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
254 machine, but none of the supported architectures have an alternate format.
256 display a symbol name for the pointer stored at the address
263 command with the last specified parameters to it
264 except that the next address displayed by it is used as the start address.
270 command with the last specified parameters to it
271 except that the last start address subtracted by the size displayed by it
272 is used as the start address.
274 .It Ic print Ns Op Li / Ns Cm acdoruxz
275 .It Ic p Ns Op Li / Ns Cm acdoruxz
278 according to the modifier character (as described above for
281 .Cm a , x , z , o , d , u , r ,
284 If no modifier is specified, the last one specified to it is used.
287 can be a string, in which case it is printed as it is.
289 .Bd -literal -offset indent
290 print/x "eax = " $eax "\enecx = " $ecx "\en"
294 .Bd -literal -offset indent
300 .Ic write Ns Op Li / Ns Cm bhl
301 .Ar addr expr1 Op Ar expr2 ...
304 .Ic w Ns Op Li / Ns Cm bhl
305 .Ar addr expr1 Op Ar expr2 ...
307 Write the expressions specified after
309 on the command line at succeeding locations starting with
311 The write unit size can be specified in the modifier with a letter
317 (long word) respectively.
319 long word is assumed.
322 since there is no delimiter between expressions, strange
324 It is best to enclose each expression in parentheses.
326 .It Ic set Li $ Ns Ar variable Oo Li = Oc Ar expr
327 Set the named variable or register with the value of
329 Valid variable names are described below.
331 .It Ic break Ns Op Li / Ns Cm u
332 .It Ic b Ns Op Li / Ns Cm u
337 is supplied, continues
339 \- 1 times before stopping at the
341 If the break point is set, a break point number is
344 This number can be used in deleting the break point
345 or adding conditions to it.
349 modifier is specified, this command sets a break point in user
353 option, the address is considered to be in the kernel
354 space, and a wrong space address is rejected with an error message.
355 This modifier can be used only if it is supported by machine dependent
359 If a user text is shadowed by a normal user space debugger,
360 user space break points may not work correctly.
362 point at the low-level code paths may also cause strange behavior.
364 .It Ic delete Ar addr
366 .It Ic delete Li # Ns Ar number
367 .It Ic d Li # Ns Ar number
368 Delete the break point.
369 The target break point can be specified by a
370 break point number with
374 specified in the original
378 .It Ic watch Ar addr Ns Li , Ns Ar size
379 Set a watchpoint for a region.
380 Execution stops when an attempt to modify the region occurs.
383 argument defaults to 4.
384 If you specify a wrong space address, the request is rejected
385 with an error message.
388 Attempts to watch wired kernel memory
389 may cause unrecoverable error in some systems such as i386.
390 Watchpoints on user addresses work best.
392 .It Ic hwatch Ar addr Ns Li , Ns Ar size
393 Set a hardware watchpoint for a region if supported by the
395 Execution stops when an attempt to modify the region occurs.
398 argument defaults to 4.
401 The hardware debug facilities do not have a concept of separate
402 address spaces like the watch command does.
405 for setting watchpoints on kernel address locations only, and avoid
406 its use on user mode address spaces.
408 .It Ic dhwatch Ar addr Ns Li , Ns Ar size
409 Delete specified hardware watchpoint.
411 .It Ic step Ns Op Li / Ns Cm p
412 .It Ic s Ns Op Li / Ns Cm p
415 times (the comma is a mandatory part of the syntax).
418 modifier is specified, print each instruction at each step.
419 Otherwise, only print the last instruction.
422 depending on machine type, it may not be possible to
423 single-step through some low-level code paths or user space code.
424 On machines with software-emulated single-stepping (e.g., pmax),
425 stepping through code executed by interrupt handlers will probably
428 .It Ic continue Ns Op Li / Ns Cm c
429 .It Ic c Ns Op Li / Ns Cm c
430 Continue execution until a breakpoint or watchpoint.
433 modifier is specified, count instructions while executing.
434 Some machines (e.g., pmax) also count loads and stores.
437 when counting, the debugger is really silently single-stepping.
