757 lines
17 KiB
Groff
757 lines
17 KiB
Groff
.\" $NetBSD: ddb.4,v 1.16 1997/11/23 18:37:33 chopps Exp $
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.\"
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.\" Copyright (c) 1997 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Luke Mewburn
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the NetBSD
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.\" Foundation, Inc. and its contributors.
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.\" 4. Neither the name of The NetBSD Foundation nor the names of its
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.\" contributors may be used to endorse or promote products derived
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.\" from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" ---
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.\" This manual page was derived from a -man.old document which bore
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.\" the following copyright message:
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.\" ---
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.\"
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.\" Mach Operating System
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.\" Copyright (c) 1991,1990 Carnegie Mellon University
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.\" All Rights Reserved.
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.\"
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.\" Permission to use, copy, modify and distribute this software and its
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.\" documentation is hereby granted, provided that both the copyright
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.\" notice and this permission notice appear in all copies of the
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.\" software, derivative works or modified versions, and any portions
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.\" thereof, and that both notices appear in supporting documentation.
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.\"
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.\" CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
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.\" CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
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.\" ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
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.\"
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.\" Carnegie Mellon requests users of this software to return to
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.\"
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.\" Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
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.\" School of Computer Science
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.\" Carnegie Mellon University
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.\" Pittsburgh PA 15213-3890
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.\"
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.\" any improvements or extensions that they make and grant Carnegie Mellon
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.\" the rights to redistribute these changes.
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.\"
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.Dd November 17, 1997
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.Dt DDB 4
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.Os NetBSD
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.Sh NAME
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.Nm ddb
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.Nd in-kernel debugger
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.Sh SYNOPSIS
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.Cd options DDB
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.Pp
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To enable history editing:
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.Cd options DDB_HISTORY_SIZE=integer
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.Pp
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To disable entering
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.Nm
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upon kernel panic:
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.Cd options DDB_ONPANIC=0
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.Sh DESCRIPTION
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.Nm
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is the in-kernel debugger.
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It may be entered at any time via a special key sequence, and
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optionally may be invoked when the kernel panics.
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.Pp
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The current memory location being edited is referred to as
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.Ar dot ,
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and the next location is
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.Ar next .
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They are displayed as hexadecimal numbers.
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.Pp
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Commands that examine and/or modify memory update
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.Ar dot
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to the address of the last line examined or the last location
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modified, and set
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.Ar next
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to the next location to be examined or modified.
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Other commands don't change
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.Ar dot ,
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and set
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.Ar next
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to be the same as
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.Ar dot .
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.Pp
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The general command syntax is:
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.Bd -ragged -offset indent
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.Ic command Ns Op Cm / Ns Ar modifier
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.Ar address
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.Op Cm , Ns Ar count
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.Ed
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.Pp
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A blank line repeats the previous command from the address
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.Ar next
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with a
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.Cm count
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of 1 and no modifiers.
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Specifying
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.Cm address
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sets
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.Em dot
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to the address.
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If
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.Cm address
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is omitted,
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.Em dot
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is used.
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A missing
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.Cm count
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is taken to be 1 for printing commands, and infinity for stack traces.
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.Pp
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.Nm
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has a
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.Xr more 1 -like
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functionality; if a number of lines in a command's output exceeds the number
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defined in the
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.Va lines
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variable, then
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.Nm
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displays
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.Dq "--db more--"
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and waits for a response, which may be one of:
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.Bl -tag -offset indent -width "<return>"
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.It <return>
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one more line.
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.It <space>
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one more page.
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.It Ic q
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abort the current command, and return to the command input mode.
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.El
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.Pp
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If
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.Nm
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history editing is enabled (by defining the
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.D1 Cd options DDB_HISTORY_SIZE=num
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kernel option), then a history of the last
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.Cm num
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commands is kept.
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The history can be manipulated with the following key sequences:
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.Bl -tag -offset indent -width "<Ctrl>-P"
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.It <Ctrl>-P
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retrieve previous command in history (if any).
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.It <Ctrl>-N
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retrieve next command in history (if any).
