core/isolinux.asm

   1 ; -*- fundamental -*- (asm-mode sucks)
   2 ; ****************************************************************************
   3 ;
   4 ;  isolinux.asm
   5 ;
   6 ;  A program to boot Linux kernels off a CD-ROM using the El Torito
   7 ;  boot standard in "no emulation" mode, making the entire filesystem
   8 ;  available.  It is based on the SYSLINUX boot loader for MS-DOS
   9 ;  floppies.
  10 ;
  11 ;   Copyright 1994-2009 H. Peter Anvin - All Rights Reserved
  12 ;   Copyright 2009 Intel Corporation; author: H. Peter Anvin
  13 ;
  14 ;  This program is free software; you can redistribute it and/or modify
  15 ;  it under the terms of the GNU General Public License as published by
  16 ;  the Free Software Foundation, Inc., 53 Temple Place Ste 330,
  17 ;  Boston MA 02111-1307, USA; either version 2 of the License, or
  18 ;  (at your option) any later version; incorporated herein by reference.
  19 ;
  20 ; ****************************************************************************
  21
  22 %define IS_ISOLINUX 1
  23 %include "head.inc"
  24
  25 ;
  26 ; Some semi-configurable constants... change on your own risk.
  27 ;
  28 my_id           equ isolinux_id
  29 NULLFILE        equ 0                   ; Zero byte == null file name
  30 NULLOFFSET      equ 0                   ; Position in which to look
  31 retry_count     equ 6                   ; How patient are we with the BIOS?
  32 %assign HIGHMEM_SLOP 128*1024           ; Avoid this much memory near the top
  33 SECTOR_SHIFT    equ 11                  ; 2048 bytes/sector (El Torito requirement)
  34 SECTOR_SIZE     equ (1 << SECTOR_SHIFT)
  35
  36 ROOT_DIR_WORD   equ 0x002F
  37
  38 ; ---------------------------------------------------------------------------
  39 ;   BEGIN CODE
  40 ; ---------------------------------------------------------------------------
  41
  42 ;
  43 ; Memory below this point is reserved for the BIOS and the MBR
  44 ;
  45                 section .earlybss
  46                 global trackbuf
  47 trackbufsize    equ 8192
  48 trackbuf        resb trackbufsize       ; Track buffer goes here
  49 ;               ends at 2800h
  50
  51                 ; Some of these are touched before the whole image
  52                 ; is loaded.  DO NOT move this to .bss16/.uibss.
  53                 section .earlybss
  54                 global BIOSName
  55                 alignb 4
  56 FirstSecSum     resd 1                  ; Checksum of bytes 64-2048
  57 ImageDwords     resd 1                  ; isolinux.bin size, dwords
  58 InitStack       resd 1                  ; Initial stack pointer (SS:SP)
  59 DiskSys         resw 1                  ; Last INT 13h call
  60 ImageSectors    resw 1                  ; isolinux.bin size, sectors
  61 ; These following two are accessed as a single dword...
  62 GetlinsecPtr    resw 1                  ; The sector-read pointer
  63 BIOSName        resw 1                  ; Display string for BIOS type
  64 %define HAVE_BIOSNAME 1
  65                 global BIOSType
  66 BIOSType        resw 1
  67 DiskError       resb 1                  ; Error code for disk I/O
  68                 global DriveNumber
  69 DriveNumber     resb 1                  ; CD-ROM BIOS drive number
  70 ISOFlags        resb 1                  ; Flags for ISO directory search
  71 RetryCount      resb 1                  ; Used for disk access retries
  72
  73                 alignb 8
  74                 global Hidden
  75 Hidden          resq 1                  ; Used in hybrid mode
  76 bsSecPerTrack   resw 1                  ; Used in hybrid mode
  77 bsHeads         resw 1                  ; Used in hybrid mode
  78
  79
  80 ;
  81 ; El Torito spec packet
  82 ;
  83
  84                 alignb 8
  85 _spec_start     equ $
  86                 global spec_packet
  87 spec_packet:    resb 1                          ; Size of packet
  88 sp_media:       resb 1                          ; Media type
  89 sp_drive:       resb 1                          ; Drive number
  90 sp_controller:  resb 1                          ; Controller index
  91 sp_lba:         resd 1                          ; LBA for emulated disk image
  92 sp_devspec:     resw 1                          ; IDE/SCSI information
  93 sp_buffer:      resw 1                          ; User-provided buffer
  94 sp_loadseg:     resw 1                          ; Load segment
  95 sp_sectors:     resw 1                          ; Sector count
  96 sp_chs:         resb 3                          ; Simulated CHS geometry
  97 sp_dummy:       resb 1                          ; Scratch, safe to overwrite
  98
  99 ;
 100 ; EBIOS drive parameter packet
 101 ;
 102                 alignb 8
 103 drive_params:   resw 1                          ; Buffer size
 104 dp_flags:       resw 1                          ; Information flags
 105 dp_cyl:         resd 1                          ; Physical cylinders
 106 dp_head:        resd 1                          ; Physical heads
 107 dp_sec:         resd 1                          ; Physical sectors/track
 108 dp_totalsec:    resd 2                          ; Total sectors
 109 dp_secsize:     resw 1                          ; Bytes per sector
 110 dp_dpte:        resd 1                          ; Device Parameter Table
 111 dp_dpi_key:     resw 1                          ; 0BEDDh if rest valid
 112 dp_dpi_len:     resb 1                          ; DPI len
 113                 resb 1
 114                 resw 1
 115 dp_bus:         resb 4                          ; Host bus type
 116 dp_interface:   resb 8                          ; Interface type
 117 db_i_path:      resd 2                          ; Interface path
 118 db_d_path:      resd 2                          ; Device path
 119                 resb 1
 120 db_dpi_csum:    resb 1                          ; Checksum for DPI info
 121
 122 ;
 123 ; EBIOS disk address packet
 124 ;
 125                 alignb 8
 126 dapa:           resw 1                          ; Packet size
 127 .count:         resw 1                          ; Block count
 128 .off:           resw 1                          ; Offset of buffer
 129 .seg:           resw 1                          ; Segment of buffer
 130 .lba:           resd 2                          ; LBA (LSW, MSW)
 131
 132 ;
 133 ; Spec packet for disk image emulation
 134 ;
 135                 alignb 8
 136 dspec_packet:   resb 1                          ; Size of packet
 137 dsp_media:      resb 1                          ; Media type
 138 dsp_drive:      resb 1                          ; Drive number
 139 dsp_controller: resb 1                          ; Controller index
 140 dsp_lba:        resd 1                          ; LBA for emulated disk image
 141 dsp_devspec:    resw 1                          ; IDE/SCSI information
 142 dsp_buffer:     resw 1                          ; User-provided buffer
 143 dsp_loadseg:    resw 1                          ; Load segment
 144 dsp_sectors:    resw 1                          ; Sector count
 145 dsp_chs:        resb 3                          ; Simulated CHS geometry
 146 dsp_dummy:      resb 1                          ; Scratch, safe to overwrite
 147
 148                 alignb 4
 149 _spec_end       equ $
 150 _spec_len       equ _spec_end - _spec_start
 151
 152                 section .init
 153 ;;
 154 ;; Primary entry point.  Because BIOSes are buggy, we only load the first
 155 ;; CD-ROM sector (2K) of the file, so the number one priority is actually
 156 ;; loading the rest.