438 This means that single-stepping on low-level code may cause strange
441 .It Ic until Ns Op Li / Ns Cm p
442 Stop at the next call or return instruction.
445 modifier is specified, print the call nesting depth and the
446 cumulative instruction count at each call or return.
448 only print when the matching return is hit.
450 .It Ic next Ns Op Li / Ns Cm p
451 .It Ic match Ns Op Li / Ns Cm p
452 Stop at the matching return instruction.
455 modifier is specified, print the call nesting depth and the
456 cumulative instruction count at each call or return.
457 Otherwise, only print when the matching return is hit.
460 .Ic trace Ns Op Li / Ns Cm u
465 .Ic t Ns Op Li / Ns Cm u
470 .Ic where Ns Op Li / Ns Cm u
475 .Ic bt Ns Op Li / Ns Cm u
482 option traces user space; if omitted,
486 The optional argument
488 is the number of frames to be traced.
491 is omitted, all frames are printed.
494 User space stack trace is valid
495 only if the machine dependent code supports it.
498 .Ic search Ns Op Li / Ns Cm bhl
506 This command might fail in interesting
507 ways if it does not find the searched-for value.
510 does not always recover from touching bad memory.
513 argument limits the search.
520 Prints the thread address for a thread kernel-mode stack of which contains the
522 If the thread is not found, search the thread stack cache and prints the
523 cached stack address.
524 Otherwise, prints nothing.
526 .It Ic show Cm all procs Ns Op Li / Ns Cm m
527 .It Ic ps Ns Op Li / Ns Cm m
528 Display all process information.
529 The process information may not be shown if it is not
530 supported in the machine, or the bottom of the stack of the
531 target process is not in the main memory at that time.
534 modifier will alter the display to show VM map
535 addresses for the process and not show other information.
538 .It Ic show Cm all trace
541 Show a stack trace for every thread in the system.
543 .It Ic show Cm all ttys
544 Show all TTY's within the system.
547 but also includes the address of the TTY structure.
550 .It Ic show Cm all vnets
551 Show the same output as "show vnet" does, but lists all
552 virtualized network stacks within the system.
555 .It Ic show Cm allchains
556 Show the same information like "show lockchain" does, but
557 for every thread in the system.
560 .It Ic show Cm alllocks
561 Show all locks that are currently held.
562 This command is only available if
564 is included in the kernel.
567 .It Ic show Cm allpcpu
568 The same as "show pcpu", but for every CPU present in the system.
571 .It Ic show Cm allrman
572 Show information related with resource management, including
573 interrupt request lines, DMA request lines, I/O ports, I/O memory
574 addresses, and Resource IDs.
578 Dump data about APIC IDT vector mappings.
581 .It Ic show Cm breaks
582 Show breakpoints set with the "break" command.
585 .It Ic show Cm bio Ar addr
586 Show information about the bio structure
594 for more details on the exact meaning of the structure fields.
597 .It Ic show Cm buffer Ar addr
598 Show information about the buf structure
604 header file for more details on the exact meaning of the structure fields.
607 .It Ic show Cm callout Ar addr
608 Show information about the callout structure
614 .It Ic show Cm cbstat
615 Show brief information about the TTY subsystem.
619 Without argument, show the list of all created cdev's, consisting of devfs
620 node name and struct cdev address.
621 When address of cdev is supplied, show some internal devfs state of the cdev.
624 .It Ic show Cm conifhk
625 Lists hooks currently waiting for completion in
626 run_interrupt_driven_config_hooks().
629 .It Ic show Cm cpusets
630 Print numbered root and assigned CPU affinity sets.
636 .It Ic show Cm cyrixreg
637 Show registers specific to the Cyrix processor.
640 .It Ic show Cm devmap
641 Prints the contents of the static device mapping table.
642 Currently only available on the
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 igi_list Ar addr
697 Show information about the IGMP structure
698 .Vt struct igmp_ifsoftc
703 .It Ic show Cm inodedeps Op Ar addr
704 Show brief information about each inodedep structure.
707 is given, only inodedeps belonging to the fs located at the
708 supplied address are shown.