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.El
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.Sh COMMANDS
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.Nm
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supports the following commands:
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.Bl -tag -width 5n
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.It Xo
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.Ic examine Ns Op Cm / Ns Ar modifier
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.Ar address Ns Op Cm , Ns Ar count
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.Xc
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Display the address locations according to the format in
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.Ar modifier .
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Multiple modifier formats display multiple locations.
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If
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.Ar modifier
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isn't specified, the modifier from the last use of
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.Ic examine
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is used.
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.Pp
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The valid format characters for
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.Ar modifier
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are:
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.Bl -tag -offset indent -width 2n
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.It Cm b
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examine bytes (8 bits).
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.It Cm h
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examine half-words (16 bits).
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.It Cm l
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examine long-words (32 bits).
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.It Cm a
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print the location being examined.
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.It Cm A
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print the location with a line number if possible.
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.It Cm x
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display in unsigned hex.
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.It Cm z
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display in signed hex.
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.It Cm o
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display in unsigned octal.
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.It Cm d
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display in signed decimal.
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.It Cm u
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display in unsigned decimal.
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.It Cm r
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display in current radix, signed.
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.It Cm c
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display low 8 bits as a character.
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Non-printing characters as displayed as an octal escape code
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(e.g.,
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.Sq \e000 ) .
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.It Cm s
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display the NUL terminated string at the location.
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Non-printing characters are displayed as octal escapes.
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.It Cm m
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display in unsigned hex with a character dump at the end of each line.
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The location is displayed as hex at the beginning of each line.
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.It Cm i
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display as a machine instruction.
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.It Cm I
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display as a machine instruction, with possible alternative formats
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depending upon the machine:
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.Bl -tag -offset indent -width "sparc"
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.It i386
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don't round to the next long word boundary
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.It mips
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print register contents
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.It vax
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don't assume that each external label is a procedure entry mask
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.El
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.El
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.It Xo
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.Ic x Ns Op Cm / Ns Ar modifier
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.Ar address Ns Op Cm , Ns Ar count
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.Xc
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A synonym for
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.Ic examine .
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.It Ic xf
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Examine forward.
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.Ic xf
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re-executes the most recent
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.Ic execute
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command with the same parameters except that
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.Ar address
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is set to
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.Ar next .
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.It Ic xb
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Examine backward.
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.Ic xb
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re-executes the most recent
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.Ic execute
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command with the same parameters, except that
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.Ar address
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is set to the last start address minus its size.
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.It Xo
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.Ic print Ns Op Cm /axzodurc
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.Ar address Op Ar address ...
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.Xc
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Print addresses
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.Ar address
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according to the modifier character, as per
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.Ic examine .
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Valid modifiers are:
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.Cm /a ,
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.Cm /x ,
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.Cm /z ,
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.Cm /o ,
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.Cm /d ,
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.Cm /u ,
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.Cm /r ,
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and
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.Cm /c
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(as per
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.Ic examine ) .
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If no modifier is specified, the most recent one specified is used.
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.Ar address
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may be a string, and is printed
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.Dq as-is .
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For example:
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.Bd -literal -offset indent
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print/x "eax = " $eax "\enecx = " $ecx "\en"
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.Ed
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.Pp
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will produce:
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.Bd -literal -offset indent
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eax = xxxxxx
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ecx = yyyyyy
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.Ed
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.It Xo
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.Ic write Ns Op Cm /bhl
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.Ar address
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.Ar expression Op Ar expression ...
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.Xc
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Write the
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.Ar expression Ns s
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at succeeding locations.
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The unit size is specified with a modifier character, as per
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.Ic examine .
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Valid modifiers are:
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.Cm /b ,
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.Cm /h ,
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and
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.Cm /l .
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If no modifier is specified,
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.Cm /l
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is used.
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.Pp
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Warning: since there is no delimiter between
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.Ar expression Ns s ,
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strange things may occur.
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It's best to enclose each
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.Ar expression
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in parentheses.
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.It Xo
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.Ic set
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.Cm $ Ns Ar variable
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.Op Cm =
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.Ar expression
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.Xc
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Set the named variable or register to the value of
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.Ar expression .
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Valid variable names are described in
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.Sx VARIABLES .
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.It Xo
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.Cm break Ns Op Cm /u
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.Ar address Ns Op Cm , Ns Ar count
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.Xc
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Set a breakpoint at
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.Ar address .
