fs/partitions/msdos.c - kernel/msm-4.9 - Gitiles

 /*
  *  fs/partitions/msdos.c
  *
  *  Code extracted from drivers/block/genhd.c
  *  Copyright (C) 1991-1998  Linus Torvalds
  *
  *  Thanks to Branko Lankester, lankeste@fwi.uva.nl, who found a bug
  *  in the early extended-partition checks and added DM partitions
  *
  *  Support for DiskManager v6.0x added by Mark Lord,
  *  with information provided by OnTrack.  This now works for linux fdisk
  *  and LILO, as well as loadlin and bootln.  Note that disks other than
  *  /dev/hda *must* have a "DOS" type 0x51 partition in the first slot (hda1).
  *
  *  More flexible handling of extended partitions - aeb, 950831
  *
  *  Check partition table on IDE disks for common CHS translations
  *
  *  Re-organised Feb 1998 Russell King
  */
 #include <linux/msdos_fs.h>

 #include "check.h"
 #include "msdos.h"
 #include "efi.h"

 /*
  * Many architectures don't like unaligned accesses, while
  * the nr_sects and start_sect partition table entries are
  * at a 2 (mod 4) address.
  */
 #include <asm/unaligned.h>

 #define SYS_IND(p)	get_unaligned(&p->sys_ind)

 static inline sector_t nr_sects(struct partition *p)
 {
 	return (sector_t)get_unaligned_le32(&p->nr_sects);
 }

 static inline sector_t start_sect(struct partition *p)
 {
 	return (sector_t)get_unaligned_le32(&p->start_sect);
 }

 static inline int is_extended_partition(struct partition *p)
 {
 	return (SYS_IND(p) == DOS_EXTENDED_PARTITION ||
 		SYS_IND(p) == WIN98_EXTENDED_PARTITION ||
 		SYS_IND(p) == LINUX_EXTENDED_PARTITION);
 }

 #define MSDOS_LABEL_MAGIC1	0x55
 #define MSDOS_LABEL_MAGIC2	0xAA

 static inline int
 msdos_magic_present(unsigned char *p)
 {
 	return (p[0] == MSDOS_LABEL_MAGIC1 && p[1] == MSDOS_LABEL_MAGIC2);
 }

 /* Value is EBCDIC 'IBMA' */
 #define AIX_LABEL_MAGIC1	0xC9
 #define AIX_LABEL_MAGIC2	0xC2
 #define AIX_LABEL_MAGIC3	0xD4
 #define AIX_LABEL_MAGIC4	0xC1
 static int aix_magic_present(struct parsed_partitions *state, unsigned char *p)
 {
 	struct partition *pt = (struct partition *) (p + 0x1be);
 	Sector sect;
 	unsigned char *d;
 	int slot, ret = 0;

 	if (!(p[0] == AIX_LABEL_MAGIC1 &&
 		p[1] == AIX_LABEL_MAGIC2 &&
 		p[2] == AIX_LABEL_MAGIC3 &&
 		p[3] == AIX_LABEL_MAGIC4))
 		return 0;
 	/* Assume the partition table is valid if Linux partitions exists */
 	for (slot = 1; slot <= 4; slot++, pt++) {
 		if (pt->sys_ind == LINUX_SWAP_PARTITION ||
 			pt->sys_ind == LINUX_RAID_PARTITION ||
 			pt->sys_ind == LINUX_DATA_PARTITION ||
 			pt->sys_ind == LINUX_LVM_PARTITION ||
 			is_extended_partition(pt))
 			return 0;
 	}
 	d = read_part_sector(state, 7, &sect);
 	if (d) {
 		if (d[0] == '_' && d[1] == 'L' && d[2] == 'V' && d[3] == 'M')
 			ret = 1;
 		put_dev_sector(sect);
 	};
 	return ret;
 }

 /*
  * Create devices for each logical partition in an extended partition.
  * The logical partitions form a linked list, with each entry being
  * a partition table with two entries.  The first entry
  * is the real data partition (with a start relative to the partition
  * table start).  The second is a pointer to the next logical partition
  * (with a start relative to the entire extended partition).
  * We do not create a Linux partition for the partition tables, but
  * only for the actual data partitions.
  */

 static void parse_extended(struct parsed_partitions *state,
 			   sector_t first_sector, sector_t first_size)
 {
 	struct partition *p;
 	Sector sect;
 	unsigned char *data;
 	sector_t this_sector, this_size;
 	sector_t sector_size = bdev_logical_block_size(state->bdev) / 512;
 	int loopct = 0;		/* number of links followed
 				   without finding a data partition */
 	int i;

 	this_sector = first_sector;
 	this_size = first_size;

 	while (1) {
 		if (++loopct > 100)
 			return;
 		if (state->next == state->limit)
 			return;
 		data = read_part_sector(state, this_sector, &sect);
 		if (!data)
 			return;

 		if (!msdos_magic_present(data + 510))
 			goto done;

 		p = (struct partition *) (data + 0x1be);

