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
267 machine, but none of the supported architectures have an alternate format
269 display a symbol name for the pointer stored at the address
276 command with the last specified parameters to it
277 except that the next address displayed by it is used as the start address.
283 command with the last specified parameters to it
284 except that the last start address subtracted by the size displayed by it
285 is used as the start address.
287 .It Ic print Ns Op Li / Ns Cm acdoruxz
288 .It Ic p Ns Op Li / Ns Cm acdoruxz
291 according to the modifier character (as described above for
294 .Cm a , x , z , o , d , u , r ,
297 If no modifier is specified, the last one specified to it is used.
300 can be a string, in which case it is printed as it is.
302 .Bd -literal -offset indent
303 print/x "eax = " $eax "\enecx = " $ecx "\en"
307 .Bd -literal -offset indent
313 .Ic write Ns Op Li / Ns Cm bhl
314 .Ar addr expr1 Op Ar expr2 ...
317 .Ic w Ns Op Li / Ns Cm bhl
318 .Ar addr expr1 Op Ar expr2 ...
320 Write the expressions specified after
322 on the command line at succeeding locations starting with
324 The write unit size can be specified in the modifier with a letter
330 (long word) respectively.
332 long word is assumed.
335 since there is no delimiter between expressions, strange
337 It is best to enclose each expression in parentheses.
339 .It Ic set Li $ Ns Ar variable Oo Li = Oc Ar expr
340 Set the named variable or register with the value of
342 Valid variable names are described below.
344 .It Ic break Ns Oo Li / Ns Cm u Oc Oo Ar addr Oc Ns Op Li , Ns Ar count
345 .It Ic b Ns Oo Li / Ns Cm u Oc Oo Ar addr Oc Ns Op Li , Ns Ar count
352 command will not stop at this break point on the first
354 \- 1 times that it is hit.
355 If the break point is set, a break point number is
358 This number can be used in deleting the break point
359 or adding conditions to it.
363 modifier is specified, this command sets a break point in user
367 option, the address is considered to be in the kernel
368 space, and a wrong space address is rejected with an error message.
369 This modifier can be used only if it is supported by machine dependent
373 If a user text is shadowed by a normal user space debugger,
374 user space break points may not work correctly.
376 point at the low-level code paths may also cause strange behavior.
378 .It Ic delete Op Ar addr
380 .It Ic delete Li # Ns Ar number
381 .It Ic d Li # Ns Ar number
382 Delete the specified break point.
383 The break point can be specified by a
384 break point number with
388 specified in the original
390 command, or by omitting
392 to get the default address of
395 .It Ic watch Oo Ar addr Oc Ns Op Li , Ns Ar size
396 Set a watchpoint for a region.
397 Execution stops when an attempt to modify the region occurs.
400 argument defaults to 4.
401 If you specify a wrong space address, the request is rejected
402 with an error message.
405 Attempts to watch wired kernel memory
406 may cause unrecoverable error in some systems such as i386.
407 Watchpoints on user addresses work best.
409 .It Ic hwatch Oo Ar addr Oc Ns Op Li , Ns Ar size
410 Set a hardware watchpoint for a region if supported by the
412 Execution stops when an attempt to modify the region occurs.
415 argument defaults to 4.
418 The hardware debug facilities do not have a concept of separate
419 address spaces like the watch command does.
422 for setting watchpoints on kernel address locations only, and avoid
423 its use on user mode address spaces.
425 .It Ic dhwatch Oo Ar addr Oc Ns Op Li , Ns Ar size
426 Delete specified hardware watchpoint.
428 .It Ic step Ns Oo Li / Ns Cm p Oc Ns Op Li , Ns Ar count
429 .It Ic s Ns Oo Li / Ns Cm p Oc Ns Op Li , Ns Ar count
435 modifier is specified, print each instruction at each step.
436 Otherwise, only print the last instruction.
439 depending on machine type, it may not be possible to
440 single-step through some low-level code paths or user space code.
441 On machines with software-emulated single-stepping (e.g., pmax),
442 stepping through code executed by interrupt handlers will probably
445 .It Ic continue Ns Op Li / Ns Cm c
446 .It Ic c Ns Op Li / Ns Cm c
447 Continue execution until a breakpoint or watchpoint.
450 modifier is specified, count instructions while executing.
