Merge branch 'include/parttypes' of https://github.com/t-8ch/util-linux

[thirdparty/util-linux.git] / libfdisk / src / dos.c

/*
 *
 * Copyright (C) 2007-2013 Karel Zak <kzak@redhat.com>
 *                    2012 Davidlohr Bueso <dave@gnu.org>
 *                    2021 Pali Rohár <pali.rohar@gmail.com>
 *
 * This is re-written version for libfdisk, the original was fdiskdoslabel.c
 * from util-linux fdisk.
 */
#include "c.h"
#include "randutils.h"
#include "pt-mbr.h"
#include "strutils.h"

#include "fdiskP.h"

#include <ctype.h>

#define MAXIMUM_PARTS   60
#define ACTIVE_FLAG     0x80

/**
 * SECTION: dos
 * @title: DOS
 * @short_description: disk label specific functions
 *
 */


#define IS_EXTENDED(i) \
        ((i) == MBR_DOS_EXTENDED_PARTITION \
         || (i) == MBR_W95_EXTENDED_PARTITION \
         || (i) == MBR_LINUX_EXTENDED_PARTITION)

/*
 * per partition table entry data
 *
 * The four primary partitions have the same sectorbuffer
 * and have NULL ex_entry.
 *
 * Each logical partition table entry has two pointers, one for the
 * partition and one link to the next one.
 */
struct pte {
        struct dos_partition *pt_entry; /* on-disk MBR entry */
        struct dos_partition *ex_entry; /* on-disk EBR entry */
        fdisk_sector_t offset;          /* disk sector number */
        unsigned char *sectorbuffer;    /* disk sector contents */

        unsigned int changed : 1,
                     private_sectorbuffer : 1;
};

/*
 * in-memory fdisk GPT stuff
 */
struct fdisk_dos_label {
        struct fdisk_label      head;           /* generic part */

        struct pte      ptes[MAXIMUM_PARTS];    /* partition */
        fdisk_sector_t  ext_offset;             /* start of the ext.partition */
        size_t          ext_index;              /* ext.partition index (if ext_offset is set) */
        unsigned int    compatible : 1,         /* is DOS compatible? */
                        non_pt_changed : 1;     /* MBR, but no PT changed */
};

/*
 * Partition types
 */
static const struct fdisk_parttype dos_parttypes[] = {
        #include "pt-mbr-partnames.h"
};

static const struct fdisk_shortcut dos_parttype_cuts[] =
{
        { .shortcut = "L", .alias = "linux",    .data = "83" },
        { .shortcut = "S", .alias = "swap",     .data = "82" },
        { .shortcut = "E", .alias = "extended", .data = "05", .deprecated = 1 }, /* collision with 0x0e type */
        { .shortcut = "Ex",.alias = "extended", .data = "05" }, /* MBR extended */
        { .shortcut = "U", .alias = "uefi",     .data = "EF" }, /* UEFI system */
        { .shortcut = "R", .alias = "raid",     .data = "FD" }, /* Linux RAID */
        { .shortcut = "V", .alias = "lvm",      .data = "8E" }, /* LVM */
        { .shortcut = "X", .alias = "linuxex",  .data = "85" }  /* Linux extended */
};


#define sector(s)       ((s) & 0x3f)
#define cylinder(s, c)  ((c) | (((s) & 0xc0) << 2))

#define alignment_required(_x)  ((_x)->grain != (_x)->sector_size)

#define is_dos_compatible(_x) \
                   (fdisk_is_label(_x, DOS) && \
                    fdisk_dos_is_compatible(fdisk_get_label(_x, NULL)))

#define cround(c, n)    fdisk_cround(c, n)


static inline struct fdisk_dos_label *self_label(struct fdisk_context *cxt)
{
        assert(cxt);
        assert(cxt->label);
        assert(fdisk_is_label(cxt, DOS));

        return (struct fdisk_dos_label *) cxt->label;
}

static inline struct pte *self_pte(struct fdisk_context *cxt, size_t i)
{
        struct fdisk_dos_label *l = self_label(cxt);

        if (i >= ARRAY_SIZE(l->ptes))
                return NULL;

        return &l->ptes[i];
}

static inline struct dos_partition *self_partition(
                                struct fdisk_context *cxt,
                                size_t i)
{
        struct pte *pe = self_pte(cxt, i);
        return pe ? pe->pt_entry : NULL;
}

struct dos_partition *fdisk_dos_get_partition(
                                struct fdisk_context *cxt,
                                size_t i)
{
        assert(cxt);
        assert(cxt->label);
        assert(fdisk_is_label(cxt, DOS));

        return self_partition(cxt, i);
}

static struct fdisk_parttype *dos_partition_parttype(
                struct fdisk_context *cxt,
                struct dos_partition *p)
{
        struct fdisk_parttype *t
                = fdisk_label_get_parttype_from_code(cxt->label, p->sys_ind);
        return t ? : fdisk_new_unknown_parttype(p->sys_ind, NULL);
}

/*
 * Linux kernel cares about partition size only. Things like
 * partition type or so are completely irrelevant -- kzak Nov-2013
 */
static int is_used_partition(struct dos_partition *p)
{
        return p && dos_partition_get_size(p) != 0;
}

static void partition_set_changed(
                                struct fdisk_context *cxt,
                                size_t i,
                                int changed)
{
        struct pte *pe = self_pte(cxt, i);

        if (!pe)
                return;

        DBG(LABEL, ul_debug("DOS: setting %zu partition to %s", i,
                                changed ? "changed" : "unchanged"));

        pe->changed = changed ? 1 : 0;
        if (changed)
                fdisk_label_set_changed(cxt->label, 1);
}

static fdisk_sector_t get_abs_partition_start(struct pte *pe)
{
        assert(pe);
        assert(pe->pt_entry);

        return pe->offset + dos_partition_get_start(pe->pt_entry);
}

static fdisk_sector_t get_abs_partition_end(struct pte *pe)
{
        fdisk_sector_t size;

        assert(pe);
        assert(pe->pt_entry);

        size = dos_partition_get_size(pe->pt_entry);
        return get_abs_partition_start(pe) + size - (size ? 1 : 0);
}

static int is_cleared_partition(struct dos_partition *p)
{
        return !(!p || p->boot_ind || p->bh || p->bs || p->bc ||
                 p->sys_ind || p->eh || p->es || p->ec ||
                 dos_partition_get_start(p) || dos_partition_get_size(p));
}

static int get_partition_unused_primary(struct fdisk_context *cxt,
                                        struct fdisk_partition *pa,
                                        size_t *partno)
{
        size_t org, n;
        int rc;

        assert(cxt);
        assert(cxt->label);
        assert(partno);

        org = cxt->label->nparts_max;

        cxt->label->nparts_max = 4;
        rc = fdisk_partition_next_partno(pa, cxt, &n);
        cxt->label->nparts_max = org;

        if (rc == 1) {
                fdisk_info(cxt, _("All primary partitions have been defined already."));
                rc = -1;
        } else if (rc == -ERANGE) {
                fdisk_warnx(cxt, _("Primary partition not available."));
        } else if (rc == 0)
                *partno = n;

        return rc;
}

static int seek_sector(struct fdisk_context *cxt, fdisk_sector_t secno)
{
        off_t offset = (off_t) secno * cxt->sector_size;

        return lseek(cxt->dev_fd, offset, SEEK_SET) == (off_t) -1 ? -errno : 0;
}

static int read_sector(struct fdisk_context *cxt, fdisk_sector_t secno,
                        unsigned char *buf)
{
        int rc = seek_sector(cxt, secno);
        ssize_t r;

        if (rc < 0)
                return rc;

        r = read(cxt->dev_fd, buf, cxt->sector_size);
        if (r == (ssize_t) cxt->sector_size)
                return 0;
        if (r < 0)
                return -errno;
        return -1;
}

/* Allocate a buffer and read a partition table sector */
static int read_pte(struct fdisk_context *cxt, size_t pno, fdisk_sector_t offset)
{
        int rc;
        unsigned char *buf;
        struct pte *pe = self_pte(cxt, pno);

        if (!pe)
                return -EINVAL;

        buf = calloc(1, cxt->sector_size);
        if (!buf)
                return -ENOMEM;

        DBG(LABEL, ul_debug("DOS: reading EBR %zu: offset=%ju, buffer=%p",
                                pno, (uintmax_t) offset, buf));

        pe->offset = offset;
        pe->sectorbuffer = buf;
        pe->private_sectorbuffer = 1;

        rc = read_sector(cxt, offset, pe->sectorbuffer);
        if (rc) {
                fdisk_warn(cxt, _("Failed to read extended partition table "
                                "(offset=%ju)"), (uintmax_t) offset);
                return rc;
        }

        pe->changed = 0;
        pe->pt_entry = pe->ex_entry = NULL;
        return 0;
}


static void clear_partition(struct dos_partition *p)
{
        if (!p)
                return;
        p->boot_ind = 0;
        p->bh = 0;
        p->bs = 0;
        p->bc = 0;
        p->sys_ind = 0;
        p->eh = 0;
        p->es = 0;
        p->ec = 0;
        dos_partition_set_start(p,0);
        dos_partition_set_size(p,0);
}

static void dos_init(struct fdisk_context *cxt)
{
        struct fdisk_dos_label *l = self_label(cxt);
        size_t i;

        assert(cxt);
        assert(cxt->label);
        assert(fdisk_is_label(cxt, DOS));

        DBG(LABEL, ul_debug("DOS: initialize, first sector buffer %p", cxt->firstsector));

        cxt->label->nparts_max = 4;     /* default, unlimited number of logical */

        l->ext_index = 0;
        l->ext_offset = 0;
        l->non_pt_changed = 0;

        memset(l->ptes, 0, sizeof(l->ptes));

        for (i = 0; i < 4; i++) {
                struct pte *pe = self_pte(cxt, i);

                assert(pe);
                pe->pt_entry = mbr_get_partition(cxt->firstsector, i);
                pe->ex_entry = NULL;
                pe->offset = 0;
                pe->sectorbuffer = cxt->firstsector;
                pe->private_sectorbuffer = 0;
                pe->changed = 0;

                DBG(LABEL, ul_debug("DOS: initialize: #%zu start=%u size=%u sysid=%02x",
                                        i,
                                        dos_partition_get_start(pe->pt_entry),
                                        dos_partition_get_size(pe->pt_entry),
                                        pe->pt_entry->sys_ind));
        }

        if (fdisk_is_listonly(cxt))
                return;
        /*
         * Various warnings...
         */
        if (fdisk_missing_geometry(cxt))
                fdisk_warnx(cxt, _("You can set geometry from the extra functions menu."));

        if (is_dos_compatible(cxt)) {
                fdisk_warnx(cxt, _("DOS-compatible mode is deprecated."));

                if (cxt->sector_size != cxt->phy_sector_size)
                        fdisk_info(cxt, _(
                "The device presents a logical sector size that is smaller than "
                "the physical sector size. Aligning to a physical sector (or optimal "
                "I/O) size boundary is recommended, or performance may be impacted."));
        }

        if (fdisk_use_cylinders(cxt))
                fdisk_warnx(cxt, _("Cylinders as display units are deprecated."));

        if (cxt->total_sectors > UINT_MAX) {
                uint64_t bytes = cxt->total_sectors * cxt->sector_size;
                char *szstr = size_to_human_string(SIZE_SUFFIX_SPACE
                                           | SIZE_SUFFIX_3LETTER, bytes);
                fdisk_warnx(cxt,
                _("The size of this disk is %s (%ju bytes). DOS "
                  "partition table format cannot be used on drives for "
                  "volumes larger than %lu bytes for %lu-byte "
                  "sectors. Use GUID partition table format (GPT)."),
                        szstr, bytes,
                        UINT_MAX * cxt->sector_size,
                        cxt->sector_size);
                free(szstr);
        }
}

