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 has most of the features of the old
107 but with a more rational syntax
110 If linked into the running kernel,
111 it can be invoked locally with the
115 The debugger is also invoked on kernel
118 .Va debug.debugger_on_panic
120 MIB variable is set non-zero,
126 The current location is called
131 a hexadecimal format at a prompt.
138 to the address of the last line
139 examined or the last location modified, and set
142 the next location to be examined or changed.
143 Other commands do not change
150 The general command syntax is:
151 .Ar command Ns Op Li / Ns Ar modifier
152 .Ar address Ns Op Li , Ns Ar count
154 A blank line repeats the previous command from the address
157 count 1 and no modifiers.
170 to be 1 for printing commands or infinity for stack traces.
174 debugger has a pager feature (like the
178 If an output line exceeds the number set in the
180 variable, it displays
182 and waits for a response.
183 The valid responses for it are:
185 .Bl -tag -compact -width ".Li SPC"
191 abort the current command, and return to the command input mode
196 provides a small (currently 10 items) command history, and offers
199 command line editing capabilities.
203 control keys, the usual
205 arrow keys might be used to
206 browse through the history buffer, and move the cursor within the
209 .Bl -tag -width indent -compact
212 Display the addressed locations according to the formats in the modifier.
213 Multiple modifier formats display multiple locations.
214 If no format is specified, the last format specified for this command
217 The format characters are:
218 .Bl -tag -compact -width indent
220 look at by bytes (8 bits)
222 look at by half words (16 bits)
224 look at by long words (32 bits)
226 print the location being displayed
228 print the location with a line number if possible
230 display in unsigned hex
232 display in signed hex
234 display in unsigned octal
236 display in signed decimal
238 display in unsigned decimal
240 display in current radix, signed
242 display low 8 bits as a character.
243 Non-printing characters are displayed as an octal escape code (e.g.,
246 display the null-terminated string at the location.
247 Non-printing characters are displayed as octal escapes.
249 display in unsigned hex with character dump at the end of each line.
250 The location is also displayed in hex at the beginning of each line.
252 display as an instruction
254 display as an instruction with possible alternate formats depending on the
256 .Bl -tag -width ".Tn powerpc" -compact
258 Show the registers of the instruction.
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 Op Li / Ns Cm u
347 .It Ic b Ns Op Li / Ns Cm u
352 is supplied, continues
354 \- 1 times before stopping at the
356 If the break point is set, a break point number is
359 This number can be used in deleting the break point
360 or adding conditions to it.
364 modifier is specified, this command sets a break point in user
368 option, the address is considered to be in the kernel
369 space, and a wrong space address is rejected with an error message.
370 This modifier can be used only if it is supported by machine dependent
374 If a user text is shadowed by a normal user space debugger,
375 user space break points may not work correctly.
377 point at the low-level code paths may also cause strange behavior.
379 .It Ic delete Ar addr
381 .It Ic delete Li # Ns Ar number
382 .It Ic d Li # Ns Ar number
383 Delete the break point.
384 The target break point can be specified by a
385 break point number with
389 specified in the original
393 .It Ic watch Ar addr Ns Li , Ns Ar size
394 Set a watchpoint for a region.
395 Execution stops when an attempt to modify the region occurs.
398 argument defaults to 4.
399 If you specify a wrong space address, the request is rejected
400 with an error message.
403 Attempts to watch wired kernel memory
404 may cause unrecoverable error in some systems such as i386.
405 Watchpoints on user addresses work best.
407 .It Ic hwatch Ar addr Ns Li , Ns Ar size
408 Set a hardware watchpoint for a region if supported by the
410 Execution stops when an attempt to modify the region occurs.
413 argument defaults to 4.
416 The hardware debug facilities do not have a concept of separate
417 address spaces like the watch command does.
420 for setting watchpoints on kernel address locations only, and avoid
421 its use on user mode address spaces.
423 .It Ic dhwatch Ar addr Ns Li , Ns Ar size
424 Delete specified hardware watchpoint.
426 .It Ic step Ns Op Li / Ns Cm p
427 .It Ic s Ns Op Li / Ns Cm p
430 times (the comma is a mandatory part of the syntax).
433 modifier is specified, print each instruction at each step.
434 Otherwise, only print the last instruction.
437 depending on machine type, it may not be possible to
438 single-step through some low-level code paths or user space code.
