Completing syslinux-udeb package contents.

[syslinux-debian/hramrach.git] / memdisk / setup.c

/* ----------------------------------------------------------------------- *
 *
 *   Copyright 2001-2009 H. Peter Anvin - All Rights Reserved
 *   Copyright 2009-2010 Intel Corporation; author: H. Peter Anvin
 *   Portions copyright 2009-2010 Shao Miller
 *                                [El Torito code, mBFT, "safe hook"]
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
 *   Boston MA 02111-1307, USA; either version 2 of the License, or
 *   (at your option) any later version; incorporated herein by reference.
 *
 * ----------------------------------------------------------------------- */

#include <stdint.h>
#include <minmax.h>
#include <suffix_number.h>
#include "bda.h"
#include "dskprobe.h"
#include "e820.h"
#include "conio.h"
#include "version.h"
#include "memdisk.h"
#include <version.h>

const char memdisk_version[] = "MEMDISK " VERSION_STR " " DATE;
const char copyright[] =
    "Copyright " FIRSTYEAR "-" YEAR_STR " H. Peter Anvin et al";

extern const char _binary_memdisk_chs_512_bin_start[];
extern const char _binary_memdisk_chs_512_bin_end[];
extern const char _binary_memdisk_chs_512_bin_size[];
extern const char _binary_memdisk_edd_512_bin_start[];
extern const char _binary_memdisk_edd_512_bin_end[];
extern const char _binary_memdisk_edd_512_bin_size[];
extern const char _binary_memdisk_iso_512_bin_start[];
extern const char _binary_memdisk_iso_512_bin_end[];
extern const char _binary_memdisk_iso_512_bin_size[];
extern const char _binary_memdisk_iso_2048_bin_start[];
extern const char _binary_memdisk_iso_2048_bin_end[];
extern const char _binary_memdisk_iso_2048_bin_size[];

/* Pull in structures common to MEMDISK and MDISKCHK.COM */
#include "mstructs.h"

/* An EDD disk packet */
struct edd_dsk_pkt {
    uint8_t size;               /* Packet size        */
    uint8_t res1;               /* Reserved           */
    uint16_t count;             /* Count to transfer  */
    uint32_t buf;               /* Buffer pointer     */
    uint64_t start;             /* LBA to start from  */
    uint64_t buf64;             /* 64-bit buf pointer */
} __attribute__ ((packed));

/* Change to 1 for El Torito debugging */
#define DBG_ELTORITO 0

#if DBG_ELTORITO
extern void eltorito_dump(uint32_t);
#endif

/*
 * Routine to seek for a command-line item and return a pointer
 * to the data portion, if present
 */

/* Magic return values */
#define CMD_NOTFOUND   ((char *)-1)     /* Not found */
#define CMD_BOOL       ((char *)-2)     /* Found boolean option */
#define CMD_HASDATA(X) ((int)(X) >= 0)

static const char *getcmditem(const char *what)
{
    const char *p;
    const char *wp = what;
    int match = 0;

    for (p = shdr->cmdline; *p; p++) {
        switch (match) {
        case 0:         /* Ground state */
            if (*p == ' ')
                break;

            wp = what;
            match = 1;
            /* Fall through */

        case 1:         /* Matching */
            if (*wp == '\0') {
                if (*p == '=')
                    return p + 1;
                else if (*p == ' ')
                    return CMD_BOOL;
                else {
                    match = 2;
                    break;
                }
            }
            if (*p != *wp++)
                match = 2;
            break;

        case 2:         /* Mismatch, skip rest of option */
            if (*p == ' ')
                match = 0;      /* Next option */
            break;
        }
    }

    /* Check for matching string at end of line */
    if (match == 1 && *wp == '\0')
        return CMD_BOOL;

    return CMD_NOTFOUND;
}

/*
 * Check to see if this is a gzip image
 */
#define UNZIP_ALIGN 512

extern const char _end[];               /* Symbol signalling end of data */

void unzip_if_needed(uint32_t * where_p, uint32_t * size_p)
{
    uint32_t where = *where_p;
    uint32_t size = *size_p;
    uint32_t zbytes;
    uint32_t startrange, endrange;
    uint32_t gzdatasize, gzwhere;
    uint32_t orig_crc, offset;
    uint32_t target = 0;
    int i, okmem;

    /* Is it a gzip image? */
    if (check_zip((void *)where, size, &zbytes, &gzdatasize,
                  &orig_crc, &offset) == 0) {

        if (offset + zbytes > size) {
            /*
             * Assertion failure; check_zip is supposed to guarantee this
             * never happens.
             */
            die("internal error: check_zip returned nonsense\n");
        }

        /*
         * Find a good place to put it: search memory ranges in descending
         * order until we find one that is legal and fits
         */
        okmem = 0;
        for (i = nranges - 1; i >= 0; i--) {
            /*
             * We can't use > 4G memory (32 bits only.)  Truncate to 2^32-1
             * so we don't have to deal with funny wraparound issues.
             */

            /* Must be memory */
            if (ranges[i].type != 1)
                continue;

            /* Range start */
            if (ranges[i].start >= 0xFFFFFFFF)
                continue;

            startrange = (uint32_t) ranges[i].start;

            /* Range end (0 for end means 2^64) */
            endrange = ((ranges[i + 1].start >= 0xFFFFFFFF ||
                         ranges[i + 1].start == 0)
                        ? 0xFFFFFFFF : (uint32_t) ranges[i + 1].start);

            /* Make sure we don't overwrite ourselves */
            if (startrange < (uint32_t) _end)
                startrange = (uint32_t) _end;

            /* Allow for alignment */
            startrange =
                (ranges[i].start + (UNZIP_ALIGN - 1)) & ~(UNZIP_ALIGN - 1);

            /* In case we just killed the whole range... */
            if (startrange >= endrange)
                continue;

