2 .\" Mach Operating System
3 .\" Copyright (c) 1991,1990 Carnegie Mellon University
4 .\" Copyright (c) 2007 Robert N. M. Watson
5 .\" All Rights Reserved.
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34 .Nd interactive kernel debugger
36 In order to enable kernel debugging facilities include:
37 .Bd -ragged -offset indent
42 To prevent activation of the debugger on kernel
44 .Bd -ragged -offset indent
45 .Cd options KDB_UNATTENDED
48 In order to print a stack trace of the current thread on the console
50 .Bd -ragged -offset indent
54 To print the numerical value of symbols in addition to the symbolic
55 representation, define:
56 .Bd -ragged -offset indent
57 .Cd options DDB_NUMSYM
62 backend, so that remote debugging with
65 .Bd -ragged -offset indent
71 kernel debugger is an interactive debugger with a syntax inspired by
73 If linked into the running kernel,
74 it can be invoked locally with the
77 action, usually mapped to Ctrl+Alt+Esc, or by setting the
80 The debugger is also invoked on kernel
83 .Va debug.debugger_on_panic
85 MIB variable is set non-zero,
91 The current location is called
96 a hexadecimal format at a prompt.
103 to the address of the last line
104 examined or the last location modified, and set
107 the next location to be examined or changed.
108 Other commands do not change
115 The general command syntax is:
116 .Ar command Ns Op Li / Ns Ar modifier
117 .Oo Ar addr Oc Ns Op , Ns Ar count
119 A blank line repeats the previous command from the address
122 count 1 and no modifiers.
135 to be 1 for printing commands or infinity for stack traces.
138 of -1 is equivalent to a missing
140 Options that are supplied but not supported by the given
146 debugger has a pager feature (like the
150 If an output line exceeds the number set in the
152 variable, it displays
154 and waits for a response.
155 The valid responses for it are:
157 .Bl -tag -compact -width ".Li SPC"
163 abort the current command, and return to the command input mode
168 provides a small (currently 10 items) command history, and offers
171 command line editing capabilities.
175 control keys, the usual
177 arrow keys may be used to
178 browse through the history buffer, and move the cursor within the
181 .Ss COMMON DEBUGGER COMMANDS
182 .Bl -tag -width indent -compact
184 Print a short summary of the available commands and command
188 .Ic examine Ns Op Li / Ns Cm AISabcdghilmorsuxz ...
189 .Oo Ar addr Oc Ns Op , Ns Ar count
192 .Ic x Ns Op Li / Ns Cm AISabcdghilmorsuxz ...
193 .Oo Ar addr Oc Ns Op , Ns Ar count
195 Display the addressed locations according to the formats in the modifier.
196 Multiple modifier formats display multiple locations.
197 If no format is specified, the last format specified for this command
200 The format characters are:
201 .Bl -tag -compact -width indent
203 look at by bytes (8 bits)
205 look at by half words (16 bits)
207 look at by long words (32 bits)
209 look at by quad words (64 bits)
211 print the location being displayed
213 print the location with a line number if possible
215 display in unsigned hex
217 display in signed hex
219 display in unsigned octal
221 display in signed decimal
223 display in unsigned decimal
225 display in current radix, signed
227 display low 8 bits as a character.
228 Non-printing characters are displayed as an octal escape code (e.g.,
231 display the null-terminated string at the location.
232 Non-printing characters are displayed as octal escapes.
234 display in unsigned hex with character dump at the end of each line.
235 The location is also displayed in hex at the beginning of each line.
237 display as a disassembled instruction
239 display as an disassembled instruction with possible alternate formats depending on the
241 On i386, this selects the alternate format for the instruction decoding
242 (16 bits in a 32-bit code segment and vice versa).
244 display a symbol name for the pointer stored at the address
251 command with the last specified parameters to it
252 except that the next address displayed by it is used as the start address.
258 command with the last specified parameters to it
259 except that the last start address subtracted by the size displayed by it
260 is used as the start address.
262 .It Ic print Ns Op Li / Ns Cm acdoruxz
263 .It Ic p Ns Op Li / Ns Cm acdoruxz
266 according to the modifier character (as described above for
269 .Cm a , x , z , o , d , u , r ,
272 If no modifier is specified, the last one specified to it is used.
275 can be a string, in which case it is printed as it is.
