dos/syslinux.c

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 1998-2008 H. Peter Anvin - All Rights Reserved
   4  *   Copyright 2009 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  * Hacked up for DOS.
  18  */
  19
  20 #include <errno.h>
  21 #include <stdio.h>
  22 #include <string.h>
  23 #include <stdlib.h>
  24 #include <stdarg.h>
  25 #include "mystuff.h"
  26
  27 #include "syslinux.h"
  28 #include "libfat.h"
  29
  30 const char *program = "syslinux";       /* Name of program */
  31 uint16_t dos_version;
  32
  33 #ifdef DEBUG
  34 # define dprintf printf
  35 void pause(void)
  36 {
  37     uint16_t ax;
  38
  39     asm volatile("int $0x16" : "=a" (ax) : "a" (0));
  40 }
  41 #else
  42 # define dprintf(...) ((void)0)
  43 # define pause() ((void)0)
  44 #endif
  45
  46 void __attribute__ ((noreturn)) usage(void)
  47 {
  48     puts("Usage: syslinux [-sfmar][-d directory] <drive>: [bootsecfile]\n");
  49     exit(1);
  50 }
  51
  52 void unlock_device(int);
  53
  54 void __attribute__ ((noreturn)) die(const char *msg)
  55 {
  56     unlock_device(0);
  57     puts("syslinux: ");
  58     puts(msg);
  59     putchar('\n');
  60     exit(1);
  61 }
  62
  63 void warning(const char *msg)
  64 {
  65     puts("syslinux: warning: ");
  66     puts(msg);
  67     putchar('\n');
  68 }
  69
  70 /*
  71  * read/write wrapper functions
  72  */
  73 int creat(const char *filename, int mode)
  74 {
  75     uint16_t rv;
  76     uint8_t err;
  77
  78     dprintf("creat(\"%s\", 0x%x)\n", filename, mode);
  79
  80     rv = 0x3C00;
  81     asm volatile ("int $0x21 ; setc %0"
  82                   : "=bcdm" (err), "+a" (rv)
  83                   : "c" (mode), "d" (filename));
  84     if (err) {
  85         dprintf("rv = %d\n", rv);
  86         die("cannot open ldlinux.sys");
  87     }
  88
  89     return rv;
  90 }
  91
  92 void close(int fd)
  93 {
  94     uint16_t rv = 0x3E00;
  95
  96     dprintf("close(%d)\n", fd);
  97
  98     asm volatile ("int $0x21":"+a" (rv)
  99                   :"b"(fd));
 100
 101     /* The only error MS-DOS returns for close is EBADF,
 102        and we really don't care... */
 103 }
 104
 105 int rename(const char *oldname, const char *newname)
 106 {
 107     uint16_t rv = 0x5600;       /* Also support 43FFh? */
 108     uint8_t err;
 109
 110     dprintf("rename(\"%s\", \"%s\")\n", oldname, newname);
 111
 112     asm volatile ("int $0x21 ; setc %0":"=bcdm" (err), "+a"(rv)
 113                   :"d"(oldname), "D"(newname));
 114
 115     if (err) {
 116         dprintf("rv = %d\n", rv);
 117         warning("cannot move ldlinux.sys");
 118         return rv;
 119     }
 120
 121     return 0;
 122 }
 123
 124 extern const char __payload_sseg[];
 125 uint16_t ldlinux_seg;
 126
 127 ssize_t write_ldlinux(int fd)
 128 {
 129     uint32_t offset = 0;
 130     uint16_t rv;
 131     uint8_t err;
 132
 133     while (offset < syslinux_ldlinux_len) {
 134         uint32_t chunk = syslinux_ldlinux_len - offset;
 135         if (chunk > 32768)
 136             chunk = 32768;
 137         asm volatile ("pushw %%ds ; "
 138                       "movw %6,%%ds ; "
 139                       "int $0x21 ; "
 140                       "popw %%ds ; " "setc %0":"=bcdm" (err), "=a"(rv)
 141                       :"a"(0x4000), "b"(fd), "c"(chunk), "d"(offset & 15),
 142                       "SD"((uint16_t) (ldlinux_seg + (offset >> 4))));