 		/*
 		 * Usually, the first entry is the real data partition,
 		 * the 2nd entry is the next extended partition, or empty,
 		 * and the 3rd and 4th entries are unused.
 		 * However, DRDOS sometimes has the extended partition as
 		 * the first entry (when the data partition is empty),
 		 * and OS/2 seems to use all four entries.
 		 */

 		/*
 		 * First process the data partition(s)
 		 */
 		for (i=0; i<4; i++, p++) {
 			sector_t offs, size, next;
 			if (!nr_sects(p) || is_extended_partition(p))
 				continue;

 			/* Check the 3rd and 4th entries -
 			   these sometimes contain random garbage */
 			offs = start_sect(p)*sector_size;
 			size = nr_sects(p)*sector_size;
 			next = this_sector + offs;
 			if (i >= 2) {
 				if (offs + size > this_size)
 					continue;
 				if (next < first_sector)
 					continue;
 				if (next + size > first_sector + first_size)
 					continue;
 			}

 			put_partition(state, state->next, next, size);
 			if (SYS_IND(p) == LINUX_RAID_PARTITION)
 				state->parts[state->next].flags = ADDPART_FLAG_RAID;
 			loopct = 0;
 			if (++state->next == state->limit)
 				goto done;
 		}
 		/*
 		 * Next, process the (first) extended partition, if present.
 		 * (So far, there seems to be no reason to make
 		 *  parse_extended()  recursive and allow a tree
 		 *  of extended partitions.)
 		 * It should be a link to the next logical partition.
 		 */
 		p -= 4;
 		for (i=0; i<4; i++, p++)
 			if (nr_sects(p) && is_extended_partition(p))
 				break;
 		if (i == 4)
 			goto done;	 /* nothing left to do */

 		this_sector = first_sector + start_sect(p) * sector_size;
 		this_size = nr_sects(p) * sector_size;
 		put_dev_sector(sect);
 	}
 done:
 	put_dev_sector(sect);
 }

 /* james@bpgc.com: Solaris has a nasty indicator: 0x82 which also
    indicates linux swap.  Be careful before believing this is Solaris. */

 static void parse_solaris_x86(struct parsed_partitions *state,
 			      sector_t offset, sector_t size, int origin)
 {
 #ifdef CONFIG_SOLARIS_X86_PARTITION
 	Sector sect;
 	struct solaris_x86_vtoc *v;
 	int i;
 	short max_nparts;

 	v = read_part_sector(state, offset + 1, &sect);
 	if (!v)
 		return;
 	if (le32_to_cpu(v->v_sanity) != SOLARIS_X86_VTOC_SANE) {
 		put_dev_sector(sect);
 		return;
 	}
 	{
 		char tmp[1 + BDEVNAME_SIZE + 10 + 11 + 1];

 		snprintf(tmp, sizeof(tmp), " %s%d: <solaris:", state->name, origin);
 		strlcat(state->pp_buf, tmp, PAGE_SIZE);
 	}
 	if (le32_to_cpu(v->v_version) != 1) {
 		char tmp[64];

 		snprintf(tmp, sizeof(tmp), "  cannot handle version %d vtoc>\n",
 			 le32_to_cpu(v->v_version));
 		strlcat(state->pp_buf, tmp, PAGE_SIZE);
 		put_dev_sector(sect);
 		return;
 	}
 	/* Ensure we can handle previous case of VTOC with 8 entries gracefully */
 	max_nparts = le16_to_cpu (v->v_nparts) > 8 ? SOLARIS_X86_NUMSLICE : 8;
 	for (i=0; i<max_nparts && state->next<state->limit; i++) {
 		struct solaris_x86_slice *s = &v->v_slice[i];
 		char tmp[3 + 10 + 1 + 1];

 		if (s->s_size == 0)
 			continue;
 		snprintf(tmp, sizeof(tmp), " [s%d]", i);
 		strlcat(state->pp_buf, tmp, PAGE_SIZE);
 		/* solaris partitions are relative to current MS-DOS
 		 * one; must add the offset of the current partition */
 		put_partition(state, state->next++,
 				 le32_to_cpu(s->s_start)+offset,
 				 le32_to_cpu(s->s_size));
 	}
 	put_dev_sector(sect);
 	strlcat(state->pp_buf, " >\n", PAGE_SIZE);
 #endif
 }

 #if defined(CONFIG_BSD_DISKLABEL)
 /*
  * Create devices for BSD partitions listed in a disklabel, under a
  * dos-like partition. See parse_extended() for more information.
  */
 static void parse_bsd(struct parsed_partitions *state,
 		      sector_t offset, sector_t size, int origin, char *flavour,
 		      int max_partitions)
 {
 	Sector sect;
 	struct bsd_disklabel *l;
 	struct bsd_partition *p;
 	char tmp[64];

 	l = read_part_sector(state, offset + 1, &sect);
 	if (!l)
 		return;
 	if (le32_to_cpu(l->d_magic) != BSD_DISKMAGIC) {
 		put_dev_sector(sect);
 		return;
 	}

 	snprintf(tmp, sizeof(tmp), " %s%d: <%s:", state->name, origin, flavour);
 	strlcat(state->pp_buf, tmp, PAGE_SIZE);

