546 lines
14 KiB
Groff
546 lines
14 KiB
Groff
.\"
|
|
.\" Mach Operating System
|
|
.\" Copyright (c) 1991,1990 Carnegie Mellon University
|
|
.\" All Rights Reserved.
|
|
.\"
|
|
.\" Permission to use, copy, modify and distribute this software and its
|
|
.\" documentation is hereby granted, provided that both the copyright
|
|
.\" notice and this permission notice appear in all copies of the
|
|
.\" software, derivative works or modified versions, and any portions
|
|
.\" thereof, and that both notices appear in supporting documentation.
|
|
.\"
|
|
.\" CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
|
|
.\" CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
|
|
.\" ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
|
|
.\"
|
|
.\" Carnegie Mellon requests users of this software to return to
|
|
.\"
|
|
.\" Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
|
|
.\" School of Computer Science
|
|
.\" Carnegie Mellon University
|
|
.\" Pittsburgh PA 15213-3890
|
|
.\"
|
|
.\" any improvements or extensions that they make and grant Carnegie Mellon
|
|
.\" the rights to redistribute these changes.
|
|
.\"
|
|
.\" changed a \# to #, since groff choked on it.
|
|
.\"
|
|
.\" HISTORY
|
|
.\" ddb.4,v
|
|
.\" Revision 1.1 1993/07/15 18:41:02 brezak
|
|
.\" Man page for DDB
|
|
.\"
|
|
.\" Revision 2.6 92/04/08 08:52:57 rpd
|
|
.\" Changes from OSF.
|
|
.\" [92/01/17 14:19:22 jsb]
|
|
.\" Changes for OSF debugger modifications.
|
|
.\" [91/12/12 tak]
|
|
.\"
|
|
.\" Revision 2.5 91/06/25 13:50:22 rpd
|
|
.\" Added some watchpoint explanation.
|
|
.\" [91/06/25 rpd]
|
|
.\"
|
|
.\" Revision 2.4 91/06/17 15:47:31 jsb
|
|
.\" Added documentation for continue/c, match, search, and watchpoints.
|
|
.\" I've not actually explained what a watchpoint is; maybe Rich can
|
|
.\" do that (hint, hint).
|
|
.\" [91/06/17 10:58:08 jsb]
|
|
.\"
|
|
.\" Revision 2.3 91/05/14 17:04:23 mrt
|
|
.\" Correcting copyright
|
|
.\"
|
|
.\" Revision 2.2 91/02/14 14:10:06 mrt
|
|
.\" Changed to new Mach copyright
|
|
.\" [91/02/12 18:10:12 mrt]
|
|
.\"
|
|
.\" Revision 2.2 90/08/30 14:23:15 dbg
|
|
.\" Created.
|
|
.\" [90/08/30 dbg]
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.Dd January 16, 1996
|
|
.Dt DDB 4
|
|
.Os FreeBSD
|
|
.Sh NAME
|
|
.Nm ddb
|
|
.Nd interactive kernel debugger
|
|
.Sh SYNOPSIS
|
|
.Cd options DDB
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm
|
|
kernel debugger has most of the features of the old kdb,
|
|
but with a more rational syntax
|
|
inspired by
|
|
.Xr gdb 1 .
|
|
.Pp
|
|
The current location is called `dot'. The `dot' is displayed with
|
|
a hexadecimal format at a prompt.
|
|
Examine and write commands update `dot' to the address of the last line
|
|
examined or the last location modified, and set `next' to the address of
|
|
the next location to be examined or changed.
|
|
Other commands don't change `dot', and set `next' to be the same as `dot'.
|
|
.Pp
|
|
The general command syntax is:
|
|
.Cm command Ns Op Li \&/ Ns Ar modifier
|
|
.Ar address Ns Op Li , Ns Ar count
|
|
.Pp
|
|
A blank line repeats the previous command from the address `next' with
|
|
count 1 and no modifiers. Specifying
|
|
.Ar address
|
|
sets `dot' to the
|
|
address. Omitting
|
|
.Ar address
|
|
uses `dot'. A missing
|
|
.Ar count
|
|
is taken
|
|
to be 1 for printing commands or infinity for stack traces.
