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 , 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 , Ns Ar count
219 .Ic x Ns Op Li / Ns Cm AISabcdghilmorsuxz ...
220 .Oo Ar addr Oc Ns Op , 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 , Ns Ar count
347 .It Ic b Ns Oo Li / Ns Cm u Oc Oo Ar addr Oc Ns Op , 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 , 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 , 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 , Ns Ar size
428 Delete specified hardware watchpoint.
430 .It Ic step Ns Oo Li / Ns Cm p Oc Ns Op , Ns Ar count
431 .It Ic s Ns Oo Li / Ns Cm p Oc Ns Op , 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 a
541 .It Ic ps Ns Op Li / Ns Cm a
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 print command line arguments for each process.
551 .It Ic show Cm all trace
553 Show a stack trace for every thread in the system.
555 .It Ic show Cm all ttys
556 Show all TTY's within the system.
559 but also includes the address of the TTY structure.
562 .It Ic show Cm all vnets
563 Show the same output as "show vnet" does, but lists all
564 virtualized network stacks within the system.
567 .It Ic show Cm allchains
568 Show the same information like "show lockchain" does, but
569 for every thread in the system.
572 .It Ic show Cm alllocks
573 Show all locks that are currently held.
574 This command is only available if
576 is included in the kernel.
579 .It Ic show Cm allpcpu
580 The same as "show pcpu", but for every CPU present in the system.
583 .It Ic show Cm allrman
584 Show information related with resource management, including
585 interrupt request lines, DMA request lines, I/O ports, I/O memory
586 addresses, and Resource IDs.
590 Dump data about APIC IDT vector mappings.
593 .It Ic show Cm breaks
594 Show breakpoints set with the "break" command.
597 .It Ic show Cm bio Ar addr
598 Show information about the bio structure
606 for more details on the exact meaning of the structure fields.
609 .It Ic show Cm buffer Ar addr
610 Show information about the buf structure
616 header file for more details on the exact meaning of the structure fields.
619 .It Ic show Cm callout Ar addr
620 Show information about the callout structure
626 .It Ic show Cm cbstat
627 Show brief information about the TTY subsystem.
631 Without argument, show the list of all created cdev's, consisting of devfs
632 node name and struct cdev address.
633 When address of cdev is supplied, show some internal devfs state of the cdev.
636 .It Ic show Cm conifhk
637 Lists hooks currently waiting for completion in
638 run_interrupt_driven_config_hooks().
641 .It Ic show Cm cpusets
642 Print numbered root and assigned CPU affinity sets.
648 .It Ic show Cm cyrixreg
649 Show registers specific to the Cyrix processor.
652 .It Ic show Cm devmap
653 Prints the contents of the static device mapping table.
654 Currently only available on the
659 .It Ic show Cm domain Ar addr
660 Print protocol domain structure
666 header file for more details on the exact meaning of the structure fields.
669 .It Ic show Cm ffs Op Ar addr
670 Show brief information about ffs mount at the address
672 if argument is given.
673 Otherwise, provides the summary about each ffs mount.
676 .It Ic show Cm file Ar addr
677 Show information about the file structure
684 Show information about every file structure in the system.
687 .It Ic show Cm freepages
688 Show the number of physical pages in each of the free lists.
691 .It Ic show Cm geom Op Ar addr
694 argument is not given, displays the entire GEOM topology.
697 is given, displays details about the given GEOM object (class, geom,
698 provider or consumer).
703 The first column specifies the IDT vector.
704 The second one is the name of the interrupt/trap handler.
705 Those functions are machine dependent.
708 .It Ic show Cm igi_list Ar addr
709 Show information about the IGMP structure
710 .Vt struct igmp_ifsoftc
715 .It Ic show Cm inodedeps Op Ar addr
716 Show brief information about each inodedep structure.
719 is given, only inodedeps belonging to the fs located at the
720 supplied address are shown.
723 .It Ic show Cm inpcb Ar addr
724 Show information on IP Control Block
731 Dump information about interrupt handlers.
734 .It Ic show Cm intrcnt
735 Dump the interrupt statistics.
739 Show interrupt lines and their respective kernel threads.
748 shows, also list kernel internal details.
752 Show information from the local APIC registers for this CPU.
755 .It Ic show Cm lock Ar addr
757 The output format is as follows:
758 .Bl -tag -width "flags"
761 Possible types include
769 Flags passed to the lock initialization function.
771 values are lock class specific.
