[libunwind] Feature request: Get an unw_dyn_info_t* from an address

[Johan Walles]

We sometimes unload dynamically generated code from memory.  When we do that we 
need to tell libunwind about it.  We do that by calling 
_U_dyn_cancel(unw_dyn_info_t *di).  For calling that function we need a pointer 
to the function's unw_dyn_info_t.

We can keep track of that pointer ourselves.  However, since libunwind already 
does (otherwise, how could it unwind the stack?), we'd prefer being able to ask 
libunwind for the unw_dyn_info_t* corresponding to a certain address.

Is that easily doable?  What kind of complexity would we be looking at for 
getting that information?  Would we be better off storing that information 
ourselves?

  Cheers //Johan