2 .\" Mach Operating System
3 .\" Copyright (c) 1991,1990 Carnegie Mellon University
4 .\" Copyright (c) 2007 Robert N. M. Watson
5 .\" All Rights Reserved.
7 .\" Permission to use, copy, modify and distribute this software and its
8 .\" documentation is hereby granted, provided that both the copyright
9 .\" notice and this permission notice appear in all copies of the
10 .\" software, derivative works or modified versions, and any portions
11 .\" thereof, and that both notices appear in supporting documentation.
13 .\" CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
14 .\" CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
15 .\" ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
17 .\" Carnegie Mellon requests users of this software to return to
19 .\" Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
20 .\" School of Computer Science
21 .\" Carnegie Mellon University
22 .\" Pittsburgh PA 15213-3890
24 .\" any improvements or extensions that they make and grant Carnegie Mellon
25 .\" the rights to redistribute these changes.
27 .\" changed a \# to #, since groff choked on it.
31 .\" Revision 1.1 1993/07/15 18:41:02 brezak
34 .\" Revision 2.6 92/04/08 08:52:57 rpd
36 .\" [92/01/17 14:19:22 jsb]
37 .\" Changes for OSF debugger modifications.
40 .\" Revision 2.5 91/06/25 13:50:22 rpd
41 .\" Added some watchpoint explanation.
44 .\" Revision 2.4 91/06/17 15:47:31 jsb
45 .\" Added documentation for continue/c, match, search, and watchpoints.
46 .\" I've not actually explained what a watchpoint is; maybe Rich can
47 .\" do that (hint, hint).
48 .\" [91/06/17 10:58:08 jsb]
50 .\" Revision 2.3 91/05/14 17:04:23 mrt
51 .\" Correcting copyright
53 .\" Revision 2.2 91/02/14 14:10:06 mrt
54 .\" Changed to new Mach copyright
55 .\" [91/02/12 18:10:12 mrt]
57 .\" Revision 2.2 90/08/30 14:23:15 dbg
68 .Nd interactive kernel debugger
70 In order to enable kernel debugging facilities include:
71 .Bd -ragged -offset indent
76 To prevent activation of the debugger on kernel
78 .Bd -ragged -offset indent
79 .Cd options KDB_UNATTENDED
82 In order to print a stack trace of the current thread on the console
84 .Bd -ragged -offset indent
88 To print the numerical value of symbols in addition to the symbolic
89 representation, define:
90 .Bd -ragged -offset indent
91 .Cd options DDB_NUMSYM
96 backend, so that remote debugging with
99 .Bd -ragged -offset indent
105 kernel debugger is an interactive debugger with a syntax inspired by
107 If linked into the running kernel,
108 it can be invoked locally with the
112 The debugger is also invoked on kernel
115 .Va debug.debugger_on_panic
117 MIB variable is set non-zero,
123 The current location is called
128 a hexadecimal format at a prompt.
135 to the address of the last line
136 examined or the last location modified, and set
139 the next location to be examined or changed.
140 Other commands do not change
147 The general command syntax is:
148 .Ar command Ns Op Li / Ns Ar modifier
149 .Ar address Ns Op Li , Ns Ar count
151 A blank line repeats the previous command from the address
154 count 1 and no modifiers.
167 to be 1 for printing commands or infinity for stack traces.
171 debugger has a pager feature (like the
175 If an output line exceeds the number set in the
177 variable, it displays
179 and waits for a response.
180 The valid responses for it are:
182 .Bl -tag -compact -width ".Li SPC"
188 abort the current command, and return to the command input mode
193 provides a small (currently 10 items) command history, and offers
196 command line editing capabilities.
