dosutil/eltorito.asm

   1
   2 ;-----------------------------------------------------------------------------
   3 ; ElTorito.asm
   4 ;
   5 ; El Torito Bootable CD-ROM driver which does not reset the CD-ROM drive upon
   6 ; loading, but instead accesses the drive through BIOS system calls
   7 ;
   8 ; MIT License
   9 ;
  10 ; (c) 2000 by Gary Tong
  11 ; (c) 2001-2009 by Bart Lagerweij
  12 ;
  13 ; Permission is hereby granted, free of charge, to any person obtaining a copy
  14 ; of this software and associated documentation files (the "Software"), to deal
  15 ; in the Software without restriction, including without limitation the rights
  16 ; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  17 ; copies of the Software, and to permit persons to whom the Software is
  18 ; furnished to do so, subject to the following conditions:
  19 ;
  20 ; The above copyright notice and this permission notice shall be included in
  21 ; all copies or substantial portions of the Software.
  22 ;
  23 ; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  24 ; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  25 ; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  26 ; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  27 ; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  28 ; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  29 ; THE SOFTWARE.
  30 ;
  31 ;-----------------------------------------------------------------------------
  32
  33 ; To assemble and link, use these commands with NASM 2.x:
  34 ;   nasm -Ox -f bin -o eltorito.sys eltorito.asm
  35
  36 ; To enable Trace markers uncomment the line below
  37 ; DEBUG_TRACERS=1
  38
  39 ; To enable debug info uncomment the line below
  40 ; DEBUG=1
  41
  42 %ifdef DEBUG_TRACERS
  43  %macro TRACER  1
  44         call debug_tracer
  45         db %1
  46  %endmacro
  47 %else
  48  %macro TRACER  1
  49  %endmacro
  50 %endif  ; DEBUG_TRACERS
  51
  52 %define Ver     '1.5'
  53 %define CR      0DH, 0Ah
  54 RPolyH          equ     0EDB8h
  55 RPolyL          equ     08320h
  56
  57                 section .text align=16
  58                 org     0
  59
  60 ;=============================================================================
  61
  62 Cdrom:
  63
  64 NextDriver      dd      -1                      ;-+
  65 Attributes      dw      0C800h                  ; |
  66 Pointers        dw      Strategy                ; |
  67                 dw      Commands                ; |   MSCDEX requires this
  68 DeviceName      db      'ELTORITO'              ; |  data in these locations
  69                 dw      0                       ; |
  70 DriveLetter     db      0                       ; |
  71 NumUnitsSupp    db      1                       ;-+
  72
  73 DriverName      db      'El-Torito CD-ROM Device Driver',0
  74                 align 4, db 0
  75 ReqHdrLoc       dd      0
  76 XferAddr        dd      0
  77 Checksum        dd      -1
  78 DriveNumber     db      0
  79 ReadBytes       db      0                       ;0 --> 2048 bytes/sector
  80                                                 ;1 --> 1024 bytes/sector
  81                                                 ;2 -->  512 bytes/sector
  82
  83 Routines        dw      Init            ;Init           ;0
  84                 dw      Unsupported     ;MediaCheck     ;1
  85                 dw      Unsupported     ;BuildBPB       ;2
  86                 dw      IoctlInput      ;IoctlInput     ;3
  87                 dw      Unsupported     ;Input          ;4
  88                 dw      Unsupported     ;NonDesInput    ;5
  89                 dw      Unsupported     ;InputStatus    ;6
  90                 dw      Unsupported     ;InputFlush     ;7
  91                 dw      Unsupported     ;Output         ;8
  92                 dw      Unsupported     ;OutputVerify   ;9
  93                 dw      Unsupported     ;OutputStatus   ;10
  94                 dw      Unsupported     ;OutputFlush    ;11
  95                 dw      IoctlOutput     ;IoctlOutput    ;12
  96                 dw      DoNothing       ;DeviceOpen     ;13
  97                 dw      DoNothing       ;DeviceClose    ;14
  98                 dw      ReadL           ;ReadL          ;128
  99
 100 IoctlICtrl      dw      Raddr           ;Raddr          ;0
 101                 dw      Unsupported     ;LocHead        ;1
 102                 dw      Unsupported     ;(Reserved)     ;2
 103                 dw      Unsupported     ;ErrStat        ;3
 104                 dw      Unsupported     ;AudInfo        ;4
 105                 dw      DrvBytes                ;DrvBytes       ;5
 106                 dw      DevStat         ;DevStat        ;6
 107                 dw      SectSize                ;SectSize       ;7
 108                 dw      VolSize         ;VolSize        ;8
 109                 dw      MedChng         ;MedChng        ;9
 110
 111 SpecPkt         times   19      db      0       ; offset 77h in 1.4
 112                 times   13      db      0       ; unknown extra 00s in 1.4
 113
 114 Greeting        db      'El-Torito Bootable CD-ROM Driver for Dos v',Ver,', http://www.nu2.nu/eltorito/',CR