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If
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.Ar count
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is supplied, continues
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.Pq Ar count Ns -1
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times before stopping at the breakpoint.
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If the breakpoint is set, a breakpoint number is printed with
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.Sq # .
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This number can be used to
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.Ic delete
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the breakpoint, or to add
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conditions to it.
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.Pp
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If
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.Cm /u
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is specified,
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set a breakpoint at a user-space address.
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Without
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.Cm /u ,
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.Ar address
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is considered to be in the kernel-space, and an address in the wrong
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space will be rejected, and an error message will be emitted.
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This modifier may only be used if it is supported by machine dependent
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routines.
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.Pp
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Warning: if a user text is shadowed by a normal user-space debugger,
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user-space breakpoints may not work correctly.
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Setting a breakpoint at the low-level code paths may also cause
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strange behavior.
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.It Xo
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.Ic delete
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.Ar "address" |
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.Cm # Ns Ar number
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.Xc
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Delete a breakpoint.
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The target breakpoint may be specified by
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.Ar address ,
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as per
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.Ic break ,
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or by the breakpoint number returned by
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.Ic break
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if it's prefixed with
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.Sq Cm # .
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.It Xo
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.Ic step Ns Op Cm /p
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.Op Cm , Ns Ar count
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.Xc
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Single-step
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.Ar count
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times.
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If
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.Cm /p
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is specified, print each instruction at each step.
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Otherwise, only print the last instruction.
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.Pp
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Warning: depending on the machine type, it may not be possible
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to single-step through some low-level code paths or user-space
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code.
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On machines with software-emulated single-stepping (e.g., pmax),
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stepping through code executed by interrupt handlers will probably
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do the wrong thing.
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.It Ic continue Ns Op Cm /c
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Continue execution until a breakpoint or watchpoint.
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If
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.Cm /c
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is specified, count instructions while executing.
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Some machines (e.g., pmax) also count loads and stores.
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.Pp
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Warning: when counting, the debugger is really silently
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single-stepping.
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This means that single-stepping on low-level may cause strange
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behavior.
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.It Ic until Ns Op Cm /p
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Stop at the next call or return instruction.
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If
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.Cm /p
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is specified, print the call nesting depth and the
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cumulative instruction count at each call or return.
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Otherwise, only print when the matching return is hit.
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.It Ic next Ns Op Cm /p
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Stop at the matching return instruction.
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If
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.Cm /p
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is specified, print the call nesting depth and the
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cumulative instruction count at each call or return.
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Otherwise, only print when the matching return is hit.
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.It Ic match Ns Op Cm /p
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A synonym for
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.Ic next .
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.It Xo
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.Cm trace Ns Op Cm /u
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.Sm off
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.Op Ar frame-address
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.Op Cm , Ar count
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.Sm on
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.Xc
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Stack trace from
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.Ar frame-address .
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If
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.Cm /u
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is specified, trace user-space, otherwise trace kernel-space.
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.Ar count
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is the number of frames to be traced.
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If
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.Ar count
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is omitted, all frames are printed.
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.Pp
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Warning: user-space stack trace is valid only if the machine dependent
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code supports it.
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.It Xo
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.Cm trace/t
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.Sm off
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.Op Ar pid
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.Op Cm , Ar count
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.Sm on
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.Xc
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Stack trace by
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.Dq thread
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(process, on NetBSD) rather than by stack frame address.
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Note that
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.Ar pid
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is interpreted using the current radix, whilst
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.Ic ps
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displays pids in decimal; prefix
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.Ar pid
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with
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.Sq 0t
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to force it to be interpreted as decimal.
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.Pp
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Warning: trace by pid is valid only if the machine dependent code
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supports it.
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.It Xo
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.Ic search Ns Op Cm /bhl
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.Ar address
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.Ar value
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.Op Ar mask
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.Op Cm , Ns Ar count
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.Xc
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Search memory from
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.Ar address
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for
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.Ar value .
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The unit size is specified with a modifier character, as per
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.Ic examine .
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Valid modifiers are:
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.Cm /b ,
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.Cm /h ,
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and
|
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.Cm /l .
|
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If no modifier is specified,
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.Cm /l
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is used.
