linux/syslinux.c

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 1998-2008 H. Peter Anvin - All Rights Reserved
   4  *   Copyright 2009-2010 Intel Corporation; author: H. Peter Anvin
   5  *
   6  *   This program is free software; you can redistribute it and/or modify
   7  *   it under the terms of the GNU General Public License as published by
   8  *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
   9  *   Boston MA 02111-1307, USA; either version 2 of the License, or
  10  *   (at your option) any later version; incorporated herein by reference.
  11  *
  12  * ----------------------------------------------------------------------- */
  13
  14 /*
  15  * syslinux.c - Linux installer program for SYSLINUX
  16  *
  17  * This is Linux-specific by now.
  18  *
  19  * This is an alternate version of the installer which doesn't require
  20  * mtools, but requires root privilege.
  21  */
  22
  23 /*
  24  * If DO_DIRECT_MOUNT is 0, call mount(8)
  25  * If DO_DIRECT_MOUNT is 1, call mount(2)
  26  */
  27 #ifdef __KLIBC__
  28 # define DO_DIRECT_MOUNT 1
  29 #else
  30 # define DO_DIRECT_MOUNT 0      /* glibc has broken losetup ioctls */
  31 #endif
  32
  33 #define _GNU_SOURCE
  34 #define _XOPEN_SOURCE 500       /* For pread() pwrite() */
  35 #define _FILE_OFFSET_BITS 64
  36 #include <alloca.h>
  37 #include <errno.h>
  38 #include <fcntl.h>
  39 #include <paths.h>
  40 #include <stdio.h>
  41 #include <string.h>
  42 #include <stdlib.h>
  43 #include <unistd.h>
  44 #include <inttypes.h>
  45 #include <sys/stat.h>
  46 #include <sys/types.h>
  47 #include <sys/wait.h>
  48 #include <sys/mount.h>
  49
  50 #include "linuxioctl.h"
  51
  52 #include <paths.h>
  53 #ifndef _PATH_MOUNT
  54 # define _PATH_MOUNT "/bin/mount"
  55 #endif
  56 #ifndef _PATH_UMOUNT
  57 # define _PATH_UMOUNT "/bin/umount"
  58 #endif
  59 #ifndef _PATH_TMP
  60 # define _PATH_TMP "/tmp/"
  61 #endif
  62
  63 #include "syslinux.h"
  64
  65 #if DO_DIRECT_MOUNT
  66 # include <linux/loop.h>
  67 #endif
  68
  69 #include <getopt.h>
  70 #include <sysexits.h>
  71 #include "syslxcom.h"
  72 #include "syslxfs.h"
  73 #include "setadv.h"
  74 #include "syslxopt.h" /* unified options */
  75
  76 extern const char *program;     /* Name of program */
  77
  78 pid_t mypid;
  79 char *mntpath = NULL;           /* Path on which to mount */
  80
  81 #if DO_DIRECT_MOUNT
  82 int loop_fd = -1;               /* Loop device */
  83 #endif
  84
  85 void __attribute__ ((noreturn)) die(const char *msg)
  86 {
  87     fprintf(stderr, "%s: %s\n", program, msg);
  88
  89 #if DO_DIRECT_MOUNT
  90     if (loop_fd != -1) {
  91         ioctl(loop_fd, LOOP_CLR_FD, 0); /* Free loop device */
  92         close(loop_fd);
  93         loop_fd = -1;
  94     }
  95 #endif
  96
  97     if (mntpath)
  98         unlink(mntpath);
  99
 100     exit(1);
 101 }
 102
 103 /*
 104  * Mount routine
 105  */
 106 int do_mount(int dev_fd, int *cookie, const char *mntpath, const char *fstype)
 107 {
 108     struct stat st;
 109
 110     (void)cookie;
 111
 112     if (fstat(dev_fd, &st) < 0)
 113         return errno;
 114
 115 #if DO_DIRECT_MOUNT
 116     {
 117         if (!S_ISBLK(st.st_mode)) {
 118             /* It's file, need to mount it loopback */
 119             unsigned int n = 0;
 120             struct loop_info64 loopinfo;
 121             int loop_fd;
 122
 123             for (n = 0; loop_fd < 0; n++) {
 124                 snprintf(devfdname, sizeof devfdname, "/dev/loop%u", n);
 125                 loop_fd = open(devfdname, O_RDWR);
 126                 if (loop_fd < 0 && errno == ENOENT) {
 127                     die("no available loopback device!");
 128                 }
 129                 if (ioctl(loop_fd, LOOP_SET_FD, (void *)dev_fd)) {
 130                     close(loop_fd);
 131                     loop_fd = -1;
 132                     if (errno != EBUSY)
 133                         die("cannot set up loopback device");
 134                     else
 135                         continue;
 136                 }
 137
 138                 if (ioctl(loop_fd, LOOP_GET_STATUS64, &loopinfo) ||
 139                     (loopinfo.lo_offset = opt.offset,
 140                      ioctl(loop_fd, LOOP_SET_STATUS64, &loopinfo)))