773 Current state of a lock.
775 values are lock class specific.
781 .It Ic show Cm lockchain Ar addr
782 Show all threads a particular thread at address
784 is waiting on based on non-spin locks.
787 .It Ic show Cm lockedbufs
788 Show the same information as "show buf", but for every locked
793 .It Ic show Cm lockedvnods
794 List all locked vnodes in the system.
798 Prints all locks that are currently acquired.
799 This command is only available if
801 is included in the kernel.
804 .It Ic show Cm locktree
807 .It Ic show Cm malloc
810 memory allocator statistics.
811 The output format is as follows:
813 .Bl -tag -compact -offset indent -width "Requests"
815 Specifies a type of memory.
816 It is the same as a description string used while defining the
817 given memory type with
818 .Xr MALLOC_DECLARE 9 .
820 Number of memory allocations of the given type, for which
822 has not been called yet.
824 Total memory consumed by the given allocation type.
826 Number of memory allocation requests for the given
830 The same information can be gathered in userspace with
834 .It Ic show Cm map Ns Oo Li / Ns Cm f Oc Ar addr
839 modifier is specified the
840 complete map is printed.
843 .It Ic show Cm msgbuf
844 Print the system's message buffer.
845 It is the same output as in the
848 It is useful if you got a kernel panic, attached a serial cable
849 to the machine and want to get the boot messages from before the
853 Displays short info about all currently mounted file systems.
855 .It Ic show Cm mount Ar addr
856 Displays details about the given mount point.
859 .It Ic show Cm object Ns Oo Li / Ns Cm f Oc Ar addr
860 Prints the VM object at
864 option is specified the
865 complete object is printed.
869 Print the panic message if set.
873 Show statistics on VM pages.
877 Show statistics on VM page queues.
880 .It Ic show Cm pciregs
881 Print PCI bus registers.
882 The same information can be gathered in userspace by running
883 .Dq Nm pciconf Fl lv .
887 Print current processor state.
888 The output format is as follows:
890 .Bl -tag -compact -offset indent -width "spin locks held:"
892 Processor identifier.
894 Thread pointer, process identifier and the name of the process.
896 Control block pointer.
902 CPU identifier coming from APIC.
905 .It Ic spin locks held
906 Names of spin locks held.
910 .It Ic show Cm pgrpdump
911 Dump process groups present within the system.
914 .It Ic show Cm proc Op Ar addr
917 is specified, print information about the current process.
918 Otherwise, show information about the process at address
922 .It Ic show Cm procvm
923 Show process virtual memory layout.
926 .It Ic show Cm protosw Ar addr
927 Print protocol switch structure
933 .It Ic show Cm registers Ns Op Li / Ns Cm u
934 Display the register set.
937 modifier is specified, it displays user registers instead of
938 kernel registers or the currently saved one.
943 modifier depends on the machine.
944 If not supported, incorrect information will be displayed.
947 .It Ic show Cm rman Ar addr
948 Show resource manager object
952 Addresses of particular pointers can be gathered with "show allrman"
957 Show real time clock value.
958 Useful for long debugging sessions.
961 .It Ic show Cm sleepchain
964 .Ic show Cm lockchain .
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 vpath Ar addr
1127 Walk the namecache to lookup the pathname of the vnode located at
1131 .It Ic show Cm watches
1132 Displays all watchpoints.
1133 Shows watchpoints set with "watch" command.
1136 .It Ic show Cm witness
1137 Shows information about lock acquisition coming from the
1143 Toggles between remote GDB and DDB mode.
1144 In remote GDB mode, another machine is required that runs
1146 using the remote debug feature, with a connection to the serial
1147 console port on the target machine.
1148 Currently only available on the
1155 .It Ic kill Ar sig pid
1160 The signal is acted on upon returning from the debugger.
1161 This command can be used to kill a process causing resource contention
1162 in the case of a hung system.
1165 for a list of signals.
1166 Note that the arguments are reversed relative to
1169 .It Ic reboot Op Ar seconds
1170 .It Ic reset Op Ar seconds
1171 Hard reset the system.
1172 If the optional argument
1174 is given, the debugger will wait for this long, at most a week,
1178 Print a short summary of the available commands and command
1183 .It Ic capture reset
1184 .It Ic capture status
1186 supports a basic output capture facility, which can be used to retrieve the
1187 results of debugging commands from userspace using
1190 enables output capture;
1194 will clear the capture buffer and disable capture.
