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 FRAME_WARN 29 int "Warn for stack frames larger than (needs gcc 4.4)" 30 range 0 8192 31 default 1024 if !64BIT 32 default 2048 if 64BIT 33 help 34 Tell gcc to warn at build time for stack frames larger than this. 35 Setting this too low will cause a lot of warnings. 36 Setting it to 0 disables the warning. 37 Requires gcc 4.4 38 39config MAGIC_SYSRQ 40 bool "Magic SysRq key" 41 depends on !UML 42 help 43 If you say Y here, you will have some control over the system even 44 if the system crashes for example during kernel debugging (e.g., you 45 will be able to flush the buffer cache to disk, reboot the system 46 immediately or dump some status information). This is accomplished 47 by pressing various keys while holding SysRq (Alt+PrintScreen). It 48 also works on a serial console (on PC hardware at least), if you 49 send a BREAK and then within 5 seconds a command keypress. The 50 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y 51 unless you really know what this hack does. 52 53config UNUSED_SYMBOLS 54 bool "Enable unused/obsolete exported symbols" 55 default y if X86 56 help 57 Unused but exported symbols make the kernel needlessly bigger. For 58 that reason most of these unused exports will soon be removed. This 59 option is provided temporarily to provide a transition period in case 60 some external kernel module needs one of these symbols anyway. If you 61 encounter such a case in your module, consider if you are actually 62 using the right API. (rationale: since nobody in the kernel is using 63 this in a module, there is a pretty good chance it's actually the 64 wrong interface to use). If you really need the symbol, please send a 65 mail to the linux kernel mailing list mentioning the symbol and why 66 you really need it, and what the merge plan to the mainline kernel for 67 your module is. 68 69config DEBUG_FS 70 bool "Debug Filesystem" 71 depends on SYSFS 72 help 73 debugfs is a virtual file system that kernel developers use to put 74 debugging files into. Enable this option to be able to read and 75 write to these files. 76 77 If unsure, say N. 78 79config HEADERS_CHECK 80 bool "Run 'make headers_check' when building vmlinux" 81 depends on !UML 82 help 83 This option will extract the user-visible kernel headers whenever 84 building the kernel, and will run basic sanity checks on them to 85 ensure that exported files do not attempt to include files which 86 were not exported, etc. 87 88 If you're making modifications to header files which are 89 relevant for userspace, say 'Y', and check the headers 90 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 91 your build tree), to make sure they're suitable. 92 93config DEBUG_SECTION_MISMATCH 94 bool "Enable full Section mismatch analysis" 95 depends on UNDEFINED 96 # This option is on purpose disabled for now. 97 # It will be enabled when we are down to a resonable number 98 # of section mismatch warnings (< 10 for an allyesconfig build) 99 help 100 The section mismatch analysis checks if there are illegal 101 references from one section to another section. 102 Linux will during link or during runtime drop some sections 103 and any use of code/data previously in these sections will 104 most likely result in an oops. 105 In the code functions and variables are annotated with 106 __init, __devinit etc. (see full list in include/linux/init.h) 107 which results in the code/data being placed in specific sections. 108 The section mismatch analysis is always done after a full 109 kernel build but enabling this option will in addition 110 do the following: 111 - Add the option -fno-inline-functions-called-once to gcc 112 When inlining a function annotated __init in a non-init 113 function we would lose the section information and thus 114 the analysis would not catch the illegal reference. 115 This option tells gcc to inline less but will also 116 result in a larger kernel. 117 - Run the section mismatch analysis for each module/built-in.o 118 When we run the section mismatch analysis on vmlinux.o we 119 lose valueble information about where the mismatch was 120 introduced. 