451 Some machines (e.g., pmax) also count loads and stores.
454 when counting, the debugger is really silently single-stepping.
455 This means that single-stepping on low-level code may cause strange
458 .It Ic until Ns Op Li / Ns Cm p
459 Stop at the next call or return instruction.
462 modifier is specified, print the call nesting depth and the
463 cumulative instruction count at each call or return.
465 only print when the matching return is hit.
467 .It Ic next Ns Op Li / Ns Cm p
468 .It Ic match Ns Op Li / Ns Cm p
469 Stop at the matching return instruction.
472 modifier is specified, print the call nesting depth and the
473 cumulative instruction count at each call or return.
474 Otherwise, only print when the matching return is hit.
477 .Ic trace Ns Op Li / Ns Cm u
482 .Ic t Ns Op Li / Ns Cm u
487 .Ic where Ns Op Li / Ns Cm u
492 .Ic bt Ns Op Li / Ns Cm u
499 option traces user space; if omitted,
503 The optional argument
505 is the number of frames to be traced.
508 is omitted, all frames are printed.
511 User space stack trace is valid
512 only if the machine dependent code supports it.
515 .Ic search Ns Op Li / Ns Cm bhl
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
552 Show a stack trace for every thread in the system.
554 .It Ic show Cm all ttys
555 Show all TTY's within the system.
558 but also includes the address of the TTY structure.
561 .It Ic show Cm all vnets
562 Show the same output as "show vnet" does, but lists all
563 virtualized network stacks within the system.
566 .It Ic show Cm allchains
567 Show the same information like "show lockchain" does, but
568 for every thread in the system.
571 .It Ic show Cm alllocks
572 Show all locks that are currently held.
573 This command is only available if
575 is included in the kernel.
578 .It Ic show Cm allpcpu
579 The same as "show pcpu", but for every CPU present in the system.
582 .It Ic show Cm allrman
583 Show information related with resource management, including
584 interrupt request lines, DMA request lines, I/O ports, I/O memory
585 addresses, and Resource IDs.
589 Dump data about APIC IDT vector mappings.
592 .It Ic show Cm breaks
593 Show breakpoints set with the "break" command.
596 .It Ic show Cm bio Ar addr
597 Show information about the bio structure
605 for more details on the exact meaning of the structure fields.
608 .It Ic show Cm buffer Ar addr
609 Show information about the buf structure
615 header file for more details on the exact meaning of the structure fields.
618 .It Ic show Cm callout Ar addr
619 Show information about the callout structure
625 .It Ic show Cm cbstat
626 Show brief information about the TTY subsystem.
630 Without argument, show the list of all created cdev's, consisting of devfs
631 node name and struct cdev address.
632 When address of cdev is supplied, show some internal devfs state of the cdev.
635 .It Ic show Cm conifhk
636 Lists hooks currently waiting for completion in
637 run_interrupt_driven_config_hooks().
640 .It Ic show Cm cpusets
641 Print numbered root and assigned CPU affinity sets.
647 .It Ic show Cm cyrixreg
648 Show registers specific to the Cyrix processor.
651 .It Ic show Cm devmap
652 Prints the contents of the static device mapping table.
653 Currently only available on the
658 .It Ic show Cm domain Ar addr
659 Print protocol domain structure
665 header file for more details on the exact meaning of the structure fields.
668 .It Ic show Cm ffs Op Ar addr
669 Show brief information about ffs mount at the address
671 if argument is given.
672 Otherwise, provides the summary about each ffs mount.
675 .It Ic show Cm file Ar addr
676 Show information about the file structure
683 Show information about every file structure in the system.
686 .It Ic show Cm freepages
687 Show the number of physical pages in each of the free lists.
690 .It Ic show Cm geom Op Ar addr
693 argument is not given, displays the entire GEOM topology.
696 is given, displays details about the given GEOM object (class, geom,
697 provider or consumer).