 143         if (err || rv == 0)
 144             die("file write error");
 145         offset += rv;
 146     }
 147
 148     return offset;
 149 }
 150
 151 ssize_t write_file(int fd, const void *buf, size_t count)
 152 {
 153     uint16_t rv;
 154     ssize_t done = 0;
 155     uint8_t err;
 156
 157     dprintf("write_file(%d,%p,%u)\n", fd, buf, count);
 158
 159     while (count) {
 160         asm volatile ("int $0x21 ; setc %0":"=bcdm" (err), "=a"(rv)
 161                       :"a"(0x4000), "b"(fd), "c"(count), "d"(buf));
 162         if (err || rv == 0)
 163             die("file write error");
 164
 165         done += rv;
 166         count -= rv;
 167     }
 168
 169     return done;
 170 }
 171
 172 static inline __attribute__ ((const))
 173 uint16_t data_segment(void)
 174 {
 175     uint16_t ds;
 176
 177     asm("movw %%ds,%0" : "=rm"(ds));
 178     return ds;
 179 }
 180
 181 void write_device(int drive, const void *buf, size_t nsecs, unsigned int sector)
 182 {
 183     uint16_t errnum;
 184     struct diskio dio;
 185
 186     dprintf("write_device(%d,%p,%u,%u)\n", drive, buf, nsecs, sector);
 187
 188     dio.startsector = sector;
 189     dio.sectors = nsecs;
 190     dio.bufoffs = (uintptr_t) buf;
 191     dio.bufseg = data_segment();
 192
 193     /* Try FAT32-aware system call first */
 194     asm volatile("int $0x21 ; jc 1f ; xorw %0,%0\n"
 195                  "1:"
 196                  : "=a" (errnum)
 197                  : "a" (0x7305), "b" (&dio), "c" (-1), "d" (drive),
 198                    "S" (1), "m" (dio)
 199                  : "memory");
 200
 201     /* If not supported, try the legacy system call (int2526.S) */
 202     if (errnum == 0x0001)
 203         errnum = int26_write_sector(drive, &dio);
 204
 205     if (errnum) {
 206         dprintf("rv = %04x\n", errnum);
 207         die("sector write error");
 208     }
 209 }
 210
 211 void read_device(int drive, const void *buf, size_t nsecs, unsigned int sector)
 212 {
 213     uint16_t errnum;
 214     struct diskio dio;
 215
 216     dprintf("read_device(%d,%p,%u,%u)\n", drive, buf, nsecs, sector);
 217
 218     dio.startsector = sector;
 219     dio.sectors = nsecs;
 220     dio.bufoffs = (uintptr_t) buf;
 221     dio.bufseg = data_segment();
 222
 223     /* Try FAT32-aware system call first */
 224     asm volatile("int $0x21 ; jc 1f ; xorw %0,%0\n"
 225                  "1:"
 226                  : "=a" (errnum)
 227                  : "a" (0x7305), "b" (&dio), "c" (-1), "d" (drive),
 228                    "S" (0), "m" (dio));
 229
 230     /* If not supported, try the legacy system call (int2526.S) */
 231     if (errnum == 0x0001)
 232         errnum = int25_read_sector(drive, &dio);
 233
 234     if (errnum) {
 235         dprintf("rv = %04x\n", errnum);
 236         die("sector read error");
 237     }
 238 }
 239
 240 /* Both traditional DOS and FAT32 DOS return this structure, but
 241    FAT32 return a lot more data, so make sure we have plenty of space */
 242 struct deviceparams {
 243     uint8_t specfunc;
 244     uint8_t devtype;
 245     uint16_t devattr;
 246     uint16_t cylinders;
 247     uint8_t mediatype;
 248     uint16_t bytespersec;
 249     uint8_t secperclust;
 250     uint16_t ressectors;
 251     uint8_t fats;
 252     uint16_t rootdirents;
 253     uint16_t sectors;
 254     uint8_t media;
 255     uint16_t fatsecs;
 256     uint16_t secpertrack;
 257     uint16_t heads;
 258     uint32_t hiddensecs;
