Automatically determine prefix when netbooted on EFI

grub-core/kern/efi/init.c

@@ -42,6 +42,10 @@ grub_efi_init (void)
   grub_efidisk_init ();
 }
 
+void (*grub_efi_net_config) (grub_efi_handle_t hnd, 
+			     char **device,
+			     char **path);
+
 void
 grub_machine_get_bootlocation (char **device, char **path)
 {
@@ -53,6 +57,8 @@ grub_machine_get_bootlocation (char **device, char **path)
     return;
   *device = grub_efidisk_get_device_name (image->device_handle);
   *path = grub_efi_get_filename (image->file_path);
+  if (!*device && grub_efi_net_config)
+    grub_efi_net_config (image->device_handle, device, path);
 
   /* Get the directory.  */
   p = grub_strrchr (*path, '/');