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 trace
553 Show a stack trace for every thread in the system.
555 .It Ic show Cm all ttys
556 Show all TTY's within the system.
559 but also includes the address of the TTY structure.
562 .It Ic show Cm allchains
563 Show the same information like "show lockchain" does, but
564 for every thread in the system.
567 .It Ic show Cm alllocks
568 Show all locks that are currently held.
569 This command is only available if
571 is included in the kernel.
574 .It Ic show Cm allpcpu
575 The same as "show pcpu", but for every CPU present in the system.
578 .It Ic show Cm allrman
579 Show information related with resource management, including
580 interrupt request lines, DMA request lines, I/O ports, I/O memory
581 addresses, and Resource IDs.
585 Dump data about APIC IDT vector mappings.
588 .It Ic show Cm breaks
589 Show breakpoints set with the "break" command.
592 .It Ic show Cm bio Ar addr
593 Show information about the bio structure
601 for more details on the exact meaning of the structure fields.
604 .It Ic show Cm buffer Ar addr
605 Show information about the buf structure
611 header file for more details on the exact meaning of the structure fields.
614 .It Ic show Cm callout Ar addr
615 Show information about the callout structure
621 .It Ic show Cm cbstat
622 Show brief information about the TTY subsystem.
626 Without argument, show the list of all created cdev's, consisting of devfs
627 node name and struct cdev address.
628 When address of cdev is supplied, show some internal devfs state of the cdev.
631 .It Ic show Cm conifhk
632 Lists hooks currently waiting for completion in
633 run_interrupt_driven_config_hooks().
636 .It Ic show Cm cpusets
637 Print numbered root and assigned CPU affinity sets.
643 .It Ic show Cm cyrixreg
644 Show registers specific to the Cyrix processor.
647 .It Ic show Cm domain Ar addr
648 Print protocol domain structure
654 header file for more details on the exact meaning of the structure fields.
657 .It Ic show Cm ffs Op Ar addr
658 Show brief information about ffs mount at the address
660 if argument is given.
661 Otherwise, provides the summary about each ffs mount.
664 .It Ic show Cm file Ar addr
665 Show information about the file structure
672 Show information about every file structure in the system.
675 .It Ic show Cm freepages
676 Show the number of physical pages in each of the free lists.
679 .It Ic show Cm geom Op Ar addr
682 argument is not given, displays the entire GEOM topology.
685 is given, displays details about the given GEOM object (class, geom,
686 provider or consumer).
691 The first column specifies the IDT vector.
692 The second one is the name of the interrupt/trap handler.
693 Those functions are machine dependent.
696 .It Ic show Cm inodedeps Op Ar addr
697 Show brief information about each inodedep structure.
700 is given, only inodedeps belonging to the fs located at the
701 supplied address are shown.
704 .It Ic show Cm inpcb Ar addr
705 Show information on IP Control Block
712 Dump information about interrupt handlers.
715 .It Ic show Cm intrcnt
716 Dump the interrupt statistics.
720 Show interrupt lines and their respective kernel threads.
729 shows, also list kernel internal details.
733 Show information from the local APIC registers for this CPU.
736 .It Ic show Cm lock Ar addr
738 The output format is as follows:
739 .Bl -tag -width "flags"
742 Possible types include
750 Flags passed to the lock initialization function.
751 For exact possibilities see manual pages of possible lock types.
753 Current state of a lock.
762 .It Ic show Cm lockchain Ar addr
763 Show all threads a particular thread at address
765 is waiting on based on non-sleepable and non-spin locks.
768 .It Ic show Cm lockedbufs
769 Show the same information as "show buf", but for every locked
774 .It Ic show Cm lockedvnods
775 List all locked vnodes in the system.
779 Prints all locks that are currently acquired.
780 This command is only available if
782 is included in the kernel.
785 .It Ic show Cm locktree
788 .It Ic show Cm malloc
791 memory allocator statistics.
792 The output format is as follows:
794 .Bl -tag -compact -offset indent -width "Requests"
796 Specifies a type of memory.
797 It is the same as a description string used while defining the
798 given memory type with
799 .Xr MALLOC_DECLARE 9 .
801 Number of memory allocations of the given type, for which
803 has not been called yet.
805 Total memory consumed by the given allocation type.
807 Number of memory allocation requests for the given
811 The same information can be gathered in userspace with
815 .It Ic show Cm map Ns Oo Li / Ns Cm f Oc Ar addr
820 modifier is specified the
821 complete map is printed.