121 Running the analysis for each module/built-in.o file 122 will tell where the mismatch happens much closer to the 123 source. The drawback is that we will report the same 124 mismatch at least twice. 125 - Enable verbose reporting from modpost to help solving 126 the section mismatches reported. 127 128config DEBUG_KERNEL 129 bool "Kernel debugging" 130 help 131 Say Y here if you are developing drivers or trying to debug and 132 identify kernel problems. 133 134config DEBUG_SHIRQ 135 bool "Debug shared IRQ handlers" 136 depends on DEBUG_KERNEL && GENERIC_HARDIRQS 137 help 138 Enable this to generate a spurious interrupt as soon as a shared 139 interrupt handler is registered, and just before one is deregistered. 140 Drivers ought to be able to handle interrupts coming in at those 141 points; some don't and need to be caught. 142 143config DETECT_SOFTLOCKUP 144 bool "Detect Soft Lockups" 145 depends on DEBUG_KERNEL && !S390 146 default y 147 help 148 Say Y here to enable the kernel to detect "soft lockups", 149 which are bugs that cause the kernel to loop in kernel 150 mode for more than 10 seconds, without giving other tasks a 151 chance to run. 152 153 When a soft-lockup is detected, the kernel will print the 154 current stack trace (which you should report), but the 155 system will stay locked up. This feature has negligible 156 overhead. 157 158 (Note that "hard lockups" are separate type of bugs that 159 can be detected via the NMI-watchdog, on platforms that 160 support it.) 161 162config SCHED_DEBUG 163 bool "Collect scheduler debugging info" 164 depends on DEBUG_KERNEL && PROC_FS 165 default y 166 help 167 If you say Y here, the /proc/sched_debug file will be provided 168 that can help debug the scheduler. The runtime overhead of this 169 option is minimal. 170 171config SCHEDSTATS 172 bool "Collect scheduler statistics" 173 depends on DEBUG_KERNEL && PROC_FS 174 help 175 If you say Y here, additional code will be inserted into the 176 scheduler and related routines to collect statistics about 177 scheduler behavior and provide them in /proc/schedstat. These 178 stats may be useful for both tuning and debugging the scheduler 179 If you aren't debugging the scheduler or trying to tune a specific 180 application, you can say N to avoid the very slight overhead 181 this adds. 182 183config TIMER_STATS 184 bool "Collect kernel timers statistics" 185 depends on DEBUG_KERNEL && PROC_FS 186 help 187 If you say Y here, additional code will be inserted into the 188 timer routines to collect statistics about kernel timers being 189 reprogrammed. The statistics can be read from /proc/timer_stats. 190 The statistics collection is started by writing 1 to /proc/timer_stats, 191 writing 0 stops it. This feature is useful to collect information 192 about timer usage patterns in kernel and userspace. This feature 193 is lightweight if enabled in the kernel config but not activated 194 (it defaults to deactivated on bootup and will only be activated 195 if some application like powertop activates it explicitly). 196 197config DEBUG_OBJECTS 198 bool "Debug object operations" 199 depends on DEBUG_KERNEL 200 help 201 If you say Y here, additional code will be inserted into the 202 kernel to track the life time of various objects and validate 203 the operations on those objects. 204 205config DEBUG_OBJECTS_SELFTEST 206 bool "Debug objects selftest" 207 depends on DEBUG_OBJECTS 208 help 209 This enables the selftest of the object debug code. 210 211config DEBUG_OBJECTS_FREE 212 bool "Debug objects in freed memory" 213 depends on DEBUG_OBJECTS 214 help 215 This enables checks whether a k/v free operation frees an area 216 which contains an object which has not been deactivated 217 properly. This can make kmalloc/kfree-intensive workloads 218 much slower. 219 220config DEBUG_OBJECTS_TIMERS 221 bool "Debug timer objects" 222 depends on DEBUG_OBJECTS 223 help 224 If you say Y here, additional code will be inserted into the 225 timer routines to track the life time of timer objects and 226 validate the timer operations. 