 141                     die("cannot set up loopback device");
 142             }
 143
 144             *cookie = loop_fd;
 145         } else {
 146             snprintf(devfdname, sizeof devfdname, "/proc/%lu/fd/%d",
 147                      (unsigned long)mypid, dev_fd);
 148             *cookie = -1;
 149         }
 150
 151         return mount(devfdname, mntpath, fstype,
 152                      MS_NOEXEC | MS_NOSUID, "umask=077,quiet");
 153     }
 154 #else
 155     {
 156         char devfdname[128], mnt_opts[128];
 157         pid_t f, w;
 158         int status;
 159
 160         snprintf(devfdname, sizeof devfdname, "/proc/%lu/fd/%d",
 161                  (unsigned long)mypid, dev_fd);
 162
 163         f = fork();
 164         if (f < 0) {
 165             return -1;
 166         } else if (f == 0) {
 167             if (!S_ISBLK(st.st_mode)) {
 168                 snprintf(mnt_opts, sizeof mnt_opts,
 169                          "rw,nodev,noexec,loop,offset=%llu,umask=077,quiet",
 170                          (unsigned long long)opt.offset);
 171             } else {
 172                 snprintf(mnt_opts, sizeof mnt_opts,
 173                          "rw,nodev,noexec,umask=077,quiet");
 174             }
 175             execl(_PATH_MOUNT, _PATH_MOUNT, "-t", fstype, "-o", mnt_opts,
 176                   devfdname, mntpath, NULL);
 177             _exit(255);         /* execl failed */
 178         }
 179
 180         w = waitpid(f, &status, 0);
 181         return (w != f || status) ? -1 : 0;
 182     }
 183 #endif
 184 }
 185
 186 /*
 187  * umount routine
 188  */
 189 void do_umount(const char *mntpath, int cookie)
 190 {
 191 #if DO_DIRECT_MOUNT
 192     int loop_fd = cookie;
 193
 194     if (umount2(mntpath, 0))
 195         die("could not umount path");
 196
 197     if (loop_fd != -1) {
 198         ioctl(loop_fd, LOOP_CLR_FD, 0); /* Free loop device */
 199         close(loop_fd);
 200         loop_fd = -1;
 201     }
 202 #else
 203     pid_t f = fork();
 204     pid_t w;
 205     int status;
 206     (void)cookie;
 207
 208     if (f < 0) {
 209         perror("fork");
 210         exit(1);
 211     } else if (f == 0) {
 212         execl(_PATH_UMOUNT, _PATH_UMOUNT, mntpath, NULL);
 213     }
 214
 215     w = waitpid(f, &status, 0);
 216     if (w != f || status) {
 217         exit(1);
 218     }
 219 #endif
 220 }
 221
 222 /*
 223  * Modify the ADV of an existing installation
 224  */
 225 int modify_existing_adv(const char *path)
 226 {
 227     if (opt.reset_adv)
 228         syslinux_reset_adv(syslinux_adv);
 229     else if (read_adv(path, "ldlinux.sys") < 0)
 230         return 1;
 231
 232     if (modify_adv() < 0)
 233         return 1;
 234
 235     if (write_adv(path, "ldlinux.sys") < 0)
 236         return 1;
 237
 238     return 0;
 239 }
 240
 241 int main(int argc, char *argv[])
 242 {
 243     static unsigned char sectbuf[SECTOR_SIZE];
 244     int dev_fd, fd;
 245     struct stat st;
 246     int err = 0;
 247     char mntname[128];
 248     char *ldlinux_name;
 249     char *ldlinux_path;
 250     char *subdir;
 251     sector_t *sectors = NULL;
 252     int ldlinux_sectors = (boot_image_len + SECTOR_SIZE - 1) >> SECTOR_SHIFT;
 253     const char *errmsg;
 254     int mnt_cookie;
 255     int patch_sectors;
 256     int i;
 257
 258     mypid = getpid();
 259     umask(077);
 260     parse_options(argc, argv, MODE_SYSLINUX);
 261
 262     /* Note: subdir is guaranteed to start and end in / */
 263     if (opt.directory && opt.directory[0]) {
 264         int len = strlen(opt.directory);
 265         int rv = asprintf(&subdir, "%s%s%s",
 266                           opt.directory[0] == '/' ? "" : "/",
 267                           opt.directory,
 268                           opt.directory[len-1] == '/' ? "" : "/");
 269         if (rv < 0 || !subdir) {
 270             perror(program);
 271             exit(1);
 272         }
 273     } else {
 274         subdir = "/";
 275     }
 276
 277     if (!opt.device || opt.install_mbr || opt.activate_partition)
 278         usage(EX_USAGE, MODE_SYSLINUX);
 279
 280     /*
 281      * First make sure we can open the device at all, and that we have
 282      * read/write permission.