/* callback called by libfdisk */
static void dos_deinit(struct fdisk_label *lb)
{
        size_t i;
        struct fdisk_dos_label *l = (struct fdisk_dos_label *) lb;

        for (i = 0; i < ARRAY_SIZE(l->ptes); i++) {
                struct pte *pe = &l->ptes[i];

                if (pe->private_sectorbuffer && pe->sectorbuffer) {
                        DBG(LABEL, ul_debug("DOS: freeing pte %zu sector buffer %p",
                                                i, pe->sectorbuffer));
                        free(pe->sectorbuffer);
                }
                pe->sectorbuffer = NULL;
                pe->private_sectorbuffer = 0;
        }

        memset(l->ptes, 0, sizeof(l->ptes));
}

static void reset_pte(struct pte *pe)
{
        assert(pe);

        if (pe->private_sectorbuffer) {
                DBG(LABEL, ul_debug("   --> freeing pte sector buffer %p",
                                        pe->sectorbuffer));
                free(pe->sectorbuffer);
        }
        memset(pe, 0, sizeof(struct pte));
}

static int delete_partition(struct fdisk_context *cxt, size_t partnum)
{
        struct fdisk_dos_label *l;
        struct pte *pe;
        struct dos_partition *p;
        struct dos_partition *q;

        assert(cxt);
        assert(cxt->label);
        assert(fdisk_is_label(cxt, DOS));

        pe = self_pte(cxt, partnum);
        if (!pe)
                return -EINVAL;

        DBG(LABEL, ul_debug("DOS: delete partition %zu (max=%zu)", partnum,
                                cxt->label->nparts_max));

        l = self_label(cxt);
        p = pe->pt_entry;
        q = pe->ex_entry;

        /* Note that for the fifth partition (partnum == 4) we don't actually
           decrement partitions. */
        if (partnum < 4) {
                DBG(LABEL, ul_debug("--> delete primary"));
                if (IS_EXTENDED(p->sys_ind) && partnum == l->ext_index) {
                        size_t i;
                        DBG(LABEL, ul_debug(" --> delete extended"));
                        for (i = 4; i < cxt->label->nparts_max; i++) {
                                DBG(LABEL, ul_debug("  --> delete logical #%zu", i));
                                reset_pte(&l->ptes[i]);

                        }
                        cxt->label->nparts_max = 4;
                        l->ptes[l->ext_index].ex_entry = NULL;
                        l->ext_offset = 0;
                        l->ext_index = 0;
                }
                partition_set_changed(cxt, partnum, 1);
                clear_partition(p);
        } else if (!q->sys_ind && partnum > 4) {
                DBG(LABEL, ul_debug("--> delete logical [last in the chain]"));
                reset_pte(&l->ptes[partnum]);
                --cxt->label->nparts_max;
                --partnum;
                /* clear link to deleted partition */
                clear_partition(l->ptes[partnum].ex_entry);
                partition_set_changed(cxt, partnum, 1);
        } else {
                DBG(LABEL, ul_debug("--> delete logical [move down]"));
                if (partnum > 4) {
                        DBG(LABEL, ul_debug(" --> delete %zu logical link", partnum));
                        p = l->ptes[partnum - 1].ex_entry;
                        *p = *q;
                        dos_partition_set_start(p, dos_partition_get_start(q));
                        dos_partition_set_size(p, dos_partition_get_size(q));
                        dos_partition_sync_chs(p, pe->offset, cxt->geom.sectors, cxt->geom.heads);
                        partition_set_changed(cxt, partnum - 1, 1);

                } else if (cxt->label->nparts_max > 5) {
                        DBG(LABEL, ul_debug(" --> delete first logical link"));
                        pe = &l->ptes[5];       /* second logical */

                        if (pe->pt_entry)       /* prevent SEGFAULT */
                                dos_partition_set_start(pe->pt_entry,
                                               get_abs_partition_start(pe) -
                                               l->ext_offset);
                        pe->offset = l->ext_offset;
                        dos_partition_sync_chs(p, pe->offset, cxt->geom.sectors, cxt->geom.heads);
                        partition_set_changed(cxt, 5, 1);
                }

                if (cxt->label->nparts_max > 5) {
                        DBG(LABEL, ul_debug(" --> move ptes"));
                        cxt->label->nparts_max--;
                        reset_pte(&l->ptes[partnum]);
                        while (partnum < cxt->label->nparts_max) {
                                DBG(LABEL, ul_debug("  --> moving pte %zu <-- %zu", partnum, partnum + 1));
                                l->ptes[partnum] = l->ptes[partnum + 1];
                                partnum++;
                        }
                        memset(&l->ptes[partnum], 0, sizeof(struct pte));
                } else {
                        DBG(LABEL, ul_debug(" --> the only logical: clear only"));
                        clear_partition(l->ptes[partnum].pt_entry);
                        cxt->label->nparts_max--;

                        if (partnum == 4) {
                                DBG(LABEL, ul_debug("  --> clear last logical"));
                                reset_pte(&l->ptes[partnum]);
                                partition_set_changed(cxt, l->ext_index, 1);
                        }
                }
        }

        fdisk_label_set_changed(cxt->label, 1);
        return 0;
}

static int dos_delete_partition(struct fdisk_context *cxt, size_t partnum)
{
        struct pte *pe;

        assert(cxt);
        assert(cxt->label);
        assert(fdisk_is_label(cxt, DOS));

        pe = self_pte(cxt, partnum);
        if (!pe || !is_used_partition(pe->pt_entry))
                return -EINVAL;

        return delete_partition(cxt, partnum);
}

static void read_extended(struct fdisk_context *cxt, size_t ext)
{
        size_t i;
        struct pte *pex, *pe;
        struct dos_partition *p, *q;
        struct fdisk_dos_label *l = self_label(cxt);

        l->ext_index = ext;
        pex = self_pte(cxt, ext);
        if (!pex) {
                DBG(LABEL, ul_debug("DOS: uninitialized pointer to %zu pex", ext));
                return;
        }
        pex->ex_entry = pex->pt_entry;

        p = pex->pt_entry;
        if (!dos_partition_get_start(p)) {
                fdisk_warnx(cxt, _("Bad offset in primary extended partition."));
                return;
        }

        DBG(LABEL, ul_debug("DOS: Reading extended %zu", ext));

        while (IS_EXTENDED (p->sys_ind)) {
                if (cxt->label->nparts_max >= MAXIMUM_PARTS) {
                        /* This is not a Linux restriction, but
                           this program uses arrays of size MAXIMUM_PARTS.
                           Do not try to `improve' this test. */
                        struct pte *pre = self_pte(cxt,
                                                cxt->label->nparts_max - 1);
                        fdisk_warnx(cxt,
                        _("Omitting partitions after #%zu. They will be deleted "
                          "if you save this partition table."),
                                cxt->label->nparts_max);

                        if (pre) {
                                clear_partition(pre->ex_entry);
                                partition_set_changed(cxt,
                                                cxt->label->nparts_max - 1, 1);
                        }
                        return;
                }

                pe = self_pte(cxt, cxt->label->nparts_max);
                if (!pe)
                        return;

                if (read_pte(cxt, cxt->label->nparts_max, l->ext_offset +
                                                dos_partition_get_start(p)))
                        return;

                if (!l->ext_offset)
                        l->ext_offset = dos_partition_get_start(p);

                assert(pe->sectorbuffer);
                q = p = mbr_get_partition(pe->sectorbuffer, 0);

                for (i = 0; i < 4; i++, p++) {
                        if (!dos_partition_get_size(p))
                                continue;

                        if (IS_EXTENDED (p->sys_ind)) {
                                if (pe->ex_entry)
                                        fdisk_warnx(cxt, _(
                                        "Extra link pointer in partition "
                                        "table %zu."),
                                                cxt->label->nparts_max + 1);
                                else
                                        pe->ex_entry = p;
                        } else if (p->sys_ind) {
                                if (pe->pt_entry)
                                        fdisk_warnx(cxt, _(
                                        "Ignoring extra data in partition "
                                        "table %zu."),
                                                cxt->label->nparts_max + 1);
                                else
                                        pe->pt_entry = p;
                        }
                }

                /* very strange code here... */
                if (!pe->pt_entry) {
                        if (q != pe->ex_entry)
                                pe->pt_entry = q;
                        else
                                pe->pt_entry = q + 1;
                }
                if (!pe->ex_entry) {
                        if (q != pe->pt_entry)
                                pe->ex_entry = q;
                        else
                                pe->ex_entry = q + 1;
                }

                p = pe->ex_entry;
                cxt->label->nparts_cur = ++cxt->label->nparts_max;

                DBG(LABEL, ul_debug("DOS: EBR[offset=%ju]: link: type=%x,  start=%u, size=%u; "
                                                         " data: type=%x, start=%u, size=%u",
                                    (uintmax_t) pe->offset,
                                    pe->ex_entry->sys_ind,
                                    dos_partition_get_start(pe->ex_entry),
                                    dos_partition_get_size(pe->ex_entry),
                                    pe->pt_entry->sys_ind,
                                    dos_partition_get_start(pe->pt_entry),
                                    dos_partition_get_size(pe->pt_entry)));

        }

        /* remove last empty EBR */
        pe = self_pte(cxt, cxt->label->nparts_max - 1);
        if (pe &&
            is_cleared_partition(pe->ex_entry) &&
            is_cleared_partition(pe->pt_entry)) {
                DBG(LABEL, ul_debug("DOS: EBR[offset=%ju]: empty, remove", (uintmax_t) pe->offset));
                reset_pte(pe);
                cxt->label->nparts_max--;
                cxt->label->nparts_cur--;
        }

        /* remove empty links */
 remove:
        q = self_partition(cxt, 4);
        for (i = 4; i < cxt->label->nparts_max; i++) {
                p = self_partition(cxt, i);

                if (p && !dos_partition_get_size(p) &&
                    (cxt->label->nparts_max > 5 || (q && q->sys_ind))) {
                        fdisk_info(cxt, _("omitting empty partition (%zu)"), i+1);
                        delete_partition(cxt, i);
                        goto remove;    /* numbering changed */
                }
        }

        DBG(LABEL, ul_debug("DOS: nparts_max: %zu", cxt->label->nparts_max));
}

static int dos_create_disklabel(struct fdisk_context *cxt)
{
        unsigned int id = 0;
        int rc, has_id = 0;
        struct fdisk_dos_label *l;

        assert(cxt);
        assert(cxt->label);
        assert(fdisk_is_label(cxt, DOS));

        DBG(LABEL, ul_debug("DOS: creating new disklabel"));

        if (cxt->script) {
                char *end = NULL;
                const char *s = fdisk_script_get_header(cxt->script, "label-id");

                if (s) {
                        errno = 0;
                        id = strtoul(s, &end, 16);
                        if (!errno && end && s < end) {
                                has_id = 1;
                                DBG(LABEL, ul_debug("DOS: re-use ID from script (0x%08x)", id));
                        } else
                                DBG(LABEL, ul_debug("DOS: failed to parse label=id '%s'", s));
                }
        }

        /* random disk signature */
        if (!has_id) {
                DBG(LABEL, ul_debug("DOS: generate new ID"));
                ul_random_get_bytes(&id, sizeof(id));
        }

        if (fdisk_has_protected_bootbits(cxt))
                rc = fdisk_init_firstsector_buffer(cxt, 0, MBR_PT_BOOTBITS_SIZE);
        else
                rc = fdisk_init_firstsector_buffer(cxt, 0, 0);
        if (rc)
                return rc;
        dos_init(cxt);

        l = self_label(cxt);

        /* Generate an MBR ID for this disk */
        mbr_set_id(cxt->firstsector, id);
        l->non_pt_changed = 1;
        fdisk_label_set_changed(cxt->label, 1);

        /* Put MBR signature */
        mbr_set_magic(cxt->firstsector);

        fdisk_info(cxt, _("Created a new DOS (MBR) disklabel with disk "
                         "identifier 0x%08x."), id);
        return 0;
}

static int dos_set_disklabel_id(struct fdisk_context *cxt, const char *str)
{
        char *buf = NULL;
        unsigned int id, old;
        struct fdisk_dos_label *l;
        int rc = 0;

        assert(cxt);
        assert(cxt->label);
        assert(fdisk_is_label(cxt, DOS));