            /*
             * Must be large enough... don't rely on gzwhere for this
             * (wraparound)
             */
            if (endrange - startrange < gzdatasize)
                continue;

            /*
             * This is where the gz image would be put if we put it in this
             * range...
             */
            gzwhere = (endrange - gzdatasize) & ~(UNZIP_ALIGN - 1);

            /* Cast to uint64_t just in case we're flush with the top byte */
            if ((uint64_t) where + size >= gzwhere && where < endrange) {
                /*
                 * Need to move source data to avoid compressed/uncompressed
                 * overlap
                 */
                uint32_t newwhere;

                if (gzwhere - startrange < size)
                    continue;   /* Can't fit both old and new */

                newwhere = (gzwhere - size) & ~(UNZIP_ALIGN - 1);
                printf("Moving compressed data from 0x%08x to 0x%08x\n",
                       where, newwhere);

                memmove((void *)newwhere, (void *)where, size);
                where = newwhere;
            }

            target = gzwhere;
            okmem = 1;
            break;
        }

        if (!okmem)
            die("Not enough memory to decompress image (need 0x%08x bytes)\n",
                gzdatasize);

        printf("gzip image: decompressed addr 0x%08x, len 0x%08x: ",
               target, gzdatasize);

        *size_p = gzdatasize;
        *where_p = (uint32_t) unzip((void *)(where + offset), zbytes,
                                    gzdatasize, orig_crc, (void *)target);
    }
}

/*
 * Figure out the "geometry" of the disk in question
 */
struct geometry {
    uint32_t sectors;           /* Sector count */
    uint32_t c, h, s;           /* C/H/S geometry */
    uint32_t offset;            /* Byte offset for disk */
    uint32_t boot_lba;          /* LBA of bootstrap code */
    uint8_t type;               /* Type byte for INT 13h AH=08h */
    uint8_t driveno;            /* Drive no */
    uint8_t sector_shift;       /* Sector size as a power of 2 */
    const char *hsrc, *ssrc;    /* Origins of H and S geometries */
};

/* Format of a DOS partition table entry */
struct ptab_entry {
    uint8_t active;
    uint8_t start_h, start_s, start_c;
    uint8_t type;
    uint8_t end_h, end_s, end_c;
    uint32_t start;
    uint32_t size;
} __attribute__ ((packed));

/* Format of a FAT filesystem superblock */
struct fat_extra {
    uint8_t bs_drvnum;
    uint8_t bs_resv1;
    uint8_t bs_bootsig;
    uint32_t bs_volid;
    char bs_vollab[11];
    char bs_filsystype[8];
} __attribute__ ((packed));
struct fat_super {
    uint8_t bs_jmpboot[3];
    char bs_oemname[8];
    uint16_t bpb_bytspersec;
    uint8_t bpb_secperclus;
    uint16_t bpb_rsvdseccnt;
    uint8_t bpb_numfats;
    uint16_t bpb_rootentcnt;
    uint16_t bpb_totsec16;
    uint8_t bpb_media;
    uint16_t bpb_fatsz16;
    uint16_t bpb_secpertrk;
    uint16_t bpb_numheads;
    uint32_t bpb_hiddsec;
    uint32_t bpb_totsec32;
    union {
        struct {
            struct fat_extra extra;
        } fat16;
        struct {
            uint32_t bpb_fatsz32;
            uint16_t bpb_extflags;
            uint16_t bpb_fsver;
            uint32_t bpb_rootclus;
            uint16_t bpb_fsinfo;
            uint16_t bpb_bkbootsec;
            char bpb_reserved[12];
            /* Clever, eh?  Same fields, different offset... */
            struct fat_extra extra;
        } fat32 __attribute__ ((packed));
    } x;
} __attribute__ ((packed));

/* Format of a DOSEMU header */
struct dosemu_header {
    uint8_t magic[7];           /* DOSEMU\0 */
    uint32_t h;
    uint32_t s;
    uint32_t c;
    uint32_t offset;
    uint8_t pad[105];
} __attribute__ ((packed));

#define FOUR(a,b,c,d) (((a) << 24)|((b) << 16)|((c) << 8)|(d))

static const struct geometry *get_disk_image_geometry(uint32_t where,
                                                      uint32_t size)
{
    static struct geometry hd_geometry;
    struct dosemu_header dosemu;
    unsigned int sectors, xsectors, v;
    unsigned int offset;
    int i;
    const char *p;

    printf("command line: %s\n", shdr->cmdline);

    hd_geometry.sector_shift = 9;       /* Assume floppy/HDD at first */

    offset = 0;
    if (CMD_HASDATA(p = getcmditem("offset")) && (v = atou(p)))
        offset = v;

    sectors = xsectors = (size - offset) >> hd_geometry.sector_shift;

    hd_geometry.hsrc = "guess";
    hd_geometry.ssrc = "guess";
    hd_geometry.sectors = sectors;
    hd_geometry.offset = offset;

