[Patch] Do not embed with multiple partmaps

["Grégoire Sutre" <gregoire.sutre@gmail.com>]

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Hi,

As a (temporary) solution to the problem of embedding with multiple
top-level partmaps, the attached patch simply disables embedding when
there are multiple partmaps (i.e. apply the same behavior as when there
is no partmap).

This prevents grub-setup from overwriting e.g. a BSD label if it finds
an msdos label first.

The only drawback I see is that grub-setup may complain about an old
obsolete disklabel, but in that case the user simply has to destroy the
obsolete label, and IMHO this is more acceptable than potentially
destroying valuable data.

Grégoire

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=== modified file 'ChangeLog'
--- ChangeLog	2010-06-17 20:54:04 +0000
+++ ChangeLog	2010-06-17 22:06:58 +0000
@@ -1,3 +1,8 @@
+2010-06-17  Grégoire Sutre  <gregoire.sutre@gmail.com>
+
+	* util/i386/pc/grub-setup.c (setup): Do not embed when there are
+	multiple (top-level) partmaps.
+
 2010-06-17  Colin Watson  <cjwatson@ubuntu.com>
 
 	* util/i386/pc/grub-setup.c (usage): Pass an extra `program_name'

=== modified file 'util/i386/pc/grub-setup.c'
--- util/i386/pc/grub-setup.c	2010-06-17 20:54:04 +0000
+++ util/i386/pc/grub-setup.c	2010-06-17 22:04:48 +0000
@@ -93,6 +93,7 @@
   grub_uint16_t core_sectors;
   grub_device_t root_dev, dest_dev;
   const char *dest_partmap;
+  int multiple_partmaps;
   grub_uint8_t *boot_drive;
   grub_disk_addr_t *kernel_sector;
   grub_uint16_t *boot_drive_check;
@@ -354,10 +355,17 @@
     {
       if (p->parent)
 	return 0;
-      dest_partmap = p->partmap->name;
-      return 1;
+      if (dest_partmap == NULL)
+	dest_partmap = p->partmap->name;
+      else if (strcmp (dest_partmap, p->partmap->name) != 0)
+	{
+	  multiple_partmaps = 1;
+	  return 1;
+	}
+      return 0;
     }
   dest_partmap = 0;
+  multiple_partmaps = 0;
   grub_partition_iterate (dest_dev->disk, identify_partmap);
 
   if (! dest_partmap)
@@ -365,6 +373,11 @@
       grub_util_warn (_("Attempting to install GRUB to a partitionless disk.  This is a BAD idea."));
       goto unable_to_embed;
     }
+  if (multiple_partmaps)
+    {
+      grub_util_warn (_("Attempting to install GRUB to a disk with multiple partition labels.  This is a BAD idea."));
+      goto unable_to_embed;
+    }
 
   if (strcmp (dest_partmap, "msdos") == 0)
     grub_partition_iterate (dest_dev->disk, find_usable_region_msdos);