|
|
.Pp
|
|
The
|
|
.Nm
|
|
debugger has a feature like the
|
|
.Xr more 1
|
|
command
|
|
for the output. If an output line exceeds the number set in the
|
|
.Li \&$lines
|
|
variable, it displays
|
|
.Dq Em --db_more--
|
|
and waits for a response.
|
|
The valid responses for it are:
|
|
.Pp
|
|
.Bl -tag -compact -width SPC
|
|
.It Li SPC
|
|
one more page
|
|
.It Li RET
|
|
one more line
|
|
.It Li q
|
|
abort the current command, and return to the command input mode
|
|
.El
|
|
.Pp
|
|
Finally,
|
|
.Nm
|
|
provides a small (currently 10 items) command history, and offers
|
|
simple emacs-style command line editing capabilities. In addition to
|
|
the emacs control keys, the usual ANSI arrow keys might be used to
|
|
browse through the history buffer, and move the cursor within the
|
|
current line.
|
|
.Sh COMMANDS
|
|
.Bl -ohang
|
|
.It Cm examine
|
|
.It Cm x
|
|
Display the addressed locations according to the formats in the modifier.
|
|
Multiple modifier formats display multiple locations.
|
|
If no format is specified, the last formats specified for this command
|
|
is used.
|
|
.Pp
|
|
The format characters are:
|
|
.Bl -tag -compact -width indent
|
|
.It Li b
|
|
look at by bytes (8 bits)
|
|
.It Li h
|
|
look at by half words (16 bits)
|
|
.It Li l
|
|
look at by long words (32 bits)
|
|
.It Li a
|
|
print the location being displayed
|
|
.It Li A
|
|
print the location with a line number if possible
|
|
.It Li x
|
|
display in unsigned hex
|
|
.It Li z
|
|
display in signed hex
|
|
.It Li o
|
|
display in unsigned octal
|
|
.It Li d
|
|
display in signed decimal
|
|
.It Li u
|
|
display in unsigned decimal
|
|
.It Li r
|
|
display in current radix, signed
|
|
.It Li c
|
|
display low 8 bits as a character.
|
|
Non-printing characters are displayed as an octal escape code (e.g., `\e000').
|
|
.It Li s
|
|
display the null-terminated string at the location.
|
|
Non-printing characters are displayed as octal escapes.
|
|
.It Li m
|
|
display in unsigned hex with character dump at the end of each line.
|
|
The location is also displayed in hex at the beginning of each line.
|
|
.It Li i
|
|
display as an instruction
|
|
.It Li I
|
|
display as an instruction with possible alternate formats depending on the
|
|
machine:
|
|
.Bl -tag -width MIPS -compact
|
|
.It Tn VAX
|
|
don't assume that each external label is a procedure entry mask
|
|
.It Tn i386
|
|
don't round to the next long word boundary
|
|
.It Tn MIPS
|
|
print register contents
|
|
.El
|
|
.El
|
|
.It Cm xf
|
|
Examine forward:
|
|
Execute an examine command with the last specified parameters to it
|
|
except that the next address displayed by it is used as the start address.
|
|
.It Cm xb
|
|
Examine backward:
|
|
Execute an examine command with the last specified parameters to it
|
|
except that the last start address subtracted by the size displayed by it
|
|
is used as the start address.
|
|
.It Cm print Ns Op Cm /acdoruxz
|
|
Print
|
|
.Ar addr Ns s
|
|
according to the modifier character (as described above for
|
|
.Li examine ) .
|
|
Valid formats are:
|
|
.Li a ,
|
|
.Li x ,
|
|
.Li z ,
|
|
.Li o ,
|
|
.Li d ,
|
|
.Li u ,
|
|
.Li r ,
|
|
and
|
|
.Li c .
|
|
If no modifier is specified, the last one specified to it is used.
