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
63 .Dd September 30, 2013
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 buffer
588 Show buffer structure of
591 Such a structure is used within the
593 kernel for the I/O subsystem
595 For an exact interpretation of the output, please see the
600 .It Ic show Cm cbstat
601 Show brief information about the TTY subsystem.
605 Without argument, show the list of all created cdev's, consisting of devfs
606 node name and struct cdev address.
607 When address of cdev is supplied, show some internal devfs state of the cdev.
610 .It Ic show Cm conifhk
611 Lists hooks currently waiting for completion in
612 run_interrupt_driven_config_hooks().
615 .It Ic show Cm cpusets
616 Print numbered root and assigned CPU affinity sets.
622 .It Ic show Cm cyrixreg
623 Show registers specific to the Cyrix processor.
626 .It Ic show Cm domain Ar addr
627 Print protocol domain structure
633 header file for more details on the exact meaning of the structure fields.
636 .It Ic show Cm ffs Op Ar addr
637 Show brief information about ffs mount at the address
639 if argument is given.
640 Otherwise, provides the summary about each ffs mount.
643 .It Ic show Cm file Ar addr
644 Show information about the file structure
651 Show information about every file structure in the system.
654 .It Ic show Cm freepages
655 Show the number of physical pages in each of the free lists.
658 .It Ic show Cm geom Op Ar addr
661 argument is not given, displays the entire GEOM topology.
664 is given, displays details about the given GEOM object (class, geom,
665 provider or consumer).
670 The first column specifies the IDT vector.
671 The second one is the name of the interrupt/trap handler.
672 Those functions are machine dependent.
675 .It Ic show Cm inodedeps Op Ar addr
676 Show brief information about each inodedep structure.
679 is given, only inodedeps belonging to the fs located at the
680 supplied address are shown.
683 .It Ic show Cm inpcb Ar addr
684 Show information on IP Control Block
691 Dump information about interrupt handlers.
694 .It Ic show Cm intrcnt
695 Dump the interrupt statistics.
699 Show interrupt lines and their respective kernel threads.
708 shows, also list kernel internal details.
712 Show information from the local APIC registers for this CPU.
715 .It Ic show Cm lock Ar addr
717 The output format is as follows:
718 .Bl -tag -width "flags"
721 Possible types include
729 Flags passed to the lock initialization function.
730 For exact possibilities see manual pages of possible lock types.
732 Current state of a lock.
741 .It Ic show Cm lockchain Ar addr
742 Show all threads a particular thread at address
744 is waiting on based on non-sleepable and non-spin locks.
747 .It Ic show Cm lockedbufs
748 Show the same information as "show buf", but for every locked
753 .It Ic show Cm lockedvnods
754 List all locked vnodes in the system.
758 Prints all locks that are currently acquired.
759 This command is only available if
761 is included in the kernel.
764 .It Ic show Cm locktree
767 .It Ic show Cm malloc
770 memory allocator statistics.
771 The output format is as follows:
773 .Bl -tag -compact -offset indent -width "Requests"
775 Specifies a type of memory.
776 It is the same as a description string used while defining the
777 given memory type with
778 .Xr MALLOC_DECLARE 9 .
780 Number of memory allocations of the given type, for which
782 has not been called yet.
784 Total memory consumed by the given allocation type.
786 Number of memory allocation requests for the given
790 The same information can be gathered in userspace with
794 .It Ic show Cm map Ns Oo Li / Ns Cm f Oc Ar addr
799 modifier is specified the
800 complete map is printed.
803 .It Ic show Cm msgbuf
804 Print the system's message buffer.
805 It is the same output as in the
808 It is useful if you got a kernel panic, attached a serial cable
809 to the machine and want to get the boot messages from before the
813 Displays short info about all currently mounted file systems.
815 .It Ic show Cm mount Ar addr
816 Displays details about the given mount point.
819 .It Ic show Cm object Ns Oo Li / Ns Cm f Oc Ar addr
820 Prints the VM object at
824 option is specified the
825 complete object is printed.
