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

[Dalibor Topic]

Hi Mark,

Mark and Janice Juszczec wrote:
> 
> 
> 
>>
>> I'm not familiar with uisng gdb over wire, but judging by 
>> http://sources.redhat.com/gdb/onlinedocs/gdb_19.html#SEC174 you need 
>> to make sure your GDB on the PC was configured and built with 
>> `--target=mips-idt-ecoff'.
>>
> 
> Yes, it was.  Its odd that the html doc you reference says I should be 
> able to do:
> 
> target r3900 <dev> to use "Densan DVE-R3900 ROM monitor for Toshiba 
> R3900 Mips."
> 
> because when I do help targets from gdb (configured with 
> --target=mips-idt-ecoff) r3900 is not in the list.

That sounds like a good question for the gdb mailing list ;)

>> the other choice may be to use the gdbserver program on the mipsel
> 
> 
> I tried this.  After stripping, gdbserver is too big to put on the Helio 
> with kaffe, rt.jar, the kernel, etc.

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.

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].

You'd also have to change kaffe's main() to add
set_debug_traps();
breakpoint();
at the beginning.

Note that I have never done this myself, that's basically the 
information I gathered by googling around for a while.

cheers,
dalibor topic

[1] include/asm-mips/gdb-stub.h and arch/mips/kernel/gdb-stub.c, 
possibly gdb-low.S as well.
[2] http://sources.redhat.com/gdb/download/onlinedocs/gdb_18.html#SEC147