824 .It Ic show Cm msgbuf
825 Print the system's message buffer.
826 It is the same output as in the
829 It is useful if you got a kernel panic, attached a serial cable
830 to the machine and want to get the boot messages from before the
834 Displays short info about all currently mounted file systems.
836 .It Ic show Cm mount Ar addr
837 Displays details about the given mount point.
840 .It Ic show Cm object Ns Oo Li / Ns Cm f Oc Ar addr
841 Prints the VM object at
845 option is specified the
846 complete object is printed.
850 Print the panic message if set.
854 Show statistics on VM pages.
858 Show statistics on VM page queues.
861 .It Ic show Cm pciregs
862 Print PCI bus registers.
863 The same information can be gathered in userspace by running
864 .Dq Nm pciconf Fl lv .
868 Print current processor state.
869 The output format is as follows:
871 .Bl -tag -compact -offset indent -width "spin locks held:"
873 Processor identifier.
875 Thread pointer, process identifier and the name of the process.
877 Control block pointer.
883 CPU identifier coming from APIC.
886 .It Ic spin locks held
887 Names of spin locks held.
891 .It Ic show Cm pgrpdump
892 Dump process groups present within the system.
895 .It Ic show Cm proc Op Ar addr
898 is specified, print information about the current process.
899 Otherwise, show information about the process at address
903 .It Ic show Cm procvm
904 Show process virtual memory layout.
907 .It Ic show Cm protosw Ar addr
908 Print protocol switch structure
914 .It Ic show Cm registers Ns Op Li / Ns Cm u
915 Display the register set.
918 modifier is specified, it displays user registers instead of
919 kernel registers or the currently saved one.
924 modifier depends on the machine.
925 If not supported, incorrect information will be displayed.
928 .It Ic show Cm rman Ar addr
929 Show resource manager object
933 Addresses of particular pointers can be gathered with "show allrman"
938 Show real time clock value.
939 Useful for long debugging sessions.
942 .It Ic show Cm sleepchain
943 Show all the threads a particular thread is waiting on based on
947 .It Ic show Cm sleepq
948 .It Ic show Cm sleepqueue
949 Both commands provide the same functionality.
951 .Vt struct sleepqueue
953 Sleepqueues are used within the
955 kernel to implement sleepable
956 synchronization primitives (thread holding a lock might sleep or
957 be context switched), which at the time of writing are:
965 .It Ic show Cm sockbuf Ar addr
966 .It Ic show Cm socket Ar addr
973 Output consists of all values present in structures mentioned.
974 For exact interpretation and more details, visit
979 .It Ic show Cm sysregs
980 Show system registers (e.g.,
983 Not present on some platforms.
986 .It Ic show Cm tcpcb Ar addr
987 Print TCP control block
991 For exact interpretation of output, visit
996 .It Ic show Cm thread Op Ar addr
999 is specified, show detailed information about current thread.
1000 Otherwise, information about thread at
1005 .It Ic show Cm threads
1006 Show all threads within the system.
1007 Output format is as follows:
1009 .Bl -tag -compact -offset indent -width "Second column"
1011 Thread identifier (TID)
1012 .It Ic Second column
1013 Thread structure address
1019 .It Ic show Cm tty Ar addr
1020 Display the contents of a TTY structure in a readable form.
1023 .It Ic show Cm turnstile Ar addr
1025 .Vt struct turnstile
1026 structure at address
1028 Turnstiles are structures used within the
1031 synchronization primitives which, while holding a specific type of lock, cannot
1032 sleep or context switch to another thread.
1033 Currently, those are:
1040 Show UMA allocator statistics.
1041 Output consists five columns:
1043 .Bl -tag -compact -offset indent -width "Requests"
1045 Name of the UMA zone.
1046 The same string that was passed to
1048 as a first argument.
1050 Size of a given memory object (slab).
1052 Number of slabs being currently used.
1054 Number of free slabs within the UMA zone.
1056 Number of allocations requests to the given zone.
1059 The very same information might be gathered in the userspace
1061 .Dq Nm vmstat Fl z .
1064 .It Ic show Cm unpcb Ar addr
1065 Shows UNIX domain socket private control block
1067 present at the address
1071 .It Ic show Cm vmochk
1072 Prints, whether the internal VM objects are in a map somewhere
1073 and none have zero ref counts.
