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 .Oo Ar addr Oc 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.
170 of -1 is equivalent to a missing
172 Options that are supplied but not supported by the given
178 debugger has a pager feature (like the
182 If an output line exceeds the number set in the
184 variable, it displays
186 and waits for a response.
187 The valid responses for it are:
189 .Bl -tag -compact -width ".Li SPC"
195 abort the current command, and return to the command input mode
200 provides a small (currently 10 items) command history, and offers
203 command line editing capabilities.
207 control keys, the usual
209 arrow keys may be used to
210 browse through the history buffer, and move the cursor within the
213 .Bl -tag -width indent -compact
215 .Ic examine Ns Op Li / Ns Cm AISabcdghilmorsuxz ...
216 .Oo Ar addr Oc Ns Op Li , Ns Ar count
219 .Ic x Ns Op Li / Ns Cm AISabcdghilmorsuxz ...
220 .Oo Ar addr Oc Ns Op Li , Ns Ar count
222 Display the addressed locations according to the formats in the modifier.
223 Multiple modifier formats display multiple locations.
224 If no format is specified, the last format specified for this command
227 The format characters are:
228 .Bl -tag -compact -width indent
230 look at by bytes (8 bits)
232 look at by half words (16 bits)
234 look at by long words (32 bits)
236 look at by quad words (64 bits)
238 print the location being displayed
240 print the location with a line number if possible
242 display in unsigned hex
244 display in signed hex
246 display in unsigned octal
248 display in signed decimal
250 display in unsigned decimal
252 display in current radix, signed
254 display low 8 bits as a character.
255 Non-printing characters are displayed as an octal escape code (e.g.,
258 display the null-terminated string at the location.
259 Non-printing characters are displayed as octal escapes.
261 display in unsigned hex with character dump at the end of each line.
262 The location is also displayed in hex at the beginning of each line.
264 display as an instruction
266 display as an instruction with possible alternate formats depending on the
268 On i386, this selects the alternate format for the instruction decoding
269 (16 bits in a 32-bit code segment and vice versa).
271 display a symbol name for the pointer stored at the address
278 command with the last specified parameters to it
279 except that the next address displayed by it is used as the start address.
285 command with the last specified parameters to it
286 except that the last start address subtracted by the size displayed by it
287 is used as the start address.
289 .It Ic print Ns Op Li / Ns Cm acdoruxz
290 .It Ic p Ns Op Li / Ns Cm acdoruxz
293 according to the modifier character (as described above for
296 .Cm a , x , z , o , d , u , r ,
299 If no modifier is specified, the last one specified to it is used.
302 can be a string, in which case it is printed as it is.
304 .Bd -literal -offset indent
305 print/x "eax = " $eax "\enecx = " $ecx "\en"
309 .Bd -literal -offset indent
315 .Ic write Ns Op Li / Ns Cm bhl
316 .Ar addr expr1 Op Ar expr2 ...
319 .Ic w Ns Op Li / Ns Cm bhl
320 .Ar addr expr1 Op Ar expr2 ...
322 Write the expressions specified after
324 on the command line at succeeding locations starting with
326 The write unit size can be specified in the modifier with a letter
332 (long word) respectively.
334 long word is assumed.
337 since there is no delimiter between expressions, strange
339 It is best to enclose each expression in parentheses.
341 .It Ic set Li $ Ns Ar variable Oo Li = Oc Ar expr
342 Set the named variable or register with the value of
344 Valid variable names are described below.
346 .It Ic break Ns Oo Li / Ns Cm u Oc Oo Ar addr Oc Ns Op Li , Ns Ar count
347 .It Ic b Ns Oo Li / Ns Cm u Oc Oo Ar addr Oc Ns Op Li , Ns Ar count
354 command will not stop at this break point on the first
356 \- 1 times that it is hit.
357 If the break point is set, a break point number is
360 This number can be used in deleting the break point
361 or adding conditions to it.
