extlinux/main.c

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 1998-2008 H. Peter Anvin - All Rights Reserved
   4  *
   5  *   This program is free software; you can redistribute it and/or modify
   6  *   it under the terms of the GNU General Public License as published by
   7  *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
   8  *   Boston MA 02111-1307, USA; either version 2 of the License, or
   9  *   (at your option) any later version; incorporated herein by reference.
  10  *
  11  * ----------------------------------------------------------------------- */
  12
  13 /*
  14  * extlinux.c
  15  *
  16  * Install the extlinux boot block on an ext2/3 filesystem
  17  */
  18
  19 #define  _GNU_SOURCE            /* Enable everything */
  20 #include <inttypes.h>
  21 /* This is needed to deal with the kernel headers imported into glibc 3.3.3. */
  22 typedef uint64_t u64;
  23 #include <alloca.h>
  24 #include <errno.h>
  25 #include <fcntl.h>
  26 #include <stdio.h>
  27 #include <unistd.h>
  28 #ifndef __KLIBC__
  29 #include <mntent.h>
  30 #endif
  31 #include <stdlib.h>
  32 #include <string.h>
  33 #include <getopt.h>
  34 #include <sysexits.h>
  35 #include <sys/ioctl.h>
  36 #include <sys/stat.h>
  37 #include <sys/types.h>
  38 #include <sys/mount.h>
  39 #include <sys/vfs.h>
  40
  41 #include <linux/fd.h>           /* Floppy geometry */
  42 #include <linux/hdreg.h>        /* Hard disk geometry */
  43 #define statfs _kernel_statfs   /* HACK to deal with broken 2.4 distros */
  44 #include <linux/fs.h>           /* FIGETBSZ, FIBMAP */
  45 #undef statfs
  46
  47 #include "ext2_fs.h"
  48 #include "../version.h"
  49 #include "syslxint.h"
  50
  51 #ifdef DEBUG
  52 # define dprintf printf
  53 #else
  54 # define dprintf(...) ((void)0)
  55 #endif
  56
  57 /* Global option handling */
  58
  59 const char *program;
  60
  61 /* These are the options we can set and their values */
  62 struct my_options {
  63     unsigned int sectors;
  64     unsigned int heads;
  65     int raid_mode;
  66     int reset_adv;
  67     const char *set_once;
  68 } opt = {
  69 .sectors = 0,.heads = 0,.raid_mode = 0,.reset_adv = 0,.set_once = NULL,};
  70
  71 static void __attribute__ ((noreturn)) usage(int rv)
  72 {
  73     fprintf(stderr,
  74             "Usage: %s [options] directory\n"
  75             "  --install    -i  Install over the current bootsector\n"
  76             "  --update     -U  Update a previous EXTLINUX installation\n"
  77             "  --zip        -z  Force zipdrive geometry (-H 64 -S 32)\n"
  78             "  --sectors=#  -S  Force the number of sectors per track\n"
  79             "  --heads=#    -H  Force number of heads\n"
  80             "  --raid       -r  Fall back to the next device on boot failure\n"
  81             "  --once=...   -o  Execute a command once upon boot\n"
  82             "  --clear-once -O  Clear the boot-once command\n"
  83             "  --reset-adv      Reset auxilliary data\n"
  84             "\n"
  85             "  Note: geometry is determined at boot time for devices which\n"
  86             "  are considered hard disks by the BIOS.  Unfortunately, this is\n"
  87             "  not possible for devices which are considered floppy disks,\n"
  88             "  which includes zipdisks and LS-120 superfloppies.\n"
  89             "\n"
  90             "  The -z option is useful for USB devices which are considered\n"
  91             "  hard disks by some BIOSes and zipdrives by other BIOSes.\n",
  92             program);
  93
  94     exit(rv);
  95 }
  96
  97 enum long_only_opt {
  98     OPT_NONE,
  99     OPT_RESET_ADV,
 100 };
 101
 102 static const struct option long_options[] = {
 103     {"install", 0, NULL, 'i'},
 104     {"update", 0, NULL, 'U'},
 105     {"zipdrive", 0, NULL, 'z'},
 106     {"sectors", 1, NULL, 'S'},
 107     {"heads", 1, NULL, 'H'},
 108     {"raid-mode", 0, NULL, 'r'},
 109     {"version", 0, NULL, 'v'},