711 .It Ic show Cm inpcb Ar addr
712 Show information on IP Control Block
719 Dump information about interrupt handlers.
722 .It Ic show Cm intrcnt
723 Dump the interrupt statistics.
727 Show interrupt lines and their respective kernel threads.
736 shows, also list kernel internal details.
740 Show information from the local APIC registers for this CPU.
743 .It Ic show Cm lock Ar addr
745 The output format is as follows:
746 .Bl -tag -width "flags"
749 Possible types include
757 Flags passed to the lock initialization function.
758 For exact possibilities see manual pages of possible lock types.
760 Current state of a lock.
769 .It Ic show Cm lockchain Ar addr
770 Show all threads a particular thread at address
772 is waiting on based on non-sleepable and non-spin locks.
775 .It Ic show Cm lockedbufs
776 Show the same information as "show buf", but for every locked
781 .It Ic show Cm lockedvnods
782 List all locked vnodes in the system.
786 Prints all locks that are currently acquired.
787 This command is only available if
789 is included in the kernel.
792 .It Ic show Cm locktree
795 .It Ic show Cm malloc
798 memory allocator statistics.
799 The output format is as follows:
801 .Bl -tag -compact -offset indent -width "Requests"
803 Specifies a type of memory.
804 It is the same as a description string used while defining the
805 given memory type with
806 .Xr MALLOC_DECLARE 9 .
808 Number of memory allocations of the given type, for which
810 has not been called yet.
812 Total memory consumed by the given allocation type.
814 Number of memory allocation requests for the given
818 The same information can be gathered in userspace with
822 .It Ic show Cm map Ns Oo Li / Ns Cm f Oc Ar addr
827 modifier is specified the
828 complete map is printed.
831 .It Ic show Cm msgbuf
832 Print the system's message buffer.
833 It is the same output as in the
836 It is useful if you got a kernel panic, attached a serial cable
837 to the machine and want to get the boot messages from before the
841 Displays short info about all currently mounted file systems.
843 .It Ic show Cm mount Ar addr
844 Displays details about the given mount point.
847 .It Ic show Cm object Ns Oo Li / Ns Cm f Oc Ar addr
848 Prints the VM object at
852 option is specified the
853 complete object is printed.
857 Print the panic message if set.
861 Show statistics on VM pages.
865 Show statistics on VM page queues.
868 .It Ic show Cm pciregs
869 Print PCI bus registers.
870 The same information can be gathered in userspace by running
871 .Dq Nm pciconf Fl lv .
875 Print current processor state.
876 The output format is as follows:
878 .Bl -tag -compact -offset indent -width "spin locks held:"
880 Processor identifier.
882 Thread pointer, process identifier and the name of the process.
884 Control block pointer.
890 CPU identifier coming from APIC.
893 .It Ic spin locks held
894 Names of spin locks held.
898 .It Ic show Cm pgrpdump
899 Dump process groups present within the system.
902 .It Ic show Cm proc Op Ar addr
905 is specified, print information about the current process.
906 Otherwise, show information about the process at address
910 .It Ic show Cm procvm
911 Show process virtual memory layout.
914 .It Ic show Cm protosw Ar addr
915 Print protocol switch structure
921 .It Ic show Cm registers Ns Op Li / Ns Cm u
922 Display the register set.
925 modifier is specified, it displays user registers instead of
926 kernel registers or the currently saved one.
931 modifier depends on the machine.
932 If not supported, incorrect information will be displayed.
935 .It Ic show Cm rman Ar addr
936 Show resource manager object
940 Addresses of particular pointers can be gathered with "show allrman"
945 Show real time clock value.
946 Useful for long debugging sessions.
949 .It Ic show Cm sleepchain
950 Show all the threads a particular thread is waiting on based on
954 .It Ic show Cm sleepq
955 .It Ic show Cm sleepqueue
956 Both commands provide the same functionality.
958 .Vt struct sleepqueue
960 Sleepqueues are used within the
962 kernel to implement sleepable
963 synchronization primitives (thread holding a lock might sleep or
964 be context switched), which at the time of writing are:
972 .It Ic show Cm sockbuf Ar addr
973 .It Ic show Cm socket Ar addr
980 Output consists of all values present in structures mentioned.
981 For exact interpretation and more details, visit
986 .It Ic show Cm sysregs
987 Show system registers (e.g.,
990 Not present on some platforms.
993 .It Ic show Cm tcpcb Ar addr
994 Print TCP control block
998 For exact interpretation of output, visit
1003 .It Ic show Cm thread Op Ar addr
1006 is specified, show detailed information about current thread.
