Skip to content

Fix LBA calculation for EBR #2

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 1 commit into
base: master
Choose a base branch
from
Open

Fix LBA calculation for EBR #2

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
13 changes: 9 additions & 4 deletions src/pyreadpartitions/__init__.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -41,9 +41,9 @@
# http://en.wikipedia.org/wiki/Master_boot_record#Partition_table_entries
MBR_PARTITION_FORMAT = [
(b'B', 'status'), # > 0x80 => active
(b'3p', 'chs_first'), # 8*h + 2*c + 6*s + 8*c
(b'3s', 'chs_first'), # 8*h + 2*c + 6*s + 8*c
(b'B', 'type'),
(b'3p', 'chs_last'), # 8*h + 2*c + 6*s + 8*c
(b'3s', 'chs_last'), # 8*h + 2*c + 6*s + 8*c
(b'L', 'lba'),
(b'L', 'sectors'),
]
Expand Down Expand Up @@ -218,9 +218,9 @@
}


def make_fmt(name, fmt, extras=[]):
def make_fmt(name, fmt, extras=None):
packfmt = b'<' + b''.join(t for t, n in fmt)
tupletype = namedtuple(name, [n for t, n in fmt if n != '_'] + extras)
tupletype = namedtuple(name, [n for t, n in fmt if n != '_'] + (extras or []))
return (packfmt, tupletype)


Expand Down Expand Up @@ -268,6 +268,10 @@ def read_ebr_partition(fp, extended_lba, lba, num):
if ebr.signature != b'\x55\xAA':
raise MBRError('Bad EBR signature')
parts = [read_mbr_partition(ebr.partition, num)]

# LBA of EBRs are relative offsets from to the start of EBR to the partition. Calculate the absolute LBA.
parts[0] = parts[0]._replace(lba=extended_lba + parts[0].lba)

if ebr.next_ebr != 16 * b'\x00':
part_next_ebr = read_mbr_partition(ebr.next_ebr, 0)
next_lba = part_next_ebr.lba
Expand Down Expand Up @@ -465,3 +469,4 @@ def main():

if __name__ == '__main__':
exit(main())