439 On machines with software-emulated single-stepping (e.g., pmax),
440 stepping through code executed by interrupt handlers will probably
443 .It Ic continue Ns Op Li / Ns Cm c
444 .It Ic c Ns Op Li / Ns Cm c
445 Continue execution until a breakpoint or watchpoint.
448 modifier is specified, count instructions while executing.
449 Some machines (e.g., pmax) also count loads and stores.
452 when counting, the debugger is really silently single-stepping.
453 This means that single-stepping on low-level code may cause strange
456 .It Ic until Ns Op Li / Ns Cm p
457 Stop at the next call or return instruction.
460 modifier is specified, print the call nesting depth and the
461 cumulative instruction count at each call or return.
463 only print when the matching return is hit.
465 .It Ic next Ns Op Li / Ns Cm p
466 .It Ic match Ns Op Li / Ns Cm p
467 Stop at the matching return instruction.
470 modifier is specified, print the call nesting depth and the
471 cumulative instruction count at each call or return.
472 Otherwise, only print when the matching return is hit.
475 .Ic trace Ns Op Li / Ns Cm u
480 .Ic t Ns Op Li / Ns Cm u
485 .Ic where Ns Op Li / Ns Cm u
490 .Ic bt Ns Op Li / Ns Cm u
497 option traces user space; if omitted,
501 The optional argument
503 is the number of frames to be traced.
506 is omitted, all frames are printed.
509 User space stack trace is valid
510 only if the machine dependent code supports it.
513 .Ic search Ns Op Li / Ns Cm bhl
521 This command might fail in interesting
522 ways if it does not find the searched-for value.
525 does not always recover from touching bad memory.
528 argument limits the search.
531 .It Ic show Cm all procs Ns Op Li / Ns Cm m
532 .It Ic ps Ns Op Li / Ns Cm m
533 Display all process information.
534 The process information may not be shown if it is not
535 supported in the machine, or the bottom of the stack of the
536 target process is not in the main memory at that time.
539 modifier will alter the display to show VM map
540 addresses for the process and not show other information.
543 .It Ic show Cm allchains
544 Show the same information like "show lockchain" does, but
545 for every thread in the system.
548 .It Ic show Cm alllocks
549 Show all locks that are currently held.
552 .It Ic show Cm allpcpu
553 The same as "show pcpu", but for every CPU present in the system.
556 .It Ic show Cm allrman
557 Show information related with resource management, including
558 interrupt request lines, DMA request lines, I/O ports and I/O memory
563 Dump data about APIC IDT vector mappings.
566 .It Ic show Cm breaks
567 Show breakpoints set with the "break" command.
570 .It Ic show Cm buffer
571 Show buffer structure of
574 Such a structure is used within the
576 kernel for the I/O subsystem
578 For an exact interpretation of the output, please see the
583 .It Ic show Cm cbstat
584 Show brief information about the TTY subsystem.
587 .It Ic show Cm cyrixreg
588 Show registers specific to the Cyrix processor.
591 .It Ic show Cm domain Ar addr
592 Print protocol domain structure
598 header file for more details on the exact meaning of the structure fields.
601 .It Ic show Cm file Ar addr
602 Show information about the file structure
609 Show information about every file structure in the system.
612 .It Ic show Cm freepages
613 Show the number of physical pages in each of the free lists.
616 .It Ic show Cm geom Op Ar addr
619 argument is not given, displays the entire GEOM topology.
622 is given, displays details about the given GEOM object (class, geom,
623 provider or consumer).
628 The first column specifies the IDT vector.
629 The second one is the name of the interrupt/trap handler.
630 Those functions are machine dependent.
633 .It Ic show Cm inpcb Ar addr
634 Show information on IP Control Block
641 Dump information about interrupt handlers.
644 .It Ic show Cm intrcnt
645 Dump the interrupt statistics.
649 Show interrupt lines and their respective kernel threads.
653 Show information from the local APIC registers for this CPU.
656 .It Ic show Cm lock Ar addr
658 The output format is as follows:
659 .Bl -tag -offset 0 -width "flags"
662 Possible types include
670 Flags passed to the lock initialization function.
671 For exact possibilities see manual pages of possible lock types.
673 Current state of a lock.
682 .It Ic show Cm lockchain Ar addr
683 Show all threads a particular thread at address
685 is waiting on based on non-sleepable and non-spin locks.
