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 "setadv.h"
  73 #include "syslxopt.h" /* unified options */
  74
  75 extern const char *program;     /* Name of program */
  76
  77 pid_t mypid;
  78 char *mntpath = NULL;           /* Path on which to mount */
  79
  80 #if DO_DIRECT_MOUNT
  81 int loop_fd = -1;               /* Loop device */
  82 #endif
  83
  84 void __attribute__ ((noreturn)) die(const char *msg)
  85 {
  86     fprintf(stderr, "%s: %s\n", program, msg);
  87
  88 #if DO_DIRECT_MOUNT
  89     if (loop_fd != -1) {
  90         ioctl(loop_fd, LOOP_CLR_FD, 0); /* Free loop device */
  91         close(loop_fd);
  92         loop_fd = -1;
  93     }
  94 #endif
  95
  96     if (mntpath)
  97         unlink(mntpath);
  98
  99     exit(1);
 100 }
 101
 102 /*
 103  * Mount routine
 104  */
 105 int do_mount(int dev_fd, int *cookie, const char *mntpath, const char *fstype)
 106 {
 107     struct stat st;
 108
 109     (void)cookie;
 110
 111     if (fstat(dev_fd, &st) < 0)
 112         return errno;
 113
 114 #if DO_DIRECT_MOUNT
 115     {
 116         if (!S_ISBLK(st.st_mode)) {
 117             /* It's file, need to mount it loopback */
 118             unsigned int n = 0;
 119             struct loop_info64 loopinfo;
 120             int loop_fd;
 121
 122             for (n = 0; loop_fd < 0; n++) {
 123                 snprintf(devfdname, sizeof devfdname, "/dev/loop%u", n);
 124                 loop_fd = open(devfdname, O_RDWR);
 125                 if (loop_fd < 0 && errno == ENOENT) {
 126                     die("no available loopback device!");
 127                 }
 128                 if (ioctl(loop_fd, LOOP_SET_FD, (void *)dev_fd)) {
 129                     close(loop_fd);
 130                     loop_fd = -1;
 131                     if (errno != EBUSY)
 132                         die("cannot set up loopback device");
 133                     else
 134                         continue;
 135                 }
 136
 137                 if (ioctl(loop_fd, LOOP_GET_STATUS64, &loopinfo) ||
 138                     (loopinfo.lo_offset = opt.offset,
 139                      ioctl(loop_fd, LOOP_SET_STATUS64, &loopinfo)))
 140                     die("cannot set up loopback device");
 141             }
 142
 143             *cookie = loop_fd;
 144         } else {
 145             snprintf(devfdname, sizeof devfdname, "/proc/%lu/fd/%d",
 146                      (unsigned long)mypid, dev_fd);
 147             *cookie = -1;
 148         }
 149
 150         return mount(devfdname, mntpath, fstype,
 151                      MS_NOEXEC | MS_NOSUID, "umask=077,quiet");
 152     }
 153 #else
 154     {
 155         char devfdname[128], mnt_opts[128];
 156         pid_t f, w;
 157         int status;
 158
 159         snprintf(devfdname, sizeof devfdname, "/proc/%lu/fd/%d",
 160                  (unsigned long)mypid, dev_fd);
 161
 162         f = fork();
 163         if (f < 0) {
 164             return -1;
 165         } else if (f == 0) {
 166             if (!S_ISBLK(st.st_mode)) {
 167                 snprintf(mnt_opts, sizeof mnt_opts,
 168                          "rw,nodev,noexec,loop,offset=%llu,umask=077,quiet",
 169                          (unsigned long long)opt.offset);
 170             } else {
 171                 snprintf(mnt_opts, sizeof mnt_opts,
 172                          "rw,nodev,noexec,umask=077,quiet");
 173             }
 174             execl(_PATH_MOUNT, _PATH_MOUNT, "-t", fstype, "-o", mnt_opts,
 175                   devfdname, mntpath, NULL);
 176             _exit(255);         /* execl failed */
 177         }
 178
 179         w = waitpid(f, &status, 0);
 180         return (w != f || status) ? -1 : 0;
 181     }