1007 Otherwise, information about thread at
1012 .It Ic show Cm threads
1013 Show all threads within the system.
1014 Output format is as follows:
1016 .Bl -tag -compact -offset indent -width "Second column"
1018 Thread identifier (TID)
1019 .It Ic Second column
1020 Thread structure address
1026 .It Ic show Cm tty Ar addr
1027 Display the contents of a TTY structure in a readable form.
1030 .It Ic show Cm turnstile Ar addr
1032 .Vt struct turnstile
1033 structure at address
1035 Turnstiles are structures used within the
1038 synchronization primitives which, while holding a specific type of lock, cannot
1039 sleep or context switch to another thread.
1040 Currently, those are:
1047 Show UMA allocator statistics.
1048 Output consists five columns:
1050 .Bl -tag -compact -offset indent -width "Requests"
1052 Name of the UMA zone.
1053 The same string that was passed to
1055 as a first argument.
1057 Size of a given memory object (slab).
1059 Number of slabs being currently used.
1061 Number of free slabs within the UMA zone.
1063 Number of allocations requests to the given zone.
1066 The very same information might be gathered in the userspace
1068 .Dq Nm vmstat Fl z .
1071 .It Ic show Cm unpcb Ar addr
1072 Shows UNIX domain socket private control block
1074 present at the address
1078 .It Ic show Cm vmochk
1079 Prints, whether the internal VM objects are in a map somewhere
1080 and none have zero ref counts.
1083 .It Ic show Cm vmopag
1084 This is supposed to show physical addresses consumed by a
1086 Currently, it is not possible to use this command when
1088 is compiled in the kernel.
1091 .It Ic show Cm vnet Ar addr
1092 Prints virtualized network stack
1094 structure present at the address
1098 .It Ic show Cm vnode Op Ar addr
1103 For the exact interpretation of the output, look at the
1108 .It Ic show Cm vnodebufs Ar addr
1109 Shows clean/dirty buffer lists of the vnode located at
1113 .It Ic show Cm watches
1114 Displays all watchpoints.
1115 Shows watchpoints set with "watch" command.
1118 .It Ic show Cm witness
1119 Shows information about lock acquisition coming from the
1125 Toggles between remote GDB and DDB mode.
1126 In remote GDB mode, another machine is required that runs
1128 using the remote debug feature, with a connection to the serial
1129 console port on the target machine.
1130 Currently only available on the
1137 .It Ic kill Ar sig pid
1142 The signal is acted on upon returning from the debugger.
1143 This command can be used to kill a process causing resource contention
1144 in the case of a hung system.
1147 for a list of signals.
1148 Note that the arguments are reversed relative to
1151 .It Ic reboot Op Ar seconds
1152 .It Ic reset Op Ar seconds
1153 Hard reset the system.
1154 If the optional argument
1156 is given, the debugger will wait for this long, at most a week,
1160 Print a short summary of the available commands and command
1165 .It Ic capture reset
1166 .It Ic capture status
1168 supports a basic output capture facility, which can be used to retrieve the
1169 results of debugging commands from userspace using
1172 enables output capture;
1176 will clear the capture buffer and disable capture.
1178 will report current buffer use, buffer size, and disposition of output
1181 Userspace processes may inspect and manage
1186 .Dv debug.ddb.capture.bufsize
1187 may be used to query or set the current capture buffer size.
1189 .Dv debug.ddb.capture.maxbufsize
1190 may be used to query the compile-time limit on the capture buffer size.