 283      */
 284     dev_fd = open(opt.device, O_RDWR);
 285     if (dev_fd < 0 || fstat(dev_fd, &st) < 0) {
 286         perror(opt.device);
 287         exit(1);
 288     }
 289
 290     if (!S_ISBLK(st.st_mode) && !S_ISREG(st.st_mode) && !S_ISCHR(st.st_mode)) {
 291         die("not a device or regular file");
 292     }
 293
 294     if (opt.offset && S_ISBLK(st.st_mode)) {
 295         die("can't combine an offset with a block device");
 296     }
 297
 298     xpread(dev_fd, sectbuf, SECTOR_SIZE, opt.offset);
 299     fsync(dev_fd);
 300
 301     /*
 302      * Check to see that what we got was indeed an FAT/NTFS
 303      * boot sector/superblock
 304      */
 305     if ((errmsg = syslinux_check_bootsect(sectbuf, &fs_type))) {
 306         fprintf(stderr, "%s: %s\n", opt.device, errmsg);
 307         exit(1);
 308     }
 309
 310     /*
 311      * Now mount the device.
 312      */
 313     if (geteuid()) {
 314         die("This program needs root privilege");
 315     } else {
 316         int i = 0;
 317         struct stat dst;
 318         int rv;
 319
 320         /* We're root or at least setuid.
 321            Make a temp dir and pass all the gunky options to mount. */
 322
 323         if (chdir(_PATH_TMP)) {
 324             fprintf(stderr, "%s: Cannot access the %s directory.\n",
 325                     program, _PATH_TMP);
 326             exit(1);
 327         }
 328 #define TMP_MODE (S_IXUSR|S_IWUSR|S_IXGRP|S_IWGRP|S_IWOTH|S_IXOTH|S_ISVTX)
 329
 330         if (stat(".", &dst) || !S_ISDIR(dst.st_mode) ||
 331             (dst.st_mode & TMP_MODE) != TMP_MODE) {
 332             die("possibly unsafe " _PATH_TMP " permissions");
 333         }
 334
 335         for (i = 0;; i++) {
 336             snprintf(mntname, sizeof mntname, "syslinux.mnt.%lu.%d",
 337                      (unsigned long)mypid, i);
 338
 339             if (lstat(mntname, &dst) != -1 || errno != ENOENT)
 340                 continue;
 341
 342             rv = mkdir(mntname, 0000);
 343
 344             if (rv == -1) {
 345                 if (errno == EEXIST || errno == EINTR)
 346                     continue;
 347                 perror(program);
 348                 exit(1);
 349             }
 350
 351             if (lstat(mntname, &dst) || dst.st_mode != (S_IFDIR | 0000) ||
 352                 dst.st_uid != 0) {
 353                 die("someone is trying to symlink race us!");
 354             }
 355             break;              /* OK, got something... */
 356         }
 357
 358         mntpath = mntname;
 359     }
 360
 361     if (fs_type == VFAT) {
 362         if (do_mount(dev_fd, &mnt_cookie, mntpath, "vfat") &&
 363             do_mount(dev_fd, &mnt_cookie, mntpath, "msdos")) {
 364             rmdir(mntpath);
 365             die("failed on mounting fat volume");
 366         }
 367     } else if (fs_type == NTFS) {
 368         if (do_mount(dev_fd, &mnt_cookie, mntpath, "ntfs-3g")) {
 369             rmdir(mntpath);
 370             die("failed on mounting ntfs volume");
 371         }
 372     }
 373
 374     ldlinux_path = alloca(strlen(mntpath) + strlen(subdir) + 1);
 375     sprintf(ldlinux_path, "%s%s", mntpath, subdir);
 376
 377     ldlinux_name = alloca(strlen(ldlinux_path) + 14);
 378     if (!ldlinux_name) {
 379         perror(program);
 380         err = 1;
 381         goto umount;
 382     }
 383     sprintf(ldlinux_name, "%sldlinux.sys", ldlinux_path);
 384
 385     /* update ADV only ? */
 386     if (opt.update_only == -1) {
