Re: readelf reporting of e_shstrndx is slightly wrong

[Nick Clifton]

Hi Mike,

> If the file has no section name string table, this member holds the value 
> |SHN_UNDEF|. 
> If the section name string table section index is greater than or equal to 
> |SHN_LORESERVE| (|0xff00|), this member has the value |SHN_XINDEX| (|0xffff|) 

> The current readelf -h seems to assume that if there are more than 0xff00 
> sections, then the shstrndx will also be past that.  But there is nothing to 
> prevent the section name string table from being section 1, in which case 
> e_shstrndx should just be 1.  But the readelf implementation has:
> 
>                else if (elf_header.e_shstrndx != SHN_UNDEF && 
> elf_header.e_shstrndx >= elf_header.e_shnum)
> 
>                    printf(_(“<corrupt: out of range>”));

I disagree.  The readelf code actually looks like this:

     if (filedata->section_headers != NULL
          && header->e_shstrndx == (SHN_XINDEX & 0xffff))
        printf (" (%u)", filedata->section_headers[0].sh_link);
      else if (header->e_shstrndx != SHN_UNDEF
               && header->e_shstrndx >= header->e_shnum)
        printf (_(" <corrupt: out of range>"));
   
There is no check that the file itself has more than 0xff00 sections.
Instead it checks to see if the e_shstrndx field is SHN_XINDEX and if
so it follows the link.  Otherwise it checks that the index is either
SHN_UNDEF or a valid section number.

Note - the use if "& 0xffff" in the above code is confusing, and looks
surplus to me, but I do not think that it makes any difference to the
behaviour.

Cheers
  Nick