It turns out that while a maximum of 8 partitions may be what people
"should" have had, you can actually fit up to 18 entries(*) in a sector.
And some people clearly were taking advantage of that, like Michael
Cree, who had ten partitions on one of his OSF disks.
(*) The OSF partition data starts at byte offset 64 in the first sector,
    and the array of 16-byte partition entries start at offset 148 in
    the on-disk partition structure.
Reported-by: Michael Cree <mcree@orcon.net.nz>
Cc: stable@kernel.org (v2.6.38)
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
		
	
			
		
			
				
	
	
		
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			86 lines
		
	
	
	
		
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			C
		
	
	
	
	
	
/*
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 *  fs/partitions/osf.c
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 *
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 *  Code extracted from drivers/block/genhd.c
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 *
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 *  Copyright (C) 1991-1998  Linus Torvalds
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 *  Re-organised Feb 1998 Russell King
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 */
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#include "check.h"
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#include "osf.h"
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#define MAX_OSF_PARTITIONS 18
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int osf_partition(struct parsed_partitions *state)
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{
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	int i;
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	int slot = 1;
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	unsigned int npartitions;
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	Sector sect;
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	unsigned char *data;
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	struct disklabel {
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		__le32 d_magic;
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		__le16 d_type,d_subtype;
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		u8 d_typename[16];
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		u8 d_packname[16];
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		__le32 d_secsize;
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		__le32 d_nsectors;
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		__le32 d_ntracks;
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		__le32 d_ncylinders;
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		__le32 d_secpercyl;
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		__le32 d_secprtunit;
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		__le16 d_sparespertrack;
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		__le16 d_sparespercyl;
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		__le32 d_acylinders;
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		__le16 d_rpm, d_interleave, d_trackskew, d_cylskew;
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		__le32 d_headswitch, d_trkseek, d_flags;
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		__le32 d_drivedata[5];
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		__le32 d_spare[5];
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		__le32 d_magic2;
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		__le16 d_checksum;
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		__le16 d_npartitions;
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		__le32 d_bbsize, d_sbsize;
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		struct d_partition {
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			__le32 p_size;
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			__le32 p_offset;
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			__le32 p_fsize;
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			u8  p_fstype;
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			u8  p_frag;
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			__le16 p_cpg;
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		} d_partitions[MAX_OSF_PARTITIONS];
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	} * label;
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	struct d_partition * partition;
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	data = read_part_sector(state, 0, §);
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	if (!data)
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		return -1;
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	label = (struct disklabel *) (data+64);
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	partition = label->d_partitions;
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	if (le32_to_cpu(label->d_magic) != DISKLABELMAGIC) {
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		put_dev_sector(sect);
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		return 0;
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	}
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	if (le32_to_cpu(label->d_magic2) != DISKLABELMAGIC) {
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		put_dev_sector(sect);
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		return 0;
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	}
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	npartitions = le16_to_cpu(label->d_npartitions);
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	if (npartitions > MAX_OSF_PARTITIONS) {
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		put_dev_sector(sect);
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		return 0;
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	}
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	for (i = 0 ; i < npartitions; i++, partition++) {
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		if (slot == state->limit)
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		        break;
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		if (le32_to_cpu(partition->p_size))
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			put_partition(state, slot,
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				le32_to_cpu(partition->p_offset),
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				le32_to_cpu(partition->p_size));
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		slot++;
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	}
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	strlcat(state->pp_buf, "\n", PAGE_SIZE);
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	put_dev_sector(sect);
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	return 1;
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}
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