1196 will report current buffer use, buffer size, and disposition of output
1199 Userspace processes may inspect and manage
1204 .Dv debug.ddb.capture.bufsize
1205 may be used to query or set the current capture buffer size.
1207 .Dv debug.ddb.capture.maxbufsize
1208 may be used to query the compile-time limit on the capture buffer size.
1210 .Dv debug.ddb.capture.bytes
1211 may be used to query the number of bytes of output currently in the capture
1214 .Dv debug.ddb.capture.data
1215 returns the contents of the buffer as a string to an appropriately privileged
1218 This facility is particularly useful in concert with the scripting and
1220 facilities, allowing scripted debugging output to be captured and
1221 committed to disk as part of a textdump for later analysis.
1222 The contents of the capture buffer may also be inspected in a kernel core dump
1230 Run, define, list, and delete scripts.
1233 section for more information on the scripting facility.
1235 .It Ic textdump dump
1237 .It Ic textdump status
1238 .It Ic textdump unset
1241 command to immediately perform a textdump.
1242 More information may be found in
1246 command may be used to force the next kernel core dump to be a textdump
1247 rather than a traditional memory dump or minidump.
1249 reports whether a textdump has been scheduled.
1251 cancels a request to perform a textdump as the next kernel core dump.
1254 The debugger accesses registers and variables as
1256 Register names are as in the
1257 .Dq Ic show Cm registers
1259 Some variables are suffixed with numbers, and may have some modifier
1260 following a colon immediately after the variable name.
1261 For example, register variables can have a
1263 modifier to indicate user register (e.g.,
1266 Built-in variables currently supported are:
1268 .Bl -tag -width ".Va tabstops" -compact
1270 Input and output radix.
1272 Addresses are printed as
1273 .Dq Ar symbol Ns Li + Ns Ar offset
1279 The width of the displayed line.
1281 The number of lines.
1282 It is used by the built-in pager.
1285 .It Va work Ns Ar xx
1288 can take values from 0 to 31.
1291 Most expression operators in C are supported except
1299 .Bl -tag -width ".No Identifiers"
1301 The name of a symbol is translated to the value of the symbol, which
1302 is the address of the corresponding object.
1306 can be used in the identifier.
1307 If supported by an object format dependent routine,
1309 .Oo Ar filename : Oc Ar func : lineno ,
1311 .Oo Ar filename : Oc Ns Ar variable ,
1313 .Oo Ar filename : Oc Ns Ar lineno
1314 can be accepted as a symbol.
1316 Radix is determined by the first two letters:
1322 decimal; otherwise, follow current radix.
1328 address of the start of the last line examined.
1333 this is only changed by
1339 last address explicitly specified.
1340 .It Li $ Ns Ar variable
1341 Translated to the value of the specified variable.
1342 It may be followed by a
1344 and modifiers as described above.
1345 .It Ar a Ns Li # Ns Ar b
1346 A binary operator which rounds up the left hand side to the next
1347 multiple of right hand side.
1350 It may be followed by a
1352 and modifiers as described above.
1356 supports a basic scripting facility to allow automating tasks or responses to
1358 Each script consists of a list of DDB commands to be executed sequentially,
1359 and is assigned a unique name.
1360 Certain script names have special meaning, and will be automatically run on
1363 events if scripts by those names have been defined.
1367 command may be used to define a script by name.
1368 Scripts consist of a series of
1370 commands separated with the
1374 .Bd -literal -offset indent
1375 script kdb.enter.panic=bt; show pcpu
1376 script lockinfo=show alllocks; show lockedvnods
1381 command lists currently defined scripts.
1385 command execute a script by name.
1387 .Bd -literal -offset indent
1393 command may be used to delete a script by name.