 259     uint32_t hugesectors;
 260     uint8_t lotsofpadding[224];
 261 } __attribute__ ((packed));
 262
 263 uint32_t get_partition_offset(int drive)
 264 {
 265     uint8_t err;
 266     uint16_t rv;
 267     struct deviceparams dp;
 268
 269     dp.specfunc = 1;            /* Get current information */
 270
 271     rv = 0x440d;
 272     asm volatile ("int $0x21 ; setc %0"
 273                   :"=abcdm" (err), "+a"(rv), "=m"(dp)
 274                   :"b" (drive), "c" (0x0860), "d" (&dp));
 275
 276     if (!err)
 277         return dp.hiddensecs;
 278
 279     rv = 0x440d;
 280     asm volatile ("int $0x21 ; setc %0"
 281                   : "=abcdm" (err), "+a" (rv), "=m" (dp)
 282                   : "b" (drive), "c" (0x4860), "d" (&dp));
 283
 284     if (!err)
 285         return dp.hiddensecs;
 286
 287     die("could not find partition start offset");
 288 }
 289
 290 struct rwblock {
 291     uint8_t special;
 292     uint16_t head;
 293     uint16_t cylinder;
 294     uint16_t firstsector;
 295     uint16_t sectors;
 296     uint16_t bufferoffset;
 297     uint16_t bufferseg;
 298 } __attribute__ ((packed));
 299
 300 static struct rwblock mbr = {
 301     .special = 0,
 302     .head = 0,
 303     .cylinder = 0,
 304     .firstsector = 0,           /* MS-DOS, unlike the BIOS, zero-base sectors */
 305     .sectors = 1,
 306     .bufferoffset = 0,
 307     .bufferseg = 0
 308 };
 309
 310 void write_mbr(int drive, const void *buf)
 311 {
 312     uint16_t rv;
 313     uint8_t err;
 314
 315     dprintf("write_mbr(%d,%p)", drive, buf);
 316
 317     mbr.bufferoffset = (uintptr_t) buf;
 318     mbr.bufferseg = data_segment();
 319
 320     rv = 0x440d;
 321     asm volatile ("int $0x21 ; setc %0" : "=bcdm" (err), "+a"(rv)
 322                   :"c"(0x0841), "d"(&mbr), "b"(drive), "m"(mbr));
 323
 324     dprintf(" rv(0841) = %04x", rv);
 325     if (!err) {
 326         dprintf("\n");
 327         return;
 328     }
 329
 330     rv = 0x440d;
 331     asm volatile ("int $0x21 ; setc %0" : "=bcdm" (err), "+a"(rv)
 332                   :"c"(0x4841), "d"(&mbr), "b"(drive), "m"(mbr));
 333
 334     dprintf(" rv(4841) = %04x\n", rv);
 335     if (err)
 336         die("mbr write error");
 337 }
 338
 339 void read_mbr(int drive, const void *buf)
 340 {
 341     uint16_t rv;
 342     uint8_t err;
 343
 344     dprintf("read_mbr(%d,%p)", drive, buf);
 345
 346     mbr.bufferoffset = (uintptr_t) buf;
 347     mbr.bufferseg = data_segment();
 348
 349     rv = 0x440d;
 350     asm volatile ("int $0x21 ; setc %0":"=abcdm" (err), "+a"(rv)
 351                   :"c"(0x0861), "d"(&mbr), "b"(drive), "m"(mbr));
 352
 353     dprintf(" rv(0861) = %04x", rv);
 354     if (!err) {
 355         dprintf("\n");
 356         return;
 357     }
 358
 359     rv = 0x440d;
 360     asm volatile ("int $0x21 ; setc %0":"=abcdm" (err), "+a"(rv)
 361                   :"c"(0x4861), "d"(&mbr), "b"(drive), "m"(mbr));
 362
 363     dprintf(" rv(4841) = %04x\n", rv);
 364     if (err)
 365         die("mbr read error");
 366
 367     dprintf("Bytes: %02x %02x %02x %02x %02x %02x %02x %02x\n",
 368             ((const uint8_t *)buf)[0],
 369             ((const uint8_t *)buf)[1],
 370             ((const uint8_t *)buf)[2],
 371             ((const uint8_t *)buf)[3],
 372             ((const uint8_t *)buf)[4],
 373             ((const uint8_t *)buf)[5],
 374             ((const uint8_t *)buf)[6],
