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 # This option is on purpose disabled for now. 86 # It will be enabled when we are down to a resonable number 87 # of section mismatch warnings (< 10 for an allyesconfig build) 88 help 89 The section mismatch analysis checks if there are illegal 90 references from one section to another section. 91 Linux will during link or during runtime drop some sections 92 and any use of code/data previously in these sections will 93 most likely result in an oops. 94 In the code functions and variables are annotated with 95 __init, __devinit etc. (see full list in include/linux/init.h) 96 which results in the code/data being placed in specific sections. 97 The section mismatch analysis is always done after a full 98 kernel build but enabling this option will in addition 99 do the following: 100 - Add the option -fno-inline-functions-called-once to gcc 101 When inlining a function annotated __init in a non-init 102 function we would lose the section information and thus 103 the analysis would not catch the illegal reference. 104 This option tells gcc to inline less but will also 105 result in a larger kernel. 106 - Run the section mismatch analysis for each module/built-in.o 107 When we run the section mismatch analysis on vmlinux.o we 108 lose valueble information about where the mismatch was 109 introduced. 110 Running the analysis for each module/built-in.o file 111 will tell where the mismatch happens much closer to the 112 source. The drawback is that we will report the same 113 mismatch at least twice. 114 - Enable verbose reporting from modpost to help solving 115 the section mismatches reported. 116 117config DEBUG_KERNEL 118 bool "Kernel debugging" 119 help 120 Say Y here if you are developing drivers or trying to debug and 121 identify kernel problems. 122 123config DEBUG_SHIRQ 124 bool "Debug shared IRQ handlers" 125 depends on DEBUG_KERNEL && GENERIC_HARDIRQS 126 help 127 Enable this to generate a spurious interrupt as soon as a shared 128 interrupt handler is registered, and just before one is deregistered. 129 Drivers ought to be able to handle interrupts coming in at those 130 points; some don't and need to be caught. 131 132config DETECT_SOFTLOCKUP 133 bool "Detect Soft Lockups" 134 depends on DEBUG_KERNEL && !S390 135 default y 136 help 137 Say Y here to enable the kernel to detect "soft lockups", 138 which are bugs that cause the kernel to loop in kernel 139 mode for more than 10 seconds, without giving other tasks a 140 chance to run. 141 142 When a soft-lockup is detected, the kernel will print the 143 current stack trace (which you should report), but the 144 system will stay locked up. This feature has negligible 145 overhead. 146 147 (Note that "hard lockups" are separate type of bugs that 148 can be detected via the NMI-watchdog, on platforms that 149 support it.) 150 151config SCHED_DEBUG 152 bool "Collect scheduler debugging info" 153 depends on DEBUG_KERNEL && PROC_FS 154 default y 155 help 156 If you say Y here, the /proc/sched_debug file will be provided 157 that can help debug the scheduler. The runtime overhead of this 158 option is minimal. 159 160config SCHEDSTATS 161 bool "Collect scheduler statistics" 162 depends on DEBUG_KERNEL && PROC_FS 163 help 164 If you say Y here, additional code will be inserted into the 165 scheduler and related routines to collect statistics about 166 scheduler behavior and provide them in /proc/schedstat. These 167 stats may be useful for both tuning and debugging the scheduler 168 If you aren't debugging the scheduler or trying to tune a specific 169 application, you can say N to avoid the very slight overhead 170 this adds. 171 172config TIMER_STATS 173 bool "Collect kernel timers statistics" 174 depends on DEBUG_KERNEL && PROC_FS 175 help 176 If you say Y here, additional code will be inserted into the 177 timer routines to collect statistics about kernel timers being 178 reprogrammed. The statistics can be read from /proc/timer_stats. 