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 <getopt.h>
  22 #include <stdio.h>
  23 #include <string.h>
  24 #include <stdlib.h>
  25 //#include <stdarg.h>
  26 #include "mystuff.h"
  27
  28 #include "syslinux.h"
  29 #include "libfat.h"
  30 #include "setadv.h"
  31 #include "sysexits.h"
  32 #include "syslxopt.h"
  33
  34 const char *program = "syslinux";       /* Name of program */
  35 uint16_t dos_version;
  36
  37 #ifdef DEBUG
  38 # define dprintf printf
  39 void pause(void)
  40 {
  41     uint16_t ax;
  42
  43     asm volatile("int $0x16" : "=a" (ax) : "a" (0));
  44 }
  45 #else
  46 # define dprintf(...) ((void)0)
  47 # define pause() ((void)0)
  48 #endif
  49
  50 void unlock_device(int);
  51
  52 void __attribute__ ((noreturn)) die(const char *msg)
  53 {
  54     unlock_device(0);
  55     puts("syslinux: ");
  56     puts(msg);
  57     putchar('\n');
  58     exit(1);
  59 }
  60
  61 void warning(const char *msg)
  62 {
  63     puts("syslinux: warning: ");
  64     puts(msg);
  65     putchar('\n');
  66 }
  67
  68 /*
  69  * read/write wrapper functions
  70  */
  71 int creat(const char *filename, int mode)
  72 {
  73     uint16_t rv;
  74     uint8_t err;
  75
  76     dprintf("creat(\"%s\", 0x%x)\n", filename, mode);
  77
  78     rv = 0x3C00;
  79     asm volatile ("int $0x21 ; setc %0"
  80                   : "=bcdm" (err), "+a" (rv)
  81                   : "c" (mode), "d" (filename));
  82     if (err) {
  83         dprintf("rv = %d\n", rv);
  84         die("cannot open ldlinux.sys");
  85     }
  86
  87     return rv;
  88 }
  89
  90 void close(int fd)
  91 {
  92     uint16_t rv = 0x3E00;
  93
  94     dprintf("close(%d)\n", fd);
  95
  96     asm volatile ("int $0x21":"+a" (rv)
  97                   :"b"(fd));
  98
  99     /* The only error MS-DOS returns for close is EBADF,
 100        and we really don't care... */
 101 }
 102
 103 int rename(const char *oldname, const char *newname)
 104 {
 105     uint16_t rv = 0x5600;       /* Also support 43FFh? */
 106     uint8_t err;
 107
 108     dprintf("rename(\"%s\", \"%s\")\n", oldname, newname);
 109
 110     asm volatile ("int $0x21 ; setc %0":"=bcdm" (err), "+a"(rv)
 111                   :"d"(oldname), "D"(newname));
 112
 113     if (err) {
 114         dprintf("rv = %d\n", rv);
 115         warning("cannot move ldlinux.sys");
 116         return rv;
 117     }
 118
 119     return 0;
 120 }
 121
 122 extern const char __payload_sseg[];
 123 uint16_t ldlinux_seg;
 124
 125 ssize_t write_ldlinux(int fd)
 126 {
 127     uint32_t offset = 0;
 128     uint16_t rv;
 129     uint8_t err;
 130
 131     while (offset < syslinux_ldlinux_len) {
 132         uint32_t chunk = syslinux_ldlinux_len - offset;
 133         if (chunk > 32768)
 134             chunk = 32768;
 135         asm volatile ("pushw %%ds ; "
 136                       "movw %6,%%ds ; "
 137                       "int $0x21 ; "
 138                       "popw %%ds ; " "setc %0":"=bcdm" (err), "=a"(rv)
 139                       :"a"(0x4000), "b"(fd), "c"(chunk), "d"(offset & 15),
 140                       "SD"((uint16_t) (ldlinux_seg + (offset >> 4))));
 141         if (err || rv == 0)
 142             die("file write error");
 143         offset += rv;
 144     }
 145
 146     return offset;
 147 }
 148
 149 ssize_t write_file(int fd, const void *buf, size_t count)
 150 {
 151     uint16_t rv;
 152     ssize_t done = 0;
 153     uint8_t err;
 154
