1 files changed, 297 insertions, 0 deletions

diff --git a/libblkid/dos.c b/libblkid/dos.c
new file mode 100644
index 000000000..58877691d
--- /dev/null
+++ b/libblkid/dos.c
@@ -0,0 +1,297 @@
+/*
+ * MS-DOS partition parsing code
+ *
+ * Copyright (C) 2009 Karel Zak <kzak@redhat.com>
+ *
+ * This file may be redistributed under the terms of the
+ * GNU Lesser General Public License.
+ *
+ * Inspired by fdisk, partx, Linux kernel and libparted.
+ */
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdint.h>
+
+#include "partitions.h"
+#include "dos.h"
+#include "aix.h"
+
+/* see superblocks/vfat.c */
+extern int blkid_probe_is_vfat(blkid_probe pr);
+
+static const struct dos_subtypes {
+	unsigned char type;
+	const struct blkid_idinfo *id;
+} dos_nested[] = {
+	{ BLKID_FREEBSD_PARTITION, &bsd_pt_idinfo },
+	{ BLKID_NETBSD_PARTITION, &bsd_pt_idinfo },
+	{ BLKID_OPENBSD_PARTITION, &bsd_pt_idinfo },
+	{ BLKID_UNIXWARE_PARTITION, &unixware_pt_idinfo },
+	{ BLKID_SOLARIS_X86_PARTITION, &solaris_x86_pt_idinfo },
+	{ BLKID_MINIX_PARTITION, &minix_pt_idinfo }
+};
+
+static inline int is_extended(struct dos_partition *p)
+{
+	return (p->sys_type == BLKID_DOS_EXTENDED_PARTITION ||
+		p->sys_type == BLKID_W95_EXTENDED_PARTITION ||
+		p->sys_type == BLKID_LINUX_EXTENDED_PARTITION);
+}
+
+static int parse_dos_extended(blkid_probe pr, blkid_parttable tab,
+		uint32_t ex_start, uint32_t ex_size, int ssf)
+{
+	blkid_partlist ls = blkid_probe_get_partlist(pr);
+	uint32_t cur_start = ex_start, cur_size = ex_size;
+	unsigned char *data;
+	int ct_nodata = 0;	/* count ext.partitions without data partitions */
+	int i;
+
+	while (1) {
+		struct dos_partition *p, *p0;
+		uint32_t start, size;
+
+		if (++ct_nodata > 100)
+			return 0;
+		data = blkid_probe_get_sector(pr, cur_start);
+		if (!data)
+			goto leave;	/* malformed partition? */
+
+		if (!is_valid_mbr_signature(data))
+			goto leave;
+
+		p0 = (struct dos_partition *) (data + BLKID_MSDOS_PT_OFFSET);
+
+		/* 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.
+		 * -- Linux kernel fs/partitions/dos.c
+		 *
+		 * See also http://en.wikipedia.org/wiki/Extended_boot_record
+		 */
+
+		/* Parse data partition */
+		for (p = p0, i = 0; i < 4; i++, p++) {
+			uint32_t abs_start;
+			blkid_partition par;
+
+			/* the start is relative to the parental ext.partition */
+			start = dos_partition_start(p) * ssf;
+			size = dos_partition_size(p) * ssf;
+			abs_start = cur_start + start;	/* absolute start */
+
+			if (!size || is_extended(p))
+				continue;
+			if (i >= 2) {
+				/* extra checks to detect real data on
+				 * 3rd and 4th entries */
+				if (start + size > cur_size)
+					continue;
+				if (abs_start < ex_start)
+					continue;
+				if (abs_start + size > ex_start + ex_size)
+					continue;
+			}
+
+			par = blkid_partlist_add_partition(ls, tab, abs_start, size);
+			if (!par)
+				goto err;
+
+			blkid_partition_set_type(par, p->sys_type);
+			blkid_partition_set_flags(par, p->boot_ind);
+			ct_nodata = 0;
+		}
+		/* The first nested ext.partition should be a link to the next
+		 * logical partition. Everything other (recursive ext.partitions)
+		 * is junk.
+		 */
+		for (p = p0, i = 0; i < 4; i++, p++) {
+			start = dos_partition_start(p) * ssf;
+			size = dos_partition_size(p) * ssf;
+
+			if (size && is_extended(p))
+				break;
+		}
+		if (i == 4)
+			goto leave;
+
+		cur_start = ex_start + start;
+		cur_size = size;
+	}
+leave:
+	return 0;
+err:
+	return -1;
+}
+
+static int probe_dos_pt(blkid_probe pr,
+		const struct blkid_idmag *mag __attribute__((__unused__)))
+{
+	int i;
+	int ssf;
+	blkid_parttable tab = NULL;
+	blkid_partlist ls;
+	struct dos_partition *p0, *p;
+	unsigned char *data;
+	uint32_t start, size, id;
+
+	data = blkid_probe_get_sector(pr, 0);
+	if (!data)
+		goto nothing;
+
+	/* ignore disks with AIX magic number -- for more details see aix.c */
+	if (memcmp(data, BLKID_AIX_MAGIC_STRING, BLKID_AIX_MAGIC_STRLEN) == 0)
+		goto nothing;
+
+	/*
+	 * Now that the 55aa signature is present, this is probably
+	 * either the boot sector of a FAT filesystem or a DOS-type
+	 * partition table.
