Add "ddb capture print" and "ddb capture status" commands do ddb(8),

alowing the DDB output capture buffer to be easily extracted from
user space.  Both of these commands include -M/-N arguments, allowing
them to be used with kernel crash dumps (or /dev/mem).

This makes it easier to use DDB scripting and output capture with
minidumps or full dumps rather than with text dumps, allowing DDB
output (scripted or otherwise) to be easily extracted from a crash
dump.

MFC after:	1 week
Discussed with:	brooks, jhb

1 files changed, 39 insertions, 2 deletions

diff --git a/sbin/ddb/ddb.8 b/sbin/ddb/ddb.8
index 0165f56..90ceb63 100644
--- a/sbin/ddb/ddb.8
+++ b/sbin/ddb/ddb.8
@@ -1,5 +1,5 @@
 .\"-
-.\" Copyright (c) 2007 Robert N. M. Watson
+.\" Copyright (c) 2007-2008 Robert N. M. Watson
 .\" All rights reserved.
 .\"
 .\" Redistribution and use in source and binary forms, with or without
@@ -25,7 +25,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd April 4, 2008
+.Dd April 24, 2008
 .Dt DDB 8
 .Os
 .Sh NAME
@@ -33,6 +33,16 @@
 .Nd "configure DDB kernel debugger properties"
 .Sh SYNOPSIS
 .Nm
+.Cm capture
+.Op Fl M core
+.Op Fl N system
+.Cm print
+.Nm
+.Cm capture
+.Op Fl M core
+.Op Fl N system
+.Cm status
+.Nm
 .Cm script
 .Ar scriptname
 .Nm
@@ -67,6 +77,33 @@ utility.
 Whitespace at the beginning of lines will be ignored as will lines where the
 first non-whitespace character is
 .Ql # .
+.Sh OUTPUT CAPTURE
+The
+.Nm
+utility can be used to extract the contents of the
+.Xr ddb 4
+output capture buffer of the current live kernel, or from the crash dump of a
+kernel on disk.
+The following debugger commands are available from the command line:
+.Bl -tag -width indent
+.It Xo
+.Ic Cm capture
+.Op Fl M Ar core
+.Op Fl N Ar system
+.Cm print
+.Xc
+Print the current contents of the
+.Xr ddb 4
+output capture buffer.
+.It Xo
+.Ic Cm capture
+.Op Fl M Ar core
+.Op Fl N Ar system
+.Cm status
+.Xc
+Print the current status of the
+.Xr ddb 4
+output capture buffer.
 .Sh SCRIPTING
 The
 .Nm