 155     dprintf("write_file(%d,%p,%u)\n", fd, buf, count);
 156
 157     while (count) {
 158         asm volatile ("int $0x21 ; setc %0":"=bcdm" (err), "=a"(rv)
 159                       :"a"(0x4000), "b"(fd), "c"(count), "d"(buf));
 160         if (err || rv == 0)
 161             die("file write error");
 162
 163         done += rv;
 164         count -= rv;
 165     }
 166
 167     return done;
 168 }
 169
 170 static inline __attribute__ ((const))
 171 uint16_t data_segment(void)
 172 {
 173     uint16_t ds;
 174
 175     asm("movw %%ds,%0" : "=rm"(ds));
 176     return ds;
 177 }
 178
 179 void write_device(int drive, const void *buf, size_t nsecs, unsigned int sector)
 180 {
 181     uint16_t errnum;
 182     struct diskio dio;
 183
 184     dprintf("write_device(%d,%p,%u,%u)\n", drive, buf, nsecs, sector);
 185
 186     dio.startsector = sector;
 187     dio.sectors = nsecs;
 188     dio.bufoffs = (uintptr_t) buf;
 189     dio.bufseg = data_segment();
 190
 191     /* Try FAT32-aware system call first */
 192     asm volatile("int $0x21 ; jc 1f ; xorw %0,%0\n"
 193                  "1:"
 194                  : "=a" (errnum)
 195                  : "a" (0x7305), "b" (&dio), "c" (-1), "d" (drive),
 196                    "S" (1), "m" (dio)
 197                  : "memory");
 198
 199     /* If not supported, try the legacy system call (int2526.S) */
 200     if (errnum == 0x0001)
 201         errnum = int26_write_sector(drive, &dio);
 202
 203     if (errnum) {
 204         dprintf("rv = %04x\n", errnum);
 205         die("sector write error");
 206     }
 207 }
 208
 209 void read_device(int drive, const void *buf, size_t nsecs, unsigned int sector)
 210 {
 211     uint16_t errnum;
 212     struct diskio dio;
 213
 214     dprintf("read_device(%d,%p,%u,%u)\n", drive, buf, nsecs, sector);
 215
 216     dio.startsector = sector;
 217     dio.sectors = nsecs;
 218     dio.bufoffs = (uintptr_t) buf;
 219     dio.bufseg = data_segment();
 220
 221     /* Try FAT32-aware system call first */
 222     asm volatile("int $0x21 ; jc 1f ; xorw %0,%0\n"
 223                  "1:"
 224                  : "=a" (errnum)
 225                  : "a" (0x7305), "b" (&dio), "c" (-1), "d" (drive),
 226                    "S" (0), "m" (dio));
 227
 228     /* If not supported, try the legacy system call (int2526.S) */
 229     if (errnum == 0x0001)
 230         errnum = int25_read_sector(drive, &dio);
 231
 232     if (errnum) {
 233         dprintf("rv = %04x\n", errnum);
 234         die("sector read error");
 235     }
 236 }
 237
 238 /* Both traditional DOS and FAT32 DOS return this structure, but
 239    FAT32 return a lot more data, so make sure we have plenty of space */
 240 struct deviceparams {
 241     uint8_t specfunc;
 242     uint8_t devtype;
 243     uint16_t devattr;
 244     uint16_t cylinders;
 245     uint8_t mediatype;
 246     uint16_t bytespersec;
 247     uint8_t secperclust;
 248     uint16_t ressectors;
 249     uint8_t fats;
 250     uint16_t rootdirents;
 251     uint16_t sectors;
 252     uint8_t media;
 253     uint16_t fatsecs;
 254     uint16_t secpertrack;
 255     uint16_t heads;
 256     uint32_t hiddensecs;
 257     uint32_t hugesectors;
 258     uint8_t lotsofpadding[224];
 259 } __attribute__ ((packed));
 260
 261 uint32_t get_partition_offset(int drive)
 262 {
 263     uint8_t err;
 264     uint16_t rv;
 265     struct deviceparams dp;
 266
 267     dp.specfunc = 1;            /* Get current information */