 115                 db      '  (c) 2000 by Gary Tong',CR
 116                 db      '  (c) 2001-2002 by Bart Lagerweij',CR,0
 117 DblSpace        db      '  ',0
 118
 119 ;=============================================================================
 120
 121 Strategy:
 122
 123                 mov     word [cs:ReqHdrLoc],bx
 124                 mov     word [cs:ReqHdrLoc+2],es
 125                 retf
 126
 127
 128 ;=============================================================================
 129
 130 Commands:
 131
 132                 push    ax
 133                 push    bx
 134                 push    cx
 135                 push    dx
 136                 push    si
 137                 push    di
 138                 push    bp
 139 ;               pushad
 140                 push    ds
 141                 push    es
 142                 TRACER 'C'
 143
 144                 cld                             ;Clear direction
 145                 sti                             ;Enable interrupts
 146
 147                 mov     ax, cs                  ;ds=cs
 148                 mov     ds, ax
 149
 150                 les     bx,[ReqHdrLoc]  ;seg:offset ptr into es:bx
 151                 xor     ax,ax
 152                 mov     al,[es:bx+2]            ;Get Command code
 153 %ifdef DEBUG
 154                 call    print_hex8
 155 %endif
 156                 cmp     al,15
 157                 jb      Mult2                   ;If 0-14
 158                 cmp     al,128
 159                 jb      UnknownCmd              ;If 15-127
 160                 cmp     al,129
 161                 jb      ShiftDown               ;If 128
 162 UnknownCmd:     mov     al,121                  ;8 = Unsupported (Reserved)
 163 ShiftDown:      sub     al,113                  ;128 --> 15, 121 --> 8
 164 Mult2:          shl     al,1                    ;Convert into offset (*2)
 165                 mov     di,Routines
 166                 add     di,ax
 167                 call    word [di]               ;Execute desired command
 168                 or      ax,100h                 ;Set Return Status's Done bit
 169                 lds     bx,[ReqHdrLoc]          ;seg:offset ptr into ds:bx
 170                 mov     [bx+3],ax               ;Save Status
 171
 172 %ifdef DEBUG
 173                 cmp     byte [cs:buffer+2048], 96h
 174                 je      buffer_ok
 175                 mov     al, '!'
 176                 call    print_char
 177                 jmp     $
 178 buffer_ok:
 179 %endif
 180
 181                 TRACER 'c'
 182                 pop     es
 183                 pop     ds
 184 ;               popad
 185                 pop     bp
 186                 pop     di
 187                 pop     si
 188                 pop     dx
 189                 pop     cx
 190                 pop     bx
 191                 pop     ax
 192                 retf
 193
 194
 195 ;=============================================================================
 196
 197 Unsupported:                    ;Unsupported Command
 198
 199                 mov     ax,8003h                ;Set Status Error bit,
 200                 TRACER 'U'
 201                 TRACER 'C'
 202                 retn                            ;   Error 3 = Unknown Command
 203
 204
 205 ;=============================================================================
 206
 207 IoctlInput:                     ;IOCTL Input Routine
 208
 209                 mov     di,[es:bx+14]           ;es:bx --> Request Header
 210                 mov     es,[es:bx+16]           ;Get Xfer Address into es:di
 211                 xor     ax,ax                   ;Get Control Block Code
 212                 mov     al,[es:di]
 213 %ifdef DEBUG
 214         TRACER 'I'
 215         TRACER 'O'
 216         call    print_hex8
 217 %endif
 218                 cmp     al,10
 219                 jb      UnkIoctlI               ;If 0-9
 220                 mov     al,2                    ;Map to Unsupported
 221 UnkIoctlI:      shl     al,1                    ;Convert into offset (*2)
 222                 mov     si,IoctlICtrl
 223                 add     si,ax
 224                 call    word [si]               ;Execute desired command
 225                 retn
 226
 227
 228 ;=============================================================================
 229
 230 Raddr:                  ;Return Device Header Address
 231
 232                 TRACER 'A'
 233                 mov     word [es:di+1],0
 234                 mov     [es:di+3],cs
 235                 xor     ax, ax                  ;Set Return Status = success
 236                 TRACER 'a'
 237                 retn
 238
 239
 240 ;=============================================================================
 241
 242 DrvBytes:                       ;Read Drive Bytes
 243
 244                 TRACER 'B'
 245                 push    di                      ;Save original Xfer Addr
 246                 add     di,2                    ;Point to 1st dest byte
 247                 mov     si,Greeting     ;Point to Greeting
 248 DrvB:           movsb                           ;Copy over a byte
 249                 cmp     byte [si],13    ;Is next char a CR?