        DBG(LABEL, ul_debug("DOS: setting Id"));

        l = self_label(cxt);
        old = mbr_get_id(cxt->firstsector);

        if (!str) {
                rc = fdisk_ask_string(cxt,
                        _("Enter the new disk identifier"), &buf);
                str = buf;
        }
        if (!rc) {
                char *end = NULL;

                errno = 0;
                id = strtoul(str, &end, 0);
                if (errno || str == end || (end && *end)) {
                        fdisk_warnx(cxt, _("Incorrect value."));
                        rc = -EINVAL;
                }
        }

        free(buf);
        if (rc)
                return -EINVAL;

        mbr_set_id(cxt->firstsector, id);
        l->non_pt_changed = 1;
        fdisk_label_set_changed(cxt->label, 1);

        fdisk_info(cxt, _("Disk identifier changed from 0x%08x to 0x%08x."),
                        old, id);
        return 0;
}

static unsigned int chs_div_minus(unsigned int a1, unsigned int a2, unsigned int b1, unsigned int b2)
{
        if (a1 > a2 && b1 > b2) {
                a1 = a1 - a2;
                b1 = b1 - b2;
        } else if (a2 > a1 && b2 > b1) {
                a1 = a2 - a1;
                b1 = b2 - b1;
        } else {
                return 0;
        }
        if (a1 % b1)
                return 0;
        return a1 / b1;
}

static inline int chs_overflowed(unsigned int c, unsigned int h, unsigned int s)
{
        /* 1023/254/63 or 1023/255/63 indicates overflowed/invalid C/H/S values */
        return (c == 1023 && (h == 254 || h == 255) && s == 63);
}

static inline int lba_overflowed(fdisk_sector_t start, fdisk_sector_t sects)
{
        /* Check if the last LBA sector can be represented by unsigned 32bit int */
        return (start + (sects-1) > UINT32_MAX);
}

static void get_partition_table_geometry(struct fdisk_context *cxt,
                        unsigned int *ph, unsigned int *ps)
{
        unsigned char *bufp = cxt->firstsector;
        struct { unsigned int c, h, o, v; } t[8];
        unsigned int n1, n2, n3, n4, n5, n6;
        const struct dos_partition *p;
        unsigned int c, h, s, l;
        unsigned int hh, ss;
        unsigned int sects;
        int i, j, dif;

#define chs_set_t(c, h, s, l, t, i) do { \
        t[i].c = c; \
        t[i].h = h; \
        t[i].o = l - (s-1); \
        t[i].v = (!chs_overflowed(c, h, s) && s && s-1 <= l); \
} while (0)

        /*
         * Conversion from C/H/S to LBA is defined by formula:
         *   LBA = (c * N_heads + h) * N_sectors + (s - 1)
         * Let o to be:
         *   o = LBA - (s - 1)
         * Then formula can be expressed as:
         *   o = (c * N_heads + h) * N_sectors
         * In general from two tuples (LBA1, c1, h1, s1), (LBA2, c2, h2, s2)
         * we can derive formulas for N_heads and N_sectors:
         *   N_heads = (o1 * h2 - o2 * h1) / (o2 * c1 - o1 * c2)
         *   N_sectors = (o2 * c1 - o1 * c2) / (c1 * h2 - c2 * h1)
         * MBR table contains for very partition start and end tuple.
         * So we have up to 8 tuples which leads to up to 28 equations
         * for calculating N_heads and N_sectors. Try to calculate
         * N_heads and N_sectors from the first possible partition and
         * if it fails then try also mixed tuples (beginning from first
         * partition and end from second). Calculation may fail if both
         * first and last sectors are on cylinder or head boundary
         * (dividend or divisor is zero). It is possible that different
         * partitions would have different C/H/S geometry. In this case
         * we want geometry from the first partition as in most cases
         * this partition is or was used by BIOS for booting.
         */

        hh = ss = 0;
        for (i = 0; i < 4; i++) {
                p = mbr_get_partition(bufp, i);
                if (!p->sys_ind)
                        continue;

                c = cylinder(p->bs, p->bc);
                h = p->bh;
                s = sector(p->bs);
                l = dos_partition_get_start(p);
                chs_set_t(c, h, s, l, t, 2*i);

                sects = dos_partition_get_size(p);
                if (!sects || lba_overflowed(l, sects))
                        continue;

                c = cylinder(p->es, p->ec);
                h = p->eh;
                s = sector(p->es);
                l += sects-1;
                chs_set_t(c, h, s, l, t, 2*i+1);
        }

        for (dif = 1; dif < 8; dif++) {
                for (i = 0; i + dif < 8; i++) {
                        j = i + dif;
                        if (!t[i].v || !t[j].v)
                                continue;
                        n1 = t[i].o * t[j].h;
                        n2 = t[j].o * t[i].h;
                        n3 = t[j].o * t[i].c;
                        n4 = t[i].o * t[j].c;
                        n5 = t[i].c * t[j].h;
                        n6 = t[j].c * t[i].h;
                        if (!hh && n1 != n2 && n3 != n4) {
                                h = chs_div_minus(n1, n2, n3, n4);
                                if (h > 0 && h <= 256)
                                        hh = h;
                        }
                        if (!ss && n3 != n4 && n5 != n6) {
                                s = chs_div_minus(n3, n4, n5, n6);
                                if (s > 0 && s <= 63)
                                        ss = s;
                        }
                        if (hh && ss)
                                break;
                }
                if (hh && ss)
                        break;
        }

        if (hh && ss) {
                *ph = hh;
                *ps = ss;
        }

        DBG(LABEL, ul_debug("DOS PT geometry: heads=%u, sectors=%u", *ph, *ps));
}

static int dos_reset_alignment(struct fdisk_context *cxt)
{
        assert(cxt);
        assert(cxt->label);
        assert(fdisk_is_label(cxt, DOS));

        /* overwrite necessary stuff by DOS deprecated stuff */
        if (is_dos_compatible(cxt)) {
                DBG(LABEL, ul_debug("DOS: resetting alignment for DOS-compatible PT"));
                if (cxt->geom.sectors)
                        cxt->first_lba = cxt->geom.sectors;     /* usually 63 */

                cxt->grain = cxt->sector_size;                  /* usually 512 */
        }

        return 0;
}

/* TODO: move to include/pt-dos.h and share with libblkid */
#define AIX_MAGIC_STRING        "\xC9\xC2\xD4\xC1"
#define AIX_MAGIC_STRLEN        (sizeof(AIX_MAGIC_STRING) - 1)

static int dos_probe_label(struct fdisk_context *cxt)
{
        size_t i;
        unsigned int h = 0, s = 0;

        assert(cxt);
        assert(cxt->label);
        assert(fdisk_is_label(cxt, DOS));

        /* ignore disks with AIX magic number */
        if (memcmp(cxt->firstsector, AIX_MAGIC_STRING, AIX_MAGIC_STRLEN) == 0)
                return 0;

        if (!mbr_is_valid_magic(cxt->firstsector))
                return 0;

        dos_init(cxt);

        get_partition_table_geometry(cxt, &h, &s);
        if (h && s) {
                cxt->geom.heads = h;
                cxt->geom.sectors = s;
                cxt->geom.cylinders = cxt->total_sectors /
                                        (cxt->geom.heads * cxt->geom.sectors);

                if (fdisk_has_user_device_geometry(cxt))
                        fdisk_apply_user_device_properties(cxt);
        }

        for (i = 0; i < 4; i++) {
                struct pte *pe = self_pte(cxt, i);

                assert(pe);
                if (is_used_partition(pe->pt_entry))
                        cxt->label->nparts_cur++;

                if (IS_EXTENDED (pe->pt_entry->sys_ind)) {
                        if (cxt->label->nparts_max != 4)
                                fdisk_warnx(cxt, _(
                                "Ignoring extra extended partition %zu"),
                                        i + 1);
                        else
                                read_extended(cxt, i);
                }
        }

        for (i = 3; i < cxt->label->nparts_max; i++) {
                struct pte *pe = self_pte(cxt, i);
                struct fdisk_dos_label *l = self_label(cxt);

                assert(pe);
                if (!mbr_is_valid_magic(pe->sectorbuffer)) {
                        fdisk_info(cxt, _(
                        "Invalid flag 0x%02x%02x of EBR (for partition %zu) will "
                        "be corrected by w(rite)."),
                                pe->sectorbuffer[510],
                                pe->sectorbuffer[511],
                                i + 1);
                        partition_set_changed(cxt, i, 1);

                        /* mark also extended as changed to update the first EBR
                         * in situation that there is no logical partitions at all */
                        partition_set_changed(cxt, l->ext_index, 1);
                }
        }

        return 1;
}

static void set_partition(struct fdisk_context *cxt,
                          int i, int doext, fdisk_sector_t start,
                          fdisk_sector_t stop, int sysid, int boot)
{
        struct pte *pe = self_pte(cxt, i);
        struct dos_partition *p;
        fdisk_sector_t offset;

        assert(!FDISK_IS_UNDEF(start));
        assert(!FDISK_IS_UNDEF(stop));
        assert(pe);

        if (doext) {
                struct fdisk_dos_label *l = self_label(cxt);
                p = pe->ex_entry;
                offset = l->ext_offset;
        } else {
                p = pe->pt_entry;
                offset = pe->offset;
        }

        DBG(LABEL, ul_debug("DOS: setting partition %d%s, offset=%zu, start=%zu, size=%zu, sysid=%02x",
                                i, doext ? " [extended]" : "",
                                (size_t) offset,
                                (size_t) (start -  offset),
                                (size_t) (stop - start + 1),
                                sysid));

        p->boot_ind = boot ? ACTIVE_FLAG : 0;
        p->sys_ind = sysid;
        dos_partition_set_start(p, start - offset);
        dos_partition_set_size(p, stop - start + 1);
        dos_partition_sync_chs(p, offset, cxt->geom.sectors, cxt->geom.heads);
        partition_set_changed(cxt, i, 1);
}


static int get_start_from_user( struct fdisk_context *cxt,
                                fdisk_sector_t *start,
                                fdisk_sector_t low,
                                fdisk_sector_t dflt,
                                fdisk_sector_t limit,
                                struct fdisk_partition *pa)
{
        assert(start);

        /* try to use template from 'pa' */
        if (pa && pa->start_follow_default)
                *start = dflt;

        else if (pa && fdisk_partition_has_start(pa)) {
                DBG(LABEL, ul_debug("DOS: start: wanted=%ju, low=%ju, limit=%ju",
                                (uintmax_t) pa->start, (uintmax_t) low, (uintmax_t) limit));
                *start = pa->start;
                if (*start < low || *start > limit) {
                        fdisk_warnx(cxt, _("Start sector %ju out of range."),
                                        (uintmax_t) *start);
                        return -ERANGE;
                }
        } else {
                /* ask user by dialog */
                struct fdisk_ask *ask = fdisk_new_ask();
                int rc;

                if (!ask)
                        return -ENOMEM;
                fdisk_ask_set_query(ask,
                        fdisk_use_cylinders(cxt) ?
                                _("First cylinder") : _("First sector"));
                fdisk_ask_set_type(ask, FDISK_ASKTYPE_NUMBER);
                fdisk_ask_number_set_low(ask, fdisk_cround(cxt, low));
                fdisk_ask_number_set_default(ask, fdisk_cround(cxt, dflt));
                fdisk_ask_number_set_high(ask, fdisk_cround(cxt, limit));

                rc = fdisk_do_ask(cxt, ask);
                *start = fdisk_ask_number_get_result(ask);
                fdisk_unref_ask(ask);
                if (rc)
                        return rc;
                if (fdisk_use_cylinders(cxt)) {
                        *start = (*start - 1)
                                * fdisk_get_units_per_sector(cxt);
                        if (*start < low)
                                *start = low;
                }
        }

        DBG(LABEL, ul_debug("DOS: start is %ju", (uintmax_t) *start));
        return 0;
}

/* Returns last available sector in the free space pointed to by start. */
static int find_last_free(
                        struct fdisk_context *cxt,
                        int logical,
                        fdisk_sector_t begin,
                        fdisk_sector_t stop,
                        fdisk_sector_t *result)
{
        fdisk_sector_t last = stop;

        size_t i = logical ? 4 : 0;

        for ( ; i < cxt->label->nparts_max; i++) {
                struct pte *pe = self_pte(cxt, i);

                assert(pe);
                fdisk_sector_t p_start = get_abs_partition_start(pe);
                fdisk_sector_t p_end = get_abs_partition_end(pe);

                if (is_cleared_partition(pe->pt_entry))
                        continue;
                /* count EBR and begin of the logical partition as used area */
                if (pe->offset)
                        p_start -= cxt->first_lba;

                if ((p_start >= begin && p_start <= last) ||
                    (p_end >= begin && p_end <= last)) {
                        last = p_start - 1;
                }
                if (last < begin) {
                        DBG(LABEL, ul_debug("no free space <%ju,%ju>",
                                        (uintmax_t) begin, (uintmax_t) stop));
                        return -ENOSPC;
                }
        }

        if (last == begin)
                last = stop;