 110     {"help", 0, NULL, 'h'},
 111     {"once", 1, NULL, 'o'},
 112     {"clear-once", 0, NULL, 'O'},
 113     {"reset-adv", 0, NULL, OPT_RESET_ADV},
 114     {0, 0, 0, 0}
 115 };
 116
 117 static const char short_options[] = "iUuzS:H:rvho:O";
 118
 119 #if defined(__linux__) && !defined(BLKGETSIZE64)
 120 /* This takes a u64, but the size field says size_t.  Someone screwed big. */
 121 # define BLKGETSIZE64 _IOR(0x12,114,size_t)
 122 #endif
 123
 124 #define LDLINUX_MAGIC   0x3eb202fe
 125
 126 enum bs_offsets {
 127     bsJump = 0x00,
 128     bsOemName = 0x03,
 129     bsBytesPerSec = 0x0b,
 130     bsSecPerClust = 0x0d,
 131     bsResSectors = 0x0e,
 132     bsFATs = 0x10,
 133     bsRootDirEnts = 0x11,
 134     bsSectors = 0x13,
 135     bsMedia = 0x15,
 136     bsFATsecs = 0x16,
 137     bsSecPerTrack = 0x18,
 138     bsHeads = 0x1a,
 139     bsHiddenSecs = 0x1c,
 140     bsHugeSectors = 0x20,
 141
 142     /* FAT12/16 only */
 143     bs16DriveNumber = 0x24,
 144     bs16Reserved1 = 0x25,
 145     bs16BootSignature = 0x26,
 146     bs16VolumeID = 0x27,
 147     bs16VolumeLabel = 0x2b,
 148     bs16FileSysType = 0x36,
 149     bs16Code = 0x3e,
 150
 151     /* FAT32 only */
 152     bs32FATSz32 = 36,
 153     bs32ExtFlags = 40,
 154     bs32FSVer = 42,
 155     bs32RootClus = 44,
 156     bs32FSInfo = 48,
 157     bs32BkBootSec = 50,
 158     bs32Reserved = 52,
 159     bs32DriveNumber = 64,
 160     bs32Reserved1 = 65,
 161     bs32BootSignature = 66,
 162     bs32VolumeID = 67,
 163     bs32VolumeLabel = 71,
 164     bs32FileSysType = 82,
 165     bs32Code = 90,
 166
 167     bsSignature = 0x1fe
 168 };
 169
 170 #define bsHead      bsJump
 171 #define bsHeadLen   (bsOemName-bsHead)
 172 #define bsCode      bs32Code    /* The common safe choice */
 173 #define bsCodeLen   (bsSignature-bs32Code)
 174
 175 #ifndef EXT2_SUPER_OFFSET
 176 #define EXT2_SUPER_OFFSET 1024
 177 #endif
 178
 179 /*
 180  * Boot block
 181  */
 182 extern unsigned char extlinux_bootsect[];
 183 extern unsigned int extlinux_bootsect_len;
 184 #define boot_block      extlinux_bootsect
 185 #define boot_block_len  extlinux_bootsect_len
 186
 187 /*
 188  * Image file
 189  */
 190 extern unsigned char extlinux_image[];
 191 extern unsigned int extlinux_image_len;
 192 #define boot_image      extlinux_image
 193 #define boot_image_len  extlinux_image_len
 194
 195 /*
 196  * Common abort function
 197  */
 198 void __attribute__ ((noreturn)) die(const char *msg)
 199 {
 200     fputs(msg, stderr);
 201     exit(1);
 202 }
 203
 204 /*
 205  * read/write wrapper functions
 206  */
 207 ssize_t xpread(int fd, void *buf, size_t count, off_t offset)
 208 {
 209     char *bufp = (char *)buf;
 210     ssize_t rv;
 211     ssize_t done = 0;
 212
 213     while (count) {
 214         rv = pread(fd, bufp, count, offset);
 215         if (rv == 0) {
 216             die("short read");
 217         } else if (rv == -1) {
 218             if (errno == EINTR) {
 219                 continue;
 220             } else {
 221                 die(strerror(errno));
 222             }
 223         } else {
 224             bufp += rv;
 225             offset += rv;
 226             done += rv;
 227             count -= rv;
 228         }
 229     }
 230
 231     return done;
 232 }
 233
 234 ssize_t xpwrite(int fd, const void *buf, size_t count, off_t offset)
 235 {
 236     const char *bufp = (const char *)buf;
 237     ssize_t rv;
 238     ssize_t done = 0;
 239
 240     while (count) {
 241         rv = pwrite(fd, bufp, count, offset);
 242         if (rv == 0) {
 243             die("short write");
 244         } else if (rv == -1) {
 245             if (errno == EINTR) {
 246                 continue;
 247             } else {
 248                 die(strerror(errno));
 249             }
 250         } else {
 251             bufp += rv;
 252             offset += rv;
 253             done += rv;
 254             count -= rv;
 255         }
 256     }
 257
