2 .\" Mach Operating System
3 .\" Copyright (c) 1991,1990 Carnegie Mellon University
4 .\" All Rights Reserved.
6 .\" Permission to use, copy, modify and distribute this software and its
7 .\" documentation is hereby granted, provided that both the copyright
8 .\" notice and this permission notice appear in all copies of the
9 .\" software, derivative works or modified versions, and any portions
10 .\" thereof, and that both notices appear in supporting documentation.
12 .\" CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
13 .\" CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
14 .\" ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
16 .\" Carnegie Mellon requests users of this software to return to
18 .\" Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
19 .\" School of Computer Science
20 .\" Carnegie Mellon University
21 .\" Pittsburgh PA 15213-3890
23 .\" any improvements or extensions that they make and grant Carnegie Mellon
24 .\" the rights to redistribute these changes.
26 .\" changed a \# to #, since groff choked on it.
30 .\" Revision 1.1 1993/07/15 18:41:02 brezak
33 .\" Revision 2.6 92/04/08 08:52:57 rpd
35 .\" [92/01/17 14:19:22 jsb]
36 .\" Changes for OSF debugger modifications.
39 .\" Revision 2.5 91/06/25 13:50:22 rpd
40 .\" Added some watchpoint explanation.
43 .\" Revision 2.4 91/06/17 15:47:31 jsb
44 .\" Added documentation for continue/c, match, search, and watchpoints.
45 .\" I've not actually explained what a watchpoint is; maybe Rich can
46 .\" do that (hint, hint).
47 .\" [91/06/17 10:58:08 jsb]
49 .\" Revision 2.3 91/05/14 17:04:23 mrt
50 .\" Correcting copyright
52 .\" Revision 2.2 91/02/14 14:10:06 mrt
53 .\" Changed to new Mach copyright
54 .\" [91/02/12 18:10:12 mrt]
56 .\" Revision 2.2 90/08/30 14:23:15 dbg
60 .\" $FreeBSD: src/share/man/man4/ddb.4,v 1.7.2.6 2001/08/17 13:08:37 ru Exp $
66 .Nd interactive kernel debugger
70 To prevent activation of the debugger on kernel
72 .Cd options DDB_UNATTENDED
76 kernel debugger has most of the features of the old kdb,
77 but with a more rational syntax
80 If linked into the running kernel,
81 it can be invoked locally with the
85 The debugger is also invoked on kernel
88 .Va debug.debugger_on_panic
90 MIB variable is set non-zero,
96 The current location is called `dot'. The `dot' is displayed with
97 a hexadecimal format at a prompt.
98 Examine and write commands update `dot' to the address of the last line
99 examined or the last location modified, and set `next' to the address of
100 the next location to be examined or changed.
101 Other commands don't change `dot', and set `next' to be the same as `dot'.
103 The general command syntax is:
104 .Cm command Ns Op Li \&/ Ns Ar modifier
105 .Ar address Ns Op Li , Ns Ar count
107 A blank line repeats the previous command from the address `next' with
108 count 1 and no modifiers. Specifying
113 uses `dot'. A missing
116 to be 1 for printing commands or infinity for stack traces.
120 debugger has a feature like the
123 for the output. If an output line exceeds the number set in the
125 variable, it displays
127 and waits for a response.
128 The valid responses for it are:
130 .Bl -tag -compact -width SPC
136 abort the current command, and return to the command input mode
141 provides a small (currently 10 items) command history, and offers
142 simple emacs-style command line editing capabilities. In addition to
143 the emacs control keys, the usual ANSI arrow keys might be used to
144 browse through the history buffer, and move the cursor within the
150 Display the addressed locations according to the formats in the modifier.
151 Multiple modifier formats display multiple locations.
152 If no format is specified, the last formats specified for this command
155 The format characters are:
156 .Bl -tag -compact -width indent
158 look at by bytes (8 bits)
160 look at by half words (16 bits)
162 look at by long words (32 bits)
164 print the location being displayed
166 print the location with a line number if possible
168 display in unsigned hex
170 display in signed hex
172 display in unsigned octal
174 display in signed decimal
176 display in unsigned decimal
178 display in current radix, signed
180 display low 8 bits as a character.
181 Non-printing characters are displayed as an octal escape code (e.g., `\e000').
183 display the null-terminated string at the location.
184 Non-printing characters are displayed as octal escapes.
186 display in unsigned hex with character dump at the end of each line.
187 The location is also displayed in hex at the beginning of each line.
189 display as an instruction
191 display as an instruction with possible alternate formats depending on the
193 .Bl -tag -width MIPS -compact
195 don't assume that each external label is a procedure entry mask
197 don't round to the next long word boundary
199 print register contents
204 Execute an examine command with the last specified parameters to it
205 except that the next address displayed by it is used as the start address.
208 Execute an examine command with the last specified parameters to it
209 except that the last start address subtracted by the size displayed by it
210 is used as the start address.
211 .It Cm print Ns Op Cm /acdoruxz
214 according to the modifier character (as described above for
226 If no modifier is specified, the last one specified to it is used.
228 can be a string, in which case it is printed as it is. For example:
229 .Bd -literal -offset indent
230 print/x \&"eax = \&" $eax \&"\enecx = \&" $ecx \&"\en\&"
234 .Bd -literal -offset indent
239 .Cm write Ns Op Cm /bhl
240 .Ar addr Ar expr1 Op Ar "expr2 ..."
242 Write the expressions specified after
244 on the command line at succeeding locations starting with
246 The write unit size can be specified in the modifier with a letter
252 (long word) respectively. If omitted,
253 long word is assumed.
