GDB - The GNU Debugger
Upstream webpage: http://sources.redhat.com/gdb/
gdb support for hppa-linux was merged upstream in GDB version 6.2. Currently, there is no official maintainer for the hppa port. Would anybody like to volunteer?
Details about the hppa implementation
StackUnwinding describes the stack layout on hppa and how unwinding works.
A description of the DWARF debug format can be found at http://www.eagercon.com/dwarf/dwarf3std.htm
Currently there is a known problem in gdb with unwinding through static functions.