 	if (le16_to_cpu(l->d_npartitions) < max_partitions)
 		max_partitions = le16_to_cpu(l->d_npartitions);
 	for (p = l->d_partitions; p - l->d_partitions < max_partitions; p++) {
 		sector_t bsd_start, bsd_size;

 		if (state->next == state->limit)
 			break;
 		if (p->p_fstype == BSD_FS_UNUSED)
 			continue;
 		bsd_start = le32_to_cpu(p->p_offset);
 		bsd_size = le32_to_cpu(p->p_size);
 		if (offset == bsd_start && size == bsd_size)
 			/* full parent partition, we have it already */
 			continue;
 		if (offset > bsd_start || offset+size < bsd_start+bsd_size) {
 			strlcat(state->pp_buf, "bad subpartition - ignored\n", PAGE_SIZE);
 			continue;
 		}
 		put_partition(state, state->next++, bsd_start, bsd_size);
 	}
 	put_dev_sector(sect);
 	if (le16_to_cpu(l->d_npartitions) > max_partitions) {
 		snprintf(tmp, sizeof(tmp), " (ignored %d more)",
 			 le16_to_cpu(l->d_npartitions) - max_partitions);
 		strlcat(state->pp_buf, tmp, PAGE_SIZE);
 	}
 	strlcat(state->pp_buf, " >\n", PAGE_SIZE);
 }
 #endif

 static void parse_freebsd(struct parsed_partitions *state,
 			  sector_t offset, sector_t size, int origin)
 {
 #ifdef CONFIG_BSD_DISKLABEL
 	parse_bsd(state, offset, size, origin, "bsd", BSD_MAXPARTITIONS);
 #endif
 }

 static void parse_netbsd(struct parsed_partitions *state,
 			 sector_t offset, sector_t size, int origin)
 {
 #ifdef CONFIG_BSD_DISKLABEL
 	parse_bsd(state, offset, size, origin, "netbsd", BSD_MAXPARTITIONS);
 #endif
 }

 static void parse_openbsd(struct parsed_partitions *state,
 			  sector_t offset, sector_t size, int origin)
 {
 #ifdef CONFIG_BSD_DISKLABEL
 	parse_bsd(state, offset, size, origin, "openbsd",
 		  OPENBSD_MAXPARTITIONS);
 #endif
 }

 /*
  * Create devices for Unixware partitions listed in a disklabel, under a
  * dos-like partition. See parse_extended() for more information.
  */
 static void parse_unixware(struct parsed_partitions *state,
 			   sector_t offset, sector_t size, int origin)
 {
 #ifdef CONFIG_UNIXWARE_DISKLABEL
 	Sector sect;
 	struct unixware_disklabel *l;
 	struct unixware_slice *p;

 	l = read_part_sector(state, offset + 29, &sect);
 	if (!l)
 		return;
 	if (le32_to_cpu(l->d_magic) != UNIXWARE_DISKMAGIC ||
 	    le32_to_cpu(l->vtoc.v_magic) != UNIXWARE_DISKMAGIC2) {
 		put_dev_sector(sect);
 		return;
 	}
 	{
 		char tmp[1 + BDEVNAME_SIZE + 10 + 12 + 1];

 		snprintf(tmp, sizeof(tmp), " %s%d: <unixware:", state->name, origin);
 		strlcat(state->pp_buf, tmp, PAGE_SIZE);
 	}
 	p = &l->vtoc.v_slice[1];
 	/* I omit the 0th slice as it is the same as whole disk. */
 	while (p - &l->vtoc.v_slice[0] < UNIXWARE_NUMSLICE) {
 		if (state->next == state->limit)
 			break;

 		if (p->s_label != UNIXWARE_FS_UNUSED)
 			put_partition(state, state->next++,
 				      le32_to_cpu(p->start_sect),
 				      le32_to_cpu(p->nr_sects));
 		p++;
 	}
 	put_dev_sector(sect);
 	strlcat(state->pp_buf, " >\n", PAGE_SIZE);
 #endif
 }

 /*
  * Minix 2.0.0/2.0.2 subpartition support.
  * Anand Krishnamurthy <anandk@wiproge.med.ge.com>
  * Rajeev V. Pillai    <rajeevvp@yahoo.com>
  */
 static void parse_minix(struct parsed_partitions *state,
 			sector_t offset, sector_t size, int origin)
 {
 #ifdef CONFIG_MINIX_SUBPARTITION
 	Sector sect;
 	unsigned char *data;
 	struct partition *p;
 	int i;

 	data = read_part_sector(state, offset, &sect);
 	if (!data)
 		return;

 	p = (struct partition *)(data + 0x1be);

