At 05:21 PM 10/25/00 +0100, Nicholas Clark wrote:
>On Wed, Oct 25, 2000 at 12:05:22PM -0400, Dan Sugalski wrote:
> > At 05:02 PM 10/25/00 +0100, Nicholas Clark wrote:
> > >On Wed, Oct 25, 2000 at 11:45:54AM -0400, Chaim Frenkel wrote:
> > > > I vaguly can see a TIL that uses machine code linkage (real machine
> code
> > > > jumps) that perhaps could use relative addressing as not needing
> > > > relocation. But I'm not sure that all architectures support long enough
> > > > relative jumps/calls.
> > >
> > >Specific example where you can't:
> > >on ARM, the branch instructions (B and BL) are PC relative, but only have
> > >a 24 bit offset field. The address space is (now) 32 bit, so there's parts
> > >you can't reach without either calculating addresses (in another register)
> > >and MOVing them to the PC, or loading the PC from a branch table in
> memory.
> >
> > I think the Alphas can be the same, though I vaguely remember the offset
> > being something like 32 bits. I'm not sure we'd trip over either, but the
> > possibility does exist.
> >
> > No matter what we do we're going to have fixup sections of some sort in
> the
> > shared code that gets loaded in. There's no real way around that.
>
>"fixup sections" sound horribly like something I've read in association
>with a.out or ELF shared libraries. (I forget which)
Both, though they may call it something else. As far as I know, *everyone*
who does shared libraries has some sort of runtime fixup that needs to be
done. I don't think you can get away from it.
Dan
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