 157 ;;
 158                 global StackBuf
 159 StackBuf        equ STACK_TOP-44        ; 44 bytes needed for
 160                                         ; the bootsector chainloading
 161                                         ; code!
 162                 global OrigESDI
 163 OrigESDI        equ StackBuf-4          ; The high dword on the stack
 164 StackHome       equ OrigESDI
 165
 166 bootsec         equ $
 167
 168 _start:         ; Far jump makes sure we canonicalize the address
 169                 cli
 170                 jmp 0:_start1
 171                 times 8-($-$$) nop              ; Pad to file offset 8
 172
 173                 ; This table hopefully gets filled in by mkisofs using the
 174                 ; -boot-info-table option.  If not, the values in this
 175                 ; table are default values that we can use to get us what
 176                 ; we need, at least under a certain set of assumptions.
 177                 global iso_boot_info
 178 iso_boot_info:
 179 bi_pvd:         dd 16                           ; LBA of primary volume descriptor
 180 bi_file:        dd 0                            ; LBA of boot file
 181 bi_length:      dd 0xdeadbeef                   ; Length of boot file
 182 bi_csum:        dd 0xdeadbeef                   ; Checksum of boot file
 183 bi_reserved:    times 10 dd 0xdeadbeef          ; Reserved
 184 bi_end:
 185
 186                 ; Custom entry point for the hybrid-mode disk.
 187                 ; The following values will have been pushed onto the
 188                 ; entry stack:
 189                 ;       - partition offset (qword)
 190                 ;       - ES
 191                 ;       - DI
 192                 ;       - DX (including drive number)
 193                 ;       - CBIOS Heads
 194                 ;       - CBIOS Sectors
 195                 ;       - EBIOS flag
 196                 ;       (top of stack)
 197                 ;
 198                 ; If we had an old isohybrid, the partition offset will
 199                 ; be missing; we can check for that with sp >= 0x7c00.
 200                 ; Serious hack alert.
 201 %ifndef DEBUG_MESSAGES
 202 _hybrid_signature:
 203                dd 0x7078c0fb                    ; An arbitrary number...
 204
 205 _start_hybrid:
 206                 pop cx                          ; EBIOS flag
 207                 pop word [cs:bsSecPerTrack]
 208                 pop word [cs:bsHeads]
 209                 pop dx
 210                 pop di
 211                 pop es
 212                 xor eax,eax
 213                 xor ebx,ebx
 214                 cmp sp,7C00h
 215                 jae .nooffset
 216                 pop eax
 217                 pop ebx
 218 .nooffset:
 219                 mov si,bios_cbios
 220                 jcxz _start_common
 221                 mov si,bios_ebios
 222                 jmp _start_common
 223 %endif
 224
 225 _start1:
 226                 mov si,bios_cdrom
 227                 xor eax,eax
 228                 xor ebx,ebx
 229 _start_common:
 230                 mov [cs:InitStack],sp   ; Save initial stack pointer
 231                 mov [cs:InitStack+2],ss
 232                 xor cx,cx
 233                 mov ss,cx
 234                 mov sp,StackBuf         ; Set up stack
 235                 push es                 ; Save initial ES:DI -> $PnP pointer
 236                 push di
 237                 mov ds,cx
 238                 mov es,cx
 239                 mov fs,cx
 240                 mov gs,cx
 241                 sti
 242                 cld
 243
 244                 mov [Hidden],eax
 245                 mov [Hidden+4],ebx
 246
 247                 mov [BIOSType],si
 248                 mov eax,[si]
 249                 mov [GetlinsecPtr],eax
 250
 251                 ; Show signs of life
 252                 mov si,syslinux_banner
 253                 call writestr_early
 254 %ifdef DEBUG_MESSAGES
 255                 mov si,copyright_str
 256 %else
 257                 mov si,[BIOSName]
 258 %endif
 259                 call writestr_early
 260
 261                 ;
 262                 ; Before modifying any memory, get the checksum of bytes
 263                 ; 64-2048
 264                 ;
 265 initial_csum:   xor edi,edi
 266                 mov si,bi_end
 267                 mov cx,(SECTOR_SIZE-64) >> 2
 268 .loop:          lodsd
 269                 add edi,eax
 270                 loop .loop
 271                 mov [FirstSecSum],edi
 272
 273                 mov [DriveNumber],dl
 274 %ifdef DEBUG_MESSAGES
 275                 mov si,startup_msg
 276                 call writemsg
 277                 mov al,dl
 278                 call writehex2
 279                 call crlf_early
 280 %endif
 281                 ;
 282                 ; Initialize spec packet buffers
 283                 ;
 284                 mov di,_spec_start
 285                 mov cx,_spec_len >> 2
 286                 xor eax,eax
 287                 rep stosd
 288
 289                 ; Initialize length field of the various packets
 290                 mov byte [spec_packet],13h
 291                 mov byte [drive_params],30
 292                 mov byte [dapa],16
 293                 mov byte [dspec_packet],13h
 294
 295                 ; Other nonzero fields
 296                 inc word [dsp_sectors]
 297
 298                 ; Are we just pretending to be a CD-ROM?
