MIPS remote debugging support (Was: Re: [kaffe] mipsel SIGSEGV)

[Dalibor Topic]

Hi Mark,

Mark and Janice Juszczec wrote:
> 
> Dalibor and all
> 
> Greetings from frosty NE Ohio.

It's cold over here in SW Germany as well, but at least we had sunshine 
this week. ;)

> Dalibor wrote:
> 

>> I guess there are two more possibilities:
>>
>> a) using kgdb to debug the kernel. Probably quite slow, if it works at 
>> all. You need a kernel that's compiled with kgdb support.
>>
> 
> Do you mean track back to kaffe from where the kernel generates the 
> SIGSEGV?

Yes, but it might be a little complicated. I don't really know how 
convenient it would be. Especially since you're trying to debug a 
stripped kaffe binary in kgdb ... so I doubt the stacktrace would be 
very useful, even if you managed to get it to work.

>> b) Adding support for gdb stubs for mips to kaffe. There is a 
>> mips-stub.c in the linux kernel sources [1] and there is some 
>> documentation on using remote stubs [2].
>>
> 
> We are thinking alike ;-)  This is the next step in my plan.  Over the 
> weekend, I dug out mips-stub.c (ok, in my kernel source its called 
> gdb-stub.c).   I've been researching what gdb required stuff is present, 
> is missing and so on.

I think that's the best chioce. I believe Tim did some work on JanosVM 
on bare metal arm architecture, but I think the JanosVM developers used 
their own networking stack, and didn't use gdb stubs. I've CC:ed him, he 
might be able to describe their experences with remote debugging.

> Do any of the kaffe mips users have mipsel appropriate debugging stubs 
> lying around. that I can look at?  I can't believe I'm the first guy to 
> do this.

Kevin Kissel would be the one to ask. I've CC:ed him as well. Atsushi 
Nemoto contributed some fixes for mipsel as well recently (that I still 
have to check in, I believe), so I've CC:ed him, too.

Now that 1.1.3 is out, I plan to go over the patch queue, and check all 
the stuff in, that's been accumulating out there.

cheers,
dalibor topic