        DBG(LABEL, ul_debug("DOS: last free sector  <%ju,%ju>: %ju",
                        (uintmax_t) begin, (uintmax_t) stop, (uintmax_t) last));

        *result = last;
        return 0;
}

static int find_last_free_sector_in_range(
                        struct fdisk_context *cxt,
                        int logical,
                        fdisk_sector_t begin,
                        fdisk_sector_t end,
                        fdisk_sector_t *result)
{
        int last_moved;
        fdisk_sector_t last = end;

        do {
                size_t i = logical ? 4 : 0;

                last_moved = 0;
                for ( ; i < cxt->label->nparts_max; i++) {
                        struct pte *pe = self_pte(cxt, i);

                        assert(pe);
                        fdisk_sector_t p_start = get_abs_partition_start(pe);
                        fdisk_sector_t p_end = get_abs_partition_end(pe);

                        if (is_cleared_partition(pe->pt_entry))
                                continue;

                        /* count EBR and begin of the logical partition as used area */
                        if (pe->offset)
                                p_start -= cxt->first_lba;

                        if (last >= p_start && last <= p_end) {
                                last = p_start - 1;
                                last_moved = 1;

                                if (last < begin) {
                                        DBG(LABEL, ul_debug("DOS: last free out of range <%ju,%ju>: %ju",
                                                (uintmax_t) begin, (uintmax_t) end, (uintmax_t) last));

                                        return -ENOSPC;
                                }
                        }
                }
        } while (last_moved == 1);

        DBG(LABEL, ul_debug("DOS: last unused sector in range <%ju,%ju>: %ju",
                        (uintmax_t) begin, (uintmax_t) end, (uintmax_t) last));

        *result = last;
        return 0;
}

static int find_first_free_sector_in_range(
                        struct fdisk_context *cxt,
                        int logical,
                        fdisk_sector_t begin,
                        fdisk_sector_t end,
                        fdisk_sector_t *result)
{
        int first_moved = 0;
        fdisk_sector_t first = begin;

        do {
                size_t i = logical ? 4 : 0;

                first_moved = 0;
                for (; i < cxt->label->nparts_max; i++) {
                        struct pte *pe = self_pte(cxt, i);

                        assert(pe);
                        fdisk_sector_t p_start = get_abs_partition_start(pe);
                        fdisk_sector_t p_end = get_abs_partition_end(pe);

                        if (is_cleared_partition(pe->pt_entry))
                                continue;
                        /* count EBR and begin of the logical partition as used area */
                        if (pe->offset)
                                p_start -= cxt->first_lba;
                        if (first < p_start)
                                continue;
                        if (first <= p_end) {
                                first = p_end + 1 + (logical ? cxt->first_lba : 0);
                                first_moved = 1;

                                if (first > end) {
                                        DBG(LABEL, ul_debug("DOS: first free out of range <%ju,%ju>: %ju",
                                                (uintmax_t) begin, (uintmax_t) end, (uintmax_t) first));
                                        return -ENOSPC;
                                }
                        }
                }
        } while (first_moved == 1);

        DBG(LABEL, ul_debug("DOS: first unused sector in range <%ju,%ju>: %ju",
                        (uintmax_t) begin, (uintmax_t) end, (uintmax_t) first));
        *result = first;
        return 0;
}

static int get_disk_ranges(struct fdisk_context *cxt, int logical,
                           fdisk_sector_t *first, fdisk_sector_t *last)
{
        if (logical) {
                /* logical partitions */
                struct fdisk_dos_label *l = self_label(cxt);
                struct pte *ext_pe = l->ext_offset ? self_pte(cxt, l->ext_index) : NULL;

                if (!ext_pe)
                        return -EINVAL;

                *first = l->ext_offset + cxt->first_lba;
                *last = get_abs_partition_end(ext_pe);

        } else {
                /* primary partitions */
                if (fdisk_use_cylinders(cxt) || !cxt->total_sectors)
                        *last = cxt->geom.heads * cxt->geom.sectors * cxt->geom.cylinders - 1;
                else
                        *last = cxt->total_sectors - 1;

                if (*last > UINT_MAX)
                        *last = UINT_MAX;
                *first = cxt->first_lba;
        }

        return 0;
}

/* first free sector on disk */
static int find_first_free_sector(struct fdisk_context *cxt,
                                int logical,
                                fdisk_sector_t start,
                                fdisk_sector_t *result)
{
        fdisk_sector_t first, last;
        int rc;

        rc = get_disk_ranges(cxt, logical, &first, &last);
        if (rc)
                return rc;

        return find_first_free_sector_in_range(cxt, logical, start, last, result);
}

static int add_partition(struct fdisk_context *cxt, size_t n,
                         struct fdisk_partition *pa)
{
        int sys, read = 0, rc, isrel = 0, is_logical;
        struct fdisk_dos_label *l = self_label(cxt);
        struct dos_partition *p = self_partition(cxt, n);
        struct fdisk_ask *ask = NULL;

        fdisk_sector_t start, stop, limit, temp;

        DBG(LABEL, ul_debug("DOS: adding partition %zu", n));

        sys = pa && pa->type ? pa->type->code : MBR_LINUX_DATA_PARTITION;
        is_logical = n >= 4;

        if (p && is_used_partition(p)) {
                fdisk_warnx(cxt, _("Partition %zu is already defined.  "
                                   "Delete it before re-adding it."),
                                n + 1);
                return -EINVAL;
        }

        rc = get_disk_ranges(cxt, is_logical, &start, &stop);
        if (rc)
                return rc;

        if (!is_logical && cxt->parent && fdisk_is_label(cxt->parent, GPT))
                start = 1;              /* Bad boy modifies hybrid MBR */

        rc = find_last_free_sector_in_range(cxt, is_logical, start, stop, &limit);
        if (rc == -ENOSPC)
                fdisk_warnx(cxt, _("No free sectors available."));
        if (rc)
                return rc;

        if ((is_logical || !cxt->parent || !fdisk_is_label(cxt->parent, GPT))
            && cxt->script && pa && fdisk_partition_has_start(pa)
            && pa->start >= (is_logical ? l->ext_offset : 1)
            && pa->start < start) {
                fdisk_set_first_lba(cxt, 1);

                rc = get_disk_ranges(cxt, is_logical, &start, &stop);
                if (rc) /* won't happen, but checking to be proper */
                        return rc;
        }

        /*
         * Ask for first sector
         */
        do {
                fdisk_sector_t dflt, aligned;

                temp = start;

                DBG(LABEL, ul_debug("DOS: >>> search for first free from %ju", start));
                rc = find_first_free_sector(cxt, is_logical, start, &dflt);
                if (rc == -ENOSPC)
                        fdisk_warnx(cxt, _("No free sectors available."));
                if (rc)
                        return rc;
                start = dflt;

                if (n >= 4 && pa && fdisk_partition_has_start(pa) && cxt->script
                    && cxt->first_lba > 1
                    && temp == start - cxt->first_lba) {
                        fdisk_set_first_lba(cxt, 1);
                        start = pa->start;
                }

                /* the default sector should be aligned and unused */
                do {
                        aligned = fdisk_align_lba_in_range(cxt, dflt, dflt, limit);
                        find_first_free_sector(cxt, is_logical, aligned, &dflt);
                } while (dflt != aligned && dflt > aligned && dflt < limit);

                if (dflt >= limit)
                        dflt = start;
                if (start > limit)
                        break;
                if (start >= temp + fdisk_get_units_per_sector(cxt)
                    && read) {
                        if (!pa || !pa->start_follow_default)
                                fdisk_info(cxt, _("Sector %ju is already allocated."),
                                                (uintmax_t) temp);
                        temp = start;
                        read = 0;
                        if (pa && fdisk_partition_has_start(pa))
                                break;
                }

                if (!read && start == temp) {
                        rc = get_start_from_user(cxt, &start, temp, dflt, limit, pa);
                        if (rc)
                                return rc;
                        read = 1;
                }
                if (pa && fdisk_partition_has_size(pa)) {
                        fdisk_sector_t last;

                        rc = find_last_free(cxt, is_logical, start, limit, &last);
                        if (rc == 0 && last - start + 1 < fdisk_partition_get_size(pa)) {
                                DBG(LABEL, ul_debug("DOS: area <%ju,%ju> too small [wanted=%ju aval=%ju]",
                                                        (uintmax_t) start, (uintmax_t) last,
                                                        fdisk_partition_get_size(pa),
                                                        last - start));

                                if (fdisk_partition_has_start(pa)
                                    && fdisk_partition_get_start(pa) <= last)
                                        rc = -ENOSPC;
                                else {
                                        start = last + 1;
                                        continue;
                                }
                        }
                        if (rc == -ENOSPC) {
                                fdisk_warnx(cxt, _("No free sectors available."));
                                return rc;
                        }
                }

        } while (start != temp || !read);

        if (n == 4) {
                /* The first EBR is stored at begin of the extended partition */
                struct pte *pe = self_pte(cxt, n);

                assert(pe);
                pe->offset = l->ext_offset;
        } else if (n > 4) {
                /* The second (and another) EBR */
                struct pte *pe = self_pte(cxt, n);

                assert(pe);
                assert(start >= cxt->first_lba);

                pe->offset = start - cxt->first_lba;
                DBG(LABEL, ul_debug("DOS: setting EBR offset to %ju [start=%ju]", pe->offset, start));

                if (pe->offset == l->ext_offset) { /* must be corrected */
                        pe->offset++;
                        if (cxt->first_lba == 1)
                                start++;
                }
        }

        rc = find_last_free(cxt, is_logical, start, limit, &stop);
        if (rc == -ENOSPC)
                fdisk_warnx(cxt, _("No free sectors available."));
        if (rc)
                return rc;
        limit = stop;

        /*
         * Ask for last sector
         */
        if (fdisk_cround(cxt, start) == fdisk_cround(cxt, limit))
                stop = limit;
        else if (pa && pa->end_follow_default)
                stop = limit;
        else if (pa && fdisk_partition_has_size(pa)) {
                stop = start + pa->size;
                isrel = pa->size_explicit ? 0 : 1;
                if ((!isrel || !alignment_required(cxt)) && stop > start)
                        stop -= 1;
        } else {
                /* ask user by dialog */
                for (;;) {
                        if (!ask)
                                ask = fdisk_new_ask();
                        else
                                fdisk_reset_ask(ask);
                        if (!ask)
                                return -ENOMEM;
                        fdisk_ask_set_type(ask, FDISK_ASKTYPE_OFFSET);

                        if (fdisk_use_cylinders(cxt)) {
                                fdisk_ask_set_query(ask, _("Last cylinder, +/-cylinders or +/-size{K,M,G,T,P}"));
                                fdisk_ask_number_set_unit(ask,
                                             cxt->sector_size *
                                             fdisk_get_units_per_sector(cxt));
                        } else {
                                fdisk_ask_set_query(ask, _("Last sector, +/-sectors or +/-size{K,M,G,T,P}"));
                                fdisk_ask_number_set_unit(ask,cxt->sector_size);
                        }

                        fdisk_ask_number_set_low(ask, fdisk_cround(cxt, start));
                        fdisk_ask_number_set_default(ask, fdisk_cround(cxt, limit));
                        fdisk_ask_number_set_high(ask, fdisk_cround(cxt, limit));
                        fdisk_ask_number_set_base(ask, fdisk_cround(cxt, start));       /* base for relative input */
                        fdisk_ask_number_set_wrap_negative(ask, 1); /* wrap negative around high */

                        rc = fdisk_do_ask(cxt, ask);
                        if (rc)
                                goto done;

                        stop = fdisk_ask_number_get_result(ask);
                        isrel = fdisk_ask_number_is_relative(ask);
                        if (fdisk_use_cylinders(cxt)) {
                                stop = stop * fdisk_get_units_per_sector(cxt) - 1;
                                if (stop >limit)
                                        stop = limit;
                        }

                        if (stop >= start && stop <= limit)
                                break;
                        fdisk_warnx(cxt, _("Value out of range."));
                }
        }

