dos/syslinux.c

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 1998-2007 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  * syslinux.c - Linux installer program for SYSLINUX
  15  *
  16  * Hacked up for DOS.
  17  */
  18
  19 #include <errno.h>
  20 #include <stdio.h>
  21 #include <string.h>
  22 #include <stdlib.h>
  23 #include "mystuff.h"
  24
  25 #include "syslinux.h"
  26 #include "libfat.h"
  27
  28 const char *program = "syslinux"; /* Name of program */
  29 uint16_t dos_version;
  30
  31 #ifdef DEBUG
  32 # define dprintf printf
  33 #else
  34 # define dprintf(...) ((void)0)
  35 #endif
  36
  37 void __attribute__((noreturn)) usage(void)
  38 {
  39   puts("Usage: syslinux [-sfma][-d directory] <drive>: [bootsecfile]\n");
  40   exit(1);
  41 }
  42
  43 void unlock_device(int);
  44
  45 void __attribute__((noreturn)) die(const char *msg)
  46 {
  47   unlock_device(0);
  48   puts("syslinux: ");
  49   puts(msg);
  50   putchar('\n');
  51   exit(1);
  52 }
  53
  54 void warning(const char *msg)
  55 {
  56   puts("syslinux: warning: ");
  57   puts(msg);
  58   putchar('\n');
  59 }
  60
  61 /*
  62  * read/write wrapper functions
  63  */
  64 int creat(const char *filename, int mode)
  65 {
  66   uint16_t rv;
  67   uint8_t err;
  68
  69   dprintf("creat(\"%s\", 0x%x)\n", filename, mode);
  70
  71   rv = 0x3C00;
  72   asm volatile("int $0x21 ; setc %0"
  73                : "=bcdm" (err), "+a" (rv)
  74                : "c" (mode), "d" (filename));
  75   if ( err ) {
  76     dprintf("rv = %d\n", rv);
  77     die("cannot open ldlinux.sys");
  78   }
  79
  80   return rv;
  81 }
  82
  83 void close(int fd)
  84 {
  85   uint16_t rv = 0x3E00;
  86
  87   dprintf("close(%d)\n", fd);
  88
  89   asm volatile("int $0x21"
  90                : "+a" (rv)
  91                : "b" (fd));
  92
  93   /* The only error MS-DOS returns for close is EBADF,
  94      and we really don't care... */
  95 }
  96
  97 int rename(const char *oldname, const char *newname)
  98 {
  99   uint16_t rv = 0x5600;         /* Also support 43FFh? */
 100   uint8_t err;
 101
 102   dprintf("rename(\"%s\", \"%s\")\n", oldname, newname);
 103
 104   asm volatile("int $0x21 ; setc %0"
 105                : "=bcdm" (err), "+a" (rv)
 106                : "d" (oldname), "D" (newname));
 107
 108   if ( err ) {
 109     dprintf("rv = %d\n", rv);
 110     warning("cannot move ldlinux.sys");
 111     return rv;
 112   }
 113
 114   return 0;
 115 }
 116
 117 ssize_t write_file(int fd, const void *buf, size_t count)
 118 {
 119   uint16_t rv;
 120   ssize_t done = 0;
 121   uint8_t err;
 122
 123   dprintf("write_file(%d,%p,%u)\n", fd, buf, count);
 124
 125   while ( count ) {
 126     rv = 0x4000;
 127     asm volatile("int $0x21 ; setc %0"
 128                  : "=abcdm" (err), "+a" (rv)
 129                  : "b" (fd), "c" (count), "d" (buf));
 130     if ( err || rv == 0 )
 131       die("file write error");
 132
 133     done += rv;
 134     count -= rv;
 135   }
 136
 137   return done;
 138 }
 139
 140 static inline __attribute__((const)) uint16_t data_segment(void)
 141 {
 142   uint16_t ds;
 143
 144   asm("movw %%ds,%0" : "=rm" (ds));
 145   return ds;
 146 }
 147
 148 struct diskio {
 149   uint32_t startsector;
 150   uint16_t sectors;
 151   uint16_t bufoffs, bufseg;
 152 } __attribute__((packed));
 153
 154 void write_device(int drive, const void *buf, size_t nsecs, unsigned int sector)
 155 {
 156   uint8_t err;
 157   struct diskio dio;
 158
 159   dprintf("write_device(%d,%p,%u,%u)\n", drive, buf, nsecs, sector);
 160
 161   dio.startsector = sector;
 162   dio.sectors     = nsecs;
 163   dio.bufoffs     = (uintptr_t)buf;
