eltorito.c

刻录光盘的程序

    {
	checksum += (unsigned int)checksum_ptr[i];
	checksum += ((unsigned int)checksum_ptr[i+1])*256;
    }
    
    /* 
     * now find out the real checksum 
     */
    checksum = -checksum;
    set_721(valid_desc.cksum, (unsigned int) checksum);
    
    /*
     * now make the initial/default entry for boot catalog 
     */
    memset(&default_desc, 0, sizeof(default_desc));
    default_desc.boot_id[0] = (char)not_bootable ? EL_TORITO_NOT_BOOTABLE : EL_TORITO_BOOTABLE;
    
    /*
     * use default BIOS loadpnt
     */ 
    set_721(default_desc.loadseg, load_addr);
    
    /*
     * figure out size of boot image in 512-byte sectors.  However,
     * round up to the nearest integral CD (2048-byte) sector.
     * This is only used for no-emulation booting.
     */
    nsectors = load_size ? load_size : ((de->size + 2047)/2048) * 4;
    fprintf(stderr, "\nSize of boot image is %d sectors -> ", nsectors); 
    
    if (hard_disk_boot) {
	/*
	 * sanity test hard disk boot image
	 */
	default_desc.boot_media[0] = EL_TORITO_MEDIA_HD;
	fprintf(stderr, "Emulating a hard disk\n");
	
	/*
	 * read MBR
	 */
	bootmbr = open(de->whole_name, O_RDONLY | O_BINARY);
	if (bootmbr == -1) {
#ifdef	USE_LIBSCHILY
	    comerr("Error opening boot image '%s' for read.\n", de->whole_name);
#else
	    fprintf(stderr,"Error opening boot image '%s' for read.\n", de->whole_name);
	    perror("");
	    exit(1);
#endif
	}
	if(read(bootmbr, &disk_mbr, sizeof(disk_mbr)) != sizeof(disk_mbr)) {
#ifdef	USE_LIBSCHILY
	    comerr("Error reading MBR from boot image '%s'.\n", de->whole_name);
#else
	    fprintf(stderr,"Error reading MBR from boot image '%s'.\n", de->whole_name);
	    exit(1);
#endif
	}
	close(bootmbr);
	if(la_to_u_2_byte(disk_mbr.magic) != MBR_MAGIC) {
#ifdef	USE_LIBSCHILY
	    errmsgno(EX_BAD, "Warning: boot image '%s' MBR is not a boot sector.\n", de->whole_name);
#else
	    fprintf(stderr, "Warning: boot image '%s' MBR is not a boot sector.\n", de->whole_name);
#endif
	}
	
	/*
	 * find partition type
	 */
	default_desc.sys_type[0] = PARTITION_UNUSED;
	for(i = 0; i < PARTITION_COUNT; ++i) {
		int	s_cyl_sec;
		int	e_cyl_sec;

		s_cyl_sec = la_to_u_2_byte(disk_mbr.partition[i].s_cyl_sec);
		e_cyl_sec = la_to_u_2_byte(disk_mbr.partition[i].e_cyl_sec);

            if(disk_mbr.partition[i].type != PARTITION_UNUSED) {
	        if(default_desc.sys_type[0] != PARTITION_UNUSED) {
#ifdef	USE_LIBSCHILY
		    comerrno(EX_BAD, "Boot image '%s' has multiple partitions.\n", de->whole_name);
#else
		    fprintf(stderr, "Boot image '%s' has multiple partitions.\n", de->whole_name);
		    exit(1);
#endif
		}
		default_desc.sys_type[0] = disk_mbr.partition[i].type;
		
		/*
		 * a few simple sanity warnings
		 */
		if(!not_bootable && disk_mbr.partition[i].status != PARTITION_ACTIVE) {
		    fprintf(stderr, "Warning: partition not marked active.\n");
		}
		if(MBR_CYLINDER(s_cyl_sec) != 0 ||
		    disk_mbr.partition[i].s_head != 1 ||
		    MBR_SECTOR(s_cyl_sec != 1)) {
	            fprintf(stderr, "Warning: partition does not start at 0/1/1.\n");
		}
		geosec = (MBR_CYLINDER(e_cyl_sec) + 1) *
		    (disk_mbr.partition[i].e_head + 1) *
		    MBR_SECTOR(e_cyl_sec);
		if(geosec != nsectors) {
		    fprintf(stderr, "Warning: image size does not match geometry (%d)\n",
		        geosec);
		}
#ifdef DEBUG_TORITO
		fprintf(stderr, "Partition start %u/%u/%u\n",
		    MBR_CYLINDER(s_cyl_sec),
		    disk_mbr.partition[i].s_head,
		    MBR_SECTOR(s_cyl_sec));
		fprintf(stderr, "Partition end %u/%u/%u\n",
		    MBR_CYLINDER(e_cyl_sec),
		    disk_mbr.partition[i].e_head,
		    MBR_SECTOR(e_cyl_sec));
#endif
	    }
	}
	if(default_desc.sys_type[0] == PARTITION_UNUSED) {
#ifdef	USE_LIBSCHILY
	    comerrno(EX_BAD, "Boot image '%s' has no partitions.\n", de->whole_name);
#else
	    fprintf(stderr, "Boot image '%s' has no partitions.\n", de->whole_name);
	    exit(1);
#endif
	}
#ifdef DEBUG_TORITO
	fprintf(stderr, "Partition type %u\n", default_desc.sys_type[0]);
#endif
	/*
	 * load single boot sector, in this case the MBR
	 */
	nsectors = 1;