227 228config DEBUG_SLAB 229 bool "Debug slab memory allocations" 230 depends on DEBUG_KERNEL && SLAB 231 help 232 Say Y here to have the kernel do limited verification on memory 233 allocation as well as poisoning memory on free to catch use of freed 234 memory. This can make kmalloc/kfree-intensive workloads much slower. 235 236config DEBUG_SLAB_LEAK 237 bool "Memory leak debugging" 238 depends on DEBUG_SLAB 239 240config SLUB_DEBUG_ON 241 bool "SLUB debugging on by default" 242 depends on SLUB && SLUB_DEBUG 243 default n 244 help 245 Boot with debugging on by default. SLUB boots by default with 246 the runtime debug capabilities switched off. Enabling this is 247 equivalent to specifying the "slub_debug" parameter on boot. 248 There is no support for more fine grained debug control like 249 possible with slub_debug=xxx. SLUB debugging may be switched 250 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 251 "slub_debug=-". 252 253config SLUB_STATS 254 default n 255 bool "Enable SLUB performance statistics" 256 depends on SLUB && SLUB_DEBUG && SYSFS 257 help 258 SLUB statistics are useful to debug SLUBs allocation behavior in 259 order find ways to optimize the allocator. This should never be 260 enabled for production use since keeping statistics slows down 261 the allocator by a few percentage points. The slabinfo command 262 supports the determination of the most active slabs to figure 263 out which slabs are relevant to a particular load. 264 Try running: slabinfo -DA 265 266config DEBUG_PREEMPT 267 bool "Debug preemptible kernel" 268 depends on DEBUG_KERNEL && PREEMPT && (TRACE_IRQFLAGS_SUPPORT || PPC64) 269 default y 270 help 271 If you say Y here then the kernel will use a debug variant of the 272 commonly used smp_processor_id() function and will print warnings 273 if kernel code uses it in a preemption-unsafe way. Also, the kernel 274 will detect preemption count underflows. 275 276config DEBUG_RT_MUTEXES 277 bool "RT Mutex debugging, deadlock detection" 278 depends on DEBUG_KERNEL && RT_MUTEXES 279 help 280 This allows rt mutex semantics violations and rt mutex related 281 deadlocks (lockups) to be detected and reported automatically. 282 283config DEBUG_PI_LIST 284 bool 285 default y 286 depends on DEBUG_RT_MUTEXES 287 288config RT_MUTEX_TESTER 289 bool "Built-in scriptable tester for rt-mutexes" 290 depends on DEBUG_KERNEL && RT_MUTEXES 291 help 292 This option enables a rt-mutex tester. 293 294config DEBUG_SPINLOCK 295 bool "Spinlock and rw-lock debugging: basic checks" 296 depends on DEBUG_KERNEL 297 help 298 Say Y here and build SMP to catch missing spinlock initialization 299 and certain other kinds of spinlock errors commonly made. This is 300 best used in conjunction with the NMI watchdog so that spinlock 301 deadlocks are also debuggable. 302 303config DEBUG_MUTEXES 304 bool "Mutex debugging: basic checks" 305 depends on DEBUG_KERNEL 306 help 307 This feature allows mutex semantics violations to be detected and 308 reported. 309 310config DEBUG_LOCK_ALLOC 311 bool "Lock debugging: detect incorrect freeing of live locks" 312 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 313 select DEBUG_SPINLOCK 314 select DEBUG_MUTEXES 315 select LOCKDEP 316 help 317 This feature will check whether any held lock (spinlock, rwlock, 318 mutex or rwsem) is incorrectly freed by the kernel, via any of the 319 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 320 vfree(), etc.), whether a live lock is incorrectly reinitialized via 321 spin_lock_init()/mutex_init()/etc., or whether there is any lock 322 held during task exit. 323 324config PROVE_LOCKING 325 bool "Lock debugging: prove locking correctness" 326 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 327 select LOCKDEP 328 select DEBUG_SPINLOCK 329 select DEBUG_MUTEXES 330 select DEBUG_LOCK_ALLOC 331 default n 332 help 333 This feature enables the kernel to prove that all locking 334 that occurs in the kernel runtime is mathematically 335 correct: that under no circumstance could an arbitrary (and 336 not yet triggered) combination of observed locking 337 sequences (on an arbitrary number of CPUs, running an 338 arbitrary number of tasks and interrupt contexts) cause a 339 deadlock. 340 341 In short, this feature enables the kernel to report locking 342 related deadlocks before they actually occur. 