sys/boot/pc32/cdboot/cdboot.S

   1 /*
   2  * Copyright (c) 2001 John Baldwin
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms are freely
   6  * permitted provided that the above copyright notice and this
   7  * paragraph and the following disclaimer are duplicated in all
   8  * such forms.
   9  *
  10  * This software is provided "AS IS" and without any express or
  11  * implied warranties, including, without limitation, the implied
  12  * warranties of merchantability and fitness for a particular
  13  * purpose.
  14  *
  15  *
  16  * $FreeBSD: src/sys/boot/i386/cdboot/cdboot.s,v 1.9 2001/11/07 01:20:33 jhb Exp $
  17  * $DragonFly: src/sys/boot/pc32/cdboot/cdboot.S,v 1.8 2007/05/18 07:41:43 dillon Exp $
  18  */
  19
  20 /*
  21  * This program is a freestanding boot program to load an a.out binary
  22  * from a CD-ROM booted with no emulation mode as described by the El
  23  * Torito standard.  Due to broken BIOSen that do not load the desired
  24  * number of sectors, we try to fit this in as small a space as possible.
  25  *
  26  * Basically, we first create a set of boot arguments to pass to the loaded
  27  * binary.  Then we attempt to load /boot/loader from the CD we were booted
  28  * off of.
  29  */
  30
  31 #include "../bootasm.h"
  32
  33                 /*
  34                  * a.out header fields
  35                  */
  36                 .set AOUT_TEXT,0x04             # text segment size
  37                 .set AOUT_DATA,0x08             # data segment size
  38                 .set AOUT_BSS,0x0c              # zerod BSS size
  39                 .set AOUT_SYMBOLS,0x10          # symbol table
  40                 .set AOUT_ENTRY,0x14            # entry point
  41                 .set AOUT_HEADER,MEM_PAGE_SIZE  # size of the a.out header
  42
  43                 /*
  44                  * Flags for kargs->bootflags
  45                  */
  46                 .set KARGS_FLAGS_CD,0x1         # flag to indicate booting from
  47                                                 #  CD loader
  48                 /*
  49                  * Segment selectors.
  50                  */
  51                 .set SEL_SDATA,0x8              # Supervisor data
  52                 .set SEL_RDATA,0x10             # Real mode data
  53                 .set SEL_SCODE,0x18             # PM-32 code
  54                 .set SEL_SCODE16,0x20           # PM-16 code
  55
  56                 /*
  57                  * BTX constants
  58                  */
  59                 .set INT_SYS,0x30               # BTX syscall interrupt
  60
  61                 /*
  62                  * Constants for reading from the CD.
  63                  */
  64                 .set ERROR_TIMEOUT,0x80         # BIOS timeout on read
  65                 .set NUM_RETRIES,3              # Num times to retry
  66                 .set SECTOR_SIZE,0x800          # size of a sector
  67                 .set SECTOR_SHIFT,11            # number of place to shift
  68                 .set BUFFER_LEN,0x100           # number of sectors in buffer
  69                 .set MAX_READ,0x10000           # max we can read at a time
  70                 .set MAX_READ_SEC,MAX_READ >> SECTOR_SHIFT
  71                 .set MEM_READ_BUFFER,0x9000     # buffer to read from CD
  72                 .set MEM_VOLDESC,MEM_READ_BUFFER # volume descriptor
  73                 .set MEM_DIR,MEM_VOLDESC+SECTOR_SIZE # Lookup buffer
  74                 .set VOLDESC_LBA,0x10           # LBA of vol descriptor
  75                 .set VD_PRIMARY,1               # Primary VD
  76                 .set VD_END,255                 # VD Terminator
  77                 .set VD_ROOTDIR,156             # Offset of Root Dir Record
  78                 .set DIR_LEN,0                  # Offset of Dir Record length
  79                 .set DIR_EA_LEN,1               # Offset of EA length
  80                 .set DIR_EXTENT,2               # Offset of 64-bit LBA
  81                 .set DIR_SIZE,10                # Offset of 64-bit length
  82                 .set DIR_NAMELEN,32             # Offset of 8-bit name len
  83                 .set DIR_NAME,33                # Offset of dir name
  84
  85                 /*
  86                  * Program start.