        DBG(LABEL, ul_debug("DOS: raw stop: %ju [limit %ju]", (uintmax_t) stop, (uintmax_t) limit));

        if (stop > limit)
                stop = limit;

        if (isrel && stop - start < (cxt->grain / fdisk_get_sector_size(cxt))) {
                /* Don't try to be smart on very small partitions and don't align so small sizes */
                isrel = 0;
                DBG(LABEL, ul_debug("DOS: don't align end of tiny partition [start=%ju, stop=%ju, grain=%lu]",
                            (uintmax_t)start,  (uintmax_t)stop, cxt->grain));
        }

        if (stop < limit && isrel && alignment_required(cxt)) {
                /* the last sector has not been exactly requested (but
                 * defined by +size{K,M,G} convention), so be smart and
                 * align the end of the partition. The next partition
                 * will start at phy.block boundary.
                 */
                stop = fdisk_align_lba_in_range(cxt, stop, start, limit);
                if (stop > start)
                        stop -= 1;      /* end one sector before aligned offset */
                if (stop > limit)
                        stop = limit;
                DBG(LABEL, ul_debug("DOS: aligned stop: %ju", (uintmax_t) stop));
        }

        set_partition(cxt, n, 0, start, stop, sys, fdisk_partition_is_bootable(pa));
        if (n > 4) {
                struct pte *pe = self_pte(cxt, n);
                assert(pe);
                set_partition(cxt, n - 1, 1, pe->offset, stop,
                                        MBR_DOS_EXTENDED_PARTITION, 0);
        }

        /* report */
        {
                struct fdisk_parttype *t =
                        fdisk_label_get_parttype_from_code(cxt->label, sys);
                fdisk_info_new_partition(cxt, n + 1, start, stop, t);
                fdisk_unref_parttype(t);
        }


        if (IS_EXTENDED(sys)) {
                struct pte *pen = self_pte(cxt, n);

                assert(pen);
                l->ext_index = n;
                l->ext_offset = start;
                pen->ex_entry = p;
        }

        fdisk_label_set_changed(cxt->label, 1);
        rc = 0;
done:
        fdisk_unref_ask(ask);
        return rc;
}

static int add_logical(struct fdisk_context *cxt,
                       struct fdisk_partition *pa,
                       size_t *partno)
{
        struct pte *pe;
        int rc;

        assert(cxt);
        assert(partno);
        assert(cxt->label);
        assert(self_label(cxt)->ext_offset);

        DBG(LABEL, ul_debug("DOS: nparts max: %zu", cxt->label->nparts_max));
        pe = self_pte(cxt, cxt->label->nparts_max);
        assert(pe);

        if (!pe->sectorbuffer) {
                pe->sectorbuffer = calloc(1, cxt->sector_size);
                if (!pe->sectorbuffer)
                        return -ENOMEM;
                DBG(LABEL, ul_debug("DOS: logical: %zu: new EBR sector buffer %p",
                                        cxt->label->nparts_max, pe->sectorbuffer));
                pe->private_sectorbuffer = 1;
        }
        pe->pt_entry = mbr_get_partition(pe->sectorbuffer, 0);
        pe->ex_entry = pe->pt_entry + 1;
        pe->offset = 0;
        partition_set_changed(cxt, cxt->label->nparts_max, 1);

        cxt->label->nparts_max++;

        /* this message makes sense only when we use extended/primary/logical
         * dialog. The dialog is disable for scripts, see dos_add_partition() */
        if (!cxt->script)
                fdisk_info(cxt, _("Adding logical partition %zu"),
                                cxt->label->nparts_max);
        *partno = cxt->label->nparts_max - 1;
        rc = add_partition(cxt, *partno, pa);

        if (rc) {
                /* reset on error */
                cxt->label->nparts_max--;
                pe->pt_entry = NULL;
                pe->ex_entry = NULL;
                pe->offset = 0;
                pe->changed = 0;
        }

        return rc;
}

static int check(struct fdisk_context *cxt, size_t n,
           unsigned int h, unsigned int s, unsigned int c,
           unsigned int lba_sector)
{
        unsigned int chs_sector, real_s, real_c;
        int nerrors = 0;

        if (!is_dos_compatible(cxt))
                return 0;

        real_s = sector(s) - 1;
        real_c = cylinder(s, c);
        chs_sector = (real_c * cxt->geom.heads + h) * cxt->geom.sectors + real_s;

        if (!chs_sector) {
                fdisk_warnx(cxt, _("Partition %zu: contains sector 0"), n);
                nerrors++;
        }
        if (h >= cxt->geom.heads) {
                fdisk_warnx(cxt, _("Partition %zu: head %d greater than "
                                   "maximum %d"), n, h + 1, cxt->geom.heads);
                nerrors++;
        }
        if (real_s >= cxt->geom.sectors) {
                fdisk_warnx(cxt, _("Partition %zu: sector %d greater than "
                                   "maximum %ju"), n, real_s + 1,
                                (uintmax_t) cxt->geom.sectors);
                nerrors++;
        }
        if (real_c >= cxt->geom.cylinders) {
                fdisk_warnx(cxt, _("Partition %zu: cylinder %d greater than "
                                   "maximum %ju"),
                                n, real_c + 1,
                                (uintmax_t) cxt->geom.cylinders);
                nerrors++;
        }
        if (lba_sector / (cxt->geom.heads * cxt->geom.sectors) < 1024 && lba_sector != chs_sector) {
                fdisk_warnx(cxt, _("Partition %zu: LBA sector %u "
                                   "disagrees with C/H/S calculated sector %u"),
                                n, lba_sector, chs_sector);
                nerrors++;
        }

        return nerrors;
}

/* check_consistency() and long2chs() added Sat Mar 6 12:28:16 1993,
 * faith@cs.unc.edu, based on code fragments from pfdisk by Gordon W. Ross,
 * Jan.  1990 (version 1.2.1 by Gordon W. Ross Aug. 1990; Modified by S.
 * Lubkin Oct.  1991). */

static void
long2chs(struct fdisk_context *cxt, unsigned long ls,
         unsigned int *c, unsigned int *h, unsigned int *s) {
        int spc = cxt->geom.heads * cxt->geom.sectors;

        *c = ls / spc;
        ls = ls % spc;
        *h = ls / cxt->geom.sectors;
        *s = ls % cxt->geom.sectors + 1;        /* sectors count from 1 */
}

static int check_consistency(struct fdisk_context *cxt, struct dos_partition *p,
                              size_t partition)
{
        unsigned int pbc, pbh, pbs;     /* physical beginning c, h, s */
        unsigned int pec, peh, pes;     /* physical ending c, h, s */
        unsigned int lbc, lbh, lbs;     /* logical beginning c, h, s */
        unsigned int lec, leh, les;     /* logical ending c, h, s */
        int nerrors = 0;

        if (!is_dos_compatible(cxt))
                return 0;

        if (!cxt->geom.heads || !cxt->geom.sectors || (partition >= 4))
                return 0;               /* do not check extended partitions */

        /* physical beginning c, h, s */
        pbc = cylinder(p->bs, p->bc);
        pbh = p->bh;
        pbs = sector(p->bs);

        /* physical ending c, h, s */
        pec = cylinder(p->es, p->ec);
        peh = p->eh;
        pes = sector(p->es);

        /* compute logical beginning (c, h, s) */
        long2chs(cxt, dos_partition_get_start(p), &lbc, &lbh, &lbs);

        /* compute logical ending (c, h, s) */
        long2chs(cxt, dos_partition_get_start(p) + dos_partition_get_size(p) - 1, &lec, &leh, &les);

        /* Same physical / logical beginning? */
        if (lbc < 1024
            && (pbc != lbc || pbh != lbh || pbs != lbs)) {
                fdisk_warnx(cxt, _("Partition %zu: different physical/logical "
                        "beginnings (non-Linux?): "
                        "phys=(%d, %d, %d), logical=(%d, %d, %d)"),
                        partition + 1,
                        pbc, pbh, pbs,
                        lbc, lbh, lbs);
                nerrors++;
        }

        /* Same physical / logical ending? */
        if (lec < 1024
            && (pec != lec || peh != leh || pes != les)) {
                fdisk_warnx(cxt, _("Partition %zu: different physical/logical "
                        "endings: phys=(%d, %d, %d), logical=(%d, %d, %d)"),
                        partition + 1,
                        pec, peh, pes,
                        lec, leh, les);
                nerrors++;
        }

        /* Ending on cylinder boundary? */
        if (peh != (cxt->geom.heads - 1) || pes != cxt->geom.sectors) {
                fdisk_warnx(cxt, _("Partition %zu: does not end on "
                                   "cylinder boundary."),
                        partition + 1);
                nerrors++;
        }

        return nerrors;
}

static void fill_bounds(struct fdisk_context *cxt,
                        fdisk_sector_t *first, fdisk_sector_t *last)
{
        size_t i;
        struct pte *pe = self_pte(cxt, 0);
        struct dos_partition *p;

        assert(pe);
        for (i = 0; i < cxt->label->nparts_max; pe++,i++) {
                p = pe->pt_entry;
                if (is_cleared_partition(p) || IS_EXTENDED (p->sys_ind)) {
                        first[i] = SIZE_MAX;
                        last[i] = 0;
                } else {
                        first[i] = get_abs_partition_start(pe);
                        last[i]  = get_abs_partition_end(pe);
                }
        }
}

static int dos_verify_disklabel(struct fdisk_context *cxt)
{
        size_t i, j;
        fdisk_sector_t total = 1, n_sectors = cxt->total_sectors;
        fdisk_sector_t *first, *last;
        struct dos_partition *p;
        struct fdisk_dos_label *l = self_label(cxt);
        int nerrors = 0;

        assert(fdisk_is_label(cxt, DOS));

        first = calloc(cxt->label->nparts_max, sizeof(*first));
        last = calloc(cxt->label->nparts_max, sizeof(*first));

        if (!first || !last) {
                free(first);
                free(last);
                return -ENOMEM;
        }

        fill_bounds(cxt, first, last);
        for (i = 0; i < cxt->label->nparts_max; i++) {
                struct pte *pe = self_pte(cxt, i);

                p = self_partition(cxt, i);
                if (p && is_used_partition(p) && !IS_EXTENDED(p->sys_ind)) {
                        nerrors += check_consistency(cxt, p, i);
                        assert(pe);
                        if (get_abs_partition_start(pe) < first[i]) {
                                fdisk_warnx(cxt, _(
                                        "Partition %zu: bad start-of-data."),
                                         i + 1);
                                nerrors++;
                        }

                        nerrors += check(cxt, i + 1, p->bh, p->bs, p->bc, first[i]);
                        nerrors += check(cxt, i + 1, p->eh, p->es, p->ec, last[i]);
                        total += last[i] + 1 - first[i];

                        if (i == 0)
                                total += get_abs_partition_start(pe) - 1;

                        for (j = 0; j < i; j++) {
                                if ((first[i] >= first[j] && first[i] <= last[j])
                                    || ((last[i] <= last[j] && last[i] >= first[j]))) {

                                        fdisk_warnx(cxt, _("Partition %zu: "
                                                "overlaps partition %zu."),
                                                j + 1, i + 1);
                                        nerrors++;

                                        total += first[i] >= first[j] ?
                                                first[i] : first[j];
                                        total -= last[i] <= last[j] ?
                                                last[i] : last[j];
                                }
                        }
                }
        }

        if (l->ext_offset) {
                fdisk_sector_t e_last;
                struct pte *ext_pe = self_pte(cxt, l->ext_index);

                assert(ext_pe);
                e_last = get_abs_partition_end(ext_pe);

                for (i = 4; i < cxt->label->nparts_max; i++) {
                        total++;
                        p = self_partition(cxt, i);
                        assert(p);

                        if (!p->sys_ind) {
                                if (i != 4 || i + 1 < cxt->label->nparts_max) {
                                        fdisk_warnx(cxt,
                                                _("Partition %zu: empty."),
                                                i + 1);
                                        nerrors++;
                                }
                        } else if (first[i] < l->ext_offset
                                   || last[i] > e_last) {