277 .Bd -literal -offset indent
278 print/x "eax = " $eax "\enecx = " $ecx "\en"
282 .Bd -literal -offset indent
288 .Ic write Ns Op Li / Ns Cm bhl
289 .Ar addr expr1 Op Ar expr2 ...
292 .Ic w Ns Op Li / Ns Cm bhl
293 .Ar addr expr1 Op Ar expr2 ...
295 Write the expressions specified after
297 on the command line at succeeding locations starting with
299 The write unit size can be specified in the modifier with a letter
305 (long word) respectively.
307 long word is assumed.
310 since there is no delimiter between expressions, strange
312 It is best to enclose each expression in parentheses.
314 .It Ic set Li $ Ns Ar variable Oo Li = Oc Ar expr
315 Set the named variable or register with the value of
317 Valid variable names are described below.
319 .It Ic break Ns Oo Li / Ns Cm u Oc Oo Ar addr Oc Ns Op , Ns Ar count
320 .It Ic b Ns Oo Li / Ns Cm u Oc Oo Ar addr Oc Ns Op , Ns Ar count
327 command will not stop at this break point on the first
329 \- 1 times that it is hit.
330 If the break point is set, a break point number is
333 This number can be used in deleting the break point
334 or adding conditions to it.
338 modifier is specified, this command sets a break point in user
342 option, the address is considered to be in the kernel
343 space, and a wrong space address is rejected with an error message.
344 This modifier can be used only if it is supported by machine dependent
348 If a user text is shadowed by a normal user space debugger,
349 user space break points may not work correctly.
351 point at the low-level code paths may also cause strange behavior.
353 .It Ic delete Op Ar addr
355 .It Ic delete Li # Ns Ar number
356 .It Ic d Li # Ns Ar number
357 Delete the specified break point.
358 The break point can be specified by a
359 break point number with
363 specified in the original
365 command, or by omitting
367 to get the default address of
373 .It Ic watch Oo Ar addr Oc Ns Op , Ns Ar size
374 Set a watchpoint for a region.
375 Execution stops when an attempt to modify the region occurs.
378 argument defaults to 4.
379 If you specify a wrong space address, the request is rejected
380 with an error message.
383 Attempts to watch wired kernel memory
384 may cause unrecoverable error in some systems such as i386.
385 Watchpoints on user addresses work best.
387 .It Ic hwatch Oo Ar addr Oc Ns Op , Ns Ar size
388 Set a hardware watchpoint for a region if supported by the
390 Execution stops when an attempt to modify the region occurs.
393 argument defaults to 4.
396 The hardware debug facilities do not have a concept of separate
397 address spaces like the watch command does.
400 for setting watchpoints on kernel address locations only, and avoid
401 its use on user mode address spaces.
403 .It Ic dhwatch Oo Ar addr Oc Ns Op , Ns Ar size
404 Delete specified hardware watchpoint.
406 .It Ic kill Ar sig pid
411 The signal is acted on upon returning from the debugger.
412 This command can be used to kill a process causing resource contention
413 in the case of a hung system.
416 for a list of signals.
417 Note that the arguments are reversed relative to
420 .It Ic step Ns Oo Li / Ns Cm p Oc Ns Op , Ns Ar count
421 .It Ic s Ns Oo Li / Ns Cm p Oc Ns Op , Ns Ar count
427 modifier is specified, print each instruction at each step.
428 Otherwise, only print the last instruction.
431 depending on machine type, it may not be possible to
432 single-step through some low-level code paths or user space code.
433 On machines with software-emulated single-stepping (e.g., pmax),
434 stepping through code executed by interrupt handlers will probably
437 .It Ic continue Ns Op Li / Ns Cm c
438 .It Ic c Ns Op Li / Ns Cm c
439 Continue execution until a breakpoint or watchpoint.
442 modifier is specified, count instructions while executing.
443 Some machines (e.g., pmax) also count loads and stores.
446 when counting, the debugger is really silently single-stepping.
447 This means that single-stepping on low-level code may cause strange
450 .It Ic until Ns Op Li / Ns Cm p
451 Stop at the next call or return instruction.
454 modifier is specified, print the call nesting depth and the
455 cumulative instruction count at each call or return.
457 only print when the matching return is hit.
459 .It Ic next Ns Op Li / Ns Cm p
460 .It Ic match Ns Op Li / Ns Cm p
461 Stop at the matching return instruction.
464 modifier is specified, print the call nesting depth and the
465 cumulative instruction count at each call or return.