343 344 The proof does not depend on how hard and complex a 345 deadlock scenario would be to trigger: how many 346 participant CPUs, tasks and irq-contexts would be needed 347 for it to trigger. The proof also does not depend on 348 timing: if a race and a resulting deadlock is possible 349 theoretically (no matter how unlikely the race scenario 350 is), it will be proven so and will immediately be 351 reported by the kernel (once the event is observed that 352 makes the deadlock theoretically possible). 353 354 If a deadlock is impossible (i.e. the locking rules, as 355 observed by the kernel, are mathematically correct), the 356 kernel reports nothing. 357 358 NOTE: this feature can also be enabled for rwlocks, mutexes 359 and rwsems - in which case all dependencies between these 360 different locking variants are observed and mapped too, and 361 the proof of observed correctness is also maintained for an 362 arbitrary combination of these separate locking variants. 363 364 For more details, see Documentation/lockdep-design.txt. 365 366config LOCKDEP 367 bool 368 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 369 select STACKTRACE 370 select FRAME_POINTER if !X86 && !MIPS 371 select KALLSYMS 372 select KALLSYMS_ALL 373 374config LOCK_STAT 375 bool "Lock usage statistics" 376 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 377 select LOCKDEP 378 select DEBUG_SPINLOCK 379 select DEBUG_MUTEXES 380 select DEBUG_LOCK_ALLOC 381 default n 382 help 383 This feature enables tracking lock contention points 384 385 For more details, see Documentation/lockstat.txt 386 387config DEBUG_LOCKDEP 388 bool "Lock dependency engine debugging" 389 depends on DEBUG_KERNEL && LOCKDEP 390 help 391 If you say Y here, the lock dependency engine will do 392 additional runtime checks to debug itself, at the price 393 of more runtime overhead. 394 395config TRACE_IRQFLAGS 396 depends on DEBUG_KERNEL 397 bool 398 default y 399 depends on TRACE_IRQFLAGS_SUPPORT 400 depends on PROVE_LOCKING 401 402config DEBUG_SPINLOCK_SLEEP 403 bool "Spinlock debugging: sleep-inside-spinlock checking" 404 depends on DEBUG_KERNEL 405 help 406 If you say Y here, various routines which may sleep will become very 407 noisy if they are called with a spinlock held. 408 409config DEBUG_LOCKING_API_SELFTESTS 410 bool "Locking API boot-time self-tests" 411 depends on DEBUG_KERNEL 412 help 413 Say Y here if you want the kernel to run a short self-test during 414 bootup. The self-test checks whether common types of locking bugs 415 are detected by debugging mechanisms or not. (if you disable 416 lock debugging then those bugs wont be detected of course.) 417 The following locking APIs are covered: spinlocks, rwlocks, 418 mutexes and rwsems. 419 420config STACKTRACE 421 bool 422 depends on STACKTRACE_SUPPORT 423 424config DEBUG_KOBJECT 425 bool "kobject debugging" 426 depends on DEBUG_KERNEL 427 help 428 If you say Y here, some extra kobject debugging messages will be sent 429 to the syslog. 430 431config DEBUG_HIGHMEM 432 bool "Highmem debugging" 433 depends on DEBUG_KERNEL && HIGHMEM 434 help 435 This options enables addition error checking for high memory systems. 436 Disable for production systems. 437 438config DEBUG_BUGVERBOSE 439 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED 440 depends on BUG 441 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \ 442 FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300 443 default !EMBEDDED 444 help 445 Say Y here to make BUG() panics output the file name and line number 446 of the BUG call as well as the EIP and oops trace. This aids 447 debugging but costs about 70-100K of memory. 448 449config DEBUG_INFO 450 bool "Compile the kernel with debug info" 451 depends on DEBUG_KERNEL 452 help 453 If you say Y here the resulting kernel image will include 454 debugging info resulting in a larger kernel image. 455 This adds debug symbols to the kernel and modules (gcc -g), and 456 is needed if you intend to use kernel crashdump or binary object 457 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 458 Say Y here only if you plan to debug the kernel. 