  87                  *
  88                  * We expect to be loaded by the BIOS at 0x7c00 (standard
  89                  * boot loader entry point)
  90                  */
  91                 .code16
  92                 .globl start
  93                 .org 0x0, 0x0
  94
  95 start:          cld                             # string ops inc
  96                 xor %ax,%ax                     # zero %ax
  97                 mov %ax,%ss                     # setup the
  98                 mov $start,%sp                  #  stack
  99                 mov %ax,%ds                     # setup the
 100                 mov %ax,%es                     #  data segments
 101                 mov %dl,drive                   # Save BIOS boot device
 102                 mov $msg_welcome,%si            # %ds:(%si) -> welcome message
 103                 call putstr                     # display the welcome message
 104
 105                 /*
 106                  * Setup the arguments that the loader is expecting from
 107                  * boot[12]
 108                  */
 109                 mov $msg_bootinfo,%si           # %ds:(%si) -> boot args message
 110                 call putstr                     # display the message
 111                 mov $MEM_ARG,%bx                # %ds:(%bx) -> boot args
 112                 mov %bx,%di                     # %es:(%di) -> boot args
 113                 xor %eax,%eax                   # zero %eax
 114                 mov $(MEM_ARG_SIZE/4),%cx       # Size of arguments in 32-bit
 115                                                 #  dwords
 116                 rep                             # Clear the arguments
 117                 stosl                           #  to zero
 118                 mov drive,%dl                   # Store BIOS boot device
 119                 mov %dl,0x4(%bx)                #  in kargs->bootdev
 120                 or $KARGS_FLAGS_CD,0x8(%bx)     # kargs->bootflags |=
 121                                                 #  KARGS_FLAGS_CD
 122                 /*
 123                  * Load Volume Descriptor
 124                  */
 125                 mov $VOLDESC_LBA,%eax           # Set LBA of first VD
 126 load_vd:
 127                 mov $1,%dh                      # One sector
 128                 mov $MEM_VOLDESC,%ebx           # Destination
 129                 call read                       # Read it in
 130                 cmpb $VD_PRIMARY,(%bx)          # Primary VD?
 131                 je have_vd                      # Yes
 132                 inc %eax                        #  try next
 133                 cmpb $VD_END,(%bx)              # Last VD?
 134                 jne load_vd                     # No, read next
 135                 mov $msg_novd,%si               # No VD
 136                 jmp error                       # Halt
 137 have_vd:                                        # Have Primary VD
 138
 139                 /*
 140                  * Lookup the loader binary.
 141                  */
 142                 mov $loader_path,%si            # File to lookup
 143                 call lookup                     # Try to find it
 144
 145                 /*
 146                  * Load the binary into the buffer.  Due to real mode
 147                  * addressing limitations we have to read it in in 64k
 148                  * chunks.
 149                  */
 150                 mov DIR_SIZE(%bx),%eax          # Read file length
 151                 add $SECTOR_SIZE-1,%eax         # Convert length to sectors
 152                 shr $11,%eax
 153                 cmp $BUFFER_LEN,%eax
 154                 jbe load_sizeok
 155                 mov $msg_load2big,%si           # Error message
 156                 call error
 157 load_sizeok:    movzbw %al,%cx                  # Num sectors to read
 158                 mov DIR_EXTENT(%bx),%eax        # Load extent
 159                 xor %edx,%edx
 160                 mov DIR_EA_LEN(%bx),%dl
 161                 add %edx,%eax                   # Skip extended
 162                 mov $MEM_READ_BUFFER,%ebx       # Read into the buffer
 163 load_loop:      mov %cl,%dh
 164                 cmp $MAX_READ_SEC,%cl           # Truncate to max read size
 165                 jbe load_notrunc
 166                 mov $MAX_READ_SEC,%dh
 167 load_notrunc:   sub %dh,%cl                     # Update count
 168                 call read                       # Read it in
 169                 add $MAX_READ_SEC,%eax          # Update LBA
 170                 add $MAX_READ,%ebx              # Update dest addr
 171                 jcxz load_done                  # Done?
