[PATCH] Fix for reads of unallocated memory in ld

[Douglas B Rupp <rupp at adacore dot com>]

I don't have commit privileges, could someone please review, and if 
found satisfactory, apply this patch?

--Douglas Rupp
AdaCore

Patch attached for errors found with valgrind while working on 
arm-wrs-vxworks-ld, e.g.:

==13043== Invalid read of size 1
==13043==    at 0x4935A2: iterative_hash (hashtab.c:974)
...
==13043==  Address 0x66e0e1b is not stack'd, malloc'd or (recently) free'd

It's not specific to arm-wrs-vxworks.  The problem is there's a path 
through elf-eh-frame.c/skip_non_nops() that doesn't set the return value 
properly, and leaves it off by 1.  Later on this value, which should be 
0, causes a problem is in this bit of code also in bfd/elf-eh-frame.c:

      insns_end = skip_non_nops (insns, end, length, &set_loc_count);
...
      this_inf->size -= end - insns_end;
      if (insns_end != end && this_inf->cie)
        {
          cie->initial_insn_length -= end - insns_end;
          cie->length -= end - insns_end;
        }

If cie->initial_insn_length is 0, the subtraction underflows to 255 
which is a bogus value. When the hashing function gets ahold of the 
value, it starts reading unallocated memory.

Attachment: nops.diff.txt
Description: Text document