365 modifier is specified, this command sets a break point in user
369 option, the address is considered to be in the kernel
370 space, and a wrong space address is rejected with an error message.
371 This modifier can be used only if it is supported by machine dependent
375 If a user text is shadowed by a normal user space debugger,
376 user space break points may not work correctly.
378 point at the low-level code paths may also cause strange behavior.
380 .It Ic delete Op Ar addr
382 .It Ic delete Li # Ns Ar number
383 .It Ic d Li # Ns Ar number
384 Delete the specified break point.
385 The break point can be specified by a
386 break point number with
390 specified in the original
392 command, or by omitting
394 to get the default address of
397 .It Ic watch Oo Ar addr Oc Ns Op Li , Ns Ar size
398 Set a watchpoint for a region.
399 Execution stops when an attempt to modify the region occurs.
402 argument defaults to 4.
403 If you specify a wrong space address, the request is rejected
404 with an error message.
407 Attempts to watch wired kernel memory
408 may cause unrecoverable error in some systems such as i386.
409 Watchpoints on user addresses work best.
411 .It Ic hwatch Oo Ar addr Oc Ns Op Li , Ns Ar size
412 Set a hardware watchpoint for a region if supported by the
414 Execution stops when an attempt to modify the region occurs.
417 argument defaults to 4.
420 The hardware debug facilities do not have a concept of separate
421 address spaces like the watch command does.
424 for setting watchpoints on kernel address locations only, and avoid
425 its use on user mode address spaces.
427 .It Ic dhwatch Oo Ar addr Oc Ns Op Li , Ns Ar size
428 Delete specified hardware watchpoint.
430 .It Ic step Ns Oo Li / Ns Cm p Oc Ns Op Li , Ns Ar count
431 .It Ic s Ns Oo Li / Ns Cm p Oc Ns Op Li , Ns Ar count
437 modifier is specified, print each instruction at each step.
438 Otherwise, only print the last instruction.
441 depending on machine type, it may not be possible to
442 single-step through some low-level code paths or user space code.
443 On machines with software-emulated single-stepping (e.g., pmax),
444 stepping through code executed by interrupt handlers will probably
447 .It Ic continue Ns Op Li / Ns Cm c
448 .It Ic c Ns Op Li / Ns Cm c
449 Continue execution until a breakpoint or watchpoint.
452 modifier is specified, count instructions while executing.
453 Some machines (e.g., pmax) also count loads and stores.
456 when counting, the debugger is really silently single-stepping.
457 This means that single-stepping on low-level code may cause strange
460 .It Ic until Ns Op Li / Ns Cm p
461 Stop at the next call or return instruction.
464 modifier is specified, print the call nesting depth and the
465 cumulative instruction count at each call or return.
467 only print when the matching return is hit.
469 .It Ic next Ns Op Li / Ns Cm p
470 .It Ic match Ns Op Li / Ns Cm p
471 Stop at the matching return instruction.
474 modifier is specified, print the call nesting depth and the
475 cumulative instruction count at each call or return.
476 Otherwise, only print when the matching return is hit.
479 .Ic trace Ns Op Li / Ns Cm u
484 .Ic t Ns Op Li / Ns Cm u
489 .Ic where Ns Op Li / Ns Cm u
494 .Ic bt Ns Op Li / Ns Cm u
501 option traces user space; if omitted,
505 The optional argument
507 is the number of frames to be traced.
510 is omitted, all frames are printed.
513 User space stack trace is valid
514 only if the machine dependent code supports it.
517 .Ic search Ns Op Li / Ns Cm bhl
527 argument limits the search.
534 Prints the thread address for a thread kernel-mode stack of which contains the
536 If the thread is not found, search the thread stack cache and prints the
537 cached stack address.
538 Otherwise, prints nothing.
540 .It Ic show Cm all procs Ns Op Li / Ns Cm m
541 .It Ic ps Ns Op Li / Ns Cm m
542 Display all process information.
543 The process information may not be shown if it is not
544 supported in the machine, or the bottom of the stack of the
545 target process is not in the main memory at that time.