1192 .Dv debug.ddb.capture.bytes
1193 may be used to query the number of bytes of output currently in the capture
1196 .Dv debug.ddb.capture.data
1197 returns the contents of the buffer as a string to an appropriately privileged
1200 This facility is particularly useful in concert with the scripting and
1202 facilities, allowing scripted debugging output to be captured and
1203 committed to disk as part of a textdump for later analysis.
1204 The contents of the capture buffer may also be inspected in a kernel core dump
1212 Run, define, list, and delete scripts.
1215 section for more information on the scripting facility.
1217 .It Ic textdump dump
1219 .It Ic textdump status
1220 .It Ic textdump unset
1223 command to immediately perform a textdump.
1224 More information may be found in
1228 command may be used to force the next kernel core dump to be a textdump
1229 rather than a traditional memory dump or minidump.
1231 reports whether a textdump has been scheduled.
1233 cancels a request to perform a textdump as the next kernel core dump.
1236 The debugger accesses registers and variables as
1238 Register names are as in the
1239 .Dq Ic show Cm registers
1241 Some variables are suffixed with numbers, and may have some modifier
1242 following a colon immediately after the variable name.
1243 For example, register variables can have a
1245 modifier to indicate user register (e.g.,
1248 Built-in variables currently supported are:
1250 .Bl -tag -width ".Va tabstops" -compact
1252 Input and output radix.
1254 Addresses are printed as
1255 .Dq Ar symbol Ns Li + Ns Ar offset
1261 The width of the displayed line.
1263 The number of lines.
1264 It is used by the built-in pager.
1267 .It Va work Ns Ar xx
1270 can take values from 0 to 31.
1273 Most expression operators in C are supported except
1281 .Bl -tag -width ".No Identifiers"
1283 The name of a symbol is translated to the value of the symbol, which
1284 is the address of the corresponding object.
1288 can be used in the identifier.
1289 If supported by an object format dependent routine,
1291 .Oo Ar filename : Oc Ar func : lineno ,
1293 .Oo Ar filename : Oc Ns Ar variable ,
1295 .Oo Ar filename : Oc Ns Ar lineno
1296 can be accepted as a symbol.
1298 Radix is determined by the first two letters:
1304 decimal; otherwise, follow current radix.
1310 address of the start of the last line examined.
1315 this is only changed by
1321 last address explicitly specified.
1322 .It Li $ Ns Ar variable
1323 Translated to the value of the specified variable.
1324 It may be followed by a
1326 and modifiers as described above.
1327 .It Ar a Ns Li # Ns Ar b
1328 A binary operator which rounds up the left hand side to the next
1329 multiple of right hand side.
1332 It may be followed by a
1334 and modifiers as described above.
1338 supports a basic scripting facility to allow automating tasks or responses to
1340 Each script consists of a list of DDB commands to be executed sequentially,
1341 and is assigned a unique name.
1342 Certain script names have special meaning, and will be automatically run on
1345 events if scripts by those names have been defined.
1349 command may be used to define a script by name.
1350 Scripts consist of a series of
1352 commands separated with the
1356 .Bd -literal -offset indent
1357 script kdb.enter.panic=bt; show pcpu
1358 script lockinfo=show alllocks; show lockedvnods
1363 command lists currently defined scripts.
1367 command execute a script by name.
1369 .Bd -literal -offset indent
1375 command may be used to delete a script by name.
1377 .Bd -literal -offset indent
1378 unscript kdb.enter.panic
1381 These functions may also be performed from userspace using the
1385 Certain scripts are run automatically, if defined, for specific
1388 The follow scripts are run when various events occur:
1389 .Bl -tag -width kdb.enter.powerfail
1390 .It Dv kdb.enter.acpi
1391 The kernel debugger was entered as a result of an
1394 .It Dv kdb.enter.bootflags
1395 The kernel debugger was entered at boot as a result of the debugger boot
1397 .It Dv kdb.enter.break
1398 The kernel debugger was entered as a result of a serial or console break.
1399 .It Dv kdb.enter.cam
1400 The kernel debugger was entered as a result of a
1403 .It Dv kdb.enter.mac
1404 The kernel debugger was entered as a result of an assertion failure in the
1407 TrustedBSD MAC Framework.
1408 .It Dv kdb.enter.ndis
1409 The kernel debugger was entered as a result of an
1412 .It Dv kdb.enter.netgraph
1413 The kernel debugger was entered as a result of a
1416 .It Dv kdb.enter.panic
1419 .It Dv kdb.enter.powerfail
1420 The kernel debugger was entered as a result of a powerfail NMI on the sparc64
1422 .It Dv kdb.enter.powerpc
1423 The kernel debugger was entered as a result of an unimplemented interrupt
1424 type on the powerpc platform.