1076 .It Ic show Cm vmopag
1077 This is supposed to show physical addresses consumed by a
1079 Currently, it is not possible to use this command when
1081 is compiled in the kernel.
1084 .It Ic show Cm vnode Op Ar addr
1089 For the exact interpretation of the output, look at the
1094 .It Ic show Cm vnodebufs Ar addr
1095 Shows clean/dirty buffer lists of the vnode located at
1099 .It Ic show Cm watches
1100 Displays all watchpoints.
1101 Shows watchpoints set with "watch" command.
1104 .It Ic show Cm witness
1105 Shows information about lock acquisition coming from the
1111 Toggles between remote GDB and DDB mode.
1112 In remote GDB mode, another machine is required that runs
1114 using the remote debug feature, with a connection to the serial
1115 console port on the target machine.
1116 Currently only available on the
1123 .It Ic kill Ar sig pid
1128 The signal is acted on upon returning from the debugger.
1129 This command can be used to kill a process causing resource contention
1130 in the case of a hung system.
1133 for a list of signals.
1134 Note that the arguments are reversed relative to
1137 .It Ic reboot Op Ar seconds
1138 .It Ic reset Op Ar seconds
1139 Hard reset the system.
1140 If the optional argument
1142 is given, the debugger will wait for this long, at most a week,
1146 Print a short summary of the available commands and command
1151 .It Ic capture reset
1152 .It Ic capture status
1154 supports a basic output capture facility, which can be used to retrieve the
1155 results of debugging commands from userpsace using
1158 enables output capture;
1162 will clear the capture buffer and disable capture.
1164 will report current buffer use, buffer size, and disposition of output
1167 Userspace processes may inspect and manage
1172 .Dv debug.ddb.capture.bufsize
1173 may be used to query or set the current capture buffer size.
1175 .Dv debug.ddb.capture.maxbufsize
1176 may be used to query the compile-time limit on the capture buffer size.
1178 .Dv debug.ddb.capture.bytes
1179 may be used to query the number of bytes of output currently in the capture
1182 .Dv debug.ddb.capture.data
1183 returns the contents of the buffer as a string to an appropriately privileged
1186 This facility is particularly useful in concert with the scripting and
1188 facilities, allowing scripted debugging output to be captured and
1189 committed to disk as part of a textdump for later analysis.
1190 The contents of the capture buffer may also be inspected in a kernel core dump
1198 Run, define, list, and delete scripts.
1201 section for more information on the scripting facility.
1203 .It Ic textdump dump
1205 .It Ic textdump status
1206 .It Ic textdump unset
1209 command to immediately perform a textdump.
1210 More information may be found in
1214 command may be used to force the next kernel core dump to be a textdump
1215 rather than a traditional memory dump or minidump.
1217 reports whether a textdump has been scheduled.
1219 cancels a request to perform a textdump as the next kernel core dump.
1222 The debugger accesses registers and variables as
1224 Register names are as in the
1225 .Dq Ic show Cm registers
1227 Some variables are suffixed with numbers, and may have some modifier
1228 following a colon immediately after the variable name.
1229 For example, register variables can have a
1231 modifier to indicate user register (e.g.,
1234 Built-in variables currently supported are:
1236 .Bl -tag -width ".Va tabstops" -compact
1238 Input and output radix.
1240 Addresses are printed as
1241 .Dq Ar symbol Ns Li + Ns Ar offset
1247 The width of the displayed line.
1249 The number of lines.
1250 It is used by the built-in pager.
1253 .It Va work Ns Ar xx
1256 can take values from 0 to 31.
1259 Most expression operators in C are supported except
1267 .Bl -tag -width ".No Identifiers"
1269 The name of a symbol is translated to the value of the symbol, which
1270 is the address of the corresponding object.
1274 can be used in the identifier.
1275 If supported by an object format dependent routine,
1277 .Oo Ar filename : Oc Ar func : lineno ,
1279 .Oo Ar filename : Oc Ns Ar variable ,
1281 .Oo Ar filename : Oc Ns Ar lineno
1282 can be accepted as a symbol.
1284 Radix is determined by the first two letters:
1290 decimal; otherwise, follow current radix.
1296 address of the start of the last line examined.
1301 this is only changed by
1307 last address explicitly specified.
1308 .It Li $ Ns Ar variable
1309 Translated to the value of the specified variable.
1310 It may be followed by a
1312 and modifiers as described above.