200 control keys, the usual
202 arrow keys may be used to
203 browse through the history buffer, and move the cursor within the
206 .Bl -tag -width indent -compact
209 Display the addressed locations according to the formats in the modifier.
210 Multiple modifier formats display multiple locations.
211 If no format is specified, the last format specified for this command
214 The format characters are:
215 .Bl -tag -compact -width indent
217 look at by bytes (8 bits)
219 look at by half words (16 bits)
221 look at by long words (32 bits)
223 look at by quad words (64 bits)
225 print the location being displayed
227 print the location with a line number if possible
229 display in unsigned hex
231 display in signed hex
233 display in unsigned octal
235 display in signed decimal
237 display in unsigned decimal
239 display in current radix, signed
241 display low 8 bits as a character.
242 Non-printing characters are displayed as an octal escape code (e.g.,
245 display the null-terminated string at the location.
246 Non-printing characters are displayed as octal escapes.
248 display in unsigned hex with character dump at the end of each line.
249 The location is also displayed in hex at the beginning of each line.
251 display as an instruction
253 display as an instruction with possible alternate formats depending on the
255 .Bl -tag -width ".Tn powerpc" -compact
268 display a symbol name for the pointer stored at the address
275 command with the last specified parameters to it
276 except that the next address displayed by it is used as the start address.
282 command with the last specified parameters to it
283 except that the last start address subtracted by the size displayed by it
284 is used as the start address.
286 .It Ic print Ns Op Li / Ns Cm acdoruxz
287 .It Ic p Ns Op Li / Ns Cm acdoruxz
290 according to the modifier character (as described above for
293 .Cm a , x , z , o , d , u , r ,
296 If no modifier is specified, the last one specified to it is used.
299 can be a string, in which case it is printed as it is.
301 .Bd -literal -offset indent
302 print/x "eax = " $eax "\enecx = " $ecx "\en"
306 .Bd -literal -offset indent
312 .Ic write Ns Op Li / Ns Cm bhl
313 .Ar addr expr1 Op Ar expr2 ...
316 .Ic w Ns Op Li / Ns Cm bhl
317 .Ar addr expr1 Op Ar expr2 ...
319 Write the expressions specified after
321 on the command line at succeeding locations starting with
323 The write unit size can be specified in the modifier with a letter
329 (long word) respectively.
331 long word is assumed.
334 since there is no delimiter between expressions, strange
336 It is best to enclose each expression in parentheses.
338 .It Ic set Li $ Ns Ar variable Oo Li = Oc Ar expr
339 Set the named variable or register with the value of
341 Valid variable names are described below.
343 .It Ic break Ns Op Li / Ns Cm u
344 .It Ic b Ns Op Li / Ns Cm u
349 is supplied, continues
351 \- 1 times before stopping at the
353 If the break point is set, a break point number is
356 This number can be used in deleting the break point
357 or adding conditions to it.
361 modifier is specified, this command sets a break point in user
365 option, the address is considered to be in the kernel
366 space, and a wrong space address is rejected with an error message.
367 This modifier can be used only if it is supported by machine dependent
371 If a user text is shadowed by a normal user space debugger,
372 user space break points may not work correctly.
374 point at the low-level code paths may also cause strange behavior.
376 .It Ic delete Ar addr
378 .It Ic delete Li # Ns Ar number
379 .It Ic d Li # Ns Ar number
380 Delete the break point.
381 The target break point can be specified by a
382 break point number with
386 specified in the original
390 .It Ic watch Ar addr Ns Li , Ns Ar size
391 Set a watchpoint for a region.
392 Execution stops when an attempt to modify the region occurs.
395 argument defaults to 4.
396 If you specify a wrong space address, the request is rejected
397 with an error message.
400 Attempts to watch wired kernel memory
401 may cause unrecoverable error in some systems such as i386.
402 Watchpoints on user addresses work best.
404 .It Ic hwatch Ar addr Ns Li , Ns Ar size
405 Set a hardware watchpoint for a region if supported by the
407 Execution stops when an attempt to modify the region occurs.
410 argument defaults to 4.
413 The hardware debug facilities do not have a concept of separate
414 address spaces like the watch command does.
417 for setting watchpoints on kernel address locations only, and avoid
418 its use on user mode address spaces.