 164   dio.bufseg      = data_segment();
 165
 166   asm volatile("int $0x26 ; setc %0 ; popfw"
 167                : "=abcdm" (err)
 168                : "a" (drive-1), "b" (&dio), "c" (-1), "d" (buf), "m" (dio));
 169
 170   if ( err )
 171     die("sector write error");
 172 }
 173
 174 void read_device(int drive, const void *buf, size_t nsecs, unsigned int sector)
 175 {
 176   uint8_t err;
 177   struct diskio dio;
 178
 179   dprintf("read_device(%d,%p,%u,%u)\n", drive, buf, nsecs, sector);
 180
 181   dio.startsector = sector;
 182   dio.sectors     = nsecs;
 183   dio.bufoffs     = (uintptr_t)buf;
 184   dio.bufseg      = data_segment();
 185
 186   asm volatile("int $0x25 ; setc %0 ; popfw"
 187                : "=abcdm" (err)
 188                : "a" (drive-1), "b" (&dio), "c" (-1), "d" (buf), "m" (dio));
 189
 190   if ( err )
 191     die("sector read error");
 192 }
 193
 194 /* Both traditional DOS and FAT32 DOS return this structure, but
 195    FAT32 return a lot more data, so make sure we have plenty of space */
 196 struct deviceparams {
 197   uint8_t specfunc;
 198   uint8_t devtype;
 199   uint16_t devattr;
 200   uint16_t cylinders;
 201   uint8_t mediatype;
 202   uint16_t bytespersec;
 203   uint8_t secperclust;
 204   uint16_t ressectors;
 205   uint8_t fats;
 206   uint16_t rootdirents;
 207   uint16_t sectors;
 208   uint8_t media;
 209   uint16_t fatsecs;
 210   uint16_t secpertrack;
 211   uint16_t heads;
 212   uint32_t hiddensecs;
 213   uint32_t hugesectors;
 214   uint8_t lotsofpadding[224];
 215 } __attribute__((packed));
 216
 217 uint32_t get_partition_offset(int drive)
 218 {
 219   uint8_t err;
 220   uint16_t rv;
 221   struct deviceparams dp;
 222
 223   dp.specfunc = 1;              /* Get current information */
 224
 225   rv = 0x440d;
 226   asm volatile("int $0x21 ; setc %0"
 227                : "=abcdm" (err), "+a" (rv), "=m" (dp)
 228                : "b" (drive), "c" (0x0860), "d" (&dp));
 229
 230   if ( !err )
 231     return dp.hiddensecs;
 232
 233   rv = 0x440d;
 234   asm volatile("int $0x21 ; setc %0"
 235                : "=abcdm" (err), "+a" (rv), "=m" (dp)
 236                : "b" (drive), "c" (0x4860), "d" (&dp));
 237
 238   if ( !err )
 239     return dp.hiddensecs;
 240
 241   die("could not find partition start offset");
 242 }
 243
 244 struct rwblock {
 245   uint8_t special;
 246   uint16_t head;
 247   uint16_t cylinder;
 248   uint16_t firstsector;
 249   uint16_t sectors;
 250   uint16_t bufferoffset;
 251   uint16_t bufferseg;
 252 } __attribute__((packed));
 253
 254 static struct rwblock mbr = {
 255   .special = 0,
 256   .head = 0,
 257   .cylinder = 0,
 258   .firstsector = 0,             /* MS-DOS, unlike the BIOS, zero-base sectors */
 259   .sectors = 1,
 260   .bufferoffset = 0,
 261   .bufferseg = 0
 262 };
 263
 264 void write_mbr(int drive, const void *buf)
 265 {
 266   uint16_t rv;
 267   uint8_t err;
 268
 269   dprintf("write_mbr(%d,%p)\n", drive, buf);
 270
 271   mbr.bufferoffset = (uintptr_t)buf;
 272   mbr.bufferseg    = data_segment();
 273
 274   rv = 0x440d;
 275   asm volatile("int $0x21 ; setc %0"
 276                : "=abcdm" (err), "+a" (rv)
 277                : "c" (0x0841), "d" (&mbr), "b" (drive), "m" (mbr));
 278
 279   if ( !err )
 280     return;
 281
 282   rv = 0x440d;
 283   asm volatile("int $0x21 ; setc %0"
 284                : "=abcdm" (err), "+a" (rv)
 285                : "c" (0x4841), "d" (&mbr), "b" (drive), "m" (mbr));
 286
 287   if ( err )
 288     die("mbr write error");
 289 }
 290
 291 void read_mbr(int drive, const void *buf)
 292 {
 293   uint16_t rv;
 294   uint8_t err;
 295
 296   dprintf("read_mbr(%d,%p)\n", drive, buf);
 297
 298   mbr.bufferoffset = (uintptr_t)buf;