548 modifier will alter the display to show VM map
549 addresses for the process and not show other information.
552 .It Ic show Cm all trace
554 Show a stack trace for every thread in the system.
556 .It Ic show Cm all ttys
557 Show all TTY's within the system.
560 but also includes the address of the TTY structure.
563 .It Ic show Cm all vnets
564 Show the same output as "show vnet" does, but lists all
565 virtualized network stacks within the system.
568 .It Ic show Cm allchains
569 Show the same information like "show lockchain" does, but
570 for every thread in the system.
573 .It Ic show Cm alllocks
574 Show all locks that are currently held.
575 This command is only available if
577 is included in the kernel.
580 .It Ic show Cm allpcpu
581 The same as "show pcpu", but for every CPU present in the system.
584 .It Ic show Cm allrman
585 Show information related with resource management, including
586 interrupt request lines, DMA request lines, I/O ports, I/O memory
587 addresses, and Resource IDs.
591 Dump data about APIC IDT vector mappings.
594 .It Ic show Cm breaks
595 Show breakpoints set with the "break" command.
598 .It Ic show Cm bio Ar addr
599 Show information about the bio structure
607 for more details on the exact meaning of the structure fields.
610 .It Ic show Cm buffer Ar addr
611 Show information about the buf structure
617 header file for more details on the exact meaning of the structure fields.
620 .It Ic show Cm callout Ar addr
621 Show information about the callout structure
627 .It Ic show Cm cbstat
628 Show brief information about the TTY subsystem.
632 Without argument, show the list of all created cdev's, consisting of devfs
633 node name and struct cdev address.
634 When address of cdev is supplied, show some internal devfs state of the cdev.
637 .It Ic show Cm conifhk
638 Lists hooks currently waiting for completion in
639 run_interrupt_driven_config_hooks().
642 .It Ic show Cm cpusets
643 Print numbered root and assigned CPU affinity sets.
649 .It Ic show Cm cyrixreg
650 Show registers specific to the Cyrix processor.
653 .It Ic show Cm devmap
654 Prints the contents of the static device mapping table.
655 Currently only available on the
660 .It Ic show Cm domain Ar addr
661 Print protocol domain structure
667 header file for more details on the exact meaning of the structure fields.
670 .It Ic show Cm ffs Op Ar addr
671 Show brief information about ffs mount at the address
673 if argument is given.
674 Otherwise, provides the summary about each ffs mount.
677 .It Ic show Cm file Ar addr
678 Show information about the file structure
685 Show information about every file structure in the system.
688 .It Ic show Cm freepages
689 Show the number of physical pages in each of the free lists.
692 .It Ic show Cm geom Op Ar addr
695 argument is not given, displays the entire GEOM topology.
698 is given, displays details about the given GEOM object (class, geom,
699 provider or consumer).
704 The first column specifies the IDT vector.
705 The second one is the name of the interrupt/trap handler.
706 Those functions are machine dependent.
709 .It Ic show Cm igi_list Ar addr
710 Show information about the IGMP structure
711 .Vt struct igmp_ifsoftc
716 .It Ic show Cm inodedeps Op Ar addr
717 Show brief information about each inodedep structure.
720 is given, only inodedeps belonging to the fs located at the
721 supplied address are shown.
724 .It Ic show Cm inpcb Ar addr
725 Show information on IP Control Block
732 Dump information about interrupt handlers.
735 .It Ic show Cm intrcnt
736 Dump the interrupt statistics.
740 Show interrupt lines and their respective kernel threads.
749 shows, also list kernel internal details.
753 Show information from the local APIC registers for this CPU.
756 .It Ic show Cm lock Ar addr
758 The output format is as follows:
759 .Bl -tag -width "flags"
762 Possible types include
770 Flags passed to the lock initialization function.
771 For exact possibilities see manual pages of possible lock types.
773 Current state of a lock.
782 .It Ic show Cm lockchain Ar addr
783 Show all threads a particular thread at address
785 is waiting on based on non-sleepable and non-spin locks.