420 .It Ic dhwatch Ar addr Ns Li , Ns Ar size
421 Delete specified hardware watchpoint.
423 .It Ic step Ns Op Li / Ns Cm p
424 .It Ic s Ns Op Li / Ns Cm p
427 times (the comma is a mandatory part of the syntax).
430 modifier is specified, print each instruction at each step.
431 Otherwise, only print the last instruction.
434 depending on machine type, it may not be possible to
435 single-step through some low-level code paths or user space code.
436 On machines with software-emulated single-stepping (e.g., pmax),
437 stepping through code executed by interrupt handlers will probably
440 .It Ic continue Ns Op Li / Ns Cm c
441 .It Ic c Ns Op Li / Ns Cm c
442 Continue execution until a breakpoint or watchpoint.
445 modifier is specified, count instructions while executing.
446 Some machines (e.g., pmax) also count loads and stores.
449 when counting, the debugger is really silently single-stepping.
450 This means that single-stepping on low-level code may cause strange
453 .It Ic until Ns Op Li / Ns Cm p
454 Stop at the next call or return instruction.
457 modifier is specified, print the call nesting depth and the
458 cumulative instruction count at each call or return.
460 only print when the matching return is hit.
462 .It Ic next Ns Op Li / Ns Cm p
463 .It Ic match Ns Op Li / Ns Cm p
464 Stop at the matching return instruction.
467 modifier is specified, print the call nesting depth and the
468 cumulative instruction count at each call or return.
469 Otherwise, only print when the matching return is hit.
472 .Ic trace Ns Op Li / Ns Cm u
477 .Ic t Ns Op Li / Ns Cm u
482 .Ic where Ns Op Li / Ns Cm u
487 .Ic bt Ns Op Li / Ns Cm u
494 option traces user space; if omitted,
498 The optional argument
500 is the number of frames to be traced.
503 is omitted, all frames are printed.
506 User space stack trace is valid
507 only if the machine dependent code supports it.
510 .Ic search Ns Op Li / Ns Cm bhl
518 This command might fail in interesting
519 ways if it does not find the searched-for value.
522 does not always recover from touching bad memory.
525 argument limits the search.
532 Prints the thread address for a thread kernel-mode stack of which contains the
534 If the thread is not found, search the thread stack cache and prints the
535 cached stack address.
536 Otherwise, prints nothing.
538 .It Ic show Cm all procs Ns Op Li / Ns Cm m
539 .It Ic ps Ns Op Li / Ns Cm m
540 Display all process information.
541 The process information may not be shown if it is not
542 supported in the machine, or the bottom of the stack of the
543 target process is not in the main memory at that time.
546 modifier will alter the display to show VM map
547 addresses for the process and not show other information.
550 .It Ic show Cm all ttys
551 Show all TTY's within the system.
554 but also includes the address of the TTY structure.
557 .It Ic show Cm allchains
558 Show the same information like "show lockchain" does, but
559 for every thread in the system.
562 .It Ic show Cm alllocks
563 Show all locks that are currently held.
564 This command is only available if
566 is included in the kernel.
569 .It Ic show Cm allpcpu
570 The same as "show pcpu", but for every CPU present in the system.
573 .It Ic show Cm allrman
574 Show information related with resource management, including
575 interrupt request lines, DMA request lines, I/O ports and I/O memory
580 Dump data about APIC IDT vector mappings.
583 .It Ic show Cm breaks
584 Show breakpoints set with the "break" command.
587 .It Ic show Cm bio Ar addr
588 Show information about the bio structure
596 for more details on the exact meaning of the structure fields.
599 .It Ic show Cm buffer Ar addr
600 Show information about the buf structure
606 header file for more details on the exact meaning of the structure fields.
609 .It Ic show Cm cbstat
610 Show brief information about the TTY subsystem.
614 Without argument, show the list of all created cdev's, consisting of devfs
615 node name and struct cdev address.
616 When address of cdev is supplied, show some internal devfs state of the cdev.
619 .It Ic show Cm conifhk
620 Lists hooks currently waiting for completion in
621 run_interrupt_driven_config_hooks().