 299   mbr.bufferseg    = data_segment();
 300
 301   rv = 0x440d;
 302   asm volatile("int $0x21 ; setc %0"
 303                : "=abcdm" (err), "+a" (rv)
 304                : "c" (0x0861), "d" (&mbr), "b" (drive), "m" (mbr));
 305
 306   if ( !err )
 307     return;
 308
 309   rv = 0x440d;
 310   asm volatile("int $0x21 ; setc %0"
 311                : "=abcdm" (err), "+a" (rv)
 312                : "c" (0x4861), "d" (&mbr), "b" (drive), "m" (mbr));
 313
 314   if ( err )
 315     die("mbr read error");
 316 }
 317
 318 /* This call can legitimately fail, and we don't care, so ignore error return */
 319 void set_attributes(const char *file, int attributes)
 320 {
 321   uint16_t rv = 0x4301;
 322
 323   dprintf("set_attributes(\"%s\", 0x%02x)\n", file, attributes);
 324
 325   asm volatile("int $0x21"
 326                : "+a" (rv)
 327                : "c" (attributes), "d" (file));
 328 }
 329
 330 /*
 331  * Version of the read_device function suitable for libfat
 332  */
 333 int libfat_xpread(intptr_t pp, void *buf, size_t secsize, libfat_sector_t sector)
 334 {
 335   read_device(pp, buf, 1, sector);
 336   return secsize;
 337 }
 338
 339 static inline void get_dos_version(void)
 340 {
 341   uint16_t ver = 0x3001;
 342   asm("int $0x21 ; xchgb %%ah,%%al" : "+a" (ver) : : "ebx", "ecx");
 343   dos_version = ver;
 344   dprintf("DOS version %d.%d\n", (dos_version >> 8), dos_version & 0xff);
 345 }
 346
 347 /* The locking interface relies on static variables.  A massive hack :( */
 348 static uint16_t lock_level;
 349
 350 static inline void set_lock_device(uint8_t device)
 351 {
 352   lock_level = device;
 353 }
 354
 355 void lock_device(int level)
 356 {
 357   uint16_t rv;
 358   uint8_t err;
 359   uint16_t lock_call;
 360
 361   if ( dos_version < 0x0700 )
 362     return;                     /* Win9x/NT only */
 363
 364 #if 0
 365   /* DOS 7.10 = Win95 OSR2 = first version with FAT32 */
 366   lock_call = (dos_version >= 0x0710) ? 0x484A : 0x084A;
 367 #else
 368   lock_call = 0x084A;           /* MSDN says this is OK for all filesystems */
 369 #endif
 370
 371   while ( (lock_level >> 8) < level ) {
 372     uint16_t new_level = lock_level + 0x0100;
 373     dprintf("Trying lock %04x...\n", new_level);
 374     rv = 0x444d;
 375     asm volatile("int $0x21 ; setc %0"
 376                  : "=abcdm" (err), "+a" (rv)
 377                  : "b" (new_level), "c" (lock_call), "d"(0x0001));
 378     if ( err ) {
 379       /* rv == 0x0001 means this call is not supported, if so we
 380          assume locking isn't needed (e.g. Win9x in DOS-only mode) */
 381       if ( rv == 0x0001 )
 382         return;
 383       else
 384         die("could not lock device");
 385     }
 386
 387     lock_level = new_level;
 388   }
 389   return;
 390 }
 391
 392 void unlock_device(int level)
 393 {
 394   uint16_t rv;
 395   uint8_t err;
 396   uint16_t unlock_call;
 397
 398   if ( dos_version < 0x0700 )
 399     return;                     /* Win9x/NT only */
 400
 401 #if 0
 402   /* DOS 7.10 = Win95 OSR2 = first version with FAT32 */
 403   unlock_call = (dos_version >= 0x0710) ? 0x486A : 0x086A;
 404 #else
 405   unlock_call = 0x086A;         /* MSDN says this is OK for all filesystems */
 406 #endif
 407
 408   while ( (lock_level >> 8) > level ) {
 409     uint16_t new_level = lock_level - 0x0100;
 410     rv = 0x440d;
 411     asm volatile("int $0x21 ; setc %0"
 412                  : "=abcdm" (err), "+a" (rv)
 413                  : "b" (new_level), "c" (unlock_call));
 414     lock_level = new_level;
 415   }
 416 }
 417
 418
 419 /*
 420  * This function does any desired MBR manipulation; called with the device lock held.