 	/* The first sector of a Minix partition can have either
 	 * a secondary MBR describing its subpartitions, or
 	 * the normal boot sector. */
 	if (msdos_magic_present (data + 510) &&
 	    SYS_IND(p) == MINIX_PARTITION) { /* subpartition table present */
 		char tmp[1 + BDEVNAME_SIZE + 10 + 9 + 1];

 		snprintf(tmp, sizeof(tmp), " %s%d: <minix:", state->name, origin);
 		strlcat(state->pp_buf, tmp, PAGE_SIZE);
 		for (i = 0; i < MINIX_NR_SUBPARTITIONS; i++, p++) {
 			if (state->next == state->limit)
 				break;
 			/* add each partition in use */
 			if (SYS_IND(p) == MINIX_PARTITION)
 				put_partition(state, state->next++,
 					      start_sect(p), nr_sects(p));
 		}
 		strlcat(state->pp_buf, " >\n", PAGE_SIZE);
 	}
 	put_dev_sector(sect);
 #endif /* CONFIG_MINIX_SUBPARTITION */
 }

 static struct {
 	unsigned char id;
 	void (*parse)(struct parsed_partitions *, sector_t, sector_t, int);
 } subtypes[] = {
 	{FREEBSD_PARTITION, parse_freebsd},
 	{NETBSD_PARTITION, parse_netbsd},
 	{OPENBSD_PARTITION, parse_openbsd},
 	{MINIX_PARTITION, parse_minix},
 	{UNIXWARE_PARTITION, parse_unixware},
 	{SOLARIS_X86_PARTITION, parse_solaris_x86},
 	{NEW_SOLARIS_X86_PARTITION, parse_solaris_x86},
 	{0, NULL},
 };

 int msdos_partition(struct parsed_partitions *state)
 {
 	sector_t sector_size = bdev_logical_block_size(state->bdev) / 512;
 	Sector sect;
 	unsigned char *data;
 	struct partition *p;
 	struct fat_boot_sector *fb;
 	int slot;

 	data = read_part_sector(state, 0, &sect);
 	if (!data)
 		return -1;
 	if (!msdos_magic_present(data + 510)) {
 		put_dev_sector(sect);
 		return 0;
 	}

 	if (aix_magic_present(state, data)) {
 		put_dev_sector(sect);
 		strlcat(state->pp_buf, " [AIX]", PAGE_SIZE);
 		return 0;
 	}

 	/*
 	 * Now that the 55aa signature is present, this is probably
 	 * either the boot sector of a FAT filesystem or a DOS-type
 	 * partition table. Reject this in case the boot indicator
 	 * is not 0 or 0x80.
 	 */
 	p = (struct partition *) (data + 0x1be);
 	for (slot = 1; slot <= 4; slot++, p++) {
 		if (p->boot_ind != 0 && p->boot_ind != 0x80) {
 			/*
 			 * Even without a valid boot inidicator value
 			 * its still possible this is valid FAT filesystem
 			 * without a partition table.
 			 */
 			fb = (struct fat_boot_sector *) data;
 			if (slot == 1 && fb->reserved && fb->fats
 				&& fat_valid_media(fb->media)) {
 				strlcat(state->pp_buf, "\n", PAGE_SIZE);
 				put_dev_sector(sect);
 				return 1;
 			} else {
 				put_dev_sector(sect);
 				return 0;
 			}
 		}
 	}

 #ifdef CONFIG_EFI_PARTITION
 	p = (struct partition *) (data + 0x1be);
 	for (slot = 1 ; slot <= 4 ; slot++, p++) {
 		/* If this is an EFI GPT disk, msdos should ignore it. */
 		if (SYS_IND(p) == EFI_PMBR_OSTYPE_EFI_GPT) {
 			put_dev_sector(sect);
 			return 0;
 		}
 	}
 #endif
 	p = (struct partition *) (data + 0x1be);

 	/*
 	 * Look for partitions in two passes:
 	 * First find the primary and DOS-type extended partitions.
 	 * On the second pass look inside *BSD, Unixware and Solaris partitions.
 	 */

 	state->next = 5;
 	for (slot = 1 ; slot <= 4 ; slot++, p++) {
 		sector_t start = start_sect(p)*sector_size;
 		sector_t size = nr_sects(p)*sector_size;
 		if (!size)
 			continue;
 		if (is_extended_partition(p)) {
 			/*
 			 * prevent someone doing mkfs or mkswap on an
 			 * extended partition, but leave room for LILO
 			 * FIXME: this uses one logical sector for > 512b
 			 * sector, although it may not be enough/proper.
 			 */
 			sector_t n = 2;
 			n = min(size, max(sector_size, n));
 			put_partition(state, slot, start, n);

 			strlcat(state->pp_buf, " <", PAGE_SIZE);
 			parse_extended(state, start, size);
 			strlcat(state->pp_buf, " >", PAGE_SIZE);
 			continue;
 		}
 		put_partition(state, slot, start, size);
 		if (SYS_IND(p) == LINUX_RAID_PARTITION)
 			state->parts[slot].flags = ADDPART_FLAG_RAID;
 		if (SYS_IND(p) == DM6_PARTITION)
 			strlcat(state->pp_buf, "[DM]", PAGE_SIZE);
 		if (SYS_IND(p) == EZD_PARTITION)
 			strlcat(state->pp_buf, "[EZD]", PAGE_SIZE);
 	}

 	strlcat(state->pp_buf, "\n", PAGE_SIZE);