702 The first column specifies the IDT vector.
703 The second one is the name of the interrupt/trap handler.
704 Those functions are machine dependent.
707 .It Ic show Cm igi_list Ar addr
708 Show information about the IGMP structure
709 .Vt struct igmp_ifsoftc
714 .It Ic show Cm inodedeps Op Ar addr
715 Show brief information about each inodedep structure.
718 is given, only inodedeps belonging to the fs located at the
719 supplied address are shown.
722 .It Ic show Cm inpcb Ar addr
723 Show information on IP Control Block
730 Dump information about interrupt handlers.
733 .It Ic show Cm intrcnt
734 Dump the interrupt statistics.
738 Show interrupt lines and their respective kernel threads.
747 shows, also list kernel internal details.
751 Show information from the local APIC registers for this CPU.
754 .It Ic show Cm lock Ar addr
756 The output format is as follows:
757 .Bl -tag -width "flags"
760 Possible types include
768 Flags passed to the lock initialization function.
769 For exact possibilities see manual pages of possible lock types.
771 Current state of a lock.
780 .It Ic show Cm lockchain Ar addr
781 Show all threads a particular thread at address
783 is waiting on based on non-sleepable and non-spin locks.
786 .It Ic show Cm lockedbufs
787 Show the same information as "show buf", but for every locked
792 .It Ic show Cm lockedvnods
793 List all locked vnodes in the system.
797 Prints all locks that are currently acquired.
798 This command is only available if
800 is included in the kernel.
803 .It Ic show Cm locktree
806 .It Ic show Cm malloc
809 memory allocator statistics.
810 The output format is as follows:
812 .Bl -tag -compact -offset indent -width "Requests"
814 Specifies a type of memory.
815 It is the same as a description string used while defining the
816 given memory type with
817 .Xr MALLOC_DECLARE 9 .
819 Number of memory allocations of the given type, for which
821 has not been called yet.
823 Total memory consumed by the given allocation type.
825 Number of memory allocation requests for the given
829 The same information can be gathered in userspace with
833 .It Ic show Cm map Ns Oo Li / Ns Cm f Oc Ar addr
838 modifier is specified the
839 complete map is printed.
842 .It Ic show Cm msgbuf
843 Print the system's message buffer.
844 It is the same output as in the
847 It is useful if you got a kernel panic, attached a serial cable
848 to the machine and want to get the boot messages from before the
852 Displays short info about all currently mounted file systems.
854 .It Ic show Cm mount Ar addr
855 Displays details about the given mount point.
858 .It Ic show Cm object Ns Oo Li / Ns Cm f Oc Ar addr
859 Prints the VM object at
863 option is specified the
864 complete object is printed.
868 Print the panic message if set.
872 Show statistics on VM pages.
876 Show statistics on VM page queues.
879 .It Ic show Cm pciregs
880 Print PCI bus registers.
881 The same information can be gathered in userspace by running
882 .Dq Nm pciconf Fl lv .
886 Print current processor state.
887 The output format is as follows:
889 .Bl -tag -compact -offset indent -width "spin locks held:"
891 Processor identifier.
893 Thread pointer, process identifier and the name of the process.
895 Control block pointer.
901 CPU identifier coming from APIC.
904 .It Ic spin locks held
905 Names of spin locks held.
909 .It Ic show Cm pgrpdump
910 Dump process groups present within the system.
913 .It Ic show Cm proc Op Ar addr
916 is specified, print information about the current process.
917 Otherwise, show information about the process at address
921 .It Ic show Cm procvm
922 Show process virtual memory layout.
925 .It Ic show Cm protosw Ar addr
926 Print protocol switch structure
932 .It Ic show Cm registers Ns Op Li / Ns Cm u
933 Display the register set.
936 modifier is specified, it displays user registers instead of
937 kernel registers or the currently saved one.
942 modifier depends on the machine.
