/* ----------------------------------------------------------------------- *
 *
 *   Copyright 1998-2008 H. Peter Anvin - All Rights Reserved
 *
 *   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.
 *
 * ----------------------------------------------------------------------- */

/*
 * extlinux.c
 *
 * Install the extlinux boot block on an ext2/3 filesystem
 */

#define  _GNU_SOURCE		/* Enable everything */
#include <inttypes.h>
/* This is needed to deal with the kernel headers imported into glibc 3.3.3. */
typedef uint64_t u64;
#include <alloca.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#ifndef __KLIBC__
#include <mntent.h>
#endif
#include <stdlib.h>
#include <string.h>
#include <getopt.h>
#include <sysexits.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/mount.h>
#include <sys/vfs.h>

#include <linux/fd.h>		/* Floppy geometry */
#include <linux/hdreg.h>	/* Hard disk geometry */
#define statfs _kernel_statfs	/* HACK to deal with broken 2.4 distros */
#include <linux/fs.h>		/* FIGETBSZ, FIBMAP */
#undef statfs

#include "ext2_fs.h"
#include "../version.h"
#include "syslxint.h"

#ifdef DEBUG
# define dprintf printf
#else
# define dprintf(...) ((void)0)
#endif

/* Global option handling */

const char *program;

/* These are the options we can set and their values */
struct my_options {
    unsigned int sectors;
    unsigned int heads;
    int raid_mode;
    int reset_adv;
    const char *set_once;
} opt = {
.sectors = 0,.heads = 0,.raid_mode = 0,.reset_adv = 0,.set_once = NULL,};

static void __attribute__ ((noreturn)) usage(int rv)
{
    fprintf(stderr,
	    "Usage: %s [options] directory\n"
	    "  --install    -i  Install over the current bootsector\n"
	    "  --update     -U  Update a previous EXTLINUX installation\n"
	    "  --zip        -z  Force zipdrive geometry (-H 64 -S 32)\n"
	    "  --sectors=#  -S  Force the number of sectors per track\n"
	    "  --heads=#    -H  Force number of heads\n"
	    "  --raid       -r  Fall back to the next device on boot failure\n"
	    "  --once=...   -o  Execute a command once upon boot\n"
	    "  --clear-once -O  Clear the boot-once command\n"
	    "  --reset-adv      Reset auxilliary data\n"
	    "\n"
	    "  Note: geometry is determined at boot time for devices which\n"
	    "  are considered hard disks by the BIOS.  Unfortunately, this is\n"
	    "  not possible for devices which are considered floppy disks,\n"
	    "  which includes zipdisks and LS-120 superfloppies.\n"
	    "\n"
	    "  The -z option is useful for USB devices which are considered\n"
	    "  hard disks by some BIOSes and zipdrives by other BIOSes.\n",
	    program);

    exit(rv);
}

enum long_only_opt {
    OPT_NONE,
    OPT_RESET_ADV,
};

static const struct option long_options[] = {
    {"install", 0, NULL, 'i'},
    {"update", 0, NULL, 'U'},
    {"zipdrive", 0, NULL, 'z'},
    {"sectors", 1, NULL, 'S'},
    {"heads", 1, NULL, 'H'},
    {"raid-mode", 0, NULL, 'r'},
    {"version", 0, NULL, 'v'},
    {"help", 0, NULL, 'h'},
    {"once", 1, NULL, 'o'},
    {"clear-once", 0, NULL, 'O'},
    {"reset-adv", 0, NULL, OPT_RESET_ADV},
    {0, 0, 0, 0}
};

static const char short_options[] = "iUuzS:H:rvho:O";

#if defined(__linux__) && !defined(BLKGETSIZE64)
/* This takes a u64, but the size field says size_t.  Someone screwed big. */
# define BLKGETSIZE64 _IOR(0x12,114,size_t)
#endif

#define LDLINUX_MAGIC	0x3eb202fe

enum bs_offsets {
    bsJump = 0x00,
    bsOemName = 0x03,
    bsBytesPerSec = 0x0b,
    bsSecPerClust = 0x0d,
    bsResSectors = 0x0e,
    bsFATs = 0x10,
    bsRootDirEnts = 0x11,
    bsSectors = 0x13,
    bsMedia = 0x15,
    bsFATsecs = 0x16,
    bsSecPerTrack = 0x18,
    bsHeads = 0x1a,
    bsHiddenSecs = 0x1c,
    bsHugeSectors = 0x20,