 	/* second pass - output for each on a separate line */
 	p = (struct partition *) (0x1be + data);
 	for (slot = 1 ; slot <= 4 ; slot++, p++) {
 		unsigned char id = SYS_IND(p);
 		int n;

 		if (!nr_sects(p))
 			continue;

 		for (n = 0; subtypes[n].parse && id != subtypes[n].id; n++)
 			;

 		if (!subtypes[n].parse)
 			continue;
 		subtypes[n].parse(state, start_sect(p) * sector_size,
 				  nr_sects(p) * sector_size, slot);
 	}
 	put_dev_sector(sect);
 	return 1;
 }
	/*
	* fs/partitions/msdos.c
	*
	* Code extracted from drivers/block/genhd.c
	* Copyright (C) 1991-1998 Linus Torvalds
	*
	* Thanks to Branko Lankester, lankeste@fwi.uva.nl, who found a bug
	* in the early extended-partition checks and added DM partitions
	*
	* Support for DiskManager v6.0x added by Mark Lord,
	* with information provided by OnTrack. This now works for linux fdisk
	* and LILO, as well as loadlin and bootln. Note that disks other than
	* /dev/hda must have a "DOS" type 0x51 partition in the first slot (hda1).
	*
	* More flexible handling of extended partitions - aeb, 950831
	*
	* Check partition table on IDE disks for common CHS translations
	*
	* Re-organised Feb 1998 Russell King
	*/
	#include <linux/msdos_fs.h>

	#include "check.h"
	#include "msdos.h"
	#include "efi.h"

	/*
	* Many architectures don't like unaligned accesses, while
	* the nr_sects and start_sect partition table entries are
	* at a 2 (mod 4) address.
	*/
	#include <asm/unaligned.h>

	#define SYS_IND(p) get_unaligned(&p->sys_ind)

	static inline sector_t nr_sects(struct partition *p)
	{
	return (sector_t)get_unaligned_le32(&p->nr_sects);
	}

	static inline sector_t start_sect(struct partition *p)
	{
	return (sector_t)get_unaligned_le32(&p->start_sect);
	}

	static inline int is_extended_partition(struct partition *p)
	{
	return (SYS_IND(p) == DOS_EXTENDED_PARTITION \|\|
	SYS_IND(p) == WIN98_EXTENDED_PARTITION \|\|
	SYS_IND(p) == LINUX_EXTENDED_PARTITION);
	}

	#define MSDOS_LABEL_MAGIC1 0x55
	#define MSDOS_LABEL_MAGIC2 0xAA

	static inline int
	msdos_magic_present(unsigned char *p)
	{
	return (p[0] == MSDOS_LABEL_MAGIC1 && p[1] == MSDOS_LABEL_MAGIC2);
	}

	/* Value is EBCDIC 'IBMA' */
	#define AIX_LABEL_MAGIC1 0xC9
	#define AIX_LABEL_MAGIC2 0xC2
	#define AIX_LABEL_MAGIC3 0xD4
	#define AIX_LABEL_MAGIC4 0xC1
	static int aix_magic_present(struct parsed_partitions state, unsigned char p)
	{
	struct partition pt = (struct partition ) (p + 0x1be);
	Sector sect;
	unsigned char *d;
	int slot, ret = 0;

	if (!(p[0] == AIX_LABEL_MAGIC1 &&
	p[1] == AIX_LABEL_MAGIC2 &&
	p[2] == AIX_LABEL_MAGIC3 &&
	p[3] == AIX_LABEL_MAGIC4))
	return 0;
	/* Assume the partition table is valid if Linux partitions exists */
	for (slot = 1; slot <= 4; slot++, pt++) {
	if (pt->sys_ind == LINUX_SWAP_PARTITION \|\|
	pt->sys_ind == LINUX_RAID_PARTITION \|\|
	pt->sys_ind == LINUX_DATA_PARTITION \|\|
	pt->sys_ind == LINUX_LVM_PARTITION \|\|
	is_extended_partition(pt))
	return 0;
	}
	d = read_part_sector(state, 7, &sect);
	if (d) {
	if (d[0] == '_' && d[1] == 'L' && d[2] == 'V' && d[3] == 'M')
	ret = 1;
	put_dev_sector(sect);
	};
	return ret;
	}

	/*
	* Create devices for each logical partition in an extended partition.
	* The logical partitions form a linked list, with each entry being
	* a partition table with two entries. The first entry
	* is the real data partition (with a start relative to the partition
	* table start). The second is a pointer to the next logical partition
	* (with a start relative to the entire extended partition).
	* We do not create a Linux partition for the partition tables, but
	* only for the actual data partitions.
	*/

	static void parse_extended(struct parsed_partitions *state,
	sector_t first_sector, sector_t first_size)
	{
	struct partition *p;
	Sector sect;
	unsigned char *data;
	sector_t this_sector, this_size;
	sector_t sector_size = bdev_logical_block_size(state->bdev) / 512;
	int loopct = 0; /* number of links followed
	without finding a data partition */
	int i;

	this_sector = first_sector;
	this_size = first_size;

	while (1) {
	if (++loopct > 100)
	return;
	if (state->next == state->limit)
	return;
	data = read_part_sector(state, this_sector, &sect);
	if (!data)
	return;

	if (!msdos_magic_present(data + 510))
	goto done;

	p = (struct partition *) (data + 0x1be);