688 .It Ic show Cm lockedbufs
689 Show the same information as "show buf", but for every locked
694 .It Ic show Cm lockedvnods
695 List all locked vnodes in the system.
699 Prints all locks that are currently acquired.
702 .It Ic show Cm locktree
705 .It Ic show Cm malloc
708 memory allocator statistics.
709 The output format is as follows:
711 .Bl -tag -compact -offset indent -width "Requests"
713 Specifies a type of memory.
714 It is the same as a description string used while defining the
715 given memory type with
716 .Xr MALLOC_DECLARE 9 .
718 Number of memory allocations of the given type, for which
720 has not been called yet.
722 Total memory consumed by the given allocation type.
724 Number of memory allocation requests for the given
728 The same information can be gathered in userspace with
732 .It Ic show Cm map Ns Oo Li / Ns Cm f Oc Ar addr
737 modifier is specified the
738 complete map is printed.
741 .It Ic show Cm msgbuf
742 Print the system's message buffer.
743 It is the same output as in the
746 It is useful if you got a kernel panic, attached a serial cable
747 to the machine and want to get the boot messages from before the
751 Displays short info about all currently mounted file systems.
753 .It Ic show Cm mount Ar addr
754 Displays details about the given mount point.
758 .It Ic show Cm object Ns Oo Li / Ns Cm f Oc Ar addr
759 Prints the VM object at
763 option is specified the
764 complete object is printed.
768 Show statistics on VM pages.
772 Show statistics on VM page queues.
775 .It Ic show Cm pciregs
776 Print PCI bus registers.
777 The same information can be gathered in userspace by running
778 .Dq Nm pciconf Fl lv .
782 Print current processor state.
783 The output format is as follows:
785 .Bl -tag -compact -offset indent -width "spin locks held:"
787 Processor identifier.
789 Thread pointer, process identifier and the name of the process.
791 Control block pointer.
797 CPU identifier coming from APIC.
800 .It Ic spin locks held
801 Names of spin locks held.
805 .It Ic show Cm pgrpdump
806 Dump process groups present within the system.
809 .It Ic show Cm proc Op Ar addr
812 is specified, print information about the current process.
813 Otherwise, show information about the process at address
817 .It Ic show Cm procvm
818 Show process virtual memory layout.
821 .It Ic show Cm protosw Ar addr
822 Print protocol switch structure
828 .It Ic show Cm registers Ns Op Li / Ns Cm u
829 Display the register set.
832 modifier is specified, it displays user registers instead of
833 kernel registers or the currently saved one.
838 modifier depends on the machine.
839 If not supported, incorrect information will be displayed.
842 .It Ic show Cm rman Ar addr
843 Show resource manager object
847 Addresses of particular pointers can be gathered with "show allrman"
852 Show real time clock value.
853 Useful for long debugging sessions.
856 .It Ic show Cm sleepchain
857 Show all the threads a particular thread is waiting on based on
861 .It Ic show Cm sleepq
862 .It Ic show Cm sleepqueue
863 Both commands provide the same functionality.
865 .Vt struct sleepqueue
867 Sleepqueues are used within the
869 kernel to implement sleepable
870 synchronization primitives (thread holding a lock might sleep or
871 be context switched), which at the time of writing are:
879 .It Ic show Cm sockbuf Ar addr
880 .It Ic show Cm socket Ar addr
887 Output consists of all values present in structures mentioned.
888 For exact interpretation and more details, visit
893 .It Ic show Cm sysregs
894 Show system registers (e.g.,
897 Not present on some platforms.
900 .It Ic show Cm tcpcb Ar addr
901 Print TCP control block
905 For exact interpretation of output, visit
910 .It Ic show Cm thread Op Ar addr
913 is specified, show detailed information about current thread.
914 Otherwise, information about thread at
919 .It Ic show Cm threads
920 Show all threads within the system.
921 Output format is as follows:
923 .Bl -tag -width "PPID" -compact -offset indent -width "Second column"
925 Thread identifier (TID)
927 Thread structure address
933 .It Ic show Cm turnstile Ar addr
938 Turnstiles are structures used within the
941 synchronization primitives which, while holding a specific type of lock, cannot
942 sleep or context switch to another thread.