    /* FAT12/16 only */
    bs16DriveNumber = 0x24,
    bs16Reserved1 = 0x25,
    bs16BootSignature = 0x26,
    bs16VolumeID = 0x27,
    bs16VolumeLabel = 0x2b,
    bs16FileSysType = 0x36,
    bs16Code = 0x3e,

    /* FAT32 only */
    bs32FATSz32 = 36,
    bs32ExtFlags = 40,
    bs32FSVer = 42,
    bs32RootClus = 44,
    bs32FSInfo = 48,
    bs32BkBootSec = 50,
    bs32Reserved = 52,
    bs32DriveNumber = 64,
    bs32Reserved1 = 65,
    bs32BootSignature = 66,
    bs32VolumeID = 67,
    bs32VolumeLabel = 71,
    bs32FileSysType = 82,
    bs32Code = 90,

    bsSignature = 0x1fe
};

#define bsHead      bsJump
#define bsHeadLen   (bsOemName-bsHead)
#define bsCode	    bs32Code	/* The common safe choice */
#define bsCodeLen   (bsSignature-bs32Code)

#ifndef EXT2_SUPER_OFFSET
#define EXT2_SUPER_OFFSET 1024
#endif

/*
 * Boot block
 */
extern unsigned char extlinux_bootsect[];
extern unsigned int extlinux_bootsect_len;
#define boot_block	extlinux_bootsect
#define boot_block_len  extlinux_bootsect_len

/*
 * Image file
 */
extern unsigned char extlinux_image[];
extern unsigned int extlinux_image_len;
#define boot_image	extlinux_image
#define boot_image_len  extlinux_image_len

/*
 * Common abort function
 */
void __attribute__ ((noreturn)) die(const char *msg)
{
    fputs(msg, stderr);
    exit(1);
}

/*
 * read/write wrapper functions
 */
ssize_t xpread(int fd, void *buf, size_t count, off_t offset)
{
    char *bufp = (char *)buf;
    ssize_t rv;
    ssize_t done = 0;

    while (count) {
	rv = pread(fd, bufp, count, offset);
	if (rv == 0) {
	    die("short read");
	} else if (rv == -1) {
	    if (errno == EINTR) {
		continue;
	    } else {
		die(strerror(errno));
	    }
	} else {
	    bufp += rv;
	    offset += rv;
	    done += rv;
	    count -= rv;
	}
    }

    return done;
}

ssize_t xpwrite(int fd, const void *buf, size_t count, off_t offset)
{
    const char *bufp = (const char *)buf;
    ssize_t rv;
    ssize_t done = 0;

    while (count) {
	rv = pwrite(fd, bufp, count, offset);
	if (rv == 0) {
	    die("short write");
	} else if (rv == -1) {
	    if (errno == EINTR) {
		continue;
	    } else {
		die(strerror(errno));
	    }
	} else {
	    bufp += rv;
	    offset += rv;
	    done += rv;
	    count -= rv;
	}
    }

    return done;
}

/*
 * Produce file map
 */
int sectmap(int fd, uint32_t * sectors, int nsectors)
{
    unsigned int blksize, blk, nblk;
    unsigned int i;

    /* Get block size */
    if (ioctl(fd, FIGETBSZ, &blksize))
	return -1;

    /* Number of sectors per block */
    blksize >>= SECTOR_SHIFT;

    nblk = 0;
    while (nsectors) {

	blk = nblk++;
	dprintf("querying block %u\n", blk);
	if (ioctl(fd, FIBMAP, &blk))
	    return -1;

	blk *= blksize;
	for (i = 0; i < blksize; i++) {
	    if (!nsectors)
		return 0;

	    dprintf("Sector: %10u\n", blk);
	    *sectors++ = blk++;
	    nsectors--;
	}
    }

    return 0;
}

/*
 * Get the size of a block device
 */
uint64_t get_size(int devfd)
{
    uint64_t bytes;
    uint32_t sects;
    struct stat st;