 387         if (opt.reset_adv || opt.set_once) {
 388             modify_existing_adv(ldlinux_path);
 389             do_umount(mntpath, mnt_cookie);
 390             sync();
 391             rmdir(mntpath);
 392             exit(0);
 393     } else if (opt.update_only && !syslinux_already_installed(dev_fd)) {
 394         fprintf(stderr, "%s: no previous syslinux boot sector found\n",
 395                 argv[0]);
 396         exit(1);
 397         } else {
 398             fprintf(stderr, "%s: please specify --install or --update for the future\n", argv[0]);
 399             opt.update_only = 0;
 400         }
 401     }
 402
 403     /* Read a pre-existing ADV, if already installed */
 404     if (opt.reset_adv)
 405         syslinux_reset_adv(syslinux_adv);
 406     else if (read_adv(ldlinux_path, "ldlinux.sys") < 0)
 407         syslinux_reset_adv(syslinux_adv);
 408     if (modify_adv() < 0)
 409         exit(1);
 410
 411     if ((fd = open(ldlinux_name, O_RDONLY)) >= 0) {
 412         uint32_t zero_attr = 0;
 413         ioctl(fd, FAT_IOCTL_SET_ATTRIBUTES, &zero_attr);
 414         close(fd);
 415     }
 416
 417     unlink(ldlinux_name);
 418     fd = open(ldlinux_name, O_WRONLY | O_CREAT | O_TRUNC, 0444);
 419     if (fd < 0) {
 420         perror(opt.device);
 421         err = 1;
 422         goto umount;
 423     }
 424
 425     /* Write it the first time */
 426     if (xpwrite(fd, boot_image, boot_image_len, 0) != (int)boot_image_len ||
 427         xpwrite(fd, syslinux_adv, 2 * ADV_SIZE,
 428                 boot_image_len) != 2 * ADV_SIZE) {
 429         fprintf(stderr, "%s: write failure on %s\n", program, ldlinux_name);
 430         exit(1);
 431     }
 432
 433     fsync(fd);
 434     /*
 435      * Set the attributes
 436      */
 437     {
 438         uint32_t attr = 0x07;   /* Hidden+System+Readonly */
 439         ioctl(fd, FAT_IOCTL_SET_ATTRIBUTES, &attr);
 440     }
 441
 442     /*
 443      * Create a block map.
 444      */
 445     ldlinux_sectors += 2; /* 2 ADV sectors */
 446     sectors = calloc(ldlinux_sectors, sizeof *sectors);
 447     if (sectmap(fd, sectors, ldlinux_sectors)) {
 448         perror("bmap");
 449         exit(1);
 450     }
 451     close(fd);
 452     sync();
 453
 454 umount:
 455     do_umount(mntpath, mnt_cookie);
 456     sync();
 457     rmdir(mntpath);
 458
 459     if (err)
 460         exit(err);
 461
 462     /*
 463      * Patch ldlinux.sys and the boot sector
 464      */
 465     i = syslinux_patch(sectors, ldlinux_sectors, opt.stupid_mode,
 466                        opt.raid_mode, subdir, NULL);
 467     patch_sectors = (i + SECTOR_SIZE - 1) >> SECTOR_SHIFT;
 468
 469     /*
 470      * Write the now-patched first sectors of ldlinux.sys
 471      */
 472     for (i = 0; i < patch_sectors; i++) {
 473         xpwrite(dev_fd, boot_image + i * SECTOR_SIZE, SECTOR_SIZE,
 474                 opt.offset + ((off_t) sectors[i] << SECTOR_SHIFT));
 475     }
 476
 477     /*
 478      * To finish up, write the boot sector
 479      */
 480
 481     /* Read the superblock again since it might have changed while mounted */
 482     xpread(dev_fd, sectbuf, SECTOR_SIZE, opt.offset);
 483
 484     /* Copy the syslinux code into the boot sector */
 485     syslinux_make_bootsect(sectbuf, fs_type);
 486
 487     /* Write new boot sector */
 488     xpwrite(dev_fd, sectbuf, SECTOR_SIZE, opt.offset);
 489
 490     close(dev_fd);
 491     sync();
 492
 493     /* Done! */
 494
 495     return 0;
 496 }