1 2config PRINTK_TIME 3 bool "Show timing information on printks" 4 depends on PRINTK 5 help 6 Selecting this option causes timing information to be 7 included in printk output. This allows you to measure 8 the interval between kernel operations, including bootup 9 operations. This is useful for identifying long delays 10 in kernel startup. 11 12config ENABLE_WARN_DEPRECATED 13 bool "Enable __deprecated logic" 14 default y 15 help 16 Enable the __deprecated logic in the kernel build. 17 Disable this to suppress the "warning: 'foo' is deprecated 18 (declared at kernel/power/somefile.c:1234)" messages. 19 20config ENABLE_MUST_CHECK 21 bool "Enable __must_check logic" 22 default y 23 help 24 Enable the __must_check logic in the kernel build. Disable this to 25 suppress the "warning: ignoring return value of 'foo', declared with 26 attribute warn_unused_result" messages. 27 28config MAGIC_SYSRQ 29 bool "Magic SysRq key" 30 depends on !UML 31 help 32 If you say Y here, you will have some control over the system even 33 if the system crashes for example during kernel debugging (e.g., you 34 will be able to flush the buffer cache to disk, reboot the system 35 immediately or dump some status information). This is accomplished 36 by pressing various keys while holding SysRq (Alt+PrintScreen). It 37 also works on a serial console (on PC hardware at least), if you 38 send a BREAK and then within 5 seconds a command keypress. The 39 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y 40 unless you really know what this hack does. 41 42config UNUSED_SYMBOLS 43 bool "Enable unused/obsolete exported symbols" 44 default y if X86 45 help 46 Unused but exported symbols make the kernel needlessly bigger. For 47 that reason most of these unused exports will soon be removed. This 48 option is provided temporarily to provide a transition period in case 49 some external kernel module needs one of these symbols anyway. If you 50 encounter such a case in your module, consider if you are actually 51 using the right API. (rationale: since nobody in the kernel is using 52 this in a module, there is a pretty good chance it's actually the 53 wrong interface to use). If you really need the symbol, please send a 54 mail to the linux kernel mailing list mentioning the symbol and why 55 you really need it, and what the merge plan to the mainline kernel for 56 your module is. 57 58config DEBUG_FS 59 bool "Debug Filesystem" 60 depends on SYSFS 61 help 62 debugfs is a virtual file system that kernel developers use to put 63 debugging files into. Enable this option to be able to read and 64 write to these files. 65 66 If unsure, say N. 67 68config HEADERS_CHECK 69 bool "Run 'make headers_check' when building vmlinux" 70 depends on !UML 71 help 72 This option will extract the user-visible kernel headers whenever 73 building the kernel, and will run basic sanity checks on them to 74 ensure that exported files do not attempt to include files which 75 were not exported, etc. 76 77 If you're making modifications to header files which are 78 relevant for userspace, say 'Y', and check the headers 79 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 80 your build tree), to make sure they're suitable. 81 82config DEBUG_SECTION_MISMATCH 83 bool "Enable full Section mismatch analysis" 84 depends on UNDEFINED 85 help 86 The section mismatch analysis checks if there are illegal 87 references from one section to another section. 88 Linux will during link or during runtime drop some sections 89 and any use of code/data previously in these sections will 90 most likely result in an oops. 91 In the code functions and variables are annotated with 92 __init, __devinit etc. (see full list in include/linux/init.h) 93 which results in the code/data being placed in specific sections. 94 The section mismatch analysis is always done after a full 95 kernel build but enabling this option will in addition 96 do the following: 97 - Add the option -fno-inline-functions-called-once to gcc 98 When inlining a function annotated __init in a non-init 99 function we would lose the section information and thus 100 the analysis would not catch the illegal reference. 101 This option tells gcc to inline less but will also 102 result in a larger kernel. 103 - Run the section mismatch analysis for each module/built-in.o 104 When we run the section mismatch analysis on vmlinux.o we 105 lose valueble information about where the mismatch was 106 introduced. 107 Running the analysis for each module/built-in.o file 108 will tell where the mismatch happens much closer to the 109 source. The drawback is that we will report the same 110 mismatch at least twice. 