#ifdef BLKGETSIZE64
    if (!ioctl(devfd, BLKGETSIZE64, &bytes))
	return bytes;
#endif
    if (!ioctl(devfd, BLKGETSIZE, &sects))
	return (uint64_t) sects << 9;
    else if (!fstat(devfd, &st) && st.st_size)
	return st.st_size;
    else
	return 0;
}

/*
 * Get device geometry and partition offset
 */
struct geometry_table {
    uint64_t bytes;
    struct hd_geometry g;
};

/* Standard floppy disk geometries, plus LS-120.  Zipdisk geometry
   (x/64/32) is the final fallback.  I don't know what LS-240 has
   as its geometry, since I don't have one and don't know anyone that does,
   and Google wasn't helpful... */
static const struct geometry_table standard_geometries[] = {
    {360 * 1024, {2, 9, 40, 0}},
    {720 * 1024, {2, 9, 80, 0}},
    {1200 * 1024, {2, 15, 80, 0}},
    {1440 * 1024, {2, 18, 80, 0}},
    {1680 * 1024, {2, 21, 80, 0}},
    {1722 * 1024, {2, 21, 80, 0}},
    {2880 * 1024, {2, 36, 80, 0}},
    {3840 * 1024, {2, 48, 80, 0}},
    {123264 * 1024, {8, 32, 963, 0}},	/* LS120 */
    {0, {0, 0, 0, 0}}
};

int get_geometry(int devfd, uint64_t totalbytes, struct hd_geometry *geo)
{
    struct floppy_struct fd_str;
    const struct geometry_table *gp;

    memset(geo, 0, sizeof *geo);

    if (!ioctl(devfd, HDIO_GETGEO, &geo)) {
	return 0;
    } else if (!ioctl(devfd, FDGETPRM, &fd_str)) {
	geo->heads = fd_str.head;
	geo->sectors = fd_str.sect;
	geo->cylinders = fd_str.track;
	geo->start = 0;
	return 0;
    }

    /* Didn't work.  Let's see if this is one of the standard geometries */
    for (gp = standard_geometries; gp->bytes; gp++) {
	if (gp->bytes == totalbytes) {
	    memcpy(geo, &gp->g, sizeof *geo);
	    return 0;
	}
    }

    /* Didn't work either... assign a geometry of 64 heads, 32 sectors; this is
       what zipdisks use, so this would help if someone has a USB key that
       they're booting in USB-ZIP mode. */

    geo->heads = opt.heads ? : 64;
    geo->sectors = opt.sectors ? : 32;
    geo->cylinders = totalbytes / (geo->heads * geo->sectors << SECTOR_SHIFT);
    geo->start = 0;

    if (!opt.sectors && !opt.heads)
	fprintf(stderr,
		"Warning: unable to obtain device geometry (defaulting to %d heads, %d sectors)\n"
		"         (on hard disks, this is usually harmless.)\n",
		geo->heads, geo->sectors);

    return 1;
}

/*
 * Query the device geometry and put it into the boot sector.
 * Map the file and put the map in the boot sector and file.
 * Stick the "current directory" inode number into the file.
 */
void patch_file_and_bootblock(int fd, int dirfd, int devfd)
{
    struct stat dirst;
    struct hd_geometry geo;
    uint32_t *sectp;
    uint64_t totalbytes, totalsectors;
    int nsect;
    unsigned char *p, *patcharea;
    int i, dw;
    uint32_t csum;

    if (fstat(dirfd, &dirst)) {
	perror("fstat dirfd");
	exit(255);		/* This should never happen */
    }

    totalbytes = get_size(devfd);
    get_geometry(devfd, totalbytes, &geo);

    if (opt.heads)
	geo.heads = opt.heads;
    if (opt.sectors)
	geo.sectors = opt.sectors;

    /* Patch this into a fake FAT superblock.  This isn't because
       FAT is a good format in any way, it's because it lets the
       early bootstrap share code with the FAT version. */
    dprintf("heads = %u, sect = %u\n", geo.heads, geo.sectors);

    totalsectors = totalbytes >> SECTOR_SHIFT;
    if (totalsectors >= 65536) {
	set_16(boot_block + bsSectors, 0);
    } else {
	set_16(boot_block + bsSectors, totalsectors);
    }
    set_32(boot_block + bsHugeSectors, totalsectors);

    set_16(boot_block + bsBytesPerSec, SECTOR_SIZE);
    set_16(boot_block + bsSecPerTrack, geo.sectors);
    set_16(boot_block + bsHeads, geo.heads);
    set_32(boot_block + bsHiddenSecs, geo.start);