 250                 jne     DrvB                    ;Loop if not
 251
 252                 sub     di,2                    ;Get #bytes copied into ax
 253                 mov     ax,di
 254                 pop     di                      ;Retrieve original Xfer Addr
 255                 sub     ax,di
 256                 mov     byte [es:di+1],al       ;and save it
 257                 mov     ax,0                    ;Set Return Status = success
 258                 TRACER 'b'
 259                 retn
 260
 261
 262 ;=============================================================================
 263
 264 DevStat:                        ;Return Device Status
 265
 266                 TRACER 'D'
 267                 mov     word [es:di+1],202h     ;Door closed
 268                 mov     word [es:di+3],0        ;Door unlocked
 269                                                 ;Supports only cooked reading
 270                                                 ;Read only
 271                                                 ;Data read only
 272                                                 ;No interleaving
 273                                                 ;No prefetching
 274                                                 ;No audio channel manipulation
 275                                                 ;Supports both HSG and Redbook
 276                                                 ;  addressing modes
 277
 278                 xor     ax, ax                  ;Set Return Status = success
 279                 TRACER 'd'
 280                 retn
 281
 282
 283 ;=============================================================================
 284
 285 SectSize:                       ;Return Sector Size
 286
 287                 TRACER 'S'
 288                 mov     word [es:di+2],2048
 289                 mov     ax,0                    ;Set Return Status = success
 290                 TRACER 's'
 291                 retn
 292
 293
 294 ;=============================================================================
 295
 296 VolSize:                        ;Return Volume Size
 297
 298                 TRACER 'V'
 299                 call    PriVolDesc              ;Get and Check Primary Volume
 300                                                 ;  Descriptor
 301                 mov     ax,800Fh                ;Assume Invalid Disk Change
 302                 jc      VolExit                 ;If Read Failure
 303
 304                 mov     ax,word [Buffer+80]     ;Read Successful
 305                 mov     word [es:di+1],ax       ;Copy over Volume Size
 306                 mov     ax,word [Buffer+82]
 307                 mov     word [es:di+3],ax
 308                 mov     ax,0                    ;Set Return Status = success
 309 VolExit:
 310                 TRACER 'v'
 311                 retn
 312
 313
 314 ;=============================================================================
 315
 316 MedChng:                        ;Return Media Changed Status
 317
 318                 TRACER 'M'
 319                 call    PriVolDesc              ;Get and Check Primary Volume
 320                                                 ;  Descriptor
 321                 mov     byte [es:di+1],-1       ;Assume Media Changed
 322                 mov     ax,800Fh                ;  and Invalid Disk Change
 323                 jc      MedExit                 ;If Media Changed or Bad
 324
 325                 mov     byte [es:di+1],1        ;Media has not changed
 326                 mov     ax,0                    ;Set Return Status = success
 327 MedExit:
 328                 TRACER 'm'
 329                 retn
 330
 331
 332 ;=============================================================================
 333
 334 PriVolDesc:                     ;Get and Check Primary Volume
 335                                                 ;  Descriptor
 336                 TRACER 'P'
 337                 mov     ax,cs                   ;Set ds:si --> SpecPkt
 338                 mov     ds,ax
 339
 340                 mov     cx, 5
 341 PriVolAgain:
 342                 mov     byte [SpecPkt],16       ;SpecPkt Size
 343                 mov     byte [SpecPkt+1],0      ;Reserved
 344                 mov     word [SpecPkt+2],1      ;Transfer one 2048-byte sector
 345                 push    cx
 346                 mov     cl,byte [ReadBytes]     ;Multiply by 4 if reading 512
 347                 shl     word [SpecPkt+2],cl     ;  bytes at a time
 348                 pop     cx
 349                 mov     word [SpecPkt+6],cs     ;Into our Buffer
 350                 mov     word [SpecPkt+4], Buffer
 351                 mov     word [SpecPkt+8],16     ;From CD Sector 16
 352                 mov     word [SpecPkt+10],0
 353                 mov     word [SpecPkt+12],0
 354                 mov     word [SpecPkt+14],0
 355
 356                 mov     si, SpecPkt
 357                 mov     dl, [DriveNumber]
 358                 mov     ah, 42h                 ;Extended Read
 359                 int     13h
 360                 jnc     PriVolPass              ;If success
 361
 362 ;               TRACER '1'
 363                 ; read error
 364                 loop    PriVolAgain
 365
 366                 TRACER '2'
 367                 ; read retries exhausted
 368                 ; flow into below
 369                 jmp     PriReadErr
 370
 371 PriVolPass:
 372                 mov     si,Buffer       ;Point input to Buffer
 373                 mov     ax,-1                   ;Init Checksum registers
 374                 mov     bx,ax                   ;  bx,ax = 0FFFFFFFFh
 375                 jc      PriNew                  ;If Read Failure
 376
 377                 push    di                      ;Read Successful,
 378                                                 ;  so Calculate Checksum
 379                 mov     di,1024                 ;Init Word counter
 380 PriWord:        mov     dx,[cs:si]              ;Grab next word from buffer
 381                 mov     cx,16                   ;Init bit counter
 382 PriBit:         shr     dx,1                    ;Shift everything right 1 bit
 383                 rcr     bx,1
 384                 rcr     ax,1
 385                 jnc     NoMult                  ;If a zero shifted out
 386
 387                 xor     bx,RPolyH               ;A one shifted out, so XOR
 388                 xor     ax,RPolyL               ;  Checksum with RPoly
 389 NoMult:
 390                 loop    PriBit
 391
 392                 add     si,2                    ;Inc Word Pointer
 393                 dec     di
 394                 ja      PriWord
 395                 TRACER '3'
 396
 397                 pop     di                      ;Checksum calculation complete
 398                 cmp     bx,[Checksum+2]         ;Has Checksum changed?