111 - Enable verbose reporting from modpost to help solving 112 the section mismatches reported. 113 114config DEBUG_KERNEL 115 bool "Kernel debugging" 116 help 117 Say Y here if you are developing drivers or trying to debug and 118 identify kernel problems. 119 120config DEBUG_SHIRQ 121 bool "Debug shared IRQ handlers" 122 depends on DEBUG_KERNEL && GENERIC_HARDIRQS 123 help 124 Enable this to generate a spurious interrupt as soon as a shared 125 interrupt handler is registered, and just before one is deregistered. 126 Drivers ought to be able to handle interrupts coming in at those 127 points; some don't and need to be caught. 128 129config DETECT_SOFTLOCKUP 130 bool "Detect Soft Lockups" 131 depends on DEBUG_KERNEL && !S390 132 default y 133 help 134 Say Y here to enable the kernel to detect "soft lockups", 135 which are bugs that cause the kernel to loop in kernel 136 mode for more than 10 seconds, without giving other tasks a 137 chance to run. 138 139 When a soft-lockup is detected, the kernel will print the 140 current stack trace (which you should report), but the 141 system will stay locked up. This feature has negligible 142 overhead. 143 144 (Note that "hard lockups" are separate type of bugs that 145 can be detected via the NMI-watchdog, on platforms that 146 support it.) 147 148config SCHED_DEBUG 149 bool "Collect scheduler debugging info" 150 depends on DEBUG_KERNEL && PROC_FS 151 default y 152 help 153 If you say Y here, the /proc/sched_debug file will be provided 154 that can help debug the scheduler. The runtime overhead of this 155 option is minimal. 156 157config SCHEDSTATS 158 bool "Collect scheduler statistics" 159 depends on DEBUG_KERNEL && PROC_FS 160 help 161 If you say Y here, additional code will be inserted into the 162 scheduler and related routines to collect statistics about 163 scheduler behavior and provide them in /proc/schedstat. These 164 stats may be useful for both tuning and debugging the scheduler 165 If you aren't debugging the scheduler or trying to tune a specific 166 application, you can say N to avoid the very slight overhead 167 this adds. 168 169config TIMER_STATS 170 bool "Collect kernel timers statistics" 171 depends on DEBUG_KERNEL && PROC_FS 172 help 173 If you say Y here, additional code will be inserted into the 174 timer routines to collect statistics about kernel timers being 175 reprogrammed. The statistics can be read from /proc/timer_stats. 176 The statistics collection is started by writing 1 to /proc/timer_stats, 177 writing 0 stops it. This feature is useful to collect information 178 about timer usage patterns in kernel and userspace. This feature 179 is lightweight if enabled in the kernel config but not activated 180 (it defaults to deactivated on bootup and will only be activated 181 if some application like powertop activates it explicitly). 182 183config DEBUG_SLAB 184 bool "Debug slab memory allocations" 185 depends on DEBUG_KERNEL && SLAB 186 help 187 Say Y here to have the kernel do limited verification on memory 188 allocation as well as poisoning memory on free to catch use of freed 189 memory. This can make kmalloc/kfree-intensive workloads much slower. 190 191config DEBUG_SLAB_LEAK 192 bool "Memory leak debugging" 193 depends on DEBUG_SLAB 194 195config SLUB_DEBUG_ON 196 bool "SLUB debugging on by default" 197 depends on SLUB && SLUB_DEBUG 198 default n 199 help 200 Boot with debugging on by default. SLUB boots by default with 201 the runtime debug capabilities switched off. Enabling this is 202 equivalent to specifying the "slub_debug" parameter on boot. 203 There is no support for more fine grained debug control like 204 possible with slub_debug=xxx. SLUB debugging may be switched 205 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 206 "slub_debug=-". 207 208config SLUB_STATS 209 default n 210 bool "Enable SLUB performance statistics" 211 depends on SLUB 212 help 213 SLUB statistics are useful to debug SLUBs allocation behavior in 214 order find ways to optimize the allocator. This should never be 215 enabled for production use since keeping statistics slows down 216 the allocator by a few percentage points. The slabinfo command 217 supports the determination of the most active slabs to figure 218 out which slabs are relevant to a particular load. 219 Try running: slabinfo -DA 220 221config DEBUG_PREEMPT 222 bool "Debug preemptible kernel" 223 depends on DEBUG_KERNEL && PREEMPT && (TRACE_IRQFLAGS_SUPPORT || PPC64) 224 default y 225 help 226 If you say Y here then the kernel will use a debug variant of the 227 commonly used smp_processor_id() function and will print warnings 228 if kernel code uses it in a preemption-unsafe way. Also, the kernel 229 will detect preemption count underflows. 