788 .It Ic show Cm lockedbufs
789 Show the same information as "show buf", but for every locked
794 .It Ic show Cm lockedvnods
795 List all locked vnodes in the system.
799 Prints all locks that are currently acquired.
800 This command is only available if
802 is included in the kernel.
805 .It Ic show Cm locktree
808 .It Ic show Cm malloc
811 memory allocator statistics.
812 The output format is as follows:
814 .Bl -tag -compact -offset indent -width "Requests"
816 Specifies a type of memory.
817 It is the same as a description string used while defining the
818 given memory type with
819 .Xr MALLOC_DECLARE 9 .
821 Number of memory allocations of the given type, for which
823 has not been called yet.
825 Total memory consumed by the given allocation type.
827 Number of memory allocation requests for the given
831 The same information can be gathered in userspace with
835 .It Ic show Cm map Ns Oo Li / Ns Cm f Oc Ar addr
840 modifier is specified the
841 complete map is printed.
844 .It Ic show Cm msgbuf
845 Print the system's message buffer.
846 It is the same output as in the
849 It is useful if you got a kernel panic, attached a serial cable
850 to the machine and want to get the boot messages from before the
854 Displays short info about all currently mounted file systems.
856 .It Ic show Cm mount Ar addr
857 Displays details about the given mount point.
860 .It Ic show Cm object Ns Oo Li / Ns Cm f Oc Ar addr
861 Prints the VM object at
865 option is specified the
866 complete object is printed.
870 Print the panic message if set.
874 Show statistics on VM pages.
878 Show statistics on VM page queues.
881 .It Ic show Cm pciregs
882 Print PCI bus registers.
883 The same information can be gathered in userspace by running
884 .Dq Nm pciconf Fl lv .
888 Print current processor state.
889 The output format is as follows:
891 .Bl -tag -compact -offset indent -width "spin locks held:"
893 Processor identifier.
895 Thread pointer, process identifier and the name of the process.
897 Control block pointer.
903 CPU identifier coming from APIC.
906 .It Ic spin locks held
907 Names of spin locks held.
911 .It Ic show Cm pgrpdump
912 Dump process groups present within the system.
915 .It Ic show Cm proc Op Ar addr
918 is specified, print information about the current process.
919 Otherwise, show information about the process at address
923 .It Ic show Cm procvm
924 Show process virtual memory layout.
927 .It Ic show Cm protosw Ar addr
928 Print protocol switch structure
934 .It Ic show Cm registers Ns Op Li / Ns Cm u
935 Display the register set.
938 modifier is specified, it displays user registers instead of
939 kernel registers or the currently saved one.
944 modifier depends on the machine.
945 If not supported, incorrect information will be displayed.
948 .It Ic show Cm rman Ar addr
949 Show resource manager object
953 Addresses of particular pointers can be gathered with "show allrman"
958 Show real time clock value.
959 Useful for long debugging sessions.
962 .It Ic show Cm sleepchain
963 Show all the threads a particular thread is waiting on based on
967 .It Ic show Cm sleepq
968 .It Ic show Cm sleepqueue
969 Both commands provide the same functionality.
971 .Vt struct sleepqueue
973 Sleepqueues are used within the
975 kernel to implement sleepable
976 synchronization primitives (thread holding a lock might sleep or
977 be context switched), which at the time of writing are:
985 .It Ic show Cm sockbuf Ar addr
986 .It Ic show Cm socket Ar addr
993 Output consists of all values present in structures mentioned.
994 For exact interpretation and more details, visit
999 .It Ic show Cm sysregs
1000 Show system registers (e.g.,
1003 Not present on some platforms.
1006 .It Ic show Cm tcpcb Ar addr
1007 Print TCP control block
1011 For exact interpretation of output, visit
1016 .It Ic show Cm thread Op Ar addr
1019 is specified, show detailed information about current thread.