 399                 jne     PriNew                  ;If Checksum Changed
 400
 401                 cmp     ax,[Checksum]
 402                 jne     PriNew                  ;If Checksum Changed
 403
 404                 clc                             ;Checksum not changed, CF=0
 405                 mov     ax,0                    ;Status = success
 406                 jmp     PriOld
 407
 408 PriReadErr:
 409                 mov     WORD [Checksum+2],bx            ;Save New Checksum
 410                 mov     [Checksum],ax           ;  or 0FFFFFFFFh if bad read
 411                 stc                             ;Checksum change, CF=1
 412                 mov     ax, 800bh               ;Status = read fault
 413                 jmp     PriOld
 414
 415 PriNew:         mov     WORD [Checksum+2],bx            ;Save New Checksum
 416                 mov     [Checksum],ax           ;  or 0FFFFFFFFh if bad read
 417                 stc                             ;Checksum Changed, CF=1
 418                 mov     ax,800Fh                ;Status = Invalid Media Change
 419 PriOld:
 420                 TRACER 'p'
 421                 retn
 422
 423
 424 ;=============================================================================
 425
 426 IoctlOutput:                    ;IOCTL Output Routine
 427
 428                 TRACER 'O'
 429                 mov     di,[es:bx+14]           ;es:bx --> Request Header
 430                 mov     es,[es:bx+16]           ;Get Xfer Address into es:di
 431                 xor     ax,ax                   ;Get Control Block Code
 432                 mov     al,[es:di]
 433                 cmp     al,2
 434                 jne     UnkIoctlO               ;If not 2 (ResetDrv)
 435                 call    DoNothing               ;Reset Drive
 436                 jmp     IoctlODone
 437 UnkIoctlO:
 438                 call    Unsupported             ;Unsupported command
 439 IoctlODone:
 440                 TRACER 'o'
 441                 retn
 442
 443
 444 ;=============================================================================
 445
 446 DoNothing:                      ;Do Nothing Command
 447
 448                 mov     ax,0                    ;Set Return Status = success
 449                 retn
 450
 451
 452 ;=============================================================================
 453
 454 ReadL:                  ;Read Long Command
 455
 456                 TRACER 'R'
 457                 mov     ax,cs                   ;Set ds=cs
 458                 mov     ds,ax
 459                                                 ;es:bx --> Request Header
 460                 cmp     byte [es:bx+24],0       ;Check Data Read Mode
 461                 jne     ReadLErr                ;If Cooked Mode
 462
 463                 cmp     byte [es:bx+13],2       ;Check Addressing Mode
 464                 jb      ReadLOK                 ;If HSG or Redbook Mode
 465
 466 ReadLErr:
 467                 TRACER '8'
 468                 mov     ax,8003h                ;Set Return Status = Unknown
 469                 jmp     ReadLExit               ;  Command Error and exit
 470
 471 ReadLOK:
 472                 mov     ax,[es:bx+20]           ;Get Starting Sector Number,
 473                 mov     dx,[es:bx+22]           ;  Assume HSG Addressing Mode
 474                 cmp     byte [es:bx+13],0       ;Check Addressing Mode again
 475                 je      ReadLHSG                ;If HSG Addressing Mode
 476
 477                 TRACER '7'
 478                 ;Using Redbook Addressing Mode.  Convert to HSG format
 479                 mov     al,dl                   ;Get Minutes
 480                 mov     dl,60
 481                 mul     dl                      ;ax = Minutes * 60
 482                 add     al,byte [es:bx+21]      ;Add in Seconds
 483                 adc     ah,0
 484                 mov     dx,75                   ;dx:ax =
 485                 mul     dx                      ;  ((Min * 60) + Sec) * 75
 486                 add     al,byte [es:bx+20]      ;Add in Frames
 487                 adc     ah,0
 488                 adc     dx,0
 489                 sub     ax,150                  ;Subtract 2-Second offset
 490                 sbb     dx,0                    ;dx:ax = HSG Starting Sector
 491
 492 ReadLHSG:
 493                 mov     word [SpecPkt+8], ax    ;Store Starting
 494                 mov     word [SpecPkt+10], dx   ;  Sector Number
 495                 mov     word [SpecPkt+12], 0    ;  (HSG Format)
 496                 mov     word [SpecPkt+14], 0
 497
 498                 mov     ax,[es:bx+14]           ;Get Transfer Address
 499                 mov     word [SpecPkt+4],ax
 500                 mov     ax,[es:bx+16]
 501                 mov     word [SpecPkt+6],ax
 502
 503                 mov     byte [SpecPkt],16       ;Size of Disk Address Packet
 504                 mov     byte [SpecPkt+1],0      ;Reserved
 505
 506                 mov     cx, 5
 507 ReadLAgain:
 508                 mov     ax,[es:bx+18]           ;Get number of sectors to read
 509                 mov     word [SpecPkt+2],ax
 510                 cmp     ax, 3FFFh               ;Too large?
