diff options
Diffstat (limited to 'libblkid/src/partitions/dos.c')
| -rw-r--r-- | libblkid/src/partitions/dos.c | 366 |
1 files changed, 366 insertions, 0 deletions
diff --git a/libblkid/src/partitions/dos.c b/libblkid/src/partitions/dos.c new file mode 100644 index 0000000..659ca9a --- /dev/null +++ b/libblkid/src/partitions/dos.c @@ -0,0 +1,366 @@ +/* + * 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 "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[] = { + { MBR_FREEBSD_PARTITION, &bsd_pt_idinfo }, + { MBR_NETBSD_PARTITION, &bsd_pt_idinfo }, + { MBR_OPENBSD_PARTITION, &bsd_pt_idinfo }, + { MBR_UNIXWARE_PARTITION, &unixware_pt_idinfo }, + { MBR_SOLARIS_X86_PARTITION, &solaris_x86_pt_idinfo }, + { MBR_MINIX_PARTITION, &minix_pt_idinfo } +}; + +static inline int is_extended(struct dos_partition *p) +{ + return (p->sys_ind == MBR_DOS_EXTENDED_PARTITION || + p->sys_ind == MBR_W95_EXTENDED_PARTITION || + p->sys_ind == MBR_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; + + DBG(LOWPROBE, ul_debug("parse EBR [start=%d, size=%d]", ex_start/ssf, ex_size/ssf)); + if (ex_start == 0) { + DBG(LOWPROBE, ul_debug("Bad offset in primary extended partition -- ignore")); + return 0; + } + + while (1) { + struct dos_partition *p, *p0; + uint32_t start, size; + + if (++ct_nodata > 100) + return BLKID_PROBE_OK; + data = blkid_probe_get_sector(pr, cur_start); + if (!data) { + if (errno) + return -errno; + goto leave; /* malformed partition? */ + } + + if (!mbr_is_valid_magic(data)) + goto leave; + + p0 = mbr_get_partition(data, 0); + + /* 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_get_start(p) * ssf; + size = dos_partition_get_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; + } + + /* Avoid recursive non-empty links, see ct_nodata counter */ + if (blkid_partlist_get_partition_by_start(ls, abs_start)) { + DBG(LOWPROBE, ul_debug("#%d: EBR duplicate data partition [abs start=%u] -- ignore", + i + 1, abs_start)); + continue; + } + + par = blkid_partlist_add_partition(ls, tab, abs_start, size); + if (!par) + return -ENOMEM; + + blkid_partition_set_type(par, p->sys_ind); + blkid_partition_set_flags(par, p->boot_ind); + blkid_partition_gen_uuid(par); + 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_get_start(p) * ssf; + size = dos_partition_get_size(p) * ssf; + + if (size && is_extended(p)) { + if (start == 0) + DBG(LOWPROBE, ul_debug("#%d: EBR link offset is zero -- ignore", i + 1)); + else + break; + } + } + if (i == 4) + goto leave; + + cur_start = ex_start + start; + cur_size = size; + } +leave: + return BLKID_PROBE_OK; +} + +static inline int is_lvm(blkid_probe pr) +{ + struct blkid_prval *v = __blkid_probe_lookup_value(pr, "TYPE"); + + return (v && v->data && strcmp((char *) v->data, "LVM2_member") == 0); +} + +static inline int is_empty_mbr(unsigned char *mbr) +{ + struct dos_partition *p = mbr_get_partition(mbr, 0); + int i, nparts = 0; + + for (i = 0; i < 4; i++) { + if (dos_partition_get_size(p) > 0) + nparts++; + p++; + } + + return nparts == 0; +} + +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; + char idstr[UUID_STR_LEN]; + + + data = blkid_probe_get_sector(pr, 0); + if (!data) { + if (errno) + return -errno; + 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 = mbr_get_partition(data, 0); + + /* + * 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(LOWPROBE, ul_debug("missing boot indicator -- ignore")); + goto nothing; + } + + /* + * GPT uses valid MBR + */ + for (p = p0, i = 0; i < 4; i++, p++) { + if (p->sys_ind == MBR_GPT_PARTITION) { + DBG(LOWPROBE, ul_debug("probably GPT -- ignore")); + 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) == 1) { + DBG(LOWPROBE, ul_debug("probably FAT -- ignore")); + goto nothing; + } + + /* + * Ugly exception, if the device contains a valid LVM physical volume + * and empty MBR (=no partition defined) then it's LVM and MBR should + * be ignored. Crazy people use it to boot from LVM devices. + */ + if (is_lvm(pr) && is_empty_mbr(data)) { + DBG(LOWPROBE, ul_debug("empty MBR on LVM device -- ignore")); + goto nothing; + } + + blkid_probe_use_wiper(pr, MBR_PT_OFFSET, 512 - MBR_PT_OFFSET); + + id = mbr_get_id(data); + if (id) + snprintf(idstr, sizeof(idstr), "%08x", id); + + /* + * Well, all checks pass, it's MS-DOS partition table + */ + if (blkid_partitions_need_typeonly(pr)) { + /* Non-binary interface -- caller does not ask for details + * about partitions, just set generic variables only. */ + if (id) + blkid_partitions_strcpy_ptuuid(pr, idstr); + return 0; + } + + ls = blkid_probe_get_partlist(pr); + if (!ls) + goto nothing; + + /* 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", MBR_PT_OFFSET); + if (!tab) + return -ENOMEM; + + if (id) + blkid_parttable_set_id(tab, (unsigned char *) idstr); + + /* Parse primary partitions */ + for (p = p0, i = 0; i < 4; i++, p++) { + blkid_partition par; + + start = dos_partition_get_start(p) * ssf; + size = dos_partition_get_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) + return -ENOMEM; + + blkid_partition_set_type(par, p->sys_ind); + blkid_partition_set_flags(par, p->boot_ind); + blkid_partition_gen_uuid(par); + } + + /* 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_get_start(p) * ssf; + size = dos_partition_get_size(p) * ssf; + + if (!size) + continue; + if (is_extended(p) && + parse_dos_extended(pr, tab, start, size, ssf) == -1) + goto nothing; + } + + /* Parse subtypes (nested partitions) on large disks */ + if (!blkid_probe_is_tiny(pr)) { + int nparts = blkid_partlist_numof_partitions(ls); + + DBG(LOWPROBE, ul_debug("checking for subtypes")); + + for (i = 0; i < nparts; i++) { + size_t n; + int type; + blkid_partition pa = blkid_partlist_get_partition(ls, i); + + if (pa == NULL + || blkid_partition_get_size(pa) == 0 + || blkid_partition_is_extended(pa) + || blkid_partition_is_logical(pa)) + continue; + + type = blkid_partition_get_type(pa); + + for (n = 0; n < ARRAY_SIZE(dos_nested); n++) { + int rc; + + if (dos_nested[n].type != type) + continue; + + rc = blkid_partitions_do_subprobe(pr, pa, + dos_nested[n].id); + if (rc < 0) + return rc; + break; + } + } + } + return BLKID_PROBE_OK; + +nothing: + return BLKID_PROBE_NONE; +} + + +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 } + } +}; + |