 258     return done;
 259 }
 260
 261 /*
 262  * Produce file map
 263  */
 264 int sectmap(int fd, uint32_t * sectors, int nsectors)
 265 {
 266     unsigned int blksize, blk, nblk;
 267     unsigned int i;
 268
 269     /* Get block size */
 270     if (ioctl(fd, FIGETBSZ, &blksize))
 271         return -1;
 272
 273     /* Number of sectors per block */
 274     blksize >>= SECTOR_SHIFT;
 275
 276     nblk = 0;
 277     while (nsectors) {
 278
 279         blk = nblk++;
 280         dprintf("querying block %u\n", blk);
 281         if (ioctl(fd, FIBMAP, &blk))
 282             return -1;
 283
 284         blk *= blksize;
 285         for (i = 0; i < blksize; i++) {
 286             if (!nsectors)
 287                 return 0;
 288
 289             dprintf("Sector: %10u\n", blk);
 290             *sectors++ = blk++;
 291             nsectors--;
 292         }
 293     }
 294
 295     return 0;
 296 }
 297
 298 /*
 299  * Get the size of a block device
 300  */
 301 uint64_t get_size(int devfd)
 302 {
 303     uint64_t bytes;
 304     uint32_t sects;
 305     struct stat st;
 306
 307 #ifdef BLKGETSIZE64
 308     if (!ioctl(devfd, BLKGETSIZE64, &bytes))
 309         return bytes;
 310 #endif
 311     if (!ioctl(devfd, BLKGETSIZE, &sects))
 312         return (uint64_t) sects << 9;
 313     else if (!fstat(devfd, &st) && st.st_size)
 314         return st.st_size;
 315     else
 316         return 0;
 317 }
 318
 319 /*
 320  * Get device geometry and partition offset
 321  */
 322 struct geometry_table {
 323     uint64_t bytes;
 324     struct hd_geometry g;
 325 };
 326
 327 /* Standard floppy disk geometries, plus LS-120.  Zipdisk geometry
 328    (x/64/32) is the final fallback.  I don't know what LS-240 has
 329    as its geometry, since I don't have one and don't know anyone that does,
 330    and Google wasn't helpful... */
 331 static const struct geometry_table standard_geometries[] = {
 332     {360 * 1024, {2, 9, 40, 0}},
 333     {720 * 1024, {2, 9, 80, 0}},
 334     {1200 * 1024, {2, 15, 80, 0}},
 335     {1440 * 1024, {2, 18, 80, 0}},
 336     {1680 * 1024, {2, 21, 80, 0}},
 337     {1722 * 1024, {2, 21, 80, 0}},
 338     {2880 * 1024, {2, 36, 80, 0}},
 339     {3840 * 1024, {2, 48, 80, 0}},
 340     {123264 * 1024, {8, 32, 963, 0}},   /* LS120 */
 341     {0, {0, 0, 0, 0}}
 342 };
 343
 344 int get_geometry(int devfd, uint64_t totalbytes, struct hd_geometry *geo)
 345 {
 346     struct floppy_struct fd_str;
 347     const struct geometry_table *gp;
 348
 349     memset(geo, 0, sizeof *geo);
 350
 351     if (!ioctl(devfd, HDIO_GETGEO, &geo)) {
 352         return 0;
 353     } else if (!ioctl(devfd, FDGETPRM, &fd_str)) {
 354         geo->heads = fd_str.head;
 355         geo->sectors = fd_str.sect;
 356         geo->cylinders = fd_str.track;
 357         geo->start = 0;
 358         return 0;
 359     }
 360
 361     /* Didn't work.  Let's see if this is one of the standard geometries */
 362     for (gp = standard_geometries; gp->bytes; gp++) {
 363         if (gp->bytes == totalbytes) {
 364             memcpy(geo, &gp->g, sizeof *geo);
 365             return 0;
 366         }
 367     }
 368
 369     /* Didn't work either... assign a geometry of 64 heads, 32 sectors; this is
 370        what zipdisks use, so this would help if someone has a USB key that
 371        they're booting in USB-ZIP mode. */
 372
 373     geo->heads = opt.heads ? : 64;
 374     geo->sectors = opt.sectors ? : 32;
 375     geo->cylinders = totalbytes / (geo->heads * geo->sectors << SECTOR_SHIFT);
 376     geo->start = 0;
 377
 378     if (!opt.sectors && !opt.heads)
 379         fprintf(stderr,
 380                 "Warning: unable to obtain device geometry (defaulting to %d heads, %d sectors)\n"
 381                 "         (on hard disks, this is usually harmless.)\n",
 382                 geo->heads, geo->sectors);
 383
 384     return 1;
 385 }
 386
 387 /*
 388  * Query the device geometry and put it into the boot sector.