 375             ((const uint8_t *)buf)[7]);
 376 }
 377
 378 /* This call can legitimately fail, and we don't care, so ignore error return */
 379 void set_attributes(const char *file, int attributes)
 380 {
 381     uint16_t rv = 0x4301;
 382
 383     dprintf("set_attributes(\"%s\", 0x%02x)\n", file, attributes);
 384
 385     asm volatile ("int $0x21":"+a" (rv)
 386                   :"c"(attributes), "d"(file));
 387 }
 388
 389 /*
 390  * Version of the read_device function suitable for libfat
 391  */
 392 int libfat_xpread(intptr_t pp, void *buf, size_t secsize,
 393                   libfat_sector_t sector)
 394 {
 395     read_device(pp, buf, 1, sector);
 396     return secsize;
 397 }
 398
 399 static inline void get_dos_version(void)
 400 {
 401     uint16_t ver;
 402
 403     asm("int $0x21 ; xchgb %%ah,%%al"
 404         : "=a" (ver)
 405         : "a" (0x3001)
 406         : "ebx", "ecx");
 407     dos_version = ver;
 408
 409     dprintf("DOS version %d.%d\n", (dos_version >> 8), dos_version & 0xff);
 410 }
 411
 412 /* The locking interface relies on static variables.  A massive hack :( */
 413 static uint8_t lock_level, lock_drive;
 414
 415 static inline void set_lock_device(uint8_t device)
 416 {
 417     lock_level  = 0;
 418     lock_drive = device;
 419 }
 420
 421 static int do_lock(uint8_t level)
 422 {
 423     uint16_t level_arg = lock_drive + (level << 8);
 424     uint16_t rv;
 425     uint8_t err;
 426 #if 0
 427     /* DOS 7.10 = Win95 OSR2 = first version with FAT32 */
 428     uint16_t lock_call = (dos_version >= 0x070a) ? 0x484A : 0x084A;
 429 #else
 430     uint16_t lock_call = 0x084A; /* MSDN says this is OK for all filesystems */
 431 #endif
 432
 433     dprintf("Trying lock %04x... ", level_arg);
 434     asm volatile ("int $0x21 ; setc %0"
 435                   : "=bcdm" (err), "=a" (rv)
 436                   : "a" (0x440d), "b" (level_arg),
 437                     "c" (lock_call), "d" (0x0001));
 438     dprintf("%s %04x\n", err ? "err" : "ok", rv);
 439
 440     return err ? rv : 0;
 441 }
 442
 443 void lock_device(int level)
 444 {
 445     static int hard_lock = 0;
 446     int err;
 447
 448     if (dos_version < 0x0700)
 449         return;                 /* Win9x/NT only */
 450
 451     if (!hard_lock) {
 452         /* Assume hierarchial "soft" locking supported */
 453
 454         while (lock_level < level) {
 455             int new_level = lock_level + 1;
 456             err = do_lock(new_level);
 457             if (err) {
 458                 if (err == 0x0001) {
 459                     /* Try hard locking next */
 460                     hard_lock = 1;
 461                 }
 462                 goto soft_fail;
 463             }
 464
 465             lock_level = new_level;
 466         }
 467         return;
 468     }
 469
 470 soft_fail:
 471     if (hard_lock) {
 472         /* Hard locking, only level 4 supported */
 473         /* This is needed for Win9x in DOS mode */
 474
 475         err = do_lock(4);
 476         if (err) {
 477             if (err == 0x0001) {
 478                 /* Assume locking is not needed */
 479                 return;
 480             }
 481             goto hard_fail;
 482         }
 483
 484         lock_level = 4;
 485         return;
 486     }
 487
 488 hard_fail:
 489     die("could not lock device");
 490 }
 491
 492 void unlock_device(int level)
 493 {
 494     uint16_t rv;
 495     uint8_t err;
 496     uint16_t unlock_call;