    if ((p = getcmditem("iso")) != CMD_NOTFOUND) {
#if DBG_ELTORITO
        eltorito_dump(where);
#endif
        struct edd4_bvd *bvd = (struct edd4_bvd *)(where + 17 * 2048);
        /* Tiny sanity check */
        if ((bvd->boot_rec_ind != 0) || (bvd->ver != 1))
            printf("El Torito BVD sanity check failed.\n");
        struct edd4_bootcat *boot_cat =
            (struct edd4_bootcat *)(where + bvd->boot_cat * 2048);
        /* Another tiny sanity check */
        if ((boot_cat->validation_entry.platform_id != 0) ||
            (boot_cat->validation_entry.key55 != 0x55) ||
            (boot_cat->validation_entry.keyAA != 0xAA))
            printf("El Torito boot catalog sanity check failed.\n");
        /* If we have an emulation mode, set the offset to the image */
        if (boot_cat->initial_entry.media_type)
            hd_geometry.offset += boot_cat->initial_entry.load_block * 2048;
        else
            /* We're a no-emulation mode, so we will boot to an offset */
            hd_geometry.boot_lba = boot_cat->initial_entry.load_block * 4;
        if (boot_cat->initial_entry.media_type < 4) {
            /* We're a floppy emulation mode or our params will be
             * overwritten by the no emulation mode case
             */
            hd_geometry.driveno = 0x00;
            hd_geometry.c = 80;
            hd_geometry.h = 2;
        }
        switch (boot_cat->initial_entry.media_type) {
        case 0:         /* No emulation   */
            hd_geometry.driveno = 0xE0;
            hd_geometry.type = 10;      /* ATAPI removable media device */
            hd_geometry.c = 65535;
            hd_geometry.h = 255;
            hd_geometry.s = 15;
            /* 2048-byte sectors, so adjust the size and count */
            hd_geometry.sector_shift = 11;
            break;
        case 1:         /* 1.2 MB floppy  */
            hd_geometry.s = 15;
            hd_geometry.type = 2;
            sectors = 2400;
            break;
        case 2:         /* 1.44 MB floppy */
            hd_geometry.s = 18;
            hd_geometry.type = 4;
            sectors = 2880;
            break;
        case 3:         /* 2.88 MB floppy */
            hd_geometry.s = 36;
            hd_geometry.type = 6;
            sectors = 5760;
            break;
        case 4:
            hd_geometry.driveno = 0x80;
            hd_geometry.type = 0;
            break;
        }
        sectors = (size - hd_geometry.offset) >> hd_geometry.sector_shift;

        /* For HDD emulation, we figure out the geometry later. Otherwise: */
        if (hd_geometry.s) {
            hd_geometry.hsrc = hd_geometry.ssrc = "El Torito";
        }
        hd_geometry.sectors = sectors;
    }

    /* Do we have a DOSEMU header? */
    memcpy(&dosemu, (char *)where + hd_geometry.offset, sizeof dosemu);
    if (!memcmp("DOSEMU", dosemu.magic, 7)) {
        /* Always a hard disk unless overruled by command-line options */
        hd_geometry.driveno = 0x80;
        hd_geometry.type = 0;
        hd_geometry.c = dosemu.c;
        hd_geometry.h = dosemu.h;
        hd_geometry.s = dosemu.s;
        hd_geometry.offset += dosemu.offset;
        sectors = (size - hd_geometry.offset) >> hd_geometry.sector_shift;

        hd_geometry.hsrc = hd_geometry.ssrc = "DOSEMU";
    }

    if (CMD_HASDATA(p = getcmditem("c")) && (v = atou(p)))
        hd_geometry.c = v;
    if (CMD_HASDATA(p = getcmditem("h")) && (v = atou(p))) {
        hd_geometry.h = v;
        hd_geometry.hsrc = "cmd";
    }
    if (CMD_HASDATA(p = getcmditem("s")) && (v = atou(p))) {
        hd_geometry.s = v;
        hd_geometry.ssrc = "cmd";
    }

    if (!hd_geometry.h || !hd_geometry.s) {
        int h, s, max_h, max_s;

        max_h = hd_geometry.h;
        max_s = hd_geometry.s;

        if (!(max_h | max_s)) {
            /* Look for a FAT superblock and if we find something that looks
               enough like one, use geometry from that.  This takes care of
               megafloppy images and unpartitioned hard disks. */
            const struct fat_extra *extra = NULL;
            const struct fat_super *fs = (const struct fat_super *)
                ((char *)where + hd_geometry.offset);

            if ((fs->bpb_media == 0xf0 || fs->bpb_media >= 0xf8) &&
                (fs->bs_jmpboot[0] == 0xe9 || fs->bs_jmpboot[0] == 0xeb) &&
                fs->bpb_bytspersec == 512 &&
                fs->bpb_numheads >= 1 && fs->bpb_numheads <= 256 &&
                fs->bpb_secpertrk >= 1 && fs->bpb_secpertrk <= 63) {
                extra =
                    fs->bpb_fatsz16 ? &fs->x.fat16.extra : &fs->x.fat32.extra;
                if (!
                    (extra->bs_bootsig == 0x29 && extra->bs_filsystype[0] == 'F'
                     && extra->bs_filsystype[1] == 'A'
                     && extra->bs_filsystype[2] == 'T'))
                    extra = NULL;
            }
            if (extra) {
                hd_geometry.driveno = extra->bs_drvnum & 0x80;
                max_h = fs->bpb_numheads;
                max_s = fs->bpb_secpertrk;
                hd_geometry.hsrc = hd_geometry.ssrc = "FAT";
            }
        }

        if (!(max_h | max_s)) {
            /* No FAT filesystem found to steal geometry from... */
            if ((sectors < 4096 * 2) && (hd_geometry.sector_shift == 9)) {
                int ok = 0;
                unsigned int xsectors = sectors;

                hd_geometry.driveno = 0;        /* Assume floppy */

                while (!ok) {
                    /* Assume it's a floppy drive, guess a geometry */
                    unsigned int type, track;
                    int c, h, s = 0;