 511                 ja      ReadLBad                ;If yes
 512
 513                 push    cx
 514                 mov     cl,byte [ReadBytes]     ;Multiply by 4 if reading 512
 515                 shl     word [SpecPkt+2],cl     ;  bytes at a time
 516                 pop     cx
 517
 518 %ifdef DEBUG
 519                 push    ax
 520                 push    cx
 521                 push    si
 522                 mov     cx, 16
 523                 mov     si,SpecPkt
 524 ReadDump:       mov     al, ' '
 525                 call    print_char
 526                 mov     al, byte [si]   ;Hexdump a SpecPkt byte
 527                 call    print_hex8
 528                 inc     si                      ;Point to next byte
 529                 loop    ReadDump
 530                 pop     si
 531                 pop     cx
 532                 pop     ax
 533 %endif
 534                 mov     si,SpecPkt
 535                 mov     dl,[DriveNumber]
 536                 mov     ah,42h                  ;Extended Read
 537                 int     13h
 538                 jnc     ReadLGd                 ;If success
 539
 540 ;hang:
 541 ;               jmp     hang
 542 ;               TRACER '1'
 543                 loop    ReadLAgain
 544                 TRACER '2'
 545                 jmp short ReadLBad
 546 ReadLGd:
 547                 TRACER '3'
 548                 xor     ax, ax                  ;Status 0 = success
 549                 jmp short ReadLExit
 550
 551 ReadLBad:
 552                 TRACER '9'
 553                 mov     ax, 800Bh               ;Set Read Fault Error
 554                 ; flow into ReadLExit
 555 ReadLExit:
 556                 TRACER 'r'
 557                 retn
 558
 559
 560
 561 %ifdef DEBUG_TRACERS
 562 debug_tracer:   pushad
 563                 pushfd
 564
 565                 mov     al, '['
 566                 mov     ah,0Eh                  ;BIOS video teletype output
 567                 xor     bh, bh
 568                 int     10h                     ;Print it
 569
 570                 mov     bp,sp
 571                 mov     bx,[bp+9*4]             ; Get return address
 572                 mov     al,[cs:bx]              ; Get data byte
 573                 inc     word [bp+9*4]   ; Return to after data byte
 574
 575                 mov     ah,0Eh                  ;BIOS video teletype output
 576                 xor     bh, bh
 577                 int     10h                     ;Print it
 578
 579                 mov     al, ']'
 580                 mov     ah,0Eh                  ;BIOS video teletype output
 581                 xor     bh, bh
 582                 int     10h                     ;Print it
 583
 584                 popfd
 585                 popad
 586                 retn
 587 %endif
 588
 589 ;-----------------------------------------------------------------------------
 590 ; PRINT_HEX4
 591 ;-----------------------------------------------------------------------------
 592 ; print a 4 bits integer in hex
 593 ;
 594 ; Input:
 595 ;       AL - 4 bits integer to print (low)
 596 ;
 597 ; Output: None
 598 ;
 599 ; Registers destroyed: None
 600 ;
 601 print_hex4:
 602
 603         push    ax
 604         and     al, 0fh         ; we only need the first nibble
 605         cmp     al, 10
 606         jae     hex_A_F
 607         add     al, '0'
 608         jmp     hex_0_9
 609 hex_A_F:
 610         add     al, 'A'-10
 611 hex_0_9:
 612         call    print_char
 613         pop     ax
 614         retn
 615
 616
 617 ;-----------------------------------------------------------------------------
 618 ; print_hex8
 619 ;-----------------------------------------------------------------------------
 620 ; print a 8 bits integer in hex
 621 ;
 622 ; Input:
 623 ;       AL - 8 bits integer to print
 624 ;
 625 ; Output: None
 626 ;
 627 ; Registers destroyed: None
 628 ;
 629 print_hex8:
 630
 631         push    ax
 632         push    bx
 633
 634         mov     ah, al
 635         shr     al, 4
 636         call    print_hex4
 637
 638         mov     al, ah
 639         and     al, 0fh
 640         call    print_hex4
 641
 642         pop     bx
 643         pop     ax
 644         retn
 645
 646
 647 ;=============================================================================
 648 ; print_hex16 - print a 16 bits integer in hex
 649 ;
 650 ; Input:
 651 ;       AX - 16 bits integer to print
 652 ;
 653 ; Output: None
 654 ;
 655 ; Registers destroyed: None
 656 ;=============================================================================
 657 print_hex16:
 658
 659         push    ax
 660         push    bx
 661         push    cx
 662
 663         mov     cx, 4
 664 print_hex16_loop:
 665         rol     ax, 4
 666         call    print_hex4
 667         loop    print_hex16_loop
 668
 669         pop     cx
 670         pop     bx
 671         pop     ax
 672         retn
 673
 674 ;=============================================================================
 675 ; print_hex32 - print a 32 bits integer in hex
 676 ;
 677 ; Input:
 678 ;       EAX - 32 bits integer to print
 679 ;
 680 ; Output: None
 681 ;
 682 ; Registers destroyed: None
 683 ;=============================================================================
 684 print_hex32:
 685
 686         push    eax
 687         push    bx
 688         push    cx
 689
 690         mov     cx, 8
 691 print_hex32_loop:
 692         rol     eax, 4
 693         call    print_hex4
 694         loop    print_hex32_loop
 695
 696         pop     cx
 697         pop     bx
 698         pop     eax
 699         retn
 700
 701 ;=============================================================================
 702 ; print_string - print string at current cursor location
 703 ;
 704 ; Input:
 705 ;       DS:SI - ASCIIZ string to print
 706 ;
 707 ; Output: None
 708 ;
 709 ; Registers destroyed: None
 710 ;=============================================================================
 711 print_string:
 712                 push    ax
 713                 push    si
 714
 715 print_string_again:
 716                 mov     al, [si]
 717                 or      al, al
 718                 jz      print_string_exit
 719                 call    print_char
 720                 inc     si
 721                 jmp     print_string_again
 722
 723 print_string_exit:
 724                 pop     si
 725                 pop     ax
 726                 retn
 727
 728 ;-----------------------------------------------------------------------------
 729 ; PRINT_CHAR
 730 ;-----------------------------------------------------------------------------
 731 ; Print's a character at current cursor position
 732 ;
 733 ; Input:
 734 ;       AL - Character to print
 735 ;
 736 ; Output: None
 737 ;
 738 ; Registers destroyed: None
 739 ;
 740 print_char:
 741
 742                 push    ax
 743                 push    bx
 744
 745                 mov     ah,0Eh                  ;BIOS video teletype output
 746                 xor     bh, bh
 747                 int     10h                     ;Print it
 748
 749 print_char_exit:
 750                 pop     bx
 751                 pop     ax
 752                 retn
 753
 754
 755 ;=============================================================================
 756
 757 ;This space is used as a 2048-byte read buffer plus one test byte.