624 .It Ic show Cm cpusets
625 Print numbered root and assigned CPU affinity sets.
631 .It Ic show Cm cyrixreg
632 Show registers specific to the Cyrix processor.
635 .It Ic show Cm domain Ar addr
636 Print protocol domain structure
642 header file for more details on the exact meaning of the structure fields.
645 .It Ic show Cm ffs Op Ar addr
646 Show brief information about ffs mount at the address
648 if argument is given.
649 Otherwise, provides the summary about each ffs mount.
652 .It Ic show Cm file Ar addr
653 Show information about the file structure
660 Show information about every file structure in the system.
663 .It Ic show Cm freepages
664 Show the number of physical pages in each of the free lists.
667 .It Ic show Cm geom Op Ar addr
670 argument is not given, displays the entire GEOM topology.
673 is given, displays details about the given GEOM object (class, geom,
674 provider or consumer).
679 The first column specifies the IDT vector.
680 The second one is the name of the interrupt/trap handler.
681 Those functions are machine dependent.
684 .It Ic show Cm inodedeps Op Ar addr
685 Show brief information about each inodedep structure.
688 is given, only inodedeps belonging to the fs located at the
689 supplied address are shown.
692 .It Ic show Cm inpcb Ar addr
693 Show information on IP Control Block
700 Dump information about interrupt handlers.
703 .It Ic show Cm intrcnt
704 Dump the interrupt statistics.
708 Show interrupt lines and their respective kernel threads.
717 shows, also list kernel internal details.
721 Show information from the local APIC registers for this CPU.
724 .It Ic show Cm lock Ar addr
726 The output format is as follows:
727 .Bl -tag -width "flags"
730 Possible types include
738 Flags passed to the lock initialization function.
739 For exact possibilities see manual pages of possible lock types.
741 Current state of a lock.
750 .It Ic show Cm lockchain Ar addr
751 Show all threads a particular thread at address
753 is waiting on based on non-sleepable and non-spin locks.
756 .It Ic show Cm lockedbufs
757 Show the same information as "show buf", but for every locked
762 .It Ic show Cm lockedvnods
763 List all locked vnodes in the system.
767 Prints all locks that are currently acquired.
768 This command is only available if
770 is included in the kernel.
773 .It Ic show Cm locktree
776 .It Ic show Cm malloc
779 memory allocator statistics.
780 The output format is as follows:
782 .Bl -tag -compact -offset indent -width "Requests"
784 Specifies a type of memory.
785 It is the same as a description string used while defining the
786 given memory type with
787 .Xr MALLOC_DECLARE 9 .
789 Number of memory allocations of the given type, for which
791 has not been called yet.
793 Total memory consumed by the given allocation type.
795 Number of memory allocation requests for the given
799 The same information can be gathered in userspace with
803 .It Ic show Cm map Ns Oo Li / Ns Cm f Oc Ar addr
808 modifier is specified the
809 complete map is printed.
812 .It Ic show Cm msgbuf
813 Print the system's message buffer.
814 It is the same output as in the
817 It is useful if you got a kernel panic, attached a serial cable
818 to the machine and want to get the boot messages from before the
822 Displays short info about all currently mounted file systems.
824 .It Ic show Cm mount Ar addr
825 Displays details about the given mount point.
828 .It Ic show Cm object Ns Oo Li / Ns Cm f Oc Ar addr
829 Prints the VM object at
833 option is specified the
834 complete object is printed.
838 Show statistics on VM pages.
842 Show statistics on VM page queues.
845 .It Ic show Cm pciregs
846 Print PCI bus registers.
847 The same information can be gathered in userspace by running
848 .Dq Nm pciconf Fl lv .
852 Print current processor state.
853 The output format is as follows:
855 .Bl -tag -compact -offset indent -width "spin locks held:"
857 Processor identifier.
859 Thread pointer, process identifier and the name of the process.
861 Control block pointer.
867 CPU identifier coming from APIC.
870 .It Ic spin locks held
871 Names of spin locks held.
875 .It Ic show Cm pgrpdump
876 Dump process groups present within the system.
879 .It Ic show Cm proc Op Ar addr
882 is specified, print information about the current process.