459 460 If unsure, say N. 461 462config DEBUG_VM 463 bool "Debug VM" 464 depends on DEBUG_KERNEL 465 help 466 Enable this to turn on extended checks in the virtual-memory system 467 that may impact performance. 468 469 If unsure, say N. 470 471config DEBUG_WRITECOUNT 472 bool "Debug filesystem writers count" 473 depends on DEBUG_KERNEL 474 help 475 Enable this to catch wrong use of the writers count in struct 476 vfsmount. This will increase the size of each file struct by 477 32 bits. 478 479 If unsure, say N. 480 481config DEBUG_LIST 482 bool "Debug linked list manipulation" 483 depends on DEBUG_KERNEL 484 help 485 Enable this to turn on extended checks in the linked-list 486 walking routines. 487 488 If unsure, say N. 489 490config DEBUG_SG 491 bool "Debug SG table operations" 492 depends on DEBUG_KERNEL 493 help 494 Enable this to turn on checks on scatter-gather tables. This can 495 help find problems with drivers that do not properly initialize 496 their sg tables. 497 498 If unsure, say N. 499 500config FRAME_POINTER 501 bool "Compile the kernel with frame pointers" 502 depends on DEBUG_KERNEL && \ 503 (X86 || CRIS || M68K || M68KNOMMU || FRV || UML || S390 || \ 504 AVR32 || SUPERH || BLACKFIN || MN10300) 505 default y if DEBUG_INFO && UML 506 help 507 If you say Y here the resulting kernel image will be slightly larger 508 and slower, but it might give very useful debugging information on 509 some architectures or if you use external debuggers. 510 If you don't debug the kernel, you can say N. 511 512config BOOT_PRINTK_DELAY 513 bool "Delay each boot printk message by N milliseconds" 514 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 515 help 516 This build option allows you to read kernel boot messages 517 by inserting a short delay after each one. The delay is 518 specified in milliseconds on the kernel command line, 519 using "boot_delay=N". 520 521 It is likely that you would also need to use "lpj=M" to preset 522 the "loops per jiffie" value. 523 See a previous boot log for the "lpj" value to use for your 524 system, and then set "lpj=M" before setting "boot_delay=N". 525 NOTE: Using this option may adversely affect SMP systems. 526 I.e., processors other than the first one may not boot up. 527 BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect 528 what it believes to be lockup conditions. 529 530config RCU_TORTURE_TEST 531 tristate "torture tests for RCU" 532 depends on DEBUG_KERNEL 533 default n 534 help 535 This option provides a kernel module that runs torture tests 536 on the RCU infrastructure. The kernel module may be built 537 after the fact on the running kernel to be tested, if desired. 538 539 Say Y here if you want RCU torture tests to be built into 540 the kernel. 541 Say M if you want the RCU torture tests to build as a module. 542 Say N if you are unsure. 543 544config RCU_TORTURE_TEST_RUNNABLE 545 bool "torture tests for RCU runnable by default" 546 depends on RCU_TORTURE_TEST = y 547 default n 548 help 549 This option provides a way to build the RCU torture tests 550 directly into the kernel without them starting up at boot 551 time. You can use /proc/sys/kernel/rcutorture_runnable 552 to manually override this setting. This /proc file is 553 available only when the RCU torture tests have been built 554 into the kernel. 555 556 Say Y here if you want the RCU torture tests to start during 557 boot (you probably don't). 558 Say N here if you want the RCU torture tests to start only 559 after being manually enabled via /proc. 560 561config KPROBES_SANITY_TEST 562 bool "Kprobes sanity tests" 563 depends on DEBUG_KERNEL 564 depends on KPROBES 565 default n 566 help 567 This option provides for testing basic kprobes functionality on 568 boot. A sample kprobe, jprobe and kretprobe are inserted and 569 verified for functionality. 570 571 Say N if you are unsure. 572 573config BACKTRACE_SELF_TEST 574 tristate "Self test for the backtrace code" 575 depends on DEBUG_KERNEL 576 default n 577 help 578 This option provides a kernel module that can be used to test 579 the kernel stack backtrace code. This option is not useful 580 for distributions or general kernels, but only for kernel 581 developers working on architecture code. 582 583 Note that if you want to also test saved backtraces, you will 584 have to enable STACKTRACE as well. 585 586 Say N if you are unsure. 