 389  * Map the file and put the map in the boot sector and file.
 390  * Stick the "current directory" inode number into the file.
 391  */
 392 void patch_file_and_bootblock(int fd, int dirfd, int devfd)
 393 {
 394     struct stat dirst;
 395     struct hd_geometry geo;
 396     uint32_t *sectp;
 397     uint64_t totalbytes, totalsectors;
 398     int nsect;
 399     unsigned char *p, *patcharea;
 400     int i, dw;
 401     uint32_t csum;
 402
 403     if (fstat(dirfd, &dirst)) {
 404         perror("fstat dirfd");
 405         exit(255);              /* This should never happen */
 406     }
 407
 408     totalbytes = get_size(devfd);
 409     get_geometry(devfd, totalbytes, &geo);
 410
 411     if (opt.heads)
 412         geo.heads = opt.heads;
 413     if (opt.sectors)
 414         geo.sectors = opt.sectors;
 415
 416     /* Patch this into a fake FAT superblock.  This isn't because
 417        FAT is a good format in any way, it's because it lets the
 418        early bootstrap share code with the FAT version. */
 419     dprintf("heads = %u, sect = %u\n", geo.heads, geo.sectors);
 420
 421     totalsectors = totalbytes >> SECTOR_SHIFT;
 422     if (totalsectors >= 65536) {
 423         set_16(boot_block + bsSectors, 0);
 424     } else {
 425         set_16(boot_block + bsSectors, totalsectors);
 426     }
 427     set_32(boot_block + bsHugeSectors, totalsectors);
 428
 429     set_16(boot_block + bsBytesPerSec, SECTOR_SIZE);
 430     set_16(boot_block + bsSecPerTrack, geo.sectors);
 431     set_16(boot_block + bsHeads, geo.heads);
 432     set_32(boot_block + bsHiddenSecs, geo.start);
 433
 434     /* If we're in RAID mode then patch the appropriate instruction;
 435        either way write the proper boot signature */
 436     i = get_16(boot_block + 0x1FE);
 437     if (opt.raid_mode)
 438         set_16(boot_block + i, 0x18CD); /* INT 18h */
 439
 440     set_16(boot_block + 0x1FE, 0xAA55);
 441
 442     /* Construct the boot file */
 443
 444     dprintf("directory inode = %lu\n", (unsigned long)dirst.st_ino);
 445     nsect = (boot_image_len + SECTOR_SIZE - 1) >> SECTOR_SHIFT;
 446     nsect += 2;                 /* Two sectors for the ADV */
 447     sectp = alloca(sizeof(uint32_t) * nsect);
 448     if (sectmap(fd, sectp, nsect)) {
 449         perror("bmap");
 450         exit(1);
 451     }
 452
 453     /* First sector need pointer in boot sector */
 454     set_32(boot_block + 0x1F8, *sectp++);
 455     nsect--;
 456
 457     /* Search for LDLINUX_MAGIC to find the patch area */
 458     for (p = boot_image; get_32(p) != LDLINUX_MAGIC; p += 4) ;
 459     patcharea = p + 8;
 460
 461     /* Set up the totals */
 462     dw = boot_image_len >> 2;   /* COMPLETE dwords, excluding ADV */
 463     set_16(patcharea, dw);
 464     set_16(patcharea + 2, nsect);       /* Not including the first sector, but
 465                                            including the ADV */
 466     set_32(patcharea + 8, dirst.st_ino);        /* "Current" directory */
 467
 468     /* Set the sector pointers */
 469     p = patcharea + 12;
 470
 471     memset(p, 0, 64 * 4);
 472     while (nsect--) {
 473         set_32(p, *sectp++);
 474         p += 4;
 475     }
 476
 477     /* Now produce a checksum */
 478     set_32(patcharea + 4, 0);
 479
 480     csum = LDLINUX_MAGIC;
 481     for (i = 0, p = boot_image; i < dw; i++, p += 4)
 482         csum -= get_32(p);      /* Negative checksum */
 483
 484     set_32(patcharea + 4, csum);
 485 }
 486
 487 /*
 488  * Read the ADV from an existing instance, or initialize if invalid.
