[patch 0/3, nios2] unbreak nios2-linux-gnu GDB

[Sandra Loosemore <sandra@codesourcery.com>]

GDB support for nios2-linux-gnu became broken during the time when glibc 
and kernel support for that target was transitioning to the upstream 
repositories.  Both ports were accepted around the first of the year, 
but then the initial 3.19 kernel was not usable for testing due to some 
unrelated problems with the ethernet support, it took a long time to 
track down a bug that caused a kernel hang, and then we ran into some 
additional bugs with kernel cache flushing.  The icache flush issues 
were fixed in time for the 4.0 kernel release and GDB is working pretty 
well with that kernel version now for manual use, but to get consistent 
results from automated testing I had to apply an additional local patch 
to flush the dcache more aggressively.  I expect some version of that 
will make it into future kernel releases since Altera is aware of the 
trouble now.

There are 3 patches:

(1) revert to using "trap 31" for breakpoints
(2) use PTRACE_GETREGSET/SETREGSET in gdbserver
(3) fixes for new implementation of signal handler trampolines

Since the old out-of-tree kernel/glibc ports are now obsolete, we 
haven't tried to maintain backward compatibility in these patches.

Yao, I noticed that you haven't updated your e-mail address in 
MAINTAINERS; are you still acting as nios2 maintainer?

-Sandra