 172                 jmp load_loop                   # Keep going
 173 load_done:
 174                 /*
 175                  * Turn on the A20 address line.
 176                  */
 177                 call seta20                     # Turn A20 on
 178
 179                 /*
 180                  * Relocate the loader and BTX using a very lazy
 181                  * protected mode.
 182                  */
 183                 mov $msg_relocate,%si           # Display the
 184                 call putstr                     #  relocation message
 185                 mov MEM_READ_BUFFER+AOUT_ENTRY,%edi # %edi is the destination
 186                 mov $(MEM_READ_BUFFER+AOUT_HEADER),%esi # %esi is
 187                                                 #  the start of the text
 188                                                 #  segment
 189                 mov MEM_READ_BUFFER+AOUT_TEXT,%ecx # %ecx = length of the text
 190                                                 #  segment
 191                 push %edi                       # Save entry point for later
 192                 lgdt gdtdesc                    # setup our own gdt
 193                 cli                             # turn off interrupts
 194                 mov %cr0,%eax                   # Turn on
 195                 or $0x1,%al                     #  protected
 196                 mov %eax,%cr0                   #  mode
 197                 ljmp $SEL_SCODE,$pm_start       # long jump to clear the
 198                                                 #  instruction pre-fetch queue
 199                 .code32
 200 pm_start:       mov $SEL_SDATA,%ax              # Initialize
 201                 mov %ax,%ds                     #  %ds and
 202                 mov %ax,%es                     #  %es to a flat selector
 203                 rep                             # Relocate the
 204                 movsb                           #  text segment
 205                 add $(MEM_PAGE_SIZE - 1),%edi   # pad %edi out to a new page
 206                 and $~(MEM_PAGE_SIZE - 1),%edi #  for the data segment
 207                 mov MEM_READ_BUFFER+AOUT_DATA,%ecx # size of the data segment
 208                 rep                             # Relocate the
 209                 movsb                           #  data segment
 210                 mov MEM_READ_BUFFER+AOUT_BSS,%ecx # size of the bss
 211                 xor %eax,%eax                   # zero %eax
 212                 add $3,%cl                      # round %ecx up to
 213                 shr $2,%ecx                     #  a multiple of 4
 214                 rep                             # zero the
 215                 stosl                           #  bss
 216                 mov MEM_READ_BUFFER+AOUT_ENTRY,%esi # %esi -> relocated loader
 217                 add $MEM_BTX_LDR_OFF,%esi       # %esi -> BTX in the loader
 218                 mov $MEM_BTX_ORG,%edi   # %edi -> where BTX needs to go
 219                 movzwl 0xa(%esi),%ecx           # %ecx -> length of BTX
 220                 rep                             # Relocate
 221                 movsb                           #  BTX
 222                 ljmp $SEL_SCODE16,$pm_16        # Jump to 16-bit PM
 223                 .code16
 224 pm_16:          mov $SEL_RDATA,%ax              # Initialize
 225                 mov %ax,%ds                     #  %ds and
 226                 mov %ax,%es                     #  %es to a real mode selector
 227                 mov %cr0,%eax                   # Turn off
 228                 and $~0x1,%al                   #  protected
 229                 mov %eax,%cr0                   #  mode
 230                 ljmp $0,$pm_end                 # Long jump to clear the
 231                                                 #  instruction pre-fetch queue
 232 pm_end:         sti                             # Turn interrupts back on now
 233
 234                 /*
 235                  * Copy the BTX client to MEM_BTX_USR.
