wic: generate PARTUUID for MDOS partitions

Added generation of partition UUIDs for MSDOS partitions.
UUID for MSDOS partitions is <disk identifier>-<partition number>,
where disk identifier is a random 4 bytes long number. It's usually
generated when MBR/partition table is initialized.

As UUID is used to point to the root partition in bootloader config
we need to generate it before the MBR is initialized.
After MBR is created we need to rewrite system identifier to match
it with what is used in bootloader config. This will be implemented
in the next commit.

(From OE-Core rev: 6ecc6addf4080eda75a15af077816c81c6bf70a5)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/lib/wic/imager/direct.py

@@ -26,6 +26,7 @@
 
 import os
 import shutil
+import uuid
 
 from wic import msger
 from wic.utils.oe.misc import get_bitbake_var
@@ -242,12 +243,23 @@ class DirectImageCreator(BaseImageCreator):
 
         self.__image = Image(self.native_sysroot)
 
-        for part in parts:
+        disk_ids = {}
+        for num, part in enumerate(parts, 1):
             # as a convenience, set source to the boot partition source
             # instead of forcing it to be set via bootloader --source
             if not self.ks.bootloader.source and part.mountpoint == "/boot":
                 self.ks.bootloader.source = part.source
 
+            # generate parition UUIDs
+            if not part.uuid and part.use_uuid:
+                if self.ptable_format == 'gpt':
+                    part.uuid = str(uuid.uuid4())
+                else: # msdos partition table
+                    if part.disk not in disk_ids:
+                        disk_ids[part.disk] = int.from_bytes(os.urandom(4), 'little')
+                    disk_id = disk_ids[part.disk]
+                    part.uuid = '%0x-%02d' % (disk_id, self.__get_part_num(num, parts))
+
         fstab_path = self._write_fstab(self.rootfs_dir.get("ROOTFS_DIR"))
 
         shutil.rmtree(self.workdir)

scripts/lib/wic/partition.py

@@ -26,7 +26,6 @@
 
 import os
 import tempfile
-import uuid
 
 from wic.utils.oe.misc import msger, parse_sourceparams
 from wic.utils.oe.misc import exec_cmd, exec_native_cmd
@@ -60,8 +59,6 @@ class Partition():
         self.system_id = args.system_id
         self.use_uuid = args.use_uuid
         self.uuid = args.uuid
-        if args.use_uuid and not self.uuid:
-            self.uuid = str(uuid.uuid4())
 
         self.lineno = lineno
         self.source_file = ""