113 lines
3.9 KiB
Python
113 lines
3.9 KiB
Python
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"""Minimal reader for Xiaomi Vela ROMFS partition images (Linux 'rom1fs' variant).
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Layout (big-endian):
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super : magic "-rom1fs-", u32 size, u32 checksum, name (NUL-term, padded to 16)
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inode : u32 next (low 4 bits = ROMFH_ type flags), u32 spec, u32 size, u32 checksum,
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name (NUL-term, padded to 16), then file data immediately after.
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type : 0=hardlink (spec = target inode offset), 1=dir (spec = offset of first child),
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2=regular file, 8=exec bit OR-ed in.
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For a directory, its children are the chain starting at `spec`, linked by
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`next & ~0xF`, and they stay inside the directory's own block.
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"""
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import struct, os
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ROUND16 = lambda n: (n + 15) & ~15
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class Inode:
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__slots__ = ('off', 'next', 'spec', 'size', 'cksum', 'name', 'namelen', 'data_off', 'kind')
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@property
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def type_flags(self):
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return self.next & 0xF
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@property
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def type(self):
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return self.next & 0x7
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@property
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def exec_bit(self):
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return bool(self.next & 0x8)
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@property
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def next_off(self):
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return self.next & ~0xF
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KIND = {0: 'HRD', 1: 'DIR', 2: 'REG', 3: 'SYM', 4: 'BLK', 5: 'CHR', 6: 'SCK', 7: 'FIF'}
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def __repr__(self):
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return (f'<Inode @0x{self.off:x} {self.KIND[self.type]}{"X" if self.exec_bit else " "} '
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f'{self.name!r} size={self.size}>')
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class Romfs:
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def __init__(self, path):
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self.path = path
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self.data = open(path, 'rb').read()
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d = self.data
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if d[0:8] != b'-rom1fs-':
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raise ValueError('not a romfs image')
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self.sb_size, self.sb_cksum = struct.unpack('>II', d[8:16])
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end = d.index(b'\x00', 16)
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self.volume = d[16:end].decode('latin1')
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self.root_off = 16 + ROUND16(end - 16 + 1)
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def inode(self, off):
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i = Inode()
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i.off = off
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i.next, i.spec, i.size, i.cksum = struct.unpack('>IIII', self.data[off:off+16])
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p = off + 16
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end = self.data.find(b'\x00', p, p + 256)
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if end < 0:
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raise ValueError(f'bad name at 0x{off:x}')
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i.name = self.data[p:end].decode('latin1')
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i.namelen = end - p
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i.data_off = off + 16 + ROUND16(i.namelen + 1)
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return i
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def walk(self, first, limit, prefix=''):
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"""Yield (path, Inode) for every entry reachable from `first` below `limit`.
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`limit` bounds the sibling chain. The LAST entry of a chain has next==0,
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but its own children still live after it: they inherit the parent's limit
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instead of being bounded by that zero.
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"""
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off = first
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seen = set()
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while off and (limit == 0 or off < limit) and off not in seen:
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seen.add(off)
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i = self.inode(off)
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path = prefix + i.name
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yield path, i
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if i.type == 1 and i.spec: # directory -> first child at spec
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yield from self.walk(i.spec, i.next_off or limit, path + '/')
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off = i.next_off
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def entries(self):
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"""All entries of the image, as (path, Inode)."""
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return self.walk(self.root_off + 0x20, len(self.data))
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def read(self, ino):
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return self.data[ino.data_off:ino.data_off + ino.size]
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def img_header(blob):
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if len(blob) < 12 or blob[0] != 0x19:
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return None
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magic, cf, flags, w, h, stride, res = struct.unpack('<BBHHHHH', blob[:12])
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return dict(magic=magic, cf=cf, flags=flags, w=w, h=h, stride=stride, reserved=res)
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if __name__ == '__main__':
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import sys
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r = Romfs(sys.argv[1])
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print(f'{os.path.basename(sys.argv[1])}: volume={r.volume!r} size={r.sb_size} '
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f'file={len(r.data)} root=0x{r.root_off:x}')
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n = 0
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for path, i in r.entries():
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n += 1
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if len(sys.argv) > 2 and sys.argv[2] not in path:
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continue
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kind = ('DIR ' if i.type == 1 else 'LNK ' if i.type == 0 else 'FILE')
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print(f'{kind} {i.size:>9} {path}')
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print(f'-- total entries: {n}')
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