124 lines
4.0 KiB
Groff
124 lines
4.0 KiB
Groff
.\" Copyright (c) 1986, 1991 Regents of the University of California.
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.\" All rights reserved.
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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 University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)kadb.4 6.3 (Berkeley) 3/28/91
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.\"
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.Dd March 28, 1991
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.Dt KADB 4
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.Os
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.Sh NAME
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.Nm kdb
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.Nd kernel debugging facility
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.Sh SYNOPSIS
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.Sy options
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.Nm KADB
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.Sh DESCRIPTION
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.Nm Kdb
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is a debugging facility for the kernel based on
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.Xr adb 1 .
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.Nm Kdb
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may be used to symbolically examine and modify memory locations,
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set breakpoints, and single step the system.
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.Pp
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Several boot time options are used in conjunction
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with the debugger. To
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.Dq enable
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the debugger, the system
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must be booted with the
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.Dv RB_KDB
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flag (0x40) specified in the
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.Em boothowto
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register. When the debugger is
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enabled the system will read
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in and initialize the symbol table from the booted system.
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If the
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.Dv RB_HALT
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flag (0x08) is also specified, the system will
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enter the debugger at the earliest possible time to allow
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breakpoints to be set before the system starts operation.
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From that point on, if the
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.Dv RB_NOSYNC
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flag (0x04) is set,
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typing
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.Ql ^[k ,
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.Ql ^[K ,
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or
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.Ql ^[^K
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at the
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console causes a trap into the debugger.
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.Pp
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.Nm Kdb
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supports most of the
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.Xr adb
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command language. The output formats
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.Ql f ,
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.Ql F ,
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.Ql Y ,
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are not
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supported. The address space maps do not exist, thus the
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.Ql \&m ,
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.Ql \&m ,
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and
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.Ql \&m
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commands do not exist. Shell escapes
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and command files are not supported. The
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.Ql \&r
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and
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.Ql \&k
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commands make no sense and are not recognized. Finally, the
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signal arguments to the continue and single step commands are
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ignored.
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.Sh NOTES
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.Nm Kdb
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normally runs at a priority level below the interrupt
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level of the clock and all devices; the level of the highest priority
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software interrupt. If the debugger is entered on the kernel's
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per-process stack at an ipl below its normal operating level it
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automatically switches to the interrupt stack to avoid potential
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overflow of the kernel stack. Should the debugger operate on
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the kernel stack the message
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.Ql (on kernel stack)
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will be printed
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on entry.
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.Pp
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Note also that because
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.Nm kdb
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uses input from the console to force entry to the debugger it may
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not be possible to force entry if the system hangs at a priority
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level higher than the console receiver interrupt.
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.Sh SEE ALSO
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.Xr adb 1
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.Sh HISTORY
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The
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.Nm
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debugging facility
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.Ud
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