883 Otherwise, show information about the process at address
887 .It Ic show Cm procvm
888 Show process virtual memory layout.
891 .It Ic show Cm protosw Ar addr
892 Print protocol switch structure
898 .It Ic show Cm registers Ns Op Li / Ns Cm u
899 Display the register set.
902 modifier is specified, it displays user registers instead of
903 kernel registers or the currently saved one.
908 modifier depends on the machine.
909 If not supported, incorrect information will be displayed.
912 .It Ic show Cm rman Ar addr
913 Show resource manager object
917 Addresses of particular pointers can be gathered with "show allrman"
922 Show real time clock value.
923 Useful for long debugging sessions.
926 .It Ic show Cm sleepchain
927 Show all the threads a particular thread is waiting on based on
931 .It Ic show Cm sleepq
932 .It Ic show Cm sleepqueue
933 Both commands provide the same functionality.
935 .Vt struct sleepqueue
937 Sleepqueues are used within the
939 kernel to implement sleepable
940 synchronization primitives (thread holding a lock might sleep or
941 be context switched), which at the time of writing are:
949 .It Ic show Cm sockbuf Ar addr
950 .It Ic show Cm socket Ar addr
957 Output consists of all values present in structures mentioned.
958 For exact interpretation and more details, visit
963 .It Ic show Cm sysregs
964 Show system registers (e.g.,
967 Not present on some platforms.
970 .It Ic show Cm tcpcb Ar addr
971 Print TCP control block
975 For exact interpretation of output, visit
980 .It Ic show Cm thread Op Ar addr
983 is specified, show detailed information about current thread.
984 Otherwise, information about thread at
989 .It Ic show Cm threads
990 Show all threads within the system.
991 Output format is as follows:
993 .Bl -tag -compact -offset indent -width "Second column"
995 Thread identifier (TID)
997 Thread structure address
1003 .It Ic show Cm tty Ar addr
1004 Display the contents of a TTY structure in a readable form.
1007 .It Ic show Cm turnstile Ar addr
1009 .Vt struct turnstile
1010 structure at address
1012 Turnstiles are structures used within the
1015 synchronization primitives which, while holding a specific type of lock, cannot
1016 sleep or context switch to another thread.
1017 Currently, those are:
1024 Show UMA allocator statistics.
1025 Output consists five columns:
1027 .Bl -tag -compact -offset indent -width "Requests"
1029 Name of the UMA zone.
1030 The same string that was passed to
1032 as a first argument.
1034 Size of a given memory object (slab).
1036 Number of slabs being currently used.
1038 Number of free slabs within the UMA zone.
1040 Number of allocations requests to the given zone.
1043 The very same information might be gathered in the userspace
1045 .Dq Nm vmstat Fl z .
1048 .It Ic show Cm unpcb Ar addr
1049 Shows UNIX domain socket private control block
1051 present at the address
1055 .It Ic show Cm vmochk
1056 Prints, whether the internal VM objects are in a map somewhere
1057 and none have zero ref counts.
1060 .It Ic show Cm vmopag
1061 This is supposed to show physical addresses consumed by a
1063 Currently, it is not possible to use this command when
1065 is compiled in the kernel.
1068 .It Ic show Cm vnode Op Ar addr
1073 For the exact interpretation of the output, look at the
1078 .It Ic show Cm vnodebufs Ar addr
1079 Shows clean/dirty buffer lists of the vnode located at
1083 .It Ic show Cm watches
1084 Displays all watchpoints.
1085 Shows watchpoints set with "watch" command.
1088 .It Ic show Cm witness
1089 Shows information about lock acquisition coming from the
1095 Toggles between remote GDB and DDB mode.
1096 In remote GDB mode, another machine is required that runs
1098 using the remote debug feature, with a connection to the serial
1099 console port on the target machine.
