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Re: Grub for ia64 - function descriptors
From: |
Hollis Blanchard |
Subject: |
Re: Grub for ia64 - function descriptors |
Date: |
Mon, 02 Oct 2006 21:17:51 -0500 |
On Mon, 02 Oct 2006 08:31:10 +0200, address@hidden said:
> Quoting Hollis Blanchard <address@hidden>:
>
> > On Fri, 2006-09-29 at 08:59 +0200, address@hidden wrote:
> > > Quoting Hollis Blanchard <address@hidden>:
> > >
> > > > On Thu, 2006-09-28 at 15:45 +0200, address@hidden wrote:
> > > > >
> > > > > if (grub_strcmp (name, "grub_mod_init") == 0)
> > > > > mod->init = (void (*) (grub_dl_t)) sym->st_value;
> > > > >
> > > > > This won't work on ia64 AFAIK.
> > > >
> > > > Can't this problem be solved with an architecture-specific macro?
> > > >
> > > > FWIW, 64-bit PowerPC also uses function descriptors. They look something
> > > > like:
> > > > long code_address
> > > > long table_of_contents
> > > > long unused
> > > >
> > > > The table_of_contents (TOC) value needs to be placed into r2 when
> > > > jumping at code_address (and of course the old one needs to be restored
> > > > when returning).
> > > Indeed, same issue.
> > >
> > > >I assume IA64 is similar here, and given that, a
> > > > module_jump function implemented in assembly by each architecture would
> > > > solve this problem.
> > > I'd prefer modules to export pointers. Seems to be easier to deal.
> >
> > I don't know what you mean; please elaborate (with pseudo-code if
> > possible).
>
> I'd propose modules export struct grub_dl. This struct contains init and
> fini
> functions pointers.
> Getting the address of a data structure is much more portable.
> Dealing with function pointers would be a matter of the relocator.
It looks like this is only done twice in the current code: mod->init and
mod->fini. Wouldn't it be easy to do this:
--- kern/dl.c 28 May 2006 23:01:43 -0000 1.12
+++ kern/dl.c 3 Oct 2006 02:15:51 -0000
@@ -380,9 +380,9 @@ grub_dl_resolve_symbols (grub_dl_t mod,
return grub_errno;
if (grub_strcmp (name, "grub_mod_init") == 0)
- mod->init = (void (*) (grub_dl_t)) sym->st_value;
+ mod->init = grub_dl_arch_func (sym->st_value);
else if (grub_strcmp (name, "grub_mod_fini") == 0)
- mod->fini = (void (*) (void)) sym->st_value;
+ mod->fini = grub_dl_arch_func (sym->st_value);
break;
case STT_SECTION:
-Hollis