                    if (xsectors < 320 * 2) {
                        c = 40;
                        h = 1;
                        type = 1;
                    } else if (xsectors < 640 * 2) {
                        c = 40;
                        h = 2;
                        type = 1;
                    } else if (xsectors < 1200 * 2) {
                        c = 80;
                        h = 2;
                        type = 3;
                    } else if (xsectors < 1440 * 2) {
                        c = 80;
                        h = 2;
                        type = 2;
                    } else if (xsectors < 2880 * 2) {
                        c = 80;
                        h = 2;
                        type = 4;
                    } else {
                        c = 80;
                        h = 2;
                        type = 6;
                    }
                    track = c * h;
                    while (c < 256) {
                        s = xsectors / track;
                        if (s < 63 && (xsectors % track) == 0) {
                            ok = 1;
                            break;
                        }
                        c++;
                        track += h;
                    }
                    if (ok) {
                        max_h = h;
                        max_s = s;
                        hd_geometry.hsrc = hd_geometry.ssrc = "fd";
                    } else {
                        /* No valid floppy geometry, fake it by simulating broken
                           sectors at the end of the image... */
                        xsectors++;
                    }

                    hd_geometry.type = type;
                }
            } else {
                /* Assume it is a hard disk image and scan for a partition table */
                const struct ptab_entry *ptab = (const struct ptab_entry *)
                    ((char *)where + hd_geometry.offset + (512 - 2 - 4 * 16));

                /* Assume hard disk */
                if (!hd_geometry.driveno)
                    hd_geometry.driveno = 0x80;

                if (*(uint16_t *) ((char *)where + hd_geometry.offset + 512 - 2) == 0xaa55) {
                    for (i = 0; i < 4; i++) {
                        if (ptab[i].type && !(ptab[i].active & 0x7f)) {
                            s = (ptab[i].start_s & 0x3f);
                            h = ptab[i].start_h + 1;

                            if (max_h < h)
                                max_h = h;
                            if (max_s < s)
                                max_s = s;

                            s = (ptab[i].end_s & 0x3f);
                            h = ptab[i].end_h + 1;

                            if (max_h < h) {
                                max_h = h;
                                hd_geometry.hsrc = "MBR";
                            }
                            if (max_s < s) {
                                max_s = s;
                                hd_geometry.ssrc = "MBR";
                            }
                        }
                    }
                }

                hd_geometry.type = 0;
            }
        }

        if (!max_h)
            max_h = xsectors > 2097152 ? 255 : 64;
        if (!max_s)
            max_s = xsectors > 2097152 ? 63 : 32;

        hd_geometry.h    = max_h;
        hd_geometry.s    = max_s;
    }

    if (!hd_geometry.c)
        hd_geometry.c = xsectors / (hd_geometry.h * hd_geometry.s);

    if ((p = getcmditem("floppy")) != CMD_NOTFOUND) {
        hd_geometry.driveno = CMD_HASDATA(p) ? atou(p) & 0x7f : 0;
    } else if ((p = getcmditem("harddisk")) != CMD_NOTFOUND) {
        hd_geometry.driveno = CMD_HASDATA(p) ? atou(p) | 0x80 : 0x80;
    }

    if (hd_geometry.driveno & 0x80) {
        hd_geometry.type = 0;   /* Type = hard disk */
    } else {
        if (hd_geometry.type == 0)
            hd_geometry.type = 0x10;    /* ATAPI floppy, e.g. LS-120 */
    }

    if ((size - hd_geometry.offset) & 0x1ff) {
        puts("MEMDISK: Image has fractional end sector\n");
    }
    if (sectors % (hd_geometry.h * hd_geometry.s)) {
        puts("MEMDISK: Image seems to have fractional end cylinder\n");
    }
    if ((hd_geometry.c * hd_geometry.h * hd_geometry.s) > sectors) {
        puts("MEMDISK: Image appears to be truncated\n");
    }

    return &hd_geometry;
}

/*
 * Find a $PnP installation check structure; return (ES << 16) + DI value
 */
static uint32_t pnp_install_check(void)
{
    uint32_t *seg;
    unsigned char *p, csum;
    int i, len;

    for (seg = (uint32_t *) 0xf0000; seg < (uint32_t *) 0x100000; seg += 4) {
        if (*seg == ('$' + ('P' << 8) + ('n' << 16) + ('P' << 24))) {
            p = (unsigned char *)seg;
            len = p[5];
            if (len < 0x21)
                continue;
            csum = 0;
            for (i = len; i; i--)
                csum += *p++;
            if (csum != 0)
                continue;

            return (0xf000 << 16) + (uint16_t) (unsigned long)seg;
        }
    }

    return 0;
}

/*
 * Relocate the real-mode code to a new segment
 */
struct gdt_ptr {
    uint16_t limit;
    uint32_t base;
} __attribute__ ((packed));

static void set_seg_base(uint32_t gdt_base, int seg, uint32_t v)
{
    *(uint16_t *) (gdt_base + seg + 2) = v;
    *(uint8_t *) (gdt_base + seg + 4) = v >> 16;
    *(uint8_t *) (gdt_base + seg + 7) = v >> 24;
}

static void relocate_rm_code(uint32_t newbase)
{
    uint32_t gdt_base;
    uint32_t oldbase = rm_args.rm_base;
    uint32_t delta = newbase - oldbase;

    cli();
    memmove((void *)newbase, (void *)oldbase, rm_args.rm_size);

    rm_args.rm_return += delta;
    rm_args.rm_intcall += delta;
    rm_args.rm_bounce += delta;
    rm_args.rm_base += delta;
    rm_args.rm_gdt += delta;
    rm_args.rm_pmjmp += delta;
    rm_args.rm_rmjmp += delta;

    gdt_base = rm_args.rm_gdt;

    *(uint32_t *) (gdt_base + 2) = gdt_base;    /* GDT self-pointer */

    /* Segments 0x10 and 0x18 are real-mode-based */
    set_seg_base(gdt_base, 0x10, rm_args.rm_base);
    set_seg_base(gdt_base, 0x18, rm_args.rm_base);

#if __SIZEOF_POINTER__ == 4
    asm volatile ("lgdtl %0"::"m" (*(char *)gdt_base));
#elif __SIZEOF_POINTER__ == 8
    asm volatile ("lgdt %0"::"m" (*(char *)gdt_base));
#else
#error "unsupported architecture"
#endif