 489  * Returns -1 on fatal errors, 0 if ADV is okay, and 1 if no valid
 490  * ADV was found.
 491  */
 492 int read_adv(const char *path)
 493 {
 494     char *file;
 495     int fd = -1;
 496     struct stat st;
 497     int err = 0;
 498
 499     asprintf(&file, "%s%sextlinux.sys",
 500              path, path[0] && path[strlen(path) - 1] == '/' ? "" : "/");
 501
 502     if (!file) {
 503         perror(program);
 504         return -1;
 505     }
 506
 507     fd = open(file, O_RDONLY);
 508     if (fd < 0) {
 509         if (errno != ENOENT) {
 510             err = -1;
 511         } else {
 512             syslinux_reset_adv(syslinux_adv);
 513         }
 514     } else if (fstat(fd, &st)) {
 515         err = -1;
 516     } else if (st.st_size < 2 * ADV_SIZE) {
 517         /* Too small to be useful */
 518         syslinux_reset_adv(syslinux_adv);
 519         err = 0;                /* Nothing to read... */
 520     } else if (xpread(fd, syslinux_adv, 2 * ADV_SIZE,
 521                       st.st_size - 2 * ADV_SIZE) != 2 * ADV_SIZE) {
 522         err = -1;
 523     } else {
 524         /* We got it... maybe? */
 525         err = syslinux_validate_adv(syslinux_adv) ? 1 : 0;
 526     }
 527
 528     if (err < 0)
 529         perror(file);
 530
 531     if (fd >= 0)
 532         close(fd);
 533     if (file)
 534         free(file);
 535
 536     return err;
 537 }
 538
 539 /*
 540  * Update the ADV in an existing installation.
 541  */
 542 int write_adv(const char *path)
 543 {
 544     unsigned char advtmp[2 * ADV_SIZE];
 545     char *file;
 546     int fd = -1;
 547     struct stat st, xst;
 548     int err = 0;
 549     int flags, nflags;
 550
 551     asprintf(&file, "%s%sextlinux.sys",
 552              path, path[0] && path[strlen(path) - 1] == '/' ? "" : "/");
 553
 554     if (!file) {
 555         perror(program);
 556         return -1;
 557     }
 558
 559     fd = open(file, O_RDONLY);
 560     if (fd < 0) {
 561         err = -1;
 562     } else if (fstat(fd, &st)) {
 563         err = -1;
 564     } else if (st.st_size < 2 * ADV_SIZE) {
 565         /* Too small to be useful */
 566         err = -2;
 567     } else if (xpread(fd, advtmp, 2 * ADV_SIZE,
 568                       st.st_size - 2 * ADV_SIZE) != 2 * ADV_SIZE) {
 569         err = -1;
 570     } else {
 571         /* We got it... maybe? */
 572         err = syslinux_validate_adv(advtmp) ? -2 : 0;
 573         if (!err) {
 574             /* Got a good one, write our own ADV here */
 575             if (!ioctl(fd, EXT2_IOC_GETFLAGS, &flags)) {
 576                 nflags = flags & ~EXT2_IMMUTABLE_FL;
 577                 if (nflags != flags)
 578                     ioctl(fd, EXT2_IOC_SETFLAGS, &nflags);
 579             }
 580             if (!(st.st_mode & S_IWUSR))
 581                 fchmod(fd, st.st_mode | S_IWUSR);
 582
 583             /* Need to re-open read-write */
 584             close(fd);
 585             fd = open(file, O_RDWR | O_SYNC);
 586             if (fd < 0) {
 587                 err = -1;
 588             } else if (fstat(fd, &xst) || xst.st_ino != st.st_ino ||
 589                        xst.st_dev != st.st_dev || xst.st_size != st.st_size) {
 590                 fprintf(stderr, "%s: race condition on write\n", file);
 591                 err = -2;
 592             }
 593             /* Write our own version ... */
 594             if (xpwrite(fd, syslinux_adv, 2 * ADV_SIZE,
 595                         st.st_size - 2 * ADV_SIZE) != 2 * ADV_SIZE) {
 596                 err = -1;
 597             }
 598
 599             sync();
 600
 601             if (!(st.st_mode & S_IWUSR))
 602                 fchmod(fd, st.st_mode);
 603
 604             if (nflags != flags)
 605                 ioctl(fd, EXT2_IOC_SETFLAGS, &flags);
 606         }
 607     }
 608
 609     if (err == -2)
 610         fprintf(stderr, "%s: cannot write auxilliary data (need --update)?\n",
 611                 file);
 612     else if (err == -1)
 613         perror(file);
 614
 615     if (fd >= 0)
 616         close(fd);
 617     if (file)
 618         free(file);
 619
 620     return err;
 621 }
 622
 623 /*
 624  * Make any user-specified ADV modifications
 625  */
 626 int modify_adv(void)
 627 {
 628     int rv = 0;
 629
 630     if (opt.set_once) {
 631         if (syslinux_setadv(ADV_BOOTONCE, strlen(opt.set_once), opt.set_once)) {
 632             fprintf(stderr, "%s: not enough space for boot-once command\n",
 633                     program);
 634             rv = -1;
 635         }
 636     }
 637
 638     return rv;
 639 }
 640
 641 /*
 642  * Install the boot block on the specified device.