	/*
	* Usually, the first entry is the real data partition,
	* the 2nd entry is the next extended partition, or empty,
	* and the 3rd and 4th entries are unused.
	* However, DRDOS sometimes has the extended partition as
	* the first entry (when the data partition is empty),
	* and OS/2 seems to use all four entries.
	*/

	/*
	* First process the data partition(s)
	*/
	for (i=0; i<4; i++, p++) {
	sector_t offs, size, next;
	if (!nr_sects(p) \|\| is_extended_partition(p))
	continue;

	/* Check the 3rd and 4th entries -
	these sometimes contain random garbage */
	offs = start_sect(p)*sector_size;
	size = nr_sects(p)*sector_size;
	next = this_sector + offs;
	if (i >= 2) {
	if (offs + size > this_size)
	continue;
	if (next < first_sector)
	continue;
	if (next + size > first_sector + first_size)
	continue;
	}

	put_partition(state, state->next, next, size);
	if (SYS_IND(p) == LINUX_RAID_PARTITION)
	state->parts[state->next].flags = ADDPART_FLAG_RAID;
	loopct = 0;
	if (++state->next == state->limit)
	goto done;
	}
	/*
	* Next, process the (first) extended partition, if present.
	* (So far, there seems to be no reason to make
	* parse_extended() recursive and allow a tree
	* of extended partitions.)
	* It should be a link to the next logical partition.
	*/
	p -= 4;
	for (i=0; i<4; i++, p++)
	if (nr_sects(p) && is_extended_partition(p))
	break;
	if (i == 4)
	goto done; /* nothing left to do */

	this_sector = first_sector + start_sect(p) * sector_size;
	this_size = nr_sects(p) * sector_size;
	put_dev_sector(sect);
	}
	done:
	put_dev_sector(sect);
	}

	/* james@bpgc.com: Solaris has a nasty indicator: 0x82 which also
	indicates linux swap. Be careful before believing this is Solaris. */

	static void parse_solaris_x86(struct parsed_partitions *state,
	sector_t offset, sector_t size, int origin)
	{
	#ifdef CONFIG_SOLARIS_X86_PARTITION
	Sector sect;
	struct solaris_x86_vtoc *v;
	int i;
	short max_nparts;

	v = read_part_sector(state, offset + 1, &sect);
	if (!v)
	return;
	if (le32_to_cpu(v->v_sanity) != SOLARIS_X86_VTOC_SANE) {
	put_dev_sector(sect);
	return;
	}
	{
	char tmp[1 + BDEVNAME_SIZE + 10 + 11 + 1];

	snprintf(tmp, sizeof(tmp), " %s%d: <solaris:", state->name, origin);
	strlcat(state->pp_buf, tmp, PAGE_SIZE);
	}
	if (le32_to_cpu(v->v_version) != 1) {
	char tmp[64];

	snprintf(tmp, sizeof(tmp), " cannot handle version %d vtoc>\n",
	le32_to_cpu(v->v_version));
	strlcat(state->pp_buf, tmp, PAGE_SIZE);
	put_dev_sector(sect);
	return;
	}
	/* Ensure we can handle previous case of VTOC with 8 entries gracefully */
	max_nparts = le16_to_cpu (v->v_nparts) > 8 ? SOLARIS_X86_NUMSLICE : 8;
	for (i=0; i<max_nparts && state->next<state->limit; i++) {
	struct solaris_x86_slice *s = &v->v_slice[i];
	char tmp[3 + 10 + 1 + 1];

	if (s->s_size == 0)
	continue;
	snprintf(tmp, sizeof(tmp), " [s%d]", i);
	strlcat(state->pp_buf, tmp, PAGE_SIZE);
	/* solaris partitions are relative to current MS-DOS
	* one; must add the offset of the current partition */
	put_partition(state, state->next++,
	le32_to_cpu(s->s_start)+offset,
	le32_to_cpu(s->s_size));
	}
	put_dev_sector(sect);
	strlcat(state->pp_buf, " >\n", PAGE_SIZE);
	#endif
	}

	#if defined(CONFIG_BSD_DISKLABEL)
	/*
	* Create devices for BSD partitions listed in a disklabel, under a
	* dos-like partition. See parse_extended() for more information.
	*/
	static void parse_bsd(struct parsed_partitions *state,
	sector_t offset, sector_t size, int origin, char *flavour,
	int max_partitions)
	{
	Sector sect;
	struct bsd_disklabel *l;
	struct bsd_partition *p;
	char tmp[64];

	l = read_part_sector(state, offset + 1, &sect);
	if (!l)
	return;
	if (le32_to_cpu(l->d_magic) != BSD_DISKMAGIC) {
	put_dev_sector(sect);
	return;
	}

	snprintf(tmp, sizeof(tmp), " %s%d: <%s:", state->name, origin, flavour);
	strlcat(state->pp_buf, tmp, PAGE_SIZE);