    *(uint32_t *) rm_args.rm_pmjmp += delta;
    *(uint16_t *) rm_args.rm_rmjmp += delta >> 4;

    rm_args.rm_handle_interrupt += delta;

    sti();
}

static uint8_t checksum_buf(const void *buf, int count)
{
    const uint8_t *p = buf;
    uint8_t c = 0;

    while (count--)
        c += *p++;

    return c;
}

static int stack_needed(void)
{
  const unsigned int min_stack = 128;   /* Minimum stack size */
  const unsigned int def_stack = 512;   /* Default stack size */
  unsigned int v = 0;
  const char *p;

  if (CMD_HASDATA(p = getcmditem("stack")))
    v = atou(p);

  if (!v)
    v = def_stack;

  if (v < min_stack)
    v = min_stack;

  return v;
}

/*
 * Set max memory by reservation
 * Adds reservations to data in INT15h to prevent access to the top of RAM
 * if there's any above the point specified.
 */
void setmaxmem(unsigned long long restop_ull)
{
    uint32_t restop;
    struct e820range *ep;
    const int int15restype = 2;

    /* insertrange() works on uint32_t */
    restop = min(restop_ull, UINT32_MAX);
    /* printf("  setmaxmem  '%08x%08x'  => %08x\n",
        (unsigned int)(restop_ull>>32), (unsigned int)restop_ull, restop); */

    for (ep = ranges; ep->type != -1U; ep++) {
        if (ep->type == 1) {    /* Only if available */
            if (ep->start >= restop) {
                /* printf("  %08x -> 2\n", ep->start); */
                ep->type = int15restype;
            } else if (ep[1].start > restop) {
                /* printf("  +%08x =2; cut %08x\n", restop, ep->start); */
                insertrange(restop, (ep[1].start - restop), int15restype);
            }
        }
    }
    parse_mem();
}

struct real_mode_args rm_args;

/*
 * Actual setup routine
 * Returns the drive number (which is then passed in %dl to the
 * called routine.)
 */
void setup(const struct real_mode_args *rm_args_ptr)
{
    unsigned int bin_size;
    char *memdisk_hook;
    struct memdisk_header *hptr;
    struct patch_area *pptr;
    struct mBFT *mbft;
    uint16_t driverseg;
    uint32_t driverptr, driveraddr;
    uint16_t dosmem_k;
    uint32_t stddosmem;
    const struct geometry *geometry;
    unsigned int total_size;
    unsigned int cmdline_len, stack_len, e820_len;
    const struct edd4_bvd *bvd;
    const struct edd4_bootcat *boot_cat = 0;
    com32sys_t regs;
    uint32_t ramdisk_image, ramdisk_size;
    uint32_t boot_base, rm_base;
    int bios_drives;
    int do_edd = 1;             /* 0 = no, 1 = yes, default is yes */
    int do_eltorito = 0;        /* default is no */
    int no_bpt;                 /* No valid BPT presented */
    uint32_t boot_seg = 0;      /* Meaning 0000:7C00 */
    uint32_t boot_len = 512;    /* One sector */
    const char *p;

    /* We need to copy the rm_args into their proper place */
    memcpy(&rm_args, rm_args_ptr, sizeof rm_args);
    sti();                      /* ... then interrupts are safe */

    /* Show signs of life */
    printf("%s  %s\n", memdisk_version, copyright);

    if (!shdr->ramdisk_image || !shdr->ramdisk_size)
        die("MEMDISK: No ramdisk image specified!\n");

    ramdisk_image = shdr->ramdisk_image;
    ramdisk_size = shdr->ramdisk_size;

    e820map_init();             /* Initialize memory data structure */
    get_mem();                  /* Query BIOS for memory map */
    parse_mem();                /* Parse memory map */

    printf("Ramdisk at 0x%08x, length 0x%08x\n", ramdisk_image, ramdisk_size);

    unzip_if_needed(&ramdisk_image, &ramdisk_size);

    geometry = get_disk_image_geometry(ramdisk_image, ramdisk_size);

    if (getcmditem("edd") != CMD_NOTFOUND ||
        getcmditem("ebios") != CMD_NOTFOUND)
        do_edd = 1;
    else if (getcmditem("noedd") != CMD_NOTFOUND ||
             getcmditem("noebios") != CMD_NOTFOUND ||
             getcmditem("cbios") != CMD_NOTFOUND)
        do_edd = 0;
    else
        do_edd = (geometry->driveno & 0x80) ? 1 : 0;

    if (getcmditem("iso") != CMD_NOTFOUND) {
        do_eltorito = 1;
        do_edd = 1;             /* Mandatory */
    }

    /* Choose the appropriate installable memdisk hook */
    if (do_eltorito) {
        if (geometry->sector_shift == 11) {
            bin_size = (int)&_binary_memdisk_iso_2048_bin_size;
            memdisk_hook = (char *)&_binary_memdisk_iso_2048_bin_start;
        } else {
            bin_size = (int)&_binary_memdisk_iso_512_bin_size;
            memdisk_hook = (char *)&_binary_memdisk_iso_512_bin_start;
        }
    } else {
        if (do_edd) {
            bin_size = (int)&_binary_memdisk_edd_512_bin_size;
            memdisk_hook = (char *)&_binary_memdisk_edd_512_bin_start;
        } else {
            bin_size = (int)&_binary_memdisk_chs_512_bin_size;
            memdisk_hook = (char *)&_binary_memdisk_chs_512_bin_start;
        }
    }

    /* Reserve the ramdisk memory */
    insertrange(ramdisk_image, ramdisk_size, 2);
    parse_mem();                /* Recompute variables */