 299                 cmp word [BIOSType],bios_cdrom
 300                 jne found_drive                 ; If so, no spec packet...
 301
 302                 ; Now figure out what we're actually doing
 303                 ; Note: use passed-in DL value rather than 7Fh because
 304                 ; at least some BIOSes will get the wrong value otherwise
 305                 mov ax,4B01h                    ; Get disk emulation status
 306                 mov dl,[DriveNumber]
 307                 mov si,spec_packet
 308                 call int13
 309                 jc award_hack                   ; changed for BrokenAwardHack
 310                 mov dl,[DriveNumber]
 311                 cmp [sp_drive],dl               ; Should contain the drive number
 312                 jne spec_query_failed
 313
 314 %ifdef DEBUG_MESSAGES
 315                 mov si,spec_ok_msg
 316                 call writemsg
 317                 mov al,byte [sp_drive]
 318                 call writehex2
 319                 call crlf_early
 320 %endif
 321
 322 found_drive:
 323                 ; Alright, we have found the drive.  Now, try to find the
 324                 ; boot file itself.  If we have a boot info table, life is
 325                 ; good; if not, we have to make some assumptions, and try
 326                 ; to figure things out ourselves.  In particular, the
 327                 ; assumptions we have to make are:
 328                 ; - single session only
 329                 ; - only one boot entry (no menu or other alternatives)
 330
 331                 cmp dword [bi_file],0           ; Address of code to load
 332                 jne found_file                  ; Boot info table present :)
 333
 334 %ifdef DEBUG_MESSAGES
 335                 mov si,noinfotable_msg
 336                 call writemsg
 337 %endif
 338
 339                 ; No such luck.  See if the spec packet contained one.
 340                 mov eax,[sp_lba]
 341                 and eax,eax
 342                 jz set_file                     ; Good enough
 343
 344 %ifdef DEBUG_MESSAGES
 345                 mov si,noinfoinspec_msg
 346                 call writemsg
 347 %endif
 348
 349                 ; No such luck.  Get the Boot Record Volume, assuming single
 350                 ; session disk, and that we're the first entry in the chain.
 351                 mov eax,17                      ; Assumed address of BRV
 352                 mov bx,trackbuf
 353                 call getonesec
 354
 355                 mov eax,[trackbuf+47h]          ; Get boot catalog address
 356                 mov bx,trackbuf
 357                 call getonesec                  ; Get boot catalog
 358
 359                 mov eax,[trackbuf+28h]          ; First boot entry
 360                 ; And hope and pray this is us...
 361
 362                 ; Some BIOSes apparently have limitations on the size
 363                 ; that may be loaded (despite the El Torito spec being very
 364                 ; clear on the fact that it must all be loaded.)  Therefore,
 365                 ; we load it ourselves, and *bleep* the BIOS.
 366
 367 set_file:
 368                 mov [bi_file],eax
 369
 370 found_file:
 371                 ; Set up boot file sizes
 372                 mov eax,[bi_length]
 373                 sub eax,SECTOR_SIZE-3           ; ... minus sector loaded
 374                 shr eax,2                       ; bytes->dwords
 375                 mov [ImageDwords],eax           ; boot file dwords
 376                 add eax,((SECTOR_SIZE-1) >> 2)
 377                 shr eax,SECTOR_SHIFT-2          ; dwords->sectors
 378                 mov [ImageSectors],ax           ; boot file sectors
 379
 380                 mov eax,[bi_file]               ; Address of code to load
 381                 inc eax                         ; Don't reload bootstrap code
 382 %ifdef DEBUG_MESSAGES
 383                 mov si,offset_msg
 384                 call writemsg
 385                 call writehex8
 386                 call crlf_early
 387 %endif
 388
 389                 ; Load the rest of the file.  However, just in case there
 390                 ; are still BIOSes with 64K wraparound problems, we have to
 391                 ; take some extra precautions.  Since the normal load
 392                 ; address (TEXT_START) is *not* 2K-sector-aligned, we round
 393                 ; the target address upward to a sector boundary,
 394                 ; and then move the entire thing down as a unit.
 395 MaxLMA          equ 384*1024            ; Reasonable limit (384K)
 396
 397                 mov bx,((TEXT_START+2*SECTOR_SIZE-1) & ~(SECTOR_SIZE-1)) >> 4
 398                 mov bp,[ImageSectors]
 399                 push bx                 ; Load segment address
 400
 401 .more:
 402                 push bx                 ; Segment address
 403                 push bp                 ; Sector count
 404                 mov es,bx
 405                 mov cx,0xfff
 406                 and bx,cx
 407                 inc cx
 408                 sub cx,bx
 409                 shr cx,SECTOR_SHIFT - 4
 410                 jnz .notaligned
 411                 mov cx,0x10000 >> SECTOR_SHIFT  ; Full 64K segment possible
 412 .notaligned:
 413                 cmp bp,cx
 414                 jbe .ok
 415                 mov bp,cx
 416 .ok:
 417                 xor bx,bx
 418                 push bp
 419                 push eax
 420                 call getlinsec
 421                 pop eax
 422                 pop cx
 423                 movzx edx,cx
 424                 pop bp
 425                 pop bx
 426
 427                 shl cx,SECTOR_SHIFT - 4
 428                 add bx,cx
 429                 add eax,edx
 430                 sub bp,dx
 431                 jnz .more
 432
 433                 ; Move the image into place, and also verify the
 434                 ; checksum
 435                 pop ax                          ; Load segment address
 436                 mov bx,(TEXT_START + SECTOR_SIZE) >> 4
 437                 mov ecx,[ImageDwords]
 438                 mov edi,[FirstSecSum]           ; First sector checksum
 439                 xor si,si
 440
 441 move_verify_image:
 442 .setseg:
 443                 mov ds,ax
 444                 mov es,bx
 445 .loop:
 446                 mov edx,[si]
 447                 add edi,edx
 448                 dec ecx
 449                 mov [es:si],edx
 450                 jz .done
 451                 add si,4
 452                 jnz .loop
 453                 add ax,1000h
 454                 add bx,1000h
 455                 jmp .setseg
 456 .done:
 457                 mov ax,cs
 458                 mov ds,ax
 459                 mov es,ax
 460
 461                 ; Verify the checksum on the loaded image.