1395 .Bd -literal -offset indent
1396 unscript kdb.enter.panic
1399 These functions may also be performed from userspace using the
1403 Certain scripts are run automatically, if defined, for specific
1406 The follow scripts are run when various events occur:
1407 .Bl -tag -width kdb.enter.powerfail
1408 .It Dv kdb.enter.acpi
1409 The kernel debugger was entered as a result of an
1412 .It Dv kdb.enter.bootflags
1413 The kernel debugger was entered at boot as a result of the debugger boot
1415 .It Dv kdb.enter.break
1416 The kernel debugger was entered as a result of a serial or console break.
1417 .It Dv kdb.enter.cam
1418 The kernel debugger was entered as a result of a
1421 .It Dv kdb.enter.mac
1422 The kernel debugger was entered as a result of an assertion failure in the
1425 TrustedBSD MAC Framework.
1426 .It Dv kdb.enter.ndis
1427 The kernel debugger was entered as a result of an
1430 .It Dv kdb.enter.netgraph
1431 The kernel debugger was entered as a result of a
1434 .It Dv kdb.enter.panic
1437 .It Dv kdb.enter.powerfail
1438 The kernel debugger was entered as a result of a powerfail NMI on the sparc64
1440 .It Dv kdb.enter.powerpc
1441 The kernel debugger was entered as a result of an unimplemented interrupt
1442 type on the powerpc platform.
1443 .It Dv kdb.enter.sysctl
1444 The kernel debugger was entered as a result of the
1447 .It Dv kdb.enter.trapsig
1448 The kernel debugger was entered as a result of a trapsig event on the sparc64
1450 .It Dv kdb.enter.unionfs
1451 The kernel debugger was entered as a result of an assertion failure in the
1453 .It Dv kdb.enter.unknown
1454 The kernel debugger was entered, but no reason has been set.
1455 .It Dv kdb.enter.vfslock
1456 The kernel debugger was entered as a result of a VFS lock violation.
1457 .It Dv kdb.enter.watchdog
1458 The kernel debugger was entered as a result of a watchdog firing.
1459 .It Dv kdb.enter.witness
1460 The kernel debugger was entered as a result of a
1465 In the event that none of these scripts is found,
1467 will attempt to execute a default script:
1468 .Bl -tag -width kdb.enter.powerfail
1469 .It Dv kdb.enter.default
1470 The kernel debugger was entered, but a script exactly matching the reason for
1471 entering was not defined.
1472 This can be used as a catch-all to handle cases not specifically of interest;
1474 .Dv kdb.enter.witness
1475 might be defined to have special handling, and
1476 .Dv kdb.enter.default
1477 might be defined to simply panic and reboot.
1480 On machines with an ISA expansion bus, a simple NMI generation card can be
1481 constructed by connecting a push button between the A01 and B01 (CHCHK# and
1483 Momentarily shorting these two fingers together may cause the bridge chipset to
1484 generate an NMI, which causes the kernel to pass control to
1486 Some bridge chipsets do not generate a NMI on CHCHK#, so your mileage may vary.
1487 The NMI allows one to break into the debugger on a wedged machine to
1489 Other bus' bridge chipsets may be able to generate NMI using bus specific
1491 There are many PCI and PCIe add-in cards which can generate NMI for
1493 Modern server systems typically use IPMI to generate signals to enter the
1497 port can be used to send the
1498 .Cd chassis power diag
1499 command which delivers an NMI to the processor.
1500 Embedded systems often use JTAG for debugging, but rarely use it in
1504 For serial consoles, you can enter the debugger by sending a BREAK
1505 condition on the serial line if
1506 .Cd options BREAK_TO_DEBUGGER
1507 is specified in the kernel.
1508 Most terminal emulation programs can send a break sequence with a
1509 special key sequence or via a menu item.
1510 However, in some setups, sending the break can be difficult to arrange
1511 or happens spuriously, so if the kernel contains
1512 .Cd options ALT_BREAK_TO_DEBUGGER
1513 then the sequence of CR TILDE CTRL-B enters the debugger;
1514 CR TILDE CTRL-P causes a panic instead of entering the
1516 CR TILDE CTRL-R causes an immediate reboot.
1517 In all the above sequences, CR is a Carriage Return and is usually
1518 sent by hitting the Enter or Return key.
1519 TILDE is the ASCII tilde character (~).
1520 CTRL-x is Control x created by hitting the control key and then x
1521 and then releasing both.
1523 The break to enter the debugger behavior may be enabled at run-time
1526 .Dv debug.kdb.break_to_debugger
1528 The alternate sequence to enter the debugger behavior may be enabled
1529 at run-time by setting the
1531 .Dv debug.kdb.alt_break_to_debugger
1533 The debugger may be entered by setting the
1538 Header files mentioned in this manual page can be found below
1548 .Pa netinet/in_pcb.h
1570 debugger was developed for Mach, and ported to
1572 This manual page translated from
1575 .An Garrett Wollman .
1577 .An Robert N. M. Watson