1020 Otherwise, information about thread at
1025 .It Ic show Cm threads
1026 Show all threads within the system.
1027 Output format is as follows:
1029 .Bl -tag -compact -offset indent -width "Second column"
1031 Thread identifier (TID)
1032 .It Ic Second column
1033 Thread structure address
1039 .It Ic show Cm tty Ar addr
1040 Display the contents of a TTY structure in a readable form.
1043 .It Ic show Cm turnstile Ar addr
1045 .Vt struct turnstile
1046 structure at address
1048 Turnstiles are structures used within the
1051 synchronization primitives which, while holding a specific type of lock, cannot
1052 sleep or context switch to another thread.
1053 Currently, those are:
1060 Show UMA allocator statistics.
1061 Output consists five columns:
1063 .Bl -tag -compact -offset indent -width "Requests"
1065 Name of the UMA zone.
1066 The same string that was passed to
1068 as a first argument.
1070 Size of a given memory object (slab).
1072 Number of slabs being currently used.
1074 Number of free slabs within the UMA zone.
1076 Number of allocations requests to the given zone.
1079 The very same information might be gathered in the userspace
1081 .Dq Nm vmstat Fl z .
1084 .It Ic show Cm unpcb Ar addr
1085 Shows UNIX domain socket private control block
1087 present at the address
1091 .It Ic show Cm vmochk
1092 Prints, whether the internal VM objects are in a map somewhere
1093 and none have zero ref counts.
1096 .It Ic show Cm vmopag
1097 This is supposed to show physical addresses consumed by a
1099 Currently, it is not possible to use this command when
1101 is compiled in the kernel.
1104 .It Ic show Cm vnet Ar addr
1105 Prints virtualized network stack
1107 structure present at the address
1111 .It Ic show Cm vnode Op Ar addr
1116 For the exact interpretation of the output, look at the
1121 .It Ic show Cm vnodebufs Ar addr
1122 Shows clean/dirty buffer lists of the vnode located at
1126 .It Ic show Cm watches
1127 Displays all watchpoints.
1128 Shows watchpoints set with "watch" command.
1131 .It Ic show Cm witness
1132 Shows information about lock acquisition coming from the
1138 Toggles between remote GDB and DDB mode.
1139 In remote GDB mode, another machine is required that runs
1141 using the remote debug feature, with a connection to the serial
1142 console port on the target machine.
1143 Currently only available on the
1150 .It Ic kill Ar sig pid
1155 The signal is acted on upon returning from the debugger.
1156 This command can be used to kill a process causing resource contention
1157 in the case of a hung system.
1160 for a list of signals.
1161 Note that the arguments are reversed relative to
1164 .It Ic reboot Op Ar seconds
1165 .It Ic reset Op Ar seconds
1166 Hard reset the system.
1167 If the optional argument
1169 is given, the debugger will wait for this long, at most a week,
1173 Print a short summary of the available commands and command
1178 .It Ic capture reset
1179 .It Ic capture status
1181 supports a basic output capture facility, which can be used to retrieve the
1182 results of debugging commands from userspace using
1185 enables output capture;
1189 will clear the capture buffer and disable capture.
1191 will report current buffer use, buffer size, and disposition of output
1194 Userspace processes may inspect and manage
1199 .Dv debug.ddb.capture.bufsize
1200 may be used to query or set the current capture buffer size.
1202 .Dv debug.ddb.capture.maxbufsize
1203 may be used to query the compile-time limit on the capture buffer size.
1205 .Dv debug.ddb.capture.bytes
1206 may be used to query the number of bytes of output currently in the capture
1209 .Dv debug.ddb.capture.data
1210 returns the contents of the buffer as a string to an appropriately privileged
1213 This facility is particularly useful in concert with the scripting and
1215 facilities, allowing scripted debugging output to be captured and
1216 committed to disk as part of a textdump for later analysis.
1217 The contents of the capture buffer may also be inspected in a kernel core dump
1225 Run, define, list, and delete scripts.
1228 section for more information on the scripting facility.