 236                  */
 237                 xor %ax,%ax                     # zero %ax and set
 238                 mov %ax,%ds                     #  %ds and %es
 239                 mov %ax,%es                     #  to segment 0
 240                 mov $MEM_BTX_USR,%di            # Prepare to relocate
 241                 mov $btx_client,%si             #  the simple btx client
 242                 mov $(btx_client_end-btx_client),%cx # length of btx client
 243                 rep                             # Relocate the
 244                 movsb                           #  simple BTX client
 245
 246                 /*
 247                  * Copy the boot[12] args to where the BTX client
 248                  * can see them.
 249                  */
 250                 mov $MEM_ARG,%si                # where the args are at now
 251                 mov $MEM_BTX_USR_ARG,%di        # where the args are moving to
 252                 mov $(MEM_ARG_SIZE/4),%cx       # size of the arguments in longs
 253                 rep                             # Relocate
 254                 movsl                           #  the words
 255
 256                 /*
 257                  * Save the entry point so the client can get to it
 258                  * later on
 259                  */
 260                 pop %eax                        # Restore saved entry point
 261                 stosl                           #  and add it to the end of
 262                                                 #  the arguments
 263                 /*
 264                  * Now we just start up BTX and let it do the rest
 265                  */
 266                 mov $msg_jump,%si               # Display the
 267                 call putstr                     #  jump message
 268                 ljmp $0,$MEM_BTX_ENTRY          # Jump to the BTX entry point
 269
 270                 /*
 271                  * Lookup the file in the path at [SI] from the root
 272                  * directory.
 273                  *
 274                  * Trashes: All but BX
 275                  * Returns: BX = pointer to record
 276                  */
 277 lookup:         mov $VD_ROOTDIR+MEM_VOLDESC,%bx # Root directory record
 278                 push %si
 279                 mov $msg_lookup,%si             # Display lookup message
 280                 call putstr
 281                 pop %si
 282                 push %si
 283                 call putstr
 284                 mov $msg_lookup2,%si
 285                 call putstr
 286                 pop %si
 287 lookup_dir:     lodsb                           # Get first char of path
 288                 cmp $0,%al                      # Are we done?
 289                 je lookup_done                  # Yes
 290                 cmp $'/',%al                    # Skip path separator.
 291                 je lookup_dir
 292                 dec %si                         # Undo lodsb side effect
 293                 call find_file                  # Lookup first path item
 294                 jnc lookup_dir                  # Try next component
 295                 mov $msg_lookupfail,%si         # Not found.
 296                 jmp error
 297 lookup_done:    mov $msg_lookupok,%si           # Success message
 298                 call putstr
 299                 ret
 300
 301                 /*
 302                  * Lookup file at [SI] in directory whose record is at [BX].
 303                  *
 304                  * Trashes: All but returns
 305                  *
 306                  * Returns:     CF = 0 (success)
 307                  *              BX = pointer to record,
 308                  *              SX = next path item
 309                  *              CF = 1 (not found)
 310                  *              SI = preserved
 311                  */
 312 find_file:      mov DIR_EXTENT(%bx),%eax        # Load extent
 313                 xor %edx,%edx
 314                 mov DIR_EA_LEN(%bx),%dl
 315                 add %edx,%eax                   # Skip extended attributes
 316                 mov %eax,rec_lba                # Save LBA
 317                 mov DIR_SIZE(%bx),%eax          # Save size
 318                 mov %eax,rec_size
 319                 xor %cl,%cl                     # Zero length
 320                 push %si                        # Save
 321 ff.namelen:     inc %cl                         # Update length
 322                 lodsb                           # Read char
 323                 cmp $0,%al                      # Nul?
 324                 je ff.namedone                  # Yes
 325                 cmp $'/',%al                    # Path separator?
