Always remote: [WIP/RFC] MIPS registers overhaul

[Andrew Cagney]

>> Another one (and it's a doozie) is that thread debugging won't work
>> due to the ABI specific libthread_db.so library that's dlopen'd by
>> RDA.  A native GDB (assuming that we did the necessary work to port it
>> to mips64-linux) would have the same problem.  We've kicked around
>> some ideas for fixing this problem in the past.  The only idea that
>> I've found compelling is from Alex Oliva (and perhaps others) who
>> suggested that it may be best for a "native" gdb to spawn an
>> ABI-specific rda or gdbserver and connect to it automatically.
> 
> 
> TBH, I'd rather like to see us develop an extended and more extensible
> remote protocol (on any number of people's TODO lists already!) and do
> _all_ native debugging this way.

FYI, one of the long ago identified scalability problems (by HP) with 
GDB was all the memory moving/sucking that it did.  HP were looking for 
ways to MMAP memory and avoiding doing all the copies.  Having GDB suck 
memory through a straw would be a odds with that.

Note, I'm talking here about megabytes of memory - people try to use the 
debuger to draw plots of their fortran arrays.

Andrew