+	 */
+	if (blkid_probe_is_vfat(pr)) {
+		DBG(DEBUG_LOWPROBE, printf("probably FAT -- ignore\n"));
+		goto nothing;
+	}
+
+	p0 = (struct dos_partition *) (data + BLKID_MSDOS_PT_OFFSET);
+
+	/*
+	 * Reject PT where boot indicator is not 0 or 0x80.
+	 */
+	for (p = p0, i = 0; i < 4; i++, p++)
+		if (p->boot_ind != 0 && p->boot_ind != 0x80) {
+			DBG(DEBUG_LOWPROBE, printf("missing boot indicator -- ignore\n"));
+			goto nothing;
+		}
+
+	/*
+	 * GPT uses valid MBR
+	 */
+	for (p = p0, i = 0; i < 4; i++, p++) {
+		if (p->sys_type == BLKID_GPT_PARTITION) {
+			DBG(DEBUG_LOWPROBE, printf("probably GPT -- ignore\n"));
+			goto nothing;
+		}
+	}
+
+	blkid_probe_use_wiper(pr, BLKID_MSDOS_PT_OFFSET,
+				  512 - BLKID_MSDOS_PT_OFFSET);
+
+	/*
+	 * Well, all checks pass, it's MS-DOS partiton table
+	 */
+	if (blkid_partitions_need_typeonly(pr))
+		/* caller does not ask for details about partitions */
+		return 0;
+
+	ls = blkid_probe_get_partlist(pr);
+
+	/* sector size factor (the start and size are in the real sectors, but
+	 * we need to convert all sizes to 512 logical sectors
+	 */
+	ssf = blkid_probe_get_sectorsize(pr) / 512;
+
+	/* allocate a new partition table */
+	tab = blkid_partlist_new_parttable(ls, "dos", BLKID_MSDOS_PT_OFFSET);
+	if (!tab)
+		goto err;
+
+	id = dos_parttable_id(data);
+	if (id) {
+		char buf[37];
+
+		snprintf(buf, sizeof(buf), "0x%08x", id);
+		blkid_parttable_set_id(tab, (unsigned char *) buf);
+	}
+
+
+	/* Parse primary partitions */
+	for (p = p0, i = 0; i < 4; i++, p++) {
+		blkid_partition par;
+
+		start = dos_partition_start(p) * ssf;
+		size = dos_partition_size(p) * ssf;
+
+		if (!size) {
+			/* Linux kernel ignores empty partitions, but partno for
+			 * the empty primary partitions is not reused */
+			blkid_partlist_increment_partno(ls);
+			continue;
+		}
+		par = blkid_partlist_add_partition(ls, tab, start, size);
+		if (!par)
+			goto err;
+
+		blkid_partition_set_type(par, p->sys_type);
+		blkid_partition_set_flags(par, p->boot_ind);
+	}
+
+	/* Linux uses partition numbers greater than 4
+	 * for all logical partition and all nested partition tables (bsd, ..)
+	 */
+	blkid_partlist_set_partno(ls, 5);
+
+	/* Parse logical partitions */
+	for (p = p0, i = 0; i < 4; i++, p++) {
+		start = dos_partition_start(p) * ssf;
+		size = dos_partition_size(p) * ssf;
+
+		if (!size)
+			continue;
+		if (is_extended(p) &&
+		    parse_dos_extended(pr, tab, start, size, ssf) == -1)
+			goto err;
+	}
+
+	/* Parse subtypes (nested partitions) on large disks */
+	if (!blkid_probe_is_tiny(pr)) {
+		for (p = p0, i = 0; i < 4; i++, p++) {
+			size_t n;
+
+			if (!dos_partition_size(p) || is_extended(p))
+				continue;
+
+			for (n = 0; n < ARRAY_SIZE(dos_nested); n++) {
+				if (dos_nested[n].type != p->sys_type)
+					continue;
+
+				if (blkid_partitions_do_subprobe(pr,
+						blkid_partlist_get_partition(ls, i),
+						dos_nested[n].id) == -1)
+					goto err;
+				break;
+			}
+		}
+	}
+	return 0;
+
+nothing:
+	return 1;
+err:
+	return -1;
+}
+
+
+const struct blkid_idinfo dos_pt_idinfo =
+{
+	.name		= "dos",
+	.probefunc	= probe_dos_pt,
+	.magics		=
+	{
+		/* DOS master boot sector:
+		 *
+		 *     0 | Code Area
+		 *   440 | Optional Disk signature
+		 *   446 | Partition table
+		 *   510 | 0x55
+		 *   511 | 0xAA
+		 */
+		{ .magic = "\x55\xAA", .len = 2, .sboff = 510 },
+		{ NULL }
+	}
+};
+