|
|
.Ar addr
|
|
can be a string, in which case it is printed as it is. For example:
|
|
.Bd -literal -offset indent
|
|
print/x \&"eax = \&" $eax \&"\enecx = \&" $ecx \&"\en\&"
|
|
.Ed
|
|
.Pp
|
|
will print like:
|
|
.Bd -literal -offset indent
|
|
eax = xxxxxx
|
|
ecx = yyyyyy
|
|
.Ed
|
|
.It Xo
|
|
.Cm write Ns Op Cm /bhl
|
|
.Ar addr Ar expr1 Op Ar "expr2 ..."
|
|
.Xc
|
|
Write the expressions specified after
|
|
.Ar addr
|
|
on the command line at succeeding locations starting with
|
|
.Ar addr
|
|
The write unit size can be specified in the modifier with a letter
|
|
.Li b
|
|
(byte),
|
|
.Li h
|
|
(half word) or
|
|
.Li l
|
|
(long word) respectively. If omitted,
|
|
long word is assumed.
|
|
.Pp
|
|
.Sy Warning :
|
|
since there is no delimiter between expressions, strange
|
|
things may happen.
|
|
It's best to enclose each expression in parentheses.
|
|
.It Xo
|
|
.Cm set
|
|
.Li \&$ Ns Ar variable
|
|
.Op Li =
|
|
.Ar expr
|
|
.Xc
|
|
Set the named variable or register with the value of
|
|
.Ar expr .
|
|
Valid variable names are described below.
|
|
.It Cm break Ns Op Cm /u
|
|
Set a break point at
|
|
.Ar addr .
|
|
If
|
|
.Ar count
|
|
is supplied, continues
|
|
.Ar count
|
|
- 1 times before stopping at the
|
|
break point. If the break point is set, a break point number is
|
|
printed with
|
|
.Sq Li \&# .
|
|
This number can be used in deleting the break point
|
|
or adding conditions to it.
|
|
.Pp
|
|
If the
|
|
.Li u
|
|
modifier is specified, this command sets a break point in user space
|
|
address. Without the
|
|
.Li u
|
|
option, the address is considered in the kernel
|
|
space, and wrong space address is rejected with an error message.
|
|
This modifier can be used only if it is supported by machine dependent
|
|
routines.
|
|
.Pp
|
|
.Sy Warning :
|
|
If a user text is shadowed by a normal user space debugger,
|
|
user space break points may not work correctly. Setting a break
|
|
point at the low-level code paths may also cause strange behavior.
|
|
.It Cm delete Ar addr
|
|
.It Cm delete Li \&# Ns Ar number
|
|
Delete the break point. The target break point can be specified by a
|
|
break point number with
|
|
.Li # ,
|
|
or by using the same
|
|
.Ar addr
|
|
specified in the original
|
|
.Cm break
|
|
command.
|
|
.It Cm step Ns Op Cm /p
|
|
Single step
|
|
.Ar count
|
|
times (the comma is a mandatory part of the syntax).
|
|
If the
|
|
.Li p
|
|
modifier is specified, print each instruction at each step.
|
|
Otherwise, only print the last instruction.
|
|
.Pp
|
|
.Sy Warning :
|
|
depending on machine type, it may not be possible to
|
|
single-step through some low-level code paths or user space code.
|
|
On machines with software-emulated single-stepping (e.g., pmax),
|
|
stepping through code executed by interrupt handlers will probably
|
|
do the wrong thing.
|
|
.It Cm continue Ns Op Cm /c
|
|
Continue execution until a breakpoint or watchpoint.
|
|
If the
|
|
.Li c
|
|
modifier is specified, count instructions while executing.
|
|
Some machines (e.g., pmax) also count loads and stores.
|
|
.Pp
|
|
.Sy Warning :
|
|
when counting, the debugger is really silently single-stepping.
|
|
This means that single-stepping on low-level code may cause strange
|
|
behavior.
|
|
.It Cm until Ns Op Cm /p
|
|
Stop at the next call or return instruction.
|
|
If the
|
|
.Li p
|
|
modifier is specified, print the call nesting depth and the
|
|
cumulative instruction count at each call or return. Otherwise,
|
|
only print when the matching return is hit.
