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wic: Add gpt-hybrid partition layout

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Add support for formatting a disk with a hybrid MBR & GPT partition
scheme. In this scheme, the primary partitioning method is GPT, but a
valid MBR header is also written than can point to a subset of the GPT
partitions on the disk (any partitions marked with the `--mbr` flag will
be included in this MBR). The primary purpose of this method is to allow
for SoCs that can only find a bootloader in an MBR partition to use GPT
once the bootloader is running. As an example, older versions of the
Raspberry Pi firmware can only parse MBR partitions to find a kernel (or
other bootloader like u-boot), but once those have booted GPT partitions
can be used.

In addition to the partitions annotated with the `--mbr`, a "protective"
GPT partition of type 0xEE is added, as the existence of such a
partition is the indication to tooling that this a hybrid MBR and that
the GPT partition table should be parsed instead.

(From OE-Core rev: e50e4c2a5ada6947b3503ca4d8e9c30d359e8a5d)

Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Joshua Watt 2023-08-30 08:20:17 -06:00 committed by Richard Purdie
parent 9d9c7d4b0b
commit 93388921ab
3 changed files with 71 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
scripts/lib/wic/ksparser.py
View File

@ -188,11 +188,12 @@ class KickStart():
part.add_argument('--uuid')
part.add_argument('--fsuuid')
part.add_argument('--no-fstab-update', action='store_true')
part.add_argument('--mbr', action='store_true')
bootloader = subparsers.add_parser('bootloader')
bootloader.add_argument('--append')
bootloader.add_argument('--configfile')
bootloader.add_argument('--ptable', choices=('msdos', 'gpt'),
bootloader.add_argument('--ptable', choices=('msdos', 'gpt', 'gpt-hybrid'),
default='msdos')
bootloader.add_argument('--timeout', type=int)
bootloader.add_argument('--source')

1
scripts/lib/wic/partition.py
View File

@ -60,6 +60,7 @@ class Partition():
self.has_fstab = False
self.update_fstab_in_rootfs = False
self.hidden = args.hidden
self.mbr = args.mbr
self.lineno = lineno
self.source_file = ""