466 Otherwise, only print when the matching return is hit.
469 .Ic trace Ns Op Li / Ns Cm u
474 .Ic t Ns Op Li / Ns Cm u
479 .Ic where Ns Op Li / Ns Cm u
484 .Ic bt Ns Op Li / Ns Cm u
491 option traces user space; if omitted,
495 The optional argument
497 is the number of frames to be traced.
500 is omitted, all frames are printed.
503 User space stack trace is valid
504 only if the machine dependent code supports it.
507 .Ic search Ns Op Li / Ns Cm bhl
517 argument limits the search.
520 .It Ic reboot Op Ar seconds
521 .It Ic reset Op Ar seconds
522 Hard reset the system.
523 If the optional argument
525 is given, the debugger will wait for this long, at most a week,
528 .It Ic thread Ar addr | tid
529 Switch the debugger to the thread with ID
531 if the argument is a decimal number, or address
535 .Ss SPECIALIZED HELPER COMMANDS
536 .Bl -tag -width indent -compact
541 Prints the thread address for a thread kernel-mode stack of which contains the
543 If the thread is not found, search the thread stack cache and prints the
544 cached stack address.
545 Otherwise, prints nothing.
547 .It Ic show Cm all procs Ns Op Li / Ns Cm a
548 .It Ic ps Ns Op Li / Ns Cm a
549 Display all process information.
550 The process information may not be shown if it is not
551 supported in the machine, or the bottom of the stack of the
552 target process is not in the main memory at that time.
555 modifier will print command line arguments for each process.
558 .It Ic show Cm all trace
560 Show a stack trace for every thread in the system.
562 .It Ic show Cm all ttys
563 Show all TTY's within the system.
566 but also includes the address of the TTY structure.
569 .It Ic show Cm all vnets
570 Show the same output as "show vnet" does, but lists all
571 virtualized network stacks within the system.
574 .It Ic show Cm allchains
575 Show the same information like "show lockchain" does, but
576 for every thread in the system.
579 .It Ic show Cm alllocks
580 Show all locks that are currently held.
581 This command is only available if
583 is included in the kernel.
586 .It Ic show Cm allpcpu
587 The same as "show pcpu", but for every CPU present in the system.
590 .It Ic show Cm allrman
591 Show information related with resource management, including
592 interrupt request lines, DMA request lines, I/O ports, I/O memory
593 addresses, and Resource IDs.
597 Dump data about APIC IDT vector mappings.
600 .It Ic show Cm breaks
601 Show breakpoints set with the "break" command.
604 .It Ic show Cm bio Ar addr
605 Show information about the bio structure
613 for more details on the exact meaning of the structure fields.
616 .It Ic show Cm buffer Ar addr
617 Show information about the buf structure
623 header file for more details on the exact meaning of the structure fields.
626 .It Ic show Cm callout Ar addr
627 Show information about the callout structure
633 .It Ic show Cm cbstat
634 Show brief information about the TTY subsystem.
638 Without argument, show the list of all created cdev's, consisting of devfs
639 node name and struct cdev address.
640 When address of cdev is supplied, show some internal devfs state of the cdev.
643 .It Ic show Cm conifhk
644 Lists hooks currently waiting for completion in
645 run_interrupt_driven_config_hooks().
648 .It Ic show Cm cpusets
649 Print numbered root and assigned CPU affinity sets.
655 .It Ic show Cm cyrixreg
656 Show registers specific to the Cyrix processor.
659 .It Ic show Cm devmap
660 Prints the contents of the static device mapping table.
661 Currently only available on the
666 .It Ic show Cm domain Ar addr
667 Print protocol domain structure
673 header file for more details on the exact meaning of the structure fields.
676 .It Ic show Cm ffs Op Ar addr
677 Show brief information about ffs mount at the address
679 if argument is given.
680 Otherwise, provides the summary about each ffs mount.
683 .It Ic show Cm file Ar addr
684 Show information about the file structure
691 Show information about every file structure in the system.
694 .It Ic show Cm freepages
695 Show the number of physical pages in each of the free lists.
698 .It Ic show Cm geom Op Ar addr
701 argument is not given, displays the entire GEOM topology.
704 is given, displays details about the given GEOM object (class, geom,
705 provider or consumer).