 182 #endif
 183 }
 184
 185 /*
 186  * umount routine
 187  */
 188 void do_umount(const char *mntpath, int cookie)
 189 {
 190 #if DO_DIRECT_MOUNT
 191     int loop_fd = cookie;
 192
 193     if (umount2(mntpath, 0))
 194         die("could not umount path");
 195
 196     if (loop_fd != -1) {
 197         ioctl(loop_fd, LOOP_CLR_FD, 0); /* Free loop device */
 198         close(loop_fd);
 199         loop_fd = -1;
 200     }
 201 #else
 202     pid_t f = fork();
 203     pid_t w;
 204     int status;
 205     (void)cookie;
 206
 207     if (f < 0) {
 208         perror("fork");
 209         exit(1);
 210     } else if (f == 0) {
 211         execl(_PATH_UMOUNT, _PATH_UMOUNT, mntpath, NULL);
 212     }
 213
 214     w = waitpid(f, &status, 0);
 215     if (w != f || status) {
 216         exit(1);
 217     }
 218 #endif
 219 }
 220
 221 /*
 222  * Modify the ADV of an existing installation
 223  */
 224 int modify_existing_adv(const char *path)
 225 {
 226     if (opt.reset_adv)
 227         syslinux_reset_adv(syslinux_adv);
 228     else if (read_adv(path, "ldlinux.sys") < 0)
 229         return 1;
 230
 231     if (modify_adv() < 0)
 232         return 1;
 233
 234     if (write_adv(path, "ldlinux.sys") < 0)
 235         return 1;
 236
 237     return 0;
 238 }
 239
 240 int main(int argc, char *argv[])
 241 {
 242     static unsigned char sectbuf[SECTOR_SIZE];
 243     int dev_fd, fd;
 244     struct stat st;
 245     int err = 0;
 246     char mntname[128];
 247     char *ldlinux_name;
 248     char *ldlinux_path;
 249     char *subdir;
 250     sector_t *sectors = NULL;
 251     int ldlinux_sectors = (boot_image_len + SECTOR_SIZE - 1) >> SECTOR_SHIFT;
 252     const char *errmsg;
 253     int mnt_cookie;
 254     int patch_sectors;
 255     int i;
 256
 257     mypid = getpid();
 258     umask(077);
 259     parse_options(argc, argv, MODE_SYSLINUX);
 260
 261     /* Note: subdir is guaranteed to start and end in / */
 262     if (opt.directory && opt.directory[0]) {
 263         int len = strlen(opt.directory);
 264         int rv = asprintf(&subdir, "%s%s%s",
 265                           opt.directory[0] == '/' ? "" : "/",
 266                           opt.directory,
 267                           opt.directory[len-1] == '/' ? "" : "/");
 268         if (rv < 0 || !subdir) {
 269             perror(program);
 270             exit(1);
 271         }
 272     } else {
 273         subdir = "/";
 274     }
 275
 276     if (!opt.device || opt.install_mbr || opt.activate_partition || opt.force)
 277         usage(EX_USAGE, MODE_SYSLINUX);
 278
 279     /*
 280      * First make sure we can open the device at all, and that we have
 281      * read/write permission.
 282      */
 283     dev_fd = open(opt.device, O_RDWR);
 284     if (dev_fd < 0 || fstat(dev_fd, &st) < 0) {
 285         perror(opt.device);
 286         exit(1);
 287     }
 288
 289     if (!S_ISBLK(st.st_mode) && !S_ISREG(st.st_mode) && !S_ISCHR(st.st_mode)) {
 290         die("not a device or regular file");
 291     }
 292
 293     if (opt.offset && S_ISBLK(st.st_mode)) {
 294         die("can't combine an offset with a block device");
 295     }
 296
 297     fs_type = VFAT;
 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 MS-DOS boot sector/superblock
 303      */
 304     if ((errmsg = syslinux_check_bootsect(sectbuf))) {
 305         fprintf(stderr, "%s: %s\n", opt.device, errmsg);
 306         exit(1);
 307     }
 308
 309     /*
 310      * Now mount the device.
 311      */
 312     if (geteuid()) {
 313         die("This program needs root privilege");
 314     } else {
 315         int i = 0;
 316         struct stat dst;
 317         int rv;
 318
 319         /* We're root or at least setuid.