    /* Figure out where it needs to go */
    hptr = (struct memdisk_header *)memdisk_hook;
    pptr = (struct patch_area *)(memdisk_hook + hptr->patch_offs);

    dosmem_k = rdz_16(BIOS_BASEMEM);
    pptr->mdi.olddosmem = dosmem_k;
    stddosmem = dosmem_k << 10;
    /* If INT 15 E820 and INT 12 disagree, go with the most conservative */
    if (stddosmem > dos_mem)
        stddosmem = dos_mem;

    pptr->driveno = geometry->driveno;
    pptr->drivetype = geometry->type;
    pptr->cylinders = geometry->c;      /* Possible precision loss */
    pptr->heads = geometry->h;
    pptr->sectors = geometry->s;
    pptr->mdi.disksize = geometry->sectors;
    pptr->mdi.diskbuf = ramdisk_image + geometry->offset;
    pptr->mdi.sector_shift = geometry->sector_shift;
    pptr->statusptr = (geometry->driveno & 0x80) ? 0x474 : 0x441;

    pptr->mdi.bootloaderid = shdr->type_of_loader;

    pptr->configflags = CONFIG_SAFEINT; /* Default */
    /* Set config flags */
    if (getcmditem("ro") != CMD_NOTFOUND) {
        pptr->configflags |= CONFIG_READONLY;
    }
    if (getcmditem("raw") != CMD_NOTFOUND) {
        pptr->configflags &= ~CONFIG_MODEMASK;
        pptr->configflags |= CONFIG_RAW;
    }
    if (getcmditem("bigraw") != CMD_NOTFOUND) {
        pptr->configflags &= ~CONFIG_MODEMASK;
        pptr->configflags |= CONFIG_BIGRAW | CONFIG_RAW;
    }
    if (getcmditem("int") != CMD_NOTFOUND) {
        pptr->configflags &= ~CONFIG_MODEMASK;
        /* pptr->configflags |= 0; */
    }
    if (getcmditem("safeint") != CMD_NOTFOUND) {
        pptr->configflags &= ~CONFIG_MODEMASK;
        pptr->configflags |= CONFIG_SAFEINT;
    }

    printf("Disk is %s%d, %u%s K, C/H/S = %u/%u/%u (%s/%s), EDD %s, %s\n",
           (geometry->driveno & 0x80) ? "hd" : "fd",
           geometry->driveno & 0x7f,
           geometry->sectors >> 1,
           (geometry->sectors & 1) ? ".5" : "",
           geometry->c, geometry->h, geometry->s,
           geometry->hsrc, geometry->ssrc,
           do_edd ? "on" : "off",
           pptr->configflags & CONFIG_READONLY ? "ro" : "rw");

    puts("Using ");
    switch (pptr->configflags & CONFIG_MODEMASK) {
    case 0:
        puts("standard INT 15h");
        break;
    case CONFIG_SAFEINT:
        puts("safe INT 15h");
        break;
    case CONFIG_RAW:
        puts("raw");
        break;
    case CONFIG_RAW | CONFIG_BIGRAW:
        puts("big real mode raw");
        break;
    default:
        printf("unknown %#x", pptr->configflags & CONFIG_MODEMASK);
        break;
    }
    puts(" access to high memory\n");

    /* Set up a drive parameter table */
    if (geometry->driveno & 0x80) {
        /* Hard disk */
        pptr->dpt.hd.max_cyl = geometry->c - 1;
        pptr->dpt.hd.max_head = geometry->h - 1;
        pptr->dpt.hd.ctrl = (geometry->h > 8) ? 0x08 : 0;
    } else {
        /* Floppy - most of these fields are bogus and mimic
           a 1.44 MB floppy drive */
        pptr->dpt.fd.specify1 = 0xdf;
        pptr->dpt.fd.specify2 = 0x02;
        pptr->dpt.fd.delay = 0x25;
        pptr->dpt.fd.sectors = geometry->s;
        pptr->dpt.fd.bps = 0x02;
        pptr->dpt.fd.isgap = 0x12;
        pptr->dpt.fd.dlen = 0xff;
        pptr->dpt.fd.fgap = 0x6c;
        pptr->dpt.fd.ffill = 0xf6;
        pptr->dpt.fd.settle = 0x0f;
        pptr->dpt.fd.mstart = 0x05;
        pptr->dpt.fd.maxtrack = geometry->c - 1;
        pptr->dpt.fd.cmos = geometry->type > 5 ? 5 : geometry->type;

        pptr->dpt.fd.old_fd_dpt = rdz_32(BIOS_INT1E);
    }

    /* Set up an EDD drive parameter table */
    if (do_edd) {
        pptr->edd_dpt.sectors = geometry->sectors;
        /* The EDD spec has this as <= 15482880  sectors (1024x240x63);
           this seems to make very little sense.  Try for something saner. */
        if (geometry->c <= 1024 && geometry->h <= 255 && geometry->s <= 63) {
            pptr->edd_dpt.c = geometry->c;
            pptr->edd_dpt.h = geometry->h;
            pptr->edd_dpt.s = geometry->s;
            /* EDD-4 states that invalid geometry should be returned
             * for INT 0x13, AH=0x48 "EDD Get Disk Parameters" call on an
             * El Torito ODD.  Check for 2048-byte sector size
             */
            if (geometry->sector_shift != 11)
                pptr->edd_dpt.flags |= 0x0002;  /* Geometry valid */
        }
        if (!(geometry->driveno & 0x80)) {
            /* Floppy drive.  Mark it as a removable device with
               media change notification; media is present. */
            pptr->edd_dpt.flags |= 0x0014;
        }

        pptr->edd_dpt.devpath[0] = pptr->mdi.diskbuf;
        pptr->edd_dpt.chksum = -checksum_buf(&pptr->edd_dpt.dpikey, 73 - 30);
    }

