[ColdFire 46/63] Add support for unwinding through signal handlers

[Roman Zippel]

Hi,

On Wed, 10 Jan 2007, Richard Sandiford wrote:

> This patch adds support for unwinding through linux signal trampolines.
> Only the ColdFire version has been properly tested, but I hope the 680x0
> version stands a good chance of being OK.

I see a few problems:
- it assumes a fixed glibc with a correct ucontext
- d0/d1/a0/a1 aren't restored from sigcontext
- unconditional fp restore (in case of an idle fpu, it would restore 
  random data)
- signal_frame isn't set
- the knowledge about the stack layout (the footer structs) is not a 
  good idea, that part is not guaranteed, a pointer to the context is 
  passed on the stack.

bye, Roman