710 The first column specifies the IDT vector.
711 The second one is the name of the interrupt/trap handler.
712 Those functions are machine dependent.
715 .It Ic show Cm igi_list Ar addr
716 Show information about the IGMP structure
717 .Vt struct igmp_ifsoftc
722 .It Ic show Cm inodedeps Op Ar addr
723 Show brief information about each inodedep structure.
726 is given, only inodedeps belonging to the fs located at the
727 supplied address are shown.
730 .It Ic show Cm inpcb Ar addr
731 Show information on IP Control Block
738 Dump information about interrupt handlers.
741 .It Ic show Cm intrcnt
742 Dump the interrupt statistics.
746 Show interrupt lines and their respective kernel threads.
755 shows, also list kernel internal details.
759 Show information from the local APIC registers for this CPU.
762 .It Ic show Cm lock Ar addr
764 The output format is as follows:
765 .Bl -tag -width "flags"
768 Possible types include
776 Flags passed to the lock initialization function.
778 values are lock class specific.
780 Current state of a lock.
782 values are lock class specific.
788 .It Ic show Cm lockchain Ar addr
789 Show all threads a particular thread at address
791 is waiting on based on non-spin locks.
794 .It Ic show Cm lockedbufs
795 Show the same information as "show buf", but for every locked
800 .It Ic show Cm lockedvnods
801 List all locked vnodes in the system.
805 Prints all locks that are currently acquired.
806 This command is only available if
808 is included in the kernel.
811 .It Ic show Cm locktree
814 .It Ic show Cm malloc Ns Op Li / Ns Cm i
817 memory allocator statistics.
820 modifier is specified, format output as machine-parseable comma-separated
822 The output columns are as follows:
824 .Bl -tag -compact -offset indent -width "Requests"
826 Specifies a type of memory.
827 It is the same as a description string used while defining the
828 given memory type with
829 .Xr MALLOC_DECLARE 9 .
831 Number of memory allocations of the given type, for which
833 has not been called yet.
835 Total memory consumed by the given allocation type.
837 Number of memory allocation requests for the given
841 The same information can be gathered in userspace with
845 .It Ic show Cm map Ns Oo Li / Ns Cm f Oc Ar addr
850 modifier is specified the
851 complete map is printed.
854 .It Ic show Cm msgbuf
855 Print the system's message buffer.
856 It is the same output as in the
859 It is useful if you got a kernel panic, attached a serial cable
860 to the machine and want to get the boot messages from before the
864 Displays short info about all currently mounted file systems.
866 .It Ic show Cm mount Ar addr
867 Displays details about the given mount point.
870 .It Ic show Cm object Ns Oo Li / Ns Cm f Oc Ar addr
871 Prints the VM object at
875 option is specified the
876 complete object is printed.
880 Print the panic message if set.
884 Show statistics on VM pages.
888 Show statistics on VM page queues.
891 .It Ic show Cm pciregs
892 Print PCI bus registers.
893 The same information can be gathered in userspace by running
894 .Dq Nm pciconf Fl lv .
898 Print current processor state.
899 The output format is as follows:
901 .Bl -tag -compact -offset indent -width "spin locks held:"
903 Processor identifier.
905 Thread pointer, process identifier and the name of the process.
907 Control block pointer.
913 CPU identifier coming from APIC.
916 .It Ic spin locks held
917 Names of spin locks held.
921 .It Ic show Cm pgrpdump
922 Dump process groups present within the system.
925 .It Ic show Cm proc Op Ar addr
928 is specified, print information about the current process.
929 Otherwise, show information about the process at address
933 .It Ic show Cm procvm
934 Show process virtual memory layout.
937 .It Ic show Cm protosw Ar addr
938 Print protocol switch structure
944 .It Ic show Cm registers Ns Op Li / Ns Cm u
945 Display the register set.
948 modifier is specified, it displays user registers instead of
949 kernel registers or the currently saved one.
954 modifier depends on the machine.
955 If not supported, incorrect information will be displayed.
958 .It Ic show Cm rman Ar addr
959 Show resource manager object
963 Addresses of particular pointers can be gathered with "show allrman"
967 .It Ic show Cm route Ar addr
968 Show route table result for destination
970 At this time, INET and INET6 formatted addresses are supported.
973 .It Ic show Cm routetable Oo Ar af Oc
974 Show full route table or tables.
977 is specified, show only routes for the given numeric address family.
978 If no argument is specified, dump the route table for all address families.
982 Show real time clock value.
983 Useful for long debugging sessions.
986 .It Ic show Cm sleepchain
989 .Ic show Cm lockchain .