179 The statistics collection is started by writing 1 to /proc/timer_stats, 180 writing 0 stops it. This feature is useful to collect information 181 about timer usage patterns in kernel and userspace. This feature 182 is lightweight if enabled in the kernel config but not activated 183 (it defaults to deactivated on bootup and will only be activated 184 if some application like powertop activates it explicitly). 185 186config DEBUG_SLAB 187 bool "Debug slab memory allocations" 188 depends on DEBUG_KERNEL && SLAB 189 help 190 Say Y here to have the kernel do limited verification on memory 191 allocation as well as poisoning memory on free to catch use of freed 192 memory. This can make kmalloc/kfree-intensive workloads much slower. 193 194config DEBUG_SLAB_LEAK 195 bool "Memory leak debugging" 196 depends on DEBUG_SLAB 197 198config SLUB_DEBUG_ON 199 bool "SLUB debugging on by default" 200 depends on SLUB && SLUB_DEBUG 201 default n 202 help 203 Boot with debugging on by default. SLUB boots by default with 204 the runtime debug capabilities switched off. Enabling this is 205 equivalent to specifying the "slub_debug" parameter on boot. 206 There is no support for more fine grained debug control like 207 possible with slub_debug=xxx. SLUB debugging may be switched 208 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 209 "slub_debug=-". 210 211config SLUB_STATS 212 default n 213 bool "Enable SLUB performance statistics" 214 depends on SLUB 215 help 216 SLUB statistics are useful to debug SLUBs allocation behavior in 217 order find ways to optimize the allocator. This should never be 218 enabled for production use since keeping statistics slows down 219 the allocator by a few percentage points. The slabinfo command 220 supports the determination of the most active slabs to figure 221 out which slabs are relevant to a particular load. 222 Try running: slabinfo -DA 223 224config DEBUG_PREEMPT 225 bool "Debug preemptible kernel" 226 depends on DEBUG_KERNEL && PREEMPT && (TRACE_IRQFLAGS_SUPPORT || PPC64) 227 default y 228 help 229 If you say Y here then the kernel will use a debug variant of the 230 commonly used smp_processor_id() function and will print warnings 231 if kernel code uses it in a preemption-unsafe way. Also, the kernel 232 will detect preemption count underflows. 233 234config DEBUG_RT_MUTEXES 235 bool "RT Mutex debugging, deadlock detection" 236 depends on DEBUG_KERNEL && RT_MUTEXES 237 help 238 This allows rt mutex semantics violations and rt mutex related 239 deadlocks (lockups) to be detected and reported automatically. 240 241config DEBUG_PI_LIST 242 bool 243 default y 244 depends on DEBUG_RT_MUTEXES 245 246config RT_MUTEX_TESTER 247 bool "Built-in scriptable tester for rt-mutexes" 248 depends on DEBUG_KERNEL && RT_MUTEXES 249 help 250 This option enables a rt-mutex tester. 251 252config DEBUG_SPINLOCK 253 bool "Spinlock and rw-lock debugging: basic checks" 254 depends on DEBUG_KERNEL 255 help 256 Say Y here and build SMP to catch missing spinlock initialization 257 and certain other kinds of spinlock errors commonly made. This is 258 best used in conjunction with the NMI watchdog so that spinlock 259 deadlocks are also debuggable. 260 261config DEBUG_MUTEXES 262 bool "Mutex debugging: basic checks" 263 depends on DEBUG_KERNEL 264 help 265 This feature allows mutex semantics violations to be detected and 266 reported. 267 268config DEBUG_SEMAPHORE 269 bool "Semaphore debugging" 270 depends on DEBUG_KERNEL 271 depends on ALPHA || FRV 272 default n 273 help 274 If you say Y here then semaphore processing will issue lots of 275 verbose debugging messages. If you suspect a semaphore problem or a 276 kernel hacker asks for this option then say Y. Otherwise say N. 277 278config DEBUG_LOCK_ALLOC 279 bool "Lock debugging: detect incorrect freeing of live locks" 280 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 281 select DEBUG_SPINLOCK 282 select DEBUG_MUTEXES 283 select LOCKDEP 284 help 285 This feature will check whether any held