                                fdisk_warnx(cxt, _("Logical partition %zu: "
                                        "not entirely in partition %zu."),
                                        i + 1, l->ext_index + 1);
                                nerrors++;
                        }
                }
        }

        if (!nerrors) {
                fdisk_info(cxt, _("No errors detected."));
                if (total > n_sectors)
                        fdisk_info(cxt, _("Total allocated sectors %ju greater "
                                "than the maximum %ju."), (uintmax_t) total, (uintmax_t) n_sectors);
                else if (total < n_sectors)
                        fdisk_info(cxt, _("Remaining %ju unallocated %ld-byte "
                                "sectors."), (uintmax_t) n_sectors - total, cxt->sector_size);
        } else
                fdisk_warnx(cxt,
                        P_("%d error detected.", "%d errors detected.", nerrors),
                        nerrors);

        free(first);
        free(last);
        return nerrors;
}

/*
 * Ask the user for new partition type information (logical, extended).
 * This function calls the actual partition adding logic - add_partition.
 *
 * API callback.
 */
static int dos_add_partition(struct fdisk_context *cxt,
                             struct fdisk_partition *pa,
                             size_t *partno)
{
        size_t i;
        uint8_t free_primary = 0, free_sectors = 0;
        fdisk_sector_t first = 0, grain;
        int rc = 0;
        struct fdisk_dos_label *l;
        struct pte *ext_pe;
        size_t res = 0;         /* partno */

        assert(cxt);
        assert(cxt->label);
        assert(fdisk_is_label(cxt, DOS));

        DBG(LABEL, ul_debug("DOS: new partition wanted"));

        l = self_label(cxt);

        if (cxt->label->nparts_max >= MAXIMUM_PARTS) {
                fdisk_warnx(cxt, _("The maximum number of partitions has "
                                  "been created."));
                return -EINVAL;
        }

        ext_pe = l->ext_offset ? self_pte(cxt, l->ext_index) : NULL;

        /*
         * partition template (@pa) based partitioning
         */

        /* A) template specifies start within extended partition; add logical */
        if (pa && fdisk_partition_has_start(pa) && ext_pe
            && pa->start >= l->ext_offset
            && pa->start <= get_abs_partition_end(ext_pe)) {
                DBG(LABEL, ul_debug("DOS: pa template %p: add logical (by offset)", pa));

                if (fdisk_partition_has_partno(pa) && fdisk_partition_get_partno(pa) < 4) {
                        DBG(LABEL, ul_debug("DOS: pa template specifies partno<4 for logical partition"));
                        return -EINVAL;
                }
                rc = add_logical(cxt, pa, &res);
                goto done;

        /* B) template specifies start out of extended partition; add primary */
        } else if (pa && fdisk_partition_has_start(pa) && ext_pe) {
                DBG(LABEL, ul_debug("DOS: pa template %p: add primary (by offset)", pa));

                if (fdisk_partition_has_partno(pa) && fdisk_partition_get_partno(pa) >= 4) {
                        DBG(LABEL, ul_debug("DOS: pa template specifies partno>=4 for primary partition"));
                        return -EINVAL;
                }
                if (ext_pe && pa->type && IS_EXTENDED(pa->type->code)) {
                        fdisk_warnx(cxt, _("Extended partition already exists."));
                        return -EINVAL;
                }
                rc = get_partition_unused_primary(cxt, pa, &res);
                if (rc == 0)
                        rc = add_partition(cxt, res, pa);
                goto done;

        /* C) template specifies start (or default), partno < 4; add primary */
        } else if (pa && (fdisk_partition_start_is_default(pa) || fdisk_partition_has_start(pa))
                   && fdisk_partition_has_partno(pa)
                   && pa->partno < 4) {
                DBG(LABEL, ul_debug("DOS: pa template %p: add primary (by partno)", pa));

                if (ext_pe && pa->type && IS_EXTENDED(pa->type->code)) {
                        fdisk_warnx(cxt, _("Extended partition already exists."));
                        return -EINVAL;
                }
                rc = get_partition_unused_primary(cxt, pa, &res);
                if (rc == 0)
                        rc = add_partition(cxt, res, pa);
                goto done;

        /* D) template specifies start (or default), partno >= 4; add logical */
        } else if (pa && (fdisk_partition_start_is_default(pa) || fdisk_partition_has_start(pa))
                   && fdisk_partition_has_partno(pa)
                   && pa->partno >= 4) {
                DBG(LABEL, ul_debug("DOS: pa template %p: add logical (by partno)", pa));

                if (!ext_pe) {
                        fdisk_warnx(cxt, _("Extended partition does not exists. Failed to add logical partition."));
                        return -EINVAL;
                }

                if (fdisk_partition_has_start(pa)
                           && pa->start < l->ext_offset
                           && pa->start > get_abs_partition_end(ext_pe)) {
                        DBG(LABEL, ul_debug("DOS: pa template specifies partno>=4, but start out of extended"));
                        return -EINVAL;
                }

                rc = add_logical(cxt, pa, &res);
                goto done;
        }

        DBG(LABEL, ul_debug("DOS: dialog driven partitioning"));
        /* Note @pa may be still used for things like partition type, etc */

        /* check if there is space for primary partition */
        grain = cxt->grain > cxt->sector_size ? cxt->grain / cxt->sector_size : 1;
        first = cxt->first_lba;

        if (cxt->parent && fdisk_is_label(cxt->parent, GPT)) {
                /* modifying a hybrid MBR, which throws out the rules */
                grain = 1;
                first = 1;
        }

        /* set @first after the last used partition, set @free_sectors if there
         * is gap in front if the first partition or between used parrtitions. */
        for (i = 0; i < 4; i++) {
                struct dos_partition *p = self_partition(cxt, i);

                if (p && is_used_partition(p)) {
                        fdisk_sector_t start = dos_partition_get_start(p);
                        if (first + grain <= start)
                                free_sectors = 1;
                        first = start + dos_partition_get_size(p);
                } else
                        free_primary++;
        }

        /* set @free_sectors if there is a space after the first usable sector */
        if (first + grain - 1 <= cxt->total_sectors - 1)
                free_sectors = 1;

        DBG(LABEL, ul_debug("DOS: primary: first free: %ju, last on disk: %ju, "
                            "free_sectors=%d, free_primary=%d",
                                (uintmax_t) first,
                                (uintmax_t) cxt->total_sectors - 1,
                                free_sectors, free_primary));

        if (!free_primary || !free_sectors) {
                DBG(LABEL, ul_debug("DOS: primary impossible"));
                if (l->ext_offset) {
                        if (!pa || fdisk_partition_has_start(pa)) {
                                /* See above case A); here we have start, but
                                 * out of extended partition */
                                const char *msg;
                                if (!free_primary)
                                        msg = _("All primary partitions are in use.");
                                else
                                        msg =  _("All space for primary partitions is in use.");

                                if (pa && fdisk_partition_has_start(pa)) {
                                        fdisk_warnx(cxt, "%s", msg);
                                        return -EINVAL;
                                }
                                fdisk_info(cxt, "%s", msg);
                        }
                        DBG(LABEL, ul_debug("DOS: trying logical"));
                        rc = add_logical(cxt, pa, &res);
                } else {
                        if (free_primary)
                                fdisk_info(cxt, _("All space for primary partitions is in use."));
                        else
                        /* TRANSLATORS: Try to keep this within 80 characters. */
                                fdisk_info(cxt, _("To create more partitions, first replace "
                                          "a primary with an extended partition."));
                        return -EINVAL;
                }
        } else {
                char hint[BUFSIZ];
                struct fdisk_ask *ask;
                int c = 0;

                /* the default layout for scripts is to create primary partitions */
                if (cxt->script || !fdisk_has_dialogs(cxt)) {
                        rc = get_partition_unused_primary(cxt, pa, &res);
                        if (rc == 0)
                                rc = add_partition(cxt, res, pa);
                        goto done;
                }

                ask = fdisk_new_ask();
                if (!ask)
                        return -ENOMEM;
                fdisk_ask_set_type(ask, FDISK_ASKTYPE_MENU);
                fdisk_ask_set_query(ask, _("Partition type"));
                fdisk_ask_menu_set_default(ask, free_primary == 1
                                                && !l->ext_offset ? 'e' : 'p');
                snprintf(hint, sizeof(hint),
                                _("%u primary, %d extended, %u free"),
                                4 - (l->ext_offset ? 1 : 0) - free_primary,
                                l->ext_offset ? 1 : 0,
                                free_primary);

                fdisk_ask_menu_add_item(ask, 'p', _("primary"), hint);
                if (!l->ext_offset)
                        fdisk_ask_menu_add_item(ask, 'e', _("extended"), _("container for logical partitions"));
                else
                        fdisk_ask_menu_add_item(ask, 'l', _("logical"), _("numbered from 5"));

                rc = fdisk_do_ask(cxt, ask);
                if (!rc)
                        fdisk_ask_menu_get_result(ask, &c);
                fdisk_unref_ask(ask);
                if (rc)
                        return rc;

                if (c == 'p') {
                        rc = get_partition_unused_primary(cxt, pa, &res);
                        if (rc == 0)
                                rc = add_partition(cxt, res, pa);
                        goto done;
                } else if (c == 'l' && l->ext_offset) {
                        rc = add_logical(cxt, pa, &res);
                        goto done;
                } else if (c == 'e' && !l->ext_offset) {
                        rc = get_partition_unused_primary(cxt, pa, &res);
                        if (rc == 0) {
                                struct fdisk_partition *xpa = NULL;
                                struct fdisk_parttype *t;

                                t = fdisk_label_get_parttype_from_code(cxt->label,
                                                MBR_DOS_EXTENDED_PARTITION);
                                if (!pa) {
                                        pa = xpa = fdisk_new_partition();
                                        if (!xpa)
                                                return -ENOMEM;
                                }
                                fdisk_partition_set_type(pa, t);
                                rc = add_partition(cxt, res, pa);
                                if (xpa) {
                                        fdisk_unref_partition(xpa);
                                        pa = NULL;
                                }
                        }
                        goto done;
                } else
                        fdisk_warnx(cxt, _("Invalid partition type `%c'."), c);
        }
done:
        if (rc == 0) {
                cxt->label->nparts_cur++;
                if (partno)
                        *partno = res;
        }
        return rc;
}

static int write_sector(struct fdisk_context *cxt, fdisk_sector_t secno,
                               unsigned char *buf)
{
        int rc;

        rc = seek_sector(cxt, secno);
        if (rc != 0) {
                fdisk_warn(cxt, _("Cannot write sector %jd: seek failed"),
                                (uintmax_t) secno);
                return rc;
        }

        DBG(LABEL, ul_debug("DOS: writing to sector %ju", (uintmax_t) secno));

        if (write(cxt->dev_fd, buf, cxt->sector_size) != (ssize_t) cxt->sector_size)
                return -errno;
        return 0;
}

static int dos_write_disklabel(struct fdisk_context *cxt)
{
        struct fdisk_dos_label *l = self_label(cxt);
        size_t i;
        int rc = 0, mbr_changed = 0;

        assert(cxt);
        assert(cxt->label);
        assert(fdisk_is_label(cxt, DOS));

        DBG(LABEL, ul_debug("DOS: write PT requested [label-changed: %d, non-pt-changed: %d]",
                                cxt->label->changed, l->non_pt_changed));

        mbr_changed = l->non_pt_changed;

        /* MBR (primary partitions) */
        if (!mbr_changed) {
                for (i = 0; i < 4; i++) {
                        struct pte *pe = self_pte(cxt, i);

                        assert(pe);
                        if (pe->changed)
                                mbr_changed = 1;
                }
        }
        if (mbr_changed) {
                DBG(LABEL, ul_debug("DOS: MBR changed, writing"));
                mbr_set_magic(cxt->firstsector);
                rc = write_sector(cxt, 0, cxt->firstsector);
                if (rc)
                        goto done;
        }

        if (cxt->label->nparts_max <= 4 && l->ext_offset) {
                /* we have empty extended partition, check if the partition has
                 * been modified and then cleanup possible remaining EBR  */
                struct pte *pe = self_pte(cxt, l->ext_index);
                unsigned char empty[512] = { 0 };
                fdisk_sector_t off = pe ? get_abs_partition_start(pe) : 0;

                if (off && pe->changed) {
                        mbr_set_magic(empty);
                        write_sector(cxt, off, empty);
                }
        }