 497
 498     if (dos_version < 0x0700)
 499         return;                 /* Win9x/NT only */
 500
 501 #if 0
 502     /* DOS 7.10 = Win95 OSR2 = first version with FAT32 */
 503     unlock_call = (dos_version >= 0x070a) ? 0x486A : 0x086A;
 504 #else
 505     unlock_call = 0x086A;       /* MSDN says this is OK for all filesystems */
 506 #endif
 507
 508     if (lock_level == 4 && level > 0)
 509         return;                 /* Only drop the hard lock at the end */
 510
 511     while (lock_level > level) {
 512         uint8_t new_level = (lock_level == 4) ? 0 : lock_level - 1;
 513         uint16_t level_arg = (new_level << 8) + lock_drive;
 514         rv = 0x440d;
 515         dprintf("Trying unlock %04x... ", new_level);
 516         asm volatile ("int $0x21 ; setc %0"
 517                       : "=bcdm" (err), "+a" (rv)
 518                       : "b" (level_arg), "c" (unlock_call));
 519         dprintf("%s %04x\n", err ? "err" : "ok", rv);
 520         lock_level = new_level;
 521     }
 522 }
 523
 524 /*
 525  * This function does any desired MBR manipulation; called with the device lock held.
 526  */
 527 struct mbr_entry {
 528     uint8_t active;             /* Active flag */
 529     uint8_t bhead;              /* Begin head */
 530     uint8_t bsector;            /* Begin sector */
 531     uint8_t bcylinder;          /* Begin cylinder */
 532     uint8_t filesystem;         /* Filesystem value */
 533     uint8_t ehead;              /* End head */
 534     uint8_t esector;            /* End sector */
 535     uint8_t ecylinder;          /* End cylinder */
 536     uint32_t startlba;          /* Start sector LBA */
 537     uint32_t sectors;           /* Length in sectors */
 538 } __attribute__ ((packed));
 539
 540 static void adjust_mbr(int device, int writembr, int set_active)
 541 {
 542     static unsigned char sectbuf[SECTOR_SIZE];
 543     int i;
 544
 545     if (!writembr && !set_active)
 546         return;                 /* Nothing to do */
 547
 548     read_mbr(device, sectbuf);
 549
 550     if (writembr) {
 551         memcpy(sectbuf, syslinux_mbr, syslinux_mbr_len);
 552         *(uint16_t *) (sectbuf + 510) = 0xaa55;
 553     }
 554
 555     if (set_active) {
 556         uint32_t offset = get_partition_offset(device);
 557         struct mbr_entry *me = (struct mbr_entry *)(sectbuf + 446);
 558         int found = 0;
 559
 560         dprintf("Searching for partition offset: %08x\n", offset);
 561
 562         for (i = 0; i < 4; i++) {
 563             if (me->startlba == offset) {
 564                 me->active = 0x80;
 565                 found++;
 566             } else {
 567                 me->active = 0;
 568             }
 569             me++;
 570         }
 571
 572         if (found < 1) {
 573             die("partition not found (-a is not implemented for logical partitions)");
 574         } else if (found > 1) {
 575             die("multiple aliased partitions found");
 576         }
 577     }
 578
 579     write_mbr(device, sectbuf);
 580 }
 581
 582 int main(int argc, char *argv[])
 583 {
 584     static unsigned char sectbuf[SECTOR_SIZE];
 585     int dev_fd, fd;
 586     static char ldlinux_name[] = "@:\\ldlinux.sys";
 587     char **argp, *opt;
 588     int force = 0;              /* -f (force) option */
 589     struct libfat_filesystem *fs;
 590     libfat_sector_t s, *secp;
 591     libfat_sector_t *sectors;
 592     int ldlinux_sectors;
