[ was: [PATCH] Fix potential wrong-code issue in write_dso ]

On 15-03-19 16:12, Tom de Vries wrote:
> Hi,
> 
> The function write_dso has the responsibility to update:
> - the file offset of the sections, and
> - the file offset of the section header table.
> 
> It does this in two steps:
> - it calculates the effects of adding, removing and updating
>   debug sections
> - it makes sure the file offsets have the required alignment
> 
> The second step may or may not update the file offsets, but if it does, it
> requires the entries in the section header table to be in file offset
> order.
> 
> However, if the second step does not update the file offsets, no check on
> section header table order is done, which implies that the first step should
> be able to handle an unsorted section header table.
> 
> That is not the case for this update loop:
> ...
>   for (j = dso->ehdr.e_shstrndx + 1; j < dso->ehdr.e_shnum; ++j)
>     dso->shdr[j].sh_offset += len;
> ...
> 
> This loop adds an increase of the size of the section header string table to
> sections 'after' the section header string table.  But the after test here is
> implemented in terms of order in the section header table, which only works if
> if the section header table is sorted.
> 
> Fix this by rewriting the after test in terms of sh_offset:
> ...
>   for (j = 1; j < dso->ehdr.e_shnum; ++j)
>     if (dso->shdr[j].sh_offset
>         > dso->shdr[dso->ehdr.e_shstrndx].sh_offset)
>       dso->shdr[j].sh_offset += len;
> ...
> 
> OK for trunk?
> 

Cleaned up rationale and committed.

Thanks,
- Tom