    /* If we're in RAID mode then patch the appropriate instruction;
       either way write the proper boot signature */
    i = get_16(boot_block + 0x1FE);
    if (opt.raid_mode)
	set_16(boot_block + i, 0x18CD);	/* INT 18h */

    set_16(boot_block + 0x1FE, 0xAA55);

    /* Construct the boot file */

    dprintf("directory inode = %lu\n", (unsigned long)dirst.st_ino);
    nsect = (boot_image_len + SECTOR_SIZE - 1) >> SECTOR_SHIFT;
    nsect += 2;			/* Two sectors for the ADV */
    sectp = alloca(sizeof(uint32_t) * nsect);
    if (sectmap(fd, sectp, nsect)) {
	perror("bmap");
	exit(1);
    }

    /* First sector need pointer in boot sector */
    set_32(boot_block + 0x1F8, *sectp++);
    nsect--;

    /* Search for LDLINUX_MAGIC to find the patch area */
    for (p = boot_image; get_32(p) != LDLINUX_MAGIC; p += 4) ;
    patcharea = p + 8;

    /* Set up the totals */
    dw = boot_image_len >> 2;	/* COMPLETE dwords, excluding ADV */
    set_16(patcharea, dw);
    set_16(patcharea + 2, nsect);	/* Not including the first sector, but
					   including the ADV */
    set_32(patcharea + 8, dirst.st_ino);	/* "Current" directory */

    /* Set the sector pointers */
    p = patcharea + 12;

    memset(p, 0, 64 * 4);
    while (nsect--) {
	set_32(p, *sectp++);
	p += 4;
    }

    /* Now produce a checksum */
    set_32(patcharea + 4, 0);

    csum = LDLINUX_MAGIC;
    for (i = 0, p = boot_image; i < dw; i++, p += 4)
	csum -= get_32(p);	/* Negative checksum */

    set_32(patcharea + 4, csum);
}

/*
 * Read the ADV from an existing instance, or initialize if invalid.
 * Returns -1 on fatal errors, 0 if ADV is okay, and 1 if no valid
 * ADV was found.
 */
int read_adv(const char *path)
{
    char *file;
    int fd = -1;
    struct stat st;
    int err = 0;

    asprintf(&file, "%s%sextlinux.sys",
	     path, path[0] && path[strlen(path) - 1] == '/' ? "" : "/");

    if (!file) {
	perror(program);
	return -1;
    }

    fd = open(file, O_RDONLY);
    if (fd < 0) {
	if (errno != ENOENT) {
	    err = -1;
	} else {
	    syslinux_reset_adv(syslinux_adv);
	}
    } else if (fstat(fd, &st)) {
	err = -1;
    } else if (st.st_size < 2 * ADV_SIZE) {
	/* Too small to be useful */
	syslinux_reset_adv(syslinux_adv);
	err = 0;		/* Nothing to read... */
    } else if (xpread(fd, syslinux_adv, 2 * ADV_SIZE,
		      st.st_size - 2 * ADV_SIZE) != 2 * ADV_SIZE) {
	err = -1;
    } else {
	/* We got it... maybe? */
	err = syslinux_validate_adv(syslinux_adv) ? 1 : 0;
    }

    if (err < 0)
	perror(file);

    if (fd >= 0)
	close(fd);
    if (file)
	free(file);

    return err;
}

/*
 * Update the ADV in an existing installation.
 */
int write_adv(const char *path)
{
    unsigned char advtmp[2 * ADV_SIZE];
    char *file;
    int fd = -1;
    struct stat st, xst;
    int err = 0;
    int flags, nflags;

    asprintf(&file, "%s%sextlinux.sys",
	     path, path[0] && path[strlen(path) - 1] == '/' ? "" : "/");