943 Currently, those are:
950 Show UMA allocator statistics.
951 Output consists five columns:
953 .Bl -tag -compact -offset indent -width "Requests"
955 Name of the UMA zone.
956 The same string that was passed to
960 Size of a given memory object (slab).
962 Number of slabs being currently used.
964 Number of free slabs within the UMA zone.
966 Number of allocations requests to the given zone.
969 The very same information might be gathered in the userspace
974 .It Ic show Cm unpcb Ar addr
975 Shows UNIX domain socket private control block
977 present at the address
981 .It Ic show Cm vmochk
982 Prints, whether the internal VM objects are in a map somewhere
983 and none have zero ref counts.
986 .It Ic show Cm vmopag
987 This is supposed to show physical addresses consumed by a
989 Currently, it is not possible to use this command when
991 is compiled in the kernel.
994 .It Ic show Cm vnode Op Ar addr
999 For the exact interpretation of the output, look at the
1004 .It Ic show Cm watches
1005 Displays all watchpoints.
1006 Shows watchpoints set with "watch" command.
1009 .It Ic show Cm witness
1010 Shows information about lock acquisition coming from the
1016 Toggles between remote GDB and DDB mode.
1017 In remote GDB mode, another machine is required that runs
1019 using the remote debug feature, with a connection to the serial
1020 console port on the target machine.
1021 Currently only available on the
1028 .It Ic kill Ar sig pid
1033 The signal is acted on upon returning from the debugger.
1034 This command can be used to kill a process causing resource contention
1035 in the case of a hung system.
1038 for a list of signals.
1039 Note that the arguments are reversed relative to
1044 Hard reset the system.
1047 Print a short summary of the available commands and command
1052 .It Ic capture reset
1053 .It Ic capture status
1055 supports a basic output capture facility, which can be used to retrieve the
1056 results of debugging commands from userpsace using
1059 enables output capture;
1063 will clear the capture buffer and disable capture.
1065 will report current buffer use, buffer size, and disposition of output
1068 Userspace processes may inspect and manage
1073 .Dv debug.ddb.capture.bufsize
1074 may be used to query or set the current capture buffer size.
1076 .Dv debug.ddb.capture.maxbufsize
1077 may be used to query the compile-time limit on the capture buffer size.
1079 .Dv debug.ddb.capture.bytes
1080 may be used to query the number of bytes of output currently in the capture
1083 .Dv debug.ddb.capture.data
1084 returns the contents of the buffer as a string to an appropriately privileged
1087 This facility is particularly useful in concert with the scripting and
1089 facilities, allowing scripted debugging output to be captured and
1090 committed to disk as part of a textdump for later analysis.
1091 The contents of the capture buffer may also be inspected in a kernel core dump
1099 Run, define, list, and delete scripts.
1102 section for more information on the scripting facility.
1105 .It Ic textdump status
1106 .It Ic textdump unset
1109 command may be used to force the next kernel core dump to be a textdump
1110 rather than a traditional memory dump or minidump.
1112 reports whether a textdump has been scheduled.
1114 cancels a request to perform a textdump as the next kernel core dump.
1115 More information may be found in
1119 The debugger accesses registers and variables as
1121 Register names are as in the
1122 .Dq Ic show Cm registers
1124 Some variables are suffixed with numbers, and may have some modifier
1125 following a colon immediately after the variable name.
1126 For example, register variables can have a
1128 modifier to indicate user register (e.g.,
1131 Built-in variables currently supported are:
1133 .Bl -tag -width ".Va tabstops" -compact
1135 Input and output radix.
1137 Addresses are printed as
1138 .Dq Ar symbol Ns Li + Ns Ar offset
1144 The width of the displayed line.
1146 The number of lines.
1147 It is used by the built-in pager.
1150 .It Va work Ns Ar xx
1153 can take values from 0 to 31.
1156 Most expression operators in C are supported except
1164 .Bl -tag -width ".No Identifiers"
1166 The name of a symbol is translated to the value of the symbol, which
1167 is the address of the corresponding object.
1171 can be used in the identifier.
1172 If supported by an object format dependent routine,
1174 .Oo Ar filename : Oc Ar func : lineno ,
1176 .Oo Ar filename : Oc Ns Ar variable ,
1178 .Oo Ar filename : Oc Ns Ar lineno
1179 can be accepted as a symbol.
1181 Radix is determined by the first two letters:
1187 decimal; otherwise, follow current radix.
1193 address of the start of the last line examined.
1198 this is only changed by
1204 last address explicitly specified.
1205 .It Li $ Ns Ar variable
1206 Translated to the value of the specified variable.
1207 It may be followed by a
1209 and modifiers as described above.