1425 .It Dv kdb.enter.sysctl
1426 The kernel debugger was entered as a result of the
1429 .It Dv kdb.enter.trapsig
1430 The kernel debugger was entered as a result of a trapsig event on the sparc64
1432 .It Dv kdb.enter.unionfs
1433 The kernel debugger was entered as a result of an assertion failure in the
1435 .It Dv kdb.enter.unknown
1436 The kernel debugger was entered, but no reason has been set.
1437 .It Dv kdb.enter.vfslock
1438 The kernel debugger was entered as a result of a VFS lock violation.
1439 .It Dv kdb.enter.watchdog
1440 The kernel debugger was entered as a result of a watchdog firing.
1441 .It Dv kdb.enter.witness
1442 The kernel debugger was entered as a result of a
1447 In the event that none of these scripts is found,
1449 will attempt to execute a default script:
1450 .Bl -tag -width kdb.enter.powerfail
1451 .It Dv kdb.enter.default
1452 The kernel debugger was entered, but a script exactly matching the reason for
1453 entering was not defined.
1454 This can be used as a catch-all to handle cases not specifically of interest;
1456 .Dv kdb.enter.witness
1457 might be defined to have special handling, and
1458 .Dv kdb.enter.default
1459 might be defined to simply panic and reboot.
1462 On machines with an ISA expansion bus, a simple NMI generation card can be
1463 constructed by connecting a push button between the A01 and B01 (CHCHK# and
1465 Momentarily shorting these two fingers together may cause the bridge chipset to
1466 generate an NMI, which causes the kernel to pass control to
1468 Some bridge chipsets do not generate a NMI on CHCHK#, so your mileage may vary.
1469 The NMI allows one to break into the debugger on a wedged machine to
1471 Other bus' bridge chipsets may be able to generate NMI using bus specific
1473 There are many PCI and PCIe add-in cards which can generate NMI for
1475 Modern server systems typically use IPMI to generate signals to enter the
1479 port can be used to send the
1480 .Cd chassis power diag
1481 command which delivers an NMI to the processor.
1482 Embedded systems often use JTAG for debugging, but rarely use it in
1486 For serial consoles, you can enter the debugger by sending a BREAK
1487 condition on the serial line if
1488 .Cd options BREAK_TO_DEBUGGER
1489 is specified in the kernel.
1490 Most terminal emulation programs can send a break sequence with a
1491 special key sequence or via a menu item.
1492 However, in some setups, sending the break can be difficult to arrange
1493 or happens spuriously, so if the kernel contains
1494 .Cd options ALT_BREAK_TO_DEBUGGER
1495 then the sequence of CR TILDE CTRL-B enters the debugger;
1496 CR TILDE CTRL-P causes a panic instead of entering the
1498 CR TILDE CTRL-R causes an immediate reboot.
1499 In all the above sequences, CR is a Carriage Return and is usually
1500 sent by hitting the Enter or Return key.
1501 TILDE is the ASCII tilde character (~).
1502 CTRL-x is Control x created by hitting the control key and then x
1503 and then releasing both.
1505 The break to enter the debugger behavior may be enabled at run-time
1508 .Dv debug.kdb.break_to_debugger
1510 The alternate sequence to enter the debugger behavior may be enabled
1511 at run-time by setting the
1513 .Dv debug.kdb.alt_break_to_debugger
1515 The debugger may be entered by setting the
1520 Header files mentioned in this manual page can be found below
1530 .Pa netinet/in_pcb.h
1552 debugger was developed for Mach, and ported to
1554 This manual page translated from
1557 .An Garrett Wollman .
1559 .An Robert N. M. Watson