230 231config DEBUG_RT_MUTEXES 232 bool "RT Mutex debugging, deadlock detection" 233 depends on DEBUG_KERNEL && RT_MUTEXES 234 help 235 This allows rt mutex semantics violations and rt mutex related 236 deadlocks (lockups) to be detected and reported automatically. 237 238config DEBUG_PI_LIST 239 bool 240 default y 241 depends on DEBUG_RT_MUTEXES 242 243config RT_MUTEX_TESTER 244 bool "Built-in scriptable tester for rt-mutexes" 245 depends on DEBUG_KERNEL && RT_MUTEXES 246 help 247 This option enables a rt-mutex tester. 248 249config DEBUG_SPINLOCK 250 bool "Spinlock and rw-lock debugging: basic checks" 251 depends on DEBUG_KERNEL 252 help 253 Say Y here and build SMP to catch missing spinlock initialization 254 and certain other kinds of spinlock errors commonly made. This is 255 best used in conjunction with the NMI watchdog so that spinlock 256 deadlocks are also debuggable. 257 258config DEBUG_MUTEXES 259 bool "Mutex debugging: basic checks" 260 depends on DEBUG_KERNEL 261 help 262 This feature allows mutex semantics violations to be detected and 263 reported. 264 265config DEBUG_SEMAPHORE 266 bool "Semaphore debugging" 267 depends on DEBUG_KERNEL 268 depends on ALPHA || FRV 269 default n 270 help 271 If you say Y here then semaphore processing will issue lots of 272 verbose debugging messages. If you suspect a semaphore problem or a 273 kernel hacker asks for this option then say Y. Otherwise say N. 274 275config DEBUG_LOCK_ALLOC 276 bool "Lock debugging: detect incorrect freeing of live locks" 277 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 278 select DEBUG_SPINLOCK 279 select DEBUG_MUTEXES 280 select LOCKDEP 281 help 282 This feature will check whether any held lock (spinlock, rwlock, 283 mutex or rwsem) is incorrectly freed by the kernel, via any of the 284 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 285 vfree(), etc.), whether a live lock is incorrectly reinitialized via 286 spin_lock_init()/mutex_init()/etc., or whether there is any lock 287 held during task exit. 288 289config PROVE_LOCKING 290 bool "Lock debugging: prove locking correctness" 291 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 292 select LOCKDEP 293 select DEBUG_SPINLOCK 294 select DEBUG_MUTEXES 295 select DEBUG_LOCK_ALLOC 296 default n 297 help 298 This feature enables the kernel to prove that all locking 299 that occurs in the kernel runtime is mathematically 300 correct: that under no circumstance could an arbitrary (and 301 not yet triggered) combination of observed locking 302 sequences (on an arbitrary number of CPUs, running an 303 arbitrary number of tasks and interrupt contexts) cause a 304 deadlock. 305 306 In short, this feature enables the kernel to report locking 307 related deadlocks before they actually occur. 308 309 The proof does not depend on how hard and complex a 310 deadlock scenario would be to trigger: how many 311 participant CPUs, tasks and irq-contexts would be needed 312 for it to trigger. The proof also does not depend on 313 timing: if a race and a resulting deadlock is possible 314 theoretically (no matter how unlikely the race scenario 315 is), it will be proven so and will immediately be 316 reported by the kernel (once the event is observed that 317 makes the deadlock theoretically possible). 318 319 If a deadlock is impossible (i.e. the locking rules, as 320 observed by the kernel, are mathematically correct), the 321 kernel reports nothing. 322 323 NOTE: this feature can also be enabled for rwlocks, mutexes 324 and rwsems - in which case all dependencies between these 325 different locking variants are observed and mapped too, and 326 the proof of observed correctness is also maintained for an 327 arbitrary combination of these separate locking variants. 328 329 For more details, see Documentation/lockdep-design.txt. 330 331config LOCKDEP 332 bool 333 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 334 select STACKTRACE 335 select FRAME_POINTER if !X86 && !MIPS 336 select KALLSYMS 337 select KALLSYMS_ALL 338 339config LOCK_STAT 340 bool "Lock usage statistics" 341 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 342 select LOCKDEP 343 select DEBUG_SPINLOCK 344 select DEBUG_MUTEXES 345 select DEBUG_LOCK_ALLOC 346 default n 347 help 348 This feature enables tracking lock contention points 349 350 For more details, see Documentation/lockstat.txt 351 352config DEBUG_LOCKDEP 353 bool "Lock dependency engine debugging" 354 depends on DEBUG_KERNEL && LOCKDEP 355 help 356 If you say Y here, the lock dependency engine will do 357 additional runtime checks to debug itself, at the price 358 of more runtime overhead. 