/* ----------------------------------------------------------------------- *
 *
 *   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.
 *
 * ----------------------------------------------------------------------- */

/*
 * syslinux.c - Linux installer program for SYSLINUX
 *
 * This is Linux-specific by now.
 *
 * This is an alternate version of the installer which doesn't require
 * mtools, but requires root privilege.
 */

/*
 * If DO_DIRECT_MOUNT is 0, call mount(8)
 * If DO_DIRECT_MOUNT is 1, call mount(2)
 */
#ifdef __KLIBC__
# define DO_DIRECT_MOUNT 1
#else
# define DO_DIRECT_MOUNT 0	/* glibc has broken losetup ioctls */
#endif

#define _GNU_SOURCE
#define _XOPEN_SOURCE 500	/* For pread() pwrite() */
#define _FILE_OFFSET_BITS 64
#include <alloca.h>
#include <errno.h>
#include <fcntl.h>
#include <paths.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <inttypes.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/mount.h>

#include <sys/ioctl.h>
#include <linux/fs.h>		/* FIGETBSZ, FIBMAP */
#include <linux/msdos_fs.h>	/* FAT_IOCTL_SET_ATTRIBUTES, SECTOR_* */
#ifndef FAT_IOCTL_SET_ATTRIBUTES
# define FAT_IOCTL_SET_ATTRIBUTES _IOW('r', 0x11, uint32_t)
#endif

#include <paths.h>
#ifndef _PATH_MOUNT
# define _PATH_MOUNT "/bin/mount"
#endif
#ifndef _PATH_UMOUNT
# define _PATH_UMOUNT "/bin/umount"
#endif
#ifndef _PATH_TMP
# define _PATH_TMP "/tmp/"
#endif

#include "syslinux.h"

#if DO_DIRECT_MOUNT
# include <linux/loop.h>
#endif

const char *program;		/* Name of program */
const char *device;		/* Device to install to */
pid_t mypid;
char *mntpath = NULL;		/* Path on which to mount */
off_t filesystem_offset = 0;	/* Filesystem offset */
#if DO_DIRECT_MOUNT
int loop_fd = -1;		/* Loop device */
#endif

void __attribute__ ((noreturn)) usage(void)
{
    fprintf(stderr, "Usage: %s [-sfr][-d directory][-o offset] device\n",
	    program);
    exit(1);
}

void __attribute__ ((noreturn)) die(const char *msg)
{
    fprintf(stderr, "%s: %s\n", program, msg);

#if DO_DIRECT_MOUNT
    if (loop_fd != -1) {
	ioctl(loop_fd, LOOP_CLR_FD, 0);	/* Free loop device */
	close(loop_fd);
	loop_fd = -1;
    }
#endif

    if (mntpath)
	unlink(mntpath);

    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;
}

/*
 * Create a block map for ldlinux.sys
 */
int make_block_map(uint32_t * sectors, int len, int dev_fd, int fd)
{
    int nsectors = 0;
    int blocksize, nblock, block;
    int i;

    (void)dev_fd;

    if (ioctl(fd, FIGETBSZ, &blocksize) < 0)
	die("ioctl FIGETBSZ failed");

    blocksize >>= SECTOR_BITS;	/* sectors/block */

    nblock = 0;
    while (len > 0) {
	block = nblock++;
	if (ioctl(fd, FIBMAP, &block) < 0)
	    die("ioctl FIBMAP failed");

	for (i = 0; i < blocksize; i++) {
	    if (len <= 0)
		break;

	    *sectors++ = (block * blocksize) + i;
	    nsectors++;
	    len -= (1 << SECTOR_BITS);
	}
    }

    return nsectors;
}

/*
 * Mount routine
 */
int do_mount(int dev_fd, int *cookie, const char *mntpath, const char *fstype)
{
    struct stat st;

    (void)cookie;

    if (fstat(dev_fd, &st) < 0)
	return errno;

#if DO_DIRECT_MOUNT
    {
	if (!S_ISBLK(st.st_mode)) {
	    /* It's file, need to mount it loopback */
	    unsigned int n = 0;
	    struct loop_info64 loopinfo;
	    int loop_fd;

	    for (n = 0; loop_fd < 0; n++) {
		snprintf(devfdname, sizeof devfdname, "/dev/loop%u", n);
		loop_fd = open(devfdname, O_RDWR);
		if (loop_fd < 0 && errno == ENOENT) {
		    die("no available loopback device!");
		}
		if (ioctl(loop_fd, LOOP_SET_FD, (void *)dev_fd)) {
		    close(loop_fd);
		    loop_fd = -1;
		    if (errno != EBUSY)
			die("cannot set up loopback device");
		    else
			continue;
		}

		if (ioctl(loop_fd, LOOP_GET_STATUS64, &loopinfo) ||
		    (loopinfo.lo_offset = filesystem_offset,
		     ioctl(loop_fd, LOOP_SET_STATUS64, &loopinfo)))
		    die("cannot set up loopback device");
	    }