 421  */
 422 struct mbr_entry {
 423   uint8_t active;               /* Active flag */
 424   uint8_t bhead;                /* Begin head */
 425   uint8_t bsector;              /* Begin sector */
 426   uint8_t bcylinder;            /* Begin cylinder */
 427   uint8_t filesystem;           /* Filesystem value */
 428   uint8_t ehead;                /* End head */
 429   uint8_t esector;              /* End sector */
 430   uint8_t ecylinder;            /* End cylinder */
 431   uint32_t startlba;            /* Start sector LBA */
 432   uint32_t sectors;             /* Length in sectors */
 433 } __attribute__((packed));
 434
 435 static void adjust_mbr(int device, int writembr, int set_active)
 436 {
 437   static unsigned char sectbuf[512];
 438   int i;
 439
 440   if ( !writembr && !set_active )
 441     return;                     /* Nothing to do */
 442
 443   read_mbr(device, sectbuf);
 444
 445   if ( writembr ) {
 446     memcpy(sectbuf, syslinux_mbr, syslinux_mbr_len);
 447     *(uint16_t *)(sectbuf+510) = 0xaa55;
 448   }
 449
 450   if ( set_active ) {
 451     uint32_t offset = get_partition_offset(device);
 452     struct mbr_entry *me = (struct mbr_entry *)(sectbuf+446);
 453     int found = 0;
 454
 455     for ( i = 0 ; i < 4 ; i++ ) {
 456       if ( me->startlba == offset ) {
 457         me->active = 0x80;
 458         found++;
 459       } else {
 460         me->active = 0;
 461       }
 462       me++;
 463     }
 464
 465     if ( found < 1 ) {
 466       die("partition not found");
 467     } else if ( found > 1 ) {
 468       die("multiple aliased partitions found");
 469     }
 470   }
 471
 472   write_mbr(device, sectbuf);
 473 }
 474
 475 int main(int argc, char *argv[])
 476 {
 477   static unsigned char sectbuf[512];
 478   int dev_fd, fd;
 479   static char ldlinux_name[] = "@:\\ldlinux.sys";
 480   char **argp, *opt;
 481   int force = 0;                /* -f (force) option */
 482   struct libfat_filesystem *fs;
 483   libfat_sector_t s, *secp, sectors[65]; /* 65 is maximum possible */
 484   int32_t ldlinux_cluster;
 485   int nsectors;
 486   const char *device = NULL, *bootsecfile = NULL;
 487   const char *errmsg;
 488   int i;
 489   int writembr = 0;             /* -m (write MBR) option */
 490   int set_active = 0;           /* -a (set partition active) option */
 491   const char *subdir = NULL;
 492
 493   dprintf("argv = %p\n", argv);
 494   for ( i = 0 ; i <= argc ; i++ )
 495     dprintf("argv[%d] = %p = \"%s\"\n", i, argv[i], argv[i]);
 496
 497   (void)argc;                   /* Unused */
 498
 499   get_dos_version();
 500
 501   for ( argp = argv+1 ; *argp ; argp++ ) {
 502     if ( **argp == '-' ) {
 503       opt = *argp + 1;
 504       if ( !*opt )
 505         usage();
 506
 507       while ( *opt ) {
 508         switch ( *opt ) {
 509         case 's':               /* Use "safe, slow and stupid" code */
 510           syslinux_make_stupid();
 511           break;
 512         case 'f':               /* Force install */
 513           force = 1;
 514           break;
 515         case 'm':               /* Write MBR */
 516           writembr = 1;
 517           break;
 518         case 'a':               /* Set partition active */
 519           set_active = 1;
 520           break;
 521         case 'd':
 522           if ( argp[1] )
 523             subdir = *++argp;
 524           break;
 525         default:
 526           usage();
 527         }
 528         opt++;
 529       }
 530     } else {
 531       if ( bootsecfile )
 532         usage();
 533       else if ( device )
 534         bootsecfile = *argp;
 535       else
 536       device = *argp;
 537     }
 538   }
 539
 540   if ( !device )
 541     usage();
 542
 543   /*
 544    * Figure out which drive we're talking to
 545    */
 546   dev_fd = (device[0] & ~0x20) - 0x40;
 547   if ( dev_fd < 1 || dev_fd > 26 || device[1] != ':' || device[2] )
 548     usage();
 549
 550   set_lock_device(dev_fd);
 551
 552   lock_device(2);               /* Make sure we can lock the device */
 553   read_device(dev_fd, sectbuf, 1, 0);
 554   unlock_device(1);
 555
 556   /*
 557    * Check to see that what we got was indeed an MS-DOS boot sector/superblock
 558    */
 559   if( (errmsg = syslinux_check_bootsect(sectbuf)) ) {
 560     unlock_device(0);
 561     puts(errmsg);
 562     putchar('\n');
 563     exit(1);
 564   }
 565
 566   ldlinux_name[0] = dev_fd | 0x40;
 567
 568   set_attributes(ldlinux_name, 0);
 569   fd = creat(ldlinux_name, 0x07); /* SYSTEM HIDDEN READONLY */
 570   write_file(fd, syslinux_ldlinux, syslinux_ldlinux_len);
 571   close(fd);
 572
 573   /*
 574    * Now, use libfat to create a block map.  This probably
 575    * should be changed to use ioctl(...,FIBMAP,...) since
 576    * this is supposed to be a simple, privileged version
 577    * of the installer.