992 .It Ic show Cm sleepq
993 .It Ic show Cm sleepqueue
994 Both commands provide the same functionality.
996 .Vt struct sleepqueue
998 Sleepqueues are used within the
1000 kernel to implement sleepable
1001 synchronization primitives (thread holding a lock might sleep or
1002 be context switched), which at the time of writing are:
1010 .It Ic show Cm sockbuf Ar addr
1011 .It Ic show Cm socket Ar addr
1012 Those commands print
1018 Output consists of all values present in structures mentioned.
1019 For exact interpretation and more details, visit
1024 .It Ic show Cm sysregs
1025 Show system registers (e.g.,
1028 Not present on some platforms.
1031 .It Ic show Cm tcpcb Ar addr
1032 Print TCP control block
1036 For exact interpretation of output, visit
1041 .It Ic show Cm thread Op Ar addr | tid
1046 is specified, show detailed information about current thread.
1047 Otherwise, print information about the thread with ID
1051 (If the argument is a decimal number, it is assumed to be a tid.)
1054 .It Ic show Cm threads
1055 Show all threads within the system.
1056 Output format is as follows:
1058 .Bl -tag -compact -offset indent -width "Second column"
1060 Thread identifier (TID)
1061 .It Ic Second column
1062 Thread structure address
1068 .It Ic show Cm tty Ar addr
1069 Display the contents of a TTY structure in a readable form.
1072 .It Ic show Cm turnstile Ar addr
1074 .Vt struct turnstile
1075 structure at address
1077 Turnstiles are structures used within the
1080 synchronization primitives which, while holding a specific type of lock, cannot
1081 sleep or context switch to another thread.
1082 Currently, those are:
1088 .It Ic show Cm uma Ns Op Li / Ns Cm i
1089 Show UMA allocator statistics.
1092 modifier is specified, format output as machine-parseable comma-separated
1094 The output contains the following columns:
1096 .Bl -tag -compact -offset indent -width "Total Mem"
1098 Name of the UMA zone.
1099 The same string that was passed to
1101 as a first argument.
1103 Size of a given memory object (slab).
1105 Number of slabs being currently used.
1107 Number of free slabs within the UMA zone.
1109 Number of allocations requests to the given zone.
1111 Total memory in use (either allocated or free) by a zone, in bytes.
1113 Number of free slabs within the UMA zone that were freed on a different NUMA
1114 domain than allocated.
1117 column is inclusive of
1121 The same information might be gathered in the userspace
1123 .Dq Nm vmstat Fl z .
1126 .It Ic show Cm unpcb Ar addr
1127 Shows UNIX domain socket private control block
1129 present at the address
1133 .It Ic show Cm vmochk
1134 Prints, whether the internal VM objects are in a map somewhere
1135 and none have zero ref counts.
1138 .It Ic show Cm vmopag
1139 This is supposed to show physical addresses consumed by a
1141 Currently, it is not possible to use this command when
1143 is compiled in the kernel.
1146 .It Ic show Cm vnet Ar addr
1147 Prints virtualized network stack
1149 structure present at the address
1153 .It Ic show Cm vnode Op Ar addr
1158 For the exact interpretation of the output, look at the
1163 .It Ic show Cm vnodebufs Ar addr
1164 Shows clean/dirty buffer lists of the vnode located at
1168 .It Ic show Cm vpath Ar addr
1169 Walk the namecache to lookup the pathname of the vnode located at
1173 .It Ic show Cm watches
1174 Displays all watchpoints.
1175 Shows watchpoints set with "watch" command.
1178 .It Ic show Cm witness
1179 Shows information about lock acquisition coming from the
1184 .Ss OFFLINE DEBUGGING COMMANDS
1185 .Bl -tag -width indent -compact
1187 Switches to remote GDB mode.
1188 In remote GDB mode, another machine is required that runs
1190 using the remote debug feature, with a connection to the serial
1191 console port on the target machine.
1193 .It Ic netdump Fl s Ar server Oo Fl g Ar gateway Fl c Ar client Fl i Ar iface Oc
1196 with the provided parameters, and immediately perform a netdump.
1198 There are some known limitations.
1201 only supports IPv4 at this time.
1202 The address arguments to the
1204 command must be dotted decimal IPv4 addresses.
1205 (Hostnames are not supported.)
1206 At present, the command only works if the machine is in a panic state.
1210 command does not provide any way to configure compression or encryption.