 268
 269     rv = 0x440d;
 270     asm volatile ("int $0x21 ; setc %0"
 271                   :"=abcdm" (err), "+a"(rv), "=m"(dp)
 272                   :"b" (drive), "c" (0x0860), "d" (&dp));
 273
 274     if (!err)
 275         return dp.hiddensecs;
 276
 277     rv = 0x440d;
 278     asm volatile ("int $0x21 ; setc %0"
 279                   : "=abcdm" (err), "+a" (rv), "=m" (dp)
 280                   : "b" (drive), "c" (0x4860), "d" (&dp));
 281
 282     if (!err)
 283         return dp.hiddensecs;
 284
 285     die("could not find partition start offset");
 286 }
 287
 288 struct rwblock {
 289     uint8_t special;
 290     uint16_t head;
 291     uint16_t cylinder;
 292     uint16_t firstsector;
 293     uint16_t sectors;
 294     uint16_t bufferoffset;
 295     uint16_t bufferseg;
 296 } __attribute__ ((packed));
 297
 298 static struct rwblock mbr = {
 299     .special = 0,
 300     .head = 0,
 301     .cylinder = 0,
 302     .firstsector = 0,           /* MS-DOS, unlike the BIOS, zero-base sectors */
 303     .sectors = 1,
 304     .bufferoffset = 0,
 305     .bufferseg = 0
 306 };
 307
 308 void write_mbr(int drive, const void *buf)
 309 {
 310     uint16_t rv;
 311     uint8_t err;
 312
 313     dprintf("write_mbr(%d,%p)", drive, buf);
 314
 315     mbr.bufferoffset = (uintptr_t) buf;
 316     mbr.bufferseg = data_segment();
 317
 318     rv = 0x440d;
 319     asm volatile ("int $0x21 ; setc %0" : "=bcdm" (err), "+a"(rv)
 320                   :"c"(0x0841), "d"(&mbr), "b"(drive), "m"(mbr));
 321
 322     dprintf(" rv(0841) = %04x", rv);
 323     if (!err) {
 324         dprintf("\n");
 325         return;
 326     }
 327
 328     rv = 0x440d;
 329     asm volatile ("int $0x21 ; setc %0" : "=bcdm" (err), "+a"(rv)
 330                   :"c"(0x4841), "d"(&mbr), "b"(drive), "m"(mbr));
 331
 332     dprintf(" rv(4841) = %04x\n", rv);
 333     if (err)
 334         die("mbr write error");
 335 }
 336
 337 void read_mbr(int drive, const void *buf)
 338 {
 339     uint16_t rv;
 340     uint8_t err;
 341
 342     dprintf("read_mbr(%d,%p)", drive, buf);
 343
 344     mbr.bufferoffset = (uintptr_t) buf;
 345     mbr.bufferseg = data_segment();
 346
 347     rv = 0x440d;
 348     asm volatile ("int $0x21 ; setc %0":"=abcdm" (err), "+a"(rv)
 349                   :"c"(0x0861), "d"(&mbr), "b"(drive), "m"(mbr));
 350
 351     dprintf(" rv(0861) = %04x", rv);
 352     if (!err) {
 353         dprintf("\n");
 354         return;
 355     }
 356
 357     rv = 0x440d;
 358     asm volatile ("int $0x21 ; setc %0":"=abcdm" (err), "+a"(rv)
 359                   :"c"(0x4861), "d"(&mbr), "b"(drive), "m"(mbr));
 360
 361     dprintf(" rv(4841) = %04x\n", rv);
 362     if (err)
 363         die("mbr read error");
 364
 365     dprintf("Bytes: %02x %02x %02x %02x %02x %02x %02x %02x\n",
 366             ((const uint8_t *)buf)[0],
 367             ((const uint8_t *)buf)[1],
 368             ((const uint8_t *)buf)[2],
 369             ((const uint8_t *)buf)[3],
 370             ((const uint8_t *)buf)[4],
 371             ((const uint8_t *)buf)[5],
 372             ((const uint8_t *)buf)[6],
 373             ((const uint8_t *)buf)[7]);
 374 }
 375
 376 /* This call can legitimately fail, and we don't care, so ignore error return */
 377 void set_attributes(const char *file, int attributes)
 378 {
 379     uint16_t rv = 0x4301;
 380
 381     dprintf("set_attributes(\"%s\", 0x%02x)\n", file, attributes);
 382