1230 .It Ic textdump dump
1232 .It Ic textdump status
1233 .It Ic textdump unset
1236 command to immediately perform a textdump.
1237 More information may be found in
1241 command may be used to force the next kernel core dump to be a textdump
1242 rather than a traditional memory dump or minidump.
1244 reports whether a textdump has been scheduled.
1246 cancels a request to perform a textdump as the next kernel core dump.
1249 The debugger accesses registers and variables as
1251 Register names are as in the
1252 .Dq Ic show Cm registers
1254 Some variables are suffixed with numbers, and may have some modifier
1255 following a colon immediately after the variable name.
1256 For example, register variables can have a
1258 modifier to indicate user register (e.g.,
1261 Built-in variables currently supported are:
1263 .Bl -tag -width ".Va tabstops" -compact
1265 Input and output radix.
1267 Addresses are printed as
1268 .Dq Ar symbol Ns Li + Ns Ar offset
1274 The width of the displayed line.
1276 The number of lines.
1277 It is used by the built-in pager.
1280 .It Va work Ns Ar xx
1283 can take values from 0 to 31.
1286 Most expression operators in C are supported except
1294 .Bl -tag -width ".No Identifiers"
1296 The name of a symbol is translated to the value of the symbol, which
1297 is the address of the corresponding object.
1301 can be used in the identifier.
1302 If supported by an object format dependent routine,
1304 .Oo Ar filename : Oc Ar func : lineno ,
1306 .Oo Ar filename : Oc Ns Ar variable ,
1308 .Oo Ar filename : Oc Ns Ar lineno
1309 can be accepted as a symbol.
1311 Radix is determined by the first two letters:
1317 decimal; otherwise, follow current radix.
1323 address of the start of the last line examined.
1328 this is only changed by
1334 last address explicitly specified.
1335 .It Li $ Ns Ar variable
1336 Translated to the value of the specified variable.
1337 It may be followed by a
1339 and modifiers as described above.
1340 .It Ar a Ns Li # Ns Ar b
1341 A binary operator which rounds up the left hand side to the next
1342 multiple of right hand side.
1345 It may be followed by a
1347 and modifiers as described above.
1351 supports a basic scripting facility to allow automating tasks or responses to
1353 Each script consists of a list of DDB commands to be executed sequentially,
1354 and is assigned a unique name.
1355 Certain script names have special meaning, and will be automatically run on
1358 events if scripts by those names have been defined.
1362 command may be used to define a script by name.
1363 Scripts consist of a series of
1365 commands separated with the
1369 .Bd -literal -offset indent
1370 script kdb.enter.panic=bt; show pcpu
1371 script lockinfo=show alllocks; show lockedvnods
1376 command lists currently defined scripts.
1380 command execute a script by name.
1382 .Bd -literal -offset indent
1388 command may be used to delete a script by name.
1390 .Bd -literal -offset indent
1391 unscript kdb.enter.panic
1394 These functions may also be performed from userspace using the
1398 Certain scripts are run automatically, if defined, for specific
1401 The follow scripts are run when various events occur:
1402 .Bl -tag -width kdb.enter.powerfail
1403 .It Dv kdb.enter.acpi
1404 The kernel debugger was entered as a result of an
1407 .It Dv kdb.enter.bootflags
1408 The kernel debugger was entered at boot as a result of the debugger boot
1410 .It Dv kdb.enter.break
1411 The kernel debugger was entered as a result of a serial or console break.
1412 .It Dv kdb.enter.cam
1413 The kernel debugger was entered as a result of a
1416 .It Dv kdb.enter.mac
1417 The kernel debugger was entered as a result of an assertion failure in the
1420 TrustedBSD MAC Framework.
1421 .It Dv kdb.enter.ndis
1422 The kernel debugger was entered as a result of an
1425 .It Dv kdb.enter.netgraph
1426 The kernel debugger was entered as a result of a
1429 .It Dv kdb.enter.panic
1432 .It Dv kdb.enter.powerfail
1433 The kernel debugger was entered as a result of a powerfail NMI on the sparc64
1435 .It Dv kdb.enter.powerpc
1436 The kernel debugger was entered as a result of an unimplemented interrupt
1437 type on the powerpc platform.