lock (spinlock, rwlock, 286 mutex or rwsem) is incorrectly freed by the kernel, via any of the 287 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 288 vfree(), etc.), whether a live lock is incorrectly reinitialized via 289 spin_lock_init()/mutex_init()/etc., or whether there is any lock 290 held during task exit. 291 292config PROVE_LOCKING 293 bool "Lock debugging: prove locking correctness" 294 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 295 select LOCKDEP 296 select DEBUG_SPINLOCK 297 select DEBUG_MUTEXES 298 select DEBUG_LOCK_ALLOC 299 default n 300 help 301 This feature enables the kernel to prove that all locking 302 that occurs in the kernel runtime is mathematically 303 correct: that under no circumstance could an arbitrary (and 304 not yet triggered) combination of observed locking 305 sequences (on an arbitrary number of CPUs, running an 306 arbitrary number of tasks and interrupt contexts) cause a 307 deadlock. 308 309 In short, this feature enables the kernel to report locking 310 related deadlocks before they actually occur. 311 312 The proof does not depend on how hard and complex a 313 deadlock scenario would be to trigger: how many 314 participant CPUs, tasks and irq-contexts would be needed 315 for it to trigger. The proof also does not depend on 316 timing: if a race and a resulting deadlock is possible 317 theoretically (no matter how unlikely the race scenario 318 is), it will be proven so and will immediately be 319 reported by the kernel (once the event is observed that 320 makes the deadlock theoretically possible). 321 322 If a deadlock is impossible (i.e. the locking rules, as 323 observed by the kernel, are mathematically correct), the 324 kernel reports nothing. 325 326 NOTE: this feature can also be enabled for rwlocks, mutexes 327 and rwsems - in which case all dependencies between these 328 different locking variants are observed and mapped too, and 329 the proof of observed correctness is also maintained for an 330 arbitrary combination of these separate locking variants. 331 332 For more details, see Documentation/lockdep-design.txt. 333 334config LOCKDEP 335 bool 336 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 337 select STACKTRACE 338 select FRAME_POINTER if !X86 && !MIPS 339 select KALLSYMS 340 select KALLSYMS_ALL 341 342config LOCK_STAT 343 bool "Lock usage statistics" 344 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 345 select LOCKDEP 346 select DEBUG_SPINLOCK 347 select DEBUG_MUTEXES 348 select DEBUG_LOCK_ALLOC 349 default n 350 help 351 This feature enables tracking lock contention points 352 353 For more details, see Documentation/lockstat.txt 354 355config DEBUG_LOCKDEP 356 bool "Lock dependency engine debugging" 357 depends on DEBUG_KERNEL && LOCKDEP 358 help 359 If you say Y here, the lock dependency engine will do 360 additional runtime checks to debug itself, at the price 361 of more runtime overhead. 362 363config TRACE_IRQFLAGS 364 depends on DEBUG_KERNEL 365 bool 366 default y 367 depends on TRACE_IRQFLAGS_SUPPORT 368 depends on PROVE_LOCKING 369 370config DEBUG_SPINLOCK_SLEEP 371 bool "Spinlock debugging: sleep-inside-spinlock checking" 372 depends on DEBUG_KERNEL 373 help 374 If you say Y here, various routines which may sleep will become very 375 noisy if they are called with a spinlock held. 376 377config DEBUG_LOCKING_API_SELFTESTS 378 bool "Locking API boot-time self-tests" 379 depends on DEBUG_KERNEL 380 help 381 Say Y here if you want the kernel to run a short self-test during 382 bootup. The self-test checks whether common types of locking bugs 383 are detected by debugging mechanisms or not. (if you disable 384 lock debugging then those bugs wont be detected of course.) 385 The following locking APIs are covered: spinlocks, rwlocks, 386 mutexes and rwsems. 387 388config STACKTRACE 389 bool 390 depends on DEBUG_KERNEL 391 depends on STACKTRACE_SUPPORT 392 393config DEBUG_KOBJECT 394 bool "kobject debugging" 395 depends on DEBUG_KERNEL 396 help 397 If you say Y here, some extra kobject debugging messages will be sent 398 to the syslog. 