61 lines
1.9 KiB
Bash
61 lines
1.9 KiB
Bash
python3 -c "
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import struct
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CHUNK = 128*512
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LV_START = 5120000*512
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BSIZE = 4096
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GDT_ENTRY = 64
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BPG = 32768
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def raw_read(virt_offset, length):
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result = bytearray(length)
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pos = virt_offset
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remaining = length
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with open('/dev/md0','rb') as f:
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while remaining > 0:
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group = pos // (5*CHUNK)
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in_group = pos % (5*CHUNK)
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chunk_idx = in_group // CHUNK
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intra = in_group % CHUNK
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seg_len = min(CHUNK-intra, remaining)
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dst_off = pos - virt_offset
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if chunk_idx != 4:
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phys = LV_START + group*4*CHUNK + chunk_idx*CHUNK + intra
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f.seek(phys)
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data = f.read(seg_len)
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result[dst_off:dst_off+len(data)] = data
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pos += seg_len
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remaining -= seg_len
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return bytes(result)
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# Read primary GDT (at block 1 = byte 4096)
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# and backup GDT (at block group 1 start + 1 block)
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# Group 1 starts at block 32768, GDT backup at block 32769 = byte 32769*4096
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# Read 1000 entries from primary GDT
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primary_gdt = bytearray(raw_read(BSIZE, 1000 * GDT_ENTRY))
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# Read 1000 entries from backup GDT at group 1
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backup_start = (BPG + 1) * BSIZE # block 32769
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backup_gdt = raw_read(backup_start, 1000 * GDT_ENTRY)
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print('Comparing primary vs backup GDT entries:')
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mismatches = 0
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zeros = 0
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for i in range(1000):
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p = primary_gdt[i*GDT_ENTRY:(i+1)*GDT_ENTRY]
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b = backup_gdt[i*GDT_ENTRY:(i+1)*GDT_ENTRY]
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p_bb = struct.unpack_from('<I',p,0)[0]
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b_bb = struct.unpack_from('<I',b,0)[0]
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if p == bytes(GDT_ENTRY):
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zeros += 1
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elif p != b:
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mismatches += 1
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if mismatches <= 5:
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print(f' Group {i}: primary bb={p_bb} vs backup bb={b_bb}')
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print(f'Zero entries in primary: {zeros}/1000')
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print(f'Mismatches: {mismatches}/1000')
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print(f'Backup GDT group 0: bb={struct.unpack_from(\"<I\",backup_gdt,0)[0]}')
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"
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