 383     asm volatile ("int $0x21":"+a" (rv)
 384                   :"c"(attributes), "d"(file));
 385 }
 386
 387 /*
 388  * Version of the read_device function suitable for libfat
 389  */
 390 int libfat_xpread(intptr_t pp, void *buf, size_t secsize,
 391                   libfat_sector_t sector)
 392 {
 393     read_device(pp, buf, 1, sector);
 394     return secsize;
 395 }
 396
 397 static inline void get_dos_version(void)
 398 {
 399     uint16_t ver;
 400
 401     asm("int $0x21 ; xchgb %%ah,%%al"
 402         : "=a" (ver)
 403         : "a" (0x3001)
 404         : "ebx", "ecx");
 405     dos_version = ver;
 406
 407     dprintf("DOS version %d.%d\n", (dos_version >> 8), dos_version & 0xff);
 408 }
 409
 410 /* The locking interface relies on static variables.  A massive hack :( */
 411 static uint8_t lock_level, lock_drive;
 412
 413 static inline void set_lock_device(uint8_t device)
 414 {
 415     lock_level  = 0;
 416     lock_drive = device;
 417 }
 418
 419 static int do_lock(uint8_t level)
 420 {
 421     uint16_t level_arg = lock_drive + (level << 8);
 422     uint16_t rv;
 423     uint8_t err;
 424 #if 0
 425     /* DOS 7.10 = Win95 OSR2 = first version with FAT32 */
 426     uint16_t lock_call = (dos_version >= 0x070a) ? 0x484A : 0x084A;
 427 #else
 428     uint16_t lock_call = 0x084A; /* MSDN says this is OK for all filesystems */
 429 #endif
 430
 431     dprintf("Trying lock %04x... ", level_arg);
 432     asm volatile ("int $0x21 ; setc %0"
 433                   : "=bcdm" (err), "=a" (rv)
 434                   : "a" (0x440d), "b" (level_arg),
 435                     "c" (lock_call), "d" (0x0001));
 436     dprintf("%s %04x\n", err ? "err" : "ok", rv);
 437
 438     return err ? rv : 0;
 439 }
 440
 441 void lock_device(int level)
 442 {
 443     static int hard_lock = 0;
 444     int err;
 445
 446     if (dos_version < 0x0700)
 447         return;                 /* Win9x/NT only */
 448
 449     if (!hard_lock) {
 450         /* Assume hierarchial "soft" locking supported */
 451
 452         while (lock_level < level) {
 453             int new_level = lock_level + 1;
 454             err = do_lock(new_level);
 455             if (err) {
 456                 if (err == 0x0001) {
 457                     /* Try hard locking next */
 458                     hard_lock = 1;
 459                 }
 460                 goto soft_fail;
 461             }
 462
 463             lock_level = new_level;
 464         }
 465         return;
 466     }
 467
 468 soft_fail:
 469     if (hard_lock) {
 470         /* Hard locking, only level 4 supported */
 471         /* This is needed for Win9x in DOS mode */
 472
 473         err = do_lock(4);
 474         if (err) {
 475             if (err == 0x0001) {
 476                 /* Assume locking is not needed */
 477                 return;
 478             }
 479             goto hard_fail;
 480         }
 481
 482         lock_level = 4;
 483         return;
 484     }
 485
 486 hard_fail:
 487     die("could not lock device");
 488 }
 489
 490 void unlock_device(int level)
 491 {
 492     uint16_t rv;
 493     uint8_t err;
 494     uint16_t unlock_call;
 495
 496     if (dos_version < 0x0700)
 497         return;                 /* Win9x/NT only */
 498
 499 #if 0
 500     /* DOS 7.10 = Win95 OSR2 = first version with FAT32 */
 501     unlock_call = (dos_version >= 0x070a) ? 0x486A : 0x086A;
 502 #else
 503     unlock_call = 0x086A;       /* MSDN says this is OK for all filesystems */