943 If not supported, incorrect information will be displayed.
946 .It Ic show Cm rman Ar addr
947 Show resource manager object
951 Addresses of particular pointers can be gathered with "show allrman"
956 Show real time clock value.
957 Useful for long debugging sessions.
960 .It Ic show Cm sleepchain
961 Show all the threads a particular thread is waiting on based on
965 .It Ic show Cm sleepq
966 .It Ic show Cm sleepqueue
967 Both commands provide the same functionality.
969 .Vt struct sleepqueue
971 Sleepqueues are used within the
973 kernel to implement sleepable
974 synchronization primitives (thread holding a lock might sleep or
975 be context switched), which at the time of writing are:
983 .It Ic show Cm sockbuf Ar addr
984 .It Ic show Cm socket Ar addr
991 Output consists of all values present in structures mentioned.
992 For exact interpretation and more details, visit
997 .It Ic show Cm sysregs
998 Show system registers (e.g.,
1001 Not present on some platforms.
1004 .It Ic show Cm tcpcb Ar addr
1005 Print TCP control block
1009 For exact interpretation of output, visit
1014 .It Ic show Cm thread Op Ar addr
1017 is specified, show detailed information about current thread.
1018 Otherwise, information about thread at
1023 .It Ic show Cm threads
1024 Show all threads within the system.
1025 Output format is as follows:
1027 .Bl -tag -compact -offset indent -width "Second column"
1029 Thread identifier (TID)
1030 .It Ic Second column
1031 Thread structure address
1037 .It Ic show Cm tty Ar addr
1038 Display the contents of a TTY structure in a readable form.
1041 .It Ic show Cm turnstile Ar addr
1043 .Vt struct turnstile
1044 structure at address
1046 Turnstiles are structures used within the
1049 synchronization primitives which, while holding a specific type of lock, cannot
1050 sleep or context switch to another thread.
1051 Currently, those are:
1058 Show UMA allocator statistics.
1059 Output consists five columns:
1061 .Bl -tag -compact -offset indent -width "Requests"
1063 Name of the UMA zone.
1064 The same string that was passed to
1066 as a first argument.
1068 Size of a given memory object (slab).
1070 Number of slabs being currently used.
1072 Number of free slabs within the UMA zone.
1074 Number of allocations requests to the given zone.
1077 The very same information might be gathered in the userspace
1079 .Dq Nm vmstat Fl z .
1082 .It Ic show Cm unpcb Ar addr
1083 Shows UNIX domain socket private control block
1085 present at the address
1089 .It Ic show Cm vmochk
1090 Prints, whether the internal VM objects are in a map somewhere
1091 and none have zero ref counts.
1094 .It Ic show Cm vmopag
1095 This is supposed to show physical addresses consumed by a
1097 Currently, it is not possible to use this command when
1099 is compiled in the kernel.
1102 .It Ic show Cm vnet Ar addr
1103 Prints virtualized network stack
1105 structure present at the address
1109 .It Ic show Cm vnode Op Ar addr
1114 For the exact interpretation of the output, look at the
1119 .It Ic show Cm vnodebufs Ar addr
1120 Shows clean/dirty buffer lists of the vnode located at
1124 .It Ic show Cm watches
1125 Displays all watchpoints.
1126 Shows watchpoints set with "watch" command.
1129 .It Ic show Cm witness
1130 Shows information about lock acquisition coming from the
1136 Toggles between remote GDB and DDB mode.
1137 In remote GDB mode, another machine is required that runs
1139 using the remote debug feature, with a connection to the serial
1140 console port on the target machine.
1141 Currently only available on the
1148 .It Ic kill Ar sig pid
1153 The signal is acted on upon returning from the debugger.
1154 This command can be used to kill a process causing resource contention
1155 in the case of a hung system.
1158 for a list of signals.
1159 Note that the arguments are reversed relative to
1162 .It Ic reboot Op Ar seconds
1163 .It Ic reset Op Ar seconds
1164 Hard reset the system.
1165 If the optional argument
1167 is given, the debugger will wait for this long, at most a week,
1171 Print a short summary of the available commands and command
1176 .It Ic capture reset
1177 .It Ic capture status
1179 supports a basic output capture facility, which can be used to retrieve the
1180 results of debugging commands from userspace using
1183 enables output capture;
1187 will clear the capture buffer and disable capture.
1189 will report current buffer use, buffer size, and disposition of output
1192 Userspace processes may inspect and manage
1197 .Dv debug.ddb.capture.bufsize
1198 may be used to query or set the current capture buffer size.
1200 .Dv debug.ddb.capture.maxbufsize
1201 may be used to query the compile-time limit on the capture buffer size.
