docs/136666: Configure serial port for remote kernel debuging.

[Balazs]

>Number:         136666
>Category:       docs
>Synopsis:       Configure serial port for remote kernel debuging.
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-doc
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          change-request
>Submitter-Id:   current-users
>Arrival-Date:   Sat Jul 11 17:50:00 UTC 2009
>Closed-Date:
>Last-Modified:
>Originator:     Balazs
>Release:        8.0-CURRENT
>Organization:
-
>Environment:
:o)
>Description:
Please extend Developer's Handbook '10.6 On-Line Kernel Debugging Using Remote GDB' section with a similar note:

It is maybe necessary to enable a serial port for remote kernel debugging. 
The "gdb: no debug ports present" dmesg message means there is no serial ports
configured for remote debugging. Edit '/boot/device.hints' and edit/insert:

hint.uart.0.flags="0x80" or 
hint.sio.0.flags="0x80"

For details please consult man uart(4) or man sio(4) depending on the serial 
driver is in use.

Thank you!
>How-To-Repeat:

>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted: