486 1487 Because of the obvious security issues, this option should only be 1488 enabled on embedded devices where you control what is run in 1489 userspace. Since that isn't generally a problem on no-MMU systems, 1490 it is normally safe to say Y here. 1491 1492 See Documentation/nommu-mmap.txt for more information. 1493 1494config PROFILING 1495 bool "Profiling support" 1496 help 1497 Say Y here to enable the extended profiling support mechanisms used 1498 by profilers such as OProfile. 1499 1500# 1501# Place an empty function call at each tracepoint site. Can be 1502# dynamically changed for a probe function. 1503# 1504config TRACEPOINTS 1505 bool 1506 1507source "arch/Kconfig" 1508 1509endmenu # General setup 1510 1511config HAVE_GENERIC_DMA_COHERENT 1512 bool 1513 default n 1514 1515config SLABINFO 1516 bool 1517 depends on PROC_FS 1518 depends on SLAB || SLUB_DEBUG 1519 default y 1520 1521config RT_MUTEXES 1522 boolean 1523 1524config BASE_SMALL 1525 int 1526 default 0 if BASE_FULL 1527 default 1 if !BASE_FULL 1528 1529menuconfig MODULES 1530 bool "Enable loadable module support" 1531 help 1532 Kernel modules are small pieces of compiled code which can 1533 be inserted in the running kernel, rather than being 1534 permanently built into the kernel. You use the "modprobe" 1535 tool to add (and sometimes remove) them. If you say Y here, 1536 many parts of the kernel can be built as modules (by 1537 answering M instead of Y where indicated): this is most 1538 useful for infrequently used options which are not required 1539 for booting. For more information, see the man pages for 1540 modprobe, lsmod, modinfo, insmod and rmmod. 1541 1542 If you say Y here, you will need to run "make 1543 modules_install" to put the modules under /lib/modules/ 1544 where modprobe can find them (you may need to be root to do 1545 this). 1546 1547 If unsure, say Y. 1548 1549if MODULES 1550 1551config MODULE_FORCE_LOAD 1552 bool "Forced module loading" 1553 default n 1554 help 1555 Allow loading of modules without version information (ie. modprobe 1556 --force). Forced module loading sets the 'F' (forced) taint flag and 1557 is usually a really bad idea. 1558 1559config MODULE_UNLOAD 1560 bool "Module unloading" 1561 help 1562 Without this option you will not be able to unload any 1563 modules (note that some modules may not be unloadable 1564 anyway), which makes your kernel smaller, faster 1565 and simpler. If unsure, say Y. 1566 1567config MODULE_FORCE_UNLOAD 1568 bool "Forced module unloading" 1569 depends on MODULE_UNLOAD && EXPERIMENTAL 1570 help 1571 This option allows you to force a module to unload, even if the 1572 kernel believes it is unsafe: the kernel will remove the module 1573 without waiting for anyone to stop using it (using the -f option to 1574 rmmod). This is mainly for kernel developers and desperate users. 1575 If unsure, say N. 1576 1577config MODVERSIONS 1578 bool "Module versioning support" 1579 help 1580 Usually, you have to use modules compiled with your kernel. 1581 Saying Y here makes it sometimes possible to use modules 1582 compiled for different kernels, by adding enough information 1583 to the modules to (hopefully) spot any changes which would 1584 make them incompatible with the kernel you are running. If 1585 unsure, say N. 1586 1587config MODULE_SRCVERSION_ALL 1588 bool "Source checksum for all modules" 1589 help 1590 Modules which contain a MODULE_VERSION get an extra "srcversion" 1591 field inserted into their modinfo section, which contains a 1592 sum of the source files which made it. This helps maintainers 1593 see exactly which source was used to build a module (since 1594 others sometimes change the module source without updating 1595 the version). With this option, such a "srcversion" field 1596 will be created for all modules. If unsure, say N. 1597 1598config MODULE_SIG 1599 bool "Module signature verification" 1600 depends on MODULES 1601 select KEYS 1602 select CRYPTO 1603 select ASYMMETRIC_KEY_TYPE 1604 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1605 select PUBLIC_KEY_ALGO_RSA 1606 select ASN1 1607 select OID_REGISTRY 1608 select X509_CERTIFICATE_PARSER 1609 help 1610 Check modules for valid signatures upon load: the signature 1611 is simply appended to the module. For more information see 1612 Documentation/module-signing.txt. 1613 1614 !!!WARNING!!! If you enable this option, you MUST make sure that the 1615 module DOES NOT get stripped after being signed. This includes the 1616 debuginfo strip done by some packagers (such as rpmbuild) and 1617 inclusion into an initramfs that wants the module size reduced. 1618 1619config MODULE_SIG_FORCE 1620 bool "Require modules to be validly signed" 1621 depends on MODULE_SIG 1622 help 1623 Reject unsigned modules or signed modules for which we don't have a 1624 key. Without this, such modules will simply taint the kernel. 1625 1626choice 1627 prompt "Which hash algorithm should modules be signed with?" 1628 depends on MODULE_SIG 1629 help 1630 This determines which sort of hashing algorithm will be used during 1631 signature generation. This algorithm _must_ be built into the kernel 1632 directly so that signature verification can take place. It is not 1633 possible to load a signed module containing the algorithm to check 1634 the signature on that module. 1635 1636config MODULE_SIG_SHA1 1637 bool "Sign modules with SHA-1" 1638 select CRYPTO_SHA1 1639 1640config MODULE_SIG_SHA224 1641 bool "Sign modules with SHA-224" 1642 select CRYPTO_SHA256 1643 1644config MODULE_SIG_SHA256 1645 bool "Sign modules with SHA-256" 1646 select CRYPTO_SHA256 1647 1648config MODULE_SIG_SHA384 1649 bool "Sign modules with SHA-384" 1650 select CRYPTO_SHA512 1651 1652config MODULE_SIG_SHA512 1653 bool "Sign modules with SHA-512" 1654 select CRYPTO_SHA512 1655 1656endchoice 1657 1658endif # MODULES 1659 1660config INIT_ALL_POSSIBLE 1661 bool 1662 help 1663 Back when each arch used to define their own cpu_online_mask and 1664 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 1665 with all 1s, and others with all 0s. When they were centralised, 1666 it was better to provide this option than to break all the archs 1667 and have several arch maintainers pursuing me down dark alleys. 1668 1669config STOP_MACHINE 1670 bool 1671 default y 1672 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU 1673 help 1674 Need stop_machine() primitive. 1675 1676source "block/Kconfig" 1677 1678config PREEMPT_NOTIFIERS 1679 bool 1680 1681config PADATA 1682 depends on SMP 1683 bool 1684 1685# Can be selected by architectures with broken toolchains 1686# that get confused by correct const<->read_only section 1687# mappings 1688config BROKEN_RODATA 1689 bool 1690 1691config ASN1 1692 tristate 1693 help 1694 Build a simple ASN.1 grammar compiler that produces a bytecode output 1695 that can be interpreted by the ASN.1 stream decoder and used to 1696 inform it as to what tags are to be expected in a stream and what 1697 functions to call on what tags. 1698 1699source "kernel/Kconfig.locks" 1700