    if (!file) {
	perror(program);
	return -1;
    }

    fd = open(file, O_RDONLY);
    if (fd < 0) {
	err = -1;
    } else if (fstat(fd, &st)) {
	err = -1;
    } else if (st.st_size < 2 * ADV_SIZE) {
	/* Too small to be useful */
	err = -2;
    } else if (xpread(fd, advtmp, 2 * ADV_SIZE,
		      st.st_size - 2 * ADV_SIZE) != 2 * ADV_SIZE) {
	err = -1;
    } else {
	/* We got it... maybe? */
	err = syslinux_validate_adv(advtmp) ? -2 : 0;
	if (!err) {
	    /* Got a good one, write our own ADV here */
	    if (!ioctl(fd, EXT2_IOC_GETFLAGS, &flags)) {
		nflags = flags & ~EXT2_IMMUTABLE_FL;
		if (nflags != flags)
		    ioctl(fd, EXT2_IOC_SETFLAGS, &nflags);
	    }
	    if (!(st.st_mode & S_IWUSR))
		fchmod(fd, st.st_mode | S_IWUSR);

	    /* Need to re-open read-write */
	    close(fd);
	    fd = open(file, O_RDWR | O_SYNC);
	    if (fd < 0) {
		err = -1;
	    } else if (fstat(fd, &xst) || xst.st_ino != st.st_ino ||
		       xst.st_dev != st.st_dev || xst.st_size != st.st_size) {
		fprintf(stderr, "%s: race condition on write\n", file);
		err = -2;
	    }
	    /* Write our own version ... */
	    if (xpwrite(fd, syslinux_adv, 2 * ADV_SIZE,
			st.st_size - 2 * ADV_SIZE) != 2 * ADV_SIZE) {
		err = -1;
	    }

	    sync();

	    if (!(st.st_mode & S_IWUSR))
		fchmod(fd, st.st_mode);

	    if (nflags != flags)
		ioctl(fd, EXT2_IOC_SETFLAGS, &flags);
	}
    }

    if (err == -2)
	fprintf(stderr, "%s: cannot write auxilliary data (need --update)?\n",
		file);
    else if (err == -1)
	perror(file);

    if (fd >= 0)
	close(fd);
    if (file)
	free(file);

    return err;
}

/*
 * Make any user-specified ADV modifications
 */
int modify_adv(void)
{
    int rv = 0;

    if (opt.set_once) {
	if (syslinux_setadv(ADV_BOOTONCE, strlen(opt.set_once), opt.set_once)) {
	    fprintf(stderr, "%s: not enough space for boot-once command\n",
		    program);
	    rv = -1;
	}
    }

    return rv;
}

/*
 * Install the boot block on the specified device.
 * Must be run AFTER install_file()!
 */
int install_bootblock(int fd, const char *device)
{
    struct ext2_super_block sb;

    if (xpread(fd, &sb, sizeof sb, EXT2_SUPER_OFFSET) != sizeof sb) {
	perror("reading superblock");
	return 1;
    }

    if (sb.s_magic != EXT2_SUPER_MAGIC) {
	fprintf(stderr, "no ext2/ext3 superblock found on %s\n", device);
	return 1;
    }

    if (xpwrite(fd, boot_block, boot_block_len, 0) != boot_block_len) {
	perror("writing bootblock");
	return 1;
    }

    return 0;
}

int install_file(const char *path, int devfd, struct stat *rst)
{
    char *file;
    int fd = -1, dirfd = -1, flags;
    struct stat st;

    asprintf(&file, "%s%sextlinux.sys",
	     path, path[0] && path[strlen(path) - 1] == '/' ? "" : "/");
    if (!file) {
	perror(program);
	return 1;
    }

    dirfd = open(path, O_RDONLY | O_DIRECTORY);
    if (dirfd < 0) {
	perror(path);
	goto bail;
    }

    fd = open(file, O_RDONLY);
    if (fd < 0) {
	if (errno != ENOENT) {
	    perror(file);
	    goto bail;
	}
    } else {
	/* If file exist, remove the immutable flag and set u+w mode */
	if (!ioctl(fd, EXT2_IOC_GETFLAGS, &flags)) {
	    flags &= ~EXT2_IMMUTABLE_FL;
	    ioctl(fd, EXT2_IOC_SETFLAGS, &flags);
	}
	if (!fstat(fd, &st)) {
	    fchmod(fd, st.st_mode | S_IWUSR);
	}
    }
    close(fd);

    fd = open(file, O_WRONLY | O_TRUNC | O_CREAT | O_SYNC,
	      S_IRUSR | S_IRGRP | S_IROTH);
    if (fd < 0) {
	perror(file);
	goto bail;
    }