359 360config TRACE_IRQFLAGS 361 depends on DEBUG_KERNEL 362 bool 363 default y 364 depends on TRACE_IRQFLAGS_SUPPORT 365 depends on PROVE_LOCKING 366 367config DEBUG_SPINLOCK_SLEEP 368 bool "Spinlock debugging: sleep-inside-spinlock checking" 369 depends on DEBUG_KERNEL 370 help 371 If you say Y here, various routines which may sleep will become very 372 noisy if they are called with a spinlock held. 373 374config DEBUG_LOCKING_API_SELFTESTS 375 bool "Locking API boot-time self-tests" 376 depends on DEBUG_KERNEL 377 help 378 Say Y here if you want the kernel to run a short self-test during 379 bootup. The self-test checks whether common types of locking bugs 380 are detected by debugging mechanisms or not. (if you disable 381 lock debugging then those bugs wont be detected of course.) 382 The following locking APIs are covered: spinlocks, rwlocks, 383 mutexes and rwsems. 384 385config STACKTRACE 386 bool 387 depends on DEBUG_KERNEL 388 depends on STACKTRACE_SUPPORT 389 390config DEBUG_KOBJECT 391 bool "kobject debugging" 392 depends on DEBUG_KERNEL 393 help 394 If you say Y here, some extra kobject debugging messages will be sent 395 to the syslog. 396 397config DEBUG_HIGHMEM 398 bool "Highmem debugging" 399 depends on DEBUG_KERNEL && HIGHMEM 400 help 401 This options enables addition error checking for high memory systems. 402 Disable for production systems. 403 404config DEBUG_BUGVERBOSE 405 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED 406 depends on BUG 407 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \ 408 FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300 409 default !EMBEDDED 410 help 411 Say Y here to make BUG() panics output the file name and line number 412 of the BUG call as well as the EIP and oops trace. This aids 413 debugging but costs about 70-100K of memory. 414 415config DEBUG_INFO 416 bool "Compile the kernel with debug info" 417 depends on DEBUG_KERNEL 418 help 419 If you say Y here the resulting kernel image will include 420 debugging info resulting in a larger kernel image. 421 This adds debug symbols to the kernel and modules (gcc -g), and 422 is needed if you intend to use kernel crashdump or binary object 423 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 424 Say Y here only if you plan to debug the kernel. 425 426 If unsure, say N. 427 428config DEBUG_VM 429 bool "Debug VM" 430 depends on DEBUG_KERNEL 431 help 432 Enable this to turn on extended checks in the virtual-memory system 433 that may impact performance. 434 435 If unsure, say N. 436 437config DEBUG_LIST 438 bool "Debug linked list manipulation" 439 depends on DEBUG_KERNEL 440 help 441 Enable this to turn on extended checks in the linked-list 442 walking routines. 443 444 If unsure, say N. 445 446config DEBUG_SG 447 bool "Debug SG table operations" 448 depends on DEBUG_KERNEL 449 help 450 Enable this to turn on checks on scatter-gather tables. This can 451 help find problems with drivers that do not properly initialize 452 their sg tables. 453 454 If unsure, say N. 455 456config FRAME_POINTER 457 bool "Compile the kernel with frame pointers" 458 depends on DEBUG_KERNEL && \ 459 (X86 || CRIS || M68K || M68KNOMMU || FRV || UML || S390 || \ 460 AVR32 || SUPERH || BLACKFIN || MN10300) 461 default y if DEBUG_INFO && UML 462 help 463 If you say Y here the resulting kernel image will be slightly larger 464 and slower, but it might give very useful debugging information on 465 some architectures or if you use external debuggers. 466 If you don't debug the kernel, you can say N. 467 468config BOOT_PRINTK_DELAY 469 bool "Delay each boot printk message by N milliseconds" 470 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 471 help 472 This build option allows you to read kernel boot messages 473 by inserting a short delay after each one. The delay is 474 specified in milliseconds on the kernel command line, 475 using "boot_delay=N". 476 477 It is likely that you would also need to use "lpj=M" to preset 478 the "loops per jiffie" value. 479 See a previous boot log for the "lpj" value to use for your 480 system, and then set "lpj=M" before setting "boot_delay=N". 481 NOTE: Using this option may adversely affect SMP systems. 482 I.e., processors other than the first one may not boot up. 483 BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect 484 what it believes to be lockup conditions. 