	    *cookie = loop_fd;
	} else {
	    snprintf(devfdname, sizeof devfdname, "/proc/%lu/fd/%d",
		     (unsigned long)mypid, dev_fd);
	    *cookie = -1;
	}

	return mount(devfdname, mntpath, fstype,
		     MS_NOEXEC | MS_NOSUID, "umask=077,quiet");
    }
#else
    {
	char devfdname[128], mnt_opts[128];
	pid_t f, w;
	int status;

	snprintf(devfdname, sizeof devfdname, "/proc/%lu/fd/%d",
		 (unsigned long)mypid, dev_fd);

	f = fork();
	if (f < 0) {
	    return -1;
	} else if (f == 0) {
	    if (!S_ISBLK(st.st_mode)) {
		snprintf(mnt_opts, sizeof mnt_opts,
			 "rw,nodev,noexec,loop,offset=%llu,umask=077,quiet",
			 (unsigned long long)filesystem_offset);
	    } else {
		snprintf(mnt_opts, sizeof mnt_opts,
			 "rw,nodev,noexec,umask=077,quiet");
	    }
	    execl(_PATH_MOUNT, _PATH_MOUNT, "-t", fstype, "-o", mnt_opts,
		  devfdname, mntpath, NULL);
	    _exit(255);		/* execl failed */
	}

	w = waitpid(f, &status, 0);
	return (w != f || status) ? -1 : 0;
    }
#endif
}

/*
 * umount routine
 */
void do_umount(const char *mntpath, int cookie)
{
#if DO_DIRECT_MOUNT
    int loop_fd = cookie;

    if (umount2(mntpath, 0))
	die("could not umount path");

    if (loop_fd != -1) {
	ioctl(loop_fd, LOOP_CLR_FD, 0);	/* Free loop device */
	close(loop_fd);
	loop_fd = -1;
    }
#else
    pid_t f = fork();
    pid_t w;
    int status;
    (void)cookie;

    if (f < 0) {
	perror("fork");
	exit(1);
    } else if (f == 0) {
	execl(_PATH_UMOUNT, _PATH_UMOUNT, mntpath, NULL);
    }

    w = waitpid(f, &status, 0);
    if (w != f || status) {
	exit(1);
    }
#endif
}

int main(int argc, char *argv[])
{
    static unsigned char sectbuf[SECTOR_SIZE];
    unsigned char *dp;
    const unsigned char *cdp;
    int dev_fd, fd;
    struct stat st;
    int nb, left;
    int err = 0;
    char mntname[128];
    char *ldlinux_name, **argp, *opt;
    const char *subdir = NULL;
    uint32_t sectors[65];	/* 65 is maximum possible */
    int nsectors = 0;
    const char *errmsg;
    int mnt_cookie;

    int force = 0;		/* -f (force) option */
    int stupid = 0;		/* -s (stupid) option */
    int raid_mode = 0;		/* -r (RAID) option */

    (void)argc;			/* Unused */

    program = argv[0];
    mypid = getpid();

    device = NULL;

    umask(077);

    for (argp = argv + 1; *argp; argp++) {
	if (**argp == '-') {
	    opt = *argp + 1;
	    if (!*opt)
		usage();

	    while (*opt) {
		if (*opt == 's') {
		    stupid = 1;
		} else if (*opt == 'r') {
		    raid_mode = 1;
		} else if (*opt == 'f') {
		    force = 1;	/* Force install */
		} else if (*opt == 'd' && argp[1]) {
		    subdir = *++argp;
		} else if (*opt == 'o' && argp[1]) {
		    /* Byte offset */
		    filesystem_offset = (off_t) strtoull(*++argp, NULL, 0);
		} else {
		    usage();
		}
		opt++;
	    }
	} else {
	    if (device)
		usage();
	    device = *argp;
	}
    }

    if (!device)
	usage();

    /*
     * First make sure we can open the device at all, and that we have
     * read/write permission.
     */
    dev_fd = open(device, O_RDWR);
    if (dev_fd < 0 || fstat(dev_fd, &st) < 0) {
	perror(device);
	exit(1);
    }

    if (!S_ISBLK(st.st_mode) && !S_ISREG(st.st_mode) && !S_ISCHR(st.st_mode)) {
	die("not a device or regular file");
    }

    if (filesystem_offset && S_ISBLK(st.st_mode)) {
	die("can't combine an offset with a block device");
    }

    xpread(dev_fd, sectbuf, SECTOR_SIZE, filesystem_offset);
    fsync(dev_fd);

