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 && SLUB_DEBUG && SYSFS 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_LOCK_ALLOC 269 bool "Lock debugging: detect incorrect freeing of live locks" 270 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 271 select DEBUG_SPINLOCK 272 select DEBUG_MUTEXES 273 select LOCKDEP 274 help 275 This feature will check whether any held lock (spinlock, rwlock, 276 mutex or rwsem) is incorrectly freed by the kernel, via any of the 277 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 278 vfree(), etc.), whether a live lock is incorrectly reinitialized via 279 spin_lock_init()/mutex_init()/etc., or whether there is any lock 280 held during task exit. 281 282config PROVE_LOCKING 283 bool "Lock debugging: prove locking correctness" 284 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 285 select LOCKDEP 286 select DEBUG_SPINLOCK 287 select DEBUG_MUTEXES 288 select DEBUG_LOCK_ALLOC 289 default n 290 help 291 This feature enables the kernel to prove that all locking 292 that occurs in the kernel runtime is mathematically 293 correct: that under no circumstance could an arbitrary (and 294 not yet triggered) combination of observed locking 295 sequences (on an arbitrary number of CPUs, running an 296 arbitrary number of tasks and interrupt contexts) cause a 297 deadlock. 298 299 In short, this feature enables the kernel to report locking 300 related deadlocks before they actually occur. 301 302 The proof does not depend on how hard and complex a 303 deadlock scenario would be to trigger: how many 304 participant CPUs, tasks and irq-contexts would be needed 305 for it to trigger. The proof also does not depend on 306 timing: if a race and a resulting deadlock is possible 307 theoretically (no matter how unlikely the race scenario 308 is), it will be proven so and will immediately be 309 reported by the kernel (once the event is observed that 310 makes the deadlock theoretically possible). 311 312 If a deadlock is impossible (i.e. the locking rules, as 313 observed by the kernel, are mathematically correct), the 314 kernel reports nothing. 315 316 NOTE: this feature can also be enabled for rwlocks, mutexes 317 and rwsems - in which case all dependencies between these 318 different locking variants are observed and mapped too, and 319 the proof of observed correctness is also maintained for an 320 arbitrary combination of these separate locking variants. 321 322 For more details, see Documentation/lockdep-design.txt. 323 324config LOCKDEP 325 bool 326 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 327 select STACKTRACE 328 select FRAME_POINTER if !X86 && !MIPS 329 select KALLSYMS 330 select KALLSYMS_ALL 331 332config LOCK_STAT 333 bool "Lock usage statistics" 334 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 335 select LOCKDEP 336 select DEBUG_SPINLOCK 337 select DEBUG_MUTEXES 338 select DEBUG_LOCK_ALLOC 339 default n 340 help 341 This feature enables tracking lock contention points 342 343 For more details, see Documentation/lockstat.txt 344 345config DEBUG_LOCKDEP 346 bool "Lock dependency engine debugging" 347 depends on DEBUG_KERNEL && LOCKDEP 348 help 349 If you say Y here, the lock dependency engine will do 350 additional runtime checks to debug itself, at the price 351 of more runtime overhead. 352 353config TRACE_IRQFLAGS 354 depends on DEBUG_KERNEL 355 bool 356 default y 357 depends on TRACE_IRQFLAGS_SUPPORT 358 depends on PROVE_LOCKING 359 360config DEBUG_SPINLOCK_SLEEP 361 bool "Spinlock debugging: sleep-inside-spinlock checking" 362 depends on DEBUG_KERNEL 363 help 364 If you say Y here, various routines which may sleep will become very 365 noisy if they are called with a spinlock held. 366 367config DEBUG_LOCKING_API_SELFTESTS 368 bool "Locking API boot-time self-tests" 369 depends on DEBUG_KERNEL 370 help 371 Say Y here if you want the kernel to run a short self-test during 372 bootup. The self-test checks whether common types of locking bugs 373 are detected by debugging mechanisms or not. (if you disable 374 lock debugging then those bugs wont be detected of course.) 375 The following locking APIs are covered: spinlocks, rwlocks, 376 mutexes and rwsems. 