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.Pp
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This command might fail in interesting ways if it doesn't find
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.Ar value .
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This is because
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.Nm
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doesn't always recover from touching bad memory.
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The optional
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.Ar count
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limits the search.
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.It Ic reboot Op Ar flags
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Reboot, using the optionally supplied boot
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.Ar flags .
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.Pp
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Note: Limitations of the command line interface preclude
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specification of a boot string.
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.It Xo
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.Sm off
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.Ic "show\ all\ procs"
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.Op Cm /a
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.Op Cm /n
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.Op Cm /w
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.Sm on
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.Xc
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Display all process information.
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Valid modifiers:
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.Bl -tag -width 3n
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.It Cm /n
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show process information in a
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.Xr ps 1
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style format (this is the default).
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Information printed includes: process ID, parent process ID,
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process group, UID, process status, process flags, process
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command name, and process wait channel message.
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.It Cm /a
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show the kernel virtual addresses of each process'
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proc structure, u-are, and vmspace structure.
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The vmspace address is also the address of the process'
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vm_map structure, and can be used in the
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.Ic "show map"
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command.
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.It Cm /w
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show each process' PID, command, system call emulation, wait channel
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address, and wait channel message.
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.El
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.It Xo
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.Sm off
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.Ic ps
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.Op Cm /a
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.Op Cm /n
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.Op Cm /w
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.Sm on
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.Xc
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A synonym for
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.Ic "show all procs" .
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.It Ic "show registers" Ns Op Cm /u
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Display the register set.
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If
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.Cm /u
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is specified, display user registers instead of kernel registers
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or the currently save one.
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.Pp
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Warning: support for
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.Cm /u
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is machine dependent.
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If not supported, incorrect information will be displayed.
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.It Xo
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.Ic "show map" Ns Op Cm /f
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.Ar address
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.Xc
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Print the vm_map at
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.Ar address .
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If
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.Cm /f
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is specified the complete map is printed.
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.It Xo
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.Ic "show object" Ns Op Cm /f
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.Ar address
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.Xc
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Print the vm_object at
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.Ar address .
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|
If
|
|
.Cm /f
|
|
is specified the complete object is printed.
|
|
.It Ic "show watches"
|
|
Display all watchpoints.
|
|
.It Xo
|
|
.Ic watch
|
|
.Sm off
|
|
.Ar address
|
|
.Op Cm , Ar size
|
|
.Sm on
|
|
.Xc
|
|
Set a watchpoint for a region.
|
|
Execution stops when an attempt to modify the region occurs.
|
|
.Ar size
|
|
defaults to 4.
|
|
.Pp
|
|
If you specify a wrong space address, the request is
|
|
rejected with an error message.
|
|
.Pp
|
|
Warning: attempts to watch wired kernel memory may cause
|
|
an unrecoverable error in some systems such as i386.
|
|
Watchpoints on user addresses work the best.
|
|
.El
|
|
.Sh VARIABLES
|
|
.Nm
|
|
accesses registers and variables as
|
|
.Cm $ Ns Ar name .
|
|
Register names are as per the
|
|
.Ic "show registers"
|
|
command.
|
|
Some variables are suffixed with numbers, and may have a modifier
|
|
following a colon immediately after the variable name.
|
|
For example, register variables may have a
|
|
.Sq u
|
|
modifier to indicate user register
|
|
(e.g.,
|
|
.Li "$eax:u" ) .
|
|
.Pp
|
|
Built-in variables currently supported are:
|
|
.Bl -tag -offset indent -width "maxwidth"
|
|
.It Va lines
|
|
The number of lines.
|
|
This is used by the
|
|
.Ic more
|
|
feature.
|
|
.It Va maxoff
|
|
Addresses are printed as
|
|
.Li 'symbol'+offset
|
|
unless
|
|
.Li offset
|
|
is greater than
|
|
.Va maxoff .
|
|
.It Va maxwidth
|
|
The width of the displayed line.
|
|
.It Va onpanic
|
|
If non-zero (the default),
|
|
.Nm
|
|
will be invoked when the kernel panics.
|
|
If the kernel configuration option
|
|
.D1 Cd options DDB_ONPANIC=0
|
|
is used,
|
|
.Va onpanic
|
|
will be initialised to off.
