.\" Copyright (c) 2003 Hidetoshi Shimokawa
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
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.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
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.\" DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
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.Dd September 29, 2022
.Dt DCONSCHAT 8
.Os
.Sh NAME
.Nm dconschat
.Nd user interface to
.Xr dcons 4
.Sh SYNOPSIS
.Nm
.Op Fl brvwRT1
.Op Fl e Ar escape-char
.Op Fl h Ar hz
.Op Fl C Ar console_port
.Op Fl G Ar gdb_port
.Op Fl M Ar core
.Op Fl N Ar system
.Nm
.Op Fl brvwR1
.Op Fl h Ar hz
.Op Fl C Ar console_port
.Op Fl G Ar gdb_port
.Op Fl a Ar address
.Op Fl u Ar bus_num
.Fl t Ar target_eui64
.Sh DESCRIPTION
The
.Nm
utility is designed to provide a way for users to access
.Xr dcons 4
(dumb console device) on a local or remote system.
The
.Nm
utility interacts with
.Xr dcons 4
using
.Xr kvm 3
or
.Xr firewire 4 ,
and interacts with the user over TTY or TCP/IP.
To access remote
.Xr dcons 4
using
.Xr firewire 4 ,
you have to specify target EUI64 address using the
.Fl t
option. Physical DMA should be enabled on the target machine for access
via FireWire.
.Pp
The
.Nm
utility and the
.Xr dcons 4
driver communicate using 2 ports, one for the console port and another
for remote
.Xr gdb 1 Pq Pa ports/devel/gdb
port.
Users are supposed to access
.Nm
using TTY,
.Xr telnet 1
and
.Xr gdb 1 Pq Pa ports/devel/gdb .
You can specify listen ports for console and
.Xr gdb 1 Pq Pa ports/devel/gdb
port using the
.Fl C
and
.Fl G
options respectively.
The port number 0 has special meaning that
current TTY (stdin/stdout) is used instead of TCP/IP.
A negative port number will disable the port.
By analogy with
.Xr pty 4
device, the
.Xr dcons 4
acts as a slave device and
.Nm
acts as a master device with
.Nm telnetd .
.Pp
Typed characters are normally transmitted directly to
.Xr dcons 4 .
A escape character (the default is
.Ql ~
) appearing as the first character of a line is an escape signal; the
following are recognized:
.Bl -tag -width indent
.It Ic ~.
Drop the connection and exit.
.It Ic ~^G
Invoke kgdb on the terminal on which dconschat is running.
.It Ic ~^R
Reset the target over FireWire if a reset address is registered in Configuration ROM.
.It Ic ~^Z
Suspend the dconschat process.
.El
.Pp
The following options are supported.
.Bl -tag -width indent
.It Fl b
Translate Ctrl-C to ALT_BREAK (CR +
.Ql ~
+ Ctrl-B) on
.Xr gdb 1 Pq Pa ports/devel/gdb
port.
.It Fl r
Replay old buffer on connection.
.It Fl v
Verbose debug output.
Multiple
.Fl v
options increase verbosity.
.It Fl w
Listen on a wildcard address rather than localhost.
.It Fl R
Read-only.
Do not write anything to the
.Xr dcons 4
buffer.
.It Fl T
Enable ad-hoc workaround for the TELNET protocol to
remove unnecessary byte sequences.
It should be set when you access
.Nm
using
.Xr telnet 1 .
.It Fl 1
One-shot.
Read available buffer, then exit.
This implies the
.Fl r
option.
.It Fl e Ar escape-char
Specify escape character.
The default is '~'.
.It Fl h Ar hz
Specify polling rate.
The default value is 100.
.It Fl C Ar console_port
Specify the console port.
The default value is 0 (stdin/stdout).
.It Fl G Ar gdb_port
Specify
.Xr gdb 1 Pq Pa ports/devel/gdb
port.
The default value is \-1 (disabled).
.It Fl M Ar core
Specify core file.
.It Fl N Ar system
Specify system file such as
.Pa /boot/kernel/kernel .