1100 Currently only available on the
1107 .It Ic kill Ar sig pid
1112 The signal is acted on upon returning from the debugger.
1113 This command can be used to kill a process causing resource contention
1114 in the case of a hung system.
1117 for a list of signals.
1118 Note that the arguments are reversed relative to
1121 .It Ic reboot Op Ar seconds
1122 .It Ic reset Op Ar seconds
1123 Hard reset the system.
1124 If the optional argument
1126 is given, the debugger will wait for this long, at most a week,
1130 Print a short summary of the available commands and command
1135 .It Ic capture reset
1136 .It Ic capture status
1138 supports a basic output capture facility, which can be used to retrieve the
1139 results of debugging commands from userpsace using
1142 enables output capture;
1146 will clear the capture buffer and disable capture.
1148 will report current buffer use, buffer size, and disposition of output
1151 Userspace processes may inspect and manage
1156 .Dv debug.ddb.capture.bufsize
1157 may be used to query or set the current capture buffer size.
1159 .Dv debug.ddb.capture.maxbufsize
1160 may be used to query the compile-time limit on the capture buffer size.
1162 .Dv debug.ddb.capture.bytes
1163 may be used to query the number of bytes of output currently in the capture
1166 .Dv debug.ddb.capture.data
1167 returns the contents of the buffer as a string to an appropriately privileged
1170 This facility is particularly useful in concert with the scripting and
1172 facilities, allowing scripted debugging output to be captured and
1173 committed to disk as part of a textdump for later analysis.
1174 The contents of the capture buffer may also be inspected in a kernel core dump
1182 Run, define, list, and delete scripts.
1185 section for more information on the scripting facility.
1187 .It Ic textdump dump
1189 .It Ic textdump status
1190 .It Ic textdump unset
1193 command to immediately perform a textdump.
1194 More information may be found in
1198 command may be used to force the next kernel core dump to be a textdump
1199 rather than a traditional memory dump or minidump.
1201 reports whether a textdump has been scheduled.
1203 cancels a request to perform a textdump as the next kernel core dump.
1206 The debugger accesses registers and variables as
1208 Register names are as in the
1209 .Dq Ic show Cm registers
1211 Some variables are suffixed with numbers, and may have some modifier
1212 following a colon immediately after the variable name.
1213 For example, register variables can have a
1215 modifier to indicate user register (e.g.,
1218 Built-in variables currently supported are:
1220 .Bl -tag -width ".Va tabstops" -compact
1222 Input and output radix.
1224 Addresses are printed as
1225 .Dq Ar symbol Ns Li + Ns Ar offset
1231 The width of the displayed line.
1233 The number of lines.
1234 It is used by the built-in pager.
1237 .It Va work Ns Ar xx
1240 can take values from 0 to 31.
1243 Most expression operators in C are supported except
1251 .Bl -tag -width ".No Identifiers"
1253 The name of a symbol is translated to the value of the symbol, which
1254 is the address of the corresponding object.
1258 can be used in the identifier.
1259 If supported by an object format dependent routine,
1261 .Oo Ar filename : Oc Ar func : lineno ,
1263 .Oo Ar filename : Oc Ns Ar variable ,
1265 .Oo Ar filename : Oc Ns Ar lineno
1266 can be accepted as a symbol.
1268 Radix is determined by the first two letters:
1274 decimal; otherwise, follow current radix.
1280 address of the start of the last line examined.
1285 this is only changed by
1291 last address explicitly specified.
1292 .It Li $ Ns Ar variable
1293 Translated to the value of the specified variable.
1294 It may be followed by a
1296 and modifiers as described above.
1297 .It Ar a Ns Li # Ns Ar b
1298 A binary operator which rounds up the left hand side to the next
1299 multiple of right hand side.
1302 It may be followed by a
1304 and modifiers as described above.
1308 supports a basic scripting facility to allow automating tasks or responses to
1310 Each script consists of a list of DDB commands to be executed sequentially,
1311 and is assigned a unique name.