    if (do_eltorito) {
        bvd = (struct edd4_bvd *)(ramdisk_image + 17 * 2048);
        boot_cat =
            (struct edd4_bootcat *)(ramdisk_image + bvd->boot_cat * 2048);
        pptr->cd_pkt.type = boot_cat->initial_entry.media_type; /* Cheat */
        pptr->cd_pkt.driveno = geometry->driveno;
        pptr->cd_pkt.start = boot_cat->initial_entry.load_block;
        boot_seg = pptr->cd_pkt.load_seg = boot_cat->initial_entry.load_seg;
        pptr->cd_pkt.sect_count = boot_cat->initial_entry.sect_count;
        boot_len = pptr->cd_pkt.sect_count * 512;
        pptr->cd_pkt.geom1 = (uint8_t)(pptr->cylinders) & 0xFF;
        pptr->cd_pkt.geom2 =
            (uint8_t)(pptr->sectors) | (uint8_t)((pptr->cylinders >> 2) & 0xC0);
        pptr->cd_pkt.geom3 = (uint8_t)(pptr->heads);
    }

    if ((p = getcmditem("mem")) != CMD_NOTFOUND) {
        setmaxmem(suffix_number(p));
    }

    /* The size is given by hptr->total_size plus the size of the E820
       map -- 12 bytes per range; we may need as many as 2 additional
       ranges (each insertrange() can worst-case turn 1 area into 3)
       plus the terminating range, over what nranges currently show. */
    total_size = hptr->total_size;      /* Actual memdisk code */
    e820_len = (nranges + 3) * sizeof(ranges[0]);
    total_size += e820_len;             /* E820 memory ranges */
    cmdline_len = strlen(shdr->cmdline) + 1;
    total_size += cmdline_len;          /* Command line */
    stack_len = stack_needed();
    total_size += stack_len;            /* Stack */
    printf("Code %u, meminfo %u, cmdline %u, stack %u\n",
           hptr->total_size, e820_len, cmdline_len, stack_len);
    printf("Total size needed = %u bytes, allocating %uK\n",
           total_size, (total_size + 0x3ff) >> 10);

    if (total_size > dos_mem)
        die("MEMDISK: Insufficient low memory\n");

    driveraddr = stddosmem - total_size;
    driveraddr &= ~0x3FF;

    printf("Old dos memory at 0x%05x (map says 0x%05x), loading at 0x%05x\n",
           stddosmem, dos_mem, driveraddr);

    /* Reserve this range of memory */
    wrz_16(BIOS_BASEMEM, driveraddr >> 10);
    insertrange(driveraddr, dos_mem - driveraddr, 2);
    parse_mem();

    pptr->mem1mb = low_mem >> 10;
    pptr->mem16mb = high_mem >> 16;
    if (low_mem == (15 << 20)) {
        /* lowmem maxed out */
        uint32_t int1588mem = (high_mem >> 10) + (low_mem >> 10);
        pptr->memint1588 = (int1588mem > 0xffff) ? 0xffff : int1588mem;
    } else {
        pptr->memint1588 = low_mem >> 10;
    }

    printf("1588: 0x%04x  15E801: 0x%04x 0x%04x\n",
           pptr->memint1588, pptr->mem1mb, pptr->mem16mb);

    driverseg = driveraddr >> 4;
    driverptr = driverseg << 16;

    /* Anything beyond the end is for the stack */
    pptr->mystack = (uint16_t) (stddosmem - driveraddr);

    pptr->mdi.oldint13.uint32 = rdz_32(BIOS_INT13);
    pptr->mdi.oldint15.uint32 = rdz_32(BIOS_INT15);

    /* Adjust the E820 table: if there are null ranges (type 0)
       at the end, change them to type end of list (-1).
       This is necessary for the driver to be able to report end
       of list correctly. */
    while (nranges && ranges[nranges - 1].type == 0) {
        ranges[--nranges].type = -1;
    }

    if (getcmditem("nopassany") != CMD_NOTFOUND) {
        printf("nopassany specified - we're the only drive of any kind\n");
        bios_drives = 0;
        pptr->drivecnt = 0;
        no_bpt = 1;
        pptr->mdi.oldint13.uint32 = driverptr + hptr->iret_offs;
        wrz_8(BIOS_EQUIP, rdz_8(BIOS_EQUIP) & ~0xc1);
        wrz_8(BIOS_HD_COUNT, 0);
    } else if (getcmditem("nopass") != CMD_NOTFOUND) {
        printf("nopass specified - we're the only drive\n");
        bios_drives = 0;
        pptr->drivecnt = 0;
        no_bpt = 1;
    } else {
        /* Query drive parameters of this type */
        memset(&regs, 0, sizeof regs);
        regs.es = 0;
        regs.eax.b[1] = 0x08;
        regs.edx.b[0] = geometry->driveno & 0x80;
        intcall(0x13, &regs, &regs);

        /* Note: per suggestion from the Interrupt List, consider
           INT 13 08 to have failed if the sector count in CL is zero. */
        if ((regs.eflags.l & 1) || !(regs.ecx.b[0] & 0x3f)) {
            printf("INT 13 08: Failure, assuming this is the only drive\n");
            pptr->drivecnt = 0;
            no_bpt = 1;
        } else {
            printf("INT 13 08: Success, count = %u, BPT = %04x:%04x\n",
                   regs.edx.b[0], regs.es, regs.edi.w[0]);
            pptr->drivecnt = regs.edx.b[0];
            no_bpt = !(regs.es | regs.edi.w[0]);
        }

        /* Compare what INT 13h returned with the appropriate equipment byte */
        if (geometry->driveno & 0x80) {
            bios_drives = rdz_8(BIOS_HD_COUNT);
        } else {
            uint8_t equip = rdz_8(BIOS_EQUIP);

            if (equip & 1)
                bios_drives = (equip >> 6) + 1;
            else
                bios_drives = 0;
        }

        if (pptr->drivecnt > bios_drives) {
            printf("BIOS equipment byte says count = %d, go with that\n",
                   bios_drives);
            pptr->drivecnt = bios_drives;
        }
    }