|
|
.It Cm next Ns Op Cm /p
|
|
.It Cm match Ns Op Cm /p
|
|
Stop at the matching return instruction.
|
|
If the
|
|
.Li p
|
|
modifier is specified, print the call nesting depth and the
|
|
cumulative instruction count at each call or return. Otherwise,
|
|
only print when the matching return is hit.
|
|
.It Xo
|
|
.Cm trace Ns Op Cm /u
|
|
.Op Ar frame
|
|
.Op , Ns Ar count
|
|
.Xc
|
|
Stack trace. The
|
|
.Li u
|
|
option traces user space; if omitted,
|
|
.Cm trace
|
|
only traces
|
|
kernel space.
|
|
.Ar count
|
|
is the number of frames to be traced.
|
|
If
|
|
.Ar count
|
|
is omitted, all frames are printed.
|
|
.Pp
|
|
.Sy Warning :
|
|
User space stack trace is valid
|
|
only if the machine dependent code supports it.
|
|
.It Xo
|
|
.Cm search Ns Op Cm /bhl
|
|
.Ar addr
|
|
.Ar value
|
|
.Op Ar mask
|
|
.Op , Ns Ar count
|
|
.Xc
|
|
Search memory for
|
|
.Ar value .
|
|
This command might fail in interesting
|
|
ways if it doesn't find the searched-for value. This is because
|
|
ddb doesn't always recover from touching bad memory. The optional
|
|
.Ar count
|
|
argument limits the search.
|
|
.It Cm show all procs Ns Op Cm /m
|
|
.It Cm ps Ns Op Cm /m
|
|
Display all process information.
|
|
The process information may not be shown if it is not
|
|
supported in the machine, or the bottom of the stack of the
|
|
target process is not in the main memory at that time.
|
|
The
|
|
.Li m
|
|
modifier will alter the display to show VM map
|
|
addresses for the process and not show other info.
|
|
.It Cm show registers Ns Op Cm /u
|
|
Display the register set.
|
|
If the
|
|
.Li u
|
|
option is specified, it displays user registers instead of
|
|
kernel or currently saved one.
|
|
.Pp
|
|
.Sy Warning :
|
|
The support of the
|
|
.Li u
|
|
modifier depends on the machine. If
|
|
not supported, incorrect information will be displayed.
|
|
.It Xo
|
|
.Cm show map Ns Op Cm /f
|
|
.Ar addr
|
|
.Xc
|
|
Prints the VM map at
|
|
.Ar addr .
|
|
If the
|
|
.Li f
|
|
modifier is specified the
|
|
complete map is printed.
|
|
.It Xo
|
|
.Cm show object Ns Op Cm /f
|
|
.Ar addr
|
|
.Xc
|
|
Prints the VM object at
|
|
.Ar addr .
|
|
If the
|
|
.Li f
|
|
option is specified the
|
|
complete object is printed.
|
|
.It Cm "show watches"
|
|
Displays all watchpoints.
|
|
.It Xo
|
|
.Cm watch
|
|
.Ar addr Ns Li \&, Ns Ar size
|
|
.Xc
|
|
Set a watchpoint for a region. Execution stops
|
|
when an attempt to modify the region occurs.
|
|
The
|
|
.Ar size
|
|
argument defaults to 4.
|
|
If you specify a wrong space address, the request is rejected
|
|
with an error message.
|
|
.Pp
|
|
.Sy Warning :
|
|
Attempts to watch wired kernel memory
|
|
may cause unrecoverable error in some systems such as i386.
|
|
Watchpoints on user addresses work best.
|
|
.It Cm gdb
|
|
Toggles between remote GDB and DDB mode. In remote GDB mode, another
|
|
machine is required that runs
|
|
.Xr gdb 1
|
|
using the remote debug feature, with a connection to the serial
|
|
console port on the target machine. Currently only available on the
|
|
.Em i386
|
|
and
|
|
.Em Alpha
|
|
architectures.
|
|
.It Cm help
|
|
Print a short summary of the available commands and command
|
|
abbreviations.
|
|
.El
|
|
.Sh VARIABLES
|
|
The debugger accesses registers and variables as
|
|
.Li \&$ Ns Em name .