587 588config LKDTM 589 tristate "Linux Kernel Dump Test Tool Module" 590 depends on DEBUG_KERNEL 591 depends on KPROBES 592 depends on BLOCK 593 default n 594 help 595 This module enables testing of the different dumping mechanisms by 596 inducing system failures at predefined crash points. 597 If you don't need it: say N 598 Choose M here to compile this code as a module. The module will be 599 called lkdtm. 600 601 Documentation on how to use the module can be found in 602 drivers/misc/lkdtm.c 603 604config FAULT_INJECTION 605 bool "Fault-injection framework" 606 depends on DEBUG_KERNEL 607 help 608 Provide fault-injection framework. 609 For more details, see Documentation/fault-injection/. 610 611config FAILSLAB 612 bool "Fault-injection capability for kmalloc" 613 depends on FAULT_INJECTION 614 help 615 Provide fault-injection capability for kmalloc. 616 617config FAIL_PAGE_ALLOC 618 bool "Fault-injection capabilitiy for alloc_pages()" 619 depends on FAULT_INJECTION 620 help 621 Provide fault-injection capability for alloc_pages(). 622 623config FAIL_MAKE_REQUEST 624 bool "Fault-injection capability for disk IO" 625 depends on FAULT_INJECTION 626 help 627 Provide fault-injection capability for disk IO. 628 629config FAULT_INJECTION_DEBUG_FS 630 bool "Debugfs entries for fault-injection capabilities" 631 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 632 help 633 Enable configuration of fault-injection capabilities via debugfs. 634 635config FAULT_INJECTION_STACKTRACE_FILTER 636 bool "stacktrace filter for fault-injection capabilities" 637 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 638 depends on !X86_64 639 select STACKTRACE 640 select FRAME_POINTER 641 help 642 Provide stacktrace filter for fault-injection capabilities 643 644config LATENCYTOP 645 bool "Latency measuring infrastructure" 646 select FRAME_POINTER if !MIPS 647 select KALLSYMS 648 select KALLSYMS_ALL 649 select STACKTRACE 650 select SCHEDSTATS 651 select SCHED_DEBUG 652 depends on HAVE_LATENCYTOP_SUPPORT 653 help 654 Enable this option if you want to use the LatencyTOP tool 655 to find out which userspace is blocking on what kernel operations. 656 657source kernel/trace/Kconfig 658 659config PROVIDE_OHCI1394_DMA_INIT 660 bool "Remote debugging over FireWire early on boot" 661 depends on PCI && X86 662 help 663 If you want to debug problems which hang or crash the kernel early 664 on boot and the crashing machine has a FireWire port, you can use 665 this feature to remotely access the memory of the crashed machine 666 over FireWire. This employs remote DMA as part of the OHCI1394 667 specification which is now the standard for FireWire controllers. 668 669 With remote DMA, you can monitor the printk buffer remotely using 670 firescope and access all memory below 4GB using fireproxy from gdb. 671 Even controlling a kernel debugger is possible using remote DMA. 672 673 Usage: 674 675 If ohci1394_dma=early is used as boot parameter, it will initialize 676 all OHCI1394 controllers which are found in the PCI config space. 677 678 As all changes to the FireWire bus such as enabling and disabling 679 devices cause a bus reset and thereby disable remote DMA for all 680 devices, be sure to have the cable plugged and FireWire enabled on 681 the debugging host before booting the debug target for debugging. 682 683 This code (~1k) is freed after boot. By then, the firewire stack 684 in charge of the OHCI-1394 controllers should be used instead. 685 686 See Documentation/debugging-via-ohci1394.txt for more information. 687 688config FIREWIRE_OHCI_REMOTE_DMA 689 bool "Remote debugging over FireWire with firewire-ohci" 690 depends on FIREWIRE_OHCI 691 help 692 This option lets you use the FireWire bus for remote debugging 693 with help of the firewire-ohci driver. It enables unfiltered 694 remote DMA in firewire-ohci. 695 See Documentation/debugging-via-ohci1394.txt for more information. 696 697 If unsure, say N. 698 699source "samples/Kconfig" 700 701source "lib/Kconfig.kgdb" 702