1212 .It Ic netgdb Fl s Ar server Oo Fl g Ar gateway Fl c Ar client Fl i Ar iface Oc
1215 session with the provided parameters.
1218 has identical limitations to
1223 .It Ic capture reset
1224 .It Ic capture status
1226 supports a basic output capture facility, which can be used to retrieve the
1227 results of debugging commands from userspace using
1230 enables output capture;
1234 will clear the capture buffer and disable capture.
1236 will report current buffer use, buffer size, and disposition of output
1239 Userspace processes may inspect and manage
1244 .Va debug.ddb.capture.bufsize
1245 may be used to query or set the current capture buffer size.
1247 .Va debug.ddb.capture.maxbufsize
1248 may be used to query the compile-time limit on the capture buffer size.
1250 .Va debug.ddb.capture.bytes
1251 may be used to query the number of bytes of output currently in the capture
1254 .Va debug.ddb.capture.data
1255 returns the contents of the buffer as a string to an appropriately privileged
1258 This facility is particularly useful in concert with the scripting and
1260 facilities, allowing scripted debugging output to be captured and
1261 committed to disk as part of a textdump for later analysis.
1262 The contents of the capture buffer may also be inspected in a kernel core dump
1270 Run, define, list, and delete scripts.
1273 section for more information on the scripting facility.
1275 .It Ic textdump dump
1277 .It Ic textdump status
1278 .It Ic textdump unset
1281 command to immediately perform a textdump.
1282 More information may be found in
1286 command may be used to force the next kernel core dump to be a textdump
1287 rather than a traditional memory dump or minidump.
1289 reports whether a textdump has been scheduled.
1291 cancels a request to perform a textdump as the next kernel core dump.
1294 The debugger accesses registers and variables as
1296 Register names are as in the
1297 .Dq Ic show Cm registers
1299 Some variables are suffixed with numbers, and may have some modifier
1300 following a colon immediately after the variable name.
1301 For example, register variables can have a
1303 modifier to indicate user register (e.g.,
1306 Built-in variables currently supported are:
1308 .Bl -tag -width ".Va tabstops" -compact
1310 Input and output radix.
1312 Addresses are printed as
1313 .Dq Ar symbol Ns Li + Ns Ar offset
1319 The width of the displayed line.
1321 The number of lines.
1322 It is used by the built-in pager.
1323 Setting it to 0 disables paging.
1326 .It Va work Ns Ar xx
1329 can take values from 0 to 31.
1332 Most expression operators in C are supported except
1340 .Bl -tag -width ".No Identifiers"
1342 The name of a symbol is translated to the value of the symbol, which
1343 is the address of the corresponding object.
1347 can be used in the identifier.
1348 If supported by an object format dependent routine,
1350 .Oo Ar filename : Oc Ar func : lineno ,
1352 .Oo Ar filename : Oc Ns Ar variable ,
1354 .Oo Ar filename : Oc Ns Ar lineno
1355 can be accepted as a symbol.
1357 Radix is determined by the first two letters:
1363 decimal; otherwise, follow current radix.
1369 address of the start of the last line examined.
1374 this is only changed by
1380 last address explicitly specified.
1381 .It Li $ Ns Ar variable
1382 Translated to the value of the specified variable.
1383 It may be followed by a
1385 and modifiers as described above.
1386 .It Ar a Ns Li # Ns Ar b
1387 A binary operator which rounds up the left hand side to the next
1388 multiple of right hand side.
1391 It may be followed by a
1393 and modifiers as described above.
1397 supports a basic scripting facility to allow automating tasks or responses to
1399 Each script consists of a list of DDB commands to be executed sequentially,
1400 and is assigned a unique name.
1401 Certain script names have special meaning, and will be automatically run on
1404 events if scripts by those names have been defined.
1408 command may be used to define a script by name.
1409 Scripts consist of a series of
1411 commands separated with the
1415 .Bd -literal -offset indent
1416 script kdb.enter.panic=bt; show pcpu
1417 script lockinfo=show alllocks; show lockedvnods
1422 command lists currently defined scripts.
1426 command execute a script by name.
1428 .Bd -literal -offset indent
1434 command may be used to delete a script by name.