    /* Write it the first time */
    if (xpwrite(fd, boot_image, boot_image_len, 0) != boot_image_len ||
	xpwrite(fd, syslinux_adv, 2 * ADV_SIZE,
		boot_image_len) != 2 * ADV_SIZE) {
	fprintf(stderr, "%s: write failure on %s\n", program, file);
	goto bail;
    }

    /* Map the file, and patch the initial sector accordingly */
    patch_file_and_bootblock(fd, dirfd, devfd);

    /* Write the first sector again - this relies on the file being
       overwritten in place! */
    if (xpwrite(fd, boot_image, SECTOR_SIZE, 0) != SECTOR_SIZE) {
	fprintf(stderr, "%s: write failure on %s\n", program, file);
	goto bail;
    }

    /* Attempt to set immutable flag and remove all write access */
    /* Only set immutable flag if file is owned by root */
    if (!fstat(fd, &st)) {
	fchmod(fd, st.st_mode & (S_IRUSR | S_IRGRP | S_IROTH));
	if (st.st_uid == 0 && !ioctl(fd, EXT2_IOC_GETFLAGS, &flags)) {
	    flags |= EXT2_IMMUTABLE_FL;
	    ioctl(fd, EXT2_IOC_SETFLAGS, &flags);
	}
    }

    if (fstat(fd, rst)) {
	perror(file);
	goto bail;
    }

    close(dirfd);
    close(fd);
    return 0;

bail:
    if (dirfd >= 0)
	close(dirfd);
    if (fd >= 0)
	close(fd);

    return 1;
}

/* EXTLINUX installs the string 'EXTLINUX' at offset 3 in the boot
   sector; this is consistent with FAT filesystems. */
int already_installed(int devfd)
{
    char buffer[8];

    xpread(devfd, buffer, 8, 3);
    return !memcmp(buffer, "EXTLINUX", 8);
}

#ifdef __KLIBC__
static char devname_buf[64];

static void device_cleanup(void)
{
    unlink(devname_buf);
}
#endif

/* Verify that a device fd and a pathname agree.
   Return 0 on valid, -1 on error. */
static int validate_device(const char *path, int devfd)
{
    struct stat pst, dst;

    if (stat(path, &pst) || fstat(devfd, &dst))
	return -1;

    return (pst.st_dev == dst.st_rdev) ? 0 : -1;
}

#ifndef __KLIBC__
static const char *find_device(const char *mtab_file, dev_t dev)
{
    struct mntent *mnt;
    struct stat dst;
    FILE *mtab;
    const char *devname = NULL;

    mtab = setmntent(mtab_file, "r");
    if (!mtab)
	return NULL;

    while ((mnt = getmntent(mtab))) {
	if ((!strcmp(mnt->mnt_type, "ext2") ||
	     !strcmp(mnt->mnt_type, "ext3")) &&
	    !stat(mnt->mnt_fsname, &dst) && dst.st_rdev == dev) {
	    devname = strdup(mnt->mnt_fsname);
	    break;
	}
    }
    endmntent(mtab);

    return devname;
}
#endif

int install_loader(const char *path, int update_only)
{
    struct stat st, fst;
    int devfd, rv;
    const char *devname = NULL;
    struct statfs sfs;

    if (stat(path, &st) || !S_ISDIR(st.st_mode)) {
	fprintf(stderr, "%s: Not a directory: %s\n", program, path);
	return 1;
    }

    if (statfs(path, &sfs)) {
	fprintf(stderr, "%s: statfs %s: %s\n", program, path, strerror(errno));
	return 1;
    }

    if (sfs.f_type != EXT2_SUPER_MAGIC) {
	fprintf(stderr, "%s: not an ext2/ext3 filesystem: %s\n", program, path);
	return 1;
    }

    devfd = -1;

