.\"     $OpenBSD: kgdb.7,v 1.7 2007/05/31 19:19:58 jmc Exp $
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.\" Copyright (c) 2001 Hugh Graham
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.Dd $Mdocdate: May 31 2007 $
.Dt KGDB 7
.Os
.Sh NAME
.Nm kgdb
.Nd remote kernel debugging with gdb
.Sh DESCRIPTION
Should a programmer be dissatisfied with the
.Ox
kernel's internal debugger
.Xr ddb 4 ,
and have appropriate hardware available, a kernel with
.Cm option KGDB
may be built to effect remote debugging with
.Xr gdb 1
instead.
.Pp
To prepare for debugging over serial line one would:
.Pp
.Bl -bullet -offset 3n -compact
.It
Obtain a second system and a crossover serial cable.
.It
Connect the systems and test the cable.
.It
Build a kernel with
.Cm option KGDB
and
.Cm makeoptions DEBUG="-g" .
.It
Copy the resultant
.Pa bsd.gdb
to the control system, and boot the corresponding
.Pa bsd
on the target system.
.It
On the control system, run gdb on the kernel just copied.
.It
Issue the command "target remote /dev/<serial port>" within gdb.
The target system should enter
.Nm
at this point.
.It
Debug as normal and detach when done, the target should resume normal operation.
.El
.Sh SEE ALSO
.Xr gdb 1 ,
.Xr ddb 4 ,
.Xr options 4
.Pp
gdb info documents and online documentation.
.Sh CAVEATS
The remote connection will introduce certain latencies a local debugger
would not see.
.Pp
Not available on all architectures.