.It Fl t Ar target_eui64
Specify the 64-bit extended unique identifier of the target,
and use FireWire to access remote
.Xr dcons 4 .
.It Fl a Ar address
Specify the physical I/O address of the
.Xr dcons 4
buffer.
See
.Xr dcons 4
for details.
If this option is not specified,
.Nm
tries to get the address from the Configuration ROM on the target.
You are supposed to enable
.Xr dcons_crom 4
on the target to omit this option.
.It Fl u Ar bus_num
Specify FireWire bus number.
The default is 0.
.El
.Sh FILES
.Bl -tag -width indent -compact
.It Pa /dev/fwmem0.0
.It Pa /dev/mem
.It Pa /dev/kmem
.El
.Sh EXAMPLES
To use
.Nm
with FireWire for remote
.Xr dcons 4 ,
you have to specify the EUI64 of the target.
You can obtain EUI64 by running
.Xr fwcontrol 8
without options.
The first EUI64 is of the host running
.Xr fwcontrol 8
and others on the bus follow.
.Bd -literal -offset indent
# fwcontrol
2 devices (info_len=2)
node           EUI64          status
   1  77-66-55-44-33-22-11-00      0
   0  00-11-22-33-44-55-66-77      1
.Ed
.Pp
The EUI64 does not change unless you change the hardware
as the ethernet address.
.Pp
Now we can run
.Nm .
.Bd -literal -offset indent
# dconschat -br -G 12345 -t 00-11-22-33-44-55-66-77
.Ed
.Pp
You will get console output of the target and login prompt if a
.Xr getty 8
is running on
.Xr dcons 4 .
You can break to DDB with ALT_BREAK (CR +
.Ql ~
+ Ctrl-B)
if
.Dv DDB
and
.Dv ALT_BREAK_TO_DEBUGGER
are enabled in the target kernel.
To quit the session, type CR +
.Ql ~
+
.Ql \&.
in the console port.
.Pp
Using
.Xr gdb 1 Pq Pa ports/devel/gdb
port is almost the same as remote
.Xr gdb 1 Pq Pa ports/devel/gdb
over serial line except
using TCP/IP instead of
.Pa /dev/cu* .
See
.Sx "On-line Kernel Debugging Using Remote GDB"
section of
.%T "The FreeBSD Developers Handbook"
and
.Xr gdb 4
for details.
.Bd -literal -offset indent
% gdb -k kernel.debug
(kgdb) target remote :12345
.Ed
.Pp
Once
.Xr gdb 1 Pq Pa ports/devel/gdb
is attached and you specified the
.Fl b
option to
.Nm ,
typing Ctrl-C in
.Xr gdb 1 Pq Pa ports/devel/gdb
causes a break to debugger.
.Pp
The following command gets the console log from the crash dump:
.Bd -literal -offset indent
# dconschat -1 -M vmcore.0 -N kernel.0
.Ed
.Pp
If you want access to the console using
.Xr telnet 1 ,
try the following:
.Bd -literal -offset indent
# dconschat -rTC 5555 &
# telnet localhost 5555
.Ed
.Pp
You may want to keep logging console output of several machines.
.Nm conserver-com
in the Ports collection may help you.
Insert the following lines in
.Pa conserver.cf :
.Bd -literal -offset indent
console local {
	master localhost;
	type exec;
	exec /usr/sbin/dconschat -rh 25;
}
console remote {
	master localhost;
	type exec;
	exec /usr/sbin/dconschat -rh 25 -t 00-11-22-33-44-55-66-77;
}
.Ed
.Sh SEE ALSO
.Xr gdb 1 Pq Pa ports/devel/gdb ,
.Xr telnet 1 ,
.Xr kvm 3 ,
.Xr dcons 4 ,
.Xr dcons_crom 4 ,
.Xr ddb 4 ,
.Xr firewire 4 ,
.Xr fwohci 4 ,
.Xr gdb 4 ,
.Xr eui64 5 ,
.Xr fwcontrol 8
.Sh AUTHORS
.An Hidetoshi Shimokawa Aq Mt simokawa@FreeBSD.org
.Sh BUGS
This utility is
.Ud