377 378config STACKTRACE 379 bool 380 depends on DEBUG_KERNEL 381 depends on STACKTRACE_SUPPORT 382 383config DEBUG_KOBJECT 384 bool "kobject debugging" 385 depends on DEBUG_KERNEL 386 help 387 If you say Y here, some extra kobject debugging messages will be sent 388 to the syslog. 389 390config DEBUG_HIGHMEM 391 bool "Highmem debugging" 392 depends on DEBUG_KERNEL && HIGHMEM 393 help 394 This options enables addition error checking for high memory systems. 395 Disable for production systems. 396 397config DEBUG_BUGVERBOSE 398 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED 399 depends on BUG 400 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \ 401 FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300 402 default !EMBEDDED 403 help 404 Say Y here to make BUG() panics output the file name and line number 405 of the BUG call as well as the EIP and oops trace. This aids 406 debugging but costs about 70-100K of memory. 407 408config DEBUG_INFO 409 bool "Compile the kernel with debug info" 410 depends on DEBUG_KERNEL 411 help 412 If you say Y here the resulting kernel image will include 413 debugging info resulting in a larger kernel image. 414 This adds debug symbols to the kernel and modules (gcc -g), and 415 is needed if you intend to use kernel crashdump or binary object 416 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 417 Say Y here only if you plan to debug the kernel. 418 419 If unsure, say N. 420 421config DEBUG_VM 422 bool "Debug VM" 423 depends on DEBUG_KERNEL 424 help 425 Enable this to turn on extended checks in the virtual-memory system 426 that may impact performance. 427 428 If unsure, say N. 429 430config DEBUG_LIST 431 bool "Debug linked list manipulation" 432 depends on DEBUG_KERNEL 433 help 434 Enable this to turn on extended checks in the linked-list 435 walking routines. 436 437 If unsure, say N. 438 439config DEBUG_SG 440 bool "Debug SG table operations" 441 depends on DEBUG_KERNEL 442 help 443 Enable this to turn on checks on scatter-gather tables. This can 444 help find problems with drivers that do not properly initialize 445 their sg tables. 446 447 If unsure, say N. 448 449config FRAME_POINTER 450 bool "Compile the kernel with frame pointers" 451 depends on DEBUG_KERNEL && \ 452 (X86 || CRIS || M68K || M68KNOMMU || FRV || UML || S390 || \ 453 AVR32 || SUPERH || BLACKFIN || MN10300) 454 default y if DEBUG_INFO && UML 455 help 456 If you say Y here the resulting kernel image will be slightly larger 457 and slower, but it might give very useful debugging information on 458 some architectures or if you use external debuggers. 459 If you don't debug the kernel, you can say N. 460 461config BOOT_PRINTK_DELAY 462 bool "Delay each boot printk message by N milliseconds" 463 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 464 help 465 This build option allows you to read kernel boot messages 466 by inserting a short delay after each one. The delay is 467 specified in milliseconds on the kernel command line, 468 using "boot_delay=N". 469 470 It is likely that you would also need to use "lpj=M" to preset 471 the "loops per jiffie" value. 472 See a previous boot log for the "lpj" value to use for your 473 system, and then set "lpj=M" before setting "boot_delay=N". 474 NOTE: Using this option may adversely affect SMP systems. 475 I.e., processors other than the first one may not boot up. 476 BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect 477 what it believes to be lockup conditions. 478 479config RCU_TORTURE_TEST 480 tristate "torture tests for RCU" 481 depends on DEBUG_KERNEL 482 depends on m 483 default n 484 help 485 This option provides a kernel module that runs torture tests 486 on the RCU infrastructure. The kernel module may be built 487 after the fact on the running kernel to be tested, if desired. 488 489 Say M if you want the RCU torture tests to build as a module. 490 Say N if you are unsure. 491 492config KPROBES_SANITY_TEST 493 bool "Kprobes sanity tests" 494 depends on DEBUG_KERNEL 495 depends on KPROBES 496 default n 497 help 498 This option provides for testing basic kprobes functionality on 499 boot. A sample kprobe, jprobe and kretprobe are inserted and 500 verified for functionality. 501 502 Say N if you are unsure. 