--- /dev/null
+/*
+ * 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"
+
+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 },
+};
+
+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;
+
+ /* 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;
+ }
+ if (!blkid_partlist_add_partition(ls, tab, p->sys_type,
+ abs_start, size))
+ goto err;
+
+ 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)
+{
+ int i;
+ int ssf;
+ blkid_parttable tab = NULL;
+ blkid_partlist ls;
+ struct dos_partition *p0, *p;
+ unsigned char *data;
+ uint32_t start, size;
+
+ 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;
+
+ p0 = (struct dos_partition *) (data + BLKID_MSDOS_PT_OFFSET);
+
+ /*
+ * 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.
+ */
+ for (p = p0, i = 0; i < 4; i++, p++) {
+ if (p->boot_ind != 0 && p->boot_ind != 0x80)
+ goto nothing;
+ }
+
+ /*
+ * GPT uses valid MBR
+ */
+ for (p = p0, i = 0; i < 4; i++, p++) {
+ if (p->sys_type == BLKID_GPT_PARTITION)
+ goto nothing;
+ }
+
+ /*
+ * 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;
+
+ /* Parse primary 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 (!blkid_partlist_add_partition(ls, tab, p->sys_type,
+ start, size))
+ goto err;
+ }
+
+ /* 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) */
+ for (p = p0, i = 0; i < 4; i++, p++) {
+ int 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 }
+ }
+};
+
projects / util-linux / commitdiff