	if (le16_to_cpu(l->d_npartitions) < max_partitions)
	max_partitions = le16_to_cpu(l->d_npartitions);
	for (p = l->d_partitions; p - l->d_partitions < max_partitions; p++) {
	sector_t bsd_start, bsd_size;

	if (state->next == state->limit)
	break;
	if (p->p_fstype == BSD_FS_UNUSED)
	continue;
	bsd_start = le32_to_cpu(p->p_offset);
	bsd_size = le32_to_cpu(p->p_size);
	if (offset == bsd_start && size == bsd_size)
	/* full parent partition, we have it already */
	continue;
	if (offset > bsd_start \|\| offset+size < bsd_start+bsd_size) {
	strlcat(state->pp_buf, "bad subpartition - ignored\n", PAGE_SIZE);
	continue;
	}
	put_partition(state, state->next++, bsd_start, bsd_size);
	}
	put_dev_sector(sect);
	if (le16_to_cpu(l->d_npartitions) > max_partitions) {
	snprintf(tmp, sizeof(tmp), " (ignored %d more)",
	le16_to_cpu(l->d_npartitions) - max_partitions);
	strlcat(state->pp_buf, tmp, PAGE_SIZE);
	}
	strlcat(state->pp_buf, " >\n", PAGE_SIZE);
	}
	#endif

	static void parse_freebsd(struct parsed_partitions *state,
	sector_t offset, sector_t size, int origin)
	{
	#ifdef CONFIG_BSD_DISKLABEL
	parse_bsd(state, offset, size, origin, "bsd", BSD_MAXPARTITIONS);
	#endif
	}

	static void parse_netbsd(struct parsed_partitions *state,
	sector_t offset, sector_t size, int origin)
	{
	#ifdef CONFIG_BSD_DISKLABEL
	parse_bsd(state, offset, size, origin, "netbsd", BSD_MAXPARTITIONS);
	#endif
	}

	static void parse_openbsd(struct parsed_partitions *state,
	sector_t offset, sector_t size, int origin)
	{
	#ifdef CONFIG_BSD_DISKLABEL
	parse_bsd(state, offset, size, origin, "openbsd",
	OPENBSD_MAXPARTITIONS);
	#endif
	}

	/*
	* Create devices for Unixware partitions listed in a disklabel, under a
	* dos-like partition. See parse_extended() for more information.
	*/
	static void parse_unixware(struct parsed_partitions *state,
	sector_t offset, sector_t size, int origin)
	{
	#ifdef CONFIG_UNIXWARE_DISKLABEL
	Sector sect;
	struct unixware_disklabel *l;
	struct unixware_slice *p;

	l = read_part_sector(state, offset + 29, &sect);
	if (!l)
	return;
	if (le32_to_cpu(l->d_magic) != UNIXWARE_DISKMAGIC \|\|
	le32_to_cpu(l->vtoc.v_magic) != UNIXWARE_DISKMAGIC2) {
	put_dev_sector(sect);
	return;
	}
	{
	char tmp[1 + BDEVNAME_SIZE + 10 + 12 + 1];

	snprintf(tmp, sizeof(tmp), " %s%d: <unixware:", state->name, origin);
	strlcat(state->pp_buf, tmp, PAGE_SIZE);
	}
	p = &l->vtoc.v_slice[1];
	/* I omit the 0th slice as it is the same as whole disk. */
	while (p - &l->vtoc.v_slice[0] < UNIXWARE_NUMSLICE) {
	if (state->next == state->limit)
	break;

	if (p->s_label != UNIXWARE_FS_UNUSED)
	put_partition(state, state->next++,
	le32_to_cpu(p->start_sect),
	le32_to_cpu(p->nr_sects));
	p++;
	}
	put_dev_sector(sect);
	strlcat(state->pp_buf, " >\n", PAGE_SIZE);
	#endif
	}

	/*
	* Minix 2.0.0/2.0.2 subpartition support.
	* Anand Krishnamurthy <anandk@wiproge.med.ge.com>
	* Rajeev V. Pillai <rajeevvp@yahoo.com>
	*/
	static void parse_minix(struct parsed_partitions *state,
	sector_t offset, sector_t size, int origin)
	{
	#ifdef CONFIG_MINIX_SUBPARTITION
	Sector sect;
	unsigned char *data;
	struct partition *p;
	int i;

	data = read_part_sector(state, offset, &sect);
	if (!data)
	return;

	p = (struct partition *)(data + 0x1be);