1203 .Dv debug.ddb.capture.bytes
1204 may be used to query the number of bytes of output currently in the capture
1207 .Dv debug.ddb.capture.data
1208 returns the contents of the buffer as a string to an appropriately privileged
1211 This facility is particularly useful in concert with the scripting and
1213 facilities, allowing scripted debugging output to be captured and
1214 committed to disk as part of a textdump for later analysis.
1215 The contents of the capture buffer may also be inspected in a kernel core dump
1223 Run, define, list, and delete scripts.
1226 section for more information on the scripting facility.
1228 .It Ic textdump dump
1230 .It Ic textdump status
1231 .It Ic textdump unset
1234 command to immediately perform a textdump.
1235 More information may be found in
1239 command may be used to force the next kernel core dump to be a textdump
1240 rather than a traditional memory dump or minidump.
1242 reports whether a textdump has been scheduled.
1244 cancels a request to perform a textdump as the next kernel core dump.
1247 The debugger accesses registers and variables as
1249 Register names are as in the
1250 .Dq Ic show Cm registers
1252 Some variables are suffixed with numbers, and may have some modifier
1253 following a colon immediately after the variable name.
1254 For example, register variables can have a
1256 modifier to indicate user register (e.g.,
1259 Built-in variables currently supported are:
1261 .Bl -tag -width ".Va tabstops" -compact
1263 Input and output radix.
1265 Addresses are printed as
1266 .Dq Ar symbol Ns Li + Ns Ar offset
1272 The width of the displayed line.
1274 The number of lines.
1275 It is used by the built-in pager.
1278 .It Va work Ns Ar xx
1281 can take values from 0 to 31.
1284 Most expression operators in C are supported except
1292 .Bl -tag -width ".No Identifiers"
1294 The name of a symbol is translated to the value of the symbol, which
1295 is the address of the corresponding object.
1299 can be used in the identifier.
1300 If supported by an object format dependent routine,
1302 .Oo Ar filename : Oc Ar func : lineno ,
1304 .Oo Ar filename : Oc Ns Ar variable ,
1306 .Oo Ar filename : Oc Ns Ar lineno
1307 can be accepted as a symbol.
1309 Radix is determined by the first two letters:
1315 decimal; otherwise, follow current radix.
1321 address of the start of the last line examined.
1326 this is only changed by
1332 last address explicitly specified.
1333 .It Li $ Ns Ar variable
1334 Translated to the value of the specified variable.
1335 It may be followed by a
1337 and modifiers as described above.
1338 .It Ar a Ns Li # Ns Ar b
1339 A binary operator which rounds up the left hand side to the next
1340 multiple of right hand side.
1343 It may be followed by a
1345 and modifiers as described above.
1349 supports a basic scripting facility to allow automating tasks or responses to
1351 Each script consists of a list of DDB commands to be executed sequentially,
1352 and is assigned a unique name.
1353 Certain script names have special meaning, and will be automatically run on
1356 events if scripts by those names have been defined.
1360 command may be used to define a script by name.
1361 Scripts consist of a series of
1363 commands separated with the
1367 .Bd -literal -offset indent
1368 script kdb.enter.panic=bt; show pcpu
1369 script lockinfo=show alllocks; show lockedvnods
1374 command lists currently defined scripts.
1378 command execute a script by name.
1380 .Bd -literal -offset indent
1386 command may be used to delete a script by name.
1388 .Bd -literal -offset indent
1389 unscript kdb.enter.panic
1392 These functions may also be performed from userspace using the
1396 Certain scripts are run automatically, if defined, for specific
1399 The follow scripts are run when various events occur:
1400 .Bl -tag -width kdb.enter.powerfail
1401 .It Dv kdb.enter.acpi
1402 The kernel debugger was entered as a result of an
1405 .It Dv kdb.enter.bootflags
1406 The kernel debugger was entered at boot as a result of the debugger boot
1408 .It Dv kdb.enter.break
1409 The kernel debugger was entered as a result of a serial or console break.
1410 .It Dv kdb.enter.cam
1411 The kernel debugger was entered as a result of a
1414 .It Dv kdb.enter.mac
1415 The kernel debugger was entered as a result of an assertion failure in the
1418 TrustedBSD MAC Framework.
1419 .It Dv kdb.enter.ndis
1420 The kernel debugger was entered as a result of an
1423 .It Dv kdb.enter.netgraph
1424 The kernel debugger was entered as a result of a
1427 .It Dv kdb.enter.panic
1430 .It Dv kdb.enter.powerfail
1431 The kernel debugger was entered as a result of a powerfail NMI on the sparc64
1433 .It Dv kdb.enter.powerpc
1434 The kernel debugger was entered as a result of an unimplemented interrupt
1435 type on the powerpc platform.