 462                 cmp [bi_csum],edi
 463                 je integrity_ok
 464
 465                 mov si,checkerr_msg
 466                 call writemsg
 467                 jmp kaboom
 468
 469 integrity_ok:
 470 %ifdef DEBUG_MESSAGES
 471                 mov si,allread_msg
 472                 call writemsg
 473 %endif
 474                 jmp all_read                    ; Jump to main code
 475
 476 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 477 ;; Start of BrokenAwardHack --- 10-nov-2002           Knut_Petersen@t-online.de
 478 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 479 ;;
 480 ;; There is a problem with certain versions of the AWARD BIOS ...
 481 ;; the boot sector will be loaded and executed correctly, but, because the
 482 ;; int 13 vector points to the wrong code in the BIOS, every attempt to
 483 ;; load the spec packet will fail. We scan for the equivalent of
 484 ;;
 485 ;;      mov     ax,0201h
 486 ;;      mov     bx,7c00h
 487 ;;      mov     cx,0006h
 488 ;;      mov     dx,0180h
 489 ;;      pushf
 490 ;;      call    <direct far>
 491 ;;
 492 ;; and use <direct far> as the new vector for int 13. The code above is
 493 ;; used to load the boot code into ram, and there should be no reason
 494 ;; for anybody to change it now or in the future. There are no opcodes
 495 ;; that use encodings relativ to IP, so scanning is easy. If we find the
 496 ;; code above in the BIOS code we can be pretty sure to run on a machine
 497 ;; with an broken AWARD BIOS ...
 498 ;;
 499 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 500                                                                              ;;
 501 %ifdef DEBUG_MESSAGES                                                        ;;
 502                                                                              ;;
 503 award_notice    db      "Trying BrokenAwardHack first ...",CR,LF,0           ;;
 504 award_not_orig  db      "BAH: Original Int 13 vector   : ",0                 ;;
 505 award_not_new   db      "BAH: Int 13 vector changed to : ",0                 ;;
 506 award_not_succ  db      "BAH: SUCCESS",CR,LF,0                               ;;
 507 award_not_fail  db      "BAH: FAILURE"                                       ;;
 508 award_not_crlf  db      CR,LF,0                                              ;;
 509                                                                              ;;
 510 %endif                                                                       ;;
 511                                                                              ;;
 512 award_oldint13  dd      0                                                    ;;
 513 award_string    db      0b8h,1,2,0bbh,0,7ch,0b9h,6,0,0bah,80h,1,09ch,09ah    ;;
 514                                                                              ;;
 515                                                 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 516 award_hack:     mov     si,spec_err_msg         ; Moved to this place from
 517                 call    writemsg                ; spec_query_failed
 518                                                 ;
 519 %ifdef DEBUG_MESSAGES                           ;
 520                                                 ;
 521                 mov     si,award_notice         ; display our plan
 522                 call    writemsg                ;
 523                 mov     si,award_not_orig       ; display original int 13
 524                 call    writemsg                ; vector
 525 %endif                                          ;
 526                 mov     eax,[13h*4]             ;
 527                 mov     [award_oldint13],eax    ;
 528                                                 ;
 529 %ifdef DEBUG_MESSAGES                           ;
 530                                                 ;
 531                 call    writehex8               ;
 532                 mov     si,award_not_crlf       ;
 533                 call    writestr_early          ;
 534 %endif                                          ;
 535                 push    es                      ; save ES
 536                 mov     ax,0f000h               ; ES = BIOS Seg
 537                 mov     es,ax                   ;
 538                 cld                             ;
 539                 xor     di,di                   ; start at ES:DI = f000:0
 540 award_loop:     push    di                      ; save DI
 541                 mov     si,award_string         ; scan for award_string
 542                 mov     cx,7                    ; length of award_string = 7dw
 543                 repz    cmpsw                   ; compare
 544                 pop     di                      ; restore DI
 545                 jcxz    award_found             ; jmp if found
 546                 inc     di                      ; not found, inc di
 547                 jno     award_loop              ;
 548                                                 ;
 549 award_failed:   pop     es                      ; No, not this way :-((
 550 award_fail2:                                    ;
 551                                                 ;
 552 %ifdef DEBUG_MESSAGES                           ;
 553                                                 ;
 554                 mov     si,award_not_fail       ; display failure ...