|
|
.It Va radix
|
|
Input and output radix.
|
|
.It Va tabstops
|
|
Tab stop width.
|
|
.It Va work Ns Sy xx
|
|
Temporary work variable.
|
|
.Sq Sy xx
|
|
is between 0 and 31.
|
|
.El
|
|
.Pp
|
|
All built-in variables are accessible via
|
|
.Xr sysctl 3 .
|
|
.Sh EXPRESSIONS
|
|
Almost all expression operators in C are supported, except
|
|
.Sq ~ ,
|
|
.Sq ^ ,
|
|
and unary
|
|
.Sq & .
|
|
Special rules in
|
|
.Nm
|
|
are:
|
|
.Bl -tag -offset indent -width "identifier"
|
|
.It Ar identifier
|
|
name of a symbol.
|
|
It is translated to the address (or value) of it.
|
|
.Sq .
|
|
and
|
|
.Sq :
|
|
can be used in the identifier.
|
|
If supported by an object format dependent routine,
|
|
.Sm off
|
|
.Xo
|
|
.Oo Ar filename : Oc
|
|
.Ar function
|
|
.Oo : Ar "line number" Oc ,
|
|
.Xc
|
|
.Xo
|
|
.Oo Ar filename : Oc
|
|
.Ar variable ,
|
|
.Xc
|
|
and
|
|
.Xo
|
|
.Ar filename
|
|
.Oo : Ar "line number" Oc ,
|
|
.Xc
|
|
.Sm on
|
|
can be accepted as a symbol.
|
|
The symbol may be prefixed with
|
|
.Ar "symbol_table_name" Ns ::
|
|
(e.g.,
|
|
.Li emulator::mach_msg_trap )
|
|
to specify other than kernel symbols.
|
|
.It Ar number
|
|
number.
|
|
Radix is determined by the first two characters:
|
|
.Sq 0x
|
|
- hex,
|
|
.Sq 0o
|
|
- octal,
|
|
.Sq 0t
|
|
- decimal,
|
|
otherwise follow current radix.
|
|
.It Cm .
|
|
.Ar dot
|
|
.It Cm +
|
|
.Ar next
|
|
.It Cm ..
|
|
address of the start of the last line examined.
|
|
Unlike
|
|
.Ar dot
|
|
or
|
|
.Ar next ,
|
|
this is only changed by the
|
|
.Ic examine
|
|
or
|
|
.Ic write
|
|
commands.
|
|
.It Cm ,
|
|
last address explicitly specified.
|
|
.It Cm $ Ns Ar name
|
|
register name or variable.
|
|
It is translated to the value of it.
|
|
It may be followed by a
|
|
.Sq :
|
|
and modifiers as described above.
|
|
.It Cm a
|
|
multiple of right-hand side.
|
|
.It Cm * Ns Ar expr
|
|
expression indirection.
|
|
It may be followed by a
|
|
.Sq :
|
|
and modifiers as described above.
|
|
.El
|
|
.Sh ENTERING THE DEBUGGER
|
|
Unless
|
|
.Va onpanic
|
|
is set to 0,
|
|
.Nm
|
|
will be activated whenever the kernel would otherwise panic.
|
|
.Pp
|
|
.Nm
|
|
may also be activated from the console.
|
|
In general, sending a break on a serial console will activate
|
|
.Nm "" .
|
|
There are also key sequences for each port that will activate
|
|
.Nm
|
|
from the keyboard:
|
|
.Bl -tag -offset indent -width "mac68k"
|
|
.It amiga
|
|
<LAlt>-<LAmiga>-<F10>
|
|
.It hp300
|
|
<Shift>-<Reset>
|
|
.It i386
|
|
<Ctrl>-<Alt>-<Esc>
|
|
.It mac68k
|
|
<Command>-<Power>, or the Interrupt switch.
|
|
.It sparc
|
|
<L1>-A, or <Stop>-A
|
|
.El
|
|
.Pp
|
|
In addition,
|
|
.Nm
|
|
may be explicitly activated by the debugging code in the kernel
|
|
if
|
|
.Cm DDB
|
|
is configured.
|
|
.Sh SEE ALSO
|
|
.Xr options 4 ,
|
|
.Xr sysctl 8
|