86
scripts/lib/wic/plugins/imager/direct.py
View File

@ -342,7 +342,7 @@ class PartitionedImage():
# generate parition and filesystem UUIDs
for part in self.partitions:
if not part.uuid and part.use_uuid:
if self.ptable_format == 'gpt':
if self.ptable_format in ('gpt', 'gpt-hybrid'):
part.uuid = str(uuid.uuid4())
else: # msdos partition table
part.uuid = '%08x-%02d' % (self.identifier, part.realnum)
@ -398,6 +398,10 @@ class PartitionedImage():
raise WicError("setting custom partition type is not " \
"implemented for msdos partitions")
if part.mbr and self.ptable_format != 'gpt-hybrid':
raise WicError("Partition may only be included in MBR with " \
"a gpt-hybrid partition table")
# Get the disk where the partition is located
self.numpart += 1
if not part.no_table:
@ -406,7 +410,7 @@ class PartitionedImage():
if self.numpart == 1:
if self.ptable_format == "msdos":
overhead = MBR_OVERHEAD
elif self.ptable_format == "gpt":
elif self.ptable_format in ("gpt", "gpt-hybrid"):
overhead = GPT_OVERHEAD
# Skip one sector required for the partitioning scheme overhead
@ -490,7 +494,7 @@ class PartitionedImage():
# Once all the partitions have been layed out, we can calculate the
# minumim disk size
self.min_size = self.offset
if self.ptable_format == "gpt":
if self.ptable_format in ("gpt", "gpt-hybrid"):
self.min_size += GPT_OVERHEAD
self.min_size *= self.sector_size
@ -511,22 +515,38 @@ class PartitionedImage():
return exec_native_cmd(cmd, self.native_sysroot)
def create(self):
logger.debug("Creating sparse file %s", self.path)
with open(self.path, 'w') as sparse:
os.ftruncate(sparse.fileno(), self.min_size)
logger.debug("Initializing partition table for %s", self.path)
exec_native_cmd("parted -s %s mklabel %s" %
(self.path, self.ptable_format), self.native_sysroot)
logger.debug("Set disk identifier %x", self.identifier)
with open(self.path, 'r+b') as img:
def _write_identifier(self, device, identifier):
logger.debug("Set disk identifier %x", identifier)
with open(device, 'r+b') as img:
img.seek(0x1B8)
img.write(self.identifier.to_bytes(4, 'little'))
img.write(identifier.to_bytes(4, 'little'))
def _make_disk(self, device, ptable_format, min_size):
logger.debug("Creating sparse file %s", device)
with open(device, 'w') as sparse:
os.ftruncate(sparse.fileno(), min_size)
logger.debug("Initializing partition table for %s", device)
exec_native_cmd("parted -s %s mklabel %s" % (device, ptable_format),
self.native_sysroot)
def create(self):
self._make_disk(self.path,
"gpt" if self.ptable_format == "gpt-hybrid" else self.ptable_format,
self.min_size)
self._write_identifier(self.path, self.identifier)
if self.ptable_format == "gpt-hybrid":
mbr_path = self.path + ".mbr"
self._make_disk(mbr_path, "msdos", self.min_size)
self._write_identifier(mbr_path, self.identifier)
logger.debug("Creating partitions")
hybrid_mbr_part_num = 0
for part in self.partitions:
if part.num == 0:
continue
@ -571,7 +591,14 @@ class PartitionedImage():
self._create_partition(self.path, part.type,
parted_fs_type, part.start, part.size_sec)
if self.ptable_format == "gpt" and (part.part_name or part.label):
if self.ptable_format == "gpt-hybrid" and part.mbr:
hybrid_mbr_part_num += 1
if hybrid_mbr_part_num > 4:
raise WicError("Extended MBR partitions are not supported in hybrid MBR")
self._create_partition(mbr_path, "primary",
parted_fs_type, part.start, part.size_sec)
if self.ptable_format in ("gpt", "gpt-hybrid") and (part.part_name or part.label):
partition_label = part.part_name if part.part_name else part.label
logger.debug("partition %d: set name to %s",
part.num, partition_label)
@ -586,7 +613,7 @@ class PartitionedImage():
(part.num, part.part_type,
self.path), self.native_sysroot)
if part.uuid and self.ptable_format == "gpt":
if part.uuid and self.ptable_format in ("gpt", "gpt-hybrid"):
logger.debug("partition %d: set UUID to %s",
part.num, part.uuid)
exec_native_cmd("sgdisk --partition-guid=%d:%s %s" % \
@ -594,12 +621,16 @@ class PartitionedImage():
self.native_sysroot)
if part.active:
flag_name = "legacy_boot" if self.ptable_format == 'gpt' else "boot"
flag_name = "legacy_boot" if self.ptable_format in ('gpt', 'gpt-hybrid') else "boot"
logger.debug("Set '%s' flag for partition '%s' on disk '%s'",
flag_name, part.num, self.path)
exec_native_cmd("parted -s %s set %d %s on" % \
(self.path, part.num, flag_name),
self.native_sysroot)
if self.ptable_format == 'gpt-hybrid' and part.mbr:
exec_native_cmd("parted -s %s set %d %s on" % \
(mbr_path, hybrid_mbr_part_num, "boot"),
self.native_sysroot)
if part.system_id:
exec_native_cmd("sfdisk --part-type %s %s %s" % \
(self.path, part.num, part.system_id),
@ -612,6 +643,25 @@ class PartitionedImage():
(self.path, part.num),
self.native_sysroot)
if self.ptable_format == "gpt-hybrid":
# Write a protective GPT partition
hybrid_mbr_part_num += 1
if hybrid_mbr_part_num > 4:
raise WicError("Extended MBR partitions are not supported in hybrid MBR")
# parted cannot directly create a protective GPT partition, so
# create with an arbitrary type, then change it to the correct type
# with sfdisk
self._create_partition(mbr_path, "primary", "fat32", 1, GPT_OVERHEAD)
exec_native_cmd("sfdisk --part-type %s %d 0xee" % (mbr_path, hybrid_mbr_part_num),
self.native_sysroot)
# Copy hybrid MBR
with open(mbr_path, "rb") as mbr_file:
with open(self.path, "r+b") as image_file:
mbr = mbr_file.read(512)
image_file.write(mbr)
def cleanup(self):
pass