1210 .It Ar a Ns Li # Ns Ar b
1211 A binary operator which rounds up the left hand side to the next
1212 multiple of right hand side.
1215 It may be followed by a
1217 and modifiers as described above.
1221 supports a basic scripting facility to allow automating tasks or responses to
1223 Each script consists of a list of DDB commands to be executed sequentially,
1224 and is assigned a unique name.
1225 Certain script names have special meaning, and will be automatically run on
1228 events if scripts by those names have been defined.
1232 command may be used to define a script by name.
1233 Scripts consist of a series of
1235 commands separated with the
1239 .Bd -literal -offset indent
1240 script kdb.enter.panic=bt; show pcpu
1241 script lockinfo=show alllocks; show lockedvnods
1246 command lists currently defined scripts.
1250 command execute a script by name.
1252 .Bd -literal -offset indent
1258 command may be used to delete a script by name.
1260 .Bd -literal -offset indent
1261 unscript kdb.enter.panic
1264 These functions may also be performed from userspace using the
1268 Certain scripts are run automatically, if defined, for specific
1271 The follow scripts are run when various events occur:
1272 .Bl -tag -width kdb.enter.powerfail
1273 .It Dv kdb.enter.acpi
1274 The kernel debugger was entered as a result of an
1277 .It Dv kdb.enter.bootflags
1278 The kernel debugger was entered at boot as a result of the debugger boot
1280 .It Dv kdb.enter.break
1281 The kernel debugger was entered as a result of a serial or console break.
1282 .It Dv kdb.enter.cam
1283 The kernel debugger was entered as a result of a
1286 .It Dv kdb.enter.mac
1287 The kernel debugger was entered as a result of an assertion failure in the
1290 TrustedBSD MAC Framework.
1291 .It Dv kdb.enter.ndis
1292 The kernel debugger was entered as a result of an
1295 .It Dv kdb.enter.netgraph
1296 The kernel debugger was entered as a result of a
1299 .It Dv kdb.enter.panic
1302 .It Dv kdb.enter.powerfail
1303 The kernel debugger was entered as a result of a powerfail NMI on the sparc64
1305 .It Dv kdb.enter.powerpc
1306 The kernel debugger was entered as a result of an unimplemented interrupt
1307 type on the powerpc platform.
1308 .It Dv kdb.enter.sysctl
1309 The kernel debugger was entered as a result of the
1312 .It Dv kdb.enter.trapsig
1313 The kernel debugger was entered as a result of a trapsig event on the sparc64
1315 .It Dv kdb.enter.unionfs
1316 The kernel debugger was entered as a result of an assertion failure in the
1318 .It Dv kdb.enter.unknown
1319 The kernel debugger was entered, but no reason has been set.
1320 .It Dv kdb.enter.vfslock
1321 The kernel debugger was entered as a result of a VFS lock violation.
1322 .It Dv kdb.enter.watchdog
1323 The kernel debugger was entered as a result of a watchdog firing.
1324 .It Dv kdb.enter.witness
1325 The kernel debugger was entered as a result of a
1330 In the event that none of these scripts is found,
1332 will attempt to execute a default script:
1333 .Bl -tag -width kdb.enter.powerfail
1334 .It Dv kdb.enter.default
1335 The kernel debugger was entered, but a script exactly matching the reason for
1336 entering was not defined.
1337 This can be used as a catch-all to handle cases not specifically of interest;
1339 .Dv kdb.enter.witness
1340 might be defined to have special handling, and
1341 .Dv kdb.enter.default
1342 might be defined to simply panic and reboot.
1345 On machines with an ISA expansion bus, a simple NMI generation card can be
1346 constructed by connecting a push button between the A01 and B01 (CHCHK# and
1348 Momentarily shorting these two fingers together may cause the bridge chipset to
1349 generate an NMI, which causes the kernel to pass control to
1351 Some bridge chipsets do not generate a NMI on CHCHK#, so your mileage may vary.
1352 The NMI allows one to break into the debugger on a wedged machine to
1354 Other bus' bridge chipsets may be able to generate NMI using bus specific
1357 Header files mention in this manual page can be found below
1367 .Pa netinet/in_pcb.h
1390 debugger was developed for Mach, and ported to
1392 This manual page translated from
1395 .An Garrett Wollman .
1397 .An Robert N. M. Watson