From 60ad0bbba55401daee3bfb7427474c211747a75c Mon Sep 17 00:00:00 2001 From: Karel Zak Date: Wed, 16 Sep 2009 16:10:43 +0200 Subject: [PATCH] libblkid: add MS-DOS partitions support Signed-off-by: Karel Zak --- shlibs/blkid/src/partitions/Makefile.am | 4 +- shlibs/blkid/src/partitions/dos.c | 256 +++++++++++++++++++++++ shlibs/blkid/src/partitions/dos.h | 36 ++++ shlibs/blkid/src/partitions/partitions.c | 1 + shlibs/blkid/src/partitions/partitions.h | 1 + 5 files changed, 297 insertions(+), 1 deletion(-) create mode 100644 shlibs/blkid/src/partitions/dos.c create mode 100644 shlibs/blkid/src/partitions/dos.h diff --git a/shlibs/blkid/src/partitions/Makefile.am b/shlibs/blkid/src/partitions/Makefile.am index ebf98fe0..906ba68c 100644 --- a/shlibs/blkid/src/partitions/Makefile.am +++ b/shlibs/blkid/src/partitions/Makefile.am @@ -14,4 +14,6 @@ libblkid_partitions_la_SOURCES = partitions.c \ solaris_x86.c \ sun.c \ sgi.c \ - mac.c + mac.c \ + dos.c \ + dos.h diff --git a/shlibs/blkid/src/partitions/dos.c b/shlibs/blkid/src/partitions/dos.c new file mode 100644 index 00000000..d03e18e6 --- /dev/null +++ b/shlibs/blkid/src/partitions/dos.c @@ -0,0 +1,256 @@ +/* + * MS-DOS partition parsing code + * + * Copyright (C) 2009 Karel Zak + * + * This file may be redistributed under the terms of the + * GNU Lesser General Public License. + * + * Inspired by fdisk, partx, Linux kernel and libparted. + */ +#include +#include +#include +#include + +#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 } + } +}; + diff --git a/shlibs/blkid/src/partitions/dos.h b/shlibs/blkid/src/partitions/dos.h new file mode 100644 index 00000000..130aa011 --- /dev/null +++ b/shlibs/blkid/src/partitions/dos.h @@ -0,0 +1,36 @@ +#ifndef BLKID_PARTITIONS_DOS_H +#define BLKID_PARTITIONS_DOS_H + +struct dos_partition { + unsigned char boot_ind; /* 0x80 - active */ + unsigned char bh, bs, bc; /* begin CHS */ + unsigned char sys_type; + unsigned char eh, es, ec; /* end CHS */ + unsigned char start_sect[4]; + unsigned char nr_sects[4]; +} __attribute__((packed)); + +#define BLKID_MSDOS_PT_OFFSET 0x1be + +/* assemble badly aligned little endian integer */ +static inline unsigned int assemble4le(unsigned char *p) +{ + return p[0] | (p[1] << 8) | (p[2] << 16) | (p[3] << 24); +} + +static inline unsigned int dos_partition_start(struct dos_partition *p) +{ + return assemble4le(&(p->start_sect[0])); +} + +static inline unsigned int dos_partition_size(struct dos_partition *p) +{ + return assemble4le(&(p->nr_sects[0])); +} + +static inline int is_valid_mbr_signature(const unsigned char *mbr) +{ + return mbr[510] == 0x55 && mbr[511] == 0xaa ? 1 : 0; +} + +#endif /* BLKID_PARTITIONS_DOS_H */ diff --git a/shlibs/blkid/src/partitions/partitions.c b/shlibs/blkid/src/partitions/partitions.c index 2fd9e2a4..064ec69a 100644 --- a/shlibs/blkid/src/partitions/partitions.c +++ b/shlibs/blkid/src/partitions/partitions.c @@ -105,6 +105,7 @@ static const struct blkid_idinfo *idinfos[] = &aix_pt_idinfo, &sgi_pt_idinfo, &sun_pt_idinfo, + &dos_pt_idinfo, &mac_pt_idinfo, &bsd_pt_idinfo, &unixware_pt_idinfo, diff --git a/shlibs/blkid/src/partitions/partitions.h b/shlibs/blkid/src/partitions/partitions.h index fd8465df..205311a5 100644 --- a/shlibs/blkid/src/partitions/partitions.h +++ b/shlibs/blkid/src/partitions/partitions.h @@ -42,5 +42,6 @@ extern const struct blkid_idinfo solaris_x86_pt_idinfo; extern const struct blkid_idinfo sun_pt_idinfo; extern const struct blkid_idinfo sgi_pt_idinfo; extern const struct blkid_idinfo mac_pt_idinfo; +extern const struct blkid_idinfo dos_pt_idinfo; #endif /* BLKID_PARTITIONS_H */ -- 2.39.5