1436 .Bd -literal -offset indent
1437 unscript kdb.enter.panic
1440 These functions may also be performed from userspace using the
1444 Certain scripts are run automatically, if defined, for specific
1447 The follow scripts are run when various events occur:
1448 .Bl -tag -width kdb.enter.powerfail
1449 .It Va kdb.enter.acpi
1450 The kernel debugger was entered as a result of an
1453 .It Va kdb.enter.bootflags
1454 The kernel debugger was entered at boot as a result of the debugger boot
1456 .It Va kdb.enter.break
1457 The kernel debugger was entered as a result of a serial or console break.
1458 .It Va kdb.enter.cam
1459 The kernel debugger was entered as a result of a
1462 .It Va kdb.enter.mac
1463 The kernel debugger was entered as a result of an assertion failure in the
1466 TrustedBSD MAC Framework.
1467 .It Va kdb.enter.ndis
1468 The kernel debugger was entered as a result of an
1471 .It Va kdb.enter.netgraph
1472 The kernel debugger was entered as a result of a
1475 .It Va kdb.enter.panic
1478 .It Va kdb.enter.powerpc
1479 The kernel debugger was entered as a result of an unimplemented interrupt
1480 type on the powerpc platform.
1481 .It Va kdb.enter.sysctl
1482 The kernel debugger was entered as a result of the
1485 .It Va kdb.enter.unionfs
1486 The kernel debugger was entered as a result of an assertion failure in the
1488 .It Va kdb.enter.unknown
1489 The kernel debugger was entered, but no reason has been set.
1490 .It Va kdb.enter.vfslock
1491 The kernel debugger was entered as a result of a VFS lock violation.
1492 .It Va kdb.enter.watchdog
1493 The kernel debugger was entered as a result of a watchdog firing.
1494 .It Va kdb.enter.witness
1495 The kernel debugger was entered as a result of a
1500 In the event that none of these scripts is found,
1502 will attempt to execute a default script:
1503 .Bl -tag -width kdb.enter.powerfail
1504 .It Va kdb.enter.default
1505 The kernel debugger was entered, but a script exactly matching the reason for
1506 entering was not defined.
1507 This can be used as a catch-all to handle cases not specifically of interest;
1509 .Va kdb.enter.witness
1510 might be defined to have special handling, and
1511 .Va kdb.enter.default
1512 might be defined to simply panic and reboot.
1515 On machines with an ISA expansion bus, a simple NMI generation card can be
1516 constructed by connecting a push button between the A01 and B01 (CHCHK# and
1518 Momentarily shorting these two fingers together may cause the bridge chipset to
1519 generate an NMI, which causes the kernel to pass control to
1521 Some bridge chipsets do not generate a NMI on CHCHK#, so your mileage may vary.
1522 The NMI allows one to break into the debugger on a wedged machine to
1524 Other bus' bridge chipsets may be able to generate NMI using bus specific
1526 There are many PCI and PCIe add-in cards which can generate NMI for
1528 Modern server systems typically use IPMI to generate signals to enter the
1532 port can be used to send the
1533 .Cd chassis power diag
1534 command which delivers an NMI to the processor.
1535 Embedded systems often use JTAG for debugging, but rarely use it in
1539 For serial consoles, you can enter the debugger by sending a BREAK
1540 condition on the serial line if
1541 .Cd options BREAK_TO_DEBUGGER
1542 is specified in the kernel.
1543 Most terminal emulation programs can send a break sequence with a
1544 special key sequence or via a menu item.
1545 However, in some setups, sending the break can be difficult to arrange
1546 or happens spuriously, so if the kernel contains
1547 .Cd options ALT_BREAK_TO_DEBUGGER
1548 then the sequence of CR TILDE CTRL-B enters the debugger;
1549 CR TILDE CTRL-P causes a panic instead of entering the
1551 CR TILDE CTRL-R causes an immediate reboot.
1552 In all the above sequences, CR is a Carriage Return and is usually
1553 sent by hitting the Enter or Return key.
1554 TILDE is the ASCII tilde character (~).
1555 CTRL-x is Control x created by hitting the control key and then x
1556 and then releasing both.
1558 The break to enter the debugger behavior may be enabled at run-time
1561 .Va debug.kdb.break_to_debugger
1563 The alternate sequence to enter the debugger behavior may be enabled
1564 at run-time by setting the
1566 .Va debug.kdb.alt_break_to_debugger
1568 The debugger may be entered by setting the
1573 Header files mentioned in this manual page can be found below
1583 .Pa netinet/in_pcb.h
1605 debugger was developed for Mach, and ported to
1607 This manual page translated from
1610 .An Garrett Wollman .
1612 .An Robert N. M. Watson