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 DEBUG_PREEMPT 209 bool "Debug preemptible kernel" 210 depends on DEBUG_KERNEL && PREEMPT && (TRACE_IRQFLAGS_SUPPORT || PPC64) 211 default y 212 help 213 If you say Y here then the kernel will use a debug variant of the 214 commonly used smp_processor_id() function and will print warnings 215 if kernel code uses it in a preemption-unsafe way. Also, the kernel 216 will detect preemption count underflows. 217 218config DEBUG_RT_MUTEXES 219 bool "RT Mutex debugging, deadlock detection" 220 depends on DEBUG_KERNEL && RT_MUTEXES 221 help 222 This allows rt mutex semantics violations and rt mutex related 223 deadlocks (lockups) to be detected and reported automatically. 224 225config DEBUG_PI_LIST 226 bool 227 default y 228 depends on DEBUG_RT_MUTEXES 229 230config RT_MUTEX_TESTER 231 bool "Built-in scriptable tester for rt-mutexes" 232 depends on DEBUG_KERNEL && RT_MUTEXES 233 help 234 This option enables a rt-mutex tester. 235 236config DEBUG_SPINLOCK 237 bool "Spinlock and rw-lock debugging: basic checks" 238 depends on DEBUG_KERNEL 239 help 240 Say Y here and build SMP to catch missing spinlock initialization 241 and certain other kinds of spinlock errors commonly made. This is 242 best used in conjunction with the NMI watchdog so that spinlock 243 deadlocks are also debuggable. 244 245config DEBUG_MUTEXES 246 bool "Mutex debugging: basic checks" 247 depends on DEBUG_KERNEL 248 help 249 This feature allows mutex semantics violations to be detected and 250 reported. 251 252config DEBUG_SEMAPHORE 253 bool "Semaphore debugging" 254 depends on DEBUG_KERNEL 255 depends on ALPHA || FRV 256 default n 257 help 258 If you say Y here then semaphore processing will issue lots of 259 verbose debugging messages. If you suspect a semaphore problem or a 260 kernel hacker asks for this option then say Y. Otherwise say N. 261 262config DEBUG_LOCK_ALLOC 263 bool "Lock debugging: detect incorrect freeing of live locks" 264 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 265 select DEBUG_SPINLOCK 266 select DEBUG_MUTEXES 267 select LOCKDEP 268 help 269 This feature will check whether any held lock (spinlock, rwlock, 270 mutex or rwsem) is incorrectly freed by the kernel, via any of the 271 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 272 vfree(), etc.), whether a live lock is incorrectly reinitialized via 273 spin_lock_init()/mutex_init()/etc., or whether there is any lock 274 held during task exit. 275 276config PROVE_LOCKING 277 bool "Lock debugging: prove locking correctness" 278 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 279 select LOCKDEP 280 select DEBUG_SPINLOCK 281 select DEBUG_MUTEXES 282 select DEBUG_LOCK_ALLOC 283 default n 284 help 285 This feature enables the kernel to prove that all locking 286 that occurs in the kernel runtime is mathematically 287 correct: that under no circumstance could an arbitrary (and 288 not yet triggered) combination of observed locking 289 sequences (on an arbitrary number of CPUs, running an 290 arbitrary number of tasks and interrupt contexts) cause a 291 deadlock. 292 293 In short, this feature enables the kernel to report locking 294 related deadlocks before they actually occur. 295 296 The proof does not depend on how hard and complex a 297 deadlock scenario would be to trigger: how many 298 participant CPUs, tasks and irq-contexts would be needed 299 for it to trigger. The proof also does not depend on 300 timing: if a race and a resulting deadlock is possible 301 theoretically (no matter how unlikely the race scenario 302 is), it will be proven so and will immediately be 303 reported by the kernel (once the event is observed that 304 makes the deadlock theoretically possible). 305 306 If a deadlock is impossible (i.e. the locking rules, as 307 observed by the kernel, are mathematically correct), the 308 kernel reports nothing. 309 310 NOTE: this feature can also be enabled for rwlocks, mutexes 311 and rwsems - in which case all dependencies between these 312 different locking variants are observed and mapped too, and 313 the proof of observed correctness is also maintained for an 314 arbitrary combination of these separate locking variants. 315 316 For more details, see Documentation/lockdep-design.txt. 317 318config LOCKDEP 319 bool 320 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 321 select STACKTRACE 322 select FRAME_POINTER if !X86 && !MIPS 323 select KALLSYMS 324 select KALLSYMS_ALL 325 326config LOCK_STAT 327 bool "Lock usage statistics" 328 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 329 select LOCKDEP 330 select DEBUG_SPINLOCK 331 select DEBUG_MUTEXES 332 select DEBUG_LOCK_ALLOC 333 default n 334 help 335 This feature enables tracking lock contention points 336 337 For more details, see Documentation/lockstat.txt 338 339config DEBUG_LOCKDEP 340 bool "Lock dependency engine debugging" 341 depends on DEBUG_KERNEL && LOCKDEP 342 help 343 If you say Y here, the lock dependency engine will do 344 additional runtime checks to debug itself, at the price 345 of more runtime overhead. 