1312 Certain script names have special meaning, and will be automatically run on
1315 events if scripts by those names have been defined.
1319 command may be used to define a script by name.
1320 Scripts consist of a series of
1322 commands separated with the
1326 .Bd -literal -offset indent
1327 script kdb.enter.panic=bt; show pcpu
1328 script lockinfo=show alllocks; show lockedvnods
1333 command lists currently defined scripts.
1337 command execute a script by name.
1339 .Bd -literal -offset indent
1345 command may be used to delete a script by name.
1347 .Bd -literal -offset indent
1348 unscript kdb.enter.panic
1351 These functions may also be performed from userspace using the
1355 Certain scripts are run automatically, if defined, for specific
1358 The follow scripts are run when various events occur:
1359 .Bl -tag -width kdb.enter.powerfail
1360 .It Dv kdb.enter.acpi
1361 The kernel debugger was entered as a result of an
1364 .It Dv kdb.enter.bootflags
1365 The kernel debugger was entered at boot as a result of the debugger boot
1367 .It Dv kdb.enter.break
1368 The kernel debugger was entered as a result of a serial or console break.
1369 .It Dv kdb.enter.cam
1370 The kernel debugger was entered as a result of a
1373 .It Dv kdb.enter.mac
1374 The kernel debugger was entered as a result of an assertion failure in the
1377 TrustedBSD MAC Framework.
1378 .It Dv kdb.enter.ndis
1379 The kernel debugger was entered as a result of an
1382 .It Dv kdb.enter.netgraph
1383 The kernel debugger was entered as a result of a
1386 .It Dv kdb.enter.panic
1389 .It Dv kdb.enter.powerfail
1390 The kernel debugger was entered as a result of a powerfail NMI on the sparc64
1392 .It Dv kdb.enter.powerpc
1393 The kernel debugger was entered as a result of an unimplemented interrupt
1394 type on the powerpc platform.
1395 .It Dv kdb.enter.sysctl
1396 The kernel debugger was entered as a result of the
1399 .It Dv kdb.enter.trapsig
1400 The kernel debugger was entered as a result of a trapsig event on the sparc64
1402 .It Dv kdb.enter.unionfs
1403 The kernel debugger was entered as a result of an assertion failure in the
1405 .It Dv kdb.enter.unknown
1406 The kernel debugger was entered, but no reason has been set.
1407 .It Dv kdb.enter.vfslock
1408 The kernel debugger was entered as a result of a VFS lock violation.
1409 .It Dv kdb.enter.watchdog
1410 The kernel debugger was entered as a result of a watchdog firing.
1411 .It Dv kdb.enter.witness
1412 The kernel debugger was entered as a result of a
1417 In the event that none of these scripts is found,
1419 will attempt to execute a default script:
1420 .Bl -tag -width kdb.enter.powerfail
1421 .It Dv kdb.enter.default
1422 The kernel debugger was entered, but a script exactly matching the reason for
1423 entering was not defined.
1424 This can be used as a catch-all to handle cases not specifically of interest;
1426 .Dv kdb.enter.witness
1427 might be defined to have special handling, and
1428 .Dv kdb.enter.default
1429 might be defined to simply panic and reboot.
1432 On machines with an ISA expansion bus, a simple NMI generation card can be
1433 constructed by connecting a push button between the A01 and B01 (CHCHK# and
1435 Momentarily shorting these two fingers together may cause the bridge chipset to
1436 generate an NMI, which causes the kernel to pass control to
1438 Some bridge chipsets do not generate a NMI on CHCHK#, so your mileage may vary.
1439 The NMI allows one to break into the debugger on a wedged machine to
1441 Other bus' bridge chipsets may be able to generate NMI using bus specific
1444 Header files mention in this manual page can be found below
1454 .Pa netinet/in_pcb.h
1476 debugger was developed for Mach, and ported to
1478 This manual page translated from
1481 .An Garrett Wollman .
1483 .An Robert N. M. Watson