 326                 jnz ff.namelen                  # No, keep going
 327 ff.namedone:    dec %cl                         # Adjust length and save
 328                 mov %cl,name_len
 329                 pop %si                         # Restore
 330 ff.load:        mov rec_lba,%eax                # Load LBA
 331                 mov $MEM_DIR,%ebx               # Address buffer
 332                 mov $1,%dh                      # One sector
 333                 call read                       # Read directory block
 334                 incl rec_lba                    # Update LBA to next block
 335 ff.scan:        mov %ebx,%edx                   # Check for EOF
 336                 sub $MEM_DIR,%edx
 337                 cmp %edx,rec_size
 338                 ja ff.scan.1
 339                 stc                             # EOF reached
 340                 ret
 341 ff.scan.1:      cmpb $0,DIR_LEN(%bx)            # Last record in block?
 342                 je ff.nextblock
 343                 push %si                        # Save
 344                 movzbw DIR_NAMELEN(%bx),%si     # Find end of string
 345 ff.checkver:    cmpb $'0',DIR_NAME-1(%bx,%si)   # Less than '0'?
 346                 jb ff.checkver.1
 347                 cmpb $'9',DIR_NAME-1(%bx,%si)   # Greater than '9'?
 348                 ja ff.checkver.1
 349                 dec %si                         # Next char
 350                 jnz ff.checkver
 351                 jmp ff.checklen                 # All numbers in name, so
 352                                                 #  no version
 353 ff.checkver.1:  movzbw DIR_NAMELEN(%bx),%cx
 354                 cmp %cx,%si                     # Did we find any digits?
 355                 je ff.checkdot                  # No
 356                 cmpb $';',DIR_NAME-1(%bx,%si)   # Check for semicolon
 357                 jne ff.checkver.2
 358                 dec %si                         # Skip semicolon
 359                 mov %si,%cx
 360                 mov %cl,DIR_NAMELEN(%bx)        # Adjust length
 361                 jmp ff.checkdot
 362 ff.checkver.2:  mov %cx,%si                     # Restore %si to end of string
 363 ff.checkdot:    cmpb $'.',DIR_NAME-1(%bx,%si)   # Trailing dot?
 364                 jne ff.checklen                 # No
 365                 decb DIR_NAMELEN(%bx)           # Adjust length
 366 ff.checklen:    pop %si                         # Restore
 367                 movzbw name_len,%cx             # Load length of name
 368                 cmp %cl,DIR_NAMELEN(%bx)        # Does length match?
 369                 je ff.checkname                 # Yes, check name
 370 ff.nextrec:     add DIR_LEN(%bx),%bl            # Next record
 371                 adc $0,%bh
 372                 jmp ff.scan
 373 ff.nextblock:   subl $SECTOR_SIZE,rec_size      # Adjust size
 374                 jnc ff.load                     # If subtract ok, keep going
 375                 ret                             # End of file, so not found
 376 ff.checkname:   lea DIR_NAME(%bx),%di           # Address name in record
 377                 push %si                        # Save
 378                 repe cmpsb                      # Compare name
 379                 jcxz ff.match                   # We have a winner!
 380                 pop %si                         # Restore
 381                 jmp ff.nextrec                  # Keep looking.
 382 ff.match:       add $2,%sp                      # Discard saved %si
 383                 clc                             # Clear carry
 384                 ret
 385
 386                 /*
 387                  * Load DH sectors starting at LBA EAX into [EBX].  No
 388                  * registers are destroyed.  Don't trust the BIOS, especially
 389                  * with regards to the msb 16 bits of our registers.
 390                  */
 391 read:           pushal                          # dont screw around
 392                 mov %eax,edd_lba                # LBA to read from
 393                 mov %ebx,%eax                   # Convert address
 394                 shr $4,%eax                     #  to segment
 395                 mov %ax,edd_addr+0x2            #  and store
 396 read.retry:     call twiddle                    # Entertain the user
 397                 push %dx                        # Save
 398                 mov $edd_packet,%si             # Address Packet
 399                 mov %dh,edd_len                 # Set length
 400                 mov drive,%dl                   # BIOS Device
 401                 mov $0x42,%ah                   # BIOS: Extended Read
 402                 int $0x13                       # Call BIOS
 403                 pop %dx                         # Restore
 404                 jc read.fail                    # Worked?