	/* The first sector of a Minix partition can have either
	* a secondary MBR describing its subpartitions, or
	* the normal boot sector. */
	if (msdos_magic_present (data + 510) &&
	SYS_IND(p) == MINIX_PARTITION) { /* subpartition table present */
	char tmp[1 + BDEVNAME_SIZE + 10 + 9 + 1];

	snprintf(tmp, sizeof(tmp), " %s%d: <minix:", state->name, origin);
	strlcat(state->pp_buf, tmp, PAGE_SIZE);
	for (i = 0; i < MINIX_NR_SUBPARTITIONS; i++, p++) {
	if (state->next == state->limit)
	break;
	/* add each partition in use */
	if (SYS_IND(p) == MINIX_PARTITION)
	put_partition(state, state->next++,
	start_sect(p), nr_sects(p));
	}
	strlcat(state->pp_buf, " >\n", PAGE_SIZE);
	}
	put_dev_sector(sect);
	#endif /* CONFIG_MINIX_SUBPARTITION */
	}

	static struct {
	unsigned char id;
	void (parse)(struct parsed_partitions , sector_t, sector_t, int);
	} subtypes[] = {
	{FREEBSD_PARTITION, parse_freebsd},
	{NETBSD_PARTITION, parse_netbsd},
	{OPENBSD_PARTITION, parse_openbsd},
	{MINIX_PARTITION, parse_minix},
	{UNIXWARE_PARTITION, parse_unixware},
	{SOLARIS_X86_PARTITION, parse_solaris_x86},
	{NEW_SOLARIS_X86_PARTITION, parse_solaris_x86},
	{0, NULL},
	};

	int msdos_partition(struct parsed_partitions *state)
	{
	sector_t sector_size = bdev_logical_block_size(state->bdev) / 512;
	Sector sect;
	unsigned char *data;
	struct partition *p;
	struct fat_boot_sector *fb;
	int slot;

	data = read_part_sector(state, 0, &sect);
	if (!data)
	return -1;
	if (!msdos_magic_present(data + 510)) {
	put_dev_sector(sect);
	return 0;
	}

	if (aix_magic_present(state, data)) {
	put_dev_sector(sect);
	strlcat(state->pp_buf, " [AIX]", PAGE_SIZE);
	return 0;
	}

	/*
	* Now that the 55aa signature is present, this is probably
	* either the boot sector of a FAT filesystem or a DOS-type
	* partition table. Reject this in case the boot indicator
	* is not 0 or 0x80.
	*/
	p = (struct partition *) (data + 0x1be);
	for (slot = 1; slot <= 4; slot++, p++) {
	if (p->boot_ind != 0 && p->boot_ind != 0x80) {
	/*
	* Even without a valid boot inidicator value
	* its still possible this is valid FAT filesystem
	* without a partition table.
	*/
	fb = (struct fat_boot_sector *) data;
	if (slot == 1 && fb->reserved && fb->fats
	&& fat_valid_media(fb->media)) {
	strlcat(state->pp_buf, "\n", PAGE_SIZE);
	put_dev_sector(sect);
	return 1;
	} else {
	put_dev_sector(sect);
	return 0;
	}
	}
	}

	#ifdef CONFIG_EFI_PARTITION
	p = (struct partition *) (data + 0x1be);
	for (slot = 1 ; slot <= 4 ; slot++, p++) {
	/* If this is an EFI GPT disk, msdos should ignore it. */
	if (SYS_IND(p) == EFI_PMBR_OSTYPE_EFI_GPT) {
	put_dev_sector(sect);
	return 0;
	}
	}
	#endif
	p = (struct partition *) (data + 0x1be);

	/*
	* Look for partitions in two passes:
	* First find the primary and DOS-type extended partitions.
	* On the second pass look inside *BSD, Unixware and Solaris partitions.
	*/

	state->next = 5;
	for (slot = 1 ; slot <= 4 ; slot++, p++) {
	sector_t start = start_sect(p)*sector_size;
	sector_t size = nr_sects(p)*sector_size;
	if (!size)
	continue;
	if (is_extended_partition(p)) {
	/*
	* prevent someone doing mkfs or mkswap on an
	* extended partition, but leave room for LILO
	* FIXME: this uses one logical sector for > 512b
	* sector, although it may not be enough/proper.
	*/
	sector_t n = 2;
	n = min(size, max(sector_size, n));
	put_partition(state, slot, start, n);

	strlcat(state->pp_buf, " <", PAGE_SIZE);
	parse_extended(state, start, size);
	strlcat(state->pp_buf, " >", PAGE_SIZE);
	continue;
	}
	put_partition(state, slot, start, size);
	if (SYS_IND(p) == LINUX_RAID_PARTITION)
	state->parts[slot].flags = ADDPART_FLAG_RAID;
	if (SYS_IND(p) == DM6_PARTITION)
	strlcat(state->pp_buf, "[DM]", PAGE_SIZE);
	if (SYS_IND(p) == EZD_PARTITION)
	strlcat(state->pp_buf, "[EZD]", PAGE_SIZE);
	}

	strlcat(state->pp_buf, "\n", PAGE_SIZE);

	/* second pass - output for each on a separate line */
	p = (struct partition *) (0x1be + data);
	for (slot = 1 ; slot <= 4 ; slot++, p++) {
	unsigned char id = SYS_IND(p);
	int n;

	if (!nr_sects(p))
	continue;

	for (n = 0; subtypes[n].parse && id != subtypes[n].id; n++)
	;

	if (!subtypes[n].parse)
	continue;
	subtypes[n].parse(state, start_sect(p) * sector_size,
	nr_sects(p) * sector_size, slot);
	}
	put_dev_sector(sect);
	return 1;
	}