Re: relocation of shared libs not based at 0

[Colin Burgess <cburgess at qnx dot com>]

You already have architecture dependant code in fetch_link_map_offsets, couldn't
you do something similar for relocate_section_addresses?

On Wed, 8 Jan 2003, Kevin Buettner wrote:

> On Jan 8,  4:52pm, Kris Warkentin wrote:
> 
> > This works fine on QNX and (I assume) NetBSD so it looks rather like we just
> > have a difference of opinion on how the shared object loader should fill
> > things in.  We wanted to keep our linker's behaviour for some future
> > enhancements (pre-relocating shared objects on flash memory, etc.) so I was
> > hoping the fix below (Paul's code with some extra comments) might be
> > acceptable.  That way Paul and I could just define LM_ADDR_IS_NOT_LOAD_BASE
> > in our tm-<host>.h and we'd be off to the races.
> > 
> > static void
> > svr4_relocate_section_addresses (struct so_list *so,
> >                                  struct section_table *sec)
> > {
> > #if LM_ADDR_IS_NOT_LOAD_BASE
> >   /* On some platforms, (ie. QNX, NetBSD) LM_ADDR is the assigned
> >      address, not the offset.
> >      The addresses are formed as follows:
> >      LM_ADDR is the target address where the shared library file
> >      is mapped, so the actual section start address is LM_ADDR plus
> >      the section offset within the shared library file.  The end
> >      address is that plus the section length.  Note that we pay no
> >      attention to the section start address as recorded in the
> >      library header.
> >   */
> >    sec->endaddr = svr4_truncate_ptr (sec->endaddr - sec->addr +
> >       sec->the_bfd_section->filepos +
> >       LM_ADDR (so));
> >    sec->addr    = svr4_truncate_ptr (sec->the_bfd_section->filepos +
> >       LM_ADDR (so));
> > #else
> >   sec->addr    = svr4_truncate_ptr (sec->addr    + LM_ADDR (so));
> >   sec->endaddr = svr4_truncate_ptr (sec->endaddr + LM_ADDR (so));
> > #endif
> > }
> 
> The problem that I have with the above is that it's not possible to
> build a cross debugger that'll have shared library support for both
> Linux and NetBSD.
> 
> If we could somehow detect (perhaps via the osabi mechanism) that we
> have one of the lm-addr-is-not-load-base platforms and enable that
> code at runtime, I wouldn't mind...
> 
> Kevin
> 

-- 
cburgess@qnx.com