503 504config BACKTRACE_SELF_TEST 505 tristate "Self test for the backtrace code" 506 depends on DEBUG_KERNEL 507 default n 508 help 509 This option provides a kernel module that can be used to test 510 the kernel stack backtrace code. This option is not useful 511 for distributions or general kernels, but only for kernel 512 developers working on architecture code. 513 514 Say N if you are unsure. 515 516config LKDTM 517 tristate "Linux Kernel Dump Test Tool Module" 518 depends on DEBUG_KERNEL 519 depends on KPROBES 520 depends on BLOCK 521 default n 522 help 523 This module enables testing of the different dumping mechanisms by 524 inducing system failures at predefined crash points. 525 If you don't need it: say N 526 Choose M here to compile this code as a module. The module will be 527 called lkdtm. 528 529 Documentation on how to use the module can be found in 530 drivers/misc/lkdtm.c 531 532config FAULT_INJECTION 533 bool "Fault-injection framework" 534 depends on DEBUG_KERNEL 535 help 536 Provide fault-injection framework. 537 For more details, see Documentation/fault-injection/. 538 539config FAILSLAB 540 bool "Fault-injection capability for kmalloc" 541 depends on FAULT_INJECTION 542 help 543 Provide fault-injection capability for kmalloc. 544 545config FAIL_PAGE_ALLOC 546 bool "Fault-injection capabilitiy for alloc_pages()" 547 depends on FAULT_INJECTION 548 help 549 Provide fault-injection capability for alloc_pages(). 550 551config FAIL_MAKE_REQUEST 552 bool "Fault-injection capability for disk IO" 553 depends on FAULT_INJECTION 554 help 555 Provide fault-injection capability for disk IO. 556 557config FAULT_INJECTION_DEBUG_FS 558 bool "Debugfs entries for fault-injection capabilities" 559 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 560 help 561 Enable configuration of fault-injection capabilities via debugfs. 562 563config FAULT_INJECTION_STACKTRACE_FILTER 564 bool "stacktrace filter for fault-injection capabilities" 565 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 566 depends on !X86_64 567 select STACKTRACE 568 select FRAME_POINTER 569 help 570 Provide stacktrace filter for fault-injection capabilities 571 572config LATENCYTOP 573 bool "Latency measuring infrastructure" 574 select FRAME_POINTER if !MIPS 575 select KALLSYMS 576 select KALLSYMS_ALL 577 select STACKTRACE 578 select SCHEDSTATS 579 select SCHED_DEBUG 580 depends on HAVE_LATENCYTOP_SUPPORT 581 help 582 Enable this option if you want to use the LatencyTOP tool 583 to find out which userspace is blocking on what kernel operations. 584 585config PROVIDE_OHCI1394_DMA_INIT 586 bool "Remote debugging over FireWire early on boot" 587 depends on PCI && X86 588 help 589 If you want to debug problems which hang or crash the kernel early 590 on boot and the crashing machine has a FireWire port, you can use 591 this feature to remotely access the memory of the crashed machine 592 over FireWire. This employs remote DMA as part of the OHCI1394 593 specification which is now the standard for FireWire controllers. 594 595 With remote DMA, you can monitor the printk buffer remotely using 596 firescope and access all memory below 4GB using fireproxy from gdb. 597 Even controlling a kernel debugger is possible using remote DMA. 598 599 Usage: 600 601 If ohci1394_dma=early is used as boot parameter, it will initialize 602 all OHCI1394 controllers which are found in the PCI config space. 603 604 As all changes to the FireWire bus such as enabling and disabling 605 devices cause a bus reset and thereby disable remote DMA for all 606 devices, be sure to have the cable plugged and FireWire enabled on 607 the debugging host before booting the debug target for debugging. 608 609 This code (~1k) is freed after boot. By then, the firewire stack 610 in charge of the OHCI-1394 controllers should be used instead. 611 612 See Documentation/debugging-via-ohci1394.txt for more information. 613 614config FIREWIRE_OHCI_REMOTE_DMA 615 bool "Remote debugging over FireWire with firewire-ohci" 616 depends on FIREWIRE_OHCI 617 help 618 This option lets you use the FireWire bus for remote debugging 619 with help of the firewire-ohci driver. It enables unfiltered 620 remote DMA in firewire-ohci. 621 See Documentation/debugging-via-ohci1394.txt for more information. 622 623 If unsure, say N. 624 625source "samples/Kconfig" 626 627source "lib/Kconfig.kgdb" 628