 320            Make a temp dir and pass all the gunky options to mount. */
 321
 322         if (chdir(_PATH_TMP)) {
 323             fprintf(stderr, "%s: Cannot access the %s directory.\n",
 324                     program, _PATH_TMP);
 325             exit(1);
 326         }
 327 #define TMP_MODE (S_IXUSR|S_IWUSR|S_IXGRP|S_IWGRP|S_IWOTH|S_IXOTH|S_ISVTX)
 328
 329         if (stat(".", &dst) || !S_ISDIR(dst.st_mode) ||
 330             (dst.st_mode & TMP_MODE) != TMP_MODE) {
 331             die("possibly unsafe " _PATH_TMP " permissions");
 332         }
 333
 334         for (i = 0;; i++) {
 335             snprintf(mntname, sizeof mntname, "syslinux.mnt.%lu.%d",
 336                      (unsigned long)mypid, i);
 337
 338             if (lstat(mntname, &dst) != -1 || errno != ENOENT)
 339                 continue;
 340
 341             rv = mkdir(mntname, 0000);
 342
 343             if (rv == -1) {
 344                 if (errno == EEXIST || errno == EINTR)
 345                     continue;
 346                 perror(program);
 347                 exit(1);
 348             }
 349
 350             if (lstat(mntname, &dst) || dst.st_mode != (S_IFDIR | 0000) ||
 351                 dst.st_uid != 0) {
 352                 die("someone is trying to symlink race us!");
 353             }
 354             break;              /* OK, got something... */
 355         }
 356
 357         mntpath = mntname;
 358     }
 359
 360     if (do_mount(dev_fd, &mnt_cookie, mntpath, "vfat") &&
 361         do_mount(dev_fd, &mnt_cookie, mntpath, "msdos")) {
 362         rmdir(mntpath);
 363         die("mount failed");
 364     }
 365
 366     ldlinux_path = alloca(strlen(mntpath) + strlen(subdir) + 1);
 367     sprintf(ldlinux_path, "%s%s", mntpath, subdir);
 368
 369     ldlinux_name = alloca(strlen(ldlinux_path) + 14);
 370     if (!ldlinux_name) {
 371         perror(program);
 372         err = 1;
 373         goto umount;
 374     }
 375     sprintf(ldlinux_name, "%sldlinux.sys", ldlinux_path);
 376
 377     /* update ADV only ? */
 378     if (opt.update_only == -1) {
 379         if (opt.reset_adv || opt.set_once) {
 380             modify_existing_adv(ldlinux_path);
 381             do_umount(mntpath, mnt_cookie);
 382             sync();
 383             rmdir(mntpath);
 384             exit(0);
 385         } else {
 386             fprintf(stderr, "%s: please specify --install or --update for the future\n", argv[0]);
 387             opt.update_only = 0;
 388         }
 389     }
 390
 391     /* Read a pre-existing ADV, if already installed */
 392     if (opt.reset_adv)
 393         syslinux_reset_adv(syslinux_adv);
 394     else if (read_adv(ldlinux_path, "ldlinux.sys") < 0)
 395         syslinux_reset_adv(syslinux_adv);
 396     if (modify_adv() < 0)
 397         exit(1);
 398
 399     if ((fd = open(ldlinux_name, O_RDONLY)) >= 0) {
 400         uint32_t zero_attr = 0;
 401         ioctl(fd, FAT_IOCTL_SET_ATTRIBUTES, &zero_attr);
 402         close(fd);
 403     }
 404
 405     unlink(ldlinux_name);
 406     fd = open(ldlinux_name, O_WRONLY | O_CREAT | O_TRUNC, 0444);
 407     if (fd < 0) {
 408         perror(opt.device);
 409         err = 1;
 410         goto umount;
 411     }
 412
 413     /* Write it the first time */
 414     if (xpwrite(fd, boot_image, boot_image_len, 0) != (int)boot_image_len ||
 415         xpwrite(fd, syslinux_adv, 2 * ADV_SIZE,
 416                 boot_image_len) != 2 * ADV_SIZE) {
 417         fprintf(stderr, "%s: write failure on %s\n", program, ldlinux_name);
 418         exit(1);
 419     }
 420
 421     fsync(fd);
 422     /*
 423      * Set the attributes
 424      */
 425     {
 426         uint32_t attr = 0x07;   /* Hidden+System+Readonly */
 427         ioctl(fd, FAT_IOCTL_SET_ATTRIBUTES, &attr);
 428     }
 429
 430     /*
 431      * Create a block map.
 432      */
 433     ldlinux_sectors += 2; /* 2 ADV sectors */
 434     sectors = calloc(ldlinux_sectors, sizeof *sectors);
 435     if (sectmap(fd, sectors, ldlinux_sectors)) {
 436         perror("bmap");
 437         exit(1);
 438     }
 439     close(fd);
 440     sync();
 441
 442 umount:
 443     do_umount(mntpath, mnt_cookie);
 444     sync();
 445     rmdir(mntpath);
 446
 447     if (err)
 448         exit(err);
 449
 450     /*
 451      * Patch ldlinux.sys and the boot sector
 452      */
 453     i = syslinux_patch(sectors, ldlinux_sectors, opt.stupid_mode,
 454                        opt.raid_mode, subdir, NULL);
 455     patch_sectors = (i + SECTOR_SIZE - 1) >> SECTOR_SHIFT;
 456
 457     /*
 458      * Write the now-patched first sectors of ldlinux.sys
 459      */
 460     for (i = 0; i < patch_sectors; i++) {
 461         xpwrite(dev_fd, boot_image + i * SECTOR_SIZE, SECTOR_SIZE,
 462                 opt.offset + ((off_t) sectors[i] << SECTOR_SHIFT));
 463     }
 464
 465     /*
 466      * To finish up, write the boot sector
 467      */
 468
 469     /* Read the superblock again since it might have changed while mounted */
 470     xpread(dev_fd, sectbuf, SECTOR_SIZE, opt.offset);
 471
 472     /* Copy the syslinux code into the boot sector */
 473     syslinux_make_bootsect(sectbuf);
 474
 475     /* Write new boot sector */
 476     xpwrite(dev_fd, sectbuf, SECTOR_SIZE, opt.offset);
 477
 478     close(dev_fd);
 479     sync();
 480
 481     /* Done! */
 482
 483     return 0;
 484 }