485 486config RCU_TORTURE_TEST 487 tristate "torture tests for RCU" 488 depends on DEBUG_KERNEL 489 depends on m 490 default n 491 help 492 This option provides a kernel module that runs torture tests 493 on the RCU infrastructure. The kernel module may be built 494 after the fact on the running kernel to be tested, if desired. 495 496 Say M if you want the RCU torture tests to build as a module. 497 Say N if you are unsure. 498 499config KPROBES_SANITY_TEST 500 bool "Kprobes sanity tests" 501 depends on DEBUG_KERNEL 502 depends on KPROBES 503 default n 504 help 505 This option provides for testing basic kprobes functionality on 506 boot. A sample kprobe, jprobe and kretprobe are inserted and 507 verified for functionality. 508 509 Say N if you are unsure. 510 511config BACKTRACE_SELF_TEST 512 tristate "Self test for the backtrace code" 513 depends on DEBUG_KERNEL 514 default n 515 help 516 This option provides a kernel module that can be used to test 517 the kernel stack backtrace code. This option is not useful 518 for distributions or general kernels, but only for kernel 519 developers working on architecture code. 520 521 Say N if you are unsure. 522 523config LKDTM 524 tristate "Linux Kernel Dump Test Tool Module" 525 depends on DEBUG_KERNEL 526 depends on KPROBES 527 default n 528 help 529 This module enables testing of the different dumping mechanisms by 530 inducing system failures at predefined crash points. 531 If you don't need it: say N 532 Choose M here to compile this code as a module. The module will be 533 called lkdtm. 534 535 Documentation on how to use the module can be found in 536 drivers/misc/lkdtm.c 537 538config FAULT_INJECTION 539 bool "Fault-injection framework" 540 depends on DEBUG_KERNEL 541 help 542 Provide fault-injection framework. 543 For more details, see Documentation/fault-injection/. 544 545config FAILSLAB 546 bool "Fault-injection capability for kmalloc" 547 depends on FAULT_INJECTION 548 help 549 Provide fault-injection capability for kmalloc. 550 551config FAIL_PAGE_ALLOC 552 bool "Fault-injection capabilitiy for alloc_pages()" 553 depends on FAULT_INJECTION 554 help 555 Provide fault-injection capability for alloc_pages(). 556 557config FAIL_MAKE_REQUEST 558 bool "Fault-injection capability for disk IO" 559 depends on FAULT_INJECTION 560 help 561 Provide fault-injection capability for disk IO. 562 563config FAULT_INJECTION_DEBUG_FS 564 bool "Debugfs entries for fault-injection capabilities" 565 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 566 help 567 Enable configuration of fault-injection capabilities via debugfs. 568 569config FAULT_INJECTION_STACKTRACE_FILTER 570 bool "stacktrace filter for fault-injection capabilities" 571 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 572 depends on !X86_64 573 select STACKTRACE 574 select FRAME_POINTER 575 help 576 Provide stacktrace filter for fault-injection capabilities 577 578config LATENCYTOP 579 bool "Latency measuring infrastructure" 580 select FRAME_POINTER if !MIPS 581 select KALLSYMS 582 select KALLSYMS_ALL 583 select STACKTRACE 584 select SCHEDSTATS 585 select SCHED_DEBUG 586 depends on HAVE_LATENCYTOP_SUPPORT 587 help 588 Enable this option if you want to use the LatencyTOP tool 589 to find out which userspace is blocking on what kernel operations. 590 591config PROVIDE_OHCI1394_DMA_INIT 592 bool "Provide code for enabling DMA over FireWire early on boot" 593 depends on PCI && X86 594 help 595 If you want to debug problems which hang or crash the kernel early 596 on boot and the crashing machine has a FireWire port, you can use 597 this feature to remotely access the memory of the crashed machine 598 over FireWire. This employs remote DMA as part of the OHCI1394 599 specification which is now the standard for FireWire controllers. 600 601 With remote DMA, you can monitor the printk buffer remotely using 602 firescope and access all memory below 4GB using fireproxy from gdb. 603 Even controlling a kernel debugger is possible using remote DMA. 604 605 Usage: 606 607 If ohci1394_dma=early is used as boot parameter, it will initialize 608 all OHCI1394 controllers which are found in the PCI config space. 609 610 As all changes to the FireWire bus such as enabling and disabling 611 devices cause a bus reset and thereby disable remote DMA for all 612 devices, be sure to have the cable plugged and FireWire enabled on 613 the debugging host before booting the debug target for debugging. 614 615 This code (~1k) is freed after boot. By then, the firewire stack 616 in charge of the OHCI-1394 controllers should be used instead. 617 618 See Documentation/debugging-via-ohci1394.txt for more information. 619 620source "samples/Kconfig" 621