link_elf.c vs link_elf_obj.c ?

[Kostik Belousov]

On Mon, Feb 05, 2007 at 04:00:38AM -0800, Luigi Rizzo wrote:
> On Mon, Feb 05, 2007 at 01:55:53PM +0200, Kostik Belousov wrote:
> > On Fri, Feb 02, 2007 at 05:27:56PM -0800, Luigi Rizzo wrote:
> > > does anyone know what is the difference between these two files ?
> > > They seem to do two similar but slightly different things related
> > > to elf file loading.
> > > 
> > > But diff shows large pieces of common code, and there is even
> > > more commonality if you factor out whitespace changes and
> > > variable renaming.
> > 
> > ELF specification defines 3 kinds of objects (putting core files aside);
> > - executables
> > - shared objects (AKA .so)
> > - relocatable objects (AKA .o, created by assembler).
> > Executables and .so are usually created by linker, while relocatables are the
> > assembler output (although ld -r can glue several .o files into one).
> > Executables and .so are in some sense finalized, and they contain a tables
> > that are useful for dynamic linker. Also, they usually carry different kind
> > of relocations then relocatables.
> > 
> > Now, in-kernel dynamic linker used for linking newly-loaded kld, shall deal
> > with either .so-kind of modules (on FreeBSD, all arches except amd64), or
> > relocatables (amd64). Two linkers you found deal with .so-kind (link_elf.c)
> > or relocatables (link_elf_obj.c).
> > 
> > Reasons why amd64 cannot use shared objects for kld mostly caused by
> > toolchains limitations and CPU architecture (it is impossible to create
> > working non-PIC .so there).
> > 
> > Note that Solaris uses relocatables for modules.
> 
> so, if one had to write a few lines of comment on top of each
> of these two files to tell what they do and how they differ,
> what would you write ?

As I said, link_elf.c is linker for kld's that are shared objects, while
link_elf_obj.c - for relocatables.
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