This patch is to introduce multiboot 2 loading capabilities to grub2

for powerpc & i386-pc. This patch was more so started by Hollis
Blanchard getting multiboot 2 working for powerpc and I added to it
and cleaned it up.

One of the ideas with this patch is to keep everything under one
command for the user. So instead of having a "multiboot2" & "module2"
command, I created a proxy like mechanism so that you have only one
command for both multiboot 1 & 2 ... "multiboot". This is where
"loader/multiboot_loader.c" comes from. I could have integrated things
more but I figure the current approach will less likely break
anything.

So if your OS is multiboot 2 capable, the user would do the following
to load it up from a grub prompt:

grub> multiboot <location of kernel> <kernel args>
grub> module <some image> <multiboot tag> <image arguments>
grub> module <isome mage> <multiboot tag> <image arguments>
grub .....


The other thing that this patch does is it begins to make the
multiboot 1 code a bit more architecture agnostic so IF someone wanted
to implement it on another architecture they can.

A bit of file moving around and definition renaming is also apart of
this patch. I have also taken the time to make sure that it does not
break multiboot 1 loading on i386-pc. But mulitboot 2 may still need a
little more testing and work for i386-pc. Powerpc multiboot 2 has been
heavily tested and does work.

loader/i386/pc/multiboot2.c

@@ -0,0 +1,101 @@
+/* multiboot2.c - boot a multiboot 2 OS image. */
+/*
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2007  Free Software Foundation, Inc.
+ *
+ *  GRUB is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  GRUB is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <multiboot2.h>
+#include <grub/multiboot2.h>
+#include <grub/elf.h>
+#include <grub/err.h>
+#include <grub/machine/loader.h>
+#include <grub/mm.h>
+
+grub_err_t
+grub_mb2_arch_elf32_hook (Elf32_Phdr *phdr, UNUSED grub_addr_t *addr)
+{
+  Elf32_Addr paddr = phdr->p_paddr;
+
+  if ((paddr < grub_os_area_addr)
+      || (paddr + phdr->p_memsz > grub_os_area_addr + grub_os_area_size))
+    return grub_error(GRUB_ERR_OUT_OF_RANGE,"Address 0x%x is out of range", 
+                      paddr);
+
+  return GRUB_ERR_NONE;
+}
+
+grub_err_t
+grub_mb2_arch_elf64_hook (Elf64_Phdr *phdr, UNUSED grub_addr_t *addr)
+{
+  Elf64_Addr paddr = phdr->p_paddr;
+
+  if ((paddr < grub_os_area_addr)
+      || (paddr + phdr->p_memsz > grub_os_area_addr + grub_os_area_size))
+    return (GRUB_ERR_OUT_OF_RANGE,"Address 0x%x is out of range",
+            paddr);
+
+  return GRUB_ERR_NONE;
+}
+
+grub_err_t
+grub_mb2_arch_module_alloc (grub_size_t size, grub_addr_t *addr)
+{
+  grub_addr_t modaddr;
+
+  modaddr = grub_memalign (MULTIBOOT2_MOD_ALIGN, size);
+  if (! modaddr)
+    return grub_errno;
+
+  *addr = modaddr;
+  return GRUB_ERR_NONE;
+}
+
+grub_err_t
+grub_mb2_arch_module_free (grub_addr_t addr, UNUSED grub_size_t size)
+{
+  grub_free((void *) addr);
+  return GRUB_ERR_NONE;
+}
+
+void
+grub_mb2_arch_boot (grub_addr_t entry, void *tags)
+{
+  grub_multiboot2_real_boot (entry, tags);
+}
+
+void
+grub_mb2_arch_unload (struct multiboot_tag_header *tags)
+{
+   struct multiboot_tag_header *tag;
+   
+   /* Free all module memory in the tag list.  */
+   for_each_tag (tag, tags)
+     {
+       if (tag->key == MULTIBOOT2_TAG_MODULE)
+         {
+           struct multiboot_tag_module *module =
+              (struct multiboot_tag_module *) tag;
+           grub_free((void *) module->addr);
+         }
+     }
+}
+
+grub_err_t
+grub_mb2_tags_arch_create (void)
+{
+  /* XXX Create boot device et al. */
+  return GRUB_ERR_NONE;
+}