 758 ;The 96h data is used for testing the number of bytes returned by an Extended
 759 ;  CD-ROM sector read
 760
 761                 align   16, db 0
 762 Buffer          times   2049    db      96h
 763
 764 ;=============================================================================
 765
 766 Init:                   ;Initialization Routine
 767
 768                 TRACER 'I'
 769                 mov     ax,cs                   ;ds=cs
 770                 mov     ds,ax
 771
 772 %ifdef DEBUG
 773 ; print CS value (load segment)
 774                 call    print_hex16
 775 %endif
 776
 777                 mov     si, Greeting    ;Display Greeting
 778                 call    print_string
 779
 780                 mov     ax,Unsupported  ;Init is executed only once
 781                 mov     [Routines],ax
 782
 783                 mov     ax, 5400h
 784                 int     13h                     ; Get diskemu status
 785                 jc      FindBoot                ; If CF=1 no diskemu loaded
 786
 787                 mov     [DriveNumber], cl               ; Store drive number
 788
 789                 call    keyflag
 790                 and     al, 8                   ; alt key ?
 791                 jz      extread
 792
 793                 mov     si, DrvNumMsg   ; Display "drive number="
 794                 call    print_string
 795                 mov     al, [DriveNumber]
 796                 call    print_hex8
 797                 mov     si, LineEnd     ; CR/LF
 798                 call    print_string
 799                 jmp     extread
 800
 801 ; Diskemu is not loaded
 802 ; so loop to find drive number
 803                 ; *** start of 1.4 changes ***
 804                 ; ??? mov dl, 0ffh              ;Start at Drive 0xff
 805                 ; *** FindBoot at c47 in 1.4, at c0c in 1.3 ***
 806 FindBoot:       call    ScanDrives              ; call new helper in 1.4
 807                 jnc     FoundBoot               ; ded*df3
 808 ;               mov     si,offset SpecPkt       ;Locate booted CD-ROM drive
 809 ;               mov     [SpecPkt],0             ;Clear 1st byte of SpecPkt
 810 ;               mov     ax,4B01h                ;Get Bootable CD-ROM Status
 811 ;               int     13h
 812 ;               jnc     FindPass                ;If booted CD found
 813 ;
 814 ; Carry is not cleared in buggy Dell BIOSes,
 815 ; so I'm checking packet size byte
 816 ; some bogus bioses (Dell Inspiron 2500) returns packet size 0xff when failed
 817 ; Dell Dimension XPsT returns packet size 0x14 when OK
 818
 819 ;               cmp     [SpecPkt], 0
 820 ;               jne     FoundBoot
 821
 822 ;               cmp     [SpecPkt], 13h  ; anything between 13h and 20h should be OK
 823 ;               jb      FindFail
 824 ;               cmp     [SpecPkt], 20h
 825 ;               ja      FindFail
 826 ;               jmp     short FoundBoot
 827 ;
 828 ; FindFail:
 829 ;               dec     dl                      ;Next drive
 830 ;               cmp     dl, 80h
 831 ;               jae     FindBoot                ;Check from ffh..80h
 832                 ; *** end of 1.4 changes ***
 833
 834                 mov     si,NoBootCD     ;No booted CD found,
 835                 call    print_string
 836                 jmp     NoEndAddr               ;Do not install driver
 837
 838 FoundBoot:
 839 ;               mov     dl, [SpecPkt+2]         ; 1.4 change
 840                 ; *** next line at c57 in 1.4, at c3d in 1.3 ***
 841                 mov     [DriveNumber],dl                ;Booted CD-ROM found,
 842                                                 ;  so save Drive #
 843
 844                 call    keyflag
 845                 and     al, 8                   ; alt key ?