256 since there is no delimiter between expressions, strange
258 It's best to enclose each expression in parentheses.
261 .Li \&$ Ns Ar variable
265 Set the named variable or register with the value of
267 Valid variable names are described below.
268 .It Cm break Ns Op Cm /u
273 is supplied, continues
275 - 1 times before stopping at the
276 break point. If the break point is set, a break point number is
279 This number can be used in deleting the break point
280 or adding conditions to it.
284 modifier is specified, this command sets a break point in user space
287 option, the address is considered in the kernel
288 space, and wrong space address is rejected with an error message.
289 This modifier can be used only if it is supported by machine dependent
293 If a user text is shadowed by a normal user space debugger,
294 user space break points may not work correctly. Setting a break
295 point at the low-level code paths may also cause strange behavior.
296 .It Cm delete Ar addr
297 .It Cm delete Li \&# Ns Ar number
298 Delete the break point. The target break point can be specified by a
299 break point number with
303 specified in the original
306 .It Cm step Ns Op Cm /p
309 times (the comma is a mandatory part of the syntax).
312 modifier is specified, print each instruction at each step.
313 Otherwise, only print the last instruction.
316 depending on machine type, it may not be possible to
317 single-step through some low-level code paths or user space code.
318 On machines with software-emulated single-stepping (e.g., pmax),
319 stepping through code executed by interrupt handlers will probably
321 .It Cm continue Ns Op Cm /c
322 Continue execution until a breakpoint or watchpoint.
325 modifier is specified, count instructions while executing.
326 Some machines (e.g., pmax) also count loads and stores.
329 when counting, the debugger is really silently single-stepping.
330 This means that single-stepping on low-level code may cause strange
332 .It Cm until Ns Op Cm /p
333 Stop at the next call or return instruction.
336 modifier is specified, print the call nesting depth and the
337 cumulative instruction count at each call or return. Otherwise,
338 only print when the matching return is hit.
339 .It Cm next Ns Op Cm /p
340 .It Cm match Ns Op Cm /p
341 Stop at the matching return instruction.
344 modifier is specified, print the call nesting depth and the
345 cumulative instruction count at each call or return. Otherwise,
346 only print when the matching return is hit.
348 .Cm trace Ns Op Cm /u
354 option traces user space; if omitted,
359 is the number of frames to be traced.
362 is omitted, all frames are printed.
365 User space stack trace is valid
366 only if the machine dependent code supports it.
368 .Cm search Ns Op Cm /bhl
376 This command might fail in interesting
377 ways if it doesn't find the searched-for value. This is because
378 ddb doesn't always recover from touching bad memory. The optional
380 argument limits the search.
381 .It Cm show all procs Ns Op Cm /m
382 .It Cm ps Ns Op Cm /m
383 Display all process information.
384 The process information may not be shown if it is not
385 supported in the machine, or the bottom of the stack of the
386 target process is not in the main memory at that time.
389 modifier will alter the display to show VM map
390 addresses for the process and not show other info.
391 .It Cm show registers Ns Op Cm /u
392 Display the register set.
395 option is specified, it displays user registers instead of
396 kernel or currently saved one.
401 modifier depends on the machine. If
402 not supported, incorrect information will be displayed.
404 .Cm show map Ns Op Cm /f
411 modifier is specified the
412 complete map is printed.
414 .Cm show object Ns Op Cm /f
417 Prints the VM object at
421 option is specified the
422 complete object is printed.
423 .It Cm "show watches"
424 Displays all watchpoints.
427 .Ar addr Ns Li \&, Ns Ar size
429 Set a watchpoint for a region. Execution stops
430 when an attempt to modify the region occurs.
433 argument defaults to 4.
434 If you specify a wrong space address, the request is rejected
435 with an error message.
438 Attempts to watch wired kernel memory
439 may cause unrecoverable error in some systems such as i386.
440 Watchpoints on user addresses work best.
442 Toggles between remote GDB and DDB mode. In remote GDB mode, another
443 machine is required that runs
445 using the remote debug feature, with a connection to the serial
446 console port on the target machine. Currently only available on the
450 Print a short summary of the available commands and command
454 The debugger accesses registers and variables as
456 Register names are as in the
457 .Dq Cm show registers
459 Some variables are suffixed with numbers, and may have some modifier
460 following a colon immediately after the variable name.
461 For example, register variables can have a
463 modifier to indicate user register (e.g.,
466 Built-in variables currently supported are:
467 .Bl -tag -width tabstops -compact
469 Input and output radix
471 Addresses are printed as 'symbol'+offset unless offset is greater than maxoff.
473 The width of the displayed line.
475 The number of lines. It is used by "more" feature.
484 Almost all expression operators in C are supported except
492 .Bl -tag -width Identifiers
494 The name of a symbol is translated to the value of the symbol, which
495 is the address of the corresponding object.
499 can be used in the identifier.
500 If supported by an object format dependent routine,
502 .Oo Em filename : Oc Em func : lineno ,
504 .Oo Em filename : Oc Ns Em variable ,
506 .Oo Em filename : Oc Ns Em lineno
507 can be accepted as a symbol.
509 Radix is determined by the first two letters:
515 decimal; otherwise, follow current radix.
521 address of the start of the last line examined.
522 Unlike `dot' or `next', this is only changed by
528 last address explicitly specified.
529 .It Li \&$ Ns Em variable
530 Translated to the value of the specified variable.
531 It may be followed by a
533 and modifiers as described above.
534 .It Em a Ns Li \&# Ns Em b
535 a binary operator which rounds up the left hand side to the next
536 multiple of right hand side.
537 .It Li \&* Ns Em expr
538 indirection. It may be followed by a
540 and modifiers as described above.
547 debugger was developed for Mach, and ported to
549 This manual page translated from
551 macros by Garrett Wollman.