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Date: Wed, 01 Nov 2006 10:10:10 -0800
From: Julian Elischer <julian@elischer.org>
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To: John Baldwin <jhb@freebsd.org>
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Cc: freebsd-current@freebsd.org
Subject: Re: remote gdb, kgdb and ddb
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John Baldwin wrote:
> On Tuesday 31 October 2006 20:13, Julian Elischer wrote:
>> it's been a bew years since I did this..
>>
>> some questions..
>>
>> why kgdb instead of gdb -k ?
>>
>> for remote, gdb seems to work fine
>> kgdb -r /dev/cuad0 kernel.debug   thinks it's working but seems to get 
>> confused a lot..
> 
> No idea, ask marcel perhaps.  I only use kgdb on coredumps.
> 
>> gdb with the following .gdbinit file seems to work as well.
>>   file kernel.debug
>>   set verbose 1
>>   set remotebreak 1
>>   set remotebaud 9600
>>   set remotedevice /dev/cuad0
>>   target remote /dev/cuad0
>>
>> though I'm not convinced I'm seeing the last frame in which the
>> trap occurs. (ddb shows one  more frame).
> 
> This is one of the things kgdb fixes (it has frame sniffers for trapframes).
>  
>> Now that I have my machine in remote gdb, the documentation
>> (as sparse as it is) doesnt't say how to make the machine reboot.
>>
>> from ddb I can do 'call cpu_reset' which seems to work, but
>> I haven't succedded in making gdb do anything similar,
>> nor to drop back into ddb. At one stage 'detach' used to do that
>> but it seems to have stopped working.
> 
> Try the following from src/tools/debugscripts/gdbinit.kernel:
> 
> # Switch back to ddb
> define ddb
> set boothowto=0x80000000
> s
> end
> document ddb
> Switch back to ddb.
> end
> 
cool

I'll try it today.

> I think I used to use that a few years ago.
>