 593     int32_t ldlinux_cluster;
 594     int nsectors;
 595     const char *device = NULL, *bootsecfile = NULL;
 596     const char *errmsg;
 597     int i;
 598     int writembr = 0;           /* -m (write MBR) option */
 599     int set_active = 0;         /* -a (set partition active) option */
 600     const char *subdir = NULL;
 601     int stupid = 0;
 602     int raid_mode = 0;
 603     int patch_sectors;
 604
 605     ldlinux_seg = (size_t) __payload_sseg + data_segment();
 606
 607     dprintf("argv = %p\n", argv);
 608     for (i = 0; i <= argc; i++)
 609         dprintf("argv[%d] = %p = \"%s\"\n", i, argv[i], argv[i]);
 610
 611     (void)argc;                 /* Unused */
 612
 613     get_dos_version();
 614
 615     for (argp = argv + 1; *argp; argp++) {
 616         if (**argp == '-') {
 617             opt = *argp + 1;
 618             if (!*opt)
 619                 usage();
 620
 621             while (*opt) {
 622                 switch (*opt) {
 623                 case 's':       /* Use "safe, slow and stupid" code */
 624                     stupid = 1;
 625                     break;
 626                 case 'r':       /* RAID mode */
 627                     raid_mode = 1;
 628                     break;
 629                 case 'f':       /* Force install */
 630                     force = 1;
 631                     break;
 632                 case 'm':       /* Write MBR */
 633                     writembr = 1;
 634                     break;
 635                 case 'a':       /* Set partition active */
 636                     set_active = 1;
 637                     break;
 638                 case 'd':
 639                     if (argp[1])
 640                         subdir = *++argp;
 641                     break;
 642                 default:
 643                     usage();
 644                 }
 645                 opt++;
 646             }
 647         } else {
 648             if (bootsecfile)
 649                 usage();
 650             else if (device)
 651                 bootsecfile = *argp;
 652             else
 653                 device = *argp;
 654         }
 655     }
 656
 657     if (!device)
 658         usage();
 659
 660     /*
 661      * Figure out which drive we're talking to
 662      */
 663     dev_fd = (device[0] & ~0x20) - 0x40;
 664     if (dev_fd < 1 || dev_fd > 26 || device[1] != ':' || device[2])
 665         usage();
 666
 667     set_lock_device(dev_fd);
 668
 669     lock_device(2);             /* Make sure we can lock the device */
 670     read_device(dev_fd, sectbuf, 1, 0);
 671     unlock_device(1);
 672
 673     /*
 674      * Check to see that what we got was indeed an MS-DOS boot sector/superblock
 675      */
 676     if ((errmsg = syslinux_check_bootsect(sectbuf))) {
 677         unlock_device(0);
 678         puts(errmsg);
 679         putchar('\n');
 680         exit(1);
 681     }
 682
 683     ldlinux_name[0] = dev_fd | 0x40;
 684
 685     set_attributes(ldlinux_name, 0);
 686     fd = creat(ldlinux_name, 0);        /* SYSTEM HIDDEN READONLY */
 687     write_ldlinux(fd);
 688     close(fd);
 689     set_attributes(ldlinux_name, 0x07); /* SYSTEM HIDDEN READONLY */
 690
 691     /*
 692      * Now, use libfat to create a block map.  This probably
 693      * should be changed to use ioctl(...,FIBMAP,...) since
 694      * this is supposed to be a simple, privileged version
 695      * of the installer.