        /* EBR (logical partitions) */
        for (i = 4; i < cxt->label->nparts_max; i++) {
                struct pte *pe = self_pte(cxt, i);

                assert(pe);
                if (!pe->changed || !pe->offset || !pe->sectorbuffer)
                        continue;

                mbr_set_magic(pe->sectorbuffer);
                rc = write_sector(cxt, pe->offset, pe->sectorbuffer);
                if (rc)
                        goto done;
        }

done:
        return rc;
}

static int dos_locate_disklabel(struct fdisk_context *cxt, int n,
                const char **name, uint64_t *offset, size_t *size)
{
        assert(cxt);

        *name = NULL;
        *offset = 0;
        *size = 0;

        switch (n) {
        case 0:
                *name = "MBR";
                *offset = 0;
                *size = 512;
                break;
        default:
                /* extended partitions */
                if ((size_t)n - 1 + 4 < cxt->label->nparts_max) {
                        struct pte *pe = self_pte(cxt, n - 1 + 4);

                        assert(pe);
                        assert(pe->private_sectorbuffer);

                        *name = "EBR";
                        *offset = (uint64_t) pe->offset * cxt->sector_size;
                        *size = 512;
                } else
                        return 1;
                break;
        }

        return 0;
}

/*
 * Check whether partition entries are ordered by their starting positions.
 * Return 0 if OK. Return i if partition i should have been earlier.
 * Two separate checks: primary and logical partitions.
 */
static int wrong_p_order(struct fdisk_context *cxt, size_t *prev)
{
        size_t last_p_start_pos = 0, p_start_pos;
        size_t i, last_i = 0;

        for (i = 0 ; i < cxt->label->nparts_max; i++) {

                struct pte *pe = self_pte(cxt, i);
                struct dos_partition *p;

                assert(pe);
                p = pe->pt_entry;

                if (i == 4) {
                        last_i = 4;
                        last_p_start_pos = 0;
                }
                if (is_used_partition(p)) {
                        p_start_pos = get_abs_partition_start(pe);

                        if (last_p_start_pos > p_start_pos) {
                                if (prev)
                                        *prev = last_i;
                                return i;
                        }

                        last_p_start_pos = p_start_pos;
                        last_i = i;
                }
        }
        return 0;
}

static int dos_get_disklabel_item(struct fdisk_context *cxt, struct fdisk_labelitem *item)
{
        int rc = 0;

        assert(cxt);
        assert(cxt->label);
        assert(fdisk_is_label(cxt, DOS));

        switch (item->id) {
        case FDISK_LABELITEM_ID:
        {
                unsigned int num = mbr_get_id(cxt->firstsector);
                item->name = _("Disk identifier");
                item->type = 's';
                if (asprintf(&item->data.str, "0x%08x", num) < 0)
                        rc = -ENOMEM;
                break;
        }
        default:
                if (item->id < __FDISK_NLABELITEMS)
                        rc = 1; /* unsupported generic item */
                else
                        rc = 2; /* out of range */
                break;
        }

        return rc;

}

static int dos_get_partition(struct fdisk_context *cxt, size_t n,
                             struct fdisk_partition *pa)
{
        struct dos_partition *p;
        struct pte *pe;
        struct fdisk_dos_label *lb;

        assert(cxt);
        assert(pa);
        assert(cxt->label);
        assert(fdisk_is_label(cxt, DOS));

        lb = self_label(cxt);

        pe = self_pte(cxt, n);
        assert(pe);

        p = pe->pt_entry;
        pa->used = !is_cleared_partition(p);
        if (!pa->used)
                return 0;

        pa->type = dos_partition_parttype(cxt, p);
        pa->boot = p->boot_ind == ACTIVE_FLAG ? 1 : 0;
        pa->start = get_abs_partition_start(pe);
        pa->size = dos_partition_get_size(p);
        pa->container = lb->ext_offset && n == lb->ext_index;

        if (n >= 4)
                pa->parent_partno = lb->ext_index;

        if (p->boot_ind && asprintf(&pa->attrs, "%02x", p->boot_ind) < 0)
                return -ENOMEM;

        /* start C/H/S */
        if (asprintf(&pa->start_chs, "%d/%d/%d",
                                cylinder(p->bs, p->bc),
                                p->bh,
                                sector(p->bs)) < 0)
                return -ENOMEM;

        /* end C/H/S */
        if (asprintf(&pa->end_chs, "%d/%d/%d",
                                cylinder(p->es, p->ec),
                                p->eh,
                                sector(p->es)) < 0)
                return -ENOMEM;

        return 0;
}

static int has_logical(struct fdisk_context *cxt)
{
        size_t i;
        struct fdisk_dos_label *l = self_label(cxt);

        for (i = 4; i < cxt->label->nparts_max; i++) {
                if (l->ptes[i].pt_entry)
                        return 1;
        }
        return 0;
}

static int dos_set_partition(struct fdisk_context *cxt, size_t n,
                             struct fdisk_partition *pa)
{
        struct fdisk_dos_label *l;
        struct dos_partition *p;
        struct pte *pe;
        int orgtype;
        fdisk_sector_t start, size;

        assert(cxt);
        assert(pa);
        assert(cxt->label);
        assert(fdisk_is_label(cxt, DOS));

        if (n >= cxt->label->nparts_max)
                return -EINVAL;

        l = self_label(cxt);
        p = self_partition(cxt, n);
        assert(p);

        pe = self_pte(cxt, n);
        if (!pe)
                return -EINVAL;

        orgtype = p->sys_ind;

        if (pa->type) {
                if (IS_EXTENDED(pa->type->code) && l->ext_offset && l->ext_index != n) {
                        fdisk_warnx(cxt, _("Extended partition already exists."));
                        return -EINVAL;
                }

                if (!pa->type->code)
                        fdisk_warnx(cxt, _("Type 0 means free space to many systems. "
                                   "Having partitions of type 0 is probably unwise."));

                if (IS_EXTENDED(p->sys_ind) && !IS_EXTENDED(pa->type->code) && has_logical(cxt)) {
                        fdisk_warnx(cxt, _(
                                "Cannot change type of the extended partition which is "
                                "already used by logical partitions. Delete logical "
                                "partitions first."));
                        return -EINVAL;
                }
        }

        FDISK_INIT_UNDEF(start);
        FDISK_INIT_UNDEF(size);

        if (fdisk_partition_has_start(pa))
                start = pa->start;
        if (fdisk_partition_has_size(pa))
                size = pa->size;

        if (!FDISK_IS_UNDEF(start) || !FDISK_IS_UNDEF(size)) {
                DBG(LABEL, ul_debug("DOS: resize partition"));

                if (FDISK_IS_UNDEF(start))
                        start = get_abs_partition_start(pe);
                if (FDISK_IS_UNDEF(size))
                        size = dos_partition_get_size(p);

                set_partition(cxt, n, 0, start, start + size - 1,
                                pa->type  ? pa->type->code : p->sys_ind,
                                FDISK_IS_UNDEF(pa->boot) ?
                                        p->boot_ind == ACTIVE_FLAG :
                                        fdisk_partition_is_bootable(pa));
        } else {
                DBG(LABEL, ul_debug("DOS: keep size, modify properties"));
                if (pa->type)
                        p->sys_ind = pa->type->code;
                if (!FDISK_IS_UNDEF(pa->boot))
                        p->boot_ind = fdisk_partition_is_bootable(pa) ? ACTIVE_FLAG : 0;
        }

        if (pa->type) {
                if (IS_EXTENDED(pa->type->code) && !IS_EXTENDED(orgtype)) {
                        /* new extended partition - create a reference  */
                        l->ext_index = n;
                        l->ext_offset = dos_partition_get_start(p);
                        pe->ex_entry = p;
                 } else if (IS_EXTENDED(orgtype)) {
                        /* remove extended partition */
                        cxt->label->nparts_max = 4;
                        l->ptes[l->ext_index].ex_entry = NULL;
                        l->ext_offset = 0;
                        l->ext_index = 0;
                 }
        }

        partition_set_changed(cxt, n, 1);
        return 0;
}

static void print_chain_of_logicals(struct fdisk_context *cxt)
{
        size_t i;
        struct fdisk_dos_label *l = self_label(cxt);

        fputc('\n', stdout);

        for (i = 4; i < cxt->label->nparts_max; i++) {
                struct pte *pe = self_pte(cxt, i);

                assert(pe);
                fprintf(stderr, "#%02zu EBR [%10ju], "
                        "data[start=%10ju (%10ju), size=%10ju], "
                        "link[start=%10ju (%10ju), size=%10ju]\n",
                        i, (uintmax_t) pe->offset,
                        /* data */
                        (uintmax_t) dos_partition_get_start(pe->pt_entry),
                        (uintmax_t) get_abs_partition_start(pe),
                        (uintmax_t) dos_partition_get_size(pe->pt_entry),
                        /* link */
                        (uintmax_t) dos_partition_get_start(pe->ex_entry),
                        (uintmax_t) l->ext_offset + dos_partition_get_start(pe->ex_entry),
                        (uintmax_t) dos_partition_get_size(pe->ex_entry));
        }
}

static int cmp_ebr_offsets(const void *a, const void *b)
{
        const struct pte *ae = (const struct pte *) a,
                         *be = (const struct pte *) b;

        if (ae->offset == 0 && be->offset == 0)
                return 0;
        if (ae->offset == 0)
                return 1;
        if (be->offset == 0)
                return -1;

        return cmp_numbers(ae->offset, be->offset);
}

/*
 * Fix the chain of logicals.
 *
 * The function does not modify data partitions within EBR tables
 * (pte->pt_entry). It sorts the chain by EBR offsets and then update links
 * (pte->ex_entry) between EBR tables.
 *
 */
static void fix_chain_of_logicals(struct fdisk_context *cxt)
{
        struct fdisk_dos_label *l = self_label(cxt);
        struct pte *last;
        size_t i;

        DBG(LABEL, print_chain_of_logicals(cxt));

        /* Sort chain by EBR offsets */
        qsort(&l->ptes[4], cxt->label->nparts_max - 4, sizeof(struct pte),
                        cmp_ebr_offsets);

again:
        /* Sort data partitions by start */
        for (i = 4; i < cxt->label->nparts_max - 1; i++) {
                struct pte *cur = self_pte(cxt, i),
                           *nxt = self_pte(cxt, i + 1);

                assert(cur);
                assert(nxt);

                if (get_abs_partition_start(cur) >
                    get_abs_partition_start(nxt)) {

                        struct dos_partition tmp = *cur->pt_entry;
                        fdisk_sector_t cur_start = get_abs_partition_start(cur),
                                 nxt_start = get_abs_partition_start(nxt);

                        /* swap data partitions */
                        *cur->pt_entry = *nxt->pt_entry;
                        *nxt->pt_entry = tmp;

                        /* Recount starts according to EBR offsets, the absolute
                         * address still has to be the same! */
                        dos_partition_set_start(cur->pt_entry, nxt_start - cur->offset);
                        dos_partition_sync_chs(cur->pt_entry, cur->offset, cxt->geom.sectors, cxt->geom.heads);
                        dos_partition_set_start(nxt->pt_entry, cur_start - nxt->offset);
                        dos_partition_sync_chs(nxt->pt_entry, nxt->offset, cxt->geom.sectors, cxt->geom.heads);

                        partition_set_changed(cxt, i, 1);
                        partition_set_changed(cxt, i + 1, 1);
                        goto again;
                }
        }

        /* Update EBR links */
        for (i = 4; i < cxt->label->nparts_max - 1; i++) {
                struct pte *cur = self_pte(cxt, i),
                           *nxt = self_pte(cxt, i + 1);

                assert(cur);
                assert(nxt);

                fdisk_sector_t noff = nxt->offset - l->ext_offset,
                 ooff = dos_partition_get_start(cur->ex_entry);

                if (noff == ooff)
                        continue;

                DBG(LABEL, ul_debug("DOS: fix EBR [%10ju] link %ju -> %ju",
                        (uintmax_t) cur->offset,
                        (uintmax_t) ooff, (uintmax_t) noff));

                set_partition(cxt, i, 1, nxt->offset,
                                get_abs_partition_end(nxt),
                                MBR_DOS_EXTENDED_PARTITION, 0);
        }

        /* always terminate the chain ! */
        last = self_pte(cxt, cxt->label->nparts_max - 1);
        if (last) {
                clear_partition(last->ex_entry);
                partition_set_changed(cxt, cxt->label->nparts_max - 1, 1);
        }