 846                 jz      extread
 847
 848                 mov     si, CDStat
 849                 call    print_string
 850                 mov     si, SpecPkt     ;Point to returned CD SpecPkt
 851                 mov     cx, 19                  ;  containing 19 bytes
 852 StatDump:       mov     al, ' '                 ;Print a space
 853                 call    print_char
 854                 mov     al, byte [si]   ;Hexdump a SpecPkt byte
 855                 call    print_hex8
 856                 inc     si                      ;Point to next byte
 857                 loop    StatDump
 858
 859                 mov     si, LineEnd     ;Print a CR/LF
 860                 call    print_string
 861
 862 extread:
 863 ;See how many CD Sector bytes are returned by an Extended Read
 864                 mov     byte [SpecPkt],16       ;SpecPkt Size
 865                 mov     byte [SpecPkt+1],0      ;Reserved
 866                 mov     word [SpecPkt+2],1      ;Transfer one sector
 867                 mov     word [SpecPkt+6],cs     ;Into our Buffer
 868                 mov     word [SpecPkt+4],Buffer
 869                 mov     word [SpecPkt+8],16     ;From CD Sector 16
 870                 mov     word [SpecPkt+10],0
 871                 mov     word [SpecPkt+12],0
 872                 mov     word [SpecPkt+14],0
 873
 874                 mov     si, SpecPkt     ;Set ds:si --> SpecPkt
 875                 mov     dl, [DriveNumber]
 876                 mov     ah, 42h                 ;Extended Read
 877                 int     13h
 878                 jnc     SecSize                 ;If success
 879
 880                 mov     ah, 42h                 ;Always make 2 read attempts
 881                 int     13h
 882                                                 ;How many bytes did we get?
 883 SecSize:        std                             ;Count down
 884                 mov     ax,cs                   ;Point to end of Buffer
 885                 mov     es,ax
 886                 mov     di,Buffer+2047  ;Find end of read data
 887                 mov     si,Buffer+2048
 888                 mov     cx,2049
 889                 repe    cmpsb                   ;cx = number of bytes read
 890
 891                 cld                             ;Restore count direction to up
 892                 mov     si,CDBytes      ;Display number of bytes read
 893                 call    print_string
 894
 895                 mov     al, [DriveNumber]
 896                 call    print_hex8
 897
 898                 mov     si,CDBytesA     ;Remainder A of message
 899                 call    print_string
 900
 901                 mov     al,ch                   ;Hex-dump cx
 902                 and     al,0Fh                  ;Second nibble
 903                 call    print_hex8              ;  (don't need the First)
 904                 mov     al,cl
 905                 call    print_hex8              ;  (don't need the First)
 906
 907                 mov     si,CDBytesB     ;Remainder B of message
 908                 call    print_string
 909
 910                 cmp     cx,2048                 ;Did we read 2048 bytes?
 911                 je      ParseParm               ;If yes <-- O.K.
 912
 913                 mov     byte [ReadBytes],1
 914                 cmp     cx,1024                 ;Did we read 1024 bytes?
 915                 je      ParseParm               ;If yes <-- O.K.
 916
 917                 mov     byte [ReadBytes],2
 918                 cmp     cx,512                  ;Did we read 512 bytes?
 919                 jne     NoEndAddr               ;If not, do not load driver
 920
 921 ParseParm:      mov     bx,word [cs:ReqHdrLoc]  ;Parse command line
 922                 mov     es,word [cs:ReqHdrLoc+2]        ;  parameters
 923                 mov     si,[es:bx+18]           ;Get BPB array ptr into DS:SI
 924                 mov     ds,[es:bx+20]
 925 FindParm:       inc     si
 926 FindParm1:      cmp     byte [si],0Dh   ;CR? (End of parameters)
 927                 je      EndOfParms
 928
 929                 cmp     byte [si],0Ah   ;LF?
 930                 je      EndOfParms
 931
 932                 cmp     byte [si],'/'   ;A parameter?
 933                 jne     FindParm
 934
 935                 inc     si
 936                 cmp     byte [si],'D'   ;Device Name parameter?
 937                 jne     FindParm1
 938
 939                 inc     si
 940                 cmp     byte [si],':'
 941                 jne     FindParm1
 942
 943 ;bbb
 944                 push    si
 945                 mov     si, DevName     ;Device Name is at ds:si
 946                 push    ds                      ;Keep ptr to Device Name
 947                 mov     ax, cs
 948                 mov     ds, ax
 949                 call    print_string
 950                 pop     ds                      ;Retrieve Device Name ptr
 951                 pop     si
 952                 mov     cx, 8                   ;Get next 8 chars
 953                 inc     si                      ;  = Device Name
 954                 mov     ax, cs
 955                 mov     es, ax
 956                 mov     di, DeviceName
 957 NextChar:       cmp     byte [si],' '
 958                 ja      AboveSpace
 959
 960                 mov     ax,cs                   ;Pad end of Device Name with
 961                 mov     ds,ax                   ;  spaces if necessary
 962                 mov     si,DblSpace     ;A space
 963 AboveSpace:     mov     al, [si]
 964                 call    print_char
 965                 movsb                           ;ds:[si] --> es:[di]
 966                 loop    NextChar
 967
 968                 mov     si,LineEnd
 969                 mov     ax,cs
 970                 mov     ds,ax
 971                 call    print_string
 972
 973                 mov     ax,Init-2       ;Last byte of driver to keep
 974                 jmp     EndAddr                 ;Install driver
 975
 976 EndOfParms:
 977                 mov     ax, cs                  ; Restore segment registers (fix)
 978                 mov     ds, ax
 979                 mov     es, ax
 980
 981                 mov     si,NoDevName    ;No Device Name Found
 982                 call    print_string
 983
 984 NoEndAddr:      mov     ax,0                    ;Do not install driver
 985
 986 EndAddr:        mov     es,[ReqHdrLoc+2]                ;Write End Address
 987                 mov     bx,[ReqHdrLoc]
 988                 mov     [es:bx+14],ax
 989                 mov     [es:bx+16],cs
 990                 mov     bx,ax                   ;Hold onto install status
 991
 992                 mov     si, DrvInst     ;Display driver install status
 993                 call    print_string
 994                 mov     si, DrvInst1    ;Assume driver installed
 995                 cmp     bx,0                    ;Was driver installed?