|
|
Register names are as in the
|
|
.Dq Cm show registers
|
|
command.
|
|
Some variables are suffixed with numbers, and may have some modifier
|
|
following a colon immediately after the variable name.
|
|
For example, register variables can have a
|
|
.Li u
|
|
modifier to indicate user register (e.g.,
|
|
.Li $eax:u ) .
|
|
.Pp
|
|
Built-in variables currently supported are:
|
|
.Bl -tag -width tabstops -compact
|
|
.It Li radix
|
|
Input and output radix
|
|
.It Li maxoff
|
|
Addresses are printed as 'symbol'+offset unless offset is greater than maxoff.
|
|
.It Li maxwidth
|
|
The width of the displayed line.
|
|
.It Li lines
|
|
The number of lines. It is used by "more" feature.
|
|
.It Li tabstops
|
|
Tab stop width.
|
|
.It Li work Ns Ar xx
|
|
Work variable.
|
|
.Ar xx
|
|
can be 0 to 31.
|
|
.El
|
|
.Sh EXPRESSIONS
|
|
Almost all expression operators in C are supported except
|
|
.Sq Li \&~ ,
|
|
.Sq Li \&^ ,
|
|
and unary
|
|
.Sq Li \&& .
|
|
Special rules in
|
|
.Nm
|
|
are:
|
|
.Bl -tag -width Identifiers
|
|
.It Em Identifiers
|
|
The name of a symbol is translated to the value of the symbol, which
|
|
is the address of the corresponding object.
|
|
.Sq Li \&.
|
|
and
|
|
.Sq Li \&:
|
|
can be used in the identifier.
|
|
If supported by an object format dependent routine,
|
|
.Sm off
|
|
.Oo Em filename : Oc Em func : lineno ,
|
|
.Sm on
|
|
.Oo Em filename : Oc Ns Em variable ,
|
|
and
|
|
.Oo Em filename : Oc Ns Em lineno
|
|
can be accepted as a symbol.
|
|
.It Em Numbers
|
|
Radix is determined by the first two letters:
|
|
.Li 0x :
|
|
hex,
|
|
.Li 0o :
|
|
octal,
|
|
.Li 0t :
|
|
decimal; otherwise, follow current radix.
|
|
.It Li \&.
|
|
`dot'
|
|
.It Li \&+
|
|
`next'
|
|
.It Li \&..
|
|
address of the start of the last line examined.
|
|
Unlike `dot' or `next', this is only changed by
|
|
.Dq Li examine
|
|
or
|
|
.Dq Li write
|
|
command.
|
|
.It Li \&'
|
|
last address explicitly specified.
|
|
.It Li \&$ Ns Em variable
|
|
Translated to the value of the specified variable.
|
|
It may be followed by a
|
|
.Li :
|
|
and modifiers as described above.
|
|
.It Em a Ns Li \&# Ns Em b
|
|
a binary operator which rounds up the left hand side to the next
|
|
multiple of right hand side.
|
|
.It Li \&* Ns Em expr
|
|
indirection. It may be followed by a
|
|
.Sq Li :
|
|
and modifiers as described above.
|
|
.El
|
|
.Sh HINTS
|
|
On machines with an ISA expansion bus, a simple NMI generation card can be
|
|
constructed by connecting a push button between the A01 and B01 (CHCHK# and
|
|
GND) card fingers.
|
|
Momentarily shorting these two fingers together may cause the bridge chipset to
|
|
generate an NMI, which causes the kernel to pass control to
|
|
.Nm .
|
|
Some bridge chipsets do not generate a NMI on CHCHK#, so your mileage may vary.
|
|
The NMI allows one to break into the debugger on a wedged machine to
|
|
diagnose problems.
|
|
Other bus' bridge chipsets may be able to generate NMI using bus specific
|
|
methods.
|
|
.Sh SEE ALSO
|
|
.Xr gdb 1
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
debugger was developed for Mach, and ported to 386BSD 0.1.
|
|
This manual page translated from
|
|
.Fl man
|
|
macros by Garrett Wollman.
|