Re: [Qemu-devel] Re: Debugging a 64-bit kernel in qemu

[Markus Duft]

On 01/03/2011 12:15 PM, Jan Kiszka wrote:
[snip]
>>
>> 1) is this a problem with qemu or was qemu "fixed" and gdb has a problem?
>>    (that's why i CCd the gdb list ;)).
>> 2) is there any plan to fix this issue?
>> 3) is there some kind of workaround i can use (i'd be happy with an 
>> ugly/unsupported patch too, since i build all my stuff myself ;)).
> 
> You see the effects of a workaround in qemu for gdb shortcomings on x86.
> See e.g. http://thread.gmane.org/gmane.comp.emulators.qemu/80327, there
> should be some threads on the gdb list as well.

Hmm, from the thread i read, that it should be possible to interrupt the code 
from gdb (by pressing CTRL-C), and set a 64 bit breakpoint then? In case this 
should work: it doesn't. I'm getting the very same packet too long error, as 
soon as i try to do _anything_ with the debugger. so, actually, the state this 
is in is completely unusable to debug 64 bit code. i cannot find any way to do 
it. 

actually, i find that Ted Harkington was right: in 0.11.1 i can debug 32 bit 
code with qemu-system-x86_64 well enough (which means i debugged all the 32 bit 
part of my kernel without ever seen _any_ problem/non-working 
feature/whatever). wouldn't it be better to have 64 bit debugging working in 
the 64 bit version, with 32 bit mode working mostly (with whatever small 
issues), rather than just completely dooming 64 bit debugging...?

any further ideas?

BTW, i did look around a little for this problem before (although i wasn't 
aware of the thread you pointed me to). All those threads don't propose any 
solution other than "fix gdb", which may or may not take ages.

Regards, Markus

> 
> Jan
>