 555                 call    writemsg                ;
 556 %endif                                          ;
 557                 mov     eax,[award_oldint13]    ; restore the original int
 558                 or      eax,eax                 ; 13 vector if there is one
 559                 jz      spec_query_failed       ; and try other workarounds
 560                 mov     [13h*4],eax             ;
 561                 jmp     spec_query_failed       ;
 562                                                 ;
 563 award_found:    mov     eax,[es:di+0eh]         ; load possible int 13 addr
 564                 pop     es                      ; restore ES
 565                                                 ;
 566                 cmp     eax,[award_oldint13]    ; give up if this is the
 567                 jz      award_failed            ; active int 13 vector,
 568                 mov     [13h*4],eax             ; otherwise change 0:13h*4
 569                                                 ;
 570                                                 ;
 571 %ifdef DEBUG_MESSAGES                           ;
 572                                                 ;
 573                 push    eax                     ; display message and
 574                 mov     si,award_not_new        ; new vector address
 575                 call    writemsg                ;
 576                 pop     eax                     ;
 577                 call    writehex8               ;
 578                 mov     si,award_not_crlf       ;
 579                 call    writestr_early          ;
 580 %endif                                          ;
 581                 mov     ax,4B01h                ; try to read the spec packet
 582                 mov     dl,[DriveNumber]        ; now ... it should not fail
 583                 mov     si,spec_packet          ; any longer
 584                 int     13h                     ;
 585                 jc      award_fail2             ;
 586                                                 ;
 587 %ifdef DEBUG_MESSAGES                           ;
 588                                                 ;
 589                 mov     si,award_not_succ       ; display our SUCCESS
 590                 call    writemsg                ;
 591 %endif                                          ;
 592                 jmp     found_drive             ; and leave error recovery code
 593                                                 ;
 594 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 595 ;; End of BrokenAwardHack ----            10-nov-2002 Knut_Petersen@t-online.de
 596 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 597
 598
 599                 ; INT 13h, AX=4B01h, DL=<passed in value> failed.
 600                 ; Try to scan the entire 80h-FFh from the end.
 601
 602 spec_query_failed:
 603
 604                 ; some code moved to BrokenAwardHack
 605
 606                 mov dl,0FFh
 607 .test_loop:     pusha
 608                 mov ax,4B01h
 609                 mov si,spec_packet
 610                 mov byte [si],13h               ; Size of buffer
 611                 call int13
 612                 popa
 613                 jc .still_broken
 614
 615                 mov si,maybe_msg
 616                 call writemsg
 617                 mov al,dl
 618                 call writehex2
 619                 call crlf_early
 620
 621                 cmp byte [sp_drive],dl
 622                 jne .maybe_broken
 623
 624                 ; Okay, good enough...
 625                 mov si,alright_msg
 626                 call writemsg
 627 .found_drive0:  mov [DriveNumber],dl
 628 .found_drive:   jmp found_drive
 629
 630                 ; Award BIOS 4.51 apparently passes garbage in sp_drive,
 631                 ; but if this was the drive number originally passed in
 632                 ; DL then consider it "good enough"
 633 .maybe_broken:
 634                 mov al,[DriveNumber]
 635                 cmp al,dl
 636                 je .found_drive
 637
 638                 ; Intel Classic R+ computer with Adaptec 1542CP BIOS 1.02
 639                 ; passes garbage in sp_drive, and the drive number originally
 640                 ; passed in DL does not have 80h bit set.
 641                 or al,80h
 642                 cmp al,dl
 643                 je .found_drive0
 644
 645 .still_broken:  dec dx
 646                 cmp dl, 80h
 647                 jnb .test_loop
 648
 649                 ; No spec packet anywhere.  Some particularly pathetic
 650                 ; BIOSes apparently don't even implement function
 651                 ; 4B01h, so we can't query a spec packet no matter
 652                 ; what.  If we got a drive number in DL, then try to
 653                 ; use it, and if it works, then well...
 654                 mov dl,[DriveNumber]
 655                 cmp dl,81h                      ; Should be 81-FF at least
 656                 jb fatal_error                  ; If not, it's hopeless
 657
 658                 ; Write a warning to indicate we're on *very* thin ice now
 659                 mov si,nospec_msg
 660                 call writemsg
 661                 mov al,dl
 662                 call writehex2
 663                 call crlf_early
 664                 mov si,trysbm_msg
 665                 call writemsg
 666                 jmp .found_drive                ; Pray that this works...
 667
 668 fatal_error:
 669                 mov si,nothing_msg
 670                 call writemsg
 671
 672 .norge:         jmp short .norge
 673
 674                 ; Information message (DS:SI) output
 675                 ; Prefix with "isolinux: "
 676                 ;
 677 writemsg:       push ax
 678                 push si
 679                 mov si,isolinux_str
 680                 call writestr_early
 681                 pop si
 682                 call writestr_early
 683                 pop ax
 684                 ret
 685
 686 writestr_early:
 687                 pushfd
 688                 pushad
 689 .top:           lodsb
 690                 and al,al
 691                 jz .end
 692                 call writechr
 693                 jmp short .top
 694 .end:           popad
 695                 popfd
 696                 ret
 697
 698 crlf_early:     push ax
 699                 mov al,CR
 700                 call writechr
 701                 mov al,LF
 702                 call writechr
 703                 pop ax
 704                 ret
 705
 706 ;
 707 ; Write a character to the screen.  There is a more "sophisticated"
 708 ; version of this in the subsequent code, so we patch the pointer
 709 ; when appropriate.
 710 ;
 711
 712 writechr:
 713 .simple:
 714                 pushfd
 715                 pushad
 716                 mov ah,0Eh
 717                 xor bx,bx
 718                 int 10h
 719                 popad
 720                 popfd
 721                 ret
 722
 723 ;
 724 ; int13: save all the segment registers and call INT 13h.
 725 ;        Some CD-ROM BIOSes have been found to corrupt segment registers
 726 ;        and/or disable interrupts.
 727 ;
 728 int13:
 729                 pushf
 730                 push bp
 731                 push ds
 732                 push es
 733                 push fs
 734                 push gs
 735                 int 13h
 736                 mov bp,sp
 737                 setc [bp+10]            ; Propagate CF to the caller
 738                 pop gs
 739                 pop fs
 740                 pop es
 741                 pop ds
 742                 pop bp
 743                 popf
 744                 ret
 745
 746 ;
 747 ; Get one sector.  Convenience entry point.
 748 ;
 749 getonesec:
 750                 mov bp,1
 751                 ; Fall through to getlinsec
 752
 753 ;
 754 ; Get linear sectors - EBIOS LBA addressing, 2048-byte sectors.