1438 .It Dv kdb.enter.sysctl
1439 The kernel debugger was entered as a result of the
1442 .It Dv kdb.enter.trapsig
1443 The kernel debugger was entered as a result of a trapsig event on the sparc64
1445 .It Dv kdb.enter.unionfs
1446 The kernel debugger was entered as a result of an assertion failure in the
1448 .It Dv kdb.enter.unknown
1449 The kernel debugger was entered, but no reason has been set.
1450 .It Dv kdb.enter.vfslock
1451 The kernel debugger was entered as a result of a VFS lock violation.
1452 .It Dv kdb.enter.watchdog
1453 The kernel debugger was entered as a result of a watchdog firing.
1454 .It Dv kdb.enter.witness
1455 The kernel debugger was entered as a result of a
1460 In the event that none of these scripts is found,
1462 will attempt to execute a default script:
1463 .Bl -tag -width kdb.enter.powerfail
1464 .It Dv kdb.enter.default
1465 The kernel debugger was entered, but a script exactly matching the reason for
1466 entering was not defined.
1467 This can be used as a catch-all to handle cases not specifically of interest;
1469 .Dv kdb.enter.witness
1470 might be defined to have special handling, and
1471 .Dv kdb.enter.default
1472 might be defined to simply panic and reboot.
1475 On machines with an ISA expansion bus, a simple NMI generation card can be
1476 constructed by connecting a push button between the A01 and B01 (CHCHK# and
1478 Momentarily shorting these two fingers together may cause the bridge chipset to
1479 generate an NMI, which causes the kernel to pass control to
1481 Some bridge chipsets do not generate a NMI on CHCHK#, so your mileage may vary.
1482 The NMI allows one to break into the debugger on a wedged machine to
1484 Other bus' bridge chipsets may be able to generate NMI using bus specific
1486 There are many PCI and PCIe add-in cards which can generate NMI for
1488 Modern server systems typically use IPMI to generate signals to enter the
1492 port can be used to send the
1493 .Cd chassis power diag
1494 command which delivers an NMI to the processor.
1495 Embedded systems often use JTAG for debugging, but rarely use it in
1499 For serial consoles, you can enter the debugger by sending a BREAK
1500 condition on the serial line if
1501 .Cd options BREAK_TO_DEBUGGER
1502 is specified in the kernel.
1503 Most terminal emulation programs can send a break sequence with a
1504 special key sequence or via a menu item.
1505 However, in some setups, sending the break can be difficult to arrange
1506 or happens spuriously, so if the kernel contains
1507 .Cd options ALT_BREAK_TO_DEBUGGER
1508 then the sequence of CR TILDE CTRL-B enters the debugger;
1509 CR TILDE CTRL-P causes a panic instead of entering the
1511 CR TILDE CTRL-R causes an immediate reboot.
1512 In all the above sequences, CR is a Carriage Return and is usually
1513 sent by hitting the Enter or Return key.
1514 TILDE is the ASCII tilde character (~).
1515 CTRL-x is Control x created by hitting the control key and then x
1516 and then releasing both.
1518 The break to enter the debugger behavior may be enabled at run-time
1521 .Dv debug.kdb.break_to_debugger
1523 The alternate sequence to enter the debugger behavior may be enabled
1524 at run-time by setting the
1526 .Dv debug.kdb.alt_break_to_debugger
1528 The debugger may be entered by setting the
1533 Header files mentioned in this manual page can be found below
1543 .Pa netinet/in_pcb.h
1565 debugger was developed for Mach, and ported to
1567 This manual page translated from
1570 .An Garrett Wollman .
1572 .An Robert N. M. Watson