 696      */
 697     ldlinux_sectors = (syslinux_ldlinux_len + SECTOR_SIZE - 1) >> SECTOR_SHIFT;
 698     sectors = calloc(ldlinux_sectors, sizeof *sectors);
 699     lock_device(2);
 700     fs = libfat_open(libfat_xpread, dev_fd);
 701     ldlinux_cluster = libfat_searchdir(fs, 0, "LDLINUX SYS", NULL);
 702     secp = sectors;
 703     nsectors = 0;
 704     s = libfat_clustertosector(fs, ldlinux_cluster);
 705     while (s && nsectors < ldlinux_sectors) {
 706         *secp++ = s;
 707         nsectors++;
 708         s = libfat_nextsector(fs, s);
 709     }
 710     libfat_close(fs);
 711
 712     /*
 713      * If requested, move ldlinux.sys
 714      */
 715     if (subdir) {
 716         char new_ldlinux_name[160];
 717         char *cp = new_ldlinux_name + 3;
 718         const char *sd;
 719         int slash = 1;
 720
 721         new_ldlinux_name[0] = dev_fd | 0x40;
 722         new_ldlinux_name[1] = ':';
 723         new_ldlinux_name[2] = '\\';
 724
 725         for (sd = subdir; *sd; sd++) {
 726             char c = *sd;
 727
 728             if (c == '/' || c == '\\') {
 729                 if (slash)
 730                     continue;
 731                 c = '\\';
 732                 slash = 1;
 733             } else {
 734                 slash = 0;
 735             }
 736
 737             *cp++ = c;
 738         }
 739
 740         /* Skip if subdirectory == root */
 741         if (cp > new_ldlinux_name + 3) {
 742             if (!slash)
 743                 *cp++ = '\\';
 744
 745             memcpy(cp, "ldlinux.sys", 12);
 746
 747             set_attributes(ldlinux_name, 0);
 748             if (rename(ldlinux_name, new_ldlinux_name))
 749                 set_attributes(ldlinux_name, 0x07);
 750             else
 751                 set_attributes(new_ldlinux_name, 0x07);
 752         }
 753     }
 754
 755     /*
 756      * Patch ldlinux.sys and the boot sector
 757      */
 758     i = syslinux_patch(sectors, nsectors, stupid, raid_mode, subdir, NULL);
 759     patch_sectors = (i + SECTOR_SIZE - 1) >> SECTOR_SHIFT;
 760
 761     /*
 762      * Overwrite the now-patched ldlinux.sys
 763      */
 764     /* lock_device(3); -- doesn't seem to be needed */
 765     for (i = 0; i < patch_sectors; i++) {
 766         uint16_t si, di, cx;
 767         si = 0;
 768         di = (size_t) sectbuf;
 769         cx = SECTOR_SIZE >> 2;
 770         asm volatile ("movw %3,%%fs ; fs ; rep ; movsl":"+S" (si), "+D"(di),
 771                       "+c"(cx)
 772                       :"abd"((uint16_t)
 773                              (ldlinux_seg + (i << (SECTOR_SHIFT - 4)))));
 774         write_device(dev_fd, sectbuf, 1, sectors[i]);
 775     }
 776
 777     /*
 778      * Muck with the MBR, if desired, while we hold the lock
 779      */
 780     adjust_mbr(dev_fd, writembr, set_active);
 781
 782     /*
 783      * To finish up, write the boot sector
 784      */
 785
 786     /* Read the superblock again since it might have changed while mounted */
 787     read_device(dev_fd, sectbuf, 1, 0);
 788
 789     /* Copy the syslinux code into the boot sector */
 790     syslinux_make_bootsect(sectbuf);
 791
 792     /* Write new boot sector */
 793     if (bootsecfile) {
 794         unlock_device(0);
 795         fd = creat(bootsecfile, 0x20);  /* ARCHIVE */
 796         write_file(fd, sectbuf, SECTOR_SIZE);
 797         close(fd);
 798     } else {
 799         write_device(dev_fd, sectbuf, 1, 0);
 800         unlock_device(0);
 801     }
 802
 803     /* Done! */
 804
 805     return 0;
 806 }