 996                 jne     DrvStatus               ;If yes
 997                 mov     si, NoDrvInst   ;Driver not installed
 998 DrvStatus:      call    print_string
 999
1000                 mov     ax,0                    ;Set Return Status = success
1001                 cmp     bx,0                    ;Was INIT successful?
1002                 jne     InitStat                ;If yes
1003                 mov     ax,800Ch                ;Status = General Failure
1004 InitStat:
1005                 push    ax                      ;Save Return Status
1006
1007                 call    keyflag
1008                 and     al, 8                   ; alt key ?
1009                 jz      InitExit
1010
1011 WaitHere:
1012                 mov     si, WaitMsg     ;Display Halted message
1013                 call    print_string
1014
1015 AltWait:
1016                 call    keyflag
1017                 and     al, 8                   ; Alt key?
1018                 jnz     AltWait                 ; Pressed? yes -> wait
1019
1020 InitExit:
1021                 pop     ax                      ;Retrieve Return Status
1022                 TRACER 'i'
1023                 retn                            ;That's it for Init!
1024
1025                 ; *** start 1.4 changes at ded ***
1026 SpecGo:         mov     si,SpecPkt
1027                 int     13h
1028                 retn
1029
1030 ScanDrives:     push    ax              ; at df3 in 1.4
1031                 push    si
1032                 mov dl, 7fh             ;Start at Drive 0x80
1033 NextDrv:        inc     dl
1034                 clc
1035                 mov     ax,4B01h        ;Get Bootable CD-ROM Status
1036                 mov     BYTE [SpecPkt],0        ;Clear 1st byte of SpecPkt
1037                 call    SpecGo
1038 ; Carry is not cleared in buggy Dell BIOSes,
1039 ; so I'm checking packet size byte
1040 ; some bogus bioses (Dell Inspiron 2500) returns packet size 0xff when failed
1041 ; Dell Dimension XPsT returns packet size 0x14 when OK
1042
1043                 cmp     BYTE [SpecPkt], 13h     ; anything between 13h and 20h should be OK
1044                 jb      FindFail
1045                 cmp     BYTE [SpecPkt], 20h
1046                 ja      FindFail        ; in 1.4 at e16
1047                 jmp     short SendFound ; in 1.4 at e26
1048
1049 FindFail:       cmp     dl, 0ffh
1050                 je      SendFail                ; Check from 80h..ffh
1051                 jmp     short NextDrv           ;Next drive
1052 SendFail:       xor     dl,dl
1053                 stc
1054                 jmp     short ThingDone
1055 SendFound:      mov     dl, [SpecPkt+2]
1056                 clc
1057 ThingDone:      pop     si
1058                 pop     ax
1059                 retn
1060                 ; *** end 1.4 changes ***
1061
1062 ;=============================================================================
1063
1064 ;------------------------------------------------------------
1065 ; keyboard flags - return keyboard flags in AL
1066 ; bit 3 = ALT key
1067 keyflag:        ; at dbc in 1.3, at e2e in 1.4
1068         push    bx
1069         mov     ah, 2
1070         int     16h
1071         pop     bx
1072         retn
1073
1074 ;=============================================================================
1075
1076 DrvNumMsg       db      '  Diskemxx.bin returned drive number=', 0
1077 NoBootCD        db      '  No booted CD-ROM found.',CR,0
1078
1079 CDStat          db      '  INT 13h / AX=4B01h Specification Packet for '
1080                 db      'Booted CD-ROM:',CR,'     ', 0
1081
1082 CDBytes         db      '  Drive ', 0
1083 CDBytesA        db      ' returns ', 0
1084 CDBytesB        db      'h bytes per Sector.',CR,0
1085
1086 DevName         db      '  Device Name: ', 0
1087 NoDevName       db      '  No Device Name found. '
1088                 db      'Usage: device=eltorito.sys /D:<DevName>',CR,0
1089
1090 DrvInst         db      '  Driver ', 0
1091 NoDrvInst       db      7,'not '                ;7 = Ctrl-G = Beep
1092 DrvInst1        db      'installed',CR,0
1093
1094 WaitMsg         db      '  Alt pressed, waiting...', CR, 0
1095 ;ContMsg                db      '  Continuing...'
1096 LineEnd         db      CR,0
1097
1098
1099 ;=============================================================================