399 400config DEBUG_HIGHMEM 401 bool "Highmem debugging" 402 depends on DEBUG_KERNEL && HIGHMEM 403 help 404 This options enables addition error checking for high memory systems. 405 Disable for production systems. 406 407config DEBUG_BUGVERBOSE 408 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED 409 depends on BUG 410 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \ 411 FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300 412 default !EMBEDDED 413 help 414 Say Y here to make BUG() panics output the file name and line number 415 of the BUG call as well as the EIP and oops trace. This aids 416 debugging but costs about 70-100K of memory. 417 418config DEBUG_INFO 419 bool "Compile the kernel with debug info" 420 depends on DEBUG_KERNEL 421 help 422 If you say Y here the resulting kernel image will include 423 debugging info resulting in a larger kernel image. 424 This adds debug symbols to the kernel and modules (gcc -g), and 425 is needed if you intend to use kernel crashdump or binary object 426 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 427 Say Y here only if you plan to debug the kernel. 428 429 If unsure, say N. 430 431config DEBUG_VM 432 bool "Debug VM" 433 depends on DEBUG_KERNEL 434 help 435 Enable this to turn on extended checks in the virtual-memory system 436 that may impact performance. 437 438 If unsure, say N. 439 440config DEBUG_LIST 441 bool "Debug linked list manipulation" 442 depends on DEBUG_KERNEL 443 help 444 Enable this to turn on extended checks in the linked-list 445 walking routines. 446 447 If unsure, say N. 448 449config DEBUG_SG 450 bool "Debug SG table operations" 451 depends on DEBUG_KERNEL 452 help 453 Enable this to turn on checks on scatter-gather tables. This can 454 help find problems with drivers that do not properly initialize 455 their sg tables. 456 457 If unsure, say N. 458 459config FRAME_POINTER 460 bool "Compile the kernel with frame pointers" 461 depends on DEBUG_KERNEL && \ 462 (X86 || CRIS || M68K || M68KNOMMU || FRV || UML || S390 || \ 463 AVR32 || SUPERH || BLACKFIN || MN10300) 464 default y if DEBUG_INFO && UML 465 help 466 If you say Y here the resulting kernel image will be slightly larger 467 and slower, but it might give very useful debugging information on 468 some architectures or if you use external debuggers. 469 If you don't debug the kernel, you can say N. 470 471config BOOT_PRINTK_DELAY 472 bool "Delay each boot printk message by N milliseconds" 473 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 474 help 475 This build option allows you to read kernel boot messages 476 by inserting a short delay after each one. The delay is 477 specified in milliseconds on the kernel command line, 478 using "boot_delay=N". 479 480 It is likely that you would also need to use "lpj=M" to preset 481 the "loops per jiffie" value. 482 See a previous boot log for the "lpj" value to use for your 483 system, and then set "lpj=M" before setting "boot_delay=N". 484 NOTE: Using this option may adversely affect SMP systems. 485 I.e., processors other than the first one may not boot up. 486 BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect 487 what it believes to be lockup conditions. 488 489config RCU_TORTURE_TEST 490 tristate "torture tests for RCU" 491 depends on DEBUG_KERNEL 492 depends on m 493 default n 494 help 495 This option provides a kernel module that runs torture tests 496 on the RCU infrastructure. The kernel module may be built 497 after the fact on the running kernel to be tested, if desired. 498 499 Say M if you want the RCU torture tests to build as a module. 500 Say N if you are unsure. 501 502config KPROBES_SANITY_TEST 503 bool "Kprobes sanity tests" 504 depends on DEBUG_KERNEL 505 depends on KPROBES 506 default n 507 help 508 This option provides for testing basic kprobes functionality on 509 boot. A sample kprobe, jprobe and kretprobe are inserted and 510 verified for functionality. 