    } else if(no_emul_boot) {
	/*
	 *  no emulation is a simple image boot of all the sectors in the boot image
	 */
	default_desc.boot_media[0] = EL_TORITO_MEDIA_NOEMUL;
    	fprintf(stderr,"No emulation\n");

    } else {
	/*
	 * choose size of emulated floppy based on boot image size 
	 */
	if (nsectors == 2880 ) 
	{
	    default_desc.boot_media[0] = EL_TORITO_MEDIA_144FLOP;
	    fprintf(stderr, "Emulating a 1.44 meg floppy\n");

	} else if (nsectors == 5760 ) {
	    default_desc.boot_media[0] = EL_TORITO_MEDIA_288FLOP;
	    fprintf(stderr,"Emulating a 2.88 meg floppy\n");

	} else if (nsectors == 2400 ) {
	    default_desc.boot_media[0] = EL_TORITO_MEDIA_12FLOP;
	    fprintf(stderr,"Emulating a 1.2 meg floppy\n");

	} else {
#ifdef	USE_LIBSCHILY
	    comerrno(EX_BAD, "Error - boot image '%s' is not the an allowable size.\n", de->whole_name);
#else
	    fprintf(stderr,"Error - boot image '%s' is not the an allowable size.\n", de->whole_name);
	    exit(1);
#endif
	}
	
	/*
	 * load single boot sector for floppies
	 */
	nsectors = 1;
    }
    
    /*
     * fill in boot image details
     */
#ifdef DEBUG_TORITO
    fprintf(stderr,"Boot %u sectors\n",nsectors);
    fprintf(stderr,"Extent of boot images is %d\n",get_733(de->isorec.extent));
#endif
    set_721(default_desc.nsect, (unsigned int) nsectors );
    set_731(default_desc.bootoff, 
	    (unsigned int) get_733(de->isorec.extent));
    
    /*
     * now write it to the virtual boot catalog
     */
    memcpy(de2->table, &valid_desc, 32);
    memcpy(de2->table + 32, &default_desc, 32);


    /*
     * If the user has asked for it, patch the boot image
     */
    if ( boot_info_table ) {
      int bootimage;
      unsigned int bi_checksum, total_len;
      static char csum_buffer[2048];
      int len;
      struct mkisofs_boot_info bi_table;

      bootimage = open(de->whole_name, O_RDWR | O_BINARY);
      if ( bootimage == -1 ) {
#ifdef	USE_LIBSCHILY
	comerr("Error opening boot image file '%s' for update.\n", de->whole_name);
#else
	fprintf(stderr,"Error opening boot image file '%s' for update.\n", de->whole_name);
	perror("");
	exit(1);
#endif
      }

      /* Compute checksum of boot image, sans 64 bytes */
      total_len = 0;  bi_checksum = 0;
      while ( (len = read(bootimage, csum_buffer, 2048)) > 0 ) {
	if ( total_len & 3 ) {
#ifdef	USE_LIBSCHILY
	  comerrno(EX_BAD, "Odd alignment at non-end-of-file in boot image '%s'.\n", de->whole_name);
#else
	  fprintf(stderr, "Odd alignment at non-end-of-file in boot image '%s'.\n", de->whole_name);
	  exit(1);
#endif
	}
	if ( total_len < 64 )
	  memset(csum_buffer, 0, 64-total_len);
	if ( len < 2048 )
	  memset(csum_buffer+len, 0, 2048-len);
	for ( i = 0 ; i < 2048 ; i += 4 )
	  bi_checksum += get_731(&csum_buffer[i]);
	total_len += len;
      }

      if ( total_len != de->size ) {
#ifdef	USE_LIBSCHILY
	comerrno(EX_BAD, "Boot image file '%s' changed underneath us!\n", de->whole_name);
#else
	fprintf(stderr, "Boot image file '%s' changed underneath us!\n", de->whole_name);
	exit(1);
#endif
      }

      /* End of file, set position to byte 8 */
      lseek(bootimage, 8, SEEK_SET);
      memset(&bi_table, 0, sizeof(bi_table));
      /* Is it always safe to assume PVD is at session_start+16? */
      set_731(bi_table.bi_pvd,    session_start+16);
      set_731(bi_table.bi_file,   de->starting_block);
      set_731(bi_table.bi_length, de->size);
      set_731(bi_table.bi_csum,   bi_checksum);
      
      write(bootimage, &bi_table, sizeof(bi_table));
      close(bootimage);
    }
} /* get_torito_desc(... */

/*
 * Function to write the EVD for the disc.
 */
static int FDECL1(tvd_write, FILE *, outfile)
{
  /*
   * check the boot image is not NULL
   */
  if(!boot_image)
  {
#ifdef	USE_LIBSCHILY
	comerrno(EX_BAD, "No boot image specified.\n");
#else
	fprintf(stderr,"No boot image specified.\n");
	exit(1);
#endif
  }

  /*
   * Next we write out the boot volume descriptor for the disc 
   */
  get_torito_desc(&gboot_desc);
  xfwrite(&gboot_desc, 1, SECTOR_SIZE, outfile);
  last_extent_written ++;
  return 0;
}

struct output_fragment torito_desc    = {NULL, oneblock_size, NULL,     tvd_write};