 504 #endif
 505
 506     if (lock_level == 4 && level > 0)
 507         return;                 /* Only drop the hard lock at the end */
 508
 509     while (lock_level > level) {
 510         uint8_t new_level = (lock_level == 4) ? 0 : lock_level - 1;
 511         uint16_t level_arg = (new_level << 8) + lock_drive;
 512         rv = 0x440d;
 513         dprintf("Trying unlock %04x... ", new_level);
 514         asm volatile ("int $0x21 ; setc %0"
 515                       : "=bcdm" (err), "+a" (rv)
 516                       : "b" (level_arg), "c" (unlock_call));
 517         dprintf("%s %04x\n", err ? "err" : "ok", rv);
 518         lock_level = new_level;
 519     }
 520 }
 521
 522 /*
 523  * This function does any desired MBR manipulation; called with the device lock held.
 524  */
 525 struct mbr_entry {
 526     uint8_t active;             /* Active flag */
 527     uint8_t bhead;              /* Begin head */
 528     uint8_t bsector;            /* Begin sector */
 529     uint8_t bcylinder;          /* Begin cylinder */
 530     uint8_t filesystem;         /* Filesystem value */
 531     uint8_t ehead;              /* End head */
 532     uint8_t esector;            /* End sector */
 533     uint8_t ecylinder;          /* End cylinder */
 534     uint32_t startlba;          /* Start sector LBA */
 535     uint32_t sectors;           /* Length in sectors */
 536 } __attribute__ ((packed));
 537
 538 static void adjust_mbr(int device, int writembr, int set_active)
 539 {
 540     static unsigned char sectbuf[SECTOR_SIZE];
 541     int i;
 542
 543     if (!writembr && !set_active)
 544         return;                 /* Nothing to do */
 545
 546     read_mbr(device, sectbuf);
 547
 548     if (writembr) {
 549         memcpy(sectbuf, syslinux_mbr, syslinux_mbr_len);
 550         *(uint16_t *) (sectbuf + 510) = 0xaa55;
 551     }
 552
 553     if (set_active) {
 554         uint32_t offset = get_partition_offset(device);
 555         struct mbr_entry *me = (struct mbr_entry *)(sectbuf + 446);
 556         int found = 0;
 557
 558         dprintf("Searching for partition offset: %08x\n", offset);
 559
 560         for (i = 0; i < 4; i++) {
 561             if (me->startlba == offset) {
 562                 me->active = 0x80;
 563                 found++;
 564             } else {
 565                 me->active = 0;
 566             }
 567             me++;
 568         }
 569
 570         if (found < 1) {
 571             die("partition not found (-a is not implemented for logical partitions)");
 572         } else if (found > 1) {
 573             die("multiple aliased partitions found");
 574         }
 575     }
 576
 577     write_mbr(device, sectbuf);
 578 }
 579
 580 int main(int argc, char *argv[])
 581 {
 582     static unsigned char sectbuf[SECTOR_SIZE];
 583     int dev_fd, fd;
 584     static char ldlinux_name[] = "@:\\ldlinux.sys";
 585     char **argp, *opt;
 586     int force = 0;              /* -f (force) option */
 587     struct libfat_filesystem *fs;
 588     libfat_sector_t s, *secp;
 589     libfat_sector_t *sectors;
 590     int ldlinux_sectors;
 591     int32_t ldlinux_cluster;
 592     int nsectors;
 593     const char *device = NULL, *bootsecfile = NULL;
 594     const char *errmsg;
 595     int i;
 596     int writembr = 0;           /* -m (write MBR) option */
 597     int set_active = 0;         /* -a (set partition active) option */