#ifdef __KLIBC__

    /* klibc doesn't have getmntent and friends; instead, just create
       a new device with the appropriate device type */
    snprintf(devname_buf, sizeof devname_buf, "/tmp/dev-%u:%u",
	     major(st.st_dev), minor(st.st_dev));

    if (mknod(devname_buf, S_IFBLK | 0600, st.st_dev)) {
	fprintf(stderr, "%s: cannot create device %s\n", program, devname);
	return 1;
    }

    atexit(device_cleanup);	/* unlink the device node on exit */
    devname = devname_buf;

#else

    devname = find_device("/proc/mounts", st.st_dev);
    if (!devname) {
	/* Didn't find it in /proc/mounts, try /etc/mtab */
	devname = find_device("/etc/mtab", st.st_dev);
    }
    if (!devname) {
	fprintf(stderr, "%s: cannot find device for path %s\n", program, path);
	return 1;
    }

    fprintf(stderr, "%s is device %s\n", path, devname);
#endif

    if ((devfd = open(devname, O_RDWR | O_SYNC)) < 0) {
	fprintf(stderr, "%s: cannot open device %s\n", program, devname);
	return 1;
    }

    /* Verify that the device we opened is the device intended */
    if (validate_device(path, devfd)) {
	fprintf(stderr, "%s: path %s doesn't match device %s\n",
		program, path, devname);
	return 1;
    }

    if (update_only && !already_installed(devfd)) {
	fprintf(stderr, "%s: no previous extlinux boot sector found\n",
		program);
	return 1;
    }

    /* Read a pre-existing ADV, if already installed */
    if (opt.reset_adv)
	syslinux_reset_adv(syslinux_adv);
    else if (read_adv(path) < 0)
	return 1;

    if (modify_adv() < 0)
	return 1;

    /* Install extlinux.sys */
    if (install_file(path, devfd, &fst))
	return 1;

    if (fst.st_dev != st.st_dev) {
	fprintf(stderr, "%s: file system changed under us - aborting!\n",
		program);
	return 1;
    }

    sync();
    rv = install_bootblock(devfd, devname);
    close(devfd);
    sync();

    return rv;
}

/*
 * Modify the ADV of an existing installation
 */
int modify_existing_adv(const char *path)
{
    if (opt.reset_adv)
	syslinux_reset_adv(syslinux_adv);
    else if (read_adv(path) < 0)
	return 1;

    if (modify_adv() < 0)
	return 1;

    if (write_adv(path) < 0)
	return 1;

    return 0;
}

int main(int argc, char *argv[])
{
    int o;
    const char *directory;
    int update_only = -1;

    program = argv[0];

    while ((o = getopt_long(argc, argv, short_options,
			    long_options, NULL)) != EOF) {
	switch (o) {
	case 'z':
	    opt.heads = 64;
	    opt.sectors = 32;
	    break;
	case 'S':
	    opt.sectors = strtoul(optarg, NULL, 0);
	    if (opt.sectors < 1 || opt.sectors > 63) {
		fprintf(stderr,
			"%s: invalid number of sectors: %u (must be 1-63)\n",
			program, opt.sectors);
		exit(EX_USAGE);
	    }
	    break;
	case 'H':
	    opt.heads = strtoul(optarg, NULL, 0);
	    if (opt.heads < 1 || opt.heads > 256) {
		fprintf(stderr,
			"%s: invalid number of heads: %u (must be 1-256)\n",
			program, opt.heads);
		exit(EX_USAGE);
	    }
	    break;
	case 'r':
	    opt.raid_mode = 1;
	    break;
	case 'i':
	    update_only = 0;
	    break;
	case 'u':
	case 'U':
	    update_only = 1;
	    break;
	case 'h':
	    usage(0);
	    break;
	case 'o':
	    opt.set_once = optarg;
	    break;
	case 'O':
	    opt.set_once = "";
	    break;
	case OPT_RESET_ADV:
	    opt.reset_adv = 1;
	    break;
	case 'v':
	    fputs("extlinux " VERSION_STR
		  "  Copyright 1994-" YEAR_STR " H. Peter Anvin \n", stderr);
	    exit(0);
	default:
	    usage(EX_USAGE);
	}
    }

    directory = argv[optind];

    if (!directory)
	usage(EX_USAGE);

    if (update_only == -1) {
	if (opt.reset_adv || opt.set_once) {
	    return modify_existing_adv(directory);
	} else {
	    usage(EX_USAGE);
	}
    }

    return install_loader(directory, update_only);
}