 755 ;
 756 ; Input:
 757 ;       EAX     - Linear sector number
 758 ;       ES:BX   - Target buffer
 759 ;       BP      - Sector count
 760 ;
 761                 global getlinsec
 762 getlinsec:      jmp word [cs:GetlinsecPtr]
 763
 764 %ifndef DEBUG_MESSAGES
 765
 766 ;
 767 ; First, the variants that we use when actually loading off a disk
 768 ; (hybrid mode.)  These are adapted versions of the equivalent routines
 769 ; in ldlinux.asm.
 770 ;
 771
 772 ;
 773 ; getlinsec_ebios:
 774 ;
 775 ; getlinsec implementation for floppy/HDD EBIOS (EDD)
 776 ;
 777 getlinsec_ebios:
 778                 xor edx,edx
 779                 shld edx,eax,2
 780                 shl eax,2                       ; Convert to HDD sectors
 781                 add eax,[Hidden]
 782                 adc edx,[Hidden+4]
 783                 shl bp,2
 784
 785 .loop:
 786                 push bp                         ; Sectors left
 787 .retry2:
 788                 call maxtrans                   ; Enforce maximum transfer size
 789                 movzx edi,bp                    ; Sectors we are about to read
 790                 mov cx,retry_count
 791 .retry:
 792
 793                 ; Form DAPA on stack
 794                 push edx
 795                 push eax
 796                 push es
 797                 push bx
 798                 push di
 799                 push word 16
 800                 mov si,sp
 801                 pushad
 802                 mov dl,[DriveNumber]
 803                 push ds
 804                 push ss
 805                 pop ds                          ; DS <- SS
 806                 mov ah,42h                      ; Extended Read
 807                 call int13
 808                 pop ds
 809                 popad
 810                 lea sp,[si+16]                  ; Remove DAPA
 811                 jc .error
 812                 pop bp
 813                 add eax,edi                     ; Advance sector pointer
 814                 adc edx,0
 815                 sub bp,di                       ; Sectors left
 816                 shl di,9                        ; 512-byte sectors
 817                 add bx,di                       ; Advance buffer pointer
 818                 and bp,bp
 819                 jnz .loop
 820
 821                 ret
 822
 823 .error:
 824                 ; Some systems seem to get "stuck" in an error state when
 825                 ; using EBIOS.  Doesn't happen when using CBIOS, which is
 826                 ; good, since some other systems get timeout failures
 827                 ; waiting for the floppy disk to spin up.
 828
 829                 pushad                          ; Try resetting the device
 830                 xor ax,ax
 831                 mov dl,[DriveNumber]
 832                 call int13
 833                 popad
 834                 loop .retry                     ; CX-- and jump if not zero
 835
 836                 ;shr word [MaxTransfer],1       ; Reduce the transfer size
 837                 ;jnz .retry2
 838
 839                 ; Total failure.  Try falling back to CBIOS.
 840                 mov word [GetlinsecPtr], getlinsec_cbios
 841                 ;mov byte [MaxTransfer],63      ; Max possibe CBIOS transfer
 842
 843                 pop bp
 844                 jmp getlinsec_cbios.loop
 845
 846 ;
 847 ; getlinsec_cbios:
 848 ;
 849 ; getlinsec implementation for legacy CBIOS
 850 ;
 851 getlinsec_cbios:
 852                 xor edx,edx
 853                 shl eax,2                       ; Convert to HDD sectors
 854                 add eax,[Hidden]
 855                 shl bp,2
 856
 857 .loop:
 858                 push edx
 859                 push eax
 860                 push bp
 861                 push bx
 862
 863                 movzx esi,word [bsSecPerTrack]
 864                 movzx edi,word [bsHeads]
 865                 ;
 866                 ; Dividing by sectors to get (track,sector): we may have
 867                 ; up to 2^18 tracks, so we need to use 32-bit arithmetric.
 868                 ;
 869                 div esi
 870                 xor cx,cx
 871                 xchg cx,dx              ; CX <- sector index (0-based)
 872                                         ; EDX <- 0
 873                 ; eax = track #
 874                 div edi                 ; Convert track to head/cyl
 875
 876                 ; We should test this, but it doesn't fit...
 877                 ; cmp eax,1023
 878                 ; ja .error
 879
 880                 ;
 881                 ; Now we have AX = cyl, DX = head, CX = sector (0-based),
 882                 ; BP = sectors to transfer, SI = bsSecPerTrack,
 883                 ; ES:BX = data target
 884                 ;
 885
 886                 call maxtrans                   ; Enforce maximum transfer size
 887
 888                 ; Must not cross track boundaries, so BP <= SI-CX
 889                 sub si,cx
 890                 cmp bp,si
 891                 jna .bp_ok
 892                 mov bp,si
 893 .bp_ok:
 894
 895                 shl ah,6                ; Because IBM was STOOPID
 896                                         ; and thought 8 bits were enough
 897                                         ; then thought 10 bits were enough...
 898                 inc cx                  ; Sector numbers are 1-based, sigh
 899                 or cl,ah
 900                 mov ch,al
 901                 mov dh,dl
 902                 mov dl,[DriveNumber]
 903                 xchg ax,bp              ; Sector to transfer count
 904                 mov ah,02h              ; Read sectors
 905                 mov bp,retry_count
 906 .retry:
 907                 pushad
 908                 call int13
 909                 popad
 910                 jc .error
 911 .resume:
 912                 movzx ecx,al            ; ECX <- sectors transferred
 913                 shl ax,9                ; Convert sectors in AL to bytes in AX
 914                 pop bx
 915                 add bx,ax
 916                 pop bp
 917                 pop eax
 918                 pop edx
 919                 add eax,ecx
 920                 sub bp,cx
 921                 jnz .loop
 922                 ret
 923
 924 .error:
 925                 dec bp
 926                 jnz .retry
 927
 928                 xchg ax,bp              ; Sectors transferred <- 0
 929                 shr word [MaxTransfer],1
 930                 jnz .resume
 931                 jmp disk_error
 932
 933 ;
 934 ; Truncate BP to MaxTransfer
 935 ;
 936 maxtrans:
 937                 cmp bp,[MaxTransfer]
 938                 jna .ok
 939                 mov bp,[MaxTransfer]
 940 .ok:            ret
 941
 942 %endif
 943
 944 ;
 945 ; This is the variant we use for real CD-ROMs:
 946 ; LBA, 2K sectors, some special error handling.
