163 lines
5.0 KiB
Groff
163 lines
5.0 KiB
Groff
.\"
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.\" Copyright (c) 2007 Robert N. M. Watson
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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(s), this list of conditions and the following disclaimer as
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.\" the first lines of this file unmodified other than the possible
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.\" addition of one or more copyright notices.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice(s), 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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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
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.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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.\" DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
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.\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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.\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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.\" 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 SUCH
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.\" DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd 26 December, 2007
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.Dt textdump 4
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.Os
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.Sh NAME
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.Nm textdump
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.Nd textdump kernel dumping facility
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.Sh SYNOPSIS
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.Cd options KDB
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.Cd options DDB
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.Sh DESCRIPTION
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The
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.Nm
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facility allows the capture of kernel debugging information to disk in a
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human-readable rather than the machine-readable form normally used with
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kernel memory dumps and minidumps.
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This representation, while less complete in that it does not capture full
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kernel state, can provide debugging information in a more compact, portable,
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and persistent form than a traditional dump.
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By combining
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.Nm
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with other
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.Xr DDB 4
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facilities, such as scripting and output capture, detailed bug information
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can be captured in a fully automated manner.
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.Sh FORMAT
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.Nm
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data is stored in a dump partition in the same style as a regular memory
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dump, and will be automatically extracted by
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.Xr savecore 8
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if present on boot.
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.Pp
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.Nm
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files are stored in the
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.Xr tar 5
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format, and consist of one or more text files, each storing a particular type
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of debugging output.
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The following parts may be present:
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.Bl -tag -width version.txt
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.It Pa ddb.txt
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Captured
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.Xr DDB 4
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output, if the capture facility has been used.
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May be disabled by clearing the
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.Dv debug.ddb.textdump.do_ddb
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sysctl.
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.It Pa config.txt
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Kernel configuration, if
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.Od options INCLUDE_CONFIG_FILE
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has been compiled into the kernel.
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May be disabled by clearing the
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.Dv debug.ddb.textdump.do_config
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sysctl.
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.It Pa msgbuf.txt
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Kernel message buffer, including recent console output if the capture
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facility has been used.
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May be disabled by clearing the
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.Dv debug.ddb.textdump.do_msgbuf
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sysctl.
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.It Pa panic.txt
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Kernel panic string, if the kernel panicked before the dump was generated.
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May be disabled by clearing the
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.Dv debug.ddb.textdump.do_panic
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sysctl.
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.It Pa version.txt
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Kernel version string.
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My be disabled by clearing the
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.Dv dbeug.ddb.textdump.do_panic
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sysctl.
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.El
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.Pp
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Kernel textdumps may be extracted using
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.Xr bsdtar 1 .
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.Sh CONFIGURATION
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The
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.Nm
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facility is enabled as part of the kernel debugger using
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.Cd options KDB
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and
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.Cd options DDB .
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By default, kernel dumps generated on panic or via explicit requests for a
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dump will be regular memory dumps; however, by using the
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.Ic textdump set
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command in
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.Xr DDB 4 ,
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or by setting the
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.Dv debug.ddb.textdump.pending
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sysctl to 1 using
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.Xr sysctl 8 ,
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it is possible to request that the next dump be a textdump.
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.Pp
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If at the
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.Xr DDB 4
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command line, the commands
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.Ic textdump set ,
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.Ic textdump status ,
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and
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.Ic textdump unset
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may be used to set, query, and clear the textdump pending flag.
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.Pp
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As with regular kernel dumps, a dump partition must be automatically or
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manually configured using
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.Xr dumpon 8 .
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.Sh EXAMPLES
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In the following example, the script
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.Dv kdb.enter.panic
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will run when the kernel debugger is entered as a result of a panic, enable
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output capture, dump several useful pieces of debugging information, and then
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invoke panic in order to force a kernel dump to be written out followed by a
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reboot:
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.Bd -literal -offset indent
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script kdb.enter.panic=textdump set; capture on; show allpcpu; bt;
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ps; alltrace; show alllock; call doadump; reset
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.Ed
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.Pp
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In the following example, the script
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.Dv kdb.enter.witness
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will run when the kernel debugger is entered as a result of a witness
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violation, printing lock-related information for the user:
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.Bd -literal -offset indent
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script kdb.enter.witness=show locks
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.Ed
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.Sh SEE ALSO
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.Xr bsdtar 1 ,
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.Xr ddb 4 ,
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.Xr tar 5 ,
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.Xr dumpon 8 ,
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.Xr savecore 8 ,
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.Xr sysctl 8
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.Sh AUTHORS
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The
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.Nm
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facility was created by
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.An Robert N. M. Watson .
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