[Gcl-devel] bfd coff back-end

[Aurelien Chanudet]

Hi Mike,

Sorry for the delay getting back to you, I'm fairly busy at the moment. 
I thought I would be more helpful in looking at the matter myself, so I 
installed mingw, compiled binutils 2.14 and ran a sample program to 
test dynamic loading. While there is probably more to it than what I 
relate below, here is a first issue :

Basically, there are two files of interest. The first one is coffcode.h 
and the second one is coff-i386.c. BFD relocation entries (of type 
arelent) have an address field, which is not an absolute address, but a 
section relative offset. As can be seen, this convention is enforced at 
coff-i386.c:144. However, this convention is violated at 
coffcode.h:5037. Running objdump -r on a sample object file reveals 
that COFF relocation entries have an r_vaddr field which looks like a 
section relative offset. Apparently, this section relative offset is 
being considered as an absolute address in coffcode.h, which is why we 
later get a segmentation violation. In coffcode.h, cache_ptr->address 
is set at line 5002, and then incorrectly adjusted at line 5037. The 
fix might be to zero out the section's vma (asect->vma) prior to 
calling bfd_get_relocated_section_contents in bfdtest.c, but I'm not 
100% sure of that. I'll continue investigating this when I have time.

Aurelien