829 Show statistics on VM pages.
833 Show statistics on VM page queues.
836 .It Ic show Cm pciregs
837 Print PCI bus registers.
838 The same information can be gathered in userspace by running
839 .Dq Nm pciconf Fl lv .
843 Print current processor state.
844 The output format is as follows:
846 .Bl -tag -compact -offset indent -width "spin locks held:"
848 Processor identifier.
850 Thread pointer, process identifier and the name of the process.
852 Control block pointer.
858 CPU identifier coming from APIC.
861 .It Ic spin locks held
862 Names of spin locks held.
866 .It Ic show Cm pgrpdump
867 Dump process groups present within the system.
870 .It Ic show Cm proc Op Ar addr
873 is specified, print information about the current process.
874 Otherwise, show information about the process at address
878 .It Ic show Cm procvm
879 Show process virtual memory layout.
882 .It Ic show Cm protosw Ar addr
883 Print protocol switch structure
889 .It Ic show Cm registers Ns Op Li / Ns Cm u
890 Display the register set.
893 modifier is specified, it displays user registers instead of
894 kernel registers or the currently saved one.
899 modifier depends on the machine.
900 If not supported, incorrect information will be displayed.
903 .It Ic show Cm rman Ar addr
904 Show resource manager object
908 Addresses of particular pointers can be gathered with "show allrman"
913 Show real time clock value.
914 Useful for long debugging sessions.
917 .It Ic show Cm sleepchain
918 Show all the threads a particular thread is waiting on based on
922 .It Ic show Cm sleepq
923 .It Ic show Cm sleepqueue
924 Both commands provide the same functionality.
926 .Vt struct sleepqueue
928 Sleepqueues are used within the
930 kernel to implement sleepable
931 synchronization primitives (thread holding a lock might sleep or
932 be context switched), which at the time of writing are:
940 .It Ic show Cm sockbuf Ar addr
941 .It Ic show Cm socket Ar addr
948 Output consists of all values present in structures mentioned.
949 For exact interpretation and more details, visit
954 .It Ic show Cm sysregs
955 Show system registers (e.g.,
958 Not present on some platforms.
961 .It Ic show Cm tcpcb Ar addr
962 Print TCP control block
966 For exact interpretation of output, visit
971 .It Ic show Cm thread Op Ar addr
974 is specified, show detailed information about current thread.
975 Otherwise, information about thread at
980 .It Ic show Cm threads
981 Show all threads within the system.
982 Output format is as follows:
984 .Bl -tag -compact -offset indent -width "Second column"
986 Thread identifier (TID)
988 Thread structure address
994 .It Ic show Cm tty Ar addr
995 Display the contents of a TTY structure in a readable form.
998 .It Ic show Cm turnstile Ar addr
1000 .Vt struct turnstile
1001 structure at address
1003 Turnstiles are structures used within the
1006 synchronization primitives which, while holding a specific type of lock, cannot
1007 sleep or context switch to another thread.
1008 Currently, those are:
1015 Show UMA allocator statistics.
1016 Output consists five columns:
1018 .Bl -tag -compact -offset indent -width "Requests"
1020 Name of the UMA zone.
1021 The same string that was passed to
1023 as a first argument.
1025 Size of a given memory object (slab).
1027 Number of slabs being currently used.
1029 Number of free slabs within the UMA zone.
1031 Number of allocations requests to the given zone.
1034 The very same information might be gathered in the userspace
1036 .Dq Nm vmstat Fl z .
1039 .It Ic show Cm unpcb Ar addr
1040 Shows UNIX domain socket private control block
1042 present at the address
1046 .It Ic show Cm vmochk
1047 Prints, whether the internal VM objects are in a map somewhere
1048 and none have zero ref counts.
1051 .It Ic show Cm vmopag
1052 This is supposed to show physical addresses consumed by a
1054 Currently, it is not possible to use this command when
1056 is compiled in the kernel.
1059 .It Ic show Cm vnode Op Ar addr
1064 For the exact interpretation of the output, look at the
1069 .It Ic show Cm vnodebufs Ar addr
1070 Shows clean/dirty buffer lists of the vnode located at
1074 .It Ic show Cm watches
1075 Displays all watchpoints.
1076 Shows watchpoints set with "watch" command.
1079 .It Ic show Cm witness
1080 Shows information about lock acquisition coming from the
1086 Toggles between remote GDB and DDB mode.
1087 In remote GDB mode, another machine is required that runs
1089 using the remote debug feature, with a connection to the serial
1090 console port on the target machine.
