Date: Sat, 21 Feb 2009 11:06:21 -0800 From: "Peter Craft" <craft@alacritech.com> To: <freebsd-questions@freebsd.org> Subject: Re: KGDB connection failure - Please help, I'm desparate! (=> or desperate) Message-ID: <071201c99457$7c1eaae0$510a010a@alacritech.com>
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First off - Make that "desperate". Sorry.
Second, an update..
I've modified remote.c in gdb to print the data coming across the
serial line. When I boot with -d and enter "gdb" followed by "s", =
absolutely
nothing comes across the serial line - readchar times out every time.
If I then reboot without -d (with the same modified gdb running) and set =
console=3Dcomconsole
I see all of the expected console characters read by readchar.
So it appears that the gdb stub on the target isn't outputing any data =
to
the serial line whatsoever. Again, I have KDB, DDB, and GDB set in the
configuration file and the sio flags set to 0x90 (I've tried 0xc0 as =
well)
in the loader.conf file. Furthermore, when I boot with -d I see the
message:
GDB: Current port: sio
Can anyone think of a reason why the target isn't outputting debug =
packets to
the serial port? Can anyone suggest a method to debug a debugger?
Thanks
----- Original Message -----=20
From: Peter Craft=20
To: freebsd-questions@freebsd.org=20
Sent: Friday, February 20, 2009 3:28 PM
Subject: KGDB connection failure - Please help, I'm desparate!
I've been trying for three days to get KGDB to work.
I've followed the instructions here:
=
http://www.freebsd.org/doc/en_US.ISO8859-1/books/developers-handbook/kern=
eldebug-online-gdb.html
and here:
http://www.lemis.com/grog/Papers/Debug-tutorial/tutorial.pdf
without success. Specifically, I've rebuilt my kernel with:
makeoptions DEBUG=3D-g # Build kernel with gdb(1) =
debug symbols
..
options KDB
options DDB
options GDB
My "boot.config" file contains -P and my /boot/loader.conf file =
contains:
hint.sio.0.flags=3D"0x90"
When I issue the "boot -d" on the target, the system breaks in to the =
"db" prompt
as expected, at which point I enter "gdb" followed by "s". All of =
which seems to
work perfectly.
On the debugger side I enter kgdb with "kgdb -r /dev/cuad0 -v =
kernel.debug"
from the build directory and I get:
Ignoring packet error, continuing...
Ignoring packet error, continuing...
Ignoring packet error, continuing...
Couldn't establish connection to remote target
Malformed response to offset query, timeout
If I boot the remote system with "set console=3Dcomconsole", I'm able =
to communicate
across the serial line as a console, so I believe that the serial =
ports and cable are
functioning properly. I just can't get gdb to connect.
Can anyone offer any suggestion on what to try next? Or tips on how =
to go
about debugging the problem? This is with FreeBSD 7.1.
Thanks in advance,
Pete
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