 598     const char *subdir = NULL;
 599     int stupid = 0;
 600     int raid_mode = 0;
 601     int patch_sectors;
 602
 603     ldlinux_seg = (size_t) __payload_sseg + data_segment();
 604
 605     dprintf("argv = %p\n", argv);
 606     for (i = 0; i <= argc; i++)
 607         dprintf("argv[%d] = %p = \"%s\"\n", i, argv[i], argv[i]);
 608
 609     (void)argc;                 /* Unused */
 610
 611     get_dos_version();
 612
 613     for (argp = argv + 1; *argp; argp++) {
 614         if (**argp == '-') {
 615             opt = *argp + 1;
 616             if (!*opt)
 617                 usage(EX_USAGE, MODE_SYSLINUX_DOSWIN);
 618
 619             while (*opt) {
 620                 switch (*opt) {
 621                 case 's':       /* Use "safe, slow and stupid" code */
 622                     stupid = 1;
 623                     break;
 624                 case 'r':       /* RAID mode */
 625                     raid_mode = 1;
 626                     break;
 627                 case 'f':       /* Force install */
 628                     force = 1;
 629                     break;
 630                 case 'm':       /* Write MBR */
 631                     writembr = 1;
 632                     break;
 633                 case 'a':       /* Set partition active */
 634                     set_active = 1;
 635                     break;
 636                 case 'd':
 637                     if (argp[1])
 638                         subdir = *++argp;
 639                     break;
 640                 default:
 641                     usage(EX_USAGE, MODE_SYSLINUX_DOSWIN);
 642                 }
 643                 opt++;
 644             }
 645         } else {
 646             if (bootsecfile)
 647                 usage(EX_USAGE, MODE_SYSLINUX_DOSWIN);
 648             else if (device)
 649                 bootsecfile = *argp;
 650             else
 651                 device = *argp;
 652         }
 653     }
 654
 655     if (!device)
 656         usage(EX_USAGE, MODE_SYSLINUX_DOSWIN);
 657
 658     /*
 659      * Create an ADV in memory... this should be smarter.
 660      */
 661     syslinux_reset_adv(syslinux_adv);
 662
 663     /*
 664      * Figure out which drive we're talking to
 665      */
 666     dev_fd = (device[0] & ~0x20) - 0x40;
 667     if (dev_fd < 1 || dev_fd > 26 || device[1] != ':' || device[2])
 668         usage(EX_USAGE, MODE_SYSLINUX_DOSWIN);
 669
 670     set_lock_device(dev_fd);
 671
 672     lock_device(2);             /* Make sure we can lock the device */
 673     read_device(dev_fd, sectbuf, 1, 0);
 674     unlock_device(1);
 675
 676     /*
 677      * Check to see that what we got was indeed an MS-DOS boot sector/superblock
 678      */
 679     if ((errmsg = syslinux_check_bootsect(sectbuf))) {
 680         unlock_device(0);
 681         puts(errmsg);
 682         putchar('\n');
 683         exit(1);
 684     }
 685
 686     ldlinux_name[0] = dev_fd | 0x40;
 687
 688     set_attributes(ldlinux_name, 0);
 689     fd = creat(ldlinux_name, 0);        /* SYSTEM HIDDEN READONLY */
 690     write_ldlinux(fd);
 691     write_file(fd, syslinux_adv, 2 * ADV_SIZE);
 692     close(fd);
 693     set_attributes(ldlinux_name, 0x07); /* SYSTEM HIDDEN READONLY */
 694
 695     /*
 696      * Now, use libfat to create a block map.  This probably
 697      * should be changed to use ioctl(...,FIBMAP,...) since
 698      * this is supposed to be a simple, privileged version
 699      * of the installer.