 947 ;
 948 getlinsec_cdrom:
 949                 mov si,dapa                     ; Load up the DAPA
 950                 mov [si+4],bx
 951                 mov [si+6],es
 952                 mov [si+8],eax
 953 .loop:
 954                 push bp                         ; Sectors left
 955                 cmp bp,[MaxTransferCD]
 956                 jbe .bp_ok
 957                 mov bp,[MaxTransferCD]
 958 .bp_ok:
 959                 mov [si+2],bp
 960                 push si
 961                 mov dl,[DriveNumber]
 962                 mov ah,42h                      ; Extended Read
 963                 call xint13
 964                 pop si
 965                 pop bp
 966                 movzx eax,word [si+2]           ; Sectors we read
 967                 add [si+8],eax                  ; Advance sector pointer
 968                 sub bp,ax                       ; Sectors left
 969                 shl ax,SECTOR_SHIFT-4           ; 2048-byte sectors -> segment
 970                 add [si+6],ax                   ; Advance buffer pointer
 971                 and bp,bp
 972                 jnz .loop
 973                 mov eax,[si+8]                  ; Next sector
 974                 ret
 975
 976                 ; INT 13h with retry
 977 xint13:         mov byte [RetryCount],retry_count
 978 .try:           pushad
 979                 call int13
 980                 jc .error
 981                 add sp,byte 8*4                 ; Clean up stack
 982                 ret
 983 .error:
 984                 mov [DiskError],ah              ; Save error code
 985                 popad
 986                 mov [DiskSys],ax                ; Save system call number
 987                 dec byte [RetryCount]
 988                 jz .real_error
 989                 push ax
 990                 mov al,[RetryCount]
 991                 mov ah,[dapa+2]                 ; Sector transfer count
 992                 cmp al,2                        ; Only 2 attempts left
 993                 ja .nodanger
 994                 mov ah,1                        ; Drop transfer size to 1
 995                 jmp short .setsize
 996 .nodanger:
 997                 cmp al,retry_count-2
 998                 ja .again                       ; First time, just try again
 999                 shr ah,1                        ; Otherwise, try to reduce
1000                 adc ah,0                        ; the max transfer size, but not to 0
1001 .setsize:
1002                 mov [MaxTransferCD],ah
1003                 mov [dapa+2],ah
1004 .again:
1005                 pop ax
1006                 jmp .try
1007
1008 .real_error:    mov si,diskerr_msg
1009                 call writemsg
1010                 mov al,[DiskError]
1011                 call writehex2
1012                 mov si,oncall_str
1013                 call writestr_early
1014                 mov ax,[DiskSys]
1015                 call writehex4
1016                 mov si,ondrive_str
1017                 call writestr_early
1018                 mov al,dl
1019                 call writehex2
1020                 call crlf_early
1021                 ; Fall through to kaboom
1022
1023 ;
1024 ; kaboom: write a message and bail out.  Wait for a user keypress,
1025 ;         then do a hard reboot.
1026 ;
1027                 global kaboom
1028 disk_error:
1029 kaboom:
1030                 RESET_STACK_AND_SEGS AX
1031                 mov si,bailmsg
1032                 pm_call pm_writestr
1033                 pm_call pm_getchar
1034                 cli
1035                 mov word [BIOS_magic],0 ; Cold reboot
1036                 jmp 0F000h:0FFF0h       ; Reset vector address
1037
1038 ; -----------------------------------------------------------------------------
1039 ;  Common modules needed in the first sector
1040 ; -----------------------------------------------------------------------------
1041
1042 %include "writehex.inc"         ; Hexadecimal output
1043
1044 ; -----------------------------------------------------------------------------
1045 ; Data that needs to be in the first sector
1046 ; -----------------------------------------------------------------------------
1047
1048                 global syslinux_banner, copyright_str
1049 syslinux_banner db CR, LF, MY_NAME, ' ', VERSION_STR, ' ', DATE_STR, ' ', 0
1050 copyright_str   db ' Copyright (C) 1994-'
1051                 asciidec YEAR
1052                 db ' H. Peter Anvin et al', CR, LF, 0
1053 isolinux_str    db 'isolinux: ', 0
1054 %ifdef DEBUG_MESSAGES
1055 startup_msg:    db 'Starting up, DL = ', 0
1056 spec_ok_msg:    db 'Loaded spec packet OK, drive = ', 0
1057 secsize_msg:    db 'Sector size ', 0
1058 offset_msg:     db 'Main image LBA = ', 0
1059 verify_msg:     db 'Image csum verified.', CR, LF, 0
1060 allread_msg     db 'Image read, jumping to main code...', CR, LF, 0
1061 %endif
1062 noinfotable_msg db 'No boot info table, assuming single session disk...', CR, LF, 0
1063 noinfoinspec_msg db 'Spec packet missing LBA information, trying to wing it...', CR, LF, 0
1064 spec_err_msg:   db 'Loading spec packet failed, trying to wing it...', CR, LF, 0
1065 maybe_msg:      db 'Found something at drive = ', 0
1066 alright_msg:    db 'Looks reasonable, continuing...', CR, LF, 0
1067 nospec_msg      db 'Extremely broken BIOS detected, last attempt with drive = ', 0
1068 nothing_msg:    db 'Failed to locate CD-ROM device; boot failed.', CR, LF
1069 trysbm_msg      db 'See http://syslinux.zytor.com/sbm for more information.', CR, LF, 0
1070 diskerr_msg:    db 'Disk error ', 0
1071 oncall_str:     db ', AX = ',0
1072 ondrive_str:    db ', drive ', 0
1073 checkerr_msg:   db 'Image checksum error, sorry...', CR, LF, 0
1074
1075 err_bootfailed  db CR, LF, 'Boot failed: press a key to retry...'