 405                 popal
 406                 ret                             # Return
 407 read.fail:      cmp $ERROR_TIMEOUT,%ah          # Timeout?
 408                 je read.retry                   # Yes, Retry.
 409 read.error:     mov %ah,%al                     # Save error
 410                 mov $hex_error,%di              # Format it
 411                 call hex8                       #  as hex
 412                 mov $msg_badread,%si            # Display Read error message
 413
 414                 /*
 415                  * Display error message at [SI] and halt.
 416                  */
 417 error:          call putstr                     # Display message
 418 halt:           hlt
 419                 jmp halt                        # Spin
 420
 421                 /*
 422                  * Display a null-terminated string.
 423                  *
 424                  * Trashes: AX, SI
 425                  */
 426 putstr:
 427 putstr.load:    lodsb                           # load %al from %ds:(%si)
 428                 test %al,%al                    # stop at null
 429                 jnz putstr.putc                 # if the char != null, output it
 430                 ret                             # return when null is hit
 431 putstr.putc:    call putc                       # output char
 432                 jmp putstr.load                 # next char
 433
 434                 /*
 435                  * Display a single char(%al).  Don't trust the bios to save
 436                  * our regs.
 437                  */
 438 putc:           pushal
 439                 mov $0x7,%bx                    # attribute for output
 440                 mov $0xe,%ah                    # BIOS: put_char
 441                 int $0x10                       # call BIOS, print char in %al
 442                 popal
 443                 ret                             # Return to caller
 444
 445                 /*
 446                  * Output the "twiddle"
 447                  */
 448 twiddle:        push %ax                        # Save
 449                 push %bx                        # Save
 450                 mov twiddle_index,%al           # Load index
 451                 mov $twiddle_chars,%bx          # Address table
 452                 inc %al                         # Next
 453                 and $3,%al                      #  char
 454                 mov %al,twiddle_index           # Save index for next call
 455                 xlat                            # Get char
 456                 call putc                       # Output it
 457                 mov $8,%al                      # Backspace
 458                 call putc                       # Output it
 459                 pop %bx                         # Restore
 460                 pop %ax                         # Restore
 461                 ret
 462
 463                 /*
 464                  * Enable A20. Put upper limit on amount of time we wait for the
 465                  * keyboard controller to get ready (65K x ISA access time). If
 466                  * we wait more than that amount it's likely that the hardware
 467                  * is legacy-free and simply doesn't have keyboard controller
 468                  * and don't need enabling A20 at all.
 469                  */
 470 seta20:         cli                             # Disable interrupts
 471                 xor %cx,%cx                     # Clear
 472 seta20.1:       inc %cx                         # Increment, overflow?
 473                 jz seta20.3                     # Yes
 474                 in $0x64,%al                    # Get status
 475                 test $0x2,%al                   # Busy?
 476                 jnz seta20.1                    # Yes
 477                 mov $0xd1,%al                   # Command: Write
 478                 out %al,$0x64                   #  output port
 479 seta20.2:       in $0x64,%al                    # Get status
 480                 test $0x2,%al                   # Busy?
 481                 jnz seta20.2                    # Yes
 482                 mov $0xdf,%al                   # Enable
 483                 out %al,$0x60                   #  A20
 484 seta20.3:       sti                             # Enable interrupts
 485                 ret                             # To caller
 486
 487                 /*
 488                  * Convert AL to hex, saving the result to [EDI].
