kgdb debugging

[Navdeep Parhar]

On Tue, Oct 7, 2008 at 10:53 AM, alan yang <alancyang at gmail.com> wrote:
> Could people shed some light how to get remote debugging going, must
> be something that i overlooked, really appreciate.
>

Do you have the right flags for sio or uart in /boot/device.hints?  I
have this (for a recent HEAD)::
hint.uart.0.flags="0x90"

You are probably using sio as it is a FreeBSD7 system.  From the man
page of sio (the part that talks about flags)::
...
0x00080   use this port for remote kernel debugging
...

Make sure you have this bit set.

Regards,
Navdeep


> Two FreeBSD7 systems, target and development, connected with null
> modem cable on each's COM1.
>
> step 1)
>        -  rebuild kernel with following options:
>                options         DDB
>                options         KDB
>                options         GDB
>
>                makeoptions     DEBUG=-g
>
> step 2)
>        -  from development system
>                cd to /usr/src/sys/i386/comiple/MYKERNEL
>                kgdb -r /dev/cuad0 kernel.debug
>
>                it displays the following:
>                Switching to remote protocol
>                Ignoring packet error, continuing
>                        .........
>                Couldn't establish connection to remote target
>                Malformed response to offset query, timeout
>
> step 3)
>        -  from targetsystem:
>                1.  Ctrl + Alt + Esc to go into db
>                2.  from db> type gdb
>                3.  it displays: "The remote GDB backend could not be selected"
>
>
>
> On Mon, Oct 6, 2008 at 5:12 PM, alan yang <alancyang at gmail.com> wrote:
>> the problem is, when entering gdb from db as described in the following:
>> --
>> Enter ing gdb from ddb
>> In FreeBSD you can build a kernel with support for both ddb and gdb.
>> You can then
>> change backwards and forwards between them. For example, if you're in
>> ddb, you can
>> go to gdb like this:
>> db> gdb
>> Next trap will enter GDB remote protocol mode
>> db> si step a single instruction to reenter ddb
>> --
>> after typing gdb command, it says: "The remote GDB backend could not
>> be selected"
>> that i am not sure what this indicates; looking at subr_kdb.c, wonder
>> maybe kdb_dbbe_set is not set?  seems kdb_dbbe_set is not referenced
>> anywhere, not sure how to get it right.
>>
>> thanks for shed some light ...
>>
>> On Mon, Oct 6, 2008 at 4:26 PM, Pietro Cerutti <gahr at freebsd.org> wrote:
>>> -----BEGIN PGP SIGNED MESSAGE-----
>>> Hash: SHA512
>>>
>>> alan yang wrote:
>>> | hi, there,
>>> |
>>> | wonder people can shed some lights on remote debugging.  i have
>>> | freebsd7 configured with option DDB / KDB / GDB but after entering the
>>> | db on the target system the command gdb gives "the remote GDB backend
>>> | could not be selected".
>>> |
>>> | i browsed through the mailing list, and do find 1 similar post but
>>> | without answer.
>>> |
>>> | thanks in advance & apology if i overlooked things ...
>>>
>>> I suggest the following tutorial:
>>> http://www.lemis.com/grog/Papers/Debug-tutorial/tutorial.pdf
>>>
>>> Have fun :)
>>>
>>> |
>>> | cheers,
>>> | alan
>>> | _______________________________________________
>>> | freebsd-hackers at freebsd.org mailing list
>>> | http://lists.freebsd.org/mailman/listinfo/freebsd-hackers
>>> | To unsubscribe, send any mail to "freebsd-hackers-unsubscribe at freebsd.org"
>>>
>>>
>>> - --
>>> Pietro Cerutti
>>> gahr at FreeBSD.org
>>>
>>> PGP Public Key:
>>> http://gahr.ch/pgp
>>>
>>> -----BEGIN PGP SIGNATURE-----
>>> Version: GnuPG v2.0.9 (FreeBSD)
>>>
>>> iEYEAREKAAYFAkjqnpQACgkQwMJqmJVx945RSwCgoDb0JTr8LSFDB1vpAbGUjb76
>>> ZH0An19HpFVJJTUB5/XnyZc0pIDzgxc3
>>> =6Pdm
>>> -----END PGP SIGNATURE-----
>>>
>>
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