1091 Currently only available on the
1098 .It Ic kill Ar sig pid
1103 The signal is acted on upon returning from the debugger.
1104 This command can be used to kill a process causing resource contention
1105 in the case of a hung system.
1108 for a list of signals.
1109 Note that the arguments are reversed relative to
1112 .It Ic reboot Op Ar seconds
1113 .It Ic reset Op Ar seconds
1114 Hard reset the system.
1115 If the optional argument
1117 is given, the debugger will wait for this long, at most a week,
1121 Print a short summary of the available commands and command
1126 .It Ic capture reset
1127 .It Ic capture status
1129 supports a basic output capture facility, which can be used to retrieve the
1130 results of debugging commands from userpsace using
1133 enables output capture;
1137 will clear the capture buffer and disable capture.
1139 will report current buffer use, buffer size, and disposition of output
1142 Userspace processes may inspect and manage
1147 .Dv debug.ddb.capture.bufsize
1148 may be used to query or set the current capture buffer size.
1150 .Dv debug.ddb.capture.maxbufsize
1151 may be used to query the compile-time limit on the capture buffer size.
1153 .Dv debug.ddb.capture.bytes
1154 may be used to query the number of bytes of output currently in the capture
1157 .Dv debug.ddb.capture.data
1158 returns the contents of the buffer as a string to an appropriately privileged
1161 This facility is particularly useful in concert with the scripting and
1163 facilities, allowing scripted debugging output to be captured and
1164 committed to disk as part of a textdump for later analysis.
1165 The contents of the capture buffer may also be inspected in a kernel core dump
1173 Run, define, list, and delete scripts.
1176 section for more information on the scripting facility.
1178 .It Ic textdump dump
1180 .It Ic textdump status
1181 .It Ic textdump unset
1184 command to immediately perform a textdump.
1185 More information may be found in
1189 command may be used to force the next kernel core dump to be a textdump
1190 rather than a traditional memory dump or minidump.
1192 reports whether a textdump has been scheduled.
1194 cancels a request to perform a textdump as the next kernel core dump.
1197 The debugger accesses registers and variables as
1199 Register names are as in the
1200 .Dq Ic show Cm registers
1202 Some variables are suffixed with numbers, and may have some modifier
1203 following a colon immediately after the variable name.
1204 For example, register variables can have a
1206 modifier to indicate user register (e.g.,
1209 Built-in variables currently supported are:
1211 .Bl -tag -width ".Va tabstops" -compact
1213 Input and output radix.
1215 Addresses are printed as
1216 .Dq Ar symbol Ns Li + Ns Ar offset
1222 The width of the displayed line.
1224 The number of lines.
1225 It is used by the built-in pager.
1228 .It Va work Ns Ar xx
1231 can take values from 0 to 31.
1234 Most expression operators in C are supported except
1242 .Bl -tag -width ".No Identifiers"
1244 The name of a symbol is translated to the value of the symbol, which
1245 is the address of the corresponding object.
1249 can be used in the identifier.
1250 If supported by an object format dependent routine,
1252 .Oo Ar filename : Oc Ar func : lineno ,
1254 .Oo Ar filename : Oc Ns Ar variable ,
1256 .Oo Ar filename : Oc Ns Ar lineno
1257 can be accepted as a symbol.
1259 Radix is determined by the first two letters:
1265 decimal; otherwise, follow current radix.
1271 address of the start of the last line examined.
1276 this is only changed by
1282 last address explicitly specified.
1283 .It Li $ Ns Ar variable
1284 Translated to the value of the specified variable.
1285 It may be followed by a
1287 and modifiers as described above.
1288 .It Ar a Ns Li # Ns Ar b
1289 A binary operator which rounds up the left hand side to the next
1290 multiple of right hand side.
1293 It may be followed by a
1295 and modifiers as described above.