511 512 Say N if you are unsure. 513 514config BACKTRACE_SELF_TEST 515 tristate "Self test for the backtrace code" 516 depends on DEBUG_KERNEL 517 default n 518 help 519 This option provides a kernel module that can be used to test 520 the kernel stack backtrace code. This option is not useful 521 for distributions or general kernels, but only for kernel 522 developers working on architecture code. 523 524 Say N if you are unsure. 525 526config LKDTM 527 tristate "Linux Kernel Dump Test Tool Module" 528 depends on DEBUG_KERNEL 529 depends on KPROBES 530 depends on BLOCK 531 default n 532 help 533 This module enables testing of the different dumping mechanisms by 534 inducing system failures at predefined crash points. 535 If you don't need it: say N 536 Choose M here to compile this code as a module. The module will be 537 called lkdtm. 538 539 Documentation on how to use the module can be found in 540 drivers/misc/lkdtm.c 541 542config FAULT_INJECTION 543 bool "Fault-injection framework" 544 depends on DEBUG_KERNEL 545 help 546 Provide fault-injection framework. 547 For more details, see Documentation/fault-injection/. 548 549config FAILSLAB 550 bool "Fault-injection capability for kmalloc" 551 depends on FAULT_INJECTION 552 help 553 Provide fault-injection capability for kmalloc. 554 555config FAIL_PAGE_ALLOC 556 bool "Fault-injection capabilitiy for alloc_pages()" 557 depends on FAULT_INJECTION 558 help 559 Provide fault-injection capability for alloc_pages(). 560 561config FAIL_MAKE_REQUEST 562 bool "Fault-injection capability for disk IO" 563 depends on FAULT_INJECTION 564 help 565 Provide fault-injection capability for disk IO. 566 567config FAULT_INJECTION_DEBUG_FS 568 bool "Debugfs entries for fault-injection capabilities" 569 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 570 help 571 Enable configuration of fault-injection capabilities via debugfs. 572 573config FAULT_INJECTION_STACKTRACE_FILTER 574 bool "stacktrace filter for fault-injection capabilities" 575 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 576 depends on !X86_64 577 select STACKTRACE 578 select FRAME_POINTER 579 help 580 Provide stacktrace filter for fault-injection capabilities 581 582config LATENCYTOP 583 bool "Latency measuring infrastructure" 584 select FRAME_POINTER if !MIPS 585 select KALLSYMS 586 select KALLSYMS_ALL 587 select STACKTRACE 588 select SCHEDSTATS 589 select SCHED_DEBUG 590 depends on HAVE_LATENCYTOP_SUPPORT 591 help 592 Enable this option if you want to use the LatencyTOP tool 593 to find out which userspace is blocking on what kernel operations. 594 595config PROVIDE_OHCI1394_DMA_INIT 596 bool "Provide code for enabling DMA over FireWire early on boot" 597 depends on PCI && X86 598 help 599 If you want to debug problems which hang or crash the kernel early 600 on boot and the crashing machine has a FireWire port, you can use 601 this feature to remotely access the memory of the crashed machine 602 over FireWire. This employs remote DMA as part of the OHCI1394 603 specification which is now the standard for FireWire controllers. 604 605 With remote DMA, you can monitor the printk buffer remotely using 606 firescope and access all memory below 4GB using fireproxy from gdb. 607 Even controlling a kernel debugger is possible using remote DMA. 608 609 Usage: 610 611 If ohci1394_dma=early is used as boot parameter, it will initialize 612 all OHCI1394 controllers which are found in the PCI config space. 613 614 As all changes to the FireWire bus such as enabling and disabling 615 devices cause a bus reset and thereby disable remote DMA for all 616 devices, be sure to have the cable plugged and FireWire enabled on 617 the debugging host before booting the debug target for debugging. 618 619 This code (~1k) is freed after boot. By then, the firewire stack 620 in charge of the OHCI-1394 controllers should be used instead. 621 622 See Documentation/debugging-via-ohci1394.txt for more information. 623 624source "samples/Kconfig" 625