346 347config TRACE_IRQFLAGS 348 depends on DEBUG_KERNEL 349 bool 350 default y 351 depends on TRACE_IRQFLAGS_SUPPORT 352 depends on PROVE_LOCKING 353 354config DEBUG_SPINLOCK_SLEEP 355 bool "Spinlock debugging: sleep-inside-spinlock checking" 356 depends on DEBUG_KERNEL 357 help 358 If you say Y here, various routines which may sleep will become very 359 noisy if they are called with a spinlock held. 360 361config DEBUG_LOCKING_API_SELFTESTS 362 bool "Locking API boot-time self-tests" 363 depends on DEBUG_KERNEL 364 help 365 Say Y here if you want the kernel to run a short self-test during 366 bootup. The self-test checks whether common types of locking bugs 367 are detected by debugging mechanisms or not. (if you disable 368 lock debugging then those bugs wont be detected of course.) 369 The following locking APIs are covered: spinlocks, rwlocks, 370 mutexes and rwsems. 371 372config STACKTRACE 373 bool 374 depends on DEBUG_KERNEL 375 depends on STACKTRACE_SUPPORT 376 377config DEBUG_KOBJECT 378 bool "kobject debugging" 379 depends on DEBUG_KERNEL 380 help 381 If you say Y here, some extra kobject debugging messages will be sent 382 to the syslog. 383 384config DEBUG_HIGHMEM 385 bool "Highmem debugging" 386 depends on DEBUG_KERNEL && HIGHMEM 387 help 388 This options enables addition error checking for high memory systems. 389 Disable for production systems. 390 391config DEBUG_BUGVERBOSE 392 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED 393 depends on BUG 394 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || FRV || SUPERH || GENERIC_BUG || BLACKFIN 395 default !EMBEDDED 396 help 397 Say Y here to make BUG() panics output the file name and line number 398 of the BUG call as well as the EIP and oops trace. This aids 399 debugging but costs about 70-100K of memory. 400 401config DEBUG_INFO 402 bool "Compile the kernel with debug info" 403 depends on DEBUG_KERNEL 404 help 405 If you say Y here the resulting kernel image will include 406 debugging info resulting in a larger kernel image. 407 This adds debug symbols to the kernel and modules (gcc -g), and 408 is needed if you intend to use kernel crashdump or binary object 409 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 410 Say Y here only if you plan to debug the kernel. 411 412 If unsure, say N. 413 414config DEBUG_VM 415 bool "Debug VM" 416 depends on DEBUG_KERNEL 417 help 418 Enable this to turn on extended checks in the virtual-memory system 419 that may impact performance. 420 421 If unsure, say N. 422 423config DEBUG_LIST 424 bool "Debug linked list manipulation" 425 depends on DEBUG_KERNEL 426 help 427 Enable this to turn on extended checks in the linked-list 428 walking routines. 429 430 If unsure, say N. 431 432config DEBUG_SG 433 bool "Debug SG table operations" 434 depends on DEBUG_KERNEL 435 help 436 Enable this to turn on checks on scatter-gather tables. This can 437 help find problems with drivers that do not properly initialize 438 their sg tables. 439 440 If unsure, say N. 441 442config FRAME_POINTER 443 bool "Compile the kernel with frame pointers" 444 depends on DEBUG_KERNEL && (X86 || CRIS || M68K || M68KNOMMU || FRV || UML || S390 || AVR32 || SUPERH || BLACKFIN) 445 default y if DEBUG_INFO && UML 446 help 447 If you say Y here the resulting kernel image will be slightly larger 448 and slower, but it might give very useful debugging information on 449 some architectures or if you use external debuggers. 450 If you don't debug the kernel, you can say N. 451 452config FORCED_INLINING 453 bool "Force gcc to inline functions marked 'inline'" 454 depends on DEBUG_KERNEL 455 default y 456 help 457 This option determines if the kernel forces gcc to inline the functions 458 developers have marked 'inline'. Doing so takes away freedom from gcc to 459 do what it thinks is best, which is desirable for the gcc 3.x series of 460 compilers. The gcc 4.x series have a rewritten inlining algorithm and 461 disabling this option will generate a smaller kernel there. Hopefully 462 this algorithm is so good that allowing gcc4 to make the decision can 463 become the default in the future, until then this option is there to 464 test gcc for this. 465 466config BOOT_PRINTK_DELAY 467 bool "Delay each boot printk message by N milliseconds" 468 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 469 help 470 This build option allows you to read kernel boot messages 471 by inserting a short delay after each one. The delay is 472 specified in milliseconds on the kernel command line, 473 using "boot_delay=N". 474 475 It is likely that you would also need to use "lpj=M" to preset 476 the "loops per jiffie" value. 477 See a previous boot log for the "lpj" value to use for your 478 system, and then set "lpj=M" before setting "boot_delay=N". 