1299 supports a basic scripting facility to allow automating tasks or responses to
1301 Each script consists of a list of DDB commands to be executed sequentially,
1302 and is assigned a unique name.
1303 Certain script names have special meaning, and will be automatically run on
1306 events if scripts by those names have been defined.
1310 command may be used to define a script by name.
1311 Scripts consist of a series of
1313 commands separated with the
1317 .Bd -literal -offset indent
1318 script kdb.enter.panic=bt; show pcpu
1319 script lockinfo=show alllocks; show lockedvnods
1324 command lists currently defined scripts.
1328 command execute a script by name.
1330 .Bd -literal -offset indent
1336 command may be used to delete a script by name.
1338 .Bd -literal -offset indent
1339 unscript kdb.enter.panic
1342 These functions may also be performed from userspace using the
1346 Certain scripts are run automatically, if defined, for specific
1349 The follow scripts are run when various events occur:
1350 .Bl -tag -width kdb.enter.powerfail
1351 .It Dv kdb.enter.acpi
1352 The kernel debugger was entered as a result of an
1355 .It Dv kdb.enter.bootflags
1356 The kernel debugger was entered at boot as a result of the debugger boot
1358 .It Dv kdb.enter.break
1359 The kernel debugger was entered as a result of a serial or console break.
1360 .It Dv kdb.enter.cam
1361 The kernel debugger was entered as a result of a
1364 .It Dv kdb.enter.mac
1365 The kernel debugger was entered as a result of an assertion failure in the
1368 TrustedBSD MAC Framework.
1369 .It Dv kdb.enter.ndis
1370 The kernel debugger was entered as a result of an
1373 .It Dv kdb.enter.netgraph
1374 The kernel debugger was entered as a result of a
1377 .It Dv kdb.enter.panic
1380 .It Dv kdb.enter.powerfail
1381 The kernel debugger was entered as a result of a powerfail NMI on the sparc64
1383 .It Dv kdb.enter.powerpc
1384 The kernel debugger was entered as a result of an unimplemented interrupt
1385 type on the powerpc platform.
1386 .It Dv kdb.enter.sysctl
1387 The kernel debugger was entered as a result of the
1390 .It Dv kdb.enter.trapsig
1391 The kernel debugger was entered as a result of a trapsig event on the sparc64
1393 .It Dv kdb.enter.unionfs
1394 The kernel debugger was entered as a result of an assertion failure in the
1396 .It Dv kdb.enter.unknown
1397 The kernel debugger was entered, but no reason has been set.
1398 .It Dv kdb.enter.vfslock
1399 The kernel debugger was entered as a result of a VFS lock violation.
1400 .It Dv kdb.enter.watchdog
1401 The kernel debugger was entered as a result of a watchdog firing.
1402 .It Dv kdb.enter.witness
1403 The kernel debugger was entered as a result of a
1408 In the event that none of these scripts is found,
1410 will attempt to execute a default script:
1411 .Bl -tag -width kdb.enter.powerfail
1412 .It Dv kdb.enter.default
1413 The kernel debugger was entered, but a script exactly matching the reason for
1414 entering was not defined.
1415 This can be used as a catch-all to handle cases not specifically of interest;
1417 .Dv kdb.enter.witness
1418 might be defined to have special handling, and
1419 .Dv kdb.enter.default
1420 might be defined to simply panic and reboot.
1423 On machines with an ISA expansion bus, a simple NMI generation card can be
1424 constructed by connecting a push button between the A01 and B01 (CHCHK# and
1426 Momentarily shorting these two fingers together may cause the bridge chipset to
1427 generate an NMI, which causes the kernel to pass control to
1429 Some bridge chipsets do not generate a NMI on CHCHK#, so your mileage may vary.
1430 The NMI allows one to break into the debugger on a wedged machine to
1432 Other bus' bridge chipsets may be able to generate NMI using bus specific
1435 Header files mention in this manual page can be found below
1445 .Pa netinet/in_pcb.h
1467 debugger was developed for Mach, and ported to
1469 This manual page translated from
1472 .An Garrett Wollman .
1474 .An Robert N. M. Watson