Add textdump(4) man page to describe the textdump facility and provide

some stock formulas for use.

Update ddb(4) to reference the textdump(4) page, list the textdump
commands, and suggest using them with scripts and output capture.
Update HISTORY section.

Hook up textdump(4) to build.

MFC after:	3 months

1 files changed, 162 insertions, 0 deletions

diff --git a/share/man/man4/textdump.4 b/share/man/man4/textdump.4
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+.\"
+.\" Copyright (c) 2007 Robert N. M. Watson
+.\" All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice(s), this list of conditions and the following disclaimer as
+.\"    the first lines of this file unmodified other than the possible
+.\"    addition of one or more copyright notices.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice(s), this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
+.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+.\" DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
+.\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+.\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+.\" CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
+.\" DAMAGE.
+.\"
+.\" $FreeBSD$
+.\"
+.Dd 16 December, 2007
+.Dt textdump 4
+.Os
+.Sh NAME
+.Nm textdump
+.Nd textdump kernel dumping facility
+.Sh SYNOPSIS
+.Cd options KDB
+.Cd options DDB
+.Sh DESCRIPTION
+The
+.Nm
+facility allows the capture of kernel debugging information to disk in a
+human-readable rather than the machine-readable form normally used with
+kernel memory dumps and minidumps.
+This representation, while less complete in that it does not capture full
+kernel state, can provide debugging information in a more compact, portable,
+and persistent form than a traditional dump.
+By combining
+.Nm
+with other
+.Xr DDB 4
+facilities, such as scripting and output capture, detailed bug information
+can be captured in a fully automated manner.
+.Sh FORMAT
+.Nm
+data is stored in a dump partition in the same style as a regular memory
+dump, and will be automatically extracted by
+.Xr savecore 8
+if present on boot.
+.Pp
+.Nm
+files are stored in the
+.Xr tar 5
+format, and consist of one or more text files, each storing a particular type
+of debugging output.
+The following parts may be present:
+.Bl -tag -width version.txt
+.It Pa ddb.txt
+Captured
+.Xr DDB 4
+output, if the capture facility has been used.
+May be disabled by clearing the
+.Dv debug.ddb.textdump.do_ddb
+sysctl.
+.It Pa config.txt
+Kernel configuration, if
+.Od options INCLUDE_CONFIG_FILE
+has been compiled into the kernel.
+May be disabled by clearing the
+.Dv debug.ddb.textdump.do_config
+sysctl.
+.It Pa msgbuf.txt
+Kernel message buffer, including recent console output if the capture
+facility has been used.
+May be disabled by clearing the
+.Dv debug.ddb.textdump.do_msgbuf
+sysctl.
+.It Pa panic.txt
+Kernel panic string, if the kernel panicked before the dump was generated.
+May be disabled by clearing the
+.Dv debug.ddb.textdump.do_panic
+sysctl.
+.It Pa version.txt
+Kernel version string.
+My be disabled by clearing the
+.Dv dbeug.ddb.textdump.do_panic
+sysctl.
+.El
+.Pp
+Kernel textdumps may be extracted using
+.Xr bsdtar 1 .
+.Sh CONFIGURATION
+The
+.Nm
+facility is enabled as part of the kernel debugger using
+.Cd options KDB
+and
+.Cd options DDB .
+By default, kernel dumps generated on panic or via explicit requests for a
+dump will be regular memory dumps; however, by using the
+.Ic textdump set
+command in
+.Xr DDB 4 ,
+or by setting the
+.Dv debug.ddb.textdump.pending
+sysctl to 1 using
+.Xr sysctl 8,
+it is possible to request that the next dump be a textdump.
+.Pp
+If at the
+.Xr DDB 4
+command line, the commands
+.Ic textdump set ,
+.Ic textdump status ,
+and
+.Ic textdump unset
+may be used to set, query, and clear the textdump pending flag.
+.Pp
+As with regular kernel dumps, a dump partition must be automatically or
+manually configured using
+.Xr dumpon 8 .
+.Sh EXAMPLES
+In the following example, the script
+.Dv kdb.enter.panic
+will run when the kernel debugger is entered as a result of a panic, enable
+output capture, dump several useful pieces of debugging information, and then
+invoke panic in order to force a kernel dump to be written out followed by a
+reboot:
+.Bd -literal -offset indent
+script kdb.enter.panic=capture on;textdump set;bt;show allpcpu;
+  ps;alltrace;show alllock;panic
+.Ed
+.Pp
+In the following example, the script
+.Dv kdb.enter.witness
+will run when the kernel debugger is entered as a result of a witness
+violation, printing lock-related information for the user:
+.Bd -literal -offset indent
+script kdb.enter.witness=show locks
+.Ed
+.Sh SEE ALSO
+.Xr bsdtar 1 ,
+.Xr ddb 4 ,
+.Xr tar 5 ,
+.Xr dumpon 8 ,
+.Xr savecore 8 ,
+.Xr sysctl 8
+.Sh AUTHORS
+The
+.Nm
+facility was created by
+.An Robert N. M. Watson .