Re: grub-pe2elf

[Christian Franke]

Hi Robert,

Robert Millan wrote:
> On a recent discussion on IRC, Bean pointed out that grub-pe2elf is essentially
> a workaround for a bug in objcopy.
>
>   

It is essentially a limitation of BFD: The object format specific 
backends are apparently not implemented such that conversion between 
different relocation formats is supported.

In particular, a relocation 'addend' (-4 in this case) is lost during 
conversion if source or target relocation format do not support it as 
separate field. Some conversions may work. PE -> ELF does not work, the 
problem is in both backends in this case.


> Bean explained that this bug is quite obvious.  It seems Christian sent them
> a patch, but it hasn't been applied (I don't know if it was rejected, or just
> ignored, Christian could you explain?).
>
>   

The patch was actually an ad-hoc approach to fix it in objcopy itself 
for the PE->ELF case only:
http://sourceware.org/ml/binutils/2007-10/msg00302.html

A generic solution which would have more chances to get accepted would 
require substantial work in BFD itself. Conversion between relocation 
formats is apparently rarely needed. A related bugzilla entry was 
reopened in 2005 and is idle since then:
http://sourceware.org/bugzilla/show_bug.cgi?id=970


> Later in July 2008, Bean added grub-pe2elf to the repository.
>
>   

Yes, and I really appreciated this :-)


> First of all, I'm worried that we have discussions to decide things and they
> are later forgotten or ignored.  Bean, please can you provide some explanation
> on what happened?
>
> Also, I think this commit should be reverted (at least the part that adds
> grub-pe2elf).  

I would regret this. Then you could also revert all my Cygwin related 
additions (some also included in Bean's r1726) because these no longer 
make much sense unless someone fixes BFD or maintains a ELF toolchain 
for Cygwin.


> Nevertheless, it's not an obligation for us to support win32.  As long as we
> can do it sanely, I'm fine with it, but I don't want to see GRUB dragged into
> a situation in which we need to preserve win32 support at all costs.
>
>   

$ find grub2 -type f -name '*.[ch]' | xargs cat | wc -l
128175

$ cat grub2/util/grub-pe2elf.c | wc -l
521

0.4% of the total LoC is IMO less than 'all costs' :-)

--
Regards
Christian Franke