 578    */
 579   lock_device(2);
 580   fs = libfat_open(libfat_xpread, dev_fd);
 581   ldlinux_cluster = libfat_searchdir(fs, 0, "LDLINUX SYS", NULL);
 582   secp = sectors;
 583   nsectors = 0;
 584   s = libfat_clustertosector(fs, ldlinux_cluster);
 585   while ( s && nsectors < 65 ) {
 586     *secp++ = s;
 587     nsectors++;
 588     s = libfat_nextsector(fs, s);
 589   }
 590   libfat_close(fs);
 591
 592   /*
 593    * If requested, move ldlinux.sys
 594    */
 595   if (subdir) {
 596     char new_ldlinux_name[160];
 597     char *cp = new_ldlinux_name+3;
 598     const char *sd;
 599     int slash = 1;
 600
 601     new_ldlinux_name[0] = dev_fd | 0x40;
 602     new_ldlinux_name[1] = ':';
 603     new_ldlinux_name[2] = '\\';
 604
 605     for (sd = subdir; *sd; sd++) {
 606       char c = *sd;
 607
 608       if (c == '/' || c == '\\') {
 609         if (slash)
 610           continue;
 611         c = '\\';
 612         slash = 1;
 613       } else {
 614         slash = 0;
 615       }
 616
 617       *cp++ = c;
 618     }
 619
 620     /* Skip if subdirectory == root */
 621     if (cp > new_ldlinux_name+3) {
 622       if (!slash)
 623         *cp++ = '\\';
 624
 625       memcpy(cp, "ldlinux.sys", 12);
 626
 627       set_attributes(ldlinux_name, 0);
 628       if (rename(ldlinux_name, new_ldlinux_name))
 629         set_attributes(ldlinux_name, 0x07);
 630       else
 631         set_attributes(new_ldlinux_name, 0x07);
 632     }
 633   }
 634
 635   /*
 636    * Patch ldlinux.sys and the boot sector
 637    */
 638   syslinux_patch(sectors, nsectors);
 639
 640   /*
 641    * Write the now-patched first sector of ldlinux.sys
 642    */
 643   lock_device(3);
 644   write_device(dev_fd, syslinux_ldlinux, 1, sectors[0]);
 645
 646   /*
 647    * Muck with the MBR, if desired, while we hold the lock
 648    */
 649   adjust_mbr(dev_fd, writembr, set_active);
 650
 651   /*
 652    * To finish up, write the boot sector
 653    */
 654
 655   /* Read the superblock again since it might have changed while mounted */
 656   read_device(dev_fd, sectbuf, 1, 0);
 657
 658   /* Copy the syslinux code into the boot sector */
 659   syslinux_make_bootsect(sectbuf);
 660
 661   /* Write new boot sector */
 662   if ( bootsecfile ) {
 663     unlock_device(0);
 664     fd = creat(bootsecfile, 0x20); /* ARCHIVE */
 665     write_file(fd, sectbuf, 512);
 666     close(fd);
 667   } else {
 668     write_device(dev_fd, sectbuf, 1, 0);
 669     unlock_device(0);
 670   }
 671
 672   /* Done! */
 673
 674   return 0;
 675 }