 700      */
 701     ldlinux_sectors = (syslinux_ldlinux_len + 2 * ADV_SIZE
 702                        + SECTOR_SIZE - 1) >> SECTOR_SHIFT;
 703     sectors = calloc(ldlinux_sectors, sizeof *sectors);
 704     lock_device(2);
 705     fs = libfat_open(libfat_xpread, dev_fd);
 706     ldlinux_cluster = libfat_searchdir(fs, 0, "LDLINUX SYS", NULL);
 707     secp = sectors;
 708     nsectors = 0;
 709     s = libfat_clustertosector(fs, ldlinux_cluster);
 710     while (s && nsectors < ldlinux_sectors) {
 711         *secp++ = s;
 712         nsectors++;
 713         s = libfat_nextsector(fs, s);
 714     }
 715     libfat_close(fs);
 716
 717     /*
 718      * If requested, move ldlinux.sys
 719      */
 720     if (subdir) {
 721         char new_ldlinux_name[160];
 722         char *cp = new_ldlinux_name + 3;
 723         const char *sd;
 724         int slash = 1;
 725
 726         new_ldlinux_name[0] = dev_fd | 0x40;
 727         new_ldlinux_name[1] = ':';
 728         new_ldlinux_name[2] = '\\';
 729
 730         for (sd = subdir; *sd; sd++) {
 731             char c = *sd;
 732
 733             if (c == '/' || c == '\\') {
 734                 if (slash)
 735                     continue;
 736                 c = '\\';
 737                 slash = 1;
 738             } else {
 739                 slash = 0;
 740             }
 741
 742             *cp++ = c;
 743         }
 744
 745         /* Skip if subdirectory == root */
 746         if (cp > new_ldlinux_name + 3) {
 747             if (!slash)
 748                 *cp++ = '\\';
 749
 750             memcpy(cp, "ldlinux.sys", 12);
 751
 752             set_attributes(ldlinux_name, 0);
 753             if (rename(ldlinux_name, new_ldlinux_name))
 754                 set_attributes(ldlinux_name, 0x07);
 755             else
 756                 set_attributes(new_ldlinux_name, 0x07);
 757         }
 758     }
 759
 760     /*
 761      * Patch ldlinux.sys and the boot sector
 762      */
 763     i = syslinux_patch(sectors, nsectors, stupid, raid_mode, subdir, NULL);
 764     patch_sectors = (i + SECTOR_SIZE - 1) >> SECTOR_SHIFT;
 765
 766     /*
 767      * Overwrite the now-patched ldlinux.sys
 768      */
 769     /* lock_device(3); -- doesn't seem to be needed */
 770     for (i = 0; i < patch_sectors; i++) {
 771         uint16_t si, di, cx;
 772         si = 0;
 773         di = (size_t) sectbuf;
 774         cx = SECTOR_SIZE >> 2;
 775         asm volatile ("movw %3,%%fs ; fs ; rep ; movsl":"+S" (si), "+D"(di),
 776                       "+c"(cx)
 777                       :"abd"((uint16_t)
 778                              (ldlinux_seg + (i << (SECTOR_SHIFT - 4)))));
 779         write_device(dev_fd, sectbuf, 1, sectors[i]);
 780     }
 781
 782     /*
 783      * Muck with the MBR, if desired, while we hold the lock
 784      */
 785     adjust_mbr(dev_fd, writembr, set_active);
 786
 787     /*
 788      * To finish up, write the boot sector
 789      */
 790
 791     /* Read the superblock again since it might have changed while mounted */
 792     read_device(dev_fd, sectbuf, 1, 0);
 793
 794     /* Copy the syslinux code into the boot sector */
 795     syslinux_make_bootsect(sectbuf);
 796
 797     /* Write new boot sector */
 798     if (bootsecfile) {
 799         unlock_device(0);
 800         fd = creat(bootsecfile, 0x20);  /* ARCHIVE */
 801         write_file(fd, sectbuf, SECTOR_SIZE);
 802         close(fd);
 803     } else {
 804         write_device(dev_fd, sectbuf, 1, 0);
 805         unlock_device(0);
 806     }
 807
 808     /* Done! */
 809
 810     return 0;
 811 }