 643  * Must be run AFTER install_file()!
 644  */
 645 int install_bootblock(int fd, const char *device)
 646 {
 647     struct ext2_super_block sb;
 648
 649     if (xpread(fd, &sb, sizeof sb, EXT2_SUPER_OFFSET) != sizeof sb) {
 650         perror("reading superblock");
 651         return 1;
 652     }
 653
 654     if (sb.s_magic != EXT2_SUPER_MAGIC) {
 655         fprintf(stderr, "no ext2/ext3 superblock found on %s\n", device);
 656         return 1;
 657     }
 658
 659     if (xpwrite(fd, boot_block, boot_block_len, 0) != boot_block_len) {
 660         perror("writing bootblock");
 661         return 1;
 662     }
 663
 664     return 0;
 665 }
 666
 667 int install_file(const char *path, int devfd, struct stat *rst)
 668 {
 669     char *file;
 670     int fd = -1, dirfd = -1, flags;
 671     struct stat st;
 672
 673     asprintf(&file, "%s%sextlinux.sys",
 674              path, path[0] && path[strlen(path) - 1] == '/' ? "" : "/");
 675     if (!file) {
 676         perror(program);
 677         return 1;
 678     }
 679
 680     dirfd = open(path, O_RDONLY | O_DIRECTORY);
 681     if (dirfd < 0) {
 682         perror(path);
 683         goto bail;
 684     }
 685
 686     fd = open(file, O_RDONLY);
 687     if (fd < 0) {
 688         if (errno != ENOENT) {
 689             perror(file);
 690             goto bail;
 691         }
 692     } else {
 693         /* If file exist, remove the immutable flag and set u+w mode */
 694         if (!ioctl(fd, EXT2_IOC_GETFLAGS, &flags)) {
 695             flags &= ~EXT2_IMMUTABLE_FL;
 696             ioctl(fd, EXT2_IOC_SETFLAGS, &flags);
 697         }
 698         if (!fstat(fd, &st)) {
 699             fchmod(fd, st.st_mode | S_IWUSR);
 700         }
 701     }
 702     close(fd);
 703
 704     fd = open(file, O_WRONLY | O_TRUNC | O_CREAT | O_SYNC,
 705               S_IRUSR | S_IRGRP | S_IROTH);
 706     if (fd < 0) {
 707         perror(file);
 708         goto bail;
 709     }
 710
 711     /* Write it the first time */
 712     if (xpwrite(fd, boot_image, boot_image_len, 0) != boot_image_len ||
 713         xpwrite(fd, syslinux_adv, 2 * ADV_SIZE,
 714                 boot_image_len) != 2 * ADV_SIZE) {
 715         fprintf(stderr, "%s: write failure on %s\n", program, file);
 716         goto bail;
 717     }
 718
 719     /* Map the file, and patch the initial sector accordingly */
 720     patch_file_and_bootblock(fd, dirfd, devfd);
 721
 722     /* Write the first sector again - this relies on the file being
 723        overwritten in place! */
 724     if (xpwrite(fd, boot_image, SECTOR_SIZE, 0) != SECTOR_SIZE) {
 725         fprintf(stderr, "%s: write failure on %s\n", program, file);
 726         goto bail;
 727     }
 728
 729     /* Attempt to set immutable flag and remove all write access */
 730     /* Only set immutable flag if file is owned by root */
 731     if (!fstat(fd, &st)) {
 732         fchmod(fd, st.st_mode & (S_IRUSR | S_IRGRP | S_IROTH));
 733         if (st.st_uid == 0 && !ioctl(fd, EXT2_IOC_GETFLAGS, &flags)) {
 734             flags |= EXT2_IMMUTABLE_FL;
 735             ioctl(fd, EXT2_IOC_SETFLAGS, &flags);
 736         }
 737     }
 738
 739     if (fstat(fd, rst)) {
 740         perror(file);
 741         goto bail;
 742     }
 743
 744     close(dirfd);
 745     close(fd);
 746     return 0;
 747
 748 bail:
 749     if (dirfd >= 0)
 750         close(dirfd);
 751     if (fd >= 0)
 752         close(fd);
 753
 754     return 1;
 755 }
 756
 757 /* EXTLINUX installs the string 'EXTLINUX' at offset 3 in the boot
 758    sector; this is consistent with FAT filesystems. */
 759 int already_installed(int devfd)
 760 {