    /* Add ourselves to the drive count */
    pptr->drivecnt++;

    /* Discontiguous drive space.  There is no really good solution for this. */
    if (pptr->drivecnt <= (geometry->driveno & 0x7f))
        pptr->drivecnt = (geometry->driveno & 0x7f) + 1;

    /* Probe for contiguous range of BIOS drives starting with driveno */
    pptr->driveshiftlimit = probe_drive_range(geometry->driveno) + 1;
    if ((pptr->driveshiftlimit & 0x80) != (geometry->driveno & 0x80))
        printf("We lost the last drive in our class of drives.\n");
    printf("Drive probing gives drive shift limit: 0x%02x\n",
        pptr->driveshiftlimit);

    /* Pointer to the command line */
    pptr->mdi.cmdline.seg_off.offset = bin_size + (nranges + 1) * sizeof(ranges[0]);
    pptr->mdi.cmdline.seg_off.segment = driverseg;

    /* Copy driver followed by E820 table followed by command line */
    {
        unsigned char *dpp = (unsigned char *)(driverseg << 4);

        /* Adjust these pointers to point to the installed image */
        /* Careful about the order here... the image isn't copied yet! */
        pptr = (struct patch_area *)(dpp + hptr->patch_offs);
        hptr = (struct memdisk_header *)dpp;

        /* Actually copy to low memory */
        dpp = mempcpy(dpp, memdisk_hook, bin_size);
        dpp = mempcpy(dpp, ranges, (nranges + 1) * sizeof(ranges[0]));
        dpp = mempcpy(dpp, shdr->cmdline, cmdline_len);
    }

    /* Note the previous INT 13h hook in the "safe hook" structure */
    hptr->safe_hook.old_hook.uint32 = pptr->mdi.oldint13.uint32;

    /* Re-fill the "safe hook" mBFT field with the physical address */
    mbft = (struct mBFT *)(((const char *)hptr) + hptr->safe_hook.mbft);
    hptr->safe_hook.mbft = (size_t)mbft;

    /* Update various BIOS magic data areas (gotta love this shit) */

    if (geometry->driveno & 0x80) {
        /* Update BIOS hard disk count */
        uint8_t nhd = pptr->drivecnt;

        if (nhd > 128)
            nhd = 128;

        if (!do_eltorito)
            wrz_8(BIOS_HD_COUNT, nhd);
    } else {
        /* Update BIOS floppy disk count */
        uint8_t equip = rdz_8(BIOS_EQUIP);
        uint8_t nflop = pptr->drivecnt;

        if (nflop > 4)          /* Limit of equipment byte */
            nflop = 4;

        equip &= 0x3E;
        if (nflop)
            equip |= ((nflop - 1) << 6) | 0x01;

        wrz_8(BIOS_EQUIP, equip);

        /* Install DPT pointer if this was the only floppy */
        if (getcmditem("dpt") != CMD_NOTFOUND ||
            ((nflop == 1 || no_bpt) && getcmditem("nodpt") == CMD_NOTFOUND)) {
            /* Do install a replacement DPT into INT 1Eh */
            pptr->mdi.dpt_ptr =
                hptr->patch_offs + offsetof(struct patch_area, dpt);
        }
    }

    /* Complete the mBFT */
    mbft->acpi.signature[0] = 'm';      /* "mBFT" */
    mbft->acpi.signature[1] = 'B';
    mbft->acpi.signature[2] = 'F';
    mbft->acpi.signature[3] = 'T';
    mbft->safe_hook = (size_t)&hptr->safe_hook;
    mbft->acpi.checksum = -checksum_buf(mbft, mbft->acpi.length);

    /* Install the interrupt handlers */
    printf("old: int13 = %08x  int15 = %08x  int1e = %08x\n",
           rdz_32(BIOS_INT13), rdz_32(BIOS_INT15), rdz_32(BIOS_INT1E));

    wrz_32(BIOS_INT13, driverptr + hptr->int13_offs);
    wrz_32(BIOS_INT15, driverptr + hptr->int15_offs);
    if (pptr->mdi.dpt_ptr)
        wrz_32(BIOS_INT1E, driverptr + pptr->mdi.dpt_ptr);

    printf("new: int13 = %08x  int15 = %08x  int1e = %08x\n",
           rdz_32(BIOS_INT13), rdz_32(BIOS_INT15), rdz_32(BIOS_INT1E));

    /* Figure out entry point */
    if (!boot_seg) {
        boot_base = 0x7c00;
        shdr->sssp = 0x7c00;
        shdr->csip = 0x7c00;
    } else {
        boot_base = boot_seg << 4;
        shdr->sssp = boot_seg << 16;
        shdr->csip = boot_seg << 16;
    }

    /* Relocate the real-mode code to below the stub */
    rm_base = (driveraddr - rm_args.rm_size) & ~15;
    if (rm_base < boot_base + boot_len)
        die("MEMDISK: bootstrap too large to load\n");

    relocate_rm_code(rm_base);

    /* Reboot into the new "disk" */
    puts("Loading boot sector... ");

    memcpy((void *)boot_base,
           (char *)pptr->mdi.diskbuf + geometry->boot_lba * 512,
           boot_len);

    if (getcmditem("pause") != CMD_NOTFOUND) {
        puts("press any key to boot... ");
        regs.eax.w[0] = 0;
        intcall(0x16, &regs, NULL);
    }

    puts("booting...\n");

    /* On return the assembly code will jump to the boot vector */
    shdr->esdi = pnp_install_check();
    shdr->edx = geometry->driveno;
}