        DBG(LABEL, print_chain_of_logicals(cxt));
}

static int dos_reorder(struct fdisk_context *cxt)
{
        struct pte *pei, *pek;
        size_t i,k;

        if (!wrong_p_order(cxt, NULL))
                return 1;

        while ((i = wrong_p_order(cxt, &k)) != 0 && i < 4) {
                /* partition i should have come earlier, move it */
                /* We have to move data in the MBR */
                struct dos_partition *pi, *pk, *pe, pbuf;
                pei = self_pte(cxt, i);
                pek = self_pte(cxt, k);

                assert(pei);
                assert(pek);

                pe = pei->ex_entry;
                pei->ex_entry = pek->ex_entry;
                pek->ex_entry = pe;

                pi = pei->pt_entry;
                pk = pek->pt_entry;

                memmove(&pbuf, pi, sizeof(struct dos_partition));
                memmove(pi, pk, sizeof(struct dos_partition));
                memmove(pk, &pbuf, sizeof(struct dos_partition));

                partition_set_changed(cxt, i, 1);
                partition_set_changed(cxt, k, 1);
        }

        if (i)
                fix_chain_of_logicals(cxt);

        return 0;
}

/**
 * fdisk_dos_fix_chs:
 * @cxt: fdisk context
 *
 * Fix beginning and ending C/H/S values for every partition
 * according to LBA relative offset, relative beginning and
 * size and fdisk idea of disk geometry (sectors per track
 * and number of heads).
 *
 * Returns: number of fixed (changed) partitions.
 */
int fdisk_dos_fix_chs(struct fdisk_context *cxt)
{
        unsigned int obc, obh, obs;     /* old beginning c, h, s */
        unsigned int oec, oeh, oes;     /* old ending c, h, s */
        unsigned int nbc, nbh, nbs;     /* new beginning c, h, s */
        unsigned int nec, neh, nes;     /* new ending c, h, s */
        fdisk_sector_t l, sects;        /* lba beginning and size */
        struct dos_partition *p;
        struct pte *pe;
        int changed = 0;
        size_t i;

        assert(fdisk_is_label(cxt, DOS));

        for (i = 0; i < cxt->label->nparts_max; i++) {
                p = self_partition(cxt, i);
                if (!p || !is_used_partition(p))
                        continue;

                pe = self_pte(cxt, i);

                /* old beginning c, h, s */
                obc = cylinder(p->bs, p->bc);
                obh = p->bh;
                obs = sector(p->bs);

                /* old ending c, h, s */
                oec = cylinder(p->es, p->ec);
                oeh = p->eh;
                oes = sector(p->es);

                /* new beginning c, h, s */
                l = get_abs_partition_start(pe);
                long2chs(cxt, l, &nbc, &nbh, &nbs);
                if (l > UINT32_MAX || nbc >= 1024) {
                        nbc = 1023;
                        nbh = cxt->geom.heads-1;
                        nbs = cxt->geom.sectors;
                }

                /* new ending c, h, s */
                sects = dos_partition_get_size(p);
                long2chs(cxt, l + sects - 1, &nec, &neh, &nes);
                if (lba_overflowed(l, sects) || nec >= 1024) {
                        nec = 1023;
                        neh = cxt->geom.heads-1;
                        nes = cxt->geom.sectors;
                }

                if (obc != nbc || obh != nbh || obs != nbs ||
                    oec != nec || oeh != neh || oes != nes) {
                        DBG(LABEL, ul_debug("DOS: changing %zu partition CHS "
                                "from (%d, %d, %d)-(%d, %d, %d) "
                                "to (%d, %d, %d)-(%d, %d, %d)",
                                i, obc, obh, obs, oec, oeh, oes,
                                nbc, nbh, nbs, nec, neh, nes));
                        p->bc = nbc & 0xff;
                        p->bh = nbh;
                        p->bs = nbs | ((nbc >> 2) & 0xc0);
                        p->ec = nec & 0xff;
                        p->eh = neh;
                        p->es = nes | ((nec >> 2) & 0xc0);
                        partition_set_changed(cxt, i, 1);
                        changed++;
                }
        }

        return changed;
}

/* TODO: use fdisk_set_partition() API */
int fdisk_dos_move_begin(struct fdisk_context *cxt, size_t i)
{
        struct pte *pe;
        struct dos_partition *p;
        unsigned int new, free_start, curr_start, last;
        uintmax_t res = 0;
        size_t x;
        int rc;

        assert(cxt);
        assert(fdisk_is_label(cxt, DOS));

        pe = self_pte(cxt, i);
        if (!pe)
                return -EINVAL;

        p = pe->pt_entry;

        if (!is_used_partition(p) || IS_EXTENDED (p->sys_ind)) {
                fdisk_warnx(cxt, _("Partition %zu: no data area."), i + 1);
                return 0;
        }

        /* The safe start is at the second sector, but some use-cases require
         * to have MBR within the first partition , so default to the first
         * sector of the disk or at the second sector of the extended partition
         */
        free_start = pe->offset ? pe->offset + 1 : 0;

        curr_start = get_abs_partition_start(pe);

        /* look for a free space before the current start of the partition */
        for (x = 0; x < cxt->label->nparts_max; x++) {
                unsigned int end;
                struct pte *prev_pe = self_pte(cxt, x);
                struct dos_partition *prev_p;

                assert(prev_pe);

                prev_p = prev_pe->pt_entry;
                if (!prev_p)
                        continue;
                end = get_abs_partition_start(prev_pe)
                      + dos_partition_get_size(prev_p);

                if (is_used_partition(prev_p) &&
                    end > free_start && end <= curr_start)
                        free_start = end;
        }

        last = get_abs_partition_end(pe);

        rc = fdisk_ask_number(cxt, free_start, curr_start, last,
                        _("New beginning of data"), &res);
        if (rc)
                return rc;

        new = res - pe->offset;

        if (new != dos_partition_get_size(p)) {
                unsigned int sects = dos_partition_get_size(p)
                                + dos_partition_get_start(p) - new;

                dos_partition_set_size(p, sects);
                dos_partition_set_start(p, new);
                dos_partition_sync_chs(p, pe->offset, cxt->geom.sectors, cxt->geom.heads);

                partition_set_changed(cxt, i, 1);

                if (new == 0)
                        fdisk_info(cxt, _("The new beginning of the partition overlaps the disk "
                                          "label area. Be very careful when using the partition. "
                                          "You can lose all your partitions on the disk."));
        }

        return rc;
}

static int dos_partition_is_used(
                struct fdisk_context *cxt,
                size_t i)
{
        struct dos_partition *p;

        assert(cxt);
        assert(cxt->label);
        assert(fdisk_is_label(cxt, DOS));

        if (i >= cxt->label->nparts_max)
                return 0;

        p = self_partition(cxt, i);

        return p && !is_cleared_partition(p);
}

static int dos_toggle_partition_flag(
                struct fdisk_context *cxt,
                size_t i,
                unsigned long flag)
{
        struct dos_partition *p;

        assert(cxt);
        assert(cxt->label);
        assert(fdisk_is_label(cxt, DOS));

        if (i >= cxt->label->nparts_max)
                return -EINVAL;

        p = self_partition(cxt, i);
        assert(p);

        switch (flag) {
        case DOS_FLAG_ACTIVE:
                if (IS_EXTENDED(p->sys_ind) && !p->boot_ind)
                        fdisk_warnx(cxt, _("Partition %zu: is an extended "
                                        "partition."), i + 1);

                p->boot_ind = (p->boot_ind ? 0 : ACTIVE_FLAG);
                partition_set_changed(cxt, i, 1);
                fdisk_info(cxt, p->boot_ind ?
                        _("The bootable flag on partition %zu is enabled now.") :
                        _("The bootable flag on partition %zu is disabled now."),
                        i + 1);
                break;
        default:
                return 1;
        }

        return 0;
}

static const struct fdisk_field dos_fields[] =
{
        /* basic */
        { FDISK_FIELD_DEVICE,   N_("Device"),    10,    0 },
        { FDISK_FIELD_BOOT,     N_("Boot"),       1,    0 },
        { FDISK_FIELD_START,    N_("Start"),      5,    FDISK_FIELDFL_NUMBER },
        { FDISK_FIELD_END,      N_("End"),        5,    FDISK_FIELDFL_NUMBER },
        { FDISK_FIELD_SECTORS,  N_("Sectors"),    5,    FDISK_FIELDFL_NUMBER },
        { FDISK_FIELD_CYLINDERS,N_("Cylinders"),  5,    FDISK_FIELDFL_NUMBER },
        { FDISK_FIELD_SIZE,     N_("Size"),       5,    FDISK_FIELDFL_NUMBER | FDISK_FIELDFL_EYECANDY },
        { FDISK_FIELD_TYPEID,   N_("Id"),         2,    FDISK_FIELDFL_NUMBER },
        { FDISK_FIELD_TYPE,     N_("Type"),     0.1,    0 },

        /* expert mode */
        { FDISK_FIELD_SADDR,    N_("Start-C/H/S"), 1,   FDISK_FIELDFL_NUMBER | FDISK_FIELDFL_DETAIL },
        { FDISK_FIELD_EADDR,    N_("End-C/H/S"),   1,   FDISK_FIELDFL_NUMBER | FDISK_FIELDFL_DETAIL },
        { FDISK_FIELD_ATTR,     N_("Attrs"),       2,   FDISK_FIELDFL_NUMBER | FDISK_FIELDFL_DETAIL }

};

static const struct fdisk_label_operations dos_operations =
{
        .probe          = dos_probe_label,
        .write          = dos_write_disklabel,
        .verify         = dos_verify_disklabel,
        .create         = dos_create_disklabel,
        .locate         = dos_locate_disklabel,
        .get_item       = dos_get_disklabel_item,
        .set_id         = dos_set_disklabel_id,

        .get_part       = dos_get_partition,
        .set_part       = dos_set_partition,
        .add_part       = dos_add_partition,
        .del_part       = dos_delete_partition,
        .reorder        = dos_reorder,

        .part_toggle_flag = dos_toggle_partition_flag,
        .part_is_used   = dos_partition_is_used,

        .reset_alignment = dos_reset_alignment,

        .deinit         = dos_deinit,
};

/*
 * allocates DOS in-memory stuff
 */
struct fdisk_label *fdisk_new_dos_label(struct fdisk_context *cxt __attribute__ ((__unused__)))
{
        struct fdisk_label *lb;
        struct fdisk_dos_label *dos;

        dos = calloc(1, sizeof(*dos));
        if (!dos)
                return NULL;

        /* initialize generic part of the driver */
        lb = (struct fdisk_label *) dos;
        lb->name = "dos";
        lb->id = FDISK_DISKLABEL_DOS;
        lb->op = &dos_operations;

        lb->parttypes = dos_parttypes;
        lb->nparttypes = ARRAY_SIZE(dos_parttypes) - 1;
        lb->parttype_cuts = dos_parttype_cuts;
        lb->nparttype_cuts = ARRAY_SIZE(dos_parttype_cuts);

        lb->fields = dos_fields;
        lb->nfields = ARRAY_SIZE(dos_fields);

        lb->geom_min.sectors = 1;
        lb->geom_min.heads = 1;
        lb->geom_min.cylinders = 1;

        lb->geom_max.sectors = 63;
        lb->geom_max.heads = 255;
        lb->geom_max.cylinders = 1048576;

        /* return calloc() result to keep static anaylizers happy */
        return (struct fdisk_label *) dos;
}

/**
 * fdisk_dos_enable_compatible:
 * @lb: DOS label (see fdisk_get_label())
 * @enable: 0 or 1
 *
 * Enables deprecated DOS compatible mode, in this mode library checks for
 * cylinders boundary, cases about CHS addressing and another obscure things.
 *
 * Returns: 0 on success, <0 on error.
 */
int fdisk_dos_enable_compatible(struct fdisk_label *lb, int enable)
{
        struct fdisk_dos_label *dos = (struct fdisk_dos_label *) lb;

        if (!lb)
                return -EINVAL;

        dos->compatible = enable;
        if (enable)
                lb->flags |= FDISK_LABEL_FL_REQUIRE_GEOMETRY;
        return 0;
}

/**
 * fdisk_dos_is_compatible:
 * @lb: DOS label
 *
 * Returns: 0 if DOS compatibility disabled, 1 if enabled
 */
int fdisk_dos_is_compatible(struct fdisk_label *lb)
{
        return ((struct fdisk_dos_label *) lb)->compatible;
}