    /*
     * Check to see that what we got was indeed an MS-DOS boot sector/superblock
     */
    if ((errmsg = syslinux_check_bootsect(sectbuf))) {
	fprintf(stderr, "%s: %s\n", device, errmsg);
	exit(1);
    }

    /*
     * Now mount the device.
     */
    if (geteuid()) {
	die("This program needs root privilege");
    } else {
	int i = 0;
	struct stat dst;
	int rv;

	/* We're root or at least setuid.
	   Make a temp dir and pass all the gunky options to mount. */

	if (chdir(_PATH_TMP)) {
	    perror(program);
	    exit(1);
	}
#define TMP_MODE (S_IXUSR|S_IWUSR|S_IXGRP|S_IWGRP|S_IWOTH|S_IXOTH|S_ISVTX)

	if (stat(".", &dst) || !S_ISDIR(dst.st_mode) ||
	    (dst.st_mode & TMP_MODE) != TMP_MODE) {
	    die("possibly unsafe " _PATH_TMP " permissions");
	}

	for (i = 0;; i++) {
	    snprintf(mntname, sizeof mntname, "syslinux.mnt.%lu.%d",
		     (unsigned long)mypid, i);

	    if (lstat(mntname, &dst) != -1 || errno != ENOENT)
		continue;

	    rv = mkdir(mntname, 0000);

	    if (rv == -1) {
		if (errno == EEXIST || errno == EINTR)
		    continue;
		perror(program);
		exit(1);
	    }

	    if (lstat(mntname, &dst) || dst.st_mode != (S_IFDIR | 0000) ||
		dst.st_uid != 0) {
		die("someone is trying to symlink race us!");
	    }
	    break;		/* OK, got something... */
	}

	mntpath = mntname;
    }

    if (do_mount(dev_fd, &mnt_cookie, mntpath, "vfat") &&
	do_mount(dev_fd, &mnt_cookie, mntpath, "msdos")) {
	rmdir(mntpath);
	die("mount failed");
    }

    ldlinux_name = alloca(strlen(mntpath) + 14 +
			  (subdir ? strlen(subdir) + 2 : 0));
    if (!ldlinux_name) {
	perror(program);
	err = 1;
	goto umount;
    }
    sprintf(ldlinux_name, "%s%s%s//ldlinux.sys",
	    mntpath, subdir ? "//" : "", subdir ? subdir : "");

    if ((fd = open(ldlinux_name, O_RDONLY)) >= 0) {
	uint32_t zero_attr = 0;
	ioctl(fd, FAT_IOCTL_SET_ATTRIBUTES, &zero_attr);
	close(fd);
    }

    unlink(ldlinux_name);
    fd = open(ldlinux_name, O_WRONLY | O_CREAT | O_TRUNC, 0444);
    if (fd < 0) {
	perror(device);
	err = 1;
	goto umount;
    }

    cdp = syslinux_ldlinux;
    left = syslinux_ldlinux_len;
    while (left) {
	nb = write(fd, cdp, left);
	if (nb == -1 && errno == EINTR)
	    continue;
	else if (nb <= 0) {
	    perror(device);
	    err = 1;
	    goto umount;
	}

	dp += nb;
	left -= nb;
    }

    fsync(fd);
    /*
     * Set the attributes
     */
    {
	uint32_t attr = 0x07;	/* Hidden+System+Readonly */
	ioctl(fd, FAT_IOCTL_SET_ATTRIBUTES, &attr);
    }

    /*
     * Create a block map.
     */
    nsectors = make_block_map(sectors, syslinux_ldlinux_len, dev_fd, fd);

    close(fd);
    sync();

umount:
    do_umount(mntpath, mnt_cookie);
    sync();
    rmdir(mntpath);

    if (err)
	exit(err);

    /*
     * Patch ldlinux.sys and the boot sector
     */
    syslinux_patch(sectors, nsectors, stupid, raid_mode);

    /*
     * Write the now-patched first sector of ldlinux.sys
     */
    xpwrite(dev_fd, syslinux_ldlinux, SECTOR_SIZE,
	    filesystem_offset + ((off_t) sectors[0] << SECTOR_BITS));

    /*
     * To finish up, write the boot sector
     */

    /* Read the superblock again since it might have changed while mounted */
    xpread(dev_fd, sectbuf, SECTOR_SIZE, filesystem_offset);

    /* Copy the syslinux code into the boot sector */
    syslinux_make_bootsect(sectbuf);

    /* Write new boot sector */
    xpwrite(dev_fd, sectbuf, SECTOR_SIZE, filesystem_offset);

    close(dev_fd);
    sync();

    /* Done! */

    return 0;
}