1436 .It Dv kdb.enter.sysctl
1437 The kernel debugger was entered as a result of the
1440 .It Dv kdb.enter.trapsig
1441 The kernel debugger was entered as a result of a trapsig event on the sparc64
1443 .It Dv kdb.enter.unionfs
1444 The kernel debugger was entered as a result of an assertion failure in the
1446 .It Dv kdb.enter.unknown
1447 The kernel debugger was entered, but no reason has been set.
1448 .It Dv kdb.enter.vfslock
1449 The kernel debugger was entered as a result of a VFS lock violation.
1450 .It Dv kdb.enter.watchdog
1451 The kernel debugger was entered as a result of a watchdog firing.
1452 .It Dv kdb.enter.witness
1453 The kernel debugger was entered as a result of a
1458 In the event that none of these scripts is found,
1460 will attempt to execute a default script:
1461 .Bl -tag -width kdb.enter.powerfail
1462 .It Dv kdb.enter.default
1463 The kernel debugger was entered, but a script exactly matching the reason for
1464 entering was not defined.
1465 This can be used as a catch-all to handle cases not specifically of interest;
1467 .Dv kdb.enter.witness
1468 might be defined to have special handling, and
1469 .Dv kdb.enter.default
1470 might be defined to simply panic and reboot.
1473 On machines with an ISA expansion bus, a simple NMI generation card can be
1474 constructed by connecting a push button between the A01 and B01 (CHCHK# and
1476 Momentarily shorting these two fingers together may cause the bridge chipset to
1477 generate an NMI, which causes the kernel to pass control to
1479 Some bridge chipsets do not generate a NMI on CHCHK#, so your mileage may vary.
1480 The NMI allows one to break into the debugger on a wedged machine to
1482 Other bus' bridge chipsets may be able to generate NMI using bus specific
1484 There are many PCI and PCIe add-in cards which can generate NMI for
1486 Modern server systems typically use IPMI to generate signals to enter the
1490 port can be used to send the
1491 .Cd chassis power diag
1492 command which delivers an NMI to the processor.
1493 Embedded systems often use JTAG for debugging, but rarely use it in
1497 For serial consoles, you can enter the debugger by sending a BREAK
1498 condition on the serial line if
1499 .Cd options BREAK_TO_DEBUGGER
1500 is specified in the kernel.
1501 Most terminal emulation programs can send a break sequence with a
1502 special key sequence or via a menu item.
1503 However, in some setups, sending the break can be difficult to arrange
1504 or happens spuriously, so if the kernel contains
1505 .Cd options ALT_BREAK_TO_DEBUGGER
1506 then the sequence of CR TILDE CTRL-B enters the debugger;
1507 CR TILDE CTRL-P causes a panic instead of entering the
1509 CR TILDE CTRL-R causes an immediate reboot.
1510 In all the above sequences, CR is a Carriage Return and is usually
1511 sent by hitting the Enter or Return key.
1512 TILDE is the ASCII tilde character (~).
1513 CTRL-x is Control x created by hitting the control key and then x
1514 and then releasing both.
1516 The break to enter the debugger behavior may be enabled at run-time
1519 .Dv debug.kdb.break_to_debugger
1521 The alternate sequence to enter the debugger behavior may be enabled
1522 at run-time by setting the
1524 .Dv debug.kdb.alt_break_to_debugger
1526 The debugger may be entered by setting the
1531 Header files mentioned in this manual page can be found below
1541 .Pa netinet/in_pcb.h
1563 debugger was developed for Mach, and ported to
1565 This manual page translated from
1568 .An Garrett Wollman .
1570 .An Robert N. M. Watson