 761     char buffer[8];
 762
 763     xpread(devfd, buffer, 8, 3);
 764     return !memcmp(buffer, "EXTLINUX", 8);
 765 }
 766
 767 #ifdef __KLIBC__
 768 static char devname_buf[64];
 769
 770 static void device_cleanup(void)
 771 {
 772     unlink(devname_buf);
 773 }
 774 #endif
 775
 776 /* Verify that a device fd and a pathname agree.
 777    Return 0 on valid, -1 on error. */
 778 static int validate_device(const char *path, int devfd)
 779 {
 780     struct stat pst, dst;
 781
 782     if (stat(path, &pst) || fstat(devfd, &dst))
 783         return -1;
 784
 785     return (pst.st_dev == dst.st_rdev) ? 0 : -1;
 786 }
 787
 788 #ifndef __KLIBC__
 789 static const char *find_device(const char *mtab_file, dev_t dev)
 790 {
 791     struct mntent *mnt;
 792     struct stat dst;
 793     FILE *mtab;
 794     const char *devname = NULL;
 795
 796     mtab = setmntent(mtab_file, "r");
 797     if (!mtab)
 798         return NULL;
 799
 800     while ((mnt = getmntent(mtab))) {
 801         if ((!strcmp(mnt->mnt_type, "ext2") ||
 802              !strcmp(mnt->mnt_type, "ext3")) &&
 803             !stat(mnt->mnt_fsname, &dst) && dst.st_rdev == dev) {
 804             devname = strdup(mnt->mnt_fsname);
 805             break;
 806         }
 807     }
 808     endmntent(mtab);
 809
 810     return devname;
 811 }
 812 #endif
 813
 814 int install_loader(const char *path, int update_only)
 815 {
 816     struct stat st, fst;
 817     int devfd, rv;
 818     const char *devname = NULL;
 819     struct statfs sfs;
 820
 821     if (stat(path, &st) || !S_ISDIR(st.st_mode)) {
 822         fprintf(stderr, "%s: Not a directory: %s\n", program, path);
 823         return 1;
 824     }
 825
 826     if (statfs(path, &sfs)) {
 827         fprintf(stderr, "%s: statfs %s: %s\n", program, path, strerror(errno));
 828         return 1;
 829     }
 830
 831     if (sfs.f_type != EXT2_SUPER_MAGIC) {
 832         fprintf(stderr, "%s: not an ext2/ext3 filesystem: %s\n", program, path);
 833         return 1;
 834     }
 835
 836     devfd = -1;
 837
 838 #ifdef __KLIBC__
 839
 840     /* klibc doesn't have getmntent and friends; instead, just create
 841        a new device with the appropriate device type */
 842     snprintf(devname_buf, sizeof devname_buf, "/tmp/dev-%u:%u",
 843              major(st.st_dev), minor(st.st_dev));
 844
 845     if (mknod(devname_buf, S_IFBLK | 0600, st.st_dev)) {
 846         fprintf(stderr, "%s: cannot create device %s\n", program, devname);
 847         return 1;
 848     }
 849
 850     atexit(device_cleanup);     /* unlink the device node on exit */
 851     devname = devname_buf;
 852
 853 #else
 854
 855     devname = find_device("/proc/mounts", st.st_dev);
 856     if (!devname) {
 857         /* Didn't find it in /proc/mounts, try /etc/mtab */
 858         devname = find_device("/etc/mtab", st.st_dev);
 859     }
 860     if (!devname) {
 861         fprintf(stderr, "%s: cannot find device for path %s\n", program, path);
 862         return 1;
 863     }
 864
 865     fprintf(stderr, "%s is device %s\n", path, devname);
 866 #endif
 867
 868     if ((devfd = open(devname, O_RDWR | O_SYNC)) < 0) {
 869         fprintf(stderr, "%s: cannot open device %s\n", program, devname);
 870         return 1;
 871     }
 872
 873     /* Verify that the device we opened is the device intended */
 874     if (validate_device(path, devfd)) {
 875         fprintf(stderr, "%s: path %s doesn't match device %s\n",
 876                 program, path, devname);
 877         return 1;
 878     }
 879
 880     if (update_only && !already_installed(devfd)) {
 881         fprintf(stderr, "%s: no previous extlinux boot sector found\n",