1313 .It Ar a Ns Li # Ns Ar b
1314 A binary operator which rounds up the left hand side to the next
1315 multiple of right hand side.
1318 It may be followed by a
1320 and modifiers as described above.
1324 supports a basic scripting facility to allow automating tasks or responses to
1326 Each script consists of a list of DDB commands to be executed sequentially,
1327 and is assigned a unique name.
1328 Certain script names have special meaning, and will be automatically run on
1331 events if scripts by those names have been defined.
1335 command may be used to define a script by name.
1336 Scripts consist of a series of
1338 commands separated with the
1342 .Bd -literal -offset indent
1343 script kdb.enter.panic=bt; show pcpu
1344 script lockinfo=show alllocks; show lockedvnods
1349 command lists currently defined scripts.
1353 command execute a script by name.
1355 .Bd -literal -offset indent
1361 command may be used to delete a script by name.
1363 .Bd -literal -offset indent
1364 unscript kdb.enter.panic
1367 These functions may also be performed from userspace using the
1371 Certain scripts are run automatically, if defined, for specific
1374 The follow scripts are run when various events occur:
1375 .Bl -tag -width kdb.enter.powerfail
1376 .It Dv kdb.enter.acpi
1377 The kernel debugger was entered as a result of an
1380 .It Dv kdb.enter.bootflags
1381 The kernel debugger was entered at boot as a result of the debugger boot
1383 .It Dv kdb.enter.break
1384 The kernel debugger was entered as a result of a serial or console break.
1385 .It Dv kdb.enter.cam
1386 The kernel debugger was entered as a result of a
1389 .It Dv kdb.enter.mac
1390 The kernel debugger was entered as a result of an assertion failure in the
1393 TrustedBSD MAC Framework.
1394 .It Dv kdb.enter.ndis
1395 The kernel debugger was entered as a result of an
1398 .It Dv kdb.enter.netgraph
1399 The kernel debugger was entered as a result of a
1402 .It Dv kdb.enter.panic
1405 .It Dv kdb.enter.powerfail
1406 The kernel debugger was entered as a result of a powerfail NMI on the sparc64
1408 .It Dv kdb.enter.powerpc
1409 The kernel debugger was entered as a result of an unimplemented interrupt
1410 type on the powerpc platform.
1411 .It Dv kdb.enter.sysctl
1412 The kernel debugger was entered as a result of the
1415 .It Dv kdb.enter.trapsig
1416 The kernel debugger was entered as a result of a trapsig event on the sparc64
1418 .It Dv kdb.enter.unionfs
1419 The kernel debugger was entered as a result of an assertion failure in the
1421 .It Dv kdb.enter.unknown
1422 The kernel debugger was entered, but no reason has been set.
1423 .It Dv kdb.enter.vfslock
1424 The kernel debugger was entered as a result of a VFS lock violation.
1425 .It Dv kdb.enter.watchdog
1426 The kernel debugger was entered as a result of a watchdog firing.
1427 .It Dv kdb.enter.witness
1428 The kernel debugger was entered as a result of a
1433 In the event that none of these scripts is found,
1435 will attempt to execute a default script:
1436 .Bl -tag -width kdb.enter.powerfail
1437 .It Dv kdb.enter.default
1438 The kernel debugger was entered, but a script exactly matching the reason for
1439 entering was not defined.
1440 This can be used as a catch-all to handle cases not specifically of interest;
1442 .Dv kdb.enter.witness
1443 might be defined to have special handling, and
1444 .Dv kdb.enter.default
1445 might be defined to simply panic and reboot.
1448 On machines with an ISA expansion bus, a simple NMI generation card can be
1449 constructed by connecting a push button between the A01 and B01 (CHCHK# and
1451 Momentarily shorting these two fingers together may cause the bridge chipset to
1452 generate an NMI, which causes the kernel to pass control to
1454 Some bridge chipsets do not generate a NMI on CHCHK#, so your mileage may vary.
1455 The NMI allows one to break into the debugger on a wedged machine to
1457 Other bus' bridge chipsets may be able to generate NMI using bus specific
1460 Header files mention in this manual page can be found below
1470 .Pa netinet/in_pcb.h
1492 debugger was developed for Mach, and ported to
1494 This manual page translated from
1497 .An Garrett Wollman .
1499 .An Robert N. M. Watson