479 NOTE: Using this option may adversely affect SMP systems. 480 I.e., processors other than the first one may not boot up. 481 BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect 482 what it believes to be lockup conditions. 483 484config RCU_TORTURE_TEST 485 tristate "torture tests for RCU" 486 depends on DEBUG_KERNEL 487 depends on m 488 default n 489 help 490 This option provides a kernel module that runs torture tests 491 on the RCU infrastructure. The kernel module may be built 492 after the fact on the running kernel to be tested, if desired. 493 494 Say M if you want the RCU torture tests to build as a module. 495 Say N if you are unsure. 496 497config KPROBES_SANITY_TEST 498 bool "Kprobes sanity tests" 499 depends on DEBUG_KERNEL 500 depends on KPROBES 501 default n 502 help 503 This option provides for testing basic kprobes functionality on 504 boot. A sample kprobe, jprobe and kretprobe are inserted and 505 verified for functionality. 506 507 Say N if you are unsure. 508 509config BACKTRACE_SELF_TEST 510 tristate "Self test for the backtrace code" 511 depends on DEBUG_KERNEL 512 default n 513 help 514 This option provides a kernel module that can be used to test 515 the kernel stack backtrace code. This option is not useful 516 for distributions or general kernels, but only for kernel 517 developers working on architecture code. 518 519 Say N if you are unsure. 520 521config LKDTM 522 tristate "Linux Kernel Dump Test Tool Module" 523 depends on DEBUG_KERNEL 524 depends on KPROBES 525 default n 526 help 527 This module enables testing of the different dumping mechanisms by 528 inducing system failures at predefined crash points. 529 If you don't need it: say N 530 Choose M here to compile this code as a module. The module will be 531 called lkdtm. 532 533 Documentation on how to use the module can be found in 534 drivers/misc/lkdtm.c 535 536config FAULT_INJECTION 537 bool "Fault-injection framework" 538 depends on DEBUG_KERNEL 539 help 540 Provide fault-injection framework. 541 For more details, see Documentation/fault-injection/. 542 543config FAILSLAB 544 bool "Fault-injection capability for kmalloc" 545 depends on FAULT_INJECTION 546 help 547 Provide fault-injection capability for kmalloc. 548 549config FAIL_PAGE_ALLOC 550 bool "Fault-injection capabilitiy for alloc_pages()" 551 depends on FAULT_INJECTION 552 help 553 Provide fault-injection capability for alloc_pages(). 554 555config FAIL_MAKE_REQUEST 556 bool "Fault-injection capability for disk IO" 557 depends on FAULT_INJECTION 558 help 559 Provide fault-injection capability for disk IO. 560 561config FAULT_INJECTION_DEBUG_FS 562 bool "Debugfs entries for fault-injection capabilities" 563 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 564 help 565 Enable configuration of fault-injection capabilities via debugfs. 566 567config FAULT_INJECTION_STACKTRACE_FILTER 568 bool "stacktrace filter for fault-injection capabilities" 569 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 570 depends on !X86_64 571 select STACKTRACE 572 select FRAME_POINTER 573 help 574 Provide stacktrace filter for fault-injection capabilities 575 576config LATENCYTOP 577 bool "Latency measuring infrastructure" 578 select FRAME_POINTER if !MIPS 579 select KALLSYMS 580 select KALLSYMS_ALL 581 select STACKTRACE 582 select SCHEDSTATS 583 select SCHED_DEBUG 584 depends on HAVE_LATENCYTOP_SUPPORT 585 help 586 Enable this option if you want to use the LatencyTOP tool 587 to find out which userspace is blocking on what kernel operations. 588 589config PROVIDE_OHCI1394_DMA_INIT 590 bool "Provide code for enabling DMA over FireWire early on boot" 591 depends on PCI && X86 592 help 593 If you want to debug problems which hang or crash the kernel early 594 on boot and the crashing machine has a FireWire port, you can use 595 this feature to remotely access the memory of the crashed machine 596 over FireWire. This employs remote DMA as part of the OHCI1394 597 specification which is now the standard for FireWire controllers. 598 599 With remote DMA, you can monitor the printk buffer remotely using 600 firescope and access all memory below 4GB using fireproxy from gdb. 601 Even controlling a kernel debugger is possible using remote DMA. 602 603 Usage: 604 605 If ohci1394_dma=early is used as boot parameter, it will initialize 606 all OHCI1394 controllers which are found in the PCI config space. 607 608 As all changes to the FireWire bus such as enabling and disabling 609 devices cause a bus reset and thereby disable remote DMA for all 610 devices, be sure to have the cable plugged and FireWire enabled on 611 the debugging host before booting the debug target for debugging. 612 613 This code (~1k) is freed after boot. By then, the firewire stack 614 in charge of the OHCI-1394 controllers should be used instead. 615 616 See Documentation/debugging-via-ohci1394.txt for more information. 617 618source "samples/Kconfig" 619