 489                  */
 490 hex8:           pushl %eax                      # Save
 491                 shrb $0x4,%al                   # Do upper
 492                 call hex8.1                     #  4
 493                 popl %eax                       # Restore
 494 hex8.1:         andb $0xf,%al                   # Get lower 4
 495                 cmpb $0xa,%al                   # Convert
 496                 sbbb $0x69,%al                  #  to hex
 497                 das                             #  digit
 498                 orb $0x20,%al                   # To lower case
 499                 stosb                           # Save char
 500                 ret                             # (Recursive)
 501
 502                 /*
 503                  * BTX client to start btxldr
 504                  */
 505                 .code32
 506 btx_client:     mov $(MEM_BTX_USR_ARG-MEM_BTX_USR+MEM_ARG_SIZE-4), %esi
 507                                                 # %ds:(%esi) -> end
 508                                                 #  of boot[12] args
 509                 mov $(MEM_ARG_SIZE/4),%ecx      # Number of words to push
 510                 std                             # Go backwards
 511 push_arg:       lodsl                           # Read argument
 512                 push %eax                       # Push it onto the stack
 513                 loop push_arg                   # Push all of the arguments
 514                 cld                             # In case anyone depends on this
 515                 pushl MEM_BTX_USR_ARG-MEM_BTX_USR+MEM_ARG_SIZE # Entry point of
 516                                                 #  the loader
 517                 push %eax                       # Emulate a near call
 518                 mov $0x1,%eax                   # "exec" system call
 519                 int $INT_SYS                    # BTX system call
 520 btx_client_end:
 521                 .code16
 522
 523                 .p2align 4
 524
 525                 /*
 526                  * Global descriptor table.
 527                  */
 528 gdt:            .word 0x0,0x0,0x0,0x0           # Null entry
 529                 .word 0xffff,0x0,0x9200,0xcf    # SEL_SDATA
 530                 .word 0xffff,0x0,0x9200,0x0     # SEL_RDATA
 531                 .word 0xffff,0x0,0x9a00,0xcf    # SEL_SCODE (32-bit)
 532                 .word 0xffff,0x0,0x9a00,0x8f    # SEL_SCODE16 (16-bit)
 533 gdt.1:
 534
 535                 /*
 536                  * Pseudo-descriptors.
 537                  */
 538 gdtdesc:        .word gdt.1-gdt-1               # Limit
 539                 .long gdt                       # Base
 540
 541                 /*
 542                  * EDD Packet
 543                  */
 544 edd_packet:     .byte 0x10                      # Length
 545                 .byte 0                         # Reserved
 546 edd_len:        .byte 0x0                       # Num to read
 547                 .byte 0                         # Reserved
 548 edd_addr:       .word 0x0,0x0                   # Seg:Off
 549 edd_lba:        .quad 0x0                       # LBA
 550
 551 drive:          .byte 0
 552
 553                 /*
 554                  * State for searching dir
 555                  */
 556 rec_lba:        .long 0x0                       # LBA (adjusted for EA)
 557 rec_size:       .long 0x0                       # File size
 558 name_len:       .byte 0x0                       # Length of current name
 559
 560 twiddle_index:  .byte 0x0
 561
 562 msg_welcome:    .asciz  "CD Loader 1.01\r\n\n"
 563 msg_bootinfo:   .asciz  "Building the boot loader arguments\r\n"
 564 msg_relocate:   .asciz  "Relocating the loader and the BTX\r\n"
 565 msg_jump:       .asciz  "Starting the BTX loader\r\n"
 566 msg_badread:    .ascii  "Read Error: 0x"
 567 hex_error:      .ascii  "00\r\n"
 568 msg_novd:       .asciz  "Could not find Primary Volume Descriptor\r\n"
 569 msg_lookup:     .asciz  "Looking up "
 570 msg_lookup2:    .asciz  "... "
 571 msg_lookupok:   .asciz  "Found\r\n"
 572 msg_lookupfail: .asciz  "File not found\r\n"
 573 msg_load2big:   .asciz  "File too big\r\n"
 574 loader_path:    .asciz  "/BOOT/LOADER"
 575 twiddle_chars:  .ascii  "|/-\\"
 576