 882                 program);
 883         return 1;
 884     }
 885
 886     /* Read a pre-existing ADV, if already installed */
 887     if (opt.reset_adv)
 888         syslinux_reset_adv(syslinux_adv);
 889     else if (read_adv(path) < 0)
 890         return 1;
 891
 892     if (modify_adv() < 0)
 893         return 1;
 894
 895     /* Install extlinux.sys */
 896     if (install_file(path, devfd, &fst))
 897         return 1;
 898
 899     if (fst.st_dev != st.st_dev) {
 900         fprintf(stderr, "%s: file system changed under us - aborting!\n",
 901                 program);
 902         return 1;
 903     }
 904
 905     sync();
 906     rv = install_bootblock(devfd, devname);
 907     close(devfd);
 908     sync();
 909
 910     return rv;
 911 }
 912
 913 /*
 914  * Modify the ADV of an existing installation
 915  */
 916 int modify_existing_adv(const char *path)
 917 {
 918     if (opt.reset_adv)
 919         syslinux_reset_adv(syslinux_adv);
 920     else if (read_adv(path) < 0)
 921         return 1;
 922
 923     if (modify_adv() < 0)
 924         return 1;
 925
 926     if (write_adv(path) < 0)
 927         return 1;
 928
 929     return 0;
 930 }
 931
 932 int main(int argc, char *argv[])
 933 {
 934     int o;
 935     const char *directory;
 936     int update_only = -1;
 937
 938     program = argv[0];
 939
 940     while ((o = getopt_long(argc, argv, short_options,
 941                             long_options, NULL)) != EOF) {
 942         switch (o) {
 943         case 'z':
 944             opt.heads = 64;
 945             opt.sectors = 32;
 946             break;
 947         case 'S':
 948             opt.sectors = strtoul(optarg, NULL, 0);
 949             if (opt.sectors < 1 || opt.sectors > 63) {
 950                 fprintf(stderr,
 951                         "%s: invalid number of sectors: %u (must be 1-63)\n",
 952                         program, opt.sectors);
 953                 exit(EX_USAGE);
 954             }
 955             break;
 956         case 'H':
 957             opt.heads = strtoul(optarg, NULL, 0);
 958             if (opt.heads < 1 || opt.heads > 256) {
 959                 fprintf(stderr,
 960                         "%s: invalid number of heads: %u (must be 1-256)\n",
 961                         program, opt.heads);
 962                 exit(EX_USAGE);
 963             }
 964             break;
 965         case 'r':
 966             opt.raid_mode = 1;
 967             break;
 968         case 'i':
 969             update_only = 0;
 970             break;
 971         case 'u':
 972         case 'U':
 973             update_only = 1;
 974             break;
 975         case 'h':
 976             usage(0);
 977             break;
 978         case 'o':
 979             opt.set_once = optarg;
 980             break;
 981         case 'O':
 982             opt.set_once = "";
 983             break;
 984         case OPT_RESET_ADV:
 985             opt.reset_adv = 1;
 986             break;
 987         case 'v':
 988             fputs("extlinux " VERSION_STR
 989                   "  Copyright 1994-" YEAR_STR " H. Peter Anvin \n", stderr);
 990             exit(0);
 991         default:
 992             usage(EX_USAGE);
 993         }
 994     }
 995
 996     directory = argv[optind];
 997
 998     if (!directory)
 999         usage(EX_USAGE);
1000
1001     if (update_only == -1) {
1002         if (opt.reset_adv || opt.set_once) {
1003             return modify_existing_adv(directory);
1004         } else {
1005             usage(EX_USAGE);
1006         }
1007     }
1008
1009     return install_loader(directory, update_only);
1010 }