1076 bailmsg         equ err_bootfailed
1077 crlf_msg        db CR, LF
1078 null_msg        db 0
1079
1080 bios_cdrom_str  db 'ETCD', 0
1081 %ifndef DEBUG_MESSAGES
1082 bios_cbios_str  db 'CHDD', 0
1083 bios_ebios_str  db 'EHDD' ,0
1084 %endif
1085
1086                 alignz 4
1087                 global bios_cdrom
1088 bios_cdrom:     dw getlinsec_cdrom, bios_cdrom_str
1089 %ifndef DEBUG_MESSAGES
1090 bios_cbios:     dw getlinsec_cbios, bios_cbios_str
1091 bios_ebios:     dw getlinsec_ebios, bios_ebios_str
1092 %endif
1093
1094 ; Maximum transfer size
1095 MaxTransfer     dw 127                          ; Hard disk modes
1096 MaxTransferCD   dw 32                           ; CD mode
1097
1098 rl_checkpt      equ $                           ; Must be <= 800h
1099
1100                 ; This pads to the end of sector 0 and errors out on
1101                 ; overflow.
1102                 times 2048-($-$$) db 0
1103
1104 ; ----------------------------------------------------------------------------
1105 ;  End of code and data that have to be in the first sector
1106 ; ----------------------------------------------------------------------------
1107
1108                 section .text16
1109
1110 all_read:
1111
1112 ; Test tracers
1113                 TRACER 'T'
1114                 TRACER '>'
1115
1116 ;
1117 ; Common initialization code
1118 ;
1119 %include "init.inc"
1120
1121 ; Tell the user we got this far...
1122 %ifndef DEBUG_MESSAGES                  ; Gets messy with debugging on
1123                 mov si,copyright_str
1124                 pm_call pm_writestr
1125 %endif
1126
1127 ;
1128 ; Now we're all set to start with our *real* business.  First load the
1129 ; configuration file (if any) and parse it.
1130 ;
1131 ; In previous versions I avoided using 32-bit registers because of a
1132 ; rumour some BIOSes clobbered the upper half of 32-bit registers at
1133 ; random.  I figure, though, that if there are any of those still left
1134 ; they probably won't be trying to install Linux on them...
1135 ;
1136 ; The code is still ripe with 16-bitisms, though.  Not worth the hassle
1137 ; to take'm out.  In fact, we may want to put them back if we're going
1138 ; to boot ELKS at some point.
1139 ;
1140
1141 ;
1142 ; Now, we need to sniff out the actual filesystem data structures.
1143 ; mkisofs gave us a pointer to the primary volume descriptor
1144 ; (which will be at 16 only for a single-session disk!); from the PVD
1145 ; we should be able to find the rest of what we need to know.
1146 ;
1147 init_fs:
1148                 pushad
1149                 mov eax,ROOT_FS_OPS
1150                 mov dl,[DriveNumber]
1151                 cmp word [BIOSType],bios_cdrom
1152                 sete dh                        ; 1 for cdrom, 0 for hybrid mode
1153                 jne .hybrid
1154                 movzx ebp,word [MaxTransferCD]
1155                 jmp .common
1156 .hybrid:
1157                 movzx ebp,word [MaxTransfer]
1158 .common:
1159                 mov ecx,[Hidden]
1160                 mov ebx,[Hidden+4]
1161                 mov si,[bsHeads]
1162                 mov di,[bsSecPerTrack]
1163                 pm_call pm_fs_init
1164                 pm_call load_env32
1165 enter_command:
1166 auto_boot:
1167                 jmp kaboom              ; load_env32() should never return. If
1168                                         ; it does, then kaboom!
1169                 popad
1170
1171                 section .rodata
1172                 alignz 4
1173 ROOT_FS_OPS:
1174                 extern iso_fs_ops
1175                 dd iso_fs_ops
1176                 dd 0
1177
1178                 section .text16
1179
1180 %ifdef DEBUG_TRACERS
1181 ;
1182 ; debug hack to print a character with minimal code impact
1183 ;
1184 debug_tracer:   pushad
1185                 pushfd
1186                 mov bp,sp
1187                 mov bx,[bp+9*4]         ; Get return address
1188                 mov al,[cs:bx]          ; Get data byte
1189                 inc word [bp+9*4]       ; Return to after data byte
1190                 call writechr
1191                 popfd
1192                 popad
1193                 ret
1194 %endif  ; DEBUG_TRACERS
1195
1196                 section .bss16
1197                 alignb 4
1198 ThisKbdTo       resd 1                  ; Temporary holder for KbdTimeout
1199 ThisTotalTo     resd 1                  ; Temporary holder for TotalTimeout
1200 KernelExtPtr    resw 1                  ; During search, final null pointer
1201 FuncFlag        resb 1                  ; Escape sequences received from keyboard
1202 KernelType      resb 1                  ; Kernel type, from vkernel, if known
1203                 global KernelName
1204 KernelName      resb FILENAME_MAX       ; Mangled name for kernel
1205
1206                 section .text16
1207 ;
1208 ; COMBOOT-loading code
1209 ;
1210 %include "comboot.inc"
1211 %include "com32.inc"
1212
1213 ;
1214 ; Boot sector loading code
1215 ;
1216
1217 ;
1218 ; Abort loading code
1219 ;
1220
1221 ;
1222 ; Hardware cleanup common code
1223 ;
1224
1225 %include "localboot.inc"
1226
1227 ; -----------------------------------------------------------------------------
1228 ;  Common modules
1229 ; -----------------------------------------------------------------------------
1230
1231 %include "common.inc"           ; Universal modules
1232
1233 ; -----------------------------------------------------------------------------
1234 ;  Begin data section
1235 ; -----------------------------------------------------------------------------
1236
1237                 section .data16
1238 err_disk_image  db 'Cannot load disk image (invalid file)?', CR, LF, 0